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Sample records for resistance kdr frequencies

  1. Resistance to DDT and pyrethroids and increased kdr mutation frequency in An. gambiae after the implementation of permethrin-treated nets in Senegal.

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    Mamadou O Ndiath

    Full Text Available The aim of this study was to evaluate the susceptibility to insecticides of An. gambiae mosquitoes sampled in Dielmo (Senegal, in 2010, 2 years after the implementation of Long Lasting Insecticide-treated Nets (LLINs and to report the evolution of kdr mutation frequency from 2006 to 2010.WHO bioassay susceptibility tests to 6 insecticides were performed on adults F0, issuing from immature stages of An. gambiae s.l., sampled in August 2010. Species and molecular forms as well as the presence of L1014F and L1014S kdr mutations were assessed by PCR. Longitudinal study of kdr mutations was performed on adult mosquitoes sampled monthly by night landing catches from 2006 to 2010.No specimen studied presented the L1014S mutation. During the longitudinal study, L1014F allelic frequency rose from 2.4% in year before the implementation of LLINs to 4.6% 0-12 months after and 18.7% 13-30 months after. In 2010, An. gambiae were resistant to DDT, Lambda-cyhalothrin, Deltamethrin and Permethrin (mortality rates ranging from 46 to 63% but highly susceptible to Fenitrothion and Bendiocarb (100% mortality. There was significantly more RR genotype among An. gambiae surviving exposure to DDT or Pyrethroids. An. arabiensis represented 3.7% of the sampled mosquitoes (11/300 with no kdr resistance allele detected. An. gambiae molecular form M represented 29.7% of the mosquitoes with, among them, kdr genotypes SR (18% and SS (82%. An. gambiae molecular form S represented 66% of the population with, among them, kdr genotype SS (33.3%, SR (55.6% and RR (11.1%. Only 2 MS hybrid mosquitoes were sampled and presented SS kdr genotype.Biological evidence of resistance to DDT and pyrethroids was detected among An. gambiae mosquitoes in Dielmo (Senegal within 24 months of community use of LLINs. Molecular identification of L1014F mutation indicated that target site resistance increased after the implementation of LLINs.

  2. Diversity and frequency of kdr mutations within Anopheles sinensis populations from Guangxi, China.

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    Yang, Chan; Feng, Xiangyang; Huang, Zushi; Li, Mei; Qiu, Xinghui

    2016-08-15

    Anopheles sinensis is a major vector of malaria in China and its control is under great threat as the development of insecticide resistance. Voltage-gated sodium channel (VGSC) is the target of several classes of insecticides. Genetic mutations of VGSC have been documented to confer knockdown resistance (kdr) to dichlorodiphenyltrichloroethane (DDT) and pyrethroids in mosquitoes. To control this vector efficiently, it is important to know the resistance-associated genetic mutations, their distribution frequencies and genealogical relations. Three hundreds and thirteen (313) adults of An. sinensis collected from nine locations across Guangxi Zhuang Autonomous Region were used. The partial sequence of the An. sinensis voltage gated sodium channel gene (AS-VGSC) containing codon 1014 was sequenced. PHASE2.1 was used to construct the haplotypes of each individual, and the accuracy of haplotypes was further confirmed by clone sequencing. The genealogical relations of kdr mutations in AS-VGSC was analysed using TCS 2.1 and Network 5.0. Sixteen AS-VGSC haplotypes including seven haplotypes carrying non-synonymous mutations at codon 1014, and fifty-five AS-VGSC genotypes were identified from 313 mosquitoes collected from nine geographical locations across Guangxi. The number of haplotypes in each of the nine populations ranged from 5 to 13. The frequency of haplotypes carrying kdr mutations ranged from 2.7 to 80.0 % within the nine populations, of which 1014C was unexpectedly high in the northeast of Guangxi. Genealogical analysis suggested multiple origins of kdr mutations in An. sinensis. Diverse haplotypes of AS-VGSC are distributed in Guangxi. The presence of haplotypes carrying mutations at codon 1014 indicates a risk of pyrethroid and DDT resistance. The kdr mutations show differential distribution geographically, with high frequencies occurred in the northeast of Guangxi. Genealogical analysis suggests multiple origins of kdr mutations in An. sinensis populations

  3. Assessing the effects of Aedes aegypti kdr mutations on pyrethroid resistance and its fitness cost.

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    Luiz Paulo Brito

    Full Text Available Pyrethroids are the most used insecticide class worldwide. They target the voltage gated sodium channel (NaV, inducing the knockdown effect. In Aedes aegypti, the main dengue vector, the AaNaV substitutions Val1016Ile and Phe1534Cys are the most important knockdown resistance (kdr mutations. We evaluated the fitness cost of these kdr mutations related to distinct aspects of development and reproduction, in the absence of any other major resistance mechanism. To accomplish this, we initially set up 68 crosses with mosquitoes from a natural population. Allele-specific PCR revealed that one couple, the one originating the CIT-32 strain, had both parents homozygous for both kdr mutations. However, this pyrethroid resistant strain also presented high levels of detoxifying enzymes, which synergistically account for resistance, as revealed by biological and biochemical assays. Therefore, we carried out backcrosses between CIT-32 and Rockefeller (an insecticide susceptible strain for eight generations in order to bring the kdr mutation into a susceptible genetic background. This new strain, named Rock-kdr, was highly resistant to pyrethroid and presented reduced alteration of detoxifying activity. Fitness of the Rock-kdr was then evaluated in comparison with Rockefeller. In this strain, larval development took longer, adults had an increased locomotor activity, fewer females laid eggs, and produced a lower number of eggs. Under an inter-strain competition scenario, the Rock-kdr larvae developed even slower. Moreover, when Rockefeller and Rock-kdr were reared together in population cage experiments during 15 generations in absence of insecticide, the mutant allele decreased in frequency. These results strongly suggest that the Ae. aegypti kdr mutations have a high fitness cost. Therefore, enhanced surveillance for resistance should be priority in localities where the kdr mutation is found before new adaptive alleles can be selected for diminishing the

  4. PCR-based methods for the detection of L1014 kdr mutation in Anopheles culicifacies sensu lato

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    Singh, Om P; Bali, Prerna; Hemingway, Janet; Subbarao, Sarala K; Dash, Aditya P; Adak, Tridibes

    2009-01-01

    Background Anopheles culicifacies s.l., a major malaria vector in India, has developed widespread resistance to DDT and is becoming resistant to pyrethroids–the only insecticide class recommended for the impregnation of bed nets. Knock-down resistance due to a point mutation in the voltage gated sodium channel at L1014 residue (kdr) is a common mechanism of resistance to DDT and pyrethroids. The selection of this resistance may pose a serious threat to the success of the pyrethroid-impregnated bed net programme. This study reports the presence of kdr mutation (L1014F) in a field population of An. culicifacies s.l. and three new PCR-based methods for kdr genotyping. Methods The IIS4-IIS5 linker to IIS6 segments of the para type voltage gated sodium channel gene of DDT and pyrethroid resistant An. culicifacies s.l. population from the Surat district of India was sequenced. This revealed the presence of an A-to-T substitution at position 1014 leading to a leucine-phenylalanine mutation (L1014F) in a few individuals. Three molecular methods viz. Allele Specific PCR (AS-PCR), an Amplification Refractory Mutation System (ARMS) and Primer Introduced Restriction Analysis-PCR (PIRA-PCR) were developed and tested for kdr genotyping. The specificity of the three assays was validated following DNA sequencing of the samples genotyped. Results The genotyping of this An. culicifacies s.l. population by the three PCR based assays provided consistent result and were in agreement with DNA sequencing result. A low frequency of the kdr allele mostly in heterozygous condition was observed in the resistant population. Frequencies of the different genotypes were in Hardy-Weinberg equilibrium. Conclusion The Leu-Phe mutation, which generates the kdr phenotype in many insects, was detected in a pyrethroid and DDT resistant An. culicifacies s.l. population. Three PCR-based methods were developed for kdr genotyping. All the three assays were specific. The ARMS method was refractory to non

  5. PCR-based methods for the detection of L1014 kdr mutation in Anopheles culicifacies sensu lato

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    Dash Aditya P

    2009-07-01

    Full Text Available Abstract Background Anopheles culicifacies s.l., a major malaria vector in India, has developed widespread resistance to DDT and is becoming resistant to pyrethroids–the only insecticide class recommended for the impregnation of bed nets. Knock-down resistance due to a point mutation in the voltage gated sodium channel at L1014 residue (kdr is a common mechanism of resistance to DDT and pyrethroids. The selection of this resistance may pose a serious threat to the success of the pyrethroid-impregnated bed net programme. This study reports the presence of kdr mutation (L1014F in a field population of An. culicifacies s.l. and three new PCR-based methods for kdr genotyping. Methods The IIS4-IIS5 linker to IIS6 segments of the para type voltage gated sodium channel gene of DDT and pyrethroid resistant An. culicifacies s.l. population from the Surat district of India was sequenced. This revealed the presence of an A-to-T substitution at position 1014 leading to a leucine-phenylalanine mutation (L1014F in a few individuals. Three molecular methods viz. Allele Specific PCR (AS-PCR, an Amplification Refractory Mutation System (ARMS and Primer Introduced Restriction Analysis-PCR (PIRA-PCR were developed and tested for kdr genotyping. The specificity of the three assays was validated following DNA sequencing of the samples genotyped. Results The genotyping of this An. culicifacies s.l. population by the three PCR based assays provided consistent result and were in agreement with DNA sequencing result. A low frequency of the kdr allele mostly in heterozygous condition was observed in the resistant population. Frequencies of the different genotypes were in Hardy-Weinberg equilibrium. Conclusion The Leu-Phe mutation, which generates the kdr phenotype in many insects, was detected in a pyrethroid and DDT resistant An. culicifacies s.l. population. Three PCR-based methods were developed for kdr genotyping. All the three assays were specific. The ARMS method

  6. Knockdown resistance (kdr)-like mutations in the voltage-gated sodium channel of a malaria vector Anopheles stephensi and PCR assays for their detection.

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    Singh, Om P; Dykes, Cherry L; Lather, Manila; Agrawal, Om P; Adak, Tridibes

    2011-03-14

    Knockdown resistance (kdr) in insects, resulting from mutation(s) in the voltage-gated sodium channel (vgsc) gene is one of the mechanisms of resistance against DDT and pyrethroid-group of insecticides. The most common mutation(s) associated with knockdown resistance in insects, including anophelines, has been reported to be present at residue Leu1014 in the IIS6 transmembrane segment of the vgsc gene. This study reports the presence of two alternative kdr-like mutations, L1014S and L1014F, at this residue in a major malaria vector Anopheles stephensi and describes new PCR assays for their detection. Part of the vgsc (IIS4-S5 linker-to-IIS6 transmembrane segment) of An. stephensi collected from Alwar (Rajasthan, India) was PCR-amplified from genomic DNA, sequenced and analysed for the presence of deduced amino acid substitution(s). Analysis of DNA sequences revealed the presence of two alternative non-synonymous point mutations at L1014 residue in the IIS6 transmembrane segment of vgsc, i.e., T>C mutation on the second position and A>T mutation on the third position of the codon, leading to Leu (TTA)-to-Ser (TCA) and -Phe (TTT) amino acid substitutions, respectively. Polymerase chain reaction (PCR) assays were developed for identification of each of these two point mutations. Genotyping of An. stephensi mosquitoes from Alwar by PCR assays revealed the presence of both mutations, with a high frequency of L1014S. The PCR assays developed for detection of the kdr mutations were specific as confirmed by DNA sequencing of PCR-genotyped samples. Two alternative kdr-like mutations, L1014S and L1014F, were detected in An. stephensi with a high allelic frequency of L1014S. The occurrence of L1014S is being reported for the first time in An. stephensi. Two specific PCR assays were developed for detection of two kdr-like mutations in An. stephensi.

  7. Investigating knockdown resistance (kdr) mechanism against pyrethroids/DDT in the malaria vector Anopheles funestus across Africa.

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    Irving, Helen; Wondji, Charles S

    2017-08-09

    Understanding the molecular basis of insecticide resistance is key to improve the surveillance and monitoring of malaria vector populations under control. In the major malaria vector Anopheles funestus, little is currently known about the role of the knockdown resistance (kdr) mechanism. Here, we investigated the presence and contribution of knockdown resistance (kdr) to pyrethroids/DDT resistance observed in Anopheles funestus across Africa. Pyrosequencing genotyping and sequencing of the voltage gated sodium channel (VGSC) gene did not detect the common L1014F mutation in field collected An. funestus across Africa. Amplification and cloning of the full-length of the sodium channel gene in pyrethroid resistant mosquitoes revealed evidences of alternative splicing events with three transcripts of 2092, 2061 and 2117 amino acids (93% average similarity to An. gambiae). Several amino acid changes were detected close to the domain II of the protein such as L928R, F938 W, I939S, L802S and T1008 M. However, all these mutations are found at low frequency and their role in pyrethroid resistance could not be established. The presence of the exclusive alternative splicing at exon 19 was not associated with resistance phenotype. Analysis of patterns of genetic diversity of the VGSC gene revealed a high polymorphism level of this gene across Africa with no evidence of directional selection suggesting a limited role for knockdown resistance in pyrethroid resistance in An. funestus. Patterns of genetic differentiation correlate with previous observations of the existence of barriers to gene flow Africa-wide with southern population significantly differentiated from other regions. Despite an apparent limited role of knockdown resistance in An. funestus, it is necessary to continue to monitor the contribution of the mutations detected here as increasing selection from insecticide-based interventions may change the dynamic in field populations as previously observed in other

  8. First report of L1014F-kdr mutation in Culex pipiens complex from Morocco.

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    Bkhache, Meriem; Tmimi, Fatim-Zohra; Charafeddine, Omar; Faraj, Chafika; Failloux, Anna-Bella; Sarih, M'hammed

    2016-12-16

    Mosquitoes of the Culex pipiens complex, competent vectors for West Nile virus (WNV) and Rift Valley fever virus (RVFV) are widely targeted by insecticide treatments. The intensive application of chemical insecticides led to the development of resistance in many insects including Culex pipiens mosquitoes. The absence of data on resistance mechanisms in Morocco allow us to assess the levels of lambda-cyhalothrin resistance and the frequency of the mutated gene L1014F kdr in different forms of Cx. pipiens complex from three regions of Morocco. Mosquito adults were reared from immature stages collected in three different regions in Morocco (Tangier, Casablanca and Marrakech). Standard WHO insecticide susceptibility tests were conducted on adults emerged from collected larvae. Specimens were identified as belonging to the Culex pipiens complex using a multiplex PCR assay with diagnostic primers designed from the flanking region of microsatellite CQ11. Identified mosquitoes were then tested for the presence of the L1014F kdr mutation using PCR assay. Our results showed that 21% of the tested population has a resistance to lambda-cyhalothrin. The molecular identification of survivors shows that 43% belonged to the Cx. pipiens pipiens and only 9.5% to the Cx. pipiens molestus form. On the other hand, 416 specimens were screened for the L1014F kdr mutation. L1014F mutation was detected in different forms of Cx. pipiens in different sites. The frequency of L1014F mutation was similar between the Cx. pipiens pipiens form and hybrid form, while it was lower in the Cx. pipiens molestus form. The presence of the L1014F kdr allele was significantly associated with resistance to lambda-cyhalothrin in Cx. pipiens pipiens (P Morocco. These findings will provide important information to propose more adapted vector control measures towards this mosquito species, potential vector of arboviruses.

  9. A simplified high-throughput method for pyrethroid knock-down resistance (kdr) detection in Anopheles gambiae

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    Lynd, Amy; Ranson, Hilary; McCall, P J; Randle, Nadine P; Black, William C; Walker, Edward D; Donnelly, Martin J

    2005-01-01

    Background A single base pair mutation in the sodium channel confers knock-down resistance to pyrethroids in many insect species. Its occurrence in Anopheles mosquitoes may have important implications for malaria vector control especially considering the current trend for large scale pyrethroid-treated bednet programmes. Screening Anopheles gambiae populations for the kdr mutation has become one of the mainstays of programmes that monitor the development of insecticide resistance. The screening is commonly performed using a multiplex Polymerase Chain Reaction (PCR) which, since it is reliant on a single nucleotide polymorphism, can be unreliable. Here we present a reliable and potentially high throughput method for screening An. gambiae for the kdr mutation. Methods A Hot Ligation Oligonucleotide Assay (HOLA) was developed to detect both the East and West African kdr alleles in the homozygous and heterozygous states, and was optimized for use in low-tech developing world laboratories. Results from the HOLA were compared to results from the multiplex PCR for field and laboratory mosquito specimens to provide verification of the robustness and sensitivity of the technique. Results and Discussion The HOLA assay, developed for detection of the kdr mutation, gives a bright blue colouration for a positive result whilst negative reactions remain colourless. The results are apparent within a few minutes of adding the final substrate and can be scored by eye. Heterozygotes are scored when a sample gives a positive reaction to the susceptible probe and the kdr probe. The technique uses only basic laboratory equipment and skills and can be carried out by anyone familiar with the Enzyme-linked immunosorbent assay (ELISA) technique. A comparison to the multiplex PCR method showed that the HOLA assay was more reliable, and scoring of the plates was less ambiguous. Conclusion The method is capable of detecting both the East and West African kdr alleles in the homozygous and

  10. A simplified high-throughput method for pyrethroid knock-down resistance (kdr detection in Anopheles gambiae

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    Walker Edward D

    2005-03-01

    Full Text Available Abstract Background A single base pair mutation in the sodium channel confers knock-down resistance to pyrethroids in many insect species. Its occurrence in Anopheles mosquitoes may have important implications for malaria vector control especially considering the current trend for large scale pyrethroid-treated bednet programmes. Screening Anopheles gambiae populations for the kdr mutation has become one of the mainstays of programmes that monitor the development of insecticide resistance. The screening is commonly performed using a multiplex Polymerase Chain Reaction (PCR which, since it is reliant on a single nucleotide polymorphism, can be unreliable. Here we present a reliable and potentially high throughput method for screening An. gambiae for the kdr mutation. Methods A Hot Ligation Oligonucleotide Assay (HOLA was developed to detect both the East and West African kdr alleles in the homozygous and heterozygous states, and was optimized for use in low-tech developing world laboratories. Results from the HOLA were compared to results from the multiplex PCR for field and laboratory mosquito specimens to provide verification of the robustness and sensitivity of the technique. Results and Discussion The HOLA assay, developed for detection of the kdr mutation, gives a bright blue colouration for a positive result whilst negative reactions remain colourless. The results are apparent within a few minutes of adding the final substrate and can be scored by eye. Heterozygotes are scored when a sample gives a positive reaction to the susceptible probe and the kdr probe. The technique uses only basic laboratory equipment and skills and can be carried out by anyone familiar with the Enzyme-linked immunosorbent assay (ELISA technique. A comparison to the multiplex PCR method showed that the HOLA assay was more reliable, and scoring of the plates was less ambiguous. Conclusion The method is capable of detecting both the East and West African kdr alleles

  11. Contrasting patterns of insecticide resistance and knockdown resistance (kdr) in the dengue vectors Aedes aegypti and Aedes albopictus from Malaysia.

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    Ishak, Intan H; Jaal, Zairi; Ranson, Hilary; Wondji, Charles S

    2015-03-25

    Knowledge on the extent, distribution and mechanisms of insecticide resistance is essential for successful insecticide-based dengue control interventions. Here, we report an extensive resistance profiling of the dengue vectors Aedes aegypti and Aedes albopictus across Malaysia and establish the contribution of knockdown resistance mechanism revealing significant contrast between both species. Aedes mosquitoes were collected from four states in Malaysia in 2010 using ovitraps and tested against six major insecticides using WHO bioassays. Knockdown resistance (kdr) was investigated in both species. A moderate resistance to temephos was detected from samples collected in 2010 in Penang, Kuala Lumpur, Johor Bharu and Kota Bharu (1.5 Malaysia but neither of these mutations were found in Ae. albopictus. Additionally, signatures of selection were detected on the Voltage-gated sodium channel gene in Ae. aegypti but not in Ae. albopictus. The presence of the 1534C allele was significantly associated with pyrethroid resistance and an additive effect to pyrethroid resistance was observed in individuals containing both kdr alleles. Findings from this study will help to design and implement successful insecticide-based interventions against Ae. aegypti and Ae. albopictus to improve dengue control across Malaysia.

  12. First detection of multiple knockdown resistance (kdr)-like mutations in voltage-gated sodium channel using three new genotyping methods in Anopheles sinensis from Guangxi Province, China.

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    Tan, Wei L; Li, Chun X; Wang, Zhong M; Liu, Mei D; Dong, Yan D; Feng, Xiang Y; Wu, Zhi M; Guo, Xiao X; Xing, Dan; Zhang, Ying M; Wang, Zhong C; Zhao, Tong Y

    2012-09-01

    To investigate knockdown resistance (kdr)-like mutations associated with pyrethroid resistance in Anopheles sinensis (Wiedemann, 1828), from Guangxi province, southwest China, a segment of a sodium channel gene was sequenced and genotyped using three new genotyping assays. Direct sequencing revealed the presence of TTG-to-TCG and TG-to-TTT mutations at allele position L1014, which led to L1014S and L1014F substitutions in a few individual and two novel substitutions of N1013S and L1014W in two DNA templates. A low frequency of the kdr allele mostly in the heterozygous state of L1014S and L1014F was observed in this mosquito population. In this study, the genotyping of An. sinensis using three polymerase chain reaction-based methods generated consistent results, which agreed with the results of DNA sequencing. In total, 52 mosquitoes were genotyped using a direct sequencing assay. The number of mosquitoes and their genotypes were as follows: L/L = 24, L/S = 19, L/F = 8, and F/W = 1. The allelic frequency of L1014, 1014S, and 1014F were 72, 18, and 9%, respectively.

  13. Absence of kdr resistance alleles in the Union of the Comoros, East Africa [v1; ref status: indexed, http://f1000r.es/5fw

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    Yoosook Lee

    2015-06-01

    Full Text Available Knockdown resistance (kdr and CYP9K1 genotypes were detected by a MOLDI-TOF based SNP genotyping assay (Sequenom iPLEX in samples of Anopheles gambiae collected at 13 sites throughout the Union of the Comoros and Dar es Salaam, Tanzania during February and March 2011. All A. gambiae specimens collected in the Comoros were homozygous for the susceptible kdr alleles (+/+ while 96% of A. gambiae from Dar es Salaam were homozygous for the East African kdr resistant genotype (E/E. In contrast, all specimens from Dar es Salaam and the Comoros were homozygous for the cyp3 allele (c3/c3 at the CYP9K1 locus; the locus has been implicated in metabolic resistance against pyrethroid insecticides in West Africa. All specimens had typical A. gambiae genotypes for SNPs within the divergence Islands on all three chromosomes. Although further spatial and temporal studies are needed, the distribution of kdr genotypes between the Comoros and Tanzania further supports isolation of the Comoros populations from A. gambiae populations on mainland Africa.

  14. Molecular modelling studies of kdr mutations in voltage gated sodium channel revealed significant conformational variations contributing to insecticide resistance.

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    Yellapu, Nanda Kumar; Gopal, Jeyakodi; Kasinathan, Gunasekaran; Purushothaman, Jambulingam

    2018-06-01

    Voltage gated sodium channels (VGSC) of mosquito vectors are the primary targets of dichlorodiphenyltrichloroethane (DDT) and other synthetic pyrethroids used in public health programmes. The knockdown resistant (kdr) mutations in VGSC are associated with the insecticide resistance especially in Anophelines. The present study is aimed to emphasize and demarcate the impact of three kdr-mutations such as L1014S, L1014F and L1014H on insecticide resistance. The membrane model of sodium transport domain of VGSC (STD-VGSC) was constructed using de novo approach based on domain and trans-membrane predictions. The comparative molecular modelling studies of wild type and mutant models of STD-VGSC revealed that L1014F mutant was observed to be near native to the wild type model in all the respects, but, L1014S and L1014H mutations showed drastic variations in the energy levels, root mean square fluctuations (RMSF) that resulted in conformational variations. The predicted binding sites also showed variable cavity volumes and RMSF in L1014S and L1014H mutants. Further, DDT also found be bound in near native manner to wild type in L1014F mutant and with variable orientation and affinities in L1014S and L1014H mutants. The variations and fluctuations observed in mutant structures explained that each mutation has its specific impact on the conformation of VGSC and its binding with DDT. The study provides new insights into the structure-function-correlations of mutant STD-VGSC structures and demonstrates the role and effects of kdr mutations on insecticide resistance in mosquito vectors.

  15. Knockdown resistance (kdr) of the voltage-gated sodium channel gene of Aedes aegypti population in Denpasar, Bali, Indonesia.

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    Hamid, Penny Humaidah; Prastowo, Joko; Widyasari, Anis; Taubert, Anja; Hermosilla, Carlos

    2017-06-05

    Aedes aegypti is the main vector of several arthropod-borne viral infections in the tropics profoundly affecting humans, such as dengue fever (DF), West Nile (WN), chikungunya and more recently Zika. Eradication of Aedes still largely depends on insecticides, which is the most cost-effective strategy, and often inefficient due to resistance development in exposed Aedes populations. We here conducted a study of Ae. aegypti resistance towards several insecticides regularly used in the city of Denpasar, Bali, Indonesia. Aedes aegypti egg samples were collected with ovitraps and thereafter hatched in the insectary of the Gadjah Mada University. The F0 generation was used for all bioassay-related experiments and knockdown resistance (kdr) assays. Results clearly showed resistance development of Ae. aegypti against tested insecticides. Mortalities of Ae. aegypti were less than 90% with highest resistance observed against 0.75% permethrin. Mosquitoes from the southern parts of Denpasar presented high level of resistance pattern in comparison to those from the western and northern parts of Denpasar. Kdr analysis of voltage-gated sodium channel (Vgsc) gene showed significant association to S989P and V1016G mutations linked to resistance phenotypes against 0.75% permethrin. Conversely, Ae. aegypti F1534C gene mutation did not result in any significant correlation to resistance development. Periodically surveillance of insecticide resistances in Ae. aegypti mosquitoes will help local public health authorities to set better goals and allow proper evaluation of on-going mosquito control strategies. Initial detection of insecticide resistance will contribute to conduct proper actions in delaying mosquito resistance development such as insecticide rotation or combination of compounds in order to prolong chemical efficacy in combating Ae. aegypti vectors in Indonesia.

  16. Knockdown resistance in pyrethroid-resistant horn fly (Diptera: Muscidae populations in Brazil Resistência Knockdown em populações de mosca-dos-chifres do Brasil resistentes aos piretróides

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    Gustavo A. Sabatini

    2009-09-01

    Full Text Available To investigate the kdr (knockdown resistance resistance-associated gene mutation and determine its frequency in pyrethroid-resistant horn fly (Haematobia irritans populations, a total of 1,804 horn flies of 37 different populations from all Brazilian regions (North, Northeast, Central-West, Southeast, and South were molecular screened through polymerase chain reaction (PCR. The kdr gene was not detected in 87.08% of the flies. However, the gene was amplified in 12.92% of the flies, of which 11.70% were resistant heterozygous and 1.22% were resistant homozygous. Deviation from Hardy-Weinberg equilibrium (HWE was found only in 1 ranch with an excess of heterozygous. When populations were grouped by region, three metapopulations showed significant deviations of HWE (Central-West population, South population and Southeast population. This indicates that populations are isolated one from another and kdr occurrence seems to be an independent effect probably reflecting the insecticide strategy used by each ranch. Although resistance to pyrethroids is disseminated throughout Brazil, only 48% of resistant populations had kdr flies, and the frequency of kdr individuals in each of these resistant populations was quite low. But this study shows that, with the apparent exception of the Northeast region, the kdr mechanism associated with pyrethroid resistance occurs all over Brazil.Com o objetivo de verificar a ocorrência e determinar a frequência da mutação kdr (knock down resistance em populações de Haematobia irritans (mosca-dos-chifres resistentes aos piretróides, foram analisados 1.804 indivíduos de 37 populações de todas as Regiões do Brasil. Com exceção da Região Nordeste, o kdr (knock down resistance gene foi encontrado em populações de todas as regiões. A mutação não foi detectada em 87,08% dos indivíduos. Entretanto, o gene foi amplificado de 12,92% das moscas, das quais 11,70% se mostraram heterozigotas resistentes e 1

  17. L1014F-kdr Mutation in Indian Anopheles subpictus (Diptera: Culicidae) Arising From Two Alternative Transversions in the Voltage-Gated Sodium Channel and a Single PIRA-PCR for Their Detection.

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    Singh, O P; Dykes, C L; Sharma, G; Das, M K

    2015-01-01

    Leucine-to-phenylalanine substitution at residue L1014 in the voltage-gated sodium channel, target site of action for dichlorodiphenyltrichloroethane (DDT) and pyrethroids, is the most common knockdown resistance (kdr) mutation reported in several insects conferring resistance against DDT and pyrethroids. Here, we report presence of two coexisting alternative transversions, A>T and A>C, on the third codon position of L1014 residue in malaria vector Anopheles subpictus Grassi (species A) from Jamshedpur (India), both leading to the same amino acid substitution of Leu-to-Phe with allelic frequencies of 19 and 67%, respectively. A single primer-introduced restriction analysis-polymerase chain reaction (PIRA-PCR) was devised for the identification of L1014F-kdr mutation in An. subpictus resulting from either type of point mutation. Genotyping of samples with PIRA-PCR revealed high frequency (82%) of L1014F-kdr mutation in the study area. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  18. Identification of an alternative knockdown resistance (kdr)-like mutation, M918L, and a novel mutation, V1010A, in the Thrips tabaci voltage-gated sodium channel gene.

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    Wu, Meixiang; Gotoh, Hiroki; Waters, Timothy; Walsh, Douglas B; Lavine, Laura Corley

    2014-06-01

    Knockdown resistance (kdr) has been identified as a main mechanism against pyrethroid insecticides in many arthropod pests including in the onion thrips, Thrips tabaci. To characterize and identify pyrethroid-resistance in onion thrips in Washington state, we conducted insecticide bioassays and sequenced a region of the voltage gated sodium channel gene from several different T. tabaci populations. Field collected Thrips tabaci were found to have large variations in resistance to the pyrethroid insecticide lambda-cyhalothrin. We identified two single nucleotide substitutions in our analysis of a partial sequence of the T. tabaci voltage-gated sodium channel gene. One mutation resulted in the non-synonymous substitution of methionine with leucine (M918L), which is well known to be responsible for super knockdown resistance in some pest species. Another non-synonymous substitution, a valine (GTT) to alanine (GCT) replacement at amino acid 1010 (V1010A) was identified in our study and was associated with lambda-cyhalothrin resistance. We have characterized a known kdr mutation and identified a novel mutation in the voltage-gated sodium channel gene of Thrips tabaci associated with resistance to lambda-cyhalothrin. This gene region and these mutations are expected to be useful in the development of a diagnostic test to detect kdr resistance in many onion thrips populations. © 2013 Society of Chemical Industry.

  19. Detection of knockdown resistance (kdr mutations in Anopheles gambiae: a comparison of two new high-throughput assays with existing methods

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    Ball Amanda

    2007-08-01

    Full Text Available Abstract Background Knockdown resistance (kdr is a well-characterized mechanism of resistance to pyrethroid insecticides in many insect species and is caused by point mutations of the pyrethroid target site the para-type sodium channel. The presence of kdr mutations in Anopheles gambiae, the most important malaria vector in Africa, has been monitored using a variety of molecular techniques. However, there are few reports comparing the performance of these different assays. In this study, two new high-throughput assays were developed and compared with four established techniques. Methods Fluorescence-based assays based on 1 TaqMan probes and 2 high resolution melt (HRM analysis were developed to detect kdr alleles in An. gambiae. Four previously reported techniques for kdr detection, Allele Specific Polymerase Chain Reaction (AS-PCR, Heated Oligonucleotide Ligation Assay (HOLA, Sequence Specific Oligonucleotide Probe – Enzyme-Linked ImmunoSorbent Assay (SSOP-ELISA and PCR-Dot Blot were also optimized. The sensitivity and specificity of all six assays was then compared in a blind genotyping trial of 96 single insect samples that included a variety of kdr genotypes and African Anopheline species. The relative merits of each assay was assessed based on the performance in the genotyping trial, the length/difficulty of each protocol, cost (both capital outlay and consumable cost, and safety (requirement for hazardous chemicals. Results The real-time TaqMan assay was both the most sensitive (with the lowest number of failed reactions and the most specific (with the lowest number of incorrect scores. Adapting the TaqMan assay to use a PCR machine and endpoint measurement with a fluorimeter showed a slight reduction in sensitivity and specificity. HRM initially gave promising results but was more sensitive to both DNA quality and quantity and consequently showed a higher rate of failure and incorrect scores. The sensitivity and specificity of AS

  20. Detection of knockdown resistance (kdr) mutations in Anopheles gambiae: a comparison of two new high-throughput assays with existing methods

    Science.gov (United States)

    Bass, Chris; Nikou, Dimitra; Donnelly, Martin J; Williamson, Martin S; Ranson, Hilary; Ball, Amanda; Vontas, John; Field, Linda M

    2007-01-01

    Background Knockdown resistance (kdr) is a well-characterized mechanism of resistance to pyrethroid insecticides in many insect species and is caused by point mutations of the pyrethroid target site the para-type sodium channel. The presence of kdr mutations in Anopheles gambiae, the most important malaria vector in Africa, has been monitored using a variety of molecular techniques. However, there are few reports comparing the performance of these different assays. In this study, two new high-throughput assays were developed and compared with four established techniques. Methods Fluorescence-based assays based on 1) TaqMan probes and 2) high resolution melt (HRM) analysis were developed to detect kdr alleles in An. gambiae. Four previously reported techniques for kdr detection, Allele Specific Polymerase Chain Reaction (AS-PCR), Heated Oligonucleotide Ligation Assay (HOLA), Sequence Specific Oligonucleotide Probe – Enzyme-Linked ImmunoSorbent Assay (SSOP-ELISA) and PCR-Dot Blot were also optimized. The sensitivity and specificity of all six assays was then compared in a blind genotyping trial of 96 single insect samples that included a variety of kdr genotypes and African Anopheline species. The relative merits of each assay was assessed based on the performance in the genotyping trial, the length/difficulty of each protocol, cost (both capital outlay and consumable cost), and safety (requirement for hazardous chemicals). Results The real-time TaqMan assay was both the most sensitive (with the lowest number of failed reactions) and the most specific (with the lowest number of incorrect scores). Adapting the TaqMan assay to use a PCR machine and endpoint measurement with a fluorimeter showed a slight reduction in sensitivity and specificity. HRM initially gave promising results but was more sensitive to both DNA quality and quantity and consequently showed a higher rate of failure and incorrect scores. The sensitivity and specificity of AS-PCR, SSOP-ELISA, PCR Dot

  1. Trends in DDT and pyrethroid resistance in Anopheles gambiae s.s. populations from urban and agro-industrial settings in southern Cameroon

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    Kerah-Hinzoumbé Clément

    2009-09-01

    Full Text Available Abstract Background Pyrethroid insecticides are widely used for insect pest control in Cameroon. In certain insect species, particularly the malaria vector Anopheles gambiae, resistance to this class of insecticides is a source of great concern and needs to be monitored in order to sustain the efficacy of vector control operations in the fields. This study highlights trends in DDT and pyrethroid resistance in wild An. gambiae populations from South Cameroon. Methods Mosquitoes were collected between 2001 and 2007 in four sites in South Cameroon, where insecticides are used for agricultural or personal protection purposes. Insecticide use was documented in each site by interviewing residents. Batches of 2-4 days old adult female mosquitoes reared from larval collections were tested for susceptibility to DDT, permethrin and deltamethrin using standard WHO procedures. Control, dead and survivors mosquitoes from bioassays were identified by PCR-RFLP and characterized for the kdr mutations using either the AS-PCR or the HOLA method. Results Four chemical insecticide groups were cited in the study sites: organochlorines, organophosphates, carbamates and pyrethroids. These chemicals were used for personal, crop or wood protection. In the four An. gambiae populations tested, significant variation in resistance levels, molecular forms composition and kdr frequencies were recorded in the time span of the study. Increases in DDT and pyrethroid resistance, as observed in most areas, were generally associated with an increase in the relative frequency of the S molecular form carrying the kdr mutations at higher frequencies. In Mangoum, however, where only the S form was present, a significant increase in the frequency of kdr alleles between 2003 to 2007 diverged with a decrease of the level of resistance to DDT and pyrethroids. Analyses of the kdr frequencies in dead and surviving mosquitoes showed partial correlation between the kdr genotypes and resistance

  2. First Detection of the Kdr Mutation T929I in Head Lice (Phthiraptera: Pediculidae) in Schoolchildren of the Metropolitan Area of Nuevo Leon and Yucatan, Mexico.

    Science.gov (United States)

    Ponce-Garcia, Gustavo; Villanueva-Segura, Karina; Trujillo-Rodriguez, Gerardo; Rodriguez-Sanchez, Iram P; Lopez-Monroy, Beatriz; Flores, Adriana E

    2017-07-01

    The head louse Pediculus humanus capitis (De Geer) is a hematophagous ectoparasite that inhabits the human scalp. Infestations by this insect are commonly known as pediculosis, which is more common in younger groups. These infestations are asymptomatic; however, skin irritation from scratching occasionally may cause secondary bacterial infections. In recent years, the prevalence of pediculosis has increased in children; this increase has been attributed to louse resistance to the insecticides used as a control measure for infestation. The aim of the present study was to determine the presence and frequency of the knockdown resistance mutation (kdr) T929I in 468 head lice collected from 32 elementary schools in the metropolitan area of Nuevo Leon (24) and Yucatan (8), Mexico. This is the first report of a knockdown resistance (kdr) mechanism in head lice from Mexico. The T929I mutation was present in all of the sampled schools, with variability observed in its allelic and genotypic frequencies. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  3. Development of an allele-specific, loop-mediated, isothermal amplification method (AS-LAMP to detect the L1014F kdr-w mutation in Anopheles gambiae s. l.

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    Badolo Athanase

    2012-07-01

    Full Text Available Abstract Background Malaria control relies heavily on treated bed nets and indoor residual spraying with pyrethroid insecticides. Unfortunately, the resistance to pyrethroid insecticides, mainly due to the kdr mutation, is spreading in the main malaria vector Anopheles gambiae s.l., decreasing the insecticides’ efficacy. To manage the insecticide resistance rapidly and flexibly, simple and effective tools for the early detection of resistant mosquitoes are needed. This study aimed to develop an allele-specific, loop-mediated, isothermal amplification (AS-LAMP method to detect the West African-type kdr mutation (kdr-w; L1014F in field-collected mosquitoes. Methods DNA fragments of the wild-type and the mutated kdr gene were used to select the primers and develop the method. The primers were designed with the mutation at the 5’ end of the backward inner primer (BIP. The AS-LAMP method was compared to the AS-PCR method using the genomic DNA of 120 field-collected mosquitoes. Results The AS-LAMP method could discriminate between the wild-type homozygote, the heterozygote, and the kdr-w homozygote within 75 min. The AS-LAMP method has the advantage of being faster and at least as sensitive and specific as the AS-PCR method. Conclusions The AS-LAMP method can be used to detect the kdr mutation for quick decision-making, even in less well-equipped laboratories.

  4. Insecticides resistance in the Culex quinquefasciatus populations from northern Thailand and possible resistance mechanisms.

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    Yanola, Jintana; Chamnanya, Saowanee; Lumjuan, Nongkran; Somboon, Pradya

    2015-09-01

    The mosquito vector Culex quinquefasciatus is known to be resistant to insecticides worldwide, including Thailand. This study was the first investigation of the insecticide resistance mechanisms, involving metabolic detoxification and target site insensitivity in C. quinquefasciatus from Thailand. Adult females reared from field-caught larvae from six provinces of northern Thailand were determined for resistant status by exposing to 0.05% deltamethrin, 0.75% permethrin and 5% malathion papers using the standard WHO susceptibility test. The overall mortality rates were 45.8%, 11.4% and 80.2%, respectively. A fragment of voltage-gated sodium channel gene was amplified and sequenced to identify the knock down resistance (kdr) mutation. The ace-1 gene mutation was determined by using PCR-RFLP. The L1014F kdr mutation was observed in all populations, but the homozygous mutant F/F1014 genotype was found only in two of the six provinces where the kdr mutation was significantly correlated with deltamethrin resistance. However, none of mosquitoes had the G119S mutation in the ace-1 gene. A laboratory deltamethrin resistant strain, Cq_CM_R, has been established showing a highly resistant level after selection for a few generations. The mutant F1014 allele frequency was significantly increased after one generation of selection. A synergist assay was performed to assess the metabolic detoxifying enzymes. Addition of bis(4-nitrophenyl)-phosphate (BNPP) and diethyl maleate (DEM), inhibitors of esterases and glutathione S-transferases (GST), respectively, into the larval bioassay of the Cq_CM strain with deltamethrin showed no significant reduction. By contrast, addition of piperonyl butoxide (PBO), an inhibitor of cytochrome P450 monooxygenases, showed a 9-fold reduction of resistance. Resistance to pyrethroids in C. quinquefasciatus is widely distributed in northern Thailand. This study reports for the first time for the detection of the L1014F kdr mutation in wild populations

  5. The role of VEGF and KDR polymorphisms in moyamoya disease and collateral revascularization.

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    Young Seok Park

    Full Text Available We conducted a case-control study to investigate whether vascular endothelial growth factor (VEGF -2578, -1154, -634, and 936 and kinase insert domain containing receptor (KDR -604, 1192, and 1719 polymorphisms are associated with moyamoya disease. Korean patients with moyamoya disease (n = 107, mean age, 20.9±15.9 years; 66.4% female and 243 healthy control subjects (mean age, 23.0±16.1 years; 56.8% female were included. The subjects were divided into pediatric and adult groups. Among the 64 surgical patients, we evaluated collateral vessel formation after 2 years and divided patients into good (collateral grade A or poor (collateral grade B and C groups. The frequencies and distributions of four VEGF (-2578, -1154, -634, and 936 and KDR (-604, 1192, and 1719 polymorphisms were assessed from patients with moyamoya disease and compared to the control group. No differences were observed in VEGF -2578, -1154, -634, and 936 or KDR -604, 1192, and 1719 polymorphisms between the control group and moyamoya disease group. However, we found the -634CC genotype occurred less frequently in the pediatric moyamoya group (p = 0.040 whereas the KDR -604C/1192A/1719T haplotype increased the risk of pediatric moyamoya (p = 0.024. Patients with the CC genotype of VEGF -634 had better collateral vessel formation after surgery. Our results suggest that the VEGF -634G allele is associated with pediatric moyamoya disease and poor collateral vessel formation.

  6. Multiple origins of knockdown resistance mutations in the Afrotropical mosquito vector Anopheles gambiae.

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    João Pinto

    2007-11-01

    Full Text Available How often insecticide resistance mutations arise in natural insect populations is a fundamental question for understanding the evolution of resistance and also for modeling its spread. Moreover, the development of resistance is regarded as a favored model to study the molecular evolution of adaptive traits. In the malaria vector Anopheles gambiae two point mutations (L1014F and L1014S in the voltage-gated sodium channel gene, that confer knockdown resistance (kdr to DDT and pyrethroid insecticides, have been described. In order to determine whether resistance alleles result from single or multiple mutation events, genotyping of the kdr locus and partial sequencing of the upstream intron-1 was performed on a total of 288 A. gambiae S-form collected from 28 localities in 15 countries. Knockdown resistance alleles were found to be widespread in West Africa with co-occurrence of both 1014S and 1014F in West-Central localities. Differences in intron-1 haplotype composition suggest that kdr alleles may have arisen from at least four independent mutation events. Neutrality tests provided evidence for a selective sweep acting on this genomic region, particularly in West Africa. The frequency and distribution of these kdr haplotypes varied geographically, being influenced by an interplay between different mutational occurrences, gene flow and local selection. This has important practical implications for the management and sustainability of malaria vector control programs.

  7. Characterizing the insecticide resistance of Anopheles gambiae in Mali.

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    Cisse, Moussa B M; Keita, Chitan; Dicko, Abdourhamane; Dengela, Dereje; Coleman, Jane; Lucas, Bradford; Mihigo, Jules; Sadou, Aboubacar; Belemvire, Allison; George, Kristen; Fornadel, Christen; Beach, Raymond

    2015-08-22

    The impact of indoor residual spraying (IRS) and long-lasting insecticide nets (LLINs), key components of the national malaria control strategy of Mali, is threatened by vector insecticide resistance. The objective of this study was to assess the level of insecticide resistance in Anopheles gambiae sensu lato populations from Mali against four classes of insecticide recommended for IRS: organochlorines (OCs), pyrethroids (PYs), carbamates (CAs) and organophosphates (OPs). Characterization of resistance was done in 13 sites across southern Mali and assessed presence and distribution of physiological mechanisms that included target-site modifications: knockdown resistance (kdr) and altered acetycholinesterase (AChE), and/or metabolic mechanisms: elevated esterases, glutathione S-transferases (GSTs), and monooxygenases. The World Health Organization (WHO) tube test was used to determine phenotypic resistance of An. gambiae s.l. to: dichlorodiphenyltrichloroethane (DDT) (OC), deltamethrin (PY), lambda-cyhalothrin (PY), bendiocarb (CA), and fenitrothion (OP). Identification of sibling species and presence of the ace-1 (R) and Leu-Phe kdr, resistance-associated mutations, were determined using polymerase chain reaction (PCR) technology. Biochemical assays were conducted to detect increased activity of GSTs, oxidases and esterases. Populations tested showed high levels of resistance to DDT in all 13 sites, as well as increased resistance to deltamethrin and lambda-cyhalothrin in 12 out of 13 sites. Resistance to fenitrothion and bendiocarb was detected in 1 and 4 out of 13 sites, respectively. Anopheles coluzzii, An. gambiae sensu stricto and Anopheles arabiensis were identified with high allelic frequencies of kdr in all sites where each of the species were found (13, 12 and 10 sites, respectively). Relatively low allelic frequencies of ace-1 (R) were detected in four sites where this assessment was conducted. Evidence of elevated insecticide metabolism, based on oxidase

  8. Polymorphism of intron-1 in the voltage-gated sodium channel gene of Anopheles gambiae s.s. populations from Cameroon with emphasis on insecticide knockdown resistance mutations.

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    Etang, Josiane; Vicente, Jose L; Nwane, Philippe; Chouaibou, Mouhamadou; Morlais, Isabelle; Do Rosario, Virgilio E; Simard, Frederic; Awono-Ambene, Parfait; Toto, Jean Claude; Pinto, Joao

    2009-07-01

    Sequence variation at the intron-1 of the voltage-gated sodium channel gene in Anopheles gambiae M- and S-forms from Cameroon was assessed to explore the number of mutational events originating knockdown resistance (kdr) alleles. Mosquitoes were sampled between December 2005 and June 2006 from three geographical areas: (i) Magba in the western region; (ii) Loum, Tiko, Douala, Kribi, and Campo along the Atlantic coast; and (iii) Bertoua, in the eastern continental plateau. Both 1014S and 1014F kdr alleles were found in the S-form with overall frequencies of 14% and 42% respectively. Only the 1014F allele was found in the M-form at lower frequency (11%). Analysis of a 455 bp region of intron-1 upstream the kdr locus revealed four independent mutation events originating kdr alleles, here named MS1 -1014F, S1-1014S and S2-1014S kdr-intron-1 haplotypes in S-form and MS3-1014F kdr-intron-1 haplotype in the M-form. Furthermore, there was evidence for mutual introgression of kdr 1014F allele between the two molecular forms, MS1 and MS3 being widely shared by them. Although no M/S hybrid was observed in analysed samples, this wide distribution of haplotypes MS1 and MS3 suggests inter-form hybridizing at significant level and emphasizes the rapid diffusion of the kdr alleles in Africa. The mosaic of genetic events found in Cameroon is representative of the situation in the West-Central African region and highlights the importance of evaluating the spatial and temporal evolution of kdr alleles for a better management of insecticide resistance.

  9. VEGF and VEGFR-2 (KDR) internalization is required for endothelial recovery during wound healing

    International Nuclear Information System (INIS)

    Constantino Rosa Santos, Susana; Miguel, Claudia; Domingues, Ines; Calado, Angelo; Zhu Zhenping; Wu Yan; Dias, Sergio

    2007-01-01

    Vascular endothelial growth factor (VEGF) receptor activation regulates endothelial cell (EC) survival, migration and proliferation. Recently, it was suggested the cross-talk between the VEGF receptors-1 (FLT-1) and -2 (KDR) modulated several of these functions, but the detailed molecular basis for such interactions remained unexplained. Here we demonstrate for the first time that VEGF stimulation of EC monolayers induced a rapid FLT-1-mediated internalization of KDR to the nucleus, via microtubules and the endocytic pathway, internalization which required the activation of PI 3-kinase/AKT. KDR deletion mutants were generated in several tyrosine residues; in these, VEGF-induced KDR internalization was impaired, demonstrating this process required activation (phosphorylation) of the receptor. Furthermore, we demonstrate that in vitro wounding of EC monolayers leads to a rapid and transient internalization of VEGF + KDR to the nucleus, which is essential for monolayer recovery. Notably, FLT-1 blockade impedes VEGF and KDR activation and internalization, blocking endothelial monolayer recovery. Our data reveal a previously unrecognized mechanism induced by VEGF on EC, which regulates EC recovery following wounding, and as such indicate novel targets for therapeutic intervention

  10. Identification of mutations associated with pyrethroid resistance in the voltage-gated sodium channel of the tomato leaf miner (Tuta absoluta).

    Science.gov (United States)

    Haddi, Khalid; Berger, Madeleine; Bielza, Pablo; Cifuentes, Dina; Field, Linda M; Gorman, Kevin; Rapisarda, Carmelo; Williamson, Martin S; Bass, Chris

    2012-07-01

    The tomato leaf miner, Tuta absoluta (Lepidoptera) is a significant pest of tomatoes that has undergone a rapid expansion in its range during the past six years and is now present across Europe, North Africa and parts of Asia. One of the main means of controlling this pest is through the use of chemical insecticides. In the current study insecticide bioassays were used to determine the susceptibility of five T. absoluta strains established from field collections from Europe and Brazil to pyrethroids. High levels of resistance to λ cyhalothrin and tau fluvalinate were observed in all five strains tested. To investigate whether pyrethroid resistance was mediated by mutation of the para-type sodium channel in T. absoluta the IIS4-IIS6 region of the para gene, which contains many of the mutation sites previously shown to confer knock down (kdr)-type resistance to pyrethroids across a range of different arthropod species, was cloned and sequenced. This revealed that three kdr/super-kdr-type mutations (M918T, T929I and L1014F), were present at high frequencies within all five resistant strains at known resistance 'hot-spots'. This is the first description of these mutations together in any insect population. High-throughput DNA-based diagnostic assays were developed and used to assess the prevalence of these mutations in 27 field strains from 12 countries. Overall mutant allele frequencies were high (L1014F 0.98, M918T 0.35, T929I 0.60) and remarkably no individual was observed that did not carry kdr in combination with either M918T or T929I. The presence of these mutations at high frequency in T. absoluta populations across much of its range suggests pyrethroids are likely to be ineffective for control and supports the idea that the rapid expansion of this species over the last six years may be in part mediated by the resistance of this pest to chemical insecticides. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  11. Evolution of resistance to pyrethroid insecticides in Musca domestica.

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    Scott, Jeffrey G

    2017-04-01

    Houseflies, Musca domestica L., are a significant pest because of the numerous diseases they transmit. Control of housefly populations, particularly at animal production facilities, is frequently done using pyrethroid insecticides which kill insects by prolonging the open time of the voltage-sensitive sodium channel (VSSC). Houseflies have evolved resistance to pyrethroids owing to mutations in Vssc and by cytochrome-P450-mediated detoxification. Three Vssc mutations are known: kdr (L1014F), kdr-his (L1014H) and super-kdr (M918T + L1014F). Generally, the levels of resistance conferred by these mutations are kdr-his resistance than kdr. P450-mediated resistance can result from overexpression of CYP6D1 or another P450 (unidentified) whose overexpression is linked to autosomes II or V. The initial use of field-stable pyrethroids resulted in different patterns of evolution across the globe, but with time these mutations have become more widespread in their distribution. What is known about the fitness costs of the resistance alleles in the absence of insecticide is discussed, particularly with respect to the current and future utility of pyrethroid insecticides. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  12. The Cytochrome P450 gene CYP6P12 confers pyrethroid resistance in kdr-free Malaysian populations of the dengue vector Aedes albopictus.

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    Ishak, Intan H; Riveron, Jacob M; Ibrahim, Sulaiman S; Stott, Rob; Longbottom, Joshua; Irving, Helen; Wondji, Charles S

    2016-04-20

    Control of Aedes albopictus, major dengue and chikungunya vector, is threatened by growing cases of insecticide resistance. The mechanisms driving this resistance remain poorly characterised. This study investigated the molecular basis of insecticide resistance in Malaysian populations of Ae. albopictus. Microarray-based transcription profiling revealed that metabolic resistance (cytochrome P450 up-regulation) and possibly a reduced penetration mechanism (consistent over-expression of cuticular protein genes) were associated with pyrethroid resistance. CYP6P12 over-expression was strongly associated with pyrethroid resistance whereas CYP6N3 was rather consistently over-expressed across carbamate and DDT resistant populations. Other detoxification genes also up-regulated in permethrin resistant mosquitoes included a glucuronosyltransferase (AAEL014279-RA) and the glutathione-S transferases GSTS1 and GSTT3. Functional analyses further supported that CYP6P12 contributes to pyrethroid resistance in Ae. albopictus as transgenic expression of CYP6P12 in Drosophila was sufficient to confer pyrethroid resistance in these flies. Furthermore, molecular docking simulations predicted CYP6P12 possessing enzymatic activity towards pyrethroids. Patterns of polymorphism suggested early sign of selection acting on CYP6P12 but not on CYP6N3. The major role played by P450 in the absence of kdr mutations suggests that addition of the synergist PBO to pyrethroids could improve the efficacy of this insecticide class and overcome resistance in field populations of Ae. albopictus.

  13. Interleukin-6 triggers human cerebral endothelial cells proliferation and migration: The role for KDR and MMP-9

    International Nuclear Information System (INIS)

    Yao, Jianhua S.; Zhai Wenwu; Young, William L.; Yang Guoyuan

    2006-01-01

    Interleukin-6 (IL-6) is involved in angiogenesis. However, the underlying mechanisms are unknown. Using human cerebral endothelial cell (HCEC), we report for First time that IL-6 triggers HCEC proliferation and migration in a dose-dependent manner, specifically associated with enhancement of VEGF expression, up-regulated and phosphorylated VEGF receptor-2 (KDR), and stimulated MMP-9 secretion. We investigated the signal pathway of IL-6/IL-6R responsible for KDR's regulation. Pharmacological inhibitor of PI3K failed to inhibit IL-6-mediated VEGF overexpression, while blocking ERK1/2 with PD98059 could abolish IL-6-induced KDR overexpression. Further, neutralizing endogenous VEGF attenuated KDR expression and phosphorylation, suggesting that IL-6-induced KDR activation is independent of VEGF stimulation. MMP-9 inhibitor GM6001 significantly decreases HCEC proliferation and migration (p < 0.05), indicating the crucial function of MMP-9 in promoting angiogenic changes in HCECs. We conclude that IL-6 triggers VEGF-induced angiogenic activity through increasing VEGF release, up-regulates KDR expression and phosphorylation through activating ERK1/2 signaling, and stimulates MMP-9 overexpression

  14. Temporal frequency of knockdown resistance mutations, F1534C and V1016G, in Aedes aegypti in Chiang Mai city, Thailand and the impact of the mutations on the efficiency of thermal fogging spray with pyrethroids.

    Science.gov (United States)

    Plernsub, Suriya; Saingamsook, Jassada; Yanola, Jintana; Lumjuan, Nongkran; Tippawangkosol, Pongsri; Walton, Catherine; Somboon, Pradya

    2016-10-01

    In Thailand, control of dengue outbreaks is currently attained by the use of space sprays, particularly thermal fogging using pyrethroids, with the aim of killing infected Aedes mosquito vectors in epidemic areas. However, the principal dengue vector, Aedes aegypti, is resistant to pyrethroids conferred mainly by mutations in the voltage-gated sodium channel gene, F1534C and V1016G, termed knockdown resistance (kdr). The objectives of this study were to determine the temporal frequencies of F1534C and V1016G in Ae. aegypti populations in relation to pyrethroid resistance in Chiang Mai city, and to evaluate the impact of the mutations on the efficacy of thermal fogging with the pyrethroid deltamethrin. Larvae and pupae were collected from several areas around Chiang Mai city during 2011-2015 and reared to adulthood for bioassays for deltamethrin susceptibility. These revealed no trend of increasing deltamethrin resistance during the study period (mortality 58.0-69.5%, average 62.8%). This corresponded to no overall change in the frequencies of the C1534 allele (0.55-0.66, average 0.62) and G1016 allele (0.34-0.45, average 0.38), determined using allele specific amplification. Only three genotypes of kdr mutations were detected: C1534 homozygous (VV/CC); G1016/C1534 double heterozygous (VG/FC); and G1016 homozygous (GG/FF) indicating that the F1534C and V1016G mutations occurred on separate haplotypic backgrounds and a lack of recombination between them to date. The F1 progeny females were used to evaluate the efficacy of thermal fogging spray with Damthrin-SP(®) (deltamethrin+S-bioallethrin+piperonyl butoxide) using a caged mosquito bioassay. The thermal fogging spray killed 100% and 61.3% of caged mosquito bioassay placed indoors and outdoors, respectively. The outdoor spray had greater killing effect on C1534 homozygous and had partially effect on double heterozygous mosquitoes, but did not kill any G1016 homozygous mutants living outdoors. As this selection

  15. Distribution of knock-down resistance mutations in Anopheles gambiae molecular forms in west and west-central Africa

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    Caccone Adalgisa

    2008-04-01

    Full Text Available Abstract Background Knock-down resistance (kdr to DDT and pyrethroids in the major Afrotropical vector species, Anopheles gambiae sensu stricto, is associated with two alternative point mutations at amino acid position 1014 of the voltage-gated sodium channel gene, resulting in either a leucine-phenylalanine (L1014F, or a leucine-serine (L1014S substitution. In An. gambiae S-form populations, the former mutation appears to be widespread in west Africa and has been recently reported from Uganda, while the latter, originally recorded in Kenya, has been recently found in Gabon, Cameroon and Equatorial Guinea. In M-form populations surveyed to date, only the L1014F mutation has been found, although less widespread and at lower frequencies than in sympatric S-form populations. Methods Anopheles gambiae M- and S-form specimens from 19 sites from 11 west and west-central African countries were identified to molecular form and genotyped at the kdr locus either by Hot Oligonucleotide Ligation Assay (HOLA or allele-specific PCR (AS-PCR. Results The kdr genotype was determined for about 1,000 An. gambiae specimens. The L1014F allele was found at frequencies ranging from 6% to 100% in all S-form samples (N = 628, with the exception of two samples from Angola, where it was absent, and coexisted with the L1014S allele in samples from Cameroon, Gabon and north-western Angola. The L1014F allele was present in M-form samples (N = 354 from Benin, Nigeria, and Cameroon, where both M- and S-forms were sympatric. Conclusion The results represent the most comprehensive effort to analyse the overall distribution of the L1014F and L1014S mutations in An. gambiae molecular forms, and will serve as baseline data for resistance monitoring. The overall picture shows that the emergence and spread of kdr alleles in An. gambiae is a dynamic process and that there is marked intra- and inter-form heterogeneity in resistance allele frequencies. Further studies are needed to

  16. Sodium Channel Mutations and Pyrethroid Resistance in Aedes aegypti

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    Yuzhe Du

    2016-10-01

    Full Text Available Pyrethroid insecticides are widely used to control insect pests and human disease vectors. Voltage-gated sodium channels are the primary targets of pyrethroid insecticides. Mutations in the sodium channel have been shown to be responsible for pyrethroid resistance, known as knockdown resistance (kdr, in various insects including mosquitoes. In Aedes aegypti mosquitoes, the principal urban vectors of dengue, zika, and yellow fever viruses, multiple single nucleotide polymorphisms in the sodium channel gene have been found in pyrethroid-resistant populations and some of them have been functionally confirmed to be responsible for kdr in an in vitro expression system, Xenopus oocytes. This mini-review aims to provide an update on the identification and functional characterization of pyrethroid resistance-associated sodium channel mutations from Aedes aegypti. The collection of kdr mutations not only helped us develop molecular markers for resistance monitoring, but also provided valuable information for computational molecular modeling of pyrethroid receptor sites on the sodium channel.

  17. Mutations in the voltage-gated sodium channel gene of anophelines and their association with resistance to pyrethroids - a review.

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    Silva, Ana Paula B; Santos, Joselita Maria M; Martins, Ademir J

    2014-10-07

    Constant and extensive use of chemical insecticides has created a selection pressure and favored resistance development in many insect species worldwide. One of the most important pyrethroid resistance mechanisms is classified as target site insensitivity, due to conformational changes in the target site that impair a proper binding of the insecticide molecule. The voltage-gated sodium channel (NaV) is the target of pyrethroids and DDT insecticides, used to control insects of medical, agricultural and veterinary importance, such as anophelines. It has been reported that the presence of a few non-silent point mutations in the NaV gene are associated with pyrethroid resistance, termed as 'kdr' (knockdown resistance) for preventing the knockdown effect of these insecticides. The presence of these mutations, as well as their effects, has been thoroughly studied in Anopheles mosquitoes. So far, kdr mutations have already been detected in at least 13 species (Anopheles gambiae, Anopheles arabiensis, Anopheles sinensis, Anopheles stephensi, Anopheles subpictus, Anopheles sacharovi, Anopheles culicifacies, Anopheles sundaicus, Anopheles aconitus, Anopheles vagus, Anopheles paraliae, Anopheles peditaeniatus and Anopheles albimanus) from populations of African, Asian and, more recently, American continents. Seven mutational variants (L1014F, L1014S, L1014C, L1014W, N1013S, N1575Y and V1010L) were described, with the highest prevalence of L1014F, which occurs at the 1014 site in NaV IIS6 domain. The increase of frequency and distribution of kdr mutations clearly shows the importance of this mechanism in the process of pyrethroid resistance. In this sense, several species-specific and highly sensitive methods have been designed in order to genotype individual mosquitoes for kdr in large scale, which may serve as important tolls for monitoring the dynamics of pyrethroid resistance in natural populations. We also briefly discuss investigations concerning the course of Plasmodium

  18. Voltage-sensitive sodium channel mutations S989P + V1016G in Aedes aegypti confer variable resistance to pyrethroids, DDT and oxadiazines.

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    Smith, Letícia B; Kasai, Shinji; Scott, Jeffrey G

    2018-03-01

    Aedes aegypti is a vector of several important human pathogens. Control efforts rely primarily on pyrethroid insecticides for adult mosquito control, especially during disease outbreaks. A. aegypti has developed resistance nearly everywhere it occurs and insecticides are used. An important mechanism of resistance is due to mutations in the voltage-sensitive sodium channel (Vssc) gene. Two mutations, in particular, S989P + V1016G, commonly occur together in parts of Asia. We have created a strain (KDR:ROCK) that contains the Vssc mutations S989P + V1016G as the only mechanism of pyrethroid resistance within the genetic background of Rockefeller (ROCK), a susceptible lab strain. We created KDR:ROCK by crossing the pyrethroid-resistant strain Singapore with ROCK followed by four backcrosses with ROCK and Vssc S989P + V1016G genotype selections. We determined the levels of resistance conferred to 17 structurally diverse pyrethroids, the organochloride DDT, and oxadiazines (VSSC blockers) indoxacarb (proinsecticide) and DCJW (the active metabolite of indoxacarb). Levels of resistance to the pyrethroids were variable, ranging from 21- to 107-fold, but no clear pattern between resistance and chemical structure was observed. Resistance is inherited as an incompletely recessive trait. KDR:ROCK had a > 2000-fold resistance to DDT, 37.5-fold cross-resistance to indoxacarb and 13.4-fold cross-resistance to DCJW. Etofenprox (and DDT) should be avoided in areas where Vssc mutations S989P + V1016G exist at high frequencies. We found that pyrethroid structure cannot be used to predict the level of resistance conferred by kdr. These results provide useful information for resistance management and for better understanding pyrethroid interactions with VSSC. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of

  19. Three years of insecticide resistance monitoring in Anopheles gambiae in Burkina Faso: resistance on the rise?

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    Badolo Athanase

    2012-07-01

    Full Text Available Abstract Background and methods A longitudinal Anopheles gambiae s.l. insecticide-resistance monitoring programme was established in four sentinel sites in Burkina Faso. For three years, between 2008 and 2010, WHO diagnostic dose assays were used to measure the prevalence of resistance to all the major classes of insecticides at the beginning and end of the malaria transmission season. Species identification and genotyping for target site mutations was also performed and the sporozoite rate in adults determined. Results At the onset of the study, resistance to DDT and pyrethroids was already prevalent in An. gambiae s.l. from the south-west of the country but mosquitoes from the two sites in central Burkina Faso were largely susceptible. Within three years, DDT and permethrin resistance was established in all four sites. Carbamate and organophosphate resistance remains relatively rare and largely confined to the south-western areas although a small number of bendiocarb survivors were found in all sites by the final round of monitoring. The ace-1R target site resistance allele was present in all localities and its frequency exceeded 20% in 2010 in two of the sites. The frequency of the 1014F kdr mutation increased throughout the three years and by 2010, the frequency of 1014F in all sites combined was 0.02 in Anopheles arabiensis, 0.56 in An. gambiae M form and 0.96 in An. gambiae S form. This frequency did not differ significantly between the sites. The 1014S kdr allele was only found in An. arabiensis but its frequency increased significantly throughout the study (P = 0.0003 and in 2010 the 1014S allele frequency was 0.08 in An. arabiensis. Maximum sporozoite rates (12% were observed in Soumousso in 2009 and the difference between sites is significant for each year. Conclusion Pyrethroid and DDT resistance is now established in An. gambiae s.l. throughout Burkina Faso. Results from diagnostic dose assays are highly variable within and

  20. Identification of TCT, a novel knockdown resistance allele mutation and analysis of resistance detection methods in the voltage-gated Na⁺ channel of Culex pipiens pallens from Shandong Province, China.

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    Liu, Hong-Mei; Cheng, Peng; Huang, Xiaodan; Dai, Yu-Hua; Wang, Hai-Fang; Liu, Li-Juan; Zhao, Yu-Qiang; Wang, Huai-Wei; Gong, Mao-Qing

    2013-02-01

    The present study aimed to investigate deltamethrin resistance in Culex pipiens pallens (C. pipiens pallens) mosquitoes and its correlation with knockdown resistance (kdr) mutations. In addition, mosquito‑resistance testing methods were analyzed. Using specific primers in polymerase chain reaction (PCR) and allele-specific (AS)-PCR, kdr gene sequences isolated from wild C. pipiens pallens mosquitoes were sequenced. Linear regression analysis was used to determine the correlation between the mutations and deltamethrin resistance. A kdr allelic gene was cloned and sequenced. Analysis of the DNA sequences revealed the presence of two point mutations at the L1014 residue in the IIS6 transmembrane segment of the voltage‑gated sodium channel (VGSC): L1014F, TTA→TTT, replacing a leucine (L) with a phenylalanine (F); L1014S, TTA→TCA, replacing leucine (L) with serine (S). Two alternative kdr-like mutations, L1014F and L1014S, were identified to be positively correlated with the deltamethrin-resistant phenotype. In addition a novel mutation, TCT, was identified in the VGSC of C. pipiens pallens. PCR and AS-PCR yielded consistent results with respect to mosquito resistance. However, the detection rate of PCR was higher than that of AS-PCR. Further studies are required to determine the specific resistance mechanism. PCR and AS-PCR demonstrated suitability for mosquito resistance field tests, however, the former method may be superior to the latter.

  1. Mechanisms of pyrethroid resistance inHaematobia irritans (Muscidae from Mato Grosso do Sul state, Brazil

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    Antonio Thadeu Medeiros Barros

    Full Text Available Horn fly resistance to pyrethroid insecticides occurs throughout Brazil, but knowledge about the involved mechanisms is still in an incipient stage. This survey was aimed to identify the mechanisms of horn fly resistance to cypermethrin in Mato Grosso do Sul state, Brazil. Impregnated filter paper bioassays using cypermethrin, synergized or not with piperonyl butoxide (PBO and triphenyl phosphate (TPP, were conducted from March 2004 to June 2005 in horn fly populations (n = 33 from all over the state. All populations were highly resistant to cypermethrin, with resistance factors (RF ranging from 89.4 to 1,020.6. Polymerase chain reaction (PCR assays to detect the knockdown resistance (kdr mutation also were performed in 16 samples. The kdr mutation was found in 75% of the tested populations, mostly with relatively low frequencies (<20%, and was absent in some highly resistant populations. Addition of TPP did not significantly reduce the LC50 in any population. However, PBO reduced LC50s above 40-fold in all tested populations, resulting in RFs ≤ 10 in most cases. Horn fly resistance to cypermethrin is widespread in the state, being primarily caused by an enhanced activity of P450 mono-oxygenases and secondarily by reduced target site sensitivity.

  2. Src Kinase becomes preferentially associated with the VEGFR, KDR/Flk-1, following VEGF stimulation of vascular endothelial cells

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    Wang Jing

    2002-12-01

    Full Text Available Abstract Background The cytoplasmic tyrosine kinase, Src, has been found to play a crucial role in VEGF (vascular endothelial growth factor – dependent vascular permeability involved in angiogenesis. The two main VEGFRs present on vascular endothelial cells are KDR/Flk-1 (kinase insert domain-containing receptor/fetal liver kinase-1 and Flt-1 (Fms-like tyrosine kinase-1. However, to date, it has not been determined which VEGF receptor (VEGFR is involved in binding to and activating Src kinase following VEGF stimulation of the receptors. Results In this report, we demonstrate that Src preferentially associates with KDR/Flk-1 rather than Flt-1 in human umbilical vein endothelial cells (HUVECs, and that VEGF stimulation resulted in an increase of Src activity associated with activated KDR/Flk-1. These findings were determined through immunoprecipitation-kinase experiments and coimmunoprecipitation studies, and were further confirmed by GST-pull-down assays and Far Western studies. However, Fyn and Yes, unlike Src, were found to associate preferentially with Flt-1. Conclusions Thus, Src preferentially associates with KDR/Flk-1, rather than with Flt-1, upon VEGF stimulation in endothelial cells. Our findings further highlight the potential significance of upregulated KDR/Flk-1-associated Src activity in the process of angiogenesis, and help to elucidate more clearly the specific roles and mechanisms involving Src family tyrosine kinase in VEGF-stimulated signal transduction events.

  3. Circulating progenitor and angiogenic cell frequencies are abnormally static over pregnancy in women with preconception diabetes: A pilot study.

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    Lima, Patricia D A; Chen, Zhilin; Tayab, Aysha; Murphy, Malia S Q; Pudwell, Jessica; Smith, Graeme N; Croy, B Anne

    2017-01-01

    Type 1 and 2 diabetes decrease the frequencies and functional capacities of circulating angiogenic cells (CAC). Diabetes also elevates gestational complications. These observations may be interrelated. We undertook pilot studies to address the hypothesis that preconception diabetes deviates known gestational increases in CACs. Cross-sectional study of type 1 diabetic, type 2 diabetic and normoglycemic pregnant women was conducted at 1st, 2nd, and 3rd trimester and compared to a 6mo postpartum surrogate baseline. Circulating progenitor cells (CPC; CD34+CD45dimSSlow) and CACs (CD34+CD45dimSSlow expressing CD133 without or with KDR) were quantified by flow cytometry and by colony assay (CFU-Hill). In pregnant normoglycemic women, CD34+CD45dimSSlow cell frequency was greater in 1st and 3rd trimester than postpartum but frequency of these cells was static over type 1 or 2 diabetic pregnancies. Type 1 and type 2 diabetic women showed CACs variance versus normal controls. Type 1 diabetic women had more total CD34+KDR+ CACs in 1st trimester and a higher ratio of CD133+KDR+ to total CD133+ cells in 1st and 2nd trimesters than control women, demonstrating an unbalance in CD133+KDR+ CACs. Type 2 diabetic women had more CD133+KDR+ CACs in 1st trimester and fewer CD133+KDR- CACs at mid-late pregnancy than normal pregnant women. Thus, pregnancy stage-specific physiological fluctuation in CPCs (CD34+) and CACs (CD133+KDR+ and CD133+KDR-) did not occur in type 1 and type 2 diabetic women. Early outgrowth colonies were stable across normal and diabetic pregnancies. Therefore, preconception diabetes blocks the normal dynamic pattern of CAC frequencies across gestation but does not alter colony growth. The differences between diabetic and typical women were seen at specific gestational stages that may be critical for initiation of the uterine vascular pathologies characterizing diabetic gestations.

  4. Circulating progenitor and angiogenic cell frequencies are abnormally static over pregnancy in women with preconception diabetes: A pilot study.

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    Patricia D A Lima

    Full Text Available Type 1 and 2 diabetes decrease the frequencies and functional capacities of circulating angiogenic cells (CAC. Diabetes also elevates gestational complications. These observations may be interrelated. We undertook pilot studies to address the hypothesis that preconception diabetes deviates known gestational increases in CACs. Cross-sectional study of type 1 diabetic, type 2 diabetic and normoglycemic pregnant women was conducted at 1st, 2nd, and 3rd trimester and compared to a 6mo postpartum surrogate baseline. Circulating progenitor cells (CPC; CD34+CD45dimSSlow and CACs (CD34+CD45dimSSlow expressing CD133 without or with KDR were quantified by flow cytometry and by colony assay (CFU-Hill. In pregnant normoglycemic women, CD34+CD45dimSSlow cell frequency was greater in 1st and 3rd trimester than postpartum but frequency of these cells was static over type 1 or 2 diabetic pregnancies. Type 1 and type 2 diabetic women showed CACs variance versus normal controls. Type 1 diabetic women had more total CD34+KDR+ CACs in 1st trimester and a higher ratio of CD133+KDR+ to total CD133+ cells in 1st and 2nd trimesters than control women, demonstrating an unbalance in CD133+KDR+ CACs. Type 2 diabetic women had more CD133+KDR+ CACs in 1st trimester and fewer CD133+KDR- CACs at mid-late pregnancy than normal pregnant women. Thus, pregnancy stage-specific physiological fluctuation in CPCs (CD34+ and CACs (CD133+KDR+ and CD133+KDR- did not occur in type 1 and type 2 diabetic women. Early outgrowth colonies were stable across normal and diabetic pregnancies. Therefore, preconception diabetes blocks the normal dynamic pattern of CAC frequencies across gestation but does not alter colony growth. The differences between diabetic and typical women were seen at specific gestational stages that may be critical for initiation of the uterine vascular pathologies characterizing diabetic gestations.

  5. Multi-country Survey Revealed Prevalent and Novel F1534S Mutation in Voltage-Gated Sodium Channel (VGSC Gene in Aedes albopictus.

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    Jiabao Xu

    2016-05-01

    Full Text Available Aedes albopictus is an important dengue vector because of its aggressive biting behavior and rapid spread out of its native home range in Southeast Asia. Pyrethroids are widely used for adult mosquito control, and resistance to pyrethroids should be carefully monitored because vector control is the only effective method currently available to prevent dengue transmission. The voltage-gated sodium channel gene is the target site of pyrethroids, and mutations in this gene cause knockdown resistance (kdr. Previous studies reported various mutations in the voltage-gated sodium channel (VGSC gene, but the spatial distribution of kdr mutations in Ae. albopictus has not been systematically examined, and the association between kdr mutation and phenotypic resistance has not been established.A total of 597 Ae. albopictus individuals from 12 populations across Asia, Africa, America and Europe were examined for mutations in the voltage-gated sodium channel gene. Three domains for a total of 1,107 bp were sequenced for every individual. Two populations from southern China were examined for pyrethroid resistance using the World Health Organization standard tube bioassay, and the association between kdr mutations and phenotypic resistance was tested.A total of 29 synonymous mutations were found across domain II, III and IV of the VGSC gene. Non-synonymous mutations in two codons of the VGSC gene were detected in 5 populations from 4 countries. A novel mutation at 1532 codon (I1532T was found in Rome, Italy with a frequency of 19.7%. The second novel mutation at codon 1534 (F1534S was detected in southern China and Florida, USA with a frequency ranging from 9.5-22.6%. The WHO insecticide susceptibility bioassay found 90.1% and 96.1% mortality in the two populations from southern China, suggesting resistance and probable resistance. Positive association between kdr mutations with deltamethrin resistance was established in these two populations.Two novel kdr

  6. Multi-country Survey Revealed Prevalent and Novel F1534S Mutation in Voltage-Gated Sodium Channel (VGSC) Gene in Aedes albopictus.

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    Xu, Jiabao; Bonizzoni, Mariangela; Zhong, Daibin; Zhou, Guofa; Cai, Songwu; Li, Yiji; Wang, Xiaoming; Lo, Eugenia; Lee, Rebecca; Sheen, Roger; Duan, Jinhua; Yan, Guiyun; Chen, Xiao-Guang

    2016-05-01

    Aedes albopictus is an important dengue vector because of its aggressive biting behavior and rapid spread out of its native home range in Southeast Asia. Pyrethroids are widely used for adult mosquito control, and resistance to pyrethroids should be carefully monitored because vector control is the only effective method currently available to prevent dengue transmission. The voltage-gated sodium channel gene is the target site of pyrethroids, and mutations in this gene cause knockdown resistance (kdr). Previous studies reported various mutations in the voltage-gated sodium channel (VGSC) gene, but the spatial distribution of kdr mutations in Ae. albopictus has not been systematically examined, and the association between kdr mutation and phenotypic resistance has not been established. A total of 597 Ae. albopictus individuals from 12 populations across Asia, Africa, America and Europe were examined for mutations in the voltage-gated sodium channel gene. Three domains for a total of 1,107 bp were sequenced for every individual. Two populations from southern China were examined for pyrethroid resistance using the World Health Organization standard tube bioassay, and the association between kdr mutations and phenotypic resistance was tested. A total of 29 synonymous mutations were found across domain II, III and IV of the VGSC gene. Non-synonymous mutations in two codons of the VGSC gene were detected in 5 populations from 4 countries. A novel mutation at 1532 codon (I1532T) was found in Rome, Italy with a frequency of 19.7%. The second novel mutation at codon 1534 (F1534S) was detected in southern China and Florida, USA with a frequency ranging from 9.5-22.6%. The WHO insecticide susceptibility bioassay found 90.1% and 96.1% mortality in the two populations from southern China, suggesting resistance and probable resistance. Positive association between kdr mutations with deltamethrin resistance was established in these two populations. Two novel kdr mutations, I1532T

  7. Dynamics of multiple insecticide resistance in the malaria vector Anopheles gambiae in a rice growing area in South-Western Burkina Faso

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    Ouédraogo Jean-Bosco

    2008-09-01

    Full Text Available Abstract Background Insecticide resistance of the main malaria vector, Anopheles gambiae, has been reported in south-western Burkina Faso, West Africa. Cross-resistance to DDT and pyrethroids was conferred by alterations at site of action in the sodium channel, the Leu-Phe kdr mutation; resistance to organophosphates and carbamates resulted from a single point mutation in the oxyanion hole of the acetylcholinesterase enzyme designed as ace-1R. Methods An entomological survey was carried out during the rainy season of 2005 at Vallée du Kou, a rice growing area in south-western Burkina Faso. At the Vallée du Kou, both insecticide resistance mechanisms have been previously described in the M and S molecular forms of An. gambiae. This survey aimed i to update the temporal dynamics and the circumsporozoite infection rate of the two molecular forms M and S of An. gambiae ii to update the frequency of the Leu-Phe kdr mutation within these forms and finally iii to investigate the occurrence of the ace-1R mutation. Mosquitoes collected by indoor residual collection and by human landing catches were counted and morphologically identified. Species and molecular forms of An. gambiae, ace-1R and Leu-Phe kdr mutations were determined using PCR techniques. The presence of the circumsporozoite protein of Plasmodium falciparum was determined using ELISA. Results Anopheles gambiae populations were dominated by the M form. However the S form occurred in relative important proportion towards the end of the rainy season with a maximum peak in October at 51%. Sporozoite rates were similar in both forms. The frequency of the Leu-Phe kdr mutation in the S form reached a fixation level while it is still spreading in the M form. Furthermore, the ace-1R mutation prevailed predominately in the S form and has just started spreading in the M form. The two mutations occurred concomitantly both in M and S populations. Conclusion These results showed that the Vallée du Kou

  8. Evidence of carbamate resistance in urban populations of Anopheles gambiae s.s. mosquitoes resistant to DDT and deltamethrin insecticides in Lagos, South-Western Nigeria

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    Oduola Adedayo O

    2012-06-01

    Full Text Available Abstract Background Resistance monitoring is essential in ensuring the success of insecticide based vector control programmes. This study was carried out to assess the susceptibility status of urban populations of Anopheles gambiae to carbamate insecticide being considered for vector control in mosquito populations previously reported to be resistant to DDT and permethrin. Methods Two – three day old adult female Anopheles mosquitoes reared from larval collections in 11 study sites from Local Government Areas of Lagos were exposed to test papers impregnated with DDT 4%, deltamethrin 0.05% and propoxur 0.1% insecticides. Additional tests were carried out to determine the susceptibility status of the Anopheles gambiae population to bendiocarb insecticide. Members of the A. gambiae complex, the molecular forms, were identified by PCR assays. The involvement of metabolic enzymes in carbamate resistance was assessed using Piperonyl butoxide (PBO synergist assays. The presence of kdr-w/e and ace-1R point mutations responsible for DDT-pyrethroid and carbamate resistance mechanisms was also investigated by PCR. Results Propoxur resistance was found in 10 out of the 11 study sites. Resistance to three classes of insecticides was observed in five urban localities. Mortality rates in mosquitoes exposed to deltamethrin and propoxur did not show any significant difference (P > 0.05 but was significantly higher (P A. gambiae s.s (M form. The kdr -w point mutation at allelic frequencies between 45%-77% was identified as one of the resistant mechanisms responsible for DDT and pyrethroid resistance. Ace-1R point mutation was absent in the carbamate resistant population. However, the possible involvement of metabolic resistance was confirmed by synergistic assays conducted. Conclusion Evidence of carbamate resistance in A. gambiae populations already harbouring resistance to DDT and permethrin is a clear indication that calls for the implementation of

  9. Molecular evidence for historical presence of knock-down resistance in Anopheles albimanus, a key malaria vector in Latin America.

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    Lol, Juan C; Castellanos, María E; Liebman, Kelly A; Lenhart, Audrey; Pennington, Pamela M; Padilla, Norma R

    2013-09-18

    Anopheles albimanus is a key malaria vector in the northern neotropics. Current vector control measures in the region are based on mass distributions of long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) with pyrethroids. Resistance to pyrethroid insecticides can be mediated by increased esterase and/or multi-function oxidase activity and/or mutations in the voltage-gated sodium channel gene. The aim of this work was to characterize the homologous kdr region of the voltage-gated sodium channel gene in An. albimanus and to conduct a preliminary retrospective analysis of field samples collected in the 1990's, coinciding with a time of intense pyrethroid application related to agricultural and public health insect control in the region. Degenerate primers were designed to amplify the homologous kdr region in a pyrethroid-susceptible laboratory strain (Sanarate) of An. albimanus. Subsequently, a more specific primer pair was used to amplify and sequence the region that contains the 1014 codon associated with pyrethroid resistance in other Anopheles spp. (L1014F, L1014S or L1014C). Direct sequencing of the PCR products confirmed the presence of the susceptible kdr allele in the Sanarate strain (L1014) and the presence of homozygous-resistant kdr alleles in field-collected individuals from Mexico (L1014F), Nicaragua (L1014C) and Costa Rica (L1014C). For the first time, the kdr region in An. albimanus is described. Furthermore, molecular evidence suggests the presence of kdr-type resistance in field-collected An. albimanus in Mesoamerica in the 1990s. Further research is needed to conclusively determine an association between the genotypes and resistant phenotypes, and to what extent they may compromise current vector control efforts.

  10. Knockdown resistance, Rdl alleles, and the annual entomological Inoculation rate of wild mosquito populations from Lower Moshi, Northern Tanzania

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    Aneth M Mahande

    2012-01-01

    Full Text Available Aim: Understanding vector behavioral response due to ecological factors is important in the control of disease vectors. This study was conducted to determine the knockdown resistance (kdr alleles, dieldrin resistance alleles, and entomological inoculation rates (EIRs of malaria vectors in lower Moshi irrigation schemes for the mitigation of disease transmission. Materials and Methods: The study was longitudinal design conducted for 14 months. Mosquitoes were collected fortnightly by using a CDC miniature light trap in 20 houses. Mosquitoes were identified morphologically in the field, of which 10% of this population was identified to species level by using molecular techniques. Samples from this study population were taken for kdr and resistance to dieldrin (rdl genes detection. Results: A total of 6220 mosquitoes were collected by using a light trap, of which 86.0% (n=5350 were Anopheles gambiae sensu lato and 14.0% (n=870 were Culex quinquefasciatus. Ten percent of the An. gambiae s.l. (n=535 collected were taken for species identification, of which 99.8% (n=534 were identified as An. arabiensis while 0.2% (n=1 were An. gambiae sensu stricto. Of the selected mosquitoes, 3.5% (n=19 were sporozoite positive. None of the mosquitoes tested had the kdr gene. The rdl resistant allele was detected at a frequency of 0.48 throughout the year. EIR was determined to be 0.54 ib/trap/year. Conclusion: The findings of this study suggest that the homozygous and the heterozygous resistance present in rdl genes demonstrated the effect of pesticide residues on resistance selection pressure in mosquitoes. A better insecticide usage protocol needs to be developed for farmers to use in order to avoid excessive use of pesticides. Key words: An. arabiensis, EIR, Knockdown mutation, Moshi, rdl locus, Tanzania

  11. Additional selection for insecticide resistance in urban malaria vectors: DDT resistance in Anopheles arabiensis from Bobo-Dioulasso, Burkina Faso.

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    Christopher M Jones

    Full Text Available In the city of Bobo-Dioulasso in Burkina Faso, Anopheles arabiensis has superseded Anopheles gambiae s.s. as the major malaria vector and the larvae are found in highly polluted habitats normally considered unsuitable for Anopheles mosquitoes. Here we show that An. gambiae s.l. adults emerging from a highly polluted site in the city centre (Dioulassoba have a high prevalence of DDT resistance (percentage mortality after exposure to diagnostic dose=65.8% in the dry season and 70.4% in the rainy season, respectively. An investigation into the mechanisms responsible found an unexpectedly high frequency of the 1014S kdr mutation (allele frequency=0.4, which is found at very low frequencies in An. arabiensis in the surrounding rural areas, and an increase in transcript levels of several detoxification genes, notably from the glutathione transferase and cytochrome P450 gene families. A number of ABC transporter genes were also expressed at elevated levels in the DDT resistant An. arabiensis. Unplanned urbanisation provides numerous breeding grounds for mosquitoes. The finding that Anopheles mosquitoes adapted to these urban breeding sites have a high prevalence of insecticide resistance has important implications for our understanding of the selective forces responsible for the rapid spread of insecticide resistant populations of malaria vectors in Africa.

  12. Anopheles gambiae distribution and insecticide resistance in the cities of Douala and Yaoundé (Cameroon): influence of urban agriculture and pollution.

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    Antonio-Nkondjio, Christophe; Fossog, Billy Tene; Ndo, Cyrille; Djantio, Benjamin Menze; Togouet, Serge Zebaze; Awono-Ambene, Parfait; Costantini, Carlo; Wondji, Charles S; Ranson, Hilary

    2011-06-08

    Urban malaria is becoming a major health priority across Africa. A study was undertaken to assess the importance of urban pollution and agriculture practice on the distribution and susceptibility to insecticide of malaria vectors in the two main cities in Cameroon. Anopheline larval breeding sites were surveyed and water samples analysed monthly from October 2009 to December 2010. Parameters analysed included turbidity, pH, temperature, conductivity, sulfates, phosphates, nitrates, nitrites, ammonia, aluminium, alkalinity, iron, potassium, manganese, magnesium, magnesium hardness and total hardness. Characteristics of water bodies in urban areas were compared to rural areas and between urban sites. The level of susceptibility of Anopheles gambiae to 4% DDT, 0.75% permethrin, 0.05% deltamethrin, 0.1% bendiocarb and 5% malathion were compared between mosquitoes collected from polluted, non polluted and cultivated areas. A total of 1,546 breeding sites, 690 in Yaoundé and 856 in Douala, were sampled in the course of the study. Almost all measured parameters had a concentration of 2- to 100-fold higher in urban compare to rural breeding sites. No resistance to malathion was detected, but bendiocarb resistance was present in Yaounde. Very low mortality rates were observed following DDT or permethrin exposure, associated with high kdr frequencies. Mosquitoes collected in cultivated areas, exhibited the highest resistant levels. There was little difference in insecticide resistance or kdr allele frequency in mosquitoes collected from polluted versus non-polluted sites. The data confirm high selection pressure on mosquitoes originating from urban areas and suggest urban agriculture rather than pollution as the major factor driving resistance to insecticide.

  13. Detection of 1014F kdr mutation in four major Anopheline malaria vectors in Indonesia

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    Sukowati Supratman

    2010-11-01

    Full Text Available Abstract Background Malaria is a serious public health problem in Indonesia, particularly in areas outside Java and Bali. The spread of resistance to the currently available anti-malarial drugs or insecticides used for mosquito control would cause an increase in malaria transmission. To better understand patterns of transmission and resistance in Indonesia, an integrated mosquito survey was conducted in three areas with different malaria endemicities, Purworejo in Central Java, South Lampung District in Sumatera and South Halmahera District in North Mollucca. Methods Mosquitoes were collected from the three areas through indoor and outdoor human landing catches (HLC and indoor restinging catches. Specimens were identified morphologically by species and kept individually in 1.5 ml Eppendorf microtube. A fragment of the VGSC gene from 95 mosquito samples was sequenced and kdr allelic variation determined. Results The molecular analysis of these anopheline mosquitoes revealed the existence of the 1014F allele in 4 major malaria vectors from South Lampung. These species include, Anopheles sundaicus, Anopheles aconitus, Anopheles subpictus and Anopheles vagus. The 1014F allele was not found in the other areas. Conclusion The finding documents the presence of this mutant allele in Indonesia, and implies that selection pressure on the Anopheles population in this area has occurred. Further studies to determine the impact of the resistance allele on the efficacy of pyrethroids in control programmes are needed.

  14. Detection of 1014F kdr mutation in four major Anopheline malaria vectors in Indonesia.

    Science.gov (United States)

    Syafruddin, Din; Hidayati, Anggi P N; Asih, Puji B S; Hawley, William A; Sukowati, Supratman; Lobo, Neil F

    2010-11-08

    Malaria is a serious public health problem in Indonesia, particularly in areas outside Java and Bali. The spread of resistance to the currently available anti-malarial drugs or insecticides used for mosquito control would cause an increase in malaria transmission. To better understand patterns of transmission and resistance in Indonesia, an integrated mosquito survey was conducted in three areas with different malaria endemicities, Purworejo in Central Java, South Lampung District in Sumatera and South Halmahera District in North Mollucca. Mosquitoes were collected from the three areas through indoor and outdoor human landing catches (HLC) and indoor restinging catches. Specimens were identified morphologically by species and kept individually in 1.5 ml Eppendorf microtube. A fragment of the VGSC gene from 95 mosquito samples was sequenced and kdr allelic variation determined. The molecular analysis of these anopheline mosquitoes revealed the existence of the 1014F allele in 4 major malaria vectors from South Lampung. These species include, Anopheles sundaicus, Anopheles aconitus, Anopheles subpictus and Anopheles vagus. The 1014F allele was not found in the other areas. The finding documents the presence of this mutant allele in Indonesia, and implies that selection pressure on the Anopheles population in this area has occurred. Further studies to determine the impact of the resistance allele on the efficacy of pyrethroids in control programmes are needed.

  15. New Introductions, Spread of Existing Matrilines, and High Rates of Pyrethroid Resistance Result in Chronic Infestations of Bed Bugs (Cimex lectularius L. in Lower-Income Housing.

    Directory of Open Access Journals (Sweden)

    Ronald W Raab

    Full Text Available Infestations of the common bed bug (Cimex lectularius L. have increased substantially in the United States in the past 10-15 years. The housing authority in Harrisonburg, Virginia, conducts heat-treatments after bed bugs are detected in a lower-income housing complex, by treating each infested unit at 60°C for 4-6 hours. However, a high frequency of recurrent infestations called into question the efficacy of this strategy. Genetic analysis using Bayesian clustering of polymorphic microsatellite loci from 123 bed bugs collected from 23 units from May 2012 to April 2013 in one building indicated that (a 16/21 (73% infestations were genetically similar, suggesting ineffective heat-treatments or reintroductions from within the building or from a common external source, followed by local spread of existing populations; and (b up to 5 of the infestations represented new genotypes, indicating that 5 new populations were introduced into this building in one year, assuming they were not missed in earlier screens. There was little to no gene flow among the 8 genetic clusters identified in the building. Bed bugs in the U.S. often possess one or both point mutations in the voltage-gated sodium channel, termed knockdown resistance (kdr, from valine to leucine (V419L and leucine to isoleucine (L925I that confer target-site resistance against pyrethroid insecticides. We found that 48/121 (40% bed bugs were homozygous for both kdr mutations (L419/I925, and a further 59% possessed at least one of the kdr mutations. We conclude that ineffective heat treatments, new introductions, reintroductions and local spread, and an exceptionally high frequency of pyrethroid resistance are responsible for chronic infestations in lower-income housing. Because heat treatments fail to protect from reintroductions, and pesticide use has not decreased the frequency of infestations, preventing new introductions and early detection are the most effective strategies to avoid bed bug

  16. Mapping insecticide resistance and characterization of resistance mechanisms in Anopheles arabiensis (Diptera: Culicidae) in Ethiopia.

    Science.gov (United States)

    Alemayehu, Eba; Asale, Abebe; Eba, Kasahun; Getahun, Kefelegn; Tushune, Kora; Bryon, Astrid; Morou, Evangelia; Vontas, John; Van Leeuwen, Thomas; Duchateau, Luc; Yewhalaw, Delenasaw

    2017-09-02

    The emergence and spread of insecticide resistance in the major African malaria vectors Anopheles gambiae (s.s.) and An. arabiensis may compromise the current vector control interventions and threatens the global malaria control and elimination efforts. Insecticide resistance was monitored in several study sites in Ethiopia from 2013 to 2015 using papers impregnated with discriminating concentrations of DDT, deltamethrin, bendiocarb, propoxur, malathion, fenitrothion and pirimiphos-methyl, following the WHO insecticide susceptibility test procedure. Mosquitoes sampled from different localities for WHO bioassay were morphologically identified as An. gambiae (s.l.) using standard taxonomic keys. Samples were identified to species using species-specific polymerase chain reaction (PCR) and screened for the presence of target site mutations L1014F, L1014S and N1575Y in the voltage gated sodium channel (VGSC) gene and G119S in the acethylcholinesterase (AChE) gene using allele-specific PCR. Biochemical assays were performed to assess elevated levels of acetylcholinesterases, carboxylcholinesterases, glutathione-S-transferases (GSTs) and cytochrome P450s monooxygenases in wild populations of An. arabiensis, compared to the fully susceptible Sekoru An. arabiensis laboratory strain. Populations of An. arabiensis were resistant to DDT and deltamethrin but were susceptible to fenitrothion in all the study sites. Reduced susceptibility to malathion, pirimiphos-methyl, propoxur and bendiocarb was observed in some of the study sites. Knockdown resistance (kdr L1014F) was detected in all mosquito populations with allele frequency ranging from 42 to 91%. Elevated levels of glutathione-S-transferases (GSTs) were detected in some of the mosquito populations. However, no elevated levels of monooxygenases and esterases were detected in any of the populations assessed. Anopheles arabiensis populations from all surveyed sites in Ethiopia exhibited resistance against DDT and pyrethroids

  17. Evidence of multiple insecticide resistance mechanisms in Anopheles gambiae populations in Bangui, Central African Republic.

    Science.gov (United States)

    Olé Sangba, Marina Lidwine; Sidick, Aboubakar; Govoetchan, Renaud; Dide-Agossou, Christian; Ossè, Razaki A; Akogbeto, Martin; Ndiath, Mamadou Ousmane

    2017-01-13

    Knowledge of insecticide resistance status in the main malaria vectors is an essential component of effective malaria vector control. This study presents the first evaluation of the status of insecticide resistance in Anopheles gambiae populations from Bangui, the Central African Republic. Anopheles mosquitoes were reared from larvae collected in seven districts of Bangui between September to November 2014. The World Health Organisation's bioassay susceptibility tests to lambda-cyhalothrin (0.05%), deltamethrin (0.05%), DDT (4%), malathion (5%), fenitrothion (1%) and bendiocarb (0.1%) were performed on adult females. Species and molecular forms as well as the presence of L1014F kdr and Ace-1 R mutations were assessed by PCR. Additional tests were conducted to assess metabolic resistance status. After 1 h exposure, a significant difference of knockdown effect was observed between districts in all insecticides tested except deltamethrin and malathion. The mortality rate (MR) of pyrethroids group ranging from 27% (CI: 19-37.5) in Petevo to 86% (CI: 77.6-92.1) in Gbanikola; while for DDT, MR ranged from 5% (CI: 1.6-11.3) in Centre-ville to 39% (CI: 29.4-49.3) in Ouango. For the organophosphate group a MR of 100% was observed in all districts except Gbanikola where a MR of 96% (CI: 90-98.9) was recorded. The mortality induced by bendiocarb was very heterogeneous, ranging from 75% (CI: 62.8-82.8) in Yapele to 99% (CI: 84.5-100) in Centre-ville. A high level of kdr-w (L1014F) frequency was observed in all districts ranging from 93 to 100%; however, no kdr-e (L1014S) and Ace-1 R mutation were found in all tested mosquitoes. Data of biochemical analysis showed significant overexpression activities of cytochrome P450, GST and esterases in Gbanikola and Yapele (χ 2  = 31.85, df = 2, P resistance to DDT and pyrethroids as well as precocious emergence of resistance to carbamates were detected among A. gambiae mosquitoes from Bangui, including target-site mutations

  18. Review of the evolution of insecticide resistance in main malaria vectors in Cameroon from 1990 to 2017.

    Science.gov (United States)

    Antonio-Nkondjio, Christophe; Sonhafouo-Chiana, N; Ngadjeu, C S; Doumbe-Belisse, P; Talipouo, A; Djamouko-Djonkam, L; Kopya, E; Bamou, R; Awono-Ambene, P; Wondji, Charles S

    2017-10-10

    Malaria remains a major public health threat in Cameroon and disease prevention is facing strong challenges due to the rapid expansion of insecticide resistance in vector populations. The present review presents an overview of published data on insecticide resistance in the main malaria vectors in Cameroon to assist in the elaboration of future and sustainable resistance management strategies. A systematic search on mosquito susceptibility to insecticides and insecticide resistance in malaria vectors in Cameroon was conducted using online bibliographic databases including PubMed, Google and Google Scholar. From each peer-reviewed paper, information on the year of the study, mosquito species, susceptibility levels, location, insecticides, data source and resistance mechanisms were extracted and inserted in a Microsoft Excel datasheet. The data collected were then analysed for assessing insecticide resistance evolution. Thirty-three scientific publications were selected for the analysis. The rapid evolution of insecticide resistance across the country was reported from 2000 onward. Insecticide resistance was highly prevalent in both An. gambiae (s.l.) and An. funestus. DDT, permethrin, deltamethrin and bendiocarb appeared as the most affected compounds by resistance. From 2000 to 2017 a steady increase in the prevalence of kdr allele frequency was noted in almost all sites in An. gambiae (s.l.), with the L1014F kdr allele being the most prevalent. Several detoxification genes (particularly P450 monooxygenase) were associated with DDT, pyrethroids and bendiocarb resistance. In An. funestus, resistance to DDT and pyrethroids was mainly attributed to the 119F-GSTe2 metabolic resistance marker and over-expression of P450 genes whereas the 296S-RDL mutation was detected in dieldrin-resistant An. funestus. The review provides an update of insecticide resistance status in malaria vector populations in Cameroon and stresses the need for further actions to reinforce malaria

  19. A multiplex PCR for detection of knockdown resistance mutations, V1016G and F1534C, in pyrethroid-resistant Aedes aegypti.

    Science.gov (United States)

    Saingamsook, Jassada; Saeung, Atiporn; Yanola, Jintana; Lumjuan, Nongkran; Walton, Catherine; Somboon, Pradya

    2017-10-10

    Mutation of the voltage-gated sodium channel (VGSC) gene, or knockdown resistance (kdr) gene, is an important resistance mechanism of the dengue vector Aedes aegypti mosquitoes against pyrethroids. In many countries in Asia, a valine to glycine substitution (V1016G) and a phenylalanine to cysteine substitution (F1534C) are common in Ae. aegypti populations. The G1016 and C1534 allele frequencies have been increasing in recent years, and hence there is a need to have a simple and inexpensive tool to monitor the alleles in large scale. A multiplex PCR to detect V1016G and F1534C mutations has been developed in the current study. This study utilized primers from previous studies for detecting the mutation at position 1016 and newly designed primers to detect variants at position 1534. The PCR conditions were validated and compared with DNA sequencing using known kdr mutant laboratory strains and field collected mosquitoes. The efficacy of this method was also compared with allele-specific PCR (AS-PCR). The results of our multiplex PCR were in complete agreement with sequencing data and better than the AS-PCR. In addition, the efficiency of two non-toxic DNA staining dyes, Ultrapower™ and RedSafe™, were evaluated by comparing with ethidium bromide (EtBr) and the results were satisfactory. Our multiplex PCR method is highly reliable and useful for implementing vector surveillance in locations where the two alleles co-occur.

  20. Effects of Cetuximab Combined with Celecoxib on Apoptosis and KDR and AQP1 
Expression in Lung Cancer

    Directory of Open Access Journals (Sweden)

    Honggang XIA

    2013-12-01

    Full Text Available Background and objective Neoadjuvant chemotherapy is a new development in the treatment of lung cancer. In recent years, cetuximab and celecoxib have been commonly used in this procedure. This study aims to explore the effect of cetuximab combined with celecoxib on apoptosis and KDR and AQP1 expression in lung cancer A549 cells. Method The cells were cultured in RPMI-1640 and then divided into four groups: control group, 1 nmol/L cetuximab group, 25 µmol/L celecoxib group, and 1 nmol/L cetuximab+25 µmol/L celecoxib group. The treatment time was 48 h. The mRNA and protein expression levels of KDR and AQP1 were detected by RT-PCR and Western blot, respectively. The apoptosis, proliferation, and invasive ability of A549 cells before and after transfection were examined using flow cytometry, MTT, and transwell methods. Results Cetuximab and celecoxib inhibited the growth of A549 cells in a dose-dependent manner. Their combination produced a greater growth inhibition than when either was used alone (P<0.01. Cetuximab and celecoxib both induced the apoptosis of A549 cells, and their combination produced a higher apoptosis rate (P<0.01. Cetuximab in combination with celecoxib also induced G1 phase arrest and downregulated the expression of KDR and AQP1 in A549 cells (P<0.05. As a result, the invasion ability of the A549 cells was significantly decreased. Conclusion Cetuximab in combination with celecoxib can synergistically inhibit the growth of A549 cells and downregulate the expression of KDR and AQP1 in A549 cells. The combination of cetuximab and celecoxib is a potential strategy for lung cancer therapy.

  1. Pyrethroid resistance in Sitophilus zeamais is associated with a mutation (T929I) in the voltage-gated sodium channel.

    Science.gov (United States)

    Araújo, Rúbia A; Williamson, Martin S; Bass, Christopher; Field, Linda M; Duce, Ian R

    2011-08-01

    The maize weevil, Sitophilus zeamais, is the most important pest affecting stored grain in Brazil and its control relies heavily on the use of insecticides. The intensive use of compounds such as the pyrethroids has led to the emergence of resistance, and previous studies have suggested that resistance to both pyrethroids and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) may result from reduced sensitivity of the insecticide target, the voltage-gated sodium channel. To identify the molecular mechanisms underlying pyrethroid resistance in S. zeamais, the domain II region of the voltage-gated sodium channel (para-orthologue) gene was amplified by PCR and sequenced from susceptible and resistant laboratory S. zeamais strains that were selected with a discriminating dose of DDT. A single point mutation, T929I, was found in the para gene of the resistant S. zeamais populations and its presence in individual weevils was strongly associated with survival after DDT exposure. This is the first identification of a target-site resistance mutation in S. zeamais and unusually it is a super-kdr type mutation occurring in the absence of the more common kdr (L1014F) substitution. A high-throughput assay based on TaqMan single nucleotide polymorphism genotyping was developed for sensitive detection of the mutation and used to screen field-collected strains of S. zeamais. This showed that the mutation is present at low frequency in field populations and is a useful tool for informing control strategies. © 2011 The Authors. Insect Molecular Biology © 2011 The Royal Entomological Society.

  2. Status of insecticide resistance in high-risk malaria provinces in Afghanistan.

    Science.gov (United States)

    Ahmad, Mushtaq; Buhler, Cyril; Pignatelli, Patricia; Ranson, Hilary; Nahzat, Sami Mohammad; Naseem, Mohammad; Sabawoon, Muhammad Farooq; Siddiqi, Abdul Majeed; Vink, Martijn

    2016-02-18

    Insecticide resistance seriously threatens the efficacy of vector control interventions in malaria endemic countries. In Afghanistan, the status of insecticide resistance is largely unknown while distribution of long-lasting insecticidal nets has intensified in recent years. The main objective of this study was thus to measure the level of resistance to four classes of insecticides in provinces with medium to high risk of malaria transmission. Adult female mosquitoes were reared from larvae successively collected in the provinces of Nangarhar, Kunar, Badakhshan, Ghazni and Laghman from August to October 2014. WHO insecticide susceptibility tests were performed with DDT (4 %), malathion (5 %), bendiocarb (0.1 %), permethrin (0.75 %) and deltamethrin (0.05 %). In addition, the presence of kdr mutations was investigated in deltamethrin resistant and susceptible Anopheles stephensi mosquitoes collected in the eastern provinces of Nangarhar and Kunar. Analyses of mortality rates revealed emerging resistance against all four classes of insecticides in the provinces located east and south of the Hindu Kush mountain range. Resistance is observed in both An. stephensi and Anopheles culicifacies, the two dominant malaria vectors in these provinces. Anopheles superpictus in the northern province of Badakhshan shows a different pattern of susceptibility with suspected resistance observed only for deltamethrin and bendiocarb. Genotype analysis of knock down resistance (kdr) mutations at the voltage-gated channel gene from An. stephensi mosquitoes shows the presence of the known resistant alleles L1014S and L1014F. However, a significant fraction of deltamethrin-resistant mosquitoes were homozygous for the 1014L wild type allele indicating that other mechanisms must be considered to account for the observed pyrethroid resistance. This study confirms the importance of monitoring insecticide resistance for the development of an integrated vector management in Afghanistan. The

  3. Characterizing Fracture Property Using Resistivity Measured at Different Frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Horne, Roland N. [Stanford Univ., CA (United States); Li, Kewen [Stanford Univ., CA (United States)

    2014-09-30

    The objective was to develop geophysical approaches to detecting and evaluating the fractures created or existing in EGS and other geothermal reservoirs by measuring the resistivity at different frequencies. This project has been divided into two phases: Phase I (first year): Proof of Concept – develop the resistivity approach and verify the effect of frequency on the resistivity in rocks with artificial or natural fractures over a wide range of frequencies. Phase II: Prototyping Part 1 (second year): measure the resistivity in rocks with fractures of different apertures, different length, and different configurations at different frequencies. Part 2 (third year): develop mathematical models and the resistivity method; infer the fracture properties using the measured resistivity data.

  4. Impact of agriculture on the selection of insecticide resistance in the malaria vector Anopheles gambiae: a multigenerational study in controlled conditions.

    Science.gov (United States)

    Nkya, Theresia Estomih; Poupardin, Rodolphe; Laporte, Frederic; Akhouayri, Idir; Mosha, Franklin; Magesa, Stephen; Kisinza, William; David, Jean-Philippe

    2014-10-16

    Resistance of mosquitoes to insecticides is mainly attributed to their adaptation to vector control interventions. Although pesticides used in agriculture have been frequently mentioned as an additional force driving the selection of resistance, only a few studies were dedicated to validate this hypothesis and characterise the underlying mechanisms. While insecticide resistance is rising dramatically in Africa, deciphering how agriculture affects resistance is crucial for improving resistance management strategies. In this context, the multigenerational effect of agricultural pollutants on the selection of insecticide resistance was examined in Anopheles gambiae. An urban Tanzanian An. gambiae population displaying a low resistance level was used as a parental strain for a selection experiment across 20 generations. At each generation larvae were selected with a mixture containing pesticides and herbicides classically used in agriculture in Africa. The resistance levels of adults to deltamethrin, DDT and bendiocarb were compared between the selected and non-selected strains across the selection process together with the frequency of kdr mutations. A microarray approach was used for pinpointing transcription level variations selected by the agricultural pesticide mixture at the adult stage. A gradual increase of adult resistance to all insecticides was observed across the selection process. The frequency of the L1014S kdr mutation rose from 1.6% to 12.5% after 20 generations of selection. Microarray analysis identified 90 transcripts over-transcribed in the selected strain as compared to the parental and the non-selected strains. Genes encoding cuticle proteins, detoxification enzymes, proteins linked to neurotransmitter activity and transcription regulators were mainly affected. RT-qPCR transcription profiling of candidate genes across multiple generations supported their link with insecticide resistance. This study confirms the potency of agriculture in selecting

  5. Insecticide resistance of Anopheles sinensis and An. vagus in Hainan Island, a malaria-endemic area of China.

    Science.gov (United States)

    Qin, Qian; Li, Yiji; Zhong, Daibin; Zhou, Ning; Chang, Xuelian; Li, Chunyuan; Cui, Liwang; Yan, Guiyun; Chen, Xiao-Guang

    2014-03-03

    Malaria is one of the most important public health problems in Southeast Asia, including Hainan Island, China. Vector control is the main malaria control measure, and insecticide resistance is a major concern for the effectiveness of chemical insecticide control programs. The objective of this study is to determine the resistance status of the main malaria vector species to pyrethroids and other insecticides recommended by the World Health Organization (WHO) for indoor residual sprays. The larvae and pupae of Anopheles mosquitoes were sampled from multiple sites in Hainan Island, and five sites yielded sufficient mosquitoes for insecticide susceptibility bioassays. Bioassays of female adult mosquitoes three days after emergence were conducted in the two most abundant species, Anopheles sinensis and An. vagus, using three insecticides (0.05% deltamethrin, 4% DDT, and 5% malathion) and following the WHO standard tube assay procedure. P450 monooxygenase, glutathione S-transferase and carboxylesterase activities were measured. Mutations at the knockdown resistance (kdr) gene and the ace-1 gene were detected by DNA sequencing and PCR-RFLP analysis, respectively. An. sinensis and An. vagus were the predominant Anopheles mosquito species. An. sinensis was found to be resistant to DDT and deltamethrin. An. vagus was susceptible to deltamethrin but resistant to DDT and malathion. Low kdr mutation (L1014F) frequency (P450 monooxygenase and carboxylesterase activities were detected in deltamethrin-resistant An. sinensis, and significantly higher P450 monooxygenase, glutathione S-transferase and carboxylesterase activities were found in malathion-resistant An. vagus mosquitoes. Multiple insecticide resistance was found in An. sinensis and An. vagus in Hainan Island, a malaria-endemic area of China. Cost-effective integrated vector control programs that go beyond synthetic insecticides are urgently needed.

  6. Fitness evaluation of two Brazilian Aedes aegypti field populations with distinct levels of resistance to the organophosphate temephos

    Directory of Open Access Journals (Sweden)

    Thiago Affonso Belinato

    2012-11-01

    Full Text Available In Brazil, decades of dengue vector control using organophosphates and pyrethroids have led to dissemination of resistance. Although these insecticides have been employed for decades against Aedes aegypti in the country, knowledge of the impact of temephos resistance on vector viability is limited. We evaluated several fitness parameters in two Brazilian Ae. aegypti populations, both classified as deltamethrin resistant but with distinct resistant ratios (RR for temephos. The insecticide-susceptible Rockefeller strain was used as an experimental control. The population presenting the higher temephos resistance level, Aparecida de Goiânia, state of Goiás (RR95 of 19.2, exhibited deficiency in the following four parameters: blood meal acceptance, amount of ingested blood, number of eggs and frequency of inseminated females. Mosquitoes from Boa Vista, state of Roraima, the population with lower temephos resistance level (RR95 of 7.4, presented impairment in only two parameters, blood meal acceptance and frequency of inseminated females. These results indicate that the overall fitness handicap was proportional to temephos resistance levels. However, it is unlikely that these disabilities can be attributed solely to temephos resistance, since both populations are also resistant to deltamethrin and harbour the kdr allele, which indicates resistance to pyrethroids. The effects of reduced fitness in resistant populations are discussed.

  7. Efficacy of bifenthrin-impregnated bednets against Anopheles funestus and pyrethroid-resistant Anopheles gambiae in North Cameroon

    Directory of Open Access Journals (Sweden)

    Chouaibou Mouhamadou

    2006-09-01

    Full Text Available Abstract Background Recent field studies indicated that insecticide-treated bednets (ITNs maintain their efficacy despite a high frequency of the knock-down resistance (kdr gene in Anopheles gambiae populations. It was essential to evaluate ITNs efficacy in areas with metabolic-based resistance. Methods Bifenthrin was used in this experiment because it is considered a promising candidate for bednets impregnation. Nets were treated at 50 mg/m2, a dose that has high insecticidal activity on kdr mosquitoes and at 5 mg/m2, a dose that kills 95% of susceptible mosquitoes under laboratory conditions with 3 minutes exposure. Bednets were holed to mimic physical damage. The trial was conducted in three experimental huts from Pitoa, North-Cameroon where Anopheles gambiae displays metabolic resistance and cohabits with An. funestus. Results Bifenthrin at 50 mg/m2 significantly reduced anophelines' entry rate (>80%. This was not observed at 5 mg/m2. Both treatments increased exophily in An. gambiae, and to a lesser extent in An. funestus. With bifenthrin at high dosage, over 60% reduction in blood feeding and 75–90% mortality rates were observed in both vectors. Despite presence of holes, only a single An. gambiae and two An. funestus females were collected inside the treated net, and all were found dead. The same trends were observed with low dosage bifenthrin though in most cases, no significant difference was found with the untreated control net. Conclusion Bifenthrin-impregnated bednets at 50 mg/m2 were efficient in the reduction of human-vector contact in Pitoa. Considerable personal protection was gained against An. funestus and metabolic pyrethroid resistant An. gambiae populations.

  8. Efficacy of bifenthrin-impregnated bednets against Anopheles funestus and pyrethroid-resistant Anopheles gambiae in North Cameroon

    Science.gov (United States)

    Chouaibou, Mouhamadou; Simard, Frédéric; Chandre, Fabrice; Etang, Josiane; Darriet, Frédéric; Hougard, Jean-Marc

    2006-01-01

    Background Recent field studies indicated that insecticide-treated bednets (ITNs) maintain their efficacy despite a high frequency of the knock-down resistance (kdr) gene in Anopheles gambiae populations. It was essential to evaluate ITNs efficacy in areas with metabolic-based resistance. Methods Bifenthrin was used in this experiment because it is considered a promising candidate for bednets impregnation. Nets were treated at 50 mg/m2, a dose that has high insecticidal activity on kdr mosquitoes and at 5 mg/m2, a dose that kills 95% of susceptible mosquitoes under laboratory conditions with 3 minutes exposure. Bednets were holed to mimic physical damage. The trial was conducted in three experimental huts from Pitoa, North-Cameroon where Anopheles gambiae displays metabolic resistance and cohabits with An. funestus. Results Bifenthrin at 50 mg/m2 significantly reduced anophelines' entry rate (>80%). This was not observed at 5 mg/m2. Both treatments increased exophily in An. gambiae, and to a lesser extent in An. funestus. With bifenthrin at high dosage, over 60% reduction in blood feeding and 75–90% mortality rates were observed in both vectors. Despite presence of holes, only a single An. gambiae and two An. funestus females were collected inside the treated net, and all were found dead. The same trends were observed with low dosage bifenthrin though in most cases, no significant difference was found with the untreated control net. Conclusion Bifenthrin-impregnated bednets at 50 mg/m2 were efficient in the reduction of human-vector contact in Pitoa. Considerable personal protection was gained against An. funestus and metabolic pyrethroid resistant An. gambiae populations. PMID:16961938

  9. Insecticide resistance mechanisms associated with different environments in the malaria vector Anopheles gambiae: a case study in Tanzania.

    Science.gov (United States)

    Nkya, Theresia E; Akhouayri, Idir; Poupardin, Rodolphe; Batengana, Bernard; Mosha, Franklin; Magesa, Stephen; Kisinza, William; David, Jean-Philippe

    2014-01-25

    Resistance of mosquitoes to insecticides is a growing concern in Africa. Since only a few insecticides are used for public health and limited development of new molecules is expected in the next decade, maintaining the efficacy of control programmes mostly relies on resistance management strategies. Developing such strategies requires a deep understanding of factors influencing resistance together with characterizing the mechanisms involved. Among factors likely to influence insecticide resistance in mosquitoes, agriculture and urbanization have been implicated but rarely studied in detail. The present study aimed at comparing insecticide resistance levels and associated mechanisms across multiple Anopheles gambiae sensu lato populations from different environments. Nine populations were sampled in three areas of Tanzania showing contrasting agriculture activity, urbanization and usage of insecticides for vector control. Insecticide resistance levels were measured in larvae and adults through bioassays with deltamethrin, DDT and bendiocarb. The distribution of An. gambiae sub-species and pyrethroid target-site mutations (kdr) were investigated using molecular assays. A microarray approach was used for identifying transcription level variations associated to different environments and insecticide resistance. Elevated resistance levels to deltamethrin and DDT were identified in agriculture and urban areas as compared to the susceptible strain Kisumu. A significant correlation was found between adult deltamethrin resistance and agriculture activity. The subspecies Anopheles arabiensis was predominant with only few An. gambiae sensu stricto identified in the urban area of Dar es Salaam. The L1014S kdr mutation was detected at elevated frequency in An gambiae s.s. in the urban area but remains sporadic in An. arabiensis specimens. Microarrays identified 416 transcripts differentially expressed in any area versus the susceptible reference strain and supported the impact

  10. Pyrethroids and DDT tolerance of Anopheles gambiae s.l. from Sengerema District, an area of intensive pesticide usage in north-western Tanzania.

    Science.gov (United States)

    Philbert, Anitha; Lyantagaye, Sylvester Leonard; Pradel, Gabriele; Ngwa, Che Julius; Nkwengulila, Gamba

    2017-04-01

    To assess the susceptibility status of malaria vectors to pyrethroids and dichlorodiphenyltrichloroethane (DDT), characterise the mechanisms underlying resistance and evaluate the role of agro-chemical use in resistance selection among malaria vectors in Sengerema agro-ecosystem zone, Tanzania. Mosquito larvae were collected from farms and reared to obtain adults. The susceptibility status of An. gambiae s.l. was assessed using WHO bioassay tests to permethrin, deltamethrin, lambdacyhalothrin, etofenprox, cyfluthrin and DDT. Resistant specimens were screened for knock-down resistance gene (kdr), followed by sequencing both Western and Eastern African variants. A gas chromatography-mass spectrophotometer (GC-MS) was used to determine pesticide residues in soil and sediments from mosquitoes' breeding habitats. Anopheles gambiae s.l. was resistant to all the insecticides tested. The population of Anopheles gambiae s.l was composed of Anopheles arabiensis by 91%. The East African kdr (L1014S) allele was found in 13 of 305 specimens that survived insecticide exposure, with an allele frequency from 0.9% to 50%. DDTs residues were found in soils at a concentration up to 9.90 ng/g (dry weight). The observed high resistance levels of An. gambiae s.l., the detection of kdr mutations and pesticide residues in mosquito breeding habitats demonstrate vector resistance mediated by pesticide usage. An integrated intervention through collaboration of agricultural, livestock and vector control units is vital. © 2017 John Wiley & Sons Ltd.

  11. Subharmonic frequency locking in the resistive Josephson thermometer

    International Nuclear Information System (INIS)

    van Veldhuizen, M.; Fowler, H.A.

    1985-01-01

    Phase-locked oscillatory solutions are examined as a basis for the dc impedance of the resistive superconducting quantum-interference device Josephson thermometer. The calculations are based on the resistively shunted junction model in the limit 2πL/sub s/I/sub c//Phi 0 > or =1, where L/sub s/ is the loop inductance and I/sub c/ is the junction critical current, and for a junction resistance large compared with the external shunt resistance. An algorithm for representing frequency entrainment in (kappa,ω) space (drive amplitude, frequency) leads to zones with rotation number p/q having the form of leaf-shaped regions joined and overlapping at their tips. High-resonance zones are very thin and locally similar. No chaotic behavior has been observed. The model can simulate the ''rising'' curves of dc impedance as a function of drive amplitude

  12. Co-occurrence and distribution of East (L1014S) and West (L1014F) African knock-down resistance in Anopheles gambiae sensu lato population of Tanzania

    Science.gov (United States)

    Kabula, Bilali; Kisinza, William; Tungu, Patrick; Ndege, Chacha; Batengana, Benard; Kollo, Douglas; Malima, Robert; Kafuko, Jessica; Mohamed, Mahdi; Magesa, Stephen

    2014-01-01

    Objective Insecticide resistance molecular markers can provide sensitive indicators of resistance development in Anopheles vector populations. Assaying these makers is of paramount importance in the resistance monitoring programme. We investigated the presence and distribution of knock-down resistance (kdr) mutations in Anopheles gambiae s.l. in Tanzania. Methods Indoor-resting Anopheles mosquitoes were collected from 10 sites and tested for insecticide resistance using the standard WHO protocol. Polymerase chain reaction-based molecular diagnostics were used to genotype mosquitoes and detect kdr mutations. Results The An. gambiae tested were resistance to lambdacyhalothrin in Muheza, Arumeru and Muleba. Out of 350 An. gambiae s.l. genotyped, 35% were An. gambiae s.s. and 65% An. arabiensis. L1014S and L1014F mutations were detected in both An. gambiae s.s. and An. arabiensis. L1014S point mutation was found at the allelic frequency of 4–33%, while L1014F was at the allelic frequency 6–41%. The L1014S mutation was much associated with An. gambiae s.s. (χ2 = 23.41; P protocolo estándar de la OMS. Mediante un diagnóstico molecular basado en la PCR se genotiparon los mosquitos y se detectaron los genotipos kdr. Resultados Los An. gambiae evaluados eran resistentes a lambdacialotrina en Muheza, Arumeru y Muleba. De 350 An. gambiae s.l. genotipados, 35% eran An. gambiae s.s. y 65% eran An. arabiensis. Se detectaron mutaciones L1014S y L1014F tanto en An. gambiae s.s. como en An. arabiensis. La mutación puntual L1014S se encontró con una frecuencia alélica de 4-33%, mientras que L1014F tenía una frecuencia alélica de 6-14%. La mutación L1014S estaba ampliamente asociada a An. gambiae s.s. (Chi-Cuadrado = 23.41; P < 0.0001) y la L1014F estaba asociada con An. arabiensis (Chi-Square = 11.21; P = 0.0008). El alelo L1014S estaba significativamente asociado con mosquitos resistentes a la lambdacialotrina (P < 0.001). Conclusión La

  13. Rapid selection of a pyrethroid metabolic enzyme CYP9K1 by operational malaria control activities.

    Science.gov (United States)

    Vontas, John; Grigoraki, Linda; Morgan, John; Tsakireli, Dimitra; Fuseini, Godwin; Segura, Luis; Niemczura de Carvalho, Julie; Nguema, Raul; Weetman, David; Slotman, Michel A; Hemingway, Janet

    2018-05-01

    Since 2004, indoor residual spraying (IRS) and long-lasting insecticide-impregnated bednets (LLINs) have reduced the malaria parasite prevalence in children on Bioko Island, Equatorial Guinea, from 45% to 12%. After target site-based (knockdown resistance; kdr ) pyrethroid resistance was detected in 2004 in Anopheles coluzzii (formerly known as the M form of the Anopheles gambiae complex), the carbamate bendiocarb was introduced. Subsequent analysis showed that kdr alone was not operationally significant, so pyrethroid-based IRS was successfully reintroduced in 2012. In 2007 and 2014-2015, mass distribution of new pyrethroid LLINs was undertaken to increase the net coverage levels. The combined selection pressure of IRS and LLINs resulted in an increase in the frequency of pyrethroid resistance in 2015. In addition to a significant increase in kd r frequency, an additional metabolic pyrethroid resistance mechanism had been selected. Increased metabolism of the pyrethroid deltamethrin was linked with up-regulation of the cytochrome P450 CYP9K1. The increase in resistance prompted a reversion to bendiocarb IRS in 2016 to avoid a resurgence of malaria, in line with the national Malaria Control Program plan. Copyright © 2018 the Author(s). Published by PNAS.

  14. Analysis of CD45- [CD34+/KDR+] endothelial progenitor cells as juvenile protective factors in a rat model of ischemic-hemorrhagic stroke.

    Directory of Open Access Journals (Sweden)

    Julius L Decano

    Full Text Available Identification of juvenile protective factors (JPFs which are altered with age and contribute to adult-onset diseases could identify novel pathways for reversing the effects of age, an accepted non-modifiable risk factor to adult-onset diseases. Since endothelial progenitor cells (EPCs have been observed to be altered in stroke, hypertension and hypercholesterolemia, said EPCs are candidate JPFs for adult-onset stroke. A priori, if EPC aging plays a 'master-switch JPF-role' in stroke pathogenesis, juvenile EPC therapy alone should delay stroke-onset. Using a hypertensive, transgenic-hyperlipidemic rat model of spontaneous ischemic-hemorrhagic stroke, spTg25, we tested the hypothesis that freshly isolated juvenile EPCs are JPFs that can attenuate stroke progression and delay stroke onset.FACS analysis revealed that CD45- [CD34+/KDR+] EPCs decrease with progression to stroke in spTg25 rats, exhibit differential expression of the dual endodthelin-1/VEGFsp receptor (DEspR and undergo differential DEspR-subtype specific changes in number and in vitro angiogenic tube-incorporation. In vivo EPC infusion of male, juvenile non-expanded cd45-[CD34+/KDR+] EPCs into female stroke-prone rats prior to stroke attenuated progression and delayed stroke onset (P<0.003. Detection of Y-chromosome DNA in brain microvessels of EPC-treated female spTg25 rats indicates integration of male EPCs into female rat brain microvessels. Gradient-echo MRI showed delay of ischemic-hemorrhagic lesions in EPC-treated rats. Real-time RT-PCR pathway-specific array-analysis revealed age-associated gene expression changes in CD45-[CD34+/KDR]EPC subtypes, which were accelerated in stroke-prone rats. Pro-angiogenic genes implicated in intimal hyperplasia were increased in stroke-prone rat EPCs (P<0.0001, suggesting a maladaptive endothelial repair system which acts like a double-edged sword repairing while predisposing to age-associated intimal hyperplasia.Altogether, the data

  15. Mapping insecticide resistance in Anopheles gambiae (s.l.) from Côte d'Ivoire.

    Science.gov (United States)

    Camara, Soromane; Koffi, Alphonsine A; Ahoua Alou, Ludovic P; Koffi, Kouakou; Kabran, Jean-Paul K; Koné, Aboubacar; Koffi, Mathieu F; N'Guessan, Raphaël; Pennetier, Cédric

    2018-01-08

    Insecticide resistance in malaria vectors is an increasing threat to vector control tools currently deployed in endemic countries. Resistance management must be an integral part of National Malaria Control Programmes' (NMCPs) next strategic plans to alleviate the risk of control failure. This obviously will require a clear database on insecticide resistance to support the development of such a plan. The present work gathers original data on insecticide resistance between 2009 and 2015 across Côte d'Ivoire in West Africa. Two approaches were adopted to build or update the resistance data in the country. Resistance monitoring was conducted between 2013 and 2015 in 35 sentinel sites across the country using the WHO standard procedure of susceptibility test on adult mosquitoes. Four insecticide families (pyrethroids, organochlorides, carbamates and organophosphates) were tested. In addition to this survey, we also reviewed the literature to assemble existing data on resistance between 2009 and 2015. High resistance levels to pyrethroids, organochlorides and carbamates were widespread in all study sites whereas some Anopheles populations remained susceptible to organophosphates. Three resistance mechanisms were identified, involving high allelic frequencies of kdr L1014F mutation (range = 0.46-1), relatively low frequencies of ace-1 R (below 0.5) and elevated activity of insecticide detoxifying enzymes, mainly mixed function oxidases (MFO), esterase and glutathione S-transferase (GST) in almost all study sites. This detailed map of resistance highlights the urgent need to develop new vector control tools to complement current long-lasting insecticidal nets (LLINs) although it is yet unclear whether these resistance mechanisms will impact malaria transmission control. Researchers, industry, WHO and stakeholders must urgently join forces to develop alternative tools. By then, NMCPs must strive to develop effective tactics or plans to manage resistance keeping in mind

  16. Levels of insecticide resistance to deltamethrin, malathion, and temephos, and associated mechanisms in Aedes aegypti mosquitoes from the Guadeloupe and Saint Martin islands (French West Indies).

    Science.gov (United States)

    Goindin, Daniella; Delannay, Christelle; Gelasse, Andric; Ramdini, Cédric; Gaude, Thierry; Faucon, Frédéric; David, Jean-Philippe; Gustave, Joël; Vega-Rua, Anubis; Fouque, Florence

    2017-02-10

    In the Guadeloupe and Saint Martin islands, Aedes aegypti mosquitoes are the only recognized vectors of dengue, chikungunya, and Zika viruses. For around 40 years, malathion was used as a mosquito adulticide and temephos as a larvicide. Since the European Union banned the use of these two insecticide molecules in the first decade of the 21st century, deltamethrin and Bacillus thuringiensis var. israelensis are the remaining adulticide and larvicide, respectively, used in Guadeloupe. In order to improve the management of vector control activities in Guadeloupe and Saint Martin, we investigated Ae. aegypti resistance to and mechanisms associated with deltamethrin, malathion, and temephos. Ae. aegypti mosquitoes were collected from six different localities of Guadeloupe and Saint Martin. Larvae were used for malathion and temephos bioassays, and adult mosquitoes for deltamethrin bioassays, following World Health Organization recommendations. Knockdown resistance (Kdr) genotyping for V1016I and F1534C mutations, and expression levels of eight enzymes involved in detoxification mechanisms were examined in comparison with the susceptible reference Bora Bora strain. Resistance ratios (RR 50 ) calculated for Ae. aegypti larvae showed high resistance levels to temephos (from 8.9 to 33.1-fold) and low resistance levels to malathion (from 1.7 to 4.4-fold). Adult females displayed moderate resistance levels to deltamethrin regarding the time necessary to affect 50% of individuals, varying from 8.0 to 28.1-fold. Molecular investigations on adult mosquitoes showed high resistant allele frequencies for V1016I and F1534C (from 85 to 96% and from 90 to 98%, respectively), as well as an overexpression of the glutathione S-transferase gene, GSTe2, the carboxylesterase CCEae3a, and the cytochrome genes 014614, CYP6BB2, CYP6M11, and CYP9J23. Ae. aegypti populations from Guadeloupe and Saint Martin exhibit multiple resistance to organophosphates (temephos and malathion), and

  17. Multiple insecticide resistance mechanisms in Anopheles gambiae s.l. populations from Cameroon, Central Africa.

    Science.gov (United States)

    Nwane, Philippe; Etang, Josiane; Chouaїbou, Mouhamadou; Toto, Jean Claude; Koffi, Alphonsine; Mimpfoundi, Rémy; Simard, Frédéric

    2013-02-22

    Increasing incidence of DDT and pyrethroid resistance in Anopheles mosquitoes is seen as a limiting factor for malaria vector control. The current study aimed at an in-depth characterization of An. gambiae s.l. resistance to insecticides in Cameroon, in order to guide malaria vector control interventions. Anopheles gambiae s.l. mosquitoes were collected as larvae and pupae from six localities spread throughout the four main biogeographical domains of Cameroon and reared to adults in insectaries. Standard WHO insecticide susceptibility tests were carried out with 4% DDT, 0.75% permethrin and 0.05% deltamethrin. Mortality rates and knockdown times (kdt50 and kdt95) were determined and the effect of pre-exposure to the synergists DEF, DEM and PBO was assessed. Tested mosquitoes were identified to species and molecular forms (M or S) using PCR-RFLP. The hot ligation method was used to depict kdr mutations and biochemical assays were conducted to assess detoxifying enzyme activities. The An. arabiensis population from Pitoa was fully susceptible to DDT and permethrin (mortality rates>98%) and showed reduced susceptibility to deltamethrin. Resistance to DDT was widespread in An. gambiae s.s. populations and heterogeneous levels of susceptibility to permethrin and deltamethrin were observed. In many cases, prior exposure to synergists partially restored insecticide knockdown effect and increased mortality rates, suggesting a role of detoxifying enzymes in increasing mosquito survival upon challenge by pyrethroids and, to a lower extent DDT. The distribution of kdr alleles suggested a major role of kdr-based resistance in the S form of An. gambiae. In biochemical tests, all but one mosquito population overexpressed P450 activity, whereas baseline GST activity was low and similar in all field mosquito populations and in the control. In Cameroon, multiple resistance mechanisms segregate in the S form of An. gambiae resulting in heterogeneous resistance profiles, whereas in

  18. Research on the Frequency Aliasing of Resistance Acceleration Guidance for Reentry Flight

    Directory of Open Access Journals (Sweden)

    Han Pengxin

    2017-01-01

    Full Text Available According to the special response of resistance acceleration during hypersonic reentry flight, different guidance frequency will result to very different flight and control response. The analysis model for the response of resistance acceleration to the attack angle and dynamic press is put forward respectively in this paper. And the frequency aliasing phenomenon of guidance is revealed. The simulation results to the same vehicle sufficiently substantiate the frequency aliasing of resistance acceleration during reentry guidance.

  19. Insecticide resistance and resistance mechanisms in bed bugs, Cimex spp. (Hemiptera: Cimicidae).

    Science.gov (United States)

    Dang, Kai; Doggett, Stephen L; Veera Singham, G; Lee, Chow-Yang

    2017-06-29

    The worldwide resurgence of bed bugs [both Cimex lectularius L. and Cimex hemipterus (F.)] over the past two decades is believed in large part to be due to the development of insecticide resistance. The transcriptomic and genomic studies since 2010, as well as morphological, biochemical and behavioral studies, have helped insecticide resistance research on bed bugs. Multiple resistance mechanisms, including penetration resistance through thickening or remodelling of the cuticle, metabolic resistance by increased activities of detoxification enzymes (e.g. cytochrome P450 monooxygenases and esterases), and knockdown resistance by kdr mutations, have been experimentally identified as conferring insecticide resistance in bed bugs. Other candidate resistance mechanisms, including behavioral resistance, some types of physiological resistance (e.g. increasing activities of esterases by point mutations, glutathione S-transferase, target site insensitivity including altered AChEs, GABA receptor insensitivity and altered nAChRs), symbiont-mediated resistance and other potential, yet undiscovered mechanisms may exist. This article reviews recent studies of resistance mechanisms and the genes governing insecticide resistance, potential candidate resistance mechanisms, and methods of monitoring insecticide resistance in bed bugs. This article provides an insight into the knowledge essential for the development of both insecticide resistance management (IRM) and integrated pest management (IPM) strategies for successful bed bug management.

  20. Inheritance of Cry1F resistance, cross-resistance and frequency of resistant alleles in Spodoptera frugiperda (Lepidoptera: Noctuidae).

    Science.gov (United States)

    Vélez, A M; Spencer, T A; Alves, A P; Moellenbeck, D; Meagher, R L; Chirakkal, H; Siegfried, B D

    2013-12-01

    Transgenic maize, Zea maize L., expressing the Cry1F protein from Bacillus thuringiensis has been registered for Spodoptera frugiperda (J. E. Smith) control since 2003. Unexpected damage to Cry1F maize was reported in 2006 in Puerto Rico and Cry1F resistance in S. frugiperda was documented. The inheritance of Cry1F resistance was characterized in a S. frugiperda resistant strain originating from Puerto Rico, which displayed >289-fold resistance to purified Cry1F. Concentration-response bioassays of reciprocal crosses of resistant and susceptible parental populations indicated that resistance is recessive and autosomal. Bioassays of the backcross of the F1 generation crossed with the resistant parental strain suggest that a single locus is responsible for resistance. In addition, cross-resistance to Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba, Cry2Aa and Vip3Aa was assessed in the Cry1F-resistant strain. There was no significant cross-resistance to Cry1Aa, Cry1Ba and Cry2Aa, although only limited effects were observed in the susceptible strain. Vip3Aa was highly effective against susceptible and resistant insects indicating no cross-resistance with Cry1F. In contrast, low levels of cross-resistance were observed for both Cry1Ab and Cry1Ac. Because the resistance is recessive and conferred by a single locus, an F1 screening assay was used to measure the frequency of Cry1F-resistant alleles from populations of Florida and Texas in 2010 and 2011. A total frequency of resistant alleles of 0.13 and 0.02 was found for Florida and Texas populations, respectively, indicating resistant alleles could be found in US populations, although there have been no reports of reduced efficacy of Cry1F-expressing plants.

  1. Malaria transmission and insecticide resistance of Anopheles gambiae in Libreville and Port-Gentil, Gabon

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    Kombila Maryvonne

    2010-11-01

    Full Text Available Abstract Background Urban malaria is a major health priority for civilian and militaries populations. A preliminary entomologic study has been conducted in 2006-2007, in the French military camps of the two mains towns of Gabon: Libreville and Port-Gentil. The aim was to assess the malaria transmission risk for troops. Methods Mosquitoes sampled by human landing collection were identified morphologically and by molecular methods. The Plasmodium falciparum circumsporozoïte (CSP indexes were measured by ELISA, and the entomological inoculation rates (EIR were calculated for both areas. Molecular assessments of pyrethroid knock down (kdr resistance and of insensitive acetylcholinesterase resistance were conducted. Results In Libreville, Anopheles gambiae s.s. S form was the only specie of the An. gambiae complex present and was responsible of 9.4 bites per person per night. The circumsporozoïte index was 0.15% and the entomological inoculation rate estimated to be 1.23 infective bites during the four months period. In Port-Gentil, Anopheles melas (75.5% of catches and An. gambiae s.s. S form (24.5% were responsible of 58.7 bites per person per night. The CSP indexes were of 1.67% for An. gambiae s.s and 0.28% for An. melas and the EIRs were respectively of 1.8 infective bites per week and of 0.8 infective bites per week. Both kdr-w and kdr-e mutations in An. gambiae S form were found in Libreville and in Port-Gentil. Insensitive acetylcholinesterase has been detected for the first time in Gabon in Libreville. Conclusion Malaria transmission exists in both town, but with high difference in the level of risk. The co-occurrence of molecular resistances to the main families of insecticide has implications for the effectiveness of the current vector control programmes that are based on pyrethroid-impregnated bed nets.

  2. Anomalous high-frequency resistivity of a plasma

    International Nuclear Information System (INIS)

    Kruer, W.L.; Dawson, J.M.

    1971-06-01

    In one- and two-dimensional computer simulations we investigate anomalous high-frequency resistivity in a plasma driven by a large electric field oscillating near the electron plasma frequency. The large field excites the oscillating two-stream and the ion-acoustic decay instabilities in agreement with the linear theory. When the ion and electron fluctuations saturate, a strong anomalous heating of the plasma sets in. This strong heating is due to an efficient coupling of the externally imposed large electric field to the plasma by ion fluctuations. We determine the anomalous collision frequency and the saturation fluctuation amplitudes as a function of the external field amplitude and frequency, and the electron-ion mass ratio. A simple nonlinear theory gives results in reasonable agreement with simulations. 24 refs., 10 figs

  3. Frequency of Cry1F resistance alleles in Spodoptera frugiperda (Lepidoptera: Noctuidae) in Brazil.

    Science.gov (United States)

    Farias, Juliano R; Andow, David A; Horikoshi, Renato J; Bernardi, Daniel; Ribeiro, Rebeca da S; Nascimento, Antonio Rb do; Santos, Antonio C Dos; Omoto, Celso

    2016-12-01

    The frequency of resistance alleles is a major factor influencing the rate of resistance evolution. Here, we adapted the F 2 screen procedure for Spodoptera frugiperda (J. E. Smith) with a discriminating concentration assay, and extended associated statistical methods to estimate the frequency of resistance to Cry1F protein in S. frugiperda in Brazil when resistance was not rare. We show that F 2 screen is efficient even when the resistance frequency is 0.250. It was possible to screen 517 isoparental lines from 12 populations sampled in five states of Brazil during the first half of 2012. Western Bahia had the highest allele frequency of Cry1F resistance, 0.192, with a 95% confidence interval (CI) between 0.163 and 0.220. All other states had a similar and lower frequency varying from 0.042 in Paraná to 0.080 in Mato Grosso do Sul. The high frequency in western Bahia may be related to year-round availability of maize, the high population density of S. frugiperda, the lack of refuges and the high adoption rate of Cry1F maize. Cry1F resistance alleles were not rare and occurred at frequencies that have already compromised the useful life of TC1507 maize in western Bahia. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  4. Insecticide resistance may enhance the response to a host-plant volatile kairomone for the codling moth, Cydia pomonella (L.)

    Science.gov (United States)

    Sauphanor, Benoît; Franck, Pierre; Lasnier, Thérèse; Toubon, Jean-François; Beslay, Dominique; Boivin, Thomas; Bouvier, Jean-Charles; Renou, Michel

    2007-06-01

    The behavioral and electroantennographic responses of Cydia pomonella (L.) to the ripe pear volatile ethyl (2 E,4 Z)-2,4-decadienoate (Et- E, Z-DD), were compared in insecticide-susceptible and -resistant populations originating from southern France. A dose-response relationship to this kairomonal attractant was established for antennal activity and did not reveal differences between susceptible and resistant strains. Conversely, males of the laboratory strains expressing metabolic [cytochrome P450-dependent mixed-function oxidases (mfo)] or physiological (kdr-type mutation of the sodium-channel gene) resistance mechanisms exhibited a significantly higher response to Et- E, Z-DD than those of the susceptible strain in a wind tunnel experiment. No response of the females to this kairomone could be obtained in our wind-tunnel conditions. In apple orchards, mfo-resistant male moths were captured at significantly higher rates in kairomone-baited traps than in traps baited with the sex pheromone of C. pomonella. Such a differential phenomenon was not verified for the kdr-resistant insects, which exhibited a similar response to both the sex pheromone and the kairomonal attractant in apple orchards. Considering the widespread distribution of metabolic resistance in European populations of C. pomonella and the enhanced behavioral response to Et- E, Z-DD in resistant moths, the development of control measures based on this kairomonal compound would be of great interest for the management of insecticide resistance in this species.

  5. Detection of low frequency multi-drug resistance and novel putative maribavir resistance in immunocompromised paediatric patients with cytomegalovirus

    Directory of Open Access Journals (Sweden)

    Charlotte Jane Houldcroft

    2016-09-01

    Full Text Available Human cytomegalovirus (HCMV is a significant pathogen in immunocompromised individuals, with the potential to cause fatal pneumonitis and colitis, as well as increasing the risk of organ rejection in transplant patients. With the advent of new anti-HCMV drugs there is therefore considerable interest in using virus sequence data to monitor emerging resistance to antiviral drugs in HCMV viraemia and disease, including the identification of putative new mutations. We used target-enrichment to deep sequence HCMV DNA from 11 immunosuppressed paediatric patients receiving single or combination anti-HCMV treatment, serially sampled over 1-27 weeks. Changes in consensus sequence and resistance mutations were analysed for three ORFs targeted by anti-HCMV drugs and the frequencies of drug resistance mutations monitored. Targeted-enriched sequencing of clinical material detected mutations occurring at frequencies of 2%. Seven patients showed no evidence of drug resistance mutations. Four patients developed drug resistance mutations a mean of 16 weeks after starting treatment. In two patients, multiple resistance mutations accumulated at frequencies of 20% or less, including putative maribavir and ganciclovir resistance mutations P522Q (UL54 and C480F (UL97. In one patient, resistance was detected 14 days earlier than by PCR. Phylogenetic analysis suggested recombination or superinfection in one patient. Deep sequencing of HCMV enriched from clinical samples excluded resistance in 7 of eleven subjects and identified resistance mutations earlier than conventional PCR-based resistance testing in 2 patients. Detection of multiple low level resistance mutations was associated with poor outcome.

  6. Experimental hut evaluation of bednets treated with an organophosphate (chlorpyrifos-methyl or a pyrethroid (lambdacyhalothrin alone and in combination against insecticide-resistant Anopheles gambiae and Culex quinquefasciatus mosquitoes

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    Corbel Vincent

    2005-05-01

    Full Text Available Abstract Background Pyrethroid resistant mosquitoes are becoming increasingly common in parts of Africa. It is important to identify alternative insecticides which, if necessary, could be used to replace or supplement the pyrethroids for use on treated nets. Certain compounds of an earlier generation of insecticides, the organophosphates may have potential as net treatments. Methods Comparative studies of chlorpyrifos-methyl (CM, an organophosphate with low mammalian toxicity, and lambdacyhalothrin (L, a pyrethroid, were conducted in experimental huts in Côte d'Ivoire, West Africa. Anopheles gambiae and Culex quinquefasciatus mosquitoes from the area are resistant to pyrethroids and organophosphates (kdr and insensitive acetylcholinesterase Ace.1R. Several treatments and application rates on intact or holed nets were evaluated, including single treatments, mixtures, and differential wall/ceiling treatments. Results and Conclusion All of the treatments were effective in reducing blood feeding from sleepers under the nets and in killing both species of mosquito, despite the presence of the kdr and Ace.1R genes at high frequency. In most cases, the effects of the various treatments did not differ significantly. Five washes of the nets in soap solution did not reduce the impact of the insecticides on A. gambiae mortality, but did lead to an increase in blood feeding. The three combinations performed no differently from the single insecticide treatments, but the low dose mixture performed encouragingly well indicating that such combinations might be used for controlling insecticide resistant mosquitoes. Mortality of mosquitoes that carried both Ace.1R and Ace.1S genes did not differ significantly from mosquitoes that carried only Ace.1S genes on any of the treated nets, indicating that the Ace.1R allele does not confer effective resistance to chlorpyrifos-methyl under the realistic conditions of an experimental hut.

  7. Frequency and antimicrobial resistance of aerobic bacteria isolated ...

    African Journals Online (AJOL)

    This study was carried out to evaluate the frequency of occurrence and antimicrobial resistance of aerobic bacteria isolated from surgical sites in human and animal patients in Nsukka, southeast Nigeria. Wound swabs from 132 patients (96 humans and 36 animals) were cultured for bacterial isolation. Antimicrobial ...

  8. Kapitza thermal resistance studied by high-frequency photothermal radiometry

    International Nuclear Information System (INIS)

    Horny, Nicolas; Chirtoc, Mihai; Hamaoui, Georges; Fleming, Austin; Ban, Heng

    2016-01-01

    Kapitza thermal resistance is determined using high-frequency photothermal radiometry (PTR) extended for modulation up to 10 MHz. Interfaces between 50 nm thick titanium coatings and silicon or stainless steel substrates are studied. In the used configuration, the PTR signal is not sensitive to the thermal conductivity of the film nor to its optical absorption coefficient, thus the Kapitza resistance is directly determined from single thermal parameter fits. Results of thermal resistances show the significant influence of the nature of the substrate, as well as of the presence of free electrons at the interface.

  9. Targeted application of an organophosphate-based paint applied on windows and doors against Anopheles coluzzii resistant to pyrethroids under real life conditions in Vallée du Kou, Burkina Faso (West Africa).

    Science.gov (United States)

    Poda, Serge B; Soma, Dieudonné D; Hien, Aristide; Namountougou, Moussa; Gnankiné, Olivier; Diabaté, Abdoulaye; Fournet, Florence; Baldet, Thierry; Mas-Coma, Santiago; Mosqueira, Beatriz; Dabiré, Roch K

    2018-04-02

    A novel strategy applying an organophosphate-based insecticide paint on doors and windows in combination with long-lasting insecticide-treated nets (LLINs) was tested for the control of pyrethroid-resistant malaria vectors in a village setting in Vallée du Kou, a rice-growing area west of Burkina Faso. Insecticide Paint Inesfly 5A IGR™, comprised of two organophosphates and an insect growth regulator, was applied to doors and windows and tested in combination with pyrethroid-treated LLINs. The killing effect was monitored for 5 months by early morning collections of anophelines and other culicids. The residual efficacy was evaluated monthly by WHO bioassays using Anopheles gambiae 'Kisumu' and local populations of Anopheles coluzzii resistant to pyrethroids. The spatial mortality efficacy (SME) at distances of 1 m was also assessed against pyrethroid-susceptible and -resistant malaria vectors. The frequency of L1014F kdr and Ace-1 R G119S mutations was, respectively, reported throughout the study. The Insecticide Paint Inesfly 5A IGR had been tested in past studies yielding a long-term mortality rate of 80% over 12 months against An. coluzzii, the local pyrethroid-resistant malaria vector. The purpose of the present study is to test if treating smaller, targeted surfaces (e.g. doors and windows) was also efficient in killing malaria vectors. Treating windows and doors alone yielded a killing efficacy of 100% for 1 month against An. coluzzii resistant to pyrethroids, but efficacy reduced quickly afterwards. Likewise, WHO cone bioassays yielded mortalities of 80-100% for 2 months but declined to 90 and 40% 2 and 3 months after treatment, respectively. Mosquitoes exposed to insecticide paint-treated surfaces at distances of 1 m, yielded mortality rates of about 90-80% against local pyrethroids-resistant An. coluzzii during the first 2 months, but decreased to 30% afterwards. Anopheles coluzzii was reported to be exclusively the local malaria vector and

  10. Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa

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    Etang Josiane

    2008-09-01

    Full Text Available Abstract Background Indoor residual spraying and insecticide-treated nets (ITN are essential components of malaria vector control in Africa. Pyrethroids are the only recommended compounds for nets treatment because they are fast-acting insecticides with low mammalian toxicity. However, there is growing concern that pyrethroid resistance may threaten the sustainability of ITN scaling-up programmes. Here, insecticide susceptibility was investigated in Anopheles gambiae sensu lato from an area of large scale ITN distribution programme in south-western Chad. Methods Susceptibility to 4% DDT, 0.05% deltamethrin, 0.75% permethrin, 0.1% bendiocarb and 5% malathion was assessed using the WHO standard procedures for adult mosquitoes. Tests were carried out with two to four days-old, non-engorged female mosquitoes. The An. gambiae Kisumu strain was used as a reference. Knockdown effect was recorded every 5 min and mortality scored 24 h after exposure. Mosquitoes were identified to species and molecular form by PCR-RFLP and genotypes at the kdr locus were determined in surviving specimens by Hot Oligonucleotide Ligation Assay (HOLA. Results During this survey, full susceptibility to malathion was recorded in all samples. Reduced susceptibility to bendiocarb (mortality rate of 96.1% was found in one sample out of nine assayed. Increased tolerance to pyrethroids was detected in most samples (8/9 with mortality rates ranging from 70.2 to 96.6% for deltamethrin and from 26.7 to 96.3% for permethrin. Pyrethroid tolerance was not associated with a significant increase of knock-down times. Anopheles arabiensis was the predominant species of the An. gambiae complex in the study area, representing 75 to 100% of the samples. Screening for kdr mutations detected the L1014F mutation in 88.6% (N = 35 of surviving An. gambiae sensu stricto S form mosquitoes. All surviving An. arabiensis (N = 49 and M form An. gambiae s.s. (N = 1 carried the susceptible allele

  11. Insecticide resistance in the dengue vector Aedes aegypti from Martinique: distribution, mechanisms and relations with environmental factors.

    Science.gov (United States)

    Marcombe, Sébastien; Mathieu, Romain Blanc; Pocquet, Nicolas; Riaz, Muhammad-Asam; Poupardin, Rodolphe; Sélior, Serge; Darriet, Frédéric; Reynaud, Stéphane; Yébakima, André; Corbel, Vincent; David, Jean-Philippe; Chandre, Fabrice

    2012-01-01

    Dengue is an important mosquito borne viral disease in Martinique Island (French West Indies). The viruses responsible for dengue are transmitted by Aedes aegypti, an indoor day-biting mosquito. The most effective proven method for disease prevention has been by vector control by various chemical or biological means. Unfortunately insecticide resistance has already been observed on the Island and recently showed to significantly reduce the efficacy of vector control interventions. In this study, we investigated the distribution of resistance and the underlying mechanisms in nine Ae. aegypti populations. Statistical multifactorial approach was used to investigate the correlations between insecticide resistance levels, associated mechanisms and environmental factors characterizing the mosquito populations. Bioassays revealed high levels of resistance to temephos and deltamethrin and susceptibility to Bti in the 9 populations tested. Biochemical assays showed elevated detoxification enzyme activities of monooxygenases, carboxylesterases and glutathione S-tranferases in most of the populations. Molecular screening for common insecticide target-site mutations, revealed the presence of the "knock-down resistance" V1016I Kdr mutation at high frequency (>87%). Real time quantitative RT-PCR showed the potential involvement of several candidate detoxification genes in insecticide resistance. Principal Component Analysis (PCA) performed with variables characterizing Ae. aegypti from Martinique permitted to underline potential links existing between resistance distribution and other variables such as agriculture practices, vector control interventions and urbanization. Insecticide resistance is widespread but not homogeneously distributed across Martinique. The influence of environmental and operational factors on the evolution of the resistance and mechanisms are discussed.

  12. Insecticide resistance in the dengue vector Aedes aegypti from Martinique: distribution, mechanisms and relations with environmental factors.

    Directory of Open Access Journals (Sweden)

    Sébastien Marcombe

    Full Text Available Dengue is an important mosquito borne viral disease in Martinique Island (French West Indies. The viruses responsible for dengue are transmitted by Aedes aegypti, an indoor day-biting mosquito. The most effective proven method for disease prevention has been by vector control by various chemical or biological means. Unfortunately insecticide resistance has already been observed on the Island and recently showed to significantly reduce the efficacy of vector control interventions. In this study, we investigated the distribution of resistance and the underlying mechanisms in nine Ae. aegypti populations. Statistical multifactorial approach was used to investigate the correlations between insecticide resistance levels, associated mechanisms and environmental factors characterizing the mosquito populations. Bioassays revealed high levels of resistance to temephos and deltamethrin and susceptibility to Bti in the 9 populations tested. Biochemical assays showed elevated detoxification enzyme activities of monooxygenases, carboxylesterases and glutathione S-tranferases in most of the populations. Molecular screening for common insecticide target-site mutations, revealed the presence of the "knock-down resistance" V1016I Kdr mutation at high frequency (>87%. Real time quantitative RT-PCR showed the potential involvement of several candidate detoxification genes in insecticide resistance. Principal Component Analysis (PCA performed with variables characterizing Ae. aegypti from Martinique permitted to underline potential links existing between resistance distribution and other variables such as agriculture practices, vector control interventions and urbanization. Insecticide resistance is widespread but not homogeneously distributed across Martinique. The influence of environmental and operational factors on the evolution of the resistance and mechanisms are discussed.

  13. Target-site resistance to pyrethroids in European populations of pollen beetle, Meligethes aeneus F

    DEFF Research Database (Denmark)

    Nauen, Ralf; Zimmer, Christoph T; Andrews, Melanie

    2012-01-01

    by cytochrome P450 monooxygenases was implicated in the resistance of several pollen beetle populations from different European regions. Here, we have also investigated the possible occurrence of a target-site mechanism caused by modification of the pollen beetle para-type voltage-gated sodium channel gene. We...... resulted in high selection pressure and subsequent development of resistance. Resistance to pyrethroid insecticides in this pest is now widespread and the levels of resistance are often sufficient to result in field control failures at recommended application rates. Recently, metabolic resistance mediated...... detected a single nucleotide change that results in an amino acid substitution (L1014F) within the domain IIS6 region of the channel protein. The L1014F mutation, often termed kdr, has been found in several other insect pests and is known to confer moderate levels of resistance to pyrethroids. We developed...

  14. Identification of Novel Voltage-Gated Sodium Channel Mutations in Human Head and Body Lice (Phthiraptera: Pediculidae).

    Science.gov (United States)

    Firooziyan, Samira; Sadaghianifar, Ali; Taghilou, Behrooz; Galavani, Hossein; Ghaffari, Eslam; Gholizadeh, Saber

    2017-09-01

    In recent years, the increase of head louse infestation in Iran (7.4%) and especially in West-Azerbaijan Province (248%) has raised the hypothesis of insecticide resistance development. There are different mechanisms of resistance to various groups of insecticides, and knockdown resistance (kdr) is a prominent mechanism of resistance to pyrethroids, an insecticide group which is used conventionally for pediculosis control. For detection of kdr-type well-known amino acid substitutions (M815I-T917I-L920F) and additional sodium channel mutations potentially associated with kdr resistance in head and body lice, louse populations were collected from West-Azerbaijan and Zanjan Provinces of Iran. Six novel mutations were found to be located in the IIS1-2 extracellular loop (H813P) and IIS5 (I927F, L928A, R929V, L930M, and L932M) of the α-subunit. Genotyping results showed that all specimens (100%) have at least one of these or the well-known mutations. Therefore, the presence of kdr-related and novel mutations in the sodium channel is likely to be the reason for the frequent use of pyrethroid insecticides due to treatment failure against lice. Further studies are now required to evaluate the prevalence of the kdr-like mutant allele for monitoring of insecticide resistance and the management of head and body lice in other provinces of the country. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. Frequency of colistin and fosfomycin resistance in carbapenem-resistant Enterobacteriaceae from a tertiary care hospital in Karachi

    Directory of Open Access Journals (Sweden)

    Qamar S

    2017-07-01

    Full Text Available Salima Qamar, Najma Shaheen, Sadia Shakoor, Joveria Farooqi, Kauser Jabeen, Rumina Hasan Clinical Microbiology, Department of Pathology And Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan Introduction: Management of infections with carbapenem-resistant Enterobacteriaceae (CRE is challenging. In recent times, agents such as colistin and fosfomycin have been used in combination with other antibiotics to treat such infections. In this study, we aim to seek frequency of colistin and fosfomycin resistance in CRE from Pakistan.Methods: This study was conducted at clinical laboratories, Aga Khan University Hospital. In total, 251 CRE were included in the study. Colistin minimum inhibitory concentrations (MICs were performed using broth microdilution (BMD method and VITEK® 2 system, whereas fosfomycin susceptibility was performed using Kirby–Bauer method. MIC50 and MIC90 were calculated for colistin and agreement between VITEK and BMD was also calculated.Results: Out of 251 strains colistin MIC of ≥4 µg/mL was seen in 40 (15.9%. Of these strains 20 (50% were Klebsiella pneumoniae. Colistin MIC50 and MIC90 were found to be 0.5 and 16 µg/mL, respectively. BMD and VITEK 2 showed 100% categorical agreement. Essential agreement was 88.5% with kappa score 0.733 indicating strong agreement between VITEK and BMD. 31 out of 251 (12.3% CREs were resistant to fosfomycin.Conclusion: Study shows frequency of colistin and fosfomycin resistance to be 15.9% and 12.3%, respectively. In countries where rate of CREs is high, emerging resistance against these last resort antibiotics is alarming as it leaves clinicians with almost no options to manage such multidrug resistant and extensively drug resistant infections. Keywords: emerging drug resistance, colistin resistance, fosfomycin resistance, carbapenam resistant enterobacteriaceae, salvage antibiotics 

  16. Genetic variation associated with increased insecticide resistance in the malaria mosquito, Anopheles coluzzii.

    Science.gov (United States)

    Main, Bradley J; Everitt, Amanda; Cornel, Anthony J; Hormozdiari, Fereydoun; Lanzaro, Gregory C

    2018-04-04

    Malaria mortality rates in sub-Saharan Africa have declined significantly in recent years as a result of increased insecticide-treated bed net (ITN) usage. A major challenge to further progress is the emergence and spread of insecticide resistance alleles in the Anopheles mosquito vectors, like An. coluzzii. A non-synonymous mutation in the para voltage-gated sodium channel gene reduces pyrethroid-binding affinity, resulting in knockdown resistance (kdr). Metabolic mechanisms of insecticide resistance involving detoxification genes like cytochrome P450 genes, carboxylesterases, and glutathione S-transferases are also important. As some gene activity is tissue-specific and/or environmentally induced, gene regulatory variation may be overlooked when comparing expression from whole mosquito bodies under standard rearing conditions. We detected complex insecticide resistance in a 2014 An. coluzzii colony from southern Mali using bottle bioassays. Additional bioassays involving recombinant genotypes from a cross with a relatively susceptible 1995 An. coluzzii colony from Mali confirmed the importance of kdr and associated increased permethrin resistance to the CYP9K1 locus on the X chromosome. Significant differential expression of CYP9K1 was not observed among these colonies in Malpighian tubules. However, the P450 gene CYP6Z1 was overexpressed in resistant individuals following sublethal permethrin exposure and the carboxylesterase gene COEAE5G was constitutively overexpressed. The significant P450-related insecticide resistance observed in the 2014 An. coluzzii colony indicates that ITNs treated with the P450 inhibitor piperonyl butoxide (PBO) would be more effective in this region. The known insecticide resistance gene CYP6Z1 was differentially expressed exclusively in the context of sublethal permethrin exposure, highlighting the importance of tissue-specificity and environmental conditions in gene expression studies. The increased activity of the carboxylesterase

  17. Co-occurrence of point mutations in the voltage-gated sodium channel of pyrethroid-resistant Aedes aegypti populations in Myanmar.

    Science.gov (United States)

    Kawada, Hitoshi; Oo, Sai Zaw Min; Thaung, Sein; Kawashima, Emiko; Maung, Yan Naung Maung; Thu, Hlaing Myat; Thant, Kyaw Zin; Minakawa, Noboru

    2014-01-01

    Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar. We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study. Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti.

  18. Co-occurrence of Point Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Aedes aegypti Populations in Myanmar

    Science.gov (United States)

    Kawada, Hitoshi; Oo, Sai Zaw Min; Thaung, Sein; Kawashima, Emiko; Maung, Yan Naung Maung; Thu, Hlaing Myat; Thant, Kyaw Zin; Minakawa, Noboru

    2014-01-01

    Background Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar. Methodology/Principal Findings We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study. Conclusions/Significance Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti. PMID:25077956

  19. Antimicrobial sensitivity and frequency of DRUG resistance among bacterial strains isolated from cancer patients

    International Nuclear Information System (INIS)

    Faiz, M.; Bashir, T.

    2004-01-01

    Blood stream infections (bacteremia) is potentially life threatening. Concomitant with a change in the incidence and epidemiology of infecting organisms, there has been an increase in resistance to many antibiotic compounds. The widespread emergence of resistance among bacterial pathogens has an impact on our ability to treat patients effectively. The changing spectrum of microbial pathogens and widespread emergence of microbial resistance to antibiotic drugs has emphasized the need to monitor the prevalence of resistance in these strains. In the present study frequency of isolation of clinically significant bacteria and their susceptibility and resistance pattern against a wide range of antimicrobial drugs from positive blood cultures collected during 2001-2003 was studied. A total of 102 consecutive isolates were found with 63% gram positive and 44% gram negative strains. The dominating pathogens were Staphylococcus aureus (51%), Streptococci (31%), Pseudomonas (40%), Proteus (13%), Klebsiella (13%). The isolated strains were tested against a wide range of antibiotics belonging to cephalosporins, aminoglycosides and quinolone derivative group by disk diffusion method. It has been observed that isolated strains among gram positive and negative strains showed different level of resistance against aminoglycosides and cephalosporin group of antibiotics with gram positives showing highest number and frequency of resistance against aminoglycosides (40-50%) and cephalosporins.(35-45%) whereas cephalosporins were found to be more effective against gram negatives with low frequency of resistant strains. Cabapenem and quinolone derivative drugs were found to be most effective among other groups in both gram positive and negative strains with 23-41% strains found sensitive to these two drugs. The frequency of sensitive strains against aminoglycoside and cephalosporin in gram negative and gram positive strains were found to be decreasing yearwise with a trend towards an

  20. Research surface resistance of copper normal and abnormal skin-effects depending on the frequency of electromagnetic field

    International Nuclear Information System (INIS)

    Kutovyi, V.A.; Komir, A.I.

    2013-01-01

    The results of the frequency dependence of surface resistance of copper in diffuse and specular reflection of electrons from the conductive surface of the high-frequency resonance of the system depending on the frequency of the electromagnetic field in the normal and anomalous skin effect. Found, the surface resistance of copper is reduced by more than 10 times at the temperature of liquid helium, as compared with a surface resistivity at room temperature, at frequencies f ≤ 173 MHz, for diffuse reflection of conduction electrons from the surface of the conductive layer, and the specular reflection - at frequencies f ≤ 346 MHz

  1. Predicting the impact of selection for scrapie resistance on PRNP genotype frequencies in goats.

    Science.gov (United States)

    Sacchi, Paola; Rasero, Roberto; Ru, Giuseppe; Aiassa, Eleonora; Colussi, Silvia; Ingravalle, Francesco; Peletto, Simone; Perrotta, Maria Gabriella; Sartore, Stefano; Soglia, Dominga; Acutis, Pierluigi

    2018-03-06

    The European Union has implemented breeding programmes to increase scrapie resistance in sheep. A similar approach can be applied also in goats since the K222 allele provides a level of resistance equivalent to that of ARR in sheep. The European Food Safety Authority stated that breeding for resistance could be offered as an option for Member States to control classical scrapie in goats. We assessed the impact of different breeding strategies on PRNP genotype frequencies using a mathematical model that describes in detail the evolution of K222 in two goat breeds, Chamois Coloured and Saanen. Different patterns of age structure and replacement rate were modelled as factors affecting response to selection. Breeding for scrapie resistance can be implemented in goats, even though the initial K222 frequencies in these breeds are not particularly favourable and the rate at which the resistant animals increase, both breeding and slaughtered for meat production, is slow. If the goal is not to achieve the fixation of resistance allele, it is advisable to carry out selection only until a desired frequency of K222-carriers has been attained. Nucleus selection vs. selection on the overall populations is less expensive but takes longer to reach the desired output. The programme performed on the two goat breeds serves as a model of the response the selection could have in other breeds that show different initial frequencies and population structure. In this respect, the model has a general applicability.

  2. Presence of two alternative kdr-like mutations, L1014F and L1014S, and a novel mutation, V1010L, in the voltage gated Na+ channel of Anopheles culicifacies from Orissa, India

    Directory of Open Access Journals (Sweden)

    Bhatt Rajendra M

    2010-05-01

    Full Text Available Abstract Background Knockdown resistance in insects resulting from mutation(s in the voltage gated Na+ channel (VGSC is one of the mechanisms of resistance against DDT and pyrethroids. Recently a point mutation leading to Leu-to-Phe substitution in the VGSC at residue 1014, a most common kdr mutation in insects, was reported in Anopheles culicifacies-a major malaria vector in the Indian subcontinent. This study reports the presence of two additional amino acid substitutions in the VGSC of an An. culicifacies population from Malkangiri district of Orissa, India. Methods Anopheles culicifacies sensu lato (s.l. samples, collected from a population of Malkangiri district of Orissa (India, were sequenced for part of the second transmembrane segment of VGSC and analyzed for the presence of non-synonymous mutations. A new primer introduced restriction analysis-PCR (PIRA-PCR was developed for the detection of the new mutation L1014S. The An. culicifacies population was genotyped for the presence of L1014F substitution by an amplification refractory mutation system (ARMS and for L1014S substitutions by using a new PIRA-PCR developed in this study. The results were validated through DNA sequencing. Results DNA sequencing of An. culicifacies individuals collected from district Malkangiri revealed the presence of three amino acid substitutions in the IIS6 transmembrane segments of VGSC, each one resulting from a single point mutation. Two alternative point mutations, 3042A>T transversion or 3041T>C transition, were found at residue L1014 leading to Leu (TTA-to-Phe (TTT or -Ser (TCA changes, respectively. A third and novel substitution, Val (GTG-to-Leu (TTG or CTG, was identified at residue V1010 resulting from either of the two transversions–3028G>T or 3028G>C. The L1014S substitution co-existed with V1010L in all the samples analyzed irrespective of the type of point mutation associated with the latter. The PIRA-PCR strategy developed for the

  3. Frequency-domain analysis of intrinsic neuronal properties using high-resistant electrodes

    Directory of Open Access Journals (Sweden)

    Christian Rössert

    2009-08-01

    Full Text Available Intrinsic cellular properties of neurons in culture or slices are usually studied by the whole cell clamp method using low-resistant patch pipettes. These electrodes allow detailed analyses with standard electrophysiological methods such as current- or voltage-clamp. However, in these preparations large parts of the network and dendritic structures may be removed, thus preventing an adequate study of synaptic signal processing. Therefore, intact in vivo preparations or isolated in vitro whole brains have been used in which intracellular recordings are usually made with sharp, high-resistant electrodes to optimize the impalement of neurons. The general non-linear resistance properties of these electrodes, however, severely limit accurate quantitative studies of membrane dynamics especially needed for precise modelling. Therefore, we have developed a frequency-domain analysis of membrane properties that uses a Piece-wise Non-linear Electrode Compensation (PNEC method. The technique was tested in second-order vestibular neurons and abducens motoneurons of isolated frog whole brain preparations using sharp potassium chloride- or potassium acetate-filled electrodes. All recordings were performed without online electrode compensation. The properties of each electrode were determined separately after the neuronal recordings and were used in the frequency-domain analysis of the combined measurement of electrode and cell. This allowed detailed analysis of membrane properties in the frequency-domain with high-resistant electrodes and provided quantitative data that can be further used to model channel kinetics. Thus, sharp electrodes can be used for the characterization of intrinsic properties and synaptic inputs of neurons in intact brains.

  4. Frequency of methicillin resistant Staphylococcus aureus in health care

    Directory of Open Access Journals (Sweden)

    Somayeh Rahimi-Alang

    2011-03-01

    Full Text Available Background: Methicillin resistant Staphylococcus aureus (MRSA is one of the most important pathogen in hospitals. Healthcare personnel are the main source of nosocomial infections and identification and control of MRSA carriers can reduce incidence of infections. The aim of this study was to determine the prevalence of MRSA and their antibiotic susceptibility profile among healthcare workers in Gorgan.Materials and Method: 333 healthcare workers were participated in this cross-sectional study in 2009. Samples were taken with sterile cotton swabs from both anterior nares and hands. Swabs were plated immediately on to the mannitol salt agar. Suspected colonies were confirmed as S. aureus by Gram staining, catalase, coagulase and DNase tests. Minimum inhibition concentration by micro dilution broth method was used to determine methicillin resistant strains. Antimicrobial susceptibility to other antibiotics was performed according to NCCLS guidelines by disc diffusion method.Result: Frequency of S.aureus and MRSA carriers among healthcare workers was 24% and 3% respectively. The highest rate of S. aureus and MRSA carriers were observed in operating room staff. Resistance to penicillin was seen in 97.5% of isolates and all strains were sensitive to vancomycin.Conclusions: Frequency of S. aureus and MRSA in healthcare workers was median and rather low respectively. Continual monitoring and control of carriers can reduce distribution of this organism and their infections

  5. A mutation (L1014F) in the voltage-gated sodium channel of the grain aphid, Sitobion avenae, is associated with resistance to pyrethroid insecticides.

    Science.gov (United States)

    Foster, Stephen P; Paul, Verity L; Slater, Russell; Warren, Anne; Denholm, Ian; Field, Linda M; Williamson, Martin S

    2014-08-01

    The grain aphid, Sitobion avenae Fabricius (Hemiptera: Aphididae), is an important pest of cereal crops. Pesticides are the main method for control but carry the risk of selecting for resistance. In response to reports of reduced efficacy of pyrethroid sprays applied to S. avenae, field samples were collected and screened for mutations in the voltage-gated sodium channel, the primary target site for pyrethroids. Aphid mobility and mortality to lambda-cyhalothrin were measured in coated glass vial bioassays. A single amino acid substitution (L1014F) was identified in the domain IIS6 segment of the sodium channel from the S. avenae samples exhibiting reduced pyrethroid efficacy. Bioassays on aphids heterozygous for the kdr mutation (SR) or homozygous for the wild-type allele (SS) showed that those carrying the mutation had significantly lower susceptibility to lambda-cyhalothrin. The L1014F (kdr) mutation, known to confer pyrethroid resistance in many insect pests, has been identified for the first time in S. avenae. Clonal lines heterozygous for the mutation showed 35-40-fold resistance to lambda-cyhalothrin in laboratory bioassays, consistent with the reported effect of this mutation on pyrethroid sensitivity in other aphid species. © 2013 Society of Chemical Industry.

  6. Frequency of antiseptic resistance genes in clinical staphycocci and enterococci isolates in Turkey

    Directory of Open Access Journals (Sweden)

    Seyda Ignak

    2017-08-01

    Full Text Available Abstract Background Disinfectants and antiseptics are biocides widely used in hospitals to prevent spread of pathogens. It has been reported that antiseptic resistance genes, qac’s, caused tolerance to a variety of biocidal agents, such as benzalkonium chloride (BAC and chlorhexidine digluconate (CHDG in Staphylococcus spp. isolates. We aimed to search the frequency of antiseptic resistance genes in clinical Staphylococcus spp. and Enterococcus spp. isolates to investigate the possible association with antiseptic tolerance and antibiotic resistance. Methods Antiseptic resistance genes (qacA/B, smr, qacG, qacH, and qacJ isolated from Gram-positive cocci (69 Staphylococcus spp. and 69 Enterococcus spp. were analyzed by PCR method. The minimum inhibitory concentrations (MICs of BAC and CHDG were determined by agar dilution method, whereas antibiotic susceptibility was analyzed by disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI criteria. Results The frequency of antiseptic resistance genes was found to be high (49/69; 71.0% in our clinical staphylococci isolates but absent (0/69; 0% in enterococci isolates. The frequency of qacA/B and smr genes was higher (25/40; 62.5% and 7/40; 17.5%, respectively in coagulase negative staphylococci (CNS when compared to Staphylococcus aureus strains (3/29; 10.3%, and 4/29; 13.8%, respectively. In contrast, the frequency of qacG and qacJ genes was higher (11/29; 37.9% and 8/29; 27.5%, respectively in S. aureus than those of CNS (5/40; 12.5%, 10/40; 25.0% strains. qacH was not identified in none of the strains. We found an association between presence of antiseptic resistance genes and increased MIC values of BAC (>4 μg/mL in staphylococci and it was found to be statistically statistically significant (p < 0.01. We also showed that MICs of BAC and CHDG of vancomycin-resistant enterococci (VRE isolates were significantly higher than those of vancomycin

  7. Study on Frequency Dependency of ON-Resistance and Pulse-Loss Calculation of MOSFETs for Switch Mode Power Supply

    Science.gov (United States)

    Yamamura, Hideho; Sato, Ryohei; Iwata, Yoshiharu

    Global efforts toward energy conservation, increasing data centers, and the increasing use of IT equipments are leading to a demand in reduced power consumption of equipments, and power efficiency improvement of power supply units is becoming a necessity. MOSFETs are widely used for their low ON-resistances. Power efficiency is designed using time-domain circuit simulators, except for transformer copper-loss, which has frequency dependency which is calculated separately using methods based on skin and proximity effects. As semiconductor technology reduces the ON-resistance of MOSFETs, frequency dependency due to the skin effect or proximity effect is anticipated. In this study, ON-resistance of MOSFETs are measured and frequency dependency is confirmed. Power loss against rectangular current pulse is calculated. The calculation method for transformer copper-loss is expanded to MOSFETs. A frequency function for the resistance model is newly developed and parametric calculation is enabled. Acceleration of calculation is enabled by eliminating summation terms. Using this method, it is shown that the frequency dependent component of the measured MOSFETs increases the dissipation from 11% to 32% at a switching frequency of 100kHz. From above, this paper points out the importance of the frequency dependency of MOSFETs' ON-resistance, provides means of calculating its pulse losses, and improves loss calculation accuracy of SMPSs.

  8. In-field frequencies and characteristics of oilseed rape with double herbicide resistance.

    Science.gov (United States)

    Dietz-Pfeilstetter, Antje; Zwerger, Peter

    2009-01-01

    When growing different transgenic herbicide-resistant oilseed rape cultivars side by side, seeds with multiple herbicide resistance can arise, possibly causing problems for the management of volunteer plants. Large-scale field experiments were performed in the years 1999/2000 and 2000/2001 in order to investigate the frequencies and the consequences of the transfer of herbicide resistance genes from transgenic oilseed rape to cultivars grown on neighboring agricultural fields. Transgenic oilseed rape with resistance to glufosinate-ammonium (LibertyLink, LL) and with glyphosate resistance (RoundupReady, RR), respectively, was sown in adjacent 0.5 ha plots, surrounded by about 8 ha non-transgenic oilseed rape. The plots and the field were either in direct contact (0.5 m gap width) or they were separated by 10 m of fallow land. Seed samples taken during harvest in the transgenic plots at different distances were investigated for progeny with resistance to the respective other herbicide. It was found that outcrossing frequencies were reduced to different extents by a 10 m isolation distance. In addition to pollen-mediated transgene flow as a result of outcrossing, we found considerable seed-mediated gene flow by adventitious dispersal of transgenic seeds through the harvesting machine. Volunteer plants with double herbicide resistance emerging in the transgenic plots after harvest were selected by suitable applications of the complementary herbicides Basta and Roundup Ultra. In both years, double-resistant volunteers were largely restricted to the inner edges of the plots. Expression analysis under controlled laboratory conditions of double-resistant plants generated by manual crosses revealed stability of transgene expression even at elevated temperatures. Greenhouse tests with double-resistant oilseed rape plants gave no indication that the sensitivity to a range of different herbicides is changed as compared to non-transgenic oilseed rape.

  9. Coevolution of the Ile1,016 and Cys1,534 Mutations in the Voltage Gated Sodium Channel Gene of Aedes aegypti in Mexico.

    Directory of Open Access Journals (Sweden)

    Farah Z Vera-Maloof

    2015-12-01

    ,534 haplotype was rarely detected; it reached a frequency of only 0.09 in one collection and subsequently declined.Pyrethroid resistance in the vgsc gene requires the sequential evolution of two mutations. The Ile1,016/Phe1,534 haplotype appears to have low fitness suggesting that Ile1,016 was unlikely to have evolved independently. Instead the Cys1,534 mutation evolved first but conferred only a low level of resistance. Ile1,016 in S6 of domain II then arose from the Val1,016/Cys1,534 haplotype and was rapidly selected because double mutants confer higher pyrethroid resistance. This pattern suggests that knowledge of the frequencies of mutations in both S6 in domains II and III are important to predict the potential of a population to evolve kdr. Susceptible populations with high Val1,016/Cys1,534 frequencies are at high risk for kdr evolution, whereas susceptible populations without either mutation are less likely to evolve high levels of kdr, at least over a 10 year period.

  10. Impact of PermaNet 3.0 on entomological indices in an area of pyrethroid resistant Anopheles gambiae in south-western Nigeria

    Science.gov (United States)

    2014-01-01

    Background PermaNet® 3.0 is an insecticide synergist-combination long-lasting insecticidal net designed to have increased efficacy against malaria vectors with metabolic resistance, even when combined with kdr. The current study reports on the impact of this improved tool on entomological indices in an area with pyrethroid-resistant malaria vectors in Nigeria. Methods Baseline entomological indices across eight villages in Remo North LGA of Ogun State provided the basis for selection of three villages (Ilara, Irolu and Ijesa) for comparing the efficacy of PermaNet® 3.0 (PN3.0), PermaNet® 2.0 (PN2.0) and untreated polyester nets as a control (UTC). In each case, nets were distributed to cover all sleeping spaces and were evaluated for insecticidal activity on a 3-monthly basis. Collection of mosquitoes was conducted monthly via window traps and indoor resting catches. The arithmetic means of mosquito catches per house, entomological inoculation rates before and during the intervention were compared as well as three other outcome parameters: the mean mosquito blood feeding rate, mean mortality and mean parity rates. Results Anopheles gambiae s.l. was the main malaria vector in the three villages, accounting for >98% of the Anopheles population and found in appreciable numbers for 6–7 months. Deltamethrin, permethrin and lambdacyhalothrin resistance were confirmed at Ilara, Irolu and Ijesa. The kdr mutation was the sole resistance mechanism at Ilara, whereas kdr plus P450-based metabolic mechanisms were detected at Irolu and Ijesa. Bioassays repeated on domestically used PN 2.0 and PN 3.0 showed persistent optimal (100%) bio-efficacy for both net types after the 3rd, 6th, 9th and 12th month following net distribution. The use of PN 3.0 significantly reduced mosquito densities with a ‘mass killing’ effect inside houses. Households with PN 3.0 also showed reduced blood feeding as well as lower mosquito parity and sporozoite rates compared to the PN 2.0 and the

  11. Frequency and Antibiogram of Vancomycin Resistant Enterococcus in a Tertiary Care Hospital

    International Nuclear Information System (INIS)

    Babar, N.; Usman, J.; Munir, T.; Gill, M. M.; Anjum, R.; Gilani, M.; Latif, M.

    2014-01-01

    Objective: To determine the frequency of Vancomycin Resistant Enterococcus (VRE) in a tertiary care hospital of Rawalpindi, Pakistan. Study Design: Observational, cross-sectional study. Place and Duration of Study: Department of Microbiology, Army Medical College, Rawalpindi, from May 2011 to May 2012. Methodology: Vancomycin resistant Enterococcus isolated from the clinical specimens including blood, pus, double lumen tip, ascitic fluid, tracheal aspirate, non-directed bronchial lavage (NBL), cerebrospinal fluid (CSF), high vaginal swab (HVS) and catheter tips were cultured on blood agar and MacConkey agar, while the urine samples were grown on cystine lactose electrolyte deficient agar. Later the antimicrobial susceptibility testing of the isolates was carried out using the modified Kirby-Bauer disc diffusion method on Mueller Hinton agar. Results: A total of 190 enterococci were isolated. Of these, 22 (11.57%) were found to be resistant to vancomycin. The antimicrobial sensitivity pattern revealed maximum resistance against ampicillin (86.36%) followed by erythromycin (81.81%) and gentamicin (68.18%) while all the isolates were 100% susceptible to chloramphenicol and linezolid. Conclusion: The frequency of VRE was 11.57% with the highest susceptibility to linezolid and chloramphenicol. (author)

  12. Low warfarin resistance frequency in Norway rats in two cities in China after 30 years usage of anticoagulant rodenticides.

    Science.gov (United States)

    Ma, Xiaohui; Wang, Da-Wei; Li, Ning; Liu, Lan; Tian, Lin; Luo, Chan; Cong, Lin; Feng, Zhiyong; Liu, Xiao-Hui; Song, Ying

    2018-04-17

    Anticoagulant rodenticides have been widely used in rodent control in China for over 30 years and resistant Norway rats have been reported. Mutations in the vitamin K epoxide reductase complex, subunit 1 (Vkorc1) gene can cause anticoagulant resistance in rodents. In this study, we analyzed the Vkorc1 polymorphisms of 681 Norway rats collected in Zhanjiang and Harbin City in China from 2008 to 2015 and evaluated the warfarin resistance frequency. Analysis revealed 4 mutations including 3 not previously reported. Two new synonymous mutations His68His and Leu105Leu are not associated with warfarin resistance. One new nonsynonymous mutation Ala140Thr was found in Zhanjiang rat samples collected in 3 years with low frequencies (3.3%-4.0%) and is likely associated with warfarin resistance. Laboratory resistance tests suggested low warfarin resistance frequencies in rats from Zhanjiang (4.9%-17.1%) and Harbin City (0-2.5%). Both genetic analysis and laboratory resistance tests suggested low warfarin resistance frequencies in rats from Zhanjiang and Harbin City. The alternative usage of FGARs and SGARs might represent an effective strategy against the development of warfarin resistance in Norway rats in China. This article is protected by copyright. All rights reserved.

  13. A Genetic Survey of Pyrethroid Insecticide Resistance in Aphids in New Brunswick, Canada, with Particular Emphasis on Aphids as Vectors of Potato virus Y.

    Science.gov (United States)

    MacKenzie, Tyler D B; Arju, Irin; Poirier, René; Singh, Mathuresh

    2018-05-28

    Aphids are viral vectors in potatoes, most importantly of Potato virus Y (PVY), and insecticides are frequently used to reduce viral spread during the crop season. Aphids collected from the potato belt of New Brunswick, Canada, in 2015 and 2016 were surveyed for known and novel mutations in the Na-channel (para) gene, coding for the target of synthetic pyrethroid insecticides. Specific genetic mutations known to confer resistance (kdr and skdr) were found in great abundance in Myzus persicae (Sulzer) (Hemiptera: Aphididae), which rose from 76% in 2015 to 96% in 2016. Aphids other than M. persicae showed lower frequency of resistance. In 2015, 3% of individuals contained the resistance mutation skdr, rising to 13% in 2016 (of 45 species). Several novel resistance mutations or mutations not before reported in aphids were identified in this gene target. One of these mutations, I936V, is known to confer pyrethroid resistance in another unrelated insect, and three others occur immediately adjacent and prompt similar chemical shifts in the primary protein structure, to previously characterized mutations associated with pyrethroid resistance. Most novel mutations were found in species other than M. persicae or others currently tracked individually by the provincial aphid monitoring program, which were determined by cytochrome C oxidase I (cox1) sequencing. Through our cox1 DNA barcoding survey, at least 45 species of aphids were discovered in NB potato fields in 2015 and 2016, many of which are known carriers of PVY.

  14. Widespread Pyrethroid and DDT Resistance in the Major Malaria Vector Anopheles funestus in East Africa Is Driven by Metabolic Resistance Mechanisms

    Science.gov (United States)

    Mulamba, Charles; Riveron, Jacob M.; Ibrahim, Sulaiman S.; Irving, Helen; Barnes, Kayla G.; Mukwaya, Louis G.; Birungi, Josephine; Wondji, Charles S.

    2014-01-01

    Background Establishing the extent, geographical distribution and mechanisms of insecticide resistance in malaria vectors is a prerequisite for resistance management. Here, we report a widespread distribution of insecticide resistance in the major malaria vector An. funestus across Uganda and western Kenya under the control of metabolic resistance mechanisms. Methodology/Principal Findings Female An. funestus collected throughout Uganda and western Kenya exhibited a Plasmodium infection rate between 4.2 to 10.4%. Widespread resistance against both type I (permethrin) and II (deltamethrin) pyrethroids and DDT was observed across Uganda and western Kenya. All populations remain highly susceptible to carbamate, organophosphate and dieldrin insecticides. Knockdown resistance plays no role in the pyrethroid and DDT resistance as no kdr mutation associated with resistance was detected despite the presence of a F1021C replacement. Additionally, no signature of selection was observed on the sodium channel gene. Synergist assays and qRT-PCR indicated that metabolic resistance plays a major role notably through elevated expression of cytochrome P450s. DDT resistance mechanisms differ from West Africa as the L119F-GSTe2 mutation only explains a small proportion of the genetic variance to DDT resistance. Conclusion The extensive distribution of pyrethroid and DDT resistance in East African An. funestus populations represents a challenge to the control of this vector. However, the observed carbamate and organophosphate susceptibility offers alternative solutions for resistance management. PMID:25333491

  15. High-frequency resistance training is not more effective than low-frequency resistance training in increasing muscle mass and strength in well-trained men.

    Science.gov (United States)

    Gomes, Gederson K; Franco, Cristiane M; Nunes, Paulo Ricardo P; Orsatti, Fábio L

    2018-02-27

    We studied the effects of two different weekly frequency resistance training (RT) protocols over eight weeks on muscle strength and muscle hypertrophy in well-trained men. Twenty-three subjects (age: 26.2±4.2 years; RT experience: 6.9±3.1 years) were randomly allocated into the two groups: low frequency (LFRT, n = 12) or high frequency (HFRT, n = 11). The LFRT performed a split-body routine, training each specific muscle group once a week. The HFRT performed a total-body routine, training all muscle groups every session. Both groups performed the same number of sets (10-15 sets) and exercises (1-2 exercise) per week, 8-12 repetitions maximum (70-80% of 1RM), five times per week. Muscle strength (bench press and squat 1RM) and lean tissue mass (dual-energy x-ray absorptiometry) were assessed prior to and at the end of the study. Results showed that both groups improved (ptrained subjects when the sets and intensity are equated per week.

  16. Impact of physiological variables and genetic background on myocardial frequency-resistivity relations in the intact beating murine heart.

    Science.gov (United States)

    Reyes, Maricela; Steinhelper, Mark E; Alvarez, Jorge A; Escobedo, Daniel; Pearce, John; Valvano, Jonathan W; Pollock, Brad H; Wei, Chia-Ling; Kottam, Anil; Altman, David; Bailey, Steven; Thomsen, Sharon; Lee, Shuko; Colston, James T; Oh, Jung Hwan; Freeman, Gregory L; Feldman, Marc D

    2006-10-01

    Conductance measurements for generation of an instantaneous left ventricular (LV) volume signal in the mouse are limited, because the volume signal is a combination of blood and LV muscle, and only the blood signal is desired. We have developed a conductance system that operates at two simultaneous frequencies to identify and remove the myocardial contribution to the instantaneous volume signal. This system is based on the observation that myocardial resistivity varies with frequency, whereas blood resistivity does not. For calculation of LV blood volume with the dual-frequency conductance system in mice, in vivo murine myocardial resistivity was measured and combined with an analytic approach. The goals of the present study were to identify and minimize the sources of error in the measurement of myocardial resistivity to enhance the accuracy of the dual-frequency conductance system. We extended these findings to a gene-altered mouse model to determine the impact of measured myocardial resistivity on the calculation of LV pressure-volume relations. We examined the impact of temperature, timing of the measurement during the cardiac cycle, breeding strain, anisotropy, and intrameasurement and interanimal variability on the measurement of intact murine myocardial resistivity. Applying this knowledge to diabetic and nondiabetic 11- and 20- to 24-wk-old mice, we demonstrated differences in myocardial resistivity at low frequencies, enhancement of LV systolic function at 11 wk and LV dilation at 20-24 wk, and histological and electron-microscopic studies demonstrating greater glycogen deposition in the diabetic mice. This study demonstrated the accurate technique of measuring myocardial resistivity and its impact on the determination of LV pressure-volume relations in gene-altered mice.

  17. Advancement in the Understanding of the Field and Frequency Dependent Microwave Surface Resistance of Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Martinello, M. [Fermilab; Aderhold, S. [Fermilab; Chandrasekaran, S. K. [Fermilab; Checchin, M. [Fermilab; Grassellino, A. [Fermilab; Melnychuk, O. [Fermilab; Posen, S. [Fermilab; Romanenko, A. [Fermilab; Sergatskov, D. A. [Fermilab

    2017-07-24

    The radio-frequency surface resistance of niobium resonators is incredibly reduced when nitrogen impurities are dissolved as interstitial in the material, conferring ultra-high Q-factors at medium values of accelerating field. This effect has been observed in both high and low temperature nitrogen treatments. As a matter of fact, the peculiar anti Q-slope observed in nitrogen doped cavities, i.e. the decreasing of the Q-factor with the increasing of the radio-frequency field, come from the decreasing of the BCS surface resistance component as a function of the field. Such peculiar behavior has been considered consequence of the interstitial nitrogen present in the niobium lattice after the doping treatment. The study here presented show the field dependence of the BCS surface resistance of cavities with different resonant frequencies, such as: 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 GHz, and processed with different state-of-the-art surface treatments. These findings show for the first time that the anti Q-slope might be seen at high frequency even for clean Niobium cavities, revealing useful suggestion on the physics underneath the anti Q-slope effect.

  18. Frequency, Antimicrobial Resistance and Genetic Diversity of Klebsiella pneumoniae in Food Samples.

    Directory of Open Access Journals (Sweden)

    Yumei Guo

    Full Text Available This study aimed to assess the frequency of Klebsiella pneumoniae in food samples and to detect antibiotic resistance phenotypes, antimicrobial resistance genes and the molecular subtypes of the recovered isolates. A total of 998 food samples were collected, and 99 (9.9% K. pneumoniae strains were isolated; the frequencies were 8.2% (4/49 in fresh raw seafood, 13.8% (26/188 in fresh raw chicken, 11.4% (34/297 in frozen raw food and 7.5% (35/464 in cooked food samples. Antimicrobial resistance was observed against 16 antimicrobials. The highest resistance rate was observed for ampicillin (92.3%, followed by tetracycline (31.3%, trimethoprim-sulfamethoxazole (18.2%, and chloramphenicol (10.1%. Two K. pneumoniae strains were identified as extended-spectrum β-lactamase (ESBL-one strain had three beta-lactamases genes (blaSHV, blaCTX-M-1, and blaCTX-M-10 and one had only the blaSHV gene. Nineteen multidrug-resistant (MDR strains were detected; the percentage of MDR strains in fresh raw chicken samples was significantly higher than in other sample types (P<0.05. Six of the 18 trimethoprim-sulfamethoxazole-resistant strains carried the folate pathway inhibitor gene (dhfr. Four isolates were screened by PCR for quinolone resistance genes; aac(6'-Ib-cr, qnrB, qnrA and qnrS were detected. In addition, gyrA gene mutations such as T247A (Ser83Ile, C248T (Ser83Phe, and A260C (Asp87Ala and a parC C240T (Ser80Ile mutation were identified. Five isolates were screened for aminoglycosides resistance genes; aacA4, aacC2, and aadA1 were detected. Pulsed-field gel electrophoresis-based subtyping identified 91 different patterns. Our results indicate that food, especially fresh raw chicken, is a reservoir of antimicrobial-resistant K. pneumoniae, and the potential health risks posed by such strains should not be underestimated. Our results demonstrated high prevalence, antibiotic resistance rate and genetic diversity of K. pneumoniae in food in China. Improved

  19. Impact of contact and access resistances in graphene field-effect transistors on quartz substrates for radio frequency applications

    International Nuclear Information System (INIS)

    Ramón, Michael E.; Movva, Hema C. P.; Fahad Chowdhury, Sk.; Parrish, Kristen N.; Rai, Amritesh; Akinwande, Deji; Banerjee, Sanjay K.; Magnuson, Carl W.; Ruoff, Rodney S.

    2014-01-01

    High-frequency performance of graphene field-effect transistors (GFETs) has been limited largely by parasitic resistances, including contact resistance (R C ) and access resistance (R A ). Measurement of short-channel (500 nm) GFETs with short (200 nm) spin-on-doped source/drain access regions reveals negligible change in transit frequency (f T ) after doping, as compared to ∼23% f T improvement for similarly sized undoped GFETs measured at low temperature, underscoring the impact of R C on high-frequency performance. DC measurements of undoped/doped short and long-channel GFETs highlight the increasing impact of R A for larger GFETs. Additionally, parasitic capacitances were minimized by device fabrication using graphene transferred onto low-capacitance quartz substrates

  20. Amino substituted nitrogen heterocycle ureas as kinase insert domain containing receptor (KDR inhibitors: Performance of structure–activity relationship approaches

    Directory of Open Access Journals (Sweden)

    Hayriye Yilmaz

    2015-06-01

    Full Text Available A quantitative structure–activity relationship (QSAR study was performed on a set of amino-substituted nitrogen heterocyclic urea derivatives. Two novel approaches were applied: (1 the simplified molecular input-line entry systems (SMILES based optimal descriptors approach; and (2 the fragment-based simplex representation of molecular structure (SiRMS approach. Comparison with the classic scheme of building up the model and balance of correlation (BC for optimal descriptors approach shows that the BC scheme provides more robust predictions than the classic scheme for the considered pIC50 of the heterocyclic urea derivatives. Comparison of the SMILES-based optimal descriptors and SiRMS approaches has confirmed good performance of both techniques in prediction of kinase insert domain containing receptor (KDR inhibitory activity, expressed as a logarithm of inhibitory concentration (pIC50 of studied compounds.

  1. Impact of contact and access resistances in graphene field-effect transistors on quartz substrates for radio frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Ramón, Michael E., E-mail: michael.ramon@utexas.edu, E-mail: hemacp@utexas.edu; Movva, Hema C. P., E-mail: michael.ramon@utexas.edu, E-mail: hemacp@utexas.edu; Fahad Chowdhury, Sk.; Parrish, Kristen N.; Rai, Amritesh; Akinwande, Deji; Banerjee, Sanjay K. [Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758 (United States); Magnuson, Carl W.; Ruoff, Rodney S. [Department of Mechanical Engineering and the Materials Science and Engineering Program, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2014-02-17

    High-frequency performance of graphene field-effect transistors (GFETs) has been limited largely by parasitic resistances, including contact resistance (R{sub C}) and access resistance (R{sub A}). Measurement of short-channel (500 nm) GFETs with short (200 nm) spin-on-doped source/drain access regions reveals negligible change in transit frequency (f{sub T}) after doping, as compared to ∼23% f{sub T} improvement for similarly sized undoped GFETs measured at low temperature, underscoring the impact of R{sub C} on high-frequency performance. DC measurements of undoped/doped short and long-channel GFETs highlight the increasing impact of R{sub A} for larger GFETs. Additionally, parasitic capacitances were minimized by device fabrication using graphene transferred onto low-capacitance quartz substrates.

  2. Simplified formulae for the estimation of the positive-sequence resistance and reactance of three-phase cables for different frequencies

    DEFF Research Database (Denmark)

    Silva, Filipe Miguel Faria da

    2015-01-01

    The installation of HVAC underground cables became more common in recent years, a trend expected to continue in the future. Underground cables are more complex than overhead lines and the calculation of their resistance and reactance can be challenging and time consuming for frequencies that are ......The installation of HVAC underground cables became more common in recent years, a trend expected to continue in the future. Underground cables are more complex than overhead lines and the calculation of their resistance and reactance can be challenging and time consuming for frequencies...... that are not power frequency. Software packages capable of performing exact calculations of these two parameters exist, but simple equations able to estimate the reactance and resistance of an underground cable for the frequencies associated to a transient or a resonance phenomenon would be helpful. This paper...

  3. Low and High Frequency Hippocampal Stimulation for Drug-Resistant Mesial Temporal Lobe Epilepsy.

    Science.gov (United States)

    Lim, Siew-Na; Lee, Ching-Yi; Lee, Shih-Tseng; Tu, Po-Hsun; Chang, Bao-Luen; Lee, Chih-Hong; Cheng, Mei-Yun; Chang, Chun-Wei; Tseng, Wei-En Johnny; Hsieh, Hsiang-Yao; Chiang, Hsing-I; Wu, Tony

    2016-06-01

    Electrical stimulation of the hippocampus offers the possibility to treat patients with mesial temporal lobe epilepsy (MTLE) who are not surgical candidates. We report long-term follow-up results in five patients receiving low or high frequency hippocampal stimulation for drug-resistant MTLE. The patients underwent stereotactic implantation of quadripolar stimulating electrodes in the hippocampus. Two of the patients received unilateral electrode implantation, while the other three received bilateral implantation. Stimulation of the hippocampal electrodes was turned ON immediately after the implantation of an implantable pulse generator, with initial stimulation parameters: 1 V, 90-150 μs, 5 or 145 Hz. The frequency of seizures was monitored and compared with preimplantation baseline data. Two men and three women, aged 27-61 years were studied, with a mean follow-up period of 38.4 months (range, 30-42 months). The baseline seizure frequency was 2.0-15.3/month. The five patients had an average 45% (range 22-72%) reduction in the frequency of seizures after hippocampal stimulation over the study period. Low frequency hippocampal stimulation decreased the frequency of seizures in two patients (by 54% and 72%, respectively). No implantation- or stimulation-related side effects were reported. Electrical stimulation of the hippocampus is a minimally invasive and reversible method that can improve seizure outcomes in patients with drug-resistant MTLE. The optimal frequency of stimulation varied from patient to patient and therefore required individual setting. These experimental results warrant further controlled studies with a large patient population to evaluate the long-term effect of hippocampal stimulation with different stimulation parameters. © 2016 The Authors. Neuromodulation: Technology at the Neural Interface published by Wiley Periodicals, Inc. on behalf of International Neuromodulation Society.

  4. An ultrathin wide-band planar metamaterial absorber based on a fractal frequency selective surface and resistive film

    International Nuclear Information System (INIS)

    Fan Yue-Nong; Cheng Yong-Zhi; Nie Yan; Wang Xian; Gong Rong-Zhou

    2013-01-01

    We propose an ultrathin wide-band metamaterial absorber (MA) based on a Minkowski (MIK) fractal frequency selective surface and resistive film. This absorber consists of a periodic arrangement of dielectric substrates sandwiched with an MIK fractal loop structure electric resonator and a resistive film. The finite element method is used to simulate and analyze the absorption of the MA. Compared with the MA-backed copper film, the designed MA-backed resistive film exhibits an absorption of 90% at a frequency region of 2 GHz–20 GHz. The power loss density distribution of the MA is further illustrated to explain the mechanism of the proposed MA. Simulated absorptions at different incidence cases indicate that this absorber is polarization-insensitive and wide-angled. Finally, further simulated results indicate that the surface resistance of the resistive film and the dielectric constant of the substrate can affect the absorbing property of the MA. This absorber may be used in many military fields

  5. ASSESSMENT OF CERAMIC TILE FROST RESISTANCE BY MEANS OF THE FREQUENCY INSPECTION METHOD

    Directory of Open Access Journals (Sweden)

    MICHAL MATYSÍK

    2011-06-01

    Full Text Available The paper presents some results of our experimental analysis of ceramic cladding element frost resistance, particular attention being paid to the application of the frequency inspection method. Three different sets of ceramic tiles of the Ia class to EN 14 411 B standard made by various manufacturers have been analyzed. The ceramic tiles under investigation have been subjected to freeze-thaw-cycle-based degradation in compliance with the relevant ČSN EN ISO 10545-12 standard. Furthermore, accelerated degradation procedure has been applied to selected test specimens, consisting in reducing the temperature of water soaked ceramic tiles in the course of the degradation cycles down –70°C. To verify the correctness of the frequency inspection results, additional physical properties of the ceramic tiles under test have been measured, such as, the ceramic tile strength limit, modulus of elasticity and modulus of deformability, resulting from the flexural tensile strength tests, integrity defect and surface micro-geometry tracking. It has been proved that the acoustic method of frequency inspection is a sensitive indicator of the structure condition and can be applied to the ceramic cladding element frost resistance and service life prediction assessment.

  6. Aedes aegypti resistance development to commonly used insecticides in Jakarta, Indonesia.

    Directory of Open Access Journals (Sweden)

    Penny Humaidah Hamid

    Full Text Available Aedes aegypti is the primary vector of various relevant arthropod-borne viral infectious diseases worldwide. The mosquito control is still mainly performed by using insecticides but their effectiveness is increasingly questioned nowadays. We here conducted a study on Ae. aegypti resistance development towards several commonly used insecticides in the capital city of Jakarta, Indonesia. In order to achieve this goal, Ae. aegypti eggs from Jakarta were collected with ovitraps and hatched in the insectary of the Gadjah Mada University, Indonesia. The F0 generations were used for WHO resistance tests and knockdown resistance (kdr assays. Presented results clearly showed that there was resistance development of Ae. aegypti populations to the here tested pyrethroid insecticides (i. e. permethrin. Observed mortalities were less than 90% with highest resistance against 0.75% permethrin concentrations. Furthermore, a significant association of V1016G gene mutations with resistance phenotypes to 0.75% permethrin was observed. Nevertheless, the F1534C mutation did not show a significant correlation to resistance development. In conclusion, our results show that populations of Ae. aegypti mosquitoes within the city of Jakarta have developed resistance against several routinely used pyrethroid insecticides in local performed control programs. Thus, the regular verification/assessment of resistance development status will hopefully help in the future to assist local public health authorities in their mosquito control programs by recommending and managing the rotation of different routinely used insecticides with diverse effector mechanisms in order to delay Ae. aegypti resistance development.

  7. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Science.gov (United States)

    Dhakal, Pashupati; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2017-03-01

    Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF) cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q0(Bp) curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q0(Bp) .

  8. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Directory of Open Access Journals (Sweden)

    Pashupati Dhakal

    2017-03-01

    Full Text Available Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q_{0}(B_{p} curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q_{0}(B_{p}.

  9. Exploring the molecular basis of insecticide resistance in the dengue vector Aedes aegypti: a case study in Martinique Island (French West Indies).

    Science.gov (United States)

    Marcombe, Sébastien; Poupardin, Rodolphe; Darriet, Frederic; Reynaud, Stéphane; Bonnet, Julien; Strode, Clare; Brengues, Cecile; Yébakima, André; Ranson, Hilary; Corbel, Vincent; David, Jean-Philippe

    2009-10-26

    The yellow fever mosquito Aedes aegypti is a major vector of dengue and hemorrhagic fevers, causing up to 100 million dengue infections every year. As there is still no medicine and efficient vaccine available, vector control largely based on insecticide treatments remains the only method to reduce dengue virus transmission. Unfortunately, vector control programs are facing operational challenges with mosquitoes becoming resistant to commonly used insecticides. Resistance of Ae. aegypti to chemical insecticides has been reported worldwide and the underlying molecular mechanisms, including the identification of enzymes involved in insecticide detoxification are not completely understood. The present paper investigates the molecular basis of insecticide resistance in a population of Ae. aegypti collected in Martinique (French West Indies). Bioassays with insecticides on adults and larvae revealed high levels of resistance to organophosphate and pyrethroid insecticides. Molecular screening for common insecticide target-site mutations showed a high frequency (71%) of the sodium channel 'knock down resistance' (kdr) mutation. Exposing mosquitoes to detoxification enzymes inhibitors prior to bioassays induced a significant increased susceptibility of mosquitoes to insecticides, revealing the presence of metabolic-based resistance mechanisms. This trend was biochemically confirmed by significant elevated activities of cytochrome P450 monooxygenases, glutathione S-transferases and carboxylesterases at both larval and adult stages. Utilization of the microarray Aedes Detox Chip containing probes for all members of detoxification and other insecticide resistance-related enzymes revealed the significant constitutive over-transcription of multiple detoxification genes at both larval and adult stages. The over-transcription of detoxification genes in the resistant strain was confirmed by using real-time quantitative RT-PCR. These results suggest that the high level of

  10. Country-level operational implementation of the Global Plan for Insecticide Resistance Management.

    Science.gov (United States)

    Hemingway, Janet; Vontas, John; Poupardin, Rodolphe; Raman, Jaishree; Lines, Jo; Schwabe, Chris; Matias, Abrahan; Kleinschmidt, Immo

    2013-06-04

    Malaria control is reliant on the use of long-lasting pyrethroid-impregnated nets and/or indoor residual spraying (IRS) of insecticide. The rapid selection and spread of operationally significant pyrethroid resistance in African malaria vectors threatens our ability to sustain malaria control. Establishing whether resistance is operationally significant is technically challenging. Routine monitoring by bioassay is inadequate, and there are limited data linking resistance selection with changes in disease transmission. The default is to switch insecticides when resistance is detected, but limited insecticide options and resistance to multiple insecticides in numerous locations make this approach unsustainable. Detailed analysis of the resistance situation in Anopheles gambiae on Bioko Island after pyrethroid resistance was detected in this species in 2004, and the IRS program switched to carbamate bendiocarb, has now been undertaken. The pyrethroid resistance selected is a target-site knock-down resistance kdr-form, on a background of generally elevated metabolic activity, compared with insecticide-susceptible A. gambiae, but the major cytochrome P450-based metabolic pyrethroid resistance mechanisms are not present. The available evidence from bioassays and infection data suggests that the pyrethroid resistance mechanisms in Bioko malaria vectors are not operationally significant, and on this basis, a different, long-lasting pyrethroid formulation is now being reintroduced for IRS in a rotational insecticide resistance management program. This will allow control efforts to be sustained in a cost-effective manner while reducing the selection pressure for resistance to nonpyrethroid insecticides. The methods used provide a template for evidence-based insecticide resistance management by malaria control programs.

  11. The frequency of resistance to antibiotics of most frequently isolated bacteria from blood cultures during the period 1997-2002

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    Mirović Veljko

    2004-01-01

    Full Text Available The aim of this study was to determine the frequency of resistance to antibiotics of the most frequently isolated bacteria from blood cultures of hospitalized patients during the period 1997-2002. The resistance to antibiotics was determined by disk diffusion method according to National Committee for Clinical Laboratory Standards procedures. The majority of staphylococci isolates were resistant to methicillin, and the proportion of methicillin-resistant Staphylococcus aureus was stable (76.8-81.6%, during the follow-up period. None of the staphylococci isolates were resistant to vancomycin, but there was a very high incidence of high-level resistance of enterococci to aminoglycosides (47.2-72.2%. In 1998, only one strain among enterococci was resistant to vancomycin (Enterococcus faecium, VanA fenotype. Enterococcus spp isolates expressed variable frequency of resistance to ampicillin (15-40.1% during the follow-up period. Among Enterobacteriaceae there were no isolates resistant to imipenem, but dramatic increase of the resistance to ceftriaxone was found from 35.9% in 1997 to 95.9% in 2002 (p<0.001. Extended spectrum beta-lactamases production was found in all the species of enterobacteria isolates. Resistance to imipenem was observed in Acinetobacter spp isolates in 2002 for the first time. Pseudomonas spp isolates expressed high and very variable resistance to all antibiotics tested during the follow-up period.

  12. Analysis of frequency-dependent series resistance and interface states of In/SiO{sub 2}/p-Si (MIS) structures

    Energy Technology Data Exchange (ETDEWEB)

    Birkan Selcuk, A. [Department of Nuclear Electronics and Instrumentation, Saraykoey Nuclear Research and Training Center, 06983 Saray, Ankara (Turkey); Tugluoglu, N. [Department of Nuclear Electronics and Instrumentation, Saraykoey Nuclear Research and Training Center, 06983 Saray, Ankara (Turkey)], E-mail: ntuglu@taek.gov.tr; Karadeniz, S.; Bilge Ocak, S. [Department of Nuclear Electronics and Instrumentation, Saraykoey Nuclear Research and Training Center, 06983 Saray, Ankara (Turkey)

    2007-11-15

    In this work, the investigation of the interface state density and series resistance from capacitance-voltage (C-V) and conductance-voltage (G/{omega}-V) characteristics in In/SiO{sub 2}/p-Si metal-insulator-semiconductor (MIS) structures with thin interfacial insulator layer have been reported. The thickness of SiO{sub 2} film obtained from the measurement of the oxide capacitance corrected for series resistance in the strong accumulation region is 220 A. The forward and reverse bias C-V and G/{omega}-V characteristics of MIS structures have been studied at the frequency range 30 kHz-1 MHz at room temperature. The frequency dispersion in capacitance and conductance can be interpreted in terms of the series resistance (R{sub s}) and interface state density (D{sub it}) values. Both the series resistance R{sub s} and density of interface states D{sub it} are strongly frequency-dependent and decrease with increasing frequency. The distribution profile of R{sub s}-V gives a peak at low frequencies in the depletion region and disappears with increasing frequency. Experimental results show that the interfacial polarization contributes to the improvement of the dielectric properties of In/SiO{sub 2}/p-Si MIS structures. The interface state density value of In/SiO{sub 2}/p-Si MIS diode calculated at strong accumulation region is 1.11x10{sup 12} eV{sup -1} cm{sup -2} at 1 MHz. It is found that the calculated value of D{sub it} ({approx}10{sup 12} eV{sup -1} cm{sup -2}) is not high enough to pin the Fermi level of the Si substrate disrupting the device operation.

  13. Insecticide resistance status of three malaria vectors, Anopheles gambiae (s.l.), An. funestus and An. mascarensis, from the south, central and east coasts of Madagascar.

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    Rakotoson, Jean-Desire; Fornadel, Christen M; Belemvire, Allison; Norris, Laura C; George, Kristen; Caranci, Angela; Lucas, Bradford; Dengela, Dereje

    2017-08-23

    Insecticide-based vector control, which comprises use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS), is the key method to malaria control in Madagascar. However, its effectiveness is threatened as vectors become resistant to insecticides. This study investigated the resistance status of malaria vectors in Madagascar to various insecticides recommended for use in ITNs and/or IRS. WHO tube and CDC bottle bioassays were performed on populations of Anopheles gambiae (s.l.), An. funestus and An. mascarensis. Adult female An. gambiae (s.l.) mosquitoes reared from field-collected larvae and pupae were tested for their resistance to DDT, permethrin, deltamethrin, alpha-cypermethrin, lambda-cyhalothrin, bendiocarb and pirimiphos-methyl. Resting An. funestus and An. mascarensis female mosquitoes collected from unsprayed surfaces were tested against permethrin, deltamethrin and pirimiphos-methyl. The effect on insecticide resistance of pre-exposure to the synergists piperonyl-butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) also was assessed. Molecular analyses were done to identify species and determine the presence of knock-down resistance (kdr) and acetylcholinesterase resistance (ace-1 R ) gene mutations. Anopheles funestus and An. mascarensis were fully susceptible to permethrin, deltamethrin and pirimiphos-methyl. Anopheles gambiae (s.l.) was fully susceptible to bendiocarb and pirimiphos-methyl. Among the 17 An. gambiae (s.l.) populations tested for deltamethrin, no confirmed resistance was recorded, but suspected resistance was observed in two sites. Anopheles gambiae (s.l.) was resistant to permethrin in four out of 18 sites (mortality 68-89%) and to alpha-cypermethrin (89% mortality) and lambda-cyhalothrin (80% and 85%) in one of 17 sites, using one or both assay methods. Pre-exposure to PBO restored full susceptibility to all pyrethroids tested except in one site where only partial restoration to permethrin was observed. DEF

  14. Host population structure and treatment frequency maintain balancing selection on drug resistance

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    Baskerville, Edward B.; Colijn, Caroline; Hanage, William; Fraser, Christophe; Lipsitch, Marc

    2017-01-01

    It is a truism that antimicrobial drugs select for resistance, but explaining pathogen- and population-specific variation in patterns of resistance remains an open problem. Like other common commensals, Streptococcus pneumoniae has demonstrated persistent coexistence of drug-sensitive and drug-resistant strains. Theoretically, this outcome is unlikely. We modelled the dynamics of competing strains of S. pneumoniae to investigate the impact of transmission dynamics and treatment-induced selective pressures on the probability of stable coexistence. We find that the outcome of competition is extremely sensitive to structure in the host population, although coexistence can arise from age-assortative transmission models with age-varying rates of antibiotic use. Moreover, we find that the selective pressure from antibiotics arises not so much from the rate of antibiotic use per se but from the frequency of treatment: frequent antibiotic therapy disproportionately impacts the fitness of sensitive strains. This same phenomenon explains why serotypes with longer durations of carriage tend to be more resistant. These dynamics may apply to other potentially pathogenic, microbial commensals and highlight how population structure, which is often omitted from models, can have a large impact. PMID:28835542

  15. Frequency of serovars and antimicrobial resistance in Shigella spp. from Brazil

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    Gisele Peirano

    2006-05-01

    Full Text Available A total of 296 Shigella spp. were received from State Public Health Laboratories, during the period from 1999 to 2004, by National Reference Laboratory for Cholera and Enteric Diseases (NRLCED - IOC/Fiocruz, Rio de Janeiro, Brazil. The frequency of Shigella spp. was: S. flexneri (52.7%, S. sonnei (44.2%, S. boydii (2.3%, and S. dysenteriae (0.6%. The most frequent S. flexneri serovars were 2a and 1b. The highest incidence rates of Shigella isolation were observed in the Southeast (39% and Northeast (34% regions and the lowest rate in the South (3% of Brazil. Strains were further analyzed for antimicrobial susceptibility by disk diffusion method as part of a surveillance program on antimicrobial resistance. The highest rates of antimicrobial resistance were to trimethoprim-sulfamethozaxole (90%, tetracycline (88%, ampicillin (56%, and chloramphenicol (35%. The patterns of antimicrobial resistance among Shigella isolates pose a major difficulty in the determination of an appropriate drug for shigellosis treatment. Continuous monitoring of antimicrobial susceptibilities of Shigella spp. through a surveillance system is thus essential for effective therapy and control measures against shigellosis.

  16. Frequency of resistance to methicillin and other antimicrobial agents among Staphylococcus aureus strains isolated from pigs and their human handlers in Trinidad

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    Annika Gordon

    2014-04-01

    Full Text Available Background: Methicillin-resistant Staphylococcus aureus (MRSA has emerged recently worldwide in production animals, particularly pigs and veal calves, which act as reservoirs for MRSA strains for human infection. The study determined the prevalence of MRSA and other resistant strains of S. aureus isolated from the anterior nares of pigs and human handlers on pig farms in Trinidad. Methods: Isolation of S. aureus was done by concurrently inoculating Baird-Parker agar (BPA and Chromagar MRSA (CHROM with swab samples and isolates were identified using standard methods. Suspect MRSA isolates from Chromagar and BPA were subjected to confirmatory test using Oxoid PBP2 latex agglutination test. The disc diffusion method was used to determine resistance to antimicrobial agents. Results: The frequency of isolation of MRSA was 2.1% (15 of 723 for pigs but 0.0% (0 of 72 for humans. Generally, for isolates of S. aureus from humans there was a high frequency of resistance compared with those from pigs, which had moderate resistance to the following antimicrobials: penicillin G (54.5%, 51.5%, ampicillin (59.1%, 49.5%, and streptomycin (59.1%, 37.1%, respectively. There was moderate resistance to tetracycline (36.4%, 41.2% and gentamycin (27.2%, 23.7% for human and pig S. aureus isolates, respectively, and low resistance to sulfamethoxazole-trimethoprim (4.5%, 6.2% and norfloxacin (9.1%, 12.4%, respectively. The frequency of resistance to oxacillin by the disc method was 36.4 and 34.0% from S. aureus isolates from humans and pigs, respectively. Out of a total of 78 isolates of S. aureus from both human and pig sources that were resistant to oxacillin by the disc diffusion method, only 15 (19.2% were confirmed as MRSA by the PBP'2 latex test kit. Conclusions: The detection of MRSA strains in pigs, albeit at a low frequency, coupled with a high frequency of resistance to commonly used antimicrobial agents in pig and humans could have zoonotic and therapeutic

  17. Efficacy of mosquito nets treated with a pyrethroid-organophosphorous mixture against Kdr- and Kdr+ malaria vectors (Anopheles gambiae

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    Darriet F.

    2003-12-01

    Full Text Available In order to prevent the resistance of Anopheles gambiae s.l. to pyrethroids from spreading too quickly and to lengthen the effectiveness of insecticide impregnated mosquito nets, it has recently been suggested to use mixtures of insecticides that have different modes of action. This study presents the results obtained with tulle mosquito nets treated with bifenthrin (a pyrethroid] and chlorpyrifos-methyl (an organophosphorous both separately and in mixture on two strains of An. gambiae, one sensitive to all insecticides, and the other resistant to pyrethroids. The values of KDt50 and KDt95 and the mortality induced with the mixture of bifenthrin (25 mg/m2 and chlorpyrifos-methyl (4.5 mg/m2 show a significant synergistic effect on the strain of An. gambiae susceptible to insecticides. However, the tested combination does not induce any synergistic effect on the VKPR strain selected with permethrin, but only enhances the effectiveness of the two insecticides taken separately.

  18. Aedes aegypti on Madeira Island (Portugal): genetic variation of a recently introduced dengue vector.

    Science.gov (United States)

    Seixas, Gonçalo; Salgueiro, Patrícia; Silva, Ana Clara; Campos, Melina; Spenassatto, Carine; Reyes-Lugo, Matías; Novo, Maria Teresa; Ribolla, Paulo Eduardo Martins; Silva Pinto, João Pedro Soares da; Sousa, Carla Alexandra

    2013-01-01

    The increasing population of Aedes aegypti mosquitoes on Madeira Island (Portugal) resulted in the first autochthonous dengue outbreak, which occurred in October 2012. Our study establishes the first genetic evaluation based on the mitochondrial DNA (mtDNA) genes [cytochrome oxidase subunit I (COI) and NADH dehydrogenase subunit 4 (ND4)] and knockdown resistance (kdr) mutations exploring the colonisation history and the genetic diversity of this insular vector population. We included mosquito populations from Brazil and Venezuela in the analysis as putative geographic sources. The Ae. aegypti population from Madeira showed extremely low mtDNA genetic variability, with a single haplotype for COI and ND4. We also detected the presence of two important kdr mutations and the quasi-fixation of one of these mutations (F1534C). These results are consistent with a unique recent founder event that occurred on the island of Ae. aegypti mosquitoes that carry kdr mutations associated with insecticide resistance. Finally, we also report the presence of the F1534C kdr mutation in the Brazil and Venezuela populations. To our knowledge, this is the first time this mutation has been found in South American Ae. aegypti mosquitoes. Given the present risk of Ae. aegypti re-invading continental Europe from Madeira and the recent dengue outbreaks on the island, this information is important to plan surveillance and control measures.

  19. Prion protein genotype survey confirms low frequency of scrapie-resistant K222 allele in British goat herds.

    Science.gov (United States)

    Goldmann, W; Marier, E; Stewart, P; Konold, T; Street, S; Langeveld, J; Windl, O; Ortiz-Pelaez, A

    2016-02-13

    Scrapie in goats is a transmissible, fatal prion disease, which is endemic in the British goat population. The recent success in defining caprine PRNP gene variants that provide resistance to experimental and natural classical scrapie has prompted the authors to conduct a survey of PRNP genotypes in 10 goat breeds and 52 herds to find goats with the resistant K222 allele. They report here the frequencies in 1236 tested animals of the resistance-associated K222 and several other alleles by breed and herd. Eight animals were found to be heterozygous QK222 goats (0.64 per cent genotype frequency, 95 per cent CI 0.28 to 1.27 per cent) but no homozygous KK222 goats were detected. The K222 allele was found in Saanen, Toggenburg and Anglo-Nubian goats. The fact that only a few goats with the K222 allele have been identified does not preclude the possibility to design and implement successful breeding programmes at national level. British Veterinary Association.

  20. Experimental Determination of Effect of Variable Resistance on Lead ZirconateTitanate (PZT-5A4Eunder various Thermal and Frequency Conditions

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    Hassan Elahi

    2014-12-01

    Full Text Available A specially designed apparatus and circuit working on the principle of inverse piezoelectricity due to the effect of polarization was used to find the relationship between resistance and peak to peak voltage of Lead Zirconate Titanate (PZT-5A4E by shocking it at variable frequencies and at variable resistances under various thermal conditions within Curie temperature limit using equivalent circuit method. It was found that by increasing temperature, peak to peak voltage increases and similarly by increasing frequency, peak to peak voltage decreases and with the increase in resistance peak to peak voltage decreases.

  1. Pseudomonas aeruginosa: freqüência de resistência a múltiplos fármacos e resistência cruzada entre antimicrobianos no Recife/PE Pseudomonas aeruginosa: frequency of resistance to multiple drugs and cross-resistance between antimicrobials in Recife/PE

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    Eduardo Andrada Pessoa de Figueiredo

    2007-12-01

    OBJECTIVES: The frequency of multiple-antibiotic resistant bacteria has been increasing in recent years. Among the gram-negative bacteria Pseudomonas aeruginosa (P. aeruginosa shows a great propensity for the development of multidrug resistance mechanisms. The objective of this study was to identify the profile of susceptibility to antibiotics, the frequency of multidrug resistance and the cross-resistance between drugs of P. aeruginosa strains in two tertiary hospitals in Recife, Pernambuco. METHODS: The study was carried out between September 2004 and January 2006. The antimicrobial susceptibility testing was performed in 304 strains of P. aeruginosa by the disc diffusion method in accordance with National Committee for Clinical and Laboratory Standards (NCCLS guidelines. RESULTS: The most frequent materials were urine (26.7% and respiratory tract secretion (26.1% The antibiotics tested and their respective susceptibilities were as follows: piperacillin-tazobactam (66.2%; aztreonam (59.8%; amikacin (59.4%; meropenem (58.2%; imipenem (57.7%; ciprofloxacin (49.7%; gentamicin and cefepime (48.6%; ceftazidime (30% and cefotaxime (6.8%. A high prevalence of multi-resistance was detected. Half (49.7% the strains showed resistance to three or more antibiotics and 28% were resistant to six antimicrobials or more. Also, cross-resistance between the beta-lactams (carbapenems and piperacilin/tazobactam and aminoglicosides and quinolones was between 22.9% and 38.1%. These drugs are commonly combined in the treatment of severe infections caused by Pseudomonas, which reflects the difficulty in choosing the appropriate option for combination therapy. CONCLUSIONS: The frequency of multidrug-resistant strains of P. aeruginosa in this study was similar to other hospitals in Brazil and higher than in other countries. In order to reduce the frequency of these multiresistant clones, epidemiologic surveillance and the rational use of antibiotic protocols need to be urgently implemented.

  2. Expression of the cytochrome P450s, CYP6P3 and CYP6M2 are significantly elevated in multiple pyrethroid resistant populations of Anopheles gambiae s.s. from Southern Benin and Nigeria

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    Ranson Hilary

    2008-11-01

    Full Text Available Abstract Background Insecticide resistance in Anopheles mosquitoes is threatening the success of malaria control programmes. This is particularly true in Benin where pyrethroid resistance has been linked to the failure of insecticide treated bed nets. The role of mutations in the insecticide target sites in conferring resistance has been clearly established. In this study, the contribution of other potential resistance mechanisms was investigated in Anopheles gambiae s.s. from a number of localities in Southern Benin and Nigeria. The mosquitoes were sampled from a variety of breeding sites in a preliminary attempt to investigate the role of contamination of mosquito breeding sites in selecting for resistance in adult mosquitoes. Results All mosquitoes sampled belonged to the M form of An. gambiae s.s. There were high levels of permethrin resistance in an agricultural area (Akron and an urban area (Gbedjromede, low levels of resistance in mosquito samples from an oil contaminated site (Ojoo and complete susceptibility in the rural Orogun location. The target site mutation kdrW was detected at high levels in two of the populations (Akron f = 0.86 and Gbedjromede f = 0.84 but was not detected in Ojoo or Orogun. Microarray analysis using the Anopheles gambiae detox chip identified two P450s, CYP6P3 and CYP6M2 up regulated in all three populations, the former was expressed at particularly high levels in the Akron (12.4-fold and Ojoo (7.4-fold populations compared to the susceptible population. Additional detoxification and redox genes were also over expressed in one or more populations including two cuticular pre-cursor genes which were elevated in two of the three resistant populations. Conclusion Multiple resistance mechanisms incurred in the different breeding sites contribute to resistance to permethrin in Benin. The cytochrome P450 genes, CYP6P3 and CYP6M2 are upregulated in all three resistant populations analysed. Several additional potential

  3. Microbial resistance and frequency of extended-spectrum beta-lactamase (ESBL in isolated from blood cultures

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    Ruan Carlos Gomes da Silva

    2014-12-01

    Full Text Available Introduction:The emergence and spread of isolated carriers of extended-spectrum beta-lactamase (ESBL have complicated the treatment of nosocomial infections, since its production is not easily identified by the sensitivity tests, routinely performed in clinical laboratories, leading to difficulties in the hospital control of resistant microorganisms and antibiotics misuse.Objective:The objective of this study was to analyze the resistance profile and the frequency of ESBL in Gram-negative bacteria isolated from blood cultures. A hundred bacterial samples from blood cultures of adult patients were analyzed, which were phenotypically identified by biochemical tests of carbohydrates fermentation and submitted to determination of the resistance profile by disc diffusion test and ESBL screening by disc approximation and disc replacement methods.Results:Among the bacterial samples tested, 30 were identified as Gram-negative bacteria, predominantly by Proteus mirabilis, Pantoea agglomerans, and Escherichia coli. Of these, 73.33% were positive for the detection of ESBL by phenotypic tests, and was found mainly in Pantoea agglomerans, Proteus mirabilis, and Enterobacter cloacae.Conclusion:The increase in the occurrence of ESBL in different Enterobacteriaceae shows the importance of the amplification of detection in other species than Escherichia coli or Klebsiella sp., so that the assistance to the patient is not restrained, since these resistant bacteria cannot be detected by the laboratories. Considering the frequency of ESBL in this study, we highlight the importance of its detection, aiming to its contribution to the development of improvements in the health care policies of hospitals.

  4. Exploring the molecular basis of insecticide resistance in the dengue vector Aedes aegypti: a case study in Martinique Island (French West Indies

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    Yébakima André

    2009-10-01

    Full Text Available Abstract Background The yellow fever mosquito Aedes aegypti is a major vector of dengue and hemorrhagic fevers, causing up to 100 million dengue infections every year. As there is still no medicine and efficient vaccine available, vector control largely based on insecticide treatments remains the only method to reduce dengue virus transmission. Unfortunately, vector control programs are facing operational challenges with mosquitoes becoming resistant to commonly used insecticides. Resistance of Ae. aegypti to chemical insecticides has been reported worldwide and the underlying molecular mechanisms, including the identification of enzymes involved in insecticide detoxification are not completely understood. Results The present paper investigates the molecular basis of insecticide resistance in a population of Ae. aegypti collected in Martinique (French West Indies. Bioassays with insecticides on adults and larvae revealed high levels of resistance to organophosphate and pyrethroid insecticides. Molecular screening for common insecticide target-site mutations showed a high frequency (71% of the sodium channel 'knock down resistance' (kdr mutation. Exposing mosquitoes to detoxification enzymes inhibitors prior to bioassays induced a significant increased susceptibility of mosquitoes to insecticides, revealing the presence of metabolic-based resistance mechanisms. This trend was biochemically confirmed by significant elevated activities of cytochrome P450 monooxygenases, glutathione S-transferases and carboxylesterases at both larval and adult stages. Utilization of the microarray Aedes Detox Chip containing probes for all members of detoxification and other insecticide resistance-related enzymes revealed the significant constitutive over-transcription of multiple detoxification genes at both larval and adult stages. The over-transcription of detoxification genes in the resistant strain was confirmed by using real-time quantitative RT

  5. On the profile of frequency and voltage dependent interface states and series resistance in MIS structures

    Energy Technology Data Exchange (ETDEWEB)

    Doekme, Ilbilge [Science Education Department, Faculty of Kirsehir Education, Gazi University, Kirsehir (Turkey)]. E-mail: ilbilgedokme@gazi.edu.tr; Altindal, Semsettin [Physics Department, Faculty of Arts and Sciences, Gazi University, 06500, Teknikokullar, Ankara (Turkey)

    2007-04-30

    The variation in the capacitance-voltage (C-V) and conductance-voltage (G/{omega}-V) characteristics of Au/SiO{sub 2}/n-Si metal-insulator-semiconductor (MIS) structure have been systematically investigated as a function of frequencies in the frequency range 0.5 kHz-10 MHz at room temperature. In addition, the forward and reverse bias current-voltage (I-V) characteristics of this structure were measured at room temperature. The high value of ideality factor was attributed to the high density of interface states localized at Si/SiO{sub 2} interface and interfacial oxide layer. The density of interface states (N{sub ss}) and the series resistance (R{sub ss}) were calculated from I-V and C-V measurements using different methods and the effect of them on C-V and G/{omega}-V characteristics were deeply researched. At the same energy position near the top of valance band, the calculated N{sub ss} values, obtained without taking into account the series resistance of the devices almost one order of magnitude larger than N{sub ss} values obtained by taking into account R{sub ss} values. It is found that the C-V and G/{omega}-V curves exhibit a peak at low frequencies and the peak values of C and G/{omega} decrease with increasing frequency. Also, the plots of R {sub s} as a function of bias give two peaks in the certain voltage range at low frequencies. These observations indicate that at low frequencies, the charges at interface states can easily follow an AC signal and the number of them increases with decreasing frequency. The I-V, C-V and G/{omega}-V characteristics of the MIS structure are affected not only with R {sub s} but also N {sub ss}. Experimental results show that both the R{sub s} and C{sub o} values should be taken into account in determining frequency-dependent electrical characteristics.

  6. Pyrethroid resistance in an Anopheles funestus population from Uganda.

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    John C Morgan

    2010-07-01

    Full Text Available The susceptibility status of Anopheles funestus to insecticides remains largely unknown in most parts of Africa because of the difficulty in rearing field-caught mosquitoes of this malaria vector. Here we report the susceptibility status of the An. funestus population from Tororo district in Uganda and a preliminary characterisation of the putative resistance mechanisms involved.A new forced egg laying technique used in this study significantly increased the numbers of field-caught females laying eggs and generated more than 4000 F1 adults. WHO bioassays indicated that An. funestus in Tororo is resistant to pyrethroids (62% mortality after 1 h exposure to 0.75% permethrin and 28% mortality to 0.05% deltamethrin. Suspected DDT resistance was also observed with 82% mortality. However this population is fully susceptible to bendiocarb (carbamate, malathion (organophosphate and dieldrin with 100% mortality observed after exposure to each of these insecticides. Sequencing of a fragment of the sodium channel gene containing the 1014 codon conferring pyrethroid/DDT resistance in An. gambiae did not detect the L1014F kdr mutation but a correlation between haplotypes and resistance phenotype was observed indicating that mutations in other exons may be conferring the knockdown resistance in this species. Biochemical assays suggest that resistance in this population is mediated by metabolic resistance with elevated level of GSTs, P450s and pNPA compared to a susceptible strain of Anopheles gambiae. RT-PCR further confirmed the involvement of P450s with a 12-fold over-expression of CYP6P9b in the Tororo population compared to the fully susceptible laboratory colony FANG.This study represents the first report of pyrethroid/DDT resistance in An. funestus from East Africa. With resistance already reported in southern and West Africa, this indicates that resistance in An. funestus may be more widespread than previously assumed and therefore this should be taken

  7. Feeding frequency affects stress, innate immunity and disease resistance of juvenile blunt snout bream Megalobrama amblycephala.

    Science.gov (United States)

    Li, Xiang-Fei; Tian, Hong-Yan; Zhang, Ding-Dong; Jiang, Guang-Zhen; Liu, Wen-Bin

    2014-05-01

    This study aimed to evaluate the effects of feeding frequency on stress, innate immunity and disease resistance of juvenile blunt snout bream Megalobrama amblycephala (average weight: 9.92 ± 0.06 g). Fish were randomly assigned to one of six feeding frequencies (1, 2, 3, 4, 5 and 6 times/day) following the same ration size for 8 weeks. After the feeding trial, fish were challenged by Aeromonas hydrophila and cumulative mortality was recorded for the next 10 days. Daily gain index of fish fed 3-5 times/day was significantly higher than that of the other groups. High feeding frequencies induced significantly elevated plasma levels of both cortisol and lactate. Fish fed 3-4 times/day exhibited relatively low liver catalase and glutathione peroxidase activities as well as malondialdehyde contents, but obtained significantly higher reduced glutathione levels and post-challenged haemato-immunological parameters (include blood leukocyte and erythrocyte counts as well as plasma lysozyme, alternative complement, acid phosphatase and myeloperoxidase activities) compared with that of the other groups. After challenge, the lowest mortality was observed in fish fed 4 times/day. It was significantly lower than that of fish fed 1-3 times/day, but exhibited no statistical difference with that of the other groups. In conclusion, both low and high feeding frequencies could cause oxidative stress of juvenile M. amblycephala, as might consequently lead to the depressed immunity and reduced resistance to A. hydrophila infection. The optimal feeding frequency to enhance growth and boost immunity of this species at juvenile stage is 4 times/day. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Two-frequency method for measuring Hall emf in high-resistive materials with charge-carrier low mobility

    International Nuclear Information System (INIS)

    Aleksandrov, A.L.; Vedeneev, A.S.; Gulyaev, I.B.; Zhdan, A.G.

    1982-01-01

    A facility for measuring Hall emf in high-resistive materials with low mobility of charge carriers by the two-frequency method using digital synchronous integration is described. The facility permits to detect the minimum Hall emf approxamatety equat to 5 μV at approximatety equal to 1 T Ohm of the investigated.sample resistance during the measuring time of approximately equal to 2000 s. Sensitivity by Hall mobility makes up >= 0.01 cm 2 /Vxs at the same measuring time. Measuring results of the Hall emf on GaAs monocrystals, CdSe films and island film of gold are presented

  9. The comprehensive electrophysiological study of curcuminoids on delayed-rectifier K+ currents in insulin-secreting cells.

    Science.gov (United States)

    Kuo, Ping-Chung; Yang, Chia-Jung; Lee, Yu-Chi; Chen, Pei-Chun; Liu, Yen-Chin; Wu, Sheng-Nan

    2018-01-15

    Curcumin (CUR) has been demonstrated to induce insulin release from pancreatic β-cells; however, how curcuminoids (including demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)) exert any possible effects on membrane ion currents inherently in insulin-secreting cells remains largely unclear. The effects of CUR and other structurally similar curcuminoids on ion currents in rat insulin-secreting (INS-1) insulinoma cells were therefore investigated in this study. The effects of these compounds on ionic currents and membrane potential were studied by patch-clamp technique. CUR suppressed the amplitude of delayed-rectifier K + current (I K(DR) ) in a time-, state- and concentration-dependent manner in these cells and the inhibition was not reversed by diazoxide, nicorandil or chlorotoxin. The value of dissociation constant for CUR-induced suppression of I K(DR) in INS-1 cells was 1.26μM. Despite the inability of CUR to alter the activation rate of I K(DR) , it accelerated current inactivation elicited by membrane depolarization. Increasing CUR concentrations shifted the inactivation curve of I K(DR) to hyperpolarized potential and slowed the recovery of I K(DR) inactivation. CUR, DMC, and BDMC all exerted depressant actions on I K(DR) amplitude to a similar magnitude, although DMC and BDMC did not increase current inactivation clearly. CUR slightly suppressed the peak amplitude of voltage-gated Na + current. CUR, DMC and BDMC depolarized the resting potential and increased firing frequency of action potentials. The CUR-mediated decrease of I K(DR) and the increase of current inactivation also occurred in βTC-6 INS-1 cells. Taken these results together, these effects may be one of the possible mechanisms contributing their insulin-releasing effect. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. The Modified Frequency Algorithm of Digital Watermarking of Still Images Resistant to JPEG Compression

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    V. A. Batura

    2015-01-01

    Full Text Available Digital watermarking is an effective copyright protection for multimedia products (in particular, still images. Digital marking represents process of embedding into object of protection of a digital watermark which is invisible for a human eye. However there is rather large number of the harmful influences capable to destroy the watermark which is embedded into the still image. The most widespread attack is JPEG compression that is caused by efficiency of this format of compression and its big prevalence on the Internet.The new algorithm which is modification of algorithm of Elham is presented in the present article. The algorithm of digital marking of motionless images carries out embedding of a watermark in frequency coefficients of discrete Hadamard transform of the chosen image blocks. The choice of blocks of the image for embedding of a digital watermark is carried out on the basis of the set threshold of entropy of pixels. The choice of low-frequency coefficients for embedding is carried out on the basis of comparison of values of coefficients of discrete cosine transformation with a predetermined threshold, depending on the product of the built-in watermark coefficient on change coefficient.Resistance of new algorithm to compression of JPEG, noising, filtration, change of color, the size and histogram equalization is in details analysed. Research of algorithm consists in comparison of the appearance taken from the damaged image of a watermark with the introduced logo. Ability of algorithm to embedding of a watermark with a minimum level of distortions of the image is in addition analysed. It is established that the new algorithm in comparison by initial algorithm of Elham showed full resistance to compression of JPEG, and also the improved resistance to a noising, change of brightness and histogram equalization.The developed algorithm can be used for copyright protection on the static images. Further studies will be used to study the

  11. Investigation of the temperature and frequency dependence of the surface resistance of superconducting Nb-resonators between 12 and 18 GHz

    International Nuclear Information System (INIS)

    Meyer, W.

    1978-08-01

    Up to now, all measurements on superconducting niobium cavities are restricted to the frequency range below 12 GHz. This paper reports on the investigation of the temperature and frequency dependence of the surface resistance of superconducting niobium between 12 and 18 GHz. Beside the study of TM modes which are important for accelerators, TE modes have been measured also to be able to separate between different loss mechanisms. The dimensions D = L = 40 mm are choosen so that the cavity is operated in higher order modes. Thereby the fabrication, especially of the coupling, and the handling of the cavity is simplified. We use a fixed magnetic hole coupling. Because the cavity was fabricated in a flanged and in a welded model, the influence of a joint could also be studied. After subtracting the residual resistance Rsub(res) the measured values obtained by the newly installed RF set-up fit in temperature and frequency dependence the superconducting surface resistance Rsub(s1) in the framework of the BCS-theory. The gap parameter Δ/kTsub(c) determined from the temperature dependence lies between 1.94 and 1.98. The frequency dependence of Rsub(s1) shows with Rsub(s1) approximately f 1 . 62 the for Nb expected shape. The highest Q 0 in the flanged cavity was 1.7 x 10 9 (f 0 = 13.260 GHz) and in the welded one 1.8 X 10 9 (f 0 = 13.310 GHz), measured in each case in a TE mode at T = 1.3 K. The residual resistance increases with f 2 and stronger and is especially high in the flanged cavity in modes with currents across the joint. (orig.) 891 WBU [de

  12. Infestation by pyrethroids resistant bed bugs in the suburb of Paris, France

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    Durand R.

    2012-11-01

    Full Text Available Bed bugs are hematophagous insects responsible for a re-emerging and challenging indoor pest in many countries. Bed bugs infestations may have health consequences including nuisance biting, cutaneous and systemic reactions. This resurgence can probably be attributed to factors such as increased international travel and development of resistance against insecticides. Resistance against pyrethroids has been reported several times from the USA and rarely in Europe. In France, very few data on bed bugs are available. The present study aimed to assess the infestation by bed bugs of a complex of two high-rise apartment buildings in the suburb of Paris and to evaluate their susceptibility to pyrethroid insecticides. We inspected for bed bugs 192 out of 198 apartments units (97% and interviewed their residents. 76 (39.6% apartments were infested. Among the 97 residents living in infested apartments, 53 (54.6% reported bed bug bites. A total of 564 bed bugs were collected in the infested units. Bioassays showed that 54 out of 143 bed bugs were resistant to pyrethroids (37.8%; 95% confidence interval: 29.9-45.7%. DNA sequencing showed that all bed bugs tested (n = 124 had homozygous L925I kdr-like gene mutation. The level of pyrethroid resistance found indicates that this phenomenon was already established in the site and prompts the need to reevaluate the wide use of pyrethroids to control bed bugs.

  13. Phenotypic- and Genotypic-Resistance Detection for Adaptive Resistance Management in Tetranychus urticae Koch.

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    Deok Ho Kwon

    Full Text Available Rapid resistance detection is necessary for the adaptive management of acaricide-resistant populations of Tetranychus urticae. Detection of phenotypic and genotypic resistance was conducted by employing residual contact vial bioassay (RCV and quantitative sequencing (QS methods, respectively. RCV was useful for detecting the acaricide resistance levels of T. urticae, particularly for on-site resistance detection; however, it was only applicable for rapid-acting acaricides (12 out of 19 tested acaricides. QS was effective for determining the frequencies of resistance alleles on a population basis, which corresponded to 12 nonsynonymous point mutations associated with target-site resistance to five types of acaricides [organophosphates (monocrotophos, pirimiphos-methyl, dimethoate and chlorpyrifos, pyrethroids (fenpropathrin and bifenthrin, abamectin, bifenazate and etoxazole]. Most field-collected mites exhibited high levels of multiple resistance, as determined by RCV and QS data, suggesting the seriousness of their current acaricide resistance status in rose cultivation areas in Korea. The correlation analyses revealed moderate to high levels of positive relationships between the resistance allele frequencies and the actual resistance levels in only five of the acaricides evaluated, which limits the general application of allele frequency as a direct indicator for estimating actual resistance levels. Nevertheless, the resistance allele frequency data alone allowed for the evaluation of the genetic resistance potential and background of test mite populations. The combined use of RCV and QS provides basic information on resistance levels, which is essential for choosing appropriate acaricides for the management of resistant T. urticae.

  14. A significant reduction in the frequency of HIV-1 drug resistance in Québec from 2001 to 2011 is associated with a decrease in the monitored viral load.

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    Hugues Charest

    Full Text Available BACKGROUND: HIV drug resistance represents a major threat for effective treatment. We assessed the trends in the frequency of drug resistance mutations and the monitored viral load (VL in treatment-naïve (TN and treatment-experienced (TE individuals infected with HIV-1 in Québec, Canada, between 2001 and 2011. METHODS AND FINDINGS: Resistance data were obtained from 4,105 and 5,086 genotypic tests performed on TN and TE patients, respectively. Concomitantly, 274,161 VL tests were carried out in the Province. Changes over time in drug resistance frequency and in different categories of VL were assessed using univariate logistic regression. Multiple logistic regression was used to evaluate associations between the rates of certain mutations and antiretroviral prescriptions. From 2001 to 2011, the proportion of undetectable VL test results continually increased, from 42.1% to 75.9%, while a significant decrease in the frequency of resistance mutations associated with protease inhibitors [PI (from 54% to 16%], nucleoside [NRTI (from 78% to 37% and non-nucleoside reverse transcriptase inhibitors [NNRTI (from 44% to 31%] was observed in TE patients. In TN individuals, the overall frequency of transmitted drug resistance was 13.1%. A multiple logistic regression analysis indicated that the introduction of co-formulated emtricitabine/tenofovir or emtricitabine/tenofovir/efavirenz was positively associated with the decrease of the frequency of the M184I/V mutations observed overtime (p = 0.0004. CONCLUSIONS: We observed a significant decrease in the frequency of drug resistance mutations in TE patients, concomitant with a decrease in the proportion of patients with detectable viremia. These findings may be related to both the increased potencies and adherence to therapy associated with newer antiretroviral regimens. Nevertheless, our data demonstrate that broad use of antiretrovirals does not increase the level of circulating drug resistant

  15. Mutagenic and epigenetic influence of caffeine on the frequencies of UV-induced ouabain-resistant Chinese hamster cells

    International Nuclear Information System (INIS)

    Chang, Chia-Cheng; Philipps, C.; Trosko, J.E.; Hart, R.W.

    1977-01-01

    Caffeine, given as a post-treatment to UV-irradiated Chinese hamster cells in vitro, modified the frequency of induced mutations at the ouabain resistance locus. Mutation frequencies were increased when caffeine was added only for the DNA repair and mutation fixation period. When caffeine was added after the DNA repair and mutation fixation period, or immediately after DNA damage and for the entire repair and selection period, mutation frequencies were reduced. A hypothesis, given to explain both results, is that caffeine, by blocking a constitutive 'error-free' postreplication repair process, allows an 'error-prone' DNA repair process to produce many mutations. Moreover, caffeine, possibly by modifying C-AMP metabolism, causes a repression of induced mutations which, in effect, explains its anti-mutagenic and anti-carcinogenic properties

  16. Evidence that agricultural use of pesticides selects pyrethroid resistance within Anopheles gambiae s.l. populations from cotton growing areas in Burkina Faso, West Africa.

    Directory of Open Access Journals (Sweden)

    Aristide Sawdetuo Hien

    Full Text Available Many studies have shown the role of agriculture in the selection and spread of resistance of Anopheles gambiae s.l. to insecticides. However, no study has directly demonstrated the presence of insecticides in breeding sources as a source of selection for this resistance. It is in this context that we investigated the presence of pesticide residues in breeding habitats and their formal involvement in vector resistance to insecticides in areas of West Africa with intensive farming. This study was carried out from June to November 2013 in Dano, southwest Burkina Faso in areas of conventional (CC and biological cotton (BC growing. Water and sediment samples collected from breeding sites located near BC and CC fields were submitted for chromatographic analysis to research and titrate the residual insecticide content found there. Larvae were also collected in these breeding sites and used in toxicity tests to compare their mortality to those of the susceptible strain, Anopheles gambiae Kisumu. All tested mosquitoes (living and dead were analyzed by PCR for species identification and characterization of resistance genes. The toxicity analysis of water from breeding sites showed significantly lower mortality rates in breeding site water from biological cotton (WBC growing sites compared to that from conventional cotton (WCC sites respective to both An. gambiae Kisumu (WBC: 80.75% vs WCC: 92.75% and a wild-type strain (49.75% vs 66.5%. The allele frequencies L1014F, L1014S kdr, and G116S ace -1R mutations conferring resistance, respectively, to pyrethroids and carbamates / organophosphates were 0.95, 0.4 and 0.12. Deltamethrin and lambda-cyhalothrin were identified in the water samples taken in October/November from mosquitoes breeding in the CC growing area. The concentrations obtained were respectively 0.0147ug/L and 1.49 ug/L to deltamethrin and lambdacyhalothrin. Our results provided evidence by direct analysis (biological and chromatographic tests

  17. Insecticide resistance in Aedes aegypti populations from Ceará, Brazil

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    Goulart Marilia OF

    2011-01-01

    Full Text Available Abstract Background Organophosphates and pyrethroids are used widely in Brazil to control Aedes aegypti, the main vector of dengue viruses, under the auspices of the National Programme for Dengue Control. Resistance to these insecticides is widespread throughout Brazil. In Ceará the vector is present in 98% of districts and resistance to temephos has been reported previously. Here we measure resistance to temephos and the pyrethroid cypermethrin in three populations from Ceará and use biochemical and molecular assays to characterise resistance mechanisms. Results Resistance to temephos varied widely across the three studied populations, with resistance ratios (RR95 of 7.2, 30 and 192.7 in Juazeiro do Norte, Barbalha and Crato respectively. The high levels of resistance detected in Barbalha and Crato (RR95 ≥ 30 imply a reduction of temephos efficacy, and indeed in simulated field tests reduced effectiveness was observed for the Barbalha population. Two populations (Crato and Barbalha were also resistant to cypermethrin, whilst Juazeiro do Norte showed only an altered susceptibility. The Ile1011Met kdr mutation was detected in all three populations and Val1016Ile in Crato and Juazeiro do Norte. 1011Met was significantly associated with resistance to cypermethrin in the Crato population. Biochemical tests showed that only the activity of esterases and GSTs, among the tested detoxification enzymes, was altered in these populations when compared with the Rockefeller strain. Conclusions Our results demonstrate that two A. aegypti populations from Ceará are under strong selection pressure by temephos, compromising the field effectiveness of this organophosphate. Our results also provide evidence that the process of reducing resistance to this larvicide in the field is difficult and slow and may require more than seven years for reversal. In addition, we show resistance to cypermethrin in two of the three populations studied, and for the first time

  18. Analysis of population structure and insecticide resistance in mosquitoes of the genus Culex, Anopheles and Aedes from different environments of Greece with a history of mosquito borne disease transmission.

    Science.gov (United States)

    Fotakis, Emmanouil A; Chaskopoulou, Alexandra; Grigoraki, Linda; Tsiamantas, Alexandros; Kounadi, Stella; Georgiou, Loukas; Vontas, John

    2017-10-01

    Greece has been recently affected by several mosquito borne diseases with the West Nile Virus (WNV) outbreak in 2010 being one of the largest reported in Europe. Currently at the epicenter of an economic and refugee crisis and visited by over 16 million tourists a year the integrated management of diseases transmitted by mosquitoes is a public health and economic priority. Vector control programs rely mainly on insecticides, however data on insecticide resistance and the mosquito fauna is essential for successful applications. We determined the mosquito species composition and population dynamics in areas of increased vulnerability to vector borne disease transmission, as well as investigated the resistance status of major nuisance and disease vectors to insecticides. High mosquito densities were recorded in Thessaloniki and Evros, with Aedes caspius, a nuisance species, Culex pipiens, a known vector of WNV and Anopheles hyrcanus a potential vector of malaria being among the most prevalent species. Both vector species populations reached their peak in late summer. Aedes albopictus was recorded at high densities in Thessaloniki, but not in Evros. Notably, Cx. pipiens hybrids, which show an opportunistic biting behavior and are suspected to be involved in the transmission of the WNV, were recorded in considerable numbers in Thessaloniki and Attica. Culex pipiens and An. hyrcanus, but not Ae. caspius mosquitoes, showed moderate levels of resistance to deltamethrin. The presence of resistance in areas not exposed to vector control indicates that other factors could be selecting for resistance, i.e. pesticide applications for agriculture. Both L1014F and L101C kdr mutations were detected in Cx. pipiens populations. Anopheles hyrcanus resistance was not associated with mutations at the L1014 site. The Ace-1 mutations conferring insensitivity to organophosphates and carbamates were detected at low frequencies in all Cx. pipiens populations. Increased activity of P450s and

  19. Evaluating the Frequency of aac(6')-IIa, ant(2″)-I, intl1, and intl2 Genes in Aminoglycosides Resistant Klebsiella pneumoniae Isolates Obtained from Hospitalized Patients in Yazd, Iran.

    Science.gov (United States)

    Mokhtari, Hesam; Eslami, Gilda; Zandi, Hengameh; Dehghan-Banadkouki, Amin; Vakili, Mahmood

    2018-01-01

    Klebsiella pneumoniae (K. pneumoniae) is an opportunistic pathogen that could be resistant to many antimicrobial agents. Resistance genes can be carried among gram-negative bacteria by integrons. Enzymatic inactivation is the most important mechanism of resistance to aminoglycosides. In this study, the frequencies of two important resistance gene aac(6')-II a and ant(2″)-I, and genes coding integrase I and II, in K. pneumoniae isolates resistant to aminoglycosides were evaluated. In this cross-sectional study, an attempt was made to assess the antibiotic susceptibility of 130 K. pneumoniae isolates obtained from different samples of patients hospitalized in training hospitals of Yazd evaluated by disk diffusion method. The frequencies of aac(6')-II a, ant(2″)-I, intl1 , and intl2 genes were determined by PCR method. Data were analyzed by chi-square method using SPSS software (Ver. 16). our results showed that resistance to gentamicin, tobramycin, kanamycin, and amikacin were 34.6, 33.8, 43.8, and 14.6%, respectively. The frequencies of aac (6')-II a, ant(2″)-I, intl1 , and intl2 genes were 44.6, 27.7, 90, and 0%, respectively. This study showed there are high frequencies of genes coding aminoglycosides resistance in K. pneumoniae isolates. Hence, it is very important to monitor and inhibit the spread of antibiotic resistance genes.

  20. Insecticide resistance, associated mechanisms and fitness aspects in two Brazilian Stegomyia aegypti (= Aedes aegypti) populations.

    Science.gov (United States)

    Viana-Medeiros, P F; Bellinato, D F; Martins, A J; Valle, D

    2017-12-01

    In Brazil, insecticide resistance in Stegomyia aegypti (= Aedes aegypti) (Diptera: Culicidae) populations to pyrethroids and to the organophosphate (OP) temephos is disseminated. Currently, insect growth regulators (IGRs) and the OP malathion are employed against larvae and adults, respectively. Bioassays with mosquitoes from two northeast municipalities, Crato and Aracaju, revealed, in both populations, susceptibility to IGRs and malathion (RR 95  ≤ 2.0), confirming the effectiveness of these compounds. By contrast, temephos and deltamethrin (pyrethroid) resistance levels were high (RR 95  > 10), which is consistent with the use of intense chemical control. In Crato, RR 95 values were > 50 for both compounds. Knock-down-resistant (kdr) mutants in the voltage-gated sodium channel, the pyrethroid target site, were found in 43 and 32%, respectively, of Aracaju and Crato mosquitoes. Biochemical assays revealed higher metabolic resistance activity (esterases, mixed function oxidases and glutathione-S-transferases) at Aracaju. With respect to fitness aspects, mating effectiveness was equivalently impaired in both populations, but Aracaju mosquitoes showed more damaging effects in terms of longer larval development, decreased bloodmeal acceptance, reduced engorgement and lower numbers of eggs laid per female. Compared with mosquitoes in Crato, Aracaju mosquitoes exhibited lower OP and pyrethroid RR 95 , increased activity of detoxifying enzymes and greater effect on fitness. The potential relationship between insecticide resistance mechanisms and mosquito viability is discussed. © 2017 The Authors. Medical and Veterinary Entomology published by John Wiley & Sons Ltd on behalf of The Royal Entomological Society.

  1. Prevalence and evolution of low frequency HIV drug resistance mutations detected by ultra deep sequencing in patients experiencing first line antiretroviral therapy failure.

    Science.gov (United States)

    Vandenhende, Marie-Anne; Bellecave, Pantxika; Recordon-Pinson, Patricia; Reigadas, Sandrine; Bidet, Yannick; Bruyand, Mathias; Bonnet, Fabrice; Lazaro, Estibaliz; Neau, Didier; Fleury, Hervé; Dabis, François; Morlat, Philippe; Masquelier, Bernard

    2014-01-01

    Clinical relevance of low-frequency HIV-1 variants carrying drug resistance associated mutations (DRMs) is still unclear. We aimed to study the prevalence of low-frequency DRMs, detected by Ultra-Deep Sequencing (UDS) before antiretroviral therapy (ART) and at virological failure (VF), in HIV-1 infected patients experiencing VF on first-line ART. Twenty-nine ART-naive patients followed up in the ANRS-CO3 Aquitaine Cohort, having initiated ART between 2000 and 2009 and experiencing VF (2 plasma viral loads (VL) >500 copies/ml or one VL >1000 copies/ml) were included. Reverse transcriptase and protease DRMs were identified using Sanger sequencing (SS) and UDS at baseline (before ART initiation) and VF. Additional low-frequency variants with PI-, NNRTI- and NRTI-DRMs were found by UDS at baseline and VF, significantly increasing the number of detected DRMs by 1.35 fold (plow-frequency DRMs modified ARV susceptibility predictions to the prescribed treatment for 1 patient at baseline, in whom low-frequency DRM was found at high frequency at VF, and 6 patients at VF. DRMs found at VF were rarely detected as low-frequency DRMs prior to treatment. The rare low-frequency NNRTI- and NRTI-DRMs detected at baseline that correlated with the prescribed treatment were most often found at high-frequency at VF. Low frequency DRMs detected before ART initiation and at VF in patients experiencing VF on first-line ART can increase the overall burden of resistance to PI, NRTI and NNRTI.

  2. Emergent HIV-1 Drug Resistance Mutations Were Not Present at Low-Frequency at Baseline in Non-Nucleoside Reverse Transcriptase Inhibitor-Treated Subjects in the STaR Study.

    Science.gov (United States)

    Porter, Danielle P; Daeumer, Martin; Thielen, Alexander; Chang, Silvia; Martin, Ross; Cohen, Cal; Miller, Michael D; White, Kirsten L

    2015-12-07

    At Week 96 of the Single-Tablet Regimen (STaR) study, more treatment-naïve subjects that received rilpivirine/emtricitabine/tenofovir DF (RPV/FTC/TDF) developed resistance mutations compared to those treated with efavirenz (EFV)/FTC/TDF by population sequencing. Furthermore, more RPV/FTC/TDF-treated subjects with baseline HIV-1 RNA >100,000 copies/mL developed resistance compared to subjects with baseline HIV-1 RNA ≤100,000 copies/mL. Here, deep sequencing was utilized to assess the presence of pre-existing low-frequency variants in subjects with and without resistance development in the STaR study. Deep sequencing (Illumina MiSeq) was performed on baseline and virologic failure samples for all subjects analyzed for resistance by population sequencing during the clinical study (n = 33), as well as baseline samples from control subjects with virologic response (n = 118). Primary NRTI or NNRTI drug resistance mutations present at low frequency (≥2% to 20%) were detected in 6.6% of baseline samples by deep sequencing, all of which occurred in control subjects. Deep sequencing results were generally consistent with population sequencing but detected additional primary NNRTI and NRTI resistance mutations at virologic failure in seven samples. HIV-1 drug resistance mutations emerging while on RPV/FTC/TDF or EFV/FTC/TDF treatment were not present at low frequency at baseline in the STaR study.

  3. Emergent HIV-1 Drug Resistance Mutations Were Not Present at Low-Frequency at Baseline in Non-Nucleoside Reverse Transcriptase Inhibitor-Treated Subjects in the STaR Study

    Directory of Open Access Journals (Sweden)

    Danielle P. Porter

    2015-12-01

    Full Text Available At Week 96 of the Single-Tablet Regimen (STaR study, more treatment-naïve subjects that received rilpivirine/emtricitabine/tenofovir DF (RPV/FTC/TDF developed resistance mutations compared to those treated with efavirenz (EFV/FTC/TDF by population sequencing. Furthermore, more RPV/FTC/TDF-treated subjects with baseline HIV-1 RNA >100,000 copies/mL developed resistance compared to subjects with baseline HIV-1 RNA ≤100,000 copies/mL. Here, deep sequencing was utilized to assess the presence of pre-existing low-frequency variants in subjects with and without resistance development in the STaR study. Deep sequencing (Illumina MiSeq was performed on baseline and virologic failure samples for all subjects analyzed for resistance by population sequencing during the clinical study (n = 33, as well as baseline samples from control subjects with virologic response (n = 118. Primary NRTI or NNRTI drug resistance mutations present at low frequency (≥2% to 20% were detected in 6.6% of baseline samples by deep sequencing, all of which occurred in control subjects. Deep sequencing results were generally consistent with population sequencing but detected additional primary NNRTI and NRTI resistance mutations at virologic failure in seven samples. HIV-1 drug resistance mutations emerging while on RPV/FTC/TDF or EFV/FTC/TDF treatment were not present at low frequency at baseline in the STaR study.

  4. Effect of Resistance Training Frequency on Gains in Muscular Strength: A Systematic Review and Meta-Analysis.

    Science.gov (United States)

    Grgic, Jozo; Schoenfeld, Brad J; Davies, Timothy B; Lazinica, Bruno; Krieger, James W; Pedisic, Zeljko

    2018-05-01

    Current recommendations on resistance training (RT) frequency for gains in muscular strength are based on extrapolations from limited evidence on the topic, and thus their practical applicability remains questionable. To elucidate this issue, we conducted a systematic review and meta-analysis of the studies that compared muscular strength outcomes with different RT frequencies. To carry out this review, English-language literature searches of the PubMed/MEDLINE, Scopus, and SPORTDiscus databases were conducted. The meta-analysis was performed using a random-effects model. The meta-analysis models were generated with RT frequencies classified as a categorical variable as either 1, 2, 3, or 4+ times/week, or, if there were insufficient data in subgroup analyses, the training frequencies were categorized as 1, 2, or 3 times/week. Subgroup analyses were performed for potential moderators, including (1) training volume; (2) exercise selection for the 1 repetition maximum (RM) test (for both multi-joint and single-joint exercises); (3) upper and lower body strength gains; (4) training to muscular failure (for studies involving and not involving training to muscular failure); (5) age (for both middle-aged/older adults and young adults); and (6) sex (for men and for women). The methodological quality of studies was appraised using the modified Downs and Black checklist. A total of 22 studies were found to meet the inclusion criteria. The average score on the Downs and Black checklist was 18 (range 13-22 points). Four studies were classified as being of good methodological quality, while the rest were classified as being of moderate methodological quality. Results of the meta-analysis showed a significant effect (p = 0.003) of RT frequency on muscular strength gains. Effect sizes increased in magnitude from 0.74, 0.82, 0.93, and 1.08 for training 1, 2, 3, and 4+ times per week, respectively. A subgroup analysis of volume-equated studies showed no significant effect (p

  5. Contact resistance measurement structures for high frequencies

    NARCIS (Netherlands)

    Roy, Deepu; Pijper, Ralf M.T.; Tiemeijer, Luuk F.; Wolters, Robertus A.M.

    2011-01-01

    Knowledge of the interfacial contact impedance offered by the device at its operating frequency range is crucial for accurate modelling and understanding of the device. In this article, a novel modified TLM test-structure has been devised to extract interfacial contact parameters at frequencies upto

  6. Radio-frequency surface resistance of tunmgsten in weak magnetic fields

    International Nuclear Information System (INIS)

    Bojko, V.V.; Toniya, V.A.

    1988-01-01

    The surface impedance of single crystal tungsten specimens under anomalous skin effect in a magnetic field H is investigated experimentally. It is found that in magnetic fields ranging from 0 to 1 kOe the surface resistance R of tungsten varies in a nonmonotonous manner and experiences several extrema. The position of the latter with respect to magnetic field strength depends on the conduction electron mean free path l, on the roughness of the specimen surface and frequency of the irradiating electromagnetic wave. It is found that such behavior of R(H) is due to variation of the nature of the conduction electron scattering at the metal-external medium interface with increasing H. The geometrical dimensions of the surface roughnesses are determined at which diffuse scattering of the current occurs. The results are compared with the theoretical calculations, and a number of contradictions between the theory and experiments are noted. The effect of the magnetic field of the electromagnetic wave H ∼ on the conductivity of tungsten in the absence of H is studied

  7. The role of creep in the time-dependent resistance of Ohmic gold contacts in radio frequency microelectromechanical system devices

    Science.gov (United States)

    Rezvanian, O.; Brown, C.; Zikry, M. A.; Kingon, A. I.; Krim, J.; Irving, D. L.; Brenner, D. W.

    2008-07-01

    It is shown that measured and calculated time-dependent electrical resistances of closed gold Ohmic switches in radio frequency microelectromechanical system (rf-MEMS) devices are well described by a power law that can be derived from a single asperity creep model. The analysis reveals that the exponent and prefactor in the power law arise, respectively, from the coefficient relating creep rate to applied stress and the initial surface roughness. The analysis also shows that resistance plateaus are not, in fact, limiting resistances but rather result from the small coefficient in the power law. The model predicts that it will take a longer time for the contact resistance to attain a power law relation with each successive closing of the switch due to asperity blunting. Analysis of the first few seconds of the measured resistance for three successive openings and closings of one of the MEMS devices supports this prediction. This work thus provides guidance toward the rational design of Ohmic contacts with enhanced reliabilities by better defining variables that can be controlled through material selection, interface processing, and switch operation.

  8. Analytical and numerical calculations of resistive wall impedances for thin beam pipe structures at low frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Niedermayer, U., E-mail: u.niedermayer@gsi.de [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstrasse 8, 64289 Darmstadt (Germany); Boine-Frankenheim, O. [Technische Universitaet Darmstadt, Institut fuer Theorie Elektromagnetischer Felder, Schlossgartenstrasse 8, 64289 Darmstadt (Germany)

    2012-09-21

    The resistive wall impedance is one of the main sources for beam instabilities in synchrotrons and storage rings. The fast ramped SIS18 synchrotron at GSI and the projected SIS100 synchrotron for FAIR both employ thin (0.3 mm) stainless steel beam pipes in order to reduce eddy current effects. The lowest betatron sidebands are at about 100 kHz, which demands accurate impedance predictions in the low frequency (LF) range where the beam pipe and possibly also the structures behind the pipe are the dominating impedance sources. The longitudinal and transverse resistive wall impedances of a circular multi-layer pipe are calculated analytically using the field matching technique. We compare the impedances obtained from a radial wave model, which corresponds to the setup used in bench measurements, with the axial wave model, which corresponds to an actual beam moving with relativistic velocity. For thin beam pipes the induced wall current and the corresponding shielding properties of the pipe are important. In both models the wall current is obtained analytically. The characteristic frequencies for the onset of the wall current are calculated from equivalent lumped element circuits corresponding to the radial model. For more complex structures, like the SIS100 beam pipe, we use a numerical method, in which the impedance is obtained from the total power loss. The method is validated by the analytic expressions for circular beam pipes.

  9. High Voltage Resistive Divider Based on Cast Microwire in Glass Insulation on 6–24 kV Alternating Current of Commercial Frequency.

    Directory of Open Access Journals (Sweden)

    Juravleov A.

    2008-12-01

    Full Text Available It is presented the analysis and description of the construction of the high voltage resistive divider on the base of cast microwire in glass insulation on 6–24 kV alternating current of commercial frequency. It is presented the procedure of compensation of frequency error during the process of fabrication of divides and results of tests of the sample model of the divider as well.

  10. Frequency of Carbapenem, Colistin and Tigecycline Resistant Enterobacteriacae in Medical ICU of a Tertiary Care Hospital in Karachi

    Directory of Open Access Journals (Sweden)

    Shobha Luxmi

    2018-01-01

    Full Text Available BACKGROUND: Resistance to antibiotics among Enterobacteriacae represents a serious therapeutic and infection control challenge. The objective of this study was to determine the frequency of carbapenem, colistin and tigecycline resistant Enterobacteriaceae isolates obtained from patients admitted in medical intensive care unit (ICU of a tertiary care hospital in Karachi, Pakistan. METHODS: This was a descriptive cross sectional study that was conducted at Liaquat National Postgraduate Medical Centre, Karachi, Pakistan during December 2015 to May 2016. Patients admitted in the medical ICU with systemic inflammatory response syndrome were included. The culture positive samples were analyzed for further identification and antimicrobial sensitivity was performed according to clinical laboratory standard institute (CLSI 2014 guidelines. RESULTS: Of the 748 samples, 177 were positive for Enterobactericae. Most samples were taken from blood 75(42.2% or tracheal secretions 67(37.9%. Most common organism isolated were Klebsiella pneumoniae 77(43.5% and Escherichia coli 71(40.1%. Out of these 10.7% organisms were resistant to meropenem, while 2.8% and 20.3% were resistant to colistin and tigecycline respectively. CONCLUSION: Increasing spread of drug resistance among Enterobacteriacae reflects an important problem that can be controlled with effective policies of infection control, surveillance and antimicrobial stewardship.

  11. Distribution of Voltage-Gated Sodium Channel (Nav) Alleles among the Aedes aegypti Populations In Central Java Province and Its Association with Resistance to Pyrethroid Insecticides.

    Science.gov (United States)

    Sayono, Sayono; Hidayati, Anggie Puspa Nur; Fahri, Sukmal; Sumanto, Didik; Dharmana, Edi; Hadisaputro, Suharyo; Asih, Puji Budi Setia; Syafruddin, Din

    2016-01-01

    The emergence of insecticide resistant Aedes aegypti mosquitoes has hampered dengue control efforts. WHO susceptibility tests, using several pyrethroid compounds, were conducted on Ae. aegypti larvae that were collected and raised to adulthood from Semarang, Surakarta, Kudus and Jepara in Java. The AaNaV gene fragment encompassing kdr polymorphic sites from both susceptible and resistant mosquitoes was amplified, and polymorphisms were associated with the resistant phenotype. The insecticide susceptibility tests demonstrated Ae, aegypti resistance to the pyrethroids, with mortality rates ranging from 1.6%-15.2%. Three non-synonymous polymorphisms (S989P, V1016G and F1534C) and one synonymous polymorphism (codon 982) were detected in the AaNaV gene. Eight AaNaV alleles were observed in specimens from Central Java. Allele 3 (SGF) and allele 7 (PGF) represent the most common alleles found and demonstrated strong associations with resistance to pyrethroids (OR = 2.75, CI: 0.97-7.8 and OR = 7.37, CI: 2.4-22.5, respectively). This is the first report of 8 Ae. aegypti AaNaV alleles, and it indicates the development of resistance in Ae. aegypti in response to pyrethroid insecticide-based selective pressure. These findings strongly suggest the need for an appropriate integrated use of insecticides in the region. The 989P, 1016G and 1534C polymorphisms in the AaNaV gene are potentially valuable molecular markers for pyrethroid insecticide resistance monitoring.

  12. Frequency of Resistance and Susceptible Bacteria Isolated from Houseflies

    Directory of Open Access Journals (Sweden)

    B Davari

    2010-12-01

    Conclusion: Houseflies collected from hospitals and slaughterhouse may be involved in the spread of drug resistant bacteria and may increase the potential of human exposure to drug resistant bacteria.

  13. Frequency of ABL gene mutations in chronic myeloid leukemia patients resistant to imatinib and results of treatment switch to second-generation tyrosine kinase inhibitors.

    Science.gov (United States)

    Marcé, Silvia; Zamora, Lurdes; Cabezón, Marta; Xicoy, Blanca; Boqué, Concha; Fernández, Cristalina; Grau, Javier; Navarro, José-Tomás; Fernández de Sevilla, Alberto; Ribera, Josep-Maria; Feliu, Evarist; Millá, Fuensanta

    2013-08-04

    Tyrosine kinase inhibitors (TKI) have improved the management of patients with chronic myeloid leukemia (CML). However, a significant proportion of patients do not achieve the optimal response or are resistant to TKI. ABL kinase domain mutations have been extensively implicated in the pathogenesis of TKI resistance. Treatment with second-generation TKI has produced high rates of hematologic and cytogenetic responses in mutated ABL patients. The aim of this study was to determine the type and frequency of ABL mutations in patients who were resistant to imatinib or had lost the response, and to analyze the effect of second-generation TKI on their outcome. The presence of ABL mutations in 45 CML patients resistant to imatinib was evaluated by direct sequencing and was correlated with the results of the cytogenetic study (performed in 39 cases). The outcome of these patients after therapy with nilotinib or dasatinib was analyzed. ABL mutations were detected in 14 out of 45 resistant patients. Patients with clonal cytogenetic evolution tended to develop mutations more frequently than those without clonal evolution. Nine out of the 15 patients with ABL mutation responded to a treatment switch to nilotinib (n=4), dasatinib (n=2), interferon (n=1) or hematopoietic stem cell transplantation (n=2). The frequency of ABL mutations in CML patients resistant to imatinib is high and is more frequent among those with clonal cytogenetic evolution. The change to second-generation TKI can overcome imatinib resistance in most of the mutated patients. Copyright © 2012 Elsevier España, S.L. All rights reserved.

  14. Increased Frequency of ColV Plasmids and Mannose-Resistant Hemagglutinating Activity in an Escherichia coli K1 Population

    OpenAIRE

    1984-01-01

    The expression of traits linked to pathogenicity was studied in a population of Escherichia coli K1 strains. It was found that E. coli K1 strains isolated from extraintestinal infection harbor the ColV plasmid and express mannose-resistant hemagglutinating activity type VI with a high frequency. The presence of these properties may play a role in the ability of some E. coli K1 serogroups to invade.

  15. Monitoring groundwater-surface water interaction using time-series and time-frequency analysis of transient three-dimensional electrical resistivity changes

    Science.gov (United States)

    Johnson, Timothy C.; Slater, Lee D.; Ntarlagiannis, Dimitris; Day-Lewis, Frederick D.; Elwaseif, Mehrez

    2012-01-01

    Time-lapse resistivity imaging is increasingly used to monitor hydrologic processes. Compared to conventional hydrologic measurements, surface time-lapse resistivity provides superior spatial coverage in two or three dimensions, potentially high-resolution information in time, and information in the absence of wells. However, interpretation of time-lapse electrical tomograms is complicated by the ever-increasing size and complexity of long-term, three-dimensional (3-D) time series conductivity data sets. Here we use 3-D surface time-lapse electrical imaging to monitor subsurface electrical conductivity variations associated with stage-driven groundwater-surface water interactions along a stretch of the Columbia River adjacent to the Hanford 300 near Richland, Washington, USA. We reduce the resulting 3-D conductivity time series using both time-series and time-frequency analyses to isolate a paleochannel causing enhanced groundwater-surface water interactions. Correlation analysis on the time-lapse imaging results concisely represents enhanced groundwater-surface water interactions within the paleochannel, and provides information concerning groundwater flow velocities. Time-frequency analysis using the Stockwell (S) transform provides additional information by identifying the stage periodicities driving groundwater-surface water interactions due to upstream dam operations, and identifying segments in time-frequency space when these interactions are most active. These results provide new insight into the distribution and timing of river water intrusion into the Hanford 300 Area, which has a governing influence on the behavior of a uranium plume left over from historical nuclear fuel processing operations.

  16. Spectral inversion of frequency-domain IP data obtained in Haenam, South Korea

    Science.gov (United States)

    Kim, B.; Nam, M. J.; Son, J. S.

    2017-12-01

    Spectral induced polarization (SIP) method using a range of source frequencies have been performed for not only exploring minerals resources, but also engineering or environmental application. SIP interpretation first makes inversion of individual frequency data to obtain complex resistivity structures, which will further analyzed employing Cole-Cole model to explain the frequency-dependent characteristics. However, due to the difficulty in fitting Cole-Cole model, there is a movement to interpret complex resistivity structure inverted only from a single frequency data: that is so-called "complex resistivity survey". Further, simultaneous inversion of multi-frequency SIP data, rather than making a single frequency SIP data, has been studied to improve ambiguity and artefacts of independent single frequency inversion in obtaining a complex resistivity structure, even though the dispersion characteristics of complex resistivity with respect to source frequency. Employing the simultaneous inversion method, this study makes inversion of field SIP data obtained over epithermal mineralized area, Haenam, in the southernmost tip of South Korea. The area has a polarizable structure because of extensive hydrothermal alteration, gold-silver deposits. After the inversion, we compare between inversion results considering multi-frequency data and single frequency data set to evaluate the performance of simultaneous inversion of multi-frequency SIP data.

  17. Frequency Of Isolation Of Salmonella From Commercial Poultry Feeds And Their Anti-Microbial Resistance Profiles, Imo State, Nigeria

    Directory of Open Access Journals (Sweden)

    Okoli IC

    2006-09-01

    Full Text Available This study was conducted to determine the frequency of isolation of salmonella and their microbial resistance profiles across different commercial poultry feeds sold in Imo State, Nigeria. Thirty-six bulk feed samples were colleted from 154 bag across different feed types and brands which included Guinea (GF, Top (TF, Vital (VF, Extra (EF, Animal care (AF and livestock (LF feeds. The salmonella isolated were tested against 14 anti-microbial drugs using the disc diffusion method. Bacterial load enumeration of the samples indicated a range of <30 colony forming unit (CFU to overgrowth at 104 serial dilutions. Eight feed samples (22.2% which cuts across the entire feed brands expect EF were positive for salmonella. The highest prevalence of 28.8% and 25.0% were recorded for LF and TF respectively, while VF, GF and AF had 11.1 and 10.0% respectively. Salmonella isolates showed high rates of resistance (51-100% against nitrofurantoin, ampicillin, tetracycline and ceftriazole, while moderate rates (31-50% were recorded for chloramphenicol, oxfloxacin and cotrimoxazole. Low resistance rates (1-30% were on the other hand recorded against ciprofloxacin and amoxycillin clavulanate (Augumentine, whereas zero resistance was demonstrated against pefloxacin, gentamycin, streptomycin and nalidixic. Commercial feeds form important channels for the dissemination of multi-drug resistant salmonella in Imo State, Nigeria.

  18. Cellular elements for seeing in the dark: voltage-dependent conductances in cockroach photoreceptors

    Directory of Open Access Journals (Sweden)

    Salmela Iikka

    2012-08-01

    Full Text Available Abstract Background The importance of voltage-dependent conductances in sensory information processing is well-established in insect photoreceptors. Here we present the characterization of electrical properties in photoreceptors of the cockroach (Periplaneta americana, a nocturnal insect with a visual system adapted for dim light. Results Whole-cell patch-clamped photoreceptors had high capacitances and input resistances, indicating large photosensitive rhabdomeres suitable for efficient photon capture and amplification of small photocurrents at low light levels. Two voltage-dependent potassium conductances were found in the photoreceptors: a delayed rectifier type (KDR and a fast transient inactivating type (KA. Activation of KDR occurred during physiological voltage responses induced by light stimulation, whereas KA was nearly fully inactivated already at the dark resting potential. In addition, hyperpolarization of photoreceptors activated a small-amplitude inward-rectifying (IR current mediated at least partially by chloride. Computer simulations showed that KDR shapes light responses by opposing the light-induced depolarization and speeding up the membrane time constant, whereas KA and IR have a negligible role in the majority of cells. However, larger KA conductances were found in smaller and rapidly adapting photoreceptors, where KA could have a functional role. Conclusions The relative expression of KA and KDR in cockroach photoreceptors was opposite to the previously hypothesized framework for dark-active insects, necessitating further comparative work on the conductances. In general, the varying deployment of stereotypical K+ conductances in insect photoreceptors highlights their functional flexibility in neural coding.

  19. Anopheles coluzzii larval habitat and insecticide resistance in the island area of Manoka, Cameroon.

    Science.gov (United States)

    Etang, Josiane; Mbida Mbida, Arthur; Ntonga Akono, Patrick; Binyang, Jerome; Eboumbou Moukoko, Carole Else; Lehman, Leopold Gustave; Awono-Ambene, Parfait; Talipouo, Abdou; Ekoko Eyisab, Wolfgang; Tagne, Darus; Tchoffo, Romeo; Manga, Lucien; Mimpfoundi, Remy

    2016-05-20

    The effectiveness of Long-Lasting Insecticidal Nets and Indoor Residual Spraying in malaria vector control is threatened by vector resistance to insecticides. Knowledge of mosquito habitats and patterns of insecticide resistance would facilitate the development of appropriate vector control strategies. Therefore, we investigated An. coluzzii larval habitats and resistance to insecticides in the Manoka rural island area compared with the Youpwe suburban inland area, in Douala VI and II districts respectively. Anopheline larvae and pupae were collected from open water bodies in December 2013 and April 2014 and reared until adult emergence. Two to four day old emerging females were morphologically identified as belonging to the An. gambiae complex and used for WHO susceptibility tests with 4 % DDT, 0.75 % permethrin, and 0.05 % deltamethrin, with or without piperonyl butoxide (PBO) synergist. Control and surviving specimens were identified down to the species using a PCR-RFLP method. Survivors were genotyped for kdr L1014 mutations using Hot Oligonucleotide Ligation Assay. In both study sites, ponds, residual puddles, boats, and drains were identified as the major An. gambiae s.l. larval habitats. A total of 1397 females, including 784 specimens from Manoka and 613 from Youpwe, were used for resistance testing. The two mosquito populations displayed resistance to DDT, permethrin and deltamethrin, with variable mortality rates from 1 % to 90 %. The knock-down times were also significantly increased (at least 2.8 fold). Pre-exposure of mosquitoes to PBO did not impact on their mortality to DDT, conversely the mortality rates to permethrin and deltamethrin were significantly increased (7.56 ≤ X(2) ≤ 48.63, df = 1, p habitats have been identified, larval source management strategies may be trialed in this area as complementary vector control interventions.

  20. Pyrethroid Susceptibility Has Been Maintained in the Dengue Vector, Aedes aegypti (Diptera: Culicidae), in Queensland, Australia.

    Science.gov (United States)

    Endersby-Harshman, Nancy M; Wuliandari, Juli Rochmijati; Harshman, Lawrence G; Frohn, Verena; Johnson, Brian J; Ritchie, Scott A; Hoffmann, Ary A

    2017-11-07

    Although pesticide resistance is common in insect vectors of human diseases, the evolution of resistance might be delayed if management practices are adopted that limit selection of resistance alleles. Outbreaks of dengue fever have occurred in Queensland, Australia, since the late 1800s, leading to ongoing attempts to control the mosquito vector, Aedes aegypti (L.). Since the 1990s, pyrethroid insecticides have been used for this purpose, but have been applied in a strategic manner with a variety of delivery methods including indoor residual spraying, lethal ovitraps, and use of insect growth regulators as larvicides. Separate selection experiments on mosquitoes from Queensland using Type I and Type II pyrethroids did not produce resistant lines of Ae. aegypti, and bioassays of field material from Queensland showed only weak tolerance in comparison with a susceptible line. There was no evidence of knockdown resistance (kdr) mutations in Ae. aegypti from Queensland, in stark contrast to the situation in nearby southeast Asia. We suspect that careful management of pyrethroid insecticide use combined with surveillance and interception of exotic incursions has helped to maintain pyrethroid (and particularly kdr-based) susceptibility in Ae. aegypti in Australia. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. Frequency Of Isolation Of Salmonella From Commercial Poultry Feeds And Their Anti-Microbial Resistance Profiles, Imo State, Nigeria

    OpenAIRE

    Okoli IC; Ndujihe GE; Ogbuewu IP

    2006-01-01

    This study was conducted to determine the frequency of isolation of salmonella and their microbial resistance profiles across different commercial poultry feeds sold in Imo State, Nigeria. Thirty-six bulk feed samples were colleted from 154 bag across different feed types and brands which included Guinea (GF), Top (TF), Vital (VF), Extra (EF), Animal care (AF) and livestock (LF) feeds. The salmonella isolated were tested against 14 anti-microbial drugs using the disc diffusion method. Bacteri...

  2. Inducible Clindamycin Resistance in Staphylococcus Species

    International Nuclear Information System (INIS)

    Afridi, F. I.; Zeb, M.; Farooqi, B. J.; Murtaza, G.; Hussain, A.

    2014-01-01

    Objective: To determine the frequency of inducible clindamycin resistance in clinical isolates of Staphylococcus species by phenotypic D-test. Study Design: Observational study. Place and Duration of Study: Ziauddin University Hospital, Karachi, from July to December 2011. Methodology: Consecutive clinical isolates of Staphylococcus species were collected and identified by conventional microbiological techniques. Antimicrobial susceptibility testing and inducible clindamycin resistance was carried out by performing D-test using CLSI criteria. Methicillin resistance was detected by using Cefoxitin disk as a surrogate marker. Statistical analysis was performed by SPSS version-17. Results: A total of 667 clinical isolates of Staphylococcus species were obtained during the study period. In these isolates, 177 (26.5%) were Staphylococcus aureus, and 490 (73.5%) were coagulase negative Staphylococci. The total frequency of inducible clindamycin resistance among isolates of Staphylococcus species was 120/667 (18%). Frequency of inducible clindamycin resistance among coagulase negative Staphylococci group and Staphylococcus aureus group were 18.57% and 16.38% respectively. Median age of patients in D-test positive group was 19.5 (1 - 54) years. Conclusion: The frequency of inducible clindamycin resistance among Staphylococcus species may differ in different hospital setup. Clinical microbiology laboratories should implement testing simple and effective D-test on all Staphylococcus species. D-test positive isolates should be reported clindamycin resistant to decrease treatment failure. (author)

  3. Resistive effect on ion fishbone mode in tokamak plasma

    International Nuclear Information System (INIS)

    Shi Bingren; Vandam, J.W.; Carrera, R.; Zhang, Y.Z.

    1992-07-01

    A consistent theoretical description of the resistive internal mode is presented to discuss the effect of resistivity on fishbone mode for different parameter regime of bulk and hot components. It is found that the ideal fishbone mode theory ceases to be correct for the low frequency fishbone branch, the so-called ion fishbone mode, which has a real frequency very close to ω *i (the diamagnetic frequency) in marginal state. The stability domain analysis in β h , γ mhd ) space based on the resistive dispersion relation shows that the transition between the stable and unstable region is more complicated than predicted by the ideal limit theory. Another salient feature of the resistive fishbone mode is the existence of a weakly unstable regime. For high frequency fishbone with ω ∼ ω dm (the toroidal precession frequency of the hot ions) resistivity has negligible effect and the ideal theory is correct

  4. Fatigue characteristics of high strength fire resistance steel for frame structure and time-frequency analysis its acoustic emission signal

    International Nuclear Information System (INIS)

    Kim, Hyun Soo; Nam, Ki Woo; Kang, Chang Young

    2000-01-01

    Demand for now nondestructive evaluation are growing to detect fatigue crack growth behavior to predict long term performance of materials and structure in aggressive environments, especially when they are in non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we analysed acoustic emission signals obtained in fatigue and tensile test of high strength fire resistance steel for frame structure with time-frequency analysis methods. The main frequency range is different in the noise and the fatigue crack propagation. It could be classified that it were also generated by composite fracture mechanics of cleavage, dimple, inclusion separation etc

  5. Frequency and Treatment of Methicillin Resistant Staphylococcus aureus in Obstetric and Gynaecological Sepsis

    International Nuclear Information System (INIS)

    Butt, I.J.; Khan, S.; Bhutta, S.; Butt, S.

    2013-01-01

    Objective: To perform culture and sensitivity for pathogens causing puerperal and postoperative wound sepsis and determine the frequency of Methicillin Resistant Staphylococcus aureus (MRSA) in such infections. Study Design: Observational study. Place and Duration of Study: Obstetrics and Gynaecology Ward, Jinnah Postgraduate Medical Centre, Karachi, from December 2008 to May 2010. Methodology: All patients presenting with puerperal sepsis or postoperative wound infection were enrolled. Pus was collected for culture and sensitivity using standard technique. Two samples were taken from each patient; one before starting the treatment and one at the end of treatment. Ames transport medium was used. Empirical treatment with triple regimen (Ampicillin, Metronidazole and Gentamicin) was started immediately to cover Gram positive as well as negative bacteria in addition to anaerobic infection. After receiving the sensitivity report, antimicrobial agent were changed accordingly. Samples from ward and theater staff and environment were also taken to look for possible mode of transmission. Data was recorded on a proforma. Discrete variables are expressed as percentages. Results: Staphylococcus aureus was the most frequent organism isolated in 34.6% cases. Methicillin sensitive Staphylococcus aureus was seen in 20% cases and methicillin resistant Staphylococcus aureus was seen in 14.6%. Out of these 14.6% MRSA, (17) 77% was associated with puerperal sepsis and rest (5) 23% was associated with postoperative wound infection. It showed best sensitivity to vancomycin. Conclusion: Staphylococcus aureus and E. coli were common causative agent of postoperative infections and puerperal sepsis. (author)

  6. Optimization study on inductive-resistive circuit for broadband piezoelectric energy harvesters

    Directory of Open Access Journals (Sweden)

    Ting Tan

    2017-03-01

    Full Text Available The performance of cantilever-beam piezoelectric energy harvester is usually analyzed with pure resistive circuit. The optimal performance of such a vibration-based energy harvesting system is limited by narrow bandwidth around its modified natural frequency. For broadband piezoelectric energy harvesting, series and parallel inductive-resistive circuits are introduced. The electromechanical coupled distributed parameter models for such systems under harmonic base excitations are decoupled with modified natural frequency and electrical damping to consider the coupling effect. Analytical solutions of the harvested power and tip displacement for the electromechanical decoupled model are confirmed with numerical solutions for the coupled model. The optimal performance of piezoelectric energy harvesting with inductive-resistive circuits is revealed theoretically as constant maximal power at any excitation frequency. This is achieved by the scenarios of matching the modified natural frequency with the excitation frequency and equating the electrical damping to the mechanical damping. The inductance and load resistance should be simultaneously tuned to their optimal values, which may not be applicable for very high electromechanical coupling systems when the excitation frequency is higher than their natural frequencies. With identical optimal performance, the series inductive-resistive circuit is recommended for relatively small load resistance, while the parallel inductive-resistive circuit is suggested for relatively large load resistance. This study provides a simplified optimization method for broadband piezoelectric energy harvesters with inductive-resistive circuits.

  7. Optimization study on inductive-resistive circuit for broadband piezoelectric energy harvesters

    Science.gov (United States)

    Tan, Ting; Yan, Zhimiao

    2017-03-01

    The performance of cantilever-beam piezoelectric energy harvester is usually analyzed with pure resistive circuit. The optimal performance of such a vibration-based energy harvesting system is limited by narrow bandwidth around its modified natural frequency. For broadband piezoelectric energy harvesting, series and parallel inductive-resistive circuits are introduced. The electromechanical coupled distributed parameter models for such systems under harmonic base excitations are decoupled with modified natural frequency and electrical damping to consider the coupling effect. Analytical solutions of the harvested power and tip displacement for the electromechanical decoupled model are confirmed with numerical solutions for the coupled model. The optimal performance of piezoelectric energy harvesting with inductive-resistive circuits is revealed theoretically as constant maximal power at any excitation frequency. This is achieved by the scenarios of matching the modified natural frequency with the excitation frequency and equating the electrical damping to the mechanical damping. The inductance and load resistance should be simultaneously tuned to their optimal values, which may not be applicable for very high electromechanical coupling systems when the excitation frequency is higher than their natural frequencies. With identical optimal performance, the series inductive-resistive circuit is recommended for relatively small load resistance, while the parallel inductive-resistive circuit is suggested for relatively large load resistance. This study provides a simplified optimization method for broadband piezoelectric energy harvesters with inductive-resistive circuits.

  8. High frequency of a single nucleotide substitution (c.-6-180T>G) of the canine MDR1/ABCB1 gene associated with phenobarbital-resistant idiopathic epilepsy in Border Collie dogs.

    Science.gov (United States)

    Mizukami, Keijiro; Yabuki, Akira; Chang, Hye-Sook; Uddin, Mohammad Mejbah; Rahman, Mohammad Mahbubur; Kushida, Kazuya; Kohyama, Moeko; Yamato, Osamu

    2013-01-01

    A single nucleotide substitution (c.-6-180T>G) associated with resistance to phenobarbital therapy has been found in the canine MDR1/ABCB1 gene in Border Collies with idiopathic epilepsy. In the present study, a PCR-restriction fragment length polymorphism assay was developed for genotyping this mutation, and a genotyping survey was carried out in a population of 472 Border Collies in Japan to determine the current allele frequency. The survey demonstrated the frequencies of the T/T wild type, T/G heterozygote, and G/G mutant homozygote to be 60.0%, 30.3%, and 9.8%, respectively, indicating that the frequency of the mutant G allele is extremely high (24.9%) in Border Collies. The results suggest that this high mutation frequency of the mutation is likely to cause a high prevalence of phenobarbital-resistant epilepsy in Border Collies.

  9. The -271 G>A polymorphism of kinase insert domain-containing receptor gene regulates its transcription level in patients with non-small cell lung cancer

    International Nuclear Information System (INIS)

    An, She-Juan; Chen, Zhi-Hong; Lin, Qiu-Xiong; Su, Jian; Chen, Hua-Jun; Lin, Jia-Ying; Wu, Yi-Long

    2009-01-01

    Kinase insert domain-containing receptor (KDR) plays a critical role in the metastasis of cancer and is used as a molecular target in cancer therapy. We investigated the characteristics of the -271 G>A polymorphism of the KDR gene to gain information that may benefit the development of individualized therapies for patients with non-small cell lung cancer (NSCLC). The -271 G>A polymorphism of the KDR gene in 106 lung cancer patients and 203 healthy control individuals was analyzed by polymerase chain reaction (PCR) and DNA sequencing methods. Real-time quantitative PCR and immunohistochemical methods were used to evaluate KDR mRNA and protein expression levels, respectively, in frozen tumor specimens. The -271 G>A polymorphism was associated with the mRNA expression level of the KDR gene in tumor tissues (t = 2.178, P = 0.032, independent samples t-test). Compared with the AG/GG genotype, the AA genotype was associated with higher KDR mRNA expression in tumor tissues. We found no relationship between the genotype and the KDR protein expression level and no significant difference in the distribution of the KDR gene polymorphism genotypes between lung cancer patients and the control group (χ 2 = 1.269, P = 0.264, Fisher's exact test). This study is the first to show that the -271 G>A polymorphism of the KDR gene may be a functional polymorphism related to the regulation of gene transcription. These findings may have important implications for therapies targeting KDR in patients with NSCLC

  10. The survey of shigellosis frequency and determination of antibiotic resistance profile of isolated strains from infected children in Tehran

    Directory of Open Access Journals (Sweden)

    Shahla Abbaspour

    2014-04-01

    Full Text Available Background: Shigellosis is endemic throughout the world and it is among the most common causes of bacterial diarrheal diseases. Antibiotic resistance of Shigella is becoming a progressive problem in world. The aim of this study was the survey of shigellosis frequency and determination of antibiotic resistance profile of isolated strains from infected children in Tehran. Material and Methods: This study conducted on 9131 patients with acute diarrheal disease. For isolation of Shigella spp. from stool samples, culture performed on different selective and differential media. After confirmation of bacteria by biochemical tests, susceptibility testing was done by disc diffusion method according to clinical and laboratory standards (CLSI recomendations. Results: Among 9131 stool samples, Shigella spp. was isolated from 90 cases. Shigella sonnei was the most common isolated species. 92/2 % of isolates were resistant to cotrimoxazole. In contrast, most of the Shigella spp. was founded to be sensitive to ciprofloxacin, imipenem and third-generation cephalosporins. Conclusion: Surveillance programs on antimicrobial resistance not only identify pathogenic bacterial species, by reporting data like serotyping, microorganisms incidence rates, and susceptibility to the antimicrobial agents currently used for treatment, but also contribute to monitoring the intervention strategies including removing organism from reservoirs.

  11. Moderate temperature-dependent surface and volume resistivity and low-frequency dielectric constant measurements of pure and multi-walled carbon nanotube (MWCNT) doped polyvinyl alcohol thin films

    Science.gov (United States)

    Edwards, Matthew; Guggilla, Padmaja; Reedy, Angela; Ijaz, Quratulann; Janen, Afef; Uba, Samuel; Curley, Michael

    2017-08-01

    Previously, we have reported measurements of temperature-dependent surface resistivity of pure and multi-walled carbon nanotube (MWNCT) doped amorphous Polyvinyl Alcohol (PVA) thin films. In the temperature range from 22 °C to 40 °C with humidity-controlled environment, we found the surface resistivity to decrease initially, but to rise steadily as the temperature continued to increase. Moreover, electric surface current density (Js) was measured on the surface of pure and MWCNT doped PVA thin films. In this regard, the surface current density and electric field relationship follow Ohm's law at low electric fields. Unlike Ohmic conduction in metals where free electrons exist, selected captive electrons are freed or provided from impurities and dopants to become conduction electrons from increased thermal vibration of constituent atoms in amorphous thin films. Additionally, a mechanism exists that seemingly decreases the surface resistivity at higher temperatures, suggesting a blocking effect for conducting electrons. Volume resistivity measurements also follow Ohm's law at low voltages (low electric fields), and they continue to decrease as temperatures increase in this temperature range, differing from surface resistivity behavior. Moreover, we report measurements of dielectric constant and dielectric loss as a function of temperature and frequency. Both the dielectric constant and dielectric loss were observed to be highest for MWCNT doped PVA compared to pure PVA and commercial paper, and with frequency and temperature for all samples.

  12. Insecticide susceptibility of natural populations of Anopheles coluzzii and Anopheles gambiae (sensu stricto) from Okyereko irrigation site, Ghana, West Africa.

    Science.gov (United States)

    Chabi, Joseph; Baidoo, Philip K; Datsomor, Alex K; Okyere, Dora; Ablorde, Aikins; Iddrisu, Alidu; Wilson, Michael D; Dadzie, Samuel K; Jamet, Helen P; Diclaro, Joseph W

    2016-03-31

    The increasing spread of insecticide resistance in malaria vectors has been well documented across sub-Saharan Africa countries. The influence of irrigation on increasing vector resistance is poorly understood, and is critical to successful and ethical implementation of food security policies. This study investigated the insecticide resistance status of An. gambiae (s.l.) mosquitoes collected from the irrigated rice area of Okyereko, a village containing about 42 hectares of irrigated field within an irrigation project plan in the Central Region of Ghana. Large amounts of insecticides, herbicides and fertilizers are commonly used in the area to boost the annual production of the rice. Mosquito larvae were collected and adults were assayed from the F1 progeny. The resistance status, allele and genotype were characterized using WHO susceptibility testing and PCR methods respectively. The An. gambiae (s.l.) populations from Okyereko are highly resistant to DDT and pyrethroid insecticides, with possible involvement of metabolic mechanisms including the elevation of P450 and GST enzyme as well as P-gp activity. The population was mostly composed of An. coluzzii specimens (more than 96 %) with kdr and ace-1 frequencies of 0.9 and 0.2 %, respectively. This study brings additional information on insecticide resistance and the characterization of An. gambiae (s.l.) mosquitoes from Okyereko, which can be helpful in decision making for vector control programmes in the region.

  13. High Frequency of a Single Nucleotide Substitution (c.-6-180T>G of the Canine MDR1/ABCB1 Gene Associated with Phenobarbital-Resistant Idiopathic Epilepsy in Border Collie Dogs

    Directory of Open Access Journals (Sweden)

    Keijiro Mizukami

    2013-01-01

    Full Text Available A single nucleotide substitution (c.-6-180T>G associated with resistance to phenobarbital therapy has been found in the canine MDR1/ABCB1 gene in Border Collies with idiopathic epilepsy. In the present study, a PCR-restriction fragment length polymorphism assay was developed for genotyping this mutation, and a genotyping survey was carried out in a population of 472 Border Collies in Japan to determine the current allele frequency. The survey demonstrated the frequencies of the T/T wild type, T/G heterozygote, and G/G mutant homozygote to be 60.0%, 30.3%, and 9.8%, respectively, indicating that the frequency of the mutant G allele is extremely high (24.9% in Border Collies. The results suggest that this high mutation frequency of the mutation is likely to cause a high prevalence of phenobarbital-resistant epilepsy in Border Collies.

  14. Frequency of Antiretroviral Resistance Mutations among Infants Exposed to Single-Dose Nevirapine and Short Course Maternal Antiretroviral Regimens: ACTG A5207.

    Science.gov (United States)

    Hitti, Jane; Halvas, Elias K; Zheng, Lu; Panousis, Constantinos G; Kabanda, Joseph; Taulo, Frank; Kumarasamy, Nagalingeswaran; Pape, Jean William; Lalloo, Umesh; Sprenger, Heather; Klingman, Karin L; Chan, Ellen S; McMahon, Deborah; Mellors, John W

    2014-11-01

    Intrapartum single-dose nevirapine (sdNVP) reduces HIV-1 perinatal transmission but selects NVP resistance among mothers and infants. We evaluated the frequency of antiretroviral resistance among infants with intrauterine HIV-1 infection exposed to sdNVP and maternal antenatal or breastfeeding antiretroviral therapy. This analysis included 429 infants from sub-Saharan Africa, India and Haiti whose 422 mothers received sdNVP plus maternal study treatment. At entry mothers had CD4>250/μL and were ART-naïve except for antenatal ZDV per local standard of care. Maternal study treatment started intrapartum and included ZDV/3TC, TDF/FTC or LPV/r for 7 or 21 days in a randomized factorial design. Infants received sdNVP study treatment and ZDV if local standard of care. Infant HIV RNA or DNA PCR and samples for genotype were obtained at birth and weeks 2, 4 and 12; infants who ever breast-fed were also tested at weeks 16, 24, 48 and 96. Samples from HIV-1-infected infants were tested for drug resistance by population genotype (ViroSeq). NVP or NRTI resistance mutations were assessed using the IAS-USA mutation list. Perinatal HIV-1 transmission occurred in 17 (4.0%) infants including 12 intrauterine infections. Resistance mutations were detected among 5 (42%) intrauterine-infected infants; of these, 3 had mutations conferring resistance to NVP alone, 1 had resistance to NRTI alone, and 1 had dual-class resistance mutations. Among the 2 infants with NRTI mutations, one (K70R) was likely maternally transmitted and one (K65R) occurred in the context of breastfeeding exposure to maternal antiretroviral therapy. Infants with intrauterine HIV infection are at risk of acquiring resistance mutations from exposure to maternal antiretroviral medications intrapartum and/or during breastfeeding. New approaches are needed to lower the risk of antiretroviral resistance in these infants.

  15. Electromagnetic fields created by a beam in an axisymmetric infinitely thick single-layer resistive pipe: general formulas and low frequency approximations

    CERN Document Server

    Mounet, Nicolas Frank; CERN. Geneva. ATS Department

    2015-01-01

    This note provides general and approximate formulas for the electromagnetic fields created by a passing beam in an axisymmetric infinitely thick resistive pipe made of a single homogeneous layer. The full derivations and their resulting approximate expressions at low and intermediate frequencies are given here, as well as the conditions under which those approximations are valid. Beam-coupling impedances are also computed, and examples are shown.

  16. Frequency response of electrochemical cells

    Science.gov (United States)

    Thomas, Daniel L.

    1990-01-01

    The main objective was to examine the feasibility of using frequency response techniques (1) as a tool in destructive physical analysis of batteries, particularly for estimating electrode structural parameters such as specific area, porosity, and tortuosity and (2) as a non-destructive testing technique for obtaining information such as state of charge and acceptability for space flight. The phenomena that contribute to the frequency response of an electrode include: (1) double layer capacitance; (2) Faradaic reaction resistance; (3) mass transfer of Warburg impedance; and (4) ohmic solution resistance. Nickel cadmium cells were investigated in solutions of KOH. A significant amount of data was acquired. Quantitative data analysis, using the developed software, is planned for the future.

  17. On-electrode autonomous current generator for multi-frequency EIT

    International Nuclear Information System (INIS)

    Jivet, I; Dragoi, B

    2008-01-01

    The paper presents an autonomous programmable current generator module for multi-frequency EIT systems. The module incorporates all stages from the sine wave generation with frequency and amplitude tuning, D/A converter and filter, a high output resistance voltage-to-current converter to the associated digital communication and control. The paper presents in depth the original digital quadrature signal generator and the output current generator with a high resistance. The other main blocks of the design use current practice specifications, since recent technological solutions proposed in the literature were found appropriate. The proposed signal generator circuit, characterized by a very low complexity, is analyzed in its capacity to produce multiple accurate signals up to 1 MHz in frequency. The precision output current source uses a modified current conveyor of type CCII with a high output resistance and low distortion. The output current frequency spectrum and linearity parameters obtained in the simulations are also described. The simulation results indicate a good linearity and high output resistance with an acceptable output voltage swing. The calculated performance parameters are validated with simulations, and future work for the prototype fabrication of the IC is outlined

  18. A Simple and Universal Resistive-Bridge Sensors Interface

    Directory of Open Access Journals (Sweden)

    Sergey Y. YURISH

    2011-02-01

    Full Text Available Resistive-bridge sensors are widely used in various sensor systems. There are many sensor signal conditioners from different manufacturers for such sensing elements. However, no one existing on the modern market integrated converter for resistive bridge sensors can work with both: resistive-bridge sensing elements and resistive-to-frequency and -duty-cycle converters’ outputs. A proposed and described in the article universal interface for resistive-bridge sensing elements and bridge-output-to-frequency and/or duty cycle converters based on the designed Universal Sensors and Transducers Interface (USTI integrated. It is based on a simple, cost effective three-point measuring technique and does not require any additional active components. The USTI IC is realized in a standard CMOS technology. The active supply current at operating voltage +4.5 V and clock frequency 20 MHz is not more than 9.5 mA This paper reports experimental results with a strain gauges bridge emulator and differential pressure resistive bridge sensor SX30GD2.

  19. Determination of the influence of dispersion pattern of pesticide-resistant individuals on the reliability of resistance estimates using different sampling plans.

    Science.gov (United States)

    Shah, R; Worner, S P; Chapman, R B

    2012-10-01

    Pesticide resistance monitoring includes resistance detection and subsequent documentation/ measurement. Resistance detection would require at least one (≥1) resistant individual(s) to be present in a sample to initiate management strategies. Resistance documentation, on the other hand, would attempt to get an estimate of the entire population (≥90%) of the resistant individuals. A computer simulation model was used to compare the efficiency of simple random and systematic sampling plans to detect resistant individuals and to document their frequencies when the resistant individuals were randomly or patchily distributed. A patchy dispersion pattern of resistant individuals influenced the sampling efficiency of systematic sampling plans while the efficiency of random sampling was independent of such patchiness. When resistant individuals were randomly distributed, sample sizes required to detect at least one resistant individual (resistance detection) with a probability of 0.95 were 300 (1%) and 50 (10% and 20%); whereas, when resistant individuals were patchily distributed, using systematic sampling, sample sizes required for such detection were 6000 (1%), 600 (10%) and 300 (20%). Sample sizes of 900 and 400 would be required to detect ≥90% of resistant individuals (resistance documentation) with a probability of 0.95 when resistant individuals were randomly dispersed and present at a frequency of 10% and 20%, respectively; whereas, when resistant individuals were patchily distributed, using systematic sampling, a sample size of 3000 and 1500, respectively, was necessary. Small sample sizes either underestimated or overestimated the resistance frequency. A simple random sampling plan is, therefore, recommended for insecticide resistance detection and subsequent documentation.

  20. Radiation induction of drug resistance in RIF-1 tumors and tumor cells

    International Nuclear Information System (INIS)

    Hopwood, L.E.; Moulder, J.E.

    1989-01-01

    The RIF-1 tumor cell line contains a small number of cells (1-20 per 10(6) cells) that are resistant to various single antineoplastic drugs, including 5-fluorouracil (5FU), methotrexate (MTX), and adriamycin (ADR). For 5FU the frequency of drug resistance is lower for tumor-derived cells than for cells from cell culture; for MTX the reverse is true, and for ADR there is no difference. In vitro irradiation at 5 Gy significantly increased the frequency of drug-resistant cells for 5FU, MTX, and ADR. In vivo irradiation at 3 Gy significantly increased the frequency of drug-resistant cells for 5FU and MTX, but not for ADR. The absolute risk for in vitro induction of MTX, 5FU, and ADR resistance, and for in vivo induction of 5FU resistance, was 1-3 per 10(6) cells per Gy; but the absolute risk for in vivo induction of MTX resistance was 54 per 10(6) cells per Gy. The frequency of drug-resistant cells among individual untreated tumors was highly variable; among individual irradiated tumors the frequency of drug-resistant cells was significantly less variable. These studies provide supporting data for models of the development of tumor drug resistance, and imply that some of the drug resistance seen when chemotherapy follows radiotherapy may be due to radiation-induced drug resistance

  1. Polymorphisms in voltage-gated sodium channel gene and susceptibility of Aedes albopictus to insecticides in three districts of northern West Bengal, India.

    Science.gov (United States)

    Chatterjee, Moytrey; Ballav, Sudeep; Maji, Ardhendu K; Basu, Nandita; Sarkar, Biplab Chandra; Saha, Pabitra

    2018-01-01

    The control and prevention of dengue largely depends on vector control measures, environmental management, and personal protection. Dengue control programmes are facing great challenges due to development of insecticide resistance among vector mosquitoes. Information on susceptibility status to different insecticides is important for national programmes to formulate vector control strategies. We have studied the larval susceptibility of Aedes albopictus to temephos and adult susceptibility to 4% DDT, 0.05% deltamethrin, and 5% malathion as per WHO protocols in the northern districts of West Bengal. Polymorphisms in the VGSC gene were studied by direct sequencing of PCR products. The Ae. albopictus larval population showed sensitive [Resistance Ratio (RR99)resistance (510) to temephos at different study sites. Adult bioassay results revealed that Ae. albopictus was highly resistant to DDT [Corrected Mortality (CM) 98%), except in Dhupguri where a low level of resistance to deltamethrin (CM = 96.25%) was recorded. None of the six important kdr mutations (S953P, I975M/V, L978, V980G, F1474C, D1703Y) were found in the VGSC of studied mosquitoes, but we identified 11 synonymous and 1 non-synonymous mutation in the VGSC gene. The higher susceptibility level to deltamethrin and malathion, along with the absence of important kdr mutations indicates that these two insecticides are still effective against Ae. albopictus in the study areas. The susceptibility status of temephos should be monitored closely as low to moderate levels of resistance were observed in few sites. A similar study is recommended for monitoring and early detection of insecticide resistance in other parts of the country.

  2. Current-to-frequency converter

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, S W [Institute of Nuclear Research, Warsaw (Poland)

    1981-07-15

    A current-to-frequency converter covering the range from 3 x 10/sup -10/ A up to 3 x 10/sup -5/ A of the input current is described. The circuit operates with nuclear detectors featuring a high internal resistance.

  3. Delineation of Gold Mineralization Zone using Resistivity and Very Low Frequency Electromagnetic Methods around, North Singhbhum Mobile Belt, India.

    Science.gov (United States)

    Upadhyay, A.; Panda, K. P.; Singh, A.; Sharma, S. P.

    2017-12-01

    The results of electrical resistivity and VLF electromagnetic surveys are presented in this study to delineate the suitable geological structure associated with gold mineralization near Lawa Village (Seraikela-Kharsawan, Jharkhand), India. The area under observation lies in North Singhbhum Mobile Belt (NSMB) which is bounded by Chotanagpur Gneiss Complex in north and Archean Singhbhum Craton in the south. Shear zone of the study area, trending E-W, is mainly associated with Cu-U mineralization which is also associated with gold. Previous geological studies have revealed that this region can be a potential site for gold prospects within NSMB. A comprehensive electrical resistivity imaging and very low frequency surveys have been performed around Lawa village to outline appropriate conducting zones, with their lateral extension and depth extent, which may be associated with gold mineralization. Resistivity survey done using Dipole-Dipole multi-electrode array reveals multiple zones of mineralization separated by variable distances. The VLF data in the current study was tainted by non-stationary and non-linear noises which cannot be eliminated by standard filtering techniques. Therefore to restore signals with significant geologic information empirical mode decomposition (EMD) technique was used. The noise free data obtained was then processed using Fast Imaging technique to obtain apparent current density pseudo-sections for interpretation. Interpretation and analysis of results from each investigating survey demonstrate a steeply dipping conductor with E-W strike direction along the shear zone. These conductive zones are characterized by low resistivity and high current density values.

  4. Exfoliated BN shell-based high-frequency magnetic core-shell materials.

    Science.gov (United States)

    Zhang, Wei; Patel, Ketan; Ren, Shenqiang

    2017-09-14

    The miniaturization of electric machines demands high frequency magnetic materials with large magnetic-flux density and low energy loss to achieve a decreased dimension of high rotational speed motors. Herein, we report a solution-processed high frequency magnetic composite (containing a nanometal FeCo core and a boron nitride (BN) shell) that simultaneously exhibits high electrical resistivity and magnetic permeability. The frequency dependent complex initial permeability and the mechanical robustness of nanocomposites are intensely dependent on the content of BN insulating phase. The results shown here suggest that insulating magnetic nanocomposites have potential for application in next-generation high-frequency electric machines with large electrical resistivity and permeability.

  5. Frequency and Circadian Timing of Eating May Influence Biomarkers of Inflammation and Insulin Resistance Associated with Breast Cancer Risk.

    Directory of Open Access Journals (Sweden)

    Catherine R Marinac

    Full Text Available Emerging evidence suggests that there is interplay between the frequency and circadian timing of eating and metabolic health. We examined the associations of eating frequency and timing with metabolic and inflammatory biomarkers putatively associated with breast cancer risk in women participating in the National Health and Nutrition Examination 2009-2010 Survey. Eating frequency and timing variables were calculated from 24-hour food records and included (1 proportion of calories consumed in the evening (5 pm-midnight, (2 number of eating episodes per day, and (3 nighttime fasting duration. Linear regression models examined each eating frequency and timing exposure variable with C-reactive protein (CRP concentrations and the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR. Each 10 percent increase in the proportion of calories consumed in the evening was associated with a 3 percent increase in CRP. Conversely, eating one additional meal or snack per day was associated with an 8 percent reduction in CRP. There was a significant interaction between proportion of calories consumed in the evening and fasting duration with CRP (p = 0.02. A longer nighttime fasting duration was associated with an 8 percent lower CRP only among women who ate less than 30% of their total daily calories in the evening (p = 0.01. None of the eating frequency and timing variables were significantly associated with HOMA-IR. These findings suggest that eating more frequently, reducing evening energy intake, and fasting for longer nightly intervals may lower systemic inflammation and subsequently reduce breast cancer risk. Randomized trials are needed to validate these associations.

  6. Frequency and Circadian Timing of Eating May Influence Biomarkers of Inflammation and Insulin Resistance Associated with Breast Cancer Risk.

    Science.gov (United States)

    Marinac, Catherine R; Sears, Dorothy D; Natarajan, Loki; Gallo, Linda C; Breen, Caitlin I; Patterson, Ruth E

    2015-01-01

    Emerging evidence suggests that there is interplay between the frequency and circadian timing of eating and metabolic health. We examined the associations of eating frequency and timing with metabolic and inflammatory biomarkers putatively associated with breast cancer risk in women participating in the National Health and Nutrition Examination 2009-2010 Survey. Eating frequency and timing variables were calculated from 24-hour food records and included (1) proportion of calories consumed in the evening (5 pm-midnight), (2) number of eating episodes per day, and (3) nighttime fasting duration. Linear regression models examined each eating frequency and timing exposure variable with C-reactive protein (CRP) concentrations and the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Each 10 percent increase in the proportion of calories consumed in the evening was associated with a 3 percent increase in CRP. Conversely, eating one additional meal or snack per day was associated with an 8 percent reduction in CRP. There was a significant interaction between proportion of calories consumed in the evening and fasting duration with CRP (p = 0.02). A longer nighttime fasting duration was associated with an 8 percent lower CRP only among women who ate less than 30% of their total daily calories in the evening (p = 0.01). None of the eating frequency and timing variables were significantly associated with HOMA-IR. These findings suggest that eating more frequently, reducing evening energy intake, and fasting for longer nightly intervals may lower systemic inflammation and subsequently reduce breast cancer risk. Randomized trials are needed to validate these associations.

  7. In Vitro Resistance Studies with Bacteria That Exhibit Low Mutation Frequencies: Prediction of “Antimutant” Linezolid Concentrations Using a Mixed Inoculum Containing both Susceptible and Resistant Staphylococcus aureus

    Science.gov (United States)

    Golikova, Maria V.; Strukova, Elena N.; Portnoy, Yury A.; Romanov, Andrey V.; Edelstein, Mikhail V.; Zinner, Stephen H.

    2014-01-01

    Bacterial resistance studies using in vitro dynamic models are highly dependent on the starting inoculum that might or might not contain spontaneously resistant mutants (RMs). To delineate concentration-resistance relationships with linezolid-exposed Staphylococcus aureus, a mixed inoculum containing both susceptible cells and RMs was used. An RM selected after the 9th passage of the parent strain (MIC, 2 μg/ml) on antibiotic-containing media (RM9; MIC, 8 μg/ml) was chosen for the pharmacodynamic studies, because the mutant prevention concentration (MPC) of linezolid against the parent strain in the presence of RM9 at 102 (but not at 104) CFU/ml did not differ from the MPC value determined in the absence of the RMs. Five-day treatments with twice-daily linezolid doses were simulated at concentrations either between the MIC and MPC or above the MPC. S. aureus RMs (resistant to 2× and 4× MIC but not 8× and 16× MIC) were enriched at ratios of the 24-h area under the concentration-time curve (AUC24) to the MIC that provide linezolid concentrations between the MIC and MPC for 100% (AUC24/MIC, 60 h) and 86% (AUC24/MIC, 120 h) of the dosing interval. No such enrichment occurred when linezolid concentrations were above the MIC and below the MPC for a shorter time (37% of the dosing interval; AUC24/MIC, 240 h) or when concentrations were consistently above the MPC (AUC24/MIC, 480 h). These findings obtained using linezolid-susceptible staphylococci supplemented with RMs support the mutant selection window hypothesis. This method provides an option to delineate antibiotic concentration-resistance relationships with bacteria that exhibit low mutation frequencies. PMID:25451050

  8. Double suicide genes selectively kill human umbilical vein endothelial cells

    Directory of Open Access Journals (Sweden)

    Liu Lunxu

    2011-02-01

    Full Text Available Abstract Background To construct a recombinant adenovirus containing CDglyTK double suicide genes and evaluate the killing effect of the double suicide genes driven by kinase domain insert containing receptor (KDR promoter on human umbilical vein endothelial cells. Methods Human KDR promoter, Escherichia coli (E. coli cytosine deaminase (CD gene and the herpes simplex virus-thymidine kinase (TK gene were cloned using polymerase chain reaction (PCR. Plasmid pKDR-CDglyTK was constructed with the KDR promoter and CDglyTK genes. A recombinant adenoviral plasmid AdKDR-CDglyTK was then constructed and transfected into 293 packaging cells to grow and harvest adenoviruses. KDR-expressing human umbilical vein endothelial cells (ECV304 and KDR-negative liver cancer cell line (HepG2 were infected with the recombinant adenoviruses at different multiplicity of infection (MOI. The infection rate was measured by green fluorescent protein (GFP expression. The infected cells were cultured in culture media containing different concentrations of prodrugs ganciclovir (GCV and/or 5-fluorocytosine (5-FC. The killing effects were measured using two different methods, i.e. annexin V-FITC staining and terminal transferase-mediated dUTP nick end-labeling (TUNEL staining. Results Recombinant adenoviruses AdKDR-CDglyTK were successfully constructed and they infected ECV304 and HepG2 cells efficiently. The infection rate was dependent on MOI of recombinant adenoviruses. ECV304 cells infected with AdKDR-CDglyTK were highly sensitive to GCV and 5-FC. The cell survival rate was dependent on both the concentration of the prodrugs and the MOI of recombinant adenoviruses. In contrast, there were no killing effects in the HepG2 cells. The combination of two prodrugs was much more effective in killing ECV304 cells than GCV or 5-FC alone. The growth of transgenic ECV304 cells was suppressed in the presence of prodrugs. Conclusion AdKDR-CDglyTK/double prodrog system may be a useful

  9. Kinase impact assessment in the landscape of fusion genes that retain kinase domains: a pan-cancer study

    Science.gov (United States)

    Kim, Pora; Jia, Peilin; Zhao, Zhongming

    2018-01-01

    Abstract Assessing the impact of kinase in gene fusion is essential for both identifying driver fusion genes (FGs) and developing molecular targeted therapies. Kinase domain retention is a crucial factor in kinase fusion genes (KFGs), but such a systematic investigation has not been done yet. To this end, we analyzed kinase domain retention (KDR) status in chimeric protein sequences of 914 KFGs covering 312 kinases across 13 major cancer types. Based on 171 kinase domain-retained KFGs including 101 kinases, we studied their recurrence, kinase groups, fusion partners, exon-based expression depth, short DNA motifs around the break points and networks. Our results, such as more KDR than 5′-kinase fusion genes, combinatorial effects between 3′-KDR kinases and their 5′-partners and a signal transduction-specific DNA sequence motif in the break point intronic sequences, supported positive selection on 3′-kinase fusion genes in cancer. We introduced a degree-of-frequency (DoF) score to measure the possible number of KFGs of a kinase. Interestingly, kinases with high DoF scores tended to undergo strong gene expression alteration at the break points. Furthermore, our KDR gene fusion network analysis revealed six of the seven kinases with the highest DoF scores (ALK, BRAF, MET, NTRK1, NTRK3 and RET) were all observed in thyroid carcinoma. Finally, we summarized common features of ‘effective’ (highly recurrent) kinases in gene fusions such as expression alteration at break point, redundant usage in multiple cancer types and 3′-location tendency. Collectively, our findings are useful for prioritizing driver kinases and FGs and provided insights into KFGs’ clinical implications. PMID:28013235

  10. IMPROVING THE STABILITY OF TONAL TRACK CIRCUITS UNDER FLUCTUATIONS OF BALLAST RESISTANCE

    Directory of Open Access Journals (Sweden)

    K. V. Honcharov

    2013-11-01

    Full Text Available Purpose.The purpose of investigation is the development of method for improving the stability of tonal track circuits that takes into account the actual insulation resistance (ballast resistance of rail line.Methodology. To achieve the research purpose it was proposed to automatically determine the insulation resistance of rail line, and depending on this value to adjust the output voltage of track generator. Ballast resistance is determined by the value of input resistance the rail line, which at high frequencies practically is equal to the wave impedance. To implement the proposed method it is necessary to connect to the track circuit additional high-frequency generators, high-frequency filters, unit for finding the ballast resistance and adjusting the output voltage of track generator. Findings. As a result of research it was found that at low values (less than 2 Ohms*km the change of ballast resistance causes significant change of voltage at the track receiver input, which may cause malfunction of the track circuit. Increasing the length of rail line leads to the reducing of its input resistance, raising the measuring frequency causes increasing the input resistance. In both cases, the input resistance tends to the value of the wave impedance. The measuring frequency should be chosen taking into account the length of rail line and the upper limit of ballast resistance, the value 5 Ohms*km can be taken as that limit. At higher values of ballast resistance its changes insignificantly influence the input voltage of track receiver. In this case, the adaptive adjustment of voltage at the track generator output is not performed. Originality. The method for measuring the insulation resistance of rail line has been improved that allows one to determine the ballast resistance automatically. The dependence between measuring frequency, length of rail line and ballast resistance have been determined. Practical value. The proposed method allows one to

  11. Frequency of escherichia coli in patients with community acquired urinary tract infection and their resistance pattern against some commonly used anti bacterials

    International Nuclear Information System (INIS)

    Ahmad, W.; Jamshed, F.; Ahmad, W.

    2015-01-01

    Urinary tract infection (UTI) is a very common health problem and Escherichia coli (E coli) are the most common organisms associated with community acquired UTI. Unfortunately these bacteria have developed extensive resistance against most of the commonly used anti-bacterials. The objective of this study was to determine the frequency and resistance pattern of E coli in patients of community acquired UTI in an area in northern part of Pakistan. Methods: Urine specimens were collected from patients who were clinically diagnosed as community acquired UTI. Urine routine examination (Urine RE) was done and samples positive for UTI (Pus cells >10/High Power Field) were included in the study. These samples were inoculated on Eosin Methylene Blue (EMB) agar plates and incubated at 37 degree C for 36 hours. Suspected colonies were then inoculated further on EMB plates for pure cultures of E coli characterized by certain morphological characteristics. IMViC was applied for the confirmation of E coli. In vitro antibiotic susceptibility tests of E coli were performed with standardized commercial susceptibility discs (OXOID). Results: Out of 50 specimens, positive for UTI by urine RE, 20 showed pure growth of E coli on culture (40%). The majority of the isolates (28%; n=14) were from women while only 12% (n=6) were from men. Escherichia coli showed a high rate of resistance towards Ampicillin (90%), Tetracycline (70%), Erythromycin (70%) and Trimethoprim-Sulfamethoxazole (55%). Sparfloxacin showed better results (45%) than ciprofloxacin (50%). Out of 20 E coli isolates, two (10%) were resistant to all the antibacterials except chloramphenicol, eight isolates (40%) showed resistance to six or more than six while 14 (70%) were resistant to four or more than four drugs. Conclusion: Rate of resistance of E coli against commonly used antibacterials was quite high and majority of the strains showed multidrug resistance. (author)

  12. Analytical method for establishing indentation rolling resistance

    Science.gov (United States)

    Gładysiewicz, Lech; Konieczna, Martyna

    2018-01-01

    Belt conveyors are highly reliable machines able to work in special operating conditions. Harsh environment, long distance of transporting and great mass of transported martials are cause of high energy usage. That is why research in the field of belt conveyor transportation nowadays focuses on reducing the power consumption without lowering their efficiency. In this paper, previous methods for testing rolling resistance are described, and new method designed by authors was presented. New method of testing rolling resistance is quite simple and inexpensive. Moreover it allows to conduct the experimental tests of the impact of different parameters on the value of indentation rolling resistance such as core design, cover thickness, ambient temperature, idler travel frequency, or load value as well. Finally results of tests of relationship between rolling resistance and idler travel frequency and between rolling resistance and idler travel speed was presented.

  13. Molecular Scree ning of Blast Resistance Genes in Rice Germplasms Resistant to Magnaporthe oryzae

    Directory of Open Access Journals (Sweden)

    Liang Yan

    2017-01-01

    Full Text Available Molecular screening of major rice blast resistance genes was determined with molecular markers, which showed close-set linkage to 11 major rice blast resistance genes (Pi-d2, Pi-z, Piz-t, Pi-9, Pi-36, Pi-37, Pi5, Pi-b, Pik-p, Pik-h and Pi-ta2, in a collection of 32 accessions resistant to Magnaporthe oryzae. Out of the 32 accessions, the Pi-d2 and Pi-z appeared to be omnipresent and gave positive express. As the second dominant, Pi-b and Piz-t gene frequencies were 96.9% and 87.5%. And Pik-h and Pik-p gene frequencies were 43.8% and 28.1%, respectively. The molecular marker linkage to Pi-ta2 produced positive bands in eleven accessions, while the molecular marker linkage to Pi-36 and Pi-37 in only three and four accessions, respectively. The natural field evaluation analysis showed that 30 of the 32 accessions were resistant, one was moderately resistant and one was susceptible. Infection types were negatively correlated with the genotype scores of Pi-9, Pi5, Pi-b, Pi-ta2 and Pik-p, although the correlation coefficients were very little. These results are useful in identification and incorporation of functional resistance genes from these germplasms into elite cultivars through marker-assisted selection for improved blast resistance in China and worldwide.

  14. Prevalence of genotypic HIV-1 drug resistance in Thailand, 2002

    Directory of Open Access Journals (Sweden)

    Watitpun Chotip

    2003-03-01

    Full Text Available Abstract Background The prices of reverse transcriptase (RT inhibitors in Thailand have been reduced since December 1, 2001. It is expected that reduction in the price of these inhibitors may influence the drug resistance mutation pattern of HIV-1 among infected people. This study reports the frequency of HIV-1 genetic mutation associated with drug resistance in antiretroviral-treated patients from Thailand. Methods Genotypic resistance testing was performed on samples collected in 2002 from 88 HIV-1 infected individuals. Automated DNA sequencing was used to genotype the HIV-1 polymerase gene isolated from patients' plasma. Results Resistance to protease inhibitors, nucleoside and non-nucleoside reverse transcriptase inhibitors were found in 10 (12%, 42 (48% and 19 (21% patients, respectively. The most common drug resistance mutations in the protease gene were at codon 82 (8%, 90 (7% and 54 (6%, whereas resistant mutations at codon 215 (45%, 67 (40%, 41 (38% and 184 (27% were commonly found in the RT gene. This finding indicates that genotypic resistance to nucleoside reverse transcriptase inhibitors was prevalent in 2002. The frequency of resistant mutations corresponding to non-nucleoside reverse transcriptase inhibitors was three times higher-, while resistant mutation corresponding to protease inhibitors was two times lower than those frequencies determined in 2001. Conclusion This study shows that the frequencies of RT inhibitor resistance mutations have been increased after the reduction in the price of RT inhibitors since December 2001. We believe that this was an important factor that influenced the mutation patterns of HIV-1 protease and RT genes in Thailand.

  15. Frequencies distribution of dihydrofolate reductase and dihydropteroate synthetase mutant alleles associated with sulfadoxine-pyrimethamine resistance in Plasmodium falciparum population from Hadhramout Governorate, Yemen.

    Science.gov (United States)

    Bamaga, Omar A A; Mahdy, Mohammed A K; Lim, Yvonne A L

    2015-12-22

    Malaria in Yemen is mainly caused by Plasmodium falciparum and 25% of the population is at high risk. Sulfadoxine-pyrimethamine (SP) had been used as monotherapy against P. falciparum. Emergence of chloroquine resistance led to the shift in anti-malarial treatment policy in Yemen to artemisinin-based combination therapy, that is artesunate (AS) plus SP as first-line therapy for uncomplicated malaria and artemether-lumefantrine as second-line treatment. This study aimed to screen mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes associated with SP resistance among P. falciparum population in Hadhramout governorate, Yemen. Genomic DNA was extracted from dried blood spots of 137 P. falciparum isolates collected from a community-based study. DNA was amplified using nested polymerase chain reaction (PCR) and subsequently sequenced for Pfdhfr and Pfdhps genes. Sequences were analysed for mutations in Pfdhfr gene codons 51, 59, 108, and 164 and in Pfdhps gene codons 436, 437, and 540. A total of 128 and 114 P. falciparum isolates were successfully sequenced for Pfdhfr and Pfdhps genes, respectively. Each Pfdhfr mutant allele (I51 and N108) in P. falciparum population had a frequency of 84%. Pfdhfr R59 mutant allele was detected in one isolate. Mutation at codon 437 (G437) in the Pfdhps gene was detected in 44.7% of falciparum malaria isolates. Frequencies of Pfdhfr double mutant genotype (I51C59N108I164) and Pfdhfr/Pfdhps triple mutant genotype (I51C59N108I164-S436G437K540) were 82.8 and 39.3%, respectively. One isolate harboured Pfdhfr triple mutant genotype (I51, R59, N108, I164) and Pfdhfr/Pfdhps quadruple mutant genotype (I51R59N108I164-S436G437K540). High frequencies of Pfdhfr and Pfdhps mutant alleles and genotypes in P. falciparum population in Hadhramout, Yemen, highlight the risk of developing resistance for SP, the partner drug of AS, which subsequently will expose the parasite to AS monotherapy increasing then the

  16. Malaria infection and disease in an area with pyrethroid-resistant vectors in southern Benin

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    Akogbéto Martin

    2010-12-01

    Full Text Available Abstract Background This study aimed to investigate baseline data on malaria before the evaluation of new vector control strategies in an area of pyrethroid-resistance of vectors. The burden of malaria was estimated in terms of infection (prevalence and parasite density and of clinical episodes. Methods Between December 2007 and December 2008 in the health district of Ouidah - Kpomassè - Tori Bossito (southern Benin, a descriptive epidemiological survey of malaria was conducted. From 28 selected villages, seven were randomized from which a total of 440 children aged 0 to 5 years were randomly selected. Clinical and parasitological information was obtained by active case detection of malaria episodes carried out during eight periods of six consecutive days scheduled at six weekly intervals and by cross-sectional surveys of asymptomatic infection. Entomological information was also collected. The ownership, the use and the correct use of long-lasting insecticide-treated nets (LLINs were checked over weekly-survey by unannounced visits at home in the late evening. Results Mean parasite density in asymptomatic children was 586 P. falciparum asexual forms per μL of blood (95%CI 504-680. Pyrogenic parasite cut-off was estimated 2,000 P. falciparum asexual blood forms per μL. The clinical incidence of malaria was 1.5 episodes per child per year (95%CI 1.2-1.9. Parasitological and clinical variables did not vary with season. Anopheles gambiae s.l. was the principal vector closely followed by Anopheles funestus. Entomological inoculation rate was 5.3 (95%CI 1.1-25.9 infective bites per human per year. Frequency of the L1014F kdr (West allele was around 50%. Annual prevalence rate of Plasmodium falciparum asymptomatic infection was 21.8% (95%CI 19.1-24.4 and increased according to age. Mean rates of ownership and use of LLINs were 92% and 70% respectively. The only correct use of LLINs (63% conferred 26% individual protection against only infection (OR

  17. Quantification of circulating endothelial progenitor cells using the modified ISHAGE protocol.

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    Caroline Schmidt-Lucke

    2010-11-01

    Full Text Available Circulating endothelial progenitor cells (EPC, involved in endothelial regeneration, neovascularisation, and determination of prognosis in cardiovascular disease can be characterised with functional assays or using immunofluorescence and flow cytometry. Combinations of markers, including CD34+KDR+ or CD133+KDR+, are used. This approach, however may not consider all characteristics of EPC. The lack of a standardised protocol with regards to reagents and gating strategies may account for the widespread inter-laboratory variations in quantification of EPC. We, therefore developed a novel protocol adapted from the standardised so-called ISHAGE protocol for enumeration of haematopoietic stem cells to enable comparison of clinical and laboratory data.In 25 control subjects, 65 patients with coronary artery disease (CAD; 40 stable CAD, 25 acute coronary syndrome/acute myocardial infarction (ACS, EPC were quantified using the following approach: Whole blood was incubated with CD45, KDR, and CD34. The ISHAGE sequential strategy was used, and finally, CD45(dimCD34(+ cells were quantified for KDR. A minimum of 100 CD34(+ events were collected. For comparison, CD45(+CD34(+ and CD45(-CD34(+ were analysed simultaneously. The number of CD45(dimCD34(+KDR(+ cells only were significantly higher in healthy controls compared to patients with CAD or ACS (p = 0.005 each, p<0.001 for trend. An inverse correlation of CD45(dimCD34(+KDR(+ with disease activity (r = -0.475, p<0.001 was confirmed. Only CD45(dimCD34(+KDR(+ correlated inversely with the number of diseased coronaries (r = -0.344; p<0.005. In a second study, a 4-week de-novo treatment of atorvastatin in stable CAD evoked an increase only of CD45(dimCD34(+KDR(+ EPC (p<0.05. CD45(+CD34(+KDR(+ and CD45(-CD34(+KDR(+ were indifferent between the three groups.Our newly established protocol adopted from the standardised ISHAGE protocol achieved higher accuracy in EPC enumeration confirming previous

  18. Analytical method for establishing indentation rolling resistance

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    Gładysiewicz Lech

    2018-01-01

    Full Text Available Belt conveyors are highly reliable machines able to work in special operating conditions. Harsh environment, long distance of transporting and great mass of transported martials are cause of high energy usage. That is why research in the field of belt conveyor transportation nowadays focuses on reducing the power consumption without lowering their efficiency. In this paper, previous methods for testing rolling resistance are described, and new method designed by authors was presented. New method of testing rolling resistance is quite simple and inexpensive. Moreover it allows to conduct the experimental tests of the impact of different parameters on the value of indentation rolling resistance such as core design, cover thickness, ambient temperature, idler travel frequency, or load value as well. Finally results of tests of relationship between rolling resistance and idler travel frequency and between rolling resistance and idler travel speed was presented.

  19. On the interface trap density and series resistance of tin oxide film prepared on n-type Si (1 1 1) substrate: Frequency dependent effects before and after 60Co γ-ray irradiation

    International Nuclear Information System (INIS)

    Karadeniz, S.; Selcuk, A. Birkan; Tugluoglu, N.; Ocak, S. Bilge

    2007-01-01

    We report the first investigation of the frequency dependent effects of gamma irradiation on interface state density and series resistance determined from capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics in SnO 2 /n-Si structures prepared by spray deposition method. The samples were irradiated using a 60 Co γ-ray source at 500 kGy at room temperature. The C-V and G-V measurements of the samples were performed in the voltage range -6 V to 2 V and at 10 kHz, 100 kHz, 500 kHz and 1 MHz at room temperature before and after 500 kGy irradiation. The measurement capacitance and conductance are corrected for series resistance. It has been seen that the value of the series resistance R s of sample decreases from 204 Ω to 55.4 Ω with increasing the frequency before irradiation while it decreases from 248 Ω to 60 Ω with increasing frequency at 500 kGy irradiation. It has been found that and D it values of MOS structure increases up to 100 kHz and then decreases up to 1 MHz while the R s increases with increasing irradiation dose for our sample. The interface state density D it ranges from 1.83 x 10 13 cm -2 eV -1 for before irradiation to 1.54 x 10 13 cm -2 eV -1 for 500 kGy irradiation dose at 500 kHz and decreases with increasing frequency

  20. Vibro-Shock Dynamics Analysis of a Tandem Low Frequency Resonator—High Frequency Piezoelectric Energy Harvester

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    Darius Žižys

    2017-04-01

    Full Text Available Frequency up-conversion is a promising technique for energy harvesting in low frequency environments. In this approach, abundantly available environmental motion energy is absorbed by a Low Frequency Resonator (LFR which transfers it to a high frequency Piezoelectric Vibration Energy Harvester (PVEH via impact or magnetic coupling. As a result, a decaying alternating output signal is produced, that can later be collected using a battery or be transferred directly to the electric load. The paper reports an impact-coupled frequency up-converting tandem setup with different LFR to PVEH natural frequency ratios and varying contact point location along the length of the harvester. RMS power output of different frequency up-converting tandems with optimal resistive values was found from the transient analysis revealing a strong relation between power output and LFR-PVEH natural frequency ratio as well as impact point location. Simulations revealed that higher power output is obtained from a higher natural frequency ratio between LFR and PVEH, an increase of power output by one order of magnitude for a doubled natural frequency ratio and up to 150% difference in power output from different impact point locations. The theoretical results were experimentally verified.

  1. Acute Frontal Lobe Dysfunction Following Prefrontal Low-Frequency Repetitive Transcranial Magnetic Stimulation in a Patient with Treatment-Resistant Depression

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    Guilhem Carle

    2017-05-01

    Full Text Available The potential of repetitive transcranial magnetic stimulation (rTMS to treat numerous neurological and psychiatric disorders has been thoroughly studied for the last two decades. Here, we report for the first time, the case of a 65-year-old woman suffering from treatment-resistant depression who developed an acute frontal lobe syndrome following eight sessions of low-frequency rTMS (LF-rTMS to the right dorsolateral prefrontal cortex while also treated with sertraline and mianserin. The pathophysiological mechanisms underlying such an unexpected acute frontal lobe dysfunction are discussed in relation to the therapeutic use of LF-rTMS in combination with pharmacotherapy in depressed patients.

  2. High-frequency CSMT (HFCSMT) survey system for fine resistivity structures in the shallow subsurface; Hyoso hiteiko seimitsu sokutei sochi (HFCSMT) no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Handa, S [Saga University, Saga (Japan); Kinoshita, T; Kozato, T [Construction Project Consultant Co. Ltd., Osaka (Japan)

    1997-10-22

    HFCSMT system has been developed to enhance resolution in CSMT technology. The system covers a frequency band of 1.4kHz-106kHz for transmission, and measurement is performed using 16 frequencies. The transmitter power amplifier operating on a 12V cell is capable of a maximum output of approximately 3A, and the signals can be received at points several 100s of meters away. As for the selection of frequencies, synchronization is ensured for the receiver set no matter what instant the measuring process is commenced, the process being fully automated including the gain control. Phase and amplification values obtained for the electric and magnetic fields are subjected to A/D conversion. The data are stored in the microcomputer memory as apparent resistivity and phase data, and are forwarded to the host computer upon termination of the measuring process. Since both analog processing and digital processing are used, the measurement process is over in approximately 96 seconds. This system is being tested in various fields of technology. 1 fig.

  3. Insecticide resistance to organophosphates in Culex pipiens complex from Lebanon

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    Osta Mike A

    2012-07-01

    Full Text Available Abstract Background Analysis of Culex pipiens mosquitoes collected from a single site in Lebanon in 2005, revealed an alarming frequency of ace-1 alleles conferring resistance to organophosphate insecticides. Following this, in 2006 the majority of municipalities switched to pyrethroids after a long history of organophosphate usage in the country; however, since then no studies have assessed the impact of changing insecticide class on the frequency of resistant ace-1 alleles in C. pipiens. Methods C. pipiens mosquitoes were captured indoors from 25 villages across the country and subjected to established methods for the analysis of gene amplification at the Ester locus and target site mutations in ace-1 gene that confer resistance to organophosphates. Results We conducted the first large-scale screen for resistance to organosphosphates in C. pipiens mosquitoes collected from Lebanon. The frequency of carboxylesterase (Ester and ace-1 alleles conferring resistance to organophosphates were assessed among C. pipiens mosquitoes collected from 25 different villages across the country between December 2008 and December 2009. Established enzymatic assay and PCR-based molecular tests, both diagnostic of the major target site mutations in ace-1 revealed the absence of the F290V mutation among sampled mosquitoes and significant reduction in the frequency of G119S mutation compared to that previously reported for mosquitoes collected from Beirut in 2005. We also identified a new duplicated ace-1 allele, named ace-1D13, exhibiting a resistant phenotype by associating a susceptible and a resistant copy of ace-1 in a mosquito line sampled from Beirut in 2005. Fisher’s exact test on ace-1 frequencies in the new sample sites, showed that some populations exhibited a significant excess of heterozygotes, suggesting that the duplicated allele is still present. Starch gel electrophoresis indicated that resistance at the Ester locus was mainly attributed to the

  4. Sulfonamide-resistant bacteria and their resistance genes in soils fertilized with manures from Jiangsu Province, Southeastern China.

    Science.gov (United States)

    Wang, Na; Yang, Xiaohong; Jiao, Shaojun; Zhang, Jun; Ye, Boping; Gao, Shixiang

    2014-01-01

    Antibiotic-resistant bacteria and genes are recognized as new environmental pollutants that warrant special concern. There were few reports on veterinary antibiotic-resistant bacteria and genes in China. This work systematically analyzed the prevalence and distribution of sulfonamide resistance genes in soils from the environments around poultry and livestock farms in Jiangsu Province, Southeastern China. The results showed that the animal manure application made the spread and abundance of antibiotic resistance genes (ARGs) increasingly in the soil. The frequency of sulfonamide resistance genes was sul1 > sul2 > sul3 in pig-manured soil DNA and sul2 > sul1 > sul3 in chicken-manured soil DNA. Further analysis suggested that the frequency distribution of the sul genes in the genomic DNA and plasmids of the SR isolates from manured soil was sul2 > sul1 > sul3 overall (psulfonamide resistance genes. The present study also indicated that Bacillus, Pseudomonas and Shigella were the most prevalent sul-positive genera in the soil, suggesting a potential human health risk. The above results could be important in the evaluation of antibiotic-resistant bacteria and genes from manure as sources of agricultural soil pollution; the results also demonstrate the necessity and urgency of the regulation and supervision of veterinary antibiotics in China.

  5. Frequency dispersion analysis of thin dielectric MOS capacitor in a five-element model

    Science.gov (United States)

    Zhang, Xizhen; Zhang, Sujuan; Zhu, Huichao; Pan, Xiuyu; Cheng, Chuanhui; Yu, Tao; Li, Xiangping; Cheng, Yi; Xing, Guichao; Zhang, Daming; Luo, Xixian; Chen, Baojiu

    2018-02-01

    An Al/ZrO2/IL/n-Si (IL: interface layer) MOS capacitor has been fabricated by metal organic decomposition of ZrO2 and thermal deposition Al. We have measured parallel capacitance (C m) and parallel resistance (R m) versus bias voltage curves (C m, R m-V) at different AC signal frequency (f), and C m, R m-f curves at different bias voltage. The curves of C m, R m-f measurements show obvious frequency dispersion in the range of 100 kHz-2 MHz. The energy band profile shows that a large voltage is applied on the ZrO2 layer and IL at accumulation, which suggests possible dielectric polarization processes by some traps in ZrO2 and IL. C m, R m-f data are used for frequency dispersion analysis. To exclude external frequency dispersion, we have extracted the parameters of C (real MOS capacitance), R p (parallel resistance), C IL (IL capacitance), R IL (IL resistance) and R s (Si resistance) in a five-element model by using a three-frequency method. We have analyzed intrinsic frequency dispersion of C, R p, C IL, R IL and R s by studying the dielectric characteristics and Si surface layer characteristics. At accumulation, the dispersion of C and R p is attributed to dielectric polarization such as dipolar orientation and oxide traps. The serious dispersion of C IL and R IL are relative to other dielectric polarization, such as border traps and fixed oxide traps. The dispersion of R s is mainly attributed to contact capacitance (C c) and contact resistance (R c). At depletion and inversion, the frequency dispersion of C, R p, C IL, R IL, and R s are mainly attributed to the depletion layer capacitance (C D). The interface trap capacitance (C it) and interface trap resistance (R it) are not dominant for the dispersion of C, R p, C IL, R IL, and R s.

  6. Toxicological, Enzymatic, and Molecular Assessment of the Insecticide Susceptibility Profile of Triatoma infestans (Hemiptera: Reduviidae, Triatominae) Populations From Rural Communities of Santa Cruz, Bolivia.

    Science.gov (United States)

    Santo-Orihuela, Pablo L; Vassena, Claudia V; Carvajal, Guillermo; Clark, Eva; Menacho, Silvio; Bozo, Ricardo; Gilman, Robert H; Bern, Caryn; Marcet, Paula L

    2017-01-01

    A wide range of insecticide resistance profiles has been reported across Bolivian domestic and sylvatic populations of Triatoma infestans (Klug, 1834) (Hemiptera, Reduviidae), including some with levels proven to be a threat for vector control. In this work, the insecticide profile of domestic T. infestans was studied with standardized toxicological bioassays, in an area that has not undergone consistent vector control. F1 first-instar nymphs hatched in laboratory from bugs captured in three communities from the Santa Cruz Department were evaluated with different insecticides. Moreover, the enzymatic activity of esterases and cytochrome P450 monooxygenases was measured in individual insects to evaluate the possible mechanism of metabolic resistance to pyrethroids. In addition, the DNA sequence of sodium channel gene (kdr) was screened for two point mutations associated with pyrethroid resistance previously reported in T. infestans.All populations showed reduced susceptibility to deltamethrin and α-cypermethrin, albeit the RR50 values varied significantly among them. Increased P450 monooxygenases and permethrate esterases suggest the contribution, as detoxifying mechanisms, to the observed resistance to deltamethrin in all studied populations. No individuals presented either mutation associated to resistance in the kdr gene. The level of susceptibility to α-cypermethrin, the insecticide used by the local vector control program, falls within an acceptable range to continue its use in these populations. However, the observed RR50 values evidence the possibility of selection for resistance to pyrethroids, especially to deltamethrin. Consequently, the use of pyrethroid insecticides should be closely monitored in these communities, which should be kept under entomological surveillance and sustained interventions. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email

  7. Insecticidal and sterilizing effect of Olyset Duo®, a permethrin and pyriproxyfen mixture net against pyrethroid-susceptible and -resistant strains of Anopheles gambiae s.s.: a release-recapture assay in experimental huts

    Directory of Open Access Journals (Sweden)

    Djènontin Armel

    2015-01-01

    Full Text Available In the context of the widespread distribution of pyrethroid resistance among malaria vectors, we did a release-recapture trial in experimental huts to investigate the insecticidal and sterilizing effects of a novel long-lasting net (LN, Olyset® Duo, incorporating a mixture of permethrin (PER and the insect growth regulator (IGR, pyri-proxyfen (PPF. An LN containing PPF alone and a classic Olyset® Net were tested in parallel as positive controls. The effect of progressive number of holes (6, 30, or 150 that may accrue in nets over time was simulated. We used two laboratory Anopheles gambiae s.s. strains: the susceptible Kisumu strain and the pyrethroid-resistant VK-Per strain having solely kdr as resistance mechanism. The effect of these nets on the reproductive success of blood-fed females that survived the different LNs conditions was recorded. Regardless of the mosquito strain, the LNs containing PPF alone with as many as 30 holes drastically reduced the number of eggs laid by females succeeding in feeding, i.e. fecundity by 98% and egg hatching rate (fertility by 93% relative to untreated control net. Very few of the resistant females blood fed and survived under the Olyset® Duo with similar number of holes (up to 30 but of these few, the inhibition of reproductive success was 100%. There was no evidence that the Olyset® Duo LN with 150 holes impacted fecundity or fertility of the resistant colony. The efficacy of Olyset® Duo is encouraging and clearly illustrates that this new net might be a promising tool for malaria transmission control and resistance management.

  8. Insecticidal and sterilizing effect of Olyset Duo®, a permethrin and pyriproxyfen mixture net against pyrethroid-susceptible and -resistant strains of Anopheles gambiae s.s.: a release-recapture assay in experimental huts.

    Science.gov (United States)

    Djènontin, Armel; Ahoua Alou, Ludovic P; Koffi, Alphonsine; Zogo, Barnabas; Duarte, Elves; N'Guessan, Raphael; Moiroux, Nicolas; Pennetier, Cédric

    2015-01-01

    In the context of the widespread distribution of pyrethroid resistance among malaria vectors, we did a release-recapture trial in experimental huts to investigate the insecticidal and sterilizing effects of a novel long-lasting net (LN), Olyset® Duo, incorporating a mixture of permethrin (PER) and the insect growth regulator (IGR), pyri-proxyfen (PPF). An LN containing PPF alone and a classic Olyset® Net were tested in parallel as positive controls. The effect of progressive number of holes (6, 30, or 150) that may accrue in nets over time was simulated. We used two laboratory Anopheles gambiae s.s. strains: the susceptible Kisumu strain and the pyrethroid-resistant VK-Per strain having solely kdr as resistance mechanism. The effect of these nets on the reproductive success of blood-fed females that survived the different LNs conditions was recorded. Regardless of the mosquito strain, the LNs containing PPF alone with as many as 30 holes drastically reduced the number of eggs laid by females succeeding in feeding, i.e. fecundity by 98% and egg hatching rate (fertility) by 93% relative to untreated control net. Very few of the resistant females blood fed and survived under the Olyset® Duo with similar number of holes (up to 30) but of these few, the inhibition of reproductive success was 100%. There was no evidence that the Olyset® Duo LN with 150 holes impacted fecundity or fertility of the resistant colony. The efficacy of Olyset® Duo is encouraging and clearly illustrates that this new net might be a promising tool for malaria transmission control and resistance management. © A. Djènontin et al., published by EDP Sciences, 2015.

  9. Restoration of uridine 5′-triphosphate-suppressed delayed rectifying K+ currents by an NO activator KMUP-1 involves RhoA/Rho kinase signaling in pulmonary artery smooth muscle cells

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    Zen-Kong Dai

    2016-12-01

    Full Text Available We have demonstrated that KMUP-1 (7-[2-[4-(2-chlorobenzenepiperazinyl]ethyl]-1,3-dimethylxanthine blunts monocrotaline-induced pulmonary arterial hypertension by altering Ca2+ sensitivity, K+-channel function, endothelial nitric oxide synthase activity, and RhoA/Rho kinase (ROCK expression. This study further investigated whether KMUP-1 impedes uridine 5′-triphosphate (UTP-inhibited delayed rectifying K+ (KDR current in rat pulmonary arteries involved the RhoA/ROCK signaling. Pulmonary artery smooth muscle cells (PASMCs were enzymatically dissociated from rat pulmonary arteries. KMUP-1 (30μM attenuated UTP (30μM-mediated membrane depolarization and abolished UTP-enhanced cytosolic Ca2+ concentration. Whole-cell patch-clamp electrophysiology was used to monitor KDR currents. A voltage-dependent KDR current was isolated and shown to consist of a 4-aminopyridine (5mM-sensitive component and an insensitive component. The 4-aminopyridine sensitive KDR current was suppressed by UTP (30μM. The ROCK inhibitor Y27632 (30μM abolished the ability of UTP to inhibit the KDR current. Like Y27632, KMUP-1 (30μM similarly abolished UTP-inhibited KDR currents. Superfused protein kinase A and protein kinase G inhibitors (KT5720, 300nM and KT5823, 300nM did not affect UTP-inhibited KDR currents, but the currents were restored by adding KMUP-1 (30μM to the superfusate. KMUP-1 reversal of KDR current inhibition by UTP predominantly involves the ROCK inhibition. The results indicate that the RhoA/ROCK signaling pathway plays a key role in eliciting PASMCs depolarization caused by UTP, which would result in pulmonary artery constriction. KMUP-1 blocks UTP-mediated PASMCs depolarization, suggesting that it would prevent abnormal pulmonary vasoconstriction.

  10. Low temperature laser scanning microscopy of a superconducting radio-frequency cavity

    Science.gov (United States)

    Ciovati, G.; Anlage, Steven M.; Baldwin, C.; Cheng, G.; Flood, R.; Jordan, K.; Kneisel, P.; Morrone, M.; Nemes, G.; Turlington, L.; Wang, H.; Wilson, K.; Zhang, S.

    2012-03-01

    An apparatus was developed to obtain, for the first time, 2D maps of the surface resistance of the inner surface of an operating superconducting radio-frequency niobium cavity by a low-temperature laser scanning microscopy technique. This allows identifying non-uniformities of the surface resistance with a spatial resolution of about 2.4 mm and surface resistance resolution of ˜1 μΩ at 3.3 GHz. A signal-to-noise ratio of about 10 dB was obtained with 240 mW laser power and 1 Hz modulation frequency. The various components of the apparatus, the experimental procedure and results are discussed in detail in this contribution.

  11. Low temperature laser scanning microscopy of a superconducting radio-frequency cavity.

    Science.gov (United States)

    Ciovati, G; Anlage, Steven M; Baldwin, C; Cheng, G; Flood, R; Jordan, K; Kneisel, P; Morrone, M; Nemes, G; Turlington, L; Wang, H; Wilson, K; Zhang, S

    2012-03-01

    An apparatus was developed to obtain, for the first time, 2D maps of the surface resistance of the inner surface of an operating superconducting radio-frequency niobium cavity by a low-temperature laser scanning microscopy technique. This allows identifying non-uniformities of the surface resistance with a spatial resolution of about 2.4 mm and surface resistance resolution of ~1 μΩ at 3.3 GHz. A signal-to-noise ratio of about 10 dB was obtained with 240 mW laser power and 1 Hz modulation frequency. The various components of the apparatus, the experimental procedure and results are discussed in detail in this contribution.

  12. Malaria vector populations across ecological zones in Guinea Conakry and Mali, West Africa.

    Science.gov (United States)

    Coulibaly, Boubacar; Kone, Raymond; Barry, Mamadou S; Emerson, Becky; Coulibaly, Mamadou B; Niare, Oumou; Beavogui, Abdoul H; Traore, Sekou F; Vernick, Kenneth D; Riehle, Michelle M

    2016-04-08

    Malaria remains a pervasive public health problem in sub-Saharan West Africa. Here mosquito vector populations were explored across four sites in Mali and the Republic of Guinea (Guinea Conakry). The study samples the major ecological zones of malaria-endemic regions in West Africa within a relatively small distance. Mosquito vectors were sampled from larval pools, adult indoor resting sites, and indoor and outdoor human-host seeking adults. Mosquitoes were collected at sites spanning 350 km that represented arid savannah, humid savannah, semi-forest and deep forest ecological zones, in areas where little was previously known about malaria vector populations. 1425 mosquito samples were analysed by molecular assays to determine species, genetic attributes, blood meal sources and Plasmodium infection status. Anopheles gambiae and Anopheles coluzzii were the major anophelines represented in all collections across the ecological zones, with A. coluzzii predominant in the arid savannah and A. gambiae in the more humid sites. The use of multiple collection methodologies across the sampling sites allows assessment of potential collection bias of the different methods. The L1014F kdr insecticide resistance mutation (kdr-w) is found at high frequency across all study sites. This mutation appears to have swept almost to fixation, from low frequencies 6 years earlier, despite the absence of widespread insecticide use for vector control. Rates of human feeding are very high across ecological zones, with only small fractions of animal derived blood meals in the arid and humid savannah. About 30 % of freshly blood-fed mosquitoes were positive for Plasmodium falciparum presence, while the rate of mosquitoes with established infections was an order of magnitude lower. The study represents detailed vector characterization from an understudied area in West Africa with endemic malaria transmission. The deep forest study site includes the epicenter of the 2014 Ebola virus epidemic

  13. Utilizing 2D Electrical Resistivity Tomography and Very Low Frequency Electromagnetics to Investigate the Hydrogeology of Natural Cold Springs Near Virginia City, Southwest Montana

    Science.gov (United States)

    Khalil, Mohamed A.; Bobst, Andrew; Mosolf, Jesse

    2018-04-01

    Virginia City, Montana, is located in the northern Rocky Mountains of the United States. Two natural springs supply the city's water; however, the source of that water is poorly understood. The springs are located on the east side of the city, on the edge of an area affected by landslides. 2D electric resistivity tomography (ERT) and very low frequency electromagnetics (VLF-EM) were used to explore the springs and landslides. Two intersecting 2D resistivity profiles were measured at each spring, and two VLF profiles were measured in a landslide zone. The inverted 2D resistivity profiles at the springs reveal high resistivity basalt flows juxtaposed with low resistivity volcanic ash. The VLF profiles within the landslide show a series of fracture zones in the basalt, which are interpreted to be a series of landslide scarps. Results show a strong correlation between the inferred scarps and local topography. This study provides valuable geological information to help understand the source of water to the springs. The contact between the fractured basalt and the ash provides a sharp contrast in permeability, which causes water to flow along the contact and discharge at outcrop. The fracture zones along the scarps in the landslide deposits provide conduits of high secondary permeability to transmit water to the springs. The fracture zones near the scarps may also provide targets for municipal supply wells.

  14. Investigation of surface resistance of copper in classical and anomalous skin-effect region

    International Nuclear Information System (INIS)

    Kutovoj, V.A.; Egorov, A.M.

    2008-01-01

    The surface resistance of copper in classical and anomalous skin-effect region has been investigated, and the surface resistance improvement factor equal to the ratio of the surface resistance of copper at room temperature to that of helium temperature, depending on the electromagnetic field frequency, has been determined. The improvement factor has been shown to have inverse power law dependence on frequency. The frequencies at which the improvement factor of copper equals 10 have been determined. It has been found that the quality factor of a resonance high-frequency system made of copper, operating at temperature T ≥ 4.2 K can be increased 10 times or more as against a quality factor of a resonance high-frequency system operating at room temperature

  15. Residual Resistance Data from Cavity Production Projects at Jefferson Lab

    International Nuclear Information System (INIS)

    Ciovati, Gianluigi; Geng, Rongli; Mammosser, John; Saunders, Jeffrey

    2010-01-01

    A fundamental limitation towards achieving high quality factors in superconducting radio-frequency cavities is the so-called residual resistance. Understanding and controlling the residual resistance has important implications towards improving the efficiency and reduce the operating cost of continuous wave superconducting linear accelerators. In this contribution we will report on the residual resistance values obtained from measurements of the quality factor of a large set of cavities, with resonant frequency between 805 MHz and 1.5 GHz, all of them processed and tested at Jefferson Lab. Surface treatments included both buffered chemical polishing and electropolishing. The results indicate an approximate value of the residual resistance of about 7-10 n Omega.

  16. Frequency-Independent Response of Self-Complementary Checkerboard Screens

    Science.gov (United States)

    Urade, Yoshiro; Nakata, Yosuke; Nakanishi, Toshihiro; Kitano, Masao

    2015-06-01

    This research resolves a long-standing problem on the electromagnetic response of self-complementary metallic screens with checkerboardlike geometry. Although Babinet's principle implies that they show a frequency-independent response, this unusual characteristic has not been observed yet due to the singularities of the metallic point contacts in the checkerboard geometry. We overcome this difficulty by replacing the point contacts with resistive sheets. The proposed structure is prepared and characterized by terahertz time-domain spectroscopy. It is experimentally confirmed that the resistive checkerboard structures exhibit a flat transmission spectrum over 0.1-1.1 THz. It is also demonstrated that self-complementarity can eliminate even the frequency-dependent transmission characteristics of resonant metamaterials.

  17. Development of vegetable farming: a cause of the emergence of insecticide resistance in populations of Anopheles gambiae in urban areas of Benin

    Science.gov (United States)

    Yadouleton, Anges William M; Asidi, Alex; Djouaka, Rousseau F; Braïma, James; Agossou, Christian D; Akogbeto, Martin C

    2009-01-01

    Background A fast development of urban agriculture has recently taken place in many areas in the Republic of Benin. This study aims to assess the rapid expansion of urban agriculture especially, its contribution to the emergence of insecticide resistance in populations of Anopheles gambiae. Methods The protocol was based on the collection of sociological data by interviewing vegetable farmers regarding various agricultural practices and the types of pesticides used. Bioassay tests were performed to assess the susceptibility of malaria vectors to various agricultural insecticides and biochemical analysis were done to characterize molecular status of population of An. gambiae. Results This research showed that: (1) The rapid development of urban agriculture is related to unemployment observed in cities, rural exodus and the search for a balanced diet by urban populations; (2) Urban agriculture increases the farmers' household income and their living standard; (3) At a molecular level, PCR revealed the presence of three sub-species of An. gambiae (An. gambiae s.s., Anopheles melas and Anopheles arabiensis) and two molecular forms (M and S). The kdr west mutation recorded in samples from the three sites and more specifically on the M forms seems to be one of the major resistance mechanisms found in An. gambiae from agricultural areas. Insecticide susceptibility tests conducted during this research revealed a clear pattern of resistance to permethrin (76% mortality rate at Parakou; 23.5% at Porto-Novo and 17% at Cotonou). Conclusion This study confirmed an increase activity of the vegetable farming in urban areas of Benin. This has led to the use of insecticide in an improper manner to control vegetable pests, thus exerting a huge selection pressure on mosquito larval population, which resulted to the emergence of insecticide resistance in malaria vectors. PMID:19442297

  18. Frequency effects and structural change – the Afrikaans preterite ...

    African Journals Online (AJOL)

    According to emergent grammar and exemplar theory in cognitive linguistics, the frequency of an item affects its behaviour in terms of structural change. In this article, I illustrate how high frequency items, such as preterital modal auxiliaries and copulas in Afrikaans, resist regularising with the rest of the Afrikaans verbal ...

  19. Simple PCR assays improve the sensitivity of HIV-1 subtype B drug resistance testing and allow linking of resistance mutations.

    Directory of Open Access Journals (Sweden)

    Jeffrey A Johnson

    Full Text Available BACKGROUND: The success of antiretroviral therapy is known to be compromised by drug-resistant HIV-1 at frequencies detectable by conventional bulk sequencing. Currently, there is a need to assess the clinical consequences of low-frequency drug resistant variants occurring below the detection limit of conventional genotyping. Sensitive detection of drug-resistant subpopulations, however, requires simple and practical methods for routine testing. METHODOLOGY: We developed highly-sensitive and simple real-time PCR assays for nine key drug resistance mutations and show that these tests overcome substantial sequence heterogeneity in HIV-1 clinical specimens. We specifically used early wildtype virus samples from the pre-antiretroviral drug era to measure background reactivity and were able to define highly-specific screening cut-offs that are up to 67-fold more sensitive than conventional genotyping. We also demonstrate that sequencing the mutation-specific PCR products provided a direct and novel strategy to further detect and link associated resistance mutations, allowing easy identification of multi-drug-resistant variants. Resistance mutation associations revealed in mutation-specific amplicon sequences were verified by clonal sequencing. SIGNIFICANCE: Combined, sensitive real-time PCR testing and mutation-specific amplicon sequencing provides a powerful and simple approach that allows for improved detection and evaluation of HIV-1 drug resistance mutations.

  20. Radio frequency-assisted fast superconducting switch

    Science.gov (United States)

    Solovyov, Vyacheslav; Li, Qiang

    2017-12-05

    A radio frequency-assisted fast superconducting switch is described. A superconductor is closely coupled to a radio frequency (RF) coil. To turn the switch "off," i.e., to induce a transition to the normal, resistive state in the superconductor, a voltage burst is applied to the RF coil. This voltage burst is sufficient to induce a current in the coupled superconductor. The combination of the induced current with any other direct current flowing through the superconductor is sufficient to exceed the critical current of the superconductor at the operating temperature, inducing a transition to the normal, resistive state. A by-pass MOSFET may be configured in parallel with the superconductor to act as a current shunt, allowing the voltage across the superconductor to drop below a certain value, at which time the superconductor undergoes a transition to the superconducting state and the switch is reset.

  1. Low-level quinolone-resistance in multi-drug resistant typhoid

    Energy Technology Data Exchange (ETDEWEB)

    Mirza, S H; Khan, M A [Armed Forces Inst. of Pathology, Rawalpindi (Pakistan). Dept. of Microbiolgy

    2008-01-15

    To find out the frequency of low-level quinolone-resistance in Multi-Drug Resistant (MDR) typhoid using nalidixic acid screening disc. Blood was obtained from suspected cases of typhoid fever and cultured in to BacT/ALERT. The positive blood cultures bottles were subcultured. The isolates were identified by colony morphology and biochemical tests using API-20E galleries. Susceptibility testing of isolates was done by modified Kirby-Bauer disc diffusion method on Muellar Hinton Agar. For the isolates, which were resistant to nalidixic acid by disc diffusion method, Minimal Inhibitory Concentrations (MICs) of ciprofloxacin and nalidixic acid were determined by using the E-test strips. Disc diffusion susceptibility tests and MICs were interpreted according to the guidelines provided by National Committee for Control Laboratory Standard (NCCLS). A total of 21(65.5%) out of 32 isolates of Salmonellae were nalidixic acid-resistant by disk diffusion method. All the nalidixic acid-resistant isolates by disc diffusion method were confirmed by MICs for both ciprofloxacin and nalidixic acid. All the nalidixic acid-resistant isolates had a ciprofloxacin MIC of 0.25-1 microg/ml (reduced susceptibility) and nalidixic acid MICs > 32 microg (resistant). Out of all Salmonella isolates, 24 (75%) were found to be MDR, and all were S. typbi. Low-level quinolone-resistance in typhoid was high in this small series. Screening for nalidixic acid resistance with a 30 microg nalidixic acid disk is a reliable and cost-effective method to detect low-level fluoroquinolone resistance, especially in the developing countries. (author)

  2. Low-level quinolone-resistance in multi-drug resistant typhoid

    International Nuclear Information System (INIS)

    Mirza, S.H.; Khan, M.A.

    2008-01-01

    To find out the frequency of low-level quinolone-resistance in Multi-Drug Resistant (MDR) typhoid using nalidixic acid screening disc. Blood was obtained from suspected cases of typhoid fever and cultured in to BacT/ALERT. The positive blood cultures bottles were subcultured. The isolates were identified by colony morphology and biochemical tests using API-20E galleries. Susceptibility testing of isolates was done by modified Kirby-Bauer disc diffusion method on Muellar Hinton Agar. For the isolates, which were resistant to nalidixic acid by disc diffusion method, Minimal Inhibitory Concentrations (MICs) of ciprofloxacin and nalidixic acid were determined by using the E-test strips. Disc diffusion susceptibility tests and MICs were interpreted according to the guidelines provided by National Committee for Control Laboratory Standard (NCCLS). A total of 21(65.5%) out of 32 isolates of Salmonellae were nalidixic acid-resistant by disk diffusion method. All the nalidixic acid-resistant isolates by disc diffusion method were confirmed by MICs for both ciprofloxacin and nalidixic acid. All the nalidixic acid-resistant isolates had a ciprofloxacin MIC of 0.25-1 microg/ml (reduced susceptibility) and nalidixic acid MICs > 32 microg (resistant). Out of all Salmonella isolates, 24 (75%) were found to be MDR, and all were S. typbi. Low-level quinolone-resistance in typhoid was high in this small series. Screening for nalidixic acid resistance with a 30 microg nalidixic acid disk is a reliable and cost-effective method to detect low-level fluoroquinolone resistance, especially in the developing countries. (author)

  3. Methods for Specific Electrode Resistance Measurement during Transcranial Direct Current Stimulation

    Science.gov (United States)

    Khadka, Niranjan; Rahman, Asif; Sarantos, Chris; Truong, Dennis Q.; Bikson, Marom

    2014-01-01

    Background Transcranial Direct Current Stimulation (tDCS) is investigated to treat a wide range of neuropsychiatric disorders, for rehabilitation, and for enhancing cognitive performance. The monitoring of electrode resistance before and during tDCS is considered important for tolerability and safety, where an unusually high resistance is indicative of undesired electrode or poor skin contact conditions. Conventional resistance measurement methods do not isolate individual electrode resistance but rather measures overall voltage. Moreover, for HD-tDCS devices, cross talk across electrodes makes concurrent resistance monitoring unreliable. Objective We propose a novel method for monitoring of the individual electrode resistance during tDCS, using a super-position of direct current with a test-signal (low-intensity and low-frequency sinusoids with electrode– specific frequencies) and a single sentinel electrode (not used for DC). Methods To validate this methodology, we developed lumped-parameter models of two and multi-electrode tDCS. Approaches with and without a sentinel electrode were solved and underlying assumptions identified. Assumptions were tested and parameterized in healthy participants using forearm stimulation combining tDCS (2 mA) and sinusoidal test-signals (38 μA and 76 μA peak to peak at 1 Hz, 10 Hz, and 100 Hz) and an in vitro test (where varied electrode failure modes were created). DC and AC component voltages across the electrodes were compared and participants were asked to rate subjective pain. Results A sentinel electrode is required to isolate electrode resistance in a two-electrode tDCS system. For multi-electrode resistance tracking, cross talk was aggravated with electrode proximity and current/resistance mismatches, but could be corrected using proposed approaches. Average voltage and average pain scores were not significantly different across test current intensities and frequencies (two-way repeated measures ANOVA) indicating the

  4. High Frequency of a Single Nucleotide Substitution (c.-6-180T>G) of the Canine MDR1/ABCB1 Gene Associated with Phenobarbital-Resistant Idiopathic Epilepsy in Border Collie Dogs

    OpenAIRE

    Mizukami, Keijiro; Yabuki, Akira; Chang, Hye-Sook; Uddin, Mohammad Mejbah; Rahman, Mohammad Mahbubur; Kushida, Kazuya; Kohyama, Moeko; Yamato, Osamu

    2013-01-01

    A single nucleotide substitution (c.-6-180T>G) associated with resistance to phenobarbital therapy has been found in the canine MDR1/ABCB1 gene in Border Collies with idiopathic epilepsy. In the present study, a PCR-restriction fragment length polymorphism assay was developed for genotyping this mutation, and a genotyping survey was carried out in a population of 472 Border Collies in Japan to determine the current allele frequency. The survey demonstrated the frequencies of the T/T wild type...

  5. Effects of Menstrual Phase-Dependent Resistance Training Frequency on Muscular Hypertrophy and Strength.

    Science.gov (United States)

    Sakamaki-Sunaga, Mikako; Min, Seokki; Kamemoto, Kayoko; Okamoto, Takanobu

    2016-06-01

    The present study investigated how different training frequencies during menstrual phases affect muscle hypertrophy and strength. Fourteen eumenorrheic women performed 3 sets of arm curls (8-15 repetitions) until failure for 12 weeks. Depending on the menstrual cycle phase, each subject trained each arm separately after either a 3- or a 1-d·wk training protocol during the follicular phase (FP-T) and a 3- or 1-d·wk training protocol during the luteal phase (LP-T). Cross-sectional area (CSA), 1 repetition maximum, and maximum voluntary contraction significantly increased 6.2 ± 4.4, 36.4 ± 11.9, and 16.7 ± 5.6%, respectively (p ≤ 0.05 vs. before training), in the FP-T group and 7.8 ± 4.2, 31.8 ± 14.1, and 14.9 ± 12.7%, respectively (p ≤ 0.05 vs. before training), in the LP-T group. Changes in CSA between the FP-T and the LP-T groups significantly and positively correlated (r = 0.54, p ≤ 0.05). There were no major differences among the different training protocols with regard to muscle hypertrophy and strength. Therefore, we suggest that variations in female hormones induced by the menstrual cycle phases do not significantly contribute to muscle hypertrophy and strength gains during 12 weeks of resistance training.

  6. Antimicrobial resistance patterns and plasmid profiles of ...

    African Journals Online (AJOL)

    Objectives: To determine the frequency of resistance of Staphylococcus aureus to various antimicrobial agents, and the relationship between antimicrobial resistance of the isolates and carriage of plasmids. Design: A random sampling of milk and meat samples was carried out. Setting: Milk was collected from various dairy ...

  7. Bioakumulasi Logam Berat oleh Beberapa Galur Bradyrhizobium japonicum

    Directory of Open Access Journals (Sweden)

    ADE NOOR SYAMSUDIN

    2005-09-01

    Full Text Available Heavy metal utilization in industry and agriculture have caused an environmental problem to existing life. Bioaccumulation is made up by a concentration of certain chemical compounds in living tissues. The objective of this research was to reveal the ability of lipopolysaccharides (LPSs of heavy metal Bradyrhizobium japonicum tolerant strains in accumulating heavy metals. The strains used were BDG 10, KDR 10, and KDR 15. The ability of each strains on heavy metal accumulation of Cu, Pb, Zn, Ni, and Cd were quantitatively determined using atomic absorption spectrophotometry. The result showed that each strains has its own capacity to accumulate heavy metals. Accumulation of Cu (0.100, Pb (0.320, and Cd (0.048 ppm/mg dry weight by KDR 10 seem higher than BDG 10 and KDR 15. The highest accumulation of Zn and Ni was shown by KDR 15 in which the value were 0.360 and 0.165 ppm/mg dry weight, respectively and the least accumulation of all heavy metal studied was shown by BDG 10.

  8. Susceptibility of Anopheles gambiae to insecticides used for malaria vector control in Rwanda.

    Science.gov (United States)

    Hakizimana, Emmanuel; Karema, Corine; Munyakanage, Dunia; Iranzi, Gad; Githure, John; Tongren, Jon Eric; Takken, Willem; Binagwaho, Agnes; Koenraadt, Constantianus J M

    2016-12-01

    The widespread emergence of resistance to pyrethroids is a major threat to the gains made in malaria control. To monitor the presence and possible emergence of resistance against a variety of insecticides used for malaria control in Rwanda, nationwide insecticide resistance surveys were conducted in 2011 and 2013. Larvae of Anopheles gambiae sensu lato mosquitoes were collected in 12 sentinel sites throughout Rwanda. These were reared to adults and analysed for knock-down and mortality using WHO insecticide test papers with standard diagnostic doses of the recommended insecticides. A sub-sample of tested specimens was analysed for the presence of knockdown resistance (kdr) mutations. A total of 14,311 mosquitoes were tested and from a sample of 1406 specimens, 1165 (82.9%) were identified as Anopheles arabiensis and 241 (17.1%) as Anopheles gambiae sensu stricto. Mortality results indicated a significant increase in resistance to lambda-cyhalothrin from 2011 to 2013 in 83% of the sites, permethrin in 25% of the sites, deltamethrin in 25% of the sites and DDT in 50% of the sites. Mosquitoes from 83% of the sites showed full susceptibility to bendiocarb and 17% of sites were suspected to harbour resistance that requires further confirmation. No resistance was observed to fenitrothion in all study sites during the entire survey. The kdr genotype results in An. gambiae s.s. showed that 67 (50%) possessed susceptibility (SS) alleles, while 35 (26.1%) and 32 (23.9%) mosquitoes had heterozygous (RS) and homozygous (RR) alleles, respectively. Of the 591 An. arabiensis genotyped, 425 (71.9%) possessed homozygous (SS) alleles while 158 (26.7%) and 8 (1.4%) had heterozygous (RS) and homozygous (RR) alleles, respectively. Metabolic resistance involving oxidase enzymes was also detected using the synergist PBO. This is the first nationwide study of insecticide resistance in malaria vectors in Rwanda. It shows the gradual increase of insecticide resistance to pyrethroids (lambda

  9. Dynamic regimes in YBCO in applied magnetic field probed by swept frequency microwave measurements

    International Nuclear Information System (INIS)

    Sarti, S; Silva, E; Giura, M; Fastampa, R; Boffa, M; Cucolo, A M

    2004-01-01

    We report measurements of the microwave resistivity in YBa 2 Cu 3 O 7-δ (YBCO), in the presence of an applied magnetic field. Measurements are performed as a function of frequency, over a continuum spectrum between 6 and 20 GHz, by means of a Corbino disc geometry. These data allow for a direct identification of different dynamical regimes in the dissipation of YBCO in the presence of an applied magnetic field. While at high temperatures a frequency independent resistivity is observed, at lower temperatures we find a marked frequency dependence. The line in the (H,T) plane at which this change in the dynamical regime is observed is clearly identified and discussed in terms of vortex motion and fluctuational resistivity

  10. Characterization of the voltage-gated sodium channel of the Asian citrus psyllid, Diaphorina citri.

    Science.gov (United States)

    Liu, Bin; Coy, Monique R; Wang, Jin-Jun; Stelinski, Lukasz L

    2017-02-01

    The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an important insect pest of citrus. It is the vector of 'Candidatus' Liberibacter asiaticus, a phloem-limited bacterium that infects citrus, resulting in the disease Huanglongbing (HLB). Disease management relies heavily on suppression of D. citri populations with insecticides, including pyrethroids. In recent annual surveys to monitor insecticide resistance, reduced susceptibility to fenpropathrin was identified in several field populations of D. citri. The primary target of pyrethroids is the voltage-gated sodium channel (VGSC). The VGSC is prone to target-site insensitivity because of mutations that either reduce pyrethroid binding and/or alter gating kinetics. These mutations, known as knockdown resistance or kdr, have been reported in a wide diversity of arthropod species. Alternative splicing, in combination with kdr mutations, has been also associated with reduced pyrethroid efficacy. Here we report the molecular characterization of the VGSC in D. citri along with a survey of alternative splicing across developmental stages of this species. Previous studies demonstrated that D. citri has an exquisite enzymatic arsenal to detoxify insecticides resulting in reduced efficacy. The results from the current investigation demonstrate that target-site insensitivity is also a potential basis for insecticide resistance to pyrethroids in D. citri. The VGSC sequence and its molecular characterization should facilitate early elucidation of the underlying cause of an established case of resistance to pyrethroids. This is the first characterization of a VGSC from a hemipteran to this level of detail, with the majority of the previous studies on dipterans and lepidopterans. © 2015 Institute of Zoology, Chinese Academy of Sciences.

  11. Resistance of Uropathogens in Asymptomatic Urinary Tract Infection ...

    African Journals Online (AJOL)

    Worldwide the surveillance of antimicrobial resistance among urinary tract pathogens is useful to determine the important trend and geographical variation of uropathogens. The study evaluated the pathogen frequency, resistance rate and pattern among HIV-infected Nigerians. Midstream urine samples taken for culture ...

  12. The spatial distribution of Anopheles gambiae sensu stricto and An. arabiensis (Diptera: Culicidae in Mali

    Directory of Open Access Journals (Sweden)

    N. Sogoba

    2007-05-01

    Full Text Available Variations in the biology and ecology and the high level of genetic polymorphism of malaria vectors in Africa highlight the value of mapping their spatial distribution to enhance successful implementation of integrated vector management. The objective of this study was to collate data on the relative frequencies of Anopheles gambiae s.s. and An. arabiensis mosquitoes in Mali, to assess their association with climate and environmental covariates, and to produce maps of their spatial distribution. Bayesian geostatistical logistic regression models were fitted to identify environmental determinants of the relative frequencies of An. gambiae s.s. and An. arabiensis species and to produce smooth maps of their geographical distribution. The frequency of An. arabiensis was positively associated with the normalized difference vegetation index, the soil water storage index, the maximum temperature and the distance to water bodies. It was negatively associated with the minimum temperature and rainfall. The predicted map suggests that, in West Africa, An. arabiensis is concentrated in the drier savannah areas, while An. gambiae s.s. prefers the southern savannah and land along the rivers, particularly the inner delta of Niger. Because the insecticide knockdown resistance (kdr gene is reported only in An. gambiae s.s. in Mali, the maps provide valuable information for vector control. They may also be useful for planning future implementation of malaria control by genetically manipulated mosquitoes.

  13. The occurrence and frequency of genomic mutations that mediate ...

    African Journals Online (AJOL)

    The occurrence and frequency of genomic mutations that mediate Isoniazid and Rifampicin resistance in Mycobacterium tuberculosis isolates from untreated pulmonary Tuberculosis cases in urban Blantyre, Malawi.

  14. Radiation induction of drug resistance in RIF-1: Correlation of tumor and cell culture results

    International Nuclear Information System (INIS)

    Moulder, J.E.; Hopwood, L.E.; Volk, D.M.; Davies, B.M.

    1991-01-01

    The RIF-1 tumor line contains cells that are resistant to various anti-neoplastic drugs, including 5-fluorouracil (5FU), methotrexate (MTX), adriamycin (ADR), and etoposide (VP16). The frequency of these drug-resistant cells is increased after irradiation. The frequency of drug-resistant cells and the magnitude of radiation-induced drug resistance are different in cell culture than in tumors. The dose-response and expression time relationships for radiation induction of drug resistance observed in RIF-1 tumors are unusual.We hypothesize that at high radiation doses in vivo, we are selecting for cells that are both drug resistant and radiation resistant due to microenvironmental factors, whereas at low radiation doses in vivo and all radiation doses in vitro, we are observing true mutants. These studies indicate that there can be significant differences in drug-resistance frequencies between tumors and their cell lines of origin, and that radiation induction of drug resistance depends significantly on whether the induction is done in tumors or in cell culture. These results imply that theories about the induction of drug resistance that are based on cell culture studies may be inapplicable to the induction of drug resistance in tumors

  15. High frequency of silver resistance genes in invasive isolates of Enterobacter and Klebsiella species.

    Science.gov (United States)

    Sütterlin, S; Dahlö, M; Tellgren-Roth, C; Schaal, W; Melhus, Å

    2017-07-01

    Silver-based products have been marketed as an alternative to antibiotics, and their consumption has increased. Bacteria may, however, develop resistance to silver. To study the presence of genes encoding silver resistance (silE, silP, silS) over time in three clinically important Enterobacteriaceae genera. Using polymerase chain reaction (PCR), 752 bloodstream isolates from the years 1990-2010 were investigated. Age, gender, and ward of patients were registered, and the susceptibility to antibiotics and silver nitrate was tested. Clonality and single nucleotide polymorphism were assessed with repetitive element sequence-based PCR, multi-locus sequence typing, and whole-genome sequencing. Genes encoding silver resistance were detected most frequently in Enterobacter spp. (48%), followed by Klebsiella spp. (41%) and Escherichia coli 4%. Phenotypical resistance to silver nitrate was found in Enterobacter (13%) and Klebsiella (3%) isolates. The lowest carriage rate of sil genes was observed in blood isolates from the neonatology ward (24%), and the highest in blood isolates from the oncology/haematology wards (66%). Presence of sil genes was observed in international high-risk clones. Sequences of the sil and pco clusters indicated that a single mutational event in the silS gene could have caused the phenotypic resistance. Despite a restricted consumption of silver-based products in Swedish health care, silver resistance genes are widely represented in clinical isolates of Enterobacter and Klebsiella species. To avoid further selection and spread of silver-resistant bacteria with a high potential for healthcare-associated infections, the use of silver-based products needs to be controlled and the silver resistance monitored. Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

  16. Carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool

    International Nuclear Information System (INIS)

    Cai, Yu; Sha, Shuang

    2016-01-01

    This paper proposes a new carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool used in a cylindrical borehole environment during oil-based mud drilling processes. The new tool is an orthogonal frequency division multiplexing access-based contactless multi-measurand detection tool. The tool can measure formation resistivity in different azimuthal angles and elevational depths. It can measure many more measurands simultaneously in a specified bandwidth than the legacy frequency division multiplexing multi-measurand tool without a channel-select filter while avoiding inter-carrier interference. The paper also shows that formation resistivity is not sensitive to frequency in certain frequency bands. The average resistivity collected from N subcarriers can increase the measurement of the signal-to-noise ratio (SNR) by N times given no amplitude clipping in the current-injection electrode. If the clipping limit is taken into account, with the phase rotation of each single carrier, the amplitude peak-to-average ratio can be reduced by 3 times, and the SNR can achieve a 9/ N times gain over the single-carrier system. The carrier-interleaving technique is also introduced to counter the carrier frequency offset (CFO) effect, where the CFO will cause inter-pad interference. A qualitative analysis and simulations demonstrate that block-interleaving performs better than tone-interleaving when coping with a large CFO. The theoretical analysis also suggests that increasing the subcarrier number can increase the measurement speed or enhance elevational resolution without sacrificing receiver performance. The complex orthogonal multi-pad multi-carrier resistivity logging tool, in which all subcarriers are complex signals, can provide a larger available subcarrier pool than other types of transceivers. (paper)

  17. Inertia and ion Landau damping of low-frequency magnetohydrodynamical modes in tokamaks

    International Nuclear Information System (INIS)

    Bondeson, A.; Chu, M.S.

    1996-01-01

    The inertia and Landau damping of low-frequency magnetohydrodynamical modes are investigated using the drift-kinetic energy principle for the motion along the magnetic field. Toroidal trapping of the ions decreases the Landau damping and increases the inertia for frequencies below (r/R) 1/2 v thi /qR. The theory is applied to toroidicity-induced Alfvacute en eigenmodes and to resistive wall modes in rotating plasmas. An explanation of the beta-induced Alfvacute en eigenmode is given in terms of the Pfirsch endash Schlueter-like enhancement of inertia at low frequency. The toroidal inertia enhancement also increases the effects of plasma rotation on resistive wall modes. copyright 1996 American Institute of Physics

  18. Treatment of Resistant Idiopathic Hiccups with Pulse Radio ...

    African Journals Online (AJOL)

    2017-09-14

    Sep 14, 2017 ... Our case suggests that administration of gabapentin after pulsed radiofrequency might be effective for the treatment of persistent hiccups. KEYWORDS: Hiccups, persistent, pulse radio frequency. Treatment of Resistant Idiopathic Hiccups with Pulse Radio Frequency on Phrenic Nerve and Gabapentin: A ...

  19. Genetic and environmental variation in rust frequency on mature mountain birch trees

    Energy Technology Data Exchange (ETDEWEB)

    Elamo, Pirjo; Saloniemi, Irma; Helander, M.L.; Neuvonen, Seppo [Turku Univ. (Finland). Dept. of Biology) and (Kevo Subarctic Research Inst., Turku (Finland)

    2000-07-01

    This study investigated genetic and environmental variation in the frequency of birch rust, the most important leaf disease of birch species, The same half-sib families of mature mountain birch trees were studied in two areas corresponding to their natural growing habitats over 3 yrs. The frequency of birch rust was examined both in the field and from detached leaves inoculated in the laboratory. The frequency of birch rust varied among the mountain birch families. However, the heritability of birch rust resistance was found to be fairly low, with the heritability of naturally occurring birch rust varying between 0.27 and 0.41. The frequency of birch rust varied highly between the two study areas and among study years. Nevertheless, the relative frequency of birch rust among tree individuals and tree families remained similar and as a result no notable genotype x environment interaction was observed. The field and in vitro results differed with respect to the ranking of birch families by birch rust resistance.

  20. Resistance to antimicrobial agents among Salmonella isolates recovered from layer farms and eggs in the Caribbean region.

    Science.gov (United States)

    Adesiyun, Abiodun; Webb, Lloyd; Musai, Lisa; Louison, Bowen; Joseph, George; Stewart-Johnson, Alva; Samlal, Sannandan; Rodrigo, Shelly

    2014-12-01

    This investigation determined the frequency of resistance of 84 isolates of Salmonella comprising 14 serotypes recovered from layer farms in three Caribbean countries (Trinidad and Tobago, Grenada, and St. Lucia) to eight antimicrobial agents, using the disc diffusion method. Resistance among isolates of Salmonella was related to the country of recovery, type of sample, size of layer farms, and isolate serotype. Overall, all (100.0%) of the isolates exhibited resistance to one or more of seven antimicrobial agents tested, and all were susceptible to chloramphenicol. The resistance detected ranged from 11.9% to sulphamethoxazole-trimethoprim (SXT) to 100.0% to erythromycin. The difference was, however, not statistically significant (P = 0.23). Across countries, for types of samples that yielded Salmonella, significant differences in frequency of resistance were detected only to SXT (P = 0.002) in Trinidad and Tobago and to gentamycin (P = 0.027) in St. Lucia. For the three countries, the frequency of resistance to antimicrobial agents was significantly different for ampicillin (P = 0.001) and SXT (P = 0.032). A total of 83 (98.8%) of the 84 isolates exhibited 39 multidrug resistance patterns. Farm size significantly (P = 0.032) affected the frequency of resistance to kanamycin across the countries. Overall, among the 14 serotypes of Salmonella tested, significant (P resistance were detected to kanamycin, ampicillin, and SXT. Results suggest that the relatively high frequency of resistance to six of the antimicrobial agents (erythromycin, streptomycin, gentamycin, kanamycin, ampicillin, and tetracycline) tested and the multidrug resistance detected may pose prophylactic and therapeutic concerns for chicken layer farms in the three countries studied.

  1. Insecticide resistance in Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and Anopheles gambiae Giles (Diptera: Culicidae) could compromise the sustainability of malaria vector control strategies in West Africa.

    Science.gov (United States)

    Gnankiné, Olivier; Bassolé, Imael H N; Chandre, Fabrice; Glitho, Isabelle; Akogbeto, Martin; Dabiré, Roch K; Martin, Thibaud

    2013-10-01

    Insecticides from the organophosphate (OP) and pyrethroid (PY) chemical families, have respectively, been in use for 50 and 30 years in West Africa, mainly against agricultural pests, but also against vectors of human disease. The selection pressure, with practically the same molecules year after year (mainly on cotton), has caused insecticide resistance in pest populations such as Bemisia tabaci, vector of harmful phytoviruses on vegetables. The evolution toward insecticide resistance in malaria vectors such as Anopheles gambiae sensus lato (s.l.) is probably related to the current use of these insecticides in agriculture. Thus, successful pest and vector control in West Africa requires an investigation of insect susceptibility, in relation to the identification of species and sub species, such as molecular forms or biotypes. Identification of knock down resistance (kdr) and acetylcholinesterase gene (Ace1) mutations modifying insecticide targets in individual insects and measure of enzymes activity typically involved in insecticide metabolism (oxidase, esterase and glutathion-S-transferase) are indispensable in understanding the mechanisms of resistance. Insecticide resistance is a good example in which genotype-phenotype links have been made successfully. Insecticides used in agriculture continue to select new resistant populations of B. tabaci that could be from different biotype vectors of plant viruses. As well, the evolution of insecticide resistance in An. gambiae threatens the management of malaria vectors in West Africa. It raises the question of priority in the use of insecticides in health and/or agriculture, and more generally, the question of sustainability of crop protection and vector control strategies in the region. Here, we review the susceptibility tests, biochemical and molecular assays data for B. tabaci, a major pest in cotton and vegetable crops, and An. gambiae, main vector of malaria. The data reviewed was collected in Benin and Burkina

  2. Murine bone marrow Lin⁻Sca⁻1⁺CD45⁻ very small embryonic-like (VSEL cells are heterogeneous population lacking Oct-4A expression.

    Directory of Open Access Journals (Sweden)

    Krzysztof Szade

    Full Text Available Murine very small embryonic-like (VSEL cells, defined by the Lin(-Sca-1(+CD45(- phenotype and small size, were described as pluripotent cells and proposed to be the most primitive hematopoietic precursors in adult bone marrow. Although their isolation and potential application rely entirely on flow cytometry, the immunophenotype of VSELs has not been extensively characterized. Our aim was to analyze the possible heterogeneity of Lin(-Sca(+CD45(- population and investigate the extent to which VSELs characteristics may overlap with that of hematopoietic stem cells (HSCs or endothelial progenitor cells (EPCs. The study evidenced that murine Lin(-Sca-1(+CD45(- population was heterogeneous in terms of c-Kit and KDR expression. Accordingly, the c-Kit(+KDR(-, c-Kit(-KDR(+, and c-Kit(-KDR(- subpopulations could be distinguished, while c-Kit(+KDR(+ events were very rare. The c-Kit(+KDR(- subset contained almost solely small cells, meeting the size criterion of VSELs, in contrast to relatively bigger c-Kit(-KDR(+ cells. The c-Kit(-KDR(-FSC(low subset was highly enriched in Annexin V-positive, apoptotic cells, hence omitted from further analysis. Importantly, using qRT-PCR, we evidenced lack of Oct-4A and Oct-4B mRNA expression either in whole adult murine bone marrow or in the sorted of Lin(-Sca-1(+CD45(-FSC(low population, even by single-cell qRT-PCR. We also found that the Lin(-Sca-1(+CD45(-c-Kit(+ subset did not exhibit hematopoietic potential in a single cell-derived colony in vitro assay, although it comprised the Sca-1(+c-Kit(+Lin(- (SKL CD34(-CD45(-CD105(+ cells, expressing particular HSC markers. Co-culture of Lin(-Sca-1(+CD45(-FSC(low with OP9 cells did not induce hematopoietic potential. Further investigation revealed that SKL CD45(-CD105(+ subset consisted of early apoptotic cells with fragmented chromatin, and could be contaminated with nuclei expelled from erythroblasts. Concluding, murine bone marrow Lin(-Sca-1(+CD45(-FSC(low cells are

  3. Resistive theory of bunch lengthening

    International Nuclear Information System (INIS)

    Month, M.; Messerschmid, E.

    1977-01-01

    A new theory of bunch lengthening in electron storage rings is proposed. The equilibrium bunch length is that length which stabilizes the bunch against the onset of ''fast'' resistive instability, caused by the combination of many high frequency resonators such as vacuum flanges. The heat dissipated in these impedance sources follows immediately from the bunch length. It is found that the anomalous bunch length is determined by a scaling parameter g = (hVcos phi/sub s/)/I. Data taken in SPEAR I and II, data in which g extends in value by more than three orders of magnitude, can be fit with an appropriate choice of high frequency, large width coupling impedance. The impedance functions for SPEAR I and II are taken to be the same, a reflection of the fact that the high frequency sources are chamber discontinuities rather than structures connected with the rf systems. A parameter search leads to an impedance characterized by a central frequency approximately 5 GHz, a width (FWHM) approximately 1.8 GHz and a peak impedance approximately 0.2 M OMEGA. The expected and observed higher mode resistance (i.e., heat dissipated) for SPEAR are compared and found to be in agreement. Predictions are given for PEP and PETRA

  4. Moving towards high-power, high-frequency and low-resistance CNT supercapacitors by tuning the CNT length, axial deformation and contact resistance

    Science.gov (United States)

    Basiricò, L.; Lanzara, G.

    2012-08-01

    In this paper it is shown that the electrochemical behaviour of vertically aligned multi-walled carbon nanotube (VANT) supercapacitors is influenced by the VANTs’ length (electrode thickness), by their axial compression and by their interface with the current collector. It is found that the VANTs, which can be interpreted as a dense array of nanochannels, have an active area available to ions that is strongly affected by the electrode’s thickness and compressional state. Consequently, the tested thinner electrodes, compressed electrodes or a combination of the two were found to be characterized by a significant improvement in terms of power density (up to 1246%), knee frequency (58 822% working up to 10 kHz), equivalent series resistance (ESR, up to 67%) and capacitance (up to 21%) when compared with thicker and/or uncompressed electrodes. These values are significantly higher than those reported in the literature where long VANTs with no control on compression are typically used. It is also shown that the ESR can be reduced not only by using shorter and compressed VANTs that have a higher conductance or by improving the electrode/collector electrical contact by changing the contact morphology at the nanoscale through compression, but also by depositing a thin platinum layer on the VANT tips in contact with the current collector (73% ESR decrease).

  5. Moving towards high-power, high-frequency and low-resistance CNT supercapacitors by tuning the CNT length, axial deformation and contact resistance

    International Nuclear Information System (INIS)

    Basiricò, L; Lanzara, G

    2012-01-01

    In this paper it is shown that the electrochemical behaviour of vertically aligned multi-walled carbon nanotube (VANT) supercapacitors is influenced by the VANTs’ length (electrode thickness), by their axial compression and by their interface with the current collector. It is found that the VANTs, which can be interpreted as a dense array of nanochannels, have an active area available to ions that is strongly affected by the electrode’s thickness and compressional state. Consequently, the tested thinner electrodes, compressed electrodes or a combination of the two were found to be characterized by a significant improvement in terms of power density (up to 1246%), knee frequency (58 822% working up to 10 kHz), equivalent series resistance (ESR, up to 67%) and capacitance (up to 21%) when compared with thicker and/or uncompressed electrodes. These values are significantly higher than those reported in the literature where long VANTs with no control on compression are typically used. It is also shown that the ESR can be reduced not only by using shorter and compressed VANTs that have a higher conductance or by improving the electrode/collector electrical contact by changing the contact morphology at the nanoscale through compression, but also by depositing a thin platinum layer on the VANT tips in contact with the current collector (73% ESR decrease). (paper)

  6. The adapter protein, Grb10, is a positive regulator of vascular endothelial growth factor signaling.

    Science.gov (United States)

    Giorgetti-Peraldi, S; Murdaca, J; Mas, J C; Van Obberghen, E

    2001-07-05

    Vascular endothelial growth factor (VEGF) is an important regulator of vasculogenesis and angiogenesis. Activation of VEGF receptors leads to the recruitment of SH2 containing proteins which link the receptors to the activation of signaling pathways. Here we report that Grb10, an adapter protein of which the biological role remains unknown, is tyrosine phosphorylated in response to VEGF in endothelial cells (HUVEC) and in 293 cells expressing the VEGF receptor KDR. An intact SH2 domain is required for Grb10 tyrosine phosphorylation in response to VEGF, and this phosphorylation is mediated in part through the activation of Src. In HUVEC, VEGF increases Grb10 mRNA level. Expression of Grb10 in HUVEC or in KDR expressing 293 cells results in an increase in the amount and in the tyrosine phosphorylation of KDR. In 293 cells, this is correlated with the activation of signaling molecules, such as MAP kinase. By expressing mutants of Grb10, we found that the positive action of Grb10 is independent of its SH2 domain. Moreover, these Grb10 effects on KDR seem to be specific since Grb10 has no effect on the insulin receptor, and Grb2, another adapter protein, does not mimic the effect of Grb10 on KDR. In conclusion, we propose that VEGF up-regulates Grb10 level, which in turn increases KDR molecules, suggesting that Grb10 could be involved in a positive feedback loop in VEGF signaling.

  7. Sulfonamide-resistant bacteria and their resistance genes in soils fertilized with manures from Jiangsu Province, Southeastern China.

    Directory of Open Access Journals (Sweden)

    Na Wang

    Full Text Available Antibiotic-resistant bacteria and genes are recognized as new environmental pollutants that warrant special concern. There were few reports on veterinary antibiotic-resistant bacteria and genes in China. This work systematically analyzed the prevalence and distribution of sulfonamide resistance genes in soils from the environments around poultry and livestock farms in Jiangsu Province, Southeastern China. The results showed that the animal manure application made the spread and abundance of antibiotic resistance genes (ARGs increasingly in the soil. The frequency of sulfonamide resistance genes was sul1 > sul2 > sul3 in pig-manured soil DNA and sul2 > sul1 > sul3 in chicken-manured soil DNA. Further analysis suggested that the frequency distribution of the sul genes in the genomic DNA and plasmids of the SR isolates from manured soil was sul2 > sul1 > sul3 overall (p<0.05. The combination of sul1 and sul2 was the most frequent, and the co-existence of sul1 and sul3 was not found either in the genomic DNA or plasmids. The sample type, animal type and sampling time can influence the prevalence and distribution pattern of sulfonamide resistance genes. The present study also indicated that Bacillus, Pseudomonas and Shigella were the most prevalent sul-positive genera in the soil, suggesting a potential human health risk. The above results could be important in the evaluation of antibiotic-resistant bacteria and genes from manure as sources of agricultural soil pollution; the results also demonstrate the necessity and urgency of the regulation and supervision of veterinary antibiotics in China.

  8. Frequency dependence of the active impedance component of silicon thin-film resistors

    International Nuclear Information System (INIS)

    Belogurov, S.V.; Gostilo, V.V.; Yurov, A.S.

    1987-01-01

    A high-resistant resistor on the silicon thin-film substrate considerably superior in noise and frequency performance than commercial resistors is described. The frequency dependence of the active impedance component is tested for determining noise and frequency dependences of silicon thin-film resistors. The obtained results permit to calculate the energy equivalent of resistor noise in nuclear radiation detection units at any temperature according to its frequency characteristic at room temperature

  9. Negative frequency-dependent selection between Pasteuria penetrans and its host Meloidogyne arenaria

    Science.gov (United States)

    In negative frequency-dependant selection (NFDS), parasite genotypes capable of infecting the numerically dominant host genotype are favored, while host genotypes resistant to the dominant parasite genotype are favored, creating a cyclical pattern of resistant genotypes in the host population and, a...

  10. Arterial Stiffness and Autonomic Modulation After Free-Weight Resistance Exercises in Resistance Trained Individuals.

    Science.gov (United States)

    Kingsley, J Derek; Mayo, Xián; Tai, Yu Lun; Fennell, Curtis

    2016-12-01

    Kingsley, JD, Mayo, X, Tai, YL, and Fennell, C. Arterial stiffness and autonomic modulation after free-weight resistance exercises in resistance trained individuals. J Strength Cond Res 30(12): 3373-3380, 2016-We investigated the effects of an acute bout of free-weight, whole-body resistance exercise consisting of the squat, bench press, and deadlift on arterial stiffness and cardiac autonomic modulation in 16 (aged 23 ± 3 years; mean ± SD) resistance-trained individuals. Arterial stiffness, autonomic modulation, and baroreflex sensitivity (BRS) were assessed at rest and after 3 sets of 10 repetitions at 75% 1-repetition maximum on each exercise with 2 minutes of rest between sets and exercises. Arterial stiffness was analyzed using carotid-femoral pulse wave velocity (cf-PWV). Linear heart rate variability (log transformed [ln] absolute and normalized units [nu] of low-frequency [LF] and high-frequency [HF] power) and nonlinear heart rate complexity (Sample Entropy [SampEn], Lempel-Ziv Entropy [LZEn]) were measured to determine autonomic modulation. BRS was measured by the sequence method. A 2 × 2 repeated measures analysis of variance (ANOVA) was used to analyze time (rest, recovery) across condition (acute resistance exercise, control). There were significant increases in cf-PWV (p = 0.05), heart rate (p = 0.0001), normalized LF (LFnu; p = 0.001), and the LF/HF ratio (p = 0.0001). Interactions were also noted for ln HF (p = 0.006), HFnu (p = 0.0001), SampEn (p = 0.001), LZEn (p = 0.005), and BRS (p = 0.0001) such that they significantly decreased during recovery from the resistance exercise compared with rest and the control. There was no effect on ln total power, or ln LF. These data suggest that a bout of resistance exercise using free-weights increases arterial stiffness and reduces vagal activity and BRS in comparison with a control session. Vagal tone may not be fully recovered up to 30 minutes after a resistance exercise bout.

  11. Insecticide resistance and, efficacy of space spraying and larviciding in the control of dengue vectors Aedes aegypti and Aedes albopictus in Sri Lanka.

    Science.gov (United States)

    Karunaratne, S H P P; Weeraratne, T C; Perera, M D B; Surendran, S N

    2013-09-01

    Unprecedented incidence of dengue has been recorded in Sri Lanka in recent times. Source reduction and use of insecticides in space spraying/fogging and larviciding, are the primary means of controlling the vector mosquitoes Aedes aegypti and Ae. albopictus in the island nation. A study was carried out to understand insecticide cross-resistance spectra and mechanisms of insecticide resistance of both these vectors from six administrative districts, i.e. Kandy, Kurunegala, Puttalam, Gampaha, Ratnapura and Jaffna, of Sri Lanka. Efficacy of the recommended dosages of frequently used insecticides in space spraying and larviciding in dengue vector control programmes was also tested. Insecticide bioassay results revealed that, in general, both mosquito species were highly resistant to DDT but susceptible to propoxur and malathion except Jaffna Ae. aegypti population. Moderate resistance to malathion shown by Jaffna Ae. aegypti population correlated with esterase and malathion carboxylesterase activities of the population. High levels of acetylcholinesterase (AChE) insensitivity in the absence of malathion and propoxur resistance may be due to non-synaptic forms of AChE proteins. Moderate pyrethroid resistance in the absence of high monooxygenase levels indicated the possible involvement of 'kdr' type resistance mechanism in Sri Lankan dengue vectors. Results of the space spraying experiments revealed that 100% mortality at a 10 m distance and >50% mortality at a 50 m distance can be achieved with malathion, pesguard and deltacide even in a ground with dense vegetation. Pesguard and deltacide spraying gave 100% mortality up to 50 m distance in open area and areas with little vegetation. Both species gave >50% mortalities for deltacide at a distance of 75 m in a dense vegetation area. Larval bioassays conducted in the laboratory showed that a 1 ppm temephos solution can maintain a larval mortality rate of 100% for ten months, and the mortality rate declined to 0% in the

  12. Frequency Response of Graphene Electrolyte-Gated Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Charles Mackin

    2018-02-01

    Full Text Available This work develops the first frequency-dependent small-signal model for graphene electrolyte-gated field-effect transistors (EGFETs. Graphene EGFETs are microfabricated to measure intrinsic voltage gain, frequency response, and to develop a frequency-dependent small-signal model. The transfer function of the graphene EGFET small-signal model is found to contain a unique pole due to a resistive element, which stems from electrolyte gating. Intrinsic voltage gain, cutoff frequency, and transition frequency for the microfabricated graphene EGFETs are approximately 3.1 V/V, 1.9 kHz, and 6.9 kHz, respectively. This work marks a critical step in the development of high-speed chemical and biological sensors using graphene EGFETs.

  13. Targeted molecular profiling of rare genetic alterations in colorectal cancer using next-generation sequencing.

    Science.gov (United States)

    Jauhri, Mayank; Bhatnagar, Akanksha; Gupta, Satish; Shokeen, Yogender; Minhas, Sachin; Aggarwal, Shyam

    2016-10-01

    Mutation frequencies of common genetic alterations in colorectal cancer have been in the spotlight for many years. This study highlights few rare somatic mutations, which possess the attributes of a potential CRC biomarker yet are often neglected. Next-generation sequencing was performed over 112 tumor samples to detect genetic alterations in 31 rare genes in colorectal cancer. Mutations were detected in 26/31 (83.9 %) uncommon genes, which together contributed toward 149 gene mutations in 67/112 (59.8 %) colorectal cancer patients. The most frequent mutations include KDR (19.6 %), PTEN (17 %), FBXW7 (10.7 %), SMAD4 (10.7 %), VHL (8 %), KIT (8 %), MET (7.1 %), ATM (6.3 %), CTNNB1 (4.5 %) and CDKN2A (4.5 %). RB1, ERBB4 and ERBB2 mutations were persistent in 3.6 % patients. GNAS, FGFR2 and FGFR3 mutations were persistent in 1.8 % patients. Ten genes (EGFR, NOTCH1, SMARCB1, ABL1, STK11, SMO, RET, GNAQ, CSF1R and FLT3) were found mutated in 0.9 % patients. Lastly, no mutations were observed in AKT, HRAS, MAP2K1, PDGFR and JAK2. Significant associations were observed between VHL with tumor site, ERBB4 and SMARCB1 with tumor invasion, CTNNB1 with lack of lymph node involvement and CTNNB1, FGFR2 and FGFR3 with TNM stage. Significantly coinciding mutation pairs include PTEN and SMAD4, PTEN and KDR, EGFR and RET, EGFR and RB1, FBXW7 and CTNNB1, KDR and FGFR2, FLT3 and CTNNB1, RET and RB1, ATM and SMAD4, ATM and CDKN2A, ERBB4 and SMARCB1. This study elucidates few potential colorectal cancer biomarkers, specifically KDR, PTEN, FBXW7 and SMAD4, which are found mutated in more than 10 % patients.

  14. Frequency of resistance in obligate anaerobic bacteria isolated from dogs, cats, and horses to antimicrobial agents.

    Science.gov (United States)

    Lawhon, S D; Taylor, A; Fajt, V R

    2013-11-01

    Clinical specimens from dogs, cats, and horses were examined for the presence of obligate anaerobic bacteria. Of 4,018 specimens cultured, 368 yielded 606 isolates of obligate anaerobic bacteria (248 from dogs, 50 from cats, and 308 from horses). There were 100 specimens from 94 animals from which only anaerobes were isolated (25 dogs, 8 cats, and 61 horses). The most common sites tested were abdominal fluid (dogs and cats) and intestinal contents (horses). The most common microorganism isolated from dogs, cats, and horses was Clostridium perfringens (75, 13, and101 isolates, respectively). The MICs of amoxicillin with clavulanate, ampicillin, chloramphenicol, metronidazole, and penicillin were determined using a gradient endpoint method for anaerobes. Isolates collected at necropsy were not tested for antimicrobial susceptibility unless so requested by the clinician. There were 1/145 isolates tested that were resistant to amoxicillin-clavulanate (resistance breakpoint ≥ 16/8 μg/ml), 7/77 isolates tested were resistant to ampicillin (resistance breakpoint ≥ 2 μg/ml), 4/242 isolates tested were resistant to chloramphenicol (resistance breakpoint ≥ 32 μg/ml), 12/158 isolates tested were resistant to clindamycin (resistance breakpoint ≥ 8 μg/ml), 10/247 isolates tested were resistant to metronidazole (resistance breakpoint ≥ 32 μg/ml), and 54/243 isolates tested were resistant to penicillin (resistance breakpoint ≥ 2 μg/ml). These data suggest that anaerobes are generally susceptible to antimicrobial drugs in vitro.

  15. Rare Mutations of Peroxisome Proliferator-Activated Receptor Gamma: Frequencies and Relationship with Insulin Resistance and Diabetes Risk in the Mixed Ancestry Population from South Africa

    Directory of Open Access Journals (Sweden)

    Z. Vergotine

    2014-01-01

    Full Text Available Background. Genetic variants in the nuclear transcription receptor, PPARG, are associated with cardiometabolic traits, but reports remain conflicting. We determined the frequency and the clinical relevance of PPARG SNPs in an African mixed ancestry population. Methods. In a cross-sectional study, 820 participants were genotyped for rs1800571, rs72551362, rs72551363, rs72551364, and rs3856806, using allele-specific TaqMan technology. The homeostatic model assessment of insulin (HOMA-IR, β-cells function (HOMA-B%, fasting insulin resistance index (FIRI, and the quantitative insulin-sensitivity check index (QUICKI were calculated. Results. No sequence variants were found except for the rs3856806. The frequency of the PPARG-His447His variant was 23.8% in the overall population group, with no difference by diabetes status (P=0.215. The His447His allele T was associated with none of the markers of insulin resistance overall and by diabetes status. In models adjusted for 2-hour insulin, the T allele was associated with lower prevalent diabetes risk (odds ratio 0.56 (95% CI 0.31–0.95. Conclusion. Our study confirms the almost zero occurrences of known rare PPARG SNPs and has shown for the first time in an African population that one of the common SNPs, His447His, may be protective against type 2 diabetes.

  16. Frequency of resistance to penicillin and erythromycin of pneumococcal strains that caused ottis media

    Directory of Open Access Journals (Sweden)

    Jovanović Luka

    2017-01-01

    Full Text Available Introduction: Streptococcus pneumoniae is an important human pathogen and the most common cause of acute otitis media (AOM, especially in children. It is also a common cause of community acquired pneumonia, sepsis and bacterial meningitis. Drug of choice in the treatment of these disease are beta lactam antibiotics, and the first alternative are macrolides. The increasing prevalence of resistance to penicillin and macrolides, among pneumococci, has considerably complicated the treatment. Aim: The aim of this study was to determine susceptibility of pneumococcal isolates from pediatric AOM in Serbia to antibiotics. Material and methods: Antimicrobial susceptibility testing of 61 pneumococcal AOM was performed, collected from December 2014 to December 2015, using disk diffusion method and E test. Macrolide resistance profile was determined by double disk diffusion test. Results: In our study, 40 strains (65.6% showed reduced sensitivity to penicillin and erythromycin. There were 9 (14.8% high resistant isolates to penicillin, while 31 (50.8% showed reduced susceptibility. The most frequent resistance phenotype was cMLS. Co-resistance to penicillin and macrolides was found in 14.8% strains. Conclusion: Our results showed high resistance rate of S. pneumoniae, which causes AOM among children, to penicillin and macrolides. Further active surveillance of pneumococcal susceptibility to antibiotics is necessary, and use of these medications in empirical therapy should be limited.

  17. Frequência e perfil de resistência de Klebsiella spp. em um hospital universitário de Natal/RN durante 10 anos Frequence and resistance profile of Klebsiella spp. isolates in a university hospital in Natal/RN during a ten-year period

    Directory of Open Access Journals (Sweden)

    Claudio Bruno Silva de Oliveira

    2011-12-01

    described. OBJECTIVES: To determine the isolation frequency and resistance profile of Klebsiella spp. at a university hospital during a ten-year period as well as to assess the increase in its resistance. Material and method: A retrospective and descriptive study was carried out based on data collected from the record books of the Laboratory of Clinical Microbiology of the investigated Hospital from January 1999 to December 2008. RESULTS: The isolation frequency of Klebsiella spp. was 13.4%, predominantly in urine cultures (56.4%. There was a significant increase in resistance to most antimicrobials tested over the analyzed period; 23% of Klebsiella spp. with ESBL phenotype was isolated over this period. DISCUSSION: Multi-resistant Klebsiella spp. isolates from clinical samples as well as its growing trend in resistance mechanisms, including to reserve drugs, are cause for great concern. The implementation of screening and confirmatory methods of bacterial resistance could aid in the diagnosis and treatment of infections caused by this microorganism. CONCLUSION: The increase in resistance to antibiotics reinforces the importance of continuous monitoring, which elucidates local characteristics and allows more suitable control measures.

  18. Copper amendment of agricultural soil selects for bacterial antibiotic resistance in the field

    DEFF Research Database (Denmark)

    Berg, J.; Tom-Petersen, A.; Nybroe, O.

    2005-01-01

    -amendment significantly increased the frequency of Cu-resistant isolates. A panel of isolates were characterized by Gram-reaction, amplified ribosomal DNA restriction analysis and resistance profiling against seven antibiotics. More than 95% of the Cu-resistant isolates were Gram-negative. Cu-resistant Gram...

  19. Voltage-gated sodium channel polymorphism and metabolic resistance in pyrethroid-resistant Aedes aegypti from Brazil.

    Science.gov (United States)

    Martins, Ademir Jesus; Lins, Rachel Mazzei Moura de Andrade; Linss, Jutta Gerlinde Birgitt; Peixoto, Alexandre Afranio; Valle, Denise

    2009-07-01

    The nature of pyrethroid resistance in Aedes aegypti Brazilian populations was investigated. Quantification of enzymes related to metabolic resistance in two distinct populations, located in the Northeast and Southeast regions, revealed increases in Glutathione-S-transferase (GST) and Esterase levels. Additionally, polymorphism was found in the IIS6 region of Ae. aegypti voltage-gated sodium channel (AaNa(V)), the pyrethroid target site. Sequences were classified in two haplotype groups, A and B, according to the size of the intron in that region. Rockefeller, a susceptible control lineage, contains only B sequences. In field populations, some A sequences present a substitution in the 1011 site (Ile/Met). When resistant and susceptible individuals were compared, the frequency of both A (with the Met mutation) and B sequences were slightly increased in resistant specimens. The involvement of the AaNa(V) polymorphism in pyrethroid resistance and the metabolic mechanisms that lead to potential cross-resistance between organophosphate and pyrethroids are discussed.

  20. Development of a Teacher Scale to Measure Presence and Frequency of Students' Resistance Behaviours

    Science.gov (United States)

    Sari, Mediha

    2018-01-01

    Student resistance, which can briefly be defined as the tendency to resist teaching activities, is student's reacting to the teaching-learning activities, teachers, or administrators knowingly and wilfully, many times intentionally in various ways. Resistance behaviours, which could be considered as the outpouring of the anger created by the…

  1. Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma

    International Nuclear Information System (INIS)

    Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.; Kakati, M.

    2011-01-01

    Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

  2. Induction of diphtheria toxin-resistant mutants in human cells by ultraviolet light

    International Nuclear Information System (INIS)

    Rocchi, P.; Ferreri, A.M.; Capucci, A.; Prodi, G.

    1981-01-01

    Stable spontaneous mutants resistant to the protein synthesis inhibitor diphtheria toxin (DT) have been selected in human cell line EUE at a very low frequency (less than 8 x 10(-6)). U.v.-induced mutation has been quantitatively measured: treatment of cells with u.v. light increased the frequencies of diphtheria toxin resistant (DTr) mutants up to 1000-fold. The maximum recovery of DTr mutants was observed after a short expression period, for all u.v. doses tested, and was followed by a decrease in mutation frequency on subsequent passages

  3. Induction of diphtheria toxin-resistant mutants in human cells by ultraviolet light

    International Nuclear Information System (INIS)

    Rocchi, P.; Ferreri, A.M.; Capucci, A.; Prodi, G.

    1981-01-01

    Stable spontaneous mutants resistant to the protein synthesis inhibitor diphtheria toxin (DT) have been selected in human cell line EUE at a very low frequency ( -6 ). U.v.-induced mutation has been quantitatively measured: treatment of cells with u.v. light increased the frequencies of diphtheria toxin resistant (DTsup(r)) mutants up to 1000-fold. The maximum recovery of DTsup(r) mutants was observed after a short expression period, for all u.v. doses tested, and was followed by a decrease in mutation frequency on subsequent passages. (author)

  4. Hypermutability of a UV-sensitive aphidicolin-resistant mutant of Chinese hamster fibroblasts

    International Nuclear Information System (INIS)

    Liu, P.K.; Chang, C.; Trosko, J.E.

    1982-01-01

    An ultraviolet light (UV)-sensitive thymidine auxotroph of Chinese hamster V79 cells that exhibits pleiotropic effects such as a high level of deoxycytidine triphosphate, slow growth, sensitivity to cytidine, and high frequencies of site-specific bromodeoxyuridine-dependent chromosomal aberrations was selected by its resistance to aphidicolin. The UV-induced mutability of this mutant and one of its revertants, which retains some of the phenotypes listed above, was studied in 3 mutation assay systems. The results showed that the mutant was hypermutable for ouabain and diphtheria-toxin-resistant mutations compared to wild-type V79 cells at the same UV dose or the same survival level. The mutant exhibits a delayed expression of maximal frequency of induced 6-thioguanine-resistant mutants. When maximal frequencies are compared at the same UV dose, the mutant also has higher mutation frequencies at the hypoxanthine-guanine phosphoribosyl transferase locus. The revertant was similar to the wild-type in UV sensitivity and mutability. (orig./AJ)

  5. Preventing drug resistance in severe influenza

    Science.gov (United States)

    Dobrovolny, Hana; Deecke, Lucas

    2015-03-01

    Severe, long-lasting influenza infections are often caused by new strains of influenza. The long duration of these infections leads to an increased opportunity for the emergence of drug resistant mutants. This is particularly problematic for new strains of influenza since there is often no vaccine, so drug treatment is the first line of defense. One strategy for trying to minimize drug resistance is to apply periodic treatment. During treatment the wild-type virus decreases, but resistant virus might increase; when there is no treatment, wild-type virus will hopefully out-compete the resistant virus, driving down the number of resistant virus. We combine a mathematical model of severe influenza with a model of drug resistance to study emergence of drug resistance during a long-lasting infection. We apply periodic treatment with two types of antivirals: neuraminidase inhibitors, which block release of virions; and adamantanes, which block replication of virions. We compare the efficacy of the two drugs in reducing emergence of drug resistant mutants and examine the effect of treatment frequency on the emergence of drug resistant mutants.

  6. Informed switching strongly decreases the prevalence of antibiotic resistance in hospital wards.

    Directory of Open Access Journals (Sweden)

    Roger D Kouyos

    2011-03-01

    Full Text Available Antibiotic resistant nosocomial infections are an important cause of mortality and morbidity in hospitals. Antibiotic cycling has been proposed to contain this spread by a coordinated use of different antibiotics. Theoretical work, however, suggests that often the random deployment of drugs ("mixing" might be the better strategy. We use an epidemiological model for a single hospital ward in order to assess the performance of cycling strategies which take into account the frequency of antibiotic resistance in the hospital ward. We assume that information on resistance frequencies stems from microbiological tests, which are performed in order to optimize individual therapy. Thus the strategy proposed here represents an optimization at population-level, which comes as a free byproduct of optimizing treatment at the individual level. We find that in most cases such an informed switching strategy outperforms both periodic cycling and mixing, despite the fact that information on the frequency of resistance is derived only from a small sub-population of patients. Furthermore we show that the success of this strategy is essentially a stochastic phenomenon taking advantage of the small population sizes in hospital wards. We find that the performance of an informed switching strategy can be improved substantially if information on resistance tests is integrated over a period of one to two weeks. Finally we argue that our findings are robust against a (moderate preexistence of doubly resistant strains and against transmission via environmental reservoirs. Overall, our results suggest that switching between different antibiotics might be a valuable strategy in small patient populations, if the switching strategies take the frequencies of resistance alleles into account.

  7. A pulse-tube refrigerator using variable-resistance orifice

    Science.gov (United States)

    Huang, B. J.; Sun, B. W.

    2003-01-01

    In the present study, we propose a new design of orifice pulse-tube refrigerator (VROPT) using a variable-resistance valve to replace the conventional orifice. The variable-resistance orifice (VRO) is basically a high-speed solenoidal valve similar to the fuel jet device widely used in automobile engines. By changing the frequency and periods of ON and OFF of the valve through an electronic device, we can change the flow resistance of the VRO. This thus provides a possibility for an OPT to be controlled on-line during operation. From the results obtained in the present study, we have shown that VROPT is able to achieve on-line control by regulating the duty cycle d or frequency fv of the VRO. We also show that VROPT will not loss its thermal performance as compared to conventional OPT.

  8. Microwave Frequency Comb from a Semiconductor in a Scanning Tunneling Microscope.

    Science.gov (United States)

    Hagmann, Mark J; Yarotski, Dmitry A; Mousa, Marwan S

    2017-04-01

    Quasi-periodic excitation of the tunneling junction in a scanning tunneling microscope, by a mode-locked ultrafast laser, superimposes a regular sequence of 15 fs pulses on the DC tunneling current. In the frequency domain, this is a frequency comb with harmonics at integer multiples of the laser pulse repetition frequency. With a gold sample the 200th harmonic at 14.85 GHz has a signal-to-noise ratio of 25 dB, and the power at each harmonic varies inversely with the square of the frequency. Now we report the first measurements with a semiconductor where the laser photon energy must be less than the bandgap energy of the semiconductor; the microwave frequency comb must be measured within 200 μm of the tunneling junction; and the microwave power is 25 dB below that with a metal sample and falls off more rapidly at the higher harmonics. Our results suggest that the measured attenuation of the microwave harmonics is sensitive to the semiconductor spreading resistance within 1 nm of the tunneling junction. This approach may enable sub-nanometer carrier profiling of semiconductors without requiring the diamond nanoprobes in scanning spreading resistance microscopy.

  9. Plasmodium falciparum resistance to anti-malarial drugs in Papua New Guinea: evaluation of a community-based approach for the molecular monitoring of resistance

    Directory of Open Access Journals (Sweden)

    Reeder John C

    2010-01-01

    Full Text Available Abstract Background Molecular monitoring of parasite resistance has become an important complementary tool in establishing rational anti-malarial drug policies. Community surveys provide a representative sample of the parasite population and can be carried out more rapidly than accrual of samples from clinical cases, but it is not known whether the frequencies of genetic resistance markers in clinical cases differ from those in the overall population, or whether such community surveys can provide good predictions of treatment failure rates. Methods Between 2003 and 2005, in vivo drug efficacy of amodiaquine or chloroquine plus sulphadoxine-pyrimethamine was determined at three sites in Papua New Guinea. The genetic drug resistance profile (i.e., 33 single nucleotide polymorphisms in Plasmodium falciparum crt, mdr1, dhfr, dhps, and ATPase6 was concurrently assessed in 639 community samples collected in the catchment areas of the respective health facilities by using a DNA microarray-based method. Mutant allele and haplotype frequencies were determined and their relationship with treatment failure rates at each site in each year was investigated. Results PCR-corrected in vivo treatment failure rates were between 12% and 28% and varied by site and year with variable longitudinal trends. In the community samples, the frequencies of mutations in pfcrt and pfmdr1 were high and did not show significant changes over time. Mutant allele frequencies in pfdhfr were moderate and those in pfdhps were low. No mutations were detected in pfATPase6. There was much more variation between sites than temporal, within-site, variation in allele and haplotype frequencies. This variation did not correlate well with treatment failure rates. Allele and haplotype frequencies were very similar in clinical and community samples from the same site. Conclusions The relationship between parasite genetics and in vivo treatment failure rate is not straightforward. The

  10. Spread of Botrytis cinerea Strains with Multiple Fungicide Resistance in German Horticulture.

    Science.gov (United States)

    Rupp, Sabrina; Weber, Roland W S; Rieger, Daniel; Detzel, Peter; Hahn, Matthias

    2016-01-01

    Botrytis cinerea is a major plant pathogen, causing gray mold rot in a variety of cultures. Repeated fungicide applications are common but have resulted in the development of fungal populations with resistance to one or more fungicides. In this study, we have monitored fungicide resistance frequencies and the occurrence of multiple resistance in Botrytis isolates from raspberries, strawberries, grapes, stone fruits and ornamental flowers in Germany in 2010 to 2015. High frequencies of resistance to all classes of botryticides was common in all cultures, and isolates with multiple fungicide resistance represented a major part of the populations. A monitoring in a raspberry field over six seasons revealed a continuous increase in resistance frequencies and the emergence of multiresistant Botrytis strains. In a cherry orchard and a vineyard, evidence of the immigration of multiresistant strains from the outside was obtained. Inoculation experiments with fungicide-treated leaves in the laboratory and with strawberry plants cultivated in the greenhouse or outdoors revealed a nearly complete loss of fungicide efficacy against multiresistant strains. B. cinerea field strains carrying multiple resistance mutations against all classes of site-specific fungicides were found to show similar fitness as sensitive field strains under laboratory conditions, based on their vegetative growth, reproduction, stress resistance, virulence and competitiveness in mixed infection experiments. Our data indicate an alarming increase in the occurrence of multiresistance in B. cinerea populations from different cultures, which presents a major threat to the chemical control of gray mold.

  11. Multi-frequency bioimpedance in equine muscle assessment

    International Nuclear Information System (INIS)

    Harrison, Adrian Paul; Elbrønd, Vibeke Sødring; Riis-Olesen, Kiwa; Bartels, Else Marie

    2015-01-01

    Multi-frequency BIA (mfBIA) equipment has been shown to be a non-invasive and reliable method to assess a muscle as a whole or at fibre level. In the equine world this may be the future method of assessment of training condition or of muscle injury. The aim of this study was to test if mfBIA reliably can be used to assess the condition of a horse’s muscles in connection with health assessment, injury and both training and re-training. mfBIA measurements was carried out on 10 ‘hobby’ horses and 5 selected cases with known anamnesis. Impedance, resistance, reactance, phase angle, centre frequency, membrane capacitance and both extracellular and intracellular resistance were measured. Platinum electrodes in connection with a conductance paste were used to accommodate the typical BIA frequencies and to facilitate accurate measurements. Use of mfBIA data to look into the effects of myofascial release treatment was also demonstrated. Our findings indicate that mfBIA provides a non-invasive, easily measurable and very precise assessment of the state of muscles in horses. This study also shows the potential of mfBIA as a diagnostic tool as well as a tool to monitor effects of treatment e.g. myofascial release therapy and metabolic diseases, respectively. (paper)

  12. Selective breeding for scrapie resistance in sheep

    Directory of Open Access Journals (Sweden)

    Cristina Santos Sotomaior

    2012-11-01

    Full Text Available It is well known that the susceptibility of sheep to scrapie is determined by the host’s prion protein gene (PRNP. PRNP polymorphisms at codons 136 (alanine, A/valine, V, 154 (histidine, H/arginine, R and 171 (glutamine, Q/histidine, H/arginine, R are the main determinants of sheep susceptibility/resistance to classical scrapie. There are four major variants of the wild-type ARQ allele: VRQ, AHQ, ARH and ARR. Breeding programs have been developed in the European Union and the USA to increase the frequency of the resistant ARR allele while decreasing the frequency of the susceptible VRQ allele in sheep populations. In Brazil, little PRNP genotyping data are available for sheep, and thus far, no controlled breeding scheme for scrapie has been implemented. This review will focus on important epidemiological aspects of scrapie and the use of genetic resistance as a tool in breeding programs to control the disease.

  13. Detection of the V1016G mutation in the voltage-gated sodium channel gene of Aedes aegypti (Diptera: Culicidae) by allele-specific PCR assay, and its distribution and effect on deltamethrin resistance in Thailand.

    Science.gov (United States)

    Stenhouse, Steven A; Plernsub, Suriya; Yanola, Jintana; Lumjuan, Nongkran; Dantrakool, Anchalee; Choochote, Wej; Somboon, Pradya

    2013-08-30

    populations cannot be explained due to kdr mutations and indicates that other resistance mechanisms are operating. The presence of this mutation alone does not fully explain the resistance phenotype we see among Thai Ae. aegypti populations.

  14. High-frequency response and the possibilities of frequency-tunable narrow-band terahertz amplification in resonant tunneling nanostructures

    International Nuclear Information System (INIS)

    Kapaev, V. V.; Kopaev, Yu. V.; Savinov, S. A.; Murzin, V. N.

    2013-01-01

    The characteristics of the high-frequency response of single- and double-well resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a time-dependent Schrödinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (high-frequency response) in In 0.53 Ga 0.47 As/AlAs/InP structures is analyzed in detail for various values of the dc voltage V dc in the negative differential resistance (NDR) region. It is shown that double-well three-barrier structures are promising for the design of terahertz-band oscillators. The presence of two resonant states with close energies in such structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrow-band amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in double-well structures, one can observe a collapse of resonances, where the structure behaves like a single-well system. This phenomenon imposes a lower limit on the oscillation frequency in three-barrier resonant tunneling structures.

  15. Frequency of isolation and antibiotic resistance patterns of bacterial isolates from wound infections

    Directory of Open Access Journals (Sweden)

    Stojanović-Radić, Z.

    2016-12-01

    Full Text Available Six hundred and thirteen bacterial strains were isolated from wound swabs and the isolates were identified on the basis of growth on differential and selective media. In order to test the sensitivity of isolated strains to different antibiotics, the disc diffusion method, according to EUCAST protocol v 5.0 was used. The most common species isolated from wound swabs was Staphylococcus epidermidis (18.4%, followed by Staphylococcus aureus, Pseudomonas aeruginosa and Enterococcus faecalis (16.8%, 12.7% and 10.4%, respectively. The maximum resistance of Gram-positive cocci was observed to penicillin and the lowest to linezolid. Gram-negative bacteria showed the highest resistance to tetracyclines, while the same strains demonstrated the highest sensitivity to polypeptide antibiotics. Comparison of the resistance patterns of Gramnegative and Gram-positive bacterial strains showed significant difference in the tetracycline efficiency.

  16. Simplified frequency-dependent formulae for series-impedance matrices of single-core HVAC cables

    DEFF Research Database (Denmark)

    Silva, Filipe Miguel Faria da

    2015-01-01

    The installation of HVAC underground cables became more common in recent years, a trend expected to continue in the future. Underground cables are more complex than overhead lines and the calculation of their resistance and reactance can be challenging and time consuming for frequencies that are ......The installation of HVAC underground cables became more common in recent years, a trend expected to continue in the future. Underground cables are more complex than overhead lines and the calculation of their resistance and reactance can be challenging and time consuming for frequencies...

  17. Investigation of series resistance and surface states in Au/n - GaP structures

    International Nuclear Information System (INIS)

    Kiymaz, A.; Onal, B.; Ozer, M.; Acar, S.

    2009-01-01

    The variation in series resistance and surface state density of Au/n - GaP Schottky diodes have been systematically investigated at room temperature by using capacitance-voltage C-V and conductance-voltage G/w-V measurements techniques. The C-V and G/w-V characteristics of these devices were investigated by considering series resistance effects in a wide frequency range. It is shown that the capacitance of the Au/n - GaP Schottky diode decreases with increasing frequency. It is assumed that the surface states were responsible for this behaviour. The distribution profile of Rs-V gives a peak in the depletion region at low frequencies and disappears with increasing frequencies

  18. The effect of larval nutritional deprivation on the life history and DDT resistance phenotype in laboratory strains of the malaria vector Anopheles arabiensis

    Science.gov (United States)

    2013-01-01

    Background Anopheles arabiensis is a major malaria vector in Africa. It thrives in agricultural areas and has been associated with increased malaria incidence in areas under rice and maize cultivation. This effect may be due to increased adult size and abundance as a consequence of optimal larval nutrition. The aim of this study was to examine the effect of larval nutrition on the life history and expression of insecticide resistance in adults of laboratory reared An. arabiensis. Methods Larvae drawn from an insecticide susceptible An. arabiensis strain (SENN) as well as a DDT-resistant strain (SENN-DDT) were subjected to three fasting regimes: 1 mg of food per larva offered once per day, once every second day and once every third day. Control cohorts included larvae offered 1 mg food thrice per day. The rate of larval development was compared between matched cohorts from each strain as well as between fasted larvae and their respective controls. The expression of DDT resistance/tolerance in adults was compared between the starved cohorts and their controls by strain. Factors potentially affecting variation in DDT resistance/tolerance were examined including: adult body size (wing length), knock-down resistance (kdr) status and levels of detoxification enzyme activity. Results and conclusion Anopheles arabiensis larval development is prolonged by nutrient deprivation and adults that eclose from starved larvae are smaller and less tolerant to DDT intoxication. This effect on DDT tolerance in adults is also associated with reduced detoxification enzyme activity. Conversely, well fed larvae develop comparatively quickly into large, more DDT tolerant (SENN) or resistant (SENN-DDT) adults. This is important in those instances where cereal farming is associated with increased An. arabiensis transmitted malaria incidence, because large adult females with high teneral reserves and decreased susceptibility to insecticide intoxication may also prove to be more

  19. The effect of larval nutritional deprivation on the life history and DDT resistance phenotype in laboratory strains of the malaria vector Anopheles arabiensis

    Directory of Open Access Journals (Sweden)

    Oliver Shüné V

    2013-02-01

    Full Text Available Abstract Background Anopheles arabiensis is a major malaria vector in Africa. It thrives in agricultural areas and has been associated with increased malaria incidence in areas under rice and maize cultivation. This effect may be due to increased adult size and abundance as a consequence of optimal larval nutrition. The aim of this study was to examine the effect of larval nutrition on the life history and expression of insecticide resistance in adults of laboratory reared An. arabiensis. Methods Larvae drawn from an insecticide susceptible An. arabiensis strain (SENN as well as a DDT-resistant strain (SENN-DDT were subjected to three fasting regimes: 1 mg of food per larva offered once per day, once every second day and once every third day. Control cohorts included larvae offered 1 mg food thrice per day. The rate of larval development was compared between matched cohorts from each strain as well as between fasted larvae and their respective controls. The expression of DDT resistance/tolerance in adults was compared between the starved cohorts and their controls by strain. Factors potentially affecting variation in DDT resistance/tolerance were examined including: adult body size (wing length, knock-down resistance (kdr status and levels of detoxification enzyme activity. Results and conclusion Anopheles arabiensis larval development is prolonged by nutrient deprivation and adults that eclose from starved larvae are smaller and less tolerant to DDT intoxication. This effect on DDT tolerance in adults is also associated with reduced detoxification enzyme activity. Conversely, well fed larvae develop comparatively quickly into large, more DDT tolerant (SENN or resistant (SENN-DDT adults. This is important in those instances where cereal farming is associated with increased An. arabiensis transmitted malaria incidence, because large adult females with high teneral reserves and decreased susceptibility to insecticide intoxication may also

  20. High frequency fatigue test of IN 718 alloy – microstructure and fractography evaluation

    Directory of Open Access Journals (Sweden)

    J. Belan

    2015-01-01

    Full Text Available INCONEL alloy 718 is a high-strength, corrosion-resistant nickel chromium material used at -253 °C to 705 °C for production of heat resistant parts of aero jet engine mostly. The fatigue test provided on this kind materials were done via low frequency loading up to this time. Nowadays, needs of results at higher volume of loading cycles leads to high frequency loading with aim to shorten testing time. Fatigue test of experimental material was carried out at frequency 20 kHz with stress ration R = - 1 (push – pull at room temperature. It was found that this superalloy can still fracture after exceeding 108 cycles. Besides fatigue test were microstructural characterisation and scanning electron microscopy (SEM fractography evaluation done.

  1. Malaria vector composition and insecticide susceptibility status in Guinea Conakry, West Africa.

    Science.gov (United States)

    Vezenegho, S B; Brooke, B D; Hunt, R H; Coetzee, M; Koekemoer, L L

    2009-12-01

    This study provides data on malaria vector species composition and insecticide susceptibility status from three localities in Guinea Conakry. A total of 497 mosquitoes were collected resting indoors and morphologically identified as belonging to the Anopheles gambiae complex. The majority of these were An. gambiae s.s. (99.6%), but a small percentage (0.4%) were identified as Anopheles arabiensis. Thirty-four Anopheles funestus s.s. were also collected. The molecular S form of An. gambiae s.s. was predominant over the M form in Siguiri (95%) and Boffa (97.4%), whereas at Mt Nimba the M form was more abundant (61.4%) than the S form (38.1%). One hybrid M/S specimen was recorded from Mt Nimba. Siguiri populations showed high levels of resistance to DDT, dieldrin and bendiocarb. Anopheles gambiae from Boffa were largely susceptible to the insecticides tested. At Mt Nimba, resistance to DDT and bendicocarb was detected. Biochemical enzyme analysis showed that an altered acetylcholinesterase is operating in the field at low levels. The frequency of the 1014F kdr allele in the An. gambiae S form was 0.24 at Siguiri and 0.14 at Mt Nimba. A single RR specimen was found in the M form. The heterogeneity in species composition and resistance profiles between sites requires vector control interventions to be tailored to each site based on the data collected from ongoing monitoring and surveillance.

  2. Antimicrobial Drug-Resistant Shiga Toxin-Producing Escherichia coli Infections, Michigan, USA.

    Science.gov (United States)

    Mukherjee, Sanjana; Mosci, Rebekah E; Anderson, Chase M; Snyder, Brian A; Collins, James; Rudrik, James T; Manning, Shannon D

    2017-09-01

    High frequencies of antimicrobial drug resistance were observed in O157 and non-O157 Shiga toxin-producing E. coli strains recovered from patients in Michigan during 2010-2014. Resistance was more common in non-O157 strains and independently associated with hospitalization, indicating that resistance could contribute to more severe disease outcomes.

  3. Trends in darunavir resistance-associated mutations and phenotypic resistance in commercially tested United States clinical samples between 2006 and 2012.

    Science.gov (United States)

    Lathouwers, Erkki; Gupta, Soumi; Haddad, Mojgan; Paquet, Agnes; de Meyer, Sandra; Baugh, Bryan

    2015-06-01

    HIV-1 samples submitted by clinicians from the United States for routine drug susceptibility testing (PhenoSense GT) were evaluated for genotypic and phenotypic resistance to darunavir and other protease inhibitors (PIs). Among these samples (Monogram Biosciences database January 2006-June 2012; N=78,843), isolates harboring zero IAS-USA darunavir resistance-associated mutations (RAMs) increased from 77.7% in 2006 to 92.8% through the first half of 2012 (H1 2012; upward trend, p=0.0008); a downward trend seen for samples with three or more darunavir RAMs (7.5% in 2006 and 2.6% in H1 2012; p=0.002). Among samples with any PI resistance (N=15,932), samples harboring zero darunavir RAMs gradually increased (39.9% in 2006 vs. 55.0% in H1 2012; upward trend, p=0.005), but three or more darunavir RAMs did not change over time (21.7% in 2006 and 19.2% in H1 2012; p=0.27). During this period, the frequency of the 11 individual darunavir RAMs (IAS-USA 2011 list) decreased among all samples. The frequency of each darunavir RAM in PI-resistant samples decreased or remained relatively stable. The prevalence of samples with phenotypic resistance to darunavir (partial-to-full) decreased over time in all samples (8.2% in 2006 vs. 2.3% in H1 2012), as did resistance to other PIs (p<0.006 for all PIs). Phenotypic resistance to darunavir and other PIs also decreased in PI-resistant samples (darunavir: 23.9% in 2006 vs. 17.1% in H1 2012; p<0.013 for all PIs). Since approval of darunavir in 2006, there was a significant decrease in prevalence of samples with genotypic and phenotypic resistance to darunavir in commercially tested HIV-1 isolates. Furthermore, the prevalence of phenotypic resistance to darunavir was lower than all other PIs.

  4. High frequency ohmic loss of beryllium and its alloy with aluminium

    International Nuclear Information System (INIS)

    Prentslau, N.N.

    1999-01-01

    The surface resistance of Be of different purity and its alloy with Al (50%Be-50%Al) is investigated at temperatures ranged from 4,2 to 300 K in the 0-10 10 Hz frequency region. It is shown that within the temperature range (in the vicinity of 77 K) where beryllium is a de hyper conductor. Its surface resistance and the surface resistance of the alloy are minimum compared to that of other metals, in particular, of aluminium. The temperature dependence of the surface resistance of Be and its alloys is well described by the classical formulae of electrodynamics

  5. Determination of nonlinear resistance voltage-current relationships by measuring harmonics

    Science.gov (United States)

    Stafford, J. M.

    1971-01-01

    Test configuration measures harmonic signal amplitudes generated in nonlinear resistance. Vacuum-type voltmeter measures low frequency sinusoidal input signal amplitude and wave-analyzer measures amplitude of harmonic signals generated in junction. Input signal harmonics amplitude must not exceed that of harmonics generated in nonlinear resistance.

  6. Investigation and optimization of low-frequency noise performance in readout electronics of dc superconducting quantum interference device

    International Nuclear Information System (INIS)

    Zhao, Jing; Zhang, Yi; Krause, Hans-Joachim; Lee, Yong-Ho

    2014-01-01

    We investigated and optimized the low-frequency noise characteristics of a preamplifier used for readout of direct current superconducting quantum interference devices (SQUIDs). When the SQUID output was detected directly using a room-temperature low-voltage-noise preamplifier, the low-frequency noise of a SQUID system was found to be dominated by the input current noise of the preamplifiers in case of a large dynamic resistance of the SQUID. To reduce the current noise of the preamplifier in the low-frequency range, we investigated the dependence of total preamplifier noise on the collector current and source resistance. When the collector current was decreased from 8.4 mA to 3 mA in the preamplifier made of 3 parallel SSM2220 transistor pairs, the low-frequency total voltage noise of the preamplifier (at 0.1 Hz) decreased by about 3 times for a source resistance of 30 Ω whereas the white noise level remained nearly unchanged. Since the relative contribution of preamplifier's input voltage and current noise is different depending on the dynamic resistance or flux-to-voltage transfer of the SQUID, the results showed that the total noise of a SQUID system at low-frequency range can be improved significantly by optimizing the preamplifier circuit parameters, mainly the collector current in case of low-noise bipolar transistor pairs

  7. Investigation and optimization of low-frequency noise performance in readout electronics of dc superconducting quantum interference device

    Science.gov (United States)

    Zhao, Jing; Zhang, Yi; Lee, Yong-Ho; Krause, Hans-Joachim

    2014-05-01

    We investigated and optimized the low-frequency noise characteristics of a preamplifier used for readout of direct current superconducting quantum interference devices (SQUIDs). When the SQUID output was detected directly using a room-temperature low-voltage-noise preamplifier, the low-frequency noise of a SQUID system was found to be dominated by the input current noise of the preamplifiers in case of a large dynamic resistance of the SQUID. To reduce the current noise of the preamplifier in the low-frequency range, we investigated the dependence of total preamplifier noise on the collector current and source resistance. When the collector current was decreased from 8.4 mA to 3 mA in the preamplifier made of 3 parallel SSM2220 transistor pairs, the low-frequency total voltage noise of the preamplifier (at 0.1 Hz) decreased by about 3 times for a source resistance of 30 Ω whereas the white noise level remained nearly unchanged. Since the relative contribution of preamplifier's input voltage and current noise is different depending on the dynamic resistance or flux-to-voltage transfer of the SQUID, the results showed that the total noise of a SQUID system at low-frequency range can be improved significantly by optimizing the preamplifier circuit parameters, mainly the collector current in case of low-noise bipolar transistor pairs.

  8. Bovine salmonellosis in Northeast of Iran: Frequency, genetic fingerprinting and antimicrobial resistance patterns of Salmonella spp.

    Directory of Open Access Journals (Sweden)

    Hessam A. Halimi

    2014-01-01

    Conclusion: The emergence of multiple antibiotic-resistant strains of Salmonella Typhimurium should be of great concern to the public. No correlation between ERIC fingerprinting and resistance patterns of Salmonella isolates was found, which indicates resistance to antimicrobial agents was not related to specific genetic background.

  9. Sucralose Increases Antimicrobial Resistance and Stimulates Recovery of Escherichia coli Mutants.

    Science.gov (United States)

    Qu, Yilin; Li, Rongyan; Jiang, Mingshan; Wang, Xiuhong

    2017-07-01

    Because of heavy use of antimicrobials, antimicrobial resistance in bacteria has become of great concern. The effect of some widely used food additives such as sucralose on bacteria in the gut and the environment has also drawn increasing attention. In this study, we investigated the interaction between antimicrobials and sucralose impacting antimicrobial resistance and mutation of Escherichia coli (E. coli). To examine antimicrobial resistance and mutation frequency, different subinhibitory concentrations of sucralose were added to cultures of E.coli BW25113 that were then treated with antimicrobials, oxolinic acid, or moxifloxacin. Then the E.coli were assayed for bacterial survival and recovery of mutants resistant to an unrelated antimicrobial, rifampicin. Pre-treatment of E.coli BW25113 with 1/2 minimal inhibitory concentration (MIC) of sucralose increased the survival rate in oxolinic acid or moxifloxacin. A 1/3 MIC of sucralose increased rifampicin-resistant mutation rate of E.coli BW25113 after 72 h, while rifampicin-resistant mutation rate was increased when co-treated with 1/8 MIC, 1/4 MIC, 1/3 MIC sucralose, and oxolinic acid after 24 h. Sucralose can increase the antimicrobial resistance and mutation frequency of E.coli to some antimicrobials.

  10. Mycoplasma genitalium in Spain: prevalence of genital infection and frequency of resistance to macrolides.

    Science.gov (United States)

    Asenjo, Alejandra; Kusters, Johannes G; Severs, Tim T; Alós, Juan-Ignacio

    2018-03-01

    The aim of this study was to determine the prevalence of Mycoplasma genitalium infection and the resistance to macrolides within a general population in Madrid in 2015. We collected 359 urine samples from a general population with symptoms of sexually transmitted infections (STIs). All samples underwent a real-time PCR. For the detection of macrolide resistance, a 283bp fragment of region V of the 23S rRNA gene of M. genitalium was amplified and sequenced. We found a prevalence of 3.34% of M. genitalium and a macrolide resistance rate of 20%. In males, the prevalence was 6.62% and in women 0.96%, being significantly higher in males. The prevalence obtained shows that it is a pathogen to consider in our environment. These findings stress the need for routine testing of M. genitalium infections and would seem to suggest the advisability of resistance testing. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

  11. Experience with dynamic reinforcement rates decreases resistance to extinction.

    Science.gov (United States)

    Craig, Andrew R; Shahan, Timothy A

    2016-03-01

    The ability of organisms to detect reinforcer-rate changes in choice preparations is positively related to two factors: the magnitude of the change in rate and the frequency with which rates change. Gallistel (2012) suggested similar rate-detection processes are responsible for decreases in responding during operant extinction. Although effects of magnitude of change in reinforcer rate on resistance to extinction are well known (e.g., the partial-reinforcement-extinction effect), effects of frequency of changes in rate prior to extinction are unknown. Thus, the present experiments examined whether frequency of changes in baseline reinforcer rates impacts resistance to extinction. Pigeons pecked keys for variable-interval food under conditions where reinforcer rates were stable and where they changed within and between sessions. Overall reinforcer rates between conditions were controlled. In Experiment 1, resistance to extinction was lower following exposure to dynamic reinforcement schedules than to static schedules. Experiment 2 showed that resistance to presession feeding, a disruptor that should not involve change-detection processes, was unaffected by baseline-schedule dynamics. These findings are consistent with the suggestion that change detection contributes to extinction. We discuss implications of change-detection processes for extinction of simple and discriminated operant behavior and relate these processes to the behavioral-momentum based approach to understanding extinction. © 2016 Society for the Experimental Analysis of Behavior.

  12. Low temperature laser scanning microscopy of a superconducting radio-frequency cavity

    OpenAIRE

    Ciovati, G.; Anlage, Steven M.; Baldwin, C.; Cheng, G.; Flood, R.; Jordan, K.; Kneisel, P.; Morrone, M.; Nemes, G.; Turlington, L.; Wang, H.; Wilson, K.; Zhang, S.

    2012-01-01

    An apparatus was developed to obtain, for the first time, 2D maps of the surface resistance of the inner surface of an operating superconducting radio-frequency niobium cavity by a low-temperature laser scanning microscopy technique. This allows identifying non-uniformities of the surface resistance with a spatial resolution of about one order of magnitude better than with earlier methods and surface resistance resolution of ~ 1 micro-Ohm at 3.3 GHz. A signal-to-noise ratio of about 10 dB was...

  13. Studies on induced resistance to blast in rice

    International Nuclear Information System (INIS)

    Zhang Mingxian

    1985-01-01

    Eleven rice varieties were treated with 60 Co gamma ray, laser and other mutagens. 154 mutants with different characters were developed. 154 mutants and their parents have been inoculated with blast (Piricularia oryzae) races. It was found that the mutants of disease-resistance could be produced. The disease-resistant mutants with various better cheracters were selected. The frequencies of mutation in disease-resistance are different with different parental varieties. After inoculation with 13 blast physiological races, the results showed that the spectrum of resistance of mutants, other characters were changed, when one character was changed. In order to get a veriety with higher yield and disease-resistance, it is important to take account of other economic charaters

  14. Theoretical study of very low-frequency wave heating of a fusion plasma

    International Nuclear Information System (INIS)

    Fiori, C.

    1980-12-01

    For a certain order of frequencies defined here we give the derivation and general solution of the 4th order differential equation obeyed by the radial MHD displacement of a cylindrical, resistive and incompressible plasma column. By means of a flux function the expressions of the elctromagnetic field and the current density in the resistive layer are obtained the power dissipated in this layer by an external wave and its limit when the resistivity disappears are then discussed [fr

  15. Induced mutations for resistance to powdery mildew in wheat

    International Nuclear Information System (INIS)

    Liu Xueyu

    1990-01-01

    The most serious diseases of wheat in the Yangtze River Valley in China are powdery mildew and scab. Breeding for disease resistance either using conventional methods or through mutation breeding is the best way of controlling these diseases. Mutation breeding may be valuable in obtaining genotypes with resistance or tolerance, or for breaking undesirable linkages involving existing genes for disease resistance. The following commercial varieties were used: Yangmai 3, Ningmai 3 and Ningmai 6. They are high-yielding varieties, but susceptible to powdery mildew. Seeds of these cultivars were treated with gamma-rays. The material was screened in the seedling stage in M 2 in the greenhouse and under field conditions in M 3 -M 4 and later generations. The seedlings were inoculated with a spore suspension of the powdery mildew fungus. The most resistant mutant selected from variety Ningmai 3 was the line 34080 with resistance to races 4, 16 and 20. According to the number of progenies in M 2 , the mutation frequency was 1.2x10 -4 . The other two mutants (34157, 34158) were screened from variety Yangmai 3. Mutant 34157 showed a stable resistance to races 4, 16 and 20; mutant 34158 was resistant to races 4 and 20 but susceptible to race 16. Tracing them back to M 2 progeny, the mutation frequency was 1.0x10 -4 . From electrophoretic analysis of mildew resistant mutant lines of wheat we found that the zymogram of peroxidase in resistant lines 34080 and 34157 was different from their parents and that these lines do not have band 3A

  16. Peak effect in surface resistance at microwave frequencies in Dy ...

    Indian Academy of Sciences (India)

    In the measurements at both frequencies the induced microwave current was always less than the critical current of the films. The reason for observation of this peak effect in these films has been explained in our earlier publication [5]. Comparing figures 1 and 2, it is observed that the peaks in sample S1 are broader and.

  17. Peripheral Circulatory Features during High-Frequency Jet Ventilation

    Directory of Open Access Journals (Sweden)

    M. B. Kontorovich

    2010-01-01

    Full Text Available The paper gives the results of a study of peripheral circulatory features during high-frequency jet ventilation (HFJV. The main specific features of peripheral circulation and oxygen transport during HFJV are formulated on the basis of a study of cardiac output (impedance cardiography, peripheral vascular resistance, peripheral vascular blood filling (photoplethysmogram analysis, adaptive peripheral blood flow reactions (spectral analysis of peripheral vascular pulsation. HFJV gives rise to the peculiar pattern of peripheral hemodynamics and tissue gas exchange, which is characterized by higher oxygen uptake without a decrease in mixed venous blood saturation, with normal extraction coefficient and preserved low peripheral vascular resistance. During HFJV, unlike traditional ventilation, the main peripheral hemodynamic feature is the increased capillary bed blood volume caused by the blood flow involvement of reserve capillaries under control of volume (parasympathetic regulation of adaptive peripheral hemodynamic reactions. Key words: high-frequency jet ventilation, oxygen transport, peripheral hemodynamics.

  18. Frequency of the Occurence of Methicilin Resistant Staphylococcus aureus (MRSA Infections in Hyderabad, Pakistan

    Directory of Open Access Journals (Sweden)

    Nazir Ahmed Brohi

    2017-06-01

    Full Text Available Staphylococcus aureus is a potential pathogen of hospital and community related infections. It secretes toxins or the enzymes as virulence factor of mild to severe infections and show resistance to beta-lactam antibiotic including penicillin, methicillin, oxacillin and now vancomycin that could alarm of equal risk factors of Methicillin Resistant Staphylococcus aureus (MRSA infections in the patients. The survey report of 381 patients of Hyderabad, Pakistan was collected from March 2013 to June 2014 in which 176 cases were reported for Staphylococcus aureus in both genders of different age groups of 3-15 y kids, 16-45 y adults and 45-70 y olds, which showed 208 and 132 specimens Staphylococcus infection and 16 and 4 cases of MRSA infections in male and female patients, respectively whereas other 31 cases showed no infection. The laboratory diagnosis of the 200 samples from various hospitalized patients revealed the highest percentage of Methicillin Resistant Staphylococcus aureus MRSA in pus and post-operative wounds (17% followed by skin swabs (10%, sputum (7% and blood (0%. The observations revealed greater prevalence of MRSA infection in elderly age 16-45 years males than the females and other age groups. Antibiotic susceptibility test of 26 antibiotics revealed resistance (R-53%, sensitive (S-39 and variable (V-7% sensitivity zones (mm. Amplification of mecA gene was done using PCR reaction that revealed mecA gene bands up to 150-200 base pairs by test resistant strains.

  19. Electromagnetic wave attenuation in the superconducting waveguides at frequencies above the critical value

    International Nuclear Information System (INIS)

    Gashimov, A.M.; Gumbatov, S.G.

    2004-01-01

    The behavior of attenuation factor α(ν) in a wide relative frequency rAe 1 c ) at microwave energy transmission by the round superconducting waveguides is investigated. It is revealed that, despite of increasing of surface resistance with increasing ν, α(ν) sharply decreases in the rAe 1 min at ν→∞. Such behavior α(ν) is due to joint appearance of opposite influences of wave frequency and surface resistance of the superconducting material. The waveguide with radius r=1 m, made of high-temperature superconductor, has the highest value of efficiency (98% at ν=4)

  20. On the evolution of pesticide resistance in Phytophthora infestans : an experimental evolution approach

    NARCIS (Netherlands)

    Bosmans, S.

    2009-01-01

    Resistance to antimicrobial agents is a serious problem for both medicine and agriculture. The initial success of such toxins is due to absence of resistant genotypes in pathogen populations before treatment. The initial low frequency of resistance may be explained by negative pleiotropic effects of

  1. Mutations in rpoB and katG genes of multidrug resistant ...

    African Journals Online (AJOL)

    Introduction: Tuberculosis remains the leading causes of death worldwide with frequencies of mutations in rifampicin and isoniazid resistant Mycobacterium tuberculosis isolates varying according to geographical location. There is limited information in Zimbabwe on specific antibiotic resistance gene mutation patterns in ...

  2. Theory of energetic trapped particle-induced resistive interchange-ballooning modes

    International Nuclear Information System (INIS)

    Biglari, H.; Chen, L.

    1986-02-01

    A theory describing the influence of energetic trapped particles on resistive interchange-ballooning modes in tokamaks is presented. It is shown that a population of hot particles trapped in the region of adverse curvature can resonantly interact with and destabilize the resistive interchange mode, which is stable in their absence because of favorable average curvature. The mode is different from the usual resistive interchange mode not only in its destabilization mechanism, but also in that it has a real component to its frequency comparable to the precessional drift frequency of the rapidly circulating energetic species. Corresponding growth rate and threshold conditions for this trapped-particle-driven instability are derived and finite banana width effects are shown to have a stabilizing effect on the mode. Finally, the ballooning/tearing dispersion relation is generalized to include hot particles, so that both the ideal and the resistive modes are derivable in the appropriate limits. 23 refs., 7 figs

  3. Detection of antibiotic resistance and tetracycline resistance genes in Enterobacteriaceae isolated from the Pearl rivers in South China

    International Nuclear Information System (INIS)

    Tao Ran; Ying Guangguo; Su Haochang; Zhou Hongwei; Sidhu, Jatinder P.S.

    2010-01-01

    This study investigated antibiotic resistance profiles and tetracycline resistance genes in Enterobacteriaceae family isolates from the Pearl rivers. The Enterobacteriaceae isolates were tested for susceptibility to seven antibiotics ampicillin, chloramphenicol, ciprofloxacin, levofloxacin, sulphamethoxazole/trimethoprim, tetracycline and trimethoprim. In Liuxi reservoir, with an exception to ampicillin resistant strains (11%) no other antibiotic resistance bacterial strains were detected. However, multiple drug resistance in bacterial isolates from the other sites of Pearl rivers was observed which is possibly due to sewage discharge and input from other anthropogenic sources along the rivers. Four tetracycline resistance genes tet A, tet B, tet C and tet D were detected in the isolates from the rivers. The genes tet A and tet B were widely detected with the detection frequencies of 43% and 40% respectively. Ciprofloxacin and levofloxacin resistant enteric bacteria were also isolated from the pig and duck manures which suggest a wider distribution of human specific drugs in the environment. This investigation provided a baseline data on antibiotic resistance profiles and tetracycline resistance genes in the Pearl rivers delta. - High rates of antibiotic resistance in Enterobacteriaceae from river water are attributed to wastewater contamination.

  4. Detection of antibiotic resistance and tetracycline resistance genes in Enterobacteriaceae isolated from the Pearl rivers in South China

    Energy Technology Data Exchange (ETDEWEB)

    Tao Ran [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe District, Guangzhou 510640 (China); Ying Guangguo, E-mail: guangguo.ying@gmail.co [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe District, Guangzhou 510640 (China); Su Haochang [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe District, Guangzhou 510640 (China); Zhou Hongwei [Department of Environmental Health, School of Public Health and Tropical Medicine, Southern Medical University, 1838 North Guangzhou Street, Baiyun District, Guangzhou 510515 (China); Sidhu, Jatinder P.S. [CSIRO Land and Water, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia QLD 4067 (Australia)

    2010-06-15

    This study investigated antibiotic resistance profiles and tetracycline resistance genes in Enterobacteriaceae family isolates from the Pearl rivers. The Enterobacteriaceae isolates were tested for susceptibility to seven antibiotics ampicillin, chloramphenicol, ciprofloxacin, levofloxacin, sulphamethoxazole/trimethoprim, tetracycline and trimethoprim. In Liuxi reservoir, with an exception to ampicillin resistant strains (11%) no other antibiotic resistance bacterial strains were detected. However, multiple drug resistance in bacterial isolates from the other sites of Pearl rivers was observed which is possibly due to sewage discharge and input from other anthropogenic sources along the rivers. Four tetracycline resistance genes tet A, tet B, tet C and tet D were detected in the isolates from the rivers. The genes tet A and tet B were widely detected with the detection frequencies of 43% and 40% respectively. Ciprofloxacin and levofloxacin resistant enteric bacteria were also isolated from the pig and duck manures which suggest a wider distribution of human specific drugs in the environment. This investigation provided a baseline data on antibiotic resistance profiles and tetracycline resistance genes in the Pearl rivers delta. - High rates of antibiotic resistance in Enterobacteriaceae from river water are attributed to wastewater contamination.

  5. Drug resistance following irradiation of RIF-1 tumors: Influence of the interval between irradiation and drug treatment

    International Nuclear Information System (INIS)

    Hopwood, L.E.; Davies, B.M.; Moulder, J.E.

    1990-01-01

    RIF-1 tumors contain a small number of cells (1 to 100 per 10(6) cells) that are resistant to 5-fluorouracil, methotrexate, or adriamycin. The frequency of drug-resistant cells among individual untreated tumors is highly variable. Radiation, delivered in vivo at doses of 3 to 12 Gy, increases the frequency of methotrexate- and 5-fluorouracil-resistant cells, but not the frequency of adriamycin-resistant cells. The magnitude of induction of 5-fluorouracil and methotrexate resistance shows a complex dependence on the radiation dose and on the interval between irradiation and assessment of drug resistance. For a dose of 3 Gy, induced 5-fluorouracil and methotrexate resistance is seen only after an interval of 5 to 7 days, whereas for a dose of 12 Gy, high levels of induced resistance are observed 1 to 3 days after irradiation. The maximum absolute risk for induction of resistance is 4 per 10(4) cells per Gy for methotrexate, and 3 per 10(6) cells per Gy for 5-fluorouracil. These results indicate that tumor hypoxia may play a role in the increased levels of drug resistance seen after irradiation, and that both genetic and environmental factors may influence radiation-induction of drug resistance. These studies provide essential data for models of the development of tumor drug resistance, and imply that some of the drug resistance seen when chemotherapy follows radiotherapy may be caused by radiation-induced drug resistance

  6. Assessment of the seismic resistance of a ventilation stack on a reactor building

    International Nuclear Information System (INIS)

    Makovicka, Daniel; Makovicka, Daniel

    2005-01-01

    The paper analyzes the seismic resistance of a ventilation stack on a reactor building, including the possible reserves of increasing the resistance. Structures of this type are highly sensitive to seismic loads, as the tuning of the stack (the spectrum of its lowest natural frequencies) corresponds with the frequency spectrum of excitation due to seismic effects. The purpose of the paper is to present an example of an actual structure to show the character of the response of the structure, and the participation of the individual frequency components of the response in the overall stress and strain state of a structure of this type. The methodology for a numerical analysis of the structure is also given. The load of the stack proper is modified by the transfer characteristics of the building. In engineering practice, the system is usually divided into two subsystems: the building with the sub-base, and the stack proper. The level of justification for the application of this simplification depends on the distance of the natural frequencies of the stack from the natural frequencies of the building. Finally, the paper deals with possible errors in determining the actual seismic resistance of the stack structure

  7. Radio frequency sheaths in an oblique magnetic field

    International Nuclear Information System (INIS)

    Myra, J. R.; D'Ippolito, D. A.

    2015-01-01

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describes the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle θ, assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numerically to obtain the rectified (dc) voltage, the rf voltage across the sheath, and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general, the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall

  8. Improvement of resistance to rust through recurrent selection in pearl millet

    Energy Technology Data Exchange (ETDEWEB)

    Tapsoba, H. [Univ. of Georgia, Athens, GA (United States); Wilson, J.P.; Hanna, W.W. [Univ. of Georgia Coastal Plain Experimental Station, Tifton, GA (United States)

    1997-04-01

    Two pearl millet [Pennisetum glaucum (L.) R.Br. = P. typhoides (Burm.) Staff & Hubb., P. americanum (L.) K. Schum.] bulk populations, Tift No. 2 and Tift No. 5, served as base populations for four cycles of recurrent selection against susceptibility to Puccinia substriata Ell. & Barth, var. indica Ramachar & Cumm. A bulk inoculum of the pathogen was used. The objectives were to evaluate the progress achieved regarding overall resistance to the pathogen in the field and resistance to different races of the pathogen, and also to evaluate changes in unselected traits. During selection, the frequency of rust resistant plants continuously increased from about 30% in each base population to more than 85% by the third cycle of selection in both populations. An average increase of about 21 and 18% per cycle was obtained in Tift No. 2 and Tift No. 5, respectively. A continuous increase of the frequency of plants resistant to some races of the pathogen was also obtained. In Tift No. 5, 80% of the plants were resistant to eight races by the third cycle of selection. The accumulation of resistance observed in the seedlings was manifested in the field, both in 1993 and 1994, by a reduction of the final rust severity from the base population to the fourth selection cycle of both populations. This improvement in resistance to the rust pathogen was accompanied by an increase in the frequency of plants resistant to Pyricularia grisea (Cooke) Sacc. only in Tift No. 2. Despite the improvement in the selected character, genetic variability for agronomic traits such as plant height, number of culms/plant, flowering date, and panicle length was successfully maintained within each population. 20 refs., 1 fig., 7 tabs.

  9. Effect of repetitive transcranial magnetic stimulation in drug resistant depressed patients

    International Nuclear Information System (INIS)

    Chung, Yong An; Yoo, Ie Ryung; Kang, Bong Joo; Chae, Jeong Ho; Lee, Hye Won; Moon, Hyun Jin; Kim, Sung Hoon; Sohn, Hyung Sun; Chung, Soo Kyo

    2007-01-01

    Repetitive transcranial magnetic stimulation (rTMS) has recently been clinically applied in the treatment of drug resistant depressed patients. There are mixed findings about the efficacy of rTMS on depression. Furthermore, the influence of rTMS on the physiology of the brain is not clear. We prospectively evaluated changes of regional cerebral blood flow (rCBF) between pre- and post-rTMS treatment in patients with drug resistant depression. Twelve patients with drug-resistant depression (7 male, 5 female; age range; 19∼ 52 years; mean age: 29.3 ± 9.3 years) were given rTMS on right prefrontal lobe with low frequency (1 Hz) and on left prefrontal lobe with high frequency (20 Hz), with 20-minute-duration each day for 3 weeks. Tc-99m ECD brain perfusion SPECT was obtained before and after rTMS treatment. The changes of cerebral perfusion were analyzed using statistical parametric mapping (SPM; t=3.14, uncorrected ρ < 0.01, voxel = 100). Following areas showed significant increase in rCBF after 3 weeks rTMS treatment: the cingulate gyrus, fusiform gyrus of right temporal lobe, precuneus, and left lateral globus pallidus. Significant decrement was noted in the precental and middle frontal gyrus of right frontal lobe, and fusiform gyrus of left occipital lobe. Low-frequency rTMS on the right prefrontal cortex and high-frequency rTMS on the left prefrontal cortex for 3 weeks as an add-on regimen have increased and decreased rCBF in the specific brain regions in drug-resistant depressed patients. Further analyses correlating clinical characteristics and treatment paradigm with functional imaging data may be helpful in clarifying the pathophysiology of drug-resistant patients

  10. Effect of repetitive transcranial magnetic stimulation in drug resistant depressed patients

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Yong An; Yoo, Ie Ryung; Kang, Bong Joo; Chae, Jeong Ho; Lee, Hye Won; Moon, Hyun Jin; Kim, Sung Hoon; Sohn, Hyung Sun; Chung, Soo Kyo [The Catholic University of Korea, Seoul (Korea, Republic of)

    2007-02-15

    Repetitive transcranial magnetic stimulation (rTMS) has recently been clinically applied in the treatment of drug resistant depressed patients. There are mixed findings about the efficacy of rTMS on depression. Furthermore, the influence of rTMS on the physiology of the brain is not clear. We prospectively evaluated changes of regional cerebral blood flow (rCBF) between pre- and post-rTMS treatment in patients with drug resistant depression. Twelve patients with drug-resistant depression (7 male, 5 female; age range; 19{approx} 52 years; mean age: 29.3 {+-} 9.3 years) were given rTMS on right prefrontal lobe with low frequency (1 Hz) and on left prefrontal lobe with high frequency (20 Hz), with 20-minute-duration each day for 3 weeks. Tc-99m ECD brain perfusion SPECT was obtained before and after rTMS treatment. The changes of cerebral perfusion were analyzed using statistical parametric mapping (SPM; t=3.14, uncorrected {rho} < 0.01, voxel = 100). Following areas showed significant increase in rCBF after 3 weeks rTMS treatment: the cingulate gyrus, fusiform gyrus of right temporal lobe, precuneus, and left lateral globus pallidus. Significant decrement was noted in the precental and middle frontal gyrus of right frontal lobe, and fusiform gyrus of left occipital lobe. Low-frequency rTMS on the right prefrontal cortex and high-frequency rTMS on the left prefrontal cortex for 3 weeks as an add-on regimen have increased and decreased rCBF in the specific brain regions in drug-resistant depressed patients. Further analyses correlating clinical characteristics and treatment paradigm with functional imaging data may be helpful in clarifying the pathophysiology of drug-resistant patients.

  11. Polymerase Chain Reaction To Determine Frequency Of ...

    African Journals Online (AJOL)

    PCR amplification of the DHFR-TS could be used to determine frequency of pyrimethamine resistant P. falciparum strains in malaria blood. Plasmodium falciparum résistant dans ... Les mutations étaient identifiées directement dans les prélèvement de sang obtenus de malades qui visitent les hôpitaux pour les services de ...

  12. Different frequencies of drug resistance mutations among HIV-1 subtypes circulating in China: a comprehensive study.

    Directory of Open Access Journals (Sweden)

    Hongshuai Sui

    Full Text Available The rapid spreading of HIV drug resistance is threatening the overall success of free HAART in China. Much work has been done on drug-resistant mutations, however, most of which were based on subtype B. Due to different genetic background, subtypes difference would have an effect on the development of drug-resistant mutations, which has already been proved by more and more studies. In China, the main epidemic subtypes are CRF07_BC, CRF08_BC, Thai B and CRF01_AE. The depiction of drug resistance mutations in those subtypes will be helpful for the selection of regimens for Chinese. In this study, the distributions difference of amino acids at sites related to HIV drug resistance were compared among subtype B, CRF01_AE, CRF07_BC and CRF08_BC strains prevalent in China. The amino acid composition of sequences belonging to different subtypes, which were obtained from untreated and treated individuals separately, were also compared. The amino acids proportions of 19 sites in RT among subtype B, CRF01_AE and CRF08_BC have significant difference in drug resistance groups (chi-square test, p<0.05. Genetic barriers analysis revealed that sites 69, 138, 181, 215 and 238 were significantly different among subtypes (Kruskal Wallis test, p<0.05. All subtypes shared three highest prevalent drug resistance sites 103, 181 and 184 in common. Many drug resistant sites in protease show surprising high proportions in almost all subtypes in drug-naïve patients. This is the first comprehensive study in China on different development of drug resistance among different subtypes. The detailed data will lay a foundation for HIV treatment regimens design and improve HIV therapy in China.

  13. Frequency of the cancer-resistant phenotype in SR/CR mice and the effect of litter seriation

    DEFF Research Database (Denmark)

    Koch, Janne; Boschian, Anna; Hau, Jann

    2008-01-01

    . The frequency of the SR/CR phenotype in the present study was 30% for the BALB/c strain and 22% for the C57BL/6 strain in the first litters, but the overall frequency was 8% for both strains. A frequency of about 30% was reported in the original US colony. A litter seriation effect on the frequency of the SR....../CR phenotype was recorded. The phenotype frequency in the first-born litters was similar to that recorded in the founder colony in the US. There was no significant difference in the frequency of the SR/CR phenotype between the two genders, but the overall frequency of the SR/CR phenotype was significantly...

  14. Frecuencia de aislamiento de Staphylococcus spp meticilina resistentes y Enterococcus spp vancomicina resistentes en hospitales de Cuba Frequency of methicilline-resistant Staphylococcus spp and vancomycin-resistant Enterococcus spp isolates in Cuban hospitals

    Directory of Open Access Journals (Sweden)

    Leonora González Mesa

    2005-12-01

    Cuba , there was no updated data either on the rate of infection by methicilline-resistant Staphylococcus spp or on the circulation of this germ in the community; neither are there reports on vancomycin-resistant Enterococcus spp presence. In this study, 774 strains collected from hospitals in the country were analyzed. The mechanism of resistance was determined by the methods suggested in the NCCLS guidelines. The 9.3 % (23 and 4.0 % (7 of S. aureus isolates from the hospitals and the community respectively were methicilline-resistant carriers of mecA gen whereas 69.9 %(72 of negative Staphylococcus coagulase isolates showed resistance to oxacillin. Also, a vancomycin-resistant Enterococcus spp-carrying strain was detected. Our results revealed that in Cuba the methicilline-resistant S. aureus is not a problem neither at hospitals nor at the community setting. Despite the fact that the circulation of these germs in the community setting and also the circulation of vancomycin-resistant Enterococcus spp at hospital setting have been reported for the first time, their frequency is very low as a consequence of the advances in the implementation of policies aimed at a more rational use and consumption of antibiotics.

  15. Frequency and voltage dependent electrical responses of poly(triarylamine) thin film-based organic Schottky diode

    Science.gov (United States)

    Anuar Mohamad, Khairul; Tak Hoh, Hang; Alias, Afishah; Ghosh, Bablu Kumar; Fukuda, Hisashi

    2017-11-01

    A metal-organic-metal (MOM) type Schottky diode based on poly (triarylamine) (PTAA) thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f) and capacitance-voltage (C-V-f) characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit). Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz) but decreases at high frequency (1 - 10 kHz). The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV-1cm-2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC) signal.

  16. Monitoring of drug resistance amplification and attenuation with the use of tetracycline-resistant bacteria during wastewater treatment

    Science.gov (United States)

    Harnisz, Monika; Korzeniewska, Ewa; Niestępski, Sebastian; Osińska, Adriana; Nalepa, Beata

    2017-11-01

    The objective of this study was to monitor changes (amplification or attenuation) in antibiotic resistance during wastewater treatment based on the ecology of tetracycline-resistant bacteria. The untreated and treated wastewater were collected in four seasons. Number of tetracycline-(TETR) and oxytetracycline-resistant (OTCR) bacteria, their qualitative composition, minimum inhibitory concentrations (MICs), sensitivity to other antibiotics, and the presence of tet (A, B, C, D, E) resistance genes were determined. TETR and OTCR counts in untreated wastewater were 100 to 1000 higher than in treated effluent. OTCR bacterial counts were higher than TETR populations in both untreated and treated wastewater. TETR isolates were not dominated by a single bacterial genus or species, whereas Aeromonas hydrophila and Aeromonas sobria were the most common in OTCR isolates. The treatment process attenuated the drug resistance of TETR bacteria and amplified the resistance of OTCR bacteria. In both microbial groups, the frequency of tet(A) gene increased in effluent in comparison with untreated wastewater. Our results also indicate that treated wastewater is a reservoir of multiple drug-resistant bacteria as well as resistance determinants which may pose a health hazard for humans and animals when released to the natural environment.

  17. Effect of Media Modified To Mimic Cystic Fibrosis Sputum on the Susceptibility of Aspergillus fumigatus, and the Frequency of Resistance at One Center.

    Science.gov (United States)

    Stevens, David A; Moss, Richard B; Hernandez, Cathy; Clemons, Karl V; Martinez, Marife

    2016-04-01

    Studies of cystic fibrosis (CF) patient exacerbations attributed toPseudomonas aeruginosainfection have indicated a lack of correlation of outcome within vitrosusceptibility results. One explanation is that the media used for testing do not mimic the airway milieu, resulting in incorrect conclusions. Therefore, media have been devised to mimic CF sputum.Aspergillus fumigatusis the leading fungal pathogen in CF, and susceptibility testing is also used to decide therapeutic choices. We assessed whether media designed to mimic CF sputa would give different fungal susceptibility results than those of classical methods, assaying voriconazole, the most utilized anti-Aspergillusdrug in this setting, and 30 CFAspergillusisolates. The frequency of marked resistance (defined as an MIC of >4 μg/ml) in our CF unit by classical methods is 7%. Studies performed with classical methods and with digested sputum medium, synthetic sputum medium, and artificial sputum medium revealed prominent differences inAspergillussusceptibility results, as well as growth rate, with each medium. Clinical correlative studies are required to determine which results are most useful in predicting outcome. Comparison of MICs with non-CF isolates also indicated the CF isolates were generally more resistant. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  18. Spatial heterogeneity, frequency-dependent selection and polymorphism in host-parasite interactions

    Directory of Open Access Journals (Sweden)

    Tellier Aurélien

    2011-11-01

    Full Text Available Abstract Background Genomic and pathology analysis has revealed enormous diversity in genes involved in disease, including those encoding host resistance and parasite effectors (also known in plant pathology as avirulence genes. It has been proposed that such variation may persist when an organism exists in a spatially structured metapopulation, following the geographic mosaic of coevolution. Here, we study gene-for-gene relationships governing the outcome of plant-parasite interactions in a spatially structured system and, in particular, investigate the population genetic processes which maintain balanced polymorphism in both species. Results Following previous theory on the effect of heterogeneous environments on maintenance of polymorphism, we analysed a model with two demes in which the demes have different environments and are coupled by gene flow. Environmental variation is manifested by different coefficients of natural selection, the costs to the host of resistance and to the parasite of virulence, the cost to the host of being diseased and the cost to an avirulent parasite of unsuccessfully attacking a resistant host. We show that migration generates negative direct frequency-dependent selection, a condition for maintenance of stable polymorphism in each deme. Balanced polymorphism occurs preferentially if there is heterogeneity for costs of resistance and virulence alleles among populations and to a lesser extent if there is variation in the cost to the host of being diseased. We show that the four fitness costs control the natural frequency of oscillation of host resistance and parasite avirulence alleles. If demes have different costs, their frequencies of oscillation differ and when coupled by gene flow, there is amplitude death of the oscillations in each deme. Numerical simulations show that for a multiple deme island model, costs of resistance and virulence need not to be present in each deme for stable polymorphism to occur

  19. Radio Frequency Transistors Using Aligned Semiconducting Carbon Nanotubes with Current-Gain Cutoff Frequency and Maximum Oscillation Frequency Simultaneously Greater than 70 GHz.

    Science.gov (United States)

    Cao, Yu; Brady, Gerald J; Gui, Hui; Rutherglen, Chris; Arnold, Michael S; Zhou, Chongwu

    2016-07-26

    In this paper, we report record radio frequency (RF) performance of carbon nanotube transistors based on combined use of a self-aligned T-shape gate structure, and well-aligned, high-semiconducting-purity, high-density polyfluorene-sorted semiconducting carbon nanotubes, which were deposited using dose-controlled, floating evaporative self-assembly method. These transistors show outstanding direct current (DC) performance with on-current density of 350 μA/μm, transconductance as high as 310 μS/μm, and superior current saturation with normalized output resistance greater than 100 kΩ·μm. These transistors create a record as carbon nanotube RF transistors that demonstrate both the current-gain cutoff frequency (ft) and the maximum oscillation frequency (fmax) greater than 70 GHz. Furthermore, these transistors exhibit good linearity performance with 1 dB gain compression point (P1dB) of 14 dBm and input third-order intercept point (IIP3) of 22 dBm. Our study advances state-of-the-art of carbon nanotube RF electronics, which have the potential to be made flexible and may find broad applications for signal amplification, wireless communication, and wearable/flexible electronics.

  20. Rapid selection of Plasmodium falciparum chloroquine resistance transporter gene and multidrug resistance gene-1 haplotypes associated with past chloroquine and present artemether-lumefantrine use in Inhambane District, southern Mozambique

    DEFF Research Database (Denmark)

    Thomsen, Thomas T; Madsen, Laura B; Hansson, Helle H

    2013-01-01

    Chloroquine (CQ) use in Mozambique was stopped in 2002 and artemether-lumefantrine (AL) was implemented in 2008. In light of no use of CQ and extensive use of AL, we determined the frequency of molecular markers of Plasmodium falciparum drug resistance/tolerance to CQ and AL in persons living...... in Linga-Linga, an isolated peninsula and in Furvela village, which is located 8 km inland. The P. falciparum chloroquine resistance transporter gene CVMNK wild type increased in frequency from 43.9% in 2009 to 66.4% in 2010 (P = 0.001), and combined P. falciparum multidrug resistance gene 1 N86-184F-D1246...... haplotype increased significantly between years (P = 0.039). The combination of P. falciparum chloroquine resistance transporter gene CVMNK and P. falciparum multidrug resistance gene NFD increased from 24.3% (2009) to 45.3% in (2010, P = 0.017). The rapid changes observed may largely be caused by decreased...

  1. Negative differential resistance in Josephson junctions coupled to a cavity

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Filatrella, G.; Pierro, V.

    2014-01-01

    or external – is often used. A cavity may also induce a negative differential resistance region at the lower side of the resonance frequency. We investigate the dynamics of Josephson junctions with a negative differential resistance in the quasi particle tunnel current, i.e. in the McCumber curve. We find...

  2. Managing anthelmintic resistance-Variability in the dose of drug reaching the target worms influences selection for resistance?

    Science.gov (United States)

    Leathwick, Dave M; Luo, Dongwen

    2017-08-30

    The concentration profile of anthelmintic reaching the target worms in the host can vary between animals even when administered doses are tailored to individual liveweight at the manufacturer's recommended rate. Factors contributing to variation in drug concentration include weather, breed of animal, formulation and the route by which drugs are administered. The implications of this variability for the development of anthelmintic resistance was investigated using Monte-Carlo simulation. A model framework was established where 100 animals each received a single drug treatment. The 'dose' of drug allocated to each animal (i.e. the concentration-time profile of drug reaching the target worms) was sampled at random from a distribution of doses with mean m and standard deviation s. For each animal the dose of drug was used in conjunction with pre-determined dose-response relationships, representing single and poly-genetic inheritance, to calculate efficacy against susceptible and resistant genotypes. These data were then used to calculate the overall change in resistance gene frequency for the worm population as a result of the treatment. Values for m and s were varied to reflect differences in both mean dose and the variability in dose, and for each combination of these 100,000 simulations were run. The resistance gene frequency in the population after treatment increased as m decreased and as s increased. This occurred for both single and poly-gene models and for different levels of dominance (survival under treatment) of the heterozygote genotype(s). The results indicate that factors which result in lower and/or more variable concentrations of active reaching the target worms are more likely to select for resistance. The potential of different routes of anthelmintic administration to play a role in the development of anthelmintic resistance is discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Pre-thymic somatic mutation leads to high mutant frequency at hypoxanthine-guanine phosphoribosyltransferase gene

    Energy Technology Data Exchange (ETDEWEB)

    Jett, J. [Lawrence Livermore National Lab., CA (United States)

    1994-12-01

    While characterizing the background mutation spectrum of the Hypoxathine-guanine phosphoribosyltransferase (HPRT) gene in a healthy population, an outlier with a high mutant frequency of thioguanine resistant lymphocytes was found. When studied at the age of 46, this individual had been smoking 60 cigarettes per day for 38 years. His mutant frequency was calculated at 3.6 and 4.2x10{sup {minus}4} for two sampling periods eight months apart. Sequencing analysis of the HPRT gene in his mutant thioguanine resistant T lymphocytes was done to find whether the cells had a high rate of mutation, or if the mutation was due to a single occurrence of mutation and, if so, when in the T lymphocyte development the mutation occurred. By T-cell receptor analysis it has been found that out of 35 thioguanine resistant clones there was no dominant gamma T cell receptor gene rearrangement. During my appointment in the Science & Engineering Research Semester, I found that 34 of those clones have the same base substitution of G{yields}T at cDNA position 197. Due to the consistent mutant frequency from both sampling periods and the varying T cell receptors, the high mutant frequency cannot be due to recent proliferation of a mature mutant T lymphocyte. From the TCR and DNA sequence analysis we conclude that the G{yields}T mutation must have occurred in a T lymphocyte precursor before thymic differentiation so that the thioguanine resistant clones share the same base substitution but not the same gamma T cell receptor gene.

  4. Combined effects of fretting and pollutant particles on the contact resistance of the electrical connectors

    Directory of Open Access Journals (Sweden)

    Zhigang Kong

    2017-06-01

    Full Text Available Usually, when electrical connectors operate in vibration environments, fretting will be produced at the contact interfaces. In addition, serious environmental pollution particles will affect contact resistance of the connectors. The fretting will worsen the reliability of connectors with the pollutant particles. The combined effects of fretting and quartz particles on the contact resistance of the gold plating connectors are studied with a fretting test system. The results show that the frequencies have obvious effect on the contact resistance. The higher the frequency, the higher the contact resistance is. The quartz particles cause serious wear of gold plating, which make the nickel and copper layer exposed quickly to increase the contact resistance. Especially in high humidity environments, water supply certain adhesion function and make quartz particles easy to insert or cover the contact surfaces, and even cause opening resistance.

  5. High frequency Soft Switching Half Bridge Series-Resonant DC-DC Converter Utilizing Gallium Nitride FETs

    DEFF Research Database (Denmark)

    Nour, Yasser; Knott, Arnold; Petersen, Lars Press

    2017-01-01

    The need for efficient, smaller, lighter and cheaper power supply units drive the investigation of using high switching frequency soft switching resonant converters. This work presents an 88% efficient 48V nominal input converter switching at 6 MHz and output power of 21 Watts achieving power...... density of 7 W/cm3 for Power-over-Ethernet LED lighting applications. The switching frequency is used to control the output current delivered to the load resistance. The converter was tested using a constant resistance load. The performance and thermal behavior were investigated and reported in this work....

  6. Analysis for the depth of underground resistivity structure by using MT method

    International Nuclear Information System (INIS)

    Matsuo, Koichi; Yokoi, Koichi; Negi, Tateyuki; Kasagi, Toshio; Takahashi, Takeharu; Teshima, Minoru

    2005-03-01

    The present document is to report the result of resistivity monitoring by using MT (Magnetotelluric) method near the site proposed for the Horonobe Underground Research Program at the Horonobe-cho, Hokkaido by the Japan Nuclear Cycle Development Institute. The stationary MT observation system, installed near the HDB-1 borehole on November 2002, was moved to a site at the Hokusei-en, 4 km west of the first site. This system is monitoring for the depth of underground resistivity. Observation data at the Hokusei-en from February 1st 2004 to January 31st 2005 was added to the investigation in 2004 fiscal year. But, data cannot be obtained from July 8th to November 11th of 2004 due to the disconnection trouble of the optical fiber cable for data transfer. The results were as follows; 1) Telluric and magnetic time series data measured by MT unit were transferred to a PC installed in an observation through optical fiber cable and processed and edited automatically. 2) The standard deviation of the apparent resistivity depends on range of frequency, 3% or less in the vicinity of the Schumann resonance frequency. The Standard deviation of data from 80 Hz to 0.56 Hz was less or 13%. But the standard deviation of low frequency data was more or 15%. 3) Amplitude of telluric and magnetic spectra below 1 Hz is coincident with Geomagnetic Activity K-index. Clear correlation was not admitted in resistivity and K-index. 4) Data quality was studied compared with weather data. Clear correlation was not admitted for windy day and rainy day. 5) Data was edited by the new criterion of K-index 1.3 or more, wind 6 m/s or less, precipitation 6 mm or less. As a result, the improvement of the data quality was admitted by 5 frequencies of 9 frequencies. Only one side of resistivity Rxy and Ryx was improved by 4 frequencies of the remainder. 6) In addition, data was edited by the new criterion of the coherence of the electric-magnetic amplitude. As a result, the improvement of the data quality

  7. Determination of optimal whole body vibration amplitude and frequency parameters with plyometric exercise and its influence on closed-chain lower extremity acute power output and EMG activity in resistance trained males

    Science.gov (United States)

    Hughes, Nikki J.

    The optimal combination of Whole body vibration (WBV) amplitude and frequency has not been established. Purpose. To determine optimal combination of WBV amplitude and frequency that will enhance acute mean and peak power (MP and PP) output EMG activity in the lower extremity muscles. Methods. Resistance trained males (n = 13) completed the following testing sessions: On day 1, power spectrum testing of bilateral leg press (BLP) movement was performed on the OMNI. Days 2 and 3 consisted of WBV testing with either average (5.8 mm) or high (9.8 mm) amplitude combined with either 0 (sham control), 10, 20, 30, 40 and 50 Hz frequency. Bipolar surface electrodes were placed on the rectus femoris (RF), vastus lateralis (VL), bicep femoris (BF) and gastrocnemius (GA) muscles for EMG analysis. MP and PP output and EMG activity of the lower extremity were assessed pre-, post-WBV treatments and after sham-controls on the OMNI while participants performed one set of five repetitions of BLP at the optimal resistance determined on Day 1. Results. No significant differences were found between pre- and sham-control on MP and PP output and on EMG activity in RF, VL, BF and GA. Completely randomized one-way ANOVA with repeated measures demonstrated no significant interaction of WBV amplitude and frequency on MP and PP output and peak and mean EMGrms amplitude and EMG rms area under the curve. RF and VL EMGrms area under the curve significantly decreased (p plyometric exercise does not induce alterations in subsequent MP and PP output and EMGrms activity of the lower extremity. Future studies need to address the time of WBV exposure and magnitude of external loads that will maximize strength and/or power output.

  8. Proton-irradiation technology for high-frequency high-current silicon welding diode manufacturing

    Science.gov (United States)

    Lagov, P. B.; Drenin, A. S.; Zinoviev, M. A.

    2017-05-01

    Different proton irradiation regimes were tested to provide more than 20 kHz-frequency, soft reverse recovery “snap-less” behavior, low forward voltage drop and leakage current for 50 mm diameter 7 kA/400 V welding diode Al/Si/Mo structure. Silicon diode with such parameters is very suitable for high frequency resistance welding machines of new generation for robotic welding.

  9. Yeasts acquire resistance secondary to antifungal drug treatment by adaptive mutagenesis.

    Directory of Open Access Journals (Sweden)

    David Quinto-Alemany

    Full Text Available Acquisition of resistance secondary to treatment both by microorganisms and by tumor cells is a major public health concern. Several species of bacteria acquire resistance to various antibiotics through stress-induced responses that have an adaptive mutagenesis effect. So far, adaptive mutagenesis in yeast has only been described when the stress is nutrient deprivation. Here, we hypothesized that adaptive mutagenesis in yeast (Saccharomyces cerevisiae and Candida albicans as model organisms would also take place in response to antifungal agents (5-fluorocytosine or flucytosine, 5-FC, and caspofungin, CSP, giving rise to resistance secondary to treatment with these agents. We have developed a clinically relevant model where both yeasts acquire resistance when exposed to these agents. Stressful lifestyle associated mutation (SLAM experiments show that the adaptive mutation frequencies are 20 (S. cerevisiae -5-FC, 600 (C. albicans -5-FC or 1000 (S. cerevisiae--CSP fold higher than the spontaneous mutation frequency, the experimental data for C. albicans -5-FC being in agreement with the clinical data of acquisition of resistance secondary to treatment. The spectrum of mutations in the S. cerevisiae -5-FC model differs between spontaneous and acquired, indicating that the molecular mechanisms that generate them are different. Remarkably, in the acquired mutations, an ectopic intrachromosomal recombination with an 87% homologous gene takes place with a high frequency. In conclusion, we present here a clinically relevant adaptive mutation model that fulfils the conditions reported previously.

  10. Frequency, serotyping and antimicrobial resistance pattern of Salmonella from feces and lymph nodes of pigs

    Directory of Open Access Journals (Sweden)

    João B.P. Guerra Filho

    Full Text Available ABSTRACT: Salmonellosis is a foodborne disease caused by bacteria of the genus Salmonella, being pigs and pork-products potentially important for its occurrence. In recent decades, some serovars of Salmonella have shown increase of resistance to conventional antimicrobials used in human and animal therapy, with serious risks for public health. The aim of this study was to evaluate feces (n=50, mediastinal (n=50, mesenteric (n=50 and mandibular (n=50 lymph nodes obtained from slaughter houses for Salmonella spp. Positive samples were serotyped and subjected to an in vitro antimicrobial susceptibility test, including the extended-spectrum beta-lactamase (ESBL production. Salmonella species were identified in 10% (20/200 of total samples. From these, 20% (10/50 were identified in the submandibular lymph nodes, 18% (9/50 in the mesenteric lymph nodes, 2% (1/50 in feces and 0% (0/50 in the mediastinal lymph nodes. The serotypes found were Salonella Typhimurium (55%, S. enterica subsp. enterica 4,5,12: i: - (35%, S. Brandenburg and S. Derby with 5% (5% each. All strains showed resistance to at least one antimicrobial; 90% were resistant to four or more antimicrobials, and 15% were multidrug-resistant. Resistance to ciprofloxacin, tetracycline and nalidixic acid was particularly prevalent amongst the tested serovars. Here, we highlighted the impact of pigs in the epidemiological chain of salmonellosis in domestic animals and humans, as well as the high antimicrobial resistance rates of Salmonella strains, reinforcing the necessity for responsible use of antimicrobials for animals as an emergent One Health issue, and to keep these drugs for human therapy approaches.

  11. Passive Super-Low Frequency electromagnetic prospecting technique

    Science.gov (United States)

    Wang, Nan; Zhao, Shanshan; Hui, Jian; Qin, Qiming

    2017-03-01

    The Super-Low Frequency (SLF) electromagnetic prospecting technique, adopted as a non-imaging remote sensing tool for depth sounding, is systematically proposed for subsurface geological survey. In this paper, we propose and theoretically illustrate natural source magnetic amplitudes as SLF responses for the first step. In order to directly calculate multi-dimensional theoretical SLF responses, modeling algorithms were developed and evaluated using the finite difference method. The theoretical results of three-dimensional (3-D) models show that the average normalized SLF magnetic amplitude responses were numerically stable and appropriate for practical interpretation. To explore the depth resolution, three-layer models were configured. The modeling results prove that the SLF technique is more sensitive to conductive objective layers than high resistive ones, with the SLF responses of conductive objective layers obviously showing uprising amplitudes in the low frequency range. Afterwards, we proposed an improved Frequency-Depth transformation based on Bostick inversion to realize the depth sounding by empirically adjusting two parameters. The SLF technique has already been successfully applied in geothermal exploration and coalbed methane (CBM) reservoir interpretation, which demonstrates that the proposed methodology is effective in revealing low resistive distributions. Furthermore, it siginificantly contributes to reservoir identification with electromagnetic radiation anomaly extraction. Meanwhile, the SLF interpretation results are in accordance with dynamic production status of CBM reservoirs, which means it could provide an economical, convenient and promising method for exploring and monitoring subsurface geo-objects.

  12. SOI MESFETs on high-resistivity, trap-rich substrates

    Science.gov (United States)

    Mehr, Payam; Zhang, Xiong; Lepkowski, William; Li, Chaojiang; Thornton, Trevor J.

    2018-04-01

    The DC and RF characteristics of metal-semiconductor field-effect-transistors (MESFETs) on conventional CMOS silicon-on-insulator (SOI) substrates are compared to nominally identical devices on high-resistivity, trap-rich SOI substrates. While the DC transfer characteristics are statistically identical on either substrate, the maximum available gain at GHz frequencies is enhanced by ∼2 dB when using the trap-rich substrates, with maximum operating frequencies, fmax, that are approximately 5-10% higher. The increased fmax is explained by the reduced substrate conduction at GHz frequencies using a lumped-element, small-signal model.

  13. Incipient resistance of Helicoverpa punctigera to the Cry2Ab Bt toxin in Bollgard II cotton.

    Directory of Open Access Journals (Sweden)

    Sharon Downes

    Full Text Available Combinations of dissimilar insecticidal proteins ("pyramids" within transgenic plants are predicted to delay the evolution of pest resistance for significantly longer than crops expressing a single transgene. Field-evolved resistance to Bacillus thuringiensis (Bt transgenic crops has been reported for first generation, single-toxin varieties and the Cry1 class of proteins. Our five year data set shows a significant exponential increase in the frequency of alleles conferring Cry2Ab resistance in Australian field populations of Helicoverpa punctigera since the adoption of a second generation, two-toxin Bt cotton expressing this insecticidal protein. Furthermore, the frequency of cry2Ab resistance alleles in populations from cropping areas is 8-fold higher than that found for populations from non-cropping regions. This report of field evolved resistance to a protein in a dual-toxin Bt-crop has precisely fulfilled the intended function of monitoring for resistance; namely, to provide an early warning of increases in frequencies that may lead to potential failures of the transgenic technology. Furthermore, it demonstrates that pyramids are not 'bullet proof' and that rapid evolution to Bt toxins in the Cry2 class is possible.

  14. Frequency and voltage dependent electrical responses of poly(triarylamine thin film-based organic Schottky diode

    Directory of Open Access Journals (Sweden)

    Mohamad Khairul Anuar

    2017-01-01

    Full Text Available A metal-organic-metal (MOM type Schottky diode based on poly (triarylamine (PTAA thin films has been fabricated by using the spin coating method. Investigation of the frequency dependent conductance-voltage (G-V-f and capacitance-voltage (C-V-f characteristics of the ITO/PTAA/Al MOM type diode were carried out in the frequency range from 12 Hz to 100 kHz using an LCR meter at room temperature. The frequency and bias voltage dependent electrical response were determined by admittance-based measured method in terms of an equivalent circuit model of the parallel combination of resistance and capacitance (RC circuit. Investigation revealed that the conductance is frequency and a bias voltage dependent in which conductance continuous increase as the increasing frequency, respectively. Meanwhile, the capacitance is dependent on frequency up to a certain value of frequency (100 Hz but decreases at high frequency (1 – 10 kHz. The interface state density in the Schottky diode was determined from G-V and C-V characteristics. The interface state density has values almost constant of 2.8 x 1012 eV−1cm−2 with slightly decrease by increasing frequencies. Consequently, both series resistance and interface trap density were found to decrease with increasing frequency. The frequency dependence of the electrical responses is attributed the distribution density of interface states that could follow the alternating current (AC signal.

  15. [Current antibiotic resistance profile of uropathogenic Escherichia coli strains and therapeutic consequences].

    Science.gov (United States)

    El Bouamri, M C; Arsalane, L; Kamouni, Y; Yahyaoui, H; Bennouar, N; Berraha, M; Zouhair, S

    2014-12-01

    Urinary tract infections (UTI) are a very common reason for consultation and prescription in current practice. Excessive or inappropriate use of antibiotics in treating urinary tract infections is responsible for the emergence and spread of multiresistant uropathogenic bacteria. To evaluate the isolation frequency and antibiotic resistance of uropathogenic Escherichia coli strains isolated at the Marrakech region. We conducted a retrospective study over a period of three years (from 1st January 2010 to 31 December 2012). It included all non-redundant uropathogenic E. coli strains isolated in the microbiology laboratory of the Avicenne hospital of Marrakech, Morocco. During this study, 1472 uropathogenic enterobacteriaceae were isolated including 924 non-repetitive E. coli strains, an overall isolation frequency of 63%. Antibiotic resistance of isolated E. coli strains showed resistance rates to amoxicillin (65%), sulfamethoxazole-triméthropime (55%), amoxicillin-clavulanic acid (43%), ciprofloxacin (22%), gentamicin (14%), nitrofurans (11%), amikacin (8%) and fosfomycin (7%). The number of E. coli strains resistant to C3G by ESBL production was 67, an average frequency of 4.5% of all isolated uropathogenic enterobacteria. The associated antibiotic resistance in the case of ESBL-producing E. coli were 82% for ciprofloxacin, 76% for sulfamethozole trimethoprim, 66% for gentamicin and 56% for amikacin. No resistance to imipenem was recorded for the isolated E. coli strains, which represents an imipenem sensitivity of 100%. Antibiotic resistance of uropathogenic E. coli strains limits treatment options and therefore constitutes a real public health problem. The regular updating of antibiotic susceptibility statistics of E. coli strains allows a better adaptation of the probabilistic antibiotic therapy to local epidemiological data. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  16. Frequency Shift of a Rotating Mass-Imbalance Immersed in an Acoustic Fluid

    International Nuclear Information System (INIS)

    Stephen R. Novascone; David M. Weinberg; Michael J. Anderson

    2005-01-01

    In this paper, we describe a physical mechanism that relates a measurable behavior of a vibrating device to the physical properties of a surrounding acoustic medium. The vibrating device under consideration is a rotating imbalance immersed in an unbounded acoustic fluid. It is assumed that the rotating imbalance is driven by an electromagnetic motor excited by a given DC voltage. If nonlinearities are ignored, the steady state operational frequency of such a device is determined by a balance between the applied electromagnetic and opposing frictional torque on the rotating imbalance. If nonlinearities are retained, it is shown that under certain circumstances, the surrounding acoustic medium exerts an additional time-averaged opposing torque on the rotating imbalance that reduces the operational frequency of the device. Consequently, the operational frequency of the device becomes linked to the physical properties of the surrounding medium. Analytical calculations showed that the radiative resistance of an acoustic fluid caused the opposing torque. The shift in frequency is proportional to the radiative resistance and the square of the rotating eccentricity, but inversely proportional the total transducer mass and the damping effect of the DC motor

  17. In Vitro Analysis of the Ability of Trichophyton rubrum To Become Resistant to Terbinafine

    Science.gov (United States)

    Osborne, Colin S.; Hofbauer, Bettina; Favre, Bertrand; Ryder, Neil S.

    2003-01-01

    In this study, we have investigated in vitro the resistance frequency and development of resistance to terbinafine of Trichophyton rubrum. Results demonstrated that naturally occurring mutants are rare and that T. rubrum appears to have little capacity to develop resistance to terbinafine even after prolonged exposure. PMID:14576134

  18. Fluxon induced resistance and field emission

    CERN Document Server

    Calatroni, Sergio; Darriulat, Pierre; Peck, M A; Valente, A M; Van't Hof, C A

    2000-01-01

    The surface resistance of superconducting niobium films induced by the presence of trapped magnetic flux, presumably in the form of a pinned fluxon lattice, is shown to be modified by the presence of a field emitting impurity or defect. The modification takes the form of an additional surface resistance proportional to the density of the fluxon lattice and increasing linearly with the amplitude of the microwave above a threshold significantly lower than the field emission threshold. Such an effect, precursor of electron emission, is observed here for the first time in a study using radiofrequency cavities operated at their fundamental 1.5 GHz frequency. The measured properties of the additional surface resistance severely constrain possible explanations of the observed effect.

  19. Impact of manure fertilization on the abundance of antibiotic-resistant bacteria and frequency of detection of antibiotic resistance genes in soil and on vegetables at harvest.

    Science.gov (United States)

    Marti, Romain; Scott, Andrew; Tien, Yuan-Ching; Murray, Roger; Sabourin, Lyne; Zhang, Yun; Topp, Edward

    2013-09-01

    Consumption of vegetables represents a route of direct human exposure to bacteria found in soil. The present study evaluated the complement of bacteria resistant to various antibiotics on vegetables often eaten raw (tomato, cucumber, pepper, carrot, radish, lettuce) and how this might vary with growth in soil fertilized inorganically or with dairy or swine manure. Vegetables were sown into field plots immediately following fertilization and harvested when of marketable quality. Vegetable and soil samples were evaluated for viable antibiotic-resistant bacteria by plate count on Chromocult medium supplemented with antibiotics at clinical breakpoint concentrations. DNA was extracted from soil and vegetables and evaluated by PCR for the presence of 46 gene targets associated with plasmid incompatibility groups, integrons, or antibiotic resistance genes. Soil receiving manure was enriched in antibiotic-resistant bacteria and various antibiotic resistance determinants. There was no coherent corresponding increase in the abundance of antibiotic-resistant bacteria enumerated from any vegetable grown in manure-fertilized soil. Numerous antibiotic resistance determinants were detected in DNA extracted from vegetables grown in unmanured soil. A smaller number of determinants were additionally detected on vegetables grown only in manured and not in unmanured soil. Overall, consumption of raw vegetables represents a route of human exposure to antibiotic-resistant bacteria and resistance determinants naturally present in soil. However, the detection of some determinants on vegetables grown only in freshly manured soil reinforces the advisability of pretreating manure through composting or other stabilization processes or mandating offset times between manuring and harvesting vegetables for human consumption.

  20. Toroidal Dielectric Tensor-Operator for Arbitrary Aspect-Ratio and Wave Frequency an Anisotropic-Resistivity MHD Formulation

    International Nuclear Information System (INIS)

    Komoshvili, K.; Cuperman, S.

    1998-01-01

    Motivated by the recently increased interest in small aspect ratio tokamaks, we have derived a 2(1/2)D dielectric tensor-operator which can properly describe the plasma response to r.f. waves, under conditions prevailing in the pre-heated stages of arbitrary aspect ratio, axisymmetric toroidal fusion devices. The derived dielectric tensor elements are based on a two-fluid, weakly collisional plasma description, with the Hall term included. They are characterized by the following features: (i) They are cast in a form evidencing the dielectric (non-operator) and operator contributions - the latter being due to the toroidal structure of the V-operators present in Maxwell's equations, on the background of equilibrium currents and pressure gradients; (ii) They are not subject to any I imitation on the (relative) magnitude of the toroidal effects - no expansion in the inverse aspect ratio parameter is used for their derivation; (iii) They include anisotropic - parallel and perpendicular to the magnetic field - contributions to the plasma resistivity; (iv) They are not Iimited by any restriction on the (relative) value of the wave frequency. The explicit, physically transparent formulation of the dielectric tensor is intended for the numerical solution of the full (E ll ≠ 0) wave equation and subsequently, evaluation of the Alfven wave current drive in small aspect ratio tokamaks

  1. Antimicrobial resistance, heavy metal resistance and integron content in bacteria isolated from a South African tilapia aquaculture system.

    Science.gov (United States)

    Chenia, Hafizah Y; Jacobs, Anelet

    2017-11-21

    Antibacterial compounds and metals co-select for antimicrobial resistance when bacteria harbour resistance genes towards both types of compounds, facilitating the proliferation and evolution of antimicrobial and heavy metal resistance. Antimicrobial and heavy metal resistance indices of 42 Gram-negative bacteria from a tilapia aquaculture system were determined to identify possible correlations between these phenotypes. Agar dilution assays were carried out to determine susceptibility to cadmium, copper, lead, mercury, chromate and zinc, while susceptibility to 21 antimicrobial agents was investigated by disk diffusion assays. Presence of merA, the mercury resistance gene, was determined by dot-blot hybridizations and PCR. Association of mercury resistance with integrons and transposon Tn21 was also investigated by PCR. Isolates displayed a high frequency of antimicrobial (erythromycin: 100%; ampicillin: 85%; trimethoprim: 78%) and heavy metal (Zn2+: 95%; Cd2+: 91%) resistance. No correlation was established between heavy metal and multiple antibiotic resistance indices. Significant positive correlations were observed between heavy metal resistance profiles, indices, Cu2+ and Cr3+ resistance with erythromycin resistance. Significant positive correlations were observed between merA (24%)/Tn21 (24%) presence and heavy metal resistance profiles and indices; however, significant negative correlations were obtained between integron-associated qacE∆1 (43%) and sulI (26%) gene presence and heavy metal resistance indices. Heavy metal and antimicrobial agents co-select for resistance, with fish-associated, resistant bacteria demonstrating simultaneous heavy metal resistance. Thus, care should be taken when using anti-fouling heavy metals as feed additives in aquaculture facilities.

  2. Damping of resistive instability in UNK-1 with digital electronics in feedback

    International Nuclear Information System (INIS)

    Zhabitskij, V.M.; Ivanov, I.N.; Korenev, I.L.; Yudin, L.A.

    1991-01-01

    The basis of resistive instability damper system for the UNK-1 is obtained. The system for each of two directions of beam transverse oscillations includes two pairs of pick-up electrodes and damping kickers connected by delayed negative feedback with digital electronics. The requirements for digital electronics in feedback are discussed. The influence of a notch filter is under consideration. In turns out that a 0.8 MHz feedback system damps the resistive instability in the UNK-1 with increment of 0.7 revolution frequency (for low frequencies). 7 refs.; 8 figs

  3. Vasculature analysis of patient derived tumor xenografts using species-specific PCR assays: evidence of tumor endothelial cells and atypical VEGFA-VEGFR1/2 signalings

    International Nuclear Information System (INIS)

    Bieche, Ivan; Marangoni, Elisabetta; Roman-Roman, Sergio; Decaudin, Didier; Dangles-Marie, Virginie; Vacher, Sophie; Vallerand, David; Richon, Sophie; Hatem, Rana; De Plater, Ludmilla; Dahmani, Ahmed; Némati, Fariba; Angevin, Eric

    2014-01-01

    Tumor endothelial transdifferentiation and VEGFR1/2 expression by cancer cells have been reported in glioblastoma but remain poorly documented for many other cancer types. To characterize vasculature of patient-derived tumor xenografts (PDXs), largely used in preclinical anti-angiogenic assays, we designed here species-specific real-time quantitative RT-PCR assays. Human and mouse PECAM1/CD31, ENG/CD105, FLT1/VEGFR1, KDR/VEGFR2 and VEGFA transcripts were analyzed in a large series of 150 PDXs established from 8 different tumor types (53 colorectal, 14 ovarian, 39 breast and 15 renal cell cancers, 6 small cell and 5 non small cell lung carcinomas, 13 cutaneous melanomas and 5 glioblastomas) and in two bevacizumab-treated non small cell lung carcinomas xenografts. As expected, mouse cell proportion in PDXs -evaluated by quantifying expression of the housekeeping gene TBP- correlated with all mouse endothelial markers and human VEGFA RNA levels. More interestingly, we observed human PECAM1/CD31 and ENG/CD105 expression in all tumor types, with higher rate in glioblastoma and renal cancer xenografts. Human VEGFR expression profile varied widely depending on tumor types with particularly high levels of human FLT1/VEGFR1 transcripts in colon cancers and non small cell lung carcinomas, and upper levels of human KDR/VEGFR2 transcripts in non small cell lung carcinomas. Bevacizumab treatment induced significant low expression of mouse Pecam1/Cd31, Eng/Cd105, Flt1/Vegfr1 and Kdr/Vefr2 while the human PECAM1/CD31 and VEGFA were upregulated. Taken together, our results strongly suggest existence of human tumor endothelial cells in all tumor types tested and of both stromal and tumoral autocrine VEGFA-VEGFR1/2 signalings. These findings should be considered when evaluating molecular mechanisms of preclinical response and resistance to tumor anti-angiogenic strategies

  4. A typology and analysis of drug resistance strategies of rural Native Hawaiian youth.

    Science.gov (United States)

    Okamoto, Scott K; Helm, Susana; Giroux, Danielle; Kaliades, Alexis; Kawano, Kaycee Nahe; Kulis, Stephen

    2010-12-01

    This study examines the drug resistance strategies described by Native Hawaiian youth residing in rural communities. Sixty-four youth from 7 middle and intermediate schools on the Island of Hawai'i participated in a series of gender-specific focus groups. Youth responded to 15 drug-related problem situations developed and validated from prior research. A total of 509 responses reflecting primary or secondary drug resistance strategies were identified by the youth, which were qualitatively collapsed into 16 different categories. Primary drug resistance strategies were those that participants listed as a single response, or the first part of a two-part response, while secondary drug resistance strategies were those that were used in tandem with primary drug resistance strategies. Over half of the responses reflecting primary drug resistance strategies fell into three different categories ("refuse," "explain," or "angry refusal"), whereas over half of the responses reflecting secondary drug resistance strategies represented one category ("explain"). Significant gender differences were found in the frequency of using different strategies as well as variations in the frequency of using different strategies based on the type of drug offerer (family versus friends/peers). Implications for prevention practice are discussed.

  5. Proton-irradiation technology for high-frequency high-current silicon welding diode manufacturing

    International Nuclear Information System (INIS)

    Lagov, P B; Drenin, A S; Zinoviev, M A

    2017-01-01

    Different proton irradiation regimes were tested to provide more than 20 kHz-frequency, soft reverse recovery “snap-less” behavior, low forward voltage drop and leakage current for 50 mm diameter 7 kA/400 V welding diode Al/Si/Mo structure. Silicon diode with such parameters is very suitable for high frequency resistance welding machines of new generation for robotic welding. (paper)

  6. Distribution of red blood cell antigens in drug-resistant and drug ...

    African Journals Online (AJOL)

    sofo

    Frequency distribution of ABO, Rh-Hr, MN, Kell blood group system antigens were studied in 277 TB patients (151-drug-sensitive and 126 drug-resistant) of pulmonary tuberculosis to know whether there was any association between them, and also between drug resistance and sensitiveness. They were compared with 485 ...

  7. Resistance to Change and Frequency of Response-Dependent Stimuli Uncorrelated with Reinforcement

    Science.gov (United States)

    Podlesnik, Christopher A.; Jimenez-Gomez, Corina; Ward, Ryan D.; Shahan, Timothy A.

    2009-01-01

    Stimuli uncorrelated with reinforcement have been shown to enhance response rates and resistance to disruption; however, the effects of different rates of stimulus presentations have not been assessed. In two experiments, we assessed the effects of adding different rates of response-dependent brief stimuli uncorrelated with primary reinforcement…

  8. Low frequency noise in resonant Josephson soliton oscillators

    DEFF Research Database (Denmark)

    Hansen, Jørn Bindslev; Holst, T.; Wellstood, Frederick C.

    1991-01-01

    The noise in the resonant soliton mode of long and narrow Josephson tunnel junctions (Josephson transmission lines or JTLs) have been measured in the frequency range from 0.1 Hz to 25 kHz by means of a DC SQUID. The measured white noise was found, to within a factor of two, to be equal...... to the Nyquist voltage noise in a resistance equal to the dynamic resistance RD of the current-voltage characteristic of the bias point. In contrast, measurements of the linewidth of the microwave radiation from the same JTL showed that the spectral density of the underlying noise voltage scaled as R D2/RS where...

  9. Induction and selection of lincomycin-resistant plants in Solanum melongena

    International Nuclear Information System (INIS)

    Sadanandam, A.; Farooqui, M.A.

    1991-01-01

    Cotyledon explants from axenic cultures of Solanum melongena were exposed to 1KR gamma rays and 0.1% ethylmethane sulphonate (EMS). Mutagenised were explants were implanted on shoot regeneration medium containing 100 mg 1 −1 limcomycin. Radiation treatment was efficient in inducing a high frequency of lincomcyn resistant shoots developing on cotyledon explants whereas EMS failed to induce antibiotic resistant shoots. The efficiency of irradiation in inducing lincomycin resistant adventitious shoots and kiloploid nature of chloroplast genome is discussed

  10. Mean annual precipitation predicts primary production resistance and resilience to extreme drought.

    Science.gov (United States)

    Stuart-Haëntjens, Ellen; De Boeck, Hans J; Lemoine, Nathan P; Mänd, Pille; Kröel-Dulay, György; Schmidt, Inger K; Jentsch, Anke; Stampfli, Andreas; Anderegg, William R L; Bahn, Michael; Kreyling, Juergen; Wohlgemuth, Thomas; Lloret, Francisco; Classen, Aimée T; Gough, Christopher M; Smith, Melinda D

    2018-04-27

    Extreme drought is increasing in frequency and intensity in many regions globally, with uncertain consequences for the resistance and resilience of ecosystem functions, including primary production. Primary production resistance, the capacity to withstand change during extreme drought, and resilience, the degree to which production recovers, vary among and within ecosystem types, obscuring generalized patterns of ecological stability. Theory and many observations suggest forest production is more resistant but less resilient than grassland production to extreme drought; however, studies of production sensitivity to precipitation variability indicate that the processes controlling resistance and resilience may be influenced more by mean annual precipitation (MAP) than ecosystem type. Here, we conducted a global meta-analysis to investigate primary production resistance and resilience to extreme drought in 64 forests and grasslands across a broad MAP gradient. We found resistance to extreme drought was predicted by MAP; however, grasslands (positive) and forests (negative) exhibited opposing resilience relationships with MAP. Our findings indicate that common plant physiological mechanisms may determine grassland and forest resistance to extreme drought, whereas differences among plant residents in turnover time, plant architecture, and drought adaptive strategies likely underlie divergent resilience patterns. The low resistance and resilience of dry grasslands suggests that these ecosystems are the most vulnerable to extreme drought - a vulnerability that is expected to compound as extreme drought frequency increases in the future. Copyright © 2018. Published by Elsevier B.V.

  11. Bovine salmonellosis in northeast of Iran: frequency, genetic fingerprinting and antimicrobial resistance patterns of Salmonella spp.

    Science.gov (United States)

    Halimi, Hessam A; Seifi, Hesam A; Rad, Mehrnaz

    2014-01-01

    To evaluate serovar and antimicrobial resistance patterns of Salmonella spp isolated from healthy, diseased and necropsied cows and calves in this observational study. Nineteen isolates recovered from feces and tissues of salmonellosis-affected animals of two commercial farms in north-east of Iran. In second part of the study, the two farms were sampled 4 times with an interval of 2 month. The samples included calves' feces, adult cows' feces, feeds, water, milk filters, and milk fed to calves. Five Salmonella were isolated from 332 fecal samples collected from calves and peri-parturient cows. No Salmonella was recovered from water, feed, milk filers and milk fed to calves. Salmonella Typhimurium was the most frequently isolate among all sero-groups. S. Dublin was only accounted for 8% (two out of 24) of isolates. Isolated Salmonella strains were used for the ERIC PCR DNA fingerprinting assay. Our results grouped Salmonella isolates into 3 clusters, suggesting that specific genotypes were responsible for each sero-group of Salmonella. The results also revealed diversity among Salmonella isolates in cluster III (sero-group B). Eighteen out of 19 Salmonella spp. were resistant to oxytetracycline. Five isolates out of 19 showed more than one drug resistance. Multi-drug resistance was seen only among Salmonella Typhimurium isolates. Enrofloxacin was the most susceptible antibiotic against all isolates in this study. The emergence of multiple antibiotic-resistant strains of Salmonella Typhimurium should be of great concern to the public. No correlation between ERIC fingerprinting and resistance patterns of Salmonella isolates was found, which indicates resistance to antimicrobial agents was not related to specific genetic background. Copyright © 2014 Asian Pacific Tropical Biomedical Magazine. Published by Elsevier B.V. All rights reserved.

  12. Electrically tunable transport and high-frequency dynamics in antiferromagnetic S r3I r2O7

    Science.gov (United States)

    Seinige, Heidi; Williamson, Morgan; Shen, Shida; Wang, Cheng; Cao, Gang; Zhou, Jianshi; Goodenough, John B.; Tsoi, Maxim

    2016-12-01

    We report dc and high-frequency transport properties of antiferromagnetic S r3I r2O7 . Temperature-dependent resistivity measurements show that the activation energy of this material can be tuned by an applied dc electrical bias. The latter allows for continuous variations in the sample resistivity of as much as 50% followed by a reversible resistive switching at higher biases. Such a switching is of high interest for antiferromagnetic applications in high-speed memory devices. Interestingly, we found the switching behavior to be strongly affected by a high-frequency (microwave) current applied to the sample. The microwaves at 3-7 GHz suppress the dc switching and produce resonancelike features that we tentatively associated with the dissipationless magnonics recently predicted to occur in antiferromagnetic insulators subject to ac electric fields. We have characterized the effects of microwave irradiation on electronic transport in S r3I r2O7 as a function of microwave frequency and power, strength and direction of external magnetic field, strength and polarity of applied dc bias, and temperature. Our observations support the potential of antiferromagnetic materials for high-speed/high-frequency spintronic applications.

  13. Characterization and transfer studies of macrolide resistance genes in Streptococcus pneumoniae from Denmark

    DEFF Research Database (Denmark)

    Nielsen, Karen L; Hammerum, Anette M; Lambertsen, Lotte M

    2010-01-01

    Over the last decade, erythromycin resistance has been increasing in frequency in Streptococcus pneumoniae in Denmark. In the present study, 49 non-related erythromycin-resistant S. pneumoniae isolates from invasive sites and 20 isolates from non-invasive sites were collected; antimicrobial...

  14. Autoradiographic detection of mutation to exotoxin-A resistance in mouse fibroblasts treated with ethyl methanesulfonate, X-rays and ultraviolet light

    International Nuclear Information System (INIS)

    Tiah, M.; Ronen, A.

    1989-01-01

    P. aeruginosa exotoxin-A (PE) blocks protein synthesis in mammalian cells by inactivating elongation factor 2 (EF-2). Toxin-resistant mutant cells can be detected autoradioraphically, in cultures grown on microscope coverslips in the presence of PE, and exposed to [ 3 H]leucine. The frequency of PE-resistant cells detected by the autoradiographic assay in non-mutagenized cells of the established mouse cell line LTKA is 9.7 j 0.6 x 10 -5 . Upon treatment with ethyl methanesulfonate (EMS), X-rays of ultraviolet (UV) light it increases in a dose-dependent fashion. The mutational nature of the resistance detected by the assay is indicated by its clonal inheritance, and by the dose-dependent increase in the frequency of resistant cells after utagenesis. On the basis of the high frequency of PE-resistant cells detected by the autoradiographic assay, and their cross-resistance to diphteria toxin (DT), the authors suggest that the PE-resistant mutants detected by the autoradiographic assay are of class II, i.e., they are altered in the structural gene for EF-2. (author). 27 refs.; 5 figs.; 3 tabs

  15. The Kapitza thermal boundary resistance between two solids

    International Nuclear Information System (INIS)

    Andersen, A.C.

    1981-01-01

    In this article, the author develops a model of the Kapitza resistance between two solids in which this resistance is seen to be related to the refraction of thermal phonons at the interface, which is a function of the accoustic properties of the two solids. By calculating a kapitza boundary resistance for the two solids in an ideal case (with ideal temperature, ideal interface, and phonon scattering produced only by the interface) and then producing a summation of the three phonon modes, the angles of incidence, and the phonon frequencies, the author produces an equation which expresses the resistance; this equation is known as the accoustic-mis-match model. By then removing the conditions of ideality and adjusting the equation accordingly, the author finds that the acoustic mismatch model is successful in describing the resistance behavior

  16. Detection, breeding, and selection of durable resistance to brown rust in sugarcane

    Science.gov (United States)

    Brown rust, caused by Puccinia melanocephala, is an important disease of sugarcane in Louisiana. The adaptability of the pathogen has repeatedly resulted in resistant cultivars becoming susceptible once they are widely grown. The frequency of the brown rust resistance gene Bru1 was low in the breedi...

  17. Antimicrobial susceptibility and presence of resistance genes in staphylococci from poultry

    DEFF Research Database (Denmark)

    Aarestrup, Frank Møller; Agersø, Yvonne; Ahrens, Peter

    2000-01-01

    of conventional biochemical testing and 16S rDNA sequencing. The most common species were Staphylococcus aureus (83), Staphylococcus hyicus (11), Staphylococcus xylosus (9) and Staphylococcus cohnii (6). The isolates were susceptible to most antimicrobials tested. A high frequency of S. aureus (30%) was resistant...... to ciprofloxacin. Only six (7%) S. aureus isolates and one Staphylococcus saprophyticus were penicillin resistant. Resistance to sulphamethoxazole was observed among 16 (19%) of S. aureus isolates and two coagulase negative staphylococci (CNS). Twenty (24%) of the S. aureus isolates were resistant to erythromycin...

  18. Emergence of fluoroquinolone resistance among drug resistant tuberculosis patients at a tertiary care facility in Karachi, Pakistan.

    Science.gov (United States)

    Zaidi, Syed Mohammad Asad; Haseeb, Abdul; Habib, Shifa Salman; Malik, Amyn; Khowaja, Saira; SaifUllah, Nausheen; Rizvi, Nadeem

    2017-07-25

    Pakistan is classified as one of the high multi-drug resistant tuberculosis (MDR-TB) burden countries. A poorly regulated private sector, over-prescription of antibiotics and self-medication has led to augmented rates of drug-resistance in the country. Pakistan's first national anti-tuberculosis drug resistance survey identified high prevalence of fluoroquinolone resistance among MDR-TB patients. Further institutional evidence of fluoroquinolone drug-resistance can support re-evaluation of treatment regimens as well as invigorate efforts to control antibiotic resistance in the country. In this study, data for drug-susceptibility testing (DST) was retrospectively analyzed for a total of 133 patients receiving MDR-TB treatment at the Chest Department of Jinnah Postgraduate Medical Center, Karachi, Pakistan. Frequency analyses for resistance patterns was carried out and association of fluoroquinolone (ofloxacin) resistance with demographics and past TB treatment category were assessed. Within first-line drugs, resistance to isoniazid was detected in 97.7% of cases, followed by rifampicin (96.9%), pyrazinamide (86.4%), ethambutol (69.2%) and streptomycin (64.6%). Within second-line drugs, ofloxacin resistance was detected in 34.6% of cases. Resistance to ethionamide and amikacin was 2.3% and 1.6%, respectively. Combined resistance of oflaxacin and isoniazid was detected in 33.9% of cases. Age, gender and past TB treatment category were not significantly associated with resistance to ofloxacin. Fluoroquinolone resistance was observed in an alarmingly high proportion of MDR-TB cases. Our results suggest caution in their use for empirical management of MDR-TB cases and recommended treatment regimens for MDR-TB may require re-evaluation. Greater engagement of private providers and stringent pharmacy regulations are urgently required.

  19. Is hormesis an underestimated factor in the development of herbicide resistance?

    Directory of Open Access Journals (Sweden)

    Belz, Regina G.

    2014-02-01

    Full Text Available The growing impact of herbicide resistant weeds increasingly affects weed management and the delay of resistance evolution has become a major task of chemical weed control. Hormesis and, thus, the phenomenon that low doses of herbicides can boost weed growth could be of importance in this regard since the recommended field rate may represent a low dose for weeds that have evolved resistance to the applied herbicide and, thus, a potential hormetic dose. Applying the field rate may thus not only directly select resistant biotypes, it may also indirectly promote the success and spread of resistant biotypes via hormesis. Nevertheless, hormetic effects in resistant weeds are hitherto merely randomly observed and, thus, a clear quantitative basis to judge the significance of hormesis for resistance evolution is lacking. Therefore, this study aimed at quantifying the degree and frequency of herbicide hormesis in sensitive and resistant weed species in order to provide a first indication of whether the phenomenon deserves consideration as a potential factor contributing to the development of herbicide resistance. In germination assays complete dose-response experiments were conducted with sensitive and resistant biotypes of Matricaria inodora (ALS-target-site resistant; treated with iodosulfuron-methyl-sodium/mesosulfuron-methyl, Eleusine indica (glyphosateresistant; treated with glyphosate, and Chenopodium album (triazine/triazinone-target-site resistant; treated with terbuthylazine. After 10 days of cultivation under controlled conditions plant growth was analyzed by measuring shoot/root length and mass. Results indicated that herbicide hormesis occurred on average with a total frequency of 29% in sensitive/resistant biotypes with an average growth increase of 53% occurring typically within a dose zone exceeding 350fold. Hormetic effects occurred, however, very variable and only for specific endpoints and not plant growth in general. If such a

  20. Genetic architecture of artemisinin-resistant Plasmodium falciparum

    Science.gov (United States)

    Miotto, Olivo; Amato, Roberto; Ashley, Elizabeth A; MacInnis, Bronwyn; Almagro-Garcia, Jacob; Amaratunga, Chanaki; Lim, Pharath; Mead, Daniel; Oyola, Samuel O; Dhorda, Mehul; Imwong, Mallika; Woodrow, Charles; Manske, Magnus; Stalker, Jim; Drury, Eleanor; Campino, Susana; Amenga-Etego, Lucas; Thanh, Thuy-Nhien Nguyen; Tran, Hien Tinh; Ringwald, Pascal; Bethell, Delia; Nosten, Francois; Phyo, Aung Pyae; Pukrittayakamee, Sasithon; Chotivanich, Kesinee; Chuor, Char Meng; Nguon, Chea; Suon, Seila; Sreng, Sokunthea; Newton, Paul N; Mayxay, Mayfong; Khanthavong, Maniphone; Hongvanthong, Bouasy; Htut, Ye; Han, Kay Thwe; Kyaw, Myat Phone; Faiz, Md Abul; Fanello, Caterina I; Onyamboko, Marie; Mokuolu, Olugbenga A; Jacob, Christopher G; Takala-Harrison, Shannon; Plowe, Christopher V; Day, Nicholas P; Dondorp, Arjen M; Spencer, Chris C A; McVean, Gilean; Fairhurst, Rick M; White, Nicholas J; Kwiatkowski, Dominic P

    2015-01-01

    We report a large multicenter genome-wide association study of Plasmodium falciparum resistance to artemisinin, the frontline antimalarial drug. Across 15 locations in Southeast Asia, we identified at least 20 mutations in kelch13 (PF3D7_1343700) affecting the encoded propeller and BTB/POZ domains, which were associated with a slow parasite clearance rate after treatment with artemisinin derivatives. Nonsynonymous polymorphisms in fd (ferredoxin), arps10 (apicoplast ribosomal protein S10), mdr2 (multidrug resistance protein 2) and crt (chloroquine resistance transporter) also showed strong associations with artemisinin resistance. Analysis of the fine structure of the parasite population showed that the fd, arps10, mdr2 and crt polymorphisms are markers of a genetic background on which kelch13 mutations are particularly likely to arise and that they correlate with the contemporary geographical boundaries and population frequencies of artemisinin resistance. These findings indicate that the risk of new resistance-causing mutations emerging is determined by specific predisposing genetic factors in the underlying parasite population. PMID:25599401

  1. Design, Simulation, and Optimization of a Frequency-Tunable Vibration Energy Harvester That Uses a Magnetorheological Elastomer

    Directory of Open Access Journals (Sweden)

    Wan Sun

    2015-01-01

    Full Text Available This study focuses on the design, simulation, and load power optimization for the development of a novel frequency-tunable electromagnetic vibrational energy harvester. The unique characteristic of a magnetorheological elastomer (MRE is utilized, that the shear modulus can be varied by changing the strength of an applied magnetic field. The electromagnetic energy harvester is fabricated, the external electric circuit is connected, and the performance is evaluated through a series of experiments. The resonant frequencies and the parasitic damping constant are measured experimentally for different tuning magnet gap distances, which validate the application of the MRE to the development of a frequency-tunable energy harvesting system. The harvested energy of the system is measured by the voltage across the load resistor. The maximum load power is attained by optimizing the external circuit connected to the coil system. The analysis results are presented for harvesting the maximum load power in terms of the coil parameters and external circuit resistance. The optimality of the load resistance is validated by comparing the analytical results with experimental results. The optimal load resistances under various resonance frequencies are also found for the design and composition of the optimal energy harvesting circuit of the energy harvester system.

  2. The antimicrobial resistance crisis: management through gene monitoring

    Science.gov (United States)

    2016-01-01

    Antimicrobial resistance (AMR) is an acknowledged crisis for humanity. Its genetic origins and dire potential outcomes are increasingly well understood. However, diagnostic techniques for monitoring the crisis are currently largely limited to enumerating the increasing incidence of resistant pathogens. Being the end-stage of the evolutionary process that produces antimicrobial resistant pathogens, these measurements, while diagnostic, are not prognostic, and so are not optimal in managing this crisis. A better test is required. Here, using insights from an understanding of evolutionary processes ruling the changing abundance of genes under selective pressure, we suggest a predictive framework for the AMR crisis. We then discuss the likely progression of resistance for both existing and prospective antimicrobial therapies. Finally, we suggest that by the environmental monitoring of resistance gene frequency, resistance may be detected and tracked presumptively, and how this tool may be used to guide decision-making in the local and global use of antimicrobials. PMID:27831476

  3. The induction of streptomycin resistance in tomato

    International Nuclear Information System (INIS)

    Jansen, D.E.; Snel, E.A.M.; Akerboom, M.; HiIle, J.

    1990-01-01

    Full text: The aim of the research is to investigate cytoplasmic genetics. For the analysis of organelle transfer and segregation in cybrids the presence of selectable and easily screenable genetic markers on organelles is indispensable. Streptomycin resistance is the best characterised cytoplasmic marker. The resistance is dominant and can be induced by a single basepair change in the chloroplast DNA. Protoplasts were treated with several MNU concentrations directly after isolation. Three months after the protoplast mutagenesis about 600 green colonies were isolated from 28x10 6 treated protoplasts. These colonies were retested several times on streptomycin containing media and approximately 150 colonies remained. We distinguished four classes of streptomycin resistance. Experiments were also done without the use of MNU. By somaclonal variation, only a small quantity of streptomycin resistant colonies was isolated at a 50 fold lower frequency. (author)

  4. Thermal heat-balance mode flow-to-frequency converter

    Science.gov (United States)

    Pawlowski, Eligiusz

    2016-11-01

    This paper presents new type of thermal flow converter with the pulse frequency output. The integrating properties of the temperature sensor have been used, which allowed for realization of pulse frequency modulator with thermal feedback loop, stabilizing temperature of sensor placed in the flowing medium. The system assures balancing of heat amount supplied in impulses to the sensor and heat given up by the sensor in a continuous way to the flowing medium. Therefore the frequency of output impulses is proportional to the heat transfer coefficient from sensor to environment. According to the King's law, the frequency of those impulses is a function of medium flow velocity around the sensor. The special feature of presented solution is total integration of thermal sensor with the measurement signal conditioning system. Sensor and conditioning system are not the separate elements of the measurement circuit, but constitute a whole in form of thermal heat-balance mode flow-to-frequency converter. The advantage of such system is easiness of converting the frequency signal to the digital form, without using any additional analogue-to-digital converters. The frequency signal from the converter may be directly connected to the microprocessor input, which with use of standard built-in counters may convert the frequency into numerical value of high precision. Moreover, the frequency signal has higher resistance to interference than the voltage signal and may be transmitted to remote locations without the information loss.

  5. Prevalence of Antibiotic-resistance Enterobacteriaceae strains Isolated from Chicken Meat at Traditional Markets in Surabaya, Indonesia

    Science.gov (United States)

    Yulistiani, R.; Praseptiangga, D.; Supyani; Sudibya; Raharjo, D.; Shirakawa, T.

    2017-04-01

    Antibiotic resistance in bacteria from the family Enterobacteriaceae is an important indicator of the emergence of resistant bacterial strains in the community. This study investigated the prevalence of antibiotic-resistant Enterobacteriaceae isolated from chicken meat sold at traditional markets in Surabaya Indonesia. In all, 203 isolates (43 Salmonella spp., 53 Escherichia coli, 16 Shigella spp., 22 Citrobacter spp., 13 Klebsiella spp, 24 Proteus spp., 15 Yersinia spp., 7 Enterobacter spp., 6 Serratia spp., 3 Edwardsiella spp. were resistant to tetracycline (69.95 %), nalidixid acid (54.19 %), sulfamethoxazole/sulfamethizole (42.36 %), chloramphenicol (12.81%), cefoxitin (6.40 %), gentamicin (5.91 %). Tetracycline was the antimicrobial that showed the highest frequency of resistance among Salmonella, E. coli, Citrobacter, Proteus and Erdwardsiella isolates, and nalidixid acid was second frequency of resistance. Overall, 124 (61.08 %) out of 203 isolates demonstrated multidrug resistance to at least two unrelated antimicrobial agents. The high rate of antimicrobial resistance in bacterial isolates from chicken meat may have major implications for human and animal health with adverse economic implications.

  6. Potent neutralization of VEGF biological activities with a fully human antibody Fab fragment directed against VEGF receptor 2

    International Nuclear Information System (INIS)

    Miao, H.-Q.; Hu, Kun; Jimenez, Xenia; Navarro, Elizabeth; Zhang, Haifan; Lu Dan; Ludwig, Dale L.; Balderes, Paul; Zhu Zhenping

    2006-01-01

    Compelling evidence suggest that vascular endothelial growth factor (VEGF) and its receptors, especially receptor 2 (VEGFR2, or kinase insert domain-containing receptor, KDR), play a critical role in angiogenesis under both physiological and pathological conditions, including cancer and angiogenic retinopathies such as age-related macular degeneration (AMD). To this end, inhibition of angiogenesis with antagonists to either VEGF or KDR has yielded significant therapeutic efficacy both in preclinical studies in animal models and in clinical trials in patients with cancer and AMD. We previously reported the identification of a high affinity, fully human anti-KDR antibody fragment, 1121B Fab, through a highly stringent affinity maturation process with a Fab originally isolated from a naive human antibody phage display library. In this study, we demonstrate that 1121B Fab is able to strongly block KDR/VEGF interaction, resulting in potent inhibition of an array of biological activities of VEGF, including activation of the receptor and its signaling pathway, intracellular calcium mobilization, and migration and proliferation of endothelial cells. Taken together, our data lend strong support to the further development of 1121B Fab fragment as an anti-angiogenesis agent in both cancer and angiogenic retinopathies

  7. Reduced angiogenic factor expression in intrauterine fetal growth restriction using semiquantitative immunohistochemistry and digital image analysis.

    Science.gov (United States)

    Alahakoon, Thushari I; Zhang, Weiyi; Arbuckle, Susan; Zhang, Kewei; Lee, Vincent

    2018-05-01

    To localize, quantify and compare angiogenic factors, vascular endothelial growth factor (VEGF), placental growth factor (PlGF), as well as their receptors fms-like tyrosine kinase receptor (Flt-1) and kinase insert domain receptor (KDR) in the placentas of normal pregnancy and complications of preeclampsia (PE), intrauterine fetal growth restriction (IUGR) and PE + IUGR. In a prospective cross-sectional case-control study, 30 pregnant women between 24-40 weeks of gestation, were recruited into four clinical groups. Representative placental samples were stained for VEGF, PlGF, Flt-1 and KDR. Analysis was performed using semiquantitative methods and digital image analysis. The overall VEGF and Flt-1 were strongly expressed and did not show any conclusive difference in the expression between study groups. PlGF and KDR were significantly reduced in expression in the placentas from pregnancies complicated by IUGR compared with normal and preeclamptic pregnancies. The lack of PlGF and KDR may be a cause for the development of IUGR and may explain the loss of vasculature and villous architecture in IUGR. Automated digital image analysis software is a viable alternative method to the manual reading of placental immunohistochemical staining. © 2018 Japan Society of Obstetrics and Gynecology.

  8. Sources of series resistance in the Harwell solid state alpha detector

    International Nuclear Information System (INIS)

    Rawlings, K.J.

    1985-12-01

    The metal-semiconductor contacts to the Harwell solid state alpha detector have been characterized and the effect of the contact geometry has been assessed. To a reasonable approximation the latter gives rise to an emitter series resistance with an expected range of 20 +- 8 ohms. The contacts behave like parallel RC networks which become noticeably frequency dependent above ca. 100 kHz. Up to this frequency the emitter contact is likely to add 6 +- 4 ohms to the series resistance and the contribution from the base contact varies inversely with the square of the diode's diameter, being 5 +- 3 ohms for a diode with a diameter of 30 mm. (author)

  9. Low frequency mechanical resonance of the vocal tract in vocal exercises that apply tubes

    Czech Academy of Sciences Publication Activity Database

    Horáček, Jaromír; Radolf, Vojtěch; Laukkanen, A. M.

    2017-01-01

    Roč. 37, August (2017), s. 39-49 ISSN 1746-8094 R&D Projects: GA ČR(CZ) GA16-01246S Institutional support: RVO:61388998 Keywords : biomechanics of voice * vocal tract acoustics * phonation into tubes * water resistance voice therapy * bubbling frequency * formant frequencies Subject RIV: BI - Acoustics OBOR OECD: Acoustics Impact factor: 2.214, year: 2016

  10. MEMS based fabrication of high-frequency integrated inductors on Ni–Cu–Zn ferrite substrates

    Energy Technology Data Exchange (ETDEWEB)

    Anthony, Ricky, E-mail: ricky.anthony@tyndall.ie; Wang, Ningning, E-mail: ning.wang@tyndall.ie; Casey, Declan P.; Ó Mathúna, Cian; Rohan, James F.

    2016-05-15

    A surface micro-machining process is described to realize planar inductors on ferrite (Ni{sub 0.49}Zn{sub 0.33}Cu{sub 0.18} Fe{sub 2}O{sub 4}) for high-frequency applications (<30 MHz). The highly resistive nature (~10{sup 8} Ω m) of the Ni–Cu–Zn substrate allows direct conductor patterning by electroplating of Cu windings through a photoresist mold on a sputtered seed layer and eliminates the need for a dielectric layer to isolate the windings from the bottom magnetic core. Measured inductances~367 nH (DC resistance~1.16 Ω and Q-value>14 at 30 MHz) and ~244 nH (DC resistance~0.86 Ω and Q-value~18 at 30 MHz) at 1 MHz for elongated racetrack (10.75 nH/mm{sup 2}) and racetrack inductors (12.5 nH/mm{sup 2}), respectively show good agreement with simulated finite element method analysis. This device can be integrated with power management ICs PMICs for cost-effective, high-performance realization of power-supply in package (PSiP) or on-chip (PSoC). This simple process lays the foundation for fabricating closed core ferrite nano-crystalline core micro-inductors. - Graphical abstract: Material Characterization of Ni–Cu–Zn ferrite substrate and process developed for on-ferrite integrated micro-inductor fabrication. - Highlights: • High-frequency microinductors have been fabricated on Ni-Cu-Zn substrates. • High-resistive ferrite substrates assist direct conductor patterning on the surface. • Uniform inductances ~365 nH over 30 MHz frequency have been achieved. • High Q-values (>18 at 30 MHz) attained are applicable for high-frequency DC–DC conversion applications. • The described process lays the foundation for fabricating closed core ferrite nano-crystalline core.

  11. Temperature and loading frequency effects of fatigue crack growth in HDPE pipe material

    International Nuclear Information System (INIS)

    Merah, N.; Khan, Z.; Bazoune, A.; Saghir, F.

    2006-01-01

    High density polyethylene (HDPE) pipes are being extensively used for gas, water, sewage and waste water distribution systems. Laboratory tests appear to show that HDPE is more able to suppress rapid crack propagation, while remaining somehow resistant to slow crack growth failures observed in service. Procedures for estimating pipe life in service have been established by making use of fatigue crack growth (FCG) results. These procedures are concerned mainly with room temperature. Applications with some safety factor to include the temperature effect. Use of HDPE pipes in water and gas distribution in the Gulf area has seen a net increase. This study addresses the combined effects of temperature and frequency on FCG properties of commercial HDPE pipe material. FCG accelerated tests were conducted on single-etch notch (SEN) specimens in the temperature range of -10 to 70C at frequencies ranging from 0.1 to 50 Hz. The FCG tests are conducted at a stress amplitude level approximately 1/4 of room temperature yield stress and crack growth behavior was investigated using linear elastic fracture mechanics concepts. The stress intensity range delta K gave satisfactory correlation of crack, growth rate (da/dN) at the temperatures of -10, 0, 23 and 40C and at frequencies of 0.1, 1, and 50 Hz. The crack growth resistance was found to decrease with increase in test temperature and decrease growth resistance was found to decrease with increase in test temperature and decrease with frequency. For 70C no crack propagation was observed, the failure was observed to occur by collapse or generalized yielding. Fractographic analyses results are used to explain temperature and frequency effects on FCG. The effect of temperature on da/dN for HDPE material was investigated by considering the variation of mechanical properties with temperature. Master curves were developed by normalizing delta K yield stress. (author)

  12. Transgene Flow from Glufosinate-Resistant Rice to Improved and Weedy Rice in China

    Directory of Open Access Journals (Sweden)

    Yong-liang LU

    2014-09-01

    Full Text Available The development of transgenic rice with novel traits in China can increase rice productivity, but transgene flow to improved or weedy rice has become a major concern. We aimed to evaluate the potential maximum frequencies of transgene flow from glufosinate-resistant rice to improved rice cultivars and weedy rice. Treatments were arranged in randomized complete blocks with three replicates. Experiments were conducted between 2009 and 2010 at the Center for Environmental Safety Supervision and Inspection for Genetically Modified Plants, China National Rice Research Institute, Hangzhou, China. Glufosinate-resistant japonica rice 99-1 was the pollen donor. The pollen recipients were two inbred japonica rice (Chunjiang 016 and Xiushui 09, two inbred indica rice (Zhongzu 14 and Zhongzao 22, two indica hybrid rice (Zhongzheyou 1 and Guodao 1, and one weedy indica rice (Taizhou weedy rice. The offspring of recipients were planted in the field and sprayed with a commercial dose of glufosinate. Leaf tissues of survivors were analyzed by polymerase chain reaction to detect the presence of the transgene. The frequency of gene flow ranged from 0 to 0.488%. In 2009, the order of gene flow frequency was as follows: weedy rice > Chunjiang 016 > Xiushui 09 and Zhongzu 14 > Guodao 1, Zhongzheyou 1 and Zhongzao 22. Gene flow frequencies were generally higher in 2009 than in 2010, but did not differ significantly among rice materials. Gene flow frequency was the highest in weedy rice followed by the inbred japonica rice. The risk of gene flow differed significantly between years and year-to-year variance could mask risk differences among pollen recipients. Gene flow was generally lesser in taller pollen recipients than in shorter ones, but plant height only accounted for about 30% of variation in gene flow. When flowering synchrony was maximized, as in this study, low frequencies of gene flow occurred from herbicide-resistant japonica rice to other cultivars and

  13. Kubo Resistivity of magnetic flux ropes

    Science.gov (United States)

    Gekelman, Walter; Dehaas, Tim; Pribyl, Pat; Vincena, Stephen; van Compernolle, Bart; Sydora, Rick; Tang, Shawn Wenjie

    2017-10-01

    Magnetic flux ropes are bundles of twisted magnetic fields and their associated current. They are common on the surface of the sun (and presumably all other stars) and are observed to have a large range of sizes and lifetimes. They can become unstable and resulting in coronal mass ejections that can travel to earth and indeed, have been observed by satellites. Two side by side flux ropes are generated in the LAPD device at UCLA. Using a series of novel diagnostics the following key quantities, B, u, Vp, n, Te have been measured at more than 48,000 spatial locations and 7,000 time steps. Every term in Ohm's law is also evaluated across and along the local magnetic field and the plasma resistivity derived and it is shown that Ohms law is non-local. The electron distribution function parallel and antiparallel to the background magnetic field was measured and found to be a drifting Kappa function. The Kubo AC conductivity at the flux rope rotation frequency, a 3X3 tensor, was evaluated using velocity correlations and will be presented. This yields meaningful results for the global resistivity. Frequency spectra and the presence of time domain structures may offer a clue to the enhanced resistivity. Work supported by the Department of Energy and National Science Foundation.

  14. Influence of the viscoelastic properties of the respiratory system on the energetically optimum breathing frequency.

    Science.gov (United States)

    Bates, J H; Milic-Emili, J

    1993-01-01

    We hypothesized that the viscoelastic properties of the respiratory system should have significant implications for the energetically optimal frequency of breathing, in view of the fact that these properties cause marked dependencies of overall system resistance and elastance on frequency. To test our hypothesis we simulated two models of canine and human respiratory system mechanics during sinusoidal breathing and calculated the inspiratory work (WI) and pressure-time integral (PTI) per minute under both resting and exercise conditions. The two models were a two-compartment viscoelastic model and a single-compartment model. Requiring minute alveolar ventilation to be fixed, we found that both models predicted almost identical optimum breathing frequencies. The calculated PTI was very insensitive to increases in breathing frequency above the optimal frequencies, while WI was found to increase slowly with frequency above its optimum. In contrast, both WI and PTI increased sharply as frequency decreased below their respective optima. A sensitivity analysis showed that the model predictions were very insensitive to the elastance and resistance values chosen to characterize tissue viscoelasticity. We conclude that the WI criterion for choosing the frequency of breathing is compatible with observations in nature, whereas the optimal frequency predictions of the PTI are rather too high. Both criteria allow for a fairly wide margin of choice in frequency above the optimum values without incurring excessive additional energy expenditure. Furthermore, contrary to our expectations, the viscoelastic properties of the respiratory system tissues do not pose a noticeable problem to the respiratory controller in terms of energy expenditure.

  15. Efficacy of verapamil as an adjunctive treatment in children with drug-resistant epilepsy

    DEFF Research Database (Denmark)

    Nicita, Francesco; Spalice, Alberto; Papetti, Laura

    2014-01-01

    Verapamil, a voltage-gated calcium channel blocker, has been occasionally reported to have some effect on reducing seizure frequency in drug-resistant epilepsy or status epilepticus. We aimed to investigate the efficacy of verapamil as add-on treatment in children with drug-resistant epilepsy....

  16. Insecticidal Activities of Bark, Leaf and Seed Extracts of Zanthoxylum heitzii against the African Malaria Vector Anopheles gambiae

    Directory of Open Access Journals (Sweden)

    Hans J. Overgaard

    2014-12-01

    Full Text Available The olon tree, Zanthoxylum heitzii (syn. Fagara heitzii is commonly found in the central-west African forests. In the Republic of Congo (Congo-Brazzaville its bark is anecdotally reported to provide human protection against fleas. Here we assess the insecticidal activities of Z. heitzii stem bark, seed and leaf extracts against Anopheles gambiae s.s, the main malaria vector in Africa. Extracts were obtained by Accelerated Solvent Extraction (ASE using solvents of different polarity and by classical Soxhlet extraction using hexane as solvent. The insecticidal effects of the crude extracts were evaluated using topical applications of insecticides on mosquitoes of a susceptible reference strain (Kisumu [Kis], a strain homozygous for the L1014F kdr mutation (kdrKis, and a strain homozygous for the G119S Ace1R allele (AcerKis. The insecticidal activities were measured using LD50 and LD95 and active extracts were characterized by NMR spectroscopy and HPLC chromatography. Results show that the ASE hexane stem bark extract was the most effective compound against An. gambiae (LD50 = 102 ng/mg female, but was not as effective as common synthetic insecticides. Overall, there was no significant difference between the responses of the three mosquito strains to Z. heitzii extracts, indicating no cross resistance with conventional pesticides.

  17. How endangered is sexual reproduction of high-mountain plants by summer frosts? Frost resistance, frequency of frost events and risk assessment.

    Science.gov (United States)

    Ladinig, Ursula; Hacker, Jürgen; Neuner, Gilbert; Wagner, Johanna

    2013-03-01

    In temperate-zone mountains, summer frosts usually occur during unpredictable cold spells with snow-falls. Earlier studies have shown that vegetative aboveground organs of most high-mountain plants tolerate extracellular ice in the active state. However, little is known about the impact of frost on reproductive development and reproductive success. In common plant species from the European Alps (Cerastium uniflorum, Loiseleuria procumbens, Ranunculus glacialis, Rhododendron ferrugineum, Saxifraga bryoides, S. moschata, S. caesia), differing in growth form, altitudinal distribution and phenology, frost resistance of reproductive and vegetative shoots was assessed in different reproductive stages. Intact plants were exposed to simulated night frosts between -2 and -14 °C in temperature-controlled freezers. Nucleation temperatures, freezing damage and subsequent reproductive success (fruit and seed set, seed germination) were determined. During all reproductive stages, reproductive shoots were significantly less frost resistant than vegetative shoots (mean difference for LT50 -4.2 ± 2.7 K). In most species, reproductive shoots were ice tolerant before bolting and during fruiting (mean LT50 -7 and -5.7 °C), but were ice sensitive during bolting and anthesis (mean LT50 around -4 °C). Only R. glacialis remained ice tolerant during all reproductive stages. Frost injury in reproductive shoots usually led to full fruit loss. Reproductive success of frost-treated but undamaged shoots did not differ significantly from control values. Assessing the frost damage risk on the basis of summer frost frequency and frost resistance shows that, in the alpine zone, low-statured species are rarely endangered as long as they are protected by snow. The situation is different in the subnival and nival zone, where frost-sensitive reproductive shoots may become frost damaged even when covered by snow. Unprotected individuals are at high risk of suffering from frost damage, particularly

  18. High-performance radio frequency transistors based on diameter-separated semiconducting carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Yu; Che, Yuchi; Zhou, Chongwu, E-mail: chongwuz@usc.edu [Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089 (United States); Seo, Jung-Woo T.; Hersam, Mark C. [Department of Materials Science and Engineering and Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States); Gui, Hui [Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089 (United States)

    2016-06-06

    In this paper, we report the high-performance radio-frequency transistors based on the single-walled semiconducting carbon nanotubes with a refined average diameter of ∼1.6 nm. These diameter-separated carbon nanotube transistors show excellent transconductance of 55 μS/μm and desirable drain current saturation with an output resistance of ∼100 KΩ μm. An exceptional radio-frequency performance is also achieved with current gain and power gain cut-off frequencies of 23 GHz and 20 GHz (extrinsic) and 65 GHz and 35 GHz (intrinsic), respectively. These radio-frequency metrics are among the highest reported for the carbon nanotube thin-film transistors. This study provides demonstration of radio frequency transistors based on carbon nanotubes with tailored diameter distributions, which will guide the future application of carbon nanotubes in radio-frequency electronics.

  19. Trends in Decline of Antiretroviral Resistance among ARV-Experienced Patients in the HIV Outpatient Study: 1999–2008

    Directory of Open Access Journals (Sweden)

    Kate Buchacz

    2012-01-01

    Full Text Available Background. Little is known about temporal trends in frequencies of clinically relevant ARV resistance mutations in HIV strains from U.S. patients undergoing genotypic testing (GT in routine HIV care. Methods. We analyzed cumulative frequency of HIV resistance among patients in the HIV Outpatient Study (HOPS who, during 1999–2008 and while prescribed antiretrovirals, underwent GT with plasma HIV RNA >1,000 copies/mL. Exposure ≥4 months to each of three major antiretroviral classes (NRTI, NNRTI and PI was defined as triple-class exposure (TCE. Results. 906 patients contributed 1,570 GT results. The annual frequency of any major resistance mutations decreased during 1999–2008 (88% to 79%, P=0.05. Resistance to PIs decreased among PI-exposed patients (71% to 46%, P=0.010 as exposure to ritonavir-boosted PIs increased (6% to 81%, P<0.001. Non-significant declines were observed in resistance to NRTIs among NRTI-exposed (82% to 67%, and triple-class-resistance among TCE patients (66% to 41%, but not to NNRTIs among NNRTI-exposed. Conclusions. HIV resistance was common but declined in HIV isolates from subgroups of ARV-experienced HOPS patients during 1999–2008. Resistance to PIs among PI-exposed patients decreased, possibly due to increased representation of patients whose only PI exposures were to boosted PIs.

  20. Stabilization of ideal plasma resistive wall modes in cylindrical geometry: The effect of resistive layers

    International Nuclear Information System (INIS)

    Finn, J.M.

    1995-01-01

    A cylindrical model with finite beta having an external resonant ideal magnetohydrodynamic instability has been constructed. This resonant mode has a mode rational surface, where the safety factor q equals m/n, within the plasma. In this model, the perturbed radial magnetic field for the ideal mode is nonzero between the mode rational surface and the wall, even though it must vanish at the mode rational surface. This property of the mode is in common with the toroidal external kink. Results are presented showing that in the parameter range for which this ideal mode is stable with a conducting wall but unstable with the wall at infinity, a resistive wall mode persists. However, in the presence of plasma resistivity in a resistive layer about the mode rational surface, this resistive wall mode can be stabilized by a plasma rotation frequency of order a nominal resistive instability growth rate. Furthermore, the stabilization occurs in a large gap in wall position or beta. It is also shown that for the ideal resonant mode, as well as resistive plasma modes and nonresonant ideal plasma modes, there is a maximum value of plasma rotation above which there is no stability gap. Discussions are presented suggesting that these properties may hold for the toroidal external kink. copyright 1995 American Institute of Physics

  1. Evolution of insecticide resistance in non-target black flies (Diptera: Simuliidae from Argentina

    Directory of Open Access Journals (Sweden)

    Cristina Mónica Montagna

    2012-06-01

    Full Text Available Black flies, a non-target species of the insecticides used in fruit production, represent a severe medical and veterinary problem. Large increases in the level of resistance to the pyrethroids fenvalerate (more than 355-fold and deltamethrin (162-fold and a small increase in resistance to the organophosphate azinphos methyl (2-fold were observed between 1996-2008 in black fly larvae under insecticide pressure. Eventually, no change or a slight variation in insecticide resistance was followed by a subsequent increase in resistance. The evolution of pesticide resistance in a field population is a complex and stepwise process that is influenced by several factors, the most significant of which is the insecticide selection pressure, such as the dose and frequency of application. The variation in insecticide susceptibility within a black fly population in the productive area may be related to changes in fruit-pest control. The frequency of individuals with esterase activities higher than the maximum value determined in the susceptible population increased consistently over the sampling period. However, the insecticide resistance was not attributed to glutathione S-transferase activity. In conclusion, esterase activity in black flies from the productive area is one mechanism underlying the high levels of resistance to pyrethroids, which have been recently used infrequently. These enzymes may be reselected by currently used pesticides and enhance the resistance to these insecticides.

  2. Evolution of insecticide resistance in non-target black flies (Diptera: Simuliidae) from Argentina.

    Science.gov (United States)

    Montagna, Cristina Mónica; Gauna, Lidia Ester; D'Angelo, Ana Pechen de; Anguiano, Olga Liliana

    2012-06-01

    Black flies, a non-target species of the insecticides used in fruit production, represent a severe medical and veterinary problem. Large increases in the level of resistance to the pyrethroids fenvalerate (more than 355-fold) and deltamethrin (162-fold) and a small increase in resistance to the organophosphate azinphos methyl (2-fold) were observed between 1996-2008 in black fly larvae under insecticide pressure. Eventually, no change or a slight variation in insecticide resistance was followed by a subsequent increase in resistance. The evolution of pesticide resistance in a field population is a complex and stepwise process that is influenced by several factors, the most significant of which is the insecticide selection pressure, such as the dose and frequency of application. The variation in insecticide susceptibility within a black fly population in the productive area may be related to changes in fruit-pest control. The frequency of individuals with esterase activities higher than the maximum value determined in the susceptible population increased consistently over the sampling period. However, the insecticide resistance was not attributed to glutathione S-transferase activity. In conclusion, esterase activity in black flies from the productive area is one mechanism underlying the high levels of resistance to pyrethroids, which have been recently used infrequently. These enzymes may be reselected by currently used pesticides and enhance the resistance to these insecticides.

  3. Temporal step fluctuations on a conductor surface: electromigration force, surface resistivity and low-frequency noise

    International Nuclear Information System (INIS)

    Williams, E D; Bondarchuk, O; Tao, C G; Yan, W; Cullen, W G; Rous, P J; Bole, T

    2007-01-01

    Scattering of charge carriers from surface structures will become an increasing factor in the resistivity as the structure decreases in size to the nanoscale. The effects of scattering at the most basic surface defect, a kink in a step edge, are here analyzed using the continuum step model. Using a Langevin analysis, it has been shown that the electromigration force on the atoms at the step edge causes changes in the temporal evolution of the step-edge. For an electromigration force acting perpendicular to the average step edge and mass-transport dominated by step-edge diffusion, significant deviations from the usual t 1/4 scaling of the displacement correlation function occur dependent on a critical time τ and the direction of the force relative to the step edge (i.e. uphill or downhill). Experimental observations of step fluctuations on Ag(111) show the predicted changes among step fluctuations without current, and with current in the up- and down-hill directions for a current density of order 10 5 A cm -2 . The results yield the magnitude of the electromigration force acting on kinked sites at the step-edge. This in turn yields the contribution of the fluctuating steps to the surface resistivity, which exceeds 1% of the bulk resistivity as wire diameters decrease below 10s of nanometres. The temporal fluctuations of kink density can thus also be related to resistivity noise. Relating the known fluctuation spectrum of the step displacements to fluctuations in their lengths, the corresponding resistivity noise is predicted to show spectral signatures of ∼f -1/2 for step fluctuations governed by random attachment/detachment, and ∼f -3/4 for step fluctuations governed by step-edge diffusion

  4. Transferable chloramphenicol resistance determinant in luminous Vibrio harveyi from penaeid shrimp Penaeus monodon larvae

    Directory of Open Access Journals (Sweden)

    Thangapalam Jawahar Abraham

    2016-12-01

    Full Text Available Antibiotic-resistant luminous Vibrio harveyi strains isolated from Penaeus monodon larvae were screened for the possession of transferable resistance determinants. All the strains were resistant to chloramphenicol and the determinant coding for chloramphenicol resistance was transferred to Escherichia coli at frequencies of 9.50x10-4 to 4.20x10-4. The results probably suggest the excessive use of chloramphenicol in shrimp hatcheries to combat luminous vibriosis.

  5. Inheritance and stability of mevinphos-resistance in Plutella xylostella (L.), with special reference to mutations of acetylcholinesterase 1.

    Science.gov (United States)

    Lin, Chia-Li; Yeh, Shih-Chia; Feng, Hai-Tung; Dai, Shu-Mei

    2017-09-01

    Diamondback moth (Plutella xylostella L.) causes enormous damage on cruciferous vegetables and can rapidly develop resistance to all kinds of insecticides. To effectively manage the insecticide resistance of P. xylostella, an understanding of its inheritance and stability is essential. Here we investigated the phenotypic and genotypic basis of mevinphos resistance by crossing two genetically pure lines of P. xylostella, an SH ggt wild-type strain and an SHM TCN resistant strain carrying 892T/T, 971C/C, and 1156T/G (TCN) mutations of the acetylcholinesterase 1 gene (Pxace1). Similar median lethal concentrations and degrees of dominance in the reciprocal cross progeny, and no plateau on the log concentration-probit line of F1 backcross and self-cross progeny, suggest that the mevinphos-resistance in P. xylostella is inherited as an autosomal and incomplete dominant trait governed by more than one gene. In the absence of mevinphos exposure, the resistance ratio and Pxace1 mutation frequency declined concomitantly in the SHM TCN strain. After 20-generation relaxation, the mevinphos resistance decreased from 52- to 6-fold and the Pxace1 mutation frequency of the TCN haplotype pair decreased from 100% to 0%. A good correlation was found between the resistance ratio and TCN frequency within the range of 12.5- to 25-fold resistance. Since there was no TCN haplotype pair detected below a resistance level of 12.5-fold, we speculate that resistance mechanisms other than target site insensitivity may exist. These observations are important for the prediction and management of mevinphos and related organophosphate resistance in field populations of P. xylostella. Copyright © 2016. Published by Elsevier Inc.

  6. Thermal boundary resistance at Si/Ge interfaces by molecular dynamics simulation

    Directory of Open Access Journals (Sweden)

    Tianzhuo Zhan

    2015-04-01

    Full Text Available In this study, we investigated the temperature dependence and size effect of the thermal boundary resistance at Si/Ge interfaces by non-equilibrium molecular dynamics (MD simulations using the direct method with the Stillinger-Weber potential. The simulations were performed at four temperatures for two simulation cells of different sizes. The resulting thermal boundary resistance decreased with increasing temperature. The thermal boundary resistance was smaller for the large cell than for the small cell. Furthermore, the MD-predicted values were lower than the diffusion mismatch model (DMM-predicted values. The phonon density of states (DOS was calculated for all the cases to examine the underlying nature of the temperature dependence and size effect of thermal boundary resistance. We found that the phonon DOS was modified in the interface regions. The phonon DOS better matched between Si and Ge in the interface region than in the bulk region. Furthermore, in interface Si, the population of low-frequency phonons was found to increase with increasing temperature and cell size. We suggest that the increasing population of low-frequency phonons increased the phonon transmission coefficient at the interface, leading to the temperature dependence and size effect on thermal boundary resistance.

  7. A self-consistent nonlinear theory of resistive-wall instability in a relativistic electron beam

    International Nuclear Information System (INIS)

    Uhm, H.S.

    1994-01-01

    A self-consistent nonlinear theory of resistive-wall instability is developed for a relativistic electron beam propagating through a grounded cylindrical resistive tube. The theory is based on the assumption that the frequency of the resistive-wall instability is lower than the cutoff frequency of the waveguide. The theory is concentrated on study of the beam current modulation directly related to the resistive-wall klystron, in which a relativistic electron beam is modulated at the first cavity and propagates downstream through the resistive wall. Because of the self-excitation of the space charge waves by the resistive-wall instability, a highly nonlinear current modulation of the electron beam is accomplished as the beam propagates downstream. A partial integrodifferential equation is obtained in terms of the initial energy modulation (ε), the self-field effects (h), and the resistive-wall effects (κ). Analytically investigating the partial integrodifferential equation, a scaling law of the propagation distance z m at which the maximum current modulation occurs is obtained. It is found in general that the self-field effects dominate over the resistive-wall effects at the beginning of the propagation. As the beam propagates farther downstream, the resistive-wall effects dominate. Because of a relatively large growth rate of the instability, the required tube length of the klystron is short for most applications

  8. High frequencies of antibiotic resistance genes in infants’ meconium and early fecal samples

    DEFF Research Database (Denmark)

    Gosalbes, M. J.; Vallès, Y.; Jiménez-Hernández, N.

    2016-01-01

    The gastrointestinal tract (GIT) microbiota has been identified as an important reservoir of antibiotic resistance genes (ARGs) that can be horizontally transferred to pathogenic species. Maternal GIT microbes can be transmitted to the offspring, and recent work indicates that such transfer start...

  9. Observations on resistive wall modes

    International Nuclear Information System (INIS)

    Gerwin, R.A.; Finn, J.M.

    1996-01-01

    Several results on resistive wall modes and their application to tokamaks are presented. First, it is observed that in the presence of collisional parallel dynamics there is an exact cancellation to lowest order of the dissipative and sound wave effects for an ideal Ohm's law. This is easily traced to the fact that the parallel dynamics occurs along the perturbed magnetic field lines for such electromagnetic modes. Such a cancellation does not occur in the resistive layer of a tearing-like mode. The relevance to models for resistive wall modes using an electrostatic Hammett-Perkins type operator to model Landau damping will be discussed. Second, we observe that with an ideal Ohm's law, resistive wall modes can be destabilized by rotation in that part of parameter space in which the ideal MHD modes are stable with the wall at infinity. This effect can easily be explained by interpreting the resistive wall instability in terms of mode coupling between the backward stable MHD mode and a stable mode locked into the wall. Such an effect can occur for very small rotation for tearing-resistive wall modes in which inertia dominates viscosity in the layer, but the mode is stabilized by further rotation. For modes for which viscosity dominates in the layer, rotation is purely stabilizing. For both tearing models, a somewhat higher rotation frequency gives stability essentially whenever the tearing mode is stable with a perfectly conducting wall. These tearing/resistive wall results axe also simply explained in terms of mode coupling. It has been shown that resonant external ideal modes can be stabilized in the presence of resistive wall and resistive plasma with rotation of order the nominal tearing mode growth rate. We show that these modes behave as resistive wall tearing modes in the sense above. This strengthens the suggestion that rotational stabilization of the external kink with a resistive wall is due to the presence of resistive layers, even for ideal modes

  10. Frequency Dependent Losses in Transmission Cable Conductors

    DEFF Research Database (Denmark)

    Olsen, Rasmus Schmidt; Holbøll, Joachim; Guðmundsdóttir, Unnur Stella

    2011-01-01

    , such as thermal conditions in and around the cable, as well as the heat generated in conductors, screens, armours etc., taking into account proximity and skin effects. The work performed and presented in this paper is concerned with an improved determination of the losses generated in the conductor, by means...... of better calculation of the AC resistance of transmission cable conductors, in particular regarding higher frequencies. In this way, also losses under harmonics can be covered. Furthermore, the model is suitable for modelling of transient attenuation in high voltage cables. The AC resistance is calculated...... based on the current density distribution in different conductor designs by means of the Finite Element Method (FEM). The obtained results and methods are compared to available standards (IEC publication 60287-1-1)....

  11. Emergence of ampicillin-resistant Enterococcus faecium in Danish hospitals

    DEFF Research Database (Denmark)

    Lester, Camilla H; Sandvang, Dorthe; Olsen, Stefan

    2008-01-01

    BACKGROUND: Ampicillin-resistant Enterococcus faecium isolates are reported in increasing numbers in many European hospitals. The clonal complex 17 (CC17) characterized by ampicillin resistance has been associated with nosocomial E. faecium outbreaks and infections in five continents. The aim...... in the number of infections caused by enterococci was observed from 2002 through 2006. The increase was mainly caused by E. faecium isolates, which tripled, whereas the number of E. faecalis isolates increased by only 23% during the same period. There was also a significant increase in the number of ampicillin......-resistant E. faecium isolates. MLST showed that 98% of the tested ampicillin-resistant E. faecium isolates belonged to CC17. PFGE showed eight different clusters and we found indications of clonal spread within the hospitals. CONCLUSIONS: Ampicillin-resistant E. faecium isolates have increased in frequency...

  12. Increased frequency of pink bollworm resistance to Bt toxin Cry1Ac in China.

    Directory of Open Access Journals (Sweden)

    Peng Wan

    Full Text Available Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt kill some key insect pests, but evolution of resistance by pests can reduce their efficacy. The main approach for delaying pest adaptation to Bt crops uses non-Bt host plants as "refuges" to increase survival of susceptible pests. To delay evolution of pest resistance to transgenic cotton producing Bt toxin Cry1Ac, the United States and some other countries have required refuges of non-Bt cotton, while farmers in China have relied on "natural" refuges of non-Bt host plants other than cotton. The "natural" refuge strategy focuses on cotton bollworm (Helicoverpa armigera, the primary target of Bt cotton in China that attacks many crops, but it does not apply to another major pest, pink bollworm (Pectinophora gossypiella, which feeds almost entirely on cotton in China. Here we report data showing field-evolved resistance to Cry1Ac by pink bollworm in the Yangtze River Valley of China. Laboratory bioassay data from 51 field-derived strains show that the susceptibility to Cry1Ac was significantly lower during 2008 to 2010 than 2005 to 2007. The percentage of field populations yielding one or more survivors at a diagnostic concentration of Cry1Ac increased from 0% in 2005-2007 to 56% in 2008-2010. However, the median survival at the diagnostic concentration was only 1.6% from 2008 to 2010 and failure of Bt cotton to control pink bollworm has not been reported in China. The early detection of resistance reported here may promote proactive countermeasures, such as a switch to transgenic cotton producing toxins distinct from Cry1A toxins, increased planting of non-Bt cotton, and integration of other management tactics together with Bt cotton.

  13. Autonomous generator based on Ni-Mn-Ga microactuator as a frequency selective element

    Directory of Open Access Journals (Sweden)

    Barandiaran J.M.

    2013-01-01

    Full Text Available In this work, we suggest the temperature-induced resistivity change at the martensitic transformation in the Ni-Mn-Ga ferromagnetic shape memory alloy as a driving mechanism enabling periodic signal generation. We demonstrated its practical importance by a design of the prototype of a low-frequency autonomous generator. A prominent feature of this new generator is a control of its frequency by the external magnetic field.

  14. The importance of the electron mean free path for superconducting radio-frequency cavities

    Science.gov (United States)

    Maniscalco, J. T.; Gonnella, D.; Liepe, M.

    2017-01-01

    Impurity-doping of niobium is an exciting new technology in the field of superconducting radio-frequency accelerators, producing cavities with record-high quality factor Q0 and Bardeen-Cooper-Schrieffer surface resistance that decreases with increasing radio-frequency field. Recent theoretical work has offered a promising explanation for this so-called "anti-Q-slope," but the link between the decreasing surface resistance and the shortened electron mean free path of doped cavities has remained elusive. In this work, we investigate this link, finding that the magnitude of this decrease varies directly with the mean free path: shorter mean free paths correspond to stronger anti-Q-slopes. We draw a theoretical connection between the mean free path and the overheating of the quasiparticles, which leads to the reduction of the anti-Q-slope towards the normal Q-slope of long-mean-free-path cavities. We also investigate the sensitivity of the residual resistance to trapped magnetic flux, a property that is greatly enhanced for doped cavities, and calculate an optimal doping regime for a given amount of trapped flux.

  15. Faradic resistance of the electrode/electrolyte interface.

    Science.gov (United States)

    Mayer, S; Geddes, L A; Bourland, J D; Ogborn, L

    1992-09-01

    A new method is used to measure the direct-current (Faradic) resistance of a single electrode/electrolyte interface. The method employs a constant-current pulse and a potential-sensing electrode. By choosing a sufficiently long pulse duration, the voltage between the test and potential-sensing electrode exhibits a three-phase response. In the steady-state phase, the voltage measured is equal to the current flowing through the electrode Faradic resistance and the resistance of the electrolyte between the test and potential-sensing electrode. By measuring this latter resistance with a high-frequency sinusoidal alternating current, the voltage drop in the electrolyte is calculated and subtracted from the voltage measured between the test and potential-sensing electrode, thereby allowing calculation of the Faradic resistance. By plotting the reciprocal of the Faradic resistance against current density and fitting the data points to a third-order polynomial, it is possible to determine the zero-current density (Faradic) resistance. This technique was used to determine the Faradic resistance of electrodes (0.1 cm2) of stainless-steel, platinum, platinum-iridium and rhodium in 0.9 per cent NaCl at 25 degrees. The zero current Faradic resistance is lowest for platinum (30.3 k omega), slightly higher for platinum-iridium (47.6k omega), much higher for rhodium (111k omega) and highest for type 316 stainless-steel (345k omega). In all cases, the Faradic resistance decreases dramatically with increasing current density.

  16. Spectrum of resistive MHD modes in cylindrical plasmas

    International Nuclear Information System (INIS)

    Ryu, C.M.; Grimm, R.C.

    1983-07-01

    A numerical study of the normal modes of a compressible resistive MHD fluid in cylindrical geometry is presented. Resistivity resolves the shear Alfven and slow magnetosonic continua of ideal MHD into discrete spectra and gives rise to heavily damped modes whose frequencies lie on specific lines in the complex plane. Fast magnetosonic waves are less affected but are also damped. Overstable modes arise from the shear Alfven spectrum. The stabilizing effect of favorable average curvature is shown. Eigenfunctions illustrating the nature of typical normal modes are displayed

  17. Pyramiding, alternating or mixing: comparative performances of deployment strategies of nematode resistance genes to promote plant resistance efficiency and durability.

    Science.gov (United States)

    Djian-Caporalino, Caroline; Palloix, Alain; Fazari, Ariane; Marteu, Nathalie; Barbary, Arnaud; Abad, Pierre; Sage-Palloix, Anne-Marie; Mateille, Thierry; Risso, Sabine; Lanza, Roger; Taussig, Catherine; Castagnone-Sereno, Philippe

    2014-02-22

    Resistant cultivars are key elements for pathogen control and pesticide reduction, but their repeated use may lead to the emergence of virulent pathogen populations, able to overcome the resistance. Increased research efforts, mainly based on theoretical studies, explore spatio-temporal deployment strategies of resistance genes in order to maximize their durability. We evaluated experimentally three of these strategies to control root-knot nematodes: cultivar mixtures, alternating and pyramiding resistance genes, under controlled and field conditions over a 3-years period, assessing the efficiency and the durability of resistance in a protected crop rotation system with pepper as summer crop and lettuce as winter crop. The choice of the resistance gene and the genetic background in which it is introgressed, affected the frequency of resistance breakdown. The pyramiding of two different resistance genes in one genotype suppressed the emergence of virulent isolates. Alternating different resistance genes in rotation was also efficient to decrease virulent populations in fields due to the specificity of the virulence and the trapping effect of resistant plants. Mixing resistant cultivars together appeared as a less efficient strategy to control nematodes. This work provides experimental evidence that, in a cropping system with seasonal sequences of vegetable species, pyramiding or alternating resistance genes benefit yields in the long-term by increasing the durability of resistant cultivars and improving the long-term control of a soil-borne pest. To our knowledge, this result is the first one obtained for a plant-nematode interaction, which helps demonstrate the general applicability of such strategies for breeding and sustainable management of resistant cultivars against pathogens.

  18. ORF Alignment: NC_004431 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available EDL933] pdb|1KDT|B Chain B, ... Cytidine Monophosphate Kinase From E.Coli In Complex ... With... 2',3'-Dideoxy-Cytidine Monophosphate pdb|1KDT|A ... Chain A, Cytidine Monophosphate Kinase From E.Coli...|1KDR|B Chain B, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara-Cytidine Monophosp...hate ... pdb|1KDR|A Chain A, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara

  19. ORF Alignment: NC_002655 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available EDL933] pdb|1KDT|B Chain B, ... Cytidine Monophosphate Kinase From E.Coli In Complex ... With... 2',3'-Dideoxy-Cytidine Monophosphate pdb|1KDT|A ... Chain A, Cytidine Monophosphate Kinase From E.Coli...|1KDR|B Chain B, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara-Cytidine Monophosp...hate ... pdb|1KDR|A Chain A, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara

  20. ORF Alignment: NC_002695 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available EDL933] pdb|1KDT|B Chain B, ... Cytidine Monophosphate Kinase From E.Coli In Complex ... With... 2',3'-Dideoxy-Cytidine Monophosphate pdb|1KDT|A ... Chain A, Cytidine Monophosphate Kinase From E.Coli...|1KDR|B Chain B, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara-Cytidine Monophosp...hate ... pdb|1KDR|A Chain A, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara

  1. ORF Alignment: NC_000913 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available EDL933] pdb|1KDT|B Chain B, ... Cytidine Monophosphate Kinase From E.Coli In Complex ... With... 2',3'-Dideoxy-Cytidine Monophosphate pdb|1KDT|A ... Chain A, Cytidine Monophosphate Kinase From E.Coli...|1KDR|B Chain B, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara-Cytidine Monophosp...hate ... pdb|1KDR|A Chain A, Cytidine Monophosphate Kinase From ... E.Coli In Complex With Ara

  2. Detection of antibiotic resistance in clinical bacterial strains from pets

    OpenAIRE

    Poeta, P.; Rodrigues, J.

    2008-01-01

    The identification of different bacterial strains and the occurrence of antibiotic resistance were investigated in several infection processes of pets as skin abscess with purulent discharge, bronco alveolar fluid, earwax, urine, mammary, and eye fluid. Streptococcus spp. and Staphylococcus spp. were the most detected in the different samples. A high frequency of antimicrobial resistance has been observed and this could reflect the wide use of antimicrobials in pets, making the effectiveness ...

  3. A vibration energy harvesting device with bidirectional resonance frequency tunability

    International Nuclear Information System (INIS)

    Challa, Vinod R; Prasad, M G; Shi Yong; Fisher, Frank T

    2008-01-01

    Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibrating structures, a general requirement independent of the energy transfer mechanism is that the vibration energy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ± 20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22–32 Hz to enable a continuous power output 240–280 µW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined

  4. Multistrain models predict sequential multidrug treatment strategies to result in less antimicrobial resistance than combination treatment

    DEFF Research Database (Denmark)

    Ahmad, Amais; Zachariasen, Camilla; Christiansen, Lasse Engbo

    2016-01-01

    generated by a mathematical model of the competitive growth of multiple strains of Escherichia coli.Results: Simulation studies showed that sequential use of tetracycline and ampicillin reduced the level of double resistance, when compared to the combination treatment. The effect of the cycling frequency...... frequency did not play a role in suppressing the growth of resistant strains, but the specific order of the two antimicrobials did. Predictions made from the study could be used to redesign multidrug treatment strategies not only for intramuscular treatment in pigs, but also for other dosing routes.......Background: Combination treatment is increasingly used to fight infections caused by bacteria resistant to two or more antimicrobials. While multiple studies have evaluated treatment strategies to minimize the emergence of resistant strains for single antimicrobial treatment, fewer studies have...

  5. Theory of resistive magnetohydrodynamic instabilities excited by energetic trapped particles in large-size tokamaks

    International Nuclear Information System (INIS)

    Biglari, H.

    1987-01-01

    A theory describing excitation of resistive magnetohydrodynamic instabilities due to a population of energetic particles, trapped in region of adverse curvature on energetic particles, trapped in region of adverse curvature in tokamaks, is presented. Theory's principal motivation is observation that high magnetic-field strengths and large geometric dimensions characteristic of present-generation thermonuclear fusion devices, places them in a frequency regime whereby processional drift frequency of auxiliary hot-ion species, in order of magnitude, falls below a typical inverse resistive interchange time scale, so that inclusion of resistive dissipation effects becomes important. Destabilization of the resistive internal kink mode by these suprathermal particles is first investigated. Using variational techniques, a generalized dispersion relation governing such modes, which recovers ideal theory in its appropriate limit, is derived and analyzed using Nyquist-diagrammatic techniques. An important implication of theory for present-generation fusion devices is that they will be stable to fishbone activity. Interaction of energetic particles with resistive interchange-ballooning modes is taken up. A population of hot particles, deeply trapped on adverse curvature side in tokamaks, can resonantly destabilize resistive interchange mode, which is stable in their absence because of favorable average curvature. Both modes are different from their usual resistive magnetohydrodynamic counterparts in their destabilization mechanism

  6. Activation of the SOS response increases the frequency of small colony variants

    DEFF Research Database (Denmark)

    Vestergaard, Martin; Paulander, Wilhelm Erik Axel; Ingmer, Hanne

    2015-01-01

    BACKGROUND: In Staphylococcus aureus sub-populations of slow-growing cells forming small colony variants (SCVs) are associated with persistent and recurrent infections that are difficult to eradicate with antibiotic therapies. In SCVs that are resistant towards aminoglycosides, mutations have been...... with different mechanism of action influence the formation of SCVs that are resistant to otherwise lethal concentrations of the aminoglycoside, gentamicin. We found that exposure of S. aureus to fluoroquinolones and mitomycin C increased the frequency of gentamicin resistant SCVs, while other antibiotic classes...... failed to do so. The higher proportion of SCVs in cultures exposed to fluoroquinolones and mitomycin C compared to un-exposed cultures correlate with an increased mutation rate monitored by rifampicin resistance and followed induction of the SOS DNA damage response. CONCLUSION: Our observations suggest...

  7. A frequency-type optically controllable YAG:Nd(3+) laser

    Energy Technology Data Exchange (ETDEWEB)

    Baliasnyi, L.M.; Groznov, M.A.; Gubanov, B.S.; Zoria, A.V.; Myl' nikov, V.S.

    1990-06-01

    The paper demonstrates the feasibility of using MOS-LC modulators based on the s-effect with an internal dividing mirror as the optically controllable mirrors of frequency-type YAG:Nd(3+) lasers. It is shown that the maximum energy of the laser in free-runnig operation of 10 mJ/sq cm is limited by the radiation resistance (not greater than 70 mJ/sq cm) of the orienting fluid, i.e., polyvinyl alcohol. The optical inhomogeneity of the modulator amounts to 20-40 percent, which is connected with the presence of a bonded single-crystal GaAs layer. The working frequency of the laser was about 20 Hz.

  8. A functional polymorphism of the microRNA-146a gene is associated with susceptibility to drug-resistant epilepsy and seizures frequency.

    Science.gov (United States)

    Cui, Lili; Tao, Hua; Wang, Yan; Liu, Zhou; Xu, Zhien; Zhou, Haihong; Cai, Yujie; Yao, Lifen; Chen, Beichu; Liang, Wandong; Liu, Yu; Cheng, Wanwen; Liu, Tingting; Ma, Guoda; Li, You; Zhao, Bin; Li, Keshen

    2015-04-01

    Epilepsy is the third most common chronic brain disorder and is characterized by an enduring predisposition for seizures. Recently, a growing body of evidence has suggested that microRNA-146a (miR-146a) is upregulated in the brains of epilepsy patients and of mouse models; furthermore, miR-146a may be involved in the development and progression of seizures through the regulation of inflammation and immune responses. In this report, we performed a case-control study to analyze the relationship between the two potentially functional single nucleotide polymorphisms (SNPs) of the miR-146a gene (rs2910464 and rs57095329) and the risk of epilepsy in a Chinese population comprising 249 cases and 249 healthy controls. Our study comprised 249 epilepsy patients and 249 healthy controls in two regions of China. The DNA was genotyped using the ABI PRISM SNapShot method. The statistical analysis was estimated using the chi-square test or Fisher's exact test. Our results indicated a significant association between the rs57095329 SNP of the miR-146a gene and the risk of drug resistant epilepsy (DRE) (genotypes, p = 0.0258 and alleles, p = 0.0108). Moreover, the rs57095329 A allele was found to be associated with a reduced risk of seizures frequency in DRE patients (all p epilepsy. Our data indicate that the rs57095329 polymorphism in the promoter region of miR-146a is involved in the genetic susceptibility to DRE and the seizures frequency. Copyright © 2015 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

  9. Isolation and identification of antibiotic resistance genes in Staphylococcus aureus isolates from respiratory system infections in shahrekord, Iran

    Directory of Open Access Journals (Sweden)

    Maryam Reisi

    2014-07-01

    Full Text Available   Introduction : Staphylococcus aureus is considered as one of pathogenic agents in humans, that engages different body parts including respiratory system and causes to spend lots of costs and extending patient’s treatment period. This study which is performed to separate and investigate the pattern of antibiotic resistance in Staphylococcus aureus isolates from upper respiratory system infections in Shahrekord.   Materials and methods: This study was done by sectional-descriptive method On 200 suspicious persons to the upper respiratory system infections who were referred to the Imam Ali clinic in Shahrekord in 2012. After isolation of Staphylococcus aureus from cultured nose discharges, antibiotic resistance genes were identified by polymerase chain reaction (PCR by using defined primer pairs .   Results : Among 200 investigated samples in 60 cases (30% Staphylococcus aureus infection (by culturing and PCR method was determined. Isolates showed the lowest amount of antibiotic resistance to vancomycin (0.5% and the highest amount of resistance to the penicillin G and cefotaxime (100%. mecA gene (encoding methicillin resistance with frequency of 85.18% and aacA-D gene (encoding resistance to aminoglycosides with frequency of 28.33% showed the highest and lowest frequency of antibiotic resistance genes coding in Staphylococcus aureus isolates respectively .   Discussion and conclusion : Notable prevalence of resistant Staphylococcus aureus isolates in community acquired respiratory infections, recommend continuous control necessity to impede the spreading of these bacteria and their infections.  

  10. Antibiotic cross-resistance in the lab and resistance co-occurrence in the clinic: Discrepancies and implications in E.coli.

    Science.gov (United States)

    Obolski, Uri; Dellus-Gur, Eynat; Stein, Gideon Y; Hadany, Lilach

    2016-06-01

    Antibiotic resistance is an important public health issue, and vast resources are invested in researching new ways to fight it. Recent experimental works have shown that resistance to some antibiotics can result in increased susceptibility to others, namely induce cross-sensitivity. This phenomenon could be utilized to increase efficiency of antibiotic treatment strategies that minimize resistance. However, as conditions in experimental settings and in the clinic may differ substantially, the implications of cross-sensitivity for clinical settings are not guaranteed and should be examined. In this work we analyzed data of Escherichia coli isolates from patients' blood, sampled in Rabin Medical Center, Israel, to examine co-occurrence of resistance to antibiotics in the clinic. We compared the co-occurrence patterns with cross-sensitivity patterns observed in the lab. Our data showed only positively associated occurrence of resistance, even with antibiotics that were shown to induce cross-sensitivity in laboratory conditions. We used a mathematical model to examine the potential effects of cross-sensitivity versus co-occurrence on the spread of drug resistance. We conclude that resistance frequencies in the clinic can have a substantial effect on the success of treatment strategies, and should be considered alongside experimental evidence of cross-sensitivity. Copyright © 2016. Published by Elsevier B.V.

  11. Antimicrobial susceptibility and occurrence of resistance genes among Salmonella enterica serovar Weltevreden from different countries

    DEFF Research Database (Denmark)

    Aarestrup, Frank Møller; Lertworapreecha, M.; Evans, M.C.

    2003-01-01

    and gentamicin. All nine ampicillin-resistant isolates contained a sequence similar to the bla(TEM-1b) gene, one of the eight chloramphenicol-resistant isolates a sequence similar to the catA1 gene, all three neomycin-resistant isolates a sequence similar to the aphA-2 gene, 16 (73%) of the 22 streptomycin...... isolates were examined for susceptibility to antimicrobial agents, and resistant isolates were examined for the presence of selected resistance genes by PCR. Results: Only 48 (9.5%) of the isolates were resistant to one or more of the antimicrobial agents tested. A low frequency of resistance was found...

  12. Nanostructured composite layers for electromagnetic shielding in the GHz frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Suchea, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Chemistry and Physics, “Al.I. Cuza” University of Iasi, Iasi (Romania); Tudose, I.V. [Chemistry and Physics, “Al.I. Cuza” University of Iasi, Iasi (Romania); Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Tzagkarakis, G. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Kenanakis, G. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Institute of Electronic Structure & Laser (IESL), Foundation for Research and Technology (FORTH) Hellas, Heraklion (Greece); Katharakis, M. [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Drakakis, E. [Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Koudoumas, E., E-mail: koudoumas@staff.teicrete.gr [Center of Materials Technology and Photonics, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece); Electrical Engineering Department, School of Engineering, Technological Educational Institute of Crete, Heraklion (Greece)

    2015-10-15

    Graphical abstract: - Highlights: • Paint-like nanocomposite layers consisting of graphene nanoplatelets, PANI:HCl and PEDOT:PSS present very effective attenuation of electromagnetic radiation in the frequency range 4–20 GHz. • The shielding performance is based mostly on the graphene nanoplatelets and supported by PANI:HCl. In contrast, PEDOT:PSS plays mainly the role of the binder. • Increasing resistivity was observed to reduce the shielding effect, while increasing thickness to favor it. - Abstract: We report on preliminary results regarding the applicability of nanostructured composite layers for electromagnetic shielding in the frequency range of 4–20 GHz. Various combinations of materials were employed including poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polyaniline, graphene nanoplatelets, carbon nanotubes, Cu nanoparticles and Poly(vinyl alcohol). As shown, paint-like nanocomposite layers consisting of graphene nanoplatelets, polyaniline PEDOT:PSS and Poly(vinyl alcohol) can offer quite effective electromagnetic shielding, similar or even better than that of commercial products, the response strongly depending on their thickness and resistivity.

  13. Nanostructured composite layers for electromagnetic shielding in the GHz frequency range

    International Nuclear Information System (INIS)

    Suchea, M.; Tudose, I.V.; Tzagkarakis, G.; Kenanakis, G.; Katharakis, M.; Drakakis, E.; Koudoumas, E.

    2015-01-01

    Graphical abstract: - Highlights: • Paint-like nanocomposite layers consisting of graphene nanoplatelets, PANI:HCl and PEDOT:PSS present very effective attenuation of electromagnetic radiation in the frequency range 4–20 GHz. • The shielding performance is based mostly on the graphene nanoplatelets and supported by PANI:HCl. In contrast, PEDOT:PSS plays mainly the role of the binder. • Increasing resistivity was observed to reduce the shielding effect, while increasing thickness to favor it. - Abstract: We report on preliminary results regarding the applicability of nanostructured composite layers for electromagnetic shielding in the frequency range of 4–20 GHz. Various combinations of materials were employed including poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polyaniline, graphene nanoplatelets, carbon nanotubes, Cu nanoparticles and Poly(vinyl alcohol). As shown, paint-like nanocomposite layers consisting of graphene nanoplatelets, polyaniline PEDOT:PSS and Poly(vinyl alcohol) can offer quite effective electromagnetic shielding, similar or even better than that of commercial products, the response strongly depending on their thickness and resistivity.

  14. High‐frequency induced polarization measurements of hydrocarbon‐bearing rocks

    DEFF Research Database (Denmark)

    Burtman, Vladimir; Endo, Masashi; Zhdanov, Michael S.

    2011-01-01

    We have investigated induced polarization (IP) effects in hydrocarbon‐bearing artificial rocks at frequencies greater than 100 Hz. We have examined the instrumental and electrode phase responses of Zonge International's complex resistivity (CR) system, and optimized the performance of the Zonge s......, and suggest the necessity to account for IP effects in the interpretations of electromagnetic data, particularly in induction logging data....

  15. Identifying dielectric and resistive electrode losses in high-density capacitors at radio frequencies

    NARCIS (Netherlands)

    Tiggelman, M.P.J.; Reimann, K.; Liu, J.; Klee, M.; Keur, W.; Mauczock, R.; Schmitz, Jurriaan; Hueting, Raymond Josephus Engelbart

    2008-01-01

    A regression-based technique is presented which distinguishes the dielectric loss from the resistive loss of high density planar capacitors in a very wide bandwidth of 0.1–8 GHz. Moreover, the procedure yields useful results if the capacitor deviates from a lumped element model and indicates when

  16. Determination of rust resistance genes in pakistani bread wheats

    International Nuclear Information System (INIS)

    Qamar, M.; Ahmad, S.D.; Rabbani, M.A.; Shinwari, Z.K.

    2014-01-01

    Stripe and leaf rusts are the major constraints to bread wheat production in Pakistan. Molecular markers were used to investigate the presence of leaf rust and stripe rust resistance gene cluster Lr34/Yr18 and stem rust resistance gene Sr2 in 52 Pakistani bread wheat cultivars/lines. PCR amplification of DNA fragments using DNA marker csLV-34 showed that 13 of the studied cultivars/lines, namely 03FJ26, NR 337, NR 339, NR 347, NR 350, Manthar, Margalla 99, Iqbal 2000, Saleem 2000, Wafaq 2001, Marwat 2001, Pirsabak 2004 and Fareed 2006 carry leaf rust and stripe rust resistance genes Lr34/Yr18. Stem rust resistance gene Sr2 was observed in 36 Pakistani spring wheat cultivars/lines using stm560.3tgag marker. The slow rusting gene Sr2 needs to be combined with additional stem rust resistance genes to establish durable resistance against Ug99 in modern wheat cultivars. Low frequency of Lr34/Yr18 was found in Pakistani wheats. This gene cluster needs to be incorporated into Pakistani wheats for durable rust resistance. (author)

  17. Frequency, virulence genes and antimicrobial resistance of Listeria spp. isolated from bovine clinical mastitis.

    Science.gov (United States)

    Jamali, Hossein; Radmehr, Behrad

    2013-11-01

    The aims of this study were to determine the prevalence, characteristics and antimicrobial resistance of Listeria spp. isolated from bovine clinical mastitis in Iran. Listeria spp. were detected in 21/207 bovine mastitic milk samples from dairy farms in Iran, comprising L. monocytogenes (n=17), L. innocua (n=3) and L. ivanovii (n=1). L. monocytogenes isolates were grouped into serogroups '4b, 4d, 4e', '1/2a, 3a', '1/2b, 3b, 7' and '1/2c, 3c'; all harboured inlA, inlC and inlJ virulence genes. Listeria spp. were most frequently resistant to penicillin G (14/21 isolates, 66.7%) and tetracyclines (11/21 isolates, 52.4%). Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Treatment with Cefotaxime Affects Expression of Conjugation Associated Proteins and Conjugation Transfer Frequency of an IncI1 Plasmid in Escherichia coli

    DEFF Research Database (Denmark)

    Møller, Thea S B; Liu, Gang; Boysen, Anders

    2017-01-01

    research suggests that the effect of antibiotic treatment on plasmid conjugation frequencies, and hence the spread of resistance plasmids, may have been overestimated. We addressed the question by quantifying transfer proteins and conjugation frequencies of a blaCTX-M-1 encoding IncI1 resistance plasmid....... The frequency of plasmid conjugation, measured in an antibiotic free environment, increased significantly when the donor was pre-grown in broth containing CTX compared to growth without this drug, regardless of whether blaCTX-M-1 was located on the plasmid or in trans on the chromosome. The results shows...

  19. In vitro induction of variability through radiation for late blight resistance and heat tolerance in potato

    International Nuclear Information System (INIS)

    Gosal, S.S.; Das, A.; Gopal, J.; Minocha, J.L.; Chopra, H.R.; Dhaliwal, H.S.

    2001-01-01

    In vitro cultured shoots of potato, cvs. 'Kufri Jyoti' and 'Kufri Chandramukhi', were irradiated with 20 and 40 Gy gamma rays. Microtubers, obtained from MIV3 shoots multiplied in vitro, were planted in pots. The resulting plants were screened for resistance to late blight, using detached leaf method. In 'Kufri Chandramukhi', 42% plants and in 'Kufri Jyoti' 36% plants, obtained from 40 Gy treatment, showed resistance to late blight. The frequency of resistant plants was lower from 20 Gy treatment. The progenies of putatively resistant plants were grown in field, and inoculated with sporangial inoculum of late blight fungus. The field grown progeny segregated for disease resistance, and approximately 56% plants showed resistance. During the next propagation, the frequency of resistant plants increased to 72%. For developing heat tolerance, microtubers obtained from 20 and 40 Gy treatments and in vitro multiplied M 1 V 3 shoots were cultured at high temperature of 28C. In both varieties, the number of the microtubers per plant was highly reduced and the resulting microtubers had distorted shape but showed better germination (62%), even in early sowing at relatively higher temperature. Of the two radiation doses, the higher dose of 40 Gy gave better results in both the varieties. Heat tolerance was also assessed from chlorophyll persistence. The progenies from putative heat-tolerant plants were tested in field by planting at higher temperature in two subsequent generations. The heat tolerant plants segregated in each generation, but the frequency of heat-tolerant plants increased. (author)

  20. Accelerated high-frequency repetitive transcranial magnetic stimulation enhances motor activity in rats

    NARCIS (Netherlands)

    El Arfani, Anissa; Parthoens, Joke; Demuyser, Thomas; Servaes, Stijn; De Coninck, Mattias; De Deyn, Peter Paul; Van Dam, Debby; Wyckhuys, Tine; Baeken, Chris; Smolders, Ilse; Staelens, Steven

    2017-01-01

    High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) is currently accepted as an evidence-based treatment option for treatment-resistant depression (TRD). Additionally, HF-rTMS showed beneficial effects on psychomotor retardation in patients. The classical HF-rTMS paradigms however

  1. Forced harmonic oscillations of the Euler-Bernoulli beam with resistance forces

    Directory of Open Access Journals (Sweden)

    Yuriy S. Krutiy

    2015-12-01

    Full Text Available The important issue in the oscillation theory is the study of resistance impact on oscillatory processes. Unlike the calculations of free oscillations, that reside in determination of natural frequencies and waveshapes and unlike the calculations of forced oscillations far away from resonance, that are performing without reference to friction, the oscillations researches in vicinity of resonance need accounting of friction forces. Special attention is paid to forced transverse fluctuations in beams as an important technical problem for engineering and building. Aim: The aim of the work is constructing of analytical solution of the problem of forced transverse vibrations of a straight rod with constant cross-section, which is under the influence of the harmonic load taking into account external and internal resistances. Materials and Methods: The internal resistance is taken into account using the corrected hypothesis of Kelvin-Voigt which reflects the empirically proven fact about the frequency-independent internal friction in the material. The external friction is also considered as frequency-independent. Results: An analytical solution is built for the differential equation of forced transverse oscillations of a straight rod with constant cross-section which is under the influence of the harmonic load taking into account external and internal resistances. As a result, analytically derived formulae are presented which describe the forced dynamic oscillations and the dynamic internal forces due to the harmonic load applied to the rod thus reducing the problem with any possible fixed ends to the search of unknown integration constants represented in a form of initial parameters.

  2. High-frequency properties of superconducting Y-Ba-Cu-oxide thin films

    International Nuclear Information System (INIS)

    Ramakrishnan, E.S.; Su, M.; Howng, W.

    1992-01-01

    rf and microwave properties of superconducting YBa 2 Cu 3 O 7-x thin films were measured and analyzed using a coplanar resonator structure. The films were developed by sequential electron-beam evaporation of the metals followed by postanneal processing. dc properties of the films were obtained from resistance-temperature and current-voltage measurements to evaluate the transition temperature and current densities. High-frequency properties were measured from 70 to 10 K and in the frequency range 1--3 GHz to determine the film characteristics as compared to pure copper films on the same substrates

  3. Fast-food habits, weight gain, and insulin resistance (the CARDIA study): 15-year prospective analysis.

    Science.gov (United States)

    Pereira, Mark A; Kartashov, Alex I; Ebbeling, Cara B; Van Horn, Linda; Slattery, Martha L; Jacobs, David R; Ludwig, David S

    Fast-food consumption has increased greatly in the USA during the past three decades. However, the effect of fast food on risk of obesity and type 2 diabetes has received little attention. We aimed to investigate the association between reported fast-food habits and changes in bodyweight and insulin resistance over a 15-year period in the USA. Participants for the CARDIA study included 3031 young (age 18-30 years in 1985-86) black and white adults who were followed up with repeated dietary assessment. We used multiple linear regression models to investigate the association of frequency of fast-food restaurant visits (fast-food frequency) at baseline and follow-up with 15-year changes in bodyweight and the homoeostasis model (HOMA) for insulin resistance. Fast-food frequency was lowest for white women (about 1.3 times per week) compared with the other ethnic-sex groups (about twice a week). After adjustment for lifestyle factors, baseline fast-food frequency was directly associated with changes in bodyweight in both black (p=0.0050) and white people (p=0.0013). Change in fast-food frequency over 15 years was directly associated with changes in bodyweight in white individuals (pfast-food restaurant use at baseline and follow-up (n=203), those with frequent (more than twice a week) visits to fast-food restaurants at baseline and follow-up (n=87) gained an extra 4.5 kg of bodyweight (p=0.0054) and had a two-fold greater increase in insulin resistance (p=0.0083). Fast-food consumption has strong positive associations with weight gain and insulin resistance, suggesting that fast food increases the risk of obesity and type 2 diabetes.

  4. Antibiotic Resistance and Carriage Integron Classes in Clinical Isolates of Acinetobacter Baumannii from Isfahan Hospitals, Iran

    Directory of Open Access Journals (Sweden)

    Fahimeh Nourbakhsh

    2017-01-01

    Full Text Available Background Acinetobacter baumannii is a significant nosocomial pathogen around the world, especially in the intensive care unit that most A. baumannii infections are caused by the outbreak strains. Objectives This study has been performed in Acinetobacter baumannii isolates, aimed to detect integron classes I, II, III and molecular typing of A. baumannii genes. Methods In this Cross-sectional study, Acinetobacter baumannii isolated from 150 patients in Isfahan hospitals then antibiotic resistance pattern was determined by disk diffusion method (Kirby Bauer. The presence of genes coding in antibiotic resistance and integrons class I, II, III were analyzed by using of M-PCR method. The data were analyzed by Chi-square, Fischer’s test and SPSS statistical software version 16. Results Antibiotic resistance pattern for Acinetobacter baumannii show that the high resistance was for ciprofloxacin with frequency of 98.3%, ceftazidime with 89.4%, and tetracycline with frequency of 87.3%. The most sensitive antibiotics were chloramphenicol, and nitrofurantoin with frequency of 3.5% and 3.2% resistance. The detection of dfrA1 (63.7%, sul1 (68.6%, aac (3-IV (54.4%, tet (B (22.4%, tet (A (78.3%, aadA1 (15.4%, CITM (17. %, vim (12.2%, Qnr (17.1%, blaSHV (19.8%, sim (7.8%, Oxa-24-like (13.2%, Oxa-51-like (11.9%, Oxa-58-like (39.4%, Oxa-23-like (12.6%, imp (9.2%, cmlA (19% and cat1 (8.6% were respectively reported too. Also in this study Frequency of integrons class 1, 2, 3 were (100%, (28%, (6.6% respectively. Conclusions High prevalence of integrons among Acinetobater baumannii isolated from Isfahan hospitals indicate the importance role of integron classes in multidrug resistance. Considering the increasing pattern of MDR infections is one of the important issues of treatment which can be effective strategy for curing.

  5. Use of a Fabry-Perot resonator at millimeter wave frequencies in the determination of thin-film resistivities

    Energy Technology Data Exchange (ETDEWEB)

    Hogan, S. J.

    1979-08-01

    A novel contact-free method of measuring resistivity of thin semiconducting films on highly conductive substrates is described. The material structure studied is commonly encountered in thin-film solar cell development. The microwave technique that involves using a semiconfocal Fabry-Perot cavity at a wavelength of 3 mm is discussed in detail. The sample consists o a thin film of CdS on a brass substrate and is mounted on the flat reflector of the cavity. Using field perturbation methods, an expression is derived that relates the film resistivity to the cavity quality factor Q. The cavity quality factor is an easily measured parameter and, by comparing measurements of Q with and without the sample mounted, an accurate measure of the resistivity is obtained. Accuracy of measurements and necessary sample constraints are discussed in detail. Three samples of CdS were measured on brass substrates spanning an order of magnitude in resistivity difference. The results of the method described agree with those of another method that involves current voltage measurement after application of a metallic contact. Unlike the latter method, however, the new technique provides a nondestructive way of measuring the resistivity of semiconductor films on conducting substrates and is amenable to automation.

  6. Geographic Variation in Phosphine Resistance Among North American Populations of the Red Flour Beetle (Coleoptera: Tenebrionidae).

    Science.gov (United States)

    Cato, A J; Elliott, Brent; Nayak, Manoj K; Phillips, Thomas W

    2017-06-01

    The red flour beetle, Tribolium castaneum (Herbst), is a common stored-product pest found worldwide. Phosphine, hydrogen phosphide (PH3), is the most commonly used fumigant for stored grains, for which genetically based resistance has been recorded for several pest species. This study assessed phosphine resistance in 25 T. castaneum populations from across the United States and Canada using a discriminating dose bioassay. Dose-mortality assays were conducted with adults from seven of these populations to categorize weak and strong resistance phenotypes. Phosphine resistance was detected in 12 out of the 25 populations, and the frequency of resistance within populations varied from 2% in Victoria, TX, to 100% in Red Level, AL. Two resistant populations from Kansas that had been sampled three years earlier were found to have similar resistance frequencies in the current study. None of the four Canadian populations had any detectable resistance among the insects tested. Resistance ratio calculations from LC50 value in resistant populations relative to the LC50 for the laboratory susceptible strain allowed resistance phenotypes to be assigned as either weak resistance, at 5- to 26-fold resistance relative to susceptible, or strong resistance at 95- to 127-fold relative to susceptible. This study suggests that proper resistance assessment techniques can help to determine occurrence of phosphine resistance in populations of T. castaneum and can further characterize the strength of resistance present. These data can be used to support resistance management programs that consider either cessation or modification of phosphine fumigation to control T. castaneum. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Resistance to K. pneumoniae in young children with congenital heart defects

    Directory of Open Access Journals (Sweden)

    V. N. Ilina

    2015-10-01

    Full Text Available Klebsiella pneumoniae is one of the leading agents of nosocomial infections (NI. In Russia, Klebsiella pneumoniae is the third in frequency of gram-negative pathogen NI. For a long time one of the major clinically relevant mechanisms of acquired resistance to K. pneumoniae is multidrug resistance caused by extended spectrum -lactamase production (ESBL. Carbapenems show the greatest resistance to the action of ESB. However, now there exist registered strains of K.pneumoniae resistant to carbapenems. In connection with this in 2008 we conducted a prospective study on resistance to K. pneumoniae in young children being treated at ICU. It was found out that resistance to III-IV-generation cephalosporines, fluoroquinolones, aminoglycosides is determined by production of ESBL, while resistance to carbapenems occurs due to reduction of permeability of cell membranes, in combination with production of ESBL. Some features of patients colonized with multidrug-resistant strains of K. pneumoniae are described.

  8. Simultaneous inversion of airborne electromagnetic data for resistivity and magnetic permeability

    International Nuclear Information System (INIS)

    Beard, L.P.; Nyquist, J.E.

    1998-01-01

    Where the magnetic permeability of rock or soil exceeds that of free space, the effect on airborne electromagnetic systems is to produce a frequency-independent shift in the in-phase response of the system while altering the quadrature response only slightly. The magnitude of the in-phase shift increases as (1) the relative magnetic permeability is increased, (2) the amount of magnetic material is increased, and (3) the airborne sensor gets nearer the earth's surface. Over resistive, magnetic ground, the shift may be evinced by negative in-phase measurements at low frequencies; but over more conductive ground, the same shift may go unnoticed because of the large positive in-phase response. If the airborne sensor is flown at low levels, the magnitude of the shift may be large enough to affect automatic inversion routines that do not take this shift into account, producing inaccurate estimated resistivities, usually overestimates. However, layered-earth inversion algorithms that incorporate magnetic permeability as an additional inversion parameter may improve the resistivity estimates. The authors demonstrate this improvement using data collected over hazardous waste sites near Oak Ridge, Tennessee, USA. Using resistivity inversion without magnetic permeability, the waste sites are almost invisible to the sensors. When magnetic permeability is included as an inversion parameter, the sites are detected, both by improved resistivity estimates and by estimated magnetic permeability

  9. Resistive effects in EXTRAP

    International Nuclear Information System (INIS)

    Tendler, M.

    1985-10-01

    Theoretical studies of the resistive equilibrium and stability of an EXTRAP z-pinch are reported. Extending the previous analysis we reassess properties of the resistive equilibrium in EXTRAP with the emphasis on the time dependence of the latter. We also qualitatively consider the role of resistive instabilities in EXTRAP, showing that the typical timescale of the filamentation of the discharge (i.e. the non-linear development of the tearing instability) is comparable at present, to the discharge duration. On the other hand, we emphasize that this phenomenon may still be consistent with the experimental observation of the Bennet's equilibrium. The processes of the current start-up and ramp up are also analysed for EXTRAP and it is shown that the peculiarities if these processes in EXTRAP may lead to the compression oscillations around and evolving rather stable equilibrium. The frequency of these oscillations is given. Finally, some consequences of the average minimum-B concept for EXTRAP are discussed and it is shown that this issue virtually reduces to the appearance of the negative curvature of the magnetic field at the periphery. The maximum attainable value of β at the periphery of the pinch is obtained, as required by the ballooning stability criterion. The influence of the finite resistivity on the ballooning mode is also estimated. With 4 figures and 21 refs. (Author)

  10. Frequency of Cry1F Non-Recessive Resistance Alleles in North Carolina Field Populations of Spodoptera frugiperda (Lepidoptera: Noctuidae).

    Science.gov (United States)

    Li, Guoping; Reisig, Dominic; Miao, Jin; Gould, Fred; Huang, Fangneng; Feng, Hongqiang

    2016-01-01

    Fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a target species of transgenic corn (Zea mays L.) that expresses single and pyramided Bacillus thuringiensis (Bt) toxin. In 2014, S. frugiperda were collected from a light trap in North Carolina, and a total of 212 F1/F2 isofemale lines of S. frugiperda were screened for resistance to Bt and non-Bt corn. All of the 212 isolines were susceptible to corn tissue expressing Cry1A.105 + Cry2Ab, Cry1F + Cry1A.105 + Cry2Ab, and Cry1F + Cry1Ab + Vip3Aa20. Growth rate bioassays were performed to isolate non-recessive Bt resistance alleles. Seven individuals out of the 212 isofemale lines carried major non-recessive alleles conferring resistance to Cry1F. A pooled colony was created from the seven individuals. This colony was 151.21 times more resistant to Cry1F than a known-susceptible population and was also resistant to Cry1A.105, but was not resistant to Cry2Ab and Vip3Aa20. The results demonstrate that field populations of S. frugiperda collected from North Carolina are generally susceptible to Cry1F, but that some individuals carry resistant alleles. The data generated in this study can be used as baseline data for resistance monitoring.

  11. Excitation block in a nerve fibre model owing to potassium-dependent changes in myelin resistance

    DEFF Research Database (Denmark)

    Brazhe, Alexey; Maksimov, G. V.; Mosekilde, Erik

    2011-01-01

    . Uptake of potassium leads to Schwann cell swelling and myelin restructuring that impacts the electrical properties of the myelin. In order to further understand the dynamic interaction that takes place between the myelin and the axon, we have modelled submyelin potassium accumulation and related changes...... in myelin resistance during prolonged high-frequency stimulation. We predict that potassium-mediated decrease in myelin resistance leads to a functional excitation block with various patterns of altered spike trains. The patterns are found to depend on stimulation frequency and amplitude and to range from...

  12. Effect of vibration frequency on microstructure and performance of high chromium cast iron prepared by lost foam casting

    Directory of Open Access Journals (Sweden)

    Wen-qi Zou

    2016-07-01

    Full Text Available In the present research, high chromium cast irons (HCCIs were prepared using the lost foam casting (LFC process. To improve the wear resistance of the high chromium cast irons (HCCIs, mechanical vibration was employed during the solidification of the HCCIs. The effects of vibration frequency on the microstructure and performance of the HCCIs under as-cast, as-quenched and as-tempered conditions were investigated. The results indicated that the microstructures of the LFC-produced HCCIs were refined due to the introduction of mechanical vibration, and the hardness was improved compared to that of the alloy without vibration. However, only a slight improvement in hardness was found in spite of the increase of vibration frequency. In contrast, the impact toughness of the as-tempered HCCIs increased with an increase in the vibration frequency. In addition, the wear resistance of the HCCIs was improved as a result of the introduction of vibration and increased with an increase in the vibration frequency.

  13. Cardiac autonomic regulation in response to a mixed meal is impaired in obese children and adolescents: the role played by insulin resistance.

    Science.gov (United States)

    Cozzolino, Domenico; Esposito, Katherine; Palmiero, Giuseppe; De Bellis, Annamaria; Furlan, Raffaello; Perrotta, Silverio; Perrone, Laura; Torella, Daniele; Miraglia del Giudice, Emanuele

    2014-09-01

    Obesity in children/adolescents has been associated with subtle cardiac abnormalities, including myocardial dysfunction and cardiac autonomic dysregulation at rest, both likely responsible for a higher mortality in adulthood. Food intake induces remarkable adjustments of cardiovascular autonomic activity in healthy subjects. The objective of the study was to evaluate in obese children/adolescents meal-induced cardiac autonomic response and the role played by insulin resistance. Sixty-eight obese and 30 matched normal-weight children/adolescents underwent blood sampling and cardiovascular autonomic analysis while recumbent and 20 minutes after a mixed meal ingestion. Spectrum analysis of the R-R interval and systolic blood pressure (SBP) variability provided the indices of sympathetic [low frequency (LFRR)] and vagal [high frequency (HFRR)] modulation of the sinoatrial node and the low frequency component of SBP. The homeostasis model assessment of insulin resistance served to separate insulin resistant (n = 35) from non insulin resistant (n = 33) obese children/adolescents. At baseline, C-reactive protein, the LFRR to HFRR ratio, SBP, and low frequency oscillatory component of SBP variability in obese children/adolescents were significantly (P meal-induced increase in the LFRR to HFRR ratio was significantly less than in controls and exaggeratedly scanty (or opposite) among insulin resistant subjects. The homeostasis model assessment of insulin resistance index strongly and inversely correlated (r = -0.871; P meal-induced changes in the LFRR to HFRR ratio among obese subjects. Autonomic modulation of the heart was impaired after eating in obese children/adolescents. This abnormality was exaggerated among insulin resistant subjects and strongly correlated with the degree of insulin resistance.

  14. [Efficacy of permethrin-impregnated Olyset Net mosquito nets in a zone with pyrethroid resistant vectors. I--Entomologic evaluation].

    Science.gov (United States)

    Doannio, J M; Dossou-Yovo, J; Diarrassouba, S; Chauvancy, G; Darriet, F; Chandre, F; Henry, M C; Nzeyimana, I; Guillet, P; Carnevale, P

    1999-01-01

    The efficacy of permethrin-treated Olyset Net mosquito nets on malaria transmission and morbidity was studied in Kafine, a village located in the savanna region of the Cote d'Ivoire in Africa. After collecting sociodemographic, entomological, and parasitological data, bednets were distributed first in the southern half of the village and then in the whole village. Throughout the study period, mosquito specimens were captured on the skin of inhabitants at four points in the village between 6 PM and 6 AM both inside (but outside bednets) and outside houses. Prior to distribution of bednets, the mean biting rate (MBR) by Anopheles gambiae was 77.4 bites per man per night (b/m/n). The mean parturity rate (MPR) was 40.6 p. 100, the sporozootic index (SI) was 0.99 p. 100, and the mean entomological inoculation rate (MEIR) was 0.7 infectious bites per man per night (b+/m/n). Six months after distribution of bednets in the southern half of the village, MBR was 80.2 b/m/n, MPR was 32 p. 100, SI was 1.8 p. 100, and MEIR was 0.83 b+/m/n. After extending distribution to the whole village, data from November 1996 to July 1997 were as follows: MBR, 67.8 b/m/n; MPR, 20.1 p. 100; SI, 0.65 p. 100; and MEIR, 0.66 p. 100. From August 1977 to July 1998, data were as follows: MBR, 102.6 b/m/n; MPR, 26.2 p. 100; SI, 1.15 p. 100; and MEIR, 0.74 b+/m/n. Comparative analysis of these data showed that use of bednets had no effect on the bite or entomological inoculation rate. This is in agreement with the documented resistance of vectors in the study zone to permethrin. Despite the known stimulation/repulsion effect of permethrin, use of treated bednets had no real impact on transmission. This inefficacy could be related to the high prevalence (80 p. 100) of the Kdr gene (responsible for resistance) in the savanna form of Anopheles gambiae.

  15. Single and multi-frequency impedance characterization of symmetric activated carbon single capacitor cells

    Directory of Open Access Journals (Sweden)

    Suzana Sopčić

    2018-05-01

    Full Text Available Electrochemical impedance spectroscopy (EIS technique is used for characterization of single cell symmetric capacitors having different mass loadings of activated carbon (AC. Relevant values of charge storage capacitance (CT and internal resistance (ESR were evaluated by the single frequency and multi-frequency analyses of measured impedance spectra. Curve fittings were based on the non-ideal R-C model that takes into account the parasitic inductance, contributions from electrode materials/contacts and the effects of AC porosity. Higher CT and lower ESR values were obtained not only for the cell with higher mass of AC, but also using the single vs. multi-frequency approach. Lower CT and higher values of ESR that are generally obtained using the multi-frequency method and curve fittings should be related to the not ideal capacitive response of porous AC material and too high frequency chosen in applying the single frequency analysis.

  16. The analysis of cable forces based on natural frequency

    Science.gov (United States)

    Suangga, Made; Hidayat, Irpan; Juliastuti; Bontan, Darwin Julius

    2017-12-01

    A cable is a flexible structural member that is effective at resisting tensile forces. Cables are used in a variety of structures that employ their unique characteristics to create efficient design tension members. The condition of the cable forces in the cable supported structure is an important indication of judging whether the structure is in good condition. Several methods have been developed to measure on site cable forces. Vibration technique using correlation between natural frequency and cable forces is a simple method to determine in situ cable forces, however the method need accurate information on the boundary condition, cable mass, and cable length. The natural frequency of the cable is determined using FFT (Fast Fourier Transform) Technique to the acceleration record of the cable. Based on the natural frequency obtained, the cable forces then can be determine by analytical or by finite element program. This research is focus on the vibration techniques to determine the cable forces, to understand the physical parameter effect of the cable and also modelling techniques to the natural frequency and cable forces.

  17. Genetic determinants of heat resistance in Escherichia coli

    Directory of Open Access Journals (Sweden)

    Ryan eMercer

    2015-09-01

    Full Text Available Escherichia coli AW1.7 is a heat resistant food isolate and the occurrence of pathogenic strains with comparable heat resistance may pose a risk to food safety. To identify the genetic determinants of heat resistance, 29 strains of E. coli that differed in their of heat resistance were analyzed by comparative genomics. Strains were classified as highly heat resistant strains, exhibiting a D60-value of more than 6 min; moderately heat resistant strains, exhibiting a D60-value of more than 1 min; or as heat sensitive. A ~14 kb genomic island containing 16 predicted open reading frames encoding putative heat shock proteins and proteases was identified only in highly heat resistant strains. The genomic island was termed the locus of heat resistance (LHR. This putative operon is flanked by mobile elements and possesses >99% sequence identity to genomic islands contributing to heat resistance in Cronobacter sakazakii and Klebsiella pneumoniae. An additional 41 LHR sequences with >87% sequence identity were identified in 11 different species of β- and γ-proteobacteria. Cloning of the full length LHR conferred high heat resistance to the heat sensitive E. coli AW1.7ΔpHR1 and DH5α. The presence of the LHR correlates perfectly to heat resistance in several species of Enterobacteriaceae and occurs at a frequency of 2% of all E. coli genomes, including pathogenic strains. This study suggests the LHR has been laterally exchanged among the β- and γ-proteobacteria and is a reliable indicator of high heat resistance in E. coli.

  18. Comparison of Periodized and Non-Periodized Resistance Training on Maximal Strength: A Meta-Analysis.

    Science.gov (United States)

    Williams, Tyler D; Tolusso, Danilo V; Fedewa, Michael V; Esco, Michael R

    2017-10-01

    Periodization is a logical method of organizing training into sequential phases and cyclical time periods in order to increase the potential for achieving specific performance goals while minimizing the potential for overtraining. Periodized resistance training plans are proposed to be superior to non-periodized training plans for enhancing maximal strength. The primary aim of this study was to examine the previous literature comparing periodized resistance training plans to non-periodized resistance training plans and determine a quantitative estimate of effect on maximal strength. All studies included in the meta-analysis met the following inclusion criteria: (1) peer-reviewed publication; (2) published in English; (3) comparison of a periodized resistance training group to a non-periodized resistance training group; (4) maximal strength measured by 1-repetition maximum (1RM) squat, bench press, or leg press. Data were extracted and independently coded by two authors. Random-effects models were used to aggregate a mean effect size (ES), 95% confidence intervals (CIs) and potential moderators. The cumulative results of 81 effects gathered from 18 studies published between 1988 and 2015 indicated that the magnitude of improvement in 1RM following periodized resistance training was greater than non-periodized resistance training (ES = 0.43, 95% CI 0.27-0.58; P training status (β = -0.59; P = 0.0305), study length (β = 0.03; P = 0.0067), and training frequency (β = 0.46; P = 0.0123) were associated with a change in 1RM. These results indicate that undulating programs were more favorable for strength gains. Improvements in 1RM were greater among untrained participants. Additionally, higher training frequency and longer study length were associated with larger improvements in 1RM. These results suggest that periodized resistance training plans have a moderate effect on 1RM compared to non-periodized training plans. Variation in training stimuli

  19. Characterisation of ALS genes in the polyploid species Schoenoplectus mucronatus and implications for resistance management.

    Science.gov (United States)

    Scarabel, Laura; Locascio, Antonella; Furini, Antonella; Sattin, Maurizio; Varotto, Serena

    2010-03-01

    The polyploid weed Schoenoplectus mucronatus (L.) Palla has evolved target-site resistance to ALS-inhibiting herbicides in Italian rice crops. Molecular and genetic characterisation of the resistance mechanism is relevant to the evolution and management of herbicide resistance. The authors aimed (a) to study the organisation of the target-site loci in two field-selected S. mucronatus populations with different cross-resistance patterns, (b) to identify the mutations endowing resistance to ALS inhibitors and determine the role of these mutations by using transgenesis and (c) to analyse the implications for the management of the S. mucronatus populations. Two complete ALS genes (ALS1 and ALS2) having an intron and a third partial intronless ALS gene (ALS3) were identified. The presence of multiple ALS genes was confirmed by Southern blot analyses, and ALS loci were characterised by examining cytosine methylation. In S. mucronatus leaves, the transcripts of ALS1, ALS2 and ALS3 were detected. Two mutations endowing resistance (Pro(197) to His and Trp(574) to Leu) were found in both resistant populations, but at different frequencies. Tobacco plants transformed with the two resistant alleles indicated that the Pro(197)-to-His substitution conferred resistance to SU and TP herbicides, while the allele with the Trp(574)-to-Leu substitution conferred cross-resistance to SU, TP, IMI and PTB herbicides. Schoenoplectus mucronatus has multiple ALS genes characterised by methylated sites that can influence the expression profile. The two mutated alleles proved to be responsible for ALS resistance. At population level, the resistance pattern depends on the frequency of various resistant genotypes, and this influences the efficacy of various ALS-inhibiting herbicides.

  20. Presence of Methicillin Resistant Staphylococcus aureus (MRSA) in sewage treatment plant.

    Science.gov (United States)

    Boopathy, Raj

    2017-09-01

    The presence of antibiotic resistant bacteria and antibiotic resistance genes in rural sewage treatment plants are not well reported in the literature. The aim of the present study was to study the frequency occurrence of Methicillin Resistant Staphylococcus aureus (MRSA) in a rural sewage treatment plant. This study was conducted using raw sewage as well as treated sewage from a small town sewage treatment plant in rural southeast Louisiana of USA. Results showed the presence of MRSA consistently in both raw and treated sewage. The presence of mecA gene responsible for methicillin resistance was confirmed in the raw and treated sewage water samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Molecular Genetics of Drug-resistance in Epilepsies

    Directory of Open Access Journals (Sweden)

    Kurupath Radhakrishnan

    2015-06-01

    Full Text Available Nearly one-third of newly diagnosed patients with epilepsy remain unresponsive to antiepileptic drugs (AEDs, etiopathogenesis of which is poorly understood. The genes encoding the proteins that regulate the pharmacokinetics such as P-glycoprotein [ABCBI], major vault protein [MVP gene] and drug metabolizing enzymes [ABCB1, ABCG2, MVP, CYP2C9, CYP2C19, CYP3A4, CYP3A5, EPHX1, UGT1A1, UGT2B7], and pharmacodynamics such as sodium channels [SCN1A, SCN2A] and GABA receptors [GABRA1, GABRA6, GABRB2, GABRG2] of AEDs are under intense investigation to unravel the mysteries of AED-resistance. However, till today, a consistent and reliable result that could help the clinician either to predict drug resistance or to overcome it has not been forthcoming. The discrepant results may be related to variations in the definition of drug-resistance, heterogeneous patient populations, ethnic variations in the frequency distribution of single nucleotide polymorphisms (SNPs and the selection of SNPs. Understanding of these limitations of existing studies, hopefully, will help in designing better studies. Nearly one-third of newly diagnosed patients with epilepsy remain unresponsive toantiepileptic drugs (AEDs, etiopathogenesis of which is poorly understood. The genesencoding the proteins that regulate the pharmacokinetics such as P-glycoprotein[ABCBI], major vault protein [MVP gene] and drug metabolizing enzymes [ABCB1,ABCG2, MVP, CYP2C9, CYP2C19, CYP3A4, CYP3A5, EPHX1, UGT1A1, UGT2B7],and pharmacodynamics such as sodium channels [SCN1A, SCN2A] and GABAreceptors [GABRA1, GABRA6, GABRB2, GABRG2] of AEDs are under intenseinvestigation to unravel the mysteries of AED-resistance. However, till today, aconsistent and reliable result that could help the clinician either to predict drugresistanceor to overcome it has not been forthcoming. The discrepant results may berelated to variations in the definition of drug-resistance, heterogeneous patientpopulations, ethnic

  2. Experimental diagnostics and modeling of inductive phenomena at low frequencies in impedance spectra of proton exchange membrane fuel cells

    Science.gov (United States)

    Pivac, Ivan; Šimić, Boris; Barbir, Frano

    2017-10-01

    Representation of fuel cell processes by equivalent circuit models, involving resistance and capacitance elements representing activation losses on both anode and cathode in series with resistance representing ohmic losses, cannot capture and explain the inductive loop that may show up at low frequencies in Nyquist diagram representation of the electrochemical impedance spectra. In an attempt to explain the cause of the low-frequency inductive loop and correlate it with the processes within the fuel cell electrodes, a novel equivalent circuit model of a Proton Exchange Membrane (PEM) fuel cell has been proposed and experimentally verified here in detail. The model takes into account both the anode and the cathode, and has an additional resonant loop on each side, comprising of a resistance, capacitance and inductance in parallel representing the processes within the catalyst layer. Using these additional circuit elements, more accurate and better fits to experimental impedance data in the wide frequency range at different current densities, cell temperatures, humidity of gases, air flow stoichiometries and backpressures were obtained.

  3. Antimicrobial Resistance of Faecal Escherichia coli Isolates from Pig Farms with Different Durations of In-feed Antimicrobial Use.

    Science.gov (United States)

    Gibbons, J F; Boland, F; Egan, J; Fanning, S; Markey, B K; Leonard, F C

    2016-05-01

    Antimicrobial use and resistance in animal and food production are of concern to public health. The primary aims of this study were to determine the frequency of resistance to 12 antimicrobials in Escherichia coli isolates from 39 pig farms and to identify patterns of antimicrobial use on these farms. Further aims were to determine whether a categorization of farms based on the duration of in-feed antimicrobial use (long-term versus short-term) could predict the occurrence of resistance on these farms and to identify the usage of specific antimicrobial drugs associated with the occurrence of resistance. Escherichia coli were isolated from all production stages on these farms; susceptibility testing was carried out against a panel of antimicrobials. Antimicrobial prescribing data were collected, and farms were categorized as long term or short term based on these. Resistance frequencies and antimicrobial use were tabulated. Logistic regression models of resistance to each antimicrobial were constructed with stage of production, duration of antimicrobial use and the use of 5 antimicrobial classes included as explanatory variables in each model. The greatest frequencies of resistance were observed to tetracycline, trimethoprim/sulphamethoxazole and streptomycin with the highest levels of resistance observed in isolates from first-stage weaned pigs. Differences in the types of antimicrobial drugs used were noted between long-term and short-term use farms. Categorization of farms as long- or short-term use was sufficient to predict the likely occurrence of resistance to 3 antimicrobial classes and could provide an aid in the control of resistance in the food chain. Stage of production was a significant predictor variable in all models of resistance constructed and did not solely reflect antimicrobial use at each stage. Cross-selection and co-selection for resistance was evident in the models constructed, and the use of trimethoprim/sulphonamide drugs in particular was

  4. Comparison of the frequency response characteristics of catheter-mounted piezoelectric and micromanometric phonotransducers.

    Science.gov (United States)

    Garcia, J C; Layton, S A; Rubal, B J

    1989-05-01

    This study compares the frequency response characteristics of catheter-mounted piezoelectric sound transducers with micromanometric transducers. The tip of a 8F catheter with two piezoelectric transducers and two micromanometers was inserted into a water-filled chamber that had a speaker fixed at one end. The speaker was driven by a power amplifier and sine wave generator. The outputs of the transducers were connected to a low-level amplifier. The piezoelectric transducer behaved as a tunable high-pass filter that could be modified by altering the input impedance of the low level amplifier; the frequency response characteristics were examined at five input impedances ranging from 0.96 to 11.8 megohms. The peak-to-peak outputs of the piezoelectric and pressure transducers were recorded at frequency ranges from DC to 1 kHz with a wide-band oscilloscope. The ratio of the outputs from the piezotransducer and micromanometer (Vph/Vpr) was plotted vs. frequency for each input impedance and analyzed to determine the piezotransducer's output resistance and equivalent capacitance; roll-off frequencies were then calculated. The equivalent capacitance of the piezo-element was determined to be 500-700 picofarads. Series capacitance acted with network resistance to produce a predictable frequency-dependent change in signal amplitude and phase angle. The inherent noise of the pressure transducer was found to be approximately 0.2 mm Hg, while the noise of the piezoelectric transducer was immeasurably low. The piezoelectric phonotransducers were superior to micromanometer transducers in their higher gain and lower noise, suggesting that these transducers may prove useful to physiologic and clinical studies for measuring intravascular sound.

  5. Wireless Damage Monitoring of Laminated CFRP Composites using Electrical Resistance Change

    National Research Council Canada - National Science Library

    Todoroki, Akira

    2007-01-01

    .... In this system, a tiny oscillation circuit is attached to the composite component. When delimitation of the component occurs, electrical resistance changes, which causes a change in the oscillating frequency of the circuit...

  6. Transmission of methicillin-resistant Staphylococcus aureus to household contacts

    NARCIS (Netherlands)

    F.P.N. Mollema (Femke); J.H. Richardus (Jan Hendrik); M.D. Behrendt (Myra); N. Vaessen (Norbert); W. Lodder; W. Hendriks; H.A. Verbrugh (Henri); A. Voss (Andreas)

    2010-01-01

    textabstractThe frequency of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) transmission from a MRSA index person to household contacts were assessed in this prospective study. Between January 2005 and December 2007, 62 newly diagnosed MRSA index persons (46 patients and 16

  7. From TER to trans- and paracellular resistance: lessons from impedance spectroscopy.

    Science.gov (United States)

    Günzel, Dorothee; Zakrzewski, Silke S; Schmid, Thomas; Pangalos, Maria; Wiedenhoeft, John; Blasse, Corinna; Ozboda, Christopher; Krug, Susanne M

    2012-06-01

    In epithelia and endothelia, overall resistance (TER) is determined by all ion-conductive structures, such as membrane channels, tight junctions, and the intercellular space, whereas the epithelial capacitance is due to the hydrophobic phase of the plasma membrane. Impedance means alternating current resistance and, in contrast to ohmic resistance, takes into account that, e.g., capacitors become increasingly conductive with increasing frequency. Impedance spectroscopy uses the association of the capacitance with the transcellular pathway to distinguish between this capacitive pathway and purely conductive components (tight junctions, subepithelium). In detail, one-path impedance spectroscopy distinguishes the resistance of the epithelium from the resistance of subepithelial tissues. Beyond that, two-path impedance spectroscopy allows for the separation of paracellular resistance (governed by tight junctional properties) from transcellular resistance (determined by conductive structures residing in the cell membranes). The present paper reviews the basic principles of these techniques, some historic milestones, as well as recent developments in epithelial physiology. © 2012 New York Academy of Sciences.

  8. Measurements of Low Frequency Noise of Infrared Photo-Detectors with Transimpedance Detection System

    Directory of Open Access Journals (Sweden)

    Ciura Łukasz

    2014-08-01

    Full Text Available The paper presents the method and results of low-frequency noise measurements of modern mid-wavelength infrared photodetectors. A type-II InAs/GaSb superlattice based detector with nBn barrier architecture is compared with a high operating temperature (HOT heterojunction HgCdTe detector. All experiments were made in the range 1 Hz - 10 kHz at various temperatures by using a transimpedance detection system, which is examined in detail. The power spectral density of the nBn’s dark current noise includes Lorentzians with different time constants while the HgCdTe photodiode has more uniform 1/f - shaped spectra. For small bias, the low-frequency noise power spectra of both devices were found to scale linearly with bias voltage squared and were connected with the fluctuations of the leakage resistance. Leakage resistance noise defines the lower noise limit of a photodetector. Other dark current components give raise to the increase of low-frequency noise above this limit. For the same voltage biasing devices, the absolute noise power densities at 1 Hz in nBn are 1 to 2 orders of magnitude lower than in a MCT HgCdTe detector. In spite of this, low-frequency performance of the HgCdTe detector at ~ 230K is still better than that of InAs/GaSb superlattice nBn detector.

  9. United States Air Force Statistical Digest, Fiscal Year 1976 and Transition Quarter (TQ). 31st Edition

    Science.gov (United States)

    1977-04-30

    JMM JMP JPB JlO J11 KBD KBK KCF KCG KCK KCM KCQ KDB KDC KDF KDM KDQ KDR KEA KEB KEC KFB KFC KFS KFU KGL KGM KGN KGX KHD KND LBM LED MBK ITEM DESCRIPTION...KDF KD1’! KDQ KDR KEA KEB KEC KFC KFS KFU KGL KGM KGN KGX KHO KND LBI’ LED MBK MBN 1’!CE MCF MOB MEA MEB MEC MGX MND RBC RED SFJ SFK YFB 474 475 490

  10. Antimicrobial Resistance and Resistance Genes in Aerobic Bacteria Isolated from Pork at Slaughter.

    Science.gov (United States)

    Li, Lili; Heidemann Olsen, Rikke; Ye, Lei; Yan, He; Nie, Qing; Meng, Hecheng; Shi, Lei

    2016-04-01

    The aim of this study was to investigate the phenotypic and genotypic antimicrobial resistance, integrons, and transferability of resistance markers in 243 aerobic bacteria recovered from pork at slaughter in the People's Republic of China. The organisms belonged to 22 genera of gram-negative bacteria (92.2%) and gram-positive bacteria (7.8%). High levels of resistance were detected to tetracycline, trimethoprim-sulfamethoxazole, and ampicillin (36.2 to 54.3%), and lower levels were detected to nitrofurantoin, cefotaxime, gentamicin, ciprofloxacin, and chloramphenicol (7.8 to 29.2%). Across species, genes conferring antimicrobial resistance were observed with the following frequencies: blaTEM, 40.7%; blaCMY-2, 15.2%; blaCTX-M, 11.5%; sul2, 27.2%; sul1, 14.4%; tet(A), 5.4%; tet(L), 5.4%; tet(M), 5.0%; tet(E), 3.7%; tet(C), 3.3%; tet(S), 2.5%; and tet(K), 0.8%. Various antimicrobial resistance genes were found in new carriers: blaTEM in Lactococcus garvieae, Myroides odoratimimus, Aeromonas hydrophila, Staphylococcus sciuri, Raoultella terrigena, Macrococcus caseolyticus, Acinetobacter ursingii, Sphingobacterium sp., and Oceanobacillus sp.; blaCMY-2 in Lactococcus lactis, Klebsiella oxytoca, Serratia marcescens, Acinetobacter baumannii, and Myroides phaeus; tet(L) in M. caseolyticus; sul1 in Vibrio cincinnatiensis; sul2 in Acinetobacter bereziniae, Acinetobacter johnsonii, and V. cincinnatiensis; and the class 1 integron and gene cassette aadA2 in V. cincinnatiensis. Approximately 6.6% of isolates contained class 1 integrons, and one isolate harbored class 2 integrons. Plasmid associated intI1 and androgen receptor- encoding genes were transferred into Escherichia coli J53 and E. coli DH5α by conjugation and transformation experiments, respectively. Our study highlights the importance of aerobic bacteria from pork as reservoirs for antimicrobial resistance genes and mobile genetic elements that can readily be transferred intra- and interspecies.

  11. Antibiotic resistance in Pseudomonas aeruginosa strains with increased mutation frequency due to inactivation of the DNA oxidative repair system

    DEFF Research Database (Denmark)

    Mandsberg, Lotte F; Ciofu, Oana; Kirkby, N

    2009-01-01

    ,8-dihydro-8-oxodeoxyguanosine) than PAO1 after exposure to PMNs, and they developed resistance to antibiotics more frequently. The mechanisms of resistance were increased β-lactamase production and overexpression of the MexCD-OprJ efflux-pump. Mutations in either the mutT or the mutY gene were found...... in resistant HP clinical isolates from patients with CF, and complementation with wild-type genes reverted the phenotype. In conclusion, oxidative stress might be involved in the development of resistance to antibiotics. We therefore suggest the possible use of antioxidants for CF patients to prevent...

  12. Novel mutations and mutation combinations of ryanodine receptor in a chlorantraniliprole resistant population of Plutella xylostella (L.)

    Science.gov (United States)

    Guo, Lei; Liang, Pei; Zhou, Xuguo; Gao, Xiwu

    2014-01-01

    A previous study documented a glycine to glutamic acid mutation (G4946E) in ryanodine receptor (RyR) was highly correlated to diamide insecticide resistance in field populations of Plutella xylostella (Lepidoptera: Plutellidae). In this study, a field population collected in Yunnan province, China, exhibited a 2128-fold resistance to chlorantraniliprole. Sequence comparison between resistant and susceptible P. xylostella revealed three novel mutations including a glutamic acid to valine substitution (E1338D), a glutamine to leucine substitution (Q4594L) and an isoleucine to methionine substitution (I4790M) in highly conserved regions of RyR. Frequency analysis of all four mutations in this field population showed that the three new mutations showed a high frequency of 100%, while the G4946E had a frequency of 20%. Furthermore, the florescent ligand binding assay revealed that the RyR containing multiple mutations displayed a significantly lower affinity to the chlorantraniliprole. The combined results suggested that the co-existence of different combinations of the four mutations was involved in the chlorantraniliprole resistance. An allele-specific PCR based method was developed for the diagnosis of the four mutations in the field populations of P. xylostella. PMID:25377064

  13. Evaluation of gamma radiation response of electrolyte, MKP and MKT capacitors in various frequencies

    International Nuclear Information System (INIS)

    Malekie, Shahryar; Salehpour, Behrooz

    2017-01-01

    In this experimental work, the effect of gamma irradiation on the capacitance and impedance of some commercial capacitors namely electrolytic, MKP, and MKT capacitors in different radiation doses up to 120 kGy and a wide range of frequencies between 42 Hz and 5 MHz were studied. Results showed that the capacitances of the electrolytic capacitors exhibited a linear decrease by increasing the radiation dose and frequencies, which can be used for high dosimetry purposes, but non-ceramic capacitors as MKP and MKT showed much higher radiation resistance, particularly for the frequencies less than ∝1 MHz.

  14. Evaluation of gamma radiation response of electrolyte, MKP and MKT capacitors in various frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Malekie, Shahryar [Nuclear Science and Technology Research Institute, Karaj (Iran, Islamic Republic of). Radiation Application Research School; Salehpour, Behrooz [Tabriz Univ. (Iran, Islamic Republic of). Faculty of Physics

    2017-09-01

    In this experimental work, the effect of gamma irradiation on the capacitance and impedance of some commercial capacitors namely electrolytic, MKP, and MKT capacitors in different radiation doses up to 120 kGy and a wide range of frequencies between 42 Hz and 5 MHz were studied. Results showed that the capacitances of the electrolytic capacitors exhibited a linear decrease by increasing the radiation dose and frequencies, which can be used for high dosimetry purposes, but non-ceramic capacitors as MKP and MKT showed much higher radiation resistance, particularly for the frequencies less than ∝1 MHz.

  15. Evaluation of the Roche prototype 454 HIV-1 ultradeep sequencing drug resistance assay in a routine diagnostic laboratory.

    Science.gov (United States)

    Garcia-Diaz, A; Guerrero-Ramos, A; McCormick, A L; Macartney, M; Conibear, T; Johnson, M A; Haque, T; Webster, D P

    2013-10-01

    Studies have shown that low-frequency resistance mutations can influence treatment outcome. However, the lack of a standardized high-throughput assay has precluded their detection in clinical settings. To evaluate the performance of the Roche prototype 454 UDS HIV-1 drug resistance assay (UDS assay) in a routine diagnostic laboratory. 50 plasma samples, previously characterized by population sequencing and that had shown ≥1 resistance associated mutation (RAM), were retrospectively tested by the UDS assay, including 18 B and 32 non-B subtypes; viral loads between 114-1,806,407 cp/ml; drug-naive (n=27) and drug-experienced (n=23) individuals. The UDS assay was successful for 37/50 (74%) samples. It detected all RAMs found by population sequencing at frequencies above 20%. In addition, 39 low-frequency RAMs were exclusively detected by the UDS assay at frequencies below 20% in both drug-naïve (19/26, 73%) and drug-experienced (9/18, 50%) individuals. UDS results would lead to changes from susceptible to resistant to efavirenz (EFV) in one drug-naive individual with suboptimal response to an EFV-containing regimen and from susceptible to resistance to lamivudine (3TC) in one drug naïve subject who subsequently failed a 3TC-containing regimen and in a treatment experienced subject who had failed a 3TC-containing regimen. The UDS assay performed well across a wide range of subtypes and viral loads; it showed perfect agreement with population sequencing for all RAMs analyzed. In addition, the UDS assay detected additional mutations at frequencies below 20% which correlate with patients' treatment history and had in some cases important prognostic implications. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Ultra-high resistive and anisotropic CoPd–CaF{sub 2} nanogranular soft magnetic films prepared by tandem-sputtering deposition

    Energy Technology Data Exchange (ETDEWEB)

    Naoe, Masayuki, E-mail: naoe@denjiken.ne.jp [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Kobayashi, Nobukiyo [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Ohnuma, Shigehiro [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8578 (Japan); Iwasa, Tadayoshi; Arai, Ken-Ichi [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Masumoto, Hiroshi [Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8578 (Japan)

    2015-10-01

    Ultra-high resistive and anisotropic soft magnetic films for gigahertz applications are desirable to demonstrate the really practical films. Here we present a study of novel nanogranular films fabricated by tandem-sputtering deposition. Their electromagnetic properties and nanostructure have also been discussed. These films consisted of nanocrystallized CoPd alloy-granules and CaF{sub 2} matrix, and a specimen having a composition of (Co{sub 0.69}Pd{sub 0.31}){sub 52}–(Ca{sub 0.31}F{sub 0.69}){sub 48} exhibited distinct in-plane uniaxial anisotropy after uniaxial field annealing with granule growth. Its complex permeability spectra have a ferromagnetic resonance frequency extending to the Super-High-Frequency band due to its higher anisotropy field, and its frequency response was quite well reproduced by a numerical calculation based on the Landau–Lifshitz–Gilbert equation. Furthermore, it was clarified that the CaF{sub 2}-based nanogranular film exhibits a hundredfold higher electrical resistivity than conventional oxide or nitride-based films. Higher resistivity enables the film thickness to achieve a margin exceeding threefold against eddy current loss. The greater resistivity of nanogranular films is attributed to the wide energy bandgap and superior crystallinity of CaF{sub 2} matrix. - Highlights: • We fabricated high-resistive and anisotropic granular films by tandem-sputtering. • CaF{sub 2}-based films exhibit a hundredfold higher resistivity than conventional films. • Uniaxial field annealing improved the magnetic properties dramatically. • High uniaxial anisotropy extended ferromagnetic resonance frequency to 4 GHz. • Annealed samples can be regarded as a ferromagnetic homogenized material.

  17. Distribution of cranberry fruit-rotting fungi in new jersey and evidence for nonspecific host resistance.

    Science.gov (United States)

    Stiles, C M; Oudemans, P V

    1999-03-01

    ABSTRACT A survey was conducted over a 3-year period to determine the frequencies and distributions of fruit-rotting fungi in New Jersey cranberry beds. In the first 2 years of the study, Physalospora vaccinii and Glomerella cingulata were the most prevalent and widespread field-rotting fungi. In the third year, the frequency of G. cingulata declined markedly. Other species such as Coleophoma empetri, Phyllosticta vaccinii, and Phomopsis vaccinii were isolated at high frequencies from a limited number of locations. Storage-rotting fungi including Allantophomopsis cytisporea and A. lycopodina were isolated at low frequencies, but were widely distributed within the growing region. On sound fruit, a somewhat different profile emerged. Fungi such as Phyllosticta elongata, Alternaria spp., and Physalospora vaccinii were commonly isolated. In comparisons among different cranberry cultivars, no differences in the fungal profiles were seen. This was interpreted to indicate that if differences in fruit-rot resistance exist, they are likely to be general forms of resistance rather than fungal species-specific mechanisms.

  18. Combining different frequencies for electrical heating of saturated and unsaturated soil zones

    Energy Technology Data Exchange (ETDEWEB)

    Roland, U.; Holzer, F.; Kopinke, F.D. [Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Engineering, Leipzig (Germany)

    2011-10-15

    In situ electrical heating of soil was studied applying different frequencies: low-frequency energy for resistive heating and radio-frequency energy for dielectric heating. Steep temperature gradients were observed for each heating mode under the condition of the coexistence of saturated and unsaturated soil zones. By combining the two heating modes, this undesired effect can be avoided, thus allowing efficient soil remediation especially when organic phases are accumulated at the capillary fringe. A parallel application of both frequencies was demonstrated as the most suitable method to reduce temperature gradients. By using electronic filters, both electric fields can be established by only one electrode array. This innovative concept is especially applicable for optimizing thermal remediation of light non-aqueous phase liquid contaminations or realizing thermally-enhanced electrokinetic removal of heavy metals. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Frequency of intrachromosomal homologous recombination induced by UV radiation in normally repairing and excision repair-deficient human cells

    International Nuclear Information System (INIS)

    Tsujimura, T.; Maher, V.M.; McCormick, J.J.; Godwin, A.R.; Liskay, R.M.

    1990-01-01

    To investigate the role of DNA damage and nucleotide excision repair in intrachromosomal homologous recombination, a plasmid containing duplicated copies of the gene coding for hygromycin resistance was introduced into the genome of a repair-proficient human cell line, KMST-6, and two repair-deficient lines, XP2OS(SV) from xeroderma pigmentosum complementation group A and XP2YO(SV) from complementation group F. Neither hygromycin-resistance gene codes for a functional enzyme because each contains an insertion/deletion mutation at a unique site, but recombination between the two defective genes can yield hygromycin-resistant cells. The rates of spontaneous recombination in normal and xeroderma pigmentosum cell strains containing the recombination substrate were found to be similar. The frequency of UV-induced recombination was determined for three of these cell strains. At low doses, the group A cell strain and the group F cell strain showed a significant increase in frequency of recombinants. The repair-proficient cell strain required 10-to 20-fold higher doses of UV to exhibit comparable increases in frequency of recombinants. These results suggest that unexcised DNA damage, rather than the excision repair process per se, stimulates such recombination

  20. Analysis of clinical isolates of Helicobacter pylori in Pakistan reveals high degrees of pathogenicity and high frequencies of antibiotic resistance.

    Science.gov (United States)

    Rasheed, Faisal; Campbell, Barry James; Alfizah, Hanafiah; Varro, Andrea; Zahra, Rabaab; Yamaoka, Yoshio; Pritchard, David Mark

    2014-10-01

    Antibiotic resistance in Helicobacter pylori contributes to failure in eradicating the infection and is most often due to point and missense mutations in a few key genes. The antibiotic susceptibility profiles of H. pylori isolates from 46 Pakistani patients were determined by Etest. Resistance and pathogenicity genes were amplified, and sequences were analyzed to determine the presence of mutations. A high percentage of isolates (73.9%) were resistant to metronidazole (MTZ), with considerable resistance to clarithromycin (CLR; 47.8%) and amoxicillin (AML; 54.3%) also observed. Relatively few isolates were resistant to tetracycline (TET; 4.3%) or to ciprofloxacin (CIP; 13%). However, most isolates (n = 43) exhibited resistance to one or more antibiotics. MTZ-resistant isolates contained missense mutations in oxygen-independent NADPH nitroreductase (RdxA; 8 mutations found) and NADH flavin oxidoreductase (FrxA; 4 mutations found). In the 23S rRNA gene, responsible for CLR resistance, a new point mutation (A2181G) and 4 previously reported mutations were identified. Pathogenicity genes cagA, dupA, and vacA s1a/m1 were detected frequently in isolates which were also found to be resistant to MTZ, CLR, and AML. A high percentage of CagA and VacA seropositivity was also observed in these patients. Phylogenetic analysis of partial sequences showed uniform distribution of the 3' region of cagA throughout the tree. We have identified H. pylori isolates in Pakistan which harbor pathogenicity genes and worrying antibiotic resistance profiles as a result of having acquired multiple point and missense mutations. H. pylori eradication regimens should therefore be reevaluated in this setting. © 2014 John Wiley & Sons Ltd.

  1. Occurrence of antibiotic resistance and characterization of resistant genes and integrons in Enterobacteriaceae isolated from integrated fish farms south China

    Science.gov (United States)

    Su, Hao-Chang; Ying, Guang-Guo; Tao, Ran; Zhang, Rui-Quan; Fogarty, Lisa R.; Kolpin, Dana W.

    2011-01-01

    Antibiotics are still widely applied in animal husbandry to prevent diseases and used as feed additives to promote animal growth. This could result in antibiotic resistance to bacteria and antibiotic residues in animals. In this paper, Enterobacteriaceae isolated from four integrated fish farms in Zhongshan, South China were tested for antibiotic resistance, tetracycline resistance genes, sulfonamide resistance genes, and class 1 integrons. The Kirby-Bauer disk diffusion method and polymerase chain reaction (PCR) assays were carried out to test antibiotic susceptibility and resistance genes, respectively. Relatively high antibiotic resistance frequencies were found, especially for ampicillin (80%), tetracycline (52%), and trimethoprim (50%). Out of 203 Enterobacteriaceae isolates, 98.5% were resistant to one or more antibiotics tested. Multiple antibiotic resistance (MAR) was found highest in animal manures with a MAR index of 0.56. Tetracycline resistance genes (tet(A), tet(C)) and sulfonamide resistance genes (sul2) were detected in more than 50% of the isolates. The intI1 gene was found in 170 isolates (83.7%). Both classic and non-classic class 1 integrons were found. Four genes, aadA5, aadA22, dfr2, and dfrA17, were detected. To our knowledge, this is the first report for molecular characterization of antibiotic resistance genes in Enterobacteriaceae isolated from integrated fish farms in China and the first time that gene cassette array dfrA17-aadA5 has been detected in such fish farms. Results of this study indicated that fish farms may be a reservoir of highly diverse and abundant antibiotic resistant genes and gene cassettes. Integrons may play a key role in multiple antibiotic resistances posing potential health risks to the general public and aquaculture.

  2. Frequency-Dependent Properties of Magnetic Nanoparticle Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Majetich, Sara [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-05-17

    In the proposed research program we will investigate the time- and frequency-dependent behavior of ordered nanoparticle assemblies, or nanoparticle crystals. Magnetostatic interactions are long-range and anisotropic, and this leads to complex behavior in nanoparticle assemblies, particularly in the time- and frequency-dependent properties. We hypothesize that the high frequency performance of composite materials has been limited because of the range of relaxation times; if a composite is a dipolar ferromagnet at a particular frequency, it should have the advantages of a single phase material, but without significant eddy current power losses. Arrays of surfactant-coated monodomain magnetic nanoparticles can exhibit long-range magnetic order that is stable over time. The magnetic domain size and location of domain walls is governed not by structural grain boundaries but by the shape of the array, due to the local interaction field. Pores or gaps within an assembly pin domain walls and limit the domain size. Measurements of the magnetic order parameter as a function of temperature showed that domains can exist at high temoerature, and that there is a collective phase transition, just as in an exchange-coupled ferromagnet. Dipolar ferromagnets are not merely of fundamental interest; they provide an interesting alternative to exchange-based ferromagnets. Dipolar ferromagnets made with high moment metallic particles in an insulating matrix could have high permeability without large eddy current losses. Such nanocomposites could someday replace the ferrites now used in phase shifters, isolators, circulators, and filters in microwave communications and radar applications. We will investigate the time- and frequency-dependent behavior of nanoparticle crystals with different magnetic core sizes and different interparticle barrier resistances, and will measure the magnetic and electrical properties in the DC, low frequency (0.1 Hz - 1 kHz), moderate frequency (10 Hz - 500

  3. Susceptibility of Australian Myzus persicae (Hemiptera: Aphididae) to Three Recently Registered Insecticides: Spirotetramat, Cyantraniliprole, and Sulfoxaflor.

    Science.gov (United States)

    de Little, Siobhan C; Umina, Paul A

    2017-08-01

    The green peach aphid, Myzus persicae (Sulzer), is a significant agricultural pest that has developed resistance to a large number of insecticides globally. Within Australia, resistance has previously been confirmed for multiple chemical groups, including pyrethroids, carbamates, organophosphates, and neonicotinoids. In this study, we use leaf-dip and topical bioassays to investigate susceptibility and potential cross-resistance of 12 field-collected populations of Australian M. persicae to three recently registered insecticides: sulfoxaflor, spirotetramat, and cyantraniliprole. Despite all 12 populations carrying known resistance mechanisms to carbamates, organophosphates, and pyrethroids, and two populations also exhibiting low-level metabolic resistance to neonicotinoids, we found little evidence of variation in susceptibility to sulfoxafor, spirotetramat, or cyantraniliprole. This provides further evidence that cross-resistance to spirotetramat, cyantraniliprole, and sulfoxaflor in M. persicae is not conferred by the commonly occurring resistance mechanisms MACE, super-kdr, amplification of the E4 esterase gene, or enhanced expression and copy number of the P450 gene, CYP6CY3. Importantly, this study also established toxicity baseline data that will be important for future monitoring of insecticide responses of M. persicae from both broadacre and horticultural crops. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. Vascular Endothelial Growth Factor Receptor-2 Polymorphisms Have Protective Effect against the Development of Tendinopathy in Volleyball Athletes.

    Science.gov (United States)

    Salles, José Inácio; Duarte, Maria Eugenia Leite; Guimarães, João Matheus; Lopes, Lucas Rafael; Vilarinho Cardoso, Jessica; Aguiar, Diego Pinheiro; Machado Neto, João Olyntho; Machado, Daniel Escorsim; Perini, Jamila Alessandra

    2016-01-01

    The aim of the study was to investigate whether genetic variants in VEGF and KDR genes can be correlated with susceptibility of tendinopathy in volleyball athletes. This study was conducted at the Brazilian Volleyball Federation, and comprised 179 volleyball athletes: 88 had a confirmed diagnosis of tendinopathy (cases), whereas 91 had no evidence of the disease (controls). The VEGF (-2578C>A, -460T>C and +936C>T) and KDR (-604C>T, 1192G>A and 1719T>A) polymorphisms were determined by TaqMan real-time polymerase chain reaction. The odds ratio (OR) with their 95% confidence intervals (CI) were calculated using an unconditional logistic regression model. The evaluation of demographic and clinical characteristics revealed the athlete age (P volleyball (P T, 1192G>A and 1719T>A) haplotypes CGA and CAT were associated with decreased tendinopathy risk (OR: 0.46, 95% CI: 0.21-0.99 and OR: 0.23, 95% CI: 0.07-0.76, respectively). With regards to pain, traumatic lesion and away from training due to injury, VEGF and KDR polymorphisms were not associated with clinical symptoms complaints. The present results provide evidence that the KDR polymorphisms were associated with development of tendinopathy, and can contribute to identify new therapeutic targets or personalized training programs to avoid tendinopathy development in athletes.

  5. Physical model of the contact resistivity of metal-graphene junctions

    Energy Technology Data Exchange (ETDEWEB)

    Chaves, Ferney A., E-mail: ferneyalveiro.chaves@uab.cat; Jiménez, David [Departament d' Enginyeria Electrònica, Escola d' Enginyeria, Universitat Autònoma de Barcelona, Campus UAB, 08193 Bellaterra, Barcelona (Spain); Cummings, Aron W. [ICN2–Institut Català de Nanociència i Nanotecnologia, Campus UAB, 08193 Bellaterra, Barcelona (Spain); Roche, Stephan [ICN2–Institut Català de Nanociència i Nanotecnologia, Campus UAB, 08193 Bellaterra, Barcelona (Spain); ICREA, Institució Catalana de Recerca i Estudis Avançats, 08070 Barcelona (Spain)

    2014-04-28

    While graphene-based technology shows great promise for a variety of electronic applications, including radio-frequency devices, the resistance of the metal-graphene contact is a technological bottleneck for the realization of viable graphene electronics. One of the most important factors in determining the resistance of a metal-graphene junction is the contact resistivity. Despite the large number of experimental works that exist in the literature measuring the contact resistivity, a simple model of it is still lacking. In this paper, we present a comprehensive physical model for the contact resistivity of these junctions, based on the Bardeen Transfer Hamiltonian method. This model unveils the role played by different electrical and physical parameters in determining the specific contact resistivity, such as the chemical potential of interaction, the work metal-graphene function difference, and the insulator thickness between the metal and graphene. In addition, our model reveals that the contact resistivity is strongly dependent on the bias voltage across the metal-graphene junction. This model is applicable to a wide variety of graphene-based electronic devices and thus is useful for understanding how to optimize the contact resistance in these systems.

  6. Physical model of the contact resistivity of metal-graphene junctions

    International Nuclear Information System (INIS)

    Chaves, Ferney A.; Jiménez, David; Cummings, Aron W.; Roche, Stephan

    2014-01-01

    While graphene-based technology shows great promise for a variety of electronic applications, including radio-frequency devices, the resistance of the metal-graphene contact is a technological bottleneck for the realization of viable graphene electronics. One of the most important factors in determining the resistance of a metal-graphene junction is the contact resistivity. Despite the large number of experimental works that exist in the literature measuring the contact resistivity, a simple model of it is still lacking. In this paper, we present a comprehensive physical model for the contact resistivity of these junctions, based on the Bardeen Transfer Hamiltonian method. This model unveils the role played by different electrical and physical parameters in determining the specific contact resistivity, such as the chemical potential of interaction, the work metal-graphene function difference, and the insulator thickness between the metal and graphene. In addition, our model reveals that the contact resistivity is strongly dependent on the bias voltage across the metal-graphene junction. This model is applicable to a wide variety of graphene-based electronic devices and thus is useful for understanding how to optimize the contact resistance in these systems

  7. Induced mutations for resistance to leaf rust in wheat

    International Nuclear Information System (INIS)

    Borojevic, K.

    1983-01-01

    Problems related to the induction of mutations for disease resistance were investigated under several aspects, using the wheat/leaf rust system. Previously selected mutant lines, tested in M 11 and M 13 , were found to differ with regard to infection type and disease severity from the original varieties. To verify the induced-mutation origin, these mutants were examined further using test crosses with carriers of known genes for leaf rust resistance and electrophoresis. A separate experiment to induce mutations for leaf rust resistance in the wheat varieties Sava, Aurora and Siete Cerros, using gamma rays, fast neutrons and EMS, yielded mutants with different disease reaction in the varieties Sava and Aurora at a frequency of about 1x10 - 3 per M 1 plant progenies. (author)

  8. Multiple populations of artemisinin-resistant Plasmodium falciparum in Cambodia

    Science.gov (United States)

    Miotto, Olivo; Almagro-Garcia, Jacob; Manske, Magnus; MacInnis, Bronwyn; Campino, Susana; Rockett, Kirk A; Amaratunga, Chanaki; Lim, Pharath; Suon, Seila; Sreng, Sokunthea; Anderson, Jennifer M; Duong, Socheat; Nguon, Chea; Chuor, Char Meng; Saunders, David; Se, Youry; Lon, Chantap; Fukuda, Mark M; Amenga-Etego, Lucas; Hodgson, Abraham VO; Asoala, Victor; Imwong, Mallika; Takala-Harrison, Shannon; Nosten, Francois; Su, Xin-zhuan; Ringwald, Pascal; Ariey, Frédéric; Dolecek, Christiane; Hien, Tran Tinh; Boni, Maciej F; Thai, Cao Quang; Amambua-Ngwa, Alfred; Conway, David J; Djimdé, Abdoulaye A; Doumbo, Ogobara K; Zongo, Issaka; Ouedraogo, Jean-Bosco; Alcock, Daniel; Drury, Eleanor; Auburn, Sarah; Koch, Oliver; Sanders, Mandy; Hubbart, Christina; Maslen, Gareth; Ruano-Rubio, Valentin; Jyothi, Dushyanth; Miles, Alistair; O’Brien, John; Gamble, Chris; Oyola, Samuel O; Rayner, Julian C; Newbold, Chris I; Berriman, Matthew; Spencer, Chris CA; McVean, Gilean; Day, Nicholas P; White, Nicholas J; Bethell, Delia; Dondorp, Arjen M; Plowe, Christopher V; Fairhurst, Rick M; Kwiatkowski, Dominic P

    2013-01-01

    We describe an analysis of genome variation in 825 Plasmodium falciparum samples from Asia and Africa that reveals an unusual pattern of parasite population structure at the epicentre of artemisinin resistance in western Cambodia. Within this relatively small geographical area we have discovered several distinct but apparently sympatric parasite subpopulations with extremely high levels of genetic differentiation. Of particular interest are three subpopulations, all associated with clinical resistance to artemisinin, which have skewed allele frequency spectra and remarkably high levels of haplotype homozygosity, indicative of founder effects and recent population expansion. We provide a catalogue of SNPs that show high levels of differentiation in the artemisinin-resistant subpopulations, including codon variants in various transporter proteins and DNA mismatch repair proteins. These data provide a population genetic framework for investigating the biological origins of artemisinin resistance and for defining molecular markers to assist its elimination. PMID:23624527

  9. A new surface resistance measurement method with ultrahigh sensitivity

    International Nuclear Information System (INIS)

    Liang, Changnian.

    1993-01-01

    A superconducting niobium triaxial cavity has been designed and fabricated to study residual surface resistance of planar superconducting materials. The edge of a 25.4 mm or larger diameter sample in the triaxial cavity is located outside the strong field region. Therefore, the edge effects and possible losses between the thin film and the substrate have been minimized, ensuring that induced RF losses are intrinsic to the test material. The fundamental resonant frequency of the cavity is the same as the working frequency of CEBAF cavities. The cavity has a compact size compared to its TE 011 counterpart, which makes it more sensitive to the sample's loss. For even higher sensitivity, a calorimetry method has been used to measure the RF losses on the superconducting sample. At 2 K, a 2 μK temperature change can be resolved by using carbon resistor sensors. The temperature distribution caused by RF heating is measured by 16 carbon composition resistor sensors. A 0.05 μW heating power can be detected as such a resolution, which translates to a surface resistance of 0.02 nΩ at a surface magnetic field of 52 Oe. This is the most sensitive device for surface resistance measurements to date. In addition, losses due to the indium seal, coupling probes, field emission sites other than the sample, and all of the high field resonator surface, are excluded in the measurement. Surface resistance of both niobium and high-Tc superconducting thin films has been measured. A low R s of 35.2 μΩ was measured for a 25.4 mm diameter YBa 2 Cu 3 O 7 thin film at 1.5 GHz and at 2 K. The measurement result is the first result for a large area epitaxially grown thin film sample at such a low RF frequency. The abrupt disappearance of multipacting between two parallel plates has been observed and monitored with the 16 temperature mapping sensors. Field emission or some field dependent anomalous RF losses on the niobium plate have also been observed

  10. Regular meal frequency creates more appropriate insulin sensitivity and lipid profiles compared with irregular meal frequency in healthy lean women.

    Science.gov (United States)

    Farshchi, H R; Taylor, M A; Macdonald, I A

    2004-07-01

    To investigate the impact of irregular meal frequency on circulating lipids, insulin, glucose and uric acid concentrations which are known cardiovascular risk factors. A randomised crossover dietary intervention study. Nottingham, UK--Healthy free-living women. A total of nine lean healthy women aged 18-42 y recruited via advertisement. A randomised crossover trial with two phases of 14 days each. In Phase 1, subjects consumed their normal diet on either 6 occasions per day (regular) or by following a variable meal frequency (3-9 meals/day, irregular). In Phase 2, subjects followed the alternative meal pattern to that followed in Phase 1, after a 2-week (wash-out) period. Subjects were asked to come to the laboratory after an overnight fast at the start and end of each phase. Blood samples were taken for measurement of circulating glucose, lipids, insulin and uric acid concentrations before and for 3 h after consumption of a high-carbohydrate test meal. Fasting glucose and insulin values were not affected by meal frequency, but peak insulin and AUC of insulin responses to the test meal were higher after the irregular compared to the regular eating patterns (P meal frequency was associated with higher fasting total (P meal frequency appears to produce a degree of insulin resistance and higher fasting lipid profiles, which may indicate a deleterious effect on these cardiovascular risk factors. : The Ministry of Health and Medical Education, IR Iran.

  11. Enhancement of DNA-transfection frequency by X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Iwamoto, Ryota; Fushimi, Kazuo; Hiraki, Yoshio; Namba, Masayoshi [Okayama University Medical School (Japan). Institute of Cellular and Molecular Biology

    1997-02-01

    This study was conducted to evaluate the frequency of DNA transfection into human cells following X-ray irradiation. We transfected plasmid DNA (pSV2neo) into human cells, HeLa and PA-1, by either calcium phosphate precipitation or the lipofection method immediately after irradiating the cells with various doses of X-rays. The transfection frequency was evaluated by counting the number of G418-resistant colonies. When circular plasmid DNA was used, irradiation up to a dose of 2 Gy dose-dependently increased the transfection frequency, which reached a maximum of 5 to 10-fold that of the control unirradiated cells. When linear plasmid DNA was used, the transfection frequency was 2 times higher than that of circular DNA. All five of the clones that were randomly chosen expressed the transfected neo gene. In addition, the pSV2neo gene was randomly integrated into the genomic DNA of each clone. These findings indicate that X-ray treatment can facilitate foreign DNA transfer into human cells and that radiation-induced DNA breaks may promote the insertion of foreign DNA into host DNA. The enhancement of DNA transfection with X-rays may be instrumental in practicing gene therapy. (author)

  12. Enhancement of DNA-transfection frequency by X-rays

    International Nuclear Information System (INIS)

    Iwamoto, Ryota; Fushimi, Kazuo; Hiraki, Yoshio; Namba, Masayoshi

    1997-01-01

    This study was conducted to evaluate the frequency of DNA transfection into human cells following X-ray irradiation. We transfected plasmid DNA (pSV2neo) into human cells, HeLa and PA-1, by either calcium phosphate precipitation or the lipofection method immediately after irradiating the cells with various doses of X-rays. The transfection frequency was evaluated by counting the number of G418-resistant colonies. When circular plasmid DNA was used, irradiation up to a dose of 2 Gy dose-dependently increased the transfection frequency, which reached a maximum of 5 to 10-fold that of the control unirradiated cells. When linear plasmid DNA was used, the transfection frequency was 2 times higher than that of circular DNA. All five of the clones that were randomly chosen expressed the transfected neo gene. In addition, the pSV2neo gene was randomly integrated into the genomic DNA of each clone. These findings indicate that X-ray treatment can facilitate foreign DNA transfer into human cells and that radiation-induced DNA breaks may promote the insertion of foreign DNA into host DNA. The enhancement of DNA transfection with X-rays may be instrumental in practicing gene therapy. (author)

  13. Insights into DDT Resistance from the Drosophila melanogaster Genetic Reference Panel.

    Science.gov (United States)

    Schmidt, Joshua M; Battlay, Paul; Gledhill-Smith, Rebecca S; Good, Robert T; Lumb, Chris; Fournier-Level, Alexandre; Robin, Charles

    2017-11-01

    Insecticide resistance is considered a classic model of microevolution, where a strong selective agent is applied to a large natural population, resulting in a change in frequency of alleles that confer resistance. While many insecticide resistance variants have been characterized at the gene level, they are typically single genes of large effect identified in highly resistant pest species. In contrast, multiple variants have been implicated in DDT resistance in Drosophila melanogaster ; however, only the Cyp6g1 locus has previously been shown to be relevant to field populations. Here we use genome-wide association studies (GWAS) to identify DDT-associated polygenes and use selective sweep analyses to assess their adaptive significance. We identify and verify two candidate DDT resistance loci. A largely uncharacterized gene, CG10737 , has a function in muscles that ameliorates the effects of DDT, while a putative detoxifying P450, Cyp6w1 , shows compelling evidence of positive selection. Copyright © 2017 by the Genetics Society of America.

  14. Material parameters from frequency dispersion simulation of floating gate memory with Ge nanocrystals in HfO2

    Science.gov (United States)

    Palade, C.; Lepadatu, A. M.; Slav, A.; Lazanu, S.; Teodorescu, V. S.; Stoica, T.; Ciurea, M. L.

    2018-01-01

    Trilayer memory capacitors with Ge nanocrystals (NCs) floating gate in HfO2 were obtained by magnetron sputtering deposition on p-type Si substrate followed by rapid thermal annealing at relatively low temperature of 600 °C. The frequency dispersion of capacitance and resistance was measured in accumulation regime of Al/HfO2 gate oxide/Ge NCs in HfO2 floating gate/HfO2 tunnel oxide/SiOx/p-Si/Al memory capacitors. For simulation of the frequency dispersion a complex circuit model was used considering an equivalent parallel RC circuit for each layer of the trilayer structure. A series resistance due to metallic contacts and Si substrate was necessary to be included in the model. A very good fit to the experimental data was obtained and the parameters of each layer in the memory capacitor, i.e. capacitances and resistances were determined and in turn the intrinsic material parameters, i.e. dielectric constants and resistivities of layers were evaluated. The results are very important for the study and optimization of the hysteresis behaviour of floating gate memories based on NCs embedded in oxide.

  15. Development of Multiple Antibiotic Resistance in Bacillus subtilis Cells Exposed to Microgravity: the BRIC-18 Experiment to the International Space Station

    Science.gov (United States)

    Fajardo-Cavazos, Patricia; Moeller, Ralf; Nicholson, Wayne; Narvel, Raed

    Increased pathogenicity of opportunistic bacteria during long-term spaceflight is considered an astronaut risk. Because only a limited pharmacy can be carried on long-duration missions, the development of resistance to multiple antibiotics is a concern for mission planning. In support of the BRIC-18 experiment to the ISS, we have performed ground-based experiments to address the question whether simulated microgravity affects the frequency of resistance to the model antibiotics rifampicin (RFM) and trimethoprim (TMP). In these experiments, the model bacteria Bacillus subtilis and Staphylococcus epidermidis were cultivated for 6 days at ISS ambient temperature in 10-ml High Aspect Ratio Vessels (HARVs) on two 4-place clinostats (Synthecon) oriented either vertically (V) or horizontally (H). Cells were harvested, enumerated and plated onto medium containing RFM (5 micrograms/ml). The frequency of mutation to RFM resistance was calculated, and RFM-resistant mutants were plated onto medium containing the second antibiotic, TMP (5 micrograms/ml) to determine the frequency of mutation to double (RFM+TMP) resistance. After 6 days of cultivation, V-cultures showed higher cell densities and than H-cultures for both bacteria. However, only in B. subtilis did V-cultures show higher frequencies of mutation to RFM resistance than H-cultures. Launch of BRIC-18 to the ISS is currently scheduled for March 16, 2014 and return 30 days later. Results from both the spaceflight and ground control experiments will be presented. Supported by NASA-SAIP fellowship to R.N. and NASA grant (NNX12AN70G) to P.F.-C., R.M., and W.L.N.

  16. Outer hair cell piezoelectricity: frequency response enhancement and resonance behavior.

    Science.gov (United States)

    Weitzel, Erik K; Tasker, Ron; Brownell, William E

    2003-09-01

    Stretching or compressing an outer hair cell alters its membrane potential and, conversely, changing the electrical potential alters its length. This bi-directional energy conversion takes place in the cell's lateral wall and resembles the direct and converse piezoelectric effects both qualitatively and quantitatively. A piezoelectric model of the lateral wall has been developed that is based on the electrical and material parameters of the lateral wall. An equivalent circuit for the outer hair cell that includes piezoelectricity shows a greater admittance at high frequencies than one containing only membrane resistance and capacitance. The model also predicts resonance at ultrasonic frequencies that is inversely proportional to cell length. These features suggest all mammals use outer hair cell piezoelectricity to support the high-frequency receptor potentials that drive electromotility. It is also possible that members of some mammalian orders use outer hair cell piezoelectric resonance in detecting species-specific vocalizations.

  17. Delayed rectifier K channels contribute to contrast adaptation in mammalian retinal ganglion cells

    Science.gov (United States)

    Weick, Michael; Demb, Jonathan B.

    2011-01-01

    SUMMARY Retinal ganglion cells adapt by reducing their sensitivity during periods of high contrast. Contrast adaptation in the firing response depends on both presynaptic and intrinsic mechanisms. Here, we investigated intrinsic mechanisms for contrast adaptation in OFF Alpha ganglion cells in the in vitro guinea pig retina. Using either visual stimulation or current injection, we show that brief depolarization evoked spiking and suppressed firing during subsequent depolarization. The suppression could be explained by Na channel inactivation, as shown in salamander cells. However, brief hyperpolarization in the physiological range (5–10 mV) also suppressed firing during subsequent depolarization. This suppression was sensitive selectively to blockers of delayed-rectifier K channels (KDR). Somatic membrane patches showed TEA-sensitive KDR currents with activation near −25 mV and removal of inactivation at voltages negative to Vrest. Brief periods of hyperpolarization apparently remove KDR inactivation and thereby increase the channel pool available to suppress excitability during subsequent depolarization. PMID:21745646

  18. In situ measurement system of electric resistivity for outcrop investigation; Roto de shiyodekiru denkihi teiko keisoku system

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, K; Tamura, T [Osaka City Univ., Osaka (Japan). Faculty of Science; Morikawa, T [Osaka Prefectural Government, Osaka (Japan)

    1997-05-27

    A simplified electrical resistivity measuring device has been developed as a trial for field and laboratory uses, and some measurements were conducted. For this device, four probe electrodes are penetrated in the clay specimen, to calculate the resistivity from the voltage between both ends of the reference resistance connected with current electrodes in a series and the voltage between intermediate two voltage electrodes. It can be used in the field measurements. For the measurements, specimens of marine and lacustrine clayey sediments with clear stratigraphic levels in southern Osaka Group were used. In the laboratory, in addition to basic physical tests, diatom analysis and measurements of conductivity of clay suspension were also conducted. As a result of the experiments, the electric resistivity of marine clay obtained at the outcrop was lower than lacustrine clay as expected. The value of the former was a half of that of the latter. The frequency dependence in the high frequency region above 1 MHz was the reverse. The difference in electrical resistivity values between non-agitated specimens was about four times. The electrical resistivity of clay suspensions varied in two orders. 3 refs., 9 figs.

  19. The differential effects of increasing frequency and magnitude of extreme events on coral populations.

    Science.gov (United States)

    Fabina, Nicholas S; Baskett, Marissa L; Gross, Kevin

    2015-09-01

    Extreme events, which have profound ecological consequences, are changing in both frequency and magnitude with climate change. Because extreme temperatures induce coral bleaching, we can explore the relative impacts of changes in frequency and magnitude of high temperature events on coral reefs. Here, we combined climate projections and a dynamic population model to determine how changing bleaching regimes influence coral persistence. We additionally explored how coral traits and competition with macroalgae mediate changes in bleaching regimes. Our results predict that severe bleaching events reduce coral persistence more than frequent bleaching. Corals with low adult mortality and high growth rates are successful when bleaching is mild, but bleaching resistance is necessary to persist when bleaching is severe, regardless of frequency. The existence of macroalgae-dominated stable states reduces coral persistence and changes the relative importance of coral traits. Building on previous studies, our results predict that management efforts may need to prioritize protection of "weaker" corals with high adult mortality when bleaching is mild, and protection of "stronger" corals with high bleaching resistance when bleaching is severe. In summary, future reef projections and conservation targets depend on both local bleaching regimes and biodiversity.

  20. Comparison study of resistance exercise nomenclature adopted among professionals and undergraduate physical education students

    Directory of Open Access Journals (Sweden)

    Leonardo Mendes de Souza

    2016-05-01

    Full Text Available DOI: http://dx.doi.org/10.5007/1980-0037.2016v18n2p233   In the past few years, increased popularity of resistance training (RT and a significant increase in the number of professionals and undergraduate in Physical Education students have been observed. A variety of names has been usually adopted for the same resistance exercise in fields. The aim of the study was to compare the resistance exercise nomenclature adopted by physical education professionals and students, and also to identify the frequencies of names adopted for these resistance exercises. The study included 191 graduate students and active physical education professionals of RT centers and gyms in the state of Rio de Janeiro, Brazil. Ten exercises traditionally performed on RT programs were selected. The results indicated that there was no association between the nomenclature of exercises and academic degree for all exercises included in the survey. However, there was significant difference (p <0.001 among response frequencies for each exercise, for the whole sample. In this sense, this study enabled identifying significant differences in the nomenclature of resistance exercises. Therefore, nomenclature standardization is essential to establish a direction and clearness in communication among professionals.