Winter Survival of Individual Honey Bees and Honey Bee Colonies Depends on Level of Varroa destructor Infestation

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Dooremalen, van C.; Gerritsen, L.J.M.; Cornelissen, B.; Steen, van der J.J.M.; Langevelde, van F.; Blacquiere, T.

2012-01-01

Background: Recent elevated winter loss of honey bee colonies is a major concern. The presence of the mite Varroa destructor in colonies places an important pressure on bee health. V. destructor shortens the lifespan of individual bees, while long lifespan during winter is a primary requirement to

Challenges for developing biopesticides against Varroa destructor (Mesostigamata: Varroidae)

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Control of the major pest of apiculture, the ectoparasitic mite Varroa destructor, using biopesticides would resolve many of the problems experienced with other forms of control, such as chemical control, hive manipulation or selection of resistant strains. Several research groups have developed and...

Interaction between Varroa destructor and imidacloprid reduces flight capacity of honeybees

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Blanken, Lisa J.; van Dooremalen, Coby

2015-01-01

Current high losses of honeybees seriously threaten crop pollination. Whereas parasite exposure is acknowledged as an important cause of these losses, the role of insecticides is controversial. Parasites and neonicotinoid insecticides reduce homing success of foragers (e.g. by reduced orientation), but it is unknown whether they negatively affect flight capacity. We investigated how exposing colonies to the parasitic mite Varroa destructor and the neonicotinoid insecticide imidacloprid affect flight capacity of foragers. Flight distance, time and speed of foragers were measured in flight mills to assess the relative and interactive effects of high V. destructor load and a field-realistic, chronic sub-lethal dose of imidacloprid. Foragers from colonies exposed to high levels of V. destructor flew shorter distances, with a larger effect when also exposed to imidacloprid. Bee body mass partly explained our results as bees were heavier when exposed to these stressors, possibly due to an earlier onset of foraging. Our findings contribute to understanding of interacting stressors that can explain colony losses. Reduced flight capacity decreases the food-collecting ability of honeybees and may hamper the use of precocious foraging as a coping mechanism during colony (nutritional) stress. Ineffective coping mechanisms may lead to destructive cascading effects and subsequent colony collapse. PMID:26631559

Host Status of Seven Weed Species and Their Effects on Ditylenchus destructor Infestation of Peanut

OpenAIRE

De Waele, D.; Jordaan, Elizabeth M.; Basson, Selmaré

1990-01-01

The host suitability to Ditylenchus destructor of seven common weed species in peanut (Arachis hypogaea) fields in South Africa was determined. Based on the number of nematodes per root unit, white goosefoot (Chenopodium album), feathertop chloris (Chloris virgata), purple nutsedge (Cyperus rotundus), jimson weed (Datura stramonium), goose grass (Eleusine indica), khaki weed (Tagetes minuta), and cocklebur (Xanthium strumarium) were poor hosts. Ditylenchus destructor survived on all weed spec...

Winter Survival of Individual Honey Bees and Honey Bee Colonies Depends on Level of Varroa destructor Infestation

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van Dooremalen, Coby; Gerritsen, Lonne; Cornelissen, Bram; van der Steen, Jozef J. M.; van Langevelde, Frank; Blacquière, Tjeerd

2012-01-01

Background Recent elevated winter loss of honey bee colonies is a major concern. The presence of the mite Varroa destructor in colonies places an important pressure on bee health. V. destructor shortens the lifespan of individual bees, while long lifespan during winter is a primary requirement to survive until the next spring. We investigated in two subsequent years the effects of different levels of V. destructor infestation during the transition from short-lived summer bees to long-lived winter bees on the lifespan of individual bees and the survival of bee colonies during winter. Colonies treated earlier in the season to reduce V. destructor infestation during the development of winter bees were expected to have longer bee lifespan and higher colony survival after winter. Methodology/Principal Findings Mite infestation was reduced using acaricide treatments during different months (July, August, September, or not treated). We found that the number of capped brood cells decreased drastically between August and November, while at the same time, the lifespan of the bees (marked cohorts) increased indicating the transition to winter bees. Low V. destructor infestation levels before and during the transition to winter bees resulted in an increase in lifespan of bees and higher colony survival compared to colonies that were not treated and that had higher infestation levels. A variety of stress-related factors could have contributed to the variation in longevity and winter survival that we found between years. Conclusions/Significance This study contributes to theory about the multiple causes for the recent elevated colony losses in honey bees. Our study shows the correlation between long lifespan of winter bees and colony loss in spring. Moreover, we show that colonies treated earlier in the season had reduced V. destructor infestation during the development of winter bees resulting in longer bee lifespan and higher colony survival after winter. PMID:22558421

Resistance to Wheat Curl Mite in Arthropod-Resistant Rye-Wheat Translocation Lines

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Lina Maria Aguirre-Rojas

2017-11-01

Full Text Available The wheat curl mite, Aceria toschiella (Keifer, and a complex of viruses vectored by A. toschiella substantially reduce wheat yields in every wheat-producing continent in the world. The development of A. toschiella-resistant wheat cultivars is a proven economically and ecologically viable method of controlling this pest. This study assessed A. toschiella resistance in wheat genotypes containing the H13, H21, H25, H26, H18 and Hdic genes for resistance to the Hessian fly, Mayetiola destructor (Say and in 94M370 wheat, which contains the Dn7 gene for resistance to the Russian wheat aphid, Diuraphis noxia (Kurdjumov. A. toschiella populations produced on plants containing Dn7 and H21 were significantly lower than those on plants of the susceptible control and no different than those on the resistant control. Dn7 resistance to D. noxia and H21 resistance to M. destructor resulted from translocations of chromatin from rye into wheat (H21—2BS/2RL, Dn7—1BL/1RS. These results provide new wheat pest management information, indicating that Dn7 and H21 constitute resources that can be used to reduce yield losses caused by A. toschiella, M. destructor, D. noxia, and wheat streak mosaic virus infection by transferring multi-pest resistance to single sources of germplasm.

The effects of clove oil on the enzyme activity of Varroa destructor Anderson and Trueman (Arachnida: Acari: Varroidae

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Li Li

2017-07-01

Full Text Available Varroa destructor, a key biotic threat to the Western honey bee, has played a major role in colony losses over the past few years worldwide. Overuse of traditional acaricides, such as tau-fluvalinate and flumethrin, on V. destructor has only increased its tolerance to them. Therefore, the application of essential oils in place of traditional pesticides is an attractive alternative, as demonstrated by its high efficiency, lack of residue and tolerance resistance. To study the acaricidal activity of essential oils, we used clove oil (Syzygium aromaticum L., a typical essential oil with a wide range of field applications, and examined its effects on the enzyme activities of Ca2+-Mg2+-ATPase, glutathione-S-transferase (GST and superoxide dismutase (SOD and its effects on the water-soluble protein content of V. destructor body extracts after exposure to 0.1 μl and 1.0 μl of clove oil for 30 min. Our results showed that the water-soluble protein content significantly decreased after the treatments, indicating that the metabolism of the mites was adversely affected. The bioactivity of GSTs increased significantly after a low dosage (0.1 μl exposure but decreased at a higher dosage (1.0 μl, while the activities of SOD and Ca2+-Mg2+-ATPase were significantly elevated after treatments. These results suggest that the protective enzyme SOD and detoxifying enzymes Ca2+-Mg2+-ATPase and GST contributed to the stress reaction of V. destructor to the essential oils and that the detoxification ability of V. destructor via GST was inhibited at higher dosages. Our findings are conducive to understanding the physiological reactions of V. destructor to treatment with essential oils and the underlying mechanisms behind the acaricidal activities of these natural products.

Honey bee Apis mellifera parasites in the absence of Nosema ceranae fungi and Varroa destructor mites.

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Shutler, Dave; Head, Krista; Burgher-MacLellan, Karen L; Colwell, Megan J; Levitt, Abby L; Ostiguy, Nancy; Williams, Geoffrey R

2014-01-01

Few areas of the world have western honey bee (Apis mellifera) colonies that are free of invasive parasites Nosema ceranae (fungi) and Varroa destructor (mites). Particularly detrimental is V. destructor; in addition to feeding on host haemolymph, these mites are important vectors of several viruses that are further implicated as contributors to honey bee mortality around the world. Thus, the biogeography and attendant consequences of viral communities in the absence of V. destructor are of significant interest. The island of Newfoundland, Province of Newfoundland and Labrador, Canada, is free of V. destructor; the absence of N. ceranae has not been confirmed. Of 55 Newfoundland colonies inspected visually for their strength and six signs of disease, only K-wing had prevalence above 5% (40/55 colonies = 72.7%). Similar to an earlier study, screenings again confirmed the absence of V. destructor, small hive beetles Aethina tumida (Murray), tracheal mites Acarapis woodi (Rennie), and Tropilaelaps spp. ectoparasitic mites. Of a subset of 23 colonies screened molecularly for viruses, none had Israeli acute paralysis virus, Kashmir bee virus, or sacbrood virus. Sixteen of 23 colonies (70.0%) were positive for black queen cell virus, and 21 (91.3%) had some evidence for deformed wing virus. No N. ceranae was detected in molecular screens of 55 colonies, although it is possible extremely low intensity infections exist; the more familiar N. apis was found in 53 colonies (96.4%). Under these conditions, K-wing was associated (positively) with colony strength; however, viruses and N. apis were not. Furthermore, black queen cell virus was positively and negatively associated with K-wing and deformed wing virus, respectively. Newfoundland honey bee colonies are thus free of several invasive parasites that plague operations in other parts of the world, and they provide a unique research arena to study independent pathology of the parasites that are present.

Varroa destructor virus 1: a new picorna-like virus in Varroa mites as well as honey bees

OpenAIRE

Ongus, J.R.

2006-01-01

Varroa destructor mite is an ectoparasite of the honey bee Apis mellifera. This species was recently differentiated from Varroa jacobsoni species which infests the Asian bee Apis cerana. Varroa mites feed entirely on the bee's haemolymph and have been associated with the spread of a number of viruses. Since the mites were first observed in Java, Indonesia in 1904, they have been reported in most regions of the world except Australia and the equatorial regions of Africa. V. destructor severely...

Selection of Entomopathogenic Fungi to Control Varroa destructor (Acari: Varroidae Selección de Hongos Entomopatógenos para el Control de Varroa destructor (Acari: Varroidae

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Marta Rodríguez

2009-12-01

Full Text Available The aim of this work was select entomopathogenic fungi tolerant to temperatures inside the brood area of honey bees (Apis mellifera for to control Varroa destructor. For this purpose, 50 Beauveria bassiana (Balsamo Vuillemin and 48 Metarhizium anisopliae (Metschn. Sorokin isolates were evaluated at 30 and 35 ºC. For each isolate, colony discs of 5 mm with mycelium were placed in the center of a Petri dish with Sabouraud dextrose agar (SDA medium. The dishes were incubated at 30 and 35 °C, without light. Radial growth of each colony was measured daily. All the B. bassiana and M. anisopliae isolates presented a lineal growth rate at a temperature of 30 ºC. However, at 35 ºC, most of the isolates did not grow, except three B. bassiana and 14 M. anisopliae isolates (P El objetivo de este trabajo fue seleccionar hongos entomopatógenos tolerantes a las temperaturas del nido de cría de las abejas (Apis mellifera, para ser utilizados en el control de Varroa destructor. Se evaluaron 50 aislamientos de Beauveria bassiana (Balsamo Vuillemin y 48 de Metarhizium anisopliae (Metschn. Sorokin a temperaturas de 30 y 35 ºC. Discos de agar de 5 mm de diámetro con micelio de colonias de cada aislamiento, se depositaron en el centro de placas Petri con medio agar Sabouraud dextrosa (ASD. Las placas fueron incubadas a 30 y 35 °C y oscuridad y diariamente se midió el radio de cada colonia. Todos los aislamientos de B. bassiana y M. anisopliae var. anisopliae presentaron una tendencia lineal a través del tiempo a temperaturas de incubación de 30 °C. A 35 °C la mayoría de los aislamientos no crecieron, excepto tres aislamientos de B. bassiana y 14 de M. anisopliae (p < 0,001. Estos aislamientos fueron seleccionados para realizar pruebas de patogenicidad sobre V. destructor, aplicando una suspensión de 10(7 conidias mL-1. El aislamiento más efectivo fue Qu-M845 de M. anisopliae (p = 0,0033, produjo una mortalidad de 85%. La capacidad patogénica de este

The Ditylenchus destructor genome provides new insights into the evolution of plant parasitic nematodes.

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Zheng, Jinshui; Peng, Donghai; Chen, Ling; Liu, Hualin; Chen, Feng; Xu, Mengci; Ju, Shouyong; Ruan, Lifang; Sun, Ming

2016-07-27

Plant-parasitic nematodes were found in 4 of the 12 clades of phylum Nematoda. These nematodes in different clades may have originated independently from their free-living fungivorous ancestors. However, the exact evolutionary process of these parasites is unclear. Here, we sequenced the genome sequence of a migratory plant nematode, Ditylenchus destructor We performed comparative genomics among the free-living nematode, Caenorhabditis elegans and all the plant nematodes with genome sequences available. We found that, compared with C. elegans, the core developmental control processes underwent heavy reduction, though most signal transduction pathways were conserved. We also found D. destructor contained more homologies of the key genes in the above processes than the other plant nematodes. We suggest that Ditylenchus spp. may be an intermediate evolutionary history stage from free-living nematodes that feed on fungi to obligate plant-parasitic nematodes. Based on the facts that D. destructor can feed on fungi and has a relatively short life cycle, and that it has similar features to both C. elegans and sedentary plant-parasitic nematodes from clade 12, we propose it as a new model to study the biology, biocontrol of plant nematodes and the interaction between nematodes and plants. © 2016 The Author(s).

Gene-knockdown in the honey bee mite Varroa destructor by a non-invasive approach: studies on a glutathione S-transferase

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Campbell Ewan M

2010-08-01

Full Text Available Abstract Background The parasitic mite Varroa destructor is considered the major pest of the European honey bee (Apis mellifera and responsible for declines in honey bee populations worldwide. Exploiting the full potential of gene sequences becoming available for V. destructor requires adaptation of modern molecular biology approaches to this non-model organism. Using a mu-class glutathione S-transferase (VdGST-mu1 as a candidate gene we investigated the feasibility of gene knockdown in V. destructor by double-stranded RNA-interference (dsRNAi. Results Intra-haemocoelic injection of dsRNA-VdGST-mu1 resulted in 97% reduction in VdGST-mu1 transcript levels 48 h post-injection compared to mites injected with a bolus of irrelevant dsRNA (LacZ. This gene suppression was maintained to, at least, 72 h. Total GST catalytic activity was reduced by 54% in VdGST-mu1 gene knockdown mites demonstrating the knockdown was effective at the translation step as well as the transcription steps. Although near total gene knockdown was achieved by intra-haemocoelic injection, only half of such treated mites survived this traumatic method of dsRNA administration and less invasive methods were assessed. V. destructor immersed overnight in 0.9% NaCl solution containing dsRNA exhibited excellent reduction in VdGST-mu1 transcript levels (87% compared to mites immersed in dsRNA-LacZ. Importantly, mites undergoing the immersion approach had greatly improved survival (75-80% over 72 h, approaching that of mites not undergoing any treatment. Conclusions Our findings on V. destructor are the first report of gene knockdown in any mite species and demonstrate that the small size of such organisms is not a major impediment to applying gene knockdown approaches to the study of such parasitic pests. The immersion in dsRNA solution method provides an easy, inexpensive, relatively high throughput method of gene silencing suitable for studies in V. destructor, other small mites and

Risk factors associated with the presence of Varroa destructor in honey bee colonies from east-central Argentina.

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Giacobino, A; Bulacio Cagnolo, N; Merke, J; Orellano, E; Bertozzi, E; Masciangelo, G; Pietronave, H; Salto, C; Signorini, M

2014-08-01

Varroa destructor is considered one of the major threats for worldwide apiculture. Damage caused by varroa mite includes body weight loss, malformation and weakening of the bees. It was also suggested as the main cause associated with colony winter mortality and as an important vector for several honey bee viruses. Little is known about multiple factors and their interaction affecting V. destructor prevalence in apiaries from South America. The aim of this study was to identify risk factors associated with V. destructor prevalence in east-central Argentina. Parasitic mite infestation level and colony strength measures were evaluated in 63 apiaries distributed in 4 different regions in east-central Argentina in a cross sectional study. Data regarding management practices in each apiary were collected by means of a questionnaire. A mixed-effects logistic regression model was constructed to associate management variables with the risk of achieving mite infestation higher than 3%. Colonies owned by beekeepers who indicated that they did not monitor colonies after mite treatment (OR=2.305; 95% CI: 0.944-5.629) nor disinfect hives woodenware material (OR=2.722; 95% CI: 1.380-5.565) were associated with an increased risk of presenting high intensity infestation with V. destructor (>3%). On the other hand, beekeepers who reported replacing more than 50% of the queens in their operation (OR=0.305; 95% CI: 0.107-0.872), feeding colonies protein substitute containing natural pollen (OR=0.348; 95% CI: 0.129-0.941) and feeding colonies High Fructose Corn Syrup (HFCS) (OR=0.108; 95% CI: 0.032-0.364), had colonies that were less likely to have V. destructor infestations above 3%, than beekeepers who did not report using these management practices. Further research should be conducted considering that certain management practices were associated to mite infestation level in order to improve the sanitary condition in the colonies. Epidemiological studies provide key information to

Exogenous Salicylic Acid Enhances the Resistance of Wheat Seedlings to Hessian Fly (Diptera: Cecidomyiidae) Infestation Under Heat Stress.

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Underwood, Joshua; Moch, John; Chen, Ming-Shun; Zhu, Lieceng

2014-10-01

Heat stress exerts significant impact on plant-parasite interactions. Phytohormones, such as salicylic acid (SA), play important roles in plant defense against parasite attacks. Here, we studied the impact of a combination of heat stress and exogenous SA on the resistance of wheat (Triticum aestivum L.) plants to the Hessian fly [Mayetiola destructor (Say)]. We found that the wheat cultivar 'Molly', which contains the resistance gene H13, lost resistance to Hessian fly under heat stress (40°C for 3 and 6 h), and that exogenous application of SA on Molly seedlings right before heat stress can partially prevent the loss of resistance of Molly plants under heat conditions. Our findings have significant implications for understanding the dynamics of plant-insect interactions in the context of heat stress. © 2014 Entomological Society of America.

Expression and Activity of Lysozyme in Apis Mellifera Carnica Brood Infested with Varroa Destructor

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Zaobidna Ewa A.

2017-12-01

Full Text Available Varroa destructor is a parasitic mite that attacks the honey bee, and previous studies have suggested that parasitosis caused by this mite is accompanied by immunosuppresion in the host. In this study, the effect of mite infestation on the expression of the lysozyme-1 (lys-1 gene and lysozyme activity in Apis mellifera carnica was determined. The experiment was carried out on the five developmental stages of honey bee workers and drones. Developmental and gender-related differences in gene expression and lysozyme activity were observed in a Varroa destructor-infested brood. The relative expression of the lys-1 gene increased in a infested worker brood and decreased in a drone brood except for P3 pupae. In the final stage of development, the lys-1 gene expression was significantly lower in infested newly emerged workers and drones. Changes in the relative expression of the lys-1 gene in infested individuals was poorly manifested at the level of enzyme activity, whereas at the two final stages of development (P5 and I there was a positive correlation between relative lys-1 expression and lysozyme activity in infested bees of both genders (r=0.988, r=0.999, respectively. The results of this study indicate that V. destructor influences the lysozyme-linked immune response in bees.

Varroa destructor Mites Can Nimbly Climb from Flowers onto Foraging Honey Bees.

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David T Peck

Full Text Available Varroa destructor, the introduced parasite of European honey bees associated with massive colony deaths, spreads readily through populations of honey bee colonies, both managed colonies living crowded together in apiaries and wild colonies living widely dispersed in natural settings. Mites are hypothesized to spread between most managed colonies via phoretically riding forager bees when they engage in robbing colonies or they drift between hives. However, widely spaced wild colonies show Varroa infestation despite limited opportunities for robbing and little or no drifting of bees between colonies. Both wild and managed colonies may also exchange mites via another mechanism that has received remarkably little attention or study: floral transmission. The present study tested the ability of mites to infest foragers at feeders or flowers. We show that Varroa destructor mites are highly capable of phoretically infesting foraging honey bees, detail the mechanisms and maneuvers by which they do so, and describe mite behaviors post-infestation.

Varroa destructor Mites Can Nimbly Climb from Flowers onto Foraging Honey Bees

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Smith, Michael L.; Seeley, Thomas D.

2016-01-01

Varroa destructor, the introduced parasite of European honey bees associated with massive colony deaths, spreads readily through populations of honey bee colonies, both managed colonies living crowded together in apiaries and wild colonies living widely dispersed in natural settings. Mites are hypothesized to spread between most managed colonies via phoretically riding forager bees when they engage in robbing colonies or they drift between hives. However, widely spaced wild colonies show Varroa infestation despite limited opportunities for robbing and little or no drifting of bees between colonies. Both wild and managed colonies may also exchange mites via another mechanism that has received remarkably little attention or study: floral transmission. The present study tested the ability of mites to infest foragers at feeders or flowers. We show that Varroa destructor mites are highly capable of phoretically infesting foraging honey bees, detail the mechanisms and maneuvers by which they do so, and describe mite behaviors post-infestation. PMID:27942015

Varroa destructor Mites Can Nimbly Climb from Flowers onto Foraging Honey Bees.

Science.gov (United States)

Peck, David T; Smith, Michael L; Seeley, Thomas D

2016-01-01

Varroa destructor, the introduced parasite of European honey bees associated with massive colony deaths, spreads readily through populations of honey bee colonies, both managed colonies living crowded together in apiaries and wild colonies living widely dispersed in natural settings. Mites are hypothesized to spread between most managed colonies via phoretically riding forager bees when they engage in robbing colonies or they drift between hives. However, widely spaced wild colonies show Varroa infestation despite limited opportunities for robbing and little or no drifting of bees between colonies. Both wild and managed colonies may also exchange mites via another mechanism that has received remarkably little attention or study: floral transmission. The present study tested the ability of mites to infest foragers at feeders or flowers. We show that Varroa destructor mites are highly capable of phoretically infesting foraging honey bees, detail the mechanisms and maneuvers by which they do so, and describe mite behaviors post-infestation.

Taxa de Infestação da Varroa destructor em colônias de Apis mellifera L. no Agreste Meridional de Pernambuco

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Deygnon Cavalcanti Clementino

2016-08-01

Full Text Available O presente trabalho teve como objetivo verificar a taxa de infestação da Varroa destructor em colônias de Apis mellifera L. proveniente de apiário no município de Lagoa do Ouro, Agreste Meridional de Pernambuco. A pesquisa foi realizada no mês de setembro de 2015. Participaram do estudo 15 colônias, em que foram coletadas em média 227 abelhas adultas de cada colmeia e acondicionadas em recipientes contendo álcool a 70%. Após as coletas a campo, as amostras foram transportadas para o laboratório de Biologia Animal da Universidade Federal Rural de Pernambuco/Unidade Acadêmica de Garanhuns, para a realização das análises e quantificação dos ácaros. Os resultados demonstraram que 100% das amostras estavam parasitadas com o ácaro, sendo que a média geral da taxa de infestação foi de 6,16%. O grau de infestação pela Varroa destructor observado nas colônias variou de 0,93% a 11,15%. Conclui-se que as colônias analisadas apresentam diferentes níveis de infestação pelo ácaro Varroa destructor.Infestation rate of Varroa destructor in Apis mellifera L. colonies in the South Agreste of PernambucoAbstract: This study aimed to verify the infestation rate of Varroa destructor in Apis mellifera L. colonies in the apiary from Lagoa do Ouro County, South Agreste of Pernambuco. The survey was conducted in September 2015. The study included 15 colonies, which were collected on average 227 adult bees in each hive and placed in vials containing 70% alcohol. After harvesting the field, the samples were transported to the Animal Biology Laboratory at the Federal Rural University of Pernambuco/Academic Unit of Garanhuns, to perform the analysis and quantification of mites. The results showed that 100% of the samples were infested with mites, and the overall average infestation rate was 6.16%. The degree of infestation by Varroa destructor observed in colonies ranged from 0.93% to 11.15%. It is concluded that the analyzed colonies have

Immunogene and viral transcript dynamics during parasitic Varroa destructor mite infection of developing honey bee (Apis mellifera) pupae.

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Kuster, Ryan D; Boncristiani, Humberto F; Rueppell, Olav

2014-05-15

The ectoparasitic Varroa destructor mite is a major contributor to the ongoing honey bee health crisis. Varroa interacts with honey bee viruses, exacerbating their pathogenicity. In addition to vectoring viruses, immunosuppression of the developing honey bee hosts by Varroa has been proposed to explain the synergy between viruses and mites. However, the evidence for honey bee immune suppression by V. destructor is contentious. We systematically studied the quantitative effects of experimentally introduced V. destructor mites on immune gene expression at five specific time points during the development of the honey bee hosts. Mites reproduced normally and were associated with increased titers of deformed wing virus in the developing bees. Our data on different immune genes show little evidence for immunosuppression of honey bees by V. destructor. Experimental wounding of developing bees increases relative immune gene expression and deformed wing virus titers. Combined, these results suggest that mite feeding activity itself and not immunosuppression may contribute to the synergy between viruses and mites. However, our results also suggest that increased expression of honey bee immune genes decreases mite reproductive success, which may be explored to enhance mite control strategies. Finally, our expression data for multiple immune genes across developmental time and different experimental treatments indicates co-regulation of several of these genes and thus improves our understanding of the understudied honey bee immune system. © 2014. Published by The Company of Biologists Ltd.

EFFICIENCY OF FORMING NUCLEUS COLONIES IN ORDER TO DECREASE POPULATION OF Varroa destructor (ANDRESON AND TRUEMAN, 2000 IN BEEHIVES

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Zlatko Puškadija

2003-12-01

Full Text Available Forming of nucleus colonies is efficient method in growth control of Varroa destructor population. Its goal is to decrease parasite’s pressure on bee colony. The advantage of this bio-technical measurement lays in its implement during vegetation season which delays use of the chemical resources for Varroa destructor control population in beehives for the post major honey harvest period. Nucleus colonies were formed from approx. half of sealed brood (35.5 ± 5.8 dm² and average of 5915 ± 912 bees. Results showed that there were 37.2 ± 5.6% mites removed from parental colonies. Minimum was 30.8%, and maximum was 45.5%. Due to such relatively small efficiency, this method cannot be recommended as unique, but it can be effective if it is applied in the post spring's honey harvest period as a part of growth reduction strategy of Varroa destructor population in beehive.

Inside Honeybee Hives: Impact of Natural Propolis on the Ectoparasitic Mite Varroa destructor and Viruses.

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Drescher, Nora; Klein, Alexandra-Maria; Neumann, Peter; Yañez, Orlando; Leonhardt, Sara D

2017-02-06

Social immunity is a key factor for honeybee health, including behavioral defense strategies such as the collective use of antimicrobial plant resins (propolis). While laboratory data repeatedly show significant propolis effects, field data are scarce, especially at the colony level. Here, we investigated whether propolis, as naturally deposited in the nests, can protect honeybees against ectoparasitic mites Varroa destructor and associated viruses, which are currently considered the most serious biological threat to European honeybee subspecies, Apis mellifera , globally. Propolis intake of 10 field colonies was manipulated by either reducing or adding freshly collected propolis. Mite infestations, titers of deformed wing virus (DWV) and sacbrood virus (SBV), resin intake, as well as colony strength were recorded monthly from July to September 2013. We additionally examined the effect of raw propolis volatiles on mite survival in laboratory assays. Our results showed no significant effects of adding or removing propolis on mite survival and infestation levels. However, in relation to V. destructor , DWV titers increased significantly less in colonies with added propolis than in propolis-removed colonies, whereas SBV titers were similar. Colonies with added propolis were also significantly stronger than propolis-removed colonies. These findings indicate that propolis may interfere with the dynamics of V. destructor -transmitted viruses, thereby further emphasizing the importance of propolis for honeybee health.

Inside Honeybee Hives: Impact of Natural Propolis on the Ectoparasitic Mite Varroa destructor and Viruses

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Drescher, Nora; Klein, Alexandra-Maria; Neumann, Peter; Yañez, Orlando; Leonhardt, Sara D.

2017-01-01

Social immunity is a key factor for honeybee health, including behavioral defense strategies such as the collective use of antimicrobial plant resins (propolis). While laboratory data repeatedly show significant propolis effects, field data are scarce, especially at the colony level. Here, we investigated whether propolis, as naturally deposited in the nests, can protect honeybees against ectoparasitic mites Varroa destructor and associated viruses, which are currently considered the most serious biological threat to European honeybee subspecies, Apis mellifera, globally. Propolis intake of 10 field colonies was manipulated by either reducing or adding freshly collected propolis. Mite infestations, titers of deformed wing virus (DWV) and sacbrood virus (SBV), resin intake, as well as colony strength were recorded monthly from July to September 2013. We additionally examined the effect of raw propolis volatiles on mite survival in laboratory assays. Our results showed no significant effects of adding or removing propolis on mite survival and infestation levels. However, in relation to V. destructor, DWV titers increased significantly less in colonies with added propolis than in propolis-removed colonies, whereas SBV titers were similar. Colonies with added propolis were also significantly stronger than propolis-removed colonies. These findings indicate that propolis may interfere with the dynamics of V. destructor-transmitted viruses, thereby further emphasizing the importance of propolis for honeybee health. PMID:28178181

Particularité du traitement à l'acide formique de varroa destructor ...

African Journals Online (AJOL)

Varroa destructor est un acarien parasite de l'abeille responsable d'un affaiblissement de la colonie et suspecté d'être impliqué dans les processus de mortalités hivernales. Pour contrôler ce parasite, plusieurs scientifiques et apiculteurs ont eu recours aux produits chimiques. En dépit de leur efficacité, la répétition de ces ...

Norwegian honey bees surviving Varroa destructor mite infestations by means of natural selection.

Science.gov (United States)

Oddie, Melissa A Y; Dahle, Bjørn; Neumann, Peter

2017-01-01

Managed, feral and wild populations of European honey bee subspecies, Apis mellifera , are currently facing severe colony losses globally. There is consensus that the ectoparasitic mite Varroa destructor , that switched hosts from the Eastern honey bee Apis cerana to the Western honey bee A. mellifera , is a key factor driving these losses. For >20 years, breeding efforts have not produced European honey bee colonies that can survive infestations without the need for mite control. However, at least three populations of European honey bees have developed this ability by means of natural selection and have been surviving for >10 years without mite treatments. Reduced mite reproductive success has been suggested as a key factor explaining this natural survival. Here, we report a managed A. mellifera population in Norway, that has been naturally surviving consistent V. destructor infestations for >17 years. Surviving colonies and local susceptible controls were evaluated for mite infestation levels, mite reproductive success and two potential mechanisms explaining colony survival: grooming of adult worker bees and Varroa Sensitive Hygiene (VSH): adult workers specifically detecting and removing mite-infested brood. Mite infestation levels were significantly lower in surviving colonies and mite reproductive success was reduced by 30% when compared to the controls. No significant differences were found between surviving and control colonies for either grooming or VSH. Our data confirm that reduced mite reproductive success seems to be a key factor for natural survival of infested A. mellifera colonies. However, neither grooming nor VSH seem to explain colony survival. Instead, other behaviors of the adult bees seem to be sufficient to hinder mite reproductive success, because brood for this experiment was taken from susceptible donor colonies only. To mitigate the global impact of V. destructor , we suggest learning more from nature, i.e., identifying the obviously

Norwegian honey bees surviving Varroa destructor mite infestations by means of natural selection

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Melissa A.Y. Oddie

2017-10-01

Full Text Available Background Managed, feral and wild populations of European honey bee subspecies, Apis mellifera, are currently facing severe colony losses globally. There is consensus that the ectoparasitic mite Varroa destructor, that switched hosts from the Eastern honey bee Apis cerana to the Western honey bee A. mellifera, is a key factor driving these losses. For >20 years, breeding efforts have not produced European honey bee colonies that can survive infestations without the need for mite control. However, at least three populations of European honey bees have developed this ability by means of natural selection and have been surviving for >10 years without mite treatments. Reduced mite reproductive success has been suggested as a key factor explaining this natural survival. Here, we report a managed A. mellifera population in Norway, that has been naturally surviving consistent V. destructor infestations for >17 years. Methods Surviving colonies and local susceptible controls were evaluated for mite infestation levels, mite reproductive success and two potential mechanisms explaining colony survival: grooming of adult worker bees and Varroa Sensitive Hygiene (VSH: adult workers specifically detecting and removing mite-infested brood. Results Mite infestation levels were significantly lower in surviving colonies and mite reproductive success was reduced by 30% when compared to the controls. No significant differences were found between surviving and control colonies for either grooming or VSH. Discussion Our data confirm that reduced mite reproductive success seems to be a key factor for natural survival of infested A. mellifera colonies. However, neither grooming nor VSH seem to explain colony survival. Instead, other behaviors of the adult bees seem to be sufficient to hinder mite reproductive success, because brood for this experiment was taken from susceptible donor colonies only. To mitigate the global impact of V. destructor, we suggest learning

Varroa destructor induces changes in the expression of immunity-related genes during the development of Apis mellifera worker and drone broods.

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Zaobidna, Ewa A; Żółtowska, Krystyna; Łopieńska-Biernat, Elżbieta

2017-12-20

The ectoparasitic mite Varroa destructor has emerged as the major pest of honeybees. Despite extensive research efforts, the pathogenesis of varroosis has not been fully explained. Earlier studies suggested that V. destructor infestation leads to the suppression of the host's immune system. The aim of this study was to analyze the immune responses of 14 genes in the Toll signal transduction pathways, including effector genes of antimicrobial peptides (AMPs), in developing Apis mellifera workers and drones infested with V. destructor. Four developmental stages (L5 larvae, prepupae, and 2 pupal stages) and newly emerged imagines were analyzed. In workers, the most significant changes were observed in L5 larvae in the initial stages of infestation. A significant increase in the relative expression of 10 of the 14 analyzed genes, including defensin-1 and defensin-2, was observed in infested bees relative to non-infested individuals. The immune response in drones developed at a slower rate. The expression of genes regulating cytoplasmic signal transduction increased in prepupae, whereas the expression of defensin-1 and defensin-2 effector genes increased in P3 pupae with red eyes. The expression of many immunity-related genes was silenced in successive life stages and in imagines, and it was more profound in workers than in drones. The results indicate that V. destructor significantly influences immune responses regulated by the Toll signal transduction pathway in bees. In infested bees, the observed changes in Toll pathway genes varied between life stages and the sexes.

Frequency of Varroa destructor, Nosema spp and Acarapis woodi in commercial colonies of bees (Apis mellifera in Yucatan, Mexico

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Martínez-Puc Jesús Froylán

2015-10-01

Full Text Available Today it has been observed that diseases affecting bees (Apis mellifera have caused significant economic losses in the European continent and in parts of the United States due to high mortality in honey bee colonies without a cause apparent, which is known as the syndrome of depopulation of hives. It is noteworthy that this mortality is not yet presented in Yucatan. In order to determine the frequency and levels of infestation Acarapis woodi and Varroa destructor, and the frequency and levels of infection Nosema spp. commercial colonies of bees (A. mellifera in Yucatan, was collected from June to December 2006, a total of 165 samples distributed in 13 towns of Yucatan. V. destructor frequency was 63.6%, with an average level of infestation of 2.85 ± 0.79 (mites / 100 bees. The frequency of Nosema spp. was 81.8%, with an average infection level = 1'234000 ± 118000 (spores / bee, the presence of A. woodi in the samples analyzed was detected. The existence of an association between V. destructor and Nosema spp was observed. (X2 = 6.53, df = 1, p = 0.01.

Challenges in devising economic spray thresholds for a major pest of Australian canola, the redlegged earth mite (Halotydeus destructor).

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Arthur, Aston L; Hoffmann, Ary A; Umina, Paul A

2015-10-01

A key component for spray decision-making in IPM programmes is the establishment of economic injury levels (EILs) and economic thresholds (ETs). We aimed to establish an EIL for the redlegged earth mite (Halotydeus destructor Tucker) on canola. Complex interactions between mite numbers, feeding damage and plant recovery were found, highlighting the challenges in linking H. destructor numbers to yield. A guide of 10 mites plant(-1) was established at the first-true-leaf stage; however, simple relationships were not evident at other crop development stages, making it difficult to establish reliable EILs based on mite number. Yield was, however, strongly associated with plant damage and plant densities, reflecting the impact of mite feeding damage and indicating a plant-based alternative for establishing thresholds for H. destructor. Drawing on data from multiple field trials, we show that plant densities below 30-40 plants m(-2) could be used as a proxy for mite damage when reliable estimates of mite densities are not possible. This plant-based threshold provides a practical tool that avoids the difficulties of accurately estimating mite densities. The approach may be applicable to other situations where production conditions are unpredictable and interactions between pests and plant hosts are complex. © 2015 Society of Chemical Industry.

Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA

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González-Cabrera, Joel; Rodríguez-Vargas, Sonia; Davies, T. G. Emyr; Field, Linda M.; Schmehl, Daniel; Ellis, James D.; Krieger, Klemens; Williamson, Martin S.

2016-01-01

The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V) of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes. PMID:27191597

Identification and gene-silencing of a putative odorant receptor transcription factor in Varroa destructor: possible role in olfaction.

Science.gov (United States)

Singh, N K; Eliash, N; Stein, I; Kamer, Y; Ilia, Z; Rafaeli, A; Soroker, V

2016-04-01

The ectoparasitic mite Varroa destructor is one of the major threats to apiculture. Using a behavioural choice bioassay, we determined that phoretic mites were more successful in reaching a bee than reproductive mites, suggesting an energy trade-off between reproduction and host selection. We used both chemo-ecological and molecular strategies to identify the regulation of the olfactory machinery of Varroa and its association with reproduction. We focused on transcription regulation. Using primers designed to the conserved DNA binding region of transcription factors, we identified a gene transcript in V. destructor homologous to the pheromone receptor transcription factor (PRTF) gene of Pediculus humanus corporis. Quantitative PCR (qPCR) revealed that this PRTF-like gene transcript is expressed in the forelegs at higher levels than in the body devoid of forelegs. Subsequent comparative qPCR analysis showed that transcript expression was significantly higher in the phoretic as compared to the reproductive stage. Electrophysiological and behavioural studies revealed a reduction in the sensitivity of PRTF RNA interference-silenced mites to bee headspace, consistent with a reduction in the mites' ability to reach a host. In addition, vitellogenin expression was stimulated in PRTF-silenced mites to similar levels as found in reproductive mites. These data shed light upon the regulatory mechanism of host chemosensing in V. destructor. © 2016 The Royal Entomological Society.

Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA.

Science.gov (United States)

González-Cabrera, Joel; Rodríguez-Vargas, Sonia; Davies, T G Emyr; Field, Linda M; Schmehl, Daniel; Ellis, James D; Krieger, Klemens; Williamson, Martin S

2016-01-01

The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V) of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes.

Naturally selected honey bee (Apis mellifera) colonies resistant to Varroa destructor do not groom more intensively

NARCIS (Netherlands)

Kruitwagen, Astrid; Langevelde, van Frank; Dooremalen, van Coby; Blacquière, Tjeerd

2017-01-01

The ectoparasitic mite Varroa destructor is an important cause of high colony losses of the honey bee Apis mellifera. In The Netherlands, two resistant A. mellifera populations developed naturally after ceasing varroa control. As a result, mite infestation levels of the colonies of these populations

Éster de sacarose no controle do Varroa destructor em abelhas africanizadas = Sucrose ester in the control of Varroa destructor in Africanized honeybees

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Guido Laércio Castagnino

2009-07-01

Full Text Available O presente trabalho teve como objetivo verificar o efeito do éster de sacarose no controle da infestação do ácaro Varroa destructor em abelhas africanizadas. Nos testes “in vitro”, testou-se o produto em abelhas e ácaros com cinco concentrações diluídas em água (T0: 100% de água destilada; T1: 0,5%; T2: 1%; T3: 2,0%; T4: 5% e T5: 10% de éster de sacarose. Nos testes de campo, o delineamento experimental utilizado foi inteiramente casualizado, com quatro tratamentos e sete repetições, totalizando 28 colônias, sendo sete delas como controle, sete com 0,1% de éster de sacarose, sete com 0,2% de éster de sacarosee sete colmeias com 0,5% éster de sacarose, diluídas em água. Nos testes “in vitro” com concentração de 0,5%, o éster de sacarose promoveu a mortalidade dos ácaros e das abelhas. Os testes em campo demonstraram que o produto reduziu a infestação do Varroa destructorem abelhas na concentração de 0,2% e pode ser uma ferramenta no controle dessa praga. Nas concentrações de 0,1; 0,2 e 0,5%, não prejudicou o desenvolvimento de área de cria aberta, operculada e de alimento estocado na colmeia, sugerindo que não é tóxico para as abelhas.This study aimed to determine the effect of sucrose ester on the control of Varroa destructor mite infestation in Africanized honeybees. For the in vitro experiments, the product was tested in bees and mites at five concentrations obtained through dilution in water (T0: 100% distilled water; T1: 0.5%; T2: 1%; T3: 2%; T4: 5%; and T5: 10% sucrose ester. For the field studies, the experimental design was completely randomized, with four treatments and seven replicates, totaling 28 colonies, from which seven were the controls,seven were treated with 0.1% sucrose ester, seven with 0.2% sucrose ester, and seven hives with 0.5% sucrose ester diluted in water. In the in vitro study, the sucrose ester at 0.5% concentration caused mite and bee mortality. In the field tests, the

Genomic survey of the ectoparasitic mite Varroa destructor, a major pest of the honey bee Apis mellifera

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Elsik Chris

2010-10-01

Full Text Available Abstract Background The ectoparasitic mite Varroa destructor has emerged as the primary pest of domestic honey bees (Apis mellifera. Here we present an initial survey of the V. destructor genome carried out to advance our understanding of Varroa biology and to identify new avenues for mite control. This sequence survey provides immediate resources for molecular and population-genetic analyses of Varroa-Apis interactions and defines the challenges ahead for a comprehensive Varroa genome project. Results The genome size was estimated by flow cytometry to be 565 Mbp, larger than most sequenced insects but modest relative to some other Acari. Genomic DNA pooled from ~1,000 mites was sequenced to 4.3× coverage with 454 pyrosequencing. The 2.4 Gbp of sequencing reads were assembled into 184,094 contigs with an N50 of 2,262 bp, totaling 294 Mbp of sequence after filtering. Genic sequences with homology to other eukaryotic genomes were identified on 13,031 of these contigs, totaling 31.3 Mbp. Alignment of protein sequence blocks conserved among V. destructor and four other arthropod genomes indicated a higher level of sequence divergence within this mite lineage relative to the tick Ixodes scapularis. A number of microbes potentially associated with V. destructor were identified in the sequence survey, including ~300 Kbp of sequence deriving from one or more bacterial species of the Actinomycetales. The presence of this bacterium was confirmed in individual mites by PCR assay, but varied significantly by age and sex of mites. Fragments of a novel virus related to the Baculoviridae were also identified in the survey. The rate of single nucleotide polymorphisms (SNPs in the pooled mites was estimated to be 6.2 × 10-5per bp, a low rate consistent with the historical demography and life history of the species. Conclusions This survey has provided general tools for the research community and novel directions for investigating the biology and control of

Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA.

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Joel González-Cabrera

Full Text Available The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes.

Comparative testing of different methods for evaluation of Varroa destructor infestation of honey bee colonies

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Nikolay D. Dobrynin

2011-09-01

Full Text Available Different methods for evaluation of the degree of Varroa destructor infestation of honey bee colonies were tested. The methods using in vivo evaluation were the most sparing for the bees but less precise. The methods using evaluation with the killing of the bees or brood were the most precise but less sparing for bees.

Norwegian honey bees surviving Varroa destructor mite infestations by means of natural selection

OpenAIRE

Oddie, Melissa AY; Dahle, Bjørn Steinar; Neumann, Peter

2017-01-01

Background Managed, feral and wild populations of European honey bee subspecies, Apis mellifera, are currently facing severe colony losses globally. There is consensus that the ectoparasitic mite Varroa destructor, that switched hosts from the Eastern honey bee Apis cerana to the Western honey bee A. mellifera, is a key factor driving these losses. For >20 years, breeding efforts have not produced European honey bee colonies that can survive infestations without the need for mite control....

Study of temperature-growth interactions of entomopathogenic fungi with potential for control of Varroa destructor (Acari: Mesostigmata) using a nonlinear model of poikilotherm development.

Science.gov (United States)

Davidson, G; Phelps, K; Sunderland, K D; Pell, J K; Ball, B V; Shaw, K E; Chandler, D

2003-01-01

To investigate the thermal biology of entomopathogenic fungi being examined as potential microbial control agents of Varroa destructor, an ectoparasite of the European honey bee Apis mellifera. Colony extension rates were measured at three temperatures (20, 30 and 35 degrees C) for 41 isolates of entomopathogenic fungi. All of the isolates grew at 20 and 30 degrees C but only 11 isolates grew at 35 degrees C. Twenty-two isolates were then selected on the basis of appreciable growth at 30-35 degrees C (the temperature range found within honey bee colonies) and/or infectivity to V. destructor, and their colony extension rates were measured at 10 temperatures (12.5-35 degrees C). This data were then fitted to Schoolfield et al. [J Theor Biol (1981)88:719-731] re-formulation of the Sharpe and DeMichele [J Theor Biol (1977)64:649-670] model of poikilotherm development. Overall, this model accounted for 87.6-93.9% of the data variance. Eleven isolates exhibited growth above 35 degrees C. The optimum temperatures for extension rate ranged from 22.9 to 31.2 degrees C. Only three isolates exhibited temperature optima above 30 degrees C. The super-optimum temperatures (temperature above the optimum at which the colony extension rate was 10% of the maximum rate) ranged from 31.9 to 43.2 degrees C. The thermal requirements of the isolates examined against V. destructor are well matched to the temperatures in the broodless areas of honey bee colonies, and a proportion of isolates, should also be able to function within drone brood areas. Potential exists for the control of V. destructor with entomopathogenic fungi in honey bee colonies. The methods employed in this study could be utilized in the selection of isolates for microbial control prior to screening for infectivity and could help in predicting the activity of a fungal control agent of V. destructor under fluctuating temperature conditions.

Varroa destructor virus 1: a new picorna-like virus in Varroa mites as well as honey bees

NARCIS (Netherlands)

Ongus, J.R.

2006-01-01

Varroa destructor mite is an ectoparasite of the honey bee Apis mellifera. This species was recently differentiated from Varroa jacobsoni species which infests the Asian bee Apis cerana. Varroa mites feed entirely on the bee's haemolymph and have been associated with the spread of a number of

Evaluación de extractos de ocho especies vegetales en el control de mildeo velloso (Peronospora destructor Berk en cebolla de bulbo (Allium cepa L.

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Pedro Enrique Cubides-Hernández

2015-01-01

Full Text Available Extractos de ocho especies vegetales: eucalipto (Eucalytus globulus, cola de caballo (Equisetum bogotense, ortiga (Urtica urens, manzanilla (Matricaria chamomilla, caléndula (Calendula officinalis, yerbabuena (Menta viridis, ajo (Allium sativum y clavo (Syzygum aromaticum, preparados por el método de decocción (100 g/l, fueron evaluados en cuanto a su eficiencia en el control de P. destructor en cebolla de bulbo. Se utilizó el diseño experimental de bloques al azar con cuatro repeticiones y siete aplicaciones (52, 60, 68, 76,84, 92 y 100 días después del trasplante, incluyendo un testigo químico Ridomil (metalaxil + mancozeb (2 g/l y el testigo absoluto; se evaluaron la incidencia y severidad de P. destructor, y el número y el peso de bulbos cosechados. El ANOVA mostró que de las siete aplicaciones realizadas, la última presentó efectos estadísticos en el control de la incidencia y severidad de P. destructor. El extracto de manzanilla superó al Ridomil en el control de la incidencia y severidad de P. destructor sin diferencias estadísticas entre sí, y fue significativamente mejor al observado con los extractos de eucalipto, cola de caballo, caléndula y el testigo; el extracto de manzanilla superó al testigo químico en el número y peso de bulbos de cebolla sin presentar diferencias estadísticas, y fue significativamente mejor al obtenido con los extractos de eucalipto, cola de caballo, ortiga, caléndula, yerbabuena, clavo y el testigo absoluto. El extracto de manzanilla es una alternativa ecológica que se debe tener en cuenta en el manejo integrado de P. destructor en cebolla de bulbo.

Virulence and site of infection of the fungus, Hirsutella thompsonii, to the honey bee ectoparasitic mite, Varroa destructor.

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Peng, Christine Y S; Zhou, Xinsheng; Kaya, Harry K

2002-11-01

The Varroa mite, Varroa destructor, is recognized as the most serious pest of both managed and feral Western honey bee (Apis mellifera) in the world. The mite has developed resistance to fluvalinate, an acaricide used to control it in beehives, and fluvalinate residues have been found in the beeswax, necessitating an urgent need to find alternative control measures to suppress this pest. Accordingly, we investigated the possibility of using the fungus, Hirsutella thompsonii, as a biocontrol agent of the Varroa mite. Among the 9 isolates of H. thompsonii obtained from the University of Florida and the USDA, only the 3 USDA isolates (ARSEF 257, 1947 and 3323) were infectious to the Varroa mite in laboratory tests. The mite became infected when it was allowed to walk on a sporulating H. thompsonii culture for 5 min. Scanning electron micrographs revealed that the membranous arolium of the mite leg sucker is the focus of infection where the fungal conidia adhered and germinated. The infected mites died from mycosis, with the lethal times to kill 50% (LT(50)s) dependent on the fungal isolates. Thus, the LT(50)s were 52.7, 77.2, and 96.7h for isolates 3323, 257, and 1947, respectively. Passage of H. thompsonii through Varroa mite three times significantly reduced the LT(50)s of isolates 257 and 1947 (P<0.05) but not the LT(50) of isolate 3323. The fungus did not infect the honey bee in larval, prepupal, pupal, and adult stages under our laboratory rearing conditions. Our encouraging results suggest that some isolates of H. thompsonii have the potential to be developed as a biocontrol agent for V. destructor. However, fungal infectivity against the mites under beehive conditions needs to be studied before any conclusion can be made.

Produtos naturais para o controle do ácaro Varroa destructor em abelhas africanizadas

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Guido Laércio Bragança Castagnino

2012-06-01

Full Text Available O objetivo deste trabalho foi avaliar os efeitos do ácido oxálico e de óleos essenciais de plantas no controle da infestação pelo ácaro Varroa destructor em colônias de Apis mellifera africanizadas. O experimento foi realizado em delineamento inteiramente casualizado, em 30 colônias, com seis tratamentos e cinco repetições. As colmeias foram tratadas com óleos essenciais de arruda (Ruta graveolens, eucalipto (Eucalyptus spp. e hortelã (Mentha piperita, além de timol, ácido oxálico e do tratamento controle sem aplicação de produtos. Foram avaliadas a mortalidade de varroas e as taxas de mortalidade de crias e de infestação de varroas em crias e em abelhas adultas, antes e depois da aplicação de cada produto. O ácido oxálico e os óleos de arruda, timol, eucalipto e de hortelã reduziram a mortalidade de crias parasitadas pelo ácaro em 92,1, 83,3, 81,7, 86,4 e 81,3%, respectivamente. O tratamento com ácido oxálico reduziu em 87,4% a infestação de varroas em abelhas adultas. O uso desses produtos é eficiente na redução da mortalidade de crias de A. mellifera parasitadas por V. destructor.

Varroa destructor resistance of honey bees in Hawaii, USA, that express various levels of Varroa sensitive hygiene (VSH)

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The Big Island of Hawaii, USA, supports an important honey bee (Apis mellifera) queen rearing industry that has been threatened by Varroa destructor since 2008. Miticides widely used to manage mites are known to interfere with queen rearing and sperm production. We investigated whether bees bred for...

Assessing in Vitro Acaricidal Effect and Joint Action of a Binary Mixture Between Essential Oil Compounds (Thymol, Phellandrene, Eucalyptol, Cinnamaldehyde, Myrcene, Carvacrol Over Ectoparasitic Mite Varroa Destructor (Acari: Varroidae

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Brasesco Constanza

2017-12-01

Full Text Available Varroa destructor (Anderson & Trueman, 2000 causes the most important parasitosis of beekeeping in the world. For this reason, prevention is needed to avoid colony death. The most typical treatments involve synthetic acaricides. However, the use of these acaricides results in the emergence of resistant populations of mites to these products and in the appearances of drug residues in products of the hives. Compounds of essential oils have emerged as an alternative to traditional acaricides; however the toxicity produced by these mixtures is currently poorly explored. The aim of this work was to assess, by means of in vitro tests with adult bees, how acaricidal action and toxic interactions in a binary mixture of essential oil compounds (Thymol, Phellandrene, Eucalyptol, Cinnamaldehyde, Myrcene, and Carvacrol affect V. destructor. Calculations of LC50 ’s of the individual compounds on A. mellifera and V. destructor made clear that the toxic effect of each compound is different for both species. Thymol and Phellandrene turned out to be lethal for mites at lower concentrations than for bees. The binary mixture of these two substances presented a different toxicity than one produced by each pure compound, as it was highly selective for mites in bioassays at 24 hours through complete exposure to both A. mellifera and V. destructor. These results make such formulations optimal substances to be considered as alternative controls for the parasitosis.

An amino acid substitution (L925V associated with resistance to pyrethroids in Varroa destructor.

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Joel González-Cabrera

Full Text Available The Varroa mite, Varroa destructor, is an important pest of honeybees and has played a prominent role in the decline in bee colony numbers over recent years. Although pyrethroids such as tau-fluvalinate and flumethrin can be highly effective in removing the mites from hives, their intensive use has led to many reports of resistance. To investigate the mechanism of resistance in UK Varroa samples, the transmembrane domain regions of the V. destructor voltage-gated sodium channel (the main target site for pyrethroids were PCR amplified and sequenced from pyrethroid treated/untreated mites collected at several locations in Central/Southern England. A novel amino acid substitution, L925V, was identified that maps to a known hot spot for resistance within the domain IIS5 helix of the channel protein; a region that has also been proposed to form part of the pyrethroid binding site. Using a high throughput diagnostic assay capable of detecting the mutation in individual mites, the L925V substitution was found to correlate well with resistance, being present in all mites that had survived tau-fluvalinate treatment but in only 8 % of control, untreated samples. The potential for using this assay to detect and manage resistance in Varroa-infected hives is discussed.

Behavioral Modulation of Infestation by Varroa destructor in Bee Colonies. Implications for Colony Stability.

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de Figueiró Santos, Joyce; Coelho, Flávio Codeço; Bliman, Pierre-Alexandre

2016-01-01

Colony Collapse Disorder (CCD) has become a global problem for beekeepers and for the crops that depend on bee pollination. While many factors are known to increase the risk of colony collapse, the ectoparasitic mite Varroa destructor is considered to be the most serious one. Although this mite is unlikely to cause the collapse of hives itself, it is the vector for many viral diseases which are among the likely causes for Colony Collapse Disorder. The effects of V. destructor infestation differ from one part of the world to another, with greater morbidity and higher colony losses in European honey bees (EHB) in Europe, Asia and North America. Although this mite has been present in Brazil for many years, there have been no reports of colony losses amongst Africanized Honey Bees (AHB). Studies carried out in Mexico have highlighted different behavioral responses by the AHB to the presence of the mite, notably as far as grooming and hygienic behavior are concerned. Could these explain why the AHB are less susceptible to Colony Collapse Disorder? In order to answer this question, we have developed a mathematical model of the infestation dynamics to analyze the role of resistance behavior by bees in the overall health of the colony, and as a consequence, its ability to face epidemiological challenges.

Behavioral Modulation of Infestation by Varroa destructor in Bee Colonies. Implications for Colony Stability.

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Joyce de Figueiró Santos

Full Text Available Colony Collapse Disorder (CCD has become a global problem for beekeepers and for the crops that depend on bee pollination. While many factors are known to increase the risk of colony collapse, the ectoparasitic mite Varroa destructor is considered to be the most serious one. Although this mite is unlikely to cause the collapse of hives itself, it is the vector for many viral diseases which are among the likely causes for Colony Collapse Disorder. The effects of V. destructor infestation differ from one part of the world to another, with greater morbidity and higher colony losses in European honey bees (EHB in Europe, Asia and North America. Although this mite has been present in Brazil for many years, there have been no reports of colony losses amongst Africanized Honey Bees (AHB. Studies carried out in Mexico have highlighted different behavioral responses by the AHB to the presence of the mite, notably as far as grooming and hygienic behavior are concerned. Could these explain why the AHB are less susceptible to Colony Collapse Disorder? In order to answer this question, we have developed a mathematical model of the infestation dynamics to analyze the role of resistance behavior by bees in the overall health of the colony, and as a consequence, its ability to face epidemiological challenges.

Expression and Activity of Lysozyme in Apis Mellifera Carnica Brood Infested with Varroa Destructor

OpenAIRE

Zaobidna Ewa A.; Żółtowska Krystyna; Łopieńska-Biernat Elżbieta

2017-01-01

Varroa destructor is a parasitic mite that attacks the honey bee, and previous studies have suggested that parasitosis caused by this mite is accompanied by immunosuppresion in the host. In this study, the effect of mite infestation on the expression of the lysozyme-1 (lys-1) gene and lysozyme activity in Apis mellifera carnica was determined. The experiment was carried out on the five developmental stages of honey bee workers and drones. Developmental and gender-related differences in gene e...

Primary structure of Lep d I, the main Lepidoglyphus destructor allergen.

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Varela, J; Ventas, P; Carreira, J; Barbas, J A; Gimenez-Gallego, G; Polo, F

1994-10-01

The most relevant allergen of the storage mite Lepidoglyphus destructor (Lep d I) has been characterized. Lep d I is a monomer protein of 13273 Da. The primary structure of Lep d I was determined by N-terminal Edman degradation and partially confirmed by cDNA sequencing. Sequence polymorphism was observed at six positions, with non-conservative substitutions in three of them. No potential N-glycosylation site was revealed by peptide sequencing. The 125-residue sequence of Lep d I shows approximately 40% identity (including the six cysteines) with the overlapping regions of group II allergens from the genus Dermatophagoides, which, however, do not share common allergenic epitopes with Lep d I.

Interactive effect of reduced pollen availability and Varroa destructor infestation limits growth and protein content of young honey bees

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Dooremalen, van C.; Stam, E.; Gerritsen, L.J.M.; Cornelissen, B.; Steen, van der J.J.M.; Langevelde, van F.; Blacquiere, T.

2013-01-01

Varroa destructor in combination with one or more stressors, such as low food availability or chemical exposure, is considered to be one of the main causes for honey bee colony losses. We examined the inter-active effect of pollen availability on the protein content and body weight of young bees

LD50 and repellent effects of essential oils from Argentinian wild plant species on Varroa destructor.

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Ruffinengo, Sergio; Eguaras, Martin; Floris, Ignazio; Faverin, Claudia; Bailac, Pedro; Ponzi, Marta

2005-06-01

The repellent and acaricidal effects of some essential oils from the most typical wild plant species of northern Patagonia, Argentina, on Varroa destructor Anderson & Trueman were evaluated using a complete exposure test. Honey bees, Apis mellifera L., and mites (five specimens of each per dish) were introduced in petri dishes having different oil concentrations (from 0.1 to 25 micro per cage). Survival of bees and mites was registered after 24, 48, and 72 h. An attraction/repellence test was performed using a wax tube impregnated with essential oil and another tube containing wax only. The lowest LD50 values for mites were registered for Acantholippia seriphioides (A. Gray) Mold. (1.27 microl per cage) and Schinus molle L. (2.65 microl per cage) after 24 h, and for Wedelia glauca (Ortega) O. Hoffm. ex Hicken (0.59 microl per cage) and A. seriphioides (1.09 microl per cage) after 72 h of treatment. The oil with the highest selectivity ratio (A. mellifera LD50/V. destructor LD50) was the one extracted from S. molle (>16). Oils of Lippia junelliana (Mold.) Troncoso, Minthostachys mollis (HBK) Grieseb., and Lippia turbinata Grieseb. mixed with wax had repellent properties. None of the oils tested had attractive effects on Varroa mites.

Infestação do ácaro Varroa destructor em colônias de abelhas africanizadas (Apis mellifera L. no Semiárido potiguar, Nordeste do Brasil

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Stephano Bismark Lopes Cavalcante Moreira

2017-02-01

Full Text Available O presente trabalho teve como objetivo analisar os índices de infestação pelo ácaro Varroa. destructor em colônias de abelhas africanizadas (Apis mellifera de apiários dos municípios de Encanto e de Marcelino Vieira, estado do Rio Grande do Norte. A pesquisa foi conduzida no período de setembro a dezembro de 2014, sendo coletadas em média de 100 a 200 abelhas adultas (nutrizes retiradas dos quadros centrais do ninho com crias de cada colmeia, aprisionadas em recipientes contendo 100 mL de álcool a 70% e encaminhadas para laboratório do Instituto Federal do Rio Grande do Norte (IFRN, para a contagem das abelhas e dos ácaros. Os resultados apresentaram ocorrência do ácaro V. destructor em todos apiários e em todas colmeias analisados, obtendo uma infestação média de 7,24% em Encanto e de 5,25% em Marcelino Vieira, níveis de infestação baixos (<15%, portanto, não acarretando risco às colônias.Varroa destructor mite infestation in colonies of Africanized honey bees (Apis mellifera L. in the potiguar Semi-arid region, Northeastern BrazilAbstract: The goal of the present work was to analyze the rates of infestation by Varroa. destructor mite in Africanized honeybees (Apis mellifera colonies from apiaries in Encanto and Marcelino Vieira cities, state of Rio Grande do Norte. The research was conducted during the period from September to December 2014. In average 100 to 200 adult bees (nursing honey bee workers were collected from the brood chamber over center frames of with brood of each hive surveyed, trapped in containers containing 100 mL of 70% alcohol and sent to the laboratory of the Federal Institute of Rio Grande do Norte (IFRN for the counting of bees and mites. The results showed an occurrence of the Varroa destructor mite in all apiaries and in all hives analyzed, obtaining an average infestation of 7.24% in Encanto city and 5.25% in Marcelino Vieira city, low infestation levels (<15%, without risk to the colonies.

Immunotherapy with the storage mite lepidoglyphus destructor.

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Armentia-Medina, A; Tapias, J A; Martín, J F; Ventas, P; Fernández, A

1995-01-01

We carried out a double-blind clinical trial of immunotherapy on 35 patients sensitized to the storage mite Lepidoglyphus destructor (Ld). Before and after 12 months of specific hyposensitization (Abelló Lab., Spain) we performed in vivo (skin tests with Ld, methacholine and challenge tests), and in vitro tests (specific IgE, IgG, IgG1 and IgG4 to Ld and specific IgE, IgG, IgG1 and IgG4 to their major allergen Lep dI). We also monitored the efficacy and safety of the immunotherapy with clinical and analytical controls (symptoms and medication score, detection of immune complexes). After therapy we found a significant decrease in specific skin reactivity, dose of positive challenge tests, and hyperresponsiveness to methacholine. Sputum eosinophilia decreased. Specific IgE to Ld was increased and we also observed an increase in specific IgG1 and IgG4 to Ld and Lep DI. The placebo group showed no changes in these variables. There were no severe secondary reactions after treatment with the extract. Patients-self-evaluation was favourable and their labour absence decreased. No development of circulating immune complexes was associated with this immunotherapy.

Sélection d'abeilles résistantes à Varroa destructor en Amérique du Nord.

OpenAIRE

Rinderer , Thomas E.; Harris , Jeffrey W.; Hunt , Gregory J.; De Guzman , Lilia I.

2010-01-01

International audience; Breeding for resistance to Varroa destructor in North America provides the long-term solution to the economic troubles the mite brings. This review reports the development of two breeding successes that have produced honey bees of commercial quality that do not require pesticide treatment to control Varroa, highlights other traits that could be combined to increase resistance and examines the potential uses of marker-assisted selection (MAS) for breeding for Varroa res...

Queen survival and oxalic acid residues in sugar stores after summer application against Varroa destructor in honey bees (Apis mellifera)

NARCIS (Netherlands)

Cornelissen, B.; Donders, J.N.L.C.; Stratum, van P.; Blacquière, T.; Dooremalen, van C.

2012-01-01

Methods using oxalic acid (OA) to control Varroa destructor in honey bee (Apis mellifera) colonies are widely applied. In this study, the effects of an OA spray application in early summer on the survival of young and old queens, and on OA residues in sugar stores were investigated. A questionnaire

Characterization of the Copy Number and Variants of Deformed Wing Virus (DWV in the Pairs of Honey Bee Pupa and Infesting Varroa destructor or Tropilaelaps mercedesae

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Yunfei Wu

2017-08-01

Full Text Available Recent honey bee colony losses, particularly during the winter, have been shown to be associated with the presence of both ectoparasitic mites and Deformed Wing Virus (DWV. Whilst the role of Varroa destructor mites as a viral vector is well established, the role of Tropilaelaps mercedesae mites in viral transmission has not been fully investigated. In this study, we tested the effects that V. destructor and T. mercedesae infestation have on fluctuation of the DWV copy number and alteration of the virus variants in honey bees by characterizing individual pupae and their infesting mites. We observed that both mite species were associated with increased viral copy number in honey bee pupae. We found a positive correlation between DWV copy number in pupae and copy number in infesting mites, and the same DWV type A variant was present in either low or high copy number in both honey bee pupae and infesting V. destructor. These data also suggest that variant diversity is similar between honey bee pupae and the mites that infest them. These results support a previously proposed hypothesis that DWV suppresses the honey bee immune system when virus copy number reaches a specific threshold, promoting greater replication.

Regular dorsal dimples and damaged mites of Varroa destructor in some Iranian honey bees (Apis mellifera)

OpenAIRE

Ardestani, Masoud M.; Ebadi, Rahim; Tahmasbi, Gholamhossein

2011-01-01

The frequency of damaged Varroa destructor Anderson and Trueman (Mesostigmata: Varroidae) found on the bottom board of hives of the honey bee, Apis mellifera L. (Hymenoptera: Apidae) has been used as an indicator of the degree of tolerance or resistance of honey bee colonies against mites. However, it is not clear that this measure is adequate. These injuries should be separated from regular dorsal dimples that have a developmental origin. To investigate damage to Varroa mites and regular dor...

Viral epidemiology of the adult Apis Mellifera infested by the Varroa destructor mite.

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Bernardi, Sara; Venturino, Ezio

2016-05-01

The ectoparasitic mite Varroa destructor has become one of the major worldwide threats for apiculture. Varroa destructor attacks the honey bee Apis mellifera weakening its host by sucking hemolymph. However, the damage to bee colonies is not strictly related to the parasitic action of the mite but it derives, above all, from its action as vector increasing the transmission of many viral diseases such as acute paralysis (ABPV) and deformed wing viruses (DWV), that are considered among the main causes of CCD (Colony Collapse Disorder). In this work we discuss an [Formula: see text] model that describes how the presence of the mite affects the epidemiology of these viruses on adult bees. The acronym [Formula: see text] means that the disease affects both populations. In fact it accounts for the bee and mite populations, that are each divided among the S (susceptible) and I (infected) states. We characterize the system behavior, establishing that ultimately either only healthy bees survive, or the disease becomes endemic and mites are wiped out. Another dangerous alternative is the Varroa invasion scenario with the extinction of healthy bees. The final possible configuration is the coexistence equilibrium in which honey bees share their infected hive with mites. The analysis is in line with some observed facts in natural honey bee colonies. Namely, these diseases are endemic. Further, if the mite population is present, necessarily the viral infection occurs. The findings of this study indicate that a low horizontal transmission rate of the virus among honey bees in beehives will help in protecting bee colonies from Varroa infestation and viral epidemics.

Using an in vitro system for maintaining Varroa destructor mites on Apis mellifera hosts: Studies of mite longevity and feeding behavior

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Varroa destructor mites (Vd) are ectoparasites of Apis mellifera honey bees, and the damage they inflict on hosts is a likely causative factor of recent poor honey bee colony performance. Much research has produced an arsenal of control agents against Vd, which have become resistant to many chemical...

Pyrethroid resistance discovered in a major agricultural pest in southern Australia: the redlegged earth mite Halotydeus destructor (Acari: Penthaleidae).

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Umina, Paul A

2007-12-01

The redlegged earth mite (Halotydeus destructor Tucker) is an important pest of field crops and pastures. Control of this pest relies heavily on chemicals, with few genuine alternatives presently available. Pesticide responses of H. destructor from the field with reported chemical control failures were compared with mites from susceptible 'control' populations. Toxicology bioassays were conducted on adult mites across multiple generations. Very high levels of resistance to two synthetic pyrethroids, bifenthrin and alpha-cypermethrin, were detected in this species for the first time. For bifenthrin, LC(50) estimates showed a difference in resistance of greater than 240 000-fold. Resistance to alpha-cypermethrin was almost 60 000-fold. This resistance was shown to be heritable, persisting after several generations of culturing. There was no evidence that resistance to organophosphorus chemicals had evolved, which is likely to be a direct consequence of the history of chemical applications these mites have experienced. These results highlight the need for more judicious management decisions in order to control pest species in a sustainable manner. The implications of these findings in regard to the management and future research of the redlegged earth mite are discussed. Copyright (c) 2007 Society of Chemical Industry.

Varroa destructor (Mesostigmata: Varroidae in Costa Rica: population dynamics and its influence on the colony condition of Africanized honey bees (Hymenoptera: Apidae

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Rafael A Calderón

2008-12-01

Full Text Available The development of Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae population dynamics in Africanized honey bees, Apis mellifera L. (Hymenoptera: Apidae colonies was monitored from February to July 2004 in Atenas, Costa Rica. A correlation between the mite infestation level and the colony condition was evaluated. For each colony, infestation of varroa in adult bees was measured twice a month. Sticky boards were placed on the bottom boards of each colony to collect fallen mites. The condition of the colonies was evaluated by measuring the amount of brood and adult bees. Our results consistently showed that mite infestation on adult bees increased significantly in the experimental colonies, rising to 10.0% by the end of the experiment. In addition, the mean mite fall increased significantly over the course of the study in the treated (R= 0.72, PLa dinámica poblacional del ácaro Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae en abejas africanizadas, Apis mellifera L. (Hymenoptera: Apidae fue monitoreada de febrero a julio 2004, en Atenas, Costa Rica. Asimismo, se analizó la relación entre el nivel de infestación de varroa y la condición de la colmena. La infestación del ácaro V. destructor fue evaluada en abejas adultas dos veces al mes. Además, se colocaron trampas adhesivas en el fondo de la colmena para recoger los ácaros que caen naturalmente. La condición de la colmena fue determinada midiendo la cantidad de cría y la población de abejas adultas. La infestación del ácaro V. destructor en abejas adultas aumentó significativamente durante el estudio hasta alcanzar un 10.0%. Igualmente, la caída natural de ácaros se incrementó, tanto en colmenas que fueron tratadas previa-mente con un acaricida químico (R= 0.72, P<0.05 como en colmenas sin tratamiento (R= 0.74, P<0.05, hasta llegar a 63.8 y 73.5 ácaros por día, respectivamente. El aumento de la infestación en las colmenas coincidió con una

Biological Activity of the Salvia officinalis L. (Lamiaceae Essential Oil on Varroa destructor Infested Honeybees

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Leila Bendifallah

2018-06-01

Full Text Available The present work is conducted as part of the development and the valorization of bioactive natural substances from Algerian medicinal and aromatic spontaneous plants, a clean alternative method in biological control. For this purpose, the bio-acaricidal activity of Salvia officinalis (sageessential oil (EOwas evaluated against the Varroa destructor, a major threat to the honey bee Apis mellifera ssp. intermissa. The aerial parts of S. officinalis L., 1753 were collected from the Chrea mountainous area in Northern Algeria. They were subjected to hydro distillation by a Clevenger apparatus type to obtain the EO, and screened for bio-acaricidal activity against Varroa destructor by the method of strips impregnated with the mixture EO and twin according to three doses. Pre-treatment results revealed infestation rates in the experimental site ranging from 3.76% to 21.22%. This showed the heterogeneity of infestations in hives according to the density of bees. This constituted a difficulty in monitoring the population dynamics of this parasite. After treatment, a difference in the acaricidal effect of Sage essential oil is noticed. It gives a mortality rate of 6.09% by the dose D1: 5%, 2.32% by the dose D2: 15%, and a low mortality rate of 0.9% by the dose D3: 20%. The chemical treatment carried out by Bayvarol gives a result close to that of the essential oil of Sage (9.97%.These results point to the fact that Sage essential oil treatments have a significant effect and good biological activity with regard to harmful species.

Effects of Bacillus thuringiensis strains virulent to Varroa destructor on larvae and adults of Apis mellifera.

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Alquisira-Ramírez, Eva Vianey; Peña-Chora, Guadalupe; Hernández-Velázquez, Víctor Manuel; Alvear-García, Andrés; Arenas-Sosa, Iván; Suarez-Rodríguez, Ramón

2017-08-01

The sublethal effects of two strains of Bacillus thuringiensis, which were virulent in vitro to Varroa destructor, were measured on Apis mellifera. The effects of five concentrations of total protein (1, 5, 25, 50 and 100μg/mL) from the EA3 and EA26.1 strains on larval and adult honey bees were evaluated for two and seven days under laboratory conditions. Based on the concentrations evaluated, total protein from the two strains did not affect the development of larvae, the syrup consumption, locomotor activity or proboscis extension response of adults. These same parameters were also tested for the effects of three concentrations (1, 10 and 15μg/kg) of cypermethrin as a positive control. Although no significant differences were observed after two days of treatment with cypermethrin, a dose-response relationship in syrup consumption and locomotor activity was observed. A significant reduction in the proboscis extension response of the bees treated with cypermethrin was also observed. Therefore, in contrast to cypermethrin, our results indicate that the EA3 and EA26.1 strains of B. thuringiensis can be used in beehives to control V. destructor and reduce the negative effects of this mite on colonies without adverse effects on the larvae and adults of A. mellifera. Additionally, the overuse of synthetic miticides, which produce both lethal and sublethal effects on bees, can be reduced. Copyright © 2017 Elsevier Inc. All rights reserved.

Differential responses of Africanized and European honey bees (Apis mellifera) to viral replication following mechanical transmission or Varroa destructor parasitism.

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Hamiduzzaman, Mollah Md; Guzman-Novoa, Ernesto; Goodwin, Paul H; Reyes-Quintana, Mariana; Koleoglu, Gun; Correa-Benítez, Adriana; Petukhova, Tatiana

2015-03-01

For the first time, adults and brood of Africanized and European honey bees (Apis mellifera) were compared for relative virus levels over 48 h following Varroa destructor parasitism or injection of V. destructor homogenate. Rates of increase of deformed wing virus (DWV) for Africanized versus European bees were temporarily lowered for 12h with parasitism and sustainably lowered over the entire experiment (48 h) with homogenate injection in adults. The rates were also temporarily lowered for 24h with parasitism but were not affected by homogenate injection in brood. Rates of increase of black queen cell virus (BQCV) for Africanized versus European bees were similar with parasitism but sustainably lowered over the entire experiment with homogenate injection in adults and were similar for parasitism and homogenate injection in brood. Analyses of sac brood bee virus and Israeli acute paralysis virus were limited as detection did not occur after both homogenate injection and parasitism treatment, or levels were not significantly higher than those following control buffer injection. Lower rates of replication of DWV and BQCV in Africanized bees shows that they may have greater viral resistance, at least early after treatment. Copyright © 2014 Elsevier Inc. All rights reserved.

A massive expansion of effector genes underlies gall-formation in the wheat pest Mayetiola destructor

DEFF Research Database (Denmark)

Zhao, Chaoyang; Escalante, Lucio Navarro; Chen, Hang

2015-01-01

Gall-forming arthropods are highly specialized herbivores that, in combination with their hosts, produce extended phenotypes with unique morphologies [1]. Many are economically important, and others have improved our understanding of ecology and adaptive radiation [2]. However, the mechanisms...... in plants and E3-ligase-mimicking effectors in plant pathogenic bacteria. SSGP-71 proteins and wheat Skp proteins interact in vivo. Mutations in different SSGP-71 genes avoid the effector-triggered immunity that is directed by the wheat resistance genes H6 and H9. Results point to effectors as the agents...

Changes in infestation, cell cap condition, and reproductive status of Varroa destructor (Mesostigmata: Varrroidae) in brood exposed to honey bees with Varroa sensitive hygiene

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Honey bees (Apis mellifera L.) bred for Varroa sensitive hygiene (VSH) selectively remove pupae infested with Varroa destructor Anderson & Trueman from capped brood that is inserted into the nest. After one week, remaining brood cells tend to have been uncapped and recapped, and remaining mites are...

Correlation of proteome-wide changes with social immunity behaviors provides insight into resistance to the parasitic mite, Varroa destructor, in the honey bee (Apis mellifera).

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Parker, Robert; Guarna, M Marta; Melathopoulos, Andony P; Moon, Kyung-Mee; White, Rick; Huxter, Elizabeth; Pernal, Stephen F; Foster, Leonard J

2012-06-29

Disease is a major factor driving the evolution of many organisms. In honey bees, selection for social behavioral responses is the primary adaptive process facilitating disease resistance. One such process, hygienic behavior, enables bees to resist multiple diseases, including the damaging parasitic mite Varroa destructor. The genetic elements and biochemical factors that drive the expression of these adaptations are currently unknown. Proteomics provides a tool to identify proteins that control behavioral processes, and these proteins can be used as biomarkers to aid identification of disease tolerant colonies. We sampled a large cohort of commercial queen lineages, recording overall mite infestation, hygiene, and the specific hygienic response to V. destructor. We performed proteome-wide correlation analyses in larval integument and adult antennae, identifying several proteins highly predictive of behavior and reduced hive infestation. In the larva, response to wounding was identified as a key adaptive process leading to reduced infestation, and chitin biosynthesis and immune responses appear to represent important disease resistant adaptations. The speed of hygienic behavior may be underpinned by changes in the antenna proteome, and chemosensory and neurological processes could also provide specificity for detection of V. destructor in antennae. Our results provide, for the first time, some insight into how complex behavioural adaptations manifest in the proteome of honey bees. The most important biochemical correlations provide clues as to the underlying molecular mechanisms of social and innate immunity of honey bees. Such changes are indicative of potential divergence in processes controlling the hive-worker maturation.

Sowing time affects the abundance of pests and weeds in winter rye

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E. HUUSELA-VEISTOLA

2008-12-01

Full Text Available Selection of an appropriate sowing time for some winter rye (Secale cereale cultivars could reduce the need for crop protection measures. In this study the occurrence and status of pests and weeds in relation to sowing time and growth habit of winter rye was studied in southern Finland. This was done using three sowing times and four rye varieties in field trials conducted at three locations in 1999–2001. The early sown rye was severely affected by pests (Oscinella frit, Mayetiola destructor and weeds, whereas postponing sowing for two weeks after the recommended sowing time in late August resulted in considerably less damage and the optimal establishment of crop stands. The German hybrid varieties Picasso and Esprit produced more tillers m-2 in autumn than the Finnish varieties Anna and Bor 7068. However, the number of pests and weeds did not differ among rye varieties. Late sowing of rye should be considered to minimize the need for plant protection. If rye is sown at the recommended time it may still require insecticide treatments promptly in the autumn whereas herbicide treatment need not be determined until spring, after recording the winter mortality of weeds.;

Transient heat stress compromises the resistance of wheat (Poales: Poaceae) seedlings to Hessian fly (Diptera: Cecidomyiidae) infestation.

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Currie, Yaleaka; Moch, John; Underwood, Joshua; Kharabsheh, Hamzah; Quesenberry, Amy; Miyagi, Risa; Thomas, Carolyn; Boney, Melanie; Woods, Samantha; Chen, Ming-Shun; Zhu, Lieceng

2014-02-01

Heat stress exerts a profound impact on the resistance of plants to parasites. In this research, we investigated the impact of an acute transient heat stress on the resistance of the wheat line 'Molly,' which contains the R gene H13, to an avirulent Hessian fly (Mayetiola destructor (Say)) population. We found that a significant portion of Molly seedlings stressed at 40 degrees C for 6 h during or after the initial Hessian fly larval attack became susceptible to otherwise avirulent insects, whereas unstressed control plants remained 100% resistant. Specifically, 77.8, 73.3, 83.3, and 46.7% of plants heat stressed at 0, 6,12, and 24 h, respectively, after the initial larval attack became susceptible. Biochemical analysis revealed that heat stress caused a transient decrease in 12-oxo-phytodienoic acid, but an increase in salicylic acid accumulation in Molly plants. The change in phytohormones after heat stress and Hessian fly infestation was not observed in 'Newton,' a near-isogenic but Hessian fly susceptible wheat line. Instead, heat stress caused a relatively prolonged reduction in palmitoleic acid. The role of phytohormones in heat-induced loss of wheat resistance was discussed.

Genomic analysis of a 1 Mb region near the telomere of Hessian fly chromosome X2 and avirulence gene vH13

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Chen Ming-Shun

2006-01-01

Full Text Available Abstract Background To have an insight into the Mayetiola destructor (Hessian fly genome, we performed an in silico comparative genomic analysis utilizing genetic mapping, genomic sequence and EST sequence data along with data available from public databases. Results Chromosome walking and FISH were utilized to identify a contig of 50 BAC clones near the telomere of the short arm of Hessian fly chromosome X2 and near the avirulence gene vH13. These clones enabled us to correlate physical and genetic distance in this region of the Hessian fly genome. Sequence data from these BAC ends encompassing a 760 kb region, and a fully sequenced and assembled 42.6 kb BAC clone, was utilized to perform a comparative genomic study. In silico gene prediction combined with BLAST analyses was used to determine putative orthology to the sequenced dipteran genomes of the fruit fly, Drosophila melanogaster, and the malaria mosquito, Anopheles gambiae, and to infer evolutionary relationships. Conclusion This initial effort enables us to advance our understanding of the structure, composition and evolution of the genome of this important agricultural pest and is an invaluable tool for a whole genome sequencing effort.

Expression of the Prophenoloxidase Gene and Phenoloxidase Activity, During the Development of Apis Mellifera Brood Infected with Varroa Destructor

OpenAIRE

Zaobidna Ewa A.; Żółtowska Krystyna; Łopieńska-Biernat Elżbieta

2015-01-01

The pathogenesis of varroasis has not been fully explained despite intensive research. Earlier studies suggested that parasitic infections caused by Varroa destructor mites were accompanied by immunosuppression in the host organism. The objective of this study was to analyse the influence of varroasis on one of the immune pathway in Apis mellifera measured by the expression of the prophenoloxidase (proPO) gene and the enzymatic activity of this gene’s product, phenoloxidase (EC 1.14.18.1). An...

Expression of the Prophenoloxidase Gene and Phenoloxidase Activity, During the Development of Apis Mellifera Brood Infected with Varroa Destructor

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Zaobidna Ewa A.

2015-12-01

Full Text Available The pathogenesis of varroasis has not been fully explained despite intensive research. Earlier studies suggested that parasitic infections caused by Varroa destructor mites were accompanied by immunosuppression in the host organism. The objective of this study was to analyse the influence of varroasis on one of the immune pathway in Apis mellifera measured by the expression of the prophenoloxidase (proPO gene and the enzymatic activity of this gene’s product, phenoloxidase (EC 1.14.18.1. An evaluation was done of five developmental stages of honey bee workers and drones. The relative expression of proPO decreased in infected individuals. The only exceptions were worker prepupae (PP and drone pupae with brown eyes and dark brown thorax (P5 where propo gene expression was 1.8-fold and 1.5-fold higher, respectively, than in the control. Phenoloxidase (PO activity was 2.8-fold higher in infected pp workers and 2-fold higher in p5 drones in comparison with uninfected bees. Phenoloxidase activity was reduced in the remaining developmental stages of infected workers and drones. The relative expression of proPO was positively correlated with the relative PO activity in both workers (r = 0.988 and drones (r = 0.996. The results of the study indicate that V. destructor significantly influences the phenoloxidase-dependent immune pathway in honey bees.

Search and studying of salt resisting bacteria -destructors of organochlorine pesticides with help of tritium labeled PCBs

International Nuclear Information System (INIS)

Kim, A.A.; Djuraeva, G.T.; Dadakhanov, J.A.; Djumaniyazova, G.I.; Yadgarov, Kh.T.; Zinovev, P.V.; Norbaeva, Kh.

2006-01-01

Full text: Salinization of soils is one of serious problems of agriculture of Uzbekistan. The problem is also aggravated as the salted soils are strongly contaminated with pesticides. We isolated aboriginal active strains of bacteria- destructors of organochlorine compounds from soils contaminated by pesticides (HCCH, DDT, PCBs). We investigated their cultural-morphological and physiological -biochemical properties and determined their taxonomic position. In laboratory experiments the effect of various concentrations of NaCl - 3%-5-7-10-20-30-40-50 % and reproduction of the active strains-destructors was investigated. It was found that the culture number 20 stands the NaCl concentration - up to 3 %, culture number 505 - up to 7 % salt in medium that specifies ability of this culture to survive in the middle salinated soils, cultures number 28 and 33 stand the NaCl concentration up to 30-40 % that characterize their survival rate in strongly salinated soils; the culture number 26 stood the NaCl concentration up to 50 % that characterizes its ability to survive and propagate in brackish soils. With the help of designed radiochemical methods we had been explored ability of the active salt resisting strains of bacteria to utilize and destroy the tritium labeled PCBs. The precise quantity and quality characteristics of the PCB-destructive activity of each investigated strain were received. The salt resisting strains of bacteria having high PCB-destructive activity were determined. At present, investigation on development of the new biological preparation designed for destruction of persistent organochlorine compounds in salted soils are carried out. (author)

Efecto del Fosfito de Potasio en Combinación con el Fungicida Metalaxyl + Mancozeb en el Control de Mildeo Velloso (Peronospora destructor Berk en Cebolla de Bulbo (Allium cepa L. Effect of the Potasium Phosphite in Combination with the Fungicide Metalaxyl plus Mancozeb on the Control of Downy Mildew (Peronospora destructor Berk in Onion Bulb (Allium cepa L.

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Jorge Velandia Monsalve

2012-06-01

Full Text Available Resumen. El hongo Peronospora destructor causa considerables pérdidas en la producción de cebolla de bulbo en el mundo. Fosfito de potasio en combinación con el fungicida Metalaxyl + Mancozeb, fue evaluado por su eficiencia en el control de este patógeno en el híbrido de cebolla de bulbo Yellow Granex. Los tratamientos consistieron en una aplicación de fosfito (5 mL L-1 alternada con una de fungicida (2 g L-1; dos y tres aplicaciones consecutivas de fosfito alternadas con una de fungicida; una aplicación de fungicida alternada con una de fosfito; dos y tres aplicaciones consecutivas de fungicida alternadas con una de fosfito; aplicaciones de sólo fosfito y sólo fungicida y un testigo. Se utilizó el diseño experimental de bloques completos al azar con tres repeticiones. Se evaluó la incidencia y severidad de la enfermedad, el número, tamaño y peso de bulbos de primera, segunda, tercera y peso total de bulbos. Los resultados mostraron que las aplicaciones de fosfito de potasio durante dos semanas consecutivas alternadas en la tercera semana con una de fungicida y las aplicaciones semanales de sólo fosfito, tuvieron efectos altamente significativos en el control de la incidencia y severidad de P. destructor y diferencias significativas en el peso de los bulbos de primera (28,1 y 27,9 t ha-1 y peso total de bulbos (55,5 y 52,1 t ha-1, representando en relación al testigo, un incremento de 200 y 196% en el peso de los bulbos de primera y de 55 y 45,7% en el peso total de bulbos, respectivamente. Se concluye que con el fosfito de potasio se reduce la aplicación de fungicidas y ello es una alternativa viable para el manejo ecológico de P. destructor en la producción de cebolla de bulbo.Abstract. Peronospora destructor fungi causes considerable loses in the production of onion bulb in the world. Potassium phosphite in combination with the fungicide Metalaxyl + Mancozeb was evaluated for its efficiency in the control of this pathogen

Biology and control of Varroa destructor.

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Rosenkranz, Peter; Aumeier, Pia; Ziegelmann, Bettina

2010-01-01

The ectoparasitic honey bee mite Varroa destructor was originally confined to the Eastern honey bee Apis cerana. After a shift to the new host Apis mellifera during the first half of the last century, the parasite dispersed world wide and is currently considered the major threat for apiculture. The damage caused by Varroosis is thought to be a crucial driver for the periodical colony losses in Europe and the USA and regular Varroa treatments are essential in these countries. Therefore, Varroa research not only deals with a fascinating host-parasite relationship but also has a responsibility to find sustainable solutions for the beekeeping. This review provides a survey of the current knowledge in the main fields of Varroa research including the biology of the mite, damage to the host, host tolerance, tolerance breeding and Varroa treatment. We first present a general view on the functional morphology and on the biology of the Varroa mite with special emphasis on host-parasite interactions during reproduction of the female mite. The pathology section describes host damage at the individual and colony level including the problem of transmission of secondary infections by the mite. Knowledge of both the biology and the pathology of Varroa mites is essential for understanding possible tolerance mechanisms in the honey bee host. We comment on the few examples of natural tolerance in A. mellifera and evaluate recent approaches to the selection of Varroa tolerant honey bees. Finally, an extensive listing and critical evaluation of chemical and biological methods of Varroa treatments is given. This compilation of present-day knowledge on Varroa honey bee interactions emphasizes that we are still far from a solution for Varroa infestation and that, therefore, further research on mite biology, tolerance breeding, and Varroa treatment is urgently needed. Copyright 2009 Elsevier Inc. All rights reserved.

Vergleichende Untersuchungen zur Widerstandsfähigkeit von \\(\\textit {Apis mellifera}\\) gegenüber \\(\\textit {Varroa destructor}\\) in Deutschland und Südafrika

OpenAIRE

Bosch, Christoph (M. Sc.)

2016-01-01

Die Milbe \\(\\textit {Varroa destructor}\\) ist einer der bedeutendsten Parasiten der Westlichen Honigbiene \\(\\textit {Apis mellifera}\\). Mit der Ausbreitung entwickelten sich \\(\\it Varroa\\)-resistenzen bei Unterarten von \\(\\textit {A. mellifera}\\). In der vorliegenden Arbeit wurden ausgewählte Faktoren, die zur Widerstandsfähigkeit beitragen können, bei der anfälligen \\(\\textit {A. m. carnica}\\) in Deutschland und der resistenten \\(\\textit {A. m. scutellata}\\) in Südafrika untersucht. Dabei wu...

Comparison of the efficacy of Apiguard (thymol and Apivar (amitraz in the control of Varroa destructor (Acari: Varroidae

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M. Mar Leza

2015-09-01

Full Text Available The present study compared the efficacy of Apivar (a.i. amitraz and Apiguard (a.i. thymol in controlling the mite Varroa destructor during spring 2010 and autumn 2011, in the Balearic Islands (Spain. Number of fallen mites (NFM was counted weekly and the efficacy of treatments was evaluated by using the percentage of reduction of the average daily fallen mites (%R. During spring assay, the average NFM was highly reduced in Apiguard (89.8% compared to Apivar (64.3% group, with significant differences between Apiguard and control group (untreated group in post-treatment week. In autumn assay, Apivar and Apiguard colonies had an average reduction of the NFM of 17.9% and 30.8% respectively, showing a tendency in reduction between control and Apiguard group in post-treatment week. In both assays, %R was higher in Apiguard than in Apivar, but no significant differences were found between treatments in any of the seasons. Apiguard was less efficacious during November-December, probably due to the low external temperatures that hampered an optimal volatilization of the product. The lower efficacy of Apivar is probably related to the resistance of V. destructor to this chemical miticide, which has been used during the last 30 years. Results of this study showed that in Mediterranean conditions, spring is an appropriate period for applying Apiguard to the colonies, whereas application in late autumn would decrease the efficacy of the product. Apiguard may represent an alternative product for integrated control due to the low risk of mite resistance and residues in bee products.

Comparison of the efficacy of Apiguard (thymol) and Apivar (amitraz) in the control of Varroa destructor (Acari: Varroidae)

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Leza, M.M.; Lladó, G.; Miranda-Chueca, M.A.

2015-07-01

The present study compared the efficacy of Apivar (a.i. amitraz) and Apiguard (a.i. thymol) in controlling the mite Varroa destructor during spring 2010 and autumn 2011, in the Balearic Islands (Spain). Number of fallen mites (NFM) was counted weekly and the efficacy of treatments was evaluated by using the percentage of reduction of the average daily fallen mites (%R). During spring assay, the average NFM was highly reduced in Apiguard (89.8%) compared to Apivar (64.3%) group, with significant differences between Apiguard and control group (untreated group) in post-treatment week. In autumn assay, Apivar and Apiguard colonies had an average reduction of the NFM of 17.9% and 30.8% respectively, showing a tendency in reduction between control and Apiguard group in post-treatment week. In both assays, %R was higher in Apiguard than in Apivar, but no significant differences were found between treatments in any of the seasons. Apiguard was less efficacious during November-December, probably due to the low external temperatures that hampered an optimal volatilization of the product. The lower efficacy of Apivar is probably related to the resistance of V. destructor to this chemical miticide, which has been used during the last 30 years. Results of this study showed that in Mediterranean conditions, spring is an appropriate period for applying Apiguard to the colonies, whereas application in late autumn would decrease the efficacy of the product. Apiguard may represent an alternative product for integrated control due to the low risk of mite resistance and residues in bee products. (Author)

Reproduction of Varroa destructor and offspring mortality in worker and drone brood cells of Africanized honey bees.

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Calderón, R A; Ureña, S; van Veen, J W

2012-04-01

Varroa destructor is known to be the most serious parasite of Apis mellifera worldwide. In order to reproduce varroa females enter worker or drone brood shortly before the cell is sealed. From March to December 2008, the reproductive rate and offspring mortality (mature and immature stages), focusing on male absence and male mortality of V. destructor, was investigated in naturally infested worker and drone brood of Africanized honey bees (AHB) in Costa Rica. Data were obtained from 388 to 403 single infested worker and drone brood cells, respectively. Mite fertility in worker and drone brood cells was 88.9 and 93.1%, respectively. There was no difference between the groups (X(2) = 3.6, P = 0.06). However, one of the most significant differences in mite reproduction was the higher percentage of mites producing viable offspring in drone cells (64.8%) compared to worker cells (37.6%) (X(2) = 57.2, P drone cells was high in the protonymph stage (mobile and immobile). A significant finding was the high rate of male mortality. The worker and drone brood revealed that 23.9 and 6.9%, respectively, of the adult male offspring was found dead. If the absence (missing) of the male and adult male mortality are taken together the percentage of cells increased to 40.0 and 21.3% in worker and drone cells, respectively (X(2) = 28.8, P < 0.05). The absence of the male or male mortality in a considerable number of worker cells naturally infested with varroa is the major factor in our study which reduces the production of viable daughters in AHB colonies in Costa Rica.

Infestation and distribution of the mite Varroa destructor in colonies of africanized bees

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G. Moretto

Full Text Available Whereas in several parts of the world varroa is the major pest affecting apiculture, in others the parasite is unknown to many beekeepers because its damage to bees is minor. The impact of the mite Varroa destructor is related to the climatic conditions and the races of Apis mellifera bees in each region where the pest exists. In the present study, the current level of infestation by the mite was assessed to determine the evolution of the pest in Africanized bee colonies in Southern Brazil. This level of infestation was considered low: approximately two mites per one hundred adult bees. This result is similar to that obtained for the same apiary almost five years ago and for others distributed in various regions of Brazil. In the present study, we also estimated the total varroa population and its distribution among brood and adults in each bee colony.

Evaluación de la resistencia del ácaro Varroa destructor al fluvalinato en colonias de abejas (Apis mellifera en Yucatán, México

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Jesús Froylán Martínez Puc

2011-01-01

Full Text Available La constante aplicación de piretroides para el control del ácaro Varroa destructor ha ocasionado la aparición de poblaciones de ácaros resistentes a este producto en diversas partes del mundo. Con la finalidad de detectar la posible existencia de poblaciones de ácaros resistentes al fluvalinato en el estado de Yucatán, uno de los principales estados productores de miel en México, se colectó un total de 12 muestras por cada apiario, seleccionando cuatro apiarios donde se ha utilizado de manera constante el fluvalinato para el control de V. destructor por un periodo de cinco años, y una cantidad de muestras similar provenientes de apiarios donde se han utilizado métodos de control alternativo durante un tiempo similar. Para determinar el porcentaje de mortalidad de los ácaros al fluvalinato, estos fueron expuestos a una pieza de 2.5 x 1.0 cm de Apistan® al 10%, por un periodo de 24 h. El porcentaje de mortalidad de varroas provenientes de apiarios tratados de manera constante con fluvalinato fue de 83.6 ± 0.51 %, inferior al porcentaje de mortalidad obtenido en los apiarios que sólo han recibido tratamiento alternativo el cual fue de 93.9 ± 1.98 %, existiendo diferencias entre ambos grupos (t=-3.93, P=0.01, gl= 46, lo cual indica una reducción en el porcentaje de mortalidad obtenido con el fluvalinato, sin embargo, esta reducción, aun no alcanza los niveles necesarios para reportar la presencia de ácaros resistentes, siendo importante cambiar las prácticas de manejo encaminadas a reducir los niveles de infestación de V. destructor, por lo que es recomendable la aplicación de métodos de control alternativo los cuales no ocasionan el desarrollo de resistencia en las poblaciones de ácaros.

Proteomic analysis of chemosensory organs in the honey bee parasite Varroa destructor: A comprehensive examination of the potential carriers for semiochemicals.

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Iovinella, Immacolata; McAfee, Alison; Mastrobuoni, Guido; Kempa, Stefan; Foster, Leonard J; Pelosi, Paolo; Dani, Francesca Romana

2018-06-15

We have performed a proteomic analysis on chemosensory organs of Varroa destructor, the honey bee mite, in order to identify putative soluble carriers for pheromones and other olfactory cues emitted by the host. In particular, we have analysed forelegs, mouthparts (palps, chelicera and hypostome) and the second pair of legs (as control tissue) in reproductive and phoretic stages of the Varroa life cycle. We identified 958 Varroa proteins, most of them common to the different organs and stages. Sequence analysis shows that four proteins can be assigned to the odorant-binding protein (OBP)-like class, which bear some similarity to insect OBPs, but so far have only been reported in some Chelicerata. In addition, we have detected the presence of two proteins belonging to the Niemann-Pick family, type C2 (NPC2), which have also been suggested as semiochemical carriers. Biological significance: The mite Varroa destructor is the major parasite of the honey bee and is responsible for great economical losses. The biochemical tools used by Varroa to detect semiochemicals produced by the host are still largely unknown. This work contributes to understand the molecular basis of olfaction in Varroa and, more generally, how detection of semiochemicals has evolved in terrestrial non-hexapod Arthropoda. Moreover, the identification of molecular carriers involved in olfaction can contribute to the development of control strategies for this important parasite. Copyright © 2018 Elsevier B.V. All rights reserved.

Control of Varroa Mite (Varroa destructor on Honeybees by Aromatic Oils and Plant Materials

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I.K. Nazer

2003-01-01

Full Text Available The effect of several volatile plant oils, plant materials and fluvalinate (Apistan® strips on the control of the mite Varroa destructor on honeybee (Apis mellifera L. colonies was studied. The volatile oils were: clove, lavender, peppermint, sage, and thyme. The plant materials were: cumin fruits, eucalyptus leaves, and worm wood flowers. For each tested material, three treatment periods were carried out. Each period lasted for 24 days followed by eight days no-treatment. Within each treatment period, an average of three to six treatments were applied. Dead mites were counted one hour before and after each treatment. An increase in dead mites was recorded for the three treatment periods. It indicated that worm wood flowers, peppermint oil and clove oil treatments gave the best results in the control of Varroa mites but not significantly different than the control. The overall increase in the dead mites was 3.92, 3.62 and 3.34 fold, respectively.

Use of costic acid, a natural extract from Dittrichia viscosa, for the control of Varroa destructor, a parasite of the European honey bee

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Kalliopi Sofou

2017-05-01

Full Text Available Costic acid has been isolated from the plant Dittrichia viscosa and its efficacy against Varroa destructor, a parasite of Apis mellifera, the European honey bee, has been studied. Costic acid exhibited potent in vivo acaricidal activity against the parasite. Initial experiments showed that the compound is not toxic for human umbilical vein endothelial cells (HUVEC at concentrations of up to 230 micromolar (μM, indicating that costic acid could be used as a safe, low-cost and efficient agent for controlling varroosis in honey bee colonies.

Toxicity of Anethole and the Essential Oils of Lemongrass and Sweet Marigold to the Parasitic Mite Varroa destructor and Their Selectivity for Honey Bee (Apis mellifera Workers and Larvae

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Qodratollah Sabahi

2018-01-01

Full Text Available This study examined the toxicity of anethole and that of the essential oils of lemongrass (Cymbopogon citratus and sweet marigold (Tagetes lucida to the mite Varroa destructor and to honey bee workers and larvae. Anethole was the most toxic compound to V. destructor (LC50: 304.9 μg/ml, whereas Tagetes oil was the least toxic (LC50: 1256.27 μg/ml. The most and least toxic compounds to worker bees were anethole and Tagetes oil with LD50s of 35942 and 85381 μg/ml, respectively. For larvae, Tagetes oil was the most toxic compound (LD50: 9580.7 μg/ml and anethole the least toxic (LD50: 14518.0 μg/ml. Anethole and Cymbopogon oil had the highest selectivity ratios. The expression of AChE, a gene that regulates the production of acetyl cholinesterase, a detoxifying enzyme, was not altered in bees treated with the plant compounds at 48 h post-treatment. This study showed that anethole and Cymbopogon oil have potential for controlling Varroa mites and seem to be relatively safe for larvae and adult honey bees.

Varroa destructor mite in Africanized honeybee colonies Apis mellifera L. under royal jelly or honey production

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Pedro da Rosa Santos

2015-08-01

Full Text Available This study evaluated the level of invasion of Varroa mite into worker brood cells, the infestation rate on adult worker honeybees, total and effective reproduction rates of the mite in Africanized honeybee colonies under royal jelly or honey production. Invasion and infestation rates were not statistically different between honeybee colonies producing honey or royal jelly and the averages for these parameters were 5.79 and 8.54%, respectively. Colonies producing honey presented a higher (p < 0.05 total and effective reproduction of Varroa than colonies producing royal jelly. There was a negative correlation between levels of invasion and infestation with minimum external temperature, relative humidity and rainfall. The variables month and season influenced the development of the mite, but rates were low and within the range normally found in Brazil for Africanized honeybee colonies, which confirm the greater resistance of these honeybees to Varroa destructor than European honeybees.

Composition of fatty acids in the Varroa destructor mites and their hosts, Apis mellifera drone-prepupae.

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Dmitryjuk, Małgorzata; Zalewski, Kazimierz; Raczkowski, Marek; Żółtowska, Krystyna

2015-01-01

The fatty acid (FA) profile of lipids extracted from the Varroa destructor parasitic mite and its host, drone-prepupae of Apis mellifera, was determined by gas chromatography (GC). The percentages of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) were generally similar in parasites and their hosts. Fatty acids were arranged in the following descending order based on their content: MUFAs (ca. 52-55%), SFAs (ca. 41%) and PUFAs (ca. 3%). The predominant fatty acids were oleic acid (46% in mites, 44% in prepupae) and palmitic acid (23% and 30%, respectively). Varroa parasites differed from their hosts in the quantity of individual FAs and in their FA profiles. Three PUFAs noted in the host were not observed in parasitic mites, whereas the presence of C21:0, C24:0 and C22:1 FAs was reported in mites, but not in drones.

A Field Experiment to Assess the Rate of Infestation in Honey Bee Populations of Two Metarhizium Anisopliae Isolates on Varroa Destructor (Acari: Mesostigmata

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Khodadad Pirali-kheirabadi

2013-03-01

Full Text Available Background: The protective effect of two isolates of an entomopathogenic fungus, Metarhizium anisopliae (DEMI 002 and Iran 437C on the adult stage of Varroa destructor was evaluated in comparison with fluvalinate strips in the field.Methods: A total of 12 honey bee colonies were provided from an apiculture farm. The selected hives were divided into 4 groups (3 hives per group. The first group was the control, treated with distilled water. The other two groups were exposed to different fungi (M. anisopliae isolates DEMI 002 and Iran 437C and the last group was treated with one strip of fluvalinate per colony. The number of fallen mites was counted using sticky traps during a 6-day period, six days before and after treatments. A fungal suspension at a concentration of 5× 106 conidia/mL was sprayed onto the frames and the number of fallen mites was counted.Results: Metarhizium anisopliae DEMI 002 and Iran 437C isolates were as effective (i.e., caused as much mite fall as the fluvalinate strip in controlling bee colonies than no treatment.Conclusion: Both M. anisopliae isolates are promising candidates as agents in the control of Varroa mites under field conditions. Isolate DEMI 002 can be considered as a possible non-chemical biocontrol agent for controlling bee infestation with V. destructor in the field. In order to substantiate this hypothesis, tests are currently being performed using larger colonies and larger doses than tested in the present study in our beekeeping.

Immune related gene expression in worker honey bee (Apis mellifera carnica) pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor).

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Tesovnik, Tanja; Cizelj, Ivanka; Zorc, Minja; Čitar, Manuela; Božič, Janko; Glavan, Gordana; Narat, Mojca

2017-01-01

Varroa destructor is one of the most common parasites of honey bee colonies and is considered as a possible co-factor for honey bee decline. At the same time, the use of pesticides in intensive agriculture is still the most effective method of pest control. There is limited information about the effects of pesticide exposure on parasitized honey bees. Larval ingestion of certain pesticides could have effects on honey bee immune defense mechanisms, development and metabolic pathways. Europe and America face the disturbing phenomenon of the disappearance of honey bee colonies, termed Colony Collapse Disorder (CCD). One reason discussed is the possible suppression of honey bee immune system as a consequence of prolonged exposure to chemicals. In this study, the effects of the neonicotinoid thiamethoxam on honey bee, Apis mellifera carnica, pupae infested with Varroa destructor mites were analyzed at the molecular level. Varroa-infested and non-infested honey bee colonies received protein cakes with or without thiamethoxam. Nurse bees used these cakes as a feed for developing larvae. Samples of white-eyed and brown-eyed pupae were collected. Expression of 17 immune-related genes was analyzed by real-time PCR. Relative gene expression in samples exposed only to Varroa or to thiamethoxam or simultaneously to both Varroa and thiamethoxam was compared. The impact from the consumption of thiamethoxam during the larval stage on honey bee immune related gene expression in Varroa-infested white-eyed pupae was reflected as down-regulation of spaetzle, AMPs abaecin and defensin-1 and up-regulation of lysozyme-2. In brown-eyed pupae up-regulation of PPOact, spaetzle, hopscotch and basket genes was detected. Moreover, we observed a major difference in immune response to Varroa infestation between white-eyed pupae and brown-eyed pupae. The majority of tested immune-related genes were upregulated only in brown-eyed pupae, while in white-eyed pupae they were downregulated.

Identification of IgE-binding proteins from Lepidoglyphus destructor and production of monoclonal antibodies to a major allergen.

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Ventas, P; Carreira, J; Polo, F

1991-08-01

The allergen composition of one of the most important storage mites, Lepidoglyphus destructor, has been studied by immunodetection after SDS-PAGE with individual patient sera. An allergenic polypeptide of 14 kDa was identified with 95% of the sera. This major allergen was isolated in the supernatant of 60% ammonium sulfate salt precipitation of the whole extract, which was subsequently used to immunize BALB/c mice so as to produce monoclonal antibodies. Four mAbs recognizing molecules with IgE-binding ability were obtained. The specificity of the mAbs was assayed against different allergenic extracts, and the molecules recognized by them were characterized by immunoblotting. Two mAbs (Le5B5 and Le9E4) were directed to the 14-kDa allergen; the other two to several proteins of lesser allergenic significance.

Evaluation of drone brood removal for management of Varroa destructor (Acari: Varroidae) in colonies of Apis mellifera (Hymenoptera: Apidae) in the northeastern United States.

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Calderone, N W

2005-06-01

The efficacy of drone brood removal for the management of Varroa destructor Anderson & Trueman in colonies of the honey bee, A. mellifera L., was evaluated. Colonies were treated with CheckMite+ in the fall of 2002. The following spring, quantities of bees and brood were equalized, but colonies were not retreated. The brood nest of each colony consisted of 18 full-depth worker combs and two full-depth drone combs. Each worker comb had drone cells. Standard management practices were used throughout the season. Colonies were randomly assigned to one of two groups. In the control group, drone combs remained in place throughout the season. In the treatment group, drone combs were removed on 16 June, 16 July, 16 August, and 16 September and replaced with empty drone combs (16 June) or with drone combs removed on the previous replacement date. In the early fall, the average mite-to-bee ratio in the control group was significantly greater than the corresponding ratio in the treatment group. Drone brood removal did not adversely affect colony health as measured by the size of the worker population or by honey production. Fall worker populations were similar in the two groups. Honey production in treatment colonies was greater than or similar to production in control colonies. These data demonstrate that drone brood removal can serve as a valuable component in an integrated pest management program for V. destructor and may reduce the need for other treatments on a colony-by-colony basis.

Control del Ácaro Varroa destructor (Mesostigmata: Varroidae en Colmenas de Apis mellifera (Hymenoptera: Apidae mediante la Aplicación de distintos Principios Activos Control of Varroa destructor (Mesostigmata: Varroidae in honeybee colonies of Apis mellifera Hymenoptera: Apidae by means of different active agents

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Jorge Augusto Marcangeli

2003-12-01

Full Text Available El objetivo de este trabajo fue evaluar la eficacia acaricida de cuatro productos utilizados para el control del ácaro Varroa destructor (Anderson & Trueman en colmenas de Apis mellifera (L.. Se seleccionaron 25 colmenas dividivas en cinco lotes iguales a las que se les suministró Apistan®, Bayvarol®, Apitol® y Folbex®. El último lote representó el control. Los ácaros muertos se recolectaron en pisos especiales que se controlaron semanalmente. Finalizada la experiencia cada lote fue sometido a un cruzamiento con otros productos con el fin de eliminar los ácaros remanentes y poder calcular las eficacias. El producto Apistan® fue el más efectivo con un valor promedio de 85,38% seguido por el Bayvarol® (83,83%, Apitol® (71,77% y Folbex® (62,78%. En todos los casos, los valores obtenidos resultaron inferiores a los estipulados por los laboratorios productores. Estos resultados alertan sobre la posible generación de resistencias por parte de las poblaciones del ácaro y la necesidad de buscar nuevos agentes de control eficaces para esta enfermedad.The aim of this work was to evaluate the acaricide efficacy of four commercial products against the mite Varroa destructor (Anderson & Trueman in honeybee colonies of Apis mellifera (L.. Twenty five honeybee colonies divided in five equal groups were selected. Groups received Apistan®, Bayvarol®, Apitol® and Folbex®. Final group was the control. Dead mites were collected weekly in special floors. After treatment, each colony received a shock treatment with the other three products to kill remnant mites and to obtain acaricide efficacy. Average values of efficacy were Apistan® 85,38%, Bayvarol® 83,83%, Apitol® 71,77% and Folbex® 62,78%. In all cases these values were lower than those reported by the laboratories that produce them. These results alert about the possible generation of resistant mite populations and justify research directed to search for alternative products for the

Importance of brood maintenance terms in simple models of the honeybee - Varroa destructor - acute bee paralysis virus complex

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Hermann J. Eberl

2010-09-01

Full Text Available We present a simple mathematical model of the infestation of a honeybee colony by the Acute Paralysis Virus, which is carried by parasitic varroa mites (Varroa destructor. This is a system of nonlinear ordinary differential equations for the dependent variables: number of mites that carry the virus, number of healthy bees and number of sick bees. We study this model with a mix of analytical and computational techniques. Our results indicate that, depending on model parameters and initial data, bee colonies in which the virus is present can, over years, function seemingly like healthy colonies before they decline and disappear rapidly (e.g. Colony Collapse Disorder, wintering losses. This is a consequence of the fact that a certain number of worker bees is required in a colony to maintain and care for the brood, in order to ensure continued production of new bees.

Evaluation of Metarhizium anisopliae var. anisopliae Qu-M845 Isolate to Control Varroa destructor (Acari: Varroidae in Laboratory and Field Trials Evaluación del Aislamiento Qu-M845 de Metarhizium anisopliae var. anisopliae para el Control de Varroa destructor (Acari: Varroidae en Ensayos de Laboratorio y Terreno

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Marta Rodríguez

2009-12-01

Full Text Available The effectiveness of the Metarhizium anisopliae (Metschinkoff Qu-M845 isolate was evaluated in laboratory and field trials. It was previously selected for thermal resistance (at 30 and 35 ºC and pathogenicity on Varroa destructor (Anderson and Trueman. In the laboratory, the first evaluations were carried out by spraying and increasing the concentration from zero to 10(8 conidia mL-1 on varroa adults. Lethal concentrations required for 50 and 90% mite mortality (LC50 and LC90 were 3.8 x 10(5 and 8 x 10(7 conidia mL-1, respectively (χ2 = 2.03. In the autumn field trials, three application methods (doses of 5 x 10(10 conidia per hive were evaluated. The treatments were: a conidia stamped on filter paper, located on every second frame inside the hive; b dry conidia sprinkled on and between frames; and c dry conidia in a dispenser path at the entrance of the hive. Furthermore, untreated hives were included as controls. After 21 days of treatment, the dry conidia sprinkled on and between frames showed 67% less bees infested by the mite than the control (p La efectividad del aislamiento Qu-M845 de Metarhizium anisopliae (Metschinkoff, seleccionado previamente por su resistencia a temperaturas de 30 y 35 ºC, y patogenicidad sobre Varroa destructor Anderson y Trueman fue evaluada en laboratorio y en ensayos de terreno. Las primeras pruebas consistieron en pulverizar concentraciones crecientes de 0 a 10(8 conidias mL-1 sobre varroas adultas. La concentración letal para matar el 50 y 90% de la población (CL50 y CL90 fueron de 3,8 x 10(5 y 8 x 10(7 conidias mL-1, respectivamente (χ² = 2,03. En otoño se evaluaron en terreno tres métodos de aplicación de una dosis de 5 x 10(10 conidias por colmena. Los tratamientos fueron: a conidias estampadas en papel filtro ubicado cada dos panales móviles al interior de la colmena; b conidias espolvoreadas sobre y entre los panales; y c dispensador de conidias ubicado en la piquera de las colmenas. Además se

Infestation rate of the mite Varroa destructor in commercial apiaries of the Vale do Paraíba and Serra da Mantiqueira, southeastern Brazil

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F.A. Pinto

2015-04-01

Full Text Available Nos últimos anos, grandes perdas de colônias de abelhas melíferas vêm sendo registradas em várias regiões do mundo. Contudo, os motivos desse acontecimento permanecem obscuros. O ácaro ectoparasita Varroa destructor Anderson e Trueman (Acari: Varroidae pode ser um dos responsáveis por esse fato, principalmente como vetor de vírus. Neste estudo, avaliaram-se as taxas de infestação (TIs do ácaro V. destructor em abelhas africanizadas Apis mellifera L. (Hymenoptera: Apidae e correlacionaram-se os dados com as médias de temperatura de 16 municípios das regiões do Vale do Paraíba e da Serra da Mantiqueira (São Paulo, Brasil, onde a apicultura comercial atua de maneira significativa. Em cada município, um apiário comercial foi selecionado para coleta de amostras de três colônias populosas (padrão Langstroth, totalizando 48 colônias amostradas. Aproximadamente 300 abelhas adultas localizadas na área de cria foram coletadas em cada colônia. As TIs variaram de 0.0 a 5.5%, níveis considerados baixos para causar danos significativos às colônias. As TIs mais baixas foram encontradas em municípios com clima mais ameno durante a estação avaliada (verão. Adicionalmente, cofatores como variações na disponibilidade de alimento entre os municípios e a variabilidade genética das abelhas podem interagir na interação entre parasita e hospedeiro. A variação nas TIs entre os municípios indica que, mesmo presente, a tolerância das abelhas africanizadas ao varroa pode variar drasticamente em uma pequena região, devido à dinâmica multifatorial de infestação do ácaro.

Selection of Apis mellifera workers by the parasitic mite Varroa destructor using host cuticular hydrocarbons.

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Del Piccolo, F; Nazzi, F; Della Vedova, G; Milani, N

2010-05-01

The parasitic mite, Varroa destructor, is the most important threat for apiculture in most bee-keeping areas of the world. The mite is carried to the bee brood cell, where it reproduces, by a nurse bee; therefore the selection of the bee stage by the parasite could influence its reproductive success. This study investigates the role of the cuticular hydrocarbons of the European honeybee (Apis mellifera) in host-selection by the mite. Preliminary laboratory bioassays confirmed the preference of the varroa mite for nurse bees over pollen foragers. GC-MS analysis of nurse and pollen bees revealed differences in the cuticular hydrocarbons of the two stages; in particular, it appeared that pollen bees have more (Z)-8-heptadecene than nurse bees. Laboratory experiments showed that treatment of nurse bees with 100 ng of the pure compound makes them repellent to the varroa mite. These results suggest that the mite can exploit the differences in the cuticular composition of its host for a refined selection that allows it to reach a brood cell and start reproduction. The biological activity of the alkene encourages further investigations for the development of novel control techniques based on this compound.

Immune related gene expression in worker honey bee (Apis mellifera carnica pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor.

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Tanja Tesovnik

Full Text Available Varroa destructor is one of the most common parasites of honey bee colonies and is considered as a possible co-factor for honey bee decline. At the same time, the use of pesticides in intensive agriculture is still the most effective method of pest control. There is limited information about the effects of pesticide exposure on parasitized honey bees. Larval ingestion of certain pesticides could have effects on honey bee immune defense mechanisms, development and metabolic pathways. Europe and America face the disturbing phenomenon of the disappearance of honey bee colonies, termed Colony Collapse Disorder (CCD. One reason discussed is the possible suppression of honey bee immune system as a consequence of prolonged exposure to chemicals. In this study, the effects of the neonicotinoid thiamethoxam on honey bee, Apis mellifera carnica, pupae infested with Varroa destructor mites were analyzed at the molecular level. Varroa-infested and non-infested honey bee colonies received protein cakes with or without thiamethoxam. Nurse bees used these cakes as a feed for developing larvae. Samples of white-eyed and brown-eyed pupae were collected. Expression of 17 immune-related genes was analyzed by real-time PCR. Relative gene expression in samples exposed only to Varroa or to thiamethoxam or simultaneously to both Varroa and thiamethoxam was compared. The impact from the consumption of thiamethoxam during the larval stage on honey bee immune related gene expression in Varroa-infested white-eyed pupae was reflected as down-regulation of spaetzle, AMPs abaecin and defensin-1 and up-regulation of lysozyme-2. In brown-eyed pupae up-regulation of PPOact, spaetzle, hopscotch and basket genes was detected. Moreover, we observed a major difference in immune response to Varroa infestation between white-eyed pupae and brown-eyed pupae. The majority of tested immune-related genes were upregulated only in brown-eyed pupae, while in white-eyed pupae they were

Emissions from the burning of vegetative debris in air curtain destructors.

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Miller, C Andrew; Lemieux, Paul M

2007-08-01

Although air curtain destructors (ACDs) have been used for quite some time to dispose of vegetative debris, relatively little in-depth testing has been conducted to quantify emissions of pollutants other than CO and particulate matter. As part of an effort to prepare for possible use of ACDs to dispose of the enormous volumes of debris generated by Hurricanes Katrina and Rita, the literature on ACD emissions was reviewed to identify potential environmental issues associated with ACD disposal of construction and demolition (C&D) debris. Although no data have been published on emissions from C&D debris combustion in an ACD, a few studies provided information on emissions from the combustion of vegetative debris. These studies are reviewed, and the results compared with studies of open burning of biomass. Combustion of vegetative debris in ACD units results in significantly lower emissions of particulate matter and CO per unit of mass of debris compared with open pile burning. The available data are not sufficient to make general estimates regarding emissions of organic or metal compounds. The highly transient nature of the ACD combustion process, a minimal degree of operational control, and significant variability in debris properties make accurate prediction of ACD emissions impossible in general. Results of scoping tests conducted in preparation for possible in-depth emissions tests demonstrate the challenges associated with sampling ACD emissions and highlight the transient nature of the process. The environmental impacts of widespread use of ACDs for disposal of vegetative debris and their potential use to reduce the volume of C&D debris in future disaster response scenarios remain a considerable gap in understanding the risks associated with debris disposal options.

Efecto del nivel de infestación de Varroa destructor sobre la producción de miel de colonias de Apis mellifera en el altiplano semiárido de México

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Carlos Aurelio Medina-Flores

2011-01-01

Full Text Available El propósito del presente trabajo fue determinar sí el ácaro Varroa destructor afecta la producción de miel en colonias de abejas melíferas (Apis mellifera del altiplano semiárido de México. Se utilizaron 32 colonias que variaban en sus niveles de infestación del ácaro y que no habían recibido ningún acaricida durante dos años. Se determinó la producción de miel y el nivel de parasitosis en abejas adultas de estas colonias y los datos se sometieron a un análisis de correlación. Se encontró una correlación negativa y significativa entre el nivel de infestación por Varroa y la producción de miel (r= -0.44, P=0.01. Los valores medios de infestación y producción de miel (±DE fueron 15.21 ± 8.44 % y 36.26 ± 29.24 kg, respectivamente. Los resultados indican que al incrementarse el nivel de varroosis, la producción de miel se reduce de manera significativa. Se recomienda que las colonias de abejas infestadas por Varroa destructor sean sometidas a métodos de control que reduzcan la población del ácaro para contribuir a incrementar la producción de miel.

Eficacia del Oxavar® para el Control del Ácaro Varroa destructor (Varroidae en Colmenas de Apis mellifera (Apidae Efficacy of Oxavar® to control the mite Varroa destructor (Varroidae in honeybee colonies of Apis mellifera (Apidae

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Jorge Augusto Marcangeli

2003-12-01

Full Text Available El objetivo del trabajo fue evaluar la eficacia del producto Oxavar® para el control del ácaro Varroa destructor (Anderson & Trueman en colmenas de abejas Apis mellifera durante la primavera de 2002 y otoño de 2003. El trabajo se llevó a cabo en el apiario experimental del Centro de Extensión Apícola ubicado en Coronel Vidal, provincia de Buenos Aires. Se trabajó sobre un total de 20 colmenas tipo Langstroth que se dividieron en dos grupos iguales. El primer grupo recibió 5 ml de Oxavar® (323 g en 5000 ml de agua destilada por cuadro cubierto por abejas. El segundo grupo, el testigo, recibió 5 ml de agua destilada por cuadro cubierto por abejas. Ambos grupos recibieron tres dosis a intervalos de siete días. Semanalmente, se recolectaron los ácaros muertos caídos en pisos especiales que evitaban que las abejas los eliminen. Posteriormente, en los dos grupos se colocaron tiras del producto Apistan® para eliminar los ácaros remanentes en las colonias y poder así calcular la eficacia del tratamiento. El producto Oxavar® presentó una eficacia promedio de 85,5 % ± 2,8 durante la primavera y 86,1% ± 2,6 durante el otoño, no mostrando diferencias significativas entre las estaciones (p> 0,05. En ambos casos se registraron diferencias significativas frente al grupo control (pThe aim of this work was to evaluate the acaricide efficacy of Oxavar® to control Varroa destructor (Anderson & Trueman in Apis mellifera (L colonies during the spring 2002 and the autumn 2003. Work was done at “Centro de Extensión Apícola” experimental apiary located in Coronel Vidal, province of Buenos Aires. Twenty Langstroth hives were used divided in two equal groups. The first group received 5 ml of Oxavar® (323 g in 5000 ml of destiled water per comb covered by honeybees and the second one received 5 ml of destiled water. Both groups received three dosages at seven day periods. Dead mites were collected weekly from special floors in order to avoid

Lower virus infections in Varroa destructor-infested and uninfested brood and adult honey bees (Apis mellifera) of a low mite population growth colony compared to a high mite population growth colony.

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Emsen, Berna; Hamiduzzaman, Mollah Md; Goodwin, Paul H; Guzman-Novoa, Ernesto

2015-01-01

A comparison was made of the prevalence and relative quantification of deformed wing virus (DWV), Israeli acute paralysis virus (IAPV), black queen cell virus (BQCV), Kashmir bee virus (KBV), acute bee paralysis virus (ABPV) and sac brood virus (SBV) in brood and adult honey bees (Apis mellifera) from colonies selected for high (HMP) and low (LMP) Varroa destructor mite population growth. Two viruses, ABPV and SBV, were never detected. For adults without mite infestation, DWV, IAPV, BQCV and KBV were detected in the HMP colony; however, only BQCV was detected in the LMP colony but at similar levels as in the HMP colony. With mite infestation, the four viruses were detected in adults of the HMP colony but all at higher amounts than in the LMP colony. For brood without mite infestation, DWV and IAPV were detected in the HMP colony, but no viruses were detected in the LMP colony. With mite infestation of brood, the four viruses were detected in the HMP colony, but only DWV and IAPV were detected and at lower amounts in the LMP colony. An epidemiological explanation for these results is that pre-experiment differences in virus presence and levels existed between the HMP and LMP colonies. It is also possible that low V. destructor population growth in the LMP colony resulted in the bees being less exposed to the mite and thus less likely to have virus infections. LMP and HMP bees may have also differed in susceptibility to virus infection.

Estudio sobre la Eficacia a Campo del Amivar® contra Varroa destructor (Mesostigmata: Varroidae en Colmenas de Apis mellifera (Hymenoptera: Apidae Research on Amivar® efficacy against Varroa destructor (Mesostigmata: Varroidae in honey bee colonies of Apis mellifera (Hymenoptera: Apidae

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Jorge Marcangeli

2005-07-01

Full Text Available El objetivo del trabajo fue evaluar la eficacia del producto Amivar® para el control del ácaro Varroa destructor Anderson & Trueman, en colmenas de abejas durante el otoño de 2003. El trabajo se llevó a cabo en el apiario experimental del Centro de Extensión Apícola ubicado en Coronel Vidal, provincia de Buenos Aires. Se trabajó sobre un total de 20 colmenas tipo Langstroth que se dividieron en dos grupos iguales. En el primer grupo se introdujo una tira de Amivar® (amitraz, 1gr, Apilab, Argentina en el centro del nido de cría de las colmenas. El segundo grupo, sólo recibió el tratamiento de Oxavar® para determinar el número total de ácaros presentes en las colmenas. Semanalmente, se recolectaron los ácaros muertos caídos en pisos especiales que evitaban que las abejas los eliminen. Posteriormente, los dos grupos recibieron tres dosis en total a intervalos de siete días de 5 ml del producto Oxavar® (Apilab-INTA, Argentina; 64,6 g/l; ácido oxálico en agua destilada por cuadro cubierto por abejas para eliminar los ácaros remanentes en las colonias y poder así calcular la eficacia del tratamiento. El producto Amivar® presentó una eficacia promedio de 85,05%±3,39 (rango=79,5 91,6, registrándose diferencias significativas frente al grupo control (pThe aim of this work was to evaluate the acaricide efficacy of Amivar® (amitraz, Apilab, Argentina to control Varroa destructor Anderson & Trueman, in Apis mellifera colonies during the autumn 2003. Work was done at "Centro de Extensión Apícola" experimental apiary located in Coronel Vidal, province of Buenos Aires. Twenty Langstroth hives were used divided in two equal groups. The first group received one strip of Amivar® (amitraz, 1 gr in the center of brood area. The second one represented the control group. Dead mites were collected weekly from special floors designed to avoid mite removal by adult honeybees. Then, a total of three doses of 5 ml of Oxavar® at seven days

Frecuencia de Varroa destructor, Nosema apis y Acarapis woodi en colonias manejadas y enjambres silvestres de abejas (Apis mellifera en Mérida, Yucatán, México

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Jesús Froylán Martínez Puc

2011-01-01

Full Text Available Las enfermedades y parasitosis que afectan a las abejas melíferas causan importantes pérdidas económicas a la actividad apícola. Sin embargo, los daños provocados por dichas parasitosis se presentan de manera heterogénea en colonias manejadas y en enjambres silvestres. Con la finalidad de determinar la frecuencia y niveles de infestación de V. destructor, N. apis y A. woodi en abejas melíferas en Yucatán, se colectaron un total de 76 muestras de abejas melíferas, durante junio a septiembre de 2006, siendo 27 de colonias manejadas y 49 de enjambres silvestres. La frecuencia de V. destructor en colonias manejadas fue de 62.9 %, con un nivel de infestación de 1.70 ± 0.26 (ácaros/100 abejas, y en los enjambres silvestres fue de 55.1 %, con un nivel de infestación de 1.96 ± 0.44. No se observaron diferencias en la frecuencia (X2 = 0.44, gl = 1, P =0.51, y niveles de infestación (t=0.14, P=0.89. La frecuencia de N. apis en las colonias manejadas fue de 74.0 %, con una media de infestación de 1´480 x 103 ± 232 x 103 (esporas/ abeja, y en los enjambres silvestres de 53.0 %, con una media de infestación de 1´416 x 103 ± 264 x 103, no se observaron diferencias en la frecuencia (X2 = 3.22, gl = 1, P= 0.07 y niveles de infestación (t=0.18, P=0.86. No se detectó la presencia de A. woodi en las muestras analizadas. Los resultados demuestran un aumento en la frecuencia de N. apis en Yucatán.

Ensayo a campo sobre la eficacia del Colmesan® contra el ácaro Varroa destructor (Varroidae en colmenas de Apis mellifera (Apidae Field assay of Colmesan® efficacy against the mite Varroa destructor (Varroidae in honey bee colonies of Apis mellifera (Apidae

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Jorge Marcangeli

2004-12-01

Full Text Available El objetivo del trabajo fue evaluar la eficacia del producto Colmesan® para el control del ácaro Varroa destructor (Anderson &Trueman en colmenas de abejas durante el otoño de 2003. El trabajo se llevó a cabo en el apiario experimental ubicado en la ciudad de La Plata, provincia de Buenos Aires. Se trabajó sobre un total de 10 colmenas tipo "Langstroth" que se dividieron en dos grupos iguales. El primer grupo recibió dos dosis de Colmesan® (amitraz, 2,05 g, aplicadas a intervalos de 10 días. El segundo grupo, no recibió ningún tipo de tratamiento. Semanalmente, se recolectaron los ácaros muertos caídos en pisos especiales que evitaban que las abejas los eliminen. Posteriormente, los dos grupos recibieron tres dosis semanales de 5 ml del producto Oxavar® (64,6g/l ácido oxálico en agua destilada por cuadro cubierto por abejas para eliminar los ácaros remanentes en las colonias y poder así calcular la eficacia del tratamiento. El producto Colmesan® presentó una eficacia promedio de 70,92% ± 11,93 (rango = 57,92 - 85,42, registrándose diferencias significativas frente al grupo control (pThe aim of this work was to evaluate the acaricide efficacy of Colmesan® to control Varroa destructor (Anderson & Trueman in Apis mellifera (L. colonies during the autumn 2003. Work was done at an experimental apiary located in La Plata city, province of Buenos Aires. Ten Langstroth hives were used divided in two equal groups. The first group received Colmesan® (amitraz, 2,05 g in 2 doses at 10 days period. The second one represented the control group. Dead mites were collected weekly from special floors designed to avoid mite removal by adult honeybees. Then, 3 weekly doses of 5 ml of Oxavar® (64.6 g/l oxalic acid in destilled water were placed in each colony to kill remanent mites and the acaricide efficacy was calculated. Colmesan® showed an average acaricide efficacy of 70.92% ± 11.93 (range = 57.92 -85.42, showing significant

Lower Virus Infections in Varroa destructor-Infested and Uninfested Brood and Adult Honey Bees (Apis mellifera) of a Low Mite Population Growth Colony Compared to a High Mite Population Growth Colony

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Emsen, Berna; Hamiduzzaman, Mollah Md.; Goodwin, Paul H.; Guzman-Novoa, Ernesto

2015-01-01

A comparison was made of the prevalence and relative quantification of deformed wing virus (DWV), Israeli acute paralysis virus (IAPV), black queen cell virus (BQCV), Kashmir bee virus (KBV), acute bee paralysis virus (ABPV) and sac brood virus (SBV) in brood and adult honey bees (Apis mellifera) from colonies selected for high (HMP) and low (LMP) Varroa destructor mite population growth. Two viruses, ABPV and SBV, were never detected. For adults without mite infestation, DWV, IAPV, BQCV and KBV were detected in the HMP colony; however, only BQCV was detected in the LMP colony but at similar levels as in the HMP colony. With mite infestation, the four viruses were detected in adults of the HMP colony but all at higher amounts than in the LMP colony. For brood without mite infestation, DWV and IAPV were detected in the HMP colony, but no viruses were detected in the LMP colony. With mite infestation of brood, the four viruses were detected in the HMP colony, but only DWV and IAPV were detected and at lower amounts in the LMP colony. An epidemiological explanation for these results is that pre-experiment differences in virus presence and levels existed between the HMP and LMP colonies. It is also possible that low V. destructor population growth in the LMP colony resulted in the bees being less exposed to the mite and thus less likely to have virus infections. LMP and HMP bees may have also differed in susceptibility to virus infection. PMID:25723540

A selective sweep in a Varroa destructor resistant honeybee (Apis mellifera) population.

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Lattorff, H Michael G; Buchholz, Josephine; Fries, Ingemar; Moritz, Robin F A

2015-04-01

The mite Varroa destructor is one of the most dangerous parasites of the Western honeybee (Apis mellifera) causing enormous colony losses worldwide. Various chemical treatments for the control of the Varroa mite are currently in use, which, however, lead to residues in bee products and often to resistance in mites. This facilitated the exploration of alternative treatment methods and breeding for mite resistant honeybees has been in focus for breeders in many parts of the world with variable results. Another approach has been applied to a honeybee population on Gotland (Sweden) that was exposed to natural selection and survived Varroa-infestation for more than 10years without treatment. Eventually this population became resistant to the parasite by suppressing the reproduction of the mite. A previous QTL mapping study had identified a region on chromosome 7 with major loci contributing to the mite resistance. Here, a microsatellite scan of the significant candidate QTL regions was used to investigate potential footprints of selection in the original population by comparing the study population on Gotland before (2000) and after selection (2007). Genetic drift had caused an extreme loss of genetic diversity in the 2007 population for all genetic markers tested. In addition to this overall reduction of heterozygosity, two loci on chromosome 7 showed an even stronger and significant reduction in diversity than expected from genetic drift alone. Within the selective sweep eleven genes are annotated, one of them being a putative candidate to interfere with reduced mite reproduction. A glucose-methanol-choline oxidoreductase (GMCOX18) might be involved in changing volatiles emitted by bee larvae that might be essential to trigger oogenesis in Varroa. Copyright © 2015 Elsevier B.V. All rights reserved.

Índices de prevalencia del ácaro Varroa destructor (Acari: Varroidae en cuadros de cría nuevos o previamente utilizados por Apis mellifera (Hymenoptera: Apidae Infestation levels of the mite Varroa destructor (Acari: Varroidae in new and old honeybee brood combs of Apis mellifera (Hymenoptera: Apidae

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Jorge, A. Marcangeli

2007-07-01

Full Text Available El objetivo de esta investigación fue comparar los niveles de infestación de Varroa destructor (Anderson & Trueman en panales de cría nuevos y viejos, en colonias de la abeja criolla (híbrido de Apis mellifera mellifera (Linnaeus y Apis mellifera ligustica Spinola. El trabajo se llevó a cabo en un apiario ubicado en Coronel Vidal, provincia de Buenos Aires, durante la primavera del año 2005. Se trabajó sobre 20 colmenas tipo Langstroth, de un híbrido de Apis mellifera (Linnaeus infestadas naturalmente por el ácaro Varroa destructor, y seleccionadas al azar. En cada una de ellas se escogió un panal de 2 años (viejo que se colocó en el centro del nido de cría, junto con un panal recientemente labrado por las abejas (nuevo. Luego de que ambos cuadros fueran operculados, se los extrajo y se llevaron al laboratorio para su posterior análisis. Cada una de las celdas de cría se desoperculó e inspeccionó en busca de ácaros, registrándose el número de hembras de ácaros que habían ingresado para su reproducción, se calculó el nivel de infestación como el cociente entre el número de celdas infestadas por ácaros y el número total de celdas inspeccionadas. Los resultados mostraron que los panales viejos presentaron niveles de infestación significativamente superiores a los registrados en panales nuevos (13,52% ± 3,35 y 6,18% ± 2,12 respectivamente; t = 10,62; p = 1,9 E-9; g. l.= 19. El mismo patrón fue observado en el número promedio de ácaros por panal (443,3 ± 70,54 y 217,85 ± 51,76 para panales viejos y nuevos respectivamente; t = 23,87; p = 1,24 E-15; g. l.= 19. Los ácaros presentan una marcada preferencia por los panales viejos. Esta selección estaría guiada por olores propios de las celdas, que actuarían como atrayentes. Además, posiblemente enmascaran su presencia de esta manera y evitan así ser detectados y eliminados por las abejas nodrizas mediante los comportamientos higiénicos.The aim of this work was to

Can We Disrupt the Sensing of Honey Bees by the Bee Parasite Varroa destructor?

Science.gov (United States)

Eliash, Nurit; Singh, Nitin Kumar; Kamer, Yosef; Pinnelli, Govardhana Reddy; Plettner, Erika; Soroker, Victoria

2014-01-01

Background The ectoparasitic mite, Varroa destructor, is considered to be one of the most significant threats to apiculture around the world. Chemical cues are known to play a significant role in the host-finding behavior of Varroa. The mites distinguish between bees from different task groups, and prefer nurses over foragers. We examined the possibility of disrupting the Varroa – honey bee interaction by targeting the mite's olfactory system. In particular, we examined the effect of volatile compounds, ethers of cis 5-(2′-hydroxyethyl) cyclopent-2-en-1-ol or of dihydroquinone, resorcinol or catechol. We tested the effect of these compounds on the Varroa chemosensory organ by electrophysiology and on behavior in a choice bioassay. The electrophysiological studies were conducted on the isolated foreleg. In the behavioral bioassay, the mite's preference between a nurse and a forager bee was evaluated. Principal findings We found that in the presence of some compounds, the response of the Varroa chemosensory organ to honey bee headspace volatiles significantly decreased. This effect was dose dependent and, for some of the compounds, long lasting (>1 min). Furthermore, disruption of the Varroa volatile detection was accompanied by a reversal of the mite's preference from a nurse to a forager bee. Long-term inhibition of the electrophysiological responses of mites to the tested compounds was a good predictor for an alteration in the mite's host preference. Conclusions These data indicate the potential of the selected compounds to disrupt the Varroa - honey bee associations, thus opening new avenues for Varroa control. PMID:25226388

Can we disrupt the sensing of honey bees by the bee parasite Varroa destructor?

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Nurit Eliash

Full Text Available BACKGROUND: The ectoparasitic mite, Varroa destructor, is considered to be one of the most significant threats to apiculture around the world. Chemical cues are known to play a significant role in the host-finding behavior of Varroa. The mites distinguish between bees from different task groups, and prefer nurses over foragers. We examined the possibility of disrupting the Varroa--honey bee interaction by targeting the mite's olfactory system. In particular, we examined the effect of volatile compounds, ethers of cis 5-(2'-hydroxyethyl cyclopent-2-en-1-ol or of dihydroquinone, resorcinol or catechol. We tested the effect of these compounds on the Varroa chemosensory organ by electrophysiology and on behavior in a choice bioassay. The electrophysiological studies were conducted on the isolated foreleg. In the behavioral bioassay, the mite's preference between a nurse and a forager bee was evaluated. PRINCIPAL FINDINGS: We found that in the presence of some compounds, the response of the Varroa chemosensory organ to honey bee headspace volatiles significantly decreased. This effect was dose dependent and, for some of the compounds, long lasting (>1 min. Furthermore, disruption of the Varroa volatile detection was accompanied by a reversal of the mite's preference from a nurse to a forager bee. Long-term inhibition of the electrophysiological responses of mites to the tested compounds was a good predictor for an alteration in the mite's host preference. CONCLUSIONS: These data indicate the potential of the selected compounds to disrupt the Varroa--honey bee associations, thus opening new avenues for Varroa control.

Can we disrupt the sensing of honey bees by the bee parasite Varroa destructor?

Science.gov (United States)

Eliash, Nurit; Singh, Nitin Kumar; Kamer, Yosef; Pinnelli, Govardhana Reddy; Plettner, Erika; Soroker, Victoria

2014-01-01

The ectoparasitic mite, Varroa destructor, is considered to be one of the most significant threats to apiculture around the world. Chemical cues are known to play a significant role in the host-finding behavior of Varroa. The mites distinguish between bees from different task groups, and prefer nurses over foragers. We examined the possibility of disrupting the Varroa--honey bee interaction by targeting the mite's olfactory system. In particular, we examined the effect of volatile compounds, ethers of cis 5-(2'-hydroxyethyl) cyclopent-2-en-1-ol or of dihydroquinone, resorcinol or catechol. We tested the effect of these compounds on the Varroa chemosensory organ by electrophysiology and on behavior in a choice bioassay. The electrophysiological studies were conducted on the isolated foreleg. In the behavioral bioassay, the mite's preference between a nurse and a forager bee was evaluated. We found that in the presence of some compounds, the response of the Varroa chemosensory organ to honey bee headspace volatiles significantly decreased. This effect was dose dependent and, for some of the compounds, long lasting (>1 min). Furthermore, disruption of the Varroa volatile detection was accompanied by a reversal of the mite's preference from a nurse to a forager bee. Long-term inhibition of the electrophysiological responses of mites to the tested compounds was a good predictor for an alteration in the mite's host preference. These data indicate the potential of the selected compounds to disrupt the Varroa--honey bee associations, thus opening new avenues for Varroa control.

Varroa destructor mite mortality rate according to the amount of worker broods in africanized honey bee (Apis mellifera L. colonies = Taxa de mortalidade do ácaro Varroa destructor de acordo com a quantidade de crias em colônias de abelhas africanizadas (Apis mellifera L.

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Geraldo Moretto

2007-07-01

Full Text Available The Varroa destructor mite has caused the death of hundreds of thousands of Apis mellifera colonies in several countries worldwide. However, the effects determined by the Varroa mite change according to the A. mellifera subspecies. In Africanized bee colonies from South and Central America, the parasite causes little damage, as the infestation levels are relatively stable and low, thus treatments against the pest are not required. Among several factors, the grooming behavior of Africanized worker bees plays an important role in the maintenance of the low infestation levels. This study determined the daily rate of live and dead mites found at the bottom of the hive in five Africanized honey bee colonies. During fifteen days of observations, a significant increase was verified in the number of live and dead mites at the bottom of the hive as the amount of worker broods from each honey bee colony decreased. This suggests a more intense grooming activity as the Varroa concentration in the adult honey bee population increases.O ácaro Varroa destructor tem causado a mortalidade de centenas de milhares de colônias de abelhas Apis mellifera em várias partes do mundo. Os efeitos determinados pelo ácaro Varroa variam com a subespécie de Apis mellifera. Nas Américas do Sul e Central, o parasita causa poucos danos às colônias de abelhas africanizadas, a taxa de infestação é estável e baixa, não sendo necessário o tratamento químico contra a praga. Entre vários fatores que são responsáveis pela tolerância das abelhas africanizadas a esse parasita, o comportamento de grooming executado pelas operárias deve exercer importante papel na manutenção dos baixos níveis deinfestação. Neste estudo, foram avaliadas as taxas diárias de ácaros vivos e mortos encontrados no fundo das colméias de cinco colônias de abelhas africanizadas. Durante 15 dias de observações, foi verificado significativo aumento de ácaros no fundo da colméia �

A Mathematical Model of Forager Loss in Honeybee Colonies Infested with Varroa destructor and the Acute Bee Paralysis Virus.

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Ratti, Vardayani; Kevan, Peter G; Eberl, Hermann J

2017-06-01

We incorporate a mathematical model of Varroa destructor and the Acute Bee Paralysis Virus with an existing model for a honeybee colony, in which the bee population is divided into hive bees and forager bees based on tasks performed in the colony. The model is a system of five ordinary differential equations with dependent variables: uninfected hive bees, uninfected forager bees, infected hive bees, virus-free mites and virus-carrying mites. The interplay between forager loss and disease infestation is studied. We study the stability of the disease-free equilibrium of the bee-mite-virus model and observe that the disease cannot be fought off in the absence of varroacide treatment. However, the disease-free equilibrium can be stable if the treatment is strong enough and also if the virus-carrying mites become virus-free at a rate faster than the mite birth rate. The critical forager loss due to homing failure, above which the colony fails, is calculated using simulation experiments for disease-free, treated and untreated mite-infested, and treated virus-infested colonies. A virus-infested colony without varroacide treatment fails regardless of the forager mortality rate.

Development of the system nematode, Ditylenchus Dipsaci (Kuehn) Filipjev, and the potato tuber nematode, D. Destructor thore, after gamma irradiation

International Nuclear Information System (INIS)

Ignatowicz, S.; Karnkowski, W.

1996-01-01

Juvenile and adult nematodes emerged from onion and garlic samples on the 3 rd week after irradiation with doses up to 0.5 kGy and from potato treated with doses up to 2.0 kGy. However, irradiation of onion infected with Ditylenchus dipsaci caused the inhibition of the development and growth of juvenile nematodes to mature forms. Doses of gamma radiation ranging from 0.1 to 0.5 kGy had only a slight effect, if any, on the development and growth of D. dipsaci nematodes infecting garlic, but they increased juvenile mortality. Gamma radiation at doses up to 2.0 kGy induced increased mortality of nematode juveniles of the potato tuber nematode, D. destructor but less so inhibited their development to mature forms. Nematodes were found to be resistant to irradiation treatment. Therefore the use of gamma irradiation for nematode disinfestation of agricultural products seems to be impractical, if the aim of the treatment is to kill these pests within a few weeks. The level of radiation required to kill nematodes in infected plants would damage plant tissues so that the further storage of vegetables will be impossible. (author). 22 refs, 3 figs, 2 tabs

Hygienic and grooming behaviors in African and European honeybees-New damage categories in Varroa destructor.

Science.gov (United States)

Nganso, Beatrice T; Fombong, Ayuka T; Yusuf, Abdullahi A; Pirk, Christian W W; Stuhl, Charles; Torto, Baldwyn

2017-01-01

Varroa destructor is an ectoparasitic pest of honeybees, and a threat to the survival of the apiculture industry. Several studies have shown that unlike European honeybees, African honeybee populations appear to be minimally affected when attacked by this mite. However, little is known about the underlying drivers contributing to survival of African honeybee populations against the mite. We hypothesized that resistant behavioral defenses are responsible for the survival of African honeybees against the ectoparasite. We tested this hypothesis by comparing grooming and hygienic behaviors in the African savannah honeybee Apis mellifera scutellata in Kenya and A. mellifera hybrids of European origin in Florida, USA against the mite. Grooming behavior was assessed by determining adult mite infestation levels, daily mite fall per colony and percentage mite damage (as an indicator of adult grooming rate), while hygienic behavior was assessed by determining the brood removal rate after freeze killing a section of the brood. Our results identified two additional undescribed damaged mite categories along with the six previously known damage categories associated with the grooming behavior of both honeybee subspecies. Adult mite infestation level was approximately three-fold higher in A. mellifera hybrids of European origin than in A. m. scutellata, however, brood removal rate, adult grooming rate and daily natural mite fall were similar in both honeybee subspecies. Unlike A. mellifera hybrids of European origin, adult grooming rate and brood removal rate did not correlate with mite infestation levels on adult worker honeybee of A. m. scutellata though they were more aggressive towards the mites than their European counterparts. Our results provide valuable insights into the tolerance mechanisms that contribute to the survival of A. m. scutellata against the mite.

Effects of Imidacloprid and Varroa destructor on survival and health of European honey bees, Apis mellifera.

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Abbo, Pendo M; Kawasaki, Joshua K; Hamilton, Michele; Cook, Steven C; DeGrandi-Hoffman, Gloria; Li, Wen Feng; Liu, Jie; Chen, Yan Ping

2017-06-01

There has been growing concern over declines in populations of honey bees and other pollinators which are a vital part to our food security. It is imperative to identify factors responsible for accelerated declines in bee populations and develop solutions for reversing bee losses. While exact causes of colony losses remain elusive, risk factors thought to play key roles are ectoparasitic mites Varroa destructor and neonicotinoid pesticides. The present study aims to investigate effects of a neonicotinoid pesticide Imidacloprid and Varroa mites individually on survivorship, growth, physiology, virus dynamics and immunity of honey bee workers. Our study provides clear evidence that the exposure to sublethal doses of Imidacloprid could exert a significantly negative effect on health and survival of honey bees. We observed a significant reduction in the titer of vitellogenin (Vg), an egg yolk precursor that regulates the honey bees development and behavior and often are linked to energy homeostasis, in bees exposed to Imidacloprid. This result indicates that sublethal exposure to neonicotinoid could lead to increased energy usage in honey bees as detoxification is a energy-consuming metabolic process and suggests that Vg could be a useful biomarker for measuring levels of energy stress and sublethal effects of pesticides on honey bees. Measurement of the quantitative effects of different levels of Varroa mite infestation on the replication dynamic of Deformed wing virus (DWV), an RNA virus associated with Varroa infestation, and expression level of immune genes yields unique insights into how honey bees respond to stressors under laboratory conditions. © 2016 Institute of Zoology, Chinese Academy of Sciences.

Effects of Imidacloprid and Varroa destructor on survival and health of European honey bees, Apis mellifera

Institute of Scientific and Technical Information of China (English)

Pendo M.Abbo; Joshua K.Kawasaki; Michele Hamilton; Steven C.Cook; Gloria DeGrandi-Hoffman; Wen Feng Li; Jie Liu; Yan Ping Chen

2017-01-01

There has been growing concern over declines in populations of honey bees and other pollinators which are a vital part to our food security.It is imperative to identify factors responsible for accelerated declines in bee populations and develop solutions for reversing bee losses.While exact causes of colony losses remain elusive,risk factors thought to play key roles are ectoparasitic mites Varroa destructor and neonicotinoid pesticides.The present study aims to investigate effects of a neonicotinoid pesticide Imidacloprid and Varroa mites individually on survivorship,growth,physiology,virus dynamics and immunity of honey bee workers.Our study provides clear evidence that the exposure to sublethal doses of Imidacloprid could exert a significantly negative effect on health and survival of honey bees.We observed a significant reduction in the titer ofvitellogenin (Vg),an egg yolk precursor that regulates the honey bees development and behavior and often are linked to energy homeostasis,in bees exposed to Imidacloprid.This result indicates that sublethal exposure to neonicotinoid could lead to increased energy usage in honey bees as detoxification is a energy-consuming metabolic process and suggests that Vg could be a useful biomarker for measuring levels of energy stress and sublethal effects of pesticideson honey bees.Measurement of the quantitative effects of different levels of Varroa mite infestation on the replication dynamic of Deformed wing virus (DWV),an RNA virus associated with Varroa infestation,and expression level of immune genes yields unique insights into how honey bees respond to stressors under laboratory conditions.

Producción de miel e infestación con Varroa destructor de abejas africanizadas (Apis mellifera con alto y bajo comportamiento higiénico

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Carlos Aurelio Medina-Flores

2014-01-01

Full Text Available El objetivo del estudio fue comparar la producción de miel y los niveles de Varroa destructor entre colonias de abejas africanizadas (AA ( Apis mellifera con alto y bajo comportamiento higiénico (CH en el altiplano semiárido de México. Se midió el nivel de CH a 57 colonias por congelamiento de la cría con nitrógeno líquido (N 2 . Las colonias se clasificaron en dos grupos: alto CH (> 95 % y bajo CH (0.05. Estos resultados sugieren que aparentemente el comportamiento higiénico no tiene un efecto mayor en la resistencia de las AA al crecimiento poblaci onal del ácaro. También sugieren que el comportamiento higiénico alto podría contribuir a incrementar la producción de miel en épocas del año con flujo reducido de néctar.

Meadow-grass gall midge

DEFF Research Database (Denmark)

Hansen, Lars Monrad

The area with meadow-grass (Poa pratensis, L.) grown for seed production in Den-mark is a significant proportion of the entire seed production. The meadow-grass gall midge (Mayetiola schoberi, Barnes 1958) is of considerable economic importance since powerful attacks can reduce the yield...

Fertility and reproductive rate of Varroa mite, Varroa destructor, in native and exotic honeybee, Apis mellifera L., colonies under Saudi Arabia conditions

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Yehya Alattal

2017-07-01

Full Text Available Varroa mite is the most destructive pest to bee colonies worldwide. In Saudi Arabia, preliminary data indicated high infestation levels in the exotic honeybee colonies; such as Apis mellifera carnica and Apis mellifera ligustica, compared to native honeybee subspecies Apis mellifera jemenitica, which may imply higher tolerance to Varroasis. In this study, fertility and reproductive rate of Varroa mite, Varroa destructor, in capped brood cells of the native honeybee subspecies were investigated and compared with an exotic honeybee subspecies, A. m. carnica. Mite fertility was almost alike (87.5% and 89.4% in the native and craniolan colonies respectively. Similarly, results did not show significant differences in reproduction rate between both subspecies (F = 0.66, Pr > F = 0.42. Number of adult Varroa daughters per fertile mother mite was 2.0 and 2.1 for native and craniolan honeybee subspecies respectively. This may indicate that mechanisms of keeping low infestation rates in the native honeybee colonies are not associated with Varroa reproduction. Therefore, potential factors of keeping lower Varroa infestation rates in native honey bee subspecies should be further investigated.

Quantitative proteomics reveals divergent responses in Apis mellifera worker and drone pupae to parasitization by Varroa destructor.

Science.gov (United States)

Surlis, Carla; Carolan, James C; Coffey, Mary; Kavanagh, Kevin

Varroa destructor is a haemophagous ectoparasite of honeybees and is considered a major causal agent of colony losses in Europe and North America. Although originating in Eastern Asia where it parasitizes Apis cerana, it has shifted hosts to the western honeybee Apis mellifera on which it has a greater deleterious effect on the individual and colony level. To investigate this important host-parasite interaction and to determine whether Varroa causes different effects on different castes we conducted a label free quantitative proteomic analysis of Varroa-parasitized and non-parasitized drone and worker Apis mellifera pupae. 1195 proteins were identified in total, of which 202 and 250 were differentially abundant in parasitized drone and worker pupae, respectively. Both parasitized drone and worker pupae displayed reduced abundance in proteins associated with the cuticle, lipid transport and innate immunity. Proteins involved in metabolic processes were more abundant in both parasitized castes although the response in workers was more pronounced. A number of caste specific responses were observed including differential abundance of numerous cytoskeletal and muscle proteins, which were of higher abundance in parasitized drones in comparison to parasitized workers. Proteins involved in fatty acid and carbohydrate metabolism were more abundant in parasitized workers as were a large number of ribosomal proteins highlighting either potentially divergent responses to Varroa or a different strategy by the mite when parasitizing the different castes. This data improves our understanding of this interaction and may provide a basis for future studies into improvements to therapy and control of Varroasis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Transfer of Hessian fly resistance from rye to wheat via radiation-induced terminal and intercalary chromosomal translocations

International Nuclear Information System (INIS)

Friebe, B.; Hatchett, J.H.; Gill, B.S.; Mukai, Y.; Sebesta, E.E.

1991-01-01

A new Hessian fly (Mayetiola destructor) resistance gene derived from 'Balbo' rye and its transfer to hexaploid wheat via radiation-induced terminal and intercalary chromosomal translocations are described. Crosses between resistant 'Balbo' rye and susceptible 'Suwon 92' wheat and between the F1 amphidiploids and susceptible 'TAM 106' and 'Amigo' wheats produced resistant BC2F3 lines that were identified by C-banding analysis as being 6RL telocentric addition lines. Comparative chromosomal analyses and resistance tests revealed that the resistance gene is located on the 6RL telocentric chromosome. X-irradiated pollen of 6RL addition plants was used to fertilize plants of susceptible wheats 'TAM 106,' 'TAM 101,' and 'Vona.' After several generations of selection for resistance, new sublines were obtained that were homogeneous for resistance. Thirteen of these lines were analyzed by C-banding, and three different wheat-6RL chromosomal translocations (T) were identified. Wheat chromosomes involved in the translocations were 6B, 4B, and 4A. Almost the complete 6RL arm is present in T6BS · 6BL-6RL. Only the distal half of 6RL is present in T4BS · 4BL-6RL, which locates the resistance gene in the distal half of 6RL. Only a very small segment (ca 1.0 μm) of the distal region of 6RL is present in an intercalary translocation (Ti) Ti4AS · 4AL-6RL-4AL. The 6RL segment is inserted in the intercalary region between the centromere of chromosome 4A and the large proximal C-band of 4AL. The break-points of the translocations are outside the region of the centromere, indicating that they were induced by the X-ray treatment. All three translocations are cytologically stable and can be used directly in wheat breeding programs

Índices de prevalencia del ácaro Varroa destructor (Acari: Varroidae en cuadros de cría nuevos o previamente utilizados por Apis mellifera (Hymenoptera: Apidae

Directory of Open Access Journals (Sweden)

Jorge, A. MARCANGELI

2007-01-01

Full Text Available El objetivo de esta investigación fue comparar los niveles de infestación de Varroa destructor (Anderson & Trueman en panales de cría nuevos y viejos, en colonias de la abeja criolla (híbrido de Apis mellifera mellifera (Linnaeus y Apis mellifera ligustica Spinola. El trabajo se llevó a cabo en un apiario ubicado en Coronel Vidal, provincia de Buenos Aires, durante la primavera del año 2005. Se trabajó sobre 20 colmenas tipo Langstroth, de un híbrido de Apis mellifera (Linnaeus infestadas naturalmente por el ácaro Varroa destructor, y seleccionadas al azar. En cada una de ellas se escogió un panal de 2 años (viejo que se colocó en el centro del nido de cría, junto con un panal recientemente labrado por las abejas (nuevo. Luego de que ambos cuadros fueran operculados, se los extrajo y se llevaron al laboratorio para su posterior análisis. Cada una de las celdas de cría se desoperculó e inspeccionó en busca de ácaros, registrándose el número de hembras de ácaros que habían ingresado para su reproducción, se calculó el nivel de infestación como el cociente entre el número de celdas infestadas por ácaros y el número total de celdas inspeccionadas. Los resultados mostraron que los panales viejos presentaron niveles de infestación significativamente superiores a los registrados en panales nuevos (13,52% ± 3,35 y 6,18% ± 2,12 respectivamente; t = 10,62; p = 1,9 E-9; g. l.= 19. El mismo patrón fue observado en el número promedio de ácaros por panal (443,3 ± 70,54 y 217,85 ± 51,76 para panales viejos y nuevos respectivamente; t = 23,87; p = 1,24 E-15; g. l.= 19. Los ácaros presentan una marcada preferencia por los panales viejos. Esta selección estaría guiada por olores propios de las celdas, que actuarían como atrayentes. Además, posiblemente enmascaran su presencia de esta manera y evitan así ser detectados y eliminados por las abejas nodrizas mediante los comportamientos higiénicos.

Efecto de la cantidad de cría de abeja Apis mellifera (Apidae sobre la eficacia del Oxavar® para el control del ácaro Varroa destructor (Varroidae Effect of Apis mellifera (Apidae honeybee brood amount on Oxavar® acaricide efficacy against the mite Varroa destructor (Varroidae

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Jorge Marcangeli

2004-12-01

Full Text Available El objetivo del presente trabajo fue evaluar la eficacia acaricida del Oxavar® en el control del ácaro ectoparásito Varroa destructor (Anderson & Trueman. El trabajo fue realizado en el apiario experimental del Centro de Extensión Apícola ubicado en Coronel Vidal, provincia de Buenos Aires. Se seleccionaron diez colmenas tipo Langstroth que fueron divididas en dos grupos: a cinco colmenas con tres cuadros cubiertos completamente de cría en desarrollo y b cinco colmenas con seis cuadros cubiertos por cría. Ambos grupos recibieron cinco ml of Oxavar® (Apilab, Argentina; 64,6 g/l de ácido oxálico en agua destilada por cuadro cubierto por abejas adultas en tres dosis a intervalos de siete días. Semanalmente, se colectaron los ácaros muertos de los pisos especiales provistos a las colmenas de estudio con el objeto de evitar su remoción por parte de las abejas. Una vez concluido el tratamiento, en cada colmena se introdujeron dos tiras plásticas de Apistan® (Roteh, Argentina para eliminar los ácaros remanentes y poder así calcular la eficacia acaricida del Oxavar®. Los resultados mostraron que la eficacia del Oxavar® en el primer grupo (85,6% ± 1,4 resultó significativamente superior a la registrada en el segundo grupo (75,7 ± 1,7. Estas diferencias fueron testeadas a partir del número total de ácaros eliminados por el Oxavar® y Apistan® en ambos grupos de colmenas (pThe aim of this work was to evaluate the effect of honeybee brood on acaricide efficacy of Oxavar® to control the ectoparasitic mite Varroa destructor (Anderson & Trueman. Work was done at Centro de Extensión Apícola experimental apiary located at Coronel Vidal, province of Buenos Aires. Ten Langstroth hives were selected and divided in two groups: a hives containing three honeybee combs full of brood and b hives containing six honeybee brood combs. Both groups received five ml of Oxavar® (Laboratorio Apilab, Argentina; 64.6 g/l oxalic acid in destilled water

Infestação pelo Ácaro Varroa destructor (Anderson & Trueman (Mesostigmata: Varroidae em Operárias Adultas e em Células de Cria de Abelhas Africanizadas Apis mellifera Linnaeus (Hymenoptera: Apidae na Região de Franca-SP

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Aline Turcatto

2012-12-01

Abstract. The mite Varroa destructor (Anderson & Trueman, has been, until now, one of the pest that causes more damage to the beekeeping worldwide, alone or associated with another bee diseases. Several factors affects the variation of the indexes of infestation and reproduction, such as climate, bee breed, development time, hygienic behavior; being that temperature is a environmental variable that acts on the variation of these indexes: the infestation increases in the colder months and decrease in warmer months, so in the months of autumn and winter occurs the biggest infestation by varroa in the beehives. Were evaluated the indexes of infestation by V. destructor on adult worker and brood cells to ascertain how these indexes rates, in months of autumn, in an africanized bees apiary located in region of Cerrado, surrounded by plantations of sugar cane, with a tropical climate and food in nature. The sample was collected in two years, in the months of May and June 2005 and April and June 2007 in the Experimental Apiary of Franca University-UNIFRAN, located in the municipality of Restiga-SP. The medium indexes of infestation in broods were higher in May/2005 (12.44% than June/2005 (7.78%, were also higher in April/2007 (3% than in June/2007 (0%; all the differences weren’t statistically significant. The medium indexes of infestation in adult workers were lesser in May/2005 (0.95% than June/2005 (1.90% and lesser in April/2007 (0.90% than in June/2007 (4.43%; the difference observed in 2005 was not statistically significant, unlike that observed in 2007 (P=0.031.

A comparison of the reproductive ability of Varroa destructor (Mesostigmata:Varroidae) in worker and drone brood of Africanized honey bees (Apis mellifera).

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Calderón, Rafael A; Zamora, Luis G; Van Veen, Johan W; Quesada, Mariela V

2007-01-01

Colony infestation by the parasitic mite, Varroa destructor is one of the most serious problems for beekeeping worldwide. In order to reproduce varroa females, enter worker or drone brood shortly before the cell is sealed. To test the hypothesis that, due to the preference of mites to invade drone brood to reproduce, a high proportion of the mite reproduction should occur in drone cells, a comparative study of mite reproductive rate in worker and drone brood of Africanized honey bees (AHB) was done for 370 mites. After determining the number, developmental stage and sex of the offspring in worker cells, the foundress female mite was immediately transferred into an uninfested drone cell. Mite fertility in single infested worker and drone brood cells was 76.5 and 79.3%, respectively. There was no difference between the groups (X(2)= 0.78, P = 0.37). However, one of the most significant differences in mite reproduction was the higher percentage of mites producing viable offspring (cells that contain one live adult male and at least one adult female mite) in drone cells (38.1%) compared to worker cells (13.8%) (X(2)= 55.4, P drone cells (X(2)= 69, P drone brood.

Exploring the host parasitism of the migratory plant-parasitic nematode Ditylenchus destuctor by expressed sequence tags analysis.

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Huan Peng

Full Text Available The potato rot nematode, Ditylenchus destructor, is a very destructive nematode pest on many agriculturally important crops worldwide, but the molecular characterization of its parasitism of plant has been limited. The effectors involved in nematode parasitism of plant for several sedentary endo-parasitic nematodes such as Heterodera glycines, Globodera rostochiensis and Meloidogyne incognita have been identified and extensively studied over the past two decades. Ditylenchus destructor, as a migratory plant parasitic nematode, has different feeding behavior, life cycle and host response. Comparing the transcriptome and parasitome among different types of plant-parasitic nematodes is the way to understand more fully the parasitic mechanism of plant nematodes. We undertook the approach of sequencing expressed sequence tags (ESTs derived from a mixed stage cDNA library of D. destructor. This is the first study of D. destructor ESTs. A total of 9800 ESTs were grouped into 5008 clusters including 3606 singletons and 1402 multi-member contigs, representing a catalog of D. destructor genes. Implementing a bioinformatics' workflow, we found 1391 clusters have no match in the available gene database; 31 clusters only have similarities to genes identified from D. africanus, the most closely related species to D. destructor; 1991 clusters were annotated using Gene Ontology (GO; 1550 clusters were assigned enzyme commission (EC numbers; and 1211 clusters were mapped to 181 KEGG biochemical pathways. 22 ESTs had similarities to reported nematode effectors. Interestedly, most of the effectors identified in this study are involved in host cell wall degradation or modification, such as 1,4-beta-glucanse, 1,3-beta-glucanse, pectate lyase, chitinases and expansin, or host defense suppression such as calreticulin, annexin and venom allergen-like protein. This result implies that the migratory plant-parasitic nematode D. destructor secrets similar effectors to

Increased tolerance and resistance to virus infections: a possible factor in the survival of Varroa destructor-resistant honey bees (Apis mellifera.

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Barbara Locke

Full Text Available The honey bee ectoparasitic mite, Varroa destructor, has a world-wide distribution and inflicts more damage than all other known apicultural diseases. However, Varroa-induced colony mortality is more accurately a result of secondary virus infections vectored by the mite. This means that honey bee resistance to Varroa may include resistance or tolerance to virus infections. The aim of this study was to see if this is the case for a unique population of mite-resistant (MR European honey bees on the island of Gotland, Sweden. This population has survived uncontrolled mite infestation for over a decade, developing specific mite-related resistance traits to do so. Using RT-qPCR techniques, we monitored late season virus infections, Varroa mite infestation and honey bee colony population dynamics in the Gotland MR population and compared this to mite-susceptible (MS colonies in a close by apiary. From summer to autumn the deformed wing virus (DWV titres increased similarly between the MR and MS populations, while the black queen cell virus (BQCV and sacbrood virus (SBV titres decreased substantially in the MR population compared to the MS population by several orders of magnitude. The MR colonies all survived the following winter with high mite infestation, high DWV infection, small colony size and low proportions of autumn brood, while the MS colonies all perished. Possible explanations for these changes in virus titres and their relevance to Varroa resistance and colony winter survival are discussed.

Reproductive ability and level of infestation of the Varroa destructor mite in Apis mellifera apiaries in Blumenau, State of Santa Catarina, Brazil - doi: 10.4025/actascibiolsci.v36i1.20366

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Francisco Estevão Carneiro

2013-08-01

Full Text Available Varroa destructor mite causes mortality of Apis mellifera bees throughout the world. Its greatest damage to these colonies has been reported in European countries and North America. The impact of the mite is related to the climate and the bee race on each region in which the plague has been established. Varroa causes little damage to the colonies of africanized honeybees in Brazil and the levels of infestation are relatively small and stable. The reproductive ability of Varroa females was evaluated in pupae of workers of 17-18 days of age, obtained from eight beehives of africanized bees for twelve months. The average number of offspring (deutonymphs, protonymphs and eggs each Varroa produced was 3.18 ± 0.19. The average total number of deutonymph and protonymph was, respectively, 1.57 ± 0.15 and 1.61 ± 0.14. The levels of infestation demonstrated that the plague continue reaching low levels, the average was 4.11 ± 3.42.

Relative abundance of deformed wing virus, Varroa destructor virus 1, and their recombinants in honey bees (Apis mellifera) assessed by kmer analysis of public RNA-Seq data

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Cornman, Robert S.

2017-01-01

Deformed wing virus (DWV) is a major pathogen of concern to apiculture, and recent reports have indicated the local predominance and potential virulence of recombinants between DWV and a related virus, Varroa destructor virus 1 (VDV). However, little is known about the frequency and titer of VDV and recombinants relative to DWV generally. In this study, I assessed the relative occurrence and titer of DWV and VDV in public RNA-seq accessions of honey bee using a rapid, kmer-based approach. Three recombinant types were detectable graphically and corroborated by de novo assembly. Recombination breakpoints did not disrupt the capsid-encoding region, consistent with previous reports, and both VDV- and DWV-derived capsids were observed in recombinant backgrounds. High abundance of VDV kmers was largely restricted to recombinant forms. Non-metric multidimensional scaling identified genotypic clusters among DWV isolates, which was corroborated by read mapping and consensus generation. The recently described DWV-C lineage was not detected in the searched accessions. The data further highlight the utility of high-throughput sequencing to monitor viral polymorphisms and statistically test biological predictors of titer, and point to the need for consistent methodologies and sampling schemes.

Removal of drone brood from Apis mellifera (Hymenoptera: Apidae) colonies to control Varroa destructor (Acari: Varroidae) and retain adult drones.

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Wantuch, Holly A; Tarpy, David R

2009-12-01

The parasitic mite Varroa destructor Anderson & Trueman (Acari: Varroidae) has plagued European honey bees, Apis mellifera L. (Hymenoptera: Apidae), in the Americas since its introduction in the 1980s. For many years, these mites were sufficiently controlled using synthetic acaricides. Recently, however, beekeepers have experienced increased resistance by mites to chemical pesticides, which are also known to leave residues in hive products such as wax and honey. Thus there has been increased emphasis on nonchemical integrated pest management control tactics for Varroa. Because mites preferentially reproduce in drone brood (pupal males), we developed a treatment strategy focusing on salvaging parasitized drones while removing mites from them. We removed drone brood from colonies in which there was no acaricidal application and banked them in separate "drone-brood receiving" colonies treated with pesticides to kill mites emerging with drones. We tested 20 colonies divided into three groups: 1) negative control (no mite treatment), 2) positive control (treatment with acaricides), and 3) drone-brood removal and placement into drone-brood receiving colonies. We found that drone-brood trapping significantly lowered mite numbers during the early months of the season, eliminating the need for additional control measures in the spring. However, mite levels in the drone-brood removal group increased later in the summer, suggesting that this benefit does not persist throughout the entire season. Our results suggest that this method of drone-brood trapping can be used as an element of an integrated control strategy to control varroa mites, eliminating a large portion of the Varroa population with limited chemical treatments while retaining the benefits of maintaining adult drones in the population.

Control del parásito Varroa destructor (Acari: Varroidae en colmenas de la abeja Apis mellifera (Hymenoptera: Apidae mediante la aplicación de la técnica de entrampado Control of the parasite Varroa destructor (Acari: Varroidae in honeybee colonies of Apis mellifera (Hymenoptera: Apidae applying brood trap combs

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Natalia Damiani

2006-07-01

Full Text Available La parasitosis causada por el ácaro Varroa destructor (Anderson & Trueman es, actualmente considerada el mayor escollo para el desarrollo de la apicultura. El objetivo del presente trabajo fue evaluar la técnica del entrampamiento de ácaros en panales de cría, como posible método de control de la parasitosis. El trabajo se llevó a cabo en Coronel Vidal, provincia de Buenos Aires. Se trabajó sobre colmenas tipo Langstroth del híbrido regional de Apis mellifera (Linneaus. En cada colmena experimental se procedió a confinar a la reina en panales trampa específicos, con el fin de poder controlar la oviposición. Estos panales, luego de ser operculados por las obreras, fueron llevados al laboratorio donde se desoperculó cada una de las celdas de cría, y se contabilizó el número de ácaros presentes. Esta técnica se aplicó variando el número de panales trampa (1-3 colocados, tanto para los constituidos por celdas de cría de obreras como de zánganos. También, se evaluó el impacto de la aplicación de esta técnica sobre el desarrollo de las colonias, mediante la medición de su productividad. Los resultados indican, que la técnica empleada sólo es efectiva, cuando se aplican tres panales de cría de zánganos de manera consecutiva, alcanzando una efectividad máxima de 84%. Cuando se aplican tres panales de obreras, la técnica mostró niveles de efectividad muy inferiores (14%. En las colonias sobre las que se aplicó esta técnica, la productividad de miel se redujo significativamente, comparada con las colonias control. Esta técnica resulta ideal para ser combinada con otros mecanismos de control, disminuyendo la aplicación de sustancias químicas que puedan contaminar la miel, y la generación de resistencia por parte del ácaro frente a los principios activos utilizados para su control.At present, Varroosis is considered the major problem to beekeeping development. The aim of this work was to evaluate brood tramp combs

Estudio sobre la Eficacia a Campo del Amivar® contra Varroa destructor (Mesostigmata: Varroidae en Colmenas de Apis mellifera (Hymenoptera: Apidae

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Jorge MARCANGELI

2005-01-01

Full Text Available El objetivo del trabajo fue evaluar la eficacia del producto Amivar® para el control del ácaro Varroa destructor Anderson & Trueman, en colmenas de abejas durante el otoño de 2003. El trabajo se llevó a cabo en el apiario experimental del Centro de Extensión Apícola ubicado en Coronel Vidal, provincia de Buenos Aires. Se trabajó sobre un total de 20 colmenas tipo Langstroth que se dividieron en dos grupos iguales. En el primer grupo se introdujo una tira de Amivar® (amitraz, 1gr, Apilab, Argentina en el centro del nido de cría de las colmenas. El segundo grupo, sólo recibió el tratamiento de Oxavar® para determinar el número total de ácaros presentes en las colmenas. Semanalmente, se recolectaron los ácaros muertos caídos en pisos especiales que evitaban que las abejas los eliminen. Posteriormente, los dos grupos recibieron tres dosis en total a intervalos de siete días de 5 ml del producto Oxavar® (Apilab-INTA, Argentina; 64,6 g/l; ácido oxálico en agua destilada por cuadro cubierto por abejas para eliminar los ácaros remanentes en las colonias y poder así calcular la eficacia del tratamiento. El producto Amivar® presentó una eficacia promedio de 85,05% ± 3,39 (rango = 79,5 – 91,6, registrándose diferencias significativas frente al grupo control (p< 0,05. No seobservaron efectos negativos del producto sobre la cría de abejas en desarrollo. Estos resultados demuestran que este producto es efectivo para el control de la parasitosis.

An Observational Study of Honey Bee Colony Winter Losses and Their Association with Varroa destructor, Neonicotinoids and Other Risk Factors

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van der Zee, Romée; Gray, Alison; Pisa, Lennard; de Rijk, Theo

2015-01-01

This article presents results of an analysis of honey bee losses over the winter of 2011-2012 in the Netherlands, from a sample of 86 colonies, located at 43 apiaries. The apiaries were selected using spatially stratified random sampling. Colony winter loss data were collected and related to various measures of colony strength recorded in summer, as well as data from laboratory analysis of sample material taken from two selected colonies in each of the 43 apiaries. The logistic regression model which best explained the risk of winter loss included, in order of statistical importance, the variables (1) Varroa destructor mite infestation rate in October 2011, (2) presence of the cyano-substituted neonicotinoids acetamiprid or thiacloprid in the first 2 weeks of August 2011 in at least one of the honey bee matrices honey, bees or bee bread (pollen), (3) presence of Brassica napus (oilseed rape) or Sinapis arvensis (wild mustard) pollen in bee bread in early August 2011, and (4) a measure of the unexplained winter losses for the postal code area where the colonies were located, obtained from a different dataset. We consider in the discussion that reduced opportunities for foraging in July and August because of bad weather may have added substantially to the adverse effects of acetamiprid and thiacloprid. A novel feature of this work is its use of postal code random effects from two other independent datasets collected in the annual national monitoring by questionnaires of winter losses of honey bees in the Netherlands. These were used to plan the sample selection and also in the model fitting of the data in this study. It should however be noted that the results of the present pilot study are based on limited data, which may consequently reveal strong factors but fail to demonstrate possible interaction effects. PMID:26154346

An Observational Study of Honey Bee Colony Winter Losses and Their Association with Varroa destructor, Neonicotinoids and Other Risk Factors.

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Romée van der Zee

Full Text Available This article presents results of an analysis of honey bee losses over the winter of 2011-2012 in the Netherlands, from a sample of 86 colonies, located at 43 apiaries. The apiaries were selected using spatially stratified random sampling. Colony winter loss data were collected and related to various measures of colony strength recorded in summer, as well as data from laboratory analysis of sample material taken from two selected colonies in each of the 43 apiaries. The logistic regression model which best explained the risk of winter loss included, in order of statistical importance, the variables (1 Varroa destructor mite infestation rate in October 2011, (2 presence of the cyano-substituted neonicotinoids acetamiprid or thiacloprid in the first 2 weeks of August 2011 in at least one of the honey bee matrices honey, bees or bee bread (pollen, (3 presence of Brassica napus (oilseed rape or Sinapis arvensis (wild mustard pollen in bee bread in early August 2011, and (4 a measure of the unexplained winter losses for the postal code area where the colonies were located, obtained from a different dataset. We consider in the discussion that reduced opportunities for foraging in July and August because of bad weather may have added substantially to the adverse effects of acetamiprid and thiacloprid. A novel feature of this work is its use of postal code random effects from two other independent datasets collected in the annual national monitoring by questionnaires of winter losses of honey bees in the Netherlands. These were used to plan the sample selection and also in the model fitting of the data in this study. It should however be noted that the results of the present pilot study are based on limited data, which may consequently reveal strong factors but fail to demonstrate possible interaction effects.

An Observational Study of Honey Bee Colony Winter Losses and Their Association with Varroa destructor, Neonicotinoids and Other Risk Factors.

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van der Zee, Romée; Gray, Alison; Pisa, Lennard; de Rijk, Theo

2015-01-01

This article presents results of an analysis of honey bee losses over the winter of 2011-2012 in the Netherlands, from a sample of 86 colonies, located at 43 apiaries. The apiaries were selected using spatially stratified random sampling. Colony winter loss data were collected and related to various measures of colony strength recorded in summer, as well as data from laboratory analysis of sample material taken from two selected colonies in each of the 43 apiaries. The logistic regression model which best explained the risk of winter loss included, in order of statistical importance, the variables (1) Varroa destructor mite infestation rate in October 2011, (2) presence of the cyano-substituted neonicotinoids acetamiprid or thiacloprid in the first 2 weeks of August 2011 in at least one of the honey bee matrices honey, bees or bee bread (pollen), (3) presence of Brassica napus (oilseed rape) or Sinapis arvensis (wild mustard) pollen in bee bread in early August 2011, and (4) a measure of the unexplained winter losses for the postal code area where the colonies were located, obtained from a different dataset. We consider in the discussion that reduced opportunities for foraging in July and August because of bad weather may have added substantially to the adverse effects of acetamiprid and thiacloprid. A novel feature of this work is its use of postal code random effects from two other independent datasets collected in the annual national monitoring by questionnaires of winter losses of honey bees in the Netherlands. These were used to plan the sample selection and also in the model fitting of the data in this study. It should however be noted that the results of the present pilot study are based on limited data, which may consequently reveal strong factors but fail to demonstrate possible interaction effects.

75 FR 5698 - Approval and Promulgation of Implementation Plans; Albuquerque-Bernalillo County, NM; Excess...

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2010-02-04

... adverse comments by March 8, 2010. If adverse comments are received, EPA will publish a timely withdrawal... also included proposed revisions to NMAC 20.11.69--Pathological Waste Destructors. NMAC 20.11.69-- Pathological Waste Destructors is not currently in the EPA-approved SIP for Albuquerque-Bernalillo County. We...

Toxicity of Selected Acaricides to Honey Bees (Apis mellifera) and Varroa (Varroa destructor Anderson and Trueman) and Their Use in Controlling Varroa within Honey Bee Colonies.

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Gregorc, Aleš; Alburaki, Mohamed; Sampson, Blair; Knight, Patricia R; Adamczyk, John

2018-05-10

The efficacies of various acaricides in order to control a parasitic mite, the Varroa mite, Varroa destructor , of honey bees, were measured in two different settings, namely, in laboratory caged honey bees and in queen-right honey bee colonies. The Varroa infestation levels before, during, and after the acaricide treatments were determined in two ways, namely: (1) using the sugar shake protocol to count mites on bees and (2) directly counting the dead mites on the hive bottom inserts. The acaricides that were evaluated were coumaphos, tau-fluvalinate, amitraz, thymol, and natural plant compounds (hop acids), which were the active ingredients. The acaricide efficacies in the colonies were evaluated in conjunction with the final coumaphos applications. All of the tested acaricides significantly increased the overall Varroa mortality in the laboratory experiment. Their highest efficiencies were recorded at 6 h post-treatment, except for coumaphos and thymol, which exhibited longer and more consistent activity. In the honey bee colonies, a higher Varroa mortality was recorded in all of the treatments, compared with the natural Varroa mortality during the pretreatment period. The acaricide toxicity to the Varroa mites was consistent in both the caged adult honey bees and workers in the queen-right colonies, although, two of these acaricides, coumaphos at the highest doses and hop acids, were comparatively more toxic to the worker bees.

A virulent strain of deformed wing virus (DWV of honeybees (Apis mellifera prevails after Varroa destructor-mediated, or in vitro, transmission.

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Eugene V Ryabov

2014-06-01

Full Text Available The globally distributed ectoparasite Varroa destructor is a vector for viral pathogens of the Western honeybee (Apis mellifera, in particular the Iflavirus Deformed Wing Virus (DWV. In the absence of Varroa low levels DWV occur, generally causing asymptomatic infections. Conversely, Varroa-infested colonies show markedly elevated virus levels, increased overwintering colony losses, with impairment of pupal development and symptomatic workers. To determine whether changes in the virus population were due Varroa amplifying and introducing virulent virus strains and/or suppressing the host immune responses, we exposed Varroa-naïve larvae to oral and Varroa-transmitted DWV. We monitored virus levels and diversity in developing pupae and associated Varroa, the resulting RNAi response and transcriptome changes in the host. Exposed pupae were stratified by Varroa association (presence/absence and virus levels (low/high into three groups. Varroa-free pupae all exhibited low levels of a highly diverse DWV population, with those exposed per os (group NV exhibiting changes in the population composition. Varroa-associated pupae exhibited either low levels of a diverse DWV population (group VL or high levels of a near-clonal virulent variant of DWV (group VH. These groups and unexposed controls (C could be also discriminated by principal component analysis of the transcriptome changes observed, which included several genes involved in development and the immune response. All Varroa tested contained a diverse replicating DWV population implying the virulent variant present in group VH, and predominating in RNA-seq analysis of temporally and geographically separate Varroa-infested colonies, was selected upon transmission from Varroa, a conclusion supported by direct injection of pupae in vitro with mixed virus populations. Identification of a virulent variant of DWV, the role of Varroa in its transmission and the resulting host transcriptome changes furthers

Comparative molecular analyses of select pH- and osmoregulatory genes in three freshwater crayfish Cherax quadricarinatus, C. destructor and C. cainii.

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Ali, Muhammad Y; Pavasovic, Ana; Dammannagoda, Lalith K; Mather, Peter B; Prentis, Peter J

2017-01-01

Systemic acid-base balance and osmotic/ionic regulation in decapod crustaceans are in part maintained by a set of transport-related enzymes such as carbonic anhydrase (CA), Na + /K + -ATPase (NKA), H + -ATPase (HAT), Na + /K + /2Cl - cotransporter (NKCC), Na + /Cl - /HCO[Formula: see text] cotransporter (NBC), Na + /H + exchanger (NHE), Arginine kinase (AK), Sarcoplasmic Ca +2 -ATPase (SERCA) and Calreticulin (CRT). We carried out a comparative molecular analysis of these genes in three commercially important yet eco-physiologically distinct freshwater crayfish , Cherax quadricarinatus, C. destructor and C. cainii , with the aim to identify mutations in these genes and determine if observed patterns of mutations were consistent with the action of natural selection. We also conducted a tissue-specific expression analysis of these genes across seven different organs, including gills, hepatopancreas, heart, kidney, liver, nerve and testes using NGS transcriptome data. The molecular analysis of the candidate genes revealed a high level of sequence conservation across the three Cherax sp. Hyphy analysis revealed that all candidate genes showed patterns of molecular variation consistent with neutral evolution. The tissue-specific expression analysis showed that 46% of candidate genes were expressed in all tissue types examined, while approximately 10% of candidate genes were only expressed in a single tissue type. The largest number of genes was observed in nerve (84%) and gills (78%) and the lowest in testes (66%). The tissue-specific expression analysis also revealed that most of the master genes regulating pH and osmoregulation (CA, NKA, HAT, NKCC, NBC, NHE) were expressed in all tissue types indicating an important physiological role for these genes outside of osmoregulation in other tissue types. The high level of sequence conservation observed in the candidate genes may be explained by the important role of these genes as well as potentially having a number of

Ratios of colony mass to thermal conductance of tree and man-made nest enclosures of Apis mellifera: implications for survival, clustering, humidity regulation and Varroa destructor

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Mitchell, Derek

2016-05-01

In the absence of human intervention, the honeybee ( Apis mellifera L.) usually constructs its nest in a tree within a tall, narrow, thick-walled cavity high above the ground (the enclosure); however, most research and apiculture is conducted in the thin-walled, squat wooden enclosures we know as hives. This experimental research, using various hives and thermal models of trees, has found that the heat transfer rate is approximately four to seven times greater in the hives in common use, compared to a typical tree enclosure in winter configuration. This gives a ratio of colony mass to lumped enclosure thermal conductance (MCR) of less than 0.8 kgW-1 K for wooden hives and greater than 5 kgW-1 K for tree enclosures. This result for tree enclosures implies higher levels of humidity in the nest, increased survival of smaller colonies and lower Varroa destructor breeding success. Many honeybee behaviours previously thought to be intrinsic may only be a coping mechanism for human intervention; for example, at an MCR of above 2 kgW-1 K, clustering in a tree enclosure may be an optional, rare, heat conservation behaviour for established colonies, rather than the compulsory, frequent, life-saving behaviour that is in the hives in common use. The implied improved survival in hives with thermal properties of tree nests may help to solve some of the problems honeybees are currently facing in apiculture.

Are Dispersal Mechanisms Changing the Host-Parasite Relationship and Increasing the Virulence of Varroa destructor (Mesostigmata: Varroidae) in Managed Honey Bee (Hymenoptera: Apidae) Colonies?

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DeGrandi-Hoffman, Gloria; Ahumada, Fabiana; Graham, Henry

2017-08-01

Varroa (Varroa destructor Anderson and Trueman) are a serious pest of European honey bees (Apis mellifera L.), and difficult to control in managed colonies. In our 11-mo longitudinal study, we applied multiple miticide treatments, yet mite numbers remained high and colony losses exceeded 55%. High mortality from varroa in managed apiaries is a departure from the effects of the mite in feral colonies where bees and varroa can coexist. Differences in mite survival strategies and dispersal mechanisms may be contributing factors. In feral colonies, mites can disperse through swarming. In managed apiaries, where swarming is reduced, mites disperse on foragers robbing or drifting from infested hives. Using a honey bee-varroa population model, we show that yearly swarming curtails varroa population growth, enabling colony survival for >5 yr. Without swarming, colonies collapsed by the third year. To disperse, varroa must attach to foragers that then enter other hives. We hypothesize that stress from parasitism and virus infection combined with effects that viruses have on cognitive function may contribute to forager drift and mite and virus dispersal. We also hypothesize that drifting foragers with mites can measurably increase mite populations. Simulations initialized with field data indicate that low levels of drifting foragers with mites can create sharp increases in mite populations in the fall and heavily infested colonies in the spring. We suggest new research directions to investigate factors leading to mite dispersal on foragers, and mite management strategies with consideration of varroa as a migratory pest. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

Varroa destructor Macula-like virus, Lake Sinai virus and other new RNA viruses in wild bumblebee hosts (Bombus pascuorum, Bombus lapidarius and Bombus pratorum).

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Parmentier, Laurian; Smagghe, Guy; de Graaf, Dirk C; Meeus, Ivan

2016-02-01

Pollinators such as bumblebees (Bombus spp.) are in decline worldwide which poses a threat not only for ecosystem biodiversity but also to human crop production services. One main cause of pollinator decline may be the infection and transmission of diseases including RNA viruses. Recently, new viruses have been discovered in honeybees, but information on the presence of these in wild bumblebees is largely not available. In this study, we investigated the prevalence of new RNA viruses in Bombus species, and can report for the first time Varroa destructor Macula-like virus (VdMLV) and Lake Sinai virus (LSV) infection in multiple wild bumblebee hosts of Bombus pascuorum, Bombus lapidarius and Bombus pratorum. We sampled in 4 locations in Flanders, Belgium. Besides, we confirmed Slow bee paralysis virus (SBPV) in wild bumblebees, but no positive samples were obtained for Big Sioux river virus (BSRV). Secondly, we screened for the influence of apiaries on the prevalence of these viruses. Our results indicated a location effect for the prevalence of VdMLV in Bombus species, with a higher prevalence in the proximity of honeybee apiaries mainly observed in one location. For LSV, the prevalence was not different in the proximity or at a 1.5 km-distance of apiaries, but we reported a different isolate with similarities to LSV-2 and "LSV-clade A" as described by Ravoet et al. (2015), which was detected both in Apis mellifera and Bombus species. In general, our results indicate the existence of a disease pool of new viruses that seems to be associated to a broad range of Apoidae hosts, including multiple Bombus species. Copyright © 2015 Elsevier Inc. All rights reserved.

A Toolbox for Quantitative Gene Expression in Varroa destructor: RNA Degradation in Field Samples and Systematic Analysis of Reference Gene Stability.

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Ewan M Campbell

Full Text Available Varroa destructor is the major pest of Apis mellifera and contributes to the global honey bee health crisis threatening food security. Developing new control strategies to combat Varroa will require the application of molecular biology, including gene expression studies by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR. Both high quality RNA samples and suitable stable internal reference genes are required for accurate gene expression studies. In this study, ten candidate genes (succinate dehydrogenase (SDHA, NADH dehydrogenase (NADH, large ribsosmal subunit, TATA-binding protein, glyceraldehyde-3-phosphate dehydrogenase, 18S rRNA (18S, heat-shock protein 90 (HSP90, cyclophilin, α-tubulin, actin, were evaluated for their suitability as normalization genes using the geNorm, Normfinder, BestKeeper, and comparative ΔCq algorithims. Our study proposes the use of no more than two of the four most stable reference genes (NADH, 18S, SDHA and HSP90 in Varroa gene expression studies. These four genes remain stable in phoretic and reproductive stage Varroa and are unaffected by Deformed wing virus load. When used for determining changes in vitellogenin gene expression, the signal-to-noise ratio (SNR for the relatively unstable genes actin and α-tubulin was much lower than for the stable gene combinations (NADH + HSP90 +18S; NADH + HSP90; or NADH. Using both electropherograms and RT-qPCR for short and long amplicons as quality controls, we demonstrate that high quality RNA can be recovered from Varroa up to 10 days later stored at ambient temperature if collected into RNAlater and provided the body is pierced. This protocol allows the exchange of Varroa samples between international collaborators and field sample collectors without requiring frozen collection or shipping. Our results make important contributions to gene expression studies in Varroa by proposing a validated sampling protocol to obtain high quality Varroa

Comparative molecular analyses of select pH- and osmoregulatory genes in three freshwater crayfish Cherax quadricarinatus, C. destructor and C. cainii

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Muhammad Y. Ali

2017-08-01

Full Text Available Systemic acid-base balance and osmotic/ionic regulation in decapod crustaceans are in part maintained by a set of transport-related enzymes such as carbonic anhydrase (CA, Na+/K+-ATPase (NKA, H+-ATPase (HAT, Na+/K+/2Cl− cotransporter (NKCC, Na+/Cl−/HCO ${}_{3}^{-}$ 3 − cotransporter (NBC, Na+/H+ exchanger (NHE, Arginine kinase (AK, Sarcoplasmic Ca+2-ATPase (SERCA and Calreticulin (CRT. We carried out a comparative molecular analysis of these genes in three commercially important yet eco-physiologically distinct freshwater crayfish, Cherax quadricarinatus, C. destructor and C. cainii, with the aim to identify mutations in these genes and determine if observed patterns of mutations were consistent with the action of natural selection. We also conducted a tissue-specific expression analysis of these genes across seven different organs, including gills, hepatopancreas, heart, kidney, liver, nerve and testes using NGS transcriptome data. The molecular analysis of the candidate genes revealed a high level of sequence conservation across the three Cherax sp. Hyphy analysis revealed that all candidate genes showed patterns of molecular variation consistent with neutral evolution. The tissue-specific expression analysis showed that 46% of candidate genes were expressed in all tissue types examined, while approximately 10% of candidate genes were only expressed in a single tissue type. The largest number of genes was observed in nerve (84% and gills (78% and the lowest in testes (66%. The tissue-specific expression analysis also revealed that most of the master genes regulating pH and osmoregulation (CA, NKA, HAT, NKCC, NBC, NHE were expressed in all tissue types indicating an important physiological role for these genes outside of osmoregulation in other tissue types. The high level of sequence conservation observed in the candidate genes may be explained by the important role of these genes as well as potentially having a number of other basic

Impact of the Phoretic Phase on Reproduction and Damage Caused by Varroa destructor (Anderson and Trueman to Its Host, the European Honey Bee (Apis mellifera L..

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Vincent Piou

Full Text Available Varroa destructor is a parasitic mite of the honeybee that causes thousands of colony losses worldwide. The parasite cycle is composed of a phoretic and a reproductive phase. During the former, mites stay on adult bees, mostly on nurses, to feed on hemolymph. During the latter, the parasites enter brood cells and reproduce. We investigated if the type of bees on which Varroa stays during the phoretic phase and if the duration of this stay influenced the reproductive success of the parasite and the damage caused to bees. For that purpose, we used an in vitro rearing method developed in our laboratory to assess egg laying rate and the presence and number of fully molted daughters. The expression level of two Varroa vitellogenin genes (VdVg1 and VdVg2, known to vary throughout reproduction, was also quantified. Results showed that the status of the bees or time spent during the phoretic phase impacts neither reproduction parameters nor the Varroa vitellogenin genes levels of expression. However, we correlated these parameters to the gene expression and demonstrated that daughters expressed the vitellogenin genes at lower levels than their mother. Regarding the damage to bees, the data indicated that a longer stay on adult bees during the phoretic phase resulted in more frequent physical deformity in newborn bees. We showed that those mites carry more viral loads of the Deformed Wing Virus and hence trigger more frequently overt infections. This study provides new perspectives towards a better understanding of the Varroa-honeybee interactions.

Population Growth of Varroa destructor (Acari: Varroidae) in Colonies of Russian and Unselected Honey Bee (Hymenoptera: Apidae) Stocks as Related to Numbers of Foragers With Mites.

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DeGrandi-Hoffman, Gloria; Ahumada, Fabiana; Danka, Robert; Chambers, Mona; DeJong, Emily Watkins; Hidalgo, Geoff

2017-06-01

Varroa (Varroa destructor Anderson and Trueman) is an external parasite of honey bees (Apis mellifera L.) and a leading cause of colony losses worldwide. Varroa populations can be controlled with miticides, but mite-resistant stocks such as the Russian honey bee (RHB) also are available. Russian honey bee and other mite-resistant stocks limit Varroa population growth by affecting factors that contribute to mite reproduction. However, mite population growth is not entirely due to reproduction. Numbers of foragers with mites (FWM) entering and leaving hives also affect the growth of mite populations. If FWM significantly contribute to Varroa population growth, mite numbers in RHB colonies might not differ from unselected lines (USL). Foragers with mites were monitored at the entrances of RHB and USL hives from August to November, 2015, at two apiary sites. At site 1, RHB colonies had fewer FWM than USL and smaller phoretic mite populations. Russian honey bee also had fewer infested brood cells and lower percentages with Varroa offspring than USL. At site 2, FWM did not differ between RHB and USL, and phoretic mite populations were not significantly different. At both sites, there were sharp increases in phoretic mite populations from September to November that corresponded with increasing numbers of FWM. Under conditions where FWM populations are similar between RHB and USL, attributes that contribute to mite resistance in RHB may not keep Varroa population levels below that of USL. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

Presence of Apis Rhabdovirus-1 in Populations of Pollinators and Their Parasites from Two Continents.

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Levin, Sofia; Galbraith, David; Sela, Noa; Erez, Tal; Grozinger, Christina M; Chejanovsky, Nor

2017-01-01

The viral ecology of bee communities is complex, where viruses are readily shared among co-foraging bee species. Additionally, in honey bees ( Apis mellifera ), many viruses are transmitted - and their impacts exacerbated - by the parasitic Varroa destructor mite. Thus far, the viruses found to be shared across bee species and transmitted by V. destructor mites are positive-sense single-stranded RNA viruses. Recently, a negative-sense RNA enveloped virus, Apis rhabdovirus-1 (ARV-1), was found in A. mellifera honey bees in Africa, Europe, and islands in the Pacific. Here, we describe the identification - using a metagenomics approach - of ARV-1 in two bee species ( A. mellifera and Bombus impatiens ) and in V. destructor mites from populations collected in the United States and Israel. We confirmed the presence of ARV-1 in pools of A. mellifera , B. impatiens , and V. destructor from Israeli and U.S. populations by RT-PCR and found that it can reach high titers in individual honey bees and mites (10 7 -10 8 viral genomic copies per individual). To estimate the prevalence of ARV-1 in honey bee populations, we screened 104 honey bee colonies across Israel, with 21 testing ARV-1-positive. Tagged-primer-mediated RT-PCR analysis detected the presence of the positive-sense ARV-1 RNA in A. mellifera and V. destructor , indicating that ARV-1 replicates in both hosts. This is the first report of the presence of ARV-1 in B. impatiens and of the replication of a rhabdovirus in A. mellifera and V. destructor . Our data suggest that Varroa mites could act as an ARV-1 vector; however, the presence of ARV-1 in B. impatiens (which are not parasitized by Varroa ) suggests that it may not require the mite for transmission and ARV-1 may be shared among co-foraging bee species. Given that ARV-1 is found in non-Apis bee species, and because "ARV" is used for the Adelaide River virus, we propose that this virus should be called bee rhabdovirus 1 and abbreviated BRV-1. These results

Genotypic variability and relationships between mite infestation levels, mite damage, grooming intensity, and removal of Varroa destructor mites in selected strains of worker honey bees (Apis mellifera L.).

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Guzman-Novoa, Ernesto; Emsen, Berna; Unger, Peter; Espinosa-Montaño, Laura G; Petukhova, Tatiana

2012-07-01

The objective of this study was to demonstrate genotypic variability and analyze the relationships between the infestation levels of the parasitic mite Varroa destructor in honey bee (Apis mellifera) colonies, the rate of damage of fallen mites, and the intensity with which bees of different genotypes groom themselves to remove mites from their bodies. Sets of paired genotypes that are presumably susceptible and resistant to the varroa mite were compared at the colony level for number of mites falling on sticky papers and for proportion of damaged mites. They were also compared at the individual level for intensity of grooming and mite removal success. Bees from the "resistant" colonies had lower mite population rates (up to 15 fold) and higher percentages of damaged mites (up to 9 fold) than bees from the "susceptible" genotypes. At the individual level, bees from the "resistant" genotypes performed significantly more instances of intense grooming (up to 4 fold), and a significantly higher number of mites were dislodged from the bees' bodies by intense grooming than by light grooming (up to 7 fold) in all genotypes. The odds of mite removal were high and significant for all "resistant" genotypes when compared with the "susceptible" genotypes. The results of this study strongly suggest that grooming behavior and the intensity with which bees perform it, is an important component in the resistance of some honey bee genotypes to the growth of varroa mite populations. The implications of these results are discussed. Copyright © 2012 Elsevier Inc. All rights reserved.

Aeroallergens in dairy barns near Cooperstown, New York and Rochester, Minnesota

International Nuclear Information System (INIS)

Campbell, A.R.; Swanson, M.C.; Fernandez-Caldas, E.; Reed, C.E.; May, J.J.; Pratt, D.S.

1989-01-01

We sampled atmospheric barn air using a volumetric air sampler in ten barns near Cooperstown, NY and six barns near Rochester, MN, and, with radioimmunoassays, measured allergens of Aspergillus fumigatus, Thermoactinomyces vulgaris, Micropolyspori faeni, short ragweed, rye grass group I pollen, Alternaria (Alt-1), Dermatophagoides sp. Lepidoglyphus destructor, common insect allergen, mouse urine, rat urine, and cattle epithelium. The most abundant allergen present was A. fumigatus followed by L. destructor. This study provides initial data on barn aerobiology and demonstrates for the first time the abundance of L. destructor allergens in North American dairy barns. More comprehensive study of barns, poultry houses, confinement houses for swine, and other agricultural environments from various geographic locations is needed to define the allergen levels to which millions of farm workers are exposed each day. While most of the allergens were expected, the presence of airborne allergens reactive with antisera to Dermatophagoides suggests indirectly that substantial amounts of pyroglyphid mites are present in some barns

Presence of Apis Rhabdovirus-1 in Populations of Pollinators and Their Parasites from Two Continents

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Sofia Levin

2017-12-01

Full Text Available The viral ecology of bee communities is complex, where viruses are readily shared among co-foraging bee species. Additionally, in honey bees (Apis mellifera, many viruses are transmitted – and their impacts exacerbated – by the parasitic Varroa destructor mite. Thus far, the viruses found to be shared across bee species and transmitted by V. destructor mites are positive-sense single-stranded RNA viruses. Recently, a negative-sense RNA enveloped virus, Apis rhabdovirus-1 (ARV-1, was found in A. mellifera honey bees in Africa, Europe, and islands in the Pacific. Here, we describe the identification – using a metagenomics approach – of ARV-1 in two bee species (A. mellifera and Bombus impatiens and in V. destructor mites from populations collected in the United States and Israel. We confirmed the presence of ARV-1 in pools of A. mellifera, B. impatiens, and V. destructor from Israeli and U.S. populations by RT-PCR and found that it can reach high titers in individual honey bees and mites (107–108 viral genomic copies per individual. To estimate the prevalence of ARV-1 in honey bee populations, we screened 104 honey bee colonies across Israel, with 21 testing ARV-1-positive. Tagged-primer-mediated RT-PCR analysis detected the presence of the positive-sense ARV-1 RNA in A. mellifera and V. destructor, indicating that ARV-1 replicates in both hosts. This is the first report of the presence of ARV-1 in B. impatiens and of the replication of a rhabdovirus in A. mellifera and V. destructor. Our data suggest that Varroa mites could act as an ARV-1 vector; however, the presence of ARV-1 in B. impatiens (which are not parasitized by Varroa suggests that it may not require the mite for transmission and ARV-1 may be shared among co-foraging bee species. Given that ARV-1 is found in non-Apis bee species, and because “ARV” is used for the Adelaide River virus, we propose that this virus should be called bee rhabdovirus 1 and abbreviated BRV-1

Plant-Derived Tick Repellents Activate the Honey Bee Ectoparasitic Mite TRPA1

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Guangda Peng

2015-07-01

Full Text Available We have identified and characterized the TRPA1 channel of Varroa destructor (VdTRPA1, a major ectoparasitic mite of honey bee. One of the two VdTRPA1 isoforms, VdTRPA1L, was activated by a variety of plant-derived compounds, including electrophilic compounds, suggesting that chemical activation profiles are mostly shared between arthropod TRPA1 channels. Nevertheless, carvacrol and α-terpineol activated VdTRPA1L but not a honey bee noxious-stimuli-sensitive TRPA, AmHsTRPA, and Drosophila melanogaster TRPA1. Activation of VdTRPA1L in D. melanogaster taste neurons by the above compounds was sufficient to modify the gustatory behaviors. Carvacrol and α-terpineol repelled V. destructor in a laboratory assay, and α-terpineol repressed V. destructor entry for reproduction into the brood cells in hives. Understanding the functions of parasite TRP channels not only gives clues about the evolving molecular and cellular mechanisms of parasitism but also helps in the development of control methods.

Emerging and re-emerging viruses of the honey bee (Apis mellifera L.).

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Genersch, Elke; Aubert, Michel

2010-01-01

Until the late 1980s, specific viral infections of the honey bee were generally considered harmless in all countries. Then, with the worldwide introduction of the ectoparasite mite Varroa destructor, beekeepers encountered increasing difficulties in maintaining their colonies. Epidemiological surveys and laboratory experiments have demonstrated that the newly acquired virulence of several viruses belonging to the family Dicistroviridae (acute bee paralysis virus, Kashmir bee virus and Israeli acute paralysis virus) in Europe and the USA had been observed in relation with V. destructor acting as a disseminator of these viruses between and within bee colonies and as an activator of virus multiplication in the infected individuals: bee larvae and adults. Equal emphasis is given to deformed wing virus (DWV) belonging to the Iflaviridae. Overt outbreaks of DWV infections have been shown to be linked to the ability of V. destructor to act not only as a mechanical vector of DWV but also as a biological vector. Its replication in mites prior to its vectoring into pupae seemed to be necessary and sufficient for the induction of a overt infection in pupae developing in non-viable bees with deformed wings. DWV in V. destructor infested colonies is now considered as one of the key players of the final collapse. Various approaches for combating bee viral diseases are described: they include selection of tolerant bees, RNA interference and prevention of new pathogen introduction. None of these approaches are expected to lead to enhanced bee-health in the short term. © INRA, EDP Sciences, 2010.

Comparación de la eficacia del ácido fórmico y del fluvalinato, como métodos de control de Varroa destructor (Acari: Varroidae en colmenas de Apis mellifera (Hymenoptera: Apidae, en Ñuble, centro sur de Chile

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Daniel GONZÁLEZ-ACUÑA

2005-01-01

Full Text Available Durante la primavera de 2000, se comparó la eficacia del ácido fórmico al 85 % y del fluvalinato como acaricidas contra Varroa destructor Anderson y Trueman en colmenas de Apis mellifera L., ubicadas en el Campus Chillán de la Universidad de Concepción (36o36‘S 72o0,6 ́W. Se formaron tres grupos de diez colmenas. El grupo 1 fue tratado con ácido fórmico al 85% aplicado en Vaporizadores Universales MHT ®; el grupo 2 se utilizó como con- trol, sin recibir ningún tipo de tratamiento; el grupo 3, se trató con tablillas de pino (Pinus radiata impregnadas en fluvalinato al 3 %. Al finalizar la aplicación de los acaricidas en estudio, las colmenas de los tres grupos fueron sometidas a un tratamiento testigo con Bayvarol® (flumetrín. La mayor eficacia se reportó en el grupo tratado con fluvalinato arrojando un promedio de 98,05 ± 2,13 %. De la misma manera con ácido fórmico se obtuvo una eficacia promedio de 88,26 ± 9,12 %, mientras que en el grupo control la mortalidad natural en promedio fue de 41,11 ± 11,52 %.

Flutuação populacional de esporângios de Peronospora destructor no ar e sua relação com a severidade do míldio da cebola

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Leandro Luiz Marcuzzo

2015-03-01

Full Text Available Em experimento de campo nos anos de 2011, 2012 e 2013 quantificou-se a flutuação de esporângios de Peronospora destructor e sua relação com a severidade de míldio em cebola. Mudas de cebola do cultivar Bola Precoce foram transplantadas em quatro repetições de 60 plantas. Os esporângios foram coletados através de um coletor de esporos tipo "cata-vento", contendo uma lâmina de microscópio untada com vaselina, a qual era quantificada semanalmente com auxílio de microscópio. A severidade da doença foi analisada através da porcentagem de área foliar afetada pela doença. O número de esporângios e a severidade do míldio da cebola foram submetidos ao cálculo do coeficiente de correlação linear de Pearson (r. Nos anos de 2011 e 2012 a coleta de esporângios ocorreu posteriormente à constatação da doença, provavelmente devido haver baixo inóculo no ar. Já no ano de 2013 a coleta de esporângios ocorreu anteriormente à ocorrência da doença, porém de forma esporádica e em pequena quantidade, presupondo que esses estavam no ar e foram capturados pelo coletor. A correlação entre as variáveis flutuações de esporângios e a severidade da doença foi significativa, r=0,90, r=0,94 e r=0,80; para os anos de 2011, 2012 e 2013 respectivamente. A severidade da doença em cebola é influenciada pela presença dos esporângios coletadas do ar.

The effect of antibiotics on associated bacterial community of stored product mites.

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Jan Kopecky

Full Text Available Bacteria are associated with the gut, fat bodies and reproductive organs of stored product mites (Acari: Astigmata. The mites are pests due to the production of allergens. Addition of antibiotics to diets can help to characterize the association between mites and bacteria.Ampicillin, neomycin and streptomycin were added to the diets of mites and the effects on mite population growth (Acarus siro, Lepidoglyphus destructor and Tyrophagus putrescentiae and associated bacterial community structure were assessed. Mites were treated by antibiotic supplementation (1 mg g(-1 of diet for 21 days and numbers of mites and bacterial communities were analyzed and compared to the untreated control. Bacterial quantities, determined by real-time PCR, significantly decreased in antibiotic treated specimens from 5 to 30 times in A. siro and T. putrescentiae, while no decline was observed in L. destructor. Streptomycin treatment eliminated Bartonella-like bacteria in the both A. siro and T. putrescentiae and Cardinium in T. putrescentiae. Solitalea-like bacteria proportion increased in the communities of neomycin and streptomycin treated A. siro specimens. Kocuria proportion increased in the bacterial communities of ampicillin and streptomycin treated A. siro and neomycin and streptomycin treated L. destructor.The work demonstrated the changes of mite associated bacterial community under antibiotic pressure in pests of medical importance. Pre-treatment of mites by 1 mg g(-1 antibiotic diets improved mite fitness as indicated accelerated population growth of A. siro pretreated streptomycin and neomycin and L. destructor pretreated by neomycin. All tested antibiotics supplemented to diets caused the decrease of mite growth rate in comparison to the control diet.

Radiation 2006. In association with the Polymer Division, Royal Australian Chemical Institute. Incorporating the 21st AINSE Radiation Chemistry Conference and the 18th Radiation Biology Conference, conference handbook

International Nuclear Information System (INIS)

Nugegoda, D.; Blackney, R.; Fuchs, A.; Smith, Suzanne

2006-01-01

Full text: The Australian yabby Cherax destructor is tolerant of exposure to many trace metals including Zn and Cd. However it is not known if this tolerance is a result of a low rate of uptake of heavy metals by the yabby, increased excretion, or a combination of both. We now report on the use of radioisotopes of two environmental trace metals 65 Zn and 109 Cd to monitor the uptake by C. destructor of the essential metal Zn and the non-essential metal Cd, at low metal concentrations exposures. Juvenile C. destructor were exposed to three concentrations of Zn with 65 Zn as a tracer for up to 48 hours. Yabbies were sampled at specific time intervals and counted live in tubes with freshwater using a gamma scintillation counter. Water was also sampled and counted at the same time intervals. At the end of the uptake phase, yabbies were dissected into the hepatopancreas, exoskeleton, tail muscle and 'the rest' and each body compartment counted individually. The associated radioactivity was used to calculate the proportional compartmentalization of the trace metals within the body tissues. A similar experiment was repeated with various concentrations of Cd and 109 Cd used to monitor its uptake at various time intervals. Unlike Zn, where its accumulation only plateaued at 72 hour the rate of uptake of Cd reached a plateau after 24 hours. A competitive study was also conducted with the yabbies. Here the yabbies were exposed to similar concentrations of Cd and Zn simultaneously and yabbies were counted to determine Zn and Cd at various intervals. The estimated rates for C. destructor are compared to those of other freshwater crustaceans in order to deduce whether its tolerance to trace metal toxicants is based on reduced rates of uptake

Perdas de colônias de Apis mellifera L. no inverno suplementadas com alimentação artificial com pólen e favos de mel

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Adhemar Pegoraro

2012-11-01

Full Text Available O objetivo deste trabalho foi avaliar o efeito do tipo de suplementação, nas áreas de cria, alimento e infestação por Varroa destructor nas colônias perdidas. Foram analisadas18 colônias de Apis mellifera L. alojadas em colméias modelo Langstroth e submetidas a dois tipos de suplementação alimentar: 1- cremosa (açúcar cristal moído, mel e pólen; 2- favos de mel. As áreas de ovo-larva e pupa, néctar, mel e pólen das 18 colônias foram fotografadas e analisadas com o auxílio do software AutoCAD. As colônias perdidas suplementadas com alimento artificial e pólen possuíam áreas de: ovo-larva (87,79 ± 70,38cm2, pupa (228,46 ± 192,94cm2, néctar (1.219 ± 149,58cm2, mel (563,47 ± 807,93cm2, pólen (139,09 ± 80,30cm2 e percentagem de infestação por V. destructor (10,50 ± 4,30%. As colônias perdidas suplementadas com favos de mel possuíam áreas de ovo-larva (7,92 ± 9,35cm2, pupas (60,71 ± 63,94 cm2, néctar (658,22 ± 1.040,94cm2, mel (122,62 ± 49,45cm2, pólen (53,58 ± 72,39cm2 e percentagem de infestação por V. destructor (14,40 ± 1,56%. As causas das perdas em parte podem ser atribuídas à infestação por V. destructor.

Impulso destructor: (SExperiencia perversa

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José Miguel Viña Hernández

2011-08-01

Full Text Available Desde la Ilustración, la sexualidad ha quedado sometida a un discurso normativo. Aspectos como la pasión y el impulso se ven rígidamente constreñidos por esquemas morales y prejuicios heredados de una idiosincrasia aburguesada. Los intentos por esquivar y transgredir estos modelos han sido llevados a la pantalla, casi siempre bajo la tónica común del fracaso y la fatalidad. Desde Hitchcock a Pasolini, pasando por Truffaut o Kubrick, se trazará un recorrido cronológico, que estudia los ejemplos más paradigmáticos de la subversión erótica.

Electron/electron acoustic instability

International Nuclear Information System (INIS)

Gary, S.P.

1987-01-01

The electron acoustic wave becomes a normal mode of an unmagnetized collisionless plasma in the presence of two electron components with similar densities, but strongly disparate temperatures. The characteristic frequency of this mode is the plasma frequency of the cooler electron component. If these two electron components have a relative drift speed several times the thermal speed of the cooler component, the electron/electron acoustic instability may arise. This paper describes the parametric dependences of the threshold drift speed and maximum growth rate of this instability, and compares these with the same properties of the electron/ion acoustic instability. Under the condition of zero current, the electron/ion acoustic instability typically has the lower threshold drift speed, so that observation of the electron/electron acoustic instability is a strong indication of the presence of an electrical current in the plasma

Electronics and electronic systems

CERN Document Server

Olsen, George H

1987-01-01

Electronics and Electronic Systems explores the significant developments in the field of electronics and electronic devices. This book is organized into three parts encompassing 11 chapters that discuss the fundamental circuit theory and the principles of analog and digital electronics. This book deals first with the passive components of electronic systems, such as resistors, capacitors, and inductors. These topics are followed by a discussion on the analysis of electronic circuits, which involves three ways, namely, the actual circuit, graphical techniques, and rule of thumb. The remaining p

Electrons, Electronic Publishing, and Electronic Display.

Science.gov (United States)

Brownrigg, Edwin B.; Lynch, Clifford A.

1985-01-01

Provides a perspective on electronic publishing by distinguishing between "Newtonian" publishing and "quantum-mechanical" publishing. Highlights include media and publishing, works delivered through electronic media, electronic publishing and the printed word, management of intellectual property, and recent copyright-law issues…

Electron-electron Bremsstrahlung for bound target electrons

International Nuclear Information System (INIS)

Haug, E.

2008-01-01

For the process of electron-electron (e-e) Bremsstrahlung the momentum and energy distributions of the recoiling electrons are calculated in the laboratory frame. In order to get the differential cross section and the photon spectrum for target electrons which are bound to an atom, these formulae are multiplied by the incoherent scattering function and numerically integrated over the recoil energy. The effect of atomic binding is most pronounced at low energies of the incident electrons and for target atoms of high atomic numbers. The results are compared to those of previous calculations. (authors)

Assessing hygienic behavior of Apis mellifera unicolor (Hymenoptera: Apidae), the endemic honey bee from Madagascar.

Science.gov (United States)

Rasolofoarivao, H; Delatte, H; Raveloson Ravaomanarivo, L H; Reynaud, B; Clémencet, J

2015-06-01

Hygienic behavior (HB) is one of the natural mechanisms of honey bee for limiting the spread of brood diseases and Varroa destructor parasitic mite. Objective of our study was to measure HB of Apis mellifera unicolor colonies (N = 403) from three geographic regions (one infested and two free of V. destructor) in Madagascar. The pin-killing method was used for evaluation of the HB. Responses were measured from 3 h 30 min to 7 h after perforation of the cells. Colonies were very effective in detecting perforated cells. In the first 4 h, on average, they detected at least 50% of the pin-killed brood. Six hours after cell perforation, colonies tested (N = 91) showed a wide range of uncapped (0 to 100%) and cleaned cells (0 to 82%). Global distribution of the rate of cleaned cells at 6 h was multimodal and hygienic responses could be split in three classes. Colonies from the three regions showed a significant difference in HB responses. Three hypotheses (geographic, genetic traits, presence of V. destructor) are further discussed to explain variability of HB responses among the regions. Levels of HB efficiency of A. mellifera unicolor colonies are among the greatest levels reported for A. mellifera subspecies. Presence of highly hygienic colonies is a great opportunity for future breeding program in selection for HB.

Interplay between electron-phonon and electron-electron interactions

International Nuclear Information System (INIS)

Roesch, O.; Gunnarsson, O.; Han, J.E.; Crespi, V.H.

2005-01-01

We discuss the interplay between electron-electron and electron-phonon interactions for alkali-doped fullerides and high temperature superconductors. Due to the similarity of the electron and phonon energy scales, retardation effects are small for fullerides. This raises questions about the origin of superconductivity, since retardation effects are believed to be crucial for reducing effects of the Coulomb repulsion in conventional superconductors. We demonstrate that by treating the electron-electron and electron-phonon interactions on an equal footing, superconductivity can be understood in terms of a local pairing. The Jahn-Teller character of the important phonons in fullerides plays a crucial role for this result. To describe effects of phonons in cuprates, we derive a t-J model with phonons from the three-band model. Using exact diagonalization for small clusters, we find that the anomalous softening of the half-breathing phonon as well as its doping dependence can be explained. By comparing the solution of the t-J model with the Hartree-Fock approximation for the three-band model, we address results obtained in the local-density approximation for cuprates. We find that genuine many-body results, due to the interplay between the electron-electron and electron-phonon interactions, play an important role for the the results in the t-J model. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Electronic emission and electron guns

International Nuclear Information System (INIS)

Roy, Amitava

2010-01-01

This paper reviews the process of electron emission from metal surface. Although electrons move freely in conductors like metals, they normally do not leave the metal without some manipulation. In fact, heating and bombardment are the two primary ways in which electrons are emitted through the use of a heating element behind the cathode (termed thermionic emission) or as a result of bombardment with a beam of electrons, ions, or metastable atoms (termed secondary emission). Another important emission mechanism called Explosive Electron Emission (EEE) is also often used in various High Voltage Pulse Power Systems to generate very high current (few hundreds of kA) pulsed electron beams. The electron gun is the device in that it shoots off a continuous (or pulsed) stream of electrons. A brief idea about the evolution of the electron gun components and their basis of functioning are also discussed. (author)

Born-Oppenheimer Dynamics, Electronic Friction, and the Inclusion of Electron-Electron Interactions

Science.gov (United States)

Dou, Wenjie; Miao, Gaohan; Subotnik, Joseph E.

2017-07-01

We present a universal expression for the electronic friction as felt by a set of classical nuclear degrees of freedom (DOFs) coupled to a manifold of quantum electronic DOFs; no assumptions are made regarding the nature of the electronic Hamiltonian and electron-electron repulsions are allowed. Our derivation is based on a quantum-classical Liouville equation for the coupled electronic-nuclear motion, followed by an adiabatic approximation whereby electronic transitions are assumed to equilibrate faster than nuclear movement. The resulting form of friction is completely general, but does reduce to previously published expressions for the quadratic Hamiltonian (i.e., Hamiltonians without electronic correlation). At equilibrium, the second fluctuation-dissipation theorem is satisfied and the frictional matrix is symmetric. To demonstrate the importance of electron-electron correlation, we study electronic friction within the Anderson-Holstein model, where a proper treatment of electron-electron interactions shows signatures of a Kondo resonance and a mean-field treatment is completely inadequate.

INCIDENCIA Y NIVEL DE INFESTACIÓN POR VARROASIS EN ABEJAS (Apis mellifera EN EL LABORATORIO DE IDENTIFICACIÓN Y DIAGNÓSTICO APÍCOLA DE 2002 A 2006

Directory of Open Access Journals (Sweden)

Agustín Ruíz-Flores

2012-01-01

Full Text Available El objetivo fue estudiar las tendencias anuales y mensuales para el número de muestras positivas (NMP y el nivel de infestación (NI por Varroa destructor en abejas (Apis mellifera. El estudio se realizó de 2002 a 2006 en el Laboratorio de Identificación y Diagnóstico Apícola de la SAGARPA. La detección del ácaro se realizó con la técnica de De Jong para V. destructor. Los estimadores de las tendencias anuales y mensuales para NMP y NI se obtuvieron mediante regresión. El promedio mensual para NMP fue 47.6 ± 49.3 (0 a 248 muestras. La tendencia anual para el incremento del NMP fue -5.69 ± 4.48 (P = 0.2087. La tendencia mensual de enero a diciembre fue 0.91 ± 1.7 (P = 0.6024. El NI promedio fue 3.27 ± 2.6 %, el promedio mensual varió de 0 a 10.06 %. La tasa media de incremento anual en el NI fue 0.34 ± 0.23 % (P = 0.2494. La tasa media de incremento mensual de enero a diciembre fue -0.17 ± 0.1 % (P = 0.1194. Los NMP con V. destructor y los NI, no mostraron incrementos significativos para el periodo estudiado. No se detectó el efecto de la estacionalidad sobre el NMP y NI.

Tropilaelaps mite: an emerging threat to European honey bee.

Science.gov (United States)

Chantawannakul, Panuwan; Ramsey, Samuel; vanEngelsdorp, Dennis; Khongphinitbunjong, Kitiphong; Phokasem, Patcharin

2018-04-01

The risk of transmission of honey bee parasites has increased substantially as a result of trade globalization and technical developments in transportation efficacy. Great concern over honey bee decline has accelerated research on newly emerging bee pests and parasites. These organisms are likely to emerge from Asia as it is the only region where all 10 honey bee species co-occur. Varroa destructor, an ectoparasitic mite, is a classic example of a pest that has shifted from A. cerana, a cavity nesting Asian honey bee to A. mellifera, the European honey bee. In this review, we will describe the potential risks to global apiculture of the global expansion of Tropilaelaps mercedesae, originally a parasite of the open-air nesting Asian giant honey bee, compared to the impact of V. destructor. Copyright © 2018 Elsevier Inc. All rights reserved.

Time-course mortality and radiosensitivity indices in Tribolium spp. developing from irradiated pupae

International Nuclear Information System (INIS)

Hasan, Md Mahbub

1999-01-01

Effects of gamma irradiation (1-5 Krad) on the time-course mortality and radiosensitivity indices in adults of Tribolium anaphe, T. brevicornis, T. castaneum, T. destructor, T. freemani developing from irradiated 1 day old and pre-emergence (4-5 day old) pupae were studied. Adult longevity was significantly (P<0.001) affected by irradiation and was linearly dose dependent. T. destructor was markedly more radioresistant than the other species at all dose levels and had a longer life expectancy. The mean survival times of adults developing from irradiated early and late pupae were shorter in females than in males for all the species. The radiosensitivity indices did not vary widely among the species and these values decreased as the dose increased in all the species which clearly indicate that the resistance of the species was dose-dependent. (author)

Control del parásito Varroa destructor (Acari: Varroidae en colmenas de la abeja Apis mellifera (Hymenoptera: Apidae mediante la aplicación de la técnica de entrampado

Directory of Open Access Journals (Sweden)

Natalia DAMIANI

2006-01-01

Full Text Available La parasitosis causada por el ácaro Varroa destructor (Anderson & Trueman es, actualmente considerada el mayor escollo para el desarrollo de la apicultura. El objetivo del presente trabajo fue evaluar la técnica del entrampamiento de ácaros en panales de cría, como posible método de control de la parasitosis. El trabajo se llevó a cabo en Coronel Vidal, provincia de Buenos Aires. Se trabajó sobre colmenas tipo Langstroth del híbrido regional de Apis mellifera (Linneaus. En cada colmena experimental se procedió a confinar a la reina en panales trampa específicos, con el fin de poder controlar la oviposición. Estos panales, luego de ser operculados por las obreras, fueron llevados al laboratorio donde se desoperculó cada una de las celdas de cría, y se contabilizó el número de ácaros presentes. Esta técnica se aplicó variando el número de panales trampa (1-3 colocados, tanto para los constituidos por celdas de cría de obreras como de zánganos. También, se evaluó el impacto de la aplicación de esta técnica sobre el desarrollo de las colonias, mediante la medición de su productividad. Los resultados indican, que la técnica empleada sólo es efectiva, cuando se aplican tres panales de cría de zánganos de manera consecutiva alcanzando una efectividad máxima de 84%. Cuando se aplican tres panales de obreras, la técnica mostró niveles de efectividad muy inferiores (14%. En las colonias sobre las que se aplicó esta técnica, la productividad de miel se redujo significativamente, comparada con las colonias control. Esta técnica resulta ideal para ser combinada con otros mecanismos de control, disminuyendo la aplicación de sustancias químicas que puedan contaminar la miel, y la generación de resistencia por parte del ácaro frente a los principios activos utilizados para su control.

Differential gene expression associated with honey bee grooming behavior in response to varroa mites

Science.gov (United States)

Honey bee (Apis mellifera) grooming behavior is an important mechanism of resistance against the parasitic mite Varroa destructor. This research was conducted to study associations between grooming behavior and the expression of selected immune, neural, detoxification, developmental and health-relat...

Migration effects on population dynamics of the honeybee-mite interactions

Science.gov (United States)

Honeybees are amazing and highly beneficial insect species that play important roles in undisturbed and agricultural ecosystems. Unfortunately, honeybees are increasingly threatened by numerous factors, most notably the parasitic Varroa mite (Varroa destructor Anderson and Trueman). A recent field s...

Leven met de varroamijt in de 21ste eeuw

NARCIS (Netherlands)

Blacquiere, T.; Cornelissen, B.; Smeekens, C.C.; Steen, van der J.J.M.

2002-01-01

Overzicht van voorhanden bestrijdingsmethoden tegen Varroa destructor op de korte termijn en vooruitzichten voor de bestrijding op langere termijn. In de nabije toekomst gaat het om bestrijding met diergeneesmiddelen van natuurlijke oorsprong (mierenzuur, oxaalzuur, thymol) in het kader van een

Effective electron-electron and electron-phonon interactions in the Hubbard-Holstein model

International Nuclear Information System (INIS)

Aprea, G.; Di Castro, C.; Grilli, M. . E-mail marco.grilli@roma1.infn.it; Lorenzana, J.

2006-01-01

We investigate the interplay between the electron-electron and the electron-phonon interaction in the Hubbard-Holstein model. We implement the flow-equation method to investigate within this model the effect of correlation on the electron-phonon effective coupling and, conversely, the effect of phonons in the effective electron-electron interaction. Using this technique we obtain analytical momentum-dependent expressions for the effective couplings and we study their behavior for different physical regimes. In agreement with other works on this subject, we find that the electron-electron attraction mediated by phonons in the presence of Hubbard repulsion is peaked at low transferred momenta. The role of the characteristic energies involved is also analyzed

Electron-electron coincidence spectroscopies at surfaces

International Nuclear Information System (INIS)

Stefani, G.; Iacobucci, S.; Ruocco, A.; Gotter, R.

2002-01-01

In the past 20 years, a steadily increasing number of electron-electron coincidence experiments on atoms and molecules have contributed to a deeper understanding of electron-electron correlation effects. In more recent years this technique has been extended to the study of solid surfaces. This class of one photon IN two electrons OUT experiments will be discussed with an emphasis on grazing incidence geometry, that is expected to be particularly suited for studying surfaces. The crucial question of which is the dominant mechanism that leads to ejection of pairs of electron from the surface will be addressed. It will be shown that, depending on the kinematics chosen, the correlated behaviour of the pairs of electrons detected might be singled out from independent particle one

Electron distribution function in electron-beam-excited plasmas

International Nuclear Information System (INIS)

Brau, C.A.

1976-01-01

In monatomic plasmas excited by high-intensity relativistic electron beams, the electron secondary distribution function is dominated by elastic electron-electron collisions at low electron energies and by inelastic electron-atom collisions at high electron energies (above the excitation threshold). Under these conditions, the total rate of excitation by inelastic collisions is limited by the rate at which electron-electron collisions relax the distribution function in the neighborhood of the excitation threshold. To describe this effect quantitatively, an approximate analytic solution of the electron Boltzmann equation is obtained, including both electron-electron and inelastic collisions. The result provides a simple formula for the total rate of excitation

Hard electronics; Hard electronics

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

Hard material technologies were surveyed to establish the hard electronic technology which offers superior characteristics under hard operational or environmental conditions as compared with conventional Si devices. The following technologies were separately surveyed: (1) The device and integration technologies of wide gap hard semiconductors such as SiC, diamond and nitride, (2) The technology of hard semiconductor devices for vacuum micro- electronics technology, and (3) The technology of hard new material devices for oxides. The formation technology of oxide thin films made remarkable progress after discovery of oxide superconductor materials, resulting in development of an atomic layer growth method and mist deposition method. This leading research is expected to solve such issues difficult to be easily realized by current Si technology as high-power, high-frequency and low-loss devices in power electronics, high temperature-proof and radiation-proof devices in ultimate electronics, and high-speed and dense- integrated devices in information electronics. 432 refs., 136 figs., 15 tabs.

Reproductive biology of varroa mites in colonies of Africanized honey bees

NARCIS (Netherlands)

Calderon Fallas, R.A.

2009-01-01

We investigated the reproductive biology of V. destructor in Africanized honeybees (AHB) in Central American conditions, specifically in Costa Rica. Attention was paid to mite fertility and production of viable female mites in worker and drone brood cells. Other reproduction parameters, like

Electron radiography

Science.gov (United States)

Merrill, Frank E.; Morris, Christopher

2005-05-17

A system capable of performing radiography using a beam of electrons. Diffuser means receive a beam of electrons and diffuse the electrons before they enter first matching quadrupoles where the diffused electrons are focused prior to the diffused electrons entering an object. First imaging quadrupoles receive the focused diffused electrons after the focused diffused electrons have been scattered by the object for focusing the scattered electrons. Collimator means receive the scattered electrons and remove scattered electrons that have scattered to large angles. Second imaging quadrupoles receive the collimated scattered electrons and refocus the collimated scattered electrons and map the focused collimated scattered electrons to transverse locations on an image plane representative of the electrons' positions in the object.

Electron transfer from electronic excited states to sub-vacuum electron traps in amorphous ice

International Nuclear Information System (INIS)

Vichnevetski, E.; Bass, A.D.; Sanche, L.

2000-01-01

We investigate the electron stimulated yield of electronically excited argon atoms (Ar * ) from monolayer quantities of Ar deposited onto thin films of amorphous ice. Two peaks of narrow width ( - electron-exciton complex into exciton states, by the transfer of an electron into a sub-vacuum electron state within the ice film. However, the 10.7 eV feature is shifted to lower energy since electron attachment to Ar occurs within small pores of amorphous ice. In this case, the excess electron is transferred into an electron trap below the conduction band of the ice layer

Potential impacts of alien freshwater crayfish in South Africa | de ...

African Journals Online (AJOL)

The habitat preferences and life history characteristics of four alien species of freshwater crayfish (Cherax tenuimanus, C. destructor, C. quadricarinatus and Procambarus clarkii) are reviewed. The potential impact of these species on South African freshwater ecosystems is assessed and the desirability of allowing their ...

Successful reproduction of unmated Tropilaelaps mercedesae and its implication on mite population growth in Apis mellifera colonies

Science.gov (United States)

Highly hygienic colonies are known to reduce the reproductive potential of Varroa destructor. For Tropilaelaps mercedesae, information on how bee behavior may influence the mite’s reproductive potential is currently unknown. In this study, we assessed the influence of recapping on the reproduction o...

Ecology, life history and management of tropilaelaps mites

Science.gov (United States)

Parasitic mites are the major threat of the Western honey bee, Apis mellifera. For much of the world, Varroa destructor single-handedly inflicts unsurmountable problems to A. mellifera beekeeping. However, A. mellifera in Asia is also faced with another genus of destructive parasitic mite, Tropilae...

Parasite-host interactions between the Varroa mite and the honey bee : a contribution to sustainable Varroa control

NARCIS (Netherlands)

Calis, J.N.M.

2001-01-01

Introduction

Varroa mites as parasites of honey bees

Varroa destructor (Anderson & Trueman, 2000), is the most important pest of European races of the Western honey bee, Apis mellifera L., weakening bees

Effectieve bestrijding van varroa (Tweede, licht gewijzigde druk)

NARCIS (Netherlands)

Cornelissen, B.; Blacquière, T.; Steen, van der J.J.M.

2013-01-01

De varroa mijtziekte (Varroa destructor) is de belangrijkste bedreiging van de Europese honingbij. Wintersterfte van honingbijen is in de meeste gevallen toe te schrijven aan deze ziekte. Deze tweede, licht gewijzigde druk biedt informatie over de biologie van varroa, de effecten van varroa op

A diverse range of novel RNA viruses in geographically distinct honey bee populations

NARCIS (Netherlands)

Remnant, Emily J.; Shi, Mang; Buchmann, Gabriele; Blacquière, Tjeerd; Holmes, Edward C.; Beekman, Madeleine; Ashe, Alyson

2017-01-01

Understanding the diversity and consequences of viruses present in honey bees is critical for maintaining pollinator health and managing the spread of disease. The viral landscape of honey bees (Apis mellifera) has changed dramatically since the emergence of the parasitic mite Varroa destructor,

Development of molecular tools for honeybee virus research: the ...

African Journals Online (AJOL)

Increasing knowledge of the association of honeybee viruses with other honeybee parasites, primarily the ectoparasitic mite Varroa destructor, and their implication in the mass mortality of honeybee colonies, has resulted in increasing awareness and interest in honeybee viruses. In addition the identification, monitoring and ...

Monte Carlo study of electron relaxation in graphene with spin polarized, degenerate electron gas in presence of electron-electron scattering

Science.gov (United States)

Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

2017-12-01

The Monte Carlo simulation method is applied to study the relaxation of excited electrons in monolayer graphene. The presence of spin polarized background electrons population, with density corresponding to highly degenerate conditions is assumed. Formulas of electron-electron scattering rates, which properly account for electrons presence in two energetically degenerate, inequivalent valleys in this material are presented. The electron relaxation process can be divided into two phases: thermalization and cooling, which can be clearly distinguished when examining the standard deviation of electron energy distribution. The influence of the exchange effect in interactions between electrons with parallel spins is shown to be important only in transient conditions, especially during the thermalization phase.

Occurrence, diversity and pattern of damage of Oplostomus species (Coleoptera: Scarabaeidae), honey bee pests in Kenya

Science.gov (United States)

Several arthropod pests including the hive beetles Aethina tumida and Oplostomus haroldi and the ectoparasite Varroa destructor have recently been identified as associated with honey bee colonies in Kenya. Here, we report the first documentation of O. fuligineus in Kenya, a related scarab of O. haro...

On the abundance of Dermatophagoides pteronyssinus (Trouessart, 1897) (Pyroglyphidae: Acarina) in house dust

NARCIS (Netherlands)

Bronswijk, van J.E.M.H.; Schoonen, J.M.C.P.; Berlie, M.A.F.; Lukoschus, F.S.

1971-01-01

The dominance of the Pyroglyphidae in house dust has been influenced by a number of factors. The humidity in houses dropped recently to such an extent that only Pyroglyphidae can survive. When temperature and relative humidity are favorable for Acarus siro and Glycyphagus destructor as well as

The Tropilaelaps mites threat: Observations of their reproductive success

Science.gov (United States)

Tropilaelaps spp. are more successful parasitic mites of Apis mellifera than Varroa destructor in Asia (Burgett et al., Bee World 64:25-28). We sought explanations to this success by assessing their fecundity on European bees in three short experiments using the mite transfer technique: 1) fecundity...

Effectieve bestrijding van varroa

NARCIS (Netherlands)

Cornelissen, B.; Blacquiere, T.; Steen, van der J.J.M.

2010-01-01

De varroa mijtziekte (Varroa destructor) is de belangrijkste bedreiging van de Europese honingbij. Wintersterfte van honingbijen is in de meeste gevallen toe te schrijven aan deze ziekte. Deze brochure van de WUR biedt informatie over de biologie van varroa, de effecten van varroa op honingbijen en

Effect varroa op volksgrootte pas zichtbaar als het te laat is?

NARCIS (Netherlands)

Dooremalen, van C.; Cornelissen, B.; Langevelde, van F.

2014-01-01

De parasitaire mijt Varroa destructor is altijd en overal aanwezig in volken van onze honingbijen. Varroa verkot het leven van de volwassen bij, wat resulteert in een verhoogde kans op wintersterfte. Ondanks leen relatief geringe wintersterfte in 2012-2013 en 2013-2014 is het identificeren van een

Responses to Varroa by honey bees with different levels of Varroa Sensitive Hygiene

Science.gov (United States)

The mite-resistance trait called suppression of mite reproduction (SMR) is a form of hygienic behavior that we have named varroa sensitive hygiene (VSH). With VSH, adult worker bees (Apis mellifera) disrupt the population growth of parasitic mites (Varroa destructor) by removing mite-infested bee p...

Simplified methods of evaluating colonies for levels of Varroa Sensitive Hygiene (VSH)

Science.gov (United States)

Varroa sensitive hygiene (VSH) is a trait of honey bees, Apis mellifera, that supports resistance to varroa mites, Varroa destructor. Components of VSH were evaluated to identify simple methods for selection of the trait. Varroa mite population growth was measured in colonies with variable levels of...

Expression of varroa sensitive hygiene (VSH) in commercial VSH honey bees (Hymenoptera: Apidae)

Science.gov (United States)

We tested six commercial sources of honey bees (Apis mellifera L.) that were bred to include the trait of varroa sensitive hygiene (VSH). VSH confers resistance to the parasitic mite Varroa destructor Anderson & Trueman. Queens from these sources were established in colonies which later were measure...

High-Resolution Linkage Analyses to Identify Genes That Influence Varroa Sensitive Hygiene Behavior in Honey Bees.

Science.gov (United States)

Varroa mites (V. destructor) are a major threat to honey bees (Apis melilfera) and beekeeping worldwide and likely lead to colony decline if colonies are not treated. Most treatments involve chemical control of the mites; however, Varroa has evolved resistance to many of these miticides, leaving be...

Bee Mite ID - an online resource on identification of mites associated with bees of the World

Science.gov (United States)

Parasitic mites are known to be a factor in recent declines in bee pollinator populations. In particular, Varroa destructor, an introduced parasite and disease vector, has decimated colonies of the western honey bee, one of the most important agricultural pollinators in the world. Further, global tr...

Electron attachment cross sections obtained from electron attachment spectroscopy

International Nuclear Information System (INIS)

Popp, P.; Baumbach, J.I.; Leonhardt, J.W.; Mothes, S.

1988-01-01

Electron capture detectors have a high sensitivity for substances with high thermal electron attachment cross sections. The electron attachment spectroscopy makes it possible to change the mean electron energy in such a way that the maximum for dissociative electron attachment is reached. Thus, best operation modes of the detection system as well as significant dependencies of electron attachment coefficients are available. Cross sections for electron attachment as a function of the electron energy are obtained with the knowledge of electron energy distribution functions from Boltzmann equation analysis by a special computer code. A disadvantage of this electron attachment spectroscopy is the superposition of space charge effects due to the decrease of the electron drift velocity with increasing mean electron energy. These influences are discussed. (author)

Electron beam effects in auger electron spectroscopy and scanning electron microscopy

International Nuclear Information System (INIS)

Fontaine, J.M.; Duraud, J.P.; Le Gressus, C.

1979-01-01

Electron beam effects on Si(100) and 5% Fe/Cr alloy samples have been studied by measurements of the secondary electron yield delta, determination of the surface composition by Auger electron spectroscopy and imaging with scanning electron microscopy. Variations of delta as a function of the accelerating voltage Esub(p) (0.5 -9 Torr has no effect on technological samples covered with their reaction layers; the sensitivities to the beam depend rather on the earlier mechanical, thermal and chemical treatment of the surfaces. (author)

The effect of electron-electron interaction induced dephasing on electronic transport in graphene nanoribbons

Energy Technology Data Exchange (ETDEWEB)

Kahnoj, Sina Soleimani; Touski, Shoeib Babaee [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Pourfath, Mahdi, E-mail: pourfath@ut.ac.ir, E-mail: pourfath@iue.tuwien.ac.at [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Institute for Microelectronics, TU Wien, Gusshausstrasse 27–29/E360, 1040 Vienna (Austria)

2014-09-08

The effect of dephasing induced by electron-electron interaction on electronic transport in graphene nanoribbons is theoretically investigated. In the presence of disorder in graphene nanoribbons, wavefunction of electrons can set up standing waves along the channel and the conductance exponentially decreases with the ribbon's length. Employing the non-equilibrium Green's function formalism along with an accurate model for describing the dephasing induced by electron-electron interaction, we show that this kind of interaction prevents localization and transport of electrons remains in the diffusive regime where the conductance is inversely proportional to the ribbon's length.

Electron Beam Generation in Tevatron Electron Lenses

International Nuclear Information System (INIS)

Kamerdzhiev, V.; Kuznetsov, G.; Shiltsev, V.; Solyak, N.; Tiunov, M.

2006-01-01

New type of high perveance electron guns with convex cathode has been developed. Three guns described in this article are built to provide transverse electron current density distributions needed for Electron Lenses for beam-beam compensation in the Tevatron collider. The current distribution can be controlled either by the gun geometry or by voltage on a special control electrode located near cathode. We present the designs of the guns and report results of beam measurements on the test bench. Because of their high current density and low transverse temperature of electrons, electron guns of this type can be used in electron cooling and beam-beam compensation devices

Electron beam generation in Tevatron electron lenses

International Nuclear Information System (INIS)

Kamerdzhiev, V.; Kuznetsov, G.; Shiltsev, V.; Solyak, N.; Tiunov, M.

2006-01-01

New type of high perveance electron guns with convex cathode has been developed. Three guns described in this article are built to provide transverse electron current density distributions needed for Electron Lenses for beam-beam compensation in the Tevatron collider. The current distribution can be controlled either by the gun geometry or by voltage on a special control electrode located near cathode. We present the designs of the guns and report results of beam measurements on the test bench. Because of their high current density and low transverse temperature of electrons, electron guns of this type can be used in electron cooling and beam-beam compensation devices

Electronic technology

International Nuclear Information System (INIS)

Kim, Jin Su

2010-07-01

This book is composed of five chapters, which introduces electronic technology about understanding of electronic, electronic component, radio, electronic application, communication technology, semiconductor on its basic, free electron and hole, intrinsic semiconductor and semiconductor element, Diode such as PN junction diode, characteristic of junction diode, rectifier circuit and smoothing circuit, transistor on structure of transistor, characteristic of transistor and common emitter circuit, electronic application about electronic equipment, communication technology and education, robot technology and high electronic technology.

The Electron

Energy Technology Data Exchange (ETDEWEB)

Thomson, George

1972-01-01

Electrons are elementary particles of atoms that revolve around and outside the nucleus and have a negative charge. This booklet discusses how electrons relate to electricity, some applications of electrons, electrons as waves, electrons in atoms and solids, the electron microscope, among other things.

Determination of the electron-electron collisional frequency by means of plasma electron spectroscopy

International Nuclear Information System (INIS)

Kolokolov, N.B.; Kudryavtsev, A.A.; Romanenko, V.A.

1989-01-01

Methods of controlling fast part of electron distribution function (DF) in nonlocal regime of current-free plasma are suggested and realized. Artificially created step in DF fast part has a simple link with frequencies of electron-electron and elastic electron-atom collisions that may be defined in the corresponding experiments

Electron beam-plasma interaction and electron-acoustic solitary waves in a plasma with suprathermal electrons

Science.gov (United States)

Danehkar, A.

2018-06-01

Suprathermal electrons and inertial drifting electrons, so called electron beam, are crucial to the nonlinear dynamics of electrostatic solitary waves observed in several astrophysical plasmas. In this paper, the propagation of electron-acoustic solitary waves (EAWs) is investigated in a collisionless, unmagnetized plasma consisting of cool inertial background electrons, hot suprathermal electrons (modeled by a κ-type distribution), and stationary ions. The plasma is penetrated by a cool electron beam component. A linear dispersion relation is derived to describe small-amplitude wave structures that shows a weak dependence of the phase speed on the electron beam velocity and density. A (Sagdeev-type) pseudopotential approach is employed to obtain the existence domain of large-amplitude solitary waves, and investigate how their nonlinear structures depend on the kinematic and physical properties of the electron beam and the suprathermality (described by κ) of the hot electrons. The results indicate that the electron beam can largely alter the EAWs, but can only produce negative polarity solitary waves in this model. While the electron beam co-propagates with the solitary waves, the soliton existence domain (Mach number range) becomes narrower (nearly down to nil) with increasing the beam speed and the beam-to-hot electron temperature ratio, and decreasing the beam-to-cool electron density ratio in high suprathermality (low κ). It is found that the electric potential amplitude largely declines with increasing the beam speed and the beam-to-cool electron density ratio for co-propagating solitary waves, but is slightly decreased by raising the beam-to-hot electron temperature ratio.

Author Details

African Journals Online (AJOL)

Abdelkader, Faten Ben. Vol 64, No 1 (2016): Special Edition - Articles Particularité du traitement à l'acide formique de varroa destructor (Acari, Varroidae), parasite d'apis mellifera dans les conditions tunisiennes. Abstract. ISSN: 0378-9721. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for ...

La eliminación higiénica de la cría congelada no predice caracteres de resistencia ante Varroa en las poblaciones no seleccionadas

NARCIS (Netherlands)

Leclercq, Gil; Blacquière, Tjeerd; Gengler, Nicolas; Francis, Frédéric

2018-01-01

In honey bees (Apis mellifera L.), hygienic behavior of workers against Varroa destructor provides the colonies with some resistance to this parasite. The removal of freeze-killed brood (FKB) has often been used as a proxy to assess the removal of Varroa-infested brood. The question is whether this

Varroa Sensitive Hygiene contributes to naturally selected varroa resistance in honey bees

NARCIS (Netherlands)

Panziera, Delphine; Langevelde, van Frank; Blacquière, Tjeerd

2017-01-01

The parasitic mite Varroa destructor is a serious threat for western honey bee colonies and beekeepers are compelled to control it to keep their colonies healthy. Yet, by controlling varroa no resistance to the parasite can evolve. As a trial, honey bee colonies have been left untreated in

Differential responses to DWV infection in honey bees: A case of tolerance or resistance?

Science.gov (United States)

Honey bees contend with a variety of abiotic and biotic stressors, and this has led to high and likely unsustainable annual colony mortality. The ectoparasitic mite Varroa destructor is the biggest threat affecting honey bee health in large part because of the viruses that mites vector while feeding...

Electronic Government and Electronic Participation

NARCIS (Netherlands)

Tambouris, E; Scholl, H.J.; Janssen, M.F.W.H.A.; Wimmer, M.A.; Tarabanis, K; Gascó, M; Klievink, A.J.; Lindgren, I; Milano, M; Panagiotopoulos, P; Pardo, T.A.; Parycek, P; Sæbø, Ø

2016-01-01

Electronic government and electronic participation continue to transform the public sector and society worldwide and are constantly being transformed themselves by emerging information and communication technologies.This book presents papers from the 14th International Federation for Information

Electronic Government and Electronic Participation

NARCIS (Netherlands)

Tambouris, E.; Scholl, H.J.; Janssen, M.F.W.H.A.; Wimmer, M.A.; Tarabanis, K.; Gascó, M.; Klievink, A.J.; Lindgren, I.; Milano, M.; Panagiotopoulos, P.; Pardo, T.A.; Parycek, P.; Sæbø, O.

2015-01-01

Electronic government and electronic participation continue to transform the public sector and society worldwide and are constantly being transformed themselves by emerging information and communication technologies. This book presents papers from the 14th International Federation for Information

Electron detector

International Nuclear Information System (INIS)

Hashimoto, H.; Mogami, A.

1975-01-01

A device for measuring electron densities at a given energy level in an electron beam or the like having strong background noise, for example, in the detection of Auger electric energy spectrums is described. An electron analyzer passes electrons at the given energy level and at the same time electrons of at least one adjacent energy level. Detecting means associated therewith produce signals indicative of the densities of the electrons at each energy level and combine these signals to produce a signal indicative of the density of the electrons of the given energy level absent background noise

Electron-electron interactions in artificial graphene

Science.gov (United States)

Rasanen, Esa

2013-03-01

Recent advances in the creation and modulation of graphenelike systems are introducing a science of ``designer Dirac materials.'' In its original definition, artificial graphene is a man-made nanostructure that consists of identical potential wells (quantum dots) arranged in an adjustable honeycomb lattice in the two-dimensional electron gas. As our ability to control the quality of artificial graphene samples improves, so grows the need for an accurate theory of its electronic properties, including the effects of electron-electron interactions. Here we determine those effects on the band structure and on the emergence of Dirac points, and discuss future investigations and challenges in this field.

Decal electronics for printed high performance cmos electronic systems

KAUST Repository

Hussain, Muhammad Mustafa

2017-11-23

High performance complementary metal oxide semiconductor (CMOS) electronics are critical for any full-fledged electronic system. However, state-of-the-art CMOS electronics are rigid and bulky making them unusable for flexible electronic applications. While there exist bulk material reduction methods to flex them, such thinned CMOS electronics are fragile and vulnerable to handling for high throughput manufacturing. Here, we show a fusion of a CMOS technology compatible fabrication process for flexible CMOS electronics, with inkjet and conductive cellulose based interconnects, followed by additive manufacturing (i.e. 3D printing based packaging) and finally roll-to-roll printing of packaged decal electronics (thin film transistors based circuit components and sensors) focusing on printed high performance flexible electronic systems. This work provides the most pragmatic route for packaged flexible electronic systems for wide ranging applications.

Electron-beam-induced-current and active secondary-electron voltage-contrast with aberration-corrected electron probes

Energy Technology Data Exchange (ETDEWEB)

Han, Myung-Geun, E-mail: mghan@bnl.gov [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Garlow, Joseph A. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Materials Science and Engineering Department, Stony Brook University, Stony Brook, NY 11794 (United States); Marshall, Matthew S.J.; Tiano, Amanda L. [Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Wong, Stanislaus S. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Cheong, Sang-Wook [Department of Physics and Astronomy, Rutgers Center for Emergent Materials, Rutgers University, Piscataway, NJ 08854 (United States); Walker, Frederick J.; Ahn, Charles H. [Department of Applied Physics and Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520 (United States); Zhu, Yimei [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States)

2017-05-15

Highlights: • Electron-beam-induced-current (EBIC) and active secondary-electron voltage-contrast (SE-VC) are demonstrated in STEM mode combined with in situ electrical biasing in a TEM. • Electrostatic potential maps in ferroelectric thin films, multiferroic nanowires, and single crystals obtained by off-axis electron holography were compared with EBIC and SE-VC data. • Simultaneous EBIC and active SE-VC performed with atomic resolution STEM are demonstrated. - Abstract: The ability to map out electrostatic potentials in materials is critical for the development and the design of nanoscale electronic and spintronic devices in modern industry. Electron holography has been an important tool for revealing electric and magnetic field distributions in microelectronics and magnetic-based memory devices, however, its utility is hindered by several practical constraints, such as charging artifacts and limitations in sensitivity and in field of view. In this article, we report electron-beam-induced-current (EBIC) and secondary-electron voltage-contrast (SE-VC) with an aberration-corrected electron probe in a transmission electron microscope (TEM), as complementary techniques to electron holography, to measure electric fields and surface potentials, respectively. These two techniques were applied to ferroelectric thin films, multiferroic nanowires, and single crystals. Electrostatic potential maps obtained by off-axis electron holography were compared with EBIC and SE-VC to show that these techniques can be used as a complementary approach to validate quantitative results obtained from electron holography analysis.

Seminario C++, parte 1

OpenAIRE

Cachero Castro, Cristina; Ponce de León Amador, Pedro José

2007-01-01

Este seminario trata sobre principios de orientación a objetos con C++. Para comprender mejor sus contenidos, se debe tener un conocimiento básico sobre programación estructurada con C++ o C. Clases en C++. Operaciones set/get/is. Tipo Referencia (&). El puntero 'this'. Los constructores. El destructor.

Browse Title Index - AJOL

African Journals Online (AJOL)

Items 5101 - 5150 of 11090 ... Vol 5, No 5 (2006), Field evaluation of selected formulations of ... virus (DWV) in honeybees (Apis mellifera L.) and mite (Varroa destructor) in Turkey, Abstract PDF ... length polymorphism (AFLP) analysis of genetic diversity and ... Vol 10, No 66 (2011), Foliar zinc fertilization improves the zinc ...

Journal of Biosciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

Amitraz is formamidine pesticide widely used as insecticide and acaricide. In veterinary medicine, amitraz has important uses against ticks, mites and lice on animals. Also, amitraz is used in apiculture to control Varroa destructor. It this study, the alkaline Comet assay was used to evaluate DNA damaging effects of amitraz ...

Electronic Commerce and Electronic Business

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

This special issue is motivated by the recent upsurge of research activity in the areas of electronic commerce and electronic business both in India and all over the world. The current ... Monte Carlo methods for pricing financial options are then.

Electron optical characteristics of a concave electrostatic electron mirror for a scanning electron microscope

International Nuclear Information System (INIS)

Hamarat, R.T.; Witzani, J.; Hoerl, E.M.

1984-08-01

Numerical computer calculations are used to explore the design characteristics of a concave electrostatic electron mirror for a mirror attachment for a conventional scanning electron microscope or an instrument designed totally as a scanning electron mirror microscope. The electron paths of a number of set-ups are calculated and drawn graphically in order to find the optimum shape and dimensions of the mirror geometry. This optimum configuration turns out to be the transition configuration between two cases of electron path deflection, towards the optical axis of the system and away from it. (Author)

Electronic processes in organic electronics bridging nanostructure, electronic states and device properties

CERN Document Server

Kudo, Kazuhiro; Nakayama, Takashi; Ueno, Nobuo

2015-01-01

The book covers a variety of studies of organic semiconductors, from fundamental electronic states to device applications, including theoretical studies. Furthermore, innovative experimental techniques, e.g., ultrahigh sensitivity photoelectron spectroscopy, photoelectron yield spectroscopy, spin-resolved scanning tunneling microscopy (STM), and a material processing method with optical-vortex and polarization-vortex lasers, are introduced. As this book is intended to serve as a textbook for a graduate level course or as reference material for researchers in organic electronics and nanoscience from electronic states, fundamental science that is necessary to understand the research is described. It does not duplicate the books already written on organic electronics, but focuses mainly on electronic properties that arise from the nature of organic semiconductors (molecular solids). The new experimental methods introduced in this book are applicable to various materials (e.g., metals, inorganic and organic mater...

Decal electronics for printed high performance cmos electronic systems

KAUST Repository

Hussain, Muhammad Mustafa; Sevilla, Galo Torres; Cordero, Marlon Diaz; Kutbee, Arwa T.

2017-01-01

High performance complementary metal oxide semiconductor (CMOS) electronics are critical for any full-fledged electronic system. However, state-of-the-art CMOS electronics are rigid and bulky making them unusable for flexible electronic applications

Precession mechanism of spin relaxation at frequent electron-electron collisions

CERN Document Server

Glazov, M M

2002-01-01

It is shown that the spin relaxation mechanism in the two-dimensional electron gas, is controlled not only through the electron pulse relaxation processes, determining the mobility, but through the electron-electron collisions as well. It is decided to use the kinetic equation, describing the electron spin mixing in the k-space, for determining the spin relaxation time tau sub s at frequent electron-electron collisions. The tau sub s time is calculated for the nondegenerated electron gas both with an account and with no account of the exchange interaction

Statistical methods to quantify the effect of mite parasitism on the probability of death in honey bee colonies

Science.gov (United States)

Varroa destructor is a mite parasite of European honey bees, Apis mellifera, that weakens the population, can lead to the death of an entire honey bee colony, and is believed to be the parasite with the most economic impact on beekeeping. The purpose of this study was to estimate the probability of ...

Practical electronics handbook

CERN Document Server

Sinclair, Ian R

2013-01-01

Practical Electronics Handbook, Third Edition provides the frequently used and highly applicable principles of electronics and electronic circuits.The book contains relevant information in electronics. The topics discussed in the text include passive and active discrete components; linear and digital I.C.s; microprocessors and microprocessor systems; digital-analogue conversions; computer aids in electronics design; and electronic hardware components.Electronic circuit constructors, service engineers, electronic design engineers, and anyone with an interest in electronics will find the book ve

Composition quantification of electron-transparent samples by backscattered electron imaging in scanning electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Müller, E., E-mail: erich.mueller@kit.edu; Gerthsen, D.

2017-02-15

The contrast of backscattered electron (BSE) images in scanning electron microscopy (SEM) depends on material parameters which can be exploited for composition quantification if some information on the material system is available. As an example, the In-concentration in thin In{sub x}Ga{sub 1−x}As layers embedded in a GaAs matrix is analyzed in this work. The spatial resolution of the technique is improved by using thin electron-transparent specimens instead of bulk samples. Although the BSEs are detected in a comparably small angular range by an annular semiconductor detector, the image intensity can be evaluated to determine the composition and local thickness of the specimen. The measured intensities are calibrated within one single image to eliminate the influence of the detection and amplification system. Quantification is performed by comparison of experimental and calculated data. Instead of using time-consuming Monte-Carlo simulations, an analytical model is applied for BSE-intensity calculations which considers single electron scattering and electron diffusion. - Highlights: • Sample thickness and composition are quantified by backscattered electron imaging. • A thin sample is used to achieve spatial resolution of few nanometers. • Calculations are carried out with a time-saving electron diffusion model. • Small differences in atomic number and density detected at low electron energies.

Nonlinear electron-acoustic rogue waves in electron-beam plasma system with non-thermal hot electrons

Science.gov (United States)

Elwakil, S. A.; El-hanbaly, A. M.; Elgarayh, A.; El-Shewy, E. K.; Kassem, A. I.

2014-11-01

The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, non-thermal hot electrons obeying a non-thermal distribution, an electron beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles on the electron beam and energetic population parameter are discussed. The results of the present investigation may be applicable in auroral zone plasma.

Electron-cyclotron-resonant-heated electron distribution functions

International Nuclear Information System (INIS)

Matsuda, Y.; Nevins, W.M.; Cohen, R.H.

1981-01-01

Recent studies at Lawrence Livermore National Laboratory (LLNL) with a bounce-averaged Fokker-Planck code indicate that the energetic electron tail formed by electron-cyclotron resonant heating (ECRH) at the second harmonic is not Maxwellian. We present the results of our bounce-averaged Fokker-Planck code along with some simple analytic models of hot-electron distribution functions

Attainment of Electron Beam Suitable for Medium Energy Electron Cooling

International Nuclear Information System (INIS)

Seletskiy, Sergey M.; Rochester U.

2005-01-01

Electron cooling of charged particle beams is a well-established technique at electron energies of up to 300 keV. However, up to the present time the advance of electron cooling to the MeV-range energies has remained a purely theoretical possibility. The electron cooling project at Fermilab has recently demonstrated the first cooling of 8.9 GeV/c antiprotons in the Recycler ring, and therefore, has proved the validity of the idea of relativistic electron cooling. The Recycler Electron Cooler (REC) is the key component of the Tevatron Run II luminosity upgrade project. Its performance depends critically on the quality of electron beam. A stable electron beam of 4.3 MeV carrying 0.5 A of DC current is required. The beam suitable for the Recycler Electron Cooler must have an angular spread not exceeding 200 (micro)rad. The full-scale prototype of the REC was designed, built and tested at Fermilab in the Wideband laboratory to study the feasibility of attaining the high-quality electron beam. In this thesis I describe various aspects of development of the Fermilab electron cooling system, and the techniques used to obtain the electron beam suitable for the cooling process. In particular I emphasize those aspects of the work for which I was principally responsible. Chapter 1 is an introduction where I describe briefly the theory and the history of electron cooling, and derive the requirements to the quality of electron beam and requirements to the basic parameters of the Recycler Electron Cooler. Chapter 2 is devoted to the theoretical consideration of the motion of electrons in the cooling section, description of the cooling section and of the measurement of the magnetic fields. In Chapter 3 I consider different factors that increase the effective electron angle in the cooling section and suggest certain algorithms for the suppression of parasitic angles. Chapter 4 is devoted to the measurements of the energy of the electron beam. In the concluding Chapter 5 I review

Double differential distributions of electron emission in ion-atom and electron-atom collisions using an electron spectrometer

International Nuclear Information System (INIS)

Misra, Deepankar; Thulasiram, K.V.; Fernandes, W.; Kelkar, Aditya H.; Kadhane, U.; Kumar, Ajay; Singh, Yeshpal; Gulyas, L.; Tribedi, Lokesh C.

2009-01-01

We study electron emission from atoms and molecules in collisions with fast electrons and heavy ions (C 6+ ). The soft collision electrons (SE), two center electron emission (TCEE), the binary encounter (BE) events and the KLL Auger lines along with the elastically scattered peaks (in electron collisions) are studied using a hemispherical electrostatic electron analyzer. The details of the measurements along with description of the spectrometer and data acquisition system are given. The angular distributions of the low energy (few eV) electrons in soft collisions and the binary encounter electrons at keV energies are compared with quantum mechanical models based on the first Born (B1) and the continuum distorted wave-Eikonal initial state approximation (CDW-EIS).

VIRTUAL ELECTRONIC COMPONENTS OF THE ELECTRONIC EQUIPMENT

Directory of Open Access Journals (Sweden)

E. Lazarevich

2013-01-01

Full Text Available The article is present new idea of the creation, developments and improvements of the electronic equipment of complex systems by means of the virtual electronic components. The idea of the virtual electronic components is a presentation and perception of the creation and developments of the equipment on two forming: real – in the manner of standard marketed block of the intellectual property and image – in the manner of virtual component. The real component in most cases slows the development of the electronic equipment. The imaginary component is the «locomotive» of development of the electronic equipment. The Imaginary component contains the scientific has brushed against developer. The scientific has brushed against developer reveals of itself in the manner of virtual component on the modern level of the design rates of microelectronics.

A new stage of nuclear electronics-particle electronics

International Nuclear Information System (INIS)

Xi Deming

1987-01-01

The rapid development of high energy physics experiments has pushed the nuclear electronics to a new stage, i.e. the particle electronics. In this paper the background, main features and recent trends of the particle electronics are expounded

Electron transport effects in ion induced electron emission

Energy Technology Data Exchange (ETDEWEB)

Dubus, A. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium)]. E-mail: adubus@ulb.ac.be; Pauly, N. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium); Roesler, M. [Karl-Pokern-Str. 12, D-12587 Berlin (Germany)

2007-03-15

Ion induced electron emission (IIEE) is usually described as a three-step process, i.e. electron excitation by the incident projectile, electron transport (and multiplication) and electron escape through the potential barrier at the surface. In many cases, the first step of the process has been carefully described. The second step of the process, i.e. electron transport and multiplication, has often been treated in a very rough way, a simple decreasing exponential law being sometimes used. It is precisely the aim of the present work to show the importance of a correct description of electron transport and multiplication in a theoretical calculation of IIEE. A short overview of the electron transport models developed for IIEE is given in this work. The so-called 'Infinite medium slowing-down model' often used in recent works is evaluated by means of Monte Carlo simulations. In particular, the importance of considering correctly the semi-infinite character of the medium and the boundary condition at the vacuum-medium interface is discussed. Quantities like the electron escape depth are also briefly discussed. This evaluation has been performed in the particular case of protons (25keV

Studying electron-PAG interactions using electron-induced fluorescence

Science.gov (United States)

Narasimhan, Amrit; Grzeskowiak, Steven; Ostrander, Jonathan; Schad, Jonathon; Rebeyev, Eliran; Neisser, Mark; Ocola, Leonidas E.; Denbeaux, Gregory; Brainard, Robert L.

2016-03-01

In extreme ultraviolet (EUV) lithography, 92 eV photons are used to expose photoresists. Typical EUV resists are organic-based and chemically amplified using photoacid generators (PAGs). Upon exposure, PAGs produce acids which catalyze reactions that result in changes in solubility. In EUV lithography, photo- and secondary electrons (energies of 10- 80 eV) play a large role in PAG acid-production. Several mechanisms for electron-PAG interactions (e.g. electron trapping, and hole-initiated chemistry) have been proposed. The aim of this study is to explore another mechanism - internal excitation - in which a bound PAG electron can be excited by receiving energy from another energetic electron, causing a reaction that produces acid. This paper explores the mechanism of internal excitation through the analogous process of electron-induced fluorescence, in which an electron loses energy by transferring that energy to a molecule and that molecule emits a photon rather than decomposing. We will show and quantify electron-induced fluorescence of several fluorophores in polymer films to mimic resist materials, and use this information to refine our proposed mechanism. Relationships between the molecular structure of fluorophores and fluorescent quantum yield may aid in the development of novel PAGs for EUV lithography.

Electron-electron Thomas peak in fast transfer ionization

International Nuclear Information System (INIS)

Tolmanov, S. G.; McGuire, J. H.

2000-01-01

''Thomas process'' is a name used for a family of singular two-step processes that can lead to electron transfer. The Thomas process of the ''second kind,'' occurring in reactions with both transfer and ionization, utilizes the e-e scattering in the second step, so this Thomas process requires the dynamics of the electron-electron interaction. We calculate numerically the second order element of an S matrix and corresponding cross sections for the transfer ionization process. We find that the position and shape of the Thomas peak depend on both electron-electron and the electron-nucleus interaction. Also the direct and exchange amplitudes are equal at the peak position. We test the peaking approximation used for transfer ionization. Our results can be compared to experimental results for p + +He→H+He 2+ +e - . (c) 2000 The American Physical Society

Electron Tree

DEFF Research Database (Denmark)

Appelt, Ane L; Rønde, Heidi S

2013-01-01

The photo shows a close-up of a Lichtenberg figure – popularly called an “electron tree” – produced in a cylinder of polymethyl methacrylate (PMMA). Electron trees are created by irradiating a suitable insulating material, in this case PMMA, with an intense high energy electron beam. Upon discharge......, during dielectric breakdown in the material, the electrons generate branching chains of fractures on leaving the PMMA, producing the tree pattern seen. To be able to create electron trees with a clinical linear accelerator, one needs to access the primary electron beam used for photon treatments. We...... appropriated a linac that was being decommissioned in our department and dismantled the head to circumvent the target and ion chambers. This is one of 24 electron trees produced before we had to stop the fun and allow the rest of the accelerator to be disassembled....

Electronic Raman response in electron-doped cuprate superconductors

International Nuclear Information System (INIS)

Geng Zhihao; Feng Shiping

2012-01-01

The electronic Raman response in the electron-doped cuprate superconductors is studied based on the t-t'-J model. It is shown that although the domelike shape of the doping dependent peak energy in the B 2g symmetry is a common feature for both electron-doped and hole-doped cuprate superconductors, there are pronounced deviations from a cubic response in the B 2g channel and a linear response in the B 2g channel for the electron-doped case in the low energy limit. It is also shown that these pronounced deviations are mainly caused by a nonmonotonic d-wave gap in the electron-doped cuprate superconductors.

Spectroscopy of electron irradiated polymers in electron microscope

International Nuclear Information System (INIS)

Faraj, S.H.; Salih, S.M.

1981-01-01

The damage induced by energetic electrons in the course of irradiation of polymers in a transmission electron microscope was investigated spectroscopically. Damage on the molecular level has been detected at very low exposure doses. These effects have been induced by electron doses less than that received by the specimen when it is situated at its usual place of the specimen stage in the electron microscope by a factor of 1,000. (author)

Electron spectroscopy in the fundamental process of electron-nucleus bremsstrahlung

International Nuclear Information System (INIS)

Hillenbrand, Pierre-Michel

2013-07-01

Within the scope of this thesis the fundamental process of electron-nucleus bremsstrahlung was studied in inverse kinematics at the Experimental Storage Ring ESR at GSI. For the system U 88+ + N 2 at 90 MeV/u it was shown, that by using inverse kinematics coincidence measurements between the scattered electron and the emitted photon can be performed for the case, in which the incoming electron transfers almost all of its kinetic energy onto the emitted photon. The sensitivity to the fundamental process could be achieved by measuring triple differential cross sections as a function of the emission angle of the photon and the scattered electron as well as the energy of the scattered electron. The optics of the magnetic electron spectrometer used were thoroughly revised and optimized to the experimental requirements. Analyzing different coincidences in this collision system, it was possible to determine the contributions to the electron distribution arising from radiative electron capture to the projectile continuum, nonradiative electron capture to the projectile continuum, and electron loss to the projectile continuum. The experimental results of each of these processes were compared to theoretical calculations. The electron spectra for the radiative and the nonradiative electron capture to continuum clearly reproduce the opposite asymmetry predicted by theory. Furthermore electron spectra for collisions of U 28+ with different gases were measured.

Risk factors for the presence of Deformed wing virus and Acute bee paralysis virus under temperate and subtropical climate in Argentinian bee colonies.

Science.gov (United States)

Molineri, Ana; Giacobino, Agostina; Pacini, Adriana; Bulacio Cagnolo, Natalia; Fondevila, Norberto; Ferrufino, Cecilia; Merke, Julieta; Orellano, Emanuel; Bertozzi, Ezequiel; Masciángelo, Germán; Pietronave, Hernán; Signorini, Marcelo

2017-05-01

Beekeepers all across the world are suffering important losses of their colonies, and the parasitic mites Varroa destructor and Nosema sp, as well as several bee viruses, are being pointed out as the possible causes of these losses, generally associated with environmental and management factors. The objective of the present study was to evaluate the presence of seven virus species (Deformed wing virus -DWV-, Acute bee paralysis virus -ABPV-, Chronic bee paralysis virus -CBPV-, Black queen cell virus -BQCV-, Kashmir bee virus -KBV-, Israeli acute bee paralysis virus -IAPV-, and Sacbrood bee virus -SBV), as well as the prevalence of Nosema sp. and Varroa destructor, and their possible associated factors, under temperate and subtropical climate conditions in Argentinean colonies. A total of 385 colonies distributed in five Argentinean eco-regions were examined after honey harvest. The final multivariable model revealed only one variable associated with the presence of DWV and two with the presence of ABPV. The apiary random effect was significant in both cases (P=0.018; P=0.006, respectively). Colonies with a Varroa infestation rate >3% showed higher presence of DWV than colonies with <3% of Varroa infestation level (OR=1.91; 95% CI: 1.02-3.57; P<0.044). The same pattern was observed for the presence of ABPV (OR=2.23; 95% CI: 1.04-4.77; P<0.039). Also, colonies where replacement of old combs was not a common practice had higher presence of ABPV (OR=6.02; 95% CI: 1.16-31.25; P<0.033). Regardless of the location of the colonies, virus presence was strongly associated with V. destructor level. Therefore, all the factors that directly or indirectly influence the levels of mites will be also influencing the presence of the viruses. Copyright © 2017 Elsevier B.V. All rights reserved.

`Twisted' electrons

Science.gov (United States)

Larocque, Hugo; Kaminer, Ido; Grillo, Vincenzo; Leuchs, Gerd; Padgett, Miles J.; Boyd, Robert W.; Segev, Mordechai; Karimi, Ebrahim

2018-04-01

Electrons have played a significant role in the development of many fields of physics during the last century. The interest surrounding them mostly involved their wave-like features prescribed by the quantum theory. In particular, these features correctly predict the behaviour of electrons in various physical systems including atoms, molecules, solid-state materials, and even in free space. Ten years ago, new breakthroughs were made, arising from the new ability to bestow orbital angular momentum (OAM) to the wave function of electrons. This quantity, in conjunction with the electron's charge, results in an additional magnetic property. Owing to these features, OAM-carrying, or twisted, electrons can effectively interact with magnetic fields in unprecedented ways and have motivated materials scientists to find new methods for generating twisted electrons and measuring their OAM content. Here, we provide an overview of such techniques along with an introduction to the exciting dynamics of twisted electrons.

The electron

International Nuclear Information System (INIS)

Hestenes, David; Weingartshofer, Antonio

1991-01-01

The stupendous successes of the Dirac equation and quantum electro-dynamics have established the electron as the best understood of the fundamental constituents of matter. Nevertheless, physicists agree that the electron still has secrets to reveal. Moreover, powerful new theoretical and experimental tools for probing those secrets have been sharpened during the last decade. This workshop was organized to bring theorists and experimentalists together to discuss their common goal of knowing the electron. Present state and future prospects for progress toward that goal are here described. The theoretical papers encompass a wide range of views on the electron. Several argue that the 'Zitter-bewegung' is more than a mathematical peculiarity of the Dirac equation, that it may well be a real physical phenomenon and worthy of serious study, theoretically and experimentally. Besides generating the electron spin and magnetic moment, the 'Zitterbewegung' may be a vital clue to electron structure and self-interaction. Some of the papers employ a radical new formulation of the Dirac theory which reveals a hidden geo-metric structure in the theory that supports a 'Zitterbewegung' inter-pretation. For the last half century the properties of electrons have been probed primarily by scattering experiments at ever higher energies. Recently, however, two powerful new experimental techniques have emerged capable of giving alternative experimental views of the electron. First, techniques for confining single electrons for long term study have led to the most accurate measurements of the electron magnetic moment. Second, the interaction of high intensity laser fields with atoms and electrons have revealed striking new phenomena such as multiphoton ionization. refs.; figs.; tabs

Basic electronics

CERN Document Server

Holbrook, Harold D

1971-01-01

Basic Electronics is an elementary text designed for basic instruction in electricity and electronics. It gives emphasis on electronic emission and the vacuum tube and shows transistor circuits in parallel with electron tube circuits. This book also demonstrates how the transistor merely replaces the tube, with proper change of circuit constants as required. Many problems are presented at the end of each chapter. This book is comprised of 17 chapters and opens with an overview of electron theory, followed by a discussion on resistance, inductance, and capacitance, along with their effects on t

Response of Pinus ponderosa Seedlings to Stylet-Bearing Nematodes

Science.gov (United States)

Viglierchio, D. R.

1979-01-01

Of 12 stylet-bearing nematodes used for inoculations, Pratylenchus penetrans, P. brachyurus, P. vulnus, Ditylenchus destructor, Meloidogyne incognita, M. javanica, and M. hapla reproduced on Pinus ponderosa, while Xiphinema index, Aphelenchus avenae, Paratylenehus neoamblycephalus, Tylenchulus semipenetrans, and Macroposthonia xenoplax did not. P. vulnus, P. brachyurus, P. penetrans, A. avenae, D. destructor, T. semipenetrans, and P. neoamblycephalus significantly suppressed both the shoot and root wet weights of ponderosa pine seedlings obtained from stands in five different locations. X. index significantly suppressed root wet weights, M. xenoplax siguificantly suppressed shoot wet weight, and M. incognita, M. javanica, and M. hapla suppressed neither at the inoculation levels used. Injurious nematodes tended to suppress root growth more than shoot growth. Seedlings from two locations produced greater shoot growth wet weight than did seedlings from the other three locations. The more injurious nematodes tended to cause an increase in the water content of shoots. Frequency analyses of seedling population shoot-root ratios indicated that ponderosa pine seedlings could be selected for better shoot-root ratios as well as for resistance to several pathogenic nematodes. PMID:19300659

Human Capital in the Entrepreneurship Ecosystem

DEFF Research Database (Denmark)

Østergaard, Annemarie; Marinova, Svetla Trifonova

2018-01-01

Since Adam Smith (1776) took consideration to human capital as an asset of economic value, academic interest has focused on the economic effects of human capital. In 1931, Schumpeter called for a focus on the individual entrepreneur or the creative destructor with his/her motives, wishes, aspirat......Since Adam Smith (1776) took consideration to human capital as an asset of economic value, academic interest has focused on the economic effects of human capital. In 1931, Schumpeter called for a focus on the individual entrepreneur or the creative destructor with his/her motives, wishes......, aspirations and activities when dealing with entrepreneurship and entrepreneurs. Along these lines, this paper focuses on an in-depth investigation of the domain of human capital in Isenbergs Entrepreneurship Ecosystem. It captures the entrepreneurial mindset of the highly complex individual as a requisite...... for entrepreneurial success and ultimately, for business growth and development. The increasing literature debating human capital confirms the relevance of locating and refining the factors for entrepreneurial success. Consequently, this paper improves the roadmap of Entrepreneurship Ecosystems by adding the innate...

Electron-electron scattering and mobilities in semiconductors and quantum wells

International Nuclear Information System (INIS)

Lyo, S.K.

1986-01-01

The effect of electron-electron scattering on the mobility in semiconductors and semiconductor quantum wells is examined. A general exact formula is derived for the mobility, when the electron-electron collision rate is much faster than other scattering rates such as those by ionized impurities and phonons. In this limit, the transport relaxation rate is independent of the carrier's energy and contributions to the inverse mobility from individual scattering mechanism add up. The mobility becomes significantly reduced from its value in the absence of electron-electron scattering. When the collision rates are not necessarily dominated by electron-electron scattering, the mobility is calculated by the Kohler-Sondheimer variational method in the presence of ionized-impurity scattering and acoustic-phonon scattering in a nondegenerate two-dimensional quantum well

Modified Monte Carlo method for study of electron transport in degenerate electron gas in the presence of electron-electron interactions, application to graphene

Science.gov (United States)

Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

2017-07-01

Standard computational methods used to take account of the Pauli Exclusion Principle into Monte Carlo (MC) simulations of electron transport in semiconductors may give unphysical results in low field regime, where obtained electron distribution function takes values exceeding unity. Modified algorithms were already proposed and allow to correctly account for electron scattering on phonons or impurities. Present paper extends this approach and proposes improved simulation scheme allowing including Pauli exclusion principle for electron-electron (e-e) scattering into MC simulations. Simulations with significantly reduced computational cost recreate correct values of the electron distribution function. Proposed algorithm is applied to study transport properties of degenerate electrons in graphene with e-e interactions. This required adapting the treatment of e-e scattering in the case of linear band dispersion relation. Hence, this part of the simulation algorithm is described in details.

Attainment of Electron Beam Suitable for Medium Energy Electron Cooling

Energy Technology Data Exchange (ETDEWEB)

Seletskiy, Sergei M. [Univ. of Rochester, NY (United States)

2005-01-01

Electron cooling of charged particle beams is a well-established technique at electron energies of up to 300 keV. However, up to the present time the advance of electron cooling to the MeV-range energies has remained a purely theoretical possibility. The electron cooling project at Fermilab has recently demonstrated the ¯rst cooling of 8.9 GeV/c antiprotons in the Recycler ring, and therefore, has proved the validity of the idea of relativistic electron cool- ing. The Recycler Electron Cooler (REC) is the key component of the Teva- tron Run II luminosity upgrade project. Its performance depends critically on the quality of electron beam. A stable electron beam of 4.3 MeV car- rying 0.5 A of DC current is required. The beam suitable for the Recycler Electron Cooler must have an angular spread not exceeding 200 ¹rad. The full-scale prototype of the REC was designed, built and tested at Fermilab in the Wideband laboratory to study the feasibility of attaining the high-quality electron beam. In this thesis I describe various aspects of development of the Fermilab electron cooling system, and the techniques used to obtain the electron beam suitable for the cooling process. In particular I emphasize those aspects of the work for which I was principally responsible.

Microfluidic electronics.

Science.gov (United States)

Cheng, Shi; Wu, Zhigang

2012-08-21

Microfluidics, a field that has been well-established for several decades, has seen extensive applications in the areas of biology, chemistry, and medicine. However, it might be very hard to imagine how such soft microfluidic devices would be used in other areas, such as electronics, in which stiff, solid metals, insulators, and semiconductors have previously dominated. Very recently, things have radically changed. Taking advantage of native properties of microfluidics, advances in microfluidics-based electronics have shown great potential in numerous new appealing applications, e.g. bio-inspired devices, body-worn healthcare and medical sensing systems, and ergonomic units, in which conventional rigid, bulky electronics are facing insurmountable obstacles to fulfil the demand on comfortable user experience. Not only would the birth of microfluidic electronics contribute to both the microfluidics and electronics fields, but it may also shape the future of our daily life. Nevertheless, microfluidic electronics are still at a very early stage, and significant efforts in research and development are needed to advance this emerging field. The intention of this article is to review recent research outcomes in the field of microfluidic electronics, and address current technical challenges and issues. The outlook of future development in microfluidic electronic devices and systems, as well as new fabrication techniques, is also discussed. Moreover, the authors would like to inspire both the microfluidics and electronics communities to further exploit this newly-established field.

Electron-electron collision effects on the bremsstrahlung emission in Lorentzian plasmas

International Nuclear Information System (INIS)

Jung, Young-Dae; Kato, Daiji

2009-01-01

Electron-electron collision effects on the electron-ion bremsstrahlung process are investigated in Lorentzian plasmas. The effective electron-ion interaction potential is obtained by including the far-field terms caused by electron-electron collisions with an effective Debye length in Lorentzian plasmas. The bremsstrahlung radiation cross section is obtained as a function of the electron energy, photon energy, collision frequency, spectral index and Debye length using the Born approximation for the initial and final states of the projectile electron. It is shown that the non-Maxwellian character suppresses the bremsstrahlung radiation cross section. It is also shown that the electron-electron collision effect enhances the bremsstrahlung emission spectrum. In addition, the bremsstrahlung radiation cross section decreases with an increase in the plasma temperature.

Electron-photon and electron-electron interactions in the presence of strong electromagnetic fields

International Nuclear Information System (INIS)

Surzhykov, A.; Fritzsche, S.; Stoehlker, Th.

2010-01-01

During the last decade, photon emission from highly-charged, heavy ions has been in the focus of intense studies at the GSI accelerator and storage ring facility in Darmstadt. These studies have revealed unique information about the electron-electron and electron-photon interactions in the presence of extremely strong nuclear fields. Apart from the radiative electron capture processes, characteristic photon emission following collisional excitation of projectile ions has also attracted much interest. In this contribution, we summarize the recent theoretical studies on the production of excited ionic states and their subsequent radiative decay. We will pay special attention to the angular and polarization properties of Kα emission from helium-like ions produced by means of dielectronic recombination. The results obtained for this (resonant) capture process will be compared with the theoretical predictions for the characteristic X-rays following Coulomb excitation and radiative recombination of few-electron, heavy ions. Work is supported by Helmholtz Association and GSl under the project VH-NG--421. (author)

Sticker electronics

KAUST Repository

Hussain, Muhammad Mustafa

2017-09-08

Electronic stickers may be manufactured on flexible substrates (110, 120, 130) as layers and packaged together. The package may then have an adhesive applied to one side to provide capability for sticking the electronic devices to surfaces. The stickers can be wrappable, placed on surfaces, glued on walls or mirrors or wood or stone, and have electronics (112, 122, 132) which may or may not be ultrathin. Packaging for the electronic sticker can use polymer on cellulose manufacturing and/or three dimensional (3-D) printing. The electronic stickers may provide lighting capability, sensing capability, and/or recharging capabilities.

Electronic Commerce

Directory of Open Access Journals (Sweden)

Slavko Đerić

2016-12-01

Full Text Available Electronic commerce can be defined in different ways. Any definition helps to understand and explain that concept as better as possible.. Electronic commerce is a set of procedures and technologies that automate the tasks of financial transactions using electronic means. Also, according to some authors, electronic commerce is defined as a new concept, which is being developed and which includes process of buying and selling or exchanging products, services or information via computer networks, including the Internet. Electronic commerce is not limited just to buying and selling, but it also includes all pre-sales and after-sales ongoing activities along the supply chain. Introducing electronic commerce, using the Internet and Web services in business, realizes the way to a completely new type of economy - internet economy.

Observation of the two-electron cusp in atomic collisions. Evidence for strong electron-electron correlation

International Nuclear Information System (INIS)

Sarkadi, L.; Orban, A.

2007-01-01

Complete text of publication follows. In this report we present experimental data for a process when two electrons with velocity vectors equal to that of the projectile are emitted from collisions. By observing the two electron cusp the study of the threshold phenomenon for two-electron break-up is possible. It is a particularly interesting question whether the outgoing charged projectile can attract the two repulsing electrons so strongly that the two-electron cusp is formed. If it is so, a further question arises: Are the two electrons correlated in the final state as it is predicted by the Wannier theory? The experiments have been done at the 1 MeV VdG accelerator of ATOMKI using our TOF spectrometer. The first measurements clearly showed the formation of the two-electron cusp and signature of the electron correlation in 200 keV He 0 +He collisions. These promising results motivated us to carry out the experiment at 100 keV beam energy where the coincidence count rate is still reasonable but the energy resolution is better. For an acceptable data acquisition time we improved our data acquisition and data processing system for triple coincidence measurements. In Fig. 1a we present our measured relative fourfold differential cross section (FDCS) that shows strong electron correlation. For a comparison, in Fig. 1b we displayed the contour plot for uncorrelated electron pair emission. These latter data were synthesized artificially, generating the energies of the electron pairs from two independent double coincidence experiments. In both figures the distributions are characterized by two ridges. In Fig. 1b the ridges are perpendicular straight lines (E 1 = E 2 .13.6 eV). As a result of the correlation, the ridges in Fig. 1a are distorted in such a way that they have a joint straight-line section following the line E 1 + E 2 = 27.2 eV. This means that the electron pairs in the vicinity of the cusp maximum are emitted with a center of- mass velocity equal to that of

Electronics and Information

Institute of Scientific and Technical Information of China (English)

无

2008-01-01

@@ Previously founded as CCPITMachinery and Electronics Sub-council and CCOIC Machinery and Electronics Chamber of Corn-merce in June, 1988, CCPIT Electronics Sub-Council and CCOIC Electronics Chamber of Commerce were established in May, 1993, and then renamed as CCPIT Electronics and Information Industry Sub-council and CCOIC Electronics and Infor-mation Industry Chamber of Commerce (CCPITECC) in September 1999.

Spontaneous and stimulated emission induced by an electron, electron bunch, and electron beam in a plasma

International Nuclear Information System (INIS)

Kuzelev, M V; Rukhadze, A A

2008-01-01

Two fundamental mechanisms - the Cherenkov effect and anomalous Doppler effect - underlying the emission by an electron during its superluminal motion in medium are considered. Cherenkov emission induced by a single electron and a small electron bunch is spontaneous. In the course of spontaneous Cherenkov emission, the translational motion of an electron is slowed down and the radiation energy grows linearly with time. As the number of radiating electrons increases, Cherenkov emission becomes stimulated. Stimulated Cherenkov emission represents a resonance beam instability. This emission process is accompanied by longitudinal electron bunching in the beam or by the breaking of an electron bunch into smaller bunches, in which case the radiation energy grows exponentially with time. In terms of the longitudinal size L e of the electron bunch there is a transition region λ e 0 -1 between the spontaneous and stimulated Cherenkov effects, where λ is the average radiation wavelength, and δ 0 is the dimensionless (in units of the radiation frequency) growth rate of the Cherenkov beam instability. The range to the left of this region is dominated by spontaneous emission, whereas the range to the right of this region is dominated by stimulated emission. In contrast to the Vavilov-Cherenkov effect, the anomalous Doppler effect should always (even for a single electron) be considered as stimulated, because it can only be explained by accounting for the reverse action of the radiation field on the moving electron. During stimulated emission in conditions where anomalous Doppler effect shows itself, an electron is slowed down and spins up; in this case, the radiation energy grows exponentially with time. (reviews of topical problems)

High perveance electron gun for the electron cooling system

International Nuclear Information System (INIS)

Korotaev, Yu.; Meshkov, I.; Petrov, A.; Sidorin, A.; Smirnov, A.; Syresin, E.; Titkova, I.

2000-01-01

The cooling time in the electron cooling system is inversely proportional to the beam current. To obtain high current of the electron beam the control electrode of the gun is provided with a positive potential and an electrostatic trap for secondary electrons appears inside the electron gun. This leads to a decrease in the gun perveance. To avoid this problem, the adiabatic high perveance electron gun with the clearing control electrode is designed in JINR (J. Bosser, Y. Korotaev, I. Meshkov, E. Syresin et al., Nucl. Instr. and Meth. A 391 (1996) 103. Yu. Korotaev, I. Meshkov, A. Sidorin, A. Smirnov, E. Syresin, The generation of electron beams with perveance of 3-6 μA/V 3/2 , Proceedings of SCHEF'99). The clearing control electrode has a transverse electric field, which clears secondary electrons. Computer simulations of the potential map were made with RELAX3D computer code (C.J. Kost, F.W. Jones, RELAX3D User's Guide and References Manual)

High perveance electron gun for the electron cooling system

CERN Document Server

Korotaev, Yu V; Petrov, A; Sidorin, A; Smirnov, A; Syresin, E M; Titkova, I

2000-01-01

The cooling time in the electron cooling system is inversely proportional to the beam current. To obtain high current of the electron beam the control electrode of the gun is provided with a positive potential and an electrostatic trap for secondary electrons appears inside the electron gun. This leads to a decrease in the gun perveance. To avoid this problem, the adiabatic high perveance electron gun with the clearing control electrode is designed in JINR (J. Bosser, Y. Korotaev, I. Meshkov, E. Syresin et al., Nucl. Instr. and Meth. A 391 (1996) 103. Yu. Korotaev, I. Meshkov, A. Sidorin, A. Smirnov, E. Syresin, The generation of electron beams with perveance of 3-6 mu A/V sup 3 sup / sup 2 , Proceedings of SCHEF'99). The clearing control electrode has a transverse electric field, which clears secondary electrons. Computer simulations of the potential map were made with RELAX3D computer code (C.J. Kost, F.W. Jones, RELAX3D User's Guide and References Manual).

Study of single-electron excitations by electron microscopy

International Nuclear Information System (INIS)

Craven, A.J.; Gibson, J.M.; Howie, A.; Spalding, D.R.

1978-01-01

The inelastic scattering of fast electrons by the excitation of L-shell electrons at a stacking fault in silicon has been studied with a scanning transmission electron microscope. It was found that the bright-field stacking fault contrast is preserved in the filtered L-shell-loss signal at 100 eV. This result is discussed in terms of the delocalization of the excitation mechanism. It is concluded that localization effects will typically become significant only for energy transfers greater than 1 keV from a fast electron of energy 80 keV. (author)

Syringe injectable electronics

Science.gov (United States)

Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M.

2015-01-01

Seamless and minimally-invasive three-dimensional (3D) interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating syringe injection and subsequent unfolding of submicrometer-thick, centimeter-scale macroporous mesh electronics through needles with a diameter as small as 100 micrometers. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with > 90% device yield. We demonstrate several applications of syringe injectable electronics as a general approach for interpenetrating flexible electronics with 3D structures, including (i) monitoring of internal mechanical strains in polymer cavities, (ii) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (iii) in vivo multiplexed neural recording. Moreover, syringe injection enables delivery of flexible electronics through a rigid shell, delivery of large volume flexible electronics that can fill internal cavities and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics. PMID:26053995

Electronic Nose and Electronic Tongue

Science.gov (United States)

Bhattacharyya, Nabarun; Bandhopadhyay, Rajib

Human beings have five senses, namely, vision, hearing, touch, smell and taste. The sensors for vision, hearing and touch have been developed for several years. The need for sensors capable of mimicking the senses of smell and taste have been felt only recently in food industry, environmental monitoring and several industrial applications. In the ever-widening horizon of frontier research in the field of electronics and advanced computing, emergence of electronic nose (E-Nose) and electronic tongue (E-Tongue) have been drawing attention of scientists and technologists for more than a decade. By intelligent integration of multitudes of technologies like chemometrics, microelectronics and advanced soft computing, human olfaction has been successfully mimicked by such new techniques called machine olfaction (Pearce et al. 2002). But the very essence of such research and development efforts has centered on development of customized electronic nose and electronic tongue solutions specific to individual applications. In fact, research trends as of date clearly points to the fact that a machine olfaction system as versatile, universal and broadband as human nose and human tongue may not be feasible in the decades to come. But application specific solutions may definitely be demonstrated and commercialized by modulation in sensor design and fine-tuning the soft computing solutions. This chapter deals with theory, developments of E-Nose and E-Tongue technology and their applications. Also a succinct account of future trends of R&D efforts in this field with an objective of establishing co-relation between machine olfaction and human perception has been included.

A theory of electron baths: One-electron system dynamics

International Nuclear Information System (INIS)

McDowell, H.K.

1992-01-01

The second-quantized, many-electron, atomic, and molecular Hamiltonian is partitioned both by the identity or labeling of the spin orbitals and by the dynamics of the spin orbitals into a system coupled to a bath. The electron bath is treated by a molecular time scale generalized Langevin equation approach designed to include one-electron dynamics in the system dynamics. The bath is formulated as an equivalent chain of spin orbitals through the introduction of equivalent-chain annihilation and creation operators. Both the dynamics and the quantum grand canonical statistical properties of the electron bath are examined. Two versions for the statistical properties of the bath are pursued. Using a weak bath assumption, a bath statistical average is defined which allows one to achieve a reduced dynamics description of the electron system which is coupled to the electron bath. In a strong bath assumption effective Hamiltonians are obtained which reproduce the dynamics of the bath and which lead to the same results as found in the weak bath assumption. The effective (but exact) Hamiltonian is found to be a one-electron Hamiltonian. A reduced dynamics equation of motion for the system population matrix is derived and found to agree with a previous version. This equation of motion is useful for studying electron transfer in the system when coupled to an electron bath

Seminario C++, parte 4

OpenAIRE

Cachero Castro, Cristina; Ponce de León Amador, Pedro José

2007-01-01

Este seminario trata sobre principios de orientación a objetos con C++. Para comprender mejor sus contenidos, se debe tener un conocimiento básico sobre programación estructurada con C++ o C. Herencia simple. El destructor abstracto. Patrón de diseño singleton. Tipos enumerados. Declaraciones forward. Conversión entre objetos (upcasting/downcasting).

Treatment of foods with 'soft-electrons' (low-energy electrons)

International Nuclear Information System (INIS)

Hayashi, Toru; Todoriki, Setsuko

2003-01-01

Electrons with energies of 300 keV or lower were defined as soft-electrons'. Soft-electrons can eradicate microorganisms residing on the surface of grains, pulses, spices, dehydrated vegetables, tea leaves and seeds, and reduce their microbial loads to levels lower than 10 CFU/g with little quality deterioration. Soft-electrons can inactivate insect pests infesting grains and pulses and inhibit sprouting of potatoes. (author)

Compact femtosecond electron diffractometer with 100 keV electron bunches approaching the single-electron pulse duration limit

International Nuclear Information System (INIS)

Waldecker, Lutz; Bertoni, Roman; Ernstorfer, Ralph

2015-01-01

We present the design and implementation of a highly compact femtosecond electron diffractometer working at electron energies up to 100 keV. We use a multi-body particle tracing code to simulate electron bunch propagation through the setup and to calculate pulse durations at the sample position. Our simulations show that electron bunches containing few thousands of electrons per bunch are only weakly broadened by space-charge effects and their pulse duration is thus close to the one of a single-electron wavepacket. With our compact setup, we can create electron bunches containing up to 5000 electrons with a pulse duration below 100 fs on the sample. We use the diffractometer to track the energy transfer from photoexcited electrons to the lattice in a thin film of titanium. This process takes place on the timescale of few-hundred femtoseconds and a fully equilibrated state is reached within 1 ps

Electron backscattering for process control in electron beam welding

International Nuclear Information System (INIS)

Ardenne, T. von; Panzer, S.

1983-01-01

A number of solutions to the automation of electron beam welding is presented. On the basis of electron backscattering a complex system of process control has been developed. It allows an enlarged imaging of the material's surface, improved adjustment of the beam focusing and definite focus positioning. Furthermore, both manual and automated positioning of the electron beam before and during the welding process has become possible. Monitoring of the welding process for meeting standard welding requirements can be achieved with the aid of a control quantity derived from the results of electronic evaluation of the high-frequency electron backscattering

Electron transfer reactions

CERN Document Server

Cannon, R D

2013-01-01

Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

Understand electronics

CERN Document Server

Bishop, Owen

2013-01-01

Understand Electronics provides a readable introduction to the exciting world of electronics for the student or enthusiast with little previous knowledge. The subject is treated with the minimum of mathematics and the book is extensively illustrated.This is an essential guide for the newcomer to electronics, and replaces the author's best-selling Beginner's Guide to Electronics.The step-by-step approach makes this book ideal for introductory courses such as the Intermediate GNVQ.

Electronic Commerce

OpenAIRE

Slavko Đerić

2016-01-01

Electronic commerce can be defined in different ways. Any definition helps to understand and explain that concept as better as possible.. Electronic commerce is a set of procedures and technologies that automate the tasks of financial transactions using electronic means. Also, according to some authors, electronic commerce is defined as a new concept, which is being developed and which includes process of buying and selling or exchanging products, services or information via computer networks...

Photon and electron collimator effects on electron output and abutting segments in energy modulated electron therapy

International Nuclear Information System (INIS)

Olofsson, Lennart; Karlsson, Magnus G.; Karlsson, Mikael

2005-01-01

In energy modulated electron therapy a large fraction of the segments will be arranged as abutting segments where inhomogeneities in segment matching regions must be kept as small as possible. Furthermore, the output variation between different segments should be minimized and must in all cases be well predicted. For electron therapy with add-on collimators, both the electron MLC (eMLC) and the photon MLC (xMLC) contribute to these effects when an xMLC tracking technique is utilized to reduce the x-ray induced leakage. Two add-on electron collimator geometries have been analyzed using Monte Carlo simulations: One isocentric eMLC geometry with an isocentric clearance of 35 cm and air or helium in the treatment head, and one conventional proximity geometry with a clearance of 5 cm and air in the treatment head. The electron fluence output for 22.5 MeV electrons is not significantly affected by the xMLC if the shielding margins are larger than 2-3 cm. For small field sizes and 9.6 MeV electrons, the isocentric design with helium in the treatment head or shielding margins larger than 3 cm is needed to avoid a reduced electron output. Dose inhomogeneity in the matching region of electron segments is, in general, small when collimator positions are adjusted to account for divergence in the field. The effect of xMLC tracking on the electron output can be made negligible while still obtaining a substantially reduced x-ray leakage contribution. Collimator scattering effects do not interfere significantly when abutting beam techniques are properly applied

Equation satisfied by electron-electron mutual Coulomb repulsion energy density functional

OpenAIRE

Joubert, Daniel P.

2011-01-01

The electron-electron mutual Coulomb repulsion energy density functional satisfies an equation that links functionals and functional derivatives at N-electron and (N-1)-electron densities for densities determined from the same adiabatic scaled external potential for the N-electron system.

Electronic Publishing.

Science.gov (United States)

Lancaster, F. W.

1989-01-01

Describes various stages involved in the applications of electronic media to the publishing industry. Highlights include computer typesetting, or photocomposition; machine-readable databases; the distribution of publications in electronic form; computer conferencing and electronic mail; collaborative authorship; hypertext; hypermedia publications;…

Syringe-injectable electronics.

Science.gov (United States)

Liu, Jia; Fu, Tian-Ming; Cheng, Zengguang; Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M

2015-07-01

Seamless and minimally invasive three-dimensional interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating the syringe injection (and subsequent unfolding) of sub-micrometre-thick, centimetre-scale macroporous mesh electronics through needles with a diameter as small as 100 μm. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with >90% device yield. We demonstrate several applications of syringe-injectable electronics as a general approach for interpenetrating flexible electronics with three-dimensional structures, including (1) monitoring internal mechanical strains in polymer cavities, (2) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (3) in vivo multiplexed neural recording. Moreover, syringe injection enables the delivery of flexible electronics through a rigid shell, the delivery of large-volume flexible electronics that can fill internal cavities, and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

Electronic excitation of Na atom by electron impact

International Nuclear Information System (INIS)

Bielschowsky, C.E.; Souza, G.G.B. de; Lucas, C.A.; Nogueira, J.C.

1988-01-01

Electronic excitation of the 3s-3p transition in the Na atom was studied by intermediate energy electron impact spectroscopy. Differential Cross Sections (DCS) and Generalized Oscillator Strenghts (GOS) were determined experimentally for 1 KeV electrons. Theoretical results within the First Born Approximation as well as Glauber theory, were also performed. (A.C.A.S.) [pt

Highly efficient electron gun with a single-atom electron source

International Nuclear Information System (INIS)

Ishikawa, Tsuyoshi; Urata, Tomohiro; Cho, Boklae; Rokuta, Eiji; Oshima, Chuhei; Terui, Yoshinori; Saito, Hidekazu; Yonezawa, Akira; Tsong, Tien T.

2007-01-01

The authors have demonstrated highly collimated electron-beam emission from a practical electron gun with a single-atom electron source; ∼80% of the total emission current entered the electron optics. This ratio was two or three orders of magnitude higher than those of the conventional electron sources such as a cold field emission gun and a Zr/O/W Schottky gun. At the pressure of less than 1x10 -9 Pa, the authors observed stable emission of 20 nA, which generates the specimen current of 5 pA required for scanning electron microscopes

Electron-electron interaction in p-SiGe/Ge quantum wells

International Nuclear Information System (INIS)

Roessner, Benjamin; Kaenel, Hans von; Chrastina, Daniel; Isella, Giovanni; Batlogg, Bertram

2005-01-01

The temperature dependent magnetoresistance of high mobility p-SiGe/Ge quantum wells is studied with hole densities ranging from 1.7 to 5.9 x 10 11 cm -2 . At magnetic fields below the onset of quantum oscillations that reflect the high mobility values (up to 75000 cm 2 /Vs), we observe the clear signatures of electron-electron interaction. We compare our experiment with the theory of electron-electron interaction including the Zeeman band splitting. The observed magnetoresistance is well explained as a superposition of band structure induced positive magnetoresistance and the negative magntoresistance due to the electron-electron interaction effect

Electron-electron interactions in disordered systems

CERN Document Server

Efros, AL

1985-01-01

``Electron-Electron Interactions in Disordered Systems'' deals with the interplay of disorder and the Coulomb interaction. Prominent experts give state-of-the-art reviews of the theoretical and experimental work in this field and make it clear that the interplay of the two effects is essential, especially in low-dimensional systems.

Narrow electron injector for ballistic electron spectroscopy

International Nuclear Information System (INIS)

Kast, M.; Pacher, C.; Strasser, G.; Gornik, E.

2001-01-01

A three-terminal hot electron transistor is used to measure the normal energy distribution of ballistic electrons generated by an electron injector utilizing an improved injector design. A triple barrier resonant tunneling diode with a rectangular transmission function acts as a narrow (1 meV) energy filter. An asymmetric energy distribution with its maximum on the high-energy side with a full width at half maximum of ΔE inj =10 meV is derived. [copyright] 2001 American Institute of Physics

Temperature Dependence of the Spin-Hall Conductivity of a Two-Dimensional Impure Rashba Electron Gas in the Presence of Electron-Phonon and Electron-Electron Interactions

Science.gov (United States)

Yavari, H.; Mokhtari, M.; Bayervand, A.

2015-03-01

Based on Kubo's linear response formalism, temperature dependence of the spin-Hall conductivity of a two-dimensional impure (magnetic and nonmagnetic impurities) Rashba electron gas in the presence of electron-electron and electron-phonon interactions is analyzed theoretically. We will show that the temperature dependence of the spin-Hall conductivity is determined by the relaxation rates due to these interactions. At low temperature, the elastic lifetimes ( and are determined by magnetic and nonmagnetic impurity concentrations which are independent of the temperature, while the inelastic lifetimes ( and related to the electron-electron and electron-phonon interactions, decrease when the temperature increases. We will also show that since the spin-Hall conductivity is sensitive to temperature, we can distinguish the intrinsic and extrinsic contributions.

Analytical local electron-electron interaction model potentials for atoms

International Nuclear Information System (INIS)

Neugebauer, Johannes; Reiher, Markus; Hinze, Juergen

2002-01-01

Analytical local potentials for modeling the electron-electron interaction in an atom reduce significantly the computational effort in electronic structure calculations. The development of such potentials has a long history, but some promising ideas have not yet been taken into account for further improvements. We determine a local electron-electron interaction potential akin to those suggested by Green et al. [Phys. Rev. 184, 1 (1969)], which are widely used in atom-ion scattering calculations, electron-capture processes, and electronic structure calculations. Generalized Yukawa-type model potentials are introduced. This leads, however, to shell-dependent local potentials, because the origin behavior of such potentials is different for different shells as has been explicated analytically [J. Neugebauer, M. Reiher, and J. Hinze, Phys. Rev. A 65, 032518 (2002)]. It is found that the parameters that characterize these local potentials can be interpolated and extrapolated reliably for different nuclear charges and different numbers of electrons. The analytical behavior of the corresponding localized Hartree-Fock potentials at the origin and at long distances is utilized in order to reduce the number of fit parameters. It turns out that the shell-dependent form of Green's potential, which we also derive, yields results of comparable accuracy using only one shell-dependent parameter

Extracting electron backscattering coefficients from backscattered electron micrographs

International Nuclear Information System (INIS)

Zupanic, F.

2010-01-01

Electron backscattering micrographs possess the so-called Z-contrast, carrying information about the chemical compositions of phases present in microstructures. The intensity at a particular point in the backscattered electron micrograph is proportional to the signal detected at a corresponding point in the scan raster, which is, in turn, proportional to the electron backscattering coefficient of a phase at that point. This article introduces a simple method for extracting the electron backscattering coefficients of phases present in the microstructure, from the backscattered electron micrographs. This method is able to convert the micrograph's greyscale to the backscattering-coefficient-scale. The prerequisite involves the known backscattering coefficients for two phases in the micrograph. In this way, backscattering coefficients of other phases can be determined. The method is unable to determine the chemical compositions of phases or the presence of an element only from analysing the backscattered electron micrograph. Nevertheless, this method was found to be very powerful when combined with energy dispersive spectroscopy, and the calculations of backscattering coefficients. - Research Highlights: →A simple method for extracting the electron backscattering coefficients →The prerequisite is known backscattering coefficients for two phases →The information is complementary to the EDS-results. →This method is especially useful when a phase contains a light element (H, Li, Be, and B)

PIC simulation of the electron-ion collision effects on suprathermal electrons

International Nuclear Information System (INIS)

Wu Yanqing; Han Shensheng

2000-01-01

The generation and transportation of suprathermal electrons are important to both traditional ICF scheme and 'Fast Ignition' scheme. The author discusses the effects of electron-ion collision on the generation and transportation of the suprathermal electrons by parametric instability. It indicates that the weak electron-ion term in the PIC simulation results in the enhancement of the collisional absorption and increase of the hot electron temperature and reduction in the maximum electrostatic field amplitude while wave breaking. Therefore the energy and distribution of the suprathermal electrons are changed. They are distributed more close to the phase velocity of the electrostatic wave than the case without electron-ion collision term. The electron-ion collision enhances the self-consistent field and impedes the suprathermal electron transportation. These factors also reduce the suprathermal electron energy. In addition, the authors discuss the effect of initial condition on PIC simulation to ensure that the results are correct

Spin Relaxation in GaAs: Importance of Electron-Electron Interactions

Directory of Open Access Journals (Sweden)

Gionni Marchetti

2014-04-01

Full Text Available We study spin relaxation in n-type bulk GaAs, due to the Dyakonov–Perel mechanism, using ensemble Monte Carlo methods. Our results confirm that spin relaxation time increases with the electronic density in the regime of moderate electronic concentrations and high temperature. We show that the electron-electron scattering in the non-degenerate regime significantly slows down spin relaxation. This result supports predictions by Glazov and Ivchenko. Most importantly, our findings highlight the importance of many-body interactions for spin dynamics: we show that only by properly taking into account electron-electron interactions within the simulations, results for the spin relaxation time—with respect to both electron density and temperature—will reach good quantitative agreement with corresponding experimental data. Our calculations contain no fitting parameters.

Secondary mineralization in carious lesions of human dentin. Electron-probe, electron microscope, and electron diffraction studies

Energy Technology Data Exchange (ETDEWEB)

Ogiwara, H [Tokyo Dental Coll. (Japan)

1975-02-01

Dentinal carious lesions having a remineralized surface layer were studied by means electron-probe microanalysis, electron microscopy, electron diffraction. As the results of electron-probe study, F, Mg, and Na were found to be distributed mainly in the remineralized surface layer and S in the decalcified region where decreases in Ca, P, and Mg concentration were usually observed. The decrease in Mg concentration always started earlier than that of Ca and P concentration. Electron microscope and electron diffraction studies revealed that apatic crystals in the remineralized surface layer were much larger than those in the intact dentin. Although they were less conspicuous, crystals in the decalcified region also were larger than those in the intact region. Dentinal tubules, occluded by many crystals, were frequently seen during the observations. Crystals in the tubules varied in morphology, showing granular, needle, rhomboid, and tabular shapes. By means of electron diffraction, the granular- or needle-shaped crystals were identified as apatite and the rhomboid-shaped crystals as whitlockite. Some of the tabular-shaped crystals appeared to be cotacalcium phosphate.

Electronic components

CERN Document Server

Colwell, Morris A

1976-01-01

Electronic Components provides a basic grounding in the practical aspects of using and selecting electronics components. The book describes the basic requirements needed to start practical work on electronic equipment, resistors and potentiometers, capacitance, and inductors and transformers. The text discusses semiconductor devices such as diodes, thyristors and triacs, transistors and heat sinks, logic and linear integrated circuits (I.C.s) and electromechanical devices. Common abbreviations applied to components are provided. Constructors and electronics engineers will find the book useful

Ion- and electron-acoustic solitons in two-electron temperature space plasmas

International Nuclear Information System (INIS)

Lakhina, G. S.; Kakad, A. P.; Singh, S. V.; Verheest, F.

2008-01-01

Properties of ion- and electron-acoustic solitons are investigated in an unmagnetized multicomponent plasma system consisting of cold and hot electrons and hot ions using the Sagdeev pseudopotential technique. The analysis is based on fluid equations and the Poisson equation. Solitary wave solutions are found when the Mach numbers exceed some critical values. The critical Mach numbers for the ion-acoustic solitons are found to be smaller than those for electron-acoustic solitons for a given set of plasma parameters. The critical Mach numbers of ion-acoustic solitons increase with the increase of hot electron temperature and the decrease of cold electron density. On the other hand, the critical Mach numbers of electron-acoustic solitons increase with the increase of the cold electron density as well as the hot electron temperature. The ion-acoustic solitons have positive potentials for the parameters considered. However, the electron-acoustic solitons have positive or negative potentials depending whether the fractional cold electron density with respect to the ion density is greater or less than a certain critical value. Further, the amplitudes of both the ion- and electron-acoustic solitons increase with the increase of the hot electron temperature. Possible application of this model to electrostatic solitary waves observed on the auroral field lines by the Viking spacecraft is discussed

Diffusive scattering of electrons by electron holes around injection fronts

Science.gov (United States)

Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; Artemyev, A. V.; Krasnoselskikh, V. V.; Bonnell, J. W.

2017-03-01

Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi-linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify them via test particle simulations. We show that the most efficiently scattered are gyroresonant electrons (crossing EH on a time scale comparable to the local electron gyroperiod). We compute bounce-averaged diffusion coefficients and demonstrate their dependence on the EH spatial distribution (latitudinal extent and spatial filling factor) and individual EH parameters (amplitude of electrostatic potential, velocity, and spatial scales). We show that EHs can drive pitch angle scattering of ≲5 keV electrons at rates 10-2-10-4 s-1 and, hence, can contribute to electron losses and conjugated diffuse aurora brightenings. The momentum and pitch angle scattering rates can be comparable, so that EHs can also provide efficient electron heating. The scattering rates driven by EHs at L shells L ˜ 5-8 are comparable to those due to chorus waves and may exceed those due to electron cyclotron harmonics.

Pseudogap in the Eliashberg approach based on electron-phonon and electron-electron-phonon interaction

Energy Technology Data Exchange (ETDEWEB)

Szczesniak, R. [Institute of Physics, Czestochowa University of Technology (Poland); Institute of Physics, Jan Dlugosz University in Czestochowa (Poland); Durajski, A.P.; Duda, A.M. [Institute of Physics, Czestochowa University of Technology (Poland)

2017-04-15

The properties of the superconducting and the anomalous normal state were described by using the Eliashberg method. The pairing mechanism was reproduced with the help of the Hamiltonian, which models the electron-phonon and the electron-electron-phonon interaction (EEPh). The set of the Eliashberg equations, which determines the order parameter function (φ), the wave function renormalization factor (Z), and the energy shift function (χ), was derived. It was proven that for the sufficiently large values of the EEPh potential, the doping dependence of the order parameter (φ/Z) has the analogous course to that observed experimentally in cuprates. The energy gap in the electron density of states is induced by Z and χ - the contribution from φ is negligible. The electron density of states possesses the characteristic asymmetric form and the pseudogap is observed above the critical temperature. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Carbon Nanotube Electron Gun

Science.gov (United States)

Nguyen, Cattien V. (Inventor); Ribaya, Bryan P. (Inventor)

2013-01-01

An electron gun, an electron source for an electron gun, an extractor for an electron gun, and a respective method for producing the electron gun, the electron source and the extractor are disclosed. Embodiments provide an electron source utilizing a carbon nanotube (CNT) bonded to a substrate for increased stability, reliability, and durability. An extractor with an aperture in a conductive material is used to extract electrons from the electron source, where the aperture may substantially align with the CNT of the electron source when the extractor and electron source are mated to form the electron gun. The electron source and extractor may have alignment features for aligning the electron source and the extractor, thereby bringing the aperture and CNT into substantial alignment when assembled. The alignment features may provide and maintain this alignment during operation to improve the field emission characteristics and overall system stability of the electron gun.

Molecular electron affinities

International Nuclear Information System (INIS)

Fukuda, E.K.

1983-01-01

Molecular electron affinities have historically been difficult quantities to measure accurately. These difficulties arise from differences in structure between the ion and neutral as well as the existence of excited negative ion states. To circumvent these problems, relative electron affinities were determined in this dissertation by studying equilibrium electron transfer reactions using a pulsed ion cyclotron resonance (ICR) spectrometer. Direct measurement of ion and neutral concentrations for reactions of the general type, A - + B = B - + A, allow calculation of the equilibrium constant and, therefore, the free energy change. The free energy difference is related to the difference in electron affinities between A and B. A relative electron affinity scale covering a range of about 45 kcal/mol was constructed with various substituted p-benzoquinones, nitrobenzenes, anhydrides, and benzophenones. To assign absolute electron affinities, various species with accurately known electron affinities are tied to the scale via ion-cyclotron double resonance bracketing techniques. After the relative scale is anchored to these species with well-known electron affinities, the scale is then used as a check on other electron affinity values as well as generating new electron affinity values. Many discrepancies were found between the electron affinities measured using the ICR technique and previous literature determinations

Nonambipolar electron source

International Nuclear Information System (INIS)

Longmier, B.; Baalrud, S.; Hershkowitz, N.

2006-01-01

A radio frequency (rf) plasma-based electron source that does not rely on electron emission at a cathode surface has been constructed. All of the random electron flux incident on an exit aperture is extracted through an electron sheath resulting in total nonambipolar flow within the device when the ratio of the ion loss area to the electron loss area is approximately equal to the square root of the ratio of the ion mass to the electron mass, and the ion sheath potential drop at the chamber walls is much larger than T e /e. The nonambipolar electron source (NES) has an axisymmetric magnetic field of 100 G at the extraction aperture that results in a uniform plasma potential across the aperture, allowing the extraction of all the incident electron flux without the use of grids. A prototype NES has produced 15 A of continuous electron current, using 15 SCCM (SCCM denotes cubic centimeter per minute at STP) Ar, 1200 W rf power at 13.56 MHz, and 6 times gas utilization. Alternatively 8 A of electron current can be produced, using 3 SCCM Ar at 1200 W rf and 20 times gas utilization. NES could replace hollow cathode electron sources in a wide variety of applications

Electron-plasmon model in the electron liquid theory

Directory of Open Access Journals (Sweden)

M.V.Vavrukh

2005-01-01

Full Text Available Here we propose an accurate approach to the description of the electron liquid model in the electron and plasmon terms. Our ideas in the present paper are close to the conception of the collective variables which was developed in the papers of Bohm and Pines. However we use another body of mathematics in the transition to the expanded space of variable particles and plasmons realized by the transition operator. It is evident that in the Random Phase Approximation (RPA, the model which consists of two interactive subsystems of electrons and plasmons is equivalent to the electron liquid model with Coulomb interaction.

Polymer electronics

CERN Document Server

Hsin-Fei, Meng

2013-01-01

Polymer semiconductor is the only semiconductor that can be processed in solution. Electronics made by these flexible materials have many advantages such as large-area solution process, low cost, and high performance. Researchers and companies are increasingly dedicating time and money in polymer electronics. This book focuses on the fundamental materials and device physics of polymer electronics. It describes polymer light-emitting diodes, polymer field-effect transistors, organic vertical transistors, polymer solar cells, and many applications based on polymer electronics. The book also disc

A direct electron detector for time-resolved MeV electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Vecchione, T.; Denes, P.; Jobe, R. K.; Johnson, I. J.; Joseph, J. M.; Li, R. K.; Perazzo, A.; Shen, X.; Wang, X. J.; Weathersby, S. P.; Yang, J.; Zhang, D.

2017-03-01

The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μmμm spatial resolution and less than 20 analogue-to-digital converter count RMS pixel noise. The unique capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.

Coherent Electron Focussing in a Two-Dimensional Electron Gas.

NARCIS (Netherlands)

Houten, H. van; Wees, B.J. van; Mooij, J.E.; Beenakker, C.W.J.; Williamson, J.G.; Foxon, C.T.

1988-01-01

The first experimental realization of ballistic point contacts in a two-dimensional electron gas for the study of transverse electron focussing by a magnetic field is reported. Multiple peaks associated with skipping orbits of electrons reflected specularly by the channel boundary are observed. At

A study on the secondary electrons in a clinical electron beam

International Nuclear Information System (INIS)

Krithivas, G.; Rao, S.N.

1989-01-01

The central axis dose of a 12 MeV clinical electron beam is investigated in terms of an axial component due to primary electrons in the central ray and a lateral component due to secondary electrons originating from multiple scattering of electrons in the off-axis rays. To this effect secondary electron fluence measurements in a polystyrene medium irradiated with a collimated beam are made with a sensitive diode detector. This leads to a construction of secondary electron depth-dose profiles for beam sizes of diameters ranging from 1.7 to 17.4 cm. The results indicate that the lateral electrons account for 25% of the dose in the therapeutic region. For these electrons, the depth of dose maximum is correlated with diffusion depth and maximum lateral excursion in the medium. Dose component due to backscatter electrons at depths is also investigated using a thin-window parallel-plate ion chamber. The role of lateral and backscatter electrons in characterising central axis per cent depth-dose is discussed. (author)

Electronics for dummies

CERN Document Server

Shamieh

2015-01-01

Explore the basic concepts of electronics, build your electronics workbench, and begin creating fun electronics projects right away! Electronics For Dummies, 3rd Edition is your guide to the world of electronics. Spanning circuitry, wiring, robotics, transmitters, amplifiers, and more, this book demystifies electricity basics and beyond. The third edition offers new content revised to reflect the latest advancements in the electronics field, and it offers full color project examples to spark your creativity and inspire you to put your new skills to use! Packed with projects that can be comple

Electron holography

CERN Document Server

Tonomura, Akira

1993-01-01

Holography was devised for breaking through the resolution limit of electron microscopes The advent of a "coherent" field emission electron beam has enabled the use of Electron Holography in various areas of magnetic domain structures observation, fluxon observation in superconductors, and fundamental experiments in physics which have been inaccessible using other techniques After examining the fundamentals of electron holography and its applications to the afore mentioned fields, a detailed discussion of the Aharonov-Bohm effect and the related experiments is presented Many photographs and illustrations are included to elucidate the text

Comprehensive analysis of electron correlations in three-electron atoms

International Nuclear Information System (INIS)

Morishita, T.; Lin, C.D.

1999-01-01

We study the electron correlations in singly, doubly, and triply excited states of a three-electron atom. While electron correlation in general is weak for singly excited states, correlation plays major roles in determining the characteristics of doubly and triply excited states. Using the adiabatic approximation in hyperspherical coordinates, we show that the distinction between singly, doubly, and triply excited states is determined by the radial correlations, while finer distinctions within doubly or triply excited states lie in the angular correlations. Partial projections of the body-fixed frame wave functions are used to demonstrate the characteristic nodal surfaces which provide clues to the energy ordering of the states. We show that doubly excited states of a three-electron atom exhibit correlations that are similar to the doubly excited states of a two-electron atom. For the triply excited states, we show that the motion of the three electrons resemble approximately that of a symmetric top. copyright 1999 The American Physical Society

Advanced electron beam techniques

International Nuclear Information System (INIS)

Hirotsu, Yoshihiko; Yoshida, Yoichi

2007-01-01

After 100 years from the time of discovery of electron, we now have many applications of electron beam in science and technology. In this report, we review two important applications of electron beam: electron microscopy and pulsed-electron beam. Advanced electron microscopy techniques to investigate atomic and electronic structures, and pulsed-electron beam for investigating time-resolved structural change are described. (author)

Effects of electron-electron interactions on electronic transport in disordered systems

International Nuclear Information System (INIS)

Foley, Simon Timothy

2002-01-01

This thesis is concerned with the role of electron-electron interactions on electronic transport in disordered systems. We first consider a novel non-linear sigma model in order to microscopically treat the effects of disorder and electronic interaction. We successfully reproduce the perturbative results for the zero-bias anomaly and the interaction correction to the conductivity in a weakly disordered system, and discuss possible directions for future work. Secondly we consider the fluctuations of the dephasing rate for a closed diffusive and quantum dot system. Using the Keldysh technique we derive an expression for the inelastic scattering rate with which we self-consistently obtain the fluctuations in the dephasing rate. For the diffusive regime we find the relative fluctuations is given by F ∼ (L φ /L) 2 /g 2 , where g is the dimensionless conductance, L φ is the dephasing length and L is the sample size. For the quantum dot regime we find a perturbative divergence due to the presence of the zero mode. By mapping divergent diagrams to those for the two-level correlation function, we conjecture the existence of an exact relation between the two. Finally we discuss the consequences of this relation. (author)

Characteristics of trapped electrons and electron traps in single crystals

International Nuclear Information System (INIS)

Budzinski, E.E.; Potter, W.R.; Potienko, G.; Box, H.C.

1979-01-01

Two additional carbohydrates are reported whose crystal structures trap electrons intermolecularly in single crystals x irradiated at low temperature, namely sucrose and rhamnose. Five carbohydrate and polyhydroxy compounds are now known which exhibit this phenomenon. The following characteristics of the phenomenon were investigated: (1) the hyperfine couplings of the electron with protons of the polarized hydroxy groups forming the trap; (2) the distances between these protons and the trapped electron; (3) the spin density of the electron at the protons and (4) the relative stabilities of the electron trapped in various crystal structures

Electron-electron scattering in linear transport in two-dimensional systems

DEFF Research Database (Denmark)

Hu, Ben Yu-Kuang; Flensberg, Karsten

1996-01-01

We describe a method for numerically incorporating electron-electron scattering in quantum wells for small deviations of the distribution function from equilibrium, within the framework of the Boltzmann equation. For a given temperature T and density n, a symmetric matrix needs to be evaluated only...... once, and henceforth it can be used to describe electron-electron scattering in any Boltzmann equation linear-response calculation for that particular T and n. Using this method, we calculate the distribution function and mobility for electrons in a quantum well, including full finite...

Terahertz Plasma Waves in Two Dimensional Quantum Electron Gas with Electron Scattering

International Nuclear Information System (INIS)

Zhang Liping

2015-01-01

We investigate the Terahertz (THz) plasma waves in a two-dimensional (2D) electron gas in a nanometer field effect transistor (FET) with quantum effects, the electron scattering, the thermal motion of electrons and electron exchange-correlation. We find that, while the electron scattering, the wave number along y direction and the electron exchange-correlation suppress the radiation power, but the thermal motion of electrons and the quantum effects can amplify the radiation power. The radiation frequency decreases with electron exchange-correlation contributions, but increases with quantum effects, the wave number along y direction and thermal motion of electrons. It is worth mentioning that the electron scattering has scarce influence on the radiation frequency. These properties could be of great help to the realization of practical THz plasma oscillations in nanometer FET. (paper)

Oblique electron cyclotron emission for electron distribution studies (invited)

International Nuclear Information System (INIS)

Preische, S.; Efthimion, P.C.; Kaye, S.M.

1997-01-01

Electron cyclotron emission (ECE) at an oblique angle to the magnetic field provides a means of probing the electron distribution function both in energy and physical space through changes in and constraints on the relativistic electron cyclotron resonance condition. Diagnostics based on this Doppler shifted resonance are able to study a variety of electron distributions through changes in the location of the resonance in physical or energy space accomplished by changes in the viewing angle and frequency, and the magnetic field. For the case of observation across a changing magnetic field, such as across the tokamak midplane, the constraint on the resonance condition for real solutions to the dispersion relation can constrain the physical location of optically thin emission. A new Oblique ECE diagnostic was installed and operated on the PBX-M tokamak for the study of energetic electrons during lower hybrid current drive. It has a view 33 degree with respect to perpendicular in the tokamak midplane, receives second harmonic X-mode emission, and is constrained to receive single pass emission by SiC viewing dumps on the tokamak walls. Spatial localization of optically thin emission from superthermal electrons (50 endash 100 keV) was obtained by observation of emission upshifted from a thermal cyclotron harmonic. The localized measurements of the electron energy distribution and the superthermal density profile made by this diagnostic demonstrate its potential to study the spatial transport of energetic electrons on fast magnetohydrodynamic time scales or anomalous diffusion time scales. Oblique ECE can also be used to study electron distributions that may have a slight deviation from a Maxwellian by localizing the emission in energy space. (Abstract Truncated)

Electron microscopy of boron carbide before and after electron irradiation

International Nuclear Information System (INIS)

Stoto, T.; Zuppiroli, L.; Beauvy, M.; Athanassiadis, T.

1984-06-01

The microstructure of boron carbide has been studied by electron microscopy and related to the composition of the material. After electron irradiations in an usual transmission electron microscope and in a high voltage electron microscope at different temperatures and fluxes no change of these microstructures have been observed but a sputtering of the surface of the samples, which has been studied quantitatively [fr

Electron Cyclotron Resonances in Electron Cloud Dynamics

International Nuclear Information System (INIS)

Celata, Christine; Celata, C.M.; Furman, Miguel A.; Vay, J.-L.; Yu, Jennifer W.

2008-01-01

We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code 'POSINST' was used to study the electron cloud buildup at different z positions in the International Linear Collider positron damping ring wiggler. An electron equilibrium density enhancement of up to a factor of 3 was found at magnetic field values for which the bunch frequency is an integral multiple of the electron cyclotron frequency. At low magnetic fields the effects of the resonance are prominent, but when B exceeds ∼(2 pi mec/(elb)), with lb = bunch length, effects of the resonance disappear. Thus short bunches and low B fields are required for observing the effect. The reason for the B field dependence, an explanation of the dynamics, and the results of the 2D simulations and of a single-particle tracking code used to elucidate details of the dynamics are discussed

Role of electron-electron interactions in the RKKY theory of magnetism

International Nuclear Information System (INIS)

Cooke, J.F.

1978-10-01

The theory of magnetism in heavy rare earth metals is based on the RKKY theory. In this formalism the indirect exchange interaction between the local 4f spins is mediated by the conduction electrons. When carried to second order in the 4f-conduction electron interaction, traditional perturbation theory leads to a Heisenberg-like interaction between the local spins which depends on the electronic energy bands and 4f-conduction electron exchange matrix elements. This derivation neglects the detailed behavior of electron-electron interaction within the conduction band, which is known to be important in metallic systems. By using an equation of motion method, an expression for the inelastic neutron scattering cross-section has been derived which includes, in an approximate way, this electron-electron interaction. The results of this calculation indicate that spin-wave peaks can be broadened and shifted if the spin-wave band lies near the conduction electron Stoner continuum. The origin of this effect is similar to that found in itinerant electron systems where the spin-wave band actually intersects the Stoner continuum, resulting in the disappearance of the spin-wave mode

Role of electron-electron interactions in the RKKY theory of magnetism

International Nuclear Information System (INIS)

Cooke, J.F.

1979-01-01

The theory of magnetism in heavy rare earth metals is based on the RKKY theory. In this formalism the indirect exchange interaction between the local 4f spins is mediated by the conduction electrons. When carried to second order in the 4f-conduction electron interaction, traditional pertubation theory leads to a Heisenberg-like interaction between the local spins which depends on the electronic energy bands and 4f-conduction electron exchange matrix elements. This derivation neglects the detailed behavior of electron-electron interaction within the conduction band, which is known to be important in metallic systems. By using an equation of motion method, an expression for the inelastic neutron scattering cross-section has been derived which includes, in an approximate way, this electron-electron interaction. The results of this calculation indicate that spin-wave peaks can be broadened and shifted if the spin-wave band lies near the conduction electron Stoner continuum. The origin of this effect is similar to that found in itinerant electron systems where the spin-wave band actually intersects the Stoner continuum, resulting in the disappearance of the spin-wave mode

Electron acoustic solitary waves in unmagnetized two electron population dense plasmas

International Nuclear Information System (INIS)

Mahmood, S.; Masood, W.

2008-01-01

The electron acoustic solitary waves are studied in unmagnetized two population electron quantum plasmas. The quantum hydrodynamic model is employed with the Sagdeev potential approach to describe the arbitrary amplitude electron acoustic waves in a two electron population dense Fermi plasma. It is found that hot electron density hump structures are formed in the subsonic region in such type of quantum plasmas. The wave amplitude as well as the width of the soliton are increased with the increase of percentage presence of cold (thinly populated) electrons in a multicomponent quantum plasma. It is found that an increase in quantum diffraction parameter broadens the nonlinear structure. Furthermore, the amplitude of the nonlinear electron acoustic wave is found to increase with the decrease in Mach number. The numerical results are also presented to understand the formation of solitons in two electron population Fermi plasmas.

Advances in imaging and electron physics the scanning transmission electron microscope

CERN Document Server

Hawkes, Peter W

2009-01-01

Advances in Imaging and Electron Physics merges two long-running serials--Advances in Electronics and Electron Physics and Advances in Optical and Electron Microscopy. This series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains.  This particular volume presents several timely articles on the scanning transmission electron microscope. Updated with contributions from leading international scholars and industry experts Discusses hot topic areas and presents current and future research trends Provides an invaluable reference and guide for physicists, engineers and mathematicians.

Attractive electron correlation in wide band gap semiconductors by electron-photon interaction

International Nuclear Information System (INIS)

Takeda, Hiroyuki; Yoshino, Katsumi

2004-01-01

We theoretically demonstrate attractive electron correlation in wide band gap semiconductors by electron-photon interaction. At low temperature, wavevectors of electromagnetic waves absorbed in wide band gap semiconductors cannot be neglected for wavevectors of electron waves; that is, electromagnetic waves affect the movements of electrons. In particular, attractive interaction occurs between two electrons when one electron changes from a valence band to a conduction band and the other electron changes from a conduction band to a valence band

Electronic Publishing or Electronic Information Handling?

Science.gov (United States)

Heck, A.

The current dramatic evolution in information technology is bringing major modifications in the way scientists communicate. The concept of 'electronic publishing' is too restrictive and has often different, sometimes conflicting, interpretations. It is thus giving way to the broader notion of 'electronic information handling' encompassing the diverse types of information, the different media, as well as the various communication methodologies and technologies. New problems and challenges result also from this new information culture, especially on legal, ethical, and educational grounds. The procedures for validating 'published material' and for evaluating scientific activities will have to be adjusted too. 'Fluid' information is becoming a common concept. Electronic publishing cannot be conceived without link to knowledge bases nor without intelligent information retrieval tools.

Theoretical study of the interplay of electron-electron interaction and disorder

International Nuclear Information System (INIS)

Brezini, A.; Behilil, S.

1988-10-01

A disordered Hubbard model with diagonal disorder is used to investigate the electron localization effects associated with both disorder and electron-electron interaction. Extensive results are reported on the ground state properties and compared to other theories. Two regimes have been found: when the electron-electron interaction u is greater than the disorder parameter w and when u < w. (author). 18 refs, 4 figs

Defining Electron Bifurcation in the Electron-Transferring Flavoprotein Family.

Science.gov (United States)

Garcia Costas, Amaya M; Poudel, Saroj; Miller, Anne-Frances; Schut, Gerrit J; Ledbetter, Rhesa N; Fixen, Kathryn R; Seefeldt, Lance C; Adams, Michael W W; Harwood, Caroline S; Boyd, Eric S; Peters, John W

2017-11-01

Electron bifurcation is the coupling of exergonic and endergonic redox reactions to simultaneously generate (or utilize) low- and high-potential electrons. It is the third recognized form of energy conservation in biology and was recently described for select electron-transferring flavoproteins (Etfs). Etfs are flavin-containing heterodimers best known for donating electrons derived from fatty acid and amino acid oxidation to an electron transfer respiratory chain via Etf-quinone oxidoreductase. Canonical examples contain a flavin adenine dinucleotide (FAD) that is involved in electron transfer, as well as a non-redox-active AMP. However, Etfs demonstrated to bifurcate electrons contain a second FAD in place of the AMP. To expand our understanding of the functional variety and metabolic significance of Etfs and to identify amino acid sequence motifs that potentially enable electron bifurcation, we compiled 1,314 Etf protein sequences from genome sequence databases and subjected them to informatic and structural analyses. Etfs were identified in diverse archaea and bacteria, and they clustered into five distinct well-supported groups, based on their amino acid sequences. Gene neighborhood analyses indicated that these Etf group designations largely correspond to putative differences in functionality. Etfs with the demonstrated ability to bifurcate were found to form one group, suggesting that distinct conserved amino acid sequence motifs enable this capability. Indeed, structural modeling and sequence alignments revealed that identifying residues occur in the NADH- and FAD-binding regions of bifurcating Etfs. Collectively, a new classification scheme for Etf proteins that delineates putative bifurcating versus nonbifurcating members is presented and suggests that Etf-mediated bifurcation is associated with surprisingly diverse enzymes. IMPORTANCE Electron bifurcation has recently been recognized as an electron transfer mechanism used by microorganisms to maximize

Effects of electron-electron interactions on the electron distribution function of a plasma in the presence of an external electric field

International Nuclear Information System (INIS)

Molinari, V.G.; Pizzio, F.; Spiga, G.

1979-01-01

The electron distribution function, the electron temperature and some transport parameters (electrical conductivity and energy flow coefficient) are obtained starting from the nonlinear Boltzmann equation for a plasma under the action of an external electric field. The Fokker-Planck approximation is used for electron-electron and electron-ion interactions. The effects of electron-electron collisions are studied for different values of collision frequencies and electric field. (author)

Application of radiochemical methods for development of new biological preparation designed for soil bioremediation

International Nuclear Information System (INIS)

Kim, A.A.; Djuraeva, G.T.; Djumaniyazova, G.I.; Yadgarov, Kh.T.

2006-01-01

Full text: Internationally the bioremediation of agricultural lands contaminated by persistent chloroorganic compounds by means of the microbial methods are used as the most low-cost and the most effective. One of the factors reducing efficacy of microbial degradation, is often the low quantity of microorganisms - destructors in the soil. Therefore, we have designed bioremediation technology of soils, contaminated by organochlorine compounds, with use of the alive microorganisms as active agent. We developed the biological preparation containing 5 aboriginal active strains of bacteria - destructors of persistent chloroorganic compounds and investigated the ability of biological preparation to increase the bioremediation potential of contaminated soils. To carry out the investigation we developed the complex of radiochemical methods with use of tritium labeled PCBs, including the following methods: 1.The method to define the accumulation and degradation of PCBs in soil bacteria in culture allows determination of quantitative characteristics of bacterial strains. 2. The method to define the PCBs degradation by soil bacteria strains in model conditions in the soil allows to estimate the PCB-destructive activity of strains after introducing in soil. 3. A method to define the PCB-destructive activity of own microbiota of contaminated soil. 4. A method to define the effect of stimulation of the PCB-destructive activity of biological preparation and own microbiota of soil with the help of biofertilizers. By using the developed radiochemical methods we have carried out investigation on creation of new biological preparation on the basis of strains of soil bacteria - destructors of PCBs. We also determined the quality and quantity characteristics of HCCH and PCBs-destructive activity of new biological preparation. It is shown that the new biological preparation is capable of accumulation and destruction of the PCBs in culture and in soil at model conditions. Thus, the

Electron-excited molecule interactions

International Nuclear Information System (INIS)

Christophorou, L.G.; Tennessee Univ., Knoxville, TN

1991-01-01

In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10 6 to 10 7 times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs

Seeing with electrons

International Nuclear Information System (INIS)

Nellist, P.

2006-01-01

Commercially available lens correctors are extending the reach of electron microscopes to unprecedented atomic scales, as Peter Nellist describes. The electron microscope was invented in 1933 and is based on the principle that electrons have a wavelength that is inversely proportional to their momentum. There are two basic types: transmission electron microscopes and scanning electron microscopes, plus a hybrid of the two. The lenses in an electron microscope are provided by electromagnetic fields, but they suffer from spherical aberration. The addition of octupole and quadrupole corrector fields has improved the resolution of the electron microscope to better than 0.1 nm in the last decade. The next step is to correct for chromatic aberration, after which the resolution of the microscope will probably be limited by the size of the atom itself. (U.K.)

Introduction to electronics

CERN Multimedia

CERN. Geneva

2005-01-01

Electronics in HEP experiments: specificities and evolution The Art of Electronics: is there something beyond Ohm's law? Basic building blocks of Analog electronics: quickly understanding a schematic Charge preamps, current preamps and future preamps, shaping and the rest Electronics noise: fundamental and practical Evolution of technology: ASICs, FPGAs...

Multiple electron generation in a sea of electronic states

Science.gov (United States)

Witzel, Wayne; Shabaev, Andrew; Efros, Alexander; Hellberg, Carl; Verne, Jacobs

2009-03-01

In traditional bulk semiconductor photovoltaics (PVs), each photon may excite a single electron-hole, wasting excess energy beyond the band-gap as heat. In nanocrystals, multiple excitons can be generated from a single photon, enhancing the PV current. Multiple electron generation (MEG) may result from Coulombic interactions of the confined electrons. Previous investigations have been based on incomplete or over-simplified electronic-state representations. We present results of quantum simulations that include hundreds of thousands of configuration states and show how the complex dynamics, even in a closed electronic system, yields a saturated MEG effect on a femtosecond timescale. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Electron collision cross sections and electron swarm parameters for gas molecules

International Nuclear Information System (INIS)

Hayashi, Makoto

1986-01-01

Elastic and inelastic electron collision cross sections for molecules which interest in radiation research have been determined from available electron beam and electron swarm data by utilizing the Boltzmann equation and Monte Carlo simulation method. Electron drift velocity data which interest in radiation Pysics have been discussed and some calculated results of electron drift velocity data for CF 4 and CF 4 -inert gases mixtures will be presented. (author)

Electronic payment systems

OpenAIRE

Mláka, Michal

2010-01-01

This bachelor thesis analysis issue of electronic payment systems. It discusses their use for payments on the internet and sending funds via e-mail. The first part is devoted to the theoretical definition and legislation of the issuance of electronic money and activities of electronic money institutions. The main part of the work clearly focuses on the use of e-wallets, which is an integral part of electronic payment systems. E-wallet of electronic payment system Moneybookers is considered as...

Wigner-like crystallization of Anderson-localized electron systems with low electron densities

CERN Document Server

Slutskin, A A; Pepper, M

2002-01-01

We consider an electron system under conditions of strong Anderson localization, taking into account interelectron long-range Coulomb repulsion. We establish that at sufficiently low electron densities and sufficiently low temperatures the Coulomb electron interaction brings about ordering of the Anderson-localized electrons into a structure that is close to an ideal (Wigner) crystal lattice, provided the dimension of the system is > 1. This Anderson-Wigner glass (AWG) is a new macroscopic electron state that, on the one hand, is beyond the conventional Fermi glass concept, and on the other hand, qualitatively differs from the known 'plain' Wigner glass (inherent in self-localized electron systems) in that the random slight electron displacements from the ideal crystal sites essentially depend on the electron density. With increasing electron density the AWG is found to turn into the plain Wigner glass or Fermi glass, depending on the width of the random spread of the electron levels. It is shown that the res...

Excess electrons in methanol clusters: Beyond the one-electron picture

Science.gov (United States)

Pohl, Gábor; Mones, Letif; Turi, László

2016-10-01

We performed a series of comparative quantum chemical calculations on various size negatively charged methanol clusters, ("separators=" CH 3 OH ) n - . The clusters are examined in their optimized geometries (n = 2-4), and in geometries taken from mixed quantum-classical molecular dynamics simulations at finite temperature (n = 2-128). These latter structures model potential electron binding sites in methanol clusters and in bulk methanol. In particular, we compute the vertical detachment energy (VDE) of an excess electron from increasing size methanol cluster anions using quantum chemical computations at various levels of theory including a one-electron pseudopotential model, several density functional theory (DFT) based methods, MP2 and coupled-cluster CCSD(T) calculations. The results suggest that at least four methanol molecules are needed to bind an excess electron on a hydrogen bonded methanol chain in a dipole bound state. Larger methanol clusters are able to form stronger interactions with an excess electron. The two simulated excess electron binding motifs in methanol clusters, interior and surface states, correlate well with distinct, experimentally found VDE tendencies with size. Interior states in a solvent cavity are stabilized significantly stronger than electron states on cluster surfaces. Although we find that all the examined quantum chemistry methods more or less overestimate the strength of the experimental excess electron stabilization, MP2, LC-BLYP, and BHandHLYP methods with diffuse basis sets provide a significantly better estimate of the VDE than traditional DFT methods (BLYP, B3LYP, X3LYP, PBE0). A comparison to the better performing many electron methods indicates that the examined one-electron pseudopotential can be reasonably used in simulations for systems of larger size.

Electron dose rate and photon contamination in electron arc therapy

International Nuclear Information System (INIS)

Pla, M.; Podgorsak, E.B.; Pla, C.

1989-01-01

The electron dose rate at the depth of dose maximum dmax and the photon contamination are discussed as a function of several parameters of the rotational electron beam. A pseudoarc technique with an angular increment of 10 degrees and a constant number of monitor units per each stationary electron field was used in our experiments. The electron dose rate is defined as the electron dose at a given point in phantom divided by the number of monitor units given for any one stationary electron beam. For a given depth of isocenter di the electron dose rates at dmax are linearly dependent on the nominal field width w, while for a given w the dose rates are inversely proportional to di. The dose rates for rotational electron beams with different di are related through the inverse square law provided that the two beams have (di,w) combinations which give the same characteristic angle beta. The photon dose at the isocenter depends on the arc angle alpha, field width w, and isocenter depth di. For constant w and di the photon dose at isocenter is proportional to alpha, for constant alpha and w it is proportional to di, and for constant alpha and di it is inversely proportional to w. The w and di dependence implies that for the same alpha the photon dose at the isocenter is inversely proportional to the electron dose rate at dmax

Power Electronics

DEFF Research Database (Denmark)

Iov, Florin; Ciobotaru, Mihai; Blaabjerg, Frede

2008-01-01

is to change the electrical power production sources from the conventional, fossil (and short term) based energy sources to renewable energy resources. The other is to use high efficient power electronics in power generation, power transmission/distribution and end-user application. This paper discuss the most...... emerging renewable energy sources, wind energy, which by means of power electronics are changing from being a minor energy source to be acting as an important power source in the energy system. Power electronics is the enabling technology and the presentation will cover the development in wind turbine...... technology from kW to MW, discuss which power electronic solutions are most feasible and used today....

Electron Emission from Ultra-Large Area MOS Electron Emitters

DEFF Research Database (Denmark)

Thomsen, Lasse Bjørchmar; Nielsen, Gunver; Vendelbo, Søren Bastholm

2009-01-01

Ultralarge metal-oxide-semiconductor (MOS) devices with an active oxide area of 1 cm2 have been fabricated for use as electron emitters. The MOS structures consist of a Si substrate, a SiO2 tunnel barrier (~5 nm), a Ti wetting layer (3–10 Å), and a Au top layer (5–60 nm). Electron emission from...... layer is varied from 3 to 10 Å which changes the emission efficiency by more than one order of magnitude. The apparent mean free path of ~5 eV electrons in Au is found to be 52 Å. Deposition of Cs on the Au film increased the electron emission efficiency to 4.3% at 4 V by lowering the work function....... Electron emission under high pressures (up to 2 bars) of Ar was observed. ©2009 American Vacuum Society...

Comparative analysis of the terms "electronic commerce" and "electronic business"

OpenAIRE

Kavaliauskienė, Virginija; Šarapovas, Tadas

2002-01-01

Establishing the terms that clearly and consistently describe growing and dynamic networked economy is a critical first step toward further analysis and evaluation of electronic commerce and electronic business processes. Electronic commerce is making an impact on the ways that purchasing activities are being conducted. Much of the early literature on this subject was very speculative. However, the growth of e-commerce has enabled more observations to be made of the use of electronic business...

Electron-electron interaction and transfer ionization in fast ion-atom collisions

International Nuclear Information System (INIS)

Voitkiv, A B

2008-01-01

Recently it was pointed out that electron capture occurring in fast ion-atom collisions can proceed via a mechanism which earlier was not considered. In the present paper we study this mechanism in more detail. Similarly as in radiative capture, where the electron transfer occurs due to the interaction with the radiation field and proceeds via emission of a photon, within this mechanism the electron capture is caused by the interaction with another atomic electron leading mainly to the emission of the latter. In contrast to the electron-electron Thomas capture, this electron-electron (E-E) mechanism is basically a first-order one having similarities to the kinematic and radiative capture channels. It also possesses important differences with the latter two. Leading to transfer ionization, this first-order capture mechanism results in the electron emission mainly in the direction opposite to the motion of the projectile ion. The same, although less pronounced, feature is also characteristic for the momenta of the target recoil ions produced via this mechanism. It is also shown that the action of the E-E mechanism is clearly seen in recent experimental data on the transfer ionization in fast proton-helium collisions.

Determination of electron temperature and electron density in ...

African Journals Online (AJOL)

It is seen that the electron temperature increases from 5.8 × 102 oK to 7.83 × 104 oK as the pd is reduced from 130mm Hg × mm to 60 mm Hg × mm for argon. The electron densities increases from 2.8 × 1011/cm3 to 3.2 × 1011 /cm3 for the same variation of pds. For air the electron temperature increases from 3.6 × 104 oK to ...

Optimising electron microscopy experiment through electron optics simulation

Energy Technology Data Exchange (ETDEWEB)

Kubo, Y. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Hitachi High-Technologies Corporation, 882, Ichige, Hitachinaka, Ibaraki 312-8504 (Japan); Gatel, C.; Snoeck, E. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Houdellier, F., E-mail: florent.houdellier@cemes.fr [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France)

2017-04-15

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

Optimising electron microscopy experiment through electron optics simulation

International Nuclear Information System (INIS)

Kubo, Y.; Gatel, C.; Snoeck, E.; Houdellier, F.

2017-01-01

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

Lead-Free Electronics: Impact for Space Electronics

Science.gov (United States)

Sampson, Michael J.

2010-01-01

Pb is used as a constituent in solder alloys used to connect and attach electronic parts to printed wiring boards (PWBs). Similar Pbbearing alloys are electroplated or hot dipped onto the terminations of electronic parts to protect the terminations and make them solderable. Changing to Pb-free solders and termination finishes has introduced significant technical challenges into the supply chain. Tin/lead (Sn/Pb) alloys have been the solders of choice for electronics for more than 50 years. Pb-free solder alloys are available but there is not a plug-in replacement for 60/40 or 63/37 (Sn/Pb) alloys, which have been the industry workhorses.

Observation of electron plasma waves in plasma of two-temperature electrons

International Nuclear Information System (INIS)

Ikezawa, Shunjiro; Nakamura, Yoshiharu.

1981-01-01

Propagation of electron plasma waves in a large and unmagnetized plasma containing two Maxwellian distributions of electrons is studied experimentally. Two kinds of plasma sources which supply electrons of different temperature are used. The temperature ratio is about 3 and the density ratio of hot to cool electrons is varied from 0 to 0.5. A small contamination of hot electrons enhances the Landau damping of the principal mode known as the Bohm-Gross mode. When the density of hot electrons is larger than about 0.2, two modes are observed. The results agree with theoretical dispersion relations when excitation efficiencies of the modes are considered. (author)

Electron energy and electron trajectories in an inverse free-electron laser accelerator based on a novel electrostatic wiggler

Science.gov (United States)

Nikrah, M.; Jafari, S.

2016-06-01

We expand here a theory of a high-gradient laser-excited electron accelerator based on an inverse free-electron laser (inverse-FEL), but with innovations in the structure and design. The electrostatic wiggler used in our scheme, namely termed the Paul wiggler, is generated by segmented cylindrical electrodes with applied oscillatory voltages {{V}\\text{osc}}(t) over {{90}\\circ} segments. The inverse-FEL interaction can be described by the equations that govern the electron motion in the combined fields of both the laser pulse and Paul wiggler field. A numerical study of electron energy and electron trajectories has been made using the fourth-order Runge-Kutta method. The results indicate that the electron attains a considerable energy at short distances in this device. It is found that if the electron has got sufficient suitable wiggler amplitude intensities, it can not only gain higher energy in longer distances, but also can retain it even after the passing of the laser pulse. In addition, the results reveal that the electron energy gains different peaks for different initial axial velocities, so that a suitable small initial axial velocity of e-beam produces substantially high energy gain. With regard to the transverse confinement of the electron beam in a Paul wiggler, there is no applied axial guide magnetic field in this device.

Plasmaspheric electron content

International Nuclear Information System (INIS)

Hartmann, G.K.

1978-01-01

Measurements of the plasmaspheric electron content are reviewed with particular reference to the ATS-6 radio beacon experiment. From the review, it appears likely that measurement of the plasmaspheric electron content is the only one capable of monitoring electron fluxes continuously between L 1 and L 2. Some recent important results deduced from plasmaspheric electron content measurements are discussed

A 20 keV electron gun system for the electron irradiation experiments

International Nuclear Information System (INIS)

Mahapatra, S.K.; Dhole, S.D.; Bhoraskar, V.N.

2005-01-01

An electron gun consisting of cathode, focusing electrode, control electrode and anode has been designed and fabricated for the electron irradiation experiments. This electron gun can provide electrons of any energy over the range 1-20 keV, with current upto 50 μA. This electron gun and a Faraday cup are mounted in the cylindrical chamber. The samples are fixed on the Faraday cup and irradiated with electrons at a pressure ∼10 -7 mbar. The special features of this electron gun system are that, at any electron energy above 1 keV, the electron beam diameter can be varied from 5 to 120 mm on the Faraday cup mounted at a distance of 200 mm from the anode in the chamber. The variation in the electron current over the beam spot of 120 mm diameter is less than 15% and the beam current stability is better than 5%. This system is being used for studying the irradiation effects of 1-20 keV energy electrons on the space quality materials in which the irradiation time may vary from a few tens of seconds to hours

A 20 keV electron gun system for the electron irradiation experiments

Energy Technology Data Exchange (ETDEWEB)

Mahapatra, S.K. [Department of Physics, University of Pune, Pune 411007 (India); Dhole, S.D. [Department of Physics, University of Pune, Pune 411007 (India); Bhoraskar, V.N. [Department of Physics, University of Pune, Pune 411007 (India)]. E-mail: vnb@physics.unipune.ernet.in

2005-01-01

An electron gun consisting of cathode, focusing electrode, control electrode and anode has been designed and fabricated for the electron irradiation experiments. This electron gun can provide electrons of any energy over the range 1-20 keV, with current upto 50 {mu}A. This electron gun and a Faraday cup are mounted in the cylindrical chamber. The samples are fixed on the Faraday cup and irradiated with electrons at a pressure {approx}10{sup -7} mbar. The special features of this electron gun system are that, at any electron energy above 1 keV, the electron beam diameter can be varied from 5 to 120 mm on the Faraday cup mounted at a distance of 200 mm from the anode in the chamber. The variation in the electron current over the beam spot of 120 mm diameter is less than 15% and the beam current stability is better than 5%. This system is being used for studying the irradiation effects of 1-20 keV energy electrons on the space quality materials in which the irradiation time may vary from a few tens of seconds to hours.

Effect of electron beam on the properties of electron-acoustic rogue waves

Science.gov (United States)

El-Shewy, E. K.; Elwakil, S. A.; El-Hanbaly, A. M.; Kassem, A. I.

2015-04-01

The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, Maxwellian hot electrons, an electron beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles and the associated electric field on the carrier wave number, normalized density of hot electron and electron beam, relative cold electron temperature and relative beam temperature are discussed. The results of the present investigation may be applicable in auroral zone plasma.

Electron cooling and recombination experiments with an adiabatically expanded electron beam

International Nuclear Information System (INIS)

Pastuszka, S.; Heidelberg Univ.; Schramm, U.; Heidelberg Univ.; Grieser, M.; Heidelberg Univ.; Broude, C.; Heidelberg Univ.; Grimm, R.; Heidelberg Univ.; Habs, D.; Heidelberg Univ.; Kenntner, J.; Heidelberg Univ.; Miesner, H.J.; Heidelberg Univ.; Schuessler, T.; Heidelberg Univ.; Schwalm, D.; Heidelberg Univ.; Wolf, A.; Heidelberg Univ.

1996-01-01

Magnetically guided electron beams with transverse temperatures reduced with respect to the cathode temperature by a factor of more than 7 were realized in the electron cooling device of the heavy-ion storage ring TSR and the effect of the reduced transverse temperature in recombination and electron cooling experiments was studied. Measured dielectronic recombination resonances at low relative energy and spectra of laser-stimulated recombination indicate that transverse electron temperatures of about 17 meV have been obtained at cathode temperatures of about 110 meV. The temperature dependence of the spontaneous electron-ion recombination rate during electron cooling was investigated and found to follow the inverse square-root law expected from the theory of radiative recombination, although the measured absolute rates are higher than predicted. A new method based on analyzing the intensity of the fluorescence light emitted during simultaneous laser and electron cooling is used to measure the longitudinal electron cooling force in a range of relative velocities extending over two orders of magnitude (10 5 -10 7 cm/s). The results confirm the occurrence of 'magnetized electron cooling' also at the reduced transverse temperature and show that, compared to earlier measurements at the high transverse temperature, the cooling force increases by about a factor of 2; a considerably larger increase by a factor of ∼5 would be expected if 'magnetized electron cooling' would not exist. (orig.)

Electronic structure of elements and compounds and electronic phases of solids

International Nuclear Information System (INIS)

Nadykto, B.A.

2000-01-01

The paper reviews technique and computed energies for various electronic states of many-electron multiply charged ions, molecular ions, and electronic phases of solids. The model used allows computation of the state energy for free many-electron multiply charged ions with relative accuracy ∼10 -4 suitable for analysis of spectroscopy data

Three-dimensional nanofabrication by electron-beam-induced deposition using 200-keV electrons in scanning transmission electron microscope

International Nuclear Information System (INIS)

Liu, Z.Q.; Mitsuishi, K.; Furuya, K.

2005-01-01

Attempts were made to fabricate three-dimensional nanostructures on and out of a substrate by electron-beam-induced deposition in a 200-kV scanning transmission electron microscope. Structures with parallel wires over the substrate surface were difficult to fabricate due to the direct deposition of wires on both top and bottom surfaces of the substrate. Within the penetration depth of the incident electron beam, nanotweezers were fabricated by moving the electron beam beyond different substrate layers. Combining the deposition of self-supporting wires and self-standing tips, complicated three-dimensional doll-like, flag-like, and gate-like nanostructures that extend out of the substrate were successfully fabricated with one-step or multi-step scans of the electron beam. Effects of coarsening, nucleation, and distortion during electron-beam-induced deposition are discussed. (orig.)

Secondary electron emission yield in the limit of low electron energy

CERN Document Server

Andronov, A.N.; Kaganovich, I.D.; Startsev, E.A.; Raitses, Y.; Demidov, V.I.

2013-04-22

Secondary electron emission (SEE) from solids plays an important role in many areas of science and technology.1 In recent years, there has been renewed interest in the experimental and theoretical studies of SEE. A recent study proposed that the reflectivity of very low energy electrons from solid surface approaches unity in the limit of zero electron energy2,3,4, If this was indeed the case, this effect would have profound implications on the formation of electron clouds in particle accelerators,2-4 plasma measurements with electrostatic Langmuir probes, and operation of Hall plasma thrusters for spacecraft propulsion5,6. It appears that, the proposed high electron reflectivity at low electron energies contradicts to numerous previous experimental studies of the secondary electron emission7. The goal of this note is to discuss possible causes of these contradictions.

Electron spectroscopy

International Nuclear Information System (INIS)

Hegde, M.S.

1979-01-01

An introduction to the various techniques in electron spectroscopy is presented. These techniques include: (1) UV Photoelectron spectroscopy, (2) X-ray Photoelectron spectroscopy, (3) Auger electron spectroscopy, (4) Electron energy loss spectroscopy, (5) Penning ionization spectroscopy and (6) Ion neutralization spectroscopy. The radiations used in each technique, the basis of the technique and the special information obtained in structure determination in atoms and molecules by each technique are summarised. (A.K.)

Perpendicular electron cyclotron emission from hot electrons in TMX-U

International Nuclear Information System (INIS)

James, R.A.; Ellis, R.F.; Lasnier, C.J.; Casper, T.A.; Celata, C.M.

1984-01-01

Perpendicular electron cyclotron emission (PECE) from the electron cyclotron resonant heating of hot electrons in TMX-U is measured at 30 to 40 and 50 to 75 GHz. This emission is optically thin and is measured at the midplane, f/sub ce/ approx. = 14 GHz, in either end cell. In the west end cell, the emission can be measured at different axial positions thus yielding the temporal history of the hot electron axial profile. These profiles are in excellent agreement with the axial diamagnetic signals. In addition, the PECE signal level correlates well with the diamagnetic signal over a wide range of hot electron densities. Preliminary results from theoretical modeling and comparisons with other diagnostics are also presented

A ferroelectric electron gun in a free-electron maser experiment

International Nuclear Information System (INIS)

Einat, M.; Jerby, E.; Rosenman, G.

2002-01-01

An electron-gun based on a ferroelectric cathode is studied in a free-electron maser (FEM) experiment. In this gun, the electrons are separated from the cathode surface plasma, and are accelerated in two stages. The electron energy-spread is reduced sufficiently for an FEM operation in the microwave regime. A 14 keV, 1-2 A e-beam is obtained in a 0.1-2.1 μs pulse width. The pulse repetition frequency attains 3.1 MHz in ∼50% duty-cycle. This gun is implemented in an FEM oscillator experiment operating around 3 GHz. The paper presents experimental results and discusses the applicability of ferroelectric guns in free-electron laser devices

A ferroelectric electron gun in a free-electron maser experiment

CERN Document Server

Einat, M; Rosenman, G

2002-01-01

An electron-gun based on a ferroelectric cathode is studied in a free-electron maser (FEM) experiment. In this gun, the electrons are separated from the cathode surface plasma, and are accelerated in two stages. The electron energy-spread is reduced sufficiently for an FEM operation in the microwave regime. A 14 keV, 1-2 A e-beam is obtained in a 0.1-2.1 mu s pulse width. The pulse repetition frequency attains 3.1 MHz in approx 50% duty-cycle. This gun is implemented in an FEM oscillator experiment operating around 3 GHz. The paper presents experimental results and discusses the applicability of ferroelectric guns in free-electron laser devices.

Paper electronics.

Science.gov (United States)

Tobjörk, Daniel; Österbacka, Ronald

2011-05-03

Paper is ubiquitous in everyday life and a truly low-cost substrate. The use of paper substrates could be extended even further, if electronic applications would be applied next to or below the printed graphics. However, applying electronics on paper is challenging. The paper surface is not only very rough compared to plastics, but is also porous. While this is detrimental for most electronic devices manufactured directly onto paper substrates, there are also approaches that are compatible with the rough and absorptive paper surface. In this review, recent advances and possibilities of these approaches are evaluated and the limitations of paper electronics are discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Destabilization of the electron Bernstein modes by runaway electrons

International Nuclear Information System (INIS)

Hitchcock, D.A.; Mahajan, S.M.

1982-01-01

It is shown that the electromagnetic finite k/sub parallel/ electron Bernstein mode can be destabilized by the runaway electron distribution which results from the quasilinear action of the magnetized plasma oscillation. This mechanism is shown to yield growth rates of the order of 10 8 sec -1 and is suggested as a mechanism for the enchanced cyclotron harmonic emission in the presence of runaway electrons

Surface-electronic-state effects in electron emission from the Be(0001) surface

International Nuclear Information System (INIS)

Archubi, C. D.; Gravielle, M. S.; Silkin, V. M.

2011-01-01

We study the electron emission produced by swift protons impinging grazingly on a Be(0001) surface. The process is described within a collisional formalism using the band-structure-based (BSB) approximation to represent the electron-surface interaction. The BSB model provides an accurate description of the electronic band structure of the solid and the surface-induced potential. Within this approach we derive both bulk and surface electronic states, with these latter characterized by a strong localization at the crystal surface. We found that such surface electronic states play an important role in double-differential energy- and angle-resolved electron emission probabilities, producing noticeable structures in the electron emission spectra.

Surface-electronic-state effects in electron emission from the Be(0001) surface

Energy Technology Data Exchange (ETDEWEB)

Archubi, C. D. [Instituto de Astronomia y Fisica del Espacio, casilla de correo 67, sucursal 28, C1428EGA, Buenos Aires (Argentina); Gravielle, M. S. [Instituto de Astronomia y Fisica del Espacio, casilla de correo 67, sucursal 28, C1428EGA, Buenos Aires (Argentina); Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Silkin, V. M. [Donostia International Physics Center, E-20018 San Sebastian (Spain); Departamento de Fisica de Materiales, Facultad de Ciencias Quimicas, Universidad del Pais Vasco, Apartado 1072, E-20080 San Sebastian (Spain); IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao (Spain)

2011-07-15

We study the electron emission produced by swift protons impinging grazingly on a Be(0001) surface. The process is described within a collisional formalism using the band-structure-based (BSB) approximation to represent the electron-surface interaction. The BSB model provides an accurate description of the electronic band structure of the solid and the surface-induced potential. Within this approach we derive both bulk and surface electronic states, with these latter characterized by a strong localization at the crystal surface. We found that such surface electronic states play an important role in double-differential energy- and angle-resolved electron emission probabilities, producing noticeable structures in the electron emission spectra.

Simulation of the electron acoustic instability for a finite-size electron beam system

International Nuclear Information System (INIS)

Lin, C.S.; Winske, D.

1987-01-01

Satellite observations at midlatitudes (≅20,000 km) near the earth's dayside polar cusp boundary layer indicate that the upward electron beams have a narrow latitudinal width up to 0.1 0 . In the cusp boundary layer where the electron population consists of a finite-size electron beam in a background of uniform cold and hot electrons, the electron acoustic mode is unstable inside the electron beam but damped outside the electron beam. Simulations of the electron acoustic instability for a finite-size beam system are carried out with a particle-in-cell code to investigate the heating phenomena associated with the instability and the width of the heating region. The simulations show that the finite-size electron beam radiates electrostatic electron acoustic waves. The decay length of the electron acoustic waves outside the beam in the simulation agrees with the spatial decay length derived from the linear dispersion equation

Arbitrary amplitude slow electron-acoustic solitons in three-electron temperature space plasmas

International Nuclear Information System (INIS)

Mbuli, L. N.; Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

2015-01-01

We examine the characteristics of large amplitude slow electron-acoustic solitons supported in a four-component unmagnetised plasma composed of cool, warm, hot electrons, and cool ions. The inertia and pressure for all the species in this plasma system are retained by assuming that they are adiabatic fluids. Our findings reveal that both positive and negative potential slow electron-acoustic solitons are supported in the four-component plasma system. The polarity switch of the slow electron-acoustic solitons is determined by the number densities of the cool and warm electrons. Negative potential solitons, which are limited by the cool and warm electron number densities becoming unreal and the occurrence of negative potential double layers, are found for low values of the cool electron density, while the positive potential solitons occurring for large values of the cool electron density are only limited by positive potential double layers. Both the lower and upper Mach numbers for the slow electron-acoustic solitons are computed and discussed

Electron cloud dynamics in the Cornell Electron Storage Ring Test Accelerator wiggler

Directory of Open Access Journals (Sweden)

C. M. Celata

2011-04-01

Full Text Available The interference of stray electrons (also called “electron clouds” with accelerator beams is important in modern intense-beam accelerators, especially those with beams of positive charge. In magnetic wigglers, used, for instance, for transverse emittance damping, the intense synchrotron radiation produced by the beam can generate an electron cloud of relatively high density. In this paper the complicated dynamics of electron clouds in wigglers is examined using the example of a wiggler in the Cornell Electron Storage Ring Test Accelerator experiment at the Cornell Electron Storage Ring. Three-dimensional particle-in-cell simulations with the WARP-POSINST computer code show different density and dynamics for the electron cloud at locations near the maxima of the vertical wiggler field when compared to locations near the minima. Dynamics in these regions, the electron cloud distribution vs longitudinal position, and the beam coherent tune shift caused by the wiggler electron cloud will be discussed.

Arbitrary amplitude fast electron-acoustic solitons in three-electron component space plasmas

Energy Technology Data Exchange (ETDEWEB)

Mbuli, L. N.; Maharaj, S. K. [South African National Space Agency (SANSA) Space Science, P.O. Box 32, Hermanus 7200, Republic of South Africa (South Africa); Department of Physics, University of the Western Cape (UWC), Robert Sobukwe Road, Bellville 7535, Republic of South Africa (South Africa); Bharuthram, R. [Department of Physics, University of the Western Cape (UWC), Robert Sobukwe Road, Bellville 7535, Republic of South Africa (South Africa); Singh, S. V.; Lakhina, G. S. [Indian Institute of Geomagnetism, New Panvel (West), Navi Mumbai 410218 (India); Department of Physics, University of the Western Cape (UWC), Robert Sobukwe Road, Bellville 7535, Republic of South Africa (South Africa)

2016-06-15

We examine the characteristics of fast electron-acoustic solitons in a four-component unmagnetised plasma model consisting of cool, warm, and hot electrons, and cool ions. We retain the inertia and pressure for all the plasma species by assuming adiabatic fluid behaviour for all the species. By using the Sagdeev pseudo-potential technique, the allowable Mach number ranges for fast electron-acoustic solitary waves are explored and discussed. It is found that the cool and warm electron number densities determine the polarity switch of the fast electron-acoustic solitons which are limited by either the occurrence of fast electron-acoustic double layers or warm and hot electron number density becoming unreal. For the first time in the study of solitons, we report on the coexistence of fast electron-acoustic solitons, in addition to the regular fast electron-acoustic solitons and double layers in our multi-species plasma model. Our results are applied to the generation of broadband electrostatic noise in the dayside auroral region.

Rapid parallel evolution overcomes global honey bee parasite.

Science.gov (United States)

Oddie, Melissa; Büchler, Ralph; Dahle, Bjørn; Kovacic, Marin; Le Conte, Yves; Locke, Barbara; de Miranda, Joachim R; Mondet, Fanny; Neumann, Peter

2018-05-16

In eusocial insect colonies nestmates cooperate to combat parasites, a trait called social immunity. However, social immunity failed for Western honey bees (Apis mellifera) when the ectoparasitic mite Varroa destructor switched hosts from Eastern honey bees (Apis cerana). This mite has since become the most severe threat to A. mellifera world-wide. Despite this, some isolated A. mellifera populations are known to survive infestations by means of natural selection, largely by supressing mite reproduction, but the underlying mechanisms of this are poorly understood. Here, we show that a cost-effective social immunity mechanism has evolved rapidly and independently in four naturally V. destructor-surviving A. mellifera populations. Worker bees of all four 'surviving' populations uncapped/recapped worker brood cells more frequently and targeted mite-infested cells more effectively than workers in local susceptible colonies. Direct experiments confirmed the ability of uncapping/recapping to reduce mite reproductive success without sacrificing nestmates. Our results provide striking evidence that honey bees can overcome exotic parasites with simple qualitative and quantitative adaptive shifts in behaviour. Due to rapid, parallel evolution in four host populations this appears to be a key mechanism explaining survival of mite infested colonies.

Stable genetic diversity despite parasite and pathogen spread in honey bee colonies

Science.gov (United States)

Jara, Laura; Muñoz, Irene; Cepero, Almudena; Martín-Hernández, Raquel; Serrano, José; Higes, Mariano; De la Rúa, Pilar

2015-10-01

In the last decades, the rapid spread of diseases, such as varroosis and nosemosis, associated with massive honey bee colonies mortality around the world has significantly decreased the number and size of honey bee populations and possibly their genetic diversity. Here, we compare the genetic diversity of Iberian honey bee colonies in two samplings performed in 2006 and 2010 in relation to the presence of the pathogenic agents Nosema apis, Nosema ceranae, and Varroa destructor in order to determine whether parasite and pathogen spread in honey bee colonies reflects changes in genetic diversity. We found that the genetic diversity remained similar, while the incidence of N. ceranae increased and the incidence of N. apis and V. destructor decreased slightly. These results indicate that the genetic diversity was not affected by the presence of these pathogenic agents in the analyzed period. However, the two groups of colonies with and without Nosema/Varroa detected showed significant genetic differentiation (G test). A detailed analysis of the allelic segregation of microsatellite loci in Nosema/Varroa-negative colonies and parasitized ones revealed two outlier loci related to genes involved in immune response.

Stable genetic diversity despite parasite and pathogen spread in honey bee colonies.

Science.gov (United States)

Jara, Laura; Muñoz, Irene; Cepero, Almudena; Martín-Hernández, Raquel; Serrano, José; Higes, Mariano; De la Rúa, Pilar

2015-10-01

In the last decades, the rapid spread of diseases, such as varroosis and nosemosis, associated with massive honey bee colonies mortality around the world has significantly decreased the number and size of honey bee populations and possibly their genetic diversity. Here, we compare the genetic diversity of Iberian honey bee colonies in two samplings performed in 2006 and 2010 in relation to the presence of the pathogenic agents Nosema apis, Nosema ceranae, and Varroa destructor in order to determine whether parasite and pathogen spread in honey bee colonies reflects changes in genetic diversity. We found that the genetic diversity remained similar, while the incidence of N. ceranae increased and the incidence of N. apis and V. destructor decreased slightly. These results indicate that the genetic diversity was not affected by the presence of these pathogenic agents in the analyzed period. However, the two groups of colonies with and without Nosema/Varroa detected showed significant genetic differentiation (G test). A detailed analysis of the allelic segregation of microsatellite loci in Nosema/Varroa-negative colonies and parasitized ones revealed two outlier loci related to genes involved in immune response.

A real-time PCR method for quantification of the total and major variant strains of the deformed wing virus.

Directory of Open Access Journals (Sweden)

Emma L Bradford

Full Text Available European honey bees (Apis mellifera are critically important to global food production by virtue of their pollination services but are severely threatened by deformed wing virus (DWV especially in the presence of the external parasite Varroa destructor. DWV exists as many viral strains with the two major variants (DWV-A and DWV-B varying in virulence. A single plasmid standard was constructed containing three sections for the specific determination of DWV-A (VP2 capsid region, DWV-B (IRES and a conserved region suitable for total DWV (helicase region. The assays were confirmed as specific and discriminatory with limits of detections of 25, 25 and 50 genome equivalents for DWV-A, DWV-B and total-DWV, respectively. The methods were successfully tested on Apis mellifera and V. destructor samples with varying DWV profiles. The new method determined a more accurate total DWV titre in samples with substantial DWV-B than the method currently described in the COLOSS Beebook. The proposed assays could be utilized for the screening of large quantities of bee material for both a total DWV load overview along with more detailed investigations into DWV-A and DWV-B profiles.

Electronic Market and Business: Cyberspace vs. Electronic Environment

Directory of Open Access Journals (Sweden)

Deniss Ščeulovs

2013-12-01

Full Text Available The authors of the article analyze the concept "electronic environment". Having studied a range of academic literature sources and other sources, the authors of the article have drawn a conclusion that the academic writings do not provide a definition of "electronic environment". Furthermore, the various opinions among specialists regarding this concept often differ. Meanwhile, there are several explanations of the term "cyberspace" overlapping the concept of "electronic environment", and these terms are often believed to be synonyms. To understand what the term "electronic environment" means and to properly and correctly employ this concept in entrepreneurship, the authors have performed a lexicographic analysis of this concept by comparing reciprocal concepts. As a result of the research, the authors propose their view on what, in their opinion, "electronic environment" is and what its connection to the concept "cyberspace" is. The topicality of the article lies in the fact that often entrepreneurs and specialists of public and other institutions, when using these terms, imply completely different concepts. It can lead to misunderstanding and misinterpreting the information, as well as to encumbering the understanding of tasks, problems, etc.

Practical XHV electron gun

International Nuclear Information System (INIS)

Urata, Tomohiro; Ishikawa, Tsuyoshi; Cho, Boklae; Oshima, Chuhei

2008-01-01

We have developed practical XHV chambers of a electron gun, of which the operating pressures are 1x10 -9 Pa in a stainless-steel one and 4x10 -9 Pa in a permalloy one. By mounting a noble single-atom electron source with high brightness and high spatial coherence on the electron gun including electron optics, we demonstrated highly collimated electron-beam emission: ∼80% of the total emission current entered the electron optics. This ratio was two or three orders of magnitude higher than those of the conventional electron sources. In XHV, in addition, we confirmed stable electron emission up to 20 nA, which results in the specimen current high enough for scanning electron microscopes. (author)

Two-Electron Transfer Pathways.

Science.gov (United States)

Lin, Jiaxing; Balamurugan, D; Zhang, Peng; Skourtis, Spiros S; Beratan, David N

2015-06-18

The frontiers of electron-transfer chemistry demand that we develop theoretical frameworks to describe the delivery of multiple electrons, atoms, and ions in molecular systems. When electrons move over long distances through high barriers, where the probability for thermal population of oxidized or reduced bridge-localized states is very small, the electrons will tunnel from the donor (D) to acceptor (A), facilitated by bridge-mediated superexchange interactions. If the stable donor and acceptor redox states on D and A differ by two electrons, it is possible that the electrons will propagate coherently from D to A. While structure-function relations for single-electron superexchange in molecules are well established, strategies to manipulate the coherent flow of multiple electrons are largely unknown. In contrast to one-electron superexchange, two-electron superexchange involves both one- and two-electron virtual intermediate states, the number of virtual intermediates increases very rapidly with system size, and multiple classes of pathways interfere with one another. In the study described here, we developed simple superexchange models for two-electron transfer. We explored how the bridge structure and energetics influence multielectron superexchange, and we compared two-electron superexchange interactions to single-electron superexchange. Multielectron superexchange introduces interference between singly and doubly oxidized (or reduced) bridge virtual states, so that even simple linear donor-bridge-acceptor systems have pathway topologies that resemble those seen for one-electron superexchange through bridges with multiple parallel pathways. The simple model systems studied here exhibit a richness that is amenable to experimental exploration by manipulating the multiple pathways, pathway crosstalk, and changes in the number of donor and acceptor species. The features that emerge from these studies may assist in developing new strategies to deliver multiple

Electron-Electron and Electron-Phonon interactions effects on the tunnel electronic spectrum of PbS quantum dots

Science.gov (United States)

Wang, Hongyue; Lhuillier, Emmanuel; Yu, Qian; Mottaghizadeh, Alireza; Ulysse, Christian; Zimmers, Alexandre; Dubertret, Benoit; Aubin, Herve

2015-03-01

We present a tunnel spectroscopy study of the electronic spectrum of single PbS Quantum Dots (QDs) trapped between nanometer-spaced electrodes, measured at low temperature T=5 K. The carrier filling of the QD can be controlled either by the drain voltage in the shell filling regime or by a gate voltage. In the empty QD, the tunnel spectrum presents the expected signature of the 8x degenerated excited levels. In the drain controlled shell filling regime, the levels degeneracies are lifted by the global electrostatic Coulomb energy of the QD; in the gate controlled shell filling regime, the levels degeneracies are lifted by the intra-Coulomb interactions. In the charged quantum dot, electron-phonons interactions lead to the apparition of Franck-Condon side bands on the single excited levels and possibly Franck Condon blockade at low energy. The sharpening of excited levels at higher gate voltage suggests that the magnitude of electron-phonon interactions is decreased upon increasing the electron filling in the quantum dot. This work was supported by the French ANR Grants 10-BLAN-0409-01, 09-BLAN-0388-01, by the Region Ile-de-France in the framework of DIM Nano-K and by China Scholarship Council.

Electron emitting filaments for electron discharge devices

International Nuclear Information System (INIS)

Leung, K.N.; Pincosy, P.A.; Ehlers, K.W.

1988-01-01

This patent describes an electron emitting device for use in an electron discharge system. It comprises: a filament having a pair of terminal ends, electrical supply means for supplying electrical power to the terminal ends of the filament for directly heating the filament by the passage of an electrical current along the filament between the terminal ends, the filament being substantially tapered in cross section continuously in one direction from one of its pair of terminal ends to another of its pair of terminal ends to achieve uniform heating of the filament along the length thereof by compensating for the nonuniform current along the filament due to the emission of electrons therefrom

Electron irradiation-induced destruction of carbon nanotubes in electron microscopes

International Nuclear Information System (INIS)

Molhave, Kristian; Gudnason, Sven Bjarke; Pedersen, Anders Tegtmeier; Clausen, Casper Hyttel; Horsewell, Andy; Boggild, Peter

2007-01-01

Observations of carbon nanotubes under exposure to electron beam irradiation in standard transmission electron microscope (TEM) and scanning electron microscope (SEM) systems show that such treatment in some cases can cause severe damage of the nanotube structure, even at electron energies far below the approximate 100 keV threshold for knock-on damage displacing carbon atoms in the graphene structure. We find that the damage we observe in one TEM can be avoided by use of a cold finger. This and the morphology of the damage imply that water vapour, which is present as a background gas in many vacuum chambers, can damage the nanotube structure through electron beam-induced chemical reactions. Though, the dependence on the background gas makes these observations specific for the presently used systems, the results demonstrate the importance of careful assessment of the level of subtle structural damage that the individual electron microscope system can do to nanostructures during standard use

Electron-attachment processes

International Nuclear Information System (INIS)

Christophorou, L.G.; McCorkle, D.L.; Christodoulides, A.A.

1982-01-01

Topics covered include: (1) modes of production of negative ions, (2) techniques for the study of electron attachment processes, (3) dissociative electron attachment to ground-state molecules, (4) dissociative electron attachment to hot molecules (effects of temperature on dissociative electron attachment), (5) molecular parent negative ions, and (6) negative ions formed by ion-pair processes and by collisions of molecules with ground state and Rydberg atoms

Acceleration of electrons using an inverse free electron laser auto- accelerator

International Nuclear Information System (INIS)

Wernick, I.K.; Marshall, T.C.

1992-07-01

We present data from our study of a device known as the inverse free electron laser. First, numerical simulations were performed to optimize the design parameters for an experiment that accelerates electrons in the presence of an undulator by stimulated absorption of radiation. The Columbia free electron laser (FEL) was configured as an auto-accelerator (IFELA) system; high power (MW's) FEL radiation at ∼1.65 mm is developed along the first section of an undulator inside a quasi-optical resonator. The electron beam then traverses a second section of undulator where a fraction of the electrons is accelerated by stimulated absorption of the 1.65 mm wavelength power developed in the first undulator section. The second undulator section has very low gain and does not generate power on its own. We have found that as much as 60% of the power generated in the first section can be absorbed in the second section, providing that the initial electron energy is chosen correctly with respect to the parameters chosen for the first and second undulators. An electron momentum spectrometer is used to monitor the distribution of electron energies as the electrons exit the IFELA. We have found; using our experimental parameters, that roughly 10% of the electrons are accelerated to energies as high as 1100 keV, in accordance with predictions from the numerical model. The appearance of high energy electrons is correlated with the abrupt absorption of millimeter power. The autoaccelerator configuration is used because there is no intense source of coherent power at the 1.65 mm design wavelength other than the FEL

Advanced Electronics

Science.gov (United States)

2017-07-21

AFRL-RV-PS- AFRL-RV-PS- TR-2017-0114 TR-2017-0114 ADVANCED ELECTRONICS Ashwani Sharma 21 Jul 2017 Interim Report APPROVED FOR PUBLIC RELEASE...NUMBER Advanced Electronics 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62601F 6. AUTHOR(S) 5d. PROJECT NUMBER 4846 Ashwani Sharma 5e. TASK NUMBER...Approved for public release; distribution is unlimited. (RDMX-17-14919 dtd 20 Mar 2018) 13. SUPPLEMENTARY NOTES 14. ABSTRACT The Space Electronics

The Downshift of Electron Plasma Oscillations in the Electron Foreshock Region.

Science.gov (United States)

1984-10-10

Ii D-Ai50 52 THE DOWNSHIFT OF ELECTRON PLASMA OSCILLATIONS IN THE i/1. ELECTRON FORESHOCK R.. (U) I0MM UNIV 10MM CITY DEPT OF PHYSICS AND ASTRONOMY 5...OSCILLATIONS 0 IN THE ELECTRON FORESHOCK REGION In by S. A. Fuselierl, D. A. Gurnett 1 , Ace NTI 0. and R. J. Fitzenreiter 2 DTI I ,3WERSflY o. 06UNDED ISAI...geleasel Ditibto Unlimited 02 1 16 U. of Iowa 84-21 THE DOWNSHIFT OF ELECTRON PLASMA OSCILLATIONSJ / IN THE ELECTRON FORESHOCK REGION t - by Z I S. A

Electronics engineer's reference book

CERN Document Server

Mazda, F F

1989-01-01

Electronics Engineer's Reference Book, Sixth Edition is a five-part book that begins with a synopsis of mathematical and electrical techniques used in the analysis of electronic systems. Part II covers physical phenomena, such as electricity, light, and radiation, often met with in electronic systems. Part III contains chapters on basic electronic components and materials, the building blocks of any electronic design. Part IV highlights electronic circuit design and instrumentation. The last part shows the application areas of electronics such as radar and computers.

Angular distribution of scattered electron and medium energy electron spectroscopy for metals

International Nuclear Information System (INIS)

Oguri, Takeo; Ishioka, Hisamichi; Fukuda, Hisashi; Irako, Mitsuhiro

1986-01-01

The angular distribution (AD) of scattered electrons produced by medium energy incident electrons (E P = 50 ∼ 300 eV) from polycrystalline Ti, Fe, Ni, Cu and Au were obtained by the angle-resolved medium energy electron spectrometer. The AD of the energy loss peaks are similar figures to AD of the elastically reflected electron peaks. Therefore, the exchanged electrons produced by the knock-on collision between the incident electrons and those of metals without momentum transfer are observed as the energy loss spectra (ELS). This interpretation differs from the inconsequent interpretation by the dielectric theory or the interband transition. The information depth and penetration length are obtained from AD of the Auger electron peaks. The contribution of the surface to spectra is 3 % at the maximum for E P = 50 eV. The true secondary peaks representing the secondary electron emission spectroscopy (SES) are caused by the emissions of the energetic electrons (kT e ≥ 4 eV), and SES is the inversion of ELS. The established fundamental view is that the medium energy electron spectra represent the total bulk density of states. (author)

Wigner-like crystallization of Anderson-localized electron systems with low electron densities

International Nuclear Information System (INIS)

Slutskin, A.A.; Kovtun, H.A.; Pepper, M.

2002-01-01

We consider an electron system under conditions of strong Anderson localization, taking into account interelectron long-range Coulomb repulsion. We establish that at sufficiently low electron densities and sufficiently low temperatures the Coulomb electron interaction brings about ordering of the Anderson-localized electrons into a structure that is close to an ideal (Wigner) crystal lattice, provided the dimension of the system is > 1. This Anderson-Wigner glass (AWG) is a new macroscopic electron state that, on the one hand, is beyond the conventional Fermi glass concept, and on the other hand, qualitatively differs from the known 'plain' Wigner glass (inherent in self-localized electron systems) in that the random slight electron displacements from the ideal crystal sites essentially depend on the electron density. With increasing electron density the AWG is found to turn into the plain Wigner glass or Fermi glass, depending on the width of the random spread of the electron levels. It is shown that the residual disorder of the AWG is characterized by a multi-valley ground-state degeneracy akin to that in a spin glass. Some general features of the AWG are discussed, and a new conduction mechanism of a creep type is predicted

3D Printed structural electronics: embedding and connecting electronic components into freeform electronic devices

NARCIS (Netherlands)

Maalderink, H.H.H.; Bruning, F.B.J.; Schipper, M.M.R. de; Werff, J.J.J. van der; Germs, W.W.C.; Remmers, J.J.C.; Meinders, E.R.

2018-01-01

The need for personalised and smart products drives the development of structural electronics with mass-customisation capability. A number of challenges need to be overcome in order to address the potential of complete free form manufacturing of electronic devices. One key challenge is the

3D Printed structural electronics : embedding and connecting electronic components into freeform electronic devices

NARCIS (Netherlands)

Maalderink, H.H.; Bruning, F.B.J.; de Schipper, M.R.; van der Werff, J.J.; Germs, W.C.; Remmers, J.J.C.; Meinders, E.R.

2018-01-01

The need for personalised and smart products drives the development of structural electronics with mass-customisation capability. A number of challenges need to be overcome in order to address the potential of complete free form manufacturing of electronic devices. One key challenge is the

27 CFR 73.32 - May I electronically sign forms I submit electronically to TTB?

Science.gov (United States)

2010-04-01

... AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) PROCEDURES AND PRACTICES ELECTRONIC SIGNATURES; ELECTRONIC SUBMISSION OF FORMS Electronic Filing of Documents with TTB § 73.32 May I electronically sign forms I submit electronically to TTB? You may electronically sign the electronic form you...

Electron Bifurcation: Thermodynamics and Kinetics of Two-Electron Brokering in Biological Redox Chemistry.

Science.gov (United States)

Zhang, Peng; Yuly, Jonathon L; Lubner, Carolyn E; Mulder, David W; King, Paul W; Peters, John W; Beratan, David N

2017-09-19

How can proteins drive two electrons from a redox active donor onto two acceptors at very different potentials and distances? And how can this transaction be conducted without dissipating very much energy or violating the laws of thermodynamics? Nature appears to have addressed these challenges by coupling thermodynamically uphill and downhill electron transfer reactions, using two-electron donor cofactors that have very different potentials for the removal of the first and second electron. Although electron bifurcation is carried out with near perfection from the standpoint of energy conservation and electron delivery yields, it is a biological energy transduction paradigm that has only come into focus recently. This Account provides an exegesis of the biophysical principles that underpin electron bifurcation. Remarkably, bifurcating electron transfer (ET) proteins typically send one electron uphill and one electron downhill by similar energies, such that the overall reaction is spontaneous, but not profligate. Electron bifurcation in the NADH-dependent reduced ferredoxin: NADP + oxidoreductase I (Nfn) is explored in detail here. Recent experimental progress in understanding the structure and function of Nfn allows us to dissect its workings in the framework of modern ET theory. The first electron that leaves the two-electron donor flavin (L-FAD) executes a positive free energy "uphill" reaction, and the departure of this electron switches on a second thermodynamically spontaneous ET reaction from the flavin along a second pathway that moves electrons in the opposite direction and at a very different potential. The singly reduced ET products formed from the bifurcating flavin are more than two nanometers distant from each other. In Nfn, the second electron to leave the flavin is much more reducing than the first: the potentials are said to be "crossed." The eventually reduced cofactors, NADH and ferredoxin in the case of Nfn, perform crucial downstream redox

Electronic Elections

DEFF Research Database (Denmark)

Schürmann, Carsten

2009-01-01

Electronic voting technology is a two edged sword. It comes with many risks but brings also many benefits. Instead of flat out rejecting the technology as uncontrollably dangerous, we advocate in this paper a different technological angle that renders electronic elections trustworthy beyond...... the usual levels of doubt. We exploit the trust that voters currently have into the democratic process and model our techniques around that observation accordingly. In particular, we propose a technique of trace emitting computations to record the individual steps of an electronic voting machine...... for a posteriori validation on an acceptably small trusted computing base. Our technology enables us to prove that an electronic elections preserves the voter’s intent, assuming that the voting machine and the trace verifier are independent....

Low-dose electron energy-loss spectroscopy using electron counting direct detectors.

Science.gov (United States)

Maigné, Alan; Wolf, Matthias

2018-03-01

Since the development of parallel electron energy loss spectroscopy (EELS), charge-coupled devices (CCDs) have been the default detectors for EELS. With the recent development of electron-counting direct-detection cameras, micrographs can be acquired under very low electron doses at significantly improved signal-to-noise ratio. In spectroscopy, in particular in combination with a monochromator, the signal can be extremely weak and the detection limit is principally defined by noise introduced by the detector. Here we report the use of an electron-counting direct-detection camera for EEL spectroscopy. We studied the oxygen K edge of amorphous ice and obtained a signal noise ratio up to 10 times higher than with a conventional CCD.We report the application of electron counting to record time-resolved EEL spectra of a biological protein embedded in amorphous ice, revealing chemical changes observed in situ while exposed by the electron beam. A change in the fine structure of nitrogen K and the carbon K edges were recorded during irradiation. A concentration of 3 at% nitrogen was detected with a total electron dose of only 1.7 e-/Å2, extending the boundaries of EELS signal detection at low electron doses.

How do electron localization functions describe π-electron delocalization?

Science.gov (United States)

Steinmann, Stephan N; Mo, Yirong; Corminboeuf, Clemence

2011-12-14

Scalar fields provide an intuitive picture of chemical bonding. In particular, the electron localization function (ELF) has proven to be highly valuable in interpreting a broad range of bonding patterns. The discrimination between enhanced or reduced electron (de)localization within cyclic π-conjugated systems remains, however, challenging for ELF. In order to clearly distinguish between the local properties of ten highly and weakly π-(de)localized prototype systems, we compare the ELFs of both the canonical wave functions and electron-localized states (diabatic) with those of two closely related scalar fields: the electron localizability indicator (ELI-D) and the localized orbital locator (LOL). The simplest LOL function distinguishes enhanced from weak π-(de)localization in an insightful and reliable manner. LOL offers the finest contrast between annulenes with 4n/4n + 2 π electrons and their inorganic analogues as well as between hyperconjugated cyclopentadiene derivatives. LOL(π) also gives an appealing and intuitive picture of the π-bond. In contrast, the most popular ELF fails to capture subtle contrasting local electronic properties and suffers from the arbitrariness of the σ/π dissection. The orbital separation of the most recent ELI-D is clear-cut but the interpretations sometime less straightforward in the present context.

Electron shuttles in biotechnology.

Science.gov (United States)

Watanabe, Kazuya; Manefield, Mike; Lee, Matthew; Kouzuma, Atsushi

2009-12-01

Electron-shuttling compounds (electron shuttles [ESs], or redox mediators) are essential components in intracellular electron transfer, while microbes also utilize self-produced and naturally present ESs for extracellular electron transfer. These compounds assist in microbial energy metabolism by facilitating electron transfer between microbes, from electron-donating substances to microbes, and/or from microbes to electron-accepting substances. Artificially supplemented ESs can create new routes of electron flow in the microbial energy metabolism, thereby opening up new possibilities for the application of microbes to biotechnology processes. Typical examples of such processes include halogenated-organics bioremediation, azo-dye decolorization, and microbial fuel cells. Herein we suggest that ESs can be applied widely to create new microbial biotechnology processes.

Treatment of foods with 'soft-electrons' (low-energy electrons)

Energy Technology Data Exchange (ETDEWEB)

Hayashi, Toru [Japan International Research Center for Agricultural Sciences (JIRCAS), Tsukuba, Ibaraki (Japan); Todoriki, Setsuko [National Food Research Institute (NFRI), Tsukuba, Ibaraki (Japan)

2003-02-01

Electrons with energies of 300 keV or lower were defined as soft-electrons'. Soft-electrons can eradicate microorganisms residing on the surface of grains, pulses, spices, dehydrated vegetables, tea leaves and seeds, and reduce their microbial loads to levels lower than 10 CFU/g with little quality deterioration. Soft-electrons can inactivate insect pests infesting grains and pulses and inhibit sprouting of potatoes. (author)

Electron beam collimation with a photon MLC for standard electron treatments

Science.gov (United States)

Mueller, S.; Fix, M. K.; Henzen, D.; Frei, D.; Frauchiger, D.; Loessl, K.; Stampanoni, M. F. M.; Manser, P.

2018-01-01

Standard electron treatments are currently still performed using standard or molded patient-specific cut-outs placed in the electron applicator. Replacing cut-outs and electron applicators with a photon multileaf collimator (pMLC) for electron beam collimation would make standard electron treatments more efficient and would facilitate advanced treatment techniques like modulated electron radiotherapy (MERT) and mixed beam radiotherapy (MBRT). In this work, a multiple source Monte Carlo beam model for pMLC shaped electron beams commissioned at a source-to-surface distance (SSD) of 70 cm is extended for SSDs of up to 100 cm and validated for several Varian treatment units with field sizes typically used for standard electron treatments. Measurements and dose calculations agree generally within 3% of the maximal dose or 2 mm distance to agreement. To evaluate the dosimetric consequences of using pMLC collimated electron beams for standard electron treatments, pMLC-based and cut-out-based treatment plans are created for a left and a right breast boost, a sternum, a testis and a parotid gland case. The treatment plans consist of a single electron field, either alone (1E) or in combination with two 3D conformal tangential photon fields (1E2X). For each case, a pMLC plan with similar treatment plan quality in terms of dose homogeneity to the target and absolute mean dose values to the organs at risk (OARs) compared to a cut-out plan is found. The absolute mean dose to an OAR is slightly increased for pMLC-based compared to cut-out-based 1E plans if the OAR is located laterally close to the target with respect to beam direction, or if a 6 MeV electron beam is used at an extended SSD. In conclusion, treatment plans using cut-out collimation can be replaced by plans of similar treatment plan quality using pMLC collimation with accurately calculated dose distributions.

Technical report of electronics shop characteristics of high speed electronics component, (1)

International Nuclear Information System (INIS)

Watanabe, Shin-ichi; Shiino, Kazuo.

1975-01-01

We must develop electronics circuits for high speed signals. The electronics components of the circuits make use of the special components. This report treats a pulse response of the electronics components (i.e. coaxial cable, connector, resistor, capacitor, diode, transistor) for high speed electronics. The results of this report was already applied constructions of high speed electronics circuits and experimental equipments of the High Energy Physics Division. (auth.)

Fully printable, strain-engineered electronic wrap for customizable soft electronics.

Science.gov (United States)

Byun, Junghwan; Lee, Byeongmoon; Oh, Eunho; Kim, Hyunjong; Kim, Sangwoo; Lee, Seunghwan; Hong, Yongtaek

2017-03-24

Rapid growth of stretchable electronics stimulates broad uses in multidisciplinary fields as well as industrial applications. However, existing technologies are unsuitable for implementing versatile applications involving adaptable system design and functions in a cost/time-effective way because of vacuum-conditioned, lithographically-predefined processes. Here, we present a methodology for a fully printable, strain-engineered electronic wrap as a universal strategy which makes it more feasible to implement various stretchable electronic systems with customizable layouts and functions. The key aspects involve inkjet-printed rigid island (PRI)-based stretchable platform technology and corresponding printing-based automated electronic functionalization methodology, the combination of which provides fully printed, customized layouts of stretchable electronic systems with simplified process. Specifically, well-controlled contact line pinning effect of printed polymer solution enables the formation of PRIs with tunable thickness; and surface strain analysis on those PRIs leads to the optimized stability and device-to-island fill factor of strain-engineered electronic wraps. Moreover, core techniques of image-based automated pinpointing, surface-mountable device based electronic functionalizing, and one-step interconnection networking of PRIs enable customized circuit design and adaptable functionalities. To exhibit the universality of our approach, multiple types of practical applications ranging from self-computable digital logics to display and sensor system are demonstrated on skin in a customized form.

Fully printable, strain-engineered electronic wrap for customizable soft electronics

Science.gov (United States)

Byun, Junghwan; Lee, Byeongmoon; Oh, Eunho; Kim, Hyunjong; Kim, Sangwoo; Lee, Seunghwan; Hong, Yongtaek

2017-03-01

Rapid growth of stretchable electronics stimulates broad uses in multidisciplinary fields as well as industrial applications. However, existing technologies are unsuitable for implementing versatile applications involving adaptable system design and functions in a cost/time-effective way because of vacuum-conditioned, lithographically-predefined processes. Here, we present a methodology for a fully printable, strain-engineered electronic wrap as a universal strategy which makes it more feasible to implement various stretchable electronic systems with customizable layouts and functions. The key aspects involve inkjet-printed rigid island (PRI)-based stretchable platform technology and corresponding printing-based automated electronic functionalization methodology, the combination of which provides fully printed, customized layouts of stretchable electronic systems with simplified process. Specifically, well-controlled contact line pinning effect of printed polymer solution enables the formation of PRIs with tunable thickness; and surface strain analysis on those PRIs leads to the optimized stability and device-to-island fill factor of strain-engineered electronic wraps. Moreover, core techniques of image-based automated pinpointing, surface-mountable device based electronic functionalizing, and one-step interconnection networking of PRIs enable customized circuit design and adaptable functionalities. To exhibit the universality of our approach, multiple types of practical applications ranging from self-computable digital logics to display and sensor system are demonstrated on skin in a customized form.

Electrons in Nanostructures

DEFF Research Database (Denmark)

Flindt, Christian

2007-01-01

in the possibilities o®ered by the quantum mechanical behavior of electrons when it comes to informa- tion processing. This branch of research is also concerned with fundamental questions in physics. Besides an introduction to the above-mentioned subjects, the thesis con- tains a number of contributions to the ¯elds...... of coherent electron manip- ulation and the statistical description of electron transport through nano- devices. The physics of the electrons are described with a combination of numerical methods, developed and applied in the thesis, and more analytical approaches, which are also discussed. The thesis......-based communication. The statistical description of electron transport through nanostructures is based on rate equations, and the primary contribution of the thesis in that respect is the development of a method that allows for the calculation of the distribution of electrons passing through a device. The method...

Identification of electrons in the ZEUS hadron-electron separator with neural networks

International Nuclear Information System (INIS)

Carstens, J.O.

1994-10-01

An electron finder for the ZEUS experiment was constructed, which is specialized to electrons in the momentum range 0.5 to 3.0 GeV/c. For the first time this electron finder connects the informations of the calorimeter with those of the hadron-electron separator (HES). For this purpose the electron finder was equipped with a neural network. The electron finder reached on a data set of photoproduction events with conversion electrons an efficiency and discriminance of E=(62.9±2.2±0.6)% and D=(91.4±0.8±1.1)%. From these two quantities it can be calculated that the electron finder the ratio electrons to background increases by the factoe E/(1-D)=7.4 (Signal amplification). For the comparison: A neural net, to which only calorimeter informations have been made available, reached at the same efficiency a signal amplification of 2.4. A simple cut in the variable HES-signal reaches a signal amplification of 6.3. Hints were given, how training data sets with electrons and hadrons of higher energies can be obtained. With such data sets the working range of the electron finder can be without problems extended to higher momenta. As preparation for the construction of the electron finder an introduction to the foundations of the mathematics and the application of neural networks was given. By means of examples different methods for the convergence improvement have been tested. Numerous representations mediate illustrative imaginations on the mathematical process of the training of neural networks

Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory

Energy Technology Data Exchange (ETDEWEB)

Weathersby, S. P.; Brown, G.; Chase, T. F.; Coffee, R.; Corbett, J.; Eichner, J. P.; Frisch, J. C.; Fry, A. R.; Gühr, M.; Hartmann, N.; Hast, C.; Hettel, R.; Jobe, R. K.; Jongewaard, E. N.; Lewandowski, J. R.; Li, R. K., E-mail: lrk@slac.stanford.edu; Lindenberg, A. M.; Makasyuk, I.; May, J. E.; McCormick, D. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); and others

2015-07-15

Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.

Secondary electron emission anisotropy in oblique incidence of electrons on the (100) Mo

International Nuclear Information System (INIS)

Gomoyunova, M.V.; Zaslavskij, S.L.; Pronin, I.I.

1978-01-01

Studied was the influence of azimuthal plane of incidence of primary particles with energies of 0.5-1.5 keV on the secondary electron emission of the (100) Mo face at the constant polar angle of 45 deg. The measurements were carried out in vacuum of (2-4)x10 -10 torr by modulation technique. It is shown that anisotropy is peculiar to the secondary electron emission of all energies. The anisotropy of emission has two maxima; the high-energy maximum connected with reflected primary electrons and situated near the elastically reflected electrons and weaker pronounced the low-energy one which is found at energies of 100-200 eV and is conditioned by truly secondary electrons. It is shown that the anisotropy, characterizing secondary electrons responsible for the appearance of structure in spectrum, particularly the Auger electrons and the electrons suffering ionizing energy losses, exceeds the anisotropy of continuous spectrum electrons possessing the same energy. The electron diffraction dynamic theory, based on the conception of the united wave field of electrons, has been used to explain the regularities stated

Kinetic and electron-electron energies for convex sums of ground state densities with degeneracies and fractional electron number

Energy Technology Data Exchange (ETDEWEB)

Levy, Mel, E-mail: ayers@mcmaster.ca, E-mail: mlevy@tulane.edu [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Department of Physics, North Carolina A and T State University, Greensboro, North Carolina 27411 (United States); Department of Chemistry, Tulane University, New Orleans, Louisiana 70118 (United States); Anderson, James S. M.; Zadeh, Farnaz Heidar; Ayers, Paul W., E-mail: ayers@mcmaster.ca, E-mail: mlevy@tulane.edu [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario (Canada)

2014-05-14

Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.

Embracing Electronic Publishing.

Science.gov (United States)

Wills, Gordon

1996-01-01

Electronic publishing is the grandest revolution in the capture and dissemination of academic and professional knowledge since Caxton developed the printing press. This article examines electronic publishing, describes different electronic publishing scenarios (authors' cooperative, consolidator/retailer/agent oligopsony, publisher oligopoly), and…

Peptide π-Electron Conjugates: Organic Electronics for Biology?

Science.gov (United States)

Ardoña, Herdeline Ann M; Tovar, John D

2015-12-16

Highly ordered arrays of π-conjugated molecules are often viewed as a prerequisite for effective charge-transporting materials. Studies involving these materials have traditionally focused on organic electronic devices, with more recent emphasis on biological systems. In order to facilitate the transition to biological environments, biomolecules that can promote hierarchical ordering and water solubility are often covalently appended to the π-electron unit. This review highlights recent work on π-conjugated systems bound to peptide moieties that exhibit self-assembly and aims to provide an overview on the development and emerging applications of peptide-based supramolecular π-electron systems.

Modified Sternglass theory for the emission of secondary electrons by fast-electron impact

International Nuclear Information System (INIS)

Suszcynsky, D.M.; Borovsky, J.E.

1992-01-01

The Sternglass theory [Sternglass, Phys. Rev. 108, 1 (1957)] for fast-ion-induced secondary-electron emission from metals has been modified to predict the secondary-electron yield from metals impacted by energetic (several keV to about 200 keV) electrons. The primary modification of the theory accounts for the contribution of the backscattered electrons to the production of secondary electrons based on a knowledge of the backscattered-electron energy distribution. The modified theory is in reasonable agreement with recent experimental data from gold targets in the 6--30-keV electron energy range

Calculation of the electron trajectory for 200 kV self-shielded electron accelerator

International Nuclear Information System (INIS)

Wang Shuiqing

2000-01-01

In order to calculate the electron trajectory of 200 kV self-shielded electron accelerator, the electric field is calculated with a TRAJ program. In this program, following electron track mash points one by one, the electron beam trajectories are calculated. Knowing the effect of grid voltage on electron optics and gaining grid voltage focusing effect in the various energy grades, the authors have gained scientific basis for adjusting grid voltage, and also accumulated a wealth of experience for designing self-shielded electron accelerator or electron curtain in future

Electronic inventions and discoveries electronics from its earliest beginnings to the present day

CERN Document Server

Dummer, G W A

1983-01-01

Electronic Inventions and Discoveries: Electronics from Its Earliest Beginnings to the Present Day provides a summary of the development of the whole field of electronics. Organized into 13 chapters, the book covers and reviews the history of electronics as a whole and its aspects. The opening chapter covers the beginnings of electronics, while the next chapter discusses the development of components, transistors, and integrated circuits. The third chapter tackles the expansion of electronics and its effects on industry. The succeeding chapters discuss the history of the aspects of electronics

Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

Science.gov (United States)

Priebe, Katharina E.; Rathje, Christopher; Yalunin, Sergey V.; Hohage, Thorsten; Feist, Armin; Schäfer, Sascha; Ropers, Claus

2017-12-01

Ultrafast electron and X-ray imaging and spectroscopy are the basis for an ongoing revolution in the understanding of dynamical atomic-scale processes in matter. The underlying technology relies heavily on laser science for the generation and characterization of ever shorter pulses. Recent findings suggest that ultrafast electron microscopy with attosecond-structured wavefunctions may be feasible. However, such future technologies call for means to both prepare and fully analyse the corresponding free-electron quantum states. Here, we introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond electron pulse trains. Phase-locked optical fields coherently control the electron wavefunction along the beam direction. We establish a new variant of quantum state tomography—`SQUIRRELS'—for free-electron ensembles. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron-matter entanglement and new forms of ultrafast electron microscopy down to the attosecond regime.

Digital electronics

CERN Document Server

Morris, John

2013-01-01

An essential companion to John C Morris's 'Analogue Electronics', this clear and accessible text is designed for electronics students, teachers and enthusiasts who already have a basic understanding of electronics, and who wish to develop their knowledge of digital techniques and applications. Employing a discovery-based approach, the author covers fundamental theory before going on to develop an appreciation of logic networks, integrated circuit applications and analogue-digital conversion. A section on digital fault finding and useful ic data sheets completes th

The magnetized electron-acoustic instability driven by a warm, field-aligned electron beam

International Nuclear Information System (INIS)

Sooklal, A.; Mace, R.L.

2004-01-01

The electron-acoustic instability in a magnetized plasma having three electron components, one of which is a field-aligned beam of intermediate temperature, is investigated. When the plasma frequency of the cool electrons exceeds the electron gyrofrequency, the electron-acoustic instability 'bifurcates' at sufficiently large propagation angles with respect to the magnetic field to yield an obliquely propagating, low-frequency electron-acoustic instability and a higher frequency cyclotron-sound instability. Each of these instabilities retains certain wave features of its progenitor, the quasiparallel electron-acoustic instability, but displays also new magnetic qualities through its dependence on the electron gyrofrequency. The obliquely propagating electron-acoustic instability requires a lower threshold beam speed for its excitation than does the cyclotron-sound instability, and for low to intermediate beam speeds has the higher maximum growth rate. When the plasma is sufficiently strongly magnetized that the plasma frequency of the cool electrons is less than the electron gyrofrequency, the only instability in the electron-acoustic frequency range is the strongly magnetized electron-acoustic instability. Its growth rate and real frequency exhibit a monotonic decrease with wave propagation angle and it grows at small to intermediate wave numbers where its parallel phase speed is approximately constant. The relevance of the results to the interpretation of cusp auroral hiss and auroral broadband electrostatic noise is briefly discussed

Starting electronics all you need to get a grounding in practical electronics

CERN Document Server

Brindley, Keith

2013-01-01

Starting Electronics is a nine-chapter introductory text to electronics based on feature articles previously published as magazine articles. The opening chapter provides an overview of the fundamentals of electronics. The succeeding chapters present details of some easy-to-do experiments and the current and voltage measurement. The remaining chapters cover some basic components of electronics, including capacitor, integrated circuit, oscillator, filter, diodes, and transistors. This book will prove useful to electronic constructors and students.

Single Electron Tunneling

International Nuclear Information System (INIS)

Ruggiero, Steven T.

2005-01-01

Financial support for this project has led to advances in the science of single-electron phenomena. Our group reported the first observation of the so-called ''Coulomb Staircase'', which was produced by tunneling into ultra-small metal particles. This work showed well-defined tunneling voltage steps of width e/C and height e/RC, demonstrating tunneling quantized on the single-electron level. This work was published in a now well-cited Physical Review Letter. Single-electron physics is now a major sub-field of condensed-matter physics, and fundamental work in the area continues to be conducted by tunneling in ultra-small metal particles. In addition, there are now single-electron transistors that add a controlling gate to modulate the charge on ultra-small photolithographically defined capacitive elements. Single-electron transistors are now at the heart of at least one experimental quantum-computer element, and single-electron transistor pumps may soon be used to define fundamental quantities such as the farad (capacitance) and the ampere (current). Novel computer technology based on single-electron quantum dots is also being developed. In related work, our group played the leading role in the explanation of experimental results observed during the initial phases of tunneling experiments with the high-temperature superconductors. When so-called ''multiple-gap'' tunneling was reported, the phenomenon was correctly identified by our group as single-electron tunneling in small grains in the material. The main focus throughout this project has been to explore single electron phenomena both in traditional tunneling formats of the type metal/insulator/particles/insulator/metal and using scanning tunneling microscopy to probe few-particle systems. This has been done under varying conditions of temperature, applied magnetic field, and with different materials systems. These have included metals, semi-metals, and superconductors. Amongst a number of results, we have

Electron transfer from nucleobase electron adducts to 5-bromouracil. Is guanine an ultimate sink for the electron in irradiated DNA?

International Nuclear Information System (INIS)

Nese, C.; Yuan, Z.; Schuchmann, M.N.; Sonntag, C. von

1992-01-01

Electron transfer to 5-bromouracil (5-BrU) from nucleobase (N) electron adducts (and their protonated forms) has been studied by product analysis and pulse radiolysis. When an electron is transferred to 5-BrU, the ensuing 5-BrU radical anion rapidly loses a bromide ion; the uracilyl radical thus formed reacts with added t-butanol, yielding uracil. From the uracil yields measured as the function of [N]/[5-BrU] after γ-radiolysis of Ar-saturated solutions it is concluded that thymine and adenine electron adducts and their heteroatom-protonated forms transfer electrons quantitatively to 5-BrU. The data raise the question whether in DNA the guanine moiety may act as the ultimate sink of the electron in competition with other processes such as protonation at C(6) of the thymine electron adduct. (Author)

Evaluation of skin sensitivity in dogs bearing allergic dermatitis to standardized allergenic extract of house dust and storage mites Avaliação da sensibilidade de cães com dermatite alérgica a extratos padronizados de ácaros da poeira domiciliar

Directory of Open Access Journals (Sweden)

Victor E.S. Cunha

2007-08-01

Full Text Available The objective of the study was to evaluate whether allergenic extracts of five house dust and storage mite species standardized for humans might be used for the diagnosis of canine atopic dermatitis (CAD. Extracts of Dermatophagoides pteronyssinus (Pyroglyphidae, D. farinae (Pyroglyphidae, Blomia tropicalis (Glycyphagidae, Lepidoglyphus destructor (Glycyphagidae and Tyrophagus putrescentiae (Acaridae were evaluated by intradermal testing in 20 healthy dogs (control and 25 dogs with allergic dermatitis. A significant difference in the response was observed between the two groups (pO presente trabalho teve como objetivo avaliar se extratos alergênicos de cinco espécies de ácaros da poeira domiciliar e produtos armazenados, padronizados para humanos, podem ser utilizados no diagnóstico da dermatite atópica canina. Extratos de Dermatophagoides pteronyssinus (Pyroglyphidae, D. farinae (Pyroglyphidae, Blomia tropicalis (Glycyphagidae, Lepidoglyphus destructor (Glycyphagidae e Tyrophagus putrescentiae (Acaridae foram avaliados através de testes intradérmicos em 45 cães, dos quais 20 normais e 25 com dermatite alérgica. Uma diferença significativa foi observada no padrão de respostas obtidas dos dois grupos (p<0.05. Apenas um animal (5% do grupo controle reagiu ao teste cutâneo, enquanto que no grupo dos alérgicos 14 cães (56% apresentaram pelo menos uma reação positiva (odds ratio = 24.2. As maiores freqüências de reações positivas observadas no grupo dos alérgicos foram aos extratos de T. putres-centiae ou L. destructor, cada um induzindo reações em 10(40% cães. Os extratos de D. farinae, D. pteronyssinus e B. tropicalis foram responsáveis por reações positivas em 7(28%, 3(12% e 3(12% cães, respectivamente. Os extratos padronizados para humanos avaliados no presente estudo podem ser utilizados como complemento no diagnóstico da doença, assim como na seleção de alérgenos para a imunoterapia alérgeno-específica.

Extreme environment electronics

CERN Document Server

Cressler, John D

2012-01-01

Unfriendly to conventional electronic devices, circuits, and systems, extreme environments represent a serious challenge to designers and mission architects. The first truly comprehensive guide to this specialized field, Extreme Environment Electronics explains the essential aspects of designing and using devices, circuits, and electronic systems intended to operate in extreme environments, including across wide temperature ranges and in radiation-intense scenarios such as space. The Definitive Guide to Extreme Environment Electronics Featuring contributions by some of the world's foremost exp

Electron-vibrational transitions under molecular ions collisions with slow electrons

International Nuclear Information System (INIS)

Andreev, E.A.

1993-01-01

A concept of a multichannel quantum defect is considered and basic theoretic ratios of inelastic collisional processes with the participation of molecular positive ions and slow electrons playing an important role both in atmospheric and laboratory plasma, are presented. The problem of scattering channel number limitation with the provision of S-matrix unique character is considered. Different models of electron rotation-vibrational connection under collision of two-atom molecular ions with slow electrons are analysed. Taking N 2 + as an example, a high efficiency of transitions between different electron states of a molecular ion is shown. 73 refs., 9 figs., 1 tab

Electron: Cluster interactions

International Nuclear Information System (INIS)

Scheidemann, A.A.; Knight, W.D.

1994-02-01

Beam depletion spectroscopy has been used to measure absolute total inelastic electron-sodium cluster collision cross sections in the energy range from E ∼ 0.1 to E ∼ 6 eV. The investigation focused on the closed shell clusters Na 8 , Na 20 , Na 40 . The measured cross sections show an increase for the lowest collision energies where electron attachment is the primary scattering channel. The electron attachment cross section can be understood in terms of Langevin scattering, connecting this measurement with the polarizability of the cluster. For energies above the dissociation energy the measured electron-cluster cross section is energy independent, thus defining an electron-cluster interaction range. This interaction range increases with the cluster size

Role of electron-electron scattering on spin transport in single layer graphene

Directory of Open Access Journals (Sweden)

Bahniman Ghosh

2014-01-01

Full Text Available In this work, the effect of electron-electron scattering on spin transport in single layer graphene is studied using semi-classical Monte Carlo simulation. The D’yakonov-P’erel mechanism is considered for spin relaxation. It is found that electron-electron scattering causes spin relaxation length to decrease by 35% at 300 K. The reason for this decrease in spin relaxation length is that the ensemble spin is modified upon an e-e collision and also e-e scattering rate is greater than phonon scattering rate at room temperature, which causes change in spin relaxation profile due to electron-electron scattering.

ELECTRONIC SIGNATURES

African Journals Online (AJOL)

10332324

"[to] promote the understanding and, acceptance of and growth in the number of electronic transactions .... Chapter III of the ECT Act is based on the UNCITRAL Model Law on Electronic. Commerce ... Communications Technology Law 146. 22.

Starting electronics

CERN Document Server

Brindley, Keith

2005-01-01

Starting Electronics is unrivalled as a highly practical introduction for hobbyists, students and technicians. Keith Brindley introduces readers to the functions of the main component types, their uses, and the basic principles of building and designing electronic circuits. Breadboard layouts make this very much a ready-to-run book for the experimenter; and the use of multimeter, but not oscilloscopes, puts this practical exploration of electronics within reach of every home enthusiast's pocket. The third edition has kept the simplicity and clarity of the original. New material

Stretchable electronics

CERN Document Server

Someya, Takao

2012-01-01

With its comprehensive coverage this handbook and ready reference brings together some of the most outstanding scientists in the field to lay down the undisputed knowledge on how to make electronics stretchable.As such, it focuses on gathering and evaluating the materials, designs, models and technologies that enable the fabrication of fully elastic electronic devices which can sustain high strain. Furthermore, it provides a review of those specific applications that directly benefit from highly compliant electronics, including transistors, photonic devices and sensors. In addition to stre

Coherent electron cooling

Energy Technology Data Exchange (ETDEWEB)

Litvinenko,V.

2009-05-04

Cooling intense high-energy hadron beams remains a major challenge in modern accelerator physics. Synchrotron radiation is still too feeble, while the efficiency of two other cooling methods, stochastic and electron, falls rapidly either at high bunch intensities (i.e. stochastic of protons) or at high energies (e-cooling). In this talk a specific scheme of a unique cooling technique, Coherent Electron Cooling, will be discussed. The idea of coherent electron cooling using electron beam instabilities was suggested by Derbenev in the early 1980s, but the scheme presented in this talk, with cooling times under an hour for 7 TeV protons in the LHC, would be possible only with present-day accelerator technology. This talk will discuss the principles and the main limitations of the Coherent Electron Cooling process. The talk will describe the main system components, based on a high-gain free electron laser driven by an energy recovery linac, and will present some numerical examples for ions and protons in RHIC and the LHC and for electron-hadron options for these colliders. BNL plans a demonstration of the idea in the near future.

Electronics pocket book

CERN Document Server

Parr, E A

1981-01-01

Electronics Pocket Book, Fourth Edition is a nonmathematical presentation of the many varied topics covered by electronics. The book tackles electron physics, electronic components (i.e. resistors, capacitors, and conductors), integrated circuits, and the principles of a.c. and d.c. amplifiers. The text also discusses oscillators, digital circuits, digital computers, and optoelectronics (i.e., sensors, emitters, and devices that utilize light). Communications (such as line and radio communications, transmitters, receivers, and digital techniques); the principles and examples of servosystems; a

Sticker electronics

KAUST Repository

Hussain, Muhammad Mustafa; Torres Sevilla, Galo Andres; Diaz Cordero, Marlon Steven

2017-01-01

Electronic stickers may be manufactured on flexible substrates (110, 120, 130) as layers and packaged together. The package may then have an adhesive applied to one side to provide capability for sticking the electronic devices to surfaces

Electronics for LHC Experiments

Energy Technology Data Exchange (ETDEWEB)

NONE

2004-07-01

This document gathers the abstracts of most presentations made at this workshop on electronics for the large hadron collider (LHC) experiments. The presentations were arranged into 6 sessions: 1) electronics for tracker, 2) trigger electronics, 3) detector control systems, 4) data acquisition, 5) electronics for calorimeters and electronics for muons, and 6) links, power systems, grounding and shielding, testing and quality assurance.

Electronics for LHC Experiments

International Nuclear Information System (INIS)

2004-01-01

This document gathers the abstracts of most presentations made at this workshop on electronics for the large hadron collider (LHC) experiments. The presentations were arranged into 6 sessions: 1) electronics for tracker, 2) trigger electronics, 3) detector control systems, 4) data acquisition, 5) electronics for calorimeters and electronics for muons, and 6) links, power systems, grounding and shielding, testing and quality assurance

Electron Bernstein wave electron temperature profile diagnostic (invited)

International Nuclear Information System (INIS)

Taylor, G.; Efthimion, P.; Jones, B.; Munsat, T.; Spaleta, J.; Hosea, J.; Kaita, R.; Majeski, R.; Menard, J.

2001-01-01

Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either ''overdense,'' operating at high density relative to the magnetic field (e.g., ω pe >>Omega ce in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition (τ>2). Electron Bernstein waves (EBWs) are electrostatic waves that can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers as a result of their large k perp . In this article we report on measurements of EBW emission on the CDX-U spherical torus, where B 0 ∼2kG, e >∼10 13 cm -3 and T e ∼10--200eV. Results are presented for electromagnetic measurements of EBW emission, mode converted near the plasma edge. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multipoint Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be ≤T e and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe and a 140 GHz interferometer were employed to measure changes in the edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where ω pe >>Omega ce

Electron energy distribution from intense electron beams in the upper mesosphere and lower thermosphere

International Nuclear Information System (INIS)

Martinez-Sanchez, M.; Cheng, Wai; Dvore, D.; Zahniser, M.S.

1992-01-01

A model was developed to calculate the electron energy spectrum created by an electron beam in the upper atmosphere. A significant feature of the model is the inclusion of the effects of electron-electron collisions which are important at high beam intensity when the ratio of the electron to ambient gas density is high. Comparing the calculated results for a 2.6-kV, 20-A beam at 110-km altitude from models with and without the electron-electron collision term, the electron-electron collisions have the effect of smoothing out the electron spectrum in the low-energy region ( 2 and O 2 are filled in, resulting in an increase in the calculated production rate of these species compared with model calculations that neglect this effect

Interaction of electrons with light metal hydrides in the transmission electron microscope.

Science.gov (United States)

Wang, Yongming; Wakasugi, Takenobu; Isobe, Shigehito; Hashimoto, Naoyuki; Ohnuki, Somei

2014-12-01

Transmission electron microscope (TEM) observation of light metal hydrides is complicated by the instability of these materials under electron irradiation. In this study, the electron kinetic energy dependences of the interactions of incident electrons with lithium, sodium and magnesium hydrides, as well as the constituting element effect on the interactions, were theoretically discussed, and electron irradiation damage to these hydrides was examined using in situ TEM. The results indicate that high incident electron kinetic energy helps alleviate the irradiation damage resulting from inelastic or elastic scattering of the incident electrons in the TEM. Therefore, observations and characterizations of these materials would benefit from increased, instead decreased, TEM operating voltage. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Sustainable Management of Electronics

Science.gov (United States)

To provide information on EPAs strategy for electronics stewardship, certified electronics recyclers and the Challenge; as well as where to donate unwanted electronics, how to calculate benefits, and what's going on with electronics mgmt in their states.

Electron acoustic solitary waves in a magnetized plasma with nonthermal electrons and an electron beam

Energy Technology Data Exchange (ETDEWEB)

Singh, S. V., E-mail: satyavir@iigs.iigm.res.in; Lakhina, G. S., E-mail: lakhina@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai (India); University of the Western Cape, Belville (South Africa); Devanandhan, S., E-mail: devanandhan@gmail.com [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai (India); Bharuthram, R., E-mail: rbharuthram@uwc.ac.za [University of the Western Cape, Belville (South Africa)

2016-08-15

A theoretical investigation is carried out to study the obliquely propagating electron acoustic solitary waves having nonthermal hot electrons, cold and beam electrons, and ions in a magnetized plasma. We have employed reductive perturbation theory to derive the Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation describing the nonlinear evolution of these waves. The two-dimensional plane wave solution of KdV-ZK equation is analyzed to study the effects of nonthermal and beam electrons on the characteristics of the solitons. Theoretical results predict negative potential solitary structures. We emphasize that the inclusion of finite temperature effects reduces the soliton amplitudes and the width of the solitons increases by an increase in the obliquity of the wave propagation. The numerical analysis is presented for the parameters corresponding to the observations of “burst a” event by Viking satellite on the auroral field lines.

Impulse approximation treatment of electron-electron excitation and ionization in energetic ion-atom collisions

International Nuclear Information System (INIS)

Zouros, T.J.M.; Lee, D.H.; Sanders, J.M.; Richard, P.

1993-01-01

The effect of electron-electron interactions between projectile and target electrons observed in recent measurements of projectile K-shell excitation and ionization using 0 projectile Auger electron spectroscopy are analysed within the framework of the impulse approximation (IA). The IA formulation is seen to give a good account of the threshold behavior of both ionization and excitation, while providing a remarkably simple intuitive picture of such electron-electron interactions in ion-atom collisions in general. Thus, the applicability of the IA treatment is extended to cover most known processes involving such interactions including resonance transfer excitation, binary encounter electron production, electron-electron excitation and ionization. (orig.)

Printed Electronics

Science.gov (United States)

Wade, Jessica; Hollis, Joseph Razzell; Wood, Sebastian

2018-04-01

The combination of printing technology with manufacturing electronic devices enables a new paradigm of printable electronics, where 'smart' functionality can be readily incorporated into almost any product at low cost. Over recent decades, rapid progress has been made in this field, which is now emerging into the industrial andcommercial realm. However, successful development and commercialisation on a large scale presents some significant technical challenges. For fully-printable electronic systems, all the component parts must be deposited from solutions (inks), requiring the development of new inorganic, organic and hybrid materials.A variety of traditional printing techniques are being explored and adapted forprinting these new materials in ways that result in the best performing electronicdevices. Whilst printed electronics research has initially focused on traditional typesof electronic device such as light-emitting diodes, transistors, and photovoltaics, it is increasingly apparent that a much wider range of applications can be realised. The soft and stretchable nature of printable materials makes them perfect candidates forbioelectronics, resulting in a wealth of research looking at biocompatible printable inks and biosensors. Regardless of application, the properties of printed electronicmaterials depend on the chemical structures, processing conditions, device architecture,and operational conditions, the complex inter-relationships of which aredriving ongoing research. We focus on three particular 'hot topics', where attention is currently focused: novel materials, characterisation techniques, and device stability. With progress advancing very rapidly, printed electronics is expected to grow over the next decade into a key technology with an enormous economic and social impact.

Engineered phages for electronics.

Science.gov (United States)

Cui, Yue

2016-11-15

Phages are traditionally widely studied in biology and chemistry. In recent years, engineered phages have attracted significant attentions for functionalization or construction of electronic devices, due to their specific binding, catalytic, nucleating or electronic properties. To apply the engineered phages in electronics, these are a number of interesting questions: how to engineer phages for electronics? How are the engineered phages characterized? How to assemble materials with engineered phages? How are the engineered phages micro or nanopatterned? What are the strategies to construct electronics devices with engineered phages? This review will highlight the early attempts to address these questions and explore the fundamental and practical aspects of engineered phages in electronics, including the approaches for selection or expression of specific peptides on phage coat proteins, characterization of engineered phages in electronics, assembly of electronic materials, patterning of engineered phages, and construction of electronic devices. It provides the methodologies and opens up ex-cit-ing op-por-tu-ni-ties for the development of a variety of new electronic materials and devices based on engineered phages for future applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field

DEFF Research Database (Denmark)

Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.

2015-01-01

We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...... of compressible strips in the potential profile and the electron density. We numerically solve the Dirac equations describing the electron dynamics in quantum dots, and we demonstrate that compressible strips lead to the appearance of plateaus in the electron energies as a function of the magnetic field. Finally...

Tunable Electron-Electron Interactions in LaAlO_{3}/SrTiO_{3} Nanostructures

Directory of Open Access Journals (Sweden)

Guanglei Cheng

2016-12-01

Full Text Available The interface between the two complex oxides LaAlO_{3} and SrTiO_{3} has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of “sketched” quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a single-electron (Andreev bound state tunneling regime where the interactions become repulsive. The electron-electron interaction sign change is associated with a Lifshitz transition where the d_{xz} and d_{yz} bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.

Polymer electronics

CERN Document Server

Geoghegan, Mark

2013-01-01

Polymer electronics is the science behind many important new developments in technology, such as the flexible electronic display (e-ink) and many new developments in transistor technology. Solar cells, light-emitting diodes, and transistors are all areas where plastic electronics is likely to, or is already having, a serious impact on our daily lives. With polymer transistors and light-emitting diodes now being commercialised, there is a clear need for a pedagogic text thatdiscusses the subject in a clear and concise fashion suitable for senior undergraduate and graduate students. The content

Electron optics

CERN Document Server

Grivet, Pierre; Bertein, F; Castaing, R; Gauzit, M; Septier, Albert L

1972-01-01

Electron Optics, Second English Edition, Part I: Optics is a 10-chapter book that begins by elucidating the fundamental features and basic techniques of electron optics, as well as the distribution of potential and field in electrostatic lenses. This book then explains the field distribution in magnetic lenses; the optical properties of electrostatic and magnetic lenses; and the similarities and differences between glass optics and electron optics. Subsequent chapters focus on lens defects; some electrostatic lenses and triode guns; and magnetic lens models. The strong focusing lenses and pris

Development of a secondary electron energy analyzer for a transmission electron microscope.

Science.gov (United States)

Magara, Hideyuki; Tomita, Takeshi; Kondo, Yukihito; Sato, Takafumi; Akase, Zentaro; Shindo, Daisuke

2018-04-01

A secondary electron (SE) energy analyzer was developed for a transmission electron microscope. The analyzer comprises a microchannel plate (MCP) for detecting electrons, a coil for collecting SEs emitted from the specimen, a tube for reducing the number of backscattered electrons incident on the MCP, and a retarding mesh for selecting the energy of SEs incident on the MCP. The detection of the SEs associated with charging phenomena around a charged specimen was attempted by performing electron holography and SE spectroscopy using the energy analyzer. The results suggest that it is possible to obtain the energy spectra of SEs using the analyzer and the charging states of a specimen by electron holography simultaneously.

Electron beam welding

International Nuclear Information System (INIS)

Schwartz, M.M.

1974-01-01

Electron-beam equipment is considered along with fixed and mobile electron-beam guns, questions of weld environment, medium and nonvacuum welding, weld-joint designs, tooling, the economics of electron-beam job shops, aspects of safety, quality assurance, and repair. The application of the process in the case of individual materials is discussed, giving attention to aluminum, beryllium, copper, niobium, magnesium, molybdenum, tantalum, titanium, metal alloys, superalloys, and various types of steel. Mechanical-property test results are examined along with the areas of application of electron-beam welding

Electronic signal conditioning

CERN Document Server

NEWBY, BRUCE

1994-01-01

At technician level, brief references to signal conditioning crop up in a fragmented way in various textbooks, but there has been no single textbook, until now!More advanced texts do exist but they are more mathematical and presuppose a higher level of understanding of electronics and statistics. Electronic Signal Conditioning is designed for HNC/D students and City & Guilds Electronics Servicing 2240 Parts 2 & 3. It will also be useful for BTEC National, Advanced GNVQ, A-level electronics and introductory courses at degree level.

Vibrational and electronic excitation of hexatriacontane thin films by low energy electron impact

International Nuclear Information System (INIS)

Vilar, M.R.; Schott, M.; Pfluger, P.

1990-01-01

Thin polycrystalline films of hexatriacontane (HTC) were irradiated with low energy (E=0.5--15 eV) electrons, and off-specular backscattered electron spectra were measured. Below E∼7 eV, single and multiple vibrational excitations only are observed, which relax the electrons down to the bottom of the HTC conduction band. Due to the negative electron affinity of HTC, thermal electrons are emitted into vacuum. Structure in the backscattered electron current at kinetic energies about 1.5 and 4 eV are associated to conduction band density of states. Above E∼7 eV, the dominant losses correspond to electronic excitations, excitons, or above a threshold (energy of the electron inside the HTC film) at 9.2±0.1 eV, electron--hole pair generation. The latter process is very efficient and reaches a yield of the order of one ∼11 eV. Evidence for chemical reaction above E∼4 eV is observed

Characterisation of 100 kW electron beam melting gun and its adaptation as electron gun for high power DC electron accelerators

International Nuclear Information System (INIS)

Banerjee, Srutarshi; Bhattacharjee, Dhruva; Waghmare, Abhay; Tiwari, Rajnish; Bakhtsingh, R.I.; Dasgupta, K.; Gupta, Sachin; Prakash, Baibhaw; Jha, M.N.

2015-01-01

The paper deals with the characterization of the 100 kW electron beam melting gun for its adaptation in high power DC Electron Accelerators. The indigenously designed electron beam melting system at BARC is chosen for characterization. It comprises of electron gun as source of electrons, two electromagnetic focusing lenses viz. upper focusing lens and lower focusing lens for beam focusing, intermediate beam aperture for vacuum decoupling between gun region and melt zone, deflection and oscillation lens for maneuvering the beam on the melt charge and water cooled crucible that acts as a beam dump. In this system, the electron gun is designed for 40 kV and 100 kW corresponding to a maximum beam current of 2.5 A. The electron gun uses directly heated spiral tungsten filament. The operating temperature of the filament is 2800 °K. The focusing electrode and the anode profile are designed based on Pierce geometry. High Power DC Electron Accelerators require high currents of 1 A. The beam must comply with the requirement of 40 mm beam diameter and 10 mrad divergence at the exit of the electron gun. The characterization of the existing electron gun was done to find out all the beam parameters, for e.g. beam size, beam divergence, perveance etc. to be adapted or to be modified for the design of electron gun for high power DC accelerators. This paper shows limitations and the possible solutions for design of high power DC accelerators. (author)

Organic High Electron Mobility Transistors Realized by 2D Electron Gas.

Science.gov (United States)

Zhang, Panlong; Wang, Haibo; Yan, Donghang

2017-09-01

A key breakthrough in inorganic modern electronics is the energy-band engineering that plays important role to improve device performance or develop novel functional devices. A typical application is high electron mobility transistors (HEMTs), which utilizes 2D electron gas (2DEG) as transport channel and exhibits very high electron mobility over traditional field-effect transistors (FETs). Recently, organic electronics have made very rapid progress and the band transport model is demonstrated to be more suitable for explaining carrier behavior in high-mobility crystalline organic materials. Therefore, there emerges a chance for applying energy-band engineering in organic semiconductors to tailor their optoelectronic properties. Here, the idea of energy-band engineering is introduced and a novel device configuration is constructed, i.e., using quantum well structures as active layers in organic FETs, to realize organic 2DEG. Under the control of gate voltage, electron carriers are accumulated and confined at quantized energy levels, and show efficient 2D transport. The electron mobility is up to 10 cm 2 V -1 s -1 , and the operation mechanisms of organic HEMTs are also argued. Our results demonstrate the validity of tailoring optoelectronic properties of organic semiconductors by energy-band engineering, offering a promising way for the step forward of organic electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Downshift of electron plasma oscillations in the electron foreshock region

International Nuclear Information System (INIS)

Fuselier, S.A.

1984-01-01

Electron plasma oscillations in the Earth's electron foreshock region are observed to shift above and below the local electron plasma frequency. As plasma oscillations shift from the plasma frequency, their bandwidth increases and their wavelength decreases. Observations of plasma oscillations well below the plasma frequency are correlated with times when ISEE-I is far downstream of the electron foreshock boundary. Although wavelengths of plasma oscillations below the plasma frequency satisfy klambda/sub De/ approx. = 1, the Doppler shift due to the motion of the solar wind is not sufficient to produce the observed frequency shifts. A beam-plasma interaction with beam velocities on the order of the electron thermal velocity is suggested as an explanation for plasma oscillations above and below the plasma frequency. Frequency, bandwidth, and wavelength changes predicted from the beam-plasma interaction are in good agreement with the observed characteristics of plasma oscillations in the foreshock region

MIS hot electron devices for enhancement of surface reactivity by hot electrons

DEFF Research Database (Denmark)

Thomsen, Lasse Bjørchmar

A Metal-Insulator-Semiconductor (MIS) based device is developed for investigation of hot electron enhanced chemistry. A model of the device is presented explaining the key concepts of the functionality and the character- istics. The MIS hot electron emitter is fabricated using cleanroom technology...... and the process sequence is described. An Ultra High Vacuum (UHV) setup is modified to facilitate experiments with electron emission from the MIS hot electron emitters and hot electron chemistry. Simulations show the importance of keeping tunnel barrier roughness to an absolute minimum. The tunnel oxide...... to be an important energy loss center for the electrons tunneling through the oxide lowering the emission e±ciency of a factor of 10 for a 1 nm Ti layer thickness. Electron emission is observed under ambient pressure conditions and in up to 2 bars of Ar. 2 bar Ar decrease the emission current by an order...

EFFECTIVE ELECTRONIC TUTORIAL

Directory of Open Access Journals (Sweden)

Andrei A. Fedoseev

2014-01-01

Full Text Available The article analyzes effective electronic tutorials creation and application based on the theory of pedagogy. Herewith the issues of necessary electronic tutorial functional, ways of the educational process organization with the use of information and communication technologies and the logistics of electronic educational resources are touched upon. 

Theoretical investigations of molecular wires: Electronic spectra and electron transport

Science.gov (United States)

Palma, Julio Leopoldo

The results of theoretical and computational research are presented for two promising molecular wires, the Nanostar dendrimer, and a series of substituted azobenzene derivatives connected to aluminum electrodes. The electronic absorption spectra of the Nanostar (a phenylene-ethynylene dendrimer attached to an ethynylperylene chromophore) were calculated using a sequential Molecular Dynamics/Quantum Mechanics (MD/QM) method to perform an analysis of the temperature dependence of the electronic absorption process. We modeled the Nanostar as a series of connected units, and performed MD simulations for each chromophore at 10 K and 300 K to study how the temperature affected the structures and, consequently, the spectra. The absorption spectra of the Nanostar were computed using an ensemble of 8000 structures for each chromophore. Quantum Mechanical (QM) ZINDO/S calculations were performed for each conformation in the ensemble, including 16 excited states, for a total of 128,000 excitation energies. The spectral intensity was then scaled linearly with the number of conjugated units. Our calculations for both the individual chromophores and the Nanostar, are in good agreement with experiments. We explain in detail the effects of temperature and the consequences for the absorption process. The second part of this thesis presents a study of the effects of chemical substituents on the electron transport properties of the azobenzene molecule, which has been proposed recently as a component of a light-driven molecular switch. This molecule has two stable conformations (cis and trans) in its electronic ground state, with considerable differences in their conductance. The electron transport properties were calculated using first-principles methods combining non-equilibrium Green's function (NEGF) techniques with density functional theory (DFT). For the azobenzene studies, we included electron-donating groups and electron-withdrawing groups in meta- and ortho-positions with

Evaluation of high-energy brachytherapy source electronic disequilibrium and dose from emitted electrons.

Science.gov (United States)

Ballester, Facundo; Granero, Domingo; Pérez-Calatayud, José; Melhus, Christopher S; Rivard, Mark J

2009-09-01

The region of electronic disequilibrium near photon-emitting brachytherapy sources of high-energy radionuclides (60Co, 137CS, 192Ir, and 169Yb) and contributions to total dose from emitted electrons were studied using the GEANT4 and PENELOPE Monte Carlo codes. Hypothetical sources with active and capsule materials mimicking those of actual sources but with spherical shape were examined. Dose contributions due to source photons, x rays, and bremsstrahlung; source beta-, Auger electrons, and internal conversion electrons; and water collisional kerma were scored. To determine if conclusions obtained for electronic equilibrium conditions and electron dose contribution to total dose for the representative spherical sources could be applied to actual sources, the 192Ir mHDR-v2 source model (Nucletron B.V., Veenendaal, The Netherlands) was simulated for comparison to spherical source results and to published data. Electronic equilibrium within 1% is reached for 60Co, 137CS, 192Ir, and 169Yb at distances greater than 7, 3.5, 2, and 1 mm from the source center, respectively, in agreement with other published studies. At 1 mm from the source center, the electron contributions to total dose are 1.9% and 9.4% for 60Co and 192Ir, respectively. Electron emissions become important (i.e., > 0.5%) within 3.3 mm of 60Co and 1.7 mm of 192Ir sources, yet are negligible over all distances for 137Cs and 169Yb. Electronic equilibrium conditions along the transversal source axis for the mHDR-v2 source are comparable to those of the spherical sources while electron dose to total dose contribution are quite different. Electronic equilibrium conditions obtained for spherical sources could be generalized to actual sources while electron contribution to total dose depends strongly on source dimensions, material composition, and electron spectra.

Direct single electron detection with a CMOS detector for electron microscopy

International Nuclear Information System (INIS)

Faruqi, A.R.; Henderson, R.; Pryddetch, M.; Allport, P.; Evans, A.

2005-01-01

We report the results of an investigation into the use of a monolithic active pixel sensor (MAPS) for electron microscopy. MAPS, designed originally for astronomers at the Rutherford Appleton Laboratories, was installed in a 120 kV electron microscope (Philips CM12) at the MRC Laboratory in Cambridge for tests which included recording single electrons at 40 and 120 keV, and measuring signal-to-noise ratio (SNR), spatial resolution and radiation sensitivity. Our results show that, due to the excellent SNR and resolution, it is possible to register single electrons. The radiation damage to the detector is apparent with low doses and gets progressively greater so that its lifetime is limited to 600,000-900,000 electrons/pixel (very approximately 10-15 krad). Provided this detector can be radiation hardened to reduce its radiation sensitivity several hundred fold and increased in size, it will provide excellent performance for all types of electron microscopy

Fundamentals of electronics

CERN Document Server

Schubert, Thomas F

2015-01-01

This book, Electronic Devices and Circuit Application, is the first of four books of a larger work, Fundamentals of Electronics. It is comprised of four chapters describing the basic operation of each of the four fundamental building blocks of modern electronics: operational amplifiers, semiconductor diodes, bipolar junction transistors, and field effect transistors. Attention is focused on the reader obtaining a clear understanding of each of the devices when it is operated in equilibrium. Ideas fundamental to the study of electronic circuits are also developed in the book at a basic level to

High-power electronics

CERN Document Server

Kapitsa, Petr Leonidovich

1966-01-01

High-Power Electronics, Volume 2 presents the electronic processes in devices of the magnetron type and electromagnetic oscillations in different systems. This book explores the problems of electronic energetics.Organized into 11 chapters, this volume begins with an overview of the motion of electrons in a flat model of the magnetron, taking into account the in-phase wave and the reverse wave. This text then examines the processes of transmission of electromagnetic waves of various polarization and the wave reflection from grids made of periodically distributed infinite metal conductors. Other

Electron Bifurcation: Thermodynamics and Kinetics of Two-Electron Brokering in Biological Redox Chemistry

Energy Technology Data Exchange (ETDEWEB)

Zhang, Peng; Yuly, Jonathon L.; Lubner, Carolyn E. [National Renewable Energy Laboratory, Golden, Colorado 80401, United States; Mulder, David W. [National Renewable Energy Laboratory, Golden, Colorado 80401, United States; King, Paul W. [National Renewable Energy Laboratory, Golden, Colorado 80401, United States; Peters, John W. [Institute; Beratan, David N. [Department

2017-08-23

How can proteins drive two electrons from a redox active donor onto two acceptors at very different potentials and distances? And how can this transaction be conducted without dissipating very much energy or violating the laws of thermodynamics? Nature appears to have addressed these challenges by coupling thermodynamically uphill and downhill electron transfer reactions, using two-electron donor cofactors that have very different potentials for the removal of the first and second electron. Although electron bifurcation is carried out with near perfection from the standpoint of energy conservation and electron delivery yields, it is a biological energy transduction paradigm that has only come into focus recently. This Account provides an exegesis of the biophysical principles that underpin electron bifurcation.

Printed Electronics

Science.gov (United States)

Korkut, Sibel (Inventor); Chiang, Katherine S. (Inventor); Crain, John M. (Inventor); Aksay, Ilhan A. (Inventor); Lettow, John S. (Inventor); Chen, Chuan-Hua (Inventor); Prud'Homme, Robert K. (Inventor)

2018-01-01

Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

Production of accelerated electrons near an electron source in the plasma resonance region

International Nuclear Information System (INIS)

Fedorov, V.A.

1989-01-01

Conditions of generation of plasma electrons accelerated and their characteristics in the vicinity of an electron source are determined. The electron source isolated electrically with infinitely conducting surface, being in unrestricted collisionless plasma ω 0 >>ν, where ω 0 - plasma frequency of nonperturbated plasma, ν - frequency of plasma electron collisions with other plasma particles, is considered. Spherically symmetric injection of electrons, which rates are simulated by ω frequency, occurs from the source surface. When describing phenomena in the vicinity of the electron source, one proceeds from the quasihydrodynamic equation set

A superconducting electron spectrometer

International Nuclear Information System (INIS)

Guttormsen, M.; Huebel, H.; Grumbkow, A. von

1983-03-01

The set-up and tests of an electron spectrometer for in-beam conversion electron measurements are described. A superconducting solenoid is used to transport the electrons from the target to cooled Si(Li) detectors. The solenoid is designed to produce either a homogeneous axially symmetric field of up to 2 Tesla or a variety of field profiles by powering the inner and outer set of coils of the solenoid separately. The electron trajectories resulting for various field profiles are discussed. In-beam electron spectra taken in coincidence with electrons, gammas and alpha-particles are shown. (Auth.)

Electron-electron interaction in Multiple Quantum Wells

Science.gov (United States)

Zybert, M.; Marchewka, M.; Tomaka, G.; Sheregii, E. M.

2012-07-01

The complex investigation of the magneto-transport effects in structures containing multiple quantum well (MQWs) based on the GaAs/AlGaAs-heterostructures has been performed. The MQWs investigated have different electron densities in QWs. The parameters of 2DEG in MQWs were determined from the data of the Integer Quantum Hall Effect (IQHE) and Shubnikov-de Haas oscillations (SdH) observed at low temperatures (0.6-4.2 K). The method of calculation of the electron states energies in MQWs has been developed which is based on the splitting of these states due to the exchange interaction (SAS-splitting, see D. Płoch et al., Phys. Rev. B 79 (2009) 195434) including the screening of this interaction. The IQHE and SdH observed in these multilayer structures with the third degree of freedom for electrons are interpreted from this.

Electronic plants

Science.gov (United States)

Stavrinidou, Eleni; Gabrielsson, Roger; Gomez, Eliot; Crispin, Xavier; Nilsson, Ove; Simon, Daniel T.; Berggren, Magnus

2015-01-01

The roots, stems, leaves, and vascular circuitry of higher plants are responsible for conveying the chemical signals that regulate growth and functions. From a certain perspective, these features are analogous to the contacts, interconnections, devices, and wires of discrete and integrated electronic circuits. Although many attempts have been made to augment plant function with electroactive materials, plants’ “circuitry” has never been directly merged with electronics. We report analog and digital organic electronic circuits and devices manufactured in living plants. The four key components of a circuit have been achieved using the xylem, leaves, veins, and signals of the plant as the template and integral part of the circuit elements and functions. With integrated and distributed electronics in plants, one can envisage a range of applications including precision recording and regulation of physiology, energy harvesting from photosynthesis, and alternatives to genetic modification for plant optimization. PMID:26702448

Radially localized measurements of superthermal electrons using oblique electron cyclotron emission

International Nuclear Information System (INIS)

Preische, S.; Efthimion, P.C.; Kaye, S.M.

1996-05-01

It is shown that radial localization of optically tin Electron Cyclotron Emission from superthermal electrons can be imposed by observation of emission upshifted from the thermal cyclotron resonance in the horizontal midplane of a tokamak. A new and unique diagnostic has been proposed and operated to make radially localized measurements of superthermal electrons during Lower Hybrid Current Drive on the PBX-M tokamak. The superthermal electron density profile as well as moments of the electron energy distribution as a function of radius are measured during Lower Hybrid Current Drive. The time evolution of these measurements after the Lower Hybrid power is turned off are given and the observed behavior reflects the collisional isotropization of the energy distribution and radial diffusion of the spatial profile

Practical microwave electron devices

CERN Document Server

Meurant, Gerard

2013-01-01

Practical Microwave Electron Devices provides an understanding of microwave electron devices and their applications. All areas of microwave electron devices are covered. These include microwave solid-state devices, including popular microwave transistors and both passive and active diodes; quantum electron devices; thermionic devices (including relativistic thermionic devices); and ferrimagnetic electron devices. The design of each of these devices is discussed as well as their applications, including oscillation, amplification, switching, modulation, demodulation, and parametric interactions.

Neutrinos in the Electron

International Nuclear Information System (INIS)

Koschmieder, E. L.

2007-01-01

I will show that one half of the rest mass of the electron consists of electron neutrinos and that the other half of the rest mass of the electron consists of the mass in the energy of electric oscillations. With this composition we can explain the rest mass of the electron, its charge, its spin and its magnetic moment We have also determined the rest masses of the muon neutrino and the electron neutrino

Downshift of electron plasma oscillations in the electron foreshock region

International Nuclear Information System (INIS)

Fuselier, S.A.; Gurnett, D.A.; Fitzenreiter, R.J.; NASA, Goddard Space Flight Center, Greenbelt, MD)

1985-01-01

Electron plasma oscillations in the earth's electron foreshock region are observed to shift above and below the local electron plasma frequency. As plasma oscillations shift downward from the plasma frequency, their bandwidth increases and their wavelength decreases. Observations of plasma oscillations well below the plasma frequency are correlated with times when ISEE 1 is far downstream of the electron foreshock boundary. Although wavelengths of plasma oscillations below the plasma frequency satisfy k x lambda-De approximately 1 the Doppler shift due to the motion of the solar wind is not sufficient to produce the observed frequency shifts. A beam-plasma interaction with beam velocities on the order of the electron thermal velocity is suggested as an explanation for plasma oscillations above and below the plasma frequency. Frequency, bandwidth, and wavelength changes predicted from the beam-plasma interaction are in good agreement with the observed characteristics of plasma oscillations in the foreshock region. 28 references

Paleoclassical electron heat transport

International Nuclear Information System (INIS)

Callen, J.D.

2005-01-01

Radial electron heat transport in low collisionality, magnetically-confined toroidal plasmas is shown to result from paleoclassical Coulomb collision processes (parallel electron heat conduction and magnetic field diffusion). In such plasmas the electron temperature equilibrates along magnetic field lines a long length L, which is the minimum of the electron collision length and a maximum effective half length of helical field lines. Thus, the diffusing field lines induce a radial electron heat diffusivity M ≅ L/(πR 0q ) ∼ 10 >> 1 times the magnetic field diffusivity η/μ 0 ≅ ν e (c/ω p ) 2 . The paleoclassical electron heat flux model provides interpretations for many features of 'anomalous' electron heat transport: magnitude and radial profile of electron heat diffusivity (in tokamaks, STs, and RFPs), Alcator scaling in high density plasmas, transport barriers around low order rational surfaces and near a separatrix, and a natural heat pinch (or minimum temperature gradient) heat flux form. (author)

Surface characterization by energy distribution measurements of secondary electrons and of ion-induced electrons

International Nuclear Information System (INIS)

Bauer, H.E.; Seiler, H.

1988-01-01

Instruments for surface microanalysis (e.g. scanning electron or ion microprobes, emission electron or ion microscopes) use the current of emitted secondary electrons or of emitted ion-induced electrons for imaging of the analysed surface. These currents, integrating over all energies of the emitted low energy electrons, are however, not well suited to surface analytical purposes. On the contrary, the energy distribution of these electrons is extremely surface-sensitive with respect to shape, size, width, most probable energy, and cut-off energy. The energy distribution measurements were performed with a cylindrical mirror analyser and converted into N(E), if necessary. Presented are energy spectra of electrons released by electrons and argon ions of some contaminated and sputter cleaned metals, the change of the secondary electron energy distribution from oxidized aluminium to clean aluminium, and the change of the cut-off energy due to work function change of oxidized aluminium, and of a silver layer on a platinum sample. The energy distribution of the secondary electrons often shows detailed structures, probably due to low-energy Auger electrons, and is broader than the energy distribution of ion-induced electrons of the same object point. (author)

Electron transfer by excited benzoquinone anions: slow rates for two-electron transitions.

Science.gov (United States)

Zamadar, Matibur; Cook, Andrew R; Lewandowska-Andralojc, Anna; Holroyd, Richard; Jiang, Yan; Bikalis, Jin; Miller, John R

2013-09-05

Electron transfer (ET) rate constants from the lowest excited state of the radical anion of benzoquinone, BQ(-•)*, were measured in THF solution. Rate constants for bimolecular electron transfer reactions typically reach the diffusion-controlled limit when the free-energy change, ΔG°, reaches -0.3 eV. The rate constants for ET from BQ(-•)* are one-to-two decades smaller at this energy and do not reach the diffusion-controlled limit until -ΔG° is 1.5-2.0 eV. The rates are so slow probably because a second electron must also undergo a transition to make use of the energy of the excited state. Similarly, ET, from solvated electrons to neutral BQ to form the lowest excited state, is slow, while fast ET is observed at a higher excited state, which can be populated in a transition involving only one electron. A simple picture based on perturbation theory can roughly account for the control of electron transfer by the need for transition of a second electron. The picture also explains how extra driving force (-ΔG°) can restore fast rates of electron transfer.

Rapid low dose electron tomography using a direct electron detection camera

NARCIS (Netherlands)

V. Migunov (Vadim); H. Ryll; X. Zhuge (Jason); M. Simson; L. Strüder; K.J. Batenburg (Joost); L. Houben; R.E. Dunin-Borkowski (Rafal)

2015-01-01

htmlabstractWe demonstrate the ability to record a tomographic tilt series containing 3487 images in only 3.5 s by using a direct electron detector in a transmission electron microscope. The electron dose is lower by at least one order of magnitude when compared with that used to record a

High-intensity-laser-electron scattering

International Nuclear Information System (INIS)

Meyerhofer, D.D.

1997-01-01

In the field of an intense laser, photon-electron scattering becomes nonlinear when the oscillatory energy of the electron approaches its rest mass. The electron wave function is dressed by the field with a concomitant increase in the effective electron mass. When the photon energy in the electron rest frame is comparable to the electron rest mass, multiphoton Compton scattering occurs. When the photon energy is significantly lower than the electron rest mass, the electron acquires momentum from the photon field and emits harmonics. This paper reviews nonlinear photon-electron scattering processes and results from two recent experiments where they have been observed

Automotive electronics design fundamentals

CERN Document Server

Zaman, Najamuz

2015-01-01

This book explains the topology behind automotive electronics architectures and examines how they can be profoundly augmented with embedded controllers. These controllers serve as the core building blocks of today’s vehicle electronics. Rather than simply teaching electrical basics, this unique resource focuses on the fundamental concepts of vehicle electronics architecture, and details the wide variety of Electronic Control Modules (ECMs) that enable the increasingly sophisticated "bells & whistles" of modern designs.  A must-have for automotive design engineers, technicians working in automotive electronics repair centers and students taking automotive electronics courses, this guide bridges the gap between academic instruction and industry practice with clear, concise advice on how to design and optimize automotive electronics with embedded controllers.