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Sample records for defects ntds ranges

  1. Neural tube defects – disorders of neurulation and related embryonic processes

    Science.gov (United States)

    Copp, Andrew J.; Greene, Nicholas D. E.

    2014-01-01

    Neural tube defects (NTDs) are severe congenital malformations affecting 1 in every 1000 pregnancies. ‘Open’ NTDs result from failure of primary neurulation as seen in anencephaly, myelomeningocele (open spina bifida) and craniorachischisis. Degeneration of the persistently open neural tube in utero leads to loss of neurological function below the lesion level. ‘Closed’ NTDs are skin-covered disorders of spinal cord structure, ranging from asymptomatic spina bifida occulta to severe spinal cord tethering, and usually traceable to disruption of secondary neurulation. ‘Herniation’ NTDs are those in which meninges, with or without brain or spinal cord tissue, become exteriorised through a pathological opening in the skull or vertebral column (e.g. encephalocele and meningocele). NTDs have multifactorial etiology, with genes and environmental factors interacting to determine individual risk of malformation. While over 200 mutant genes cause open NTDs in mice, much less is known about the genetic causation of human NTDs. Recent evidence has implicated genes of the planar cell polarity signalling pathway in a proportion of cases. The embryonic development of NTDs is complex, with diverse cellular and molecular mechanisms operating at different levels of the body axis. Molecular regulatory events include the BMP and Sonic hedgehog pathways which have been implicated in control of neural plate bending. Primary prevention of NTDs has been implemented clinically following the demonstration that folic acid, when taken as a peri-conceptional supplement, can prevent many cases. Not all NTDs respond to folic acid, however, and adjunct therapies are required for prevention of this folic acid-resistant category. PMID:24009034

  2. Detecting Topological Defect Dark Matter Using Coherent Laser Ranging System

    Science.gov (United States)

    Yang, Wanpeng; Leng, Jianxiao; Zhang, Shuangyou; Zhao, Jianye

    2016-01-01

    In the last few decades, optical frequency combs with high intensity, broad optical bandwidth, and directly traceable discrete wavelengths have triggered rapid developments in distance metrology. However, optical frequency combs to date have been limited to determine the absolute distance to an object (such as satellite missions). We propose a scheme for the detection of topological defect dark matter using a coherent laser ranging system composed of dual-combs and an optical clock via nongravitational signatures. The dark matter field, which comprises a defect, may interact with standard model particles, including quarks and photons, resulting in the alteration of their masses. Thus, a topological defect may function as a dielectric material with a distinctive frequency-depend index of refraction, which would cause the time delay of a periodic extraterrestrial or terrestrial light. When a topological defect passes through the Earth, the optical path of long-distance vacuum path is altered, this change in optical path can be detected through the coherent laser ranging system. Compared to continuous wavelength(cw) laser interferometry methods, dual-comb interferometry in our scheme excludes systematic misjudgement by measuring the absolute optical path length. PMID:27389642

  3. Syndromes, disorders and maternal risk factors associated with neural tube defects (I).

    Science.gov (United States)

    Chen, Chih-Ping

    2008-03-01

    Fetuses with neural tube defects (NTDs) may be associated with syndromes, disorders, and maternal risk factors. This article provides a comprehensive review of syndromes, disorders, and maternal risk factors associated with NTDs, such as acrocallosal syndrome, autosomal dominant brachydactyly-clinodactyly syndrome, Manouvrier syndrome, short rib-polydactyly syndrome, Disorganization ( Ds )-like human malformations, isolated hemihyperplasia, X-linked NTDs, meroanencephaly, schisis association, diprosopus, fetal valproate syndrome, DiGeorge syndrome/velocardiofacial syndrome, Waardenburg syndrome, folic acid antagonists, diabetes mellitus, and obesity. NTDs associated with syndromes, disorders, and maternal risk factors are a rare but important cause of NTDs. The recurrence risk and the preventive effect of maternal folic acid intake in NTDs associated with syndromes, disorders, and maternal risk factors may be different from those of non-syndromic multifactorial NTDs. Perinatal identification of NTDs should alert one to the syndromes, disorders, and maternal risk factors associated with NTDs, and prompt a thorough etiologic investigation and genetic counseling.

  4. Thermal neutron equivalent doses assessment around KFUPM neutron source storage area using NTDs

    Energy Technology Data Exchange (ETDEWEB)

    Abu-Jarad, F.; Fazal-ur-Rehman; Al-Haddad, M.N.; Al-Jarrallah, M.I.; Nassar, R

    2002-07-01

    Area passive neutron dosemeters based on nuclear track detectors (NTDs) have been used for 13 days to assess accumulated low doses of thermal neutrons around neutron source storage area of the King Fahd University of Petroleum and Minerals (KFUPM). Moreover, the aim of this study is to check the effectiveness of shielding of the storage area. NTDs were mounted with the boron converter on their surface as one compressed unit. The converter is a lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) layer for thermal neutron detection via {sup 10}B(N,{alpha}){sup 7}Li and {sup 6}Li(n,{alpha}){sup 3}H nuclear reactions. The area passive dosemeters were installed on 26 different locations around the source storage area and adjacent rooms. The calibration factor for NTD-based area passive neutron dosemeters was found to be 8.3 alpha tracks.cm{sup -2}.{mu}Sv{sup -1} using active snoopy neutron dosemeters in the KFUPM neutron irradiation facility. The results show the variation of accumulated dose with locations around the storage area. The range of dose rates varied from as low as 40 nSv.h{sup -1} up to 11 {mu}Sv.h{sup -1}. The study indicates that the area passive neutron dosemeter was able to detect accumulated doses as low as 40 nSv.h{sup -1}, which could not be detected with the available active neutron dosemeters. The results of the study also indicate that an additional shielding is required to bring the dose rates down to background level. The present investigation suggests extending this study to find the contribution of doses from fast neutrons around the neutron source storage area using NTDs through proton recoil. The significance of this passive technique is that it is highly sensitive and does not require any electronics or power supplies, as is the case in active systems. (author)

  5. Genetic interactions between planar cell polarity genes cause diverse neural tube defects in mice

    Directory of Open Access Journals (Sweden)

    Jennifer N. Murdoch

    2014-10-01

    Full Text Available Neural tube defects (NTDs are among the commonest and most severe forms of developmental defect, characterized by disruption of the early embryonic events of central nervous system formation. NTDs have long been known to exhibit a strong genetic dependence, yet the identity of the genetic determinants remains largely undiscovered. Initiation of neural tube closure is disrupted in mice homozygous for mutations in planar cell polarity (PCP pathway genes, providing a strong link between NTDs and PCP signaling. Recently, missense gene variants have been identified in PCP genes in humans with NTDs, although the range of phenotypes is greater than in the mouse mutants. In addition, the sequence variants detected in affected humans are heterozygous, and can often be detected in unaffected individuals. It has been suggested that interactions between multiple heterozygous gene mutations cause the NTDs in humans. To determine the phenotypes produced in double heterozygotes, we bred mice with all three pairwise combinations of Vangl2Lp, ScribCrc and Celsr1Crsh mutations, the most intensively studied PCP mutants. The majority of double-mutant embryos had open NTDs, with the range of phenotypes including anencephaly and spina bifida, therefore reflecting the defects observed in humans. Strikingly, even on a uniform genetic background, variability in the penetrance and severity of the mutant phenotypes was observed between the different double-heterozygote combinations. Phenotypically, Celsr1Crsh;Vangl2Lp;ScribCrc triply heterozygous mutants were no more severe than doubly heterozygous or singly homozygous mutants. We propose that some of the variation between double-mutant phenotypes could be attributed to the nature of the protein disruption in each allele: whereas ScribCrc is a null mutant and produces no Scrib protein, Celsr1Crsh and Vangl2Lp homozygotes both express mutant proteins, consistent with dominant effects. The variable outcomes of these genetic

  6. Neural tube defects in Malaysia: data from the Malaysian National Neonatal Registry.

    Science.gov (United States)

    Boo, Nem-Yun; Cheah, Irene G S; Thong, Meow-Keong

    2013-10-01

    This study aimed to determine the prevalence and early outcome of neural tube defects (NTDs) in Malaysia. This prospective study included all neonates with NTDs (spina bifida, anencephaly, encephalocoele) born in 2009 in 32 Malaysian hospitals in the Malaysian National Neonatal Network. The prevalence of NTDs was 0.42 per 1000 live births, being highest among the indigenous people of Sarawak (1.09 per 1000 live births) and lowest among Malaysians of Chinese descent (0.09 per 1000 live births). The most common type of NTDs was anencephaly (0.19 per 1000 live births), followed by spina bifida (0.11 per 1000 live births) and encephalocoele (0.07 per 1000 live births). Majority of the infants with anencephaly (94.5%, n = 51), 45.8% (n = 11) with encephalocoele and 9.5% (n = 4) with spina bifida died. The median duration of hospital stay was 4 (range: 0-161) days. NTDs were common in Malaysia. Mortality was high. Long-term monitoring of NTD prevalence following folic fortification of food is recommended.

  7. Syndromes, Disorders and Maternal Risk Factors Associated With Neural Tube Defects (VI

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2008-09-01

    Full Text Available Neural tube defects (NTDs may be associated with syndromes, disorders, and maternal and fetal risk factors. This article provides a comprehensive review of the syndromes, disorders, and maternal and fetal risk factors associated with NTDs, including maternal fumonisin consumption, periconceptional zinc deficiency, parental occupational exposure and residential proximity to pesticides, lower socioeconomic status, fetal alcohol syndrome, mutations in the VANGL1 gene, human athymic Nude/SCID fetus, and single nucleotide polymorphism in the NOS3 gene. NTDs associated with these syndromes, disorders, and maternal and fetal risk factors are a rare but important cause of NTDs. The recurrence risk and the preventive effect of maternal folic acid intake in NTDs associated with syndromes, disorders and maternal risk factors may be different from those of nonsyndromic multifactorial NTDs. Perinatal diagnosis of NTDs should alert doctors to the syndromes, disorders, and maternal and fetal risk factors associated with NTDs, and prompt thorough etiologic investigation and genetic counseling.

  8. Pipeline defect prediction using long range ultrasonic testing and intelligent processing

    International Nuclear Information System (INIS)

    Dino Isa; Rajprasad Rajkumar

    2009-01-01

    This paper deals with efforts to improve nondestructive testing (NDT) techniques by using artificial intelligence in detecting and predicting pipeline defects such as cracks and wall thinning. The main emphasis here will be on the prediction of corrosion type defects rather than just detection after the fact. Long range ultrasonic testing will be employed, where a ring of piezoelectric transducers are used to generate torsional guided waves. Various defects such as cracks as well as corrosion under insulation (CUI) will be simulated on a test pipe. The machine learning algorithm known as the Support Vector Machine (SVM) will be used to predict and classify transducer signals using regression and large margin classification. Regression results show that the SVM is able to accurately predict future defects based on trends of previous defect. The classification performance was also exceptional showing a facility to detect defects at different depths as well as for distinguishing closely spaced defects. (author)

  9. Threats from emerging and re-emerging neglected tropical diseases (NTDs).

    Science.gov (United States)

    Mackey, Tim K; Liang, Bryan A

    2012-01-01

    Neglected tropical diseases impact over 1 billion of the world's poorest populations and require special attention. However, within the NTDs recognized by the World Health Organization, some are also dually categorized as emerging and re-emerging infectious diseases requiring more detailed examination on potential global health risks. We reviewed the 17 NTDs classified by the WHO to determine if those NTDs were also categorized by the US Centers for Disease Control and Prevention as emerging and re-emerging infectious diseases (''EReNTDs''). We then identified common characteristics and risks associated with EReNTDs. Identified EReNTDs of dengue, rabies, Chagas Disease, and cysticercosis disproportionately impact resource-poor settings with poor social determinants of health, spread through globalization, are impacted by vector control, lack available treatments, and threaten global health security. This traditionally neglected subset of diseases requires urgent attention and unique incentive structures to encourage investment in innovation and coordination. Multi-sectorial efforts and targeted public-private partnerships would spur needed R&D for effective and accessible EReNTD treatments, improvement of social determinants of health, crucial low-income country development, and health system strengthening efforts. Utilization of One Health principles is essential for enhancing knowledge to efficaciously address public health aspects of these EReNTDs globally.

  10. Threats from emerging and re-emerging neglected tropical diseases (NTDs

    Directory of Open Access Journals (Sweden)

    Tim K. Mackey

    2012-08-01

    Full Text Available Background: Neglected tropical diseases impact over 1 billion of the world's poorest populations and require special attention. However, within the NTDs recognized by the World Health Organization, some are also dually categorized as emerging and re-emerging infectious diseases requiring more detailed examination on potential global health risks. Methods: We reviewed the 17 NTDs classified by the WHO to determine if those NTDs were also categorized by the US Centers for Disease Control and Prevention as emerging and re-emerging infectious diseases (‘‘EReNTDs’’. We then identified common characteristics and risks associated with EReNTDs. Results: Identified EReNTDs of dengue, rabies, Chagas Disease, and cysticercosis disproportionately impact resource-poor settings with poor social determinants of health, spread through globalization, are impacted by vector control, lack available treatments, and threaten global health security. This traditionally neglected subset of diseases requires urgent attention and unique incentive structures to encourage investment in innovation and coordination. Discussion: Multi-sectorial efforts and targeted public–private partnerships would spur needed R&D for effective and accessible EReNTD treatments, improvement of social determinants of health, crucial low-income country development, and health system strengthening efforts. Utilization of One Health principles is essential for enhancing knowledge to efficaciously address public health aspects of these EReNTDs globally.

  11. Impact of dopant profiles on the end of range defects for low energy germanium preamorphized silicon

    International Nuclear Information System (INIS)

    Camillo-Castillo, R.A.; Law, M.E.; Jones, K.S.

    2004-01-01

    As the industry continues to aggressively scale CMOS technology, the shift to lower energy ion implantation becomes essential. The consequent shallower amorphous layers result in dopant profiles that are in closer proximity to the end of range (EOR) damage and therefore a better understanding of the interaction between the dopant atoms and the EOR is required. A study is conducted on the influence of dopant profiles on the behavior of the EOR defects. Czochralski-grown silicon wafers are preamorphized with 1 x 10 15 cm -2 , 10 keV Ge + ions and subsequently implanted with 1 x 10 15 cm -2 , 1 keV B + ions. A sequence of rapid thermal and furnace anneals are performed at 750 deg. C under a nitrogen ambient for periods of 1 s up to 6 h. Plan view transmission electron microscopy (PTEM) reveals a significant difference in the defect evolution for samples with and without boron, suggesting that the boron influences the evolution of the EOR defects. The extended defects observed for samples which contain boron appear as dot-like defects which are unstable and dissolve after very short anneal times. The defect evolution however, in samples without boron follows an Oswald ripening behavior and form {3 1 1}-type defects and dislocation loops. Hall effect measurements denote a high initial activation and subsequent deactivation of the dopant atoms which is characteristic of the formation of boron interstitial clusters. Diffusion analyses via secondary ion mass spectroscopy (SIMS) support this theory

  12. Syndromes, Disorders and Maternal Risk Factors Associated with Neural Tube Defects (II

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2008-03-01

    Full Text Available Fetuses with neural tube defects (NTDs maybe associated with syndromes, disorders, and maternal risk factors. This article provides a comprehensive review of syndromes, disorders, and maternal risk factors associated with NTDs, such as Currarino syndrome, sacral defect with anterior meningocele, Jarcho-Levin syndrome (spondylo-costal dysostosis, lateral meningocele syndrome, neurofibromatosis type I, Marfan syndrome, and hyperthermia. The recurrence risk and the preventive effect of maternal folic acid intake in NTDs associated with syndromes, disorders, and maternal risk factors may be different from those of non-syndromic multifactorial NTDs. Perinatal identification of NTDs should alert one to the syndromes, disorders, and maternal risk factors associated with NTDs, and prompt a thorough etiologic investigation and genetic counseling.

  13. [Comparing the ranges of defect measured with standard white on white and Pulsar perimetries].

    Science.gov (United States)

    González de la Rosa, M; González-Hernández, M; García-Feijoo, J; Sánchez Méndez, M; García-Sánchez, J

    2011-04-01

    Normal thresholds on Pulsar perimetry fall faster than those of standard perimetry in the peripheral visual field. Two related studies were performed. Firstly, the frequency distributions of glaucoma defects on standard automated perimetry (SAP) and the relationship of the centre and periphery (Study A) were studied first, followed by an attempt to establish the limits of pulsar perimetry (Study B). A: frequency of defects was calculated in 78.663 SAP perimetries (G1-TOP, Octopus 1-2-3, Haag-Streit). Study B: 204 eyes with mean defect (MD-SAP) lower than 9 dB were examined 8.92 ± 4.19 times with SAP (TOP-32, Octopus 311) and temporal modulation perimetry (T30W, Pulsar Perimeter, Haag-Streit). Study A: 50.7% of the SAP examinations showed MD values lower than 9 dB and 32.7% bellow 6 dB. The MD correlation of the central 20° with the MD of the most peripheral points was r=0.933. Study B: in cases with MD-TOP-32 lower than 6 dB, SAP had the maximum possibility of detecting defect in 0.02% of points and Pulsar in 0.29%. In subjects with MD-TOP-32 between 6 and 9 dB frequencies were 0.38% in SAP and 3.5% in Pulsar (5.1% for eccentricities higher than 20°). Pulsar allows detecting defects, without range limitations, in the initial half of SAP frequencies expected on glaucoma patients. In order to study the progression of deeper defects the examination should focus on the central points, where the dynamic range of both systems is more equivalent. Copyright © 2010 Sociedad Española de Oftalmología. Published by Elsevier Espana. All rights reserved.

  14. Syndromes, Disorders and Maternal Risk Factors Associated with Neural Tube Defects (IV

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2008-06-01

    Full Text Available Fetuses with neural tube defects (NTDs may be associated with maternal and fetal risk factors. This article provides a comprehensive review of maternal and fetal risk factors associated with NTDs, such as infertility, periconceptional clomiphene use and assisted reproductive technology, periconceptional folic acid deficiency and effects offolic acid supplementation and fortification on NTD rates, periconceptional vitamin B1 2 deficiency, single nucleotide polymorphisms and polymorphisms in genes of folate metabolism, and maternal autoantibodies to folate receptors. NTDs associated with maternal and fetal risk factors are an important cause of NTDs. Perinatal identification of NTDs should alert the clinician to the maternal and fetal risk factors associated with NTDs, and prompt a thorough etiologic investigation and genetic counseling. [Taiwan J Obstet Cynecol 2008;47(2:141-1 50

  15. Chromosomal Abnormalities Associated with Neural Tube Defects (I: Full Aneuploidy

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    Chih-Ping Chen

    2007-12-01

    Full Text Available Fetuses with neural tube defects (NTDs carry a risk of chromosomal abnormalities. The risk varies with maternal age, gestational age at diagnosis, association with other structural abnormalities, and family history of chromosome aberrations. This article provides an overview of chromosomal abnormalities associated with NTDs in embryos, fetuses, and newborn patients, and a comprehensive review of numerical chromosomal abnormalities associated with NTDs, such as trisomy 18, trisomy 13, triploidy, trisomy 9, trisomy 2, trisomy 21, trisomy 7, trisomy 8, trisomy 14, trisomy 15, trisomy 16, trisomy 5 mosaicism, trisomy 11 mosaicism, trisomy 20 mosaicism, monosomy X, and tetraploidy. NTDs may be associated with aneuploidy. Perinatal identification of NTDs should alert one to the possibility of chromosomal abnormalities and prompt a thorough cytogenetic investigation and genetic counseling.

  16. Neural Tube Defects, Folic Acid and Methylation

    Science.gov (United States)

    Imbard, Apolline; Benoist, Jean-François; Blom, Henk J.

    2013-01-01

    Neural tube defects (NTDs) are common complex congenital malformations resulting from failure of the neural tube closure during embryogenesis. It is established that folic acid supplementation decreases the prevalence of NTDs, which has led to national public health policies regarding folic acid. To date, animal studies have not provided sufficient information to establish the metabolic and/or genomic mechanism(s) underlying human folic acid responsiveness in NTDs. However, several lines of evidence suggest that not only folates but also choline, B12 and methylation metabolisms are involved in NTDs. Decreased B12 vitamin and increased total choline or homocysteine in maternal blood have been shown to be associated with increased NTDs risk. Several polymorphisms of genes involved in these pathways have also been implicated in risk of development of NTDs. This raises the question whether supplementation with B12 vitamin, betaine or other methylation donors in addition to folic acid periconceptional supplementation will further reduce NTD risk. The objective of this article is to review the role of methylation metabolism in the onset of neural tube defects. PMID:24048206

  17. Syndromes, Disorders and Maternal Risk Factors Associated with Neural Tube Defects (I

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2008-03-01

    Full Text Available Fetuses with neural tube defects (NTDs maybe associated with syndromes, disorders, and maternal risk factors. This article provides a comprehensive review of syndromes, disorders, and maternal risk factors associated with NTDs, such as acrocallosal syndrome, autosomal dominant brachydactyly-clinodactyly syndrome, Manouvrier syndrome, short rib-polydactyly syndrome, Disorganization (Ds-like human malformations, isolated hemihyper-plasia, X-linked NTDs, meroanencephaly, schisis association, diprosopus, fetal valproate syndrome, DiGeorge syndrome/velocardiofacial syndrome, Waardenburg syndrome, folic acid antagonists, diabetes mellitus, and obesity. NTDs associated with syndromes, disorders, and maternal risk factors are a rare but important cause of NTDs. The recurrence risk and the preventive effect of maternal folic acid intake in NTDs associated with syndromes, disorders, and maternal risk factors may be different from those of non-syndromic multifactorial NTDs. Perinatal identification of NTDs should alert one to the syndromes, disorders, and maternal risk factors associated with NTDs, and prompt a thorough etiologic investigation and genetic counseling.

  18. Syndromes, Disorders and Maternal Risk Factors Associated With Neural Tube Defects (VII

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2008-09-01

    Full Text Available Neural tube defects (NTDs may be associated with syndromes, disorders and maternal risk factors. This article provides a comprehensive review of the syndromes, disorders and maternal risk factors associated with NTDs, including DK phocomelia syndrome (von Voss-Cherstvoy syndrome, Siegel-Bartlet syndrome, fetal warfarin syndrome, craniotelencephalic dysplasia, Czeizel-Losonci syndrome, maternal cocaine abuse, Weissenbacher-Zweymüller syndrome, parietal foramina (cranium bifidum, Apert syndrome, craniomicromelic syndrome, XX-agonadism with multiple dysraphic lesions including omphalocele and NTDs, Fryns microphthalmia syndrome, Gershoni-Baruch syndrome, PHAVER syndrome, periconceptional vitamin B6 deficiency, and autosomal dominant Dandy-Walker malformation with occipital cephalocele. NTDs associated with these syndromes, disorders and maternal risk factors are a rare but important cause of NTDs. The recurrence risk and the preventive effect of maternal folic acid intake in NTDs associated with syndromes, disorders and maternal risk factors may be different from those of nonsyndromic multifactorial NTDs. Perinatal diagnosis of NTDs should alert doctors to the syndromes, disorders and maternal risk factors associated with NTDs, and prompt thorough etiologic investigation and genetic counseling.

  19. Syndromes, Disorders and Maternal Risk Factors Associated with Neural Tube Defects (III

    Directory of Open Access Journals (Sweden)

    Chih-Ping Chen

    2008-06-01

    Full Text Available Fetuses with neural tube defects (NTDs may be associated with syndromes, disorders, and maternal and fetal risk factors. This article provides a comprehensive review of syndromes, disorders, and maternal and fetal risk factors associated with NTDs, such as omphalocele, OEIS (omphalocele-exstrophy-imperforate anus-spinal defects complex, pentalogy of Cantrell, amniotic band sequence, limb-body wall complex, Meckel syndrome, Joubert syndrome, skeletal dysplasia, diabetic embryopathy, and single nucleotide polymorphisms in genes of glucose metabolism. NTDs associated with syndromes, disorders, and maternal and fetal risk factors are a rare but important cause of NTDs. The recurrence risk and the preventive effect of maternal folic acid intake in NTDs associated with syndromes, disorders and maternal risk factors may be different from those of nonsyndromic multi facto rial NTDs. Perinatal identification of NTDs should alert the clinician to the syndromes, disorders, and maternal and fetal risk factors associated with NTDs, and prompt a thorough etiologic investigation and genetic counseling. [Taiwan J Obstet Cynecol 2008;47(2:131-140

  20. Interaction of low-intensity nuclear radiation dose with the human blood: Using the new technique of CR-39NTDs for an in vitro study

    International Nuclear Information System (INIS)

    Ismail, Asaad H.; Jaafar, Mohamad S.

    2011-01-01

    Complete blood counts were analyzed for 30 samples of human blood with radiation dose rate ranging between 10 and 41 μSv/h using a Radium-226 source with different time of exposure. A new technique involving a nuclear track detector type CR-39(CR-39 NTDs) was used to estimate the alpha particle density incident on the blood samples. The results show that the ranges of alpha particle in blood samples and on the surface of CR-39NTDs vary exponentially with energy of alpha particles. This depends on the restricted energy loss and target density. Changes in the blood components due to irradiation occurred for different durations of irradiation, and the duration of irradiation that influenced the blood samples in this study was 6 min. The change in red blood cell (RBC) was negligible, so it is less affected than other blood components. In addition, most changes in the blood contents began at a low radiation dose (10.38-13.41 μSv/h). For the doses 13.41-21.77 μSv/h, platelet (PLT) counts increased rapidly and adversely with the RBC and white blood cell (WBC) due to chromosomal aberration. Besides, rapid PLT count reduction rapidly at high dose (42.1 μSv h) causes thrombocytopenia; in contrast, WBC increased, which is an indication of cancer caused due to increase in alpha particle dose. Generally, our results are in agreement with the essentials of blood content and the principles of biological radiation interaction.

  1. Observation of silicon self-diffusion enhanced by the strain originated from end-of-range defects using isotope multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Isoda, Taiga; Uematsu, Masashi; Itoh, Kohei M., E-mail: kitoh@appi.keio.ac.jp [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

    2015-09-21

    Si self-diffusion in the presence of end-of-range (EOR) defects is investigated using {sup nat}Si/{sup 28}Si isotope multilayers. The isotope multilayers were amorphized by Ge ion implantation, and then annealed at 800–950 °C. The behavior of Si self-interstitials is investigated through the {sup 30}Si self-diffusion. The experimental {sup 30}Si profiles show further enhancement of Si self-diffusion at the EOR defect region, in addition to the transient enhanced diffusion via excess Si self-interstitials by EOR defects. To explain this additional enhanced diffusion, we propose a model which takes into account enhanced diffusion by tensile strain originated from EOR defects. The calculation results based on this model have well reproduced the experimental {sup 30}Si profiles.

  2. Defect-impurity complex induced long-range ferromagnetism in GaN nanowires

    KAUST Repository

    Assa Aravindh, S

    2015-12-14

    Present work investigates the structural, electronic and magnetic properties of Gd doped wurtzite GaN nanowires (NWs) oriented along the [0001] direction in presence of intrinsic defects by employing the GGA + U approximation. We find that Ga vacancy (VGa) exhibits lower formation energy compared to N vacancy. Further stabilization of point defects occurs due to the presence of Gd. The strength of ferromagnetism (FM) increases by additional positive charge induced by the VGa. Electronic structure analysis shows that VGa introduces defect levels in the band gap leading to ferromagnetic coupling due to the hybridization of the p states of the Ga and N atoms with the Gd d and f states. Ferromagnetic exchange coupling energy of 76.4 meV is obtained in presence of Gd-VGa complex; hence, the FM is largely determined by the cation vacancy-rare earth complex defects in GaN NWs.

  3. Defect-impurity complex induced long-range ferromagnetism in GaN nanowires

    KAUST Repository

    Assa Aravindh, S; Roqan, Iman S.

    2015-01-01

    Present work investigates the structural, electronic and magnetic properties of Gd doped wurtzite GaN nanowires (NWs) oriented along the [0001] direction in presence of intrinsic defects by employing the GGA + U approximation. We find that Ga vacancy (VGa) exhibits lower formation energy compared to N vacancy. Further stabilization of point defects occurs due to the presence of Gd. The strength of ferromagnetism (FM) increases by additional positive charge induced by the VGa. Electronic structure analysis shows that VGa introduces defect levels in the band gap leading to ferromagnetic coupling due to the hybridization of the p states of the Ga and N atoms with the Gd d and f states. Ferromagnetic exchange coupling energy of 76.4 meV is obtained in presence of Gd-VGa complex; hence, the FM is largely determined by the cation vacancy-rare earth complex defects in GaN NWs.

  4. #Globalhealth Twitter Conversations on #Malaria, #HIV, #TB, #NCDS, and #NTDS: a Cross-Sectional Analysis.

    Science.gov (United States)

    Fung, Isaac Chun-Hai; Jackson, Ashley M; Ahweyevu, Jennifer O; Grizzle, Jordan H; Yin, Jingjing; Tse, Zion Tsz Ho; Liang, Hai; Sekandi, Juliet N; Fu, King-Wa

    Advocates use the hashtag #GlobalHealth on Twitter to draw users' attention to prominent themes on global health, to harness their support, and to advocate for change. We aimed to describe #GlobalHealth tweets pertinent to given major health issues. Tweets containing the hashtag #GlobalHealth (N = 157,951) from January 1, 2014, to April 30, 2015, were purchased from GNIP Inc. We extracted 5 subcorpora of tweets, each with 1 of 5 co-occurring disease-specific hashtags (#Malaria, #HIV, #TB, #NCDS, and #NTDS) for further analysis. Unsupervised machine learning was applied to each subcorpus to categorize the tweets by their underlying topics and obtain the representative tweets of each topic. The topics were grouped into 1 of 4 themes (advocacy; epidemiological information; prevention, control, and treatment; societal impact) or miscellaneous. Manual categorization of most frequent users was performed. Time zones of users were analyzed. In the entire #GlobalHealth corpus (N = 157,951), there were 40,266 unique users, 85,168 retweets, and 13,107 unique co-occurring hashtags. Of the 13,087 tweets across the 5 subcorpora with co-occurring hashtag #malaria (n = 3640), #HIV (n = 3557), #NCDS (noncommunicable diseases; n = 2373), #TB (tuberculosis; n = 1781), and #NTDS (neglected tropical diseases; n = 1736), the most prevalent theme was prevention, control, and treatment (4339, 33.16%), followed by advocacy (3706, 28.32%), epidemiological information (1803, 13.78%), and societal impact (1617, 12.36%). Among the top 10 users who tweeted the highest number of tweets in the #GlobalHealth corpus, 5 were individual professionals, 3 were news media, and 2 were organizations advocating for global health. The most common users' time zone was Eastern Time (United States and Canada). This study highlighted the specific #GlobalHealth Twitter conversations pertinent to malaria, HIV, tuberculosis, noncommunicable diseases, and neglected tropical diseases. These

  5. Syndromes, Disorders and Maternal Risk Factors Associated with Neural Tube Defects (IV)

    OpenAIRE

    Chen, Chih-Ping

    2008-01-01

    Fetuses with neural tube defects (NTDs) may be associated with maternal and fetal risk factors. This article provides a comprehensive review of maternal and fetal risk factors associated with NTDs, such as infertility, periconceptional clomiphene use and assisted reproductive technology, periconceptional folic acid deficiency and effects offolic acid supplementation and fortification on NTD rates, periconceptional vitamin B1 2 deficiency, single nucleotide polymorphisms and polymorphisms in g...

  6. Oxygen vacancy defects in Ta{sub 2}O{sub 5} showing long-range atomic re-arrangements

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yuzheng; Robertson, John [Engineering Department, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2014-03-17

    The structure, formation energy, and energy levels of the various oxygen vacancies in Ta{sub 2}O{sub 5} have been calculated using the λ phase model. The intra-layer vacancies give rise to unusual, long-range bonding rearrangements, which are different for each defect charge state. The 2-fold coordinated intra-layer vacancy is the lowest cost vacancy and forms a deep level 1.5 eV below the conduction band edge. The 3-fold intra-layer vacancy and the 2-fold inter-layer vacancy are higher cost defects, and form shallower levels. The unusual bonding rearrangements lead to low oxygen migration barriers, which are useful for resistive random access memory applications.

  7. Defect formation energies and homogeneity ranges of rock salt-, pyrite-, chalcopyrite- and molybdenite-type compound semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Fiechter, S. [Hahn-Meitner-Institut, Glienicker Strasse 100, Berlin D-14109 (Germany)

    2004-07-01

    Employing the generalisation of Van Vechten's cavity model, formation energies of neutral point defects in pyrites (FeS{sub 2}, RuS{sub 2}), chalcopyrites (II-IV-V{sub 2} and I-III-VI{sub 2}) as well as molybdenites (MoS{sub 2}, WS{sub 2}) have been estimated. As input parameters the fundamental band gaps, work functions, electron affinities, surface energies, coordination numbers, covalent or ionic radii and unit cell parameters were used. The values calculated for tetrahedrally and octahedrally coordinated compounds agreed well with measured values. The data obtained can be used to calculate point defect concentrations and homogeneity ranges as a function of partial pressure and temperature. Introducing charged vacancies, the conductivity type can be predicted.

  8. Sanitation for all: the global opportunity to increase transgenerational health gains and better understand the link between NCDs and NTDs, a scoping review

    OpenAIRE

    Mishra, Shiva Raj; Dhimal, Meghnath; Bhandari, Parash Mani; Adhikari, Bipin

    2017-01-01

    The global sanitation divide is narrowing. However, in many countries in Asia and Africa, the gap between rural and urban sanitation coverage is rather widening. Moreover, there is an increase in the burden of non-communicable diseases (NCDs), notwithstanding to the already high burden of neglected tropical diseases (NTDs). A scientific query is building on how the global ?sanitation for all? goal will address the dual burden of NTDs and NCDs, and help further understand the link between the ...

  9. Drinking water treatment is not associated with an observed increase in neural tube defects in mice

    Science.gov (United States)

    Melin, Vanessa E.; Johnstone, David W.; Etzkorn, Felicia A.

    2018-01-01

    Disinfection by-products (DBPs) arise when natural organic matter in source water reacts with disinfectants used in the water treatment process. Studies have suggested an association between DBPs and birth defects. Neural tube defects (NTDs) in embryos of untreated control mice were first observed in-house in May 2006 and have continued to date. The source of the NTD-inducing agent was previously determined to be a component of drinking water. Tap water samples from a variety of sources were analyzed for trihalomethanes (THMs) to determine if they were causing the malformations. NTDs were observed in CD-1 mice provided with treated and untreated surface water. Occurrence of NTDs varied by water source and treatment regimens. THMs were detected in tap water derived from surface water but not detected in tap water derived from a groundwater source. THMs were absent in untreated river water and laboratory purified waters, yet the percentage of NTDs in untreated river water were similar to the treated water counterpart. These findings indicate that THMs were not the primary cause of NTDs in the mice since the occurrence of NTDs was unrelated to drinking water disinfection. PMID:24497082

  10. Describing the Prevalence of Neural Tube Defects Worldwide: A Systematic Literature Review.

    Science.gov (United States)

    Zaganjor, Ibrahim; Sekkarie, Ahlia; Tsang, Becky L; Williams, Jennifer; Razzaghi, Hilda; Mulinare, Joseph; Sniezek, Joseph E; Cannon, Michael J; Rosenthal, Jorge

    2016-01-01

    Folate-sensitive neural tube defects (NTDs) are an important, preventable cause of morbidity and mortality worldwide. There is a need to describe the current global burden of NTDs and identify gaps in available NTD data. We conducted a systematic review and searched multiple databases for NTD prevalence estimates and abstracted data from peer-reviewed literature, birth defects surveillance registries, and reports published between January 1990 and July 2014 that had greater than 5,000 births and were not solely based on mortality data. We classified countries according to World Health Organization (WHO) regions and World Bank income classifications. The initial search yielded 11,614 results; after systematic review we identified 160 full text manuscripts and reports that met the inclusion criteria. Data came from 75 countries. Coverage by WHO region varied in completeness (i.e., % of countries reporting) as follows: African (17%), Eastern Mediterranean (57%), European (49%), Americas (43%), South-East Asian (36%), and Western Pacific (33%). The reported NTD prevalence ranges and medians for each region were: African (5.2-75.4; 11.7 per 10,000 births), Eastern Mediterranean (2.1-124.1; 21.9 per 10,000 births), European (1.3-35.9; 9.0 per 10,000 births), Americas (3.3-27.9; 11.5 per 10,000 births), South-East Asian (1.9-66.2; 15.8 per 10,000 births), and Western Pacific (0.3-199.4; 6.9 per 10,000 births). The presence of a registry or surveillance system for NTDs increased with country income level: low income (0%), lower-middle income (25%), upper-middle income (70%), and high income (91%). Many WHO member states (120/194) did not have any data on NTD prevalence. Where data are collected, prevalence estimates vary widely. These findings highlight the need for greater NTD surveillance efforts, especially in lower-income countries. NTDs are an important public health problem that can be prevented with folic acid supplementation and fortification of staple foods.

  11. Describing the Prevalence of Neural Tube Defects Worldwide: A Systematic Literature Review.

    Directory of Open Access Journals (Sweden)

    Ibrahim Zaganjor

    Full Text Available Folate-sensitive neural tube defects (NTDs are an important, preventable cause of morbidity and mortality worldwide. There is a need to describe the current global burden of NTDs and identify gaps in available NTD data.We conducted a systematic review and searched multiple databases for NTD prevalence estimates and abstracted data from peer-reviewed literature, birth defects surveillance registries, and reports published between January 1990 and July 2014 that had greater than 5,000 births and were not solely based on mortality data. We classified countries according to World Health Organization (WHO regions and World Bank income classifications. The initial search yielded 11,614 results; after systematic review we identified 160 full text manuscripts and reports that met the inclusion criteria. Data came from 75 countries. Coverage by WHO region varied in completeness (i.e., % of countries reporting as follows: African (17%, Eastern Mediterranean (57%, European (49%, Americas (43%, South-East Asian (36%, and Western Pacific (33%. The reported NTD prevalence ranges and medians for each region were: African (5.2-75.4; 11.7 per 10,000 births, Eastern Mediterranean (2.1-124.1; 21.9 per 10,000 births, European (1.3-35.9; 9.0 per 10,000 births, Americas (3.3-27.9; 11.5 per 10,000 births, South-East Asian (1.9-66.2; 15.8 per 10,000 births, and Western Pacific (0.3-199.4; 6.9 per 10,000 births. The presence of a registry or surveillance system for NTDs increased with country income level: low income (0%, lower-middle income (25%, upper-middle income (70%, and high income (91%.Many WHO member states (120/194 did not have any data on NTD prevalence. Where data are collected, prevalence estimates vary widely. These findings highlight the need for greater NTD surveillance efforts, especially in lower-income countries. NTDs are an important public health problem that can be prevented with folic acid supplementation and fortification of staple foods.

  12. Example of an application of an assessment procedure for defects in plant operating in the creep range

    International Nuclear Information System (INIS)

    Ainsworth, R.; Coleman, M.C.

    1986-10-01

    A worked example is presented to illustrate the application of a CEGB procedure for the assessment of defects in plant that operates within the creep range. The example chosen is a large cylindrical pressure vessel with a fully circumferential crack for which experimental results are available. The example demonstrates that it is straightforward to perform the calculations required in the procedure for the time for structural failure by continuum damage mechanisms, the time for crack incubation and the time for crack growth. It is predicted that crack incubation in the pressure vessel occurs at about one-third of life with the remaining life being taken up by crack growth. The predictions are in close agreement with the experimentally observed incubation, growth and final failure times. (UK)

  13. Association of main folate metabolic pathway gene polymorphisms with neural tube defects in Han population of Northern China.

    Science.gov (United States)

    Fang, Yulian; Zhang, Ruiping; Zhi, Xiufang; Zhao, Linsheng; Cao, Lirong; Wang, Yizheng; Cai, Chunquan

    2018-04-01

    Neural tube defects (NTDs) are one of the most prevalent and the most severe congenital malformations worldwide. Studies have confirmed that folic acid supplementation could effectively reduce NTDs risk, but the genetic mechanism remains unclear. In this study, we explored association of single nucleotide polymorphisms (SNP) within folate metabolic pathway genes with NTDs in Han population of Northern China. We performed a case-control study to compare genotype and allele distributions of SNPs in 152 patients with NTDs and 169 controls. A total of 16 SNPs within five genes were genotyped by the Sequenom MassARRAY assay. Our results indicated that three SNPs associated significantly with NTDs (P<0.05). For rs2236225 within MTHFD1, children with allele A or genotype AA had a high NTDs risk (OR=1.500, 95%CI=1.061~2.120; OR=2.862, 95%CI=1.022~8.015, respectively). For rs1801133 within MTHFR, NTDs risk markedly increased in patients with allele T or genotype TT (OR=1.552, 95%CI=1.130~2.131; OR=2.344, 95%CI=1.233~4.457, respectively). For rs1801394 within MTRR, children carrying allele G and genotype GG had a higher NTDs risk (OR=1.533, 95%CI=1.102~2.188; OR=2.355, 95%CI=1.044~5.312, respectively). Our results suggest that rs2236225 of MTHFD1 gene, rs1801133 of MTHFR gene and rs1801394 of MTRR gene were associated with NTDs in Han population of Northern China.

  14. Maternal Antenatal Bereavement and Neural Tube Defect in Live-Born Offspring: A Cohort Study.

    Directory of Open Access Journals (Sweden)

    Katja Glejsted Ingstrup

    Full Text Available Maternal emotional stress during pregnancy has previously been associated with congenital neural malformations, but most studies are based on data collected retrospectively. The objective of our study was to investigate associations between antenatal maternal bereavement due to death of a close relative and neural tube defects (NTDs in the offspring.We performed a register-based cohort study including all live-born children (N = 1,734,190 from 1978-2008. Exposure was bereavement due to loss of a close relative from one year before conception to the end of the first trimester of pregnancy. The outcome was NTDs in the offspring according to the International Classification of Disease. We used multivariate logistic regression to estimate prevalence odds ratios (ORs.A total of 2% children were born to mothers who lost a close relative prenatally. During 30 years of follow-up, 1,115 children were diagnosed with any NTDs: spina bifida (n = 889, anencephaly (n = 85 and encephalocele (n = 164. And 23 children were diagnosed with two types of NTDs. Overall, when comparing bereaved mothers to non-bereaved mothers, no significant increased prevalence of NTDs in the offspring was seen (OR = 0.84; 95% confidence interval: 0.52-1.33.Overall maternal bereavement in the antenatal period was not related to NTDs in liveborn offspring.

  15. Nutrition, One-Carbon Metabolism and Neural Tube Defects: A Review

    Directory of Open Access Journals (Sweden)

    Kelei Li

    2016-11-01

    Full Text Available Neural tube defects (NTDs are a group of severe congenital malformations, induced by the combined effects of genes and the environment. The most valuable finding so far has been the protective effect of folic acid supplementation against NTDs. However, many women do not take folic acid supplements until they are pregnant, which is too late to prevent NTDs effectively. Long-term intake of folic acid–fortified food is a good choice to solve this problem, and mandatory folic acid fortification should be further promoted, especially in Europe, Asia and Africa. Vitamin B2, vitamin B-6, vitamin B-12, choline, betaine and n-3 polyunsaturated fatty acids (PUFAs can also reduce the NTD risk by interacting with the one-carbon metabolism pathway. This suggest that multivitamin B combined with choline, betaine and n-3 PUFAs supplementation may have a better protective effect against NTDs than folic acid alone. Genetic polymorphisms involved in one-carbon metabolism are associated with NTD risk, and gene screening for women of childbearing age prior to pregnancy may help prevent NTDs induced by the risk allele. In addition, the consumption of alcohol, tea and coffee, and low intakes of fruit and vegetable are also associated with the increased risk of NTDs, and should be avoided by women of childbearing age.

  16. Inositol- and folate-resistant neural tube defects in mice lacking the epithelial-specific factor Grhl-3.

    Science.gov (United States)

    Ting, Stephen B; Wilanowski, Tomasz; Auden, Alana; Hall, Mark; Voss, Anne K; Thomas, Tim; Parekh, Vishwas; Cunningham, John M; Jane, Stephen M

    2003-12-01

    The neural tube defects (NTDs) spina bifida and anencephaly are widely prevalent severe birth defects. The mouse mutant curly tail (ct/ct) has served as a model of NTDs for 50 years, even though the responsible genetic defect remained unrecognized. Here we show by gene targeting, mapping and genetic complementation studies that a mouse homolog of the Drosophila grainyhead (grh) gene, grainyhead-like-3 (Grhl3), is a compelling candidate for the gene underlying the curly tail phenotype. The NTDs in Grhl3-null mice are more severe than those in the curly tail strain, as the Grhl3 alleles in ct/ct mice are hypomorphic. Spina bifida in ct/ct mice is folate resistant, but its incidence can be markedly reduced by maternal inositol supplementation periconceptually. The NTDs in Grhl3-/- embryos are also folate resistant, but unlike those in ct/ct mice, they are resistant to inositol. These findings suggest that residual Grhl3 expression in ct/ct mice may be required for inositol rescue of folate-resistant NTDs.

  17. Folic acid supplementation influences the distribution of neural tube defect subtypes : A registry-based study

    NARCIS (Netherlands)

    Bergman, J. E. H.; Otten, E.; Verheij, J. B. G. M.; de Walle, H. E. K.

    Periconceptional folic acid (FA) reduces neural tube defect (NTD) risk, but seems to have a varying effect per NTD subtype. We aimed to study the effect of FA supplementation on NTD subtype distribution using data from EUROCAT Northern Netherlands. We included all birth types with non-syndromal NTDs

  18. Genetic, chromosomal, and syndromic causes of neural tube defects

    Science.gov (United States)

    Seidahmed, Mohammed Z.; Abdelbasit, Omer B.; Shaheed, Meeralebbae M.; Alhussein, Khalid A.; Miqdad, Abeer M.; Samadi, Abdulmohsen S.; Khalil, Mohammed I.; Al-Mardawi, Elham; Salih, Mustafa A.

    2014-01-01

    Objective: To ascertain the incidence, and describe the various forms of neural tube defects (NTDs) due to genetic, chromosomal, and syndromic causes. Methods: We carried out a retrospective analysis of data retrieved from the medical records of newborn infants admitted to the Neonatal Intensive Care Unit with NTDs and their mothers spanning 14 years (1996-2009) at the Security Forces Hospital, Riyadh, Saudi Arabia. The cases were ascertained by a perinatologist, neonatologist, geneticist, radiologist, and neurologist. The literature was reviewed via a MEDLINE search. Only liveborn babies were included. Permission from the Educational Committee at the Security Forces Hospital was obtained prior to the collection of data. Results: Out of 103 infants with NTDs admitted during this period, 20 (19.4%) were found to have an underlying genetic syndromic, chromosomal and/or other anomalies. There were 5 cases of Meckel-Gruber syndrome, 2 Joubert syndrome, one Waardenburg syndrome, one Walker-Warburg syndrome, 2 chromosomal disorders, 2 caudal regression, one amniotic band disruption sequence, one associated with omphalocele, one with diaphragmatic hernia, and 4 with multiple congenital anomalies. Conclusions: There is a high rate of underlying genetic syndromic and/or chromosomal causes of NTDs in the Saudi Arabian population due to the high consanguinity rate. Identification of such association can lead to more accurate provisions of genetic counseling to the family including preimplantation genetic diagnosis or early termination of pregnancies associated with lethal conditions. PMID:25551112

  19. Genetic, chromosomal, and syndromic causes of neural tube defects.

    Science.gov (United States)

    Seidahmed, Mohammed Z; Abdelbasit, Omer B; Shaheed, Meeralebbae M; Alhussein, Khalid A; Miqdad, Abeer M; Samadi, Abdulmohsen S; Khalil, Mohammed I; Al-Mardawi, Elham; Salih, Mustafa A

    2014-12-01

    To ascertain the incidence, and describe the various forms of neural tube defects (NTDs) due to genetic, chromosomal, and syndromic causes. We carried out a retrospective analysis of data retrieved from the medical records of newborn infants admitted to the Neonatal Intensive Care Unit with NTDs and their mothers spanning 14 years (1996-2009) at the Security Forces Hospital, Riyadh, Saudi Arabia. The cases were ascertained by a perinatologist, neonatologist, geneticist, radiologist, and neurologist. The literature was reviewed via a MEDLINE search. Only liveborn babies were included. Permission from the Educational Committee at the Security Forces Hospital was obtained prior to the collection of data. Out of 103 infants with NTDs admitted during this period, 20 (19.4%) were found to have an underlying genetic syndromic, chromosomal and/or other anomalies. There were 5 cases of Meckel-Gruber syndrome, 2 Joubert syndrome, one Waardenburg syndrome, one Walker-Warburg syndrome, 2 chromosomal disorders, 2 caudal regression, one amniotic band disruption sequence, one associated with omphalocele, one with diaphragmatic hernia, and 4 with multiple congenital anomalies. There is a high rate of underlying genetic syndromic and/or chromosomal causes of NTDs in the Saudi Arabian population due to the high consanguinity rate. Identification of such association can lead to more accurate provisions of genetic counseling to the family including preimplantation genetic diagnosis or early termination of pregnancies associated with lethal conditions.

  20. Arsenate-induced maternal glucose intolerance and neural tube defects in a mouse model

    International Nuclear Information System (INIS)

    Hill, Denise S.; Wlodarczyk, Bogdan J.; Mitchell, Laura E.; Finnell, Richard H.

    2009-01-01

    Background: Epidemiological studies have linked environmental arsenic (As) exposure to increased type 2 diabetes risk. Periconceptional hyperglycemia is a significant risk factor for neural tube defects (NTDs), the second most common structural birth defect. A suspected teratogen, arsenic (As) induces NTDs in laboratory animals. Objectives: We investigated whether maternal glucose homeostasis disruption was responsible for arsenate-induced NTDs in a well-established dosing regimen used in studies of arsenic's teratogenicity in early neurodevelopment. Methods: We evaluated maternal intraperitoneal (IP) exposure to As 9.6 mg/kg (as sodium arsenate) in LM/Bc/Fnn mice for teratogenicity and disruption of maternal plasma glucose and insulin levels. Selected compounds (insulin pellet, sodium selenate (SS), N-acetyl cysteine (NAC), L-methionine (L-Met), N-tert-Butyl-α-phenylnitrone (PBN)) were investigated for their potential to mitigate arsenate's effects. Results: Arsenate caused significant glucose elevation during an IP glucose tolerance test (IPGTT). Insulin levels were not different between arsenate and control dams before (arsenate, 0.55 ng/dl; control, 0.48 ng/dl) or after glucose challenge (arsenate, 1.09 ng/dl; control, 0.81 ng/dl). HOMA-IR index was higher for arsenate (3.9) vs control (2.5) dams (p = 0.0260). Arsenate caused NTDs (100%, p < 0.0001). Insulin pellet and NAC were the most successful rescue agents, reducing NTD rates to 45% and 35%. Conclusions: IPGTT, insulin assay, and HOMA-IR results suggest a modest failure of glucose stimulated insulin secretion and insulin resistance characteristic of glucose intolerance. Insulin's success in preventing arsenate-induced NTDs provides evidence that these arsenate-induced NTDs are secondary to elevated maternal glucose. The NAC rescue, which did not restore maternal glucose or insulin levels, suggests oxidative disruption plays a role.

  1. Maternal Use of Weight Loss Products and the Risk of Neural Tube Defects in Offspring: A Systematic Literature Review.

    Science.gov (United States)

    Hoang, Thanh T; Agopian, A J; Mitchell, Laura E

    2018-01-15

    Several studies have assessed potential associations between use of weight loss products in the periconceptional period and neural tube defects (NTDs). However, the individual studies are inconclusive and there has not been a systematic review of this literature. We conducted a systematic search, using Ovid MEDLINE and PubMed, to identify studies that evaluated the association between products used for weight loss and the risk of NTDs. Because many studies of birth defects only evaluate a composite birth defect outcome, we evaluated studies that defined the outcome as "any major birth defect" or as NTDs. We abstracted data on study design, exposure definition, outcome definition, covariates and effect size estimates from each article that met our inclusion criteria. For studies that evaluated a composite birth defect outcome, we also abstracted the number of NTD cases included in the composite outcome. We used a modified version of the Newcastle-Ottawa Scale to assess the quality of each article. We screened 865 citations and identified nine articles that met our inclusion criteria. The majority of studies reported positive associations between maternal use of weight loss products and birth defects (overall and NTDs). However, there were few significant associations and there was considerable heterogeneity in the specific exposures assessed across the nine studies. Our systematic review of weight loss products and NTDs indicates that the literature on this topic is sparse. Because several studies reported modest, positive associations between risk and use of weight loss products, additional studies are warranted. Birth Defects Research 110:48-55, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  2. Folic Acid and Birth Defects: A Case Study (Iran

    Directory of Open Access Journals (Sweden)

    Mohammad Bager Hosseini

    2011-01-01

    Full Text Available The aim of this study was to evaluate the impact of folic acid use in pregnancy for the reduction of neural tube defects (NTDs in the northwest region of Iran. We studied 243 women with pregnancies complicated by some forms of birth defect(s. These patients were identified by medical diagnostic tests as having a fetus with some types of congenital anomalies. The prevalence of NTDs among pregnant women who were referred for therapeutic termination of pregnancy was 24.7 percent. Consumption of folic acid prevented NTDs by 79 percent (Odds Ratio = 0.21, CI 95%: 0.12–0.40 and 94 percent (Odds Ratio = 0.06, CI 95%: 0.03–0.15 compared to pregnancies complicated by other anomalies and normal pregnancies, respectively. Hydrops fetalis, hydrocephaly, Down syndrome, and limb anomalies did not have any significant association with the folic acid use. Along with the advice for the consumption of folic acid for pregnant women, they should be offered prenatal screening or diagnostic tests to identify fetal abnormalities for possible termination of pregnancy.

  3. A regulating element essential for PDGFRA transcription is recognized by neural tube defect-associated PRX homeobox transcription factors

    NARCIS (Netherlands)

    Joosten, Paul H. L. J.; Toepoel, Mascha; van Oosterhout, Dirk; Afink, Gijs B.; van Zoelen, Everardus J. J.

    2002-01-01

    We have previously shown that deregulated expression of the platelet-derived growth factor alpha-receptor (PDGFRA) can be associated with neural tube defects (NTDs) in both men and mice. In the present study, we have investigated the transcription factors that control the up-regulation of PDGFRA

  4. Epigenetic profiles in children with a neural tube defect; a case-control study in two populations

    NARCIS (Netherlands)

    L. Stolk (Lisette); M.I. Both (Marieke); N.H. van Mill (Nina); M.M.P.J. Verbiest (Michael); P.H.C. Eilers (Paul); H. Zhu (Huiping); L. Suarez (Lucina); A.G. Uitterlinden (André); R.P.M. Steegers-Theunissen (Régine)

    2013-01-01

    textabstractFolate deficiency is implicated in the causation of neural tube defects (NTDs). The preventive effect of periconceptional folic acid supplement use is partially explained by the treatment of a deranged folate-dependent one carbon metabolism, which provides methyl groups for

  5. Detection of copy number variants reveals association of cilia genes with neural tube defects.

    Directory of Open Access Journals (Sweden)

    Xiaoli Chen

    Full Text Available BACKGROUND: Neural tube defects (NTDs are one of the most common birth defects caused by a combination of genetic and environmental factors. Currently, little is known about the genetic basis of NTDs although up to 70% of human NTDs were reported to be attributed to genetic factors. Here we performed genome-wide copy number variants (CNVs detection in a cohort of Chinese NTD patients in order to exam the potential role of CNVs in the pathogenesis of NTDs. METHODS: The genomic DNA from eighty-five NTD cases and seventy-five matched normal controls were subjected for whole genome CNVs analysis. Non-DGV (the Database of Genomic Variants CNVs from each group were further analyzed for their associations with NTDs. Gene content in non-DGV CNVs as well as participating pathways were examined. RESULTS: Fifty-five and twenty-six non-DGV CNVs were detected in cases and controls respectively. Among them, forty and nineteen CNVs involve genes (genic CNV. Significantly more non-DGV CNVs and non-DGV genic CNVs were detected in NTD patients than in control (41.2% vs. 25.3%, p<0.05 and 37.6% vs. 20%, p<0.05. Non-DGV genic CNVs are associated with a 2.65-fold increased risk for NTDs (95% CI: 1.24-5.87. Interestingly, there are 41 cilia genes involved in non-DGV CNVs from NTD patients which is significantly enriched in cases compared with that in controls (24.7% vs. 9.3%, p<0.05, corresponding with a 3.19-fold increased risk for NTDs (95% CI: 1.27-8.01. Pathway analyses further suggested that two ciliogenesis pathways, tight junction and protein kinase A signaling, are top canonical pathways implicated in NTD-specific CNVs, and these two novel pathways interact with known NTD pathways. CONCLUSIONS: Evidence from the genome-wide CNV study suggests that genic CNVs, particularly ciliogenic CNVs are associated with NTDs and two ciliogenesis pathways, tight junction and protein kinase A signaling, are potential pathways involved in NTD pathogenesis.

  6. Ectopic cross-talk between thyroid and retinoic acid signaling: A possible etiology for spinal neural tube defects.

    Science.gov (United States)

    Li, Huili; Bai, Baoling; Zhang, Qin; Bao, Yihua; Guo, Jin; Chen, Shuyuan; Miao, Chunyue; Liu, Xiaozhen; Zhang, Ting

    2015-12-01

    Previous studies have highlighted the connections between neural tube defects (NTDs) and both thyroid hormones (TH) and vitamin A. However, whether the two hormonal signaling pathways interact in NTDs has remained unclear. We measured the expression levels of TH signaling genes in human fetuses with spinal NTDs associated with maternal hyperthyroidism as well as levels of retinoic acid (RA) signaling genes in mouse fetuses exposed to an overdose of RA using NanoString or real-time PCR on spinal cord tissues. Interactions between the two signaling pathways were detected by ChIP assays. The data revealed attenuated DIO2/DIO3 switching in fetuses with NTDs born to hyperthyroid mothers. The promoters of the RA signaling genes CRABP1 and RARB were ectopically occupied by increased RXRG and RXRB but displayed decreased levels of inhibitory histone modifications, suggesting that elevated TH signaling abnormally stimulates RA signaling genes. Conversely, in the mouse model, the observed decrease in Dio3 expression could be explained by increased levels of inhibitory histone modifications in the Dio3 promoter region, suggesting that overactive RA signaling may ectopically derepress TH signaling. This study thus raises in vivo a possible abnormal cross-promotion between two different hormonal signals through their common RXRs and the subsequent recruitment of histone modifications, prompting further investigation into their involvement in the etiology of spinal NTDs. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. A targeted sequencing panel identifies rare damaging variants in multiple genes in the cranial neural tube defect, anencephaly.

    Science.gov (United States)

    Ishida, M; Cullup, T; Boustred, C; James, C; Docker, J; English, C; Lench, N; Copp, A J; Moore, G E; Greene, N D E; Stanier, P

    2018-04-01

    Neural tube defects (NTDs) affecting the brain (anencephaly) are lethal before or at birth, whereas lower spinal defects (spina bifida) may lead to lifelong neurological handicap. Collectively, NTDs rank among the most common birth defects worldwide. This study focuses on anencephaly, which despite having a similar frequency to spina bifida and being the most common type of NTD observed in mouse models, has had more limited inclusion in genetic studies. A genetic influence is strongly implicated in determining risk of NTDs and a molecular diagnosis is of fundamental importance to families both in terms of understanding the origin of the condition and for managing future pregnancies. Here we used a custom panel of 191 NTD candidate genes to screen 90 patients with cranial NTDs (n = 85 anencephaly and n = 5 craniorachischisis) with a targeted exome sequencing platform. After filtering and comparing to our in-house control exome database (N = 509), we identified 397 rare variants (minor allele frequency, MAF < 1%), 21 of which were previously unreported and predicted damaging. This included 1 frameshift (PDGFRA), 2 stop-gained (MAT1A; NOS2) and 18 missense variations. Together with evidence for oligogenic inheritance, this study provides new information on the possible genetic causation of anencephaly. © 2017 The Authors. Clinical Genetics published by John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Global Burden of Neural Tube Defects, Risk Factors, and Prevention

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    Joseph E

    2014-11-01

    Full Text Available Neural tube defects (NTDs, serious birth defects of the brain and spine usually resulting in death or paralysis, affect an estimated 300,000 births each year worldwide. Although the majority of NTDs are preventable with adequate folic acid consumption during the preconception period and throughout the first few weeks of gestation, many populations, in particular those in low and middle resource settings, do not have access to fortified foods or vitamin supplements containing folic acid. Further, accurate birth defects surveillance data, which could help inform mandatory fortification and other NTD prevention initiatives, are lacking in many of these settings. The burden of birth defects in South East Asia is among the highest in the world. Expanding global neural tube defects prevention initiatives can support the achievement of the United Nations Millennium Development Goal 4 to reduce child mortality, a goal which many countries in South East Asia are currently not poised to reach, and the 63rd World Health Assembly Resolution on birth defects. More work is needed to develop and implement mandatory folic acid fortification policies, as well as supplementation programs in countries where the reach of fortification is limited.

  9. Magnitude of Neural Tube Defects and Associated Risk Factors at Three Teaching Hospitals in Addis Ababa, Ethiopia

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    Abel Gedefaw

    2018-01-01

    Full Text Available There is scarcity of data on prevalence of neural tube defects (NTDs in lower-income countries. Local data are important to understand the real burden of the problem and explore risk factors to design and implement preventive approaches. This study aimed to determine prevalence and risk factors of NTDs. A hospital-based cross-sectional and unmatched case-control study was conducted at three teaching hospitals of Addis Ababa University. NTDs were defined as cases of anencephaly, spina bifida, and encephalocele based on ICD-10 criteria. The prevalence of NTDs was calculated per 10,000 births for both birth and total prevalence. During seven months, we observed 55 cases of NTDs out of 8677 births after 28 weeks of gestation—birth prevalence of 63.4 per 10,000 births (95% confidence interval (CI, 51–77. A total of 115 cases were medically terminated after 12 weeks of gestation. Fifty-six of these terminations (48.7% were due to NTDs. Thus, total prevalence of NTDs after 12 weeks’ gestation is 126 per 10,000 births (95% CI, 100–150. Planned pregnancy (adjusted odds ratio (aOR, 0.47; 95% CI, 0.24–0.92, male sex (aOR, 0.56; 95% CI, 0.33–0.94, normal or underweight body mass index (aOR, 0.49; 95%, 0.29–0.95, and taking folic acid or multivitamins during first trimester (aOR, 0.47; 95%, 0.23–0.95 were protective of NTDs. However, annual cash family income less than $1,300 USD (aOR, 2.5; 95%, 1.2–5.5, $1,300–1,800 USD (aOR, 2.8; 95%, 1.3–5.8, and $1,801–2,700 USD (aOR, 2.6; 95%, 1.2–5.8 was found to be risk factors compared to income greater than $2,700 USD. The prevalence of NTDs was found to be high in this setting. Comprehensive preventive strategies focused on identified risk factors should be urgently established. More studies on prevention strategies, including folic acid supplementations, should be conducted in the setting.

  10. Magnitude of Neural Tube Defects and Associated Risk Factors at Three Teaching Hospitals in Addis Ababa, Ethiopia.

    Science.gov (United States)

    Gedefaw, Abel; Teklu, Sisay; Tadesse, Birkneh Tilahun

    2018-01-01

    There is scarcity of data on prevalence of neural tube defects (NTDs) in lower-income countries. Local data are important to understand the real burden of the problem and explore risk factors to design and implement preventive approaches. This study aimed to determine prevalence and risk factors of NTDs. A hospital-based cross-sectional and unmatched case-control study was conducted at three teaching hospitals of Addis Ababa University. NTDs were defined as cases of anencephaly, spina bifida, and encephalocele based on ICD-10 criteria. The prevalence of NTDs was calculated per 10,000 births for both birth and total prevalence. During seven months, we observed 55 cases of NTDs out of 8677 births after 28 weeks of gestation-birth prevalence of 63.4 per 10,000 births (95% confidence interval (CI), 51-77). A total of 115 cases were medically terminated after 12 weeks of gestation. Fifty-six of these terminations (48.7%) were due to NTDs. Thus, total prevalence of NTDs after 12 weeks' gestation is 126 per 10,000 births (95% CI, 100-150). Planned pregnancy (adjusted odds ratio (aOR), 0.47; 95% CI, 0.24-0.92), male sex (aOR, 0.56; 95% CI, 0.33-0.94), normal or underweight body mass index (aOR, 0.49; 95%, 0.29-0.95), and taking folic acid or multivitamins during first trimester (aOR, 0.47; 95%, 0.23-0.95) were protective of NTDs. However, annual cash family income less than $1,300 USD (aOR, 2.5; 95%, 1.2-5.5), $1,300-1,800 USD (aOR, 2.8; 95%, 1.3-5.8), and $1,801-2,700 USD (aOR, 2.6; 95%, 1.2-5.8) was found to be risk factors compared to income greater than $2,700 USD. The prevalence of NTDs was found to be high in this setting. Comprehensive preventive strategies focused on identified risk factors should be urgently established. More studies on prevention strategies, including folic acid supplementations, should be conducted in the setting.

  11. INCREASED MATERNAL SERUM ALPHA-FETOPROTEIN AND HUMAN CHORIONIC-GONADOTROPIN IN COMPROMISED PREGNANCIES OTHER THAN FOR NEURAL-TUBE DEFECTS OR DOWN-SYNDROME

    NARCIS (Netherlands)

    BEEKHUIS, [No Value; VANLITH, JMM; DEWOLF, BTHM; MANTINGH, A

    Intrauterine fetal death occurred in four women who were 'screen-positive' in a screening programme for neural tube defects (NTDs) and Down syndrome (DS). These women had very high levels of maternal serum alpha-fetoprotein (MSAFP) and maternal serum human chorionic gonadotropin (MShCG). Therefore,

  12. Levels of Polycyclic Aromatic Hydrocarbons in Maternal Serum and Risk of Neural Tube Defects in Offspring

    Science.gov (United States)

    2015-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants, and have been reported to be a risk factor for human neural tube defects (NTDs). We investigated the relationship between PAH concentrations in maternal serum and NTD risk in offspring using a case-control study design, and explored the link between PAH concentrations to household energy usage characteristics and life styles. One hundred and seventeen women who had NTD-affected pregnancies (cases) and 121 women who delivered healthy infants (controls) were recruited in Northern China. Maternal blood samples were collected at pregnancy termination or at delivery. Twenty-seven PAHs were measured by gas chromatography–mass spectrometry. The concentrations of 13 individual PAHs detected were significantly higher in the cases than in the controls. Clear dose–response relationships between concentrations of most individual PAHs and the risk of total NTDs or subtypes were observed, even when potential covariates were adjusted for. High-molecular-weight PAHs (H-PAHs) showed higher risk than low-molecular-weight PAHs (L-PAHs). No associations between PAH concentrations and indoor life styles and energy usage characteristics were observed. It was concluded that maternal exposure to PAHs was associated with an increased risk of NTDs, and H-PAHs overall posed a higher risk for NTDs than L-PAHs. PMID:25488567

  13. Skin disease prevalence study in schoolchildren in rural Côte d'Ivoire: Implications for integration of neglected skin diseases (skin NTDs).

    Science.gov (United States)

    Yotsu, Rie Roselyne; Kouadio, Kouamé; Vagamon, Bamba; N'guessan, Konan; Akpa, Amari Jules; Yao, Aubin; Aké, Julien; Abbet Abbet, Rigobert; Tchamba Agbor Agbor, Barbine; Bedimo, Roger; Ishii, Norihisa; Fuller, L Claire; Hay, Roderick; Mitjà, Oriol; Drechsler, Henning; Asiedu, Kingsley

    2018-05-01

    Early detection of several skin-related neglected tropical diseases (skin NTDs)-including leprosy, Buruli ulcer, yaws, and scabies- may be achieved through school surveys, but such an approach has seldom been tested systematically on a large scale in endemic countries. Additionally, a better understanding of the spectrum of skin diseases and the at-risk populations to be encountered during such surveys is necessary to facilitate the process. We performed a school skin survey for selected NTDs and the spectrum of skin diseases, among primary schoolchildren aged 5 to 15 in Côte d'Ivoire, West Africa. This 2-phase survey took place in 49 schools from 16 villages in the Adzopé health district from November 2015 to January 2016. The first phase involved a rapid visual examination of the skin by local community healthcare workers (village nurses) to identify any skin abnormality. In a second phase, a specialized medical team including dermatologists performed a total skin examination of all screened students with any skin lesion and provided treatment where necessary. Of a total of 13,019 children, 3,504 screened positive for skin lesions and were listed for the next stage examination. The medical team examined 1,138 of these children. The overall prevalence of skin diseases was 25.6% (95% CI: 24.3-26.9%). The predominant diagnoses were fungal infections (n = 858, prevalence: 22.3%), followed by inflammatory skin diseases (n = 265, prevalence: 6.9%). Skin diseases were more common in boys and in children living along the main road with heavy traffic. One case of multi-bacillary type leprosy was detected early, along with 36 cases of scabies. Our survey was met with very good community acceptance. We carried out the first large-scale integrated, two-phase pediatric multi-skin NTD survey in rural Côte d'Ivoire, effectively reaching a large population. We found a high prevalence of skin diseases in children, but only limited number of skin NTDs. With the lessons learned

  14. Folic Acid and Birth Defects: A Case Study (Iran

    Directory of Open Access Journals (Sweden)

    Saeid Dastgiri

    2015-07-01

    Full Text Available Background and Objectives : The aim of this study was to evaluate the impact of using folic acid during pregnancy for the reduction of neural tube defects (NTDs in the northwest region of Iran. Material and Methods : In this study, 243 pregnant women that were identified by medical diagnostic tests as having a fetus with some types of congenital anomalies were evaluated. They were referred to Legal Medicine Organization of East Azarbaijan province to get permission for therapeutic termination of pregnancy. Results : The prevalence of NTDs among pregnant women who were referred for therapeutic termination of pregnancy was 24.7%. Consumption of folic acid prevented NTDs by 79% (Odds Ratio = 0.21, CI 95%: 0.12–0.40 and 94% (Odds Ratio = 0.06, CI 95%: 0.03–0.15 compared to pregnancies complicated by other anomalies and normal pregnancies, respectively. Hydrops fetalis, hydrocephaly, Down syndrome and limb anomalies did not have any significant association with use folic acid. Conclusion : Along with the advice for the consumption of folic acid for pregnant women, they should be offered prenatal screening or diagnostic tests to identify fetal abnormalities for possible termination of pregnancy for maternal and child health promotion. ​

  15. NMDA Receptor Signaling Is Important for Neural Tube Formation and for Preventing Antiepileptic Drug-Induced Neural Tube Defects.

    Science.gov (United States)

    Sequerra, Eduardo B; Goyal, Raman; Castro, Patricio A; Levin, Jacqueline B; Borodinsky, Laura N

    2018-05-16

    Failure of neural tube closure leads to neural tube defects (NTDs), which can have serious neurological consequences or be lethal. Use of antiepileptic drugs (AEDs) during pregnancy increases the incidence of NTDs in offspring by unknown mechanisms. Here we show that during Xenopus laevis neural tube formation, neural plate cells exhibit spontaneous calcium dynamics that are partially mediated by glutamate signaling. We demonstrate that NMDA receptors are important for the formation of the neural tube and that the loss of their function induces an increase in neural plate cell proliferation and impairs neural cell migration, which result in NTDs. We present evidence that the AED valproic acid perturbs glutamate signaling, leading to NTDs that are rescued with varied efficacy by preventing DNA synthesis, activating NMDA receptors, or recruiting the NMDA receptor target ERK1/2. These findings may prompt mechanistic identification of AEDs that do not interfere with neural tube formation. SIGNIFICANCE STATEMENT Neural tube defects are one of the most common birth defects. Clinical investigations have determined that the use of antiepileptic drugs during pregnancy increases the incidence of these defects in the offspring by unknown mechanisms. This study discovers that glutamate signaling regulates neural plate cell proliferation and oriented migration and is necessary for neural tube formation. We demonstrate that the widely used antiepileptic drug valproic acid interferes with glutamate signaling and consequently induces neural tube defects, challenging the current hypotheses arguing that they are side effects of this antiepileptic drug that cause the increased incidence of these defects. Understanding the mechanisms of neurotransmitter signaling during neural tube formation may contribute to the identification and development of antiepileptic drugs that are safer during pregnancy. Copyright © 2018 the authors 0270-6474/18/384762-12$15.00/0.

  16. Risk factors of neural tube defects: A reality of Batna region in Algeria

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    Romyla Bourouba

    2018-07-01

    Full Text Available Background: Neural tube defects (NTDs are severe birth defects, with genetic and/or environmental risk factors. Aim: The objective of this study was to analyze data on NTDs cases at the Batna Maternity Hospital and to investigate some environmental and two genetic risk factors suspected in the etiology of NTDs. Subjects and methods: This study was conducted on 82 healthy participants and 48 mothers with an NTD child. Peripheral blood samples were collected, in EDTA tubes and frozen at −20 °C until DNA extraction by conventional method. Genetic analysis of methylene tetrahydrofolate reductase C677T polymorphism was determined by real time PCR, while cystathionine-beta-synthase 844 insertion was investigated by traditional PCR. Chi-square analyses were used to evaluate differences in the distribution of data. The odds-ratio was also calculated. A P-value less than 0.05 were significant. Results: The incidence of NTD in Batna region was 1.58 per 1000 births. The rate of NTD was significantly higher in females than males, highest affected NTD newborn’s was observed in mothers aged between 25 and 29 years and the consanguinity among all NTD cases was 30%. Data showed no significant association of NTDs with personal education, obesity, diabetes, but regarding folic acid consumption, about 86% of NTD’s mothers in our region didn’t take pre-conceptional supplementation with this vitamin .Genetic factors results didn't show a significant association of NTDs with specific mutations of the variant C677T MTHFR, and no gene-gene interaction of CBS insertion and C677T polymorphism was found, despite a significant difference in heterozygote frequency of CBS 844ins68 genotype between NTD’s mothers and controls, OR: 2.85(1.18–6.88. Conclusion: NTD represents a real public health problem in Batna, Algeria. Various genetic and/or nutritional factors are implicated, although the mechanism is not clear. We suggest that further research should continue

  17. Evaluation of common genetic variants in 82 candidate genes as risk factors for neural tube defects

    LENUS (Irish Health Repository)

    Pangilinan, Faith

    2012-08-02

    AbstractBackgroundNeural tube defects (NTDs) are common birth defects (~1 in 1000 pregnancies in the US and Europe) that have complex origins, including environmental and genetic factors. A low level of maternal folate is one well-established risk factor, with maternal periconceptional folic acid supplementation reducing the occurrence of NTD pregnancies by 50-70%. Gene variants in the folate metabolic pathway (e.g., MTHFR rs1801133 (677 C > T) and MTHFD1 rs2236225 (R653Q)) have been found to increase NTD risk. We hypothesized that variants in additional folate\\/B12 pathway genes contribute to NTD risk.MethodsA tagSNP approach was used to screen common variation in 82 candidate genes selected from the folate\\/B12 pathway and NTD mouse models. We initially genotyped polymorphisms in 320 Irish triads (NTD cases and their parents), including 301 cases and 341 Irish controls to perform case–control and family based association tests. Significantly associated polymorphisms were genotyped in a secondary set of 250 families that included 229 cases and 658 controls. The combined results for 1441 SNPs were used in a joint analysis to test for case and maternal effects.ResultsNearly 70 SNPs in 30 genes were found to be associated with NTDs at the p < 0.01 level. The ten strongest association signals (p-value range: 0.0003–0.0023) were found in nine genes (MFTC, CDKN2A, ADA, PEMT, CUBN, GART, DNMT3A, MTHFD1 and T (Brachyury)) and included the known NTD risk factor MTHFD1 R653Q (rs2236225). The single strongest signal was observed in a new candidate, MFTC rs17803441 (OR = 1.61 [1.23-2.08], p = 0.0003 for the minor allele). Though nominally significant, these associations did not remain significant after correction for multiple hypothesis testing.ConclusionsTo our knowledge, with respect to sample size and scope of evaluation of candidate polymorphisms, this is the largest NTD genetic association study reported to date. The scale of the study and the

  18. Investigation of alpha emitters in fresh and powdered blood of fertile women: an in vitro application of CR-39 NTDs

    International Nuclear Information System (INIS)

    Salih, N.F.; University of Koya, Kurdistan; Jaafar, M.S.

    2014-01-01

    Blood samples were acquired from 60 women aged 20-44 years having decreased fertility, infertile or with uterine tumors in the Iraqi Kurdistan region. The concentrations of α emitters in fresh blood ranged from 0.0029 to 0.0088 ppm, whereas those in powdered blood ranged from 0.0036 ppm in Eiskan to 0.0096 ppm in Halabjay-Kon in Sulaymania. The α emitter concentrations in fresh blood ranged from 0.0029 to 0.0139 ppm, whereas those in powdered blood ranged from 0.0031 ppm in Shorsh to 0.0146 ppm in Sedakan in the Erbil Governorate. However, the concentrations of α emitters in the blood of women with decreased fertility were higher in the North than women from South Iraq. The difference significantly p < 0.001 revealed higher means of track density of fresh and powder blood in Erbil compared to Sulaymania. α are more damaging to the living tissue and exposure of the gonads leads to decreased fertility in women, most of data have been significant therefore, the result shown the radiation effect on women fertility. (author)

  19. Mediterranean diet, folic acid, and neural tube defects.

    Science.gov (United States)

    Fischer, Maximilian; Stronati, Mauro; Lanari, Marcello

    2017-08-17

    The Mediterranean diet has been for a very long time the basis of food habits all over the countries of the Mediterranean basin, originally founded on rural models and low consumption of meat products and high-fat/high-processed foods. However, in the modern era, the traditional Mediterranean diet pattern is now progressively eroding due to the widespread dissemination of the Western-type economy, life-style, technology-driven culture, as well as the globalisation of food production, availability and consumption, with consequent homogenisation of food culture and behaviours. This transition process may affect many situations, including pregnancy and offspring's health. The problem of the diet during pregnancy and the proper intake of nutrients are nowadays a very current topic, arousing much debate. The Mediterranean dietary pattern, in particular, has been associated with the highest risk reduction of major congenital anomalies, like the heterogeneous class of neural tube defects (NTDs). NTDs constitute a major health burden (0.5-2/1000 pregnancies worldwide) and still remain a preventable cause of still birth, neonatal and infant death, or significant lifelong disabilities. Many studies support the finding that appropriate folate levels during pregnancy may confer protection against these diseases. In 1991 one randomised controlled trial (RCT) demonstrated for the first time that periconceptional supplementation of folic acid is able to prevent the recurrence of NTDs, finding confirmed by many other subsequent studies. Anyway, the high rate of unplanned/unintended pregnancies and births and other issues hindering the achievement of adequate folate levels in women in childbearing age, induced the US government and many other countries to institute mandatory food fortification with folic acid. The actual strategy adopted by European Countries (including Italy) suggests that women take 0,4 mg folic acid/die before conception. The main question is which intervention

  20. Developmental and Post-Eruptive Defects in Molar Enamel of Free-Ranging Eastern Grey Kangaroos (Macropus giganteus Exposed to High Environmental Levels of Fluoride.

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    Uwe Kierdorf

    Full Text Available Dental fluorosis has recently been diagnosed in wild marsupials inhabiting a high-fluoride area in Victoria, Australia. Information on the histopathology of fluorotic marsupial enamel has thus far not been available. This study analyzed the developmental and post-eruptive defects in fluorotic molar enamel of eastern grey kangaroos (Macropus giganteus from the same high-fluoride area using light microscopy and backscattered electron imaging in the scanning electron microscope. The fluorotic enamel exhibited a brownish to blackish discolouration due to post-eruptive infiltration of stains from the oral cavity and was less resistant to wear than normally mineralized enamel of kangaroos from low-fluoride areas. Developmental defects of enamel included enamel hypoplasia and a pronounced hypomineralization of the outer (sub-surface enamel underneath a thin rim of well-mineralized surface enamel. While the hypoplastic defects denote a disturbance of ameloblast function during the secretory stage of amelogenesis, the hypomineralization is attributed to an impairment of enamel maturation. In addition to hypoplastic defects, the fluorotic molars also exhibited numerous post-eruptive enamel defects due to the flaking-off of portions of the outer, hypomineralized enamel layer during mastication. The macroscopic and histopathological lesions in fluorotic enamel of M. giganteus match those previously described for placental mammals. It is therefore concluded that there exist no principal differences in the pathogenic mechanisms of dental fluorosis between marsupial and placental mammals. The regular occurrence of hypomineralized, opaque outer enamel in the teeth of M. giganteus and other macropodids must be considered in the differential diagnosis of dental fluorosis in these species.

  1. Developmental and Post-Eruptive Defects in Molar Enamel of Free-Ranging Eastern Grey Kangaroos (Macropus giganteus) Exposed to High Environmental Levels of Fluoride

    Science.gov (United States)

    Kierdorf, Uwe; Death, Clare; Hufschmid, Jasmin; Witzel, Carsten; Kierdorf, Horst

    2016-01-01

    Dental fluorosis has recently been diagnosed in wild marsupials inhabiting a high-fluoride area in Victoria, Australia. Information on the histopathology of fluorotic marsupial enamel has thus far not been available. This study analyzed the developmental and post-eruptive defects in fluorotic molar enamel of eastern grey kangaroos (Macropus giganteus) from the same high-fluoride area using light microscopy and backscattered electron imaging in the scanning electron microscope. The fluorotic enamel exhibited a brownish to blackish discolouration due to post-eruptive infiltration of stains from the oral cavity and was less resistant to wear than normally mineralized enamel of kangaroos from low-fluoride areas. Developmental defects of enamel included enamel hypoplasia and a pronounced hypomineralization of the outer (sub-surface) enamel underneath a thin rim of well-mineralized surface enamel. While the hypoplastic defects denote a disturbance of ameloblast function during the secretory stage of amelogenesis, the hypomineralization is attributed to an impairment of enamel maturation. In addition to hypoplastic defects, the fluorotic molars also exhibited numerous post-eruptive enamel defects due to the flaking-off of portions of the outer, hypomineralized enamel layer during mastication. The macroscopic and histopathological lesions in fluorotic enamel of M. giganteus match those previously described for placental mammals. It is therefore concluded that there exist no principal differences in the pathogenic mechanisms of dental fluorosis between marsupial and placental mammals. The regular occurrence of hypomineralized, opaque outer enamel in the teeth of M. giganteus and other macropodids must be considered in the differential diagnosis of dental fluorosis in these species. PMID:26895178

  2. Interaction between the SLC19A1 gene and maternal first trimester fever on offspring neural tube defects.

    Science.gov (United States)

    Pei, Lijun; Zhu, Huiping; Ye, Rongwei; Wu, Jilei; Liu, Jianmeng; Ren, Aiguo; Li, Zhiwen; Zheng, Xiaoying

    2015-01-01

    Many studies have indicated that the reduced folate carrier gene (SLC19A1) is associated with an increased risk of neural tube defects (NTDs). However, the interaction between the SLC19A1 gene variant and maternal fever exposure and NTD risk remains unknown. The aim of this study was to investigate whether the risk for NTDs was influenced by the interactions between the SLC19A1 (rs1051266) variant and maternal first trimester fever. We investigated the potential interaction between maternal first trimester fever and maternal or offspring SLC19A1 polymorphism through a population-based case-control study. One hundred and four nuclear families with NTDs and 100 control families with nonmal newborns were included in the study. SLC19A1 polymorphism was determined using polymerase chain reaction-restricted fragment length polymorphism. Mothers who had the GG/GA genotype and first trimester fever had an elevated risk of NTDs (adjusted odds ratio, 11.73; 95% confidence interval, 3.02-45.58) as compared to absence of maternal first trimester fever and AA genotype after adjusting for maternal education, paternal education, and age, and had a significant interactive coefficient (γ = 3.17) between maternal GG/GA genotype and first trimester fever. However, there was no interaction between offspring's GG/GA genotype and maternal first trimester fever (the interactive coefficient γ = 0.97) after adjusting for confounding factors. Our findings suggested that the risk of NTDs was potentially influenced by a gene-environment interaction between maternal SLC19A1 rs1051266 GG/GA genotype and first trimester fever. Maternal GG/GA genotype may strengthen the effect of maternal fever exposure on NTD risk in this Chinese population. © 2014 Wiley Periodicals, Inc.

  3. Folic acid and pantothenic acid protection against valproic acid-induced neural tube defects in CD-1 mice

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, Jennifer E [Department of Pharmacology and Toxicology and School of Environmental Studies, Queen' s University, Kingston, Ontario, K7L 3N6 (Canada); Raymond, Angela M [Department of Pharmacology and Toxicology and School of Environmental Studies, Queen' s University, Kingston, Ontario, K7L 3N6 (Canada); Winn, Louise M [Department of Pharmacology and Toxicology and School of Environmental Studies, Queen' s University, Kingston, Ontario, K7L 3N6 (Canada)

    2006-03-01

    In utero exposure to valproic acid (VPA) during pregnancy is associated with an increased risk of neural tube defects (NTDs). Although the mechanism by which VPA mediates these effects is unknown, VPA-initiated changes in embryonic protein levels have been implicated. The objectives of this study were to investigate the effect of in utero VPA exposure on embryonic protein levels of p53, NF-{kappa}B, Pim-1, c-Myb, Bax, and Bcl-2 in the CD-1 mouse. We also evaluated the protective effects of folic acid and pantothenic acid on VPA-induced NTDs and VPA-induced embryonic protein changes in this model. Pregnant CD-1 mice were administered a teratogenic dose of VPA prior to neural tube closure and embryonic protein levels were analyzed. In our study, VPA (400 mg/kg)-induced NTDs (24%) and VPA-exposed embryos with an NTD showed a 2-fold increase in p53, and 4-fold decreases in NF-{kappa}B, Pim-1, and c-Myb protein levels compared to their phenotypically normal littermates (P < 0.05). Additionally, VPA increased the ratio of embryonic Bax/Bcl-2 protein levels (P < 0.05). Pretreatment of pregnant dams with either folic acid or pantothenic acid prior to VPA significantly protected against VPA-induced NTDs (P < 0.05). Folic acid also reduced VPA-induced alterations in p53, NF-{kappa}B, Pim-1, c-Myb, and Bax/Bcl-2 protein levels, while pantothenic acid prevented VPA-induced alterations in NF-{kappa}B, Pim-1, and c-Myb. We hypothesize that folic acid and pantothenic acid protect CD-1 embryos from VPA-induced NTDs by independent, but not mutually exclusive mechanisms, both of which may be mediated by the prevention of VPA-induced alterations in proteins involved in neurulation.

  4. Maternal Consumption of Non-Staple Food in the First Trimester and Risk of Neural Tube Defects in Offspring

    Directory of Open Access Journals (Sweden)

    Meng Wang

    2015-04-01

    Full Text Available To study the associations between maternal consumption of non-staple food in the first trimester and risk of neural tube defects (NTDs in offspring. Data collected from a hospital-based case-control study conducted between 2006 and 2008 in Shandong/Shanxi provinces including 459 mothers with NTDs-affected births and 459 mothers without NTDs-affected births. Logistic regression models were used to examine the associations between maternal consumption of non-staple food in the first trimester and risk of NTDs in offspring. The effects were evaluated by odds ratio (OR and 95% confidence intervals (95% CIs with SAS9.1.3.software. Maternal consumption of milk, fresh fruits and nuts in the first trimester were protective factors for total NTDs. Compared with consumption frequency of ˂1 meal/week, the ORs for milk consumption frequency of 1–2, 3–6, ≥7 meals/week were 0.50 (95% CI: 0.28–0.88, 0.56 (0.32–0.99, and 0.59 (0.38–0.90, respectively; the ORs for fresh fruits consumption frequency of 1–2, 3–6, ≥7 meals/week were 0.29 (95% CI: 0.12–0.72, 0.22 (0.09–0.53, and 0.32 (0.14–0.71, respectively; the ORs for nuts consumption frequency of 1–2, 3–6, ≥7 meals/week were 0.60 (95% CI: 0.38–0.94, 0.49 (0.31–0.79, and 0.63 (0.36–1.08, respectively. Different effects of above factors on NTDs were found for subtypes of anencephaly and spina bifida. Maternal non-staple food consumption of milk, fresh fruits and nuts in the first trimester was associated with reducing NTDs risk in offspring.

  5. Embedded defects

    International Nuclear Information System (INIS)

    Barriola, M.; Vachaspati, T.; Bucher, M.

    1994-01-01

    We give a prescription for embedding classical solutions and, in particular, topological defects in field theories which are invariant under symmetry groups that are not necessarily simple. After providing examples of embedded defects in field theories based on simple groups, we consider the electroweak model and show that it contains the Z string and a one-parameter family of strings called the W(α) string. It is argued that although the members of this family are gauge equivalent when considered in isolation, each member becomes physically distinct when multistring configurations are considered. We then turn to the issue of stability of embedded defects and demonstrate the instability of a large class of such solutions in the absence of bound states or condensates. The Z string is shown to be unstable for all values of the Higgs boson mass when θ W =π/4. W strings are also shown to be unstable for a large range of parameters. Embedded monopoles suffer from the Brandt-Neri-Coleman instability. Finally, we connect the electroweak string solutions to the sphaleron

  6. Birth Defects

    Science.gov (United States)

    A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of ... in the United States is born with a birth defect. A birth defect may affect how the ...

  7. Optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects: World Health Organization guidelines.

    Science.gov (United States)

    Cordero, Amy M; Crider, Krista S; Rogers, Lisa M; Cannon, Michael J; Berry, R J

    2015-04-24

    Neural tube defects (NTDs) such as spina bifida, anencephaly, and encephalocele are serious birth defects of the brain and spine that occur during the first month of pregnancy when the neural tube fails to close completely. Randomized controlled trials and observational studies have shown that adequate daily consumption of folic acid before and during early pregnancy considerably reduces the risk for NTDs. The U.S. Public Health Service recommends that women capable of becoming pregnant consume 400 µg of folic acid daily for NTD prevention. Furthermore, fortification of staple foods (e.g., wheat flour) with folic acid has decreased folate-sensitive NTD prevalence in multiple settings and is a highly cost-effective intervention.

  8. Melatonin prevents neural tube defects in the offspring of diabetic pregnancy.

    Science.gov (United States)

    Liu, Shangming; Guo, Yuji; Yuan, Qiuhuan; Pan, Yan; Wang, Liyan; Liu, Qian; Wang, Fuwu; Wang, Jingjing; Hao, Aijun

    2015-11-01

    Melatonin, an endogenous neurohormone secreted by the pineal gland, has a variety of physiological functions and neuroprotective effects. However, its protective role on the neural tube defects (NTDs) was not very clear. The aim of this study was to investigate the effects of melatonin on the incidence of NTDs (including anencephaly, encephalocele, and spina bifida) of offspring from diabetic pregnant mice as well as its underlying mechanisms. Pregnant mice were given 10 mg/kg melatonin by daily i.p. injection from embryonic day (E) 0.5 until being killed on E11.5. Here, we showed that melatonin decreased the NTDs (especially exencephaly) rate of embryos exposed to maternal diabetes. Melatonin stimulated proliferation of neural stem cells (NSCs) under hyperglycemic condition through the extracellular regulated protein kinases (ERK) pathway. Furthermore, as a direct free radical scavenger, melatonin decreased apoptosis of NSCs exposed to hyperglycemia. In the light of these findings, it suggests that melatonin supplementation may play an important role in the prevention of neural malformations in diabetic pregnancy. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  9. Neural tube defects in the Republic of Ireland in 2009-11.

    LENUS (Irish Health Repository)

    McDonnell, R

    2014-03-18

    Neural tube defects (NTDs) are associated with deficient maternal folic acid peri-conceptionally. In Ireland, there is no mandatory folic acid food fortification, partly due to declining NTD rates in recent years. The aim of this study was to ascertain the incident rate of NTD during the period 2009-11 and describe epidemiologically NTD in Ireland.METHODSCases were ascertained through multiple sources, including three regional congenital anomaly registers, all maternity hospitals nationally and paediatric hospitals providing care for children with spina bifida in the Republic of Ireland during the period 2009-11.RESULTSFrom 225 998 total births, 236 NTDs were identified, giving an incidence of 1.04\\/1 000 births, increasing from 0.92\\/1 000 in 2009 to 1.17\\/1 000 in 2011. Of all cases, 45% (n = 106) had anencephaly, 49% (n = 115) had spina bifida and 6% (n = 15) had an encephalocoele; 78% (n = 184) were liveborn or stillborn and 22% (n = 52) were terminations abroad. Peri-conceptional folic acid supplement intake was 13.7% among the 52.5% (n = 124) of cases whose folic acid supplement intake was known.CONCLUSIONThe incidence of NTDs in the Republic of Ireland appears to be increasing. Renewed public health interventions, including mandatory folic acid food fortification, must be considered to reduce the incidence of NTD.

  10. Neural tube defects – recent advances, unsolved questions and controversies

    Science.gov (United States)

    Copp, Andrew J.; Stanier, Philip; Greene, Nicholas D. E.

    2014-01-01

    Neural tube defects (NTDs) are severe congenital malformations affecting around 1 in every 1000 pregnancies. Here we review recent advances and currently unsolved issues in the NTD field. An innovation in clinical management has come from the demonstration that closure of open spina bifida lesions in utero can diminish neurological dysfunction in children. Primary prevention by folic acid has been enhanced through introduction of mandatory food fortification in some countries, although not yet in UK. Genetic predisposition comprises the majority of NTD risk, and genes that regulate folate one-carbon metabolism and planar cell polarity have been strongly implicated. The sequence of human neural tube closure events remains controversial, but study of mouse NTD models shows that anencephaly, open spina bifida and craniorachischisis result from failure of primary neurulation, while skin-covered spinal dysraphism results from defective secondary neurulation. Other ‘NTD’ malformations, such as encephalocele, are likely to be post-neurulation disorders. PMID:23790957

  11. Pulse height defect in ion implanted silicon detector for heavy ions with Z=6-28 in the energy range ∼ 0.25-2.5 MeV/u

    International Nuclear Information System (INIS)

    Diwan, P.K.; Sharma, V.; Shyam Kumar; Avasthi, D.K.

    2005-01-01

    The response of ion implanted silicon detector has been studied for heavy ions with Z= 6-28 in the energy range ∼ 0.25-2.5 MeV/u utilizing the 15UD Pelletron Accelerator facility at Nuclear Science Centre, New Delhi, India. The variation of pulse height in ion implanted silicon detector with projectile's atomic number and its energy have been investigated. It has been observed that pulse height-energy calibration for a given projectile is described well by a linear relationship indicating no pulse height defect with the variation in energy for specific Z projectile. Pulse height defect has been found to increase with increasing projectile atomic number. The mean slope of the collected charge signal versus projectile energy depends significantly on the atomic number of the projectile. (author)

  12. Preventing neural tube defects in Europe: a missed opportunity.

    Science.gov (United States)

    Busby, Araceli; Abramsky, Lenore; Dolk, Helen; Armstrong, Ben; Addor, Marie-Claude; Anneren, Goran; Armstrong, Nicola; Baguette, Andre; Barisic, Ingeborg; Berghold, Andrea; Bianca, Sebastiano; Braz, Paula; Calzolari, Elisa; Christiansen, Marianne; Cocchi, Guido; Daltveit, Anne Kjersti; De Walle, Hermien; Edwards, Grace; Gatt, Miriam; Gener, Blanca; Gillerot, Yves; Gjergja, Romana; Goujard, Janine; Haeusler, Martin; Latos-Bielenska, Anna; McDonnell, Robert; Neville, Amanda; Olars, Birgitta; Portillo, Isabel; Ritvanen, Annukka; Robert-Gnansia, Elizabeth; Rösch, Christine; Scarano, Gioacchino; Steinbicker, Volker

    2005-01-01

    Each year, more than 4500 pregnancies in the European Union are affected by neural tube defects (NTD). Unambiguous evidence of the effectiveness of periconceptional folic acid in preventing the majority of neural tube defects has been available since 1991. We report on trends in the total prevalence of neural tube defects up to 2002, in the context of a survey in 18 European countries of periconceptional folic acid supplementation (PFAS) policies and their implementation. EUROCAT is a network of population-based registries in Europe collaborating in the epidemiological surveillance of congenital anomalies. Representatives from 18 participating countries provided information about policy, health education campaigns and surveys of PFAS uptake. The yearly total prevalence of neural tube defects including livebirths, stillbirths and terminations of pregnancy was calculated from 1980 to 2002 for 34 registries, with UK and Ireland estimated separately from the rest of Europe. A meta-analysis of changes in NTD total prevalence between 1989-1991 and 2000-2002 according to PFAS policy was undertaken for 24 registries. By 2005, 13 countries had a government recommendation that women planning a pregnancy should take 0.4mg folic acid supplement daily, accompanied in 7 countries by government-led health education initiatives. In the UK and Ireland, countries with PFAS policy, there was a 30% decline in NTD total prevalence (95% CI 16-42%) but it was difficult to distinguish this from the pre-existing strong decline. In other European countries with PFAS policy, there was virtually no decline in NTD total prevalence whether a policy was in place by 1999 (2%, 95% CI 28% reduction to 32% increase) or not (8%, 95% CI 26% reduction to 16% increase). The potential for preventing NTDs by periconceptional folic acid supplementation is still far from being fulfilled in Europe. Only a public health policy including folic acid fortification of staple foods is likely to result in large

  13. Defect modelling

    International Nuclear Information System (INIS)

    Norgett, M.J.

    1980-01-01

    Calculations, drawing principally on developments at AERE Harwell, of the relaxation about lattice defects are reviewed with emphasis on the techniques required for such calculations. The principles of defect modelling are outlined and various programs developed for defect simulations are discussed. Particular calculations for metals, ionic crystals and oxides, are considered. (UK)

  14. Studies of defects and defect agglomerates by positron annihilation spectroscopy

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Singh, B.N.

    1997-01-01

    A brief introduction to positron annihilation spectroscopy (PAS), and in particular lo its use for defect studies in metals is given. Positrons injected into a metal may become trapped in defects such as vacancies, vacancy clusters, voids, bubbles and dislocations and subsequently annihilate from...... the trapped state iri the defect. The annihilation characteristics (e.g., the lifetime of the positron) can be measured and provide information about the nature of the defect (e.g., size, density, morphology). The technique is sensitive to both defect size (in the range from monovacancies up to cavities...

  15. Plasma folate levels and associated factors in women planning to become pregnant in a population with high prevalence of neural tube defects.

    Science.gov (United States)

    Ma, Rui; Wang, Linlin; Jin, Lei; Li, Zhiwen; Ren, Aiguo

    2017-07-17

    Optimal blood folate levels of women before pregnancy are critical to the prevention of neural tube defects (NTDs). However, few studies have focused on blood folate levels of women planning to become pregnant. The aims of this study were to assess plasma folate levels in women who planned to become pregnant in a population with high prevalence of NTDs, to identify factors associated with plasma folate levels, and to evaluate the risk of NTDs at the population level. A total of 2065 women were enrolled at the time of premarital health check-up in two rural counties in northern China from November 2009 to December 2012. Fasting venous blood samples were collected and plasma folate concentrations were measured by microbiological method. The overall median of plasma folate was 10.5 nmol/L. 50% of the women had a plasma folate level below 10.5 nmol/L, a cutoff for megaloblastic anemia, and 88% below 18 nmol/L, a proposed optimal plasma folate level for the prevention of NTDs. Folic acid supplementation was the only factor to be associated with plasma folate concentrations, but only 1.9% of the women reported having taken folic acid supplements. A population risk of 29.3 NTD cases per 10,000 births was predicted. Women who planned to become pregnant had very low plasma folate in the population. Folic acid supplementation was the only factor to be associated with a high plasma folate concentration. High NTD risk would remain if women would get pregnant without having taken folic acid supplements. Birth Defects Research 109:1039-1047, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  16. Genome-wide association mapping in dogs enables identification of the homeobox gene, NKX2-8, as a genetic component of neural tube defects in humans.

    Directory of Open Access Journals (Sweden)

    Noa Safra

    Full Text Available Neural tube defects (NTDs is a general term for central nervous system malformations secondary to a failure of closure or development of the neural tube. The resulting pathologies may involve the brain, spinal cord and/or vertebral column, in addition to associated structures such as soft tissue or skin. The condition is reported among the more common birth defects in humans, leading to significant infant morbidity and mortality. The etiology remains poorly understood but genetic, nutritional, environmental factors, or a combination of these, are known to play a role in the development of NTDs. The variable conditions associated with NTDs occur naturally in dogs, and have been previously reported in the Weimaraner breed. Taking advantage of the strong linkage-disequilibrium within dog breeds we performed genome-wide association analysis and mapped a genomic region for spinal dysraphism, a presumed NTD, using 4 affected and 96 unaffected Weimaraners. The associated region on canine chromosome 8 (pgenome  =3.0 × 10(-5, after 100,000 permutations, encodes 18 genes, including NKX2-8, a homeobox gene which is expressed in the developing neural tube. Sequencing NKX2-8 in affected Weimaraners revealed a G to AA frameshift mutation within exon 2 of the gene, resulting in a premature stop codon that is predicted to produce a truncated protein. The exons of NKX2-8 were sequenced in human patients with spina bifida and rare variants (rs61755040 and rs10135525 were found to be significantly over-represented (p=0.036. This is the first documentation of a potential role for NKX2-8 in the etiology of NTDs, made possible by investigating the molecular basis of naturally occurring mutations in dogs.

  17. Immobile defects in ferroelastic walls: Wall nucleation at defect sites

    Science.gov (United States)

    He, X.; Salje, E. K. H.; Ding, X.; Sun, J.

    2018-02-01

    Randomly distributed, static defects are enriched in ferroelastic domain walls. The relative concentration of defects in walls, Nd, follows a power law distribution as a function of the total defect concentration C: N d ˜ C α with α = 0.4 . The enrichment Nd/C ranges from ˜50 times when C = 10 ppm to ˜3 times when C = 1000 ppm. The resulting enrichment is due to nucleation at defect sites as observed in large scale MD simulations. The dynamics of domain nucleation and switching is dependent on the defect concentration. Their energy distribution follows the power law with exponents during yield between ɛ ˜ 1.82 and 2.0 when the defect concentration increases. The power law exponent is ɛ ≈ 2.7 in the plastic regime, independent of the defect concentration.

  18. Defects and defect processes in nonmetallic solids

    CERN Document Server

    Hayes, W

    2004-01-01

    This extensive survey covers defects in nonmetals, emphasizing point defects and point-defect processes. It encompasses electronic, vibrational, and optical properties of defective solids, plus dislocations and grain boundaries. 1985 edition.

  19. Epigenetic profiles in children with a neural tube defect; a case-control study in two populations.

    Directory of Open Access Journals (Sweden)

    Lisette Stolk

    Full Text Available Folate deficiency is implicated in the causation of neural tube defects (NTDs. The preventive effect of periconceptional folic acid supplement use is partially explained by the treatment of a deranged folate-dependent one carbon metabolism, which provides methyl groups for DNA-methylation as an epigenetic mechanism. Here, we hypothesize that variations in DNA-methylation of genes implicated in the development of NTDs and embryonic growth are part of the underlying mechanism. In 48 children with a neural tube defect and 62 controls from a Dutch case-control study and 34 children with a neural tube defect and 78 controls from a Texan case-control study, we measured the DNA-methylation levels of imprinted candidate genes (IGF2-DMR, H19, KCNQ1OT1 and non-imprinted genes (the LEKR/CCNL gene region associated with birth weight, and MTHFR and VANGL1 associated with NTD. We used the MassARRAY EpiTYPER assay from Sequenom for the assessment of DNA-methylation. Linear mixed model analysis was used to estimate associations between DNA-methylation levels of the genes and a neural tube defect. In the Dutch study group, but not in the Texan study group we found a significant association between the risk of having an NTD and DNA methylation levels of MTHFR (absolute decrease in methylation of -0.33% in cases, P-value = 0.001, and LEKR/CCNL (absolute increase in methylation: 1.36% in cases, P-value = 0.048, and a borderline significant association for VANGL (absolute increase in methylation: 0.17% in cases, P-value = 0.063. Only the association between MTHFR and NTD-risk remained significant after multiple testing correction. The associations in the Dutch study were not replicated in the Texan study. We conclude that the associations between NTDs and the methylation of the MTHFR gene, and maybe VANGL and LEKKR/CNNL, are in line with previous studies showing polymorphisms in the same genes in association with NTDs and embryonic development

  20. Maternal dietary intake of nitrates, nitrites and nitrosamines and selected birth defects in offspring: a case-control study.

    Science.gov (United States)

    Huber, John C; Brender, Jean D; Zheng, Qi; Sharkey, Joseph R; Vuong, Ann M; Shinde, Mayura U; Griesenbeck, John S; Suarez, Lucina; Langlois, Peter H; Canfield, Mark A; Romitti, Paul A; Weyer, Peter J

    2013-03-21

    Dietary intake of nitrates, nitrites, and nitrosamines can increase the endogenous formation of N-nitroso compounds in the stomach. Results from animal studies suggest that these compounds might be teratogenic. We examined the relationship between maternal dietary intake of nitrates, nitrites (including plant and animal sources as separate groups), and nitrosamines and several types of birth defects in offspring. For this population-based case-control study, data from a 58-question food frequency questionnaire, adapted from the short Willett Food Frequency Questionnaire and administered as part of the National Birth Defects Prevention Study (NBDPS), were used to estimate daily intake of dietary nitrates, nitrites, and nitrosamines in a sample of 6544 mothers of infants with neural tube defects (NTD)s, oral clefts (OC)s, or limb deficiencies (LD)s and 6807 mothers of unaffected control infants. Total daily intake of these compounds was divided into quartiles based on the control mother distributions. Odds ratios (OR)s and 95% confidence intervals (CI)s were estimated using logistic regression; estimates were adjusted for maternal daily caloric intake, maternal race-ethnicity, education, dietary folate intake, high fat diet (>30% of calories from fat), and state of residence. While some unadjusted ORs for NTDS had 95% (CI)s that excluded the null value, none remained significant after adjustment for covariates, and the effect sizes were small (adjusted odds ratios [aOR]nitrate, nitrite, and nitrosamines.

  1. Are concentrations of alkaline earth elements in maternal hair associated with risk of neural tube defects?

    Science.gov (United States)

    Li, Zhenjiang; Wang, Bin; Huo, Wenhua; Liu, Yingying; Zhu, Yibing; Xie, Jing; Li, Zhiwen; Ren, Aiguo

    2017-12-31

    The relationship between maternal intake of alkaline earth elements (AEEs) during the period of neural tube closure and the risk of neural tube defects (NTDs) is still unclear. We propose that AEE deficiency during the early period of pregnancy is associated with an elevated risk of NTDs in the offspring. In this study, we recruited 191 women with NTD-affected pregnancies (cases) and 261 women who delivered healthy infants (controls). The concentrations of four AEEs (Ca, Mg, Sr, Ba) in maternal hair sections that grew during early pregnancy were analyzed. Information on the dietary habits of the mothers was also collected by questionnaire. Higher concentrations of the four AEEs in hair had protective effects against the risk of total NTDs, with odds ratios with 95% confidence interval (comparing groups separated by each median level) of 0.44 (0.28-0.68) for Mg, 0.56 (0.36-0.87) for Ca, 0.45 (0.28-0.70) for Sr, and 0.41 (0.26-0.65) for Ba. Significant negative dose-response trends were identified for the relationships between the four AEE concentrations in maternal hair and the risks of anencephaly and spina bifida, but not for encephalocele. The frequencies of maternal consumption of fresh green vegetables, fresh fruit, and meat or fish were positively correlated with the concentrations of AEEs in hair. We concluded that the maternal intake of AEEs may play an important role in preventing NTD formation in offspring, and that this intake is related to maternal dietary habits of consuming fresh green vegetables, fresh fruit, and fish or meat. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Spontaneous neural tube defects in splotch mice supplemented with selected micronutrients

    International Nuclear Information System (INIS)

    Wlodarczyk, Bogdan J.; Tang, Louisa S.; Triplett, Aleata; Aleman, Frank; Finnell, Richard H.

    2006-01-01

    Splotch (Sp/Sp) mice homozygous for a mutation in the Pax3 gene inevitably present with neural tube defects (NTDs), along with other associated congenital anomalies. The affected mutant embryos usually die by gestation days (E) 12-13. In the present study, the effect of modifier genes from a new genetic background (CXL-Sp) and periconceptional supplementation with selected micronutrients (folic acid, 5-formyltetrahydrofolate, 5-methyltetrahydrofolate, methionine, myoinositol, thiamine, thymidine, and α-tocopherol) was determined with respect to the incidence of NTDs. In order to explore how different exposure parameters (time, dose, and route of compound administration) modulate the beneficial effects of micronutrient supplementation, female mice received either short- or long-term nutrient supplements via enteral or parenteral routes. Embryos were collected on E12.5 and examined for the presence of anterior or posterior NTDs. Additionally, whole mount in situ hybridization studies were conducted in order to reveal/confirm normal expression patterns of the Pax3 gene during neurulation in the wild-type and Sp/Sp homozygous mutant mouse embryos utilized in this study. A strong Pax3 signal was demonstrated in CXL-Sp embryos during neural tube closure (E9.5 to E10.5). The intensity and spatial pattern of expression were similar to other Splotch mutant mice. Of all the micronutrients tested, only supplementation with folic acid or 5-methyltetrahydrofolate rescued the normal phenotype in Sp/Sp embryos. When the folate supplementation dose was increased to 200 mg/kg in the diet, the incidence of rescued splotch homozygotes reached 30%; however, this was accompanied by six-fold increased resorption rate

  3. Is 5-methyltetrahydrofolate an alternative to folic acid for the prevention of neural tube defects?

    Science.gov (United States)

    Obeid, Rima; Holzgreve, Wolfgang; Pietrzik, Klaus

    2013-09-01

    Women have higher requirements for folate during pregnancy. An optimal folate status must be achieved before conception and in the first trimester when the neural tube closes. Low maternal folate status is causally related to neural tube defects (NTDs). Many NTDs can be prevented by increasing maternal folate intake in the preconceptional period. Dietary folate is protective, but recommending increasing folate intake is ineffective on a population level particularly during periods of high demands. This is because the recommendations are often not followed or because the bioavailability of food folate is variable. Supplemental folate [folic acid (FA) or 5-methyltetrahydrofolate (5-methylTHF)] can effectively increase folate concentrations to the level that is considered to be protective. FA is a synthetic compound that has no biological functions unless it is reduced to dihydrofolate and tetrahydrofolate. Unmetabolized FA appears in the circulation at doses of >200 μg. Individuals show wide variations in their ability to reduce FA. Carriers of certain polymorphisms in genes related to folate metabolism or absorption can better benefit from 5-methylTHF instead of FA. 5-MethylTHF [also known as (6S)-5-methylTHF] is the predominant natural form that is readily available for transport and metabolism. In contrast to FA, 5-methylTHF has no tolerable upper intake level and does not mask vitamin B12 deficiency. Supplementation of the natural form, 5-methylTHF, is a better alternative to supplementation of FA, especially in countries not applying a fortification program. Supplemental 5-methylTHF can effectively improve folate biomarkers in young women in early pregnancy in order to prevent NTDs.

  4. Formate supplementation enhances folate-dependent nucleotide biosynthesis and prevents spina bifida in a mouse model of folic acid-resistant neural tube defects.

    Science.gov (United States)

    Sudiwala, Sonia; De Castro, Sandra C P; Leung, Kit-Yi; Brosnan, John T; Brosnan, Margaret E; Mills, Kevin; Copp, Andrew J; Greene, Nicholas D E

    2016-07-01

    The curly tail mouse provides a model for neural tube defects (spina bifida and exencephaly) that are resistant to prevention by folic acid. The major ct gene, responsible for spina bifida, corresponds to a hypomorphic allele of grainyhead-like 3 (Grhl3) but the frequency of NTDs is strongly influenced by modifiers in the genetic background. Moreover, exencephaly in the curly tail strain is not prevented by reinstatement of Grhl3 expression. In the current study we found that expression of Mthfd1L, encoding a key component of mitochondrial folate one-carbon metabolism (FOCM), is significantly reduced in ct/ct embryos compared to a partially congenic wild-type strain. This expression change is not attributable to regulation by Grhl3 or the genetic background at the Mthfd1L locus. Mitochondrial FOCM provides one-carbon units as formate for FOCM reactions in the cytosol. We found that maternal supplementation with formate prevented NTDs in curly tail embryos and also resulted in increased litter size. Analysis of the folate profile of neurulation-stage embryos showed that formate supplementation resulted in an increased proportion of formyl-THF and THF but a reduction in proportion of 5-methyl THF. In contrast, THF decreased and 5-methyl THF was relatively more abundant in the liver of supplemented dams than in controls. In embryos cultured through the period of spinal neurulation, incorporation of labelled thymidine and adenine into genomic DNA was suppressed by supplemental formate, suggesting that de novo folate-dependent biosynthesis of nucleotides (thymidylate and purines) was enhanced. We hypothesise that reduced Mthfd1L expression may contribute to susceptibility to NTDs in the curly tail strain and that formate acts as a one-carbon donor to prevent NTDs. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  5. Periodontal wound healing/regeneration following implantation of recombinant human growth/differentiation factor-5 (rhGDF-5) in an absorbable collagen sponge carrier into one-wall intrabony defects in dogs: a dose-range study.

    Science.gov (United States)

    Kim, Tae-Gyun; Wikesjö, Ulf M E; Cho, Kyoo-Sung; Chai, Jung-Kiu; Pippig, Susanne D; Siedler, Michael; Kim, Chong-Kwan

    2009-07-01

    Recombinant human growth/differentiation factor-5 (rhGDF-5) is being evaluated as a candidate therapy in support of periodontal regeneration. The objective of this study was to evaluate cementum and alveolar bone formation, and aberrant healing events following surgical implantation of rhGDF-5 in an absorbable collagen sponge (ACS) carrier using an established periodontal defect model. Bilateral 4 x 5 mm (width x depth), one-wall, critical-size, intrabony periodontal defects were surgically created at the mandibular second and fourth pre-molar teeth in 15 Beagle dogs. Five animals received 1 microg/defect and five animals 20 microg/defect rhGDF-5 in unilateral defect sites. Contralateral sites received treatments reported elsewhere. Five animals received rhGDF-5/ACS with 0 (buffer control) and 100 microg/defect rhGDF-5 in contralateral defect sites. The animals were euthanized at 8 weeks post-surgery for histologic and histometric evaluation. Surgical implantation of rhGDF-5 stimulated significant periodontal regeneration. Cementum formation was significantly enhanced in sites implanted with rhGDF-5 (1 and 100 microg) compared with control (phealing/regeneration in intrabony periodontal defects without complications.

  6. Who named the quantum defect?

    International Nuclear Information System (INIS)

    Rau, A.R.P.; Inokuti, M.

    1997-01-01

    The notion of the quantum defect is important in atomic and molecular spectroscopy and also in unifying spectroscopy with collision theory. In the latter context, the quantum defect may be viewed as an ancestor of the phase shift. However, the origin of the term quantum defect does not seem to be explained in standard textbooks. It occurred in a 1921 paper by Schroedinger, preceding quantum mechanics, yet giving the correct meaning as an index of the short-range interactions with the core of an atom. The authors present the early history of the quantum-defect idea, and sketch its recent developments

  7. Levels of PAH-DNA adducts in cord blood and cord tissue and the risk of fetal neural tube defects in a Chinese population.

    Science.gov (United States)

    Yi, Deqing; Yuan, Yue; Jin, Lei; Zhou, Guodong; Zhu, Huiping; Finnell, Richard H; Ren, Aiguo

    2015-01-01

    Maternal exposure to polycyclic aromatic hydrocarbons (PAHs) has been shown to be associated with an elevated risk for neural tube defects (NTDs). In the human body, PAHs are bioactivated and the resultant reactive epoxides can covalently bind to DNA to form PAH-DNA adducts, which may, in turn, cause transcription errors, changes in gene expression or altered patterns of apoptosis. During critical developmental phases, these changes can result in abnormal morphogenesis. We aimed to examine the relationship between the levels of PAH-DNA adducts in cord blood and cord tissue and the risk of NTDs. From 2010 to 2012, 60 NTD cases and 60 healthy controls were recruited from a population-based birth defects surveillance system in five counties of Shanxi Province in Northern China, where the emission of PAHs remains one of the highest in the country and PAHs exposure is highly prevalent. PAH-DNA adducts in cord blood of 15 NTD cases and 15 control infants, and in cord tissue of 60 NTD cases and 60 control infants were measured using the (32)P-postlabeling method. PAH-DNA adduct levels in cord blood tend to be higher in the NTD group (28.5 per 10(8) nucleotides) compared with controls (19.7 per 10(8) nucleotides), although the difference was not statistically significant (P=0.377). PAH-DNA adducts in cord tissue were significantly higher in the NTD group (24.6 per 10(6) nucleotides) than in the control group (15.3 per 10(6) nucleotides), P=0.010. A positive dose-response relationship was found between levels of PAH-DNA adducts in cord tissue and the risk of NTDs (P=0.009). When the lowest tertile was used as the referent and potential confounding factors were adjusted for, a 1.03-fold (95% CI, 0.37-2.89) and 2.96-fold (95% CI, 1.16-7.58) increase in the risk of NTDs was observed for fetuses whose cord tissue PAH-DNA adduct levels were in the second and highest tertile, respectively. High levels of PAH-DNA adducts in fetal tissues were associated with increased risks of

  8. Modulation of nuclear factor-κB signaling and reduction of neural tube defects by quercetin-3-glucoside in embryos of diabetic mice.

    Science.gov (United States)

    Tan, Chengyu; Meng, Fantong; Reece, E Albert; Zhao, Zhiyong

    2018-05-04

    Diabetes mellitus in early pregnancy increases the risk of birth defects in infants. Maternal hyperglycemia stimulates the expression of nitric oxide (NO) synthase 2 (NOS2), which can be regulated by transcription factors of the nuclear factor-κB (NF-κB) family. Increases in reactive nitrogen species (RNS) generate intracellular stress conditions, including nitrosative, oxidative, and endoplasmic reticulum (ER) stresses, and trigger programmed cell death (or apoptosis) in the neural folds, resulting in neural tube defects (NTDs) in the embryo. Inhibiting NOS2 can reduce NTDs; however, the underlying mechanisms require further delineation. Targeting NOS2 and associated nitrosative stress using naturally occurring phytochemicals is a potential approach to preventing birth defects in diabetic pregnancies. This study aims to investigate the effect of quercetin-3-glucoside (Q3G), a polyphenol flavonoid found in fruit, in reducing maternal diabetes-induced NTDs in an animal model, and to delineate the molecular mechanisms underlying Q3G action in regulating NOS2 expression. Female mice (C57BL/6) were induced to develop diabetes using streptozotocin before pregnancy. Diabetic pregnant mice were administered Q3G (100 mg/kg) daily via gavage feeding, introduction of drug to the stomach directly via a feeding needle, during neurulation from embryonic (E) day 6.5 to E9.5. After treatment, E10.5 embryos were collected and examined for the presence of NTDs and apoptosis in the neural tube. Expression of Nos2 and superoxide dismutase 1 (Sod1; an antioxidative enzyme) was quantified using Western blot assay. Nitrosative, oxidative, and endoplasmic reticulum (ER) stress conditions were assessed using specific biomarkers. Expression and posttranslational modification of factors in the NF-κB system were investigated. Treatment with Q3G (suspended in water) significantly decreased NTD rate (24.7%) and apoptosis in the embryos of diabetic mice, compared with those in the water

  9. Management of abnormal serum markers in the absence of aneuploidy or neural tube defects

    Science.gov (United States)

    Schnettler, William T.; Hacker, Michele R.; Barber, Rachel E.; Rana, Sarosh

    2013-01-01

    Objective Few guidelines address the management of pregnancies complicated by abnormal maternal serum analytes (MSAs) in the absence of aneuploidy or neural tube defects (NTDs). Our objective was to gather preliminary data regarding current opinions and management strategies among perinatologists in the US. Methods This survey of Maternal Fetal Medicine (MFM) physicians and fellows used a secure electronic web-based data capture tool. Results A total of 545 potential participants were contacted, and 136 (25%) responded. The majority were experienced academic physicians with robust practices. Nearly all (97.7%) respondents reported a belief in an association between abnormal MSAs and adverse pregnancy outcomes other than aneuploidy or NTDs. Plasma protein A (PAPP-A) and α-fetoprotein (AFP) were most often chosen as markers demonstrating a strong association with adverse outcomes. Most (86.9%) respondents acknowledged that abnormal MSAs influenced their counseling approach, and the majority (80.1%) offered additional ultrasound examinations. Nearly half started at 28 weeks and almost one-third at 32 weeks. Respondents acknowledging a relevant protocol in their hospital or practice were more likely to offer additional antenatal testing (p = 0.01). Conclusions Although most perinatologists were in agreement regarding the association of MSAs with adverse pregnancy outcomes, a lack of consensus exists regarding management strategies. PMID:22372385

  10. Novel Mutation of LRP6 Identified in Chinese Han Population Links Canonical WNT Signaling to Neural Tube Defects.

    Science.gov (United States)

    Shi, Zhiwen; Yang, Xueyan; Li, Bin-Bin; Chen, Shuxia; Yang, Luming; Cheng, Liangping; Zhang, Ting; Wang, Hongyan; Zheng, Yufang

    2018-01-15

    Neural tube defects (NTDs), the second most frequent cause of human congenital abnormalities, are debilitating birth defects due to failure of neural tube closure. It has been shown that noncanonical WNT/planar cell polarity (PCP) signaling is required for convergent extension (CE), the initiation step of neural tube closure (NTC). But the effect of canonical WNT//β-catenin signaling during NTC is still elusive. LRP6 (low density lipoprotein receptor related proteins 6) was identified as a co-receptor for WNT/β-catenin signaling, but recent studies showed that it also can mediate WNT/PCP signaling. In this study, we screened mutations in the LRP6 gene in 343 NTDs and 215 ethnically matched normal controls of Chinese Han population. Three rare missense mutations (c.1514A>G, p.Y505C); c.2984A>G, p.D995G; and c.4280C>A, p.P1427Q) of the LRP6 gene were identified in Chinese NTD patients. The Y505C mutation is a loss-of-function mutation on both WNT/β-catenin and PCP signaling. The D995G mutation only partially lost inhibition on PCP signaling without affecting WNT/β-catenin signaling. The P1427Q mutation dramatically increased WNT/β-catenin signaling but only mildly loss of inhibition on PCP signaling. All three mutations failed to rescue CE defects caused by lrp6 morpholino oligos knockdown in zebrafish. Of interest, when overexpressed, D995G did not induce any defects, but Y505C and P1427Q caused more severe CE defects in zebrafish. Our results suggested that over-active canonical WNT signaling induced by gain-of-function mutation in LRP6 could also contribute to human NTDs, and a balanced WNT/β-catenin and PCP signaling is probably required for proper neural tube development. Birth Defects Research 110:63-71, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  11. Survey of prenatal screening policies in Europe for structural malformations and chromosome anomalies, and their impact on detection and termination rates for neural tube defects and Down's syndrome

    DEFF Research Database (Denmark)

    Boyd, P A; Devigan, C; Khoshnood, B

    2008-01-01

    tube defects (NTDs) using the EUROCAT database. MAIN OUTCOME MEASURES: Existence of national prenatal screening policies, legal gestation limit for TOPFA, prenatal detection and termination rates for Down's syndrome and NTD. RESULTS: Ten of the 18 countries had a national country-wide policy for Down...... cases. Six of the 18 countries had a legal gestational age limit for TOPFA, and in two countries, termination of pregnancy was illegal at any gestation. CONCLUSIONS: There are large differences in screening policies between countries in Europe. These, as well as organisational and cultural factors...

  12. Toward Intelligent Software Defect Detection

    Science.gov (United States)

    Benson, Markland J.

    2011-01-01

    Source code level software defect detection has gone from state of the art to a software engineering best practice. Automated code analysis tools streamline many of the aspects of formal code inspections but have the drawback of being difficult to construct and either prone to false positives or severely limited in the set of defects that can be detected. Machine learning technology provides the promise of learning software defects by example, easing construction of detectors and broadening the range of defects that can be found. Pinpointing software defects with the same level of granularity as prominent source code analysis tools distinguishes this research from past efforts, which focused on analyzing software engineering metrics data with granularity limited to that of a particular function rather than a line of code.

  13. Epidemiology of neural tube defects in Saudi Arabia.

    Science.gov (United States)

    AlShail, Essam; De Vol, Edward; Yassen, Ahsan; Elgamal, Essam A

    2014-12-01

    To evaluate the distribution and pattern of neural tube defects in Saudi Arabia by creating a hospital based registry. All cases registered in the King Faisal Specialist Hospital and Research Center (KFSH&RC) neural tube defect (NTD) registry since it was established in October 2000 until December 2012 were studied through active surveillance comprising a registrar who collects NTD information by reviewing the patient's medical records, and interviewing patient's families. The total number of patients registered from October 2000 to December 2012 was 718 patients. There were more females (417, 58%) than males (301, 42%). Of 620 mothers who underwent antenatal ultrasonography; 392 (63%) were diagnosed at birth, and 204 (33%) were diagnosed with antenatal hydrocephalus. In our registry sample, most mothers (95%) did not take folic acid 3 months prior to pregnancy, and 76% did not take folic acid during the 3 months after conception with the affected child. Only 5% received folic acid prior to conception. The KFSH&RC-NTD registry has met its objectives as a source of data that may significantly contribute to the prevention of NTDs, and improving quality of care for NTD patients through active publication of registry findings and management approaches.

  14. Neutron diffraction and lattice defects

    International Nuclear Information System (INIS)

    Hamaguchi, Yoshikazu

    1974-01-01

    Study on lattice defects by neutron diffraction technique is described. Wave length of neutron wave is longer than that of X-ray, and absorption cross-section is small. Number of defects observed by ESR is up to several defects, and the number studied with electron microscopes is more than 100. Information obtained by neutron diffraction concerns the number of defects between these two ranges. For practical analysis, several probable models are selected from the data of ESR or electron microscopes, and most probable one is determined by calculation. Then, defect concentration is obtained from scattering cross section. It is possible to measure elastic scattering exclusively by neutron diffraction. Minimum detectable concentration estimated is about 0.5% and 10 20 - 10 21 defects per unit volume. A chopper and a time of flight system are used as a measuring system. Cold neutrons are obtained from the neutron sources inserted into reactors. Examples of measurements by using similar equipments to PTNS-I system of Japan Atomic Energy Research Institute are presented. Interstitial concentration in the graphite irradiated by fast neutrons is shown. Defects in irradiated MgO were also investigated by measuring scattering cross section. Study of defects in Ge was made by measuring total cross section, and model analysis was performed in comparison with various models. (Kato, T.)

  15. Cadmium-induced neural tube defects and fetal growth restriction: Association with disturbance of placental folate transport

    International Nuclear Information System (INIS)

    Zhang, Gui-Bin; Wang, Hua; Hu, Jun; Guo, Min-Yin; Wang, Ying; Zhou, Yan; Yu, Zhen; Fu, Lin; Chen, Yuan-Hua; Xu, De-Xiang

    2016-01-01

    Previous studies found that maternal Cd exposure on gestational day (GD)9 caused forelimb ectrodactyly and tail deformity, the characteristic malformations. The aim of the present study was to investigate whether maternal Cd exposure on GD8 induces fetal neural tube defects (NTDs). Pregnant mice were intraperitoneally injected with CdCl 2 (2.5 or 5.0 mg/kg) on GD8. Neither forelimb ectrodactyly nor tail deformity was observed in mice injected with CdCl 2 on GD8. Instead, maternal Cd exposure on GD8 resulted in the incidence of NTDs. Moreover, maternal Cd exposure on GD8 resulted in fetal growth restriction. In addition, maternal Cd exposure on GD8 reduced placental weight and diameter. The internal space of maternal and fetal blood vessels in the labyrinth layer was decreased in the placentas of mice treated with CdCl 2 . Additional experiment showed that placental PCFT protein and mRNA, a critical folate transporter, was persistently decreased when dams were injected with CdCl 2 on GD8. Correspondingly, embryonic folate content was markedly decreased in mice injected with CdCl 2 on GD8, whereas Cd had little effect on folate content in maternal serum. Taken together, these results suggest that maternal Cd exposure during organogenesis disturbs transport of folate from maternal circulation to the fetuses through down-regulating placental folate transporters. - Highlights: • Maternal Cd exposure during organogenesis causes NTDs and FGR. • Maternal Cd exposure during organogenesis impairs placental development. • Cd disturbs transport of folate by down-regulating placental folate transporters.

  16. Cadmium-induced neural tube defects and fetal growth restriction: Association with disturbance of placental folate transport

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Gui-Bin; Wang, Hua, E-mail: wanghuadev@126.com; Hu, Jun; Guo, Min-Yin; Wang, Ying; Zhou, Yan; Yu, Zhen; Fu, Lin; Chen, Yuan-Hua; Xu, De-Xiang, E-mail: xudex@126.com

    2016-09-01

    Previous studies found that maternal Cd exposure on gestational day (GD)9 caused forelimb ectrodactyly and tail deformity, the characteristic malformations. The aim of the present study was to investigate whether maternal Cd exposure on GD8 induces fetal neural tube defects (NTDs). Pregnant mice were intraperitoneally injected with CdCl{sub 2} (2.5 or 5.0 mg/kg) on GD8. Neither forelimb ectrodactyly nor tail deformity was observed in mice injected with CdCl{sub 2} on GD8. Instead, maternal Cd exposure on GD8 resulted in the incidence of NTDs. Moreover, maternal Cd exposure on GD8 resulted in fetal growth restriction. In addition, maternal Cd exposure on GD8 reduced placental weight and diameter. The internal space of maternal and fetal blood vessels in the labyrinth layer was decreased in the placentas of mice treated with CdCl{sub 2}. Additional experiment showed that placental PCFT protein and mRNA, a critical folate transporter, was persistently decreased when dams were injected with CdCl{sub 2} on GD8. Correspondingly, embryonic folate content was markedly decreased in mice injected with CdCl{sub 2} on GD8, whereas Cd had little effect on folate content in maternal serum. Taken together, these results suggest that maternal Cd exposure during organogenesis disturbs transport of folate from maternal circulation to the fetuses through down-regulating placental folate transporters. - Highlights: • Maternal Cd exposure during organogenesis causes NTDs and FGR. • Maternal Cd exposure during organogenesis impairs placental development. • Cd disturbs transport of folate by down-regulating placental folate transporters.

  17. Facts about Birth Defects

    Science.gov (United States)

    ... label> Information For… Media Policy Makers Facts about Birth Defects Language: English (US) Español (Spanish) Recommend on ... having a baby born without a birth defect. Birth Defects Are Common Every 4 ½ minutes, a ...

  18. Neural Tube Defects

    Science.gov (United States)

    Neural tube defects are birth defects of the brain, spine, or spinal cord. They happen in the ... that she is pregnant. The two most common neural tube defects are spina bifida and anencephaly. In ...

  19. Interaction between Maternal and Paternal SHMT1 C1420T Predisposes to Neural Tube Defects in the Fetus: Evidence from Case-Control and Family-Based Triad Approaches.

    Science.gov (United States)

    K Rebekah, Prasoona; Tella, Sunitha; Buragadda, Srinadh; Tiruvatturu, Muni Kumari; Akka, Jyothy

    2017-07-17

    Neural tube defects (NTDs) are caused by the failure of neural tube formation which occurs during early embryonic development. NTDs are the most severe and leading cause of fetal mortality. Serine hydroxymethyl transferase (SHMT1) provides one-carbon units necessary for embryogenesis and defects in one-carbon production result in specific pathological conditions during pregnancy. The present study is aimed to evaluate the association of SHMT1 C1420T with NTD risk in the fetus using fetal, maternal and paternal groups by applying both case-control and family-based triad approaches. A total of 924 subjects including 124 NTD case-parent trios (n = 124 × 3 = 372) and 184 healthy control-parent trios (n = 184 × 3 = 552) from Telangana State, South India were analyzed. DNA from umbilical cord tissues and parental blood samples were extracted, and genotyped by polymerase chain reaction-restriction fragment length polymorphism. Statistical analysis used were SPSS, parent-of-origin effect (POE) analysis. Case-control study design demonstrated fetuses with homozygous variant genotype (TT) to be at risk toward spina bifida subtype (p = 0.022). Among parents, fathers with TT genotype were associated with anencephaly (p = 0.018) and spina bifida subtypes (p = 0.027) in the offspring. Of interest, maternal-paternal-offspring genotype incompatibility revealed maternal CT genotype in combination with paternal TT genotype increased risk for NTDs in the fetus (CTxTT = TT; p = 0.021). Family-based parent-of-origin effect linkage analysis revealed significant maternal over-transmission of variant allele to NTD fetuses (p < 0.01). The present study, using both case-control and family-based triad approach is the first report to demonstrate parental association of SHMT1 C1420T variant in conferring NTD risk in the fetus. Birth Defects Research 109:1020-1029, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  20. Myo-inositol soft gel capsules may prevent the risk of coffee-induced neural tube defects.

    Science.gov (United States)

    De Grazia, Sara; Carlomagno, Gianfranco; Unfer, Vittorio; Cavalli, Pietro

    2012-09-01

    Neural tube defects (NTDs) are classified as folate sensitive (about 70%) and folate resistant (about 30%); although folic acid is able to prevent the former, several data have shown that inositol may prevent the latter. It has recently been proposed that coffee intake might represent a risk factor for NTD, likely by interfering with the inositol signaling. In the present study, we tested the hypothesis that, beside affecting the inositol signaling pathway, coffee also interferes with inositol absorption. In order to evaluate coffee possible negative effects on inositol gastrointestinal absorption, a single-dose bioavailability trial was conducted. Pharmacokinetics (PK) parameters of myo-inositol (MI) powder and MI soft gelatin capsules swallowed with water and with a single 'espresso' were compared. PK profiles were obtained by analysis of MI plasma concentration, and the respective MI bioavailability was compared. Myo-inositol powder administration was negatively affected by coffee intake, thus suggesting an additional explanation to the interference between inositol deficiency and coffee consumption. On the contrary, the concomitant single 'espresso' consumption did not affect MI absorption following MI soft gelatin capsules administration. Furthermore, it was observed that MI soft gelatin capsule administration resulted in improved bioavailability compared to the MI powder form. Myo-inositol soft gelatin capsules should be considered for the preventive treatment of NTDs in folate-resistant subjects due to their higher bioavailability and to the capability to reduce espresso interference.

  1. Defect detection based on extreme edge of defective region histogram

    Directory of Open Access Journals (Sweden)

    Zouhir Wakaf

    2018-01-01

    Full Text Available Automatic thresholding has been used by many applications in image processing and pattern recognition systems. Specific attention was given during inspection for quality control purposes in various industries like steel processing and textile manufacturing. Automatic thresholding problem has been addressed well by the commonly used Otsu method, which provides suitable results for thresholding images based on a histogram of bimodal distribution. However, the Otsu method fails when the histogram is unimodal or close to unimodal. Defects have different shapes and sizes, ranging from very small to large. The gray-level distributions of the image histogram can vary between unimodal and multimodal. Furthermore, Otsu-revised methods, like the valley-emphasis method and the background histogram mode extents, which overcome the drawbacks of the Otsu method, require preprocessing steps and fail to use the general threshold for multimodal defects. This study proposes a new automatic thresholding algorithm based on the acquisition of the defective region histogram and the selection of its extreme edge as the threshold value to segment all defective objects in the foreground from the image background. To evaluate the proposed defect-detection method, common standard images for experimentation were used. Experimental results of the proposed method show that the proposed method outperforms the current methods in terms of defect detection.

  2. Epidemiologic study of neural tube defects in Los Angeles County. I. Prevalence at birth based on multiple sources of case ascertainment

    Energy Technology Data Exchange (ETDEWEB)

    Sever, L.E. (Pacific Northwest Lab., Richland, WA); Sanders, M.; Monsen, R.

    1982-01-01

    Epidemiologic studies of the neural tube defects (NTDs), anencephalus and spina bifida, have for the most part been based on single sources of case ascertainment in past studies. The present investigation attempts total ascertainment of NTD cases in the newborn population of Los Angeles County residents for the period 1966 to 1972. Design of the study, sources of data, and estimates of prevalence rates based on single and multiple sources of case ascertainment are here discussed. Anencephalus cases totaled 448, spina bifida 442, and encephalocele 72, giving prevalence rates of 0.52, 0.51, and 0.08 per 1000 total births, respectively, for these neural tube defects - rates considered to be low. The Los Angeles County prevalence rates are compared with those of other recent North American studies and support is provided for earlier suggestions of low rates on the West Coast.

  3. Maternal exposure to arsenic, cadmium, lead, and mercury and neural tube defects in offspring

    International Nuclear Information System (INIS)

    Brender, Jean D.; Suarez, Lucina; Felkner, Marilyn; Gilani, Zunera; Stinchcomb, David; Moody, Karen; Henry, Judy; Hendricks, Katherine

    2006-01-01

    Arsenic, cadmium, lead, and mercury are neurotoxins, and some studies suggest that these elements might also be teratogens. Using a case-control study design, we investigated the relation between exposure to these heavy metals and neural tube defects (NTDs) in offspring of Mexican-American women living in 1 of the 14 Texas counties bordering Mexico. A total of 184 case-women with NTD-affected pregnancies and 225 control-women with normal live births were interviewed about their environmental and occupational exposures during the periconceptional period. Biologic samples for blood lead and urinary arsenic, cadmium, and mercury were also obtained for a subset of these women. Overall, the median levels of these biomarkers for heavy metal exposure did not differ significantly (P>0.05) between case- and control-women. However, among women in the highest income group, case-women were nine times more likely (95% confidence interval (CI) 1.4-57) than control-women to have a urinary mercury >=5.62μg/L. Case-women were 4.2 times more likely (95% CI 1.1-16) to report burning treated wood during the periconceptional period than control-women. Elevated odds ratios (ORs) were observed for maternal and paternal occupational exposures to arsenic and mercury, but the 95% CIs were consistent with unity. The 95% CIs of the ORs were also consistent with unity for higher levels of arsenic, cadmium, lead, and mercury in drinking water and among women who lived within 2 miles at the time of conception to industrial facilities with reported emissions of any of these heavy metals. Our findings suggest that maternal exposures to arsenic, cadmium, or lead are probably not significant risk factors for NTDs in offspring. However, the elevated urinary mercury levels found in this population and exposures to the combustion of treated wood may warrant further investigation

  4. Theory of Defects in Semiconductors

    CERN Document Server

    Drabold, David A

    2007-01-01

    Semiconductor science and technology is the art of defect engineering. The theoretical modeling of defects has improved dramatically over the past decade. These tools are now applied to a wide range of materials issues: quantum dots, buckyballs, spintronics, interfaces, amorphous systems, and many others. This volume presents a coherent and detailed description of the field, and brings together leaders in theoretical research. Today's state-of-the-art, as well as tomorrow’s tools, are discussed: the supercell-pseudopotential method, the GW formalism,Quantum Monte Carlo, learn-on-the-fly molecular dynamics, finite-temperature treatments, etc. A wealth of applications are included, from point defects to wafer bonding or the propagation of dislocation.

  5. Craniotomy Frontal Bone Defect

    African Journals Online (AJOL)

    2018-03-01

    Mar 1, 2018 ... Defect reconstruction and fixation of the graft: The defect of ... where all loose fragments of fractured frontal bone was removed via the ... Mandible. • Ilium. • Allograft ... pediatric patients owing to skull growth. Thus, autologous ...

  6. Congenital platelet function defects

    Science.gov (United States)

    ... pool disorder; Glanzmann's thrombasthenia; Bernard-Soulier syndrome; Platelet function defects - congenital ... Congenital platelet function defects are bleeding disorders that cause reduced platelet function. Most of the time, people with these disorders have ...

  7. High glucose-induced oxidative stress represses sirtuin deacetylase expression and increases histone acetylation leading to neural tube defects.

    Science.gov (United States)

    Yu, Jingwen; Wu, Yanqing; Yang, Peixin

    2016-05-01

    Aberrant epigenetic modifications are implicated in maternal diabetes-induced neural tube defects (NTDs). Because cellular stress plays a causal role in diabetic embryopathy, we investigated the possible role of the stress-resistant sirtuin (SIRT) family histone deacetylases. Among the seven sirtuins (SIRT1-7), pre-gestational maternal diabetes in vivo or high glucose in vitro significantly reduced the expression of SIRT 2 and SIRT6 in the embryo or neural stem cells, respectively. The down-regulation of SIRT2 and SIRT6 was reversed by superoxide dismutase 1 (SOD1) over-expression in the in vivo mouse model of diabetic embryopathy and the SOD mimetic, tempol and cell permeable SOD, PEGSOD in neural stem cell cultures. 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), a superoxide generating agent, mimicked high glucose-suppressed SIRT2 and SIRT6 expression. The acetylation of histone 3 at lysine residues 56 (H3K56), H3K14, H3K9, and H3K27, putative substrates of SIRT2 and SIRT6, was increased by maternal diabetes in vivo or high glucose in vitro, and these increases were blocked by SOD1 over-expression or tempol treatment. SIRT2 or SIRT6 over-expression abrogated high glucose-suppressed SIRT2 or SIRT6 expression, and prevented the increase in acetylation of their histone substrates. The potent sirtuin activator (SRT1720) blocked high glucose-increased histone acetylation and NTD formation, whereas the combination of a pharmacological SIRT2 inhibitor and a pan SIRT inhibitor mimicked the effect of high glucose on increased histone acetylation and NTD induction. Thus, diabetes in vivo or high glucose in vitro suppresses SIRT2 and SIRT6 expression through oxidative stress, and sirtuin down-regulation-induced histone acetylation may be involved in diabetes-induced NTDs. The mechanism underlying pre-gestational diabetes-induced neural tube defects (NTDs) is still elusive. Our study unravels a new epigenetic mechanism in which maternal diabetes-induced oxidative stress represses

  8. Defect of the Eyelids.

    Science.gov (United States)

    Lu, Guanning Nina; Pelton, Ron W; Humphrey, Clinton D; Kriet, John David

    2017-08-01

    Eyelid defects disrupt the complex natural form and function of the eyelids and present a surgical challenge. Detailed knowledge of eyelid anatomy is essential in evaluating a defect and composing a reconstructive plan. Numerous reconstructive techniques have been described, including primary closure, grafting, and a variety of local flaps. This article describes an updated reconstructive ladder for eyelid defects that can be used in various permutations to solve most eyelid defects. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Point defects in solids

    International Nuclear Information System (INIS)

    Anon.

    1978-01-01

    The principal properties of point defects are studied: thermodynamics, electronic structure, interactions with etended defects, production by irradiation. Some measuring methods are presented: atomic diffusion, spectroscopic methods, diffuse scattering of neutron and X rays, positron annihilation, molecular dynamics. Then points defects in various materials are investigated: ionic crystals, oxides, semiconductor materials, metals, intermetallic compounds, carbides, nitrides [fr

  10. Fibrous metaphyseal defects

    International Nuclear Information System (INIS)

    Ritschl, P.; Hajek, P.C.; Pechmann, U.

    1989-01-01

    Sixteen patients with fibrous metaphyseal defects were examined with both plain radiography and magnetic resonance (MR) imaging. Depending on the age of the fibrous metaphyseal defects, characteristic radiomorphologic changes were found which correlated well with MR images. Following intravenous Gadolinium-DTPA injection, fibrous metaphyseal defects invariably exhibited a hyperintense border and signal enhancement. (orig./GDG)

  11. Birth Defects (For Parents)

    Science.gov (United States)

    ... Staying Safe Videos for Educators Search English Español Birth Defects KidsHealth / For Parents / Birth Defects What's in ... Prevented? Print en español Anomalías congénitas What Are Birth Defects? While still in the womb, some babies ...

  12. Dirichlet topological defects

    International Nuclear Information System (INIS)

    Carroll, S.M.; Trodden, M.

    1998-01-01

    We propose a class of field theories featuring solitonic solutions in which topological defects can end when they intersect other defects of equal or higher dimensionality. Such configurations may be termed open-quotes Dirichlet topological defects,close quotes in analogy with the D-branes of string theory. Our discussion focuses on defects in scalar field theories with either gauge or global symmetries, in 3+1 dimensions; the types of defects considered include walls ending on walls, strings on walls, and strings on strings. copyright 1998 The American Physical Society

  13. Synthetic Defects for Vibrothermography

    Science.gov (United States)

    Renshaw, Jeremy; Holland, Stephen D.; Thompson, R. Bruce; Eisenmann, David J.

    2010-02-01

    Synthetic defects are an important tool used for characterizing the performance of nondestructive evaluation techniques. Viscous material-filled synthetic defects were developed for use in vibrothermography (also known as sonic IR) as a tool to improve inspection accuracy and reliability. This paper describes how the heat-generation response of these VMF synthetic defects is similar to the response of real defects. It also shows how VMF defects can be applied to improve inspection accuracy for complex industrial parts and presents a study of their application in an aircraft engine stator vane.

  14. Defect production in ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J. [Oak Ridge National Lab., TN (United States); Kinoshita, C. [Kyushu Univ. (Japan)

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  15. Tissue-Specific Methylation of Long Interspersed Nucleotide Element-1 of Homo Sapiens (L1Hs) During Human Embryogenesis and Roles in Neural Tube Defects.

    Science.gov (United States)

    Wang, L; Chang, S; Guan, J; Shangguan, S; Lu, X; Wang, Z; Wu, L; Zou, J; Zhao, H; Bao, Y; Qiu, Z; Niu, B; Zhang, T

    2015-01-01

    Epigenetic regulation of long interspersed nucleotide element-1 (LINE-1) retrotransposition events plays crucial roles during early development. Previously we showed that LINE-1 hypomethylation in neuronal tissues is associated with pathogenesis of neural tube defect (NTD). Herein, we further evaluated LINE-1 Homo sapiens (L1Hs) methylation in tissues derived from three germ layers of stillborn NTD fetuses, to define patterns of tissue specific methylation and site-specific hypomethylation at CpG sites within an L1Hs promoter region. Stable, tissue-specific L1Hs methylation patterns throughout three germ layer lineages of the fetus, placenta, and maternal peripheral blood were observed. Samples from maternal peripheral blood exhibited the highest level of L1Hs methylation (64.95%) and that from placenta showed the lowest (26.82%). Between samples from NTDs and controls, decrease in L1Hs methylation was only significant in NTD-affected brain tissue at 7.35%, especially in females (8.98%). L1Hs hypomethylation in NTDs was also associated with a significant increase in expression level of an L1Hs-encoded transcript in females (r = -0.846, p = 0.004). This could be due to genomic DNA instability and alternation in chromatins accessibility resulted from abnormal L1Hs hypomethylation, as showed in this study with HCT-15 cells treated with methylation inhibitor 5-Aza.

  16. Association of neural tube defects in children of mothers with MTHFR 677TT genotype and abnormal carbohydrate metabolism risk: a case-control study.

    Science.gov (United States)

    Cadenas-Benitez, N M; Yanes-Sosa, F; Gonzalez-Meneses, A; Cerrillos, L; Acosta, D; Praena-Fernandez, J M; Neth, O; Gomez de Terreros, I; Ybot-González, P

    2014-03-26

    Abnormalities in maternal folate and carbohydrate metabolism have both been shown to induce neural tube defects (NTD) in humans and animal models. However, the relationship between these two factors in the development of NTDs remains unclear. Data from mothers of children with spina bifida seen at the Unidad de Espina Bífida del Hospital Infantil Virgen del Rocío (case group) were compared to mothers of healthy children with no NTD (control group) who were randomly selected from patients seen at the outpatient ward in the same hospital. There were 25 individuals in the case group and 41 in the control group. Analysis of genotypes for the methylenetetrahydrofolate reductase (MTHFR) 677CT polymorphism in women with or without risk factors for abnormal carbohydrate metabolism revealed that mothers who were homozygous for the MTHFR 677TT polymorphism and at risk of abnormal carbohydrate metabolism were more likely to have offspring with spina bifida and high levels of homocysteine, compared to the control group. The increased incidence of NTDs in mothers homozygous for the MTHFR 677TT polymorphism and at risk of abnormal carbohydrate metabolism stresses the need for careful metabolic screening in pregnant women, and, if necessary, determination of the MTHFR 677CT genotype in those mothers at risk of developing abnormal carbohydrate metabolism.

  17. Bose-glass behavior in Bi2Sr2Ca1-xYxCu2O8 crystals with columnar defects: Experimental evidence for variable-range hopping

    International Nuclear Information System (INIS)

    Ta Phuoc, V.; Sousa, R. de; Ammor, L.; Soret, J.C.; Ruyter, A.; Wahl, A.

    1998-01-01

    Disorder plays a crucial role in the static and dynamic properties of the mixed state of high-T c cuprates. A main feature of the diagram phase is the phase transition separating a high temperature vortex liquid-like state from a low temperature vortex solid-like state. In particular, the nature of the latter depends on the strength and the dimensionality of disorder. In the presence of an unidimensional disorder, Nelson and Vinokur predict a Bose-glass. In this paper, the authors concern themselves with the variable-range vortex hopping transport predicted in a Bose-glass. They report on vortex transport in Bi 2 Sr 2 Ca 1-x Y x Cu 2 O 8 crystals irradiated at different doses of heavy ions. They show evidence of a flux-creep resistivity typical of a variable-range vortex hopping mechanism as predicted by Nelson and Vinokur

  18. On holographic defect entropy

    International Nuclear Information System (INIS)

    Estes, John; Jensen, Kristan; O’Bannon, Andy; Tsatis, Efstratios; Wrase, Timm

    2014-01-01

    We study a number of (3+1)- and (2+1)-dimensional defect and boundary conformal field theories holographically dual to supergravity theories. In all cases the defects or boundaries are planar, and the defects are codimension-one. Using holography, we compute the entanglement entropy of a (hemi-)spherical region centered on the defect (boundary). We define defect and boundary entropies from the entanglement entropy by an appropriate background subtraction. For some (3+1)-dimensional theories we find evidence that the defect/boundary entropy changes monotonically under certain renormalization group flows triggered by operators localized at the defect or boundary. This provides evidence that the g-theorem of (1+1)-dimensional field theories generalizes to higher dimensions

  19. Trends of selected malformations in relation to folic acid recommendations and fortification: an international assessment.

    LENUS (Irish Health Repository)

    Botto, Lorenzo D

    2006-10-01

    Two crucial issues relative to the benefits and impact of folic acid in the prevention of birth defects are whether supplementation recommendations alone, without fortification, are effective in reducing the population-wide rates of neural tube defects (NTDs), and whether such policies can reduce the occurrence of other birth defects. Using data from 15 registries, we assessed rates and trends of 14 major defects, including NTDs, in areas with official recommendations or fortification to assess the effectiveness of recommendations and fortification on a wide range of major birth defects.

  20. Genital and Urinary Tract Defects

    Science.gov (United States)

    ... conditions > Genital and urinary tract defects Genital and urinary tract defects E-mail to a friend Please fill ... and extra fluids. What problems can genital and urinary tract defects cause? Genital and urinary tract defects affect ...

  1. Reduced folate carrier polymorphism (80A-->G) and neural tube defects.

    Science.gov (United States)

    De Marco, Patrizia; Calevo, Maria Grazia; Moroni, Anna; Merello, Elisa; Raso, Alessandro; Finnell, Richard H; Zhu, Huiping; Andreussi, Luciano; Cama, Armando; Capra, Valeria

    2003-03-01

    Transport of folates in mammalian cells occurs by a carrier-mediated mechanism. The human folate carrier (RFC-1) gene has been isolated and characterized. Within this gene, a common polymorphism, 80A-->G, changing a histidine to an arginine in exon 2 (H27R), was recently identified. Defects in folate metabolism, such as defective carrier molecules, could be implicated in the etiology of neural tube defects (NTDs). In the present case-control study, we recruited 174 Italian probands with nonsyndromic NTD, 43 mothers, 53 fathers and 156 control individuals and evaluated the impact of RFC-1 variant on NTD risk. A statistically significant risk was calculated for the 80GG genotype of the NTD cases (OR=2.35; 95% CI 1.21-4.58) and mothers (OR=2.74; 95% CI 0.92-8.38). On the contrary, the heterozygous genotype of the mothers and both heterozygous and homozygous genotypes of the fathers did not seem to be significant NTD risk factors. Furthemore, according to the multifactorial inheritance of NTDs, we demonstrated that the combined genotypes for MTHFR 1298A-->C and RFC-1 80A-->G polymorphisms of cases resulted in greater NTD risk than heterozygosity or homozygosity for RFC-1 80A-->G variant alone. Conversely, our data provide no evidence for an association between NTD phenotype and combined MTHFR C677T/RFC-1 A80G genotypes. Moreover, here we describe the combinations of the two MTHFR polymorphic sites (677CT and 1298AC) with RFC-1 genotypes. We found that both patients and controls could have at most quadruple-mutation combinations. Interestingly, 27% (7/26) of the mothers and 18.75% (30/160) of the cases genotyped presented four mutant alleles in comparison with 8.5% (11/129) of the controls. Finally, the frequency of NTD cases and mothers carrying combined heterozygosity for the two MTHFR polymorphisms and RFC-1 80GG homozygosity (677CT/1298AC/80GG) (cases=11.3%; mothers 11.5%) was increased compared with controls (1.6%). Altogether, our findings support the hypothesis

  2. Defects in semiconductors

    CERN Document Server

    Romano, Lucia; Jagadish, Chennupati

    2015-01-01

    This volume, number 91 in the Semiconductor and Semimetals series, focuses on defects in semiconductors. Defects in semiconductors help to explain several phenomena, from diffusion to getter, and to draw theories on materials' behavior in response to electrical or mechanical fields. The volume includes chapters focusing specifically on electron and proton irradiation of silicon, point defects in zinc oxide and gallium nitride, ion implantation defects and shallow junctions in silicon and germanium, and much more. It will help support students and scientists in their experimental and theoret

  3. Nanocarbon: Defect Architectures and Properties

    Science.gov (United States)

    Vuong, Amanda

    The allotropes of carbon make its solid phases amongst the most diverse of any element. It can occur naturally as graphite and diamond, which have very different properties that make them suitable for a wide range of technological and commercial purposes. Recent developments in synthetic carbon include Highly Oriented Pyrolytic Graphite (HOPG) and nano-carbons, such as fullerenes, nanotubes and graphene. The main industrial application of bulk graphite is as an electrode material in steel production, but in purified nuclear graphite form, it is also used as a moderator in Advanced Gas-cooled Reactors across the United Kingdom. Both graphene and graphite are damaged over time when subjected to bombardment by electrons, neutrons or ions, and these have a wide range of effects on their physical and electrical properties, depending on the radiation flux and temperature. This research focuses on intrinsic defects in graphene and dimensional change in nuclear graphite. The method used here is computational chemistry, which complements physical experiments. Techniques used comprise of density functional theory (DFT) and molecular dynamics (MD), which are discussed in chapter 2 and chapter 3, respectively. The succeeding chapters describe the results of simulations performed to model defects in graphene and graphite. Chapter 4 presents the results of ab initio DFT calculations performed to investigate vacancy complexes that are formed in AA stacked bilayer graphene. In AB stacking, carbon atoms surrounding the lattice vacancies can form interlayer structures with sp2 bonding that are lower in energy compared to in-plane reconstructions. From the investigation of AA stacking, sp2 interlayer bonding of adjacent multivacancy defects in registry creates a type of stable sp2 bonded wormhole between the layers. Also, a new class of mezzanine structure characterised by sp3 interlayer bonding, resembling a prismatic vacancy loop has also been identified. The mezzanine, which is a

  4. A comprehensive evaluation of food fortification with folic acid for the primary prevention of neural tube defects

    Directory of Open Access Journals (Sweden)

    Lam Angeline

    2004-09-01

    Full Text Available Abstract Background Periconceptional use of vitamin supplements containing folic acid reduces the risk of a neural tube defect (NTD. In November 1998, food fortification with folic acid was mandated in Canada, as a public health strategy to increase the folic acid intake of all women of childbearing age. We undertook a comprehensive population based study in Newfoundland to assess the benefits and possible adverse effects of this intervention. Methods This study was carried out in women aged 19–44 years and in seniors from November 1997 to March 1998, and from November 2000 to March 2001. The evaluation was comprised of four components: I Determination of rates of NTDs; II Dietary assessment; III Blood analysis; IV Assessment of knowledge and use of folic acid supplements. Results The annual rates of NTDs in Newfoundland varied greatly between 1976 and 1997, with a mean rate of 3.40 per 1,000 births. There was no significant change in the average rates between 1991–93 and 1994–97 (relative risk [RR] 1.01, 95% confidence interval [CI] 0.76–1.34. The rates of NTDs fell by 78% (95% CI 65%–86% after the implementation of folic acid fortification, from an average of 4.36 per 1,000 births during 1991–1997 to 0.96 per 1,000 births during 1998–2001 (RR 0.22, 95% CI 0.14–0.35. The average dietary intake of folic acid due to fortification was 70 μg/day in women aged 19–44 years and 74 μg/day in seniors. There were significant increases in serum and RBC folate levels for women and seniors after mandatory fortification. Among seniors, there were no significant changes in indices typical of vitamin B12 deficiencies, and no evidence of improved folate status masking haematological manifestations of vitamin B12 deficiency. The proportion of women aged 19–44 years taking a vitamin supplement containing folic acid increased from 17% to 28%. Conclusions Based on these findings, mandatory food fortification in Canada should continue at the

  5. Metallography of defects

    International Nuclear Information System (INIS)

    Borisova, E.A.; Bochvar, G.A.; Brun, M.Ya.

    1980-01-01

    Different types of defects of metallurgical, technological and exploitation origin in intermediate and final products of titanium alloys, are considered. The examples of metallic and nonmetallic inclusions, chemical homogeneity, different grains, bands, cracks, places of searing, porosity are given; methods of detecting the above defects are described. The methods of metallography, X-ray spectral analysis, measuring microhardness are used

  6. Beating Birth Defects

    Centers for Disease Control (CDC) Podcasts

    Each year in the U.S., one in 33 babies is affected by a major birth defect. Women can greatly improve their chances of giving birth to a healthy baby by avoiding some of the risk factors for birth defects before and during pregnancy. In this podcast, Dr. Stuart Shapira discusses ways to improve the chances of giving birth to a healthy baby.

  7. Defects at oxide surfaces

    CERN Document Server

    Thornton, Geoff

    2015-01-01

    This book presents the basics and characterization of defects at oxide surfaces. It provides a state-of-the-art review of the field, containing information to the various types of surface defects, describes analytical methods to study defects, their chemical activity and the catalytic reactivity of oxides. Numerical simulations of defective structures complete the picture developed. Defects on planar surfaces form the focus of much of the book, although the investigation of powder samples also form an important part. The experimental study of planar surfaces opens the possibility of applying the large armoury of techniques that have been developed over the last half-century to study surfaces in ultra-high vacuum. This enables the acquisition of atomic level data under well-controlled conditions, providing a stringent test of theoretical methods. The latter can then be more reliably applied to systems such as nanoparticles for which accurate methods of characterization of structure and electronic properties ha...

  8. Defects in dilute nitrides

    International Nuclear Information System (INIS)

    Chen, W.M.; Buyanova, I.A.; Tu, C.W.; Yonezu, H.

    2005-01-01

    We provide a brief review our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in dilute nitrides, i.e. Ga(In)NAs and Ga(Al,In)NP. Defect complexes involving intrinsic defects such as As Ga antisites and Ga i self interstitials were positively identified.Effects of growth conditions, chemical compositions and post-growth treatments on formation of the defects are closely examined. These grown-in defects are shown to play an important role in non-radiative carrier recombination and thus in degrading optical quality of the alloys, harmful to performance of potential optoelectronic and photonic devices based on these dilute nitrides. (author)

  9. Underwater Ranging

    OpenAIRE

    S. P. Gaba

    1984-01-01

    The paper deals with underwater laser ranging system, its principle of operation and maximum depth capability. The sources of external noise and methods to improve signal-to-noise ratio are also discussed.

  10. Evaluation of common genetic variants in 82 candidate genes as risk factors for neural tube defects

    Directory of Open Access Journals (Sweden)

    Pangilinan Faith

    2012-08-01

    Full Text Available Abstract Background Neural tube defects (NTDs are common birth defects (~1 in 1000 pregnancies in the US and Europe that have complex origins, including environmental and genetic factors. A low level of maternal folate is one well-established risk factor, with maternal periconceptional folic acid supplementation reducing the occurrence of NTD pregnancies by 50-70%. Gene variants in the folate metabolic pathway (e.g., MTHFR rs1801133 (677 C > T and MTHFD1 rs2236225 (R653Q have been found to increase NTD risk. We hypothesized that variants in additional folate/B12 pathway genes contribute to NTD risk. Methods A tagSNP approach was used to screen common variation in 82 candidate genes selected from the folate/B12 pathway and NTD mouse models. We initially genotyped polymorphisms in 320 Irish triads (NTD cases and their parents, including 301 cases and 341 Irish controls to perform case–control and family based association tests. Significantly associated polymorphisms were genotyped in a secondary set of 250 families that included 229 cases and 658 controls. The combined results for 1441 SNPs were used in a joint analysis to test for case and maternal effects. Results Nearly 70 SNPs in 30 genes were found to be associated with NTDs at the p MFTC, CDKN2A, ADA, PEMT, CUBN, GART, DNMT3A, MTHFD1 and T (Brachyury and included the known NTD risk factor MTHFD1 R653Q (rs2236225. The single strongest signal was observed in a new candidate, MFTC rs17803441 (OR = 1.61 [1.23-2.08], p = 0.0003 for the minor allele. Though nominally significant, these associations did not remain significant after correction for multiple hypothesis testing. Conclusions To our knowledge, with respect to sample size and scope of evaluation of candidate polymorphisms, this is the largest NTD genetic association study reported to date. The scale of the study and the stringency of correction are likely to have contributed to real associations failing to survive

  11. Formation of topological defects

    International Nuclear Information System (INIS)

    Vachaspati, T.

    1991-01-01

    We consider the formation of point and line topological defects (monopoles and strings) from a general point of view by allowing the probability of formation of a defect to vary. To investigate the statistical properties of the defects at formation we give qualitative arguments that are independent of any particular model in which such defects occur. These arguments are substantiated by numerical results in the case of strings and for monopoles in two dimensions. We find that the network of strings at formation undergoes a transition at a certain critical density below which there are no infinite strings and the closed-string (loop) distribution is exponentially suppressed at large lengths. The results are contrasted with the results of statistical arguments applied to a box of strings in dynamical equilibrium. We argue that if point defects were to form with smaller probability, the distance between monopoles and antimonopoles would decrease while the monopole-to-monopole distance would increase. We find that monopoles are always paired with antimonopoles but the pairing becomes clean only when the number density of defects is small. A similar reasoning would also apply to other defects

  12. Ventricular Septal Defect (VSD)

    Science.gov (United States)

    ... Call your doctor if your baby or child: Tires easily when eating or playing Is not gaining ... heart procedures. Risk factors Ventricular septal defects may run in families and sometimes may occur with other ...

  13. Birth Defects: Cerebral Palsy

    Science.gov (United States)

    ... Loss > Birth defects & other health conditions > Cerebral palsy Cerebral palsy E-mail to a friend Please fill in ... this page It's been added to your dashboard . Cerebral palsy (also called CP) is a group of conditions ...

  14. Endocardial cushion defect

    Science.gov (United States)

    ... Philadelphia, PA: Elsevier; 2016:chap 426. Kouchoukos NT, Blackstone EH, Hanley FL, Kirklin JK. Atrioventricular septal defect. In: Kouchoukos NT, Blackstone EH, Hanley FL, Kirklin JK, eds. Kirklin/Barratt- ...

  15. Repairing Nanoparticle Surface Defects

    NARCIS (Netherlands)

    Marino, Emanuele; Kodger, Thomas E.; Crisp, R.W.; Timmerman, Dolf; MacArthur, Katherine E.; Heggen, Marc; Schall, Peter

    2017-01-01

    Solar devices based on semiconductor nanoparticles require the use of conductive ligands; however, replacing the native, insulating ligands with conductive metal chalcogenide complexes introduces structural defects within the crystalline nanostructure that act as traps for charge carriers. We

  16. Point defects in platinum

    International Nuclear Information System (INIS)

    Piercy, G.R.

    1960-01-01

    An investigation was made of the mobility and types of point defect introduced in platinum by deformation in liquid nitrogen, quenching into water from 1600 o C, or reactor irradiation at 50 o C. In all cases the activation energy for motion of the defect was determined from measurements of electrical resistivity. Measurements of density, hardness, and x-ray line broadening were also made there applicable. These experiments indicated that the principal defects remaining in platinum after irradiation were single vacant lattice sites and after quenching were pairs of vacant lattice sites. Those present after deformation In liquid nitrogen were single vacant lattice sites and another type of defect, perhaps interstitial atoms. (author)

  17. Residual Defect Density in Random Disks Deposits.

    Science.gov (United States)

    Topic, Nikola; Pöschel, Thorsten; Gallas, Jason A C

    2015-08-03

    We investigate the residual distribution of structural defects in very tall packings of disks deposited randomly in large channels. By performing simulations involving the sedimentation of up to 50 × 10(9) particles we find all deposits to consistently show a non-zero residual density of defects obeying a characteristic power-law as a function of the channel width. This remarkable finding corrects the widespread belief that the density of defects should vanish algebraically with growing height. A non-zero residual density of defects implies a type of long-range spatial order in the packing, as opposed to only local ordering. In addition, we find deposits of particles to involve considerably less randomness than generally presumed.

  18. Low maternal folate concentrations and maternal MTHFR C677T polymorphism are associated with an increased risk for neural tube defects in offspring: a case-control study among Pakistani case and control mothers.

    Science.gov (United States)

    Nauman, Nuzhat; Jalali, Samina; Shami, Sajjad; Rafiq, Shireen; Große, Greta; Hilger, Alina C; Zhang, Rhong; Mansoor, Saira; Ludwig, Michael; Reutter, Heiko

    2018-01-01

    There is considerable evidence that periconceptional maternal folate deficiency and coding variants in maternal genes coding for critical enzymes in the folate pathway are associated with neural tube defects (NTDs) in offspring. In a case-control study we investigated C677T polymorphism in the 5,10- methylenetetrahydrofolate reductase (MTHFR) gene in case and control mothers of Pakistani origin, and compared these with the respective maternal folate concentrations measured at the time of delivery. A case-control study was conducted among 109 case and 100 control mothers identified through the Holy Family Hospital Rawalpindi, Quaid-i-Azam University, Islamabad, Pakistan. Red blood cell (RBC) and serum folate concentrations and MTHFRC677T polymorphism were compared between case and control mothers. Mean RBC folate and serum folate concentrations were significantly lower in cases compared with control mothers (pcases compared with control mothers (CC vs TT pcases compared with control mothers (C vs T pCase mothers with 677CT or 677TT genotypes had significantly lower serum (pstudy provides further evidence that maternal folate deficiency and MTHFRC677T polymorphism might be associated with an increased risk for NTDs in offspring. Our results are limited by the fact that maternal folate concentrations were not obtained during the periconceptional period, but at delivery. Further analyses, including maternal folate levels during the periconceptional period, are warranted.

  19. Population-Based Surveillance of Birth Defects Potentially Related to Zika Virus Infection - 15 States and U.S. Territories, 2016.

    Science.gov (United States)

    Delaney, Augustina; Mai, Cara; Smoots, Ashley; Cragan, Janet; Ellington, Sascha; Langlois, Peter; Breidenbach, Rebecca; Fornoff, Jane; Dunn, Julie; Yazdy, Mahsa; Scotto-Rosato, Nancy; Sweatlock, Joseph; Fox, Deborah; Palacios, Jessica; Forestieri, Nina; Leedom, Vinita; Smiley, Mary; Nance, Amy; Lake-Burger, Heather; Romitti, Paul; Fall, Carrie; Prado, Miguel Valencia; Barton, Jerusha; Bryan, J Michael; Arias, William; Brown, Samara Viner; Kimura, Jonathan; Mann, Sylvia; Martin, Brennan; Orantes, Lucia; Taylor, Amber; Nahabedian, John; Akosa, Amanda; Song, Ziwei; Martin, Stacey; Ramlal, Roshan; Shapiro-Mendoza, Carrie; Isenburg, Jennifer; Moore, Cynthia A; Gilboa, Suzanne; Honein, Margaret A

    2018-01-26

    Zika virus infection during pregnancy can cause serious birth defects, including microcephaly and brain abnormalities (1). Population-based birth defects surveillance systems are critical to monitor all infants and fetuses with birth defects potentially related to Zika virus infection, regardless of known exposure or laboratory evidence of Zika virus infection during pregnancy. CDC analyzed data from 15 U.S. jurisdictions conducting population-based surveillance for birth defects potentially related to Zika virus infection.* Jurisdictions were stratified into the following three groups: those with 1) documented local transmission of Zika virus during 2016; 2) one or more cases of confirmed, symptomatic, travel-associated Zika virus disease reported to CDC per 100,000 residents; and 3) less than one case of confirmed, symptomatic, travel-associated Zika virus disease reported to CDC per 100,000 residents. A total of 2,962 infants and fetuses (3.0 per 1,000 live births; 95% confidence interval [CI] = 2.9-3.2) (2) met the case definition. † In areas with local transmission there was a non-statistically significant increase in total birth defects potentially related to Zika virus infection from 2.8 cases per 1,000 live births in the first half of 2016 to 3.0 cases in the second half (p = 0.10). However, when neural tube defects and other early brain malformations (NTDs) § were excluded, the prevalence of birth defects strongly linked to congenital Zika virus infection increased significantly, from 2.0 cases per 1,000 live births in the first half of 2016 to 2.4 cases in the second half, an increase of 29 more cases than expected (p = 0.009). These findings underscore the importance of surveillance for birth defects potentially related to Zika virus infection and the need for continued monitoring in areas at risk for Zika.

  20. Unjoined primary and secondary neural tubes: junctional neural tube defect, a new form of spinal dysraphism caused by disturbance of junctional neurulation.

    Science.gov (United States)

    Eibach, Sebastian; Moes, Greg; Hou, Yong Jin; Zovickian, John; Pang, Dachling

    2017-10-01

    Primary and secondary neurulation are the two known processes that form the central neuraxis of vertebrates. Human phenotypes of neural tube defects (NTDs) mostly fall into two corresponding categories consistent with the two types of developmental sequence: primary NTD features an open skin defect, an exposed, unclosed neural plate (hence an open neural tube defect, or ONTD), and an unformed or poorly formed secondary neural tube, and secondary NTD with no skin abnormality (hence a closed NTD) and a malformed conus caudal to a well-developed primary neural tube. We encountered three cases of a previously unrecorded form of spinal dysraphism in which the primary and secondary neural tubes are individually formed but are physically separated far apart and functionally disconnected from each other. One patient was operated on, in whom both the lumbosacral spinal cord from primary neurulation and the conus from secondary neurulation are each anatomically complete and endowed with functioning segmental motor roots tested by intraoperative triggered electromyography and direct spinal cord stimulation. The remarkable feature is that the two neural tubes are unjoined except by a functionally inert, probably non-neural band. The developmental error of this peculiar malformation probably occurs during the critical transition between the end of primary and the beginning of secondary neurulation, in a stage aptly called junctional neurulation. We describe the current knowledge concerning junctional neurulation and speculate on the embryogenesis of this new class of spinal dysraphism, which we call junctional neural tube defect.

  1. Point defects and defect clusters examined on the basis of some fundamental experiments

    International Nuclear Information System (INIS)

    Zuppiroli, L.

    1975-01-01

    On progressing from the centre of the defect to the surface the theoretical approach to a point defect passes from electronic theories to elastic theory. Experiments by which the point defect can be observed fall into two categories. Those which detect long-range effects: measurement of dimensional variations in the sample; measurement of the mean crystal parameter variation; elastic X-ray scattering near the nodes of the reciprocal lattice (Huang scattering). Those which detect more local effects: low-temperature resistivity measurement; positron capture and annihilation; local scattering far from the reciprocal lattice nodes. Experiments involving both short and long-range effects can always be found. This is the case for example with the dechanneling of α particles by defects. Certain of the experimental methods quoted above apply also to the study of point defect clusters. These methods are illustrated by some of their most striking results which over the last twenty years have refined our knowledge of point defects and defect clusters: length and crystal parameter measurements; diffuse X-ray scattering; low-temperature resistivity measurements; ion emission microscopy; electron microscopy; elastoresistivity [fr

  2. Norwegian Pitched Roof Defects

    Directory of Open Access Journals (Sweden)

    Lars Gullbrekken

    2016-06-01

    Full Text Available The building constructions investigated in this work are pitched wooden roofs with exterior vertical drainpipes and wooden load-bearing system. The aim of this research is to further investigate the building defects of pitched wooden roofs and obtain an overview of typical roof defects. The work involves an analysis of the building defect archive from the research institute SINTEF Building and Infrastructure. The findings from the SINTEF archive show that moisture is a dominant exposure factor, especially in roof constructions. In pitched wooden roofs, more than half of the defects are caused by deficiencies in design, materials, or workmanship, where these deficiencies allow moisture from precipitation or indoor moisture into the structure. Hence, it is important to increase the focus on robust and durable solutions to avoid defects both from exterior and interior moisture sources in pitched wooden roofs. Proper design of interior ventilation and vapour retarders seem to be the main ways to control entry from interior moisture sources into attic and roof spaces.

  3. Computer experiment studies on mechanisms for irradiation induced defect production and annealing processes. Final report

    International Nuclear Information System (INIS)

    Beeler, J.R. Jr.; Beeler, M.F.

    1979-06-01

    This research is based on pair potentials used in the Brookhaven work. It extends their use in defect production simulations to the 5 MeV range and characterizes the short term annealing of the primary defect states. Defect properties and interactions are studied. Defect interactions include carbon, helium, and misfit metallic substitutional impurity interactions with vacancy and interstitial defects as well as vacancy-vacancy, interstitial-interstitial and vacancy-interstitial interactions

  4. Computer experiment studies on mechanisms for irradiation induced defect production and annealing processes. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Beeler, J.R. Jr.; Beeler, M.F.

    1979-06-01

    This research is based on pair potentials used in the Brookhaven work. It extends their use in defect production simulations to the 5 MeV range and characterizes the short term annealing of the primary defect states. Defect properties and interactions are studied. Defect interactions include carbon, helium, and misfit metallic substitutional impurity interactions with vacancy and interstitial defects as well as vacancy-vacancy, interstitial-interstitial and vacancy-interstitial interactions. (FS)

  5. The effect of a defective BSF layer on solar cell open circuit voltage. [Back Surface Field

    Science.gov (United States)

    Weizer, V. G.

    1985-01-01

    A straightforward analysis of special limiting cases has permitted the determination of the range of possible open circuit voltage losses due to a defective BSF (back surface field) layer. An important result of the analysis is the finding that it is possible to have a fully effective BSF region, regardless of the spatial distribution of the defective areas, as long as the total defective area is reduced below certain limits. Distributed defects were found to be much more harmful than lumped defects.

  6. Secondary defects in non-metallic solids

    International Nuclear Information System (INIS)

    Ashbee, K.H.G.; Hobbs, L.W.

    1977-01-01

    This paper points out features of secondary defect formation which are peculiar to non-metallic solids (excluding elemental semiconductors). Most of the materials of interest are compounds of two or more (usually more or less ionic) atomic species, and immediate consequence of which is a need to maintain both stoichiometry (or accommodate non-stoichiometry) and order. Primary defects in these solids, whether produced thermally, chemically or by irradiation, seldom are present or aggregate in exactly stoichiometric proportions, and the resulting extending defect structures can be quite distinct from those found in metallic solids. Where stoichiometry is maintained, it is often convenient to describe extended defects in terms of alterations in the arrangement of 'molecular' units. The adoption of this procedure enables several novel features of extended defect structures in non-metals to be explained. There are several ways in which a range of non-stoichiometry can be accommodated, which include structural elimination of point defects, nucleation of new coherent phases of altered stoichiometry, and decomposition. (author)

  7. Defect assessment procedures at high temperature

    International Nuclear Information System (INIS)

    Ainsworth, R.A.

    1991-01-01

    A comprehensive assessment procedure for the high-temperature response of structures is being produced. The procedure is referred to as R5 and is written as a series of step-by-step instructions in a number of volumes. This paper considers in detail those parts of R5 which address the behaviour of defects. The defect assessment procedures may be applied to defects found in service, postulated defects, or defects formed during operation as a result of creep-fatigue loading. In the last case, a method is described for deducing from endurance data the number of cycles to initiate a crack of a specified size. Under steady loading, the creep crack tip parameter C * is used to assess crack growth. Under cyclic loading, the creep crack growth during dwell periods is stiell governed by C * but crack growth due to cyclic excursions must also be included. This cyclic crack growth is described by an effective stress intensity factor range. A feature of the R5 defect assessment procedures in that they are based on simplified methods and approximate reference stress methods are described which enable C * in a component to be evaluated. It is shown by comparison with theoretical calculations and experimental data that reliable estimates of C * and the associated crack growth are obtained provided realistic creep strain rate date are used in the reference stress approximation. (orig./HP)

  8. Repairing Nanoparticle Surface Defects.

    Science.gov (United States)

    Marino, Emanuele; Kodger, Thomas E; Crisp, Ryan W; Timmerman, Dolf; MacArthur, Katherine E; Heggen, Marc; Schall, Peter

    2017-10-23

    Solar devices based on semiconductor nanoparticles require the use of conductive ligands; however, replacing the native, insulating ligands with conductive metal chalcogenide complexes introduces structural defects within the crystalline nanostructure that act as traps for charge carriers. We utilized atomically thin semiconductor nanoplatelets as a convenient platform for studying, both microscopically and spectroscopically, the development of defects during ligand exchange with the conductive ligands Na 4 SnS 4 and (NH 4 ) 4 Sn 2 S 6 . These defects can be repaired via mild chemical or thermal routes, through the addition of L-type ligands or wet annealing, respectively. This results in a higher-quality, conductive, colloidally stable nanomaterial that may be used as the active film in optoelectronic devices. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  9. Defect identification using positrons

    International Nuclear Information System (INIS)

    Beling, C.D.; Fung, S.

    2001-01-01

    The current use of the lifetime and Doppler broadening techniques in defect identification is demonstrated with two studies, the first being the identification of carbon vacancy in n-6H SiC through lifetime spectroscopy, and the second the production of de-hydrogenated voids in α-Si:H through light soaking. Some less conventional ideas are presented for more specific defect identification, namely (i) the amalgamation of lifetime and Doppler techniques with conventional deep level transient spectroscopy in what may be called ''positron-deep level transient spectroscopy'', and (ii) the extraction of more spatial information on vacancy defects by means of what may be called ''Fourier transform Doppler broadening of annihilation radiation spectroscopy'' (orig.)

  10. Quantum computing with defects

    Science.gov (United States)

    Varley, Joel

    2011-03-01

    The development of a quantum computer is contingent upon the identification and design of systems for use as qubits, the basic units of quantum information. One of the most promising candidates consists of a defect in diamond known as the nitrogen-vacancy (NV-1) center, since it is an individually-addressable quantum system that can be initialized, manipulated, and measured with high fidelity at room temperature. While the success of the NV-1 stems from its nature as a localized ``deep-center'' point defect, no systematic effort has been made to identify other defects that might behave in a similar way. We provide guidelines for identifying other defect centers with similar properties. We present a list of physical criteria that these centers and their hosts should meet and explain how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate systems. To elucidate these points, we compare electronic structure calculations of the NV-1 center in diamond with those of several deep centers in 4H silicon carbide (SiC). Using hybrid functionals, we report formation energies, configuration-coordinate diagrams, and defect-level diagrams to compare and contrast the properties of these defects. We find that the NC VSi - 1 center in SiC, a structural analog of the NV-1 center in diamond, may be a suitable center with very different optical transition energies. We also discuss how the proposed criteria can be translated into guidelines to discover NV analogs in other tetrahedrally coordinated materials. This work was performed in collaboration with J. R. Weber, W. F. Koehl, B. B. Buckley, A. Janotti, C. G. Van de Walle, and D. D. Awschalom. This work was supported by ARO, AFOSR, and NSF.

  11. Folate status in women of reproductive age as basis of neural tube defect risk assessment.

    Science.gov (United States)

    Bailey, Lynn B; Hausman, Dorothy B

    2018-02-01

    Reliable folate status data for women of reproductive age (WRA) to assess global risk for neural tube defects (NTDs) are needed. We focus on a recent recommendation by the World Health Organization that a specific "optimal" red blood cell (RBC) folate concentration be used as the sole indicator of NTD risk within a population and discuss how to best apply this guidance to reach the goal of assessing NTD risk globally. We also emphasize the importance of using the microbiologic assay (MBA) as the most reliable assay for obtaining comparable results for RBC folate concentration across time and countries, the need for harmonization of the MBA through use of consistent key reagents and procedures within laboratories, and the requirement to apply assay-matched cutoffs for folate deficiency and insufficiency. To estimate NTD risk globally, the ideal scenario would be to have country-specific population-based surveys of RBC folate in WRA determined utilizing a harmonized MBA, as was done in recent studies in Guatemala and Belize. We conclude with guidance on next steps to best navigate the road map toward the goal of generating reliable folate status data on which to assess NTD risk in WRA in low- and middle-income countries. © 2017 The Authors. Annals of the New York Academy of Sciences published by Wiley Periodicals, Inc. on behalf of New York Academy of Sciences.

  12. Triple surveillance: a proposal for an integrated strategy to support and accelerate birth defect prevention.

    Science.gov (United States)

    Botto, Lorenzo D; Mastroiacovo, Pierpaolo

    2018-02-01

    Preventing neural tube defects (NTDs) easily qualifies as a high-value opportunity to improve childhood survival and health: the unmet need is significant (major preventable burden), the intervention is transformative (providing sufficient folic acid), and delivery strategies (e.g., fortification) are effective in low-resource countries. Yet, NTD prevention is lagging. Can public health surveillance help fix this problem? Critics contend that surveillance is largely unnecessary, that limited resources are best spent on interventions, and that surveillance is unrealistic in developing countries. The counterargument is twofold: (1) in the absence of surveillance, interventions will provide fewer benefits and cost more and (2) effective surveillance is likely possible nearly everywhere, with appropriate strategies. As a base strategy, we propose "triple surveillance:" integrating surveillance of cause (folate insufficiency), of disease occurrence (NTD prevalence), and of health outcomes (morbidity, mortality, and disability). For better sustainability and usefulness, it is crucial to refocus and streamline surveillance activities (no recreational data collection), weave surveillance into clinical care (integrate in clinical workflow), and, later, work on including additional risk factors and pediatric outcomes (increase benefits at low marginal cost). By doing so, surveillance becomes not a roadblock but a preferential path to prevention and better care. © 2018 The Authors. Annals of the New York Academy of Sciences published by Wiley Periodicals, Inc. on behalf of New York Academy of Sciences.

  13. Defects introduced by Ar plasma exposure in GaAs probed by monoenergetic positron beam

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Kawano, Takao; Wada, Kazumi; Nakanishi, Hideo

    1994-10-01

    Ar-plasma-induced defects in n-type GaAs were probed by a monoenergetic positron beam. The depth distribution of the defects was obtained from measurements of Doppler broadening profiles of the annihilation radiation as a function of incident positron energy. The damaged layer induced by the exposure was found to extend far beyond the stopping range of Ar ions, and the dominant defects were identified as interstitial-type defects. After 100degC annealing, such defects were annealed. Instead, vacancy-type defects were found to be the dominant defects in the subsurface region. (author).

  14. Defects in semiconductors

    International Nuclear Information System (INIS)

    Pimentel, C.A.F.

    1983-01-01

    Some problems openned in the study of defects in semiconductors are presented. In particular, a review is made of the more important problems in Si monocrystals of basic and technological interest: microdefects and the presence of oxigen and carbon. The techniques usually utilized in the semiconductor material characterization are emphatized according its potentialities. Some applications of x-ray techniques in the epitaxial shell characterization in heterostructures, importants in electronic optics, are shown. The increase in the efficiency of these defect analysis methods in semiconductor materials with the use of synchrotron x-ray sources is shown. (L.C.) [pt

  15. Developing effective campaign messages to prevent neural tube defects: a qualitative assessment of women's reactions to advertising concepts.

    Science.gov (United States)

    Massi Lindsey, Lisa L; Silk, Kami J; Von Friederichs-Fitzwater, Marlene M; Hamner, Heather C; Prue, Christine E; Boster, Franklin J

    2009-03-01

    The incidence of neural tube defects (NTDs), serious birth defects of the brain and spine that affect approximately 3,000 pregnancies in the United States each year, can be reduced by 50-70% with daily periconceptional consumption of the B vitamin folic acid. Two studies were designed to assess college women's reactions to and perceptions of potential campaign advertising concepts derived from preproduction formative research to increase folic acid consumption through the use of a daily multivitamin. Study one assessed draft advertising concepts in eight focus groups (N = 71) composed of college-enrolled women in four cities geographically dispersed across the United States. Based on study one results, the concepts were revised and reassessed in study two with a different sample (eight focus groups; N = 73) of college women in the same four cities. Results indicated that participants generally responded favorably to concepts in each of the two studies, and provided insight into individual concepts to increase their overall appeal and effectiveness. The specific findings and implications of these results are discussed.

  16. Defect detection module

    International Nuclear Information System (INIS)

    Ernwein, R.; Westermann, G.

    1986-01-01

    The ''defect detector'' module is aimed at exceptional event or state recording. Foreseen for voltage presence monitoring on high supply voltage module of drift chambers, its characteristics can also show up the vanishing of supply voltage and take in account transitory fast signals [fr

  17. Quantum computing with defects.

    Science.gov (United States)

    Weber, J R; Koehl, W F; Varley, J B; Janotti, A; Buckley, B B; Van de Walle, C G; Awschalom, D D

    2010-05-11

    Identifying and designing physical systems for use as qubits, the basic units of quantum information, are critical steps in the development of a quantum computer. Among the possibilities in the solid state, a defect in diamond known as the nitrogen-vacancy (NV(-1)) center stands out for its robustness--its quantum state can be initialized, manipulated, and measured with high fidelity at room temperature. Here we describe how to systematically identify other deep center defects with similar quantum-mechanical properties. We present a list of physical criteria that these centers and their hosts should meet and explain how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate defect systems. To illustrate these points in detail, we compare electronic structure calculations of the NV(-1) center in diamond with those of several deep centers in 4H silicon carbide (SiC). We then discuss the proposed criteria for similar defects in other tetrahedrally coordinated semiconductors.

  18. Covering the Dorsal Finger Defect with Reverse Cross Finger Flap

    Directory of Open Access Journals (Sweden)

    Kaan Gurbuz

    2014-12-01

    Full Text Available Reconstruction of finger extensor zone defects with or without tendon gaps still remains a challenge for surgeons. Although surgical treatments may differ, and range from the use of local, regional, to free flaps, the outcomes for all cases are not satisfactory. In this case report, we present a case of a 3rd finger extensor side crush injury including a defect of Dd (Digit Dorsal 1, Dd2 and Dd3 defects of extensor zones with tendon gap. Tendon gap was reconstructed using m. palmaris longus tendon graft and the defect was covered with reversed cross-finger flap (random pattern with good cosmetic and excellent functional results.

  19. Point defect relaxation volumes for copper

    International Nuclear Information System (INIS)

    Miller, K.M.

    1979-11-01

    The methods used for the determination of point defect relaxation volumes are discussed and it is shown that a previous interatomic potential derived for copper is inaccurate and results obtained using it are invalid. A new interatomic potential has been produced for copper and a computer simulation of point and planar defects carried out. A vacancy relaxation volume of -0.33 atomic volumes has been found with interstitial values in the range 1.7 to 2.0 atomic volumes. It is shown that these values in current theories of irradiation induced swelling lead to an anomalously high value for dislocation bias compared with that determined experimentally. (author)

  20. Folate and neural tube defects - Recommendations from a Danish working group

    DEFF Research Database (Denmark)

    Rasmussen, Lone Banke; Andersen, Niels Lyhne; Andersson, G.

    1998-01-01

    acid daily from a multivitamin/folic acid tablet. Women who have had a child with NTD and women who themselves have NTDs are recommended a supplement of 5 mg folic acid daily. Dietary changes and supplements should be initiated when pregnancy is planned........ Folate is a B-vitamin found in most food groups. In case-control studies and randomised studies, a protective effect of folic acid supplements on NTDs has been found. The studies show that a periconceptional folic acid supplement df 360 mu g to 4 mg daily decreases the recurrence rate of NTDs. Likewise......, in the few studies which calculate folate intake from the diet, a lower risk of NTD with higher intake of folate from the diet has been found. The folate intake can be increased by the diet, by folic acid supplements or by fortification of food a with folic acid. It is concluded that the incidence of NTDs...

  1. Electronic structure of point defects in semiconductors

    International Nuclear Information System (INIS)

    Bruneval, Fabien

    2014-01-01

    trace concentration (of the order of one part per million). However, owing to the heavy burden of the quantum-mechanical electronic structure calculations, which grow very rapidly with the number of electrons, the present day simulations do not easily exceed a few hundred atoms nowadays. This induces effective defect concentrations of the order of one percent which are very far from the diluted defects observed in the experiments. The extrapolation of high concentrations to low concentrations is difficult because defects in semiconductors often bear a net electric charge which induces long-range interactions between the spuriously interacting charged defects. The first part of my work presents the techniques available in this area, improvements in the techniques and some understanding of these spurious interactions. The second topic addressed in this memoir focuses on improving the electronic structure of defects in semiconductors and insulators. Defects in these materials introduce discrete electronic levels within the band gap of the pristine bulk material. These electronic levels correspond to the electrons involved in the defect states. Their wave function is more or less localized around the defect region and the filling of the state may also vary with the thermodynamic conditions (Fermi level). These levels inside the band gap govern the modification of the properties of electronic and optical transport. Unfortunately the standard ab initio approaches, in the context of Density Functional Theory (DFT), are unable to get the correct band gaps of semiconductors and insulators. This is why many defect properties cannot be predicted with certainty within these approaches. This second part demonstrates how the introduction of the many-body perturbation theory in the so-called GW approximation solves the problem of band gaps and thus allows one to obtain more reliable defect properties. Of course, the field of ab initio electronic structure for defects is far from being

  2. Effect of defect length on rolling contact fatigue crack propagation in high strength steel

    Directory of Open Access Journals (Sweden)

    T. Makino

    2015-10-01

    Full Text Available The objective of the present paper is to clarify the effect of defect length in depth direction on rolling contact fatigue (RCF crack propagation in high strength steel. RCF test and synchrotron radiation micro computed tomography (SR micro CT imaging were conducted. In the case of the defect with the 15 m diameter, flaking life decreased with increasing defect length. In a comparison of the CT image and the SEM view, the shapes of defects and the locations of the horizontal cracks were almost the same respectively. The mechanism of RCF crack propagation was discussed by finite element (FE analysis. Defects led to higher tensile residual stress than that without defects in the region where the defect exists. The shear stress range at 0.1 mm in depth on the middle line of the defect and the range of mode II stress intensity factor at the bottom of a vertical crack increased with increasing defect length.

  3. Epidemiologic study of neural tube defects in Los Angeles County. II. Etiologic factors in an area with low prevalence at birth

    Energy Technology Data Exchange (ETDEWEB)

    Sever, L.E.

    1982-01-01

    Epidemiologic characteristics of neural tube defect (NTD) births occurring in Los Angeles County, California, residents during the period 1966-1972 are presented. The prevalence at birth was 0.52/1000 births for anencephalus, 0.51/1000 for spina bifida, and 0.08/1000 for encephalocele, rates considered to be low for a predominantly white population. We hypothesized that environmental (nongenetic) factors are of less etiologic importance in a low-prevalence population than in areas or time periods with high prevalence. We tested that hypothesis by examining epidemiologic characteristics of NTDs in Los Angeles County and comparing them with high-prevalence populations. The data did not support a major etiologic role for environmental factors: (1) no significant differences between rates by month of birth or conception; (2) no significant association with maternal age or parity for anencephalus; for spina bifida a significant maternal age effect (P < 0.01) and for encephalocele a parity effect (P < 0.02); and (3) no significant relationship with father's occupational class for either anencephalus or encephalocele but a marginally significant (P < 0.05) inverse association for spina bifida when a statistic based on ordinal relationships was used. Findings supporting the importance of genetic factors in etiology included: (1) a high percentage of males; (2) a higher twin concordance rate than in high-prevalence populations; and (3) an anencephalus rate among blacks comparable with rates for blacks in other United States populations. Our findings in conjunction with those from other areas and times of low prevalence suggest environmental factors play a relatively insignificant role in the etiology of NTDs in such populations.

  4. Knowledge and periconceptional use of folic acid for the prevention of neural tube defects in ethnic communities in the United Kingdom: systematic review and meta-analysis.

    Science.gov (United States)

    Peake, Jordana N; Copp, Andrew J; Shawe, Jill

    2013-07-01

    It is widely accepted that periconceptional supplementation with folic acid can prevent a significant proportion of neural tube defects (NTDs). The present study evaluated how folic acid knowledge and periconceptional use for NTD prevention varies by ethnicity in the United Kingdom (U.K.). A literature search was conducted to identify studies that included assessment of folic acid knowledge or use in U.K. women of different ethnicities. Only research and referenced sources published after 1991, the year of the landmark Medical Research Council's Vitamin Study, were included. A meta-analysis was performed of studies that assessed preconceptional folic acid use in Caucasians and non-Caucasians. Five studies met the inclusion criteria for assessment of knowledge and/or use of folic acid supplements in U.K. women including non-Caucasians. The available evidence indicates that South Asians specifically have less knowledge and lower periconceptional use of folic acid than Caucasians; one study found that West Indian and African women also had lower folic acid uptake. A synthesis of results from three of the studies, in a meta-analysis, shows that Caucasians are almost three times more likely to take folic acid before conception than non-Caucasians. From the limited evidence available, U.K. women of non-Caucasian ethnicity appear to have less knowledge and a lower uptake of folic acid supplementation than Caucasians during the periconceptional period. Implementing targeted, innovative education campaigns together with a mandatory fortification policy, including the fortification of ethnic minority foods, will be required for maximum prevention of folic acid-preventable NTDs across different ethnic groups. Copyright © 2013 Wiley Periodicals, Inc.

  5. Surgical pathology report defects: a College of American Pathologists Q-Probes study of 73 institutions.

    Science.gov (United States)

    Volmar, Keith E; Idowu, Michael O; Hunt, Jennifer L; Souers, Rhona J; Meier, Frederick A; Nakhleh, Raouf E

    2014-05-01

    The rate of surgical pathology report defects is an indicator of quality and it affects clinician satisfaction. To establish benchmarks for defect rates and defect fractions through a large, multi-institutional prospective application of standard taxonomy. Participants in a 2011 Q-Probes study of the College of American Pathologists prospectively reviewed all surgical pathology reports that underwent changes to correct defects and reported details regarding the defects. Seventy-three institutions reported 1688 report defects discovered in 360,218 accessioned cases, for an aggregate defect rate of 4.7 per 1000 cases. Median institutional defect rate was 5.7 per 1000 (10th to 90th percentile range, 13.5-0.9). Defect rates were higher in institutions with a pathology training program (8.5 versus 5.0 per 1000, P = .01) and when a set percentage of cases were reviewed after sign-out (median, 6.7 versus 3.8 per 1000, P = .10). Defect types were as follows: 14.6% misinterpretations, 13.3% misidentifications, 13.7% specimen defects, and 58.4% other report defects. Overall, defects were most often detected by pathologists (47.4%), followed by clinicians (22.0%). Misinterpretations and specimen defects were most often detected by pathologists (73.5% and 82.7% respectively, P benchmarking data on report defects and defect fractions using standardized taxonomy.

  6. Congenital Heart Defects (For Parents)

    Science.gov (United States)

    ... to be associated with genetic disorders, such as Down syndrome . But the cause of most congenital heart defects isn't known. While they can't be prevented, many treatments are available for the defects and related health ...

  7. Antigravity from a spacetime defect

    OpenAIRE

    Klinkhamer, F. R.; Queiruga, J. M.

    2018-01-01

    We argue that there may exist spacetime defects embedded in Minkowski spacetime, which have negative active gravitational mass. One such spacetime defect then repels a test particle, corresponding to what may be called "antigravity."

  8. Study of the thermodynamic properties and defect structure of the binary system Fesub(1-y)O (Wuestite) in the range 0.0467<= y <=0.1103, between 600 deg C and 1050 deg C, using solid electrolyte galvanic cells

    International Nuclear Information System (INIS)

    Barbero, J.A.

    1984-01-01

    A device, consisting of galvanic cells composed of solid electrolytes, was specially designed and constructed for this study. The most adequate cells for obtaining the thermodynamic data in a fast and accurate way was determined. This experimental set-up can also be used for indirect measurements in gases and liquids. Results of the measurements of the electromotive force versus temperature, performed for different samples, having an O/Fe ratio from 1.049 to 1.124 are given. From the experimental data, the following information was obtained: partial molar quantities corresponding to both Fe and O (enthalpy ΔH; entropy ΔS, and free energy ΔG). The oxide's phase boundaries between 600 and 1050 deg C were determined, showing the existence of a subphase within the range of stability of Fesub(1-y)O. The development of a theoretical model allowed to make a semiquantitative fit of the enthalpies of formation and to advance in the knowledge on the defect structure of this oxided system. According to certain theories, the wuestite, whose crystalline structure is of the NaCl type, with O in excess leads to the formation of magnetite (Fe 3 O 4 ) of spinel structure, this being the main agent causing the corrosion processes in the primary and secondary circuits of the nuclear reactors. Owing to the fact that the wuestite is similar to other transition metal oxides, such as NiO; CoO and MnO, this model may be also applied to these oxides. (M.E.L.) [es

  9. Polydispersity-driven topological defects as order-restoring excitations.

    Science.gov (United States)

    Yao, Zhenwei; Olvera de la Cruz, Monica

    2014-04-08

    The engineering of defects in crystalline matter has been extensively exploited to modify the mechanical and electrical properties of many materials. Recent experiments on manipulating extended defects in graphene, for example, show that defects direct the flow of electric charges. The fascinating possibilities offered by defects in two dimensions, known as topological defects, to control material properties provide great motivation to perform fundamental investigations to uncover their role in various systems. Previous studies mostly focus on topological defects in 2D crystals on curved surfaces. On flat geometries, topological defects can be introduced via density inhomogeneities. We investigate here topological defects due to size polydispersity on flat surfaces. Size polydispersity is usually an inevitable feature of a large variety of systems. In this work, simulations show well-organized induced topological defects around an impurity particle of a wrong size. These patterns are not found in systems of identical particles. Our work demonstrates that in polydispersed systems topological defects play the role of restoring order. The simulations show a perfect hexagonal lattice beyond a small defective region around the impurity particle. Elasticity theory has demonstrated an analogy between the elementary topological defects named disclinations to electric charges by associating a charge to a disclination, whose sign depends on the number of its nearest neighbors. Size polydispersity is shown numerically here to be an essential ingredient to understand short-range attractions between like-charge disclinations. Our study suggests that size polydispersity has a promising potential to engineer defects in various systems including nanoparticles and colloidal crystals.

  10. Congenital Heart Defects and CCHD

    Science.gov (United States)

    ... and more. Stony Point, NY 10980 Close X Home > Complications & Loss > Birth defects & other health conditions > Congenital heart defects and ... in congenital heart defects. You have a family history of congenital heart ... syndrome or VCF. After birth Your baby may be tested for CCHD as ...

  11. Benign gastric filling defect

    International Nuclear Information System (INIS)

    Oh, K. K.; Lee, Y. H.; Cho, O. K.; Park, C. Y.

    1979-01-01

    The gastric lesion is a common source of complaints to Orientals, however, evaluation of gastric symptoms and laboratory examination offer little specific aid in the diagnosis of gastric diseases. Thus roentgenography of gastrointestinal tract is one of the most reliable method for detail diagnosis. On double contract study of stomach, gastric filling defect is mostly caused by malignant gastric cancer, however, other benign lesions can cause similar pictures which can be successfully treated by surgery. 66 cases of benign causes of gastric filling defect were analyzed at this point of view, which was verified pathologically by endoscope or surgery during recent 7 years in Yensei University College of Medicine, Severance Hospital. The characteristic radiological picture of each disease was discussed for precise radiologic diagnosis. 1. Of total 66 cases, there were 52 cases of benign gastric tumor 10 cases of gastric varices, 5 cases of gastric bezoar, 5 cases of corrosive gastritis, 3 cases of granulomatous disease and one case of gastric hematoma. 2. The most frequent causes of benign tumors were adenomatous polyp (35/42) and the next was leiomyoma (4/42). Others were one of case of carcinoid, neurofibroma and cyst. 3. Characteristic of benign adenomatous polyp were relatively small in size, smooth surface and were observed that large size, benign polyp was frequently type IV lesion with a stalk. 4. Submucosal tumors such as leiomyoma needed differential diagnosis with polypoid malignant cancer. However, the characteristic points of differentiation was well circumscribed smooth margined filling defect without definite mucosal destruction on surface. 5. Gastric varices showed multiple lobulated filling defected especially on gastric fundus that changed its size and shape by respiration and posture of patients. Same varices lesions on esophagus and history of liver disease were helpful for easier diagnosis. 6. Gastric bezoar showed well defined movable mass

  12. Benign gastric filling defect

    Energy Technology Data Exchange (ETDEWEB)

    Oh, K. K.; Lee, Y. H.; Cho, O. K.; Park, C. Y. [Yonsei University College of Medicine, Seoul (Korea, Republic of)

    1979-06-15

    The gastric lesion is a common source of complaints to Orientals, however, evaluation of gastric symptoms and laboratory examination offer little specific aid in the diagnosis of gastric diseases. Thus roentgenography of gastrointestinal tract is one of the most reliable method for detail diagnosis. On double contract study of stomach, gastric filling defect is mostly caused by malignant gastric cancer, however, other benign lesions can cause similar pictures which can be successfully treated by surgery. 66 cases of benign causes of gastric filling defect were analyzed at this point of view, which was verified pathologically by endoscope or surgery during recent 7 years in Yensei University College of Medicine, Severance Hospital. The characteristic radiological picture of each disease was discussed for precise radiologic diagnosis. 1. Of total 66 cases, there were 52 cases of benign gastric tumor 10 cases of gastric varices, 5 cases of gastric bezoar, 5 cases of corrosive gastritis, 3 cases of granulomatous disease and one case of gastric hematoma. 2. The most frequent causes of benign tumors were adenomatous polyp (35/42) and the next was leiomyoma (4/42). Others were one of case of carcinoid, neurofibroma and cyst. 3. Characteristic of benign adenomatous polyp were relatively small in size, smooth surface and were observed that large size, benign polyp was frequently type IV lesion with a stalk. 4. Submucosal tumors such as leiomyoma needed differential diagnosis with polypoid malignant cancer. However, the characteristic points of differentiation was well circumscribed smooth margined filling defect without definite mucosal destruction on surface. 5. Gastric varices showed multiple lobulated filling defected especially on gastric fundus that changed its size and shape by respiration and posture of patients. Same varices lesions on esophagus and history of liver disease were helpful for easier diagnosis. 6. Gastric bezoar showed well defined movable mass

  13. Benign gastric filling defect

    Energy Technology Data Exchange (ETDEWEB)

    Oh, K K; Lee, Y H; Cho, O K; Park, C Y [Yonsei University College of Medicine, Seoul (Korea, Republic of)

    1979-06-15

    The gastric lesion is a common source of complaints to Orientals, however, evaluation of gastric symptoms and laboratory examination offer little specific aid in the diagnosis of gastric diseases. Thus roentgenography of gastrointestinal tract is one of the most reliable method for detail diagnosis. On double contract study of stomach, gastric filling defect is mostly caused by malignant gastric cancer, however, other benign lesions can cause similar pictures which can be successfully treated by surgery. 66 cases of benign causes of gastric filling defect were analyzed at this point of view, which was verified pathologically by endoscope or surgery during recent 7 years in Yensei University College of Medicine, Severance Hospital. The characteristic radiological picture of each disease was discussed for precise radiologic diagnosis. 1. Of total 66 cases, there were 52 cases of benign gastric tumor 10 cases of gastric varices, 5 cases of gastric bezoar, 5 cases of corrosive gastritis, 3 cases of granulomatous disease and one case of gastric hematoma. 2. The most frequent causes of benign tumors were adenomatous polyp (35/42) and the next was leiomyoma (4/42). Others were one of case of carcinoid, neurofibroma and cyst. 3. Characteristic of benign adenomatous polyp were relatively small in size, smooth surface and were observed that large size, benign polyp was frequently type IV lesion with a stalk. 4. Submucosal tumors such as leiomyoma needed differential diagnosis with polypoid malignant cancer. However, the characteristic points of differentiation was well circumscribed smooth margined filling defect without definite mucosal destruction on surface. 5. Gastric varices showed multiple lobulated filling defected especially on gastric fundus that changed its size and shape by respiration and posture of patients. Same varices lesions on esophagus and history of liver disease were helpful for easier diagnosis. 6. Gastric bezoar showed well defined movable mass

  14. Surface defects and chiral algebras

    Energy Technology Data Exchange (ETDEWEB)

    Córdova, Clay [School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr, Princeton, NJ 08540 (United States); Gaiotto, Davide [Perimeter Institute for Theoretical Physics,31 Caroline St N, Waterloo, ON N2L 2Y5 (Canada); Shao, Shu-Heng [School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr, Princeton, NJ 08540 (United States)

    2017-05-26

    We investigate superconformal surface defects in four-dimensional N=2 superconformal theories. Each such defect gives rise to a module of the associated chiral algebra and the surface defect Schur index is the character of this module. Various natural chiral algebra operations such as Drinfeld-Sokolov reduction and spectral flow can be interpreted as constructions involving four-dimensional surface defects. We compute the index of these defects in the free hypermultiplet theory and Argyres-Douglas theories, using both infrared techniques involving BPS states, as well as renormalization group flows onto Higgs branches. In each case we find perfect agreement with the predicted characters.

  15. Implications of defect clusters formed in cascades on free defect generation and microstructural development

    International Nuclear Information System (INIS)

    Wiedersich, H.

    1992-12-01

    A large fraction of the defects produced by irradiation with energetic neutrons or heavy ions originates in cascades. Not only increased recombination of vacancy and interstitial defects but also significant clustering of like defects occur. Both processes reduce the number of point defects available for long range migration. Consequences of defect clustering in cascades will be discussed in a semi-quantitative form with the aid of calculations using a very simplified model: Quasi-steady-state distributions of immobile vacancy and/or interstitial clusters develop which, in turn, can become significant sinks for mobile defects, and, therefore reduce their lifetime. Although cluster sinks will cause segregation and, potentially, precipitation of second phases due to local changes of composition, the finite lifetime of clusters will not lead to lasting, local compositional changes. A transition from highly dense interstitial and vacancy cluster distributions to the void swelling regime occurs when the thermal evaporation of vacancies from small vacancy clusters becomes significant at higher temperatures. Unequal clustering of vacancies and interstitials leads to an imbalance of their fluxes of in the matrix and, hence, to unequal contributions to atom transport by interstitials and by vacancies even in the quasi-steady state approximation

  16. Ultrasonic defect detection method for socket welding joint

    International Nuclear Information System (INIS)

    Tominaga, Masaaki; Matsuo, Toshiyuki; Ueno, Akihiro; Watanabe, Kunimichi; Kawamata, Kunio.

    1995-01-01

    The present invention provides a method of detecting defects over a wide range of a socket weld portion of various kinds of pipelines used, for example, in a nuclear power plant. Namely, an inclined probe is disposed to a jig for detecting defects by ultrasonic waves. This is rotated at least by one turn along the peripheral surface of the material to be detected such as weld tube joints. Defects of weld portion of the material can be detected automatically by using ultrasonic waves during the rotation. The inclined probe for detecting defects by ultrasonic waves comprises a transmission portion having a planar transmittance oscillator disposed to a wedge on the transmission side and a receiving portion comprising a planar receiving oscillator disposed to a wedge on the receiving side. With such a constitution, ultrasonic waves are emitted from the transmission portion to the defect detection portion in the welded portion. If a defect is present, defective echo is reflected to the receiving portion disposed ahead of the probe. Since the defective echo changes depending on the height of the detective portion, the estimation of the height of the defect can be facilitated. (I.S.)

  17. Strip defect recognition in electrical tests of silicon microstrip sensors

    Energy Technology Data Exchange (ETDEWEB)

    Valentan, Manfred, E-mail: valentan@mpp.mpg.de

    2017-02-11

    This contribution describes the measurement procedure and data analysis of AC-coupled double-sided silicon microstrip sensors with polysilicon resistor biasing. The most thorough test of a strip sensor is an electrical measurement of all strips of the sensor; the measured observables include e.g. the strip's current and the coupling capacitance. These measurements are performed to find defective strips, e.g. broken capacitors (pinholes) or implant shorts between two adjacent strips. When a strip has a defect, its observables will show a deviation from the “typical value”. To recognize and quantify certain defects, it is necessary to determine these typical values, i.e. the values the observables would have without the defect. As a novel approach, local least-median-of-squares linear fits are applied to determine these “would-be” values of the observables. A least-median-of-squares fit is robust against outliers, i.e. it ignores the observable values of defective strips. Knowing the typical values allows to recognize, distinguish and quantify a whole range of strip defects. This contribution explains how the various defects appear in the data and in which order the defects can be recognized. The method has been used to find strip defects on 30 double-sided trapezoidal microstrip sensors for the Belle II Silicon Vertex Detector, which have been measured at the Institute of High Energy Physics, Vienna (Austria).

  18. Point defects in nickel

    International Nuclear Information System (INIS)

    Peretto, P.

    1969-01-01

    The defects in electron irradiated nickel (20 deg. K) or neutron irradiated nickel (28 deg. K) are studied by simultaneous analysis using the magnetic after-effect, electron microscopy and electrical resistivity recovery. We use zone refined nickel (99.999 per cent) which, for some experiments, is alloyed with a small amount of iron (for example 0.1 per cent Fe). The temperature dependant electrical recovery may be divided in four stages. The sub-stages I B (31 deg. K), I C (42 deg. K), I D (from to 57 deg. K) and I E (62 deg. K) of stage I are due to the disappearance of single interstitials into vacancies. The interstitial defect has a split configuration with a migration energy of about 0.15 eV. In the close pair which disappears in stage I B the interstitial is found to be in a 3. neighbour position whilst in stage I D it is near the direction from the vacancy. In stage I E there is no longer any interaction between the interstitial and the vacancy. The stage II is due to more complicated interstitial defects: di-interstitials for stage II B (84 deg. K) and larger and larger interstitial loops for the following sub-stages. The loops may be seen by electron microscopy. Impurities can play the role of nucleation centers for the loops. Stages III A (370 deg. K) and III B (376 deg. K) are due to two types of di-vacancies. During stage IV (410 deg. K) the single vacancies migrate. Vacancy type loops and interstitial type loops grow concurrently and disappear at about 800 deg. K as observed by electron microscopy. (author) [fr

  19. Single ventricle cardiac defect

    International Nuclear Information System (INIS)

    Eren, B.; Turkmen, N.; Fedakar, R.; Cetin, V.

    2010-01-01

    Single ventricle heart is defined as a rare cardiac abnormality with a single ventricle chamber involving diverse functional and physiological defects. Our case is of a ten month-old baby boy who died shortly after admission to the hospital due to vomiting and diarrhoea. Autopsy findings revealed cyanosis of finger nails and ears. Internal examination revealed; large heart, weighing 60 grams, single ventricle, without a septum and upper membranous part. Single ventricle is a rare pathology, hence, this paper aims to discuss this case from a medico-legal point of view. (author)

  20. Atomistic simulations of divacancy defects in armchair graphene nanoribbons: Stability, electronic structure, and electron transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jun [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China); Zeng, Hui, E-mail: zenghui@yangtzeu.edu.cn [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China); Wei, Jianwei [College of Optoelectronic Information, Chongqing University of Technology, Chongqing 400054 (China); Li, Biao; Xu, Dahai [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China)

    2014-01-17

    Using the first principles calculations associated with nonequilibrium Green's function, we have studied the electronic structures and quantum transport properties of defective armchair graphene nanoribbon (AGNR) in the presence of divacancy defects. The triple pentagon–triple heptagon (555–777) defect in the defective AGNR is energetically more favorable than the pentagon–octagon–pentagon (5–8–5) defect. Our calculated results reveal that both 5–8–5-like defect and 555–777-like defect in AGNR could improve the electron transport. It is anticipated that defective AGNRs can exhibit large range variations in transport behaviors, which are strongly dependent on the distributions of the divacancy defect.

  1. Defect detection using transient thermography

    International Nuclear Information System (INIS)

    Mohd Zaki Umar; Ibrahim Ahmad; Ab Razak Hamzah; Wan Saffiey Wan Abdullah

    2008-08-01

    An experimental research had been carried out to study the potential of transient thermography in detecting sub-surface defect of non-metal material. In this research, eight pieces of bakelite material were used as samples. Each samples had a sub-surface defect in the circular shape with different diameters and depths. Experiment was conducted using one-sided Pulsed Thermal technique. Heating of samples were done using 30 kWatt adjustable quartz lamp while infra red (IR) images of samples were recorded using THV 550 IR camera. These IR images were then analysed with ThermofitTMPro software to obtain the Maximum Absolute Differential Temperature Signal value, ΔΤ m ax and the time of its appearance, τ m ax (ΔΤ). Result showed that all defects were able to be detected even for the smallest and deepest defect (diameter = 5 mm and depth = 4 mm). However the highest value of Differential Temperature Signal (ΔΤ m ax), were obtained at defect with the largest diameter, 20 mm and at the shallowest depth, 1 mm. As a conclusion, the sensitivity of the pulsed thermography technique to detect sub-surface defects of bakelite material is proportionately related with the size of defect diameter if the defects are at the same depth. On the contrary, the sensitivity of the pulsed thermography technique inversely related with the depth of defect if the defects have similar diameter size. (Author)

  2. Dipole defects in beryl

    International Nuclear Information System (INIS)

    Holanda, B A; Cordeiro, R C; Blak, A R

    2010-01-01

    Dipole defects in gamma irradiated and thermally treated beryl (Be 3 Al 2 Si 6 O 18 ) samples have been studied using the Thermally Stimulated Depolarization Currents (TSDC) technique. TSDC experiments were performed in pink (morganite), green (emerald), blue (aquamarine) and colourless (goshenite) natural beryl. TSDC spectra present dipole peaks at 190K, 220K, 280K and 310K that change after gamma irradiation and thermal treatments. In morganite samples, for thermal treatments between 700K and 1100K, the 280K peak increase in intensity and the band at 220K disappears. An increase of the 280K peak and a decrease of the 190K peak were observed in the TSDC spectra of morganite after a gamma irradiation of 25kGy performed after the thermal treatments. In the case of emerald samples, thermal treatments enhanced the 280K peak and gamma irradiation partially destroyed this band. The goshenite TSDC spectra present only one band at 280K that is not affected either by thermal treatments or by gamma irradiation. All the observed peaks are of dipolar origin because the intensity of the bands is linearly dependent on the polarization field, behaviour of dipole defects. The systematic study, by means of TSDC measurements, of ionizing irradiation effects and thermal treatments in these crystals makes possible a better understanding of the role played by the impurities in beryl crystals.

  3. Mean Glenoid Defect Size and Location Associated With Anterior Shoulder Instability

    Science.gov (United States)

    Gottschalk, Lionel J.; Bois, Aaron J.; Shelby, Marcus A.; Miniaci, Anthony; Jones, Morgan H.

    2017-01-01

    Background: There is a strong correlation between glenoid defect size and recurrent anterior shoulder instability. A better understanding of glenoid defects could lead to improved treatments and outcomes. Purpose: To (1) determine the rate of reporting numeric measurements for glenoid defect size, (2) determine the consistency of glenoid defect size and location reported within the literature, (3) define the typical size and location of glenoid defects, and (4) determine whether a correlation exists between defect size and treatment outcome. Study Design: Systematic review; Level of evidence, 4. Methods: PubMed, Ovid, and Cochrane databases were searched for clinical studies measuring glenoid defect size or location. We excluded studies with defect size requirements or pathology other than anterior instability and studies that included patients with known prior surgery. Our search produced 83 studies; 38 studies provided numeric measurements for glenoid defect size and 2 for defect location. Results: From 1981 to 2000, a total of 5.6% (1 of 18) of the studies reported numeric measurements for glenoid defect size; from 2001 to 2014, the rate of reporting glenoid defects increased to 58.7% (37 of 63). Fourteen studies (n = 1363 shoulders) reported defect size ranges for percentage loss of glenoid width, and 9 studies (n = 570 shoulders) reported defect size ranges for percentage loss of glenoid surface area. According to 2 studies, the mean glenoid defect orientation was pointing toward the 3:01 and 3:20 positions on the glenoid clock face. Conclusion: Since 2001, the rate of reporting numeric measurements for glenoid defect size was only 58.7%. Among studies reporting the percentage loss of glenoid width, 23.6% of shoulders had a defect between 10% and 25%, and among studies reporting the percentage loss of glenoid surface area, 44.7% of shoulders had a defect between 5% and 20%. There is significant variability in the way glenoid bone loss is measured, calculated

  4. Risk factors, organ weight deviation and associated anomalies in neural tube defects: A prospective fetal and perinatal autopsy series

    Directory of Open Access Journals (Sweden)

    Asaranti Kar

    2015-01-01

    Full Text Available Introduction: Neural tube defects (NTD are a group of serious birth defects occurring due to defective closure of neural tube during embryonic development. It comprises of anencephaly, encephalocele and spina bifida. We conducted this prospective fetal autopsy series to study the rate and distribution of NTD, analyze the reproductive factors and risk factors, note any associated anomalies and evaluate the organ weights and their deviation from normal. Materials and Methods: This was a prospective study done over a period of 6 years from August, 2007 to July, 2013. All cases of NTDs delivered as abortion, still born and live born were included. The reproductive and risk factors like age, parity, multiple births, previous miscarriage, obesity, diabetes mellitus, socioeconomic status and use of folic acid during pregnancy were collected.Autopsy was performed according to Virchow′s technique. Detail external and internal examination were carried out to detect any associated anomalies. Gross and microscopic examination of organs were done. Results: Out of 210 cases of fetal and perinatal autopsy done, 72 (34.28% had NTD constituting 49 cases of anencephaly, 16 spina bifida and 7 cases of encephalocele. The mothers in these cases predominantly were within 25-29 years (P = 0.02 and primy (P = 0.01. Female sex was more commonly affected than males (M:F = 25:47, P = 0.0005 There was no history of folate use in majority of cases. Organ weight deviations were >2 standard deviation low in most of the cases. Most common associated anomalies were adrenal hypoplasia and thymic hyperplasia. Conclusion: The authors have made an attempt to study NTD cases in respect to maternal reproductive and risk factors and their association with NTD along with the organ weight deviation and associated anomalies. This so far in our knowledge is an innovative study which was not found in literature even after extensive search.

  5. Defects in low temperature electron irradiated InP

    International Nuclear Information System (INIS)

    Suski, J.; Bourgoin, J.

    1984-01-01

    n and p-InP has been irradiated at 25K with 1MeV electrons and the created defects were studied by deep level transient spectroscopy (DLTS) in the range 25K-400K. In n-InP, four traps are directly observed, with low introduction rates except for one. They anneal in three stages, and four new centers of still lower concentration appear after 70 0 C heat treatment. In p-InP, two dominant traps stable up to approx.= 400K with introduction rates close to the theoretical ones, which might be primary defects are found, while another one is clearly a secondary defect likely associated to Zn dopant. At least two of the low concentration irradiation induced electron traps, created between 25K and 100K are also secondary defects, which implies a mobility of some primary defects down to 100K at least. (author)

  6. Computer simulation of defect cluster

    Energy Technology Data Exchange (ETDEWEB)

    Kuramoto, Eiichi [Kyushu Univ., Kasuga, Fukuoka (Japan). Research Inst. for Applied Mechanics

    1996-04-01

    In order to elucidate individual element process of various defects and defect clusters of used materials under irradiation environments, interatomic potential with reliability was investigated. And for comparison with experimental results, it is often required to adopt the temperature effect and to investigate in details mechanism of one dimensional motion of micro conversion loop and so forth using the molecular dynamic (MD) method. Furthermore, temperature effect is also supposed for stable structure of defects and defect clusters, and many problems relating to alloy element are also remained. And, simulation on photon life at the defects and defect clusters thought to be important under comparison with equipment can also be supposed an improvement of effectiveness due to relation to theses products. In this paper, some topics in such flow was extracted to explain them. In particular, future important problems will be potential preparation of alloy, structure, dynamic behavior and limited temperature of intralattice atomic cluster. (G.K.)

  7. Defects and Disorder in the Drosophila Eye

    Science.gov (United States)

    Kim, Sangwoo; Carthew, Richard; Hilgenfeldt, Sascha

    Cell division and differentiation tightly control the regular pattern in the normal eye of the Drosophila fruit fly while certain genetic mutations introduce disorder in the form of topological defects. Analyzing data from pupal retinas, we develop a model based on Voronoi construction that explains the defect statistics as a consequence of area variation of individual facets (ommatidia). The analysis reveals a previously unknown systematic long-range area variation that spans the entire eye, with distinct effects on topological disorder compared to local fluctuations. The internal structure of the ommatidia and the stiffness of their interior cells also plays a crucial role in the defect generation. Accurate predictions of the correlation between the area variation and the defect density in both normal and mutant animals are obtained without free parameters. This approach can potentially be applied to cellular systems in many other contexts to identify size-topology correlations near the onset of symmetry breaking. This work has been supported by the NIH (GM098077) and the NSF (Grant No. 1504301).

  8. Topological defects in extended inflation

    International Nuclear Information System (INIS)

    Copeland, E.J.; Kolb, E.W.; Chicago Univ., IL; Liddle, A.R.

    1990-04-01

    We consider the production of topological defects, especially cosmic strings, in extended inflation models. In extended inflation, the Universe passes through a first-order phase transition via bubble percolation, which naturally allows defects to form at the end of inflation. The correlation length, which determines the number density of the defects, is related to the mean size of bubbles when they collide. This mechanism allows a natural combination of inflation and large-scale structure via cosmic strings. 18 refs

  9. Defects in new protective aprons

    International Nuclear Information System (INIS)

    Glaze, S.; LeBlanc, A.D.; Bushong, S.C.

    1984-01-01

    Upon careful examination, several defects have been detected in new protective aprons. The nature of the defects is identified and described. Although the occurrence of such defects has not exceeded 5%, they are significant enough to warrant return of the lead apron to the supplier. It is recommended that the integrity of all new protective aprons be verified upon receipt as well as at yearly intervals

  10. Topological defects in extended inflation

    International Nuclear Information System (INIS)

    Copeland, E.J.; Kolb, E.W.; Liddle, A.R.

    1990-01-01

    We consider the production of topological defects, especially cosmic strings, in extended-inflation models. In extended inflation, the Universe passes through a first-order phase transition via bubble percolation, which naturally allows defects to form at the end of inflation. The correlation length, which determines the number density of the defects, is related to the mean size of the bubbles when they collide. This mechanism allows a natural combination of inflation and large-scale structure via cosmic strings

  11. Metastable gravity on classical defects

    International Nuclear Information System (INIS)

    Ringeval, Christophe; Rombouts, Jan-Willem

    2005-01-01

    We discuss the realization of metastable gravity on classical defects in infinite-volume extra dimensions. In dilatonic Einstein gravity, it is found that the existence of metastable gravity on the defect core requires violation of the dominant energy condition for codimension N c =2 defects. This is illustrated with a detailed analysis of a six-dimensional hyperstring minimally coupled to dilaton gravity. We present the general conditions under which a codimension N c >2 defect admits metastable modes, and find that they differ from lower codimensional models in that, under certain conditions, they do not require violation of energy conditions to support quasilocalized gravity

  12. Defect Characterization of Pyroelectric Materials

    National Research Council Canada - National Science Library

    Keeble, David

    2002-01-01

    Two methods for identify point defects applicable to the study of technologically relevant pyroelectric oxide materials have been investigated, namely Positron Annihilation Lifetime Spectroscopy (PALS...

  13. Fibrous metaphyseal defects

    International Nuclear Information System (INIS)

    Hajek, P.C.; Ritschi, P.; Kramer, J.; Imhof, H.; Karnel, F.

    1988-01-01

    Eighty-two patients (107 fibrous metaphyseal defects [FMDs]) were investigated with standard radiography and MR imaging (N = 15). Twenty-two of these were followed up sequentially up to 10 years (mean, 7.3 years). Histologic studies proved that FMDs originate at the site of insertion of a tendon in the perichondrium of the epiphyseal cartilage. After normal bone growth is regained, all FMDs were found to move diaphysically, following a straight line parallel to the long axis of the FMDs. This line pointed to the insertion of the tendon originally involved, a fact that was proved with MR imaging. Four characteristic stages were found to define a typical radiomorphologic course of an FMD

  14. Angiographic differentiation of type of ventricular septal defects

    International Nuclear Information System (INIS)

    Cheon, Mal Soon; Park, Hee Young; Kim, Yang Sook

    1989-01-01

    Defects of the ventricular septum are the commonest type of congenital cardiac malformations. A classification with axial angiography of the subtypes of ventricular septal defects is proposed on the study of 126 patients with defects of the ventricular septum. The results were as follows: 1. The incidence of the ventricular septal defects was 39.6% of congenital heart malformation. 2. The sex distribution of cases were 70 males and 56 females, the age ranged from 13 months to 26 years. 3. Angiographic features seen by axial angiography were as follows: a. Perimembranous defects as seen on long axial view of left ventriculogram were in continuity wity aortic valve. The relation of the defect to the tricuspid valve allows distinction of the extension of the preimembranous defect toward inlet, trabecular, or infundibular zones. This relation was determined angiographically, using the course of the contrast medium from the left ventricle through the ventricular septal defect, opacifying the right ventricle. In inlet excavation, the shunted blood opacified the recess between septal leaflet of tricuspid valve and interventricular septum in early phase, in infundibular excavation, opacified the recess between anterior leaflet of tricuspid valve and anterior free wall of right ventricle and in trabecular excavation, the shunted blood traversed anterior portion of tricuspid valve ring, opacified trabecular portion of right ventricle. b. Muscular defects were separated from the semilunar and atrioventricular valves. c, Subarterial defects were related to both semilunar valves, and they were best demonstrated on the elongated right anterior oblique view of the left ventriculogram. d. Total infundibular defects were profiled in right anterior oblique 30 and long axial view, subaortic in location in both views

  15. Defect structure in proton-irradiated copper and nickel

    International Nuclear Information System (INIS)

    Tsukuda, Noboru; Ehrhart, P.; Jaeger, W.; Schilling, W.; Dworschak, F.; Gadalla, A.A.

    1987-01-01

    This single crystals of copper or nickel with a thickness of about 10 μm are irradiated with 3 MeV protons at room temperature and the structures of resultant defects are investigated based on measurements of the effects of irradiation on the electrical resistivity, length, lattice constants, x-ray diffraction line profile and electron microscopic observations. The measurements show that the electrical resistivity increases with irradiation dose, while leveling off at high dose due to overlapping of irradiation cascades. The lattice constants decreases, indicating that many vacancies still remain while most of the interstitial stoms are eliminated, absorbed or consumed for dislocation loop formation. The x-ray line profile undergoes broadening, which is the result of dislocation loops, dislocation networks and SFT's introduced by the proton irradiation. Various defects have different effects though they cannot be identified separately from the profile alone. A satellite peak appears at a low angle, which seems to arise from periodic defect structures that are found in electron microscopic observations. In both copper and nickel, such periodic defect structures are seen over a wide range from high to low dose. Defect-free and defect-rich domains (defect walls), 0.5 to several μm in size, are alingned parallel to the {001} plane at intervals of 60 nm. The defect walls, which consist of dislocations, dislocation loops and SFT's, is 20 - 40 nm thick. (Nogami, K.)

  16. The quantum defect: Early history and recent developments

    International Nuclear Information System (INIS)

    Rau, A.R.; Inokuti, M.

    1997-01-01

    The notion of the quantum defect is important in atomic and molecular spectroscopy and also in unifying spectroscopy with collision theory. In the latter context, the quantum defect may be viewed as an ancestor of the phase shift. However, the origin of the term open-quotes quantum defectclose quotes does not seem to be explained in standard textbooks. It occurred in a 1921 paper by Schroedinger, preceding quantum mechanics, yet giving the correct meaning as an index of the short-range interactions with the core of an atom. We present the early history of the quantum-defect idea, and sketch its recent developments. copyright 1997 American Association of Physics Teachers

  17. Computed tomography on a defective CANDU fuel pencil end cap

    International Nuclear Information System (INIS)

    Lupton, L.R.

    1985-09-01

    Five tomographic slices through a defective end cap from a CANDU fuel pencil have been generated using a Co-60 source and a first generation translate-rotate tomography scanner. An anomaly in the density distribution that is believed to have resulted from the defect has been observed. However, with the 0.30 mm spatial resolution used, it has not been possible to state unequivocally whether the change in density is caused by a defect in the weld or a statistical anomaly in the data. It is concluded that a microtomography system, with a spatial resolution in the range of 0.1 mm, could detect the flaw

  18. Defect phase diagram for doping of Ga2O3

    OpenAIRE

    Stephan Lany

    2018-01-01

    For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have d...

  19. Folic acid supplementation is not the sole factor in determining ...

    African Journals Online (AJOL)

    user user

    2012-07-10

    Jul 10, 2012 ... Neural tube defects (NTDs) are severe but common congenital malformations. Neonates who ... malformations that affect the central nervous system. NTDs are costly .... protective effect of folic acid supplementation on NTD.

  20. Lumber defect detection by ultrasonics

    Science.gov (United States)

    K. A. McDonald

    1978-01-01

    Ultrasonics, the technology of high-frequency sound, has been developed as a viable means for locating most defects In lumber for use in digital form in decision-making computers. Ultrasonics has the potential for locating surface and internal defects in lumber of all species, green or dry, and rough sawn or surfaced.

  1. Lectures on cosmic topological defects

    Energy Technology Data Exchange (ETDEWEB)

    Vachaspati, T [Department of Astronomy and Astrophysics, Colaba, Mumbai (India) and Physics Department, Case Western Reserve University, Cleveland (United States)

    2001-11-15

    These lectures review certain topological defects and aspects of their cosmology. Unconventional material includes brief descriptions of electroweak defects, the structure of domain walls in non-Abelian theories, and the spectrum of magnetic monopoles in SU(5) Grand Unified theory. (author)

  2. Study of point defects in bismuth

    International Nuclear Information System (INIS)

    Bois, P.

    1987-03-01

    Single crystalline samples of bismuth, pure and n or p - doped by adding tellurium or tin, were electron irradiated at low temperature (4.2 K and 20 K). In the energy range 0.7 - 2.5 MeV, a displacement threshold energy of 13 eV and an athermal recombination volume of 150 atomic volumes were determined. Joint measurements of resistivity, magnetotransport and positron annihilation enabled to precised the nature of the annealing stages: 40-50 K, free migration of interstitials; 90-120 K long range migration of vacancy. Point defects have according to their nature a different effect on the electronic properties of bismuth: isolated Frenkel pairs are globally donnors with a charge of + 0.16 e- and the vacancy is donnor, which seems to attribute to it a negative formation volume. A simple model with non-deformating bands is no longer sufficient to explain the behaviour under irradiation: one has to take into account an acceptor level with a charge of - 0,27 e-, linked to the cascade-type defects and resonating with the valence band. It's position in the band overlap and it's width (8 meV) could be precised. In first approximation this coupling with less mobile carriers does not affect the simple additive rule which exists for relaxation times. Some yet obscure magnetic properties seem to be linked to this defect level [fr

  3. Structural defects in monocrystalline silicon: from radiation ones to growing and technological

    International Nuclear Information System (INIS)

    Gerasimenko, N.N.; Pavlyuchenko, M.N.; Dzhamanbalin, K.K.

    2001-01-01

    The systematical review of properties and conditions of radiation structures in monocrystalline silicon including own defects (elementary and complex, disordered fields) as well as defect-impurity formations is presented. The most typical examples of principle effects influence of known defects on radiation-induced processes (phase transformations, diffusion and heteration and others are considered. Experimental facts and models of silicon radiation amorphization have been analyzed in comparison of state of the radiation amorphization radiation problem of metals and alloys. The up-to-date status of the problem of the radiation defects physics are discussed, including end-of-range -, n+-, rod-like- defects. The phenomenon self-organization in crystals with defects has been considered. The examples of directed using radiation defects merged in independent trend - defects engineering - are given

  4. Holographic Chern-Simons defects

    International Nuclear Information System (INIS)

    Fujita, Mitsutoshi; Melby-Thompson, Charles M.; Meyer, René; Sugimoto, Shigeki

    2016-01-01

    We study SU(N) Yang-Mills-Chern-Simons theory in the presence of defects that shift the Chern-Simons level from a holographic point of view by embedding the system in string theory. The model is a D3-D7 system in Type IIB string theory, whose gravity dual is given by the AdS soliton background with probe D7 branes attaching to the AdS boundary along the defects. We holographically renormalize the free energy of the defect system with sources, from which we obtain the correlation functions for certain operators naturally associated to these defects. We find interesting phase transitions when the separation of the defects as well as the temperature are varied. We also discuss some implications for the Fractional Quantum Hall Effect and for 2-dimensional QCD.

  5. Defect forces, defect couples and path integrals in fracture mechanics

    International Nuclear Information System (INIS)

    Roche, R.L.

    1979-07-01

    In this work, it is shown that the path integrals can be introduced without any reference to the material behavior. The method is based on the definition in a continuous medium of a set of vectors and couples having the dimension of a force or a moment. More precisely, definitions are given of volume defect forces, surface defect forces, volume defect couples, and surface defect couples. This is done with the help of the stress working variation of a particule moving through the solid. The most important result is: the resultant of all the defect forces included in a volume V is the J integral on the surface surrounding V and the moment resultant is the L integral. So these integrals are defined without any assumption on the material constitutive equation. Another result is the material form of the virtual work principle - defect forces are acting like conventional forces in the conventional principles of virtual work. This lead to the introduction of the energy momentum tensor and of the associated couple stress. Application of this method is made to fracture mechanics in studying the defect forces distribution around a crack [fr

  6. Effect of triangular vacancy defect on thermal conductivity and thermal rectification in graphene nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ping, E-mail: yangpingdm@ujs.edu.cn [Laboratory of Advanced Manufacturing and Reliability for MEMS/NEMS/OEDS, Jiangsu University, Zhenjiang 212013 (China); Li, Xialong; Zhao, Yanfan [Laboratory of Advanced Manufacturing and Reliability for MEMS/NEMS/OEDS, Jiangsu University, Zhenjiang 212013 (China); Yang, Haiying [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Wang, Shuting, E-mail: wangst@mail.hust.edu.cn [School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2013-11-01

    We investigate the thermal transport properties of armchair graphene nanoribbons (AGNRs) possessing various sizes of triangular vacancy defect within a temperature range of 200–600 K by using classical molecular dynamics simulation. The results show that the thermal conductivities of the graphene nanoribbons decrease with increasing sizes of triangular vacancy defects in both directions across the whole temperature range tested, and the presence of the defect can decrease the thermal conductivity by more than 40% as the number of removed cluster atoms is increased to 25 (1.56% for vacancy concentration) owing to the effect of phonon–defect scattering. In the meantime, we find the thermal conductivity of defective graphene nanoribbons is insensitive to the temperature change at higher vacancy concentrations. Furthermore, the dependence of temperatures and various sizes of triangular vacancy defect for the thermal rectification ration are also detected. This work implies a possible route to achieve thermal rectifier for 2D materials by defect engineering.

  7. Mechanical properties of highly defective graphene: from brittle rupture to ductile fracture

    International Nuclear Information System (INIS)

    Xu, Lanqing; Wei, Ning; Zheng, Yongping

    2013-01-01

    Defects are generally believed to deteriorate the superlative performance of graphene-based devices but may also be useful when carefully engineered to tailor the local properties and achieve new functionalities. Central to most defect-associated applications is the defect coverage and arrangement. In this work, we investigate, by molecular dynamics simulations, the mechanical properties and fracture dynamics of graphene sheets with randomly distributed vacancies or Stone–Wales defects under tensile deformations over a wide defect coverage range. With defects presented, an sp–sp 2 bonding network and an sp–sp 2 –sp 3 bonding network are observed in vacancy-defected and Stone–Wales-defected graphene, respectively. The ultimate strength degrades gradually with increasing defect coverage and saturates in the high-ratio regime, whereas the fracture strain presents an unusual descending–saturating–improving trend. In the dense vacancy defect situation, the fracture becomes more plastic and super-ductility is observed. Further fracture dynamics analysis reveals that the crack trapping by sp–sp 2 and sp–sp 2 –sp 3 rings and the crack-tip blunting account for the ductile fracture, whereas geometric rearrangement on the entire sheet for vacancy defects and geometric rearrangement on the specific defect sites for Stone–Wales defects account for their distinctive rules of the evolution of the fracture strain. (paper)

  8. Mechanical properties of highly defective graphene: from brittle rupture to ductile fracture.

    Science.gov (United States)

    Xu, Lanqing; Wei, Ning; Zheng, Yongping

    2013-12-20

    Defects are generally believed to deteriorate the superlative performance of graphene-based devices but may also be useful when carefully engineered to tailor the local properties and achieve new functionalities. Central to most defect-associated applications is the defect coverage and arrangement. In this work, we investigate, by molecular dynamics simulations, the mechanical properties and fracture dynamics of graphene sheets with randomly distributed vacancies or Stone-Wales defects under tensile deformations over a wide defect coverage range. With defects presented, an sp-sp(2) bonding network and an sp-sp(2)-sp(3) bonding network are observed in vacancy-defected and Stone-Wales-defected graphene, respectively. The ultimate strength degrades gradually with increasing defect coverage and saturates in the high-ratio regime, whereas the fracture strain presents an unusual descending-saturating-improving trend. In the dense vacancy defect situation, the fracture becomes more plastic and super-ductility is observed. Further fracture dynamics analysis reveals that the crack trapping by sp-sp(2) and sp-sp(2)-sp(3) rings and the crack-tip blunting account for the ductile fracture, whereas geometric rearrangement on the entire sheet for vacancy defects and geometric rearrangement on the specific defect sites for Stone-Wales defects account for their distinctive rules of the evolution of the fracture strain.

  9. Defect assessment benchmark studies

    International Nuclear Information System (INIS)

    Hooton, D.G.; Sharples, J.K.

    1995-01-01

    Assessments of the resistance to fast fracture of the beltline region of a PWR vessel subjected to a pressurized thermal shock (PTS) transient have been carried out using the procedures of French (RCC-M) and German (KTA) design codes, and comparisons made with results obtained using the R6 procedure as applied for Sizewell B. The example chosen for these comparisons is of a generic nature, and is taken as the PTS identified by the Hirsch addendum to the Second Marshall report (1987) as the most severe transient with regard to vessel integrity. All assessment methods show the beltline region of the vessel to be safe from the risk of fast fracture, but by varying factors of safety. These factors are discussed in terms of margins between limiting and reference defect sizes, fracture toughness and stress intensity factor, and material temperature and temperature at the onset of upper-shelf materials behaviour. Based on these studies, consideration is given to issues involved in the harmonization of those sections of the design codes which are concerned with methods for the demonstration of the avoidance of the risk of failure by fast fracture. (author)

  10. Serine biosynthesis and transport defects.

    Science.gov (United States)

    El-Hattab, Ayman W

    2016-07-01

    l-serine is a non-essential amino acid that is biosynthesized via the enzymes phosphoglycerate dehydrogenase (PGDH), phosphoserine aminotransferase (PSAT), and phosphoserine phosphatase (PSP). Besides its role in protein synthesis, l-serine is a potent neurotrophic factor and a precursor of a number of essential compounds including phosphatidylserine, sphingomyelin, glycine, and d-serine. Serine biosynthesis defects result from impairments of PGDH, PSAT, or PSP leading to systemic serine deficiency. Serine biosynthesis defects present in a broad phenotypic spectrum that includes, at the severe end, Neu-Laxova syndrome, a lethal multiple congenital anomaly disease, intermediately, infantile serine biosynthesis defects with severe neurological manifestations and growth deficiency, and at the mild end, the childhood disease with intellectual disability. A serine transport defect resulting from deficiency of the ASCT1, the main transporter for serine in the central nervous system, has been recently described in children with neurological manifestations that overlap with those observed in serine biosynthesis defects. l-serine therapy may be beneficial in preventing or ameliorating symptoms in serine biosynthesis and transport defects, if started before neurological damage occurs. Herein, we review serine metabolism and transport, the clinical, biochemical, and molecular aspects of serine biosynthesis and transport defects, the mechanisms of these diseases, and the potential role of serine therapy. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. First-Principles Investigations of Defects in Minerals

    Science.gov (United States)

    Verma, Ashok K.

    2011-07-01

    The ideal crystal has an infinite 3-dimensional repetition of identical units which may be atoms or molecules. But real crystals are limited in size and they have disorder in stacking which as called defects. Basically three types of defects exist in solids: 1) point defects, 2) line defects, and 3) surface defects. Common point defects are vacant lattice sites, interstitial atoms and impurities and these are known to influence strongly many solid-state transport properties such as diffusion, electrical conduction, creep, etc. In thermal equilibrium point defects concentrations are determined by their formation enthalpies and their movement by their migration barriers. Line and surface defects are though absent from the ideal crystal in thermal equilibrium due to higher energy costs but they are invariably present in all real crystals. Line defects include edge-, screw- and mixed-dislocations and their presence is essential in explaining the mechanical strength and deformation of real crystals. Surface defects may arise at the boundary between two grains, or small crystals, within a larger crystal. A wide variety of grain boundaries can form in a polycrystal depending on factors such growth conditions and thermal treatment. In this talk we will present our first-principles density functional theory based defect studies of SiO2 polymorphs (stishovite, CaCl2-, α-PbO2-, and pyrite-type), Mg2SiO4 polymorphs (forsterite, wadsleyite and ringwoodite) and MgO [1-3]. Briefly, several native point defects including vacancies, interstitials, and their complexes were studied in silica polymorphs upto 200 GPa. Their values increase by a factor of 2 over the entire pressure range studied with large differences in some cases between different phases. The Schottky defects are energetically most favorable at zero pressure whereas O-Frenkel pairs become systematically more favorable at pressures higher than 20 GPa. The geometric and electronic structures of defects and migrating

  12. Optical coherence tomography use in the diagnosis of enamel defects

    Science.gov (United States)

    Al-Azri, Khalifa; Melita, Lucia N.; Strange, Adam P.; Festy, Frederic; Al-Jawad, Maisoon; Cook, Richard; Parekh, Susan; Bozec, Laurent

    2016-03-01

    Molar incisor hypomineralization (MIH) affects the permanent incisors and molars, whose undermineralized matrix is evidenced by lesions ranging from white to yellow/brown opacities to crumbling enamel lesions incapable of withstanding normal occlusal forces and function. Diagnosing the condition involves clinical and radiographic examination of these teeth, with known limitations in determining the depth extent of the enamel defects in particular. Optical coherence tomography (OCT) is an emerging hard and soft tissue imaging technique, which was investigated as a new potential diagnostic method in dentistry. A comparison between the diagnostic potential of the conventional methods and OCT was conducted. Compared to conventional imaging methods, OCT gave more information on the structure of the enamel defects as well as the depth extent of the defects into the enamel structure. Different types of enamel defects were compared, each type presenting a unique identifiable pattern when imaged using OCT. Additionally, advanced methods of OCT image analysis including backscattered light intensity profile analysis and enface reconstruction were performed. Both methods confirmed the potential of OCT in enamel defects diagnosis. In conclusion, OCT imaging enabled the identification of the type of enamel defect and the determination of the extent of the enamel defects in MIH with the advantage of being a radiation free diagnostic technique.

  13. Modeling charged defects inside density functional theory band gaps

    International Nuclear Information System (INIS)

    Schultz, Peter A.; Edwards, Arthur H.

    2014-01-01

    Density functional theory (DFT) has emerged as an important tool to probe microscopic behavior in materials. The fundamental band gap defines the energy scale for charge transition energy levels of point defects in ionic and covalent materials. The eigenvalue gap between occupied and unoccupied states in conventional DFT, the Kohn–Sham gap, is often half or less of the experimental band gap, seemingly precluding quantitative studies of charged defects. Applying explicit and rigorous control of charge boundary conditions in supercells, we find that calculations of defect energy levels derived from total energy differences give accurate predictions of charge transition energy levels in Si and GaAs, unhampered by a band gap problem. The GaAs system provides a good theoretical laboratory for investigating band gap effects in defect level calculations: depending on the functional and pseudopotential, the Kohn–Sham gap can be as large as 1.1 eV or as small as 0.1 eV. We find that the effective defect band gap, the computed range in defect levels, is mostly insensitive to the Kohn–Sham gap, demonstrating it is often possible to use conventional DFT for quantitative studies of defect chemistry governing interesting materials behavior in semiconductors and oxides despite a band gap problem

  14. Quantitative Evaluation of Remote Field Eddy Current Defect Signals

    International Nuclear Information System (INIS)

    Jeong, Jin Oh; Yi, Jae Kyung; Kim, Hyoung Jean

    2000-01-01

    The remote field eddy current (RFEC) inspection was performed on the ductile cast iron pipes with nominal outer diameter of 100mm, which were machined with various shapes and sizes of defects. Ductile cast iron pipes which are used as water supply pipe have the non-uniform thickness and asymmetric cross section due to relatively high degree of allowable errors during the manufacturing processes. These characteristics of ductile cast in pipes cause the long range background noises in RFEC signals along the pipe. In this study, tile machined defects in pipes were effectively classified by the moving window average (MWA) method which eliminated the long-range noise. The voltage plane polar plots (VPPP) method was used to quantitatively evaluate the depth and circumferential degree of defects. The VPPP signatures showed that the angle between defect signature and the normalized in-phase component on the VPPP is linear to the depth of defects. The nondestructive RFEC technique proved to be capable of quantitatively evaluating the machined defects of underground water supply pipe

  15. Automated defect location and sizing by advanced ultrasonic techniques

    International Nuclear Information System (INIS)

    Murgatroyd, R.A.

    1983-01-01

    From this assessment of advanced automated defect location and sizing techniques it is concluded that, 1. Pulse-echo techniques, when used at high sensitivity, are capable of detecting all known defects in the test weldments inspected; 2. Search sensitivity has a marked influence on defect detection at both 1 and 2 MHz, and it is considered that 20% DAC is the highest amplitude threshold level which could be prudently adopted at the search stage; 3. The important through-thickness dimension of deeply buried defects in the height range 5 to 50mm can be sized to an estimated accuracy of +2mm using the Silk technique and that applying a SAFT-type algorithm to the data gives good lateral positioning of defects; 4. The 70 0 longitudinal wave twin-crystal technique has proved to be a highly effective method of detecting underclad cracks. A 70 0 shear wave, pulse-echo technique and a 0 0 longitudinal wave twin crystal method also give good detection results in the near surface region; 5. The Silk technique has been effective in sizing defects in the height range 5 to 35mm in the near-surface region

  16. Facts about Congenital Heart Defects

    Science.gov (United States)

    ... types of CHDs. The types marked with a star (*) are considered critical CHDs. Atrial Septal Defect Atrioventricular ... for Disease Control and Prevention Email Recommend Tweet YouTube Instagram Listen Watch RSS ABOUT About CDC Jobs ...

  17. Birth Defects Data and Statistics

    Science.gov (United States)

    ... Submit" /> Information For… Media Policy Makers Data & Statistics Recommend on Facebook Tweet Share Compartir On This ... and critical. Read below for the latest national statistics on the occurrence of birth defects in the ...

  18. Defects in semiconductors

    International Nuclear Information System (INIS)

    Tilly, L.

    1993-04-01

    In this thesis, experimental results of the transition metals Ti, V, Nb, Mo, and W as impurity centres in silicon are presented. Transition metal doping was accomplished by ion implantation. Emphasis is put on energy level position, electrical and optical properties of the encountered defect levels. Junction space charge methods (JSCM) such as DLTS, photocapacitance and photocurrent techniques are employed. Three energy levels are found for the 3d-transition metals Ti(E c -0.06eV, E c -0.30eV, E v +0.26) and V(E c -0.21eV, E c -0,48e, E v +0.36eV), and for the 4d-element Nb(E c -0.29eV, E c -0.58eV, E v +0.163eV) in Silicon, whereas only one transition metal induced level is found for Mo(E v +0.30eV) and W(E v +0.38eV) respectively. Electrical and optical characteristics of Si 1-x Ge x ,0.7 7 cm -2 . The solvent Bi, used in the LPE-process, is found to be the dominant impurity element. Furthermore, liquid phase epitaxy of high purity In 0.53 Ga 0.57 As on InP, together with the properties of the Cu-induced acceptor in this material are examined. Free electron concentrations of n=5x10 14 cm -3 and electron Hall-mobilities of μ 77K = 44000 cm 2 /Vs are achieved. The energy level position of the Cu-acceptor is found to be E v +0.025eV. Photoluminescence and Hall-effect measurements, together with JSCM are the main characterization methods used. The band linups of In 0.53 Ga 0.47 As with GaAs and with InP are determined according to the Cu-acceptor energy level position in these materials. Additionally, the hydrostatic pressure dependence of the Cu-acceptor energy level position in In 0.53 Ga 0.47 As is examined. (103 refs.)

  19. ONLINE TECHNOLOGICAL MONITORING OF INSULATION DEFECTS IN ENAMELED WIRES

    Directory of Open Access Journals (Sweden)

    V. M. Zolotaryov

    2017-08-01

    Full Text Available In this paper the authors used non-destructive technological monitoring of defects insulation enameled wire with poliimid polymer. The paper is devoted to the statistical method for processing, comparison and analysis of results of measurements of parameters of insulation of enameled wire because of mathematical model of trend for application in active technological monitoring is developed; the recommendations for parameters of such monitoring are used. It is theoretically justified and the possibility of determination of dependence of the error on the velocity of movement of a wire for want of quantifying of defects in enameled insulation by non-destructive tests by high voltage. The dependence of average value of amount of defects for enameled wire with two-sheeted poliimid insulation in a range of nominal diameter 0.56 mm is experimentally determined. The technological monitoring purpose is to reduce the quantifying defects of enameled insulation.

  20. Ion-irradiation-induced defects in bundles of carbon nanotubes

    International Nuclear Information System (INIS)

    Salonen, E.; Krasheninnikov, A.V.; Nordlund, K.

    2002-01-01

    We study the structure and formation yields of atomic-scale defects produced by low-dose Ar ion irradiation in bundles of single-wall carbon nanotubes. For this, we employ empirical potential molecular dynamics and simulate ion impact events over an energy range of 100-1000 eV. We show that the most common defects produced at all energies are vacancies on nanotube walls, which at low temperatures are metastable but long-lived defects. We further calculate the spatial distribution of the defects, which proved to be highly non-uniform. We also show that ion irradiation gives rise to the formations of inter-tube covalent bonds mediated by carbon recoils and nanotube lattice distortions due to dangling bond saturation. The number of inter-tube links, as well as the overall damage, linearly grows with the energy of incident ions

  1. Tuning thermal conduction via extended defects in graphene

    Science.gov (United States)

    Huang, Huaqing; Xu, Yong; Zou, Xiaolong; Wu, Jian; Duan, Wenhui

    2013-05-01

    Designing materials for desired thermal conduction can be achieved via extended defects. We theoretically demonstrate the concept by investigating thermal transport in graphene nanoribbons (GNRs) with the extended line defects observed by recent experiments. Our nonequilibrium Green's function study excluding phonon-phonon interactions finds that thermal conductance can be tuned over wide ranges (more than 50% at room temperature), by controlling the orientation and the bond configuration of the embedded extended defect. Further transmission analysis reveals that the thermal-conduction tuning is attributed to two fundamentally different mechanisms, via modifying the phonon dispersion and/or tailoring the strength of defect scattering. The finding, applicable to other materials, provides useful guidance for designing materials with desired thermal conduction.

  2. Topological defects from the multiverse

    Science.gov (United States)

    Zhang, Jun; Blanco-Pillado, Jose J.; Garriga, Jaume; Vilenkin, Alexander

    2015-05-01

    Many theories of the early universe predict the existence of a multiverse where bubbles continuously nucleate giving rise to observers in their interior. In this paper, we point out that topological defects of several dimensionalities will also be produced in de Sitter like regions of the multiverse. In particular, defects could be spontaneously nucleated in our parent vacuum. We study the evolution of these defects as they collide with and propagate inside of our bubble. We estimate the present distribution of defects in the observable part of the universe. The expected number of such nearby defects turns out to be quite small, even for the highest nucleation rate. We also study collisions of strings and domain walls with our bubble in our past light cone. We obtain simulated full-sky maps of the loci of such collisions, and find their angular size distribution. Similarly to what happens in the case of bubble collisions, the prospect of detecting any collisions of our bubble with ambient defects is greatly enhanced in the case where the cosmological constant of our parent vacuum is much higher than the vacuum energy density during inflation in our bubble.

  3. Topological defects from the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jun [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Blanco-Pillado, Jose J. [Department of Theoretical Physics, University of the Basque Country UPV/EHU, 48080 Bilbao (Spain); IKERBASQUE, Basque Foundation for Science, 48013, Bilbao (Spain); Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, 08028, Barcelona (Spain); Vilenkin, Alexander [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)

    2015-05-28

    Many theories of the early universe predict the existence of a multiverse where bubbles continuously nucleate giving rise to observers in their interior. In this paper, we point out that topological defects of several dimensionalities will also be produced in de Sitter like regions of the multiverse. In particular, defects could be spontaneously nucleated in our parent vacuum. We study the evolution of these defects as they collide with and propagate inside of our bubble. We estimate the present distribution of defects in the observable part of the universe. The expected number of such nearby defects turns out to be quite small, even for the highest nucleation rate. We also study collisions of strings and domain walls with our bubble in our past light cone. We obtain simulated full-sky maps of the loci of such collisions, and find their angular size distribution. Similarly to what happens in the case of bubble collisions, the prospect of detecting any collisions of our bubble with ambient defects is greatly enhanced in the case where the cosmological constant of our parent vacuum is much higher than the vacuum energy density during inflation in our bubble.

  4. Topological defects from the multiverse

    International Nuclear Information System (INIS)

    Zhang, Jun; Vilenkin, Alexander; Blanco-Pillado, Jose J.; Garriga, Jaume

    2015-01-01

    Many theories of the early universe predict the existence of a multiverse where bubbles continuously nucleate giving rise to observers in their interior. In this paper, we point out that topological defects of several dimensionalities will also be produced in de Sitter like regions of the multiverse. In particular, defects could be spontaneously nucleated in our parent vacuum. We study the evolution of these defects as they collide with and propagate inside of our bubble. We estimate the present distribution of defects in the observable part of the universe. The expected number of such nearby defects turns out to be quite small, even for the highest nucleation rate. We also study collisions of strings and domain walls with our bubble in our past light cone. We obtain simulated full-sky maps of the loci of such collisions, and find their angular size distribution. Similarly to what happens in the case of bubble collisions, the prospect of detecting any collisions of our bubble with ambient defects is greatly enhanced in the case where the cosmological constant of our parent vacuum is much higher than the vacuum energy density during inflation in our bubble

  5. Electrical fingerprint of pipeline defects

    International Nuclear Information System (INIS)

    Mica, Isabella; Polignano, Maria Luisa; Marco, Cinzia De

    2004-01-01

    Pipeline defects are dislocations that connect the source region of the transistor with the drain region. They were widely reported to occur in CMOS, BiCMOS devices and recently in SOI technologies. They can reduce device yield either by affecting the devices functionality or by increasing the current consumption under stand-by conditions. In this work the electrical fingerprint of these dislocations is studied, its purpose is to enable us to identify these defects as the ones responsible for device failure. It is shown that the pipeline defects are responsible for a leakage current from source to drain in the transistors. This leakage has a resistive characteristic and it is lightly modulated by the body bias. It is not sensitive to temperature; vice versa the off-current of a good transistor exhibits the well-known exponential dependence on 1/T. The emission spectrum of these defects was studied and compared with the spectrum of a good transistor. The paper aims to show that the spectrum of a defective transistor is quite peculiar; it shows well defined peaks, whereas the spectrum of a good transistor under saturation conditions is characterized by a broad spectral light emission distribution. Finally the deep-level transient spectroscopy (DLTS) is tried on defective diodes

  6. Automatically high accurate and efficient photomask defects management solution for advanced lithography manufacture

    Science.gov (United States)

    Zhu, Jun; Chen, Lijun; Ma, Lantao; Li, Dejian; Jiang, Wei; Pan, Lihong; Shen, Huiting; Jia, Hongmin; Hsiang, Chingyun; Cheng, Guojie; Ling, Li; Chen, Shijie; Wang, Jun; Liao, Wenkui; Zhang, Gary

    2014-04-01

    Defect review is a time consuming job. Human error makes result inconsistent. The defects located on don't care area would not hurt the yield and no need to review them such as defects on dark area. However, critical area defects can impact yield dramatically and need more attention to review them such as defects on clear area. With decrease in integrated circuit dimensions, mask defects are always thousands detected during inspection even more. Traditional manual or simple classification approaches are unable to meet efficient and accuracy requirement. This paper focuses on automatic defect management and classification solution using image output of Lasertec inspection equipment and Anchor pattern centric image process technology. The number of mask defect found during an inspection is always in the range of thousands or even more. This system can handle large number defects with quick and accurate defect classification result. Our experiment includes Die to Die and Single Die modes. The classification accuracy can reach 87.4% and 93.3%. No critical or printable defects are missing in our test cases. The missing classification defects are 0.25% and 0.24% in Die to Die mode and Single Die mode. This kind of missing rate is encouraging and acceptable to apply on production line. The result can be output and reloaded back to inspection machine to have further review. This step helps users to validate some unsure defects with clear and magnification images when captured images can't provide enough information to make judgment. This system effectively reduces expensive inline defect review time. As a fully inline automated defect management solution, the system could be compatible with current inspection approach and integrated with optical simulation even scoring function and guide wafer level defect inspection.

  7. A study of the electrical properties of defects in silicon

    International Nuclear Information System (INIS)

    Blood, A.M.

    1998-01-01

    This work contains the most comprehensive qualitative and quantitative electron beam induced current (EBIC) study of recombination at contaminated defects in silicon. It is also a rigorous quantitative investigation of the effect of hydrogen on individual transition metal contaminated defects. In addition, the recombination behaviour exhibited by point and extended defects has been investigated using EBIC and deep level transient spectroscopy (DLTS). As a result of these measurements, techniques for the preparation of transition metal contaminated specimens have been refined. Successful hydrogen passivation of copper, nickel and iron contaminated silicon specimens containing oxidation-induced stacking faults has been achieved in two experimental systems. It is found that hydrogen passivates those states that are deepest in the semiconductor band gap in preference to those that are shallow. Furthermore, it has been concluded that during hydrogen passivation treatment, even at low temperatures, unwanted metallic impurities can be introduced. Three types of recombination behaviour have been identified from the defects-studied in this work and they are discussed with relevance to present recombination models. An investigation of the recombination behaviour of defects that lie in the depletion region and in the specimen bulk has concluded that the recombination type observed is independent of the depth of the defect. Evidence for the presence of compound defects showing mixed recombination behaviour type is presented. In conclusion, it is postulated that the transition metal impurities introduce a 'band of states' with a range of energies rather than a single energy state. This proposal is provided as an explanation for the recombination types found in this work and the effect of the hydrogen passivation. This work is placed in context of previous investigations into the behaviour of dislocations in silicon in the presence of transition metals, and the ability of

  8. Entropy-driven metastable defects in silicon

    International Nuclear Information System (INIS)

    Hamilton, B.; Peaker, A.R.; Pantelides, S.T.

    1989-01-01

    The known metastable defects are usually describable by a configuration coordinate diagram in which two energy minima are separated by a barrier. This diagram does not change with temperature and each configuration is stable over some temperature range. Here we report the observation of a novel metastability: A configuration change occurs spontaneously and abruptly at a critical temperature, giving rise to a discontinuous DLTS (deep level transient spectroscopy) spectrum. We propose that this phenomenon is a manifestation of entropy variations in the configurational space. (author) 12 refs., 4 figs

  9. Tunable single photonic defect-mode in cholesteric liquid crystals with laser-induced local modifications of helix

    International Nuclear Information System (INIS)

    Yoshida, Hiroyuki; Lee, Chee Heng; Fujii, Akihiko; Ozaki, Masanori

    2006-01-01

    The authors demonstrate a tunable single photonic defect-mode in a single cholesteric liquid crystal material based on a structural defect introduced by local modification of the helix. An unpolymerized region of cholesteric liquid crystal acting as the defect was left between two polymerized regions via a two-photon excitation laser-lithography process. Upon polymerization, the cholesteric liquid crystal helix elongated and became thermally stable, and a single photonic defect mode was exhibited due to the contrast in the helix pitch at the defect. The defect mode showed tunability upon heating, and a 36 nm redshift was seen over a temperature range of 30 deg. C

  10. Implantation processing of Si: A unified approach to understanding ion-induced defects and their impact

    International Nuclear Information System (INIS)

    Holland, O.W.; Roth, E.G.

    1997-05-01

    A model is presented to account for the effects of ion-induced defects during implantation processing of Si. It will be shown that processing is quite generally affected by the presence of defect excesses rather than the total number of defects. a defect is considered excess if it represents a surplus locally of one defect type over its compliment. Processing spanning a wide range of implantation conditions will be presented to demonstrate that the majority of the total defects played little or no role in the process. This is a direct result of the ease with which the spatially correlated Frenkel pairs recombine either dynamically or during a post-implantation annealing. Based upon this model, a method will be demonstrated for manipulating or engineering the excess defects to modify their effects. In particular high-energy, self-ions are shown to inject vacancies into a boron implanted region resulting in suppression of transient enhanced diffusion of the dopant

  11. Dual approaches for defects condensation

    Energy Technology Data Exchange (ETDEWEB)

    Rougemont, Romulo; Grigorio, Leonardo de Souza; Wotzasek, Clovis [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Guimaraes, Marcelo Santos [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)

    2009-07-01

    Full text. Due to the fact that the QCD running coupling constant becomes larger as we go into the low energy (or large distance) limit of the theory, a perturbative treatment of its infrared (IR) region is impossible. In particular, a formal mathematical demonstration of color confinement and a complete physical understanding of the exact mechanism that confines quarks and gluons are two missing points in our current knowledge of the IR-QCD. It was known that due to the Meissner effect of expulsion of magnetic fields in a electric condensate that usual superconductors should confine magnetic monopoles. That point led to the conjecture that the QCD vacuum could be a condensate of chromomagnetic monopoles, a dual superconductor (DSC). Such a chromomagnetic condensate should be responsible for the dual Meissner effect which is expected to lead to the confinement of color charges immersed in this medium. In dual superconductor models of color confinement, magnetic monopoles appear as topological defects in points of the space where the abelian projection becomes singular. Also, condensation of other kinds of defects such as vortices in superfluids and line-like defects in solids are responsible for a great variety of phase transitions, which once more proves the relevance of the subject. In the present work we review two methods that allow us to approach the condensation of defects: the Kleinert Mechanism (KM) and the Julia-Toulouse Mechanism (JTM). We show that in the limit where the vortex gauge field goes to zero, which we identify as the signature of the condensation of defects in the dual picture, these are two equivalent dual prescriptions for obtaining an effective theory for a phase where defects are condensed, starting from the fundamental theory defined in the normal phase where defects are diluted. (author)

  12. Determination of defect content and defect profile in semiconductor heterostructures

    International Nuclear Information System (INIS)

    Zubiaga, A; Garcia, J A; Plazaola, F; Zuniga-Perez, J; Munoz-Sanjose, V

    2011-01-01

    In this article we present an overview of the technique to obtain the defects depth profile and width of a deposited layer and multilayer based on positron annihilation spectroscopy. In particular we apply the method to ZnO and ZnO/ZnCdO layers deposited on sapphire substrates. After introducing some terminology we first calculate the trend that the W/S parameters of the Doppler broadening measurements must follow, both in a qualitative and quantitative way. From this point we extend the results to calculate the width and defect profiles in deposited layer samples.

  13. Determination of defect content and defect profile in semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zubiaga, A [Laboratory of Physics, HUT, PO Box 1100, 02015 TKK, Espoo (Finland); Garcia, J A; Plazaola, F [Zientzia eta Teknologia Fakultatea, Euskal Herriko Unbertsitatea, P. K. 644, 48080, Bilbao (Spain); Zuniga-Perez, J; Munoz-Sanjose, V, E-mail: fernando.plazaola@ehu.es [Universitat de Valencia, Departamento de Fisica Aplicada i Electromagnetisme, Dr. Moliner 50, 46100 Burjassot, Valencia (Spain)

    2011-01-10

    In this article we present an overview of the technique to obtain the defects depth profile and width of a deposited layer and multilayer based on positron annihilation spectroscopy. In particular we apply the method to ZnO and ZnO/ZnCdO layers deposited on sapphire substrates. After introducing some terminology we first calculate the trend that the W/S parameters of the Doppler broadening measurements must follow, both in a qualitative and quantitative way. From this point we extend the results to calculate the width and defect profiles in deposited layer samples.

  14. Defects in conformal field theory

    International Nuclear Information System (INIS)

    Billò, Marco; Gonçalves, Vasco; Lauria, Edoardo; Meineri, Marco

    2016-01-01

    We discuss consequences of the breaking of conformal symmetry by a flat or spherical extended operator. We adapt the embedding formalism to the study of correlation functions of symmetric traceless tensors in the presence of the defect. Two-point functions of a bulk and a defect primary are fixed by conformal invariance up to a set of OPE coefficients, and we identify the allowed tensor structures. A correlator of two bulk primaries depends on two cross-ratios, and we study its conformal block decomposition in the case of external scalars. The Casimir equation in the defect channel reduces to a hypergeometric equation, while the bulk channel blocks are recursively determined in the light-cone limit. In the special case of a defect of codimension two, we map the Casimir equation in the bulk channel to the one of a four-point function without defect. Finally, we analyze the contact terms of the stress-tensor with the extended operator, and we deduce constraints on the CFT data. In two dimensions, we relate the displacement operator, which appears among the contact terms, to the reflection coefficient of a conformal interface, and we find unitarity bounds for the latter.

  15. Defects in conformal field theory

    Energy Technology Data Exchange (ETDEWEB)

    Billò, Marco [Dipartimento di Fisica, Università di Torino, and Istituto Nazionale di Fisica Nucleare - sezione di Torino,Via P. Giuria 1 I-10125 Torino (Italy); Gonçalves, Vasco [Centro de Física do Porto,Departamento de Física e Astronomia Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); ICTP South American Institute for Fundamental Research Instituto de Física Teórica,UNESP - University Estadual Paulista,Rua Dr. Bento T. Ferraz 271, 01140-070, São Paulo, SP (Brazil); Lauria, Edoardo [Institute for Theoretical Physics, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Meineri, Marco [Perimeter Institute for Theoretical Physics,Waterloo, Ontario, N2L 2Y5 (Canada); Scuola Normale Superiore, and Istituto Nazionale di Fisica Nucleare - sezione di Pisa,Piazza dei Cavalieri 7 I-56126 Pisa (Italy)

    2016-04-15

    We discuss consequences of the breaking of conformal symmetry by a flat or spherical extended operator. We adapt the embedding formalism to the study of correlation functions of symmetric traceless tensors in the presence of the defect. Two-point functions of a bulk and a defect primary are fixed by conformal invariance up to a set of OPE coefficients, and we identify the allowed tensor structures. A correlator of two bulk primaries depends on two cross-ratios, and we study its conformal block decomposition in the case of external scalars. The Casimir equation in the defect channel reduces to a hypergeometric equation, while the bulk channel blocks are recursively determined in the light-cone limit. In the special case of a defect of codimension two, we map the Casimir equation in the bulk channel to the one of a four-point function without defect. Finally, we analyze the contact terms of the stress-tensor with the extended operator, and we deduce constraints on the CFT data. In two dimensions, we relate the displacement operator, which appears among the contact terms, to the reflection coefficient of a conformal interface, and we find unitarity bounds for the latter.

  16. Characterization of defects in Si and SiO2-Si using positrons

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Lynn, K.G.

    1993-01-01

    Positron annihilation spectroscopy of overlayers, interfaces, and buried regions of semiconductors has seen a rapid growth in recent years. The characteristics of the annihilation gamma rays depend strongly on the local environment of the annihilation sites, and can be used to probe defect concentrations in a range inaccessible to conventional defect probes. Some of the recent success of the technique in examining low concentrations of point defects in technologically important Si-based structures is discussed

  17. Low-temperature annealing of radiation defects in electron-irradiated gallium phosphide

    International Nuclear Information System (INIS)

    Kolb, A.A.; Megela, I.G.; Buturlakin, A.P.; Goyer, D.B.

    1990-01-01

    The isochronal annealing of radiation defects in high-energy electron irradiated n-GaP monocrystals within the 77 to 300 K range has been investigated by optical and electrical techniques. The changes in conductance and charge carrier mobility as functions of annealing temperature as well as the variation of optical absorption spectra of GaP under irradiation and annealing provide evidence that most of radiation defects are likely secondary complexes of defects

  18. Point defects and transport properties in carbides

    International Nuclear Information System (INIS)

    Matzke, Hj.

    1984-01-01

    Carbides of transition metals and of actinides are interesting and technologically important. The transition-metal carbides (or carbonitrides) are extensively being used as hard materials and some of them are of great interest because of the high transition temperature for superconductivity, e.g. 17 K for Nb(C,N). Actinide carbides and carbonitrides, (U,Pu)C and (U,Pu)(C,N) are being considered as promising advanced fuels for liquid metal cooled fast breeder nuclear reactors. Basic interest exists in all these materials because of their high melting points (e.g. 4250 K for TaC) and the unusually broad range of homogeneity of nonstoichiometric compositions (e.g. from UCsub(0.9) to UCsub(1.9) at 2500 K). Interaction of point defects to clusters and short-range ordering have recently been studied with elastic neutron diffraction and diffuse scattering techniques, and calculations of energies of formation and interaction of point defects became available for selected carbides. Diffusion measurements also exist for a number of carbides, in particular for the actinide carbides. The existing knowledge is discussed and summarized with emphasis on informative examples of particular technological relevance. (Auth.)

  19. Crystal defect studies using x-ray diffuse scattering

    International Nuclear Information System (INIS)

    Larson, B.C.

    1980-01-01

    Microscopic lattice defects such as point (single atom) defects, dislocation loops, and solute precipitates are characterized by local electronic density changes at the defect sites and by distortions of the lattice structure surrounding the defects. The effect of these interruptions of the crystal lattice on the scattering of x-rays is considered in this paper, and examples are presented of the use of the diffuse scattering to study the defects. X-ray studies of self-interstitials in electron irradiated aluminum and copper are discussed in terms of the identification of the interstitial configuration. Methods for detecting the onset of point defect aggregation into dislocation loops are considered and new techniques for the determination of separate size distributions for vacancy loops and interstitial loops are presented. Direct comparisons of dislocation loop measurements by x-rays with existing electron microscopy studies of dislocation loops indicate agreement for larger size loops, but x-ray measurements report higher concentrations in the smaller loop range. Methods for distinguishing between loops and three-dimensional precipitates are discussed and possibilities for detailed studies considered. A comparison of dislocation loop size distributions obtained from integral diffuse scattering measurements with those from TEM show a discrepancy in the smaller sizes similar to that described above

  20. Crystal defect studies using x-ray diffuse scattering

    Energy Technology Data Exchange (ETDEWEB)

    Larson, B.C.

    1980-01-01

    Microscopic lattice defects such as point (single atom) defects, dislocation loops, and solute precipitates are characterized by local electronic density changes at the defect sites and by distortions of the lattice structure surrounding the defects. The effect of these interruptions of the crystal lattice on the scattering of x-rays is considered in this paper, and examples are presented of the use of the diffuse scattering to study the defects. X-ray studies of self-interstitials in electron irradiated aluminum and copper are discussed in terms of the identification of the interstitial configuration. Methods for detecting the onset of point defect aggregation into dislocation loops are considered and new techniques for the determination of separate size distributions for vacancy loops and interstitial loops are presented. Direct comparisons of dislocation loop measurements by x-rays with existing electron microscopy studies of dislocation loops indicate agreement for larger size loops, but x-ray measurements report higher concentrations in the smaller loop range. Methods for distinguishing between loops and three-dimensional precipitates are discussed and possibilities for detailed studies considered. A comparison of dislocation loop size distributions obtained from integral diffuse scattering measurements with those from TEM show a discrepancy in the smaller sizes similar to that described above.

  1. Defect phase diagram for doping of Ga2O3

    Science.gov (United States)

    Lany, Stephan

    2018-04-01

    For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2) conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  2. Defect phase diagram for doping of Ga2O3

    Directory of Open Access Journals (Sweden)

    Stephan Lany

    2018-04-01

    Full Text Available For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn, a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T, O partial pressures (pO2, and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2 conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  3. Detection of paint polishing defects

    Science.gov (United States)

    Rebeggiani, S.; Wagner, M.; Mazal, J.; Rosén, B.-G.; Dahlén, M.

    2018-06-01

    Surface finish plays a major role on perceived product quality, and is the first thing a potential buyer sees. Today end-of-line repairs of the body of cars and trucks are inevitably to secure required surface quality. Defects that occur in the paint shop, like dust particles, are eliminated by manual sanding/polishing which lead to other types of defects when the last polishing step is not performed correctly or not fully completed. One of those defects is known as ‘polishing roses’ or holograms, which are incredibly hard to detect in artificial light but are clearly visible in sunlight. This paper will present the first tests with a measurement set-up newly developed to measure and analyse polishing roses. The results showed good correlations to human visual evaluations where repaired panels were estimated based on the defects’ intensity, severity and viewing angle.

  4. Defect CFTs and holographic multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Fiol, Bartomeu, E-mail: bfiol@ub.edu [Departament de Física Fonamental i Institut de Ciències del Cosmos, Universitat de Barcelona, Martí i Franquès 1, 08193 Barcelona (Spain)

    2010-07-01

    We investigate some aspects of a recent proposal for a holographic description of the multiverse. Specifically, we focus on the implications on the suggested duality of the fluctuations of a bubble separating two universes with different cosmological constants. We do so by considering a similar problem in a 2+1 CFT with a codimension one defect, obtained by an M5-brane probe embedding in AdS{sub 4} × S{sup 7}, and studying its spectrum of fluctuations. Our results suggest that the kind of behavior required by the spectrum of bubble fluctuations is not likely to take place in defect CFTs with an AdS dual, although it might be possible if the defect supports a non-unitary theory.

  5. Defect CFTs and holographic multiverse

    International Nuclear Information System (INIS)

    Fiol, Bartomeu

    2010-01-01

    We investigate some aspects of a recent proposal for a holographic description of the multiverse. Specifically, we focus on the implications on the suggested duality of the fluctuations of a bubble separating two universes with different cosmological constants. We do so by considering a similar problem in a 2+1 CFT with a codimension one defect, obtained by an M5-brane probe embedding in AdS 4 × S 7 , and studying its spectrum of fluctuations. Our results suggest that the kind of behavior required by the spectrum of bubble fluctuations is not likely to take place in defect CFTs with an AdS dual, although it might be possible if the defect supports a non-unitary theory

  6. Irradiated strut allografts for reconstructing tumour defects: how effective?

    International Nuclear Information System (INIS)

    Astrid Lobo Gajiwala; Manish Agarwal; Ajay Puri; Cynthia D Lima

    2008-01-01

    Full text: Allografts are biological options for reconstructing large bone defects. We report our experience with 87 irradiated (25 kGy of gamma radiation) strut allografts used in various defects following tumour surgery. Reconstruction in 35 full segment defects involved 22 full segment allografts used alone, 4 allograft prosthetic composites (APC) and 9 allografts combined with a vascularized fibula. Twelve partial segment defects were reconstructed with allograft struts (including 2 APC). Full segment allograft struts (mainly fibulae) were used in 40 contained post-curettage defects. The cases were studied for time to incorporation and complications. The follow-up ranged from 12 to 72 months. Of the 26 full segment defects where allograft alone or APC was used, 2 were lost to follow-up, 5 died before incorporation and 3 grafts were removed (2 infection and 1 local recurrence). Six united primarily at 2-4 years. Seven patients with non union were autografted at both junctions resulting in 6 unions. One patient had early plate breakage and refused further treatment. One allograft fractured after union after autografting. Two of 4 APC also united. In contrast, the 9 allograft-vascularized fibula combinations showed unambiguous incorporation between 5-9 months with only one junction requiring bone grafting. Of the 12 partial segment struts, barring one removed for infection, 11 have completely incorporated. Thirty one out of 40 struts placed within contained post curettage defects have incorporated (2 removed for infection and seven lost to follow-up). There were total 6 infections (7%) 4 of which occurred 1-2 years after surgery. Irradiated full segment struts alone incorporate poorly and are best used combined with a live fibula. Irradiated full and partial segment allografts used inside contained defects give consistently good results. Frozen grafts seem to incorporate faster and better than lyophilised grafts. (Author)

  7. Displacement cascades and defects annealing in tungsten, Part I: Defect database from molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Setyawan, Wahyu [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nandipati, Giridhar [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Roche, Kenneth J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of Washington, Seattle, WA (United States); Heinisch, Howard L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wirth, Brian D. [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab., Oak Ridge, TN (United States); Kurtz, Richard J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-07-01

    Molecular dynamics simulations have been used to generate a comprehensive database of surviving defects due to displacement cascades in bulk tungsten. Twenty-one data points of primary knock-on atom (PKA) energies ranging from 100 eV (sub-threshold energy) to 100 keV (~780×Ed, where Ed = 128 eV is the average displacement threshold energy) have been completed at 300 K, 1025 K and 2050 K. Within this range of PKA energies, two regimes of power-law energy-dependence of the defect production are observed. A distinct power-law exponent characterizes the number of Frenkel pairs produced within each regime. The two regimes intersect at a transition energy which occurs at approximately 250×Ed. The transition energy also marks the onset of the formation of large self-interstitial atom (SIA) clusters (size 14 or more). The observed defect clustering behavior is asymmetric, with SIA clustering increasing with temperature, while the vacancy clustering decreases. This asymmetry increases with temperature such that at 2050 K (~0.5Tm) practically no large vacancy clusters are formed, meanwhile large SIA clusters appear in all simulations. The implication of such asymmetry on the long-term defect survival and damage accumulation is discussed. In addition, <100> {110} SIA loops are observed to form directly in the highest energy cascades, while vacancy <100> loops are observed to form at the lowest temperature and highest PKA energies, although the appearance of both the vacancy and SIA loops with Burgers vector of <100> type is relatively rare.

  8. Rail inspection of RCF defects

    Directory of Open Access Journals (Sweden)

    Z. Popović

    2013-10-01

    Full Text Available Rail defects due to rolling contact fatigue (RCF threaten the traffic safety around the world. That hazard is more distinct on railways without adequate maintenance strategy. Realization of interoperability of European railway network demands from every infrastructure manager to have a maintenance plan for the infrastructure subsystem. Besides that, this plan includes rail inspection and strategy against RCF defects. This paper emphasizes the importance of rail inspection and early detection of RCF because the most of RCF crack should be removed in rail grinding campaigns (preventive, cyclical and corrective activities during the whole rail service life.

  9. Defect characterization with positron annihilation

    International Nuclear Information System (INIS)

    Granatelli, L.; Lynn, K.G.

    1980-01-01

    Positron annihilation in metal crystals is reviewed. A brief introduction to the positron annihilation technique is presented first. Then the ability of the positron technique to perform microstructural characterization of four types of lattice defects (vacancies, voids, dislocations, grain boundaries) is discussed. It is frequently not possible to obtain samples that contain only one type of defect in nonnegligible concentrations. Such situations exist for some alloys and for fatigued metal samples. Finally, the current limitations and some future prospects of the technique are presented. 79 references, 14 figures, 1 table

  10. Loop Growth and Point-Defect Profiles during HVEM Irradiation

    DEFF Research Database (Denmark)

    Leffers, Torben; Singh, Bachu Narain

    1979-01-01

    The point-defect profile in a thin foil is included in the model for the growth of dislocation loops during HVEM irradiation suggested by Kiritani, Yoshida, Takata, and Maehara, and the possible effect of divacancies is discussed. It is found that there is a fairly wide transition range between...

  11. Structure defects in malachite revealed by positron annihilation

    International Nuclear Information System (INIS)

    Geffroy, B.; Diallo, I.; Paulin, R.

    1984-01-01

    Positron lifetime is measured between 77 and 400 K in two malachite samples with different mineralogical structures. The complex spectrum found in zoned malachite reveals a microporosity which remains stable in this range of temperature. Besides, above 200 K, equilibrium defects appear. Their formation energy is estimated to be Esub(f) = 0.27 +- 0.02 eV [fr

  12. Structure defects in malachite revealed by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Geffroy, B; Diallo, I; Paulin, R [Institut National des Sciences et Techniques Nucleaires, CEN/Saclay, 91 - Gif-sur-Yvette (France)

    1984-01-01

    Positron lifetime is measured between 77 and 400 K in two malachite samples with different mineralogical structures. The complex spectrum found in zoned malachite reveals a microporosity which remains stable in this range of temperature. Besides, above 200 K, equilibrium defects appear. Their formation energy is estimated to be Esub(f) = 0.27 +- 0.02 eV.

  13. Influence of structural defects on excitonic photoluminescence of pentacene

    International Nuclear Information System (INIS)

    Piryatins'kij, Yu.P.; Kurik, M.V.

    2011-01-01

    The exciton reflection, absorption, and photoluminescence spectra for single crystals and polycrystalline films have been studied in the temperature range of 4.2-296 K. A significant influence of structural defects arising during phase transitions on the exciton spectra of pentacene has been detected. The mechanisms of photoluminescence in single crystals and crystalline films of pentacene have been considered.

  14. What Are Congenital Heart Defects?

    Science.gov (United States)

    ... a baby with a congenital heart defect. Family history and genetics Congenital heart disease is not usually passed along ... you or your child to a specialist in genetic testing. Cardiac MRI to diagnose a ... Factors to review family history, smoking, and medicines that increase your risk of ...

  15. Nuclear Pasta: Topology and Defects

    Science.gov (United States)

    da Silva Schneider, Andre; Horowitz, Charles; Berry, Don; Caplan, Matt; Briggs, Christian

    2015-04-01

    A layer of complex non-uniform phases of matter known as nuclear pasta is expected to exist at the base of the crust of neutron stars. Using large scale molecular dynamics we study the topology of some pasta shapes, the formation of defects and how these may affect properties of neutron star crusts.

  16. Defect branes as Alice strings

    International Nuclear Information System (INIS)

    Okada, Takashi; Sakatani, Yuho

    2015-01-01

    There exist various defect-brane backgrounds in supergravity theories which arise as the low energy limit of string theories. These backgrounds typically have non-trivial monodromies, and if we move a charged probe around the center of a defect, its charge will be changed by the action of the monodromy. During the process, the charge conservation law seems to be violated. In this paper, to resolve this puzzle, we examine a dynamics of the charge changing process and show that the missing charge of the probe is transferred to the background. We then explicitly construct the resultant background after the charge transfer process by utilizing dualities. This background has the same monodromy as the original defect brane, but has an additional charge which does not have any localized source. In the literature, such a charge without localized source is known to appear in the presence of Alice strings. We argue that defect branes can in fact be regarded as a realization of Alice strings in string theory and examine the charge transfer process from that perspective.

  17. Defect branes as Alice strings

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Takashi [Theoretical Biology Laboratory, RIKEN,Wako 351-0198 (Japan); Sakatani, Yuho [Department of Physics and Astronomy,Seoul National University, Seoul 151-747 (Korea, Republic of)

    2015-03-25

    There exist various defect-brane backgrounds in supergravity theories which arise as the low energy limit of string theories. These backgrounds typically have non-trivial monodromies, and if we move a charged probe around the center of a defect, its charge will be changed by the action of the monodromy. During the process, the charge conservation law seems to be violated. In this paper, to resolve this puzzle, we examine a dynamics of the charge changing process and show that the missing charge of the probe is transferred to the background. We then explicitly construct the resultant background after the charge transfer process by utilizing dualities. This background has the same monodromy as the original defect brane, but has an additional charge which does not have any localized source. In the literature, such a charge without localized source is known to appear in the presence of Alice strings. We argue that defect branes can in fact be regarded as a realization of Alice strings in string theory and examine the charge transfer process from that perspective.

  18. Ocular defects in cerebral palsy

    Directory of Open Access Journals (Sweden)

    Katoch Sabita

    2007-01-01

    Full Text Available There is a high prevalence of ocular defects in children with developmental disabilities. This study evaluated visual disability in a group of 200 cerebral palsy (CP patients and found that 68% of the children had significant visual morbidity. These findings emphasize the need for an early ocular examination in patients with CP.

  19. Characterization of point defects in monolayer arsenene

    Science.gov (United States)

    Liang, Xiongyi; Ng, Siu-Pang; Ding, Ning; Wu, Chi-Man Lawrence

    2018-06-01

    Topological defects that are inevitably found in 2D materials can dramatically affect their properties. Using density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) method, the structural, thermodynamic, electronic and magnetic properties of six types of typical point defects in arsenene, i.e. the Stone-Wales defect, single and double vacancies and adatoms, were systemically studied. It was found that these defects were all more easily generated in arsenene with lower formation energies than those with graphene and silicene. Stone-Wales defects can be transformed from pristine arsenene by overcoming a barrier of 2.19 eV and single vacancy defects tend to coalesce into double vacancy defects by diffusion. However, a type of adatom defect does not exhibit kinetic stability at room temperature. In addition, SV defects and another type of adatom defect can remarkably affect the electronic and magnetic properties of arsenene, e.g. they can introduce localized states near the Fermi level, as well as a strongly local magnetic moment due to dangling bond and unpaired electron. Furthermore, the simulated scanning tunneling microscopy (STM) and Raman spectroscopy were computed and the types of point defects can be fully characterized by correlating the STM images and Raman spectra to the defective atomistic structures. The results provide significant insights to the effect of defects in arsenene for potential applications, as well as identifications of two helpful tools (STM and Raman spectroscopy) to distinguish the type of defects in arsenene for future experiments.

  20. Fatigue Strength of Titanium Risers - Defect Sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Babalola, Olusegun Tunde

    2001-07-01

    This study is centred on assessment of the fatigue strength of titanium fusion welds for deep-water riser's applications. Deep-water risers are subjected to significant fatigue loading. Relevant fatigue data for titanium fusion welds are very scarce. Hence there is a need for fatigue data and life prediction models for such weldments. The study has covered three topics: Fatigue testing, Fractography and defect assessment, and Fracture Mechanics modelling of fatigue crack growth. Two series of welded grade of titanium consisting of 14 specimens in each series were fatigue tested under constant amplitude loading. Prior to fatigue testing, strain gauge measurements of some specimens was conducted to enable the definition of stress range in the fatigue assessment procedure. The results were compared with finite solid element analysis and related to fatigue stresses in a riser pipe wall. Distribution and geometry of internal and surface defects both in the as-welded and in the post-weld machined conditions were assessed using fractography. This served as a tool to determine the fatigue initiation point in the welds. Fracture mechanics was applied to model fatigue strength of titanium welds with initiation from weld defects. Two different stress intensity factor formulations for embedded eccentrically placed cracks were used for analysis of elliptical cracks with the major axis parallel and close to one of the free surfaces. The methods were combined to give a satisfactory model for crack growth analysis. The model analyses crack growth of elliptical and semi-elliptical cracks in two directions, with updating of the crack geometry. Fatigue strength assessment was conducted using two crack growth models, the Paris-Erdogan relation with no threshold and the Donahue et al. relation with an implied threshold. The model was validated against experimental data, with a discussion on the choice of crack growth model. (author)

  1. Tonopah Test Range - Index

    Science.gov (United States)

    Capabilities Test Operations Center Test Director Range Control Track Control Communications Tracking Radars Photos Header Facebook Twitter YouTube Flickr RSS Tonopah Test Range Top TTR_TOC Tonopah is the testing range of choice for all national security missions. Tonopah Test Range (TTR) provides research and

  2. Prediction of high-temperature point defect formation in TiO2 from combined ab initio and thermodynamic calculations

    International Nuclear Information System (INIS)

    He, J.; Behera, R.K.; Finnis, M.W.; Li, X.; Dickey, E.C.; Phillpot, S.R.; Sinnott, S.B.

    2007-01-01

    A computational approach that integrates ab initio electronic structure and thermodynamic calculations is used to determine point defect stability in rutile TiO 2 over a range of temperatures, oxygen partial pressures and stoichiometries. Both donors (titanium interstitials and oxygen vacancies) and acceptors (titanium vacancies) are predicted to have shallow defect transition levels in the electronic-structure calculations. The resulting defect formation energies for all possible charge states are then used in thermodynamic calculations to predict the influence of temperature and oxygen partial pressure on the relative stabilities of the point defects. Their ordering is found to be the same as temperature increases and oxygen partial pressure decreases: titanium vacancy → oxygen vacancy → titanium interstitial. The charges on these defects, however, are quite sensitive to the Fermi level. Finally, the combined formation energies of point defect complexes, including Schottky, Frenkel and anti-Frenkel defects, are predicted to limit the further formation of point defects

  3. 2012 Gordon Research Conference on Defects in Semiconductors - Formal Schedule and Speaker/Poster Program

    Energy Technology Data Exchange (ETDEWEB)

    Glaser, Evan [Naval Research Lab. (NRL), Washington, DC (United States)

    2012-08-17

    The meeting shall strive to develop and further the fundamental understanding of defects and their roles in the structural, electronic, optical, and magnetic properties of bulk, thin film, and nanoscale semiconductors and device structures. Point and extended defects will be addressed in a broad range of electronic materials of particular current interest, including wide bandgap semiconductors, metal-oxides, carbon-based semiconductors (e.g., diamond, graphene, etc.), organic semiconductors, photovoltaic/solar cell materials, and others of similar interest. This interest includes novel defect detection/imaging techniques and advanced defect computational methods.

  4. Fibrous metaphyseal defect (fibrous cortical defect, non-ossifying fibroma)

    International Nuclear Information System (INIS)

    Freyschmidt, J.; Saure, D.; Dammenhain, S.

    1981-01-01

    Fibrous cortical defect and nonossifying fibromas can be classified together as fibrous metaphyseal defects (FMD) since they have the same pahtological substrate, with a tendency to the same localisation around the knee, and occuring at the same age. They have a tendency to spontaneous healing, are clinically silent and are usually discovered accidentally during radiological examination. A radiological survey fo 5.674 metaphyseal regions in the upper and lower extremities of 2.065 unselected patients aged one to 20 years revealed an incidence of 1.8%; exlcusive examination of the distal femur showed an incidence of 2.7%. 96% of all lesions were in the lower extremities and only 4% in the upper. The marked discrepancy in the incidence rate between American and German publications is discussed. (orig.) [de

  5. Stone-Wales defects can cause a metal-semiconductor transition in carbon nanotubes depending on their orientation

    International Nuclear Information System (INIS)

    Partovi-Azar, P; Namiranian, A

    2012-01-01

    It has been shown that the two different orientations of Stone-Wales (SW) defects, i.e. longitudinal and circumferential SW defects, on carbon nanotubes (CNTs) result in two different electronic structures. Based on density functional theory we have shown that the longitudinal SW defects do not open a bandgap near the Fermi energy, while a relatively small bandgap emerges in tubes with circumferential defects. We argue that the bandgap opening in the presence of circumferential SW defects is a consequence of long-range symmetry breaking which can spread all the way along the tube. Specifically, the distribution of contracted and stretched bond lengths due to the presence of defects, and hopping energies for low-energy electrons, i.e. the 2p z electrons, show two different patterns for the two types of defects. Interplay between the geometric features and the electronic properties of the tubes have also been studied for different defect concentrations. Considering π-orbital charge density, it has also been shown that the deviations of bond lengths from their relaxed length result in different doping for two defect orientations around the defects - electron-rich for a circumferential defect and hole-rich for a longitudinal one. We have also shown that, in the tubes having both types of defects, circumferential defects would dominate and impose their electronic properties. (paper)

  6. Predicting internal red oak (Quercus rubra) log defect features using surface defect defect measurements

    Science.gov (United States)

    R. Edward. Thomas

    2013-01-01

    Determining the defects located within a log is crucial to understanding the tree/log resource for efficient processing. However, existing means of doing this non-destructively requires the use of expensive x-ray/CT (computerized tomography), MRI (magnetic resonance imaging), or microwave technology. These methods do not lend themselves to fast, efficient, and cost-...

  7. [Agnosia for streets and defective root finding].

    Science.gov (United States)

    Takahashi, Nobuyoshi

    2011-08-01

    Topographical disorientation is identified as a condition in which patients are unable to find their way in familiar surroundings, such as their home neighborhood or the admitting hospital after the onset of illness. I proposed to classify topographical disorientation into two categories: agnosia for streets (landmark agnosia) and defective root finding (heading disorientation). Patients with agnosia for streets are unable to identify familiar buildings and landscapes. They can, however, morphologically perceive them and remember their way around familiar areas. The lesions are located in the right posterior part of the parahippocampus gyrus, anterior half of the lingual gyrus and adjacent fusiform gyrus. Clinical findings and functional imaging studies suggest that these regions play a crucial role in the interaction between the visual information of streets and memories of them, which are thought to be retained in the right anterior part of the temporal lobe. In particular, the posterior part of the parahippocampus gyrus is critical for the acquisition of novel information. On the other hand, patients with defective root finding can identify familiar streets, but cannot remember their own location or positional relation between two points within a comparatively wide range not surveyable at one time. The lesions are located in the right retrosplenial cortex (Areas 29, 30), posterior cingulate cortex (Areas 23, 31) and precuneus. Clinical findings and functional imaging studies suggest that these regions are involved in the orientation function for navigating in wide spaces. In particular, the retrosplenial cortex is critical for encoding novel information.

  8. Agnosia for streets and defective root finding

    International Nuclear Information System (INIS)

    Takahashi, Nobuyoshi

    2011-01-01

    Topographical disorientation is identified as a condition in which patients are unable to find their way in familiar surroundings, such as their home neighborhood or the admitting hospital after the onset of illness. I proposed to classify topographical disorientation into two categories: agnosia for streets (landmark agnosia) and defective root finding (heading disorientation). Patients with agnosia for streets are unable to identify familiar buildings and landscapes. They can, however, morphologically perceive them and remember their way around familiar areas. The lesions are located in the right posterior part of the parahippocampus gyrus, anterior half of the lingual gyrus and adjacent fusiform gyrus. Clinical findings and functional imaging studies suggest that these regions play a crucial role in the interaction between the visual information of streets and memories of them, which are thought to be retained in the right anterior part of the temporal lobe. In particular, the posterior part of the parahippocampus gyrus is critical for the acquisition of novel information. On the other hand, patients with defective root finding can identify familiar streets, but cannot remember their own location or positional relation between two points within a comparatively wide range not surveyable at one time. The lesions are located in the right retrosplenial cortex (Areas 29, 30), posterior cingulate cortex (Areas 23, 31) and precuneus. Clinical findings and functional imaging studies suggest that these regions are involved in the orientation function for navigating in wide spaces. In particular, the retrosplenial cortex is critical for encoding novel information. (author)

  9. Determination of defects in depth (stereoradiography)

    International Nuclear Information System (INIS)

    Carvalho, Gilberto

    2000-01-01

    After the identification of an internal defect, by means of the single radiographic process, it can be necessary to determine it's position to evaluate the importance of the service and to specify which side of the weld the piece should be cut in order to reduce the amount of material to be removed and, in a lot, the cost of repair. The single radiography image does not have perspective and can not show the tri-dimensional vision, and so, do not clearly indicate the relative positions of the various parts of the object, in the direction of the vision. Stereoradiography was idealized to overcome that limitation of the standard radiography and it requests the accomplishment of two exposures, separated by the normal interpupillary distance. In the present work, we use this technique in a simulated pore defect, commonly found in the welding processes, and we present the efficiency of the technique. The material employed was SAE 1020 steel, in several thickness pieces, covering the range of thickness that the use Ir-192 source is recommended. (author)

  10. N+ ion-implantation-induced defects in ZnO studied with a slow positron beam

    International Nuclear Information System (INIS)

    Chen, Z Q; Sekiguchi, T; Yuan, X L; Maekawa, M; Kawasuso, A

    2004-01-01

    Undoped ZnO single crystals were implanted with multiple-energy N + ions ranging from 50 to 380 keV with doses from 10 12 to 10 14 cm -2 . Positron annihilation measurements show that vacancy defects are introduced in the implanted layers. The concentration of the vacancy defects increases with increasing ion dose. The annealing behaviour of the defects can be divided into four stages, which correspond to the formation and recovery of large vacancy clusters and the formation and disappearance of vacancy-impurity complexes, respectively. All the implantation-induced defects are removed by annealing at 1200 deg. C. Cathodoluminescence measurements show that the ion-implantation-induced defects act as nonradiative recombination centres to suppress the ultraviolet (UV) emission. After annealing, these defects disappear gradually and the UV emission reappears, which coincides with positron annihilation measurements. Hall measurements reveal that after N + implantation, the ZnO layer still shows n-type conductivity

  11. Defect disorder of undoped and Sr-doped LaCoO3-δ

    International Nuclear Information System (INIS)

    Nowotny, J.; Rekas, M.

    2002-01-01

    The paper considers defect disorder models of undoped lanthanum cobaltate LaCoO 3-δ , and Sr-doped LaCoO 3-δ , La 1-x Sr x Co) 3-δ (LSC), involving both random defect model and cluster defect model. The models are derived using the nonstoichiometry data reported in the literature. Doubly ionized oxygen vacancies are assumed to be the predominate ionic defects within the entire range of compositions. The effect of Sr content on defect disorder of LSC is discussed in terms of both defect models. Impact of segregation on surface composition of ionic solids in general and LSC materials in particular is briefly outlined. The effect of the interface layer on functional properties of LSC as electrode material is briefly discussed. (author)

  12. Positron lifetime calculation for defects and defect clusters in graphite

    International Nuclear Information System (INIS)

    Onitsuka, T.; Ohkubo, H.; Takenaka, M.; Tsukuda, N.; Kuramoto, E.

    2000-01-01

    Calculations of positron lifetime have been made for vacancy type defects in graphite and compared with experimental results. Defect structures were obtained in a model graphite lattice after including relaxation of whole lattice as determined by the molecular dynamics method, where the interatomic potential given by Pablo Andribet, Dominguez-Vazguez, Mari Carmen Perez-Martin, Alonso, Jimenez-Rodriguez [Nucl. Instrum. and Meth. 115 (1996) 501] was used. For the defect structures obtained via lattice relaxation positron lifetime was calculated under the so-called atomic superposition method. Positron lifetimes 204 and 222 ps were obtained for the graphite matrix and a single vacancy, respectively, which can be compared with the experimental results 208 and 233 ps. For planar vacancy clusters, e.g., vacancy loops, lifetime calculation was also made and indicated that lifetime increases with the number of vacancies in a cluster. This is consistent with the experimental result in the region of higher annealing temperature (above 1200 deg. C), where the increase of positron lifetime is seen, probably corresponding to the clustering of mobile vacancies

  13. Radiation defects in electron-irradiated InP crystals

    International Nuclear Information System (INIS)

    Brailovskii, E.Yu.; Karapetyan, F.K.; Megela, I.G.; Tartachnik, V.P.

    1982-01-01

    The results are presented of formation and annealing of defects in InP crystals at 1 to 50 MeV electron irradiation. The recovery of electrical properties in the range of 77 to 970 K during annealing processes is studied. Five low temperature annealing states in n-InP and the reverse annealing in p-InP are observed at 77 to 300 K. Four annealing stages at temperatures higher than 300 K are present. When the electron energy is increased more complicated thermostable defects are formed, and at 50 MeV electron energy besides of the point defect clusters are formed, which anneal at temperatures of 800 to 970 K. It is shown that the peculiarities of the Hall mobility at irradiation and annealing are caused by the scattering centres E/sub c/ - 0.2 eV. The 'limiting' position of the Fermi level in electron irradiated InP crystals is discussed. (author)

  14. Management of the Sequelae of Severe Congenital Abdominal Wall Defects

    Directory of Open Access Journals (Sweden)

    Sara Fuentes

    2016-05-01

    Full Text Available BackgroundThe survival rate of newborns with severe congenital abdominal wall defects has increased. After successfully addressing life-threatening complications, it is necessary to focus on the cosmetic and functional outcomes of the abdominal wall.MethodsWe performed a chart review of five cases treated in our institution.ResultsFive patients, ranging from seven to 18 years of age, underwent the following surgical approaches: simple approximation of the rectus abdominis fascia, the rectus abdominis sheath turnover flap, the placement of submuscular tissue expanders, mesh repair, or a combination of these techniques depending on the characteristics of each individual case.ConclusionsPatients with severe congenital abdominal wall defects require individualized surgical treatment to address both the aesthetic and functional issues related to the sequelae of their defects.

  15. Charged Semiconductor Defects Structure, Thermodynamics and Diffusion

    CERN Document Server

    Seebauer, Edmund G

    2009-01-01

    The technologically useful properties of a solid often depend upon the types and concentrations of the defects it contains. Not surprisingly, defects in semiconductors have been studied for many years, in many cases with a view towards controlling their behavior through various forms of "defect engineering." For example, in the bulk, charging significantly affects the total concentration of defects that are available to mediate phenomena such as solid-state diffusion. Surface defects play an important role in mediating surface mass transport during high temperature processing steps such as epitaxial film deposition, diffusional smoothing in reflow, and nanostructure formation in memory device fabrication. Charged Semiconductor Defects details the current state of knowledge regarding the properties of the ionized defects that can affect the behavior of advanced transistors, photo-active devices, catalysts, and sensors. Features: Group IV, III-V, and oxide semiconductors; Intrinsic and extrinsic defects; and, P...

  16. High resolution deep level transient spectroscopy and process-induced defects in silicon

    International Nuclear Information System (INIS)

    Evans-Freeman, J.H.; Emiroglu, D.; Vernon-Parry, K.D.

    2004-01-01

    High resolution, or Laplace, deep level transient spectroscopy (LDLTS) enables the identification of very closely spaced energetic levels in a semiconductor bandgap. DLTS may resolve peaks with a separation of tens of electron volts, but LDLTS can resolve defect energy separations as low as a few MeV. In this paper, we present results from LDLTS applied to ion implantation-induced defects in silicon, with particular emphasis on characterisation of end-of-range interstitial type defects. Silicon was implanted with a variety of ions from mass 28 to 166. A combination of LDLTS and direct capture cross-section measurements was employed to show that electrically active small extended defects were present in the as-implanted samples. Larger dislocations were then generated in Si by oxygenation to act as a control sample. These stacking faults had typical lengths of microns, and their electrical activity was subsequently characterised by LDLTS. This was to establish the sensitivity of LDLTS to defects whose carrier capture is characterised by a non-exponential filling process and an evolving band structure as carrier capture proceeds. The LDLTS spectra show several components in capacitance transients originating from both the end-of-range defects, and the stacking faults, and also clearly show that the carrier emission rates reduce as these extended defects fill with carriers. The end-of-range defects and the stacking faults are shown to have the same electrical behaviour

  17. Automatic classification of blank substrate defects

    Science.gov (United States)

    Boettiger, Tom; Buck, Peter; Paninjath, Sankaranarayanan; Pereira, Mark; Ronald, Rob; Rost, Dan; Samir, Bhamidipati

    2014-10-01

    Mask preparation stages are crucial in mask manufacturing, since this mask is to later act as a template for considerable number of dies on wafer. Defects on the initial blank substrate, and subsequent cleaned and coated substrates, can have a profound impact on the usability of the finished mask. This emphasizes the need for early and accurate identification of blank substrate defects and the risk they pose to the patterned reticle. While Automatic Defect Classification (ADC) is a well-developed technology for inspection and analysis of defects on patterned wafers and masks in the semiconductors industry, ADC for mask blanks is still in the early stages of adoption and development. Calibre ADC is a powerful analysis tool for fast, accurate, consistent and automatic classification of defects on mask blanks. Accurate, automated classification of mask blanks leads to better usability of blanks by enabling defect avoidance technologies during mask writing. Detailed information on blank defects can help to select appropriate job-decks to be written on the mask by defect avoidance tools [1][4][5]. Smart algorithms separate critical defects from the potentially large number of non-critical defects or false defects detected at various stages during mask blank preparation. Mechanisms used by Calibre ADC to identify and characterize defects include defect location and size, signal polarity (dark, bright) in both transmitted and reflected review images, distinguishing defect signals from background noise in defect images. The Calibre ADC engine then uses a decision tree to translate this information into a defect classification code. Using this automated process improves classification accuracy, repeatability and speed, while avoiding the subjectivity of human judgment compared to the alternative of manual defect classification by trained personnel [2]. This paper focuses on the results from the evaluation of Automatic Defect Classification (ADC) product at MP Mask

  18. Cooperation and Defection in Ghetto

    Science.gov (United States)

    Kułakowski, Krzysztof

    We consider ghetto as a community of people ruled against their will by an external power. Members of the community feel that their laws are broken. However, attempts to leave ghetto makes their situation worse. We discuss the relation of the ghetto inhabitants to the ruling power in context of their needs, organized according to the Maslow hierarchy. Decisions how to satisfy successive needs are undertaken in cooperation with or defection the ruling power. This issue allows to construct the tree of decisions and to adopt the pruning technique from the game theory. Dynamics of decisions can be described within the formalism of fundamental equations. The result is that the strategy of defection is stabilized by the estimated payoff.

  19. Quasi-one-dimensional metals on semiconductor surfaces with defects

    International Nuclear Information System (INIS)

    Hasegawa, Shuji

    2010-01-01

    Several examples are known in which massive arrays of metal atomic chains are formed on semiconductor surfaces that show quasi-one-dimensional metallic electronic structures. In this review, Au chains on Si(557) and Si(553) surfaces, and In chains on Si(111) surfaces, are introduced and discussed with regard to the physical properties determined by experimental data from scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES) and electrical conductivity measurements. They show quasi-one-dimensional Fermi surfaces and parabolic band dispersion along the chains. All of them are known from STM and ARPES to exhibit metal-insulator transitions by cooling and charge-density-wave formation due to Peierls instability of the metallic chains. The electrical conductivity, however, reveals the metal-insulator transition only on the less-defective surfaces (Si(553)-Au and Si(111)-In), but not on a more-defective surface (Si(557)-Au). The latter shows an insulating character over the whole temperature range. Compared with the electronic structure (Fermi surfaces and band dispersions), the transport property is more sensitive to the defects. With an increase in defect density, the conductivity only along the metal atomic chains was significantly reduced, showing that atomic-scale point defects decisively interrupt the electrical transport along the atomic chains and hide the intrinsic property of transport in quasi-one-dimensional systems.

  20. Simulating the production of free defects in irradiated metals

    International Nuclear Information System (INIS)

    Heinisch, H.L.

    1995-01-01

    Under cascade-producing irradiation by high energy neutrons or charged particles, only a small fraction of the initially displaced atoms contribute to the population of free defects that are available to migrate throughout the metal and cause microstructural changes. Although, in principle, computer simulations of free defect production could best be done using molecular dynamics, in practice, the wide ranges of time and distance scales involved can be done only by a combination of atomistic models that employ various levels of approximation. An atomic-scale, multi-model approach has been developed that combines molecular dynamics, binary collision models and stochastic annealing simulation. The annealing simulation is utilized in calibrating binary collision simulations to the results of molecular dynamics calculations, as well as to model the subsequent migration of the defects on more macroscopic time and size scales. The annealing simulation and the method of calibrating the multi-model approach are discussed, and the results of simulations of cascades in copper are presented. The temperature dependence of free defect production following simulated annealing of isolated cascades in copper shows a differential in the fractions of free vacancies and interstitial defects escaping from the cascade above stage V. This differential, a consequence of the direct formation of interstitial clusters in cascades and the relative thermal stability of vacancy and interstitial clusters during subsequent annealing, is the basis for the production bias mechanism of void swelling. (orig.)

  1. SiC substrate defects and III-N heteroepitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Poust, B D [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Koga, T S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Sandhu, R [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Heying, B [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Hsing, R [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Wojtowicz, M [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Khan, A [Department of Electrical Engineering, University of South Carolina, Columbia, SC (United States); Goorsky, M S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States)

    2003-05-21

    This study addressed how defects in SiC substrates influence the crystallographic properties of AlGaN/GaN layers deposited by metallorganic vapour phase epitaxy and by molecular beam epitaxy. We employed double crystal reflection x-ray topography using symmetric (0008) and (00012) reflections with CuK{alpha} radiation ({lambda} = 1.54 A) to image dislocations, micropipes, and low angle boundaries in SiC substrates. Lattice strain near the core of a micropipe defect was estimated to be of the order of 10{sup -7}. The substrates investigated exhibited radial patterns of strain and, primarily, of tilt of the order of tens of arcsec. After deposition of the AlGaN and GaN layers, DCXRT images were generated from the substrate (0008) or (00012) and GaN epitaxial layer (0004) reflections. Full-width at half-maximum values ranging from {approx}100 to 300 arcsec were typical of the GaN reflections, while those of the 4H-SiC reflections were {approx}20-70 arcsec. Micropipes, tilt boundaries, and inclusions in the SiC were shown to produce structural defects in the GaN layers. A clear correlation between SiC substrate defects and GaN defects has been established.

  2. SiC substrate defects and III-N heteroepitaxy

    International Nuclear Information System (INIS)

    Poust, B D; Koga, T S; Sandhu, R; Heying, B; Hsing, R; Wojtowicz, M; Khan, A; Goorsky, M S

    2003-01-01

    This study addressed how defects in SiC substrates influence the crystallographic properties of AlGaN/GaN layers deposited by metallorganic vapour phase epitaxy and by molecular beam epitaxy. We employed double crystal reflection x-ray topography using symmetric (0008) and (00012) reflections with CuKα radiation (λ = 1.54 A) to image dislocations, micropipes, and low angle boundaries in SiC substrates. Lattice strain near the core of a micropipe defect was estimated to be of the order of 10 -7 . The substrates investigated exhibited radial patterns of strain and, primarily, of tilt of the order of tens of arcsec. After deposition of the AlGaN and GaN layers, DCXRT images were generated from the substrate (0008) or (00012) and GaN epitaxial layer (0004) reflections. Full-width at half-maximum values ranging from ∼100 to 300 arcsec were typical of the GaN reflections, while those of the 4H-SiC reflections were ∼20-70 arcsec. Micropipes, tilt boundaries, and inclusions in the SiC were shown to produce structural defects in the GaN layers. A clear correlation between SiC substrate defects and GaN defects has been established

  3. Topological defects in open string field theory

    Science.gov (United States)

    Kojita, Toshiko; Maccaferri, Carlo; Masuda, Toru; Schnabl, Martin

    2018-04-01

    We show how conformal field theory topological defects can relate solutions of open string field theory for different boundary conditions. To this end we generalize the results of Graham and Watts to include the action of defects on boundary condition changing fields. Special care is devoted to the general case when nontrivial multiplicities arise upon defect action. Surprisingly the fusion algebra of defects is realized on open string fields only up to a (star algebra) isomorphism.

  4. Various Stone-Wales defects in phagraphene

    Science.gov (United States)

    Openov, L. A.; Podlivaev, A. I.

    2016-08-01

    Various Stone-Wales defects in phagraphene, which is a graphene allotrope, predicted recently are studied in terms of the nonorthogonal tight-binding model. The energies of the defect formation and the heights of energy barriers preventing the formation and annealing of the defects are found. Corresponding frequency factors in the Arrhenius formula are calculated. The evolution of the defect structure is studied in the real-time mode using the molecular dynamics method.

  5. Iatrogenic Urethral Defect Repairment: A Case Report

    Directory of Open Access Journals (Sweden)

    Ulas Fidan

    2013-10-01

    Full Text Available    Iatrogenic urethral defect is a complication that occurs after vaginal surgical procedures. Many surgical methods according to place of defect are described in case of injury of urethra. In this article, we reported the repairment of distal urethral defect with the help of greft taken from labia minor. This defect is made by the excision of the granulation tissue that occurred after chronic paraurethral  gland infection.

  6. Defect relaxation in disordered materials

    International Nuclear Information System (INIS)

    Crandell, R.S.

    1989-01-01

    Using an exponential distribution of activation barriers, annealing data for metastable effects in hydrogenated amorphous silicon, a-Si:H, are quantitatively explained. This includes the stretched exponential time dependence of annealing and a Meyer-Neldel rule for the annealing time constant. An exponential distribution of annealing energies arises because defects are frozen in during growth at high temperature. Mechanisms that lead to an exponential distribution of annealing energies are weak bond-breaking and charge trapping

  7. Quantum defect theory and asymptotic methods

    International Nuclear Information System (INIS)

    Seaton, M.J.

    1982-01-01

    It is shown that quantum defect theory provides a basis for the development of various analytical methods for the examination of electron-ion collision phenomena, including di-electronic recombination. Its use in conjuction with ab initio calculations is shown to be restricted by problems which arise from the presence of long-range non-Coulomb potentials. Empirical fitting to some formulae can be efficient in the use of computer time but extravagant in the use of person time. Calculations at a large number of energy points which make no use of analytical formulae for resonance structures may be made less extravagant in computer time by the development of more efficient asymptotic methods. (U.K.)

  8. Curvature-Controlled Topological Defects

    Directory of Open Access Journals (Sweden)

    Luka Mesarec

    2017-05-01

    Full Text Available Effectively, two-dimensional (2D closed films exhibiting in-plane orientational ordering (ordered shells might be instrumental for the realization of scaled crystals. In them, ordered shells are expected to play the role of atoms. Furthermore, topological defects (TDs within them would determine their valence. Namely, bonding among shells within an isotropic liquid matrix could be established via appropriate nano-binders (i.e., linkers which tend to be attached to the cores of TDs exploiting the defect core replacement mechanism. Consequently, by varying configurations of TDs one could nucleate growth of scaled crystals displaying different symmetries. For this purpose, it is of interest to develop a simple and robust mechanism via which one could control the position and number of TDs in such atoms. In this paper, we use a minimal mesoscopic model, where variational parameters are the 2D curvature tensor and the 2D orientational tensor order parameter. We demonstrate numerically the efficiency of the effective topological defect cancellation mechanism to predict positional assembling of TDs in ordered films characterized by spatially nonhomogeneous Gaussian curvature. Furthermore, we show how one could efficiently switch among qualitatively different structures by using a relative volume v of ordered shells, which represents a relatively simple naturally accessible control parameter.

  9. Defect grating modes as superimposed grating states

    NARCIS (Netherlands)

    van Groesen, Embrecht W.C.; Sopaheluwakan, A.; Andonowati, A.; de Ridder, R.M; de Ridder, R.M.; Altena, G; Altena, G.; Geuzebroek, D.H.; Geuzenboek, D.; Dekker, R.; Dekker, R

    2003-01-01

    For a symmetric grating structure with a defect, we show that a fully transmitted defect mode in the band gap can be obtained as a superposition of two steady states: an amplified and an attenuated defect state. Without scanning the whole band gap by transmission calculations, this simplifies the

  10. Disc defect classification for optical disc drives

    NARCIS (Netherlands)

    Helvoirt, van J.; Leenknegt, G.A.L.; Steinbuch, M.; Goossens, H.J.

    2005-01-01

    Optical disc drives are subject to various disturbances and faults. A special type of fault is the so-called disc defect. In this paper we present an approach for disc defect classification. It is based on hierarchical clustering of measured signals that are affected by disc defects. The

  11. Metastable and bistable defects in silicon

    International Nuclear Information System (INIS)

    Mukashev, Bulat N; Abdullin, Kh A; Gorelkinskii, Yurii V

    2000-01-01

    Existing data on the properties and structure of metastable and bistable defects in silicon are analyzed. Primary radiation-induced defects (vacancies, self-interstitial atoms, and Frenkel pairs), complexes of oxygen, carbon, hydrogen, and other impurity atoms and defects with negative correlation energy are considered. (reviews of topical problems)

  12. Peru's national folic acid fortification program and its effect on neural tube defects in Lima Programa nacional del Perú de fortificación con ácido fólico y su efecto sobre los defectos del tubo neural en Lima

    Directory of Open Access Journals (Sweden)

    Daniel J. Ricks

    2012-12-01

    Full Text Available OBJECTIVE: To evaluate the impact of Peru's national folic acid fortification program on folic acid content in wheat flour, and the effect on birth prevalence of neural tube defects (NTDs in Lima, and to compare the program's legislative requirements with international standards. METHODS: Bread was sampled from six sites across Peru and tested for folic acid. Data were obtained from the largest obstetric hospital in Lima on the prevalence of births (live and still with NTDs during both the pre-fortification period (2004-2005 and post-fortification years (2007-2008. RESULTS: Folic acid content in the sampled bread met national legislative requirements but was less than one-half of the level recommended for Peru by the World Health Organization (WHO (2.6 mg/kg wheat flour. Birth prevalence of NTDs was 18.4/10 000 in the pre-fortification period and 20.0/10 000 during post-fortification years. Relative risk for NTDs after fortification was 1.02 (95% confidence interval 0.77-1.35, P = 0.90. CONCLUSIONS: Peruvian legislative requirements for folic acid fortification are below international (WHO recommendations; birth prevalence of NTDs in Lima is higher than international benchmarks; and no decrease in NTDs following fortification of flour with folic acid (according to Peruvian national standards was observed. As increasing the level of folic acid in flour remains the most sustainable way of preventing NTDs, it is recommended that Peru increase its folic acid fortification requirements to meet those recommended by WHO (2.6 mg/kg.OBJETIVO: Evaluar la repercusión que el programa nacional del Perú de fortificación con ácido fólico tiene en el contenido de ácido fólico de la harina de trigo y en la prevalencia de nacimientos de niños con defectos del tubo neural en Lima, así como comparar los requisitos legislativos del programa con las normas internacionales. MÉTODOS: Se hizo un muestreo del pan en seis zonas de Perú y se analizó su

  13. Photographic guide of selected external defect indicators and associated internal defects in sugar maple

    Science.gov (United States)

    Everette D. Rast; John A. Beaton; David L. Sonderman

    1991-01-01

    To properly classify or grade logs or trees, one must be able to correctly identify defect indicators and assess the effect of the underlying defect on possible end products. This guide assists the individual in identifying the surface defect indicator and shows the progressive stages of the defect throughout its development for sugar maple. Eleven types of external...

  14. Photographic guide of selected external defect indicators and associated internal defects in yellow-poplar

    Science.gov (United States)

    Everette D. Rast; John A. Beaton; David L. Sonderman

    1991-01-01

    To properly classify or grade logs or trees, one must be able to correctly identify defect indicators and assess the effect of the underlying defect on possible end products. This guide assists the individual in identifying the surface defect indicator and shows the progressive stages of the defect throughout its development for yellow-poplar. Twelve types of external...

  15. Photographic guide of selected external defect indicators and associated internal defects in yellow birch

    Science.gov (United States)

    Everette D. Rast; John A. Beaton; David L. Sonderman

    1991-01-01

    To properly classify or grade logs or trees, one must be able to correctly identify defect indicators and assess the effect of the underlying defect on possible end products. This guide assists the individual in identifying the surface defect indicator and shows the progressive stages of the defect throughout its development for yellow birch. Eleven types of external...

  16. Silicon exfoliation by hydrogen implantation: Actual nature of precursor defects

    Energy Technology Data Exchange (ETDEWEB)

    Kuisseu, Pauline Sylvia Pokam, E-mail: pauline-sylvia.pokam-kuisseu@cnrs-orleans.fr [CEMHTI-CNRS, 3A, rue de la férollerie, 45071 Orléans (France); Pingault, Timothée; Ntsoenzok, Esidor [CEMHTI-CNRS, 3A, rue de la férollerie, 45071 Orléans (France); Regula, Gabrielle [IM2NP-CNRS-Université d’Aix-Marseille, Avenue Escadrille Normandie Niemen, 13397 Marseille (France); Mazen, Frédéric [CEA-Leti, MINATEC campus, 17, rue des Martyrs, 38054 Grenoble Cedex 9 (France); Sauldubois, Audrey [Université d’Orléans, rue de Chartres – Collegium ST, 45067 Orléans (France); Andreazza, Caroline [ICMN-CNRS-Université d’Orléans, 1b rue de la férollerie, 45071 Orléans (France)

    2017-06-15

    MeV energy hydrogen implantation in silicon followed by a thermal annealing is a very smart way to produce high crystalline quality silicon substrates, much thinner than what can be obtained by diamond disk or wire sawing. Using this kerf-less approach, ultra-thin substrates with thicknesses between 15 µm and 100 µm, compatible with microelectronic and photovoltaic applications are reported. But, despite the benefits of this approach, there is still a lack of fundamental studies at this implantation energy range. However, if very few papers have addressed the MeV energy range, a lot of works have been carried out in the keV implantation energy range, which is the one used in the smart-cut® technology. In order to check if the nature and the growth mechanism of extended defects reported in the widely studied keV implantation energy range could be extrapolated in the MeV range, the thermal evolution of extended defects formed after MeV hydrogen implantation in (100) Si was investigated in this study. Samples were implanted at 1 MeV with different fluences ranging from 6 × 10{sup 16} H/cm{sup 2} to 2 × 10{sup 17} H/cm{sup 2} and annealed at temperatures up to 873 K. By cross-section transmission electron microscopy, we found that the nature of extended defects in the MeV range is quite different of what is observed in the keV range. In fact, in our implantation conditions, the generated extended defects are some kinds of planar clusters of gas-filled lenses, instead of platelets as commonly reported in the keV energy range. This result underlines that hydrogen behaves differently when it is introduced in silicon at high or low implantation energy. The activation energy of the growth of these extended defects is independent of the chosen fluence and is between (0.5–0.6) eV, which is very close to the activation energy reported for atomic hydrogen diffusion in a perfect silicon crystal.

  17. Concurrence of metaphyseal fibrous defect and osteosarcoma

    International Nuclear Information System (INIS)

    Kyriakos, M.; Murphy, W.A.

    1981-01-01

    The case of a 15-year-old girl with juxtaposition of a femoral metaphyseal fibrous defect (fibrous cortical defect) and an osteosarcoma is reported. Despite the relatively common occurrence of metaphyseal fibrous defects, their reported association with other bone tumors is exceedingly rare. Only two previous acceptable examples of this association were found. Reports of malignant transformation of metaphyseal fibrous defect were reviewed and rejected because they lacked convincing radiologic or histopathologic evidence of a pre-existent benign fibrous lesion. The finding of a malignant bone tumor in association with a metaphyseal fibrous defect appears to be a chance occurrence. (orig.)

  18. Compressive laser ranging.

    Science.gov (United States)

    Babbitt, Wm Randall; Barber, Zeb W; Renner, Christoffer

    2011-12-15

    Compressive sampling has been previously proposed as a technique for sampling radar returns and determining sparse range profiles with a reduced number of measurements compared to conventional techniques. By employing modulation on both transmission and reception, compressive sensing in ranging is extended to the direct measurement of range profiles without intermediate measurement of the return waveform. This compressive ranging approach enables the use of pseudorandom binary transmit waveforms and return modulation, along with low-bandwidth optical detectors to yield high-resolution ranging information. A proof-of-concept experiment is presented. With currently available compact, off-the-shelf electronics and photonics, such as high data rate binary pattern generators and high-bandwidth digital optical modulators, compressive laser ranging can readily achieve subcentimeter resolution in a compact, lightweight package.

  19. Dryden Aeronautical Test Range

    Data.gov (United States)

    Federal Laboratory Consortium — Recently redesignated to honor Dr. Hugh L. Dryden, NASA's Dryden Aeronautical Test Range (DATR) supports aerospace flight research and technology integration, space...

  20. Compact Antenna Range

    Data.gov (United States)

    Federal Laboratory Consortium — Facility consists of a folded compact antenna range including a computer controlled three axis position table, parabolic reflector and RF sources for the measurement...

  1. Areva solutions for management of defective fuel

    International Nuclear Information System (INIS)

    Morlaes, I.; Vo Van, V.

    2014-01-01

    Defective fuel management is a major challenge for nuclear operators when all fuel must be long-term managed. This paper describes AREVA solutions for managing defective fuel. Transport AREVA performs shipments of defective fuel in Europe and proposes casks that are licensed for that purpose in Europe and in the USA. The paper presents the transport experience and the new European licensing approach of defective fuel transport. Dry Interim Storage AREVA is implementing the defective fuel storage in the USA, compliant with the Safety Authority's requirements. In Europe, AREVA is developing a new, more long-term oriented storage solution for defective fuel, the best available technology regarding safety requirements. The paper describes these storage solutions. Treatment Various types of defective fuel coming from around the world have been treated in the AREVA La Hague plant. Specific treatment procedures were developed when needed. The paper presents operational elements related to this experience. (authors)

  2. Point defects and atomic transport in crystals

    International Nuclear Information System (INIS)

    Lidiard, A.B.

    1981-02-01

    There are two principle aspects to the theory of atomic transport in crystals as caused by the action of point defects, namely (1) the calculation of relevant properties of the point defects (energies and other thermodynamic characteristics of the different possible defects, activation energies and other mobility parameters) and (2) the statistical mechanics of assemblies of defects, both equilibrium and non-equilibrium assemblies. In the five lectures given here both these aspects are touched on. The first two lectures are concerned with the calculation of relevant point defect properties, particularly in ionic crystals. The first lecture is more general, the second is concerned particularly with some recent calculations of the free volumes of formation of defects in various ionic solids; these solve a rather long-standing problem in this area. The remaining three lectures are concerned with the kinetic theory of defects mainly in relaxation, drift and diffusion situations

  3. Maternal obesity and congenital heart defects: a population-based study123

    Science.gov (United States)

    Mills, James L; Troendle, James; Conley, Mary R; Carter, Tonia; Druschel, Charlotte M

    2010-01-01

    Background: Obesity affects almost one-third of pregnant women and causes many complications, including neural tube defects. It is not clear whether the risk of congenital heart defects, the most common malformations, is also increased. Objective: This study was conducted to determine whether obesity is associated with an increased risk of congenital heart defects. Design: A population-based, nested, case-control study was conducted in infants born with congenital heart defects and unaffected controls from the cohort of all births (n = 1,536,828) between 1993 and 2003 in New York State, excluding New York City. The type of congenital heart defect, maternal body mass index (BMI; in kg/m2), and other risk factors were obtained from the Congenital Malformations Registry and vital records. Mothers of 7392 congenital heart defect cases and 56,304 unaffected controls were studied. Results: All obese women (BMI ≥ 30) were significantly more likely than normal-weight women (BMI: 19–24.9) to have children with a congenital heart defect [odds ratio (OR): 1.15; 95% CI: 1.07, 1.23; P heart defects with increasing maternal obesity (P heart syndrome, aortic stenosis, pulmonic stenosis, and tetralogy of Fallot. Conclusions: Obese, but not overweight, women are at significantly increased risk of bearing children with a range of congenital heart defects, and the risk increases with increasing BMI. Weight reduction as a way to reduce risk should be investigated. PMID:20375192

  4. Edge dislocations as sinks for sub-nanometric radiation induced defects in α-iron

    Science.gov (United States)

    Anento, N.; Malerba, L.; Serra, A.

    2018-01-01

    The role of edge dislocations as sinks for small radiation induced defects in bcc-Fe is investigated by means of atomistic computer simulation. In this work we investigate by Molecular Statics (T = 0K) the interaction between an immobile dislocation line and defect clusters of small sizes invisible experimentally. The study highlights in particular the anisotropy of the interaction and distinguishes between absorbed and trapped defects. When the considered defect intersects the dislocation glide plane and the distance from the dislocation line to the defect is on the range between 2 nm and 4 nm, either total or partial absorption of the cluster takes place leading to the formation of jogs. Residual defects produced during partial absorption pin the dislocation. By the calculation of stress-strain curves we have assessed the strength of those residues as obstacles for the motion of the dislocation, which is reflected on the unpinning stresses and the binding energies obtained. When the defect is outside this range, but on planes close to the dislocation glide plane, instead of absorption we have observed a capture process. Finally, with a view to introducing explicitly in kinetic Monte Carlo models a sink with the shape of a dislocation line, we have summarized our findings on a table presenting the most relevant parameters, which define the interaction of the dislocation with the defects considered.

  5. Detection of defects in electron-irradiated synthetic silica quartz probed by positron annihilation

    International Nuclear Information System (INIS)

    Watauchi, Satoshi; Uedono, Akira; Ujihira, Yusuke; Yoda, Osamu.

    1994-01-01

    Defects in amorphous SiO 2 films, formed on MOS(metal/oxide/semiconductor) devices as gates, perturb its operation. The positron annihilation techniques, were applied to the study of the annealing behavior of the defects, introduced in the high purity synthetic quartz glass by the irradiation of 3-MeV electrons up to the 1x10 18 e - /cm 2 dosage. It was proved that the positron annihilation techniques were sufficiently sensitive to detect the defects in the electron-irradiated silica glasses. Three types of open-space defects were detected by the positron lifetime measurements. These can be attributed to monovacancy or divacancy type defects, vacancy clusters, and open-volume defects. A high formation probability (∼90%) of positroniums(Ps) was found in unirradiated specimens. These Ps were considered to be formed in open-volume defects. The formation probability of Ps was drastically decreased by the electron irradiation. But the size of open-volume defects was kept unchanged by the irradiation. These facts suggest that vacancy-type defects were introduced by the electron irradiation and that positrons were trapped in these defects. By the isochronal annealing in nitrogen atmosphere, the lifetime component (τ 2 ) and its relative intensity (I 2 ), attributed to positrons trapped in monovacancy or divacancy type defects and annihilated there, changed remarkably. τ 2 was constant in the temperature range up to 300degC, getting slightly shorter between 300degC and 700degC, and constant above 700degC. I 2 decreased gradually up to 300degC, constant between 300degC and 550degC, decreased above 550degC, and constant above 700degC. This revealed that the behavior of the defects, in which positrons were trapped, change by the elevation of the annealing temperature. (author)

  6. Range Scheduling Aid (RSA)

    Science.gov (United States)

    Logan, J. R.; Pulvermacher, M. K.

    1991-01-01

    Range Scheduling Aid (RSA) is presented in the form of the viewgraphs. The following subject areas are covered: satellite control network; current and new approaches to range scheduling; MITRE tasking; RSA features; RSA display; constraint based analytic capability; RSA architecture; and RSA benefits.

  7. On Range of Skill

    DEFF Research Database (Denmark)

    Hansen, Thomas Dueholm; Miltersen, Peter Bro; Sørensen, Troels Bjerre

    2008-01-01

    size (and doubly exponential in its depth). We also provide techniques that yield concrete bounds for unbalanced game trees and apply these to estimate the Range of Skill of Tic-Tac-Toe and Heads-Up Limit Texas Hold'em Poker. In particular, we show that the Range of Skill of Tic-Tac-Toe is more than...

  8. Packing defects into ordered structures

    DEFF Research Database (Denmark)

    Bechstein, R.; Kristoffersen, Henrik Høgh; Vilhelmsen, L.B.

    2012-01-01

    . With the help of density functional theory calculations we develop a complete structural model for the entire strand and demonstrate these adstructures to be more stable than an equivalent amount of bulk defects such as Ti interstitials. We argue that strands can form particularly easy on stepped surfaces......We have studied vicinal TiO2(110) surfaces by high-resolution scanning tunneling microscopy and density functional theory calculations. On TiO2 surfaces characterized by a high density of ⟨11̅ 1⟩ steps, scanning tunneling microscopy reveals a high density of oxygen-deficient strandlike adstructures...

  9. Home range and travels

    Science.gov (United States)

    Stickel, L.F.; King, John A.

    1968-01-01

    The concept of home range was expressed by Seton (1909) in the term 'home region,' which Burr (1940, 1943) clarified with a definition of home range and exemplified in a definitive study of Peromyscus in the field. Burt pointed out the ever-changing characteristics of home-range area and the consequent absence of boundaries in the usual sense--a finding verified by investigators thereafter. In the studies summarized in this paper, sizes of home ranges of Peromyscus varied within two magnitudes, approximately from 0.1 acre to ten acres, in 34 studies conducted in a variety of habitats from the seaside dunes of Florida to the Alaskan forests. Variation in sizes of home ranges was correlated with both environmental and physiological factors; with habitat it was conspicuous, both in the same and different regions. Food supply also was related to size of home range, both seasonally and in relation to habitat. Home ranges generally were smallest in winter and largest in spring, at the onset of the breeding season. Activity and size also were affected by changes in weather. Activity was least when temperatures were low and nights were bright. Effects of rainfall were variable. Sizes varied according to sex and age; young mice remained in the parents' range until they approached maturity, when they began to travel more widely. Adult males commonly had larger home ranges than females, although there were a number of exceptions. An inverse relationship between population density and size of home range was shown in several studies and probably is the usual relationship. A basic need for activity and exploration also appeared to influence size of home range. Behavior within the home range was discussed in terms of travel patterns, travels in relation to home sites and refuges, territory, and stability of size of home range. Travels within the home range consisted of repeated use of well-worn trails to sites of food, shelter, and refuge, plus more random exploratory travels

  10. Autonomous Target Ranging Techniques

    DEFF Research Database (Denmark)

    Jørgensen, Peter Siegbjørn; Jørgensen, John Leif; Denver, Troelz

    2003-01-01

    of this telescope, a fast determination of the range to and the motion of the detected targets are important. This is needed in order to prepare the future observation strategy for each target, i.e. when is the closest approach where imaging will be optimal. In order to quickly obtain such a determination two...... ranging strategies are presented. One is an improved laser ranger with an effective range with non-cooperative targets of at least 10,000 km, demonstrated in ground tests. The accuracy of the laser ranging will be approximately 1 m. The laser ranger may furthermore be used for trajectory determination...... of nano-gravity probes, which will perform direct mass measurements of selected targets. The other is triangulation from two spacecraft. For this method it is important to distinguish between detection and tracking range, which will be different for Bering since different instruments are used...

  11. Soliton microcomb range measurement

    Science.gov (United States)

    Suh, Myoung-Gyun; Vahala, Kerry J.

    2018-02-01

    Laser-based range measurement systems are important in many application areas, including autonomous vehicles, robotics, manufacturing, formation flying of satellites, and basic science. Coherent laser ranging systems using dual-frequency combs provide an unprecedented combination of long range, high precision, and fast update rate. We report dual-comb distance measurement using chip-based soliton microcombs. A single pump laser was used to generate dual-frequency combs within a single microresonator as counterpropagating solitons. We demonstrated time-of-flight measurement with 200-nanometer precision at an averaging time of 500 milliseconds within a range ambiguity of 16 millimeters. Measurements at distances up to 25 meters with much lower precision were also performed. Our chip-based source is an important step toward miniature dual-comb laser ranging systems that are suitable for photonic integration.

  12. Additive manufacturing for in situ repair of osteochondral defects

    International Nuclear Information System (INIS)

    Cohen, Daniel L; Lipton, Jeffrey I; Bonassar, Lawrence J; Lipson, Hod

    2010-01-01

    Tissue engineering holds great promise for injury repair and replacement of defective body parts. While a number of techniques exist for creating living biological constructs in vitro, none have been demonstrated for in situ repair. Using novel geometric feedback-based approaches and through development of appropriate printing-material combinations, we demonstrate the in situ repair of both chondral and osteochondral defects that mimic naturally occurring pathologies. A calf femur was mounted in a custom jig and held within a robocasting-based additive manufacturing (AM) system. Two defects were induced: one a cartilage-only representation of a grade IV chondral lesion and the other a two-material bone and cartilage fracture of the femoral condyle. Alginate hydrogel was used for the repair of cartilage; a novel formulation of demineralized bone matrix was used for bone repair. Repair prints for both defects had mean surface errors less than 0.1 mm. For the chondral defect, 42.8 ± 2.6% of the surface points had errors that were within a clinically acceptable error range; however, with 1 mm path planning shift, an estimated ∼75% of surface points could likely fall within the benchmark envelope. For the osteochondral defect, 83.6 ± 2.7% of surface points had errors that were within clinically acceptable limits. In addition to implications for minimally invasive AM-based clinical treatments, these proof-of-concept prints are some of the only in situ demonstrations to-date, wherein the substrate geometry was unknown a priori. The work presented herein demonstrates in situ AM, suggests potential biomedical applications and also explores in situ-specific issues, including geometric feedback, material selection and novel path planning techniques.

  13. Magnetoencephalography signals are influenced by skull defects.

    Science.gov (United States)

    Lau, S; Flemming, L; Haueisen, J

    2014-08-01

    Magnetoencephalography (MEG) signals had previously been hypothesized to have negligible sensitivity to skull defects. The objective is to experimentally investigate the influence of conducting skull defects on MEG and EEG signals. A miniaturized electric dipole was implanted in vivo into rabbit brains. Simultaneous recording using 64-channel EEG and 16-channel MEG was conducted, first above the intact skull and then above a skull defect. Skull defects were filled with agar gels, which had been formulated to have tissue-like homogeneous conductivities. The dipole was moved beneath the skull defects, and measurements were taken at regularly spaced points. The EEG signal amplitude increased 2-10 times, whereas the MEG signal amplitude reduced by as much as 20%. The EEG signal amplitude deviated more when the source was under the edge of the defect, whereas the MEG signal amplitude deviated more when the source was central under the defect. The change in MEG field-map topography (relative difference measure, RDM(∗)=0.15) was geometrically related to the skull defect edge. MEG and EEG signals can be substantially affected by skull defects. MEG source modeling requires realistic volume conductor head models that incorporate skull defects. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  14. Dopants and defects in semiconductors

    CERN Document Server

    McCluskey, Matthew D

    2012-01-01

    "The book goes beyond the usual textbook in that it provides more specific examples of real-world defect physics … The book will be most useful for beginning graduate students in materials science. … an easy reading, broad introductory overview of the field …"-Materials Today, July-August 2012"… well written, with clear, lucid explanations …"-Chemistry World"The scientific development towards the method of controllable doping transformed the erratic and not reproducible family of semiconductor materials into the truly wonderful basis of modern microelectronics. This book tells the remarkable success story and I recommend it!"-Hans J. Queisser, Max-Planck-Institute, Stuttgart, Germany"McCluskey and Haller have written an outstanding modern guide to this field that will be useful to newcomers, and also to active researchers who want to broaden their horizons, as a means to learn the capabilities and limitations of the many techniques that are used in semiconductor-defect science."-Professor Michael J....

  15. Prediction ranges. Annual review

    Energy Technology Data Exchange (ETDEWEB)

    Parker, J.C.; Tharp, W.H.; Spiro, P.S.; Keng, K.; Angastiniotis, M.; Hachey, L.T.

    1988-01-01

    Prediction ranges equip the planner with one more tool for improved assessment of the outcome of a course of action. One of their major uses is in financial evaluations, where corporate policy requires the performance of uncertainty analysis for large projects. This report gives an overview of the uses of prediction ranges, with examples; and risks and uncertainties in growth, inflation, and interest and exchange rates. Prediction ranges and standard deviations of 80% and 50% probability are given for various economic indicators in Ontario, Canada, and the USA, as well as for foreign exchange rates and Ontario Hydro interest rates. An explanatory note on probability is also included. 23 tabs.

  16. Structural defects in electrodeposited Ni studied by positron annihilation

    International Nuclear Information System (INIS)

    Vertes, A.; Szeles, C.; Czako-Nagy, I.; Lakatos-Varsanyi, M.

    1982-01-01

    Structural investigation of electrodeposited Ni was carried out by positron annihilation (PA) technique. Additional Moessbauer effect and X-ray diffraction measurements were also performed. The samples were produced under different plating conditions resulting in stress in the range -100 to +600 N/mm 2 . From the positron lifetime measurements it seems that the defect pattern of electrodeposited Ni samples might be substantially different from sample to sample with different deposition and plating conditions. (Auth.)

  17. Antenna Pattern Range (APR)

    Data.gov (United States)

    Federal Laboratory Consortium — TheAntenna Pattern Range (APR)features a non-metallic arch with a trolley to move the transmit antenna from the horizon to zenith. At the center of the ground plane,...

  18. Atlantic Test Range (ATR)

    Data.gov (United States)

    Federal Laboratory Consortium — ATR controls fully-instrumented and integrated test ranges that provide full-service support for cradle-to-grave testing. Airspace and surface target areas are used...

  19. EV range sensitivity analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ostafew, C. [Azure Dynamics Corp., Toronto, ON (Canada)

    2010-07-01

    This presentation included a sensitivity analysis of electric vehicle components on overall efficiency. The presentation provided an overview of drive cycles and discussed the major contributors to range in terms of rolling resistance; aerodynamic drag; motor efficiency; and vehicle mass. Drive cycles that were presented included: New York City Cycle (NYCC); urban dynamometer drive cycle; and US06. A summary of the findings were presented for each of the major contributors. Rolling resistance was found to have a balanced effect on each drive cycle and proportional to range. In terms of aerodynamic drive, there was a large effect on US06 range. A large effect was also found on NYCC range in terms of motor efficiency and vehicle mass. figs.

  20. Defects and properties of cadmium oxide based transparent conductors

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Kin Man, E-mail: kinmanyu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Kowloon (Hong Kong); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Detert, D. M.; Dubon, O. D. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Chen, Guibin [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Physics Department and Jiangsu Key Laboratory for Chemistry of Low Dimensional Materials, Huaiyin Normal University, Jiangsu 223300 (China); Zhu, Wei [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics and The Center for Physical Experiments, University of Science and Technology of China, Hefei, Anhui 230026 (China); Liu, Chaoping [Department of Physics and Materials Science, City University of Hong Kong, Kowloon (Hong Kong); Grankowska, S. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Institute of Experimental Physics (IEP UW), Warsaw University, Warsaw (Poland); Hsu, L. [Department of Postsecondary Teaching and Learning, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Walukiewicz, Wladek [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2016-05-14

    Transparent conductors play an increasingly important role in a number of semiconductor technologies. This paper reports on the defects and properties of Cadmium Oxide, a transparent conducting oxide which can be potentially used for full spectrum photovoltaics. We carried out a systematic investigation on the effects of defects in CdO thin films undoped and intentionally doped with In and Ga under different deposition and annealing conditions. We found that at low growth temperatures (<200 °C), sputter deposition tends to trap both oxygen vacancies and compensating defects in the CdO film resulting in materials with high electron concentration of ∼2 × 10{sup 20}/cm{sup 3} and mobility in the range of 40–100 cm{sup 2}/V s. Thermal annealing experiments in different ambients revealed that the dominating defects in sputtered CdO films are oxygen vacancies. Oxygen rich CdO films grown by sputtering with increasing O{sub 2} partial pressure in the sputter gas mixture results in films with resistivity from ∼4 × 10{sup −4} to >1 Ω cm due to incorporation of excess O in the form of O-related acceptor defects, likely to be O interstitials. Intentional doping with In and Ga donors leads to an increase of both the electron concentration and the mobility. With proper doping CdO films with electron concentration of more than 10{sup 21 }cm{sup −3} and electron mobility higher than 120 cm{sup 2}/V s can be achieved. Thermal annealing of doped CdO films in N{sub 2} ambient can further improve the electrical properties by removing native acceptors and improving film crystallinity. Furthermore, the unique doping behavior and electrical properties of CdO were explored via simulations based on the amphoteric defect model. A comparison of the calculations and experimental results show that the formation energy of native donors and acceptors at the Fermi stabilization energy is ∼1 eV and that the mobility of sputtered deposited CdO is limited

  1. Defects and properties of cadmium oxide based transparent conductors

    International Nuclear Information System (INIS)

    Yu, Kin Man; Detert, D. M.; Dubon, O. D.; Chen, Guibin; Zhu, Wei; Liu, Chaoping; Grankowska, S.; Hsu, L.; Walukiewicz, Wladek

    2016-01-01

    Transparent conductors play an increasingly important role in a number of semiconductor technologies. This paper reports on the defects and properties of Cadmium Oxide, a transparent conducting oxide which can be potentially used for full spectrum photovoltaics. We carried out a systematic investigation on the effects of defects in CdO thin films undoped and intentionally doped with In and Ga under different deposition and annealing conditions. We found that at low growth temperatures (<200 °C), sputter deposition tends to trap both oxygen vacancies and compensating defects in the CdO film resulting in materials with high electron concentration of ∼2 × 10 20 /cm 3 and mobility in the range of 40–100 cm 2 /V s. Thermal annealing experiments in different ambients revealed that the dominating defects in sputtered CdO films are oxygen vacancies. Oxygen rich CdO films grown by sputtering with increasing O 2 partial pressure in the sputter gas mixture results in films with resistivity from ∼4 × 10 −4 to >1 Ω cm due to incorporation of excess O in the form of O-related acceptor defects, likely to be O interstitials. Intentional doping with In and Ga donors leads to an increase of both the electron concentration and the mobility. With proper doping CdO films with electron concentration of more than 10 21  cm −3 and electron mobility higher than 120 cm 2 /V s can be achieved. Thermal annealing of doped CdO films in N 2 ambient can further improve the electrical properties by removing native acceptors and improving film crystallinity. Furthermore, the unique doping behavior and electrical properties of CdO were explored via simulations based on the amphoteric defect model. A comparison of the calculations and experimental results show that the formation energy of native donors and acceptors at the Fermi stabilization energy is ∼1 eV and that the mobility of sputtered deposited CdO is limited by a background acceptor concentration of

  2. Influence of radiation defects on tritium release parameters from Li2O

    International Nuclear Information System (INIS)

    Grishmanov, V.; Tanaka, S.; Yoneoka, T.

    1998-01-01

    The study of the influence of radiation defects on tritium release behavior from polycrystalline Li 2 O was performed by simultaneous measurements of the luminescence emission and tritium release. It was found that the radiation defects in Li 2 O introduced by electron irradiation cause the retention of tritium. It is thought that the tritium recovery is affected by the formation of a Li-T bond, which is tolerant of high temperatures. The retardation of tritium decreases with increasing absorbed dose in the dose range from 50 to 140 MGy. The aggregation of radiation defects at high irradiation doses is considered to be responsible for the decrease of the interaction of tritium with radiation defects. The mechanism of the interaction of radiation defects with tritium is discussed. (orig.)

  3. Young's modulus of defective graphene sheet from intrinsic thermal vibrations

    International Nuclear Information System (INIS)

    Thomas, Siby; Mrudul, M S; Ajith, K M; Valsakumar, M C

    2016-01-01

    Classical molecular dynamics simulations have been performed to establish a relation between thermally excited ripples and Young's modulus of defective graphene sheet within a range of temperatures. The presence of the out-of-plane intrinsic ripples stabilizes the graphene membranes and the mechanical stability is analyzed by means of thermal mean square vibration amplitude in the long wavelength regime. We observed that the presence of vacancy and Stone-Wales (SW) defects reduces the Young's modulus of graphene sheets. Graphene sheet with vacancy defects possess superior Young's modulus to that of a sheet with Stone-Wales defects. The obtained room temperature Young's modulus of pristine and defective graphene sheet is ∼ 1 TPa, which is comparable to the results of earlier experimental and atomistic simulation studies. (paper)

  4. A defect model for UO2+x based on electrical conductivity and deviation from stoichiometry measurements

    Science.gov (United States)

    Garcia, Philippe; Pizzi, Elisabetta; Dorado, Boris; Andersson, David; Crocombette, Jean-Paul; Martial, Chantal; Baldinozzi, Guido; Siméone, David; Maillard, Serge; Martin, Guillaume

    2017-10-01

    Electrical conductivity of UO2+x shows a strong dependence upon oxygen partial pressure and temperature which may be interpreted in terms of prevailing point defects. A simulation of this property along with deviation from stoichiometry is carried out based on a model that takes into account the presence of impurities, oxygen interstitials, oxygen vacancies, holes, electrons and clusters of oxygen atoms. The equilibrium constants for each defect reaction are determined to reproduce the experimental data. An estimate of defect concentrations and their dependence upon oxygen partial pressure can then be determined. The simulations carried out for 8 different temperatures (973-1673 K) over a wide range of oxygen partial pressures are discussed and resulting defect equilibrium constants are plotted in an Arrhenius diagram. This provides an estimate of defect formation energies which may further be compared to other experimental data or ab-initio and empirical potential calculations.

  5. Investigation on the effect of atomic defects on the breaking behaviors of gold nanowires

    International Nuclear Information System (INIS)

    Wang Fenying; Sun Wei; Wang Hongbo; Zhao Jianwei; Kiguchi, Manabu; Sun Changqing

    2012-01-01

    The mechanical properties and breaking behaviors of the [100]-oriented single-crystal gold nanowires containing a set of defect ratios have been studied at different temperatures using molecular dynamics simulations. The size of the nanowire is 10a × 10a × 30a (a stands for lattice constant, 0.408 nm for gold). The mechanical strengths of the nanowires decrease with the increasing temperature. However, the defects that enhance the local thermal energy have improved the nanowire mechanical strength under a wide range of temperature. Comparing to the single-crystal nanowire, the existence of the atomic defects extends the elastic deformation showing a larger yield strain. By summarizing 300 samples at each temperature, the statistical breaking position distribution shows that the nanowire breaking behavior is sensitive to the atomic defects when the defect ratio is 5 % at 100 K, whereas the ratio is 1 % when temperatures are 300 and 500 K.

  6. Optimizing the hydrogen storage in boron nitride nanotubes by defect engineering

    Energy Technology Data Exchange (ETDEWEB)

    Oezdogan, Kemal; Berber, Savas [Physics Department, Gebze Institute of Technology, Cayirova Kampusu, Gebze, 41400 Kocaeli (Turkey)

    2009-06-15

    We use ab initio density functional theory calculations to study the interaction of hydrogen with vacancies in boron nitride nanotubes to optimize the hydrogen storage capacity through defect engineering. The vacancies reconstruct by forming B-B and N-N bonds across the defect site, which are not as favorable as heteronuclear B-N bonds. Our total energy and structure optimization results indicate that the hydrogen cleaves these reconstructing bonds to form more stable atomic structures. The hydrogenated defects offer smaller charge densities that allow hydrogen molecule to pass through the nanotube wall for storing hydrogen inside the nanotubes. Our optimum reaction pathway search revealed that hydrogen molecules could indeed go through a hydrogenated defect site with relatively small energy barriers compared to the pristine nanotube wall. The calculated activation energies for different diameters suggest a preferential diameter range for optimum hydrogen storage in defective boron nitride nanotubes. (author)

  7. Bone tissue ultrastructural defects in a mouse model for osteogenesis imperfecta: a Raman spectroscopy study

    Science.gov (United States)

    Chen, Tsoching; Kozloff, Kenneth M.; Goldstein, Steven A.; Morris, Michael D.

    2004-07-01

    Osteogenesis imperfecta (OI) is genetic defect in which the genes that code for the α1(I) or α2(I) chains of type I collagen are defective. The defects often result in substitution of a bulky amino acid for glycine, causing formation of collagen that can not form the normal triple helix. Depending on the details of the defects, the outcomes range from controllable to lethal. This study focuses on OI type IV, a more common and moderately severe form of the disease. People with the disease have a substantial increase in the risk and rate of fracture. We examine the spectroscopic consequences of these defects, using a mouse model (BRTL) that mimics OI type IV. We compare Raman images from tibial cortical tissue of wild-type mice and BRTL mice with single copy of mutation and show that both mineral to matrix ratios and collagen inter-fibril cross-links are different in wild-type and mutant mice.

  8. Point defects and magnetic properties of neutron irradiated MgO single crystal

    Directory of Open Access Journals (Sweden)

    Mengxiong Cao

    2017-05-01

    Full Text Available (100-oriented MgO single crystals were irradiated to introduce point defects with different neutron doses ranging from 1.0×1016 to 1.0×1020 cm-2. The point defect configurations were studied with X-ray diffuse scattering and UV-Vis absorption spectra. The isointensity profiles of X-ray diffuse scattering caused by the cubic and double-force point defects in MgO were theoretically calculated based on the Huang scattering theory. The magnetic properties at different temperature were measured with superconducting quantum interference device (SQUID. The reciprocal space mappings (RSMs of irradiated MgO revealed notable diffuse scattering. The UV-Vis spectra indicated the presence of O Frenkel defects in irradiated MgO. Neutron-irradiated MgO was diamagnetic at room temperature and became ferromagnetic at low temperature due to O Frenkel defects induced by neutron-irradiation.

  9. A magnetically tunable non-Bragg defect mode in a corrugated waveguide filled with liquid crystals

    Science.gov (United States)

    Zhang, Lu; Fan, Ya-Xian; Liu, Huan; Han, Xu; Lu, Wen-Qiang; Tao, Zhi-Yong

    2018-04-01

    A magnetically tunable, non-Bragg defect mode (NBDM) was created in the terahertz frequency range by inserting a defect in the middle of a periodically corrugated waveguide filled with liquid crystals (LCs). In the periodic waveguide, non-Bragg gaps beyond the Bragg ones, which appear in the transmission spectra, are created by different transverse mode resonances. The transmission spectra of the waveguide containing a defect showed that a defect mode was present inside the non-Bragg gap. The NBDM has quite different features compared to the Bragg defect mode, which includes more complex, high-order guided wave modes. In our study, we filled the corrugated waveguide with LCs to realize the tunability of the NBDM. The simulated results showed that the NBDM in a corrugated waveguide filled with LCs can be used in filters, sensors, switches, and other terahertz integrated devices.

  10. P-N defect in GaNP studied by optically detected magnetic resonance

    International Nuclear Information System (INIS)

    Chen, W.M.; Thinh, N.Q.; Vorona, I.P.; Buyanova, I.A.; Xin, H.P.; Tu, C.W.

    2003-01-01

    We provide experimental evidence for an intrinsic defect in GaNP from optically detected magnetic resonance (ODMR). This defect is identified as a P-N complex, exhibiting hyperfine structure due to interactions with a nuclear spin I=((1)/(2)) of one P atom and also a nuclear spin I=1 due to one N atom. The introduction of the defect is assisted by the incorporation of N within the studied N composition range of up to 3.1%, under non-equilibrium growth conditions during gas-source molecular beam epitaxy. The corresponding ODMR spectrum was found to be isotropic, suggesting an A 1 symmetry of the defect state. The localization of the electron wave function at the P-N defect in GaNP is found to be even stronger than that for the isolated P Ga antisite in its parent binary compound GaP

  11. Effects of in-cascade defect clustering on near-term defect evolution

    Energy Technology Data Exchange (ETDEWEB)

    Heinisch, H.L. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-08-01

    The effects of in-cascade defect clustering on the nature of the subsequent defect population are being studied using stochastic annealing simulations applied to cascades generated in molecular dynamics (MD) simulations. The results of the simulations illustrates the strong influence of the defect configuration existing in the primary damage state on subsequent defect evolution. The large differences in mobility and stability of vacancy and interstitial defects and the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades have been shown to be significant factors affecting the evolution of the defect distribution. In recent work, the effects of initial cluster sizes appear to be extremely important.

  12. Positron annihilation spectroscopy in defects of semiconductors

    International Nuclear Information System (INIS)

    Fujinami, Masanori

    2002-01-01

    Interaction of positron and defects, application to research of defects of semiconductor and defects on the surface of semiconductor are explained. Cz (Czochralski)-Si single crystal with 10 18 cm -3 impurity oxygen was introduced defects by electron irradiation and the positron lifetime was measured at 90K after annealing. The defect size and recovery temperature were determined by the lifetime measurement. The distribution of defects in the depth direction is shown by S-E curve. The chemical state analysis is possible by CBS (Coincidence Doppler Broadening) spectra. The application to silicon-implanted (100 keV, 2x10 15 cm -2 ) silicon and oxygen-implanted (180 keV, 2x10 15 cm -2 ) silicon are stated. On the oxygen-implanted silicon, the main product was V2 after implantation, V 6 O 2 at 600degC and V 10 O 6 at 800degC. (S.Y.)

  13. Perception of risk from automobile safety defects.

    Science.gov (United States)

    Slovic, P; MacGregor, D; Kraus, N N

    1987-10-01

    Descriptions of safety engineering defects of the kind that compel automobile manufacturers to initiate a recall campaign were evaluated by individuals on a set of risk characteristic scales that included overall vehicle riskiness, manufacturer's ability to anticipate the defect, importance for vehicle operation, severity of consequences and likelihood of compliance with a recall notice. A factor analysis of the risk characteristics indicated that judgments could be summarized in terms of two composite scales, one representing the uncontrollability of the damage the safety defect might cause and the other representing the foreseeability of the defect by the manufacturer. Motor vehicle defects were found to be highly diverse in terms of the perceived qualities of their risks. Location of individual defects within the factor space was closely associated with perceived riskiness, perceived likelihood of purchasing another car from the same manufacturer, perceived likelihood of compliance with a recall notice, and actual compliance rates.

  14. Automatic classification of defects in weld pipe

    International Nuclear Information System (INIS)

    Anuar Mikdad Muad; Mohd Ashhar Hj Khalid; Abdul Aziz Mohamad; Abu Bakar Mhd Ghazali; Abdul Razak Hamzah

    2000-01-01

    With the advancement of computer imaging technology, the image on hard radiographic film can be digitized and stored in a computer and the manual process of defect recognition and classification may be replace by the computer. In this paper a computerized method for automatic detection and classification of common defects in film radiography of weld pipe is described. The detection and classification processes consist of automatic selection of interest area on the image and then classify common defects using image processing and special algorithms. Analysis of the attributes of each defect such as area, size, shape and orientation are carried out by the feature analysis process. These attributes reveal the type of each defect. These methods of defect classification result in high success rate. Our experience showed that sharp film images produced better results

  15. Strained interface defects in silicon nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Benjamin G.; Stradins, Paul [National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, CO (United States); Hiller, Daniel; Zacharias, Margit [IMTEK - Faculty of Engineering, Albert-Ludwigs-University Freiburg (Germany); Luo, Jun-Wei; Beard, Matthew C. [Chemical and Materials Science, National Renewable Energy Laboratory, Golden, CO (United States); Semonin, Octavi E. [Chemical and Materials Science, National Renewable Energy Laboratory, Golden, CO (United States); Department of Physics, University of Colorado, Boulder, CO (United States)

    2012-08-07

    The surface of silicon nanocrystals embedded in an oxide matrix can contain numerous interface defects. These defects strongly affect the nanocrystals' photoluminescence efficiency and optical absorption. Dangling-bond defects are nearly eliminated by H{sub 2} passivation, thus decreasing absorption below the quantum-confined bandgap and enhancing PL efficiency by an order of magnitude. However, there remain numerous other defects seen in absorption by photothermal deflection spectroscopy; these defects cause non-radiative recombination that limits the PL efficiency to <15%. Using atomistic pseudopotential simulations, we attribute these defects to two specific types of distorted bonds: Si-Si and bridging Si-O-Si bonds between two Si atoms at the nanocrystal surface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Altering graphene line defect properties using chemistry

    Science.gov (United States)

    Vasudevan, Smitha; White, Carter; Gunlycke, Daniel

    2012-02-01

    First-principles calculations are presented of a fundamental topological line defect in graphene that was observed and reported in Nature Nanotech. 5, 326 (2010). These calculations show that atoms and smaller molecules can bind covalently to the surface in the vicinity of the graphene line defect. It is also shown that the chemistry at the line defect has a strong effect on its electronic and magnetic properties, e.g. the ferromagnetically aligned moments along the line defect can be quenched by some adsorbates. The strong effect of the adsorbates on the line defect properties can be understood by examining how these adsorbates affect the boundary-localized states in the vicinity of the Fermi level. We also expect that the line defect chemistry will significantly affect the scattering properties of incident low-energy particles approaching it from graphene.

  17. Primordial inhomogeneities from massive defects during inflation

    Energy Technology Data Exchange (ETDEWEB)

    Firouzjahi, Hassan; Karami, Asieh; Rostami, Tahereh, E-mail: firouz@ipm.ir, E-mail: karami@ipm.ir, E-mail: t.rostami@ipm.ir [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

    2016-10-01

    We consider the imprints of local massive defects, such as a black hole or a massive monopole, during inflation. The massive defect breaks the background homogeneity. We consider the limit that the physical Schwarzschild radius of the defect is much smaller than the inflationary Hubble radius so a perturbative analysis is allowed. The inhomogeneities induced in scalar and gravitational wave power spectrum are calculated. We obtain the amplitudes of dipole, quadrupole and octupole anisotropies in curvature perturbation power spectrum and identify the relative configuration of the defect to CMB sphere in which large observable dipole asymmetry can be generated. We observe a curious reflection symmetry in which the configuration where the defect is inside the CMB comoving sphere has the same inhomogeneous variance as its mirror configuration where the defect is outside the CMB sphere.

  18. Automatic classification of defects in weld pipe

    International Nuclear Information System (INIS)

    Anuar Mikdad Muad; Mohd Ashhar Khalid; Abdul Aziz Mohamad; Abu Bakar Mhd Ghazali; Abdul Razak Hamzah

    2001-01-01

    With the advancement of computer imaging technology, the image on hard radiographic film can be digitized and stored in a computer and the manual process of defect recognition and classification may be replaced by the computer. In this paper, a computerized method for automatic detection and classification of common defects in film radiography of weld pipe is described. The detection and classification processes consist of automatic selection of interest area on the image and then classify common defects using image processing and special algorithms. Analysis of the attributes of each defect such area, size, shape and orientation are carried out by the feature analysis process. These attributes reveal the type of each defect. These methods of defect classification result in high success rate. Our experience showed that sharp film images produced better results. (Author)

  19. Little string origin of surface defects

    Energy Technology Data Exchange (ETDEWEB)

    Haouzi, Nathan; Schmid, Christian [Center for Theoretical Physics, University of California, Berkeley,LeConte Hall, Berkeley (United States)

    2017-05-16

    We derive a large class of codimension-two defects of 4d N=4 Super Yang-Mills (SYM) theory from the (2,0) little string. The origin of the little string is type IIB theory compactified on an ADE singularity. The defects are D-branes wrapping the 2-cycles of the singularity. We use this construction to make contact with the description of SYM defects due to Gukov and Witten https://arxiv.org/abs/hep-th/0612073. Furthermore, we provide a geometric perspective on the nilpotent orbit classification of codimension-two defects, and the connection to ADE-type Toda CFT. The only data needed to specify the defects is a set of weights of the algebra obeying certain constraints, which we give explicitly. We highlight the differences between the defect classification in the little string theory and its (2,0) CFT limit.

  20. Agricultural Compounds in Water and Birth Defects.

    Science.gov (United States)

    Brender, Jean D; Weyer, Peter J

    2016-06-01

    Agricultural compounds have been detected in drinking water, some of which are teratogens in animal models. The most commonly detected agricultural compounds in drinking water include nitrate, atrazine, and desethylatrazine. Arsenic can also be an agricultural contaminant, although arsenic often originates from geologic sources. Nitrate has been the most studied agricultural compound in relation to prenatal exposure and birth defects. In several case-control studies published since 2000, women giving birth to babies with neural tube defects, oral clefts, and limb deficiencies were more likely than control mothers to be exposed to higher concentrations of drinking water nitrate during pregnancy. Higher concentrations of atrazine in drinking water have been associated with abdominal defects, gastroschisis, and other defects. Elevated arsenic in drinking water has also been associated with birth defects. Since these compounds often occur as mixtures, it is suggested that future research focus on the impact of mixtures, such as nitrate and atrazine, on birth defects.

  1. PISC II: Parametric studies. Summary of the PISC II Parametric studies on the Effect of defect Characteristics (EDC)

    International Nuclear Information System (INIS)

    Crutzen, S.; Murgatroyd, R.; Dombret, P.

    1989-09-01

    Studies on the effect of defect characteristics and selected inspection parameters on the detection and sizing of defects in ferritic steel blocks have been performed by: - United Kingdom Atomic Energy Authority (UKAEA, Risley and Harwell), - CISE, (Italy, Milan), - VINCOTTE (Belgium, Brussels), - CEC, JRC (Ispra Site; complementary measurements), as part of a larger Commission of the European Communities (CEC) programme in support to the PISC (Programme for the Inspection of Steel Components), jointly sponsored by OECD (Organization for Economic Coordination and Development) and CEC and operated by the Joint Research Centre (JRC), Ispra Establishment. The purpose of the programme was to acquire reliable experimental data that could be used both to explain results of the PISC I and II Round Robin Tests (RRT) and to test and validate theoretical models of the ultrasonic testing techniques. For these studies, eighteen test blocks were manufactured by JRC Ispra, Operating Agent and Reference Laboratory of PISC. A range of defect types was inserted with great care covering aspects such as defect shape, defect size, defect surface roughness, defect position in depth, defect orientation. Several of these blocks (defects) were selected by the participating institutions. Each of these participants applied well specified usual ultrasonic techniques: echo techniques, tandem technique, focusing probe technique at 45 0 and time of flight diffraction (TOFD). Results of such measurements propose clear correlation between defect characteristics and amplitude of response of these defects

  2. Coherent defects in superconducting circuits

    International Nuclear Information System (INIS)

    Mueller, Clemens

    2011-01-01

    The interaction of superconducting circuits with additional quantum systems is a topic that has found extensive study in the recent past. In the limit where the added system are incoherent, this is the standard field of decoherence and the system dynamics can be described by a simple master equation. In the other limit however, when the additional parts are coherent, the resulting time-evolution can become more complicated. In this thesis we have investigated the interaction of superconducting circuits with coherent and incoherent two-level defects. We have shown theoretical calculations characterizing this interaction for all relevant parameter regimes. In the weak coupling limit, the interaction can be described in an effective bath picture, where the TLS act as parts of a large, decohering environment. For strong coupling, however, the coherent dynamics of the full coupled system has to be considered. We show the calculations of the coupled time-evolution and again characterize the interaction by an effective decoherence rate. We also used experimental data to characterize the microscopic origin of the defects and the details of their interaction with the circuits. The results obtained by analyzing spectroscopic data allow us to place strong constraint on several microscopic models for the observed TLS. However, these calculations are not yet fully conclusive as to the physical nature of the TLS. We propose additional experiments to fully characterize the interaction part of the Hamiltonian, thus providing the answer to the question of the physical origin of the coupling. Additionally we have developed a method to directly drive individual defect states via virtual excitation of the qubit. This method allows one to directly probe the properties of single TLS and possibly make use of their superior coherence times for quantum information purposes. The last part of this thesis provided a way for a possible implementation of geometric quantum computation in

  3. A conceptual model for the fuel oxidation of defective fuel

    International Nuclear Information System (INIS)

    Higgs, J.D.; Lewis, B.J.; Thompson, W.T.; He, Z.

    2007-01-01

    A mechanistic conceptual model has been developed to predict the fuel oxidation behaviour in operating defective fuel elements for water-cooled nuclear reactors. This theoretical work accounts for gas-phase transport and sheath reactions in the fuel-to-sheath gap to determine the local oxygen potential. An improved thermodynamic analysis has also been incorporated into the model to describe the equilibrium state of the oxidized fuel. The fuel oxidation kinetics treatment accounts for multi-phase transport including normal diffusion and thermodiffusion for interstitial oxygen migration in the solid, as well as gas-phase transport in the fuel pellet cracks. The fuel oxidation treatment is further coupled to a heat conduction equation. A numerical solution of the coupled transport equations is obtained by a finite-element technique with the FEMLAB 3.1 software package. The model is able to provide radial-axial profiles of the oxygen-to-uranium ratio and the fuel temperatures as a function of time in the defective element for a wide range of element powers and defect sizes. The model results are assessed against coulometric titration measurements of the oxygen-to-metal profile for pellet samples taken from ten spent defective elements discharged from the National Research Universal Reactor at the Chalk River Laboratories and commercial reactors

  4. Enhanced defects recombination in ion irradiated SiC

    International Nuclear Information System (INIS)

    Izzo, G.; Litrico, G.; Grassia, F.; Calcagno, L.; Foti, G.

    2010-01-01

    Point defects induced in SiC by ion irradiation show a recombination at temperatures as low as 320 K and this process is enhanced after running current density ranging from 80 to 120 A/cm 2 . Ion irradiation induces in SiC the formation of different defect levels and low-temperature annealing changes their concentration. Some levels (S 0 , S x and S 2 ) show a recombination and simultaneously a new level (S 1 ) is formed. An enhanced recombination of defects is besides observed after running current in the diode at room temperature. The carriers introduction reduces the S 2 trap concentration, while the remaining levels are not modified. The recombination is negligible up to a current density of 50 A/cm 2 and increases at higher current density. The enhanced recombination of the S 2 trap occurs at 300 K, which otherwise requires a 400 K annealing temperature. The process can be related to the electron-hole recombination at the associated defect.

  5. Point defects and diffusion in alloys: correlation effects

    International Nuclear Information System (INIS)

    Barbe, Vincent

    2006-01-01

    Kinetic models in alloys aim at predicting the transport properties of a system starting from the microscopic jump frequencies of defects. Such properties are of prior importance in systems which stay out of equilibrium for a long time, as for example irradiated alloys in nuclear reactors. We hereby propose several developments of the recent self-consistent mean field (SCMF) kinetic theory, which deals particularly with the correlation effects due to the coupling of atomic and defect fluxes. They are taken into account through a non-equilibrium distribution function of the system, which is derived from the time evolution of small clusters (of two or more atoms or defects). We therefore introduce a set of 'dynamic' interactions called effective Hamiltonian. The SCMF theory is extended to treat high jump frequency ratios for the vacancy mechanism, as well as the transport through interstitial defects. We use in both cases an atomic model which accounts for the thermodynamic properties of the alloy, as e.g. the short-range order. Those models are eventually applied to predict the diffusion properties in two model alloys of nuclear interest: the concentrated Fe-Ni-Cr solid solution and the dilute Fe(P) alloy. We present adapted atomic models and compare our predictions to experimental data. (author)

  6. Defect formation in heavily doped Si upon irradiation

    International Nuclear Information System (INIS)

    Gubskaya, V.I.; Kuchinskii, P.V.; Lomako, V.M.

    1981-01-01

    The rates of the carrier removal and radiation defect introduction into n- and p-Si in the concentration range of 10 14 to 10 17 cm -3 upon 7-MeV-electron irradiation have been studied. The spectrum of the vacancy-type defects, defining the carrier removal rate in lightly doped crystals has been found. With doping level increase the carrier removal rate grows irrespective of conductivity type, and at n 0 , p 0 > 10 17 cm -3 is close to the total displacement number. At the same time a decrease in the introduction rate of the known vacancy-type defects is observed. x It is shown that a considerable growth of the carrier removal rate is defined neither by introduction of shallow compensating centers, nor by change in the primary defect charge state. It is suggested that at high doping impurity concentrations compensation in Si is due to the introduction of complexes doping impurity-interstitial or (impurity atom-interstitial) + vacancy, which give deep levels. (author)

  7. Effects of mass defect in atomic clocks

    Science.gov (United States)

    Taichenachev, A. V.; Yudin, V. I.

    2018-01-01

    We consider some implications of the mass defect on the frequency of atomic transitions. We have found that some well-known frequency shifts (such as gravitational and quadratic Doppler shifts) can be interpreted as consequences of the mass defect, i.e., without the need for the concept of time dilation used in special and general relativity theories. Moreover, we show that the inclusion of the mass defect leads to previously unknown shifts for clocks based on trapped ions..

  8. Phosphorous–vacancy–oxygen defects in silicon

    KAUST Repository

    Wang, Hao

    2013-07-30

    Electronic structure calculations employing the hybrid functional approach are used to gain fundamental insight in the interaction of phosphorous with oxygen interstitials and vacancies in silicon. It recently has been proposed, based on a binding energy analysis, that phosphorous–vacancy–oxygen defects may form. In the present study we investigate the stability of this defect as a function of the Fermi energy for the possible charge states. Spin polarization is found to be essential for the charge neutral defect.

  9. Research In Diagnosing Bearing Defects From Vibrations

    Science.gov (United States)

    Zoladz, T.; Earhart, E.; Fiorucci, T.

    1995-01-01

    Report describes research in bearing-defect signature analysis - use of vibration-signal analysis to diagnose defects in roller and ball bearings. Experiments performed on bearings in good condition and other bearings in which various parts scratched to provide known defects correlated with vibration signals. Experiments performed on highly instrumented motor-driven rotor assembly at speeds up to 10,050 r/min, using accelerometers, velocity probes, and proximity sensors mounted at various locations on assembly to measure vibrations.

  10. Thermophysical spectroscopy of defect states in silicon

    International Nuclear Information System (INIS)

    Igamberdyev, Kh.T.; Mamadalimov, A.T.; Khabibullaev, P.K.

    1989-01-01

    The present work deals with analyzing the possibilities of using the non-traditional thermophysical methods to study a defect structure in silicon. For this purpose, the temperature dependences of thermophysical properties of defect silicon are investigated. A number of new, earlier unknown physical phenomena in silicon are obtained, and their interpretation has enabled one to establish the main physical mechanisms of formation of deep defect states in silicon

  11. Range Selection and Median

    DEFF Research Database (Denmark)

    Jørgensen, Allan Grønlund; Larsen, Kasper Green

    2011-01-01

    and several natural special cases thereof. The rst special case is known as range median, which arises when k is xed to b(j 􀀀 i + 1)=2c. The second case, denoted prex selection, arises when i is xed to 0. Finally, we also consider the bounded rank prex selection problem and the xed rank range......Range selection is the problem of preprocessing an input array A of n unique integers, such that given a query (i; j; k), one can report the k'th smallest integer in the subarray A[i];A[i+1]; : : : ;A[j]. In this paper we consider static data structures in the word-RAM for range selection...... selection problem. In the former, data structures must support prex selection queries under the assumption that k for some value n given at construction time, while in the latter, data structures must support range selection queries where k is xed beforehand for all queries. We prove cell probe lower bounds...

  12. Renyi entropy and conformal defects

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, Lorenzo [Humboldt-Univ. Berlin (Germany). Inst. fuer Physik; Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik; Meineri, Marco [Scuola Normale Superiore, Pisa (Italy); Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Istituto Nazionale di Fisica Nucleare, Pisa (Italy); Myers, Robert C. [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Smolkin, Michael [California Univ., Berkely, CA (United States). Center for Theoretical Physics and Department of Physics

    2016-04-18

    We propose a field theoretic framework for calculating the dependence of Renyi entropies on the shape of the entangling surface in a conformal field theory. Our approach rests on regarding the corresponding twist operator as a conformal defect and in particular, we define the displacement operator which implements small local deformations of the entangling surface. We identify a simple constraint between the coefficient defining the two-point function of the displacement operator and the conformal weight of the twist operator, which consolidates a number of distinct conjectures on the shape dependence of the Renyi entropy. As an example, using this approach, we examine a conjecture regarding the universal coefficient associated with a conical singularity in the entangling surface for CFTs in any number of spacetime dimensions. We also provide a general formula for the second order variation of the Renyi entropy arising from small deformations of a spherical entangling surface, extending Mezei's results for the entanglement entropy.

  13. Universe as a topological defect

    International Nuclear Information System (INIS)

    Anabalon, Andres; Willison, Steven; Zanelli, Jorge

    2008-01-01

    Four-dimensional Einstein's general relativity is shown to arise from a gauge theory for the conformal group, SO(4,2). The theory is constructed from a topological dimensional reduction of the six-dimensional Euler density integrated over a manifold with a four-dimensional topological defect. The resulting action is a four-dimensional theory defined by a gauged Wess-Zumino-Witten term. An ansatz is found which reduces the full set of field equations to those of Einstein's general relativity. When the same ansatz is replaced in the action, the gauged WZW term reduces to the Einstein-Hilbert action. Furthermore, the unique coupling constant in the action can be shown to take integer values if the fields are allowed to be analytically continued to complex values

  14. Neural Tube Defects and Pregnancy

    Directory of Open Access Journals (Sweden)

    Emine Çoşar

    2009-09-01

    Full Text Available OBJECTIVE: Neural tube defects are congenital malformations those mostly causing life-long morbidities. They are prevented by the periconseptional folic acid usage and prenatal diagnostic methods. MATERIALS-METHODS: Pregnants from Afyonkarahisar and neighbourhood cities applied to our hospital and determined NTD, were investigated. RESULTS: In our obstetrics clinic 1403 delivery were made and 43 of them had fetus with NTD. Among these fetuses 41.3% had meningomyelocel, 17.4% had meningocel, 21.7% had encephalocel, 8.7% had unencephali and 4.3% had iniencephali. CONCLUSION: Incidence of NTD is high in our region and geographic region, nutrition and other socioeconomic factors may be related to the high incidence. Education of the mother and periconceptional folic acid usage may reduce teh incidence of NTD.

  15. Renyi entropy and conformal defects

    International Nuclear Information System (INIS)

    Bianchi, Lorenzo; Myers, Robert C.; Smolkin, Michael

    2016-01-01

    We propose a field theoretic framework for calculating the dependence of Renyi entropies on the shape of the entangling surface in a conformal field theory. Our approach rests on regarding the corresponding twist operator as a conformal defect and in particular, we define the displacement operator which implements small local deformations of the entangling surface. We identify a simple constraint between the coefficient defining the two-point function of the displacement operator and the conformal weight of the twist operator, which consolidates a number of distinct conjectures on the shape dependence of the Renyi entropy. As an example, using this approach, we examine a conjecture regarding the universal coefficient associated with a conical singularity in the entangling surface for CFTs in any number of spacetime dimensions. We also provide a general formula for the second order variation of the Renyi entropy arising from small deformations of a spherical entangling surface, extending Mezei's results for the entanglement entropy.

  16. Vacancy-type defects induced by grinding of Si wafers studied by monoenergetic positron beams

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Yoshihara, Nakaaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Mizushima, Yoriko [Devices and Materials Labs Fujitsu Laboratories Ltd., Atsugi, Kanagawa 243-0197 (Japan); ICE Cube Center, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Kim, Youngsuk [ICE Cube Center, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Disco Corporation, Ota, Tokyo 143-8580 (Japan); Nakamura, Tomoji [Devices and Materials Labs Fujitsu Laboratories Ltd., Atsugi, Kanagawa 243-0197 (Japan); Ohba, Takayuki [ICE Cube Center, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Oshima, Nagayasu; Suzuki, Ryoichi [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2014-10-07

    Vacancy-type defects introduced by the grinding of Czochralski-grown Si wafers were studied using monoenergetic positron beams. Measurements of Doppler broadening spectra of the annihilation radiation and the lifetime spectra of positrons showed that vacancy-type defects were introduced in the surface region (<98 nm), and the major defect species were identified as (i) relatively small vacancies incorporated in dislocations and (ii) large vacancy clusters. Annealing experiments showed that the defect concentration decreased with increasing annealing temperature in the range between 100 and 500°C. After 600–700°C annealing, the defect-rich region expanded up to about 170 nm, which was attributed to rearrangements of dislocation networks, and a resultant emission of point defects toward the inside of the sample. Above 800°C, the stability limit of those vacancies was reached and they started to disappear. After the vacancies were annealed out (900°C), oxygen-related defects were the major point defects and they were located at <25 nm.

  17. Paternal occupation and birth defects: findings from the National Birth Defects Prevention Study.

    NARCIS (Netherlands)

    Desrosiers, T.A.; Herring, A.H.; Shapira, S.K.; Hooiveld, M.; Luben, T.J.; Herdt-Losavio, M.L.; Lin, S.; Olshan, A.F.

    2012-01-01

    Objectives: Several epidemiological studies have suggested that certain paternal occupations may be associated with an increased prevalence of birth defects in offspring. Using data from the National Birth Defects Prevention Study, the authors investigated the association between paternal occupation

  18. Defining defect specifications to optimize photomask production and requalification

    Science.gov (United States)

    Fiekowsky, Peter

    2006-10-01

    Reducing defect repairs and accelerating defect analysis is becoming more important as the total cost of defect repairs on advanced masks increases. Photomask defect specs based on printability, as measured on AIMS microscopes has been used for years, but the fundamental defect spec is still the defect size, as measured on the photomask, requiring the repair of many unprintable defects. ADAS, the Automated Defect Analysis System from AVI is now available in most advanced mask shops. It makes the use of pure printability specs, or "Optimal Defect Specs" practical. This software uses advanced algorithms to eliminate false defects caused by approximations in the inspection algorithm, classify each defect, simulate each defect and disposition each defect based on its printability and location. This paper defines "optimal defect specs", explains why they are now practical and economic, gives a method of determining them and provides accuracy data.

  19. Online Sorted Range Reporting

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Fagerberg, Rolf; Greve, Mark

    2009-01-01

    is motivated by (and is a generalization of) a problem with applications in search engines: On a tree where leaves have associated rank values, report the highest ranked leaves in a given subtree. Finally, the problem studied generalizes the classic range minimum query (RMQ) problem on arrays....

  20. Substring Range Reporting

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li

    2014-01-01

    We revisit various string indexing problems with range reporting features, namely, position-restricted substring searching, indexing substrings with gaps, and indexing substrings with intervals. We obtain the following main results. We give efficient reductions for each of the above problems...

  1. Substring Range Reporting

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li

    2011-01-01

    We revisit various string indexing problems with range reporting features, namely, position-restricted substring searching, indexing substrings with gaps, and indexing substrings with intervals. We obtain the following main results. – We give efficient reductions for each of the above problems...

  2. Range-clustering queries

    NARCIS (Netherlands)

    Abrahamsen, M.; de Berg, M.T.; Buchin, K.A.; Mehr, M.; Mehrabi, A.D.

    2017-01-01

    In a geometric k -clustering problem the goal is to partition a set of points in R d into k subsets such that a certain cost function of the clustering is minimized. We present data structures for orthogonal range-clustering queries on a point set S : given a query box Q and an integer k>2 , compute

  3. Maxillectomy defects - to reconstruct or not? Pilot survey of Nigerian oral and maxillofacial surgeons

    Directory of Open Access Journals (Sweden)

    Abdurrazaq Olanrewaju Taiwo

    2017-01-01

    Full Text Available Background: The choice of reconstruction options for maxillectomy defects varies significantly. Factors affecting it range from the type of defect to the surgeon's expertise. This study aims to evaluate the practice of Nigerian Oral and Maxillofacial surgeons in the reconstruction of post-maxillectomy defects. Materials and Methods: The survey was conducted by use of questionnaires administered at the annual scientific meeting of the oral and maxillofacial surgeons of Nigeria in Ibadan 2012. Results: A response rate of 66.7% was achieved. All of our respondents are consultant oral and maxillofacial surgeons, 80% of whom practice in a teaching hospital. All but one of them perform maxillectomies, however only 25% of them offer surgical reconstruction of the resulting defects to patients. Flaps have been used by 25% of the respondents, while none of them has employed microvascular reconstruction. Prosthetic rehabilitation of patients is pervasive among the respondents. Conclusion: Maxillectomy defects have far-reaching consequences on patients' quality of life and attempts should be made to reconstruct such defects. Although maxillectomy is a commonly performed procedure among oral and maxillofacial surgeons in Nigeria, especially for malignancies of the oral and paranasal sinuses, surgical reconstruction of resulting defects is not so frequently done. Microvascular surgery, which is becoming a frequently utilized option among surgeons in developed nations, is still infrequently used in our environment. There is a need for oral and maxillofacial surgeons in our climes to improve their skills so as to increase the range of reconstructive options offered.

  4. Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide.

    Science.gov (United States)

    Sun, Xiaoli; Wang, Zhiguo; Fu, Y Q

    2015-12-22

    Monolayer Molybdenum Disulfide (MoS2) is a promising anode material for lithium ion batteries because of its high capacities. In this work, first principle calculations based on spin density functional theory were performed to investigate adsorption and diffusion of lithium on monolayer MoS2 with defects, such as single- and few-atom vacancies, antisite, and grain boundary. The values of adsorption energies on the monolayer MoS2 with the defects were increased compared to those on the pristine MoS2. The presence of defects causes that the Li is strongly bound to the monolayer MoS2 with adsorption energies in the range between 2.81 and 3.80 eV. The donation of Li 2s electron to the defects causes an enhancement of adsorption of Li on the monolayer MoS2. At the same time, the presence of defects does not apparently affect the diffusion of Li, and the energy barriers are in the range of 0.25-0.42 eV. The presence of the defects can enhance the energy storage capacity, suggesting that the monolayer MoS2 with defects is a suitable anode material for the Li-ion batteries.

  5. Modeling the relationships among internal defect features and external Appalachian hardwood log defect indicators

    Science.gov (United States)

    R. Edward. Thomas

    2009-01-01

    As a hardwood tree grows and develops, surface defects such as branch stubs and wounds are overgrown. Evidence of these defects remain on the log surface for decades and in many instances for the life of the tree. As the tree grows the defect is encapsulated or grown over by new wood. During this process the appearance of the defect in the tree's bark changes. The...

  6. Annealing of radiation-induced defects in silicon in a simplified phenomenological model

    International Nuclear Information System (INIS)

    Lazanu, S.; Lazanu, I.

    2001-01-01

    The concentration of primary radiation-induced defects has been previously estimated considering both the explicit mechanisms of the primary interaction between the incoming particle and the nuclei of the semiconductor lattice, and the recoil energy partition between ionisation and displacements, in the frame of the Lindhard theory. The primary displacement defects are vacancies and interstitials that are essentially unstable in silicon. They interact via migration, recombination, annihilation or produce other defects. In the present work, the time evolution of the concentration of defects induced by pions in medium and high resistivity silicon for detectors is modelled, after irradiation. In some approximations, the differential equations representing the time evolution processes could be decoupled. The theoretical equations so obtained are solved analytically in some particular cases, with one free parameter, for a wide range of particle fluences and/or for a wide energy range of incident particles, for different temperatures; the corresponding stationary solutions are also presented

  7. Lattice defects in ion-implanted aluminium studied by means of perturbed angular correlations. Pt. 1

    International Nuclear Information System (INIS)

    Pleiter, F.; Prasad, K.G.

    1984-01-01

    Migration and clustering of lattice defects after implantation of 111 In in Al and subsequent annealing at temperatures in the range from 80 to 800 K were investigated applying the DPAC technique. The effects of implantation dose, implantation temperature, laser irradiation, and plastic deformation were studied. The measurements on plastically deformed Al were complemented by positron lifetime measurements. Four In-defect clusters were observed that can be flagged by well-defined hyperfine interaction parameters, and their symmetry properties were determined by using single-crystal samples. Important conclusions are: (i) monovacancies are not trapped by In-atoms, (ii) small In-defect clusters are formed by direct trapping of divacancies and/or trivacancies, and (iii) extended In-defect clusters are very stable and anneal in the temperature range 600-700 K. Consequences for the interpretation of other measurements on dilute Al(In) alloys are discussed. (Auth.)

  8. CoFFEE: Corrections For Formation Energy and Eigenvalues for charged defect simulations

    Science.gov (United States)

    Naik, Mit H.; Jain, Manish

    2018-05-01

    Charged point defects in materials are widely studied using Density Functional Theory (DFT) packages with periodic boundary conditions. The formation energy and defect level computed from these simulations need to be corrected to remove the contributions from the spurious long-range interaction between the defect and its periodic images. To this effect, the CoFFEE code implements the Freysoldt-Neugebauer-Van de Walle (FNV) correction scheme. The corrections can be applied to charged defects in a complete range of material shapes and size: bulk, slab (or two-dimensional), wires and nanoribbons. The code is written in Python and features MPI parallelization and optimizations using the Cython package for slow steps.

  9. Precise design-based defect characterization and root cause analysis

    Science.gov (United States)

    Xie, Qian; Venkatachalam, Panneerselvam; Lee, Julie; Chen, Zhijin; Zafar, Khurram

    2017-03-01

    that human operators will typically miss), to obtain the exact defect location on design, to compare all defective patterns thus detected against a library of known patterns, and to classify all defective patterns as either new or known. By applying the computer to these tasks, we automate the entire process from defective pattern identification to pattern classification with high precision, and we perform this operation en masse during R & D, ramp, and volume production. By adopting the methodology, whenever a specific weak pattern is identified, we are able to run a series of characterization operations to ultimately arrive at the root cause. These characterization operations can include (a) searching all pre-existing Review SEM images for the presence of the specific weak pattern to determine whether there is any spatial (within die or within wafer) or temporal (within any particular date range, before or after a mask revision, etc.) correlation and (b) understanding the failure rate of the specific weak pattern to prioritize the urgency of the problem, (c) comparing the weak pattern against an OPC (Optical Procimity Correction) Verification report or a PWQ (Process Window Qualification)/FEM (Focus Exposure Matrix) result to assess the likelihood of it being a litho-sensitive pattern, etc. After resolving the specific weak pattern, we will categorize it as known pattern, and the engineer will move forward with discovering new weak patterns.

  10. Acoustic emission test on a 25mm thick mild steel pressure vessel with inserted defects

    International Nuclear Information System (INIS)

    Bentley, P.G.; Dawson, D.G.; Hanley, D.J.; Kirby, N.

    1976-12-01

    Acoustic emission measurements have been taken on an experimental mild steel vessel with 4 inserted defects ranging in severity up to 90% of through thickness. The vessel was subjected to a series of pressure excursions of increasing magnitude until failure occurred by extension of the largest inserted defect through the vessel wall. No acoustic emission was detected throughout any part of the tests which would indicate the presence of such serious defects or of impending failure. Measurements of acoustic emission from metallurgical specimens are included and the results of post test inspection using conventional NDT and metallographic techniques are reported. (author)

  11. A Novel Method for Surface Defect Detection of Photovoltaic Module Based on Independent Component Analysis

    Directory of Open Access Journals (Sweden)

    Xuewu Zhang

    2013-01-01

    Full Text Available This paper proposed a new method for surface defect detection of photovoltaic module based on independent component analysis (ICA reconstruction algorithm. Firstly, a faultless image is used as the training image. The demixing matrix and corresponding ICs are obtained by applying the ICA in the training image. Then we reorder the ICs according to the range values and reform the de-mixing matrix. Then the reformed de-mixing matrix is used to reconstruct the defect image. The resulting image can remove the background structures and enhance the local anomalies. Experimental results have shown that the proposed method can effectively detect the presence of defects in periodically patterned surfaces.

  12. Defect-band mediated ferromagnetism in Gd-doped ZnO thin films

    KAUST Repository

    Venkatesh, S.

    2015-01-07

    Gd-doped ZnO thin films prepared by pulsed laser deposition with Gd concentrations varying from 0.02–0.45 atomic percent (at. %) showed deposition oxygen pressure controlled ferromagnetism. Thin films prepared with Gd dopant levels (defect band formed due to oxygen deficiency related defect complexes. Mott\\'s theory of variable range of hopping conduction confirms the formation of the impurity/defect band near the Fermi level.

  13. Repair of tetralogy of Fallot associated with atrioventricular septal defect.

    Science.gov (United States)

    Tláskal, T; Hucín, B; Kostelka, M; Chaloupecký, V; Marek, J; Tax, P; Janouàek, J; Kuèera, V; Hruda, J; Reich, O; Skovránek, J

    1998-01-01

    Tetralogy of Fallot, when associated with atrioventricular septal defect permitting shunting at ventricular level, represents a complex cyanotic congenital malformation. Experience with surgical repair is limited, and results vary considerably. Between 1984 and 1996, we repaired 14 consecutive patients with this combination seen in our center. Their ages ranged from 8 months to 21 years (median 7.4 years). Six (42.9%) had Down's syndrome. In eight patients the correct diagnosis was made using echocardiography alone. In the remaining six patients, who had previously-constructed arterial shunts and/or suspected pulmonary arterial stenosis, catheterization and angiocardiography were also performed. The repair consisted of double patch closure of the septal defect, reconstruction of two atrioventricular orifices, and relief of pulmonary stenosis at all levels. In five patients with a hypoplastic pulmonary trunk, a monocusp transannular patch (four patients) or an allograft (one patient) was used for restoration of continuity from the right ventricle to the pulmonary arteries. Patch enlargement of one or both pulmonary arteries was necessary in five patients. One patient (7.1%) died early, and another late. The twelve surviving (85.8%) patients have been followed for 1.2-12.5 years after surgery (median 4.9 years, mean 5.9+/-3.9 years). During the follow-up, reoperation was necessary for repair of residual ventricular septal defect and pulmonary regurgitation in two patients, and closure of an atrial septal defect and alteration to left atrioventricular valvar regurgitation in one patient. Seven patients are in class I of the New York Heart Association, four in class II, and one in class III. Tetralogy of Fallot associated with atrioventricular septal defect can be corrected with low mortality and good long-term results. Residual lesions, however, have a tendency to progress, especially when seen in combination. After surgery, all patients need long-term close follow-up.

  14. Congenital heart defects in molecularly proven Kabuki syndrome patients.

    Science.gov (United States)

    Digilio, Maria Cristina; Gnazzo, Maria; Lepri, Francesca; Dentici, Maria Lisa; Pisaneschi, Elisa; Baban, Anwar; Passarelli, Chiara; Capolino, Rossella; Angioni, Adriano; Novelli, Antonio; Marino, Bruno; Dallapiccola, Bruno

    2017-11-01

    The prevalence of congenital heart defects (CHD) in Kabuki syndrome ranges from 28% to 80%. Between January 2012 and December 2015, 28 patients had a molecularly proven diagnosis of Kabuki syndrome. Pathogenic variants in KMT2D (MLL2) were detected in 27 patients, and in KDM6A gene in one. CHD was diagnosed in 19/27 (70%) patients with KMT2D (MLL2) variant, while the single patient with KDM6A change had a normal heart. The anatomic types among patients with CHD included aortic coarctation (4/19 = 21%) alone or associated with an additional CHD, bicuspid aortic valve (4/19 = 21%) alone or associated with an additional CHD, perimembranous subaortic ventricular septal defect (3/19 = 16%), atrial septal defect ostium secundum type (3/19 = 16%), conotruncal heart defects (3/19 = 16%). Additional CHDs diagnosed in single patients included aortic dilatation with mitral anomaly and hypoplastic left heart syndrome. We also reviewed CHDs in patients with a molecular diagnosis of Kabuki syndrome reported in the literature. In conclusion, a CHD is detected in 70% of patients with KMT2D (MLL2) pathogenic variants, most commonly left-sided obstructive lesions, including multiple left-sided obstructions similar to those observed in the spectrum of the Shone complex, and septal defects. Clinical management of Kabuki syndrome should include echocardiogram at the time of diagnosis, with particular attention to left-sided obstructive lesions and mitral anomalies, and annual monitoring for aortic arch dilatation. © 2017 Wiley Periodicals, Inc.

  15. Extended Range Intercept Technology

    Science.gov (United States)

    1991-09-01

    1988). Desert bighorn ewes with lambs show a stronger response than do groups of only rams, only ewes, or mixed groups of adults (Miller and Smith...1985). While all startle events may affect desert bighorns, those occurring during the lambing period (February-April) would represent the highest...35807 U.S. Army Pueblo Depot Activity SDSTE-PU-EE Pueblo, CO 81001-5000 U.S. Army White Sands Missile Range STEWS -EL-N White Sands, NM 88002-5076

  16. ORANGE: RANGE OF BENEFITS

    OpenAIRE

    Parle Milind; Chaturvedi Dev

    2012-01-01

    No wonder that oranges are one of the most popular fruits in the world. Orange (citrus sinensis) is well known for its nutritional and medicinal properties throughout the world. From times immemorial, whole Orange plant including ripe and unripe fruits, juice, orange peels, leaves and flowers are used as a traditional medicine. Citrus sinensis belongs to the family Rutaceae. The fruit is a fleshy, indehiscent, berry that ranges widely in size from 4 cm to 12 cm. The major medicinal proper...

  17. Failures and Defects in the Building Process

    DEFF Research Database (Denmark)

    Jørgensen, Kirsten

    2009-01-01

    Function failures, defects, mistakes and poor communication are major problems for the construction sector. As the empirical element in the research, a large construction site was observed from the very start to the very end and all failures and defects of a certain size were recorded and analysed...

  18. Treatment of osteochondral defects of the talus

    NARCIS (Netherlands)

    van Bergen, C. J. A.; de Leeuw, P. A. J.; van Dijk, C. N.

    2008-01-01

    This review article provides a current concepts overview of osteochondral defects of the talus, with special emphasis on treatment options, their indications and future developments. Osteochondral defects of the talar dome are mostly caused by a traumatic event. They may lead to deep ankle pain on

  19. Indicators for Building Process without Final Defects -

    DEFF Research Database (Denmark)

    Jørgensen, Kirsten; Rasmussen, Grane Mikael Gregaard; Thuesen, Christian Langhoff

    2011-01-01

    This article introduces the preliminary data analysis, as well as the underlying theories and methods for identifying the indicators for building process without final defects. Since 2004, the Benchmark Centre for the Danish Construction Sector (BEC) has collected information about legal defects...

  20. Positron analysis of defects in metals

    NARCIS (Netherlands)

    van Veen, A.; Kruseman, A.C.; Schut, H.; Mijnarends, P.E.; Kooi, B.J.; de Hosson, J.T.M.; Jean, YC; Eldrup, M; Schrader, DM; West, RN

    1997-01-01

    New methods are discussed to improve defect analysis. The first method employs mapping of two shape parameters, S and W, of the positron annihilation photopeak. It is demonstrated that the combined use of S and W allows to a better discrimination of defects. The other method is based on background

  1. Defect structure of electrodeposited chromium layers

    International Nuclear Information System (INIS)

    Marek, T.; Suevegh, K.; Vertes, A.; El-Sharif, M.; McDougall, J.; Chisolm, C.U.

    2000-01-01

    Positron annihilation spectroscopy was applied to study the effects of pre-treatment and composition of substrates on the quality and defect structure of electrodeposited thick chromium coatings. The results show that both parameters are important, and a scenario is proposed why the mechanically polished substrate gives more defective film than the electro polished one.

  2. Defect structure of electrodeposited chromium layers

    Energy Technology Data Exchange (ETDEWEB)

    Marek, T. E-mail: marek@para.chem.elte.hu; Suevegh, K.; Vertes, A.; El-Sharif, M.; McDougall, J.; Chisolm, C.U

    2000-06-01

    Positron annihilation spectroscopy was applied to study the effects of pre-treatment and composition of substrates on the quality and defect structure of electrodeposited thick chromium coatings. The results show that both parameters are important, and a scenario is proposed why the mechanically polished substrate gives more defective film than the electro polished one.

  3. Birth defects in children with newborn encephalopathy

    NARCIS (Netherlands)

    Felix, JF; Badawi, N; Kurinczuk, JJ; Bower, C; Keogh, JM; Pemberton, PJ

    2000-01-01

    This study was designed to investigate birth defects found in association with newborn encephalopathy. All possible birth defects were ascertained in a population-based study of 276 term infants with moderate or severe encephalopathy and 564 unmatched term control infants. A strong association

  4. Iodide-trapping defect of the thyroid

    International Nuclear Information System (INIS)

    Pannall, P.R.; Steyn, A.F.; Van Reenen, O.

    1978-01-01

    We describe a grossly hypothyroid 50-year-old woman, mentally retarded since birth. On the basis of her history of recurrent goitre, absence of 131 I neck uptake and a low saliva/plasma 131 I ratio, congenital hypothyroidism due to a defect of the iodide-trapping mechanism was diagnosed. Other family members studied did not have the defect

  5. Impurity Role In Mechanically Induced Defects

    International Nuclear Information System (INIS)

    Howell, R.H.; Asoka-Kumar, P.; Hartley, J.; Sterne, P.

    2000-01-01

    An improved understanding of dislocation dynamics and interactions is an outstanding problem in the multi scale modeling of materials properties, and is the current focus of major theoretical efforts world wide. We have developed experimental and theoretical tools that will enable us to measure and calculate quantities defined by the defect structure. Unique to the measurements is a new spectroscopy that determines the detailed elemental composition at the defect site. The measurements are based on positron annihilation spectroscopy performed with a 3 MeV positron beam [1]. Positron annihilation spectroscopy is highly sensitive to dislocations and associated defects and can provide unique elements of the defect size and structure. Performing this spectroscopy with a highly penetrating positron beam enables flexibility in sample handling. Experiments on fatigued and stressed samples have been done and in situ measurement capabilities have been developed. We have recently performed significant upgrades to the accelerator operation and novel new experiments have been performed [2-4] To relate the spectrographic results and the detailed structure of a defect requires detailed calculations. Measurements are coupled with calculated results based on a description of positions of atoms at the defect. This gives an atomistic view of dislocations and associated defects including impurity interactions. Our ability to probe impurity interactions is a unique contribution to defect understanding not easily addressed by other atomistic spectroscopies

  6. A study of point defects in UO 2+x and their impact upon fuel properties

    OpenAIRE

    Ma , Yue

    2017-01-01

    Uranium dioxide is an oxygen excess, non-stoichiometric, fluorite material which exists over a wide range of compositions. At temperatures and oxygen activities that are relevant to its in-reactor behaviour, it has been reported that various types of point defects and clusters thereof may exist with different charge states and different compositions on both the anion and cation sublattices. These defects have a major influence on certain key engineering properties such as cation self -diffusi...

  7. Range Flight Safety Requirements

    Science.gov (United States)

    Loftin, Charles E.; Hudson, Sandra M.

    2018-01-01

    The purpose of this NASA Technical Standard is to provide the technical requirements for the NPR 8715.5, Range Flight Safety Program, in regards to protection of the public, the NASA workforce, and property as it pertains to risk analysis, Flight Safety Systems (FSS), and range flight operations. This standard is approved for use by NASA Headquarters and NASA Centers, including Component Facilities and Technical and Service Support Centers, and may be cited in contract, program, and other Agency documents as a technical requirement. This standard may also apply to the Jet Propulsion Laboratory or to other contractors, grant recipients, or parties to agreements to the extent specified or referenced in their contracts, grants, or agreements, when these organizations conduct or participate in missions that involve range flight operations as defined by NPR 8715.5.1.2.2 In this standard, all mandatory actions (i.e., requirements) are denoted by statements containing the term “shall.”1.3 TailoringTailoring of this standard for application to a specific program or project shall be formally documented as part of program or project requirements and approved by the responsible Technical Authority in accordance with NPR 8715.3, NASA General Safety Program Requirements.

  8. Long-range spin wave mediated control of defect qubits in nanodiamonds

    Energy Technology Data Exchange (ETDEWEB)

    Andrich, Paolo; de las Casas, Charles F.; Liu, Xiaoying; Bretscher, Hope L.; Berman, Jonson R.; Heremans, F. Joseph; Nealey, Paul F.; Awschalom, David D.

    2017-07-17

    Hybrid architectures that combine nitrogen-vacancy (NV) centers in diamond with other materials and physical systems have been proposed to enhance the NV center’s capabilities in many quantum sensing and information applications. In particular, spin waves (SWs) in ferromagnetic materials are a promising candidate to implement these platforms due to their strong magnetic fields, which could be used to efficiently interact with the NV centers. Here we develop an yttrium iron garnet-nanodiamond hybrid architecture constructed with the help of directed assembly and transfer printing techniques. Operating at ambient conditions, we demonstrate that surface confined SWs excited in the ferromagnet (FM) can strongly amplify the interactions between a microwave source and the NV centers by enhancing the local microwave magnetic field by several orders of magnitude. Crucially, we show the existence of a regime in which coherent interactions between SWs and NV centers dominate over incoherent mechanisms associated with the broadband magnetic field noise generated by the FM. These accomplishments enable the SW mediated coherent control of spin qubits over distances larger than 200 um, and allow low power operations for future spintronic technologies.

  9. Luminescent diagnostics of skin defects in the near-infrared range

    Science.gov (United States)

    Alekseev, Yuriy V.; Rumyantseva, Valentina D.; Gorshkova, Anastasiya S.; Shchelkunova, Anastasiya E.; Shilov, Igor P.; Ivanov, Andrey V.

    2017-09-01

    Photodynamic therapy becomes a widely spread method due to cancer growth in the world. However, to detect tumors at early stages, it is necessary to carry out diagnostic measures in a timely manner. Our aim was to test the developed pharmaceutical composition, which can be used for external application in early fluorescent diagnostics even in the absence of visual changes, as well as for therapy effectiveness control. Pharmacokinetic studies on laboratory animals and volunteers were carried out. The results have shown that the dipotassium salt of Yb3+-dimethoxyhematoporphyrin IX, which is highly soluble in water and stable in storage, is a promising marker for earlier diagnostics of tumors and can be used in dermatology, dentistry, gynecology, cosmetology, ear, nose, and throat diseases, veterinary, and in other areas of medicine.

  10. The effect of magnetic field on bistability in 1D photonic crystal doped by magnetized plasma and coupled nonlinear defects

    International Nuclear Information System (INIS)

    Mehdian, H.; Mohammadzahery, Z.; Hasanbeigi, A.

    2014-01-01

    In this work, we study the defect mode and bistability behavior of 1-D photonic band gap structure with magnetized plasma and coupled nonlinear defects. The transfer matrix method has been employed to investigate the magnetic field effect on defect mode frequency and bistability threshold. The obtained results show that the frequency of defect mode and bistability threshold can be altered, without changing the structure of the photonic multilayer. Therefore, the bistability behavior of the subjected structure in the presence of magnetized plasma can be utilized in manufacturing wide frequency range devices

  11. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Rasmussen, Filip Anselm; Kuhar, Korina

    2016-01-01

    Localized electronic states formed inside the band gap of a semiconductor due to crystal defects can be detrimental to the material's optoelectronic properties. Semiconductors with a lower tendency to form defect induced deep gap states are termed defect-tolerant. Here we provide a systematic first...... the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within......-principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only...

  12. Teratology: from science to birth defects prevention.

    Science.gov (United States)

    Rasmussen, Sonja A; Erickson, J David; Reef, Susan E; Ross, Danielle S

    2009-01-01

    One of the goals of birth defects research is to better understand risk or preventive factors for birth defects so that strategies for prevention can be developed. In this article, we have selected four areas of birth defects research that have led to the development of prevention strategies. These areas include rubella virus as a cause of congenital rubella syndrome, folic acid as a preventive factor for neural tube defects, cytomegalovirus infection as a cause of birth defects and developmental disabilities, and alcohol as a cause of fetal alcohol spectrum disorders. For each of these areas, we review key clinical and research findings that led to the identification of the risk or preventive factor, milestones in the development of prevention strategies, and the progress made thus far toward prevention.

  13. Defective Reduction in Frozen Pie Manufacturing Process

    Science.gov (United States)

    Nooted, Oranuch; Tangjitsitcharoen, Somkiat

    2017-06-01

    The frozen pie production has a lot of defects resulting in high production cost. Failure mode and effect analysis (FMEA) technique has been applied to improve the frozen pie process. Pareto chart is also used to determine the major defects of frozen pie. There are 3 main processes that cause the defects which are the 1st freezing to glazing process, the forming process, and the folding process. The Risk Priority Number (RPN) obtained from FMEA is analyzed to reduce the defects. If RPN of each cause exceeds 45, the process will be considered to be improved and selected for the corrective and preventive actions. The results showed that RPN values decreased after the correction. Therefore, the implementation of FMEA technique can help to improve the performance of frozen pie process and reduce the defects approximately 51.9%.

  14. Defect accumulation under cascade damage conditions

    DEFF Research Database (Denmark)

    Trinkaus, H.; Singh, B.N.; Woo, C.H.

    1994-01-01

    in terms of this reaction kinetics taking into account cluster production, dissociation, migration and annihilation at extended sinks. Microstructural features which are characteristic of cascade damage and cannot be explained in terms of the conventional single defect reaction kinetics are emphasized......There is now ample evidence from both experimental and computer simulation studies that in displacement cascades not only intense recombination takes place but also efficient clustering of both self-interstitial atoms (SIAs) and vacancies. The size distributions of the two types of defects produced...... reactions kinetics associated with the specific features of cascade damage is described, with emphasis on asymmetries between SIA and vacancy type defects concerning their production, stability, mobility and interactions with other defects. Defect accumulation under cascade damage conditions is discussed...

  15. Defect pin behaviour in the DFR

    International Nuclear Information System (INIS)

    Sloss, W.M.; Bagley, K.Q.; Edmonds, E.; Potter, P.E.

    1979-01-01

    A program of defective fuel pin irradiations has been carried out in the DFR. This program employed fuel pins which had failed during previous irradiations (natural defects) and pins in which simulated failures (artificial defects) had been induced prior to irradiation or during an intermediate examination stage at moderate or substantial burnups. The artificial defects simulated longitudinal ruptures and were normally located at positions near the top, middle and bottom of the pin where clad temperatures were 450, 540 and 630 0 C respectively. The fuel was mixed U-Pu oxide, and fuel form, stoichiometry, clad type, pin diameter, linear rating, and burnup were among the variables examined. The defect pin tests were normally carried out in single pin or trefoil type vehicles. After irradiation all the pins were subjected to the normal nondestructive examination procedures and the visual, radiographic, gamma-scanning, and dimensional change results are presented. Several pins were destructively examined and the metallographic data are discussed

  16. Tritium releases, birth defects and infant deaths

    International Nuclear Information System (INIS)

    1991-01-01

    The AECB has published a report 'Tritium releases from the Pickering Nuclear Generating Station and Birth Defects and Infant Mortality in Nearby Communities 1971-1988' (report number INFO-0401). This presents the results of a detailed analysis of deaths and birth defects occurring in infants born to mothers living in the area (25 Km radius) of the Pickering nuclear power plant, over an 18-year period. The analysis looked at the frequency of these defects and deaths in comparison to the general rate for Ontario, and also in relation to airborne and waterborne releases of tritium from the power plant. The overall conclusion was that the rates of infant death and birth defects were generally not higher in the study population than in all of Ontario. There was no prevalent relationship between these deaths and defects and tritium releases measured either at the power plant or by ground monitoring stations t some distance from the facility

  17. Is Women's Multivitamin Consumption Reasoned, Planned, or Socially Cognitive? A Test of Three Social Influence Models

    OpenAIRE

    Lindsey, Lisa L. Massi; Kopfman, Jennifer E.; Prue, Christine E.

    2008-01-01

    Neural tube defects (NTDs) are serious birth defects that affect approximately 3,000 pregnancies in the United States each year. Consuming the B vitamin folic acid can reduce the incidence of NTDs 50%–70%, and recent efforts to reduce NTD rates have focused on increasing the number of childbearing-aged women who take a vitamin containing folic acid every day. Future declines in NTDs must come from creative and compelling education and communication campaigns that will inc...

  18. Magnetic resonance of native defects of spin-Peierls magnetics CuGeO3

    International Nuclear Information System (INIS)

    Smirnov, A.I.; Glazkov, V.N.; Leonyuk, L.I.; Vetkin, A.G.; Eremina, R.M.

    1998-01-01

    Magnetic resonance within 9-75 GHz frequency range and 1.2-25 K temperature range was studied in pure monocrystalline spin-Peierls CuGwO 3 . Splitting of the magnetic resonance line is observed within temperature range below 5 K. Analysis of magnetic resonance spectra at various directions of magnetic field and under various temperatures enables to set off EPR-signals of spin-Peierls phase defects with S=1/2 and defects with S=1 from these components; g-factor corresponding to these EPR signals is similar one and close to values typical for Cu 2+ ion [ru

  19. Carbon related defects in irradiated silicon revisited

    KAUST Repository

    Wang, H.

    2014-05-09

    Electronic structure calculations employing hybrid functionals are used to gain insight into the interaction of carbon (C) atoms, oxygen (O) interstitials, and self-interstitials in silicon (Si). We calculate the formation energies of the C related defects Ci (SiI), Ci O i, Ci Cs, and Ci Oi (SiI) with respect to the Fermi energy for all possible charge states. The Ci (SiL) 2+ state dominates in almost the whole Fermi energy range. The unpaired electron in the Ci O i + state is mainly localized on the C interstitial so that spin polarization is able to lower the total energy. The three known atomic configurations of the Ci Cs pair are reproduced and it is demonstrated that hybrid functionals yield an improved energetic order for both the A and B-types as compared to previous theoretical studies. Different structures of the Ci Oi (SiL) cluster result for positive charge states in dramatically distinct electronic states around the Fermi energy and formation energies.

  20. Carbon related defects in irradiated silicon revisited

    KAUST Repository

    Wang, H.; Chroneos, A.; Londos, C.A.; Sgourou, E.N.; Schwingenschlö gl, Udo

    2014-01-01

    Electronic structure calculations employing hybrid functionals are used to gain insight into the interaction of carbon (C) atoms, oxygen (O) interstitials, and self-interstitials in silicon (Si). We calculate the formation energies of the C related defects Ci (SiI), Ci O i, Ci Cs, and Ci Oi (SiI) with respect to the Fermi energy for all possible charge states. The Ci (SiL) 2+ state dominates in almost the whole Fermi energy range. The unpaired electron in the Ci O i + state is mainly localized on the C interstitial so that spin polarization is able to lower the total energy. The three known atomic configurations of the Ci Cs pair are reproduced and it is demonstrated that hybrid functionals yield an improved energetic order for both the A and B-types as compared to previous theoretical studies. Different structures of the Ci Oi (SiL) cluster result for positive charge states in dramatically distinct electronic states around the Fermi energy and formation energies.

  1. Study of defects near molybdenum surface using thermal desorption spectrometer

    International Nuclear Information System (INIS)

    Naik, P.K.

    1980-01-01

    Thermal desorption spectrometry is utilized to study the migration of atoms and defects near molybdenum surface. The thermal desorption spectra of inert gas ions (neon, argon and krypton) injected with various energies (430-1950 eV) into a polycrystalline molybdenum target with various dosages (6.4 x 10sup(12) - 3.9 x 10sup(14) ions/cmsup(2)) are investigated. Four different states of binding of the trapped atoms corresponding to the activation energies for desorption have been revealed from the spectra. The activation energies are found to be relatively insensitive to the species of the bombarding ion, incident ion energy and the dosage. The patterns of the spectra are strongly influenced by the mean projected range of the ions into the solid. The activation energies deduced are in good agreement with those reported for the migration of atoms and defects in molybdenum. (auth.)

  2. Mobility of point defects induced by subthreshold collisions

    International Nuclear Information System (INIS)

    Tenenbaum, A.; Nguyen Van Doan

    1976-01-01

    The effect of thermal vibrations on atomic collision focusing was studied with the view to demonstrate that such collisions may induce point defect migration through the crystal. The persistence of the phenomenon of focused atomic collisions in a crystal at thermal equilibrium was studied, using a computer simulation by the Molecular Dynamics Technique. In the temperature range (0 to 500K) matter and momentum transfers in c.f.c. crystals proceed mainly by focused collisions along and directions. Their contribution to the induced migration of radiation defects was determined from the threshold energy of every primary able to be involved in the process. As an example, the quantitative model is applied to electron irradiation along the crystallographic directions [fr

  3. Thermal equilibrium defects in anthracene probed by positron annihilation

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro; Tachibana, Masaru; Shimizu, Mikio; Satoh, Masaaki; Kojima, Kenichi; Ishibashi, Shoji; Kawano, Takao.

    1996-01-01

    Defects in anthracene were investigated by the positron annihilation technique. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured in the temperature range between 305 K and 516 K. The lifetime of positrons annihilated from the delocalized state was determined to be 0.306 ns around room temperature. Below the melting point, the observed temperature dependence of the line shape parameter S was explained assuming the formation energy of thermal equilibrium defects was 1 eV. Above the melting point, the pick-off annihilation of ortho-positronium in open spaces was observed, where the size of these spaces was estimated to be 0.2 nm 3 . The annihilation of positrons from the self-trapped state was also discussed. (author)

  4. Thermal equilibrium defects in anthracene probed by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Tachibana, Masaru; Shimizu, Mikio; Satoh, Masaaki; Kojima, Kenichi; Ishibashi, Shoji; Kawano, Takao

    1996-06-01

    Defects in anthracene were investigated by the positron annihilation technique. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured in the temperature range between 305 K and 516 K. The lifetime of positrons annihilated from the delocalized state was determined to be 0.306 ns around room temperature. Below the melting point, the observed temperature dependence of the line shape parameter S was explained assuming the formation energy of thermal equilibrium defects was 1 eV. Above the melting point, the pick-off annihilation of ortho-positronium in open spaces was observed, where the size of these spaces was estimated to be 0.2 nm{sup 3}. The annihilation of positrons from the self-trapped state was also discussed. (author)

  5. Stress and accidental defect detection on rolling mill rolls

    International Nuclear Information System (INIS)

    Auzas, J.-D.

    1999-01-01

    During the rolling mill process, rolls are submitted to high pressures that can lead to local decohesion or metallurgical changes. Both these cracks or softened areas must be detected as soon as they appear because of the risk of spalling, marks on the product, and mill wreck. These defects can be detected using the eddy current method, and particularly sensors specially developed for micro-defects detection. These sensors must be adapted to the environment of a roll grinding machine on which they must be installed. Users' schedule of conditions also require them to be attached to a wide range of eddy current generator and automatic computerized interpretation. Mill requirements for new high tech roll grades and quality lead to continuous development and improvement of the tools that will provide immediate 'go - no go' information. This paper is an update of these developments. (author)

  6. Wafer plane inspection for advanced reticle defects

    Science.gov (United States)

    Nagpal, Rajesh; Ghadiali, Firoz; Kim, Jun; Huang, Tracy; Pang, Song

    2008-05-01

    Readiness of new mask defect inspection technology is one of the key enablers for insertion & transition of the next generation technology from development into production. High volume production in mask shops and wafer fabs demands a reticle inspection system with superior sensitivity complemented by a low false defect rate to ensure fast turnaround of reticle repair and defect disposition (W. Chou et al 2007). Wafer Plane Inspection (WPI) is a novel approach to mask defect inspection, complementing the high resolution inspection capabilities of the TeraScanHR defect inspection system. WPI is accomplished by using the high resolution mask images to construct a physical mask model (D. Pettibone et al 1999). This mask model is then used to create the mask image in the wafer aerial plane. A threshold model is applied to enhance the inspectability of printing defects. WPI can eliminate the mask restrictions imposed on OPC solutions by inspection tool limitations in the past. Historically, minimum image restrictions were required to avoid nuisance inspection stops and/or subsequent loss of sensitivity to defects. WPI has the potential to eliminate these limitations by moving the mask defect inspections to the wafer plane. This paper outlines Wafer Plane Inspection technology, and explores the application of this technology to advanced reticle inspection. A total of twelve representative critical layers were inspected using WPI die-to-die mode. The results from scanning these advanced reticles have shown that applying WPI with a pixel size of 90nm (WPI P90) captures all the defects of interest (DOI) with low false defect detection rates. In validating CD predictions, the delta CDs from WPI are compared against Aerial Imaging Measurement System (AIMS), where a good correlation is established between WPI and AIMSTM.

  7. A proposed defect tracking model for classifying the inserted defect reports to enhance software quality control.

    Science.gov (United States)

    Sultan, Torky; Khedr, Ayman E; Sayed, Mostafa

    2013-01-01

    NONE DECLARED Defect tracking systems play an important role in the software development organizations as they can store historical information about defects. There are many research in defect tracking models and systems to enhance their capabilities to be more specifically tracking, and were adopted with new technology. Furthermore, there are different studies in classifying bugs in a step by step method to have clear perception and applicable method in detecting such bugs. This paper shows a new proposed defect tracking model for the purpose of classifying the inserted defects reports in a step by step method for more enhancement of the software quality.

  8. How to 'visualize' lattice defects

    International Nuclear Information System (INIS)

    Doi, Kenji

    1974-01-01

    Methods to recognize objects are discussed. In case of optics, lenses are used, and light from objects passing through the lenses focuses on focal planes. The amplitude of light on the focal planes in given as a function of the structure factor of scattering light from objects, images of objects are made on image planes. In case of X-ray or neutron diffraction, lenses which make images by X-ray or neutrons can not be made, accordingly images cannot be obtained. Images can be seen with electron microscopes. By X-ray or thermal neutron diffraction, intensity on focal planes in observed, and the defects to be studied are recognized as diffuse scattering. Since it is necessary to minimize aberration in case of image observation with electron microscopes, slits are used to utilize electron beam near optical axis exclusively. Therefore large resolving power cannot be expected. The information concerning structure obtained from focal planes is of statistical nature, and that from image planes is local information. The principle of neutron topography, by which the informations concerning local points are obtained, is explained. A photograph of LiF irradiated by 0.5 MeV proton beam was taken by the topographic method, and shown in this paper. (Kato, T.)

  9. Birth defects in perinatal infants in areas contiguous to Hongyanhe Nuclear Power Plant before its normal operation

    International Nuclear Information System (INIS)

    Zhou Ling; Yin Zhihua; Han Zhonghui

    2011-01-01

    Objective: To understand the status of birth defects among the perinatal infants in the areas contiguous to Hongyanhe nuclear power plant before its normal operation, so as to provide background information for the evaluation of the impact of nuclear power plant on birth defects. Methods: From 1 October 1995 to 30 September 2009 the midwifery units at second class and above of Wafangdian City were asked to be in charge of recording the birth defects among the perinatal infants born during this period within the range of 50 km around the Hongyanhe nuclear power plant. Results: The total number of birth defects was 697, and the maternal number Was 83779. The average defect rate Was 83.20/10 4 . There were significant differences in the birth defect rate among different years (χ 2 =39.54, P<0.05), however, without linear trend therein,and among the survey areas (χ 2 =15.36, P<0.05) as well. The top five birth defects were congenital heart disease (148 cases), cleft lip with cleft palate (67 cases), congenital hydrocephalus (63 cases), and spina bifida (37 cases) and cleft lip (36 cases). Conclusions: The birth defect rate within the range of 50 km around the Hongyanhe nuclear power plant is lower than that of the region of Liaoning Province and the national rate of birth defects. (authors)

  10. Capture of impurity atoms by defects and the distribution of the complexes under ion bormbardment of growing films

    International Nuclear Information System (INIS)

    Radzhabov, T.D.; Iskanderova, Z.A.; Arutyunova, E.O.; Samigulin, K.R.

    1982-01-01

    Theoretical study of capture of impurity gas atoms with defects during ion introduction of the impurity in the process of film growth with simultaneous diffusion has been carried out. Concentration profiles of forned impurity-defect complexes have been calculated analytically and numerically by means of a computer in film depth and in a substrate; basic peculiarities of impurity component formation captured with defects in a wide range of changing basic experimental parameters have been revealed. Effect of impurity capture with defects on amount and distribution of total concentration of impurity atoms and intensity of complete absorption of bombarding ions in films have been analyzed. Shown is a possibility for producing films with a high concentration level and almost uniform distribution of the impurity-defect complexes for real, achievable an experiment, values of process parameters as well as a possibility for increasing complete absorption of gaseous impurity wiht concentration growth of capture defects-traps

  11. Long-range antigravity

    Energy Technology Data Exchange (ETDEWEB)

    Macrae, K.I.; Riegert, R.J. (Maryland Univ., College Park (USA). Center for Theoretical Physics)

    1984-10-01

    We consider a theory in which fermionic matter interacts via long-range scalar, vector and tensor fields. In order not to be in conflict with experiment, the scalar and vector couplings for a given fermion must be equal, as is natural in a dimensionally reduced model. Assuming that the Sun is not approximately neutral with respect to these new scalar-vector charges, and if the couplings saturate the experimental bounds, then their strength can be comparable to that of gravity. Scalar-vector fields of this strength can compensate for a solar quadrupole moment contribution to Mercury's anomalous perihelion precession.

  12. Long-range antigravity

    International Nuclear Information System (INIS)

    Macrae, K.I.; Riegert, R.J.

    1984-01-01

    We consider a theory in which fermionic matter interacts via long-range scalar, vector and tensor fields. In order not to be in conflict with experiment, the scalar and vector couplings for a given fermion must be equal, as is natural in a dimensionally reduced model. Assuming that the Sun is not approximately neutral with respect to these new scalar-vector charges, and if the couplings saturate the experimental bounds, then their strength can be comparable to that of gravity. Scalar-vector fields of this strength can compensate for a solar quadrupole moment contribution to Mercury's anomalous perihelion precession. (orig.)

  13. Birth defects surveillance·

    African Journals Online (AJOL)

    1989-07-01

    Jul 1, 1989 ... to potential changes in water quality in the Cape Peninsula. The methodology used for .... (Spain and Mexico), the ranges shown for the two countries overlap the 95% .... Water Pollution Control Federation. Water Reuse: ...

  14. On the dependence of static flat seal efficiency to surface defects

    International Nuclear Information System (INIS)

    Ledoux, Y.; Lasseux, D.; Favreliere, H.; Samper, S.; Grandjean, J.

    2011-01-01

    We report on the role of the modal content of surface defects on static flat seal efficiency. The configuration under consideration is an annular contact between two surfaces, one holding all the defects, the other being assumed flat and infinitely rigid. The analysis is carried out on synthetic 'turned-like' surfaces generated by combinations of the first 50 vibrational eigen modes determined from modal discrete decomposition. The transmissivity of the contact, that fully characterizes the seal efficiency, is computed on the basis of a Reynolds model for incompressible flow. The dependence of the transmissivity upon the modal content of the surface defects is analyzed on a contact pressure range of common use employing a simplified deformation algorithm. Impact of the defects modal content is investigated statistically through a pair of experimental designs. It is shown that, i) the uncertainty on transmissivity, while considering a series of parts, can be drastically reduced if defect modes are well selected; ii) the transmissivity itself can be very significantly decreased when the defects modal content is conveniently controlled. While clearly indicating that the common surface roughness specification is generally not a relevant one to ensure a required seal performance, this work opens wide perspectives on the seal improvement by surface defects optimization only. - Highlights: → Computation of contact transmissivity qualifying static seal efficiency. → Statistical analysis of surface defects modal content on static flat seal. → Improvement of static flat seal efficiency. → Significant transmissivity reduction by convenient control of surface defects modes. → Drastic reduction of transmissivity uncertainty by surface defects modes selection.

  15. Characterization of the structure and chemistry of defects in materials

    International Nuclear Information System (INIS)

    Larson, B.C.; Ruehle, M.; Seidman, D.N.

    1988-01-01

    Research programs, presented at the materials research symposium, on defects in materials are presented. Major areas include: point defects, defect aggregates, and ordering; defects in non-metals and semiconductors; atomic resolution imaging of defects; and gain boundaries, interfaces, and layered materials. Individual projects are processed separately for the data bases

  16. Distribution of defects in wind turbine blades and reliability assessment of blades containing defects

    DEFF Research Database (Denmark)

    Stensgaard Toft, Henrik; Branner, Kim; Berring, Peter

    2009-01-01

    on the assumption that one error in the production process tends to trigger several defects. For both models additional information about number, type and size of the defects is included as stochastic variables. The probability of failure for a wind turbine blade will not only depend on variations in the material......In the present paper two stochastic models for the distribution of defects in wind turbine blades are proposed. The first model assumes that the individual defects are completely randomly distributed in the blade. The second model assumes that the defects occur in clusters of different size based...... properties and the load but also on potential defects in the blades. As a numerical example the probability of failure is calculated for the main spar both with and without defects in terms of delaminations. The delaminations increase the probability of failure compared to a perfect blade, but by applying...

  17. Range Process Simulation Tool

    Science.gov (United States)

    Phillips, Dave; Haas, William; Barth, Tim; Benjamin, Perakath; Graul, Michael; Bagatourova, Olga

    2005-01-01

    Range Process Simulation Tool (RPST) is a computer program that assists managers in rapidly predicting and quantitatively assessing the operational effects of proposed technological additions to, and/or upgrades of, complex facilities and engineering systems such as the Eastern Test Range. Originally designed for application to space transportation systems, RPST is also suitable for assessing effects of proposed changes in industrial facilities and large organizations. RPST follows a model-based approach that includes finite-capacity schedule analysis and discrete-event process simulation. A component-based, scalable, open architecture makes RPST easily and rapidly tailorable for diverse applications. Specific RPST functions include: (1) definition of analysis objectives and performance metrics; (2) selection of process templates from a processtemplate library; (3) configuration of process models for detailed simulation and schedule analysis; (4) design of operations- analysis experiments; (5) schedule and simulation-based process analysis; and (6) optimization of performance by use of genetic algorithms and simulated annealing. The main benefits afforded by RPST are provision of information that can be used to reduce costs of operation and maintenance, and the capability for affordable, accurate, and reliable prediction and exploration of the consequences of many alternative proposed decisions.

  18. Reduction in Defect Content in ODS Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ritherdon, J.; Jones, A.R.

    2000-02-01

    The work detailed within this report is a continuation of earlier work that was carried out under contract number IDX-SY382V. The earlier work comprised a literature review of the sources and types of defects found principally in Fe-based ODS alloys together with a series of experiments designed to identify defects in ODS Fe{sub 3}Al material and recommend methods of defect reduction. Defects found in the Mechanically Alloyed (MA) ODS Fe{sub 3}Al included regions of incomplete MA, porosity, intrusions and fine-grained stringers. Some defects tended to be found in association with one another e.g. intrusions and fine-grained stringers. Preliminary powder separation experiments were also performed. The scope and objectives of the present work were laid out in the technical proposal ``Reduction in Defect Content in ODS Alloys--II'' which formed the basis of amendment 3 of the current contract. The current studies were devised in the context of the preceding work with a view to extending and concluding certain experiments while exploring new avenues of investigation of defect control and reduction where appropriate. All work proposed was within the context of achieving an ODS Fe{sub 3}Al alloy of improved overall quality and potential creep performance (particularly) in the consolidated, release condition. The interim outturn of the experimental work performed is also reported.

  19. Modeling of Powder Bed Manufacturing Defects

    Science.gov (United States)

    Mindt, H.-W.; Desmaison, O.; Megahed, M.; Peralta, A.; Neumann, J.

    2018-01-01

    Powder bed additive manufacturing offers unmatched capabilities. The deposition resolution achieved is extremely high enabling the production of innovative functional products and materials. Achieving the desired final quality is, however, hampered by many potential defects that have to be managed in due course of the manufacturing process. Defects observed in products manufactured via powder bed fusion have been studied experimentally. In this effort we have relied on experiments reported in the literature and—when experimental data were not sufficient—we have performed additional experiments providing an extended foundation for defect analysis. There is large interest in reducing the effort and cost of additive manufacturing process qualification and certification using integrated computational material engineering. A prerequisite is, however, that numerical methods can indeed capture defects. A multiscale multiphysics platform is developed and applied to predict and explain the origin of several defects that have been observed experimentally during laser-based powder bed fusion processes. The models utilized are briefly introduced. The ability of the models to capture the observed defects is verified. The root cause of the defects is explained by analyzing the numerical results thus confirming the ability of numerical methods to provide a foundation for rapid process qualification.

  20. Human diseases associated with defective DNA repair

    International Nuclear Information System (INIS)

    Friedberg, E.C.; Ehmann, U.K.; Williams, J.I.

    1979-01-01

    The observations on xeroderma pigmentosum (XP) cells in culture were the first indications of defective DNA repair in association with human disease. Since then, a wealth of information on DNA repair in XP, and to a lesser extent in other diseases, has accumulated in the literature. Rather than clarifying the understanding of DNA repair mechanisms in normal cells and of defective DNA repair in human disease, the literature suggests an extraordinary complexity of both of the phenomena. In this review a number of discrete human diseases are considered separately. An attempt was made to systematically describe the pertinent clinical features and cellular and biochemical defects in these diseases, with an emphasis on defects in DNA metabolism, particularly DNA repair. Wherever possible observations have been correlated and unifying hypotheses presented concerning the nature of the basic defect(s) in these diseases. Discussions of the following diseases are presented: XP, ataxia telangiectasia; Fanconi's anemia; Hutchinson-Gilford progeria syndrome; Bloom's syndrome, Cockayne's syndrome; Down's syndrome; retinoblastoma; chronic lymphocytic leukemia; and other miscellaneous human diseases with possble DNA repair defects

  1. Extrusion product defects: a statistical study

    International Nuclear Information System (INIS)

    Qamar, S.Z.; Arif, A.F.M.; Sheikh, A.K.

    2003-01-01

    In any manufacturing environment, defects resulting in rework or rejection are directly related to product cost and quality, and indirectly linked with process, tooling and product design. An analysis of product defects is therefore integral to any attempt at improving productivity, efficiency and quality. Commercial aluminum extrusion is generally a hot working process and consists of a series of different but integrated operations: billet preheating and sizing, die set and container preheating, billet loading and deformation, product sizing and stretching/roll-correction, age hardening, and painting/anodizing. Product defects can be traced back to problems in billet material and preparation, die and die set design and maintenance, process variable aberrations (ram speed, extrusion pressure, container temperature, etc), and post-extrusion treatment (age hardening, painting/anodizing, etc). The current paper attempts to analyze statistically the product defects commonly encountered in a commercial hot aluminum extrusion setup. Real-world rejection data, covering a period of nine years, has been researched and collected from a local structural aluminum extrusion facility. Rejection probabilities have been calculated for all the defects studied. The nine-year rejection data have been statistically analyzed on the basis of (i) an overall breakdown of defects, (ii) year-wise rejection behavior, (iii) breakdown of defects in each of three cost centers: press, anodizing, and painting. (author)

  2. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

    2015-01-01

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm '2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  3. Platelet rich fibrin in jaw defects

    Science.gov (United States)

    Nica, Diana; Ianes, Emilia; Pricop, Marius

    2016-03-01

    Platelet rich fibrin (PRF) is a tissue product of autologous origin abundant in growth factors, widely used in regenerative procedures. Aim of the study: Evaluation of the regenerative effect of PRF added in the bony defects (after tooth removal or after cystectomy) Material and methods: The comparative nonrandomized study included 22 patients divided into 2 groups. The first group (the test group) included 10 patients where the bony defects were treated without any harvesting material. The second group included 12 patients where the bony defects were filled with PRF. The bony defect design was not critical, with one to two walls missing. After the surgeries, a close clinically monitoring was carried out. The selected cases were investigated using both cone beam computer tomography (CBCT) and radiographic techniques after 10 weeks postoperatively. Results: Faster bone regeneration was observed in the bony defects filled with PRF comparing with the not grafted bony defects. Conclusions: PRF added in the bony defects accelerates the bone regeneration. This simplifies the surgical procedures and decreases the economic costs.

  4. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua

    2015-02-19

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  5. Defect Chemistry of Oxides for Energy Applications.

    Science.gov (United States)

    Schweke, Danielle; Mordehovitz, Yuval; Halabi, Mahdi; Shelly, Lee; Hayun, Shmuel

    2018-05-31

    Oxides are widely used for energy applications, as solid electrolytes in various solid oxide fuel cell devices or as catalysts (often associated with noble metal particles) for numerous reactions involving oxidation or reduction. Defects are the major factors governing the efficiency of a given oxide for the above applications. In this paper, the common defects in oxide systems and external factors influencing the defect concentration and distribution are presented, with special emphasis on ceria (CeO 2 ) based materials. It is shown that the behavior of a variety of oxide systems with respect to properties relevant for energy applications (conductivity and catalytic activity) can be rationalized by general considerations about the type and concentration of defects in the specific system. A new method based on transmission electron microscopy (TEM), recently reported by the authors for mapping space charge defects and measuring space charge potentials, is shown to be of potential importance for understanding conductivity mechanisms in oxides. The influence of defects on gas-surface reactions is exemplified on the interaction of CO 2 and H 2 O with ceria, by correlating between the defect distribution in the material and its adsorption capacity or splitting efficiency. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Calculation of projected ranges

    International Nuclear Information System (INIS)

    Biersack, J.P.

    1980-09-01

    The concept of multiple scattering is reconsidered for obtaining the directional spreading of ion motion as a function of energy loss. From this the mean projection of each pathlength element of the ion trajectory is derived which - upon summation or integration - leads to the desired mean projected range. In special cases, the calculation can be carried out analytically, otherwise a simple general algorithm is derived which is suitable even for the smallest programmable calculators. Necessary input for the present treatment consists only of generally accessable stopping power and straggling formulas. The procedure does not rely on scattering cross sections, e.g. power potential or f(t 1 sup(/) 2 ) approximations. The present approach lends itself easily to include electronic straggling or to treat composed target materials, or even to account for the so-called time integral. (orig.)

  7. Interdisciplinary Management of an Isolated Intrabony Defect

    Directory of Open Access Journals (Sweden)

    Sheetal Ghivari

    2014-01-01

    Full Text Available The treatment of intrabony defects is a real challenge in molar teeth as it is chronic, slowly progressing disease which needs timely intervention. Periodontal inflammation associated with intrabony defect is not a separate entity as it secondarily affects the pulp causing retrograde pulpitis. However, treatment of these lesions will be complicated due to extensive bone loss. The tooth was endodontically treated followed by periodontal surgery to eliminate the deep periodontal pocket and promote bone fill in osseous defect. PepGen P-15 composited with platelet rich plasma was utilized for enhancing bone formation. The combination of these graft materials provides synergistic effect on bone regeneration.

  8. Mass defect effects in atomic clocks

    Science.gov (United States)

    Yudin, Valeriy; Taichenachev, Alexey

    2018-03-01

    We consider some implications of the mass defect on the frequency of atomic transitions. We have found that some well-known frequency shifts (the gravitational shift and motion-induced shifts such as quadratic Doppler and micromotion shifts) can be interpreted as consequences of the mass defect in quantum atomic physics, i.e. without the need for the concept of time dilation used in special and general relativity theories. Moreover, we show that the inclusion of the mass defect leads to previously unknown shifts for clocks based on trapped ions.

  9. Tibial and fibular developmental fields defects

    International Nuclear Information System (INIS)

    Khoury, N.J.; Haddad, M.C.; Hourani, M.H.

    1999-01-01

    Malformations of the lower limbs are rare and heterogeneous anomalies. To explain the diversity and complexity of these abnormalities, authors introduced the concept of tibial and fibular developmental fields. Defects in these fields are responsible for different malformations, which have been described, to our knowledge, in only one report in the radiology literature. We present a case of a newborn with femoral bifurcation, absent fibulae and talar bones, ankle and foot malformations, and associated atrial septal defect. Our case is an example of defects in both fibular and tibial developmental fields. (orig.)

  10. Study of irradiation induced defects in silicon

    International Nuclear Information System (INIS)

    Pal, Gayatri; Sebastian, K.C.; Somayajulu, D.R.S.; Chintalapudi, S.N.

    2000-01-01

    Pure high resistivity (6000 ohm-cm) silicon wafers were recoil implanted with 1.8 MeV 111 In ions. As-irradiated wafers showed a 13 MHz quadrupole interaction frequency, which was not observed earlier. The annealing behaviour of these defects in the implanted wafers was studied between room temperature and 1073 K. At different annealing temperatures two more interaction frequencies corresponding to defect complexes D2 and D3 are observed. Even though the experimental conditions were different, these are identical to the earlier reported ones. Based on an empirical point charge model calculation, an attempt is made to identify the configuration of these defect complexes. (author)

  11. Dimensions of defects determined by radiographical testing

    International Nuclear Information System (INIS)

    Oesterberg, J.

    Normally industrial radiography using x-rays or radionuclides gives information on the existence of defects in welds. These defects may in some instances be harmless, the size of the flaw is important. Radiography may be used for determining the thickness of the defect in many cases, by measuring the blackening of the photographic film used. The report gives a theoretical treatment of the problems and goes on to practical examples of the application. For flaws that have a width of at least 0.3 mm, a thickness of the order 0.1 mm can be determined with sufficient accuracy in materials 40 mm thick.(P.Aa.)

  12. Knowledge of birth defects among nursing mothers in a developing ...

    African Journals Online (AJOL)

    sponsibility is placed on parents in the recognition of these defects. Objectives: The .... be prevented, detected, inherited or treated; and if they knew that folic ... could be used to prevent certain birth defects. ..... birth defects such as smoking.

  13. Vertebral defect, anal atresia, cardiac defect, tracheoesophageal fistula/esophageal atresia, renal defect, and limb defect association with Mayer-Rokitansky-Küster-Hauser syndrome in co-occurrence

    DEFF Research Database (Denmark)

    Bjørsum-Meyer, Thomas; Herlin, Morten; Qvist, Niels

    2016-01-01

    Background: The vertebral defect, anal atresia, cardiac defect, tracheoesophageal fistula/esophageal atresia, renal defect, and limb defect association and Mayer-Rokitansky-Küster-Hauser syndrome are rare conditions. We aimed to present two cases with the vertebral defect, anal atresia, cardiac...... defect, tracheoesophageal fistula/esophageal atresia, renal defect, and limb defect association and Mayer-Rokitansky-Küster-Hauser co-occurrence from our local surgical center and through a systematic literature search detect published cases. Furthermore, we aimed to collect existing knowledge...... in the embryopathogenesis and genetics in order to discuss a possible link between the vertebral defect, anal atresia, cardiac defect, tracheoesophageal fistula/esophageal atresia, renal defect, and limb defect association and Mayer-Rokitansky-Küster-Hauser syndrome. Case presentation: Our first case was a white girl...

  14. Elastic fields, dipole tensors, and interaction between self-interstitial atom defects in bcc transition metals

    Science.gov (United States)

    Dudarev, S. L.; Ma, Pui-Wai

    2018-03-01

    Density functional theory (DFT) calculations show that self-interstitial atom (SIA) defects in nonmagnetic body-centered-cubic (bcc) metals adopt strongly anisotropic configurations, elongated in the direction [S. Han et al., Phys. Rev. B 66, 220101 (2002), 10.1103/PhysRevB.66.220101; D. Nguyen-Manh et al., Phys. Rev. B 73, 020101 (2006), 10.1103/PhysRevB.73.020101; P. M. Derlet et al., Phys. Rev. B 76, 054107 (2007), 10.1103/PhysRevB.76.054107; S. L. Dudarev, Annu. Rev. Mater. Res. 43, 35 (2013), 10.1146/annurev-matsci-071312-121626]. Elastic distortions, associated with such anisotropic atomic structures, appear similar to distortions around small prismatic dislocation loops, although the extent of this similarity has never been quantified. We derive analytical formulas for the dipole tensors of SIA defects, which show that, in addition to the prismatic dislocation looplike character, the elastic field of a SIA defect also has a significant isotropic dilatation component. Using empirical potentials and DFT calculations, we parametrize dipole tensors of defects for all the nonmagnetic bcc transition metals. This enables a quantitative evaluation of the energy of elastic interaction between the defects, which also shows that in a periodic three-dimensional simple cubic arrangement of crowdions, long-range elastic interactions between a defect and all its images favor a orientation of the defect.

  15. Neutron cross sections for defect production by high-energy displacement cascades in copper

    International Nuclear Information System (INIS)

    Heinisch, H.L.; Mann, F.M.

    1983-08-01

    Defect production cross sections for copper have been devised, based on computer simulations of displacement cascades. One thousand cascades ranging in energy from 200 eV to 200 keV were generated with the MARLOWE computer code. The cascades were subjected to a semi-empirical cascade quenching procedure and to short-term annealing with the ALSOME computer code. Functions were fitted to the numbers of defects produced as a function of primary knock-on atom (PKA) damage energy for the following defect types: 1) the total number of point defects after quenching and after short-term annealing, 2) the numbers of free interstitials and free vacancies after shortterm annealing, and 3) the numbers and sizes of vacancy and interstitial clusters after shortterm annealing. In addition, a function describing the number of distinct damage regions (lobes) per cascade was fitted to results of a graphical analysis of the cascade configurations. The defect production functions have been folded into PKA spectra using the NJOY nuclear data processing code system with ENDF/B-V nuclear data to yield neutron cross sections for defect production in copper. The free vacancy cross section displays much less variation with neutron energy than the cross sections for damage energy or total point defects

  16. Global collapse and J integral analysis for inner-diameter defected curved plates in tension

    International Nuclear Information System (INIS)

    Hertelé, Stijn; Verstraete, Matthias; Denys, Rudi; De Waele, Wim

    2013-01-01

    Reference stress equations are widely used to predict both the limit load and the J integral response of defected structures. Their validity is key to performing a safe assessment of structural integrity (plastic collapse and fracture). An analytical reference stress equation based upon global collapse has recently been developed for curved plates with a part-through defect located at the inner diameter surface. This equation predicts decreasing reference stress values as plate curvature increases. To qualify the predictions, the authors have performed a series of finite element analyses covering a wide range of possible geometries. This paper compares the numerically obtained limit loads and J integral responses with the analytical predictions of the reference stress equation. The finite element results generally confirm the decrease of reference stress with increasing plate curvature. Highly pronounced differences may occur between flat plates and slightly curved plates. Overall, the analytically predicted decrease in reference stress is overestimated for small defects but is representative for larger defects. -- Highlights: • A reference stress equation for inner-diameter defected curved plates in tension was developed earlier. • The equation predicts a lower reference stress as plate curvature increases. • The analytical predictions are validated through finite element analysis. • Collapse and J integral are insensitive to curvature for small defects. • For large defects, the analytically predicted trend is confirmed

  17. Human vision-based algorithm to hide defective pixels in LCDs

    Science.gov (United States)

    Kimpe, Tom; Coulier, Stefaan; Van Hoey, Gert

    2006-02-01

    Producing displays without pixel defects or repairing defective pixels is technically not possible at this moment. This paper presents a new approach to solve this problem: defects are made invisible for the user by using image processing algorithms based on characteristics of the human eye. The performance of this new algorithm has been evaluated using two different methods. First of all the theoretical response of the human eye was analyzed on a series of images and this before and after applying the defective pixel compensation algorithm. These results show that indeed it is possible to mask a defective pixel. A second method was to perform a psycho-visual test where users were asked whether or not a defective pixel could be perceived. The results of these user tests also confirm the value of the new algorithm. Our "defective pixel correction" algorithm can be implemented very efficiently and cost-effectively as pixel-dataprocessing algorithms inside the display in for instance an FPGA, a DSP or a microprocessor. The described techniques are also valid for both monochrome and color displays ranging from high-quality medical displays to consumer LCDTV applications.

  18. Extrinsic- and intrinsic-defect creation in amorphous SiO2

    International Nuclear Information System (INIS)

    Devine, R.A.B.; Francou, J.

    1990-01-01

    We have studied the creation efficiency of various intrinsic and extrinsic defects in high-[OH] amorphous silica subjected to the ultraviolet emission from an O 2 plasma or 60 Co γ-ray radiation. Both oxygen-vacancy- and nitrogen-related defects are observed following γ-ray irradiation or ultraviolet exposure. The wavelength range responsible for defect creation is estimated to be 200 approx-lt λ approx-lt 300 nm (4 approx-lt E photon approx-lt 5.9 eV). The ultraviolet power output of the plasma estimated by comparing defect yields with those from a Hg lamp (λ=185 and 254 nm) suggests 200 approx-lt P approx-lt 900 mW cm -2 for a plasma power density ∼300 mW cm -3 . Nonbridging oxygen-hole centers and hydrogen-related defect centers as well as methyl radical (CH 3 . ) defects are observed after γ-ray irradiation but not after ultraviolet exposure. The efficiency of creation of the various defects is material dependent

  19. Neutron cross sections for defect production by high energy displacement cascades in copper

    International Nuclear Information System (INIS)

    Heinisch, H.L.; Mann, F.M.

    1984-01-01

    Defect production cross sections for copper have been devised, based on computer simulations of displacement cascades. One thousand cascades ranging in energy from 200 eV to 200 keV were generated with the MARLOWE computer code. The cascades were subjected to a semi-empirical cascade quenching procedure and to short-term annealing with the ALSOME computer code. Functions were fitted to the numbers of defects produced as a function of primary knock-on atom (PKA) damage energy for the following defect types: 1) the total number of point defects after quenching and after short-term annealing, 2) the numbers of free interstitials and free vacancies after short-term annealing, and 3) the numbers and sizes of vacancy and interstitial clusters after short-term annealing. In addition, a function describing the number of distinct damage regions (lobes) per cascade was fitted to results of a graphical analysis of the cascade configurations. The defect production functions have been folded into PKA spectra using the NJOY nuclear data processing code system with ENDF/B-V nuclear data to yield neutron cross sections for defect production in copper. The free vacancy cross section displays much less variation with neutron energy than the cross sections for damage energy or total point defects. (orig.)

  20. The electronic and optical properties of amorphous silica with hydrogen defects by ab initio calculations

    Science.gov (United States)

    Ren, Dahua; Xiang, Baoyan; Hu, Cheng; Qian, Kai; Cheng, Xinlu

    2018-04-01

    Hydrogen can be trapped in the bulk materials in four forms: interstitial molecular H2, interstitial atom H, O‑H+(2Si=O–H)+, Si‑H‑( {{4O}}\\bar \\equiv {{Si&x2212H}})‑ to affect the electronic and optical properties of amorphous silica. Therefore, the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory. Initially, the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom. However, the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy. Subsequently, the optical properties such as absorption spectra, conductivity and loss functions were analyzed. It is indicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 eV while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 eV. However, the neutral hydrogen defects just improved the intensity of absorption spectrum. This may give insights into understanding the mechanism of laser-induced damage for optical materials. Project supported by the Science and Technology of Hubei Provincial Department of Education (No. B2017098).

  1. Function of TiO2 Lattice Defects toward Photocatalytic Processes: View of Electronic Driven Force

    Directory of Open Access Journals (Sweden)

    Huanan Cui

    2013-01-01

    Full Text Available Oxygen vacancies and Ti-related defects (OTDs are the main lattice defects of TiO2, which have great influence on its photocatalytic activity. To understand the relationship between the defects and photocatalytic activities, detailed discussions based on the electronic driven force provided by these defects are carried out during the three commonly accepted processes in photocatalytic reactions. It is found that these defects inevitably (i influence the energy structure of the pristine TiO2 as the isolate acceptor/donor level or hybrid with the original orbital, (ii provide a disordered short-range force that confuses the charge carriers transferring to surface active sites, (iii act not only as the surface active sites for trapping the charge carriers but also as the main chemisorption sites for O2, H2O, and organic species. These effects of the defects make them one of the key factors that determine the efficiency of heterogeneous photocatalysis. Clarifying the role of the defects will further facilitate the exploration and the construction of high-performance photocatalysts for practical applications.

  2. Defect study of Zn-doped p-type gallium antimonide using positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Ling, C. C.; Fung, S.; Beling, C. D.; Huimin, Weng

    2001-01-01

    Defects in p-type Zn-doped liquid-encapsulated Czochralski--grown GaSb were studied by the positron lifetime technique. The lifetime measurements were performed on the as-grown sample at temperature varying from 15 K to 297 K. A positron trapping center having a characteristic lifetime of 317 ps was identified as the neutral V Ga -related defect. Its concentration in the as-grown sample was found to be in the range of 10 17 --10 18 cm -3 . At an annealing temperature of 300 o C, the V Ga -related defect began annealing out and a new defect capable of trapping positrons was formed. This newly formed defect, having a lifetime value of 379 ps, is attributed to a vacancy--Zn-defect complex. This defect started annealing out at a temperature of 580 o C. A positron shallow trap having binding energy and concentration of 75 meV and 10 18 cm -3 , respectively, was also observed in the as-grown sample. This shallow trap is attributed to positrons forming hydrogenlike Rydberg states with the ionized dopant acceptor Zn

  3. Blockage of ultrafast and directional diffusion of Li atoms on phosphorene with intrinsic defects.

    Science.gov (United States)

    Zhang, Ruiqi; Wu, Xiaojun; Yang, Jinlong

    2016-02-21

    The diffusion of Li in electrode materials is a key factor for the charging/discharging rate capacity of a Li-ion battery (LIB). Recently, two-dimensional phosphorene has been proposed as a very promising electrode material due to its ultrafast and directional lithium diffusion, as well as large energy capacity. Herein, on the basis of density functional theory, we report that intrinsic point defects, including vacancy and stone-wales defects, will block the directional ultrafast diffusion of lithium in phosphorene. On the defect-free phosphorene, diffusion of Li along the zig-zag lattice direction is 1.6 billion times faster than along the armchair lattice direction, and 260 times faster than that in graphite. After introducing intrinsic vacancy and stone-wales defect, the diffusion energy barrier of Li along the zig-zag lattice direction increases sharply to the range of 0.17-0.49 eV, which blocks the ultrafast migration of lithium along the zig-zag lattice direction. Moreover, the open circuit voltage increases with the emergence of defects, which is not suitable for anode materials. In addition, the formation energies of the defects in phosphorene are considerably lower than those in graphene and silicene sheet; therefore, it is highly important to generate defect-free phosphorene for LIB applications.

  4. Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon

    International Nuclear Information System (INIS)

    Astakhov, Oleksandr; Carius, Reinhard; Finger, Friedhelm; Petrusenko, Yuri; Borysenko, Valery; Barankov, Dmytro

    2009-01-01

    The influence of dangling-bond defects and the position of the Fermi level on the charge carrier transport properties in undoped and phosphorous doped thin-film silicon with structure compositions all the way from highly crystalline to amorphous is investigated. The dangling-bond density is varied reproducibly over several orders of magnitude by electron bombardment and subsequent annealing. The defects are investigated by electron-spin-resonance and photoconductivity spectroscopies. Comparing intrinsic amorphous and microcrystalline silicon, it is found that the relationship between defect density and photoconductivity is different in both undoped materials, while a similar strong influence of the position of the Fermi level on photoconductivity via the charge carrier lifetime is found in the doped materials. The latter allows a quantitative determination of the value of the transport gap energy in microcrystalline silicon. The photoconductivity in intrinsic microcrystalline silicon is, on one hand, considerably less affected by the bombardment but, on the other hand, does not generally recover with annealing of the defects and is independent from the spin density which itself can be annealed back to the as-deposited level. For amorphous silicon and material prepared close to the crystalline growth regime, the results for nonequilibrium transport fit perfectly to a recombination model based on direct capture into neutral dangling bonds over a wide range of defect densities. For the heterogeneous microcrystalline silicon, this model fails completely. The application of photoconductivity spectroscopy in the constant photocurrent mode (CPM) is explored for the entire structure composition range over a wide variation in defect densities. For amorphous silicon previously reported linear correlation between the spin density and the subgap absorption is confirmed for defect densities below 10 18 cm -3 . Beyond this defect level, a sublinear relation is found i.e., not

  5. ILT based defect simulation of inspection images accurately predicts mask defect printability on wafer

    Science.gov (United States)

    Deep, Prakash; Paninjath, Sankaranarayanan; Pereira, Mark; Buck, Peter

    2016-05-01

    At advanced technology nodes mask complexity has been increased because of large-scale use of resolution enhancement technologies (RET) which includes Optical Proximity Correction (OPC), Inverse Lithography Technology (ILT) and Source Mask Optimization (SMO). The number of defects detected during inspection of such mask increased drastically and differentiation of critical and non-critical defects are more challenging, complex and time consuming. Because of significant defectivity of EUVL masks and non-availability of actinic inspection, it is important and also challenging to predict the criticality of defects for printability on wafer. This is one of the significant barriers for the adoption of EUVL for semiconductor manufacturing. Techniques to decide criticality of defects from images captured using non actinic inspection images is desired till actinic inspection is not available. High resolution inspection of photomask images detects many defects which are used for process and mask qualification. Repairing all defects is not practical and probably not required, however it's imperative to know which defects are severe enough to impact wafer before repair. Additionally, wafer printability check is always desired after repairing a defect. AIMSTM review is the industry standard for this, however doing AIMSTM review for all defects is expensive and very time consuming. Fast, accurate and an economical mechanism is desired which can predict defect printability on wafer accurately and quickly from images captured using high resolution inspection machine. Predicting defect printability from such images is challenging due to the fact that the high resolution images do not correlate with actual mask contours. The challenge is increased due to use of different optical condition during inspection other than actual scanner condition, and defects found in such images do not have correlation with actual impact on wafer. Our automated defect simulation tool predicts

  6. Reconstruction of soft tissue defects around the ankle and foot

    Directory of Open Access Journals (Sweden)

    Bharat Bhushan Dogra

    2014-01-01

    Full Text Available Introduction: Soft tissue defects over ankle and foot region are encountered quite frequently following road traffic trauma and surgery. Management of such cases is a challenging task for any reconstructive surgeon because of paucity of skin and relative poor vascular status of skin in this region. Hence, invariably such cases require microsurgical free flap coverage, expertise for which may not be available at all the centers, such procedures require long operating hours and suitable recipient vessel may not be available in crush injuries. Materials and Methods: Thirty consecutive patients having soft tissue defects around ankle and foot region who underwent various reconstructive procedures in a medical college hospital during last 2 years form the basis of this study. This study was carried out to enlist various etiological factors and reconstructive surgical procedures employed to manage such cases without microsurgery. Results: The age of these patients ranged from 9 to 72 years. Twenty-five patients were males while 05 were females, with a mean age of 25 years. Road traffic accidents happened to be the primary cause of such defects in as many as 15 patients, cycle spoke trauma in 02 patients, implant exposure following orthopedic surgery in 6 patients, diabetic angiopathy in 4 patients and chronic osteomyelitis in 3 patients. The site of the defect was lower fourth of tibia in 16 patients, dorsum of foot in 2 patients, sole in 5 patients, medial aspect of ankle in 02 cases, lateral aspect in 02 cases and retro calcaneal region in 03 cases. In 10 cases distally based superficial sural artery flap was used to reconstruct the defect. In step rotation flap was used to provide sensory flap cover in the weight bearing heel in 04 cases. Inferiorly based fasciocutanenous flaps in 09 cases and muscle flaps were used in 07 cases. Conclusion: Distally based sural artery based flaps are very handy to provide skin cover around ankle and malleolar

  7. Infrared Thermography Characterization of Defects in Seamless Pipes Using an Infrared Reflector

    International Nuclear Information System (INIS)

    Park, Hee Sang; Choi, Man Yong; Park, Jeong Hak; Lee, Jae Jung; Kim, Won Tae; Lee, Bo Young

    2012-01-01

    Infrared thermography uses infrared energy radiated from any objects above absolute zero temperature, and the range of its application has been constantly broadened. As one of the active test techniques detecting radiant energy generated when energy is applied to an object, ultrasound infrared thermography is a method of detecting defects through hot spots occurring at a defect area when 15-100 kHz of ultrasound is excited to an object. This technique is effective in detecting a wide range affected by ultrasound and vibration in real time. Especially, it is really effective when a defect area is minute. Therefore, this study conducted thermography through lock-in signal processing when an actual defect exists inside the austenite STS304 seamless pipe, which simulates thermal fatigue cracks in a nuclear power plant pipe. With ultrasound excited, this study could detect defects on the rear of a pipe by using an aluminium reflector. Besides, by regulating the angle of the aluminium reflector, this study could detect both front and rear defects as a single infrared thermography image.

  8. Topological Defects in a Living Nematic Ensnare Swimming Bacteria

    Science.gov (United States)

    Genkin, Mikhail M.; Sokolov, Andrey; Lavrentovich, Oleg D.; Aranson, Igor S.

    2017-01-01

    Active matter exemplified by suspensions of motile bacteria or synthetic self-propelled particles exhibits a remarkable propensity to self-organization and collective motion. The local input of energy and simple particle interactions often lead to complex emergent behavior manifested by the formation of macroscopic vortices and coherent structures with long-range order. A realization of an active system has been conceived by combining swimming bacteria and a lyotropic liquid crystal. Here, by coupling the well-established and validated model of nematic liquid crystals with the bacterial dynamics, we develop a computational model describing intricate properties of such a living nematic. In faithful agreement with the experiment, the model reproduces the onset of periodic undulation of the director and consequent proliferation of topological defects with the increase in bacterial concentration. It yields a testable prediction on the accumulation of bacteria in the cores of +1 /2 topological defects and depletion of bacteria in the cores of -1 /2 defects. Our dedicated experiment on motile bacteria suspended in a freestanding liquid crystalline film fully confirms this prediction. Our findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter.

  9. The low-temperature thermopower of Frenkel defects in aluminium

    International Nuclear Information System (INIS)

    Sieber, G.; Wehr, G.; Boening, K.

    1977-01-01

    The thermopower S has been measured in the temperature range 1.3 to 13 K (reference: superconductor) on aluminium containing Frenkel defects (FD), i.e. self-interstitials and vacancies of equal concentration c (maximum 850 PPM). The FD have been produced in varying concentration and configuration by reactor irradiation at 15 K ('isolated' FD) and subsequent annealing ('agglomerated' FD). A whole such cycle could be made on the same sample, and the measuring accuracy was very high. The theoretical law S = AT + BT 3 was always fulfilled below 8 K. The 'diffusion' coefficient A was shown to be qualitatively consistent with the Mott formula, determined only by the scattering anisotropy of various defect types (e.g. isolated or agglomerated FD), while the Al bandstructure was essentially unaffected by the defects. Applying the Nordheim-Gorter rule the specific coefficients of vacancies Asub(V) and interstitials Asub(I) were obtained. The 'phonon drag' coefficient B, however, was independent of the electron scattering anisotropy. This behaviour is unexpected from the Bailyn theory and obviously has to do with the exceptionally strong phonon scattering on the FD. (author)

  10. Argon defect complexes in low energy Ar irradiated molybdenum

    International Nuclear Information System (INIS)

    Veen, A. van; Buters, W.T.M.; Kolk, G.J. van der; Caspers, L.M.; Armstrong, T.R.

    1982-01-01

    Thermal desorption spectrometry has been used to study the defects created in Mo irradiated along the direction with Ar ions ranging in energy from 0.1 to 2 keV. In addition to monitoring the release of the implanted Ar, additional information has been obtained by decoration of the defects with low energy helium and subsequent monitoring of the helium release. The studies show evidence that the Ar can be trapped in both substitutional sites and in a configuration in which the Ar is associated with vacancies (ArVsub(n), n >= 2). Most of the Ar implanted at high energy is released at approx. equal to 1500 K by thermal vacancy assisted diffusion. Argon trapped closer to the surface is released at lower temperatures via at least three different surface related release mechanisms. Additional results are presented on the interaction of self interstitial atoms (introduced by 100 eV Xe bombardment) with the Ar defects. Substitutional Ar is found to convert to interstitial Ar which seems to be mobile at room temperature. The Ar-vacancy complexes are found to be reduced to substitutional Ar. The results of atomistic calculations of the release mechanisms will also be presented. (orig.)

  11. Radiation defects in electron-irradiated InP crystals

    Energy Technology Data Exchange (ETDEWEB)

    Brailovskii, E.Yu.; Karapetyan, F.K.; Megela, I.G.; Tartachnik, V.P. (AN Ukrainskoj SSR, Kiev. Inst. Yadernykh Issledovanij)

    1982-06-16

    The results are presented of formation and annealing of defects in InP crystals at 1 to 50 MeV electron irradiation. The recovery of electrical properties in the range of 77 to 970 K during annealing processes is studied. Five low temperature annealing states in n-InP and the reverse annealing in p-InP are observed at 77 to 300 K. Four annealing stages at temperatures higher than 300 K are present. When the electron energy is increased more complicated thermostable defects are formed, and at 50 MeV electron energy besides of the point defect clusters are formed, which anneal at temperatures of 800 to 970 K. It is shown that the peculiarities of the Hall mobility at irradiation and annealing are caused by the scattering centres E/sub c/ - 0.2 eV. The 'limiting' position of the Fermi level in electron irradiated InP crystals is discussed.

  12. Holographic entanglement entropy of surface defects

    Energy Technology Data Exchange (ETDEWEB)

    Gentle, Simon A.; Gutperle, Michael; Marasinou, Chrysostomos [Department of Physics and Astronomy, University of California,Los Angeles, CA 90095 (United States)

    2016-04-12

    We calculate the holographic entanglement entropy in type IIB supergravity solutions that are dual to half-BPS disorder-type surface defects in N=4 supersymmetric Yang-Mills theory. The entanglement entropy is calculated for a ball-shaped region bisected by a surface defect. Using the bubbling supergravity solutions we also compute the expectation value of the defect operator. Combining our result with the previously-calculated one-point function of the stress tensor in the presence of the defect, we adapt the calculation of Lewkowycz and Maldacena http://dx.doi.org/10.1007/JHEP05(2014)025 to obtain a second expression for the entanglement entropy. Our two expressions agree up to an additional term, whose possible origin and significance is discussed.

  13. Holographic entanglement entropy of surface defects

    International Nuclear Information System (INIS)

    Gentle, Simon A.; Gutperle, Michael; Marasinou, Chrysostomos

    2016-01-01

    We calculate the holographic entanglement entropy in type IIB supergravity solutions that are dual to half-BPS disorder-type surface defects in N=4 supersymmetric Yang-Mills theory. The entanglement entropy is calculated for a ball-shaped region bisected by a surface defect. Using the bubbling supergravity solutions we also compute the expectation value of the defect operator. Combining our result with the previously-calculated one-point function of the stress tensor in the presence of the defect, we adapt the calculation of Lewkowycz and Maldacena http://dx.doi.org/10.1007/JHEP05(2014)025 to obtain a second expression for the entanglement entropy. Our two expressions agree up to an additional term, whose possible origin and significance is discussed.

  14. Di-interstitial defect in silicon revisited

    International Nuclear Information System (INIS)

    Londos, C. A.; Antonaras, G.; Chroneos, A.

    2013-01-01

    Infrared spectroscopy was used to study the defect spectrum of Cz-Si samples following fast neutron irradiation. We mainly focus on the band at 533 cm −1 , which disappears from the spectra at ∼170 °C, exhibiting similar thermal stability with the Si-P6 electron paramagnetic resonance (EPR) spectrum previously correlated with the di-interstitial defect. The suggested structural model of this defect comprises of two self-interstitial atoms located symmetrically around a lattice site Si atom. The band anneals out following a first-order kinetics with an activation energy of 0.88 ± 0.3 eV. This value does not deviate considerably from previously quoted experimental and theoretical values for the di-interstitial defect. The present results indicate that the 533 cm −1 IR band originates from the same structure as that of the Si-P6 EPR spectrum

  15. Microcephaly and Other Birth Defects: Zika

    Science.gov (United States)

    ... Español (Spanish) Recommend on Facebook Tweet Share Compartir Zika and Microcephaly Microcephaly is a birth defect in ... pregnancy or has stopped growing after birth. Congenital Zika Syndrome Congenital Zika syndrome is a unique pattern ...

  16. Ultrasonic determination of the size of defects

    International Nuclear Information System (INIS)

    Zetterwall, T.

    1989-01-01

    The paper presents results from a study of ultrasonic testing of materials. The main topic has been the determination of the size, length and deep, of cracks or defects in stainless steel plates. (K.A.E)

  17. Focal skin defect, limb anomalies and microphthalmia.

    NARCIS (Netherlands)

    Jackson, K.E.; Andersson, H.C.

    2004-01-01

    We describe two unrelated female patients with congenital single focal skin defects, unilateral microphthalmia and limb anomalies. Growth and psychomotor development were normal and no brain malformation was detected. Although eye and limb anomalies are commonly associated, clinical anophthalmia and

  18. Genetic Counseling for Congenital Heart Defects

    Science.gov (United States)

    ... Artery Disease Venous Thromboembolism Aortic Aneurysm More Genetic Counseling for Congenital Heart Defects Updated:Jan 19,2018 ... with congenital heart disease considers having children. Genetic counseling can help answer these questions and address your ...

  19. Reduction of Defects in Jewelry Manufacturing

    Science.gov (United States)

    Ayudhya, Phitchaya Phanomwan na; Tangjitsitcharoen, Somkiat

    2017-06-01

    The aim of this research was to reduce the defects of gem bracelet found during manufacturing process at a jewelry company. It was found that gem bracelet product has the highest rejects compared to the rejects found in ring, earring, and pendant products. Types of defect were classified by using Pareto Diagram consisting of gem falling, seam, unclean casting, impinge, and deformation. The causes of defect were analyzed by Cause and Effect Diagram and applied Failure Mode and Effects Analysis (FMEA) was applied during manufacturing processes. This research found that the improvement of manufacturing process could reduce the Risk Priority Number (RPN) and total of all defects by 48.70% and 48.89%, respectively.

  20. Dental Enamel Defects and Celiac Disease

    Science.gov (United States)

    ... Digestive System & How it Works Zollinger-Ellison Syndrome Dental Enamel Defects and Celiac Disease Celiac disease manifestations ... affecting any organ or body system. One manifestation—dental enamel defects—can help dentists and other health ...

  1. Creation of radiation defects in KCl crystals

    International Nuclear Information System (INIS)

    Lushchik, A.Ch.; Pung, L.A.; Khaldre, Yu.Yu.; Kolk, Yu.V.

    1981-01-01

    Optical and EPR methods were used to study the creation of anion and cation Frenkel defects in KCl crystals irradiated by X-ray and VUV-radiation. The decay of excitons with the creation of charged Frenkel defects (α and I centres) was detected and investigated at 4.2 K. The decay of excitons as well as the recombination of electrons with self-trapped holes leads to the creation of neutral Frenkel defects (F and H centres). The creation of Cl 3 - and Vsub(F) centres (cation vacancy is a component of these centres) by X-irradiation at 80 K proves the possibility of cation defects creation in KCl [ru

  2. Infrared computations of defect Schur indices

    Energy Technology Data Exchange (ETDEWEB)

    Córdova, Clay [School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr., Princeton, NJ (United States); Gaiotto, Davide [Perimeter Institute for Theoretical Physics,31 Caroline St., Waterloo, Ontario, N2L 2Y5 (Canada); Shao, Shu-Heng [Jefferson Physical Laboratory, Harvard University,17 Oxford St., Cambridge, MA (United States); School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr., Princeton, NJ (United States)

    2016-11-18

    We conjecture a formula for the Schur index of four-dimensional N=2 theories in the presence of boundary conditions and/or line defects, in terms of the low-energy effective Seiberg-Witten description of the system together with massive BPS excitations. We test our proposal in a variety of examples for SU(2) gauge theories, either conformal or asymptotically free. We use the conjecture to compute these defect-enriched Schur indices for theories which lack a Lagrangian description, such as Argyres-Douglas theories. We demonstrate in various examples that line defect indices can be expressed as sums of characters of the associated two-dimensional chiral algebra and that for Argyres-Douglas theories the line defect OPE reduces in the index to the Verlinde algebra.

  3. Intrinsic defects in 3D printed materials

    OpenAIRE

    Bolton, Christopher; Dagastine, Raymond

    2015-01-01

    We discuss the impact of bulk structural defects on the coherence, phase and polarisation of light passing through transparent 3D printed materials fabricated using a variety of commercial print technologies.

  4. International conference on defects in insulating crystals

    International Nuclear Information System (INIS)

    1977-01-01

    Short summaries of conference papers are presented. Some of the conference topics included transport properties, defect levels, superionic conductors, radiation effects, John-Teller effect, electron-lattice interactions, and relaxed excited states

  5. Apparatus for locating defective nuclear fuel elements

    International Nuclear Information System (INIS)

    Lawrie, W.E.

    1979-01-01

    An ultrasonic search unit for locating defective fuel elements within a fuel assembly used in a water cooled nuclear reactor is presented. The unit is capable of freely traversing the restricted spaces between the fuel elements

  6. Point defects dynamics in a stress field

    International Nuclear Information System (INIS)

    Smetniansky de De Grande, Nelida.

    1989-01-01

    The dependence of anisotropic defect diffusion on stress is studied for a hexagonal close packed (hcp) material under irradiation and uniaxially stressed. The diffusion is described as a discrete process of thermally activated jumps. It is shown that the presence of an external stress field enhances the intrinsic anisotropic diffusion, being this variation determined by the defect dipole tensors' symmetry in the equilibrium and saddle point configurations. Also, the point defect diffusion equations to sinks, like edge dislocations and spherical cavities, are solved and the sink strengths are calculated. The conclusion is that the dynamics of the interaction between defects and sinks is controlled by the changes in diffusivity induced by stress fields. (Author) [es

  7. Genetics Home Reference: abdominal wall defect

    Science.gov (United States)

    ... are two main types of abdominal wall defects: omphalocele and gastroschisis . Omphalocele is an opening in the center of the ... covering the exposed organs in gastroschisis. Fetuses with omphalocele may grow slowly before birth (intrauterine growth retardation) ...

  8. Defect networks and supersymmetric loop operators

    Energy Technology Data Exchange (ETDEWEB)

    Bullimore, Mathew [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5 (Canada)

    2015-02-10

    We consider topological defect networks with junctions in A{sub N−1} Toda CFT and the connection to supersymmetric loop operators in N=2 theories of class S on a four-sphere. Correlation functions in the presence of topological defect networks are computed by exploiting the monodromy of conformal blocks, generalising the notion of a Verlinde operator. Concentrating on a class of topological defects in A{sub 2} Toda theory, we find that the Verlinde operators generate an algebra whose structure is determined by a set of generalised skein relations that encode the representation theory of a quantum group. In the second half of the paper, we explore the dictionary between topological defect networks and supersymmetric loop operators in the N=2{sup ∗} theory by comparing to exact localisation computations. In this context, the the generalised skein relations are related to the operator product expansion of loop operators.

  9. Elastic interaction energies of defect structures

    International Nuclear Information System (INIS)

    Seitz, E.; de Fontaine, D.

    1976-01-01

    The elastic strain energy between point defects and small disk-shaped clusters of defects are calculated to determine stable configurations. A distortion tensor of tetragonal symmetry is assigned to each impurity atom. The tetragonality ratio t is varied to cover needle-type (t greater than 1), spherical (t = 1) and disk-type (t less than 0) strain fields. To vary the elastic properties of the host material, Fe, Cu, Al, and V were chosen as examples. Computer calculations are based on the microscopic theory of elasticity which emphasizes calculations in discrete Fourier space. Pairs of point defects order along [001] for t less than 1 and along (001) for t = 1 for all host elements. For t greater than 1 fcc lattices and bcc lattices behave differently. It is shown that only certain three dimensional periodic arrangements of parallel and perpendicular disk-like defect clusters are realized for given tetragonality ratio t and host element

  10. International conference on defects in insulating crystals

    Energy Technology Data Exchange (ETDEWEB)

    1977-01-01

    Short summaries of conference papers are presented. Some of the conference topics included transport properties, defect levels, superionic conductors, radiation effects, John-Teller effect, electron-lattice interactions, and relaxed excited states. (SDF)

  11. Theory of defects in Si and Ge: Past, present and recent developments

    International Nuclear Information System (INIS)

    Estreicher, S.K.; Backlund, D.; Gibbons, T.M.

    2010-01-01

    Over the past few decades, considerable progress has been achieved in the theoretical predictions of a wide range of properties of defects in semiconductors. In addition to structures, energetics, spin and charge densities, theory now routinely predicts accurate vibrational properties of defects, and thus connects to the optical characterization of light impurities. However, the positions of gap levels have yet to be predicted with systemically reliable accuracy. Today, supercells much larger than in the past are being used to describe defect centers from first principles. Systems large enough to study the dynamics of extended defects can be handled near the first-principles level. This paper contains a brief review of the key developments that have rendered theory quantitatively useful to experimentalists and an overview of the current 'state-of-the-art' and ongoing developments. Some of the remaining challenges are discussed, with examples in Si and Ge.

  12. Response to defects in multipartite and bipartite entanglement of isotropic quantum spin networks

    Science.gov (United States)

    Roy, Sudipto Singha; Dhar, Himadri Shekhar; Rakshit, Debraj; SenDe, Aditi; Sen, Ujjwal

    2018-05-01

    Quantum networks are an integral component in performing efficient computation and communication tasks that are not accessible using classical systems. A key aspect in designing an effective and scalable quantum network is generating entanglement between its nodes, which is robust against defects in the network. We consider an isotropic quantum network of spin-1/2 particles with a finite fraction of defects, where the corresponding wave function of the network is rotationally invariant under the action of local unitaries. By using quantum information-theoretic concepts like strong subadditivity of von Neumann entropy and approximate quantum telecloning, we prove analytically that in the presence of defects, caused by loss of a finite fraction of spins, the network, composed of a fixed numbers of lattice sites, sustains genuine multisite entanglement and at the same time may exhibit finite moderate-range bipartite entanglement, in contrast to the network with no defects.

  13. Application of artificial neural networks to evaluate weld defects of nuclear components

    International Nuclear Information System (INIS)

    Amin, E.S.

    2007-01-01

    Artificial neural networks (ANNs) are computational representations based on the biological neural architecture of the brain. ANNs have been successfully applied to a wide range of engineering and scientific applications, such as signal, image processing and data analysis. Although Radiographic testing is widely used for welding defects, it is unsuccessful in identifying some welding defects because of the nature of image formation and quality. Neoteric algorithms have been used for the purpose of weld defects identifications in radiographic images to replace the expert knowledge. The application of artificial neural networks in noise detection of radiographic films is used. Radial Basis (RB) and learning vector quantization (LVQ) were applied. The method shows good performance in weld defects recognition and classification problems.

  14. Optical transitions in two-dimensional topological insulators with point defects

    Science.gov (United States)

    Sablikov, Vladimir A.; Sukhanov, Aleksei A.

    2016-12-01

    Nontrivial properties of electronic states in topological insulators are inherent not only to the surface and boundary states, but to bound states localized at structure defects as well. We clarify how the unusual properties of the defect-induced bound states are manifested in optical absorption spectra in two-dimensional topological insulators. The calculations are carried out for defects with short-range potential. We find that the defects give rise to the appearance of specific features in the absorption spectrum, which are an inherent property of topological insulators. They have the form of two or three absorption peaks that are due to intracenter transitions between electron-like and hole-like bound states.

  15. Splitting, linking, knotting, and solitonic escape of topological defects in nematic drops with handles.

    Science.gov (United States)

    Tasinkevych, Mykola; Campbell, Michael G; Smalyukh, Ivan I

    2014-11-18

    Topologically nontrivial field excitations, including solitonic, linked, and knotted structures, play important roles in physical systems ranging from classical fluids and liquid crystals, to electromagnetism, classic, and quantum field theories. These excitations can appear spontaneously during symmetry-breaking phase transitions. For example, in cosmological theories, cosmic strings may have formed knotted configurations influencing the Early Universe development, whereas in liquid crystals transient tangled defect lines were observed during isotropic-nematic transitions, eventually relaxing to defect-free states. Knotted and solitonic fields and defects were also obtained using optical manipulation, complex-shaped colloids, and frustrated cholesterics. Here we use confinement of nematic liquid crystal by closed surfaces with varied genus and perpendicular boundary conditions for a robust control of appearance and stability of such field excitations. Theoretical modeling and experiments reveal structure of defect lines as a function of the surface topology and material and geometric parameters, establishing a robust means of controlling solitonic, knotted, linked, and other field excitations.

  16. Energetics of intrinsic point defects in uranium dioxide from electronic-structure calculations

    International Nuclear Information System (INIS)

    Nerikar, Pankaj; Watanabe, Taku; Tulenko, James S.; Phillpot, Simon R.; Sinnott, Susan B.

    2009-01-01

    The stability range of intrinsic point defects in uranium dioxide is determined as a function of temperature, oxygen partial pressure, and non-stoichiometry. The computational approach integrates high accuracy ab initio electronic-structure calculations and thermodynamic analysis supported by experimental data. In particular, the density functional theory calculations are performed at the level of the spin polarized, generalized gradient approximation and includes the Hubbard U term; as a result they predict the correct anti-ferromagnetic insulating ground state of uranium oxide. The thermodynamic calculations enable the effects of system temperature and partial pressure of oxygen on defect formation energy to be determined. The predicted equilibrium properties and defect formation energies for neutral defect complexes match trends in the experimental literature quite well. In contrast, the predicted values for charged complexes are lower than the measured values. The calculations predict that the formation of oxygen interstitials becomes increasingly difficult as higher temperatures and reducing conditions are approached

  17. Diffuse scattering from crystals with point defects

    International Nuclear Information System (INIS)

    Andrushevsky, N.M.; Shchedrin, B.M.; Simonov, V.I.; Malakhova, L.F.

    2002-01-01

    The analytical expressions for calculating the intensities of X-ray diffuse scattering from a crystal of finite dimensions and monatomic substitutional, interstitial, or vacancy-type point defects have been derived. The method for the determination of the three-dimensional structure by experimental diffuse-scattering data from crystals with point defects having various concentrations is discussed and corresponding numerical algorithms are suggested

  18. [SOX2 defect and anophthalmia and microphthalmia].

    Science.gov (United States)

    Ye, Fu-xiang; Fan, Xian-qun

    2012-11-01

    As a severe congenital developmental disorder, anophthalmia and microphthalmia are usually accompanied with vision impairment and hypoevolutism of the orbit in the affected side. Many genes are involved in anophthalmia and microphthalmia, in which, SOX2 is an important one. The defect of SOX2 causes multiple system disorders, including anophthalmia and microphthalmia. We describe the relationship between the SOX2 defect and anophthalmia/microphthalmia, in order to offer some proposals for the differential diagnosis, treatment and research of anophthalmia and microphthalmia.

  19. Virtues and defects of peruvians colonial heritage

    OpenAIRE

    León, Ramón

    2014-01-01

    This communication reports a study in 691 students (414 women, 277 men, 16-60 years old), who were asked to rate (on a scale of 0 to 4) ten virtues and ten defects of an average Peruvian. The virtues considered were hard-working, honest, enterprising, ambitious, thrifty, sympathetic, creative, tidy, proud, and wel.organized; the defects were lazy, corrupt, conformist, fatalist, spendthrift, individualist, passive, envious, inhibited, talkative. They were asked too to rate the influence of col...

  20. Radioactive fallout and neural tube defects

    Directory of Open Access Journals (Sweden)

    Nejat Akar

    2015-10-01

    Full Text Available Possible link between radioactivity and the occurrence of neural tube defects is a long lasting debate since the Chernobyl nuclear fallout in 1986. A recent report on the incidence of neural defects in the west coast of USA, following Fukushima disaster, brought another evidence for effect of radioactive fallout on the occurrence of NTD’s. Here a literature review was performed focusing on this special subject.

  1. Dural sinus filling defect: intrasigmoid encephalocele

    Science.gov (United States)

    Karatag, Ozan; Cosar, Murat; Kizildag, Betul; Sen, Halil Murat

    2013-01-01

    Filling defects of dural venous sinuses are considered to be a challenging problem especially in case of symptomatic patients. Many lesions have to be ruled out such as sinus thrombosis, arachnoid granulations and tumours. Encephalocele into dural sinus is also a rare cause of these filling defects of dural sinuses. Here, we report an extremely rare case with spontaneous occult invagination of temporal brain tissue into the left sigmoid sinus and accompanying cerebellar ectopia. PMID:24311424

  2. Defect core detection in radiata pine logs

    International Nuclear Information System (INIS)

    Wallace, G.

    1993-01-01

    Internal defect cores in Pinus radiata logs arise primarily from the practice in New Zealand of pruning trees to increase the amount of clear wood. Realising the benefits of this practice when milling the logs is hampered by the lack of a practical method for detecting the defect cores. This report attempts to establish industry requirements for detections and examine techniques which may be suitable. Some trials of a novel technique are described. (author) 19 refs.; 11 figs

  3. Digitized Speech Characteristics in Patients with Maxillectomy Defects.

    Science.gov (United States)

    Elbashti, Mahmoud E; Sumita, Yuka I; Hattori, Mariko; Aswehlee, Amel M; Taniguchi, Hisashi

    2017-12-06

    Accurate evaluation of speech characteristics through formant frequency measurement is important for proper speech rehabilitation in patients after maxillectomy. This study aimed to evaluate the utility of digital acoustic analysis and vowel pentagon space for the prediction of speech ability after maxillectomy, by comparing the acoustic characteristics of vowel articulation in three classes of maxillectomy defects. Aramany's classifications I, II, and IV were used to group 27 male patients after maxillectomy. Digital acoustic analysis of five Japanese vowels-/a/, /e/, /i/, /o/, and /u/-was performed using a speech analysis system. First formant (F1) and second formant (F2) frequencies were calculated using an autocorrelation method. Data were plotted on an F1-F2 plane for each patient, and the F1 and F2 ranges were calculated. The vowel pentagon spaces were also determined. One-way ANOVA was applied to compare all results between the three groups. Class II maxillectomy patients had a significantly higher F2 range than did Class I and Class IV patients (p = 0.002). In contrast, there was no significant difference in the F1 range between the three classes. The vowel pentagon spaces were significantly larger in class II maxillectomy patients than in Class I and Class IV patients (p = 0.014). The results of this study indicate that the acoustic characteristics of maxillectomy patients are affected by the defect area. This finding may provide information for obturator design based on vowel articulation and defect class. © 2017 by the American College of Prosthodontists.

  4. EUV actinic defect inspection and defect printability at the sub-32 nm half pitch

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Sungmin; Kearney, Patrick; Wurm, Stefan; Goodwin, Frank; Han, Hakseung; Goldberg, Kenneth; Mochi, Iacopp; Gullikson, Eric M.

    2009-08-01

    Extreme ultraviolet (EUV) mask blanks with embedded phase defects were inspected with a reticle actinic inspection tool (AIT) and the Lasertec M7360. The Lasertec M7360, operated at SEMA TECH's Mask Blank Development Center (MBDC) in Albany, NY, has a sensitivity to multilayer defects down to 40-45 nm, which is not likely sufficient for mask blank development below the 32 nm half-pitch node. Phase defect printability was simulated to calculate the required defect sensitivity for a next generation blank inspection tool to support reticle development for the sub-32 nm half-pitch technology node. Defect mitigation technology is proposed to take advantage of mask blanks with some defects. This technology will reduce the cost of ownership of EUV mask blanks. This paper will also discuss the kind of infrastructure that will be required for the development and mass production stages.

  5. Characterization of lacunar defects by positrons annihilation

    International Nuclear Information System (INIS)

    Barthe, M.F.; Corbel, C.; Blondiaux, G.

    2003-01-01

    Among the nondestructive methods for the study of matter, the positrons annihilation method allows to sound the electronic structure of materials by measuring the annihilation characteristics. These characteristics depend on the electronic density as seen by the positon, and on the electron momentums distribution which annihilate with the positon. The positon is sensible to the coulombian potential variations inside a material and sounds preferentially the regions away from nuclei which represent potential wells. The lacunar-type defects (lack of nuclei) represent deep potential wells which can trap the positon up to temperatures close to the melting. This article describes the principles of this method and its application to the characterization of lacunar defects: 1 - positrons: matter probes (annihilation of electron-positon pairs, annihilation characteristics, positrons sources); 2 - positrons interactions in solids (implantation profiles, annihilation states, diffusion and trapping, positon lifetime spectrum: evolution with the concentration of defects); 3 - measurement of annihilation characteristics with two gamma photons (lifetime spectroscopy with the β + 22 Na isotope, spectroscopy of Doppler enlargement of the annihilation line); 4 - determination of the free volume of defects inside or at the surface of materials (annihilation signature in lacunar defects, lacuna, lacunar clusters and cavities, acceptors nature in semiconductors: ionic or lacunar, interface defects, precipitates in alloys); 5 - conclusions. (J.S.)

  6. Positron annihilation spectroscopy in defects of semiconductors

    CERN Document Server

    Fujinami, M

    2002-01-01

    Interaction of positron and defects, application to research of defects of semiconductor and defects on the surface of semiconductor are explained. Cz (Czochralski)-Si single crystal with 10 sup 1 sup 8 cm sup - sup 3 impurity oxygen was introduced defects by electron irradiation and the positron lifetime was measured at 90K after annealing. The defect size and recovery temperature were determined by the lifetime measurement. The distribution of defects in the depth direction is shown by S-E curve. The chemical state analysis is possible by CBS (Coincidence Doppler Broadening) spectra. The application to silicon-implanted (100 keV, 2x10 sup 1 sup 5 cm sup - sup 2) silicon and oxygen-implanted (180 keV, 2x10 sup 1 sup 5 cm sup - sup 2) silicon are stated. On the oxygen-implanted silicon, the main product was V2 after implantation, V sub 6 O sub 2 at 600degC and V sub 1 sub 0 O sub 6 at 800degC. (S.Y.)

  7. Reduction in Defect Content of ODS Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ritherdon, J

    2001-05-15

    The work detailed within this report is a continuation of earlier work carried out under contract number 1DX-SY382V. The earlier work comprises a literature review of the sources and types of defects found principally in Fe-based ODS alloys as well as experimental work designed to identify defects in the prototype ODS-Fe{sub 3}Al alloy, deduce their origins and to recommend methods of defect reduction. The present work is an extension of the experimental work already reported and concentrates on means of reduction of defects already identified rather than the search for new defect types. This report also includes results gathered during powder separation trials, conducted by the University of Groningen, Netherlands and coordinated by the University of Liverpool, involving the separation of different metallic powders in terms of their differing densities. The scope and objectives of the present work were laid out in the technical proposal ''Reduction in Defect Content in ODS Alloys-III''. All the work proposed in the ''Statement of Work'' section of the technical proposal has been carried out and all work extra to the ''Statement of Work'' falls within the context of an ODS-Fe{sub 3}Al alloy of improved overall quality and potential creep performance in the consolidated form. The outturn of the experimental work performed is reported in the following sections.

  8. Congenital heart defects in Williams syndrome.

    Science.gov (United States)

    Yuan, Shi-Min

    2017-01-01

    Yuan SM. Congenital heart defects in Williams syndrome. Turk J Pediatr 2017; 59: 225-232. Williams syndrome (WS), also known as Williams-Beuren syndrome, is a rare genetic disorder involving multiple systems including the circulatory system. However, the etiologies of the associated congenital heart defects in WS patients have not been sufficiently elucidated and represent therapeutic challenges. The typical congenital heart defects in WS were supravalvar aortic stenosis, pulmonary stenosis (both valvular and peripheral), aortic coarctation and mitral valvar prolapse. The atypical cardiovascular anomalies include tetralogy of Fallot, atrial septal defects, aortic and mitral valvular insufficiencies, bicuspid aortic valves, ventricular septal defects, total anomalous pulmonary venous return, double chambered right ventricle, Ebstein anomaly and arterial anomalies. Deletion of the elastin gene on chromosome 7q11.23 leads to deficiency or abnormal deposition of elastin during cardiovascular development, thereby leading to widespread cardiovascular abnormalities in WS. In this article, the distribution, treatment and surgical outcomes of typical and atypical cardiac defects in WS are discussed.

  9. A novel inspection system for cosmetic defects

    Science.gov (United States)

    Hazra, S.; Roy, R.; Williams, D.; Aylmore, R.; Hollingdale, D.

    2013-12-01

    The appearance of automotive skin panels creates desirability for a product and differentiates it from the competition. Because of the importance of skin panels, considerable care is taken in minimizing defects such as the 'hollow' defect that occur around door-handle depressions. However, the inspection process is manual, subjective and time-consuming. This paper describes the development of an objective and inspection scheme for the 'hollow' defect. In this inspection process, the geometry of a panel is captured using a structured lighting system. The geometry data is subsequently analyzed by a purpose-built wavelet-based algorithm to identify the location of any defects that may be present and to estimate the perceived severity of the defects without user intervention. This paper describes and critically evaluates the behavior of this physically-based algorithm on an ideal and real geometry and compares its result to an actual audit. The results show that the algorithm is capable of objectively locating and classifying 'hollow' defects in actual panels.

  10. Autograft reconstructions for bone defects in primary total knee replacement in severe varus knees

    Directory of Open Access Journals (Sweden)

    Yatinder Kharbanda

    2014-01-01

    Full Text Available Background: Large posteromedial defects encountered in severe varus knees during primary total knee arthroplasty can be treated by cementoplasty, structural bone grafts or metallic wedges. The option is selected depending upon the size of the defect. We studied the outcome of autograft (structural and impaction bone grafting reconstruction of medial tibial bone defects encountered during primary total knee replacement in severe varus knees. Materials and Methods: Out of 675 primary varus knees operated, bone defects in proximal tibia were encountered in 54 knees. Posteromedial defects involving 25-40% of the tibial condyle cut surface and measuring more than 5 mm in depth were grafted using a structural graft obtained from cut distal femur or proximal tibia in 48 knees. For larger, peripheral uncontained vertical defects in six cases, measuring >25 mm in depth and involving >40% cut surface of proximal tibial condyle, impaction bone grafting with a mesh support was used. Results: Bone grafts incorporated in 54 knees in 6 months. There was no graft collapse or stress fractures, loosening or nonunion. The average followup period was 7.8 years (range 5-10 years. We observed an average postoperative increase in the Knee Society Score from 40 to 90 points. There was improvement in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC scores in terms of pain, stiffness and physical function during activities of daily living. Conclusion: Bone grafting for defects in primary total knee is justified as it is biological, available then and is cost effective besides preserving bone stock for future revisions. Structural grafts should be used in defects >5 mm deep and involving 25-40% of the cut proximal tibial condyle surface. For larger peripheral vertical defects, impaction bone grafting contained in a mesh should be done.

  11. Advanced defect detection algorithm using clustering in ultrasonic NDE

    Science.gov (United States)

    Gongzhang, Rui; Gachagan, Anthony

    2016-02-01

    A range of materials used in industry exhibit scattering properties which limits ultrasonic NDE. Many algorithms have been proposed to enhance defect detection ability, such as the well-known Split Spectrum Processing (SSP) technique. Scattering noise usually cannot be fully removed and the remaining noise can be easily confused with real feature signals, hence becoming artefacts during the image interpretation stage. This paper presents an advanced algorithm to further reduce the influence of artefacts remaining in A-scan data after processing using a conventional defect detection algorithm. The raw A-scan data can be acquired from either traditional single transducer or phased array configurations. The proposed algorithm uses the concept of unsupervised machine learning to cluster segmental defect signals from pre-processed A-scans into different classes. The distinction and similarity between each class and the ensemble of randomly selected noise segments can be observed by applying a classification algorithm. Each class will then be labelled as `legitimate reflector' or `artefacts' based on this observation and the expected probability of defection (PoD) and probability of false alarm (PFA) determined. To facilitate data collection and validate the proposed algorithm, a 5MHz linear array transducer is used to collect A-scans from both austenitic steel and Inconel samples. Each pulse-echo A-scan is pre-processed using SSP and the subsequent application of the proposed clustering algorithm has provided an additional reduction to PFA while maintaining PoD for both samples compared with SSP results alone.

  12. Defect engineering: design tools for solid state electrochemical devices

    International Nuclear Information System (INIS)

    Tuller, Harry L.

    2003-01-01

    The interest in solid state electrochemical devices including sensors, fuel cells, batteries, oxygen permeation membranes, etc. has grown rapidly in recent years. Many of the same figures of merit apply to these different applications, the key ones being ionic conduction in solid electrolytes, mixed ionic-electronic conduction (MIEC) in electrodes and permeation membranes, and gas-solid reaction kinetics in sensors and fuel cells. Optimization of device performance often relies on the careful understanding and control of both ionic and electronic defects in the materials that make up the key device components. To date, most materials in use have been discovered serendipitously. A key focus of this paper is on the tools available to scientists and engineers to practice 'defect engineering' for the purpose of optimizing the performance of such materials. Dopants, controlled structural disorder, and interfaces are examined in relation to increasing the conductivity of solid electrolytes. The creation of defect bands is demonstrated as a means for introducing high levels of electronic conductivity into a solid electrolyte for the purpose of creating a mixed conductor and thereby a monolithic fuel cell structure. Dopants are also examined as a means of reducing losses in a high temperature resonant sensor platform. The control of microstructure, down to the nano-scale, is shown capable of inverting the predominant ionic to an electronic charge carrier and thereby markedly modifying electrical properties. Electrochemical bias and light are also discussed in terms of creating defects locally thereby providing means for micromachining a broad range of materials with precise dimensional control, low residual stress and controlled etch rates

  13. Long range trajectories

    Energy Technology Data Exchange (ETDEWEB)

    Allen, P. W.; Jessup, E. A.; White, R. E. [Air Resources Field Research Office, Las Vegas, Nevada (United States)

    1967-07-01

    A single air molecule can have a trajectory that can be described with a line, but most meteorologists use single lines to represent the trajectories of air parcels. A single line trajectory has the disadvantage that it is a categorical description of position. Like categorized forecasts it provides no qualification, and no provision for dispersion in case the parcel contains two or more molecules which may take vastly different paths. Diffusion technology has amply demonstrated that an initial aerosol cloud or volume of gas in the atmosphere not only grows larger, but sometimes divides into puffs, each having a different path or swath. Yet, the average meteorologist, faced with the problem of predicting the future motion of a cloud, usually falls back on the line trajectory approach with the explanation that he had no better tool for long range application. In his more rational moments, he may use some arbitrary device to spread his cloud with distance. One such technique has been to separate the trajectory into two or more trajectories, spaced about the endpoint of the original trajectory after a short period of travel, repeating this every so often like a chain reaction. This has the obvious disadvantage of involving a large amount of labor without much assurance of improved accuracy. Another approach is to draw a circle about the trajectory endpoint, to represent either diffusion or error. The problem then is to know what radius to give the circle and also whether to call it diffusion or error. Meteorologists at the Nevada Test Site (NTS) are asked frequently to provide advice which involves trajectory technology, such as prediction of an aerosol cloud path, reconstruction of the motion of a volume of air, indication of the dilution, and the possible trajectory prediction error over great distances. Therefore, we set out, nearly three years ago, to provide some statistical knowledge about the status of our trajectory technology. This report contains some of the

  14. On genealogy of defect electron states in semiconductor materials

    International Nuclear Information System (INIS)

    Makhmudov, A.Sh.

    1984-01-01

    Main factors of formation of defect electron structure in semiconductors are considered. It is concluded on the basis of analysis of papers published earlier that it is necessary to take account of two factors: long- and short-range orders i.e. the nature of the atom interaction with the several nearest neighbours as well as crystal periodicity, correctly formulated boundary conditions. One of possible wayes of the given task realization is the combination of a traditional scheme of the solid body theory- the Green function method and the semiempirical quantum-chemical method of equivalent orbitales

  15. Primary defect production by high energy displacement cascades in molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Selby, Aaron P. [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Xu, Donghua, E-mail: xudh@utk.edu [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Juslin, Niklas; Capps, Nathan A. [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Wirth, Brian D. [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Oak Ridge National Laboratory, P.O. Box 2008, MS6003, Oak Ridge, TN 37831 (United States)

    2013-06-15

    We report molecular dynamics simulations of primary damage in molybdenum produced by high energy displacement cascades on the femto- to pico-second and Angstrom to nanometer scales. Clustering directly occurred for both interstitials and vacancies in the 1–50 keV cascade energy range explored. Point defect survival efficiency and partitioning probabilities into different sized clusters were quantified. The results will provide an important reference for kinetic models to describe the microstructural evolution in Mo under ion or neutron irradiations over much longer time and length scales.

  16. Dislocation-defect interactions and mechanical properties of crystals

    International Nuclear Information System (INIS)

    Granato, A.V.

    1975-01-01

    The influence of dislocation-defect interactions on mechanical properties of crystals is reviewed. Interactions are separated into those producing pinning and those producing viscous drag. Deformation behavior is classified according to the strength of the drag. For small drag, inertial effects become important. For intermediate drag, traditional theories resting on rate theory treatments become applicable. For large drag, viscoelastic behavior is obtained. Measurements are examined for information concerning the basic nature of different sources of short and long range pinning and of drag

  17. Positron Annihilation Study of Radiation Defects in Zinc Oxide

    OpenAIRE

    Tomiyama, Noriyuki; Takenaka, Minoru; Kuramoto, Eiichi

    1992-01-01

    Positron annihilation studies have been carried out to clarify the radiation induced defects in ZnO single crystals. Vapor-grown ZnO crystals were irradiated at 77 K with 28 MeV electrons. Before irradiation as-grown specimens showed the mean positron lifetime in the range of 160-195 ps. Electron irradiation increased the mean positron lifetime up to 205-210 ps.This long-lifetime disappeared until 473 K during successive isochronal annealing steps. The radiation-induced coloration was anneale...

  18. Folic acid supplementation is not the sole factor in determining ...

    African Journals Online (AJOL)

    Folic acid supplementation is not the sole factor in determining neural tube defects: The possible role of autoantibodies. Keat Wei Loo, Siew Hua Gan. Abstract. Neural tube defects (NTDs) are severe but common congenital malformations. Neonates who suffer from NTDs may experience long-term complications throughout ...

  19. Modelling NDE pulse-echo inspection of misorientated planar rough defects using an elastic finite element method

    Energy Technology Data Exchange (ETDEWEB)

    Pettit, J. R.; Lowe, M. J. S. [UK Research Centre for NDE, Imperial College London, Exhibition Road, London, SW7 2AZ (United Kingdom); Walker, A. E. [Rolls-Royce Nuclear, PO BOX 2000, Derby, DE21 7XX (United Kingdom)

    2015-03-31

    Pulse-echo ultrasonic NDE examination of large pressure vessel forgings is a design and construction code requirement in the power generation industry. Such inspections aim to size and characterise potential defects that may have formed during the forging process. Typically these defects have a range of orientations and surface roughnesses which can greatly affect ultrasonic wave scattering behaviour. Ultrasonic modelling techniques can provide insight into defect response and therefore aid in characterisation. However, analytical approaches to solving these scattering problems can become inaccurate, especially when applied to increasingly complex defect geometries. To overcome these limitations a elastic Finite Element (FE) method has been developed to simulate pulse-echo inspections of embedded planar defects. The FE model comprises a significantly reduced spatial domain allowing for a Monte-Carlo based approach to consider multiple realisations of defect orientation and surface roughness. The results confirm that defects aligned perpendicular to the path of beam propagation attenuate ultrasonic signals according to the level of surface roughness. However, for defects orientated away from this plane, surface roughness can increase the magnitude of the scattered component propagating back along the path of the incident beam. This study therefore highlights instances where defect roughness increases the magnitude of ultrasonic scattered signals, as opposed to attenuation which is more often assumed.

  20. Geometrically unrestricted, topologically constrained control of liquid crystal defects using simultaneous holonomic magnetic and holographic optical manipulation

    Science.gov (United States)

    Varney, Michael C. M.; Jenness, Nathan J.; Smalyukh, Ivan I.

    2014-02-01

    Despite the recent progress in physical control and manipulation of various condensed matter, atomic, and particle systems, including individual atoms and photons, our ability to control topological defects remains limited. Recently, controlled generation, spatial translation, and stretching of topological point and line defects have been achieved using laser tweezers and liquid crystals as model defect-hosting systems. However, many modes of manipulation remain hindered by limitations inherent to optical trapping. To overcome some of these limitations, we integrate holographic optical tweezers with a magnetic manipulation system, which enables fully holonomic manipulation of defects by means of optically and magnetically controllable colloids used as "handles" to transfer forces and torques to various liquid crystal defects. These colloidal handles are magnetically rotated around determined axes and are optically translated along three-dimensional pathways while mechanically attached to defects, which, combined with inducing spatially localized nematic-isotropic phase transitions, allow for geometrically unrestricted control of defects, including previously unrealized modes of noncontact manipulation, such as the twisting of disclination clusters. These manipulation capabilities may allow for probing topological constraints and the nature of defects in unprecedented ways, providing the foundation for a tabletop laboratory to expand our understanding of the role defects play in fields ranging from subatomic particle physics to early-universe cosmology.