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Sample records for defects prevention study

  1. National Birth Defects Prevention Study (NBDPS)

    MedlinePlus

    ... were taking multivitamins before their pregnancy. [ Read Summary ] Air Pollution and Congenital Heart Defects Many pregnant women, especially ... research is needed to learn what levels of air pollution affect an unborn baby. [ Read Summary ] The Potential ...

  2. Laterality defects in the national birth defects prevention study 1998-2007 birth prevalence and descriptive epidemiology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Little is known epidemiologically about laterality defects. Using data from the National Birth Defects Prevention Study (NBDPS), a large multi-site case-control study of birth defects, we analyzed prevalence and selected characteristics in children born with laterality defects born from 1998 to 2007...

  3. Maternal intake of vitamin E and birth defects, National Birth Defects Prevention Study, 1997–2005

    PubMed Central

    Gilboa, Suzanne M.; Lee, Kyung A.; Cogswell, Mary E.; Traven, Flavia K.; Botto, Lorenzo D.; Riehle-Colarusso, Tiffany; Correa, Adolfo; Boyle, Coleen A.

    2015-01-01

    Background In a recent study, high maternal periconceptional intake of vitamin E was found to be associated with risk of congenital heart defects (CHDs). To explore this association further, we investigated the association between total daily vitamin E intake and selected birth defects. Methods We analyzed data from 4,525 controls and 8,665 cases from the 1997–2005 National Birth Defects Prevention Study. We categorized estimated periconceptional energy-adjusted total daily vitamin E intake from diet and supplements into quartiles (referent, lowest quartile). Associations between quartiles of energy-adjusted vitamin E intake and selected birth defects were adjusted for demographic, lifestyle, and nutritional factors. Results We observed a statistically significant association with the third quartile of vitamin E intake (OR 1.17; 95% CI 1.01 – 1.35) and all CHDs combined. Among CHD sub-types, we observed associations with left ventricular outflow tract obstruction defects, and its sub-type, coarctation of the aorta and the third quartile of vitamin E intake. Among defects other than CHDs, we observed associations between anorectal atresia and the third quartile of vitamin E intake (OR 1.66; 95% CI 1.01 – 2.72) and hypospadias and the fourth quartile of vitamin E intake (OR 1.42; 95% CI 1.09 – 1.87). Conclusions Selected quartiles of energy-adjusted estimated total daily vitamin E intake were associated with selected birth defects. However, because these few associations did not exhibit exposure-response patterns consistent with increasing risk associated with increasing intake of vitamin E, further studies are warranted to corroborate our findings. PMID:24740457

  4. Birth defects, causal attributions, and ethnicity in the national birth defects prevention study.

    PubMed

    Case, Amy P; Royle, Marjorie; Scheuerle, Angela E; Carmichael, Suzan L; Moffitt, Karen; Ramadhani, Tunu

    2014-10-01

    In order to translate research findings into effective prevention strategies, it is important to understand people's beliefs about the causes of poor health outcomes. However, with the exception of knowledge and beliefs about folic acid supplementation, little is known regarding women's causal attributions women regarding birth defects. We employed Attribution Theory constructs to analyze open-text interview responses from 2,672 control mothers in the National Birth Defects Prevention Study who gave birth in 1997-2005. Common themes included use of alcohol, tobacco, illicit drugs, and medications during pregnancy. Stress and emotional upset were also suggested as possible causes of birth defects. Genetic- and heredity-related responses were more likely to be mentioned by Asian/Pacific Islander women compared to non-Hispanic Whites. Hispanic women were less likely to suggest several specific possible teratogens, such as paint, pesticides, or other chemicals, but were more likely to suggest events occurring during childbirth. Differences also emerged among ethnic groups for theoretical constructs, although most responses were categorized as controllable, changeable over time, and with an internal locus of causality. PMID:24682893

  5. Maternal Exposure to Criteria Air Pollutants and Congenital Heart Defects in Offspring: Results from the National Birth Defects Prevention Study

    PubMed Central

    Luben, Thomas J.; Daniels, Julie L.; Fuentes, Montserrat; Richardson, David B.; Aylsworth, Arthur S.; Herring, Amy H.; Anderka, Marlene; Botto, Lorenzo; Correa, Adolfo; Gilboa, Suzanne M.; Langlois, Peter H.; Mosley, Bridget; Shaw, Gary M.; Siffel, Csaba; Olshan, Andrew F.

    2014-01-01

    Background: Epidemiologic literature suggests that exposure to air pollutants is associated with fetal development. Objectives: We investigated maternal exposures to air pollutants during weeks 2–8 of pregnancy and their associations with congenital heart defects. Methods: Mothers from the National Birth Defects Prevention Study, a nine-state case–control study, were assigned 1-week and 7-week averages of daily maximum concentrations of carbon monoxide, nitrogen dioxide, ozone, and sulfur dioxide and 24-hr measurements of fine and coarse particulate matter using the closest air monitor within 50 km to their residence during early pregnancy. Depending on the pollutant, a maximum of 4,632 live-birth controls and 3,328 live-birth, fetal-death, or electively terminated cases had exposure data. Hierarchical regression models, adjusted for maternal demographics and tobacco and alcohol use, were constructed. Principal component analysis was used to assess these relationships in a multipollutant context. Results: Positive associations were observed between exposure to nitrogen dioxide and coarctation of the aorta and pulmonary valve stenosis. Exposure to fine particulate matter was positively associated with hypoplastic left heart syndrome but inversely associated with atrial septal defects. Examining individual exposure-weeks suggested associations between pollutants and defects that were not observed using the 7-week average. Associations between left ventricular outflow tract obstructions and nitrogen dioxide and between hypoplastic left heart syndrome and particulate matter were supported by findings from the multipollutant analyses, although estimates were attenuated at the highest exposure levels. Conclusions: Using daily maximum pollutant levels and exploring individual exposure-weeks revealed some positive associations between certain pollutants and defects and suggested potential windows of susceptibility during pregnancy. Citation: Stingone JA, Luben TJ

  6. The Association Between Reported Venlafaxine Use in Early Pregnancy and Birth Defects, National Birth Defects Prevention Study, 1997–2007

    PubMed Central

    Polen, Kara ND; Rasmussen, Sonja A; Riehle-Colarusso, Tiffany; Reefhuis, Jennita

    2015-01-01

    Background Few epidemiologic studies have investigated the use of venlafaxine (Effexor®), an antidepressant used to treat major depression and anxiety disorders in adults, during pregnancy. Our objective was to determine whether use of venlafaxine during pregnancy is associated with specific birth defects. Methods We used data from the National Birth Defects Prevention Study (NBDPS), a population-based, case-control study in the United States. Our analysis included mothers with pregnancies affected by one of 30 selected birth defects (cases) and babies without birth defects (controls) with estimated dates of delivery between 1997–2007. Exposure was any reported use of venlafaxine from one month preconception through the third month of pregnancy. We calculated adjusted odds ratios (aORs) and 95% Fisher’s Exact confidence intervals (CIs) for 24 birth defect groups for which at least 400 case mothers were interviewed. Our adjusted analyses controlled for maternal age and race-ethnicity. Results Among the 27,045 NBDPS participants who met inclusion criteria, 0.17% (14/8,002) of control mothers and 0.40% (77/19,043) of case mothers reported any use of venlafaxine from one month preconception through the third month of pregnancy. Statistically significant associations were found for anencephaly, atrial septal defect (ASD) secundum or ASD not otherwise specified, coarctation of the aorta, cleft palate, and gastroschisis. Conclusions Our data suggest associations between periconceptional use of venlafaxine and some birth defects. However, sample sizes were small, confidence intervals were wide, and additional studies are needed to confirm these results. PMID:23281074

  7. Maternal Occupational Exposure to Polycyclic Aromatic Hydrocarbons and Congenital Heart Defects among Offspring in the National Birth Defects Prevention Study

    PubMed Central

    Lupo, Philip J.; Symanski, Elaine; Langlois, Peter H.; Lawson, Christina C.; Malik, Sadia; Gilboa, Suzanne M.; Lee, Laura J.; Agopian, A. J.; Desrosiers, Tania A.; Waters, Martha A.; Romitti, Paul A.; Correa, Adolfo; Shaw, Gary M.; Mitchell, Laura E.

    2015-01-01

    BACKGROUND There is evidence in experimental model systems that exposure to polycyclic aromatic hydrocarbons (PAHs) results in congenital heart defects (CHDs); however, to our knowledge, this relationship has not been examined in humans. Therefore, we conducted a case-control study assessing the association between estimated maternal occupational exposure to PAHs and CHDs in offspring. METHODS Data on CHD cases and control infants were obtained from the National Birth Defects Prevention Study for the period of 1997 to 2002. Exposure to PAHs was assigned by industrial hygienist consensus, based on self-reported maternal occupational histories from 1 month before conception through the third month of pregnancy. Logistic regression was used to evaluate the association between maternal occupational PAH exposure and specific CHD phenotypic subtypes among offspring. RESULTS The prevalence of occupational PAH exposure was 4.0% in CHD case mothers (76/1907) and 3.6% in control mothers (104/2853). After adjusting for maternal age, race or ethnicity, education, smoking, folic acid supplementation, and study center, exposure was not associated with conotruncal defects (adjusted odds ratio [AOR], 0.98; 95% confidence interval [CI], 0.58–1.67), septal defects (AOR, 1.28; 95% CI, 0.86–1.90), or with any isolated CHD subtype. CONCLUSIONS Our findings do not support an association between potential maternal occupational exposure to PAHs and various CHDs in a large, population-based study. For CHD phenotypic subtypes in which modest nonsignificant associations were observed, future investigations could be improved by studying populations with a higher prevalence of PAH exposure and by incorporating information on maternal and fetal genotypes related to PAH metabolism. PMID:22945317

  8. Association between maternal occupational exposure to organic solvents and congenital heart defects, National Birth Defects Prevention Study, 1997–2002

    PubMed Central

    Gilboa, SM; Desrosiers, TA; Lawson, CC; Lupo, PJ; Riehle-Colarusso, T; Stewart, PA; van Wijngaarden, E; Waters, MA; Correa, A

    2015-01-01

    Objective To examine the relation between congenital heart defects (CHDs) in offspring and estimated maternal occupational exposure to chlorinated solvents, aromatic solvents, and Stoddard solvent during the period from one month before conception through the first trimester. Methods The study population included mothers of infants with simple, isolated CHDs and mothers of control infants who delivered from 1997 through 2002 and participated in the National Birth Defects Prevention Study. Two methods to assess occupational solvent exposure were employed: an expert consensus-based approach and a literature-based approach. Multiple logistic regression was used to calculate adjusted odds ratios (OR) and 95% confidence intervals (CI) for the association between solvent classes and CHDs. Results 2,951 control mothers and 2,047 CHD case mothers were included. Using the consensus-based approach, associations were observed for exposure to any solvent and any chlorinated solvent with perimembranous ventricular septal defects (OR 1.6; 95% CI 1.0 to 2.6 and OR 1.7; 95% CI 1.0 to 2.8 respectively). Using the literature-based approach, associations were observed for: any solvent exposure with aortic stenosis (OR 2.1; 95% CI 1.1 to 4.1); and Stoddard solvent exposure with d-transposition of the great arteries (OR 2.0; 95% CI 1.0 to 4.2), right ventricular outflow tract obstruction defects (OR 1.9; 95% CI 1.1 to 3.3), and pulmonary valve stenosis (OR 2.1; 95% CI 1.1 to 3.8). Conclusions We found evidence of associations between occupational exposure to solvents and several types of CHDs. These results should be interpreted in light of the potential for misclassification of exposure. PMID:22811060

  9. The National Birth Defects Prevention Study: a review of the methods

    PubMed Central

    Reefhuis, Jennita; Gilboa, Suzanne M.; Anderka, Marlene; Browne, Marilyn L.; Feldkamp, Marcia L.; Hobbs, Charlotte A.; Jenkins, Mary M.; Langlois, Peter H.; Newsome, Kimberly B.; Olshan, Andrew F.; Romitti, Paul A.; Shapira, Stuart K.; Shaw, Gary M.; Tinker, Sarah C.; Honein, Margaret A.

    2015-01-01

    Background The National Birth Defects Prevention Study (NBDPS) is a large population-based multi-center case-control study of major birth defects in the United States. Methods Data collection took place from 1998 through 2013 on pregnancies ending between October 1997 and December 2011. Cases could be live born, stillborn or induced terminations, and were identified from birth defects surveillance programs in Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York, North Carolina, Texas and Utah. Controls were live born infants without major birth defects identified from the same geographical regions and time periods as cases via either vital records or birth hospitals. Computer-assisted telephone interviews were completed with women between 6 weeks and 24 months after the estimated date of delivery. After completion of interviews, families received buccal cell collection kits for the mother, father and infant (if living). Results There were 47,832 eligible cases and 18,272 eligible controls. Among these, 32,187 (67%) and 11,814 (65%) respectively, provided interview information about their pregnancies. Buccal cell collection kits with a cytobrush for at least one family member were returned by 19,065 case and 6,211 control families (65% and 59% of those who were sent a kit). More than 500 projects have been proposed by the collaborators and over 200 manuscripts published using data from the NBDPS through December 2014. Conclusion The NBDPS has made substantial contributions to the field of birth defects epidemiology through its rigorous design, including case classification, detailed questionnaire and specimen collection, large study population, and collaborative activities across Centers. PMID:26033852

  10. Diabetes and obesity-related genes and the risk of neural tube defects in the national birth defects prevention study.

    PubMed

    Lupo, Philip J; Canfield, Mark A; Chapa, Claudia; Lu, Wei; Agopian, A J; Mitchell, Laura E; Shaw, Gary M; Waller, D Kim; Olshan, Andrew F; Finnell, Richard H; Zhu, Huiping

    2012-12-15

    Few studies have evaluated genetic susceptibility related to diabetes and obesity as a risk factor for neural tube defects (NTDs). The authors investigated 23 single nucleotide polymorphisms among 9 genes (ADRB3, ENPP1, FTO, LEP, PPARG, PPARGC1A, SLC2A2, TCF7L2, and UCP2) associated with type 2 diabetes or obesity. Samples were obtained from 737 NTD case-parent triads included in the National Birth Defects Prevention Study during 1999-2007. Log-linear models were used to evaluate maternal and offspring genetic effects. After application of the false discovery rate, there were 5 significant maternal genetic effects. The less common alleles at the 4 FTO single nucleotide polymorphisms showed a reduction of NTD risk (for rs1421085, relative risk (RR) = 0.73 (95% confidence interval (CI): 0.62, 0.87); for rs8050136, RR = 0.79 (95% CI: 0.67, 0.93); for rs9939609, RR = 0.79 (95% CI: 0.67, 0.94); and for rs17187449, RR = 0.80 (95% CI: 0.68, 0.95)). Additionally, maternal LEP rs2071045 (RR = 1.31, 95% CI: 1.08, 1.60) and offspring UCP2 rs660339 (RR = 1.32, 95% CI: 1.06, 1.64) were associated with NTD risk. Furthermore, the maternal genotype for TCF7L2 rs3814573 suggested an increased NTD risk among obese women. These findings indicate that maternal genetic variants associated with glucose homeostasis may modify the risk of having an NTD-affected pregnancy. PMID:23132673

  11. Spatial analysis of gastroschisis in the National Birth Defects Prevention Study

    PubMed Central

    Yazdy, Mahsa M.; Werler, Martha M.; Feldkamp, Marcia L.; Shaw, Gary M; Mosley, Bridget S.; Vieira, Veronica M.

    2015-01-01

    Background Gastroschisis is a birth defect where loops of bowel are protruding from the abdominal wall at birth. Previous research has suggested that gastroschisis cases can occur in clusters. The objective of this study was to identify if there were areas of elevated gastroschisis risk using data from the National Birth Defects Prevention Study (NBDPS), 1997 through 2007. Methods We obtained data on cases (n=371) through population-based birth defects surveillance systems in Arkansas, California, and Utah; controls (n=2,359) were selected from the same geographic areas as cases. Mothers were interviewed on demographic information and exposures during pregnancy, including residential history. We used first trimester maternal addresses and generalized additive models to create a continuous map surface of odds ratios (OR) by smoothing over latitude and longitude. Permutation tests were used to assess whether location of maternal residence was important and identify locations with statistically significant ORs. Results In Arkansas, adjusted ORs in the southwest corner were 2.0 and the global deviance was not statistically significant (p-value: 0.57). Adjusted ORs for California indicated areas of increased risk with ORs 1.3 (p-value: 0.34). In Utah, the adjusted ORs were elevated (OR: 2.4) in the south-eastern corner of the study area (p-value: 0.34). Conclusion The results of this study, while not statistically significant, suggest there were spatial variations in gastroschisis births. We cannot rule out that these variations were due to edge effects or residual confounding. PMID:25850424

  12. Epidemiology of twinning in the National Birth Defects Prevention Study, 1997–2007

    PubMed Central

    Dawson, April L.; Tinker, Sarah C.; Jamieson, Denise J.; Hobbs, Charlotte A.; Rasmussen, Sonja A.; Reefhuis, Jennita

    2015-01-01

    Background Our objective was to evaluate associations between twinning and maternal demographic factors and periconceptional exposures among infants with and without orofacial clefts. Methods We used data from the National Birth Defects Prevention Study; 228 twins and 8,242 singletons without birth defects (controls), and 117 twins and 2,859 singletons with orofacial clefts, born 1997–2007, were included in the analyses. Because of the occurrence of twinning due to the use of assisted reproductive technologies, logistic regression models were computed to estimate odds ratios (OR) and 95% confidence intervals (CIs) for each exposure, stratified by fertility treatment use. To evaluate factors by zygosity, we used sex-pairing data and a simulation approach to estimate the zygosity of like-sex twin pairs for unassisted conceptions. Results Among control mothers who did not use fertility treatments, predictors of twinning included non-Hispanic black maternal race (adjusted OR: 1.6, 95% CI: 1.0–2.4), and tobacco smoking (1.6, 1.1–2.4). Among control mothers who used fertility treatments, older maternal age, higher income, and state of residence were associated with twinning. Associations were generally stronger among mothers of dizygotic (estimated) twins than monozygotic (estimated) twins. Results for mothers of infants with isolated orofacial clefts were similar to those of controls. Conclusion We observed an increased twinning frequency with increasing maternal age, but factors such as maternal race/ethnicity and socioeconomic status may also contribute. Among women receiving fertility treatments, factors associated with twinning suggested a relation with treatment specifics (e.g., treatment type and number of embryos implanted) and availability of insurance coverage. PMID:25359509

  13. Prenatal Nitrate Intake from Drinking Water and Selected Birth Defects in Offspring of Participants in the National Birth Defects Prevention Study

    PubMed Central

    Weyer, Peter J.; Romitti, Paul A.; Mohanty, Binayak P.; Shinde, Mayura U.; Vuong, Ann M.; Sharkey, Joseph R.; Dwivedi, Dipankar; Horel, Scott A.; Kantamneni, Jiji; Huber, John C.; Zheng, Qi; Werler, Martha M.; Kelley, Katherine E.; Griesenbeck, John S.; Zhan, F. Benjamin; Langlois, Peter H.; Suarez, Lucina; Canfield, Mark A.

    2013-01-01

    Background: Previous studies of prenatal exposure to drinking-water nitrate and birth defects in offspring have not accounted for water consumption patterns or potential interaction with nitrosatable drugs. Objectives: We examined the relation between prenatal exposure to drinking-water nitrate and selected birth defects, accounting for maternal water consumption patterns and nitrosatable drug exposure. Methods: With data from the National Birth Defects Prevention Study, we linked addresses of 3,300 case mothers and 1,121 control mothers from the Iowa and Texas sites to public water supplies and respective nitrate measurements. We assigned nitrate levels for bottled water from collection of representative samples and standard laboratory testing. Daily nitrate consumption was estimated from self-reported water consumption at home and work. Results: With the lowest tertile of nitrate intake around conception as the referent group, mothers of babies with spina bifida were 2.0 times more likely (95% CI: 1.3, 3.2) to ingest ≥ 5 mg nitrate daily from drinking water (vs. < 0.91 mg) than control mothers. During 1 month preconception through the first trimester, mothers of limb deficiency, cleft palate, and cleft lip cases were, respectively, 1.8 (95% CI: 1.1, 3.1), 1.9 (95% CI: 1.2, 3.1), and 1.8 (95% CI: 1.1, 3.1) times more likely than control mothers to ingest ≥ 5.42 mg of nitrate daily (vs. < 1.0 mg). Higher water nitrate intake did not increase associations between prenatal nitrosatable drug use and birth defects. Conclusions: Higher water nitrate intake was associated with several birth defects in offspring, but did not strengthen associations between nitrosatable drugs and birth defects. Citation: Brender JD, Weyer PJ, Romitti PA, Mohanty BP, Shinde MU, Vuong AM, Sharkey JR, Dwivedi D, Horel SA, Kantamneni J, Huber JC Jr., Zheng Q, Werler MM, Kelley KE, Griesenbeck JS, Zhan FB, Langlois PH, Suarez L, Canfield MA, and the National Birth Defects Prevention Study

  14. Next steps for birth defects research and prevention: The Birth Defects Study To Evaluate Pregnancy exposureS (BD-STEPS)

    PubMed Central

    Tinker, Sarah C.; Carmichael, Suzan L.; Anderka, Marlene; Browne, Marilyn L.; Caspers Conway, Kristin M.; Meyer, Robert E.; Nembhard, Wendy N.; Olney, Richard S.; Reefhuis, Jennita

    2015-01-01

    Background The Birth Defects Study To Evaluate Pregnancy exposureS (BD-STEPS) is a population-based, multi-Center case-control study of modifiable risk factors for selected birth defects in the United States. BD-STEPS is the second major research effort of the Centers for Birth Defects Research and Prevention, which extends and expands the initial research effort, the National Birth Defects Prevention Study (NBDPS). Methods BD-STEPS focuses on 17 categories of structural birth defects selected based on severity, prevalence, consistent ascertainment, and previous findings that warrant additional research. Cases are identified through existing birth defects surveillance programs; controls are from vital records or birth hospital logs from the same catchment area. BD-STEPS usess a standardized computer-assisted telephone interview to collect information from case and control mothers on topics including demographics, health conditions, and medication use. Following the maternal interview, selected Centers request permission to sample residual newborn screening blood spots from state repositories for genetic analyses. New components planned for BD-STEPS include linkages with external datasets and use of online questionnaires to collect in-depth information on selected exposures. Results BD-STEPS extends NBDPS by continuing to collect data on many exposures that were assessed in NBDPS, allowing data from both studies to be combined and providing an unprecedented sample size to analyze rare exposures. BD-STEPS expands upon NBDPS by collecting more detailed information on existing exposures as well as new exposures. Conclusions The goal of BD-STEPS is to provide women and healthcare providers with information they need to make decisions to promote the healthiest pregnancy possible. PMID:25846741

  15. Urgent global opportunities to prevent birth defects.

    PubMed

    Kancherla, Vijaya; Oakley, Godfrey P; Brent, Robert L

    2014-06-01

    Birth defects are an urgent global health priority. They affect millions of births worldwide. But their prevalence and impact are largely under-ascertained, particularly in middle- and low-income countries. Fortunately, a large proportion of birth defects can be prevented. This review examines the global prevalence and primary prevention methods for major preventable birth defects: congenital rubella syndrome, folic acid-preventable spina bifida and anencephaly, fetal alcohol syndrome, Down syndrome, rhesus hemolytic disease of the fetus and the newborn; and those associated with maternal diabetes, and maternal exposure to valproic acid or iodine deficiency during pregnancy. Challenges to prevention efforts are reviewed. The aim of this review is to bring to the forefront the urgency of birth defects prevention, surveillance, and prenatal screening and counseling; and to help public health practitioners develop population-based birth defects surveillance and prevention programs, and policy-makers to develop and implement science-based public health policies. PMID:24333206

  16. Guidance for Preventing Birth Defects

    MedlinePlus

    ... Lip and Palate Craniosynostosis Down Syndrome Eye Defects Fetal Alcohol Syndrome Disorders Gastroschisis Heart Defects Coarctation of the Aorta ... drank alcohol during the pregnancy, are known as fetal alcohol spectrum disorders (FASDs) . The best advice for women is to ...

  17. Folic Acid Helps Prevent Neural Tube Defects

    MedlinePlus

    ... Features Folic Acid Helps Prevent Neural Tube Defects Language: English Español (Spanish) Recommend on Facebook Tweet Share Compartir The feature you selected is no longer available. In 10 seconds you will be automatically redirected to the CDC. ...

  18. Maternal occupation and the risk of major birth defects: a follow-up analysis from the National Birth Defects Prevention Study.

    PubMed

    Lin, Shao; Herdt-Losavio, Michele L; Chapman, Bonnie R; Munsie, Jean-Pierre; Olshan, Andrew F; Druschel, Charlotte M

    2013-06-01

    This study further examined the association between selected maternal occupations and a variety of birth defects identified from prior analysis and explored the effect of work hours and number of jobs held and potential interaction between folic acid and occupation. Data from a population-based, multi-center case-control study was used. Analyses included 45 major defects and specific sub-occupations under five occupational groups: healthcare workers, cleaners, scientists, teachers and personal service workers. Both logistic regression and Bayesian models (to minimize type-1 errors) were used, adjusted for potential confounders. Effect modification by folic acid was also assessed. More than any other occupation, nine different defects were positively associated with maids or janitors [odds ratio (OR) range: 1.72-3.99]. Positive associations were also seen between the following maternal occupations and defects in their children (OR range: 1.35-3.48): chemists/conotruncal heart and neural tube defects (NTDs), engineers/conotruncal defects, preschool teachers/cataracts and cleft lip with/without cleft palate (CL/P), entertainers/athletes/gastroschisis, and nurses/hydrocephalus and left ventricular outflow tract heart defects. Non-preschool teachers had significantly lower odds of oral clefts and gastroschisis in their offspring (OR range: 0.53-0.76). There was a suggestion that maternal folic acid use modified the effects with occupations including lowering the risk of NTDs and CL/P. No consistent patterns were found between maternal work hours or multiple jobs by occupation and the risk of birth defects. Overall, mothers working as maids, janitors, biologists, chemists, engineers, nurses, entertainers, child care workers and preschool teachers had increased risks of several malformations and non-preschool teachers had a lower risk of some defects. Maternal folic acid use reduced the odds of NTDs and CL/P among those with certain occupations. This hypothesis

  19. Maternal Medication and Herbal Use and Risk for Hypospadias: Data from the National Birth Defects Prevention Study, 1997--2007

    PubMed Central

    Lind, Jennifer N.; Tinker, Sarah C.; Broussard, Cheryl S.; Reefhuis, Jennita; Carmichael, Suzan L.; Honein, Margaret A.; Olney, Richard S.; Parker, Samantha E.; Werler, Martha M.

    2014-01-01

    Purpose Investigate associations between maternal use of common medications and herbals during early pregnancy and risk for hypospadias in male infants. Methods We used data from the National Birth Defects Prevention Study, a multi-site, population-based, case-control study. We analyzed data from 1,537 infants with second-or third-degree isolated hypospadias and 4,314 liveborn male control infants without major birth defects, with estimated dates of delivery from 1997–2007. Exposure was reported use of prescription or over-the-counter medications or herbal products, from 1 month before to 4 months after conception. Adjusted odds ratios (aORs) and 95% confidence intervals (CI) were estimated using multivariable logistic regression, adjusting for maternal age, race/ethnicity, education, pre-pregnancy BMI, previous live births, maternal sub-fertility, study site, and year. Results We assessed 64 medication and 24 herbal components. Maternal uses of most components were not associated with an increased risk of hypospadias. Two new associations were observed for venlafaxine (aOR 2.4; 95% CI 1.0, 6.0) and progestin only oral contraceptives (aOR 1.9, 95% CI 1.1, 3.2). The previously reported association for clomiphene citrate was confirmed (aOR 1.9, 95% CI 1.2, 3.0). Numbers were relatively small for exposure to other specific patterns of fertility agents, but elevated aORs were observed for the most common of them. Conclusions Overall, findings were reassuring that hypospadias is not associated with most medication components examined in this analysis. New associations will need to be confirmed in other studies. Increased risks for hypospadias associated with various fertility agents raises the possibility of confounding by underlying subfertility. PMID:23620412

  20. Descriptive and risk factor analysis for choanal atresia: The National Birth Defects Prevention Study, 1997-2007.

    PubMed

    Kancherla, Vijaya; Romitti, Paul A; Sun, Lixian; Carey, John C; Burns, Trudy L; Siega-Riz, Anna Maria; Druschel, Charlotte M; Lin, Angela E; Olney, Richard S

    2014-04-01

    Choanal atresia causes serious posterior nasal obstruction. This defect is the leading cause of nasal surgery in newborns, although its etiology is largely unknown. Data from the National Birth Defects Prevention Study, a population-based case-control study, were used to examine associations between maternal self-reports of exposures and occurrence of choanal atresia in their offspring. Overall, 117 case and 8350 control mothers with deliveries from 1997 through 2007 provided telephone interview reports of pre-pregnancy (one year before conception) and periconceptional (one month before through three months after conception) exposures. The exposures analyzed were pre-pregnancy dietary intake, pre-pregnancy and periconceptional caffeine consumption, and periconceptional cigarette smoking, alcohol drinking, and medication use. Independent associations between each exposure and all choanal atresia cases combined (n = 117) and isolated choanal atresia cases (those without additional unrelated major defects; n = 61) were examined. Odds ratios (ORs), both unadjusted (uORs) and adjusted (aORs) for potential confounders, and 95% confidence intervals (CIs) were estimated using unconditional logistic regression analysis. For all choanal atresia cases combined, positive associations were observed with maternal pre-pregnancy intake in the highest quartile for vitamin B-12 (aOR = 1.9; CI = 1.1,3.1), zinc (aOR = 1.7; CI = 1.0,3.1), and niacin (aOR = 1.8; CI = 1.0,3.1), and intake in the lowest quartile for methionine (aOR = 1.6; CI = 1.0,2.6) and vitamin D (aOR = 1.6; CI = 1.0,2.4) compared to intake in the two intermediate quartiles combined. Further, a positive association was observed with periconceptional use of thyroid medications (uOR = 2.6; CI = 1.0,6.3) compared to no use of such medications. Among isolated choanal atresia cases, negative associations were observed for pantothenic acid (aOR = 0.4; CI = 0.2,0.9) and fat (aOR = 0.5; 95% CI = 0.2,1.0) intake in the lowest

  1. Folic acid and birth defect prevention

    MedlinePlus

    ... of certain birth defects. These include spina bifida, anencephaly, and some heart defects. Experts recommend women who ... Women who have had a baby with a neural tube defect may need a higher dose of folic acid. ...

  2. Prevention of neural tube defects by the fortification of flour with folic acid: a population-based retrospective study in Brazil

    PubMed Central

    Lecca, Roberto Carlos Reyes; Cortez-Escalante, Juan Jose; Sanchez, Mauro Niskier; Rodrigues, Humberto Gabriel

    2016-01-01

    Abstract Objective To determine if the fortification of wheat and maize flours with iron and folic acid – which became mandatory in Brazil from June 2004 – is effective in the prevention of neural tube defects. Methods Using data from national information systems on births in central, south-eastern and southern Brazil, we determined the prevalence of neural tube defects among live births and stillbirths in a pre-fortification period – i.e. 2001–2004 – and in a post-fortification period – i.e. 2005–2014. We distinguished between anencephaly, encephalocele, meningocele, myelomeningocele and other forms of spina bifida. Findings There were 8554 neural tube defects for 17 925 729 live births notified between 2001 and 2014. For the same period, 2673 neural tube defects were reported for 194 858 stillbirths. The overall prevalence of neural tube defects fell from 0.79 per 1000 pre-fortification to 0.55 per 1000 post-fortification (prevalence ratio, PR: 1.43; 95% confidence interval, CI: 1.38–1.50). For stillbirths, prevalence fell from 17.74 per 1000 stillbirths pre-fortification to 11.70 per 1000 stillbirths post-fortification. The corresponding values among live births were 0.57 and 0.44, respectively. Conclusion The introduction of the mandatory fortification of flour with iron and folic acid in Brazil was followed by a significant reduction in the prevalence of neural tube defects in our study area. PMID:26769993

  3. [Folic acid: Primary prevention of neural tube defects. Literature Review].

    PubMed

    Llamas Centeno, M J; Miguélez Lago, C

    2016-03-01

    Neural tube defects (NTD) are the most common congenital malformations of the nervous system, they have a multifactorial etiology, are caused by exposure to chemical, physical or biological toxic agents, factors deficiency, diabetes, obesity, hyperthermia, genetic alterations and unknown causes. Some of these factors are associated with malnutrition by interfering with the folic acid metabolic pathway, the vitamin responsible for neural tube closure. Its deficit produce anomalies that can cause abortions, stillbirths or newborn serious injuries that cause disability, impaired quality of life and require expensive treatments to try to alleviate in some way the alterations produced in the embryo. Folic acid deficiency is considered the ultimate cause of the production of neural tube defects, it is clear the reduction in the incidence of Espina Bifida after administration of folic acid before conception, this leads us to want to further study the action of folic acid and its application in the primary prevention of neural tube defects. More than 40 countries have made the fortification of flour with folate, achieving encouraging data of decrease in the prevalence of neural tube defects. This paper attempts to make a literature review, which clarify the current situation and future of the prevention of neural tube defects. PMID:26959966

  4. The primary prevention of birth defects: Multivitamins or folic acid?

    PubMed

    Czeizel, Andrew E

    2004-01-01

    Periconceptional use of folic acid alone or in multivitamin supplements is effective for the primary prevention of neural-tube defects. The Hungarian randomized and two-cohort controlled trials showed that periconceptional multivitamin supplementation can reduce the occurrence of some other structural birth defects, i.e. congenital abnormalities. These findings were supported by many, but not all observational studies. Recently there have been two main debated questions. The first one is whether the use of folic acid alone or folic acid-containing multivitamins is better. The second one is connected with the dilemma of whether high dose of folic acid (e.g. 5 mg) might be better than a daily multivitamin with 0.4 - 0.8 mg of folic acid. Comparison of the pooled data of two Hungarian trials using a multivitamin containing 0.8 mg folic acid and the data of the Hungarian Case-Control Surveillance of Congenital Abnormalities using high dose of folic acid seemed to be appropriate to answer these questions. Multivitamins containing 0.4 - 0.8 mg of folic acid were more effective for the reduction of neural-tube defects than high dose of folic acid. Both multivitamins and folic acid can prevent some part of congenital cardiovascular malformations. Only multivitamins were able to reduce the prevalence at birth of obstructive defects of urinary tract, limb deficiencies and congenital pyloric stenosis. However, folic acid was effective in preventing some part of rectal/anal stenosis/atresia, and high dose of folic acid had effect in preventing some orofacial clefts. The findings are consistent that periconceptional multivitamin and folic acid supplementation reduce the overall occurrence of congenital abnormalities in addition to the demonstrated effect on neural-tube defects. PMID:15912190

  5. Pathophysiology, prevention, and potential treatment of neural tube defects.

    PubMed

    Manning, S M; Jennings, R; Madsen, J R

    2000-01-01

    Neural tube defects (NTD) remain a major cause of morbidity in spite of the reduction in liveborn incidence with periconceptional folic acid. However, the etiology remains unknown. This article reviews studies that address causation and potential treatment of NTD in humans and in animal models that resemble aspects of the common human NTD. Studies of nutritional markers of vitamin B12 and folic acid support a defect in homocysteine metabolism; a thermolabile variant of methylene tetrahydrofolate reductase, an enzyme that remethylates homocysteine to methionine, correlates with a risk of NTD in some human populations. Numerous mouse mutant models of NTD exist, attesting to the ease of disruption of neurulation, and a genetic basis for this malformation. Of these models, the curly tail mouse mutant most closely resembles the common human NTD. Folic acid does not prevent NTD in this model; however inositol supplementation does result in a significant reduction in incidence. Recent advances in fetal surgery, and evidence from mechanically created myelomeningocele in large animals amenable to surgical intervention suggest that the handicaps associated with myelomeningocele and associated Chiari Type II malformation may be prevented by in utero NTD closure. Success will depend on preservation of neurological tissue until such intervention is possible. Further research in animal models at the genetic and cellular levels, together with technological surgical advances, provide hope that prevention of more NTD and the associated handicaps may be possible. MRDD Research Reviews 6:6-14, 2000. PMID:10899792

  6. Folic acid and primary prevention of birth defects.

    PubMed

    Taruscio, Domenica; Carbone, Pietro; Granata, Orietta; Baldi, Francesca; Mantovani, Alberto

    2011-01-01

    Birth defects (BDs) are an important public health problem, due to their overall incidence, occurring in 2-3% of live births in European Union. Neural tube defects (NTDs) are among major NTDs, due to their severity and relatively high incidence; in the meanwhile NTDs are also the most effectively preventable BDs to date. In particular, an adequate folic acid (FA) intake reduces both the occurrence and the recurrence of NTDs; FA is the synthetic form of folates, naturally occurring vitamins in a number of foods, especially vegetables. The daily intake of 0.4 mg of FA should be recommended to all women of childbearing age who plan to become pregnant. The Italian Network for Primary Prevention of BDs through FA Promotion has achieved a significant improvement in FA awareness and use in the periconceptional period. Nevertheless, primary prevention of BDs needs to make further progress; the Italian National Centre for Rare Diseases participates in european sureveillance of congenital anomalies (EUROCAT) Joint Action as coordinator of activities on the effectiveness of BDs prevention. Mandatory food fortification with FA has not been introduced in any European country. The health benefits of FA in reducing the risk of NTDs are undisputed; however mechanistic and animal studies suggest a relationship between high FA intakes and increased cancer promotion, while human studies are still inconsistent and inconclusive. A Working Group organized by the European Food Safety Authority pointed out significant uncertainties about fortification safety and the need for more studies; currently, FA intake from fortified foods and supplements should not exceed 1 mg/day in adults. In conclusion, based on up-to-date scientific evidence, the Italian Network strategy pivots on periconceptional supplementation integrated with promotion of healthy eating habits, support to health education, enhancing the role of women in managing life choices about their health and pregnancy and increasing

  7. A Prescription for the Prevention of Birth Defects.

    ERIC Educational Resources Information Center

    Slavkin, Harold C.

    1984-01-01

    Factors influencing birth defects include maternal age (teenagers and women over 32 are at risk), genetics, drug use, diet habits, and environmental hazards. The physical, social, and economic costs of birth defects are extreme. Prevention must involve efforts to change some of these factors. (Author/CS)

  8. Investigation of scum type growing defects on attenuated PSM and its prevention

    NASA Astrophysics Data System (ADS)

    Choi, Jihwan; Kim, Yongho; Lee, Dongwook; Jung, Hoyong; Kim, Snagpyo; Yim, Donggyu

    2015-10-01

    The abnormal growing defect (we called this defect 'scum haze defect') in the photomask which is generated during the wafer lithography process is very important issue on semiconductor industry. Because wafer yield loss could be caused by the mask CD variation and the transmittance loss due to the growing defects on the photomask, many studies have been done about the mechanism and the solution of the general type growing defects such as haze and Cr migration so far, However we still need to clarify some abnormal types of the growing defects such as scum haze defect. In this paper, we investigated the generation mechanism and prevention techniques of the scum haze defect on the attenuated phase shift mask. This defect composed of CrOx is caused by the increase of the accumulated exposure energy on photomask. This phenomenon is remarkably similar to the Cr migration on binary mask. But, the apparent difference is that this scum type defect is observed on the attenuated phase shift mask which mainly consists of MoSiON film, and it is difficult to control this defect because of its irregular generation characteristic. Additionally, this defect is not generally removed through the conventional wet cleaning process but it only could be removed by a kind of plasma treatment. In this study, the difference of generation mechanism between the scum haze defect and the general haze was discussed, and the optimal process for controlling scum haze defect in the mask manufacturing was described.

  9. Systems Biology and Birth Defects Prevention: Blockade of the Glucocorticoid Receptor Prevents Arsenic-Induced Birth Defects

    PubMed Central

    Ahir, Bhavesh K.; Sanders, Alison P.; Rager, Julia E.

    2013-01-01

    Background: The biological mechanisms by which environmental metals are associated with birth defects are largely unknown. Systems biology–based approaches may help to identify key pathways that mediate metal-induced birth defects as well as potential targets for prevention. Objectives: First, we applied a novel computational approach to identify a prioritized biological pathway that associates metals with birth defects. Second, in a laboratory setting, we sought to determine whether inhibition of the identified pathway prevents developmental defects. Methods: Seven environmental metals were selected for inclusion in the computational analysis: arsenic, cadmium, chromium, lead, mercury, nickel, and selenium. We used an in silico strategy to predict genes and pathways associated with both metal exposure and developmental defects. The most significant pathway was identified and tested using an in ovo whole chick embryo culture assay. We further evaluated the role of the pathway as a mediator of metal-induced toxicity using the in vitro midbrain micromass culture assay. Results: The glucocorticoid receptor pathway was computationally predicted to be a key mediator of multiple metal-induced birth defects. In the chick embryo model, structural malformations induced by inorganic arsenic (iAs) were prevented when signaling of the glucocorticoid receptor pathway was inhibited. Further, glucocorticoid receptor inhibition demonstrated partial to complete protection from both iAs- and cadmium-induced neurodevelopmental toxicity in vitro. Conclusions: Our findings highlight a novel approach to computationally identify a targeted biological pathway for examining birth defects prevention. PMID:23458687

  10. Neural tube defects: prevention by folic acid and other vitamins.

    PubMed

    Copp, A J; Greene, N D

    2000-12-01

    Folic acid has been demonstrated in clinical trials to reduce significantly the recurrence (and probably occurrence) of neural tube defects (NTD). In the U.K., there has been no decline in prevalence of NTD since the publication of the findings with folic acid. This article examines a series of questions relating to the action of folic acid, with emphasis on the use of mouse models as a source of experimental information which cannot easily be obtained by direct study of humans. Several mouse genetic NTD models exhibit sensitivity to prevention by folic acid, whereas other mice which develop morphologically similar NTD are resistant. Folic acid normalises neurulation in the sensitive mouse strains, providing evidence for a direct effect on the developing embryo, not on the pregnant female: Mouse studies do not support the proposed action of folic acid in encouraging the in utero demise of affected fetuses (i.e. terathanasia). Polymorphic variants of several folate-related enzymes have been shown to influence risk of NTD in humans and an inherited abnormality of folate metabolism has been demonstrated in one mouse NTD model. However, the biochemical basis of the action of folic acid in preventing NTD remains to be determined in detail. NTD in one folate-resistant mouse strain can be prevented by myo-inositol, both in utero and in vitro, raising the possibility of a therapeutic role also in humans. Gene-gene interactions seem likely to underlie the majority of NTD, suggesting that poly-therapy involving folic acid and other agents, such as myo-inositol, may prove more effective in preventing NTD than folic acid treatment alone. PMID:11262991

  11. Folic Acid for the Prevention of Infant Neural Tube Defects: U.S. Preventive Services Task Force Recommendation

    MedlinePlus

    Annals of Internal Medicine Summaries for Patients Folic Acid for the Prevention of Infant Neural Tube Defects: ... modern medicine. The full reports are titled “Folic Acid for the Prevention of Neural Tube Defects: U.S. ...

  12. Mouse models of neural tube defects: investigating preventive mechanisms.

    PubMed

    Greene, Nicholas D E; Copp, Andrew J

    2005-05-15

    Neural tube defects (NTD), including anencephaly and spina bifida, are a group of severe congenital abnormalities in which the future brain and/or spinal cord fail to close. In mice, NTD may result from genetic mutations or knockouts, or from exposure to teratogenic agents, several of which are known risk factors in humans. Among the many mouse NTD models that have been identified to date, a number have been tested for possible primary prevention of NTD by exogenous agents, such as folic acid. In genetic NTD models such as Cart1, splotch, Cited2, and crooked tail, and NTD induced by teratogens including valproic acid and fumonisins, the incidence of defects is reduced by maternal folic acid supplementation. These folate-responsive models provide an opportunity to investigate the possible mechanisms underlying prevention of NTD by folic acid in humans. In another group of mouse models, that includes curly tail, axial defects, and the Ephrin-A5 knockout, NTD are not preventable by folic acid, reflecting the situation in humans in which a subset of NTD appear resistant to folic acid therapy. In this group of mutants alternative preventive agents, including inositol and methionine, have been shown to be effective. Overall, the data from mouse models suggests that a broad-based in utero therapy may offer scope for prevention of a greater proportion of NTD than is currently possible. PMID:15800852

  13. Who Should Be Targeted for the Prevention of Birth Defects? A Latent Class Analysis Based on a Large, Population-Based, Cross-Sectional Study in Shaanxi Province, Western China

    PubMed Central

    Yang, Wenfang; Li, Danyang; Yang, Xue; Liu, Danli; Zhang, Min; Yan, Hong; Zeng, Lingxia

    2016-01-01

    Background The wide range and complex combinations of factors that cause birth defects impede the development of primary prevention strategies targeted at high-risk subpopulations. Methods Latent class analysis (LCA) was conducted to identify mutually exclusive profiles of factors associated with birth defects among women between 15 and 49 years of age using data from a large, population-based, cross-sectional study conducted in Shaanxi Province, western China, between August and October, 2013. The odds ratios (ORs) and 95% confidence intervals (CIs) of associated factors and the latent profiles of indicators of birth defects and congenital heart defects were computed using a logistic regression model. Results Five discrete subpopulations of participants were identified as follows: No folic acid supplementation in the periconceptional period (reference class, 21.37%); low maternal education level + unhealthy lifestyle (class 2, 39.75%); low maternal education level + unhealthy lifestyle + disease (class 3, 23.71%); unhealthy maternal lifestyle + advanced age (class 4, 4.71%); and multi-risk factor exposure (class 5, 10.45%). Compared with the reference subgroup, the other subgroups consistently had a significantly increased risk of birth defects (ORs and 95% CIs: class 2, 1.75 and 1.21–2.54; class 3, 3.13 and 2.17–4.52; class 4, 5.02 and 3.20–7.88; and class 5, 12.25 and 8.61–17.42, respectively). For congenital heart defects, the ORs and 95% CIs were all higher, and the magnitude of OR differences ranged from 1.59 to 16.15. Conclusions A comprehensive intervention strategy targeting maternal exposure to multiple risk factors is expected to show the strongest results in preventing birth defects. PMID:27183231

  14. Postmarketing analysis of medicines: methodology and value of the spanish case-control study and surveillance system in preventing birth defects.

    PubMed

    Martínez-Frías, María Luisa

    2007-01-01

    There are many surveillance systems of congenital defects all over the world; several of them have developed specific approaches to generate and test selected hypotheses regarding human teratogens. However, to the best of our knowledge, none of them have a permanent and systematised programme for the study of the risk and safety of drugs. The aim of this article is to describe the research programme on the potential effects of drugs in pregnancy followed by the Spanish Collaborative Study of Congenital Malformations (ECEMC), which is a permanent ongoing case-control study and surveillance system. The programme to analyse drugs includes a continuous and systematic study on the potential effects of medicines used during pregnancy. This programme has several characteristics that make it different from other current systems: (i) the collection of numerous datapoints (up to 312 per infant) in a case-control design; (ii) the use of a versatile and specific coding of birth defects; (iii) a specific programme for the continuous analysis of the potential effects of each type of drugs used during pregnancy that has been developed specifically for the ECEMC methodology, including its dysmorphological coding system. The description of the ECEMC's approach to surveillance of the effects of drug use during pregnancy may help researches in this area, particularly those using data from birth defects registries. PMID:17408307

  15. Enzyme replacement prevents enamel defects in hypophosphatasia mice.

    PubMed

    Yadav, Manisha C; de Oliveira, Rodrigo Cardoso; Foster, Brian L; Fong, Hanson; Cory, Esther; Narisawa, Sonoko; Sah, Robert L; Somerman, Martha; Whyte, Michael P; Millán, José Luis

    2012-08-01

    Hypophosphatasia (HPP) is the inborn error of metabolism characterized by deficiency of alkaline phosphatase activity, leading to rickets or osteomalacia and to dental defects. HPP occurs from loss-of-function mutations within the gene that encodes the tissue-nonspecific isozyme of alkaline phosphatase (TNAP). TNAP knockout (Alpl(-/-), aka Akp2(-/-)) mice closely phenocopy infantile HPP, including the rickets, vitamin B6-responsive seizures, improper dentin mineralization, and lack of acellular cementum. Here, we report that lack of TNAP in Alpl(-/-) mice also causes severe enamel defects, which are preventable by enzyme replacement with mineral-targeted TNAP (ENB-0040). Immunohistochemistry was used to map the spatiotemporal expression of TNAP in the tissues of the developing enamel organ of healthy mouse molars and incisors. We found strong, stage-specific expression of TNAP in ameloblasts. In the Alpl(-/-) mice, histological, µCT, and scanning electron microscopy analysis showed reduced mineralization and disrupted organization of the rods and inter-rod structures in enamel of both the molars and incisors. All of these abnormalities were prevented in mice receiving from birth daily subcutaneous injections of mineral-targeting, human TNAP at 8.2 mg/kg/day for up to 44 days. These data reveal an important role for TNAP in enamel mineralization and demonstrate the efficacy of mineral-targeted TNAP to prevent enamel defects in HPP. PMID:22461224

  16. Epidemiology, prenatal management, and prevention of neural tube defects

    PubMed Central

    Salih, Mustafa A.; Murshid, Waleed R.; Seidahmed, Mohammed Z.

    2014-01-01

    This review article discusses the epidemiology, risk factors, prenatal screening, diagnosis, prevention potentials, and epidemiologic impact of neural tube defects (NTDs). The average incidence of NTDs is 1/1000 births, with a marked geographic variation. In the developed countries, the incidence of NTDs has fallen over recent decades. However, it still remains high in the less-developed countries in Latin America, Africa, the Middle East, Asia, and the Far East (>1 to 11/1000 births). Recognized NTDs risks include maternal diabetes, obesity, lower socioeconomic status, hyperthermia, and exposure to certain teratogens during the periconceptional period. Periconceptional folic acid supplementation decreased the prevalence of NTDs by 50-70%, and an obligatory folic acid fortification of food was adopted in several countries to reach women with unplanned pregnancies and those facing social deprivation. Prevention of NTDs can be accelerated if more, especially low income countries, adopted fortification of the staple food in their communities. PMID:25551106

  17. Defect Prevention and Detection in Software for Automated Test Equipment

    SciTech Connect

    E. Bean

    2006-11-30

    Software for automated test equipment can be tedious and monotonous making it just as error-prone as other software. Active defect prevention and detection are also important for test applications. Incomplete or unclear requirements, a cryptic syntax used for some test applications—especially script-based test sets, variability in syntax or structure, and changing requirements are among the problems encountered in one tester. Such problems are common to all software but can be particularly problematic in test equipment software intended to test another product. Each of these issues increases the probability of error injection during test application development. This report describes a test application development tool designed to address these issues and others for a particular piece of test equipment. By addressing these problems in the development environment, the tool has powerful built-in defect prevention and detection capabilities. Regular expressions are widely used in the development tool as a means of formally defining test equipment requirements for the test application and verifying conformance to those requirements. A novel means of using regular expressions to perform range checking was developed. A reduction in rework and increased productivity are the results. These capabilities are described along with lessons learned and their applicability to other test equipment software. The test application development tool, or “application builder”, is known as the PT3800 AM Creation, Revision and Archiving Tool (PACRAT).

  18. Folate Deficiency and Folic Acid Supplementation: The Prevention of Neural-Tube Defects and Congenital Heart Defects

    PubMed Central

    Czeizel, Andrew E.; Dudás, Istvan; Vereczkey, Attila; Bánhidy, Ferenc

    2013-01-01

    Diet, particularly vitamin deficiency, is associated with the risk of birth defects. The aim of this review paper is to show the characteristics of common and severe neural-tube defects together with congenital heart defects (CHD) as vitamin deficiencies play a role in their origin. The findings of the Hungarian intervention (randomized double-blind and cohort controlled) trials indicated that periconceptional folic acid (FA)-containing multivitamin supplementation prevented the major proportion (about 90%) of neural-tube defects (NTD) as well as a certain proportion (about 40%) of congenital heart defects. Finally the benefits and drawbacks of three main practical applications of folic acid/multivitamin treatment such as (i) dietary intake; (ii) periconceptional supplementation; and (iii) flour fortification are discussed. The conclusion arrived at is indeed confirmation of Benjamin Franklin’s statement: “An ounce of prevention is better than a pound of care”. PMID:24284617

  19. Preventing birth defects: The value of the NBDPS case-control approach.

    PubMed

    Dolk, Helen

    2015-08-01

    Birth Defect Registries provide a basis for epidemiological research into risk factors, thus facilitating a growing understanding of what causes congenital anomalies and how one might target preventive public health actions and reduce inequalities. The National Birth Defects Prevention Study (NBDPS) has used 10 U.S. registries as a basis for a large case-control study. This commentary reviews its methodology and selected areas of output. The strengths of NBDPS lie in the quality of diagnostic coding and classification of birth defects and its size. The sources of bias in NBDPS data relate particularly to retrospective exposure ascertainment entailing a long period of recall, incomplete ascertainment of terminations of pregnancy for fetal anomaly, and unknown bias in case selection. NBDPS results have shown the protective effect of healthy dietary patterns, but have not been as informative as expected in relation to furthering understanding of the protective effect of folic acid. NBDPS medication studies are making important contributions to addressing the gap in existing evidence systematically across a wide range of birth defects, but are challenged by the quality of information on exposure, dose and underlying disease condition, and the interpretation of results of multiple testing. Studies of environmental contaminants in collaboration with experts in exposure assessment have linked addresses to residential exposure measures, using the advantages of information on residential history and confounders, but are challenged by the need to consider exposure mixtures. NBDPS could increase its public health impact by placing more emphasis on socioeconomic inequalities. PMID:26172859

  20. Prevention of Neural Tube Defects. ARC Q&A #101-45.

    ERIC Educational Resources Information Center

    Arc, Arlington, TX.

    This fact sheet uses a question-and-answer format to summarize issues related to the prevention of neural tube defects. Questions and answers address the following topics: what neural tube defects are and the most common types (spina bifida and anencephaly); occurrence of neural tube defects during the first month of pregnancy; the frequency of…

  1. A Birth Defects Prevention Curriculum for Inner-City Junior High School Students.

    ERIC Educational Resources Information Center

    Cohen, Ellen J.; Cohen, Carl I.

    1981-01-01

    Educators have begun to recognize that the public school system is an ideal setting in which to introduce the topic of birth defects prevention. A highly structured two week curriculum was developed using March of Dimes materials to teach inner-city school children about birth defects prevention. (JN)

  2. N-Acetylcysteine prevents congenital heart defects induced by pregestational diabetes

    PubMed Central

    2014-01-01

    Background Pregestational diabetes is a major risk factor of congenital heart defects (CHDs). Glutathione is depleted and reactive oxygen species (ROS) production is elevated in diabetes. In the present study, we aimed to examine whether treatment with N-acetylcysteine (NAC), which increases glutathione synthesis and inhibits ROS production, prevents CHDs induced by pregestational diabetes. Methods Female mice were treated with streptozotocin (STZ) to induce pregestational diabetes prior to breeding with normal males to produce offspring. Some diabetic mice were treated with N-acetylcysteine (NAC) in drinking water from E0.5 to the end of gestation or harvesting of the embryos. CHDs were identified by histology. ROS levels, cell proliferation and gene expression in the fetal heart were analyzed. Results Our data show that pregestational diabetes resulted in CHDs in 58% of the offspring, including ventricular septal defect (VSD), atrial septal defect (ASD), atrioventricular septal defects (AVSD), transposition of great arteries (TGA), double outlet right ventricle (DORV) and tetralogy of Fallot (TOF). Treatment with NAC in drinking water in pregestational diabetic mice completely eliminated the incidence of AVSD, TGA, TOF and significantly diminished the incidence of ASD and VSD. Furthermore, pregestational diabetes increased ROS, impaired cell proliferation, and altered Gata4, Gata5 and Vegf-a expression in the fetal heart of diabetic offspring, which were all prevented by NAC treatment. Conclusions Treatment with NAC increases GSH levels, decreases ROS levels in the fetal heart and prevents the development of CHDs in the offspring of pregestational diabetes. Our study suggests that NAC may have therapeutic potential in the prevention of CHDs induced by pregestational diabetes. PMID:24533448

  3. Etiology, pathogenesis and prevention of neural tube defects.

    PubMed

    Padmanabhan, Rengasamy

    2006-06-01

    Spina bifida, anencephaly, and encephalocele are commonly grouped together and termed neural tube defects (NTD). Failure of closure of the neural tube during development results in anencephaly or spina bifida aperta but encephaloceles are possibly post-closure defects. NTD are associated with a number of other central nervous system (CNS) and non-neural malformations. Racial, geographic and seasonal variations seem to affect their incidence. Etiology of NTD is unknown. Most of the non-syndromic NTD are of multifactorial origin. Recent in vitro and in vivo studies have highlighted the molecular mechanisms of neurulation in vertebrates but the morphologic development of human neural tube is poorly understood. A multisite closure theory, extrapolated directly from mouse experiments highlighted the clinical relevance of closure mechanisms to human NTD. Animal models, such as circle tail, curly tail, loop tail, shrm and numerous knockouts provide some insight into the mechanisms of NTD. Also available in the literature are a plethora of chemically induced preclosure and a few post-closure models of NTD, which highlight the fact that CNS malformations are of hetergeneitic nature. No Mendelian pattern of inheritance has been reported. Association with single gene defects, enhanced recurrence risk among siblings, and a higher frequency in twins than in singletons indicate the presence of a strong genetic contribution to the etiology of NTD. Non-availability of families with a significant number of NTD cases makes research into genetic causation of NTD difficult. Case reports and epidemiologic studies have implicated a number of chemicals, widely differing therapeutic drugs, environmental contaminants, pollutants, infectious agents, and solvents. Maternal hyperthermia, use of valproate by epileptic women during pregnancy, deficiency and excess of certain nutrients and chronic maternal diseases (e.g. diabetes mellitus) are reported to cause a manifold increase in the

  4. Inositol for the prevention of neural tube defects: a pilot randomised controlled trial.

    PubMed

    Greene, Nicholas D E; Leung, Kit-Yi; Gay, Victoria; Burren, Katie; Mills, Kevin; Chitty, Lyn S; Copp, Andrew J

    2016-03-01

    Although peri-conceptional folic acid (FA) supplementation can prevent a proportion of neural tube defects (NTD), there is increasing evidence that many NTD are FA non-responsive. The vitamin-like molecule inositol may offer a novel approach to preventing FA-non-responsive NTD. Inositol prevented NTD in a genetic mouse model, and was well tolerated by women in a small study of NTD recurrence. In the present study, we report the Prevention of Neural Tube Defects by Inositol (PONTI) pilot study designed to gain further experience of inositol usage in human pregnancy as a preliminary trial to a future large-scale controlled trial to evaluate efficacy of inositol in NTD prevention. Study subjects were UK women with a previous NTD pregnancy who planned to become pregnant again. Of 117 women who made contact, ninety-nine proved eligible and forty-seven agreed to be randomised (double-blind) to peri-conceptional supplementation with inositol plus FA or placebo plus FA. In total, thirty-three randomised pregnancies produced one NTD recurrence in the placebo plus FA group (n 19) and no recurrences in the inositol plus FA group (n 14). Of fifty-two women who declined randomisation, the peri-conceptional supplementation regimen and outcomes of twenty-two further pregnancies were documented. Two NTD recurred, both in women who took only FA in their next pregnancy. No adverse pregnancy events were associated with inositol supplementation. The findings of the PONTI pilot study encourage a large-scale controlled trial of inositol for NTD prevention, but indicate the need for a careful study design in view of the unwillingness of many high-risk women to be randomised. PMID:26847388

  5. Prevention of neural tube defects in the UK: a missed opportunity

    PubMed Central

    Morris, JK; Rankin, J; Draper, ES; Kurinczuk, JJ; Springett, A; Tucker, D; Wellesley, D; Wreyford, B; Wald, NJ

    2016-01-01

    Objective In 1991, the Medical Research Council (MRC) Vitamin Study demonstrated that folic acid taken before pregnancy and in early pregnancy reduced the risk of a neural tube defect (NTD). We aimed to estimate the number of NTD pregnancies that would have been prevented if flour had been fortified with folic acid in the UK from 1998 as it had been in the USA. Design Estimates of NTD prevalence, the preventive effect of folic acid and the proportion of women taking folic acid supplements before pregnancy were used to predict the number of NTD pregnancies that would have been prevented if folic acid fortification had been implemented. Setting Eight congenital anomaly registers in England and Wales. Main outcome measures The prevalence of pregnancies with an NTD in the UK and the number of these pregnancies that would have been prevented if folic acid fortification had been implemented. Results From 1991 to 2012, the prevalence of NTD pregnancies was 1.28 (95% CI 1.24 to 1.31) per 1000 total births (19% live births, 81% terminations and 0.5% stillbirths and fetal deaths ≥20 weeks’ gestation). If the USA levels of folic acid fortification from 1998 onwards had been adopted in the UK, an estimated 2014 fewer NTD pregnancies would have occurred. Conclusions Failure to implement folic acid fortification in the UK has caused, and continues to cause, avoidable terminations of pregnancy, stillbirths, neonatal deaths and permanent serious disability in surviving children. PMID:26681697

  6. Trehalose prevents neural tube defects by correcting maternal diabetes-suppressed autophagy and neurogenesis

    PubMed Central

    Xu, Cheng; Li, Xuezheng; Wang, Fang; Weng, Hongbo

    2013-01-01

    Preexisting maternal diabetes increases the risk of neural tube defects (NTDs). The mechanism underlying maternal diabetes-induced NTDs is not totally defined, and its prevention remains a challenge. Autophagy, an intracellular process to degrade dysfunction protein and damaged cellular organelles, regulates cell proliferation, differentiation, and apoptosis. Because autophagy impairment causes NTDs reminiscent of those observed in diabetic pregnancies, we hypothesize that maternal diabetes-induced autophagy impairment causes NTD formation by disrupting cellular homeostasis, leading to endoplasmic reticulum (ER) stress and apoptosis, and that restoration of autophagy by trehalose, a natural disaccharide, prevents diabetes-induced NTDs. Embryos from nondiabetic and type 1 diabetic mice fed with or without 2 or 5% trehalose water were used to assess markers of autophagy, ER stress, and neurogenesis, numbers of autophagosomes, gene expression that regulates autophagy, NTD rates, indices of mitochondrial dysfunction, and neuroepithelial cell apoptosis. Maternal diabetes suppressed autophagy by significantly reducing LC3-II expression, autophagosome numbers, and GFP-LC3 punctate foci in neuroepithelial cells and by altering autophagy-related gene expression. Maternal diabetes delayed neurogenesis by blocking Sox1 neural progenitor differentiation. Trehalose treatment reversed autophagy impairment and prevented NTDs in diabetic pregnancies. Trehalose resolved homeostatic imbalance by correcting mitochondrial defects, dysfunctional proteins, ER stress, apoptosis, and delayed neurogenesis in the neural tubes exposed to hyperglycemia. Our study demonstrates for the first time that maternal diabetes suppresses autophagy in neuroepithelial cells of the developing neural tube, leading to NTD formation, and provides evidence for the potential efficacy of trehalose as an intervention against hyperglycemia-induced NTDs. PMID:23880312

  7. [Neural tube defects and folic acid: a historical overview of a highly successful preventive intervention].

    PubMed

    Vásquez, Adriana Ordoñez; Suarez-Obando, Fernando

    2015-12-01

    This article gives a broad overview of part of the historical evolution of medical knowledge about neural tube defects (NTD) and the discovery of vitamin B9 or folic acid, as well as some relevant research events that, over the course of several centuries, defined the relationships between the understanding of central nervous system embryology, the discovery of the vitamin, the correlation between folic acid and cell proliferation and lastly the development of preventive measures for this type of defects. This narrative allows us to examine historically relevant concepts underlying clinical actions with a populational impact that prevent NTDs via folic acid consumption prior to conception. PMID:25650704

  8. Prevention of late blowing defect by reuterin produced in cheese by a Lactobacillus reuteri adjunct.

    PubMed

    Gómez-Torres, Natalia; Ávila, Marta; Gaya, Pilar; Garde, Sonia

    2014-09-01

    In this study, reuterin-producing Lactobacillus reuteri INIA P572 was added to cheese as an adjunct culture together with 50 or 100 mM glycerol (required for reuterin production), with the aim of controlling Clostridium tyrobutyricum CECT 4011 growth and preventing the late blowing defect (LBD) of cheese caused by this strain. L. reuteri survived cheese manufacture and produced reuterin in situ, detected at 6 and 24 h. However, the produced reuterin was enough to inhibit the growth of Clostridium, showing undetectable spore counts from day 30 onward and, therefore, to prevent cheese LBD during ripening (60 d, 14 °C). The acidification of these cheeses was not affected, although from day 14 they showed significantly lower lactococci counts than cheese made only with the starter (control cheese). Cheeses with LBD showed lower levels of lactic acid than control cheese and the formation of propionic and butyric acids, but cheeses with reuterin showed the same organic acids profile than control cheese. The cheese made with L. reuteri and 100 mM glycerol showed a light pink colour, not observed in the cheese made with L. reuteri and 50 mM glycerol. These results demonstrated a potent anti-clostridial activity of reuterin produced in an actual food product like cheese, and proved to be a novel approach to prevent LBD of cheese. PMID:24929721

  9. Long Term Maintenance of Neural Tube Defects Prevention in a High Prevalence State

    PubMed Central

    Collins, Julianne S.; Atkinson, Kristy K.; Dean, Jane H.; Best, Robert G.; Stevenson, Roger E.

    2011-01-01

    Objective To assess the efficacy of folic acid (FA) supplementation and fortification in preventing neural tube defects (NTDs) in a high prevalence region of the US. Study design Active and passive surveillance methods were used to identify all fetuses/infants affected by an NTD in South Carolina. Prevalence rates were compared with FA intake to determine the effects of increased intake on NTD occurrence and recurrence. Results From 1992–2009, 916 NTD cases occurred in South Carolina with isolated defects comprising 79% of cases. The NTD rate decreased 58% during this period. There was one NTD-affected pregnancy among 418 subsequent pregnancies (0.2%) in mothers with previous NTD-affected pregnancies who consumed periconceptional FA supplements and four NTDs among 66 pregnancies (6.1%) in which the mother did not take FA supplements. Folic acid supplementation increased from 8% to 35% from 1992–2007 and knowledge of the protective benefits of FA increased from 8% to 65% in women of childbearing age. Conclusions Increased periconceptional intake of FA appeared to reduce NTDs in a high prevalence region. The rate of spina bifida and anencephaly in South Carolina is now essentially the same (0.69 cases per 1000 live births and fetal deaths) as the 1998–2005 US rate (0.69). PMID:21345450

  10. Risk reduction using DDP (Defect Detection and Prevention): Software support and software applications

    NASA Technical Reports Server (NTRS)

    Feather, M. S.

    2001-01-01

    Risk assessment and mitigation is the focus of the Defect Detection and Prevention (DDP) process, which has been applied to spacecraft technology assessments and planning, both hardware and software. DDP's major elements and their relevance to core requirement engineering concerns are summarized. The accompanying research demonstration illustrates DDP's tool support, and further customizations for application to software.

  11. Specific isoforms of protein kinase C are essential for prevention of folate-resistant neural tube defects by inositol.

    PubMed

    Cogram, Patricia; Hynes, Andrew; Dunlevy, Louisa P E; Greene, Nicholas D E; Copp, Andrew J

    2004-01-01

    A proportion of neural tube defects (NTDs) can be prevented by maternal folic acid supplementation, although some cases are unresponsive. The curly tail mutant mouse provides a model of folate-resistant NTDs, in which defects can be prevented by inositol therapy in early pregnancy. Hence, inositol represents a possible novel adjunct therapy to prevent human NTDs. The present study investigated the molecular mechanism by which inositol prevents mouse NTDs. Activation of protein kinase C (PKC) is known to be essential, and we examined neurulation-stage embryos for PKC expression and applied PKC inhibitors to curly tail embryos developing in culture. Although all known PKC isoforms were detected in the closing neural tube, use of chemical PKC inhibitors identified a particular requirement for 'conventional' PKC isoforms. Peptide inhibitors offer selective inhibition of individual PKCs, and we demonstrated isoform-specific inhibition of PKC in embryonic cell cultures. Application of peptide inhibitors to neurulation-stage embryos revealed an absolute dependence on the activity of PKCbetaI and gamma for prevention of NTDs by inositol, and partial dependence on PKCzeta, whereas other PKCs (alpha, betaII delta, and epsilon) were dispensable. To investigate the cellular action of inositol and PKCs in NTD prevention, we examined cell proliferation in curly tail embryos. Defective proliferation of hindgut cells is a key component of the pathogenic sequence leading to NTDs in curly tail. Hindgut cell proliferation was stimulated specifically by inositol, an effect that required activation of PKCbetaI. Our findings reveal an essential role of specific PKC isoforms in mediating the prevention of mouse NTDs by inositol. PMID:14613966

  12. How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces.

    PubMed

    Töpfer, Kai; Tremblay, Jean Christophe

    2016-07-21

    In this contribution, we study using first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: (1) co-adsorption is weakly supported at F(0) and F(2+) defects but not at F(1+) sites, (2) electron redistribution from the F(0) vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, (3) a metastable carbonate intermediate can form on defects of the F(0) type, (4) only a small activation barrier exists for the highly favorable dissociation of CO2 from F(0), and (5) the moderate adsorption energy of the gold atom on the F(0) defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken in the first oxidation step. PMID:27345190

  13. Studying post-etching silicon crystal defects on 300mm wafer by automatic defect review AFM

    NASA Astrophysics Data System (ADS)

    Zandiatashbar, Ardavan; Taylor, Patrick A.; Kim, Byong; Yoo, Young-kook; Lee, Keibock; Jo, Ahjin; Lee, Ju Suk; Cho, Sang-Joon; Park, Sang-il

    2016-03-01

    Single crystal silicon wafers are the fundamental elements of semiconductor manufacturing industry. The wafers produced by Czochralski (CZ) process are very high quality single crystalline materials with known defects that are formed during the crystal growth or modified by further processing. While defects can be unfavorable for yield for some manufactured electrical devices, a group of defects like oxide precipitates can have both positive and negative impacts on the final device. The spatial distribution of these defects may be found by scattering techniques. However, due to limitations of scattering (i.e. light wavelength), many crystal defects are either poorly classified or not detected. Therefore a high throughput and accurate characterization of their shape and dimension is essential for reviewing the defects and proper classification. While scanning electron microscopy (SEM) can provide high resolution twodimensional images, atomic force microscopy (AFM) is essential for obtaining three-dimensional information of the defects of interest (DOI) as it is known to provide the highest vertical resolution among all techniques [1]. However AFM's low throughput, limited tip life, and laborious efforts for locating the DOI have been the limitations of this technique for defect review for 300 mm wafers. To address these limitations of AFM, automatic defect review AFM has been introduced recently [2], and is utilized in this work for studying DOI on 300 mm silicon wafer. In this work, we carefully etched a 300 mm silicon wafer with a gaseous acid in a reducing atmosphere at a temperature and for a sufficient duration to decorate and grow the crystal defects to a size capable of being detected as light scattering defects [3]. The etched defects form a shallow structure and their distribution and relative size are inspected by laser light scattering (LLS). However, several groups of defects couldn't be properly sized by the LLS due to the very shallow depth and low

  14. Topological Defects in Liquid Crystals: Studying the Correlation between Defects and Curvature

    NASA Astrophysics Data System (ADS)

    Melton, Charles

    2015-03-01

    Topological defects have recently been the subject of many fascinating studies in soft condensed matter physics. In particular, linking the evolution of topological defects to curvature changes has been a focus, leading possible applications in the areas such as cosmetics, pharmaceuticals, and electronics. In this study, defects in nematic liquid crystal droplets are investigated via laboratory and theoretical techniques. Nematic liquid crystal defects are reproduced via Monte Carlo simulations using a modified 2D XY-Model Hamiltonian. The simulation is performed on a curved surface to replicate a nematic droplet and examine possible defect configurations. To complement this theoretical work, we have trapped nematic droplets inside a dual-beam optical trap. This system allows controllable non-contact droplet deformation on a microscope based platform. Future work will focus on using the trap to stretch nematic droplets, correlating the changing topological defects with theoretical predictions.

  15. Study Explores Mechanism Between Zika Virus, Birth Defects

    MedlinePlus

    ... fullstory_158048.html Study Explores Mechanism Between Zika Virus, Birth Defects Protein on fetal stem cells provides ... Scientists say they've discovered how the Zika virus might cause severe brain and eye birth defects. ...

  16. Inositol prevents folate-resistant neural tube defects in the mouse.

    PubMed

    Greene, N D; Copp, A J

    1997-01-01

    Clinical trials demonstrate that up to 70% of neural tube defects (NTDs) can be prevented by folic acid supplementation in early pregnancy, whereas the remaining NTDs are resistant to folate. Here, we show that a second vitamin, myo-inositol, is capable of significantly reducing the incidence of spinal NTDs in curly tail mice, a genetic model of folate-resistant NTDs. Inositol increases flux through the inositol/lipid cycle, stimulating protein kinase C activity and upregulating expression of retinoic acid receptor beta, specifically in the caudal portion of the embryonic hindgut. This reduces the delay in closure of the posterior neuropore, the embryonic defect that is known to lead directly to spina bifida in curly tail embryos. Our findings reveal a molecular pathway of NTD prevention and suggest the possible efficacy of combined treatment with folate and inositol in overcoming the majority of human NTDs. PMID:8986742

  17. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel.

    PubMed

    Gilbert, C A; Smith, R; Kenny, S D; Murphy, S T; Grimes, R W; Ball, J A

    2009-07-01

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters. PMID:21828490

  18. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Gilbert, C. A.; Smith, R.; Kenny, S. D.; Murphy, S. T.; Grimes, R. W.; Ball, J. A.

    2009-07-01

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

  19. PREFACE: The International Workshop on Positron Studies of Defects 2014

    NASA Astrophysics Data System (ADS)

    Sugita, Kazuki; Shirai, Yasuharu

    2016-01-01

    The International Workshop on Positron Studies of Defects 2014 (PSD-14) was held in Kyoto, Japan from 14-19 September, 2014. The PSD Workshop brought together positron scientists interested in studying defects to an international platform for presenting and discussing recent results and achievements, including new experimental and theoretical methods in the field. The workshop topics can be characterized as follows: • Positron studies of defects in semiconductors and oxides • Positron studies of defects in metals • New experimental methods and equipment • Theoretical calculations and simulations of momentum distributions, positron lifetimes and other characteristics for defects • Positron studies of defects in combination with complementary methods • Positron beam studies of defects at surfaces, interfaces, in sub-surface regions and thin films • Nanostructures and amorphous materials

  20. Orally administered melatonin prevents lipopolysaccharide-induced neural tube defects in mice.

    PubMed

    Fu, Lin; Yu, Zhen; Chen, Yuan-Hua; Xia, Mi-Zhen; Wang, Hua; Zhang, Cheng; Tao, Fang-Biao; Xu, De-Xiang

    2014-01-01

    Lipopolysaccharide (LPS) has been associated with adverse pregnant outcomes, including fetal demise, intra-uterine growth restriction (IUGR), neural tube defects (NTDs) and preterm delivery in rodent animals. Previous studies demonstrated that melatonin protected against LPS-induced fetal demise, IUGR and preterm delivery. The aim of the present study was to investigate the effects of melatonin on LPS-induced NTDs. All pregnant mice except controls were intraperitoneally injected with LPS (25 µg/kg) daily from gestational day (GD)8 to GD12. Some pregnant mice were orally administered with melatonin (MT, 50 mg/kg) before each LPS injection. A five-day LPS injection resulted in 27.5% of fetuses with anencephaly, exencephaly or encephalomeningocele. Additional experiment showed that maternal LPS exposure significantly down-regulated placental proton-coupled folate transporter (pcft) and disturbed folate transport from maternal circulation through the placentas into the fetus. Interestingly, melatonin significantly attenuated LPS-induced down-regulation of placental pcft. Moreover, melatonin markedly improved the transport of folate from maternal circulation through the placentas into the fetus. Correspondingly, orally administered melatonin reduced the incidence of LPS-induced anencephaly, exencephaly or encephalomeningocele. Taken together, these results suggest that orally administered melatonin prevents LPS-induced NTDs through alleviating LPS-induced disturbance of folate transport from maternal circulation through the placenta into the fetus. PMID:25420102

  1. Defectivity reduction studies for ArF immersion lithography

    NASA Astrophysics Data System (ADS)

    Matsunaga, Kentaro; Kondoh, Takehiro; Kato, Hirokazu; Kobayashi, Yuuji; Hayasaki, Kei; Ito, Shinichi; Yoshida, Akira; Shimura, Satoru; Kawasaki, Tetsu; Kyoda, Hideharu

    2007-03-01

    Immersion lithography is widely expected to meet the manufacturing requirements of future device nodes. A critical development in immersion lithography has been the construction of a defect-free process. Two years ago, the authors evaluated the impact of water droplets made experimentally on exposed resist films and /or topcoat. (1) The results showed that the marks of drying water droplet called watermarks became pattern defects with T-top profile. In the case that water droplets were removed by drying them, formation of the defects was prevented. Post-exposure rinse process to remove water droplets also prevented formation of the defects. In the present work, the authors evaluated the effect of pre- and post-exposure rinse processes on hp 55nm line and space pattern with Spin Rinse Process Station (SRS) and Post Immersion Rinse Process Station (PIR) modules on an inline lithography cluster with the Tokyo Electron Ltd. CLEAN TRACK TM LITHIUS TM i+ and ASML TWINSCAN XT:1700Fi , 193nm immersion scanner. It was found that total defectivity is decreased by pre- and post-exposure rinse. In particular, bridge defects and large bridge defects were decreased by pre- and post-exposure rinse. Pre- and post-exposure rinse processes are very effective to reduce the bridge and large bridge defects of immersion lithography.

  2. Optical Studies of Defects in Aluminum Oxide.

    NASA Astrophysics Data System (ADS)

    James, Floyd Jasper

    Defects in aluminum oxide single crystals were studied using optical absorption, photoluminescence, and thermally stimulated luminescence. The primary defect in Al(,2)O(,3) is the oxygen vacancy. A vacancy trapping 2 electrons, the F center, absorbs at 6.0 eV, and the F('+) center, trapping 1 electron, absorbs at 4.8 eV, 5.4 eV, and possibly 6.1 eV. Neutron bombardment produces F and F('+) centers, while electron bombardment or treatment by growth in a reducing atmosphere makes predominantly F centers. Isochronal and isothermal anneals of neutron-irradiated material show no discrete stages in the annealing of the oxygen vacancy, as monitored by the decrease in optical absorption of the F center, and so no activation energy for the process could be determined. Photoluminescence studies of neutron-irradiated, additively colored, electron irradiated, and growth colored crystals shows the mainly the 6.0 eV - 3.0 eV F center absorption-emission pair, while bombarded samples show reduced F emission, and also F('+) emissions, including the dominant 4.8 - 3.2 eV peak. By using computer controlled excitation and analyzing monochromators, luminescence peak detection was improved, and several new absorption-emission pairs were found. Thermally stimulated luminescence (TSL) was conducted from 77 K to room temperature on growth-colored and non growth-colored samples, using ultraviolet light as the exciting agent. The common 260 K TSL peak is largest at 6.0 eV in exciting wavelength, and shows emission similar to that of the F center. This was not seen in a crystal not containing F centers. Also, a peak at 230 K can be produced in growth-colored crystals by bleaching at about 200 K.

  3. Defect stability in thorium monocarbide: An ab initio study

    NASA Astrophysics Data System (ADS)

    Wang, Chang-Ying; Han, Han; Shao, Kuan; Cheng, Cheng; Huai, Ping

    2015-09-01

    The elastic properties and point defects of thorium monocarbide (ThC) have been studied by means of density functional theory based on the projector-augmented-wave method. The calculated electronic and elastic properties of ThC are in good agreement with experimental data and previous theoretical results. Five types of point defects have been considered in our study, including the vacancy defect, interstitial defect, antisite defect, schottky defect, and composition-conserving defect. Among these defects, the carbon vacancy defect has the lowest formation energy of 0.29 eV. The second most stable defect (0.49 eV) is one of composition-conserving defects in which one carbon is removed to another carbon site forming a C2 dimer. In addition, we also discuss several kinds of carbon interstitial defects, and predict that the carbon trimer configuration may be a transition state for a carbon dimer diffusion in ThC. Project supported by the International S&T Cooperation Program of China (Grant No. 2014DFG60230), the National Natural Science Foundation of China (Grant No. 91326105), the National Basic Research Program of China (Grant No. 2010CB934504), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA02040104).

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

    PubMed

    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. PMID:26475080

  5. Regular bottlenecks and restrictions to somatic fusion prevent the accumulation of mitochondrial defects in Neurospora

    PubMed Central

    Bastiaans, E.; Aanen, D. K.; Debets, A. J. M.; Hoekstra, R. F.; Lestrade, B.; Maas, M. F. P. M.

    2014-01-01

    The replication and segregation of multi-copy mitochondrial DNA (mtDNA) are not under strict control of the nuclear DNA. Within-cell selection may thus favour variants with an intracellular selective advantage but a detrimental effect on cell fitness. High relatedness among the mtDNA variants of an individual is predicted to disfavour such deleterious selfish genetic elements, but experimental evidence for this hypothesis is scarce. We studied the effect of mtDNA relatedness on the opportunities for suppressive mtDNA variants in the fungus Neurospora carrying the mitochondrial mutator plasmid pKALILO. During growth, this plasmid integrates into the mitochondrial genome, generating suppressive mtDNA variants. These mtDNA variants gradually replace the wild-type mtDNA, ultimately culminating in growth arrest and death. We show that regular sequestration of mtDNA variation is required for effective selection against suppressive mtDNA variants. First, bottlenecks in the number of mtDNA copies from which a ‘Kalilo’ culture started significantly increased the maximum lifespan and variation in lifespan among cultures. Second, restrictions to somatic fusion among fungal individuals, either by using anastomosis-deficient mutants or by generating allotype diversity, prevented the accumulation of suppressive mtDNA variants. We discuss the implications of these results for the somatic accumulation of mitochondrial defects during ageing. PMID:24864316

  6. Regular bottlenecks and restrictions to somatic fusion prevent the accumulation of mitochondrial defects in Neurospora.

    PubMed

    Bastiaans, E; Aanen, D K; Debets, A J M; Hoekstra, R F; Lestrade, B; Maas, M F P M

    2014-07-01

    The replication and segregation of multi-copy mitochondrial DNA (mtDNA) are not under strict control of the nuclear DNA. Within-cell selection may thus favour variants with an intracellular selective advantage but a detrimental effect on cell fitness. High relatedness among the mtDNA variants of an individual is predicted to disfavour such deleterious selfish genetic elements, but experimental evidence for this hypothesis is scarce. We studied the effect of mtDNA relatedness on the opportunities for suppressive mtDNA variants in the fungus Neurospora carrying the mitochondrial mutator plasmid pKALILO. During growth, this plasmid integrates into the mitochondrial genome, generating suppressive mtDNA variants. These mtDNA variants gradually replace the wild-type mtDNA, ultimately culminating in growth arrest and death. We show that regular sequestration of mtDNA variation is required for effective selection against suppressive mtDNA variants. First, bottlenecks in the number of mtDNA copies from which a 'Kalilo' culture started significantly increased the maximum lifespan and variation in lifespan among cultures. Second, restrictions to somatic fusion among fungal individuals, either by using anastomosis-deficient mutants or by generating allotype diversity, prevented the accumulation of suppressive mtDNA variants. We discuss the implications of these results for the somatic accumulation of mitochondrial defects during ageing. PMID:24864316

  7. A Optical Study of Defects in Diamond.

    NASA Astrophysics Data System (ADS)

    Beard, Darren R.

    Available from UMI in association with The British Library. The one-phonon defect-induced infrared absorption in Type I diamonds has been studied. The previously reported spectral forms of the F and G spectra have been altered. Three components labelled J, K and L, are presented. A data base of 75 infrared spectra has been decomposed and classified. New computer programs have been produced to cope with up to 12 components in the one-phonon region simultaneously. Black diamond surfaces have been examined using photoluminescence spectroscopy. Laser cutting in air is found to result in black surfaces. Diamonds were examined both before and after cutting and changes in the spectra monitored. In Type Ib and Type IIb diamonds, the typical diamond spectrum was changed into a broad band spectrum. The first order diamond Raman was not detectable after laser cutting. Type Ia and Type IIa diamonds did not show any changes due to being cut. To investigate the graphitization process further, diamonds were heated to 850^circC in gas flows at 0.38 torr (50.7 Pa). Using oxygen, it was found that the intensity of H3 luminescence was reduced and that a broad band spectrum was produced. The spectral changes were reversed by treating with hydrogen. Two types of thin carbonaceous films have been examined, those grown by vapour deposition and those produced by scanning a high energy density laser beam across an amorphous carbon sample. The photoluminescence spectra obtained from the two sample types were different. Discs of sintered diamond have also been examined with a view to determining the strain distribution within the samples. Finally, the production mechanism of the H3 defect has been considered. A grown-in theory is developed. It is supported quantitatively with experimental results and explains the ubiquity of H3, even in synthetic crystals. The C centre is thought to be incorporated equally on all of the low index faces of diamond. Consideration of the A centre showed that it

  8. CDC Grand Rounds: Understanding the Causes of Major Birth Defects - Steps to Prevention.

    PubMed

    Simeone, Regina M; Feldkamp, Marcia L; Reefhuis, Jennita; Mitchell, Allen A; Gilboa, Suzanne M; Honein, Margaret A; Iskander, John

    2015-10-01

    Major birth defects (birth defects) are defined as structural abnormalities, present at birth, with surgical, medical, or cosmetic importance. Each year in the United States, 3% of live births (approximately 120,000 infants) have an identifiable structural birth defect. Examples of birth defects include neural tube defects, such as spina bifida; orofacial clefts; abdominal wall defects, such as gastroschisis; and congenital heart defects, such as hypoplastic left heart syndrome. Collectively, congenital heart defects are the most common birth defects (27%), followed by musculoskeletal defects (18%), genitourinary defects (15%), orofacial defects (5%), and neural tube defects (2%). PMID:26447345

  9. A population-based study of birth defects in Malaysia.

    PubMed

    Thong, M K; Ho, J J; Khatijah, N N

    2005-01-01

    Birth defects are one of the leading causes of paediatric disability and mortality in developed and developing countries. Data on birth defects from population-based studies originating from developing countries are lacking. One of the objectives of this study was to determine the epidemiology of major birth defects in births during the perinatal period in Kinta district, Perak, Malaysia over a 14-month period, using a population-based birth defect register. There were 253 babies with major birth defects in 17,720 births, giving an incidence of 14.3/1000 births, a birth prevalence of 1 in 70. There were 80 babies with multiple birth defects and 173 with isolated birth defects. The exact syndromic diagnosis of the babies with multiple birth defects could not be identified in 18 (22.5%) babies. The main organ systems involved in the isolated birth defects were cardiovascular (13.8%), cleft lip and palate (11.9%), clubfeet (9.1%), central nervous system (CNS) (including neural tube defects) (7.9%), musculoskeletal (5.5%) and gastrointestinal systems (4.7%), and hydrops fetalis (4.3%). The babies with major birth defects were associated with lower birth weights, premature deliveries, higher Caesarean section rates, prolonged hospitalization and increased specialist care. Among the cohort of babies with major birth defects, the mortality rate was 25.2% during the perinatal period. Mothers with affected babies were associated with advanced maternal age, birth defects themselves or their relatives but not in their other offspring, and significantly higher rates of previous abortions. The consanguinity rate of 2.4% was twice that of the control population. It is concluded that a birth defects register is needed to monitor these developments and future interventional trials are needed to reduce birth defects in Malaysia. PMID:16096215

  10. Using Defects in Materials to Store Energy: a Theoretical Study

    NASA Astrophysics Data System (ADS)

    Lu, I.-Te; Bernardi, Marco

    We study the energy stored by defects in materials using density functional theory (DFT) calculations. Leveraging experimental data to estimate the energy density of defects, expressed as the defect formation energy per unit volume (units of MJ/L) or weight (units of MJ/kg), we identify candidates for high energy density storage, including tungsten, diamond, graphite, silicon, and graphene. DFT calculations are applied to these materials to study the formation energy of vacancies, interstitials, and Frenkel pairs. Our results indicate that the energy density stored by defects in these materials, with experimentally accessible non-equilibrium defect concentrations, can be higher than that of common energy storage technologies such as lithium batteries and supercapacitors. We discuss storage of solar energy and electrical energy (through ion bombardment) using defects.

  11. Study of post-develop defect on typical EUV resist

    NASA Astrophysics Data System (ADS)

    Harumoto, Masahiko; Suyama, Sadayasu; Miyagi, Tadashi; Morita, Akihiko; Asai, Masaya; Kaneyama, Koji; Itani, Toshiro

    2011-04-01

    This study reports on post-develop defect for EUV resist process. Presently, research and development of EUV resists are continuously being carried out in terms of resolution, sensitivity, LWR. However, in the preparation of EUV lithography for mass-production, research on the reduction of pattern defects, especially post-develop defect is also necessary. As observed during the early stages of resist development for the various lithographic technologies, a large number of pattern defects are commonly coming from the resist dissolution process. As previously reported, utilizing an EUV exposure tool, we have classified several EUV specific defects on exposed and un-exposed area. And also we have reported approaches of defect reduction. In this work, using some types developer solution (TBAH, TBAH+, etc) comparing with current developer solution (TMAH), EUV specific defects were evaluated. Furthermore, we investigated the defect appearing-mechanism and approached defect reduction by track process. Finally, based on these results, the direction of defect reduction approaches applicable for EUV resist processing was discussed.

  12. Prevention of birth defects in the pre-conception period: knowledge and practice of health care professionals (nurses and doctors) in a city of Southern Brazil

    PubMed Central

    Ferreira, Flávia Romariz; Russo Akiba, Heloisa Regina; Júnior, Edward Araujo; Figueiredo, Elisabeth Niglio; Abrahão, Anelise Riedel

    2015-01-01

    Background: Some congenital defects can be prevented in the pregestational stage. However, many health professionals are not prepared to provide counselling to couples regarding the same. Objective: This study aimed to assess the performance of doctors and nurses from a primary health-care unit in Florianopolis, Brazil, in preventing birth defects in the preconception period based on the recommendations of the Control Center of Disease Prevention. Materials and Methods: This descriptive cross sectional study was performed at a tertiary referral center. In this study, a semi-structured questionnaire was provided to 160 health professionals comprising doctors and nurses who were actively involved in providing primary health care in family health programs. The non-parametric Chi-square (χ2) test was used to analyse the data obtained through multiple choice questions. Results: Our results showed that although 81.9% of health professionals provided health-care assistance based on protocols, and only 46.2% professionals were aware of the presence of the topic in the protocol. Of the recommendations provided by the Control Center of Disease Prevention, the use of folic acid was the most prescribed. However, this prescription was not statistically different between nurses and doctors (P=0.85). Conclusion: This study identified the fragile nature in these professional’s knowledge about the prevention of birth defects in pre-conception period, as evidenced by the inconsistency in their responses. PMID:26644794

  13. Maternal Exposure to Methotrexate and Birth Defects: a Population-Based Study

    PubMed Central

    Dawson, April L.; Riehle-Colarusso, Tiffany; Reefhuis, Jennita; Arena, J. Fernando

    2015-01-01

    Methotrexate is an anti-folate medication that is associated with increased risk of multiple birth defects. Using data from the National Birth Defects Prevention Study, a case-control study of major birth defects in the United States, we examined mothers exposed to methotrexate. The study population included mothers of live-born infants without major birth defects (controls) and mothers of fetuses or infants with a major birth defect (cases), with expected dates of delivery between October 1997 and December 2009. Mothers of cases and controls were asked detailed questions concerning pregnancy history, demographic information, and exposures in a telephone interview. Approximately 0.06% (n=16/27,623) of case and 0.04% (n=4/10,113) of control mothers reported exposure to methotrexate between three months prior to conception through the end of pregnancy. Of the 16 case infants, 11 (68.8%) had a congenital heart defect (CHD). The observed CHDs included atrial septal defects, tetralogy of Fallot, valvar pulmonary stenosis, ventricular septal defects (VSDs), and total anomalous pulmonary venous return. One case infant had microtia in addition to a VSD and another had VACTER association. Exposed cases without a CHD had one of the following birth defects: cleft palate, hypospadias, congenital diaphragmatic hernia, or craniosynostosis. Based on a limited number of methotrexate-exposed mothers, our findings support recent case reports suggesting an association between early pregnancy exposure to methotrexate and CHDs. Because of the rarity of maternal periconceptional exposure to methotrexate, long-term, population-based case-control studies are needed to confirm these findings and better evaluate the association between methotrexate and birth defects. PMID:24898111

  14. Positron studies of defected metals, metallic surfaces

    SciTech Connect

    Bansil, A.

    1991-01-01

    Specific problems proposed under this project included the treatment of electronic structure and momentum density in various disordered and defected systems. Since 1987, when the new high-temperature superconductors were discovered, the project focused extensively on questions concerning the electronic structure and Fermiology of high-[Tc] superconductors, in particular, (i) momentum density and positron experiments, (ii) angle-resolved photoemission intensities, (iii) effects of disorder and substitutions in the high-[Tc]'s.

  15. Enzyme replacement therapy prevents dental defects in a model of hypophosphatasia.

    PubMed

    McKee, M D; Nakano, Y; Masica, D L; Gray, J J; Lemire, I; Heft, R; Whyte, M P; Crine, P; Millán, J L

    2011-04-01

    Hypophosphatasia (HPP) occurs from loss-of-function mutation in the tissue-non-specific alkaline phosphatase (TNALP) gene, resulting in extracellular pyrophosphate accumulation that inhibits skeletal and dental mineralization. TNALP-null mice (Akp2(-/-)) phenocopy human infantile hypophosphatasia; they develop rickets at 1 week of age, and die before being weaned, having severe skeletal and dental hypomineralization and episodes of apnea and vitamin B(6)-responsive seizures. Delay and defects in dentin mineralization, together with a deficiency in acellular cementum, are characteristic. We report the prevention of these dental abnormalities in Akp2(-/-) mice receiving treatment from birth with daily injections of a mineral-targeting, human TNALP (sALP-FcD(10)). sALP-FcD(10) prevented hypomineralization of alveolar bone, dentin, and cementum as assessed by micro-computed tomography and histology. Osteopontin--a marker of acellular cementum--was immuno-localized along root surfaces, confirming that acellular cementum, typically missing or reduced in Akp2(-/-) mice, formed normally. Our findings provide insight concerning how acellular cementum is formed on tooth surfaces to effect periodontal ligament attachment to retain teeth in their osseous alveolar sockets. Furthermore, they provide evidence that this enzyme-replacement therapy, applied early in post-natal life--where the majority of tooth root development occurs, including acellular cementum formation--could prevent the accelerated tooth loss seen in individuals with HPP. PMID:21212313

  16. Myocardial Defect Detection Using PET-CT: Phantom Studies

    PubMed Central

    Mananga, Eugene S.; El Fakhri, Georges; Schaefferkoetter, Joshua; Bonab, Ali A.; Ouyang, Jinsong

    2014-01-01

    It is expected that both noise and activity distribution can have impact on the detectability of a myocardial defect in a cardiac PET study. In this work, we performed phantom studies to investigate the detectability of a defect in the myocardium for different noise levels and activity distributions. We evaluated the performance of three reconstruction schemes: Filtered Back-Projection (FBP), Ordinary Poisson Ordered Subset Expectation Maximization (OP–OSEM), and Point Spread Function corrected OSEM (PSF–OSEM). We used the Channelized Hotelling Observer (CHO) for the task of myocardial defect detection. We found that the detectability of a myocardial defect is almost entirely dependent on the noise level and the contrast between the defect and its surroundings. PMID:24505429

  17. Folic Acid supplementation and pregnancy: more than just neural tube defect prevention.

    PubMed

    Greenberg, James A; Bell, Stacey J; Guan, Yong; Yu, Yan-Hong

    2011-01-01

    Folate (vitamin B(9)) is an essential nutrient that is required for DNA replication and as a substrate for a range of enzymatic reactions involved in amino acid synthesis and vitamin metabolism. Demands for folate increase during pregnancy because it is also required for growth and development of the fetus. Folate deficiency has been associated with abnormalities in both mothers (anemia, peripheral neuropathy) and fetuses (congenital abnormalities). This article reviews the metabolism of folic acid, the appropriate use of folic acid supplementation in pregnancy, and the potential benefits of folic acid, as well as the possible supplementation of l-methylfolate for the prevention of pregnancy-related complications other than neural tube defects. PMID:22102928

  18. Aurora B prevents chromosome arm separation defects by promoting telomere dispersion and disjunction

    PubMed Central

    Reyes, Céline; Serrurier, Céline; Gauthier, Tiphaine

    2015-01-01

    The segregation of centromeres and telomeres at mitosis is coordinated at multiple levels to prevent the formation of aneuploid cells, a phenotype frequently observed in cancer. Mitotic instability arises from chromosome segregation defects, giving rise to chromatin bridges at anaphase. Most of these defects are corrected before anaphase onset by a mechanism involving Aurora B kinase, a key regulator of mitosis in a wide range of organisms. Here, we describe a new role for Aurora B in telomere dispersion and disjunction during fission yeast mitosis. Telomere dispersion initiates in metaphase, whereas disjunction takes place in anaphase. Dispersion is promoted by the dissociation of Swi6/HP1 and cohesin Rad21 from telomeres, whereas disjunction occurs at anaphase after the phosphorylation of condensin subunit Cnd2. Strikingly, we demonstrate that deletion of Ccq1, a telomeric shelterin component, rescued cell death after Aurora inhibition by promoting the loading of condensin on chromosome arms. Our findings reveal an essential role for telomeres in chromosome arm segregation. PMID:25778919

  19. Aurora B prevents chromosome arm separation defects by promoting telomere dispersion and disjunction.

    PubMed

    Reyes, Céline; Serrurier, Céline; Gauthier, Tiphaine; Gachet, Yannick; Tournier, Sylvie

    2015-03-16

    The segregation of centromeres and telomeres at mitosis is coordinated at multiple levels to prevent the formation of aneuploid cells, a phenotype frequently observed in cancer. Mitotic instability arises from chromosome segregation defects, giving rise to chromatin bridges at anaphase. Most of these defects are corrected before anaphase onset by a mechanism involving Aurora B kinase, a key regulator of mitosis in a wide range of organisms. Here, we describe a new role for Aurora B in telomere dispersion and disjunction during fission yeast mitosis. Telomere dispersion initiates in metaphase, whereas disjunction takes place in anaphase. Dispersion is promoted by the dissociation of Swi6/HP1 and cohesin Rad21 from telomeres, whereas disjunction occurs at anaphase after the phosphorylation of condensin subunit Cnd2. Strikingly, we demonstrate that deletion of Ccq1, a telomeric shelterin component, rescued cell death after Aurora inhibition by promoting the loading of condensin on chromosome arms. Our findings reveal an essential role for telomeres in chromosome arm segregation. PMID:25778919

  20. A single-molecule approach to ZnO defect studies: Single photons and single defects

    SciTech Connect

    Jungwirth, N. R.; Pai, Y. Y.; Chang, H. S.; MacQuarrie, E. R.; Nguyen, K. X.; Fuchs, G. D.

    2014-07-28

    Investigations that probe defects one at a time offer a unique opportunity to observe properties and dynamics that are washed out of ensemble measurements. Here, we present confocal fluorescence measurements of individual defects in ZnO nanoparticles and sputtered films that are excited with sub-bandgap energy light. Photon correlation measurements yield both antibunching and bunching, indicative of single-photon emission from isolated defects that possess a metastable shelving state. The single-photon emission is in the range of ∼560–720 nm and typically exhibits two broad spectral peaks separated by ∼150 meV. The excited state lifetimes range from 1 to 13 ns, consistent with the finite-size and surface effects of nanoparticles and small grains. We also observe discrete jumps in the fluorescence intensity between a bright state and a dark state. The dwell times in each state are exponentially distributed and the average dwell time in the bright (dark) state does (may) depend on the power of the exciting laser. Taken together, our measurements demonstrate the utility of a single-molecule approach to semiconductor defect studies and highlight ZnO as a potential host material for single-defect based applications.

  1. Theoretical studies of native defects in cubic boron nitride

    SciTech Connect

    Piquini, P.; Mota, R.; Schmidt, T.M.; Fazzio, A.

    1997-08-01

    We have studied the electronic and structural properties of native defects in cubic boron nitride (nitrogen vacancy, boron antisite, and oxygen substitutional) using all-electron first-principles total-energy calculations. We find that all defects introduce a deep state above the middle-energy gap. These defects present a C{sub 3v}-local symmetry. In the case of nitrogen vacancy the possibility of the F-center formation is discussed. {copyright} {ital 1997} {ital The American Physical Society}

  2. Crystal defect studies using x-ray diffuse scattering

    SciTech Connect

    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.

  3. Pollution Prevention Wipe Application Study

    SciTech Connect

    Lopez, E.P.; Modderman, W.E.; Montoya, M.G.

    1999-02-10

    As part of a pollution prevention program, a study was conducted at Sandia National Laboratories and at the Amarillo, ''Pantex Plant'' to identify a suitable replacement solvent(s) for cleaning hardware during routine maintenance operations. Current cleaning is performed using solvents (e.g. acetone, toluene, MEK, alcohols) that are classified as Resource Conservation and Recovery Act (RCW) materials. The Environmental Protection Agency (EPA) has assigned four characteristics as the criteria for determining whether a material is identified as hazardous under RCRA: Ignitability, Corrosivity, Reactivity and Toxicity. Within the DOE and DoD sector, these solvents are used with hand wipes to clean surfaces prior to O-ring replacement, to remove decals for new labeling, to clean painted surfaces prior to reconditioning, and for other general maintenance purposes. In some cases, low level radioactive contamination during cleaning necessitates that the RCIL4 solvent-containing wipes be classified as mixed waste. To avoid using RCRA materials, cleaning candidates were sought that had a flashpoint greater than 140 F, a pH between 2.5 and 12.5, and did not fail the reactivity and toxicity criteria. Three brominated cleaners, two hydrofluoroether azeotropes and two aliphatic hydrocarbon cleaner formulations were studied as potential replacements. Cleaning efficacy, materials compatibility, corrosion and accelerated aging studies were conducted and used to screen potential candidates. Hypersolve NPB (an n-propyl bromide based formulation) consistently ranked high in removing typical contaminants for weapons applications.

  4. Nitrotyrosine adsorption on defective graphene: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Majidi, R.; Karami, A. R.

    2015-06-01

    We have applied density functional theory to study adsorption of nitrotyrosine on perfect and defective graphene sheets. The graphene sheets with Stone-Wales (SW) defect, pentagon-nonagon (5-9) single vacancy, and pentagon-octagon-pentagon (5-8-5) double vacancy were considered. The calculations of adsorption energy showed that nitrotyrosine presents a more strong interaction with defective graphene rather than with perfect graphene sheet. The order of interaction strength is: SW>5-9>5-8-5>perfect graphene. It is found that the electronic properties of perfect and defective graphene are sensitive to the presence of nitrotyrosine. Hence, graphene sheets can be considered as a good sensor for detection of nitrotyrosine molecule which is observed in connection with several human disorders, such as Parkinson's and Alzheimer's disease.

  5. Insights into prevention of human neural tube defects by folic acid arising from consideration of mouse mutants.

    PubMed

    Harris, Muriel J

    2009-04-01

    Almost 30 years after the initial study by Richard W. Smithells and coworkers, it is still unknown how maternal periconceptional folic acid supplementation prevents human neural tube defects (NTDs). In this article, questions about human NTD prevention are considered in relation to three groups of mouse models: NTD mutants that respond to folate, NTD mutants and strains that do not respond to folate, and mutants involving folate-pathway genes. Of the 200 mouse NTD mutants, only a few have been tested with folate; half respond and half do not. Among responsive mutants, folic acid supplementation reduces exencephaly and/or spina bifida aperta frequency in the Sp(2H), Sp, Cd, Cited2, Cart1, and Gcn5 mutants. Prevention ranges from 35 to 85%. The responsive Sp(2H) (Pax3) mutant has abnormal folate metabolism, but the responsive Cited2 mutant does not. Neither folic nor folinic acid reduces NTD frequency in Axd, Grhl3, Fkbp8, Map3k4, or Nog mutants or in the curly tail or SELH/Bc strains. Spina bifida frequency is reduced in Axd by methionine and in curly tail by inositol. Exencephaly frequency is reduced in SELH/Bc by an alternative commercial ration. Mutations in folate-pathway genes do not cause NTDs, except for 30% exencephaly in folate-treated Folr1. Among folate-pathway mutants, neural tube closure is normal in Cbs, Folr2, Mthfd1, Mthfd2, Mthfr, and Shmt1 mutants. Embryos die by midgestation in Folr1, Mtr, Mtrr, and RFC1 mutants. The mouse models point to genetic heterogeneity in the ability to respond to folic acid and also to heterogeneity in genetic cause of NTDs that can be prevented by folic acid. PMID:19117321

  6. Prevention of neural tube defects with folic acid: The Chinese experience.

    PubMed

    Ren, Ai-Guo

    2015-08-01

    Neural tube defects (NTDs) are a group of congenital malformations of the central nervous system that are caused by the closure failure of the embryonic neural tube by the 28(th) day of conception. Anencephaly and spina bifida are the two major subtypes. Fetuses with anencephaly are often stillborn or electively aborted due to prenatal diagnosis, or they die shortly after birth. Most infants with spina bifida are live-born and, with proper surgical treatment, can survive into adulthood. However, these children often have life-long physical disabilities. China has one of the highest prevalence of NTDs in the world. Inadequate dietary folate intake is believed to be the main cause of the cluster. Unlike many other countries that use staple fortification with folic acid as the public health strategy to prevent NTDs, the Chinese government provides all women who have a rural household registration and who plan to become pregnant with folic acid supplements, free of charge, through a nation-wide program started in 2009. Two to three years after the initiation of the program, the folic acid supplementation rate increased to 85% in the areas of the highest NTD prevalence. The mean plasma folate level of women during early and mid-pregnancy doubled the level before the program was introduced. However, most women began taking folic acid supplements when they knew that they were pregnant. This is too late for the protection of the embryonic neural tube. In a post-program survey of the women who reported folic acid supplementation, less than a quarter of the women began taking supplements prior to pregnancy, indicating that the remaining three quarters of the fetuses remained unprotected during the time of neural tube formation. Therefore, staple food fortification with folic acid should be considered as a priority in the prevention of NTDs. PMID:26261765

  7. Prevention of neural tube defects with folic acid: The Chinese experience

    PubMed Central

    Ren, Ai-Guo

    2015-01-01

    Neural tube defects (NTDs) are a group of congenital malformations of the central nervous system that are caused by the closure failure of the embryonic neural tube by the 28th day of conception. Anencephaly and spina bifida are the two major subtypes. Fetuses with anencephaly are often stillborn or electively aborted due to prenatal diagnosis, or they die shortly after birth. Most infants with spina bifida are live-born and, with proper surgical treatment, can survive into adulthood. However, these children often have life-long physical disabilities. China has one of the highest prevalence of NTDs in the world. Inadequate dietary folate intake is believed to be the main cause of the cluster. Unlike many other countries that use staple fortification with folic acid as the public health strategy to prevent NTDs, the Chinese government provides all women who have a rural household registration and who plan to become pregnant with folic acid supplements, free of charge, through a nation-wide program started in 2009. Two to three years after the initiation of the program, the folic acid supplementation rate increased to 85% in the areas of the highest NTD prevalence. The mean plasma folate level of women during early and mid-pregnancy doubled the level before the program was introduced. However, most women began taking folic acid supplements when they knew that they were pregnant. This is too late for the protection of the embryonic neural tube. In a post-program survey of the women who reported folic acid supplementation, less than a quarter of the women began taking supplements prior to pregnancy, indicating that the remaining three quarters of the fetuses remained unprotected during the time of neural tube formation. Therefore, staple food fortification with folic acid should be considered as a priority in the prevention of NTDs. PMID:26261765

  8. A Knowledge-Based System For Analysis, Intervention Planning and Prevention of Defects in Immovable Cultural Heritage Objects and Monuments

    NASA Astrophysics Data System (ADS)

    Valach, J.; Cacciotti, R.; Kuneš, P.; ČerÅanský, M.; Bláha, J.

    2012-04-01

    The paper presents a project aiming to develop a knowledge-based system for documentation and analysis of defects of cultural heritage objects and monuments. The MONDIS information system concentrates knowledge on damage of immovable structures due to various causes, and preventive/remedial actions performed to protect/repair them, where possible. The currently built system is to provide for understanding of causal relationships between a defect, materials, external load, and environment of built object. Foundation for the knowledge-based system will be the systemized and formalized knowledge on defects and their mitigation acquired in the process of analysis of a representative set of cases documented in the past. On the basis of design comparability, used technologies, materials and the nature of the external forces and surroundings, the developed software system has the capacity to indicate the most likely risks of new defect occurrence or the extension of the existing ones. The system will also allow for a comparison of the actual failure with similar cases documented and will propose a suitable technical intervention plan. The system will provide conservationists, administrators and owners of historical objects with a toolkit for defect documentation for their objects. Also, advanced artificial intelligence methods will offer accumulated knowledge to users and will also enable them to get oriented in relevant techniques of preventive interventions and reconstructions based on similarity with their case.

  9. Controlled samples for silicon defect and impurity studies

    SciTech Connect

    Ciszek, T.F.

    1995-08-01

    Because of the diverse defects and impurities that are present in any given sample of silicon material, it can be extremely difficult to conduct a controlled experiment to study the influence of any particular defect or impurity on photovoltaic properties such as minority charge carrier lifetime {tau} or solar cell efficiency q. For example, the influence of iron may be different if boron is present, or the influence of silicon self interstitial clusters may be different if oxygen is present. It thus becomes important to conduct such studies on controlled samples where the influence of secondary effects is minimized. At NREL, over the past several years, we have focused on using the high-purity float-zone (FZ) growth method to obtain controlled samples. Because the silicon melt is not in contact with a container, and no heated components are in the growth region, very high purities and low defect levels can be achieved in baseline material. The baseline can be controllably perturbed by introduction of specific defects or impurities. The chart shown below lists some of the types of defect and impurity. combinations that can be studied in this way. The boxes marked with an {open_quotes}x{close_quotes} represent combinations we have studied to some extent.

  10. Resolvability of defect ensembles with positron annihilation studies

    SciTech Connect

    Fluss, M.J.; Howell, R.H.; Rosenberg, I.J.; Meyer, P.

    1984-11-12

    Recent advances in the use of positron annihilation to study defect ensembles in and on the surfaces of metals, are pointing the way towards studies where particular positron-electron annihilation modes may be identified and studied in the presence of one another. Although a great deal is understood about the annihilation of positrons in ostensibly defect-free metals, much less is understood when the positron annihilates in complex defect systems such as liquid metals, amorphous solids, or at or near the vacuum-solid interface. In this paper the results of three experiments, all of which demonstrate means by which we can resolve various poistron annihilation channels from one another, are discussed.

  11. Defect studies in low-temperature-grown GaAs

    SciTech Connect

    Bliss, D.E.

    1992-11-01

    High content of excess As is incorporated in GaAs grown by low-temperature molecular-beam-epitaxy (LTMBE). The excess As exists primarily as As antisite defects AsGa and a lesser extent of gallium vacancies V[sub Ga]. The neutral AsGa-related defects were measured by infrared absorption at 1[mu]m. Gallium vacancies, V[sub Ga], was investigated by slow positron annihilation. Dependence of defect contents on doping was studied by Si and Be dopants. No free carriers are generated by n-type or p-type doping up to 10[sup 19] cm[sup [minus]3] Si or Be. Raman data indicate Be occupies Ga substitutional sites but Si atom is not substitutional. Si induces more As[sub Ga] in the layer. As As[sub Ga] increases, photoquenchable As[sub Ga] decreases. Fraction of photoquenchable defects correlates to defects within 3 nearest neighbor separations disrupting the metastability. Annealing reduces neutral As[sub Ga] content around 500C, similar to irradiation damaged and plastically deformed Ga[sub As], as opposed to bulk grown GaAs in which As[sub Ga]-related defects are stable up to 1100C. The lower temperature defect removal is due to V[sub Ga] enhanced diffusion of As[sub Ga] to As precipitates. The supersaturated V[sub GA] and also decreases during annealing. Annealing kinetics for As[sub Ga]-related defects gives 2.0 [plus minus] 0.3 eV and 1.5 [plus minus] 0.3 eV migration enthalpies for the As[sub Ga] and V[sub Ga]. This represents the difference between Ga and As atoms hopping into the vacancy. The non-photoquenchable As[sub Ga]-related defects anneal with an activation energy of 1.1 [plus minus] 0.3eV. Be acceptors can be activated by 800C annealing. Temperature difference between defect annealing and Be activation formation of As[sub Ga]-Be[sub Ga] pairs. Si donors can only be partially activated.

  12. Defect studies in low-temperature-grown GaAs

    SciTech Connect

    Bliss, D.E.

    1992-11-01

    High content of excess As is incorporated in GaAs grown by low-temperature molecular-beam-epitaxy (LTMBE). The excess As exists primarily as As antisite defects AsGa and a lesser extent of gallium vacancies V{sub Ga}. The neutral AsGa-related defects were measured by infrared absorption at 1{mu}m. Gallium vacancies, V{sub Ga}, was investigated by slow positron annihilation. Dependence of defect contents on doping was studied by Si and Be dopants. No free carriers are generated by n-type or p-type doping up to 10{sup 19} cm{sup {minus}3} Si or Be. Raman data indicate Be occupies Ga substitutional sites but Si atom is not substitutional. Si induces more As{sub Ga} in the layer. As As{sub Ga} increases, photoquenchable As{sub Ga} decreases. Fraction of photoquenchable defects correlates to defects within 3 nearest neighbor separations disrupting the metastability. Annealing reduces neutral As{sub Ga} content around 500C, similar to irradiation damaged and plastically deformed Ga{sub As}, as opposed to bulk grown GaAs in which As{sub Ga}-related defects are stable up to 1100C. The lower temperature defect removal is due to V{sub Ga} enhanced diffusion of As{sub Ga} to As precipitates. The supersaturated V{sub GA} and also decreases during annealing. Annealing kinetics for As{sub Ga}-related defects gives 2.0 {plus_minus} 0.3 eV and 1.5 {plus_minus} 0.3 eV migration enthalpies for the As{sub Ga} and V{sub Ga}. This represents the difference between Ga and As atoms hopping into the vacancy. The non-photoquenchable As{sub Ga}-related defects anneal with an activation energy of 1.1 {plus_minus} 0.3eV. Be acceptors can be activated by 800C annealing. Temperature difference between defect annealing and Be activation formation of As{sub Ga}-Be{sub Ga} pairs. Si donors can only be partially activated.

  13. Maternal age and birth defects: a population study.

    PubMed

    Baird, P A; Sadovnick, A D; Yee, I M

    1991-03-01

    Since more and more women in developed countries are delaying childbearing to an older age, it is important to find out whether birth defects, other than those resulting from chromosomal anomalies, are related to maternal age. We have studied all 26,859 children with birth defects of unknown aetiology identified among 576,815 consecutive livebirths in British Columbia. All these cases' records were linked with provincial birth records to allow determination of maternal age at birth. We excluded children with chromosomal anomalies and those with other birth defects of known aetiology. Only 3 of the 43 birth defect categories studied showed significant maternal-age-specific trends: there were decreasing linear trends with maternal age for patent ductus arteriosus (chi 2 = 36.65, 1 df, p less than 0.01) and hypertrophic pyloric stenosis (chi 2 = 4.90, 1 df, p less than 0.05) and a bell-shaped curve (risk increasing to maternal age 30 then falling) for congenital dislocatable hip/hip click. The findings from this population-based analysis of no association between the incidence of birth defects of unknown aetiology and advancing maternal age should be reassuring to healthy women who opt to delay childbearing. PMID:1671898

  14. First principles study of electronic structures of defects in zirconium germanium phosphate and defect chalcopyrites

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaoshu

    2005-11-01

    This thesis mainly focuses on a study of the point defects in ZnGeP 2. Density functional theory (DFT) is used in the local density approximation (LDA) in conjunction with the full-potential linearized muffin-tin orbital (FP-LMTO) method, modeling defects with the supercell approach. Under prevalent Zn-poor conditions, the GeZn double donor and VZn shallow acceptor are found to have the lowest formation energies, which explains the compensated p-type nature of the material. Good agreement is obtained with the energy levels deduced from optical quenching and activation of the EPR signals, if a direct transfer of electrons from V2-Zn to Ge2+Zn is assumed to occur rather than a process via the conduction band. The VGe is found to have high energy of formation under any chemical potential conditions and is found to be unstable towards formation of VZn and GeZn. Structural relaxation of all defects is performed but no symmetry breaking distortions are found. The defect wavefunctions of the unpaired electron in the V-Zn is found to be spread equally over the four neighboring P atoms, in disagreement with electron nuclear double resonance (ENDOR) data which indicate primary localization on a pair of P atoms. Several possible origins for this discrepancy are examined. Alternative assignments of the AL1 EPR signal to ZnGe, or complexes such as Zni-VZn, V-Zn -G2+Zn-V- Zn are discarded although the latter complex is found to be favorable in energy. The possibility of a failure of the LDA due to its incompletely cancelled self-interaction is examined using Hartree-Fock cluster calculations. A distortion is found to occur in Hartree-Fock but not in LDA. However, it is different from the experimental one. Finally, a dangling bond and group theory model is proposed for a Jahn-Teller distortion which can explain the localization observed by ENDOR. In the final chapter, the electronic band structures of the ordered vacancy defect chalcopyrites with formula II-III2-VI4 for II=Zn, Cd

  15. HOSPITAL POLLUTION PREVENTION CASE STUDY

    EPA Science Inventory

    The U.S. Environmental Protection Agency has instituted a broad pollution prevention research program through the Office of Research and Development to support continued environmental improvements throughout the nation. he Agency is also responding to the national concern in rega...

  16. Multiphasic construct studied in an ectopic osteochondral defect model

    PubMed Central

    Jeon, June E.; Vaquette, Cédryck; Theodoropoulos, Christina; Klein, Travis J.; Hutmacher, Dietmar W.

    2014-01-01

    In vivo osteochondral defect models predominantly consist of small animals, such as rabbits. Although they have an advantage of low cost and manageability, their joints are smaller and more easily healed compared with larger animals or humans. We hypothesized that osteochondral cores from large animals can be implanted subcutaneously in rats to create an ectopic osteochondral defect model for routine and high-throughput screening of multiphasic scaffold designs and/or tissue-engineered constructs (TECs). Bovine osteochondral plugs with 4 mm diameter osteochondral defect were fitted with novel multiphasic osteochondral grafts composed of chondrocyte-seeded alginate gels and osteoblast-seeded polycaprolactone scaffolds, prior to being implanted in rats subcutaneously with bone morphogenic protein-7. After 12 weeks of in vivo implantation, histological and micro-computed tomography analyses demonstrated that TECs are susceptible to mineralization. Additionally, there was limited bone formation in the scaffold. These results suggest that the current model requires optimization to facilitate robust bone regeneration and vascular infiltration into the defect site. Taken together, this study provides a proof-of-concept for a high-throughput osteochondral defect model. With further optimization, the presented hybrid in vivo model may address the growing need for a cost-effective way to screen osteochondral repair strategies before moving to large animal preclinical trials. PMID:24694896

  17. Multiphasic construct studied in an ectopic osteochondral defect model.

    PubMed

    Jeon, June E; Vaquette, Cédryck; Theodoropoulos, Christina; Klein, Travis J; Hutmacher, Dietmar W

    2014-06-01

    In vivo osteochondral defect models predominantly consist of small animals, such as rabbits. Although they have an advantage of low cost and manageability, their joints are smaller and more easily healed compared with larger animals or humans. We hypothesized that osteochondral cores from large animals can be implanted subcutaneously in rats to create an ectopic osteochondral defect model for routine and high-throughput screening of multiphasic scaffold designs and/or tissue-engineered constructs (TECs). Bovine osteochondral plugs with 4 mm diameter osteochondral defect were fitted with novel multiphasic osteochondral grafts composed of chondrocyte-seeded alginate gels and osteoblast-seeded polycaprolactone scaffolds, prior to being implanted in rats subcutaneously with bone morphogenic protein-7. After 12 weeks of in vivo implantation, histological and micro-computed tomography analyses demonstrated that TECs are susceptible to mineralization. Additionally, there was limited bone formation in the scaffold. These results suggest that the current model requires optimization to facilitate robust bone regeneration and vascular infiltration into the defect site. Taken together, this study provides a proof-of-concept for a high-throughput osteochondral defect model. With further optimization, the presented hybrid in vivo model may address the growing need for a cost-effective way to screen osteochondral repair strategies before moving to large animal preclinical trials. PMID:24694896

  18. Use of Family History Information for Neural Tube Defect Prevention: Integration into State-Based Recurrence Prevention Programs

    ERIC Educational Resources Information Center

    Green, Ridgely Fisk; Ehrhardt, Joan; Ruttenber, Margaret F.; Olney, Richard S.

    2011-01-01

    A family history of neural tube defects (NTDs) can increase the risk of a pregnancy affected by an NTD. Periconceptional folic acid use decreases this risk. Purpose: Our objective was to determine whether second-degree relatives of NTD-affected children showed differences in folic acid use compared with the general population and to provide them…

  19. Electron Microscopy and Luminescence Study of Defects in Semiconductor Silicon

    NASA Astrophysics Data System (ADS)

    Johnson, Fiona Jane

    1990-03-01

    Available from UMI in association with The British Library. Dislocations and defects in semiconductor silicon have been the subject of much research in the last thirty years. However, to date some of the mechanisms involved in the nucleation and growth of oxidation induced defects remain uncertain, as does the origin of luminescence lines in heat treated and dislocated material. Defects introduced into silicon single crystals by three different mechanisms have been examined using Cathodoluminescence (CL), Photoluminescence (PL) and Transmission Electron Microscopy (TEM). The mechanisms employed were heat treatments, electron irradiation and plastic deformation. The CL system at Bristol had previously been developed for the study of II-VI and III-V semiconductors, the subsequent addition of the near infra-red detector enabled the luminescence from silicon to be studied. The first phase of this thesis explores the capability of the CL system in detecting and spatially resolving luminescence from silicon using the Germanium detector. The second phase involved the study of different defect systems with the aim of studying luminescence emitted from TEM thin samples. Transmission Electron Microscopy was used to examine large scale defects nucleated after single and multiple medium and high temperature anneals. Electron irradiation damage introduced in the 300kV TEM was studied in the CL system. The threshold energy for silicon displacement via 'knock-on' interactions was found to be 155keV. Dislocation related D line luminescence in plastically deformed silicon was examined using both PL and CL spectroscopy. D line emission from thermally annealed silicon, previously thought to be associated with energy states at the Si-SiO _{rm x} interface, was spatially resolved in the CL system. D line emission was detected close to the cleaved edges of samples studied.

  20. Treatment of Bone Defects in War Wounds: Retrospective Study

    PubMed Central

    Grubor, Predrag; Milicevic, Snjezana; Grubor, Milan; Meccariello, Luigi

    2015-01-01

    Introduction: Results of the treatment of open fractures primarily depend on the treatment of connected soft tissue injuries. Objective: The aim was to present the experience and methods gained during the treatment of diaphyseal bone defects as a consequence of gunshot fracture soft war trauma. Patients and Methods: The study consisted of 116 patients with the diaphyseal bone defect who were treated with the usage of primary and delayed autotransplantation of bones, transplants of the fibula and Ilizarov distraction osteogenesis. Results: The results of compensation of bone defect less than 4 cm and conducted by an early cortico-spongioplastics were as follows: good in 8 respondents (45%), satisfactory in 6 (34%) and poor in 4 respondents (21%). In cases of delayed cortico-spongioplastics, the above mentioned results were: good in 36 (41%) respondents, satisfactory in 24 (34%) and poor in 16 (25%) respondents. The results of compensation of bone defect greater than 4 cm with the usage of fibular transplant were as follows: good in 3 (38%) respondents, satisfactory in 3 (38%) and poor in 2 (24%), and with the usage of using the Ilizarov method, the results were as follows: good in 8 (57%) respondents, satisfactory in 3 (21.5%) and poor in 3(21.5%) respondents. Conclusion: The results showed that, in cases of compensation of bone defects less than 4 cm, the advantage is given to the primary spongioplastics over the delayed one. In cases of compensation of bone defects greater than 4 cm, the advantage is given to the Ilizarov distraction osteogenesis when compared to the fibular transplant. PMID:26543315

  1. Ab initio study of tungsten defects near the surface

    NASA Astrophysics Data System (ADS)

    Guerrero, C. L.; Gordillo, N.; Iglesias, R.; Perlado, J. M.; Gonzalez, C.

    2016-05-01

    A first principles analysis of the behaviour of point defects, namely, self-interstitial atoms, a single vacancy and light impurity atoms such as H and He in tungsten is reported. These defects can be produced in the first wall of the future nuclear fusion reactors due to the high radiation fluxes present. The evolution of defects that appear in the bulk and end up reaching the surface has been followed. An energetic study has been combined with a detailed charge density analysis of the system by means of the SIESTA code. The resulting data have been validated by confronting them with those obtained with a more precise plane wave code, namely VASP. Meanwhile, the structural and the mechanical properties of the system have been positively compared with experimental measurements. Such comparisons have led us to present a new SIESTA basis for tungsten. This complete analysis establishes a nanoscopic view of the phenomena involving the presence of light atoms at native defects in tungsten, paying special attention to the vicinity of surfaces.

  2. First-principles study of point defects in thorium carbide

    NASA Astrophysics Data System (ADS)

    Pérez Daroca, D.; Jaroszewicz, S.; Llois, A. M.; Mosca, H. O.

    2014-11-01

    Thorium-based materials are currently being investigated in relation with their potential utilization in Generation-IV reactors as nuclear fuels. One of the most important issues to be studied is their behavior under irradiation. A first approach to this goal is the study of point defects. By means of first-principles calculations within the framework of density functional theory, we study the stability and formation energies of vacancies, interstitials and Frenkel pairs in thorium carbide. We find that C isolated vacancies are the most likely defects, while C interstitials are energetically favored as compared to Th ones. These kind of results for ThC, to the best authors' knowledge, have not been obtained previously, neither experimentally, nor theoretically. For this reason, we compare with results on other compounds with the same NaCl-type structure.

  3. Updated estimates of neural tube defects prevented by mandatory folic Acid fortification - United States, 1995-2011.

    PubMed

    Williams, Jennifer; Mai, Cara T; Mulinare, Joe; Isenburg, Jennifer; Flood, Timothy J; Ethen, Mary; Frohnert, Barbara; Kirby, Russell S

    2015-01-16

    In 1992, the U.S. Public Health Service recommended that all women capable of becoming pregnant consume 400 µg of folic acid daily to prevent neural tube defects (NTDs). NTDs are major birth defects of the brain and spine that occur early in pregnancy as a result of improper closure of the embryonic neural tube, which can lead to death or varying degrees of disability. The two most common NTDs are anencephaly and spina bifida. Beginning in 1998, the United States mandated fortification of enriched cereal grain products with 140 µg of folic acid per 100 g. Immediately after mandatory fortification, the birth prevalence of NTD cases declined. Fortification was estimated to avert approximately 1,000 NTD-affected pregnancies annually. To provide updated estimates of the birth prevalence of NTDs in the period after introduction of mandatory folic acid fortification (i.e., the post-fortification period), data from 19 population-based birth defects surveillance programs in the United States, covering the years 1999-2011, were examined. After the initial decrease, NTD birth prevalence during the post-fortification period has remained relatively stable. The number of births occurring annually without NTDs that would otherwise have been affected is approximately 1,326 (95% confidence interval = 1,122-1,531). Mandatory folic acid fortification remains an effective public health intervention. There remain opportunities for prevention among women with lower folic acid intakes, especially among Hispanic women, to further reduce the prevalence of NTDs in the United States. PMID:25590678

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

    PubMed

    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. PMID:25905896

  5. 10 Projects for Preventing Fetal Alcohol Syndrome and Other Alcohol-Related Birth Defects and Have You Heard about Alcohol and Pregnancy.

    ERIC Educational Resources Information Center

    Adams, Jerry; And Others

    A set of two pamphlets is presented on the topic of Fetal Alcohol Syndrome and Alcohol-Related Birth Defects. "Ten Projects for Preventing Fetal Alcohol Syndrome and Other Alcohol-Related Birth Defects" provides ideas and materials for students and others to use in educating the public about the dangers of alcohol use during pregnancy. It offers…

  6. Evaluation and Visualization of Surface Defects — a Numerical and Experimental Study on Sheet-Metal Parts

    NASA Astrophysics Data System (ADS)

    Andersson, A.

    2005-08-01

    The ability to predict surface defects in outer panels is of vital importance in the automotive industry, especially for brands in the premium car segment. Today, measures to prevent these defects can not be taken until a test part has been manufactured, which requires a great deal of time and expense. The decision as to whether a certain surface is of acceptable quality or not is based on subjective evaluation. It is quite possible to detect a defect by measurement, but it is not possible to correlate measured defects and the subjective evaluation. If all results could be based on the same criteria, it would be possible to compare a surface by both FE simulations, experiments and subjective evaluation with the same result. In order to find a solution concerning the prediction of surface defects, a laboratory tool was manufactured and analysed both experimentally and numerically. The tool represents the area around a fuel filler lid and the aim was to recreate surface defects, so-called "teddy bear ears". A major problem with the evaluation of such defects is that the panels are evaluated manually and to a great extent subjectivity is involved in the classification and judgement of the defects. In this study the same computer software was used for the evaluation of both the experimental and the numerical results. In this software the surface defects were indicated by a change in the curvature of the panel. The results showed good agreement between numerical and experimental results. Furthermore, the evaluation software gave a good indication of the appearance of the surface defects compared to an analysis done in existing tools for surface quality measurements. Since the agreement between numerical and experimental results was good, this indicates that these tools can be used for an early verification of surface defects in outer panels.

  7. Fermi-level pinning through defects at GaAs/oxide interfaces: A density functional study

    NASA Astrophysics Data System (ADS)

    Colleoni, Davide; Miceli, Giacomo; Pasquarello, Alfredo

    2015-09-01

    Using density functional calculations, we study a set of candidate defects for Fermi-level pinning at GaAs/oxide interfaces. The set of considered defects comprises both bulklike and interfacial defects, including As antisites, Ga and As dangling bonds, the As-As dimer/dangling bond defect, and several defect complexes. The defects are generated within atomistic model structures representing the GaAs /Al2O3 interface. Formation energies of bulklike defects are obtained and compared with those of corresponding bulk defects, while interfacial defects are studied through their relative defect energies. Finite-size corrections to the defect energies are applied through a scheme that accounts for the interfacial geometry of our models. Defect levels are defined as thermodynamic transition levels between different charge states and are calculated for all considered defects. Through an alignment procedure based on hybrid functional calculations, the defect levels are then positioned within the calculated band gap of GaAs that reproduces the experimental one, thereby enabling direct comparisons with the experimental density of defect states. Our study shows that several As-related defects show a similar amphoteric bistability between an As-As dimer state and a configuration with two doubly occupied As dangling bonds. The associated charge transition levels generally lie in the midgap region, in accord with experimental observations. This mechanism is proposed as the origin of the observed Fermi-level pinning at GaAs/oxide interfaces.

  8. Computational study of hydroxyapatite structures, properties and defects

    NASA Astrophysics Data System (ADS)

    Bystrov, V. S.; Coutinho, J.; Bystrova, A. V.; Dekhtyar, Yu D.; Pullar, R. C.; Poronin, A.; Palcevskis, E.; Dindune, A.; Alkan, B.; Durucan, C.; Paramonova, E. V.

    2015-03-01

    Hydroxyapatite (HAp) was studied from a first principle approach using the local density approximation (LDA) method in AIMPRO code, in combination with various quantum mechanical (QM) and molecular mechanical (MM) methods from HypemChem 7.5/8.0. The data obtained were used for studies of HAp structures, the physical properties of HAp (density of electronic states—DOS, bulk modulus etc) and defects in HAp. Computed data confirmed that HAp can co-exist in different phases—hexagonal and monoclinic. Ordered monoclinic structures, which could reveal piezoelectric properties, are of special interest. The data obtained allow us to characterize the properties of the following defects in HAp: O, H and OH vacancies; H and OH interstitials; substitutions of Ca by Mg, Sr, Mn or Se, and P by Si. These properties reveal the appearance of additional energy levels inside the forbidden zone, shifts of the top of the valence band or the bottom of the conduction band, and subsequent changes in the width of the forbidden zone. The data computed are compared with other known data, both calculated and experimental, such as alteration of the electron work functions under different influences of various defects and treatments, obtained by photoelectron emission. The obtained data are very useful, and there is an urgent need for such analysis of modified HAp interactions with living cells and tissues, improvement of implant techniques and development of new nanomedical applications.

  9. MP2 Study of Physisorption of Molecular Hydrogen onto Defective Nanotubes: Cooperative Effect in Stone-Wales Defects.

    PubMed

    Lugo, G; Cuesta, I G; Sánchez Marín, J; Sánchez de Merás, A

    2016-07-14

    We use large-scale MP2 calculations to investigate the physisorption of molecular hydrogen on (9,0) defective carbon nanotubes (CNTs) of C72H18. These large (supra)molecular systems are typically studied using conventional DFT methods, which do not describe well the van der Waals interactions responsible for this process. Here we use CCSD(T)-calibrated MP2 calculations to estimate binding energies by considering four defective structures (hydrogenated divacancy, octagon-pentagon, and two Stone-Wales defects). The largest physisorption energies for the nondefective CNT are for configurations in which H2 points toward the center of one ring. The computed interaction energies for defect-free CNT are in the range 5.7 to 5.9 kJ/mol, in good agreement with the experimental value of 5.98 kJ/mol. The defects introduced in the (9,0)-CNT increase the surface area of the nanotube, such that the largest surface in found in the 55-77 Stone-Wales defective CNT that furthermore is the most aromatic. Only that defect enlarges the physisorption binding energy, which can become >25% larger. Moreover, a cooperative effect in the adsorption of H2 not appearing in the regular structure is found. PMID:27045203

  10. Ab initio studies of niobium defects in uranium

    SciTech Connect

    Xiang, S; Huang, H; Hsiung, L

    2007-06-01

    Uranium (U), with the addition of small amount of niobium (Nb), is stainless. The Nb is fully miscible with the high temperature phase of U and tends to segregate upon cooling below 647 C. The starting point of segregation is the configuration of Nb substitutional or interstitial defects. Using density-functional-theory based ab initio calculations, the authors find that the formation energy of a single vacancy is 1.08 eV, that of Nb substitution is 0.59 eV, that of Nb interstitial at octahedral site is 1.58 eV, and that of Nb interstitial at tetrahedral site is 2.35 eV; all with reference to a reservoir of {gamma} phase U and pure Nb. The formation energy of Nb defects correlates with the local perturbation of electron distribution; higher formation energy to larger perturbation. Based on this study, Nb atoms thermodynamically prefer to occupy substitutional sites in {gamma} phase U, and they prefer to be in individual substitutional defects than clusters.

  11. Pain, Epilepsy Drug Lyrica May Increase Birth Defects Risk, Study Suggests

    MedlinePlus

    ... 158906.html Pain, Epilepsy Drug Lyrica May Increase Birth Defects Risk, Study Suggests Expectant mothers should probably ... pregabalin (Lyrica) may slightly increase the risk for birth defects, a new study suggests. In a small ...

  12. Theoretical studies of defects in binary and ternary oxides

    SciTech Connect

    Ching, W.Y.; Ellis, D.E.; Lam, D.J.

    1986-01-01

    This paper presents some preliminary results of electronic structure of substitutional defects and vacancy in binary and ternary cubic zirconium oxides obtained by the embedded molecular-cluster model calculation. The importance of electronic charge redistribution in the solids where the defect is introduced into the perfect lattice is highlighted and the effect of electron polarization of the surrounding ions of the defect discussed.

  13. Not all cases of neural-tube defect can be prevented by increasing the intake of folic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to evaluate the beneficial effects of different levels of folic acid administration on the prevalence of neural tube defects, with a concurrent assessment of other potential benefits or adverse effects. The evaluation was based on a systematic review of the published ...

  14. Functional studies on three novel HCNH2 mutations in Taiwan: Identification of distinct mechanisms of channel defect and dissociation between glycosylation defect and assembly defect

    SciTech Connect

    Hsueh, C.-H.; Chen, W.-P.; Lin, J.-L.; Liu, Y.-B.; Su, M.-J.; Lai, L.-P.

    2008-09-05

    Mutations of the KCNH2 with decreased channel activity lead to congenital long QT syndrome (LQTS). We studied the electrophysiological, glycosylation, trafficking and assembly properties of three novel KCNH2 mutations identified in Taiwanese patients with LQTS (p.N633D, p.R744fs, and p.P923fs). When expressed in HEK293T cells, p.N633D and p.R744fs HERG channels displayed no HERG current while p.P923fs HERG channel showed HERG current with significantly lower (34%) current density and faster inactivation kinetics. In Western blot analysis, pR744fs was the only one with glycosylation defect, which was in consistence with the confocal microscopic findings showing that p.R744fs-GFP was the only one with trafficking defect. However, p.R744fs-GFP differed from pR744fs in being fully glycosylated while p.R744fs fusion with GFP at the N-terminus revealed glycosylation defect. To access the assembly capacity of each mutant, co-immunoprecipitation was conducted. Wild type (WT), p.N633D, and p.P923fs HERG protein showed assembly ability while p.R744fs failed to assemble with neither WT nor itself. In conclusion, we identified three novel LQTS-related KCNH2 mutations and each had a distinct mechanism of channel defect. For p.R744fs mutant, adding GFP to the C-terminus rescued the glycosylation defect but the channel was still assembly defective indicating a dissociation between glycosylation and assembly defects.

  15. Consanguinity and Birth Defects in the Jerusalem Perinatal Study Cohort

    PubMed Central

    Harlap, S.; Kleinhaus, K.; Perrin, M.C.; Calderon-Margalit, R.; Paltiel, O.; Deutsch, L.; Manor, O.; Tiram, E.; Yanetz, R.; Friedlander, Y.

    2008-01-01

    Background While parental consanguinity is known to increase the risk of birth defects in offspring, it is hard to quantify this risk in populations where consanguinity is prevalent. Methods To support ongoing studies of cancer and of psychiatric disease, we studied relationships of consanguinity to 1,053 major birth defects in 29,815 offspring, born in 1964–1976. To adjust for confounding variables (geographic origin, social class and hospital), we constructed logistic regression models, using GEE to take into account correlations between sibs. Odds ratios (ORs) and 95% confidence limits were estimated in comparison to a reference group of offspring with grandfathers born in different countries. Results With 10.1% of offspring having consanguineous parents, the adjusted OR for major birth defect was 1.41 (1.12–1.74). Offspring of marriages between uncles-nieces, first cousins and more distant relatives showed adjusted ORs of 2.36 (0.98–5.68), 1.59 (1.22–2.07) and 1.20 (0.89–1.59) respectively. For descendents of grandfathers born in the same country, but not known to be related, the OR was 1.05 (0.91–1.21); these showed increased risk associated with ancestries in Western Asia (1.27, 1.04–1.55, p < 0.02) or Europe (1.13, 0.79–1.80). Conclusions A strong association of consanguinity with poverty and low education points to the need to avoid exposure to environmental hazards in these families. PMID:18493143

  16. Repair of spinal dural defects. An experimental study.

    PubMed

    Keller, J T; Ongkiko, C M; Saunders, M C; Mayfield, F H; Dunsker, S B

    1984-05-01

    The search for an ideal substance for duraplasty has stimulated clinical and experimental investigations. To date a large number of materials have been employed for dural repair, although there is as yet no unanimity regarding the ideal material. Most of these studies have been concerned with cranial dura, and spinal duraplasty has received less attention. This study was designed to examine the repair of spinal dural defects in the dog. The materials chosen for this experiment were autologous fat, a polyester fiber mesh (Mersilene) and silicone-coated Dacron (Dura Film). Nineteen dogs were used in this study. Following lumbar laminectomy and the excision of elliptical pieces of dura (1.0 X 0.5 cm) at three noncontiguous levels, each of the defects was repaired using one of the three materials. Groups of animals were sacrificed at each of 3, 6, 12, and 24 weeks after dural repair. The lumbar region was removed en bloc and prepared for histological examination. Repair of the dural opening was achieved in all cases. The polyester fiber mesh was quite effective for dural repair, serving as a scaffold through which a neomembrane grew and united the dural edges. The results with autologous fat were similarly favorable. On the other hand, results with silicone-coated Dacron showed encapsulation by connective tissue, with the ventral aspect of the graft frequently compressing the underlying cord. PMID:6232352

  17. Sirt3 prevents maternal obesity-associated oxidative stress and meiotic defects in mouse oocytes

    PubMed Central

    Zhang, Liang; Han, Longsen; Ma, Rujun; Hou, Xiaojing; Yu, Yang; Sun, Shaochen; Xu, Yinxue; Schedl, Tim; Moley, Kelle H; Wang, Qiang

    2015-01-01

    Maternal obese environment has been reported to induce oxidative stress and meiotic defects in oocytes, however the underlying molecular mechanism remains unclear. Here, using mice fed a high fat diet (HFD) as an obesity model, we first detected enhanced reactive oxygen species (ROS) content and reduced Sirt3 expression in HFD oocytes. We further observed that specific depletion of Sirt3 in control oocytes elevates ROS levels while Sirt3 overexpression attenuates ROS production in HFD oocytes, with significant suppression of spindle disorganization and chromosome misalignment phenotypes that have been reported in the obesity model. Candidate screening revealed that the acetylation status of lysine 68 on superoxide dismutase (SOD2K68) is dependent on Sirt3 deacetylase activity in oocytes, and acetylation-mimetic mutant SOD2K68Q results in almost threefold increase in intracellular ROS. Moreover, we found that acetylation levels of SOD2K68 are increased by ∼80% in HFD oocytes and importantly, that the non-acetylatable-mimetic mutant SOD2K68R is capable of partially rescuing their deficient phenotypes. Together, our data identify Sirt3 as an important player in modulating ROS homeostasis during oocyte development, and indicate that Sirt3-dependent deacetylation of SOD2 plays a protective role against oxidative stress and meiotic defects in oocytes under maternal obese conditions. PMID:25790176

  18. Heterogeneity of Nasolabial Flap- Role in Prevention of Morbidity Associated with Reconstruction of Orofacial Defects.

    PubMed

    Abida, Roshni; Ayyallil, Muhamed Sajid

    2015-09-01

    Reconstructive technique after surgical excision of malignancy in orofacial region should be planned in preoperative period itself. Surgery is the preferred modality of treatment if the tumour is small and located in an accessible area. Nasolabial flap is a versatile flap which is well suited to cover small defects in maxillofacial region. Nasolabial flap can be used as an alternative to other distant pedicled flaps in selected cases. A retrospective analysis of 12 cases of oral cancer treated with primary excision and reconstruction using nasolabial flap was done. Patients who underwent resection of tumour and reconstruction with nasolabial flap in selected cases reduced the morbidity associated with Distant pedicled flaps. Two selected cases are described in detail. PMID:26501027

  19. The study of develop optimization to control various resist defect in Photomask fabrication

    NASA Astrophysics Data System (ADS)

    Lim, JongHoon; Kim, ByungJu; Son, JaeSik; Park, EuiSang; Kim, SangPyo; Yim, DongGyu

    2015-07-01

    To reduce the pattern size in photomask is an inevitable trend because of the minimization of chip size. So it makes a big challenge to control defects in photomask industry. Defects below a certain size that had not been any problem in previous technology node are becoming an issue as the patterns are smaller. Therefore, the acceptable tolerance levels for current defect size and quantity are dramatically reduced. Because these defects on photomask can be the sources of the repeating defects on wafer, small size defects smaller than 200nm should not be ignored any more. Generally, almost defects are generated during develop process and etch process. Especially it is difficult to find the root cause of defects formed during the develop process because of their various types and very small size. In this paper, we studied how these small defects can be eliminated by analyzing the defects and tuning the develop process. There are 3 types of resist defects which are named as follows. The first type is `Popcorn' defect which is mainly occurred in negative resist and exists on the dark features. The second type is `Frog eggs' defect which is occurred in 2nd process of HTPSM and exists on the wide space area. The last type is `Spot' defect which also exists on the wide space area. These defects are generally appeared on the entire area of a plate and the number of these defects is about several hundred. It is thought that the original source is the surface's hydrophilic state before develop process or the incongruity between resist and developer. This study shows that the optimizing the develop process can be a good solution for some resist defects.

  20. Computer programs for eddy-current defect studies

    SciTech Connect

    Pate, J. R.; Dodd, C. V.

    1990-06-01

    Several computer programs to aid in the design of eddy-current tests and probes have been written. The programs, written in Fortran, deal in various ways with the response to defects exhibited by four types of probes: the pancake probe, the reflection probe, the circumferential boreside probe, and the circumferential encircling probe. Programs are included which calculate the impedance or voltage change in a coil due to a defect, which calculate and plot the defect sensitivity factor of a coil, and which invert calculated or experimental readings to obtain the size of a defect. The theory upon which the programs are based is the Burrows point defect theory, and thus the calculations of the programs will be more accurate for small defects. 6 refs., 21 figs.

  1. Oxygen defects in GaAs: A hybrid functional study

    NASA Astrophysics Data System (ADS)

    Colleoni, Davide; Pasquarello, Alfredo

    2016-03-01

    Using hybrid density functional calculations, we address the structural properties, formation energies, and charge transition levels of a variety of oxygen defects in GaAs. The set of considered defects comprises the bridging O atom in a As-O-Ga configuration, interstitial O atoms in tetrahedral sites, and O atoms substitutional to either Ga (OGa) or As atoms (OAs). In addition, we consider an As vacancy containing two O atoms, for which the most stable configurations are found through the use of molecular dynamics simulations, and defect complexes involving a OAs defect bound to either one or two AsGa antisites, denoted AsGa-OAs and (AsGa)2-OAs , respectively. We find that the bridging O defect and the AsGa-OAs and (AsGa)2-OAs complexes are the most stable oxygen defects in GaAs. The actual occurrence of these defects is examined against two criteria. The first criterion concerns the stability against O dissociation and is evaluated via the calculation of dissociation energies. The second criterion involves the defect formation at thermodynamic equilibrium and is inferred from the comparison between the formation energy of the oxygen defect and that of its O-related dissociation product (bridging O defect). Both the AsGa-OAs and (AsGa)2-OAs complexes satisfy these criteria and are stable against O dissociation. Further analysis in cooled-down conditions leads us to dismiss the AsGa-OAs defect due to the more favorable bonding of two rather than one AsGa antisites. The conclusion that only the bridging O defect and the (AsGa)2-OAs complex are expected to occur is in accord with experimental observations.

  2. Analytic study to evaluate associations between hazardous waste sites and birth defects. Final report

    SciTech Connect

    Marshall, E.G.; Gensburg, L.J.; Geary, N.S.; Deres, D.A.; Cayo, M.R.

    1995-06-01

    A study was conducted to evaluate the risk of two types of birth defects (central nervous system and musculoskeletal defects) associated with mothers` exposure to solvents, metals, and pesticides through residence near hazardous waste sites. The only environmental factor showing a statistically significant elevation in risk was living within one mile of industrial or commercial facilities emitting solvents into the air. Residence near these facilities showed elevated risk for central nervous system defects but no elevated risks for musculoskeletal defects.

  3. Birth Defects

    MedlinePlus

    ... with birth defects may need surgery or other medical treatments. Today, doctors can diagnose many birth defects in the womb. This enables them to treat or even correct some problems before the baby is born. Centers for Disease Control and Prevention

  4. Maternally provided LSD1/KDM1A enables the maternal-to-zygotic transition and prevents defects that manifest postnatally

    PubMed Central

    Wasson, Jadiel A; Simon, Ashley K; Myrick, Dexter A; Wolf, Gernot; Driscoll, Shawn; Pfaff, Samuel L; Macfarlan, Todd S; Katz, David J

    2016-01-01

    Somatic cell nuclear transfer has established that the oocyte contains maternal factors with epigenetic reprogramming capacity. Yet the identity and function of these maternal factors during the gamete to embryo transition remains poorly understood. In C. elegans, LSD1/KDM1A enables this transition by removing H3K4me2 and preventing the transgenerational inheritance of transcription patterns. Here we show that loss of maternal LSD1/KDM1A in mice results in embryonic arrest at the 1-2 cell stage, with arrested embryos failing to undergo the maternal-to-zygotic transition. This suggests that LSD1/KDM1A maternal reprogramming is conserved. Moreover, partial loss of maternal LSD1/KDM1A results in striking phenotypes weeks after fertilization; including perinatal lethality and abnormal behavior in surviving adults. These maternal effect hypomorphic phenotypes are associated with alterations in DNA methylation and expression at imprinted genes. These results establish a novel mammalian paradigm where defects in early epigenetic reprogramming can lead to defects that manifest later in development. DOI: http://dx.doi.org/10.7554/eLife.08848.001 PMID:26814574

  5. Maternally provided LSD1/KDM1A enables the maternal-to-zygotic transition and prevents defects that manifest postnatally.

    PubMed

    Wasson, Jadiel A; Simon, Ashley K; Myrick, Dexter A; Wolf, Gernot; Driscoll, Shawn; Pfaff, Samuel L; Macfarlan, Todd S; Katz, David J

    2016-01-01

    Somatic cell nuclear transfer has established that the oocyte contains maternal factors with epigenetic reprogramming capacity. Yet the identity and function of these maternal factors during the gamete to embryo transition remains poorly understood. In C. elegans, LSD1/KDM1A enables this transition by removing H3K4me2 and preventing the transgenerational inheritance of transcription patterns. Here we show that loss of maternal LSD1/KDM1A in mice results in embryonic arrest at the 1-2 cell stage, with arrested embryos failing to undergo the maternal-to-zygotic transition. This suggests that LSD1/KDM1A maternal reprogramming is conserved. Moreover, partial loss of maternal LSD1/KDM1A results in striking phenotypes weeks after fertilization; including perinatal lethality and abnormal behavior in surviving adults. These maternal effect hypomorphic phenotypes are associated with alterations in DNA methylation and expression at imprinted genes. These results establish a novel mammalian paradigm where defects in early epigenetic reprogramming can lead to defects that manifest later in development. PMID:26814574

  6. A biodegradable antibiotic-impregnated scaffold to prevent osteomyelitis in a contaminated in vivo bone defect model.

    PubMed

    McLaren, J S; White, L J; Cox, H C; Ashraf, W; Rahman, C V; Blunn, G W; Goodship, A E; Quirk, R A; Shakesheff, K M; Bayston, R; Scammell, B E

    2014-01-01

    Open fractures are at risk of serious infection and, if infected, require several surgical interventions and courses of systemic antibiotics. We investigated a new injectable formulation that simultaneously hardens in vivo to form a porous scaffold for bone repair and delivers antibiotics at high concentrations to the local site of infection. Duration of antimicrobial activity against Staphylococcus aureus was determined using the serial plate transfer test. Ultimate compressive strength and porosity of the material was measured with and without antibiotics. The material was evaluated in vivo in an ovine medial femoral condyle defect model contaminated with S. aureus. Sheep were sacrificed at either 2 or 13 weeks and the defect and surrounding bone assessed using micro-computed tomography and histology. Antimicrobial activity in vitro persisted for 19-21 days. Sheep with antibiotic-free material and bacteria became infected, while those with antibiotic-containing material and bacteria did not. Similarly, new bone growth was seen in uninoculated animals with plain polymer, and in those with antibiotic polymer with bacteria, but not in sheep with plain polymer and bacteria. The antibiotic-impregnated scaffolds were effective in preventing S. aureus infections whilst supporting bone growth and repair. If translated into clinical practice, this approach might reduce the need for systemic antibiotics. PMID:24908426

  7. Defect studies in ion irradiated AlGaN

    SciTech Connect

    Jagielski, Jacek; Thome, Lionel; Zhang, Yanwen; Wang, Chong M.; Turos, Andrzej; Nowicki, L.; Pagowska, K.; Jozwik, I.

    2010-06-01

    Defects created in Al0.4Ga0.6N crystals by 320 keV Ar ion irradiation were studied by using RBS/C and TEM techniques. One of the main aims of the work was to use a new version of McChasy, a Monte – Carlo simulation code of backscattering spectra, for the analysis of experimental results obtained for a dislocations-containing crystal. Transmission Electron Microscopy technique was used to get a better insight into dislocation and dislocation loop geometries in order to restrict the range of parameters used in simulations. RBS/C analysis was performed in a 1.5 MeV – 3 MeV energy range in order to check if MC simulations correctly reproduce backscattering spectra at different energies.

  8. Theoretical study of intrinsic defects in CdTe

    NASA Astrophysics Data System (ADS)

    Menéndez-Proupin, E.; Orellana, W.

    2016-05-01

    The quantum states and thermodynamical properties of the Cd and Te vacancies in CdTe are studied by first principles calculations. It is shown that the band structure of a cubic 64-atoms supercell with a Te vacancy is dramatically different from the band structure of the perfect crystal, suggesting that it cannot be used as model to calculate isolated defects. This flaw is solved modeling the Te vacancy within a cubic 216-atoms supercell. However, even with this large supercell, the 2— charge state relaxes to an incorrect distorted structure. This distortion is driven by partial filling of the conduction band induced by the k-point sampling. The correct structures and formation energies are obtained by relaxation with restriction of system symmetry, followed by band-filling correction to the energy, or by using a larger supercell that allows sampling the Brillouin zone with a single k-point.

  9. Preventing farnesylation of the dynein adaptor Spindly contributes to the mitotic defects caused by farnesyltransferase inhibitors

    PubMed Central

    Holland, Andrew J.; Reis, Rita M.; Niessen, Sherry; Pereira, Cláudia; Andres, Douglas A.; Spielmann, H. Peter; Cleveland, Don W.; Desai, Arshad; Gassmann, Reto

    2015-01-01

    The clinical interest in farnesyltransferase inhibitors (FTIs) makes it important to understand how these compounds affect cellular processes involving farnesylated proteins. Mitotic abnormalities observed after treatment with FTIs have so far been attributed to defects in the farnesylation of the outer kinetochore proteins CENP-E and CENP-F, which are involved in chromosome congression and spindle assembly checkpoint signaling. Here we identify the cytoplasmic dynein adaptor Spindly as an additional component of the outer kinetochore that is modified by farnesyltransferase (FTase). We show that farnesylation of Spindly is essential for its localization, and thus for the proper localization of dynein and its cofactor dynactin, to prometaphase kinetochores and that Spindly kinetochore recruitment is more severely affected by FTase inhibition than kinetochore recruitment of CENP-E and CENP-F. Molecular replacement experiments show that both Spindly and CENP-E farnesylation are required for efficient chromosome congression. The identification of Spindly as a new mitotic substrate of FTase provides insight into the causes of the mitotic phenotypes observed with FTase inhibitors. PMID:25808490

  10. Printability study of pattern defects in the EUV mask as a function of hp nodes

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Geun; Seo, Hwan-Seok; Kang, In-Yong; Jeong, Chang Young; Huh, Sungmin; Na, Jihoon; Kim, Seong-Sue; Jeon, Chan-Uk; Mochi, Iacopo; Goldberg, Kenneth A.

    2012-03-01

    Amplitude defects (or absorber defects), which are located in absorber patterns or multilayer surface, can be repaired during mask process while phase defects (or multilayer defects) cannot. Hence, inspection and handling of both defects should be separately progressed. Defect printability study of pattern defects is very essential since it provides criteria for mask inspection and repair. Printed defects on the wafer kill cells and reduce the device yield in wafer processing, and thus all the printable defects have to be inspected and repaired during the mask fabrication. In this study, pattern defect printability of the EUV mask as a function of hp nodes is verified by EUV exposure experiments. For 3x nm hp nodes, defect printability is evaluated by NXE3100. For 2x nm hp node, since resolution of a current EUV scanner is not enough, SEMATECH-Berkeley actinic inspection tool (AIT) as well as micro-field exposure tool (MET) in LBNL are utilized to verify it,. Furthermore those printability results are compared with EUV simulations. As a result, we define size of defects to be controlled in each device node.

  11. EPIDEMIOLOGY STUDY OF BIRTH DEFECTS AND DISINFECTION BYPRODUCTS

    EPA Science Inventory

    Birth defects are the leading cause of infant mortality in the US, accounting for more than 20% of all infant deaths. In addition, birth defects are the fifth leading cause of years of potential lief life lost and contribute substantially to childhood morbidity and long-term disa...

  12. EPIDEMIOLOGY STUDY OF BIRTH DEFECTS AND DISINFECTION BYPRODUCTS (DBPS)

    EPA Science Inventory

    Birth defects are the leading cause of infant mortality in the US, accounting for more than 20% of all infant deaths. In addition, birth defects are the fifth leading cause of years of potential life lost and contribute substantially to childhood morbidity and long-term disabilit...

  13. Hybrid functional studies of defects and hole polarons in oxides

    NASA Astrophysics Data System (ADS)

    Varley, Joel

    Transparent conducting oxides (TCOs) are ubiquitous, appearing in windows, flat-panel displays, solar cells, solid-state lighting, and transistors that all exploit TCOs' combination of high electrical conductivity and optical transparency. Thanks to this large and growing list of applications, there has been a surge of interest in the science of these materials, focusing on the fundamental properties and doping opportunities in traditional TCOs as well as the exploration of promising new candidate materials. Hybrid density functional theory has proven instrumental in elucidating the physics of TCOs. One example is the study of dopants and defects that determine the conductivity. Accurate formation energies and charge-state transition levels can now be obtained thanks to the accurate electronic structure provided by a hybrid functional. This allows us to address the origins of unintentional conductivity: for SnO2, In2O3, and Ga2O3, we demonstrate that this is not due to native defects such as oxygen vacancies, but must be attributed to unintentional incorporation of impurities. We can also provide guidelines for achieving higher doping levels, suggesting several impurities as candidate donors with high solubility. Limitations on doping due to the formation or incorporation of compensating centers are addressed as well. Hybrid functional calculations also overcome the shortcomings associated with traditional local or semi-local functionals, which do not properly describe charge localization. Hybrid functionals accurately describe polaron formation, i.e., the self-trapping of holes when p - type doping of the oxide materials is attempted. Consequences of polaron formation for optical characterization of the material will be discussed. This work was performed in collaboration with Anderson Janotti and Chris G. Van de Walle, and was in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. Supplemental vitamin A prevents the acute radiation-induced defect in wound healing

    SciTech Connect

    Levenson, S.M.; Gruber, C.A.; Rettura, G.; Gruber, D.K.; Demetriou, A.A.; Seifter, E.

    1984-10-01

    Acute radiation injury leads to thymic involution, adrenal enlargement, leukopenia, thrombocytopenia, gastrointestinal ulceration, and impaired wound healing. The authors hypothesized that supplemental vitamin A would mitigate these adverse effects in rats exposed to acute whole-body radiation. To test their hypothesis, dorsal skin incisions and subcutaneous implantation of polyvinyl alcohol sponges were performed in anesthetized Sprague-Dawley rats at varying times following sham radiation or varying doses of whole-body radiation (175-850 rad). In each experiment, the control diet (which contains about 18,000 IU vit. A/kg chow (3 X the NRC RDA for normal rats)) was supplemented with 150,000 IU vit. A/kg diet beginning at, before, or after sham radiation and wounding or radiation and wounding. The supplemental vitamin A prevented the impaired wound healing and lessened the weight loss, leukopenia, thrombocytopenia, thymic involution, adrenal enlargement, decrease in splenic weight, and gastric ulceration of the radiated (750-850 rad) wounded rats. This was true whether the supplemental vitamin A was begun before (2 or 4 days) or after (1-2 hours to 4 days) radiation and wounding; the supplemental vitamin A was more effective when started before or up to 2 days after radiation and wounding. The authors believe that prevention of the impaired wound healing following radiation by supplemental vitamin A is due to its enhancing the early inflammatory reaction to wounding, including increasing the number of monocytes and macrophages at the wound site; possible effect on modulating collagenase activity; effect on epithelial cell (and possible mesenchymal cell) differentiation; stimulation of immune responsiveness; and lessening of the adverse effects of radiation.

  15. Immersion defectivity study with volume production immersion lithography tool for 45 nm node and below

    NASA Astrophysics Data System (ADS)

    Nakano, Katsushi; Nagaoka, Shiro; Yoshida, Masato; Iriuchijima, Yasuhiro; Fujiwara, Tomoharu; Shiraishi, Kenichi; Owa, Soichi

    2008-03-01

    Volume production of 45nm node devices utilizing Nikon's S610C immersion lithography tool has started. Important to the success in achieving high-yields in volume production with immersion lithography has been defectivity reduction. In this study we evaluate several methods of defectivity reduction. The tools used in our defectivity analysis included a dedicated immersion cluster tools consisting of a Nikon S610C, a volume production immersion exposure tool with NA of 1.3, and a resist coater-developer LITHIUS i+ from TEL. In our initial procedure we evaluated defectivity behavior by comparing on a topcoat-less resist process to a conventional topcoat process. Because of its simplicity the topcoatless resist shows lower defect levels than the topcoat process. In a second study we evaluated the defect reduction by introducing the TEL bevel rinse and pre-immersion bevel cleaning techniques. This technique was shown to successfully reduce the defect levels by reducing the particles at the wafer bevel region. For the third defect reduction method, two types of tool cleaning processes are shown. Finally, we discuss the overall defectivity behavior at the 45nm node. To facilitate an understanding of the root cause of the defects, defect source analysis (DSA) was applied to separate the defects into three classes according to the source of defects. DSA analysis revealed that more than 99% of defects relate to material and process, and less than 1% of the defects relate to the exposure tool. Material and process optimization by collaborative work between exposure tool vendors, track vendors and material vendors is a key for success of 45nm node device manufacturing.

  16. Deep Inspiration and the Emergence of Ventilation Defects during Bronchoconstriction: A Computational Study

    PubMed Central

    Golnabi, Amir H.; Harris, R. Scott; Venegas, Jose G.; Winkler, Tilo

    2014-01-01

    Deep inspirations (DIs) have a dilatory effect on airway smooth muscle (ASM) that helps to prevent or reduce more severe bronchoconstriction in healthy individuals. However, this bronchodilation appears to fail in some asthmatic patients or under certain conditions, and the reason is unclear. Additionally, quantitative effects of the frequency and magnitude of DIs on bronchodilation are not well understood. In the present study, we used a computational model of bronchoconstriction to study the effects of DI volumes, time intervals between intermittent DIs, relative speed of ASM constriction, and ASM activation on bronchoconstriction and the emergence of ventilation defects (VDefs). Our results showed a synergistic effect between the volume of DIs and the time intervals between them on bronchoconstriction and VDefs. There was a domain of conditions with sufficiently large volumes of DIs and short time intervals between them to prevent VDefs. Among conditions without VDefs, larger volumes of DIs resulted in greater airway dilation. Similarly, the time interval between DIs, during which the activated ASM re-constricts, affected the amplitude of periodic changes in airway radii. Both the relative speed of ASM constriction and ASM activation affected what volume of DIs and what time interval between them could prevent the emergence of VDefs. In conclusion, quantitative characteristics of DIs, such as their volume and time interval between them, affect bronchoconstriction and may contribute to difficulties in asthma. Better understanding of the quantitative aspects of DIs may result in novel or improved therapeutic approaches. PMID:25402457

  17. Supplemental vitamin A prevents the acute radiation-induced defect in wound healing.

    PubMed Central

    Levenson, S M; Gruber, C A; Rettura, G; Gruber, D K; Demetriou, A A; Seifter, E

    1984-01-01

    Acute radiation injury leads to thymic involution, adrenal enlargement, leukopenia, thrombocytopenia, gastrointestinal ulceration, and impaired wound healing. The authors hypothesized that supplemental vitamin A would mitigate these adverse effects in rats exposed to acute whole-body radiation. This hypothesis was based on previous experiments in their laboratory that showed that supplemental vitamin A is thymotropic for normal rodents and lessens the thymic involution, lymphopenia, and adrenal enlargement that follows stress, trauma, and neoplasia, largely obviates the impaired wound healing induced by the radiomimetic drugs streptozotocin and cyclophosphamide, lessens the systemic response (thymic involution, adrenal enlargement, leukopenia, lymphocytopenia) to local radiation, and shifts the median lethal dose (LD50/30) following whole-body radiation to the right. To test their hypothesis, dorsal skin incisions and subcutaneous implantation of polyvinyl alcohol sponges were performed in anesthetized Sprague-Dawley rats at varying times following sham radiation or varying doses of whole-body radiation (175-850 rad). In each experiment, the control diet [which contains about 18,000 IU vit. A/kg chow (3 X the NRC RDA for normal rats)] was supplemented with 150,000 IU vit. A/kg diet beginning at, before, or after sham radiation and wounding or radiation and wounding. The supplemental vitamin A prevented the impaired wound healing and lessened the weight loss, leukopenia, thrombocytopenia, thymic involution, adrenal enlargement, decrease in splenic weight, and gastric ulceration of the radiated (750-850 rad) wounded rats. This was true whether the supplemental vitamin A was begun before (2 or 4 days) or after (1-2 hours to 4 days) radiation and wounding; the supplemental vitamin A was more effective when started before or up to 2 days after radiation and wounding. The authors believe that prevention of the impaired wound healing following radiation by supplemental

  18. Defect studies in 4H- Silicon Carbide PVT grown bulk crystals, CVD grown epilayers and devices

    NASA Astrophysics Data System (ADS)

    Byrappa, Shayan M.

    postulated fault vectors by macrostep overgrowth of surface outcrops, has revealed faults to be of four types of which one of the following are discussed in detail which is the Shockley faults. The fault vector were determined by taking into account the contrast from stacking faults in SWBXT undergoing phase shift as the X-ray wave fields cross the fault plane. The deflected dislocations onto the basal plane were responsible for the stacking faults and were observed to be detrimental to the devices grown on them as they replicate to the epilayer. In the wafers studied at different stages of the SiC crystal boule resulted in reduction of threading defects as they at certain stage get deflected out of the crystal causing drop of defects density. [2] A novel technique known as the Ray Tracing Simulation was used to determine the sense of c/c+a dislocations obtained via Grazing-Incidence X-ray Topography. Determination of the complete sense and burgers vector of these dislocations was very important to augment our proposed models on stacking faults associated with these defects. Orientation contrast mechanism in X- ray diffraction topography was previously determined to be the dominant factor in SiC by our group and the same principles were used for the simulation. The results were surmised after extensive comparison between experimental and simulation images for the c+2a defects. [3] With the BPD density down to a record level of few hundred per square centimeter in several wafers in multiple regions made it possible to observe the conversion of sessile Threading Edge Dislocations [TED] to glissile BPDs with this repeating multiple times. Previously the high density of Basal Plane Dislocations [BPD] prevented from discerning the details accurately in the SiC images taken by SWBXT. The contribution of SWBXT in accurately categorizing the nature of dislocations in SiC has enabled the crystal growth community to incorporate strategies to mitigate their influence. One of them has

  19. Correlation between electron-irradiation defects and applied stress in graphene: A molecular dynamics study

    SciTech Connect

    Kida, Shogo; Yamamoto, Masaya; Kawata, Hiroaki; Hirai, Yoshihiko; Yasuda, Masaaki; Tada, Kazuhiro

    2015-09-15

    Molecular dynamics (MD) simulations are performed to study the correlation between electron irradiation defects and applied stress in graphene. The electron irradiation effect is introduced by the binary collision model in the MD simulation. By applying a tensile stress to graphene, the number of adatom-vacancy (AV) and Stone–Wales (SW) defects increase under electron irradiation, while the number of single-vacancy defects is not noticeably affected by the applied stress. Both the activation and formation energies of an AV defect and the activation energy of an SW defect decrease when a tensile stress is applied to graphene. Applying tensile stress also relaxes the compression stress associated with SW defect formation. These effects induced by the applied stress cause the increase in AV and SW defect formation under electron irradiation.

  20. Regulation of Budding Yeast CENP-A levels Prevents Misincorporation at Promoter Nucleosomes and Transcriptional Defects

    PubMed Central

    Hildebrand, Erica M.; Biggins, Sue

    2016-01-01

    The exclusive localization of the histone H3 variant CENP-A to centromeres is essential for accurate chromosome segregation. Ubiquitin-mediated proteolysis helps to ensure that CENP-A does not mislocalize to euchromatin, which can lead to genomic instability. Consistent with this, overexpression of the budding yeast CENP-ACse4 is lethal in cells lacking Psh1, the E3 ubiquitin ligase that targets CENP-ACse4 for degradation. To identify additional mechanisms that prevent CENP-ACse4 misincorporation and lethality, we analyzed the genome-wide mislocalization pattern of overexpressed CENP-ACse4 in the presence and absence of Psh1 by chromatin immunoprecipitation followed by high throughput sequencing. We found that ectopic CENP-ACse4 is enriched at promoters that contain histone H2A.ZHtz1 nucleosomes, but that H2A.ZHtz1 is not required for CENP-ACse4 mislocalization. Instead, the INO80 complex, which removes H2A.ZHtz1 from nucleosomes, promotes the ectopic deposition of CENP-ACse4. Transcriptional profiling revealed gene expression changes in the psh1Δ cells overexpressing CENP-ACse4. The down-regulated genes are enriched for CENP-ACse4 mislocalization to promoters, while the up-regulated genes correlate with those that are also transcriptionally up-regulated in an htz1Δ strain. Together, these data show that regulating centromeric nucleosome localization is not only critical for maintaining centromere function, but also for ensuring accurate promoter function and transcriptional regulation. PMID:26982580

  1. Regulation of Budding Yeast CENP-A levels Prevents Misincorporation at Promoter Nucleosomes and Transcriptional Defects.

    PubMed

    Hildebrand, Erica M; Biggins, Sue

    2016-03-01

    The exclusive localization of the histone H3 variant CENP-A to centromeres is essential for accurate chromosome segregation. Ubiquitin-mediated proteolysis helps to ensure that CENP-A does not mislocalize to euchromatin, which can lead to genomic instability. Consistent with this, overexpression of the budding yeast CENP-A(Cse4) is lethal in cells lacking Psh1, the E3 ubiquitin ligase that targets CENP-A(Cse4) for degradation. To identify additional mechanisms that prevent CENP-A(Cse4) misincorporation and lethality, we analyzed the genome-wide mislocalization pattern of overexpressed CENP-A(Cse4) in the presence and absence of Psh1 by chromatin immunoprecipitation followed by high throughput sequencing. We found that ectopic CENP-A(Cse4) is enriched at promoters that contain histone H2A.Z(Htz1) nucleosomes, but that H2A.Z(Htz1) is not required for CENP-A(Cse4) mislocalization. Instead, the INO80 complex, which removes H2A.Z(Htz1) from nucleosomes, promotes the ectopic deposition of CENP-A(Cse4). Transcriptional profiling revealed gene expression changes in the psh1Δ cells overexpressing CENP-A(Cse4). The down-regulated genes are enriched for CENP-A(Cse4) mislocalization to promoters, while the up-regulated genes correlate with those that are also transcriptionally up-regulated in an htz1Δ strain. Together, these data show that regulating centromeric nucleosome localization is not only critical for maintaining centromere function, but also for ensuring accurate promoter function and transcriptional regulation. PMID:26982580

  2. Density functional study of silver defects in telluride thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Ryu, Byungki; Oh, Min-Wook; Park, Su-Dong

    2015-03-01

    Silver impurity in telluride thermoelectric materials forms various defect and impurity structures, such as AgSb rich nanoregion in Ag-Sb-Pb-Te, Ag2Te and metallic silver in PbTe. To understand the atomic, electronic, energetic, and diffusion properties of silver impurities in telluride systems, we have performed the density functional theory and density functional perturbation theory calculations of silver doped PbTe. Under Te and Ag rich condition, silver telluride impurity phase or Ag-dimer defects are expected to be easily formed. Under Te poor condition, silver point defects are calculated to be easily formed and they are more stable than native point defects of PbTe, implying that silver point defect might be the major dopant responsible for the carrier generation in PbTe. We also calculated the diffusion coefficient and diffusion length of silver point defect in PbTe. Based on the results, we discussed the electrical and thermoelectric properties of silver doped PbTe. This work was supported by the National Institute of Supercomputing and Network/Korea Institute of Science and Technology Information with supercomputing resources including technical support (KSC-2014-C1-022).

  3. Kinetic Defects Induced by Melittin in Model Lipid Membranes: A Solution Atomic Force Microscopy Study.

    PubMed

    Pan, Jianjun; Khadka, Nawal K

    2016-05-26

    Quantitative characterization of membrane defects (pores) is important for elucidating the molecular basis of many membrane-active peptides. We study kinetic defects induced by melittin in vesicular and planar lipid bilayers. Fluorescence spectroscopy measurements indicate that melittin induces time-dependent calcein leakage. Solution atomic force microscopy (AFM) is used to visualize melittin-induced membrane defects. After initial equilibration, the most probable defect radius is ∼3.8 nm in 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) bilayers. Unexpectedly, defects become larger with longer incubation, accompanied by substantial shape transformation. The initial defect radius is ∼4.7 nm in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers. Addition of 30 mol % cholesterol to DOPC bilayers suppresses defect kinetics, although the inhibitory impact is negated by longer incubation. Overall, the kinetic rate of defect development follows DLPC > DOPC > DOPC/cholesterol. Kinetic defects are also observed when anionic lipids are present. Based on the observation that defects can occupy as large as 40% of the bilayer surface, we propose a kinetic defect growth model. We also study the effect of melittin on the phase behavior of DOPC/egg-sphingomyelin/cholesterol bilayers. We find that melittin initially suppresses or eliminates liquid-ordered (Lo) domains; Lo domains gradually emerge and become the dominant species with longer incubation; and defects in phase-coexisting bilayers have a most probable radius of ∼5 nm and are exclusively localized in the liquid-disordered (Ld) phase. Our experimental data highlight that melittin-induced membrane defects are not static; conversely, spontaneous defect growth is intrinsically associated with membrane permeabilization exerted by melittin. PMID:27167473

  4. Laser annealing and defect study of chalcogenide photovoltaic materials

    NASA Astrophysics Data System (ADS)

    Bhatia, Ashish

    Cu(In,Ga)Se2 (CIGSe), CuZnSn(S,Se)4(CZTSSe), etc., are the potential chalcogenide semiconductors being investigated for next-generation thin film photovoltaics (TFPV). While the champion cell efficiency of CIGSe has exceeded 20%, CZTSSe has crossed the 10% mark. This work investigates the effect of laser annealing on CISe films, and compares the electrical characteristics of CIGSe (chalcopyrite) and CZTSe (kesterite) solar cells. Chapter 1 through 3 provide a background on semiconductors and TFPV, properties of chalcopyrite and kesterite materials, and their characterization using deep level transient spectroscopy (DLTS) and thermal admittance spectroscopy (TAS). Chapter 4 investigates electrochemical deposition (nonvacuum synthesis) of CISe followed by continuous wave laser annealing (CWLA) using a 1064 nm laser. It is found that CWLA at ≈ 50 W/cm2 results in structural changes without melting and dewetting of the films. While Cu-poor samples show about 40% reduction in the full width at half maximum of the respective x-ray diffraction peaks, identically treated Cu-rich samples register more than 80% reduction. This study demonstrates that an entirely solid-phase laser annealing path exists for chalcopyrite phase formation and crystallization. Chapter 5 investigates the changes in defect populations after pulse laser annealing in submelting regime of electrochemically deposited and furnace annealed CISe films. DLTS on Schottky diodes reveal that the ionization energy of the dominant majority carrier defect state changes nonmonotonically from 215+/-10 meV for the reference sample, to 330+/-10 meV for samples irradiated at 20 and 30 mJ/cm2, and then back to 215+/-10 meV for samples irradiated at 40 mJ/cm2. A hypothesis involving competing processes of diffusion of Cu and laser-induced generation of In vacancies may explain this behavior. Chapter 6 compares the electrical characteristics of chalcopyrite and kesterite materials. Experiments reveal CZTSe cell has an

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

    PubMed

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

    2016-01-01

    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 born in 1997-2012. By Fisher's exact test we analyzed possible differences in NTD subtype distribution between a correct FA supplementation group and incorrect FA supplementation group. We found proportionally fewer cervical/thoracic spina bifida cases and more lumbar/sacral spina bifida cases in the correct FA supplementation group, irrespective of the presence of the main NTD risk factors. The effect on NTD subtype distribution was only seen when FA supplementation was started before conception. We conclude that FA not only prevents the occurrence of a significant proportion of NTDs, but might also decrease the severity of NTDs, as long as supplementation is started before conception. PMID:26627544

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

    PubMed

    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. PMID:26924399

  7. First-principles study of electronic and elastic properties of Stone-Wales defective zigzag carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Pan, Lijun; Shen, Zigang; Jia, Yu; Dai, Xianqi

    2012-07-01

    The interaction and coupling between the electrical, mechanical properties and formation energy for SW defective (10,0) carbon nanotube is studied in density functional theory. The investigated configurations include the axial and circumferential orientations for single defect as well as four distribution types for double ones. The more stable defective configurations, namely, SW-I configurations for single SW defective carbon nanotube and II-II-(2) and I-I ones for double SW defective tubes are related to high symmetry distribution of the defects. Moreover, we found that the σ*-π* hybridization induced by curvature effect causes the semiconductor to metal transition for double axial SW defects case. Young's modulus reduction of SW defective carbon nanotube with respect to defect-free one is less than 8%. The energy bands and Young's moduli of double SW defective tubes are mostly affected by the defect distribution and concentration but insensitive to the circumferential distance between the double defects.

  8. Theoretical study of OH-defects in pure enstatite

    NASA Astrophysics Data System (ADS)

    Balan, Etienne; Blanchard, Marc; Yi, Haohao; Ingrin, Jannick

    2013-01-01

    The infrared spectroscopic properties of selected defects in orthoenstatite are investigated by first-principles calculations. The considered defects include doubly protonated Mg vacancies at M1 and M2 sites, fully protonated SiA and SiB vacancies (hydrogarnet defects), and doubly protonated SiA and SiB vacancies associated with interstitial Mg2+ cations. The bands observed at 3,070 and 3,360 cm-1 in the spectrum of synthetic enstatite samples are ascribed to O2A-H and O2B-H groups, respectively, associated with M2 vacancies. The theoretical models suggest that bands observed at 3,590 and 3,690 cm-1 in the spectrum of enstatite samples synthesized under low silica-activity conditions correspond to O2H and O1H groups associated with SiB vacancies partially compensated by interstitial Mg2+ cations in fivefold coordination. The theoretical relation between the integrated absorption coefficient of OH-defects and vibrational frequencies is consistent with previous observations indicating that the absorption coefficients of OH-defects are comparatively stronger in enstatite than in the olivine polymorphs.

  9. EBIC and luminescence studies of defects in solar cells.

    PubMed

    Breitenstein, O; Bauer, J; Kittler, M; Arguirov, T; Seifert, W

    2008-01-01

    Electron beam-induced current (EBIC) can be used to detect electronic irregularities in solar cells, such as shunts and precipitates, and to perform physical characterization of defects by, e.g. measuring the temperature dependence of their recombination activity. Recently also luminescence methods such as electroluminescence (EL) and photoluminescence (PL) have been shown to provide useful information on crystal defects in solar cells. In this contribution it will be shown that the combined application of EBIC, EL and PL may deliver useful information on the presence and on the physical properties of crystal defects in silicon solar cells. Also pre-breakdown sites in multicrystalline cells can be investigated by reverse-bias EL and by microplasma-type EBIC, in comparison with lock-in thermography investigations. PMID:18561253

  10. Lithium-ion drifting: Application to the study of point defects in floating-zone silicon

    NASA Technical Reports Server (NTRS)

    Walton, J. T.; Wong, Y. K.; Zulehner, W.

    1997-01-01

    The use of lithium-ion (Li(+)) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li(+) drift technique is used to detect the presence of vacancy-related defects (D defects) in certain p-type FZ silicon crystals. SUPREM-IV modeling suggests that the silicon point defect diffusivities are considerably higher than those commonly accepted, but are in reasonable agreement with values recently proposed. These results demonstrate the utility of Li(+) drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li(+) compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.

  11. Defects in Peroxisomal 6-Phosphogluconate Dehydrogenase Isoform PGD2 Prevent Gametophytic Interaction in Arabidopsis thaliana.

    PubMed

    Hölscher, Christian; Lutterbey, Marie-Christin; Lansing, Hannes; Meyer, Tanja; Fischer, Kerstin; von Schaewen, Antje

    2016-05-01

    We studied the localization of 6-phosphogluconate dehydrogenase (PGD) isoforms of Arabidopsis (Arabidopsis thaliana). Similar polypeptide lengths of PGD1, PGD2, and PGD3 obscured which isoform may represent the cytosolic and/or plastidic enzyme plus whether PGD2 with a peroxisomal targeting motif also might target plastids. Reporter-fusion analyses in protoplasts revealed that, with a free N terminus, PGD1 and PGD3 accumulate in the cytosol and chloroplasts, whereas PGD2 remains in the cytosol. Mutagenesis of a conserved second ATG enhanced the plastidic localization of PGD1 and PGD3 but not PGD2. Amino-terminal deletions of PGD2 fusions with a free C terminus resulted in peroxisomal import after dimerization, and PGD2 could be immunodetected in purified peroxisomes. Repeated selfing of pgd2 transfer (T-)DNA alleles yielded no homozygous mutants, although siliques and seeds of heterozygous plants developed normally. Detailed analyses of the C-terminally truncated PGD2-1 protein showed that peroxisomal import and catalytic activity are abolished. Reciprocal backcrosses of pgd2-1 suggested that missing PGD activity in peroxisomes primarily affects the male gametophyte. Tetrad analyses in the quartet1-2 background revealed that pgd2-1 pollen is vital and in vitro germination normal, but pollen tube growth inside stylar tissues appeared less directed. Mutual gametophytic sterility was overcome by complementation with a genomic construct but not with a version lacking the first ATG. These analyses showed that peroxisomal PGD2 activity is required for guided growth of the male gametophytes and pollen tube-ovule interaction. Our report finally demonstrates an essential role of oxidative pentose-phosphate pathway reactions in peroxisomes, likely needed to sustain critical levels of nitric oxide and/or jasmonic acid, whose biosynthesis both depend on NADPH provision. PMID:26941195

  12. Laser Scattering Tomography for the Study of Defects in Protein Crystals

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.; DeLucas, Lawrence; DeMattei, R. C.

    1997-01-01

    The goal of this research is to explore the application of the non-destructive technique of Laser Scattering Tomography (LST) to study the defects in protein crystals and relate them to the x-ray diffraction performance of the crystals. LST has been used successfully for the study of defects in inorganic crystals and. in the case of lysozyme, for protein crystals.

  13. Diamond deposition and defect chemistry studied via solid state NMR

    NASA Astrophysics Data System (ADS)

    Gleason, Karen K.

    1994-06-01

    Diamond defects were quantified by nuclear magnetic resonance (NMR). While maintaining the macroscopic integrity of the films, concentrations between 0.001 and 1.0 at.% H were measured, among the lowest ever reported by solid-state 1H NMR. These concentrations were correlated to infrared absorption in the 8 to 10 micron region and to thermal conductivity. Despite the low concentrations, Multiple Quantum NMR reveals a high degree of hydrogen clustering consistent with grain boundary passivation. Most hydrogen is rigidly held, but some, probably in -OCH3 and -NCH3 defects, undergoes rotation at room temperature. Similar results were obtained for hot-filament, microwave-plasma and DC arc-jet films, suggesting a common surface chemistry, but no hydrogen was detected in an as-deposited combustion film. 13C NMR provided the first quantitative determination of non-diamond bonded carbon defects, providing a benchmark for Raman spectroscopy, the primary characterization method for diamond. Selective 13C labeling demonstrated heterogeneous reactions involving carbon occur at the hot-filament. With high-speed magic-angle-spinning 19F NMR, CFx (x=1-3) functionalities were resolved on the surface of plasma-treated diamond powder. Understanding these defects impacts the understanding of film growth mechanisms and structure-property relationships for CVD diamond.

  14. Defect studies of zirconia implanted by high energy Xe ions

    NASA Astrophysics Data System (ADS)

    Melikhova, O.; Čížek, J.; Procházka, I.; Hruška, P.; Skuratov, V. A.; Konstantinova, T. E.; Danilenko, I. A.

    2016-01-01

    In the present work positron lifetime spectroscopy was employed for characterization of radiation-induced defects in yttria stabilized zirconia (YSZ) implanted by 167 MeV Xe ions. Positron lifetime data were interpreted with aid of ab-initio theoretical modelling of defects in YSZ lattice. Damage caused by Xe implantation was investigated in two YSZ samples with different microstructure: (i) single crystal and (ii) sintered ceramic. The virgin YSZ single crystal exhibits single component spectrum with lifetime of ≈ 180 ps. Similar lifetime component was found also in the virgin sample of sintered YSZ ceramic. Since this lifetime is significantly higher than the YSZ bulk lifetime the virgin YSZ crystal and the sintered ceramic both contain vacancy-like defects. Xe implantation leads to appearance of additional defect component with longer lifetime ≈ 370 ps which comes obviously from vacancy clusters fonned by agglomeration of irradiation induced vacancies. A broad absorption band with peak absorption at ≈ 518 nm was found in Xe-implanted crystal by optical measurements.

  15. Discussions about preventive services: a qualitative study

    PubMed Central

    Lasser, Karen E; Kelly, Bridget; Maier, Jan; Murillo, Jennifer; Hoover, Sonia; Isenberg, Karen; Osber, Deborah; Pilkauskas, Natasha; Willis, Bayo C; Hersey, James

    2008-01-01

    Background Elderly minority patients are less likely to receive influenza vaccination and colorectal cancer screening than are other patients. Communication between primary care providers (PCPs) and patients may affect service receipt. Methods Encounters between 7 PCPs and 18 elderly patients were observed and audiotaped at 2 community health centers. Three investigators coded transcribed audiotapes and field notes. We used qualitative analysis to identify specific potential barriers to completion of preventive services and to highlight examples of how physicians used patient-centered communication and other facilitation strategies to overcome those barriers. Results Sharing of power and responsibility, the use of empathy, and treating the patient like a person were all important communication strategies which seemed to help address barriers to vaccination and colonoscopy. Other potential facilitators of receipt of influenza vaccine included (1) cultural competence, (2) PCP introduction of the discussion, (3) persistence of the PCP (revisiting the topic throughout the visit), (4) rapport and trust between the patient and PCP, and (5) PCP vaccination of the patient. PCP persistence as well as rapport and trust also appeared to facilitate receipt of colorectal cancer screening. Conclusion Several communications strategies appeared to facilitate PCP communications with older patients to promote acceptance of flu vaccination and colorectal cancer screening. These strategies should be studied with larger samples to determine which are most predictive of compliance with prevention recommendations. PMID:18768086

  16. A Study on the Effects of Ball Defects on the Fatigue Life in Hybrid Bearings

    NASA Technical Reports Server (NTRS)

    Tang, Ching-Yao; Foerster, Chad E.; O'Brien, Michael J.; Hardy, Brian S.; Goyal, Vinay K.; Nelson, Benjamin A.; Robinson, Ernest Y.; Ward, Peter C.; Hilton, Michael R.

    2014-01-01

    Hybrid ball bearings using silicon nitride ceramic balls with steel rings are increasingly being used in space mechanism applications due to their high wear resistance and long rolling contact fatigue life. However, qualitative and quantitative reports of the effects of ball defects that cause early fatigue failure are rare. We report on our approach to study these effects. Our strategy includes characterization of defects encountered in use, generation of similar defects in a laboratory setting, execution of full-scale bearing tests to obtain lifetimes, post-test characterization, and related finite-element modeling to understand the stress concentration of these defects. We have confirmed that at least one type of defect of appropriate size can significantly reduce fatigue life. Our method can be used to evaluate other defects as they occur or are encountered.

  17. Positron annihilation study of the micro-defects induced by cavitation in mild steel

    NASA Astrophysics Data System (ADS)

    Zhao, Ming; Wang, Jiadao; Chen, Darong; Hao, Xiaopeng; Wang, Baoyi

    2008-08-01

    Cavitation-induced micro-defects in mild steel after cavitation experiment in the fluid field have been studied by positron Doppler broadening measurement and positron annihilation lifetime spectra (PALS). Depth-resolved positron Doppler S-parameter (DPDS) results showed that S-parameter increased and micro-defects between the surface and the bulk has obvious variation with depth during the cavitation process. From the positron lifetime results, it was found that the size and number of micro-defects increase with the development of cavitation. These results suggest that more micro-defects are generated in mild steel bulk during the cavitation process than those in the mild steel surface layer region, although more mico-defects seen in the mild steel surface layer. Moreover, the size of micro-defects in mild steel bulk increases remarkably owing to their transfer and aggregation.

  18. Long term effects of periconceptional multivitamin supplements for prevention of neural tube defects: a seven to 10 year follow up.

    PubMed Central

    Holmes-Siedle, M; Dennis, J; Lindenbaum, R H; Galliard, A

    1992-01-01

    Periconceptional supplementation with Pregnavite Forte F was offered to women who presented consecutively to the Oxford genetic counselling service in the early 1980s who had previously had one or more pregnancies complicated by a neural tube defect. The first 100 children born alive to these women are the subject of this study. Birth weight, gestation, and congenital abnormalities were recorded. At age 2-5 years all 96 children remaining in the United Kingdom were assessed clinically and developmentally and behavioural information was obtained by questionnaire. At age 7-10 years, follow up of 91 children by telephone and postal questionnaire yielded further information about growth, general health, vision, hearing, and educational and behavioural status. Entry criteria excluded single mothers but the social class distribution of the sample was otherwise representative of the Oxfordshire population. There were no recurrences of neural tube defects. One child had radiological evidence of spina bifida occulta affecting only the fifth lumbar vertebra. One had an autosomal recessive disorder. Eight had random minor congenital anomalies. Birth weight for gestational age was significantly greater than for the local population and at age 7-10 years the girls were considerably taller than expected. Health, auditory, visual, and developmental status were no different from the general population. None of the children had special educational needs. None showed a major behaviour disorder but worries, fussiness, and fearfulness were highly significantly over represented. PMID:1489221

  19. Maternal and perinatal aspects of birth defects: a case-control study

    PubMed Central

    Nhoncanse, Geiza César; Germano, Carla Maria R.; de Avó, Lucimar Retto da S.; Melo, Débora Gusmão

    2014-01-01

    Objective: To assess the prevalence of congenital defects and to investigate their maternal and perinatal associated aspects by reviewing Birth Certificates. Methods: Among all born alive infants from January 2003 to December 2007 in Maternidade da Santa Casa de Misericórdia of São Carlos, Southeast Brazil (12,199 infants), cases were identified as the newborns whose Birth Certificates registered any congenital defect. The same sex neonate born immediately after the case was chosen as a control. In total, 13 variables were analyzed: six were maternal related, three represented labor and delivery conditions and four were linked to fetal status. The chi-square and Fisher's exact tests were used to compare the variables, being significant p<0.05. Results: The prevalence of congenital defects was 0.38% and the association of two or more defects represented 32% of all cases. The number of mothers whose education level was equal or less than eight years was significantly higher among the group with birth defects (p=0.047). A higher frequency of prematurity (p<0.001) and cesarean delivery (p=0.004) was observed among children with birth defects. This group also showed lower birth weight and Apgar scores in the 1st and the 5th minute (p<0.001). Conclusions: The prevalence of congenital defect of 0.38% is possibly due to underreporting. The defects notified in the Birth Certificates were only the most visible ones, regardless of their severity. There is a need of adequate epidemiological monitoring of birth defects in order to create and expand prevention and treatment programs. PMID:24676186

  20. New Techniques for the Study of Neural Tube Defects

    PubMed Central

    Lei, Yunping; Finnell, Richard H

    2016-01-01

    Neural tube defects (NTDs) are among the most common complex congenital malformations observed in newborns. When the neural tube fails to close completely, severe malformations of the brain and/or spinal cord and subsequent neurologic impairment occurs. It is widely believed that nutritional, environmental and genetic interactions contribute to NTDs. It is well established that low folate levels during pregnancy increases a mother’s risk of having pregnancy complicated by an NTD, and providing periconceptional folate supplementation reduces this risk. The underlying genetic mechanisms of NTDs are still unclear. We review the many new approaches to better understand the etiology, especially the genetic etiology, underlying this family of birth defects. PMID:27066597

  1. A molecular dynamics simulation study of defect production in vanadium

    SciTech Connect

    Morishita, K. |; Diaz de la Rubia, T.

    1995-01-23

    We performed molecular dynamics simulations to investigate the process of defect production in pure vanadium. The interaction of atoms was described by the EAM interatomic potential modified at short range to merge smoothly with the universal potential for description of the high energy recoils in cascades. The melting point of this EAM model of vanadium was found to be consistent with the experimental melting temperature. The threshold energies of displacement events in the model system are also consistent with experimental minimum threshold in vanadium, and its average was found to be 44 eV. We evaluated the efficiencies of defect production in the displacement events initiated by recoils with kinetic energy up to 5 keV, and found that the probability of cluster formation is smaller than that of simulated events in fcc metals reported in the literature.

  2. REVIEWS OF TOPICAL PROBLEMS: Defects in liquid crystals: homotopy theory and experimental studies

    NASA Astrophysics Data System (ADS)

    Kurik, Mikhail V.; Lavrentovich, O. D.

    1988-03-01

    The fundamental concepts of the homotopy theory of defects in liquid crystals and the results of experimental studies in this field are presented. The concepts of degeneracy space, homotopy groups, and topological charge, which are used for classifying the topologically stable inhomogeneous distributions in different liquid-crystalline phases are examined (uni and biaxial nematics, cholesterics, smectics, and columnar phases). Experimental data are given for the different mesophases on the structure and properties of dislocations, disclinations, point defects in the volume (hedgehogs) and on the surface of the medium (boojums), monopoles, domain formations, and solitons. Special attention is paid to the results of studies of defects in closed volumes (spherical drops, cylindrical capillaries), and to the connection between the topological charges of these defects and the character of the orientation of the molecules of the liquid crystal at the surface. A set of fundamentally new effects that can occur in studying the topological properties of defects in liquid crystals is discussed.

  3. Studies on the Protein Defect in Tangier Disease

    PubMed Central

    Lux, Samuel E.; Levy, Robert I.; Gotto, Antonio M.; Fredrickson, Donald S.

    1972-01-01

    High density lipoproteins (d 1.063-1.210 g/ml) were isolated from the plasma of normal individuals (HDL) and seven homozygous patients with Tangier disease (HDLt). In Tangier patients, the concentration of protein in the high density region (HDLt) was only 0.5-4.5% of normal. Immunochemical studies, including mixing experiments conducted in vivo and in vitro, indicated that HDLt was different from HDL. HDLt was the only high density lipoprotein detectable in the plasma of Tangier homozygotes. In heterozygotes both HDL and HDLt were present. HDLt was not detected in the plasma of over 300 normal persons and 10 patients with secondary high density lipoprotein deficiency and appeared to be a unique marker for Tangier disease. ApoHDL contained two major apoproteins designated apoLp-Gln-I and apoLp-Gln-II; together they comprised 85-90% of the total protein content. Both of the major HDL apoproteins were present in apoHDLt; but apoLp-Gln-I was disproportionately decreased with respect to apoLp-Gln-II, the ratio of their concentrations being 1: 12 in apoHDLt as compared with 3: 1 in apoHDL. Several minor apoprotein components which together comprise 5-15% of apoHDL were present in approximately normal proportions in apoHDLt. In the HDL of Tangier patients it was estimated that, compared with normal individuals, the concentration of apoLp-Gln-I was decreased about 600-fold and the concentration of apoLp-Gln-II about 17-fold. The decrease in these apoproteins was not due to preferential segregation with the lipoprotein fractions of d < 1.063 g/ml or with the plasma proteins of d > 1.21 g/ml. Tangier apoLp-Gln-I and apoLp-Gln-II appeared to be immunochemically identical with their normal counterparts, and no differences between the two sets of apoproteins were detected on polyacrylamide gel electrophoresis at pH 9.4 or 2.9. These results are most compatible with the hypothesis that the hereditary defect in Tangier disease is a mutation in an allele-regulating synthesis of

  4. MTHFR C677T polymorphism as a risk factor of neural tube defects in Malay: a case control study.

    PubMed

    Hayati, A R; Zainal, A I; Tan, G C; Ong, L C; Khoo, T B

    2008-12-01

    Major congenital malformations occur in about 3% of newborn. Several studies have suggested that homozygosity for the C677T methylenetetrahydrofolate reductase (MTHFR) variant is a potential risk factor for neural tube defects (NTDs). It has been hypothesized that the maternal folic acid supplementation prevents NTDs by partially correcting reduced MTHFR activity associated with the variant form of the enzyme. This association has not been found in some ethnic groups. In this study, we attempted to assess the association between NTDs and MTHFR C677T in Malaysian Malay population. Results show that MTHFR 677TT genotype was absent in both patient and control groups. PMID:19803295

  5. New Study Designs | Division of Cancer Prevention

    Cancer.gov

    The Division of Cancer Prevention is expanding clinical research beyond standard trial designs to find interventions that may play a role in more than one prevalent disease. | The Division of Cancer Prevention is expanding clinical research beyond standard trial designs to find interventions that may play a role in more than one prevalent disease.

  6. Defects in electron-irradiated GaAs studied by positron lifetime spectroscopy

    SciTech Connect

    Polity, A.; Rudolf, F.; Nagel, C.; Eichler, S.; Krause-Rehberg, R.

    1997-04-01

    A systematic study of electron-irradiation-induced defects in GaAs was carried out. The irradiation was performed at low temperature (4 K) with an incident energy of 2 MeV. Both, the defect formation and annealing behavior were studied in dependence on the fluence (10{sup 15}--10{sup 19} cm{sup {minus}2}) in undoped, n-, and p-doped GaAs. Temperature-dependent positron lifetime measurements were performed between 20 and 600 K. The thermal stability of defects was studied by annealing experiments in the temperature range of 90--600 K. A defect complex, which anneals in a main stage at 300 K, was found in all GaAs samples after electron irradiation. A possible candidate for this defect is a complex of a vacancy connected with an intrinsic defect. A second vancancylike defect was observed in n-type material after annealing at 550 K. This defect was assumed to be in the As sublattice. {copyright} {ital 1997} {ital The American Physical Society}

  7. Evaluation of Respiratory Motion Effect on Defect Detection in Myocardial Perfusion SPECT: A Simulation Study

    PubMed Central

    Yang, Yu-Wen; Chen, Jyh-Cheng; He, Xin; Wang, Shyh-Jen; Tsui, Benjamin M. W.

    2010-01-01

    The objective of this study is to investigate the effects of respiratory motion (RM) on defect detection in Tc-99m sestamibi myocardial perfusion SPECT (MPS) using a phantom population that includes patient variability. Three RM patterns are included, namely breath-hold, slightly enhanced normal breathing, and deep breathing. For each RM pattern, six 4-D NCAT phantoms were generated, each with anatomical variations. Anterior, lateral and inferior myocardial defects with different sizes and contrasts were inserted. Noise-free SPECT projections were simulated using an analytical projector. Poisson noise was then added to generate noisy realizations. The projection data were reconstructed using the OS-EM algorithm with 1 and 4 subsets/iteration and at 1, 2, 3, 5, 7, and 10 iterations. Short-axis images centered at the centroid of the myocardial defect were extracted, and the channelized Hotelling observer (CHO) was applied for the detection of the defect. The CHO results show that the value of the area under the receiver operating characteristics (ROC) curve (AUC) is affected by the RM amplitude. For all the defect sizes and contrasts studied, the highest or optimal AUC values indicate maximum detectability decrease with the increase of the RM amplitude. With no respiration, the ranking of the optimal AUC value in decreasing order is anterior then lateral, and finally inferior defects. The AUC value of the lateral defect drops more severely as the RM amplitude increases compared to other defect locations. Furthermore, as the RM amplitude increases, the AUC values of the smaller defects drop more quickly than the larger ones. We demonstrated that RM affects defect detectability of MPS imaging. The results indicate that developments of optimal data acquisition methods and RM correction methods are needed to improve the defect detectability in MPS. PMID:21731107

  8. Tight-binding calculation studies of vacancy and adatom defects in graphene

    DOE PAGESBeta

    Zhang, Wei; Lu, Wen-Cai; Zhang, Hong-Xing; Ho, K. M.; Wang, C. Z.

    2016-02-19

    Computational studies of complex defects in graphene usually need to deal with a larger number of atoms than the current first-principles methods can handle. We show a recently developed three-center tight-binding potential for carbon is very efficient for large scale atomistic simulations and can accurately describe the structures and energies of various defects in graphene. Using the three-center tight-binding potential, we have systematically studied the stable structures and formation energies of vacancy and embedded-atom defects of various sizes up to 4 vacancies and 4 embedded atoms in graphene. In conclusion, our calculations reveal low-energy defect structures and provide a moremore » comprehensive understanding of the structures and stability of defects in graphene.« less

  9. A Raman Study of the Origin of Oxygen Defects in Hexagonal Manganite Thin Films

    NASA Astrophysics Data System (ADS)

    Chen, Xiang-Bai; Hien Nguyen Thi, Minh; Yang, In-Sang; Lee, Daesu; Noh, Tae-Won

    2012-12-01

    Oxygen defects are usually unavoidable when synthesizing oxide thin films. We study the origin of the oxygen defects in hexagonal manganite HoMnO3 epitaxial thin films through Raman scattering spectroscopy. Our results show that the oxygen defects in hexagonal HoMnO3 thin films have distinct effects on different phonon modes and on magnon scattering. Our analyses indicate that the oxygen defects in hexagonal HoMnO3 thin films mainly originate from the basal O3 and/or O4 oxygen vacancies. Furthermore, our analyses of oxygen defects predict that the Mn 3d orbitals would be more strongly hybridized with the apical O1 and/or O2 2p orbitals than the basal O3 and/or O4 2p orbitals. This prediction is consistent with our resonant Raman scattering study and earlier first-principle calculations of the electronic structures of hexagonal manganites.

  10. Exploring the interaction between lithium ion and defective graphene surface using dispersion corrected DFT studies

    SciTech Connect

    Vijayakumar, M.; Hu, Jian Z.

    2013-10-15

    To analyze the lithium ion interaction with realistic graphene surfaces, we carried out dispersion corrected DFT-D3 studies on graphene with common point defects and chemisorbed oxygen containing functional groups along with defect free graphene surface. Our study reveals that, the interaction between lithium ion (Li+) and graphene is mainly through the delocalized π electron of pure graphene layer. However, the oxygen containing functional groups pose high adsorption energy for lithium ion due to the Li-O ionic bond formation. Similarly, the point defect groups interact with lithium ion through possible carbon dangling bonds and/or cation-π type interactions. Overall these defect sites render a preferential site for lithium ions compared with pure graphene layer. Based on these findings, the role of graphene surface defects in lithium battery performance were discussed.

  11. Comparative theoretical study of adsorption of lithium polysulfides (Li2Sx) on pristine and defective graphene

    NASA Astrophysics Data System (ADS)

    Jand, Sara Panahian; Chen, Yanxin; Kaghazchi, Payam

    2016-03-01

    Adsorption of Li2Sx on pristine and defective (Stone-Wales (SW) and vacancy) graphene is studied using density functional theory. Results show that the interaction between Li2Sx and graphene is dominated by dispersion interaction (physisorption), which depends on the size of molecule as well as the existence and type of defect sites on graphene. We find that single Li2Sx molecules interact only slightly stronger to the SW sites than to the defect-free sites, but they interact very strongly with single-vacant defects. In the later cases, the vacant site catches one S atom from the Li2Sx molecule, leading to the formation of a Li2Sx-1 molecule, which adsorbs weakly on the created S-doped graphene. This study suggests that defect sites can not improve the ability of graphene to catch lithium polysulfides in Li-S batteries.

  12. Atrial septal defect

    MedlinePlus

    ... Coronary angiography (for patients over 35 years old) ECG Heart MRI Transesophageal echocardiography (TEE) Treatment ASD may ... of the complications can be prevented with early detection. Alternative Names Congenital heart defect - ASD; Birth defect ...

  13. Study Sees No Link Between Common Epilepsy Drug, Certain Birth Defects

    MedlinePlus

    ... 158169.html Study Sees No Link Between Common Epilepsy Drug, Certain Birth Defects Large review found no ... Despite initial concern from early studies, taking the epilepsy drug lamotrigine (Lamictal) during pregnancy may not raise ...

  14. Pain, Epilepsy Drug Lyrica May Increase Birth Defects Risk, Study Suggests

    MedlinePlus

    ... nih.gov/medlineplus/news/fullstory_158906.html Pain, Epilepsy Drug Lyrica May Increase Birth Defects Risk, Study ... prescribed for a range of health problems, including epilepsy, fibromyalgia and anxiety. The new study findings should ...

  15. Study Hints At HPV Vaccine's Cancer Prevention Promise

    MedlinePlus

    ... gov/news/fullstory_159696.html Study Hints at HPV Vaccine's Cancer Prevention Promise Fewer vaccinated young women ... July 4, 2016 (HealthDay News) -- The human papillomavirus (HPV) vaccine appears to prevent abnormalities that can lead ...

  16. Study Hints At HPV Vaccine's Cancer Prevention Promise

    MedlinePlus

    ... news/fullstory_159696.html Study Hints at HPV Vaccine's Cancer Prevention Promise Fewer vaccinated young women had ... 4, 2016 (HealthDay News) -- The human papillomavirus (HPV) vaccine appears to prevent abnormalities that can lead to ...

  17. Technology Solutions Case Study: Preventing Thermal Bypass

    SciTech Connect

    none,

    2012-10-01

    This project highlights the importance of continuous air barriers in full alignment with insulation to prevent thermal bypasses and achieve high energy performance, and recommends use of ENERGY STAR's Thermal Bypass Inspection Checklist.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Inversion of tone burst eddy current thermography data for defect sizing - A simulation study

    NASA Astrophysics Data System (ADS)

    Biju, N.; Ganesan, N.; Krishnamurthy, C. V.; Balasubramaniam, Krishnan

    2013-01-01

    In this paper, the results of the simulation study to reconstruct the size of the defects from the data obtained using the active thermography technique based on transient induction heating, will be presented. The forward problem of electro-magnetic induction was solved with an axi-symmetric model using finite element method and from the temperature history profiles, an inverse analysis was performed using Genetic Algorithm (GA) to size the defect. Simulations were performed using the finite element model to obtain the temperature data which are then used to reconstruct the radius (rd) and depth (dd) of the wall thinning defects in aluminum plate using inversion method. Two cases, coil inner radius less than the defect radius (rcdefect radius (rc>rd), were considered. The analysis of the sensitivity of coil dimensions to the calculated peak temperature at the observation point was carried out.

  20. Oxygen defects in amorphous Al2O3: A hybrid functional study

    NASA Astrophysics Data System (ADS)

    Guo, Zhendong; Ambrosio, Francesco; Pasquarello, Alfredo

    2016-08-01

    The electronic properties of the oxygen vacancy and interstitial in amorphous Al2O3 are studied via ab initio molecular dynamics simulations and hybrid functional calculations. Our results indicate that these defects do not occur in amorphous Al2O3, due to structural rearrangements which assimilate the defect structure and cause a delocalization of the associated defect levels. The imbalance of oxygen leads to a nonstoichiometric compound in which the oxygen occurs in the form of O2- ions. Intrinsic oxygen defects are found to be unable to trap excess electrons. For low Fermi energies, the formation of peroxy linkages is found to be favored leading to the capture of holes. The relative +2/0 defect levels occur at 2.5 eV from the valence band.

  1. A neutron diffraction study of local stress concentrations surrounding defects in pipeline steel

    NASA Astrophysics Data System (ADS)

    Clapham, L.; Sabet-Sharghi, R.; Holden, T.; Atherton, D. L.

    Magnetic flux leakage (MFL) is the most commonly used technique for the in-service inspection of both gas and oil pipelines. However, MFL is sensitive to the stress state of the pipe wall and the area surrounding defects. MFL tools are often calibrated using pipe sections with defects artificially introduced into the pipe wall prior to the pipe being pressurized. Naturally occurring defects, however, occur while the pipe wall is under stress due to line pressure. In this study, neutron diffraction is used to map the strain surrounding the two defects that have been introduced into plates of pipeline grade steel, one into a plate prior to uniaxial loading, the second into a plate held at a constant background load high enough to ensure that stress at the edge of the defect exceeds the elastic limit of the material.

  2. A study of defects on EUV mask using blank inspection, patterned mask inspection, and wafer inspection

    SciTech Connect

    Huh, S.; Ren, L.; Chan, D.; Wurm, S.; Goldberg, K. A.; Mochi, I.; Nakajima, T.; Kishimoto, M.; Ahn, B.; Kang, I.; Park, J.-O.; Cho, K.; Han, S.-I.; Laursen, T.

    2010-03-12

    The availability of defect-free masks remains one of the key challenges for inserting extreme ultraviolet lithography (EUVL) into high volume manufacturing. yet link data is available for understanding native defects on real masks. In this paper, a full-field EUV mask is fabricated to investigate the printability of various defects on the mask. The printability of defects and identification of their source from mask fabrication to handling were studied using wafer inspection. The printable blank defect density excluding particles and patterns is 0.63 cm{sup 2}. Mask inspection is shown to have better sensitivity than wafer inspection. The sensitivity of wafer inspection must be improved using through-focus analysis and a different wafer stack.

  3. PIXE studies of osteoporosis preventive treatments

    NASA Astrophysics Data System (ADS)

    Ynsa, M. D.; Pinheiro, T.; Ager, F. J.; Alves, L. C.; Millán, J. C.; Gómez-Zubelbia, M. A.; Respaldiza, M. A.

    2002-04-01

    Particle induced X-ray emission (PIXE) and nuclear microprobe (NMP) have been used in an exploratory work to study elemental alterations in tissues of experimental animals submitted to osteoporosis preventive treatments. Osteopathologies have been associated with several factors, such as hormonal disturbances, metabolic aberrations, low dietary Ca and vitamin D intake, excess of iron, among other possible factors. Hormonal treatments seem to be beneficial to the incorporation of Ca in bone but breast and endometrial cancers constitute significant side effects that cannot be ignored. Wistar female rats were used to test the effect of estrogen therapy in osteoporosis progression. The variations of elemental concentrations in uterus and the Ca content of femoral bones of ovariectomised rats under estrogen therapy were investigated. PIXE, Rutherford backscattering spectrometry and secondary electron microscopy techniques were applied for the characterisation of biological materials, with respect to morphology and trace element distribution determination. The increase of Ca and Fe concentrations in uterus and the variations for Ca distribution patterns in bone of rats submitted to estrogen therapy were the major features observed.

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

    SciTech Connect

    Uedono, Akira; Yoshihara, Nakaaki; Mizushima, Yoriko; Kim, Youngsuk; Nakamura, Tomoji; Ohba, Takayuki; Oshima, Nagayasu; Suzuki, Ryoichi

    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.

  5. Li NMR study of heavy-fermion LiV2O4 containing magnetic defects

    SciTech Connect

    Zong, X.; Das, S.; Borsa, F.; Vannette, M.; Prozorov, R.; Schmalian, J.; Johnston, D.

    2008-04-21

    We present a systematic study of the variations of the {sup 7}Li NMR properties versus magnetic defect concentration up to 0.83 mol% within the spinel structure of polycrystalline powder samples and a collection of small single crystals of LiV2O4 in the temperature range from 0.5 to 4.2 K. We also report static magnetization measurements and ac magnetic susceptibility measurements at 14 MHz on the samples at low temperatures. Both the NMR spectrum and nuclear spin-lattice relaxation rate are inhomogeneous in the presence of the magnetic defects. The NMR data for the powders are well explained by assuming that (i) there is a random distribution of magnetic point defects, (ii) the same heavy Fermi liquid is present in the samples containing the magnetic defects as in magnetically pure LiV2O4, and (iii) the influences of the magnetic defects and of the Fermi liquid on the magnetization and NMR properties are separable. In the single crystals, somewhat different behaviors are observed. Remarkably, the magnetic defects in the powder samples show evidence of spin freezing below T {approx} 1.0 K, whereas in the single crystals with similar magnetic defect concentration no spin freezing was found down to 0.5 K. Thus different types of magnetic defects and/or interactions between them appear to arise in the powders versus the crystals, possibly due to the substantially different synthesis conditions of the powders and crystals.

  6. Interaction between epidemiology and laboratory sciences in the study of birth defects: Design of birth defects risk factor surveillance in metropolitan Atlanta

    SciTech Connect

    Lynberg, M.C.; Khoury, M.J. )

    1993-01-01

    Despite years of research, the etiology of most birth defects remains largely unknown. Interview instruments have been the major tools in the search for environmental causes of birth defects. Because of respondents' problems with recognition and recall, interviews are limited in their capacity to measure certain exposures. Laboratory scientists can have a major impact on defining markers of environmental exposure and genetic susceptibility. The Centers for Disease Control is starting a case-control study of serious birth defects on the basis of a population-based surveillance system for birth defects diagnosed during the first year of life in metropolitan Atlanta, Each year, 300 infants with selected birth defects (case subjects) and 100 population-based control subjects (infants without birth defects) will be enrolled in an ongoing study that will supplement surveillance. In addition to conducting extensive maternal interviews, we will collect blood and urine specimens from case and control subjects and their mothers for laboratory testing. Eventually, some environmental sampling may be incorporated. Particular areas of emphasis are (1) nutritional factors, specifically measuring maternal folic acid levels and other micronutrients (e.g., zinc) to explore their role in the etiology of neural tube defects, (2) substance use, specifically measuring cocaine metabolites in the blood and urine to explore their role for specific vascular disruption defects, and (3) environmental factors such as pesticides and aflatoxins, to explore their potential relationships with specific defects. In addition, a DNA bank will be maintained to evaluate the role of specific candidate genes in the etiology of birth defects. The development and testing of these methods could be useful to assess the interaction between environmental exposures and genetic susceptibility in the etiology of birth defects. 15 refs., 1 fig., 1 tab.

  7. Risk factors for neural tube defects in Riyadh City, Saudi Arabia: Case-control study

    PubMed Central

    Salih, Mustafa A M; Murshid, Waleed R; Mohamed, Ashry Gad; Ignacio, Lena C; de Jesus, Julie E; Baabbad, Rubana; El Bushra, Hassan M

    2014-01-01

    Both genetic and non-genetic environmental factors are involved in the etiology of neural tube defects (NTD) which affect 0.5-2/1000 pregnancies worldwide. This study aimed to explore the risk factors for the development of NTD in Saudi population, and highlight identifiable and preventable causes. Similar studies are scarce in similar populations ofthe Arabian Peninsula and North Africa. This is an unmatched concurrent case-control study including NTD cases born at King Khalid University Hospital, Riyadh during a 4-year period (2002-2006). The case-control study included 25 cases and 125 controls (case: control ratio of 1:5). Years of formal education, employment, household environment (including availability of air conditioning) and rate of parental consanguinity did not differ between mothers of cases and controls. Significantly higher proportion of mothers of cases had history of stillbirth compared to control mothers (16% vs 4.1%, P=0.02). Also family history of hydrocephalus and congenital anomalies were more prevalent in cases than controls (P values=0.0000 and 0.003, respectively). There was significant protective effect of periconceptional folic acid consumption both prior to conception (OR 0.02, 95% CI 0.00-0.07) and during the first 6 weeks of conception (OR 0.13, 95% CI 0.04-0.39). Further research, including a larger cohort, is required to enable ascertainment of gene-nutrient and gene environment interactions associated with NTD in Saudi Arabia. PMID:27493405

  8. Ab Initio Study of Defect Properties in YPO4

    SciTech Connect

    Gao, Fei; Xiao, Haiyan Y.; Zhou, Yungang; Devanathan, Ramaswami; Hu, Shenyang Y.; Li, Yulan; Sun, Xin; Khaleel, Mohammad A.

    2012-03-01

    Ab initio methods based on density functional theory have been used to calculate the formation energies of intrinsic defects, including vacancies, interstitials, antisites and Frenkel pairs in YPO4 under the O-rich and Y2O3-rich, and the O-rich and Y-rich conditions. The larger size of the yttrium atom may give rise to higher formation energy of the phosphorus antisite defect. In general, the formation energies of anion interstitials are much smaller than those of cation interstitials for both conditions considered. It is of greatly interest to find that the relative stabilities among the same types of interstitials are independent of the reference states. The most stable configuration for oxygen interstitials is an O-O split interstitial near the Ta site, while the most stable configuration for cation interstitials is a tetrahedral interstitial near the Ta site. The cation split interstitials are unfavorable in YPO4, with much higher formation energies. Furthermore, the properties of Frenkel pairs are compared with those calculated using empirical potentials. The results reveal that both ab initio and empirical potential calculations show a similar trend in the formation energies of Frenkel pairs, but the formation energies obtained by empirical potentials are much larger than those calculated by ab initio method.

  9. Radiation defect dynamics in Si at room temperature studied by pulsed ion beams

    SciTech Connect

    Wallace, J. B.; Myers, M. T.; Charnvanichborikarn, S.; Bayu Aji, L. B.; Kucheyev, S. O.; Shao, L.

    2015-10-07

    The evolution of radiation defects after the thermalization of collision cascades often plays the dominant role in the formation of stable radiation disorder in crystalline solids of interest to electronics and nuclear materials applications. Here, we explore a pulsed-ion-beam method to study defect interaction dynamics in Si crystals bombarded at room temperature with 500 keV Ne, Ar, Kr, and Xe ions. The effective time constant of defect interaction is measured directly by studying the dependence of lattice disorder, monitored by ion channeling, on the passive part of the beam duty cycle. The effective defect diffusion length is revealed by the dependence of damage on the active part of the beam duty cycle. Results show that the defect relaxation behavior obeys a second order kinetic process for all the cases studied, with a time constant in the range of ∼4–13 ms and a diffusion length of ∼15–50 nm. Both radiation dynamics parameters (the time constant and diffusion length) are essentially independent of the maximum instantaneous dose rate, total ion dose, and dopant concentration within the ranges studied. However, both the time constant and diffusion length increase with increasing ion mass. This demonstrates that the density of collision cascades influences not only defect production and annealing efficiencies but also the defect interaction dynamics.

  10. Structure and energy of point defects in TiC: An ab initio study

    NASA Astrophysics Data System (ADS)

    Sun, Weiwei; Ehteshami, Hossein; Korzhavyi, Pavel A.

    2015-04-01

    We employ first-principles calculations to study the atomic and electronic structure of various point defects such as vacancies, interstitials, and antisites in the stoichiometric as well as slightly off-stoichiometric Ti1 -cCc (including both C-poor and C-rich compositions, 0.49 ≤c ≤0.51 ). The atomic structure analysis has revealed that both interstitial and antisite defects can exist in split conformations involving dumbbells. To characterize the electronic structure changes caused by a defect, we introduce differential density of states (dDOS) defined as a local perturbation of the density of states (DOS) on the defect site and its surrounding relative to the perfect TiC. This definition allows us to identify the DOS peaks characteristic of the studied defects in several conformations. So far, characteristic defect states have been discussed only in connection with carbon vacancies. Here, in particular, we have identified dDOS peaks of carbon interstitials and dumbbells, which can be used for experimental detection of such defects in TiC. The formation energies of point defects in TiC are derived in the framework of a grand-canonical formalism. Among the considered defects, carbon vacancies and interstitials are shown to have, respectively, the lowest and the second-lowest formation energies. Their formation energetics are consistent with the thermodynamic data on the phase stability of nonstoichiometric TiC. A cluster type of point defect is found to be next in energy, a titanium [100] dumbbell terminated by two carbon vacancies.

  11. Effectiveness of Folic Acid Fortified Flour for Prevention of Neural Tube Defects in a High Risk Region

    PubMed Central

    Wang, Haochen; De Steur, Hans; Chen, Gong; Zhang, Xiaotian; Pei, Lijun; Gellynck, Xavier; Zheng, Xiaoying

    2016-01-01

    Despite efforts to tackle folate deficiency and Neural Tube Defects (NTDs) through folic acid fortification, its implementation is still lacking where it is needed most, highlighting the need for studies that evaluate the effectiveness of folic acid fortified wheat flour in a poor, rural, high-risk, NTD region of China. One of the most affected regions, Shanxi Province, was selected as a case study. A community intervention was carried out in which 16,648 women of child-bearing age received fortified flour (eight villages) and a control group received ordinary flour (three villages). NTD birth prevalence and biological indicators were measured two years after program initiation at endline only. The effect on the NTD burden was calculated using the disability-adjusted life years (DALYs) method. In the intervention group, serum folate level was higher than in the control group. NTDs in the intervention group were 68.2% lower than in the control group (OR = 0.313, 95% CI = 0.207–0473, p < 0.001). In terms of DALYs, burden in intervention group was approximately 58.5% lower than in the control group. Flour fortification was associated with lower birth prevalence and burden of NTDs in economically developing regions with a high risk of NTDs. The positive findings confirm the potential of fortification when selecting an appropriate food vehicle and target region. As such, this study provides support for decision makers aiming for the implementation of (mandatory) folic acid fortification in China. PMID:27005659

  12. Effectiveness of Folic Acid Fortified Flour for Prevention of Neural Tube Defects in a High Risk Region.

    PubMed

    Wang, Haochen; De Steur, Hans; Chen, Gong; Zhang, Xiaotian; Pei, Lijun; Gellynck, Xavier; Zheng, Xiaoying

    2016-03-01

    Despite efforts to tackle folate deficiency and Neural Tube Defects (NTDs) through folic acid fortification, its implementation is still lacking where it is needed most, highlighting the need for studies that evaluate the effectiveness of folic acid fortified wheat flour in a poor, rural, high-risk, NTD region of China. One of the most affected regions, Shanxi Province, was selected as a case study. A community intervention was carried out in which 16,648 women of child-bearing age received fortified flour (eight villages) and a control group received ordinary flour (three villages). NTD birth prevalence and biological indicators were measured two years after program initiation at endline only. The effect on the NTD burden was calculated using the disability-adjusted life years (DALYs) method. In the intervention group, serum folate level was higher than in the control group. NTDs in the intervention group were 68.2% lower than in the control group (OR = 0.313, 95% CI = 0.207-0473, p < 0.001). In terms of DALYs, burden in intervention group was approximately 58.5% lower than in the control group. Flour fortification was associated with lower birth prevalence and burden of NTDs in economically developing regions with a high risk of NTDs. The positive findings confirm the potential of fortification when selecting an appropriate food vehicle and target region. As such, this study provides support for decision makers aiming for the implementation of (mandatory) folic acid fortification in China. PMID:27005659

  13. Studies of oxygen- and carbon-related defects in high-efficiency silicon solar cells

    NASA Technical Reports Server (NTRS)

    Corbett, J.

    1984-01-01

    Studies were conducted to investigate the vague nature of carbon and oxygen related defects in high efficiency silicon solar cells. High temperature tests were employed to perform these investigations.

  14. Exploiting Defect Clustering to Screen Bare Die for Infant Mortality Failure: An Experimental Study

    NASA Technical Reports Server (NTRS)

    Lakin, David R., II; Singh, Adit D.

    1999-01-01

    We present the first experimental results to establish that a binning strategy based on defect clustering can be used to screen bare die for early life failures. The data for this study comes from the SEMATECH test methods experiment.

  15. Recommendations on the use of folic acid supplementation to prevent the recurrence of neural tube defects. Clinical Teratology Committee, Canadian College of Medical Geneticists.

    PubMed Central

    Van Allen, M I; Fraser, F C; Dallaire, L; Allanson, J; McLeod, D R; Andermann, E; Friedman, J M

    1993-01-01

    OBJECTIVE: To prevent the recurrence of neural tube defects (NTDs) in families at increased risk of having offspring with NTDs with the use of periconceptional folic acid supplementation. OPTIONS: Genetic counselling and prenatal diagnosis of NTDs. OUTCOMES: NTDs cause stillbirth, neonatal death and severe disabilities. The cost for medical care and rehabilitation in the first 10 years of life of a child with spina bifida cystica was estimated to be $42,507 in 1987. EVIDENCE: The authors reviewed the medical literature, communicated with investigators from key studies, reviewed policy recommendations from other organizations and drew on their own expertise. A recent multicentre randomized controlled trial showed that among women at high risk of having a child with an NTD those who received 4 mg/d of folic acid had 72% fewer cases of NTD-affected offspring than nonsupplemented women. Two previous intervention studies also demonstrated that folic acid supplementation was effective in reducing the rate of NTD recurrence. Several retrospective studies support this conclusion. VALUES: Recommendations are the consensus of the Clinical Teratology Committee of the Canadian College of Medical Geneticists (CCMG) and have been approved by the CCMG Board. The committee believes that primary prevention of NTDs is preferable to treatment or to prenatal detection and abortion. BENEFITS, HARMS AND COSTS: Folic acid supplementation should result in fewer NTDs among infants in Canada and ancillary savings in medical costs. The recommended dosage of folic acid is not known to be associated with adverse effects. Higher dosages of folic acid may make vitamin B12 deficiency difficult to diagnose and may alter seizure frequency in patients with epilepsy due to drug interactions with anticonvulsants. RECOMMENDATIONS: A minimum dosage of folic acid of 0.8 mg/d, not to exceed 5.0 mg/d, is recommended along with a well-balanced, nutritious diet for all women who are at increased risk of

  16. Evaluation of accuracy of cone beam computed tomography for measurement of periodontal defects: A clinical study

    PubMed Central

    Banodkar, Akshaya Bhupesh; Gaikwad, Rajesh Prabhakar; Gunjikar, Tanay Udayrao; Lobo, Tanya Arthur

    2015-01-01

    Aims: The aim of the present study was to evaluate the accuracy of Cone Beam Computed Tomography (CBCT) measurements of alveolar bone defects caused due to periodontal disease, by comparing it with actual surgical measurements which is the gold standard. Materials and Methods: Hundred periodontal bone defects in fifteen patients suffering from periodontitis and scheduled for flap surgery were included in the study. On the day of surgery prior to anesthesia, CBCT of the quadrant to be operated was taken. After reflection of the flap, clinical measurements of periodontal defect were made using a reamer and digital vernier caliper. The measurements taken during surgery were then compared to the measurements done with CBCT and subjected to statistical analysis using the Pearson's correlation test. Results: Overall there was a very high correlation of 0.988 between the surgical and CBCT measurements. In case of type of defects the correlation was higher in horizontal defects as compared to vertical defects. Conclusions: CBCT is highly accurate in measurement of periodontal defects and proves to be a very useful tool in periodontal diagnosis and treatment assessment. PMID:26229268

  17. [Occupational medicine preventive studies in West Germany].

    PubMed

    Valentin, H

    1986-01-01

    Prevention is of increasing importance in medicine, particularly in occupational medicine. The programs of health surveillance at the workplace in the Federal Republic of Germany are discussed. In 1983, 1,400,000 examinations of employees were performed; exclusion criteria were fulfilled in 2.1% (0.9% only temporarily). In 1984 the respective numbers were 1,450,000 examinations (1.8%, 0.8%). During the last few years, health surveillance programs markedly have improved the efficiency of prevention of occupational diseases. They will be an important task for occupational physicians in the future. PMID:3087086

  18. Methanol adsorption on magnesium oxide surface with defects: a DFT study

    NASA Astrophysics Data System (ADS)

    Branda, M. M.; Ferullo, R. M.; Belelli, P. G.; Castellani, N. J.

    2003-03-01

    The methanol adsorption on several defects of the magnesium oxide surface were studied. Structural and electronic study with geometrical optimization and natural bond orbital (NBO) analysis were performed using a density functional theory (DFT) method. Oxygen and magnesium with different coordination numbers have very different reactivity in this surface producing dissociated and non-dissociated species. These results are in agreement with infrared spectroscopy observations where CH 3OH, OCH 3 and OH species were found in defective MgO surfaces.

  19. Dropout Prevention: A Study of Prevention Programs Used by High Schools to Increase Graduation Rate

    ERIC Educational Resources Information Center

    Simmons, Christopher L.

    2013-01-01

    This mixed methods study focused on the relationship between dropout prevention programs and graduation rates in one school district in Florida during the 2010-2011 school year. The dropout prevention program data analyzed included high school principals' perceptions in regard to perceived effectiveness, fidelity of implementation, cost efficacy,…

  20. The repair of segmental bone defects with porous bioglass: an experimental study in goat.

    PubMed

    Nandi, Samit K; Kundu, Biswanath; Datta, Someswar; De, Dipak K; Basu, Debabrata

    2009-02-01

    This study was exclusively conducted to evaluate healing of surgically created defects on the radius of adult Black Bengal goat after implantation of porous bioglass blocks and compare the process kinetics with normal healing. Twelve Black Bengal goats were divided randomly into two groups: control and experimental group implanted with bioglass blocks. Unicortical bone defects in radius were generated in all animals under aseptic condition. Local inflammatory reaction and healing of wound, radiological investigations, histological studies, oxytetracycline leveling and angiographic studies were performed up to 90th day post-operatively and compared with normal healing. It has been found that extensive new bone formation originating from host bone towards the implant whereas in control, the process was active from both the ends; the defect site appeared as homogenous nonfluorescent area. Thus, porous bioglass promoted bone formation over the entire extension of the defect independent of size of block in comparison to control group. PMID:18602125

  1. Cofilin 1 activation prevents the defects in axon elongation and guidance induced by extracellular alpha-synuclein

    PubMed Central

    Tilve, Sharada; Difato, Francesco; Chieregatti, Evelina

    2015-01-01

    Impaired adult neurogenesis and axon traumatic injury participate in the severity of neurodegenerative diseases. Alpha-synuclein, a cytosolic protein involved in Parkinson’s disease, may be released from neurons, suggesting a role for excess secreted alpha-synuclein in the onset and spread of the pathology. Here we provide evidence that long term exposure of young neurons to extracellular alpha-synuclein hampers axon elongation and growth cone turning. We show that actin turnover and the rate of movement of actin waves along the axon are altered, due to alpha-synuclein-induced inactivation of cofilin. Upon laser disruption of microfilaments, healing of axons is favored by the increased phosphorylation of cofilin, however, at later time points; the defect in neurite extension prevails, being lost the regulation of cofilin activity. Importantly, overexpression of the active form of cofilin in neurons exposed to alpha-synuclein is able to restore the movement of actin waves, physiological axon elongation and growth cone turning. Our study reveals the molecular basis of alpha-synuclein-driven deficits in growth and migration of newborn neurons, and in elongation and regeneration of adult neurons. PMID:26558842

  2. Bar Study Stories. Issues in Prevention

    ERIC Educational Resources Information Center

    Higher Education Center for Alcohol, Drug Abuse, and Violence Prevention, 2012

    2012-01-01

    This issue of "Issues in Prevention" focuses on the impact of the availability of drinks in licensed establishments, such as bars and taverns on student drinking. This issue contains the following articles: (1) Cheap Drinks at College Bars Can Escalate Student Drinking (John D. Clapp); (2) High Alcohol Outlet Density: A Problem for Campuses and…

  3. Prevention

    MedlinePlus

    ... our e-newsletter! Aging & Health A to Z Prevention Basic Facts & Information Some factors that affect your ... control of the things that you can change. Preventive Recommendations for Adults Aged 65 and Older The ...

  4. Native defects in GaN: a hybrid functional study

    NASA Astrophysics Data System (ADS)

    Diallo, Ibrahima Castillo; Demchenko, Denis

    Intrinsic defects play an important role in the performance of GaN-based devices. We present hybrid density functional calculations of the electronic and possible optical properties of interstitial N (Ni-Ni) , N antisite (NGa) , interstitial Ga (Gai) , Ga antisite (GaN) , Ga vacancy (VGa) , N vacancy (VN) and Ga-N divacancies (VGaVN) in GaN. Our results show that the vacancies display relatively low formation energies in certain samples, whereas antisites and interstitials are energetically less favorable. However, interstitials can be created by electron irradiation. For instance, in 2.5 MeV electron-irradiated GaN samples, a strong correlation between the frequently observed photoluminescence (PL) band centered around 0.85 eV accompanied with a rich phonon sideband of ~0.88 eV and the theoretical optical behavior of interstitial Ga is discussed. N vacancies are found to likely contribute to the experimentally obtained green luminescence band (GL2) peaking at 2.24 eV in high-resistivity undoped and Mg-doped GaN. National Science Foundation (DMR-1410125) and the Thomas F. and Kate Miller Jeffress Memorial Trust.

  5. First-principles study of He point-defects in HCP rare-earth metals

    SciTech Connect

    Li, Yang; Chen, Ru; Peng, SM; Long, XG; Wu, Z.; Gao, Fei; Zu, Xiaotao

    2011-05-01

    He defect properties in Sc, Y, Gd, Tb, Dy, Ho, Er and Lu were studied using first-principles calculations based on density functional theory. The results indicate that the formation energy of an interstitial He atom is smaller than that of a substitutional He atom in all hcp rare-earth metals considered. Furthermore, the tetrahedral interstitial position is more favorable than an octahedral position for He defects. The results are compared with those from bcc and fcc metals.

  6. A Resorbable Antibiotic-Eluting Polymer Composite Bone Void Filler for Perioperative Infection Prevention in a Rabbit Radial Defect Model

    PubMed Central

    Brooks, Benjamin D.; Sinclair, Kristofer D.; Grainger, David W.; Brooks, Amanda E.

    2015-01-01

    Nearly 1.3 million total joint replacement procedures are performed in the United States annually, with numbers projected to rise exponentially in the coming decades. Although finite infection rates for these procedures remain consistently low, device-related infections represent a significant cause of implant failure, requiring secondary or revision procedures. Revision procedures manifest several-fold higher infection recurrence rates. Importantly, many revision surgeries, infected or not, require bone void fillers to support the host bone and provide a sufficient tissue bed for new hardware placement. Antibiotic-eluting bone void fillers (ABVF), providing both osteoconductive and antimicrobial properties, represent one approach for reducing rates of orthopedic device-related infections. Using a solvent-free, molten-cast process, a polymer-controlled antibiotic-eluting calcium carbonate hydroxyapatite (HAP) ceramic composite BVF (ABVF) was fabricated, characterized, and evaluated in vivo using a bacterial challenge in a rabbit radial defect window model. ABVF loaded with tobramycin eliminated the infectious burden in rabbits challenged with a clinically relevant strain of Staphylococcus aureus (inoculum as high as 107 CFU). Histological, microbiological, and radiographic methods were used to detail the effects of ABVF on microbial challenge to host bone after 8 weeks in vivo. In contrast to the HAP/BVF controls, which provided no antibiotic protection and required euthanasia 3 weeks post-operatively, tobramycin-releasing ABVF animals showed no signs of infection (clinical, microbiological, or radiographic) when euthanized at the 8-week study endpoint. ABVF sites did exhibit fibrous encapsulation around the implant at 8 weeks. Local antibiotic release from ABVF to orthopedic sites requiring bone void fillers eliminated the periprosthetic bacterial challenge in this 8-week in vivo study, confirming previous in vitro results. PMID:25815727

  7. A resorbable antibiotic-eluting polymer composite bone void filler for perioperative infection prevention in a rabbit radial defect model.

    PubMed

    Brooks, Benjamin D; Sinclair, Kristofer D; Grainger, David W; Brooks, Amanda E

    2015-01-01

    Nearly 1.3 million total joint replacement procedures are performed in the United States annually, with numbers projected to rise exponentially in the coming decades. Although finite infection rates for these procedures remain consistently low, device-related infections represent a significant cause of implant failure, requiring secondary or revision procedures. Revision procedures manifest several-fold higher infection recurrence rates. Importantly, many revision surgeries, infected or not, require bone void fillers to support the host bone and provide a sufficient tissue bed for new hardware placement. Antibiotic-eluting bone void fillers (ABVF), providing both osteoconductive and antimicrobial properties, represent one approach for reducing rates of orthopedic device-related infections. Using a solvent-free, molten-cast process, a polymer-controlled antibiotic-eluting calcium carbonate hydroxyapatite (HAP) ceramic composite BVF (ABVF) was fabricated, characterized, and evaluated in vivo using a bacterial challenge in a rabbit radial defect window model. ABVF loaded with tobramycin eliminated the infectious burden in rabbits challenged with a clinically relevant strain of Staphylococcus aureus (inoculum as high as 10⁷ CFU). Histological, microbiological, and radiographic methods were used to detail the effects of ABVF on microbial challenge to host bone after 8 weeks in vivo. In contrast to the HAP/BVF controls, which provided no antibiotic protection and required euthanasia 3 weeks post-operatively, tobramycin-releasing ABVF animals showed no signs of infection (clinical, microbiological, or radiographic) when euthanized at the 8-week study endpoint. ABVF sites did exhibit fibrous encapsulation around the implant at 8 weeks. Local antibiotic release from ABVF to orthopedic sites requiring bone void fillers eliminated the periprosthetic bacterial challenge in this 8-week in vivo study, confirming previous in vitro results. PMID:25815727

  8. Antisite defects at oxide interfaces

    NASA Astrophysics Data System (ADS)

    Chen, Hanghui; Millis, Andrew

    We use ab initio calculations to estimate formation energies of cation (transition metal) antisite defects at oxide interfaces and to understand the basic physical effects that drive or suppress the formation of these defects. We find that antisite defects are favored in systems with substantial charge transfer across the interface, while Jahn-Teller distortions and itinerant ferromagnetism can prevent antisite defects and help stabilize atomically sharp interfaces. Our results enable identification of classes of systems that are more and less susceptible to the formation of antisite defects and motivate a range of experimental studies and further theoretical calculations to further explicate the oxide interface systems. This research was supported by National Science Foundation under Grant No. DMR-1120296 (H. Chen) and DOE-ER-046169 (A. J. Millis).

  9. Preventing Fetal Alcohol Syndrome and Other Alcohol-Related Birth Defects: Teacher's Manual and Student Text. High School Edition.

    ERIC Educational Resources Information Center

    Howard, Elizabeth; And Others

    This teacher's manual presents lesson plans for a high-school instructional unit on Fetal Alcohol Syndrome and its less severe manifestations, Alcohol-Related Birth Defects. The lessons cover alcohol's effects during pregnancy, the history of concern about alcohol's effects, consequences of alcohol use in pregnancy, lifestyle risk reduction, and…

  10. Study of mitochondrial respiratory defects on reprogramming to human induced pluripotent stem cells.

    PubMed

    Hung, Sandy S C; Van Bergen, Nicole J; Jackson, Stacey; Liang, Helena; Mackey, David A; Hernández, Damián; Lim, Shiang Y; Hewitt, Alex W; Trounce, Ian; Pébay, Alice; Wong, Raymond C B

    2016-05-01

    Reprogramming of somatic cells into a pluripotent state is known to be accompanied by extensive restructuring of mitochondria and switch in metabolic requirements. Here we utilized Leber's hereditary optic neuropathy (LHON) as a mitochondrial disease model to study the effects of homoplasmic mtDNA mutations and subsequent oxidative phosphorylation (OXPHOS) defects in reprogramming. We obtained fibroblasts from a total of 6 LHON patients and control subjects, and showed a significant defect in complex I respiration in LHON fibroblasts by high-resolution respiratory analysis. Using episomal vector reprogramming, our results indicated that human induced pluripotent stem cell (hiPSC) generation is feasible in LHON fibroblasts. In particular, LHON-specific OXPHOS defects in fibroblasts only caused a mild reduction and did not significantly affect reprogramming efficiency, suggesting that hiPSC reprogramming can tolerate a certain degree of OXPHOS defects. Our results highlighted the induction of genes involved in mitochondrial biogenesis (TFAM, NRF1), mitochondrial fusion (MFN1, MFN2) and glycine production (GCAT) during reprogramming. However, LHON-associated OXPHOS defects did not alter the kinetics or expression levels of these genes during reprogramming. Together, our study provides new insights into the effects of mtDNA mutation and OXPHOS defects in reprogramming and genes associated with various aspects of mitochondrial biology. PMID:27127184

  11. Study of mitochondrial respiratory defects on reprogramming to human induced pluripotent stem cells

    PubMed Central

    Hung, Sandy S.C.; Van Bergen, Nicole J.; Jackson, Stacey; Liang, Helena; Mackey, David A.; Hernández, Damián; Lim, Shiang Y.; Hewitt, Alex W.; Trounce, Ian; Pébay, Alice; Wong, Raymond C.B.

    2016-01-01

    Reprogramming of somatic cells into a pluripotent state is known to be accompanied by extensive restructuring of mitochondria and switch in metabolic requirements. Here we utilized Leber's hereditary optic neuropathy (LHON) as a mitochondrial disease model to study the effects of homoplasmic mtDNA mutations and subsequent oxidative phosphorylation (OXPHOS) defects in reprogramming. We obtained fibroblasts from a total of 6 LHON patients and control subjects, and showed a significant defect in complex I respiration in LHON fibroblasts by high-resolution respiratory analysis. Using episomal vector reprogramming, our results indicated that human induced pluripotent stem cell (hiPSC) generation is feasible in LHON fibroblasts. In particular, LHON-specific OXPHOS defects in fibroblasts only caused a mild reduction and did not significantly affect reprogramming efficiency, suggesting that hiPSC reprogramming can tolerate a certain degree of OXPHOS defects. Our results highlighted the induction of genes involved in mitochondrial biogenesis (TFAM, NRF1), mitochondrial fusion (MFN1, MFN2) and glycine production (GCAT) during reprogramming. However, LHON-associated OXPHOS defects did not alter the kinetics or expression levels of these genes during reprogramming. Together, our study provides new insights into the effects of mtDNA mutation and OXPHOS defects in reprogramming and genes associated with various aspects of mitochondrial biology. PMID:27127184

  12. Positron and positronium studies of irradiation-induced defects and microvoids in vitreous metamict silica

    NASA Astrophysics Data System (ADS)

    Hasegawa, M.; Saneyasu, M.; Tabata, M.; Tang, Z.; Nagai, Y.; Chiba, T.; Ito, Y.

    2000-05-01

    To study irradiation-induced defects and structural microvoids in vitreous silica (v-SiO2), positron lifetime, angular correlation of positron annihilation radiation (ACAR), and electron spin resonance (ESR) were measured on v-SiO2 and quartz (c-SiO2) samples irradiated with fast neutrons up to a dose of 4.1×1020 n/cm2. Two kinds of positron-trapping defects have been found to form in v-SiO2 by fast neutron irradiation: type-I and type-II defects. Similar defects also appear in the irradiated c-SiO2, indicating that both the defects are common in v-SiO2 and c-SiO2. The detailed annealing and photo-illumination studies of positron annihilation and ESR for these two defects suggest that the type-I defects are non-bridging oxygen hole centers (NBOHC), while the type-II defects are oxygen molecules which cannot be detected by ESR. Higher dose irradiation than 1.0×1020 n/cm2 causes c-SiO2 to change to metamict (amorphous) phase (m-SiO2). Positronium (Ps) atoms are found to form in microvoids with an average radius of about 0.3 nm in the v-SiO2 and m-SiO2. This suggests that microvoids proved by Ps are structurally intrinsic open spaces and reflect the topologically disordered structure of these phases in the subnanometer scale.

  13. Craniofacial Birth Defects: The Role of Neural Crest Cells in the Etiology and Pathogenesis of Treacher Collins Syndrome and the Potential for Prevention

    PubMed Central

    Trainor, Paul A.

    2013-01-01

    Of all the babies born with birth defects, approximately one-third display anomalies of the head and face [Gorlin et al., 1990] including cleft lip, cleft palate, small or absent facial and skull bones and improperly formed nose, eyes, ears, and teeth. Craniofacial disorders are a primary cause of infant mortality and have serious lifetime functional, esthetic, and social consequences that are devastating to both children and parents alike. Comprehensive surgery, dental care, psychological counseling, and rehabilitation can help ameliorate-specific problems but at great cost over many years which dramatically affects national health care budgets. For example, the Center for Disease Control and Prevention estimates that the lifetime cost of treating the children born each year with cleft lip and/or cleft palate alone to be US$697 million. Treating craniofacial malformations, of which in excess of 700 distinct syndromes have been described, through comprehensive, well-coordinated and integrated strategies can provide satisfactory management of individual conditions, however, the results are often variable and rarely fully corrective. Therefore, better techniques for tissue repair and regeneration need to be developed and therapeutic avenues of prevention need to be explored in order to eliminate the devastating consequences of head and facial birth defects. To do this requires a thorough understanding of the normal events that control craniofacial development during embryogenesis. This review therefore focuses on recent advances in our understanding of the basic etiology and pathogenesis of a rare craniofacial disorder known as Treacher Collins syndrome and emerging prospects for prevention that may have broad application to congenital craniofacial birth defects. PMID:20734335

  14. Intrinsic defect in BiNbO{sub 4}: A density functional theory study

    SciTech Connect

    Lai Kangrong; Zhu Yingtao; Dai Ying; Huang Baibiao

    2012-08-15

    Formation energies, transition energy levels, and electronic properties of various intrinsic defects in BiNbO{sub 4} systems are studied based on the first-principles density-functional theory. Our results indicate that the acceptor defects form easier than donor defects under O rich condition, while it is opposite under Bi rich condition. Under O-rich condition, Bi vacancies (Bi{sub vac}) leading to p-type conductivity are the dominant intrinsic defects, whereas O vacancies (O{sub vac}) inducing moderate n-type conductivity are the dominant intrinsic defects under Bi-rich condition. Among these intrinsic defects, O{sub vac} is a deep donor; to the contrary, Bi{sub vac} is found to be a shallow acceptor which is benefit to the separation and migration of the photogenerated carriers. Consequently, the BiNbO{sub 4} with Bi{sub vac} under O-rich growth condition should be of better photocatalytic performance.

  15. A new approach to study vacancy defects in high-temperature intermetallic compounds

    SciTech Connect

    Collins, G.S.; Sinha, P.

    1995-08-01

    Perturbed angular correlations of gamma rays (PAC) is being applied to study defects in ordered intermetallic alloys. Vacancies on both Pd and In sublattices in the B2 system PdIn were detected after quenching through quadrupole interactions induced at nearby {sup 111}In probe atoms. Fractions of probe atoms having each type of neighboring defect were observed to increase monotonically with quenching temperature over the range 825--1,500 K. For compositions close to 50.15 at.% Pd, nearly equal site fractions were observed for Pd and In vacancies, indicating that the Schottky vacancy-pair defect is the thermal defect at high temperature. The formation enthalpy of the Schottky defect was determined to be 1.3(2) eV through analysis of quenching data from in the range 825--1,200 K. Above 1200 K, however, the vacancy concentration was observed to saturate at a value of 1.4(2) atomic percent, perhaps due to breakdown of the law of mass action for high defect concentrations.

  16. Acquired Color Vision Defects and Hexane Exposure: A Study of San Francisco Bay Area Automotive Mechanics.

    PubMed

    Beckman, Stella; Eisen, Ellen A; Bates, Michael N; Liu, Sa; Haegerstrom-Portnoy, Gunilla; Hammond, S Katharine

    2016-06-01

    Occupational exposure to solvents, including n-hexane, has been associated with acquired color vision defects. Blue-yellow defects are most common and may be due to neurotoxicity or retinal damage. Acetone may potentiate the neurotoxicity of n-hexane. We present results on nonhexane solvent and hexane exposure and color vision from a cross-sectional study of 835 automotive repair workers in the San Francisco Bay Area, California (2007-2013). Cumulative exposure was estimated from self-reported work history, and color vision was assessed using the Lanthony desaturated D-15 panel test. Log-binomial regression was used to estimate prevalence ratios for color vision defects. Acquired color vision defects were present in 29% of participants, of which 70% were blue-yellow. Elevated prevalence ratios were found for nonhexane solvent exposure, with a maximum of 1.31 (95% confidence interval (CI): 0.86, 2.00) for blue-yellow. Among participants aged ≤50 years, the prevalence ratio for blue-yellow defects was 2.17 (95% CI: 1.03, 4.56) in the highest quartile of nonhexane solvent exposure and 1.62 (95% CI: 0.97, 2.72) in the highest category of exposure to hexane with acetone coexposure. Cumulative exposures to hexane and nonhexane solvents in the highest exposure categories were associated with elevated prevalence ratios for color vision defects in younger participants. PMID:27188942

  17. Migrations of pentagon-heptagon defects in hexagonal boron nitride monolayer: the first-principles study.

    PubMed

    Wang, J; Li, S N; Liu, J B

    2015-04-16

    The first-principles calculations are employed to study the migrations of pentagon-heptagon (5-7) defects in hexagonal boron nitride monolayer (h-BN). A type of grain boundaries, consisted of 5-7 defects, is constructed on the basis of experimental observations. With the absorption of a pair of atoms, one 5-7 defect in the grain boundary migrates apart by one unit cell and afterward migrates again through the bond rotation. It is also found that the two migrations could be replaced by one single step when the pair of absorbed atoms is located at another specific site in the same heptagon. Energy barriers and reaction paths for the migrations of 5-7 defects in h-BN by the bond rotation are theoretically investigated by the standard nudged elastic band method and the generalized solid-state nudged elastic band method. To elucidate the difference between the bond rotation process of the 5-7 defects with N-N bonds and those with B-B bonds, a couple of typical 21.7° grain boundaries with either N-N or B-B bonds are investigated. It is shown that the energy barrier of the migration of defects with N-N bonds is lower than that with B-B bonds in this type of grain boundaries. PMID:25811102

  18. Theoretical and positron annihilation study of point defects in intermetallic compound Ni{sub 3}Al

    SciTech Connect

    Jian Sun; Dongliang Lin

    1994-01-01

    The equilibrium equation of point defects in Ll{sub 2} types of intermetallic compounds was established in a new simple method, which is independent of the chemical potentials. The formation energies of the relevant point defects in Ni{sub 3}Al were calculated by EAM potentials and statical relaxations. The concentration of point defects at 1,000 K as a function of bulk composition and the effect of temperature on them were studied for Ni{sub 3}Al alloy. The results show that the Al-antisites are the constitutional defects in hypostoichiometric Ni{sub 3}Al, and the Ni-antisite defects in hyperstoichiometric Ni{sub 3}Al. The two types of vacancies belong to thermal defects. The positron annihilation technique was also conducted to measure the concentration of vacancies in Ni{sub 3}Al alloys with and without boron. Although vacancies interact with the boron dopant, the changes of vacancy concentration Ni{sub 3}Al alloys can not be considered as the main reason in explaining the effect of stoichiometry on the segregation of boron. The effect of stoichiometry on diffusion in Ni{sub 3}Al alloys was discussed additionally.

  19. Study of Morphological Defects on Dual-Band HgCdTe on CdZnTe

    NASA Astrophysics Data System (ADS)

    Reddy, M.; Radford, W. A.; Lofgreen, D. D.; Olsson, K. R.; Peterson, J. M.; Johnson, S. M.

    2014-08-01

    HgCdTe dual-band epitaxial layers on lattice-matched CdZnTe substrates often have morphological defects. These defects, unlike normal void and microvoid defects, do not contain a polycrystalline core and, therefore, do not offer a good contrast for observation using optical and electron microscopes. This paper reports a way of identifying these defects by using a Nomarski optical microscopy image overlay on focused ion beam microscopy images for preparation of thin cross-sectional foils of these defects. Transmission electron microscopy was used to study the defect cross-sections to identify the origin and evolution of the morphological defects and their effect on the epitaxial layer. This paper reports cross-sectional analysis of four morphological defects of different shape and size.

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

    PubMed Central

    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 < 0.0001]. Overweight women were not at increased risk (OR: 1.00; 95% CI: 0.94, 1.06). The risk in morbidly obese women (BMI ≥ 40) was higher (OR: 1.33; 95% CI: 1.15, 1.54; P = 0.0001) than that in obese women with a BMI of 30–39.9 (OR: 1.11; 95% CI: 1.04, 1.20; P = 0.004). There was a highly significant trend of increasing OR for congenital heart defects with increasing maternal obesity (P < 0.0001). The offspring of obese women had significantly higher ORs for atrial septal defects, hypoplastic left 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

  1. Prevention of Defective Placentation and Pregnancy Loss by Blocking Innate Immune Pathways in a Syngeneic Model of Placental Insufficiency.

    PubMed

    Gelber, Shari E; Brent, Elyssa; Redecha, Patricia; Perino, Giorgio; Tomlinson, Stephen; Davisson, Robin L; Salmon, Jane E

    2015-08-01

    Defective placentation and subsequent placental insufficiency lead to maternal and fetal adverse pregnancy outcome, but their pathologic mechanisms are unclear, and treatment remains elusive. The mildly hypertensive BPH/5 mouse recapitulates many features of human adverse pregnancy outcome, with pregnancies characterized by fetal loss, growth restriction, abnormal placental development, and defects in maternal decidual arteries. Using this model, we show that recruitment of neutrophils triggered by complement activation at the maternal/fetal interface leads to elevation in local TNF-α levels, reduction of the essential angiogenic factor vascular endothelial growth factor, and, ultimately, abnormal placentation and fetal death. Blockade of complement with inhibitors specifically targeted to sites of complement activation, depletion of neutrophils, or blockade of TNF-α improves spiral artery remodeling and rescues pregnancies. These data underscore the importance of innate immune system activation in the pathogenesis of placental insufficiency and identify novel methods for treatment of pregnancy loss mediated by abnormal placentation. PMID:26071558

  2. Air Pollution and the Risk of Cardiac Defects: A Population-Based Case-Control Study.

    PubMed

    Hwang, Bing-Fang; Lee, Yungling Leo; Jaakkola, Jouni J K

    2015-11-01

    Previous epidemiologic studies have assessed the role of the exposure to ambient air pollution in the development of cardiac birth defects, but they have provided somewhat inconsistent results. To assess the associations between exposure to ambient air pollutants and the risk of cardiac defects, a population-based case-control study was conducted using 1087 cases of cardiac defects and a random sample of 10,870 controls from 1,533,748 Taiwanese newborns in 2001 to 2007.Logistic regression was performed to calculate odds ratios for 10 ppb increases in O3 and 10 μg/m increases in PM10. In addition, we compared the risk of cardiac defects in 4 categories-high exposure (>75th percentile); medium exposure (75th to 50th percentile); low exposure (<50th-25th percentile); reference (<25th percentile) based on the distribution of each pollutant. The risks of ventricular septal defects (VSD), atrial septal defects (ASD), and patent ductus arteriosus (PDA) were associated with 10 ppb increases in O3 exposure during the first 3 gestational months among term and preterm babies. In comparison between high PM10 exposure and reference category, there were statistically significant elevations in the effect estimates of ASD for all and terms births. In addition, there was a negative or weak association between SO2, NO2, CO, and cardiac defects.The study proved that exposure to outdoor air O3 and PM10 during the first trimester of gestation may increase the risk of VSD, ASD, and PDA. PMID:26554783

  3. Defect-related internal dissipation in mechanical resonators and the study of coupled mechanical systems.

    SciTech Connect

    Friedmann, Thomas Aquinas; Czaplewski, David A.; Sullivan, John Patrick; Modine, Normand Arthur; Wendt, Joel Robert; Aslam, Dean (Michigan State University, Lansing, MI); Sepulveda-Alancastro, Nelson (University of Puerto Rico, Mayaguez, PR)

    2007-01-01

    Understanding internal dissipation in resonant mechanical systems at the micro- and nanoscale is of great technological and fundamental interest. Resonant mechanical systems are central to many sensor technologies, and microscale resonators form the basis of a variety of scanning probe microscopies. Furthermore, coupled resonant mechanical systems are of great utility for the study of complex dynamics in systems ranging from biology to electronics to photonics. In this work, we report the detailed experimental study of internal dissipation in micro- and nanomechanical oscillators fabricated from amorphous and crystalline diamond materials, atomistic modeling of dissipation in amorphous, defect-free, and defect-containing crystalline silicon, and experimental work on the properties of one-dimensional and two-dimensional coupled mechanical oscillator arrays. We have identified that internal dissipation in most micro- and nanoscale oscillators is limited by defect relaxation processes, with large differences in the nature of the defects as the local order of the material ranges from amorphous to crystalline. Atomistic simulations also showed a dominant role of defect relaxation processes in controlling internal dissipation. Our studies of one-dimensional and two-dimensional coupled oscillator arrays revealed that it is possible to create mechanical systems that should be ideal for the study of non-linear dynamics and localization.

  4. Genome-Wide Association Study of Down Syndrome-Associated Atrioventricular Septal Defects

    PubMed Central

    Ramachandran, Dhanya; Zeng, Zhen; Locke, Adam E.; Mulle, Jennifer G.; Bean, Lora J.H.; Rosser, Tracie C.; Dooley, Kenneth J.; Cua, Clifford L.; Capone, George T.; Reeves, Roger H.; Maslen, Cheryl L.; Cutler, David J.; Feingold, Eleanor; Sherman, Stephanie L.; Zwick, Michael E.

    2015-01-01

    The goal of this study was to identify the contribution of common genetic variants to Down syndrome−associated atrioventricular septal defect, a severe heart abnormality. Compared with the euploid population, infants with Down syndrome, or trisomy 21, have a 2000-fold increased risk of presenting with atrioventricular septal defects. The cause of this increased risk remains elusive. Here we present data from the largest heart study conducted to date on a trisomic background by using a carefully characterized collection of individuals from extreme ends of the phenotypic spectrum. We performed a genome-wide association study using logistic regression analysis on 452 individuals with Down syndrome, consisting of 210 cases with complete atrioventricular septal defects and 242 controls with structurally normal hearts. No individual variant achieved genome-wide significance. We identified four disomic regions (1p36.3, 5p15.31, 8q22.3, and 17q22) and two trisomic regions on chromosome 21 (around PDXK and KCNJ6 genes) that merit further investigation in large replication studies. Our data show that a few common genetic variants of large effect size (odds ratio >2.0) do not account for the elevated risk of Down syndrome−associated atrioventricular septal defects. Instead, multiple variants of low-to-moderate effect sizes may contribute to this elevated risk, highlighting the complex genetic architecture of atrioventricular septal defects even in the highly susceptible Down syndrome population. PMID:26194203

  5. Autologous serum eyedrops for dry eyes and epithelial defects: clinical and in vitro toxicity studies

    PubMed Central

    Poon, A.; Geerling, G.; Dart, J.; Fraenkel, G.; Daniels, J.

    2001-01-01

    BACKGROUND/AIMS—Autologous serum drops have been reported to be beneficial in keratoconjunctivitis sicca (KCS) and persistent epithelial defects (PED). A clinical pilot study was carried out to examine these potential uses and in vitro toxicity testing on corneal epithelial cell cultures was performed to compare the effect of serum drops with unpreserved hypromellose (hydroxypropylmethylcellulose 0.3%).
METHODS—Patients with KCS and PED, unresponsive to conventional treatment were recruited. Patients were examined before treatment, at 1 and 2 weeks after initiation, and then 2 weekly until treatment ceased. Symptoms were assessed at each visit. Clinical examination included Schirmer's test without anaesthesia, rose bengal staining, and fluorescein staining. Epithelial defects were measured with the slit beam. In the laboratory, cultured human corneal epithelial cells were exposed to serum drops and hypromellose, and their viability evaluated with fluorescent viability staining (Calcein AM ethidium homodimer) and an ATP assay.
RESULTS—Autologous serum was used in 15 eyes of 13 patients with PED and 11 eyes of nine patients with KCS. In two patients serum drops were started after penetrating keratoplasty (PK). The PKs were performed for perforations secondary to PEDs. Of the 15 eyes with PED, nine healed at a mean of 29 days and six failed. The mean duration of PED before the use of serum drops was 48.2 days. Of the 11 eyes with KCS, six had improved subjective scores and fluorescein scores, and five had improved rose bengal scores after the use of serum drops. For the two patients who used serum eyedrops post-PK, there was a stable and intact epithelium at 1 week. Cessation of serum drops during the postoperative period led to deterioration in the subjective and objective scores in both patients. One developed a PED that responded to reinstitution of serum drops. The morphology and ATP levels of cultured epithelial cells exposed to serum were

  6. Use of Fisiograft in Intrabony Defects- A Clinical and Radiological Study

    PubMed Central

    Pandey, Ruchi; Madhumala, R.; Saranyan, R.; Sreekanth, P.

    2013-01-01

    Aim: To evaluate the efficacy of Polylactic Acid/Polygycolic Acid (PLA/PGA -Fisiograft®) with Open Flap Debridement (OFD) and OFD alone in the treatment of intrabony defects over a period of 9 months. Material and Methods: Twenty Nine systemically healthy subjects with total of 30 defects were included in the present, randomized, controlled and two arm parallel study. Tests were treated with OFD along with Fisiograft® and controls with OFD alone. Results: On intra-group comparison, clinical parameters at 6 and 9 months showed statistically significant results. On comparing between the two groups, the reduction in Defect Specific Bleeding Score (DSBS), Defect Specific Plaque Score (DSPS), Probing Depth (PD) and gain in Clinical Attachment Level (CAL) revealed no statistical significances other than Recession Depth (REC) which was more in controls. The mean radiographic parameters at 9 months post-operatively in both the groups were statistically significant. However, the inter-group comparison revealed no statistically significant values. Conclusions: The overall results at the end study proved that the adjunctive use of Fisiograft® was not beneficial when compared with OFD alone. Clinical Significance: Synthetic bone replacement graft materials are commonly used for periodontal regeneration. The present study was conducted by using PLA/PGA reveals no additional benefit over OFD alone in treatment of intrabony defects. PMID:24298530

  7. Obesity Prevention Opinions of School Stakeholders: A Qualitative Study

    ERIC Educational Resources Information Center

    Della Torre, Sophie Bucher; Akre, Christina; Suris, Joan-Carles

    2010-01-01

    Background: In general, schools are an important setting to implement current recommendations for obesity prevention in children because the vast majority of children attend school. This study investigated the opinions of different school stakeholders on the feasibility and acceptability of current obesity prevention strategies that could be…

  8. Behavior of chemically amplified resist defects in TMAH solution: III

    NASA Astrophysics Data System (ADS)

    Ono, Yuko; Shimoaoki, Takeshi; Naito, Ryoichiro; Kitano, Junichi

    2004-05-01

    As the minimum feature size of electronic devices shrinks to less than 0.25 μm, it is critically important that we reduce the defects that occur in lithography processes. Moreover, as the defects to be controlled become ever smaller, this makes them increasingly difficult to detect by conventional fault detection equipment. In order to detect these minute defects in the context of shrinking device geometries, it is essential that we develop a clear understanding of the behavior of micro defects in developer. In principle, there are three ways in which these defects might be dealt with: (1) defects can be prevented from occurring in the first place, (2) defects can be prevented from adhering to the device, or (3) defects can be eliminated after they occur. Our recent work has mainly been concerned with the first and most effective approach of preventing defects from occurring in the first place, and this motivated the present study to investigate the mechanisms by which defects occur. We believe that defects occur in chemically amplified (CA) resists that are insufficiently unprotected at boundary regions between unexposed and exposed areas or in unexposed areas, so that the de-protection reaction in the resist suns to different degrees of completion due to varying exposure doses. In this study we investigate the number of defects in various developers, and determine the size distribution of the defects. Based on analysis of the behavior of defects from their size distribution in develop we conclude that: (1) the size of defects increases when the exposure dose is reduced by appropriate Eops, (2) defects originate in the boundary area between unexposed and exposed areas, and (3) a portion of CA resist polymer that is insufficiently deprotected is dispersed in the developer, coalesces and is deposited in a form that is not very soluble, and is manifested as relatively large particle defects.

  9. Laron's Dwarfism: Studies on the Nature of the Defect

    ERIC Educational Resources Information Center

    Elders, M. Joycelyn; And Others

    1973-01-01

    Laron's syndrome, characterized by severe dwarfism, high circulating levels of immunoreactive growth hormone, and failure to generate somatomedin after administration of human growth hormone, was studied in a boy 7 1/2 years of age. (MC)

  10. Dementia in Ageing Mental Defectives: A Clinical and Neuropathological Study.

    ERIC Educational Resources Information Center

    Reid, A. H.; And Others

    1978-01-01

    The study was aimed at establishing the prevalence and clinical features of the psychoses of senescence (senile, presenile, and cerebral arteriosclerotic dementias) in 155 mentally retarded patients over the age of 45. (SBH)

  11. Prevention

    MedlinePlus

    ... Prevention Treatment 2003 U.S. Outbreak African Rodent Importation Ban For Clinicians Clinical Recognition Specimen Collection Treatment Smallpox ... Examining Animals with Suspected Monkeypox African Rodent Importation Ban Resources Related Links Poxvirus Molluscum Contagiosum Orf Virus ( ...

  12. Intracytoplasmic morphologically selected sperm injection and congenital birth defects: a retrospective cohort study.

    PubMed

    Hershko-Klement, A; Sukenik-Halevy, R; Biron Shental, T; Miller, N; Berkovitz, A

    2016-09-01

    Our objective was to study the birth defect rates in intracytoplasmic morphologically selected sperm injection (IMSI) pregnancies. A cohort of couples presenting male factor infertility between January 2006 and January 2014 was retrospectively analyzed. Discharge letters and a telephone interview were performed for assessing pregnancy outcome. All clinical data were reviewed by a board certified medical geneticist. Main outcomes were fetal/birth defect and chromosomal abnormality rates. Two thousand two hundred and fifty-eight pregnancies were available for analysis, of them, 1669 (73.9%) resulting from ICSI and 2258 (26.1%) achieved by IMSI. Pregnancy outcome distribution did not show a significant difference. For the fresh embryo transfer cohort, fetal/birth defect rate was 4.5%, chromosomal aberration rate was 1.0%, and structural malformation rate was 3.5%. IMSI vs. ICSI pregnancies were less likely to involve a fetal/birth defect: 3.5% vs. 4.8%, respectively, but did not reach a statistical significance OR 0.71 (95% CI 0.39-1.22). Split by multiplicity, this trend existed only for singleton pregnancies; 1.4% structural malformations rate vs. 3.8%, respectively, OR 0.35 (95% CI 0.11-0.9). The frozen cohort demonstrated a significantly lower birth defect rate (OR 0.25, 95% CI 0.09-0.58). We conclude that IMSI procedure does not involve an increased malformation rate and may offer a reduced anomaly incidence. Further studies are required. PMID:27317040

  13. Towards optically-integrated scanning tunneling microscopy studies of defects in semiconductors

    NASA Astrophysics Data System (ADS)

    Benjamin, Anne; Lang, Evan; Werner, Kevin; Chowdhury, Enam; Gupta, Jay

    As electronic devices approach the nanoscale, their function is increasingly dependent on the local environment of individual defects. We are developing a combination of optical illumination and scanning tunneling microscopy techniques to study how the properties of individual defects depend on aspects of the local environment, such surface or defect proximity, applied electric fields, and illumination. Here we present studies of individual Zn and Er impurities in GaAs(110).We use controlled motion of the STM tip during voltage sweeps to resolve previously hidden in-gap states of Zn acceptors and probe Zn further from the surface than previously accessible. We discovered two classes of Zn acceptors, one with defect states that did not shift with tip-induced band bending (TIBB), and one with states that do. Similar behavior was observed for above-gap illumination, consistent with the surface photovoltage effect (SPV). For Er on GaAs(110), we discovered three different adsorption states sharing two different sites. We found defect states near the conduction band edge, which shifted with TIBB as well as IR illumination resonant with the Er f-shell transitions.

  14. Monte Carlo study of crystalline order and defects on weakly curved surfaces.

    PubMed

    Hexemer, A; Vitelli, V; Kramer, E J; Fredrickson, G H

    2007-11-01

    We numerically study the ground states of particles interacting via a repulsive Yukawa potential on two rigid substrates shaped as isolated and periodically arranged bumps characterized by a spatially varying Gaussian curvature. Below a critical aspect ratio that describes the substrate deformation, the lattice is frustrated, but defect free. A further increase of the aspect ratio triggers defect unbinding transitions that lower the total potential energy by introducing dislocations either in isolation or within grain boundaries. In the presence of very strong deformations, isolated disclinations are nucleated. We show that the character and spatial distribution of defects observed in the ground state reflect the symmetries and periodicity of the two model surfaces investigated in this study. PMID:18233666

  15. Ab-initio study of magnetism behavior in TiO2 semiconductor with structural defects

    NASA Astrophysics Data System (ADS)

    Zarhri, Z.; Houmad, M.; Ziat, Y.; El Rhazouani, O.; Slassi, A.; Benyoussef, A.; El Kenz, A.

    2016-05-01

    Magnetic, electronic and structural properties of titanium dioxide material with different structural defects are studied using the first-principles ab-initio calculations and the Korringa-Kohn-Rostoker method (KKR) combined with the coherent potential approximation (CPA) method in connection with the local density approximation (LDA). We investigated all structural defects in rutile TiO2 such as Titanium interstitial (Tii), Titanium anti-sites (Tio), Titanium vacancies (VTi), Oxygen interstitial (Oi), Oxygen anti-sites (OTi) and oxygen vacancies (Vo). Mechanisms of hybridization and interaction between magnetic atoms are investigated. The transition temperature is computed using the Mean Field Approximation (MFA).Magnetic stability energy of ferromagnetic and disordered local moment states is calculated to determine the most stable state. Titanium anti-sites have a half-metallic aspect. We also studied the change type caused by structural defects in this material.

  16. A Comparison Study of Creep-Fatigue Defect Growth Evaluations for a SFR IHTS Piping

    NASA Astrophysics Data System (ADS)

    Park, Chang-Gyu; Kim, Jong-Bum; Lee, Jae-Han

    A defect behavior is one of the principal concerns to be dealt with for a structural integrity since defects may lead to the failure of a SFR(Sodium-cooled Fast Reactor) structure under high temperature loading conditions. A thin-walled and large diametric piping is adopted for the IHTS (Intermediate Heat Transport System) piping system of a SFR to enhance the system's economy and to reduce the thermal stress level. The structural material for the piping is Type 316 austenitic stainless steel. In this study, a defect growth evaluation of IHTS piping was performed for a semi-elliptical surface defect subjected to a combined mechanical loading and thermal loading of a high temperature above 500°C including a cyclic loading condition corresponding to a reactor refueling cycle. The creep-fatigue defect behavior evaluations were carried out by following the French Assessment Procedure A16, the UK Assessment Procedure R5 and the JNC procedure. The results were compared with each other and their strong and weak points were discussed. Also the degree of conservatism of each procedure was reviewed.

  17. Study of Near-Neighbor Structure of Point Defects in α-FE by Displacement Cascade

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Lu; Liu, Wei; Wu, Xuebang; Fang, Q. F.; Liu, C. S.; Huang, Qun-Ying; Wu, Y. C.

    2012-07-01

    Molecular dynamics simulations have been performed to study the primary damage formation in α-Fe by collision cascades in the recoil energy range 0.5-20 keV. Two near-neighbor analysis methods including the near-neighbor defect density (NPDD) analysis and cluster analysis were introduced to characterize the spatial aggregation of point defects and the morphologies of clusters, respectively. It is found that the NPDD of self-interstitial atom (SIA) and the number of Frenkel pairs show a similar variation trend, while the NPDD of vacancy exhibits a peak at shorter time than that of SIA. Furthermore, we find that the clusters of point defects exist mostly in the form of chainlike structure in the course and the end of cascades, but the proportion of chainlike clusters decreases with increasing the number of point defects included in one cluster. Therefore, the present methods are found to be effective to characterize the aggregation and the near-neighbor structure of point defects by displacement cascades at any time.

  18. Defect chemistry and electronic transport in low-κ dielectrics studied with electrically detected magnetic resonance

    NASA Astrophysics Data System (ADS)

    Mutch, Michael J.; Lenahan, Patrick M.; King, Sean W.

    2016-03-01

    Defect mediated electronic transport phenomena in low-κ dielectric films are of great technological interest for state-of-the-art and next generation microprocessors. At the present time, the leading low-κ interlayer dielectrics and etch-stop layers are based upon a-SiOC:H and a-SiCN:H, respectively. In this study, we utilize electrically detected magnetic resonance (EDMR), a derivative of electron paramagnetic resonance, to provide physical insight into electronic transport, as well as the nature and origin of defects in dense and porous a-SiOC:H and dense a-SiCN:H films. Resonance measurements are performed before and after the removal of sacrificial porogens via UV treatments to understand the role of specific defect centers in electronic transport in a-SiOC:H systems, and the nature of defects created by UV treatments. Unfortunately, a-SiOC:H and a-SiCN:H EDMR spectra are relatively broad and featureless. These featureless spectra are consistent with fairly complex a-SiOC:H and a-SiCN:H systems. We argue that physical insight may be gleaned from featureless spectra via multiple frequency EDMR. Baseline multiple frequency EDMR measurements are performed in a-Si:H and a-C:H to illustrate the nature of line broadening mechanisms of silicon and carbon related defects.

  19. Comparative Study of Defect Properties in GaN: Ab initio and Empirical Potential Calculations

    SciTech Connect

    Gao, Fei; Bylaska, Eric J.; El-Azab, Anter; Weber, William J.; LM Wang, R Fromknecht, LL Snead, DF Downey and H Takahashi

    2004-04-05

    Density functional theory (DFT) is used to study the formation, properties and atomic configurations of monovacancies, antisite defects and possible interstitials in GaN. The relaxation around a vacancy is generally small, but the relaxation around antisite defects is large, particularly for a Ga antisite defect, which is not stable and converts to an N-N<0001> split interstitial. All N interstitials, starting from any possible sites, eventually transfer into the N-N split interstitials, forming N molecules. In the case of Ga interstitials, the most favorable configuration is the Ga octahedral interstitial. However, it is found that the Ga-Ga<> split interstitial can bridge the gap between non-bonded Ga atoms along the <11-2> direction, which leads to the formation of Ga atomic wires in GaN, with bond distance close to those noted in bulk Ga. In addition, two representative potentials, namely Stillinger-Weber and Tersoff-Brenner potentials, have been employed to deter mine the formation of defects using molecular dynamics (MD) method in GaN. The MD results are discussed and compared to DFT calculations. The present DFT and MD results provide guidelines for evaluating the quality and fit of empirical potentials for large-scale simulations of ion-solid interaction and thermal annealing of defects in GaN.

  20. The Mitochondrial Quality Control Protein Yme1 Is Necessary to Prevent Defective Mitophagy in a Yeast Model of Barth Syndrome*

    PubMed Central

    Gaspard, Gerard J.; McMaster, Christopher R.

    2015-01-01

    The Saccharomyces cerevisiae TAZ1 gene is an orthologue of human TAZ; both encode the protein tafazzin. Tafazzin is a transacylase that transfers acyl chains with unsaturated fatty acids from phospholipids to monolysocardiolipin to generate cardiolipin with unsaturated fatty acids. Mutations in human TAZ cause Barth syndrome, a fatal childhood cardiomyopathy biochemically characterized by reduced cardiolipin mass and increased monolysocardiolipin levels. To uncover cellular processes that require tafazzin to maintain cell health, we performed a synthetic genetic array screen using taz1Δ yeast cells to identify genes whose deletion aggravated its fitness. The synthetic genetic array screen uncovered several mitochondrial cellular processes that require tafazzin. Focusing on the i-AAA protease Yme1, a mitochondrial quality control protein that degrades misfolded proteins, we determined that in cells lacking both Yme1 and Taz1 function, there were substantive mitochondrial ultrastructural defects, ineffective superoxide scavenging, and a severe defect in mitophagy. We identify an important role for the mitochondrial protease Yme1 in the ability of cells that lack tafazzin function to maintain mitochondrial structural integrity and mitochondrial quality control and to undergo mitophagy. PMID:25688091

  1. The mitochondrial quality control protein Yme1 is necessary to prevent defective mitophagy in a yeast model of Barth syndrome.

    PubMed

    Gaspard, Gerard J; McMaster, Christopher R

    2015-04-01

    The Saccharomyces cerevisiae TAZ1 gene is an orthologue of human TAZ; both encode the protein tafazzin. Tafazzin is a transacylase that transfers acyl chains with unsaturated fatty acids from phospholipids to monolysocardiolipin to generate cardiolipin with unsaturated fatty acids. Mutations in human TAZ cause Barth syndrome, a fatal childhood cardiomyopathy biochemically characterized by reduced cardiolipin mass and increased monolysocardiolipin levels. To uncover cellular processes that require tafazzin to maintain cell health, we performed a synthetic genetic array screen using taz1Δ yeast cells to identify genes whose deletion aggravated its fitness. The synthetic genetic array screen uncovered several mitochondrial cellular processes that require tafazzin. Focusing on the i-AAA protease Yme1, a mitochondrial quality control protein that degrades misfolded proteins, we determined that in cells lacking both Yme1 and Taz1 function, there were substantive mitochondrial ultrastructural defects, ineffective superoxide scavenging, and a severe defect in mitophagy. We identify an important role for the mitochondrial protease Yme1 in the ability of cells that lack tafazzin function to maintain mitochondrial structural integrity and mitochondrial quality control and to undergo mitophagy. PMID:25688091

  2. First-principles study on the effects of the intrinsic defects in GaAs saturable absorber

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoyang; Li, Dechun; Zhao, Shengzhi; Cong, Wen; Li, Guiqiu; Yang, Kejian

    2014-11-01

    First-principles calculations are performed for the effects of the intrinsic defects in GaAs saturable absorber, using the state-of-the-art computational method with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional to correct the band gap. The defect energy levels corresponding to all point defects and their electrical characteristics are analyzed from the aspects of density of states and band structures. Furthermore, the partial band decomposed charge density of the defect bands are also been studied. The relationships between defect energy levels and EL2 deep-level defect will be helpful in ascertaining the origin of the EL2 deep-level defect in GaAs.

  3. Numerical study on localized defect modes in two-dimensional lattices: a high Q-resonant cavity

    NASA Astrophysics Data System (ADS)

    Moussa, R.; Salomon, L.; de Fornel, F.; Aourag, H.

    2003-10-01

    The spectral widths and the quality factors of defect modes localized for different defects structures formed in a 2D photonic crystal composed of a square lattice of circular rods of indium antimonide (InSb) are theoretically investigated. It is first shown that some factors such as the lattice nature, the line defect orientation, the nature and the defect width have a significant influence on the optical properties of the studied structures and can improve the Q factor and defect peak transmission intensity. Particularly, the transmission spectra of the defects calculated by means the transfer-matrix-method for a particular structure of eight line defects introduced in its center showed a high-quality factor which exceeded 4×10 5. This is an important issue for the fabrication of photonic crystals with such desired properties.

  4. First-principles study of the structure and stability of oxygen defects in zinc oxide

    NASA Astrophysics Data System (ADS)

    Erhart, Paul; Klein, Andreas; Albe, Karsten

    2005-08-01

    A comparative study on the structure and stability of oxygen defects in ZnO is presented. By means of first-principles calculations based on local density functional theory we investigate the oxygen vacancy and different interstitial configurations of oxygen in various charge states. Our results reveal that dumbbell-like structures are thermodynamically the most stable interstitial configurations for neutral and positive charge states due to the formation of a strongly covalent oxygen-oxygen bond. For negative charge states the system prefers a split-interstitial configuration with two oxygen atoms in almost symmetric positions with respect to the associated perfect lattice site. The calculated defect formation energies imply that interstitial oxygen atoms may provide both donor- and acceptor-like defects.

  5. Encapsulation of fluoroethanols in pristine and Stone-Wales defect boron nitride nanotube - A DFT study

    NASA Astrophysics Data System (ADS)

    Umadevi, P.; Aiswarya, T.; Senthilkumar, L.

    2015-08-01

    The encapsulation of ethanol and fluoroethanols in pristine and Stone-Wales (SW) defect boron nitride nanotubes (BNNT) with and without hydrogen passivation has been investigated using density functional theory method (DFT). The fluoroethanols are physisorped with the charge transfer from alcohols to BNNTs. The adsorption of ethanol is weak in all forms of BNNTs. The hydrogen passivated SW defect BNNTs show strong fluoroethanols adsorption capacity. The deformation energy for SW defect tubes is reduced due to hydrogen passivation. The HOMO-LUMO gap and Fermi level of the BNNTs are altered due to fluoroethanols encapsulation, which subsequently has reduced the work function and improved the electron emission property. The study concludes that BNNTs are efficient materials for ethanol storage and fluoroethanol capture.

  6. Density functional theory study of skyrmion pinning by atomic defects in MnSi

    NASA Astrophysics Data System (ADS)

    Choi, Hong Chul; Lin, Shi-Zeng; Zhu, Jian-Xin

    2016-03-01

    A magnetic skyrmion observed experimentally in chiral magnets is a topologically protected spin texture. For their unique properties, such as high mobility under current drive, skyrmions have a huge potential for applications in next-generation spintronic devices. Defects naturally occurring in magnets have profound effects on the static and dynamical properties of skyrmions. In this work we study the effect of an atomic defect on a skyrmion by performing the first-principles calculations within the density functional theory, taking MnSi as an example. By substituting one site of Mn or Si with different elements, we can tune the pinning energy. The effects of pinning by an atomic defect can be understood qualitatively within a phenomenological model.

  7. Influence of defects on excess charge carrier kinetics studied by transient PC and transient PA

    SciTech Connect

    Feist, H.; Kunst, M.; Swiatkowski, C.

    1997-07-01

    By comparison of transient photoconductivity (TPC) and transient photoinduced absorption (PA) the influence of the density of states in the bandgap on excess charge carrier kinetics is studied for a-Si:H films deposited at different temperatures and for state of the art a-Si:H films in two different states of light soaking. In both series the rising deep defect density leads to an enhancement of electron trapping rather than recombination via deep defects. The samples deposited at temperatures lower than 250 C additionally show a lower effective electron mobility, i.e., a broader conduction band tail.

  8. Positron-annihilation 2D-ACAR studies of disordered and defected alloys

    SciTech Connect

    Bansil, A.; Prasad, R.; Smedskjaer, L.C.; Benedek, R.; Mijnarends, P.E.

    1987-09-01

    Theoretical and experimental progess in connection with 2D-ACAR positron annihilation studies of ordered, disordered, and defected alloys is discussed. We present, in particular, some of the recent developments concerning the electronic structure of disordered alloys, and the work in the area of annihilation from positrons trapped at vacancy-type defects in metals and alloys. The electronic structure and properties of a number of compounds are also discussed briefly; we comment specifically on high T/sub c/ ceramic superconductors, Heusler alloys, and transition-metal aluminides. 58 refs., 116 figs.

  9. Signal to Noise Studies on Thermographic Data with Fabricated Defects for Defense Structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Rajic, Nik; Genest, Marc

    2006-01-01

    There is a growing international interest in thermal inspection systems for asset life assessment and management of defense platforms. The efficacy of flash thermography is generally enhanced by applying image processing algorithms to the observations of raw temperature. Improving the defect signal to noise ratio (SNR) is of primary interest to reduce false calls and allow for easier interpretation of a thermal inspection image. Several factors affecting defect SNR were studied such as data compression and reconstruction using principal component analysis and time window processing.

  10. First-Principles study of defects in transparent conducting oxide materials

    NASA Astrophysics Data System (ADS)

    Amini, Mozhgan

    The study of defects and impurities is an important area in semiconductor physics. Defects can be used to control the electronic and optoelectronic properties of materials. However, to achieve such control, knowledge of the fundamental processes that control doping is necessary. First-principles calculations have already made important contributions to the understanding of these fundamental processes of doping in different semiconductors. An important class of materials with an already widespread application area is the transparent conducting oxides (TCOs). These materials combine electrical conductivity and optical transparency and are essential for photovoltaic and optoelectronic applications. The electronic structure of TCOs has therefore been a subject of interest for a long time. In this thesis we provide a first-principles study of defects in TCO materials using density functional theory (DFT). An introduction to TCO materials, their properties, fabrications, and applications are presented in chapter 1. It is followed by a general explanation of the basics of DFT, a quantum mechanical approach for ground state calculations, in chapter 2. Then in chapter 3, different kinds of defects are classified and some important issues such as donor, acceptor, shallow, deep, formation energy, transition level, optical and thermal ionization energies are introduced. In chapter 4, we have used first principles calculations based on DFT to study point defects in CdO within the local density approximation and beyond (LDA+U). Chapter 5 presented the electronic structure and formation energies of group III elements (Al, Ga, In) doped in ZnO. Then in chapter 6, the effect of the presence of both hydrogen and an extrinsic defect (Al, Ga or In) in ZnO is studied. In chapter 7, ZnM2O4 (M=Co, Rh, Ir) spinels are considered as a class of potential p-type transparent conducting oxides and the formation energies of acceptor-like defects are reported with an advanced hybrid exchange

  11. Atomistic study of multimechanism diffusion by self-interstitial defects in -Fe.

    SciTech Connect

    Anento, Napoleon; Serra, Anna; Osetskiy, Yury N

    2010-01-01

    We present the results of an extensive molecular dynamics study of self-interstitial atom (SIA) clusters containing up to 37 defects over a wide range of temperatures in iron. A long simulation time and high statistics of defect jumps allowed a detailed treatment of the data to be performed. Diffusion exhibits a change in mechanism from three-dimensional to one-dimensional for clusters of 4-7 SIAs. Stable sessile configurations present in the diffusion process are described and their influence on the diffusion parameters is discussed. Diffusion coefficients, correlation factors estimated, and mechanisms observed, are compared with previously published results, and the influence of the interatomic potential is considered.

  12. Simulation studies of defect textures and dynamics in 3-d cholesteric droplets

    NASA Astrophysics Data System (ADS)

    Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Selinger, Robin

    2010-03-01

    We model defect texture evolution in droplets of cholesteric liquid crystals by solving for the dynamics of the nematic director field. In order to accommodate defects in the simulated texture, we use a finite difference formulation that is explicitly independent of sign reversal of the director at any position in the sample. Textures are visualized using either the Berreman 4x4 matrix method or by mapping free energy density. We study both planar and focal conic cholesteric textures in 3-d spherical and cylindrical droplets, with the goal to optimize device geometries for bistable display applications.

  13. Simulation studies of dynamics and defect textures in 3-d cholesteric droplets

    NASA Astrophysics Data System (ADS)

    Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Selinger, Robin

    2010-04-01

    We model defect texture evolution in droplets of cholesteric liquid crystals by solving for the dynamics of the nematic director field. In order to accommodate defects in the simulated texture, we use a finite difference formulation that is explicitly independent of sign reversal of the director at any position in the sample. Textures are visualized using either the Berreman 4x4 matrix method or by mapping free energy density. We study both planar and focal conic cholesteric textures in 3-d spherical and cylindrical droplets, with the goal to optimize device geometries for bistable display applications.

  14. Proton Conduction and Defect Studies in Acceptor - Potassium Tantalate Crystals.

    NASA Astrophysics Data System (ADS)

    Lee, Wing Kit

    The protonic transport properties of the cubic perovskite structured crystal KTaO(,3) doped with transition metal ions (Fe('3+), Cu('2+), etc.) are studied. These dopants substitute for the Ta('5+) ions and require oxygen vacancies for charge compensation. Protons are introduced by annealing the doped crystals in water vapor. A sharp IR peak at 3472 cm('-1) is observed at room temperature. This OH('-) band can be removed by vacuum annealing. Undoped crystals are not susceptible to H('+) incorporation. A reaction is proposed for the incorporation of H('+): H(,2)O + V(,o) (--->) O(,o)('x) + 2H(.). A saturation content of H('+) is always attained which is independent of both pH(,2)O and annealing temperature. Impendence analysis is employed to obtain the bulk electrical conductivity, (sigma). The (sigma) of H('+) charged samples is an order of magnitude higher than that without H('+). The activation energy for conduction, E(,H), for H('+) charged samples is close to 1.05 eV, irrespective of nature of dopants. A rough monotonic relation between (sigma) and (alpha)(,OH), the IR absorption coefficient, is observed. Conductivity calculated from diffusion data is in rough agreement with the measured (sigma). In addi- tion, the protonic transport number is found to be almost unity in an electrochemical cell experiment. The position of the IR peak is the same for different dopants, suggesting no association between dopant and H('+). The presence of an EPR axial spectrum in H('+) free Fe-doped samples and its conversion to a cubic spectrum after charging with H('+) favors the suggestion that H('+) dissociates from dopants. No dielectric relaxa- tion peak related to H('+) is ever observed. E(,H) thus corresponds to migrational energy only. The migration of the proton is probably just the jump of H('+) between neighboring O('2-) ions in the direction of O-H vibration. The isotope effect on (sigma) is also studied when H('+) is replaced entirely by D('+). The result is non

  15. Epigenetic Profiles in Children with a Neural Tube Defect; A Case-Control Study in Two Populations

    PubMed Central

    Stolk, Lisette; Bouwland-Both, Marieke I.; van Mill, Nina H.; Verbiest, Michael M. P. J.; Eilers, Paul H. C.; Zhu, Huiping; Suarez, Lucina; Uitterlinden, André G.; Steegers-Theunissen, Régine P. M.

    2013-01-01

    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, respectively. PMID

  16. A Pilot Study of Emollient Therapy for the Primary Prevention of Atopic Dermatitis

    PubMed Central

    Simpson, Eric L.; Berry, Trista M.; Brown, Peter A.; Hanifin, Jon M.

    2011-01-01

    Background Prevention strategies in atopic dermatitis (AD) using allergen avoidance have not been consistently effective. New research reveals the importance of the skin barrier in the development of AD and possibly food allergy and asthma. Correcting skin barrier defects from birth may prevent AD onset or moderate disease severity. Objective We sought to determine the feasibility of skin barrier protection as a novel AD prevention strategy. Methods We enrolled 22 neonates at high risk for developing AD in a feasibility pilot study using emollient therapy from birth. Results No intervention-related adverse events occurred in our cohort followed up for a mean time of 547 days. Of the 20 subjects who remained in the study, 3 (15.0%) developed AD, suggesting a protective effect when compared with historical controls. Skin barrier measurements remained within ranges seen in normal-appearing skin. Limitations No conclusions regarding efficacy can be made without a control group. Conclusions Skin barrier repair from birth represents a novel and feasible approach to AD prevention. Further studies are warranted to determine the efficacy of this approach. PMID:20692725

  17. Birth Defects. Matrix No. 2.

    ERIC Educational Resources Information Center

    Brent, Robert L.

    This report discusses the magnitude of the problem of birth defects, outlines advances in the birth defects field in the past decade, and identifies those areas where research is needed for the prevention, treatment, and management of birth defects. The problem of birth defects has consumed a greater portion of our health care resources because of…

  18. Profile and risk factors for congenital heart defects: A study in a tertiary care hospital

    PubMed Central

    Abqari, Shaad; Gupta, Akash; Shahab, Tabassum; Rabbani, MU; Ali, S Manazir; Firdaus, Uzma

    2016-01-01

    Introduction: Congenital heart defects (CHDs) are an important cause of mortality and morbidity in children representing a major global health burden. It is thus important to determine their prevalence and spectrum and identify risk factors associated with the development of heart defects. Materials and Methods: A case-control study was carried out in the Department of Pediatrics and Center of Cardiology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh, India, from February 2014 to August 2015. All patients referred with complaints or clinical examination suggestive of CHDs were further evaluated with echocardiography. On Echocardiography, patients having CHDs were included as cases and those having a normal echocardiographic study were included as controls. Healthy controls were also included. 400 cases and 400 controls were thus identified; preterms having patent ductus arteriosus and patent foramen ovale and those with acquired heart defects were excluded. Risk factors among cases and controls were further studied. Results: Acyanotic heart defects were 290 (72.50%) of the total heart defects, whereas the contribution of cyanotic heart defects was 110 (27.50%). Out of all CHDs, ventricular septal defect was the most common lesion with contribution of 152 (38%) cases, whereas among the cyanotic heart defects, Tetralogy of Fallot was the most common lesion (18% of total cases). Out of the total 400 cases, 261 were males (65.25%). On univariate analysis, paternal age (odds ratio, OR, 2.01), bad obstetric history (OR, 2.65), antenatal febrile illness (OR, 4.12), and advanced maternal age (OR, 3.28) were found to increase the risk of CHD whereas intake of multivitamin (OR, 3.02) was found to be protective. The risk factors were further analyzed with multivariate logistic regression analysis and all the above factors were found to be significantly associated. Conclusion: We noted that the profile of CHD in our population was similar

  19. Osteoporosis prevention using soy: the OPUS study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soy isoflavones are believed to have anti-osteoporotic properties. To evaluate the effect of soy isoflavones on bone loss, 403 early postmenopausal women (54.0+/-4.0 y) were enrolled in an intent-to-treat, multi-site, 2-year follow-up, randomized, double-blind study with 1/3 on placebo, 1/3 on 80 mg...

  20. COMPARISON OF GEOCODING METHODS USED IN CASE-CONTROL STUDY OF AIR QUALITY AND BIRTH DEFECTS

    EPA Science Inventory

    Introduction: Accurate geocoding of maternal residence is critical to the success of an ongoing case-control study of exposure to five criteria air pollutants and the risk of selected birth defects in seven Texas counties between 1997 and 2000. The geocoded maternal residence a...

  1. RELATIONAHIP BETWEEN AMBIENT AIR QUALITY AND SELECTED BIRTH DEFECTS, SEVEN COUNTY STUDY, TEXAS, 1997-2000

    EPA Science Inventory

    A population-based case-control study investigated the association between maternal exposure to criteria air pollutants, CO, NO2, O3, SO2, and PM10 during weeks three through eight of pregnancy, and the risk of selected cardiac birth defects and oral clefts among live births and ...

  2. Use of nerve elongator to repair short-distance peripheral nerve defects: a prospective randomized study

    PubMed Central

    Bai, Lu; Wang, Tian-bing; Wang, Xin; Zhang, Wei-wen; Xu, Ji-hai; Cai, Xiao-ming; Zhou, Dan-ya; Cai, Li-bing; Pan, Jia-dong; Tian, Min-tao; Chen, Hong; Zhang, Dian-ying; Fu, Zhong-guo; Zhang, Pei-xun; Jiang, Bao-guo

    2015-01-01

    Repair techniques for short-distance peripheral nerve defects, including adjacent joint flexion to reduce the distance between the nerve stump defects, “nerve splint” suturing, and nerve sleeve connection, have some disadvantages. Therefore, we designed a repair technique involving intraoperative tension-free application of a nerve elongator and obtained good outcomes in the repair of short-distance peripheral nerve defects in a previous animal study. The present study compared the clinical outcomes between the use of this nerve elongator and performance of the conventional method in the repair of short-distance transection injuries in human elbows. The 3-, 6-, and 12-month postoperative follow-up results demonstrated that early neurological function recovery was better in the nerve elongation group than in the conventional group, but no significant difference in long-term neurological function recovery was detected between the two groups. In the nerve elongation group, the nerves were sutured without tension, and the duration of postoperative immobilization of the elbow was decreased. Elbow function rehabilitation was significantly better in the nerve elongation group than in the control group. Moreover, there were no security risks. The results of this study confirm that the use of this nerve elongator for repair of short-distance peripheral nerve defects is safe and effective. PMID:25788924

  3. Association between Prenatal Exposure to Antiretroviral Therapy and Birth Defects: An Analysis of the French Perinatal Cohort Study (ANRS CO1/CO11)

    PubMed Central

    Sibiude, Jeanne; Mandelbrot, Laurent; Blanche, Stéphane; Le Chenadec, Jérôme; Boullag-Bonnet, Naima; Faye, Albert; Dollfus, Catherine; Tubiana, Roland; Bonnet, Damien; Lelong, Nathalie; Khoshnood, Babak; Warszawski, Josiane

    2014-01-01

    Background Antiretroviral therapy (ART) has major benefits during pregnancy, both for maternal health and to prevent mother-to-child transmission of HIV. Safety issues, including teratogenic risk, need to be evaluated. We estimated the prevalence of birth defects in children born to HIV-infected women receiving ART during pregnancy, and assessed the independent association of birth defects with each antiretroviral (ARV) drug used. Methods and Findings The French Perinatal Cohort prospectively enrolls HIV-infected women delivering in 90 centers throughout France. Children are followed by pediatricians until 2 y of age according to national guidelines. We included 13,124 live births between 1994 and 2010, among which, 42% (n = 5,388) were exposed to ART in the first trimester of pregnancy. Birth defects were studied using both European Surveillance of Congenital Anomalies (EUROCAT) and Metropolitan Atlanta Congenital Defects Program (MACDP) classifications; associations with ART were evaluated using univariate and multivariate logistic regressions. Correction for multiple comparisons was not performed because the analyses were based on hypotheses emanating from previous findings in the literature and the robustness of the findings of the current study. The prevalence of birth defects was 4.4% (95% CI 4.0%–4.7%), according to the EUROCAT classification. In multivariate analysis adjusting for other ARV drugs, maternal age, geographical origin, intravenous drug use, and type of maternity center, a significant association was found between exposure to zidovudine in the first trimester and congenital heart defects: 2.3% (74/3,267), adjusted odds ratio (AOR) = 2.2 (95% CI 1.3–3.7), p = 0.003, absolute risk difference attributed to zidovudine +1.2% (95% CI +0.5; +1.9%). Didanosine and indinavir were associated with head and neck defects, respectively: 0.5%, AOR = 3.4 (95% CI 1.1–10.4), p = 0.04; 0.9%, AOR = 3.8 (95% CI 1.1–13.8), p = 0

  4. Effect of hole doping on the magnetism of point defects in graphene: A theoretical study

    NASA Astrophysics Data System (ADS)

    Yndurain, Felix

    2014-12-01

    Using ab initio methods based on the density functional theory, we study the magnetic properties of different point defects in graphene. We consider separately, atomic hydrogen, atomic fluorine, and single vacancies. The three defects have completely different magnetic properties. A local spin one-half magnetic moment is well defined at a hydrogen impurity, while single fluorine adatoms do not induce a well-defined magnetic moment unless there is a fluorine concentration of at least of a 0.5%. In this case, the induced magnetic moment is of the order of 0.45 μB per defect. This behavior is interpreted as being due to the charge transfer between fluorine and graphene. The case of magnetic moments localized at π electrons near vacancies is different from both previous cases; the size of the induced magnetic moment decreases with the dilution of defects and it is compatible with zero in the isolated vacancy. The effect of hole doping on these magnetic behaviors is studied and compared with the available experimental data. In the three cases, hole doping inhibits the formation of π states magnetic moments.

  5. Periodic health examination, 1994 update: 3. Primary and secondary prevention of neural tube defects. Canadian Task Force on the Periodic Health Examination.

    PubMed Central

    1994-01-01

    OBJECTIVE: To make recommendations on nutritional interventions and screening manoeuvres to prevent the birth of infants with neural tube defects (NTDs). OPTIONS: Folic acid consumption through diet or supplementation in women at low risk and at high risk of having a fetus with an NTD, and maternal serum alpha-fetoprotein (MSAFP) screening in low-risk pregnancies. OUTCOMES: A reduction in the incidence rate of NTDs and potentially harmful effects of false-positive results of screening tests (i.e., abortion of a normal fetus). EVIDENCE: A MEDLINE search with the use of medical subject headings "neural tube defects," "prenatal diagnosis" and "prevention and control" identified 103 original articles published between January 1979 and March 1993. Two reviewers extracted the data by applying the rules of evidence developed by the Canadian Task Force on the Periodic Health Examination. VALUES: The task force's evidence-based methods and values were used; high value was placed on prevention of NTDs and on limitation of the harmful effects of a pregnancy involving a fetus with an NTD. BENEFITS, HARMS AND COSTS: Evidence suggests that folic acid supplementation can decrease the incidence rate of NTDs in low-risk pregnancies by 40% to 60% with no adverse effects. MSAFP screening between the 16th and 18th weeks of gestation can reach a sensitivity of 83% and a specificity of 98% when it is used as part of an organized program. The effect of screening on the incidence rate of NTDs depends on whether affected fetuses are aborted. RECOMMENDATIONS: All women of childbearing age should be advised to increase their consumption of folic acid through diet or supplementation to 0.4 mg/d beginning 1 month before pregnancy and ending at the start of the second trimester. MSAFP screening is recommended in low-risk pregnancies only when it is part of a screening program that includes access to all necessary diagnostic services. High-risk women should be referred to genetic counselling

  6. Atomic-Scale Studies of Defect Interactions with Homo- and Heterophase Interfaces

    NASA Astrophysics Data System (ADS)

    Martínez, Enrique; Uberuaga, Blas P.; Beyerlein, Irene J.

    2016-04-01

    Interfaces are planar metastable defects with singular features capable of controlling diverse material properties, including mechanical response and the microstructure evolution in materials under irradiation. This ability of interfaces to dictate the material response resides inherently in their atomic structure, which controls the interactions of dislocations as well as point and defect clusters with the interface. We recently showed how dislocations nucleated from defect clusters interact with a heterophase interface in Cu-Nb layered composites. We also showed how the ability of the interface to absorb vacancy clusters depends on the atomic structure at the interface. Herein, we elaborate on the effect of the atomic structure on the ability of the interface to absorb dislocations as well as vacancy and self-interstitial defect clusters. We study a physical-vapor-deposited Kurdjumov-Sachs orientation in a Cu-Nb interface and an asymmetric Σ 11 grain boundary in pure Cu. On the one hand, the manner in which dislocations react with the interface depends on the misfit dislocation arrangement, which substantially differs between these two cases. On the other hand, vacancy and self-interstitial clusters are absorbed similarly upon interaction with both structures.

  7. Point defects in YBa2Cu3O7-x studied using positron annihilation

    NASA Astrophysics Data System (ADS)

    Chudy, Michal; Eisterer, M.; Weber, H. W.; Veterníková, J.; Sojak, S.; Slugeň, V.

    2012-07-01

    Fast neutron irradiation is a powerful technique for introducing additional pinning centers into high temperature superconductors. The spherical defects with sizes of a few nanometers are considered to be effective pinning centers, enhancing Jc. Their morphology is well-known and has already been investigated by several authors in great detail. However, only very little is known about the nature and density of smaller and point defects, which are invisible in transmission electron microscopy. Positron annihilation lifetime spectroscopy was applied to investigate the nature and the concentration of small point-like defects. In this work, the influence of small point defects, such as vacancies and vacancy clusters, on the superconducting properties of YBa2Cu3O7-x bulks was studied; these were introduced by irradiation in the TRIGA Mark II reactor in Vienna. Jc and Tc measurements were performed prior to and after each irradiation step. The samples were irradiated up to a fast neutron ( > 0.1 MeV) fluence of 6 × 1021 m-2. The two kinds of defects—the large collision cascades and the small point-like defects—contribute to the decrease of Tc as well as to the Jc enhancement in astonishingly similar ways.

  8. Adipose derived stem cells for treatment of mandibular bone defects: An autologous study in dogs

    PubMed Central

    Haghighat, Abbas; Akhavan, Ali; Hashemi-Beni, Batool; Deihimi, Parviz; Yadegari, Afshin; Heidari, Fariba

    2011-01-01

    Background: The aim of this research was to evaluate the effect of adipose derived stem cells on bone repair in through and through mandibular bone defects of canine. Materials and Methods: In this prospective comparative study, adipose-derived stem cells were isolated from subcutaneous fat of lateral thoracic area of 4 dogs. The isolated cells were cultured and expanded through 3 passages. The undifferentiated stem cells were seeded in Collatamp and transferred into mandibular bone through-and-through defects. Similar defects on control group were filled with cell-free Collatamp. After 6 weeks, biopsies were taken and histomorphometric analysis was performed. The percentage of new bone formation was measured in each case. The data were subject to statistical analysis using the Wilcoxon test. Differences at P≤0.05 were considered significant. Results: H and E staining of decalcified samples revealed more bone formation in the group, which stem cells were seeded. Cell-free collatamp group revealed an average bone regeneration of %41±13.21, while adipose derived stem cell-seeded collatamp group showed %49±8.24. Conclusion: The use of stem cell seeded collatamp scaffold in mandibular defects caused more bone regeneration. PMID:23372596

  9. Evaluation of bone response to various anorganic bovine bone xenografts: an experimental calvaria defect study.

    PubMed

    Tovar, N; Jimbo, R; Gangolli, R; Perez, L; Manne, L; Yoo, D; Lorenzoni, F; Witek, L; Coelho, P G

    2014-02-01

    This in vivo study investigated the in vivo performance of two newly developed synthetic bone substitutes and compared them to commercially available xenografts (Bio-Oss, Geistlich Pharma AG, Switzerland; OsteoGraf, Dentsply, USA). The materials were tested in a rabbit calvaria model, and the bone forming properties were observed at 4 and 8 weeks after implantation by means of histomorphometry and micro computed tomography (micro-CT). Defects without any graft material were used as negative controls. Micro-CT showed that all materials tested presented new bone formation that filled the defects at both time points, whereas the negative control presented less bone formation, with soft tissue infiltration into the defects. Comparable bone fill percentages were observed for histomorphometric and micro-CT results. Even though no statistically significant difference was found quantitatively between all of the bone graft substitute groups, a higher mean decrease in graft material filling the defects, along with higher remodelling activity, was evident for the experimental materials compared to the commercially available xenografts at 8 weeks. The results indicate that the experimental materials possess high degradability, along with osteoconduction comparable to commercially available xenografts. PMID:23948358

  10. Electron spin resonance study of point defects in thermal GaAs/GaAs-oxide structures

    NASA Astrophysics Data System (ADS)

    Nguyen, S.; Afanas'ev, V. V.; Stesmans, A.

    2012-12-01

    In an attempt to atomically assess interface and oxide-related point defects, a first basic multifrequency low-temperature electron spin resonance study has been carried out on semi-insulating (Fe compensated) GaAs/oxide structures, implying both powders and (100)GaAs/oxide slices, thermally grown in the range Tox=350-615 °C. Various spectra are observed: As for powders, this includes the 4-line EL2 defect spectrum centered at g~2.043 and characterized by the isotropic hyperfine constant Aiso~ 910 G, ascribed to the 75AsGa+ antisite defect. Observed in freshly crushed powder, it substantially increases in density with oxidation, in line with theoretical expectation; A maximum appears reached for at Tox~440 °C. It is not observed in the parent c-GaAs wafer. A second isotropic signal is observed at g~1.937 in powders for Tox in the range 510-615 °C, but only after additional VUV irradiation; it may correspond to As clusters. In bulk (100)GaAs, we observe the 5-branch spectrum of substitutional Fe impurities (spin S=5/2) in GaAs, with inferred crystal field constant a ≈ 360 G, well in line with previous observations. The results are discussed within the framework of advanced theoretical interface and defect models and previous experimental assessment.

  11. Atomic-Scale Studies of Defect Interactions with Homo- and Heterophase Interfaces

    NASA Astrophysics Data System (ADS)

    Martínez, Enrique; Uberuaga, Blas P.; Beyerlein, Irene J.

    2016-06-01

    Interfaces are planar metastable defects with singular features capable of controlling diverse material properties, including mechanical response and the microstructure evolution in materials under irradiation. This ability of interfaces to dictate the material response resides inherently in their atomic structure, which controls the interactions of dislocations as well as point and defect clusters with the interface. We recently showed how dislocations nucleated from defect clusters interact with a heterophase interface in Cu-Nb layered composites. We also showed how the ability of the interface to absorb vacancy clusters depends on the atomic structure at the interface. Herein, we elaborate on the effect of the atomic structure on the ability of the interface to absorb dislocations as well as vacancy and self-interstitial defect clusters. We study a physical-vapor-deposited Kurdjumov-Sachs orientation in a Cu-Nb interface and an asymmetric Σ 11 grain boundary in pure Cu. On the one hand, the manner in which dislocations react with the interface depends on the misfit dislocation arrangement, which substantially differs between these two cases. On the other hand, vacancy and self-interstitial clusters are absorbed similarly upon interaction with both structures.

  12. Comparison of residential geocoding methods in population-based study of air quality and birth defects.

    PubMed

    Gilboa, Suzanne M; Mendola, Pauline; Olshan, Andrew F; Harness, Catherine; Loomis, Dana; Langlois, Peter H; Savitz, David A; Herring, Amy H

    2006-06-01

    Our population-based case-control study of air quality and birth defects in Texas relied on the geocoding of maternal residence from vital records for the assignment of air pollution exposures during early pregnancy. We attempted to geocode the maternal addresses for 5,338 birth defect cases and 4,574 frequency-matched controls using an automated procedure with standard matching criteria in ArcGIS 8.2 and 8.3. Initially, we matched 7,266 observations (73%). To increase the proportion of successful matches, we used an interactive procedure for the 2,646 addresses that were initially not geocoded by the software. This yielded an additional 985 matches (37%). Using the same 2,646 initially unmatched addresses, we compared the results of this interactive procedure to those of an automated procedure using lower standards. The automated procedure with lower standards yielded more matches (n=1,559, 59%) but with questionable accuracy. We included the interactively geocoded observations in our final data set. Their inclusion did not affect the estimates of air pollution exposure but increased our statistical power to detect associations between air quality and risk of selected birth defects. The geocoded and not geocoded populations differed in the distribution of Latino ethnicity (51% vs 59%) and ethnicity was independently associated with air pollution exposures (P<0.05). Geocoding status also appeared to modify the association between ethnicity and risk of birth defects; Latina women appeared to have a slightly lower risk of birth defects than non-Latina women in the geocoded population and to have a slightly higher risk in the not geocoded population. Incomplete geocoding may have resulted in a selection bias because of the under-representation of Latinas in our study population. PMID:16483563

  13. A study of vacancy defects related to gray tracks in KTiOPO{sub 4} (KTP) using positron annihilation

    SciTech Connect

    Zhang, Yang; Li, Jing; Wang, Jiyang Jiang, Huaidong; Cao, Xingzhong; Yang, Jing

    2014-12-15

    For the first time to our knowledge, positron annihilation spectroscopy (PAS) was used to study vacancy defects in KTiOPO{sub 4} (KTP) single crystals. Positron annihilation lifetime spectroscopy combined with dielectric measurements identified the existence of oxygen vacancies and reflected the concentration of vacancy defects in three samples. The vacancy defects in KTP do not consist of monovacancies, but rather vacancy complexes. Doppler broadening indicates that the vacancy defects are distributed uniformly. A relationship is established where a crystal with a low oxygen vacancy concentration and a highly balanced stoichiometry has a higher resistance to gray track formation.

  14. A study of vacancy defects related to gray tracks in KTiOPO4 (KTP) using positron annihilation

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Li, Jing; Cao, Xingzhong; Yang, Jing; Wang, Jiyang; Jiang, Huaidong

    2014-12-01

    For the first time to our knowledge, positron annihilation spectroscopy (PAS) was used to study vacancy defects in KTiOPO4 (KTP) single crystals. Positron annihilation lifetime spectroscopy combined with dielectric measurements identified the existence of oxygen vacancies and reflected the concentration of vacancy defects in three samples. The vacancy defects in KTP do not consist of monovacancies, but rather vacancy complexes. Doppler broadening indicates that the vacancy defects are distributed uniformly. A relationship is established where a crystal with a low oxygen vacancy concentration and a highly balanced stoichiometry has a higher resistance to gray track formation.

  15. Stability of tibial defect reconstruction with fibular graft and unilateral external fixation: a finite element study

    PubMed Central

    Chen, Huiqiang; Zhang, Ying; Xia, Hong; Wang, Fei; Li, Zhibo; Chen, Xuxiang

    2014-01-01

    Tibial defect is generally caused by high-energy injury, tumor, osteomyelitis, development deformity and bone non-union after internal fixation. This study was to determine stability of tibial defect reconstruction with fibular graft (FG) of different lengths by single free vascularized fibular graft (SFVFG) and double-barrel free vascularized fibular graft (DBFVFG). The left lower extremity of a male volunteer was scanned with computer tomography scanner. The contours of the tibia and fibula were extracted and the geometry of both bones rebuilt. From this intact model, the models of tibial defect reconstruction with fibular graft and external fixation were developed. Inter-fragmentary motion (IFM) and Von Mises stress on the fibular bone flap, and the locations of maximum Von Mises stress were introduced to quantify the biomechanical environment. Under the condition of the same graft length, the Von Mises stress value in DBFVFG group was 1.37 to 1.77 times higher than that in SFVFG group. When the length of graft was greater than 15 cm in the SFVFG group, the IFM exceeded 1 mm, but the IFM of the graft in the DBFVFG group was always less than 1 mm. The maximum Von Mises stress of models was frequently located at the second or third pin-bone interface. Thus, external fixation can provide a stable biomechanical environment for the reconstruction of tibial defect by both SFVFG and DBFVFG. The second or third pin-bone interface requires intensive care and that in the reconstruction of tibial defect by SFVFG, the graft length should not exceed 15 cm. PMID:24482691

  16. The Influence of Grain Boundaries on Radiation-Induced Point Defect Production in Materials: A Review of Atomistic Studies

    SciTech Connect

    Xian-Ming Bai; Blas P. Uberuaga

    2013-03-01

    Radiation-induced defects cause severe degradation of materials properties during irradiation that can ultimately cause the material to fail. Consequences of these defects include swelling, embrittlement, and undesirable phase transformations. Nanocrystalline materials, which contain a high density of grain boundaries, have demonstrated enhanced radiation tolerance compared to large grain counterparts under certain conditions. This is because, as has long been recognized, grain boundaries can serve as defect sinks for absorbing and annihilating radiation-induced defects. Increasingly, researchers have examined how grain boundaries influence the direct production of defects during collision cascade, the origin of the radiation-induced defects. In this review article, we analyze the computational studies in this area that have been performed during the past two decades. These studies examine defect production near grain boundaries in metallic, ionic, and covalent systems. It is found that, in most systems, grain boundaries absorb more interstitials than vacancies during the defect production stage. While this is generically true of most boundaries, the detailed interaction between defects and grain boundaries does depend on boundary atomic structure, the stress state near the boundary, cascade-boundary separation, and materials properties. Furthermore, the defect distribution near boundaries is qualitatively different from that in single crystals, with the former often exhibiting larger vacancy clusters and smaller interstitial clusters than the latter. Finally, grain boundaries that are damaged after cascades have occurred exhibit different interaction behavior with defects than their pristine counterparts. Together, these atomistic simulation results provide useful insight for both developing higher-level modeling of defect evolution at long timescales and how interfaces influence radiation damage evolution.

  17. One-Step Surgical Procedure for the Treatment of Osteochondral Defects with Adipose-Derived Stem Cells in a Caprine Knee Defect: A Pilot Study

    PubMed Central

    Jurgens, Wouter J.F.M.; Kroeze, Robert Jan; Zandieh-Doulabi, Behrouz; van Dijk, Annemieke; Renders, Greetje A.P.; Smit, Theo H.; van Milligen, Florine J.; Ritt, Marco J.P.F.

    2013-01-01

    Abstract Regenerative therapies offer attractive alternatives for the treatment of osteochondral defects. Adipose-derived stromal vascular fraction (SVF) cells allow the development of one-step surgical procedures by their abundant availability and high frequency. In this pilot study we evaluated the in vivo safety, feasibility, and efficacy of this concept using scaffolds seeded with freshly isolated (SVF) or cultured adipose stem cells (ASCs), and compared these to their acellular counterparts. Osteochondral defects were created in medial condyles and trochlear grooves in knees of eight goats. Defects were filled with acellular collagen I/III scaffolds or scaffolds seeded with SVF cells or cultured ASCs. Osteochondral regeneration was evaluated after 1 and 4 months by macroscopy, immunohistochemistry, biomechanical analysis, microCT analysis, and biochemistry. After 1 month, no adverse effects were noted. Microscopic, but not macroscopic evaluation showed considerable yet not significant differences, with cell-loaded constructs showing more extensive regeneration. After 4 months, acellular constructs displayed increased regeneration, however, to a lesser degree than cell-treated constructs. The latter exhibited more extensive collagen type II, hyaline-like cartilage, and higher elastic moduli, and their glycosaminoglycan content in the cartilaginous layer better approached native tissue values. Moreover, their defect regions contained higher levels of regenerated, mature subchondral bone with more intense collagen type I staining. SVF cells tended to perform best on all parameters. In summary, this pilot study demonstrated the preclinical safety and feasibility of a one-step surgical procedure for osteochondral defect regeneration. Similar regeneration was found between freshly isolated SVF cells and cultured ASCs. Larger studies with longer follow-up are required to substantiate these findings. PMID:23914338

  18. Study of defects in insulators by the hybrid method with floating 1-s Gaussian basis

    NASA Astrophysics Data System (ADS)

    Song, K. S.; Emery, L.; Brunet, G.; Leung, C. H.

    1984-02-01

    A hybrid method is developed for the study of electronic states of localized defects in insulators. In this method, the inner shells of an atom (or ion) are represented by the first few orders of the ion size terms, while the outmost s and p shells are treated exactly as in the extended ion model. By the use of floating 1-s Gaussians as basis functions for the defect states, it is shown that the various terms (Coulomb, exchange and overlap) for the outermost s and p shells can be accurately represented by simple interpolation forms. This hybrid method retains the essential features of the extended ion model, but is much more efficient to apply. The method is first applied to study the electronic structure of the atomic-type self-trapped excitons in solid Ne. The results are in good agreement with experiment. The stability of the electron-bubble state in solid Ne is examined by the same method. Electronic states of F-centers in alkali halides are also studied. In this case, the effect of core wavefunctions on the defect states is examined by employing two different sets of core wavefunctions in the calculation: (1) free ion core wavefunctions and (2) core wavefunctions of ions in the crystal. The latter set of core wavefunctions is found to give energies in better agreement with experiment. A preliminary study of the self-trapped excitons in alkali halides is also reported.

  19. Bioactive glass in cavitary bone defects: a comparative experimental study in rabbits

    PubMed Central

    Camargo, André Ferrari de França; Baptista, André Mathias; Natalino, Renato; de Camargo, Olavo Pires

    2015-01-01

    OBJECTIVES: To compare bioactive glass and autograft regarding their histomorphometric characteristics. METHODS: The authors conducted a prospective case-control experimental study on animals in order to compare the histomorphometric characteristics of bioactive glass versus autograft. Eight rabbits underwent surgery in which a cavitary defect was created in both proximal femurs. One side was filled with bioactive glass granules and the other, with autograft grafted from the contralateral side. The sides were randomized. Fourteen days after surgery, the animals were euthanized. RESULTS: Histologic analysis revealed that bone neoformation was equivalent among the two groups and the osteoblasts cell-count was higher in the femurs treated with bioactive glass. The osteocytes cell-count, however, was lower. The similarity in bone formation between both groups was consistent to literature findings. CONCLUSION: Bioactive glass is similar to autograft regarding bone neoformation in this animal model of cavitary bone defects. Level of Evidence III, Case-Control Study. PMID:26327802

  20. Mechanism of forming defects in roll-to-roll hot embossing of micro-pyramid arrays: II. Numerical study

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Yi, Peiyun; Deng, Yujun; Peng, Linfa; Lai, Xinmin; Ni, Jun

    2015-11-01

    Roll-to-roll (R2R) hot embossing is a continuous imprinting technique for the replication of large-area microstructures. Polymer deformation and recovery behavior is more complicated in this process than in the traditional plate-to-plate mode, especially for the embossing of 3-dimensional (3D) structures, such as the micro-pyramid structure used for reflective film. As a result, forming defects of poor shape and dimensional accuracy are more likely to emerge and are of greater diversity, which may negatively influence product quality and must be eliminated. In our previous experimental study, we have defined several types of forming defects that are commonly seen in embossed micro-pyramid arrays and have discussed the influence of processing parameters on the forming defects systematically. What is presented in this article is devoted to the simulation analysis of the forming mechanism of three typical types of forming defect: the platform-like defect, the bubble-like defect and the collapse-like defect. A 3D finite element model is established for the simulation analysis, in which the polymer resist is treated as a viscoelastic material based on the general Maxwell model. The simulation results clearly reveal the correlation between the forming defects and the processing conditions, indicating that the platform-like defect and the bubble-like defect are caused by material transport problems while the collapse-like defect results from polymer recovery. The underlying mechanisms for the forming defects disclosed in this research can provide effective guidelines for better process control as well as for improved design of the R2R hot embossing system.

  1. The numerical study of first order wetting transition with two defect lines

    NASA Astrophysics Data System (ADS)

    Wu, X. T.

    2016-09-01

    The first order wetting transition with two defect lines, one near a wall and another at a distance N1, in the d = 2 Ising model is studied by the bond propagation algorithm. The numerical calculations are carried out on very large lattices with size up to 1602 × 160. The finite size effects of the first order transition in that model are discussed. The magnetization profile is also calculated. The numerical results agree with the exact results very well.

  2. The epidemiology of cardiovascular defects, part 2: a study based on data from three large registries of congenital malformations.

    PubMed

    Harris, J A; Francannet, C; Pradat, P; Robert, E

    2003-01-01

    There were three objectives of this study: to investigate possible specificity in the association between specific cardiac defects and chromosomal anomalies; to evaluate ways of categorizing cardiac defects into larger groups with epidemiological similarities that could indicate similarities in etiology or pathogenesis; and to analyze the relationship between specific cardiac defects and diabetes. We pooled data on infants (aged 1 year or younger) with congenital cardiovascular defects from three large birth defect registries in California, Sweden, and France. The registries in Sweden and France obtained data through reporting from various sources; in California, medical records were reviewed. For severe congenital heart defects, the percentage of infants with identified chromosomal anomalies varied between 0.9% for d-TGV to 68.4% for ECD. In general, specific cardiac conditions have different risk factors. For example, conotruncal defects have been traditionally grouped, but the data presented in this paper indicates more differences for risk factors for the components of conotruncal defects: tetralogy of Fallot, d-TGV, common truncus, and DORV. In general, we suggest the strategy of "splitting" rather than "lumping" when searching for specific genetic factors and/or teratogens. Adequate analysis thus requires large registries or collaboration among registries. The findings did not support constellations between mothers' diabetes and specific defects. PMID:12632214

  3. [Pressure ulcer prevention and therapy: results of a descriptive study].

    PubMed

    Schlüer, Anna-Barbara; Cignacco, Eva; Halfens, Ruud J

    2008-03-01

    Pressure ulcers are a common nursing care issue in hospitals. Sick children, premature infants and toddlers, but also disabled and impaired children are at a high risk of developing pressure ulcers. The aim of this descriptive cross-sectional study was to describe the patients at risk as well as to identify the preventive and therapeutic interventions in a pediatric care setting. Of 213 hospitalised children, 155 (82 percent) from the age of 0 to 18 years could be included in the study. Altogether, preventive actions of any kind were performed with 92 percent of the patients. These were repositioning (84 percent), mobilisation of the patients (75 percent), followed by skin inspection (61 percent) and the application of lotions (56 percent). The high risk rate of pediatric patients considered at risk according to the Braden Scale is disconcerting and requires further exploration in terms of effective preventive and therapeutic interventions to improve the outcome for this patient group. PMID:18450264

  4. Overview study of LNG release prevention and control systems

    SciTech Connect

    Pelto, P.J.; Baker, E.G.; Holter, G.M.; Powers, T.B.

    1982-03-01

    The liquefied natural gas (LNG) industry employs a variety of release prevention and control techniques to reduce the likelihood and the consequences of accidental LNG releases. A study of the effectiveness of these release prevention and control systems is being performed. Reference descriptions for the basic types of LNG facilities were developed. Then an overview study was performed to identify areas that merit subsequent and more detailed analyses. The specific objectives were to characterize the LNG facilities of interest and their release prevention and control systems, identify possible weak links and research needs, and provide an analytical framework for subsequent detailed analyses. The LNG facilities analyzed include a reference export terminal, marine vessel, import terminal, peakshaving facility, truck tanker, and satellite facility. A reference description for these facilities, a preliminary hazards analysis (PHA), and a list of representative release scenarios are included. The reference facility descriptions outline basic process flows, plant layouts, and safety features. The PHA identifies the important release prevention operations. Representative release scenarios provide a format for discussing potential initiating events, effects of the release prevention and control systems, information needs, and potential design changes. These scenarios range from relatively frequent but low consequence releases to unlikely but large releases and are the principal basis for the next stage of analysis.

  5. Porous tantalum and poly-epsilon-caprolactone biocomposites for osteochondral defect repair: preliminary studies in rabbits.

    PubMed

    Mrosek, Eike H; Schagemann, Jan C; Chung, Hsi-Wei; Fitzsimmons, James S; Yaszemski, Michael J; Mardones, Rodrigo M; O'Driscoll, Shawn W; Reinholz, Gregory G

    2010-02-01

    Currently, various techniques are in use for the repair of osteochondral defects, none of them being truly satisfactory and they are often two step procedures. Comorbidity due to cancellous bone harvest from the iliac crest further complicates the procedure. Our previous in vitro studies suggest that porous tantalum (TM) or poly-epsilon-caprolactone scaffolds (PCL) in combination with periosteal grafts could be used for osteochondral defect repair. In this in vivo study, cylindrical osteochondral defects were created on the medial and lateral condyles of 10 rabbits and filled with TM/periosteum or PCL/periosteum biosynthetic composites (n = 8 each). The regenerated osteochondral tissue was then analyzed histologically, and evaluated in an independent and blinded manner by five different observers using a 30-point histological score. The overall histological score for PCL/periosteum was significantly better than for TM/periosteum. However, most of the regenerates were well integrated with the surrounding bone (PCL/periosteum, n = 6.4; TM/periosteum, n = 7) along with partial restoration of the tidemark (PCL/periosteum, n = 4.4; TM/periosteum, n = 5.6). A cover of hyaline-like morphology was found after PCL/periosteum treatment (n = 4.8), yet the cartilage yields were inconsistent. In conclusion, the applied TM and PCL scaffolds promoted excellent subchondral bone regeneration. Neo-cartilage formation from periosteum supported by a scaffold was inconsistent. This is the first study to show in vivo results of both PCL and TM scaffolds for a novel approach to osteochondral defect repair. PMID:19743507

  6. X-ray topographic study of growth defects of trans-stilbene crystals grown from solutions

    NASA Astrophysics Data System (ADS)

    Klapper, Helmut; Zaitseva, Natalia; Carman, Leslie

    2015-11-01

    Single crystals of trans-stilbene, C14H12, with properties suitable for high-energy neutron detection were grown from solution in anisole and toluene by the temperature reduction method with growth rates up to 6 mm/day. From these crystals, slices of appropriate orientation and thickness of 2-4 mm were cut and studied by X-ray diffraction topography applying the Lang method using CuKα radiation. The topographs exhibit growth defects such as liquid inclusions, dislocations, striations, and faulty growth-sector boundaries. These defects occur in the same typical arrangements and geometries as is observed in all kinds of crystals grown on habit faces from solution. Besides growth dislocations originating from inclusions and propagating with the growth front, many plastic glide dislocations in the shape of loops or half-loops emitted from inclusions by stress relaxation are observed. The glide system underlying this plasticity is discussed.

  7. Density functional study of H-induced defects as nucleation sites in hybrid carbon nanomaterials.

    SciTech Connect

    Barnard, A.; Terranova, M. L.; Rossi, M.; Dip. Scienze e Tecnologie Chimiche; Dip di Energetica; INFM

    2005-01-01

    Recently we have reported on the growth of an exciting new class of hybrid nanostructured carbon materials, coupling nanosized diamond with single-walled carbon nanotubes. The inner structures were shown to be single-walled C nanotubes or bundles of single-walled nanotubes up to 15 {micro}m long, and the outer deposit consisted of faceted diamond crystallites with diameters in the range of 20-100 nm. To aid in understanding the mechanisms responsible for the formation of such materials, the present study uses density functional theory to examine the role of atomic hydrogen in creating localized sp{sup 3} hybridized defects on the outer wall of carbon nanotubes. The results illustrate that certain absorption configurations may produce defects containing dangling carbon bonds, and thus promote the formation of suitable sites for nanodiamond nucleation.

  8. A Study of Network Defects of a Phosphated Si-containing Low Alloy Steel

    NASA Astrophysics Data System (ADS)

    Chang, Yao-Nan; Liou, Horng-Yih; Chen, Pei-Li

    2008-10-01

    This study was to investigate the formation of network defects that appeared on a phosphated low alloy steel rod containing 1.1% Si. Laboratory oxidation, pickling, annealing, and phosphating were performed. A scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) was employed to analyze the surface morphology and the elemental distribution of the specimen from each stage. From the results, a mechanism of formation of network defects has been proposed. Fast finish rolling produced fragments of Si-containing iron oxides, which were not removed completely through primary pickling → annealing → secondary pickling. Then, small pits occurred on the substrate near the interface of the substrate and the residual scale. After phosphating, small pits grew to large pits and propagated along the grain boundaries. Some grains spalled off eventually and looked like a network by human naked eyes.

  9. Line defects in boron nitride nanostructures: A first-principles study

    NASA Astrophysics Data System (ADS)

    Guerra, T.; Azevedo, S.; Machado, M.

    2016-05-01

    Using first-principles calculations we have explored the structural reconstruction of a special type of line defect (LD), formed as the result of a defective growth of a given monolayer (ML) or nanoribbon (NR). More specifically, we have studied the presence of tetragonal rings at boron nitride monolayers (BNMLs) and zigzag boron nitride nanoribbons (ZBNNRs). Different reconstruction processes are observed forming different types of LD depending on the nature of the atoms into the grain boundary between two BN domains as well as the structures type. The structural, magnetic, energetic, and electronic properties of the reconstructed BNMLs and ZBNNRs are calculated. These structures show a wide range of electronic structures going from semiconducting to semimetallic and metallic.

  10. Effects of vacancy defects on thermal conductivity in crystalline silicon: A nonequilibrium molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Lee, Yongjin; Lee, Sangheon; Hwang, Gyeong S.

    2011-03-01

    We examine the effects of vacancy defects on thermal conductivity in bulk crystalline silicon (c-Si) using nonequilibrium molecular dynamics simulations. While most vacancies are thought to remain in the form of clusters in bulk c-Si, recent theoretical studies have predicted that small vacancy clusters energetically prefer to be fourfold coordinated by nullifying dangling bonds. Hence, in this work, we consider three different-sized fourfold vacancy clusters, tetra- (V4), hexa- (V6), and dodeca-vacancy (V12), with particular interest in studying how phonon transport is affected by vacancy concentration and cluster size in association with fourfold coordination-induced lattice distortions. Our simulations show that thermal conductivity (κ) rapidly drops with vacancy concentration (nv) with an inverse power-law relation (κ∝nv-α, with α ≈ 0.7-1.1 depending on cluster size); the presence of 1.5% vacancies leads to a 95% reduction in κ as compared to the defect free c-Si. When nv is low (<1%), the reduction of κ with nv appears to be a function of cluster size, and the size effect becomes unimportant as nv increases above 1%. We discuss the correlation between phone scattering and cluster size, based on the relative rates of phonon-vacancy scattering associated with defect-induced strain fields. We also estimate the dependence of phonon mean free path on vacancy concentration and cluster size.

  11. A method to study the history of a double oxide film defect in liquid aluminum alloys

    NASA Astrophysics Data System (ADS)

    Raiszadeh, R.; Griffiths, W. D.

    2006-12-01

    Entrained double oxide films have been held responsible for reductions in mechanical properties in aluminum casting alloys. However, their behavior in the liquid metal, once formed, has not been studied directly. It has been proposed that the atmosphere entrapped in the double oxide film defect will continue to react with the liquid metal surrounding it, perhaps leading to its elimination as a significant defect. A silicon-nitride rod with a hole in one end was plunged into liquid aluminum to hold a known volume of air in contact with the liquid metal at a constant temperature. The change in the air volume with time was recorded by real-time X-ray radiography to determine the reaction rates of the trapped atmosphere with the liquid aluminum, creating a model for the behavior of an entrained double oxide film defect. The results from this experiment showed that first oxygen, and then nitrogen, was consumed by the aluminum alloy, to form aluminum oxide and aluminum nitride, respectively. The effect of adding different elements to the liquid aluminum and the effect of different hydrogen contents were also studied.

  12. Improving the Prevention of Cardiovascular Disease in Primary Health Care: The Model for Prevention Study Protocol

    PubMed Central

    Davey, Rachel C; Cochrane, Thomas; Williams, Lauren T; Clancy, Tanya

    2014-01-01

    Background Cardiovascular disease (CVD) is the leading cause of death globally, and accounted for nearly 31% of all deaths in Australia in 2011. The primary health care sector is at the frontline for addressing CVD, however, an evidence-to-practice gap exists in CVD risk assessment and management. General practice plays a key role in CVD risk assessment and management, but this sector cannot provide ongoing lifestyle change support in isolation. Community-based lifestyle modification services and programs provided outside the general practice setting have a key role in supporting and sustaining health behavior change. Fostering linkages between the health sector and community-based lifestyle services, and creating sustainable systems that support these sectors is important. Objective The objective of the study Model for Prevention (MoFoP) is to take a case study approach to examine a CVD risk reduction intervention in primary health care, with the aim of identifying the key elements required for an effective and sustainable approach to coordinate CVD risk reduction across the health and community sectors. These elements will be used to consider a new systems-based model for the prevention of CVD that informs future practice. Methods The MoFoP study will use a mixed methods approach, comprising two complementary research elements: (1) a case study, and (2) a pre/post quasi-experimental design. The case study will consider the organizations and systems involved in a CVD risk reduction intervention as a single case. The pre/post experimental design will be used for HeartLink, the intervention being tested, where a single cohort of patients between 45 and 74 years of age (or between 35 and 74 years of age if Aboriginal or Torres Strait Islander) considered to be at high risk for a CVD event will be recruited through general practice, provided with enhanced usual care and additional health behavior change support. A range of quantitative and qualitative data will be

  13. a Study of Two Electron Defect Systems in Alkali Halide Crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Chang Gang

    1993-01-01

    The structures of two electron defect systems in alkali halide crystals are studied. The systems which have been studied include: two electrons localized at an anion vacancy (F^'-centre); positronium self-trapped at an anion vacancy (Fe ^+-centre); positron self-trapped at a cation vacancy (F_{rm anti} -centre); positronium self-trapped at an interstice; and positronium in a Bloch state. An improved version of the extended-ion method which is based on the one electron Hartree-Fock approximation is used to perform these calculations. Its main feature is the exclusive use of floating 1s Gaussian functions as basis. For the multi-electron defect systems, the calculation of matrix elements of two electron interaction terms is a most difficult problem. We developed an effective approach to treat this interaction approximately. The correlation effect of defect electrons is partly accounted for by properly arranged Gaussian basis. The binding energy, thermal dissociation energy, and transition energy between ground state and excited state are calculated for F ^'-centres. A defect model with negative-U properties was introduced to interpret the deeply bound F^'-centre. Calculations of positron binding energies are made for Fe^+ -centres and F_{rm anti }-centres. In addition, we evaluate the angular correlation and lifetime of an annihilated electron-positron pair for Fe^+-centres, localized positronium and Bloch state positronium. The observed phenomena such as the transition of positronium from Bloch state to localized state, and the crystallographic effect are examined theoretically. The calculated results regarding various properties of crystals are in reasonably good agreement with experiment.

  14. Violence Prevention in Middle School: A Preliminary Study

    ERIC Educational Resources Information Center

    KIllam, Wendy K.; Roland, Catherine B.; Weber, Bill

    2014-01-01

    Violence in schools continues reflecting violence within society. There is a growing need for violence prevention programs within the schools that provide students with the skills needed to cope with interpersonal and relationship is-sues effectively. This study was conducted at a middle school and there were 345 middle school students (6th to 8th…

  15. A Case Study of Violence Prevention in an Elementary School

    ERIC Educational Resources Information Center

    Crawford, Diane Lynn

    2013-01-01

    This case study was initiated to explore how 6 fourth-grade student mediators implemented an inner-city elementary school's violence prevention program based on peer mediation in the context of psychosocial theory. The participants were trained in conflict resolution to intervene with disputants who experienced unresolved disagreements. To…

  16. A Study of a Violence Prevention Program in Prekindergarten Classrooms

    ERIC Educational Resources Information Center

    Allen, Susan F.

    2009-01-01

    Prevention programs in schools are one response to youth, community, and family violence. Many of these programs target older children and adolescents. This quasi-experimental study evaluated the preschool curriculum of the Peacemakers program, which was developed by a consortium of social service agencies for implementation in schools. This…

  17. Defect Chemistry Study of Nitrogen Doped ZnO Thin Films

    SciTech Connect

    Miami University: Dr. Lei L. Kerr Wright State University: Dr. David C. Look and Dr. Zhaoqiang Fang

    2009-11-29

    Our team has investigated the defect chemistry of ZnO:N and developed a thermal evaporation (vapor-phase) method to synthesis p-type ZnO:N. Enhanced p-type conductivity of nitrogen doped ZnO via nano/micro structured rods and Zn-rich Co-doping process were studied. Also, an extended X-Ray absorption fine structure study of p-type nitrogen doped ZnO was conducted. Also reported are Hall-effect, photoluminescence, and DLTS studies.

  18. Nutri-epigenomic Studies Related to Neural Tube Defects: Does Folate Affect Neural Tube Closure Via Changes in DNA Methylation?

    PubMed

    Rochtus, Anne; Jansen, Katrien; Van Geet, Chris; Freson, Kathleen

    2015-01-01

    Neural tube defects (NTDs), affecting 1-2 per 1000 pregnancies, are severe congenital malformations that arise from the failure of neurulation during early embryonic development. The methylation hypothesis suggests that folate prevents NTDs by stimulating cellular methylation reactions. Folate is central to the one-carbon metabolism that produces pyrimidines and purines for DNA synthesis and for the generation of the methyldonor S-adenosyl-methionine. This review focuses on the relation between the folate-mediated one-carbon metabolism, DNA methylation and NTDs. Studies will be discussed that investigated global or locus-specific DNA methylation differences in patients with NTDs. Folate deficiency may increase NTD risk by decreasing DNA methylation, but to date, human studies vary widely in study design in terms of analyzing different clinical subtypes of NTDs, using different methylation quantification assays and using DNA isolated from diverse types of tissues. Some studies have focused mainly on global DNA methylation differences while others have quantified specific methylation differences for imprinted genes, transposable elements and DNA repair enzymes. Findings of global DNA hypomethylation and LINE-1 hypomethylation suggest that epigenetic alterations may disrupt neural tube closure. However, current research does not support a linear relation between red blood cell folate concentration and DNA methylation. Further studies are required to better understand the interaction between folate, DNA methylation changes and NTDs. PMID:26349489

  19. STM study on the surface defects of SnSe induced by thermal annealing

    NASA Astrophysics Data System (ADS)

    Thi Ly, Trinh; Kim, Sang-Ui; Kim, Tae Hoon; Duong, Anh Tuan; Cho, Sunglae; Rhim, S. H.; Kim, Jungdae

    SnSe is a IV - VI semiconductor with 0.86 eV gap, and a single crystal SnSe usually exhibits a p-type characteristic. SnSe is one of 2D layered materials, and it has attracted researchers' attentions due to excellent physical properties for future applications. In particular, exceptionally high ZT value (ZT = ~2.6 at 923 K) was reported for SnSe single crystal (Zhao et al., Nature 508 373 (2014). Even though many researches on SnSe have proposed the possibilities of various applications so far, surprisingly little information is available regarding the microscopic structure of SnSe surfaces. We conducted a systematic study on the surface defect of SnSe induced by thermal annealing via a home-built low temperature scanning tunneling microscopy (STM). Various defects were characterized by STM/STS, and we found that Sn vacancy is a dominating intrinsic defect. The size of vacancy was changed after annealing process in UHV at different temperatures. This work was supported by the National Research Foundation of Korea(NRF) [Nos. NRF-2013R1A1A1008724, NRF-2009-0093818, and NRF-2014R1A4A1071686].

  20. Vibrational contributions to the stability of point defects in bcc iron: A first-principles study

    NASA Astrophysics Data System (ADS)

    Lucas, G.; Schäublin, R.

    2009-09-01

    The purpose of this study is to investigate the modes of vibration of the self-interstitial atoms and the vacancy in bcc iron and to estimate how the vibrational properties can affect the stability of these defects. The phonon density of states of the vacancy and the self-interstitials have been calculated within the quasi harmonic approximation using density functional theory calculations. It was observed that self-interstitial atoms have several localized high frequency modes of vibration related to the stretching of the dumbbell bond, but also soft modes favoring their migration. From the phonon density of states, the vibrational contributions to the free energy have been estimated for finite temperatures. Results are compared to previous work performed by others using empirical potentials. We found a rather large formation entropy for the vacancy, SVf = 4.08 kB. Our results show that the vibrational entropy can have a significant influence on the formation of the point defects even at moderate temperature. Possible consequences on the mobility of these defects are also discussed.

  1. Electrostatic force microscopy studies of surface defects on GaAs/Ge films

    SciTech Connect

    Xu, Q.; Hsu, J.W.

    1999-03-01

    We apply electrostatic force microscopy (EFM) to study defects in GaAs films grown on Ge. On a GaAs film with surface antiphase boundaries (APBs), we reproducibly measure the surface contact potential (SCP) at the APBs to be (30{plus_minus}5) mV higher than that of the domains, due to the surface Fermi level at APBs being pinned closer to the valence band maximum. On a thick film which contains buried APBs and wedge-shaped depressions on the surface, we find that the SCP of the wedge-shaped depressions is (25{plus_minus}5) mV lower than that of the GaAs surface. Hence, these wedge-shaped depressions have defect electronic states different from those of APBs. The capacitance gradient ({partial_derivative}C/{partial_derivative}z) contrasts on the two samples are also shown to arise from different origins. Factors that can affect the measured SCP and {partial_derivative}C/{partial_derivative}z values are discussed. We demonstrate a new application of EFM to distinguish different types of defects by measuring variations in relative SCP (thus the work function or position of Fermi level) and/or {partial_derivative}C/{partial_derivative}z on sample surfaces. The spatial resolutions of SCP and {partial_derivative}C/{partial_derivative}z are 30 nm, limited by the tip size. {copyright} {ital 1999 American Institute of Physics.}

  2. Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

    PubMed Central

    König, Thomas; Simon, Georg H; Heinke, Lars; Lichtenstein, Leonid

    2011-01-01

    Summary Surfaces of thin oxide films were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001) and line defects in aluminum oxide on NiAl(110), respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM) and the electronic structure by scanning tunneling spectroscopy (STS). On magnesium oxide, different color centers, i.e., F0, F+, F2+ and divacancies, have different effects on the contact potential. These differences enabled classification and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F2+-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide films beyond imaging the topography of the surface atoms. PMID:21977410

  3. Bone Regeneration in Iliac Crestal Defects: An Experimental Study on Sheep

    PubMed Central

    Lorusso, Felice; Ravera, Lorenzo; Mortellaro, Carmen; Piattelli, Adriano

    2016-01-01

    Background. Oral rehabilitation of partially fully edentulous patients with dental implants has become a routine procedure in clinical practice. In a site with a lack of bone GBR is a surgical procedure that provides an augmentation in terms of volume for the insertion of dental implants. Materials and Methods. In the iliac crest of six sheep 4 defects were created where an implant was inserted, three of them with different biomaterials and a control site. All animals were sacrificed after a 4-month healing period. All specimens were processed and analyzed with histomorphometry. Statistical evaluation was done to evaluate percentage of bone defect filled by new bone. Results. All experimental groups showed an increase of the new bone. Higher and highly statistically significant differences were found in the percentages of bone defect filled by new bone in group filled with corticocancellous 250–1000 microns particulate porcine bone mix. Conclusions. This study demonstrates that particulate porcine bone mix and porcine corticocancellous collagenate prehydrated bone mix when used as scaffold are able to induce bone regeneration. Moreover, these data suggest that these biomaterials have higher biocompatibility and are capable of inducing faster and greater bone formation. PMID:27413746

  4. Comparative study of nonabsorbable and absorbable barrier membranes in periodontal osseous defects by guided tissue regeneration

    PubMed Central

    Kaushal, Shalini; Kumar, Avadhesh; Khan, M.A.; Lal, Nand

    2016-01-01

    Background Periodontal invasion of furcation area in multirooted teeth represents one of the most demanding therapeutic challenges in periodontics. Furcation therapy includes various treatment modalities like either maintenance or elimination of furcation or increased access to furcation area. Recent treatment modalities include regenerative procedures like placement of different type of bone grafts with nonabsorbable or absorbable barrier membranes, through guided tissue regeneration. This study compared the clinical efficacy of nonabsorbable barrier membrane with absorbable membrane when used with hydroxyapatite bone graft (G-Graft) in grade II buccal furcation defects in mandibular 1st molars. Materials and methods Fourteen subjects with bilateral grade II buccal furcation defects in lower 1st molars were selected and treated in a split-mouth design. After phase I therapy, molars were divided randomly into two groups for the treatment with either resorbable or nonresorbable membrane in conjunction with G-Graft in both groups. Results All the clinical parameters recorded showed statistically significant improvement in both the groups but no significant difference between two groups was observed. Conclusion Both nonabsorbable and absorbable barrier membranes were equally effective in treating grade II buccal furcation defects in lower molars when used in conjunction with G-Graft except with respect to horizontal bone fill in which absorbable barrier membrane showed better results. PMID:27195208

  5. A novel silk fibroin nanofibrous membrane for guided bone regeneration: a study in rat calvarial defects

    PubMed Central

    Lu, Shijun; Wang, Peng; Zhang, Feng; Zhou, Xichao; Zuo, Baoqi; You, Xinran; Gao, Yang; Liu, Hongchen; Tang, Hailiang

    2015-01-01

    A novel membrane for guided bone regeneration (GBR), constituting silk fibroin (SF) nanofiber from native silk nanofibril solution, was prepared by electrospinning process. Another barrier membrane, a collagen-type membrane (Bio-Gide®), was used as a comparative sample. Twelve healthy male Sprague-Dawley rats were used in this study. Bilateral round defects were created in the calvarial bone. The bone regenerative efficacy was evaluated in rat calvarial defects. Animals were killed at 4 and 12 weeks. Bone regeneration was analyzed using micro-computed tomography and histological analysis. The SF nanofibrous membrane showed superior results with regard to mechanical tensile properties. At 4 weeks, the bone volume and collagen I positive areas in the SF group were greater than in the Bio-Gide group. At 12 weeks, the defect had completely healed with new bone in both the groups. In conclusion, the SF nanofibrous membranes showed satisfactory mechanical stability, good biocompatibility, slow degradability, and improved new bone regeneration without any adverse inflammatory reactions. Considering the low cost and low risk of disease transmission, the SF nanofibrous membrane is a potential candidate for GBR therapy compared with the widely used collagen membranes. PMID:26807172

  6. Lattice and defect structures of polymerizable diacetylene Langmuir-Blodgett films studied by scanning force microscopy

    NASA Astrophysics Data System (ADS)

    Vithana, Hemasiri; Johnson, David; Shih, Raymond; Mann, J. A., Jr.; Lando, Jerome

    The Scanning Force Microscope has been used to study the lattice and defect structures of multilayers of the unsaturated fatty acid, 12-8- diacetylene (10,12-Pentacosadiynoic Acid) in ambient conditions. Films were prepared by the Langmuir-Blodgett technique on ordinary microscope glass and Indium Tin Oxide coated glass. Lattice structures were deduced from the well resolved molecular images and before polymerization found to be nearly centered rectangular with lattice parameters (0.88 +/- 0.06)nm and (0.51 +/- 0.04)nm. After exposing to UV radiation for polymerization the lattice structure changed to an oblique lattice with lattice parameters (0.466 +/- 0.008)nm and (0.55 +/- 0.01)nm. Molecular level defects such as dislocations and grain boundaries were resolved in these films very clearly. Observation of these kind of defects implies that it is possible to reliably image the real surface molecules under ambient conditions. Polymerization was found to take place in one of the lattice directions and the modulation perpendicular to that direction was more pronounced than along the polymer backbone.

  7. Ab initio study of point defects near stacking faults in 3C-SiC

    DOE PAGESBeta

    Xi, Jianqi; Liu, Bin; Zhang, Yanwen; Weber, William J.

    2016-07-02

    Interactions between point defects and stacking faults in 3C-SiC are studied using an ab initio method based on density functional theory. The results show that the discontinuity of the stacking sequence considerably affects the configurations and behavior of intrinsic defects, especially in the case of silicon interstitials. The existence of an intrinsic stacking fault (missing a C-Si bilayer) shortens the distance between the tetrahedral-center site and its second-nearest-neighboring silicon layer, making the tetrahedral silicon interstitial unstable. Instead of a tetrahedral configuration with four C neighbors, a pyramid-like interstitial structure with a defect state within the band gap becomes a stablemore » configuration. In addition, orientation rotation occurs in the split interstitials that has diverse effects on the energy landscape of silicon and carbon split interstitials in the stacking fault region. Moreover, our analyses of ionic relaxation and electronic structure of vacancies show that the built-in strain field, owing to the existence of the stacking fault, makes the local environment around vacancies more complex than that in the bulk.« less

  8. First-principles study of native point defects in Bi2Se3

    NASA Astrophysics Data System (ADS)

    Xue, L.; Zhou, P.; Zhang, C. X.; He, C. Y.; Hao, G. L.; Sun, L. Z.; Zhong, J. X.

    2013-05-01

    Using first-principles method within the framework of the density functional theory, we study the influence of native point defect on the structural and electronic properties of Bi2Se3. Se vacancy in Bi2Se3 is a double donor, and Bi vacancy is a triple acceptor. Se antisite (SeBi) is always an active donor in the system because its donor level (ɛ(+1/0)) enters into the conduction band. Interestingly, Bi antisite (BiSe1) in Bi2Se3 is an amphoteric dopant, acting as a donor when μe < 0.119 eV (the material is typical p-type) and as an acceptor when μe > 0.251 eV (the material is typical n-type). The formation energies under different growth environments (such as Bi-rich or Se-rich) indicate that under Se-rich condition, SeBi is the most stable native defect independent of electron chemical potential μe. Under Bi-rich condition, Se vacancy is the most stable native defect except for under the growth window as μe > 0.262 eV (the material is typical n-type) and ΔμSe < -0.459 eV (Bi-rich), under such growth window BiSe1 carrying one negative charge is the most stable one.

  9. Paternal Age and Offspring Congenital Heart Defects: A National Cohort Study

    PubMed Central

    Huang, Guo Ying; Olsen, Jørn; Li, Jiong

    2015-01-01

    Paternal age has been associated with offspring congenital heart defects (CHDs), which might be caused by increased mutations in the germ cell line because of cumulated cell replications. Empirical evidences, however, remain inconclusive. Furthermore, it is unknown whether all subtypes of CHDs are affected by paternal age. We aimed to explore the relationship between paternal age and the risk of offspring CHDs and its five common subtypes using national register data in Denmark. A total of 1 893 899 singletons born in Denmark from 1977 to 2008 were included in this national-based cohort study. Cox’s proportion hazards model with robust sandwich estimate option was used to estimate the hazards ratio (95% confidence interval) for the associations between paternal age and all CHDs, as well as subtypes of CHDs (patent ductus arteriosus (PDA), ventricular septal defect (VSD), atrial septal defect (ASD), tetralogy of fallot (TOF) and coarctation of the aorta (CoA)). We did not observe an overall association between paternal age and offspring CHDs. However, compared to the paternal age of 25–29 years, paternal age of older than 45 years was associated with a 69% increased risk of PDA (HR45+ = 1.69, 95%CI:1.17–2.43). We observed similar results when subanalyses were restricted to children born to mothers of 27–30 years old. After taking into consideration of maternal age, our data suggested that advanced paternal age was associated with an increased prevalence of one subtype of offspring congenital heart defects (CHDs), namely patent ductus arteriosus (PDA). PMID:25806788

  10. A study of the mechanism of laser welding defects in low thermal expansion superalloy GH909

    SciTech Connect

    Yan, Fei; Wang, Chunming Wang, Yajun; Hu, Xiyuan; Wang, Tianjiao; Li, Jianmin; Li, Guozhu

    2013-04-15

    In this paper, we describe experimental laser welding of low-thermal-expansion superalloy GH909. The main welding defects of GH909 by laser in the weld are liquation cracks and porosities, including hydrogen and carbon monoxide porosity. The forming mechanism of laser welding defects was investigated. This investigation was conducted using an optical microscope, scanning electron microscope, energy diffraction spectrum, X-ray diffractometer and other methodologies. The results demonstrated that porosities appearing in the central weld were related to incomplete removal of oxide film on the surface of the welding samples. The porosities produced by these bubbles were formed as a result of residual hydrogen or oxygenium in the weld. These elements failed to escape from the weld since laser welding has both a rapid welding speed and cooling rate. The emerging crack in the heat affected zone is a liquation crack and extends along the grain boundary as a result of composition segregation. Laves–Ni{sub 2}Ti phase with low melting point is a harmful phase, and the stress causes grain boundaries to liquefy, migrate and even crack. Removing the oxides on the surface of the samples before welding and carefully controlling technological parameters can reduce welding defects and improve formation of the GH909 alloy weld. - Highlights: ► It is a new process for the forming of GH909 alloy via laser welding. ► The forming mechanism of laser welding defects in GH909 has been studied. ► It may be a means to improve the efficiency of aircraft engine production.

  11. A theoretical study of the stability of anionic defects in cubic ZrO2 at extreme conditions

    DOE PAGESBeta

    Samanta, Amit

    2016-02-19

    Using first principles density functional theory calculations, we present a study of the structure, mobility, and the thermodynamic stability of anionic defects in the high-temperature cubic phase of ZrO2. Our results suggest that the local structure of an oxygen interstitial depends on the charge state and the cubic symmetry of the anionic sublattice is unstable at 0 K. In addition, the oxygen interstitials and the vacancies exhibit symmetry breaking transitions to low-energy structures with tetragonal distortion of the oxygen sublattice at 0 K. However, the vibrational entropy stabilizes the defect structures with cubic symmetry at 2600–2980 K. The formation freemore » energies of the anionic defects and Gibbs free energy changes associated with different defect reactions are calculated by including the vibrational free energy contributions and the effect of pressure on these defect structures. By analyzing the defect chemistry, we obtain the defect concentrations at finite temperature and pressure conditions using the zero temperature ab initio results as input and find that at low oxygen partial pressures, neutral oxygen vacancies are most dominant and at high oxygen partial pressures, doubly charged anionic defects are dominant. As a result, the relevance of the results to the thermal protective coating capabilities of zirconium-based ceramic composites is elucidated.« less

  12. Epidemiological studies of CHD and the evolution of preventive cardiology.

    PubMed

    Wong, Nathan D

    2014-05-01

    Cardiovascular diseases (CVDs) cause nearly one-third of all deaths worldwide. Coronary heart disease (CHD) accounts for the greatest proportion of CVDs, and risk factors such as hypertension, cigarette smoking, diabetes mellitus or elevated glucose level, elevated cholesterol levels, and obesity or being overweight are the top six causes of death globally. Ecological and population-based longitudinal studies, conducted globally or within individual countries, have established the role of traditional and novel risk factors and measures of subclinical disease in the prediction of CHD. Risk assessment with short-term or long-term risk prediction algorithms can help to identify individuals who would benefit most from risk-factor interventions. Evaluation of novel risk factors and screening for subclinical atherosclerosis can also help to identify individuals at highest cardiovascular risk. Prevention of CHD focuses on identifying and managing risk factors at both the population and individual levels through primordial, primary, and secondary prevention. Epidemiological studies have provided the hypotheses for subsequent clinical trials that have documented the efficacy of risk-factor interventions, which are the basis of preventive cardiology. Future research efforts will determine the screening and intervention strategies that have the greatest effect on CHD prevention. PMID:24663092

  13. First principles study of band line up at defective metal-oxide interface: oxygen point defects at Al/SiO2 interface

    NASA Astrophysics Data System (ADS)

    Tea, Eric; Huang, Jianqiu; Hin, Celine

    2016-03-01

    The dielectric breakdown at metal-oxide interfaces is a critical electronic device failure mechanism. Electronic tunneling through dielectric layers is a well-accepted explanation for this phenomenon. Theoretical band alignment studies, providing information about tunneling, have already been conducted in the literature for metal-oxide interfaces. However, most of the time materials were assumed defect free. Oxygen vacancies being very common in oxides, their effect on band lineup is of prime importance in understanding electron tunneling in realistic materials and devices. This work explores the effect of oxygen vacancy and oxygen di-vacancy at the Al/SiO2 interface on the band line up within Density Functional Theory using PBE0 hybrid exchange and correlation functional. It is found that the presence of defects at the interface, and their charge state, strongly alters the band line up.

  14. Induction of fully stabilized cortical bone defects to study intramembranous bone regeneration

    PubMed Central

    McGee-Lawrence, Meghan E.; Razidlo, David F.

    2015-01-01

    Summary Bone is a regenerative tissue with an innate ability to self-remodel in response to environmental stimuli and the need to repair damage. Rodent models of fracture healing, and in particular genetic mouse models, can be used to study the contributions of specific molecular switches to skeletal repair, as well as to recreate and exacerbate biological development and repair mechanisms in postnatal skeletons. Here, we describe methodology for producing fully stabilized, single-cortex defects in mouse femurs to study mechanisms of intramembranous bone regeneration. PMID:25331051

  15. Chromatin defects in normal and malformed human ejaculated and epididymal spermatozoa: a cytochemical ultrastructural study.

    PubMed

    Francavilla, S; Cordeschi, G; Gabriele, A; Gianaroli, L; Properzi, G

    1996-03-01

    Cytochemical defects in chromatin were examined by transmission electron microscopy (TEM) after the staining by alcoholic phosphotungstic acid (PTA) of normal and malformed ejaculated spermatozoa from 35 male partners of infertile couples, and in six sperm samples retrieved from the caput epididymidis of men affected by obstructive azoospermia. PTA staining was also analysed in normal ejaculates of fertile men after incubation of the washed spermatozoa with dithiothreitol (DTT) to reduce disulfides to thiols, or with DTT followed by iodoacetamide, a blocking agent for thiol groups. PTA stained 63 (27-100)% of malformed heads and 25 (10-100)% of normal sperm heads (median (range) n = 35; P = 0.0001, Wilcoxon matched pairs test). The percentage of normal heads stained by PTA was negatively correlated with the percentage of heads of normal form, with condensed chromatin and a normal acrosome (Spearman r = 0.75; P = 0.0001), and positively correlated with the percentage of malformed heads after conventional TEM analysis (Spearman r 0.60; P = 0.0001). Staining with PTA in normal heads was not correlated with the presence of non-condensed chromatin in otherwise normal sperm heads evaluated by conventional TEM analysis. In spermatozoa recovered from the caput epididymidis, 15% of normal heads were stained with PTA, significantly fewer than in ejaculated sperm samples (P = 0.014). The reduction of disulfides to thiols was associated with PTA staining of all normal heads, and this was prevented by incubation with iodoacetamide. We conclude that PTA staining of the nuclei of human ejaculated spermatozoa may indicate a defect of chromatin condensation, owing to an excess of free thiol groups. The lower percentage of normal epididymal sperm heads that stained with PTA in cases of obstructive azoospermia compared with ejaculated sperm may be related to an overoxidation of thils owing to the ageing of spermatozoa. PMID:8699409

  16. 5-HT(2C) serotonin receptor blockade prevents tau protein hyperphosphorylation and corrects the defect in hippocampal synaptic plasticity caused by a combination of environmental stressors in mice.

    PubMed

    Busceti, Carla Letizia; Di Pietro, Paola; Riozzi, Barbara; Traficante, Anna; Biagioni, Francesca; Nisticò, Robert; Fornai, Francesco; Battaglia, Giuseppe; Nicoletti, Ferdinando; Bruno, Valeria

    2015-09-01

    Exposure to multimodal sensory stressors is an everyday occurrence and sometimes becomes very intense, such as during rave parties or other recreational events. A growing body of evidence suggests that strong environmental stressors might cause neuronal dysfunction on their own in addition to their synergistic action with illicit drugs. Mice were exposed to a combination of physical and sensory stressors that are reminiscent of those encountered in a rave party. However, this is not a model of rave because it lacks the rewarding properties of rave. A 14-h exposure to environmental stressors caused an impairment of hippocampal long-term potentiation (LTP) and spatial memory, and an enhanced phosphorylation of tau protein in the CA1 and CA3 regions. These effects were transient and critically depended on the activation of 5-HT2C serotonin receptors, which are highly expressed in the CA1 region. Acute systemic injection of the selective 5-HT2C antagonist, RS-102,221 (2 mg/kg, i.p., 2 min prior the onset of stress), prevented tau hyperphosphorylation and also corrected the defects in hippocampal LTP and spatial memory. These findings suggest that passive exposure to a combination of physical and sensory stressors causes a reversible hippocampal dysfunction, which might compromise mechanisms of synaptic plasticity and spatial memory for a few days. Drugs that block 5-HT2C receptors might protect the hippocampus against the detrimental effect of environmental stressors. PMID:26145279

  17. Core-level photoabsorption study of defects and metastable bonding configurations in boron nitride

    SciTech Connect

    Jimenez, I.; Jankowski, A.F.; Terminello, L.J.

    1997-04-01

    Boron nitride is an interesting material for technological applications and for fundamental solid state physics investigations. It is a compound isoelectronic with carbon and, like carbon can possess sp{sup 2} and sp{sup 3} bonded phases resembling graphite and diamond. BN crystallizes in the sp{sup 2}-bonded hexagonal (h-BN), rhombohedral (r-BN) and turbostratic phases, and in the sp{sup 3}-bonded cubic (c-BN) and wurtzite (w-BN) phases. A new family of materials is obtained when replacing C-C pairs in graphite with isoelectronic B-N pairs, resulting in C{sub 2}BN compounds. Regarding other boron compounds, BN is exceptional in the sense that it has standard two-center bonds with conventional coordination numbers, while other boron compounds (e.g. B{sub 4}C) are based on the boron icosahedron unit with three-center bonds and high coordination numbers. The existence of several allotropic forms and fullerene-like structures for BN suggests a rich variety of local bonding and poses the questions of how this affects the local electronic structure and how the material accommodates the stress induced in the transition regions between different phases. One would expect point defects to play a crucial role in stress accommodation, but these must also have a strong influence in the electronic structure, since the B-N bond is polar and a point defect will thus be a charged structure. The study of point defects in relationship to the electronic structure is of fundamental interest in these materials. Recently, the authors have shown that Near-Edge X-ray Absorption Fine Structure (NEXAFS) is sensitive to point defects in h-BN, and to the formation of metastable phases even in amorphous materials. This is significant since other phase identification techniques like vibrational spectroscopies or x-ray diffraction yield ambiguous results for nanocrystalline and amorphous samples. Serendipitously, NEXAFS also combines chemical selectivity with point defect sensitivity.

  18. Study of elementary point defects and of the dynamic of defects associated to irradiation in alpha AgZn solid solutions

    NASA Astrophysics Data System (ADS)

    Beretz, D.

    1980-11-01

    After briefly recalling the structural defects created in a crystal lattice during irradiation and the evolution in the concentrations of defects under irradiation, some particulars are given respecting the parameters which describe the relaxation defects associated with the short distance variations of the order brought about by applied stress, and the mechanical hauling appliances developed for effecting measurements in a pool reactor, and in line behind a Van de Graaff accelerator, as well as on the irradiation conditions. The results are presented of the comparative study of the effects of gamma radiation irradiation, of fast electrons, reactor neutrons, and 14 MeV neutrons made on the same alloy namely: Ag - 24% atomic Zn. The aspect specific to the cascades of atomic movements brought about by the neutron bombardment are emphasized: asymmetry of the emission of vacancies and auto-interstitials and production of holes by the collapse of the cascades. The results relative to the mobility of the vacancies and auto-interstitials are presented. The entire range of the alpha-AgZn solid solutions extending from pure silver to the levels next to the thirty percent atomic of zinc is covered. Finally the very marked slowing down of the auto-interstitial observed in this system is discussed in terms of the effect of the zinc level of the measured mobility parameters.

  19. Hydrogen adsorption and storage on palladium-decorated graphene with boron dopants and vacancy defects: A first-principles study

    NASA Astrophysics Data System (ADS)

    Ma, Ling; Zhang, Jian-Min; Xu, Ke-Wei; Ji, Vincent

    2015-02-01

    The geometric stability and hydrogen capacity of Pd-decorated graphene with experimentally realizable boron dopants and various vacancy defects including single carbon vacancy (SV), "585"-type double carbon vacancy (585 DCV) and "555-777"-type double carbon vacancy (555-777 DCV) are investigated using the first-principles calculations based on density functional theory (DFT). It is found that among the four types of defective structures, Pd‧s binding energies on SV and 585 DCV defect graphene sheets exceed the cohesive energy of the Pd metal bulk, thus Pd atoms are well dispersed above defective graphene sheets and effectively prevent Pd clustering. Up to three H2 molecules can bind to Pd atom on graphene with B dopants, SV and 555-777 DCV defects. For the cases of Pd-decorated graphene with B dopants and 555-777 DCV defect, a single H2 or two H2 are molecularly chemisorbed to Pd atom in the form of Pd-H2 Kubas complex, where the stretched H-H bond is relaxed but not dissociated. Out of two adsorbed H2, the third H2 binds to Pd atom by small van der Waals (vdW) forces and the nature of bonding is very weak physisorption. Different from above two cases, three H2 are all molecularly chemisorbed to Pd atom with stretched H-H bond for Pd-decorated SV defect graphene, the hybridization of the Pd-4d orbitals with the H2-σ orbitals and the electrostatic interaction between the Pd cation and the induced H2 dipole both contribute to the H2 molecules binding, and the binding energies of 0.25-0.41 eV/H2 is in the range that can permit H2 molecules recycling at ambient conditions.

  20. Birth Defects

    MedlinePlus

    ... NICHD Research Information Clinical Trials Resources and Publications Birth Defects: Condition Information Skip sharing on social media links Share this: Page Content What are birth defects? Birth defects are structural or functional abnormalities present ...

  1. Osteoarthritis prevention and meniscus regeneration induced by transplantation of mesenchymal stem cell sheet in a rat meniscal defect model

    PubMed Central

    QI, YIYING; CHEN, GUANGNAN; FENG, GANG

    2016-01-01

    Transplantation of mesenchymal stem cells (MSCs) is a potential therapy for meniscus regeneration. However, when using single cell suspension injection, there is frequently a significant loss of cells, with only a small percentage of cells remaining at the target site. This issue may be solved with the use of MSC sheets. In the present study, we investigated whether the use of MSC sheets were able to regenerate the meniscus effectively in a rat meniscectomized model. The anterior half of the medial meniscus in 10 rats was excised and an MSC sheet was transplanted in the MSC sheet treatment group, while untreated rats served as the control. After 4 and 8 weeks, the knee joints were examined by gross and histological observation. Histological observation revealed that the anterior portion of meniscus was similar to the native tissue, showing typical fibrochondrocytes surrounded by richer extracellular matrix in the MSC sheet group. In addition, predominant collagen-rich matrix bridging the interface was observed and the neo-meniscus integrated well with its host meniscus. Furthermore, degenerative changes of tibial plateau and femoral condyle occurred in the two groups. MSC sheet transplantation alleviated the degenerative changes efficiently. In conclusion, transplantation of MSC sheets may efficiently promote meniscus regeneration, as well as inhibit the progression of osteoarthritis in knee joints. PMID:27347022

  2. Defects in Peroxisomal 6-Phosphogluconate Dehydrogenase Isoform PGD2 Prevent Gametophytic Interaction in Arabidopsis thaliana1[OPEN

    PubMed Central

    Hölscher, Christian; Meyer, Tanja; Fischer, Kerstin

    2016-01-01

    We studied the localization of 6-phosphogluconate dehydrogenase (PGD) isoforms of Arabidopsis (Arabidopsis thaliana). Similar polypeptide lengths of PGD1, PGD2, and PGD3 obscured which isoform may represent the cytosolic and/or plastidic enzyme plus whether PGD2 with a peroxisomal targeting motif also might target plastids. Reporter-fusion analyses in protoplasts revealed that, with a free N terminus, PGD1 and PGD3 accumulate in the cytosol and chloroplasts, whereas PGD2 remains in the cytosol. Mutagenesis of a conserved second ATG enhanced the plastidic localization of PGD1 and PGD3 but not PGD2. Amino-terminal deletions of PGD2 fusions with a free C terminus resulted in peroxisomal import after dimerization, and PGD2 could be immunodetected in purified peroxisomes. Repeated selfing of pgd2 transfer (T-)DNA alleles yielded no homozygous mutants, although siliques and seeds of heterozygous plants developed normally. Detailed analyses of the C-terminally truncated PGD2-1 protein showed that peroxisomal import and catalytic activity are abolished. Reciprocal backcrosses of pgd2-1 suggested that missing PGD activity in peroxisomes primarily affects the male gametophyte. Tetrad analyses in the quartet1-2 background revealed that pgd2-1 pollen is vital and in vitro germination normal, but pollen tube growth inside stylar tissues appeared less directed. Mutual gametophytic sterility was overcome by complementation with a genomic construct but not with a version lacking the first ATG. These analyses showed that peroxisomal PGD2 activity is required for guided growth of the male gametophytes and pollen tube-ovule interaction. Our report finally demonstrates an essential role of oxidative pentose-phosphate pathway reactions in peroxisomes, likely needed to sustain critical levels of nitric oxide and/or jasmonic acid, whose biosynthesis both depend on NADPH provision. PMID:26941195

  3. Perturbed angular correlation study of radiation-induced defects in Rh metal

    NASA Astrophysics Data System (ADS)

    Chawda, M.; Patel, N.; Sebastian, K. C.; Somayajulu, D. R. S.; Sarkar, M.; Singh, R. P.; Murlithar, S.; Awasthi, D. K.

    2006-06-01

    Radiation-induced defects are studied in cubic rhodium metal, using the local probe technique 'Time differential perturbed angular correlation (TDPAC) at liquid N-2 temperature. Isochronal annealing was done at 300, 1073 and 1473 K temperatures. The irradiated sample showed two quadrupole interaction frequencies at 1150 and 93 MHz. The low frequency disappeared at room-temperature annealing, which was assigned to In trapped at a vacancy, whereas the higher frequency remained up to high temperatures and was attributed to In trapped at Rh-C complexes in the Rh matrix.

  4. First-principles study of point defects at a semicoherent interface

    PubMed Central

    Metsanurk, E.; Tamm, A.; Caro, A.; Aabloo, A.; Klintenberg, M.

    2014-01-01

    Most of the atomistic modeling of semicoherent metal-metal interfaces has so far been based on the use of semiempirical interatomic potentials. We show that key conclusions drawn from previous studies are in contradiction with more precise ab-initio calculations. In particular we find that single point defects do not delocalize, but remain compact near the interfacial plane in Cu-Nb multilayers. We give a simple qualitative explanation for this difference on the basis of the well known limited transferability of empirical potentials. PMID:25524061

  5. First-principles study of point defects at a semicoherent interface

    DOE PAGESBeta

    Metsanurk, E.; Tamm, A.; Caro, A.; Aabloo, A.; Klintenberg, M.

    2014-12-19

    Most of the atomistic modeling of semicoherent metal-metal interfaces has so far been based on the use of semiempirical interatomic potentials. Here, we show that key conclusions drawn from previous studies are in contradiction with more precise ab-initio calculations. In particular we find that single point defects do not delocalize, but remain compact near the interfacial plane in Cu-Nb multilayers. Lastly, we give a simple qualitative explanation for this difference on the basis of the well known limited transferability of empirical potentials.

  6. Study of mercury thiogallate in defect stannite structure: A first-principle approach

    NASA Astrophysics Data System (ADS)

    Nayak, Vikas; Verma, U. P.

    2016-05-01

    Quantum mechanical based first principle calculations have been employed to obtain the unit cell lattice parameters of mercury thiogallate (HgGa2S4) in defect stannite structure for the first time. For this, we treated HgGa2S4 in two different types of site symmetries in the same space group. In both the cases obtained unit cell parameters are same, which shows the accuracy of present approach. The electronic band structures show the semiconducting behavior in both the cases. The density of states plot are also studied and discussed.

  7. [Study on prevention of untoward reaction of glucose tolerance test].

    PubMed

    Fan, L F; Li, H Y; Wang, G H

    1996-03-01

    The prevention methods of the side effects of 75g glucose tolerance test were studied. The results showed that the speed of taking glucose water was 3-5 minutes; the water temperature was 20-30 degrees C; water volume of dissolving glucose was 300ml; 0.25g citric acid was added, the side effects will be avoided or reduced. PMID:8826187

  8. A study on effect of point-of-use filters on defect reduction for advanced 193nm processes

    NASA Astrophysics Data System (ADS)

    Vitorino, Nelson; Wolfer, Elizabeth; Cao, Yi; Lee, DongKwan; Wu, Aiwen

    2009-03-01

    Bottom Anti-Reflective Coatings (BARCs) have been widely used in the lithography process for decades. BARCs play important roles in controlling reflections and therefore improving swing ratios, CD variations, reflective notching, and standing waves. The implementation of BARC processes in 193nm dry and immersion lithography has been accompanied by defect reduction challenges on fine patterns. Point-of-Use filters are well known among the most critical components on a track tool ensuring low wafer defects by providing particle-free coatings on wafers. The filters must have very good particle retention to remove defect-causing particulate and gels while not altering the delicate chemical formulation of photochemical materials. This paper describes a comparative study of the efficiency and performance of various Point-of-Use filters in reducing defects observed in BARC materials. Multiple filter types with a variety of pore sizes, membrane materials, and filter designs were installed on an Entegris Intelligent(R) Mini dispense pump which is integrated in the coating module of a clean track. An AZ(R) 193nm organic BARC material was spin-coated on wafers through various filter media. Lithographic performance of filtered BARCs was examined and wafer defect analysis was performed. By this study, the effect of filter properties on BARC process related defects can be learned and optimum filter media and design can be selected for BARC material to yield the lowest defects on a coated wafer.

  9. Prevention praised, cure preferred: results of between-subjects experimental studies comparing (monetary) appreciation for preventive and curative interventions

    PubMed Central

    2013-01-01

    Background 'An ounce of prevention is worth a pound of cure’ is a common saying, and indeed, most health economic studies conclude that people are more willing to pay for preventive measures than for treatment activities. This may be because most health economic studies ask respondents to compare preventive measures with treatment, and thus prompt respondents to consider other uses of resources. However, psychological theorizing suggests that, when methods do not challenge subjects to consider other uses of resources, curative treatment is favored over prevention. Could it be that while prevention is praised, cure is preferred? Methods In two experimental studies, we investigated, from a psychological perspective and using a between-subjects design, whether prevention or treatment is preferred and why. In both studies, participants first read a lung cancer prevention or treatment intervention scenario that varied on the prevention-treatment dimension, but that were the same on factors like 'costs per saved life’ and kind of disease. Then participants completed a survey measuring appreciation (general and monetary) as well as a number of potential mediating variables. Results Both studies clearly demonstrated that, when the design was between-subjects, participants had greater (general and monetary) appreciation for treatment interventions than for preventive interventions with perceived urgency of the intervention quite consistently mediating this effect. Differences in appreciation of treatment over preventive treatment were shown to be .59 (Study 1) and .45 (Study 2) on a 5-point scale. Furthermore, participants thought that health insurance should compensate more for the treatment than for preventive measures, differences of 16% (Study 1), and 22% (Study 2). When participants were asked to directly compare both interventions on the basis of a short description, they preferred the preventive intervention. Conclusion It appears that people claim to prefer

  10. Studies of point-defect interactions in solids using perturbed angular correlations

    SciTech Connect

    Schuhmann, R.B.

    1988-01-01

    Vacancy defect production and migration in {sup 111}In doped Au, Pt and Ni following plastic deformation are studied via {sup 111}Cd perturbed {gamma}-{gamma} angular correlations (TDPAC). In all three metals, deformation produces the same defect species as are seen following irradiation. In Au, a particular In-vacancy complex which is probably a trapped divacancy exists in two distinct configurations. Thermal conversion from one configuration to the other occurs near 200K. In Pt, an In-vacancy complex exhibits a strongly temperature dependent electric field gradient, indicating the presence of local resonant modes. In Ni, a relaxed In-trivacancy complex forms via simple, single-step trapping of a migrating trivacancy. Once formed, the In-trivacancy complex in Ni can trap up to four guest H or D atoms. These are bound to the complex with an energy of {approximately}0.5 eV, irrespective of isotopic mass. By monitoring the damping of the TDPAC precession not associated with a bound defect, the author observed release of untrapped interstitial H from the lattice. These experiments give a consistent, microscopic picture of H diffusion and release from Ni. The use of BaF{sub 2} scintillators allows for an eightfold improvement in TDPAC time resolution. This makes possible experiments in systems previously inaccessible due to large precessional frequencies. The author demonstrates the utility of BaF{sub 2} in several examples, including {sup 100}RhNi, {sup 99}TcFe, {sup 101}RuFe, {sup 100}RhCo and {sup 100}RhFe, systems which had not been studied previously due to time resolution limitation. The Larmor frequency for {sup 100}RhFe, 5565 Mrad/s, is the highest frequency ever measured via TDPAC.

  11. Electrical and Optical Studies of Defect Structure of HgCdTe Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Świątek, Z.; Ozga, P.; Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytsky, H. V.

    2016-07-01

    Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 1017 cm-3, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As2 dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor As2Te3 complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy.

  12. ASPREE Cancer Endpoints Study | Division of Cancer Prevention

    Cancer.gov

    The ASPREE Cancer Endpoint Study (ACES), an ancillary study of the ASPirin in the Prevention of Events in the Elderly (ASPREE) Study, will allow for the examination of the effect of daily low-dose aspirin (100 mg) compared to placebo, on specific DNA biomarkers and selected specific incident and recurrent cancer and metastases. The establishment of this ACES biobank will allow for the exploration of DNA-related molecular mechanisms of aspirin's protective effect against cancer, cancer associated mortality and metastases, using blood or saliva DNA specimens, urine, and tumor tissue. |

  13. Density Functional Theory Studies of Li-ion interaction with defected group 14 heteronuclear nanotubes and nanosheets

    NASA Astrophysics Data System (ADS)

    Pasipanodya, Tichakunda; Wanaguru, Prabath; Atta-Fynn, Raymond

    2015-03-01

    Nanomaterials show significant promise in enhancing Lithium ion (Li-ion) battery properties. Using density functional theory, we study the binding and diffusion of Li on defected nanotubes and nanosheets of silicon carbide (SiC) and silicon germanium (SiGe). Point and extended defects are considered to fully evaluate the influence of defects on the adsorption and diffusion properties. The trends in the adsorption-induced changes in the geometric and electronic properties will be presented. Furthermore, room temperature ab initio molecular dynamics simulations will be carried out to investigate finite temperature effects on the binding mechanisms and electronic structure.

  14. A study of void size growth in nonequilibrium stochastic systems of point defects

    NASA Astrophysics Data System (ADS)

    Kharchenko, Dmitrii O.; Kharchenko, Vasyl O.; Bashtova, Anna I.

    2016-05-01

    We study properties of voids growth dynamics in a stochastic system of point defects in solids under nonequilibrium conditions (sustained irradiation). It is shown that fluctuations of defect production rate (external noise) increase the critical void radius comparing to a deterministic system. An automodel regime of void size growth in a stochastic system is studied in detail. Considering a homogeneous system, it is found that external noise does not change the universality of the void size distribution function; the mean void size evolves according to classical nucleation theory. The noise increases the mean void size and spreads the void size distribution. Studying dynamics of spatially extended systems it was shown that vacancies remaining in a matrix phase are able to organize into vacancy enriched domains due to an instability caused by an elastic lattice deformation. It is shown that dynamics of voids growth is defined by void sinks strength with void size growth exponent varying from 1/3 up to 1/2.

  15. First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

    NASA Astrophysics Data System (ADS)

    Piochaud, J. B.; Klaver, T. P. C.; Adjanor, G.; Olsson, P.; Domain, C.; Becquart, C. S.

    2014-01-01

    The influence of the local environment on vacancy and self-interstitial formation energies has been investigated in a face-centered-cubic (fcc) Fe-10Ni-20Cr model alloy by analyzing an extensive set of first-principle calculations based on density functional theory. Chemical disorder has been considered by designing special quasirandom structures and four different collinear magnetic structures have been investigated in order to determine a relevant reference state to perform point defect calculations at 0 K. Two different convergence methods have also been used to characterize the importance of the method on the results. Although our fcc Fe-10Ni-20Cr would be better represented in terms of applications by the paramagnetic state, we found that the antiferromagnetic single-layer magnetic structure was the most stable at 0 K and we chose it as a reference state to determine the point defect properties. Point defects have been introduced in this reference state, i.e., vacancies and Fe-Fe, Fe-Ni, Fe-Cr, Cr-Cr, Ni-Ni, and Ni-Cr dumbbell interstitials oriented either parallel or perpendicular to the single layer antiferromagnetic planes. Each point defect studied was introduced at different lattice sites to consider a sufficient variety of local environments and analyze its influence on the formation energy values. We have estimated the point defect formation energies with linear regressions using variables which describe the local environment surrounding the point defects. The number and the position of Ni and Cr first nearest neighbors to the point defects were found to drive the evolution of the formation energies. In particular, Ni is found to decrease and Cr to increase the vacancy formation energy of the model alloy, while the opposite trends are found for the dumbbell interstitials. This study suggested that, to a first approximation, the first nearest atoms to point defects can provide reliable estimates of point defect formation energies.

  16. Systematic Review of Community-Based Childhood Obesity Prevention Studies

    PubMed Central

    Segal, Jodi; Wu, Yang; Wilson, Renee; Wang, Youfa

    2013-01-01

    OBJECTIVE: This study systematically reviewed community-based childhood obesity prevention programs in the United States and high-income countries. METHODS: We searched Medline, Embase, PsychInfo, CINAHL, clinicaltrials.gov, and the Cochrane Library for relevant English-language studies. Studies were eligible if the intervention was primarily implemented in the community setting; had at least 1 year of follow-up after baseline; and compared results from an intervention to a comparison group. Two independent reviewers conducted title scans and abstract reviews and reviewed the full articles to assess eligibility. Each article received a double review for data abstraction. The second reviewer confirmed the first reviewer’s data abstraction for completeness and accuracy. RESULTS: Nine community-based studies were included; 5 randomized controlled trials and 4 non–randomized controlled trials. One study was conducted only in the community setting, 3 were conducted in the community and school setting, and 5 were conducted in the community setting in combination with at least 1 other setting such as the home. Desirable changes in BMI or BMI z-score were found in 4 of the 9 studies. Two studies reported significant improvements in behavioral outcomes (1 in physical activity and 1 in vegetable intake). CONCLUSIONS: The strength of evidence is moderate that a combined diet and physical activity intervention conducted in the community with a school component is more effective at preventing obesity or overweight. More research and consistent methods are needed to understand the comparative effectiveness of childhood obesity prevention programs in the community setting. PMID:23753099

  17. A theoretical model for smoking prevention studies in preteen children.

    PubMed

    McGahee, T W; Kemp, V; Tingen, M

    2000-01-01

    The age of the onset of smoking is on a continual decline, with the prime age of tobacco use initiation being 12-14 years. A weakness of the limited research conducted on smoking prevention programs designed for preteen children (ages 10-12) is a well-defined theoretical basis. A theoretical perspective is needed in order to make a meaningful transition from empirical analysis to application of knowledge. Bandura's Social Cognitive Theory (1977, 1986), the Theory of Reasoned Action (Ajzen & Fishbein, 1980), and other literature linking various concepts to smoking behaviors in preteens were used to develop a model that may be useful for smoking prevention studies in preteen children. PMID:12026266

  18. Promoting the Adsorption of Metal Ions on Kaolinite by Defect Sites: A Molecular Dynamics Study

    PubMed Central

    Li, Xiong; Li, Hang; Yang, Gang

    2015-01-01

    Defect sites exist abundantly in minerals and play a crucial role for a variety of important processes. Here molecular dynamics simulations are used to comprehensively investigate the adsorption behaviors, stabilities and mechanisms of metal ions on defective minerals, considering different ionic concentrations, defect sizes and contents. Outer-sphere adsorbed Pb2+ ions predominate for all models (regular and defective), while inner-sphere Na+ ions, which exist sporadically only at concentrated solutions for regular models, govern the adsorption for all defective models. Adsorption quantities and stabilities of metal ions on kaolinite are fundamentally promoted by defect sites, thus explaining the experimental observations. Defect sites improve the stabilities of both inner- and outer-sphere adsorption, and (quasi) inner-sphere Pb2+ ions emerge only at defect sites that reinforce the interactions. Adsorption configurations are greatly altered by defect sites but respond weakly by changing defect sizes or contents. Both adsorption quantities and stabilities are enhanced by increasing defect sizes or contents, while ionic concentrations mainly affect adsorption quantities. We also find that adsorption of metal ions and anions can be promoted by each other and proceeds in a collaborative mechanism. Results thus obtained are beneficial to comprehend related processes for all types of minerals. PMID:26403873

  19. The electronic states of a double carbon vacancy defect in pyrene: a model study for graphene.

    PubMed

    Machado, Francisco B C; Aquino, Adélia J A; Lischka, Hans

    2015-05-21

    The electronic states occurring in a double vacancy defect for graphene nanoribbons have been calculated in detail based on a pyrene model. Extended ab initio calculations using the MR configuration interaction (MRCI) method have been performed to describe in a balanced way the manifold of electronic states derived from the dangling bonds created by initial removal of two neighboring carbon atoms from the graphene network. In total, this study took into account the characterization of 16 electronic states (eight singlets and eight triplets) considering unrelaxed and relaxed defect structures. The ground state was found to be of (1)Ag character with around 50% closed shell character. The geometry optimization process leads to the formation of two five-membered rings in a pentagon-octagon-pentagon (5-8-5) structure. The closed shell character increases thereby to ∼70%; the analysis of unpaired density shows only small contributions confirming the chemical stability of that entity. For the unrelaxed structure the first five excited states ((3)B3g, (3)B2u, (3)B1u, (3)Au and (1)Au) are separated from the ground state by less than 2.5 eV. For comparison, unrestricted density functional theory (DFT) calculations using several types of functionals have been performed within different symmetry subspaces defined by the open shell orbitals. Comparison with the MRCI results gave good agreement in terms of finding the (1)Ag state as a ground state and in assigning the lowest excited states. Linear interpolation curves between the unrelaxed and relaxed defect structures also showed good agreement between the two classes of methods opening up the possibilities of using extended nanoflakes for multistate investigations at the DFT level. PMID:25905682

  20. Is Preventative Long-Segment Surgery for Multi-Level Spondylolysis Necessary? A Finite Element Analysis Study

    PubMed Central

    Zhong, Dongyan; Xu, Hao; Wang, Lan; Yu, Jia; Luo, Zongping

    2016-01-01

    Objective For multi-level spondylolysis patients, surgeons commonly choose to fix all the segments with pars interarticularis defect even those without slippage and not responsible for clinical symptoms. In this study, we tried to study the necessity of the preventative long-segment surgery for the defected segment without slippage in treatment of multi-level spondylolysis patients from a biomechanical perspective. Method We established a bi-level spondylolysis model with pars defects at L4 and L5 segments, and simulated posterior lumbar interbody fusion (PLIF) and pedicle screw fixation at L5-S1 level. Then we compared the biomechanical changes at L4 segment before and after surgery in neutral, flexion, extension, lateral bending and axial rotation position. Results The stress on L4 pars interarticularis was very similar before and after surgery, and reached the highest in axial rotation. The L3-L4 intradiscal pressure was almost the same, while L4-L5 intradiscal pressure changed a little in lateral bending (increase from 1.993 to 2.160 MPa) and axial rotation (decrease from 1.639 to 1.307 MPa) after surgery. The PLIF surgery caused a little increase of range of motion at adjacent L4-L5 and L3-L4 levels, but the change is very tiny (1 degree). Conclusion The PLIF surgery will not cause significant biomechanical change at adjacent segment with pars defect in multi-level spondylolysis. On the contrary, excessive long-segment surgery will damage surrounding soft tissues which are important for maintaining the stability of spine. So a preventative long-segment surgery is not necessary for multi-level spondylolysis as long as there are no soft tissue degeneration signs at adjacent level. PMID:26918333

  1. First-principles study of self-interstitial point defects in BCC metals

    NASA Astrophysics Data System (ADS)

    Seungwu, Han; Luis, Zepeda-Ruiza; Roberto, Car; David, Srolovitz; Graeme, Ackland

    2002-03-01

    We report a study of the energetics of self-interstitial defects in V and Mo based on plane-wave supercell density functional calculations. We use a 128 atom cubic supercell and 2x2x2 k-point grid for BZ sampling, which we found to be sufficient to obtain accurate results on the basis of a careful convergence study. In our calculations, all the atoms of the supercell are allowed to fully relax in presence of the self-interstitial defect. We find that, both in V and in Mo, the most stable orientation of the self-interstitial is [111]. This is different from predictions based on commonly available empirical potentials. We also find that the [111] self-interstitial can easily migrate along the [111] direction passing through an intermediate crowdion configuration. This [111] pathway is essentially barrierless within density functional theory, consistent with experimental data. Finally, we construct a Finnis-Sinclair type potential that reproduces well the first-principles results. This potential will be useful to model self-interstitial diffusion processes, which play a key role in radiation damage cascade evolution.

  2. Recent studies on neural tube defects in embryos of diabetic pregnancy: an overview.

    PubMed

    Dheen, S Thameem; Tay, Samuel S W; Boran, Jiang; Ting, Loh Wan; Kumar, S Dinesh; Fu, Jiang; Ling, Eng-Ang

    2009-01-01

    Maternal diabetes develops in 2-6% of total pregnancies, depending on geographical and ethnic background. About 10% of fetuses from diabetic pregnancy display congenital malformations in various organ systems including cardiovascular, gastrointestinal, genitourinary and neurological systems, among which the neural tube defects (NTDs) such as anencephaly, holoprosencephaly and syntelencephaly were more frequently demonstrated. Recent studies by the Diabetes Control and Complications Trial Research Group show that tight glycemic control early in pregnancy decreases the progression of a number of diabetic complications. However, it appears that the pre-existing tissue damage cannot be reversed even after normoglycemic levels are achieved during pregnancy. In recent years, considerable efforts have been made to investigate the etiology of birth defects among infants of diabetic mothers. It has been shown that diabetes-induced fetal abnormalities are accompanied by some metabolic disturbances including elevated superoxide dismutase (SOD) activity, reduced levels of myoinositol and arachidonic acid and inhibition of the pentose phosphate shunt pathway. Moreover, the frequency of fetal malformations in diabetic pregnancy has been reported to be markedly reduced by dietary supplements of antioxidants such as vitamin E, vitamin C and butylated hy- droxytoluene, suggesting that oxidative stress is involved in the etiology of fetal dysmorphogenesis. Furthermore, several experimental studies have shown that NTDs in embryos of diabetic mice are associated with altered expression of genes, which control development of the neural tube. In this review, recent findings of possible molecular mechanisms which cause morphological changes during neural tube development in embryos of diabetic pregnancy are discussed. PMID:19519395

  3. Racial/Ethnic Differences in Survival of United States Children with Birth Defects: A Population-Based Study

    PubMed Central

    Wang, Ying; Liu, Gang; Canfield, Mark A.; Mai, Cara T.; Gilboa, Suzanne M.; Meyer, Robert E.; Anderka, Marlene; Copeland, Glenn E.; Kucik, James E.; Nembhard, Wendy N.; Kirby, Russell S.

    2015-01-01

    Objectives To examine racial/ethnic-specific survival of children with major birth defects in the US. Study design We pooled data on live births delivered during 1999-2007 with any of 21 birth defects from 12 population-based birth defects surveillance programs. We used the Kaplan-Meier method to calculate cumulative survival probabilities and Cox proportional hazards models to estimate mortality risk. Results For most birth defects, there were small-to-moderate differences in neonatal (<28 days) survival among racial/ethnic groups. However, compared with children born to non-Hispanic white mothers, postneonatal infant (28 days to <1 year) mortality risk was significantly greater among children born to non-Hispanic black mothers for 13 of 21 defects (hazard ratios [HRs] 1.3-2.8) and among children born to Hispanic mothers for 10 of 21 defects (HRs 1.3-1.7). Compared with children born to non-Hispanic white mothers, a significantly increased childhood (≤8 years) mortality risk was found among children born to Asian/Pacific Islander mothers for encephalocele (HR 2.6), tetralogy of Fallot, and atrioventricular septal defect (HRs 1.6-1.8) and among children born to American Indian/Alaska Native mothers for encephalocele (HR 2.8), whereas a significantly decreased childhood mortality risk was found among children born to Asian/Pacific Islander mothers for cleft lip with or without cleft palate (HR 0.6). Conclusion Children with birth defects born to non-Hispanic black and Hispanic mothers carry a greater risk of mortality well into childhood, especially children with congenital heart defect. Understanding survival differences among racial/ethnic groups provides important information for policy development and service planning. PMID:25641238

  4. Reduced Prostasin (CAP1/PRSS8) Activity Eliminates HAI-1 and HAI-2 Deficiency–Associated Developmental Defects by Preventing Matriptase Activation

    PubMed Central

    Szabo, Roman; Uzzun Sales, Katiuchia; Kosa, Peter; Shylo, Natalia A.; Godiksen, Sine; Hansen, Karina K.; Friis, Stine; Gutkind, J. Silvio; Vogel, Lotte K.; Hummler, Edith; Camerer, Eric; Bugge, Thomas H.

    2012-01-01

    Loss of either hepatocyte growth factor activator inhibitor (HAI)-1 or -2 is associated with embryonic lethality in mice, which can be rescued by the simultaneous inactivation of the membrane-anchored serine protease, matriptase, thereby demonstrating that a matriptase-dependent proteolytic pathway is a critical developmental target for both protease inhibitors. Here, we performed a genetic epistasis analysis to identify additional components of this pathway by generating mice with combined deficiency in either HAI-1 or HAI-2, along with genes encoding developmentally co-expressed candidate matriptase targets, and screening for the rescue of embryonic development. Hypomorphic mutations in Prss8, encoding the GPI-anchored serine protease, prostasin (CAP1, PRSS8), restored placentation and normal development of HAI-1–deficient embryos and prevented early embryonic lethality, mid-gestation lethality due to placental labyrinth failure, and neural tube defects in HAI-2–deficient embryos. Inactivation of genes encoding c-Met, protease-activated receptor-2 (PAR-2), or the epithelial sodium channel (ENaC) alpha subunit all failed to rescue embryonic lethality, suggesting that deregulated matriptase-prostasin activity causes developmental failure independent of aberrant c-Met and PAR-2 signaling or impaired epithelial sodium transport. Furthermore, phenotypic analysis of PAR-1 and matriptase double-deficient embryos suggests that the protease may not be critical for focal proteolytic activation of PAR-2 during neural tube closure. Paradoxically, although matriptase auto-activates and is a well-established upstream epidermal activator of prostasin, biochemical analysis of matriptase- and prostasin-deficient placental tissues revealed a requirement of prostasin for conversion of the matriptase zymogen to active matriptase, whereas prostasin zymogen activation was matriptase-independent. PMID:22952456

  5. Birth Defects

    MedlinePlus

    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 ...

  6. Atomistic simulation study of the effects of point defects on the inception of plastic deformation in metals

    NASA Astrophysics Data System (ADS)

    Salehinia, Iman

    Atomistic simulations have been used to study the effect of various types of point defects on the mechanical response of FCC single crystals in nanoindentation and uniaxial tests. To study the effect of spatial distribution of defects in nanoindentation testing, various point defects were located in different relative positions to the indenter. When the defect position was close to the regions of high shear stresses the nucleation of dislocations was related to the location of the defect; however homogeneous nucleation of dislocations was also observed for defect-containing crystals. The effect of the point defects was independent of the indenter size, and the applied pressure needed to initiate plasticity, when compared to defect-free crystals, was a reduction of approximately 10%, 20%, 20% and 50% for a single vacancy, di-vacancy, self-interstitial atom and stacking fault tetrahedron (SFT), respectively. The stochastic nature of the pop-in loads was further explored for different orientations using molecular dynamics and complementary nanoindentation experiments on (100), (101) and (111) single crystals of copper and Ni200. The sensitivity of the crystal to the presence of internal structural defects depends strongly on its crystallographic orientation. The simulations suggest that the first event observed experimentally may not correspond to the first plastic deformation event. Anisotropy effects were also studied for various orientations in uniaxial tests in the presence of a centered SFT. Both the normal stresses to the slip plane and the relative values of Schmid factor in compression and tension affect the observed compression/tension yield asymmetry. The reduction in yield stress was found to be larger in compression than in tension for almost all orientations. The simulations suggest that compression is a more reliable experimental tool for studying the effect of structural defects on the mechanical behavior of the FCC crystals, while tension may be more

  7. Preferential Cu precipitation at extended defects in bcc Fe: An atomistic study

    SciTech Connect

    Zhang, Yongfeng; Millett, Paul C.; Tonks, Michael R.; Bai, Xian-Ming; Biner, S. Bulent

    2015-04-01

    As a starting point to understand Cu precipitation in RPV alloys, molecular dynamics and Metropolis Monte-Carlo simulations are carried out to study the effect of lattice defects on Cu precipitation by taking Fe-Cu system as a model alloy. Molecular dynamics simulations show that owing to the high heat of mixing and positive size mismatch, Cu is attracted by vacancy type defects such as vacancies and voids, and tensile stress fields. In accordance, preferential precipitation of Cu is observed in Metropolis Monte-Carlo simulations at dislocations, prismatic loops and voids. The interaction of Cu with a stress field, e.g., that associated with a dislocation or a prismatic loop, is dominated by elastic effect and can be well described by the linear-elasticity theory. For prismatic loops, the attraction to Cu is found to be size-dependent with opposite trends displayed by vacancy and interstitial loops. The size-dependences can be explained by considering the stress fields produced by these loops. The current results will be useful for understanding the effect of neutron irradiation on Cu precipitation in reactor-pressure-vessel steels.

  8. Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

    SciTech Connect

    Kovács, A.; Duchamp, M.; Boothroyd, C. B.; Dunin-Borkowski, R. E.; Ney, A.; Ney, V.; Galindo, P. L.; Kaspar, T. C.; Chambers, S. A.

    2013-12-28

    We study planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al{sub 2}O{sub 3}), as well as the Co:ZnO/Al{sub 2}O{sub 3} interface, using aberration-corrected transmission electron microscopy and electron energy-loss spectroscopy. Co:ZnO samples that were deposited using pulsed laser deposition and reactive magnetron sputtering are both found to contain extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3–4 Co:ZnO layers next to the Al{sub 2}O{sub 3} substrate. The stacking fault density is in the range of 10{sup 17} cm{sup −3}. We also measure the local lattice distortions around the stacking faults. It is shown that despite the relatively high density of planar defects, lattice distortions, and small compositional variation, the Co:ZnO films retain paramagnetic properties.

  9. Positron annihilation studies of vacancy related defects in ceramic and thin film Pb(Zr,Ti)O{sub 3} materials

    SciTech Connect

    Keeble, D.J.; Krishnan, A.; Umlor, M.T.; Lynn, K.G.; Warren, W.L.; Dimos, D.; Tuttle, B.A.; Ramesh, R.; Poindexter, E.H.

    1994-07-01

    Preliminary positron annihilation studies of ceramic and thin film Pb(Zr,Ti)O{sub 3} (PZT) materials have been completed. This paper examines effects of processing conditions on vacancy related defects. Positron lifetime measurements on bulk PLZT plates showed an increase in positron trapping to a defect state with increasing grain size consistent with trapping to lead vacancy related defects formed through lead oxide loss during processing. Variable energy positron beam measurements were completed on bulk PLZT plates, sol-gel PZT thin films and laser ablated PLZT thin films. Films processed in a reduced oxygen atmosphere were found to give a higher S-parameter, due to an increase in concentration of neutral or negatively charged vacancy type defects, compared with material processed in an oxidizing ambient.

  10. Study of radiation induced deep-level defects in proton irradiated AlGaAs-GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Li, S. S.

    1980-01-01

    Radiation induced deep-level defects (both electron and hole traps) in proton irradiated AlGaAs-GaAs p-n junction solar cells are investigated along with the correlation between the measured defect parameters and the solar cell performance parameters. The range of proton energies studied was from 50 KeV to 10 MeV and the proton fluence was varied from 10 to the 10th power to 10 to the 13th power P/sq cm. Experimental tools employed include deep-level transient spectroscopy, capacitance-voltage, current voltage, and SEM-EBIC methods. Defect and recombination parameters such as defect density and energy level, capture cross section, carrier lifetimes and effective hole diffusion lengths in n-GaAs LPE layers were determined from these measurements.

  11. Effects of boron-nitride substrates on Stone-Wales defect formation in graphene: An ab initio molecular dynamics study

    SciTech Connect

    Jin, K.; Xiao, H. Y.; Zhang, Y.; Weber, W. J.

    2014-05-19

    Ab initio molecular dynamics simulations are performed to investigate the effects of a boron nitride (BN) substrate on Stone-Wales (SW) defect formation and recovery in graphene. It is found that SW defects can be created by an off-plane recoil atom that interacts with the BN substrate. A mechanism with complete bond breakage for formation of SW defects in suspended graphene is also revealed for recoils at large displacement angles. In addition, further irradiation can result in recovery of the SW defects through a bond rotation mechanism in both graphene and graphene/BN, and the substrate has little effect on the recovery process. This study indicates that the BN substrate enhances the irradiation resistance of graphene.

  12. Case-control study of statin prevention of mould infections.

    PubMed

    Thompson, Jessica N; Huycke, Mark M; Greenfield, Ronald A; Kurdgelashvili, George; Gentry, Chris A

    2011-09-01

    Invasive mould infections (IMI) are associated with significant morbidity and mortality. In vitro studies have demonstrated that hydroxymethylglutaryl-CoA (HMG-CoA) reductase inhibitors (statins) have activity against several pathogenic moulds including Zygomycetes and Aspergillus spp. The aim of our study was to determine if statin use is a preventive factor for the development of IMI. This was a retrospective case-control study of 10 United States Veterans Affairs Medical Centers that comprise the Veterans Integrated Service Network (VISN) 16. Cases with IMI and controls were identified from 2001 to 2008. Controls were matched by age, facility, history of transplantation, presence of chronic steroid use and presence of human immunodeficiency virus infection (HIV). Two hundred and thirty-eight patients were included. Independent variables associated with the development of IMI were history of solid malignant tumours (OR 2.63, 1.41-4.87) and hypertension (OR 2.29, 1.13-4.68). Statin use within 3 months of index date was not an independent variable for prevention or development of IMI. No level of exposure to a statin drug appeared to influence the development of infection. This retrospective case-control study suggests that despite evidence of in vitro activity, statins may not decrease risk of IMI. Prospective, controlled trials may be necessary to investigate any potential clinical benefit. PMID:21554419

  13. Evaluation of dentinal defect formation after root canal preparation with two reciprocating systems and hand instruments: an in vitro study

    PubMed Central

    Helvacioglu-Yigit, Dilek; Aydemir, Seda; Yilmaz, Ayca

    2015-01-01

    The purpose of this study was to evaluate the presence of dentinal defects after root canal preparation with hand instruments and two different reciprocating instruments. Sixty freshly extracted mandibular incisor teeth were selected for this in vitro study. On the basis of root length, mesiodistal and buccolingual dimensions, the teeth were allocated into three identical experimental groups (n = 15) and one control group (n = 15). The teeth in the control group were left unprepared. The other groups were: stainless steel hand instruments, WaveOne® Primary instruments and RECIPROC® R25 instruments. The reciprocating instruments were used with a reciprocating gentle in-and-out motion in a torque-limited electric motor at the appropriate preset mode. Horizontal sections were made 3, 6 and 9 mm from the apex. Samples were stained with methylene blue and viewed through a stereomicroscope. The presence of dentinal defects (fractures, incomplete cracks and craze lines) and their locations were investigated by two endodontists. These data were analysed statistically by Fisher's exact and chi-square tests. No defects were observed in the unprepared group. All instruments caused dentinal defects, with no significant differences between the instrument systems. All experimental groups demonstrated significantly more defects at the 3-mm level in comparison with the unprepared group (p = 0.032). At the other levels, there was no significant difference between the experimental groups and the control group. The use of hand or reciprocating instruments could induce the formation of dentinal defects during root canal preparation. PMID:26019654

  14. Risk and protective factors in the origin of conotruncal defects of heart--a population-based case-control study.

    PubMed

    Csáky-Szunyogh, Melinda; Vereczkey, Attila; Kósa, Zsolt; Gerencsér, Balázs; Czeizel, Andrew E

    2013-10-01

    Congenital heart defect (CHD) cases have been evaluated together as a group in some previous epidemiological studies. However, different CHD entities have different etiologies, and the underlying causes are unclear in the vast majority of patients. Thus the aim of this study was to analyze the possible association of different maternal diseases with the risk of four types of conotruncal defects (CTD), that is, truncus arteriosus, d-transposition of the great arteries, tetralogy of Fallot, and double-outlet right ventricle based on autopsy or surgical report diagnosis. Acute and chronic diseases with related drug treatments and peri-conceptual folic acid or multivitamin supplementations were compared in mothers of 598 CTD cases, of 902 matched controls, and 38,151 population controls without any defects, and with 20,896 malformed controls with other isolated non-cardiac defects in the population-based large dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities. Mothers who had medically recorded influenza and the common cold with secondary complications in the prenatal maternity logbook during the second and/or third gestational months were associated with a higher risk of CTD (OR with 95% CI: 2.22, 1.19-3.88). The common denominator of these maternal diseases may be high fever, which could be prevented by antifever therapies. On the other hand, high doses of medically recorded folic acid in early pregnancy were able to reduce the birth prevalence of CTD (OR with 95% CI: 0.54, 0.39-0.73), and this reduction was significant in transposition of the great arteries (0.46, 0.29-0.71) as well. In conclusion, high fever related maternal diseases may have a role in the origin of CTD, while high doses of folic acid in early pregnancy were able to reduce of CTD, particularly transposition of great vessels. PMID:23950097

  15. Experimental study of passive defect localization in plates using ambient noise.

    PubMed

    Chehami, Lynda; de Rosny, Julien; Prada, Claire; Moulin, Emmanuel; Assaad, Jamal

    2015-08-01

    Passive listening methodology has been shown to be a practical and effective method for passive structural health monitoring. In this work, this approach is applied experimentally to monitor the occurrence of defects in thin aluminum plates. A correlation matrix is estimated from noise vibrations recorded on a transducer array. A defect is localized by applying a beamforming algorithm to the difference between the correlation matrices obtained with and without the defect. We successfully detect defects for different kinds of noise sources. Moreover, we show that this technique is robust to detect massive inclusions, holes, and cracks. With a vibrometer, we observe that the fidelity of the estimated transient responses strongly depends on the number of uncorrelated noise sources. Finally, we show that the defect is successfully localized even if the noise source distribution is not uniform, provided that it remains spatially stationary between the states with and without defect. A simple theoretical framework is proposed to interpret these results. PMID:26276962

  16. [Experimental study of coral implantation in repair of skull bone defect in rabbit: histomorphometry of bone].

    PubMed

    Miao, L; Liu, B

    1997-05-01

    In order to evaluate coral as a bone graft substitute in repair of bone defect, particulates of coral were implanted into skull bone defect of rabbit, 1.5 cm in diameter. Hydroxyapatite and blank were taken as controls. The rabbits were sacrificed at the second, fourth, eighth and twelveth weeks after the operation. The specimens were taken and performed histological examination and histomorphometry observation. Results were as follows: at the second week many multinucleus giant cells infiltrated. As time elapsed, the coral were progressively degenerated and new bone was formed to fill the defect. Up to the twelveth week, the coral degenerated completely and new bone formed in the center of the defect. Percentage of new bone was in defect was 36.9%. Compared with the controls, there were significant differences (P < 0.01). It was suggested that coral had good osteoconductility. Howevel, coral underwent rapid degeneration, it might result in inconplete repair of bone defect. PMID:9867910

  17. In situ study of defect migration kinetics in nanoporous Ag with enhanced radiation tolerance

    PubMed Central

    Sun, C.; Bufford, D.; Chen, Y.; Kirk, M. A.; Wang, Y. Q.; Li, M.; Wang, H.; Maloy, S. A.; Zhang, X.

    2014-01-01

    Defect sinks, such as grain boundaries and phase boundaries, have been widely accepted to improve the irradiation resistance of metallic materials. However, free surface, an ideal defect sink, has received little attention in bulk materials as surface-to-volume ratio is typically low. Here by using in situ Kr ion irradiation technique in a transmission electron microscope, we show that nanoporous (NP) Ag has enhanced radiation tolerance. Besides direct evidence of free surface induced frequent removal of various types of defect clusters, we determined, for the first time, the global and instantaneous diffusivity of defect clusters in both coarse-grained (CG) and NP Ag. Opposite to conventional wisdom, both types of diffusivities are lower in NP Ag. Such a surprise is largely related to the reduced interaction energy between isolated defect clusters in NP Ag. Determination of kinetics of defect clusters is essential to understand and model their migration and clustering in irradiated materials. PMID:24435181

  18. Surface scanning techniques to locate and study defects in painted zinc and zinc alloy coated steels

    SciTech Connect

    Isaacs, H.S.; Aldykiewicz, A.J. Jr.; Thierry, D.; Simpson, T.C.

    1995-02-01

    Current density and impedance mapping measurements have been used to locate and monitor corrosion and defects on painted surfaces in solution. Measurements are reported for painted zinc and aluminum-zinc alloy coated steel surfaces. When scratched, current density mapping showed corrosion of the metal coating started at localized sites in both dilute chloride and sulfate solutions. Different scribing techniques were tested exposing only the metal coating and both the coating and the underlying steel. Effect of roll forming was investigated. Current density mapping located corrosion susceptible defects on painted roll formed materials that were not readily discernible optically. Scanning ac mapping showed that artificially formed defects were readily observed. Local impedance variations with frequency were measured for simulated defects and defect free areas of painted surfaces. Variations in paint thickness and the presence of defects were detected using the ac techniques.

  19. In situ study of defect migration kinetics in nanoporous Ag with enhanced radiation tolerance.

    PubMed

    Sun, C; Bufford, D; Chen, Y; Kirk, M A; Wang, Y Q; Li, M; Wang, H; Maloy, S A; Zhang, X

    2014-01-01

    Defect sinks, such as grain boundaries and phase boundaries, have been widely accepted to improve the irradiation resistance of metallic materials. However, free surface, an ideal defect sink, has received little attention in bulk materials as surface-to-volume ratio is typically low. Here by using in situ Kr ion irradiation technique in a transmission electron microscope, we show that nanoporous (NP) Ag has enhanced radiation tolerance. Besides direct evidence of free surface induced frequent removal of various types of defect clusters, we determined, for the first time, the global and instantaneous diffusivity of defect clusters in both coarse-grained (CG) and NP Ag. Opposite to conventional wisdom, both types of diffusivities are lower in NP Ag. Such a surprise is largely related to the reduced interaction energy between isolated defect clusters in NP Ag. Determination of kinetics of defect clusters is essential to understand and model their migration and clustering in irradiated materials. PMID:24435181

  20. Spatial correlation between chemical and topological defects in vitreous silica: UV-resonance Raman study

    SciTech Connect

    Saito, M. D’Amico, F.; Bencivenga, F.; Cucini, R.; Gessini, A.; Principi, E.; Masciovecchio, C.

    2014-06-28

    A spatial correlation between chemical and topological defects in the tetrahedron network in vitreous silica produced by a fusion process of natural quartz crystals was found by synchrotron-based UV resonance Raman experiments. Furthermore, a quantitative correlation between these defects was obtained by comparing visible Raman and UV absorption spectra. These results indicate that in vitreous silica produced by the fusion process the topological defects disturb the surrounding tetrahedral silica network and induce further disorder regions with sub nanometric sizes.

  1. Study of EUVL mask defect inspection using 199-nm inspection tool with super-resolution method

    NASA Astrophysics Data System (ADS)

    Shigemura, Hiroyuki; Amano, Tsuyoshi; Arisawa, Yukiyasu; Suga, Osamu; Hashimoto, Hideaki; Saito, Masanori; Takeda, Masaya; Kikuiri, Nobutaka; Hirano, Ryoichi

    2009-10-01

    In this paper, we will report on our experimental results on the impact of inspection system optics on mask defect detection sensitivity. We evaluated the capability of detecting defects on the EUVL masks by using a new inspection tool (NPI6000EUVα) made by NuFlare Technology, Inc. (NFT) and Advanced Mask Inspection Technology, Inc. (AMiT). This tool is based on NPI-5000 which is the leading-edge photomask defect inspection system using 199nm wavelength inspection optics. The programmed defect mask with LR-TaBN absorber was used which had various sized opaque and clear extension defects on hp-180nm, hp-128nm, and hp-108nm line and space patterns. According to the analysis, to obtain optimum sensitivity for various types of defects, using both C- and P-polarized illumination conditions were found to be effective. At present, sufficient defect-detection sensitivity is achieved for opaque and clear extension defects in hp128nm (hp32nm at wafer). For hp108nm (hp27nm at wafer), using both C- and P- polarized illumination is effective. However, further developments in defect-detection sensitivity are necessary.

  2. Effects of liquid nitrogen cryotherapy and bone grafting on artificial bone defects in minipigs: a preliminary study.

    PubMed

    Pogrel, M A; Regezi, J A; Fong, B; Hakim-Faal, Z; Rohrer, M; Tran, C; Schiff, T

    2002-06-01

    Liquid nitrogen cryotherapy has been advocated as an adjunct in the enucleation and curettage of locally aggressive lesions of the jaws. Simultaneous autogenous bone grafting has also been advocated to accelerate bone formation and reduce morbidity. There is, however, relatively little scientific basis for either of these hypotheses. In this study, nine Yucatan minipigs had artificial defects created in the mandible, which were treated with liquid nitrogen spray. Half of the defects were grafted with autogenous bone from the chin and half were closed primarily. Two animals were sacrificed 3 days postoperatively to measure the width of necrosis and the rest were sacrificed at 3 months to assess healing and new bone formation. It was found that drilling the artificial defects alone caused bone necrosis for a mean depth of 0.09 mm. Liquid nitrogen cryospray caused a mean depth of bone necrosis of 0.82 mm (range 0.51-1.52 mm). The defects that were bone grafted healed well clinically. Defects not bone grafted showed a 50% rate of wound breakdown and sequestrum formation with delayed healing. Vital staining showed a non-significantly greater rate of bone formation in the grafted defects. Digitally superimposed radiography showed a non-significantly greater bone density in the non-grafted defects at 3 months postoperatively. It appears that liquid nitrogen cryospray does devitalize an area of bone around defects in the mandible. The width of necrosis is usually less than 1 mm and subsequent healing is enhanced by autogenous bone grafting. This has clinical implications. PMID:12190137

  3. 76 FR 81959 - Notice of Proposed Information Collection: Comment Request; Homelessness Prevention Study Site...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-29

    ... Study Site Visits AGENCY: Office of the Chief Information Officer, HUD. ACTION: Notice. SUMMARY: The... following information: Title of Proposal: Homelessness Prevention Study Site Visits. OMB Control Number, if... requirements associated with HUD's Homelessness Prevention Study Site Visits. This information...

  4. Relationship Satisfaction Among Mothers of Children With Congenital Heart Defects: A Prospective Case-Cohort Study

    PubMed Central

    Solberg, Øivind; Holmstrøm, Henrik; Landolt, Markus A.; Eskedal, Leif T.; Vollrath, Margarete E.

    2013-01-01

    Objective To assess the level of partner relationship satisfaction among mothers of children with different severity of congenital heart defects (CHD) compared with mothers in the cohort. Methods Mothers of children with mild, moderate, or severe CHD (n = 182) and a cohort of mothers of children without CHD (n = 46,782) from the Norwegian Mother and Child Cohort Study were assessed at 5 time points from pregnancy to 36 months postpartum. A 5-item version of the Relationship Satisfaction scale was used, and relevant covariates were explored. Results The trajectories of relationship satisfaction among mothers of children with varying CHD severity did not differ from the trajectories in the cohort. All women in the cohort experienced decreasing relationship satisfaction from 18 months after delivery up to 36 months after delivery. Conclusions Having a child with CHD, regardless of severity, does not appear to exacerbate the decline in relationship satisfaction. PMID:23792348

  5. An electrically detected magnetic resonance study of performance limiting defects in SiC metal oxide semiconductor field effect transistors

    NASA Astrophysics Data System (ADS)

    Cochrane, C. J.; Lenahan, P. M.; Lelis, A. J.

    2011-01-01

    In this study, we utilize electrically detected magnetic resonance (EDMR) techniques and electrical measurements to study defects in SiC based metal oxide semiconductor field effect transistors (MOSFETs). We compare results on a series of SiC MOSFETs prepared with significantly different processing parameters. The EDMR is detected through spin dependent recombination (SDR) in most cases. However, in some devices at a fairly high negative bias, the EDMR likely also involves spin dependent trap-assisted tunneling (SDT) between defects on both sides of the SiC/SiO2 interface. At least three different defects have been detected in the magnetic resonance measurements. The defects observed include two at the SiC/SiO2 interface or on the SiC side of the SiC/SiO2 interface: one is very likely a vacancy center with a distribution which extends into the bulk of the SiC and the other is likely a "dangling bond" defect. A third defect, located on the SiO2 side of the SiC/SiO2 interface, has a spectrum very similar to that previously reported for an oxygen deficient silicon coupled to a hydrogen atom. In nearly all cases, we observe a strong dominating single line EDMR spectrum with an isotropic g≈2.0027. In some samples, this strong central line is accompanied by two pairs of considerably weaker side peaks which we link to hyperfine interactions with nearby Si and C atoms. The pattern is physically reasonable for a silicon vacancy in SiC. We therefore tentatively assign it to a silicon vacancy or silicon vacancy associated defect in the SiC. In one set of devices with very high interface trap density we observe another dominating spectrum with g∥=2.0026 and g⊥=2.0010 with the symmetry axis coincident with the [0001] and nearly the SiC/SiO2 interface normal. We ascribe this EDMR spectrum to a "dangling bond" defect. A third EDMR spectrum shows up in some devices at a fairly large negative gate bias. The phase of this spectrum is quite consistently opposite to that of the

  6. An in vivo study on the effect of scaffold geometry and growth factor release on the healing of bone defects.

    PubMed

    Yilgor, P; Yilmaz, G; Onal, M B; Solmaz, I; Gundogdu, S; Keskil, S; Sousa, R A; Reis, R L; Hasirci, N; Hasirci, V

    2013-09-01

    The hypothesis of this study was that the extent of bone regeneration could be enhanced by using scaffolds with appropriate geometry, and that such an effect could be further increased by mimicking the natural timing of appearance of bone morphogenetic proteins BMP-2 and BMP-7 after fracture. Bioplotted poly(ε-caprolactone) (PCL) disks with four different fibre organizations were used to study the effect of 3D scaffold architecture on the healing of bone defects in a rat pelvis model. Moreover, one PCL construct was further modified by introducing a nanoparticulate sequential BMP-2/BMP-7 delivery system into this scaffold. Scaffolds and functionalized construct along with free nanocapsules were implanted using a rat iliac crest defect model. Six weeks post-implantation, the defects were evaluated by CT scan and histology. Analysis revealed that the basic architecture, having the highest pore volume for tissue ingrowth, presented the highest bone formation as determined by the bone mineral density (BMD) within the defect (144.2 ± 7.1); about four-fold higher than that of the empty defect (34.9 ± 10.7). It also showed the highest histological analysis scores with a high amount of bone formation within the defect, within the scaffold pores and along the outer surfaces of the scaffold. The basic scaffold carrying the BMP-2/BMP-7 delivery system showed significantly higher bone formation than the growth factor-free basic scaffold at 6 weeks (BMD 206.8 ± 15.7). Histological analysis also revealed new bone formation in close to or in direct contact with the construct interface. This study indicates the importance of open and interconnecting pore geometry on the better healing of bone defects, and that this effect could be further increased by supplying growth factors, as is the case in nature. PMID:22396311

  7. A randomized controlled experimental study comparing chitosan coated polypropylene mesh and Proceed™ mesh for abdominal wall defect closure

    PubMed Central

    Jayanth, S.T.; Pulimood, Anna; Abraham, Deepak; Rajaram, A.; Paul, M.J.; Nair, Aravindan

    2015-01-01

    Background Abdominal wall defects and hernias are commonly repaired with synthetic or biological materials. Adhesions and recurrences are a common problem. A study was conducted to compare Chitosan coated polypropylene mesh and a polypropylene–polydioxanone composite with oxidized cellulose coating mesh (Proceed™) in repair of abdominal wall defect in a Rabbit hernia model. Methods A randomized controlled experimental study was done on twelve New Zealand white rabbits. A ventral abdominal defect was created in each of the rabbits. The rabbits were divided into two groups. In one group the defect was repaired with Chitosan coated polypropylene mesh and Proceed mesh™ in the other. The rabbits were operated in two phases. They were followed up at four weeks and twelve weeks respectively after which the rabbits were sacrificed. They were evaluated by open exploration and histopathological examination. Their efficacy in reducing adhesion and ability of remodeling and tissue integration were studied. Results There was no statistical significance in the area of adhesion, the force required to remove the adhesions, tissue integration and remodeling between Chitosan and Proceed™ group. Histological analysis revealed that the inflammatory response, fibrosis, material degradation and remodeling were similar in both the groups. There were no hernias, wound infection or dehiscence in any of the studied animals. Conclusion Chitosan coated polypropylene mesh was found to have similar efficacy to Proceed™ mesh. Chitosan coated polypropylene mesh, can act as an anti adhesive barrier when used in the repair of incisional hernias and abdominal wall defects. PMID:26594357

  8. An Empirical Case Study of a Child Sexual Abuse Prevention Initiative in Georgia

    ERIC Educational Resources Information Center

    Schober, Daniel J.; Fawcett, Stephen B.; Thigpen, Sally; Curtis, Anna; Wright, Renee

    2012-01-01

    Objective: This empirical case study describes Prevent Child Abuse Georgia's effort to prevent child sexual abuse (CSA) by educating communities throughout the state on supporting preventive behaviour. The initiative consisted of three major components: (1) dissemination of CSA prevention messages and materials; (2) a statewide helpline that…

  9. A comparative study on defect estimation using XPS and Raman spectroscopy in few layer nanographitic structures.

    PubMed

    Ganesan, K; Ghosh, Subrata; Gopala Krishna, Nanda; Ilango, S; Kamruddin, M; Tyagi, A K

    2016-08-10

    Defects in planar and vertically oriented nanographitic structures (NGSs) synthesized by plasma enhanced chemical vapor deposition (PECVD) have been investigated using Raman and X-ray photoelectron spectroscopy. While Raman spectra reveal the dominance of vacancy and boundary type defects respectively in vertical and planar NGSs, XPS provides additional information on vacancy related defect peaks in the C 1s spectrum, which originate from non-conjugated carbon atoms in the hexagonal lattice. Although an excellent correlation prevails between these two techniques, our results show that estimation of surface defects by XPS is more accurate than Raman analysis. Nuances of these techniques are discussed in the context of assessing defects in nanographitic structures. PMID:27445041

  10. Ab initio study of He point defects in fcc Au-Ag alloys

    SciTech Connect

    Zhu, Zi Qiang; Yang, Li; Nie, JL; Peng, SM; Long, XG; Zhou, X. S.; Zu, Xiaotao; Gao, Fei

    2013-04-25

    The relative stabilities of He defects in two fcc Au-Ag alloys (Au3Ag2 and AuAg) are investigated using ab initio method based on density functional theory. The results show that the stabilities of He defects in the two alloys mainly depend on the atomic arrangements of the nearest neighboring host metals. A He interstitial prefers to stay at a site with more Ag neighboring atoms, while the favorable substitutional site has more Au neighboring atoms in Au-Ag alloys. Moreover, the substitutional He defects are the most stable configurations in both the alloys, and the octahedral He interstitials are energetically more favorable than the tetrahedral interstitials. It is of interest to note that the properties of He defects slightly depend on the mass-density of Au-Ag alloys. The results also demonstrate that the relative stabilities of He defects are primarily attributed to the hybridization between metals d states and He p states.

  11. Evaluation of the Esthetic Properties of Developmental Defects of Enamel: A Spectrophotometric Clinical Study

    PubMed Central

    Guerra, Fabrizio; Mazur, Marta; Corridore, Denise; Pasqualotto, Debora; Nardi, Gianna Maria; Ottolenghi, Livia

    2015-01-01

    Objectives. Detailed clinical quantification of optical properties of developmental defect of enamel is possible with spectrophotometric evaluation. Developmental defects of enamel (DDE) are daily encountered in clinical practice. DDE are an alteration in quality and quantity of the enamel, caused by disruption and/or damage to the enamel organ during amelogenesis. Methods. Several clinical indices have been developed to categorize enamel defects based on their nature, appearance, microscopic features, or cause. A sample of 39 permanent teeth presenting DDE on labial surface was examined using the DDE Modified Index and SpectroShade evaluation. The spectrophotometric approach quantifies L* (luminosity), a* (quantity of green-red), and b* (quantity of blue-yellow) of different DDE. Conclusions. SpectroShade evaluation of the optical properties of the enamel defect enhances clinical understanding of severity and extent of the defect and characterizes the enamel alteration in terms of color discrepancy and surface characterization. PMID:25874260

  12. Proton irradiation induced defects in GaN: Rutherford backscattering and thermally stimulated current studies

    NASA Astrophysics Data System (ADS)

    Nakamura, T.; Nishikata, N.; Kamioka, K.; Kuriyama, K.; Kushida, K.

    2016-03-01

    The proton irradiation induced defects in GaN are studied by combining elastic recoil detection analysis (ERDA), thermally stimulated current (TSC), and Rutherford backscattering spectroscopy (RBS) measurements. The proton irradiation (peak concentration: 1.0 × 1015 cm-2) into GaN films with a thickness of 3 μm is performed using a 500 keV implanter. The proton concentration by a TRIM simulation is maximum at 3600 nm in depth, which means that the proton beam almost passes through the GaN film. The carrier concentration decreases three orders of magnitude to 1015 cm-3 by the proton irradiation, suggesting the existence of the proton irradiation-induced defects. The ERDA measurements using the 1.5 MeV helium beam can evaluate hydrogen from the surface to ∼300 nm. The hydrogen concentration at ∼220 nm is ∼8.3 × 1013 cm-2 and ∼1.0 × 1014 cm-2 for un-irradiated and as-irradiated samples, respectively, suggesting that electrical properties are almost not affected by hydrogen. TSC measurements show a broad spectrum at around 110 K which can be divided into three traps, P1 (ionization energy 173 meV), P2 (251 meV), and P3 (330 meV). The peak intensity of P1 is much larger than that of P2 and P3. These traps are related to the N vacancy and/or complex involving N vacancy (P1), neutral Ga vacancy (VGa) (P2), and complex involving VGa (P3). The Ga displacement concentration evaluated by RBS measurements is 1.75 × 1019 cm-3 corresponding to 1/1000 of the Ga concentration in GaN. The observed Ga displacement may be origins of P2 and P3 traps.

  13. SENSITIVITY STUDIES FOR AN IN-SITU PARTIAL DEFECT DETECTOR (PDET) IN SPENT FUEL USING MONTE CARLO TECHNIQUES

    SciTech Connect

    Sitaraman, S; Ham, Y S

    2008-04-28

    This study presents results from Monte Carlo radiation transport calculations aimed at characterizing a novel methodology being developed to detect partial defects in Pressurized Water Reactor (PWR) spent fuel assemblies (SFAs). The methodology uses a combination of measured neutron and gamma fields inside a spent fuel assembly in an in-situ condition where no movement of the fuel assembly is required. Previous studies performed on single isolated assemblies resulted in a unique base signature that would change when some of the fuel in the assembly is replaced with dummy fuel. These studies indicate that this signature is still valid in the in-situ condition enhancing the prospect of building a practical tool, Partial Defect Detector (PDET), which can be used in the field for partial defect detection.

  14. METROPOLITAN ATLANTA CONGENITAL DEFECTS PROGRAM (MACDP)

    EPA Science Inventory

    The Metropolitan Atlanta Congenital Defects Program (MACDP) was established in 1967 by the Centers for Disease Control and Prevention with Emory University and the Georgia Mental Health Institute as the nation's first population-based active ascertainment birth defects surveillan...

  15. Three-dimensional interactive Molecular Dynamics program for the study of defect dynamics in crystals

    NASA Astrophysics Data System (ADS)

    Patriarca, M.; Kuronen, A.; Robles, M.; Kaski, K.

    2007-01-01

    The study of crystal defects and the complex processes underlying their formation and time evolution has motivated the development of the program ALINE for interactive molecular dynamics experiments. This program couples a molecular dynamics code to a Graphical User Interface and runs on a UNIX-X11 Window System platform with the MOTIF library, which is contained in many standard Linux releases. ALINE is written in C, thus giving the user the possibility to modify the source code, and, at the same time, provides an effective and user-friendly framework for numerical experiments, in which the main parameters can be interactively varied and the system visualized in various ways. We illustrate the main features of the program through some examples of detection and dynamical tracking of point-defects, linear defects, and planar defects, such as stacking faults in lattice-mismatched heterostructures. Program summaryTitle of program:ALINE Catalogue identifier:ADYJ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADYJ_v1_0 Program obtainable from: CPC Program Library, Queen University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Computers:DEC ALPHA 300, Intel i386 compatible computers, G4 Apple Computers Installations:Laboratory of Computational Engineering, Helsinki University of Technology, Helsinki, Finland Operating systems under which the program has been tested:True64 UNIX, Linux-i386, Mac OS X 10.3 and 10.4 Programming language used:Standard C and MOTIF libraries Memory required to execute with typical data:6 Mbytes but may be larger depending on the system size No. of lines in distributed program, including test data, etc.:16 901 No. of bytes in distributed program, including test data, etc.:449 559 Distribution format:tar.gz Nature of physical problem:Some phenomena involving defects take place inside three-dimensional crystals at times which can be hardly predicted. For this reason they are

  16. Evolution of extended defects in polycrystalline UO2 under heavy ion irradiation: combined TEM, XRD and Raman study

    NASA Astrophysics Data System (ADS)

    Onofri, C.; Sabathier, C.; Palancher, H.; Carlot, G.; Miro, S.; Serruys, Y.; Desgranges, L.; Legros, M.

    2016-05-01

    A well-suited way to understand the behavior under irradiation of the UO2 nuclear fuel is to use ion implantations and further analyze the microstructure. The present work is focused on the characteristics of extended defects created by Kr implantations in UO2 polycrystals. The influence of many parameters on these extended defects has been studied separately: irradiation temperature (room temperature, 500 and 600 °C), ion fluence (5 × 1015 and 1.26 × 1017 i/cm2), ion energy (4 and 27 MeV) and conditions of subsequent thermal annealing. The evolution of extended defects characteristics and density was determined using transmission electron microscopy and additional damage characterizations were performed by X-ray diffraction and Raman spectroscopy. Results obtained by the different analytical techniques are shown to be in excellent agreement and to complement literature data. In addition, this work presents the extended defect transformation induced by fluence (dislocation loops and lines → tangled dislocation network) and shows that temperature influences directly their evolution kinetics. Moreover we demonstrate that the temperature to allow extended defects mobility is different during irradiation and under thermal annealing conditions. Finally dislocation line density and swelling obtained from this study are found in the same order of magnitude as the ones obtained from in pile irradiations.

  17. Study of the defect structure of paratellurite crystal using multiwave diffraction and normal X-ray diffractometry methods

    SciTech Connect

    Marchenkov, N. V. Blagov, A. E.; Lomonov, B. A.; Pisarevsky, Yu. V.; Kovalchuk, M. V.

    2013-03-15

    Multiwave X-ray diffraction has been used to study the structure of crystalline samples. A cycle of local measurements of rocking curves (RCs) of the (220) and (371) reflections under conditions of multiwave diffraction (MD) has been carried out in a paratellurite crystal. The data obtained are used to compare the sensitivity to structure defects of two-beam diffraction with that of MD, which makes it possible to study the X-ray wave phase. The comparison has revealed a higher ability of the phase-sensitive method to detect defects.

  18. Nuclear magnetic resonance zeugmatographic imaging of the heart: application to the study of ventricular septal defect. [Lambs

    SciTech Connect

    Heneghan, M.A.; Biancaniello, T.M.; Heidel, E.; Peterson, S.B.; Marsh, M.J.; Lauterbur, P.C.

    1982-04-01

    The present work was undertaken to determine the applicability of nuclear magnetic resonance (NMR) imaging to the study of congenital heart disease. Three-dimensional proton density images of preserved lamb hearts with and without an artificially created ventricular septal defect were reconstructed and displayed in multiple planes. Sections obtained in the sagittal plane through the ventricular septum clearly showed the size, shape, and location of the defect. Results of these experiments suggest that NMR zeugmatography will become a valuable addition to existing imaging techniques for the study of congenital heart disease.

  19. [Prevention from secondary nerve root adhesion: an experimental study].

    PubMed

    Yao, M; Sun, Y; Yan, J

    1996-06-01

    In the study, 27 dogs were divided into three groups: A, B and C. Then all of the dogs had their lumbar intervertebral disks removed. Into the wounded cavity of group A, 1 ml of dimethicone was dropped and gelatin sponge was applied on the surface of the nerve root of group B. Group C was served as the control. The dogs were killed and the operation area was removed respectively 2 weeks, 4 weeks, and 12 weeks after the operation for macroscopical observation, nerve root motility measurement and histological examination. The result of the experiment proved that dimethicone was fairly effective in the prevention from secondary nerve root adhesion. While gelatin sponge in the process of its absorption induced the formation of quite a few scar tissues, thus aggrevating nerve root adhesion. PMID:9594172

  20. Caries prevention during pregnancy: results of a 30-month study.

    PubMed

    Brambilla, E; Felloni, A; Gagliani, M; Malerba, A; García-Godoy, F; Strohmenger, L

    1998-07-01

    The purpose of this 30-month study was to explore the effectiveness of a caries-preventive regimen in lowering the salivary mutans streptococci level in pregnant women and, subsequently, in inhibiting the growth of these bacteria in their young children. Beginning at the end of the sixth month of pregnancy and continuing until delivery, subjects rinsed daily with 0.05 percent sodium fluoride and 0.12 percent chlorhexidine. The authors monitored the salivary mutans streptococci levels during the last six months of pregnancy and every six months thereafter for 24 months. They also measured bacterial levels in the children every six months until they reached age 24 months. The results show that treatment significantly reduced salivary mutans streptococci levels in mothers and delayed the colonization of bacteria in their children for about four months. PMID:9685762

  1. Native defects in LiNH2: A first-principles study

    NASA Astrophysics Data System (ADS)

    Wang, Jianchuan; Du, Yong; Xu, Honghui; Jiang, Chao; Kong, Yi; Sun, Lixian; Liu, Zi-Kui

    2011-07-01

    Native defects in lithium amide (LiNH2), a promising candidate for hydrogen storage, are investigated by first-principles calculations based on density functional theory. We examine the structural properties and formation energies of H-, Li-, and N-related defects in all possible states. We find that the dominant H- and Li-related defects are in charged states, i.e., negatively charged H vacancy (VH-), positively charged H interstitial (Hi+), negatively charged Li vacancy (VLi-), and positively charged Li interstitial (ILi+). VLi- and ILi+ are present in the highest concentration. The positively charged NH2 vacancy has the lowest formation energy among N-related defects. Furthermore, migration processes of the dominant defects are investigated. VLi- diffuses most rapidly with the lowest migration energy of 0.20 eV. Both formation and migration energies of Li-related dominant defects are found to be lower than those of H-related dominant defects. With an activation energy of 0.72 eV, VLi- is the major diffusive species in LiNH2. Our results further indicate that the formation of Hi is the bottleneck for H transport.

  2. A study on the factors that affect the advanced mask defect verification

    NASA Astrophysics Data System (ADS)

    Woo, Sungha; Jang, Heeyeon; Lee, Youngmo; Kim, Sangpyo; Yim, Donggyu

    2015-10-01

    Defect verification has become significantly difficult to higher technology nodes over the years. Traditional primary method of defect (include repair point) control consists of inspection, AIMS and repair steps. Among them, AIMS process needs various wafer lithography conditions, such as NA, inner/outer sigma, illumination shape and etc. It has a limit to analyze for every layer accurately because AIMS tool uses the physical aperture system. And it requires meticulous management of exposure condition and CD target value which change frequently in advanced mask. We report on the influence of several AIMS parameters on the defect analysis including repair point. Under various illumination conditions with different patterns, it showed the significant correlation in defect analysis results. It is able to analyze defect under certain error budget based on the management specification required for each layer. In addition, it provided us with one of the clues in the analysis of wafer repeating defect. Finally we will present 'optimal specification' for defect management with common AIMS recipe and suggest advanced mask process flow.

  3. A systematic study of ball passing frequencies based on dynamic modeling of rolling ball bearings with localized surface defects

    NASA Astrophysics Data System (ADS)

    Niu, Linkai; Cao, Hongrui; He, Zhengjia; Li, Yamin

    2015-11-01

    Ball passing frequencies (BPFs) are very important features for condition monitoring and fault diagnosis of rolling ball bearings. The ball passing frequency on outer raceway (BPFO) and the ball passing frequency on inner raceway (BPFI) are usually calculated by two well-known kinematics equations. In this paper, a systematic study of BPFs of rolling ball bearings is carried out. A novel method for accurately calculating BPFs based on a complete dynamic model of rolling ball bearings with localized surface defects is proposed. In the used dynamic model, three-dimensional motions, relative slippage, cage effects and localized surface defects are all considered. Moreover, localized surface defects are modeled accurately with consideration of the finite size of the ball, the additional clearance due to material absence, and changes of contact force directions. The reasonability of the proposed method for the prediction of dynamic behaviors of actual ball bearings with localized surface defects and for the calculation of BPFs is discussed by investigating the motion characteristics of a ball when it rolls through a defect. Parametric investigation shows that the shaft speed, external loads, the friction coefficient, raceway groove curvature factors, the initial contact angle, and defect sizes have great effects on BPFs. For a loaded ball bearing, the combination of rolling and sliding in contact region occurs, and the BPFs calculated by simple kinematical relationships are inaccurate, especially for high speed, low external load, and large initial contact angle conditions where severe skidding occurs. The hypothesis that the percentage variation of the spacing between impulses in a defective ball bearing was about 1-2% reported in previous investigations can be satisfied only for the conditions where the skidding effect in a bearing is slight. Finally, the proposed method is verified with two experiments.

  4. Thrombus deflector stent for stroke prevention: A simulation study.

    PubMed

    Choi, Hyo Won; Navia, Jose A; Kassab, Ghassan S

    2015-07-16

    Atrial fibrillation (AF) is a dysfunction of heart rhythm and represents an increased predisposition to ischemic stroke in AF patients. It has been shown that the AF-induced hemodynamic conditions may contribute to the increased embolic propensity through the carotid arteries. We simulated a stroke-prevention device with a unique strut structure to deflect the trajectory of a blood clot to the carotid artery. We identified the important determinants of functionality in a device design using computational fluid dynamics simulations. Quantitative assessment of deflection efficacy over various clot dimensions was carried out for the device with different strut configurations under AF flow conditions. The simulations demonstrate that the trajectory of a clot destined to the left common carotid artery (LCCA) can be deflected by a strut-structured device at the LCCA inlet with virtually no change in flow resistance. The deflection efficacy of the device is dependent on the clot properties and strut designs of the device. A configuration of 0.75 mm thick and 0.75 mm distant struts with 50% of surface convexity were found to provide maximum deflection efficacy (e.g., 36% greater deflection efficacy than a flat filter) among the strut structures considered. The results suggest that a deflector stent implanted in the aortic branch may be an effective stroke-prevention device. The present simulations motivate pre-clinical animal studies as well as further studies on patient-specific design of the device that maximize the deflection efficacy while minimizing device safety issues. PMID:26049978

  5. Nematic ordering and defects on the surface of a sphere: A Monte Carlo simulation study

    NASA Astrophysics Data System (ADS)

    Bates, Martin A.

    2008-03-01

    We examine the ordering of hard rods on the surface of a sphere using computer simulations. As predicted by previous theories of thin nematic shells we observe four s =+1/2 defects. However, the predicted tetrahedral symmetry for the defects and the "baseball" director configuration is not observed. Instead the four defects are located, on average, on a great circle which splits the sphere into two hemispheres, each of which has a splay dominated director configuration. We argue that this result occurs as the bend elastic constant for hard rods is much larger than the splay elastic constant.

  6. The Violence Prevention Community Meeting: A Multi-Site Study

    PubMed Central

    Lanza, Marilyn; Ridenour, Marilyn; Hendricks, Scott; Rierdan, Jill; Zeiss, Robert; Schmidt, Satu; Lovelace, Jeff; Amandus, Harlan

    2016-01-01

    Objective The Violence Prevention Community Meeting (VPCM) is a specialized form of community meeting in which avoiding violence and promoting non-violent problem solving and interpersonal civility are focal points. A nationwide study to assess the VPCM as an effective intervention to reduce workplace violence was undertaken. Participants Seven acute locked psychiatric units of the Veterans Health Administration (VHA) throughout the United States participated in the study. Methods All patients and all staff on the seven in-patient locked psychiatry units participated in the intervention (VPCM) or as a control (treatment as usual). The study was 21 weeks at each site. The three time periods were pre-treatment weeks 1 – 3, treatment weeks 4 – 18, and post-treatment weeks 19 – 21. The VPCM was conducted during the treatment weeks. Results Overall rates of aggression declined by 0.6% (95%CI: −5.6%, 6.5%; nonsignificant) per week in the intervention hospitals and by 5.1% (95%CI: 0.4%, 9.6%; significant) per week for the control hospitals. Conclusions Aggression decreased for both the intervention and control hospitals which could be due to enrollment in a research study and thus being more aware of their ability to address workplace violence at their site. PMID:27256945

  7. Defective support network: a major obstacle to coping for patients with heart failure: a qualitative study

    PubMed Central

    Shahrbabaki, Parvin Mangolian; Nouhi, Esmat; Kazemi, Majid; Ahmadi, Fazlollah

    2016-01-01

    Background Heart failure as a chronic disease poses many challenges for a patient in his or her everyday life. Support in various aspects of life positively affects coping strategies and influences the well-being and health outcomes of heart failure patients. Inadequate support may lead to a worsening of symptoms, increased hospital readmissions, psychological disorders, and a reduced quality of life. Objective This study explored obstacles to coping related to support for heart failure patients as viewed by the patients themselves and their family members and caregivers. Design This qualitative study was conducted using content analysis. The 20 Iranian participants included 11 patients with heart failure, three cardiologists, three nurses, and three family members of heart failure patients selected through purposive sampling. Data were collected through semi-structured interviews and analyzed using the Lundman and Graneheim qualitative content analysis method. Results During data analysis, ‘defective support network’ developed as the main theme along with four other categories of ‘inadequate family performance’, ‘inadequate support by the healthcare team’, ‘distorted societal social support’, and ‘inadequate welfare support’. Conclusion The findings of the current study can assist health authorities and planners in identifying the needs of patients with heart failure so as to focus and plan on facilitating their coping as much as possible by obviating the existing obstacles. PMID:27041539

  8. Ear defects.

    PubMed

    Shonka, David C; Park, Stephen S

    2009-08-01

    The projection and exposure of the auricle make it particularly susceptible to actinic injury and thus to cutaneous malignancies. Auricular reconstruction is challenging because of its unique surface anatomy and undulating topography. This article organizes auricular defects into different categories based on anatomic location and extent of tissue loss, including skin-only defects, small composite defects, full-thickness defects involving or sparing the upper third of the ear, and total auricular loss. The authors share an algorithm for repair of the array of auricular defects. PMID:19698921

  9. The periodontal tissues in healed degree III furcation defects. An experimental study in dogs.

    PubMed

    Araújo, M; Berglundh, T; Lindhe, J

    1996-06-01

    The aim of the present study was (i) to describe the periodontal tissue that formed in degree III furcation defects in mandibular molars of dogs following GTR therapy and (ii) to compare this healed periodontium to the corresponding tissue of pristine furcations. The study was performed in 10 mongrels dogs. In 6 of the dogs (group A), the 2nd and 4th premolars in both sides of the mandible were extracted 2 months prior to the start of the study. The 4 remaining dogs (group B) were used as normal untreated controls. In the dogs of group A, a furcation defect was produced in the 3rd mandibular premolars and reconstructive surgery was later performed in accordance with the GTR technique. 5 months after reconstructive surgery, all 10 animals (groups A+B) were sacrificed and perfused with a solution of 10% neutral, buffered formalin through the carotid arteries. Tissue blocks containing the experimental teeth were excised, demineralized in EDTA, embedded in paraffin. Serial sections were cut in the mesiodistal plane and parallel with the long axis of the roots. The microtome was set at 7 microns. The sections were stained in hematoxyline and eosin or Van Gieson's connective tissue staining. From each biopsy, 3 sections, 14 microns apart, and representing the central part of the furcation, were selected for light microscopic examination. In the healed furcation sites, histometric and morphometric measurements were performed at different levels (zones), either at the mesial or distal root surfaces; (zone 1) immediately apical of the notch; (zone 2) coronal to the notch where the newly formed alveolar bone was in continuity with the reduced bone crest; (zone 3) coronal to the notch; representing the most coronally positioned area of new bone formation; (zone 4) coronal to the notch; representing areas with no alveolar bone present. In the pristine furcation sites, the measurements were made at zones which corresponded to the location of the zones in the healed furcations

  10. Prevalence, profile and predictors of malnutrition in children with congenital heart defects: a case–control observational study

    PubMed Central

    Okoromah, Christy A N; Ekure, Ekanem N; Lesi, Foluso E A; Okunowo, Wahab O; Tijani, Bolande O; Okeiyi, Jonathan C

    2011-01-01

    Objective To investigate the prevalence, profile and predictors of severe malnutrition in children with congenital heart defects (CHDs). Design Case–control, observational study. Setting Tertiary teaching hospital in Lagos, Nigeria (March 2006 to March 2008). Participants Children aged 3–192 months with uncorrected symptomatic CHD and healthy controls, frequency matched for age and sex. Main outcome measures Prevalence of malnutrition based on WHO/National Center for Health Statistics/Centers for Disease Control and Prevention z score ≤−2; weight for age, weight for height/length and height for age; proportions of underweight, wasting and stunting in cases and controls, and in acyanotic and cyanotic CHD; and predictors of malnutrition using multivariate logistic analysis. Results 90.4% of cases and 21.1% of controls had malnutrition (p=0.0001), and 61.2% and 2.6%, respectively, had severe malnutrition (p=0.0001). Wasting, stunting and underweight were identified in 41.1%, 28.8% and 20.5%, and 2.6%, 3.9% and 14.5% of cases and controls, respectively. Wasting was significantly higher (58.3%) in acyanotic CHD (p=0.0001), and stunting (68.0%) in cyanotic CHD (p=0.0001). Age at weaning was significantly lower in cases than controls (3.24±0.88 and 7.04±3.04 months, respectively; p=0.0001) and in acyanotic than cyanotic CHD (2.14±0.33 and 5.33±1.22 months, respectively; p=0.004). Predictors of malnutrition in CHD were anaemia, moderate to severe congestive heart failure (CHF), poor dietary intake of fat and prolonged unoperated disease. Conclusion Severe malnutrition in association with anaemia and moderate to severe CHF is highly prevalent in CHD preoperatively in these children. Early weaning may be a marker of feeding difficulties in heart failure. PMID:21266339

  11. First-Principles Study of Antisite Defect Configurations in ZnGa2O4:Cr Persistent Phosphors.

    PubMed

    De Vos, Arthur; Lejaeghere, Kurt; Vanpoucke, Danny E P; Joos, Jonas J; Smet, Philippe F; Hemelsoet, Karen

    2016-03-01

    Zinc gallate doped with chromium is a recently developed near-infrared emitting persistent phosphor, which is now extensively studied for in vivo bioimaging and security applications. The precise mechanism of this persistent luminescence relies on defects, in particular, on antisite defects and antisite pairs. A theoretical model combining the solid host, the dopant, and/or antisite defects is constructed to elucidate the mutual interactions in these complex materials. Energies of formation as well as dopant, and defect energies are calculated through density-functional theory simulations of large periodic supercells. The calculations support the chromium substitution on the slightly distorted octahedrally coordinated gallium site, and additional energy levels are introduced in the band gap of the host. Antisite pairs are found to be energetically favored over isolated antisites due to significant charge compensation as shown by calculated Hirshfeld-I charges. Significant structural distortions are found around all antisite defects. The local Cr surrounding is mainly distorted due to a ZnGa antisite. The stability analysis reveals that the distance between both antisites dominates the overall stability picture of the material containing the Cr dopant and an antisite pair. The findings are further rationalized using calculated densities of states and Hirshfeld-I charges. PMID:26866779

  12. Line and Point Defects in MoSe2 Bilayer Studied by Scanning Tunneling Microscopy and Spectroscopy.

    PubMed

    Liu, Hongjun; Zheng, Hao; Yang, Fang; Jiao, Lu; Chen, Jinglei; Ho, Wingkin; Gao, Chunlei; Jia, Jinfeng; Xie, Maohai

    2015-06-23

    Bilayer (BL) MoSe2 films grown by molecular-beam epitaxy (MBE) are studied by scanning tunneling microscopy and spectroscopy (STM/S). Similar to monolayer (ML) films, networks of inversion domain boundary (DB) defects are observed both in the top and bottom layers of BL MoSe2, and often they are seen spatially correlated such that one is on top of the other. There are also isolated ones in the bottom layer without companion in the top-layer and are detected by STM/S through quantum tunneling of the defect states through the barrier of the MoSe2 ML. Comparing the DB states in BL MoSe2 with that of ML film reveals some common features as well as differences. Quantum confinement of the defect states is indicated. Point defects in BL MoSe2 are also observed by STM/S, where ionization of the donor defect by the tip-induced electric field is evidenced. These results are of great fundamental interests as well as practical relevance of devices made of MoSe2 ultrathin layers. PMID:26051223

  13. Ab initio study of point defects in PbSe and PbTe: Bulk and nanowire

    SciTech Connect

    Wrasse, E. O.; Venezuela, P.; Baierle, R. J.

    2014-11-14

    First principles investigations, within the spin-polarized density functional theory, are performed to study energetic stability and electronic properties of point defects (vacancies and antisites) in PbSe and PbTe: bulk and nanowire (NW). Our results show that the energetic stability of these defects is ruled by relaxation process. These defects have lower formation energies in the nanowire structures as compared to the bulk, being more stable in the surface of the NWs. We also show that in the bulk system only one charge state is stable, otherwise, due to the larger band gaps, more than one charge state may be stable in the NWs. In addition, we have investigated how the presence of intrinsic defects affects the electronic properties of bulk and NW systems. Vacancies give rise to new electronic states near to the edges of the valence and conduction bands while the energetic position of the electronic states from antisites depends on the charge state, being localized inside the band gap or near the edges of the valence or conduction bands. We discuss how these changes in the electronic properties due to intrinsic defects may affect the thermoelectric properties of PbSe and PbTe NWs.

  14. Annealing study of a bistable defect in proton-implanted n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Nielsen, H. Kortegaard; Martin, D. M.; Lévêque, P.; Hallén, A.; Svensson, B. G.

    2003-12-01

    The thermal stability and annealing kinetics of a bistable defect, recently reported by Martin (Master Thesis, KTH/ELE/FTE/2003-1) employing deep level transient spectroscopy and labelled the M-centre, has been studied using n-type epitaxially grown 4H-SiC layers implanted with 2.5 MeV protons to a dose of 1×1012 cm-2. One configuration of the bistable defect leads to two levels in the band gap, 0.42 eV (M1) and 0.7-0.8 eV (M3) below the conduction band edge (EC), and another leads to one level (M2) at EC-0.7 eV. The defect can be switched back and forth between the two configurations by varying the applied bias and the sample temperature. Isochronal and isothermal annealing shows that the defect anneals out between 310°C and 370°C with a first-order kinetics process. The origin of the defect is not known but it is implantation-induced and a low-order complex.

  15. CERAMENT treatment of fracture defects (CERTiFy): protocol for a prospective, multicenter, randomized study investigating the use of CERAMENT™ BONE VOID FILLER in tibial plateau fractures

    PubMed Central

    2014-01-01

    Background Bone graft substitutes are widely used for reconstruction of posttraumatic bone defects. However, their clinical significance in comparison to autologous bone grafting, the gold-standard in reconstruction of larger bone defects, still remains under debate. This prospective, randomized, controlled clinical study investigates the differences in pain, quality of life, and cost of care in the treatment of tibia plateau fractures-associated bone defects using either autologous bone grafting or bioresorbable hydroxyapatite/calcium sulphate cement (CERAMENT™|BONE VOID FILLER (CBVF)). Methods/Design CERTiFy (CERament™ Treatment of Fracture defects) is a prospective, multicenter, controlled, randomized trial. We plan to enroll 136 patients with fresh traumatic depression fractures of the proximal tibia (types AO 41-B2 and AO 41-B3) in 13 participating centers in Germany. Patients will be randomized to receive either autologous iliac crest bone graft or CBVF after reduction and osteosynthesis of the fracture to reconstruct the subchondral bone defect and prevent the subsidence of the articular surface. The primary outcome is the SF-12 Physical Component Summary at week 26. The co-primary endpoint is the pain level 26 weeks after surgery measured by a visual analog scale. The SF-12 Mental Component Summary after 26 weeks and costs of care will serve as key secondary endpoints. The study is designed to show non-inferiority of the CBVF treatment to the autologous iliac crest bone graft with respect to the physical component of quality of life. The pain level at 26 weeks after surgery is expected to be lower in the CERAMENT bone void filler treatment group. Discussion CERTiFy is the first randomized multicenter clinical trial designed to compare quality of life, pain, and cost of care in the use of the CBVF and the autologous iliac crest bone graft in the treatment of tibia plateau fractures. The results are expected to influence future treatment

  16. First principles study on defectives BN nanotubes for water splitting and hydrogen storage

    NASA Astrophysics Data System (ADS)

    Bevilacqua, Andressa C.; Rupp, Caroline J.; Baierle, Rogério J.

    2016-06-01

    First principles calculations within the spin polarized density functional approximation have been addressed to investigate the energetic stability, electronic and optical properties of defective BN nanotubes. Our results show that the presence of carbon impurities interacting with vacancies gives rise to defective electronic levels inside the nanotube band gap. By calculating the absorbance index, we have obtained a strong inter-band optical absorption in the visible region (around 2.1 eV) showing that defective BN nanotubes could be an efficient catalytic semiconductor material to be used within solar energy for water splitting. In addition, we observe that the adsorption energy for one and two H2 molecules on the defective surface is in the desired window for the system to be useful as a hydrogen storage medium.

  17. Proceedings of the TMS symposium on radiation facilities and defect studies

    SciTech Connect

    Snead, C.L. Jr.

    1992-11-01

    Intent of the symposium is to highlight the various means of producing and characterizing irradition-induced defects in materials of interest in nuclear applications. Viewgraphs are presented for 18 papers. Separate abstracts were prepared for the data base.

  18. Proceedings of the TMS symposium on radiation facilities and defect studies

    SciTech Connect

    Snead, C.L. Jr.

    1992-01-01

    Intent of the symposium is to highlight the various means of producing and characterizing irradition-induced defects in materials of interest in nuclear applications. Viewgraphs are presented for 18 papers. Separate abstracts were prepared for the data base.

  19. Study of critical defects in ablative heat shield systems for the space shuttle

    NASA Technical Reports Server (NTRS)

    Miller, C. C.; Rummel, W. D.

    1974-01-01

    Experimental results are presented for a program conducted to determine the effects of fabrication-induced defects on the performance of an ablative heat shield material. Exposures representing a variety of space shuttle orbiter mission environments-humidity acoustics, hot vacuum and cold vacuum-culuminating in entry heating and transonic acoustics, were simulated on large panels containing intentional defects. Nondestructive methods for detecting the defects, were investigated. The baseline materials were two honeycomb-reinforced low density, silicone ablators, MG-36 and SS-41. Principal manufacturing-induced defects displaying a critical potential included: off-curing of the ablator, extreme low density, undercut (or crushed) honeycomb reinforcements, and poor wet-coating of honeycomb.

  20. Study of design-based e-beam defect inspection for hotspot detection and process window characterization on 10nm logic device

    NASA Astrophysics Data System (ADS)

    Leray, Philippe; Halder, Sandip; Di Lorenzo, Paolo; Wang, Fei; Zhang, Pengcheng; Fang, Wei; Liu, Kevin; Jau, Jack

    2016-03-01

    With the continuous shrink of design rules from 14nm to 10nm to 7nm, conserving process windows in a high volume manufacturing environment is becoming more and more difficult. Masks, scanners, and etch processes have to meet very tight specifications in order to keep defect, CD, as well as overlay within the margins of the process window. In this work, we study a design-based e-beam defect inspection technology for wafer level process window characterization and intra-field defect variability on 10nm logic devices. Due to high resolution, e-beam technology is the natural choice for review and/or detection of subtle pattern deviations, aka defects. The capability of integrating design information (GDS file) with defect detection, dimension measurement of critical structure, and defect classification provides added values for engineers to identify yield limiting systematic defects and to provide feedback to design.

  1. Ab-initio study of oxygen defects in pure ThO2

    NASA Astrophysics Data System (ADS)

    Ghosh, Partha S.; Gupta, S. K.; Ali, K.; Arya, A.; Dey, G. K.

    2016-05-01

    First principles calculations using projector augmented wave potentials and generalized gradient approximations predicts the structural relaxations due to neutral and positively charged oxygen defects (+1 and +2) in bulk thoria leads to symmetric distortion around the vacancy site. Electronic Density of states (DOS) analysis shows presence of defects states mainly contributed by Th d and f states near the conduction band minima for the double positively charged oxygen vacancy which is having lowest energy of formation.

  2. Spectroscopic study of impurities and associated defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) meteorites

    NASA Astrophysics Data System (ADS)

    Shiryaev, A. A.; Fisenko, A. V.; Vlasov, I. I.; Semjonova, L. F.; Nagel, P.; Schuppler, S.

    2011-06-01

    The results of spectroscopic and structural studies of phase composition and defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) chondrites indicate that nitrogen atomic environment in meteoritic nanodiamonds (MND) is similar to that observed in synthetic counterparts produced by detonation and by the Chemical Vapor Deposition (CVD)-process. Most of the nitrogen in MND appears to be confined to lattice imperfections, such as crystallite/twin boundaries and other extended defects, while the concentration of nitrogen in the MND lattice is low. It is suggested that the N-rich sub-population of MND grains may have been formed with high growth rates in environments rich in accessible N (i.e., N in atomic form or as weakly bonded compounds). For the first time the silicon-vacancy complex (the "silicon" defect) is observed in MND by photoluminescence spectroscopy.

  3. Study about locomotory ability of dystrophin-defected C.elegans after spaceflight

    NASA Astrophysics Data System (ADS)

    Gao, Ying; Sun, Yeqing; Lei, Huang; Xu, Dan

    2012-07-01

    Space microgravity could induce a variety of biological changes such as muscular atrophy. Recent studies show that gravisensing is a key point in muscular atrophy process, but the molecular mechanism is still unknown. Dystrophin, a muscle-related protein, plays an important role in muscle development. It is reported that mutation of human dystrophin gene could cause muscular atrophy. In this study, we focus on whether dystrophin gene acts as a gravisensing factor and observe locomotory ability of dystrophin-defected Caenorhabditis elegans (C.elegans) after spaceflight. We used wild-type (WT) and dystrophin-defected (dys-1) mutant of C.elegans, which were cultured to dauer stage and sent to space by Shenzhou 8 spacecraft (from Nov 1st to 17th, 2011). These worms were divided into three groups: space group (space radiation and microgravity conditions), space control group (space radiation and chmetcnvTCSC0NumberType1NegativeFalseHasSpaceFalseSourceValue1UnitNameg1g centrifuge force conditions) and ground control group.We already observed the progeny (generation F1 and F2) of worms which were sent to space, the movement of C. elegans is restricted to a two-dimensional sinusoidal pattern, and evaluated locomotory ability by the ratio (length/width) in crawl trace wave of C. elegans. The increased value of ratio indicates the decrease in locomotory ability of C. elegans. Our results from generation F1 showed that WT worms in space group(7.7±1.8) demonstrated the significant decrease in locomotory ability about 15%, compared with those in space control group(6.7±1.2). This finding indicates that locomotory ability of C. elegans progeny could be affected by microgravity in space environment. In comparison to the obvious difference in ratio between space group and space control group for WT worms, there is no significant difference between two space groups of generation F2 .For dys-1 mutant of C.elegans (generation F1 and F2), the results show that dystrophin deficiency

  4. EPR and ENDOR studies of point defects in lithium tetraborate crystals

    NASA Astrophysics Data System (ADS)

    Buchanan, Douglas A.

    Lithium tetraborate (Li2B4O7 or LTB) is a promising material for both radiation dosimetry and neutron detection applications. LTB crystals can be grown pure or doped with different impurities including transition-metal and rare-earth ions. Research in this dissertation focuses on undoped LTB crystals and LTB crystals doped with copper and silver. Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to characterize point defects in the lithium tetraborate crystals. Thermoluminescence (TL), photoluminescence (PL), photoluminescence excitation (PLE), and optical absorption (OA) are also used. An intrinsic hole trap associated with lithium vacancies is characterized with EPR and ENDOR and its thermal stability is determined using thermoluminescence. A "perturbed" hole trap due to Ag2+ ions is characterized in doped crystals using EPR data alone. This method is tested on a previously studied hole center where both EPR and ENDOR were used. New x-ray induced centers are identified in copper-doped crystals. These include two Cu 2+ hole centers and two Cu0 electron centers. These centers are characterized with EPR and their thermal stability explains TL peaks in glow curves. Finally, a comprehensive study utilizing EPR, OA, PL, and PLE data provide convincing explanations for the absorption and emission features of silver-doped crystals.

  5. Short-term studies using ceramic scaffolds in lapine model for osteochondral defect amelioration.

    PubMed

    Fernandez, F B; Shenoy, Sachin; Suresh Babu, S; Varma, H K; John, Annie

    2012-06-01

    This study was undertaken to glean preliminary information on the role of triphasic ceramic coated hydroxyapatite (HASi) and biphasic (alpha-tricalcium phosphate and hydroxyapatite based) calcium phosphate (BCP) for the development of osteochondral constructs. The proposed constructs were tested for performance in vitro with rabbit adipose-derived mesenchymal stem cells (RADMSCs) and further analysed in vivo in a lapine model for osteochondral defect amelioration. Desirable scaffolding architecture ensuring favourable conditions for cell attachment, nutrient exchange and neo-tissue organization was achieved by the synthesis of porous ceramic blocks and characterizations were carried out using x-ray diffraction and Fourier transform infrared spectroscopy. The cytocompatibility of the scaffold-cell combination product was evaluated using microscopy techniques that proved the scaffold to be non-cytotoxic and favourable for cell growth and proliferation. Short-term implantation studies were conducted with bare cylindrical HASi and BCP scaffolds, press fit deep into the bony bed of the median femoral condyles of the rabbit, which resulted in favourable specific in vivo response of de novo cartilage-like cells on the surface and sub-surface bony trabeculae. The generated pilot data will help to assess the severity of proposed procedures before embarking on scaled-up efforts. PMID:22406527

  6. First-principles study of line-defect-embedded zigzag graphene nanoribbons: electronic and magnetic properties.

    PubMed

    Guan, Zhaoyong; Si, Chen; Hu, Shuanglin; Duan, Wenhui

    2016-04-28

    Based on first-principles calculations, we present the electronic and magnetic properties of a class of line defect-embedded zigzag graphene nanoribbons, with one edge saturated by two hydrogen atoms per carbon atom and the other edge terminated by only one hydrogen atom. Such edge-modified nanoribbons without line defects are found to be typical bipolar magnetic semiconductors (BMS). In contrast, when the line defect is introduced into the ribbons, the ground state is ferromagnetic, and the resulting nanoribbons can be tuned to spin-polarized metal, metal with Dirac point, or half-metal by varying the position of the line defect, owing to the defect-induced self-doping of the BMS. Specifically, when the line defect is far away from the edges of the ribbon, the system shows half-metallicity. We further confirm the structural and magnetic stability at room temperature by first-principles molecular dynamics simulations. Our findings reveal the possibility of building metal-free electronic/spintronic devices with magnetic/half-metallic graphene nanoribbons. PMID:27087060

  7. Theoretical studies of point defects and diffusion in Nb/sub 3/Sn

    SciTech Connect

    Welch, D.; Diennes, G.; Hatcher, R.; Lazareth, O.

    1983-05-01

    The structure and energetics of several simple point defects in A15 Nb/sub 3/Sn were investigated by means of computer simulations based on a pair-potential model of cohesion. The properties of vacancies on both the Nb and Sn sublattices, as well as those of simple antisite defects, were examined, and estimates were made of the energetics of several types of atom vacancy exchange (''jump'') processes. The results show an unusual structure for the vacancy on the Nb sublattice: the vacancy is ''split'' between two adjacent sites along the Nb chain with an atom midway between them. We find the Sn vacancy (on the Sn sublattice) to be metastable; this vacancy will ''decompose'' by an activated process into a more stable configuration consisting of a Nb atom on a Sn site adjacent to a split Nb-sublattice vacancy. The authors find that the lowest energy grouping of defects compatible with maintaining sublattice sites in the proper three-toone ratio is the antisite defect pair; the lowest energy grouping which contains vacancies is found to consist of Nb-sublattice vacancies and Nb-on-Sn sublattice antisite defects in the ratio of four of the former to one of the latter (quintuple defects). The results also suggest that bulk Sn diffusion is slower than Nb diffusion; this is consistent with the belief that rapid Sn diffusion during Nb/sub 3/Sn layer growth does not occur by bulk but by grain-boundary diffusion.

  8. Theoretical studies of point defects and diffusion in Nb/sub 3/Sn

    SciTech Connect

    Welch, D.O.; Dienes, G.J.; Lazareth, O.W. Jr.; Hatcher, R.D.

    1982-01-01

    The structure and energetics of several simple point defects in A15 Nb/sub 3/Sn were investigated by means of computer simulations based on a pair-potential model of cohesion. The properties of vacancies on both the Nb and Sn sublattices, as well as those of simple antisite defects, were examined, and estimates were made of the energetics of several types of atom-vacancy exchange (jump) processes. The results show an unusual structure for the vacancy on the Nb sublattice: the vacancy is split between two adjacent sites along the Nb chain with an atom midway between them. We find the Sn vacancy (on the Sn sublattice) to be metastable; this vacancy will decompose by an activated process into a more stable configuration consisting of a Nb atom on a Sn site adjacent to a split Nb-sublattice vacancy. We find that the lowest energy grouping of defects compatible with maintaining sublattice sites in the proper three-to-one ratio is the antisite defect pair; the lowest energy grouping which contains vacancies is found to consist of Nb-sublattice vacancies and Nb-on-Sn-sublattice antisite defects in the ratio of four of the former to one of the latter (quintuple defects). Results also suggest that bulk Sn diffusion is slower than Nb diffusion; this is consistent with the belief that rapid Sn diffusion during Nb/sub 3/Sn layer growth does not occur by bulk but by grain-boundary diffusion.

  9. Secondary prevention of stroke--results from the Southern Africa Stroke Prevention Initiative (SASPI) study.

    PubMed Central

    Thorogood, M.; Connor, M. D.; Lewando-Hundt, G.; Tollman, S.; Ngoma, B.

    2004-01-01

    OBJECTIVE: To describe the prevalence of risk factors and experience of preventive interventions in stroke survivors, and identilfy barriers to secondary prevention in rural South Africa. METHODS: A clinician visited individuals in the Agincourt field site (in South Africa's rural north east) who were identified in a census as possible stroke victims to confirm the diagnosis of stroke. We explored the impact of stroke on the individual's family, and health-seeking behaviour following stroke by conducting in-depth interviews in the households of 35 stroke survivors. We held two workshops to understand the knowledge, experience, and views of primary care nurses, who provide the bulk of professional health care. FINDINGS :We identified 103 stroke survivors (37 men), 73 (71%) of whom had hypertension, but only 8 (8%) were taking anti-hypertensive treatment. Smoking was uncommon; 8 men and 1 woman smoked a maximum of ten cigarettes daily. 94 (91%) stroke survivors had sought help, which involved allopathic health care for most of them (81; 79%). 42 had also sought help from traditional healers and churches, while another 13 people had sought help only from those sources. Of the 35 survivors who were interviewed, 29 reported having been prescribed anti-hypertensive pills after their stroke. Barriers to secondary prevention included cost of treatment, reluctance to use pills, difficulties with access to drugs, and lack of equipment to measure blood pressure. A negative attitude to allopathic care was not an important factor. CONCLUSION: In this rural area hypertension is the most important modifiable risk factor in stroke survivors. Effective secondary prevention may reduce the incidence of recurrent strokes, but there is no system to deliver such care. New strategies for care are needed involving both allopathic and non-allopathic-health care providers. PMID:15500283

  10. Biorepositories for the Breast Cancer Prevention Trial (BCPT) and the Study of Tamoxifen and Raloxifene (STAR) | Division of Cancer Prevention

    Cancer.gov

    The National Surgical Adjuvant Breast and Bowel Project (NSABP) has a serum and lymphocyte bank with specimens on more than 90% of the 33,000 women in the Breast Cancer Prevention Trial (BCPT) and Study of Tamoxifen and Raloxifene (STAR). They also have tumor blocks on the majority of the breast cancers that have occurred in women on these studies. |

  11. Ventricular Septal Defect

    MedlinePlus

    ... Cardiac Rhythm Disturbances Thoracic Aortic Aneurysm Pediatric and Congenital Heart Disease Heart abnormalities that are present at birth in ... common, accounting for 20% to 30% of all congenital heart defects. The US Centers for Disease Control and Prevention (CDC) estimates that 42 out ...

  12. CASE-CONTROL STUDY OF AIR QUALITY AND BIRTH DEFECTS: COMPARISON OF GEOCODED AND NON-GEOCODED POPULATIONS

    EPA Science Inventory

    Unbiased geocoding of maternal residence is critical to the success of an ongoing case-control study of exposure to five criteria air pollutants and the risk of selected birth defects in seven Texas counties between 1997 and 2000. The geocoded residence at delivery will be used ...

  13. A study of the prevention of hot tapwater burns.

    PubMed

    Murray, J P

    1988-06-01

    A 4-year retrospective study of hot tapwater scalds admitted to Mount Vernon Hospital Burns Unit suggested that the three high-risk groups are young children, the elderly and the mentally and physically handicapped. A household survey was conducted of 60 homes inhabited by people over 70 years of age and 60 homes inhabited by families with toddlers to identify what measures could be taken to prevent hot tapwater scalds. The survey showed that over half of the old people did not have adequate bathing aids and that one-third of all the homes visited had a hot tapwater temperature greater than 60 degrees C, which is the temperature recommended by British Building Services Engineers. The survey also revealed that 50 per cent of the immersion heaters and 25 per cent of the gas boiler central heating systems produced an excessively high hot tapwater temperature. The study thus indicated that both the wider provision of bathing aids to the elderly and a nationwide programme to update old inefficient immersion heater and gas boiler central heating systems would reduce the risk of hot tapwater scalds. The installation of a 'thermoscopic' mixing valve, pre-set and locked at 43 degrees C, at bath and shower outlets can totally eliminate the risk of hot tapwater scalds. At present it is not a feasible option to install these valves in every household, but there is a strong case for installing them in hospitals and residential homes for paediatric, geriatric and mentally/physically handicapped patients. PMID:2971424

  14. Cell-Seeded Tubularized Scaffolds for Reconstruction of Long Urethral Defects: A Preclinical Study

    PubMed Central

    Orabi, Hazem; AbouShwareb, Tamer; Zhang, Yuanyuan; Yoo, James J.; Atala, Anthony

    2012-01-01

    . Conclusions Cell-seeded tubularized collagen scaffolds can be used to repair long urethral defects, whereas scaffolds without cells lead to poor tissue development and strictures. This study demonstrates that long tissue-engineered tubularized urethral segments may be used for urethroplasty in patients. PMID:22877501

  15. First-Principles Study of the Geometric and Electronic Structures of Zinc Ferrite with Vacancy Defect

    NASA Astrophysics Data System (ADS)

    Yao, Jinhuan; Li, Yanwei; Li, Xuanhai; Zhu, Xiaodong

    2016-04-01

    The effects of Zn-vacancy (Zn7Fe16O32), Fe-vacancy (Zn8Fe15O32), and O-vacancy (Zn8Fe16O31) on the geometric and electronic structures of normal spinel ZnFe2O4 (Zn8Fe16O32) are studied by using a first-principles method based on density functional theory (DFT) at a generalized gradient approximation (GGA) level. Compared with perfect ZnFe2O4, the lattice parameters of ZnFe2O4 with Zn-vacancy or Fe-vacancy increase slightly, while the lattice parameters of ZnFe2O4 with O-vacancy decrease significantly. All the vacancy defects induce the distortion of the unit cell structure, especially for the O-vacancy. Zn-vacancy, Fe-vacancy, and O-vacancy in ZnFe2O4 cannot be formed spontaneously, but Zn-vacancy is the most prone to form, followed by Fe-vacancy and O-vacancy under the condition of external energy supply. Zn-vacancy, Fe-vacancy, and O-vacancy change the properties of ZnFe2O4 from a semiconducting character to a metallic character. Either ZnFe2O4 or ZnFe2O4 has various vacancy defects, the strength of the O-Zn bond is stronger than that of the O-Fe bond, and both of them have a covalent bond character. Zn-vacancy enhances the strength of O-Fe bonds and slightly weakens the strength of O-Zn bonds around Zn-vacancy. Fe-vacancy induces a significant increase of the strength of O-Fe bonds and O-Zn bonds around Fe-vacancy. O-vacancy leads to a significant decrease in the strength of O-Zn bonds and to a slight increase in the strength of O-Fe bonds around O-vacancy.

  16. First-Principles Study of the Geometric and Electronic Structures of Zinc Ferrite with Vacancy Defect

    NASA Astrophysics Data System (ADS)

    Yao, Jinhuan; Li, Yanwei; Li, Xuanhai; Zhu, Xiaodong

    2016-07-01

    The effects of Zn-vacancy (Zn7Fe16O32), Fe-vacancy (Zn8Fe15O32), and O-vacancy (Zn8Fe16O31) on the geometric and electronic structures of normal spinel ZnFe2O4 (Zn8Fe16O32) are studied by using a first-principles method based on density functional theory (DFT) at a generalized gradient approximation (GGA) level. Compared with perfect ZnFe2O4, the lattice parameters of ZnFe2O4 with Zn-vacancy or Fe-vacancy increase slightly, while the lattice parameters of ZnFe2O4 with O-vacancy decrease significantly. All the vacancy defects induce the distortion of the unit cell structure, especially for the O-vacancy. Zn-vacancy, Fe-vacancy, and O-vacancy in ZnFe2O4 cannot be formed spontaneously, but Zn-vacancy is the most prone to form, followed by Fe-vacancy and O-vacancy under the condition of external energy supply. Zn-vacancy, Fe-vacancy, and O-vacancy change the properties of ZnFe2O4 from a semiconducting character to a metallic character. Either ZnFe2O4 or ZnFe2O4 has various vacancy defects, the strength of the O-Zn bond is stronger than that of the O-Fe bond, and both of them have a covalent bond character. Zn-vacancy enhances the strength of O-Fe bonds and slightly weakens the strength of O-Zn bonds around Zn-vacancy. Fe-vacancy induces a significant increase of the strength of O-Fe bonds and O-Zn bonds around Fe-vacancy. O-vacancy leads to a significant decrease in the strength of O-Zn bonds and to a slight increase in the strength of O-Fe bonds around O-vacancy.

  17. Studying two-level systems in Josephson junctions with a Josephson junction defect spectrometer

    NASA Astrophysics Data System (ADS)

    Stoutimore, M. J. A.; Khalil, M. S.; Gladchenko, Sergiy; Simmonds, R. W.; Lobb, C. J.; Osborn, K. D.

    2012-02-01

    We have fabricated and measured Josephson junction defect spectrometers (JJDSs), which are frequency-tunable, nearly-harmonic oscillators that probe two-level systems (TLSs) in the barrier of a Josephson junction (JJ). A JJDS consists of the JJ under study fabricated with a parallel capacitor and inductor such that it can accommodate a wide range of junction inductances, LJ0, while maintaining an operating frequency, f01, in the range of 4-8 GHz. In this device, the parallel inductance helps the JJ maintain linearity over a wide range of frequencies. This architecture allows for the testing of JJs with a wide range of areas and barrier materials, and in the first devices we have tested Al/AlOx/Al JJs. By applying a magnetic flux bias to tune f01, we detect TLSs in the JJ barrier as splittings in the device spectrum. We will present our results toward identifying and quantifying these TLSs, which are known to cause decoherence in quantum devices that rely on JJs.

  18. Animal Experimental Study of the Fully Biodegradable Atrial Septal Defect (ASD) Occluder

    PubMed Central

    Zhu, Yu-feng; Huang, Xin-miao; Cao, Jiang; Hu, Jian-qiang; Bai, Yuan; Jiang, Hai-bing; Li, Zhao-feng; Chen, Ying; Wang, Wei; Qin, Yong-wen; Zhao, Xian-xian

    2012-01-01

    This study was conducted to evaluate the feasibility, safety, biocompatibility, and degradation features of a fully biodegradable occluder for closure of atrial septal defect (ASD) in an acute canine model. The ASD was created in 20 healthy mongrel dogs by the brockenbrough needle, and the fully biodegradable occluders were implanted by self-made delivery system. The success rate and complications were observed. Acute ASD models were successfully created in 18 dogs, and 16 occluders were successfully implanted in the ASD models. Animals were sacrificed at different times after procedure. The cardiac gross anatomy showed that all occluders were stable in the interatrial septum, no vegetation or thrombus formation was observed on the surface of all occluders. They were embedded into endogenous host tissue gradually at 12-week follow-up. Different periods of pathological observations suggested that the occluders degraded gradually over about 24 weeks and essentially became an integral part of the septum. Transcatheter closure of ASD in acute canine model using the fully biodegradable ASD occluder has the potential of a high successful rate of technique, excellent biocompatibility, and fewer complications with adequate, immediate, and short-term results. PMID:23093859

  19. Studies on intrinsic defects related to Zn vacancy in ZnO nanoparticles

    SciTech Connect

    Singh, V.P.; Das, D.; Rath, Chandana

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Williamson–Hall analysis of ZnO indicates strain in the lattice and size is of 20 nm. ► PL shows a broad emission peak in visible range due to native defects. ► Raman active modes corresponding to P6{sub 3}mc and a few additional modes are observed. ► FTIR detects few local vibrational modes of hydrogen attached to zinc vacancies. ► V{sub Zn}-H and Zn + O divacancies are confirmed by PAS. -- Abstract: ZnO being a well known optoelectronic semiconductor, investigations related to the defects are very promising. In this report, we have attempted to detect the defects in ZnO nanoparticles synthesized by the conventional coprecipitation route using various spectroscopic techniques. The broad emission peak observed in photoluminescence spectrum and the non zero slope in Williamson–Hall analysis indicate the defects induced strain in the ZnO lattice. A few additional modes observed in Raman spectrum could be due to the breakdown of the translation symmetry of the lattice caused by defects and/or impurities. The presence of impurities can be ruled out as XRD pattern shows pure wurtzite structure. The presence of the vibrational band related to the Zn vacancies (V{sub Zn}), unintentional hydrogen dopants and their complex defects confirm the defects in ZnO lattice. Positron life time components τ{sub 1} and τ{sub 2} additionally support V{sub Zn} attached to hydrogen and to a cluster of Zn and O di-vacancies respectively.

  20. The defect chemistry of nitrogen in oxides: A review of experimental and theoretical studies

    SciTech Connect

    Polfus, Jonathan M.; Norby, Truls; Haugsrud, Reidar

    2013-02-15

    Incorporation of nitrogen into oxides has in recent years received increased attention as a variable for tuning their functional properties. A vast number of reports have been devoted to improving the photocatalytic properties of TiO{sub 2}, p-type charge carrier concentration in ZnO and the ionic transport properties of ZrO{sub 2} by nitrogen doping. In comparison, the fundamentals of the nitrogen related defect chemistry for a wider range of oxides have been less focused upon. In the present contribution, we review experimental and computational investigations of the nitrogen related defect chemistry of insulating and semiconducting oxides. The interaction between nitrogen and protons is important and emphasized. Specifically, the stability of nitrogen defects such as N{sub O}{sup /}, NH{sub O}{sup Multiplication-Sign} and (NH{sub 2}){sub O}{sup Bullet} is evaluated under various conditions and their atomistic and electronic structure is presented. A final discussion is devoted to the role of nitrogen with respect to transport properties and photocatalytic activity of oxides. - Graphical abstract: Experimental and theoretical investigations of the nitrogen related defect chemistry of a range of wide band gap oxides is reviewed. The interaction between nitrogen dopants and protons is emphasized and described through the atomistic and electronic structure as well as defect chemical processes involving NH and NH{sub 2} defects. Consequently, the physical properties of oxides containing such species are discussed with respect to e.g., diffusion and photocatalytic properties. Highlights: Black-Right-Pointing-Pointer Experimental and theoretical investigations of the nitrogen and hydrogen related defect chemistry of wide band gap oxides is reviewed. Black-Right-Pointing-Pointer The interaction between nitrogen dopants and protons is important and emphasized. Black-Right-Pointing-Pointer Diffusion and photocatalytic properties of N-doped oxides are discussed.

  1. Non-Destructive Evaluation of Kissing Bonds using Local Defect Resonance (LDR) Spectroscopy: A Simulation Study

    NASA Astrophysics Data System (ADS)

    Delrue, S.; Tabatabaeipour, M.; Hettler, J.; Van Den Abeele, K.

    With the growing demand from industry to optimize and further develop existing Non-Destructive Testing & Evaluation (NDT&E) techniques or new methods to detect and characterize incipient damage with high sensitivity and increased quality, ample efforts have been devoted to better understand the typical behavior of kissing bonds, such as delaminations and cracks. Recently, it has been shown experimentally that the nonlinear ultrasonic response of kissing bonds could be enhanced by using Local Defect Resonance (LDR) spectroscopy. LDR spectroscopy is an efficient NDT technique that takes advantage of the characteristic fre- quencies of the defect (defect resonances) in order to provide maximum acoustic wave-defect interaction. In fact, for nonlinear methodologies, the ultrasonic excitation of the sample should occur at either multiples or integer ratios of the characteristic defect resonance frequencies, in order to obtain the highest signal-to-noise response in the nonlinear LDR spectroscopy. In this paper, the potential of using LDR spectroscopy for the detection, localization and characterization of kissing bonds is illustrated using a 3D simulation code for elastic wave propagation in materials containing closed but dynamically active cracks or delaminations. Using the model, we are able to define an appropriate method, based on the Scaling Subtraction Method (SSM), to determine the local defect resonance frequencies of a delamination in a composite plate and to illustrate an increase in defect nonlinearity due to LDR. The simulation results will help us to obtain a better understanding of the concept of LDR and to assist in the further design and testing of LDR spectroscopy for the detection, localization and characterization of kissing bonds.

  2. Evaluation of efficacy of enamel matrix derivative in the treatment of intrabony defects: a 24-month multicenter study.

    PubMed

    Francetti, Luca; Trombelli, Leonardo; Lombardo, Giorgio; Guida, Luigi; Cafiero, Carlo; Roccuzzo, Mario; Carusi, Giorgio; Del Fabbro, Massimo

    2005-10-01

    The aim of this prospective multicenter controlled clinical study was to evaluate the efficacy of Emdogain (Biora), an enamel matrix derivative (EMD), when combined with surgical treatment of periodontal angular defects, as compared to surgery alone, for up to 24 months of follow-up. The study was performed at six Italian universities and 11 private practices. Patients with one-, two-, or three-wall angular defects were enrolled if intrabony defect depth (IBD) was 4 mm or more and probing pocket depth (PPD) was at least 6 mm. They were randomly allocated to either test or control groups. The test group was treated by the simplified papilla preservation (SPP) flap plus Emdogain after root conditioning with ethylenediaminetetraacetic acid. The control group was treated by SPP alone. Plaque Index, Gingival Index, PPD, and periodontal attachment level (PAL) at surgical sites were assessed at the presurgical examination (baseline). IBD was measured intraoperatively after debridement. IBD was also evaluated with a computer-aided technique, from periapical radiographs. Plaque Index, Gingival Index, PPD, PAL, and IBD were assessed at 12 and 24 months postsurgery. Data were further divided in two subgroups according to baseline IBD (6 mm or less and more than 6 mm). The differences between each follow-up and baseline, and between groups at each follow-up, for the above parameters were evaluated by standard statistical methods. One hundred fifty-three patients were recruited, accounting for 195 intrabony defects: 83 patients (108 defects) and 70 patients (87 defects) were allocated to the test and control groups, respectively. All parameters were improved at both 12 and 24 months, compared to baseline in both groups. In the test group, IBD, PPD, and PAL at 12 months were significantly better than these parameters in the control group. The test subgroup with IBD of more than 6 mm at baseline displayed a better outcome when compared to the 6 mm or less IBD subgroup. No

  3. Water nitrates and CNS birth defects: a population-based case-control study

    SciTech Connect

    Arbuckle, T.E.; Sherman, G.J.; Corey, P.N.; Walters, D.; Lo, B.

    1988-03-01

    The relation between maternal exposure to nitrates in drinking water and risk of delivering an infant with a central nervous system (CNS) malformation was examined by means of a case-control study in New Brunswick, Canada. All cases of CNS defects for a high and a low prevalence area of New Brunswick, for the years 1973-1983, were included in the study. Controls were selected randomly from the livebirth files for the province, matched on county of maternal residence and date of birth. One hundred and thirty (130) cases were identified and individually matched with two controls each. Individual water samples were collected from the case and control mother's address given on the birth or stillbirth records. The study revealed that the effect of nitrate exposure in water was modified by whether the source of the drinking water was a private well or a public municipal distribution system. Compared to a baseline nitrate level of 0.1 ppm, exposure to nitrate levels of 26 ppm from private well water sources was associated with a moderate, but not statistically significant, increase in risk (risk odds ratio = 2.30; 95% confidence interval = 0.73-7.29). If the source of drinking water was a municipal distribution system or a private spring, an increase in nitrate exposure was associated with a decrease in risk of delivering a CNS-malformed infant; however, these effect estimates were not statistically significant. The positive increase in risk with nitrate exposure from well water sources requires further study using a larger case series and a larger proportion of exposures to nitrate levels exceeding 5 ppm.

  4. The Eyesight of School Children: Defective Vision as Related to School Environment, and Methods of Prevention and Correction. Bulletin, 1919, No. 65

    ERIC Educational Resources Information Center

    Berkowitz, J. H.

    1920-01-01

    Competent authorities seem to agree as to the causes of eye strain in school children other than congenital defects. Standard works on diseases of the eye are practically unanimous in declaring that myopia results from the protracted and unhygienic use of the eyes in near work. Most of the factors tending to cause eye strain exist in the schools.…

  5. Experimental and simulation studies of printability of buried EUV mask defects and study of EUV reflectivity loss mechanisms due to standard EUV mask cleaning processes

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Mihirkant

    There's a big push for development and commercialization of extreme ultraviolet (EUV) lithography for high-volume semiconductor manufacturing of 14 nm half-pitch patterning and beyond. One of the primary concerns for making this a reality has been the ability to achieve defect-free masks. My study is focused on two aspects related to the performance degradation of the EUV masks namely EUV mask cleaning induced reflectivity loss mechanisms, and the buried multilayer phase defects in EUV masks. Standard EUV mask cleaning processes involve various steps and chemistries that lead to degradation of the multilayer structure, in turn leading to EUV reflectivity loss, hence impacting the throughput. In this work, we developed an understanding of the root causes of how different cleaning chemistries cause EUV reflectivity loss, and quantified these losses. Upon subjecting the mask blanks to multiple cleaning cycles, multilayer degradation observed was in terms of multilayer etching and pitting, surface roughness increase and surface oxidation. We studied each of these phenomena through experiments and simulations, and correlated the extent of EUV reflectivity loss to each of the degradation phenomena. The second aspect of this work involved investigating the printability behavior of buried native phase defects in EUV mask blanks. Since completely defect-free masks will be hard to achieve, it is essential to have a good understanding of the printability of EUV mask defects. In this work, the printability of native mask defects was studied using a novel level-set multilayer growth model that took into account the tool deposition conditions where the multilayer deposition took place. For this study, the native mask blank defects were characterized using atomic force microscopy (AFM) and cross-section transmission electron microscopy (TEM), and the defect printability of these defects was evaluated using simulations implementing the finite-difference time-domain (FDTD) and the

  6. Defect sites in highly siliceous HZSM-5 zeolites: A study performed by alumination and IR spectroscopy

    SciTech Connect

    Yamagishi, Kouji; Namba, Seitaro; Yashima, Tatsuaki )

    1991-01-24

    The concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 type zeolite was estimated by the {sup 18}O-exchange reaction between C{sup 18}O{sub 2} and the zeolite. The concentration of oxygen atoms on defect sites could be controlled by means of changes of the gel composition and of the use of various silica sources in the hydrothermal synthesis. The relationship between the concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 and the concentration of aluminum introduced into the framework of the HZSM-5 by an alumination was examined. The concentration of the framework aluminum was the same as one-fourth that of the oxygen atoms on defect sites. These results suggest that the defect sites into which aluminum atoms are introduced tetrahedrally can be identified with hydroxyl nests that consist of four silanol groups. The existence of hydroxyl nests could be confirmed by IR spectroscopy. From the {sup 18}O-exchange reaction and IR measurements, the authors conclude that the sharp band at 3,740 cm{sup {minus}1} can be attributed to both isolated SiOH groups on the external surface and intracrystalline isolated SiOH groups and that the broad band at 3,505 cm{sup {minus}1} can be attributed to the SiOH groups in hydroxyl nests.

  7. Raman study of the effect of LED light on grafted bone defects

    NASA Astrophysics Data System (ADS)

    Soares, Luiz G. G. P.; Aciole, Jouber M. S.; Aciole, Gilbeth T. S.; Barbosa, Artur F. S.; Silveira-Júnior, Landulfo; Pinheiro, Antônio L. B.

    2013-03-01

    Benefits of the isolated or combined use light and biomaterials on bone healing have been suggested. Our group has used several models to assess the effects of laser on bone. A Raman spectral analysis on surgical bone defects grafted or not with Hydroxyapatite (HA), treated or not with LED was carried out. 40 rats were divided into 4 groups. On Group I the defect was filled with the clot. On Group II, the defect was filled with the HA. On groups III the defect was filled with Clot and further irradiated with LED and on group IV the defects was filled with the HA and further irradiated with LED. LED (λ850 +/- 10nm, 150mW, A= 0.5cm2, 68s, 20 J/cm2 per session, 140 J/cm2 per treatment) was applied at 48 h intervals during 15 days. Specimens were taken after 15 and 30 days after surgery and kept on liquid nitrogen, and underwent Raman analysis. For this, the peak of hydroxyapatite (~960 cm-1) was used as marker of bone mineralization. Significant difference was observed at both times (p<0.05). When the biomaterial was used higher peaks were observed. Association with LED further improved the intensity. Conclusion: It is concluded that LED light improved the effect of the HA.

  8. Steaming of cotton to prevent byssinosis—a plant study

    PubMed Central

    Imbus, Harold R.; Suh, Moon W.

    1974-01-01

    Imbus, H. R. and Suh, M. W. (1974).British Journal of Industrial Medicine,31, 209-219. Steaming of cotton to prevent byssinosis—a plant study. Pulmonary function tests, respiratory questionnaires, and dust measurements were made in a cotton spinning plant during the processing of steamed cotton and after its discontinuance. During steaming the average drop in FEV1 (Δ FEV1) from the beginning to six hours into the work shift was 19 ml, and after steaming was discontinued 62 ml. In addition, the FEV1 measurements, before work on the first day of the work week, were 60 to 100 ml higher during the time of steaming. The improvement in Δ FEV1 with steaming was much greater for males than for females. Improvement was greatest in the higher dust areas, namely, opening, picking, blending, and carding, and less in spinning, winding, and twisting. Questionnaire results did not reveal any significant difference in the incidence of symptoms of byssinosis during the two periods, the reasons for which are not clear. There was an approximately 30% reduction in elutriated and total dust. PMID:4415886

  9. Ab inito study of Ag-related defects in ZnO

    NASA Astrophysics Data System (ADS)

    Wan, Qixin; Xiong, Zhihua; Li, Dongmei; Liu, Guodong

    2008-12-01

    Using first-principles calculations, we investigated the structure and electronic properties of Ag-related defects in ZnO. The calculation results indicate that AgZn behaves as acceptor. Simultaneously, by comparing the formation energy and electronic structure of Ag-related defects in ZnO, Oi-AgZn behaves as acceptor in Ag-doped ZnO and it is better to gain p-type ZnO. However, Hi-AgZn complex has the lowest formation energy. Thus, the formation of the other point defects is greatly suppressed by the formation of Hi in Ag-doped ZnO. Moreover, the H atoms can be easily dissociated from hydrogen-passivated complexes by post-annealing at moderate temperatures, thus, codoping Ag with H may be a good method to achieve p-type in Ag-doped ZnO.

  10. Study of extended-defect formation in Ge and Si after H ion implantation

    SciTech Connect

    Akatsu, T.; Bourdelle, K.K.; Richtarch, C.; Faure, B.; Letertre, F.

    2005-05-02

    Extended defects formed after hydrogen implantation into Si and Ge (100) substrates and subsequent thermal anneals were investigated by transmission electron microscopy. The majority of the extended defects formed in both materials were platelet-like structures lying on {l_brace}100{r_brace} and {l_brace}111{r_brace} planes. We found {l_brace}100{r_brace} platelets not only parallel but also perpendicular to the surface. In Ge wafers, high density of {l_brace}311{r_brace} defects and nanobubbles with the average size of 2 nm were observed. The difference between two materials can be attributed to the weaker strength of Ge-H bond.

  11. Ab initio study of intrinsic, H and He point defects in hcp-Er

    SciTech Connect

    Yang, Li; Peng, SM; Long, XG; Gao, Fei; Heinisch, Howard L.; Kurtz, Richard J.; Zu, Xiaotao T.

    2010-03-01

    Ab initio calculations based on density functional theory have been performed to determine the properties of self-interstitial atoms (SIAs), vacancies, and single H and He atoms in hcp-Er. The results show that the most stable configuration for an SIA is a basal octahedral (BO) configuration, while the octahedral (O), basal split (BS) and crowdion (C) interstitial configurations are less stable, followed by the split <0001> dumbbell and tetrahedral configurations. For both H and He defects, the formation energy of an interstitial atom is less than that of a substitutional atom in hcp-Er. Furthermore, the tetrahedral interstitial position is more stable than an octahedral position for both He and H interstitials. The hybridization of the He and H defects with Er atoms has been used to explain the relative stabilities of these defects in hcp-Er.

  12. Defective α-Fe2O3(0001): an ab initio study.

    PubMed

    Nguyen, Manh-Thuong; Seriani, Nicola; Gebauer, Ralph

    2014-10-01

    By using density functional theory calculations at the PBE+U level, we investigated the properties of hematite (0001) surfaces decorated with adatoms/vacancies/substituents. For the most stable surface termination over a large range of oxygen chemical potentials (muO), the vacancy formation and adsorption energies were determined as a function of muO. Under oxygen-rich conditions, all defects are metastable with respect to the ideal surface. Under oxygen-poor conditions, O vacancies and Fe adatoms become stable. Under ambient conditions, all defects are metastable; in the bulk, O vacancies form more easily than Fe vacancies, whereas at the surface the opposite is true. All defects, that is, O and Fe vacancies, Fe and Al adatoms, and Al substituents, induce important modifications to the geometry of the surface in their vicinity. Dissociative adsorption of molecular oxygen is likely to be exothermic on surfaces with Fe/Al adatoms or O vacancies. PMID:25045043

  13. Biomechanical and morphological study of a new elastic mesh (Ciberlastic) to repair abdominal wall defects.

    PubMed

    Calvo, B; Pascual, G; Peña, E; Pérez-Khöler, B; Rodríguez, M; Bellón, J M

    2016-06-01

    The aim of this study was to conduct a preclinical evaluation of the behaviour of a new type of abdominal LW prosthesis (Ciberlastic), which was designed with a non-absorbable elastic polyurethane monofilament (Assuplus, Assut Europe, Italy) to allow greater adaptability to mechanical area requirements and higher bio-mimicking with the newly formed surrounding tissues. Our hypothesis was that an increase in the elasticity of the mesh filament could improve the benefits of LW prostheses. To verify our hypothesis, we compared the short- and long-term behaviour of Ciberlastic and Optilene(®) elastic commercial meshes by repairing the partially herniated abdomen in New Zealand White rabbits. The implanted meshes were mechanically and histologically assessed at 14 and 180 days post-implant. We mechanically characterized the partially herniated repaired muscle tissue and also determined mesh shrinkage at different post-implant times. This was followed by a histological study in which the tissue incorporation process was analysed over time. The new prosthesis designed by our group achieved good behaviour that was similar to that of Optilene(®), one of the most popular LW prostheses on the market, with the added advantage of its elastic property. The mechanical properties are significantly lower than those of the polypropylene Optilene(®) mesh, and the new elastic mesh meets the basic mechanical requirements for positioning in the abdominal wall, which was also demonstrated by the absence of recurrences after implantation in the experimental model. We found that the growth of a connective tissue rich in collagen over the hernial defect and the proper deposit of the collagen fibres in the regenerated tissue substantially modified the original properties of the mesh, thereby increasing its biomechanical strength and making the whole tissue/mesh stiffer. PMID:26905037

  14. Birth defects in pregestational diabetes: Defect range, glycemic threshold and pathogenesis.

    PubMed

    Gabbay-Benziv, Rinat; Reece, E Albert; Wang, Fang; Yang, Peixin

    2015-04-15

    Currently, 60 million women of reproductive age (18-44 years old) worldwide, and approximately 3 million American women have diabetes mellitus, and it has been estimated that this number will double by 2030. Pregestational diabetes mellitus (PGD) is a significant public health problem that increases the risk for structural birth defects affecting both maternal and neonatal pregnancy outcome. The most common types of human structural birth defects associated with PGD are congenital heart defects and central nervous system defects. However, diabetes can induce birth defects in any other fetal organ. In general, the rate of birth defects increases linearly with the degree of maternal hyperglycemia, which is the major factor that mediates teratogenicity of PGD. Stringent prenatal care and glycemic control are effective means to reduce birth defects in PGD pregnancies, but cannot reduce the incidence of birth defects to the rate of that is seen in the nondiabetic population. Studies in animal models have revealed that PGD induces oxidative stress, which activates cellular stress signalling leading to dysregulation of gene expression and excess apoptosis in the target organs, including the neural tube and embryonic heart. Activation of the apoptosis signal-regulating kinase 1 (ASK1)-forkhead transcription factor 3a (FoxO3a)-caspase 8 pathway causes apoptosis in the developing neural tube leading to neural tube defects (NTDs). ASK1 activates the c-Jun-N-Terminal kinase 1/2 (JNK1/2), which leads to activation of the unfolded protein response and endoplasmic reticulum (ER) stress. Deletion of the ASK1 gene, the JNK1 gene, or the JNK2 gene, or inhibition of ER stress by 4-Phenylbutyric acid abrogates diabetes-induced apoptosis and reduces the formation of NTDs. Antioxidants, such as thioredoxin, which inhibits the ASK1-FoxO3a-caspase 8 pathway or ER stress inhibitors, may prevent PGD-induced birth defects. PMID:25897357

  15. Birth defects in pregestational diabetes: Defect range, glycemic threshold and pathogenesis

    PubMed Central

    Gabbay-Benziv, Rinat; Reece, E Albert; Wang, Fang; Yang, Peixin

    2015-01-01

    Currently, 60 million women of reproductive age (18-44 years old) worldwide, and approximately 3 million American women have diabetes mellitus, and it has been estimated that this number will double by 2030. Pregestational diabetes mellitus (PGD) is a significant public health problem that increases the risk for structural birth defects affecting both maternal and neonatal pregnancy outcome. The most common types of human structural birth defects associated with PGD are congenital heart defects and central nervous system defects. However, diabetes can induce birth defects in any other fetal organ. In general, the rate of birth defects increases linearly with the degree of maternal hyperglycemia, which is the major factor that mediates teratogenicity of PGD. Stringent prenatal care and glycemic control are effective means to reduce birth defects in PGD pregnancies, but cannot reduce the incidence of birth defects to the rate of that is seen in the nondiabetic population. Studies in animal models have revealed that PGD induces oxidative stress, which activates cellular stress signalling leading to dysregulation of gene expression and excess apoptosis in the target organs, including the neural tube and embryonic heart. Activation of the apoptosis signal-regulating kinase 1 (ASK1)-forkhead transcription factor 3a (FoxO3a)-caspase 8 pathway causes apoptosis in the developing neural tube leading to neural tube defects (NTDs). ASK1 activates the c-Jun-N-Terminal kinase 1/2 (JNK1/2), which leads to activation of the unfolded protein response and endoplasmic reticulum (ER) stress. Deletion of the ASK1 gene, the JNK1 gene, or the JNK2 gene, or inhibition of ER stress by 4-Phenylbutyric acid abrogates diabetes-induced apoptosis and reduces the formation of NTDs. Antioxidants, such as thioredoxin, which inhibits the ASK1-FoxO3a-caspase 8 pathway or ER stress inhibitors, may prevent PGD-induced birth defects. PMID:25897357

  16. Defect levels in Cu(In,Ga)Se2 studied using capacitance and photocurrent techniques.

    PubMed

    Urbaniak, A; Macielak, K; Igalson, M; Szaniawski, P; Edoff, M

    2016-06-01

    This work contributes to the discussion on defect levels in Cu(In,Ga)Se2 photovoltaic material. CuInSe2- and Cu(In,Ga)Se2- based Schottky junctions, solar cells and thin films were investigated using complementary capacitance and current spectroscopic techniques. Depending on the applied technique and type of investigated structure, six different signals were observed. Out of the signals identified, three were ascribed to responses from bulk defects-two electron and one hole trap. The remainder were discussed in light of available in-literature models including carrier mobility freeze-out and non-ohmic back junction. PMID:27125196

  17. The OAs defect in GaAs: A hybrid density functional study

    NASA Astrophysics Data System (ADS)

    Colleoni, Davide; Pasquarello, Alfredo

    2014-02-01

    The O center substitutional to As (OAs) is addressed through hybrid functional calculations as a candidate defect to explain the Fermi-level pinning in oxygen-doped GaAs. The defect center shows amphoteric behavior which could lead to Fermi-level pinning. However, the calculated charge transition levels only moderately agree with the experimental pinning level. Furthermore, the first-neighbor shell of the O atom and the absence of negative-U behavior clearly contrast with the experimental characterization. Thus, the present results do not support the OAs center as origin of the observed Fermi-level pinning in oxygen-doped GaAs.

  18. Teachers' Responsibilities in Preventing School Violence: A Case Study in Turkey

    ERIC Educational Resources Information Center

    Yavuzer, Yasemin; Gundogdu, Rezzan

    2012-01-01

    It is generally acknowledged that teachers play an important role in preventing or reducing violence in schools. The objectives of this study were: (a) to identify teachers' responsibilities in terms of preventing violence among school children and (b) to solicit teachers' views as what they have been doing in preventing violence. Sample for the…

  19. Long term trends in prevalence of neural tube defects in Europe: population based study

    PubMed Central

    Loane, Maria; de Walle, Hermien; Arriola, Larraitz; Addor, Marie-Claude; Barisic, Ingeborg; Beres, Judit; Bianchi, Fabrizio; Dias, Carlos; Draper, Elizabeth; Garne, Ester; Gatt, Miriam; Haeusler, Martin; Klungsoyr, Kari; Latos-Bielenska, Anna; Lynch, Catherine; McDonnell, Bob; Nelen, Vera; Neville, Amanda J; O’Mahony, Mary T; Queisser-Luft, Annette; Rankin, Judith; Rissmann, Anke; Ritvanen, Annukka; Rounding, Catherine; Sipek, Antonin; Tucker, David; Verellen-Dumoulin, Christine; Wellesley, Diana; Dolk, Helen

    2015-01-01

    Study question What are the long term trends in the total (live births, fetal deaths, and terminations of pregnancy for fetal anomaly) and live birth prevalence of neural tube defects (NTD) in Europe, where many countries have issued recommendations for folic acid supplementation but a policy for mandatory folic acid fortification of food does not exist? Methods This was a population based, observational study using data on 11 353 cases of NTD not associated with chromosomal anomalies, including 4162 cases of anencephaly and 5776 cases of spina bifida from 28 EUROCAT (European Surveillance of Congenital Anomalies) registries covering approximately 12.5 million births in 19 countries between 1991 and 2011. The main outcome measures were total and live birth prevalence of NTD, as well as anencephaly and spina bifida, with time trends analysed using random effects Poisson regression models to account for heterogeneities across registries and splines to model non-linear time trends. Summary answer and limitations Overall, the pooled total prevalence of NTD during the study period was 9.1 per 10 000 births. Prevalence of NTD fluctuated slightly but without an obvious downward trend, with the final estimate of the pooled total prevalence of NTD in 2011 similar to that in 1991. Estimates from Poisson models that took registry heterogeneities into account showed an annual increase of 4% (prevalence ratio 1.04, 95% confidence interval 1.01 to 1.07) in 1995-99 and a decrease of 3% per year in 1999-2003 (0.97, 0.95 to 0.99), with stable rates thereafter. The trend patterns for anencephaly and spina bifida were similar, but neither anomaly decreased substantially over time. The live birth prevalence of NTD generally decreased, especially for anencephaly. Registration problems or other data artefacts cannot be excluded as a partial explanation of the observed trends (or lack thereof) in the prevalence of NTD. What this study adds In the absence of mandatory fortification

  20. Study of Defects in GaN In Situ Doped with Eu3+ Ion Grown by OMVPE

    NASA Astrophysics Data System (ADS)

    Wang, Jingzhou; Koizumi, Atsushi; Fujiwara, Yasufumi; Jadwisienczak, Wojciech M.

    2016-04-01

    In this work, GaN epilayer in situ doped with Eu3+ ions was deposited on the top of an undoped n-GaN/LT-GaN/sapphire structure by organometallic vapor-phase epitaxy. A set of different ohmic and Schottky contacts on GaN:Eu3+ surface was fabricated by electron-beam evaporation for performing deep level transient spectroscopy (DLTS) measurement. The deep defect energy levels in GaN:Eu3+ epilayer were assessed by standard DLTS and high resolution Laplace DLTS (L-DLTS). Three dominant DLTS peaks were observed in the temperature range from 35 K to 400 K. The calculated activation energies of these defect energy levels were 0.108 ± 0.03 eV (Trap A), 0.287 ± 0.04 eV (Trap B) and 0.485 ± 0.06 eV (Trap C) below conduction band edge, respectively. High resolution L-DLTS conducted for the GaN:Eu3+ epilayer revealed at least four closely spaced defect energy levels associated with Trap B. It is proposed that these defect energy levels correspond to the selected optically active Eu3+ ion centers in GaN host previously identified by optical studies in this material (Fujiwara and Dierolf in Jpn J Appl Phys 53:05FA13, 2014).

  1. Hybrid Hamiltonian and Green's Function Approach for Studying Native Point Defect Levels in Semiconductor Compounds and Superlattices

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Srini; Van Orden, Derek; Yu, Zhi-Gang

    2016-04-01

    We have developed a hybrid method that can be applied to study isolated defects in semiconductor compounds and superlattices. The method is a combination of (1) a long-range tight-binding (TB) Hamiltonian, (2) a first-principles Hamiltonian, and (3) a Green's function (GF) formalism. The calculation of the GF requires accurate energy band structure, wave functions, and defect potentials. The TB Hamiltonian with sp 3 orbitals basis ensures accurate band gaps and band masses while providing the functional form for the wave functions. We calculated the band gaps of InAs/GaSb and InAs/InAsSb strained-layer superlattices and found them to agree well with measurements. The change in potentials caused by native point defects (NPDs) was obtained from a first-principles method using Spanish Initiative for Electronic Simulations with Thousands of Atoms, which also uses sp 3 basis. We describe the method of calculating NPD energy levels in compounds and superlattices, obtain some defect levels in GaAs, InAs, InSb, and GaSb compounds, and provide details of the NPD-level calculations.

  2. Hybrid Hamiltonian and Green's Function Approach for Studying Native Point Defect Levels in Semiconductor Compounds and Superlattices

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, Srini; Van Orden, Derek; Yu, Zhi-Gang

    2016-09-01

    We have developed a hybrid method that can be applied to study isolated defects in semiconductor compounds and superlattices. The method is a combination of (1) a long-range tight-binding (TB) Hamiltonian, (2) a first-principles Hamiltonian, and (3) a Green's function (GF) formalism. The calculation of the GF requires accurate energy band structure, wave functions, and defect potentials. The TB Hamiltonian with sp 3 orbitals basis ensures accurate band gaps and band masses while providing the functional form for the wave functions. We calculated the band gaps of InAs/GaSb and InAs/InAsSb strained-layer superlattices and found them to agree well with measurements. The change in potentials caused by native point defects (NPDs) was obtained from a first-principles method using Spanish Initiative for Electronic Simulations with Thousands of Atoms, which also uses sp 3 basis. We describe the method of calculating NPD energy levels in compounds and superlattices, obtain some defect levels in GaAs, InAs, InSb, and GaSb compounds, and provide details of the NPD-level calculations.

  3. The “excluding” suture technique for surgical closure of ventricular septal defects: A retrospective study comparing the standard technique

    PubMed Central

    Varghese, Roy; Saheed, Sanni; Ravi, Amrutha K; Sherrif, Ejaz Ahmed; Agarwal, Ravi; Kothandam, Sivakumar

    2016-01-01

    Background: Conventional methods of closure of ventricular septal defects involve placement of sutures 4-5 mm from the posterior inferior margin. This study compares the conventional method with an alternative technique wherein sutures are placed along the edge of the defect thereby “excluding” the conduction system and the tensor apparatus of the tricuspid valve from the suture line. Materials and Methods: Between January 2013 and January 2016, 409 consecutive patients were retrospectively reviewed and divided into two matched groups. Group A (n = 174) underwent closure using the alternative technique and Group B (n = 235) with the conventional technique. Patients with isolated ventricular septal defects (VSDs) (n = 136) were separately analyzed as were infants within this subset. Results: Immediate postoperative results were similar with no statistically significant differences in either group in terms of incidence of residual defects or postoperative tricuspid regurgitation. There was however a significantly increased incidence of post operative complete heart block (CHB) among patients in the conventional group (P = 0.02). Incidence of temporary heart block that reverted to sinus rhythm was also more in the conventional method group (Group B) (P = 0.03) as was right bundle branch block (P ≤ 0.05) in all the subsets of patients analyzed. Conclusion: Surgical closure of VSDs can be accomplished by placing sutures along the margins or away with comparable results. The incidence of CHB, however, seems to be less when the “excluding” technique is employed. PMID:27625520

  4. Towards more reliable automated multi-dose dispensing: retrospective follow-up study on medication dose errors and product defects.

    PubMed

    Palttala, Iida; Heinämäki, Jyrki; Honkanen, Outi; Suominen, Risto; Antikainen, Osmo; Hirvonen, Jouni; Yliruusi, Jouko

    2013-03-01

    To date, little is known on applicability of different types of pharmaceutical dosage forms in an automated high-speed multi-dose dispensing process. The purpose of the present study was to identify and further investigate various process-induced and/or product-related limitations associated with multi-dose dispensing process. The rates of product defects and dose dispensing errors in automated multi-dose dispensing were retrospectively investigated during a 6-months follow-up period. The study was based on the analysis of process data of totally nine automated high-speed multi-dose dispensing systems. Special attention was paid to the dependence of multi-dose dispensing errors/product defects and pharmaceutical tablet properties (such as shape, dimensions, weight, scored lines, coatings, etc.) to profile the most suitable forms of tablets for automated dose dispensing systems. The relationship between the risk of errors in dose dispensing and tablet characteristics were visualized by creating a principal component analysis (PCA) model for the outcome of dispensed tablets. The two most common process-induced failures identified in the multi-dose dispensing are predisposal of tablet defects and unexpected product transitions in the medication cassette (dose dispensing error). The tablet defects are product-dependent failures, while the tablet transitions are dependent on automated multi-dose dispensing systems used. The occurrence of tablet defects is approximately twice as common as tablet transitions. Optimal tablet preparation for the high-speed multi-dose dispensing would be a round-shaped, relatively small/middle-sized, film-coated tablet without any scored line. Commercial tablet products can be profiled and classified based on their suitability to a high-speed multi-dose dispensing process. PMID:22458299

  5. Programmed defects study on masks for 45nm immersion lithography using the novel AIMS 45-193i

    NASA Astrophysics Data System (ADS)

    Scherübl, Thomas; Dürr, Arndt C.; Böhm, Klaus; Birkner, Robert; Richter, Rigo; Strößner, Ulrich

    2007-02-01

    Mask manufacturing for the 45nm node for hyper NA lithography requires tight defect and printability control at small features sizes. The AIMS TM1 technology is a well established methodology to analyze printability of mask defects, repairs and critical features by scanner emulation. With the step towards hyper NA imaging by immersion lithography the AIMS TM technology has been faced with new challenges like vector effects, polarized illumination and tighter specs for repeatability and tool stability. These requirements pushed the development of an entirely new AIMS TM generation. The AIMS TM 45-193i has been designed and developed by Carl Zeiss to address these challenges. A new mechanical platform with a thermal and environmental control unit enables high tool stability. Thus a new class of specification becomes available. The 193nm optical beam path together with an improved beam homogenizer is dedicated to emulate scanners up to 1.4 NA. New features like polarized illumination and vector effect emulation make the AIMS TM 45- 193i a powerful tool for defect disposition and scanner emulation for 45nm immersion lithography. In this paper results from one of the first production tools will be presented. Aerial images from phase shifting and binary masks with different immersion relevant settings will be discussed. Also, data from a long term repeatability study performed on masks with programmed defects will be shown. This study demonstrates the tool's ability to perform defect disposition with high repeatability. It is found that the tool will fulfill the 45nm node requirements to perform mask qualification for production use.

  6. The use of embryonic cells in the treatment of osteochondral defects of the knee: an ovine in vivo study

    PubMed Central

    MANUNTA, ANDREA FABIO; ZEDDE, PIETRO; PILICCHI, SUSANNA; ROCCA, STEFANO; POOL, ROY R.; DATTENA, MARIA; MASALA, GEROLAMO; MARA, LAURA; CASU, SARA; SANNA, DANIELA; MANUNTA, MARIA LUCIA; PASSINO, ERALDO SANNA

    2016-01-01

    Purpose the aim of this study was to determine whether local delivery of embryonic stem-like (ESL) cells into osteochondral defects in the femoral condyles of sheep would enhance regeneration of hyaline articular cartilage. Methods male ESL cells embedded in fibrin glue were engrafted into osteochondral defects in the medial condyles (ESL-M) of the left femur in 22 ewes. An identical defect was created in the medial condyle of the contralateral stifle joint and left untreated as a control (empty defect, ED). The ewes were divided into 5 groups. Four sheep each were euthanized at 1, 2, 6, and 12 months from surgery, and 6 ewes were euthanized 24 months post-implantation. To study the effect of varying loads on the long-term regeneration process, an identical defect was also created and ESL cell engraftment performed in the lateral condyle (ESL-L) of the left stifle joint of the animals in the 12- and 24-month groups. The evaluation of regenerated tissue was performed by biomechanical, macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays. Results no significant differences were found between treated and control sites in the biomechanical assays at any time point. ESL cell grafts showed significantly greater macroscopic evidence of regeneration as compared to controls at 24 months after surgery; significantly better histological evidence of repair in ESL-M samples versus controls was found throughout the considered period. At 24 months from surgery there was significantly improved integration of graft edges with the host tissue in the ESL-M as compared to the ESL-L samples, demonstrating that load bearing positively affects the long-term regeneration process. Conclusions ESL cells enhanced the regeneration of hyaline cartilage. FISH confirmed that the regenerative tissue originated from ESL cells. Clinical Relevance ESL cells are able to self-renew for prolonged periods without differentiation and, most

  7. Experimental study on structural defect detection by monitoring distributed dynamic strain

    NASA Astrophysics Data System (ADS)

    Liu, R. M.; Babanajad, S. K.; Taylor, T.; Ansari, F.

    2015-11-01

    A defect detection method of civil structures is studied. In order to complete the task, the proposed detection method is based on the analysis of distributed dynamic strains using Brillouin scattering based fiber optic sensors along large span structures. The current challenges in the detection of localized damage fundamentally include monitoring the dynamic strain as well as eliminating the system noise and the distortion of the changing distributed strain. Due to the capability of Brillouin scattering based methods in distributed monitoring of large structures, Brillouin optical time-domain analysis approach is implemented for assessing damage. In order to highlight the singularity at the damage location, Fourier as well as dual tree complex wavelet transform approaches were conducted. During the processing, the dynamic distributed strain in the time domain was transformed into the frequency domain for extraction of natural and forced frequencies. Then, the data was decomposed, filtered for extraction of crack features and reconstructed. The feasibility of the proposed method is evaluated through an experimental program involving the use of pulse-pre-pump Brillouin optical time domain analysis for the distributed measurement of dynamic strain with 13 Hz sampling speed and detection of simulated cracks in a 15 m long steel beam. The beam mimics a bridge girder with two artificial cracks along its length subjected to free and forced vibrations. The results indicate that the method based on the discontinuities in the strain distribution is applicable in the detection of very small damage as small as 40 micro strains. A crack gauge independently monitored the crack opening displacements during the experiments, and the limit of detected crack openings based on the first appearance of strain singularities was 30 μm.

  8. Maternal ethnicity and risk of neural tube defects: a population-based study

    PubMed Central

    Ray, Joel G.; Vermeulen, Marian J.; Meier, Chris; Cole, David E.C.; Wyatt, Philip R.

    2004-01-01

    Background Maternal body mass and the presence of diabetes mellitus are probable risk factors for neural tube defects (NTDs). The association between maternal ethnicity and the risk of NTDs remains poorly understood, however. Methods We performed a retrospective population-based study and included all women in Ontario who underwent antenatal maternal screening (MSS) at 15 to 20 weeks' gestation between 1994 and late 2000. Self-declared maternal date of birth, ethnicity and weight and the presence of pregestational diabetes mellitus were recorded in a standardized fashion on the MSS requisition sheet. NTDs were detected antenatally by ultrasonography or fetal autopsy and postnatally by considering all live and stillborn affected infants beyond 20 weeks' gestation. The risk of open NTD was evaluated across the 5 broad ethnic groups used for MSS, with white ethnicity as the referent. Results Compared with white women (n = 290 799), women of First Nations origin (n = 1551) were at increased associated risk of an NTD-affected pregnancy (adjusted odds ratio [OR] 5.2, 95% confidence interval [CI] 2.1–12.9). Women of other ethnic origins were not at increased associated risk compared with white women (women of Asian origin [n = 75 590]: adjusted OR 0.9, 95% CI 0.6–1.3; black women [n = 25 966]: adjusted OR 0.6, 95% CI 0.3–1.1; women of “other” ethnic origin [n = 10 009]: adjusted OR 0.1, 95% CI 0.02–0.9). Interpretation The associated risk of NTD-affected pregnancies was higher among women of First Nations origin than among women of other ethnic origins. The mechanisms for this discrepancy should be explored. PMID:15313993

  9. COMPARATIVE STUDY OF BONE NEOFORMATION USING AUTOLOGOUS GRAFTING AND THREE REPLACEMENTS: BONE DEFECTS IN RATS

    PubMed Central

    Stein, Rodrigo Steffen; Silva, Jefferson Braga; Silva, Vinicius Duval da

    2015-01-01

    Objective: Compare the percentage of bone neoformation promoted by autologous bone grafting and three kinds of replacement materials with different characteristics in rats' femoral holes. Methods: Two holes measuring 5.4×2.7mm, were produced on each femur (right and left) of 14 isogenic Wistar rats. Each of the four defects produced was filled by autologous bone or by one of three tested materials-hydroxyapatite (HA), Genphos® (HA+ β-TCP) and GenMix® (a combined bovine bone graft). In the end of the 6-week (n = 6) and 12-week (n = 8) periods, the animals were sacrificed. The sections (stained with Picro-Sirius) were assessed by optical microscopy and specific software. Results: The groups with autologous bone were shown to be significantly superior to the others at both assessed times, showing a mean bone formation rate ± SD of 90.6 ± 10.8% in six weeks, and 98 ± 9.2% in 12 weeks (p > 0.0001 for both assessed times). In six weeks, the results for the other groups were the following: Genphos®, 46 ± 7.1%; HA, 43.1 ± 8.4%; and GenMix®, 57.3 ± 4.5%. In 12 weeks: Genphos®, 47.8 ± 11.1%; HA, 39.9 ± 5.4%; GenMix®, 59.7 ± 4.8%, significant (p = 0.007). Conclusions: In both assessed times, the three bone replacement materials tested in the study showed to be inferior to autologous bone graft for bone neoformation percentage. PMID:27022515

  10. Studying injury prevention: practices, problems, and pitfalls in implementation.

    PubMed

    Sangvai, Shilpa; Cipriani, Lynne; Colborn, D Kathleen; Wald, Ellen R

    2007-04-01

    This prospective, randomized, controlled trial was conducted to determine feasibility and effectiveness of a chronic care model approach to injury prevention compared with standard anticipatory guidance. Enrolled caregivers of children aged 0 to 5 years received focused counseling from a physician and health assistant, educational handouts, phone follow-up, and access to free safety devices and automobile restraint evaluations. Only 35.1% of eligible parents participated. Home visits were completed at 6 months to observe safety practices. Injuries were gleaned from parent report and medical record review. Safety practices were evaluated in 27 households. Chart review showed no significant difference in the number of medically attended injuries between groups (P = 0.6). The impact of the chronic care model on injury prevention in primary care could not be determined with certainty. Evaluating effectiveness of injury prevention strategies on actual safety practices with direct observation is challenging. PMID:17416878

  11. Experimental studies on elastic cooling and pyromagnetic effect of polyvinyl chloride sheets with defects

    NASA Astrophysics Data System (ADS)

    Luo, Yingshe; Chen, Shengming; Zhang, Liang; Su, Jianxin; Zhang, Yongzhong; Luo, Shuling

    2012-09-01

    Polyvinyl Chloride (PVC) sheets were made into samples with precast defects for uniaxial tensile test. The tests are carried out under room temperature with conditions of same displacement rate but different defect sizes or of same defect but different displacement rates. The local nonuniform temperature field on whole deformation area of specimen is recorded with a thermal infrared imager and the whole coupling magnetic field with thermal changes in experiments is detected and measured by a self-developed sensors system. The experimental results show that, in a complete tensile test process of PVC samples, the temperature reduction phenomenon emerges firstly in its elastic deformation stage (areas) that temperature of specimen is cooler than room temperature. And then in viscoplastic deformation period (areas), the temperature increases sharply to be obviously higher than room temperature due to the thermo-mechanical coupling effection of tensile load and viscoplastic deformation heat. These thermal variations lead a coupling pyromagnetic effect occur and the effect intensity is dependent strongly on the strain rate and/or the size of defects. The temperature prejudgment conditions for materials yield are preliminary discussed based on this effect.

  12. Density functional study of gold and iron clusters on perfect and defected graphene

    NASA Astrophysics Data System (ADS)

    Srivastava, Manoj K.; Wang, Yan; Kemper, A. F.; Cheng, Hai-Ping

    2012-04-01

    Metal clusters adsorbed on graphene can give rise to interesting physical properties. Using density-functional theory calculations, we investigate Aun and Fen (n=1-5) clusters adsorbed on perfect and defected graphene with a single vacancy. With the exception of Fe clusters on defected graphene, clusters are bonded to graphene through an anchor atom. Geometries of clusters on graphene are similar to their free-standing structures except for the Fe5 cluster on perfect graphene. Compared to Au, Fe clusters are more strongly bonded to graphene. We find that it is important to include long-range van der Waals interactions for Au clusters adsorbed on perfect graphene. An Au5 cluster becomes parallel to the graphene only when the van der Waals interactions are taken into account. Charge transfer between clusters and graphene shows strong size dependency, and the amount is larger in the presence of the single vacancy on the graphene than a pristine sheet. Perfect graphene is found to be doped for Au clusters with an odd number of atoms and undoped with an even number of atoms. Magnetic moments are also calculated as a function of cluster size and an odd-even oscillation is observed in Aun-perfect as well as defected graphene system. While Fen clusters remain to be magnetic for all n, the spin of a single Fe atom on a defect site is very small due to a covalent bonding to C atoms.

  13. Positron annihilation studies of defects in molecular beam epitaxy grown III-V layers

    SciTech Connect

    Umlor, M.T.; Keeble, D.J.; Asoka-Kumar, P.; Lynn, K.G.; Cooke, P.W.

    1994-08-01

    A summary of recent positron annihilation experiments on molecular beam epitaxy (MBE) grown III-V layers is Presented. Variable energy positron beam measurements on Al{sub 0.32}Ga{sub 0.68}As undoped and Si doped have been completed. Positron trapping at a open volume defect in Al{sub 0.32}Ga{sub 0.68}:Si for temperatures from 300 to 25 K in the dark was observed. The positron trap was lost after 1.3 eV illumination at 25K. These results indicate an open volume defect is associated with the local structure of the deep donor state of the DX center. Stability of MBE GaAs to thermal annealing war, investigated over the temperature range of 230 to 700{degrees}C, Proximity wafer furnace anneals in flowing argon were used, Samples grown above 450{degrees}C were shown to be stable but for sample below this temperature an anneal induced vacancy related defect was produced for anneals between 400 and 500{degrees}C. The nature of the defect was shown to be different for material grown at 350 and 230{degrees}C. Activation energies of 2.5 eV to 2.3 eV were obtained from isochronal anneal experiments for samples grown at 350 and 230{degrees}C, respectively.

  14. Parental Reactions to an Infant with a Birth Defect: A Study of Five Families.

    ERIC Educational Resources Information Center

    Mintzer, Dorian

    Five families whose first born infant experienced a birth anomaly were followed for two years through a combination of home and laboratory visits. Findings suggested that the birth of an infant with a defect was experienced by the parents as a narcissistic injury and a series of narcissistic insults that affect the parents' self esteem, interfere…

  15. A Modified Rabbit Ulna Defect Model for Evaluating Periosteal Substitutes in Bone Engineering: A Pilot Study

    PubMed Central

    El Backly, Rania M.; Chiapale, Danilo; Muraglia, Anita; Tromba, Giuliana; Ottonello, Chiara; Santolini, Federico; Cancedda, Ranieri; Mastrogiacomo, Maddalena

    2014-01-01

    The present work defines a modified critical size rabbit ulna defect model for bone regeneration in which a non-resorbable barrier membrane was used to separate the radius from the ulna to create a valid model for evaluation of tissue-engineered periosteal substitutes. Eight rabbits divided into two groups were used. Critical defects (15 mm) were made in the ulna completely eliminating periosteum. For group I, defects were filled with a nanohydroxyapatite poly(ester urethane) scaffold soaked in PBS and left as such (group Ia) or wrapped with a tissue-engineered periosteal substitute (group Ib). For group II, an expanded-polytetrafluoroethylene (e-PTFE) (GORE-TEX®) membrane was inserted around the radius then the defects received either scaffold alone (group IIa) or scaffold wrapped with periosteal substitute (group IIb). Animals were euthanized after 12–16 weeks, and bone regeneration was evaluated by radiography, computed microtomography (μCT), and histology. In the first group, we observed formation of radio-ulnar synostosis irrespective of the treatment. This was completely eliminated upon placement of the e-PTFE (GORE-TEX®) membrane in the second group of animals. In conclusion, modification of the model using a non-resorbable e-PTFE membrane to isolate the ulna from the radius was a valuable addition allowing for objective evaluation of the tissue-engineered periosteal substitute. PMID:25610828

  16. Atomistic Studies on Tensile Mechanics of BN Nanotubes in the Presence of Defects

    NASA Astrophysics Data System (ADS)

    Sarma, J. V. N.; Chowdhury, Rajib; Jayaganthan, R.; Scarpa, F.

    2014-03-01

    Boron nitride nanotubes (BNNTs) are of immense importance due to their many interesting functional features, notably biocompatibility and piezoelectricity and dominant mechanical strength as compared to carbon nanotubes (CNTs). The reliable implementation of these structures in an application is inherently related to its mechanical characteristics under external loads. The presence of defects in these structures severely affects the tensile properties. The effect of presence of point, line and Stone-Wales (SW) defects on the tensile behavior of BNNTs is systematically investigated by applying reactive force fields in molecular dynamics (MD) framework. Reactive force fields effectively describe the bond breaking and bond forming mechanism for BNNTs that are important for a practical situation. The Young's modulus of single-walled (10,0) BNNTs of length 100 nm has been found to be nearly 1.098 TPa, in good agreement with the available reports. The presence of defects has been shown to significantly reduce the tensile strength of the tube, while the number and separation of the defects effectively contribute to the percentage reduction. In addition, the effect of tube diameter and also the initial temperature are observed to strongly influence the tensile characteristics of BNNTs, indicating increased auxetic behavior than CNTs.

  17. A modified rabbit ulna defect model for evaluating periosteal substitutes in bone engineering: a pilot study.

    PubMed

    El Backly, Rania M; Chiapale, Danilo; Muraglia, Anita; Tromba, Giuliana; Ottonello, Chiara; Santolini, Federico; Cancedda, Ranieri; Mastrogiacomo, Maddalena

    2014-01-01

    The present work defines a modified critical size rabbit ulna defect model for bone regeneration in which a non-resorbable barrier membrane was used to separate the radius from the ulna to create a valid model for evaluation of tissue-engineered periosteal substitutes. Eight rabbits divided into two groups were used. Critical defects (15 mm) were made in the ulna completely eliminating periosteum. For group I, defects were filled with a nanohydroxyapatite poly(ester urethane) scaffold soaked in PBS and left as such (group Ia) or wrapped with a tissue-engineered periosteal substitute (group Ib). For group II, an expanded-polytetrafluoroethylene (e-PTFE) (GORE-TEX(®)) membrane was inserted around the radius then the defects received either scaffold alone (group IIa) or scaffold wrapped with periosteal substitute (group IIb). Animals were euthanized after 12-16 weeks, and bone regeneration was evaluated by radiography, computed microtomography (μCT), and histology. In the first group, we observed formation of radio-ulnar synostosis irrespective of the treatment. This was completely eliminated upon placement of the e-PTFE (GORE-TEX(®)) membrane in the second group of animals. In conclusion, modification of the model using a non-resorbable e-PTFE membrane to isolate the ulna from the radius was a valuable addition allowing for objective evaluation of the tissue-engineered periosteal substitute. PMID:25610828

  18. [Experimental studies of the prevention of postoperative adhesions].

    PubMed

    Schwarz, J; Donat, H

    1989-01-01

    Female wistar rats were used for the testing of different substances to prevent postoperative intraabdominal adhesions. It could be demonstrated that the best results were obtained by dextran 70 with a concentration of 10%. Good effects were seen also by contrykal (aprotinin) and hylase (hyaluronidase). By the combination of dextran 70 30% with contrykal the spread of adhesions was very low but the effect was not significant better than with dextran 70 10% alone. For the prevention of intraabdominal adhesions operative techniques with minimal lesions are important too of the peritoneal epithelium. PMID:2466384

  19. A study of two-level system defects in dielectric films using superconducting resonators

    NASA Astrophysics Data System (ADS)

    Khalil, Moe Shwan

    In this dissertation I describe measurements of dielectric loss at microwave frequencies due to two level systems (TLS) using superconducting resonators. Most measurements were performed in a dilution refrigerator at temperatures between 30 and 200 mK and all resonators discussed were fabricated with thin-film superconducting aluminum. I derive the transmission through a non-ideal (mismatched) resonant circuit and find that in general the resonance line-shape is asymmetric. I describe an analysis method for extracting the internal quality factor (Q i), the diameter correction method (DCM), and compare it to a commonly used phenomenological method, the phi rotation method (phiRM). I analytically find that the phiRM deterministically overestimates Qi when the asymmetry of the resonance line-shape is high. Four coplanar resonator geometries were studied, with frequencies spanning 5-7 GHz. They were all superconducting aluminum fabricated on sapphire and silicon substrates. These include a quasi-lumped element resonator, a coplanar strip transmission line resonator, and two hybrid designs that contain both a coplanar strip and a quasi-lumped element. Measured Qi's were as high as 2 x 105 for single photon excitations and there was no systematic variation in loss between quasi-lumped and coplanar strip resonance modes. I also measured the microwave loss tangent of several atomic layer deposition (ALD) grown dielectrics and obtained secondary ion mass spectrometry (SIMS) measurements of the same films. I found that hydrogen defect concentrations were correlated with low temperature microwave loss. In amorphous films that showed excess hydrogen defects on the surface, two independent TLS distributions were required to fit the loss tangent, one for the surface and one for the bulk. In crystalline dielectrics where hydrogen contamination was uniform throughout the bulk, a single bulk TLS distribution was sufficient. Finally, I measured the TLS loss in 250 nm thick HD

  20. Defect study in molecular beam epitaxy-grown HgCdTe films with activated and unactivated arsenic

    SciTech Connect

    Izhnin, I. I.; Dvoretsky, S. A.; Mikhailov, N. N.; Varavin, V. S.; Mynbaev, K. D.; Fitsych, O. I.; Pociask-Bialy, M.; Sheregii, E.; Voitsekhovskii, A. V.

    2014-04-28

    A defect study was performed on molecular beam epitaxy-grown HgCdTe films in situ doped with arsenic. Doping was performed from either effusion cell or cracker cell, and studied were both as-grown samples and samples subjected to arsenic activation annealing. Electrical properties of the films were investigated with the use of ion milling as a means of “stirring” defects in the material. As a result of the study, it was confirmed that the most efficient incorporation of electrically active arsenic occurs at the cracking zone temperature of 700 °C. Interaction between arsenic and tellurium during the growth was observed and is discussed in the paper.

  1. Photocatalytic studies of Ho–Zr–O nano-composite with controllable composition and defects

    SciTech Connect

    Du, Weimin; Zhao, Guoyan; Chang, Hongxun; Shi, Fei; Zhu, Zhaoqiang; Qian, Xuefeng

    2013-09-15

    With the help of sol–gel method assisted by melting salt, a series of Ho–Zr–O nano-composite with controllable composition and defects have been successfully prepared. Characterization results show that the positions, intensity, and width of the X-ray diffraction peaks of the products have a regular variation with the increase of zirconium element which implies the gradual changes of crystal spacing and product size. At the same time, the molar ratios between holmium and zirconium ions are consistent with the chemical formula and both of them are uniformly distributed in products further showing the perfect formation of targeted materials. Optical properties reveal that diversified defect forms of Ho–Zr–O nano-composite lead to the different absorptions of visible light. Photocatalytic experiments demonstrate Zr{sub 0.8}Ho{sub 0.2}O{sub 2−δ} nano-crystals have excellent visible-light-responsive photocatalytic activities on some familiar dyes (e.g.: methylene blue and Rhodamine B) which results from the special defect structure, better absorption of visible light and larger specific surface area. It follows that Zr{sub 0.8}Ho{sub 0.2}O{sub 2−δ} nano-crystals are a new kind of visible-light-responsive photocatalysts with better prospects in conversion and utilization of solar energy. Also, the present melting salt assisted route might be generalized to synthesize other AxByOz composite oxide nano-crystals with more complicated structures. - Highlights: • Ho–Zr–O nano-composite with controllable composition and defects has been obtained. • Diversified defect forms of products lead to the different visible light absorption. • Zr{sub 0.8}Ho{sub 0.2}O{sub 2−δ} nano-crystals have excellent photocatalytic activities.

  2. First principles study of defect formation in thermoelectric zinc antimonide, β-Zn4Sb3

    NASA Astrophysics Data System (ADS)

    Faghaninia, Alireza; Lo, Cynthia S.

    2015-04-01

    Understanding the formation of various point defects in the promising thermoelectric material, β-Zn4Sb3, is crucial for theoretical determination of the origins of its p-type behavior and considerations of potential n-type dopability. While n-type conductivity has been fleetingly observed in Te:ZnSb, there have been no reports, to the best of our knowledge, of stable n-type behavior in β-Zn4Sb3. To understand the origin of this difficulty, we investigated the formation of intrinsic point defects in β-Zn4Sb3 density functional theory calculations. We found that a negatively charged zinc vacancy is the dominant defect in β-Zn4Sb3, as it is also in ZnSb. This explains the unintentional p-type behavior of the material and makes n-doping very difficult since the formation of the defect becomes more favorable at higher Fermi levels, near the conduction band minimum (CBM). We also calculated the formation energy of the cation dopants: Li, Na, B, Al, Ga, In, Tl; of these, only Li and Na are thermodynamically favorable compared to the acceptor Zn vacancy over a range of Fermi levels along the band gap. Further analysis of the band structure shows that Li:Zn4Sb3 has a partially occupied topmost valence band, making this defect an acceptor so that Li:Zn4Sb3 is indeed a p-type thermoelectric material. The introduction of Li, however, creates a more orderly and symmetric configuration, which stabilizes the host structure. Furthermore, Li reduces the concentration of holes and increases the Seebeck coefficient; hence, Li:Zn4Sb3 is more stable and better performing as a thermoelectric material than undoped β-Zn4Sb3.

  3. Markedly different adsorption behaviors of gas molecules on defective monolayer MoS2: a first-principles study.

    PubMed

    Li, Hongxing; Huang, Min; Cao, Gengyu

    2016-06-01

    Sulfur vacancy (SV) is one of the most typical defects in two-dimensional monolayer MoS2, leading to reactive sites. We presented a systematic study of the adsorption behaviors of gas molecules, CO2, N2, H2O, CO, NH3, NO, O2, H2 and NO2, on monolayer MoS2 with single SV by first-principles calculations. It was found that CO2, N2 and H2O molecules physisorbed at the proximity of single SV. Our adsorption energy calculations and charge transfer analysis showed that the interactions between CO2, N2 and H2O molecules and defective MoS2 are stronger than the cases of CO2, N2 and H2O molecules adsorbed on pristine MoS2, respectively. The defective MoS2 based gas sensors may be more sensitive to CO2, N2 and H2O molecules than pristine MoS2 based ones. CO, NO, O2 and NH3 molecules were found to chemisorb at the S vacancy site and thus modify the electronic properties of defective monolayer MoS2. Magnetism was induced upon adsorption of NO molecules and the defective states induced by S vacancy can be completely removed upon adsorption of O2 molecules, which may provide some helpful information for designing new MoS2 based nanoelectronic devices in future. The H2 and NO2 molecules were found to dissociate at S vacancy. The dissociation of NO2 molecules resulted in O atoms located at the S vacancy site and NO molecules physisorbed on O-doped MoS2. The calculated results showed that NO2 molecules can help heal the S vacancy of the MoS2 monolayer. PMID:27198064

  4. A Comprehensive Study of Formic Acid Oxidation on Palladium Nanocrystals with Different Types of Facets and Twin Defects

    SciTech Connect

    Choi, Sang; Herron, Jeffrey A.; Scaranto, Jessica; Huang, Hongwen; Wang, Yi; Xia, Xiaohu; Lv, Tian; Park, Jinho; Peng, Hsin-Chieh; Mavrikakis, Manos; Xia, Younan

    2015-07-13

    Palladium has been recognized as the best anodic, monometallic electrocatalyst for the formic acid oxidation (FAO) reaction in a direct formic acid fuel cell. Here we report a systematic study of FAO on a variety of Pd nanocrystals, including cubes, right bipyramids, octahedra, tetrahedra, decahedra, and icosahedra. These nanocrystals were synthesized with approximately the same size, but different types of facets and twin defects on their surfaces. Our measurements indicate that the Pd nanocrystals enclosed by {1 0 0} facets have higher specific activities than those enclosed by {1 1 1} facets, in agreement with prior observations for Pd single-crystal substrates. If comparing nanocrystals predominantly enclosed by a specific type of facet, {1 0 0} or {1 1 1}, those with twin defects displayed greatly enhanced FAO activities compared to their single-crystal counterparts. To rationalize these experimental results, we performed periodic, self-consistent DFT calculations on model single-crystal substrates of Pd, representing the active sites present in the nanocrystals used in the experiments. The calculation results suggest that the enhancement of FAO activity on defect regions, represented by Pd(2 1 1) sites, compared to the activity of both Pd(1 0 0) and Pd(1 1 1) surfaces, could be attributed to an increased flux through the HCOO-mediated pathway rather than the COOH-mediated pathway on Pd(2 1 1). Since COOH has been identified as a precursor to CO, a site-poisoning species, a lower coverage of CO at the defect regions will lead to a higher activity for the corresponding nanocrystal catalysts, containing those defect regions.

  5. A Mixed Methods Study of High School Dropout Prevention Programs

    ERIC Educational Resources Information Center

    Hibler, Derrick, Sr.

    2013-01-01

    In the United States in 2011, 6,000 students between the ages of 16 and 24 dropped out of high school on a daily basis. Educators have developed numerous dropout prevention programs to address this problem. However, little research exists examining how high school principals and counselors engage students in these programs. The purpose of this…

  6. A Community Case Study on Underage Drinking Prevention.

    ERIC Educational Resources Information Center

    National Association of Governors' Highway Safety Representatives.

    The National Association of Governors' Highway Safety Representatives (NAGHSR), with funding from the National Highway Traffic Safety Administration (NHTSA), pilot tested a comprehensive underage drinking prevention program in a number of communities across the country. In 1995, NAGHSR launched the effort in five communities, which received…

  7. Engaging Community Businesses in HIV Prevention: A Feasibility Study

    PubMed Central

    Rovniak, Liza S.; Hovell, Melbourne F.; Hofstetter, C. Richard; Blumberg, Elaine J.; Sipan, Carol L.; Batista, Marcia F.; Martinez-Donate, Ana P.; Mulvihill, Mary M.; Ayala, Guadalupe X.

    2009-01-01

    Purpose To explore the feasibility of engaging community businesses in HIV prevention. Design Randomly selected business owners/managers were asked to display discreetly wrapped condoms and brochures provided free-of-charge for 3 months. Assessments were conducted at baseline, mid-, and post-program. Customer feedback was obtained through an online survey. Setting San Diego, California neighborhood with a high rate of AIDS. Subjects Fifty-one business owners/managers representing 10 retail categories, and 52 customers. Measures Participation rates, descriptive characteristics, number of condoms and brochures distributed, customer feedback, business owners'/managers' program satisfaction and willingness to provide future support for HIV prevention. Analysis Kruskal-Wallis, Mann-Whitney U, Fisher's exact, and McNemar's tests were used to analyze data. Results The 20 business owners/managers (39%) who agreed to distribute condoms and brochures reported fewer years in business and more employees than those who agreed only to distribute brochures (20%) or refused to participate (41%), p <.05. Bars were the easiest of ten retail categories to recruit. Businesses with more employees and customers distributed more condoms and brochures, p < .05. More than 90% of customers supported distributing condoms and brochures in businesses and 96% of business owners/managers described their program experience as “positive.” Conclusion Businesses are willing to distribute condoms and brochures to prevent HIV. Policies to increase business participation in HIV prevention should be developed and tested. PMID:20465150

  8. Defects and alloying in semiconductors: Computational studies of clusters and surfaces

    NASA Astrophysics Data System (ADS)

    Maddox, Willie Burton, IV

    This thesis addresses two main systems that are important in the lore of energy efficient nanomaterials, titanium dioxide and group IV alloy nanoclusters. Titanium dioxide, widely used in heterogeneous catalysis, photocatalysis, solar cells, or gas sensors, has become the prototype material for studying the reactivity of metal-oxide surfaces. Defects such as oxygen vacancies are always present on rutile surfaces and, depending on their coverage and spatial distribution, can strongly influence the reactivity of the surface. The interactions between vacancies determine their spatial distribution on the surface. Highly reactive vacancy clusters or pairs have not been expected to form because of vacancy repulsions, but recent experiments do show the possibility of spontaneously formed oxygen vacancy pairs. In this thesis, The interaction between oxygen vacancies is studied, as well as their electronic properties and scanning tunneling microscopy signature. The second thrust of the thesis concerns group IV nanomaterials, which are important semiconductors for photovoltaic applications due to their relative abundance and nontoxicity. Alloy nanoclusters, specifically germanium-tin (GeSn) nanoclusters show great promise for achieving higher photoconversion efficiencies since the band gap can be tuned by adjusting the Ge/Sn ratio. To accurately model alloy nanoclusters one must first verify that the physical properties of the constituent nanoclusters are described correctly. As these nanoclusters are composed of thousands to hundreds of thousands of atoms, we employ molecular dynamics (MD) simulations which are capable of calculating properties for large systems in reasonable timeframes. In MD simulations, atomic interactions are described using empirical potentials. The well-known Tersoff potential has proven to describe well the properties of group IV elements up to Ge. As Sn is also a group IV element, we have extended this potential to include parameters for Sn by

  9. NMR Studies of the original magnetic properties of the cuprates: influence of impurities and defects.

    NASA Astrophysics Data System (ADS)

    Alloul, Henri

    1998-03-01

    The cuprates display original magnetic properties, both in their insulating and metallic phases. In underdoped metallic systems, a pseudo gap in the density of magnetic q=3D0 excitations is observed from local susceptibility measurements, as well as from specific heat and transport properties. A pseudo spin-gap in the AF excitations at the AF wave vector is detected both by NMR and inelastic neutron scattering. From the NMR measurements it can be concluded that these magnetic anomalies are quite similar in single layer(J. Bobroff, H.. Alloul, P. Mendels, V. Viallet, J. F. Marucco and D. Colson, Phys. Rev. Letters 78, 3757 (1997).), bilayer and trilayer underdoped cuprates. The modifications of magnetic properties induced by substitutions or defects in the planes, which do not modify appreciably the charge transfer have been studied. The spatial dependence of the spin susceptibility \\chi ' (r) of the pure material can be directly probed through the study of the modifications of the NMR spectra of various nuclei (^89Y, ^17O, ^63Cu) induced by such localised magnetic impurities. Large qualitative differences between the underdoped and slightly overdoped YBCO are evidenced from ^17O NMR line broadening in Ni substituted YBCO. This allows us to propose a quite powerful method for studying the q and T dependence of the static magnetic susceptibility (J. Bobroff et al, Phys. Rev. Letters 78, 3757 (1997).). The impurity magnetic state also directly reflects the occurence of electronic correlations in the metallic state. The case of Zn will be examined in some detail. ^89Y NMR has revealed that the substitution of this 3d^10 non magnetic atom on a Cu site induces a Curie like contribution to the local susceptibility on the near neighbour coppers ( A. V. Mahajan, H. Alloul, G. Collin and J. F. Marucco, Physical Review Letters 72, 3100 (1994).). The effective induced moment decreases with hole doping and becomes rather weak, but is still present for optimal doping

  10. Transmission electron microscopic study of pyrochlore to defect-fluorite transition in rare-earth pyrohafnates

    SciTech Connect

    Karthik, Chinnathambi; Anderson, Thomas J.; Gout, Delphine; Ubic, Rick

    2012-10-15

    A structural transition in rare earth pyrohafnates, Ln{sub 2}Hf{sub 2}O{sub 7} (Ln=Y, La, Pr, Nd, Tb, Dy, Yb and Lu), has been identified. Neutron diffraction showed that the structure transforms from well-ordered pyrochloric to fully fluoritic through the lanthanide series from La to Lu with a corresponding increase in the position parameter x of the 48f (Fd3{sup Macron }m) oxygen site from 0.330 to 0.375. As evidenced by the selected area electron diffraction, La{sub 2}Hf{sub 2}O{sub 7}, Pr{sub 2}Hf{sub 2}O{sub 7} and Nd{sub 2}Hf{sub 2}O{sub 7} exhibited a well-ordered pyrocholoric structure with the presence of intense superlattice spots, which became weak and diffuse (in Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}) before disappearing completely as the series progressed towards the Lu end. High resolution electron microscopic studies showed the breakdown of the pyrochlore ordering in the form of antiphase domains resulting in diffused smoke-like superlattice spots in the case of Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}. - Graphical abstract: Transmission electron microscopic studies showed the ordered pyrochlore to defect fluorite transition in rare-earth pyrohafnates to occur via the formation of anti-phase domains to start with. Highlights: Black-Right-Pointing-Pointer Pyrochlore to fluorite structural transition in rare earth pyrohafnates. Black-Right-Pointing-Pointer La{sub 2}Hf{sub 2}O{sub 7}, Pr{sub 2}Hf{sub 2}O{sub 7} and Nd{sub 2}Hf{sub 2}O{sub 7} showed well ordered pyrochlore structure. Black-Right-Pointing-Pointer Short range ordering in Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}. Black-Right-Pointing-Pointer Break down of pyrochlore ordering due to antiphase boundaries. Black-Right-Pointing-Pointer Rest of the series showed fluoritic structure.

  11. Study of the effect of annealing on defects in Fe Mn Si Cr Ni C alloy by slow positron beam

    NASA Astrophysics Data System (ADS)

    Mostafa, Khaled. M.; De Baerdemaeker, J.; Van Caenegem, N.; Segers, D.; Houbaert, Y.

    2008-10-01

    FeMnSi shape memory alloys (SMAs) have received much attention as one-way SMAs due to their cost-effectiveness. Variable-energy (0-30 keV) positron beam studies have been carried out on a Fe-Mn-Si-Cr-Ni-C alloy with different degrees of deformation. Doppler broadening profiles of the positron annihilation as a function of incident positron energy were shown to be quite sensitive to defects introduced by deformation. The variation of the nature and the concentration of defects are studied as a function of isochronal annealing temperature. These results are correlated with the data measured with the positron annihilation lifetime spectroscopy (PALS). The positron annihilation results are compared to XRD and optical microscopy (OM).

  12. First principle study of the effect of defects on performance of single-molecule pentacene field effect transistors

    NASA Astrophysics Data System (ADS)

    Ghosh, Bahniman; Gramin, Akash

    2015-07-01

    In this work, we have performed first principle study on a single-molecule pentacene field effect transistor and studied various oxygen- and hydrogen-induced defects in the same device configuration. Further, we have investigated the effect of these defects on the various electronic transport properties of the device and compared them with those of the original device along with reporting the negative differential region window and the peak-to-valley ratio in different cases. For this purpose, we have applied the density functional theory in conjugation with non-equilibrium green's function (NEGF) formalism on a 14.11 Å pentacene device to obtain the I-V characteristics, conductance curves and transmission spectra in various device scenarios.

  13. Unraveling energy conversion modeling in the intrinsic persistent upconverted luminescence of solids: a study of native point defects in antiferromagnetic Er2O3.

    PubMed

    Huang, Bolong

    2016-05-11

    We investigated the mechanism of the intrinsic persistent luminescence of Er2O3 in the A-type lattice based on first-principles calculations. We found that the native point defects were engaged in mutual subtle interactions in the form of chemical reactions between different charge states. The release of energy related to lattice distortion facilitates the conversion of energy for electrons to be transported between the valence band and the trap levels or even between the deep trap levels so as to generate persistent luminescence. The defect transitions that take place along the zero-phonon line release energy to enable optical transitions, with the exact amount of negative effective correlation energy determined by the lattice distortions. Our calculations on the thermodynamic transition levels confirm that both the visible and NIR experimentally observed intrinsic persistent luminescence (phosphor or afterglow) are related to the thermodynamic transition levels of oxygen-related defects, and the thermodynamic transition levels within different charge states for these defects are independent of the chemical potentials of the given species. Lattice distortion defects such as anion Frenkel (a-Fr) pair defects play an important role in transporting O-related defects between different lattice sites. To obtain red persistent luminescence that matches the biological therapeutic window, it is suggested to increase the electron transition levels between high-coordinated O vacancies and related metastable a-Fr defects; a close-packed core-shell structure is required to quench low-coordinated O-related defects so as to reduce the green band luminescence. We further established a conversed chain reaction (CCR) model to interpret the energy conversion process of persistent luminescence in terms of the inter-reactions of native point defects between different charge states. It is advantageous to use the study of defect levels combined with formation energies to suggest limits

  14. [Experimental study of pBMP/MPTCP in bone defects therapy].

    PubMed

    Yi, W H; Lu, C; Zhou, J N

    2001-06-28

    To develop a new substitute of bone graft, which is composed of porcine bone morphogenetic protein (pBMP) and the magnetic porous tricalcium phosphate (MPTCP), we investigated the effects of pBMP/MPTCP (Group A), autologous red bone marrow/porus tricalcium phosphate (BM/PTCP) (Group B), pBMP/PTCP(Group C) on the repair of bone defects created surgically in rabbits. By gross inspection, roentgenography examination, histological examination, immunohistochemistry test of osteocalcim, quantitive histological measurement of new bone formation and biomechanical test, three kinds of substitutes were proved to be biocompatible. Group A induced more new bone formation than other two groups, and showed a better biomechanical function(P < 0.01). It is believed that pBMP/MPTCP has characteristics of strong osteoinductive capacity, good biocompatibility, excellent filling of bone defects and gradual biodegradation. PMID:12536687

  15. Power-law defect energy in a single-crystal gradient plasticity framework: a computational study

    NASA Astrophysics Data System (ADS)

    Bayerschen, E.; Böhlke, T.

    2016-03-01

    A single-crystal gradient plasticity model is presented that includes a power-law type defect energy depending on the gradient of an equivalent plastic strain. Numerical regularization for the case of vanishing gradients is employed in the finite element discretization of the theory. Three exemplary choices of the defect energy exponent are compared in finite element simulations of elastic-plastic tricrystals under tensile loading. The influence of the power-law exponent is discussed related to the distribution of gradients and in regard to size effects. In addition, an analytical solution is presented for the single slip case supporting the numerical results. The influence of the power-law exponent is contrasted to the influence of the normalization constant.

  16. Power-law defect energy in a single-crystal gradient plasticity framework: a computational study

    NASA Astrophysics Data System (ADS)

    Bayerschen, E.; Böhlke, T.

    2016-07-01

    A single-crystal gradient plasticity model is presented that includes a power-law type defect energy depending on the gradient of an equivalent plastic strain. Numerical regularization for the case of vanishing gradients is employed in the finite element discretization of the theory. Three exemplary choices of the defect energy exponent are compared in finite element simulations of elastic-plastic tricrystals under tensile loading. The influence of the power-law exponent is discussed related to the distribution of gradients and in regard to size effects. In addition, an analytical solution is presented for the single slip case supporting the numerical results. The influence of the power-law exponent is contrasted to the influence of the normalization constant.

  17. Defect measurement and analysis of JPL ground software: a case study

    NASA Technical Reports Server (NTRS)

    Powell, John D.; Spagnuolo, John N., Jr.

    2004-01-01

    Ground software systems at JPL must meet high assurance standards while remaining on schedule due to relatively immovable launch dates for spacecraft that will be controlled by such systems. Toward this end, the Software Quality Improvement (SQI) project's Measurement and Benchmarking (M&B) team is collecting and analyzing defect data of JPL ground system software projects to build software defect prediction models. The aim of these models is to improve predictability with regard to software quality activities. Predictive models will quantitatively define typical trends for JPL ground systems as well as Critical Discriminators (CDs) to provide explanations for atypical deviations from the norm at JPL. CDs are software characteristics that can be estimated or foreseen early in a software project's planning. Thus, these CDs will assist in planning for the predicted degree to which software quality activities for a project are likely to deviation from the normal JPL ground system based on pasted experience across the lab.

  18. A study on the effects of amphoteric defect concentration on the characteristics parameters of In x Ga1- x N thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Movla, Hossein; Babazadeh, Mohammad; Esmaeili, Seyed Vahid

    2016-07-01

    Group III nitride semiconductors can partly cover the solar spectrum from ultraviolet to infrared spectra due to their ability to vary their band gap. These semiconductors have a substantial potential to develop ultra-high efficiency solar cells. However, defects have a profound effect on their power conversion efficiency. Since defects lead to dramatic changes in electronic and optoelectronic properties, controlling process to get acceptable defects density in solar cells is a noteworthy parameter in technological and device applications. This paper indicates a numerical simulation study to optimize the p-i-n InGaN homojunction solar cells by investigation of defect density in the whole cell structure. In this study, we assumed that the p-region and n-region thicknesses are 100 and 150 nm, respectively, and the optimized value of cell thickness is 1.3 μm. Similarly, we chose amphoteric defect density from 1015 to 1019 cm-3, and then the effects of defects density on characteristic parameters of cell have been studied. Based on our results, when the amphoteric defect concentration is below the 1015 cm-3, constant value for FF values in all layers was obtained. Therefore, cell efficiency remains the same in lower amphoteric defect density where all FF, V OC and J SC are constant. By increasing the amphoteric defect density from 1015 cm-3, the cell efficiency falls down dramatically from 20 to about 1 % at 1019 cm-3. In our simulated structure, the cell efficiency parameter decreases with increasing the defects density until it reaches the 1015 cm-3. Above this value, no change in the parameters was observed. Our results revealed that the high defect density range 1015-1019 cm-3 may be an equally significant cause of performance loss.

  19. Positron studies of defected metals, metallic surfaces. Final report, July 1, 1985--December 1, 1991

    SciTech Connect

    Bansil, A.

    1991-12-31

    Specific problems proposed under this project included the treatment of electronic structure and momentum density in various disordered and defected systems. Since 1987, when the new high-temperature superconductors were discovered, the project focused extensively on questions concerning the electronic structure and Fermiology of high-{Tc} superconductors, in particular, (i) momentum density and positron experiments, (ii) angle-resolved photoemission intensities, (iii) effects of disorder and substitutions in the high-{Tc}`s.

  20. Genomic approach to studying nutritional requirements of Clostridium tyrobutyricum and other Clostridia causing late blowing defects.

    PubMed

    Storari, Michelangelo; Kulli, Sandra; Wüthrich, Daniel; Bruggmann, Rémy; Berthoud, Hélène; Arias-Roth, Emmanuelle

    2016-10-01

    Clostridium tyrobutyricum is the main microorganism responsible for the late blowing defect in hard and semi-hard cheeses, causing considerable economic losses to the cheese industry. Deeper knowledge of the metabolic requirements of this microorganism can lead to the development of more effective control approaches. In this work, the amino acids and B vitamins essential for sustaining the growth of C. tyrobutyricum were investigated using a genomic approach. As the first step, the genomes of four C. tyrobutyricum strains were analyzed for the presence of genes putatively involved in the biosynthesis of amino acids and B vitamins. Metabolic pathways could be reconstructed for all amino acids and B vitamins with the exception of biotin (vitamin B7) and folate (vitamin B9). The biotin pathway was missing the enzyme amino-7-oxononanoate synthase that catalyzes the condensation of pimeloyl-ACP and l-alanine to 8-amino-7-oxononanoate. In the folate pathway, the missing genes were those coding for para-aminobenzoate synthase and aminodeoxychorismate lyase enzymes. These enzymes are responsible for the conversion of chorismate into para-aminobenzoate (PABA). Two C. tyrobutyircum strains whose genome was analyzed in silico as well as other 10 strains isolated from cheese were tested in liquid media to confirm these observations. 11 strains showed growth in a defined liquid medium containing biotin and PABA after 6-8 days of incubation. No strain showed growth when only one or none of these compounds were added, confirming the observations obtained in silico. Furthermore, the genome analysis was extended to genomes of single strains of other Clostridium species potentially causing late blowing, namely Clostridium beijerinckii, Clostridium sporogenes and Clostridium butyricum. Only the biotin biosynthesis pathway was incomplete for C. butyricum and C. beijerincki. In contrast, C. sporogenes showed missing enzymes in biosynthesis pathways of several amino acids as well

  1. Comparative study of survived displacement damage defects in iron irradiated in IFMIF and fusion power reactors

    NASA Astrophysics Data System (ADS)

    Simakov, S. P.; Konobeyev, A. Yu.; Fischer, U.; Heinzel, V.

    2009-04-01

    The assessment of the primary survived defects rates in iron such as vacancies-interstitials pairs and simplest clusters have been performed for the IFMIF, fusion power plant and research reactor. This was achieved by a modified version of the NJOY code, when processing evaluated nuclear cross section file. The modifications accounted for the reduction of the available damage energy predicted by the standard NRT model by the surviving defects fractions. These fractions were picked-up from the molecular dynamics and binary collisions simulation results available in the literature. The number of primary survived and clustered defects in the α-iron irradiated in the high flux test module of IFMIF was estimated as 10 and 6 dpa/fpy or several times less than standard NRT estimates at the level of 30 dpa/fpy. The comparison with damages in iron calculated for irradiation in the first wall of fusion power plant gave however the same reduction factors, that supports the qualification of IFMIF as a fusion material irradiation facility.

  2. Chemical exposures at work in early pregnancy and congenital defect: a case-referent study.

    PubMed Central

    McDonald, J C; Lavoie, J; Côté, R; McDonald, A D

    1987-01-01

    Three hundred and one women who in their most recent pregnancy had given birth to an infant with an important congenital defect were individually matched with 301 women whose children were normal. Both cases and referents were drawn from a comprehensive survey of pregnancies in Montreal, 1982-4, and limited to women employed 30 or more hours a week until at least the 13th week of gestation. Occupational exposure to chemicals was investigated and the results classified without knowledge of case-referent status. In matched pair analysis the overall frequency of chemical exposure was higher in cases than referents (63:47), due to excesses in the cardiac and miscellaneous defect groups (ratios of 10:5 and 15:7 respectively). In analyses by nine chemical categories only exposure to aromatic solvents showed a clear excess (18:8; p approximately equal to 0.04), most evident in the urinary tract group (9:0). A comparison of cases and referents exposed to aromatic solvents showed that most of the excess was associated with toluene; the defects were varied but predominantly renal-urinary or gastrointestinal. PMID:3651351

  3. Light-induced defects in hydrogenated amorphous silicon studied by the constant-photocurrent method

    NASA Astrophysics Data System (ADS)

    Schmidt, J. A.; Arce, R.; Buitrago, R. H.; Koropecki, R. R.

    1997-04-01

    The light-induced creation of metastable defects in undoped hydrogenated amorphous silicon has been followed using photoconductivity and absorption coefficient measurements. The density of states in the gap was obtained from the deconvolution of the subgap absorption coefficient measured by the constant-photocurrent method. We found that the decay of the photoconductivity and the evolution of the integrated density of subgap states follow the dependence on illumination time (till) predicted by the ``bond-breaking'' model. The density of occupied states obtained from the deconvolution procedure shows the presence of two peaks within the gap. After subtracting the valence band-tail contribution, these peaks can be well fitted with two Gaussians. The areas of both Gaussians increase as t1/3ill while their positions and widths remain unchanged. According to the energy position of these peaks, they are ascribed to the neutral and negatively charged silicon dangling bonds D0 and D-. We found that in this intrinsic sample the density of charged defects exceeds that of neutral defects, their ratio D-/D0 being approximately 2.6. This ratio is independent of the illumination time.

  4. Effects of defects in composite structures

    NASA Technical Reports Server (NTRS)

    Sendeckyj, G. P.

    1983-01-01

    The effect of defects in composite structures is addressed. Defects in laminates such as wrinkles, foreign particles, scratches and breaks are discussed. Effects of plygap plywaviness and machining defects are also studied.

  5. Micrograph Defect Indentifier

    Energy Science and Technology Software Center (ESTSC)

    2012-10-11

    Micrograph image defect identifier is a computer code written in MATLAB to automatically detect defects on scanned image of thin film membrane samples employing three methods: global threshold, line detection and k-means segmentation. The results are segmented binary images of thin film with defects identified. Defect area fractions are also calculated. The users may use default functional variables calculated by program, or input preferred value from user’s experience. This will empower the user to processingmore » the image with more flexibility. MDI was designed to identify defects of thin films fabricated. It is also used in phase identification, porosity study on SEM, OM, TEM images. Different methods were applied in this software package: global threshold, line detection and k-means segmentation.« less

  6. Micrograph Defect Indentifier

    SciTech Connect

    None, None

    2012-10-11

    Micrograph image defect identifier is a computer code written in MATLAB to automatically detect defects on scanned image of thin film membrane samples employing three methods: global threshold, line detection and k-means segmentation. The results are segmented binary images of thin film with defects identified. Defect area fractions are also calculated. The users may use default functional variables calculated by program, or input preferred value from user’s experience. This will empower the user to processing the image with more flexibility. MDI was designed to identify defects of thin films fabricated. It is also used in phase identification, porosity study on SEM, OM, TEM images. Different methods were applied in this software package: global threshold, line detection and k-means segmentation.

  7. Development of a New Membrane Casting Apparatus for Studying Macrovoid Defects in Low-G

    NASA Technical Reports Server (NTRS)

    Lee, Hanyong; Hwang, Sun-Tak; Krantz, William B.; Greenberg, Alan R.; Khare, Vivek; Zartman, Jeremiah; Todd, Paul W.

    2002-01-01

    A new membrane-casting apparatus is developed for studying macrovoid defects in polymeric membranes made by the wet- and dry-casting process in low-gravity. Macrovoids are large (10-50 micron), open cavities interspersed among the smaller pores in the substructure under the gelled skin surface layer of the cast membrane. Although their occurrence is considered endemic to the wet- and dry-casting process since they can lead to compaction or skin rupture in the membrane process, recent studies suggest several useful applications such as transdermal and osmotic drug delivery systems, miniature bioreactors, etc. However, lack of knowledge about the macrovoid formation mechanism is an obstacle to further development of applications using them. An on-going debate is the role of the surface-tension-driven solutocapillary convection during macrovoid formation. The rapid growth of macrovoids within 1-5 seconds and the high polymer concentration in and near macrovoids make it difficult to explain the mechanism of macrovoid growth by diffusion alone, which is the widely accepted hypothesis proposed by Reuvers et al. The hypothesis advanced by our research group can explain this rapid growth via a mechanism that involves diffusion from the casting solution in the meta-stable region to the macrovoid enhanced by solutocapillary convection induced by the steep nonsolvent concentration gradient in the vicinity of the macrovoid. Since macrovoid growth is hypothesized to be the interplay of a solutocapillary-induced driving force counteracted by viscous drag and buoyancy, eliminate the latter provides a means for testing this hypothesis. Moreover, free convection mass transfer in the nonsolvent immersion bath used to cause phase-separation in membrane casting complicates developing a model for both the wet-casting process and macrovoid growth. The low-g environment minimizes gravitationally induced free convection thereby permitting a tractable solution to the ternary diffusion

  8. Hydrogen defects in tetragonal ZrO2 studied using density functional theory.

    PubMed

    Youssef, Mostafa; Yildiz, Bilge

    2014-01-28

    In the energy-structure paradigm, we analyzed the defects that can arise in tetragonal zirconium oxide (T-ZrO2) involving the hydrogen atom or the hydrogen molecule using density functional theory. Our results indicate that the dominant hydrogen defect under reducing conditions is H(·)(0), a complex formed between the hydride ion and a doubly charged oxygen vacancy. This result is consistent with the experimental observation that under reducing conditions, the solubility of hydrogen is proportional to the degree of hypostoichiometry of T-ZrO2. Under oxidizing conditions we found three different hydrogen defects, each predominating in a specific range of the chemical potential of electrons. Starting from the valence band top toward the conduction band bottom, these defects are the interstitial proton, H(·)(i), a complex formed between two hydrogen species and a zirconium vacancy with a net effective charge of (2-), (2H)"(Zr), and finally a complex similar to the latter but with a net effective charge of (4-), (H(2))'''(Zr). In (2H)"(Zr)the two hydrogens exist in the form of hydroxyl groups, while in (H(2))" " (Zr) they exist in the form of a hydrogen molecule. In addition, we found that up to three hydrogen species can favorably accumulate in a zirconium vacancy under oxidizing conditions. The clustering of hydrogen in cation vacancies can be a precursor for the deleterious effects of hydrogen on the mechanical properties and stability of metal oxides, in analogy with hydrogen embrittlement in metals. Finally we observed a red-shift and a blue-shift for the vibrational frequencies of all the hydroxyl groups and all the hydrogen molecules, respectively, in T-ZrO2 when compared to the gas phase frequencies. This is an important characteristic for guiding future experimental efforts to detect and identify hydrogen defects in T-ZrO2. The insights presented in this work advance our predictive understanding of the degradation behavior of T-ZrO2 as a corrosion resistant

  9. Single nickel-related defects in molecular-sized nanodiamonds for multicolor bioimaging: an ab initio study.

    PubMed

    Thiering, Gergő; Londero, Elisa; Gali, Adam

    2014-10-21

    Fluorescent nanodiamonds constitute an outstanding alternative to semiconductor quantum dots and dye molecules for in vivo biomarker applications, where the fluorescence comes from optically active point defects acting as color centers in the nanodiamonds. For practical purposes, these color centers should be photostable as a function of the laser power or the surface termination of nanodiamonds. Furthermore, they should exhibit a sharp and nearly temperature-independent zero-phonon line. In this study, we show by hybrid density functional theory calculations that nickel doped nanodiamonds exhibit the desired properties, thus opening the avenue to practical applications. In particular, harnessing the strong quantum confinement effect in molecule-sized nanodiamonds is very promising for achieving multicolor imaging by single nickel-related defects. PMID:25180791

  10. Positron annihilation study of vacancy-type defects in Al single crystal foils with the tweed structures across the surface

    SciTech Connect

    Kuznetsov, Pavel; Cizek, Jacub Hruska, Petr; Anwad, Wolfgang; Bordulev, Yuri; Lider, Andrei; Laptev, Roman; Mironov, Yuri

    2015-10-27

    The vacancy-type defects in the aluminum single crystal foils after a series of the cyclic tensions were studied using positron annihilation. Two components were identified in the positron lifetime spectra associated with the annihilation of free positrons and positrons trapped by dislocations. With increasing number of cycles the dislocation density firstly increases and reaches a maximum value at N = 10 000 cycles but then it gradually decreases and at N = 70 000 cycles falls down to the level typical for the virgin samples. The direct evidence on the formation of a two-phase system “defective near-surface layer/base Al crystal” in aluminum foils at cyclic tension was obtained using a positron beam with the variable energy.

  11. Experimental and ab initio study of the hyperfine parameters of ZnFe 2 O 4 with defects

    NASA Astrophysics Data System (ADS)

    Quintero, J. Melo; Salcedo Rodríguez, K. L.; Pasquevich, G. A.; Zélis, P. Mendoza; Stewart, S. J.; Rodríguez Torres, C. E.; Errico, L. A.

    2016-12-01

    We present a combined Mössbauer and ab initio study on the influence of oxygen-vacancies on the hyperfine and magnetic properties of the ZnFe 2 O 4 spinel ferrite. Samples with different degree of oxygen-vacancies were obtained from zinc ferrite powder that was thermally treated at different temperatures up to 650 ∘C under vacuum.Theoretical calculations of the hyperfine parameters, magnetic moments and magnetic alignment have been carried out considering different defects such as oxygen vacancies and cation inversion. We show how theoretical and experimental approaches are complementary to characterize the local structure around Fe atoms and interpret the observed changes in the hyperfine parameters as the level of defects increases.

  12. STUDY ON CHARACTERISTICS OF RESIDUAL STRENGTH OF RC BEAMS WITH DEFECTIVE ANCHORAGES DUE TO CORROSION OF REINFORCEMENTS

    NASA Astrophysics Data System (ADS)

    Murakami, Yuki; Dong, Wei; Oshita, Hideki; Suzuki, Shuichi; Tsutsumi, Tomoaki

    In this study, to evaluate flexural strength and shear strength with def ective anchorages due to corrosion of reinforcemen t, the bending test of the RC beams r eceived damage in the anchorage region due to corrosion was carried out. As a result, it is se ems that the residual shear strength of RC beams with defective anchorages depends on shear span ratio in addition to the anchorage performance. Furthermore, the authors propose an evaluation model for an shear strength of RC beams with defective anchorages on the basis of these experimental results and analy tical result. The value of residual shear strength calculated using this model corresponds to the test results in the past.

  13. The Ptch1DL mouse: a new model to study lambdoid craniosynostosis and basal cell nevus syndrome associated skeletal defects

    PubMed Central

    Feng, Weiguo; Choi, Irene; Clouthier, David E.; Niswander, Lee; Williams, Trevor

    2013-01-01

    Mouse models provide valuable opportunities for probing the underlying pathology of human birth defects. Employing an ENU-based screen for recessive mutations affecting craniofacial anatomy we isolated a mouse strain, Dogface-like (DL), with abnormal skull and snout morphology. Examination of the skull indicated that these mice developed craniosynostosis of the lambdoid suture. Further analysis revealed skeletal defects related to the pathology of basal cell nevus syndrome (BCNS) including defects in development of the limbs, scapula, ribcage, secondary palate, cranial base, and cranial vault. In humans, BCNS is often associated with mutations in the Hedgehog receptor PTCH1 and genetic mapping in DL identified a point mutation at a splice donor site in Ptch1. Using genetic complementation analysis we determined that DL is a hypomorphic allele of Ptch1, leading to increased Hedgehog signaling. Two aberrant transcripts are generated by the mutated Ptch1DL gene, which would be predicted to reduce significantly the levels of functional Patched1 protein. This new Ptch1 allele broadens the mouse genetic reagents available to study the Hedgehog pathway and provides a valuable means to study the underlying skeletal abnormalities in BCNS. In addition, these results strengthen the connection between elevated Hedgehog signaling and craniosynostosis. PMID:23897749

  14. Neural tube defects.

    PubMed

    Greene, Nicholas D E; Copp, Andrew J

    2014-01-01

    Neural tube defects (NTDs), including spina bifida and anencephaly, are severe birth defects of the central nervous system that originate during embryonic development when the neural tube fails to close completely. Human NTDs are multifactorial, with contributions from both genetic and environmental factors. The genetic basis is not yet well understood, but several nongenetic risk factors have been identified as have possibilities for prevention by maternal folic acid supplementation. Mechanisms underlying neural tube closure and NTDs may be informed by experimental models, which have revealed numerous genes whose abnormal function causes NTDs and have provided details of critical cellular and morphological events whose regulation is essential for closure. Such models also provide an opportunity to investigate potential risk factors and to develop novel preventive therapies. PMID:25032496

  15. Neural Tube Defects

    PubMed Central

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

    2015-01-01

    Neural tube defects (NTDs), including spina bifida and anencephaly, are severe birth defects of the central nervous system that originate during embryonic development when the neural tube fails to close completely. Human NTDs are multifactorial, with contributions from both genetic and environmental factors. The genetic basis is not yet well understood, but several nongenetic risk factors have been identified as have possibilities for prevention by maternal folic acid supplementation. Mechanisms underlying neural tube closure and NTDs may be informed by experimental models, which have revealed numerous genes whose abnormal function causes NTDs and have provided details of critical cellular and morphological events whose regulation is essential for closure. Such models also provide an opportunity to investigate potential risk factors and to develop novel preventive therapies. PMID:25032496

  16. Identification of open-volume defects in disordered and amorphized Si: A depth-resolved positron annihilation study

    SciTech Connect

    Amarendra, G.; Rajaraman, R.; Venugopal Rao, G.; Nair, K. G. M.; Viswanathan, B.; Suzuki, R.; Ohdaira, T.; Mikado, T.

    2001-06-01

    Depth-resolved positron beam studies have been carried out on Ar-irradiated Si using Doppler S parameter and lifetime measurements. Si samples have been irradiated with 140-keV Ar ions to a dose of 2{times}10{sup 13} and 5{times}10{sup 16} Ar/cm{sup 2}, respectively, so as to produce disordered and amorphous states in near-surface regions. The observed features of the defect sensitive line shape S parameter indicate the presence of small vacancylike defects in the disordered sample and higher-order vacancy clusters in an amorphous sample. Pulsed positron beam lifetime results indicate that the disordered Si sample exhibits lifetime distribution ascribable to mostly divacancies. In the case of an amorphous sample, the lifetime distribution is broad with larger lifetime values indicating the presence of a distribution of large vacancy clusters or nanovoids. By using theoretical lifetime values for Si reported in the literature, an empirical fit to the lifetime variation as a function of vacancy cluster size is obtained. By comparing the experimental lifetime distribution with this data, the vacancy cluster size distribution in disordered and amorphous Si is deduced. In disordered Si, divacancies are found to be the dominant defects species followed by small concentration of V{sub 3}. In amorphous Si, nanovoids in the size range of four to seven vacancy clusters are present with V{sub 5} and V{sub 6} clusters being the dominant defect species. The implication of these results is discussed in light of recent computer-simulation studies.

  17. Fundamental Study of Micro-Defects in Electropolished EB-Welded and Hydroformed SRF Accelerating Structures

    SciTech Connect

    Sumption, Mike

    2014-08-29

    In the area of niobium elecropolishing fundamentals, we focused on understanding the influence of the surface topology, and geometry (with effects from gravity included. The formation of a viscous film is essential for the electropolishing process to take place. The exact nature and composition of the film formed on niobium is still unknown because of its solubility in the electrolyte. Extensive pitting may take place at surface where a stable film cannot form. This has to be taken into consideration while determining the speed with which the SRF cavities are rotated while EP. Hydrodynamic aspects must be taken into consideration while optimizing the polishing parameters. There is improvement in surface finish with polishing time. There is a huge change in surface quality when the EP time is increased from 2 hours to 4 hours but not much change takes place when the time is further increased to 6 hours. So keeping the economic points in view, about 100 um defect layer removal may be sufficient to get the desired performance. In the area of Electropolishing of untreated and treated niobium with Weld Joints we studied untreated and treated Nb, especially for the heat affected areas next to welded bumps, electropolished for different durations. The electropolishing of the untreated Nb caused the formation of pits on the surface at about 15 min but they disappeared when the electropolishing duration was more than 15 min. Electropolishing for 120 min smoothened the surface of untreated Nb by levelling the surface, but the severe formation of pits on the whole surface was found after 240 min. The treatment of Nb significantly changed the Nb surface morphology which was covered by grains of different size that looked light or dark in the optical microscope. The treated Nb was susceptible to pitting during the entire electropolishing starting from 15 min and the dark grains had more susceptibility to pitting than the light grains. In addition, electropolishing for 240 min

  18. Recruitment strategies for preventive trials. The MAPT study (MultiDomain Alzheimer Preventive Trial).

    PubMed

    Carrié, I; van Kan, G Abellan; Gillette-Guyonnet, S; Andrieu, S; Dartigues, J-F; Touchon, J; Dantoine, T; Rouaud, O; Bonnefoy, M; Robert, P; Cuffi, M-N; Bories, L; Bordes, S; Gasnier, Y; Desclaux, F; Sudres, K; Pesce, A; Vellas, B

    2012-04-01

    1680 participants were randomized over the recruitment period in MAPT study. A total of 1290 participants were recruited in the 7 University Hospital centers, and 390 participants in the 6 memory clinics around Toulouse Gerontopole / Alzheimer Disease research clinical center. The first randomization was on May 30, 2008, and the targeted number of randomized participants was reached on February 24, 2011; 2595 subjects were finally screened, of which 1680 fulfilled the eligibility criteria which represents 64.8%. Approximately, one quarter of screened people refused to participate after the detailed presentation of the study and 4.3% were still interested in participating but missed for unknown reasons the baseline visit even after repeated contacts. Of the 1810 subjects who signed the consent for participating to the study at the baseline visit, 130 (7.1%) were excluded because one of the eligibility criteria was not satisfied. Interestingly, the higher percentage of randomizations compared to screened participants is the personal contact source; almost 85 % of screened participants entered in the study. In an equivalent way, Medias and conferences are efficient recruiting sources to enrol volunteers in the study. Unexpectedly, only about 60% of screened participants from the hospital and GP sources were randomized and 33.2% from health care services. Almost a quarter of the randomized participants come from the hospital outpatients clinics and approximately 20% from public conferences. A total of 1128 contacts yielded to 556 screened volunteers and 345 randomized participants in the coordinating center of Toulouse. Thus, 30 % of contacts were recruited. PMID:22499458

  19. New structural and functional defects in polyphosphate deficient bacteria: A cellular and proteomic study

    PubMed Central

    2010-01-01

    Background Inorganic polyphosphate (polyP), a polymer of tens or hundreds of phosphate residues linked by ATP-like bonds, is found in all organisms and performs a wide variety of functions. PolyP is synthesized in bacterial cells by the actions of polyphosphate kinases (PPK1 and PPK2) and degraded by exopolyphosphatase (PPX). Bacterial cells with polyP deficiencies due to knocking out the ppk1 gene are affected in many structural and important cellular functions such as motility, quorum sensing, biofilm formation and virulence among others. The cause of this pleiotropy is not entirely understood. Results The overexpression of exopolyphosphatase in bacteria mimicked some pleitropic defects found in ppk1 mutants. By using this approach we found new structural and functional defects in the polyP-accumulating bacteria Pseudomonas sp. B4, which are most likely due to differences in the polyP-removal strategy. Colony morphology phenotype, lipopolysaccharide (LPS) structure changes and cellular division malfunction were observed. Finally, we used comparative proteomics in order to elucidate the cellular adjustments that occurred during polyP deficiency in this bacterium and found some clues that helped to understand the structural and functional defects observed. Conclusions The results obtained suggest that during polyP deficiency energy metabolism and particularly nucleoside triphosphate (NTP) formation were affected and that bacterial cells overcame this problem by increasing the flux of energy-generating metabolic pathways such as tricarboxilic acid (TCA) cycle, β-oxidation and oxidative phosphorylation and by reducing energy-consuming ones such as active transporters and amino acid biosynthesis. Furthermore, our results suggest that a general stress response also took place in the cell during polyP deficiency. PMID:20067623

  20. Point defect study of CuTi and CuTi sub 2

    SciTech Connect

    Shoemaker, J.R.; Lutton, R.T.; Wesley, D.; Wharton, W.R.; Oehrli, M.L.; Herte, M.S.; Sabochick, M.J. ); Lam, N.Q. )

    1991-03-01

    The energies and configurations of interstitials and vacancies in the ordered compounds CuTi and CuTi{sub 2} were determined using atomistic simulation with realistic embedded-atom potentials. The formation energy of an antisite pair was found to be 0.385 and 0.460 eV in CuTi and CuTi{sub 2}, respectively. In both compounds, the creation of a vacancy by the removal of either a Cu or Ti atom resulted in a vacant Cu site, with an adjacent antisite defect in the case of the Ti vacancy. The vacant Cu site in CuTi was found to be very mobile within two adjacent (001) Cu planes, with a migration energy of 0.19 eV, giving rise to two-dimensional migration. The vacancy migration energy across (001) Ti planes, however, was 1.32 eV, which could be lowered to 0.75 or 0.60 eV if one or two Cu antisite defects were initially present in these planes. In CuTi{sub 2}, the vacancy migration energy of 0.92 eV along the (001) Cu plane was significantly higher than in CuTi. The effective vacancy formation energies were calculated to be 1.09 eV and 0.90 eV in CuTi and CuTi{sub 2}, respectively. Interstitials created by inserting either a Cu or Ti atom had complicated configurations in which a Cu {l angle}111{r angle} split interstitial was surrounded by two or three Ti antisite defects. The interstitial formation energy was estimated to be 1.7 eV in CuTi and 1.9 eV in CuTi{sub 2}.