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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.

  5. Laterality Defects in the National Birth Defects Prevention Study (1998–2007): Birth Prevalence and Descriptive Epidemiology

    PubMed Central

    Lin, Angela E.; Krikov, Sergey; Riehle-Colarusso, Tiffany; Frías, Jaime L.; Belmont, John; Anderka, Marlene; Geva, Tal; Getz, Kelly D.; Botto, Lorenzo D.

    2015-01-01

    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. We identified 517 nonsyndromic cases (378 heterotaxy, 73.1%; 139 situs inversus totalis [SIT], 26.9%) resulting in an estimated birth prevalence of 1.1 per 10,000 live births (95% confidence interval 1.0–1.2). Prevalence did not differ significantly across sites, over time, or by inclusion of pregnancy termination. Laterality defects were more common among preterm cases compared to term cases, and in children born to mothers who were non-white or younger than 20 years compared to white mothers or those age 25–29 years. The distribution of associated cardiac and extracardiac defects, excluding the expected heterotaxy anomalies, varied by type of laterality defect. Cases with heterotaxy were significantly more likely than those with SIT to have double outlet right ventricle, atrioventricular canal defects, pulmonary stenosis, non-tetralogy of Fallot pulmonary atresia with ventricular septal defect, totally and partially anomalous pulmonary venous return; also more likely to have orofacial clefts, esophageal atresia, bowel atresias, and omphalocele, though not reaching statistical significance. Relatively more common among cases with SIT were Dandy-Walker malformation, anotia/microtia, and limb deficiency. The similarity in the demographic characteristics of heterotaxy and SIT supports the hypothesis that they are part of a continuum of abnormal left-right axis patterning. These findings on laterality defects may help guide clinical care, future research, and prevention strategies. PMID:25099286

  6. 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

  7. 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

  8. Are epidemiological approaches suitable to study risk/preventive factors for human birth defects?

    PubMed Central

    Oberg, Anna Sara

    2015-01-01

    Birth defects are a major cause of infant morbidity and mortality and contribute substantially to long-term disability. One out of every 33 babies is born with some type of birth defect. Despite decades of research on environmental, behavioral and genetic risk factors, the vast majority of birth defects still occur without known cause. It is possible that birth defects are largely stochastic (and unavoidable) events, at which efforts to investigate their causes would be futile and unjustified. In this commentary we argue for the continued research into risk/preventive factors of human birth defects, and outline why epidemiological studies are suitable for such endeavors. First we discuss what factors to target (genetic or environmental) and how to define the pertinent research questions. Then we present a short review of both epidemiological contributions in the past and approaches to advance the field in the future. After considering also their limitations, we conclude that modern epidemiologic approaches are invaluable to advance our understanding of risk factors for human birth defects, and that interdisciplinary collaborations will also be essential to further our knowledge. PMID:25722958

  9. 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

  10. Maternal Occupational Pesticide Exposure and Risk of Congenital Heart Defects in the National Birth Defects Prevention Study

    PubMed Central

    Rocheleau, Carissa M.; Bertke, Stephen J.; Lawson, Christina C.; Romitti, Paul A.; Sanderson, Wayne T.; Malik, Sadia; Lupo, Philip J.; Desrosiers, Tania A.; Bell, Erin; Druschel, Charlotte; Correa, Adolfo; Reefhuis, Jennita

    2015-01-01

    BACKGROUND Congenital heart defects (CHDs) are common birth defects, affecting approximately 1% of live births. Pesticide exposure has been suggested as an etiologic factor for CHDs, but previous results were inconsistent. METHODS We examined maternal occupational exposure to fungicides, insecticides, and herbicides for 3328 infants with CHDs and 2988 unaffected control infants of employed mothers using data for 1997 through 2002 births from the National Birth Defects Prevention Study, a population-based multisite case-control study. Potential pesticide exposure from 1 month before conception through the first trimester of pregnancy was assigned by an expert-guided task-exposure matrix and job history details self-reported by mothers. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using multivariable logistic regression. RESULTS Maternal occupational exposure to pesticides was not associated with CHDs overall. In examining specific CHD subtypes compared with controls, some novel associations were observed with higher estimated pesticide exposure: insecticides only and secundum atrial septal defect (OR =1.8; 95% CI, 1.3–2.7, 40 exposed cases); both insecticides and herbicides and hypoplastic left heart syndrome (OR =5.1; 95% CI, 1.7–15.3, 4 exposed cases), as well as pulmonary valve stenosis (OR =3.6; 95% CI, 1.3–10.1, 5 exposed cases); and insecticides, herbicides, and fungicides and tetralogy of Fallot (TOF) (OR =2.2; 95% CI, 1.2–4.0, 13 exposed cases). CONCLUSION Broad pesticide exposure categories were not associated with CHDs overall, but examining specific CHD subtypes revealed some increased odds ratios. These results highlight the importance of examining specific CHDs separately. Because of multiple comparisons, additional work is needed to verify these associations. PMID:26033688

  11. 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.

  12. Risk factors for isolated biliary atresia, National Birth Defects Prevention Study, 1997-2002.

    PubMed

    The, Natalie S; Honein, Margaret A; Caton, Alissa R; Moore, Cynthia A; Siega-Riz, Anna Maria; Druschel, Charlotte M

    2007-10-01

    Biliary atresia is a rare birth defect that affects 1 in 12,000 to 1 in 19,500 live births. We used data from the National Birth Defects Prevention Study, a multistate case-control study, to identify potential risk factors for isolated biliary atresia (no additional unrelated major birth defects diagnosed). Infants were identified from eight states from 1997 to 2002, with clinical information abstracted from medical records. Potential risk factors assessed include: demographic factors, seasonality, preterm birth, maternal smoking, maternal alcohol use, maternal illicit drug use, maternal health, maternal medication use, maternal vitamin use, and maternal nutrition. Infants of non-Hispanic black mothers were more likely to have biliary atresia than infants of non-Hispanic white mothers (adjusted odds ratio (aOR) = 2.29, 95% confidence interval (CI) 1.07-4.93) and infants conceived during the spring season were more likely to have biliary atresia than infants conceived in winter (aOR = 2.33, 95%CI 1.05-5.16). Low intakes of vitamin E, copper, phosphorus, and beta tocopherol were associated with the occurrence of isolated biliary atresia (borderline significance). Low iron intake had a borderline inverse association with biliary atresia. While this analysis provides support for previous reports of a possible association between seasonal variation and the occurrence of biliary atresia, more data are needed to evaluate whether the seasonal variation is related to infectious agents. The role of nutrients in the development of biliary atresia remains unclear. Further studies of genetic, infectious, and nutrient exposures and the association of biliary atresia are warranted.

  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. Control selection and participation in an ongoing, population-based, case-control study of birth defects: the National Birth Defects Prevention Study.

    PubMed

    Cogswell, Mary E; Bitsko, Rebecca H; Anderka, Marlene; Caton, Alissa R; Feldkamp, Marcia L; Hockett Sherlock, Stacey M; Meyer, Robert E; Ramadhani, Tunu; Robbins, James M; Shaw, Gary M; Mathews, T J; Royle, Marjorie; Reefhuis, Jennita

    2009-10-15

    To evaluate the representativeness of controls in an ongoing, population-based, case-control study of birth defects in 10 centers across the United States, researchers compared 1997-2003 birth certificate data linked to selected controls (n = 6,681) and control participants (n = 4,395) with those from their base populations (n = 2,468,697). Researchers analyzed differences in population characteristics (e.g., percentage of births at > or =2,500 g) for each group. Compared with their base populations, control participants did not differ in distributions of maternal or paternal age, previous livebirths, maternal smoking, or diabetes, but they did differ in other maternal (i.e., race/ethnicity, education, entry into prenatal care) and infant (i.e., birth weight, gestational age, and plurality) characteristics. Differences in distributions of maternal, but not infant, characteristics were associated with participation by selected controls. Absolute differences in infant characteristics for the base population versus control participants were < or =1.3 percentage points. Differences in infant characteristics were greater at centers that selected controls from hospitals compared with centers that selected controls from electronic birth certificates. These findings suggest that control participants in the National Birth Defects Prevention Study generally are representative of their base populations. Hospital-based control selection may slightly underascertain infants affected by certain adverse birth outcomes.

  15. Analysis of Selected Maternal Exposures and Non-Syndromic Atrioventricular Septal Defects in the National Birth Defects Prevention Study, 1997–2005

    PubMed Central

    Patel, Sonali S.; Burns, Trudy L.; Botto, Lorenzo D.; Riehle-Colarusso, Tiffany J.; Lin, Angela E.; Shaw, Gary M.; Romitti, Paul A.

    2015-01-01

    Although the descriptive epidemiology of atrioventricular septal defects (AVSDs), a group of serious congenital heart defects (CHDs), has been recently reported, non-genetic risk factors have not been consistently identified. Using data (1997–2005) from the National Birth Defects Prevention Study, an ongoing multisite population-based case–control study, the association between selected non-genetic factors and non-syndromic AVSDs was examined. Data on periconceptional exposures to such factors were collected by telephone interview from 187 mothers of AVSD case infants and 6,703 mothers of unaffected infants. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were estimated from logistic regression models. Mothers who reported cigarette smoking during the periconceptional period were more likely to have infants with AVSDs compared with non-smokers, independent of maternal age, periconceptional alcohol consumption, infant gestational age, family history of CHDs, and study site (aOR 1.5, 95% CI 1.1–2.4). The association was strongest in mothers who smoked more than 25 cigarettes/day. In addition, mothers with periconceptional passive smoke exposure were more likely to have infants with AVSDs than unexposed mothers, independent of maternal age, active periconceptional smoking, infant gestational age, and family history of CHDs (aOR 1.4, 95% CI 1.0–2.0). No associations were observed between AVSDs and maternal history of a urinary tract infection or pelvic inflammatory disease, maternal use of a wide variety of medications, maternal occupational exposure, parental drug use, or maternal alcohol consumption. If the results of this preliminary study can be replicated, minimizing maternal active and passive smoke exposure may decrease the incidence of AVSDs. PMID:22903798

  16. Maternal Occupational Exposure to Polycyclic Aromatic Hydrocarbons and Craniosynostosis among Offspring in the National Birth Defects Prevention Study

    PubMed Central

    O’Brien, Jacqueline L.; Langlois, Peter H.; Lawson, Christina C.; Scheuerle, Angela; Rocheleau, Carissa M.; Waters, Martha A.; Symanski, Elaine; Romitti, Paul A.; Agopian, A.J.; Lupo, Philip J.

    2015-01-01

    Background Evidence in animal models and humans suggests that exposure to polycyclic aromatic hydrocarbons (PAHs) may lead to birth defects. To our knowledge, this relationship has not been evaluated for craniosynostosis, a birth defect characterized by the premature closure of sutures in the skull. We conducted a case-control study to examine associations between maternal occupational exposure to PAHs and craniosynostosis. Methods We used data from craniosynostosis cases and control infants in the National Birth Defects Prevention Study (NBDPS) with estimated delivery dates from 1997–2002. Industrial hygienists reviewed occupational data from the computer-assisted telephone interview and assigned a yes/no rating of probable occupational PAH exposure for each job from one month before conception through delivery. We used logistic regression to assess the association between occupational exposure to PAHs and craniosynostosis. Results The prevalence of exposure was 5.3% in case mothers (16/300) and 3.7% in control mothers (107/2,886). We observed a positive association between exposure to PAHs during the one month before conception through the third month of pregnancy and craniosynostosis [odds ratio (OR) = 1.75; 95% confidence interval (CI): 1.01, 3.05] after adjusting for maternal age and maternal education. The number of cases for each craniosynostosis subtype limited subtype analyses to sagittal craniosynostosis; the odds ratio remained similar (OR = 1.76, 95% CI: 0.82–3.75), but was not significant. Conclusions Our findings support a moderate association between maternal occupational exposure to PAHs and craniosynostosis. Additional work is needed to better characterize susceptibility and the role PAHs may play on specific craniosynostosis subtypes. PMID:26033890

  17. Differences in risk factors for 2nd and 3rd degree hypospadias in the National Birth Defects Prevention Study

    PubMed Central

    in 't Woud, Sander Groen; van Rooij, Iris A.L.M.; van Gelder, Marleen M.H.J.; Olney, Richard S.; Carmichael, Suzan L.; Roeleveld, Nel; Reefhuis, Jennita

    2015-01-01

    Background Hypospadias is a frequent birth defect with three phenotypic subtypes. With data from the National Birth Defects Prevention Study, a large, multi-state, population-based, case-control study, we compared risk factors for second and third degree hypospadias. Methods A wide variety of data on maternal and pregnancy-related risk factors for isolated second and third degree hypospadias was collected via computer-assisted telephone interviews to identify potential etiological differences between the two phenotypes. Logistic regression was used to calculate odds ratios including a random effect by study center. Results In total, 1547 second degree cases, 389 third degree cases, and 5183 male controls were included in our study. Third degree cases were more likely to have a non-Hispanic black or Asian/Pacific Islander mother, be delivered preterm, have a low birth weight, be small for gestational age, and be conceived with fertility treatments than second degree cases and controls. Associations with both second and third degree hypospadias were observed for maternal age, family history, parity, plurality, and hypertension during pregnancy. Risk estimates were generally higher for third degree hypospadias except for family history. Conclusions Most risk factors were associated with both or neither phenotype. Therefore, it is likely that the underlying mechanism is at least partly similar for both phenotypes. However, some associations were different between 2nd and 3rd degree hypospadias, and went in opposite directions for second and third degree hypospadias for Asian/Pacific Islander mothers. Effect estimates for subtypes of hypospadias may be over- or underestimated in studies without stratification by phenotype. PMID:25181604

  18. Risk factors for non-syndromic holoprosencephaly in the National Birth Defects Prevention Study.

    PubMed

    Miller, Eric A; Rasmussen, Sonja A; Siega-Riz, Anna Maria; Frías, Jaime L; Honein, Margaret A

    2010-02-15

    Holoprosencephaly (HPE) is a complex structural brain anomaly that results from incomplete cleavage of the forebrain. The prevalence of HPE at birth is low, and risk factors have been difficult to identify. Using data from a large multi-state population-based case-control study, we examined risk factors for non-syndromic HPE. Data from maternal telephone interviews were available for 74 infants with HPE and 5871 controls born between 1997 and 2004. Several characteristics and exposures were examined, including pregnancy history, medical history, maternal diet and use of nutritional supplements, medications, tobacco, alcohol, and illegal substances. We used chi(2)-tests and logistic regression (excluding women with pre-existing diabetes) to examine associations with HPE. Except for diet (year before pregnancy) and sexually transmitted infections (STIs) (throughout pregnancy), most exposures were examined for the time period from the month before to the third month of pregnancy. HPE was found to be associated with pre-existing diabetes (chi(2) = 6.0; P = 0.01), aspirin use [adjusted odds ratio (aOR) = 3.4; 95% confidence interval (CI) 1.6-6.9], lower education level (aOR = 2.5; 95%CI 1.1-5.6), and use of assisted reproductive technologies (ART) (crude OR = 4.2; 95%CI 1.3-13.7). Consistent maternal folic acid use appeared to be protective (aOR = 0.4; 95%CI 0.2-1.0), but the association was of borderline statistical significance. While some of these findings support previous observations, other potential risk factors identified warrant further study.

  19. 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

  20. [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.

  1. Folic acid and birth defect prevention

    MedlinePlus

    ... Women who have had a baby with a neural tube defect may need a higher dose of folic acid. If you have had a baby with a neural tube defect, you should take 400 micrograms of folic acid every day, even when you are not planning ...

  2. 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.

  3. 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

  4. 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

  5. Enzyme replacement prevents enamel defects in hypophosphatasia mice

    PubMed Central

    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

    2012-01-01

    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−/−, a.k.a. 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 (sALP-FcD10, a.k.a. ENB-0040) 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

  6. 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

  7. Study of lattice defect vibration

    NASA Technical Reports Server (NTRS)

    Elliott, R. J.

    1969-01-01

    Report on the vibrations of defects in crystals relates how defects, well localized in a crystal but interacting strongly with the other atoms, change the properties of a perfect crystal. The methods used to solve defect problems relate the properties of an imperfect lattice to the properties of a perfect lattice.

  8. 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).

  9. Folate deficiency and folic acid supplementation: the prevention of neural-tube defects and congenital heart defects.

    PubMed

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

    2013-11-21

    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".

  10. 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.

  11. 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…

  12. Human neural tube defects: genetic causes and prevention.

    PubMed

    De Marco, Patrizia; Merello, Elisa; Cama, Armando; Kibar, Zoha; Capra, Valeria

    2011-01-01

    Neural tube defects (NTDs) are severe congenital malformations affecting 1-2 in 1,000 live births, whose etiology is multifactorial, involving environmental and genetic factors. NTDs arise as consequence of the failure of fusion of the neural tube early during embryogenesis. NTDs' pathogenesis has been linked to genes involved in folate metabolism, consistent with an epidemiologic evidence that 70% of NTDs can be prevented by maternal periconceptional supplementation. However, polymorphisms in such genes are not linked in all populations, suggesting that other genetic factors and environmental factors could be involved. Animal models have provided crucial mechanistic information and possible candidate genes to explain susceptibility to NTDs. A crucial role has been assigned to the planar cell polarity (PCP) pathway, a highly conserved, non-canonical Wnt-frizzled-dishevelled signaling cascade that plays a key role in establishing and maintaining polarity in the plane of the epithelium and in the process of convergent extension during gastrulation and neurulation in vertebrates. The Loop-tail (Lp) mouse that develops craniorachischisis carry missense mutations in the PCP core gene Vangl2, that is the mammalian homolog of the Drosophila Strabismus/Van gogh (Stbm/Vang). The presence of mutations in human VANGL1 and VANGL2 genes encourages us to extend the investigation to other PCP genes that, with VANGL, play an essential role in neurulation during development.

  13. 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

  14. Data Linkage Between the National Birth Defects Prevention Study and the Occupational Information Network (O*NET) to Assess Workplace Physical Activity, Sedentary Behaviors, and Emotional Stressors During Pregnancy

    PubMed Central

    Lee, Laura J.; Symanski, Elaine; Lupo, Philip J.; Tinker, Sarah C.; Razzaghi, Hilda; Pompeii, Lisa A.; Hoyt, Adrienne T.; Canfield, Mark A.; Chan, Wenyaw

    2016-01-01

    Background Knowledge of the prevalence of work-related physical activities, sedentary behaviors, and emotional stressors among pregnant women is limited, and the extent to which these exposures vary by maternal characteristics remains unclear. Methods Data on mothers of 6,817 infants without major birth defects, with estimated delivery during 1997 through 2009 who worked during pregnancy were obtained from the ‘National Birth Defects Prevention Study. Information on multiple domains of occupational exposures was gathered by linking mother’s primary job to the Occupational Information Network Version 9.0. Results The most frequent estimated physical activity associated with jobs during pregnancy was standing. Of 6,337 mothers, 31.0% reported jobs associated with standing for ≥ 75% of their time. There was significant variability in estimated occupational exposures by maternal age, race/ethnicity, and educational level. Conclusions Our findings augment existing literature on occupational physical activities, sedentary behaviors, emotional stressors, and occupational health disparities during pregnancy. PMID:26681357

  15. 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

    2016-03-28

    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.

  16. Geocoding capacity of birth defects surveillance programs: results from the National Birth Defects Prevention Network Geocoding Survey.

    PubMed

    Wang, Ying; O'Leary, Leslie A; Rickard, Russel S; Mason, Craig A

    2010-01-01

    A Web-based survey focusing on geocoding of birth defects data was developed and administrated to gain an understanding of the capacity of state birth defects programs to geocode maternal residence and to identify barriers to geocoding birth defects data. The survey consisted of 21 questions related to geocoding of maternal residence, type of software used, barriers to geocoding, and data linkage. In August 2007, an e-mail with a Web link to the survey was sent to all state birth defects program contacts in the United States, including the District of Columbia, Puerto Rico, and the Centers for Disease Control and Prevention (CDC) requesting they complete the online survey. By October 2007, 39 (74%) out of 53 birth defects program contacts completed the survey. Although nearly all birth defects programs collect maternal residential data, many are not currently geocoding that data. Results indicated that 97% of the programs that completed the survey reported they collected data on maternal residence, 53% of which reported that the birth defects surveillance data were geocoded to the street address level using maternal residential address at delivery. Twenty six percent of the programs that do not currently geocode the data identified "Software and address reference file are not available" as the most significant barrier to geocoding; another 16% chose "Lack of funding" as the most significant barrier to geocoding. Since geocoding is an important component of spatial analyses used to detect potential clusters of birth defects, leveraging resources to overcome the barriers that prevent programs from geocoding is important.

  17. Inositol, neural tube closure and the prevention of neural tube defects

    PubMed Central

    Leung, Kit‐Yi; Copp, Andrew J.

    2017-01-01

    Susceptibility to neural tube defects (NTDs), such as anencephaly and spina bifida is influenced by genetic and environmental factors including maternal nutrition. Maternal periconceptional supplementation with folic acid significantly reduces the risk of an NTD‐affected pregnancy, but does not prevent all NTDs, and “folic acid non‐responsive” NTDs continue to occur. Similarly, among mouse models of NTDs, some are responsive to folic acid but others are not. Among nutritional factors, inositol deficiency causes cranial NTDs in mice while supplemental inositol prevents spinal and cranial NTDs in the curly tail (Grhl3 hypomorph) mouse, rodent models of hyperglycemia or induced diabetes, and in a folate‐deficiency induced NTD model. NTDs also occur in mice lacking expression of certain inositol kinases. Inositol‐containing phospholipids (phosphoinositides) and soluble inositol phosphates mediate a range of functions, including intracellular signaling, interaction with cytoskeletal proteins, and regulation of membrane identity in trafficking and cell division. Myo‐inositol has been trialed in humans for a range of conditions and appears safe for use in human pregnancy. In pilot studies in Italy and the United Kingdom, women took inositol together with folic acid preconceptionally, after one or more previous NTD‐affected pregnancies. In nonrandomized cohorts and a randomized double‐blind study in the United Kingdom, no recurrent NTDs were observed among 52 pregnancies reported to date. Larger‐scale fully powered trials are needed to determine whether supplementation with inositol and folic acid would more effectively prevent NTDs than folic acid alone. Birth Defects Research 109:68–80, 2017. © 2016 The Authors Birth Defects Research Published by Wiley Periodicals, Inc. PMID:27324558

  18. Mothers' beliefs as to causation and prevention of birth defects in Ile-Ife, Nigeria.

    PubMed

    Ojofeitimi, E O; Elegbe, I

    1984-06-01

    The type of birth defects ever seen or heard of and beliefs as to the causation and means of preventing the defects were investigated among 225 newly deliverd and nursing mothers through interviews. The majority were between the ages of 20 to 29 years; 9.3% were between 35 and 40 years. The bulk of the respondents are illiterates. More than 75% of the mothers had 2 or more children. The most common birth defects seen were amputated leg; dislocated hips; lamed hand or funny elbows or ankles; extra digits; and missing digits. Common perceptions of the causes were God's will (32.9%) and evil doers or evil powers due to witchcraft or sorcery (40.9%). Poor nutrition or poor antenatal care was reported by only 2.2%; while 1.3% attributed the cause to an excessive combination of native and modern drugs. The majority believed that avoidance of walking at night and midafternoon during pregnancy would prevent birth defects. 10.2% and 5.3% were of the opinion that praying to God and going to the herbalist respectively would prevent birth defects. Prevention of birth defects is an essential task for all health workers in Nigeria. The causes of birth defects should be brodcast on radio and television and published in national dialects in the newspapers. 83.6% claimed that they were not informed of various means of preventing birth defects during prenatal clinic visits. The schools should include prevention and causation of birth defects in a health education curriculum.

  19. 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

  20. Complex cardiac defects after ethanol exposure during discrete cardiogenic events in zebrafish: Prevention with folic acid

    PubMed Central

    Sarmah, Swapnalee; Marrs, James A.

    2014-01-01

    BACKGROUND Fetal alcohol spectrum disorder (FASD) describes a range of birth defects including various congenital heart defects (CHDs). Mechanisms of FASD-associated CHDs are not understood. Whether alcohol interferes with a single critical event or with multiple events in heart formation is not known. RESULTS Our zebrafish embryo experiments showed that ethanol interrupts different cardiac regulatory networks and perturbed multiple steps of cardiogenesis (specification, myocardial migration, looping, chamber morphogenesis and endocardial cushion formation). Ethanol exposure during gastrulation until cardiac specification or during myocardial midline migration did not produce severe or persistent heart development defects. However, exposure comprising gastrulation until myocardial precursor midline fusion or during heart patterning stages produced aberrant heart looping and defective endocardial cushions. Continuous exposure during entire cardiogenesis produced complex cardiac defects leading to severely defective myocardium, endocardium, and endocardial cushions. Supplementation of retinoic acid with ethanol partially rescued early heart developmental defects, but the endocardial cushions did not form correctly. In contrast, supplementation of folic acid rescued normal heart development, including the endocardial cushions. CONCLUSIONS Our results indicate that ethanol exposure interrupted divergent cardiac morphogenesis events causing heart defects. Folic acid supplementation was effective in preventing a wide spectrum of ethanol-induced heart developmental defects. PMID:23832875

  1. Nucleotide precursors prevent folic acid-resistant neural tube defects in the mouse.

    PubMed

    Leung, Kit-Yi; De Castro, Sandra C P; Savery, Dawn; Copp, Andrew J; Greene, Nicholas D E

    2013-09-01

    Closure of the neural tube during embryogenesis is a crucial step in development of the central nervous system. Failure of this process results in neural tube defects, including spina bifida and anencephaly, which are among the most common birth defects worldwide. Maternal use of folic acid supplements reduces risk of neural tube defects but a proportion of cases are not preventable. Folic acid is thought to act through folate one-carbon metabolism, which transfers one-carbon units for methylation reactions and nucleotide biosynthesis. Hence suboptimal performance of the intervening reactions could limit the efficacy of folic acid. We hypothesized that direct supplementation with nucleotides, downstream of folate metabolism, has the potential to support neural tube closure. Therefore, in a mouse model that exhibits folic acid-resistant neural tube defects, we tested the effect of specific combinations of pyrimidine and purine nucleotide precursors and observed a significant protective effect. Labelling in whole embryo culture showed that nucleotides are taken up by the neurulating embryo and incorporated into genomic DNA. Furthermore, the mitotic index was elevated in neural folds and hindgut of treated embryos, consistent with a proposed mechanism of neural tube defect prevention through stimulation of cellular proliferation. These findings may provide an impetus for future investigations of supplemental nucleotides as a means to prevent a greater proportion of human neural tube defects than can be achieved by folic acid alone.

  2. [Folic acid and prevention of neural tube closure defects: the question is not solved yet].

    PubMed

    Vidailhet, M; Bocquet, A; Bresson, J-L; Briend, A; Chouraqui, J-P; Dupont, C; Darmaun, D; Frelut, M-L; Ghisolfi, J; Girardet, J-P; Goulet, O; Putet, G; Rieu, D; Rigo, J; Turck, D

    2008-07-01

    Between 1981 and 1996, several interventional studies proved the efficacy of periconceptional folic acid supplementation in the prevention of neural tube closure defects (NTCD), first in women at risk (with a previous case of NTCD) and also in women of the general population in age to become pregnant. The poor observance of this supplementation led several countries (USA, Canada, Chile...) to decide mandatory folic acid fortification of cereals, which permitted a 30% (USA) to 46% (Canada) reduction in the incidence of NTCD. Moreover, this benefit was accompanied by a diminished incidence of several other malformations and of stroke and coronary accidents in elderly people. However, several papers drew attention to an increased risk of colorectal and breast cancer in relation with high blood folate levels and the use of folic acid supplements. A controlled interventional study showed a higher rate of recurrence of colic adenomas and a higher percentage of advanced adenomas in subjects receiving 1mg/day of folic acid. A recent study demonstrated an abrupt reversal of the downward trend in colorectal cancer 1 year after the beginning of cereal folic acid fortification in the USA and Canada. Two studies also reported impaired cognitive functions in elder persons with defective vitamin B(12) status. Taken in aggregate, these studies question the wisdom of a nationwide, mandatory, folic acid fortification of cereals. As of today, despite their limited preventive efficacy, a safe approach is to keep our current French recommendations and to increase the awareness of all caregivers, so as to improve the observance of these recommendations.

  3. 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.

  4. Folate and Prevention of Neural Tube Defects: New Insights from a Bayesian Model.

    PubMed

    Ströhle, Alexander; Bohn, Torsten

    2015-01-01

    Maternal folate status before and during pregnancy influences a woman's risk of having a pregnancy affected by congenital malformations of the neural tube (neural tube defects, NTD). For NTD prevention, it is recommended that women use periconceptional supplementation of folic acid. However, the recommended dose varies considerably (400 - 800 µg folic acid/day). Insufficient data exists on the relation between folate status and the risk of NTD. A recent study published in the British Medical Journal provides evidence for a generalizable dose-response relation between folate status and risk of NTD. The lowest risk of having a child with NTD was related to red blood cell (RBC) folate concentrations of ≥ 1000 nmol/L.

  5. 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.

  6. 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

  7. The Left Shifted Oxyhemoglobin Curve in Sepsis: A Preventable Defect

    PubMed Central

    Watkins, George M.; Rabelo, Alvaro; Plzak, Louis F.; Sheldon, George F.

    1974-01-01

    Nine patients with severe sepsis were studied to determine causes for any alterations in oxygen dissociation. Seven of the patients had oxyhemoglobin curves shifted to the left of expected and diminished DPG levels. These deficiences were not corrected in one case. The other eight patients survived or expired with normal to elevated P50T and DPG levels. In this study, three factors occurring either individually, in concordance, or in sequence were present when P50T was decreased. Correction of these deficiencies lead to normalization and, in one case, exceedingly high P50T and DPG levels. Where hypophosphatemia, acidosis, and transfusion of DPG deficient blood were avoided, no such change occurred. Hypophosphatemia is a common occurrence in the seriously ill patient whether or not hyperalimentation is used and may occur in spite of phosphate supplementation. Blood transfusions with CPD as the preservative are effective in reducing the severity of this disorder by the addition of an inorganic phosphate load. Septic shock itself had no untoward effect on oxygen dissociation. This held true even in the terminal stages of the disease process. PMID:4842983

  8. The continuing challenge of understanding, preventing, and treating neural tube defects.

    PubMed

    Wallingford, John B; Niswander, Lee A; Shaw, Gary M; Finnell, Richard H

    2013-03-01

    Human birth defects are a major public health burden: The Center for Disease Control estimates that 1 of every 33 United States newborns presents with a birth defect, and worldwide the estimate approaches 6% of all births. Among the most common and debilitating of human birth defects are those affecting the formation of the neural tube, the precursor to the central nervous system. Neural tube defects (NTDs) arise from a complex combination of genetic and environmental interactions. Although substantial advances have been made in the prevention and treatment of these malformations, NTDs remain a substantial public health problem, and we are only now beginning to understand their etiology. Here, we review the process of neural tube development and how defects in this process lead to NTDs, both in humans and in the animal models that serve to inform our understanding of these processes. The insights we are gaining will help generate new intervention strategies to tackle the clinical challenges and to alleviate the personal and societal burdens that accompany these defects.

  9. 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.

  10. 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.

  11. 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.

  12. 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).

  13. 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.

  14. 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

    2015-10-09

    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%).

  15. Understanding the causes and prevention of neural tube defects: Insights from the splotch mouse model.

    PubMed

    Greene, Nicholas D E; Massa, Valentina; Copp, Andrew J

    2009-04-01

    Splotch mutant mice develop neural tube defects (NTDs), comprising exencephaly and/or spina bifida, as well as neural crest-related defects and abnormalities of limb musculature. Defects in splotch mice result from mutations in Pax3, and some human NTDs may also result from mutations in the human PAX3 gene. Pax3 encodes a transcription factor whose function may influence expression of multiple downstream genes associated with a variety of cellular properties (including apoptosis, adhesion, proliferation, and differentiation), that could be important for neural tube closure. The frequency of NTDs varies between mutant alleles and is also influenced by genetic background and environmental factors. Notably, splotch provides a model for folic acid-preventable NTDs, and conversely, dietary folate deficiency exacerbates NTDs. Understanding the molecular and cellular basis of splotch NTDs, as well as the mechanisms by which the frequency of defects is influenced by genetic and environmental factors (such as sub-optimal folate status), may provide insight into the causation of these severe congenital malformations in humans.

  16. [Folic acid use by pregnant women in Israel for preventing neural tube defects].

    PubMed

    Gil, Z; Aran, A; Friedman, O; Beni-Adani, L; Constantini, S

    2000-12-01

    Spina bifida and anencephaly are the most common, serious malformations in neural tube defects (NTD). Randomized trials in the last 2 decades have demonstrated that folic acid, 0.4 mg/d, reduces the incidence of NTD by more than 50%. We investigated the use of folic acid and multivitamins containing folic acid in childbearing women. Of 221 women interviewed, 67 (30%) regularly took pills containing 0.4 mg folic acid. Women with higher educational levels were more likely to take multivitamins with folic acid than were the less educated (p = 0.05). Of the women who took folic acid, only 5 (7.5%) used separate folic acid tablets, before and during their pregnancy. The rest used multivitamins containing folic acid. The 5 women who took folic acid separately were college-educated and nonreligious, and they took multivitamins in addition (p > 0.05). Of the women interviewed, 58 (26.2%) were Bedouin of the Negev. 24 (41.4%) of them took pills containing folic acid on a regular basis. This percentage is higher than that in the Jewish women in the study who took folic acid for prevention of NTD (17%; p = 0.038). Most of the women took folic acid after the first trimester. Only a minority took daily periconceptional folic acid. Multivitamins containing 0.4 mg of folic acid were more popular than folic acid tablets alone. This study emphasizes the need for continuing efforts to increase consumption of folic acid and awareness of its benefits among women of childbearing age.

  17. First-principles studies of native defects in olivine phosphates

    NASA Astrophysics Data System (ADS)

    Hoang, Khang; Johannes, Michelle

    2011-03-01

    Olivine phosphates Li M PO4 (M = Mn, Fe, Co, Ni) are promising candidates for rechargeable Li-ion battery electrodes because of their energy storage capacity and electrochemical and thermal stability. It is known that native defects have strong effects on the performance of olivine phosphates. Yet, the formation and migration of these defects are not fully understood, and we expect that once such understanding has been established, one can envisage a solution for improving the materials' performance. In this talk, we present our first-principles density-functional theory studies of native point defects and defect complexes in Li M PO4 , and discuss the implications of these defects on the performance of the materials. Our results also provide guidelines for obtaining different native defects in experiments.

  18. Making birth defects 'preventable': pre-conceptional vitamin supplements and the politics of risk reduction.

    PubMed

    Al-Gailani, Salim

    2014-09-01

    Since the mid-1990s, governments and health organizations around the world have adopted policies designed to increase women's intake of the B-vitamin 'folic acid' before and during the first weeks of pregnancy. Building on initial clinical research in the United Kingdom, folic acid supplementation has been shown to lower the incidence of neural tube defects (NTDs). Recent debate has focused principally on the need for mandatory fortification of grain products with this vitamin. This article takes a longer view, tracing the transformation of folic acid from a routine prenatal supplement to reduce the risk of anaemia to a routine 'pre-conceptional' supplement to 'prevent' birth defects. Understood in the 1950s in relation to social problems of poverty and malnutrition, NTDs were by the end of the century more likely to be attributed to individual failings. This transition was closely associated with a second. Folic acid supplements were initially prescribed to 'high-risk' women who had previously borne a child with a NTD. By the mid-1990s, they were recommended for all women of childbearing age. The acceptance of folic acid as a 'risk-reducing drug' both relied upon and helped to advance the development of preventive and clinical practices concerned with women's health before pregnancy.

  19. 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.

  20. 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

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

    SciTech Connect

    Andersson, A.

    2005-08-05

    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.

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  4. 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.

  5. 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.

  6. 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.

  7. Diffusion and Defect Characterization Studies of Mercury Cadmium Telluride

    DTIC Science & Technology

    1989-08-01

    Mercury Cadmium Telluride" Principal Investigator: D. A. Stevenson Department of Materials Science and Engineering Stanford University Stanford, CA 94305...Include Security Classificatton, Difuson Defect Characterization Studies of Mercury Cadmium Telluride 12 PERSONAL AUTHOR(S) ProfessJL Ddvid A. Stevenson 13a...diffusion and defect chemistry of mercury cadmium telluride (MCT; Hg Cd Te). In this study, we have measured tracer self- diffusion and interdiffusion

  8. 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.

  9. Diabetes mellitus and birth defects

    PubMed Central

    Correa, Adolfo; Gilboa, Suzanne M.; Besser, Lilah M.; Botto, Lorenzo D.; Moore, Cynthia A.; Hobbs, Charlotte A.; Cleves, Mario A.; Riehle-Colarusso, Tiffany J.; Waller, D. Kim; Reece, E. Albert

    2016-01-01

    OBJECTIVE The purpose of this study was to examine associations between diabetes mellitus and 39 birth defects. STUDY DESIGN This was a multicenter case-control study of mothers of infants who were born with (n = 13,030) and without (n = 4895) birth defects in the National Birth Defects Prevention Study (1997–2003). RESULTS Pregestational diabetes mellitus (PGDM) was associated significantly with noncardiac defects (isolated, 7/23 defects; multiples, 13/23 defects) and cardiac defects (isolated, 11/16 defects; multiples, 8/16 defects). Adjusted odds ratios for PGDM and all isolated and multiple defects were 3.17 (95% CI, 2.20–4.99) and 8.62 (95% CI, 5.27–14.10), respectively. Gestational diabetes mellitus (GDM) was associated with fewer noncardiac defects (isolated, 3/23 defects; multiples, 3/23 defects) and cardiac defects (isolated, 3/16 defects; multiples, 2/16 defects). Odds ratios between GDM and all isolated and multiple defects were 1.42 (95% CI, 1.17–1.73) and 1.50 (95% CI, 1.13–2.00), respectively. These associations were limited generally to offspring of women with prepregnancy body mass index ≥25 kg/m2. CONCLUSION PGDM was associated with a wide range of birth defects; GDM was associated with a limited group of birth defects. PMID:18674752

  10. 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.

  11. Defective pyrite (100) surface: An ab initio study

    SciTech Connect

    Stirling, Andras; Bernasconi, Marco; Parrinello, Michele

    2007-04-15

    The structural and electronic properties of sulfur monomeric defects at the FeS{sub 2}(100) surface have been studied by periodic density-functional calculations. We have shown that for a monomeric sulfur bound to an originally fivefold coordinated surface Fe site, the defect core features a triplet electronic ground state with unpaired spins localized on the exposed Fe-S unit. At this site, the iron and sulfur ions have oxidation states +4 and -2, respectively. This defect can be seen as produced via heterolytic bond breaking of the S-S sulfur dimer followed by a Fe-S redox reaction. The calculated sulfur 2p core-level shifts of the monomeric defects are in good agreement with experimental photoemission spectra, which allow a compelling assignment of the different spectroscopic features. The effect of water on the stability of the defective surface has also been studied, and it has been shown that the triplet state is stable against the wetting of the surface. The most important implications of the presence of the monomeric sulfur defect on the reactivity are also discussed.

  12. 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.

  13. 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.

  14. Adjusting for bias due to incomplete case ascertainment in case-control studies of birth defects.

    PubMed

    Howards, Penelope P; Johnson, Candice Y; Honein, Margaret A; Flanders, W Dana

    2015-04-15

    Case-control studies of birth defects might be subject to selection bias when there is incomplete ascertainment of cases among pregnancies that are terminated after a prenatal diagnosis of the defect. We propose a simple method to estimate inverse probability of selection weights (IPSWs) for cases ascertained from both pregnancies that end in termination and those that do not end in termination using data directly available from the National Birth Defects Prevention Study and other published information. The IPSWs can then be used to adjust for selection bias analytically. We can also allow for uncertainty in the selection probabilities through probabilistic bias analysis. We provide an illustrative example using data from National Birth Defects Prevention Study (1997-2009) to examine the association between prepregnancy obesity (body mass index, measured as weight in kilograms divided by height in meters squared, of ≥30 vs. <30) and spina bifida. The unadjusted odds ratio for the association between prepregnancy obesity and spina bifida was 1.48 (95% confidence interval: 1.26, 1.73), and the simple selection bias-adjusted odds ratio was 1.26 (95% confidence interval: 1.04, 1.53). The probabilistic bias analysis resulted in a median adjusted odds ratio of 1.22 (95% simulation interval: 0.97, 1.47). The proposed method provides a quantitative estimate of the IPSWs and the bias introduced by incomplete ascertainment of cases among terminated pregnancies conditional on a set of assumptions.

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

    PubMed

    Obeid, Rima; Holzgreve, Wolfgang; Pietrzik, Klaus

    2013-09-01

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

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

    PubMed

    Ren, Ai-Guo

    2015-08-08

    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.

  17. Hybrid functional studies of defects in layered transition metal oxides

    NASA Astrophysics Data System (ADS)

    Hoang, Khang; Johannes, Michelle

    2014-03-01

    Layered oxides LiMO2 (M is a transition metal) have been studied extensively for Li-ion battery cathodes. It is known that defects have strong impact on the electrochemical performance. A detailed understanding of native point defects in LiMO2 is however still lacking, thus hindering rational design of more complex materials for battery applications. In fact, first-principles defect calculations in LiMO2 are quite challenging because standard density functional theory (DFT) calculations using the generalized gradient approximation (GGA) of the exchange-correlation functional fail to reproduce the correct physics. The GGA+U extension can produce reasonable results, but the transferability of U across the compounds is limited. In this talk, we present our DFT studies of defects in LiMO2 (M=Co, Ni) using the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional. The dominant point defects will be identified and compared with experiment; and their impact on the structural stability and the charge (electronic and ionic) and mass transport will be addressed. We will also discuss possible shortcomings of the HSE functional in the study of these electron-correlated materials.

  18. 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.

  19. 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.

  20. 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.

  1. Primary prevention of neural-tube defects and some other congenital abnormalities by folic acid and multivitamins: history, missed opportunity and tasks.

    PubMed

    Czeizel, Andrew E; Bártfai, Zoltán; Bánhidy, Ferenc

    2011-08-01

    The history of intervention trials of periconception folic acid with multivitamin and folic acid supplementation in women has shown a recent breakthrough in the primary prevention of structural birth defects, namely neural-tube defects and some other congenital abnormalities. Recently, some studies have demonstrated the efficacy of this new method in reducing congenital abnormalities with specific origin; for example, in the offspring of diabetic and epileptic mothers, and in pregnancy with high fever. The benefits and drawbacks of four possible uses of periconception folate/folic acid and multivitamin supplementation are discussed: we believe there has been a missed opportunity to implement this preventive approach in medical practice. The four methods are as follows: (i) dietary intake of folate and other vitamins, (ii) periconception folic acid/multivitamin supplementation, (iii) food fortification with folic acid, and (iv) the combination of oral contraceptives with 6S-5-methytetrahydrofolate ('folate').

  2. Point defects in thorium nitride: A first-principles study

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    Thorium and its compounds (carbides and nitrides) are being investigated as possible materials to be used as nuclear fuels for Generation-IV reactors. As a first step in the research of these materials under irradiation, we study the formation energies and stability of point defects in thorium nitride by means of first-principles calculations within the framework of density functional theory. We focus on vacancies, interstitials, Frenkel pairs and Schottky defects. We found that N and Th vacancies have almost the same formation energy and that the most energetically favorable defects of all studied in this work are N interstitials. These kind of results for ThN, to the best authors' knowledge, have not been obtained previously, neither experimentally, nor theoretically.

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

    PubMed

    Heseker, Helmut B; Mason, Joel B; Selhub, Jacob; Rosenberg, Irwin H; Jacques, Paul F

    2009-07-01

    Some countries have introduced mandatory folic acid fortification, whereas others support periconceptional supplementation of women in childbearing age. Several European countries are considering whether to adopt a fortification policy. Projections of the possible beneficial effects of increased folic acid intake assume that the measure will result in a considerable reduction in neural-tube defects (NTD) in the target population. Therefore, the objective of the present study is to evaluate the beneficial effects of different levels of folic acid administration on the prevalence of NTD. Countries with mandatory fortification achieved a significant increase in folate intake and a significant decline in the prevalence of NTD. This was also true for supplementation trials. However, the prevalence of NTD at birth declined to approximately five cases at birth per 10 000 births and seven to eight cases at birth or abortion per 10 000 births. This decline was independent of the amount of folic acid administered and apparently reveals a 'floor effect' for folic acid-preventable NTD. This clearly shows that not all cases of NTD are preventable by increasing the folate intake. The relative decline depends on the initial NTD rate. Countries with NTD prevalence close to the observed floor may have much smaller reductions in NTD rates with folic acid fortification. Additionally, potential adverse effects of fortification on other vulnerable population groups have to be seriously considered. Policy decisions concerning national mandatory fortification programmes must take into account realistically projected benefits as well as the evidence of risks to all vulnerable groups.

  4. Retinoblastoma protein prevents enteric nervous system defects and intestinal pseudo-obstruction

    PubMed Central

    Fu, Ming; Landreville, Solange; Agapova, Olga A.; Wiley, Luke A.; Shoykhet, Michael; Harbour, J. William; Heuckeroth, Robert O.

    2013-01-01

    The retinoblastoma 1 (RB1) tumor suppressor is a critical regulator of cell cycle progression and development. To investigate the role of RB1 in neural crest–derived melanocytes, we bred mice with a floxed Rb1 allele with mice expressing Cre from the tyrosinase (Tyr) promoter. TyrCre+;Rb1fl/fl mice exhibited no melanocyte defects but died unexpectedly early with intestinal obstruction, striking defects in the enteric nervous system (ENS), and abnormal intestinal motility. Cre-induced DNA recombination occurred in all enteric glia and most small bowel myenteric neurons, yet phenotypic effects of Rb1 loss were cell-type specific. Enteric glia were twice as abundant in mutant mice compared with those in control animals, while myenteric neuron number was normal. Most myenteric neurons also appeared normal in size, but NO-producing myenteric neurons developed very large nuclei as a result of DNA replication without cell division (i.e., endoreplication). Parallel studies in vitro found that exogenous NO and Rb1 shRNA increased ENS precursor DNA replication and nuclear size. The large, irregularly shaped nuclei in NO-producing neurons were remarkably similar to those in progeria, an early-onset aging disorder that has been linked to RB1 dysfunction. These findings reveal a role for RB1 in the ENS. PMID:24177421

  5. Prevention of valproic acid-induced neural tube defects by sildenafil citrate.

    PubMed

    Tiboni, Gian Mario; Ponzano, Adalisa

    2015-08-15

    This study was undertaken to test the effects of sildenafil citrate (SC), a type 5 phosphodiesterase inhibitor, on valproic acid (VPA)-induced teratogenesis. On gestation day (GD) 8, ICR (CD-1) mice were treated by gastric intubation with SC at 0 (vehicle), 1.0, 2.5, 5.0 or 10mg/kg. One hour later, animals received a teratogenic dose of VPA (600mg/kg) or vehicle. Developmental endpoints were evaluated near the end of gestation. Twenty-eighth percent of fetuses exposed to VPA had neural tube defects (exencephaly). Pretreatment with SC at 2.5, 5.0 or 10mg/kg significantly reduced the rate of VPA-induced exencephaly to 15.9%, 13.7%, and 10.0%, respectively. Axial skeletal defects were observed in 75.8% of VPA-exposed fetuses. Pre-treatment with SC at 10mg/kg, but not at lower doses, significantly decreased the rate of skeletally affected fetuses to 61.6%. These results show that SC, which prolongs nitric oxide (NO) signaling action protects from VPA-induced teratogenesis.

  6. 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.

  7. Parents of Kids with Heart Defects Face PTSD Risk: Study

    MedlinePlus

    ... Feb. 1, 2017 (HealthDay News) -- Parents of children born with serious heart defects may be at high risk for post-traumatic stress disorder (PTSD) and other mental health problems, a new study suggests. PTSD refers to anxiety and fear ...

  8. 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

  9. Magnitude of Birth Defects in Central and Northwest Ethiopia from 2010-2014: A Descriptive Retrospective Study

    PubMed Central

    Taye, Molla; Afework, Mekbeb; Fantaye, Wondwossen; Diro, Ermias; Worku, Alemayehu

    2016-01-01

    Background Birth defects are defined as structural and functional defects that develop during the organogenesis period and present at birth or detected later in life. They are one of the leading causes of infant and child mortality, morbidity, and long term disability. The magnitude of birth defects varies from country to country and from race/ethnicity to race/ethnicity, and about 40–60% of their causes are unknown. The known causes of birth defects are genetic and environmental factors which may be prevented. For various reasons, there is lack of data and research on birth defects in Ethiopia. Objective The major objective of this study is to estimate the magnitude of birth defects in Ethiopia. Subject and Methods A hospital based, retrospective, cross sectional, descriptive study was conducted. The subjects were babies/children aged 0–17years who visited selected hospitals between 2010 and 2014. Fourteen hospitals (8 in Addis Ababa, 6 in Amhara Region) were selected purposively based on case load. A data retrieving form was developed to extract relevant information from record books. Results In the hospitals mentioned, 319,776 various medical records of children aged 0–17years were found. Of these, 6,076 (1.9% with 95% CI: 1.85%–1.95%) children were diagnosed as having birth defects. The majority (58.5%) of the children were male and 41.5% female. A slightly more than half (51.1%) of the children were urban dwellers, while 48.9% were from rural areas. Among the participants of the study the proportion of birth defects ranged as follows: orofacial (34.2%), neural tube (30.8%), upper and lower limb (12.8%), cardiovascular system (10.3%), digestive system and abdominal wall (4.8%), unspecified congenital malformations (2.5%), Down syndrome (2%), genitourinary system (2%), head, face, and neck defects (0.4%), and others (0.3%). The trend of birth defects increased linearly over time [Extended Mantel-Haenszel chi square for linear trend = 356.7 (P<0

  10. 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…

  11. Ab-intitio Studies of Defects in Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Poykko, Sami

    2000-03-01

    Defects, defect complexes and domain walls in PbTiO3 have been studied using a first-principles method. Platinum is a widely used electrode material for PZT. Due to relatively high deposition temperatures a large concentration of Pt atoms diffuse into PZT, where they occupy Ti-sites and act as acceptors. Platinum impurity is shown to form a tightly bond pair with oxygen vacancy. This complex can have a significant role in fatigue, since each of these strongly polar defect also pin a polarization of a surrounding lattice. This result implies that in order to increase fatigue resistance of PZT it is extremely important to minimize especially acceptor type impurities [1]. We have shown that oxygen and lead vacancies do not form strongly bound defect complexes in PZT and therefore their creation does not seem to be directly involved in fatigue or imprint. According to our calculations a formation of a oxygen-vacancy lead-vacancy pair (close or distant) becomes exothermic under certain conditions. Therefore large number of vacancies are produced to PZT leading to resistance degradation and overall crystal quality also becomes worse [2]. An 180 degree domain wall has been shown to have an energy density of 150 erg/cm^2 and is lead-centered (ie. symmetry plane goes along Pb-atoms). A minimum width of a domain is calculated to be 4 lattice constants, narrower domains are found to be thermodynamically unstable [3]. footnote[1]S. Poykko and D. J. Chadi, "Dipolar Defect Model for Fatigue in Ferroelectric Perovskites" Physical Review Letters 83, 1231 (1999). footnote[2]S. Poykko and D. J. Chadi, "First principles study of Pb-vacancies in PbTiO_3", Applied Physics Letters, in print (2000). footnote[3]S. Poykko and D. J. Chadi, "Ab initio study of 180 degree domain wall energy and structure in PbTiO_3" Applied Physics Letters, 75, 2830 (1999).

  12. Calculation studies on point defects in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Han, Dan; Dai, Chenmin; Chen, Shiyou

    2017-01-01

    The close-to-optimal band gap, large absorption coefficient, low manufacturing cost and rapid increase in power conversion efficiency make the organic–inorganic hybrid halide (CH3NH3PbI3) and related perovskite solar cells very promising for commercialization. The properties of point defects in the absorber layer semiconductors have important influence on the photovoltaic performance of solar cells, so the investigation on the defect properties in the perovskite semiconductors is necessary for the optimization of their photovoltaic performance. In this work, we give a brief review to the first-principles calculation studies on the defect properties in a series of perovskite semiconductors, including the organic–inorganic hybrid perovskites and inorganic halide perovskites. Experimental identification of these point defects and characterization of their properties are called for. Project supported by the National Natural Science Foundation of China (No. 61574059), the Shanghai Rising-Star Program (No. 14QA1401500), the Shu-Guang Program (15SG20), and the CC of ECNU.

  13. 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.

  14. 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.

  15. A biomechanical study of periacetabular defects and cement filling.

    PubMed

    Li, Zuoping; Butala, Neha B; Etheridge, Brandon S; Siegel, Herrick J; Lemons, Jack E; Eberhardt, Alan W

    2007-04-01

    Periacetabular bone metastases cause severe pain and functional disability in cancer patients. Percutaneous acetabuloplasty (PCA) is a minimally invasive, image-guided procedure whereby cement is injected into lesion sites. Pain relief and functional restoration have been observed clinically; however, neither the biomechanical consequences of the lesions nor the effectiveness of the PCA technique are well understood. The objective of this study was to investigate how periacetabular lesion size, cortex involvement, and cement modulus affect pelvic bone stresses and strains under single-legged stance loading. Experiments were performed on a male cadaver pelvis under conditions of intact, periacetabular defect, and cement-filling with surface strains recorded at three strain gage locations. The experimental data were then employed to validate three-dimensional finite element models of the same pelvis, developed using computed tomography data. The models demonstrated that increases in cortical stresses were highest along the posterior column of the acetabulum, adjacent to the defect. Cortical stresses were more profoundly affected in the presence of transcortical defects, as compared to those involving only trabecular bone. Cement filling with a modulus of 2.2 GPa was shown to restore cortical stresses to near intact values, while a decrease in cement modulus due to inclusion of BaSO(4) reduced the restorative effect. Peak acetabular contact pressures increased less than 15% for all simulated defect conditions; however, the contact stresses were reduced to levels below intact in the presence of either cement filling. These results suggest that periacetabular defects may increase the vulnerability of the pelvis to fracture depending on size and cortical involvement and that PCA filling may lower the risk of periacetabular fractures.

  16. Defect metastability in surfaces: A study of EL2 defect in GaAs(110)

    SciTech Connect

    Zhang, S.B.

    1999-08-01

    Although it has been widely accepted that EL2 in GaAs is an As antisite, the identity of the metastable state of EL2thinsp(=EL2{sup {asterisk}}) has not been confirmed by experiment. Here it is suggested that cross-sectional scanning tunneling microscopy may be used to identify EL2{sup {asterisk}}. My suggestion is based on a comprehensive first-principles total energy study of surface defect metastability. It reveals rich structures of the EL2{sup {asterisk}} near the surface. The energy difference between EL2{sup {asterisk}} and EL2 can be reduced to only a tenth of that bulk due to interaction with relaxed surface atoms. {copyright} {ital 1999} {ital The American Physical Society}

  17. Awareness and intake of folic acid for the prevention of neural tube defects among Lebanese women of childbearing age.

    PubMed

    Nasr Hage, Claudine; Jalloul, Maya; Sabbah, Mohamad; Adib, Salim M

    2012-01-01

    Since the early 1990s, international recommendations have promoted folic acid supplementation during the periconception period as an effective way of preventing neural tube defects (NTDs). However, the adoption of this recommendation remains insufficient. To assess the awareness and actual intake of folic acid among married Lebanese women aged 18-45 years, a cross-sectional study was conducted among 600 women selected from all five administrative districts in Lebanon, using a multistage cluster sampling procedure. An anonymous questionnaire was completed which covered measures of knowledge and use of folate supplements, as well as demographic, socioeconomic and obstetrical factors. Sixty percent of surveyed women (60%; n = 360) had heard about folic acid. Doctors were the most frequent source of information (61.1%) but only 24.7% of women have been told of the correct period during which folic acid supplementation was useful. Overall, only 6.2% had taken folic acid tablets during the adequate period. Younger age, higher education level and stability/sufficiency of income appeared to be significant predictors of awareness among Lebanese women. Actual folic acid intake was significantly associated with younger age, higher number of pregnancies, planning the last pregnancy and having had that last one after 1990. In Lebanon, the level of folic acid awareness and adequate intake remain relatively low. Several approaches should be used to promote folic acid intake including awareness campaigns, and routine counseling by primary health care physicians on folic acid during preconception visits.

  18. C5a receptor signaling prevents folate deficiency-induced neural tube defects in mice.

    PubMed

    Denny, Kerina J; Coulthard, Liam G; Jeanes, Angela; Lisgo, Steven; Simmons, David G; Callaway, Leonie K; Wlodarczyk, Bogdan; Finnell, Richard H; Woodruff, Trent M; Taylor, Stephen M

    2013-04-01

    The complement system is involved in a range of diverse developmental processes, including cell survival, growth, differentiation, and regeneration. However, little is known about the role of complement in embryogenesis. In this study, we demonstrate a novel role for the canonical complement 5a receptor (C5aR) in the development of the mammalian neural tube under conditions of maternal dietary folic acid deficiency. Specifically, we found C5aR and C5 to be expressed throughout the period of neurulation in wild-type mice and localized the expression to the cephalic regions of the developing neural tube. C5aR was also found to be expressed in the neuroepithelium of early human embryos. Ablation of the C5ar1 gene or the administration of a specific C5aR peptide antagonist to folic acid-deficient pregnant mice resulted in a high prevalence of severe anterior neural tube defect-associated congenital malformations. These findings provide a new and compelling insight into the role of the complement system during mammalian embryonic development.

  19. 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.

  20. 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.…

  1. Study of point defects in alkaline-earth sulfides

    SciTech Connect

    Pandey, R.; Kunz, A.B.; Vail, J.M.

    1988-11-01

    The results of a computer simulation study of point defects including vacancy, interstitial, and F/sup +/ center in alkaline-earth sulfides are presented. The study is based on ICECAP/HADES simulation procedures and uses empirical interionic potentials obtained from the analysis of macroscopic data for these materials. The results predict the dominance of Schottky disorder and suggest that vacancy migration predominates in alkaline-earth sulfides. Furthermore, the calculated F/sup +/ center absorption energy is in good agreement with the experimental data deduced from the optical stimulated studies in these materials.

  2. 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.

  3. Extended defect study in Si: EBIC versus LBIC

    NASA Astrophysics Data System (ADS)

    Orlov, V. I.; Yakimov, E. B.

    2016-11-01

    A comparative study of multicrystalline Si and plastically deformed single crystalline Si by the electron (EBIC) and laser beam induced current (LBIC) methods has been carried out. It is shown that the LBIC contrast of two-dimensional defects in crystals with large diffusion length can be a few times higher than that in the EBIC method. Thus, in recent Si structures the LBIC method allows to reveal grain boundaries with the lower recombination velocity than the EBIC on. The advantages of LBIC for the dislocation trail study in Si and for backside metallization effects in solar cells are demonstrated.

  4. 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

  5. Thermal buckling behavior of defective CNTs under pre-load: A molecular dynamics study.

    PubMed

    Mehralian, Fahimeh; Tadi Beni, Yaghoub; Kiani, Yaser

    2017-05-01

    Current study is concentrated on the extraordinary properties of defective carbon nanotubes (CNTs). The role of vacancy defects in thermal buckling response of precompressed CNTs is explored via molecular dynamics (MD) simulations. Defective CNTs are initially compressed at a certain ratio of their critical buckling strain and then undergo a uniform temperature rise. Comprehensive study is implemented on both armchair and zigzag CNTs with different vacancy defects including monovacancy, symmetric bivacancy and asymmetric bivacancy. The results reveal that defects have a pronounced impact on the buckling behavior of CNTs; interestingly, defective CNTs under compressive pre-load show higher resistance to thermal buckling than pristine ones. In the following, the buckling response of defective CNTs is shown to be dependent on the vacancy defects, location of defects and chirality.

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

    PubMed

    Hsueh, Chia-Hsiang; Chen, Wen-Pin; Lin, Jiunn-Lee; Liu, Yen-Bin; Su, Ming-Jai; Lai, Ling-Ping

    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.

  7. 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.

  8. Positron-annihilation study of radiation defects in sodium azide

    SciTech Connect

    Etin, G.I.; Ryabykh, S.M.

    1987-07-01

    Annihilation-photon angular correlation has been used to examine radiation defects in sodium azide capable of trapping positrons. The calculated and measured characteristics have been determined for various defects, including micropores filled by radiolytic nitrogen. The positron annihilation rates have been determined for the regions around radiation defects.

  9. Dissociation and diffusion of hydrogen on defect-free and vacancy defective Mg (0001) surfaces: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Han, Zongying; Chen, Haipeng; Zhou, Shixue

    2017-02-01

    First-principles calculations with the density functional theory (DFT) have been carried out to study dissociation and diffusion of hydrogen on defect-free and vacancy defective Mg (0001) surfaces. Results show that energy barriers of 1.42 eV and 1.28 eV require to be overcome for H2 dissociation on defect-free and vacancy defective Mg (0001) surfaces respectively, indicating that reactivity of Mg (0001) surface is moderately increased due to vacancy defect. Besides, the existence of vacancy defect changes the preferential H atom diffusion entrance to the subsurface and reduces the diffusion energy barrier. An interesting remark is that the minimum energy diffusion path of H atom from magnesium surface into bulk is a spiral channel formed by staggered octahedral and tetrahedral interstitials. The diffusion barriers computed for H atom penetration from the surface into inner-layers are all less than 0.70 eV, which is much smaller than the activation energy for H2 dissociation on the Mg (0001) surface. This suggests that H2 dissociation is more likely than H diffusion to be rate-limiting step for magnesium hydrogenation.

  10. Triple-negative breast cancer risk in women is defined by the defect of estrogen signaling: preventive and therapeutic implications

    PubMed Central

    Suba, Zsuzsanna

    2014-01-01

    Epidemiologic studies strongly support that triple-negative breast cancers (TNBCs) may be distinct entities as compared with estrogen receptor (ER)+ tumors, suggesting that the etiologic factors, clinical characteristics, and therapeutic possibilities may vary by molecular subtypes. Many investigations propose that reproductive factors and exogenous hormone use differently or even quite inversely affect the risk of TNBCs and ER+ cancers. Controversies concerning the exact role of even the same risk factor in TNBC development justify that the biological mechanisms behind the initiation of both TNBCs and non-TNBCs are completely obscure. To arrive at a comprehensive understanding of the etiology of different breast cancer subtypes, we should also reconsider our traditional concepts and beliefs regarding cancer risk factors. Malignancies are multicausal, but the disturbance of proper estrogen signaling seems to be a crucial risk factor for the development of mammary cancers. The grade of defect in metabolic and hormonal equilibrium is directly associated with TNBC risk for women during their whole life. Inverse impact of menopausal status or parity on the development of ER+ and ER− breast cancers may not be possible; these controversial results derive from the misinterpretation of percentage-based statistical evaluations. Exogenous or parity-associated excessive estrogen supply is suppressive against breast cancer, though the lower the ER expression of tumors, the weaker the anticancer capacity. In women, the most important preventive strategy against breast cancers – included TNBCs – is the strict control and maintenance of hormonal equilibrium from early adolescence through the whole lifetime, particularly during the periods of great hormonal changes. PMID:24482576

  11. Threshold residual ion concentration on photomask surface to prevent haze defects

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Min; Lee, Jae-Chul; Kang, Dong-Shik; Lee, Dong-Heok; Shin, Chul; Choi, Moon-Hwan; Choi, Sang-Soo

    2007-05-01

    Haze generation has been serious issue on wafer lithography process, as illumination wavelength become shorter with 248nm and 193nm. Several published papers have been reported that ammonium and sulfate residual ion on mask surface is major source of haze generation. These ions are come from conventional photomask cleaning process. PKL have been studied new cleaning process to minimize haze generation and found cleaning process condition. Also, PKL found that residual ammonium ion is major source of haze generation than residual sulfate ion. New cleaning process improved residual ammonium ion concentration to less than 45 ppb from 900 ppb with conventional RCA cleaning. And illumination doses generating haze have been tested on five residual ammonium ion, 1500 ppb, 900 ppb, 160 ppb, 70 ppb, 45 ppb, respectively. In house designed Haze Acceleration Test Bench (HATB) was used to expose masks. Haze were not generated until from 25 kJ to 100 kJ, on 160 ppb to 45 ppb of ammonium ion concentration, respectively. And the residual of sulfate ion and its haze generation dose did not correspond. Residual ammonium ions need to be controlled tightly than sulfate ion. PKL concentrated on minimizing ammonium residual with new cleaning process and found the optimized cleaning process for preventing 100kJ of cumulative energy on ArF embedded attenuated PSM (EAPSM).

  12. 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 ...

  13. Folic acid in the prevention of neural tube defect--a programme for Malaysia?

    PubMed

    Ho, J J

    2004-03-01

    There is good evidence that folic acid is safe and efficacious for reducing neural tube defect (NTD). All women capable of becoming pregnant should take 400 microgram daily. This can be given in the form of a daily vitamin supplement, by food fortification, or by increasing natural dietary folates. Compulsory grain fortification has been shown to reduce NTD in a population but supplementation and dietary advice have not. Malaysia should work towards a programme of grain fortification and use alternative strategies to reach sections of the population that would not be covered but several research questions need to be answered before a programme could be implemented in Malaysia.

  14. Use of an Osteoplastic Flap for the Prevention of Mastoidectomy Retroauricular Defects

    PubMed Central

    Bento, Ricardo Ferreira; Tsuji, Robinson Koji; Fonseca, Anna Carolina de Oliveira; Alves, Ricardo Dourado

    2016-01-01

    Introduction After mastoidectomy, patients usually complain of bone depressions in the retroauricular region in the surgical site, especially in procedures that require extensive cortical resections. This causes inconveniences such as difficulty wearing glasses, cleaning, and aesthetics complaints. Objective This study aims to describe a vascularized flap surgical technique that uses the mastoid cortical bone adhered to the periosteum, which is pedicled on the anterior portion and repositioned at the end of the surgery. This ensures the coverage of the mastoid cavity generated by surgery and prevents ear retraction into the cavity. This preliminary report describes the technique and intraoperative and immediate postoperative complications. Methods After retroauricular incision, periosteal exposure is performed. A U-shaped incision is required for the procedure and delimits a periosteum area appropriate to the size of the mastoidectomy. The cortical bone is opened using a 2.5 mm drill around the perimeter of the “U,” at a 3 mm depth. A chisel is introduced through the surface cells of the mastoid, and a hammer evolves into the anterior direction. The flap is lifted, leaving the periosteum adhered to it and forming a cap. The flap is anteriorly fixed to not hinder the surgery, and repositioned at the end. The periosteum is then sutured to the adjacent periosteum. Results The first 14 cases had no intraoperative complications and were firm and stable when digital pressure was applied during the intraoperative and immediate postoperative periods. Conclusion The osteoplastic flap pedicle is a safe and simple procedure, with good results in the immediate postoperative period. PMID:28382122

  15. 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.

  16. 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.

  17. Transient inhibition of the ERK pathway prevents cerebellar developmental defects and improves long-term motor functions in murine models of neurofibromatosis type 1.

    PubMed

    Kim, Edward; Wang, Yuan; Kim, Sun-Jung; Bornhorst, Miriam; Jecrois, Emmanuelle S; Anthony, Todd E; Wang, Chenran; Li, Yi E; Guan, Jun-Lin; Murphy, Geoffrey G; Zhu, Yuan

    2014-12-23

    Individuals with neurofibromatosis type 1 (NF1) frequently exhibit cognitive and motor impairments and characteristics of autism. The cerebellum plays a critical role in motor control, cognition, and social interaction, suggesting that cerebellar defects likely contribute to NF1-associated neurodevelopmental disorders. Here we show that Nf1 inactivation during early, but not late stages of cerebellar development, disrupts neuronal lamination, which is partially caused by overproduction of glia and subsequent disruption of the Bergmann glia (BG) scaffold. Specific Nf1 inactivation in glutamatergic neuronal precursors causes premature differentiation of granule cell (GC) precursors and ectopic production of unipolar brush cells (UBCs), indirectly disrupting neuronal migration. Transient MEK inhibition during a neonatal window prevents cerebellar developmental defects and improves long-term motor performance of Nf1-deficient mice. This study reveals essential roles of Nf1 in GC/UBC migration by generating correct numbers of glia and controlling GC/UBC fate-specification/differentiation, identifying a therapeutic prevention strategy for multiple NF1-associcated developmental abnormalities.

  18. 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.

  19. 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.

  20. Pollution Abatement and Prevention Analysis (PAPA) Study.

    DTIC Science & Technology

    1994-07-01

    and prevention opportunities and activities that are in research , development, demonstration, and commercialization. (5) Selected case studies jointly...organizes Army policy into four categories: compliance, restoration , prevention, and conservation. These categories are referred to as the four "pillars" of...this pillar are generally categorized as "must fund" projects. (2) The restoration pillar focuses on cleaning up contaminated sites at Army

  1. DLTS and EPR study of defects in H implanted silicon

    NASA Astrophysics Data System (ADS)

    Mikšić, V.; Pivac, B.; Rakvin, B.; Zorc, H.; Corni, F.; Tonini, R.; Ottaviani, G.

    2002-01-01

    Single crystal CZ Si samples were implanted with hydrogen ions to the dose of 2E16 He ions/cm 2 at room temperature and subsequently annealed in vacuum in the temperature interval from 100 to 900 °C. The aim of the experiment was to determine the conditions for bubble formation within the solid film, which may have important technological application. Defects produced in such samples were studied by deep-level transient spectroscopy (DLTS) and electron paramagnetic resonance (EPR) spectroscopy. It is shown that high dose hydrogen implantation produces vacancy-related and silicon selfinterstitial clusters. The latter are thought to be responsible for the formation of the weak displacement field. The annealing at higher temperatures creates multivacancy-related clusters responsible for the strong displacement field formation.

  2. 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

  3. 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.

  4. Vandalism Prevention Programs: A Case Study Approach.

    ERIC Educational Resources Information Center

    White, James; Fallis, Anita

    The objective of this study was to identify, describe, and appraise existing behavior-oriented, vandalism-prevention programs using a case-study approach. This report summarizes an investigation of three programs in Ontario (Canada): Project PRIDE (Pupils Responsible in Determining their own Environment); Operation Aware; and a Diversion program.…

  5. Enhancing native defect sensitivity for EUV actinic blank inspection: optimized pupil engineering and photon noise study

    NASA Astrophysics Data System (ADS)

    Wang, Yow-Gwo; Neureuther, Andrew; Naulleau, Patrick

    2016-03-01

    In this paper, we discuss the impact of optimized pupil engineering and photon noise on native defect sensitivity in EUV actinic blank inspection. Native defects include phase-dominated defects, absorber defects, and defects with a combination of phase and absorption behavior. First, we extend the idea of the Zernike phase contrast (ZPC) method and study the impact of optimum phase shift in the pupil plane on native defect sensitivity, showing a 23% signal-to-noise ratio (SNR) enhancement compare to bright field (BF) for a phase defect with 20% absorption. We also describe the possibility to increase target defect SNR on target defect sizes at the price of losing the sensitivity on smaller (non-critical) defects. Moreover, we show the advantage of the optimized phase contrast (OZPC) method over BF EUV actinic blank inspection. A single focus scan from OZPC has better inspection efficiency over BF. Second, we make a detailed comparison between the phase contrast with apodization (AZPC) method and dark field (DF) method based on defect sensitivity in the presence of both photon shot noise and camera noise. Performance is compared for a variety of photon levels, mask roughness conditions, and combinations of defect phase and absorption.

  6. 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.

  7. Assessment of non-carious root surface defects in areas of gingival recession: A descriptive study

    PubMed Central

    Jacob, Caroline-Annette; Nainar, Deepavalli-Arumuga

    2016-01-01

    Background The purpose of this descriptive study was to observe the distribution of four different classes of non-carious cervical root surface discrepancies in teeth with gingival recession. Additionally to explore the different treatment modalities in the literature for each of these defects. Material and Methods A total of 150 subjects with at least one labial gingival recession were included in the study. 1400 teeth were evaluated using 2.5 X magnification loupes and UNC -15 probe for the presence of the cemento-enamel junction and step like defects according to Pini-Prato’s classification: A-, identifiable CEJ without defect; A+, identifiable CEJ with defect; B-, unidentifiable CEJ without defect, B+, unidentifiable CEJ with defect. Further a comprehensive electronic and hand search of pubmed indexed journals was performed to identify appropriate treatment modalities for these defects and their predictability following restorative/surgical or combination of both. Results A total of 1400 teeth with exposed root surfaces were examined (793 Maxillary; 607 mandibular). 499 teeth were A-, 405 were A+, 322 were B+ and 174 were B-. The distribution of these defects in different teeth was: 36% premolars, 32% molars, 21% incisors and 11% canines, collectively 68% in the aesthetic zone. Conclusions Majority of these lesions are in the maxillary aesthetic zone. Hence the presence of the CEJ and the defect must be taken into account while managing these defects surgically. Key words:Cervical abrasion, gingival recession, magnification loupes, root coverage, step defects. PMID:27703607

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. A study on limb reduction defects in six European regions.

    PubMed

    Stoll, C; Calzolari, E; Cornel, M; Garcia-Minaur, S; Garne, E; Nevin, N; Ten Kate, L

    1996-01-01

    Limb reduction defects (LRD) gained special attention after the thalidomide tragedy in 1962. LRD are common congenital malformations which present as obvious congenital anomalies recognized at birth. Therefore it might be assumed that they are well documented. However classification of LRDs is disputed as the identification of the exact site of the reduction(s) is hindered by imprecise information. This study was undertaken in 6 European countries to evaluate the use of the new classification proposed by EUROCAT for the epidemiologic and genetic study of LRD. The total number of births including livebirths, still-births and terminations, surveyed during 7 years by the 6 registries of congenital anomalies participating to this study was 611.150. The total prevalence of LRD was 7.06 per 10.000 births including the following categories prevalence : terminal transverse, 3.97, longitudinal, 1.75, proximal-intercalary, 0.10, split hand/foot 0.54 and multiple types 0.70. The prevalence of LRD was statistically higher in Basque Country, Odense, Strasbourg and Groningen than in Belfast and Emilia Romagna. Six per cent of the cases were chromosomal anomalies, including 15 trisomies 18 out of 26 cases, 49.5% (201 cases) were isolated LRD and 50.5% (206 cases) had other major non LRD associated malformations. Sex ratio and maternal age were not statistically different between regions and from the normal population. Multiply malformed with LRD had statistically significantly lower birthweight and lower gestational age than isolated cases with LRD, where available prenatal detection of LRD was higher in multiple malformed children with LRD than in isolated cases, 19.9% and 4.8% respectively. The precurrence risk was 1 in 37.

  14. Remaining Visual Field and Preserved Subjective Visual Functioning Prevent Mental Distress in Patients with Visual Field Defects

    PubMed Central

    Gall, Carolin; Brösel, Doreen; Sabel, Bernhard A.

    2013-01-01

    Background: Patients with visual field defects after visual pathway lesion may experience reduced vision-related quality of life (vrQoL). It has not been clarified how vrQoL impairments contribute to vision-related mental distress. Methods: One hundred and eight subjects with visual field defects caused by optic neuropathies (age M = 57.6; SD = 13.7 years) answered the National Eye Institute Visual-Functioning Questionnaire 39 (NEI-VFQ) for vrQoL and the SF-12 Short Form Health Survey for health-related quality of life. A 10 item composite of NEI-VFQ “visual functioning” and 5 items of “mental-health symptoms due to vision problems” were subjected to Rasch analysis. The test battery comprised static and High Resolution Perimetry (HRP). Regression and path analysis were used to investigate associations between QoL, mental distress, and perimetry results. Results: A higher level of “visual functioning” was associated with monocular impairment and a larger remaining visual field compared to binocular impairment. Subjective “visual functioning” but not visual field parameters predicted “mental-health symptoms due to vision problems” which was the only variable associated with the SF-12 mental component score. The SF-12 physical component score was less strongly associated with “mental-health symptoms due to vision problems.” Here, reaction time in HRP and mean threshold in perimetry were additional significant variables. Path analysis revealed a significant path from remaining visual field via visual functioning on mental health. Conclusion: Subjective consequences of visual impairments in everyday life impact mental health rather than “objective” visual function loss as measured by perimetry. Since a higher extent of vrQoL was related to lower levels of mental distress, the maintenance of vrQoL could reduce and prevent mental distress due to vision problems. Patients with persisting visual field defects may benefit from

  15. Observed Prevalence of Congenital Heart Defects From a Surveillance Study in China

    PubMed Central

    Zhang, Yali; Riehle-Colarusso, Tiffany; Correa, Adolfo; Li, Song; Feng, Xinheng; Gindler, Jacqueline; Lin, Hui; Webb, Catherine; Li, Wei; Trines, Jean; Berry, Robert J.; Yeung, Lorraine; Luo, Ying; Jiang, Meifang; Chen, Hua; Sun, Xiamei; Li, Zhu

    2015-01-01

    Objectives The purpose of this study was to estimate the prevalence of major and minor congenital heart defects among fetuses and neonates using sonography in a general population of 4 areas surrounding Shanghai, China. Methods Pregnant women were recruited between April 2004 and December 2005 in Jiaxing City, Suzhou City, Changshu County, and Haining County. All participants could have 3 sonographic examinations performed by specially trained physicians regardless of medical indication: a fetal sonographic screen and fetal echocardiography between 20 and 28 weeks’ gestation and neonatal echocardiography. Diagnoses of congenital heart defects were made on the basis of review of all available scans by an international group of experts in pediatric cardiology. Prevalence rates were calculated per 1000 births. Results Among 4006 scanned fetuses and neonates, there were 75 congenital heart defects, including 12 major defects. The observed prevalence for all congenital heart defects was 18.7 (95% confidence interval, 14.8–23.5) per 1000 births, and the prevalence for major defects was 3.0 (95% confidence interval, 1.6–5.2) per 1000 births. The most common defects were ventricular septal defects (n = 47 [62.7%]), atrial septal defects (n = 14 [18.7%]), tetralogy of Fallot (n = 4 [5.3%]), and hypoplastic left heart syndrome (n = 3 [4.0%]). Conclusions The prevalence of all congenital heart defects in the 4 areas of China studied was higher than that reported in other countries, with ventricular septal defects being the most frequent defects. Our data likely reflect a better estimate of the total prevalence of congenital heart defects in China than reported previously. PMID:21705732

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

    PubMed

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

    2009-03-01

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

  17. 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.

  18. C-V and DLTS studies of radiation induced Si-SiO2 interface defects

    NASA Astrophysics Data System (ADS)

    Capan, I.; Janicki, V.; Jacimovic, R.; Pivac, B.

    2012-07-01

    Interface traps at the Si-SiO2 interface have been and will be an important performance limit in many (future) semiconductor devices. In this paper, we present a study of fast neutron radiation induced changes in the density of Si-SiO2 interface-related defects. Interface related defects (Pb centers) are detected before and upon the irradiation. The density of interface-related defects is increasing with the fast neutron fluence.

  19. 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.

  20. First principles study of O defects in CdSe

    NASA Astrophysics Data System (ADS)

    T-Thienprasert, J.; Limpijumnong, S.; Du, M.-H.; Singh, D. J.

    2012-08-01

    Recently, the vibrational signatures related to oxygen defects in oxygen-doped CdSe were measured using ultrahigh resolution Fourier transform infrared (FTIR) spectroscopy by Chen et al.(2008) [1]. They observed two absorption bands centered at ∼1991.77 and 2001.3 cm-1, which they attributed to the LVMs of OCd, in the samples grown with the addition of CdO and excess Se. For the samples claimed to be grown with even more excess Se, three high-frequency modes (1094.11, 1107.45, and 1126.33) were observed and assigned to the LVMs of OSe-VCd complex. In this work, we explicitly calculated the vibrational signatures of OCd and OSe-VCd complex defects based on first principles approach. The calculated vibrational frequencies of OCd and OSe-VCd complex are inconsistent with the frequencies observed by Chen et al., indicating that their observed frequencies are from other defects. Potential defects that could explain the experimentally observed modes are suggested.

  1. 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.

  2. Intrinsic defect in BiNbO4: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Lai, Kangrong; Zhu, Yingtao; Dai, Ying; Huang, Baibiao

    2012-08-01

    Formation energies, transition energy levels, and electronic properties of various intrinsic defects in BiNbO4 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 (Bivac) leading to p-type conductivity are the dominant intrinsic defects, whereas O vacancies (Ovac) inducing moderate n-type conductivity are the dominant intrinsic defects under Bi-rich condition. Among these intrinsic defects, Ovac is a deep donor; to the contrary, Bivac is found to be a shallow acceptor which is benefit to the separation and migration of the photogenerated carriers. Consequently, the BiNbO4 with Bivac under O-rich growth condition should be of better photocatalytic performance.

  3. 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.

  4. Study on distortion correction for image mosaic of surface defects

    NASA Astrophysics Data System (ADS)

    Wang, Shitong; Liu, Dong; Chen, Xiaoyu; Cao, Pin; Yang, Yongying

    2012-10-01

    It is hard to quantitate the micron-scale defects on large aperture (102mm×102mm) optical components by the conventional optical testing methods. This paper proposes a super-smooth surface defects measurement and evaluation system, achieved by using microscopic dark-field scattering imaging device, two-dimensional sub-image scanning mechanism and multi-cycle image mosaic algorithm. The defects detecting system, with a lateral resolution of 0.5μm, applies a large field of view design (largest FOV: 15mm×15mm). In order to test the largest element (430mm×430mm), however, over 1000 sub-pictures are captured. It takes more than 30 minutes to process these sub-pictures by multi-cycle image mosaic algorithm. This paper also presents a distortion correction method to revise the image mosaic mismatch caused by the optical distortion in the defects testing system on the platform of MATLAB. A binary optical grid plate (BOE) is fabricated as standard board to evaluate distortion. The proposed method applies image division multi-steps to build a look-up matrix of distortion parameters. According to the look-up matrix, all pixels on a sub-image are repositioned from the distortion Cartesian coordinates to the ideal Cartesian coordinates. Finally, feasibility of the distortion correction method is demonstrated by comparing the mosaic results of defect images before and after this process. The full field view distortion is reduced from more than 4% to less than 0.1%. After distortion correction, subimages can be directly mosaicked without using multi-cycle image mosaic algorithm, which improves test efficiency significantly. The method mentioned in this paper may also apply to other optical testing systems for image mosaic.

  5. Structural transformations from point to extended defects in silicon: A molecular dynamics study

    SciTech Connect

    Marques, Luis A.; Pelaz, Lourdes; Santos, Ivan; Lopez, Pedro; Aboy, Maria

    2008-11-15

    We use classical molecular dynamics simulation techniques to study how point defects aggregate to form extended defects in silicon. We have found that <110> chains of alternating interstitials and bond defects, a generalization of the Si di-interstitial structure, are metastable at room temperature but spontaneously transform into (311) defects when annealed at higher temperatures. Obtained atomic configurations and energetics are in good agreement with experiments and previous theoretical calculations. We have found a (311) structural unit which consists of two interstitial chains along <110> but arranged differently with respect to the known (311) units.

  6. 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

  7. Associations of birth defects with adult intellectual performance, disability and mortality: population-based cohort study.

    PubMed

    Eide, Martha G; Skjaerven, Rolv; Irgens, Lorentz M; Bjerkedal, Tor; Oyen, Nina

    2006-06-01

    Infants born with birth defects have poorer outcomes in terms of mortality and disability, but the long-term intellectual outcome in children with birth defects is generally unknown. We assessed the long-term associations of various birth defects with mortality and disability, and evaluated whether high mortality and disability were reflected in impaired intellectual performance at age 18. In this nationwide cohort study, records of 9,186 males with and 384,384 without birth defects, registered in the Medical Birth Registry of Norway (1967-1979) were linked to the National Conscript Service (1984-1999). Mortality and disability before military draft, and intelligence test score at conscription were the main outcome measures. Males with birth defects had a relative risk for disability of 6.0 compared with males without defects. Disability was low within categories of birth defects associated with low mortality, and high within defect categories associated with high mortality. The relative risk for not being drafted was highest if maternal educational level was low. Heart defects and cleft palate were the only subgroups in which intellectual performance was lower after adjustment for maternal education, maternal age, marital status and birth order. In particular, intellectual performance was not impaired among those with multiple compared with single defects. We conclude that for the majority of birth defect categories in the present birth cohort, our hypothesis that intellectual performance would be impaired was not confirmed. Thus, there seems to be little reason to fear an adverse intellectual outcome in non-disabled surviving infants with birth defects.

  8. [Electron microscopic study of wedge-shaped defects of teeth on initial stage].

    PubMed

    Makeeva, I M; Biakova, S F; Chuev, V P; Sheveliuk, Iu V

    2009-01-01

    The aim of thes; study was to observe initial stage of wedge-shaped defects under scanning electron microscopy without prior samples preparation. There were revealed special features of structure of enamel and cement at initial stage of wedge-shaped defects in comparison to normal tissues.

  9. Defectivity study of directed self-assembly of cylindrical diblock copolymers in laterally confined thin channels

    NASA Astrophysics Data System (ADS)

    Kim, Bongkeun; Laachi, Nabil; Fredrickson, Glenn H.

    2013-03-01

    We use self-consistent field theory (SCFT) to study the directed self-assembly of cylinder-forming diblock copolymers laterally confined in narrow channels. The side walls and top/bottom surfaces of the channel are either all major block attractive, all minor block attractive, or a combination of major block attractive on the top surface and minor block attractive on the remaining film surfaces. We focus on systems in which the self-assembled cylinders form a monolayer oriented parallel to the sidewalls in a thin channel. Experimentally and theoretically, well-ordered perfect cylinders are observed in narrow channels, but undesirable defective structures are also found. We investigate the energetics of isolated, meta-stable defects and compare them with two types of defects (dislocations and disclinations) recently investigated in laterally confined lamellar block copolymer systems using SCFT. Our simulation results are also compared with defect energy estimates for lying down cylinder monolayers extracted from experimental work by Mishra and coworkers. Parametric studies include the effects of film thickness, domain spacing, χN, and composition on defect energies with various wall wetting conditions in narrow channels of varying widths. A major finding is that defects of cylindrical directed self-assembly in a confined channel have a smaller free energy cost (tens of kT) in comparison with defects in laterally confined, vertically oriented lamellae (many tens of kT). We also discovered a novel vertically branched cylinder defect in the case of neutral top and bottom surfaces with significantly lower defect energy than a corresponding dislocation defect. More broadly, this study reveals unexpected dependences of equilibrium defect densities on a wide range of parameters that must be carefully controlled in order to successfully implement a directed self-assembly process with block-copolymers.

  10. 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

  11. 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.

  12. 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.

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

    DOE PAGES

    Zhang, Wei; Lu, Wen-Cai; Zhang, Hong-Xing; ...

    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

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

    SciTech Connect

    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 more comprehensive understanding of the structures and stability of defects in graphene.

  15. Mothers of Kids with Severe Birth Defects May Have Shorter Lives: Study

    MedlinePlus

    ... With Severe Birth Defects May Have Shorter Lives: Study But the overall risk of early death is ... women just don't die very frequently," stressed study lead author Dr. Eyal Cohen. He's a physician ...

  16. First-Principles Study of Defects in GaN

    DTIC Science & Technology

    2009-07-29

    energies and other properties of the Gai – VGa and Ni – VN Frenkel pairs in GaN. o Results on the binding energies and stabilities of Frenkel pairs as...Frenkel pair are interstitial Ga ( Gai ) and Ga vacancy (VGa). Gallium interstitial can occur in 3+, 2+, and 1+ charge states, depending on the Fermi...distance to the six Ga nearest neighbors are roughly the same (to within 0.15 Å). The defect level of Gai is found to lie in the upper part of the

  17. 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.

  18. Positron annihilation in (Ga, Mn)N: A study of vacancy-type defects

    SciTech Connect

    Yang, X. L.; Zhu, W. X.; Wang, C. D.; Fang, H.; Yu, T. J.; Yang, Z. J.; Zhang, G. Y.; Qin, X. B.; Yu, R. S.; Wang, B. Y.

    2009-04-13

    The vacancy-type defects in (Ga,Mn)N films grown by metal organic chemical vapor deposition were studied by positron annihilation technique. Doppler broadening spectra were measured for the films. Compared to the undoped GaN film, the positron trapping defects in the (Ga,Mn)N films have been changed to a new type defects and its concentration increases with the increasing Mn concentration. By analyzing the S-W correlation plots and our previous results, we identify this type defects in the (Ga,Mn)N as V{sub N}-Mn{sub Ga} complex. This type of defects should be considered when understand the magnetic properties in a real (Ga,Mn)N system.

  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. First-principles study of native point defects in hafnia and zirconia

    NASA Astrophysics Data System (ADS)

    Zheng, J. X.; Ceder, G.; Maxisch, T.; Chim, W. K.; Choi, W. K.

    2007-03-01

    A first-principles study of native point defects in hafnia (HfO2) and zirconia (ZrO2) is carried out to identify dominant defects under different oxygen chemical potentials and Fermi levels. Oxygen vacancies and oxygen interstitials in both HfO2 and ZrO2 show negative- U behavior. It is shown that HfO2 is less prone to the formation of oxygen point defects than ZrO2 under the same oxygen chemical potential. When the Fermi level is constrained to be within the band gap of silicon, the dominant defects are negatively charged hafnium or zirconium vacancies under intermediate to high oxygen chemical potential. We find no evidence for magnetic defects.

  1. Theoretical Studies on the Extrinsic Defects of Montmorillonite in Soft Rock

    NASA Astrophysics Data System (ADS)

    He, Man-Chao; Fang, Zhi-Jie; Zhang, Ping

    Using the first-principles methods, we study the formation energetics and charge doping properties of the extrinsic substitutional defects in montmorillonite. Especially, we choose Be, Mg, Ca, Fe, Cr, Mn, Cu, Zn as extrinsic defects to substitute for Al atoms. By systematically calculating the impurity formation energies and transition energy levels, we find that all Group II defects introduce the relative shallow transition energy levels in montmorillonite. Among them, MgAl has the shallowest transition energy level at 0.10 eV above the valence band maximum. The transition-elemental defects FeAl, CrAl, and MnAl are found to have relatively low formation energies, suggesting their easy formation in montmorillonite under natural surrounding conditions. Our calculations show that the defects CuAl and ZnAl have high formation energies, which exclude the possibility of their formation in montmorillonite.

  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. 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.

  4. Defect-tuning exchange bias of ferromagnet/antiferromagnet core/shell nanoparticles by numerical study.

    PubMed

    Mao, Zhongquan; Zhan, Xiaozhi; Chen, Xi

    2012-07-11

    The influence of non-magnetic defects on the exchange bias (EB) of ferromagnet (FM)/antiferromagnet (AFM) core/shell nanoparticles is studied by Monte Carlo simulations. It is found that the EB can be tuned by defects in different positions. Defects at both the AFM and FM interfaces reduce the EB field while they enhance the coercive field by decreasing the effective interface coupling. However, the EB field and the coercive field show respectively a non-monotonic and a monotonic dependence on the defect concentration when the defects are located inside the AFM shell, indicating a similar microscopic mechanism to that proposed in the domain state model. These results suggest a way to optimize the EB effect for applications.

  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. 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.

  7. Prevention of ultrasonic coagulator-mediated mucoperiosteal flap injury and defects by using a clip manipulation in the resection of the posterior nasal nerve.

    PubMed

    Ikeda, Katsuhisa; Yokoi, Hidenori; Saito, Tatsuya; Kawano, Kenji; Yao, Toru; Furukawa, Masayuki; Kusunoki, Takeshi

    2009-03-01

    We previously reported on the clinical effectiveness of functional inferior turbinosurgery utilizing modified vidian neurectomy, the resection of the posterior nasal nerve (PNN), combined with inferior turbinoplasty. In order to prevent re-innervation of the PNN after resection and to avoid postoperative massive hemorrhage--presumably resulting from insufficient fixation and unexpected exposure of the bony or cartilaginous fragments covered on the resected neurovascular bundle containing the sphenopalatine vessels and the PNN--we designed a surgical technique during which a vascular clip was used in order to provide traction of the mucoperiosteal flap. Then we compared it with the previous procedure (without the use of the clip). The injury and defects of the mucoperiosteal flap were evaluated by the degree of exposure to the bony or cartilaginous fragments and scored on a scale of 0 to 2 points. The defects of the mucoperiosteal flap were reduced by using a vascular clip. The average score of the defects was 0.97 +/- 0.73 (n = 64) in the conventional procedure without any manipulation and 0.27 +/- 0.45 (n = 60) in the procedure using a vascular clip. The difference observed between the two gropups was statistically significant (p < 0.001). These results demonstrated that this is a safe technique to prevent injury and defects of the mucoperiosteal flap in gaining access to expose the PNN. This should promote early wound healing, reduce the chance of recurrence and of postoperative massive hemorrhage.

  8. 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.

  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. Long-term effect on tooth vitality of regenerative therapy in deep periodontal bony defects: a retrospective study.

    PubMed

    de Sanctis, Massimo; Goracci, Cecilia; Zucchelli, Giovanni

    2013-01-01

    Over the last few decades, many authors have investigated the effect of periodontal disease and treatment on pulpal status with controversial results. This study was conducted to verify whether periodontal disease in a deep intrabony defect and complex therapy, including aggressive root planing such as in periodontal regeneration, have an influence on tooth vitality. One hundred thirty-seven patients who fulfilled the requirements were included. The collected data did not support the need for "preventive" root canal treatment in severely compromised teeth that are planned to undergo periodontal regenerative surgery.

  11. Paramagnetic resonance studies of defects in titanium dioxide crystals

    NASA Astrophysics Data System (ADS)

    Yang, Shan

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize point defects in TiO2 crystals having the rutile structure. Defect production occurs at low temperature during illumination with 442 nm laser light. Spectra with S = 1/2 and S = 1 are assigned to singly ionized and neutral oxygen vacancies, respectively. These oxygen vacancies have their unpaired spins localized on the two neighboring titanium ions aligned along the [001] axis. A Ti3+ ion next to a substitutional Si4+ ion, a Ti3+ self-trapped electron, and a self-trapped hole on the oxygen sublattice are also observed. Fluorine ions substitute for oxygen and are present as unintentional impurities in TiO2 crystals. Isolated singly ionized fluorine donors in an as-grown (fully oxidized) crystal convert to their neutral charge state during exposure to 442 nm laser light at 6 K. These donors return to the singly ionized charge state within a few seconds when the light is removed. In contrast, the neutral fluorine donors are observed at 6 K without photoexcitation after a crystal is reduced at 600 ºC in flowing nitrogen gas. The angular dependences of the EPR and ENDOR spectra provide a complete set of spin-Hamiltonian parameters (principal values are 1.9746, 1.9782, and 1.9430 for the g matrix and -0.23, 0.47, and 5.15 MHz for the 19F hyperfine matrix). These matrices suggest that the unpaired electron is localized primarily on one of the two equivalent neighboring substitutional titanium ions, i.e., the ground state of the neutral fluorine donor in rutile-structured TiO2 is a Ti 3+ ion adjacent to a F- ion. Hydrogen, in the form of an OH- ion, is a shallow donor in TiO2. In the neutral charge state, the unpaired electron forms an adjacent Ti3+ ion. The hydrogen EPR signal cannot be produced in oxidized crystals containing fluorine donors, which suggest that hydrogen is a shallower donor than fluorine in TiO2 (rutile) crystals. The hydrogen EPR

  12. 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.

  13. 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

  14. 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

    2016-03-09

    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.

  15. Study on dynamic compression performance of K9 glass with prefabricated defects

    NASA Astrophysics Data System (ADS)

    Hu, Changming; Wang, Xiang; Cai, Lingcang; Liu, Cangli

    2012-03-01

    We conducted several planar impact experiments to study dynamic compression properties of K9 glass on powder gun using Photon Doppler Velocimetry (PDV) measure system. Samples are prefabricated some internal meso-defects by laser three-dimensional erosion technique before shock loading. Free surface velocities recorded by high temporal-spatial resolution PDV array or multi-point PDV. All these experimental results show some different properties influenced by evolutions of pre-existed internal defects face on free surface velocity profiles. The critical compression strength and dynamic evolution information of pre-existed internal defects can be derived from the experimental results tentatively.

  16. 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.

  17. First-principles study of point defects in CePO4 monazite

    NASA Astrophysics Data System (ADS)

    Yi, Yong; Zhao, Xiaofeng; Teng, Yuancheng; Bi, Beng; Wang, Lili; Wu, Lang; Zhang, Kuibao

    2016-12-01

    CePO4 monazite is an important radiation-resistant material that may act as a potential minor actinides waste form. Here, we present the results of the calculations for the basic radiation defect modellings in CePO4 crystals, along with the examination of their defect formation energies and effect of the defect concentrations. This study focused on building a fully-relaxed CePO4 model with the step iterative optimization from the DFT-GGA calculations using the VASP and CASTEP databases. The results show that the Frenkel defect configuration resulting from the center interstitials has a lower energy when compared to two adjacent orthophosphate centers (the saddle point position). High formation energies were found for all the types of intrinsic Frenkel and vacancy defects. The formation energies conform to the following trend (given in the decreasing order of energy): Ce Frenkel (12.41 eV) > O Frenkel (11.02 eV) > Ce vacancy (9.09 eV) > O vacancy (6.69 eV). We observed almost no effect from the defect concentrations on the defect formation energies.

  18. Theoretical study of boron nitride nanotubes with defects in nitrogen-rich synthesis.

    PubMed

    Kang, Hong Seok

    2006-03-16

    On the basis of calculations using the density functional theory, it is shown that BNNT synthesis could produce tubes deprived of one (B1 hole) or two (B2 hole) boron atoms under the condition where nitrogen atoms exist in excess throughout this study. The relative populations of various isomers of defective tubes will depend on the chirality of the tube. Interestingly, calculations show that B2 holes are much more favored than B1 holes, particularly in armchair tubes. Electronic properties are modified in such a way that the band gap is decreased through the introduction of defect states inside the gap. Magnetic properties will also be dependent on the chirality. The majority of armchair tubes with B2 holes will be nonmagnetic, while the majority of zigzag tubes with defects will exhibit magnetism. Contrary to the case of defect-free BNNT, the defective tubes are expected to be easily subject to reduction by accommodating excess electrons in the presence of Li atoms. In addition, the defect sites will show a higher affinity toward hydrogenation than the defect-free sites.

  19. Anisotropic compressive response of Stone-Thrower-Wales defects in graphene: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Rajasekaran, G.; Parashar, Avinash

    2016-09-01

    The mechanical properties of graphene sheet can be tailored with the help of topological defects. In this research article, the effects of Stone-Thrower-Wales (STW) defects on the mechanical properties of graphene sheet was investigated with the help of molecular dynamics based simulations. Authors has made an attempt to analyse the stress field developed in and around the vicinity of defect due to bond reorientation and further systematic evaluation has been carried out to study the effect of these stress fields against the applied axial compressive load. The results obtained with the pristine graphene were made to compare with the available open literature and the results were reported to be in good agreement with theoretical and experimental data. It was predicted that graphene with STW defect cannot able to bear compressive strength in zigzag direction, whereas on the other hand it was predicted that graphene sheet containing STW defect can bear higher compressive load in armchair direction, which shows an anisotropic response of STW defects in graphene. From the obtained results it can be observed that orientation of STW defects and the loading direction plays an important role to alter the strength of graphene under axial compression.

  20. High resolution Laplace DLTS studies of defects in ion-implanted silicon

    NASA Astrophysics Data System (ADS)

    Evans-Freeman, J. H.; Abdelgader, N.; Kan, P. Y. Y.; Peaker, A. R.

    2002-01-01

    We have used high resolution Laplace deep level transient spectroscopy (LDLTS) to investigate defects in n-type silicon caused by implantation of Si, Ge or Er with doses of the order of 1×10 9 cm-2. These are compared with defects created in proton irradiated n-type silicon. Unlike the simple proton irradiated case, LDLTS spectra of ion implanted silicon show that there are many emission rates associated with defects with energies in the region of Ec-400 meV. We have carried out annealing studies and Laplace DLTS depth profiling and show that the complex spectra measured from a region less than half way through the implant simplify as the profile is moved through the implant and towards the tail. Annealing studies show that these defects survive an anneal that should remove the E-centre.

  1. 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.

  2. High Serum Estradiol and Heavy Metals Responsible for Human Spermiation Defect-A Pilot Study

    PubMed Central

    Jain, Manish; Kalsi, Amanpreet Kaur; Srivastava, Amita; Gupta, Yogendra Kumar

    2016-01-01

    Introduction Spermiation is a process of releasing sperm into the lumen of seminiferous tubules. Failure in releasing sperm into the lumen is designated as spermiation defect. Spermiation defect cases present as oligo-azoospermia or azoospermia despite normal gonadotropins and testicular histology/cytology. Human spermiation defect never got attention to investigate infertility practice. Most of the information on spermiation defect, so far is from animal experiments. We assume some cases of non-obstructive azoospermia with normal gonadotropins and testicular histology/cytology could be due to spermiation defect. Aim The aim of the study was to find out the underlying aetiology in cases of human spermiation defect. Materials and Methods A total of 13 cases of spermiation defect and 20 fertile men as control constituted study material. Cases were studied for chromosomal abnormalities by conventional karyotyping, sex chromosome mosaicism by interphase XY FISH, Yq microdeletion by STS PCR, sertoli cell quality (function) and quantity (numbers) by serum Anti-Mullerian Hormone (AMH) and inhibin B besides other hormones like Follicular Stimulating Hormone (FSH), prolactin, testosterone and estradiol. Vitamin A concentration in serum was also measured. Presence of heavy metal was investigated by elemental electron microscopy in seminal cells (eight cases) & by spectrometry in serum as well as seminal plasma. Results Chromosomal and Yq microdeletion study failed to detect any abnormalities. AMH, inhibin B and vitamin A were also normal. Estradiol level was high in 6 out of 13 cases (46%) while platinum in seminal cells was high in 4 cases (50%). High (four times or more) serum level of lead and nickel was observed in 11 (85%) and 6 (46%) cases, respectively. Conclusion High serum concentration of heavy metals like lead & nickel or high platinum accumulation in seminal cells or high serum estradiol alone or in combinations may be underlying aetiologic factors in human

  3. 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).

  4. DJ-1-binding compounds prevent oxidative stress-induced cell death and movement defect in Parkinson's disease model rats.

    PubMed

    Miyazaki, Shin; Yanagida, Takashi; Nunome, Kana; Ishikawa, Shizuma; Inden, Masatoshi; Kitamura, Yoshihisa; Nakagawa, Shinsuke; Taira, Takahiro; Hirota, Kosaku; Niwa, Masami; Iguchi-Ariga, Sanae M M; Ariga, Hiroyoshi

    2008-06-01

    Parkinson's disease (PD) is caused by neuronal cell death. Although a precursor of dopamine and inhibitors of dopamine degradation have been used for PD therapy, cell death progresses during treatment. DJ-1, a causative gene product of a familial form of PD, PARK7, plays roles in transcriptional regulation and anti-oxidative stress, and loss of its function is thought to result in the onset of PD. Superfluous oxidation of cysteine at amino acid 106 (C106) of DJ-1 renders DJ-1 inactive, and such oxidized DJ-1 has been observed in patients with the sporadic form of PD. In this study, we isolated compounds that bind to the region at C106 by a virtual screening. These compounds prevented oxidative stress-induced death of SH-SY5Y cells, embryonic stem cell-derived dopaminergic cells and primary neuronal cells of the ventral mesencephalon, but not that of DJ-1-knockdown cells of SH-SY5Y and NIH3T3 cells, indicating that the effect of the compounds is specific to DJ-1. These compounds inhibited production of reactive oxygen species and restored activities of mitochondrial complex I and tyrosine hydroxylase that had been compromised by oxidative stress. These compounds prevented dopaminergic cell death in the substantia nigra and restored movement abnormality in 6-hydroxyldopamine-injected PD model rats. One mechanism of action of these compounds is prevention of superfluous oxidation of DJ-1, and the compounds passed through the blood-brain barrier in vitro. Taken together, the results indicate that these compounds should become fundamental drugs for PD therapy.

  5. 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.

  6. A study of photovoltaic loss-mechanisms due to defects and grain boundaries in polycrystalline silicon

    NASA Astrophysics Data System (ADS)

    Sopori, B. L.

    1980-01-01

    Various photovoltaic loss mechanisms associated with defects and grain boundaries (gbs) in polycrystalline silicon have been experimentally studied. Analysis was carried out on two types of substrates/cells viz. Wacker Silso and laser-crystallized RTR ribbons. Solar cells were fabricated on selected regions of the substrates and their characteristics related to the substrate structure. Mechanisms related to photovoltaic losses are divided into two categories: electronic and physical. Parameters describing electronic loss mechanisms, such as changes in minority carrier diffusion length, dark current and local photo-current losses were measured, and their dependence on density and type of defects was determined. A variety of analytical techniques were used for this study. These include I-V characterization of solar cells, I-V characterization of gbs, and light intensity dependences of some material parameters. Loss mechanisms associated with physical effects are defect-defect and impurity-defect interactions. It is shown that physical effects such as impurity segregation and defect annihilation can lead to significant loss/gain in photovoltaic characteristics.

  7. U.S. Centers for Disease Control and Prevention and Environmental Protection Agency Urge Commonwealth of Puerto Rico to Consider Aerial Spraying as Part of Integrated Mosquito Control to Reduce Zika-Associated Birth Defects

    EPA Pesticide Factsheets

    EPA News Release: U.S. Centers for Disease Control and Prevention and Environmental Protection Agency Urge Commonwealth of Puerto Rico to Consider Aerial Spraying as Part of Integrated Mosquito Control to Reduce Zika-Associated Birth Defects

  8. 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.

  9. 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.

  10. 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…

  11. Ab initio study of dopant-defect interactions in graphene sheets and graphene nano-ribbons

    NASA Astrophysics Data System (ADS)

    Tawalbeh, Tarek

    Theoretical studies of nanostructured systems, such as doped, defective and pristine graphene and graphene nanoribbons, present a major challenge to conventional computational methods. This thesis presents ab initio calculations based on density functional theory (DFT) to study the structural and electronic properties of doped and defective graphene and graphene 'nanoribbons. Our calculations are carried-out using density-functional pseudopotential approximations combined with the generalized gradient approximation (GGA) for the exchange-correlation functional. Structural optimizations are executed by iterative force minimization using the conjugate gradient algorithm. We investigate the effect of dopants and point defects on graphene and graphene nanoribbons and study the interactions between the two. Binding energies, equilibrium geometries, charge transfer, and exchange-splitting-induced magnetism are calculated. The dependence of dopant-defect separation distance on interaction energy and interaction energy is examined in detail. We find that the interaction energy for on-defect dopant sites is dominated by how well defect geometry accommodates the dopant-carbon interatomic distance. Depending on the site dopant-defect interaction is either attractive or repulsive. Stone-Wales defect-nitrogen pairing was found to induce exchange splitting and magnetism in certain configurations. Nitrogen was also found to passivate single-vacancy dangling bonds and eliminate exchange-splitting induced magnetism; vacancy-nitrogen interactions were found to be mostly attractive. Boron-vacancy pairing can result in a favorable symmetric sp3 configuration, this is the only vacancy-boron pairing were dangling bonds are passivated and magnetism is eliminated; other favorable boron-vacancy pairings maintain exchange splitting and can in some cases enhance it. We found that the effect of dopant-defect separation distance follows a simple inverse power law. Our results indicate that

  12. 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

  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

    Trainor, Paul A

    2010-12-01

    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.

  14. 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

  15. 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.

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

    PubMed

    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

    2015-07-20

    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.

  17. 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…

  18. 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

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

    PubMed

    Liu, Shiliang; West, Roy; Randell, Edward; Longerich, Linda; O'connor, Kathleen Steel; Scott, Helen; Crowley, Marian; Lam, Angeline; Prabhakaran, Victor; McCourt, Catherine

    2004-09-27

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

  20. Structural birth defects associated with neural tube defects in Hawai'i from 1986 until 2001.

    PubMed

    Forrester, Mathias B; Merz, Ruth D

    2007-09-01

    Using birth defects registry data, this study identified birth defects associated with anencephaly, spina bifida, and encephalocele. Musculoskeletal defects were associated with anencephaly; central nervous system defects, gastrointestinal atresia/stenosis, genitourinary system defects, and musculoskeletal system defects with spina bifida; and central nervous system defects, respiratory defects, oral clefts, genitourinary system defects, and musculoskeletal system defects with encephalocele.

  1. 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 ...

  2. Prevention

    MedlinePlus

    ... Is Strong Error processing SSI file About Heart Disease & Stroke Prevention Heart disease and stroke are an epidemic in ... to avoid secondhand smoke. Barriers to Effective Heart Disease & Stroke Prevention Many people with key risk factors for heart ...

  3. 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.

  4. 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)

  5. Defective Infant Formulas and Expressive Language Problems: A Case Study.

    ERIC Educational Resources Information Center

    Wing, Clara S.

    1990-01-01

    Children who used chloride-deficient soy-based infant formulas (Neo-Mull-Soy and Cho-Free) have been found to exhibit expressive language disorders. Medical studies of such children are reviewed, and a case study compares the language development deficits of an eight-year-old boy who used the formula with that of his fraternal twin who did not.…

  6. 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.

  7. Basic Study of Detecting Defects in Solid Materials Using High-Intensity Aerial Ultrasonic Waves

    NASA Astrophysics Data System (ADS)

    Osumi, Ayumu; Kobayashi, Hiromasa; Ito, Youichi

    2012-07-01

    Recently, developments have improved methods employing aerial ultrasonic waves for detecting defects in solid materials such as metals, pipe walls, and fiber-reinforced plastics. These methods can be performed using a noncontacting aerial ultrasonic probe. In a previous study, we developed a new method using high-intensity aerial ultrasonic waves to successfully detect peeling, artificially created by inserting an air gap between tiles and concrete plates. In the present study, we use the same method to detect the depth and size of defects in a homogeneous medium.

  8. First-Principles Study of Defects in GaN, AlN and Their Alloys

    DTIC Science & Technology

    2010-08-31

    studied the similar type of pairs in GaN, i.e. Gai -VGa. These types of defect complexes are called Frenkel pairs which are believed to form when the...defects have been carried out.[17-21] In our previous program, we studied the GaGa i V− pairs in GaN. We found that Gai can occur in 3+, 2+, and 1...charge states, depending on the Fermi energy of the sample. VGa can occur in 3−, 2−, 1−, and neutral charge states. Because Gai and VGa have

  9. Light Activated Copper Defects in P-Type Silicon Studied by PCD

    NASA Astrophysics Data System (ADS)

    Yli-Koski, M.; Väinölä, H.; Haarahiltunen, A.; Storgårds, J.; Saarnilehto, E.; Sinkkonen, J.

    2004-01-01

    We have studied copper defects in p-type silicon by measuring its precipitation kinetics by means of the microwave photoconductive decay (µPCD) technique. Copper atoms precipitated during high intensity light treatment at room temperature. We used the total reflection X-ray fluorescence (TXRF) and the transient ion drift (TID) techniques to determine the bulk concentration of copper. We estimated the density and the radius of the copper precipitates as well as the average capture cross-section for precipitated copper atoms from the measured copper precipitation time constant, bulk concentration of copper, and the change in the recombination rate. We also studied how the density of oxygen defect affects the copper precipitation. Our results show that copper precipitates at two different kinds of defects.

  10. (Defect studies in III-V thin film semiconductors)

    SciTech Connect

    Not Available

    1991-01-01

    Our primary research objective in 90/91 has been to continue studying misfit dislocation confinement by patterning substrates into mesas before the epitaxial growth of strained layers. This report presents progress for many of the areas of our research. (JL)

  11. Think Tank: Identifying and Creating the Next Generation of Community-Based Cancer Prevention Studies | Division of Cancer Prevention

    Cancer.gov

    In late 2015, the NCI Division of Cancer Prevention convened cancer prevention research experts and stakeholders to discuss the current state of cancer prevention research, identify key prevention research priorities for the NCI, and identify studies that could be conducted within the NCI Community Oncology Research Program. Read the Cancer Prevention Research journal article (PDF, 532KB). |

  12. Study of the nature of extended defects of copper oxide

    NASA Astrophysics Data System (ADS)

    Kryukova, G. N.; Zaikovskii, V. I.; Sadykov, V. A.; Tikhov, S. F.; Popovskii, V. V.; Bulgakov, N. N.

    1988-05-01

    A sample of powdered copper oxide suitable for studying its real structure with the help of electron microscopy was prepared by slow decomposition of copper nitrate. It is shown that in particles of oxide there are (001) and (100) twins and screw dislocations with Burgers vector along <010>. The lattice of CuO near the twins is strongly deformed. The structures of the composition planes for both types of twins as well as their relative stabilities are analyzed.

  13. Diamond Deposition and Defect Chemistry Studied via Solid State NMR

    DTIC Science & Technology

    1994-06-30

    same integrated NMR signal, regardless of its chemical environment, provided complete spin-lattice relaxation occurs between averages 3 . Gem -quality...occurs between averages, and broadening from years, a large research effort has been devoted to the study paramagnetic centers is insignificant. Gem ...information on the distribution and motion mond’s durability very attractive. However, while gem - of hydrogen can be obtained from the solid-state NMR

  14. High-temperature study of defects and homogeneity in glass

    NASA Astrophysics Data System (ADS)

    Yoon, Chang Hyun

    Glass frit has many useful applications in the glass and ceramic industries. Several attempts were made in this study to understand the origin of problems that generally occur when using glass frit. The effect of water/glass interactions on the rheology of glass suspension and the final properties of glass and glaze were studied. The dissolution of refractory inclusions and its influence on the bubble evolution, glass structure, and homogeneity of the resulting melt were also studied. The effects of long-term interaction of water with various frit suspensions were considered. The change in suspension rheology is associated with the ion concentration of the frit suspension, which strongly depends on the frit composition, additives, and solid content of frit suspension. Physical property and compositional variations resulted from dealkalization reactions between the frit particles and water. New investigative techniques for continuous monitoring and quantitative analysis of the dissolution of refractory inclusions in glass have been developed utilizing high-temperature microscopy with computer image analysis. The dissolution rates of refractory oxides in glass frit were measured utilizing hot-stage microscopy in the temperature range from 1050°C to 1400°C. The effects of dissolution on the structure of the final glass, were monitored by infrared spectroscopy. Homogenization of the resulting melts was studied using a Christiansen filter. It was found that melting temperature and time strongly influence the dissolution of refractory batch materials and subsequent homogenization rates, leading to large differences in final structures for glass melts and glazes which have not attained equilibrium.

  15. The role of point defects in PbS, PbSe and PbTe: a first principles study.

    PubMed

    Li, Wun-Fan; Fang, Chang-Ming; Dijkstra, Marjolein; van Huis, Marijn A

    2015-09-09

    Intrinsic defects are of central importance to many physical and chemical processes taking place in compound nanomaterials, such as photoluminescence, accommodation of off-stoichiometry and cation exchange. Here, the role of intrinsic defects in the above mentioned processes inside rock salt (RS) lead chalcogenide systems PbS, PbSe and PbTe (PbX) was studied systematically using first principles density functional theory. Vacancy, interstitial, Schottky and Frenkel defects were considered. Rock salt PbO was included for comparison. The studied physical properties include defect formation energy, local geometry relaxation, Bader charge analysis, and electronic structure. The defect formation energies show that monovacancy defects and Schottky defects are favoured over interstitial and Frenkel defects. Schottky dimers, where the cation vacancy and anion vacancy are adjacent to each other, have the lowest defect formation energies at 1.27 eV, 1.29 eV and 1.21 eV for PbS, PbSe and PbTe, respectively. Our results predict that a Pb monovacancy gives rise to a shallow acceptor state, while an X vacancy generates a deep donor state, and Schottky defects create donor-acceptor pairs inside the band gap. The surprisingly low formation energy of Schottky dimers suggests that they may play an important role in cation exchange processes, in contrast to the current notion that only single point defects migrate during cation exchange.

  16. Defective germanene as a high-efficiency helium separation membrane: a first-principles study.

    PubMed

    Zhu, Lei; Chang, Xiao; He, Daliang; Xue, Qingzhong; Li, Xiaofang; Jin, Yakang; Zheng, Haixia; Ling, Cuicui

    2017-03-01

    Development of low energy cost membranes for separating helium from natural gas is highly desired. Using van der Waals-corrected first-principles density functional theory (DFT) calculations, we theoretically investigate the helium separation performance of divacancy-defective germanene. The 555 777 divacancy-defective germanene presents a 0.53 eV energy barrier for helium, which is slightly larger than the energy threshold value of gas molecule penetration of a membrane (0.5 eV). Thus, the 555 777 divacancy-defective germanene is difficult for helium to permeate, except under high temperature or pressure. However, the 585 divacancy-defective germanene presents a surmountable energy barrier (0.27 eV) for helium, and it shows extremely high helium selectivities relative to other studied gas molecules. Especially, the He/Ne selectivity can be as high as 1 × 10(4) at room temperature. Together with the acceptable permeance for helium, the 585 divacancy-defective germanene can be used for helium separation with remarkably good performance.

  17. Defective germanene as a high-efficiency helium separation membrane: a first-principles study

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Chang, Xiao; He, Daliang; Xue, Qingzhong; Li, Xiaofang; Jin, Yakang; Zheng, Haixia; Ling, Cuicui

    2017-03-01

    Development of low energy cost membranes for separating helium from natural gas is highly desired. Using van der Waals-corrected first-principles density functional theory (DFT) calculations, we theoretically investigate the helium separation performance of divacancy-defective germanene. The 555 777 divacancy-defective germanene presents a 0.53 eV energy barrier for helium, which is slightly larger than the energy threshold value of gas molecule penetration of a membrane (0.5 eV). Thus, the 555 777 divacancy-defective germanene is difficult for helium to permeate, except under high temperature or pressure. However, the 585 divacancy-defective germanene presents a surmountable energy barrier (0.27 eV) for helium, and it shows extremely high helium selectivities relative to other studied gas molecules. Especially, the He/Ne selectivity can be as high as 1 × 104 at room temperature. Together with the acceptable permeance for helium, the 585 divacancy-defective germanene can be used for helium separation with remarkably good performance.

  18. HgCdTe Surface and Defect Study Program.

    DTIC Science & Technology

    1983-07-01

    as "independent" entities as is the case (to the first approximation) with all other semiconductors studied to date. These results have given rise to...all cases but one (Prof. Walter Harrison’s invited paper on the theory of bonding in MCT) have been written up as full articles for the conference...properties. In the case of PhotoxT Si0 2 on HgCdTe, the inter- face state structure which is controlled by the details of the bonding at the interface

  19. 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.

  20. First principles study of phosphorus and boron defects in Si-XII

    NASA Astrophysics Data System (ADS)

    Malone, Brad D.; Cohen, Marvin L.

    2011-03-01

    We present a first-principles study of phosphorus and boron substitutional defects in Si-XII, a polytype of silicon in the R8 structure. Recent results from nanoindentation experiments reveal that this phase is semiconducting and has the interesting property that it can be doped n- and p-type at room temperature without an annealing step. We examine the formation energies of the B and P defects at the two distinct atomic sites in the R8 structure. We also calculate the thermodynamic transition levels of each defect in its relevant charge states. This work was supported by National Science Foundation Grant No. DMR10-1006184, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Computational resources have been provided by the Lawrencium cluster at LBNL.

  1. An experimental study on the application of radionuclide imaging in repair of the bone defect.

    PubMed

    Zhu, Weimin; Wang, Daping; Zhang, Xiaojun; Lu, Wei; Liu, Jianquan; Peng, Liangquan; Li, Hao; Han, Yun; Zeng, Yanjun

    2011-08-01

    The aim of our study was to validate the effect of radionuclide imaging in early monitoring of the bone's reconstruction, the animal model of bone defect was made on the rabbits repaired with HA artificial bone. The ability of bone defect repair was evaluated by using radionuclide bone imaging at 2, 4, 8 and 12 weeks postoperatively. The results indicate that the experimental group stimulated more bone formation than that of the control group. The differences of the bone reconstruction ability were statistically significant (p<0.05). The nano-HA artificial has good bone conduction, and it can be used for the treatment of bone defects. Radionuclide imaging may be an effective and first choice method for the early monitoring of the bone's reconstruction.

  2. EBIC and LBIC studies of the properties of extended defects in plastically deformed silicon

    SciTech Connect

    Orlov, V. I.; Feklisova, O. V.; Yakimov, E. B.

    2015-06-15

    The results of comparative experimental studies of one- and two-dimensional defects in plastically deformed silicon by the electron-beam-induced current (EBIC) and light-beam-induced current (LBIC) techniques are reported. It is shown that the contrast of two-dimensional defects (dislocation trails) in the LBIC method can by much more pronounced than that in the EBIC technique, which is in good agreement with the results of calculations. The higher sensitivity of the LBIC technique is mainly due to deeper penetration of the optical beam into the material in comparison to the penetration of the electron beam of a scanning electron microscope.

  3. 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.

  4. 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.

  5. 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

  6. 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…

  7. 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 ...

  8. 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...

  9. [Prevalence of dentition defects among pre-school children of Tver region according to epidemiological study].

    PubMed

    Beliaev, V V; Bobrov, D V; Chumakov, A N; Al'-Zrir, O; El'-Aĭdi, M A

    2015-01-01

    Epidemiological dental study of 724 pre-school children in Tver region revealed high prevalence of dentition defects due to premature removal of temporary molars. Dependence of pediatric population need for prosthetic dentistry from regional dental care system staff competence is shown. The date proved the need for standard correction of orthodontists number and broad application of pediatric prosthetics in daily practice.

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

    NASA Technical Reports Server (NTRS)

    Corbett, J. W.

    1985-01-01

    Oxygen and carbon related defects in silicon, particularly as related to high-efficiency silicon solar cells were studied. A summary of oxygen processes in silicon versus process temperature was shown along with experimental results. The anamolous diffusion of oxygen was explained by the dissociation of the center allowing O sub i to move through the lattices.

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

    PubMed

    Stolk, Lisette; Bouwland-Both, Marieke I; van Mil, Nina H; 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.

  12. A codon-shuffling method to prevent reversion during production of replication-defective herpesvirus stocks: Implications for herpesvirus vaccines.

    PubMed

    Li, Gang; Ward, Charles; Yeasmin, Rukhsana; Skiena, Steven; Krug, Laurie T; Forrest, J Craig

    2017-03-13

    Herpesviruses establish life-long chronic infections that place infected hosts at risk for severe disease. Herpesvirus genomes readily undergo homologous recombination (HR) during productive replication, often leading to wild-type (WT) reversion during complementation of replication-defective and attenuated viruses via HR with the helper gene provided in trans. To overcome this barrier, we developed a synthetic-biology approach based on a technique known as codon shuffling. Computer-assisted algorithms redistribute codons in a helper gene, thereby eliminating regions of homology, while enabling manipulation of factors such as codon-pair bias and CpG content to effectively titrate helper-gene protein levels. We apply this technique to rescue the replication of a murine gammaherpesvirus engineered with a mutation in the major immediate-early transactivator protein RTA. Complementation with codon-shuffled RTA constructs did not yield any WT revertant virus, a sharp contrast to WT virus contamination frequently observed during complementation with an unmodified helper gene. We further demonstrate the importance of eliminating WT virus contamination in an animal model of gammaherpesvirus lethality. We propose complementation by codon shuffling as a means to produce replication-defective or attenuated viruses. This method has immediate utility for investigating roles of essential genes in viral replication and will better enable future development of herpesvirus vaccines.

  13. A codon-shuffling method to prevent reversion during production of replication-defective herpesvirus stocks: Implications for herpesvirus vaccines

    PubMed Central

    Li, Gang; Ward, Charles; Yeasmin, Rukhsana; Skiena, Steven; Krug, Laurie T.; Forrest, J. Craig

    2017-01-01

    Herpesviruses establish life-long chronic infections that place infected hosts at risk for severe disease. Herpesvirus genomes readily undergo homologous recombination (HR) during productive replication, often leading to wild-type (WT) reversion during complementation of replication-defective and attenuated viruses via HR with the helper gene provided in trans. To overcome this barrier, we developed a synthetic-biology approach based on a technique known as codon shuffling. Computer-assisted algorithms redistribute codons in a helper gene, thereby eliminating regions of homology, while enabling manipulation of factors such as codon-pair bias and CpG content to effectively titrate helper-gene protein levels. We apply this technique to rescue the replication of a murine gammaherpesvirus engineered with a mutation in the major immediate-early transactivator protein RTA. Complementation with codon-shuffled RTA constructs did not yield any WT revertant virus, a sharp contrast to WT virus contamination frequently observed during complementation with an unmodified helper gene. We further demonstrate the importance of eliminating WT virus contamination in an animal model of gammaherpesvirus lethality. We propose complementation by codon shuffling as a means to produce replication-defective or attenuated viruses. This method has immediate utility for investigating roles of essential genes in viral replication and will better enable future development of herpesvirus vaccines. PMID:28287622

  14. In Situ Studies on Twin-Thickness-Dependent Distribution of Defect Clusters in Heavy Ion-Irradiated Nanotwinned Ag

    NASA Astrophysics Data System (ADS)

    Li, Jin; Chen, Y.; Wang, H.; Zhang, X.

    2017-01-01

    Recent studies have shown that twin boundaries are effective defect sinks in heavy ion irradiated nanotwinned (nt) metals. Prior in situ radiation studies on nt Ag at room temperature indicate that the accumulative defect concentration is higher in center areas in the 60-nm-thick twins, and twin boundaries are distorted and self-heal during the absorption of different types of defect clusters. In this follow-up study, we show that the spatial distribution of accumulative defect concentrations in nt metals has a clear dependence on twin thickness, and in certain cases, the trend of spatial distribution is reversed. Potential mechanisms for the counterintuitive findings are discussed.

  15. In Situ Studies on Twin-Thickness-Dependent Distribution of Defect Clusters in Heavy Ion-Irradiated Nanotwinned Ag

    NASA Astrophysics Data System (ADS)

    Li, Jin; Chen, Y.; Wang, H.; Zhang, X.

    2017-03-01

    Recent studies have shown that twin boundaries are effective defect sinks in heavy ion irradiated nanotwinned (nt) metals. Prior in situ radiation studies on nt Ag at room temperature indicate that the accumulative defect concentration is higher in center areas in the 60-nm-thick twins, and twin boundaries are distorted and self-heal during the absorption of different types of defect clusters. In this follow-up study, we show that the spatial distribution of accumulative defect concentrations in nt metals has a clear dependence on twin thickness, and in certain cases, the trend of spatial distribution is reversed. Potential mechanisms for the counterintuitive findings are discussed.

  16. Maternal and infant genetic variants, maternal periconceptional use of selective serotonin reuptake inhibitors, and risk of congenital heart defects in offspring: population based study.

    PubMed

    Nembhard, Wendy N; Tang, Xinyu; Hu, Zhuopei; MacLeod, Stewart; Stowe, Zachary; Webber, Daniel

    2017-03-06

    Objective To evaluate whether the association between maternal periconceptional use of selective serotonin reuptake inhibitors (SSRIs) and increased risk of congenital heart defects in offspring is modified by maternal or infant genetic variants in folate, homocysteine, or transsulfuration pathways.Design Population based study. DNA from mothers, fathers, and infants was genotyped with an Illumina GoldenGate custom single nucleotide polymorphism panel. A hybrid design based on a log linear model was used to calculate relative risks and Bayesian false discovery probabilities (BFDP) to identify polymorphisms associated with congenital heart defects modified by SSRI use.Data sources Data from the US National Birth Defects Prevention Study on 1180 liveborn infants with congenital heart defects and 1644 controls, born 1997-2008.Main outcome measures Cases included infants with selected congenital heart defects and control infants had no major defects. SSRI use was obtained from telephone interviews with mothers.Results For women who reported taking SSRIs periconceptionally, maternal SHMT1 (rs9909104) GG and AGgenotypes were associated with a 5.9 and 2.4 increased risk of select congenital heart defects in offspring, respectively, versus the AA genotype (BFDP=0.69). Compared with the AA genotype, BHMT (rs492842 and rs542852) GG and AG genotypes were associated with twice the riskof congenital heart defects (BFDP=0.74 and 0.79, respectively). MGST1 (rs2075237) CC and ACgenotypes were associated with an increased risk compared with the GG genotype (8.0 and 2.8, respectively; BFDP=0.79). Single nucleotide polymorphism in infant genes in the folate (MTHFS rs12438477), homocysteine (TRDMT1 rs6602178 and GNMT rs11752813) and transsulfuration (GSTP1 rs7941395 and MGST1 rs7294985) pathways were also associated with an increased risk of congenital heart defects.Conclusions Common maternal or infant genetic variants in folate, homocysteine, or transsulfuration pathways are

  17. Delayed primary closure of contaminated abdominal wall defects with non-crosslinked porcine acellular dermal matrix compared with conventional staged repair: a retrospective study

    PubMed Central

    2014-01-01

    Introduction Synthetic mesh has been used traditionally to repair abdominal wall defects, but its use is limited in the case of bacterial contamination. New biological materials are now being used successfully for delayed primary closure of contaminated abdominal wall defects. The costs of biological materials may prevent surgeons from using them. We compared the conventional staged repair of contaminated abdominal wall defects with a single-stage procedure using a non-crosslinked porcine acellular dermal matrix. Methods A total of 14 cases with Grade 3 contaminated abdominal wall defects underwent delayed primary closure of the abdomen using a non-crosslinked porcine acellular dermal matrix (Strattice™ Reconstructive Tissue Matrix, LifeCell Corp., Branchburg, NJ, USA). The results were compared with a group of 14 patients who had received conventional treatment for the repair of contaminated abdominal wall defects comprising a staged repair during two separate hospital admissions employing synthetic mesh. Treatment modalities, outcomes, and costs were compared. Results In all cases treated with delayed primary closure employing non-crosslinked porcine acellular dermal matrix, there were no complications related to its use. Two patients died due to unrelated events. Although treatment costs were estimated to be similar in the two groups, the patients treated with porcine acellular dermal matrix spent less time as an inpatient than those receiving conventional two-stage repair. Conclusions Delayed primary closure of contaminated abdominal wall defects using a non-crosslinked porcine acellular dermal matrix may be a suitable alternative to conventional staged repair. In our patients, it resulted in early restoration of abdominal wall function and shorter hospitalization. The costs for treating contaminated abdominal wall defects using porcine acellular dermal matrix during a single hospital admission were not higher than costs for conventional two-stage repair

  18. A clinical study on the efficacy of hydroxyapatite - Bioactive glass composite granules in the management of periodontal bony defects

    PubMed Central

    Debnath, Tirthankar; Chakraborty, Abhijit; Pal, Tamal Kanti

    2014-01-01

    Background: In periodontal regeneration, several alloplastic materials are being used with a goal to reconstruct new osseous tissue in the infrabony defect sites. The present study was undertaken to evaluate the efficacy of hydroxyapatite–bioactive glass (HA:BG) composite granules in the management of periodontal bony defects. Materials and Methods: A randomized control study was conducted. Subjects with infrabony defects were divided into three groups. Test Group 1 (n = 10): Defect site was treated with HA:BG, with a biodegradable membrane. Test Group 2 (n = 10): Defect site was treated with HAP, with a biodegradable membrane. Control group (n = 10): Defect site was treated with open flap debridement with a biodegradable membrane Results: The healing of defects was uneventful and free of any biological complications. The gain in clinical attachment level, reduction of probing pocket depth, and defect fill were statistically significant in all three groups. TG1 sites showed significant defect fill than TG2 and CG sites. Conclusion: The performance of HA:BG was better compared to HAP and open flap debridement for the reconstruction of infrabony defects. PMID:25425821

  19. TEM study on the effects of intermediate quenching on some defects in high Jc Bi-2223 tapes

    NASA Astrophysics Data System (ADS)

    Yao, P.; Zeng, R.; Liu, H. K.; Dou, S. X.

    2000-07-01

    The microstructure of the 69-filamentary Bi-2223 tapes with high Jc of 51 000 A/cm 2 at 77 K and self-field has been studied by using the transmission electron microscopy (TEM) method. The tapes were treated by two steps sintering with intermediate quenching (IQ) and pressing [S.X. Dou, R. Zeng, T.P. Beals, H.K. Liu, Physica C 303 (1998) 21]. The diversified defects in the grains or colonies that influence the properties of the tapes were thoroughly observed by TEM. IQ is an effective method to promote the healing of the cracks, prevent the forming of the large secondary phases, and affects the critical current density of the tapes.

  20. 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

  1. Grain boundary defects initiation at the outer surface of dissimilar welds: Corrosion mechanism studies

    SciTech Connect

    Bouvier, O. De; Yrieix, B.

    1995-12-31

    Dissimilar welds located on the primary coolant system of the French PWR plants exhibit grain boundary defects in the true austenitic zones of the first buttering layer. If grain boundaries reach the interface, they can extend to the martensitic band. Those defects are filled with compact oxides. In addition, the ferritic base metal presents some pits along the interface. Nowadays, three mechanisms are proposed to explain the initiation of those defects: stress corrosion cracking, intergranular corrosion and high temperature intergranular oxidation. This paper is dealing with the study of the mechanisms involved in the corrosion phenomenon. Intergranular corrosion tests performed on different materials show that only the first buttering layer, even with some {delta} ferrite, is sensitized. The results of stress corrosion cracking tests in water solutions show that intergranular cracking is possible on a bulk material representative of the first buttering layer. It is unlikely on actual dissimilar welds where the ferritic base metal protects the first austenitic layer by galvanic coupling. Therefore, the stress corrosion cracking assumption cannot explain the initiation of the defects in aqueous environment. The results of the investigations and of the corrosion studies led to the conclusion that the atmosphere could be the only possible aggressive environment. This conclusion is based on natural atmospheric exposure and accelerated corrosion tests carried out with SO{sub 2} additions in controlled atmosphere. They both induce a severe intergranular corrosion on true sensitized austenitic materials.

  2. Exploring the microbiota of the red-brown defect in smear-ripened cheese by 454-pyrosequencing and its prevention using different cleaning systems.

    PubMed

    Guzzon, Raffaele; Carafa, Ilaria; Tuohy, Kieran; Cervantes, Gonzalo; Vernetti, Luca; Barmaz, Andrea; Larcher, Roberto; Franciosi, Elena

    2017-04-01

    Red-brown pigmentation can occasionally form in smeared-ripened cheese such as Fontina during the ripening process. This reaction is due to over-development of the typical microbiota present on the rind. Previous studies have demonstrated the relationship between red-brown pigmentation and the traditional utilization of wooden shelves during cheese ripening. The first part of the paper focuses on the characterisation of yeast and bacterial microbiota: plate counts and 454-pyrosequencing were performed in spoiled (n = 6) and non-spoiled cheeses (n = 6) and on the wooden shelves used during ripening. The second part shows different systems tested for cleaning the wooden shelves and avoiding the development of the red-brown defect in cheese: washing with hot water and ozone treatment. Actinobacteria, dominated on the wooden shelves, suggesting to be responsible for the red-brown pigmentation; they were also found in traces in the defected cheese samples. Galactomyces and Debaryomyces were the main species characterizing the yeast population, with Debaryomyces being the most dominant species on the shelves used during ripening of the red-brown defective cheese. Hot water treatment reduced the microbial contamination of shelves, whereas only the ozone treatment ensured complete elimination of both yeast and bacteria, resulting in the cheese rind not having the red-brown defect.

  3. 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…

  4. Effect of dolomite on the repair of bone defects in rats: histological study.

    PubMed

    Moreschi, Eduardo; Hernandes, Luzmarina; Dantas, Jailson Araujo; da Silva, Maria Angélica Raffaini Covas Pereira; Casaroto, Ana Regina; Bersani-Amado, Ciomar Aparecida

    2010-12-01

    The aim of the present study was to evaluate histologically and radiographically the tissue response to dolomite [CaMg(CO3)2] and its osteogenic potential in the repair of bone cavities in the calvaria of rats. A bone defect 10 mm in diameter and 1 mm deep was made in the calvaria of male Wistar rats. The defects were filled with dolomite, inorganic bovine bone (positive control), or coagulum (negative control). The animals were euthanized 7, 15, 30, and 60 days after surgery, and specimens were collected for radiographic and microscopic analyses. The bone defects were processed for paraffin embedding and H&E staining. The histological study revealed that dolomite stimulated a moderate inflammatory response, with programmed cell death in the first 15 days, compared to bovine bone which showed a moderate to intense acute response. In the chronic phase, the inflammatory response was characterized by the occurrence of macrophages organized as epithelioid cells in the dolomite group, and giant cells in the bovine-bone group. Fibrosis developed in all three groups; however, encapsulation of the fragments, reabsorption, and osteoconductive activity occurred only in the defects filled with bovine bone. The radiographic analysis showed that the bovine bone was most efficient in the repair of the defects, followed by the dolomite and the coagulum. This study demonstrated that the dolomite stimulated a moderate acute inflammatory response with programmed cell death, and a chronic inflammatory response by means of the phagocytic mononuclear system. Although osteo-conductive activity was not shown, the dolomite favored the repair process, compared to the coagulum group.

  5. Native Point Defects in GaN: A Hybrid-Functional Study

    NASA Astrophysics Data System (ADS)

    Diallo, I. C.; Demchenko, D. O.

    2016-12-01

    We present a systematic study of properties of common native point defects in GaN based on hybrid density-functional calculations. These defects include vacancies, interstitials, antisites, and common complexes. Using configuration coordinate diagrams, we estimate the likelihood of defects to be radiative or nonradiative. Our results show that gallium vacancies exhibit a large magnetic moment in the neutral charge state and are most likely nonradiative. This is in contrast to nitrogen vacancies, which are probable sources of the experimentally observed green-luminescence band peaking at 2.35 eV in undoped GaN. We also show that infrared photoluminescence (PL) bands that are created by 2.5-MeV electron irradiation in GaN can be explained by the formation of native defects. Namely, the interstitial gallium is likely to be responsible for the narrow infrared PL band centered around 0.85 eV, with a phonon fine structure at 0.88 eV; the gallium-nitrogen divacancies are possible sources of the broad PL band with a peak at 0.95 eV.

  6. Positron annihilation study of defects in electron-irradiated single crystal zinc oxide

    NASA Astrophysics Data System (ADS)

    To, C. K.; Yang, B.; Beling, C. D.; Fung, S.; Ling, C. C.; Gong, M.

    2011-01-01

    Pressurized melt grown zinc oxide (ZnO) single crystals purchased from Cermet Inc. were irradiated by 2MeV electrons with fluence of 6x1017cm-2. Isochronal annealing from 100°C-800°C was performed on the crystals under argon and air ambience. Variable Energy Doppler Broadening Spectroscopy (VEDBS) was carried out on both the as-grown and the irradiated samples at each annealing step. The migration, agglomeration and annealing of grown-in and irradiated-introduced defects were studied. It was observed that the grown-in vacancy-type defects concentration decreased at 300°C and 600 °C. For the irradiated sample annealed in argon, the positron trapping vacancy-type defect concentration decreased at 300°C and 600°C. Further annealing the as-grown and irradiated samples in argon increased the S parameter further. For the irradiated sample annealed in air, the vacancy-type defect concentration decreases at 300°C and 700°C.

  7. 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.

  8. The contribution of chromosomal abnormalities to congenital heart defects: a population-based study.

    PubMed

    Hartman, Robert J; Rasmussen, Sonja A; Botto, Lorenzo D; Riehle-Colarusso, Tiffany; Martin, Christa L; Cragan, Janet D; Shin, Mikyong; Correa, Adolfo

    2011-12-01

    We aimed to assess the frequency of chromosomal abnormalities among infants with congenital heart defects (CHDs) in an analysis of population-based surveillance data. We reviewed data from the Metropolitan Atlanta Congenital Defects Program, a population-based birth-defects surveillance system, to assess the frequency of chromosomal abnormalities among live-born infants and fetal deaths with CHDs delivered from January 1, 1994, to December 31, 2005. Among 4430 infants with CHDs, 547 (12.3%) had a chromosomal abnormality. CHDs most likely to be associated with a chromosomal abnormality were interrupted aortic arch (type B and not otherwise specified; 69.2%), atrioventricular septal defect (67.2%), and double-outlet right ventricle (33.3%). The most common chromosomal abnormalities observed were trisomy 21 (52.8%), trisomy 18 (12.8%), 22q11.2 deletion (12.2%), and trisomy 13 (5.7%). In conclusion, in our study, approximately 1 in 8 infants with a CHD had a chromosomal abnormality. Clinicians should have a low threshold at which to obtain testing for chromosomal abnormalities in infants with CHDs, especially those with certain types of CHDs. Use of new technologies that have become recently available (e.g., chromosomal microarray) may increase the identified contribution of chromosomal abnormalities even further.

  9. Preventing postoperative congestion in reverse pedicle digital island flaps when reconstructing composite tissue defects in the fingertip: a patient series.

    PubMed

    Matsuzaki, Hironori; Kouda, Hisao; Yamashita, Haruyoshi

    2012-01-01

    For reconstructing an injured fingertip, a reverse pedicle digital island flap can restore excellent function and appearance. However, postoperative flap congestion may lead to flap necrosis. We tested a method for dissecting the vascular pedicle to prevent congestion and to provide more reliable results. Between August 2002 and December 2010, we reconstructed 14 fingertips in 13 patients (average age, 43 years; range, 24 to 68 years; 9 men). Through a small zigzag incision, the digital artery and a 4-mm-wide subcutaneous venous network were elevated in retrograde fashion to facilitate venous drainage. All flaps healed completely without severe congestion or necrosis. Slight flexion contractures remained in the PIP (mean, 12°) and DIP (mean, 14°) joints. Our procedure is simpler and more reliable than other techniques, such as adding a narrow skin bridge to the pedicle or a venous anastomosis to prevent venous congestion, and it assures the survival of the flap.

  10. Prevention

    MedlinePlus

    ... Ban For Clinicians Clinical Recognition Specimen Collection Treatment Smallpox Vaccine Guidance Infection Control: Hospital Infection Control: Home ... Mouth Infection) Poxvirus and Rabies Branch Travelers’ Health: Smallpox & Other Orthopoxvirus-Associated Infections Poxvirus Prevention Recommend on ...

  11. Light-induced creation of metastable defects in hydrogenated amorphous silicon studied by computer simulations of constant photocurrent measurements

    NASA Astrophysics Data System (ADS)

    Schmidt, J. A.; Arce, R. D.; Koropecki, R. R.; Buitrago, R. H.

    1999-02-01

    The light-induced degradation of an intrinsic hydrogenated amorphous silicon sample has been studied from the evolution of the sub-band-gap absorption coefficient. The experimental results have been modeled using detailed numerical analysis, obtaining the defect distribution within the gap for each illumination time. These results have been compared with those previously obtained from a direct deconvolution of the absorption coefficient spectra [J. A. Schmidt, R. Arce, R. H. Buitrago, and R. R. Koropecki, Phys. Rev. B 55, 9621 (1997)]. We have found, in agreement with our previous work, that (i) the defect density shows the presence of more charged than neutral defects, as predicted by the defect pool model, and (ii) the concentration of charged and neutral defects evolve with the same time dependence, thus contradicting Schumm's generalized model of defect equilibration.

  12. 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.

  13. Association of GDF1 rs4808863 with fetal congenital heart defects: a case–control study

    PubMed Central

    Zhang, Juan; Wu, Qingqing; Wang, Li; Li, Xiaofei; Ma, Yuqing; Yao, Ling

    2015-01-01

    Background Congenital heart defects (CHDs) are the most common fetal defects and the most important cause of child mortality and morbidity. Objective To investigate the association between growth/differentiation factor 1 (GDF1) polymorphisms and fetal CHDs, by evaluating the association of GDF1 rs4808863 with fetal CHDs. Design A case–control study. Setting Beijing, China. Participants We selected 124 fetuses with a CHD and a normal karyotype and normal array-based comparative genomic hybridisation analysis and compared them with 124 normal fetuses matched for gestational age and sex. Fetuses with a CHD, from 20 to 32 weeks of gestation were included. Fetuses with any chromosomal abnormalities, and fetuses from multiple pregnancies and those carried by pregnant women with chronic diseases, were excluded from this research. DNA extraction and genotyping were carried out for all cases to investigate the genotype distributions of GDF1 rs4808863. Results A significant difference was noted for the CT phenotype of GDF1 rs4808863 between the controls and the fetuses with CHDs using homozygote and heterozygote comparisons. The minor allele (T allele) of GDF1 rs4808863 was associated with an increased risk of CHD (p<0.05). A statistically significant difference between controls and fetuses with CHDs was noted in a comparison with the mutation genotype CT+TT and wild-type genotype CC (p<0.05) using dominant modal analysis. After stratification analysis, the CT phenotype, the minor allele (T allele) and the mutation genotype CT+TT of the rs4808863 polymorphism were associated with atrioventricular septal defect (AVSD), left ventricular outflow tract obstruction (LVOTO) and left–right laterality defects (p<0.05). Conclusions Our results suggest that the GDF1 rs4808863 polymorphism contributes to an increased risk of fetal CHDs, especially the subtypes of AVSD, LVOTO and left–right laterality defects. PMID:26656983

  14. 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

  15. 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.

  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. Genetic ablation of cyclophilin D rescues mitochondrial defects and prevents muscle apoptosis in collagen VI myopathic mice.

    PubMed

    Palma, Elena; Tiepolo, Tania; Angelin, Alessia; Sabatelli, Patrizia; Maraldi, Nadir M; Basso, Emy; Forte, Michael A; Bernardi, Paolo; Bonaldo, Paolo

    2009-06-01

    Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy are inherited muscle disorders caused by mutations of genes encoding the extracellular matrix protein collagen VI (ColVI). Mice lacking ColVI (Col6a1(-/-)) display a myopathic phenotype associated with ultrastructural alterations of mitochondria and sarcoplasmic reticulum, mitochondrial dysfunction with abnormal opening of the permeability transition pore (PTP) and increased apoptosis of muscle fibers. Treatment with cyclosporin (Cs) A, a drug that desensitizes the PTP by binding to cyclophilin (Cyp)-D, was shown to rescue myofiber alterations in Col6a1(-/-) mice and in UCMD patients, suggesting a correlation between PTP opening and pathogenesis of ColVI muscular dystrophies. Here, we show that inactivation of the gene encoding for Cyp-D rescues the disease phenotype of ColVI deficiency. In the absence of Cyp-D, Col6a1(-/-) mice show negligible myofiber degeneration, rescue from mitochondrial dysfunction and ultrastructural defects, and normalized incidence of apoptosis. These findings (i) demonstrate that lack of Cyp-D is equivalent to its inhibition with CsA at curing the mouse dystrophic phenotype; (ii) establish a cause-effect relationship between Cyp-D-dependent PTP regulation and pathogenesis of the ColVI muscular dystrophy and (iii) validate Cyp-D and the PTP as pharmacological targets for the therapy of human ColVI myopathies.

  18. 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...

  19. Tea and cancer prevention: epidemiological studies.

    PubMed

    Yuan, Jian-Min; Sun, Canlan; Butler, Lesley M

    2011-08-01

    Experimental studies have consistently shown the inhibitory activities of tea extracts on tumorigenesis in multiple model systems. Epidemiological studies, however, have produced inconclusive results in humans. A comprehensive review was conducted to assess the current knowledge on tea consumption and risk of cancers in humans. In general, consumption of black tea was not associated with lower risk of cancer. High intake of green tea was consistently associated with reduced risk of upper gastrointestinal tract cancers after sufficient control for confounders. Limited data support a protective effect of green tea on lung and hepatocellular carcinogenesis. Although observational studies do not support a beneficial role of tea intake on prostate cancer risk, phase II clinical trials have demonstrated an inhibitory effect of green tea extract against the progression of prostate pre-malignant lesions. Green tea may exert beneficial effects against mammary carcinogenesis in premenopausal women and recurrence of breast cancer. There is no sufficient evidence that supports a protective role of tea intake on the development of cancers of the colorectum, pancreas, urinary tract, glioma, lymphoma, and leukemia. Future prospective observational studies with biomarkers of exposure and phase III clinical trials are required to provide definitive evidence for the hypothesized beneficial effect of tea consumption on cancer formation in humans.

  20. 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

  1. Defect induced magnetism in highly oriented pyrolytic graphite: bulk magnetization and 19F hyperfine interaction studies.

    PubMed

    Mohanta, S K; Mishra, S N; Davane, S M; Srivastava, S K

    2012-02-29

    We have made bulk and local investigations on defect induced magnetism in highly oriented pyrolytic graphite (HOPG) irradiated with a 40 MeV carbon beam. The local magnetic response of irradiated HOPG was studied by measuring the hyperfine field of recoil implanted (19)F using γ-ray time differential perturbed angular distribution (TDPAD) measurements. While the bulk magnetic properties of the irradiated sample show features characteristic of room temperature ferromagnetism, the hyperfine field data reflect enhanced paramagnetism with no indication of long range magnetic ordering. The experimental studies are further supported by ab initio density functional calculations. We believe that the ferromagnetic response in irradiated HOPG arises mostly from defect induced magnetic moments of carbon atoms in the near surface region, while those deep inside the host matrix remain paramagnetic.

  2. Defect study in ZnO related structures—A multi-spectroscopic approach

    NASA Astrophysics Data System (ADS)

    Ling, C. C.; Cheung, C. K.; Gu, Q. L.; Dai, X. M.; Xu, S. J.; Zhu, C. Y.; Luo, J. M.; Zhu, C. Y.; Tam, K. H.; Djurišić, A. B.; Beling, C. D.; Fung, S.; Lu, L. W.; Brauer, G.; Anwand, W.; Skorupa, W.; Ong, H. C.

    2008-10-01

    ZnO has attracted a great deal of attention in recent years because of its potential applications for fabricating optoelectronic devices. Using a multi-spectroscopic approach including positron annihilation spectroscopy (PAS), deep level transient spectroscopy (DLTS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS), we have studied the two observed phenomena from ZnO related structures. They namely included the H 2O 2 pre-treatment induced ohmic to rectifying contact conversion on Au/ n-ZnO contact and the p-type doping by nitrogen ion implantation. The aim of the studies was to offering comprehensive views as to how the defects influenced the structures electrical and optical properties of the structures. It was also shown that PAS measurement using the monoenergetic positron beam could offer valuable information of vacancy type defects in the vertical ZnO nanorod array structure.

  3. Study of the interplay between N-graphene defects and small Pd clusters for enhanced hydrogen storage via a spill-over mechanism.

    PubMed

    Rangel, E; Sansores, E; Vallejo, E; Hernández-Hernández, A; López-Pérez, P A

    2016-12-07

    The hydrogen spill-over mechanism was studied by applying Density Functional Theory. We used small palladium clusters to act as the catalyst supported on the substrate (comprised of pyridinic and pyrrolic nitrogen doped graphene), in order to study hydrogen dissociation, migration and diffusion. Charge transfer and strong binding between the catalyst and the substrate lead to dissociated states of H2 and prevent clusters from detaching and coalescing. In dissociated cases of H2 on Pd clusters, energy barriers below 0.6 eV were found. Likewise, concerning hydrogen migration from the catalyst to the substrate, energy barrier values of 0.8 eV (pyridinic defect) and 0.5 eV (pyrrolic defect) were apparent in the case of the Pd4 cluster at full hydrogen saturation. This indicates that hydrogen dissociation and migration may occur spontaneously at room temperature. This result shows that the interaction between the defects and the small metal clusters may explain the role that defects play in hydrogen migration from the catalyst to the substrate. Subsequently, it was found that thermal desorption does not limit chemisorbed hydrogen diffusion on the substrate. This work may thus help to determine experimental strategies with the capacity to enhance hydrogen storage.

  4. 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.

  5. 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.

  6. 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.

  7. Defect studies in copper-based p-type transparent conducting oxides

    NASA Astrophysics Data System (ADS)

    Ameena, Fnu

    Among other intrinsic open-volume defects, copper vacancy (VCu) has been theoretically identified as the major acceptor in p-type Cu-based semiconducting transparent oxides, which has potential as low-cost photovoltaic absorbers in semi-transparent solar cells. A series of positron annihilation experiments with pure Cu, Cu2O, and CuO presented strong presence of VCu and its complexes in the copper oxides. The lifetime data also showed that the density of VCu was becoming higher as the oxidation state of Cu increased which was consistent with the decrease in the formation energy of VCu. Doppler broadening measurements further indicated that electrons with low momentum made more contribution to the contributed as pure Cu oxidizes to copper oxides. The metastable defects are known to be generated in Cu2O upon illumination and it has been known to affect the performance of Cu2O-based hetero-junctions used in solar cells. The metastable effect was studied using positron annihilation lifetime spectroscopy and its data showed the change in the defect population upon light exposure and the minimal effect of light-induced electron density increase in the bulk of materials to the average lifetime of the positrons. The change in the defect population is concluded to be related to the dissociation and association of VCu -- V Cu complexes. For example, the shorter lifetime under light was ascribed to the annihilation with smaller size vacancies, which explains the dissociation of the complexes with light illumination. Doppler broadening of the annihilation was independent of light illumination, which suggested that the chemical nature of the defects remained without change upon their dissociation and association -- only the size distribution of copper vacancies varied. The delafossite metal oxides, CuMIIIO2 are emerging wide-bandgap p-type semiconductors. In this research, the formation energies of structural vacancies are calculated using Van Vechten cavity model as an attempt

  8. Indium-defect interactions in FCC and BCC metals studied using the modified embedded atom method

    NASA Astrophysics Data System (ADS)

    Zacate, M. O.

    2016-12-01

    With the aim of developing a transferable potential set capable of predicting defect formation, defect association, and diffusion properties in a wide range of intermetallic compounds, the present study was undertaken to test parameterization strategies for determining empirical pair-wise interaction parameters in the modified embedded atom method (MEAM) developed by Baskes and coworkers. This report focuses on indium-solute and indium-vacancy interactions in FCC and BCC metals, for which a large set of experimental data obtained from perturbed angular correlation measurements is available for comparison. Simulation results were found to be in good agreement with experimental values after model parameters had been adjusted to reproduce as best as possible the following two sets of quantities: (1) lattice parameters, formation enthalpies, and bulk moduli of hypothetical equiatomic compounds with the NaCl crystal structure determined using density functional theory and (2) dilute solution enthalpies in metals as predicted by Miedema's semi-empirical model.

  9. DLTS study of defects in hydrogen plasma treated p-type silicon

    NASA Astrophysics Data System (ADS)

    Wu, L.; Leitch, A. W. R.

    2001-12-01

    A deep level transient spectroscopy (DLTS) study of defects found in float-zone p-type silicon exposed to a DC hydrogen plasma is reported. DLTS measurements of these samples revealed three deep levels. Two of the levels are broad, with ET- EV in the range 0.34-0.39 eV (H2) and 0.40-0.44 eV (H3); these appear as bands in the Arrhenius plot. The third level has an activation energy of 0.09 eV (H1). The variations in the capture cross-sections of H2 and H3 are believed to be strain-related. The concentration of H3 exceeds the other two levels and decreases rapidly into the samples with ∼10 15 cm -3 at a depth of 0.20 μm. H3 is tentatively ascribed to an extended defect.

  10. Thermal annealing of C ion irradiation defects in nuclear graphite studied by positron annihilation

    NASA Astrophysics Data System (ADS)

    Shi, C. Q.; Schut, H.; Li, Z. C.

    2016-01-01

    In order to investigate the thermal behaviour of radiation induced point defects in nuclear graphite, ETU10 graphite was implanted with 350 keV C+ ion to doses of 1015 and 1016 cm-2. The point defects introduced by the implantation were characterized by Positron Annihilation Doppler Broadening (PADB) and their thermal behaviour was studied during “in situ” annealing at Delft Variable Energy Positron beam (VEP). The annealing was performed for 5 minutes at temperatures ranging from 300 K (as implanted) to 1500 K in steps of 100 K. For both doses, an annealing stage at around 450 K is observed followed by a second stage around 700 K. For the high dose implantation vacancy complexes are found which are stable up to a temperature around 1400K.

  11. First-principles study on native point defects of cubic cuprite Ag2O

    NASA Astrophysics Data System (ADS)

    Yin, Yuan; Chen, Guangde; Duan, Xiangyang; Ye, Honggang; Jin, Wentao; Zhu, Youzhang; Wu, Yelong

    2016-12-01

    Using the first-principles calculations, we have systematically investigated the atomic configurations, electronic structures, formation energies and transition energies of native point defects in cuprite Ag2O. Under the conditions of Ag-rich, we find that the oxygen vacancy (VO) and the oxygen interstitial (Oi) have the lowest formation energies in p-type and n-type conditions, respectively. Silver vacancy (VAg) acts as a shallow acceptor, which has high formation energy in p-type sample. Oxygen anti-site (OAg) is the most stable state and acts as an acceptor-type point defect in the O-rich conditions. Ag interstitial (Agi) is a shallow donor, which can be formed easily in the Ag-rich conditions. Moreover, we study the band offsets of heterojunction between Ag2O in cuprite structure and ZnO, GaN, and AlN in the wurtzite structure. These results would provide guidance for the experimental studies of point defects in cuprite Ag2O.

  12. Comparative study of the transcatheter and transthoracic device closure treatments for atrial septal defect

    PubMed Central

    Chen, Qiang; Cao, Hua; Chen, Zhao-yang; Zhang, Gui-Can; Chen, Liang-wan; Xu, Fan; He, Jia-jun

    2017-01-01

    Abstract The purpose of this study was to compare patient populations, safety, feasibility, complications, and total costs of the transcatheter and transthoracic device closure treatments for secundum atrial septal defect. From January 2014 to December 2014, we enrolled 155 patients with secundum atrial septal defects in our hospital. The patients were divided into 2 groups: the 70 patients in group A underwent transcatheter device closure, and the 85 patients in group B underwent transthoracic intraoperative device closure with a right lateral mini-thoracotomy. In group A, the total occlusion rate was 94.3% immediately after the operation, 100% at 3 months, and 100% at 12 months of follow-up; the group A results were not statistically different from the group B results (94.1%, 98.8%, 98.8%, respectively). There was a statistically significant difference in the minor complication rate (P < 0.05), and there were no reported deaths. There was a greater indicated scope using the transthoracic closure device to treat atrial septal defects. In our comparative study, the patients in group B had longer intensive care unit stays and hospital stays than group A (P < 0.05). Both of the device closure treatment options for secundum atrial septal defect are safe and feasible. The transcatheter device closure approach has the advantages of more cosmetic results, less trauma, and a shorter hospital stay than the transthoracic approach. On the contrary, the transthoracic closure device is an economical alternative choice, particularly for patients who are not eligible for the transcatheter closure device. PMID:28296745

  13. Vacancy defects and defect clusters in alkali metal ion-doped MgO nanocrystallites studied by positron annihilation and photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Sellaiyan, S.; Uedono, A.; Sivaji, K.; Janet Priscilla, S.; Sivasankari, J.; Selvalakshmi, T.

    2016-10-01

    Pure and alkali metal ion (Li, Na, and K)-doped MgO nanocrystallites synthesized by solution combustion technique have been studied by positron lifetime and Doppler broadening spectroscopy methods. Positron lifetime analysis exhibits four characteristic lifetime components for all the samples. Doping reduces the Mg vacancy after annealing to 800 °C. It was observed that Li ion migrates to the vacancy site to recover Mg vacancy-type defects, reducing cluster vacancies and micropores. For Na- and K-doped MgO, the aforementioned defects are reduced and immobile at 800 °C. Coincidence Doppler broadening studies show the positron trapping sites as vacancy clusters. The decrease in the S parameter is due to the particle growth and reduction in the defect concentration at 800 °C. Photoluminescence study shows an emission peak at 445 nm and 498 nm, associated with F2 2+ and recombination of higher-order vacancy complexes. Further, annealing process is likely to dissociate F2 2+ to F+ and this F+ is converted into F centers at 416 nm.

  14. Photoluminescence Studies of Point Defects in ZnGeP_2

    NASA Astrophysics Data System (ADS)

    Giles, N. C.; Halliburton, L. E.; Schunemann, P. G.; Pollak, T. M.

    1996-03-01

    Zinc germanium diphosphide (ZnGeP_2) is a II-IV-V2 ternary chalcopyrite sem iconductor, and is a prime candidate for frequency-conversion applications in th e mid-infrared. Device performance at high powers has been hampered by a near-i nfrared absorption band. We present a photoluminescence (PL) study performed on a series of bulk ZnGeP2 single crystals grown by the horizontal gradient-fre eze technique. Two broad overlapping emission bands are observed at about 1.4 e V and 1.6 eV. PL data have been recorded as a function of temperature, excitati on power density, and excitation wavelength. An analysis of the polarization of the emitted PL reveals two distinct transitions. The PL data are correlated wi th electron paramagnetic resonance data, which identified zinc vacancies and pho sphorus vacancies as the dominant acceptor and donor centers in these samples. The PL data thus provide electronic energy levels related to these defect center s and give the crucial tie between defect identification and ab sorption measurements. A comparison between PL and paramagnetic defects in self -nucleated crystals will also be presented. Work supported by NSF (DMR-9409276) and NASA (NCCW-0051).

  15. First-principles study of point defects in chalcopyrite ZnSnP2

    NASA Astrophysics Data System (ADS)

    Kumagai, Yu; Choi, Minseok; Nose, Yoshitaro; Oba, Fumiyasu

    2014-09-01

    Chalcopyrite ZnSnP2 is an alternative photoabsorber material for solar cells because of its controllable band gap, high absorption coefficient, and earth abundant constituents. In this study we systematically investigate its native point defects including vacancies, interstitials, and antisites using first-principles calculations with the Heyd-Scuseria-Ernzerhof hybrid functional. We evaluate the defect formation energies and defect single-particle levels at the dilute limit using finite-size image-charge corrections and compare them with those reported for CuInSe2 and CuGaSe2. The most likely donors and acceptors are cation antisites, Sn-on-Zn and Zn-on-Sn, respectively. Because of their significantly low formation energies, they lead to Fermi level pinning in the band gap under any growth condition, and constrain the carrier concentration. The Sn-on-Zn antisite in the neutral charge state becomes an intrinsic DX center, a complex of the Sn interstitial and Zn vacancy, and shows a deep donor level as reported for CuGaSe2.

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

    DOE PAGES

    Xi, Jianqi; Liu, Bin; Zhang, Yanwen; ...

    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

  17. First Principles Study on Orientational Defects in Ice Ih: Effect of Adsorbates

    NASA Astrophysics Data System (ADS)

    Maşlakcı, Z.; Uras-Aytemiz, N.

    2009-04-01

    Orientational, Bjerrum, defects in ice are the intrinsic property and believed that the reason of proton conductivity in ice [1]. In this study, energy of formation and dynamics of the Bjerrum defects were investigated in the presence of small adsorbates, such as dimethyl ether, CO2 etc.. The main tool of this investigation is ab initio molecular dynamics as implemented in the density functional code QUICKSTEP [2] which is part of CP2K package [3]. A crystal slab of three bilayers of hexagonal ice containing 72 water molecules were used as a model. The energy cost for the formation of orientation defects that are solvated by adsorbates as well as trajectories calculated on DFT level will be presented. 1. Petrenko V. F. and Whitworth R. W., Physics of Ice Oxford University Press, Oxford, 1999. 2. CP2K, http://cp2k.berlios.de (2000-2004) 3. VandeVondele, J.; Krack M.; Mohamed F.; Parrinello M.; Chassaing T.; Hutter J. Comp. Phys. Comm. 2005, 167, 103.

  18. Behavior of bioactive glass-ceramic implanted into long bone defects: a scintigraphic study.

    PubMed

    Sponer, Pavel; Urban, Karel; Urbanová, Elen; Karpas, Karel; Mathew, Pradeep George

    2010-01-01

    The purpose of the study was to assess the long-term behavior and incorporation of the bioactive oxyhydroxyapatite glass-ceramic used to fill defects of long bones after curettage of bone cysts in 17 patients. The method of evaluation was a three-phase bone scintigraphy combined with radiographic and clinical evaluation. At a mean follow-up of 7 years, the glass-ceramic material had been completely incorporated. Mean uptake ratio was 1.31+/-0.25 after implantation of glass-ceramic in the metaphyseal region and 2.07+/-0.62 after implantation of glass-ceramic in the diaphyseal region (P<0.05). Mean uptake ratio was 1.40+/-0.30 in patients without persistent pain and 2.07+/-0.69 in patients who complained of pain in the area of synthetic filling (P<0.05). The bioactive glass-ceramic can be implanted into the metaphyseal defects of long bones, but this material is not suitable for filling the diaphyseal defects.

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

    PubMed

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

    2011-01-01

    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., F(0), F(+), F(2+) 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 F(2+)-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.

  20. Photoluminescence study of self-interstitial clusters and extended defects in ion-implanted silicon

    NASA Astrophysics Data System (ADS)

    Giri, P. K.

    2003-12-01

    We report on the photoluminescence (PL) studies of self-interstitial (I) clustering in ion-implanted Si at various stages of post-implantation annealing. Low-temperature PL measurements on as-implanted and low-temperature annealed (up to 450°C) samples show sharp X and W bands at 1200 and 1218 nm which are attributed to I4 and I3 clusters, respectively. Annealing at 600°C shows a drastic change in the PL spectra. In case of high-energy self-ion-implanted samples, 600°C annealing produces several peaks in the range 1250-1400 nm. For longer duration annealing, two broad bands form at 1322 and 1392 nm irrespective of the ion fluence. These PL signatures are attributed to I8 clusters and/or (1 0 0) I-chains, and they are believed to be the precursor of {3 1 1} rod-like defects. For annealing above 600°C and for fluence ⩾1×1013 cm-2, a sharp PL band is observed at 1376 nm and it is attributed to {3 1 1} rod-like defects. At higher fluences, an additional broad band appears in the PL spectrum at ∼1576 nm which is related to residual ion-damage or extended defect formation. These results illustrate the potential of silicon I-clusters as a possible source of light emission from Si.

  1. 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].

  2. 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

  3. Defects in a-Si and a-Si:H: A numerical study

    NASA Astrophysics Data System (ADS)

    Knief, Simone; von Niessen, Wolfgang; Koslowski, Thorsten

    1998-08-01

    We present a numerical study of the electronic properties of various structural models of amorphous silicon and hydrogenated amorphous silicon. Starting from an ideal random network, dangling bonds, floating bonds, double bonds, microvoids, hydrogenated dangling bonds, and hydrogenated floating bonds are introduced. The concentrations of these defects can be varied independently, the amount of disorder introduced to the system is therefore strictly controllable. Two continuous random networks, the vacancy model of Duffy, Boudreaux, and Polk and the bond switching model of Wooten, Winer, and Weaire (WWW model) are investigated. For the relaxation of the structures the potentials of Keating and of Stillinger and Weber are employed. The electronic structure is described by a tight-binding Hamiltonian; the localized or extended character of the eigenstates is investigated via a scaling approach. The vacancy model shows a band gap for small defect concentrations but this fills up with increasing disorder. Similar behavior is found for the case of the other models. In general defects introduce states into the gap region of a-Si, where the dangling bonds lead to the largest density of states in the gap region for a given defect concentration. This model turns out to be unique. For small system sizes an impurity band results that dramatically changes its character for large systems above 4000 atoms to a nearly uniform density of states as observed experimentally. In a-Si:H the dangling and floating bonds are removed and a mobility gap results with a width in good agreement with experiment. The experimentally observed tailing of the band into the gap region (first linear, then exponential) is well described only for the a-Si:H model derived from the vacancy model and for very large system sizes above 4000 atoms. The WWW model does not lead to this tail behavior. Localized states are found at all band edges but states at the bottom of the conduction band are more strongly

  4. 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.

  5. New Round of Studies Begin in Phase 0/I/II Cancer Prevention Clinical Trials Program | Division of Cancer Prevention

    Cancer.gov

    The NCI Division of Cancer Prevention’s Phase 0/I/II Cancer Prevention Clinical Trials Program, also known as the Consortia for Early Phase Prevention Trials, is beginning a new round of studies in the effort toward systematic early clinical development of promising preventive agents for people at increased risk of developing cancer. Infographic Highlight New Round of Studies Begin in Phase 0/I/II Cancer Prevention Clinical Trials Program |

  6. 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.

  7. Nutritional and genetic determinants of vitamin B and homocysteine metabolisms in neural tube defects: a multicenter case-control study.

    PubMed

    Candito, Mirande; Rivet, Romain; Herbeth, Bernard; Boisson, Catherine; Rudigoz, René-Charles; Luton, Dominique; Journel, Hubert; Oury, Jean-François; Roux, François; Saura, Robert; Vernhet, Isabelle; Gaucherand, Pascal; Muller, Françoise; Guidicelli, Béatrice; Heckenroth, Hélène; Poulain, Patrice; Blayau, Martine; Francannet, Christine; Roszyk, Laurence; Brustié, Cécile; Staccini, Pascal; Gérard, Philippe; Fillion-Emery, Nathalie; Guéant-Rodriguez, Rosa-Maria; Van Obberghen, Emmanuel; Guéant, Jean-Louis

    2008-05-01

    Neural tube defects (NTDs) are severe congenital malformations due to failure of neural tube formation in early pregnancy. The proof that folic acid prevents NTDs raises the question of whether other parts of homocysteine (Hcy) metabolism may affect rates of NTDs. This French case-control study covered: 77 women aged 17-42 years sampled prior to elective abortion for a severe NTDs (cases) and 61 women aged 20-43 years with a normal pregnancy. Plasma and erythrocyte folate, plasma B6, B12 and Hcy were tested as five polymorphisms MTHFR 677 C --> T, MTHFR 1298 A --> C, MTR 2756 A --> G, MTTR 66 A --> G and TCN2 776 C --> G. Cases had significantly lower erythrocyte folate, plasma folate, B12 and B6 concentrations than the controls, and higher Hcy concentration. The odds ratio was 2.15 (95% CI: 1.00-4.59) for women with the MTRR 66 A --> G allele and it was decreased for mothers carrying the MTHFR 1298 A --> C allele. In multivariate analysis, only the erythrocyte folate concentration (P = 0.005) and plasma B6 concentration (P = 0.020) were predictors. Red cell folate is the main determinant of NTDs in France. Folic acid supplement or flour fortification would prevent most cases. Increased consumption of vitamins B12 and B6 could contribute to the prevention of NTDs. Genetic polymorphisms played only a small role. Until folic acid fortification becomes mandatory, all women of reproductive age should consume folic acid in a multivitamin that also contains B12 and B6.

  8. Study on the Microwave Transmission Characteristics of a Three-Dimensional Electromagnetic Bandgap Structure with Coupled Defects

    NASA Astrophysics Data System (ADS)

    Chen, Shibin; Li, Dichen; Tian, Xiaoyong; Han, Haoxue; Wu, Haihua

    2012-03-01

    The influence of a vertical coupled defect on the localized properties of a diamond electromagnetic bandgap (EBG) structure has been studied in the present research. The diamond EBG structure with a cavity defect was fabricated by stereolithography and gel-casting processes with alumina slurry. The resonant peaks of two kinds of defects were compared by measuring their microwave transmission characteristics using a network analyzer. A higher quality factor ( Q) was obtained for the diamond EBG structure with a vertical coupled defect, and the transmission efficiency of resonant peak was improved by 29.6% in comparison with a single defect. Experimental results agreed with the simulation results. These microwave transmission characteristics of the three-dimensional (3D) EBG structures indicate that they can be applied in microwave devices to improve transmission efficiency.

  9. Structures and Energetics of Defects: A Comparative Study of 3C- and 4H-SiC

    SciTech Connect

    Gao, Fei; Posselt, Matthias; Belko, V; Zhang, Yanwen; Weber, William J.

    2004-05-01

    The structures, formation energies and stable configurations of elementary defects (vacancies, antisite defects and self interstitials) in 3C- and 4H-SiC are studied using classical molecular dynamics simulation with a recently developed interatomic potential. The defect structures in 3C-SiC are relatively simple, but those in 4H-SiC are more complicated. The interstitials between hexagonal and trigonal rings are characteristic for 4H-SiC and other hexagonal polytypes, but not for 3C-SiC. The number of non-equivalent defects in 4H-SiC is much higher than that in 3C-SiC, and a considerable difference is found for some complex and anisotropic defects, in particular for the dumbbells D1Si-Si, D1Si-C and D2Si-C. The lattice deformation beyond the first nearest neighbor shell, which depends strongly on the polytype structure, plays an important role on these effects. However, the polytypism does not have a significant influence on the structure and energetics of the more compact and isotropic defects, such as vacancies and antisite defects. Despite the complexity of defect configurations, the tetrahedral interstitials have very similar properties in 3C- and 4H-SiC because their first, second and third nearest neighbor shells are identical.

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

    DOE PAGES

    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

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

    SciTech Connect

    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 free 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.

  12. Assessment of the LED phototherapy on femoral bone defects of ovariectomized rats: a Raman spectral study.

    PubMed

    Aciole, Jouber Mateus dos Santos; de Castro, Isabele Cardoso Vieira; Soares, Luiz Guilherme Pinheiro; Barbosa, Artur Felipe Santos; Aciole, Gilberth Tadeu dos Santos; Silveira, Landulfo; Pinheiro, Antonio L B

    2014-05-01

    Osteoporosis is a disease characterized by the reduction of bone mineral density. LED wavelengths seem to have similar photo-stimulating effects to laser light. The aim of this study was to assess the Raman shifts: ∼ 960 (phosphate hydroxyapatite), ∼ 1,070 (carbonate hydroxyapatite), and ∼ 1,454 cm (-1) (lipids and proteins) on bone defects of ovariectomized rats treated or not with LED phototherapy (LED-PT). Thirty female rats were divided into four groups (Basal, OVX, OVX+Clot, and OVX+Clot+LED), then subdivided into two subgroups (15 and 30 days after surgery). Osteoporosis induction by ovariectomy (OVX) was performed in all groups, except for the normal basal group. Following development of osteoporosis, one surgical bone defect (5 mm(2)) was created on the femur of each animal. Defects were irradiated with LED light (λ = 850 ± 10 nm, P = 150 mW, CW, Ф = 0.5 cm(2), 20.4 J/cm(2) per session, t = 128 s, 163.2 J/cm(2) per treatment) at 48 h interval during 2 weeks. Raman measurements were taken at the surface of the defects 30 days after surgery. Significant difference between groups Basal, OVX+Clot, and OVX+Clot+LED for the peaks at ∼ 960 (p ≤ 0.001; 15 and 30 days), ∼ 1,070 (p ≤ 0.001; 15 and 30 days), and ∼ 1,450 cm(-1) (p = 0.002; 15 days; p = 0.004; 30 days) were detected. In addition, statistical differences were obtained between groups OVX, OVX+Clot, and OVX+Clot+LED for these same peaks at all time points (p ≤ 0.001). At 15 and 30 days, there were statistical differences between groups OVX+Clot and OVX+Clot+LED for the peaks at ∼ 960 (p ≤ 0.001), ∼ 1,070 (p ≤ 0.001; p = 0.003), and ∼ 1,450 cm(-1) (p ≤ 0.001; p = 0.002). The results of this study are indicative that infrared LED-PT improved the deposition of HA on bone defects of ovariectomized rats.

  13. In situ study of defect migration kinetics and self-healing of twin boundaries in heavy ion irradiated nanotwinned metals.

    PubMed

    Li, J; Yu, K Y; Chen, Y; Song, M; Wang, H; Kirk, M A; Li, M; Zhang, X

    2015-05-13

    High energy particles introduce severe radiation damage in metallic materials, such as Ag. Here we report on the study on twin boundary (TB) affected zone in irradiated nanotwinned Ag wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. In situ studies also reveal surprising resilience and self-healing of TBs in response to radiation. This study provides further support for the design of radiation-tolerant nanotwinned metallic materials.

  14. 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.

  15. Assessment of visual space recognition in patients with visual field defects using head mounted display (HMD) system: case study with severe visual field defect.

    PubMed

    Sugihara, Shunichi; Tanaka, Toshiaki; Miyasaka, Tomoya; Izumi, Takashi; Shimizu, Koichi

    2013-01-01

    For the quantitative assessment of visual field defects of cerebrovascular patients, we developed a new measurement system that could present various kinds of visual information to the patient. In this system, we use a head mounted display as the display device. The quantitative assessment becomes possible by adding the capability to measure the eye movement and the head movement simultaneously by means of a video apparatus of motion analysis. In our study, we examined the effectiveness of this system by applying it to a patient with serious visual field defects. The visual image of the reduced test paper was presented to the patient, the effect on his/her spatial recognition and eye movement was investigated. The results indicated the increase in the ration of visual search in the reduced side. With the reduced image, the decrease of the angular velocity of eye movement was recognized in the visual search in the defected side. In the motion analysis, the head movement was not observed while the eye movements appeared corresponding to each different conditions. This fact led us to confirm that the patient coped with this kind of test by the eye movement. In this analysis, the effectiveness and the usefulness of the developed system were confirmed that enables us to evaluate the abnormal and compensation movement of the eyes.

  16. [Allograft of cultured chondrocytes into articular cartilage defects in rabbits--experimental study of the repair of articular cartilage injuries].

    PubMed

    Tsuge, H; Sasaki, T; Susuda, K; Abe, K

    1983-08-01

    Articular cartilage defects were created by dill holes, 2 mm wide and 3 mm deep, through the articular cartilage into the subchondral bone in the patellar groove of the femur in mature rabbits. The defects received graft of cultured chondrocytes and the matrix obtained from the primary culture of chondrocytes isolated from the articular cartilage or auricular cartilage in immature rabbits. The isolated cells were cultured for 10 to 14 days. For graft, the cultured chondrocytes together with the matrix were detached from the culture chamber using rubber policemen and centrifuged. The repair of the grafted defects or defects without graft (control) was histologically studied 2 to 12 weeks after operation. The defects without the graft were progressively filled with fibrous tissue containing spindle shaped cells, fibers perpendicular to the surface, and matrix showing weak metachromasia with toluidin blue at 8 weeks. The defects received articular cartilage cell graft were occupied by new cartilage tissue consisting colonylike crumps of chondrocytes 2 weeks after operation. The crumps showed strong metachromasia with toluidin blue and strong stainability for safranin-O. By 4-8 weeks, the defects were filled with homogeneous cartilage. At 12 weeks, arrangement of the chondrocytes of the superficial layer of the new cartilage became columnar as seen in the normal articular cartilage. The defects received elastic cartilage cell graft were filled by reformed cartilage with chondrocytes surrounded by elastic fibers 2-12 weeks after operation. The results indicate that allograft of cultured chondrocytes with matrix into the articular cartilage defects accerated the repair process of the defects by formation of the new cartilage derived from the grafted chondrocytes.

  17. 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.

  18. 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.

  19. 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

  20. Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

    SciTech Connect

    Kovacs, Andras; Ney, A.; Duchamp, Martial; Ney, V.; Boothroyd, Chris; Galindo, Pedro L.; Kaspar, Tiffany C.; Chambers, Scott A.; Dunin-Borkowski, Rafal

    2013-12-23

    We have studied planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al2O3) and the Co:ZnO/Al2O3 interface structure at atomic resolution using aberration-corrected transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). Comparing Co:ZnO samples deposited by pulsed laser deposition and reactive magnetron sputtering, both exhibit extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3-4 Co:ZnO layers at the interface.. In addition, we have measured the local strain which reveals the lattice distortion around the stacking faults.

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

    DOE PAGES

    Metsanurk, E.; Tamm, A.; Caro, A.; ...

    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.

  2. Influences of Stone-Wales defects on the structure, stability and electronic properties of antimonene: A first principle study

    NASA Astrophysics Data System (ADS)

    Hu, Yonghong; Wu, Yunyi; Zhang, Shengli

    2016-12-01

    Defects are inevitably present in materials, and their existence strongly affects the fundamental physical properties of 2D materials. Here, we performed first-principles calculations to study the structural and electronic properties of antimonene with Stone-Wales defects, highlighting the differences in the structure and electronic properties. Our calculations show that the presence of a SW defect in antimonene changes the geometrical symmetry. And the band gap decreases in electronic band structure with the decrease of the SW defect concentration. The formation energy and cohesive energy of a SW defect in antimonene are studied, showing the possibility of its existence and its good stability, respectively. The difference charge density near the SW defect is explored, by which the structural deformations of antimonene are explained. At last, we calculated the STM images for the SW defective antimonene to provide more information and characters for possible experimental observation. These results may provide meaningful references to the development and design of novel nanodevices based on new 2D materials.

  3. 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.

  4. 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.

  5. Transplantation of free tibial periosteal grafts for the repair of articular cartilage defect: An experimental study

    PubMed Central

    Singh, Ravijot; Chauhan, Vijendra; Chauhan, Neena; Sharma, Sansar

    2009-01-01

    Background: Articular chondrocytes have got a long lifespan but rarely divides after maturity. Thus, an articular cartilage has a limited capacity for repair. Periosteal grafts have chondrogenic potential and have been used to repair defects in the articular cartilage. The purpose of the present study is to investigate the differentiation of free periosteal grafts in the patellofemoral joint where the cambium layer faces the subchondral bone and to investigate the applicability of periosteal grafts in the reconstruction of articular surfaces. Materials and Methods: The study was carried out over a period of 1 year on 25 adult, male Indian rabbits after obtaining permission from the institutional animal ethical committee. A full-thickness osteochondral defect was created by shaving off the whole articular cartilage of the patella of the left knee. The defect thus created was grafted with free periosteal graft. The patella of the right knee was taken as a control where no grafting was done after shaving off the articular cartilage. The first animal was used to study the normal histology of the patellar articular cartilage and periosteum obtained from the medial surface of tibial condyle. Rest 24 animals were subjected to patellectomy, 4 each at serial intervals of 2, 4, 8, 16, 32 and 48 weeks and the patellar articular surfaces were examined macroscopically and histologically. Results: The grafts got adherent to the underlying patellar articular surface at the end of 4 weeks. Microscopically, graft incorporation could be appreciated at 4 weeks. Mesenchymal cells of the cambium layer were seen differentiating into chondrocytes by the end of 4 weeks in four grafts (100%) and they were arranged in a haphazard manner. Till the end of 8 weeks, the cellular arrangement was mostly wooly. At 16 weeks, one graft (25%) had wooly arrangement of chondrocytes and three grafts (75%) had columnar formation of cells. Same percentage was maintained at 32 weeks. Four grafts (100%) at

  6. 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.

  7. Diverse types of epineural conduits for bridging short nerve defects. An experimental study in the rabbit.

    PubMed

    Ignatiadis, Ioannis A; Yiannakopoulos, Christos K; Barbitsioti, Antonia D; Avram, Adrian M; Patralexis, Haralambos G; Tsolakis, Charilaos K; Papalois, Apostolos E; Xenakis, Theodoros H; Beris, Alexandros E; Soucacos, Panayiotis N

    2007-01-01

    In this study the process of peripheral nerve regeneration through an epineural flap conduit was examined using four groups of 126 New Zealand rabbits. There were three study groups (A, B, and C) and 1 control group (D). A 10-mm long sciatic nerve defect was bridged either with 3 variations of an epineural flap (Groups A, B, and C) or with a nerve autograft (Group D). Animals from all groups were examined 21, 42, and 91 days postoperatively to evaluate nerve regeneration employing light microscopy and immunocytochemistry. Nerve regeneration was studied in transverse sections at 3, 6, and 9 mm from the proximal stump. The gastrocnemius muscle contractility was also examined prior to euthanasia at 91 days postsurgery in all groups using electromyography. Immunohistochemical, histochemical and functional evaluation showed the presence of nerve regeneration resembling the control group D, especially in group A, where an advancement epineural flap was used. In this experimental model an epineural flap can be used to bridge a nerve defect successfully.

  8. Study of Cu-related Defect States in Single-crystal CdTe

    NASA Astrophysics Data System (ADS)

    Corwine, Caroline; Sites, James; Gessert, Timothy; Metzger, Wyatt; Dippo, Pat; Duda, Anna

    2003-10-01

    We have studied single-crystal CdTe using low-temperature photoluminescence (PL) in an effort to understand the effects of copper on the deep levels, as well as the effect of a bromine methanol (BrMe) etch on subsequent copper diffusion into CdTe. In present polycrystalline CdS/CdTe solar cell technology, the use of a back contact that contains Cu is necessary to produce high-efficiency cells. However, it is not generally understood why Cu is necessary for these devices to function well. In order to obtain further advances in the efficiencies of these solar cells, it is important to know how the back contact process may affect the defect states in CdTe. PL is one tool used to study defect states. However, before PL can be used effectively for polycrystalline CdTe solar cells, relevant spectral features first must be interpreted for single-crystal CdTe. All PL in this study was taken at 4.5 K. We report on PL peaks at 1.40 and 1.45 eV, which are seen only after Cu is diffused into single-crystal CdTe.

  9. 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.

  10. 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…

  11. 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…

  12. 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…

  13. Adsorption, intercalation and diffusion of Na on defective bilayer graphene: a computational study

    NASA Astrophysics Data System (ADS)

    Yang, Shaobin; Li, Sinan; Tang, Shuwei; Shen, Ding; Dong, Wei; Sun, Wen

    2017-04-01

    The interaction between inserted/adsorbed Na and the structures of pristine and defective bilayer graphene (BLG) with Stone-Wales (SW), mono-vacancy (MV) and divacancy (DV) defects have been investigated by the first-principles calculations. The computational results show that the intercalation of Na in the interlayer of BLG with DV defects is more energetically favorable than Na adsorption on the surface. The lower formation energies of Na adsorption/intercalation on/in the BLG with DV defect reflect a stronger attraction between Na and DV defects compared with MV and SW defects. A significant charge transfer occurs from Na to near graphene layer(s) of BLG. The adsorption and intercalation of Na not only induce more significant structural distortion into the upper layer graphene with SW defect but also spin polarization for MV and DV defects. The results of migration energy barriers show that Na prefers to diffuse toward the DV site, and the diffusion outward the DV site is more difficult in comparison with the SW and MV defects. As a consequence, more Na atoms would be trapped in the region of the DV defect, leading to larger capacity than SW and MV defects.

  14. 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

  15. 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

  16. Prevention of missing data in clinical research studies.

    PubMed

    Wisniewski, Stephen R; Leon, Andrew C; Otto, Michael W; Trivedi, Madhukar H

    2006-06-01

    Missing data is a problem that is ubiquitous to all clinical studies and a source of multiple problems from an analytic point of view (reduced statistical power, increased the type I error, bias) Statistical approaches have been developed to analyze data collected from trials with missing data. Understanding and implementing the appropriate statistical technique is essential but should be differentiated from preventive approaches that are designed to reduce rates of missing data In this article, we draw attention to these preventive efforts. Seven steps to minimizing the amount of missing data are defined as documentation, training, monitoring reports, patient contact, data entry and management, pilot studies, and communication. Although the implementation of these approaches is time consuming and costly, the overall quality of the study is increased. Despite efforts devoted to areas, no study is without missing data. Once the study is completed, it is essential to assess the pattern of missing data and apply the appropriate statistical analysis.

  17. Birth Defects

    MedlinePlus

    ... how the body looks, works or both. Some birth defects like cleft lip or neural tube defects are structural problems that can be easy to see. To find others, like heart defects, doctors use special tests. Birth defects can vary from mild to severe. Some ...

  18. 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.

  19. Study of the diffusion of points defects in crystalline silicon using the kinetic ART method

    NASA Astrophysics Data System (ADS)

    Trochet, Mickael; Brommer, Peter; Beland, Laurent-Karim; Joly, Jean-Francois; Mousseau, Normand

    2013-03-01

    Because of the long-time scale involved, the activated diffusion of point defects is often studied in standard molecular dynamics at high temperatures only, making it more difficult to characterize complex diffusion mechanisms. Here, we turn to the study of point defect diffusion in crystalline silicon using kinetic ART (kART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building based on the activation-relaxation technique (ART nouveau). By generating catalogs of diffusion mechanisms and fully incorporating elastic and off-lattice effects, kART is a unique tool for characterizing this problem. More precisely, using kART with the standard Stillinger-Weber potential we consider the evolution of crystalline cells with 1 to 4 vacancies and 1 to 4 interstitials at various temperatures and to provide a detailed picture of both the atomistic diffusion mechanisms and overall kinetics in addition to identifying special configurations such as a 2-interstitial super-diffuser.

  20. A genetic association study detects haplotypes associated with obstructive heart defects.

    PubMed

    Li, Ming; Cleves, Mario A; Mallick, Himel; Erickson, Stephen W; Tang, Xinyu; Nick, Todd G; Macleod, Stewart L; Hobbs, Charlotte A

    2014-09-01

    The development of congenital heart defects (CHDs) involves a complex interplay between genetic variants, epigenetic variants, and environmental exposures. Previous studies have suggested that susceptibility to CHDs is associated with maternal genotypes, fetal genotypes, and maternal-fetal genotype (MFG) interactions. We conducted a haplotype-based genetic association study of obstructive heart defects (OHDs), aiming to detect the genetic effects of 877 SNPs involved in the homocysteine, folate, and transsulfuration pathways. Genotypes were available for 285 mother-offspring pairs with OHD-affected pregnancies and 868 mother-offspring pairs with unaffected pregnancies. A penalized logistic regression model was applied with an adaptive least absolute shrinkage and selection operator (lasso), which dissects the maternal effect, fetal effect, and MFG interaction effects associated with OHDs. By examining the association between 140 haplotype blocks, we identified 9 blocks that are potentially associated with OHD occurrence. Four haplotype blocks, located in genes MGMT, MTHFS, CBS, and DNMT3L, were statistically significant using a Bayesian false-discovery probability threshold of 0.8. Two blocks in MGMT and MTHFS appear to have significant fetal effects, while the CBS and DNMT3L genes may have significant MFG interaction effects.

  1. Indium donor/metal vacancy defect complexes in cadmium telluride studied with perturbed angular correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Griffith, John Warren

    Semi-insulating, powder samples of Cadmium Telluride (CdTe) have been studied using 111In Time Differential Perturbed Angular Correlation (PAC) Spectroscopy. The samples have been lightly doped (˜10 12 cm-3) with 111In atoms, which occupy well-defined metal (Cd) lattice sites and act as probes of the local environment. These substitutional donors form a single defect complex in CdTe. This complex has been identified and characterized as a function of temperature. Those indium probes that are not complexed occupy metal lattice sites with no defect in the local vicinity. Samples containing metal vacancy concentrations as large as 500 ppm have been prepared by a high temperature anneal and quench. The defect complex involves the trapping of a cadmium metal vacancy bound to the indium probe. The electric field gradient (EFG) experienced by probe atoms has a coupling constant of nuQ = 61.5(5) MHz and is not axially symmetric, with the asymmetry parameter given by eta = 0.16(4). It is believed that this asymmetry results from a relaxation of the chalcogen (Te) atoms adjacent to the metal vacancy, with the tellurium atom shared by the probe atom and the vacancy providing the dominant contribution. The fraction of complexed probe atoms increases as the sample temperature is decreased, and is still increasing at room temperature. Complexed fractions are reproducible on cycling within the temperature range 40 to 200°C. The binding energy of the complex has been measured to be 0.15(2) eV and is independent of metal vacancy concentration, which varies and is dependent on the details of the quench. In rapidly cooled samples, a non-equilibrium number of these defect complexes is observed. This state equilibrates with a time constant of 45(5) hours at 15°C, implying that at least one of the two constituents involved in the complex has a significant diffusion rate at this temperature. Under the assumption that vacancy diffusion mechanisms dominate at this temperature, it is

  2. Orbital dystopia due to orbital roof defect.

    PubMed

    Rha, Eun Young; Joo, Hong Sil; Byeon, Jun Hee

    2013-01-01

    We performed a retrospective review of patients who presented with delayed dystopia as a consequence of an orbital roof defect due to fractures and nontraumatic causes to search for a correlation between orbital roof defect size and surgical indications for the treatment thereof. Retrospective analyses were performed in 7 patients, all of whom presented with delayed dystopia due to orbital roof defects, between January 2001 and June 2011. The causes of orbital roof defects were displaced orbital roof fractures (5 cases), tumor (1 case), and congenital sphenoid dysplasia (1 case). All 7 patients had initially been treated conservatively and later presented with significant dystopia. The sizes of the defects were calculated on computed tomographic scans. Among the 7 patients, aspiration of cerebrospinal fluid, which caused ocular symptoms, in 1 patient with minimal displaced orbital roof and reconstruction with calvarial bone, titanium micromesh, or Medpor in 6 other patients were performed. The minimal size of the orbital roof in patients who underwent orbital roof reconstruction was 1.2 cm (defect height) x 1.0 cm (defect length), 0.94 cm(2). For all patients with orbital dystopia, displacement of the globe was corrected without any complications, regardless of whether the patient was evaluated grossly or by radiology. In this retrospective study, continuous monitoring of clinical signs and active surgical management should be considered for cases in which an orbital roof defect is detected, even if no definite symptoms are noted, to prevent delayed sequelae.

  3. Guidance for Preventing Birth Defects

    MedlinePlus

    ... some health problems for the baby, such as low birth weight. It’s never too late to quit smoking. Learn more about smoking during pregnancy » Avoid marijuana and other “street drugs”. A ... a baby who is born preterm, of low birth weight, or has other health problems, such as ...

  4. Dyslipidemia in pregnancy may contribute to increased risk of neural tube defects -a pilot study in north Indian population.

    PubMed

    Gupta, Supriya; Arora, Sarika; Trivedi, S S; Singh, Ritu

    2009-04-01

    Neural tube defects are congenital structural abnormalities of the brain and vertebral column resulting from improper or non-timely closure of the neural tube. Prevalence of neural tube defects is reported to be higher among women with diabetes mellitus and obesity. This study was designed to investigate the relation between the presence of dyslipidemia in antenatal patients and the risk of fetal neural tube defects. The present study was an observational, cross-sectional study involving 129 pregnant women in 16 to 18 weeks gestation period. Of these, 80 women had normal pregnancies and 49 were clinically high-risk cases for neural tube defects. Fasting blood samples were analyzed for blood sugar and lipid profile by enzymatic assay and alpha-fetoprotein levels using Enzyme Immunoassay. Alpha-fetoprotein (AFP) values were converted to Multiples of Median (MoM) appropriate for the gestational age. Based on AFP values, women were labeled as screen negative (AFP <2 MoM, n= 102) and screen positive (AFP > 2 MoM, n =27). Screen positive women were further evaluated by ultrasound and 21 women were found to carry a neural tube defects positive pregnancy. Statistical analysis was done on SPSS software. Body weight of the women showed a significant positive correlation with serum triglycerides, plasma sugar and AFP MoM values. A significant difference was observed in serum cholesterol levels (p= 0.038), triglycerides (p=0.001) and plasma sugar levels (p=0.002) between normal women and those with neural tube defects positive pregnancy. The Odds ratio for neural tube defects risk in dyslipidemic cases was 24.23 (CI 4.73 - 148.60) with a relative risk of 12.12. Dyslipidemia especially hypertriglyceridemia was found to be significantly associated with fetal neural tube defects.

  5. Osteoarthrosis of Temporomandibular Joint Related to the Defects of Posterior Dentition: A Retrospective Study.

    PubMed

    Levorová, Jitka; Machoň, Vladimír; Guha, Anasuya; Foltán, René

    2016-01-01

    Osteoarthrosis (OA) of temporomandibular joint (TMJ) is a progressive degenerative disease, gradually affecting cartilage, synovial membrane and bone structures. OA of TMJ clinically manifests with joint noises, pain and restricted mouth opening. In late stages, it results in severe damage of TMJ structures and development of ankylosis. Osteoarthrosis is a multifactorial disease; the occurrence is associated with TMJ overloading. The cohort included 619 patients [538 women (87%) and 81 men (13%), with average age 40.6 years (age range 8-89 years)] with TMJ disorder, who were examined in the year 2014 in Department of Dental Medicine, First Faculty of Medicine, Charles University and General University Hospital in Prague, Czech Republic. The aim of this retrospective study was to analyse, if the lack of posterior teeth (supporting teeth zones) is the main etiologic factor of osteoarthrosis of TMJ. Diagnosis of OA was established on the clinical signs and the panoramic X-ray signs. Simultaneously other etiologic factors of OA were assessed. The presence of OA changes on X-ray had 171 patients (i.e. 27.6% of the total number of 619). 17.5% from these patients with OA had defect in posterior dentition. Other aetiological factors (stress, skeletal or vertebrogenous disorders) showed higher incidence of OA changes on X-ray. Defect of posterior dentition is not negligible, but it is not the main aetiological factor for osteoarthrosis of TMJ.

  6. Small-angle neutron scattering study of radiation-induced defects in synthetic quartz

    SciTech Connect

    Lebedev, V. M. Lebedev, V. T.; Orlov, S. P.; Pevzner, B. Z.; Tolstikhin, I. N.

    2006-12-15

    The supraatomic structure of single crystals of synthetic quartz was studied by thermal neutron small-angle scattering in the initial state (dislocation densities 54 and 570 cm{sup -2}) and after irradiation in the WWR-M reactor (Petersburg Nuclear Physics Institute) by fast neutrons with energies E{sub n} > 0.1 MeV at fluences F{sub n} = 0.2 x 10{sup 17} -5 x 10{sup 18} neutrons/cm{sup 2}. It is established that fast neutrons form point, linear, and volume defects in the lattice throughout the entire volume of a sample. Large-volume structures-amorphous-phase nuclei-reach sizes of {approx}100 nm in quartz, while occupying a small total volume of {approx}0.3% even at the maximum fluence 5 x 10{sup 18} neutrons/cm{sup 2}. The main fraction of the damaged volume (up to 5%) corresponds to point (with a radius of gyration of 1-2 nm) and linear defects, giving a comparable contribution ({approx}1-4%). The extended linear structures with a radius of 2 nm, even at a moderate fluence of 7.7 x 10{sup 17} neutrons/cm{sup 2}, have a significant total length per volume unit ({approx}10{sup 11} cm/cm{sup 3}) and can form a connected network with a cell {approx}30 nm in size in the sample. Foreign atoms and molecules can migrate through channels of this network.

  7. 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.

  8. Association study of PARD3 gene polymorphisms with neural tube defects in a Chinese Han population.

    PubMed

    Gao, Yonghui; Chen, Xiaoli; Shangguan, Shaofang; Bao, Yihua; Lu, Xiaoli; Zou, Jizhen; Guo, Jin; Dai, Yaohua; Zhang, Ting

    2012-07-01

    Partitioning defective 3 homolog (PARD3) is an attractive candidate gene for screening neural tube defect (NTD) risk. To investigate the role of genetic variants in PARD3 on NTD risk, a case-control study was performed in a region of China with a high prevalence of NTDs. Total 53 single-nucleotide polymorphisms (SNPs) in PARD3 were genotyped in 224 fetuses with NTDs and in 253 normal fetuses. We found that 6 SNPs (rs2496720, rs2252655, rs3851068, rs118153230, rs10827337, and rs12218196) were statistically associated with NTDs (P < .05). After stratifying participants by NTD phenotypes, the significant association only existed in cases with anencephaly rather than spina bifida. Further haplotype analysis confirmed the association between PARD3 polymorphisms and NTD risk (global test P = 3.41e-008). Our results suggested that genetic variants in PARD3 were associated with susceptibility to NTDs in a Chinese Han population, and this association was affected by NTD phenotypes.

  9. Defect studies of Vanadium doped 4H-SiC using optical admittance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Wonwoo

    2005-03-01

    Semi-insulating SiC is an excellent candidate for a variety of applications, including microwave FET's and other devices for high power and high temperature applications. Vanadium acts as an amphoteric impurity in 4H-SiC with a V^3+/4+ acceptor level thought to be within 1 eV of the conduction band edge and a V^4+/5+ donor level known to be 1.6 eV below the conduction band edge. Vanadium is an efficient carrier trap and recombination center. We have studied vanadium doped 4H-SiC with the optical admittance spectroscopy (OAS) at room temperature. After taking into account phonon-assisted optical transitions, the estimated threshold energies can be compared with defect levels measured using thermal techniques. Compared with data reported in the literature, our results show that the defect level Ec -1.5 eV is close to the vanadium donor level and the other level Ec -0.67 eV is within the range of the value attributed to the vanadium acceptor level.

  10. 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.

  11. A numerical study of defect detection in a plaster dome ceiling using structural acoustics.

    PubMed

    Bucaro, J A; Romano, A J; Valdivia, N; Houston, B H; Dey, S

    2009-07-01

    A numerical study is carried out to evaluate the effectiveness of using measured surface displacements resulting from acoustic speaker excitation to detect and localize flaws in a domed, plaster ceiling. The response of the structure to an incident acoustic pressure is obtained at four frequencies between 100 and 400 Hz using a parallel h-p structural acoustic finite element-based code. Three ceiling conditions are modeled: the pristine ceiling considered rigidly attached to the domed-shape support, partial detachment of a segment of the plaster layer from the support, and an interior pocket of plaster deconsolidation modeled as a heavy fluid. Spatial maps of the normal displacement resulting from speaker excitation are interpreted with the help of predictions based on static analysis. It is found that acoustic speaker excitation can provide displacement levels readily detected by commercially available laser Doppler vibrometer systems. Further, it is concluded that for 1 in. thick plaster layers, detachment sizes as small as 4 cm are detectable by direct observation of the measured displacement maps. Finally, spatial structure differences are observed in the displacement maps beneath the two defect types, which may provide a wavenumber-based feature useful for distinguishing plaster detachment from other defects such as deconsolidation.

  12. 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.

  13. Understanding of the formation of shallow level defects from the intrinsic defects of lead tri-halide perovskites.

    PubMed

    Kim, Jongseob; Chung, Choong-Heui; Hong, Ki-Ha

    2016-10-05

    Organic-inorganic hybrid perovskites have unique electronic properties in which deep level defects are rarely formed. This unique defect characteristic is the source of the long carrier diffusion length. This theoretical study shows what causes this characteristic formation of shallow level defects in lead tri-halide perovskites. Comparative studies between iodides and other halides showed that deep level defect states were generated for Cl based perovskites. Longer Pb-halide bond lengths and narrower band gaps are beneficial for preventing deep level defect states. Additionally, our study shows that the formation of shallow level defects does not change even when the lattice structures of the perovskites do not reach their equilibrium structures.

  14. 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

  15. Evaluation of a bioresorbable collagen membrane of fish origin in the treatment of periodontal intrabony defects: A prospective clinical study

    PubMed Central

    Santosh Kumar, B.B.; Aruna, D.R.; Gowda, S. Vinayak; Galagali, R. Sushama

    2013-01-01

    Background: Recently, there has been interest in non-mammalian collagen sources such as fish collagen in the development of biomatrices and scaffolds for periodontal regeneration. In the present study, a novel collagen barrier membrane of fish origin was assessed in the treatment of periodontal intra-bony defects. Materials and Methods: Ten systemically healthy chronic periodontitis patients having an osseous defect in the mandibular posterior teeth were selected and following the open flap debridement, a collagen membrane was placed over the defect and the flap was sutured with interrupted sutures. Clinical parameters such as Plaque Index, Gingival Bleeding Index, probing pocket depth (PPD), relative attachment level (RAL), and recession (R) were recorded at baseline, 6 and 9 months, whereas radiographic evaluation was done to assess alveolar crestal bone level and defect depth fill at 6 and 9 months using Auto-computer aided design (ACAD) 2007 software. Statistical significance was set at 5% level of significance. Results: There was statistical significant differences with respect to periodontal clinical parameters such as Plaque Index, Gingival Bleeding Index, PPD, RAL, and gingival recession assessed at baseline, at 6 and 9 months respectively (P < 0.05), and radiographic evaluation showed a defect fill of 58.62 median % at 9 months. Conclusion: This preliminary study has shown predictable results in using fish collagen membrane, for treating periodontal intra-bony defects. Further, long-term clinical trials are needed to validate the effectiveness of this membrane. PMID:23946741

  16. Evaluation of dentinal defect formation after root canal preparation with two reciprocating systems and hand instruments: an in vitro study.

    PubMed

    Helvacioglu-Yigit, Dilek; Aydemir, Seda; Yilmaz, Ayca

    2015-03-04

    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.

  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. A study of crack propagation in metals in the presence of defects

    NASA Astrophysics Data System (ADS)

    Petucci, Justin M.

    Molecular dynamics (MD) and molecular statics (MS) simulations of crack propagation in the presence of defects in crystalline FCC metals under mode I loading are carried out on the (001)[100] crack system using the embedded atom method (EAM) interatomic potential. Substitutional impurity point defects are introduced into a 3D thin-strip slab of 160000 atoms at various distances from the crack tip. The critical load required for the initiation of crack propagation is obtained, along with the atomic level stress distribution near the crack tip. The results indicate that the critical load is dependent on the defect species, geometry, and position. When located directly at the crack tip, the defects reduce the peak internal stress, increasing the critical load relative to the defect-free system. As the defects are moved away from the crack tip the critical load goes through a minimum and approaches the value of the pure material asymptotically.

  19. Feasibility of ultrasound imaging of osteochondral defects in the ankle: a clinical pilot study.

    PubMed

    Kok, A C; Terra, M P; Muller, S; Askeland, C; van Dijk, C N; Kerkhoffs, G M M J; Tuijthof, G J M

    2014-10-01

    Talar osteochondral defects (OCDs) are imaged using magnetic resonance imaging (MRI) or computed tomography (CT). For extensive follow-up, ultrasound might be a fast, non-invasive alternative that images both bone and cartilage. In this study the potential of ultrasound, as compared with CT, in the imaging and grading of OCDs is explored. On the basis of prior CT scans, nine ankles of patients without OCDs and nine ankles of patients with anterocentral OCDs were selected and classified using the Loomer CT classification. A blinded expert skeletal radiologist imaged all ankles with ultrasound and recorded the presence of OCDs. Similarly to CT, ultrasound revealed typical morphologic OCD features, for example, cortex irregularities and loose fragments. Cartilage disruptions, Loomer grades IV (displaced fragment) and V (cyst with fibrous roof), were visible as well. This study encourages further research on the use of ultrasound as a follow-up imaging modality for OCDs located anteriorly or centrally on the talar dome.

  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. Congenital defects of sheep.

    PubMed

    Dennis, S M

    1993-03-01

    With increasing incrimination of viruses, plants, and drugs as causes of ovine congenital defects, concerted efforts are required to identify environmental teratogens. Expanding knowledge of congenital defects requires studying as many defective lambs as possible; recording and documenting; detailed diagnostic examinations; genetic analyses and chromosomal examinations, whenever possible; and field investigations. Adopting standardized classification, terminology, and diagnostic procedures should improve descriptions, diagnoses, and interdisciplinary exchange of information. That, in turn, should improve our knowledge of and diagnosis of congenital defects of sheep in the future. Finally, veterinary clinicians and diagnosticians are encouraged to take an interest in congenital defects and teratology.

  2. Feasibility study on the concept of thermal contact sensor for nanometre-level defect inspections on smooth surfaces

    NASA Astrophysics Data System (ADS)

    Shimizu, Yuki; Lu, Wenjian; Ohba, Yuta; Gao, Wei

    2014-06-01

    This paper presents a feasibility study on the concept of a thermal contact sensor that detects nanometre-scale defects on smoothly finished surfaces such as bare silicon wafers, magnetic disks and so on. The contact sensor has a thermal element, which is composed of thin-film structures with a thermally sensitive area of several tens of µm2 on its tip surface. In the proposed concept, the thermal element detects the existence of asperity-type defects on smooth surfaces by capturing frictional heats due to slight contacts between the thermal element surface and defects. During the defect detection, a gap between the thermal element surface and the smooth surface being rotated by a precision spindle would be maintained. By monitoring deviation of the electrical resistance of the thermal element while scanning the contact sensor across the rotating surface, defects on the target surface can be detected. In this paper, a fabrication process for the thermal element has been designed based on the photolithography process, and the first prototype of the thermal element has been fabricated. Results of laser exposure tests have revealed that the fabricated thermal element can detect a rate of heat supply of 10 µW, which is the same order as the rate of heat supply assumed to be generated at defect detection by the contact sensor. In addition, results of contact detection tests have confirmed the feasibility of the fabricated thermal element as a contact detection sensor.

  3. An epidemiologic study of mitochondrial membrane transporter protein gene polymorphism and risk factors for neural tube defects in Shanxi, China.

    PubMed

    Liu, Zhizhen; Xie, Jun; Luo, Tian'e; Zhang, Tao; Zhao, Xia; Zhao, Hong; Li, Peizhen

    2012-02-25

    The present study involved a questionnaire survey of 156 mothers that gave birth to children with neural tube defects or had a history of pregnancy resulting in children with neural tube defects (case group) and 156 control mothers with concurrent healthy children (control group) as well as detection of mitochondrial membrane transporter protein gene [uncoupling protein 2 (UCP2)] polymorphism. The maternal UCP2 3' untranslated region (UTR) D/D genotype and D allele frequency were significantly higher in the case group compared with the control group (odds ratio (OR) 3.233; 95% confidence interval (CI) 1.103-9.476; P = 0.040; OR: 3.484; 95% CI: for neural tube defects 2.109-5.753; P < 0.001). Univariate and multivariate logistic regression analysis of risk factors for neural tube defects showed that a maternal UCP2 3' UTR D/D genotype was negatively interacted with the mothers' consumption of frequent fresh fruit and vegetables (S = 0.007), positively interacted with the mothers' frequency of germinated potato consumption (S = 2.15) and positively interacted with the mothers' body mass index (S = 3.50). These findings suggest that maternal UCP2 3' UTR gene polymorphism, pregnancy time, consumption of germinated potatoes and body mass index are associated with an increased risk for neural tube defects in children from mothers living in Shanxi province, China. Moreover, there is an apparent gene-environment interaction involved in the development of neural tube defects in offspring.

  4. Yttrium aluminum garnet Nanoparticles with low antisite Defects studied with neutron and X-ray diffraction

    SciTech Connect

    Sang Yuanhua; Yu Dehong; Avdeev, Maxim; Qin Haiming; Wang Jiyang; Liu Hong; Lv Yaohui

    2012-08-15

    The presence of cation antisite defects is considered to be one of the most important factors determining the fluorescence, laser, and scintillation properties of rare earth-doped yttrium aluminum garnet (YAG) materials. However, no direct evidence or systematic investigation of antisite defect evolution as a function of cation composition variation in YAG has been reported in the previous literature. In this paper, we report a combined neutron and X-ray diffraction investigation on cation antisite defects performed on specially synthesized nonstoichiometric yttrium aluminum garnet nanoparticles to try to understand the defect chemistry in the YAG system. No evidence was found for Y{sub Al,16a}, Y{sub Al,24d} and Al{sub Y,24c} antisite defects in these specially fabricated samples within the limit of diffraction techniques. The results suggest that YAG materials containing low level or no antisite defects can be achieved through low temperature synthesis process. - Graphical Abstract: Through combined Rietveld refinement against both the NPD and XRD data, no or low level antisite defect exists in the low temperature synthesized YAG powders, bond lengths are changeless as a function of the nominal Y/Al ratio, nonstoichiometry has little influence on antisite defect formation. Highlights: Black-Right-Pointing-Pointer Defects investigation with combined Rietveld refinement of NPD and XRD. Black-Right-Pointing-Pointer No or less than 2at% for Y{sub Al,16a} and Y{sub Al,24d} antisite defects. Black-Right-Pointing-Pointer Nonstoichiometry has little influence on antisite defect formation.

  5. DLTS and PL studies of proton radiation defects in tin-doped FZ silicon

    NASA Astrophysics Data System (ADS)

    Simoen, E.; Claeys, C.; Privitera, V.; Coffa, S.; Kokkoris, M.; Kossionides, E.; Fanourakis, G.; Nylandsted Larsen, A.; Clauws, P.

    2002-01-01

    In this paper, deep level transient spectroscopy (DLTS) is applied to study the deep levels in tin-doped and high-energy proton irradiated n-type float-zone (FZ) silicon. The results will be compared with irradiated tin-free FZ reference material, in order to evaluate the hardening potential. It will be shown that in Sn-doped silicon (FZ:Sn), a number of additional deep levels can be observed, two of which have been identified as acceptors associated with Sn-V. Furthermore, optically active recombination centres have been probed by photoluminescence (PL) spectroscopy. The PL results confirm the reduction of electrically active radiation-defect formation in FZ:Sn. At the same time, no Sn-related optically active centres have been found so far.

  6. Thermally stimulated current studies on neutron irradiation induced defects in GaN

    NASA Astrophysics Data System (ADS)

    Kuriyama, K.; Ooi, M.; Onoue, A.; Kushida, K.; Okada, M.; Xu, Q.

    2006-03-01

    The evaluation of the neutron irradiation induced defects in GaN is studied using a thermally stimulated current (TSC) method with excitation above (below) the energy band gap using ultraviolet (blue, green, red, and infrared) emitting diodes. Annealing at 1000°C, a broad TSC spectrum for excitation by the ultraviolet light is resolved by five traps, P1 (ionization energy is 200meV), P2 (270meV), P3 (380meV), P4 (490meV), and P5 (595meV). Infrared illumination shows a remarkable reduction in TSC for the P2 and P3 traps, indicating the photoquenching behavior. The possible origins of the observed five traps are discussed.

  7. 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

  8. Density functional theory study of phase stability and defect thermodynamics in iron-oxyhydroxide mineral materials

    NASA Astrophysics Data System (ADS)

    Pinney, Nathan Douglas

    Due to their high surface area and reactivity toward a variety of heavy metal and oxyanion species of environmental concern, Fe-(oxyhydr)oxide materials play an important role in the geochemical fate of natural and anthropogenic contaminants in soils, aquifers and surface water environments worldwide. In this research, ab initio simulations describe the bulk structure, magnetic properties, and relative phase stability of major Fe-(oxyhydr)oxide materials, including hematite, goethite, lepidocrocite, and ferrihydrite.These bulk models are employed in further studies of point defect and alloy/dopant thermodynamics in these materials, allowing construction of a phase stability model that better replicates the structure and composition of real materials. Li + adsorption at the predominant goethite (101) surface is simulated using ab initio methods, offering energetic and structural insight into the binding mechanisms of metal cations over a range of surface protonation conditions.

  9. 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

  10. Evidence-Based Obesity Prevention in Childhood and Adolescence: Critique of Recent Etiological Studies, Preventive Interventions, and Policies123

    PubMed Central

    Reilly, John J.

    2012-01-01

    Prevention of obesity in childhood and adolescence remains a worthwhile and realistic goal, but preventive efforts have been beset by a number of problems, which are the subject of this review. The review draws on recent systematic reviews and evidence appraisals and has a United Kingdom (UK) perspective because there is a rich evidence base in the United Kingdom that may be helpful to obesity prevention researchers elsewhere. Recent evidence of a leveling off in child and adolescent obesity prevalence in some Western nations should not encourage the belief that the obesity prevention problem has been solved, although a better understanding of recent secular trends might be helpful for prevention strategy in future. An adequate body of evidence provides behavioral targets of preventive interventions, and there are frameworks for prioritizing these targets logically and models for translating them into generalizable interventions with a wide reach (e.g., school-based prevention interventions such as Planet Health). An improved understanding of the “energy gap” that children and adolescents experience would be helpful to the design of preventive interventions and to their tailoring to particular groups. In the United Kingdom, some recent etiological evidence has been taken as indicative of the need for paradigm shifts in obesity prevention, but this evidence from single studies has not been replicated, and paradigm shifts probably occur only rarely. Ensuring that the evidence base on etiology and prevention influences policy effectively remains one of the greatest challenges for childhood obesity researchers. PMID:22798005

  11. Comparison of techniques for transdiaphragmatic thoracic drainage after diaphragmatic defect closure in dogs: a cadaveric study.

    PubMed

    Yoon, Hun-Young; Mann, F A; Lee, Suhwon; Jeong, Soon-wuk

    2013-01-01

    Four thoracic evacuation techniques for pneumothorax elimination after diaphragmatic defect closure were compared in 40 canine cadavers. After creating a defect in the left side of the diaphragm, thoracic drainage was performed by thoracostomy tube insertion through the defect and a small (DD-SP) or large (DD-LP) puncture created in the caudal mediastinum, or through both the diaphragmatic defect and intact contralateral diaphragm with a small (DI-SP) or large (DI-LP) puncture in made in the caudal mediastinum. Differences in intrapleural pressure (IPP) between the right and left hemithoraxes after air evacuation along with differences in IPP before making a defect and after air evacuation in each hemithorax were calculated. A difference (p ≤ 0.0011) in IPP between the left and right hemithoraxes after air evacuation as well as before making a defect and after air evacuation in the right hemithorax was detected for the DD-SP group. No significant differences (p ≥ 0.0835) were observed for the DI-LP, DD-LP, or DI-SP groups. Creation of a large mediastinal puncture or thoracic evacuation through both a diaphragmatic defect and intact contralateral diaphragm can facilitate proper pneumothorax elimination bilaterally after diaphragmatic defect closure in dogs with a small puncture in the caudal mediastinum.

  12. Time trends in the prevalence and epidemiological characteristics of neural tube defects in Liaoning Province, China, 2006-2015: A population-based study.

    PubMed

    Zhang, Tie-Ning; Gong, Ting-Ting; Chen, Yan-Ling; Wu, Qi-Jun; Zhang, Yuan; Jiang, Cheng-Zhi; Li, Jing; Li, Li-Li; Zhou, Chen; Huang, Yan-Hong

    2017-02-03

    To evaluate the time trends in the prevalence of neural tube defects and all their subtypes as well as to identify the epidemiological characteristics of these malformations documented in the Liaoning Province of northeast China from 2006 to 2015. This was a population-based observational study using data from 3,248,954 live births as well as from 6217 cases of neural tube defects, 1,600 cases of anencephaly, 2,029 cases of spina bifida, 404 cases of encephalocele, and 3,008 cases of congenital hydrocephalus from 14 cities in Liaoning Province from 2006 to 2015. All analyses were conducted using SPSS software. During the observational period, the prevalence of neural tube defects, anencephaly, spina bifida, encephalocele, and congenital hydrocephalus was 19.1, 4.9, 6.2, 1.2, and 9.3 per 10,000 live births, respectively. Significantly decreasing trends were observed in the prevalence of all these malformations except for encephalocele. Notably, relatively higher prevalence rates were found in isolated compared with non-isolated malformations, with significant differences in selected characteristics (e.g., prognosis status, gestational age, and birth weight) between isolated and non-isolated cases of these malformations. The prevalence of neural tube defects showed a downward trend in Liaoning Province from 2006 to 2015. However, more attention should be focused on non-isolated cases in the future because of the severe clinical manifestations. Future prevention efforts should be strengthened to reduce the risk of these malformations, especially the non-isolated subtype, in areas with high prevalence.

  13. First principles study of defects in high-k HfO2

    NASA Astrophysics Data System (ADS)

    Wang, Baozhu; Wang, Min; Duan, Fengxia; Ren, Jie; Li, Ying; Zhou, Tiege

    2016-11-01

    Intrinsic defects and doping N, Si, Al, and Ta defects in monoclinic HfO2 were investigated by using the first-principle calculations based on density functional theory (DFT). The results show that the defects of TaHf+1, AlHf-1, VHf-4 are stable under oxygen-rich conditions; while the Hfi+4, VO3+2, NO4-1 are stable when the conditions are hafnium-rich. It is revealed that the defects under hafnium-rich conditions are easy to form, and the results also show the properties of negative -U. Defects of the thermodynamic transition levels in the Si band gap can capture or release the charge. It will result in the effect of Fermi level pinning, so it can seriously affect the stability of the device.

  14. 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

  15. Charge Carrier Trapping at Surface Defects of Perovskite Solar Cell Absorbers: A First-Principles Study.

    PubMed

    Uratani, Hiroki; Yamashita, Koichi

    2017-02-16

    The trapping of charge carriers at defects on surfaces or grain boundaries is detrimental for the performance of perovskite solar cells (PSCs). For example, it is the main limiting factor for carrier lifetime. Moreover, it causes hysteresis in the current-voltage curves, which is considered to be a serious issue for PSCs' operation. In this work, types of surface defects responsible for carrier trapping are clarified by a comprehensive first-principles investigation into surface defects of tetragonal CH3NH3PbI3 (MAPbI3). Considering defect formation energetics, it is proposed that a Pb-rich condition is preferred to an I-rich one; however, a moderate condition might possibly be the best choice. Our result paves the way for improving the performance of PSCs through a rational strategy of suppressing carrier trapping at surface defects.

  16. The Positron as a Probe for Studying Bulk and Defect Properties in Semiconductors

    NASA Astrophysics Data System (ADS)

    Dlubek, G.; Brümmer, O.

    Positron lifetime measurements are used to study various doped and undoped III-V compound semiconductors like GaAs, GaP, InAs and InP. In some as-grown crystals native vacancies (V, V) or their complexes with dopants (TeAsV, VPZnInV) are detected with maximum concentrations of a few 1018 cm-3. In undoped GaAs neutral As vacancies V are identified, the concentration of which varies locally. The vacancies have their origin in deviations from the stoichiometrie composition of the compound. They disappear at 500°C. At this temperature defects created by irradiation with fast neutrons anneal also out. The relation between the bulk positron lifetime and the density and polarization of valence electrons is analyzed. Further, the potential of the positron annihilation method in identifying and characterizing vacancy-type defects in semiconductors is discussed.Translated AbstractDas Positron als Sonde zur Untersuchung der Volumen- und Fehlstelleneigenschaften in HalbleiternPositronenlebensdauermessungen werden angewandt, um verschiedene dotierte und undotierte AIIIBV-Verbindungshalbleiter, wie GaAs, GaP, InAs und InP, zu untersuchen. In einigen Kristallen werden Leerstellen (V, V) oder ihre Komplexe mit Dotierungen (TeAsV, VPZnInV) mit maximalen Konzentrationen von einigen 1018 cm-3 nachgewiesen. In undotierten GaAs werden neutrale As-Leerstellen V identifiziert, deren Konzentration lokal variiert. Die Leerstellen haben ihren Ursprung in Abweichungen von der stöchiometrischen Zusammensetzung der Verbindung. Sie verschwinden bei 500°C. Bei dieser Temperatur heilen auch Defekte aus, welche durch Bestrahlung mit schnellen Neutronen erzeugt wurden. Die Beziehung zwischen der Positronenlebensdauer im Kristall und der Dichte und Polarisierung der Valenzelektronen wird analysiert. Weiterhin wird das Potential der Methode der Positronenannihilation zur Identifizierung und Charakterisierung leerstellenartiger Defekte in Halbleitern diskutiert.

  17. 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.

  18. Implementation salvage experiences from the Melbourne diabetes prevention study

    PubMed Central

    2012-01-01

    Background Many public health interventions based on apparently sound evidence from randomised controlled trials encounter difficulties when being scaled up within health systems. Even under the best of circumstances, implementation is exceedingly difficult. In this paper we will describe the implementation salvage experiences from the Melbourne Diabetes Prevention Study, which is a randomised controlled trial of the effectiveness and cost-effectiveness nested in the state-wide Life! Taking Action on Diabetes program in Victoria, Australia. Discussion The Melbourne Diabetes Prevention Study sits within an evolving larger scale implementation project, the Life! program. Changes that occurred during the roll-out of that program had a direct impact on the process of conducting this trial. The issues and methods of recovery the study team encountered were conceptualised using an implementation salvage strategies framework. The specific issues the study team came across included continuity of the state funding for Life! program and structural changes to the Life! program which consisted of adjustments to eligibility criteria, referral processes, structure and content, as well as alternative program delivery for different population groups. Staff turnover, recruitment problems, setting and venue concerns, availability of potential participants and participant characteristics were also identified as evaluation roadblocks. Each issue and corresponding salvage strategy is presented. Summary The experiences of conducting such a novel trial as the preliminary Melbourne Diabetes Prevention Study have been invaluable. The lessons learnt and knowledge gained will inform the future execution of this trial in the coming years. We anticipate that these results will also be beneficial to other researchers conducting similar trials in the public health field. We recommend that researchers openly share their experiences, barriers and challenges when conducting randomised controlled

  19. Preventable anesthesia mishaps: a study of human factors*

    PubMed Central

    Cooper, J.; Newbower, R.; Long, C.; McPeek, B.

    2002-01-01

    

 A modified critical-incident analysis technique was used in a retrospective examination of the characteristics of human error and equipment failure in anesthetic practice. The objective was to uncover patterns of frequently occurring incidents that are in need of careful prospective investigation. Forty seven interviews were conducted with staff and resident anesthesiologists at one urban teaching institution, and descriptions of 359 preventable incidents were obtained. Twenty three categories of details from these descriptions were subjected to computer-aided analysis for trends and patterns. Most of the preventable incidents involved human error (82%), with breathing-circuit disconnections, inadvertent changes in gas flow, and drug syringe errors being frequent problems. Overt equipment failures constituted only 14% of the total number of preventable incidents, but equipment design was indictable in many categories of human error, as were inadequate experience and insufficient familiarity with equipment or with the specific surgical procedure. Other factors frequently associated with incidents were inadequate communication among personnel, haste or lack of precaution, and distraction. Results from multi-hospital studies based on the methodology developed could be used for more objective determination of priorities and planning of specific investments for decreasing the risk associated with anesthesia. PMID:12486995

  20. Epidemiological study on cancer prevention by ginseng: are all kinds of cancers preventable by ginseng?

    PubMed Central

    Yun, T K; Choi, S Y; Yun, H Y

    2001-01-01

    In the light of experimental results, two case-control studies and one cohort study in a population of ginseng cultivation area were conducted to confirm whether ginseng has any anticarcinogenic effect on human cancers. All participants were interviewed using a standardised questionnaire to obtain the information on demographics, cigarette smoking, alcohol consumption and ginseng intake. In 905 pairs case-control study, 62% had a history of ginseng intake compared to 75% of the controls, a statistically significant difference (p<0.01). The odds ratio (OR) for cancer in relation to ginseng intake was 0.56. In extended case-control study with 1987 pairs, the ORs for cancer were 0.37 in fresh ginseng extract users, 0.57 in white ginseng extract users, 0.30 in white ginseng extract users, 0.30 in white ginseng powder users, and 0.20 in red ginseng users. Those who took fresh ginseng slices, fresh ginseng juice, and white ginseng tea, however, did not show decrease in the risk. Overall, the risk decreased as the frequency and duration of ginseng intake increased. With respect to the site of cancer, the ORs for cancers of the lip, oral cavity, pharynx, esophagus, stomach, colorectum, liver, pancreas, larynx, lung and ovary were significantly reduced by ginseng intake. Smokers with ginseng intake showed lower ORs for cancers of lung, lip, oral cavity and pharynx and liver than those without ginseng intake. In 5 yr follow- up cohort study conducted in the ginseng cultivation area, Kangwha-eup, ginseng intakers had significantly lower risk than non-intakers. As for the type of ginseng, cancer risk significantly decreased among intakers of fresh ginseng extract, alone or together with other ginseng preparations. Among 24 red ginseng intakers, no cancer death occurred during the follow-up period. The risk for stomach and lung cancers was significantly reduced by ginseng intake, showing a statistically significant dose-response relationship in each follow-up year. In

  1. The Secondary Prevention of Small Subcortical Strokes (SPS3) study

    PubMed Central

    Benavente, Oscar R.; White, Carole L.; Pearce, Lesly; Pergola, Pablo; Roldan, Ana; Benavente, Marie-France; Coffey, Christopher; McClure, Leslie A.; Szychowski, Jeff M.; Conwit, Robin; Heberling, Patricia A.; Howard, George; Bazan, Carlos; Vidal-Pergola, Gabriela; Talbert, Robert; Hart, Robert G.

    2014-01-01

    Background Small subcortical strokes, also known as lacunar strokes, comprise more than 25% of brain infarcts, and the underlying vasculopathy is the most common cause of vascular cognitive impairment. How to optimally prevent stroke recurrence and cognitive decline in S3 patients is unclear. The aim of the Secondary Prevention of Small Subcortical Strokes study (Trial registration: NCT00059306) is to define strategies for reducing stroke recurrence, cognitive decline, and major vascular events. Methods Secondary Prevention of Small Subcortical Strokes is a randomised, multicentre clinical trial (n = 3000) being conducted in seven countries, and sponsored by the US NINDS/NIH. Patients with symptomatic small subcortical strokes in the six-months before and an eligible lesion on magnetic resonance imaging are simultaneously randomised, in a 2 × 2 factorial design, to antiplatelet therapy – 325 mg aspirin daily plus 75 mg clopidogrel daily, vs. 325 mg aspirin daily plus placebo, double-blind – and to one of two levels of systolic blood pressure targets –‘intensive’ (<130 mmHg) vs. ‘usual’ (130–149 mmHg). Participants are followed for an average of four-years. Time to recurrent stroke (ischaemic or haemorrhagic) is the primary outcome and will be analysed separately for each intervention. The secondary outcomes are the rate of cognitive decline and major vascular events. The primary and most secondary outcomes are adjudicated centrally by those unaware of treatment assignment. Conclusions Secondary Prevention of Small Subcortical Strokes will address several important clinical and scientific questions by testing two interventions in patients with recent magnetic resonance imaging-defined lacunar infarcts, which are likely due to small vessel disease. The results will inform the management of millions of patients with this common vascular disorder. PMID:21371282

  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. The repair of critical-size defects with porous hydroxyapatite/polyamide nanocomposite: an experimental study in rabbit mandibles.

    PubMed

    Zhang, J C; Lu, H Y; Lv, G Y; Mo, A C; Yan, Y G; Huang, C

    2010-05-01

    This study was conducted to evaluate the healing of critical-size surgical defects after implantation of porous nano-hydroxyapatite/polyamide composite (nHA/PA) blocks based on a bilateral mandible model using adult New Zealand white rabbits. 15 rabbits were divided randomly into three groups according to the observation period: 4, 12 and 24 weeks. The defects on one side were implanted with nHA/PA blocks and the contralateral defects were kept empty as blank controls. A combination of macroscopic, radiographic, histological and histomorphometric studies were performed up to 24 weeks postoperatively and compared with normal healing. Large amounts of callus and active osteoblasts were found in the pore structure after 4 weeks of implantation, and the defects were completely occupied by neo-bone with density comparable with that of host bone at 24 weeks. Significant difference was found between nHA/PA groups and blank controls regarding X-ray opacity over the whole period and bone parameters at 4 weeks postoperation (P<0.05). The porous nHA/PA composite promotes bone formation over the extension of the defect, particularly in the early stage. Porous nHA/PA offers interesting potential for maxillofacial reconstructive procedures in load-free areas.

  4. 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.

  5. Defect study in fused silica using near field scanning optical microscopy

    SciTech Connect

    Yan, M.; Wang, L.; Siekhaus, W.; Kozlowski, M.; Yang, J.; Mohideen, U.

    1998-01-21

    Surface defects in fused silica have been characterized using Near Field Scanning Optical Microscopy (NSOM). Using total internal reflection of a p- or s- polarized laser beam, optical scattering from defects located on the surface itself as well as in the subsurface layer of polished fused silica has been measured by NSOM. The local scattering intensity has been compared with simultaneously measured surface topography. In addition, surface defects intentionally created on a fused silica surface by nano-indentation have been used to establish a correlation between optical scattering of s- and p- polarized light, surface morphology and the well known subsurface stress-field associated with nano-indentation.

  6. 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.

  7. Cancer prevention by green tea: evidence from epidemiologic studies.

    PubMed

    Yuan, Jian-Min

    2013-12-01

    In contrast to the consistent results of an inhibitory effect of green tea extracts and tea polyphenols on the development and growth of carcinogen-induced tumors in experimental animal models, results from human studies are mixed. Both observational and intervention studies have provided evidence in support of a protective role of green tea intake in the development of oral-digestive tract cancer or an inhibitory role of oral supplementation of green tea extract on a precancerous lesion of oral cavity. Evidence in support of green tea intake against the development of liver cancer risk is limited and inconsistent. An inverse association between green tea intake and lung cancer risk has been observed among never smokers but not among smokers. Although observational studies do not support a beneficial role of tea intake against the development of prostate cancer, several phase 2 clinical trials have shown an inhibitory effect of green tea extract against the progression of prostate premalignant lesions to malignant tumors. Prospective epidemiologic studies so far have not provided evidence for a protective effect of green tea consumption on breast cancer development. Current data neither confirm nor refute a definitive cancer-preventive role of green tea intake. Large randomized intervention trials on the efficacy of green tea polyphenols or extracts are required before a recommendation for green tea consumption for cancer prevention should be made.

  8. 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

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

    PubMed Central

    Ingstrup, Katja Glejsted; Wu, Chun Sen; Olsen, Jørn; Nohr, Ellen Aagaard; Bech, Bodil Hammer; Li, Jiong

    2016-01-01

    Background Maternal emotional stress during pregnancy has previously been associated with congenital neural malformations, but most studies are based on data collected retrospectively. The objective of our study was to investigate associations between antenatal maternal bereavement due to death of a close relative and neural tube defects (NTDs) in the offspring. Methods We performed a register-based cohort study including all live-born children (N = 1,734,190) from 1978–2008. Exposure was bereavement due to loss of a close relative from one year before conception to the end of the first trimester of pregnancy. The outcome was NTDs in the offspring according to the International Classification of Disease. We used multivariate logistic regression to estimate prevalence odds ratios (ORs). Results A total of 2% children were born to mothers who lost a close relative prenatally. During 30 years of follow-up, 1,115 children were diagnosed with any NTDs: spina bifida (n = 889), anencephaly (n = 85) and encephalocele (n = 164). And 23 children were diagnosed with two types of NTDs. Overall, when comparing bereaved mothers to non-bereaved mothers, no significant increased prevalence of NTDs in the offspring was seen (OR = 0.84; 95% confidence interval: 0.52–1.33). Conclusion Overall maternal bereavement in the antenatal period was not related to NTDs in liveborn offspring. PMID:27685943

  10. 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.

  11. Study on intelligent recognition detection technology of debond defects for ceramic matrix composites based on terahertz time domain spectroscopy.

    PubMed

    Ren, Jiaojiao; Li, Lijuan; Zhang, Dandan; Qiao, Xiaoli; Lv, Qiongying; Cao, Guohua

    2016-09-10

    With the wide use of high-temperature-resistant ceramic matrix composites (CMCs) in aviation and space flight, it is important to detect the quality of the bonding. This paper used terahertz (THz) time-domain spectroscopy nondestructive testing technology to inspect the bonding defects of the CMC. This paper puts forward a method-extraction method, which is applied to make samples to simulate the bonding defect of CMC by embedding polytetrafluoroethylene (PTFE) sheets with 0.12 mm thickness into the adhesive layer and extracting it after curing and presetting the bonding defects. On the basis of the classical and analytical algorithms, such as the maximum in time-domain and power spectrum integration, through further study in the THz spectral characteristics of bonding samples for CMC, we specifically introduce the upper debond coefficient, lower debond coefficient, average absorption coefficient for the frequency domain, centroid coefficient for the frequency domain, and other characteristics. By optimizing the THz detection characteristics set, as a sample, we adopt the neural network intelligent recognition algorithm to detect the upper and lower debond defects in samples and realize the intelligent identification for CMC debond defects.

  12. An evaluation of a resorbable (semirigid) GTR membrane in human periodontal intraosseous defects: A clinicoradiological re-entry study

    PubMed Central

    Gowda, Vinayak S.; Chava, Vijay; Kumara, Ajeya E. G.

    2011-01-01

    Aim: To evaluate the effectiveness of a resorbable, semi rigid guided tissue regeneration (GTR) membrane in the treatment of periodontal intraosseous defects. Settings and Design: Randomized controlled clinicoradiological re-entry study. Materials and Methods: Eight patients with bilateral, identical intraosseous defects were selected. The sides for test and control group were randomly allocated to treat either with bioresorbable semi rigid membrane (test group) or open flap debridement (control group). Radiographic analysis was done by comparing intraoral peri apical radiographs taken at baseline and at six months. Extended cone paralleling device with grid was used to standardize radiographs. Auto CAD software was used for the analysis. Statistical Analysis Used: Paired-t test. Results: On surgical reentry at six months, the mean reduction in depth of the defect at the test site was 2.63 mm. The mean gain in Relative attachment level was 1.75 mm. The control sites showed a statistically insignificant gain. The mean percentage defect fill assessed on radiographs using auto CAD software was 15.54%. Conclusion: The resorbable, semi-rigid GTR membrane can be effectively used for the treatment of human one-walled angular defects. PMID:22368366

  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. A novel anion interstitial defect structure in zinc-blende materials: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yin, Yuan; Chen, Guangde; Ye, Honggang; Duan, Xiangyang; Zhu, Youzhang; Wu, Yelong

    2016-05-01

    The low-formation energy structure of anion interstitial defect in zinc-blende materials is usually identified as the tetrahedron central structure where the anion interstitial atom is surrounded by four countercation atoms. A line-type anion interstitial defect structure AD_il , however, is found to be lower in energy than the tetrahedron central anion interstitial defect structure by first-principles calculations. By analyzing the structural and electronical characters of this line-type defect in relative compounds of zinc-blende materials, we attribute this to the electronegativity shift trends and the bond forming, which lead to the hybridization types varying from sp 3 to sp-like and ending at sp.

  15. 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.

  16. 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.

  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. 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.

  19. Defect inspection and printability study for 14 nm node and beyond photomask

    NASA Astrophysics Data System (ADS)

    Seki, Kazunori; Yonetani, Masashi; Badger, Karen; Dechene, Dan J.; Akima, Shinji

    2016-10-01

    Two different mask inspection techniques are developed and compared for 14 nm node and beyond photomasks, High resolution and Litho-based inspection. High resolution inspection is the general inspection method in which a 19x nm wavelength laser is used with the High NA inspection optics. Litho-based inspection is a new inspection technology. This inspection uses the wafer lithography information, and as such, this method has automatic defect classification capability which is based on wafer printability. Both High resolution and Litho-based inspection methods are compared using 14 nm and 7 nm node programmed defect and production design masks. The defect sensitivity and mask inspectability is compared, in addition to comparing the defect classification and throughput. Additionally, the Cost / Infrastructure comparison is analyzed and the impact of each inspection method is discussed.

  20. New Guidelines Reaffirm Prenatal Folic Acid to Curb Birth Defects

    MedlinePlus

    ... that folic acid supplements reduce the risk of neural tube defects. As it advised in 2009, the independent ... acid to prevent these potentially fatal birth defects. Neural tube defects occur when the brain or spinal cord ...

  1. Delamination initiated by a defect

    NASA Astrophysics Data System (ADS)

    Biel, A.; Toftegaard, H.

    2016-07-01

    Composite materials in wind turbines are mainly joined with adhesives. Adhesive joining is preferable since it distributes the stresses over a larger area. This study shows how a defect can influence the fracture behaviour of adhesively joined composite. Repeated experiments are performed using double cantilever beam specimens loaded with bending moments. The specimens consist of two 8 mm thick GFRP-laminates which are joined by a 3 mm thick epoxy adhesive. A thin foil close to one of the laminates is used to start the crack. For some of the specimens a defect is created by an initial load-unload operation. During this operation, a clamp is used in order to prevent crack propagation in the main direction. For the specimens without defect, the crack propagates in the middle of the adhesive layer. For the specimens with defect, the crack directly deviates into the laminate. After about 25 mm propagation in the laminate, the crack returns to the adhesive. Compared to the adhesive the fracture energy for the laminate is significantly higher.

  2. 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

  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. Electron Paramagnetic Resonance Study of Defects in γ-irradiated Marine Mussel (Mytilus galloprovincialis) and Scallop (Pecten jacobaeus) Shells

    NASA Astrophysics Data System (ADS)

    Köseoğlu, R.; Köksal, F.; Birey, M.

    2004-11-01

    EPR studies have been performed on some gamma-irradiated marine mussels (Mytilus galloprovincialis) and scallops (Pecten jacobaeus) from the families of Mytilidae and Pectinidae, respectively. Before γ-irradiation, the EPR lines of Mytilus galloprovincialis indicated the existence of Mn2+ ions, which were not observed in the powders of scallop shells. γ -irradiation induced defects in powders of Mytilus galloprovincialis shells, were attributed to orthorhombic CO-3 , axial CO3-3 , orthorhombic CO-2 , freely rotating CO-2 , freely rotating SO-2 , axial SO-3 , isotropic PO2-4 and organic free radicals. γ -irradiation induced defects in powders of Pecten jacobaeus shells were attributed to orthorhombic CO-3 , axial CO3-3 , orthorhombic CO-2 , freely rotating CO-2 , freely rotating SO-2 , and axial SO-3 free radicals. The EPR parameters of the free radicals were compared with literature data on similar defects

  5. 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.

  6. 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

  7. 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

  8. 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 ...

  9. 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.

  10. Brownian dynamics studies on DNA gel electrophoresis. II. ``Defect'' dynamics in the elongation-contraction motion

    NASA Astrophysics Data System (ADS)

    Azuma, Ryuzo

    2002-10-01

    By means of the Brownian dynamics (BD) method of simulations we have developed, we study the dynamics of individual DNA molecules which are undergoing constant field gel electrophoresis (CFGE), focusing on the relevance of the "defect" concept due to de Gennes in CFGE. The corresponding objects, which we call slack beads (s-beads), are explicitly introduced in our BD model. In equilibrium under a vanishing field, the distance between s-beads and their hopping range is found to be randomly distributed following a Poisson distribution. In strong fields, where a chain undergoes elongation-contraction motion, s-beads are observed to be alternately annihilated in elongation and created in the contraction of the chain. On the other hand, the distribution of hopping ranges of s-beads does not differ much from that in equilibrium. The results indicate that in the elongation-contraction motion of the chain, a large number of random movements of s-beads are involved. We have also confirmed that these features of s-beads agree qualitatively with those of s-monomers in the extended bond fluctuation model (EBFM) which we recently proposed. This agreement strongly supports the stochastic semilocal movement of s-monomers which we a priori introduced into the EBFM.

  11. [Salmonella typhi vaccination response study reveals defective antibody production selective IgA deficiency patient].

    PubMed

    Pleguezuelo, Daniel E; Gianelli, Carla

    2015-01-01

    Selective IgA deficiency (SIgAD) is the most prevalent immunodeficiency worldwide, progressing to common variable immunodeficiency only in few reported cases. We report the case of a Spanish female aged 22 and diagnosed of selective IgA deficiency, a long history of bronchitis, several episodes of pneumonia, bilateral bronchiectasis, normal IgG, IgM, IgG subclasses, and detectable pre-vaccination IgG antibodies against tetanus toxoid and Streptococcus pneumoniae. She was evaluated in our clinic in order to rule out common variable immunodeficiency. We observed good antibody response to tetanus toxoid, absence of circulating switched memory B cells, decreased response to pneumococcal polysaccharide antigens and a lack of response to Salmonella typhi vaccine. Most SIgAD patients presents with upper respiratory tract infections or mild diarrhea. Those with lower tract infections, pneumonia or untreatable diarrhea should follow B-cell subpopulations' study and antibody response to vaccines. Absence of response to Salmonella typhi vaccine allowed us to expose the defective antibody production.

  12. 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

  13. Defects studies in wide band gap semiconductors using optical admittance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Wonwoo; Zvanut, Mary E.

    2004-11-01

    Semi-insulating SiC and GaN are excellent candidates for a variety of applications including microwave field effect transistors and other devices for high power and high temperature applications. Vanadium doping is one way to make semi-insulating material (SI). Vanadium acts as an amphoteric impurity in 4H-SiC with a V^3+/4+ acceptor level reported to be 0.8 eV below the conduction band edge and V^5+/4+ donor level reported to be 1.6 eV below the conduction band edge. Optical admittance spectroscopy (OAS) is a technique which measures the AC capacitance and conductance in the depletion region of a Schottky diode under illumination as a function of photon energy. OAS may be used to determine the deep levels of impurities such as vanadium. We have studied the OAS spectra of SI SiC, and will discuss the relevance of the spectra we observe with respect to the deep defect levels reported in the literature.

  14. Cancer prevention by tea: Evidence from laboratory studies.

    PubMed

    Yang, Chung S; Wang, Hong; Li, Guang Xun; Yang, Zhihong; Guan, Fei; Jin, Huanyu

    2011-08-01

    The cancer preventive activities of tea (Camellia sinensis Theaceae) have been studied extensively. Inhibition of tumorigenesis by green tea extracts and tea polyphenols has been demonstrated in different animal models, including those for cancers of the skin, lung, oral cavity, esophagus, stomach, small intestine, colon, bladder, liver, pancreas, prostate, and mammary glands. Many studies in cell lines have demonstrated the modulation of signal transduction and metabolic pathways by (-)-epigallocatechin-3-gallate (EGCG), the most abundant and active polyphenol in green tea. These molecular events can result in cellular changes, such as enhancement of apoptosis, suppression of cell proliferation, and inhibition of angiogenesis. Nevertheless, the molecular mechanisms of inhibition of carcinogenesis in animals and humans remain to be further investigated. Future research directions in this area are discussed.

  15. 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.

  16. Cyclopia: An Epidemiologic Study in a Large Dataset From the International Clearinghouse of Birth Defects Surveillance and Research

    PubMed Central

    Orioli, Iêda M.; Amar, Emmanuelle; Bakker, Marian K.; Bermejo-Sánchez, Eva; Bianchi, Fabrizio; Canfield, Mark A.; Clementi, Maurizio; Correa, Adolfo; Csáky-Szunyogh, Melinda; Feldkamp, Marcia L.; Landau, Danielle; Leoncini, Emanuele; Li, Zhu; Lowry, R. Brian; Mastroiacovo, Pierpaolo; Morgan, Margery; Mutchinick, Osvaldo M.; Rissmann, Anke; Ritvanen, Annukka; Scarano, Gioacchino; Szabova, Elena; Castilla, Eduardo E.

    2015-01-01

    Cyclopia is characterized by the presence of a single eye, with varying degrees of doubling of the intrinsic ocular structures, located in the middle of the face. It is the severest facial expression of the holoprosencephaly (HPE) spectrum. This study describes the prevalence, associated malformations, and maternal characteristics among cases with cyclopia. Data originated in 20 Clearinghouse (ICBDSR) affiliated birth defect surveillance systems, reported according to a single pre-established protocol. A total of 257 infants with cyclopia were identified. Overall prevalence was 1 in 100,000 births (95%CI: 0.89–1.14), with only one program being out of range. Across sites, there was no correlation between cyclopia prevalence and number of births (r = 0.08; P=0.75) or proportion of elective termination of pregnancy (r= −0.01; P=0.97). The higher prevalence of cyclopia among older mothers (older than 34) was not statistically significant. The majority of cases were liveborn (122/200; 61%) and females predominated (male/total: 42%). A substantial proportion of cyclopias (31%) were caused by chromosomal anomalies, mainly trisomy 13. Another 31% of the cases of cyclopias were associated with defects not typically related to HPE, with more hydrocephalus, heterotaxia defects, neural tube defects, and preaxial reduction defects than the chromosomal group, suggesting the presence of ciliopathies or other unrecognized syndromes. Cyclopia is a very rare defect without much variability in prevalence by geographic location. The heterogeneous etiology with a high prevalence of chromosomal abnormalities, and female predominance in HPE, were confirmed, but no effect of increased maternal age or association with twinning was observed. PMID:22006661

  17. Cyclopia: an epidemiologic study in a large dataset from the International Clearinghouse of Birth Defects Surveillance and Research.

    PubMed

    Orioli, Iêda M; Amar, Emmanuelle; Bakker, Marian K; Bermejo-Sánchez, Eva; Bianchi, Fabrizio; Canfield, Mark A; Clementi, Maurizio; Correa, Adolfo; Csáky-Szunyogh, Melinda; Feldkamp, Marcia L; Landau, Danielle; Leoncini, Emanuele; Li, Zhu; Lowry, R Brian; Mastroiacovo, Pierpaolo; Morgan, Margery; Mutchinick, Osvaldo M; Rissmann, Anke; Ritvanen, Annukka; Scarano, Gioacchino; Szabova, Elena; Castilla, Eduardo E

    2011-11-15

    Cyclopia is characterized by the presence of a single eye, with varying degrees of doubling of the intrinsic ocular structures, located in the middle of the face. It is the severest facial expression of the holoprosencephaly (HPE) spectrum. This study describes the prevalence, associated malformations, and maternal characteristics among cases with cyclopia. Data originated in 20 Clearinghouse (ICBDSR) affiliated birth defect surveillance systems, reported according to a single pre-established protocol. A total of 257 infants with cyclopia were identified. Overall prevalence was 1 in 100,000 births (95%CI: 0.89-1.14), with only one program being out of range. Across sites, there was no correlation between cyclopia prevalence and number of births (r = 0.08; P = 0.75) or proportion of elective termination of pregnancy (r = -0.01; P = 0.97). The higher prevalence of cyclopia among older mothers (older than 34) was not statistically significant. The majority of cases were liveborn (122/200; 61%) and females predominated (male/total: 42%). A substantial proportion of cyclopias (31%) were caused by chromosomal anomalies, mainly trisomy 13. Another 31% of the cases of cyclopias were associated with defects not typically related to HPE, with more hydrocephalus, heterotaxia defects, neural tube defects, and preaxial reduction defects than the chromosomal group, suggesting the presence of ciliopathies or other unrecognized syndromes. Cyclopia is a very rare defect without much variability in prevalence by geographic location. The heterogeneous etiology with a high prevalence of chromosomal abnormalities, and female predominance in HPE, were confirmed, but no effect of increased maternal age or association with twinning was observed.

  18. [Experimental study of poly-DL-lactic acid membrane guided bone regeneration in rabbit radii bone defects].

    PubMed

    Duan, Hong; Fan, Yubo; Dou, Jun; Pei, Fuxing

    2004-10-01

    This study was conducted to observe bone regeneration guided by poly-DL-latic acid (PDLLA) membrane in rabbit radii bone defects and to explore the mechanism of the membrane guided bone regeneration (MGBR). The animal models of bony and periosteous defects were established in both radii of 40 adult New Zealand white rabbits. The left defect as the experimental side was bridged with PDLLA membrane tube, the right side as the controlled side was untreated. The specimens were collected at 2, 4, 8 and 12 weeks postoperatively. General observation, X-ray, histological observation and biomechanical examination were applied to the repair of the models of MGBR in both groups. Two weeks after operation, with much new bony callus formed outside the tube at both fragments, the membrane tube covered with connective tissues was filled with haematoma and fibrous callus. Twelve weeks after operation, the PDLLA membrane became white and its tube shape was still maintained. However, new bone callus outside the tube almost completely disappeared, and inside the tubes all radii bone defects were successfully repaired with bony union. On the controlled sides, bone defects were filled with connective tissues 2 weeks postoperatively. And 12 weeks after operation, the typical nonunion that had been formed after bone marrow canals were sealed with cortical bone. On the experimental side, the strength of the newly formed bone at the 12th week was higher than that at the 8th week (P<0.05), whereas the biomechanical examination could not be done on the controlled side. Therefore, these findings suggested that the bone regeneration could be successfully guided by PDLLA membrane, and this MGBR technique might be generally used in the treatment of bone defects and nonunion.

  19. 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…

  20. Study of program defects of 22nm nanoimprint template with an advanced e-beam inspection system

    NASA Astrophysics Data System (ADS)

    Hiraka, Takaaki; Mizuochi, Jun; Nakanishi, Yuko; Yusa, Satoshi; Sasaki, Shiho; Kurihara, Masaaki; Toyama, Nobuhito; Morikawa, Yasutaka; Mohri, Hiroshi; Hayashi, Naoya; Xiao, Hong; Kuan, Chiyan; Wang, Fei; Ma, Long; Zhao, Yan; Jau, Jack

    2009-10-01

    Nanoimprint lithography (NIL) is a candidate of alternative, low cost of ownership lithography solution for deep nano-meter device manufacturing12. For the NIL template pattern making, we have been developing the processes with 100keV SB EB writer and 50keV VSB EB writer to achieve the fine resolution of near 20nm1-7. However, inspection of nanoimprint template posed a big challenge to inspection system due to the small geometry, 1x comparing to 4x of Optical mask and EUV mask. Previous studies of nanoimprint template inspection were performed indirectly on a stamped wafer and/or on a round quartz wafer13. Electron beam inspection (EBI) systems have been widely used in semiconductor fabs in nanometer technology nodes. Most commonly EBI applications are electrical defects, or voltage contrast (VC) defects detection and monitoring8-11. In this study, we used a mask EBI system developed by Hermes Microvision, Inc. (HMI) to directly inspect a NIL template with line/space and hole patterns half pitched from 22nm to 90nm and with program defects sized from 4nm to 92nm. Capability of inspection with 10nm pixel size has been demonstrated and capability of capturing program defects sized 12nm and smaller has been shown. This study proved the feasibility of EBI as inspection solution of nanoimprint template for 22nmHP and beyond.

  1. A comparative study of combined treatment with a collagen membrane and enamel matrix proteins for the regeneration of intraosseous defects.

    PubMed

    Minabe, Masato; Kodama, Toshiro; Kogou, Tatsuji; Takeuchi, Kayo; Fushimi, Hajime; Sugiyama, Takashi; Mitarai, Eiko

    2002-12-01

    Recent clinical study shows that periodontal regeneration therapy using enamel matrix proteins (Emdogain; EMD) is expected to have the same therapeutic effect as guided tissue regeneration (GTR). However, reports on the combined effect of both therapies are limited, and the clinical significance is not definite. In this study, clinical effects were studied by comparing a combination of EMD and GTR using a collagen membrane for intrabony defects with GTR monotherapy and EMD monotherapy. Sixty-one patients with 69 intrabony defects were included. Efficacy of treatment was evaluated at 6 months and 1 year by assessment of reduction of probing depth, probing attachment gain, and radiographic bone gain. There were no statistically significant differences between presurgical soft tissue measurements and defect characteristics for the three treatment groups. The results showed no significant differences in reduction of probing depth, probing attachment gain, or radiographic bone gain between the three treatment groups at both evaluation times. The combination of GTR using a resorbable membrane for intrabony defects and EMD did not enhance the therapeutic effect compared with each monotherapy.

  2. 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.

  3. A DLTS study of defects formed in silicon during ion beam mixing

    NASA Astrophysics Data System (ADS)

    Auret, F. D.; Malherbe, J. B.; Nel, M.; Myburg, G.

    1988-12-01

    Ion beam mixing in Schottky barrier diodes (SBDs), achieved by implanting ions through the metal gate of the SBD, has been shown to cause substantial changes in its electrical properties. During the implantation structural damage is caused, both in the metal gate and in the Si substrate. In the latter this damage gives rise to electrically active defects. We report here on these defects caused by implanting 100 keV Si + ions through 400 Å thick Ni Schottky barrier diodes on n- and p-Si with doses ranging between 10 12 and 10 16 cm -2. The results obtained using deep level transient spectroscopy (DLTS) showed the presence of several implantation-induced defects. For some of them the DLTS "signatures" correspond to those of defects caused by high energy (1 Mev) electron irradiation. Further, IV and CV measurements in conjunction with isochronal annealing revealed a definite trend between the properties of the Schottky barrier diodes and the deep level defects caused by ion beam mixing.

  4. Defect-induced selective oxidation of graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Xing, Yu-heng; Lu, Peng-fei; Wang, Jian; Yang, Jin-peng; Chen, Yong-ping

    2017-02-01

    Controlled oxidation of graphene is extremely important for nanopatterning and chemical functionalization. It is generally assumed in experiments that the oxidizing agent in the liquid-phase oxidation first attacks the defective sites in carbon lattices. To explore how the oxidation in the graphene sheet first begins, we have investigated the oxidization process with the structural defect using the density functional theory. Ten reaction pathways in the frame of the transition state theory are considered. We find that the most preferential reaction locus is located at the center of defect. It has also been observed that the preexistence of hydroxyl functional group on the graphene surface substantially decrease energy barrier for oxidization. Such facilitation of oxidation due to hydroxyl can explain how the oxidation process continues after its first oxidation around defects. The uneven redistributions of electron density caused both by defect and by the hydroxyl functional group account for the mechanism of the oxidization process on graphene sheet. Our calculation fully verifies the experimental assumption and is consistent with the recent experimental observations.

  5. 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.

  6. Risk Factors of Developmental Defects of Enamel-A Prospective Cohort Study

    PubMed Central

    Wong, Hai Ming; Peng, Si-Min; Wen, Yi Feng; King, Nigel M.; McGrath, Colman P. J.

    2014-01-01

    Background and objective Current studies on the aetiology of developmental defects of enamel (DDE) are subject to recall bias because of the retrospective collection of information. Our objective was to investigate potential risk factors associated with the occurrence of DDE through a prospective cohort study. Methods Using a random community sample of Hong Kong children born in 1997, we performed a cohort study in which the subjects’ background information, medical and dental records were prospectively collected. A clinical examination to identify DDE was conducted in 2010 when the subjects were 12 years old. The central incisor, lateral incisor and first molar in each quadrant were chosen as the index teeth and were examined ‘wet’ by two trained and calibrated examiners using the modified FDI (DDE) Index. Results With a response rate of 74.9%, the 514 examined subjects had matched data for background information. Diffuse opacites were the most common type of DDE. Of the various possible aetiological factors considered, only experience of severe diseases during the period 0–3 years was associated with the occurrence of ‘any defect’ (p = 0.017) and diffuse opacities (p = 0.044). The children with experience of severe diseases before 3 years of age were 7.89 times more likely to be affected by ‘any defect’ compared with those who did not have the experience (OR 7.89; 95% CI 1.07, 58.14; p = 0.043). However, after adjusting for confounding factors, the association no longer existed. Conclusion No variables could be identified as risk factors of DDE in this Hong Kong birth cohort. PMID:25275499

  7. Riboflavin crosslinked high-density collagen gel for the repair of annular defects in intervertebral discs: An in vivo study.

    PubMed

    Grunert, Peter; Borde, Brandon H; Towne, Sara B; Moriguchi, Yu; Hudson, Katherine D; Bonassar, Lawrence J; Härtl, Roger

    2015-10-01

    Open annular defects compromise the ability of the annulus fibrosus to contain nuclear tissue in the disc space, and therefore lead to disc herniation with subsequent degenerative changes to the entire intervertebral disc. This study reports the use of riboflavin crosslinked high-density collagen gel for the repair of annular defects in a needle-punctured rat-tail model. High-density collagen has increased stiffness and greater hydraulic permeability than conventional low-density gels; riboflavin crosslinking further increases these properties. This study found that treating annular defects with crosslinked high-density collagen inhibited the progression of disc degeneration over 18 weeks compared to untreated control discs. Histological sections of FITC-labeled collagen gel revealed an early tight attachment to host annular tissue. The gel was subsequently infiltrated by host fibroblasts which remodeled it into a fibrous cap that bridged the outer disrupted annular fibers and partially repaired the defect. This repair tissue enhanced retention of nucleus pulposus tissue, maintained physiological disc hydration, and preserved hydraulic permeability, according to MRI, histological, and mechanical assessments. Degenerative changes were partially reversed in treated discs, as indicated by an increase in nucleus pulposus size and hydration between weeks 5 and 18. The collagen gel appeared to work as an instant sealant and by enhancing the intrinsic healing capabilities of the host tissue.

  8. 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.

  9. Absorption of NH3 on pristine and defected boron nitride nanosheets: A first principle study

    NASA Astrophysics Data System (ADS)

    Li, Hui; Chen, Zheng; Fang, Xiaoliang; Tie, Deyou

    2015-12-01

    Versatile functional groups can be connected to Boron Nitride nanosheet (BNNS) through Lewis acid/base interaction for targeted applications. However, there have been few experimental reports about Lewis acid attack at the N atoms on BNNS, so far as we see. VdW-DFT is employed in this paper to investigate the interaction between NH3 representing Lewis base and pristine or defected BNNS. Comparing the binding energy, separation and charge distribution of NH3 and pristine or defected BNNS systems, the distinctive defect in BNNS is found to be the key role in the absorption progress. Thus, it is supposed that the missing of Lewis acid and BNNS complex can be attributed to the absence of N vacancies and B-edges in BNNS.

  10. A qualitative study of spin polarization effect in defect tuned Co/graphene/Co nanostructures

    SciTech Connect

    Mandal, Sumit E-mail: cnssks@iacs.res.in; Saha, Shyamal K. E-mail: cnssks@iacs.res.in

    2014-10-15

    Theoretical reports predict that in contact with a ferromagnetic giant spin, spin polarization evolves in defective graphene since defects in graphene act as local spin moments. We have synthesized different Co/graphene/Co nano spin valve like structures tuning the degree of defect applying ultrasonic vibration and characterized them by Raman spectroscopy. Initially with increasing I{sub D}/I{sub G} ratio in Raman spectra, antiferromagnetic coupling between the Co nanosheets on either sides of graphene enhances leading to betterment in spin transport through graphene. But for highest I{sub D}/I{sub G}, a totally new phenomenon called antiferro quadrupolar ordering (AFQ) takes place which eventually reduces the spin polarization effect.

  11. 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.

  12. An EPR study on a new triclinic symmetry defect in neutron-irradiated FZ-silicon

    NASA Astrophysics Data System (ADS)

    En, Wu; Shu-xian, Wu; Jin-Chang, Mao; Mao-Xun, Yan; Guo-gang, Qin

    1987-01-01

    A new defect, labled as Si-PK1, has been observed with EPR (Electron Paramagnetic Resonance) in neutron irradiated FZ-Si grown in argon, hydrogen and vacuum. Its symmetry has been determined to be triclinic symmetry, the lowest possible symmetry. Si-PK1 has not been observed in CZ-Si. It is not related to any common impurities in Si, like oxygen, carbon, phosphorus and boron, and it should be an intrinsic defect. Combining with the empirical classification of g tensor, it is concluded that Si-PK1 may be a multi-vacancy cluster.

  13. A study of flatness defect in strip rolling occurred in tension unloading

    NASA Astrophysics Data System (ADS)

    Abdelkhalek, Sami; Zahrouni, Hamid; Legrand, Nicolas; Potier-Ferry, Michel

    2016-10-01

    Strips are usually fabricated under tension in tandem mill. They look flat if the tension is large and flatness control is performed via the measurement of transverse residual stress shape. Since compressive residual stresses are the main cause of geometric defect, actuator forces are changed in line to reduce or eliminate them. It is commonly supposed that strips buckle where residual stress field remain compressive. In this paper we show that this relation between residual stress fields and flatness defect is not always valid.

  14. A Roentgen-anatomic study of the relationships between conduction defects and coronary disease.

    PubMed

    Veress, G; Romoda, T; Szatmáry, L; Keltai, M; Palik, I; Gábor, G

    1979-01-01

    Intraventricular conduction defects of various types were correlated to the extent of coronary disease and to the parameters reflecting the function of the left ventricle in 125 patients who had been subjected to coronary arteriography. In the patients with conduction disturbances, coronary disease was found to be more extensive and the proportion of abnormal parameters of left ventricular function higher than in those with normal conduction. The relationship of the various conduction defects with the lesions of the individual coronary branches and with the parameters of left ventricular function are discussed in detail.

  15. Periodic DFT study of Ti deposition on defective Si(1 0 0) surfaces

    NASA Astrophysics Data System (ADS)

    Añez, Rafael; Sierraalta, Anibal; Díaz, Lenin; Bastardo, Anelisse; Coll, David

    2015-04-01

    Defective Si(1 0 0) surfaces have been used with the aim to explore from a theoretical point of view, the effect of the defects in the Ti/Si interface formation when Ti is deposited on a clean Si surface at room temperature. Results indicate that a complex mechanism occurs where the Si surface stability is an important point to take into account to obtain titanium silicides species of different thickness and Si concentration. Even at room temperature, the thickness of the Ti/Si interface depends not only of the Ti diffusion on the Si surface but also of the Si diffusion on the Ti slab deposited on the Si surface.

  16. 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.

  17. 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.…

  18. 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

  19. 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).

  20. 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

  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

    2016-09-01

    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.

  2. 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

  3. 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

  4. 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.

  5. First principles study of oxygen vacancy defects in amorphous SiO2

    NASA Astrophysics Data System (ADS)

    Yue, Yunliang; Song, Yu; Zuo, Xu

    2017-01-01

    The oxygen vacancy defects of amorphous SiO2 (a-SiO2) in different charge states are investigated by the periodic density functional theory. Five types of the positively charged configurations are obtained including the dimer, forward-oriented, puckered 4×, 5× and back-projected unpuckered configurations. The energy, geometry structure, spin density, Bader charge and Fermi contact are concerned for these systems. These defects can be regarded as the potential microscopic structures for the corresponding centers including Eα', Eγ' and Eδ' in the electron paramagnetic resonance (EPR) experiments. Then, the charge-state transitions of these defects are investigated by intentionally adding one electron to the positively charged systems. For the dimer, puckered 4× and back-projected unpuckered configurations, all of the corresponding neutral species maintain their initial types of geometry structures. For the forward-oriented configurations, the corresponding neutral species transform into the structures of the divalent Si atom. The puckered 5× configurations have the most abundant neutral species: some of them could maintain its style of the puckered 5× configurations, and some collapse to the neutral dimer or forward-oriented configurations. The dimer configurations have the lowest thermodynamic charge-state levels, and the puckered 4× configurations have the highest thermodynamic charge-state levels among the five types of configurations. This work is of benefit to identifying and controlling the oxygen defects in a-SiO2.

  6. First-principles study of the mechanism of wettability transition of defective graphene

    NASA Astrophysics Data System (ADS)

    Błoński, Piotr; Otyepka, Michal

    2017-02-01

    Hydrophobicity of graphene limits its application potential in polar media, therefore modifications of graphene wettability have been in an area of active research for many years. Recently, a reversible wettability transition of graphene has been reported (Xu et al 2014 Sci. Rep. 4 6450). The presence of undercoordinated carbon atoms in otherwise hydrophobic graphene is believed to trigger the hydrophobic to hydrophilic transition, but the underlying mechanism, especially of the reverse process, remained unclear. Using density functional theory with range-separated hybrid functional HSE06, we investigate the dissociative adsorption of up to two water molecules on the defective graphene layer containing odd number of missing lattice atoms. We show, that depending on the defect type either a full dissociation of the water molecule or a partial splitting of H2O to OH and H takes place leading to the saturation of graphene dangling bonds due to the formation of oxiranes or by hydroxyls, respectively. The dissociation barriers are significantly lower for the water dimer than for the single molecule. Our findings providing detailed insights into the remarkable differences between the reactivity of vacancy defects with water shed new light on the wettability-transition mechanism of defective graphene.

  7. Annealing studies of cluster defects in ion-implanted silicon using high resolution DLTS

    NASA Astrophysics Data System (ADS)

    Gad, M. A.; Evans-Freeman, J. H.

    2006-12-01

    High resolution Laplace deep level transient spectroscopy (LDLTS) has been applied to investigate the annealing behaviour of small cluster defects in n-type Si. The Si was implanted with either Ge or Si, with energies 1500 keV and 850 keV respectively, and doses of 1 × 10 10 cm -2. The low dose ensured that there was a minimum of carrier removal due to deep defect states after implantation. Defect states in the as-implanted samples were attributed to VO pairs, divacancies and very small interstitial cluster defects, after detailed depth profiling. LDLTS of Ge + and Si + implanted silicon shows that there are three closely spaced deep levels associated with these clusters, with energies in the region of Ec-400 meV. Samples were then isochronally annealed in very small temperature intervals up to 560 K, in situ in our high temperature measurement cryostat, and the LDLTS re-examined as a function of annealing temperature. A new deeper energy level emerges as the cluster-related signal reduces, and it is suggested that this new trap is a major recombination centre, by comparison with current-voltage data.

  8. 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.

  9. A Single Molecule Approach to Defect Studies in ZnO

    NASA Astrophysics Data System (ADS)

    Jungwirth, N. R.; Pai, Y. Y.; Chang, H. S.; Macquarrie, E. R.; Fuchs, G. D.

    2014-03-01

    Single molecule investigations are a powerful tool for understanding molecular systems with inhomogeneous behavior that is either broadened or completely washed out of ensemble measurements. Here we apply single molecule microscopy methods to defects in ZnO. In addition to its status as an emerging optoelectronic material, ZnO hosts point defects which may have useful quantum properties akin to those of nitrogen-vacancy centers in diamond, which are promising as single photon sources and solid-state qubits. We present confocal fluorescence measurements of single defects in ZnO nanoparticles and sputtered films that are selectively excited by sub-bandgap light. The resulting 560-720 nm emission often exhibits two broad spectral peaks separated by approximately 100 meV. Photon correlation measurements yield both antibunching and bunching, indicative of single photon emission from isolated defects with a metastable shelving state. Excited state lifetimes span 1-13 ns and are uncorrelated with doping concentration. We report discrete jumps in the fluorescence intensity between a bright and dark state. The dwell times are exponentially distributed in each state and the average dwell time in the bright (dark) state does (may) depend on the power of the excitation laser.

  10. 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.

  11. 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

  12. 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

  13. The Child Anxiety Prevention Study: Intervention Model and Primary Outcomes

    ERIC Educational Resources Information Center

    Ginsburg, Golda S.

    2009-01-01

    The article presents the intervention model and primary outcomes of a preventive intervention designed to reduce anxiety symptoms and prevent the onset of anxiety disorders in the offspring of parents with anxiety disorders. Participants were 40 volunteer children (mean age = 8.94 years; 45% girls; 90% Caucasian) whose parents met criteria for a…

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. A silver carp skin derived collagen in bone defect treatment-A histological study in a rat model.

    PubMed

    Hadzik, Jakub; Kubasiewicz-Ross, Paweł; Kunert-Keil, Christiane; Jurczyszyn, Kamil; Nawrot-Hadzik, Izabela; Dominiak, Marzena; Gedrange, Tomasz

    2016-11-01

    In recent years, there has been increasing interest in elaboration of novel therapeutic strategies, such as the use of the marine collagen products. Biochemical properties of marine collagen are different from those of mammalian collagen; e.g., its extremely high solubility in diluted acid. Extracts produced using low temperature techniques contain a number of small proteins and collagen with preserved triple helix structure. The aim of the study was to evaluate the influence of a new marine product Collgel(®) obtained with a unique method from a silver carp (Hypophthalmichthys molitrix) on bone defect healing in a rat study. For this purpose bone defects with diameters of 5mm were created in 15 animals and subsequently filled with Collgel combined with another commercially available material. Samples were processed for histological evaluation and a Micro-CT study was performed. Histological analysis showed new bone formation in all groups after 8 weeks. The bone formation was significantly increased in treated bone lesions compared to untreated bone tissue. However no significant difference was noted between the healing of the defects filled with xenogenic bovine derived bone substitute alone and xenogenic, bovine derived bone substitute combined with a marine delivered collagen. Finding from the histological examination was confirmed in a Micro-CT study. The study has shown that the new marine product can be used instead of conventional porcine or bovine collagen membranes in guided bone regeneration.

  1. 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. |

  2. Periconceptional Folate Deficiency and Implications in Neural Tube Defects

    PubMed Central

    Safi, J.; Joyeux, L.; Chalouhi, G. E.

    2012-01-01

    Nutritional deficiencies are preventable etiological and epigenetic factors causing congenital abnormalities, first cause of infant mortality. Folate deficiency has a well-established teratogenic effect, leading to an increasing risk of neural tube defects. This paper highlights the most recent medical literature about folate deficiency, be it maternal or paternal. It then focuses on associated deficiencies as nutritional deficiencies are multiple and interrelated. Observational and interventional studies have all been consistent with a 50–70% protective effect of adequate women consumption of folates on neural tube defects. Since strategies to modify women's dietary habits and vitamin use have achieved little progress, scientific as well as political effort is mandatory in order to implement global preventive public health strategies aimed at improving the alimentation of women in reproductive age, especially folic acid supplementation. Even with the recent breakthrough of fetal surgery for myelomeningocele, the emphasis should still be on prevention as the best practice rather than treatment of neural tube defects. PMID:22900183

  3. 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.

  4. Preventive innovation: an Australian case study on HPV vaccination.

    PubMed

    D'Souza, Clare; Mort, Gillian Sullivan; Zyngier, Suzanne; Robinson, Priscilla; Schlotterlein, Morgan

    2013-01-01

    Much of the literature has been conducted on innovation; this research provides new insights for preventive innovations that increase our understanding of vaccination diffusion and the reasons underlying the complexity of preventive diffusion. The research uses adoption of Rogers' ( 1983 ) perceived characteristics and considers the rate by which a product diffuses in a market. Qualitative empirical evidence collected via focus groups is used to identify human papillomavirus vaccine issues against the salience of perceived characteristics. Several impediments are identified and the application of marketing strategies is suggested for preventive innovations to improve the diffusion process and for designing proactive adoption.

  5. 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

  6. Study of magnetic defects in Nb2VSbO10

    NASA Astrophysics Data System (ADS)

    Typek, J.; Cyran, A.; Zolnierkiewicz, G.; Bobrowska, M.; Filipek, E.; Piz, M.

    2017-02-01

    Magnetic properties of Nb2VSbO10, the compound formed in V-Sb-Nb oxide system, were investigated by dc magnetisation measurements using an MPMS-7 SQUID magnetometer and EPR conventional X-band Bruker E 500 spectrometer. Although the nominal valences of the constituting metal ions indicated a diamagnetic material, Nb2VSbO10 displayed rich and interesting magnetic behaviour due to the existence of numerous defects related to oxygen vacancies. Isothermal magnetisation has revealed the presence of three spin subsystems - two different paramagnetic systems and antiferromagnetic spin clusters. EPR spectra showed the presence of three components, involving isolated and interacting V4+ ions as well as antiferromagnetic spin clusters. All these magnetic defects are the result of valence changes of metal ions due to charge compensation in the neighborhood of oxygen vacancies, most probably located on grains boundaries.

  7. 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.

  8. Children's views of accident risks and prevention: a qualitative study

    PubMed Central

    Green, J.; Hart, L.

    1998-01-01

    Objectives—To examine children's accounts of injury risks and opportunities for prevention. Setting—Schools, youth clubs, and a holiday activity scheme in the south east of England. Methods—Sixteen focus groups were held with 7–11 year old children. Transcripts of the discussions were analysed using qualitative methods. Results—Children were knowledgeable about injury risks and how to reduce them. They also saw injury prevention as primarily their own responsibility. However, they were also sophisticated in their criticisms of generalised prevention advice, and evaluated safety messages in the light of local environmental and social knowledge. Personal experience was more often reported as a reason for risk reduction than formal prevention advice. Risks for injury were not isolated from other risks faced. Conclusions—Effective educational interventions aimed at changing children's risk behaviour should build more on children's own competence and knowledge of their local environment, and stress the need to manage risks rather than avoid dangers. PMID:9595326

  9. Prevention of radioinduced cystitis by orgotein: a randomized study.

    PubMed

    Sanchiz, F; Millá, A; Artola, N; Julià, J C; Moya, L M; Pedro, A; Vila, A

    1996-01-01

    On the basis of previous experiences indicating that the anti-oxidant agent Cu/Zn superoxide dismutase (SOD) is an effective drug in reducing acute and late radiation-induced tissue injury, in the Center of Radiotherapy and Oncology of Catalonia, Barcelona, Spain in 1990 we implemented a randomized prospective study to analyze the incidence and grade of side effects in a group of bladder cancer patients. After surgery patients were randomly allocated to receive either: Option A: Radiotherapy or Option B: Radiotherapy + SOD 8 mgr/IM/day, after each radiotherapeutic application. Between January 1990 and January 1995 a total of 448 patients were included (226 A/ 222 B). Apart from cutaneous side effects, a highly significant incidence of radioinduced acute cystitis and rectitis was detected in patients not treated by SOD. Which was similar to the delayed side effects. From our data we can conclude that SOD is effective in decreasing acute radioinduced damage, and also in preventing the appearance of more delayed disorders.

  10. 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

  11. 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

  12. Enhanced gas adsorption on graphitic substrates via defects and local curvature: A density functional theory study

    SciTech Connect

    Dutta, Debosruti; Wood, Brandon C.; Bhide, Shreyas Y.; Ayappa, K. Ganapathy; Narasimhan, Shobhana

    2014-03-24

    Using van-der-Waals-corrected density functional theory calculations, we explore the possibility of engineering the local structure and morphology of high-surface-area graphene-derived materials to improve the uptake of methane and carbon dioxide for gas storage and sensing. We test the sensitivity of the gas adsorption energy to the introduction of native point defects, curvature, and the application of strain. The binding energy at topological point defect sites is inversely correlated with the number of missing carbon atoms, causing Stone–Wales defects to show the largest enhancement with respect to pristine graphene (~20%). Improvements of similar magnitude are observed at concavely curved surfaces in buckled graphene sheets under compressive strain, whereas tensile strain tends to weaken gas binding. Trends for CO2 and CH4 are similar, although CO2 binding is generally stronger by ~4 to 5 kJ mol–1. Furthermore, the differential between the adsorption of CO2 and CH4 is much higher on folded graphene sheets and at concave curvatures; this could possibly be leveraged for CH4/CO2 flow separation and gas-selective sensors.

  13. Stability of Ptn cluster on free/defective graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yang, G. M.; Fan, X. F.; Shi, S.; Huang, H. H.; Zheng, W. T.

    2017-01-01

    With first-principles methods, we investigate the stability of isolated Ptn clusters from Sutton-Chen model and close-packed model, and their adsorption on defected graphene. The single-vacancy in graphene is found to enhance obviously the adsorption energy of Pt cluster on graphene due to the introduction of localized states near Fermi level. It is found that the close-packed model is more stable than Sutton-Chen model for the adsorption of Ptn cluster on single-vacancy graphene, except the magic number n = 13. The cluster Pt13 may be the richest one for small Pt clusters on defected graphene due to the strong adsorption on single-vacancy. The larger cluster adsorbed on defected graphene is predicted with the close-packed crystal structure. The charge is found to transfer from the Pt atom/cluster to graphene with the charge accumulation at the interface and the charge polarization on Pt cluster. The strong interaction between Pt cluster and single vacancy can anchor effectively the Pt nanoparticles on graphene and is also expected that the new states introduced near Fermi level can enhance the catalytic characteristic of Pt cluster.

  14. Adsorption of Mn atom on pristine and defected graphene: a density functional theory study.

    PubMed

    Anithaa, V S; Shankar, R; Vijayakumar, S

    2017-04-01

    The functionalization of graphene with transition metals is of great interest due to its wide range of applications, such as hydrogen storage, spintronics, information storage, etc. Due to its magnetic property adsorption of Mn atom on graphene has a high consequence on the electronic properties of graphene. The increase in size of the graphene sheet with hydrogen termination has a high impact on the transformation of electronic properties of the graphene sheet. Hence in this work, we investigate the size as well as change in structural and electronic properties of pristine/defective graphene sheets on adsorption of Mn atom using density functional theory methods. From the results obtained a higher adsorption energy value of 3.04 eV is found for Mn adatom on the defected graphene sheet than the pristine, 1.85 eV. It is subject to the coverage effect which decreases on increasing number of carbon atoms. Moreover, a decrease in energy gap is observed in pristine and defected graphene sheets with a high number of carbon atoms. The density of states illustrates the significant effect for hydrogen termination in the conduction band of the Mn adsorbed graphene sheet with low carbon atoms. Graphical Abstract Mn adatom on graphene at different sites.

  15. Enhanced gas adsorption on graphitic substrates via defects and local curvature: A density functional theory study

    DOE PAGES

    Dutta, Debosruti; Wood, Brandon C.; Bhide, Shreyas Y.; ...

    2014-03-24

    Using van-der-Waals-corrected density functional theory calculations, we explore the possibility of engineering the local structure and morphology of high-surface-area graphene-derived materials to improve the uptake of methane and carbon dioxide for gas storage and sensing. We test the sensitivity of the gas adsorption energy to the introduction of native point defects, curvature, and the application of strain. The binding energy at topological point defect sites is inversely correlated with the number of missing carbon atoms, causing Stone–Wales defects to show the largest enhancement with respect to pristine graphene (~20%). Improvements of similar magnitude are observed at concavely curved surfaces inmore » buckled graphene sheets under compressive strain, whereas tensile strain tends to weaken gas binding. Trends for CO2 and CH4 are similar, although CO2 binding is generally stronger by ~4 to 5 kJ mol–1. Furthermore, the differential between the adsorption of CO2 and CH4 is much higher on folded graphene sheets and at concave curvatures; this could possibly be leveraged for CH4/CO2 flow separation and gas-selective sensors.« less

  16. General practitioners' relationship with preventive knowledge: a qualitative study.

    PubMed

    Bloy, Géraldine; Rigal, Laurent

    2015-09-09

    General practitioners (GPs) do not provide enough preventive care. Nonetheless, without a detailed understanding of the logical processes that underlie their practices, it remains difficult to develop effective means of improvement. Their relationship to knowledge is one of three elements that strongly structure GPs' preventive work (together with the doctor-patient relationship and the organisation of their professional space).The objective of this article was to explore the question of GPs' relationship to knowledge about prevention. In 2010-2011, semi-directive interviews with a diverse sample of 100 GPs practising in the Paris metropolitan area were conducted. These interviews were coded according a reading grid that was developed collectively and analysed in the framework of grounded theory. The cognitive universe of GPs is neither homogeneous nor stable. It is composed of biomedical knowledge (delivered via guidelines, the professional press, opinion leaders and pharmaceutical companies), clinical knowledge (fed by individual situations from their daily experience and often conflicting with epidemiologic reasoning and data) and lay knowledge (from folk culture). Plunged into this complex cognitive universe that is difficult for them to master, doctors construct their own idiosyncratic preventive style by themselves, mostly in isolation. Two types of actions emerged as likely to help GPs better appropriate preventive knowledge: clarification of scientific data (especially from epidemiology and the social sciences) but also development of a collective analysis of the cognitive work required to integrate the different types of knowledge mobilised daily in their preventive practices.

  17. 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

  18. 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.

  19. Single nickel-related defects in molecular-sized nanodiamonds for multicolor bioimaging: an ab initio study

    NASA Astrophysics Data System (ADS)

    Thiering, Gergő; Londero, Elisa; Gali, Adam

    2014-09-01

    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.

  20. 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.

  1. DEFECT SELECTIVE ETCHING OF THICK ALN LAYERS GROWN ON 6H-SIC SEEDS - A TRANSMISSION ELECTRON MICROSCOPY STUDY

    SciTech Connect

    Nyakiti, Luke; Chaudhari, Jharna; Kenik, Edward A; Lu, Peng; Edgar, J H

    2008-01-01

    In the present study, the type and densities of defects in AlN crystals grown on 6H-SiC seeds by the sublimation-recombination method were assessed. The positions of the defects in AlN were first identified by defect selective etching (DSE) in molten NaOH-KOH at 400 C for 2 minutes. Etching produced pits of three different sizes: 1.77 m, 2.35 m , and 2.86 m. The etch pits were either aligned together forming a sub-grain boundary or randomly distributed. The smaller etch pits were either isolated or associated with larger etch pits. After preparing crosssections of the pits by the focused ion beam (FIB) technique, transmission electron microscopy (TEM) was performed to determine which dislocation type (edge, mixed or screw) produced a specific etch pit sizes. Preliminary TEM bright field and dark field study using different zone axes and diffraction vectors indicates an edge dislocation with a Burgers vector 1/3[1120] is associated with the smallest etch pit size.

  2. Deep level transient spectroscopy (DLTS) study of defects introduced in antimony doped Ge by 2 MeV proton irradiation

    NASA Astrophysics Data System (ADS)

    Nyamhere, C.; Das, A. G. M.; Auret, F. D.; Chawanda, A.; Pineda-Vargas, C. A.; Venter, A.

    2011-08-01

    Deep level transient spectroscopy (DLTS) and Laplace-DLTS have been used to investigate the defects created in Sb doped Ge after irradiation with 2 MeV protons having a fluence of 1×10 13 protons/cm 2. The results show that proton irradiation resulted in primary hole traps at E V +0.15 and E V +0.30 eV and electron traps at E C -0.38, E C -0.32, E C -0.31, E C -0.22, E C -0.20, E C -0.17, E C -0.15 and E C -0.04 eV. Defects observed in this study are compared with those introduced in similar samples after MeV electron irradiation reported earlier. E C -0.31, E C -0.17 and E C -0.04, and E V +0.15 eV were not observed previously in similar samples after high energy irradiation. Results from this study suggest that although similar defects are introduced by electron and proton irradiation, traps introduced by the latter are dose dependent.

  3. Periodontal regeneration in intrabony defects after application of enamel matrix proteins with guided tissue regeneration: an experimental study in dogs.

    PubMed

    Onodera, Hiroko; Shibukawa, Yoshihiro; Sugito, Hiroki; Ota, Mikio; Yamada, Satoru

    2005-04-01

    The aim of this study was to evaluate the effects of enamel matrix proteins (EMP) at the early stage of wound healing in the periodontal tissues by a combination treatment with guided tissue regeneration (GTR). Intrabony defects were produced surgically at the distal aspects of both mandibles in six beagle dogs. At 12 weeks following the surgery, the defects were exposed using a full thickness mucoperiosteal flap procedure. Subsequently, the defects were treated by the following treatments: a control group treated with GTR alone, and an experimental group treated with a combination of GTR and EMP. After one, two, four and eight weeks of the treatment, the animals were sacrificed, and sections of the tissue were stained and evaluated microscopically. After one and two weeks, the proliferating cell nuclear antigen (PCNA)-positive cell ratios of the experimental group were significantly greater than that of the control group. After 2 and 4 weeks, new bone and new cementum formation in the experimental group were significantly greater than those in the control group (P < 0.05). However, after 8 weeks, no statistical difference was found between the two groups in new bone or cementum formation. The study results suggest that a maturation of periodontal ligament cells might contribute, during the early stage of periodontal healing, to stimulate a proliferation of periodontal ligament cells.

  4. UV Photofunctionalization Effect on Bone Graft in Critical One-Wall Defect around Implant: A Pilot Study in Beagle Dogs

    PubMed Central

    Kim, Min-Young; Lee, Jae-Hoon; Kim, Jee-Hwan; Jung, Han-Sung; Park, Young-Bum

    2016-01-01

    The purpose of this study was to compare and evaluate, through histomorphometric and radiological analysis, the effects of UV photofunctionalization on an implant placed over a critical defect area with and without a bone graft. Four female beagle dogs were first divided into control and bone graft groups. Each group was then subdivided into UV-treated and UV-untreated groups. The mandibular premolars in each dog were extracted. 12 weeks after extraction, implants were placed according to the condition of each group. Four and 12 weeks after implantation on left and right mandible, the dogs were sacrificed. The specimens were prepared for histomorphometric and micro-computed tomographic analysis. In both 4-week and 12-week groups, UV-treated implant surfaces showed better osseointegration than SA implant surfaces. Also, with implant surfaces placed over the critical defect with bone graft, UV photofunctionalization increased bone-to-implant contact (BIC) and new bone formation at the initial stage (4 weeks). Based on the results of this study, it can be suggested that UV photofunctionalization on the surface of implants placed over large critical defects with bone graft aids initial osseointegration and osteogenesis. PMID:28116296

  5. Improved tensile and buckling behavior of defected carbon nanotubes utilizing boron nitride coating - A molecular dynamic study

    NASA Astrophysics Data System (ADS)

    Badjian, H.; Setoodeh, A. R.

    2017-02-01

    Synthesizing inorganic nanostructures such as boron nitride nanotubes (BNNTs) have led to immense studies due to their many interesting functional features such as piezoelectricity, high temperature resistance to oxygen, electrical insulation, high thermal conductivity and very long lengths as physical features. In order to utilize the superior properties of pristine and defected carbon nanotubes (CNTs), a hybrid nanotube is proposed in this study by forming BNNTs surface coating on the CNTs. The benefits of such coating on the tensile and buckling behavior of single-walled CNTs (SWCNTs) are illustrated through molecular dynamics (MD) simulations of the resulted nanostructures during the deformation. The AIREBO and Tersoff-Brenner potentials are employed to model the interatomic forces between the carbon and boron nitride atoms, respectively. The effects of chiral indices, aspect ratio, presence of mono-vacancy defects and coating dimension on coated/non-coated CNTs are examined. It is demonstrated that the coated defective CNTs exhibit remarkably enhanced ultimate strength, buckling load capacity and Young's modulus. The proposed coating not only enhances the mechanical properties of the resulted nanostructure, but also conceals it from few external factors impacting the behavior of the CNT such as humidity and high temperature.

  6. Folate supplementation, MTHFR gene polymorphism and neural tube defects: a community based case control study in North India.

    PubMed

    Deb, Roumi; Arora, Jyoti; Meitei, Sanjenbam Yaiphaba; Gupta, Sangeeta; Verma, Vanita; Saraswathy, Kallur Nava; Saran, Sunil; Kalla, Aloke Kumar

    2011-09-01

    The present study analyses the potential role of MTHFR gene polymorphism, folate supplementation and dietary pattern among the mothers of NTD neonates and controls in heterogeneous populations of North India, with the special focus on their ethnic labels. Results indicated significant increased risk for neural tube defects with respect to low folic acid supplementation and vegetarian diet in univariate and multivariate analyses. There was no significant difference in the genotypic or allelic distribution of MTHFR C677T polymorphism, however, high frequency of CT genotype, as observed, among controls suggests heterozygous advantage probably due to supplementary folate. Among the two communities, Muslim NTD mothers had higher TT genotype showing increased risk for neural tube defects (adjusted OR: 12.9; 95% CI: 1.21-136.8) and lower folic acid supplementation (adjusted OR: 3.5; 95% CI: 1.18-10.22). Whereas, marginal increased risk for NTDs with vegetarian diet was observed among Hindus. Cultural and ethnic variation in the risk factors for neural tube defects is highlighted in the study.

  7. 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

  8. 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.

  9. Comparative study of the transcatheter and transthoracic device closure treatments for atrial septal defect: A Chinese single-institution experience.

    PubMed

    Chen, Qiang; Cao, Hua; Chen, Zhao-Yang; Zhang, Gui-Can; Chen, Liang-Wan; Xu, Fan; He, Jia-Jun

    2017-03-01

    The purpose of this study was to compare patient populations, safety, feasibility, complications, and total costs of the transcatheter and transthoracic device closure treatments for secundum atrial septal defect.From January 2014 to December 2014, we enrolled 155 patients with secundum atrial septal defects in our hospital. The patients were divided into 2 groups: the 70 patients in group A underwent transcatheter device closure, and the 85 patients in group B underwent transthoracic intraoperative device closure with a right lateral mini-thoracotomy.In group A, the total occlusion rate was 94.3% immediately after the operation, 100% at 3 months, and 100% at 12 months of follow-up; the group A results were not statistically different from the group B results (94.1%, 98.8%, 98.8%, respectively). There was a statistically significant difference in the minor complication rate (P < 0.05), and there were no reported deaths. There was a greater indicated scope using the transthoracic closure device to treat atrial septal defects. In our comparative study, the patients in group B had longer intensive care unit stays and hospital stays than group A (P < 0.05).Both of the device closure treatment options for secundum atrial septal defect are safe and feasible. The transcatheter device closure approach has the advantages of more cosmetic results, less trauma, and a shorter hospital stay than the transthoracic approach. On the contrary, the transthoracic closure device is an economical alternative choice, particularly for patients who are not eligible for the transcatheter closure device.

  10. 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

  11. 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…

  12. 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.

  13. First-principles study of native point defects in crystalline indium gallium zinc oxide

    NASA Astrophysics Data System (ADS)

    Omura, Hideyuki; Kumomi, Hideya; Nomura, Kenji; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2009-05-01

    Materials in In-Ga-Zn-O system are promising candidates for channel layers of high-performance thin-film transistors (TFTs). We investigated the atomic arrangements and the electronic structures of crystalline InGaZnO4 containing point defects such as oxygen vacancy (VO), interstitial hydrogen (Hi), and interstitial oxygen (Oi) by density functional theory (DFT) using a plane-wave pseudopotential method. The calculations for the atomic structure relaxation suggest that Hi bonds to a lattice oxygen (OO), and Oi occupies a split interstitial site [Oi(split)] forming a chemical bond with OO which is similar to O2 molecule, or Oi occupies an octahedral interstitial site [Oi(oct)]. The electronic structure calculations reveal that VO forms fully occupied states around the middle of the DFT band gap, while Hi does not form a defect level in the band gap but raises the Fermi level above the conduction band minimum. Oi(split) forms fully occupied states above the valence band maximum of the defect-free model (VBM0), while Oi(oct) forms both occupied and unoccupied states above the VBM0. It is thus suggested that VO and Oi(split) are electrically inactive for electrons but work as hole traps, Hi acts as a donor, and Oi(oct) is electrically active, trapping both electrons and holes. These observations imply that VO and Oi(split) do not but Hi and Oi(oct) influence electrical properties of the n-channel TFTs based on the In-Ga-Zn-O semiconductor materials.

  14. The application of porous tantalum cylinder to the repair of comminuted bone defects: a study of rabbit firearm injuries

    PubMed Central

    Ren, Bo; Zhai, Zhenbo; Guo, Kai; Liu, Yanpu; Hou, Weihuan; Zhu, Qingsheng; Zhu, Jinyu

    2015-01-01

    The aim of this study is to investigate the effect of porous tantalum material in repair tibial defects caused by firearm injuries in a rabbit model. A multifunctional biological impact machine was used to establish a rabbit tibial defect model of firearm injury. Porous tantalum rods were processed into a hollow cylinder. Kirschner wires were used for intramedullary fixation. We compared the differences of the bone ingrowth of the porous tantalum material by gross observations, X-rays and histological evaluations. The radiographic observations revealed that fibrous tissue covered the material surface after 4 weeks, and periosteal reactions and new bone callus extending materials appeared after 8 weeks. After 16 weeks, the calluses of the firearm injury group were completely wrapped around a porous tantalum material. The group with the highest Lane-Sandhu X-rays cores was the firearm injury and tantalum implant group, and the blank control group exhibited the lowest scores. The histological evaluations revealed that the presence of new bone around the biomaterial had grown into the porous tantalum. By the 16th week, the areas of bone tissue of the firearm injury group was significant higher than that of non-firearm injury group (P<0.05). The comminuted fractures treated with tantalum cylinders exhibited greater bone ingrowth in the firearm injury group. In conditions of firearm injuries, the porous tantalum biomaterial exhibited bone ingrowth that was beneficial to the treatment of bone defects. PMID:26131078

  15. Reconstruction of large-size abdominal wall defect using biodegradable poly-p-dioxanone mesh: an experimental canine study

    PubMed Central

    2014-01-01

    Background Reconstruction of large-size abdominal wall defect (AWDs) is a huge challenge faced in current surgical practice. In this study, we aimed to evaluate the effectiveness and safety of biodegradable poly-p-dioxanone (PDO) mesh for reconstructing large-size AWDs in an experimental canine model. Methods Eighteen experimental canines were randomly and equally divided into three groups, namely, a PDO group, a Marlex group and a control group (n = 6 each). Following the creation of a 6 cm × 5.5 cm AWD, PDO mesh and Marlex mesh were used to reconstruct the defect in the PDO and Marlex groups, respectively. The defect was closed using relaxation sutures alone in the control group. Animals were killed 24 weeks after surgery, and reconstruction outcomes were evaluated using radiography, histology and biomechanical testing. Results All animals except those in the control group survived the experiment. The PDO group showed no wound dehiscence, herniation or infection, whereas the animals in the Marlex group exhibited marked foreign body reactions. The PDO group had less intraabdominal adhesion than the Marlex group. As shown by radiography, histology and biomechanical testing, PDO mesh exhibited complete degradation and favorable biochemical strength at 24 weeks postsurgery. Conclusions PDO mesh implantation is an effective, safe treatment modality for reconstructing large-size AWDs. PMID:24625138

  16. X-ray photoelectron spectroscopy analysis of boron defects in silicon crystal: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yamauchi, Jun; Yoshimoto, Yoshihide; Suwa, Yuji

    2016-05-01

    We carried out a comprehensive study on the B 1s core-level X-ray photoelectron spectroscopy (XPS) binding energies and formation energies for boron defects in crystalline silicon by first-principles calculation with careful evaluation of the local potential boundary condition for the model system using the supercell corresponding to 1000 Si atoms. It is reconfirmed that the cubo-octahedral B12 cluster in silicon crystal is unstable and exists at the saddle point decaying to the icosahedral and S4 B12 clusters. The electrically active clusters without any postannealing of ion-implanted Si are identified as icosahedral B12 clusters. The experimentally proposed threefold coordinated B is also identified as a ⟨ 001 ⟩ B - Si defect. For an as-doped sample prepared by plasma doping, the calculated XPS spectra for complexes consisting of vacancies and substitutional B atoms are consistent with the experimental spectra. It is proposed that, assuming that the XPS peak at 187.1 eV is due to substitutional B (Bs), the experimental XPS peaks at 187.9 and 186.7 eV correspond to interstitial B at the H-site and ⟨ 001 ⟩ B - Si defects, respectively. In the annealed samples, the complex of Bs and interstitial Si near the T-site is proposed as a candidate for the experimental XPS peak at 188.3 eV.

  17. Interstitial-related defect reactions in electron-irradiated oxygen-rich Ge crystals: A DLTS study

    NASA Astrophysics Data System (ADS)

    Markevich, V. P.; Peaker, A. R.; Lastovskii, S. B.; Murin, L. I.; Litvinov, V. V.; Emtsev, V. V.; Dobaczewski, L.

    2009-12-01

    Electrically active defects induced in oxygen-rich Ge:Sb crystals by irradiation with MeV electrons at 80 or 300 K have been studied by means of capacitance transient techniques. Transformations of the defects upon post-irradiation isochronal anneals have also been investigated. It is argued that a radiation-induced electron trap with an energy level at about 110 meV below the conduction band edge (E110) can be associated with electron emission from an energy level of the Ge self-interstitial (IGe). The E110 trap is eliminated in the temperature range 150-200 K upon 15 min isochronal annealing. No other traps in the upper half of the gap emerge simultaneously with the disappearance of the E110 trap. It is argued that Ge self-interstitials become mobile at temperatures higher than 150 K and in oxygen-rich Ge interact with interstitial oxygen atoms (Oi). The resulting IGeOi complexes do not have energy levels in the upper half of the Ge gap. Diffusion and interaction of the IGeOi defects with interstitial oxygen atoms at T>50 °C result in the formation of IGeO2i complexes. In the most stable configuration the IGeO2i complex has orthorhombic (C2v) symmetry.

  18. Defects and annealing studies in 1-Me electron irradiated (AlGa)As-GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Li, S. S.; Wang, W. L.; Loo, R. Y.; Rahilly, W. P.

    1982-01-01

    The deep-level defects and recombination mechanisms in the one-MeV electron irradiated (AlGa)As-GaAs solar cells under various irradiation and annealing conditions are discussed. Deep-level transient spectroscopy (DLTS) and capacitance-voltage (CV) techniques were used to determine the defect and recombination parameters such as energy levels and defect density, carrier capture cross sections and lifetimes for both electron and hole traps as well as hole diffusion lengths in these electron irradiated GaAs solar cells. GaAs solar cells used in this study were prepared by the infinite solution melt liquid phase epitaxial (LPE) technique at Hughes Research Lab., with (Al0.9Ga0.1)-As window layer, Be-diffused p-GaAs layer on Sn-doped n-GaAs or undoped n-GaAs active layer grown on n(+)-GaAs substrate. Mesa structure with area of 5.86x1000 sq cm was fabricated. Three different irradiation and annealing experiments were performed on these solar cells.

  19. The influence of cooperation and defection on social decision making in depression: A study of the iterated Prisoner's Dilemma Game.

    PubMed

    Sorgi, Kristen M; van 't Wout, Mascha

    2016-12-30

    This study evaluated the influence of self-reported levels of depression on interpersonal strategic decision making when interacting with partners who differed in their predetermined tendency to cooperate in three separate computerized iterated Prisoner's Dilemma Games (iPDGs). Across 29 participants, cooperation was lowest when interacting with a predominantly defecting partner and highest when interacting with a predominantly cooperating partner. Greater depression severity was related to steadier and continued cooperation over trials with the cooperating partner, seeming to reflect a prosocial response tendency when interacting with this partner. With the unbiased partner, depression severity was associated with a more volatile response pattern in reaction to cooperation and defection by this partner. Severity of depression did not influence cooperation with a defecting partner or expectations about partner cooperation reported before the task began. Taken together, these data appear to show that in predominately positive interactions, as in the cooperating partner condition, depression is associated with less volatile, more consistent cooperation. When such clear feedback is absent, as in the unbiased partner condition, depression is associated with more volatile behavior. Nonetheless, participants were generally able to adapt their behavior accordingly in this dynamic interpersonal decision making context.

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

    SciTech Connect

    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 stable 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.

  1. Outcome of bone defect reconstruction with clavicle bone cement prosthesis after tumor resection: a case series study

    PubMed Central

    2014-01-01

    Background To investigate the short and medium term outcomes of bone defect reconstruction with bone cement prosthesis after clavicle malignancies resection. Methods A total of 5 clavicular malignancy patients experienced bone cement prosthesis reconstruction after subtotal claviculectomy were enrolled the study from January 2005 to May 2012. Musculoskeletal Tumor Society score (MSTS), Visual Analogue scale (VAS) and American Shoulder and Elbow Surgeons shoulder outcome score (ASES) were adopted for assessment. Results The mean follow-up period was 25.8 months. All patients were performed bone cement defect reconstruction after claviculectomy. In which, 3 cases showed disease-free and other 2 cases were alive with sickness. The average Musculoskeletal Tumor Society score was 85.40% ± 5.68%(77%-90%), Visual Analogue Scale was 1.40 ± 0.55 (1–2) and American Shoulder and Elbow Surgeons Shoulder Outcome Score was 92.40 ± 3.29(87–96). Conclusions Adoption of clavicle bone cement prosthesis for bone defect reconstruction after tumor resection can maintain the contour of shoulder and reduce the complications ascribe to the claviculectomy. It is an effective and feasible therapeutic procedure in clinical setting. PMID:24885109

  2. Computational study of Au_4 cluster on a carbon nanotube with and without defects using QM/MM methodology.

    PubMed

    Barraza-Jimenez, Diana; Galvan, D H; Posada-Amarillas, Alvaro; Flores-Hidalgo, Manuel Alberto; Glossman-Mitnik, Daniel; Jose-Yacaman, Miguel

    2012-11-01

    We use ONIOM (QM/MM) methodology to carry out geometry calculations in a 4-atom nanocluster supported by an (8, 8) armchair carbon nanotube with and without defects employing LSDA/SDD for the QM system and UFF for MM. In two particular cases, defects were added in the carbon nanotube wall. These defects are a double oxygenated vacancy (Vac₂O₂) and a double vacancy but without oxygen which creates two pentagons and an octagon. Our results show how geometries using QM/MM and energies calculations carried out with QM, change on both the gold nanocluster and the carbon nanotube. In addition, an application of ONIOM methodology in a comparative study to predict behavior of structures as hybrid materials based in carbon nanotubes combined with gold nanoclusters is shown. In this work we examine geometry changes on both the gold nanocluster and the carbon nanotube. A comparison is made with the binding energy resulting values as well as with the orbital energies such as the frontier orbitals HOMO and LUMO.

  3. Review on first-principles study of defect properties of CdTe as a solar cell absorber

    NASA Astrophysics Data System (ADS)

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Ma, Jie; Wei, Su-Huai

    2016-08-01

    CdTe is one of the leading materials for high-efficiency, low-cost, and thin-film solar cells. In this work, we review the recent first-principles study of defect properties of CdTe and present that: (1) When only intrinsic defects are present, p-type doping in CdTe is weak and the hole density is low due to the relatively deep acceptor levels of Cd vacancy. (2) When only intrinsic defects present, the dominant non-radiative recombination center in p-type CdTe is T{e}Cd2+, which limits the carrier lifetime to be around 200 ns. (3) Extrinsic p-type doping in CdTe by replacing Te with group V elements generally will be limited by the formation of AX centers. This could be overcome through a non-equilibrium cooling process and the hole density can achieve {10}17 {{{cm}}}-3. However, the long-term stability will be a challenging issue. (4) Extrinsic p-type doping by replacing Cd with alkaline group I elements is limited by alkaline interstitials and a non-equilibrium cooling process can efficiently enhance the hole density to the order of {10}17 {{{cm}}}-3. (5) Cu and Cl treatments are discussed. In bulk CdTe, Cu can enhance p-type doping, but Cl is found to be unsuitable for this. Both Cu and Cl show segregation at grain boundaries, especially at those with Te-Te wrong bonds. (6) External impurities are usually incorporated by diffusion. Therefore, the diffusion processes in CdTe are investigated. We find that cation interstitial (Nai, Cui) diffusion follows relatively simple diffusion paths, but anion diffusion (Cli, Pi) follows more complicated paths due to the degenerated defect wavefunctions.

  4. Remineralization of demineralized bone matrix in critical size cranial defects in rats: A 6-month follow-up study.

    PubMed

    Horváthy, Dénes B; Vácz, Gabriella; Toró, Ildikó; Szabó, Tamás; May, Zoltán; Duarte, Miguel; Hornyák, István; Szabó, Bence T; Dobó-Nagy, Csaba; Doros, Attila; Lacza, Zsombor

    2016-10-01

    The key drawback of using demineralized bone matrix (DBM) is its low initial mechanical stability due to the severe depletion of mineral content. In the present study, we investigated the long-term regeneration of DBM in a critical size bone defect model and investigated the remineralization after 6 months. Bone defects were created in the cranium of male Wistar rats which were filled with DBM or left empty as negative control. In vivo bone formation was monitored with computed tomography after 11, 19, and 26 weeks postoperatively. After 6 months, parietal bones were subjected to micro-CT. Mineral content was determined with spectrophotometric analysis. After 11 weeks the DBM-filled bone defects were completely closed, while empty defects were still open. Density of the DBM-treated group increased significantly while the controls remained unchanged. Quantitative analysis by micro-CT confirmed the in vivo results, bone volume/tissue volume was significantly lower in the controls than in the DBM group. The demineralization procedure depleted the key minerals of the bone to a very low level. Six months after implantation Ca, P, Na, Mg, Zn, and Cr contents were completely restored to the normal level, while K, Sr, and Mn were only partially restored. The remineralization process of DBM is largely complete by the 6th month after implantation in terms of bone density, structure, and key mineral levels. Although DBM does not provide sufficient sources for any of these minerals, it induces a faster and more complete regeneration process. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1336-1342, 2016.

  5. A Population-Based Study of the Association of Prenatal Diagnosis With Survival Rate for Infants With Congenital Heart Defects

    PubMed Central

    Oster, Matthew E.; Kim, Christopher H.; Kusano, Aaron S.; Cragan, Janet D.; Dressler, Paul; Hales, Alice R.; Mahle, William T.; Correa, Adolfo

    2015-01-01

    Prenatal diagnosis has been shown to improve preoperative morbidity in newborns with congenital heart defects (CHDs), but there are conflicting data as to the association with mortality. We performed a population-based, retrospective, cohort study of infants with prenatally versus postnatally diagnosed CHDs from 1994 to 2005 as ascertained by the Metropolitan Atlanta Congenital Defects Program. Among infants with isolated CHDs, we estimated 1-year Kaplan-Meier survival probabilities for prenatal versus postnatal diagnosis and estimated Cox proportional hazard ratios adjusted for critical CHD status, gestational age, and maternal race/ethnicity. Of 539,519 live births, 4,348 infants had CHDs (411 prenatally diagnosed). Compared with those with noncritical defects, those with critical defects were more likely to be prenatally diagnosed (58% vs 20%, respectively, p <0.001). Of the 3,146 infants with isolated CHDs, 1-year survival rate was 77% for those prenatally diagnosed (n = 207) versus 96% for those postnatally diagnosed (n = 2,939, p <0.001). Comparing 1-year survival rate among those with noncritical CHDs alone (n = 2,455) showed no difference between prenatal and postnatal diagnoses (96% vs 98%, respectively, p = 0.26), whereas among those with critical CHDs (n = 691), prenatally diagnosed infants had significantly lower survival rate (71% vs 86%, respectively, p <0.001). Among infants with critical CHDs, the adjusted hazard ratio for 1-year mortality rate for those prenatally versus postnatally (reference) diagnosed was 2.51 (95% confidence interval 1.72 to 3.66). In conclusion, prenatal diagnosis is associated with lower 1-year survival rate for infants with isolated critical CHDs but shows no change for those with isolated noncritical CHDs. More severe disease among the critical CHD subtypes diagnosed prenatally might explain these findings. PMID:24472597

  6. Intermittent administration of parathyroid hormone improves the repairing process of rat calvaria defects: A histomorphometric and radiodensitometric study

    PubMed Central

    Silva, Eduardo-de-Paula; Marques, Marcelo-Rocha; Dias da Silva, Marco-Antônio; Manzi, Flávio-Ricardo; Barros, Silvana-Pereira

    2015-01-01

    Background The aim of this study was to evaluate the effects of intermittent treatment of parathyroid hormone (PTH (1-34)) on the bone regeneration of critically-sized rat calvarial bone defects. Material and Methods Thirty-two male rats were trephined (4mm fullthickness diameter), in the central part of the parietal bones and divided into 2 groups of 16. The PTH group received subcutaneous injections of PTH (1-34) at 40µg/kg, 3 times a week and the control (CTL) group received the vehicle in the same regimen. The rats were sacrificed at 4 weeks post-treatment regimen, the parietal bones were extracted and samples were evaluated through histomorphometry and radiodensitometry. Results The histological observations showed that the PTH group presented more “island-like” new bone between the defect margins with fibrous tissues than did the CTL group. The PTH group significantly exhibited greater histologic bone formation than did the CTL group (1.5mm ±0.7; 1.9 mm ± 0.6, p<0.05/ for residual bone defect). The radiodensitometry analysis revealed significant differences among the PTH and CTL groups (2.1 Al eq. ±0.04; 1.8Al eq. ±0.06, p<0.05), demonstrating an increase in bone mineral density. The PTH treatment contributed to the bone formation with a higher amount of mineral and/or fibrous tissue when compared with the CTL group. Conclusions The results suggest that it was possible to increase the process of bone regeneration by accelerating the healing process in rat calvarial defects through intermittent administration of the PTH treatment. Key words: Bone, skull, rats, bone regeneration, bone density. PMID:26034928

  7. Review on first-principles study of defect properties of CdTe as a solar cell absorber

    SciTech Connect

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Ma, Jie; Wei, Su-Huai

    2016-07-15

    CdTe is one of the leading materials for high-efficiency, low-cost, and thin-film solar cells. In this work, we review the recent first-principles study of defect properties of CdTe and present that: (1) When only intrinsic defects are present, p-type doping in CdTe is weak and the hole density is low due to the relatively deep acceptor levels of Cd vacancy. (2) When only intrinsic defects present, the dominant non-radiative recombination center in p-type CdTe is Te-2+/Cd, which limits the carrier lifetime to be around 200 ns. (3) Extrinsic p-type doping in CdTe by replacing Te with group V elements generally will be limited by the formation of AX centers. This could be overcome through a non-equilibrium cooling process and the hole density can achieve 10^17 cm-3. However, the long-term stability will be a challenging issue. (4) Extrinsic p-type doping by replacing Cd with alkaline group I elements is limited by alkaline interstitials and a non-equilibrium cooling process can efficiently enhance the hole density to the order of 10^17 cm-3. (5) Cu and Cl treatments are discussed. In bulk CdTe, Cu can enhance p-type doping, but Cl is found to be unsuitable for this. Both Cu and Cl show segregation at grain boundaries, especially at those with Te-Te wrong bonds. (6) External impurities are usually incorporated by diffusion. Therefore, the diffusion processes in CdTe are investigated. We find that cation interstitial (Nai, Cui) diffusion follows relatively simple diffusion paths, but anion diffusion (Cli, Pi) follows more complicated paths due to the degenerated defect wavefunctions.

  8. Sulfur immobilization and lithium storage on defective graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Zhao, Wen; Chen, Pengcheng; Tang, Peizhe; Li, Yuanchang; Wu, Jian; Duan, Wenhui

    2014-01-01</