Search results for "defect"
showing 10 items of 879 documents
Computational analysis of positron experiments
1984
A number of applications of the calculational scheme developed by Puska and Nieminen (1982-3) are reported and the predictive power of the scheme is substantiated. Effects on positron parameters of relaxation and of N or H impurities in vacancies in Mo are calculated and employed to analyse recent experiments. Predictions pertaining to H decoration of vacancies in Al and Ni suggest the use of positron lifetime studies of these systems. Positron responses to submicroscopic vacancy clusters decorated with Kr and to large Kr bubbles in Cu are calculated and used to analyse recent experiments. To accomplish this the scheme is generalised to incorporate crystals of inert gas. In turn this makes …
Semi-empirical defect calculations for the perovskite KNbO3
2000
A new parametrization of the classical shell model for the cubic phase of the perovskite KNbO3 has been derived and used to calculate the structural, elastic and dielectric properties of this material. Using this parametrization, the defect formation and migration energies, as well as atomic displacements, have been calculated. In parallel, the quantum mechanical method of the intermediate neglect of the differential overlap (INDO) has been applied to the same problem. The migration energies for the O vacancy obtained by these quite different methods are reasonably close (0.68 eV and 0.79 eV, respectively) and also agree with the only experimental estimate available of approximately 1 eV. A…
Quantum chemical modelling of point defects in KNbO3 perovskite crystals
2000
Abstract We present results of semi-empirical quantum chemical calculations for several perovskite KNb x Ta 1−x O 3 (KTN) solid solutions, as well as point intrinsic defects – F centers and hole polarons bound to K vacancy – in KNbO 3 . Method of the intermediate neglect of the differential overlap (INDO) was combined with typically 320-atom supercells and atomic geometry optimization. Analysis of the optimized atomic and electronic structure has clearly demonstrated that several nearest Nb atoms substituting for Ta in KTaO 3 – unlike Ta impurities in KNbO 3 – reveal the self-ordering effect, which probably triggers the ferroelectricity observed in KTN. We predict co-existence of one-site (…
Predictive validity of the GOSLON Yardstick index in patients with unilateral cleft lip and palate: A systematic review
2017
Among the various indices developed for measuring the results of treatment in patients born with unilateral cleft lip and palate (UCLP), the GOSLON Yardstick index is the most widely used to assess the efficacy of treatment and treatment outcomes, which in UCLP cases are closely linked to jaw growth. The aim of this study was to conduct a systematic review to validate the predictability of growth using the GOSLON Yardstick in patients born with UCLP. A systematic literature review was conducted in four Internet databases: Medline, Cochrane Library, Scopus and Embase, complemented by a manual search and a further search in the databases of the leading journals that focus on this topic. An el…
Caracterización de la suplementación de folatos en el embarazo a partir de la combinación de sistemas de información sanitaria.
2012
ResumenObjetivosExplorar la utilidad de la combinación de los sistemas de información sanitaria de la Agencia Valenciana de Salud (AVS) para caracterizar la suplementación de folatos en la población de embarazadas de la Comunidad Valenciana.MétodosCohorte de todas las mujeres que parieron en hospitales de la AVS durante 2009, que fueron seguidas retrospectivamente en la historia clínica electrónica ABUCASIS y el sistema GAIA de gestión de la prescripción para identificar el consumo de folatos en los 3 meses previos y posteriores a la concepción.ResultadosDe los 38.069 partos realizados en 2009 en hospitales de la AVS, 37.040 (97,3%) pudieron incluirse en los análisis. Un 34,0% de las mujere…
Clinical cardiac assessment in newborns with prenatally diagnosed intrathoracic masses
2018
Abstract Background Congenital space-occupying thoracic malformations and diaphragmatic hernia have in common pulmonary hypoplasia. Our study aims to assess cardiac involvement during post-natal adaptation. Methods A retrospective study was carried out on newborns with prenatally diagnosed intrathoracic mass. Gathering for respiratory distress syndrome (RDS), 35 neonates were compared for clinical course, cardiovascular enzymes, ECG, and ultrasound. Results The analysis revealed a high left heart defect rate in patients with severe RDS, without being influenced by the laterality. Ultrasound or laboratory assessment did not detect altered cardiac dimension or cardiomyopathy. Solely ECG signs…
Intelligence in DSM-IV combined type attention-deficit/hyperactivity disorder is not predicted by either dopamine receptor/transporter genes or other…
2008
Contains fulltext : 69677.pdf (Publisher’s version ) (Closed access) A major goal of genetic studies of attention deficit hyperactivity disorder (ADHD) is to identify individual characteristics that might help segregate the disorder's inherent heterogeneity. [Mill et al. (2006); Arch Ger Psychiatry 63:462-469] recently reported a potentially important association between two dopamine-related risk polymorphisms (DRD4 variable number tandem repeat (VNTR) in exon 3 and DAT1 VNTR in the 3' UTR) and lowered IQ in ADHD. The objective of the current study was to replicate the [Mill et al. (2006); Arch Ger Psychiatry 63:462-469] findings in a clinical sample and to extend the analysis to a large ra…
Genetic heterogeneity in ADHD: DAT1 gene only affects probands without CD
2008
Contains fulltext : 70183.pdf (Publisher’s version ) (Closed access) Previous studies have found heterogeneous association between DAT1-3'-UTR-VNTR and attention deficit hyperactivity disorder (ADHD). Various proportions of conduct disorder (CD) comorbidity in their ADHD samples may partially explain the observational discrepancies. Evidence for this comes from family and twin studies which found ADHD probands with CD (ADHD + CD) are genetically different from those without CD (ADHD - CD). Genotypes of 20 DAT1 markers were analyzed in 576 trios, consisting of 141 ADHD + CD and 435 ADHD - CD. In addition to the classical TDT test, a specific genetic heterogeneity test was performed to identi…
A new capability index for dynamic process analysis
2013
Nowadays, the trend to produce with reduced specification limits width and at a low defectives rate seems to be irreversible. In such conditions, reliable evaluation of the process capability level represents a crucial activity to assess the quality related performance of a production process. By adopting the classical approach, such evaluation is performed by verifying the process in-control condition and by evaluating suitable capability indices. However, considering the natural dynamic behavior of production processes, i.e. the process variability over the time domain, the in-control condition characterizes only a part of the production process functioning cycle, the one with the lowest …
Defect incorporation in In-containing layers and quantum wells: Experimental analysis via deep level profiling and optical spectroscopy
2020
Abstract Recent studies demonstrated that the performance of InGaN/GaN quantum well (QW) light emitting diodes (LEDs) can be significantly improved through the insertion of an InGaN underlayer (UL). The current working hypothesis is that the presence of the UL reduces the density of non-radiative recombination centers (NRCs) in the QW itself: during the growth of the UL, surface defects are effectively buried in the UL, without propagating towards the QW region. Despite the importance of this hypothesis, the concentration profile of defects in the quantum wells of LEDs with and without the UL was never investigated in detail. This paper uses combined capacitance-voltage and steady-state pho…