311 research outputs found

    Structure and optical properties of high light output halide scintillators

    Full text link
    Structural and optical properties of several high light output halide scintillators and closely related materials are presented based on first principles calculations. The optical properties are based on the Engel-Vosko generalized gradient approximation and the recently developed density functional of Tran and Blaha. The materials investigated are BaBr2_2, BaIBr, BaCl2_2, BaF2_2, BaI2_2, BiI3_3, CaI2_2, Cs2LiYCl_2LiYCl_6,CsBa, CsBa_2BrBr_5,CsBa, CsBa_2II_5,K, K_2LaBrLaBr_5,K, K_2LaClLaCl_5,K,K_2LaILaI_5,LaBr, LaBr_3,LaCl, LaCl_3,SrBr, SrBr_2,andYI, and YI_3.ForcomparisonresultsarepresentedfortheoxideCdWO. For comparison results are presented for the oxide CdWO_4.WefindthattheTranBlahafunctionalgivesgreatlyimprovedbandgapsandopticalpropertiesinthisclassofmaterials.Furthermore,wefindthatunlikeCdWO. We find that the Tran Blaha functional gives greatly improved band gaps and optical properties in this class of materials. Furthermore, we find that unlike CdWO_4$, most of these halides are highly isotropic from an optical point of view even though in many cases the crystal structures and other properties are not. This general result is rationalized in terms of halide chemistry. Implications for the development of ceramic halide scintillators are discussed

    Pressure-induced hole doping of the Hg-based cuprate superconductors

    Full text link
    We investigate the electronic structure and the hole content in the copper-oxygen planes of Hg based high Tc cuprates for one to four CuO2 layers and hydrostatic pressures up to 15 GPa. We find that with the pressure-induced additional number of holes of the order of 0.05e the density of states at the Fermi level changes approximately by a factor of 2. At the same time the saddle point is moved to the Fermi level accompanied by an enhanced k_z dispersion. This finding explains the pressure behavior of Tc and leads to the conclusion that the applicability of the van Hove scenario is restricted. By comparison with experiment, we estimate the coupling constant to be of the order of 1, ruling out the weak coupling limit.Comment: 4 pages, 4 figure

    Electron-phonon superconductivity in non-centrosymmetric LaNiC2_2: first principles calculations

    Full text link
    We report first principles calculations of the electronic structure and electron-phonon coupling in the non-centrosymmetric superconductor LaNiC2_2. These show that the material is a conventional electron-phonon superconductor with intermediate coupling. There are large contributions to the coupling by two low frequency C non-bond-stretching modes, one of which has strong Kohn anomalies. Since LaNiC2_2 lacks inversion symmetry, the pairing is of dominant s-wave type with some mixture of p-wave character. This will give exponential decay in the specific heat.Comment: Corrected versio

    BoltzTraP. A code for calculating band-structure dependent quantities

    Full text link
    A program for calculating the semi-classic transport coefficients is described. It is based on a smoothed Fourier interpolation of the bands. From this analytical representation we calculate the derivatives necessary for the transport distributions. The method is compared to earlier calculations, which in principle should be exact within Boltzmann theory, and a very convincing agreement is found

    Design of a low band gap oxide ferroelectric: Bi6_6Ti4_4O17_{17}

    Full text link
    A strategy for obtaining low band gap oxide ferroelectrics based on charge imbalance is described and illustrated by first principles studies of the hypothetical compound Bi6_6Ti4_4O17_{17}, which is an alternate stacking of the ferroelectric Bi4_4Ti3_3O12_{12}. We find that this compound is ferroelectric, similar to Bi4_4Ti3_3O12_{12} although with a reduced polarization. Importantly, calculations of the electronic structure with the recently developed functional of Tran and Blaha yield a much reduced band gap of 1.83 eV for this material compared to Bi4_4Ti3_3O12_{12}. Therefore, Bi6_6Ti4_4O17_{17} is predicted to be a low band gap ferroelectric material

    Совершенствование ценообразования на предприятии

    Get PDF
    Выпускная квалификационная работа 105 с., 7 рис., 29 табл., 22 источника. Цель работы - экономическое обоснование оптимальной цены на продукцию. В процессе исследования проводились статистические исследования. В результате исследования была разработана оптимальная цена на продукцию. Основные технологические и управленческие характеристики: организационная структура является линейной, списочная численность предприятия - 150 человек.Final qualifying work 105 p., 7 Fig., 29 tab., 22 source. Purpose - the economic rationale for the optimal prices for the products. During the study, carried out statistical studies. The study developed the optimal price for the products. Basic technological and managerial characteristics: organizational structure is linear, the headcount of the enterprise - 150 people

    Evaluation of the Suitability of a Commercially Available ELISA Test as a Monitoring Tool for Estimating the Salmonella Prevalence of Commercial Swine Herds

    Get PDF
    In this study we evaluate the suitability of the Salmotype® (Labordiagnostik Leipzig) Enzyme Linked Immunosorbent Assay (ELISA) in swine. The study demonstrated no association between either individual or pen fecal culture and serologic status when examined by linear regression. Culture positive pigs had a tendency to be seropositive based on the individual fecal culture and only at pen and individual levels based on the pen fecal culture. Lowering the suggested cutoff of 40 % to 13 % gave an equal number of culture and seropositive individuals. Therefore further adaptation of Salmotype®to the US swine industry and further additional field studies need to be done

    Gait Speed and Mood, Cognition, and Quality of Life in Older Adults With Atrial Fibrillation

    Get PDF
    Background: Low gait speed has been linked with impaired mood, cognition, and quality of life (QOL) in older adults. We examined whether low gait speed was associated with impaired mood, cognition, and QOL among older adults with atrial fibrillation (AF). Methods and Results: Participants (n=1185) had a diagnosis of AF, aged \u3e /=65 years, CHA2DS2VASc \u3e /=2 and had no contraindications to anticoagulation. Participants completed a 15-foot walk test, and low gait speed was categorized using cutoffs from the Fried Frailty Index. Participants self-reported measures of depressive symptoms (Patient Health Questionnaire 9 \u3e /=10), anxiety symptoms (Generalized Anxiety Disorder 7 \u3e /=10), cognitive impairment (Montreal Cognitive Assessment \u3c /=23), and potentially impaired Atrial Fibrillation Effect Quality-of-Life Questionnaire \u3c 80. Participants were on average aged 75.3 (SD: 7.0) years, 48.0% were women, and 85.5% were non-Hispanic white; 85.6% were taking an oral anticoagulant, 26.1% had low gait speed, 8.4% had elevated depressive symptoms, 5.7% had elevated anxiety symptoms, 41.1% were cognitively impaired, and 41.6% had potentially impaired AF-related QOL. Participants with low gait speed were significantly more likely to have elevated depressive symptoms (adjusted odds ratio: 2.1, 95% CI: 1.3-3.4), elevated anxiety symptoms (adjusted odds ratio: 2.2, 95% CI: 1.2-3.9), and cognitive impairment (adjusted odds ratio: 1.5, 95% CI: 1.1-2.1). Impaired AF-related QOL did not differ by gait speed after adjustment for clinical characteristics (adjusted odds ratio: 1.1, 95% CI: 0.8-1.5). Conclusions: Twenty-six percent of older adults with AF had low gait speed, and low gait speed was associated with impaired mood and cognition. Further research is needed to determine whether declines in gait speed lead to impaired mood and cognition or whether these conditions develop concurrently

    Bariatric Endocrinology: Principles of Medical Practice

    Get PDF
    Obesity, is a chronic, biological, preventable, and treatable disease. The accumulation of fat mass causes physical changes (adiposity), metabolic and hormonal changes due to adipose tissue dysfunction (adiposopathy), and psychological changes. Bariatric endocrinology was conceived from the need to address the neuro-endocrinological derangements that are associated with adiposopathy, and from the need to broaden the scope of the management of its complications. In addition to the well-established metabolic complications of overweight and obesity, adiposopathy leads to hyperinsulinemia, hyperleptinemia, hypoadiponectinemia, dysregulation of gut peptides including GLP-1 and ghrelin, the development of an inflammatory milieu, and the strong risk of vascular disease. Therapy for adiposopathy hinges on effectively lowering the ratio of orexigenic to anorexigenic signals reaching the the hypothalamus and other relevant brain regions, favoring a lower caloric intake. Adiposopathy, overweight and obesity should be treated indefinitely with the specific aims to reduce fat mass for the adiposity complications, and to normalize adipose tissue function for the adiposopathic complications. This paper defines the principles of medical practice in bariatric endocrinology—the treatment of overweight and obesity as means to treat adiposopathy and its accompanying metabolic and hormonal derangements

    Utility of Nontraditional Risk Markers in Atherosclerotic Cardiovascular Disease Risk Assessment

    Get PDF
    AbstractBackgroundThe improvement in discrimination gained by adding nontraditional cardiovascular risk markers cited in the 2013 American College of Cardiology/American Heart Association cholesterol guidelines to the atherosclerotic cardiovascular disease (ASCVD) risk estimator (pooled cohort equation [PCE]) is untested.ObjectivesThis study assessed the predictive accuracy and improvement in reclassification gained by the addition of the coronary artery calcium (CAC) score, the ankle–brachial index (ABI), high-sensitivity C-reactive protein (hsCRP) levels, and family history (FH) of ASCVD to the PCE in participants of MESA (Multi-Ethnic Study of Atherosclerosis).MethodsThe PCE was calibrated (cPCE) and used for this analysis. The Cox proportional hazards survival model, Harrell’s C statistics, and net reclassification improvement analyses were used. ASCVD was defined as myocardial infarction, coronary heart disease–related death, or fatal or nonfatal stroke.ResultsOf 6,814 MESA participants not prescribed statins at baseline, 5,185 had complete data and were included in this analysis. Their mean age was 61 years; 53.1% were women, 9.8% had diabetes, and 13.6% were current smokers. After 10 years of follow-up, 320 (6.2%) ASCVD events occurred. CAC score, ABI, and FH were independent predictors of ASCVD events in the multivariable Cox models. CAC score modestly improved the Harrell’s C statistic (0.74 vs. 0.76; p = 0.04); ABI, hsCRP levels, and FH produced no improvement in Harrell’s C statistic when added to the cPCE.ConclusionsCAC score, ABI, and FH were independent predictors of ASCVD events. CAC score modestly improved the discriminative ability of the cPCE compared with other nontraditional risk markers
    corecore