176 research outputs found

    A new model for high value meetings

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    The purpose of this research is to consider how organisations can increase competiveness by maximising the value of meetings whilst minimising their cost. This involves the development of a model which considers both the scheduling and management of meetings, whilst taking into account importance, value and cost where previously there has been no measure of these elements. This work will provide not only academic research within this under-represented area, but through a case study, a practical application. As time lost through unproductive meetings is estimated to cost billions, the potential saving through the application of this research is significant

    Role of lattice distortion and A site cation in the phase transitions of methylammonium lead halide perovskites

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    The rapid increase in power conversion efficiencies of photovoltaic devices incorporating lead halide perovskites has resulted in intense interest in the cause of their excellent properties. In the present paper, resonant ultrasound spectroscopy has been used to determine the elastic and anelastic properties of CH3NH3PbX3(where X=Cl, Br, or I) and CD3ND3PbI3 perovskites in the 5–380 K temperature range. This is coupled with differential scanning calorimetry, variable temperature neutron powder diffraction, and variable temperature photoluminescence studies to provide insights into the underlying processes and structural instabilities in the crystal structure. By comparing measurements on CH3NH3PbI3 with the deuterated equivalent, it has been possible to distinguish processes which are related to the hydrogen bonding between the methylammonium cation and the perovskite framework. We observe that replacing hydrogen with deuterium has a significant impact on both the elastic and photophysical properties, which shows that hydrogen bonding plays a crucial role in the material performance. Temperature-dependent photoluminescence studies show that the light emission is unaffected by the tetragonal-orthorhombic phase transition, but a blueshift in the emission and a steep increase in photoluminescence quantum yield are seen at temperatures below 150 K. Finally, observations of peaks in acoustic loss occurring in CH3NH3PbCl3 have revealed freezing processes in the vicinity of ∼150−170K, with activation energies in the range of 300 to 650 meV. These processes are attributed to freezing of the motion of methylammonium cations, and could explain the changes in photoluminescence seen in CH3NH3PbI3 at the same temperature. © 2018 American Physical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at: https://doi.org/10.1103/PhysRevMaterials.2.06540

    Genetic effects on alcohol dependence risk : Re-evaluating the importance of psychiatric and other heritable risk factors

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    Background. Genetic influences have been shown to play a major role in determining the risk of alcohol dependence (AD) in both women and men; however, little attention has been directed to identifying the major sources of genetic variation in AD risk. Method. Diagnostic telephone interview data from young adult Australian twin pairs born between 1964 and 1971 were analyzed. Cox regression models were fitted to interview data from a total of 2708 complete twin pairs (690 MZ female, 485 MZ male, 500 DZ female, 384 DZ male, and 649 DZ female/male pairs). Structural equation models were fitted to determine the extent of residual genetic and environmental influences on AD risk while controlling for effects of sociodemographic and psychiatric predictors on risk. Results. Risk of AD was increased in males, in Roman Catholics, in those reporting a history of major depression, social anxiety problems, and conduct disorder, or (in females only) a history of suicide attempt and childhood sexual abuse; but was decreased in those reporting Baptist, Methodist, or Orthodox religion, in those who reported weekly church attendance, and in university-educated males. After allowing for the effects of sociodemographic and psychiatric predictors, 47% (95% CI 28–55) of the residual variance in alcoholism risk was attributable to additive genetic effects, 0% (95% CI 0–14) to shared environmental factors, and 53% (95% CI 45–63) to non-shared environmental influences. Conclusions. Controlling for other risk factors, substantial residual heritability of AD was observed, suggesting that psychiatric and other risk factors play a minor role in the inheritance of AD

    Enhanced Photoluminescence Emission and Thermal Stability from Introduced Cation Disorder in Phosphors

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    Optimizing properties of phosphors for use in white-light-emitting diodes (WLEDs) is an important materials challenge. Most phosphors have a low level of lattice disorder due to mismatch between the host and activator cations. Here we show that deliberate introduction of high levels of cation disorder leads to significant improvements in quantum efficiency, stability to thermal quenching, and emission lifetime in Sr<sub>1.98–<i>x</i></sub>(Ca<sub>0.55</sub>Ba<sub>0.45</sub>)<sub><i>x</i></sub>Si<sub>5</sub>N<sub>8</sub>:Eu<sub>0.02</sub> (<i>x</i> = 0–1.5) phosphors. Replacing Sr by a (Ca<sub>0.55</sub>Ba<sub>0.45</sub>) mixture with the same average radius increases cation size variance, resulting in photoluminescence emission increases of 20–26% for the <i>x</i> = 1.5 sample relative to the <i>x</i> = 0 parent across the 25–200 °C range that spans WLED working temperatures. Cation disorder suppresses nonradiative processes through disruption of lattice vibrations and creates deep traps that release electrons to compensate for thermal quenching. Introduction of high levels of cation disorder may thus be a very useful general approach for improving the efficiency of luminescent materials

    Genome-wide association study identifies two loci strongly affecting transferrin glycosylation

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    Polysaccharide sidechains attached to proteins play important roles in cell-cell and receptor-ligand interactions. Variation in the carbohydrate component has been extensively studied for the iron transport protein transferrin, because serum levels of the transferrin isoforms asialotransferrin + disialotransferrin (carbohydrate-deficient transferrin, CDT) are used as biomarkers of excessive alcohol intake. We conducted a genome-wide association study to assess whether genetic factors affect CDT concentration in serum. CDT was measured in three population-based studies: one in Switzerland (CoLaus study, n = 5181) and two in Australia (n = 1509, n = 775). The first cohort was used as the discovery panel and the latter ones served as replication. Genome-wide single-nucleotide polymorphism (SNP) typing data were used to identify loci with significant associations with CDT as a percentage of total transferrin (CDT%). The top three SNPs in the discovery panel (rs2749097 near PGM1 on chromosome 1, and missense polymorphisms rs1049296, rs1799899 in TF on chromosome 3) were successfully replicated , yielding genome-wide significant combined association with CDT% (P = 1.9 × 10−9, 4 × 10−39, 5.5 × 10−43, respectively) and explain 5.8% of the variation in CDT%. These allelic effects are postulated to be caused by variation in availability of glucose-1-phosphate as a precursor of the glycan (PGM1), and variation in transferrin (TF) structur

    Ab initio constrained crystal-chemical Rietveld refinement of Ca10(VxP1-xO4)6F2 apatites

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    Extraction of reliable bond distances and angles for Ca10(VxP1-xO4)6F2 apatites using standard Rietveld refinement with Cu K(alpha) X-ray powder data was significantly impaired by large imprecision for the O-atom coordinates. An initial attempt to apply crystal-chemical Rietveld refinements to the same compounds was partly successful, and exposed the problematic determination of two oxygen\u8211metal\u8211oxygen angles. Ab initio modeling with VASP in space groups P63/m, P21/m and Pm showed that both these angular parameters exhibited a linear dependence with the vanadium content. Stable crystal-chemical Rietveld refinements in agreement with quantum results were obtained by fixing these angles at the values from ab initio simulations. Residuals were comparable with the less precise standard refinements. The larger vanadium ion is accommodated primarily by uniform expansion and rotation of BO4 tetrahedra combined with a rotation of the Ca\u8211Ca\u8211Ca triangular units. It is proposed that the reduction of symmetry for the vanadium end-member is necessary to avoid considerable departures from formal valences at the AII and B sites in P63/m. The complementarity of quantum methods and structural analysis by powder diffraction in cases with problematic least-squares extraction of the crystal chemistry is discussed.Peer reviewed: YesNRC publication: Ye

    Role of lattice distortion and A site cation in the phase transitions of methylammonium lead halide perovskites

    Get PDF
    The rapid increase in power conversion efficiencies of photovoltaic devices incorporating lead halide perovskites has resulted in intense interest in the cause of their excellent properties. In the present paper, resonant ultrasound spectroscopy has been used to determine the elastic and anelastic properties of CH3NH3PbX3 (where X=Cl, Br, or I) and CD3ND3PbI3 perovskites in the 5–380 K temperature range. This is coupled with differential scanning calorimetry, variable temperature neutron powder diffraction, and variable temperature photoluminescence studies to provide insights into the underlying processes and structural instabilities in the crystal structure. By comparing measurements on CH3NH3PbI3 with the deuterated equivalent, it has been possible to distinguish processes which are related to the hydrogen bonding between the methylammonium cation and the perovskite framework. We observe that replacing hydrogen with deuterium has a significant impact on both the elastic and photophysical properties, which shows that hydrogen bonding plays a crucial role in the material performance. Temperature-dependent photoluminescence studies show that the light emission is unaffected by the tetragonal-orthorhombic phase transition, but a blueshift in the emission and a steep increase in photoluminescence quantum yield are seen at temperatures below 150 K. Finally, observations of peaks in acoustic loss occurring in CH3NH3PbCl3 have revealed freezing processes in the vicinity of ∼150−170K, with activation energies in the range of 300 to 650 meV. These processes are attributed to freezing of the motion of methylammonium cations, and could explain the changes in photoluminescence seen in CH3NH3PbI3 at the same temperature
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