Light Induced Increase of Electron Diffusion Length in a p n Junction Type CH3NH3PbBr3 Perovskite Solar Cell

High band gap, high open circuit voltage solar cells with methylammonium lead tribromide MAPbBr3 perovskite absorbers are of interest for spectral splitting and photoelectrochemical applications, because of their good performance and ease of processing. The physical origin of high performance in these and similar perovskite based devices remains only partially understood. Using cross sectional electron beaminduced current EBIC measurements, we find an increase in carrier diffusion length in MAPbBr3 Cl based solar cells upon low intensity a few percent of 1 sun intensity blue laser illumination. Comparing dark and illuminated conditions, the minority carrier electron diffusion length increases about 3.5 times from Ln 100 50 nm to 360 22 nm. The EBIC cross section profile indicates a p amp; 8722;n structure between the n FTO TiO2 and p perovskite, rather than the p amp; 8722;i amp; 8722;n structure, reported for the iodide derivative. On the basis of the variation in space charge region width with varying bias, measured by EBIC and capacitance amp; 8722;voltage measurements, we estimate the net doping concentration in MAPbBr3 Cl to be 3 amp; 8722;6 1017 cm amp; 8722;

Epidemiological surveillance study of female genital mutilation in the UK

OBJECTIVES: Describe cases of female genital mutilation (FGM) presenting to consultant paediatricians and sexual assault referral centres (SARCs), including demographics, medical symptoms, examination findings and outcome. DESIGN: The well-established epidemiological surveillance study performed through the British Paediatric Surveillance Unit included FGM on the monthly returns. SETTING: All consultant paediatricians and relevant SARC leads across the UK and Ireland. PATIENTS: Under 16 years old with FGM. INTERVENTIONS: Data on cases from November 2015 to November 2017 and 12 months later meeting the case definition of FGM. MAIN OUTCOMES MEASURES: Returns included 146 cases, 103 (71%) had confirmed FGM and 43 (29%) did not meet the case definition. There were none from Northern Ireland. RESULTS: The mean reported age was 3 years. Using the WHO classification of FGM, 58% (n=60) had either type 1 or type 2, 8% (n=8) had type 3 and 21% (n=22) had type 4. 13% (n=13) of the cases were not classified and none had piercings or labiaplasty. The majority, 70% had FGM performed in Africa with others from Europe, Middle East and South-East Asia. There were few physical and mental health symptoms. Only one case resulted in a successful prosecution. CONCLUSIONS: There were low numbers of children presenting with FGM and in the 2 years there was only one prosecution. The findings may be consistent with attitude changes in FGM practising communities and those at risk should be protected and supported by culturally competent national policie

Evaluation of machine-learning methods for ligand-based virtual screening

Machine-learning methods can be used for virtual screening by analysing the structural characteristics of molecules of known (in)activity, and we here discuss the use of kernel discrimination and naive Bayesian classifier (NBC) methods for this purpose. We report a kernel method that allows the processing of molecules represented by binary, integer and real-valued descriptors, and show that it is little different in screening performance from a previously described kernel that had been developed specifically for the analysis of binary fingerprint representations of molecular structure. We then evaluate the performance of an NBC when the training-set contains only a very few active molecules. In such cases, a simpler approach based on group fusion would appear to provide superior screening performance, especially when structurally heterogeneous datasets are to be processed

Quantum line bundles on noncommutative sphere

Noncommutative (NC) sphere is introduced as a quotient of the enveloping algebra of the Lie algebra su(2). Using the Cayley-Hamilton identities we introduce projective modules which are analogues of line bundles on the usual sphere (we call them quantum line bundles) and define a multiplicative structure in their family. Also, we compute a pairing between certain quantum line bundles and finite dimensional representations of the NC sphere in the spirit of the NC index theorem. A new approach to constructing the differential calculus on a NC sphere is suggested. The approach makes use of the projective modules in question and gives rise to a NC de Rham complex being a deformation of the classical one.Comment: LaTeX file, 15 pp, no figures. Some clarifying remarks are added at the beginning of section 2 and into section

Beta-glucan reflects liver injury after preservation and transplantation in dogs.

Graft failure and extrahepatic organ complications, which frequently develop after transplantation, may be related to inflammatory mediators stimulated by endotoxin (ET). The role of endotoxemia after liver transplantation is controversial and may depend upon differences in the ET assay method used in the various contradicting studies. While the standard Limulus amebocyte lysate (LAL) is reactive for ET and beta-glucan, a novel turbidimetric assay method enables separate determinations of ET and beta-glucan. Beagle dogs undergoing orthotopic liver transplantation were divided into two groups. In Group I (n = 6) the grafts were transplanted immediately and in Group II (n = 6) grafts were preserved for 48 h in University of Wisconsin (UW) solution. Animals received cyclosporine immunosuppression and were followed for 14 days. Daily measurements of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) were performed. Samples for ET and beta-glucan measurement were collected serially and processed using the turbidimetric assay method. While no graft failure was seen in Group I, three of six Group II animals died from graft failure within 1 day after transplantation. Preservation and reperfusion injury was much more severe in the Group II grafts than in Group I grafts. While endotoxemia could not be detected, postoperative beta-glucan levels (undetectable pretransplant) were seen in both groups. Beta-glucan levels were much higher in Group II grafts than in Group I grafts, and correlated with the severity of liver damage. In conclusion, this study shows that beta-glucan, instead of ET, appears during the early posttransplant period. We believe that posttransplant elevation of beta-glucan is related to liver damage, especially endothelial damage by preservation and reperfusion

Acute bilateral anterior circulation stroke due to anomalous cerebral vasculature: a case report

<p>Abstract</p> <p>Introduction</p> <p>Simultaneous bilateral cerebrovascular infarction is relatively rare and its initial presentation as a space-occupying lesion is extremely uncommon. However, bilateral infarction can result from unilateral occlusion of anomalous cerebral vasculature.</p> <p>Case presentation</p> <p>We report the case of a man presenting with lower limb weakness and aphasia of acute onset with initial computerised tomography suggesting bifrontal neoplasm. However, further investigation confirmed bilateral anterior cerebral artery territory infarction with a hypoplastic left anterior cerebral artery with the right anterior cerebral artery supplying both frontal lobes (an anatomical variant). We present the clinical and diagnostic features of this presentation and attempt to ascertain, by reviewing existent medical literature, the frequency and patterns of structural variations in cerebral vasculature.</p> <p>Conclusion</p> <p>Simultaneous bilateral cerebral infarction can be the result of a unilateral cerebral artery occlusion and this can potentially mimic a space-occupying lesion. Anomalies of cerebral vasculature are not as rare as is usually believed and this should be borne in mind when investigating unusual presentations of cerebrovascular infarction.</p

Sex differences in nucleus accumbens transcriptome profiles associated with susceptibility versus resilience to subchronic variable stress

Depression and anxiety disorders are more prevalent in females, but the majority of research in animal models, the first step in finding new treatments, has focused predominantly on males. Here we report that exposure to subchronic variable stress (SCVS) induces depression-associated behaviors in female mice, whereas males are resilient as they do not develop these behavioral abnormalities. In concert with these different behavioral responses, transcriptional analysis of nucleus accumbens (NAc), a major brain reward region, by use of RNA sequencing (RNA-seq) revealed markedly different patterns of stress regulation of gene expression between the sexes. Among the genes displaying sex differences was DNA methyltransferase 3a (Dnmt3a), which shows a greater induction in females after SCVS. Interestingly, Dnmt3a expression levels were increased in the NAc of depressed humans, an effect seen in both males and females. Local overexpression of Dnmt3a in NAc rendered male mice more susceptible to SCVS, whereas Dnmt3a knock-out in this region rendered females more resilient, directly implicating this gene in stress responses. Associated with this enhanced resilience of female mice upon NAc knock-out of Dnmt3a was a partial shift of the NAc female transcriptome toward the male pattern after SCVS. These data indicate that males and females undergo different patterns of transcriptional regulation in response to stress and that a DNA methyltransferase in NAc contributes to sex differences in stress vulnerability

Direct Probing of Gap States and Their Passivation in Halide Perovskites by High-Sensitivity, Variable Energy Ultraviolet Photoelectron Spectroscopy

Direct detection of intrinsic defects in halide perovskites (HaPs) by standard methods utilizing optical excitation is quite challenging, due to the low density of defects in most samples of this family of materials (≤10^{15} cm^{–3} in polycrystalline thin films and ≤10^{11} cm^{–3} in single crystals, except melt-grown ones). While several electrical methods can detect defect densities 2 eV) HaPs. By measuring HaP layers on both hole- and electron-contact layers, as well as single crystals without contacts, we conclude that the observed deep defects are intrinsic to the Br-based HaP, and we propose a passivation route via the incorporation of a 2D-forming ligand into the precursor solution

Artificial Intelligence

Contains research objectives and reports on five research projects.Computation Center, M.I.T