241 research outputs found

    Scattering of positronium by H, He, Ne, and Ar

    Get PDF
    The low-energy scattering of ortho positronium (Ps) by H, He, Ne, and Ar atoms has been investigated in the coupled-channel framework by using a recently proposed time-reversal-symmetric nonlocal electron-exchange model potential with a single parameter CC. For H and He we use a three-Ps-state coupled-channel model and for Ar and Ne we use a static-exchange model. The sensitivity of the results is studied with respect to the parameter CC. Present low-energy cross sections for He, Ne and Ar are in good agreement with experiment.Comment: 8 pages Latex with 4 postscript figure

    Orbifolds and Flows from Gauged Supergravity

    Get PDF
    We examine orbifolds of the IIB string via gauged supergravity. For the gravity duals of the A_{n-1} quiver gauge theories, we extract the massless degrees of freedom and assemble them into multiplets of N=4 gauged supergravity in five dimensions. We examine the embedding of the gauge group into the isometry group of the scalar manifold, as well as the symmetries of the scalar potential. From this we find that there is a large SU(1,n) symmetry group which relates different RG flows in the dual quiver gauge theory. We find that this symmetry implies an extension of the usual duality between ten-dimensional IIB solutions which involves exchanging geometric moduli with background fluxes.Comment: 37 pages, harvma

    Nature-based Solutions for Climate Change in the UK

    Get PDF
    Nature-based solutions (NbS) address societal problems in ways that benefit both people and nature. The main focus of this report is the joint role of NbS for addressing the climate and biodiversity crises we currently face. Natural habitats act as NbS for climate if they sequester carbon (contributing to Net Zero targets) or provide adaptation to climate change effects (for example, reducing flooding, protecting coastline against sea-level rise or creating cool spaces in cities). As well as these climate benefits, they can enhance biodiversity, create improved and more resilient ecosystem functioning, enhance human wellbeing and provide economic benefits, in terms of monetary value and job creation. Despite the huge range of benefits NbS have, they should be seen as complementary to other climate and conservation actions, not as a replacement to them. NbS have great potential to tackle the two defining crises of our age. The BES report provides examples of opportunities for NbS across a range of habitats, as well as discussion of some of the complexities involved in planning for NbS. The report also outlines a detailed analysis of the tools, financial mechanisms and policies required for effective delivery in a UK context. Policy change will be necessary to overcome some of the challenges associated with NbS and to ensure that they fulfil their potential, yet the rewards are vital in meeting national climate change and biodiversity targets. The Executive Summary provides five key themes which emerge across the report, across the multiple habitats and multiple NbS studied. Six ‘priority’ habitats for NbS are given at the end of the summary. However, we emphasise that all habitats covered in the report can act as NbS and all can play a role in addressing the climate and biodiversity crises

    Enhanced Symmetries in Multiparameter Flux Vacua

    Full text link
    We give a construction of type IIB flux vacua with discrete R-symmetries and vanishing superpotential for hypersurfaces in weighted projective space with any number of moduli. We find that the existence of such vacua for a given space depends on properties of the modular group, and for Fermat models can be determined solely by the weights of the projective space. The periods of the geometry do not in general have arithmetic properties, but live in a vector space whose properties are vital to the construction.Comment: 32 pages, LaTeX. v2: references adde

    Massless Localized Vector Field on a Wall in D=5 SQED with Tensor Multiplets

    Full text link
    Massless localized vector field is obtained in five-dimensional supersymmetric (SUSY) QED coupled to tensor multiplets as a half BPS solution. The four-dimensional gauge coupling is obtained as a topological charge. We also find all the (bosonic) massive modes exactly for a particular value of a parameter, demonstrating explicitly the existence of a mass gap. The four-dimensional Coulomb law is shown to hold for sources placed on the wall.Comment: 18 pages, 3 figures, First version is completely replaced due to an error of submitting a different pape

    Flux Compactifications on Calabi-Yau Threefolds

    Get PDF
    The presence of RR and NS three-form fluxes in type IIB string compactification on a Calabi-Yau orientifold gives rise to a nontrivial superpotential W for the dilaton and complex structure moduli. This superpotential is computable in terms of the period integrals of the Calabi-Yau manifold. In this paper, we present explicit examples of both supersymmetric and nonsupersymmetric solutions to the resulting 4d N=1 supersymmetric no-scale supergravity, including some nonsupersymmetric solutions with relatively small values of W. Our examples arise on orientifolds of the hypersurfaces in WP1,1,1,1,44WP^{4}_{1,1,1,1,4} and WP1,1,2,2,64WP^{4}_{1,1,2,2,6}. They serve as explicit illustrations of several of the ingredients which have played a role in the recent proposals for constructing de Sitter vacua of string theory.Comment: 30 pages, harvmac big; refs and minor comments adde

    Meta-analysis of 49 549 individuals imputed with the 1000 Genomes Project reveals an exonic damaging variant in ANGPTL4 determining fasting TG levels

    Get PDF
    Background So far, more than 170 loci have been associated with circulating lipid levels through genomewide association studies (GWAS). These associations are largely driven by common variants, their function is often not known, and many are likely to be markers for the causal variants. In this study we aimed to identify more new rare and low-frequency functional variants associated with circulating lipid levels. Methods We used the 1000 Genomes Project as a reference panel for the imputations of GWAS data from ~60 000 individuals in the discovery stage and ~90 000 samples in the replication stage. Results Our study resu

    Genome-wide association and Mendelian randomisation analysis provide insights into the pathogenesis of heart failure

    Get PDF
    Heart failure (HF) is a leading cause of morbidity and mortality worldwide. A small proportion of HF cases are attributable to monogenic cardiomyopathies and existing genome-wide association studies (GWAS) have yielded only limited insights, leaving the observed heritability of HF largely unexplained. We report results from a GWAS meta-analysis of HF comprising 47,309 cases and 930,014 controls. Twelve independent variants at 11 genomic loci are associated with HF, all of which demonstrate one or more associations with coronary artery disease (CAD), atrial fibrillation, or reduced left ventricular function, suggesting shared genetic aetiology. Functional analysis of non-CAD-associated loci implicate genes involved in cardiac development (MYOZ1, SYNPO2L), protein homoeostasis (BAG3), and cellular senescence (CDKN1A). Mendelian randomisation analysis supports causal roles for several HF risk factors, and demonstrates CAD-independent effects for atrial fibrillation, body mass index, and hypertension. These findings extend our knowledge of the pathways underlying HF and may inform new therapeutic strategies

    Associations of autozygosity with a broad range of human phenotypes

    Get PDF
    In many species, the offspring of related parents suffer reduced reproductive success, a phenomenon known as inbreeding depression. In humans, the importance of this effect has remained unclear, partly because reproduction between close relatives is both rare and frequently associated with confounding social factors. Here, using genomic inbreeding coefficients (F-ROH) for >1.4 million individuals, we show that F-ROH is significantly associated (p <0.0005) with apparently deleterious changes in 32 out of 100 traits analysed. These changes are associated with runs of homozygosity (ROH), but not with common variant homozygosity, suggesting that genetic variants associated with inbreeding depression are predominantly rare. The effect on fertility is striking: F-ROH equivalent to the offspring of first cousins is associated with a 55% decrease [95% CI 44-66%] in the odds of having children. Finally, the effects of F-ROH are confirmed within full-sibling pairs, where the variation in F-ROH is independent of all environmental confounding.Peer reviewe

    School-Based Programs to Reduce Bullying and Victimization

    Get PDF
    School bullying has serious short-term and long-term effects on children’s physical and mental health. Various anti-bullying programs have been implemented world wide and, more rarely, evaluated. Previous narrative reviews, summarizing the work done on bullying prevention, as well as previous meta-analyses of anti-bullying programs, are limited. The definition of school bullying includes several key elements: physical, verbal, or psychological attack or intimidation that is intended to cause fear, distress, or harm to the victim; an imbalance of power (psychological or physical), with a more powerful child (or children) oppressing less powerful ones; and repeated incidents between the same children over a prolonged period. School bullying can occur in school or on the way to or from school. It is not bullying when two persons of the same strength (physical, psychological, or verbal) victimize each other. This report presents a systematic review and meta-analysis of the effectiveness of programs designed to reduce school bullying perpetration and victimization (i.e. being bullied). The authors indicate the pitfalls of previous reviews and explain in detail how the present systematic review and meta-analysis addresses the gaps in the existing literature on bullying prevention
    corecore