1,107 research outputs found

    New-physics contributions to the forward-backward asymmetry in B -> K* mu+ mu-

    Full text link
    We study the forward-backward asymmetry (AFB) and the differential branching ratio (DBR) in B -> K* mu+ mu- in the presence of new physics (NP) with different Lorentz structures. We consider NP contributions from vector-axial vector (VA), scalar-pseudoscalar (SP), and tensor (T) operators, as well as their combinations. We calculate the effects of these new Lorentz structures in the low-q^2 and high-q^2 regions, and explain their features through analytic approximations. We find two mechanisms that can give a significant deviation from the standard-model predictions, in the direction indicated by the recent measurement of AFB by the Belle experiment. They involve the addition of the following NP operators: (i) VA, or (ii) a combination of SP and T (slightly better than T alone). These two mechanisms can be distinguished through measurements of DBR in B -> K* mu+ mu- and AFB in B -> K mu+ mu-.Comment: 33 pages, revtex, 9 figures. Paper originally submitted with the wrong figures. This is corrected in the replacement. An incorrect factor of 2 found in a formula. This is corrected and figures modified. Conclusions unchanged. Typos correcte

    Discipline-Specific Compared to Generic Training of Teachers in Higher Education

    Get PDF
    A recurrent theme arising in the higher education sector is the suitability and effectiveness of generic versus discipline-specific training of university teachers, who are often recruited based on their disciplinary specialties to become teachers in higher education. We compared two groups of participants who had undergone training using a generic post-graduate certificate in higher education (PGCertGeneric) versus a discipline-specific course in veterinary education (PGCertVetEd). The study was conducted using a survey that allowed comparison of participants who completed PGCertGeneric (n=21) with PGCertVetEd (n=22). Results indicated that participants from both PGCertGeneric and PGCertVetEd considered teaching to be satisfying and important to their careers, valued the teaching observation component of the course, and identified similar training needs. However, the participants of the PGCertVetEd felt that the course made them better teachers, valued the relevance of the components taught, understood course design better, were encouraged to do further courses/reading in teaching and learning, changed their teaching as a result of the course, and were less stressed about teaching as compared to the PGCertGeneric participants (p<.05). It is likely that the PGCertVetEd, which was designed and developed by veterinarians with a wider understanding of the veterinary sector, helped the participants perceive the training course as suited to their needs

    Static non-reciprocity in mechanical metamaterials

    Full text link
    Reciprocity is a fundamental principle governing various physical systems, which ensures that the transfer function between any two points in space is identical, regardless of geometrical or material asymmetries. Breaking this transmission symmetry offers enhanced control over signal transport, isolation and source protection. So far, devices that break reciprocity have been mostly considered in dynamic systems, for electromagnetic, acoustic and mechanical wave propagation associated with spatio-temporal variations. Here we show that it is possible to strongly break reciprocity in static systems, realizing mechanical metamaterials that, by combining large nonlinearities with suitable geometrical asymmetries, and possibly topological features, exhibit vastly different output displacements under excitation from different sides, as well as one-way displacement amplification. In addition to extending non-reciprocity and isolation to statics, our work sheds new light on the understanding of energy propagation in non-linear materials with asymmetric crystalline structures and topological properties, opening avenues for energy absorption, conversion and harvesting, soft robotics, prosthetics and optomechanics.Comment: 19 pages, 3 figures, Supplementary information (11 pages and 5 figures

    Forward-backward Asymmetry and Branching Ratio of B \rar K_1 \ell^+ \ell^- Transition in Supersymmetric Models

    Full text link
    The mass eigen states K1(1270)K_1(1270) and K1(1400)K_1(1400) are mixture of the strange members of two axial-vector SU(3) octet, 3P1(K1A)^3P_1(K_1^A) and 1P1(K1B)^1P_1(K_1^B). Taking into account this mixture, the forward-backward asymmetry and branching ratio of B \rar K_1(1270,1400) \ell^+ \ell^- transitions are studied in the framework of different supersymmetric models. It is found that the results have considerable deviation from the standard model predictions. Any measurement of these physical observables and their comparison with the results obtained in this paper can give useful information about the nature of interactions beyond the standard model.Comment: 14 pages, 4 figure

    Discovery of a small molecule agonist of phosphatidylinositol 3-kinase p110α that reactivates latent HIV-1

    Get PDF
    Combination antiretroviral therapy (cART) can effectively suppress HIV-1 replication, but the latent viral reservoir in resting memory CD4+ T cells is impervious to cART and represents a major barrier to curing HIV-1 infection. Reactivation of latent HIV-1 represents a possible strategy for elimination of this reservoir. In this study we describe the discovery of 1,2,9,10-tetramethoxy-7H-dibenzo[de,g]quinolin-7-one (57704) which reactivates latent HIV-1 in several cell-line models of latency (J89GFP, U1 and ACH-2). 57704 also increased HIV-1 expression in 3 of 4 CD8+-depleted blood mononuclear cell preparations isolated from HIV-1-infected individuals on suppressive cART. In contrast, vorinostat increased HIV-1 expression in only 1 of the 4 donors tested. Importantly, 57704 does not induce global T cell activation. Mechanistic studies revealed that 57704 reactivates latent HIV-1 via the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway. 57704 was found to be an agonist of PI3K with specificity to the p110a isoform, but not the p110β, δ or γ isoforms. Taken together, our work suggests that 57704 could serve as a scaffold for the development of more potent activators of latent HIV-1. Furthermore, it highlights the involvement of the PI3K/Akt pathway in the maintenance of HIV-1 latency. © 2014 Doyon et al

    Floral temperature and optimal foraging: is heat a feasible floral reward for pollinators?

    Get PDF
    As well as nutritional rewards, some plants also reward ectothermic pollinators with warmth. Bumble bees have some control over their temperature, but have been shown to forage at warmer flowers when given a choice, suggesting that there is some advantage to them of foraging at warm flowers (such as reducing the energy required to raise their body to flight temperature before leaving the flower). We describe a model that considers how a heat reward affects the foraging behaviour in a thermogenic central-place forager (such as a bumble bee). We show that although the pollinator should spend a longer time on individual flowers if they are warm, the increase in total visit time is likely to be small. The pollinator's net rate of energy gain will be increased by landing on warmer flowers. Therefore, if a plant provides a heat reward, it could reduce the amount of nectar it produces, whilst still providing its pollinator with the same net rate of gain. We suggest how heat rewards may link with plant life history strategies

    Ages for exoplanet host stars

    Full text link
    Age is an important characteristic of a planetary system, but also one that is difficult to determine. Assuming that the host star and the planets are formed at the same time, the challenge is to determine the stellar age. Asteroseismology provides precise age determination, but in many cases the required detailed pulsation observations are not available. Here we concentrate on other techniques, which may have broader applicability but also serious limitations. Further development of this area requires improvements in our understanding of the evolution of stars and their age-dependent characteristics, combined with observations that allow reliable calibration of the various techniques.Comment: To appear in "Handbook of Exoplanets", eds. Deeg, H.J. & Belmonte, J.A, Springer (2018

    Lung Cancer in Pulmonary Fibrosis: Tales of Epithelial Cell Plasticity

    Get PDF
    Lung epithelial cells exhibit a high degree of plasticity. Alterations to lung epithelial cell function are critically involved in several chronic lung diseases such as pulmonary fibrosis. Pulmonary fibrosis is characterized by repetitive injury and subsequent impaired repair of epithelial cells, which leads to aberrant growth factor activation and fibroblast accumulation. Increased proliferation and hyper- and metaplasia of epithelial cells upon injury have also been observed in pulmonary fibrosis; this epithelial cell activation might represent the basis for lung cancer development. Indeed, several studies have provided histopathological evidence of an increased incidence of lung cancer in pulmonary fibrosis. The mechanisms involved in the development of cancer in pulmonary fibrosis, however, remain poorly understood. This review highlights recently uncovered molecular mechanisms shared between lung cancer and fibrosis, which extend the current evidence of a common trait of cancer and fibrosis, as provided by histopathological observations. Copyright (C) 2011 S. Karger AG, Base

    Counting and effective rigidity in algebra and geometry

    Full text link
    The purpose of this article is to produce effective versions of some rigidity results in algebra and geometry. On the geometric side, we focus on the spectrum of primitive geodesic lengths (resp., complex lengths) for arithmetic hyperbolic 2-manifolds (resp., 3-manifolds). By work of Reid, this spectrum determines the commensurability class of the 2-manifold (resp., 3-manifold). We establish effective versions of these rigidity results by ensuring that, for two incommensurable arithmetic manifolds of bounded volume, the length sets (resp., the complex length sets) must disagree for a length that can be explicitly bounded as a function of volume. We also prove an effective version of a similar rigidity result established by the second author with Reid on a surface analog of the length spectrum for hyperbolic 3-manifolds. These effective results have corresponding algebraic analogs involving maximal subfields and quaternion subalgebras of quaternion algebras. To prove these effective rigidity results, we establish results on the asymptotic behavior of certain algebraic and geometric counting functions which are of independent interest.Comment: v.2, 39 pages. To appear in Invent. Mat
    • …
    corecore