6,423 research outputs found

    K→(ππ)I=2K\to(\pi\pi)_{I=2} decays and twisted boundary conditions

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    We propose a new method to evaluate the Lellouch-L\"uscher factor which relates the ΔI=3/2\Delta I=3/2 K→ππK\to\pi\pi matrix elements computed on a finite lattice to the physical (infinite-volume) decay amplitudes. The method relies on the use of partially twisted boundary conditions, which allow the s-wave ππ\pi\pi phase shift to be computed as an almost continuous function of the centre-of-mass relative momentum and hence for its derivative to be evaluated. We successfully demonstrate the feasibility of the technique in an exploratory computation.Comment: 19 pages, 7 figure

    In situ aerosol measurements taken during the 2007 COPS field campaign at the Hornisgrinde ground site

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    Copyright @ 2011 Royal Meteorological Society.The Convective and Orographically-induced Precipitation Study (COPS) campaign was conducted during the summer of 2007. A suite of instruments housed at the top of the Hornisgrinde Mountain (1156 m) in the Black Forest region of south-west Germany provided datasets that allow an investigation into the physical, chemical and hygroscopic properties of the aerosol particles sampled during COPS. Organic mass loadings were found to dominate the aerosol composition for the majority of the project, exceeding 8 µg m−3 during a period of high pressure, high temperature, and low wind speed. The ratio of organic:sulphate sub-micron mass concentration exceeds 10:1 during the same time period. Back trajectories show air from this time-frame passing slowly over the local forest and not passing over any local anthropogenic sources. Occasional peaks in nitrate mass loadings were associated with changes in the typical wind direction from south-westerly to north-westerly where air had passed over the Stuttgart region. Size distribution data shows a dominant accumulation-mode when the measurement site was free from precipitation events. A sharp increase in ultrafine particle number concentration was seen during most days commencing around noon. The apparent growth of these particles is associated with an increase in organic mass loading, suggesting condensational growth. For the most part, with the exception of the high pressure period, the aerosol properties recorded during COPS were comparable to previous studies of continental aerosol properties.NER

    A dynamical and kinematical model of the Galactic stellar halo and possible implications for galaxy formation scenarios

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    We re-analyse the kinematics of the system of blue horizontal branch field (BHBF) stars in the Galactic halo (in particular the outer halo), fitting the kinematics with the model of radial and tangential velocity dispersions in the halo as a function of galactocentric distance r proposed by Sommer-Larsen, Flynn & Christensen (1994), using a much larger sample (almost 700) of BHBF stars. The basic result is that the character of the stellar halo velocity ellipsoid changes markedly from radial anisotropy at the sun to tangential anisotropy in the outer parts of the Galactic halo (r greater than approx 20 kpc). Specifically, the radial component of the stellar halo's velocity ellipsoid decreases fairly rapidly beyond the solar circle, from approx 140 +/- 10 km/s at the sun, to an asymptotic value of 89 +/- 19 km/s at large r. The rapid decrease in the radial velocity dispersion is matched by an increase in the tangential velocity dispersion, with increasing r. Our results may indicate that the Galaxy formed hierarchically (partly or fully) through merging of smaller subsystems - the 'bottom-up' galaxy formation scenario, which for quite a while has been favoured by most theorists and recently also has been given some observational credibility by HST observations of a potential group of small galaxies, at high redshift, possibly in the process of merging to a larger galaxy (Pascarelle et al 1996).Comment: Latex, 16 pages. 2 postscript figures. Submitted to the Astrophysical Journal. also available at http://astro.utu.fi/~cflynn/outerhalo.htm

    Preventing and responding to depression, self-harm, and suicide in older people living in long term care settings: a systematic review

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    Abstract Objective: The well documented demographic shift to an aging population means that more people will in future be in need of long term residential care. Previous research has reported an increased risk of mental health issues and suicidal ideation among older people living in residential care settings. However, there is little information on the actual prevalence of depression, self-harm, and suicidal behavior in this population, how it is measured and how care homes respond to these issues. Method: This systematic review of international literature addressed three research questions relating to; the prevalence of mental health problems in this population; how they are identified and; how care homes try to prevent or respond to mental health issues. Results: Findings showed higher reported rates of depression and suicidal behavior in care home residents compared to matched age groups in the community, variation in the use of standardised measures across studies and, interventions almost exclusively focused on increasing staff knowledge about mental health but with an absence of involvement of older people themselves in these programmes. Conclusion: We discuss the implications of these findings in the context of addressing mental health difficulties experienced by older people in residential care and future research in this area

    Heavy quark mass dependence of semileptonic form factors for B decays

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    We present our study of the dependence of the heavy-to-light semileptonic B decay form factors on the heavy-light meson mass MPSM_{PS}. Simulations are made over a range of the heavy quark mass covering both the charm and bottom quarks using the O(a)O(a)-improved clover action at β=5.9\beta=5.9 on a 163×4016^3\times 40 and 243×6424^3\times 64 lattice. We find that a weak dependence of form factors on MPSM_{PS} observed in previous studies in the region of charm quark persists up to the region ofbb quark. The soft pion relation f0(qmax2)=fB/fπf^0(q^2_{max})=f_B/f_\pi is examined and found to be largely violated.Comment: 3 pages, latex source-file, 4 figures as epsf-file, uses espcrc2.sty. Talk presented by S. Tominaga at Lattice 97, Edinburgh, Scotland, 22-26 Jul 199

    A lattice NRQCD computation of the bag parameters for ΔB\Delta B = 2 operators

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    We present an update of our NRQCD calculation of BBB_B at β\beta=5.9 with increased statistics. We also discuss a calculation of BSB_S, which is relevant to the width difference in the Bs−BˉsB_s-\bar{B}_s mixing.Comment: LATTICE99 (Heavy Quarks), 3 pages, 2 figures, espcrc2.st

    The kaon semileptonic form factor in Nf=2+1 domain wall lattice QCD with physical light quark masses

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    We present the first calculation of the kaon semileptonic form factor with sea and valence quark masses tuned to their physical values in the continuum limit of 2+1 flavour domain wall lattice QCD. We analyse a comprehensive set of simulations at the phenomenologically convenient point of zero momentum transfer in large physical volumes and for two different values of the lattice spacing. Our prediction for the form factor is f+(0)=0.9685(34)(14) where the first error is statistical and the second error systematic. This result can be combined with experimental measurements of K->pi decays for a determination of the CKM-matrix element for which we predict |Vus|=0.2233(5)(9) where the first error is from experiment and the second error from the lattice computation.Comment: 21 pages, 7 figures, 6 table

    Boosting BCG with recombinant modified vaccinia ankara expressing antigen 85A: Different boosting intervals and implications for efficacy trials

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    Objectives. To investigate the safety and immunogenicity of boosting BCG with modified vaccinia Ankara expressing antigen 85A (MVA85A), shortly after BCG vaccination, and to compare this first with the immunogenicity of BCG vaccination alone and second with a previous clinical trial where MVA85A was administered more than 10 years after BCG vaccination. Design. There are two clinical trials reported here: a Phase I observational trial with MVA85A; and a Phase IV observational trial with BCG. These clinical trials were all conducted in the UK in healthy, HIV negative, BCG naı¨ve adults. Subjects were vaccinated with BCG alone; or BCG and then subsequently boosted with MVA85A four weeks later (short interval). The outcome measures, safety and immunogenicity, were monitored for six months. The immunogenicity results from this short interval BCG prime–MVA85A boost trial were compared first with the BCG alone trial and second with a previous clinical trial where MVA85A vaccination was administered many years after vaccination with BCG. Results. MVA85A was safe and highly immunogenic when administered to subjects who had recently received BCG vaccination. When the short interval trial data presented here were compared with the previous long interval trial data, there were no significant differences in the magnitude of immune responses generated when MVA85A was administered shortly after, or many years after BCG vaccination. Conclusions. The clinical trial data presented here provides further evidence of the ability of MVA85A to boost BCG primed immune responses. This boosting potential is not influenced by the time interval between prior BCG vaccination and boosting with MVA85A. These findings have important implications for the design of efficacy trials with MVA85A. Boosting BCG induced anti-mycobacterial immunity in either infancy or adolescence are both potential applications for this vaccine, given the immunological data presented here. Trial Registration. ClinicalTrials.Oxford University was the sponsor for all the clinical trials reported here

    BB Decay Constants from NRQCD with Dynamical Fermions

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    We present a lattice investigation of the heavy-light meson decay constants using Wilson light quarks and NRQCD heavy quarks, partially including the effects of dynamical sea quarks. We calculate the pseudoscalar and vector decay constants over a wide range in heavy quark mass and are able to perform a detailed analysis of heavy quark symmetry. We find consistency between the extrapolation of the NRQCD results and the static case, as expected. We find the slope of the decay constants with 1/M1/M is significantly larger than naive expectations and the results of previous lattice calculations. For the first time we extract the non-perturbative coefficients of the slope arising from the O(1/M)O(1/M) heavy quark interactions separately and show the kinetic energy of the heavy quark is dominant and responsible for the large slope. In addition, we find that significant systematic errors remain in the decay constant extracted around the BB meson mass due to truncating the NRQCD series at O(1/M)O(1/M). We estimate the higher order contributions to fBf_B are approximately 20%20\%; roughly the same size as the systematic errors introduced by using the Wilson action for light quarks.Comment: 30 pages, Latex, 14 postscript figure
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