4,645 research outputs found

    ScotGrid: A Prototype Tier 2 Centre

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    ScotGrid is a prototype regional computing centre formed as a collaboration between the universities of Durham, Edinburgh and Glasgow as part of the UK's national particle physics grid, GridPP. We outline the resources available at the three core sites and our optimisation efforts for our user communities. We discuss the work which has been conducted in extending the centre to embrace new projects both from particle physics and new user communities and explain our methodology for doing this.Comment: 4 pages, 4 diagrams. Presented at Computing for High Energy and Nuclear Physics 2004 (CHEP '04). Interlaken, Switzerland, September 200

    Application of integrated fluid-thermal-structural analysis methods

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    Hypersonic vehicles operate in a hostile aerothermal environment which has a significant impact on their aerothermostructural performance. Significant coupling occurs between the aerodynamic flow field, structural heat transfer, and structural response creating a multidisciplinary interaction. Interfacing state-of-the-art disciplinary analysis methods is not efficient, hence interdisciplinary analysis methods integrated into a single aerothermostructural analyzer are needed. The NASA Langley Research Center is developing such methods in an analyzer called LIFTS (Langley Integrated Fluid-Thermal-Structural) analyzer. The evolution and status of LIFTS is reviewed and illustrated through applications

    Semileptonic Hyperon Decays

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    We review the status of hyperon semileptonic decays. The central issue is the VusV_{us} element of the CKM matrix, where we obtain Vus=0.2250(27)V_{us}=0.2250 (27). This value is of similar precision, but higher, than the one derived from Kl3K_{l3}, and in better agreement with the unitarity requirement, Vud2+Vus2+Vub2=1|V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=1. We find that the Cabibbo model gives an excellent fit of the existing form factor data on baryon beta decays (χ2=2.96\chi^{2} = 2.96 for 3 degrees of freedom) with F+D=1.2670±0.0030F + D = 1.2670 \pm 0.0030, FD=0.341±0.016F - D = -0.341 \pm 0.016, and no indication of flavour-SU(3)-breaking effects. We indicate the need of more experimental and theoretical work, both on hyperon beta decays and on Kl3K_{l3} decays.Comment: 37 pages, 8 figures, 4 tables, Final version of this material is scheduled to appear in the Annual Review of Nuclear and Particle Science Vol. 5

    The impact of cognitive functioning on mortality and the development of functional disability in older adults with diabetes: the second longitudinal study on aging

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    BACKGROUND: For older adults without diabetes, cognitive functioning has been implicated as a predictor of death and functional disability for older adults and those with mild to severe cognitive impairment. However, little is known about the relationship between cognition functioning on mortality and the development of functional disability in late life for persons with diabetes. We examined the relative contribution of cognitive functioning to mortality and functional disability over a 2-year period in a sample of nationally representative older US adults with diabetes who were free from cognitive impairment through secondary data analyses of the Second Longitudinal Study of Aging (LSOA II). METHODS: Participants included 559 US adults (232 males and 327 females) ≥ 70 years old who had diabetes and who were free from cognitive impairment were examined using an adapted Telephone Interview of Cognitive Status (TICS), Activities of Daily Living (ADL), and Instrumental Activities of Daily Living (IADL). RESULTS: Multivariate logistic regression was conducted to investigate the independent contribution of cognitive functioning to three mutually exclusive outcomes of death and two measures of functional disability status. The covariates included in the model were participants' sex, age, race, marital status, educational level, duration of diabetes, cardiovascular disease (CVD) status, and self-rated health. Persons with diabetes who had the lowest levels of cognitive functioning relative to the highest level of cognitive functioning had a greater odds of dying (AOR = 0.80, 95% CI = 0.67–0.96) or becoming disabled (AOR = 0.87, 95% CI = 0.78–0.97) compared to those people who were disability free. CONCLUSION: Older adults with diabetes and low normal levels of cognition, yet within normal ranges, were approximately 20% more likely to die and 13% more likely to become disabled than those with higher levels of cognitive functioning over a 2-year period. Brief screening measures of cognitive functioning could be used to identify older adults with diabetes who are at increased risk for mortality and functional disability, as well as those who may benefit from interventions to prevent or minimize further disablement and declines in cognitive functioning

    A Fresh Catch of Massive Binaries in the Cygnus OB2 Association

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    Massive binary stars may constitute a substantial fraction of progenitors to supernovae and gamma-ray bursts, and the distribution of their orbital characteristics holds clues to the formation process of massive stars. As a contribution to securing statistics on OB-type binaries, we report the discovery and orbital parameters for five new systems as part of the Cygnus OB2 Radial Velocity Survey. Four of the new systems (MT070, MT174, MT267, and MT734 (a.k.a. VI Cygni #11) are single-lined spectroscopic binaries while one (MT103) is a double-lined system (B1V+B2V). MT070 is noteworthy as the longest period system yet measured in Cyg OB2, with P=6.2 yr. The other four systems have periods ranging between 4 and 73 days. MT174 is noteworthy for having a probable mass ratio q<0.1, making it a candidate progenitor to a low-mass X-ray binary. These measurements bring the total number of massive binaries in Cyg OB2 to 25, the most currently known in any single cluster or association.Comment: Accepted for publication in the Astrophysical Journa

    Status report on a natural laminar-flow nacelle flight experiment

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    The natural laminar flow (NLF) nacelle experiment is part of a drag reduction production program, and has the dual objectives of studying the extent of NLF on full scale nacelles in a flight environment and the effect of acoustic disturbance on the location of transition on the nacelle surface. The experiment is being conducted in two phases: (1) an NLF fairing was flown on a full scale Citation nacelle to develop the experiment technique and establish feasibility; (2) full scale, flow through, NLF nacelles located below the right wing of an experimental NASA OV-1 aircraft are evaluated. The measurements of most interest are the static pressure distribution and transition location on the nacelle surface, and the fluctuating pressure levels associated with the noise sources. Data are collected in combinations of acoustic frequencies and sound pressure levels. The results of phase 2 tests to date indicate that on shape GE2, natural laminar flow was maintained as far aft as the afterbody joint at 50 percent of the nacelle length. An aft facing step at this joint caused premature transition at this station. No change was observed in the transition pattern when the noise sources were operated

    Semileptonic Hyperon Decays and CKM Unitarity

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    Using a technique that is not subject to first-order SU(3) symmetry breaking effects, we determine the VusV_{us} element of the CKM matrix from data on semileptonic hyperon decays. We obtain VusV_{us} =0.2250(27). This value is of similar precision to the one derived from Kl3K_{l3}, but higher and in better agreement with the unitarity requirement, Vud2+Vus2+Vub2=1|V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=1.Comment: 3 pages, 1 tabl
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