4,179 research outputs found

    Fermionic and Scalar Corrections for the Abelian Form Factor at Two Loops

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    Two-loop corrections for the form factor in a massive Abelian theory are evaluated, which result from the insertion of massless fermion or scalar loops into the massive gauge boson propagator. The result is valid for arbitrary energies and gauge boson mass. Power-suppressed terms vanish rapidly in the high energy region where the result is well approximated by a polynomial of third order in ln(s/M^2). The relative importance of subleading logarithms is emphasised.Comment: Latex, 10 pages, 5 figures. B. Feucht is B. Jantzen in later publications. (The contents of the paper is unchanged.

    Maximizing phonon thermal conductance for ballistic membranes

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    At low temperatures, phonon scattering can become so weak that phonon transport becomes ballistic. We calculate the ballistic phonon conductance G for membranes using elasticity theory, considering the transition from three to two dimensions. We discuss the temperature and thickness dependence and especially concentrate on the issue of material parameters. For all membrane thicknesses, the best conductors have, counter-intuitively, the lowest speed of sound.Comment: 4 pages, 4 figures, proceedings to phonons 2007 conferenc

    QCD Corrections to Electroweak Annihilation Decays of Superheavy Quarkonia

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    QCD corrections to all the allowed decays of superheavy groundstate quarkonia into electroweak gauge and Higgs bosons are presented. For quick estimates, approximations that reproduce the exact results within less than at worst two percent are also given.Comment: 20 pages RevTeX, 9 figures. The complete paper, including figures, is also available via anonymous ftp at (129.13.102.139) as ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-05/ttp95-05.ps, or via www at http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints

    Gluon Fragmentation into Heavy Quarkonium

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    The dominant production mechanism for heavy quark-antiquark bound states in very high energy processes is fragmentation, the splitting of a high energy parton into a quarkonium state and other partons. We show that the fragmentation functions D(z,μ)D(z,\mu) describing these processes can be calculated using perturbative QCD. We calculate the fragmentation functions for a gluon to split into S-wave quarkonium states to leading order in the QCD coupling constant. The leading logarithms of μ/mQ\mu/m_Q, where μ\mu is the factorization scale and mQm_Q is the heavy quark mass, are summed up using Altarelli-Parisi evolution equations.Comment: LateX 11 pages (3 figures available upon request). NUHEP-TH-92-2

    Selenium-Binding Protein 1 Indicates Myocardial Stress and Risk for Adverse Outcome in Cardiac Surgery

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    Selenium-binding protein 1 (SELENBP1) is an intracellular protein that has been detected in the circulation in response to myocardial infarction. Hypoxia and cardiac surgery affect selenoprotein expression and selenium (Se) status. For this reason, we decided to analyze circulating SELENBP1 concentrations in patients (n = 75) necessitating cardioplegia and a cardiopulmonary bypass (CPB) during the course of the cardiac surgery. Serum samples were collected at seven time-points spanning the full surgical process. SELENBP1 was quantified by a highly sensitive newly developed immunological assay. Serum concentrations of SELENBP1 increased markedly during the intervention and showed a positive association with the duration of ischemia (ρ = 0.6, p < 0.0001). Elevated serum SELENBP1 concentrations at 1 h after arrival at the intensive care unit (post-surgery) were predictive to identify patients at risk of adverse outcome (death, bradycardia or cerebral ischemia, "endpoint 1"; OR 29.9, CI 3.3-268.8, p = 0.00027). Circulating SELENBP1 during intervention (2 min after reperfusion or 15 min after weaning from the CPB) correlated positively with an established marker of myocardial infarction (CK-MB) measured after the intervention (each with ρ = 0.5, p < 0.0001). We concluded that serum concentrations of SELENBP1 were strongly associated with cardiac arrest and the duration of myocardial ischemia already early during surgery, thereby constituting a novel and promising quantitative marker for myocardial hypoxia, with a high potential to improve diagnostics and prediction in combination with the established clinical parameters
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