排序方式: 共有23条查询结果,搜索用时 15 毫秒
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Aubin C Bernard C Detar C Di Pierro M Freeland ED Gottlieb S Heller UM Hetrick JE El-Khadra AX Kronfeld AS Levkova L Mackenzie PB Menscher D Maresca F Nobes M Okamoto M Renner D Simone J Sugar R Toussaint D Trottier HD;Fermilab Lattice Collaboration;MILC Collaboration;HPQCD Collaboration 《Physical review letters》2005,95(12):122002
We present the first lattice QCD calculation with realistic sea quark content of the D+-meson decay constant f(D+). We use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). We obtain f(D+)=201+/-3+/-17 MeV, where the errors are statistical and a combination of systematic errors. We also obtain f(Ds)=249+/-3+/-16 MeV for the Ds meson. 相似文献
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Gabriela Ionita Petre Ionita Victor EM. Sahini Constantin Luca 《Journal of inclusion phenomena and macrocyclic chemistry》2001,39(3-4):269-271
The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin. 相似文献
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We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux
lines in low T
c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line
lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends
to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the
destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has
employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo
technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing
μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation
of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors. 相似文献
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Beth M. Campbell Hetrick Rhonda J. Hughes 《Journal of Mathematical Analysis and Applications》2007,331(1):342-357
We apply semigroup theory and other operator-theoretic methods to prove Hölder-continuous dependence on modeling for the inhomogeneous ill-posed Cauchy problem in Banach space. The inhomogeneous ill-posed Cauchy problem is given by , u(0)=χ, 0?t<T; where −A is the infinitesimal generator of a holomorphic semigroup on a Banach space X, χ∈X, and . For a suitable function f, the approximate problem is given by , v(0)=χ. Under certain stabilizing conditions, we prove that for a related norm, where and M are computable constants independent of β, 0<β<1, and ω(t) is a harmonic function. These results extend earlier work of Ames and Hughes on the homogeneous ill-posed problem. 相似文献
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KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Aubin C Bernard C Detar C Dipierro M El-Khadra A Gottlieb S Gregory EB Heller UM Hetrick J Kronfeld AS Mackenzie PB Menscher D Nobes M Okamoto M Oktay MB Osborn J Simone J Sugar R Toussaint D Trottier HD;Fermilab Lattice;MILC;HPQCD 《Physical review letters》2005,94(1):011601
We present the first three-flavor lattice QCD calculations for D-->pilnu and D-->Klnu semileptonic decays. Simulations are carried out using ensembles of unquenched gauge fields generated by the MILC Collaboration. With an improved staggered action for light quarks, we are able to simulate at light quark masses down to 1/8 of the strange mass. Consequently, the systematic error from the chiral extrapolation is much smaller than in previous calculations with Wilson-type light quarks. Our results for the form factors at q(2)=0 are f(D-->pi)(+)(0)=0.64(3)(6) and f(D-->K)(+)(0)=0.73(3)(7), where the first error is statistical and the second is systematic, added in quadrature. Combining our results with experimental branching ratios, we obtain the Cabibbo-Kobayashi-Maskawa matrix elements |V(cd)|=0.239(10)(24)(20) and |V(cs)|=0.969(39)(94)(24), where the last errors are from experimental uncertainties. 相似文献
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