5,690 research outputs found
Irreversibility line and low-field grain-boundary pinning in electron-doped superconducting thin films
AC magnetic susceptibilities of electron-doped Pr_{1.85}Ce_{0.15}CuO_4 (PCCO)
and Sm_{1.85}Ce_{0.15}CuO_4 (SCCO) granular thin films have been measured as a
function of temperature and magnetic-field strength. Depending on the level of
homogeneity of our films, two different types of the irreversibility line (IL)
defined as the intergrain-loss peak temperature in the imaginary part of
susceptibility have been found. The obtained results are described via the
critical-state model taking into account the low-field grain-boundary pinning.
The extracted pinning-force densities in more granular SCCO films turn out to
be four times larger than their counterparts in less granular PCCO films
Scaling and Further Tests of Heavy Meson Decay Constant Determinations from Nonrelativistic QCD
We present results for the B_s meson decay constant f_{B_s} from simulations
at three lattice spacings in the range a^{-1}=1.1 to 2.6 GeV using NRQCD heavy
quarks and clover light quarks in the quenched approximation. We study scaling
of this quantity and check the consistency between mesons decaying from rest
and from a state with nonzero spatial momentum. The cancellation of power law
contributions that arise in the NRQCD formulation of heavy-light currents is
discussed. On the coarsest lattice the D_s meson decay constant f_{D_s} is
calculated. Our best values for the decay constants are given by f_{B_s} =
187(4)(4)(11)(2)(7)(6) MeV and f_{D_s} = 223(6)(31)(38)(23)(9)(^{+3}_{-1}) MeV.Comment: 29 pages with 7 postscript figures, improved error analysis, version
to appear in Physical Review
Bipartite all-versus-nothing proofs of Bell's theorem with single-qubit measurements
If we distribute n qubits between two parties, which quantum pure states and
distributions of qubits would allow all-versus-nothing (or
Greenberger-Horne-Zeilinger-like) proofs of Bell's theorem using only
single-qubit measurements? We show a necessary and sufficient condition for the
existence of these proofs for any number of qubits, and provide all distinct
proofs up to n=7 qubits. Remarkably, there is only one distribution of a state
of n=4 qubits, and six distributions, each for a different state of n=6 qubits,
which allow these proofs.Comment: REVTeX4, 4 pages, 2 figure
Radiative diffusivity factors in cirrus and stratocumulus clouds: Application to two-stream models
A diffusion-like description of radiative transfer in clouds and the free atmosphere is often used. The two stream model is probably the best known example of such a description. The main idea behind the approach is that only the first few moments of radiance are needed to describe the radiative field correctly. Integration smooths details of the angular distribution of specific intensity and it is assumed that the closure parameters of the theory (diffusivity factors) are only weakly dependent on the distribution. The diffusivity factors are investigated using the results obtained from both Stratocumulus and Cirrus phases of FIRE experiment. A new theoretical framework is described in which two (upwards and downwards) diffusivity factors are used and a detailed multistream model is used to provide further insight about both the diffusivity factors and their dependence on scattering properties of clouds
F_B from moving B mesons
We show results for the B meson decay constant calculated both for B mesons
at rest and those with non-zero momentum and using both the temporal and
spatial components of the axial vector current. It is an important check of
lattice systematic errors that all these determinations of f_B should agree. We
also describe how well different smearings for the B meson work at non-zero
momentum - the optimal smearing has a narrow smearing for the b quark.Comment: Lattice2001(heavyquark
Contribution of an alveolar cell of origin to the high-grade malignant phenotype of pregnancy-associated breast cancer.
Pregnancy-associated breast cancers (PABCs) are tumors diagnosed during pregnancy or up to 5 years following parturition, and are usually high-grade, connective tissue-rich, and estrogen receptor (ER)/progesterone receptor-negative. Little is known about the cellular origin of PABCs or the mechanisms by which PABCs are initiated. Using the RCAS retrovirus to deliver the ErbB2 oncogene into the mammary epithelium of our previously reported MMTV-tva transgenic mice, we detected high-grade, poorly differentiated, stroma-rich and ER-negative tumors during pregnancy and lactation. These high-grade and stroma-rich tumors were less frequent in involuted mice or in age-matched nulliparous mice. More importantly, by generating a WAP-tva transgenic line for expression of ErbB2 selectively in WAP(+) mammary alveolar cells, we found that tumors had similar morphological phenotypes (high grade, poorly differentiated, stroma-rich and ER-negative), irrespective of the time since pregnancy and even in the absence of pregnancy. These data suggest that PABCs arise preferentially from an alveolar cell population that expands during pregnancy and lactation. This somatic mouse model may also be useful for preclinical testing of new prophylactic and therapeutic strategies against PABC
Semileptonic B Decays from an NRQCD/D234 Action
Semileptonic B decays are studied on quenched anisotropic lattices using
Symanzik improved glue, NRQCD heavy quark and D234 light quark actions. We
employ constrained fits to extract ground state contributions to two- and
three-point correlators. Results for the B --> pi, l nubar decay form factors
are compared with previous lattice results. We find that our systematic errors
(excluding quenching errors) are dominated by chiral extrapolation
uncertainties.Comment: Lattice2002(Heavy quark physics
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