10,512 research outputs found
The \gamma-ray production in neutral-current neutrino oxygen interaction in the energy range above 100 MeV
We calculate the cross section of the gamma-ray production from
neutral-current neutrino-oxygen quasi-elastic interaction, , or , in
which the residual nuclei (15N* or 15O*) lead to the gamma-ray emission with
gamma-ray energy >6 MeV at the branching ratio of 41%. Above 200 MeV, this
cross section dominates over that of gamma-ray production from the inelastic
reaction, . In the present calculation, spectral
function and the spectroscopic factors of
states are essential. The gamma-ray production is dominated by the deexcitation
of state of the residual nucleus
Segmentação de sistemas de produção de leite como instrumento de apoio a decisão e gestão da atividade leiteira.
Qualquer sistema de produção pode ser considerado como um caixa preta, em que os insumos e produtos são conhecidos e mensuráveis, embora o processo de transformação dos insumos em produtos seja desconhecidos. Neles, a correta colocação de recursos, muitas vezes, fica prejudicada pela impossibilidade de se conhecer a exata dimensão ou quantidade de recursos utilizados em cada uma das fases do processo produtivo. Uma das formas de melhorar o entendimento de processos produtivos complexos é segmentar o sistema em partes menores, ou seja em abrir alguns dos compartimentos ue compõem a caixa preta, em que cada um representa uma parte do processo de transformacao. O que se propoe neste estudo e segmentar o sistema global de producao de leite em quatro setores quais sejam: a) producao de leite; b) producao de novilhas para reposição do plantel de vacas; c)producao de alimentos volumosos; e d)maquinas e implementos. Acredita-se que a analise segmentada da atividade leiteira traga grandes vantagens em vista da organização e administracao da producao
Semi-classical open string corrections and symmetric Wilson loops
In the AdS/CFT correspondence, an AdS_2 x S^2 D3-brane with electric flux in
AdS_5 x S^5 spacetime corresponds to a circular Wilson loop in the symmetric
representation or a multiply wound one in N=4 super Yang-Mills theory. In order
to distinguish the symmetric loop and the multiply wound loop, one should see
an exponentially small correction in large 't Hooft coupling. We study
semi-classically the disk open string attached to the D3-brane. We obtain the
exponent of the term and it agrees with the result of the matrix model
calculation of the symmetric Wilson loop.Comment: 14 pages, 4 figures. v2: explanation improved. v3: argument in
section 2 is improved, result not change
Evolution of superconductivity in LaO1-xFxBiS2 prepared by high pressure technique
Novel BiS2-based superconductors LaO1-xFxBiS2 prepared by the high pressure
synthesis technique were systematically studied. It was found that the high
pressure annealing strongly the lattice as compared to the LaO1-xFxBiS2 samples
prepared by conventional solid state reaction at ambient pressure. Bulk
superconductivity was observed within a wide F-concentration range of x = 0.2 ~
0.7. On the basis of those results, we have established a phase diagram of
LaO1-xFxBiS2.Comment: 11 pages, 6 figure
A note on Kerr/CFT and free fields
The near-horizon geometry of the extremal four-dimensional Kerr black hole
and certain generalizations thereof has an SL(2,R) x U(1) isometry group.
Excitations around this geometry can be controlled by imposing appropriate
boundary conditions. For certain boundary conditions, the U(1) isometry is
enhanced to a Virasoro algebra. Here, we propose a free-field construction of
this Virasoro algebra.Comment: 10 pages, v2: comments and references adde
Evolution of superconductivity by oxygen annealing in FeTe0.8S0.2
Oxygen annealing dramatically improved the superconducting properties of
solid-state-reacted FeTe0.8S0.2, which showed only a broad onset of
superconducting transition just after the synthesis. The zero resistivity
appeared and reached 8.5 K by the oxygen annealing at 200\degree C. The
superconducting volume fraction was also enhanced from 0 to almost 100%. The
lattice constants were compressed by the oxygen annealing, indicating that the
evolution of bulk superconductivity in FeTe0.8S0.2 was correlated to the
shrinkage of lattice.Comment: 13 pages, 6 figure
Bubbling Calabi-Yau geometry from matrix models
We study bubbling geometry in topological string theory. Specifically, we
analyse Chern-Simons theory on both the 3-sphere and lens spaces in the
presence of a Wilson loop insertion of an arbitrary representation. For each of
these three manifolds we formulate a multi-matrix model whose partition
function is the vev of the Wilson loop and compute the spectral curve. This
spectral curve is the reduction to two dimensions of the mirror to a Calabi-Yau
threefold which is the gravitational dual of the Wilson loop insertion. For
lens spaces the dual geometries are new. We comment on a similar matrix model
which appears in the context of Wilson loops in AdS/CFT.Comment: 30 pages; v.2 reference added, minor correction
Coordination and chemical effects on the structural, electronic and magnetic properties in Mn pnictides
Simple structures of MnX binary compounds, namely hexagonal NiAs and
zincblende, are studied as a function of the anion (X = Sb, As, P) by means of
the all-electron FLAPW method within local spin density and generalized
gradient approximations. An accurate analysis of the structural, electronic and
magnetic properties reveals that the cubic structure greatly favours the
magnetic alignment in these compounds leading to high magnetic moments and
nearly half-metallic behaviour for MnSb and MnAs. The effect of the anion
chemical species is related to both its size and the possible hybridization
with the Mn states; both contributions are seen to hinder the magnitude of
the magnetic moment for small and light anions. Our results are in very good
agreement with experiment - where available - and show that the generalized
gradient approximation is essential to correctly recover both the equilibrium
volume and magnetic moment.Comment: 18 pages and 4 figures, Latex-file, submitted to Phys.Rev.
Energy Storage in a Hamiltonian System in Partial Contact with a Heat Bath
To understand the mechanism allowing for the long-term storage of excess
energy in proteins, we study a Hamiltonian system consisting of several coupled
pendula in partial contact with a heat bath. It is found that energy storage is
possible when the motion of each pendulum switches between oscillatory
(vibrational) and rotational (phase-slip) modes. The storage time increases
almost exponentially to the square root of the injected energy. The relevance
of our mechanism to protein motors is discussed.Comment: 8 pages, 4 figures, to appear in J.Phys.Soc.Jp
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