8,996 research outputs found
Peixes herbivoros da planicie inundavel do Rio Miranda, Pantanal, Mato Grosso do Sul, Brasil.
Na planicie inundavel do baixo rio Miranda, foram encontradas 12 especies de peixes de habitos alimentares herbivoros. Sao: Markiana nigripinnis, Piabucus melanostoma, Metynnis mola, Metynnis maculatus, Mylossoma paraguayensis, Mylossoma orbignyanum, Myloplus levis, Hemiodus orthonops, Leporinus elongatus, Leporinus friderici, Leporinus lacustris e Schizodon borellii. Destas, 4 apresentam importancia economica para a pesca profissional e esportiva (M. paraguayensis, M. orbinyanum, L. elongatus e L. friderici). E discutida a importancia da herbivoria na cadeia alimentar dos peixes sulamericanos.bitstream/item/37446/1/BP10.pd
On the Infrared Behavior of the Pressure in Thermal Field Theories
We study non-perturbatively, via the Schwinger-Dyson equations, the leading
infrared behavior of the pressure in the ladder approximation. This problem is
discussed firstly in the context of a thermal scalar field theory, and the
analysis is then extended to the Yang-Mills theory at high temperatures. Using
the Feynman gauge, we find a system of two coupled integral equations for the
gluon and ghost self-energies, which is solved analytically. The solutions of
these equations show that the contributions to the pressure, when calculated in
the ladder approximation, are finite in the infrared domain.Comment: 20 pages plus 4 figures available by request, IFUSP/P-100
Tetragonal tungsten bronze compounds: relaxor vs mixed ferroelectric - dipole glass behavior
We demonstrate that recent experimental data (E. Castel et al J.Phys. Cond.
Mat. {\bf 21} (2009), 452201) on tungsten bronze compound (TBC)
BaPrNdFeNbO can be well explained in our model
predicting a crossover from ferroelectric () to orientational (dipole)
glass (), rather then relaxor, behavior. We show, that since a "classical"
perovskite relaxor like Pb(Mn Nb)O is never a
ferroelectric, the presence of ferroelectric hysteresis loops in TBC shows that
this substance actually transits from ferroelectric to orientational glass
phase with growth. To describe the above crossover theoretically, we use
the simple replica-symmetric solution for disordered Ising model.Comment: 5 two-column pages, 4 figure
Caracterização físico-química de misturas de óleos vegetais para fins alimentares.
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Previous issue date: 2014-03-10201
Superconductivity and spin-glass like behavior in system with Pd sheet sandwiched between graphene sheets
Pd-metal graphite (Pd-MG) has a layered structure, where each Pd sheet is
sandwiched between adjacent graphene sheets. DC magnetization and AC magnetic
susceptibility of Pd-MG have been measured using a SQUID magnetometer. Pd-MG
undergoes a superconducting transition at ( K). The
superconductivity occurs in Pd sheets. The relaxation of (aging),
which is common to spin glass systems, is also observed below . The
relaxation rate shows a peak at a characteristic time , which is
longer than a wait time . The irreversibility between and
occurs well above . The susceptibility obeys a
Curie-Weiss behavior with a negative Curie-Weiss temperature ( K). The growth of antiferromagnetic order is limited by the
disordered nature of nanographites, forming spin glass-like behavior at low
temperatures in graphene sheets.Comment: 21 pages, 15 figures; submitted to J. Phys.: Condensed Matte
Lattice Gas Analogue Of SK Model: A paradigm for the glass transition
We investigate the connection between the well known Sherrington-Kirkpatrick
Ising Spin Glass and the corresponding Lattice Gas model by analyzing the
relation between their thermodynamical functions. We present results of replica
approach in the Replica Symmetric approximation and discuss its stability as a
function of temperature and external source. Next we examine the effects of
first order Replica Symmetry Breaking at zero temperature. We finally compare
SK results with ours and suggest how the latter could be relevant to a
description of the structural glass transition.Comment: 33 Pages, LaTeX file; 15 Figures added, some grammatical corrections.
To appear in Journal of Physics
Biogás da agrosuinocultura: alternativa energética na borda do Pantanal.
bitstream/item/79978/1/ADM138.pdfFormato eletronico. Disponível também em: Corumbá online, AgoraMS, Agronline, Campo Grande News, BBC News, Infobibos Energias Alternativas Renováveis (blog), Agrosoft
Semiclassical Evolution of Dissipative Markovian Systems
A semiclassical approximation for an evolving density operator, driven by a
"closed" hamiltonian operator and "open" markovian Lindblad operators, is
obtained. The theory is based on the chord function, i.e. the Fourier transform
of the Wigner function. It reduces to an exact solution of the Lindblad master
equation if the hamiltonian operator is a quadratic function and the Lindblad
operators are linear functions of positions and momenta.
Initially, the semiclassical formulae for the case of hermitian Lindblad
operators are reinterpreted in terms of a (real) double phase space, generated
by an appropriate classical double Hamiltonian. An extra "open" term is added
to the double Hamiltonian by the non-hermitian part of the Lindblad operators
in the general case of dissipative markovian evolution. The particular case of
generic hamiltonian operators, but linear dissipative Lindblad operators, is
studied in more detail. A Liouville-type equivariance still holds for the
corresponding classical evolution in double phase, but the centre subspace,
which supports the Wigner function, is compressed, along with expansion of its
conjugate subspace, which supports the chord function.
Decoherence narrows the relevant region of double phase space to the
neighborhood of a caustic for both the Wigner function and the chord function.
This difficulty is avoided by a propagator in a mixed representation, so that a
further "small-chord" approximation leads to a simple generalization of the
quadratic theory for evolving Wigner functions.Comment: 33 pages - accepted to J. Phys.
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