482 research outputs found
Uma análise das barreiras tarifárias no comércio internacional de lácteos.
bitstream/item/57090/1/BOP-32-Uma-Analise-das-Barreiras-Tarifarias-no-Comercio-Internacional-de-Lacteos.pd
Manifestations of fine features of the density of states in the transport properties of KOs2O6
We performed high-pressure transport measurements on high-quality single
crystals of KOs2O6, a beta-pyrochlore superconductor. While the resistivity at
high temperatures might approach saturation, there is no sign of saturation at
low temperatures, down to the superconducting phase. The anomalous resistivity
is accompanied by a nonmetallic behavior in the thermoelectric power (TEP) up
to temperatures of at least 700 K, which also exhibits a broad hump with a
maximum at 60 K. The pressure influences mostly the low-energy electronic
excitations. A simple band model based on enhanced density of states in a
narrow window around the Fermi energy (EF) explains the main features of this
unconventional behavior in the transport coefficients and its evolution under
pressure
O perfil da indústria de laticínios na Zona da Mata e Campo das Vertentes de Minas Gerais.
Cenário econômico mundial; Cenário econômico brasileiro; Cenário macroeconômico regional: Zona da Mata e Campo das Vertentes; Evolução do setor lácteo brasileiro.bitstream/item/132488/1/Livro-O-perfil-da-industria-de-laticinios.pd
Path Integral Solubility of a General Two-Dimensional Model
The solubility of a general two dimensional model, which reduces to various
models in different limits, is studied within the path integral formalism.
Various subtleties and interesting features are pointed out.Comment: 7 pages, UR1386, ER40685-83
Effect of Impurity Scattering on the Nonlinear Microwave Response in High-Tc Superconductors
We theoretically investigate intermodulation distortion in high-Tc
superconductors. We study the effect of nonmagnetic impurities on the real and
imaginary parts of nonlinear conductivity. The nonlinear conductivity is
proportional to the inverse of temperature owing to the dependence of the
damping effect on energy, which arises from the phase shift deviating from the
unitary limit. It is shown that the final-states interaction makes the real
part predominant over the imaginary part. These effects have not been included
in previous theories based on the two-fluid model, enabling a consistent
explanation for the experiments with the rf and dc fields
Electron-Phonon Coupling and the Soft Phonon Mode in TiSe
We report high-resolution inelastic x-ray measurements of the soft phonon
mode in the charge-density-wave compound TiSe. We observe a complete
softening of a transverse optic phonon at the L point, i.e. q = (0.5, 0, 0.5),
at T ~ T_{CDW}. Renormalized phonon energies are observed over a large
wavevector range . Detailed
ab-initio calculations for the electronic and lattice dynamical properties of
TiSe2 are in quantitative agreement with experimental frequencies for the
phonon branch involving the soft mode. The observed broad range of renormalized
phonon frequencies is directly related to a broad peak in the electronic
susceptibility stabilizing the charge-density-wave ordered state. Our analysis
demonstrates that a conventional electron-phonon coupling mechanism can explain
a structural instability and the charge-density-wave order in TiSe_2 although
other mechanisms might further boost the transition temperature
Effects of hydroxyapatite and PDGF concentrations on osteoblast growth in a nanohydroxyapatite-polylactic acid composite for guided tissue regeneration
The technique of guided tissue regeneration (GTR) has evolved over recent years in an attempt to achieve periodontal tissue regeneration by the use of a barrier membrane. However, there are significant limitations in the currently available membranes and overall outcomes may be limited. A degradable composite material was investigated as a potential GTR membrane material. Polylactic acid (PLA) and nanohydroxyapatite (nHA) composite was analysed, its bioactive potential and suitability as a carrier system for growth factors were assessed. The effect of nHA concentrations and the addition of platelet derived growth factor (PDGF) on osteoblast proliferation and differentiation was investigated. The bioactivity was dependent on the nHA concentration in the films, with more apatite deposited on films containing higher nHA content. Osteoblasts proliferated well on samples containing low nHA content and differentiated on films with higher nHA content. The composite films were able to deliver PDGF and cell proliferation increased on samples that were pre absorbed with the growth factor. nHA–PLA composite films are able to deliver active PDGF. In addition the bioactivity and cell differentiation was higher on films containing more nHA. The use of a nHA–PLA composite material containing a high concentration of nHA may be a useful material for GTR membrane as it will not only act as a barrier, but may also be able to enhance bone regeneration by delivery of biologically active molecules
THERMAL EFFECTS ON THE CATALYSIS BY A MAGNETIC FIELD
We show that the formation of condensates in the presence of a constant
magnetic field in 2+1 dimensions is extremely unstable. It disappears as soon
as a heat bath is introduced with or without a chemical potential. We point out
some new nonanalytic behavior that develops in this system at finite
temperature.Comment: 10 pages, plain Te
On the Derivative Expansion at Finite Temperature
In this short note, we indicate the origin of nonanalyticity in the method of
derivative expansion at finite temperature and discuss some of its
consequences.Comment: 7 pages, UR-1363, ER40685-81
Fermion localization on asymmetric two-field thick branes
In this paper we investigate the localization of fermions on asymmetric thick
branes generated by two scalars and . In order to trap fermions on
the asymmetric branes with kink-like warp factors, the couplings with the
background scalars are introduced, where
is a function of and . We find that the coupling
do not support the localization of 4-dimensional
fermions on the branes. While, for the case
, which is the kink-fermion
coupling corresponding to one-scalar-generated brane scenarios, the zero mode
of left-handed fermions could be trapped on the branes under some conditions.Comment: v2: 11 pages, 4 figures, accepted by CQ
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