Velocidade de crescimento, características da carcaça, análise hormonal e morfologia do epitélio intestinal de cordeiros sob dois fotoperíodos

Com o objetivo de avaliar o efeito do fotoperíodo sobre o desenvolvimento de ovinos até o peso vivo em torno de 38-40kg, foram utilizados 26 cordeiros Ile de France x Corriedale, divididos aleatoriamente em 2 grupos: fotoperíodo longo(18h de luz/ 6h de escuridão) e fotoperíodo controle(12h de luz/ 12h de escuridão). Diariamente, dados sobre consumo alimentar foram coletados e, semanalmente, os animais eram pesados e amostras de sangue eram colhidas para dosagem dos níveis plasmáticos dos hormônios Triiodotironina(T3), Tiroxina(T4) e Cortisol. Amostras de jejuno e íleo foram coletadas para análise morfométrica do epitélio intestinal, e foram estudadas características da carcaça. Os cordeiros submetidos ao fotoperíodo longo, apresentaram maior consumo alimentar e maior ganho de peso (P<0,05). Não se verificou diferença significativa nas concentrações plasmáticas dos hormônios estudados, na morfometria intestinal e nas características da carcaça. Concluiu-se que o fotoperíodo longo influencia, positivamente, o desempenho dos cordeiros, sendo esta prática economicamente viável.

QUANTUM BROWNIAN PARTICLE AND MEMORY EFFECTS

The quantum Brownian particle, immersed in a heat bath, is described by a statistical operator whose evolution is ruled by a generalized master equation (GME). The heat bath's degrees of freedom are considered to be either white-noise or colored-noise correlated, while the GME is considered under either the Markov or non-Markov approaches. The comparisons between these considerations are fully developed, and their physical meaning is discussed.

Monte Carlo renormalization group with evolution in the space of parameters

Using data from a single simulation we obtain Monte Carlo renormalization-group information in a finite region of parameter space by adapting the Ferrenberg-Swendsen histogram method. Several quantities are calculated in the two-dimensional N 2 Ashkin-Teller and Ising models to show the feasibility of the method. We show renormalization-group Hamiltonian flows and critical-point location by matching of correlations by doing just two simulations at a single temperature in lattices of different sizes to partially eliminate finite-size effects.

Hanbury-Brown-Twiss interferometry for sonoluminescence bubble

Two-photon correlation of the light pulse emitted from a sonoluminescence bubble is discussed. It is shown that several important features of the mechanism of light emission, such as the time scale and the shape of the emission region, could be obtained from Hanbury-Brown-Twiss interferometry. We also argue that such a measurement may serve to reject one of the two currently suggested emission mechanisms, i.e., the thermal process versus the dynamical Casimir effect.

Quasicausal expansion of the quantum Liouville propagator

The quasicausal expansion of the quantum Liouville propagator is introduced into the Weyl-Wigner picture. The zeroth-order term is shown to lead to the statistical quasiclassical method of Lee and Scully [J. Chem. Phys. 73, 2238 (1980)].

Effect of processing route on the phase formation and properties of Bi4Ti3O12 ceramics

Our efforts were directed to the preparation of bismuth titanate-Bi4Ti3O12 (BIT) by two procedures: mechanically assisted synthesis and polymeric precursor method to display a variety of their advantages. To follow the nucleation and phase formation of BIT, XRD and Rietveld refinement analysis were used and it was shown that Bi4Ti3O12 ceramic can been successfully prepared from nano-sized powders obtained by both methods. The ferroelectric properties were determined and the loops from BIT obtained by polymeric precursor method were not fully saturated with a remnant polarization of 20 mu C/cm(2) and coercitive field of 1500 kV/cm. BIT obtained from powders prepared by mechanically assisted synthesis shows a remnant polarization of 0.65 mu C/cm(2) and coercitive field of 1050 kV/cm. The grain morphology may be the factor causing the observed differences. (C) 2005 Published by Elsevier Ltd and Techna Group S.r.l.

Non-Hermitian multichannel theory of ultracold collisions modified by intense light fields tuned to the red of the trapping transition

We develop a systematic scheme to treat binary collisions between ultracold atoms in the presence of a strong laser field, tuned to the red of the trapping transition. We assume that the Rabi frequency is much less than the spacing between adjacent bound-state resonances, In this approach we neglect fine and hyperfine structures, but consider fully the three-dimensional aspects of the scattering process, up to the partial d wave. We apply the scheme to calculate the S matrix elements up to the second order in the ratio between the Rabi frequency and the laser detuning, We also obtain, fur this simplified multichannel model, the asymmetric line shapes of photoassociation spectroscopy, and the modification of the scattering length due to the light field at low, but finite, entrance kinetic energy. We emphasize that the present calculations can be generalized to treat more realistic models, and suggest how to carry out a thorough numerical comparison to this semianalytic theory. [S1050-2947(98)04902-6].

The absolute configuration of 1-(3 ',4 '-dihydroxycinnamoyl)cyclopentane-2,3-diol from the Amazonian tree Chimarrhis turbinata

An antioxidant, 1-(3',4'-dihydroxycinnamoyl) cyclopentane-2,3-diol [ or ( E)-2,3-dihydroxycyclopentyl-3-(3',4'-dihydroxyphenyl) acrylate ( 1)], and two known trans- and cis-chlorogenic acid methyl esters were isolated from the ethanolic extract of the leaves of Chimarrhis turbinata. The relative configuration of 1 was determined by NMR and by comparison of the circular dichroic spectrum ( CD) with those of the enantiomers of synthetic 3', 4'-dimethoxycinnamoyl analogues. The absolute configuration of one of the synthetic enantiomers was determined using the CD exciton chirality method. This established the structure of naturally occurring 1 as (E)- 2,3-dihydroxycyclopentyl- 3-(3', 4'-dihydroxyphenyl) acrylate.

DERIVATION OF THE ENERGY-TIME UNCERTAINTY RELATION

A derivation from first principles is given of the energy-time uncertainty relation in quantum mechanics. A canonical transformation is made in classical mechanics to a new canonical momentum, which is energy E, and a new canonical coordinate T, which is called tempus, conjugate to the energy. Tempus T, the canonical coordinate conjugate to the energy, is conceptually different from the time t in which the system evolves. The Poisson bracket is a canonical invariant, so that energy and tempus satisfy the same Poisson bracket as do p and q. When the system is quantized, we find the energy-time uncertainty relation DELTAEDELTAT greater-than-or-equal-to HBAR/2. For a conservative system the average of the tempus operator T is the time t plus a constant. For a free particle and a particle acted on by a constant force, the tempus operators are constructed explicitly, and the energy-time uncertainty relation is explicitly verified.

Coupling between muscle activities and muscle torques during horizontal-planar arm movements with direction reversal

In this study we investigated the hypothesis that the simple set of rules used to explain the modulation of muscle activities during single-joint movements could also be applied for reversal movements of the shoulder and elbow joints. The muscle torques of both joints were characterized by a triphasic impulse. The first impulse of each joint accelerated the limb to the target and was generated by an initial burst of the muscles activated first (primary mover). The second impulse decelerated the limb to the target, reversed movement direction and accelerated the limb back to the initial position, and was generated by an initial burst of the muscles activated second (secondary movers). A third impulse, in each joint, decelerated the limb to the initial position due to the generation of a second burst of the primary movers. The first burst of the primary mover decreased abruptly, and the latency between the activation of the primary and secondary movers varied in proportion with target distances for the elbow, but not for the shoulder muscles. All impulses and bursts increased with target distances and were well coupled. Therefore, as predicted, the bursts of muscle activities were modulated to generate the appropriate level of muscle torque. (C) 2005 Elsevier Ltd. All rights reserved.

Positronium-alkali-ion scattering in the close-coupling approximation

We present results for low- and medium-energy elastic and capture cross sections for positronium-atom-alkali-ion scattering using the coupled static close-coupling approximation.

Exhumation of high-pressure granulites of the Guaxupe Complex, southeastern Brazil

This paper describes tectonic and metamorphic features of Precambrian rocks from the Guaxupe Complex and Varginha Shear Zone (VSZ) near the city of Guaxupe in the southern part of the Sao Francisco Craton, southeastern Brazil. The VSZ separates the metasediments of Araxa Group to the north from the granulites of Guaxupe Complex to the south. The sinistral transcurrent VSZ crosses the entire area striking approximately E-W, bending towards SE in the eastern part. Because of this bend, transpressional movement occurred, facilitating the exhumation of the garnet-rich rocks of the deepest exposed part of the granulite-facies terrane.In the garnet granulites the highest pressure-temperature conditions recorded are approximately 1040 degreesC and 14.4 kbar. The rocks underwent decompression from 14.0 kbar to 8.0 kbar, cooling from 980 degreesC to 710 degreesC, the retrograde path following the boundary between the kyanite and sillimanite stability fields. This interval is interpreted to record the uplift of the lower crustal granulite-facies terrane and re-equilibration during magmatic intrusions. For the felsic granulites an interval of 700-810 degreesC and 8.0-11.5 kbar was attained, also pointing to regional decompression.The granulites of the Guaxupe Complex comprise a medium- to high-pressure lower-crustal terrane, with local occurrences of higher-pressure garnet-rich gneisses, which were uplifted along a transpressional segment of the VSZ. Copyright (C) 2000 John Wiley & Sons, Ltd.

LOW-ENERGY BEHAVIOR OF FEW-PARTICLE SCATTERING-AMPLITUDES IN 2 DIMENSIONS

A study of the analytic behavior of different few-particle scattering amplitudes at low energies in two space dimensions is presented. Such a study is of use in modeling and understanding different few-particle processes at low energies. A detailed discussion of the energy and the momentum dependence of the partial-wave on-the-energy-shell and off-the-energy-shell two-particle t matrices is given. These t-matrix elements tend to zero as the energy and momentum variables tend to zero. The multiple-scattering series is used to show that the connected three-to-three amplitudes diverge in the low-energy-momentum limit. Unitarity relations are used to show that the connected two-to-three and one-to-three amplitudes have specific logarithmic singularities at the m-particle breakup threshold. The subenergy singularity in the two-to-three amplitudes is also studied, and comments are made on some applications of the present study in different problems of ph cal interest.

Collisional semiclassical approximations in phase-space representation

The Gaussian wave-packet phase-space representation is used to show that the expansion in powers of a of the quantum Liouville propagator leads, in the zeroth-order term, to results close to those obtained in the statistical quasiclassical method of Lee and Scully in the Weyl-Wigner picture. It is also verified that, propagating the Wigner distribution along the classical trajectories, the amount of error is less than that coming from propagating the Gaussian distribution along classical trajectories.