Resumen en Inglés:

The fusion crust of eight Antarctic meteorite finds show natural thermoluminescence (TL) levels about 100 times higher than the levels in the fusion crust of freshly fallen meteorites, Dhajala, Jilin and Bansur. If it is assumed that this TL is due to cosmic ray received on the surface of Antarctica, the terrestrial residence times of the meteorites is calculated to lie between 104 - 105 years. Strictly, these periods represent lower limits of terrestrial ages of these meteorites, and are generally consistent with terrestrial ages calculated from cosmogenic radionuclides

Resumen en Inglés:

The structure of infinite nuclear matter is studied with two of the Zimanyi - Moszkowski (ZM) models in the framework of a relativistic approximation which takes into account Hartree terms and beyond and is compared with the results which come out of the relativistic Hartree - Fock approach in the linear Walecka model. The simple treatment applied to these models can be used in substitution to the more complicated Dirac - Brueckner - Hartree - Fock method to perform future calculations in finite nuclei

Resumen en Inglés:

We present results of theoretical calculations together with simulations for some observables of the reaction <img SRC="http://www.bireme.br/img/fbpe/bjp/v27n3/image369.gif" WIDTH="56" HEIGHT="19">at energies close to the threshold. This approach allows the selection of the set of observables and the best kinematical conditions in order to probe different potentials. The simulations used the parameters of the forthcoming São Paulo Microtron accelerator and photon tagging facilities.

Resumen en Inglés:

In this work we extend previous kaon loop calculations, including the vector K* meson and estimate the strangeness radius of the nucleon and its strange magnetic moment. We find out that, in contrast to naive expectations, this contribution is very important and gives large values for both the radius and the magnetic moment

Resumen en Inglés:

The nuclear reaction rate formula used in stellar evolution calculation is carefully examined. A uniform expansion is performed up to fourth order in the relevant physical parameter. The convergence of the series is assessed and a semianalytical expression is derived, valid for all values of the expansion parameter. The formulae with electron screening and plasma dissipative collision effects are also evaluated. The agreement of the approximate analytical formulae with the exact result is excellent over a wide range of values of the parameters

Resumen en Inglés:

We use path-integrals to derive a general expression for the semiclassical approximation to the partition function of a one-dimensional quantum-mechanical system. Our expression depends solely on ordinary integrals which involve the potential. For high temperatures, the semiclassical expression is dominated by single closed paths. As we lower the temperature, new closed paths may appear, including tunneling paths. The transition from single to multiple-path regime corresponds to well-defined catastrophes. Tunneling sets in whenever they occur. Our formula fully accounts for this feature

Resumen en Inglés:

The influence of viscoelastic properties in sound propagation is analyzed. A generalization of Oldroyd viscoelastic model for incompressible solutions is made for the case of compressible fluids, introducing viscoelastic effects in normal stresses. This generalized model allows us to obtain an integro-differential equation for the small oscillations of pressure in the sound wave. The dispersion relations obtained from this equation are valid in any range of frequency and contain as particular case results reported in the literature

Resumen en Inglés:

We find exact analytical expressions for mixing angles in matter in the context of three generation neutrino oscillations in matter to discuss the role of resonances in this phenomenon. We show that some knowledge from conventional two neutrino MSW effect, which has been extended to approximated solutions to three neutrino oscillations, has to be abandoned in this exact approach. We observe that maximal values for the mixing angles in matter are found in nonresonant regions and stationary phases do not coincide anymore with resonances in this simple extension of the MSW effect. We present a general way to identify a resonance and discuss what we can physically expect in these regions

Resumen en Inglés:

This paper describes the theoretical models and the method used in the design of the poloidal field coils system for the ETE (Experimento Tokamak Esférico small-aspect-ratio tokamak. The method is illustrated with the equilibrium configurations obtained for ETE.

Resumen en Inglés:

A specially designed probe system was constructed and installed at the TBR tokamak to investigate the relation between plasma transport and plasma turbulence. The experimental data confirm the influence of temperature fluctuations in the amplitude and correlation of density and potential fluctuations, and consequently on transport parameters.

Resumen en Inglés:

Based on kinetic theory of gases and on the combined method of Chapman-Enskog and Grad, the laws of Ohm, Fourier and Navier-Stokes are derived for a non-relativistic fully ionized gas. Moreover, the combined method is applied to the BGK model of the relativistic Boltzmann equation and the Ohm's law is derived for a relativistic fully ionized gas.

Resumen en Inglés:

The nature of the L- to H-mode transition is re-examined on the basis of the more recent experimental data, especially that obtained from Ohmically-heated plasmas where the transition is generally more gradual. This raises the question whether the transition is better explained as a gradual change in the characteristics of the turbulence at the plasma edge rather than by a sudden bifurcation in the transport process.