Interface Formation and Electrical Transport in SnO2:Eu3+/GaAs Heterojunction Deposited by Sol-Gel Dip-Coating and Resistive Evaporation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Stabilization of a (3+1)-dimensional soliton in a Kerr medium by a rapidly oscillating dispersion coefficient

Using the numerical solution of the nonlinear Schrodinger equation and a variational method it is shown that (3 + 1)-dimensional spatiotemporal optical solitons can be stabilized by a rapidly oscillating dispersion coefficient in a Kerr medium with cubic nonlinearity. This has immediate consequence in generating dispersion-managed robust optical soliton in communication as well as possible stabilized Bose-Einstein condensates in periodic optical-lattice potential via an effective-mass formulation. We also critically compare the present stabilization with that obtained by a rapid sinusoidal oscillation of the Kerr nonlinearity parameter.

Mean-field equations for cigar- and disc-shaped Bose and Fermi superfluids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Gap solitons in fermion superfluids

We consider a dynamical model of a superfluid Fermi gas in the Bardeen-Cooper-Schrieffer regime trapped in a periodic optical lattice (OL) potential. The model is based on an equation for complex order parameter phi of the superfluid, which is derived from the relevant energy density and includes a self-repulsive term similar to phi(7/3). By means of the variational approximation (VA) and numerical simulations, we find families of stable one- and two-dimensional (I D and 2D) gap solitons (GSs) in this model. Chiefly, they are compact objects trapped in a single cell of the OL. Families of stable even and odd bound states of these GSs are also found in one dimension. A 3D GS family is constructed too, but solely within the framework of the VA. In the linear limit, the VA predicts an almost exact position of the left edge of the first band-gap in the OL-induced spectrum. The full VA provides an accurate description of families of I D and 2D fundamental GSs. We also demonstrate that a I D GS can be safely transported by an OL moving at a moderate velocity. (C) 2009 IMACS. Published by Elsevier B.V. All rights reserved.

Study of a degenerate dipolar Fermi gas of Dy-161 atoms

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dimensional reduction of the ABJM model

We dimensionally reduce the ABJM model, obtaining a two-dimensional theory that can be thought of as a 'master action'. This encodes information about both T- and S-duality, i.e. describes fundamental (F1) and D-strings (D1) in 9 and 10 dimensions. The Higgsed theory at large VEV, (v) over tilde, and large k yields D1-brane actions in 9d and 10d, depending on which auxiliary fields are integrated out. For N = 1 there is a map to a Green-Schwarz string wrapping a nontrivial circle in C(4)/Z(k).

Semiclassical scattering in two dimensions

The semiclassical limit of quantum mechanical scattering in two dimensions is developed and the Wentzel-Kramers-Brillouin and eikonal results for two-dimensional scattering is derived. No backward or forward glory scattering is present in two dimensions. Other phenomena, such as rainbows and orbiting, do occur. (C) 2008 American Association of Physics Teachers.

Dissipative area-preserving one-dimensional Fermi accelerator model

The influence of dissipation on the simplified Fermi-Ulam accelerator model (SFUM) is investigated. The model is described in terms of a two-dimensional nonlinear mapping obtained from differential equations. It is shown that a dissipative SFUM possesses regions of phase space characterized by the property of area preservation.

A bouncing ball model with two nonlinearities: a prototype for Fermi acceleration

Some dynamical properties of a bouncing ball model under the presence of an external force modelled by two nonlinear terms are studied. The description of the model is made by the use of a two-dimensional nonlinear measure-preserving map on the variable's velocity of the particle and time. We show that raising the straight of a control parameter which controls one of the nonlinearities, the positive Lyapunov exponent decreases in the average and suffers abrupt changes. We also show that for a specific range of control parameters, the model exhibits the phenomenon of Fermi acceleration. The explanation of both behaviours is given in terms of the shape of the external force and due to a discontinuity of the moving wall's velocity.

O problema de corte de estoque em indústrias de móveis de pequeno e médio portes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development and applications of three-dimensional gamma ray tomography system using ray casting volume rendering techniques

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SUPERSYMMETRIC SOLUTION FOR 2-DIMENSIONAL SCHRODINGER-EQUATION

We use a non usual realization of the superalgebra to resolve certain two-dimensional potentials. The Hartmann and an anisotropic ring-shaped oscillator are explicitly solved.

SEMICLASSICAL THEORY OF MAGNETIZATION FOR A 2-DIMENSIONAL NONINTERACTING ELECTRON-GAS

We compute the semiclassical magnetization and susceptibility of non-interacting electrons, confined by a smooth two-dimensional potential and subjected to a uniform perpendicular magnetic field, in the general case when their classical motion is chaotic. It is demonstrated that the magnetization per particle m(B) is directly related to the staircase function N(E), which counts the single-particle levels up to energy E. Using Gutzwiller's trace formula for N, we derive a semiclassical expression for m. Our results show that the magnetization has a non-zero average, which arises from quantum corrections to the leading-order Weyl approximation to the mean staircase and which is independent of whether the classical motion is chaotic or not. Fluctuations about the average are due to classical periodic orbits and do represent a signature of chaos. This behaviour is confirmed by numerical computations for a specific system.

Thiobacillus ferrooxidans response to copper and other heavy metals: growth, protein synthesis and protein phosphorylation

Respirometric experiments demonstrated that the oxygen uptake by Thiobacillus ferrooxidans strain LR was not inhibited in the presence of 200 mM copper. Copper-treated and untreated cells from this T. ferrooxidans strain were used in growth experiments in the presence of cadmium, copper, nickel and zinc. Growth in the presence of copper was improved by the copper-treated cells. However, no growth was observed for these cells, within 190 h of culture, when cadmium, nickel and zinc were added to the media. Changes in the total protein synthesis pattern were detected by two-dimensional polyacrylamide gel electrophoresis for T. ferrooxidans LR cells grown in the presence of different heavy metals. Specific proteins were induced by copper (16, 28 and 42 kDa) and cadmium (66 kDa), whereas proteins that had their synthesis repressed were observed for all the heavy metals tested. Protein induction was also observed in the cytosolic and membrane fractions from T. ferrooxidans LR cells grown in the presence of copper. The level of protein phosphorylation was increased in the presence of this metal.

Many-body effects in wide parabolic AlGaAs quantum wells

Photoluminescence measurements at different temperatures have been performed to investigate the optical response of a two-dimensional electron gas in n-type wide parabolic quantum wells. A series of samples with different well widths in the range of 1000-3000 A was analyzed. Many-body effects, usually observed in the recombination process of a two-dimensional electron gas, appear as a strong enhancement in the photoluminescence spectra at the Fermi level at low temperature only in the thinnest parabolic quantum wells. The suppression of the many-body effect in the thicker quantum wells was attributed to the decrease of the overlap between the wavefunctions of the photocreated holes and the two-dimensional electrons belonging to the highest occupied electron subband. (C) 2007 American Institute of Physics.