On closed Einstein-de Sitter universes

We briefly summarize the idea of cosmological models with compact, flat spatial sections. It has been suggested that, because of the COBE satellite's maps of the microwave background, such models cannot be small in the sense of Ellis, and hence are no longer interesting. Here we use the method of cosmic crystallography by Lehoucq et al. to show that these models are physically meaningful even if the size of the spatial sections is of the same order of magnitude as the radius of the observational horizon. © 1998 Elsevier Science B.V.

Gel'fand-Levitan equation for deletion of states from Coulomb spectra

The Gel'fand-Levitan formalism is used to study how a selected set of bound states can be eliminated from the spectrum of the Coulomb potential and also how to construct a bound state in the Coulomb continuum. It is demonstrated that a sizeable quantum well can be produced by deleting a large number of levels from the s spectral series and the edge of the Coulomb potential alone can support the von Neumann-Wigner states in the continuum. © 1998 Elsevier Science B.V.

Cosmic crystallography with a pullback

We present a modified version of the cosmic crystallography method, especially useful for testing closed models of negative spatial curvature. The images of clusters of galaxies in simulated catalogs are 'pulled back' to the fundamental domain before the set of distances is calculated. © 1999 Published by Elsevier Science B.V. All rights reserved.

Bell's locality condition confronting perfect anti-correlations

We show that Local Realistic Theories, defined as obeying the Bells's locality condition, cannot satisfy the prefect anti-correlations without at the same time maximally violating rotational symmetry at the hidden variable level. We examine whether the rotational symmetry can be restored after the statistical average. We also comment on the question whether such theories are necessarily deterministic at the hidden variable leva. © 1999 Elsevier Science B.V. All rights reserved.

Two-dimensional integrable generalization of the Camassa-Holm equation

In this letter we discuss the (2 + 1)-dimensional generalization of the Camassa-Holm equation. We require that this generalization be, at the same time, integrable and physically derivable under the same asymptotic analysis as the original Camassa-Holm equation. First, we find the equation in a perturbative calculation in shallow-water theory. We then demonstrate its integrability and find several particular solutions describing (2 + 1) solitary-wave like solutions. © 1999 Published by Elsevier Science B.V. All rights reserved.

L-Histidine-europium(III) complex: A spectroscopical study

Chemical characterization as well as spectroscopical study of the L-histidine-europium(III) complex were developed both experimental and theoretically. Molecular mechanics (MM) simulation was performed in order to have indication of the compound structure and the Eu 3+ chemical environment. The Simple Overlap Model (SOM) was applied to predict spectroscopic quantities as 5D 0→ 7F 0/ 5D 0→ 7F 2 intensity ratio, 5D 0→ 7F 1 transition splitting and the intensity Ω λ parameters (λ = 2 and 4). Satisfactory results are obtained with 0.1 and 2/3 as the effective charges of the nitrogen (gN) and oxygen (gO) respectively, and their polarizabilities (α) depend on the distance. © 1999 Elsevier Science B.V. All rights reserved.

Exact solvability of potentials with spatially dependent effective masses

We discuss the relationship between exact solvability of the Schroedinger equation, due to a spatially dependent mass, and the ordering ambiguity. Some examples show that, even in this case, one can find exact solutions. Furthermore, it is demonstrated that operators with linear dependence on the momentum are nonambiguous. (C) 2000 Elsevier Science B.V.

Mapping deformed hyperbolic potentials into nondeformed ones

In this work we introduce a mapping between the so-called deformed hyperbolic potentials, which are presenting a continuous interest in the last few years, and the corresponding nondeformed ones. As a consequence, we conclude that these deformed potentials do not pertain to a new class of exactly solvable potentials, but to the same one of the corresponding nondeformed ones. Notwithstanding, we can reinterpret this type of deformation as a kind of symmetry of the nondeformed potentials. © 2005 Elsevier B.V. All rights reserved.

Analysis of the influence of pre-loading in the rating life calculation of tapered roller bearings applied to lightweight front-axle differentials

For intricate automotive systems that enclose several components, such as gearboxes, an important aspect of the design is defining the correct assembly parameters. A proper assembly can ensure optimized operating conditions and therefore the components can achieve a longer life. In the case of the support bearings applied to front-axle lightweight differentials, the assembly preload is a major aspect for an adequate performance of the system. During the design phase it is imperative to define reference values to this preload, so the application would endure its requirements. However, with the assistance of computer simulations, it is possible to determine an optimum condition of operation, i.e. optimum pre-load, which would increase the system reliability. This paper presents a study on the influence of preload on the rating life of tapered roller bearings applied to light-weight front axle differentials, evaluating how preload affects several key parameters such as rating life and displacement of components, taking into account the flexibility of the surrounding differential housing. Copyright © 2012 SAE International.

Plane waves in noncommutative fluids

We study the dynamics of the noncommutative fluid in the Snyder space perturbatively at the first order in powers of the noncommutative parameter. The linearized noncommutative fluid dynamics is described by a system of coupled linear partial differential equations in which the variables are the fluid density and the fluid potentials. We show that these equations admit a set of solutions that are monochromatic plane waves for the fluid density and two of the potentials and a linear function for the third potential. The energy-momentum tensor of the plane waves is calculated. © 2013 Elsevier B.V.

Dynamical properties for an ensemble of classical particles moving in a driven potential well with different time perturbation

We consider dynamical properties for an ensemble of classical particles confined to an infinite box of potential and containing a time-dependent potential well described by different nonlinear functions. For smooth functions, the phase space contains chaotic trajectories, periodic islands and invariant spanning curves preventing the unlimited particle diffusion along the energy axis. Average properties of the chaotic sea are characterised as a function of the control parameters and exponents describing their behaviour show no dependence on the perturbation functions. Given invariant spanning curves are present in the phase space, a sticky region was observed and show to modify locally the diffusion of the particles. © 2013 Elsevier B.V.

A marcação de pluralidade no SN na fala e na escrita de adolescentes da região de São José do Rio Preto

Pós-graduação em Estudos Linguísticos - IBILCE

Caracterização fenotípica e genética e do comportamento de reintegração social de perdizes (Rhynchotus rufescens) criadas em cativeiro

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação das propriedades mecânicas de fios de Níquel-Titânio após incorporação de dobras e/ou tratamento elétrico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação tomográfica tridimensional do tratamento da classe II divisão 1 com aparelho de Herbst

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)