Rotação diferencial em estrelas do tipo solar

Stellar differential rotation is an important key to understand hydromagnetic stellar dynamos, instabilities, and transport processes in stellar interiors as well as for a better treatment of tides in close binary and star-planet systems. The space-borne high-precision photometry with MOST, CoRoT, and Kepler has provided large and homogeneous datasets. This allows, for the first time, the study of differential rotation statistically robust samples covering almost all stages of stellar evolution. In this sense, we introduce a method to measure a lower limit to the amplitude of surface differential rotation from high-precision evenly sampled photometric time series such as those obtained by space-borne telescopes. It is designed for application to main-sequence late-type stars whose optical flux modulation is dominated by starspots. An autocorrelation of the time series is used to select stars that allow an accurate determination of spot rotation periods. A simple two-spot model is applied together with a Bayesian Information Criterion to preliminarily select intervals of the time series showing evidence of differential rotation with starspots of almost constant area. Finally, the significance of the differential rotation detection and a measurement of its amplitude and uncertainty are obtained by an a posteriori Bayesian analysis based on a Monte Carlo Markov Chain (hereafter MCMC) approach. We apply our method to the Sun and eight other stars for which previous spot modelling has been performed to compare our results with previous ones. The selected stars are of spectral type F, G and K. Among the main results of this work, We find that autocorrelation is a simple method for selecting stars with a coherent rotational signal that is a prerequisite to a successful measurement of differential rotation through spot modelling. For a proper MCMC analysis, it is necessary to take into account the strong correlations among different parameters that exists in spot modelling. For the planethosting star Kepler-30, we derive a lower limit to the relative amplitude of the differential rotation. We confirm that the Sun as a star in the optical passband is not suitable for a measurement of the differential rotation owing to the rapid evolution of its photospheric active regions. In general, our method performs well in comparison with more sophisticated procedures used until now in the study of stellar differential rotation

A modified Primal-Dual Logarithmic-Barrier Method for solving the Optimal Power Flow problem with discrete and continuous control variables

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

Low-altitude, near-polar and near-circular orbits around Europa

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

Exploring S-type orbits in the Pluto-Charon binary system

This work generates, through a sample of numerical simulations of the restricted three-body problem, diagrams of semimajor axis and eccentricity which defines stable and unstable zones for particles in S-type orbits around Pluto and Charon. Since we consider initial conditions with 0 <= e <= 0.99, we found several new stable regions. We also identified the nature of each one of these newly found stable regions. They are all associated to families of periodic orbits derived from the planar circular restricted three-body problem. We have shown that a possible eccentricity of the Pluto-Charon system slightly reduces, but does not destroy, any of the stable regions.

Irregular satellites of Jupiter: capture configurations of binary-asteroids

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Probing the Specificity of Binding to the Major Nuclear Localization Sequence-binding Site of Importin-alpha Using Oriented Peptide Library Screening

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

Relation of pretreatment sequence diversity in NS5A region of HCV genotype 1 with immune response between pegylated-INF/ribavirin therapy outcomes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The water factor in the protein-folding problem

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

The Effectiveness of Low-Intensity Red Laser for Activating a Bleaching Gel and Its Effect in Temperature of the Bleaching Gel and the Dental Pulp

Statement of the Problem: The effectiveness of low-intensity red laser for activating a bleaching gel and its effect in pulp temperature was not investigated in dental literature. Purpose: The objective of this study was to assess the effectiveness of low-intensity red laser for activating a bleaching gel, as well as its effect in temperature of the bleaching gel and the dental pulp. Materials and Methods: Forty extracted bovine teeth were immersed in a solution of coffee 14 days for darkening. The initial colors were recorded by spectrophotometric analysis. The specimens were randomly distributed into two groups (N = 20): the control, which did not receive light and the experimental group that received light from an appliance fitted with three red light-emitting laser diodes (? = 660 nm). A green-colored, 35% H2O2based bleaching gel was applied for 30 minutes, and changed three times. After bleaching, the colors were again measured to obtain the L*a*b* values. Color variation was calculated (?E) and the data submitted to the non-paired t-test (5%). To assess temperature, 10 human incisors were prepared, in which one thermocouple was placed on the bleaching gel applied on the surface of the teeth and another inside the pulp chamber. Results: There was a significant difference between the groups (p = 0.016), and the experimental group presented a significantly higher mean variation (7.21 +/- 2.76) in comparison with the control group (5.37 +/- 1.76). There was an increase in pulp temperature, but it was not sufficient to cause damage to the pulp. Conclusion: Bleaching gel activation with low-intensity red laser was capable of increasing the effectiveness of bleaching treatment and did not increase pulp temperature to levels deleterious to the pulp. CLINICAL SIGNIFICANCE The application of a low-intensity red laser was effective for activating a bleaching gel with green dye, without any deleterious increases in pulpal temperature. (J Esthet Restor Dent 24:126134, 2012)

Self-trapping of a binary Bose-Einstein condensate induced by interspecies interaction

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

Localized modes of binary mixtures of Bose-Einstein condensates in nonlinear optical lattices

The properties of the localized states of a two-component Bose-Einstein condensate confined in a nonlinear periodic potential (nonlinear optical lattice) are investigated. We discuss the existence of different types of solitons and study their stability by means of analytical and numerical approaches. The symmetry properties of the localized states with respect to nonlinear optical lattices are also investigated. We show that nonlinear optical lattices allow the existence of bright soliton modes with equal symmetry in both components and bright localized modes of mixed symmetry type, as well as dark-bright bound states and bright modes on periodic backgrounds. In spite of the quasi-one-dimensional nature of the problem, the fundamental symmetric localized modes undergo a delocalizing transition when the strength of the nonlinear optical lattice is varied. This transition is associated with the existence of an unstable solution, which exhibits a shrinking (decaying) behavior for slightly overcritical (undercritical) variations in the number of atoms.

A generalized alternating-direction implicit scheme for incompressible magnetohydrodynamic viscous flows at low magnetic Reynolds number

This paper presents numerical simulations of incompressible fluid flows in the presence of a magnetic field at low magnetic Reynolds number. The equations governing the flow are the Navier-Stokes equations of fluid motion coupled with Maxwell's equations of electromagnetics. The study of fluid flows under the influence of a magnetic field and with no free electric charges or electric fields is known as magnetohydrodynamics. The magnetohydrodynamics approximation is considered for the formulation of the non-dimensional problem and for the characterization of similarity parameters. A finite-difference technique is used to discretize the equations. In particular, an extension of the generalized Peaceman and Rachford alternating-direction implicit (ADI) scheme for simulating two-dimensional fluid flows is presented. The discretized conservation equations are solved in stream function-vorticity formulation. We compare the ADI and generalized ADI schemes, and show that the latter is more efficient in simulating low Reynolds number and magnetic Reynolds number problems. Numerical results demonstrating the applicability of this technique are also presented. The simulation of incompressible magneto hydrodynamic fluid flows is illustrated by numerical solution for two-dimensional cases. (c) 2007 Elsevier B.V. All rights reserved.

Analytical study of the nonlinear behavior of a shape memory oscillator: Part I-primary resonance and free response at low temperatures

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Solid-phase peptide synthesis in highly loaded conditions

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

Podzolization as a deferralitization process: a study of an Acrisol-Podzol sequence derived from Palaeozoic sandstones in the northern upper Amazon Basin

Morphological, geochemical and mineralogical studies were carried out in a representative soil catena of the low-elevation plateaux of the upper Amazon Basin to interpret the steps and mechanisms involved in the podzolization of low-activity clay soils. The soils are derived from Palaeozoic sandstones. They consist of Hydromorphic Podzols under tree savannah in the depressions of the plateaux and predominantly of Acrisols covered by evergreen forest elsewhere.Incipient podzolization in the uppermost Acrisols is related to the formation of organic-rich A and Bhs horizons slightly depleted in fine-size particles by both mechanical particle transfer and weathering. Weathering of secondary minerals by organic acids and formation of organo-metallic complexes act simultaneously over short distances. Their vertical transfer is limited. Selective dissolution of aluminous goethite, then gibbsite and finally kaolinite favour the preferential cheluviation of first Fe and secondly Al. The relatively small amount of organo-metallic complexes produced is related to the quartzitic parent materials, and the predominance of Al over Fe in the spodic horizons is due to the importance of gibbsite in these low-activity clay soils.Morphologically well-expressed podzols occur in strongly iron-depleted topsoils of the depression. Mechanical transfer and weathering of gibbsite and kaolinite by organic acids is enhanced and leads to residual accumulation of sands. Organo-metallic complexes are translocated in strongly permeable sandy horizons and impregnate at depth the macro-voids of embedded soil and saprolite materials to form the spodic Bs and 2BCs horizons. Mechanical transfer of black particulate organic compounds devoid of metals has occurred later within the sandy horizons of the podzols. Their vertical transfer has formed well-differentiated A and Bh horizons. Their lateral removal by groundwater favours the development of an albic E horizon. In an open and waterlogged environment, the general trend is therefore towards the removal of all the metals that have initially accumulated as a response to the ferralitization process and have temporarily been sequestrated in organic complexes in previous stages of soil podzolization.