157 resultados para non-smooth dynamical systems


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

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We construct new examples of cylinder flows, given by skew product extensions of irrational rotations on the circle, that are ergodic and rationally ergodic along a subsequence of iterates. In particular, they exhibit a law of large numbers. This is accomplished by explicitly calculating, for a subsequence of iterates, the number of visits to zero, and it is shown that such number has a Gaussian distribution.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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In this work we study some topics of Celestial Mechanics, namely the problem of rigid body rotation and “spin-orbit” resonances. Emphasis is placed on the problem formulation and applications to some exoplanets with physical parameters (e.g. mass and radius) compatible with a terrestrial type constitution (e.g. rock) belonging to multiple planetary systems. The approach is both analytical and numerical. The analytical part consists of: i) the deduction of the equation of motion for the rotation problem of a spherical body with no symmetry, disturbed by a central body; ii) modeling the same problem by including a third-body in the planet-star system; iii) formulation of the concept of “spin-orbit” resonance in which the orbital period of the planet is an integer multiple of the rotation’s period. Topics of dynamical systems (e.g. equilibrium points, chaos, surface sections, etc.) will be included at this stage. In the numerical part simulations are performed with numerical models developed in the previous analytical section. As a first step we consider the orbit of the planet not perturbed by a third-body in the star-planet system. In this case the eccentricity and orbital semi-major axis of the planet are constants. Here the technique of surface sections, widely used in dynamical systems are applied. Next, we consider the action of a third body, developing a more realistic model for planetary rotation. The results in both cases are compared. Since the technique of disturbed surface sections is no longer applicable, we quantitatively evaluate the evolution of the characteristic angles of rotation (e.g. physical libration) by studying the evolution of individual orbits in the dynamically important regions of phase space, the latter obtained in the undisturbed case

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Vulnerability of patients with Down syndrome (DS) to oxidative stress and damage has been attributed to the overexpression of the superoxide dismutase gene, which is located in the triplicated critical region 21q22.2 of chromosome 21. The objective of this study was to investigate enzymatic and non-enzymatic antioxidant systems and levels of biomarkers of oxidative damage in saliva of patients with DS. Saliva samples were collected from 30 patients with DS and 30 controls, ranging in age from 14 to 24 years. The following parameters were analyzed: superoxide dismutase activity, concentration of malondialdehyde, carbonylated proteins, uric acid, vitamin C and total protein, peroxidase activity, and total antioxidant capacity. Patients with DS presented significantly higher superoxide dismutase activity and malondialdehyde levels than controls (p<0.05). On the other hand, no difference in carbonylated proteins or antioxidants (uric acid, vitamin C, peroxidase, and total antioxidant capacity) was observed between DS patients and controls (p>0.05). Patients with DS also presented higher salivary total protein content (p<0.05). In conclusion, despite similar antioxidant levels patients with DS are more vulnerable to oxidative stress in saliva as indicated by a significant increase in malondialdehyde concentration and superoxide dismutase activity

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Pós-graduação em Matemática em Rede Nacional - IBILCE

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Códigos esféricos n-dimensionais gerados por grupos comutativos em dimensão par, n = 2m, podem ser determinados pelo quociente de reticulados m-dimensionais, quando os vetores que geram o sub-reticulado são mutuamente ortogonais [4]. Apresentamos a construção de sub-reticulados nestas condições, a partir do reticulado hexagonal, A2. Comparamos a distância mínima do código esfé- rico construído através do quociente destes reticulados com o limitante da distância mínima estabelecido em [5].

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Pós-graduação em Matemática Universitária - IGCE

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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