Navegando por Palavras-chave "Dynamics"

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    Exoplanets in binary star systems: on the switch from prograde to retrograde orbits
    (Springer, 2016) Carvalho, Jean Paulo de Sousa; Mourão, Daniela Cardoso de; Vilhena de Moraes, Rodolpho [UNIFESP]; Prado, Antonio Fernando Bertachini de Almeida; Winter, Othon Cabo
    The eccentric Kozai-Lidov mechanism, based on the secular theory, has been proposed as a mechanism that plays an important role in producing orbits that switch from prograde to retrograde. In the present work we study the secular dynamics of a triple system composed of a Sun-like central star and a Jupiter-like planet, which are under the gravitational influence of another perturbing star (brown dwarf). The perturbation potential is developed in closed form up to the fifth order in a small parameter (), where is the semimajor axis of the extrasolar planet and is the semimajor axis of the perturbing star. To eliminate the short-period terms of the perturbation potential, the double-average method is applied. In this work we do not eliminate the nodes, a standard method in the literature, before deriving the equations of motion. The main goal is to study the effects of the higher-order terms of the expansion of the perturbing force due to the third body in the orbital evolution of the planet. In particular, we investigate the inclination and the shape (eccentricity) of these orbits. We show the importance of the higher-order terms in changing the inversion times of the flip, i.e., the times where the inclination of the inner planet flips from prograde to retrograde trajectories. We also show the dependence of the first flip with respect to the semimajor axis and eccentricity of the orbit of the planet. The general conclusion is that the analytical model increases its accuracy with the inclusion of higher-order terms. We also performed full numerical integrations using the Bulirsch-Stoer method available in the Mercury package for comparison with the analytical model. The results obtained with the equations developed in this work are in accordance with direct numerical simulations.
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    Redes de sistemas dinâmicos acoplados com estrutura gradiente ou hamiltoniana
    (Universidade Federal de São Paulo (UNIFESP), 2020-03-03) Melo Junior, Antonio Edimar De [UNIFESP]; Antoneli Jr, Fernando Martins [UNIFESP]; Universidade Federal de São Paulo
    A recent generalization of the group-theoretic notion of symmetry replaces global symmetries by bijections between certain subsets of the digraph of a network, the “input sets”. A symmetry group becomes a groupoid and this formalism makes it possible to extend group theoretic methods to more general networks, and in particular it leads to a classification of patterns of synchrony in terms of the structure of the network. A network of dynamical systems is equipped with a canonical set of observables for the states of its individual nodes. Moreover, the form of the underlying ODE is constrained by the network topology and how those equations relate to each other. For the coupled systems associated with a network, there can be flow-invariant spaces (synchrony subspaces where some subsystems evolve synchronously), whose existence is independent of the systems equations and depends only on the network topology. Furthermore, any coupled system on the network, when restricted to such a synchrony subspace, determines a new coupled system associated with a smaller network (quotient). A regular network is a network with one kind of node and one kind of coupling. We show conditions for a codimension one bifurcation from a synchronous equilibrium in a regular network at linear level be isomorphic to a generalized eigenspace of the adjacency matrix of the network. We then focus on coupled cell systems in which individual cells are also gradient or Hamiltonian. In broad terms, we prove that only systems with bidirectionally coupled digraphs can be gradient or Hamiltonian. We characterize the conditions for the coupled systems property of being gradient or Hamiltonian to be preserved by the lift and quotient coupled systems. Aside from the topological criteria, we also study the linear theory of regular gradient (Hamiltonian) coupled cell systems. We then prove results on steady-state bifurcations and a version of the Equivariant Branching Lemma and the Equivariant Hopf Theorem. We illustrate a neural network given by two sets of neurons that are mutually coupled through either excitatory or inhibitory synapses, which is modelled by a coupled system exhibiting both gradient and Hamiltonian structures, and how periodic solutions from equilibrium appear in the Restricted Three Body Problem.
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    Structural characterization of beta-carotene-incorporated nanovesicles produced with non-purified phospholipids
    (Elsevier science bv, 2016) Michelon, Mariano; Mantovani, Raphaela Araujo; Sinigaglia-Coimbra, Rita [UNIFESP]; de la Torre, Lucimara Gaziola; Cunha, Rosiane Lopes
    The technical feasibility of obtaining beta-carotene-incorporated phospholipid nanovesicles using non-purified soybean lecithins was studied. For this purpose, three lecithin-types were evaluated. Nanovesicles were characterized by average hydrodynamic diameter, particle size distribution, polydispersity index, zeta-potential, transmission electron microscopy, membrane microviscosity, small angle X-ray scattering and capacity of lipid peroxidation inhibition. In general, the beta-carotene incorporation did not promote a significant increase on average hydrodynamic diameter, but vesicles produced from lecithins containing triglycerides showed lower polydispersity. The lecithin type used to produce nanovesicles did not influence the beta-carotene loading capacity, but significantly influenced the microviscosity of liposomal membrane and lipid peroxidation inhibition capacity. Non-enzymatically modified lecithin (containing or not triglycerides) showed similar efficiency and peroxidation inhibition capacity considering beta-carotene incorporation. Therefore, low-cost non-purified lecithin can be employed for production of liposomal systems as an encapsulating and/or delivery system to be used in food products. (C) 2015 Elsevier Ltd. All rights reserved.