Dynamics of a class of ODEs more general than almost periodic

A temporally global solution, if it exists, of a nonautonomous ordinary differential equation need not be periodic, almost periodic or almost automorphic when the forcing term is periodic, almost periodic or almost automorphic, respectively. An alternative class of functions extending periodic and almost periodic functions which has the property that a bounded temporally global solution solution of a nonautonomous ordinary differential equation belongs to this class when the forcing term does is introduced here. Specifically, the class of functions consists of uniformly continuous functions, defined on the real line and taking values in a Banach space, which have pre-compact ranges. Besides periodic and almost periodic functions, this class also includes many nonrecurrent functions. Assuming a hyperbolic structure for the unperturbed linear equation and certain properties for the linear and nonlinear parts, the existence of a special bounded entire solution, as well the existence of stable and unstable manifolds of this solution are established. Moreover, it is shown that this solution and these manifolds inherit the temporal behaviour of the vector field equation. In the stable case it is shown that this special solution is the pullback attractor of the system. A class of infinite dimensional examples involving a linear operator consisting of a time independent part which generates a C(0)-semigroup plus a small time dependent part is presented and applied to systems of coupled heat and beam equations. (C) 2010 Elsevier Ltd. All rights reserved.

Tokamak magnetic field lines described by simple maps

The magnetic field line structure in a tokamak can be obtained by direct numerical integration of the field line equations. However, this is a lengthy procedure and the analysis of the solution may be very time-consuming. Otherwise we can use simple two-dimensional, area-preserving maps, obtained either by approximations of the magnetic field line equations, or from dynamical considerations. These maps can be quickly iterated, furnishing solutions that mirror the ones obtained from direct numerical integration, and which are useful when long-term studies of field line behavior are necessary (e.g. in diffusion calculations). In this work we focus on a set of simple tokamak maps for which these advantages are specially pronounced.

Stochastic lattice gas model describing the dynamics of the SIRS epidemic process

We study a stochastic process describing the onset of spreading dynamics of an epidemic in a population composed of individuals of three classes: susceptible (S), infected (I), and recovered (R). The stochastic process is defined by local rules and involves the following cyclic process: S -> I -> R -> S (SIRS). The open process S -> I -> R (SIR) is studied as a particular case of the SIRS process. The epidemic process is analyzed at different levels of description: by a stochastic lattice gas model and by a birth and death process. By means of Monte Carlo simulations and dynamical mean-field approximations we show that the SIRS stochastic lattice gas model exhibit a line of critical points separating the two phases: an absorbing phase where the lattice is completely full of S individuals and an active phase where S, I and R individuals coexist, which may or may not present population cycles. The critical line, that corresponds to the onset of epidemic spreading, is shown to belong in the directed percolation universality class. By considering the birth and death process we analyze the role of noise in stabilizing the oscillations. (C) 2009 Elsevier B.V. All rights reserved.

Fock space for fermion-like lattices and the linear Glauber model

The concept of Fock space representation is developed to deal with stochastic spin lattices written in terms of fermion operators. A density operator is introduced in order to follow in parallel the developments of the case of bosons in the literature. Some general conceptual quantities for spin lattices are then derived, including the notion of generating function and path integral via Grassmann variables. The formalism is used to derive the Liouvillian of the d-dimensional Linear Glauber dynamics in the Fock-space representation. Then the time evolution equations for the magnetization and the two-point correlation function are derived in terms of the number operator. (C) 2008 Elsevier B.V. All rights reserved.

Combined Crystallographic and Solution Molecular Dynamics Study of Allosteric Effects in Ester and Ketone p-tert-Butylcalix[4]arene Derivatives and Their Complexes with Acetonitrile, Cd(II), and Pb(II)

We describe here a procedure to bridge the gap in the field of calixarene physicochemistry between solid-state atomic-resolution structural information and the liquid-state low-resolution thermodynamics and spectroscopic data. We use MD simulations to study the kinetics and energetics involved in the complexation of lower rim calix[4]arene derivatives (L), containing bidentate ester (1) and ketone (2) pendant groups, with acetonitrile molecule (MeCN) and Cd2+ and Pb2+ ions (M2+) in acetonitrile solution. On one hand, we found that the prior inclusion of MeCN into the calix to form a L(MeCN) adduct has only a weak effect in preorganizing the hydrophilic cavity toward metal ion binding. On the other hand, the strong ion-hydrophilic cavity interaction produces a wide open calix which enhances the binding of one MeCN molecule (allosteric effect) to stabilize the whole (M2+)1(MeCN) bifunctional complex. We reach two major conclusions: (i) the MD results for the (M2+)1(MeCN) binding are in close agreement with the ""endo"", fully encapsulated, metal complex found by X-ray diffraction and in vacuo MD calculations, and (ii) the MD structure for the more flexible 2 ligand, however, differs from the also endo solid-state molecule. In fact, it shows strong solvation effects at the calixarene lower bore by competing MeCN molecules that share the metal coordination sphere with the four C=O oxygens of an ""exo"" (M2+)2(MeCN) complex.

Ligand dissociation from estrogen receptor is mediated by receptor dimerization: Evidence from molecular dynamics simulations

Estrogen Receptor (ER) is an important target for pharmaceutical design. Like other ligand-dependent transcription factors, hormone binding regulates ER transcriptional activity. Nevertheless, the mechanisms by which ligands enter and leave ERs and other nuclear receptors remain poorly understood. Here, we report results of locally enhanced sampling molecular dynamics simulations to identify dissociation pathways of two ER ligands [the natural hormone 17 beta-estradiol (E-2) and the selective ER modulator raloxifene (RAL)] from the human ER alpha ligand-binding domain in monomeric and dimeric forms. E-2 dissociation occurs via three different pathways in ER monomers. One resembles the mousetrap mechanism (Path I), involving repositioning of helix 12 (H12), others involve the separation of H8 and H11 (Path II), and a variant of this pathway at the bottom of the ligand-binding domain (Path II`). RAL leaves the receptor through Path I and a Path I variant in which the ligand leaves the receptor through the loop region between H11 and H12 (Path I`). Remarkably, ER dimerization strongly suppresses Paths II and II` for E-2 dissociation and modifies RAL escape routes. We propose that differences in ligand release pathways detected in the simulations for ER monomers and dimers provide an explanation for previously observed effects of ER quaternary state on ligand dissociation rates and suggest that dimerization may play an important, and hitherto unexpected, role in regulation of ligand dissociation rates throughout the nuclear receptor family.

Three-dimensional, fully adaptive simulations of phase-field fluid models

We present an efficient numerical methodology for the 31) computation of incompressible multi-phase flows described by conservative phase-field models We focus here on the case of density matched fluids with different viscosity (Model H) The numerical method employs adaptive mesh refinements (AMR) in concert with an efficient semi-implicit time discretization strategy and a linear, multi-level multigrid to relax high order stability constraints and to capture the flow`s disparate scales at optimal cost. Only five linear solvers are needed per time-step. Moreover, all the adaptive methodology is constructed from scratch to allow a systematic investigation of the key aspects of AMR in a conservative, phase-field setting. We validate the method and demonstrate its capabilities and efficacy with important examples of drop deformation, Kelvin-Helmholtz instability, and flow-induced drop coalescence (C) 2010 Elsevier Inc. All rights reserved

Temperature Dynamics Investigation At Small And Shallow Lakes Using Hydrodynamic Model

A three-dimensional time-dependent hydrodynamic and heat transport model of Lake Binaba, a shallow and small dam reservoir in Ghana, emphasizing the simulation of dynamics and thermal structure has been developed. Most numerical studies of temperature dynamics in reservoirs are based on one- or two-dimensional models. These models are not applicable for reservoirs characterized with complex flow pattern and unsteady heat exchange between the atmosphere and water surface. Continuity, momentum and temperature transport equations have been solved. Proper assignment of boundary conditions, especially surface heat fluxes, has been found crucial in simulating the lake’s hydrothermal dynamics. This model is based on the Reynolds Average Navier-Stokes equations, using a Boussinesq approach, with a standard k − ε turbulence closure to solve the flow field. The thermal model includes a heat source term, which takes into account the short wave radiation and also heat convection at the free surface, which is function of air temperatures, wind velocity and stability conditions of atmospheric boundary layer over the water surface. The governing equations of the model have been solved by OpenFOAM; an open source, freely available CFD toolbox. As its core, OpenFOAM has a set of efficient C++ modules that are used to build solvers. It uses collocated, polyhedral numerics that can be applied on unstructured meshes and can be easily extended to run in parallel. A new solver has been developed to solve the hydrothermal model of lake. The simulated temperature was compared against a 15 days field data set. Simulated and measured temperature profiles in the probe locations show reasonable agreement. The model might be able to compute total heat storage of water bodies to estimate evaporation from water surface.

New business dynamics and agressiveness between competitors

Pesquisas recentes tem se concentrado em analisar se as vantagens competitivas podem ser sustentáveis em um contexto hipercompetitivo. Literatura existente que tem analisado economias emergentes descobriu que o desenvolvimento do contexto institucional contribui para a criação de condições hipercompetitivas. Reconhecendo a importância dessas pesquisas no campo da gestão estratégica, mas ao invés de concentrar a atenção em países emergentes, este trabalho considera crucial ter um espectro mais amplo como objeto de estudo com países que diferem em suas características. Nesta pesquisa foi usada uma metodologia diferente dos estudos que foram tomados como referência para o trabalho, como a feita por Hermelo e Vassolo (2010) que centraram a sua atenção nos países em desenvolvimento analisando o efeito das instituições e os ambientes hipercompetitivos na sustentabilidade das vantagens competitivas. As pesquisas anteriores foram complementadas incluindo dados de empresas em países em desenvolvimento e desenvolvidos, isto para determinar a diferença de desempenho econômico superior persistente ao longo do tempo entre eles com a ideia de mostrar como o meio ambiente não é apenas um fator-chave, mas também um componente principal no desenvolvimento de vantagens competitivas. Usando o test Kolmogorov Smirnov e o Propensity Score Matching para reduzir viés, as questões de vantagem competitiva sustentável e os efeitos do contexto institucional foram analisados, tomando cuidado com a comparação uma vez que as suas diferenças podem trazer resultados incorretos. Os resultados empíricos sustentam a tese de que há uma diferença significativa no desempenho econômico superior e sua sustentabilidade entre as empresas em países com essas diferenças. Considerando-se que o foco de estudo está nas instituições e reconhecendo a importância que elas têm na sociedade e crescimento econômico, estudá-las pode nos ajudar a determinar como o desempenho economico superior e o desempenho economico superior persistente poderiam ser alcançados com a estabilidade das instituições e fatores macroeconômicos favoráveis. Uma contribuição importante deste trabalho é que ele usa outras teorias relacionadas com as vantagens competitivas e as relaciona com o entorno macroeconomico e institucional com o proposito de comparar países com realidades muito diferentes através de testes estatísticos que dão uma resposta à hipótese formulada.

Terms of trade, macroeconomic dynamics and default decisions

A evidência empírica aponta que Termos de Troca é uma variável relevante tanto para dinâmica macroeconômica como para o risco de default em países emergentes. No entanto, a literatura de dívida soberana baseada nos trabalhos de Eaton e Gerzovitz (1981) e Arellano (2008) ainda não explorou de forma adequada as conecções entre a dinâmica de termos de troca e incentivos ao default. Nós contribuímos nessa área, introduzindo volatilidade de Termos de Troca no modelo proposto por Mendoza e Yue (2012), no qual as decisões de dívida soberana são vinculadas à um modelo de equilíbrio geral para a economia doméstica. Nós encontramos que uma economia exposta à volatilidade dos termos de troca consegue produzir uma variabilidade do consumo que supera significativamente a variabilidade do produto, característica que constitui um fato estilizado chave de business cycles de países emergentes. Nossos exercícios também mostram que decisões de default são geradas por mudanças bruscas nos termos de troca, mas não necessariamente estão vinculados à estados ruins da economia.

Local Field Potentials in the Gustatory Cortex Carry Taste Information

It has been recently shownthat localfield potentials (LFPs)fromthe auditory and visual cortices carry information about sensory stimuli, but whether this is a universal property of sensory cortices remains to be determined. Moreover, little is known about the temporal dynamics of sensory information contained in LFPs following stimulus onset. Here we investigated the time course of the amount of stimulus information in LFPs and spikes from the gustatory cortex of awake rats subjected to tastants and water delivery on the tongue. We found that the phase and amplitude of multiple LFP frequencies carry information about stimuli, which have specific time courses after stimulus delivery. The information carried by LFP phase and amplitude was independent within frequency bands, since the joint information exhibited neither synergy nor redundancy. Tastant information in LFPs was also independent and had a different time course from the information carried by spikes. These findings support the hypothesis that the brain uses different frequency channels to dynamically code for multiple features of a stimulus.

DYNAMICS AT INFINITY of A CUBIC CHUA'S SYSTEM

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Global dynamics of the Rikitake system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Vortex-Antivortex Dynamics in a Mesoscopic Superconducting Prism with a Centered Antidot

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Vortex dynamics in mesoscopic superconducting square of variable surface

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