A Semi-Lagrangian scheme for a modified version of the Hughes model for pedestrian flow

In this paper we present a Semi-Lagrangian scheme for a regularized version of the Hughes model for pedestrian flow. Hughes originally proposed a coupled nonlinear PDE system describing the evolution of a large pedestrian group trying to exit a domain as fast as possible. The original model corresponds to a system of a conservation law for the pedestrian density and an Eikonal equation to determine the weighted distance to the exit. We consider this model in presence of small diffusion and discuss the numerical analysis of the proposed Semi-Lagrangian scheme. Furthermore we illustrate the effect of small diffusion on the exit time with various numerical experiments

Experimental properties of Bose-Einstein condensates in 1D optical lattices: Bloch oscillations, Landau-Zener tunneling and mean-field effects

We report experimental results on the properties of Bose-Einstein condensates in 1D optical lattices. By accelerating the lattice, we observed Bloch oscillations of the condensate in the lowest band, as well as Landau-Zener (L-Z) tunneling into higher bands when the lattice depth was reduced and/or the acceleration of the lattice was increased. The dependence of the L-Z tunneling rate on the condensate density was then related to mean-field effects modifying the effective potential acting on the condensate, yielding good agreement with recent theoretical work. We also present several methods for measuring the lattice depth and discuss the effects of the micromotion in the TOP-trap on our experimental results.Comment: 11 pages, 14 figure

Efeito da fenilalanina sobre a atividade da enzima hexoquinase de córtex cerebral de ratos jovens

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Bloch oscillations and mean-field effects of Bose-Einstein condensates in 1-D optical lattices

We have loaded Bose-Einstein condensates into one-dimensional, off-resonant optical lattices and accelerated them by chirping the frequency difference between the two lattice beams. For small values of the lattice well-depth, Bloch oscillations were observed. Reducing the potential depth further, Landau-Zener tunneling out of the lowest lattice band, leading to a breakdown of the oscillations, was also studied and used as a probe for the effective potential resulting from mean-field interactions as predicted by Choi and Niu [Phys. Rev. Lett. {\bf 82}, 2022 (1999)]. The effective potential was measured for various condensate densities and trap geometries, yielding good qualitative agreement with theoretical calculations.Comment: 5 pages, 3 figures; accepted for publication in Physical Review Letter

Excitations of a Bose-Einstein condensate in a one-dimensional optical lattice

We investigate the low-lying excitations of a stack of weakly-coupled two-dimensional Bose-Einstein condensates that is formed by a one-dimensional optical lattice. In particular, we calculate the dispersion relations of the monopole and quadrupole modes, both for the ground state as well as for the case in which the system contains a vortex along the direction of the lasers creating the optical lattice. Our variational approach enables us to determine analytically the dispersion relations for an arbitrary number of atoms in every two-dimensional condensate and for an arbitrary momentum. We also discuss the feasibility of experimentally observing our results.Comment: 16 pages, 5 figures, minor changes,accepted for publication in Phys. Rev.

Atividade da Na+/K+ -ATPase na doença do xarope do bordo : estudos "in vitro"

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Uncertainty quantification for kinetic models in socio-economic and life sciences

Kinetic equations play a major rule in modeling large systems of interacting particles. Recently the legacy of classical kinetic theory found novel applications in socio-economic and life sciences, where processes characterized by large groups of agents exhibit spontaneous emergence of social structures. Well-known examples are the formation of clusters in opinion dynamics, the appearance of inequalities in wealth distributions, flocking and milling behaviors in swarming models, synchronization phenomena in biological systems and lane formation in pedestrian traffic. The construction of kinetic models describing the above processes, however, has to face the difficulty of the lack of fundamental principles since physical forces are replaced by empirical social forces. These empirical forces are typically constructed with the aim to reproduce qualitatively the observed system behaviors, like the emergence of social structures, and are at best known in terms of statistical information of the modeling parameters. For this reason the presence of random inputs characterizing the parameters uncertainty should be considered as an essential feature in the modeling process. In this survey we introduce several examples of such kinetic models, that are mathematically described by nonlinear Vlasov and Fokker--Planck equations, and present different numerical approaches for uncertainty quantification which preserve the main features of the kinetic solution.Comment: To appear in "Uncertainty Quantification for Hyperbolic and Kinetic Equations

Glassy dynamics in thin films of polystyrene

Glassy dynamics was investigated for thin films of atactic polystyrene by complex electric capacitance measurements using dielectric relaxation spectroscopy. During the isothermal aging process the real part of the electric capacitance increased with time, whereas the imaginary part decreased with time. It follows that the aging time dependences of real and imaginary parts of the electric capacitance were primarily associated with change in volume (film thickness) and dielectric permittivity, respectively. Further, dielectric permittivity showed memory and rejuvenation effects in a similar manner to those observed for poly(methyl methacrylate) thin films. On the other hand, volume did not show a strong rejuvenation effect.Comment: 7 pages, 7 figures. Phys. Rev. E (in press

A hierarchy of heuristic-based models of crowd dynamics

International audienceWe derive a hierarchy of kinetic and macroscopic models from a noisy variant of the heuristic behavioral Individual-Based Model of Moussaid et al, PNAS 2011, where the pedestrians are supposed to have constant speeds. This IBM supposes that the pedestrians seek the best compromise between navigation towards their target and collisions avoidance. We first propose a kinetic model for the probability distribution function of the pedestrians. Then, we derive fluid models and propose three different closure relations. The first two closures assume that the velocity distribution functions are either a Dirac delta or a von Mises-Fisher distribution respectively. The third closure results from a hydrodynamic limit associated to a Local Thermodynamical Equilibrium. We develop an analogy between this equilibrium and Nash equilibia in a game theoretic framework. In each case, we discuss the features of the models and their suitability for practical use

High density lipoprotein (HDL) as carrier of serum amyloid protein A (SAA) to inflammatory sites: lipids, apolipoproteins and inflammatory cytokines in pleural exudate

Resultados obtidos anteriormente pelo nosso grupo mostraram que a proteína de fase aguda amilóide sérica A (SAA) é um potente estímulo para a expressão de mRNA e liberação de TNF-α, IL-1-β e IL-8 em leucócitos humanos, além de atuar como priming para a liberação de espécies reativas de oxigênio (EROs) por neutrófilos. Nosso objetivo, nesse trabalho, foi mostrar a presença de SAA em exsudatos e definir sua origem, além de verificar sua atividade pró-inflamatória in vivo. Para tanto, utilizamos soro e exsudatos pleurais de 32 pacientes com pneumonia. Mostramos primeíramente a presença da SAA no material inflamatório através de SDS-PAGE, immunoblotting e HPLC. A quantificação de SAA nas amostras foi realizada por ELISA. Nestas amostras também foram determinadas as concentrações de proteína total, proteína C reativa (PCR), apo A-I, apo A-II, apo B, colesterol total, triglicérides, TNF-α, IL-1-β e IL-8. A análise integrada dos nossos resultados indica que há uma passagem preferencial da HDL para o foco inflamatório, quando comparada as demais lipoproteínas. A SAA presente em exsudatos é originada do soro e deve sofrer intensa degradação ou associação com células. O efeito da SAA no exsudato é pró-inflamatório, sendo que esta proteína poderia ser um dos alvos para as enzimas proteolíticas e EROs presentes em exsudatos. Acreditamos que este trabalho contribua significamente para a compreensão do, ainda incerto, papel da SAA no processo inflamatório e dá nova abrangência para as funções da HDL e sua participação na reposta imune.Previous results from our lab showed that the acute phase protein serum amyloid A (SAA) is a potent stimulus for the expression of mRNA and secretion of TNF-α, IL-1-β and IL-8 from human leukocytes. Furthermore SAA primes neutrophils for the generation of reactive oxygen species (ROS). Our goal here was to show the presence of SAA in exudates and define its origin, besides the verification of its proinflammatory activity in vivo. To achieve this goal we used serum and pleural exudates from 32 patients with pneumonia. At first, we showed the presence of SAA in the exudate through SDS-PAGE, immunoblotting and HPLC. SAA was quantified by ELISA. Besides SAA, we also determined the concentrations of total protein, C reactive protein, apo A-I, apo A-II, apo B, cholesterol, triglyceride, TNF-α, IL-1-β e IL-8. The integrate analysis of our results indicates that there is a preferential leakage of HDL to the inflammatory focus when compared to other lipoproteins. SAA present in exudates is originated from serum and may be intensively degraded or associated to cells. The effect of SAA in the exudate is proinflammatory and this protein may be a target for proteolytic enzymes and for ROS present in exudates. We believed that this work adds new insights to the, yet undefined, role of SAA in the inflammatory process and gives a broader compreension to the functions of HDL and its participation in the on the immune response