Heat conduction in a chain of harmonic and anharmonic oscillators under the presence of an energy conserving noise

Reproducing Fourier's law of heat conduction from a microscopic stochastic model is a long standing challenge in statistical physics. As was shown by Rieder, Lebowitz and Lieb many years ago, a chain of harmonically coupled oscillators connected to two heat baths at different temperatures does not reproduce the diffusive behaviour of Fourier's law, but instead a ballistic one with an infinite thermal conductivity. Since then, there has been a substantial effort from the scientific community in identifying the key mechanism necessary to reproduce such diffusivity, which usually revolved around anharmonicity and the effect of impurities. Recently, it was shown by Dhar, Venkateshan and Lebowitz that Fourier's law can be recovered by introducing an energy conserving noise, whose role is to simulate the elastic collisions between the atoms and other microscopic degrees of freedom, which one would expect to be present in a real solid. For a one-dimensional chain this is accomplished numerically by randomly flipping - under the framework of a Poisson process with a variable “rate of collisions" - the sign of the velocity of an oscillator. In this poster we present Langevin simulations of a one-dimensional chain of oscillators coupled to two heat baths at different temperatures. We consider both harmonic and anharmonic (quartic) interactions, which are studied with and without the energy conserving noise. With these results we are able to map in detail how the heat conductivity k is influenced by both anharmonicity and the energy conserving noise. We also present a detailed analysis of the behaviour of k as a function of the size of the system and the rate of collisions, which includes a finite-size scaling method that enables us to extract the relevant critical exponents. Finally, we show that for harmonic chains, k is independent of temperature, both with and without the noise. Conversely, for anharmonic chains we find that k increases roughly linearly with the temperature of a given reservoir, while keeping the temperature difference fixed

O corpo na pele da floresta : a floresta na pele do corpo : uma poética do encontro entre o humano e o vegetal através do desenho

A presente pesquisa articula a mistura entre seres humanos e seres da floresta através do desenho. A flora Amazônica tem uma das maiores diversidades do mundo, é nela que encontramos os recursos necessários para prover os desenhos de todo o nosso estudo. O objetivo deste trabalho é criar obras com novas texturas para o corpo humano usando as texturas das folhas encontradas na floresta amazônica. Para compor os desenhos, usamos as ideias gerais sobre as teorias evolutivas que pressupõem a fusão de seres de espécies diferentes, a relação entre corpo e desenho, diferentes métodos de processos artísticos, trazendo o conceito de mimetismo encontrado na natureza que transforma os seres, mas não muda a sua essência. Walmor Corrêa e Giambattista Della Porta são alguns dos artistas estudados que condensam as ideias da nossa pesquisa, com seus trabalhos artísticos de transformação e comparação entre os seres humanos e animais. Conseguimos sintetizar através de desenhos a fusão de texturas encontradas na floresta com a pele humana.The present research articulates the mixture between human beings and forest beings through drawing. The Amazonian flora has one of the greatest diversities in the world, it is in it that we find the necessary resources to provide the designs of our entire study. The objective of this work is to create works with new textures for the human body using the textures of leaves found in the Amazon rainforest. To compose the drawings, we used general ideas about evolutionary theories that presuppose the fusion of beings of different species, the relationship between body and drawing, different methods of artistic processes, bringing the concept of mimicry found in nature that transforms beings, but does not change its essence. Walmor Corrêa and Giambattista Della Porta are some of the studied artists who condense the ideas of our research, with their artistic works of transformation and comparison between human beings and animals. We managed to synthesize through drawings the fusion of textures found in the forest with human skin

Dependence of the crossover exponent with the diffusion rate in the generalized contact process model

We study how the crossover exponent, phi, between the directed percolation (DP) and compact directed percolation (CDP) behaves as a function of the diffusion rate in a model that generalizes the contact process. Our conclusions are based in results pointed by perturbative series expansions and numerical simulations, and are consistent with a value phi = 2 for finite diffusion rates and phi = 1 in the limit of infinite diffusion rate.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq(FAPERJ) Fundacao de Amparo a Pesquisa do Estado do Rio de Janeir

Entropy Production in Nonequilibrium Systems at Stationary States

We present a stochastic approach to nonequilibrium thermodynamics based on the expression of the entropy production rate advanced by Schnakenberg for systems described by a master equation. From the microscopic Schnakenberg expression we get the macroscopic bilinear form for the entropy production rate in terms of fluxes and forces. This is performed by placing the system in contact with two reservoirs with distinct sets of thermodynamic fields and by assuming an appropriate form for the transition rate. The approach is applied to an interacting lattice gas model in contact with two heat and particle reservoirs. On a square lattice, a continuous symmetry breaking phase transition takes place such that at the nonequilibrium ordered phase a heat flow sets in even when the temperatures of the reservoirs are the same. The entropy production rate is found to have a singularity at the critical point of the linear-logarithm type

Evaluation Of Phenyl-propanedione On Yellowing And Chemical-mechanical Properties Of Experimental Dental Resin-based Materials

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)To evaluate the influence of phenyl-propanedione on yellowing and chemical-mechanical properties of experimental resin-based materials photoactivated using different light curing units (LCUs). Material and Methods: Experimental resin-based materials with the same organic matrix (60:40 wt% BisGMA:TEGDMA) were mechanically blended using a centrifugal mixing device. To this blend, different photoinitiator systems were added in equimolar concentrations with aliphatic amine doubled by wt%: 0.4 wt% CQ; 0.38 wt% PPD; or 0.2 wt% CQ and 0.19 wt% PPD. The degree of conversion (DC), flexural strength (FS), Youngs modulus (YM), Knoop hardness (KNH), crosslinking density (CLD), and yellowing (Y) were evaluated (n=10). All samples were light cured with the following LCUs: a halogen lamp (XL 2500), a monowave LED (Radii), or a polywave LED (Valo) with 16 J/cm2. The results were analysed by two-way ANOVA and Tukeys test (alpha=0.05). Results: No statistical differences were found between the different photoinitiator systems to KNH, CLS, FS, and YM properties (p >= 0.05). PPD/CQ association showed the higher DC values compared with CQ and PPD isolated systems when photoactivated by a polywave LED (p <= 0.05). Y values were highest for the CQ compared with the PPD systems (p?0.05). Conclusion: PPD isolated system promoted similar chemical and mechanical properties and less yellowing compared with the CQ isolated system, regardless of the LCU used.246555560FAPESP - Sao Paulo Research Foundation [2013/04241-2]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Stochastic lattice model describing a vector-borne disease

We employ the approach of stochastic dynamics to describe the dissemination of vector-borne diseases such as\ud dengue, and we focus our attention on the characterization of the threshold of the epidemic. The coexistence\ud space comprises two representative spatial structures for both human and mosquito populations. The human\ud population has its evolution described by a process that is similar to the Susceptible-Infected-Recovered (SIR)\ud dynamics. The population of mosquitoes follows a dynamic of the type of the Susceptible Infected-Susceptible\ud (SIS) model. The coexistence space is a bipartite lattice constituted by two structures representing the human\ud and mosquito populations. We develop a truncation scheme to solve the evolution equations for the densities and\ud the two-site correlations from which we get the threshold of the disease and the reproductive ratio. We present\ud a precise deØnition of the reproductive ratio which reveals the importance of the correlations developed in the\ud early stage of the disease. According to our deØnition, the reproductive rate is directed related to the conditional\ud probability of the occurrence of a susceptible human (mosquito) given the presence in the neighborhood of an\ud infected mosquito (human). The threshold of the epidemic as well as the phase transition between the epidemic\ud and the non-epidemic states are also obtained by performing Monte Carlo simulations.\ud References: [1] David R. de Souza, T^ania Tom∂e, , Suani R. T. Pinho, Florisneide R. Barreto and M∂ario J. de\ud Oliveira, Phys. Rev. E 87, 012709 (2013). [2] D. R. de Souza, T. Tom∂e and R. M. ZiÆ, J. Stat. Mech. P03006\ud (2011)

O impacto da biblioteca acadêmica de odontologia: estudo de caso na ULisboa e na FOUSP

A importância da avaliação da biblioteca é amplamente reconhecida como um procedimento útil para entender e intervir melhor na realidade desses serviços. De fato, as metodologias de avaliação buscam não apenas medir desempenhos e impactos, mas também preparar uma ação sequencial para melhorar seus serviços oferecidos. Este artigo apresenta a pesquisa realizada para verificar, descrever e avaliar o impacto da biblioteca acadêmica como espaço de apoio e investigação na área da saúde oral com base em um instrumento concreto - padrões ISO 16439: 2014 (E) a ser aplicados na forma questionário presencial e/ou on-line na Faculdade de Medicina Dentária da Universidade de Lisboa e na Faculdade de Odontologia da Universidade de São Paulo (FOUSP), desenvolvendo-se uma reflexão teórica com base nos conceitos de espaços de biblioteca no contexto universitário sobre tais impactos dessas bibliotecas universitárias no comportamento dos usuários em relação à informação

Pair approximation for a model of vertical and horizontal transmission of parasites.

We apply Stochastic Dynamics method for a differential equations model, proposed by Marc Lipsitch and collaborators (Proc. R. Soc. Lond. B 260, 321, 1995), for which the transmission dynamics of parasites occurs from a parent to its offspring (vertical transmission), and by contact with infected host (horizontal transmission). Herpes, Hepatitis and AIDS are examples of diseases for which both horizontal and vertical transmission occur simultaneously during the virus spreading. Understanding the role of each type of transmission in the infection prevalence on a susceptible host population may provide some information about the factors that contribute for the eradication and/or control of those diseases. We present a pair mean-field approximation obtained from the master equation of the model. The pair approximation is formed by the differential equations of the susceptible and infected population densities and the differential equations of pairs that contribute to the former ones. In terms of the model parameters, we obtain the conditions that lead to the disease eradication, and set up the phase diagram based on the local stability analysis of fixed points. We also perform Monte Carlo simulations of the model on complete graphs and Erdös-Rényi graphs in order to investigate the influence of population size and neighborhood on the previous mean-field results; by this way, we also expect to evaluate the contribution of vertical and horizontal transmission on the elimination of parasite. Pair Approximation for a Model of Vertical and Horizontal Transmission of Parasites

A stochastic spatially structured epidemic model with diffusive processes

We developed a stochastic lattice model to describe the vector-borne disease (like yellow fever or dengue). The model is spatially structured and its dynamical rules take into account the diffusion of vectors. We consider a bipartite lattice, forming a sub-lattice of human and another occupied by mosquitoes. At each site of lattice we associate a stochastic variable that describes the occupation and the health state of a single individual (mosquito or human). The process of disease transmission in the human population follows a similar dynamic of the Susceptible-Infected-Recovered model (SIR), while the disease transmission in the mosquito population has an analogous dynamic of the Susceptible-Infected-Susceptible model (SIS) with mosquitos diffusion. The occurrence of an epidemic is directly related to the conditional probability of occurrence of infected mosquitoes (human) in the presence of susceptible human (mosquitoes) on neighborhood. The probability of diffusion of mosquitoes can facilitate the formation of pairs Susceptible-Infected enabling an increase in the size of the epidemic. Using an asynchronous dynamic update, we study the disease transmission in a population initially formed by susceptible individuals due to the introduction of a single mosquito (human) infected. We find that this model exhibits a continuous phase transition related to the existence or non-existence of an epidemic. By means of mean field approximations and Monte Carlo simulations we investigate the epidemic threshold and the phase diagram in terms of the diffusion probability and the infection probability