Monte Carlo thermodynamic and structural properties of the TIP4P water model: dependence on the computational conditions

Classical Monte Carlo simulations were carried out on the NPT ensemble at 25°C and 1 atm, aiming to investigate the ability of the TIP4P water model [Jorgensen, Chandrasekhar, Madura, Impey and Klein; J. Chem. Phys., 79 (1983) 926] to reproduce the newest structural picture of liquid water. The results were compared with recent neutron diffraction data [Soper; Bruni and Ricci; J. Chem. Phys., 106 (1997) 247]. The influence of the computational conditions on the thermodynamic and structural results obtained with this model was also analyzed. The findings were compared with the original ones from Jorgensen et al [above-cited reference plus Mol. Phys., 56 (1985) 1381]. It is notice that the thermodynamic results are dependent on the boundary conditions used, whereas the usual radial distribution functions g(O/O(r)) and g(O/H(r)) do not depend on them.

Bifurcation of limit cycles from an n-dimensional linear center inside a class of piecewise linear differential systems

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

Desenvolvimento de chatterbots educacionais: um estudo de caso voltado ao ensino de algoritmos

In development of Synthetic Agents for Education, the doubt still resides about what would be a behavior that could be considered, in fact, plausible for this agent's type, which can be considered as effective on the transmission of the knowledge by the agent and the function of emotions this process. The purpose of this labor has an investigative nature in an attempt to discover what aspects are important for this behavior consistent and practical development of a chatterbot with the function of virtual tutor, within the context of learning algorithms. In this study, we explained the agents' basics, Intelligent Tutoring Systems, bots, chatterbots and how these systems need to provide credibility to report on their behavior. Models of emotions, personality and humor to computational agents are also covered, as well as previous studies by other researchers at the area. After that, the prototype is detailed, the research conducted, a summary of results achieved, the architectural model of the system, vision of computing and macro view of the features implemented.

Influence of different light sources and photo-activation methods on degree of conversion and polymerization shrinkage of a nanocomposite resin

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Leaf structure of the cerrado (Brazilian savanna) woody plants

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

Black hole entropy associated with the supersymmetric sigma model

By means of an identity that equates the elliptic genus partition function of a supersymmetric sigma model on the N-fold symmetric product (SX)-X-N of X ((SX)-X-N=X-N/S-N, where S-N is the symmetric group of N elements) to the partition function of a second-quantized string theory, we derive the asymptotic expansion of the partition function as well as the asymptotic for the degeneracy of spectrum in string theory. The asymptotic expansion for the state counting reproduces the logarithmic correction to the black hole entropy.

Numerical approximation of the Ginzburg-Landau equation with memory effects in the dynamics of phase transitions

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Crystallization study of molybdate phosphate glasses by thermal analysis

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

Variabilidade espacial do pH, Ca, Mg e V% do solo em diferentes formas do relevo sob cultivo de cana-de-açúcar

Em uma paisagem natural, os solos apresentam uma ampla variação dos atributos químicos, tanto vertical como horizontal, resultante da interação dos diversos fatores de formação envolvidos. Este trabalho foi desenvolvido em Guariba-SP, com o objetivo de avaliar a variabilidade espacial do pH, cálcio (Ca), magnésio (Mg) e saturação por bases (V%) em um Latossolo Vermelho eutroférrico sob cultivo de cana-de-açúcar, utilizando-se métodos da estatística clássica, análise geoestatística e técnica de interpolação de dados, com a finalidade de observar padrões de ocorrência destes atributos na paisagem. No terço inferior da encosta, após análise detalhada da variação do gradiente do declive, caracterizaram-se dois compartimentos (I e II), sob os quais os solos foram amostrados nos pontos de cruzamento de uma malha, com intervalos regulares de 50m, perfazendo um total de 206 pontos, nas profundidades de 0,0-0,2m e 0,6-0,8m. Os maiores alcances foram observados na profundidade de 0,0-0,2m para todos os atributos estudados, com exceção do cálcio que apresentou comportamento inverso, refletindo os efeitos do maior grau de intemperismo e do manejo na variabilidade natural dos solos. Pequenas variações, nas formas do relevo, condicionam variabilidade diferenciada para os atributos químicos.

Comparação de métodos de agrupamento para o estudo da divergência genética em cultivares de feijão

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A historiografia das produções em periódicos de Sadao Omote

buscamos através deste texto materializar o percurso histórico trilhado pelos artigos em periódicos de Sadao Omote ao longo de suas três décadas de produção acadêmico - científica. Para tanto, recorremos ao currículo Lattes do referido autor e listamos todos seus artigos (41) incorporados na referida plataforma. Após este breve caminho exploratório, realizamos uma árida busca pela totalidade destes textos, apenas consubstanciada com a ajuda do próprio autor, o qual nos disponibilizou os textos faltantes. Feito isto, lemos minuciosamente cada artigo três vezes, extraindo deles os principais conceitos referentes à Educação Especial como campo de conhecimento. A intersecção destes elementos corporifica-se na presente análise, dividida em três partes, a saber: a) conceitos basilares trabalhados por Omote no campo da Educação Especial; b) idéias e apontamentos sobre o fenômeno da inclusão, dirigindo especial ênfase aos aspectos relacionados ao ambiente escolar, e; c) principais referências e temas retratados pelo referido autor; cuja concretude objetiva destacar criticamente os principais apontamentos de Sadao Omote referente à Educação Especial, nosso campo de estudo, e possíveis caminhos dialéticos à edificação de um sistema educacional que seja radical na qualidade de ensino por ele ministrada.

C-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonds in liquid amides investigated by Monte Carlo simulation

Monte Carlo simulations of liquid formamide, N-methylformamide (MF), and N,N-dimethylformamide (DMF) have been performed in the isothermal and isobaric ensemble at 298 K and 1 atm, aiming to investigate the C-H ... O and N-H ... O hydrogen bonds. The interaction energy was calculated using the classical 6-12 Lennard-Jones pairwise potential plus a Coulomb term on a rigid six-site molecular model with the potential parameters being optimized in this work. Theoretical values obtained for heat of vaporization and liquid densities are in good agreement with the experimental data. The radial distribution function [RDF, g(r)] obtained compare well with R-X diffraction data available. The RDF and molecular mechanics (MM2) minimization show that the C-H ... O interaction has a significant role in the structure of the three liquids. These results are supported by ab initio calculations. This Interaction is particularly important in the structure of MF. The intensity of the N-H ... O hydrogen bond is greater in the MF than formamide. This could explain some anomalous properties verified in MF. (C) 1997 John Wiley & Sons, Inc.

The application of interpolating MLS approximations to the analysis of MHD flows

The element-free Galerkin method (EFGM) is a very attractive technique for solutions of partial differential equations, since it makes use of nodal point configurations which do not require a mesh. Therefore, it differs from FEM-like approaches by avoiding the need of meshing, a very demanding task for complicated geometry problems. However, the imposition of boundary conditions is not straightforward, since the EFGM is based on moving-least-squares (MLS) approximations which are not necessarily interpolants. This feature requires, for instance, the introduction of modified functionals with additional unknown parameters such as Lagrange multipliers, a serious drawback which leads to poor conditionings of the matrix equations. In this paper, an interpolatory formulation for MLS approximants is presented: it allows the direct introduction of boundary conditions, reducing the processing time and improving the condition numbers. The formulation is applied to the study of two-dimensional magnetohydrodynamic flow problems, and the computed results confirm the accuracy and correctness of the proposed formulation. (C) 2002 Elsevier B.V. All rights reserved.

Predição de propagação de fissuras através de modelos constitutivos locais e técnica de construção progressiva da trajetória de descontinuidade

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

C - H ⋯ 0 and N - H ⋯ 0 hydrogen bonds in liquid amides investigated by monte carlo simulation

Monte Carlo simulations of liquid formamide, N-methylformamide (MF), and N, N-dimethytformamide (DMF) have been performed in the isothermal and isobaric ensemble at 298 K and 1 atm, aiming to investigate the C-H ⋯ O and N-H ⋯ O hydrogen bonds. The interaction energy was calculated using the classical 6-12 Lennard-Jones pairwise potential plus a Coulomb term on a rigid six-site molecular model with the potential parameters being optimized in this work. Theoretical values obtained for heat of vaporization and liquid densities are in good agreement with the experimental data. The radial distribution function [RDF, g(r)] obtained compare well with R-X diffraction data available. The RDF and molecular mechanics (MM2) minimization show that the C-H ⋯ O interaction has a significant role in the structure of the three liquids. These results are supported by ab initio calculations. This interaction is particularly important in the structure of MF. The intensity of the N - H ⋯ O hydrogen bond is greater in the MF than formamide. This could explain some anomalous properties verified in MF. © 1997 John Wiley & Sons, Inc.