Yukawa potentials in systems with partial periodic boundary conditions II : Lekner sums for quasi-two dimensional systems

Yukawa potentials may be long ranged when the Debye screening length is large. In computer simulations, such long ranged potentials have to be taken into account with convenient algorithms to avoid systematic bias in the sampling of the phase space. Recently, we have provided Ewald sums for quasi-two dimensional systems with Yukawa interaction potentials [M. Mazars, {\it J. Chem. Phys.}, {\bf 126}, 056101 (2007) and M. Mazars, {\it Mol. Phys.}, Paper I]. Sometimes, Lekner sums are used as an alternative to Ewald sums for Coulomb systems. In the present work, we derive the Lekner sums for quasi-two dimensional systems with Yukawa interaction potentials and we give some numerical tests for pratical implementations. The main result of this paper is to outline that Lekner sums cannot be considered as an alternative to Ewald sums for Yukawa potentials. As a conclusion to this work : Lekner sums should not be used for quasi-two dimensional systems with Yukawa interaction potentials.Comment: 25 pages, 5 figures and 1 tabl

Friendship and gender in preschoolers’ conflicts

Investigated the role of friendship and gender on conflict episodes of 48 preschoolers aged approximately 5 years and 8 months. Children were organized in dyads of same-sex friends and non-friends. Conflict situations were coded according to incidence, type, termination strategies, and finalizations. Gender differences were detected for type of conflict, with girls using more reasons for oppositions than boys. Termination strategies were used with a joint effect of friendship and gender: girl-friends preferred the tactic of standing firm whereas boy-friends chose more negotiation as means to deal with a disagreement, compared to the non-friend dyads. As for the results on conflict finalizations, friendship relations accounted for a significant difference found for agreement, while gender showed to be related to the use of disengagement among girls. Combined analysis between termination strategies and conflict finalizations indicated two significant differences: the first was related to friendship, through which children used more negotiation leading to agreement; the second showed a joint effect of friendship and gender, where non-friend girls tended to negotiate to reach disengagement, more often that non-friend boys. Findings for termination strategies – with girl-friends being more incisive and firm with their partners – diverge from the results provided by empirical literature, where boys are described as more autonomy- and domain oriented, and girls are prone to intimacy and social well-being in their relationships. Results are discussed with basis on previous studies conducted on conflict among preschoolers with considerations about the effects of gender and type of relationship

Definição de uma metodologia para modelagem de agentes inteligentes difusos a partir da técnica de mapas mentais : um estudo de caso baseado na percepção e comportamento de usuários da praia Brava, SC – Brasil

Copyright © 2005 OLAMA partir da premissa de que os conhecimentos da percepção e do comportamento humanos são importantes para o entendimento de seus valores, e que estes podem influenciar no uso e ocupação do espaço, este artigo considera crucial ao processo de gestão ambiental a compreensão destes elementos. A pesquisa apresentada é de caráter exploratório, qualitativo e associa a investigação em cognição ambiental com inteligência artificial através do empreendimento da técnica de mapa mental para caracterização do perfil de grupos de usuários da praia Brava, Itajaí – SC, Brasil, a partir da percepção e comportamento de cada indivíduo frente a atributos espaciais do meio. Os perfis obtidos por este tipo de metodologia são testados num modelo de simulação baseada em agentes inteligentes difusos, uma técnica de inteligência artificial bastante recente. O uso da ferramenta de simulação para a gestão ambiental em áreas costeiras, em particular em praias, é uma importante forma de entender o impacto humano através da previsão de situações e medidas que visam o gerenciamento mais adequado do lugar.ABSTRACT: Understand people’s values and spatial behavior is important toward a successful environmental planning and management. This paper merge environmental perception and spatial behavior with simulation through the employment of a new simulation paradigm called intelligent fuzzy agent-based model. In this research, sketch maps and questionnaires were apply to study coastal zones user group’s perceptions and spatial behavior in order to provide information for modelling reasons. It was selected as study case the Praia Brava, Itajaí – SC, Brazil due to its diverse environment. As conclusion was proven that the methodology is an excellent method to categorize user’s perception and spatial behavior for computational codification

Counterions at charge-modulated substrates

We consider counterions in the presence of a single planar surface with a spatially inhomogeneous charge distribution using Monte-Carlo simulations and strong-coupling theory. For high surface charges, multivalent counterions, or pronounced substrate charge modulation the counterions are laterally correlated with the surface charges and their density profile deviates strongly from the limit of a smeared-out substrate charge distribution, in particular exhibiting a much increased laterally averaged density at the surface.Comment: 7 page

Strong-Coupling Theory for Counter-Ion Distributions

The Poisson-Boltzmann approach gives asymptotically exact counter-ion density profiles around charged objects in the weak-coupling limit of low valency and high temperature. In this paper we derive, using field-theoretic methods, a theory which becomes exact in the opposite limit of strong coupling. Formally, it corresponds to a standard virial expansion. Long-range divergences, which render the virial expansion intractable for homogeneous bulk systems, are shown to be renormalizable for the case of inhomogeneous distribution functions by a systematic expansion in inverse powers of the coupling parameter. For a planar charged wall, our analytical results compare quantitatively with extensive Monte-Carlo simulations.Comment: 7 pages, 3 figures; to appear in Europhys. Let

On the lowest eigenvalue of Laplace operators with mixed boundary conditions

In this paper we consider a Robin-type Laplace operator on bounded domains. We study the dependence of its lowest eigenvalue on the boundary conditions and its asymptotic behavior in shrinking and expanding domains. For convex domains we establish two-sided estimates on the lowest eigenvalues in terms of the inradius and of the boundary conditions

Two isoperimetric inequalities for the Sobolev constant

In this note we prove two isoperimetric inequalities for the sharp constant in the Sobolev embedding and its associated extremal function. The first such inequality is a variation on the classical Schwarz Lemma from complex analysis, similar to recent inequalities of Burckel, Marshall, Minda, Poggi-Corradini, and Ransford, while the second generalises an isoperimetric inequality for the first eigenfunction of the Laplacian due to Payne and Rayner.Comment: 11 page

Parâmetros hematológicos e bioquímicos em três raças de cavalos de alta performance do Sul do Brasil

The hematological and biochemical parameters are useful tools for clinics and feeding management of athlete equines. The population of high performance horses consists of different breed groups, displaying specific phenotypic and metabolic characteristics related to the type of sport activity they perform. In the state of Rio Grande do Sul, in the South of Brazil, racing, jumping, polo, endurance, reigning, and dressage are the main activities. This study investigated the hemato-biochemical parameters in three high performance horse breeds from Southern Brazil. A total number of 154 horses belonging to the breeds Thoroughbred, Brasileiro de Hipismo, and Criollo, were selected for this study. Within each breed, samples were collected from males (n=12) and non-pregnant females (n=12) of two ages: 1 to 3 years of age (n=12) and over five years of age (n=12). Hematological (total count of erythrocytes and leukocytes, blood cell volume, hemoglobin, and differential count of leukocytes) and biochemical (lactate, fructosamine, glucose, cholesterol, total protein, albumin, globulins, fibrinogen, urea, calcium, magnesium, phosphorus, and enzymes LDH, AST, GGT, and CK) parameters were analyzed. Significant differences were observed in hematological and biochemical parameters, except for calcium and albumin, among breeds. There was no significant effect of age or sex within breed. This study shows that the local population, the breed and the type of sport activity are important variables to be considered in the analysis of blood parameters of horses.Os parâmetros hematológicos e bioquímicos são ferramentas que auxiliam na clínica e no manejo alimentar do eqüino atleta. Na população eqüina de alta performance existem diferentes grupos raciais que apresentam características fenotípicas e metabólicas específicas, relacionadas com o tipo de atividade esportiva que exercem. Atualmente, no Rio Grande do Sul (Sul do Brasil), são reconhecidas as modalidades esportivas de corrida, salto, polo, enduro, provas de rédeas e provas funcionais. O presente trabalho estudou os parâmetros hemato-bioquímicos em três raças de eqüinos de alta performance no Sul do Brasil. Um total de 154 animais das raças Puro Sangue Inglês, Brasileiro de Hipismo e Crioula foram selecionados para este estudo. Em cada grupo racial foram obtidas amostras de machos (n=12) e fêmeas não gestantes (n=12) e de duas faixas etárias: de 1 a 3 anos (n=12) e de mais de cinco anos (n=12). Foram analisados parâmetros hematológicos (contagem total de eritrócitos e leucócitos, hematócrito, hemoglobina e contagem diferencial de leucócitos) e bioquímicos (lactato, fructosamina, glicose, colesterol, proteína total, albumina, globulinas, fibrinogênio, uréia, cálcio, magnésio, fósforo e enzimas LDH, AST, GGT e CK). Foram observadas diferenças significativas nos parâmetros hematológicos e bioquímicos, exceto para cálcio e albumina, entre os grupos raciais. Não houve efeito significativo da idade e do sexo dentro da mesma raça. O presente trabalho mostra que o fator racial e o tipo de atividade esportiva são variáveis importantes que devem ser consideradas na análise de parâmetros sangüíneos em eqüinos

Global existence for semilinear reaction-diffusion systems on evolving domains

We present global existence results for solutions of reaction-diffusion systems on evolving domains. Global existence results for a class of reaction-diffusion systems on fixed domains are extended to the same systems posed on spatially linear isotropically evolving domains. The results hold without any assumptions on the sign of the growth rate. The analysis is valid for many systems that commonly arise in the theory of pattern formation. We present numerical results illustrating our theoretical findings.Comment: 24 pages, 3 figure

Diferenças de gênero no comportamento exploratório de crianças de dois anos de idade

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