Wang-Landau sampling in three-dimensional polymers

Monte Carlo simulations using Wang-Landau sampling are performed to study three-dimensional chains of homopolymers on a lattice. We confirm the accuracy of the method by calculating the thermodynamic properties of this system. Our results are in good agreement with those obtained using Metropolis importance sampling. This algorithm enables one to accurately simulate the usually hardly accessible low-temperature regions since it determines the density of states in a single simulation.Comment: 5 pages, 9 figures arch-ive/Brazilian Journal of Physic

Exchange Narrowing Effects in the EPR Linewidth of Gd Diluted in Ce Compounds

Anomalous thermal behavior on the EPR linewidths of Gd impurities diluted in Ce compounds has been observed. In metals, the local magnetic moment EPR linewidth, \Delta H, is expected to increase linearly with the temperature. In contrast, in Ce_{x}La_{1-x}Os_{2} the Gd EPR spectra show a nonlinear increase. In this work, the mechanisms that are responsible for the thermal behavior of the EPR lines in Ce_{x}La_{1-x}Os_{2} are examined. We show that the exchange interaction between the local magnetic moments and the conduction electrons are responsible for the narrowing of the spectra at low temperatures. At high temperatures, the contribution to the linewidth of the exchange interaction between the local magnetic moments and the $Ce$ ions has an exponential dependence on the excitation energy of the intermediate valent ions. A complete fitting of the EPR spectra for powdered samples is obtained.Comment: 11 pages, 1 figur

On the relation between Transversal and Longitudinal Scaling in Cities

Given that a group of cities follows a scaling law connecting urban population with socio-economic or infrastructural metrics (transversal scaling), should we expect that each city would follow the same behavior over time (longitudinal scaling)? This assumption has important policy implications, although rigorous empirical tests have been so far hindered by the lack of suitable data. Here, we advance the debate by looking into the temporal evolution of the scaling laws for 5507 municipalities in Brazil. We focus on the relationship between population size and two urban variables, GDP and water network length, analyzing the time evolution of the system of cities as well as their individual trajectory. We find that longitudinal (individual) scaling exponents are city-specific, but they are distributed around an average value that approaches to the transversal scaling exponent when the data are decomposed to eliminate external factors, and when we only consider cities with a sufficiently large growth rate. Such results give support to the idea that the longitudinal dynamics is a micro-scaling version of the transversal dynamics of the entire urban system. Finally, we propose a mathematical framework that connects the microscopic level to global behavior, and, in all analyzed cases, we find good agreement between theoretical prediction and empirical evidence

Dano mecânico em sementes peletizadas de sorgo sacarino.

Edição dos resumos do 18º Congresso Brasileiro de Sementes, 2013, Florianópolis

Model to predict shrinkage and ejection forces of injection moulded tubular parts of short glass fiber reinforced thermoplastics

This work presents a model to predict shrinkage and ejection forces for glass fiber reinforced thermoplastics of tubular geometry. This mathematical model was based in Jansen’s Model to predict shrinkage and residual stresses in fiber reinforced injection molded products and Pontes’s Model to predict ejection forces for tubular parts of pure PP. The model used the modified classical laminate theory applied to injection moulding and it uses the fiber orientation state, temperature and pressure field as input and which predicts the shrinkage and ejection forces. The fiber orientation state was determined experimentally and the temperature and pressure fields were obtained by MOLDFLOW simulations. The model to predict ejection forces considers also the fiber orientation state, friction coefficient between steel and polymer, elastic modulus of polymer, both in the ejection temperature and diametrical shrinkage. The model is validated by experimental results

Estrutura do sub-bosque em manchas florestais no Pantanal da Nhecolândia: efeitos da presença de gado.

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Ocupação de manchas florestais por espécies de pica-paus e arapaçus no Pantanal.

Neste estudo avaliamos a influência de algumas variáveis de paisagem e habitat nas probabildades de ocupação de manchas florestais naturais por seis espécies deste tipo de aves no Pantanal da Nhecolândia. O estudo foi realizado em 2008 na fazenda Nhumirim e arredores, nas estações chuvosa e seca

Assessment of the shrinkage and ejection forces of reinforced polypropylene based on nanoclays and short glass fibre

In this study the influence of nanoclay and glass fibre in the shrinkage and ejection forces in polypropylene matrix in tubular parts moulded by injection moulding were analysed. An instrumented mould was used to measure the part surface temperature and ejection forces in tubular parts. The materials used were a polypropylene homopolymer Domolen 1100L nanoclay for polyolefin nanocomposites P-802 Nanomax in percentages of 2%, 6% and 10% and a polypropylene homopolymer with content of 10% of glass fibre Domolen P1-013-V10-N and 30% of glass fibre Domolen P1-102-V30-N with 2% of nanoclay. The shrinkage and ejection forces were analysed. The results show that the incorporation of nanoclays decreases the shrinkage and ejection forces whereas glass fibre decreases the shrinkage and increase ejection forces due to the increase of the elastic modulus. The nanoclays decrease the ejection force when compared with glass fibre and pure PP. The effects of nanoclays are less pronounced than those of glass fibre. The effect of the mould temperatures on the ejection forces in the mouldings produced with the mentioned materials were also analysed. The ejection force decreases with the increase of the temperature of the mould

Qualidade fisiológica de sementes de milheto armazenadas.

A cultura do trigo tem grande importância comercial, contudo ainda são escassos, resultados científicos referente ao uso de herbicidas nesta cultura. Em termos de mercado é notório a pequena quantidade de produtos recomendados para o controle de plantas daninhas em pós-emergência desta cultura, e limitadas são as informações sobre os efeitos que estes causam. Neste contexto, o objetivo do presente trabalho foi avaliar o desempenho agronômico e a qualidade fisiológica das sementes sob o efeito da aplicação de doses crescentes de Metsulfuron methyl (Ally) em estádios de desenvolvimento diferentes, assumindo que altas doses de Ally podem ser utilizadas em dois estádios de desenvolvimento e supondo que o emprego de altas doses em combinação com o estádio de desenvolvimento possa afetar a planta. Com este intuito foi conduzido um ensaio a campo, no Município de Marialva - PR, com delineamento em blocos completos casualizados, com quatro repetições, em que os tratamentos foram compostos por cinco doses do herbicida Ally O; 30; 60; 90; 120g i.a. ha; aplicadas em dois estádios da cultura: 4 e 10.4. As variáveis avaliadas foram: produtividade, massa de mil sementes, germinação e vigor (pela primeira contagem do teste de germinação). A partir dos resultados obtidos, pode-se inferir que: o herbicida Ally aplicado em altas doses no período reprodutivo tende a diminuir a produtividade (P<O, 1 O) e o vigor (P<0,03) de suas sementes, porém aplicações no vegetativo não apresentam efeitos significativos ai, 5 e 10% de probabilidade, com relação aos caracteres observados aqui.Edição dos Resumos do XVI Congresso Brasileiro de Sementes, Curitiba, PR, set. 2003