Asymptotic behavior of the entropy of chains placed on stripes

By using the transfer matrix approach, we investigate the asymptotic behavior of the entropy of flexible chains with $M$ monomers each placed on stripes. In the limit of high density of monomers, we study the behavior of the entropy as a function of the density of monomers and the width of the stripe, inspired by recent analytical studies of this problem for the particular case of dimers (M=2). We obtain the entropy in the asymptotic regime of high densities for chains with $M=2,..,9$ monomers, as well as for the special case of polymers, where $M\to\infty$, and find that the results show a regular behavior similar to the one found analytically for dimers. We also verify that in the low-density limit the mean-field expression for the entropy is followed by the results from our transfer matrix calculations

Stability of soybean yield through different sowing periods.

Soybean yield is highly affected by sowing period and there are significant productivity losses when sowings are done outward a relatively restricted period in many regions of Brazil. Breeding cultivars less sensitive to photoperiod and to temperature variations is desirable for adaptation to wider sowing period and wider latitude range and also make irrigated soybean cultivation possible during the fall-winter seasons in frost free regions. The possibility of selecting high yielding and stable lines for yield during various sowing periods wasstudied by analyzing the behavior of 100 non-selected advanced lines (F9 and F10), from each one of all possible biparental crosses involving the genotypes BR85-29009, OCEPAR 8, FT-2, and BR-13. Experiments were set up in a completely randomized design with single-plant hill plots and received supplementary irrigation. Sowing was on Sept 27, Oct 20, Nov 17, and Dec 17 in 1993/94 and Sept 20, Oct 20, Nov 17, and Dec 14 in 1994/95 at Londrina, PR, Brazil. Procedures of regression analysis and minimum variance among planting date means were efficient for selecting stable lines during the four sowing seasons. It was possible to select stable and high yielding genotypes through the four sowing periods in all the crosses. No specific cross was clearly better to produce a greater number of stable genotypes

The Efficiency of Gravitational Bremsstrahlung Production in the Collision of Two Schwarzschild Black Holes

We examine the efficiency of gravitational bremsstrahlung production in the process of head-on collision of two boosted Schwarzschild black holes. We constructed initial data for the characteristic initial value problem in Robinson-Trautman spacetimes, that represent two instantaneously stationary Schwarzschild black holes in motion towards each other with the same velocity. The Robinson-Trautman equation was integrated for these initial data using a numerical code based on the Galerkin method. The final resulting configuration is a boosted black hole with Bondi mass greater than the sum of the individual mass of each initial black hole. Two relevant aspects of the process are presented. The first relates the efficiency $\Delta$ of the energy extraction by gravitational wave emission to the mass of the final black hole. This relation is fitted by a distribution function of non-extensive thermostatistics with entropic parameter $q \simeq 1/2$; the result extends and validates analysis based on the linearized theory of gravitational wave emission. The second is a typical bremsstrahlung angular pattern in the early period of emission at the wave zone, a consequence of the deceleration of the black holes as they coalesce; this pattern evolves to a quadrupole form for later times.Comment: 16 pages, 4 figures, to appear in Int. J. Modern Phys. D (2008

Irreversible spherical model and its stationary entropy production rate

The nonequilibrium stationary state of an irreversible spherical model is investigated on hypercubic lattices. The model is defined by Langevin equations similar to the reversible case, but with asymmetric transition rates. In spite of being irreversible, we have succeeded in finding an explicit form for the stationary probability distribution, which turns out to be of the Boltzmann-Gibbs type. This enables one to evaluate the exact form of the entropy production rate at the stationary state, which is non-zero if the dynamical rules of the transition rates are asymmetric

Métodos de manejo de plantas daninhas.

As preocupações com a disponibilidade de alimentos em quantidade e qualidade para a população em geral têm direcionado demandas de pesquisas visando o desenvolvimento de sistemas de produção de grãos de menor impacto ambiental. Isso porque os consumidores têm se tornado mais exigentes quanto aos padrões de qualidade dos produtos e do ambiente. Adicionalmente, demandam-se métodos de produção que promovam a permanência do agricultor no campo e com redução no custo de produção. Novos nichos de mercado, mesmo que pequenos, têm surgido. A área de orgânicos no Brasil é de cerca de 750 mil hectares, contando com mais de 10 mil produtores e aproximadamente 13 mil unidades de produção, mas com grande potencial de crescimento. A produção de milho orgânico exige prática que permita a produção sem a utilização de herbicidas. Dados sobre a composição do custo total na produção do milho cultivado organicamente têm demonstrado que aproximadamente 18% do custo tem sido com o manejo de daninhas. Dentro desta visão, demandam-se informações sobre a convivência da cultura com as plantas daninhas em sistemas de produção orgânico tropicais gerando subsídios para o estabelecimento de estratégias de manejo das plantas daninhas. Manejo de plantas daninhas exige do produtor o aprofundamento no conhecimento da diversidade e particularidades relativas à dispersão dessas plantas e de aspectos do manejo que afetam a sua dispersão. Este documento tem como objetivo principal descrever os fatores envolvidos na coexistência das plantas daninhas com as culturas, assim como as tecnologias ou métodos de manejo de plantas daninhas na cultura do milho orgânico.bitstream/item/142570/1/ct-213.pd

Behavior of Eucalyptus grandis and E. cloeziana seedlings grown in arsenic-contaminated soil.

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Potencial de quatro espécies herbáceas forrageiras para fitorremediação de solo contaminado por arsênio.

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