Hamiltonian Dynamics and the Phase Transition of the XY Model

A Hamiltonian dynamics is defined for the XY model by adding a kinetic energy term. Thermodynamical properties (total energy, magnetization, vorticity) derived from microcanonical simulations of this model are found to be in agreement with canonical Monte-Carlo results in the explored temperature region. The behavior of the magnetization and the energy as functions of the temperature are thoroughly investigated, taking into account finite size effects. By representing the spin field as a superposition of random phased waves, we derive a nonlinear dispersion relation whose solutions allow the computation of thermodynamical quantities, which agree quantitatively with those obtained in numerical experiments, up to temperatures close to the transition. At low temperatures the propagation of phonons is the dominant phenomenon, while above the phase transition the system splits into ordered domains separated by interfaces populated by topological defects. In the high temperature phase, spins rotate, and an analogy with an Ising-like system can be established, leading to a theoretical prediction of the critical temperature $T_{KT}\approx 0.855$.Comment: 10 figures, Revte

Why place matters in residential care: the mediating role of place attachment in the relation between adolescents’ rights and psychological well-being

Little evidence exists on the relationship between rights’ perceptions and well-being outcomes during the adolescence, and particularly in care, as well as on the mediating role of place attachment. Young people in residential care are psychologically and socially vulnerable, showing greater difficulties than their peers do in the family. Youth’s rights fulfilment in residential care may positively affect their psychological functioning together with positive attachments to this place. A sample of 365 adolescents in residential care settings (M = 14.71, SD = 1.81) completed a set of self-reported measures, specifically, the Rights perceptions scale, the Place attachment scale and Scales of psychological well-being. Results revealed significant mediating effects of place attachment (Global scale and subscales of Friends Bonding and Place Dependence) on the relationship between Participation and Protection rights in residential care and Psychological well-being (Positive Relations with others, Personal Growth and Self-Acceptance). The positive role of rights fulfilment in residential care, specifically participation opportunities, as well as the role of youth’s attachment to the care setting are discussed based on previous evidence and theoretical assumptions. A set of practical implications is described.info:eu-repo/semantics/acceptedVersio

Chemical-bromatological composition of silages from biomass sorghum genotypes.

The biomass sorghum [Sorghum bicolor (L.) Moench] was developed for energy production, but its agronomic characteristics make it an alternative plant for silage production. This study aimed to evaluate the chemical-bromatological composition of silages from biomass sorghum genotypes. The experimental genotypes B004, B005, B009, B010, B011, B013, B015 and B020, as well as three commercially available genotypes (BRS655, Volumax and K1009), were evaluated. The pH, dry matter, ash, organic matter, crude protein, neutral detergent fiber, acid detergent fiber, hemicellulose and lignin were analyzed. A completely randomized design, with four replications, was used, having the genotypes as treatments. Although significant differences were observed among the 11 genotypes, the chemical-bromatological composition of all them showed their potential to be used for silage production

Black-wattle growth in reponse to application of nitrogen, phosphorus and potassium

Due to the lack of information about Black-wattle fertilization, this study evaluated black-wattle plants growth in response to different fertilization levels of nitrogen, phosphorus and potassium six years after implantation. The statistical design used was a randomized blocks with trifatorial distribution. Total height (m), diameter at breast height (DBH) (cm) and stem volume with bark (m³ ha-1) were evaluated. Black-wattle showed a positive and significant growth response to N and P (interaction) fertilizations and absence for K. m To obtain the maximum development of black-wattle, for the soil and climate condition studied, it is required the use of the maximum dose of nitrogen (40.0 kg ha-1 N) and 78.9 kg ha-1 phosphorus, not requiring the addition of potassium

Integração de dados de georeferenciamento e dados genéticos para o manejo da biodiversidade de recursos genéticos de ovinos no Brasil.

Existem relativamente poucas coleções de germoplasma/bancos de DNA de animais domésticos de produção distribuídos pelo Brasil. Estas coleções precisam de estudos básicos, a fim de atender as demandas futuras no país e até do mundo. O objetivo deste trabalho foi realizar uma análise crítica de um Banco de DNA a partir de dados espaciais (dados georreferenciados) e genéticos em relação aos locais de origem a partir de 3518 amostras de DNA originados de 17 diferentes grupos genéticos ou raças de ovelhas do Banco de DNA e Tecidos localizado no Laboratório de Genética Animal da Embrapa Recursos Genéticos e Biotecnologia. O georeferenciamento mostrou que nem todos os grupos genéticos têm amostras no banco e as coletas foram concentradas no núcleo de conservação. Apenas 21% dos estados com uma determinada raça têm amostras no banco de genes. O número médio de animais amostrados por coleta foi de 32, enquanto a distância média entre pontos de coleta e núcleos de conservação foi 550 km. A raça Somalis Brasileira foi coletada apenas no seu núcleo de conservação. Não foram coletadas amostras para a raça Cariri. Apenas duas fazendas e uma raça no banco são da região norte. Dos 27 estados brasileiros, 13 proveram amostras ao banco de germoplasma, o que mostra a necessidade de coletas em rebanhos fora do sistema oficial de rebanhos de conservação para garantir que os estudos realizados utilizando este germoplasma não são tendenciosos. Sugestões são dadas para a melhoria da quantidade e diversidade de amostras do referido Banco de DNA