Critical aspects of the random-field Ising model

We investigate the critical behavior of the three-dimensional random-field Ising model (RFIM) with a Gaussian field distribution at zero temperature. By implementing a computational approach that maps the ground-state of the RFIM to the maximum-flow optimization problem of a network, we simulate large ensembles of disorder realizations of the model for a broad range of values of the disorder strength h and system sizes  = L3, with L ≤ 156. Our averaging procedure outcomes previous studies of the model, increasing the sampling of ground states by a factor of 103. Using well-established finite-size scaling schemes, the fourth-order’s Binder cumulant, and the sample-to-sample fluctuations of various thermodynamic quantities, we provide high-accuracy estimates for the critical field hc, as well as the critical exponents ν, β/ν, and γ̅/ν of the correlation length, order parameter, and disconnected susceptibility, respectively. Moreover, using properly defined noise to signal ratios, we depict the variation of the self-averaging property of the model, by crossing the phase boundary into the ordered phase. Finally, we discuss the controversial issue of the specific heat based on a scaling analysis of the bond energy, providing evidence that its critical exponent α ≈ 0−

Composição de carcaça de frangos de corte alimentados com farelo de canola Carcass composition of broilers fed canola meal

Avaliou-se o efeito da utilização de farelo de canola sobre a composição de carcaça de frangos de corte da linhagem Ross. As aves foram alimentadas com dietas contendo farelo de canola em substituição parcial (0, 10, 20, 30 ou 40%) ao farelo de soja. Mil e duzentos pintos foram distribuídos em unidades experimentais de 30 animais, de acordo com o sexo e peso inicial. As dietas continham 22, 20 e 18% de proteína bruta e 3000, 3100 e 3150kcal de energia metabolizável/kg de ração, respectivamente nos períodos entre 0 e 21, 22 e 35, e 36 e 42 dias de idade. No 42º dia, um frango de cada unidade experimental foi abatido e a composição de sua carcaça foi determinada. Níveis crescentes de farelo de canola nas dietas elevaram o teor de proteína bruta na carcaça e reduziram o teor de extrato etéreo na carcaça. O rendimento de carcaça não foi alterado, nem os teores de energia bruta e de cinzas na carcaça. O uso de farelo de canola nas dietas melhorou a qualidade das carcaças sem prejudicar seu peso ou rendimento, logo seu uso é recomendado.<br>An evaluation of the effects of using canola meal on the carcass composition of broilers was performed. Soybean meal was partially substituted (0, 10, 20, 30, or 40%) by canola meal in the diets. Fourty experimental units of 30 birds each were formed according to the bird=s initial weight and sex. The diets were formulated to contain 22, 20, or 18% of crude protein and 3000, 3100 or 3150kcal of metabolizable energy per kg of diet, and broilers were fed respectively in the periods between 0 and 21, 22 and 35, and 36 and 42 days. On day 42, a bird from each experimental unit was killed and its carcass composition was determined. Carcass protein increased and carcass fat decreased linearly with the amount of canola meal used in the diets. The percentage of carcass fat remained unchanged with the inclusion of canola meal in the diets. Neither carcass yield nor the levels of crude energy and ashes in the carcasses were changed. The use of canola meal in the diets can be recommended because the quality of the carcasses was improved. Quality improvement was achieved without losses in carcass weight or yield