Ab initio calculation of the dynamical properties of PPP and PPV

In this work, we have calculated the vibrational modes and frequencies of the crystalline PPP (in both the Pbam and Pnnm symmetries) and PPV (in the P21/c symmetry). Our results are in good agreement with the available experimental data. Also, we have calculated the temperature dependence of their specific heats at constant volume, and of their vibrational entropies. Based on our results, at high temperatures, the PPP is more stable in the Pnnm structure than in the Pbam one.Comment: 5 pages, 7 figures, accepted for publication in Braz. J. Phys., special number, Proceedings of BWSP-12, 12th Brazilian Workshop on Semiconductor Physic

How the Polyakov loop and the regularization affect strangeness and restoration of symmetries at finite T

The effects of the Polyakov loop and of a regularization procedure that allows the presence of high momentum quark states at finite temperature is investigated within the Polyakov-loop extended Nambu--Jona-Lasinio model. The characteristic temperatures, as well as the behavior of observables that signal deconfinement and restoration of chiral and axial symmetries, are analyzed, paying special attention to the behavior of strangeness degrees of freedom. We observe that the cumulative effects of the Polyakov loop and of the regularization procedure contribute to a better description of the thermodynamics, as compared with lattice estimations. We find a faster partial restoration of chiral symmetry and the restoration of the axial symmetry appears as a natural consequence of the full recovering of the chiral symmetry that was dynamically broken. These results show the relevance of the effects of the interplay among the Polyakov loop dynamics, the high momentum quark sates and the restoration of the chiral and axial symmetries at finite temperature.Comment: Talk given at XIII International Conference on Hadron Spectroscopy (Hadron 2009), Tallahassee, Florida, USA, 29 Nov - 4 Dec, 200

Self-Similarity of Friction Laws

The change of the friction law from a mesoscopic level to a macroscopic level is studied in the spring-block models introduced by Burridge-Knopoff. We find that the Coulomb law is always scale invariant. Other proposed scaling laws are only invariant under certain conditions.}Comment: Plain TEX. Figures not include

Understanding social enterprises in the United Kingdom: the case of South Yorkshire

Purpose-- This study analyses the development of social enterprises in the UK, in the context of the increased need for creative solutions to ameliorate deprivation and deliver effective public services. Design/methodology/approach-- The investigation draws on a mixed method approach, using a postal survey of 102 social enterprises complemented by detailed analysis of two selected cases and key informant interviews. Findings-- The results of the study show that there is a paradigm shift in the practice and conceptualisation of social enterprises in South Yorkshire as they are increasingly taking a more corporate approach to achieve their outcomes. Research limitations/implications-- The study is limited to social enterprises in South Yorkshire, UK. Further comparative analysis in other regions and social contexts is required in order to explore if these results are widely applicable. Practical implications-- This study is of potential benefit to researchers and those involved in formulating policies for the development and support of social enterprise. Originality/value-- The study contributes to the extant literature by investigation of the development of social enterprise in competitive markets, which is an area that requires further academic scrutiny. The South Yorkshire region presents an interesting case that extends our understanding of the operations of social enterprises in the UK given the high levels of deprivation due to the steady decline of its industrial base ( Bache and Chapman, 2008)

Ovinos Santa Inês: estado de arte e perspectivas.

[Santa Inês hair sheep: state of art and perspectives]. Abstract: The Santa Inês hair sheep breed is found in whole to areas of Brazil. Its origin has been object of vary speculations. However, the most probable could be traced starting from combinations of four genetic sources: a) Criuola is wool type of sheep, brought by Portuguese and Spanish settlers, but that eliminated the wool under tropical conditions was; b) Hair sheep breeds originating from of the African continent, which originated most of the hair sheep breeds from Brazil, Central America and Caribbean; c) Bergamácia sheep breed from Italian, which was crossed with the remaining sheep of those originating from of the African continent, and Morada Nova, followed by adaptation, selection and evolution for absence of wool; d) finally, in the end of the decade of 80, a small group of the breeders added to Santa Inês the Somalis and Suffolk breeds. The breed presents good reproductive, adaptability and growth potential. The pattern of the coat calor includes the white, the red, the black and the mailed. In field conditions the ewes reach weights of 40-60 kg and the males can reach up to 120 kg. The selection practiced in the breed has been done in direction for size and body weight, absence of wool and horns and, presence of an intense pigmentation. The females present good maternal ability and they get easily to give birth vigorous lambs. The age to the puberty and first lambing, lambing interval, fertility, the prolificacy and the survival rate from weaning found in the literature, vary from: 274 to 376 days, 442 to 551 days, 227 to 307 days, 83,6 to 93%, 1,1 to 1,4 and, from 69 to 87%, respectively. The Santa Inês lamb can reach 23-32 kg at weaning and gain 166 -336 kg. At slaughter, Santa Inês Lamb, had dressing percentage of approximately 48,0 %. The animals generally demonstrate capacity to develop a strong answer immunology against the nematodes gastrontestinais, even before of the weaning. That skin presents great market value, due to the high quality pattern, resultant of its largest elasticity and excellent flexibility, and great resistance, associated to a fine texture, being rendered for use in several manufactured products. In spite of the few studies involving the face Santa Inês the breed has been demonstrating to be an excellent alternative to increase the production of meat in the main areas of the country, considering its reproductive capacity, resistance sponges it gastrontestinais, skin quality and adaptability , besides good growth rate

Negative Energy Densities in Extended Sources Generating Closed Timelike Curves in General Relativity with and without Torsion

Near a spinning point particle in (2+1)-dimensional gravity (or near an infinitely thin, straight, spinning string in 3+1 dimensions) there is a region of space-time with closed timelike curves. Exact solutions for extended sources with apparently physically acceptable energy-momentum tensors, have produced the same exterior space-time structure. Here it is pointed out that in the case with torsion, closed timelike curves appear only for spin densities so high that the spin energy density is higher than the net effective energy density. In models without torsion, the presence of closed time-like curves is related to a heat flow of unphysical magnitude. This corroborates earlier arguments against the possibility of closed timelike curves in space-time geometries generated by physical sources.Comment: (to be published in Phys. Rev. D), 5 pages, REVTEX 3.0, NORDITA 93/62 A (Sept. 10/Revised Nov. 1, 1993

Comparação de homogeneidade e heteroneneidade de variância residual em modelos de regressão aleatória na descrição do crescimento de ovinos Santa Inês.

Resumo: Utilizaram-se 17.767 registros de pesos de cordeiros da raça Santa Inês com o objetivo de comparar modelos de regressão aleatória com diferentes estruturas para modelar a variância residual. As regressões fixas e aleatórias foram ajustadas por meio de polinômios de Legendre de ordens quatro e três, respectivamente. A variância residual foi ajustada por meio de classes e funções de variâncias. O modelo considerando homogeneidade de variâncias residuais mostrou-se inadequado. De acordo com os critérios utilizados, a variância residual contendo sete classes heterogêneas proporcionou melhor ajuste, embora um mais parcimonioso, com cinco classes, poderia ser utilizado. O ajuste de funções de variâncias com qualquer ordem foi melhor que o obtido por meio de classes, sendo que o polinômio ordinário de ordem seis proporcionou melhor ajuste dentre as estruturas testadas. A modelagem do resíduo interferiu nas estimativas dos parâmetros genéticos. Além da alteração da classificação dos reprodutores, constataramse, também, alterações consideráveis na magnitude dos valores genéticos preditos em função do ajuste da variância residual empregado. Portanto, faz-se necessário a utilização de heterogeneidade de variâncias residuais para modelar as variâncias associadas à curva de crescimento dos ovinos Santa Inês em estudo. Comparison of homogeneity and heterogeneity of residual variance in random regression models in the description of the growth of Santa Inês sheep]. Abstract: Data set of 17,767 records of 4,210 Santa Inês lambs were used aiming to compare random regression models with different structures to fit the residual variance. Fixed and random regressions were fitted by Legendre polynomials of orders four and three, respectively. The residual variance was fitted by classes and functions of variances. The model considering homogeneity of residual variances was inadequate. According to the criteria used, the residual variance containing seven heterogeneous classes provided the best fit, although a more parsimonious one, with five classes, could be used. The fit of variances functions with any order was better than that obtained by classes and the ordinary polynomial of order six provided best fit among the tested structures. The modelling of the residue interfered the estimative of the genetic parameters. Beyond the Change in the classification of the reproducers it was verified alterations in the magnitude of the genetic values predicted as function of the fit of the variance residual studied. Therefore, it is necessary the use of residual heterogeneity variances to model the variances associated to the growth curve of Santa Inês sheep in study

Modeling of average growth curve in Santa Ines sheep using random regression models.

Abstract: Polynomial functions of age of different orders were evaluated in the modeling of the average growth trajectory in Santa Ines sheep in random regression models. Initially, the analyses were performed not considering the animal effect. Subsequently, the random regression analyses were performed including the random effects of the animal and its mother (genetic and permanent environment). The linear fit was lower, and the other orders were similar until near 100 days of age. The cubic function provided the closest fit of the observed averages, mainly at the end of the curve. Orders superior to this one tended to present incoherent behavior with the observed weights. The estimated direct heritabilities, considering the linear fit, were higher to those estimated by considering other functions. The changes in animal ranking based on predicted breeding values using linear fit and superior orders were small; however, the difference in magnitude of the predicted breeding values was higher, reaching values 77% higher than those obtained with the cubic function. The cubic polynomial function is efficient in describing the average growth curve. [Modelagem da curva média de crescimento de ovinos Santa Inês em modelos de regressão aleatória]. Resumo: Funções polinomiais da idade de diferentes ordens foram avaliadas na modelagem da trajetória média de crescimento de ovinos Santa Inês em modelos de regressão aleatória. As análises foram executadas inicialmente desconsiderando o efeito de animal. Posteriormente, as análises de regressão aleatória foram realizadas incluindo-se os efeitos aleatórios de animal e da mãe (genético e de ambiente permanente). O ajuste linear foi inferior, e as demais ordens foram semelhantes até próximo dos 100 dias de idade. A função cúbica proporcionou o ajuste mais próximo das médias observadas, principalmente ao final da curva. Ordens superiores a esta tenderam a apresentar comportamento incoerente com os pesos observados. As herdabilidades diretas estimadas considerando ajuste linear foram superiores às estimadas considerando as demais funções. As mudanças no ordenamento dos animais, com base nos valores genéticos preditos empregando ajuste linear e de ordens superiores, foram pequenas, porém, a diferença na magnitude dos valores genéticos preditos foi maior, chegando a valores 77% maiores que os obtidos com a função cúbica. A função polinomial cúbica é eficiente para descrever a curva média de crescimento