Dark spinor models in gravitation and cosmology

We introduce and carefully define an entire class of field theories based on non-standard spinors. Their dominant interaction is via the gravitational field which makes them naturally dark; we refer to them as Dark Spinors. We provide a critical analysis of previous proposals for dark spinors noting that they violate Lorentz invariance. As a working assumption we restrict our analysis to non-standard spinors which preserve Lorentz invariance, whilst being non-local and explicitly construct such a theory. We construct the complete energy-momentum tensor and derive its components explicitly by assuming a specific projection operator. It is natural to next consider dark spinors in a cosmological setting. We find various interesting solutions where the spinor field leads to slow roll and fast roll de Sitter solutions. We also analyse models where the spinor is coupled conformally to gravity, and consider the perturbations and stability of the spinor.Comment: 43 pages. Several new sections and details added. JHEP in prin

Performance of Beef Cattle Fed Diets Containing \u3cem\u3eStylosanthes\u3c/em\u3e and Corn Silages

Reports of the use of tropical legumes in silage production are scarce as these legumes have high contents of crude protein, low water soluble carbohydrate and high buffering capacity, which inhibit the production of silages with good fermentation and nutritional characteristics. Recent research has, however, shown that it is possible to produce good quality silages using tropical legumes (Pereira et al. 2012). Souza et al. (2012) concluded that silage produced from Stylosanthes cv. Campo Grande (Stylosanthes capitata + Stylosanthes macrocephala) at 60% proportion of the dry matter of the diet can replace corn silage in diets for beef cattle in feedlots without altering their intake and productive performance. However, the ideal proportion of this silage in the diets for beef cattle is still unknown. Thus, the objective of this study was to evaluate the intake and performance of beef cattle fed diets with Stylosanthes and corn silages

Superfield covariant analysis of the divergence structure of noncommutative supersymmetric QED4_4

Commutative supersymmetric Yang-Mills is known to be renormalizable for ${\cal N} = 1, 2$, while finite for ${\cal N} = 4$. However, in the noncommutative version of the model (NCSQED$_4$) the UV/IR mechanism gives rise to infrared divergences which may spoil the perturbative expansion. In this work we pursue the study of the consistency of NCSQED$_4$ by working systematically within the covariant superfield formulation. In the Landau gauge, it has already been shown for ${\cal N} = 1$ that the gauge field two-point function is free of harmful UV/IR infrared singularities, in the one-loop approximation. Here we show that this result holds without restrictions on the number of allowed supersymmetries and for any arbitrary covariant gauge. We also investigate the divergence structure of the gauge field three-point function in the one-loop approximation. It is first proved that the cancellation of the leading UV/IR infrared divergences is a gauge invariant statement. Surprisingly, we have also found that there exist subleading harmful UV/IR infrared singularities whose cancellation only takes place in a particular covariant gauge. Thus, we conclude that these last mentioned singularities are in the gauge sector and, therefore, do not jeopardize the perturbative expansion and/or the renormalization of the theory.Comment: 36 pages, 11 figures. Minor correction

The influence of Fe2O3 doping on the pore structure and mechanical strength of TiO2-containing alumina obtained by freeze-casting

This work investigated TiO/FeO doped alumina prepared by the freeze-casting technique and using camphene as the solvent. Dendritic pores were formed in the TiO doped alumina, a structure conferred by the frozen camphene. Contrary to this trend, further FeO doping of TiO-containing alumina resulted in the formation of non-dendritic structures. This behavior was attributed to the higher density of α-FeO (5.24 g cm) when compared to α-AlO (3.95 g cm) and anatase TiO (3.89 g cm), which reduced critical solidification front velocity, thus forming material with different pore shape. FeO doping also improved the densification of TiO-alumina and inhibited the formation of cracks, reflected by superior mechanical strength with best results ∼150% higher for 10% FeO loaded samples as compared to TiO-alumina samples

Effect of titania addition on the properties of freeze-cast alumina samples

This work investigated the behavior of TiO2-containing α-Al2O3 samples prepared by the freeze-casting technique. Camphene and liquid nitrogen were used as the solvent and cooling fluid, respectively. Camphene resulted in the formation of dendritic pores, in the direction of the freeze-casting cold front during sample preparation. The formation of β-Al2TiO5 phase occurred at 1300°C, and became more evident as the sintering temperatures reached 1500°C. The TiO2 loading did not affect the sample porosity at a given temperature, but it was detrimental in the case of mechanical properties under certain conditions. For instance, the flexural strength slightly improved with increasing the TiO2 loading and sintering temperature from 1100 to 1300°C. This effect was attributed to the occurrence of a more effective sintering of alumina. However, as the heat treatment temperature was raised from 1300 to 1500°C, the flexural strength did not increase as a function of the TiO2 loading, even though the densification occurred with loss of porosity. The loss of mechanical strength was found to be associated with the formation of microcracks which stemmed from the formation of β-Al2TiO5 phase for TiO2 loadings in excess of 4wt% at these high sintering temperatures

Diagnóstico pré-natal de doenças genéticas / Pré natal diagnostic of genetic disease

O diagnóstico pré-natal de doenças genéticas envolve exames invasivos, testes de rastreamento e métodos de triagem, para acompanhamento da viabilidade fetal durante o período gestacional. Neste artigo de revisão foram enfatizadas as principais indicações, contra-indicações, complicações, diferenças entre cada um dos procedimentos. Idade materna, período gestacional, presença de anomalia genética na família são os principais pré-requisitos para a escolha do método mais adequado a ser utilizado, sendo de caráter obrigatório o prévio conhecimento dos pais a respeito do risco-benefício do mesmo. O aconselhamento genético para este tipo de exame diagnóstico é de fundamental importância uma vez que o resultado pode mudar completamente as perspectivas de uma família. Esse tema é rodeado de questionamentos éticos visto que a vida de um concepto encontra-se em questão.