Constraining the dark energy with galaxy clusters X-ray data

The equation of state characterizing the dark energy component is constrained by combining Chandra observations of the X-ray luminosity of galaxy clusters with independent measurements of the baryonic matter density and the latest measurements of the Hubble parameter as given by the HST key project. By assuming a spatially flat scenario driven by a "quintessence" component with an equation of state $p_x = \omega \rho_x$ we place the following limits on the cosmological parameters $\omega$ and $\Omega_{\rm{m}}$: (i) $-1 \leq \omega \leq -0.55$ and $\Omega_{\rm m} = 0.32^{+0.027}_{-0.014}$ (1$\sigma$) if the equation of state of the dark energy is restricted to the interval $-1 \leq \omega < 0$ (\emph{usual} quintessence) and (ii) $\omega = -1.29^{+0.686}_{-0.792}$ and $\Omega_{\rm{m}} = 0.31^{+0.037}_{-0.034}$ ($1\sigma$) if $\omega$ violates the null energy condition and assume values $< -1$ (\emph{extended} quintessence or ``phantom'' energy). These results are in good agreement with independent studies based on supernovae observations, large-scale structure and the anisotropies of the cosmic background radiation.Comment: 6 pages, 4 figures, LaTe

Some Observational Consequences of Brane World Cosmologies

The presence of dark energy in the Universe is inferred directly and indirectly from a large body of observational evidence. The simplest and most theoretically appealing possibility is the vacuum energy density (cosmological constant). However, although in agreement with current observations, such a possibility exacerbates the well known cosmological constant problem, requiring a natural explanation for its small, but nonzero, value. In this paper we focus our attention on another dark energy candidate, one arising from gravitational \emph{leakage} into extra dimensions. We investigate observational constraints from current measurements of angular size of high-$z$ compact radio-sources on accelerated models based on this large scale modification of gravity. The predicted age of the Universe in the context of these models is briefly discussed. We argue that future observations will enable a more accurate test of these cosmologies and, possibly, show that such models constitute a viable possibility for the dark energy problem.Comment: 6 pages, 4 figures, to appear in Phys. Rev. D (minor revisions

Níveis de lisina para leitoas selecionadas geneticamente para deposição de carne magra na carcaça, dos 30 aos 60 kg Levels of lysine for gilts with high genetic potential for lean gain from 30 to 60 kg

Foram utilizadas 50 leitoas híbridas, com alto potencial genético para deposição de carne magra na carcaça e pesos inicial e final de 30,0 &plusmn; 0,45 e 59,9 &plusmn; 2,53 kg, respectivamente, para avaliar diferentes níveis de lisina. O delineamento experimental foi o de blocos ao acaso, com cinco tratamentos, cinco repetições e dois animais por unidade experimental. Os tratamentos corresponderam a uma ração basal com 17,5% de proteína bruta, suplementada com cinco níveis de L-lisina HCl, resultando em rações com 0,80; 0,90; 1,00; 1,10; e 1,20% de lisina total. Não se observou efeito dos tratamentos sobre o ganho de peso diário e a concentração de uréia no soro sangüíneo dos animais, entretanto, o consumo de ração e o consumo de lisina diário aumentaram linearmente. Houve efeito quadrático dos níveis de lisina sobre a conversão alimentar, que melhorou até o nível de 1,16% de lisina total (0,347%/Mcal de ED) ou 1,05% de lisina digestível (0,315%/Mcal de ED), correspondendo a um consumo estimado de lisina total e digestível de 21,8 e 19,7 g/dia, respectivamente. Não se observou efeito dos tratamentos sobre a porcentagem de proteína da carcaça, porém a de água diminuiu de maneira linear. Houve efeito quadrático dos tratamentos sobre a porcentagem e taxa de deposição de gordura na carcaça, que diminuíram até o nível de 1,09 e 1,12% de lisina, respectivamente, e sobre a taxa de deposição de proteína, que foi máxima no nível de 1,04% de lisina. Concluiu-se que leitoas selecionadas geneticamente para deposição de carne magra na carcaça, dos 30 aos 60 kg, exigem 1,16% de lisina total ou 1,05% de lisina digestível verdadeira, para melhor desempenho, correspondendo a um consumo diário de lisina total e digestível de 21,77 e 19,72 g, respectivamente. O nível de 1,04% de lisina total ou 0,93% de lisina digestível proporciona a melhor taxa de deposição de proteína na carcaça.<br>Fifty hybrid gilts, with high genetic potential for lean gain and initial and final average weight of 30.0 &plusmn; 0.45 and 59.9 &plusmn; 2.53 kg, respectively, were used in an experiment to evaluate diet with different levels of lysine. An experimental design of randomized blocks, with five treatments, five replicates and two animals per experimental unit, was used. The treatments corresponded to a basal diet with 17.5% crude protein, supplemented with five levels of HCl-L-lysine, resulting in diets with 0.80, 0.90, 1.00, 1.10, and 1.20% of total lysine. There were no effects of treatments on daily weight gain and serum urea concentration, however, daily feed intake and daily lysine intake increased linearly with the dietary lysine level. There was a quadratic effect of lysine levels on feed:gain ratio, that increased up to the total lysine level of 1.16% (0.347%/Mcal of DE) or 1.05% (0.315%/Mcal of DE) of digestible lysine, corresponding to the total and digestible lysine intake of 21.8 and 19.7 g/day, respectively. There was no effect of treatments on protein percentage, however, the water percentage in carcass linearly decreased. There was quadratic effect of treatments on fat percentage and fat deposition rate in carcass, that decreased up to the lysine level of 1.09 and 1.12%, respectively. The protein deposition rate improved quadraticly up to the level of lysine of 1.04%. It was concluded that gilts with high genetic potential for lean gain, from 30 to 60 kg require 1.16% of total lysine or 1.05% (0.315%/Mcal of DE) of true digestible lysine, corresponding to total and digestible lysine intake of 21.8 and 19.72 g/day, respectively, for maximal performance. The level of total lysine of 1.04% or 0,93% of digestible lysine proportioned the best protein deposition rate