Exact Hypersurface-Homogeneous Solutions in Cosmology and Astrophysics

A framework is introduced which explains the existence and similarities of most exact solutions of the Einstein equations with a wide range of sources for the class of hypersurface-homogeneous spacetimes which admit a Hamiltonian formulation. This class includes the spatially homogeneous cosmological models and the astrophysically interesting static spherically symmetric models as well as the stationary cylindrically symmetric models. The framework involves methods for finding and exploiting hidden symmetries and invariant submanifolds of the Hamiltonian formulation of the field equations. It unifies, simplifies and extends most known work on hypersurface-homogeneous exact solutions. It is shown that the same framework is also relevant to gravitational theories with a similar structure, like Brans-Dicke or higher-dimensional theories.Comment: 41 pages, REVTEX/LaTeX 2.09 file (don't use LaTeX2e !!!) Accepted for publication in Phys. Rev.

Beneficial effect of a daily continuous 8 hours artificial light exposition on ram spermatogenesis in Brazil

La spermatogénèse des béliers est très nettement améliorée lorsque ceux-ci sont soumis à une période d’éclairement artificiel de 8 h par jour, avec 16 h d’obscurité. Le volume de l’éjaculat et le nombre des spermato zoïdes qu’il contient sont augmentés, en moyenne et respectivement, de 42,6 et 56,9 %, alors que la proportion des spermatozoïdes anormaux régresse de 72 %.Spermatogenesis was highly improved when rams were submitted to an 8 hour artificial light exposition, with 16 hour darkness. Mean volume and sperm number of ejaculate were respectively increased by 42.6 and 56.9 % .while the proportion of abnormal sperm decreased by 72 %

Entropy and universality of Cardy-Verlinde formula in dark energy universe

We study the entropy of a FRW universe filled with dark energy (cosmological constant, quintessence or phantom). For general or time-dependent equation of state $p=w\rho$ the entropy is expressed in terms of energy, Casimir energy, and $w$. The correspondent expression reminds one about 2d CFT entropy only for conformal matter. At the same time, the cosmological Cardy-Verlinde formula relating three typical FRW universe entropies remains to be universal for any type of matter. The same conclusions hold in modified gravity which represents gravitational alternative for dark energy and which contains terms growing at low curvature. It is interesting that BHs in modified gravity are more entropic than in Einstein gravity. Finally, some hydrodynamical examples testing new shear viscosity bound, which is expected to be the consequence of the holographic entropy bound, are presented for the early universe in the plasma era and for the Kasner metric. It seems that the Kasner metric provides a counterexample to the new shear viscosity bound.Comment: LaTeX file, 39 pages, references are adde

Black Hole Thermodynamics and Statistical Mechanics

We have known for more than thirty years that black holes behave as thermodynamic systems, radiating as black bodies with characteristic temperatures and entropies. This behavior is not only interesting in its own right; it could also, through a statistical mechanical description, cast light on some of the deep problems of quantizing gravity. In these lectures, I review what we currently know about black hole thermodynamics and statistical mechanics, suggest a rather speculative "universal" characterization of the underlying states, and describe some key open questions.Comment: 35 pages, Springer macros; for the Proceedings of the 4th Aegean Summer School on Black Hole

<i>Ex vivo</i> peripheral blood mononuclear cell response to R848 in children after supplementation with the probiotic <i>Lactobacillus acidophilus</i> NCFM/<i>Bifidobacterium lactis</i> Bi-07

Several studies have demonstrated a decrease in upper respiratory infection (URI) frequency and severity in subjects taking probiotic supplements. We hypothesised beneficial effects of probiotics on viral URI in children are due to modulation of inflammatory innate immune responses. We tested this hypothesis, providing children with a probiotic combination of Lactobacillus acidophilus/Bidfidobacterium animalis ssp. lactis Bi-07 (NCFM/Bi-07) and measuring levels of cytokines in response to stimulation of peripheral blood mononuclear cells (PBMCs) to toll-like receptor (TLR) 7/8 agonist resiquimod (R848). In this open label study, 21 (2 dropouts) children received probiotic containing 5×109 cfu each of NCFM/(Bi-07) daily for 30 days. Whole blood was taken from each subject at study entry and 30 days for culture of PBMCs. PBMCs stimulated with resiquimod (R848) or unstimulated were incubated and a panel of immune markers was measured. There was a significant decrease in the net (stimulated-null) level of myeloid progenitor inhibitory factor 1 (MPIF-1) (mean decrease 0.1 ng/ml, 95% confidence interval 0.01-0.24, P=0.032) following probiotic supplementation. The change in immune marker levels after supplementation, when analysed together with respect to expected inflammatory/anti-inflammatory effects, was increased for interleukin (IL)-10 and decreased for MPIF-1, IL-8, interferon gamma induced protein 10, macrophage inflammatory protein 3 alpha (MIP-3α) and E-selectin (P=0.01). Adverse events were mild. In conclusion, supplementation with this probiotic combination was safe and resulted in significant modulation of PBMC limited immune response to TLR7/8 agonist R848 and in levels of MPIF-1 and MIP-3α. The anti-inflammatory effect may be one mechanism by which probiotics modulate the immune system however further study is needed. </jats:p