Coordinated balancing of muscle oxidative metabolism through PGC-1α increases metabolic flexibility and preserves insulin sensitivity

The peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) enhances oxidative metabolism in skeletal muscle. Excessive lipid oxidation and electron transport chain activity can, however, lead to the accumulation of harmful metabolites and impair glucose homeostasis. Here, we investigated the effect of over-expression of PGC-1α on metabolic control and generation of insulin desensitizing agents in extensor digitorum longus (EDL), a muscle that exhibits low levels of PGC-1α in the untrained state and minimally relies on oxidative metabolism. We demonstrate that PGC-1α induces a strictly balanced substrate oxidation in EDL by concomitantly promoting the transcription of activators and inhibitors of lipid oxidation. Moreover, we show that PGC-1α enhances the potential to uncouple oxidative phosphorylation. Thereby, PGC-1α boosts elevated, yet tightly regulated oxidative metabolism devoid of side products that are detrimental for glucose homeostasis. Accordingly, PI3K activity, an early phase marker for insulin resistance, is preserved in EDL muscle. Our findings suggest that PGC-1α coordinately coactivates the simultaneous transcription of gene clusters implicated in the positive and negative regulation of oxidative metabolism and thereby increases metabolic flexibility. Thus, in mice fed a normal chow diet, over-expression of PGC-1α does not alter insulin sensitivity and the metabolic adaptations elicited by PGC-1α mimic the beneficial effects of endurance training on muscle metabolism in this context

Extracting constraints from direct detection searches of supersymmetric dark matter in the light of null results from the LHC in the squark sector

The comparison of the results of direct detection of Dark Matter, obtained with various target nuclei, requires model-dependent, or even arbitrary, assumptions. Indeed, to draw conclusions either the spin-dependent (SD) or the spin-independent (SI) interaction has to be neglected. In the light of the null results from supersymmetry searches at the LHC, the squark sector is pushed to high masses. We show that for a squark sector at the TeV scale, the framework used to extract contraints from direct detection searches can be redefined as the number of free parameters is reduced. Moreover, the correlation observed between SI and SD proton cross sections constitutes a key issue for the development of the next generation of Dark Matter detectors.Comment: Figure 3 has been updated. Conclusions unchange

Kerr Geodesics, the Penrose Process and Jet Collimation by a Black Hole

We re-examine the possibility that astrophysical jet collimation may arise from the geometry of rotating black holes and the presence of high-energy particles resulting from a Penrose process, without the help of magnetic fields. Our analysis uses the Weyl coordinates, which are revealed better adapted to the desired shape of the jets. We numerically integrate the 2D-geodesics equations. We give a detailed study of these geodesics and give several numerical examples. Among them are a set of perfectly collimated geodesics with asymptotes $\rho =\rho_{1}$ parallel to the $z-$ axis, with $\rho_{1}$ only depending on the ratios $\frac{\mathcal{Q}}{E^{2}-1}$ and $\frac{a}{M}$, where $a$ and $M$ are the parameters of the Kerr black hole, $E$ the particle energy and $\mathcal{Q}$ the Carter's constant.Comment: Accepted by Astronomy and Astrophysics. AA style with 3 EPS figures. Content amended after AA's refereeing. Discussion of geodesics also corrected and expanded earlier. Conclusions amended accordingl

A superfluid He3 detector for direct dark matter search

MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for direct Dark Matter Search. The idea is to use superfluid He3 as a sensitive medium. The existing device, the superfluid He3 cell, will be briefly introduced. Then a description of the MACHe3 project will be presented, in particular the background rejection and the neutralino event rate that may be achieved with such a device.Comment: 6 pages, 3 figures, Proceedings of the 3rd International Workshop on the Identification of Dark Matter (York, UK, 09/18/2000-09/22/2000

Expansion-Free Evolving Spheres Must Have Inhomogeneous Energy Density Distributions

In a recent paper a systematic study on shearing expansion-free spherically symmetric distributions was presented. As a particular case of such systems, the Skripkin model was mentioned, which corresponds to a nondissipative perfect fluid with a constant energy density. Here we show that such a model is inconsistent with junction conditions. It is shown that in general for any nondissipative fluid distribution, the expansion-free condition requires the energy density to be inhomogeneous. As an example we consider the case of dust, which allows for a complete integration.Comment: 8 pages, Latex. To appear in Phys. Rev.D. Typos correcte

A project of a new detector for direct Dark Matter search: MACHe3

MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for direct Dark Matter (DM) search. A cell of superfluid He3 has been developed and the idea of using a large number of such cells in a high granularity detector is proposed.This contribution presents, after a brief description of the superfluid He3 cell, the simulation of the response of different matrix configurations allowing to define an optimum design as a function of the number of cells and the volume of each cell. The exclusion plot and the predicted interaction cross-section for the neutralino as a photino are presented.Comment: 8 pages, 7 figures, Proceedings of Dark Matter 2000 (Marina Del Rey, Los Angeles, USA, 02/23/2000-02/25/2000

A Note on Segre Types of Second Order Symmetric Tensors in 5-D Brane-world Cosmology

Recent developments in string theory suggest that there might exist extra spatial dimensions, which are not small nor compact. The framework of most brane cosmological models is that in which the matter fields are confined on a brane-world embedded in five dimensions (the bulk). Motivated by this we reexamine the classification of the second order symmetric tensors in 5--D, and prove two theorems which collect together some basic results on the algebraic structure of these tensors in 5-dimensional space-times. We also briefly indicate how one can obtain, by induction, the classification of symmetric two-tensors (and the corresponding canonical forms) on n-dimensional spaces from the classification on 4-dimensional spaces. This is important in the context of 11--D supergravity and 10--D superstrings.Comment: 12 pages, to appear in Mod. Phys. Lett. A (2003) in the present for

The Mass of the Convective Zone in FGK Main Sequence Stars and the Effect of Accreted Planetary Material on Apparent Metallicity Determinations

The mass of the outer convective zone in FGK main sequence stars decreases dramatically with stellar mass. Therefore, any contamination of a star's atmosphere by accreted planetary material should affect hotter stars much more than cool stars. If recent suggestions that high metal abundances in stars with planets are caused by planetesimal accretion are correct, then metallicity enhancements in earlier-type stars with planets should be very pronounced. No such trend is seen, however.Comment: Submitted ApJ Letters March 26th; accepted April 30th. 12 pages, 2 figure

Mapeamento digital de classes e atributos de solos: métodos, paradigmas e novas técnicas.

Panorama geral sobre os métodos de mapeamento de solos e/ou de suas propriedades, assim como sobre as principais técnicas quantitativas usadas.bitstream/CNPS/11588/1/doc55_mapeamentodigital.pd