Electric and magnetic Weyl tensors in higher dimensions

Recent results on purely electric (PE) or magnetic (PM) spacetimes in n dimensions are summarized. These include: Weyl types; diagonalizability; conditions under which direct (or warped) products are PE/PM.Comment: 4 pages; short summary of (parts of) arXiv:1203.3563. Proceedings of "Relativity and Gravitation - 100 Years after Einstein in Prague", Prague, June 25-29, 2012 (http://ae100prg.mff.cuni.cz/

Oxidation and erythropoiesis

Purpose of review Erythropoiesis is a complex multistep process going from committed erythroid progenitors to mature red cells. Although recent advances allow the characterization of some components of erythropoiesis, much still remains to be investigated particularly on stress erythropoiesis. This review summarizes recent progresses made to understand the impact of oxidative stress on normal and pathologic erythropoiesis. Recent findings During erythroid maturation, reactive oxygen species might function as second messenger through either transient oxidation of cysteine residues on signaling targets or modulation of intracellular signaling pathways. Thus, in erythropoiesis, efficient cytoprotective systems are required to limit possible reactive oxygen species-related toxic effects especially in stress erythropoiesis characterized by severe oxidation such as b-thalassemia. In addition, prolonged or severe oxidative stress impairs autophagy, which might contribute to the block of erythroid maturation in stress erythropoiesis. Understanding the functional role of cytoprotective systems such as peroxiredoxin-2 or classical molecular chaperones such as the heat shock proteins will contribute to develop innovative therapeutic strategies for ineffective erythropoiesis. Summary We provide an update on cytoprotective mechanisms against oxidation in normal and stress erythropoiesis. We discuss the role of oxidative sensors involved in modulation of intracellular signaling during erythroid maturation process in normal and stress erythropoiesis

Semi-classical Green kernel asymptotics for the Dirac operator

We consider a semi-classical Dirac operator in arbitrary spatial dimensions with a smooth potential whose partial derivatives of any order are bounded by suitable constants. We prove that the distribution kernel of the inverse operator evaluated at two distinct points fulfilling a certain hypothesis can be represented as the product of an exponentially decaying factor involving an associated Agmon distance and some amplitude admitting a complete asymptotic expansion in powers of the semi-classical parameter. Moreover, we find an explicit formula for the leading term in that expansion.Comment: 46 page

Sistema Agrossilvipastoril na região sudoeste do Estado do Rio Grande do Sul.

bitstream/item/24472/1/Sistema-agrossilvipastoril-na-regiao-sudoeste-do-estado-do-Rio-Grande-do-Sul.pd

Evaluation of salt tolerance of in vitro-grown grapevine rootstock varieties

The response of 11 grapevine rootstock varieties to increasing salt concentrations (0, 50, 85, 120, 155 mM NaCl) was studied under in vitro and growth chamber conditions. The effect of salinity on the mortality of explants was compared with that of plantlets grown under growth chamber conditions and with data in literature on rootstock resistance under field conditions. In addition, in vitro stem elongation bud number, and rooting ability were related to salinity. The rootstock varieties can be divided into sensitive (41 B, R.Lot, 110 R, 140 R and 161-49), moderately tolerant (13.5 and Ramsey) and tolerant (196-17, CH-1, CH-2 and Superior). Measurements of the water and nutrient contents of plantlets indicate that increasing salt concentrations decreased the hydration of aerial parts and roots of all plants; however, the decrease of hydration was smaller in salt tolerant varieties. Increasing salt concentrations significantly reduced the K content and, to a smaller extent, the P and Ca contents. With and without salt treatments the levels of K and P were lower in sensitive plants. Na and Cl accumulated to a higher extent in tolerant plants. The tolerance to NaCl of in vitro-grown rootstocks seems to be due to their capacity to accumulate salt, to increase K concentration in the tissue and to maintain a high water content. Our results indicate that salt tolerance of grapevine varieties may be tested under growth chamber conditions and using in vitro explants

S15RS SGFB No. 10 (Union Seating)

A FINANCE BILL To allocate a maximum of seven thousand seven hundred fifty-seven dollars and ninety-three cents ($7,757.93) from the Student Government Senate General Contingency Account to fund nine new round tables and thirty new chairs for the LSU Student Union

Structural snapshots of Escherichia coli histidinol phosphate phosphatase along the reaction pathway.

HisB from Escherichia coli is a bifunctional enzyme catalyzing the sixth and eighth steps of l-histidine biosynthesis. The N-terminal domain (HisB-N) possesses histidinol phosphate phosphatase activity, and its crystal structure shows a single domain with fold similarity to the haloacid dehalogenase (HAD) enzyme family. HisB-N forms dimers in the crystal and in solution. The structure shows the presence of a structural Zn(2+) ion stabilizing the conformation of an extended loop. Two metal binding sites were also identified in the active site. Their presence was further confirmed by isothermal titration calorimetry. HisB-N is active in the presence of Mg(2+), Mn(2+), Co(2+), or Zn(2+), but Ca(2+) has an inhibitory effect. We have determined structures of several intermediate states corresponding to snapshots along the reaction pathway, including that of the phosphoaspartate intermediate. A catalytic mechanism, different from that described for other HAD enzymes, is proposed requiring the presence of the second metal ion not found in the active sites of previously characterized HAD enzymes, to complete the second half-reaction. The proposed mechanism is reminiscent of two-Mg(2+) ion catalysis utilized by DNA and RNA polymerases and many nucleases. The structure also provides an explanation for the inhibitory effect of Ca(2+)

The Lazarus Project. II. Spacelike extraction with the quasi-Kinnersley tetrad

The Lazarus project was designed to make the most of limited 3D binary black-hole simulations, through the identification of perturbations at late times, and subsequent evolution of the Weyl scalar $\Psi_4$ via the Teukolsky formulation. Here we report on new developments, employing the concept of the ``quasi-Kinnersley'' (transverse) frame, valid in the full nonlinear regime, to analyze late-time numerical spacetimes that should differ only slightly from Kerr. This allows us to extract the essential information about the background Kerr solution, and through this, to identify the radiation present. We explicitly test this procedure with full numerical evolutions of Bowen-York data for single spinning black holes, head-on and orbiting black holes near the ISCO regime. These techniques can be compared with previous Lazarus results, providing a measure of the numerical-tetrad errors intrinsic to the method, and give as a by-product a more robust wave extraction method for numerical relativity.Comment: 17 pages, 10 figures. Journal version with text changes, revised figures. [Note updated version of original Lazarus paper (gr-qc/0104063)

Complete classification of purely magnetic, non-rotating and non-accelerating perfect fluids

Recently the class of purely magnetic non-rotating dust spacetimes has been shown to be empty (Wylleman, Class. Quant. Grav. 23, 2727). It turns out that purely magnetic rotating dust models are subject to severe integrability conditions as well. One of the consequences of the present paper is that also rotating dust cannot be purely magnetic when it is of Petrov type D or when it has a vanishing spatial gradient of the energy density. For purely magnetic and non-rotating perfect fluids on the other hand, which have been fully classified earlier for Petrov type D (Lozanovski, Class. Quant. Grav. 19, 6377), the fluid is shown to be non-accelerating if and only if the spatial density gradient vanishes. Under these conditions, a new and algebraically general solution is found, which is unique up to a constant rescaling, which is spatially homogeneous of Bianchi type $VI_0$, has degenerate shear and is of Petrov type I($M^\infty)$ in the extended Arianrhod-McIntosh classification. The metric and the equation of state are explicitly constructed and properties of the model are briefly discussed. We finally situate it within the class of normal geodesic flows with degenerate shear tensor.Comment: 12 pages; introduction partly rewritten, notation made more clear, table of results adde

Exponential localization of hydrogen-like atoms in relativistic quantum electrodynamics

We consider two different models of a hydrogenic atom in a quantized electromagnetic field that treat the electron relativistically. The first one is a no-pair model in the free picture, the second one is given by the semi-relativistic Pauli-Fierz Hamiltonian. We prove that the no-pair operator is semi-bounded below and that its spectral subspaces corresponding to energies below the ionization threshold are exponentially localized. Both results hold true, for arbitrary values of the fine-structure constant, $e^2$, and the ultra-violet cut-off, $\Lambda$, and for all nuclear charges less than the critical charge without radiation field, $Z_c=e^{-2}2/(2/\pi+\pi/2)$. We obtain similar results for the semi-relativistic Pauli-Fierz operator, again for all values of $e^2$ and $\Lambda$ and for nuclear charges less than $e^{-2}2/\pi$.Comment: 37 page