On computations of angular momentum and its flux in numerical relativity

The purpose of this note is to point out ambiguities that appear in the calculation of angular momentum and its radiated counterpart when some simple formulae are used to compute them. We illustrate, in two simple different examples, how incorrect results can be obtained with them. Additionally, we discuss the magnitude of possible errors in well known situations.Comment: 8 pages. Minor improvements . To appear in Class. Quantum Gra

Estimates of the total gravitation radiation in the head-on black hole collision

We report on calculations of the total gravitational energy radiated in the head-on black hole collision, where we use the geometry of the Robinson-Trautman metrics.Comment: 10 pages, 2 figures, LaTeX2

Quasigroups, Asymptotic Symmetries and Conservation Laws in General Relativity

A new quasigroup approach to conservation laws in general relativity is applied to study asymptotically flat at future null infinity spacetime. The infinite-parametric Newman-Unti group of asymptotic symmetries is reduced to the Poincar\'e quasigroup and the Noether charge associated with any element of the Poincar\'e quasialgebra is defined. The integral conserved quantities of energy-momentum and angular momentum are linear on generators of Poincar\'e quasigroup, free of the supertranslation ambiguity, posess the flux and identically equal to zero in Minkowski spacetime.Comment: RevTeX4, 5 page

The AdS/CFT Correspondence and a New Positive Energy Conjecture for General Relativity

We examine the AdS/CFT correspondence when the gauge theory is considered on a compactified space with supersymmetry breaking boundary conditions. We find that the corresponding supergravity solution has a negative energy, in agreement with the expected negative Casimir energy in the field theory. Stability of the gauge theory would imply that this supergravity solution has minimum energy among all solutions with the same boundary conditions. Hence we are lead to conjecture a new positive energy theorem for asymptotically locally Anti-de Sitter spacetimes. We show that the candidate minimum energy solution is stable against all quadratic fluctuations of the metric.Comment: 25 pages, harvma

Glutamine dipeptide supplementation improves clinical responses in patients with diabetic foot syndrome

ABSTRACT The effect of glutamine dipeptide (GDP) supplementation in patients with diabetic foot syndrome was evaluated. A total of 22 patients took part in the study. GDP was supplied in 10 g sachets, and was dissolved in water immediately before use, with ingestion once a day, after lunch or after dinner (20 g/day) over a period of 30 days. Quantification of foot insensitive areas, oxidative stress, blood cytokines, and biochemical, hematological and toxicological parameters was performed before and after GDP supplementation. We observed an increase in blood levels of interferon-&#945; (P=0.023), interferon-&#947; (P=0.038), interleukin-4 (P=0.003), interleukin-6 (P=0.0025), interleukin-7 (P=0.028), interleukin-12 p40 (P=0.017), interleukin-13 (P=0.001), leukocytes (P=0.037), eosinophils (P=0.049), and typical lymphocytes (P<0.001) due to GDP administration. In addition, we observed a reduced number (P=0.048) of insensitive areas on the foot, and reduction (P=0.047) of fasting hyperglycemia. Patients also showed increased blood high density lipoprotein (P<0.01) and protein thiol groups (P=0.004). These favorable results were associated with the absence of renal and hepatic toxicity. These results are of clinical relevance, since supplementation with GDP over 30 days improved clinical responses in patients with diabetic foot syndrome

Development of selective agonists and antagonists of P2Y receptors

Although elucidation of the medicinal chemistry of agonists and antagonists of the P2Y receptors has lagged behind that of many other members of group A G protein-coupled receptors, detailed qualitative and quantitative structure–activity relationships (SARs) were recently constructed for several of the subtypes. Agonists selective for P2Y1, P2Y2, and P2Y6 receptors and nucleotide antagonists selective for P2Y1 and P2Y12 receptors are now known. Selective nonnucleotide antagonists were reported for P2Y1, P2Y2, P2Y6, P2Y11, P2Y12, and P2Y13 receptors. At the P2Y1 and P2Y12 receptors, nucleotide agonists (5′-diphosphate derivatives) were converted into antagonists of nanomolar affinity by altering the phosphate moieties, with a focus particularly on the ribose conformation and substitution pattern. Nucleotide analogues with conformationally constrained ribose-like rings were introduced as selective receptor probes for P2Y1 and P2Y6 receptors. Screening chemically diverse compound libraries has begun to yield new lead compounds for the development of P2Y receptor antagonists, such as competitive P2Y12 receptor antagonists with antithrombotic activity. Selective agonists for the P2Y4, P2Y11, and P2Y13 receptors and selective antagonists for P2Y4 and P2Y14 receptors have not yet been identified. The P2Y14 receptor appears to be the most restrictive of the class with respect to modification of the nucleobase, ribose, and phosphate moieties. The continuing process of ligand design for the P2Y receptors will aid in the identification of new clinical targets

Activation of the P2X7 ion channel by soluble and covalently bound ligands

The homotrimeric P2X7 purinergic receptor has sparked interest because of its capacity to sense adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide (NAD) released from cells and to induce calcium signaling and cell death. Here, we examine the response of arginine mutants of P2X7 to soluble and covalently bound ligands. High concentrations of ecto-ATP gate P2X7 by acting as a soluble ligand and low concentrations of ecto-NAD gate P2X7 following ADP-ribosylation at R125 catalyzed by toxin-related ecto-ADP-ribosyltransferase ART2.2. R125 lies on a prominent cysteine-rich finger at the interface of adjacent receptor subunits, and ADP-ribosylation at this site likely places the common adenine nucleotide moiety into the ligand-binding pocket of P2X7