501 research outputs found

    Current Perspective on the Location and Function of Gamma- Aminobutyric Acid (GABA) and its Metabolic Partners in the Kidney.

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    Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter located in the mammalian central nervous system, which binds to GABAA and GABAB receptors to mediate its neurological effects. In addition to its role in the CNS, an increasing number of publications have suggested that GABA might also play a role in the regulation of renal function. All three enzymes associated with GABA metabolism; glutamic acid decarboxylase, GABA ?-oxoglutarate transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH) have been localised to the kidney providing the necessary machinery for localised GABA synthesis and metabolism. Moreover GABA receptors have been localised to both tubular and vascular structures in the kidney, and GABA is excreted in urine (~3 ?M) in humans. Despite the collective evidence describing the presence of a GABA system in the kidney, the precise function of such a system requires further clarification. Here we provide an overview of the current renal GABA literature and provide novel data that indicates GABA can act at contractile pericyte cells located along vasa recta capillaries in the renal medulla to potentially regulate medullary blood flow

    Constrained dogleg methods for nonlinear systems with simple bounds

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    We focus on the numerical solution of medium scale bound-constrained systems of nonlinear equations. In this context, we consider an affine-scaling trust region approach that allows a great flexibility in choosing the scaling matrix used to handle the bounds. The method is based on a dogleg procedure tailored for constrained problems and so, it is named Constrained Dogleg method. It generates only strictly feasible iterates. Global and locally fast convergence is ensured under standard assumptions. The method has been implemented in the Matlab solver CoDoSol that supports several diagonal scalings in both spherical and elliptical trust region frameworks. We give a brief account of CoDoSol and report on the computational experience performed on a number of representative test problem

    Bottom-Tau Unification in SUSY SU(5) GUT and Constraints from b to s gamma and Muon g-2

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    An analysis is made on bottom-tau Yukawa unification in supersymmetric (SUSY) SU(5) grand unified theory (GUT) in the framework of minimal supergravity, in which the parameter space is restricted by some experimental constraints including Br(b to s gamma) and muon g-2. The bottom-tau unification can be accommodated to the measured branching ratio Br(b to s gamma) if superparticle masses are relatively heavy and higgsino mass parameter \mu is negative. On the other hand, if we take the latest muon g-2 data to require positive SUSY contributions, then wrong-sign threshold corrections at SUSY scale upset the Yukawa unification with more than 20 percent discrepancy. It has to be compensated by superheavy threshold corrections around the GUT scale, which constrains models of flavor in SUSY GUT. A pattern of the superparticle masses preferred by the three requirements is also commented.Comment: 21pages, 6figure

    Neutralino Dark Matter, b-tau Yukawa Unification and Non-Universal Sfermion Masses

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    We study the implications of minimal non-Universal Boundary Conditions in the sfermion Soft SUSY Breaking (SSB) masses of mSUGRA. We impose asymptotic b-tau Yukawa coupling Unification and we resort to a parameterization of the deviation from Universality in the SSB motivated by the multiplet structure of SU(5) GUT. A set of cosmo-phenomenological constraints, including the recent results from WMAP, determines the allowed parameter space of the models under consideration. We highlight a new coannihilation corridor where neutralino-sbottom and neutralino-tau sneutrino-stau coannihilations significantly contribute to the reduction of the neutralino relic density.Comment: 38 pages, 27 Figures, Latex; Version accepted for publication in PR

    Nonlinear Integer Programming

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    Research efforts of the past fifty years have led to a development of linear integer programming as a mature discipline of mathematical optimization. Such a level of maturity has not been reached when one considers nonlinear systems subject to integrality requirements for the variables. This chapter is dedicated to this topic. The primary goal is a study of a simple version of general nonlinear integer problems, where all constraints are still linear. Our focus is on the computational complexity of the problem, which varies significantly with the type of nonlinear objective function in combination with the underlying combinatorial structure. Numerous boundary cases of complexity emerge, which sometimes surprisingly lead even to polynomial time algorithms. We also cover recent successful approaches for more general classes of problems. Though no positive theoretical efficiency results are available, nor are they likely to ever be available, these seem to be the currently most successful and interesting approaches for solving practical problems. It is our belief that the study of algorithms motivated by theoretical considerations and those motivated by our desire to solve practical instances should and do inform one another. So it is with this viewpoint that we present the subject, and it is in this direction that we hope to spark further research.Comment: 57 pages. To appear in: M. J\"unger, T. Liebling, D. Naddef, G. Nemhauser, W. Pulleyblank, G. Reinelt, G. Rinaldi, and L. Wolsey (eds.), 50 Years of Integer Programming 1958--2008: The Early Years and State-of-the-Art Surveys, Springer-Verlag, 2009, ISBN 354068274

    The PHENIX Experiment at RHIC

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    The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program available at http://www.rhic.bnl.gov/phenix

    Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

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    A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters
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