A phenomenological description of quantum-gravity-induced space-time noise

I propose a phenomenological description of space-time foam and discuss the experimental limits that are within reach of forthcoming experiments.Comment: 10 pages, LaTex, 1 figure. Short paper, omitting most technical details. More detailed analysis was reported in gr-qc/010400

Detection of hCG Responsive Expression of the Steroidogenic Acute Regulatory Protein in Mouse Leydig Cells

The steroidogenic acute regulatory (StAR) protein, a novel mitochondrial protein, is involved in the regulation of steroid hormone biosynthesis through its mediation of the intramitochondrial transport of the steroid substrate, cholesterol, to the cytochrome P450 cholesterol side chain cleavage (P450scc) enzyme. The expression of StAR protein is regulated by cAMP-dependent signaling in steroidogenic cells. During the course of our studies in mouse Leydig cells, we employ several methods for studying the regulation of StAR protein expression by human chorionic gonadotropin (hCG). A sensitive quantitative reverse transcription and polymerase chain reaction (RT-PCR) was utilized for determining StAR mRNA expression. Stimulation of mLTC-1 mouse Leydig tumor cells with hCG resulted in the coordinate regulation of StAR mRNA expression and progesterone accumulation in a time-response manner. The validity and accuracy of quantitative RT-PCR results in mLTC-1 cells were verified by a competitive PCR approach and were further confirmed in primary cultures of isolated mouse Leydig cells. Immunoblotting studies demonstrated an increase in the levels of the StAR protein in a concentration dependent manner following hCG stimulation in mLTC-1 cells. Northern hybridization analysis revealed three StAR transcripts, all of which were of sufficient size to encode functional StAR protein, and which were coordinately expressed in response to hCG. Collectively, the experimental approaches utilized in the present investigation allow for the demonstration and characterization of hCG mediated regulation of StAR mRNA and StAR protein expression in mouse Leydig cells

Altered Neurocircuitry in the Dopamine Transporter Knockout Mouse Brain

The plasma membrane transporters for the monoamine neurotransmitters dopamine, serotonin, and norepinephrine modulate the dynamics of these monoamine neurotransmitters. Thus, activity of these transporters has significant consequences for monoamine activity throughout the brain and for a number of neurological and psychiatric disorders. Gene knockout (KO) mice that reduce or eliminate expression of each of these monoamine transporters have provided a wealth of new information about the function of these proteins at molecular, physiological and behavioral levels. In the present work we use the unique properties of magnetic resonance imaging (MRI) to probe the effects of altered dopaminergic dynamics on meso-scale neuronal circuitry and overall brain morphology, since changes at these levels of organization might help to account for some of the extensive pharmacological and behavioral differences observed in dopamine transporter (DAT) KO mice. Despite the smaller size of these animals, voxel-wise statistical comparison of high resolution structural MR images indicated little morphological change as a consequence of DAT KO. Likewise, proton magnetic resonance spectra recorded in the striatum indicated no significant changes in detectable metabolite concentrations between DAT KO and wild-type (WT) mice. In contrast, alterations in the circuitry from the prefrontal cortex to the mesocortical limbic system, an important brain component intimately tied to function of mesolimbic/mesocortical dopamine reward pathways, were revealed by manganese-enhanced MRI (MEMRI). Analysis of co-registered MEMRI images taken over the 26 hours after introduction of Mn^(2+) into the prefrontal cortex indicated that DAT KO mice have a truncated Mn^(2+) distribution within this circuitry with little accumulation beyond the thalamus or contralateral to the injection site. By contrast, WT littermates exhibit Mn^(2+) transport into more posterior midbrain nuclei and contralateral mesolimbic structures at 26 hr post-injection. Thus, DAT KO mice appear, at this level of anatomic resolution, to have preserved cortico-striatal-thalamic connectivity but diminished robustness of reward-modulating circuitry distal to the thalamus. This is in contradistinction to the state of this circuitry in serotonin transporter KO mice where we observed more robust connectivity in more posterior brain regions using methods identical to those employed here

Distinct phosphorylation requirements regulate cortactin activation by TirEPEC and its binding to N-WASP

<p>Abstract</p> <p>Background</p> <p>Cortactin activates the actin-related 2/3 (Arp2/3) complex promoting actin polymerization to remodel cell architecture in multiple processes (e.g. cell migration, membrane trafficking, invadopodia formation etc.). Moreover, it was called the Achilles' heel of the actin cytoskeleton because many pathogens hijack signals that converge on this oncogenic scaffolding protein. Cortactin is able to modulate N-WASP activation <it>in vitro </it>in a phosphorylation-dependent fashion. Thus Erk-phosphorylated cortactin is efficient in activating N-WASP through its SH3 domain, while Src-phosphorylated cortactin is not. This could represent a switch on/off mechanism controlling the coordinated action of both nucleator promoting factors (NPFs). Pedestal formation by enteropathogenic <it>Escherichia coli </it>(EPEC) requires N-WASP activation. N-WASP is recruited by the cell adapter Nck which binds a major tyrosine-phosphorylated site of a bacterial injected effector, Tir (translocated intimin receptor). Tir-Nck-N-WASP axis defines the current major pathway to actin polymerization on pedestals. In addition, it was recently reported that EPEC induces tyrosine phosphorylation of cortactin.</p> <p>Results</p> <p>Here we demonstrate that cortactin phosphorylation is absent on N-WASP deficient cells, but is recovered by re-expression of N-WASP. We used purified recombinant cortactin and Tir proteins to demonstrate a direct interaction of both that promoted Arp2/3 complex-mediated actin polymerization <it>in vitro</it>, independently of cortactin phosphorylation.</p> <p>Conclusion</p> <p>We propose that cortactin binds Tir through its N-terminal part in a tyrosine and serine phosphorylation independent manner while SH3 domain binding and activation of N-WASP is regulated by tyrosine and serine mediated phosphorylation of cortactin. Therefore cortactin could act on Tir-Nck-N-WASP pathway and control a possible cycling activity of N-WASP underlying pedestal formation.</p

Deep-Inelastic Inclusive ep Scattering at Low x and a Determination of alpha_s

A precise measurement of the inclusive deep-inelastic e^+p scattering cross section is reported in the kinematic range 1.5<= Q^2 <=150 GeV^2 and 3*10^(-5)<= x <=0.2. The data were recorded with the H1 detector at HERA in 1996 and 1997, and correspond to an integrated luminosity of 20 pb^(-1). The double differential cross section, from which the proton structure function F_2(x,Q^2) and the longitudinal structure function F_L(x,Q^2) are extracted, is measured with typically 1% statistical and 3% systematic uncertainties. The measured partial derivative (dF_2(x,Q^2)/dln Q^2)_x is observed to rise continuously towards small x for fixed Q^2. The cross section data are combined with published H1 measurements at high Q^2 for a next-to-leading order DGLAP QCD analysis.The H1 data determine the gluon momentum distribution in the range 3*10^(-4)<= x <=0.1 to within an experimental accuracy of about 3% for Q^2 =20 GeV^2. A fit of the H1 measurements and the mu p data of the BCDMS collaboration allows the strong coupling constant alpha_s and the gluon distribution to be simultaneously determined. A value of alpha _s(M_Z^2)=0.1150+-0.0017 (exp) +0.0009-0.0005 (model) is obtained in NLO, with an additional theoretical uncertainty of about +-0.005, mainly due to the uncertainty of the renormalisation scale.Comment: 68 pages, 24 figures and 18 table

Physics, Astrophysics and Cosmology with Gravitational Waves

Gravitational wave detectors are already operating at interesting sensitivity levels, and they have an upgrade path that should result in secure detections by 2014. We review the physics of gravitational waves, how they interact with detectors (bars and interferometers), and how these detectors operate. We study the most likely sources of gravitational waves and review the data analysis methods that are used to extract their signals from detector noise. Then we consider the consequences of gravitational wave detections and observations for physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version <http://www.livingreviews.org/lrr-2009-2

Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal