1,179 research outputs found
Construction and Expected Performance of the Hadron Blind Detector for the PHENIX Experiment at RHIC
A new Hadron Blind Detector (HBD) for electron identification in high density
hadron environment has been installed in the PHENIX detector at RHIC in the
fall of 2006. The HBD will identify low momentum electron-positron pairs to
reduce the combinatorial background in the mass spectrum, mainly
in the low-mass region below 1 GeV/c. The HBD is a windowless
proximity-focusing Cherenkov detector with a radiator length of 50 cm, a CsI
photocathode and three layers of Gas Electron Multipliers (GEM). The HBD uses
pure CF as a radiator and a detector gas. Construction details and the
expected performance of the detector are described.Comment: QM2006 proceedings, 4 pages 3 figure
Adenosine A2A receptor modulation of hippocampal CA3-CA1 synapse plasticity during associative learning in behaving mice
© 2009 Nature Publishing Group All rights reservedPrevious in vitro studies have characterized the electrophysiological and molecular signaling pathways of adenosine tonic modulation on long-lasting synaptic plasticity events, particularly for hippocampal long-term potentiation(LTP). However, it remains to be elucidated
whether the long-term changes produced by endogenous adenosine in the efficiency of synapses are related to those required for
learning and memory formation. Our goal was to understand how endogenous activation of adenosine excitatory A2A receptors modulates the associative learning evolution in conscious behaving mice. We have studied here the effects of the application of a highly selective A2A receptor antagonist, SCH58261, upon a well-known associative learning paradigm - classical eyeblink conditioning. We used a trace paradigm, with a tone as the conditioned stimulus (CS) and an electric shock presented to the supraorbital nerve as the unconditioned stimulus(US). A single electrical pulse was presented to the Schaffer collateral–commissural pathway to evoke field EPSPs (fEPSPs) in the pyramidal CA1 area during the CS–US interval. In vehicle-injected animals, there was a progressive increase in the percentage of conditioning responses (CRs) and in the slope of fEPSPs through conditioning sessions, an effect that was completely prevented (and lost) in SCH58261 (0.5 mg/kg, i.p.)-injected animals. Moreover, experimentally evoked LTP was impaired in SCH58261- injected mice. In conclusion, the endogenous activation of adenosine A2A receptors plays a pivotal effect on the associative learning process and its relevant hippocampal circuits, including activity-dependent changes at the CA3-CA1 synapse.This study was supported by grants from the Spanish Ministry of Education and Research (BFU2005-01024 and BFU2005-02512), Spanish Junta de Andalucía (BIO-122 and CVI-02487), and the Fundación Conocimiento y Cultura of
the Pablo de Olavide University (Seville, Spain).B. Fontinha was in receipt of a studentship from a project grant (POCI/SAU-NEU/56332/2004) supported by Fundação para a Ciência e Tecnologia (FCT, Portugal), and of an STSM from Cost B30 concerted action of the EU
Directed flow of antiprotons in Au+Au collisions at AGS
Directed flow of antiprotons is studied in Au+Au collisions at a beam
momentum of 11.5A GeV/c. It is shown that antiproton directed flow is
anti-correlated to proton flow. The measured transverse momentum dependence of
the antiproton flow is compared with predictions of the RQMD event generator.Comment: 16 pages, 6 figure
Dissecting the substrate recognition of 3-O-sulfotransferase for the biosynthesis of anticoagulant heparin
Heparin is a polysaccharide-based natural product that is used clinically as an anticoagulant drug. Heparan sulfate 3-O-sulfotransferase (3-OST) is an enzyme that transfers a sulfo group to the 3-OH position of a glucosamine unit. 3-OST is present in multiple isoforms, and the polysaccharides modified by these different isoforms perform distinct biological functions. 3-OST isoform 1 (3-OST-1) is the key enzyme for the biosynthesis of anticoagulant heparin. Here, we report the crystal structure of the ternary complex of 3-OST-1, 3′-phosphoadenosine 5′-phosphate, and a heptasaccharide substrate. Comparisons to previously determined structures of 3-OST-3 reveal unique binding modes used by the different isoforms of 3-OST for distinguishing the fine structures of saccharide substrates. Our data demonstrate that the saccharide substrates display distinct conformations when interacting with the different 3-OST isoforms. Site-directed mutagenesis data suggest that several key amino residues, including Lys259, Thr256, and Trp283 in 3-OST-3 and Arg268 in 3-OST-1, play important roles in substrate binding and specificity between isoforms. These results deepen our understanding of the biosynthetic mechanism of heparan sulfate and provide structural information for engineering enzymes for an enhanced biosynthetic approach to heparin production
Proton and Pion Production Relative to the Reaction Plane in Au + Au Collisions at AGS Energies
Results are presented of an analysis of proton and charged pion azimuthal
distributions measured with respect to the reaction plane in Au + Au collisions
at a beam momentum of about 11 AGeV/c. The azimuthal anisotropy is studied as a
function of particle rapidity and transverse momentum for different
centralities of the collisions. The triple differential (in rapidity,
transverse momentum, and azimuthal angle) distributions are reconstructed. A
comparison of the results with a previous analysis of charged particle and
transverse energy flow as well as with model predictions is presented.Comment: 23 pages (LaTeX), 12 figure
The Caltech Millimeter Wave Interferometer
The Caltech Millimeter-Wave Interferometer has recently begun observations at a wavelength of 2.6 mm. We describe the instrument and some of the first results from it
J/psi suppression at forward rapidity in Au+Au collisions at sqrt(s_NN)=39 and 62.4 GeV
We present measurements of the J/psi invariant yields in sqrt(s_NN)=39 and
62.4 GeV Au+Au collisions at forward rapidity (1.2<|y|<2.2). Invariant yields
are presented as a function of both collision centrality and transverse
momentum. Nuclear modifications are obtained for central relative to peripheral
Au+Au collisions (R_CP) and for various centrality selections in Au+Au relative
to scaled p+p cross sections obtained from other measurements (R_AA). The
observed suppression patterns at 39 and 62.4 GeV are quite similar to those
previously measured at 200 GeV. This similar suppression presents a challenge
to theoretical models that contain various competing mechanisms with different
energy dependencies, some of which cause suppression and others enhancement.Comment: 365 authors, 10 pages, 11 figures, 4 tables. Submitted to Phys. Rev.
C. Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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