224 research outputs found
Metabotropic glutamate receptor 1 (mGluR1) and 5 (mGluR5) regulate late phases of LTP and LTD in the hippocampal CA1 region in vitro
The group I metabotropic glutamate receptors, mGluR1 and mGluR5, exhibit differences in their regulation of synaptic plasticity, suggesting that these receptors may subserve separate functional roles in information storage. In addition, although effects in vivo are consistently described, conflicting reports of the involvement of mGluRs in hippocampal synaptic plasticity in vitro exist. We therefore addressed the involvement of mGluR1 and mGluR5 in long-term potentiation (LTP) and long-term depression (LTD) in the hippocampal CA1 region of adult male rats in vitro. The mGluR1 antagonist (S)-(+)-α-amino-4-carboxy-2-methylbenzene-acetic acid (LY367385) impaired both induction and late phases of both LTP and LTD, when applied before high-frequency tetanization (HFT; 100 Hz) or low-frequency stimulation (LFS; 1 Hz), respectively. Application after either HFT or LFS had no effect. The mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP), when given before HFT, inhibited both the induction and late phases of LTP. When given after HFT, late LTP was inhibited. MPEP, given prior to LFS, impaired LTD induction, although stable LTD was still expressed. Application after LFS significantly impaired late phases of LTD. Activation of protein synthesis may comprise a key mechanism underlying the group I mGluR contribution to synaptic plasticity. The mGluR5 agonist (R,S)-2-chloro-5-hydroxyphenylglycine (CHPG) converted short-term depression into LTD. Effects were prevented by application of the protein synthesis inhibitor anisomycin, suggesting that protein synthesis is triggered by group I mGluR activation to enable persistency of synaptic plasticity. Taken together, these data support the notion that both mGluR1 and mGluR5 are critically involved in bidirectional synaptic plasticity in the CA1 region and may enable functional differences in information encoding through LTP and LTD
The Outer Tracker Detector of the HERA-B Experiment Part I: Detector
The HERA-B Outer Tracker is a large system of planar drift chambers with
about 113000 read-out channels. Its inner part has been designed to be exposed
to a particle flux of up to 2.10^5 cm^-2 s^-1, thus coping with conditions
similar to those expected for future hadron collider experiments. 13
superlayers, each consisting of two individual chambers, have been assembled
and installed in the experiment. The stereo layers inside each chamber are
composed of honeycomb drift tube modules with 5 and 10 mm diameter cells.
Chamber aging is prevented by coating the cathode foils with thin layers of
copper and gold, together with a proper drift gas choice. Longitudinal wire
segmentation is used to limit the occupancy in the most irradiated detector
regions to about 20 %. The production of 978 modules was distributed among six
different laboratories and took 15 months. For all materials in the fiducial
region of the detector good compromises of stability versus thickness were
found. A closed-loop gas system supplies the Ar/CF4/CO2 gas mixture to all
chambers. The successful operation of the HERA-B Outer Tracker shows that a
large tracker can be efficiently built and safely operated under huge radiation
load at a hadron collider.Comment: 28 pages, 14 figure
The Outer Tracker Detector of the HERA-B Experiment. Part II: Front-End Electronics
The HERA-B Outer Tracker is a large detector with 112674 drift chamber
channels. It is exposed to a particle flux of up to 2x10^5/cm^2/s thus coping
with conditions similar to those expected for the LHC experiments. The
front-end readout system, based on the ASD-8 chip and a customized TDC chip, is
designed to fulfil the requirements on low noise, high sensitivity, rate
tolerance, and high integration density. The TDC system is based on an ASIC
which digitizes the time in bins of about 0.5 ns within a total of 256 bins.
The chip also comprises a pipeline to store data from 128 events which is
required for a deadtime-free trigger and data acquisition system. We report on
the development, installation, and commissioning of the front-end electronics,
including the grounding and noise suppression schemes, and discuss its
performance in the HERA-B experiment
Multi-response analysis in the material characterisation of electrospun poly (lactic acid)/halloysite nanotube composite fibres based on Taguchi design of experiments: fibre diameter, non-intercalation and nucleation effects
Poly (lactic acid) (PLA)/halloysite nanotube (HNT) composite fibres were prepared by using a simple and versatile electrospinning technique. The systematic approach via Taguchi design of experiments (DoE) was implemented to investigate factorial effects of applied voltage, feed rate of solution, collector distance and HNT concentration on the fibre diameter, HNT non-intercalation and nucleation effects. The HNT intercalation level, composite fibre morphology, their associated fibre diameter and thermal properties were evaluated by means of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), imaging analysis and differential scanning calorimetry (DSC), respectively. HNT non-intercalation phenomenon appears to be manifested as reflected by the minimal shift of XRD peaks for all electrospun PLA/HNT composite fibres. The smaller-fibre-diameter characteristic was found to be sequentially associated with the feed rate of solution, collector distance and applied voltage. The glass transition temperature (T g) and melting temperature (T m) are not highly affected by varying the material and electrospinning parameters. However, as the indicator of the nucleation effect, the crystallisation temperature (T c) of PLA/HNT composite fibres is predominantly impacted by HNT concentration and applied voltage. It is evident that HNT’s nucleating agent role is confirmed when embedded with HNTs to accelerate the cold crystallisation of composite fibres. Taguchi DoE method has been found to be an effective approach to statistically optimise critical parameters used in electrospinning in order to effectively tailor the resulting physical features and thermal properties of PLA/HNT composite fibres
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
The pole in
Using a sample of 58 million events recorded in the BESII detector,
the decay is studied. There are conspicuous
and signals. At low mass, a large
broad peak due to the is observed, and its pole position is determined
to be - MeV from the mean of six analyses.
The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL
Search for the Lepton Flavor Violation Processes and
The lepton flavor violation processes and are
searched for using a sample of 5.8 events collected with
the BESII detector. Zero and one candidate events, consistent with the
estimated background, are observed in and
decays, respectively. Upper limits on the branching ratios are determined to be
and at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure
Observation of the decay \psip\rar\kstark
Using 14 million events collected with the BESII detector,
branching fractions of \psip\rar\kstarkpm and \kstarknn are determined to
be: \calB(\psip\rar\kstarkpm)=(2.9^{+1.3}_{-1.7}\pm0.4)\times 10^{-5} and
\calB(\psip\rar\kstarknn)=(13.3^{+2.4}_{-2.7}\pm1.9)\times 10^{-5}. The
results confirm the violation of the "12%" rule for these two decay channels
with higher precision. A large isospin violation between the charged and
neutral modes is observed.Comment: 5 pages, 3 figure
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