646 research outputs found
Time and position sensitive single photon detector for scintillator read-out
We have developed a photon counting detector system for combined neutron and
gamma radiography which can determine position, time and intensity of a
secondary photon flash created by a high-energy particle or photon within a
scintillator screen. The system is based on a micro-channel plate
photomultiplier concept utilizing image charge coupling to a position- and
time-sensitive read-out anode placed outside the vacuum tube in air, aided by a
standard photomultiplier and very fast pulse-height analyzing electronics. Due
to the low dead time of all system components it can cope with the high
throughput demands of a proposed combined fast neutron and dual discrete energy
gamma radiography method (FNDDER). We show tests with different types of
delay-line read-out anodes and present a novel pulse-height-to-time converter
circuit with its potential to discriminate gamma energies for the projected
FNDDER devices for an automated cargo container inspection system (ACCIS).Comment: Proceedings of FNDA 201
Beam tests of a large-scale TORCH time-of-flight demonstrator
The TORCH time-of-flight detector is designed to provide particle
identification in the momentum range 2-10 GeV/c over large areas. The detector
exploits prompt Cherenkov light produced by charged particles traversing a 10
mm thick quartz plate. The photons propagate via total internal reflection and
are focused onto a detector plane comprising position-sensitive Micro-Channel
Plate Photo-Multiplier Tubes (MCP-PMT) detectors. The goal is to achieve a
single-photon timing resolution of 70 ps, giving a timing precision of 15 ps
per charged particle by combining the information from around 30 detected
photons. The MCP-PMT detectors have been developed with a commercial partner
(Photek Ltd, UK), leading to the delivery of a square tube of active area 53
53mm with a granularity of 8 128 pixels equivalent. A
large-scale demonstrator of TORCH, having a quartz plate of dimensions 660
1250 10 mm and read out by a pair of MCP-PMTs with custom
readout electronics, has been verified in a test beam campaign at the CERN PS.
Preliminary results indicate that the required performance is close to being
achieved. The anticipated performance of a full-scale TORCH detector at the
LHCb experiment is presented.Comment: 12 pages, 7 figures, Paper submitted to Nuclear Instruments & Methods
in Physics Research, Section A - Special Issue VCI 201
Suppression of hole-hole scattering in GaAs/AlGaAs heterostructures under uniaxial compression
Resistance, magnetoresistance and their temperature dependencies have been
investigated in the 2D hole gas at a [001] p-GaAs/AlGaAs
heterointerface under [110] uniaxial compression. Analysis performed in the
frame of hole-hole scattering between carriers in the two spin splitted
subbands of the ground heavy hole state indicates, that h-h scattering is
strongly suppressed by uniaxial compression. The decay time of the
relative momentum reveals 4.5 times increase at a uniaxial compression of 1.3
kbar.Comment: 5 pages, 3 figures. submitted to Phys.Rev.
Angiotensin 1-7 Rescues Cognitive Decline and Neuronal Loss Following Traumatic Brain Injury in Mice
Purpose of study: Traumatic brain injury (TBI) is a leading cause of death and disability in the U.S., accounting for approximately 30% of all injury deaths and 3 million TBI-related emergency visits yearly. There is limited research in the area of mitigating the post-inflammatory effects of non-fatal traumatic brain injury. Angiotensin 1-7, an endogenous peptide that acts on the MAS receptor, has recently shown to be anti-inflammatory, anti-oxidative, and vasodilatory unlike its relative, angiotensin II. We asked the question of whether Ang 1-7 modulates neuroinflammation and improves cognitive function in mice following traumatic brain injury.
Methods: A controlled cortical impactor with a retractable piston was used to model a mild traumatic brain injury (mTBI). Mice either received Ang 1-7 (1 mg/kg, n=12) or normal saline (0.9%, n=12) 2 hours post-TBI and 30 minutes prior to novel objection recognition (NOR) testing on days 1, 3, 7, 14 post-TBI with tissue harvesting for hematoxylin and eosin (H&E) staining.
Results: Between-group studies showed that Ang 1-7 treated mice showed significantly higher NOR ratios compared to that of the control group. Additionally, statistically significant higher neuronal count in the ipsilateral hippocampal and cortical tissues days 1, 3, 7, and 14 post-TBI was observed in the Ang-1-7 group.
Conclusion: Together, these results demonstrate that Ang 1-7 significantly improves cognitive function and rescues further cell loss against secondary intrinsic injury following extrinsic mTBI and suggest that it may be a novel therapy to the effects of mild traumatic brain injury
Ruling out the impact of defects on the below band gap photoconductivity of Ti supersaturated Si
In this study, we present a structural and optoelectronic characterization of high dose Ti implanted Si subsequently pulsed-laser melted (Ti supersaturated Si). Time-of-flight secondary ion mass spectrometry analysis reveals that the theoretical Mott limit has been surpassed after the laser process and transmission electron microscopy images show a good lattice reconstruction. Optical characterization shows strong sub-band gap absorption related to the high Ti concentration. Photoconductivity measurements show that Ti supersaturated Si presents spectral response orders of magnitude higher than unimplanted Si at energies below the band gap. We conclude that the observed below band gap photoconductivity cannot be attributed to structural defects produced by the fabrication processes and suggest that both absorption coefficient of the new material and lifetime of photoexcited carriers have been enhanced due to the presence of a high Ti concentration. This remarkable result proves that Ti supersaturated Si is a promising material for both infrared detectors and high efficiency photovoltaic devices
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