1,471 research outputs found
Effects of balloon injury on neointimal hyperplasia in steptozotocin-induced diabetes and in hyperinsulinemic nondiabetic pancreatic islet-transplanted rats.
BACKGROUND:
The mechanisms of increased neointimal hyperplasia after coronary interventions in diabetic patients are still unknown.
METHODS AND RESULTS:
Glucose and insulin effects on in vitro vascular smooth muscle cell (VSMC) proliferation and migration were assessed. The effect of balloon injury on neointimal hyperplasia was studied in streptozotocin-induced diabetic rats with or without adjunct insulin therapy. To study the effect of balloon injury in nondiabetic rats with hyperinsulinemia, pancreatic islets were transplanted under the kidney capsule in normal rats. Glucose did not increase VSMC proliferation and migration in vitro. In contrast, insulin induced a significant increase in VSMC proliferation and migration in cell cultures. Furthermore, in VSMC culture, insulin increased MAPK activation. A reduction in neointimal hyperplasia was consistently documented after vascular injury in hyperglycemic streptozotocin-induced diabetic rats. Insulin therapy significantly increased neointimal hyperplasia in these rats. This effect of hyperinsulinemia was totally abolished by transfection on the arterial wall of the N17H-ras-negative mutant gene. Finally, after experimental balloon angioplasty in hyperinsulinemic nondiabetic islet-transplanted rats, a significant increase in neointimal hyperplasia was observed.
CONCLUSIONS:
In rats with streptozotocin-induced diabetes, balloon injury was not associated with an increase in neointimal formation. Exogenous insulin administration in diabetic rats and islet transplantation in nondiabetic rats increased both blood insulin levels and neointimal hyperplasia after balloon injury. Hyperinsulinemia through activation of the ras/MAPK pathway, rather than hyperglycemia per se, seems to be of crucial importance in determining the exaggerated neointimal hyperplasia after balloon angioplasty in diabetic animals
Study of timing characteristics of a 3 m long plastic scintillator counter using waveform digitizers
A plastic scintillator bar with dimensions 300 cm x 2.5 cm x 11 cm was
exposed to a focused muon beam to study its light yield and timing
characteristics as a function of position and angle of incidence. The
scintillating light was read out at both ends by photomultiplier tubes whose
pulse shapes were recorded by waveform digitizers. Results obtained with the
WAVECATCHER and SAMPIC digitizers are analyzed and compared. A discussion of
the various factors affecting the timing resolution is presented. Prospects for
applications of plastic scintillator technology in large-scale particle physics
detectors with timing resolution around 100 ps are provided in light of the
results
VHMPID: a new detector for the ALICE experiment at LHC
This article presents the basic idea of VHMPID, an upgrade detector for the
ALICE experiment at LHC, CERN. The main goal of this detector is to extend the
particle identification capabilities of ALICE to give more insight into the
evolution of the hot and dense matter created in Pb-Pb collisions. Starting
from the physics motivations and working principles the challenges and current
status of development is detailed.Comment: 4 pages, 6 figures. To be published in EPJ Web of Conference
Contribution of the HMPID detector to the high-pT physics at LHC
The LHC will deliver unexplored energy regimes for proton-proton and
heavy-ion collisions. As shown by the RHIC experiments, particle identification
over a large momentum range is essential to disentangle physics processes,
especially in the intermediate p (1 GeV/c) region. The novel
design of the High-Momentum Particle Identification Detector (HMPID), based on
large surface CsI photocathodes, is able to identify , ,
and in the momentum region where bulk medium properties and hard
scatterings interplay. Furthermore, measurement of resonance particles such as
the could provide information on the system evolution. The
HMPID layout and segmentation are optimized to study particle correlations at
high momenta describing the early phase and the dynamical evolution of the
collision. At LHC, the increased hard cross section will significantly be
enhanced compared to RHIC. Jet reconstruction via Deterministic Annealing can
address jet quenching and detailed measurements of jet properties. In this
paper, we present these selected topics from the possible HMPID contributions
to the physics goals of LHC.Comment: 6 pages, 7 figures, Contribution to QCD @ Work 2007: International
Workshop on Quantum Chromodynamics Theory and Experiment, Martina Franca,
Italy, 16-20 June 200
Global and regional IUCN Red List Assessments: 1
In this contribution, the conservation status assessment of six plant species according to IUCN categories and criteria are presented. It includes the assessment at global level of Linaria tonzigii Lona, Allium garganicum Brullo, Pavone, Salmeri & Terrasi, Ferula arrigonii Bocchieri, Orchis patens Desf. subsp. patens and Armeria saviana Selvi and the assessment at regional level (Italy) of Viola jordanii Hanry
Dark matter search in a Beam-Dump eXperiment (BDX) at Jefferson Lab
MeV-GeV dark matter (DM) is theoretically well motivated but remarkably
unexplored. This Letter of Intent presents the MeV-GeV DM discovery potential
for a 1 m segmented plastic scintillator detector placed downstream of the
beam-dump at one of the high intensity JLab experimental Halls, receiving up to
10 electrons-on-target (EOT) in a one-year period. This experiment
(Beam-Dump eXperiment or BDX) is sensitive to DM-nucleon elastic scattering at
the level of a thousand counts per year, with very low threshold recoil
energies (1 MeV), and limited only by reducible cosmogenic backgrounds.
Sensitivity to DM-electron elastic scattering and/or inelastic DM would be
below 10 counts per year after requiring all electromagnetic showers in the
detector to exceed a few-hundred MeV, which dramatically reduces or altogether
eliminates all backgrounds. Detailed Monte Carlo simulations are in progress to
finalize the detector design and experimental set up. An existing 0.036 m
prototype based on the same technology will be used to validate simulations
with background rate estimates, driving the necessary RD towards an
optimized detector. The final detector design and experimental set up will be
presented in a full proposal to be submitted to the next JLab PAC. A fully
realized experiment would be sensitive to large regions of DM parameter space,
exceeding the discovery potential of existing and planned experiments by two
orders of magnitude in the MeV-GeV DM mass range.Comment: 28 pages, 17 figures, submitted to JLab PAC 4
Test of the CLAS12 RICH large scale prototype in the direct proximity focusing configuration
A large area ring-imaging Cherenkov detector has been designed to provide
clean hadron identification capability in the momentum range from 3 GeV/c up to
8 GeV/c for the CLAS12 experiments at the upgraded 12 GeV continuous electron
beam accelerator facility of Jefferson Laboratory. The adopted solution
foresees a novel hybrid optics design based on aerogel radiator, composite
mirrors and high-packed and high-segmented photon detectors. Cherenkov light
will either be imaged directly (forward tracks) or after two mirror reflections
(large angle tracks). We report here the results of the tests of a large scale
prototype of the RICH detector performed with the hadron beam of the CERN T9
experimental hall for the direct detection configuration. The tests
demonstrated that the proposed design provides the required pion-to-kaon
rejection factor of 1:500 in the whole momentum range.Comment: 15 pages, 23 figures, to appear on EPJ
Ageing test of the ATLAS RPCs at X5-GIF
An ageing test of three ATLAS production RPC stations is in course at X5-GIF,
the CERN irradiation facility. The chamber efficiencies are monitored using
cosmic rays triggered by a scintillator hodoscope. Higher statistics
measurements are made when the X5 muon beam is available. We report here the
measurements of the efficiency versus operating voltage at different source
intensities, up to a maximum counting rate of about 700Hz/cm^2. We describe the
performance of the chambers during the test up to an overall ageing of 4 ATLAS
equivalent years corresponding to an integrated charge of 0.12C/cm^2, including
a safety factor of 5.Comment: 4 pages. Presented at the VII Workshop on Resistive Plate Chambers
and Related Detectors; Clermont-Ferrand October 20th-22nd, 200
Subthreshold rho^0 photoproduction on 3He
A large reduction of the rho^0 mass in the nuclear medium is reported,
inferred from dipion photoproduction spectra in the 1 GeV region, for the
reaction 3He(gamma,pi+ pi-)X with a 10% duty factor tagged-photon beam and the
TAGX multi-particle spectrometer. The energy range covered (800 < E(gamma) <
1120 MeV) lies mostly below the free rho^0 production threshold, a region which
is believed sensitive to modifications of light vector-meson properties at
nuclear-matter densities. The rho^0 masses extracted from the MC fitting of the
data, m*(rho^0) = 642 +/- 40, 669 +/- 32, and 682 +/- 56 MeV/c^2 for E(gamma)
in the 800-880, 880-960, and 960-1040 MeV regions respectively, are
independently corroborated by a measured, assumption-free, kinematical
observable. This mass shift, far exceeding current mean-field driven
theoretical predictions, may be suggestive of rho^0 decay within the range of
the nucleonic field.Comment: 40 pages, 13 figures, submitted to Phys. Rev.
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