2,890 research outputs found
Liver Graft Revascularization by Donor Portal Vein Arterialization Following âNo Touchâ Donor Hepatectomy
Unsatisfactory immediate function of the transplanted liver together with technical complications
contribute to a persisting early mortality for hepatic transplantation in the 20% range. We report our
initial clinical experience with methods, one not previously used clinically, that resulted in uniformly well-functioning
liver grafts in 11 patients and contributed to a satisfactory success rate for the procedure.
Donors were heart-beating. During the donor operation all manipulations of the liver were avoided until
after cold preservation, achieved by external cooling at the same time as circulatory interruption, donor
exsanguination and perfusion of the liver with cold oxygenated fluid of âextracellularÌ” type. The organs
were then gently dissected. At transplantation the livers were revascularized with arterial blood shunted
from the recipient iliac artery to the graft portal vein after completion of the suprahepatic IVC
anastomosis. The infrahepatic IVCs and hepatic arteries were then joined, the iliac artery shunts
discontinued and the portal veins joined. Total ischaemic intervals for the allografts were 3Âœâ8 (average
5). Anhepatic intervals were 1â2ÂŒ (average 2). The arterio-portal shunts were operating for 18â85 (mean
46) min. Blood loss and haemodynamic, acid-base and electrolyte abnormalities at revascularization were
minimal. All grafts secreted bile immediately and all parameters reflected continuing improvement of
liver function thereafter. Nine patients (82%) are alive between 4 and 18 (mean 11) months after
transplantation. We conclude that these methods offer effective avoidance of serious organ damage
during donor hepatectomy and preservation, reduced allograft ischaemic interval and reduced recipient
anhepatic time. They result in avoidance of blood loss at the time of revascularization, together with
minimal haemodynamic, acid-base or biochemical changes. In addition, they allow the surgeon to
perform and test all anastomoses without time constraints, provide the capability to deal with unexpected
complications, and assure good early graft function
Performance of a Large-Area GEM Detector Prototype for the Upgrade of the CMS Muon Endcap System
Gas Electron Multiplier (GEM) technology is being considered for the forward
muon upgrade of the CMS experiment in Phase 2 of the CERN LHC. Its first
implementation is planned for the GE1/1 system in the region of the muon endcap mainly to control muon level-1 trigger rates
after the second long LHC shutdown. A GE1/1 triple-GEM detector is read out by
3,072 radial strips with 455 rad pitch arranged in eight -sectors.
We assembled a full-size GE1/1 prototype of 1m length at Florida Tech and
tested it in 20-120 GeV hadron beams at Fermilab using Ar/CO 70:30 and
the RD51 scalable readout system. Four small GEM detectors with 2-D readout and
an average measured azimuthal resolution of 36 rad provided precise
reference tracks. Construction of this largest GEM detector built to-date is
described. Strip cluster parameters, detection efficiency, and spatial
resolution are studied with position and high voltage scans. The plateau
detection efficiency is [97.1 0.2 (stat)]\%. The azimuthal resolution is
found to be [123.5 1.6 (stat)] rad when operating in the center of
the efficiency plateau and using full pulse height information. The resolution
can be slightly improved by 10 rad when correcting for the bias due
to discrete readout strips. The CMS upgrade design calls for readout
electronics with binary hit output. When strip clusters are formed
correspondingly without charge-weighting and with fixed hit thresholds, a
position resolution of [136.8 2.5 stat] rad is measured, consistent
with the expected resolution of strip-pitch/ = 131.3 rad. Other
-sectors of the detector show similar response and performance.Comment: 8 pages, 32 figures, submitted to Proc. 2014 IEEE Nucl. Sci.
Symposium, Seattle, WA, reference adde
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Search for MSSM Higgs bosons decaying to ÎŒ+ÎŒ-in proton-proton collisions at âs=13TeV
A search is performed for neutral non-standard-model Higgs bosons decaying to two muons in the context of the minimal supersymmetric standard model (MSSM). Proton-proton collision data recorded by the CMS experiment at the CERN Large Hadron Collider at a center-of-mass energy of 13TeVwere used, corresponding to an integrated luminosity of 35.9fb-1. The search is sensitive to neutral Higgs bosons produced via the gluon fusion process or in association with a bbquark pair. No significant deviations from the standard model expectation are observed. Upper limits at 95% confidence level are set in the context of the mmod+hand phenomenological MSSM scenarios on the parameter tanÎČas a function of the mass of the pseudoscalar Aboson, in the range from 130 to 600GeV. The results are also used to set a model-independent limit on the product of the branching fraction for the decay into a muon pair and the cross section for the production of a scalar neutral boson, either via gluon fusion, or in association with bquarks, in the mass range from 130 to 1000GeV
Overview of large area triple-GEM detectors for the CMS forward muon upgrade
In order to cope with the harsh environment expected from the high luminosity LHC, the CMS forward muon system requires an upgrade. The two main challenges expected in this environment are an increase in the trigger rate and increased background radiation leading to a potential degradation of the particle ID performance. Additionally, upgrades to other subdetectors of CMS allow for extended coverage for particle tracking, and adding muon system coverage to this region will further enhance the performance of CMS
A novel application of Fiber Bragg Grating (FBG) sensors in MPGD
We present a novel application of Fiber Bragg Grating (FBG) sensors in the
construction and characterisation of Micro Pattern Gaseous Detector (MPGD),
with particular attention to the realisation of the largest triple (Gas
electron Multiplier) GEM chambers so far operated, the GE1/1 chambers of the
CMS experiment at LHC. The GE1/1 CMS project consists of 144 GEM chambers of
about 0.5 m2 active area each, employing three GEM foils per chamber, to be
installed in the forward region of the CMS endcap during the long shutdown of
LHC in 2108-2019. The large active area of each GE1/1 chamber consists of GEM
foils that are mechanically stretched in order to secure their flatness and the
consequent uniform performance of the GE1/1 chamber across its whole active
surface. So far FBGs have been used in high energy physics mainly as high
precision positioning and re-positioning sensors and as low cost, easy to
mount, low space consuming temperature sensors. FBGs are also commonly used for
very precise strain measurements in material studies. In this work we present a
novel use of FBGs as flatness and mechanical tensioning sensors applied to the
wide GEM foils of the GE1/1 chambers. A network of FBG sensors have been used
to determine the optimal mechanical tension applied and to characterise the
mechanical tension that should be applied to the foils. We discuss the results
of the test done on a full-sized GE1/1 final prototype, the studies done to
fully characterise the GEM material, how this information was used to define a
standard assembly procedure and possible future developments.Comment: 4 pages, 4 figures, presented by Luigi Benussi at MPGD 2015 (Trieste,
Italy). arXiv admin note: text overlap with arXiv:1512.0848
Development and performance of Triple-GEM detectors for the upgrade of the muon system of the CMS experiment
The CMS Collaboration is evaluating GEM detectors for the upgrade of the muon system. This contribution will focus on the R&D performed on chambers design features and will discuss the performance of the upgraded detector
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Studies of Bs2â(5840)0 and Bs1(5830)0 mesons including the observation of the Bs2â(5840)0âB0KS0 decay in proton-proton collisions at s=8TeV.
Measurements of Bs2â(5840)0 and Bs1(5830)0 mesons are performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of , collected with the CMS detector at the LHC at a centre-of-mass energy of 8TeV . The analysis studies P-wave Bs0 meson decays into B(â)+K- and B(â)0KS0 , where the B+ and B0 mesons are identified using the decays B+âJ/ÏK+ and B0âJ/ÏKâ(892)0 . The masses of the P-wave Bs0 meson states are measured and the natural width of the Bs2â(5840)0 state is determined. The first measurement of the mass difference between the charged and neutral Bâ mesons is also presented. The Bs2â(5840)0 decay to B0KS0 is observed, together with a measurement of its branching fraction relative to the Bs2â(5840)0âB+K- decay
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