6,301 research outputs found
A study of gas contaminants and interaction with materials in RPC closed loop systems
Resistive Plate Counters (RPC) detectors at the Large Hadron Collider (LHC)
experiments use gas recirculation systems to cope with large gas mixture
volumes and costs. In this paper a long-term systematic study about gas
purifiers, gas contaminants and detector performance is discussed. The study
aims at measuring the lifetime of purifiers with unused and used cartridge
material along with contaminants release in the gas system. During the
data-taking the response of several RPC double-gap detectors was monitored in
order to characterize the correlation between dark currents, filter status and
gas contaminants
Gas Analysis and Monitoring Systems for the RPC Detector of CMS at LHC
The Resistive Plate Chambers (RPC) detector of the CMS experiment at the LHC
proton collider (CERN, Switzerland) will employ an online gas analysis and
monitoring system of the freon-based gas mixture used. We give an overview of
the CMS RPC gas system, describe the project parameters and first results on
gas-chromatograph analysis. Finally, we report on preliminary results for a set
of monitor RPC.Comment: 9 pages, 8 figures. Presented by Stefano Bianco (Laboratori Nazionali
di Frascati dell'INFN) at the IEEE NSS, San Diego (USA), October 200
The Upgrade of the CMS RPC System during the First LHC Long Shutdown
The CMS muon system includes in both the barrel and endcap region Resistive
Plate Chambers (RPC). They mainly serve as trigger detectors and also improve
the reconstruction of muon parameters. Over the years, the instantaneous
luminosity of the Large Hadron Collider gradually increases. During the LHC
Phase 1 (~first 10 years of operation) an ultimate luminosity is expected above
its design value of 10^34/cm^2/s at 14 TeV. To prepare the machine and also the
experiments for this, two long shutdown periods are scheduled for 2013-2014 and
2018-2019. The CMS Collaboration is planning several detector upgrades during
these long shutdowns. In particular, the muon detection system should be able
to maintain a low-pT threshold for an efficient Level-1 Muon Trigger at high
particle rates. One of the measures to ensure this, is to extend the present
RPC system with the addition of a 4th layer in both endcap regions. During the
first long shutdown, these two new stations will be equipped in the region
|eta|<1.6 with 144 High Pressure Laminate (HPL) double-gap RPCs operating in
avalanche mode, with a similar design as the existing CMS endcap chambers.
Here, we present the upgrade plans for the CMS RPC system for the fist long
shutdown, including trigger simulation studies for the extended system, and
details on the new HPL production, the chamber assembly and the quality control
procedures.Comment: 9 pages, 6 figures, presented by M.Tytgat at the XI workshop on
Resistive Plate Chambers and Related Detectors (RPC2012), INFN - Laboratori
Nazionali di Frascati, February 5-10, 201
Three-dimensional structure of human cyclooxygenase (hCOX)-1
The beneficial effects of Cyclooxygenases (COX) inhibitors on human health have been known for thousands of years. Nevertheless, COXs, particularly COX-1, have been linked to a plethora of human diseases such as cancer, heart failure, neurological and neurodegenerative diseases only recently. COXs catalyze the first step in the biosynthesis of prostaglandins (PGs) and are among the most important mediators of inflammation. All published structural work on COX-1 deals with the ovine isoenzyme, which is easier to produce in milligram-quantities than the human enzyme and crystallizes readily. Here, we report the long-sought structure of the human cyclooxygenase-1 (hCOX-1) that we refined to an R/Rfree of 20.82/26.37, at 3.36 Ă… resolution. hCOX-1 structure provides a detailed picture of the enzyme active site and the residues crucial for inhibitor/substrate binding and catalytic activity. We compared hCOX-1 crystal structure with the ovine COX-1 and human COX-2 structures by using metrics based on Cartesian coordinates, backbone dihedral angles, and solvent accessibility coupled with multivariate methods. Differences and similarities among structures are discussed, with emphasis on the motifs responsible for the diversification of the various enzymes (primary structure, stability, catalytic activity, and specificity). The structure of hCOX-1 represents an essential step towards the development of new and more selective COX-1 inhibitors of enhanced therapeutic potential
The CMS RPC gas gain monitoring system: an overview and preliminary results
The status of the CMS RPC Gas Gain Monitoring (GGM) system developed at the
Frascati Laboratory of INFN (Istituto Nazionale di Fisica Nucleare) is reported
on. The GGM system is a cosmic ray telescope based on small RPC detectors
operated with the same gas mixture used by the CMS RPC system. The GGM gain and
efficiency are continuously monitored on-line, thus providing a fast and
accurate determination of any shift in working point conditions. The
construction details and the first result of GGM commissioning are described.Comment: 8 pages, 9 figures, uses lnfprepCMS.sty, presented by L. Benussi at
RPC07, Mumbai, INDIA 200
Monte Carlo study of 3D image reconstruction for boron dose distribution in BNCT with CZT-based Compton camera
Boron Neutron Capture Therapy is an innovative and highly selective treatment against cancer. Nowadays in vivo boron dosimetry is an important issue to carry out such therapy in clinical environments. In this work, we study the
performance of a Compton camera detector based on a 3D CZT crystal for online dosimetry in BNCT using Monte Carlo simulations and the maximum likelihood expectation maximization method for tomography reconstruction
Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions
Data taken with the ALEPH detector at LEP1 have been used to search for gamma
gamma production of the glueball candidates f0(1500) and fJ(1710) via their
decay to pi+pi-. No signal is observed and upper limits to the product of gamma
gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have
been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) <
0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV
at 95% confidence level.Comment: 10 pages, 3 figure
Adult-onset pulmonary involvement in Niemann-Pick disease type B
Niemann-Pick disease type B is caused by a deficiency in acid sphingomyelinase activity; among the six variants of Niemann-Pick disease known to date, it is the most frequently associated with lung involvement, a major cause of morbidity and mortality in this subtype in patients of all ages. Nevertheless, the vast majority of reports in the literature concern infantile forms, while less reported is, for several reasons, the onset in adults being consequently still poorly understood and characterized its clinical, radiographic and functional manifestations. We report a case of a 37 years-old female patient affected by subtype B since she was an infant, operated for aortic valve replacement two years before and came to our attention for the onset of a worsening exertional dyspnoea which proved, through a series of functional tests and radiological exams, to be a consequence of the diffuse lung involvement by the metabolic disorder; we performed a review on this topic through a Medline search of all the available “adult-onset” case reports published since the first description in 1964, also considering the possible association between NPDB and, more generally lysosomal storage disorders, and the valvular disease, already suggested by several Authors in previous works
Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV
A search for pair-production of supersymmetric particles under the assumption
that R-parity is violated via a dominant LQDbar coupling has been performed
using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV.
The observed candidate events in the data are in agreement with the Standard
Model expectation. This result is translated into lower limits on the masses of
charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for
m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81
GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the
95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure
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