2,794 research outputs found
Drift velocity and gain in argon- and xenon-based mixtures
We present measurements of drift velocities and gains in gas mixtures based
on Ar and Xe, with CO2, CH4, and N2 as quenchers, and compare them with
calculations. In particular, we show the dependence of Ar- and Xe-CO2 drift
velocities and gains on the amount of nitrogen contamination in the gas, which
in real experiments may build up through leaks. A quantification of the Penning
mechanism which contributes to the Townsend coefficients of a given gas mixture
is proposed.Comment: 11 pages, 7 figures, accepted for publication in Nucl.Instrum.Meth.
A. Data files available at http://www-alice.gsi.de/tr
New Data on the Archaeological Obsidians of the Banat and Transylvania
SocietĂ per la Preistoria e Protostoria della Regione Friuli-Venezia Giulia, Quaderno 12 - ISSN
Obesity and the Mediterranean Diet: A Review of Evidence of the Role and Sustainability of the Mediterranean Diet
Several different socio-economic factors have caused a large portion of the population to adopt unhealthy eating habits that can undermine healthcare systems, unless current trends are inverted towards more sustainable lifestyle models. Even though a dietary plan inspired by the principles of the Mediterranean Diet is associated with numerous health benefits and has been demonstrated to exert a preventive effect towards numerous pathologies, including obesity, its use is decreasing and it is now being supplanted by different nutritional models that are often generated by cultural and social changes. Directing governments' political actions towards spreading adherence to the Mediterranean Diet's principles as much as possible among the population could help to tackle the obesity epidemic, especially in childhood. This document intends to reiterate the importance of acting in certain age groups to stop the spread of obesity and proceeds with a critical review of the regulatory instruments used so far, bearing in mind the importance of the scientific evidence that led to the consideration of the Mediterranean Diet as not just a food model, but also as the most appropriate regime for disease prevention, a sort of complete lifestyle plan for the pursuit of healthcare sustainability
Charge Transfer and Charge Broadening of GEM Structures in High Magnetic Fields
We report on measurements of charge transfer in GEM structures in high
magnetic fields. These were performed in the framework of the R&D work for a
Time Projection Chamber at a future Linear Collider. A small test chamber has
been installed into the aperture of a superconducting magnet with the GEM
structures mounted perpendicular to the B field direction. The charge transfer
is derived from the electrical currents monitored during irradiation with an
Fe source. No severe loss of primary ionisation charge is observed,
but an improved ion feedback suppression is achieved for high magnetic fields.
Additionally, the width of the charge cloud released by individual Fe
photons is measured using a finely segmented strip readout after the triple GEM
structure. Charge widths between 0.3 and 0.5 mm RMS are observed, which
originate from the charge broadening inside the GEM readout. This charge
broadening is only partly suppressed at high magnetic fields.Comment: 11 pages, 9 figure
lHuman cytotoxic T lymphocytes with reduced sensitivity to Fas-induced apoptosis
Effector-memory T cells expressing Fas (Apo-1/CD95) are switched to an apoptotic program by cross-linking with Fas-ligand (FasL). Consequently, tumors that express FasL can induce apoptosis of infiltrating Fas-positive T lymphocytes and subdue any antitumor host immune response. Since Epstein-Barr virus (EBV)-associated tumors such as Hodgkin lymphoma (HL) and nasopharyngeal carcinoma (NPC) express FasL, we determined whether EBV-specific cytotoxic T lymphocytes (EBV-CTLs) could be modified to resist this evasion strategy. We show that long-term down-modulation of Fas can be achieved in EBV-CTLs by transduction with small interfering RNA (siRNA) encoded in a retrovirus. Modified T cells resisted Fas/FasL-mediated apoptosis compared with control cells and showed minimal cleavage of the caspase3 substrate poly(ADP-ribose) polymerase (PARP) protein after Fas engagement. Prolonged Fas stimulation selected a uniformly Fas(low) and FasL resistant population. Removal of responsiveness to this single death signal had no other discernible effects on EBV-CTLs. In particular, it did not lead to their autonomous growth since the modified EBV-CTLs remained polyclonal, and their survival and proliferation retained dependence on antigen-specific stimulation and on the presence of other physiologic growth signals. EBV-CTLs with knocked down Fas should have a selective functional and survival advantage over unmodified EBV-CTLs in the presence of tumors expressing FasL and may be of value for adoptive cellular therapy. (c) 2005 by The American Society of Hematology
A Comparative Numerical Study on GEM, MHSP and MSGC
In this work, we have tried to develop a detailed understanding of the
physical processes occurring in those variants of Micro Pattern Gas Detectors
(MPGDs) that share micro hole and micro strip geometry, like GEM, MHSP and MSGC
etc. Some of the important and fundamental characteristics of these detectors
such as gain, transparency, efficiency and their operational dependence on
different device parameters have been estimated following detailed numerical
simulation of the detector dynamics. We have used a relatively new simulation
framework developed especially for the MPGDs that combines packages such as
GARFIELD, neBEM, MAGBOLTZ and HEED. The results compare closely with the
available experimental data. This suggests the efficacy of the framework to
model the intricacies of these micro-structured detectors in addition to
providing insight into their inherent complex dynamical processes
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