828 research outputs found
Construction and Test of New Precision Drift-Tube Chambers for the ATLAS Muon Spectrometer
ATLAS muon detector upgrades aim for increased acceptance for muon triggering
and precision tracking and for improved rate capability of the muon chambers in
the high-background regions of the detector with increasing LHC luminosity. The
small-diameter Muon Drift Tube (sMDT) chambers have been developed for these
purposes. With half of the drift-tube diameter of the MDT chambers and
otherwise unchanged operating parameters, sMDT chambers share the advantages of
the MDTs, but have an order of magnitude higher rate capability and can be
installed in detector regions where MDT chambers do not fit in. The chamber
assembly methods have been optimized for mass production, minimizing
construction time and personnel. Sense wire positioning accuracies of 5 ?micons
have been achieved in serial production for large-size chambers comprising
several hundred drift tubes. The construction of new sMDT chambers for
installation in the 2016/17 winter shutdown of the LHC and the design of sMDT
chambers in combination with new RPC trigger chambers for replacement of the
inner layer of the barrel muon spectrometer are in progress
Optimisation of the Read-out Electronics of Muon Drift-Tube Chambers for Very High Background Rates at HL-LHC and Future Colliders
In the ATLAS Muon Spectrometer, Monitored Drift Tube (MDT) chambers and sMDT
chambers with half of the tube diameter of the MDTs are used for precision muon
track reconstruction. The sMDT chambers are designed for operation at high
counting rates due to neutron and gamma background irradiation expected for the
HL-LHC and future hadron colliders. The existing MDT read-out electronics uses
bipolar signal shaping which causes an undershoot of opposite polarity and same
charge after a signal pulse. At high counting rates and short electronics dead
time used for the sMDTs, signal pulses pile up on the undershoot of preceding
background pulses leading to a reduction of the signal amplitude and a jitter
in the drift time measurement and, therefore, to a degradation of drift tube
efficiency and spatial resolution. In order to further increase the rate
capability of sMDT tubes, baseline restoration can be used in the read-out
electronics to suppress the pile-up effects. A discrete bipolar shaping circuit
with baseline restoration has been developed and used for reading out sMDT
tubes under irradiation with a 24 MBq 90Sr source. The measurements results
show a substantial improvement of the performance of the sMDT tubes at high
counting rates
Risks of pyrrolizidine alkaloids in tea and herbal infusions
Pyrrolizidinalkaloide (PA) sind sekundĂ€re Pflanzeninhaltsstoffe, die von einer Vielzahl von Pflanzen gebildet werden und u. a. zur Abwehr von FraĂfeinden dienen. Toxikologisch bedeutsam sind die PA, die eine Doppelbindung in 1,2-Position aufweisen. Diese können zu gesundheitlichen SchĂ€den bei Mensch und Tier fĂŒhren, wobei die Leber das Hauptzielorgan darstellt. Neben den bekannten hepatotoxischen Effekten können 1,2-ungesĂ€ttigte PA auch die DNA schĂ€digen und krebserzeugend wirken. Die Verbindungen gelangen in erster Linie ĂŒber Wild- und BeikrĂ€uter in die Lebensmittelkette. In der im Jahr 2016 durch das BundesÂinstitut fĂŒr Risikobewertung (BfR) veröffentlichten Bewertung stellte der Verzehr von kontaminiertem Tee und KrĂ€utertee die wesentliche Expositionsquelle fĂŒr die Bevölkerung gegenĂŒber 1,2-ungesĂ€ttigten PA in Deutschland dar; aber auch andere Lebensmittel können zur Aufnahme beitragen. In der vorliegenden Arbeit, in der ausschlieĂlich Tee und KrĂ€utertee berĂŒcksichtigt werden, zeigt sich, dass die Gehalte an 1,2-ungesĂ€ttigten PA in dieser Lebensmittelgruppe im Vergleich zu 2016 deutlich gesunken sind. Dennoch kann es insbesondere bei Personen, die langfristig hohe Mengen KrĂ€utertee bzw. Rooibostee verzehren, auch gegenwĂ€rtig noch zu Aufnahmemengen kommen, die in einem Margin of Exposure von unter 10.000 resultieren, weshalb es auch weiterhin angezeigt scheint, MaĂnahmen zur Senkung der Gehalte durchzufĂŒhren.Pyrrolizidine alkaloids (PA) are secondary plant metabolites which are produced by a large number of plants, e. g. to ward off herbivores. PA with a double bond in the 1,2-position are of toxicological relevance. These derivatives can cause adverse health effects in humans and animals, with the liver being the major target organ. Besides the known hepatotoxic effects, 1,2-unsaturated PA may also damage DNA and may be carcinogenic. The occurrence of these compounds in foods is primarily caused by contamination with wild herbs. In the assessment published in 2016 by the German Federal Institute for Risk Assessment (BfR), consumption of contaminated tea and herbal tea was the main source of exposure for the population to 1.2-unsaturated PA in Germany; however, other foods can also contribute to intake. The present study, which focuses exclusively on tea and herbal tea, shows that levels of 1,2-unsaturated PA in this food group have decreased significantly compared to 2016. Nevertheless, persons who consume high amounts of herbal tea or rooibos tea in the long term may still be exposed to intakes that result in a margin of exposure of less than 10,000, which is why it still seems appropriate to implement measures to reduce the levels
Coulomb induced positive current-current correlations in normal conductors
In the white-noise limit current correlations measured at different contacts
of a mesoscopic conductor are negative due to the antisymmetry of the wave
function (Pauli principle). We show that current fluctuations at capacitive
contacts induced via the long range Coulomb interaction as consequence of
charge fluctuations in the mesoscopic sample can be {\it positively}
correlated. The positive correlations are a consequence of the extension of the
wave-functions into areas near both contacts. As an example we investigate in
detail a quantum point contact in a high magnetic field under conditions in
which transport is along an edge state.Comment: Revtex, 4 pages includes 2 figure
Use of IFNÎł/IL10 Ratio for Stratification of Hydrocortisone Therapy in Patients With Septic Shock
Large clinical trials testing hydrocortisone therapy in septic shock have produced conflicting results. Subgroups may benefit of hydrocortisone treatment depending on their individual immune response. We performed an exploratory analysis of the database from the international randomized controlled clinical trial Corticosteroid Therapy of Septic Shock (CORTICUS) employing machine learning to a panel of 137 variables collected from the Berlin subcohort comprising 83 patients including demographic and clinical measures, organ failure scores, leukocyte counts and levels of circulating cytokines. The identified theranostic marker was validated against data from a cohort of the Hellenic Sepsis Study Group (HSSG) (n = 246), patients enrolled in the clinical trial of Sodium Selenite and Procalcitonin Guided Antimicrobial Therapy in Severe Sepsis (SISPCT, n = 118), and another, smaller clinical trial (Crossover study, n = 20). In addition, in vitro blood culture experiments and in vivo experiments in mouse models were performed to assess biological plausibility. A low serum IFNÎł/IL10 ratio predicted increased survival in the hydrocortisone group whereas a high ratio predicted better survival in the placebo group. Using this marker for a decision rule, we applied it to three validation sets and observed the same trend. Experimental studies in vitro revealed that IFNÎł/IL10 was negatively associated with the load of (heat inactivated) pathogens in spiked human blood and in septic mouse models. Accordingly, an in silico analysis of published IFNÎł and IL10 values in bacteremic and non-bacteremic patients with the Systemic Inflammatory Response Syndrome supported this association between the ratio and pathogen burden. We propose IFNÎł/IL10 as a molecular marker supporting the decision to administer hydrocortisone to patients in septic shock. Prospective clinical studies are necessary and standard operating procedures need to be implemented, particularly to define a generic threshold. If confirmed, IFNÎł/IL10 may become a suitable theranostic marker for an urging clinical need
Use of IFNÎł/IL10 Ratio for Stratification of Hydrocortisone Therapy in Patients With Septic Shock
Large clinical trials testing hydrocortisone therapy in septic shock have produced
conflicting results. Subgroups may benefit of hydrocortisone treatment depending on
their individual immune response. We performed an exploratory analysis of the database
from the international randomized controlled clinical trial Corticosteroid Therapy of Septic
Shock (CORTICUS) employing machine learning to a panel of 137 variables collected
from the Berlin subcohort comprising 83 patients including demographic and clinical
measures, organ failure scores, leukocyte counts and levels of circulating cytokines. The
identified theranostic marker was validated against data from a cohort of the Hellenic
Sepsis Study Group (HSSG) (n = 246), patients enrolled in the clinical trial of Sodium
Selenite and Procalcitonin Guided Antimicrobial Therapy in Severe Sepsis (SISPCT, n
= 118), and another, smaller clinical trial (Crossover study, n = 20). In addition, in vitro
blood culture experiments and in vivo experiments in mouse models were performed to
assess biological plausibility. A low serum IFNg/IL10 ratio predicted increased survival in
the hydrocortisone group whereas a high ratio predicted better survival in the placebo
group. Using this marker for a decision rule, we applied it to three validation sets and
observed the same trend. Experimental studies in vitro revealed that IFNg/IL10 was
negatively associated with the load of (heat inactivated) pathogens in spiked human blood
and in septic mouse models. Accordingly, an in silico analysis of published IFNg and
IL10 values in bacteremic and non-bacteremic patients with the Systemic Inflammatory
Response Syndrome supported this association between the ratio and pathogen burden.
We propose IFNg/IL10 as a molecular marker supporting the decision to administer
hydrocortisone to patients in septic shock. Prospective clinical studies are necessary
and standard operating procedures need to be implemented, particularly to define a
generic threshold. If confirmed, IFNg/IL10 may become a suitable theranostic marker for
an urging clinical need
Progress in Classical and Quantum Variational Principles
We review the development and practical uses of a generalized Maupertuis
least action principle in classical mechanics, in which the action is varied
under the constraint of fixed mean energy for the trial trajectory. The
original Maupertuis (Euler-Lagrange) principle constrains the energy at every
point along the trajectory. The generalized Maupertuis principle is equivalent
to Hamilton's principle. Reciprocal principles are also derived for both the
generalized Maupertuis and the Hamilton principles. The Reciprocal Maupertuis
Principle is the classical limit of Schr\"{o}dinger's variational principle of
wave mechanics, and is also very useful to solve practical problems in both
classical and semiclassical mechanics, in complete analogy with the quantum
Rayleigh-Ritz method. Classical, semiclassical and quantum variational
calculations are carried out for a number of systems, and the results are
compared. Pedagogical as well as research problems are used as examples, which
include nonconservative as well as relativistic systems
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at â s = 8 TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fbâ1 of â s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in âs=13âTeV pp collisions with the ATLAS detector
A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of âs=13ââTeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139ââfbâ1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015â2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV
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