166 research outputs found
Segregation by thermal diffusion of an intruder in a moderately dense granular fluid
A solution of the inelastic Enskog equation that goes beyond the weak
dissipation limit and applies for moderate densities is used to determine the
thermal diffusion factor of an intruder immersed in a dense granular gas under
gravity. This factor provides a segregation criterion that shows the transition
between the Brazil-nut effect (BNE) and the reverse Brazil-nut effect (RBNE) by
varying the parameters of the system (masses, sizes, density and coefficients
of restitution). The form of the phase-diagrams for the BNE/RBNE transition
depends sensitively on the value of gravity relative to the thermal gradient,
so that it is possible to switch between both states for given values of the
parameters of the system. Two specific limits are considered with detail: (i)
absence of gravity, and (ii) homogeneous temperature. In the latter case, after
some approximations, our results are consistent with previous theoretical
results derived from the Enskog equation. Our results also indicate that the
influence of dissipation on thermal diffusion is more important in the absence
of gravity than in the opposite limit. The present analysis extends previous
theoretical results derived in the dilute limit case [V. Garz\'o, Europhys.
Lett. {\bf 75}, 521 (2006)] and is consistent with the findings of some recent
experimental results.Comment: 10 figure
NEST: A Comprehensive Model for Scintillation Yield in Liquid Xenon
A comprehensive model for explaining scintillation yield in liquid xenon is
introduced. We unify various definitions of work function which abound in the
literature and incorporate all available data on electron recoil scintillation
yield. This results in a better understanding of electron recoil, and
facilitates an improved description of nuclear recoil. An incident gamma energy
range of O(1 keV) to O(1 MeV) and electric fields between 0 and O(10 kV/cm) are
incorporated into this heuristic model. We show results from a Geant4
implementation, but because the model has a few free parameters, implementation
in any simulation package should be simple. We use a quasi-empirical approach,
with an objective of improving detector calibrations and performance
verification. The model will aid in the design and optimization of future
detectors. This model is also easy to extend to other noble elements. In this
paper we lay the foundation for an exhaustive simulation code which we call
NEST (Noble Element Simulation Technique).Comment: 24 pages, 9 figures, 3 table
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
Search for electroweak production of single top quarks in collisions.
We present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb. (arXiv
Determinants of penetrance and variable expressivity in monogenic metabolic conditions across 77,184 exomes
Hundreds of thousands of genetic variants have been reported to cause severe monogenic diseases, but the probability that a variant carrier develops the disease (termed penetrance) is unknown for virtually all of them. Additionally, the clinical utility of common polygenetic variation remains uncertain. Using exome sequencing from 77,184 adult individuals (38,618 multi-ancestral individuals from a type 2 diabetes case-control study and 38,566 participants from the UK Biobank, for whom genotype array data were also available), we apply clinical standard-of-care gene variant curation for eight monogenic metabolic conditions. Rare variants causing monogenic diabetes and dyslipidemias display effect sizes significantly larger than the top 1% of the corresponding polygenic scores. Nevertheless, penetrance estimates for monogenic variant carriers average 60% or lower for most conditions. We assess epidemiologic and genetic factors contributing to risk prediction in monogenic variant carriers, demonstrating that inclusion of polygenic variation significantly improves biomarker estimation for two monogenic dyslipidemias
Spredningsstudier i elver
Det ble foretatt spredningsstudier i ei elv ved hjelp av radioaktive isotoper. 82Br ble benyttet som sporstoff for vannets bevegelse og 32p som sporstoff for løst fosfor. Den merkede fosformengden ble raskt redusert med transportavstanden. Transporten ble simulert med matematiske modeller. Overensstemmelsen med observasjonsdataene var gode. Renneforsøk viste at fosforet i stor grad ble bundet til suspenderte partikle
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