7,389 research outputs found
Overview and Recent Results from BRAHMS
The BRAHMS experiment was designed to measure and characterize in particular
the properties of rapidity dependence of particle production in heavy ion
collisions. The data-taking is now over, results of several years of analysis
have been published and demonstrates several important features of the rapidity
dependence, not envisioned from the start of the RHIC program. The bulk
properties of the system formed at high rapidity resemble that of systems at
lower energies at mid-rapidity when referenced via the baryo-chemical
potential. New physics in AA are essentially observed at mid-rapidity including
the demonstration that high-\pT suppression is a final state effect. Another
key result is that in d+A collisions at forward rapidities where the very low-x
region of the nucleus was probed, a strong suppression of pion production was
observed consistent with the picture of gluon saturation. The latest results
examines the centrality and rapidity dependence of nuclear stopping, the
particle production of pions, collective expansion vs. rapidity, and the baryon
enhancement at intermediate values of \pT .Comment: 8 pages, 6 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee Fixed typos and
minor text issues as per organizers review reques
Influence of Hydrodynamic Interactions on the Kinetics of Colloidal Particle's Adsorption
The kinetics of irreversible adsorption of spherical particles onto a flat
surface is theoretically studied. Previous models, in which hydrodynamic
interactions were disregarded, predicted a power-law behavior for
the time dependence of the coverage of the surface near saturation.
Experiments, however, are in agreement with a power-law behavior of the form
. We outline that, when hydrodynamic interactions are considered, the
assymptotic behavior is found to be compatible with the experimental results in
a wide region near saturation.Comment: 4 pages, 1 figures, Phys. Rev. Lett. (in press
Genetics of rapid eye movement sleep in humans.
The trait-like nature of electroencephalogram (EEG) is well established. Furthermore, EEG of wake and non-rapid eye movement (non-REM) sleep has been shown to be highly heritable. However, the genetic effects on REM sleep EEG microstructure are as yet unknown. REM sleep is of special interest since animal and human data suggest a connection between REM sleep abnormalities and the pathophysiology of psychiatric and neurological diseases. Here we report the results of a study in monozygotic (MZ) and dizygotic (DZ) twins examining the heritability of REM sleep EEG. We studied the architecture, spectral composition and phasic parameters of REM sleep and identified genetic effects on whole investigated EEG frequency spectrum as well as phasic REM parameters (REM density, REM activity and organization of REMs in bursts). In addition, cluster analysis based on the morphology of the EEG frequency spectrum revealed that the similarity among MZ twins is close to intra-individual stability. The observed strong genetic effects on REM sleep characteristics establish REM sleep as an important source of endophenotypes for psychiatric and neurological diseases
Social Welfare in One-Sided Matching Mechanisms
We study the Price of Anarchy of mechanisms for the well-known problem of
one-sided matching, or house allocation, with respect to the social welfare
objective. We consider both ordinal mechanisms, where agents submit preference
lists over the items, and cardinal mechanisms, where agents may submit
numerical values for the items being allocated. We present a general lower
bound of on the Price of Anarchy, which applies to all
mechanisms. We show that two well-known mechanisms, Probabilistic Serial, and
Random Priority, achieve a matching upper bound. We extend our lower bound to
the Price of Stability of a large class of mechanisms that satisfy a common
proportionality property, and show stronger bounds on the Price of Anarchy of
all deterministic mechanisms
Asymmetries in random motions of neutral Hydrogen gas in spiral galaxies
(Abridged). It has been recently shown that random motions of the neutral
Hydrogen gas of the Triangulum galaxy (M33) exhibit a bisymmetric perturbation
which is aligned with the minor axis of the galaxy, suggesting a projection
effect. To investigate if perturbations in the velocity dispersion of nearby
discs are comparable to those of M33, the sample is extended to 32 galaxies
from The HI Nearby Galaxy Survey and the Westerbork HI Survey of Spiral and
Irregular Galaxies. We study velocity asymmetries in the disc planes by
performing Fourier transforms of high-resolution HI velocity dispersion maps
corrected for beam smearing effects, and measure the amplitudes and phase
angles of the Fourier harmonics. We find strong perturbations of first, second
and fourth orders. The strongest asymmetry is the bisymmetry, which is
predominantly associated with the presence of spiral arms. The first order
asymmetry is generally oriented close to the disc major axis, and the second
and fourth order asymmetries are preferentially oriented along intermediate
directions between the major and minor axes of the discs. These results are
evidence that strong projection effects shape the HI velocity dispersion maps.
The most likely source of systematic orientations is the anisotropy of
velocities, through the projection of streaming motions stronger along one of
the planar directions in the discs. Moreover, systematic phase angles of
asymmetries in the HI velocity dispersion could arise from tilted velocity
ellipsoids. We expect a larger incidence of correlation between the radial and
tangential velocities of HI gas. Our methodology is a powerful tool to
constrain the dominant direction of streaming motions and thus the shape of the
velocity ellipsoid of HI gas, which is de facto anisotropic at the angular
scales probed by the observations.Comment: 40 pages, 33 figures. Accepted for publication in Astronomy &
Astrophysics. Full resolution version available upon reques
Measurement of the Luminosity in the ZEUS Experiment at HERA II
The luminosity in the ZEUS detector was measured using photons from electron
bremsstrahlung. In 2001 the HERA collider was upgraded for operation at higher
luminosity. At the same time the luminosity-measuring system of the ZEUS
experiment was modified to tackle the expected higher photon rate and
synchrotron radiation. The existing lead-scintillator calorimeter was equipped
with radiation hard scintillator tiles and shielded against synchrotron
radiation. In addition, a magnetic spectrometer was installed to measure the
luminosity independently using photons converted in the beam-pipe exit window.
The redundancy provided a reliable and robust luminosity determination with a
systematic uncertainty of 1.7%. The experimental setup, the techniques used for
luminosity determination and the estimate of the systematic uncertainty are
reported.Comment: 25 pages, 11 figure
A Deterministic Transport Code for Space Environment Electrons
A deterministic computational procedure has been developed to describe transport of space environment electrons in various shield media. This code is an upgrade and extension of an earlier electron code. Whereas the former code was formulated on the basis of parametric functions derived from limited laboratory data, the present code utilizes well established theoretical representations to describe the relevant interactions and transport processes. The shield material specification has been made more general, as have the pertinent cross sections. A combined mean free path and average trajectory approach has been used in the transport formalism. Comparisons with Monte Carlo calculations are presented
Which are the most burdensome functioning areas in depression? A cross-national study
BACKGROUND: The study aimed to identify the most burdensome functioning domains in depression and their differential impact on the quality of life (QoL) of individuals from nine countries in Asia, Africa, Europe, and Latin America. MATERIALS AND METHODS: Data from two multi-country projects-the World Health Organization's Study on Global Ageing and Adult Health (SAGE) and the Collaborative Research on Ageing in Europe (COURAGE)-were analyzed. Eight functioning domains (pain, mobility, self-care, cognition, interpersonal activities, domestic life, and work, sleep and energy, and affect) and QoL were assessed in 4051 individuals with depression. RESULTS: The analyses of the pooled sample showed that affect (ß = -0.21, p < 0.001), domestic life and work (ß = -0.16, p < 0.001) and interpersonal activities (ß = -0.15, p < 0.001) were the most affected functioning domains. When the analysis was stratified by gender, women showed similar patterns to the total sample, whereas mobility, self-care, cognition and pain were not significant amongst men. The cross-national analysis revealed that difficulties in affect and interpersonal activities were common across countries, whereas the rest of the domains showed country variability. In addition, being a woman (ß = -0.05), being older (ß = 0.07), being married (ß = 0.05), not having a comorbid condition (ß = -0.03) and having a higher education (ß = 0.04) were all factors associated with higher levels of QoL. CONCLUSION: There was a variation in the level of decrements in different functioning domains across countries. This is in line with the growing evidence that reporting functioning sum-scores obscures potential differences among people. Functioning tools should capture the distinctiveness among individuals in order to provide tailored responses
OC-0473: Intraoperative radiotherapy (IORT) in breast cancer: analysis of 6,816 cases from ISIORT database
Nuclear Modification Factor for Charged Pions and Protons at Forward Rapidity in Central Au+Au Collisions at 200 GeV
We present spectra of charged pions and protons in 0-10% central Au+Au
collisions at GeV at mid-rapidity () and forward
pseudorapidity () measured with the BRAHMS experiment at RHIC. The
spectra are compared to spectra from p+p collisions at the same energy scaled
by the number of binary collisions. The resulting nuclear modification factors
for central Au+Au collisions at both and exhibit suppression
for charged pions but not for (anti-)protons at intermediate . The
ratios have been measured up to GeV/ at the two
rapidities and the results indicate that a significant fraction of the charged
hadrons produced at intermediate range are (anti-)protons at both
mid-rapidity and
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