2,630 research outputs found
Finding counterparts for All-sky X-ray surveys with Nway: a Bayesian algorithm for cross-matching multiple catalogues
We release the AllWISE counterparts and Gaia matches to 106,573 and 17,665
X-ray sources detected in the ROSAT 2RXS and XMMSL2 surveys with |b|>15. These
are the brightest X-ray sources in the sky, but their position uncertainties
and the sparse multi-wavelength coverage until now rendered the identification
of their counterparts a demanding task with uncertain results. New all-sky
multi-wavelength surveys of sufficient depth, like AllWISE and Gaia, and a new
Bayesian statistics based algorithm, NWAY, allow us, for the first time, to
provide reliable counterpart associations. NWAY extends previous distance and
sky density based association methods and, using one or more priors (e.g.,
colors, magnitudes), weights the probability that sources from two or more
catalogues are simultaneously associated on the basis of their observable
characteristics. Here, counterparts have been determined using a WISE
color-magnitude prior. A reference sample of 4524 XMM/Chandra and Swift X-ray
sources demonstrates a reliability of ~ 94.7% (2RXS) and 97.4% (XMMSL2).
Combining our results with Chandra-COSMOS data, we propose a new separation
between stars and AGN in the X-ray/WISE flux-magnitude plane, valid over six
orders of magnitude. We also release the NWAY code and its user manual. NWAY
was extensively tested with XMM-COSMOS data. Using two different sets of
priors, we find an agreement of 96% and 99% with published Likelihood Ratio
methods. Our results were achieved faster and without any follow-up visual
inspection. With the advent of deep and wide area surveys in X-rays (e.g.
SRG/eROSITA, Athena/WFI) and radio (ASKAP/EMU, LOFAR, APERTIF, etc.) NWAY will
provide a powerful and reliable counterpart identification tool.Comment: MNRAS, Paper accepted for publication. Updated catalogs are available
at www.mpe.mpg.de/XraySurveys/2RXS_XMMSL2 . NWAY available at
https://github.com/JohannesBuchner/nwa
Psychostimulant Drug Abuse and Personality Factors in Medical Students
Purpose:
This study was designed to examine the prevalence of psychostimulant drug abuse among medical students and to test the hypothesis that medical students who use psychostimulant drugs for non-medical reasons are characterized by a sensation seeking and aggressive-hostility personality and exhibit lower empathy
Spin pseudogap in Ni-doped SrCuO2
The S=1/2 spin chain material SrCuO2 doped with 1% S=1 Ni-impurities is
studied by inelastic neutron scattering. At low temperatures, the spectrum
shows a pseudogap \Delta ~ 8 meV, absent in the parent compound, and not
related to any structural phase transition. The pseudogap is shown to be a
generic feature of quantum spin chains with dilute defects. A simple model
based on this idea quantitatively accounts for the exprimental data measured in
the temperature range 2-300 K, and allows to represent the momentum-integrated
dynamic structure factor in a universal scaling form.Comment: 5 pages, 3 figure
Impact of 5-HT3 receptor antagonists on chemotherapy-induced nausea and vomiting: a retrospective cohort study
BACKGROUND: 1(st) generation 5-hydroxytryptamine receptor antagonists (5-HT(3) RAs), and palonosetron, a 2(nd) generation 5-HT(3) RA, are indicated for the prevention of chemotherapy (CT)-induced nausea and vomiting (CINV) associated with moderately (MEC) and highly emetogenic CT agents (HEC). This study explores the impact of step therapy policies requiring use of an older 5-HT(3) RA before palonosetron on risk of CINV associated with hospital or emergency department (ED) admissions. METHODS: Patients who received cyclophosphamide post breast cancer (BC) surgery or who were diagnosed with lung cancer on carboplatin (LC-carboplatin) or cisplatin (LC-cisplatin) were selected from PharMetricsâ (IMS LifeLink) claims dataset (2005-2008). Patients were followed for 6âmonths from initial CT administration for CINV events identified through ICD-9-CM codes. Patients were grouped into those initiated with older, generic 5-HT(3) RAs (ondansetron, granisetron, and dolasetron) and those initiated and maintained on palonosetron throughout study follow-up. CINV events and CINV days were analyzed using multivariate regressions controlling for demographic and clinical variables. RESULTS: Eligible patients numbered 3,606 in BC, 4,497 in LC-carboplatin and 1,154 in LC-cisplatin cohorts, with 52%, 40%, and 34% in the palonosetron group, respectively. There was no significant difference between the two 5-HT(3) RA groups in age or Charlson Comorbidity Index among the two MEC cohorts (BC and LC-carboplatin). Among the LC-cisplatin cohort, palonosetron users were older with more males than the older 5-HT(3) RA group (age: 60.1 vs. 61.3; males, 66.9% vs. 56.9%). Compared to the older 5-HT(3) RAs, the palonosetron groups incurred 22%-51% fewer 5-HT(3) RA pharmacy claims, had fewer patients with CINV events (3.5% vs. 5.5% in BC, 9.5% vs. 12.8% in LC-carboplatin, 16.4% vs. 21.7% in LC-cisplatin), and had lower risk for CINV events (odds ratios 0.62, 0.71, or 0.71, respectively; pâ<â0.05). The BC and LC-carboplatin palonosetron groups experienced 50% and 30% fewer CINV days than the generic 5-HT(3) RA group (pâ<â0.05). CONCLUSIONS: Patients with breast or lung cancer initiated and maintained on palonosetron were at significantly lower risk for potentially costly CINV versus those on older 5-HT(3) RAs. Further studies on impact of step therapy policy are warranted in order to minimize the clinical and economic burden of CINV
X-ray constraints on the fraction of obscured AGN at high accretion luminosities
The wide-area XMM-XXL X-ray survey is used to explore the fraction of
obscured AGN at high accretion luminosities, , and out to redshift . The sample covers an area
of about and provides constraints on the space density of
powerful AGN over a wide range of neutral hydrogen column densities extending
beyond the Compton-thick limit, . The fraction
of obscured Compton-thin () AGN is estimated
to be for luminosities
independent of redshift. For less luminous sources the fraction of obscured
Compton-thin AGN increases from at to at
. Studies that select AGN in the infrared via template fits to the
observed Spectral Energy Distribution of extragalactic sources estimate space
densities at high accretion luminosities consistent with the XMM-XXL
constraints. There is no evidence for a large population of AGN (e.g. heavily
obscured) identified in the infrared and missed at X-ray wavelengths. We
further explore the mid-infrared colours of XMM-XXL AGN as a function of
accretion luminosity, column density and redshift. The fraction of XMM-XXL
sources that lie within the mid-infrared colour wedges defined in the
literature to select AGN is primarily a function of redshift. This fraction
increases from about 20-30% at z=0.25 to about 50-70% at .Comment: MNRAS accepte
The X-ray luminosity function of Active Galactic Nuclei in the redshift interval z=3-5
We combine deep X-ray survey data from the Chandra observatory and the
wide-area/shallow XMM-XXL field to estimate the AGN X-ray luminosity function
in the redshift range z=3-5. The sample consists of nearly 340 sources with
either photometric (212) or spectroscopic (128) redshift in the above range.
The combination of deep and shallow survey fields provides a luminosity
baseline of three orders of magnitude, Lx(2-10keV)~1e43-1e46erg/s at z>3. We
follow a Bayesian approach to determine the binned AGN space density and
explore their evolution in a model-independent way. Our methodology accounts
for Poisson errors in the determination of X-ray fluxes and uncertainties in
photometric redshift estimates. We demonstrate that the latter is essential for
unbiased measurement of space densities. We find that the AGN X-ray luminosity
function evolves strongly between the redshift intervals z=3-4 and z=4-5. There
is also suggestive evidence that the amplitude of this evolution is luminosity
dependent. The space density of AGN with Lx<1e45erg/s drops by a factor of 5
between the redshift intervals above, while the evolution of brighter AGN
appears to be milder. Comparison of our X-ray luminosity function with that of
UV/optical selected QSOs at similar redshifts shows broad agreement at bright
luminosities, Lx>1e45erg/s. The faint-end slope of UV/optical luminosity
functions however, is steeper than for X-ray selected AGN. This implies that
the type-I AGN fraction increases with decreasing luminosity at z>3, opposite
to trends established at lower redshift. We also assess the significance of AGN
in keeping the hydrogen ionised at high redshift. Our X-ray luminosity function
yields ionising photon rate densities that are insufficient to keep the
Universe ionised at redshift z>4. A source of uncertainty in this calculation
is the escape fraction of UV photons for X-ray selected AGN.Comment: MNRAS accepte
Instantaneous Normal Mode analysis of liquid HF
We present an Instantaneous Normal Modes analysis of liquid HF aimed to
clarify the origin of peculiar dynamical properties which are supposed to stem
from the arrangement of molecules in linear hydrogen-bonded network. The
present study shows that this approach is an unique tool for the understanding
of the spectral features revealed in the analysis of both single molecule and
collective quantities. For the system under investigation we demonstrate the
relevance of hydrogen-bonding ``stretching'' and fast librational motion in the
interpretation of these features.Comment: REVTeX, 7 pages, 5 eps figures included. Minor changes in the text
and in a figure. Accepted for publication in Phys. Rev. Let
- âŚ