526 research outputs found
Clinical factors associated with the non-utilization of an anaesthesia incident reporting system
Background Incident reporting is a widely recommended method to measure undesirable events in anaesthesia. Under-utilization is a major weakness of voluntary incident reporting systems. Little is known about factors influencing reporting practices, particularly the clinical environment, anaesthesia team composition, severity of the incident, and perceived risk of litigation. The purpose of this study was to assess each of these, using an existing anaesthesia database. Methods We performed a retrospective cohort study and analysed 46 207 surgical patients. We used multivariate analysis to identify factors associated with the non-utilization of the reporting system. Results We found that in 7022 (15.1%) of the procedures performed, the incident reporting system was not used. Factors associated with the non-use of the system were regional anaesthesia/local anaesthesia, odds ratio (OR) 1.64 [95% confidence interval (CI) 1.03-2.62], emergency procedures OR 1.15 (95% CI: 1.05-1.27), and a consultant anaesthetist working without a trainee, OR 1.71 (95% CI: 1.03-2.82). In contrast, factors such as longer duration of surgery, OR 0.85 (95% CI: 0.76-0.94), the presence of a senior anaesthesia trainee, OR 0.86 (95% CI: 0.81-0.92), and the occurrence of severe complications with a high risk of litigation (i.e. death, nerve injuries) were less associated with a non-use of the reporting system, OR 0.65 (95% CI: 0.44-0.97). Team composition and time of day had no measurable impact on reporting practices. Conclusions Clinical factors play a significant role in the utilization of an anaesthesia incident reporting system and more particularly, severity of complications and higher liability risks which appear more as incentives than barriers to incident reportin
Magnetic Stress at the Marginally Stable Orbit: Altered Disk Structure, Radiation, and Black Hole Spin Evolution
Magnetic connections to the plunging region can exert stresses on the inner
edge of an accretion disk around a black hole. We recompute the relativistic
corrections to the thin-disk dynamics equations when these stresses take the
form of a time-steady torque on the inner edge of the disk. The additional
dissipation associated with these stresses is concentrated relatively close
outside the marginally stable orbit, scaling as r to the -7/2 at large radius.
As a result of these additional stresses: spin-up of the central black hole is
retarded; the maximum spin-equilibrium accretion efficiency is 36%, and occurs
at a/M=0.94; the disk spectrum is extended toward higher frequencies; line
profiles (such as Fe K-alpha) are broadened if the line emissivity scales with
local flux; limb-brightening, especially at the higher frequencies, is
enhanced; and the returning radiation fraction is substantially increased, up
to 58%. This last effect creates possible explanations for both synchronized
continuum fluctuations in AGN, and polarization rises shortward of the Lyman
edge in quasars. We show that no matter what additional stresses occur, when
a/M < 0.36, the second law of black hole dynamics sets an absolute upper bound
on the accretion efficiency.Comment: 11 pages, 15 figures, accepted for publication in the Astrophysical
Journa
Long Term Variability of SDSS Quasars
We use a sample of 3791 quasars from the Sloan Digital Sky Survey (SDSS)
Early Data Release (EDR), and compare their photometry to historic plate
material for the same set of quasars in order to study their variability
properties. The time base-line we attain this way ranges from a few months to
up to 50 years. In contrast to monitoring programs, where relatively few
quasars are photometrically measured over shorter time periods, we utilize
existing databases to extend this base-line as much as possible, at the cost of
sampling per quasar. Our method, however, can easily be extended to much larger
samples. We construct variability Structure Functions and compare these to the
literature and model functions. From our modeling we conclude that 1) quasars
are more variable toward shorter wavelengths, 2) their variability is
consistent with an exponentially decaying light-curve with a typical time-scale
of ~2 years, 3) these outbursts occur on typical time-scales of ~200 years.
With the upcoming first data release of the SDSS, a much larger quasar sample
can be used to put these conclusions on a more secure footing.Comment: 16 pages, accepted for publication in AJ, Sept issu
Les impacts des écrans tactiles sur les visiteurs dans les musées
L’étude présentée ici met en évidence les nouvelles possibilités et appréhensions qu’ont les visiteurs lorsqu’ils pénètrent dans un espace muséal qui propose, au sein de ses expositions, des interfaces tactiles fixes : elle pointe les implications de ce phénomène qui se généralise dans les institutions muséales
30 years of multi-wavelength observations of 3C 273
We present a wide multi-wavelength database of most observations of the
quasar 3C 273 obtained during the last 30 years. This database is the most
complete set of observations available for an active galactic nucleus (AGN). It
contains nearly 20'000 observations grouped together into 70 light curves
covering 16 orders of magnitude in frequency from the radio to the gamma-ray
domain.
The database is constituted of many previously unpublished observations and
of most publicly available data gathered in the literature and on the World
Wide Web (WWW). It is complete to the best of our knowledge, except in the
optical (UBV) domain where we chose not to add all observations from the
literature. In addition to the photometric data, we present the spectra of 3C
273 obtained by the International Ultraviolet Explorer (IUE) satellite. In the
X-ray domain, we used the spectral fit parameters from the literature to
construct the light curves.
Apart from describing the data, we show the most representative light curves
and the average spectrum of 3C 273. The database is available on the WWW in a
homogeneous and clear form and we wish to update it regularly by adding new
observations.Comment: 12 pages, 6 figures, to be published in A&AS, data available at:
http://obswww.unige.ch/3c273
A historic jet-emission minimum reveals hidden spectral features in 3C 273
Aims. The aim of this work is to identify and study spectral features in the
quasar 3C 273 usually blended by its strong jet emission. Method. A historic
minimum in the sub-millimetre emission of 3C 273 triggered coordinated
multi-wavelength observations in June 2004. X-ray observations from the
INTEGRAL, XMM-Newton and RXTE satellites are complemented by ground-based
optical, infrared, millimetre and radio observations. The overall spectrum is
used to model the infrared and X-ray spectral components. Results. Three
thermal dust emission components are identified in the infrared. The dust
emission on scales from 1 pc to several kpc is comparable to that of other
quasars, as expected by AGN unification schemes. The observed weakness of the
X-ray emission supports the hypothesis of a synchrotron self-Compton origin for
the jet component. There is a clear soft-excess and we find evidence for a very
broad iron line which could be emitted in a disk around a Kerr black hole.
Other signatures of a Seyfert-like X-ray component are not detected.Comment: 4 pages. Accepted for publication in A&A Letter
Very Extended X-ray and H-alpha Emission in M82: Implications for the Superwind Phenomenon
We discuss the properties and implications of a 3.7x0.9 kpc region of
spatially-coincident X-ray and H-alpha emission about 11.6 kpc to the north of
the galaxy M82 previously discussed by Devine and Bally (1999). The PSPC X-ray
spectrum is fit by thermal plasma (kT=0.80+-0.17 keV) absorbed by only the
Galactic foreground column density. We evaluate the relationship of the
X-ray/H-alpha ridge to the M82 superwind. The main properties of the X-ray
emission can all be explained as being due to shock-heating driven as the
superwind encounters a massive ionized cloud in the halo of M82. This encounter
drives a slow shock into the cloud, which contributes to the excitation of the
observed H-alpha emission. At the same time, a fast bow-shock develops in the
superwind just upstream of the cloud, and this produces the observed X-ray
emission. This interpretation would imply that the superwind has an outflow
speed of roughly 800 km/s, consistent with indirect estimates based on its
general X-ray properties and the kinematics of the inner kpc-scale region of
H-alpha filaments. The gas in the M82 ridge is roughly two orders-of-magnitude
hotter than the minimum "escape temperature" at this radius, so this gas will
not be retained by M82.
(abridged)Comment: 24 pages (latex), 3 figures (2 gif files and one postscript),
accepted for publication in Part 1 of The Astrophysical Journa
The Rich Mid-Infrared Environments of Two Highly-Obscured X-ray Binaries: Spitzer Observations of IGR J16318-4848 and GX 301-2
We present the results of Spitzer mid-infrared spectroscopic observations of
two highly-obscured massive X-ray binaries: IGR J16318-4848 and GX301-2. Our
observations reveal for the first time the extremely rich mid-infrared
environments of this type of source, including multiple continuum emission
components (a hot component with T > 700 K and a warm component with T ~ 180 K)
with apparent silicate absorption features, numerous HI recombination lines,
many forbidden ionic lines of low ionization potentials, and pure rotational H2
lines. This indicates that both sources have hot and warm circumstellar dust,
ionized stellar winds, extended low-density ionized regions, and
photo-dissociated regions. It appears difficult to attribute the total optical
extinction of both sources to the hot and warm dust components, which suggests
that there could be an otherwise observable colder dust component responsible
for the most of the optical extinction and silicate absorption features. The
observed mid-infrared spectra are similar to those from Luminous Blue
Variables, indicating that the highly-obscured massive X-ray binaries may
represent a previously unknown evolutionary phase of X-ray binaries with
early-type optical companions. Our results highlight the importance and utility
of mid-infrared spectroscopy to investigate highly-obscured X-ray binaries.Comment: To appear in ApJ Letter
Extracting Structural Information of a Heteropolymer from Force-Extension Curves
We present a theory for the reverse analysis on the sequence information of a
single H/P two-letter random hetero-polymer (RHP) from its force-extension(f-z)
curves during quasi static stretching. Upon stretching of a self-assembled RHP,
it undergoes several structural transitions. The typical elastic response of a
hetero-polymeric globule is a set of overlapping saw-tooth patterns. With
consideration of the height and the position of the overlapping saw-tooth
shape, we analyze the possibility of extracting the binding energies of the
internal domains and the corresponding block sizes of the contributing
conformations.Comment: 5 figures 7 page
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