89 research outputs found
Hard X-ray emission from Eta Carinae
Context : If relativistic particle acceleration takes place in colliding-wind
binaries, hard X-rays and gamma-rays are expected through inverse Compton
emission, but to date these have never been unambiguously detected.
Aims : To detect this emission, observations of Eta Carinae were performed
with INTEGRAL, leveraging its high spatial resolution.
Methods : Deep hard X-ray images of the region of Eta Car were constructed in
several energy bands.
Results : The hard X-ray emission previously detected by BeppoSax around Eta
Car originates from at least 3 different point sources. The emission of Eta Car
itself can be isolated for the first time, and its spectrum unambiguously
analyzed. The X-ray emission of Eta Car in the 22-100 keV energy range is very
hard (photon index around 1) and its luminosity is 7E33 erg/s.
Conclusions : The observed emission is in agreement with the predictions of
inverse Compton models, and corresponds to about 0.1% of the energy available
in the wind collision. Eta Car is expected to be detected in the GeV energy
range.Comment: 5 pages with 2 figures. Accepted as a Letter in Astronomy &
Astrophysic
Motor ability in children treated for idiopathic clubfoot. A controlled pilot study
<p>Abstract</p> <p>Background</p> <p>To study motor ability at seven years of age in children treated for idiopathic clubfoot and its relation to clubfoot laterality, foot status and the amount of surgery performed.</p> <p>Methods</p> <p>Twenty children (mean age 7.5 years, SD 3.2 months) from a consecutive birth cohort from our hospital catchments area (300.000 inhabitants from southern Sweden) were assessed with the Movement Assessment Battery for Children (MABC) and the Clubfoot Assessment Protocol (CAP).</p> <p>Results</p> <p>Compared to typically developing children an increased prevalence of motor impairment was found regarding both the total score for MABC (p < 0.05) and the subtest ABC-Ball skills (p < 0.05). No relationship was found between the child's actual foot status, laterality or the extent of foot surgery with the motor ability as measured with MABC. Only the CAP item "one-leg stand" correlated significantly with the MABC (rs = -0.53, p = 0.02).</p> <p>Conclusions</p> <p>Children with idiopathic clubfoot appear to have an increased risk of motor activity limitations and it is possible that other factors, independent of the clinical status, might be involved. The ability to keep balance on one leg may be a sufficient tool for determining which children in the orthopedic setting should be more thoroughly evaluated regarding their neuromotor functioning.</p
Improving Quinolone Use in Hospitals by Using a Bundle of Interventions in an Interrupted Time Series Analysis
The objectives of the present study were to determine the effects of multiple targeted interventions on the level of use of quinolones and the observed rates of resistance to quinolones in Escherichia coli isolates from hospitalized patients. A bundle consisting of four interventions to improve the use of quinolones was implemented. The outcome was measured from the monthly levels of use of intravenous (i.v.) and oral quinolones and the susceptibility patterns for E. coli isolates from hospitalized patients. Statistical analyses were performed using segmented regression analysis and segmented Poisson regression models. Before the bundle was implemented, the annual use of quinolones was 2.7 defined daily doses (DDDs)/100 patient days. After the interventions, in 2007, this was reduced to 1.7 DDDs/100 patient days. The first intervention, a switch from i.v. to oral medication, was associated with a stepwise reduction in i.v. quinolone use of 71 prescribed daily doses (PDDs) per month (95% confidence interval [CI] = 47 to 95 PDDs/month, P < 0.001). Intervention 2, introduction of a new antibiotic guideline and education program, was associated with a stepwise reduction in the overall use of quinolones (reduction, 107 PDDs/month [95% CI = 58 to 156 PDDs/month). Before the interventions the quinolone resistance rate was increasing, on average, by 4.6% (95% CI = 2.6 to 6.1%) per year. This increase leveled off, which was associated with intervention 2 and intervention 4, active monitoring of prescriptions and feedback. Trends in resistance to other antimicrobial agents did not change. This study showed that the hospital-wide use of quinolones can be significantly reduced by an active policy consisting of multiple interventions. There was also a stepwise reduction in the rate of quinolone resistance associated with the bundle of interventions
Benchmarking Crimes: An Emerging Threat in Systems Security
Properly benchmarking a system is a difficult and intricate task. Unfortunately, even a seemingly innocuous benchmarking mistake can compromise the guarantees provided by a given systems security defense and also put its reproducibility and comparability at risk. This threat is particularly insidious as it is generally not a result of malice and can easily go undetected by both authors and reviewers. Moreover, as modern defenses often trade off security for performance in an attempt to find an ideal design point in the performance-security space, the damage caused by benchmarking mistakes is increasingly worrisome. To analyze the magnitude of the phenomenon, we identify a set of 22 "benchmarking crimes" that threaten the validity of systems security evaluations and perform a survey of 50 defense papers published in top venues. To ensure the validity of our results, we perform the complete survey twice, with two independent readers. We find only a very small number of disagreements between readers, showing that our assessment of benchmarking crimes is highly reproducible. We show that benchmarking crimes are widespread even in papers published at tier-1 venues. We find that tier-1 papers commit an average of five benchmarking crimes and we find only a single paper in our sample that committed no benchmarking crimes. Moreover, we find that the scale of the problem is constant over time, suggesting that the community is not yet addressing it despite the problem being now more relevant than ever. This threatens the scientific process, which relies on reproducibility and comparability to ensure that published research advances the state of the art. We hope to raise awareness of these issues and provide recommendations to improve benchmarking quality and safeguard the scientific process in our community. Computer Systems, Imagery and Medi
Hard X-ray identification of Eta Carinae and steadiness close to periastron
Context: The colliding-wind binary Eta Car exhibits soft X-ray thermal
emission that varies strongly around periastron, and non-thermal emission seen
in hard X-rays and gamma-rays.
Aims: To definitively identify Eta Car as the source of the hard X-ray
emission, to examine how changes in the 2-10 keV band influence changes in the
hard X-ray band, and to understand more clearly the mechanisms producing the
non-thermal emission using new INTEGRAL observations obtained close to
periastron.
Methods: A Chandra observation encompassing the ISGRI error circle was
analysed, and all other soft X-ray sources (including the outer shell of Eta
Car itself) were discarded as likely counter-parts. New hard X-ray images of
Eta Car were studied close to periastron, and compared to previous observations
far from periastron.
Results: The INTEGRAL component, when represented by a power law (with a
photon index of 1.8), would produce more emission in the Chandra band than
observed from any point source in the ISGRI error circle apart from Eta Car, as
long as the hydrogen column density to the ISGRI source is lower than 1E24
cm^{-2}. Such sources are rare, thus the ISGRI emission is very likely to be
associated with Eta Car. The eventual contribution of the outer shell to the
non-thermal component also remains fairly limited. Close to periastron, a
3-sigma detection is achieved for the hard X-ray emission of Eta Car, with a
flux similar to the average value far from periastron.
Conclusions: Assuming a single absorption component for both the thermal and
non-thermal sources, this detection can be explained with a hydrogen column
density that does not exceed 6E23 cm^{-2} without resorting to an intrinsic
increase in the hard X-ray emission. The energy injected in hard X-rays
(averaged over a month) appears rather constant as close as a few stellar
radii, well within the acceleration region of the wind.Comment: 9 pages with 5 figures. Accepted for publication in Astronomy &
Astrophysic
Constraints on new interactions from neutron scattering experiments
Constraints for the constants of hypothetical Yukawa-type corrections to the
Newtonian gravitational potential are obtained from analysis of neutron
scattering experiments. Restrictions are obtained for the interaction range
between 10^{-12} and 10^{-7} cm, where Casimir force experiments and atomic
force microscopy are not sensitive. Experimental limits are obtained also for
non-electromagnetic inverse power law neutron-nucleus potential. Some
possibilities are discussed to strengthen these constraints.Comment: 18 pages, 3 figure
Evaluation of a fourth-generation latex agglutination test for the identification of Staphylococcus aureus
In this study, we evaluated a fourth-generation agglutination assay (Staph Plus; DiaMondiaL[DML]) for the rapid identification of Staphylococcus aureus. First, comparison with three third-generation assays (Slidex Staph Plus, bioMérieux; Staphaurex Plus, Murex Diagnostics; Pastorex Staph-Plus, Sanofi Diagnostics Pasteur) was performed on a predefined strain collection: 265 coagulase-negative staphylococci (CNS), 266 methicillin-resistant S. aureus (MRSA) and 262 methicillin-susceptible S. aureus (MSSA) strains (“strain study”). Second, patient material-derived strains (883 CNS, 847 MSSA and 135 MRSA) were tested concurrently with both the DML and Slidex assays (“daily practice study”). In the strain study, the overall sensitivity and specificity of the DML, Slidex, Staphaurex and Pastorex assays were 99.2% and 100%, 98.1% and 100%, 95.2% and 100%, and 98.2% and 98.8%, respectively. Using the respective tests, the result was indeterminate in 0.0%, 0.6%, 0.4% and 1.5% of the strains. Overall, the sensitivity of the DML and Slidex assays were comparable in both sub-studies. However, in MRSA strains, the sensitivity of the DML assay was significantly lower than the Slidex assay. The specificity of the Slidex assay was significantly higher than the DML assay. However, the percentage of indeterminate results was much higher for the Slidex than the DML assay. In conclusion, the presumptive identification of S. aureus by the DML assay proved to be equal to third-generation latex agglutination assays
Molecular velocity auto-correlation of simple liquids observed by NMR MGSE method
The velocity auto-correlation spectra of simple liquids obtained by the NMR
method of modulated gradient spin echo show features in the low frequency range
up to a few kHz, which can be explained reasonably well by a long
time tail decay only for non-polar liquid toluene, while the spectra of polar
liquids, such as ethanol, water and glycerol, are more congruent with the model
of diffusion of particles temporarily trapped in potential wells created by
their neighbors. As the method provides the spectrum averaged over ensemble of
particle trajectories, the initial non-exponential decay of spin echoes is
attributed to a spatial heterogeneity of molecular motion in a bulk of liquid,
reflected in distribution of the echo decays for short trajectories. While at
longer time intervals, and thus with longer trajectories, heterogeneity is
averaged out, giving rise to a spectrum which is explained as a combination of
molecular self-diffusion and eddy diffusion within the vortexes of hydrodynamic
fluctuations.Comment: 8 pages, 6 figur
The DIRTY Model II: Self-Consistent Treatment of Dust Heating and Emission in a 3-D Radiative Transfer Code
In this paper and a companion paper we present the DIRTY model, a Monte Carlo
radiative transfer code, self-consistently including dust heating and emission,
and accounting for the effects of the transient heating of small grains. The
code is completely general; the density structure of the dust, the number and
type of heating sources, and their geometric configurations can be specified
arbitrarily within the model space. Source photons are tracked through the
scattering and absorbing medium using Monte Carlo techniques and the effects of
multiple scattering are included. The dust scattering, absorbing, and emitting
properties are calculated from realistic dust models derived by fitting
observed extinction curves in Local Group galaxies including the Magellanic
Clouds and the Milky Way. The dust temperature and the emitted dust spectrum
are calculated self consistently from the absorbed energy including the effects
of temperature fluctuations in small grains. Dust self-absorption is also
accounted for, allowing the treatment of high optical depths, by treating
photons emitted by the dust as an additional heating source and adopting an
iterative radiative transfer scheme. As an illustrative case, we apply the
DIRTY radiative transfer code to starburst galaxies wherein the heating sources
are derived from stellar evolutionary synthesis models. Within the context of
the starburst model, we examine the dependence of the UV to FIR SED, dust
temperatures, and dust masses predicted by DIRTY on variations of the input
parameters.Comment: 23 pages (emulateapj, single column), 17 figures. To appear in the
ApJ, in pres
Cost-Effectiveness of Preoperative Screening and Eradication of Staphylococcus aureus Carriage
BACKGROUND: Preoperative screening for nasal S. aureus carriage, followed by eradication treatment of identified carriers with nasal mupirocine ointment and chlorhexidine soap was highly effective in preventing deep-seated S. aureus infections. It is unknown how cost-effectiveness of this intervention is affected by suboptimal S. aureus screening. We determined cost-effectiveness of different preoperative S. aureus screening regimes. METHODS: We compared different screening scenarios (ranging from treating all patients without screening to treating only identified S. aureus carriers) to the base case scenario without any screening and treatment. Screening and treatment costs as well as costs and mortality due to deep-seated S. aureus infection were derived from hospital databases and prospectively collected data, respectively. RESULTS: As compared to the base case scenario, all scenarios are associated with improved health care outcomes at reduced costs. Treating all patients without screening is most cost-beneficial, saving €7339 per life year gained, as compared to €3330 when only identified carriers are treated. In sensitivity analysis, outcomes are susceptible to the sensitivity of the screening test and the efficacy of treatment. Reductions in these parameters would reduce the cost-effectiveness of scenarios in which treatment is based on screening. When only identified S. aureus carriers are treated costs of screening should be less than €6.23 to become the dominant strategy. CONCLUSIONS: Preoperative screening and eradication of S. aureus carriage to prevent deep-seated S. aureus infections saves both life years and medical costs at the same time, although treating all patients without screening is the dominant strategy, resulting in most health gains and largest savings
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