1,441 research outputs found
Clinical prediction rules for adverse evolution in patients with COVID-19 by the Omicron variant
Objective: We identify factors related to SARS-CoV-2 infection linked to hospitalization, ICU admission, and mortality and develop clinical prediction rules.
Methods: Retrospective cohort study of 380,081 patients with SARS-CoV-2 infection from March 1, 2020 to January 9, 2022, including a subsample of 46,402 patients who attended Emergency Departments (EDs) having data on vital signs. For derivation and external validation of the prediction rule, two different periods were considered: before and after emergence of the Omicron variant, respectively. Data collected included sociodemographic data, COVID-19 vaccination status, baseline comorbidities and treatments, other background data and vital signs at triage at EDs. The predictive models for the EDs and the whole samples were developed using multivariate logistic regression models using Lasso penalization.
Results: In the multivariable models, common predictive factors of death among EDs patients were greater age; being male; having no vaccination, dementia; heart failure; liver and kidney disease; hemiplegia or paraplegia; coagulopathy; interstitial pulmonary disease; malignant tumors; use chronic systemic use of steroids, higher temperature, low O2 saturation and altered blood pressure-heart rate. The predictors of an adverse evolution were the same, with the exception of liver disease and the inclusion of cystic fibrosis. Similar predictors were found to be related to hospital admission, including liver disease, arterial hypertension, and basal prescription of immunosuppressants. Similarly, models for the whole sample, without vital signs, are presented.
Conclusions: We propose risk scales, based on basic information, easily-calculable, high-predictive that also function with the current Omicron variant and may help manage such patients in primary, emergency, and hospital care.
Keywords: COVID-19; Clinical decision rules; Health care; Outcome assessment; SARS-CoV-2
New distance measures for classifying X-ray astronomy data into stellar classes
The classification of the X-ray sources into classes (such as extragalactic
sources, background stars, ...) is an essential task in astronomy. Typically,
one of the classes corresponds to extragalactic radiation, whose photon
emission behaviour is well characterized by a homogeneous Poisson process. We
propose to use normalized versions of the Wasserstein and Zolotarev distances
to quantify the deviation of the distribution of photon interarrival times from
the exponential class. Our main motivation is the analysis of a massive dataset
from X-ray astronomy obtained by the Chandra Orion Ultradeep Project (COUP).
This project yielded a large catalog of 1616 X-ray cosmic sources in the Orion
Nebula region, with their series of photon arrival times and associated
energies. We consider the plug-in estimators of these metrics, determine their
asymptotic distributions, and illustrate their finite-sample performance with a
Monte Carlo study. We estimate these metrics for each COUP source from three
different classes. We conclude that our proposal provides a striking amount of
information on the nature of the photon emitting sources. Further, these
variables have the ability to identify X-ray sources wrongly catalogued before.
As an appealing conclusion, we show that some sources, previously classified as
extragalactic emissions, have a much higher probability of being young stars in
Orion Nebula.Comment: 29 page
The Cherenkov Telescope Array Large Size Telescope
The two arrays of the Very High Energy gamma-ray observatory Cherenkov
Telescope Array (CTA) will include four Large Size Telescopes (LSTs) each with
a 23 m diameter dish and 28 m focal distance. These telescopes will enable CTA
to achieve a low-energy threshold of 20 GeV, which is critical for important
studies in astrophysics, astroparticle physics and cosmology. This work
presents the key specifications and performance of the current LST design in
the light of the CTA scientific objectives.Comment: 4 pages, 5 figures, In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at
arXiv:1307.223
Upper limit for gamma-ray emission above 140 GeV from the dwarf spheroidal galaxy Draco
The nearby dwarf spheroidal galaxy Draco with its high mass to light ratio is
one of the most auspicious targets for indirect dark matter searches.
Annihilation of hypothetical DM particles can result in high-energy gamma-rays,
e.g. from neutralino annihilation in the supersymmetric framework. With the
MAGIC telescope a search for a possible DM signal originating from Draco was
performed during 2007. The analysis of the data results in a flux upper limit
of 1.1x10^-11 photons cm^-2 sec^-1 for photon energies above 140 GeV, assuming
a point like source. Furthermore, a comparison with predictions from
supersymmetric models is given. While our results do not constrain the mSUGRA
phase parameter space, a very high flux enhancement can be ruled out.Comment: Accepted for publication by Astrophysical Journa
First bounds on the high-energy emission from isolated Wolf-Rayet binary systems
High-energy gamma-ray emission is theoretically expected to arise in tight
binary star systems (with high mass loss and high velocity winds), although the
evidence of this relationship has proven to be elusive so far. Here we present
the first bounds on this putative emission from isolated Wolf-Rayet (WR) star
binaries, WR 147 and WR 146, obtained from observations with the MAGIC
telescope.Comment: (Authors are the MAGIC Collaboration.) Manuscript in press at The
Astrophysical Journal Letter
Unfolding of differential energy spectra in the MAGIC experiment
The paper describes the different methods, used in the MAGIC experiment, to
unfold experimental energy distributions of cosmic ray particles (gamma-rays).
Questions and problems related to the unfolding are discussed. Various
procedures are proposed which can help to make the unfolding robust and
reliable. The different methods and procedures are implemented in the MAGIC
software and are used in most of the analyses.Comment: Submitted to NIM
Implementation of the Random Forest Method for the Imaging Atmospheric Cherenkov Telescope MAGIC
The paper describes an application of the tree classification method Random
Forest (RF), as used in the analysis of data from the ground-based gamma
telescope MAGIC. In such telescopes, cosmic gamma-rays are observed and have to
be discriminated against a dominating background of hadronic cosmic-ray
particles. We describe the application of RF for this gamma/hadron separation.
The RF method often shows superior performance in comparison with traditional
semi-empirical techniques. Critical issues of the method and its implementation
are discussed. An application of the RF method for estimation of a continuous
parameter from related variables, rather than discrete classes, is also
discussed.Comment: 16 pages, 8 figure
Systematic search for VHE gamma-ray emission from X-ray bright high-frequency BL Lac objects
All but three (M87, BL Lac and 3C 279) extragalactic sources detected so far
at very high energy (VHE) gamma-rays belong to the class of high-frequency
peaked BL Lac (HBL) objects. This suggested to us a systematic scan of
candidate sources with the MAGIC telescope, based on the compilation of X-ray
blazars by Donato et al. (2001). The observations took place from December 2004
to March 2006 and cover sources on the northern sky visible under small zenith
distances zd < 30 degrees at culmination. The sensitivity of the search was
planned for detecting X-ray bright F(1 keV) > 2 uJy) sources emitting at least
the same energy flux at 200 GeV as at 1 keV. In order to avoid strong gamma-ray
attenuation close to the energy threshold, the redshift of the sources was
constrained to values z<0.3. Of the fourteen sources observed, 1ES 1218+304 and
1ES 2344+514 have been detected in addition to the known bright TeV blazars Mrk
421 and Mrk 501. A marginal excess of 3.5 sigma from the position of 1ES
1011+496 was observed and has been confirmed as a source of VHE gamma-rays by a
second MAGIC observation triggered by a high optical state (Albert et al.
2007). For the remaining sources, we present here the 99% confidence level
upper limits on the integral flux above ~200 GeV. We characterize the sample of
HBLs (including all HBLs detected at VHE so far) by looking for correlations
between their multi-frequency spectral indices determined from simultaneous
optical, archival X-ray, and radio luminosities, finding that the VHE emitting
HBLs do not seem to constitute a unique subclass. The absorption corrected
gamma-ray luminosities at 200 GeV of the HBLs are generally not higher than
their X-ray luminosities at 1 keV.Comment: 15 pages, 7 figures, 5 tables, submitted to ApJ (revised version
Discovery of Very High Energy gamma-rays from 1ES 1011+496 at z=0.212
We report on the discovery of Very High Energy (VHE) gamma-ray emission from
the BL Lacertae object 1ES1011+496. The observation was triggered by an optical
outburst in March 2007 and the source was observed with the MAGIC telescope
from March to May 2007. Observing for 18.7 hr we find an excess of 6.2 sigma
with an integrated flux above 200 GeV of (1.58 photons
cm s. The VHE gamma-ray flux is >40% higher than in March-April
2006 (reported elsewhere), indicating that the VHE emission state may be
related to the optical emission state. We have also determined the redshift of
1ES1011+496 based on an optical spectrum that reveals the absorption lines of
the host galaxy. The redshift of z=0.212 makes 1ES1011+496 the most distant
source observed to emit VHE gamma-rays up to date.Comment: 4 pages, 6 figures, minor changes to fit the ApJ versio
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