7,625 research outputs found
The band gap problem: the accuracy of the Wien2k code confronted
This paper is a continuation of our detailed study [Phys. Rev. B 86, 195106
(2012)] of the performance of the recently proposed modified Becke-Jonhson
potential (mBJLDA) within the known Wien2k code. From the 41 semiconductors
that we have considered in our previous paper to compute the band gap value, we
selected 27 for which we found low temperature experimental data in order to
pinpoint the relative situation of the newly proposed Wien2k(mBJLDA) method as
compared to other methods in the literature. We found that the GWA gives the
most accurate predictions. The Wien2k (mBJLDA) code is slightly less precise,
in general. The Hybrid functionals are less accurate, on the overall. The GWA
is definitely the most precise existing method nowadays. In 88% of the
semiconductors considered the error was less than 10%. Both, the GWA and the
mBJLDA potential, reproduce the band gap of 15 of the 27 semiconductors
considered with a 5% error or less. An extra factor to be taken into account is
the computational cost. If one would seek for precision without taking this
factor into account, the GWA is the method to use. If one would prefer to
sacrifice a little the precision obtained against the savings in computational
cost, the empirical mBJLDA potential seems to be the appropriate method. We
include a graph that compares directly the performance of the best three
methods, according to our analysis, for each of the 27 semiconductors studied.
The situation is encouraging but the problem is not yet a closed issue.Comment: 8 pages, 1 figur
Weyl geometry, anti-De Sitter space, and -theory
We study the Gaussian approximation to the quantum fluctuations of the metric
of the four dimensional anti-De Sitter spacetime. The associated massless
scalar field has a quartic self interaction, for which we construct the
generating functional of the -point correlation functions. The concomitant
infrared divergence is cured by a mass renormalization provided by the
cosmological constant, which is also responsible for the renormalization of the
coupling constant of the field theory.Comment: 9 pages, 1 figur
Intermingled basins in coupled Lorenz systems
We consider a system of two identical linearly coupled Lorenz oscillators,
presenting synchro- nization of chaotic motion for a specified range of the
coupling strength. We verify the existence of global synchronization and
antisynchronization attractors with intermingled basins of attraction, such
that the basin of one attractor is riddled with holes belonging to the basin of
the other attractor and vice versa. We investigated this phenomenon by
verifying the fulfillment of the mathematical requirements for intermingled
basins, and also obtained scaling laws that characterize quantitatively the
riddling of both basins for this system
Near-universal hospitalization of US emergency department patients with cancer and febrile neutropenia
IMPORTANCE:
Febrile neutropenia (FN) is the most common oncologic emergency and is among the most deadly. Guidelines recommend risk stratification and outpatient management of both pediatric and adult FN patients deemed to be at low risk of complications or mortality, but our prior single-center research demonstrated that the vast majority (95%) are hospitalized.
OBJECTIVE:
From a nationwide perspective, to determine the proportion of cancer patients of all ages hospitalized after an emergency department (ED) visit for FN, and to analyze variability in hospitalization rates. Our a priori hypothesis was that >90% of US cancer-associated ED FN visits would end in hospitalization.
DESIGN:
Analysis of data from the Nationwide Emergency Department Sample, 2006-2014.
SETTING:
Stratified probability sample of all US ED visits.
PARTICIPANTS:
Inclusion criteria were: (1) Clinical Classification Software code indicating cancer, (2) diagnostic code indicating fever, and (3) diagnostic code indicating neutropenia. We excluded visits ending in transfer.
EXPOSURE:
The hospital at which the visit took place.
MAIN OUTCOMES AND MEASURES:
Our main outcome is the proportion of ED FN visits ending in hospitalization, with an a priori hypothesis of >90%. Our secondary outcomes are: (a) hospitalization rates among subsets, and (b) proportion of variability in the hospitalization rate attributable to which hospital the patient visited, as measured by the intra-class correlation coefficient (ICC).
RESULTS:
Of 348,868 visits selected to be representative of all US ED visits, 94% ended in hospitalization (95% Confidence Interval [CI] 93-94%). Each additional decade of age conferred 1.23x increased odds of hospitalization. Those with private (92%), self-pay (92%), and other (93%) insurance were less likely to be hospitalized than those with public insurance (95%, odds ratios [OR] 0.74-0.76). Hospitalization was least likely at non-metropolitan hospitals (84%, OR 0.15 relative to metropolitan teaching hospitals), and was also less likely at metropolitan non-teaching hospitals (94%, OR 0.64 relative to metropolitan teaching hospitals). The ICC adjusted for hospital random effects and patient and hospital characteristics was 26% (95%CI 23-29%), indicating that 26% of the variability in hospitalization rate was attributable to which hospital the patient visited.
CONCLUSIONS AND RELEVANCE:
Nearly all cancer-associated ED FN visits in the US end in hospitalization. Inter-hospital variation in hospitalization practices explains 26% of the limited variability in hospitalization decisions. Simple, objective tools are needed to improve risk stratification for ED FN patients
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bitstream/CNPUV/8129/1/cir051.pd
Astrometry of mutual approximations between natural satellites. Application to the Galilean moons
Typically we can deliver astrometric positions of natural satellites with
errors in the 50-150 mas range. Apparent distances from mutual phenomena, have
much smaller errors, less than 10 mas. However, this method can only be applied
during the equinox of the planets. We developed a method that can provide
accurate astrometric data for natural satellites -- the mutual approximations.
The method can be applied when any two satellites pass close by each other in
the apparent sky plane. The fundamental parameter is the central instant
of the passage when the distances reach a minimum.
We applied the method for the Galilean moons. All observations were made with
a 0.6 m telescope with a narrow-band filter centred at 889 nm with width of 15
nm which attenuated Jupiter's scattered light. We obtained central instants for
14 mutual approximations observed in 2014-2015. We determined with an
average precision of 3.42 mas (10.43 km). For comparison, we also applied the
method for 5 occultations in the 2009 mutual phenomena campaign and for 22
occultations in the 2014-2015 campaign. The comparisons of determined by
our method with the results from mutual phenomena show an agreement by less
than 1-sigma error in , typically less than 10 mas. This new method is
particularly suitable for observations by small telescopes.Comment: 13 pages, 11 figures and 8 tables. Based on observations made at the
Laborat\'orio Nacional de Astrof\'isica (LNA), Itajub\'a-MG, Brazi
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