5,093 research outputs found
Wave number-Explicit Analysis for Galerkin Discretizations of Lossy Helmholtz Problems
We present a stability and convergence theory for the lossy Helmholtz
equation and its Galerkin discretization. The boundary conditions are of Robin
type. All estimates are explicit with respect to the real and imaginary part of
the complex wave number , ,
. For the extreme cases and , the estimates
coincide with the existing estimates in the literature and exhibit a seamless
transition between these cases in the right complex half plane.Comment: 29 pages, 1 figur
Gluon propagator in diffractive scattering
In this work, we perform a comparison of the employ of distinct gluon
propagators with the experimental data in diffractive processes, elastic
scattering and light meson photo-production. The gluon propagators are
calculated through non-perturbative methods, being justified their use in this
class of events, due to the smallness of the momentum transfer. Our results are
not able to select the best choice for the modified gluon propagator among the
analyzed ones, showing that the application of this procedure in this class of
high energy processes, although giving a reasonable fit to the experimental
data, should be taken with same caution.Comment: 14 pages, 4 figures, accepted for publication in Int. J. Mod. Phys. A
(uses ws-ijmpa.cls). Authors correcte
Two-scale composite finite element method for Dirichlet problems on complicated domains
In this paper, we define a new class of finite elements for the discretization of problems with Dirichlet boundary conditions. In contrast to standard finite elements, the minimal dimension of the approximation space is independent of the domain geometry and this is especially advantageous for problems on domains with complicated micro-structures. For the proposed finite element method we prove the optimal-order approximation (up to logarithmic terms) and convergence estimates valid also in the cases when the exact solution has a reduced regularity due to re-entering corners of the domain boundary. Numerical experiments confirm the theoretical results and show the potential of our proposed metho
Damping of electromagnetic waves due to electron-positron pair production
The problem of the backreaction during the process of electron-positron pair
production by a circularly polarized electromagnetic wave propagating in a
plasma is investigated. A model based on the relativistic Boltzmann-Vlasov
equation with a source term corresponding to the Schwinger formula for the pair
creation rate is used. The damping of the wave, the nonlinear up-shift of its
frequency due to the plasma density increase and the effect of the damping on
the wave polarization and on the background plasma acceleration are
investigated as a function of the wave amplitude.Comment: 11 pages, 5 figures; revtex
Nittka's invariance criterion and Hilbert space valued parabolic equations in
Nittka gave an efficient criterion on a form defined on which
implies that the associated semigroup is -invariant for some given . We extend this criterion to the Hilbert space
valued~. As an application we consider elliptic systems of pure
second order. Our main result shows that the induced semigroup is
-contractive for all for some
Diagnostic error increases mortality and length of hospital stay in patients presenting through the emergency room
Background: Diagnostic errors occur frequently, especially in the emergency room. Estimates about the
consequences of diagnostic error vary widely and little is known about the factors predicting error. Our
objectives thus was to determine the rate of discrepancy between diagnoses at hospital admission and
discharge in patients presenting through the emergency room, the discrepanciesâ consequences, and factors
predicting them.
Methods: Prospective observational clinical study combined with a survey in a University-affiliated tertiary
care hospital. Patientsâ hospital discharge diagnosis was compared with the diagnosis at hospital admittance
through the emergency room and classified as similar or discrepant according to a predefined scheme by
two independent expert raters. Generalized linear mixed-effects models were used to estimate the effect of
diagnostic discrepancy on mortality and length of hospital stay and to determine whether characteristics of
patients, diagnosing physicians, and context predicted diagnostic discrepancy.
Results: 755 consecutive patients (322 [42.7%] female; mean age 65.14 years) were included.
The discharge diagnosis differed substantially from the admittance diagnosis in 12.3% of cases. Diagnostic
discrepancy was associated with a longer hospital stay (mean 10.29 vs. 6.90 days; Cohenâs d 0.47; 95%
confidence interval 0.26 to 0.70; P = 0.002) and increased patient mortality (8 (8.60%) vs. 25(3.78%); OR 2.40; 95% CI 1.05
to 5.5 P = 0.038). A factor available at admittance that predicted diagnostic discrepancy was the diagnosing physicianâs
assessment that the patient presented atypically for the diagnosis assigned (OR 3.04; 95% CI 1.33â6.96; P = 0.009).
Conclusions: Diagnostic discrepancies are a relevant healthcare problem in patients admitted through the
emergency room because they occur in every ninth patient and are associated with increased in-hospital
mortality. Discrepancies are not readily predictable by fixed patient or physician characteristics; attention
should focus on context
Robots in Industry. Past,present and future of a growing collaboration with humans
Robots have been part of automation systems for a very long time, and in public perception, they are often synonymous with automation and industrial revolution perse. Fueled by Industry 4.0 and Internet of Things (IoT) concepts as well as by new software technologies, the field of robotics in industry is currently undergoing a revolution on its own. This article gives an overview of the evolution of robotics from its beginnings to recent trends like collaborative robotics, autonomous robots, and human- robot interaction. Particular attention is devoted to the deep changes of the last decades, from the traditional industrial scenario based on isolated robotic cells up to the most recent coworking and collaborative robots. The role of robotics in the Industry 4.0 framework is analyzed, and the relationships with industrial communications and software technologies are also discussed. Some future directions for robotics are envisaged, focusing on the contributions coming from new materials, sensors, actuators, and technologies. Open issues are highlighted as well as the main barriers that currently limit the deployment of industrial robots in the small and medium enterprise (SME) world
Breast cancer biomarkers predict weight loss after gastric bypass surgery
<p>Abstract</p> <p>Background</p> <p>Obesity has long been associated with postmenopausal breast cancer risk and more recently with premenopausal breast cancer risk. We previously observed that nipple aspirate fluid (n) levels of prostate specific antigen (PSA) were associated with obesity. Serum (s) levels of adiponectin are lower in women with higher body mass index (BMI) and with breast cancer. We conducted a prospective study of obese women who underwent gastric bypass surgery to determine: 1) change in n- and s-adiponectin and nPSA after surgery and 2) if biomarker change is related to change in BMI. Samples (30-s, 28-n) and BMI were obtained from women 0, 3, 6 and 12 months after surgery.</p> <p>Findings</p> <p>There was a significant increase after surgery in pre- but not postmenopausal women at all time points in s-adiponectin and at 3 and 6 months in n-adiponectin. Low n-PSA and high s-adiponectin values were highly correlated with decrease in BMI from baseline.</p> <p>Conclusions</p> <p>Adiponectin increases locally in the breast and systemically in premenopausal women after gastric bypass. s-adiponectin in pre- and nPSA in postmenopausal women correlated with greater weight loss. This study provides preliminary evidence for biologic markers to predict weight loss after gastric bypass surgery.</p
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