27,102 research outputs found
Correctors for the Neumann problem in thin domains with locally periodic oscillatory structure
In this paper we are concerned with convergence of solutions of the Poisson
equation with Neumann boundary conditions in a two-dimensional thin domain
exhibiting highly oscillatory behavior in part of its boundary. We deal with
the resonant case in which the height, amplitude and period of the oscillations
are all of the same order which is given by a small parameter .
Applying an appropriate corrector approach we get strong convergence when we
replace the original solutions by a kind of first-order expansion through the
Multiple-Scale Method.Comment: to appear in Quarterly of Applied Mathematic
Fisher Information and Kinetic-energy Functionals: A Dequantization Approach
We strengthen the connection between Information Theory and
quantum-mechanical systems using a recently developed dequantization procedure
whereby quantum fluctuations latent in the quantum momentum are suppressed. The
dequantization procedure results in a decomposition of the quantum kinetic
energy as the sum of a classical term and a purely quantum term. The purely
quantum term, which results from the quantum fluctuations, is essentially
identical to the Fisher information. The classical term is complementary to the
Fisher information and, in this sense, it plays a role analogous to that of the
Shannon entropy. We demonstrate the kinetic energy decomposition for both
stationary and nonstationary states and employ it to shed light on the nature
of kinetic-energy functionals.Comment: 13 pages, 3 figures. To appear in J. Comput. Appl. Mat
Mass dependent Evolution of Field Early-Type Galaxies Since z=1
We present the Fundamental Plane (FP) of field early-type galaxies at
0.5<z<1.0. Our project is a continuation of our efforts to understand the
formation and evolution of early-type galaxies in different environments. The
target galaxies were selected from the comprehensive and homogeneous data set
of the Gemini/HST Galaxy Cluster Project. The distant field early-type galaxies
follow a steeper FP relation compared to the local FP. The change in the slope
of the FP can be interpreted as a mass-dependent evolution. Similar results
have been found for cluster early-type galaxies in high redshift galaxy
clusters at 0.8<z<1. Therefore, the slope change of the FP appears to be
independent of the environment of the galaxies.Comment: 2 pages, 1 figure, to appear in the proceedings of the IAU Symposium
no. 262, "Stellar Populations - Planning for the Next Decade", eds. G. R.
Bruzual and S. Charlo
Can we measure hospital quality from physicians' choices?
In this paper, we propose an alternative methodology for ranking hospitals based on the choices of Medical School graduates over hospital training vacancies. Our methodology is therefore a revealed preference approach. Our methodology for measuring relative hospital quality has the following desirable properties: a) robust to manipulation from hospital administrators; b) conditional on having enough observations, it allows for differences in quality across specialties within a hospital; c) inexpensive in terms of data requirements, d) not subject to selection bias from patients nor hospital screening of patients; and e) unlike other rankings based on experts' evaluations, it does not require physicians to provide a complete ranking of all hospitals. We apply our methodology to the Spanish case and find, among other results, the following: First, the probability of choosing the best hospital relative to the worst hospital is statistically significantly different from zero. Second, physicians value proximity and nearby hospitals are seen as more substitutable. Third, observable time-invariant city characteristics are unrelated to results. Finally, our estimates for physicians' hospital valuations are significantly correlated to more traditional hospital quality measures
A methodology to measure hospital quality using physicians' choices over training vacancies
In this paper, we propose an alternative methodology to rank hospitals based on the choices of Medical Schools graduates over training vacancies. We argue that our measure of relative hospital quality has the following desirable properties: a) robustness to manipulation from the hospital's administrators; b) comprehensiveness in the scope of the services analyzed; c) inexpensive in terms of data requirements, and d) not subject to selection biases. Accurate measures of health provider quality are needed in order to establish incentive mechanisms, to assess the need for quality improvement, or simply to increase market transparency and competition. Public report cards in certain US states and the NHS ranking system in the UK are two attempts at constructing quality rankings of health care providers. Although the need for such rankings is widely recognized, the criticisms at these attempts reveal the difficulties involved in this task. Most criticisms alert to the inadequate risk-adjustment and the potential for perverse consequences such as patient selection. The recent literature, using sophisticated econometric models is capable of controlling for case-mix, hospital and patient selection, and measurement error. The detailed data needed for these evaluations is, however, often unavailable to researchers. In those countries, such as Spain, where there is neither public hospital rankings nor public data on hospital output measures such as mortality rates our methodology is a valid alternative. We develop this methodology for the Spanish case. In a follow-up paper we will present results using Spanish data. In Spain graduates choose hospital training vacancies in a sequential manner that depends on their average grade. Our framework relies on three assumptions. First, high quality hospitals provide high quality training. Second, graduates are well informed decision makers who are well qualified to assess hospital quality. Third, they prefer to choose a high quality vacancy rather than a low quality one ceteris paribus. If these assumptions hold, then the first physicians to choose are likely to grab the best vacancies while the ones who choose last are stuck with the worst available. Thus, it is possible to infer from physicans' choices quality differentials amongst hospitals. We model the physician's decision as a nested-logit a la McFadden. Unlike in standard applications of McFadden's model, in our application the choice set is not constant across physicians but it shrinks along the sequential hospital choice proces
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