29,582 research outputs found
Field-induced Coulomb coupling in semiconductor macroatoms: application to "single-electron" quantum devices
A novel approach for the control of exciton-exciton Coulomb coupling in
semiconductor macroatoms/molecules is proposed. We show that by applying
properly tailored external fields, we can induce ---or significantly
reinforce--- excitonic dipoles, which in turn allows to control and magnify
intra- as well as inter-dot few-exciton effects. Such dipole-dipole interaction
mechanism will be accounted for within a simple analytical model, which is
found to be in good agreement with fully three-dimensional calculations. The
proposed approach may play an important role for the design and realization of
fully-optical quantum gates as well as ultrafast optical switches
Radio-X-ray Synergy to discover and Study Jetted Tidal Disruption Events
Observational consequences of tidal disruption of stars (TDEs) by
supermassive black holes (SMBHs) can enable us to discover quiescent SMBHs,
constrain their mass function, study formation and evolution of transient
accretion disks and jet formation. A couple of jetted TDEs have been recently
claimed in hard X-rays, challenging jet models, previously applied to
-ray bursts and active galactic nuclei. It is therefore of paramount
importance to increase the current sample. In this paper, we find that the best
strategy is not to use up-coming X-ray instruments alone, which will yield
between several (e-Rosita) and a couple of hundreds (Einstein Probe) events per
year below redshift one. We rather claim that a more efficient TDE hunter will
be the Square Kilometer Array (SKA) operating {\it in survey mode} at 1.4 GHz.
It may detect up to several hundreds of events per year below with
a peak rate of a few tens per year at . Therefore, even if the
jet production efficiency is {\it not } as assumed here, the predicted
rates should be large enough to allow for statistical studies. The
characteristic TDE decay of , however, is not seen in radio, whose
flux is quite featureless. {\it Identification} therefore requires localization
and prompt repointing by higher energy instruments. If radio candidates would
be repointed within a day by future X-ray observatories (e.g. Athena and
LOFT-like missions), it will be possible to detect up to X-ray
counterparts, almost up to redshift . The shortcome is that only for
redshift below the trigger times will be less than 10 days from
the explosion. In this regard the X-ray surveys are better suited to probe the
beginning of the flare, and are therefore complementary to SKA.Comment: Astrophysical Journal (revised version
Horizontal Inequity in Access to Health Care in Four South American Cities
ResumenEl objetivo de este trabajo es analizar el grado de inequidad socioeconómica en el uso de servicios médicos de la población adulta mayor en cinco ciudades latinoamericanas (Buenos Aires, Ciudad de México, Santiago de Chile, San Pablo y Montevideo), en base a los datos de la Encuesta de Salud, Bienestar y Envejecimiento relevada entre 1999 y 2000 (SABE, OPS/OMS, 2001). El análisis imputa el ingreso equivalente del hogar a través de la utilización de las encuestas de hogares de los distintos países, y considerando una amplia serie de indicadores de acceso, calidad y uso de servicios de salud. Una vez estandarizado el uso de servicios por las necesidades de cuidados, se encuentran desigualdades socioeconómicas pro-rico en el uso de servicios preventivos en todas las ciudades, desigualdades en la realización de visitas médicas en Santiago y Montevideo, y desigualdades en la calidad de acceso a la atención en todas las ciudades salvo Montevideo. Las desigualdades socioeconómicas dentro de los sistemas de salud públicos o privados explican una mayor proporción de las desigualdades en el acceso a la atención. Nuestros resultados son informativos en el contexto de las políticas recientes destinadas a la aplicación de paquetes mínimos de servicios. AbstractThe objective of this paper is compare socioeconomic inequalities in the use of healthcare services in four South-American cities: Buenos Aires, Santiago, Montevideo, and San Pablo. We use secondary data from SABE, a survey on Health, Well-being and Aging administered in 2000 under the sponsorship of the Panamerican Health Organization, and representative of the elderly population in each of the analyzed cities. We construct concentration indices of access to and quality of healthcare services, and decompose them in socioeconomic, need, and non-need contributors. We assess the weight of each contributor to the overall index and compare indices across cities. Our results show high levels of pro-rich socioeconomic inequities in the use of preventive services in all cities, inequities in medical visits in Santiago and Montevideo, and inequities in quality of access to care in all cities but Montevideo. Socioeconomic inequality within private or public health systems explains a higher portion of inequalities in access to care than the fragmented nature of health systems. Our results are informative given recent policies aimed at enforcing minimum packages of services and given policies exclusively focused on defragmenting health systems.Desigualdad horizontal, acceso al sistema de salud, Suramérica.
Lower and upper bounds for the first eigenvalue of nonlocal diffusion problems in the whole space
We find lower and upper bounds for the first eigenvalue of a nonlocal
diffusion operator of the form T(u) = - \int_{\rr^d} K(x,y) (u(y)-u(x)) \,
dy. Here we consider a kernel where
is a bounded, nonnegative function supported in the unit ball and means a
diffeomorphism on \rr^d. A simple example being a linear function .
The upper and lower bounds that we obtain are given in terms of the Jacobian of
and the integral of . Indeed, in the linear case we
obtain an explicit expression for the first eigenvalue in the whole \rr^d and
it is positive when the the determinant of the matrix is different from
one. As an application of our results, we observe that, when the first
eigenvalue is positive, there is an exponential decay for the solutions to the
associated evolution problem. As a tool to obtain the result, we also study the
behaviour of the principal eigenvalue of the nonlocal Dirichlet problem in the
ball and prove that it converges to the first eigenvalue in the whole
space as
Horizontal inequity in access to health care in four South American cities
This paper analyzes and compares socioeconomic inequalities in the use of healthcare services by the elderly in four South-American cities: Buenos Aires (Argentina), Santiago (Chile), Montevideo (Uruguay) and San Pablo (Brazil). We use data from SABE, a survey on Health, Well-being and Aging administered in several Latin American cities in 2000. After having accounted for socioeconomic inequalities in healthcare needs, we find socioeconomic inequities favoring the rich in the use of preventive services (mammograms, pap tests, breast examinations, and prostate exams) in all of the studied cities. We also find inequities in the likelihood of having a medical visit in Santiago and Montevideo, and in some measures of quality of access in Santiago, Sao Paulo, and Buenos Aires. Santiago depicts the highest inequities in medical visits and Uruguay the worse indicators in mammograms and pap scans tests. For all cities, inequities in preventive services at least double inequities in other services. We do not find evidence of a trade-off between levels of access and equity in access to healthcare services. The decomposition of healthcare inequalities suggests that inequities within each health system (public or private) are more important than between systems.inequalities, healthcare, medical visit, preventive services.
The Rainbow Prim Algorithm for Selecting Putative Orthologous Protein Sequences
We present a selection method designed for eliminating species redundancy in clusters of putative orthologous sequences, to be applied as a post-processing procedure to pre-clustered data obtained from other methods. The algorithm can always zero-out the cluster redundancy while preserving the number of species of the original cluster
A Compact Apparatus for Muon Lifetime Measurement and Time Dilation Demonstration in the Undergraduate Laboratory
We describe a compact apparatus that automatically measures the charge
averaged lifetime of atmospheric muons in plastic scintillator using low-cost,
low-power electronics and that measures the stopping rate of atmospheric muons
as a function of altitude to demonstrate relativistic time dilation. The
apparatus is designed for the advanced undergraduate physics laboratory and is
suitable for field measurements.Comment: 5 pages, 2 figure
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