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 $\gamma$-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 $z \sim 2.5$ with a peak rate of a few tens per year at $z\approx 0.5$. Therefore, even if the jet production efficiency is {\it not } $100\%$ as assumed here, the predicted rates should be large enough to allow for statistical studies. The characteristic TDE decay of $t^{-5/3}$, 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 $\approx 400$ X-ray counterparts, almost up to redshift $2$. The shortcome is that only for redshift below $\approx 0.4$ 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 $K(x,y)=\psi (y-a(x))+\psi(x-a(y))$ where $\psi$ is a bounded, nonnegative function supported in the unit ball and $a$ means a diffeomorphism on \rr^d. A simple example being a linear function $a(x)= Ax$. The upper and lower bounds that we obtain are given in terms of the Jacobian of $a$ and the integral of $\psi$. Indeed, in the linear case $a(x) = Ax$ 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 $A$ 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 $B_R$ and prove that it converges to the first eigenvalue in the whole space as $R\to \infty$

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