Cramer-Rao bounds in the estimation of time of arrival in fading channels

This paper computes the Cramer-Rao bounds for the time of arrival estimation in a multipath Rice and Rayleigh fading scenario, conditioned to the previous estimation of a set of propagation channels, since these channel estimates (correlation between received signal and the pilot sequence) are sufficient statistics in the estimation of delays. Furthermore, channel estimation is a constitutive block in receivers, so we can take advantage of this information to improve timing estimation by using time and space diversity. The received signal is modeled as coming from a scattering environment that disperses the signal both in space and time. Spatial scattering is modeled with a Gaussian distribution and temporal dispersion as an exponential random variable. The impact of the sampling rate, the roll-off factor, the spatial and temporal correlation among channel estimates, the number of channel estimates, and the use of multiple sensors in the antenna at the receiver is studied and related to the mobile subscriber positioning issue. To our knowledge, this model is the only one of its kind as a result of the relationship between the space-time diversity and the accuracy of the timing estimation.Peer ReviewedPostprint (published version

Space-Time diversity for NLOS mitigation in TDOA-based positioning systems

This paper studies the potential impact of using space-Time information in the mitigation of the Non-LineOf-Sight condition in mobile subscriber's positioning systems. First of all, this work discusses the positioning problem based on measures of Time Differences Of Arrival departing from a more exact characterization of the signal statistics and including some geometrical restrictions to achieve an improved accurate. Furthermore, a novel approach that integrates signal propagation characteristics to information provided by a suitable timing estimation model based on Cramer Rao Bound for a Rayleigh-fading channel, when antenna arrays are used at the receiver and when a set ofchannel vector estimates are available, has been introduced to study the positive benefits of space-Time diversity. These approaches are evaluated within a realistic simulation scenario.Peer ReviewedPostprint (published version

ASSESSING ADMINISTRATION CHARGES FOR THE AFFILIATE IN INDIVIDUAL ACCOUNT SYSTEMS

In any pension system based on capitalization, affiliates have to cover certain explicit costs which in a pay-as-you-go system would be implicit. In this paper we set out a model based on Whitehouse (2000) and Diamond (1999) to enable the explicit costs borne by the affiliate both during his working life and his retirement period to be assessed. It also shows the relationships between the different ways of measuring the costs that make up the total price finally paid by the contributors. Included in the model is the notable effect that some factors -such as gaps in contribution profiles, account transfers and changes in salary profiles- have on projecting the costs borne by the affiliates. Finally we carry out an international comparison of administration costs from the point of view of the affiliate, focusing special attention on the countries of Latin America and Spain. This has a double objective: 1.- To test the validity of criticisms made by some researchers as to whether the new capitalization systems introduced in Latin America are too expensive to run for the affiliates. 2.- To serve as a reference for the individual pension scheme system in Spain. En un sistema de pensiones basado en la capitalización los afiliados deben hacer frentea unos costes explícitos que en el sistema de reparto son implícitos. En este trabajo sedesarrolla un modelo, basado en Whitehouse (2000) y Diamond (1999), que permite evaluarlas comisiones explícitas que soporta el afiliado, tanto durante la vida laboral como durante laetapa de jubilación y que, además, muestra la relación entre las diferentes medidas de loscostes que integran el precio total que finalmente pagan los cotizantes. En el modelo seintroduce el efecto de algunos aspectos que tienen una repercusión muy importante en laproyección de los costes que soportan los afiliados: ¿vacíos¿ en los perfiles de aportación,efecto de los traspasos de fondos y cambio en los perfiles de salarios. Por último, se realizauna comparación internacional de los costes de administración desde la óptica de los afiliadoscon un doble objetivo:1.-Contrastar la validez de la crítica realizada por algunos investigadores a los nuevossistemas de capitalización individual implantados en América Latina, en el sentido de que sonexcesivamente caros de gestionar para los afiliados.2.-Servir de referencia para el sistema de planes de pensiones individuales en España.Capitalización, Costes de Administración, Fondo de pensiones, América Latina. Capitalization, Administration Costs, Pension Funds, Latin America

- LA VIABILIDAD FINANCIERA DEL SISTEMA DE PENSIONES DE REPARTO: APLICACIÓN A LA CONTINGENCIA DE JUBILACIÓN DEL RÉGIMEN GENERAL DE LA SEGURIDAD SOCIAL ESPAÑOLA

The main idea upon which this paper is based is that outlined by Samuelson (1958) -that a pensions system, financed by way of transfers between generations, will only be viable in the long term if the internal rate of return of the system does not exceed the growth rate of salaries plus the stable growth rate of the contributors- .Thisis linked to the debate that has been reopened and carried on with renewed force over the last few years as to the viability and suitablility of Social Security (SS) systems, a phenomenon which is analysed briefly in the introduction. This is followed by a short review of the main literature available on the subject of applying theinternal rate of return to pay-as-you-go systems. After defining the concept of the internal rate of return as applied to a contributor, this is extended to the system as a whole, using the model put forward by Bravo (1996) as a referent. Thus two approximate expressions are obtained, basic and derived, which provide us with a complete idea of the demographic, financial and economic elements and the rules of application that have an influence on this rate of return. Finally, given that the resulting model enables the internal rate of return to be calculated very easily by defining the basic parameters estimated or observed in the system, this is applied to determine the future financial viability of the general Spanish retirement pensions system, using the two basic expressions developed. La proposición de Samuelson (1958) -un sistema de pensiones, financiado a través detransferencias intergeneracionales, sólo será viable en el largo plazo si el TIR del sistema nosupera la tasa de crecimiento de los salarios más la tasa de crecimiento estable de la poblacióncotizante- es la idea principal sobre la que se edifica el trabajo realizado. Enlaza con el debatereabierto, con impulso renovado en los últimos años, sobre la viabilidad y adecuación de lossistemas de Seguridad Social (S.S.); fenómeno que es analizado concisamente en laintroducción. A continuación, se efectúa una breve revisión de la principal literatura disponiblerelacionada con la aplicación del tanto interno de rendimiento (TIR) a los sistemas de reparto.Tras definir el concepto del TIR aplicado a un cotizante, se realiza una extensión del mismo alconjunto del sistema, con el modelo de Bravo (1996) como referente, obteniéndose dosexpresiones aproximadas, básica y derivada, que nos proporciona una visión muy rica de loselementos demográficos, financieros, económicos y reglas de aplicación que influyen en dichotanto. Por último, dado que el modelo resultante permite calcular el TIR con suma facilidad, apartir de la definición de los parámetros básicos estimados u observados en el sistema, se aplicapara determinar la viabilidad financiera futura del sistema de pensiones de jubilación español,régimen general, utilizando las dos expresiones fundamentales desarrolladas.España, Jubilación, Pensiones, Sistema de reparto, Seguridad Social, Tanto interno de rendimiento (TIR) Internal rate of return, Pay-as-you-go systems, Pensions, Retirement, Social Security Spain.

ANÁLISIS Y VALORACIÓN DE LOS SISTEMAS DE PENSIONES REFORMADOS EN LATINOAMÉRICA

The transformation of the public pensions system in Chile has served as a model for later reforms carried out in other Latin American countries, and has attracted the attention of a number of researchers. The aim of this paper is to make a (provisional) technical analysis of the workings of these systems, which incorporate many elements traditionally associated with the financial sector and private insurance. The main characteristics are identified, analyzed and explored: operating structure, profitability, level of pensions provided, real cover, administrative costs, size and composition of fund portfolios, level of implicit debt, transition costs, and the problems arising due to the existence of alternative methods of pension provision. A minimum statistical base is available for most of the aspects analyzed, which enables assessments and/or comparisons to be made with the systems before they were reformed, amongst the systems after reform, and with other countries. La transformación del sistema público de pensiones en Chile ha servido de modelo para posteriores reformas llevadas a cabo en otros países latinoamericanos y ha captado la atención de numerosos investigadores. En este trabajo, con el objetivo de realizar una valoración técnica (provisional) del funcionamiento de estos sistemas, que incorporan muchos elementos tradicionalmente vinculados al sector financiero y asegurador privado, se identifican, analizan y exploran las principales características: estructura operativa, rentabilidad, cuantía de las pensiones proporcionadas, cobertura real, costes administrativos, tamaño y composición de las carteras de los fondos, cuantía de la deuda implícita, costes de transición, y la problemática derivada de la existencia de diversas alternativas disponibles para el cobro de la pensión. La mayoría de los aspectos analizados cuentan con una base estadística mínima, lo que permite facilitar la valoración y/o comparación bien sea con los sistemas antes de la reforma, entre los propios sistemas reformados o con otros países.Jubilación, Sistema de capitalización, Sistema de reparto. Capitalization, Pay-as-you-go, Retirement.

Doença de Carrión (Bartonelose baciliforme) confirmada por histopatologia na Selva Alta do Peru

Bartonellosis or Carrion's disease is endemic in some regions of Peru, classically found in the inter-Andean valleys located between 500 and 3200 meters above sea level. We report the case of a 43 year-old male patient, farmer, who was born in the Pichanaki district (Chanchamayo, Junin), located in the High Forest of Peru. He presented with disseminated, raised, erythematous cutaneous lesions, some of which bled. The distribution of these lesions included the nasal mucosa and penile region. Additionally subcutaneous nodules were distributed over the trunk and extremities. Hematologic exams showed a moderate anemia. Serologic studies for HIV and Treponema pallidum were negative. The histopathologic results of two biopsies were compatible with Peruvian wart. Oral treatment with ciprofloxacin (500 mg BID) was begun. Over 10 days, the patient showed clinical improvement. This is the first report of a confirmed case of bartonellosis in the eruptive phase originating from the Peruvian High Forest, showing the geographical expansion of the Carrion's disease.A bartonelose ou doença de Carrión é endêmica em algumas regiões do Peru, descrevendo-se classicamente nos vales inter-andinos, entre 500 e 3.200 metros acima do nível do mar. Os autores relatam o caso de um paciente de 43 anos de idade, fazendeiro, natural do distrito de Pichanaki (Chanchamayo, Junín), localizado na Selva Alta do Peru. O paciente apresentou-se com lesões disseminadas, elevadas e eritematosas, algumas delas com sinais de sangramento. Distribuiam-se também na mucosa nasal e no penis. Foram também observados nódulos subcutâneos no tronco e nas extremidades. Os exames laboratorais evidenciaram anemia moderada. Os testes sorológicos para detectar anticorpos contra o HIV e Treponema pallidum foram negativos. Os resultados dos estudos histopatológicos de duas biópsias de pele foram compatíveis com verruga peruana. Iniciou-se antibioticoterapia com ciprofloxacina (500 mg duas vezes ao dia). Após dez dias de tratamento, o paciente apresentou melhora clínica importante. Este relato representa o primeiro caso autóctone confirmado da fase eruptiva da bartonelose em um paciente da Selva Alta do Peru, sugestiva da expansão geográfica da doença

Buccodental health and oral mucositis : clinical study in patients with hematological diseases

El objetivo del presente trabajo fue valorar si un buen estado buco-dental (valorado mediante índices dento-gingivales), se asociaba a una menor incidencia y gravedad de mucositis oral en pacientes con enfermedades hematológicas que iban a recibir tratamiento con quimioterapia o un trasplante de médula ósea. Diseño del estudio: El estudio se llevó a cabo en 97 pacientes ingresados en el Servicio de Hematología del Hospital Duran y Reynals en Barcelona en los años 2002-2003. Estos pacientes recibían tratamiento con quimioterapia o bien el acondicionamiento previo a un trasplante de médula ósea. Se realizó un estudio descriptivo analizando un índice dental, dos índices gingivales y la higiene oral y su relación con la aparición de mucositis. Resultados: Los pacientes que durante la quimioterapia mostraron valores elevados del índice de placa (IP) y gingival (IG) presentaron un mayor porcentaje de mucositis (77.4% y 65.7% respectivamente) frente a los que tenían poca placa o ésta no era visible. En el caso del IP las diferentas fueron estadísticamente significativas (p=0.015). Asimismo los pacientes que cepillaban los dientes 3veces/día sólo presentaron mucositis en un 26.7% de los casos, frente a los que no cepillaban o lo hacían una vez al día (65.9% y 68.4%), siendo estas diferencias también estadísticamente significativas (p=0.013). El ICAO mostró resultados similares en los pacientes con o sin mucositis (7.59 y 7.03 respectivamente). Conclusiones: En nuestro trabajo, un buen estado gingival así como una buena higiene oral durante la quimiorradioterapia, se asocian a una menor incidencia y gravedad de mucositis

Optical constants of evaporation-deposited silicon monoxide films in the 7.1-800 eV photon energy range

8 págs.; 11 figs.The transmittance of silicon monoxide films prepared by thermal evaporation was measured from 7.1 to 800 eV and used to determine the optical constants of the material. SiO films deposited onto C-coated microgrids in ultrahigh vacuum conditions were measured in situ from 7.1 to 23.1 eV. Grid-supported SiO films deposited in high vacuum conditions were characterized ex situ from 28.5 to 800 eV. At each photon energy, transmittance, and thickness data were used to calculate the extinction coefficient k. The obtained k values combined with data from the literature, and with interpolations and extrapolations in the rest of the electromagnetic spectrum provided a complete set of k values that was used in a Kramers-Kronig analysis to obtain the real part of the index of refraction, n. Two different sum-rule tests were performed that indicated good consistency of the data. © 2009 American Institute of Physics.This work was supported by the National Programme for Space Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia y Tecnología, Project Nos. ESP2002-01391 and ESP2005-02650. This work was also performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Berkeley National Laboratory under Contract No. DE-AC03-76F00098 and by the University of California Lawrence Livermore National Laboratory under Contract No. DE-AC52- 07NA27344. M.F.-P. is thankful to Consejo Superior de Investigaciones Científicas Spain for funding under the Programa I3P Contract No. I3P-BPD2004, partially supported by the European Social Fund. M.V.-D. acknowledges financial support from a FPI Contract No. BES-2006-14047 fellowship.Peer Reviewe

Psychological factors explaining perceived impact of COVID-19 on travel

This cross-sectional study aims to determine the psychological factors that contribute to the perceived impact of COVID-19 on travel using a convenience sample (N = 1122) from the general population to whom instruments assessing the perception of the COVID-19 pandemic’s impact on travel, anxiety, fear, phobia, risk perception, and stress were applied. The participants were mainly female (65.6%), had not attended university, and who were professionally active, with a mean age of around 30-years-old (M = 31.91, SD = 13.76, Min = 18, Max = 81). The perceived impact of COVID-19 on travel correlates with all of the psychological variables, mainly in terms of the emotional fear of COVID-19. Together with the perceived risk of COVID-19, social phobia due to COVID-19, and COVID-19 stress contamination, these variables explain 20% of the perceived impact of COVID-19 on travel variance. The relationship between COVID-19 stress socio-economic consequences and the perception of the pandemic’s impact on travel is moderated by the emotional perceived risk of COVID-19. Fear and perception of this risk explain the impact of the COVID-19 on travel in pandemic times, suggesting that the psychological impact of fear and anxiety induced by the pandemic needs to be handled as a public health priority.info:eu-repo/semantics/publishedVersio

Portuguese Version of COVID-19 Perceived Risk Scale and COVID-19 Phobia Scale: psychometric properties

The COVID-19 pandemic scenario has a psychological impact on individuals and society. A higher level of perceived risk concerning COVID-19 has been found when compared to other potential health threats. A misperception of risk in contrast with the real risk may lead people to develop disruptive cognitive, affective, or behavioral responses to the COVID-19 pandemic, namely, coronaphobia. Validated instruments are needed to evaluate such responses. This work aims to validate the COVID-19 Perceived Risk Scale (C19PRS) and the COVID-19 Phobia Scale (C19PS) in the Portuguese population. The two scales were translated from English to Portuguese using the back-translation technique. The cultural adaptation was framed in the context of establishing the validity and reliability of the instruments. In two studies, C19PRS and C19PS were validated for the adult Portuguese population (N = 1122; women = 725 (64.6%); mean age of 31.91 years old) through exploratory factorial analysis, followed by a confirmatory factorial analysis. Convergent validity was calculated by composite reliability (CR) and average variance extracted (AVE) values. Discriminant validity was assessed by square roots of the AVE values and their comparison with the C19PRS and C19PS dimensions’ cross-correlations. Both C19PRS and C19PS present a good adjustment model and solid reliability and validity and have significant correlations with fear of COVID-19 and COVID-19 anxiety scales.info:eu-repo/semantics/publishedVersio