Radiative Correction to the Dirichlet Casimir Energy for λϕ4\lambda\phi^{4} Theory in Two Spatial Dimensions

In this paper, we calculate the next to the leading order Casimir energy for real massive and massless scalar fields within $\lambda\phi^{4}$ theory, confined between two parallel plates with the Dirichlet boundary condition in two spatial dimensions. Our results are finite in both cases, in sharp contrast to the infinite result reported previously for the massless case. In this paper we use a renormalization procedure introduced earlier, which naturally incorporates the boundary conditions. As a result our radiative correction term is different from the previously calculated value. We further use a regularization procedure which help us to obtain the finite results without resorting to any analytic continuation techniques.Comment: 8 pages, 3 figure

Stochastic Approximation to Understand Simple Simulation Models

This paper illustrates how a deterministic approximation of a stochastic process can be usefully applied to analyse the dynamics of many simple simulation models. To demonstrate the type of results that can be obtained using this approximation, we present two illustrative examples which are meant to serve as methodological references for researchers exploring this area. Finally, we prove some convergence results for simulations of a family of evolutionary games, namely, intra-population imitation models in n-player games with arbitrary payoffs.Ministerio de Educación (JC2009- 00263), Ministerio de Ciencia e Innovación (CONSOLIDER-INGENIO 2010: CSD2010-00034, DPI2010-16920

Renormalization Group Flows from D=3, N=2 Matter Coupled Gauged Supergravities

We study holographic RG flows of N=2 matter couple AdS_3 supergravities which admit both compact and non-compact sigma manifolds. For the compact case the supersymmetric domain wall solution interpolates between a conformal IR region and flat spacetime and this corresponds to a deformation of the CFT by an irrelevant operator. When it is non-compact, the solution can be interpreted as a flow between an UV fixed point and a non-conformal(singular) IR region. This is an exact example of a deformation flow when the singularity is physical. We also find a non-supersymmetric deformation flow when the scalar potential has a second AdS vacua. The ratio of the central charges is rational for certain values of the size of the sigma model. Next, we analyze the spectrum of a massless scalar on our background by transforming the problem into Schroedinger form. The spectrum is continuous for the compact model, yet it can be both continuous (with or without mass gap) and discrete otherwise. Finally, 2-point functions are computed for two examples whose quantum mechanical potentials are of Calogero type.Comment: 15 pages, 5 figures, Latex; v2 minor improvements, references added; v3 a footnote added, typos correcte

Crowd computing as a cooperation problem: an evolutionary approach

Cooperation is one of the socio-economic issues that has received more attention from the physics community. The problem has been mostly considered by studying games such as the Prisoner's Dilemma or the Public Goods Game. Here, we take a step forward by studying cooperation in the context of crowd computing. We introduce a model loosely based on Principal-agent theory in which people (workers) contribute to the solution of a distributed problem by computing answers and reporting to the problem proposer (master). To go beyond classical approaches involving the concept of Nash equilibrium, we work on an evolutionary framework in which both the master and the workers update their behavior through reinforcement learning. Using a Markov chain approach, we show theoretically that under certain----not very restrictive-conditions, the master can ensure the reliability of the answer resulting of the process. Then, we study the model by numerical simulations, finding that convergence, meaning that the system reaches a point in which it always produces reliable answers, may in general be much faster than the upper bounds given by the theoretical calculation. We also discuss the effects of the master's level of tolerance to defectors, about which the theory does not provide information. The discussion shows that the system works even with very large tolerances. We conclude with a discussion of our results and possible directions to carry this research further.This work is supported by the Cyprus Research Promotion Foundation grant TE/HPO/0609(BE)/05, the National Science Foundation (CCF-0937829, CCF-1114930), Comunidad de Madrid grant S2009TIC-1692 and MODELICO-CM, Spanish MOSAICO, PRODIEVO and RESINEE grants and MICINN grant TEC2011-29688-C02-01, and National Natural Science Foundation of China grant 61020106002.Publicad

Comparación de distintas estrategias para la predicción de muerte a corto plazo en el paciente anciano infectado

Objective. The aim of this study was to determine the utility of a post hoc lactate added to SIRS and qSOFA score to predict 30-day mortality in older non-severely dependent patients attended for infection in the Emergency Department (ED). Methods. We performed an analytical, observational, prospective cohort study including patients of 75 years of age or older, without severe functional dependence, attended for an infectious disease in 69 Spanish ED for 2-day three seasonal periods. Demographic, clinical and analytical data were collected. The primary outcome was 30-day mortality after the index event. Results. We included 739 patients with a mean age of 84.9 (SD 6.0) years; 375 (50.7%) were women. Ninety-one (12.3%) died within 30 days. The AUC was 0.637 (IC 95% 0.587-0.688; p= 2 and 0.698 (IC 95% 0.635- 0.761; p= 2. Comparing receiver operating characteristic (ROC) there was a better accuracy of qSOFA vs SIRS (p=0.041). Both scales improve the prognosis accuracy with lactate inclusion. The AUC was 0.705 (IC95% 0.652-0.758; p<0.001) for SIRS plus lactate and 0.755 (IC95% 0.696-0.814; p<0.001) for qSOFA plus lactate, showing a trend to statistical significance for the second strategy (p=0.0727). Charlson index not added prognosis accuracy to SIRS (p=0.2269) or qSOFA (p=0.2573). Conclusions. Lactate added to SIRS and qSOFA score improve the accuracy of SIRS and qSOFA to predict short-term mortality in older non-severely dependent patients attended for infection. There is not effect in adding Charlson index

Publishing science in the digital age: the case of Neurocirugía

Neurocirugía publica una edición impresa por suscripción y una edición electrónica en Internet de acceso gratuito. La convivencia de estos dos esquemas plantea algunos interrogantes sobre su justificación y sobre su evolución esperada, tales como ¿Por qué un acceso de pago y otro gratuito? ¿Conviene cobrar o limitar el acceso electrónico? ¿Cómo cambia Internet el servicio a la sociedad que proporciona la revista? ¿Seguirán conviviendo la versión impresa y la electrónica? En este artículo presentamos algunas respuestas y reflexiones sobre las preguntas anteriores. Muchas de estas reflexiones se basan en ideas presentadas y discutidas en editoriales previos de Neurocirugía (ver Neurocirugía 17 (2), 2006), y son aquí reorganizadas, reenfocadas o complementadas de forma conveniente para responder a los interrogantes planteados. A partir de un análisis de costes y beneficios para los distintos agentes implicados (autores, lectores, la propia revista, la Sociedad Española de Neurocirugía, la sociedad en su conjunto), justificamos la coexistencia actual de los dos esquemas de publicación, defendemos el acceso gratuito por Internet, y exponemos nuestra visión sobre la evolución esperada. Si bien nos centramos particularmente en Neurocirugía, la mayoría de las consideraciones realizadas son extensibles a la publicación y al futuro esperado de otras revistas científicas

Incidence and prevalence of multiple sclerosis in China and other Asian countries

The prevalence of multiple sclerosis (MS) in Asian countries is thought to be lower than in Western countries, with Asian populations presenting 80% less risk of MS than white populations. Incidence and prevalence rates in Asian countries are therefore not well defined and their association with rates in neighboring countries, as well as with ethnic, environmental, and socioeconomic factors, are not well understood.We performed a comprehensive literature review of epidemiological data from China and neighbouring countries to study the frequency of the disease, focusing on prevalence, and the progression over time and the influence of sex-related, environmental, dietary, and sociocultural factors.Prevalence rates in China range between 0.88 cases/100,000 population in 1986 and 5.2 cases/100,000 population in 2013, with a non-significant upwards trend (p = .08). The increase observed in Japan, where figures ranged between 8.1 and 18.6 cases/100,000 population was highly significant (p < .001). Prevalence rates in countries with predominantly white populations are considerably higher and have increased over time, reaching 115 cases/100,000 population in 2015 (r2 = 0.79, p < .0001).In conclusion, the prevalence of MS in China appears to have risen in recent years, although Asian populations (including Chinese and Japanese populations, among others) appear to present less risk than other populations. Within Asia, geographical latitude appears not to be a determining factor for developing MS. Resumen: La prevalencia de la esclerosis múltiple (EM) en los países asiáticos se considera que es más baja que en los países occidentales, las poblaciones asiáticas tienen un 80% menos de riesgo de EM que las caucásicas. No se conocen bien las cifras de incidencia, prevalencia y su relación con otros países de su entorno y su relación con factores étnicos, ambientales y socioeconómicos.Hemos realizado una revisión bibliográfica exhaustiva de los datos epidemiológicos existentes en China y países limítrofes, para estudiar la frecuencia de la enfermedad, centrándonos en la prevalencia, sus cambios evolutivos a lo largo del tiempo y su relación con factores de género, ambientales, alimenticios y socioculturales.La prevalencia en China oscila en cifras que van desde 0,88 en 1986 a 5,2 en 2013 por 100.000 habitantes con una tendencia a aumentar que no es estadísticamente significativa (p = 0,08), mientras que en Japón este incremento es muy significativo, con cifras que oscilan entre 8,1 y 18,6 (p < 0,001). La prevalencia en los países donde predomina la raza caucásica son mucho más elevadas y aumentan con el tiempo, llegando a 115 por 100.000 habitantes en 2015 (r2 = 0,79, p = 0,0001).En conclusión, la prevalencia de la EM en China parece está aumentando en los últimos años, aunque la raza amarilla (chinos y japoneses, entre otros) tienen menor riesgo de padecerla que el resto de las poblaciones. La latitud no parece ser un factor muy determinante en Asia para presentar un mayor riesgo de padecer EM

Sleep disorders in patients with multiple sclerosis in Spain

Objective: This study assesses the presence of sleep disturbances and their relationship with clinical and demographic variables in patients with MS, with a view to establishing correlations between the different variables and the frequency of sleep disturbances. Methods: The Pittsburgh Sleep Quality Index (PSQI) was used to detect sleep disorders. We contacted patients treated at the MS unit and distributed a questionnaire (PSQI) to 221 patients, receiving 142 usable questionnaires between 8 and 30 September 2019. Results: The prevalence of patients with sleep disturbances in our study was 74.7% (73.7% in women and 76.8% in men). Therefore, sleep disorders are pervasive in patients with MS, with 3 out of 4 patients experiencing them, a higher rate than that observed in the population without the disease. The frequency of sleep disorders gradually increased in line with age. In the 2 age groups analyzed, 44–54 years and 55–68 years, the proportion of moderate and severe sleep disorders was 42.8% and 53.9%, respectively. Moderate and severe sleep disturbances were observed in 27.5%, 44.7%, and 58.3% of patients with Expanded Disability Status Scale scores of 0–3, 3–6, and >6, respectively. Conclusion: Our results indicate that sleep disorders are more common in patients with MS than in other populations. Patients with secondary progressive forms of MS more frequently present sleep disturbances, while patients with primary progressive forms report them less frequently. Age and degree of disability were positively correlated with the prevalence and severity of sleep disorders in MS patients. Resumen: Objetivo: Evaluamos la presencia de alteraciones del sueño en pacientes con EM y su relación con variables clínicas y demográficas en esta población para establecer correlaciones entre diversas variables y la frecuencia de trastornos del sueño. Métodos: Se utilizó el Índice de Calidad de Sueño de Pittsburgh para identificar la presencia de trastornos del sueño. Distribuimos el cuestionario a 221 pacientes de nuestra unidad de EM, y recibimos respuesta de 142 de ellos entre el 8 y el 30 de septiembre de 2019. Resultados: En nuestra muestra, el 74,7% de los pacientes presentaban trastornos del sueño (73,7% de las mujeres y 76,8% de los hombres). Nuestros resultados muestran que los trastornos del sueño están muy presentes en la EM, detectándose en 3 de cada 4 pacientes, lo que supone una proporción mayor que en la población general. La presencia de trastornos del sueño aumenta con la edad. En los 2 grupos etarios analizados (44-54 años y 55-68 años), la proporción de pacientes con trastornos del sueño moderados o graves fue del 42,8% y el 53,9%, respectivamente. El 27,5%, el 44,7% y el 58,3% de los pacientes con puntuaciones de 0-3, 3-6 y >6 puntos en la Escala Expandida del Estado de Discapacidad, respectivamente, presentaron trastornos del sueño moderados o graves. Conclusión: Nuestros resultados indican que los trastornos del sueño son más prevalentes en los pacientes con EM que en otras poblaciones. Dichos trastornos son más frecuentes en pacientes con EM secundaria progresiva que en pacientes con la forma primaria progresiva. La edad y el grado de discapacidad mostraron una correlación positiva con la prevalencia y la gravedad de los trastornos del sueño