Very large stochastic resonance gains in finite sets of interacting identical subsystems driven by subthreshold rectangular pulses

We study the phenomenon of nonlinear stochastic resonance (SR) in a complex noisy system formed by a finite number of interacting subunits driven by rectangular pulsed time periodic forces. We find that very large SR gains are obtained for subthreshold driving forces with frequencies much larger than the values observed in simpler one-dimensional systems. These effects are explained using simple considerations.Comment: 4 pages, 5 figures. to appear in Phys. Rev.

Irrationality and quasiperiodicity in driven nonlinear systems

We analyse the relationship between irrationality and quasiperiodicity in nonlinear driven systems. To that purpose we consider a nonlinear system whose steady-state response is very sensitive to the periodic or quasiperiodic character of the input signal. In the infinite time limit, an input signal consisting of two incommensurate frequencies will be recognised by the system as quasiperiodic. We show that this is in general not true in the case of finite interaction times. An irrational ratio of the driving frequencies of the input signal is not sufficient for it to be recognised by the nonlinear system as quasiperiodic, resulting in observations which may differ by several orders of magnitude from the expected quasiperiodic behavior. Thus, the system response depends on the nature of the irrational ratio, as well as the observation time. We derive a condition for the input signal to be identified by the system as quasiperiodic. Such a condition also takes into account the sub-Fourier response of the nonlinear system.Comment: accepted in Phys. Rev. Let

Representaciones paracientíficas de cuerpo y persistencias tecnológicas

El objetivo del trabajo es mostrar que las representaciones corporales actuales están lejos de los cyborgs. La opción más realista es la concepción moderna del cuerpo asentada en procesos de racionalización, secularización y medicalización. Para ello me remitiré a la imagen de cuerpo como máquina mostrando ejemplos representativos.The aim of this article is to show that actual bodily performances are far from de cyborgs. The most realistic option is the modern conception of the body established in processes of rationalization, secularization and medicalization. For this I refer to the body as machine image showing representative example

La atención a la dependencia en España

ResumenHasta el momento, tanto en España como en la mayoría de los países de la Unión Europea, el fenómeno de la dependencia se ha considerado implícitamente un problema de índole fundamentalmente privada que debe ser resuelto por las familias. Así, ya sea mediante cuidadores informales o contratando la ayuda de profesionales, bien en el ámbito doméstico o en residencias asistidas, son las propias personas dependientes y sus familias las que hoy por hoy soportan la mayor parte de los costes implicados. Así las cosas, la preocupación actual reside en que los cambios sociales que se avecinan, principalmente el incremento de la esperanza de vida y la mayor participación laboral de las mujeres, acentúan la necesidad de organizar colectivamente lo que hasta el momento se ha resuelto en el ámbito familiar.En este contexto, coincidiendo con el anuncio del gobierno de una «Ley de Dependencia» para finales de 2005, el presente trabajo se propone analizar brevemente las cuatro cuestiones que nos parecen más importantes para centrar el debate: el alcance actual de los problemas de dependencia y su posible evolución futura, las características del presente modelo de atención y sus posibles problemas, el papel que desempeñan y deberían desempeñar los servicios sanitarios en materia de dependencia y, finalmente, las ventajas y los inconvenientes de las distintas alternativas de que dispone la Administración si pretende aumentar su grado de implicación en este ámbito.AbstractTo date, both in Spain and virtually all the other European Union (EU) countries, dependency has been seen to be a fundamentally private problem to be dealt with by the family concerned. In this way, whether through informal carers or contracted professionals, in the domestic environment or in care homes, it is the dependent person themselves and their families who currently bear the majority of the costs. In light of this, current concern lies in the social change that is coming on, mainly the accelerated aging process and the increased participation of middle-aged women in the labour market, which heighten the need for collective organisation of that which until now has been resolved within family circles.In this context, at the same time that the Government announces to issue a «Long Term Care Law» by the end of 2005, our paper briefly analyzes what we consider the four crucial issues in this area: the current scope of dependency problems and its possible future evolution, the characteristics of the current spanish long-term care system and its main problems; the role that health services should have in the dependency issue; and finally, the benefits and drawbacks of the main alternatives that the Administration could manage in case it intends to increase its involvement in this field

'Corpore sano in mens sana'. La dimensión moral de la sangre en la donación de sangre

La concepción moderna de la salud nos remite a la dualidad cartesiana según la cual el ser humano es cuerpo y alma. En la donación de sangre esta división parece claramente marcada, la encarnación es un proceso de civilización, en la donación de sangre el altruismo es la base moral que sustenta esa encarnación. El cuerpo de la persona donante se considera sustancialmente sangre, un mero continente que hace llegar este fluido a los bancos de sangre. El uso biomédico de la sangre donada no anula o excluye una dimensión o aspectos morales, es más, se hace necesario recurrir a una moral para garantizar el don (regalo) de la sangre; así el altruismo se concibe como un fenómeno fisiológico a través de una asimilación entre altruismo y disponibilidad extractiva.Modern conceptions of health separate body from soul in the familiar Cartesian dualism. In blood donation this separation is easy to identify: embodiment is a civilizing process, and altruism is the moral basis that supports it. The donor is treated as essentially a vessel of blood, a mere container which can be directed to discharge its contents into blood banks. The biomedical use of blood is not morally neutral; indeed, the donor's moral conscience is mobilised in order to get them to donate blood as a gift, or offering. By associating donors' altruism with their bodies' physical nature as a container from which blood can be extracted, altruism is treated as a physiological phenomenon

Artefactos. De vuelta a la Humanidad

Introduction to "Artefacts" monograph

Generalized optimization models of linguistic laws

Quantitative linguistics studies human language using statistical methods. It aims to build general theories from the statistical laws observed in a wide variety of languages. As part of the scientific method, these theories should be able to make novel predictions. This thesis is based on a family of models of human language. These models have shown to reproduce language laws, such as Zipf's law. They have also been used to make predictions, such as the biases present in child word learning. This family of models is based on the minimization of a cost function. The cost function is defined using a combination of information theoretic measures on a bipartite graph of associations between words (or, more generally, forms) and meanings (more generally, counterparts). It balances between the entropy of words and the mutual information of words and meanings. Entropy is a measure of surprisal, the cost of the speaker, and should be minimized. Mutual information is the amount of information obtained from a meaning while observing a word, the cost of the listener, and it should be maximized. The model is then optimized with a Markov Chain Monte Carlo method at zero temperature. This thesis is centered on two models belonging to this family, the "internal model" and the "external model". This thesis makes several contributions in relation to these models. The mathematical equations defining them are derived, including dynamic equations which reduce the computational complexity of the optimization process. In addition, several techniques are introduced which aim to reduce the significant problem of numerical error due to floating point arithmetic without compromising efficiency. Another contribution is the replication of results obtained by previous models based on this family which had been published originally with replicability issues. The models go through an optimization process. After this process the linguistic laws they can predict are examined, as well as to which degree they can be predicted. A key contribution is that these models are able predict the relationship between the age of a word and its frequency. This prediction is robust and appears in all cases with any combinations of parameters. The effects of several initial conditions in the optimization process is also studied. Finally, a tool has been developed and released as open source with the aim that others can easily replicate these results and investigate other properties of this family of models

Overdamped Deterministic Ratchets Driven By Multifrequency Forces

We investigate a dissipative, deterministic ratchet model in the overdamped regime driven by a {\it rectangular force}. Extensive numerical calculations are presented in a diagram depicting the drift velocity as a function of a wide range of the driving parameter values. We also present some theoretical considerations which explain some features of the mentioned diagram. In particular, we proof the existence of regions in the driving parameter space with bounded particle motion possessing zero current. Moreover, we present an explicit analytical expression for the drift velocity in the adiabatic limit.Comment: 12 pages, 6 figure