Statistical Behavior Of Domain Systems

We study the statistical behavior of two out of equilibrium systems. The first one is a quasi one-dimensional gas with two species of particles under the action of an external field which drives each species in opposite directions. The second one is a one-dimensional spin system with nearest neighbor interactions also under the influence of an external driving force. Both systems show a dynamical scaling with domain formation. The statistical behavior of these domains is compared with models based on the coalescing random walk and the interacting random walk. We find that the scaling domain size distribution of the gas and the spin systems is well fitted by the Wigner surmise, which lead us to explore a possible connection between these systems and the circular orthogonal ensemble of random matrices. However, the study of the correlation function of the domain edges, show that the statistical behavior of the domains in both gas and spin systems, is not completely well described by circular orthogonal ensemble, nor it is by other models proposed such as the coalescing random walk and the interacting random walk. Nevertheless, we find that a simple model of independent intervals describe more closely the statistical behavior of the domains formed in these systems.Comment: v2: minor change

Sensores: De los biosensores a la nariz electrónica

The recent advances in sensor devices have allowed the developing of new applications in many technological fields. This review describes the current state-of-the-art of this sensor technology, placing special emphasis on the food applications. The design, technology and sensing mechanism of each type of sensor are analysed. A description of the main characteristics of the electronic nose and electronic tongue (taste sensors) is also given. Finally, the applications of some statistical procedures in sensor systems are described briefly.Los recientes avances en los sistemas de sensores han permitido el desarrollo de nuevas aplicaciones en muchos campos tecnológicos. Este artículo de revisión describe el estado actual de esta nueva tecnología, con especial énfasis en las aplicaciones alimentarias. El diseño, la tecnología y el mecanismo sensorial de cada tipo de sensor son analizados en el artículo. También se describen las principales características de la nariz y la lengua electrónica (sensores de sabor). Finalmente, se describe brevemente el uso de algunos procedimientos estadísticos en sistemas de sensores.Peer reviewe

Three-frequency resonances in dynamical systems

We investigate numerically and experimentally dynamical systems having three interacting frequencies: a discrete mapping (a circle map), an exactly solvable model (a system of coupled ordinary differential equations), and an experimental device (an electronic oscillator). We compare the hierarchies of three-frequency resonances we find in each of these systems. All three show similar qualitative behaviour, suggesting the existence of generic features in the parameter-space organization of three-frequency resonances.Comment: See home page http://lec.ugr.es/~julya

Delay of Gratification in Costa Rican Preschoolers: Effect of Trust in the Experimenter and the Socio-Economic Status: Postergación de la gratificación en preescolares costarricenses: efecto de la confianza en el experimentador y el estatus socioeconómico

This study analyzed the effect of confidence in the experimenter on the performance of a group of Costa Rican preschoolers on self-control. In addition, the effect of socioeconomic status on performance on the marshmallow task was analyzed by a comparison of children from both different schools (public vs private) and different socioeconomic contexts within each school. The sample of participants was 67 children (26 girls, M of age = 63 months, SD = 6.03). Effects were found, both of the confidence in the experimenter and of the socio-economic status in self-control. The implications of this study for future studies with children and families are discussed.Este estudio analizó el efecto de la confianza en la persona experimentadora sobre el desempeño de un grupo de niñas(os) preescolares costarricenses en el autocontrol. Adicionalmente, se analizó el efecto del estatus socioeconómico en el desempeño en la tarea de la golosina por medio de una comparación de niños provenientes tanto de diferentes escuelas (pública vs privada) como de distintos contextos socioeconómicos al interior de cada escuela. La muestra de participantes fue de 67 niños(as) (26 niñas, M de edad = 63 meses, D.T. = 6.03). Se encontraron efectos, tanto de la confianza en la persona experimentadora, como del contexto socioeconómico en el autocontrol. Se discuten las implicaciones de este estudio para futuros trabajos con niñas y niños, y familias

Non-power positional number representation systems, bijective numeration, and the Mesoamerican discovery of zero

Pre-Columbian Mesoamerica was a fertile crescent for the development of number systems. A form of vigesimal system seems to have been present from the first Olmec civilization on wards, to which succeeding peoples made contributions. We discuss the Maya use of the representational redundancy present in their Long Count calendar, a non-power positional number representation system with multipliers 1, 20, 18 x 20, ..., 18 x 20(n). We demonstrate that the Mesoamericans did not need to invent positional notation and discover zero at the same time because they were not afraid of using a number system in which the same number can be written indifferent ways. A Long Count number system with digits from 0 to 20 is seen later to pass to one using digits 0 to 19, which leads us to propose that even earlier there may have been an initial zeroless bijective numeration system whose digits ran from 1 to 20. Mesoamerica was able to make this conceptual leap to the concept of a cardinal zero to perform arithmetic owing to a familiarity with multiple and redundant number representation systems

Subharmonic stochastic synchronization and resonance in neuronal systems.

4 pages, 4 figures.-- PACS: 87.19.La, 05.40.Ca, 87.10.+eWe study the response of a model neuron, driven simultaneously by noise and at least two weak periodic signals. We focus on signals with frequencies components kf0,(k+1)f0,…(k+n)f0 with k>1. The neuron’s output is a sequence of pulses spaced at random interpulse intervals. We find an optimum input noise intensity for which the output pulses are spaced ∼1/f0, i.e., there is a stochastic resonance (SR) at a frequency missing in the input. Even higher noise intensities uncover additional, but weaker, resonances at frequencies present in the input. This is a different form of SR whereby the most robust resonance is the one enhancing a frequency, which is absent in the input, and which is not possible to recover via any linear processing. This can be important in understanding sensory systems including the neuronal mechanism for perception of complex tones.This work was supported by Spanish Ministerio de Ciencia y Technologia, Proyecto CONOCE contract BFM2000-1106, and by NIH-HL62543.Peer reviewe

Mean-Field Approximation for Spacing Distribution Functions in Classical Systems

We propose a mean-field method to calculate approximately the spacing distribution functions $p^{(n)}(s)$ in 1D classical many-particle systems. We compare our method with two other commonly used methods, the independent interval approximation (IIA) and the extended Wigner surmise (EWS). In our mean-field approach, $p^{(n)}(s)$ is calculated from a set Langevin equations which are decoupled by using a mean-field approximation. We found that in spite of its simplicity, the mean-field approximation provides good results in several systems. We offer many examples in which the three methods mentioned previously give a reasonable description of the statistical behavior of the system. The physical interpretation of each method is also discussed