Birth, death and diffusion of interacting particles

Individual-based models of chemical or biological dynamics usually consider individual entities diffusing in space and performing a birth-death type dynamics. In this work we study the properties of a model in this class where the birth dynamics is mediated by the local, within a given distance, density of particles. Groups of individuals are formed in the system and in this paper we concentrate on the study of the properties of these clusters (lifetime, size, and collective diffusion). In particular, in the limit of the interaction distance approaching the system size, a unique cluster appears which helps to understand and characterize the clustering dynamics of the model.Comment: 15 pages, 6 figures, Iop style. To appear in Journal of Physics A: Condensed matte

Modeling dust emission in PN IC 418

We investigated the infrared (IR) dust emission from PN IC 418, using a detailed model controlled by a previous determination of the stellar properties and the characteristics of the photoionized nebula, keeping as free parameters the dust types, amounts and distributions relative to the distance of the central star. The model includes the ionized region and the neutral region beyond the recombination front (Photodissociation region, or PDR), where the [OI] and [CII] IR lines are formed. We succeeded in reproducing the observed infrared emission from 2 to 200~\mm. The global energy budget is fitted by summing up contributions from big grains of amorphous carbon located in the neutral region and small graphite grains located in the ionized region (closer to the central star). Two emission features seen at 11.5 and 30~\mm are also reproduced by assuming them to be due to silicon carbide (SiC) and magnesium and iron sulfides (Mg$_x$Fe$_{1-x}$S), respectively. For this, we needed to consider ellipsoidal shapes for the grains to reproduce the wavelength distribution of the features. Some elements are depleted in the gaseous phase: Mg, Si, and S have sub-solar abundances (-0.5 dex below solar by mass), while the abundance of C+N+O+Ne by mass is close to solar. Adding the abundances of the elements present in the dusty and gaseous forms leads to values closer to but not higher than solar, confirming that the identification of the feature carriers is plausible. Iron is strongly depleted (3 dex below solar) and the small amount present in dust in our model is far from being enough to recover the solar value. A remaining feature is found as a residue of the fitting process, between 12 and 25~\mm, for which we do not have identification.Comment: Accepted for publication in Astronomy & Astrophysics. V2: adding reference

On the frequency dependence of p-mode frequency shifts induced by magnetic activity in Kepler solar-like stars

The variations of the frequencies of the low-degree acoustic oscillations in the Sun induced by magnetic activity show a dependence with radial order. The frequency shifts are observed to increase towards higher-order modes to reach a maximum of about 0.8 muHz over the 11-yr solar cycle. A comparable frequency dependence is also measured in two other main-sequence solar-like stars, the F-star HD49933, and the young 1-Gyr-old solar analog KIC10644253, although with different amplitudes of the shifts of about 2 muHz and 0.5 muHz respectively. Our objective here is to extend this analysis to stars with different masses, metallicities, and evolutionary stages. From an initial set of 87 Kepler solar-like oscillating stars with already known individual p-mode frequencies, we identify five stars showing frequency shifts that can be considered reliable using selection criteria based on Monte Carlo simulations and on the photospheric magnetic activity proxy Sph. The frequency dependence of the frequency shifts of four of these stars could be measured for the l=0 and l=1 modes individually. Given the quality of the data, the results could indicate that a different physical source of perturbation than in the Sun is dominating in this sample of solar-like stars.Comment: Accepted for publication in A&

Análisis temporal del combate de judo en competición

This study seeks to analyze the temporal structure of combat in judo competition. Therefore, 14 finals of men¿s and women¿s under-23 Spanish Championship were studied. Variables such as time of total work, total and mean rest time, time of total and mean work on the floor, time of total and mean work while standing, the total and mean number of work and rest sequences were analyzed. Among the results that can be highlighted include the significant differences among men and women in mean rest time, and the mean time of standing judo work. This type of analysis tries to contribute different aspects in planning and organizing the practice of judo in a more specific wayEl presente trabajo pretende analizar la estructura temporal del combate de judo de competición. Para ello, se consideraron 14 finales del Campeonato de España sub¿23 tanto en categoría masculina como femenina. En ellas se analizaron variables como tiempo de trabajo total, tiempo de descanso total y medio, tiempo de trabajo total y medio en suelo, tiempo de trabajo total y medio en pie, y el número total y medio de secuencias de trabajo y descanso. Entre los resultados destacan las diferencias significativas entre sexos del tiempo medio de pausa, y el tiempo medio de trabajo de judo pie. Este tipo de análisis intentarán aportar diferentes aspectos para planificar y organizar el entrenamiento de judo de una forma más específic

Spatial clustering of interacting bugs: Levy flights versus Gaussian jumps

A biological competition model where the individuals of the same species perform a two-dimensional Markovian continuous-time random walk and undergo reproduction and death is studied. The competition is introduced through the assumption that the reproduction rate depends on the crowding in the neighborhood. The spatial dynamics corresponds either to normal diffusion characterized by Gaussian jumps or to superdiffusion characterized by L\'evy flights. It is observed that in both cases periodic patterns occur for appropriate parameters of the model, indicating that the general macroscopic collective behavior of the system is more strongly influenced by the competition for the resources than by the type of spatial dynamics. However, some differences arise that are discussed.Comment: This version incorporates in the text the correction published as an Erratum in Europhysics Letters (EPL) 95, 69902 (2011) [doi: 10.1209/0295-5075/95/69902

Clavo gamma en el tratamiento de las fracturas del macizo trocantérico: estudio comparativo entre el Clavo Gamma Trocantérico y el Gamma 3

El clavo Gamma es una técnica bien establecida en el tratamiento de las fracturas del macizo trocantéreo. Hemos realizado un estudio prospectivo en 40 pacientes para comparar dos tipos de clavos. En 20 se utilizó el clavo gamma trocantérico y en 20 un nuevo dispositivo llamado Gamma3 fabricado en titanio y con modificaciones en el diseño para permitir una menor incisión y mayor faciliad en su implante. De todos los parámetros estudiados tanto intra como postoperatorios sólo hemos encontrado diferencias en cuanto al tiempo del acto quirúrgico y al tamaño de la incisión, encontrando menor tiempo y menor tamaño de la incisión en el clavo gamma 3. No encontramos diferencias en cuanto a las complicaciones técnicas, ni en cuanto al dolor, tiempo transcurrido hasta la consolidación o grado de independencia obtenido. Consideramos el clavo Gamma3 como una técnica valiosa que disminuye el tiempo de cirugía y el traumatismo de las partes blandas.The nail Gamma is a well-established technique in the treatment of the trochanteric fractures. We have made a prospective study in 40 patients for compare two Gamma nail types. In 20 we use the Trochanteric Gamma Nail and in 20 a new device called Gamma 3 manufactured in titanium and with modifications in the design to permit a less incision and most facilities in his implantation. Of all of the parameters studied both intra and postoperative we have found differences in the time of surgical act and in the size of the incision, finding less time and less size of the approach in the gamma 3 nail. We do not find differences about technical complications, neither as to the pain, time to the consolidation or independence grade obtained. We regard to the nail Gamma 3 as a valuable technique that decreases the time of surgery and the traumatism of the soft tissues