On the mechanism of branching in negative ionization fronts

We explain a mechanism for branching of a planar negative front. Branching occurs as the result of a balance between the destabilizing effect of impact ionization and the stabilizing effect of electron diffusion on ionization fronts. The dispersion relation for transversal perturbation is obtained analytically and reads: $s = |k|/[2 (1 + |k|)] - D |k|^2$, where $D$, which is assumed to be small, is the ratio between the electron diffusion coefficient and the intensity of the externally imposed electric field. We estimate the spacing $\lambda$ between streamers in a planar discharge and deduce a scaling law $\lambda \sim D^{1/3}$

Ionization fronts in negative corona discharges

In this paper we use a hydrodynamic minimal streamer model to study negative corona discharge. By reformulating the model in terms of a quantity called shielding factor, we deduce laws for the evolution in time of both the radius and the intensity of ionization fronts. We also compute the evolution of the front thickness under the conditions for which it diffuses due to the geometry of the problem and show its self-similar character.Comment: 4 pages, 4 figure

Revisión bibliográfica sobre la investigación en la formación inicial y continua del profesor de educación física (2000-2010)

En los últimos años, ha surgido un creciente interés por la formación del profesorado: tanto inicial, como permanente o continua. De ahí que este estudio tenga como objetivo comprobar qué y cuánto se está investigando en relación a la formación de profesionales en el ámbito de la Educación Física (en adelante EF). Para ello, hemos seleccionado tres de las revistas de EF de mayor impacto nacional para posteriormente realizar una revisión de las mismas. Tras esto se realizó una clasificación de los artículos encontrados y un posterior análisis cuantitativo.Los resultados obtenidos son bastante elocuentes ya que la producción científica en materia de formación del profesorado es bastante escasa aunque cabe destacar, que de aquellas publicaciones encontradas sobre formación del profesorado, la amplia mayoría tratan la formación inicial y permanente o continua.In the last few years, an increasing interest on the education of the faculty has appeared: initial, as well as permanent or continuous. Thus, this study has as aim to check what, and how much subjects related to the education of professionals within Physical Education’s field (PE), is been investigated. Therefore, we have selected three of the magazines of PE with the greater national impact, to subsequently carry out a review of them. Afterwards, a classification of the articles found was made, and also a quantitative analysis. The obtained results are quite eloquent, since the scientific production in the area of teacher training is rather scarce; but it must be highlight that out of those publications found about the education of the faculty, the vast majority deal with the initial and permanent or continuous education

Stability of negative ionization fronts: regularization by electric screening?

We recently have proposed that a reduced interfacial model for streamer propagation is able to explain spontaneous branching. Such models require regularization. In the present paper we investigate how transversal Fourier modes of a planar ionization front are regularized by the electric screening length. For a fixed value of the electric field ahead of the front we calculate the dispersion relation numerically. These results guide the derivation of analytical asymptotes for arbitrary fields: for small wave-vector k, the growth rate s(k) grows linearly with k, for large k, it saturates at some positive plateau value. We give a physical interpretation of these results.Comment: 11 pages, 2 figure

Power laws and self-similar behavior in negative ionization fronts

We study anode-directed ionization fronts in curved geometries. When the magnetic effects can be neglected, an electric shielding factor determines the behavior of the electric field and the charged particle densities. From a minimal streamer model, a Burgers type equation which governs the dynamics of the electric shielding factor is obtained. A Lagrangian formulation is then derived to analyze the ionization fronts. Power laws for the velocity and the amplitude of streamer fronts are observed numerically and calculated analytically by using the shielding factor formulation. The phenomenon of geometrical diffusion is explained and clarified, and a universal self-similar asymptotic behavior is derived.Comment: 25 pages, 9 figure

Endophytic Microbes Are Tools to Increase Tolerance in Jasione Plants Against Arsenic Stress

Seed microbiota is becoming an emergent area of research. Host plant microbial diversity is increasingly well described, yet relatively little is known about the stressors driving plant endomicrobiota at the metaorganism level. The present work examines the role of horizontal and vertical transmission of bacterial microbiota in response to abiotic stress generated by arsenic. Horizontal transmission is achieved by bioaugmentation with the endophyte Rhodococcus rhodochrous, while vertical transmission comes via maternal inheritance from seeds. To achieve this goal, all experiments were conducted with two Jasione species. J. montana is tolerant to arsenic (As), whereas J. sessiliflora, being phylogenetically close to J. montana, was not previously described as As tolerant. The Jasione core bacterial endophytes are composed of genera Pseudomonas, Ralstonia, Undibacterium, Cutibacterium, and Kocuria and family Comamanadaceae across different environmental conditions. All these operational taxonomic units (OTUs) coexisted from seeds to the development of the seedling, independently of As stress, or bioaugmentation treatment and Jasione species. R. rhodochrous colonized efficiently both species, driving the endomicrobiota structure of Jasione with a stronger effect than As stress. Despite the fact that most of the OTUs identified inside Jasione seeds and seedlings belonged to rare microbiota, they represent a large bacterial reservoir offering important physiological and ecological traits to the host. Jasione traits co-regulated with R. rhodochrous, and the associated microbiota improved the host response to As stress. NGS-Illumina tools provided further knowledge about the ecological and functional roles of plant endophytes.This work has been supported by the Research grant from Universidad Rey Juan Carlos (AYUDA PUENTE 2019-DRIADES Project). IM-R gratefully acknowledges PEJD-2019-PRE/AMB-16306 from the Madrid Community program. Funding support was also provided by USDA-NIFA Multistate Project W4147 and the New Jersey Agricultural Experiment Station.N

Diferencias de sexo en la imagen corporal de los adolescentes de Huelva atendiendo a su índice de masa corporal

The main objective of this study is to check the differences in the perception of the body image (hereinafter IC) of the adolescents of Huelva according to their body mass index (hereinafter BMI). The sample consisted of 226 students, aged between 12 and 18 years (M= 13.94; DT= 1.41). The distribution by sex was 54.9% of boys (n=124) and 45.1% of girls (n=102). The instruments used to evaluate the different components of the CI were: 1) To evaluate the perceptual component, the global body estimation method of Gardner, Stark, Jackson and Friedman (1999) was used, adapted to Spanish by Rodríguez, Beato, Rodríguez and Martínez (2003). 2) To evaluate the subjective component, the Eating Disorders Inventory subscale of body dissatisfaction by Garner, Polivy and Olmstead (1983), adapted to the Spanish population by Garner (1998), was used. 3) The Body Image Avoidance Questionnaire (BIAQ) by Rosen, Salzberg, Srebnik and Went (1991) was used to evaluate the behavioral component. As the BMI increases, so does the degree of dissatisfaction, the obsession with thinness, the BIAQ base score, and food restriction in both boys and girls. Also, as the BMI increases, boys' bulimia decreases and girls' tendency to weigh and groom themselves increases. More than half of boys and girls, regardless of BMI category, are dissatisfied with their desire to lose weight.El objetivo principal de este estudio es comprobar las diferencias en la percepción de la imagen corporal (en adelante IC) de los adolescentes de Huelva atendiendo a su índice de masa corporal (en adelante IMC). La muestra estuvo compuesta por 226 estudiantes, con edades comprendidas entre 12 y 18 años (M= 13,94; DT= 1,41). La distribución por sexo fue de 54,9% de chicos (n= 124) y 45,1% de chicas (n= 102). Los instrumentos que se utilizaron para evaluar los diferentes componentes de la IC fueron: 1) Para evaluar el componente perceptual se utilizó el método de estimación corporal global de Gardner, Stark, Jackson y Friedman (1999), adaptado al español por Rodríguez, Beato, Rodríguez y Martínez (2003). 2) Para evaluar el componente subjetivo se utilizó la subescala de insatisfacción corporal del Eating Disorders Inventory de Garner, Polivy y Olmstead (1983), adaptado a la población española por Garner (1998). 3) Para evaluar el componente conductual se utilizó el Body Image Avoidance Questionnaire (BIAQ), de Rosen, Salzberg, Srebnik y Went (1991). A medida que aumenta el IMC aumenta el grado de insatisfacción, la obsesión por la delgadez, la puntuación total del BIAQ y la restricción de comida tanto en chicos como en chicas. Asimismo, a medida que aumenta el IMC desciende la bulimia de los chicos y aumenta la tendencia a pesarse y acicalarse de las chicas. Más de la mitad de chicos y chicas independientemente de la categoría del IMC presentan insatisfacción corporal con el deseo de perder peso

Niveles de personalidad, inteligencia emocional y actividad física en alumnos de primero de Grado de Ciencias de la Actividad Física y del Deporte

Los objetivos del presente trabajo son comprobar la posible relación entre la personalidad, la inteligencia emocional y el nivel de actividad física. La muestra utilizada estaba compuesta por alumnos del Grado de Ciencias de la Actividad Física y el Deporte (CCAFD) de la Facultad de Educación de la Universidad de Huelva. Para medir la personalidad se utilizó el cuestionario NEO-PI-R y para la inteligencia emocional dos cuestionarios: el TMMS-24 y el TEIQue. Por último, para medir el nivel de actividad física se utilizó el Compendium de actividad física de Ainsworth et al. (2011) y el cuestionario Ipad. El estudio esta en proceso de obtención de resultadosThe objectives of this work are to verify the possible relationship between personality, emotional intelligence and the level of physical activity. The sample used was composed of students of the Degree in Sciences of Physical Activity and Sport (CCAFD) of the Faculty of Education of the University of Huelva. To measure personality, the NEO-PI-R questionnaire was used and for emotional intelligence two questionnaires were used: the TMMS-24 and the TEIQue. Finally, to measure the level of physical activity we used the Physical Activity Compendium of Ainsworth et al. (2011) and the Ipad questionnaire. The study is in the process of obtaining results