Vorticity cutoff in nonlinear photonic crystals

Using group theory arguments, we demonstrate that, unlike in homogeneous media, no symmetric vortices of arbitrary order can be generated in two-dimensional (2D) nonlinear systems possessing a discrete-point symmetry. The only condition needed is that the non-linearity term exclusively depends on the modulus of the field. In the particular case of 2D periodic systems, such as nonlinear photonic crystals or Bose-Einstein condensates in periodic potentials, it is shown that the realization of discrete symmetry forbids the existence of symmetric vortex solutions with vorticity higher than two.Comment: 4 pages, 5 figures; minor changes in address and reference

A topological charge selection rule for phase singularities

We present an study of the dynamics and decay pattern of phase singularities due to the action of a system with a discrete rotational symmetry of finite order. A topological charge conservation rule is identified. The role played by the underlying symmetry is emphasized. An effective model describing the short range dynamics of the vortex clusters has been designed. A method to engineer any desired configuration of clusters of phase singularities is proposed. Its flexibility to create and control clusters of vortices is discussed.Comment: 4 pages, 3 figure

Vortex transmutation

Using group theory arguments and numerical simulations, we demonstrate the possibility of changing the vorticity or topological charge of an individual vortex by means of the action of a system possessing a discrete rotational symmetry of finite order. We establish on theoretical grounds a "transmutation pass rule'' determining the conditions for this phenomenon to occur and numerically analize it in the context of two-dimensional optical lattices or, equivalently, in that of Bose-Einstein condensates in periodic potentials.Comment: 4 pages, 4 figure

A software system to teach economics to secondary school and first year engineering students

[EN] In this paper, we present a graphical user interface which has been devised to teach the basic concepts of economics in secondary schools and first year engineering courses. The application allows students to vary certain parameters and visually observe the effect on the supply and demand curves. The system has been developed in Matlab and employed in a secondary school in Spain. The first results are presented.[ES] Presentamos una interfaz gráfica desarrollada mediante Matlab diseñada para complementar el aprendizaje de los conceptos básicos de economía en Bachillerato, grado superior de ciclos formativos y cursos universitarios de introducción a la economía. La aplicación informática permite que los estudiantes varíen los parámetros de los que dependen las curvas de oferta y demanda, y visualicen el efecto sobre el equilibrio de mercado de estas variaciones. Se presentan los resultados de una primera experiencia de aplicación del programa en enseñanza secundaria en España.García-March, M.; Zacarés, M.; Isidro, J.; Monreal, L.; López-Javier, C.; Arevalillo-Herráez, M. (2009). A software system to teach economics to secondary school and first year engineering students. Modelling in Science Education and Learning. 2:105-113. doi:10.4995/msel.2009.3126SWORD105113

Teaching classical mechanics using an applied example: Modelling and Software

[EN] We present our experience in using a common mechanism in engineering, such as a slider-crank, to explain classical mechanics in physics and engineering degrees. We also present a graphical user interface that permits the student to visualize the results of different simulations varying the conditions of the numerical experiment.[ES] Presentamos la experiencia docente obtenida al utilizar un mecanismo muy común en ingeniería, como el mecanismo biela-manivela-deslizadera, como un ejemplo práctico en la asignatura ”mecánica clásica” que se imparte en los grados de física e ingeniería. También presentamos una interfaz gráfica que permite al estudiante visualizar los resultados obtenidos al simular en el ordenador el movimiento de dicho mecanismo variando las condiciones en las que se realiza el experimento numérico.García-March, M.; Isidro, J.; Zacarés, M.; Arevalillo, M.; González-Santander, J.; Monreal, L.; López-Javier, C. (2009). Teaching classical mechanics using an applied example: Modelling and Software. Modelling in Science Education and Learning. 2:35-43. doi:10.4995/msel.2009.3116SWORD35432H.Goldstein, Mecánica Clásica. Ed. Reverté, Barcelona, (1987). C.Lanczos, The variational principles of mechanics. Dover, New York, (1986).M.A. García-March, I. Orquín, P. Fernández de Córdoba, A. Montero, J. Urchueguía, M.H. Giménez y J.A. Monsoriu, Formulación Lagrangiana del Sistema Biela-Manivela- Deslizadera. Anales de Ingeniería Mecánica. Revista de la Asociación Espa-ola de Ingeniería Mecánica. 2 1077-1086 (2004)

Angular Pseudomomentum Theory for the Generalized Nonlinear Schr\"{o}dinger Equation in Discrete Rotational Symmetry Media

We develop a complete mathematical theory for the symmetrical solutions of the generalized nonlinear Schr\"odinger equation based on the new concept of angular pseudomomentum. We consider the symmetric solitons of a generalized nonlinear Schr\"odinger equation with a nonlinearity depending on the modulus of the field. We provide a rigorous proof of a set of mathematical results justifying that these solitons can be classified according to the irreducible representations of a discrete group. Then we extend this theory to non-stationary solutions and study the relationship between angular momentum and pseudomomentum. We illustrate these theoretical results with numerical examples. Finally, we explore the possibilities of the generalization of the previous framework to the quantum limit.Comment: 18 pages; submitted to Physica

Photonic Nambu-Goldstone bosons

We study numerically the spatial dynamics of light in periodic square lattices in the presence of a Kerr term, emphasizing the peculiarities stemming from the nonlinearity. We find that, under rather general circumstances, the phase pattern of the stable ground state depends on the character of the nonlinearity: the phase is spatially uniform if it is defocusing whereas in the focusing case, it presents a chessboard pattern, with a difference of π between neighboring sites. We show that the lowest-lying perturbative excitations can be described as perturbations of the phase and that finite-sized structures can act as tunable metawaveguides for them. The tuning is made by varying the intensity of the light that, because of the nonlinearity, affects the dynamics of the phase fluctuations. We interpret the results using methods of condensed-matter physics, based on an effective description of the optical system. This interpretation sheds light on the phenomena, facilitating the understanding of individual systems and leading to a framework for relating different problems with the same symmetry. In this context, we show that the perturbative excitations of the phase are Nambu-Goldstone bosons of a spontaneously broken U(1) symmetry

Fracturas de radio distal. ¿Progresa el desplazamiento entre la segunda y la sexta semana?.

Las fracturas de radio distal son las más frecuentes en nuestra especialidad. El tratamiento conservador con inmovilización, basado en una serie de parámetros radiológicos, sigue siendo el más utilizado hoy en día. El objetivo de nuestro estudio ha sido evaluar el desplazamiento secundario de estas fracturas entre la segunda y sexta semana de evolución. Para ello hemos evaluado las fracturas de radio distal tratadas de forma conservadora en nuestro Servicio, durante el año 2016. De un total de 53 fracturas de muñeca tratadas de forma conservadora, un 49% de los casos presentó algún tipo de desplazamiento, si bien la mayor parte de estos tuvieron lugar antes de la segunda semana. Nuestros resultados fueron similares a los revisados en la literatura, en cuanto a datos demográficos y tasa de desplazamiento. Por lo que recomendamos intercalar algunos controles radiográficos semanales en aquellas fracturas que presenten desde el inicio algún parámetro de inestabilidad

Estudio de las lesiones en el judo

Judo is a martial art whose origins come from jujutsu, created in 1882 by the master Jigoro Kano, who proposed a method that was based on techniques that could be applied in real combat, as well as practiced with the partner without risk of injury .The objective of the present study is to assess the prevalence, type and distribution of the injuries suffered. Check whether sex or sports performance influences the appearance of injuries, determine which technique intervenes more frequently, assess whether they occur mostly in training or competition, and analyze how they act.This is a descriptive crosssectional observational study, in which four clubs were asked to participate, in which they had to answer an anonymous survey.Regarding the results, a total of 652 injuries were registered, in 63 men and 38 women. The most commonly injured body regions were the upper limbs 254 (38.95 %%). Contusions and sprains were the most frequent injuries and the most frequently associated technique was Seoi Nage. The number of injuries was higher during the competition if we take into account time. Most of the injuries (74.1%) were of slight characteristics, with a sports rest of less than a week and only 38.95% forced the judoka to interrupt the sport.After the study carried out, we can conclude that the results obtained are comparable to the bibliography, confirming the stated objective

Effect of the Mediterranean diet supplemented with nicotinamide riboside and pterostilbene and/or coconut oil on anthropometric variables in amyotrophic lateral sclerosis. A pilot study

Amyotrophic Lateral Sclerosis (ALS) is a chronic and progressive neurodegenerative disease that causes the death of motor neurons and alters patients’ body composition. Supplementation with the antioxidants nicotinamide riboside (NR) and pterostilbene (PTER) can combat associated oxidative stress. Additionally, coconut oil is an alternative energy substrate that can address mitochondrial dysfunction. The aim of the present study is to assess the impact of a Mediterranean Diet supplemented with NR and PTER and/or with coconut oil on the anthropometric variables of patients with ALS. A prospective, mixed, randomized, analytical and experimental pilot study in humans was performed through a clinical trial (registered with ClinicalTrials.gov under number NCT03489200) with pre- and post-intervention assessments. The sample was made up of 40 subjects categorized into four study groups (Control, Antioxidants, Coconut oil, and Antioxidants + Coconut oil). Pre- and post-intervention anthropometric assessments were carried out to determine the following data: weight, percentage of fat and muscle mass, skinfolds, body perimeters, Body Mass Index (BMI), Waste-to-Hip Index (WHI) and Waist-Height Ratio (WHR). Compared to the Control group, GAx significantly increased muscle mass percentage and decreased fat mass percentage, triceps, iliac crest, and abdominal skinfolds. GCoco significantly increased muscle mass percentage and decreased fat mass percentage, subscapular skinfolds, and abdominal skinfolds. GAx + coco significantly increased muscle mass percentage and decreased abdominal skinfolds. Therefore, our results suggest that the Mediterranean Diet supplemented with NR and PTER and the Mediterranean Diet supplemented with coconut oil (ketogenic diet) are the two nutritional interventions that have reported the greatest benefits, at anthropometric level