A method to construct refracting profiles

We propose an original method for determining suitable refracting profiles between two media to solve two related problems: to produce a given wave front from a single point source after refraction at the refracting profile, and to focus a given wave front in a fixed point. These profiles are obtained as envelopes of specific families of Cartesian ovals. We study the singularities of these profiles and give a method to construct them from the data of the associated caustic.Comment: 12 pages, 5 figure

Solving the brachistochrone and other variational problems with soap films

We show a method to solve the problem of the brachistochrone as well as other variational problems with the help of the soap films that are formed between two suitable surfaces. We also show the interesting connection between some variational problems of dynamics, statics, optics, and elasticity.Comment: 16 pages, 11 figures. This article, except for a small correction, has been submitted to the American Journal of Physic

The Rich Globular Cluster System of Abell 1689 and the Radial Dependence of the Globular Cluster Formation Efficiency

We study the rich globular cluster (GC) system in the center of the massive cluster of galaxies Abell 1689 (z=0.18), one of the most powerful gravitational lenses known. With 28 HST/ACS orbits in the F814W bandpass, we reach magnitude I_814=29 with >90% completeness and sample the brightest ~5% of the GC system. Assuming the well-known Gaussian form of the GC luminosity function (GCLF), we estimate a total population of N(GC_total) = 162,850 GCs within a projected radius of 400kpc. As many as half may comprise an intracluster component. Even with the sizable uncertainties, which mainly result from the uncertain GCLF parameters, this is by far the largest GC system studied to date. The specific frequency S_N is high, but not uncommon for central galaxies in massive clusters, rising from S_N~5 near the center to ~12 at large radii. Passive galaxy fading would increase S_N by ~20% at z=0. We construct the radial mass profiles of the GCs, stars, intracluster gas, and lensing-derived total mass, and we compare the mass fractions as a function of radius. The estimated mass in GCs, M(GC_total)=3.9x10^10 Msun, is comparable to ~80% of the total stellar mass of the Milky Way. The shape of the GC mass profile appears intermediate between those of the stellar light and total cluster mass. Despite the extreme nature of this system, the ratios of the GC mass to the baryonic and total masses, and thus the GC formation efficiency, are typical of those in other rich clusters when comparing at the same physical radii. The GC formation efficiency is not constant, but varies with radius, in a manner that appears similar for different clusters; we speculate on the reasons for this similarity in profile.Comment: 13 pages, 11 figures; accepted for publication in Ap

Seasonal abundance of oyster spat and four animal associates on an oyster reef in the James River, Virginia

Five species of invertebrates collected at bi-weekly to monthly intervals from an oyster reef in the James River, Virginia. between September 1984 and August 1985 exhibited similar patterns of fluctuation in abundance throughout most of the period. The species were: spat of the oyster Crassostrea virginica: two species that feed on oysters. the flatworm Stylochus ellipticus, and the gastropod Boonea impressa. as well as two others with no known direct trophic interactions with the oyster. the isopod Cassidinidea lunifrons and the nudibranch Doridella obscura. B. impressa was many times more abundant than S. ellipticus but because of the difference in feeding habits between the two species it is speculated that S. ellipticus has a greater harmful effect on oysters than its abundance would suggest. Densities of all species declined sharply between early October and early November; the decline was probably related to seasonal mortality associated with declining water temperatures. B. impressa and C. lunifrons were the most abundant species throughout most of the sampling period , but only oyster spat showed a definite high peak in recruitment in 1985. Failure of the data to show reproduction peaks for three of the other species was attributed to incomplete retention of smaller individuals in the 0.5 mm-mesh screen used: large variations in density did not permit clear definition of a peak in C. lunifrons. lt is recommended that studies of oysters on their reefs include other abundant noncommercial species to provide a stronger foundation for management of the resource than if only the oyster was studied

Análisis de la organización funcional en el fútbol

De manera tradicional, el estudio de la estrategia motriz (táctica) en el fútbol se ha venido realizando tomando como referencia de partida, la distribución espacial de los jugadores al inicio de cada parte de los encuentros y las denominadas "jugadas estratégicas" o "jugadas a balón parado". Este trabajo es una investigación sobre la estrategia motriz en el fútbol, la cual tiene como referente teórico a la Praxiología motriz. Sus objetivos son el estudio de la estrategia motriz (táctica), específicamente la organización funcional: usos de los subroles estratégico motores, de los equipos, en tanto que interacción motriz; considerando también las acciones con balón y su gestió

Reclamaciones de pacientes en el servicio de emergencia adultos de un hospital de tercer nivel de atención: Patient complaints in the adult emergency department of a tertiary referral hospital

Introduction: The critical condition of the patient who presents to an emergency department creates a need to provide timely, safe and warm care. Failing to meet these expectations causes patient dissatisfaction, reflected by complaints, which are mostly justified and lead to opportunities for improvement and corrective measures. Objective: To analyze complaints presented by patients and their relatives at the Adult Emergency Department of the Edgardo Rebagliati Martins National Hospital. Methods: Nonexperimental, descriptive, cross-sectional study. Our sample was comprised of 109 complaints between May and November 2019. We used a data collection sheet based on the information in the complaints book for health care services. Results: We identified 187 reasons for complaints. Our results show that direct relatives filed 47.7%; 43% involved Internal Medicine consultations. In the dimension “inadequate treatment by healthcare workers,” 13.9% of patients complained about impolite and rude treatment. In the dimension “delay in care”, 12.8% were discontent due to the lack of timely care. In the dimension “user disagreement with care or treatment received,” 10.2% were dissatisfied with the care they were provided. 60.6% of complaints were satisfactorily resolved within the period specified by current regulations. Conclusion: Most complaints were related to the direct care of the patient.Introducción: La condición crítica del paciente que acude a emergencia genera la necesidad de otorgar una atención oportuna, segura y cálida. No cubrir estas expectativas desencadena en la insatisfacción del paciente, reflejada mediante reclamaciones, las cuales en su mayoría resultan justificadas, generando oportunidades de mejora y medidas correctivas. Objetivo: Analizar las reclamaciones presentadas por el paciente y sus familiares en el servicio de emergencia adultos del Hospital Nacional Edgardo Rebagliati Martins. Métodos: Diseño no experimental, descriptivo, de corte transversal. La muestra estuvo conformada por 109 reclamaciones durante el periodo comprendido de mayo a noviembre 2019. Se utilizó una ficha de recolección de datos con la información del Libro de Reclamaciones en Salud. Resultados: Se identificaron 187 motivos de reclamaciones. Los resultados mostraron que 47,7% fueron presentadas por familiares directos y que 43% correspondieron al área de medicina interna. En la dimensión inadecuado trato por parte del personal asistencial, 13,9% de pacientes mostraron disconformidad frente al trato descortés y grosero; en la dimensión demora en la atención, 12,8% manifestaron encontrarse descontentos por la falta de atención oportuna y, en la dimensión desacuerdo del usuario con la atención o tratamiento recibido, 10,2% quedaron insatisfechos con la atención recibida. 60,6% de reclamaciones se resolvieron satisfactoriamente dentro del plazo exigido en la norma. Conclusión: La mayor cantidad de reclamaciones correspondieron al tipo prestacional, asociadas a la atención directa del paciente

Estudio y análisis de los sistemas de juego en fútbol

Se trata de una investigación de tipo deportiva, enmarcada dentro de la Praxiología Motriz, en la que hemos empleado una metodología observacional sistemática, activa no participante y directa. El instrumento de observación ha sido un formato de campo y un sistema de categorías. Un registro sistematizado, con un muestreo focal y un control de la fiabilidad del dato por concordancia consensuada e ínter observadores. Los datos obtenidos se tratarán teniendo en cuenta el doble criterio de ocurrencia y base (Anguera, M. T et Alt. 1993) son secuencias y tiempo base, en la que se anota los eventos y el orden de ocurrencia de los mismos. Y siendo las categorías mutuamente excluyentes y exhaustivas. La población está constituida por encuentros de fútbol español, de las categorías 2a A, 2a B y 3a. La muestra está constituida por 45 encuentros (15 de cada categoría) de fútbol de las categorías: 2a A, 2a B y 3a División (grupo canario) nacional masculina. Para este estudio preliminar tomaremos 6 partidos de 2ª División A en el que participan equipos canarios de dicha categorí