InAs/InP single quantum wire formation and emission at 1.5 microns

Isolated InAs/InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5 microns. Additional sharp features are related to monolayer fluctuations of the two dimensional InAs layer present during the early stages of the quantum wire self-assembling process.Comment: 4 pages and 3 figures submitted to Applied Physics Letter

Abordaje de un mal rendimiento académico en estudiante universitaria: Estudio de caso único

El mal rendimiento académico es un problema ampliamente extendido entre la población universitaria y uno de los problemas más habituales junto a aquellos relacionados con la ansiedad y las técnicas de estudio. En el Gabinete de Psicología de la Universidad de Jaén tratamos a una estudiante cuyo motivo de consulta es la ansiedad ante los exámenes y el mal rendimiento. En relación a ello, se le aplican diferentes pruebas de evaluación: autorresgistro de hábitos de estudio diseñado desde este Gabinete, Inventario de Ansiedad Rasgo-Estado - STAI- (Spielberger, Gorsuch y Lushene, 1981), Adaptación española del Inventario para la Depresión de Beck—II (BDI-II) (Sanz y cols., 2005) y Cuestionario de Ansiedad ante los exámenes (Valero, 1997). Tras la corrección de dichas pruebas se elabora una intervención con el objetivo de mejorar los hábitos de estudio y, como actividad complementaria, disminuir los niveles de ansiedad. Las actividades que se desarrollan a lo largo de las sesiones son, en primer lugar, el aprendizaje de técnicas de respiración y relajación. Posteriormente, sesiones dedicadas a la adquisición de técnicas de estudio. Por un lado el aprendizaje de la gestión del tiempo, planificación y priorización de las actividades diarias académicas; por otra parte, el aprendizaje de tareas de síntesis de la información como son el subrayado o la elaboración de esquemas que faciliten la comprensión de la materia y el almacenamiento de tal información para su ulterior recuperación en situación de examen. Durante el período de intervención, la usuaria del servicio psicológico del gabinete sigue algunas de las recomendaciones por lo que consigue sutiles logros en planificación de tareas académicas aunque continúa mostrando dificultades en comprensión y síntesis de la información dando lugar a pobres resultados. Se recomienda a la usuaria continuar el entrenamiento en comprensión, tarea que excede de la competencia de este Gabinete de Psicología por lo que se da por concluida la intervención

Generation of rotationally dominated galaxies by mergers of pressure-supported progenitors

Through the analysis of a set of numerical simulations of major mergers between initially non-rotating, pressure supported progenitor galaxies with a range of central mass concentrations, we have shown that: (1) it is possible to generate elliptical-like galaxies, with v/sigma > 1 outside one effective radius, as a result of the conversion of orbital- into internal-angular momentum; (2) the outer regions acquire part of the angular momentum first; (3) both the baryonic and the dark matter components of the remnant galaxy acquire part of the angular momentum, the relative fractions depend on the initial concentration of the merging galaxies. For this conversion to occur the initial baryonic component must be sufficiently dense and/or the encounter should take place on a orbit with high angular momentum. Systems with these hybrid properties have been recently observed through a combination of stellar absorption lines and planetary nebulae for kinematic studies of early-type galaxies. Our results are in qualitative agreement with such observations and demonstrate that even mergers composed of non-rotating, pressure-supported progenitor galaxies can produce early-type galaxies with significant rotation at large radii.Comment: 5 pages, 6 figures, 2 tables. Accepted for publication in A&A Letter

Operating Speed models for heavy vehicles on tangents of Spanish two-lane rural roads

Road safety is one of the most important public health concern in our society. In Spain, the most of the traffic accidents involving a heavy vehicle occur on two-lane rural roads. Current consistency models only rely on the analysis of the operating speed profile for passenger cars due to the few speed models available for heavy vehicles. Therefore, the main objective of this research was to analyze and model the free flow speed developed by heavy vehicles on tangents of two-lane rural roads. Thus, this research presents new speed models for estimating heavy vehicle speeds on tangents of two-lane rural roads. To do this, truck speeds were collected by means of Global Positioning System tracking devices, on 49 tangents sections that were identified from 12 road sections. Two different patterns were detected, which were associated with loaded and unloaded trucks. The combined effect of geometric and operational variables was analyzed. As a result, the most influential variables on loaded truck speeds were the speed of the preceding horizontal curve and the grade of the tangent, whereas unloaded truck speeds were significantly influenced by the length of the tangent and the speed of the preceding horizontal curve. Finally, several regression models were calibrated to predict the 85th and 15th percentile speeds for both loaded and unloaded trucks

Recent Approaches for the Manufacturing of Polymeric Cranial Prostheses by Incremental Sheet Forming

This paper presents recent research experiences developed with the aim of manufacturing cranial prostheses in polymeric sheet using Incremental Sheet Forming (ISF) technologies. With this purpose, different approaches have been carried out in Single-Point Incremental Forming (SPIF) and Two-Point Incremental Forming (TPIF) in order to produce customized cranial implants using different polymeric materials. In this context, this research work provides a methodology to design and manufacture polymer customized cranial prostheses using the ISF technologies starting from a patient’s computerized tomography (CT). The results demonstrate the potential of manufacturing polymeric cranial prostheses by ISF in terms of the high formability achievable and show the appropriate geometrical accuracy at affordable manufacturing costs provided by these processes.Ministerio de Economía y Competitividad DPI2015-64047-

On the ubiquity of trivial torsion on elliptic curves

The purpose of this paper is to give a "down--to--earth" proof of the well--known fact that a randomly chosen elliptic curve over the rationals is most likely to have trivial torsion

Introducción de demostraciones prácticas para la enseñanza de la física en las aulas universitarias

An analysis about utility, characteristics and structure of the so called «practical demonstrations» is presented in order to introduce a dynamic element in the classroom. Although in apparent contradiction with didactic modern trends that proclaim «what students are able to do by themselves, teachers should not do "practical demonstrations" should be placed in an active methodological approach as a complement in the exposition of the contents, getting some importance concerning student passivity, lack of didactic facilities and high number of students per classroom

The structure of the class of maximum tsallis-havrda-chavat entropy copulas

A maximum entropy copula is the copula associated with the joint distribution, with prescribed marginal distributions on [0, 1], which maximizes the Tsallis-Havrda-Chavat entropy with q = 2. We find necessary and sufficient conditions for each maximum entropy copula to be a copula in the class introduced in Rodriguez-Lallena and Ubeda-Flores (2004), and we also show that each copula in that class is a maximum entropy copula.A maximum entropy copula is the copula associated with the joint distribution, with prescribed marginal distributions on [0, 1], which maximizes the Tsallis-Havrda-Chavat entropy with q = 2. We find necessary and sufficient conditions for each maximum entropy copula to be a copula in the class introduced in Rodriguez-Lallena and Ubeda-Flores (2004), and we also show that each copula in that class is a maximum entropy copula.18