Rheological measurements of large particles in high shear rate flows

This paper presents experimental measurements of the rheological behavior of liquid-solid mixtures at moderate Stokes and Reynolds numbers. The experiments were performed in a coaxial rheometer that was designed to minimize the effects of secondary flows. By changing the shear rate, particle size, and liquid viscosity, the Reynolds numbers based on shear rate and particle diameter ranged from 20 to 800 (Stokes numbers from 3 to 90), which is higher than examined in earlier rheometric studies. Prior studies have suggested that as the shear rate is increased, particle-particle collisions also increase resulting in a shear stress that depends non-linearly on the shear rate. However, over the range of conditions that were examined in this study, the shear stress showed a linear dependence on the shear rate. Hence, the effective relative viscosity is independent of the Reynolds and Stokes numbers and a non-linear function of the solid fraction. The present work also includes a series of rough-wall experiments that show the relative effective viscosity is also independent of the shear rate and larger than in the smooth wall experiments. In addition, measurements were made of the near-wall particle velocities, which demonstrate the presence of slip at the wall for the smooth-walled experiments. The depletion layer thickness, a region next to the walls where the solid fraction decreases, was calculated based on these measurements. The relative effective viscosities in the current work are larger than found in low-Reynolds number suspension studies but are comparable with a few granular suspension studies from which the relative effective viscosities can be inferred

El aprendizaje de la matemática en alumnos con déficit de atención: una aplicación del aprendizaje mediado

Las dificultades de aprendizaje escolar tienden a ser identificadas cuando los niños ingresan a la escuela. Esto es porque en la escuela se centran en situaciones que pueden ser difíciles para el niño como leer, escribir, aprender Matemática, el escuchar, hablar y razonar. Los maestros y padres observan que el niño no está aprendiendo como se esperaba. Con la ayuda apropiada, los niños pueden aprender más fácil y exitosamente. Así, diseñar las estrategias necesarias para una evaluación de identificación de las habilidades y debilidades académicas, reflejará las necesidades que el niño requiere para la adquisición de las habilidades escolares. Frecuentemente todos tenemos la experiencia de que a veces no prestamos atención a las cosas que ocurren en nuestro alrededor, aun sabiendo que es necesario, por ejemplo concentrarnos en estudiar para un examen o que nos distraemos fácilmente porque oímos un ruido a nuestro alrededor. Entonces de forma continua, la mayoría de personas sufrimos algún fallo de atención, pero ¿cuándo podemos hablar realmente de un problema atencional? Según la pedagoga Gloria Martí un problema atencional se refiere a aquellos fallos en los mecanismos de funcionamiento de la atención que producen una falta de adaptación a las exigencias del ambiente. En el caso de los niños este problema de atención ocasiona dificultades de rendimiento escolar a pesar de tener un cociente intelectual normal. Observamos que un niño tiene problemas de atención cuando en las aulas manifiesta conductas de falta de atención como: oscilaciones continúas de la atención por presencia de distractores, cuando tiene un bajo rendimiento en pruebas o tareas que exigen fundamentalmente habilidades atencionales. Pero hay que tener cuidado porque si una disfunción atencional es la falta de adaptabilidad a las demandas del ambiente,esto puede ocurrir tanto por defecto como por exceso

Human vs. Computer Slot Car Racing using an Event and Frame-Based DAVIS Vision Sensor

This paper describes an open-source implementation of an event-based dynamic and active pixel vision sensor (DAVIS) for racing human vs. computer on a slot car track. The DAVIS is mounted in "eye-of-god" view. The DAVIS image frames are only used for setup and are subsequently turned off because they are not needed. The dynamic vision sensor (DVS) events are then used to track both the human and computer controlled cars. The precise control of throttle and braking afforded by the low latency of the sensor output enables consistent outperformance of human drivers at a laptop CPU load of <3% and update rate of 666Hz. The sparse output of the DVS event stream results in a data rate that is about 1000 times smaller than from a frame-based camera with the same resolution and update rate. The scaled average lap speed of the 1/64 scale cars is about 450km/h which is twice as fast as the fastest Formula 1 lap speed. A feedbackcontroller mode allows competitive racing by slowing the computer controlled car when it is ahead of the human. In tests of human vs. computer racing the computer still won more than 80% of the races.Unión Europea FP7-ICT-270324Unión Europea FP7-ICT-60095

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. In this work we use Swift data obtained after the long and bright 2011 and 2013 outbursts, as well as the short and faint 2015 outburst, to investigate the hypothesis that cooling of the accretion-heated neutron star crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that the X-ray light curves and measured neutron star surface temperatures are consistent with the expectations of the crust cooling paradigm. By using a thermal evolution code, we find that ~1.2-3.2 MeV/nucleon of shallow heat release describes the observational data well, depending on the assumed mass-accretion rate and temperature of the stellar core. We find no evidence for varying strengths of this shallow heating after different outbursts, but this could be due to limitations of the data. We argue that monitoring Aql X-1 for up to ~1 year after future outbursts can be a powerful tool to break model degeneracies and solve open questions about the magnitude, depth and origin of shallow heating in neutron star crusts.Comment: 14 pages, 5 figures, 3 tables, accepted to MNRA

Instabilities in Zakharov Equations for Laser Propagation in a Plasma

F.Linares, G.Ponce, J-C.Saut have proved that a non-fully dispersive Zakharov system arising in the study of Laser-plasma interaction, is locally well posed in the whole space, for fields vanishing at infinity. Here we show that in the periodic case, seen as a model for fields non-vanishing at infinity, the system develops strong instabilities of Hadamard's type, implying that the Cauchy problem is strongly ill-posed

Diagnostico genético prenatal y aborto. Dos cuestiones de eugenesia y discriminación

Los avances en genética seguidos de las nuevas tecnologías en la detección temprana de afecciones genéticas conllevan dilemas bioéticos sobre el uso adecuado de estas técnicas, la información que se le da a la mujer embarazada y la decisión que ella tomará al recibirla. Detectar a tiempo anomalías genéticas permite, en algunas ocasiones, el inicio de un tratamiento adecuado que permita que el niño por nacer no desarrolle una enfermedad discapacitante, como el caso de la fenilcetonuria, o una intervención quirúrgica para un feto con espina bífida, pero en caso que no se tenga ningún tratamiento disponible el aborto sigue siendo la última alternativa. Aunque para muchos cualquier tipo de aborto es eugenésico, esto es busca eliminar individuos no deseados, el objetivo de este artículo es revisar los diferentes tipos de aborto y diferenciar entre el aborto propiamente eugenésico del aborto terapéutico, del aborto con fines sociales o demográficos y del realizado por selección de sexo, para al final proponer que en ciertos casos el aborto eugenésico podría considerarse como bioéticamente aceptable. Advances in genetics followed by the new technologies in the early detection of genetic disorders involving bioethical dilemmas about the proper use of these techniques, the information given to pregnant women and the decision that she will take to receive it. Early detection of genetic abnormalities allow, in some cases, the initiation of appropriate treatment to allow the unborn child does not develop a disabling disease, as the case of phenylketonuria, or surgery for a fetus with spina bifida, but If you do not have any treatment available abortion remains the last alternative. Although for many, any type of abortion is eugenics, that is seeking to eliminate unwanted individuals, the aim of this paper is to review the different types of abortion and the difference between eugenic abortion, therapeutic abortion, abortion for social or demographic ends and Sex-selection made for the for the final proposal that in some cases eugenic abortion could be considered acceptable for bioethics