A Neural Circuit for Coordinating Reaching with Grasping: Autocompensating Variable Initial Apertures, Perturbations to Target Size, and Perturbations to Target Orientation

A neural network model is presented, that extends principles of the VITE (vector integration to end-point) model [1, 2, 3, 4] of primate reaching to the more complex case of reach-grasp coordination. The main new planning problem addressed by the model is how to simulate human data on temporal coordination between reaching and grasping, while at the same time remaining stable and compensating for altered initial apertures and perturbations of object size and object location/ orientation. Simulations of the model replicate key features of four different experimental protocols with a single set of parameters. The proposed circuit computes reaching to grasp trajectories in real-time, by continuously updating vector positioning commands, and with no precomputation of total or component movement times. The model consists of three generator channels: transport, which generates a reaching trajectory; aperture, which controls distance between thumb and index finger; and orientation, which controls hand orientation vis-a-vis target's orientation.CONACYT of Mexico; Defense Advanced Research Projects Agency and Office of Naval Research (N00014-95-1-0409

A Neural Circuit for Coordinating Reaching with Grasping: Autocompensating Variable Initial Apertures, Perturbations to Target Size, and Perturbations to Target Orientation

A neural network model is presented, that extends principles of the VITE (vector integration to end-point) model [1, 2, 3, 4] of primate reaching to the more complex case of reach-grasp coordination. The main new planning problem addressed by the model is how to simulate human data on temporal coordination between reaching and grasping, while at the same time remaining stable and compensating for altered initial apertures and perturbations of object size and object location/ orientation. Simulations of the model replicate key features of four different experimental protocols with a single set of parameters. The proposed circuit computes reaching to grasp trajectories in real-time, by continuously updating vector positioning commands, and with no precomputation of total or component movement times. The model consists of three generator channels: transport, which generates a reaching trajectory; aperture, which controls distance between thumb and index finger; and orientation, which controls hand orientation vis-a-vis target's orientation.CONACYT of Mexico; Defense Advanced Research Projects Agency and Office of Naval Research (N00014-95-1-0409

A Model of Cerebellar Adaptation of Grip Forces During Lifting

We investigated adaptive neural control of precision grip forces during object lifting. A model is presented that adjusts reactive and anticipatory grip forces to a level just above that needed to stabilize lifted objects in the hand. The model obeys priciples of cerebellar structure and function by using slip sensations as error signals to adapt phasic motor commands to tonic force generators associated with output synergies controlling grip aperture. The learned phasic commands are weight and texture-dependent. Simulations of the new curcuit model reproduce key aspects of experimental observations of force application. Over learning trials, the onset of grip force buildup comes to lead the load force buildup, and the rate-of-rise of grip force, but not load force, scales inversely with the friction of the gripped object.CONACYT of Mexico (No. 65907); Defense Advanced Research Projects Agency/Office of Naval Research (N00014-95-1-0409, NIMH R01 DC02852

SEGURIDAD E HIGIENE EN LAS EMPRESAS DE MANUFACTURA “LA RESISTENCIA DE LOS TRABAJADORES AL USO DE IMPLEMENTOS DE TRABAJO”

Las empresas de manufactura tienen como característica principal la transformación de la materia prima, en este sentido los empleados forman parte fundamental en el proceso mencionado.En el presente ensayo se abordaran temas relacionados con la seguridad e higiene en las empresas de manufactura, como seguridad, accidentes de trabajo, higiene, enfermedades laborales entre otro temas de interés, con el fin de conocer la resistencia de los trabajadores al uso de los implementos de trabajo, describiendo la función de cada uno de esos, y cada una de sus principales funciones, con el fin de conocer cada una de las causas del porque se resisten a su uso de los mismos

Análisis de un modelo de radiocanal aeronáutico para la banda de 40 Ghz

En esta comunicación se lleva a cabo un primer análisis de un modelo de radio canal aeronáutico para comunicaciones entre estaciones embarcadas en aeronaves (plataformas estratosféricas) y estaciones terrestres fijas. La banda de soporte es la de 40 Ghz.Peer ReviewedPostprint (published version

Gold nanoparticles modification with liquid crystalline polybenzylic dendrons via 1,3-Dipolar cycloaddition

A series of six polybenzylic dendrons with an alkynyl focal point were synthesized for their incorporation to gold nanoparticles. Five of these compounds showed columnar mesomorphism in a wide range of temperatures. These dendrons were reacted with gold nanoparticles stabilized with a combination of a dodecanethiol and 11-azidoundecane-1-thiol. The azido group of the last compound allowed the functionalization of the nanoparticles with the six polybenzylic dendrons by 1,3-dipolar cycloaddition between their alkynyl groups and the terminal azido groups of the thiols. A high efficiency of the cycloaddition process (47–69%) was confirmed by several experimental techniques and no decomposition or aggregation phenomena were detected in the dendron-coated nanoparticles. The involved mechanism and the resulting percentage composition of the final materials are discussed. The results of the ulterior growth of the nanoparticles by thermal treatment are influenced by the size and the shape of the dendron and the temperature of the process. The structures of the final nanoparticles were investigated by TEM, DSC, TGA, NMR and UV-Vis spectroscopy. These nanoparticles do not show liquid crystal properties. However, a melting process between a crystalline and a fluid phase is observed. In the solid phase, the nanomaterials prepared show a short-range interaction between nanoparticles with a 2D local hexagonal order. A near-field effect was observed in the UV-vis spectra by coupling of different surface plasmon resonance bands (SPR) probably due to the short-range interactions. The main novelty of this work lies in the scarcity of previous studies of gold nanoparticles coated with dendrons forming themselves columnar mesophases. Most of the studies reported in the literature deal with gold nanoparticles coated with calamitic mesogens. Additionally, the effect of the thermal treatment, which in a previous paper was shown to increase the mean size of the nanoparticles without increasing their size polydispersity, has been studied in these materials

Análisis de la gestión de seguridad de los protocolos WPA y WPA2 en el tráfico de datos de una red LAN con tecnología WiFi

Este documento pretende explicar paso a paso el sistema utilizado por los protocolos de seguridad de acceso e intercambio de datos WPA Y WPA2 utilizados por el sistema de comunicaciones WiFi. En primera instancia, debemos comprender el funcionamiento y régimen que lleva consigo una red LAN, tratando de enfocarnos en lo que es la tecnología WiFi. Hablaremos de los estándares que rigen la tecnología WiFi y su evolución lo cual nos permite tener una introducción al tema principal y que veremos reflejado en lo que llamamos el Capítulo 1. En el capítulo 2, llevamos a cabo la explicación del funcionamiento y gestión que realizan los protocolos WPA y WPA2, los cuales utilizan sistemas conocidos e implementados desde hace muchos años y aplicados a lenguaje de computadora como es la encriptación y la autenticación que serán las principales herramientas en la defensa de una red WiFi. El paso a seguir ahora, será, el de identificar los ataques que podemos tener en nuestra red casera o empresarial, puesto que desde la implementación de las redes inalámbricas se han generado una serie de ataques con enfoque malicioso,por lo que es indispensable el uso de sistemas de protección. También mostraremos la gestión y los pasos que debemos seguir para minimizar estos riesgos

Macro- and micronutrients availability in a cropped soil in Mabegondo (A Coruña)

Abstract] The Mehlich–3 extraction reagent recommended for use on a wide range of acid soil types was utilised for extracting in a simple step, both major elements (P, Ca, Mg) and micronutrients (Fe, Mn, Cu and Zn,). The study area was an elementary agricultural catchment of about 25 ha, located in the Mabegondo Experimental farm, near A Coruña, where soils develop over a basic schist underneath, referred to as Ordenes Complejo. 65 punctual soil samples were taken for nutrient determination at 0-30 cm depth. The frequency distributions for each of the seven studied elements were analized. There were wide ranges of variation between maxima and minima. Coefficients of skewness and kurtosis indicate that micronutrient contents can be approximated by a normal distribution. Coefficients of variation were medium to high, ranging from 30% to 62%. Strong correlations were found between extractable Fe, Mn, Cu and Zn. Furthermore, the relationship between the concentration of nutrients and routine analysis of organic matter content, pH and texture was ascertained. The dependence between pH and extractable Ca content was not as high as expected because of the scatter of a few (one or two) individual points. The usefulness of regression analysis between extracted nutrient concentrations and on the other hand between nutrient contents and general soil properties for detecting outliers was discusse

Variación histórica y espacial de la estrutura genética de dos poblaciones de Ceroxylon echinulatum Galeano (palma de ramos, Arecaceae) bajo diferentes niveles de impacto humano

Los bosques de las estribaciones noroccidentales andinas del Ecuador están amenazados por las actividades humanas, alterando de esta manera la ecología y consecuentemente la estructura genética y dinámica poblacional de muchas especies. El estado y la conservación de un ecosistema depende de la condición poblacional de las especies claves (especies que tienen múltiples interacciones ecológicas). Ceroxylon echinulatum (palma de ramos o palma de cera) es un componente importante dentro de los bosques andinos (>1000 metros sobre el nivel del mar)