Reversible Resistance Switching Effect in Amorphous Ge1Sb4Te7 Thin Films without Phase Transformation

We demonstrate a reversible resistance switching effect that does not rely on amorphous-crystalline phase transformation in a nanoscale capacitor-like cell using Ge1Sb4Te7 films as the working material. The polarity and amplitude of the applied electric voltage switches the cell resistance between low- and high-resistance states, as revealed in the current-voltage characteristics of the film by conductive atomic force microscopy (CAFM). This reversible SET/RESET switching effect is induced by voltage pulses and their polarity. The change of electrical resistance due to the switching effect is approximately two orders of magnitude.

Physiological modules for generating discrete and rhythmic movements: action identification by a dynamic recurrent neural network

In this study we employed a dynamic recurrent neural network (DRNN) in a novel fashion to reveal characteristics of control modules underlying the generation of muscle activations when drawing figures with the outstretched arm. We asked healthy human subjects to perform four different figure-eight movements in each of two workspaces (frontal plane and sagittal plane). We then trained a DRNN to predict the movement of the wrist from information in the EMG signals from seven different muscles. We trained different instances of the same network on a single movement direction, on all four movement directions in a single movement plane, or on all eight possible movement patterns and looked at the ability of the DRNN to generalize and predict movements for trials that were not included in the training set. Within a single movement plane, a DRNN trained on one movement direction was not able to predict movements of the hand for trials in the other three directions, but a DRNN trained simultaneously on all four movement directions could generalize across movement directions within the same plane. Similarly, the DRNN was able to reproduce the kinematics of the hand for both movement planes, but only if it was trained on examples performed in each one. As we will discuss, these results indicate that there are important dynamical constraints on the mapping of EMG to hand movement that depend on both the time sequence of the movement and on the anatomical constraints of the musculoskeletal system. In a second step, we injected EMG signals constructed from different synergies derived by the PCA in order to identify the mechanical significance of each of these components. From these results, one can surmise that discrete-rhythmic movements may be constructed from three different fundamental modules, one regulating the co-activation of all muscles over the time span of the movement and two others elliciting patterns of reciprocal activation operating in orthogonal directions.

A Data Dropout Compensation Algorithm Based on the Iterative Learning Control Methodology for Discrete-Time Systems

This paper deals with the convergence of a remote iterative learning control system subject to data dropouts. The system is composed by a set of discrete-time multiple input-multiple output linear models, each one with its corresponding actuator device and its sensor. Each actuator applies the input signals vector to its corresponding model at the sampling instants and the sensor measures the output signals vector. The iterative learning law is processed in a controller located far away of the models so the control signals vector has to be transmitted from the controller to the actuators through transmission channels. Such a law uses the measurements of each model to generate the input vector to be applied to its subsequent model so the measurements of the models have to be transmitted from the sensors to the controller. All transmissions are subject to failures which are described as a binary sequence taking value 1 or 0. A compensation dropout technique is used to replace the lost data in the transmission processes. The convergence to zero of the errors between the output signals vector and a reference one is achieved as the number of models tends to infinity.

Physiological modules for generating discrete and rhythmic movements: Component analysis of EMG signals

A central question in Neuroscience is that of how the nervous system generates the spatiotemporal commands needed to realize complex gestures, such as handwriting. A key postulate is that the central nervous system (CNS) builds up complex movements from a set of simpler motor primitives or control modules. In this study we examined the control modules underlying the generation of muscle activations when performing different types of movement: discrete, point-to-point movements in eight different directions and continuous figure-eight movements in both the normal, upright orientation and rotated 90 degrees. To test for the effects of biomechanical constraints, movements were performed in the frontal-parallel or sagittal planes, corresponding to two different nominal flexion/abduction postures of the shoulder. In all cases we measured limb kinematics and surface electromyographic activity (EMB) signals for seven different muscles acting around the shoulder. We first performed principal component analysis (PCA) of the EMG signals on a movement-by-movement basis. We found a surprisingly consistent pattern of muscle groupings across movement types and movement planes, although we could detect systematic differences between the PCs derived from movements performed in each sholder posture and between the principal components associated with the different orientations of the figure. Unexpectedly we found no systematic differences between the figute eights and the point-to-point movements. The first three principal components could be associated with a general co-contraction of all seven muscles plus two patterns of reciprocal activatoin. From these results, we surmise that both "discrete-rhythmic movements" such as the figure eight, and discrete point-to-point movement may be constructed from three different fundamental modules, one regulating the impedance of the limb over the time span of the movement and two others operating to generate movement, one aligned with the vertical and the other aligned with the horizontal.

Análise de custo de um programa de prevenção de internação para idosos no ambiente da saúde suplementar

Esta tese realiza uma análise de custo de um programa de prevenção de internação hospitalar para idosos (acima de 65 anos), no ambiente da saúde suplementar. Trata-se um programa voltado para idosos considerados de risco, de acordo com um questionário que avalia a probabilidade de risco de internação hospitalar. Indivíduos de risco são convidados a participar do programa, quando se estabelecem dois grupos: um que aceita a intervenção do programa (Grupo Bem Viver) e outro que recusa (Grupo Recusa). A intervenção do programa está voltada para o acompanhamento domiciliar, com equipe multidisciplinar, que se efetiva de acordo com uma estratificação, segundo a avaliação da dependência funcional para os indivíduos. Essa estratificação funcional divide os idosos do programa em cinco grupos distintos, denominados grupos funcionais. Indivíduos que recusam a intervenção mantêm a assistência com cuidado usual. A análise de custo é uma avaliação econômica parcial que estabelece uma comparação da utilização de serviços de saúde entre os dois grupos de idosos: um sob intervenção, grupo Bem Viver, e outro em cuidado usual, grupo Recusa. Esta análise foi realizada para um período dividido em 12 meses antes do evento (intervenção ou recusa) e 12 meses após o evento. Levantou-se a utilização de serviços de saúde de acordo com os indicadores de consultas, exames, procedimentos ambulatoriais, internações e consultas hospitalares. O custo do programa foi incluído também na análise final. Comparações foram estabelecidas entre os grupos no padrão de utilização, considerando-se os períodos antes e depois do evento. Os grupos funcionais foram analisados dentro da perspectiva da utilização para os mesmos períodos. Os resultados demonstraram que o grupo com adesão tem um grande percentual de indivíduos com dependência funcional, sugerindo que existe uma seleção adversa na aceitação do programa, quando indivíduos de maior risco têm adesão. Para o grupo sob intervenção, ocorreu um aumento da utilização com os serviços de saúde no conjunto de consultas, exames e procedimentos ambulatoriais, havendo diminuição com o custo unitário das internações hospitalares e consultas hospitalares. O grupo que recusa tem discreto aumento para o conjunto de consultas, exames e procedimentos ambulatoriais e um grande percentual de aumento para as internações (+40.2%) e consultas hospitalares (34.3%). Este resultado para internações foi analisado também através da transformação logarítmica, com uso da função inversa para a base de cálculo. Nesta aplicação estatística foi confirmado esse resultado para o padrão de utilização de internações. Na análise final, que incluiu o custo do programa propriamente dito, foi apresentada uma hipótese de avaliação para o grupo Bem Viver, sem a intervenção do programa. Desta maneira, realizou-se uma projeção para a utilização do grupo Bem Viver, a partir dos percentuais atingidos pelo grupo Recusa.

Effect of lithium-sodium mixed-alkali on phase transformation kinetics in Er3+/Yb3+ co-doped aluminophosphate glasses

Er3+ doped aluminophosphate glasses with various Na2O/Li2O ratios were prepared at 1250 degrees C using a silica crucible to study mixed alkali effect (MAE). The effect of relative alkali content on glass transition temperature, crystallization temperature and thermal stability were investigated using differential scanning calorimetry (DSC). In addition, apparent activation energies for crystallization, E, were determined employing the Kissinger equation. The effect of Al2O3 content on the magnitude of MAE was also discussed. No mixed-alkali effect is observed on crystallization temperature. (c) 2006 Elsevier B.V. All rights reserved.

SupraMOFs: Supramolecular porous materials assembled from metal-nucleobase discrete entities

289 p.

Transformation empirique des tables numeriques de Galton en tables des probits

Comparison between Galton equation and preston normal logarithms models allowed an empirical reconstitution of probits tables.