NMR and conductivity study of the protonic conductor HPb2Nb3O10 center dot nH(2)O

Electrical conductivity and H-1 Nuclear Magnetic Resonance (NMR) techniques were used to investigate the ion-exchanged layered lead-niobate perovskite HPb2Nb3O10. nH(2)O, over the temperature range 90-350 K. Compounds were synthesized by the sol-gel method and calcinated at 650 degreesC. Analysis of the NMR data gives activation energies for the proton motion in the range 0.14-0.40 eV, which are dependent on the water content. The frequency and temperature dependencies of the proton spin-lattice relaxation times show that the character of the motion of the: water molecules is essentially two-dimensional, reflecting the layered structure of the material. The H-1 line-narrowing transition and the single spin-lattice relaxation rate maximum, observed in the hydrated compounds, are consistent with a Grotthuss-like mechanism for the proton diffusion. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Control and chaos for vibro-impact and non-ideal oscillators

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Constantes de Movimento para um Potencial Dependente da Velocidade

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Kramers equation for a charged Brownian particle: the exact solution

We report the exact fundamental solution for Kramers equation associated to a Brownian gas of charged particles, under the influence of homogeneous (spatially uniform) otherwise arbitrary, external mechanical, electrical and magnetic fields. Some applications are presented, namely the hydrothermodynamical picture for Brownian motion in the long-time regime. (c) 2005 Elsevier B.V. All rights reserved.

Differential scanning calorimetry, x-ray diffraction and F-19 nuclear magnetic resonance investigations of the crystallization of InF3-based glasses

Results of differential scanning calometry (DSC), x-ray diffraction (XRD), and F-19 nuclear magnetic resonance (NMR) of InF3-based glasses, treated at different temperatures, ranging from glass transition temperature (T-g) to crystallization temperature (T-c), are reported. The main features of the experimental results are as follows. DSC analysis emphasizes several steps in the crystallization process. Heat treatment at temperatures above T-g enhances the nucleation of the first growing phases but has little influence on the following ones. XRD results show that several crystalline phases are formed, with solid state transitions when heated above 680 K, the F-19 NMR results show that the spin-lattice relaxation, for the glass samples heat treated above 638 K, is described by two time constants. For samples treated below this temperature a single time constant T-1 was observed. Measurements of the F-19 spin-lattice relaxation time (T-1), as a function of temperature,made possible the identification of the mobile fluoride ions. The activation energy, for the ionic motion, in samples treated at crystallization temperature was found to be 0.18 +/- 0.01 eV. (C) 1998 American Institute of Physics.

INFLUENCE of HIP EXTERNAL ROTATION on HIP ADDUCTOR and RECTUS FEMORIS MYOELECTRIC ACTIVITY DURING A DYNAMIC PARALLEL SQUAT

Pereira, GR, Leporace, G, Chagas, DV, Furtado, LFL, Praxedes, J, and Batista, LA. Influence of hip external rotation on hip adductor and rectus femoris myoelectric activity during a dynamic parallel squat. J Strength Cond Res 24(10): 27492754, 2010-This study sought to compare the myoelectric activity of the hip adductors (HAs) and rectus femoris (RF) when the hip was in a neutral position or externally rotated by 30 degrees or 50 degrees (H0, H30, and H50, respectively) during a parallel squat. Ten healthy subjects performed 10 repetitions of squats in each of the 3 hip positions and the myoelectric activities of the HAs and RF were recorded. The signal was then divided into categories representing concentric (C) and eccentric (E) contractions in the following ranges of motion: 0-30 degrees (C1 and E1), 30-60 degrees (C2 and E2), and 60-90 degrees (C3 and E3) of knee flexion. From those signals, an root mean square (RMS) value for each range of motion in each hip position was obtained. All values were normalized to those obtained during maximum voluntary isometric contraction. We found that HAs showed a significant increase in myoelectric activity during C3 and E3 in the H30 and H50 positions, as compared with H0. Meanwhile, RF activity did not significantly differ between hip positions. Both muscles showed higher activation during 60-90 degrees (C3 and E3) of knee flexion, as compared with 0-30 degrees (C1 and E1) and 30-60 degrees (C2 and E2). The results suggest that if the aim is to increase HA activity despite the low percentage of muscle activation, squats should be performed with 30 degrees of external rotation and at least 90 degrees of knee flexion.

Dynamics of a piecewise-linear oscillator with limited power supply

We discuss dynamics of a vibro-impact system consisting of a cart with an piecewise-linear restoring force, which vibrates under driving by a source with limited power supply. From the point of view of dynamical systems, vibro-impact systems exhibit a rich variety of phenomena, particularly chaotic motion. In our analyzes, we use bifurcation diagrams, basins of attractions, identifying several non-linear phenomena, such as chaotic regimes, crises, intermittent mechanisms, and coexistence of attractors with complex basins of attraction. © 2009 by ASME.

Estudio sobre la amplitud del movimiento articular de la rodilla en el proceso de marcha de niños con parálisis cerebral espástica

Introduction: To analyze the contribution of knee range of motion in walking of hemiplegic and diplegic children, considering their asymmetries. Material and method: Twelve children, 6 hemiplegics and 6 diplegics, from 7 to 12 years of age (9.5 ± 1.93) participated. Spasticity was assessed with the Ashworth's Modified Scale and the passive knee range of motion using an electrogoniometer. The task was to walk on an 8 m long walkway, using their preferred speed. Six attempts were made, three of which were on the right and three on the left sagittal planes. Results: The Mann-Whitney's U test found differences in the type of cerebral palsy for knee extension/hyperextension, for the relative angle of the knee at the load acceptance phase and for the knee range of motion during stride. The Wilcoxon's test revealed differences in hemibody for hemiplegics in the relative angle of the knee in acceptance of the load. Conclusions: Children with spastic cerebral palsy use compensation strategies between the lower limbs during walking. These strategies differed according to the type of cerebral palsy. The knee joint has an important function in those strategies, especially in the load acceptance and propulsion phases. © 2010 Elsevier España, S.L. y SERMEF. Todos los derechos reservados.

Nonlinear control system applied to atomic force microscope including parametric errors

The performance of the optimal linear feedback control and of the state-dependent Riccati equation control techniques applied to control and to suppress the chaotic motion in the atomic force microscope are analyzed. In addition, the sensitivity of each control technique regarding to parametric uncertainties are considered. Simulation results show the advantages and disadvantages of each technique. © 2013 Brazilian Society for Automatics - SBA.

Convergência de linguagens nas artes visuais: cinema, vídeo, teatro e internet

Pós-graduação em Artes - IA

Teatro Ventoforte de 1985 a 1995: a formação de um artista e arte-educador

Pós-graduação em Artes - IA

A representação do feio na arte: um breve estudo sobre quatro gravuras de Francisco Goya

Pós-graduação em Artes - IA

Território contemporâneo em jogo: uma proposta lúdica para o ensino da arte

Pós-graduação em Artes - IA

Arte, vida e formação de professores

Pós-graduação em Artes - IA

Arte em cerâmica e a memória como elemento criativo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)