When using visual and proprioceptive information to plan a reach, it has been proposed that the brain combines these cues to estimate the object and/or limb’s location. Specifically, according to the maximum-likelihood estimation (MLE) model, more reliable sensory inputs are assigned a greater weight (Ernst & Banks, 2002). In this research we examined if the brain is able to adjust which sensory cue it weights the most. Specifically, we asked if the brain changes how it weights sensory information when the availability of a visual cue is manipulated. Twenty-four healthy subjects reached to visual (V), proprioceptive (P), or visual + proprioceptive (VP) targets under different visual delay conditions (e.g. on V and VP trials, the visual target was available for the entire reach, it was removed with the go-signal or it was removed 1, 2 or 5 seconds before the go-signal). Subjects completed 5 blocks of trials, with 90 trials per block. For 12 subjects, the visual delay was kept consistent within a block of trials, while for the other 12 subjects, different visual delays were intermixed within a block of trials. To establish which sensory cue subjects weighted the most, we compared endpoint positions achieved on V and P reaches to VP reaches. Results indicated that all subjects weighted sensory cues in accordance with the MLE model across all delay conditions and that these weights were similar regardless of the visual delay. Moreover, while errors increased with longer visual delays, there was no change in reaching variance. Thus, manipulating the visual environment was not enough to change subjects’ weighting strategy, further i

When using visual and proprioceptive information to plan a reach, it has been proposed that the brain combines these cues to estimate the object and/or limb’s location. Specifically, according to the maximum-likelihood estimation (MLE) model, more reliable sensory inputs are assigned a greater weight (Ernst & Banks, 2002). In this research we examined if the brain is able to adjust which sensory cue it weights the most. Specifically, we asked if the brain changes how it weights sensory information when the availability of a visual cue is manipulated. Twenty-four healthy subjects reached to visual (V), proprioceptive (P), or visual + proprioceptive (VP) targets under different visual delay conditions (e.g. on V and VP trials, the visual target was available for the entire reach, it was removed with the go-signal or it was removed 1, 2 or 5 seconds before the go-signal). Subjects completed 5 blocks of trials, with 90 trials per block. For 12 subjects, the visual delay was kept consistent within a block of trials, while for the other 12 subjects, different visual delays were intermixed within a block of trials. To establish which sensory cue subjects weighted the most, we compared endpoint positions achieved on V and P reaches to VP reaches. Results indicated that all subjects weighted sensory cues in accordance with the MLE model across all delay conditions and that these weights were similar regardless of the visual delay. Moreover, while errors increased with longer visual delays, there was no change in reaching variance. Thus, manipulating the visual environment was not enough to change subjects’ weighting strategy, further i

Orientador: José Angelo Barela / Banca: Sérgio Tosi Rodrigues / Banca: Ronald Dennis Paul Kenneth Clive Ranvaud / Banca: Renato de Moraes / Banca: Dora S. Fix Ventura / Resumo: Três experimentos foram propostos para investigar os ajustes dinâmicos nos pesos de múltiplas fontes de informação sensorial. O primeiro experimento investigou as respostas posturais de 18 bebês frente às mudanças abruptas na amplitude do estímulo visual. Eles permaneceram sentados dentro de uma sala móvel por 8 tentativas de 60 segundos cada. A sala ficou estacionária na primeira tentativa. Nas sete tentativas seguintes, a sala foi oscilada em 0,2 Hz com amplitude de 1,1 cm, com exceção da quinta tentativa, na qual a sala foi movimentada em amplitude mais alta (3,2 cm). Os resultados mostraram fraco acoplamento entre informação visual e oscilação corporal. Contudo, a variabilidade de oscilação foi maior em bebês experientes no sentar independente. Nós concluímos que bebês não foram capazes de se adaptar às pequenas alterações na amplitude do estímulo visual. O segundo experimento investigou como o controle postural de crianças se adapta às abruptas mudanças no ambiente visual. Trinta crianças de 4, 8 e 12 anos de idade e dez adultos, permaneceram em pé dentro de uma sala móvel. A situação experimental foi similar a do primeiro experimento exceto que a amplitude baixa da sala foi de 0,5 cm e a amplitude alta foi de 3,2 cm. As respostas posturais de crianças mais velhas e adultas diminuíram mais para o estímulo visual do que aquelas de crianças mais novas quando a amplitude da sala foi aumentada. A variabilidade de oscilação diminuiu com a idade e foi maior durante a tentativa de alta amplitude. Crianças tão novas quanto 4 anos de idade já têm desenvolvida a capacidade de rapidamente diminuir a influência do estimulo visual. Contudo, os mais altos valores de ganho e variabilidade residual para crianças de 4 e 8 anos de idade sugerem que elas não apresentam respostas totalmente calibradas ao nível adulto... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Three experiments were designed to investigate the dynamic adjustments in the weights of multiple sensory modalities. The first experiment investigated the postural responses of 18 infants to abrupt changes in the amplitude of visual stimulus. They seated inside of a moving room for eight trials of 60 sec apiece. The room was stationary in the first trial. In the following seven trials, the room oscillated at 0.2 Hz with amplitude of 1.1 cm, with the exception of the fifth trial, in which the room moved at higher amplitude (3.2 cm). The results showed weak coupling between visual stimulus and body sway. However, sway variability of experienced sitters was higher in the high-amplitude trial. We concluded that infants were not able to adapt to low range of visual stimulus amplitude. The second experiment investigated how children’s postural control adapt to abrupt changes in the surrounding visual environment. Thirty children from 4-, 8- and 12-year olds and ten adults stood upright inside of a moving room. The experimental set-up was similar to the first experiment except that low-amplitude was 0.5 cm and high-amplitude was 3.2 cm. Body sway responses of old children and adults downweight more to the visual stimulus than young children when the amplitude of the room increased. Sway variability decreased with age and was largest during the high-amplitude trial. Children as young as four years of age have already developed the adaptive capability to quickly downweight visual information. However, the higher gain values and residual variability observed for the 4 and 8 year-old children suggest that they have not fully calibrated their response to the adult level. The third experiment investigated the postural responses of two sensory modalities measured simultaneously... (Complete abstract click electronic access below) / Doutor

When using visual and proprioceptive information to plan a reach, it has been proposed that the brain combines these cues to estimate the object and/or limb’s location. Specifically, according to the maximum-likelihood estimation (MLE) model, more reliable sensory inputs are assigned a greater weight (Ernst & Banks, 2002). In this research we examined if the brain is able to adjust which sensory cue it weights the most. Specifically, we asked if the brain changes how it weights sensory information when the availability of a visual cue is manipulated. Twenty-four healthy subjects reached to visual (V), proprioceptive (P), or visual + proprioceptive (VP) targets under different visual delay conditions (e.g. on V and VP trials, the visual target was available for the entire reach, it was removed with the go-signal or it was removed 1, 2 or 5 seconds before the go-signal). Subjects completed 5 blocks of trials, with 90 trials per block. For 12 subjects, the visual delay was kept consistent within a block of trials, while for the other 12 subjects, different visual delays were intermixed within a block of trials. To establish which sensory cue subjects weighted the most, we compared endpoint positions achieved on V and P reaches to VP reaches. Results indicated that all subjects weighted sensory cues in accordance with the MLE model across all delay conditions and that these weights were similar regardless of the visual delay. Moreover, while errors increased with longer visual delays, there was no change in reaching variance. Thus, manipulating the visual environment was not enough to change subjects’ weighting strategy, further i

In this study, an efficient coupling between Monte Carlo (MC) molecular simulation and Darcy-scale flow in porous media is presented. The cell-centered finite difference method with a non-uniform rectangular mesh were used to discretize the simulation domain and solve the governing equations. To speed up the MC simulations, we implemented a recently developed scheme that quickly generates MC Markov chains out of pre-computed ones, based on the reweighting and reconstruction algorithm. This method astonishingly reduces the required computational time by MC simulations from hours to seconds. In addition, the reweighting and reconstruction scheme, which was originally designed to work with the LJ potential model, is extended to work with a potential model that accounts for the molecular quadrupole moment of fluids with non-spherical molecules such as CO2. The potential model was used to simulate the thermodynamic equilibrium properties for single-phase and two-phase systems using the canonical ensemble and the Gibbs ensemble, respectively. Comparing the simulation results with the experimental data showed that the implemented model has an excellent fit outperforming the standard LJ model. To demonstrate the strength of the proposed coupling in terms of computational time efficiency and numerical accuracy in fluid properties, various numerical experiments covering different compressible single-phase flow scenarios were conducted. The novelty in the introduced scheme is in allowing an efficient coupling of the molecular scale and Darcy scale in reservoir simulators. This leads to an accurate description of the thermodynamic behavior of the simulated reservoir fluids; consequently enhancing the confidence in the flow predictions in porous media.

Context: Individuals with chronic ankle instability (CAI) rely more on visual information during postural control due to impaired proprioceptive function. The increased reliance on visual information may increase the risk of injury when their vision is limited during complex sports activities. Stroboscopic glasses may help elicit sensory reweighting during postural control. Therefore, we assumed that the glasses would induce and train CAI patients to reweight sensory information for the somatosensory system during dynamic balance training. Purpose: (1) to identify the effects of the 4-week dynamic balance training on the reliance of visual information during postural control in patients with CAI and (2) to compare the effects of the 4-week dynamic balance with and without stroboscopic glasses on postural control in patients with CAI. Methods: This study was a randomized controlled trial. Twenty-eight CAI patients were equally assigned to one of 2 groups: a strobe group (6 males and 8 females) or a control group (8 males and 6 females). The 4-week dynamic balance training consisted of multiple single-legged exercises. The strobe group wore stroboscopic glasses during the training, but the control group did not. The main outcome measures included the following: self-reported function measures, static postural control (center of posture (COP)-based measures), and dynamic postural control including the Dynamic Postural Stability Index (DPSI), and the Star Excursion Balance Test (SEBT). There were 3 visual conditions in the static postural control (eyes-open (EO), strobe vision (SV), and eyes-closed (EC)), and 2 conditions in the dynamic postural control (EO and SV). Two-way randomized block ANOVAs were used to assess changes in postural control in each group and condition by using pretest-posttest mean differences. Results: The strobe group showed a higher difference in COP velocity in medial-lateral direction (VelML) and vertical stability index (VSI) under the SV condition compared with the control group (p = .005 and .004, respectively). In addition, the strobe group had significant decreases in VelML, DPSI, and VSI at the posttest compared with the pretest (p = .0001, .01, and .005, respectively). Conclusion: The 4-week dynamic balance training with stroboscopic glasses appeared to be effective in improving postural control and altering visual reliance in patients with CAI.

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La simulación molecular presenta la ventaja de ofrecer un marco teórico importante para predecir propiedades termodinámicas y de transporte de fluidos con aplicaciones industriales. En este trabajo, se explotó está ventaja para predecir el equilibrio líquido vapor de agua, compuestos aromáticos y sus mezclas a condiciones tanto sub- como supercríticas. Se realizó una comparación de diferentes potenciales intermoleculares conocidos mediante el cálculo de propiedades termodinámicas de sistemas puros que sirvió de punto de partida para llevar a cabo una optimización de parámetros transferibles para un potencial intermolecular de agua y compuestos aromáticos. En el caso de agua, se llevo a cabo el análisis y evaluación de propiedades termodinámicas de un modelo simple de agua. En este modelo, las contribuciones electrostáticas se aproximan mediante interacciones de corto alcance en vez de las típicas fuerzas de Coulomb de largo alcance. En general, se han encontrado grandes desviaciones con respecto a los datos experimentales, tal como un valor de temperatura crítica de 360K, valor 50% alejado del valor experimental. Debido a que estos resultados nos indican la importancia de incluir las fuerzas de Coulomb en el modelo molecular empleado para reproducir correctamente las propiedades de agua, el trabajo de investigación se ha enfocado en la optimización de los parámetros de los potenciales TIP4P y SPC/E. Los resultados obtenidos muestran que es posible encontrar una mejor aproximación al punto crítico experimental a partir de la optimización del modelo SPC/E. Sin embargo, el buen acuerdo con los experimentos del modelo original a condiciones ambiente se pierde usando los parámetros del modelo optimizado. Por otro lado, la estimación de propiedades de compuestos aromáticos esta de acuerdo con los datos experimentales permitiendo la reproducción de la densidad de líquido saturado, presión de saturación y entalpía de vaporización para compuestos puros. Finalmente, en el caso de mezclas se ha aplicado el conjunto de parámetros obtenidos para aromáticos. Las propiedades termodinámicas de la mezcla binaria aromático-aromático y aromático agua son analizadas en un amplio rango de temperaturas y presiones. Las desviaciones encontradas entre los valores calculados y los experimentales sugieren aplicar un mejor método de optimización para sistemas puros o por otro lado, promover un potencial de interacción intermolecular más sofisticado. Las estimaciones a condiciones cercanas al punto crítico están en buen acuerdo con los datos experimentales. / La simulació molecular presenta l'avantatge d'oferir un marc teòric important per a cercar propietats termodinàmiques i de transport de fluids amb aplicacions industrials. En aquest treball es va explotar aquesta avantatge per predir l'equilibri líquid vapor d'aigua, components aromàtics i les seves mescles, tant a condicions sub com supercrítiques. Es va realitzar una comparació de diferents potencials intermoleculars, coneguts mitjançant el càlcul de propietats termodinàmiques de sistemes purs, que ha servit de punt de sortida per portar a terme una optimització de paràmetres transferibles per a un potencial intermolecular de propietats termodinàmiques d'un model simple d'aigua. En aquest model, les contribucions electrostàtiques s'aproximen mitjançant interaccions de curt abast en lloc de les típiques forces de Coulomb de llarg abast. En general, s'ha trobat grans desviacions respecte a les dades experimentals, tal com un valor de temperatura crítica de 360K, valor 50% allunyat del valor experimental. Degut a que aquests resultats ens indiquen la importància d'incloure les forces de Coulomb en el model molecular emprat per reproduir correctament les propietats d'aigua, el treball d'investigació s'ha enfocat en l'optimització dels paràmetres dels potencials TIP4P i SPC/E. Els resultats obtinguts mostren que és possible trobar una millor aproximació al punt crític experimental a partir de l'optimització del model SPC/E. No obstant, el bon acord amb els experiments del model original a condicions ambientals es perden usant els paràmetres del model optimitzat. Per altre banda, l'estimació de propietats de compostos aromàtics esta d'acord amb les dades experimentals permetent la reproducció de la densitat de líquid saturat, pressió de saturació i entalpia de vaporització per a compostos purs mitjançant el potencial AUA-Aromátics proposat. Finalment, en el cas de mescles s'ha aplicat el conjunt de paràmetres obtinguts per aromàtics. Les propietats termodinàmiques de la mescla binària aromàtic-aromàtic i aromàtic-aigua són analitzades en un ample rang de temperatures i pressions. Les desviacions trobades entre els valors calculats i els experimentals suggereixen aplicar un millor mètode d'optimització per a sistemes purs o, per altre banda, promoure un potencial d'interacció intermolecular més sofisticat. Les estimacions en condicions properes al punt crític tenen un bon acord amb les dades experimentals. / Molecular simulation presents the advantage of providing a unified theoretical framework to model fluid properties for industrial applications. In this work we exploit this advantage to predict thermodynamic properties of pure water and aromatics and their mixtures at sub- and supercritical conditions. A comprehensive comparison of different intermolecular potentials has been carried out in order to analyze model predictions for pure component properties. In addition, an optimization of transferable parameters has been performed for an intermolecular potential for aromatics and water. In the case of water, an analysis and evaluation of the thermodynamic properties of a simple model has been performed. In this model, the electrostatic contributions are approximated by short-range interactions instead of the typical long-range Coulombic forces. On the whole, we found huge deviations with experimental data, such as a critical temperature value of 360K, 50% far away from the experimental value. Since, these calculations indicate the importance of including the electrostatic contribution in order to correctly model water, we also focus on reproducing critical properties from an optimization of the well known TIP4P and SPC/E water model parameters. Results obtained show that a better approximation to the critical point prediction is possible from the optimization of the SPC/E parameters, however, the good agreement with experiments for the original model at room conditions vanishes using the optimized parameters. On the other hand, thermodynamic property estimations of aromatic molecules are in good agreement with experimental data and we are able to reproduce saturation liquid densities, saturation pressures, vaporization enthalpies and liquid structure for pure compounds. Finally, in the case of mixtures, we applied the optimized set of parameters obtained for aromatics. The thermodynamic properties of binary aromatic-aromatic and aromatic water mixtures are analyzed over a wide range of temperatures and pressures. Deviations between the predicted and experimental values are found at low temperatures and high densities suggesting that a better optimization process needs to be performed for the pure systems or a more sophisticated intermolecular interaction potential is needed. Nevertheless, the estimations close to critical conditions are in good agreement with experimental data.

Made available in DSpace on 2014-06-11T19:30:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-06Bitstream added on 2014-06-13T19:19:36Z : No. of bitstreams: 1 zago_pfp_dr_rcla.pdf: 1617834 bytes, checksum: 193398c19868a245f447705bc0bf0861 (MD5) / Três experimentos foram propostos para investigar os ajustes dinâmicos nos pesos de múltiplas fontes de informação sensorial. O primeiro experimento investigou as respostas posturais de 18 bebês frente às mudanças abruptas na amplitude do estímulo visual. Eles permaneceram sentados dentro de uma sala móvel por 8 tentativas de 60 segundos cada. A sala ficou estacionária na primeira tentativa. Nas sete tentativas seguintes, a sala foi oscilada em 0,2 Hz com amplitude de 1,1 cm, com exceção da quinta tentativa, na qual a sala foi movimentada em amplitude mais alta (3,2 cm). Os resultados mostraram fraco acoplamento entre informação visual e oscilação corporal. Contudo, a variabilidade de oscilação foi maior em bebês experientes no sentar independente. Nós concluímos que bebês não foram capazes de se adaptar às pequenas alterações na amplitude do estímulo visual. O segundo experimento investigou como o controle postural de crianças se adapta às abruptas mudanças no ambiente visual. Trinta crianças de 4, 8 e 12 anos de idade e dez adultos, permaneceram em pé dentro de uma sala móvel. A situação experimental foi similar a do primeiro experimento exceto que a amplitude baixa da sala foi de 0,5 cm e a amplitude alta foi de 3,2 cm. As respostas posturais de crianças mais velhas e adultas diminuíram mais para o estímulo visual do que aquelas de crianças mais novas quando a amplitude da sala foi aumentada. A variabilidade de oscilação diminuiu com a idade e foi maior durante a tentativa de alta amplitude. Crianças tão novas quanto 4 anos de idade já têm desenvolvida a capacidade de rapidamente diminuir a influência do estimulo visual. Contudo, os mais altos valores de ganho e variabilidade residual para crianças de 4 e 8 anos de idade sugerem que elas não apresentam respostas totalmente calibradas ao nível adulto... / Three experiments were designed to investigate the dynamic adjustments in the weights of multiple sensory modalities. The first experiment investigated the postural responses of 18 infants to abrupt changes in the amplitude of visual stimulus. They seated inside of a moving room for eight trials of 60 sec apiece. The room was stationary in the first trial. In the following seven trials, the room oscillated at 0.2 Hz with amplitude of 1.1 cm, with the exception of the fifth trial, in which the room moved at higher amplitude (3.2 cm). The results showed weak coupling between visual stimulus and body sway. However, sway variability of experienced sitters was higher in the high-amplitude trial. We concluded that infants were not able to adapt to low range of visual stimulus amplitude. The second experiment investigated how children s postural control adapt to abrupt changes in the surrounding visual environment. Thirty children from 4-, 8- and 12-year olds and ten adults stood upright inside of a moving room. The experimental set-up was similar to the first experiment except that low-amplitude was 0.5 cm and high-amplitude was 3.2 cm. Body sway responses of old children and adults downweight more to the visual stimulus than young children when the amplitude of the room increased. Sway variability decreased with age and was largest during the high-amplitude trial. Children as young as four years of age have already developed the adaptive capability to quickly downweight visual information. However, the higher gain values and residual variability observed for the 4 and 8 year-old children suggest that they have not fully calibrated their response to the adult level. The third experiment investigated the postural responses of two sensory modalities measured simultaneously... (Complete abstract click electronic access below)

The thesis apply to reliability problems approach of Voronoi tessellation, typically used in the field of samples designs evaluation and for Monte Carlo samples reweighing. It is shown, this general technique estimation converges to that of Importance Sampling method despite it does not rely on Importance Sampling's auxiliary density. Consequently, reliability analysis could be divided into sampling itself and assessment of simulation results. As an extension of this idea, adaptive statistical sampling using QHull library was attempted.