Orientador: Gil Lucio Almeida / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-05T17:19:49Z (GMT). No. of bitstreams: 1 Dionisio_ValdeciCarlos_D.pdf: 5165065 bytes, checksum: 671e611cd8ab8c54d1ba86b902bcb5e6 (MD5) Previous issue date: 2005 / Resumo: A síndrome da dor fêmoro-patelar (SDFP) acomete uma em cada quatro pessoas da população em geral, e é composta por várias lesões que acometem a articulação fêmoro-patelar. O tratamento fisioterapêutico é fundamental na reabilitação dos portadores dessa síndrome, e que tem como uma de suas principais ferramentas o treinamento em cadeia cinética fechada. Dentre as várias formas de realizar esse treinamento, o agachamento é uma das mais utilizadas. Contudo, quando realizado o agachamento, a pessoa nem sempre tem o controle adequado da posição do tronco e dos membros, o que pode favorecer diferentes padrões cinemáticos, cinéticos e eletromiográficos. Portanto o presente estudo teve por objetivo identificar e descrever a estratégia cinética e eletromiográfica usada para realizar o agachamento nas fases ascendente e descendente em sujeitos saudáveis e portadores da SDFP, quando os movimentos são restritos no plano sagital, com padrão cinemático similar na maioria das articulações envolvidas. Oito sujeitos saudáveis e oito portadores da SDFP participaram deste estudo e realizaram o agachamento mantendo os braços flexionados à frente do corpo em duas distâncias, semi-agachamento (de 30º a 50º) e meio-agachamento (de 60º a 80º) na fase descendente. Para a fase ascendente eles realizaram a subida a partir do meio-agachamento. A atividade eletromiográfica dos músculos vasto medial oblíquo, vasto medial longo, reto femoral, vasto lateral, bíceps femoral, semitendinoso, gastrocnêmio lateral e tibial anterior foi registrada. A cinemática das articulações do membro inferior foi reconstruída utilizando-se um sistema óptico de análise de movimento. O centro de pressão (COP) foi obtido utilizando-se dados de uma plataforma de força, e os torques no tornozelo e joelho foram calculados por meio da dinâmica inversa. As tarefas foram eficazes em restringir o movimento no sentido céfalo-caudal em ambos os grupos. Também foi possível identificar e descrever uma estratégia clara para ambas as fases ascendente e descendente do agachamento. O músculo tibial anterior foi o responsável por iniciar o agachamento na fase descendente e se manteve coativado com o gastrocnêmio durante todo o movimento. O quadríceps foi o principal responsável em desacelerar o movimento e não houve grande atividade dos isquiotibiais. Comparado com o grupo controle, o grupo SDFP apresentou menor torque no joelho e menor atividade eletromiográfica do quadríceps, mas o torque no tornozelo e o deslocamento anterior do COP foram maiores durante as duas distâncias, na fase descendente do agachamento. Para a fase ascendente do agachamento, o grupo SDFP apresentou diferença na posição inicial, revelando uma estratégia protetora da articulação fêmoro-patelar. Antes de iniciar o movimento, houve forte ativação do quadríceps, isquiotibiais e gastrocnêmio para vencer a ação gravitacional em ambos os grupos. Comparado com o grupo controle, o grupo SDFP apresentou menor torque no joelho e menor atividade eletromiográfica do quadríceps, mas o torque no tornozelo e o deslocamento anterior do COP foram maiores. As fases de cada tarefa foram descritas e as implicações clínicas discutidas. Palavras chave: torque, centro de pressão, eletromiografia, patela, agachamento / Abstract: The patellofemoral pain syndrome (PFPS) affects one in four people in the general population, and is composed of several lesions of the patellofemoral joint. The physical therapy is essential for the rehabilitation of the population with this syndrome, and one of its main tools is the training in closed kinetic chain. Among the several ways of performing that training, the squat is one of the most used. However, when performing it, a person does not always have a proper control of the position of the trunk and of the limbs, what can produce different kinematic, kinetic and electromyographic patterns. Therefore, the present study had as an objective identifying and describing the kinetic and electromyographic strategy used to perform the squat in the ascending and descending phases by people with and without PFPS, when the movements are restricted in the sagittal plane, with a similar kinematic pattern in most of the involved joints. Eight healthy subjects and eight with PFPS participated in this study and they performed the squat keeping the upper arm elevated at 90º at the shoulder joint, just in front of the body in two distances, semisquatting (30º to 50º) and half squatting (60º to 80º) in the descending phase. For the ascending phase they performed the ascent from the half squatting. The electromyographic activity of the vastus medialis oblique, vastus medialis longus, rectus femoris, vastus lateralis, biceps femoris, semitendineous, gastrocnemius lateralis and tibialis anterior muscles was registered. The joint kinematics of the inferior limbs was reconstructed using an optical system for movement analysis. The center of the pressure (COP) was obtained using data from a force plate and the joint torques in the ankle and knee were calculated using inverse dynamics. The tasks were effective in restricting the movement in the cefalo-caudal direction for both groups. Moreover, it was possible to identify and to describe a clear strategy for both the ascending and the descending phases of the squat. The anterior tibialis muscle was the responsible for beginning the squatting in the descending phase, and kept co-activated with the gastrocnemius during the whole movement. The quadriceps was mainly responsible for decelerating the movement and there was not great activity of the hamstrings. Compared to the control group, the PFPS group presented smaller knee torque and smaller quadriceps electromyographic activity, but the ankle torque and the COP displacement to the anterior direction were larger in the two distances, in the descending phase of the squatting. For the ascending phase of the squatting the PFPS group presented difference in the initial position, revealing a protecting strategy for the patellofemoral joint. Before beginning the movement, there was a strong activation of the quadriceps, hamstrings and gastrocnemius. This was necessary for the motor control system to generate the forces that overcome the inertia of the limb and resist the flexion force acting on the knee due to gravity in both groups. Compared to the control group, the PFPS group presented smaller torque in the knee and smaller electromyographic activity of the quadriceps, but the ankle torque and the COP displacement to the anterior direction were larger. The phases of each task were described and clinical implications were discussed. Key words: torque, center of the pressure, electromyographic activity, patella, squat / Doutorado / Fisiologia / Doutor em Biologia Funcional e Molecular

The goal of effective rehabilitation should always be to restore “normal” function if possible. What is “normal” function? Although many subjective definitions may describe what is “normal”, it is the search for objective criteria of what constitutes “normality” that inspires exercise scientists worldwide! The primary aim of this study was to establish normative isokinetic torque values in young males, for rehabilitation purposes in South Africa. Four hundred and forty four (444) healthy male subjects participated in the study. A Cybex 340 isokinetic dynamometer was used to measure peak torque, using a quantitative experimental design. No correction was made for the effects of gravity. The following movement patterns were included: ankle plantar/dorsiflexion, knee flexion/extension, shoulder external/internal rotation, shoulder horizontal abduction/adduction, shoulder flexion/extension, elbow flexion/extension (using two different grip positions), and forearm pronation/supination. Descriptive statistics together with percentile scaling were used to develop normative values for the movement patterns studied. Normative values were presented in relative terms and expressed as a percentage in terms of Nm torque per kg body mass (% BM). In addition to the relative isokinetic torque values, the agonist/antagonist ratios were also expressed as a percentage. The percentile scales were also included to be used by clinicians involved in talent identification programmes and the screening of elite athletes. To conclude, normative isokinetic values were developed for young South African males. To enable subjects with large variations in body weight to utilize these norms, they were expressed in relative terms (% BM) instead of absolute terms (Nm). The possible benefit of the study was that population-specific and objective normative values were established for rehabilitation purposes and for use in sport science programs. / Thesis (DPhil (Human Movement Studies))--University of Pretoria, 2006. / Arts, Languages and Human Movement Studies Education / unrestricted

In the present thesis we introduce the reader to the field of spintronics and explore new phenomena, such as spin transfer torques, spin filtering, and three types of spin-orbit torques, Rashba, spin Hall, and spin swapping, which have emerged very recently and are promising candidates for a new generation of memory devices in computer technology. A general overview of these phenomena is presented in Chap. 1. In Chap. 2 we study spin transfer torques in tunnel junctions in the presence of spin filtering. In Chap. 3 we discuss the Rashba torque in ferromagnetic films, and in Chap. 4 we study spin Hall effect and spin swapping in ferromagnetic films, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives are summarized in Chap. 5.

Electrons not only have charges but also have spin. By utilizing the electron spin, the energy consumption of electronic devices can be reduced, their size can be scaled down and the efficiency of `read' and `write' in memory devices can be significantly improved. Hence, the manipulation of electron spin in electronic devices becomes more and more appealing for the advancement of microelectronics. In spin-based devices, the manipulation of ferromagnetic order parameter using electrical currents is a very useful means for current-driven operation. Nowadays, most of magnetic memory devices are based on the so-called spin transfer torque, which stems from the spin angular momentum transfer between a spin-polarized current and the magnetic order parameter. Recently, a novel spin torque effect, exploiting spin-orbit coupling in non-centrosymmetric magnets, has attracted a massive amount of attention. This thesis addresses the nature of spin-orbit coupled transport and torques in non-centrosymmetric magnetic semiconductors. We start with the theoretical study of spin orbit torque in three dimensional ferromagnetic GaMnAs. Using the Kubo formula, we calculate both the current-driven field-like torque and anti-damping-like torque. We compare the numerical results with the analytical expressions in the model case of a magnetic Rashba two-dimensional electron gas. Parametric dependencies of the different torque components and similarities to the analytical results of the Rashba two-dimensional electron gas in the weak disorder limit are described. Subsequently we study spin-orbit torques in two dimensional hexagonal crystals such as graphene, silicene, germanene and stanene. In the presence of staggered potential and exchange field, the valley degeneracy can be lifted and we obtain a valley-dependent Berry curvature, leading to a tunable antidamping torque by controlling the valley degree of freedom. This thesis then addresses the influence of the quantum spin Hall effect on spin orbit torque in nanoribbons with a hexagonal lattice. We find a dramatic modification of the nature of the torque (field like and damping-like component) when crossing the topological phase transition. The relative agnitude of the two torque components can be significantly modifies by changing the magnetization direction. Finally, motivated by recent experimental results, we conclude by investigating the features of spin-orbit torque in magnetic transition metal dichalcogenides. We find the torque is associated with the valley polarization. By changing the magnetization direction, the torque can be changed from a finite value to zero when the valley polarization decreases from a finite value to zero.

Spintronics is a rapidly growing research field due to scalability, integrablility within existing VLSI architecture, significantly reduced switching energy and latency while maintaining stable bit orientation (Spin-up, Spin-down). For the first time sub-5nm Spin Transfer Torque –Magnetic Tunneling Junctions (STT-MTJ) were investigated utilizing various Integrated Circuit (IC) fabrication techniques to evaluate novel concepts in logic switches. Tunneling Magnetoresistance (TMR) was measured in STT-MTJ stacks of Ta/CoFeB/MgO/CoFeB/Ta with differing diameter ferrimagnetic CoFe2O4 nanoparticles (10nm, 4nm and 2nm) embedded in the MgO layer. MR was detected in the 2nm and 4nm particle devices and demonstrated evidence of single electron transport. Tri-layer STT-MTJ devices were fabricated using a thin film stack of Ta/Ru/Ta/CoFeB(M1)/MgO/CoFeB(M2)/MgO/CoFeB(M3)/Ta. The overall diameter of the stack was reduced to sub-20nm using Focused Ion Beam (FIB) to mill away extra material. The coercivities of the ferrimagnetic CoFeB layers were modified during thin film deposition by altering sputter conditions. Field Applied- Magnetic Force Microscopy (FA-MFM) was used to detect four different magnetic intensities corresponding to three discreet resistances in the singly addressed device, making this architecture a candidate for neuromorphic computational applications. Lastly a lithographic-less architecture was developed to mass fabricate and electo-mechanically probe multi-layered, single point, sub-5nm particle based STT-MTJ devices using off-the-shelf anodized nanoporous alumina. Once fabricated, the devices were probed to measure their IV characteristics and magnetoresistance (MR). The unprecedented MR changes on the order of 50,000% at room temperature suggest quantum mechanical behavior.

No description available.

<p> Under certain conditions, an induced torque measurement is a measure of the ratio of the resistivity to the square of the Hall constant. Induced torque measurements can be directly related to the connectivity of the Fermi surface.</p> <p> A modulation technique for measuring induced torque is justifield theoretically, and an instrument employing this technique is characterized. Operational limitations on parameters such as sample resistivity and modulation rate are specified. A new procedure is proposed to extract more information from induced torque measurements. This procedure would allow the measurement of resistivity and Hall constant of ellipsoidal samples. The procedure is untested but appears to be feasible.</p> <p> Observations of the induced torque of Hg3-δAsF6 show that the Fermi surface supports an open orbit in one direction. This is discussed in the context of a model (Razavi et al., 1979), which has Fermi surface cylinders of common direction. This is based on conduction in Hg chain directions, which lie in only two directions. At magnetic fields greater than 3.0 Tesla, magnetic breakdown is observed. A Brillouin zone constructed using Hg chain symmetry and crystal parameters yields reciprocal lattice vectors compatible with the observed magnetic breakdown. The model is confirmed but a refinement is needed to allow an undulation of the Fermi surface cylinders.</p> / Thesis / Master of Science (MSc)

No description available.

Cavitation inside an automotive torque converter running at various pump speeds was simulated by using the Computational Fluid Dynamics (CFD) commercial package ANSYS-CFX 10.0/11.0. The numerical solution obtained for the case with no cavitation was used as an initial condition for the case of flow with cavitation to accelerate convergence. The converter was initially modeled using several grid sizes to evaluate the effect of grid density on the numerical solution and to select the optimum grid size for subsequent simulations. Comparison of CFD to actual test results demonstrates that the cavitation model built in the commercial code, which was developed by Zwart et. al. (2004) based on the simplified Rayleigh-Plesset equation of bubble dynamics, does not capture the full effect of cavitation inside the converter. Modifications to this model have been investigated in this study. The effect of the variation of the automotive transmission oil vapor pressure due to the rise in temperature during normal operating conditions was also investigated and found not to cause any significant change to the area of vapor formation, and hence did not have a significant effect on the converter performance. Values of the empirical coefficients of the cavitation model had to be modified in order for the model to capture the full effect of cavitation on the performance of the converter operating at high pump speeds. Results showed a much larger area of vapor over the converter stator and traces of vapor appeared inside the pump, and turbine blades. With these modifications, the model produced results in better agreement with the available experimental data. Moreover, simulations have been carried out in both steady and transient states using various turbulence models available in CFX10.0/11.0 in order to evaluate the effect of the choice of turbulence models on cavitation prediction. / Thesis / Master of Applied Science (MASc)

There are millions of pieces of space debris in orbit around Earth that pose threats to operating spacecraft. Some of these debris can be attributed to satellite failure, or end-of-life protocols. With a continual increase in commercial satellite launches per year, decommissioned spacecraft act as more debris polluting the space environment. Not only can robotic arms assist with active orbital debris removal to be more sustainable, they also support robotic on-orbit servicing (OOS). Additionally, using a robotic manipulator enables different servicing operations to take place, allowing for life extension capabilities for expired spacecraft. These life extension services allow for a broader application for robotic arms, which includes rendezvous proximity operations and docking. Robotic arms can also be used for assembly and manufacturing cases, establishing a more sustained presence and creating permanent structures in space. When considering any robotic rendezvous maneuvers or servicing, assembly, and manufacturing tasks aboard a spacecraft, it is important for the parent satellite to maintain attitude throughout robot motion, as in a zero gravity setting, any forces created by the robot act as equal and opposite forces applied to the parent spacecraft. The research performed in this thesis aims to create a model to describe changes in attitude throughout planned robot motion, as well as introduce methods for compensating for potential disturbances. Additionally, methods for describing the kinematics of a robot manipulator are presented and the forces and torques experienced by each joint are calculated using Newton-Euler inverse dynamics. Based on a calculated trajectory of the end effector, these torques are propagated to the parent spacecraft to determine the change in angular velocity. The results of this analysis are used to determine the required angular velocity to apply to the parent spacecraft in order to maintain attitude. / Master of Science / There are millions of pieces of space debris in orbit that threaten operating spacecraft. Spacecraft that are no longer working, yet continue to orbit, are considered space debris. As commercial satellite launches increase each year, orbital debris becomes more of a problem. Instead of disregarding broken satellites and adding to the orbital debris problem, robotic arms can be used to help fix and extend the lives of these spacecraft through acts of refueling or docking with an expired satellite to assume control, as well as provide assistance with orbital debris removal. In a broader sense, robotic arms can help two satellites dock together as well as assist in proximity operations. Robotic arms can be used to manufacture parts and build space structures, establishing a more permanent human presence in space. Because these robot servicing tasks can be very precise, it is important for the attached spacecraft to maintain position and orientation. During any servicing, assembly, or manufacturing task, the motion of a robotic arm produces forces that propagate to the parent spacecraft. If the spacecraft were on the ground, these forces would absorb into the ground, not affecting the position or orientation of the spacecraft. In zero gravity, any forces created by the robot arm act as equal and opposite forces applied to the parent spacecraft. These forces can cause shifts in the satellites position and orientation which need to be compensated for. Methods for describing the motion of the robotic arm are presented, and a model for how the parent spacecraft reacts to this motion is created. The results from this analysis are used to determine the appropriate counterforce to apply to the parent spacecraft in order to maintain desired orientation.