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Introduction: Claims that foot orthoses can resolve low-back pain are common in the marketing of these devices. The claims are based on the notion that wearing the orthoses will limit excess pronation at the subtalar joint thus reducing excessive internal tibial and femoral rotations. Excess leg rotations increase the anterior tilt of the pelvis and subsequently the degree of lumbar lordosis. Since lumbar lordosis has been suggested as a cause of low-back pain, it is speculated that foot orthoses could be used to treat and prevent pain to the low-back by reducing the forward curvature of the spine. This mechanical link between foot function and the low-back has not been investigated by experimental studies. Purpose: The purpose of this thesis was to investigate whether increased internal rotation of the femur induced an anterior tilt of the pelvis thus increasing the degree of lumbar lordosis and if external rotation induced a posterior pelvic tilt thus decreasing the degree of lumbar lordosis. Methods: In order to internally and externally rotate the femur, participants placed their feet in 18 different foot positions. Seven of these positions ranged from 15 degrees of foot eversion to 15 degrees of foot inversion and 11 positions ranged from 40 degrees of external foot rotation to 40 degrees of internal foot rotation. Six cameras surrounded the motion capture area and angles of pelvic tilt and lumbar lordosis were calculated. Results: Foot eversion and inversion did not have a statistically significant effect on pelvic tilt and lumbar lordosis. In-toeing had a statistically significant linear relationship with anterior pelvic tilt (R2=0.35, F1,131=69.79, p=0.00). Internally and externally rotating the feet had no effect on lumbar lordosis (R2=0.001, F1,153=0.09, p=0.77). Conclusion: Internally rotating the legs caused the pelvis to tilt anteriorly but only at extreme ranges of motion, much greater than what would normally be seen during gait. At which point, lumbar angles remained unaffected. This study does not dispute the effectiveness of foot orthoses to treat low-back pain but the results do not support the mechanical link proposed as the mechanism by which they work.

Chalcopyrite (CuFeS2) is the most abundant of the copper sulfides and also one of the most refractory for leaching. Several processing routes have been proposed to overcome drawbacks associated with environmental problems related to copper extraction from this mineral. Atmospheric leaching in acidic ferric sulfate is regarded as being particularly attractive over other hydrometallurgical systems. However, the challenge has been to overcome the problem of slow extraction rates due to passivity encountered at high solution potentials in this system. This highlights the need to investigate better operating conditions to optimize copper extraction and prevent the problem of passivation, and to develop suitable modeling tools to assess and diagnose leaching performance. In this work, a dissolution rate expression for chalcopyrite leaching in acidic ferric sulfate media is proposed accounting for effects in the active and passive regions under potentials from 415 to 550 mV (Ag/AgCl). A model of chemical speciation in the bulk solution elucidates the idea of passivation caused by precipitation of ferric species and their consequent adsorption onto the chalcopyrite surface. Electrochemical studies on massive samples of chalcopyrite involving characterization and modeling of the anodic and cathodic half-cell reactions of chalcopyrite leaching together with mixed potential considerations lead to the development of the mathematical expression for dissolution rate. The mathematical model was calibrated with electrochemical parameters and results are in good agreement with real leaching data from batch tests for solution potential regions where passivity is not observed. On the other hand, the passive region was modeled by means of adjusting parameters related to adsorption energies of the passivating species. Results of the model for this region deviate from real data as potential becomes higher probably due to diffusion resistance through a layer composed of ferric complexes.

The main hypothesis of this thesis was that the regulation of oxygen uptake (VO2) kinetics at the onset of exercise in trained young men is linked to cardiovascular adaptations. Two studies were conducted to investigate the interrelationships between oxygen (O2) transport and O2 utilization in accelerating VO2 kinetics at the onset of exercise. In the first study, simultaneous kinetics of VO2 and cardiac output (Q) were studied during the transition to heavy and moderate cycling exercise (Chapter 2). The acceleration of VO2 kinetics during the heavy exercise that followed prior moderate or heavy exercise was enabled by the rapid increase in Q; whereas, the acceleration of VO2 kinetics during moderate exercise that followed a heavy warm-up was associated with small changes in Q kinetics. The objective of the second study was to determine, in a model of forearm exercise, if the elevation of forearm blood flow (FBF) prior to the onset of exercise by prior circulatory occlusion would accelerate FBF and muscle oxygen uptake (VO2mus)kinetics during subsequent exercise as demonstrated previously for prior exercise (Chapter 3). Prolonged ischemia (15 min occlusion) followed by 3 min recovery reduced FBF and impaired VO2mus kinetics during subsequent heavy hand-grip exercise. However, prior heavy exercise confirmed the previous findings and resulted in a faster FBF and VO2mus kinetics. There was a high positive correlation between the time course of change in FBF and VO2mus at the onset heavy exercise. In a follow up of the second study, to investigate a possible mechanism for the slower adaptation of VO2mus following ischemia, the prior occlusion condition was repeated after ingesting a high dose of ibuprofen. Prostaglandin inhibition by ibuprofen augmented the FBF response during reactive hyperaemia and restored FBF during the heavy exercise that followed 15 min of circulatory occlusion to the control level. These two studies provide evidence that O2 delivery plays a dominant role in accelerating VO2 kinetics at the onset of heavy exercise in trained young men. The findings exposed differences in the mechanisms regulating pulmonary VO2 and VO2mus with prior exercise resulting in higher Q and FBF, but no changes in O2 extraction to yield the faster increase in pulmonary VO2 and VO2 at the onset of subsequent heavy exercise. In contrast, prior occlusion slightly retarded the increase in FBF and significantly reduced O2 extraction thus delaying VO2 kinetics. The precise mechanisms impairing VO2mus kinetics at the onset of heavy forearm hand-grip exercise that starts after a brief recovery from prolonged occlusion are still unknown, but this impairment may be partially due to a vasoconstrictor effect restricting blood flow during the adaptation to exercise and redistribution of the blood to the periphery. In a third study, the influence of muscle activity on the VO2 slow component during heavy exercise and O2 cost during moderate exercise that followed a heavy warm-up were examined (Chapter 4). The heavy exercise VO2 slow component was attenuated in a graded fashion by prior moderate and heavy warm-ups, and the principal components analysis showed a moderate but significant correlation between the changes in the integrated electromyographic activity and the VO2 slow component amplitude. The higher O2 cost of moderate exercise following a heavy warm-up was associated with higher mean power frequency. Changes in VO2 slow component and increased O2 cost during moderate exercise after prior heavy warm-up appear to be related to some changes in surface electromyographic activity which may provide some evidence for increased muscle fibres recruitment.

Over the past few decades, combustion of fossil fuels has released greenhouse gases such as CO2 and NOx into the atmosphere. It has been realized that a mean temperature increase of the Earth, also known as global warming, has resulted from the increase of CO2 concentration in the air. Hence, there is a growing tendency to establish novel methods of burning fossil fuels in order to mitigate CO2 concentration. Chemical Looping Combustion (CLC) is a method of burning fuel with inherent separation of CO2 while curbing the formation of NOx, typically by circulating an oxygen carrier between an air (oxidation) reactor and a fuel (reduction) reactor. An oxygen carrier, mainly a metal oxide, circulates between the reactors providing the oxygen for conversion of fuel to CO2 and H2O. Thus, having a pure CO2 stream, CO2 sequestration becomes economically feasible. Fe2O3, due to its availability and properties, could be an apposite oxygen carrier for CLC. Reaction kinetics of reduction of Hematite with methane, in the absence of gaseous oxidant, was studied. Temperature Program Reduction (TPR) experiments were carried out in a fixed bed tubular reactor. Reduction gas was composed of 15% methane and 85% argon. Thermogravimetric Analysis (TGA) was carried out on TPR products using air as the oxidant. Iron oxide samples were analyzed through X-ray diffraction (XRD) analysis and scanning electron microscopy. Two-stage reduction of iron oxide was observed: Fe2O3 reduced to Fe3O4 and then reduced to FeO. The activation energy of each stage was calculated from Kissinger’s method. For the first and second stage of reduction the activation energies were 10.58±0.86 and 25.77±0.83 kJ/mol, respectively. In addition, different kinetic models were assumed and compared to the actual data. A random nucleation mechanism can be assigned to the first stage and a two-dimensional diffusion mechanism can be assigned to the second stage of the reduction.

Due to increasing atmospheric carbon dioxide (CO2) concentration, energy sources that release to the atmosphere smaller amounts of CO2 are of interest. Initially, all the efforts were focused on increasing the system efficiency, now more attention is being paid recently on capturing and sequestering CO2 from combustion process and eliminating discharge to the atmosphere from the major source points. In these circumstances, the chemical-looping combustion (CLC) is a promising concept that can be used in power generation which integrates power production and CO2 capture. The aim of this work is to study reaction kinetics of Chemical-Looping Combustion. In order to come up with a suitable reactor design we should have a good knowledge of the reaction kinetics happening in the air and fuel reactor; then, to get such an information as will be mentioned later, reactivity investigation was carried out in thermogravimetric analysis (TGA).