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No description available.

No description available.

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. / Education, Faculty of / Kinesiology, School of / Graduate

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. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

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Rate constants for the pyridine catalyzed ionic decomposition of t-butylperoxyformate (TBF) are measured in 15 non-hydroxylic solvents. The second order rate constants varied by a factor of 40 from the "slowest" solvent, tetra-chloroethylene, to the "fastest", 1,2-dichloroethahe. Ten different empirical equations are found and their ability to correlate the rate constants with bulk solvent properties is compared. The best of the ten equations involves the polarizability and dipole moment of the solvent as follows. log krel = 1.207 (no²-1/no²+2) + 3.99 μ + 0.003 -3 The rate constants for TBF decomposition in other non-hydroxylic solvents are calculated by the empirical equations and are compared with values previously reported. The average deviation of the log k is 0.22. The rate constants for the reaction of methyl iodide with triethylamine are calculated from solvent properties and the values compared to literature values. In this case the average deviation of the log k is 0.31. / Science, Faculty of / Chemistry, Department of / Graduate

The mechanism of permanganate oxidation of fluoral hydrate and its analogue, substituted with deuterium at position-1, has been extensively investigated throughout the pH region 0.7 to 14 and a successful study was made of the behaviour of permanganate in the sulfuric acid region from pH 0.7 to 46.3% H₂SO₄. Compared with 2,2,2-trifluoroethanol and other substituted ethanols which ionise in the pH region, fluoral hydrate is unique since it has two acidic hydrogens, both of which can ionise. The pK[subscript a] for the first ionisation process has been determined to be 10.1. From the kinetic data as well as other supporting evidence, at least four different reaction paths can be distinguished for the permanganate oxidation of fluoral hydrate: (i) Reaction of the di-anion of fluoral hydrate, (ii) Reaction of the mono-anion, (iii) Reaction of the unionised fluoral hydrate with permanganate anion, and (iv) Tentatively proposed reaction of the unionised fluoral hydrate with permanganic acid. The deuterium isotope effects range from k[subscript H]/k[subscript D] = 5 for the oxidation of the di-anion, k[subscript H]/k[subscript D] = 10 for the mono-anion reaction, k[subscript H]/k[subscript D] = 4 for the neutral molecule reaction and k[subscript H]/k[subscript D] = 6 for the permanganic acid oxidation of unionised fluoral hydrate in strong acid. Activation parameters and a positive salt effect show that the transition state formation involves a reaction of similarly charged species; proton tunneling is considered unlikely on the basis of a temperature study. The rate determining step is most consistent with a hydride ion transfer to the permanganate ion. In connexion with the above study, 2,2,2-trifluoroethanol, 1,1,1;3,3,3-hexafluoropropanol-2 and the corresponding 2-d analogue have been examined in somewhat lesser detail. An isotope effect k[subscript H]/k[subscript D] = 20 has been observed for the oxidation of 1,1,1;3,3,3-hexafluoropropanol-2. The pK[subscript a] of permanganic acid has been determined in sulfuric acid by a spectrophotometry method, using two different methods of calculation; pK[subscript a] = -5.1. Formic acid has been oxidised by permanganate in the region 25 to 72 % H₂SO₄ and the reaction in the region from 25 to about 40 % H₂SO₄ is interpreted as the oxidation of the unionised formic acid by permanganic acid. An isotope effect of about 7 is observed in the very strongly acidic region (72 % H₂SO₄), which decreases upon going to 25 % H₂SO₄. Certain 4,4'-disubstituted benzhydrols were oxidised by permanganate in 0.1 M sodium hydroxide, however solubility difficulties prevented any extensive studies. [ ... ] / Science, Faculty of / Chemistry, Department of / Graduate

Kinetics of the Dissolution of Copper in Aqueous Aliphatic Amines. An investigation was made of the dissolution of copper metal in aqueous solutions of methyl, ethyl and n-butyl amine and ammonia, as well as in solutions of their aminium and ammonium ions, under oxygen pressure. Study of the kinetics of the dissolution was carried out over a wide range of concentrations. It was observed that there are two regions of oxygen pressure dependency of the rate. The range of oxygen pressure, where rate is independent of oxygen pressure, was investigated in detail. The rate process has been established to obey the relation R = [formula omitted] [k₂(A) + k₃ (AH⁻⁺)] for all the systems studied. A mechanism for the dissolution reaction has been proposed. Catalytic Reduction of Nickel Ion by Molecular Hydrogen. The rate of precipitation of nickel from salt solution by molecular hydrogen in the presence of catalyst has been investigated over a wide range of concentrations. The variables studied are concentration of nickel, hydrogen pressure, amount of catalyst, concentration of- hydrogen ion and temperature. The rate of reduction is found to obey an equation of the form: [formula omitted] = -k₁[S][PH₂]½[Ni⁺⁺] + k₂[S][H⁺] The activation energy is found to be 25±2 kcal/mol. The equilibrium constant k for the reaction Ni⁺⁺ H2 Ni° + H₂ ⇌ Nº + 2 H⁺ is found to be 4.65 x 10⁻⁶ atm⁻¹ at 140°C. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate