published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

The LMVD Method of Planes has been used for many years by the New Orleans District of the U.S. Army Corps of Engineers to analyze the stability of flood control structures in the New Orleans hurricane protections system. The Method of Planes assumes a three-part, noncircular slip surface and generally does not satisfy any form of static equilibrium. In computing a factor of safety, the Method of Planes considers a balance of horizontal “resisting” and “driving” forces in computing a factor of safety. To better understand how the results of slope stability analyses with the Method of Planes compare with results from more rigorous procedures capable of analyzing slip surfaces with different shapes, a parametric study was performed by analyzing twenty earthen levee cross sections believed to represent the various levee configurations in southeastern Louisiana. Analyses were performed with a force equilibrium procedure that assumed a horizontal inclination for the interslice forces and Spencer’s (1967) procedure, and the results were compared with the solutions from the Method of Planes. The force equilibrium procedure with horizontal side forces was selected because the procedure is believed to yield results that are similar to results from the Method of Planes, and Spencer’s procedure was utilized because it is the only procedure considered in this study to completely satisfy static equilibrium. The analyses performed with the force equilibrium and Spencer’s procedures included analyses for the critical slip surfaces from the Method of Planes as well as analyses for critical circular and noncircular slip surfaces. It was shown with the results of the analyses that the shape of the assumed slip surface has a great effect on the differences in the factors of safety from Spencer’s procedure and the Method of Planes. / text

The ability to formulate monoclonal antibodies at high concentration in a low-viscosity form is of broad interest in drug delivery, as monoclonal antibody-based drugs are now prescribed for cancer, autoimmune disorders, and many other diseases. Herein, we create highly concentrated antibody dispersions (up to 260 mg/mL) via three different methods, utilizing proline as an interacting depletant or trehalose as a non-interacting depletant. These dispersions are able to achieve viscosities an order of magnitude lower than similarly concentrated antibody solutions over a range of formulation pHs. When diluted, these antibody dispersions return to monomer. The proline acts to minimize protein zeta potential, thus reducing the electrostatic repulsion on the protein, even when formulated 3 pH units away from the antibody pI. In addition, it acts as a depletant, forcing the monomers into cluster via osmotic effects / text

The work presented in this thesis is a collection of four different research projects, conducted at the intersection between academic and industrial fields, and related to the restructuring of the electricity industry. Many models have been proposed to organise restructured electricity systems. We first propose a unified mathematical framework for expressing them, using variational inequalities. This allows the use of existence and uniqueness theorems, but also leads to models that can be solved by existing numerical algorithms. In the second part, we present a model of the European Commission proposals on cross-border trade, in particular access to the network and congestion issues. The model allows for various domestic regulation of the national non-eligible market, and different forms of competition in the eligible market. We illustrate this flexibility on a stylised example, and identify policy issues to be studied in a more realistic case study. The third contribution elaborates on the modelling of imperfect competition on electricity markets, more specifically the integration of imperfect competition behaviours in power models, through conjectural variations. We propose a consistent estimation procedure. Finally, a model of the EU Emission Trading Scheme, limiting the total CO2 emissions, is proposed. We illustrate the effect of some basic economic assumptions on the investment and generation mix, and how these assumptions impact the permit price and affect profitability. The novel part is in the way allocation mechanisms for subsequent commitment periods can potentially distort the behaviour of CO2 emitting agents.

No description available.

Interfacially active reagents are utilized in metal solvent extraction processes and it is therefore important to understand the role of the liquid-liquid interface in the study of the kinetics and equilibria of extraction. The diffusion problems encountered in the traditional apparatus were overcome by using a high speed stirring apparatus. The microporous teflon membrane phase separator permitted more accurate measurements of interfacial areas, characterization of extraction kinetics of metal chelates, and a greater understanding of the phase separation mechanism. In contrast to the neutral ligands, the anionic ligand of dithizones and substituted dithizones showed significant interfacial adsorption at the chloroform/water interface as monitored spectro-photometrically. Equilibrium studies on p-halodithizones indicated that the adsorption constant increased as the substituent was altered from chloro to bromo to iodo, and with the distribution ratio of the ligand. Kinetic studies on dithizone and p-iododithizone with Ni(II) and Zn(II) indicated that the extent of participation of the interface in solvent extraction kinetics of these metal ions is dictated by the interfacial activity of the extractant and the mechanisms of the rate limiting step in the bulk aqueous and interfacial regions.

The vapour recirculation apparatus of Moodley [2002] was modified, reconstructed, and commissioned in order to be used in the acquisition of high-pressure vapour-liquid equilibrium (HPVLE) data at low temperatures. The original equipment of Moodley [2002] was modified with the aim of achieving the desired operating temperature range which the original equipment was unable to achieve. Major modifications were carried out on the cooling circuit allowing the equipment to reach temperatures as low as -30°C, a significant improvement to the original equipments minimum attainable temperature of -5°C. Modifications were also successfully carried out on the vapour recirculation pump of Moodley [2002], which failed when operated over extended periods at high pressures thus enabling the equipment to operate at pressures up to 10.0 bar, an improvement on the previous pressure operating limit of 6.9 bar. The operating limits of the equipment were tested through measurement of pure-component vapour-pressures of isopentane at temperatures between -14 and +27.9°C and pressures up to 10.1 bar and on propane at temperatures between -30.1 and +26.0°C and pressures up to 9.7 bar. The isopentane vapour-pressure measurements had an average deviation of ±0.49% when compared to literature data while the propane vapour-measurements had a maximum average deviation of ±0.35% when compared to literature data indicating that the equipment was capable of measuring accurate vapour-pressure data at temperatures down to -30°C and pressures up to 10.0 bar. The equipment was thereafter used in the acquisition of binary HPVLE data. Considerable time was spent developing and practicing the techniques used in the binary HPVLE measurements. Binary measurements were performed on the test system propane + 1- propanol at 19.9°C. To gain more confidence in the binary HPVLE measurements another test system, propane + isopentane was selected and binary HPVLE measurements were performed at 25°C and 0°C. The equipment was able to reproduce relatively accurate binary HPVLE results for the test systems at the selected isotherms. The equipment was thereafter used in the acquisition of a new set of binary HPVLE data for the propane + isopentane system at -10°C however owing to time constraints and chemical availability the acquisition of a complete set of data was not possible. The binary HPVLE data was thereafter regressed via the direct method. The Peng-Robinson (PR) equation of state (EOS) and the Soave-Redlich-Kwong (SRK) EOS were each coupled with the Mathias Copeman alpha function together with the Wong-Sandler mixing rule and the NRTL local composition model and applied to the binary systems at each of the isotherms investigated. Regressed data showed a relatively good agreement with measured experimental data for both binary systems investigated at all of the isotherms except the new -10°C isotherm of the propane + isopentane system. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

A number of industrially relevant separation processes involve carboxylic acids. Carboxylic acids are also amongst the various oxygenated products found in aqueous waste streams or as by-products of industrial operations in Sasol’s Fischer Tropsch processes. Other by-products include alcohols and ketones. Accurate vapour-liquid-equilibrium (VLE) data are required for the efficient and optimal modeling and simulation of these processes. In addition, removing and separating these components will help to prevent their pollution and the associated impact on the environment. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

Over the last few decades the interests of statistical physicists have broadened to include the detailed quantitative study of many systems - chemical, biological and even social - that were not traditionally part of the discipline. These systems can feature rich and complex spatiotemporal behaviour, often due to continued interaction with the environment and characterised by the dissipation of flows of energy and/or mass. This has led to vigorous research aimed at extending the established theoretical framework and adapting analytical methods that originate in the study of systems at thermodynamic equilibrium to deal with out-of-equilibrium situations, which are much more prevalent in nature. This thesis focuses on a microscopic model known as the asymmetric exclusion process, or ASEP, which describes the stochastic motion of particles on a one-dimensional lattice. Though in the first instance a model of a lattice gas, it is sufficiently general to have served as the basis to model a wide variety of phenomena. That, as well as substantial progress made in analysing its stationary behaviour, including the locations and nature of phase transitions, have led to it becoming a paradigmatic model of an exactly solvable nonequilibrium system. Recently an exact solution for the dynamics found a somewhat enigmatic transition, which has not been well understood. This thesis is an attempt to verify and better understand the nature of that dynamical transition, including its relation, if any, to the static phase transitions. I begin in Chapter 2 by reviewing known results for the ASEP, in particular the totally asymmetric variant (TASEP), driven at the boundaries. I present the exact dynamical transition as it was first derived, and a reduced description of the dynamics known as domain wall theory (DWT), which locates the transition at a different place. In Chapter 3, I investigate solutions of a nonlinear PDE that constitutes a mean-field, continuum approximation of the ASEP, namely the Burgers equation, and find that a similar dynamical transition occurs there at the same place as predicted by DWT but in disagreement with the exact result. Next, in Chapter 4 I report on efforts to observe and measure the dynamical transition through Monte Carlo simulation. No directly obvious physical manifestation of the transition was observed. The relaxation of three different observables was measured and found to agree well with each other but only slightly better with the exact transition than with DWT. In Chapter 5 I apply a numerical renormalisation scheme known as the Density Matrix Renormalisation Group (DMRG) method and find that it confirms the exact dynamical transition, ruling out the behaviour predicted by DWT. Finally in Chapter 6 I demonstrate that a perturbative calculation, involving the crossing of eigenvalues, allows us to rederive the location of the dynamical transition found exactly, thereby offering some insight into the nature of the transition.

Call number: LD2668 .T4 1959 T34