title: The in vitro activity of the herpes simplex virus virion host shutoff (vhs) protein

contributor:
Smiley, James R.
Biology

subject: Biology Biology

abstract: The herpes simplex virus (HSV) virion contains the virion host shutoff protein (vhs, product of the UL41 gene) that induces inhibition of host cell protein synthesis, disaggregation of pre-existing polyribosomes, and degradation of mRNA during early times of infection. The data presented in this thesis describe the development of a rabbit reticulocyte lysate-based in vitro system for analysis of the vhs protein activity. I show that vhs protein produced, as the sole HSV protein, in rabbit reticulocyte lysates inhibits translation and induces degradation of reporter RNAs. Detailed analysis of the vhs-dependent RNA decay revealed that it proceeds through an endoribonucleolytic cleavage mechanism that is not affected by the presence of a 5' cap structure or a 3' poly(A) tail in the RNA substrate. The vhs-dependent RNA degradation activity requires Mg++ ions and occurs in the absence of ATP and ribosomes. Characterization of the decay profile of two unrelated substrates indicated that they were initially cleaved at preferential sites non-randomly distributed over their 5' quadrants. This activity is greatly altered by placing an internal ribosome entry site (IRES) from encephalomyocarditis virus (EMCV) or poliovirus in the transcript. Transcripts bearing the IRES were preferentially cleaved by the vhs-dependent endoribonuclease at multiple sites clustered in a narrow zone located immediately downstream of the element. "Targeting" was observed when the IRES was located at the 5' end or placed at internal sites in the substrate, indicating that it is independent of position or sequence context. As with cleavage over the 5' quadrant, cleavage downstream of the IRES elements requires Mg ++ ion but not ATP and ribosomes. Transcripts containing internal IRES elements were also independently cleaved over their 5' quadrant. The vhs-induced RNA decay activity is not restricted to HSV-1 vhs, in that the vhs proteins from HSV-2 and pseudorabies virus also induce RNA degradation in vitro . I also show that the RNA degradation activity of the HSV-1 vhs protein is reproducible when vhs is produced in HeLa, but not wheat germ, cell-free extracts. These data indicate that the vhs-dependent nuclease can be selectively targeted by specific cis -acting elements in the RNA substrate, possibly through secondary structure or a component of the translational machinery.

abstract: Doctor of Philosophy (PhD)


title: Biochemical Basis for Inhibitory Control of Colon Function

contributor:
Daniel, Edwin
Medical Sciences

subject:
Medical Sciences
Medicine and Health Sciences
Medical Sciences

abstract:
Direct VIP-nerve and indirect ICC-mediated inhibitory control of colon motility were studied using biochemical techniques. In order to define a basis for VIP action in colon, longitudinal muscle, ICC-poor circular muscle and ICC-rich layers separated by dissection were characterized by electron microscopy and subcellular fractionation using markers for synaptosomes, smooth muscle membrane and mitochondria. Synaptosmal, mitochondrial and smooth muscle enriched membrane fractions were isolated but a putative ICC membrane enriched fractions has the highest 5'nucleotidase, Mg2+ATPASE activities and density of 125 I-VIP binding followed by synaptosome and smooth muscle membranes. High VIP binding density can be used as a marker for ICC membrane.

The study of nitric oxide production in fractions from ICC-rich and-poor preparation by measuring nitrite levels showed that mitochondrial, synaptosome and ICC-rich membrane fractions produced nitric oxide but greater levels were seen in the ICC-membrane rich fraction. Nitric oxide synthase activity on ICC membrane was constitutive and calcium-dependant. VIP increased (2-fold) nitric oxide production in ICC-rich strips which was inhibited by L-NAME, reduced by EGTA and increased by exogenous calcium. Partial inhibition of VIP-induce nitric oxide production by ω-Conotoxin GVIA was recorded in the absence (22%) and presence (32%) of L-arginine suggesting that the source of nitric oxide was in large part non-neural, from ICC.

I conclude that direct nerve-mediated control of longitudinal and circular muscle occurs through VIP binding on membrane receptors while indirect control of circular muscle occur through VIP-nerve induced production of nitric oxide from ICC to cause smooth muscle relaxation.

abstract: Doctor of Philosophy (PhD)


title: Fundamental Research on a Unique Rotary Machine

contributor:
Round, G.F.
Mechanical Engineering

subject:
Mechanical Engineering
Mechanical Engineering

abstract:
A unique rotary machine, which can be modified to function as an air motor, a hydraulic pump or a rotary combustion engine, has been developed. This thesis is concerned with both theoretical modelling of the engine aspects of the machine and the testing of a model and prototype. The machine is a simple rotational machine with an internal parallel axis arrangement. It is unique in the sense that there are two rotors turning in the same direction on their own stationary centres of gravity and working with the fluid around a full 360° degree path.

Using CAD/CAM techniques a model of the air motor and a prototype hydraulic pump were built and tested. Both of them have demonstrated very good performance features.

The engine described in this work is a true rotary engine with a unique semi-internal/external combustion system. It has a large power/weight ratio with a unique eight power strokes per revolution feature. Its multi fuel capability is a special contribution to the development of internal combustion engines where and when it is necessary to use alternative fuels.

A three zone turbulence eddy entrance thermodynamic model has been developed to predict the performance of the engine and optimize some of the structural and operational parameters. The results of the theoretical analysis indicate that this engine has excellent features which are improvements over those of the reciprocating engines as well as the Wankel rotary engine.

abstract: Doctor of Philosophy (PhD)


title: Control of Cellular Gene Expression by Viral Regulatory Proteins

contributor:
Smiley, J. R.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract: Herpes simplex virus type 1 and adenovirus type 5 are nuclear DNA viruses that encode a number of regulatory polypeptides that serve to facilitate expression of the viral genome at the expense of host gene expression. These viruses depend on cellular transcriptional apparatus, and viral regulatory proteins flmction primarily to ensure that host factors engage the viral template and that viral genes are expressed in the correct spatial and temporal sequence. The results presented in this thesis demonstrate that regulatory proteins encoded by herpes simplex virus and adenovirus modulate the expression of two classes of cellular genes: the globin genes and Alu repetitive sequences. Herpes simplex virus gene products were required to stimulate the expression of human α-globin, rabbit β-globin genes and Alu elements introduced into cells as part of the herpes genome. In addition, infection with herpes simplex virus or adenovirus stimulated expression of host α-globin and Alu sequences and de novo synthesized viral gene products were required for induction of these cellular genes. Viral induction of α-globin and Alu expression are both unusual instances of activated gene expression: viral infection allows the α-globin gene to escape its erythroid~restricted transcription pattern, and the viral activation of RNA polymerase III transcription of Alu sequences is the first instance of high level class III transcription of these repetitive DNA elements in vivo. The identification of the herpes implex virus and adenovirus gene products which mediate the transcriptional activation of these host sequences has contributed to the understanding of the mechanisms which regulate expression of α-globin genes and Alu repetitive elements and also of the mechanisms by which viral regulatory proteins modulate gene expression.

abstract: Doctor of Philosophy (PhD)


title: An Income Disaggregated Model of Urban Spatial Structure

contributor:
Webber, M.J.
Geography

subject: Geography Geography

abstract:
The task of this paper is to evaluate, in some detail, the effects of income disaggregation upon the predictive and descriptive abilities of a comprehensive, information-minimising, spatial interaction model. The model is comprehensive in that it predicts the probability that an individual household chooses a particular residential location, work place and shopping trip pattern subject to expectations based upon survey data about the average cost of shopping and work trips and the average number of shopping trips per week per household. This probability is information minimising compared to a prior probability distribution which is chosen to reflect residential land availability.

The purpose of the analysis is to determine whether or not the income group disaggregated model provides a more accurate representation of observed spatial structure than does the aggregate model (treating the sample data as a homogeneous group).

It is concluded that although some descriptive advantages accrue to the disaggregated model, there is generally little predictive advantage to be gained by income group disaggregation unless the specific aim of the study is to discern the differences the exist in locational and trip making behaviour between income categories.

abstract: Master of Arts (MA)


title: Influence of Oxygen Partial Pressure and Temperature on the Formation and Stability of 110K Phase in the BiPbSrCaCuO Superconducting System

contributor:
Nicholson, Patrick S.
Materials Science and Engineering

subject:
Materials Science and Engineering
Materials Science and Engineering

abstract: A systematic study of the influence of oxygen partial pressure, temperature and time on 110K phase formation in the BiPbSrCaCuO system has been undertaken. The optimum nominal composition to promote the Bi₂Sr₂Ca₂Cu₃Ow (2223, 110K) phase, ie; Bi₁.₈₄Pb₀.₃₄Sr₁.₉₁Ca₂.₀₀Cu₃.₀₄Ow was studied. The relationships between 110K phase fraction, oxygen partial pressure, sintering temperature and time has been mapped for this composition via experimental data. The preferred conditions for 110K phase formation were identified as 0.01 atm≤Po₂≤0.35 atm, at 820≤T≤880°C for ≤36 hours with an intermediate grinding of the material every 6 hours. The optimum conditions for pure 110K phase were Po₂=0.08 atm at 845-865°C for 12 hours with grinding every 6 hours. The oxygen partial pressure range for single 110K phase stability was determined as 0.001 atm

abstract: Doctor of Philosophy (PhD)


title: The Structure of Homoserine Dehydrogenase from Saccharomyces cerevisiae

contributor:
Berghuis, A.M.
Biochemistry

subject: Biochemistry Biochemistry

abstract: The core of this work is the structural determination of the enzyme homoserine dehydrogenase from Saccharomyces cerevisiae . The structure has been determined in three different states of ligation: apo form, in a binary form complexed with nicotinamide cofactor, and in a ternary form complexed with both L-homoserine and a nicotinamide cofactor analogue. The structures were determined by X-ray diffraction studies to resolutions of 2.3, 2.3, and 2.6 Å, respectively. Due to problems with non-isomorphism, the measured amplitudes were phased from a single heavy atom derivative. Data averaging about a local two-fold axis (non-crystallographic symmetry) was used in combination with other density modification techniques to resolve the phase ambiguity problem arising from single isomorphous replacement. Because traditional techniques failed to locate the axis, a novel technique for locating the symmetry axis was devised. The fold of the catalytic/substrate binding portion of the structure establishes homoserine dehydrogenase as a unique dehydrogenase. The ternary complex reveals that the amino acid substrate binds to the enzyme in an unusual manner. Site directed mutagenesis data based upon the structure validates the selection of active site residues. Furthermore, the combination of residues employed for catalysis of the hydride transfer suggests that the bound form may be a gem -diol form. Reaction mechanisms in both the forward and reverse directions are proposed. This is the first structural determination of homoserine dehydrogenase. A comparison of the Saccharomyces cerevisiae homoserine dehydrogenase primary sequence with sequences from other homoserine dehydrogenases reveals that the fold of this enzyme is conserved across species. The structure explains the effect monovalent cations have upon the enzyme, how it is affected by an inhibitory compound and suggests a possible mechanism for allosteric control.

abstract: Doctor of Philosophy (PhD)


title: Tracking of Multiple Moving Targets by Passive Arrays and Asymptotic Performance Analysis

contributor:
Yip, Patrick C.
Electrical and Computer Engineering

subject:
Electrical and Computer Engineering
Electrical and Computer Engineering

abstract:
This thesis is focused on the topic of tracking multiple moving targets by combining the spatial and temporal information obtained by a passive array. For stationary sources a unified constrained subspace fitting approach for estimating the DOA's of spatially close source signals is presented. The algorithm is based on the Karhunen-Loève expansion of the covariance matrix of the array manifold in a sector of interest and searches for an optimal signal subspace over the array manifold space, which has minimum principal angles with the data signal subspace generated from the array data. This method is shown to be asymptotically consistent. Although this algorithm involves only one-dimensional researches, its performance is comparable to those in which multi-dimensional optimization is used.

We propose a maximum likelihood approach for tracking moving targets by passive arrays. A locally linear model is used for the source target motion dynamics, and the target state is shown to be strongly observable. An MTS (multiple target state) vector is defined to describe the source target state. The maximum likelihood estimator is based on a batch of array data. The initial MTS is estimated as the maximizing point of the likelihood function of a batch of array data, and the subsequent MTS vectors are predicted by the target dynamics. Since the association problem is embedded in the estimation problem, the natural ordering of the target state is kept as long as the initial target DOA.'s can be successfully resolved by the array. To cope with difficulties involved in the nonlinear optimization process a modified Gauss-Newton algorithm is proposed in which the Hessian is approximated by a positive semi-definite matrix to guarantee that the algorithm is descent. The asymptotic performance analysis has also been fully investigated, We show that the ML estimates of the MTS variables are asymptotically consistent. We also derive explicit formulas for the asYIitptotic covariance and the Cramér-Rao bounds for the MTS estimates, and it is found that the ML estimator is relatively efficient. To show the effectiveness of the ML tracking technique we compare the asymptotic performance of the ML estimator with that of the extended Kalman filter (EKF). Its performance is superior to that of the EKF. Numerical results are provided to demonstrate the performance of the ML tracking technique via computer simulations.

abstract: Doctor of Philosophy (PhD)


title: Product Quality Control in Reduced Dimension Spaces

contributor:
MacGregor, John F.
Chemical Engineering

subject:
Chemical Engineering
Chemical Engineering

abstract: In the first part of the thesis, control of the full molecular weight distribution (MWD) in a semi-batch polymerization reactor is considered. A new batch-to-batch optimization methodology for producing a desired MWD using an approximate fundamental model is presented. The optimization approach is also extended for use as an on-line control method by incorporating a multivariable statistical process control (MSPC) monitoring scheme. The combined MSPC/batch-to-batch optimizer is demonstrated on a simulated semi-batch polystyrene reactor and is shown to be very effective in reacting to large process upsets. Despite significant process/model mismatch, the batch-to-batch optimizer is able to adjust the process and produce the desired MWD within several batches following a process upset. In the remainder of the thesis, dimensionality issues in product quality control are addressed. First, indirect control of the full MWD by directly controlling only the average of the distribution is illustrated. It is shown that the choice of manipulated variables has an important impact on the controller performance when the full MWD is considered, and controlling a single average chain length sometimes causes the MWD to degrade. A simple analysis tool, called the Disturbance Inflation Factor (DIF), is introduced to evaluate which controlled and manipulated variables result in the best overall control of the full MWD. It is shown that with prudent choices of manipulated and controlled variables, simple single variable control can provide significant improvements in the full MWD. Controlling new linear combinations of the original inputs and outputs is also shown to be a feasible option for minimizing the overall effect of the disturbances. Finally, the thesis concludes with a critical review and unification of existing methods for Reduced Dimension Control. It was found that due to the different industries from which the applications originate, there is little or no comparison of similar approaches, thus there is the need for a unification. (Abstract shortened by UMI.)

abstract: Doctor of Philosophy (PhD)


title: Beta and electron dose imaging using a microspectrophotometer system and radiochromic film

contributor:
Prestwich, W. V.
Physics

subject: Physics Physics

abstract: A dose imaging technique of measuring the distribution of beta particles and high energy electrons, using a microspectrophotometer system and radiochromic film, has been investigated. The investigation entailed the commissioning of the microspectrophotometer and the development of a newly proposed method in film calibration. It was tested successfully by comparing the measured dose, determined using the calibration method, of films irradiated by a 32 P source, and the expected dose, determined by beta counting based on the equilibrium geometry with dose loss correction to the film substrate (20%). This method was also demonstrated to extend the usable dose range of the film. The dose imaging technique was applied to two experiments. The first experiment examines the beta depth dose distribution in Lucite, irradiated by a 32 P volume source. The experimental results were compared to Monte Carlo simulation, performed using the ITS code. The experimental distributions were found to agree closely with the Monte Carlo values up to a depth of 3 mm, but were significantly higher beyond. The second experiment examines the electron dose distribution in Lucite, irradiated by a narrow 10 MeV electron beam. The lateral experimental dose distributions were found to agree well, except at the tail end, with Monte Carlo values up to about 20 mm depth. Elsewhere, the experimental dose was found to be higher. The disagreement with Monte Carlo simulations at low doses in both experiments perhaps indicates a real discrepancy; further experimental investigations are required. The lateral spread of the beam was also investigated by determining the linear scattering power. The experimental values of the linear scattering power were found to be smaller than those quoted in the ICRU report 35 by a factor of 1.8 or less.

abstract: Doctor of Philosophy (PhD)


title: Brillouin Spectroscopy of Gelatin Gel and the Use of a CD Area Detector

contributor:
Walton, D.
Physics

subject: Physics Physics

abstract: Brillouin scattering method was used to study two kinds of materials: gelatin gel and quasicrystal Al₆₃.₅Cu₂₄.₅Fe₁₂. The measurements of Brillouin shift and width for gelatin-water system were carried out as a function of temperature, concentration, time and thermal history. New results and a phase diagram for melting were obtained. The results are discussed using different models. The longitudinal storage modulus of the gel network, the frictional damping parameter and the melting enthalpy have been evaluated. However, in order to explain all the experimental results and get the more accurate values for those parameters, a more perfect theory for this biopolymer system is needed. A more efficient technique -- CCD used as a detector, is described, too.

abstract: Doctor of Philosophy (PhD)


title: Transcriptional Regulation of Rat Peroxisomal Enoyl-CoA Hydratase/3-hydroxy Acyl-CoA Dehydrogenase

contributor:
Rachubinski, R.A.
Biochemistry

subject: Biochemistry Biochemistry

abstract:
Structurally diverse peroxisome proliferators induce in rodents a remarkable increase in the activities of peroxisomal fatty acid β-oxidation enzymes. The transcriptional induction of these peroxisomal enzymes in liver has been mechanistically associated with the subsequent pleiotropic responses such as peroxisome proliferation, hypolipidemia, hepatomegaly, and hepatocellular carcinomas. This project was designed to investigate the mechanisms of transcriptional regulation of the rat peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (HD) by hypolipidemic peroxisome proliferators.

In search of a peroxisome proliferator responsive element in the promoter region of the HD gene, the 5. 8 kbp upstream region of the HD gene and its deletion mutated fragments were subcloned into a reporter plasmid that contained a luciferase gene. The recombinant plasmids were introduced into H4IIEC3 cells in the presence of ciprofibrate, a hypolipidemic drug. Luciferase activity was measured to assay the inducibility of the promoter mutants. The sequence between nucleotides -3040 and -2845 behaved as a minimal peroxisome proliferator responsive element (PPRE). DNase I footprint analysis of this PPRE fragment with H4IIEC3 nuclear proteins revealed two protected regions. Region I contains consensus hormone responsive motifs: two inverted TGACCT-like sequences followed by a third. Region II contains two protein binding sites: a site containing several CACCC boxes and the other consisting of three directly repeated TGACCT core motifs. In transient transfection assays, the oligonucleotide containing these TGACCT direct repeats, nucleotides -2956 to -2919, conferred a ciprofibrate response, which was independent of its position and orientation relative to the transcription start site. In mobility shift assays, this sequence was recognized by liver specific nuclear proteins.

The three TGACCT-like motifs were further characterized by mutational analysis. Mutations that reduced the intensity of the liver factor binding in mobility shift assays resulted in a decrease in the responsiveness to ciprofibrate in transfection assays. Mutation of a single G residue in the middle core motif completely abolished both the factor binding in vitro and the responsiveness to ciprofibrate in vivo. Modulation of this core HD PPRE involved several known transcription factors. PPAR, RXRα, COUP-TF1, and, weakly, HNF4, were detected to be present in the complex of liver factors with HD PPRE by mobility shift assays with the addition of the respective antibodies. This result was confirmed by similar experiments with the in vitro translated products of mRNAs of these proteins. PPAR and RXRα required the second and third repeats of the HD PPRE whereas COUP-TF1 and, probably also HNF4, recognized the first and second repeats. PPAR and RXRa cooperatively transactivated a reporter gene via this HD PPRE in response to ciprofibrate in several cell lines. COUP-TF1 antagonized the up regulation by PPAR and RXRα.

In conclusion, the major cis element responsible for the ciprofibrate-induction of the ED gene consists of three directly-repeated TGACCT-like motifs. Its function is independent of its position and orientation relative to the transcription start site. Binding of liver specific factors to the element is a prerequisite for its ciprofibrate responsiveness. The overall integrity of the three motifs and the correct spacing between the motifs are critical determinants for the nuclear factor recognition and the transcriptional activation. The transcriptional regulation of the ED gene is achieved by a cooperation of several liver specific transcription factors.

abstract: Doctor of Philosophy (PhD)


title: Thermochemical and mechanistic investigation of carbocation isomerizations

contributor:
Childs, R.F.
Chemistry

subject: Chemistry Chemistry

abstract: This thesis describes experiments focussed on the isomerizations of carbocations, in particular, hydroxy-substituted carbocations produced by the protonation of ketones or phenols. Three classes of isomerization were investigated with the goal of determining the effect of substituents on the energetics of isomerization (carbocation stability, activation energy) and to probe the mechanisms of these reactions. It was proposed that differential scanning calorimetry (DSC) could be used to measure heats of isomerization to determine the effect of substituents on the energies of carbocations. Results presented in chapters 2, 3 and 4 demonstrate that DSC is a reliable technique for the determination of accurate and reproducible heats of isomerization of carbocations in superacid solution. As described in chapter 2, methyl migrations in cyclohexadienyl, cyclohexenyl and cyclopentenyl cations were investigated and the effect of moving methyl groups on to charge bearing positions of the carbocations was quantified. In addition, the energetic advantage of having a hydroxy group on the central 3-position rather than the terminal 1-position of the pentadienyl cation π-system was determined. Methyl substitution has pronounced effects upon the energetics of the isomerization of protonated bicyclo[3.1.0]hexenones to protonated phenols or cyclohexadienones and these results are described in chapter 3. These effects are consistent with the known charge distributions in the product and reactant cations. In addition, it was shown that the improved charge stabilization in the cyclohexadienyl cation product is a driving force for the isomerization, in contrast to the conclusions of an earlier study. A series of protonated cyclopropyl ketones in triflic acid were found to undergo ring expansion to oxolanylium ions except for two bicyclic ketones where steric constraints prevented ring expansion and ring opening to protonated enones occurred instead. The course of each reaction was determined and the reactant and product cations were characterized by 1 H and 13 C NMR spectroscopy. For use in later mechanistic studies, the stereochemistry of a set of dimethyl substituted cyclopropyl and oxolanylium compounds were established. The heats of isomerization of protonated cyclopropyl ketones were measured and found to fall in a narrow range which indicated that substituent effects were similar in the reactant and product cations. The substituents on the cyclopropyl ring and on the carbonyl carbon affected the rates of ring expansion of protonated cyclopropyl ketones which, provided information about the charge distribution in the reactant and the transition state, and the charge stabilizing abilities of the substituents. The list of possible mechanistic pathways was narrowed with a combination of information (product studies, substituent effects, entropies of activation). Finally, evidence is provided for the occurrence of a concerted 1,3-sigmatropic migration during the ring expansion of protonated cyclopropyl ketones in triflic acid. However, other reaction pathways can be made competitive with minor changes in reactant structure or reaction medium.

abstract: Doctor of Philosophy (PhD)


title: Subcooled Flow Boiling and Condensation

contributor:
Shoukri, M.
Mechanical Engineering

abstract:
Fundamental problems in two different flow regimes; subcooled water-steam bubbly condensing flow and subcooled flow boiling, in vertical conduits under low pressure and mass flux conditions, were investigated.

For subcooled water-steam condensing bubbly flow, experiments were carried out to obtain a data base for the axial distribution of area-averaged void fraction, interfacial area concentration, interfacial condensation heat transfer and bubble relative velocity. The interfacial area concentration was obtained by measuring the distributions of bubble volume and surface area, using high speed photography and digital image processing techniques, as well as the area-averaged void fraction, using a single beam gamma densitometer, at various axial locations. The interfacial heat transfer coefficient was obtained by monitoring the rate of change of the volume of individual bubbles as a function of local conditions. The data was used to develop new correlations for interfacial area concentration and interfacial condensation heat transfer coefficients. The applicability of the proposed correlations, as closure equations in existing two-fluid model based computer codes, was checked by including them in a two-fluid model to predict the axial void fraction profiles. The prediction of the current two-fluid model was compared with the measured axial void fraction profiles as well as available data from literature with good agreement.

For subcooled flow boiling, experimental data on the axial profile of void fraction, wall superheat and liquid subcooling along the test section were generated for various levels of mass flux, heat flux and inlet subcooling. The high speed photographic results confirmed the fact that the bubble parallel, or normal, detachment from the heating surface is not the reason of the NVG phenomenon. The digital image processing technique was used to measure the bubble size distributions as function of the local conditions. A correlation for the mean bubble diameter as a function of the mass flux, heat flux and local subcooling was obtained. Physical mechanisms causing the NVG phenomenon were investigated using the high speed photographic results. A net vapour generation model was proposed. The proposed model was based on the balance between the vapour generation and condensation rates at this point. A two-fluid model for the axial void fraction profile in subcooled boiling flow was introduced. A heat flux division model was proposed. The proposed two-fluid model was reasonably capable of predicting the axial void fraction profiles in subcooled flow boiling, without the need for prior identification of the location of the NVG point.

abstract: Doctor of Philosophy (PhD)


title: Vibration control of flexible structures using smart materials

contributor:
Dokanish, Mohamed
Mechanical Engineering

abstract: This work presents the analytic and experimental development of active vibration control of large flexible space structures (LFSS) using smart materials. Two basic configurations were studied: flexible manipulators, and truss structures, which encompass most of the flexible structures in space applications. The dynamics of LFSS are characterized by their high order and the significant presence of lightly damped, closely spaced low frequency modes. In space applications, space structures are required to perform precision trajectory tracking and attitude regulation, tasks that introduce disturbance torques and forces that may excite vibrational modes in the flexible parts of the structures, degrading their performance. To solve this problem, the use of piezoelectric materials coupled to structural members, to form smart structural members, is proposed for the implementation of active control techniques. For the flexible manipulator, the use of shaped piezoelectric sensors is presented. Piezoelectric sensors can be shaped to provide state feedback, which can be used as part of a control law to compensate vibrations induced by flexible degrees of freedom. A robust H∞ state feedback control law is obtained. The control law is implemented using the shaped sensor to stabilize the flexible manipulator. Simulation and experimental results in a single link flexible manipulator confirm the effectiveness of the proposed approach. The design of a truss structure and the control for active damping of vibration is presented, taking advantage of the use of piezoelectric actuators and sensors. Three control techniques are tested: negative velocity feedback, LQG and H∞ control. Simulations and experiments are performed on the closed loop to assess the relative merits of each control technique. Results show that the controllers increase the damping of the structure noticeably. The robust H∞ controller provides the better performance of the control techniques presented, even in the presence of higher order modes and parametric uncertainties not accounted for in the control design process.

abstract: Doctor of Philosophy (PhD)


title: Open Channel Overflow Diversion Structures with Side-Weirs

contributor:
James, Wm.
Civil Engineering

subject:
Civil Engineering
Civil Engineering

abstract:
Combined sewer systems are designed to bypass excess flows directly to the receiving water during rainstorm events. This is commonly achieved by means of diversion structures incorporating side spillways, oblique weirs or orifices.

The simulation of diversion devices by the EXTRAN Block of the Stormwater Management Model is examined. Results for the weir algorithm were not satisfactory. Therefore, a new procedure is written to compute the overflow and the water surface profile along the side weir. The hydraulics of flow over side weirs is reviewed in detail. The momentum approach is used in computing the water surface profile. The coefficient of discharge is estimated from a newly proposed relationship. A method for predicting the formation of a hydraulic jump along the weir section is derived from the momentum balance between the upstream and downstream side of the jump.

A computer program called OVRFLO3 is developed to compute the overflow and the water surface profile. Validation tests show good agreement with observations.

Finally, OVRFLO3 is adjusted to fit the SWMM package. The new Block is called SIDWEIR.

abstract: Master of Engineering (ME)


title: Non-Newtonian Fluid Flow in annuli

contributor:
Round, G.F.
Mechanical Design

abstract: The flow of non-Newtonian fluids in both concentric and eccentric annuli was investigated in this thesis. The model for generalized Bingham (Herschel-Bulkley) fluids was used in the studies, which included fully developed flow, entrance flow, start-up flow and pulsating flow in a concentric annulus and start-up flow in an eccentric annulus. A set of mathematical formulations has been developed for fully developed flow of generalized Bingham fluids in a concentric annulus. Velocity profiles are presented by using a numerical scheme to solve the equations. The position of the unsheared plug in the annulus may be determined by the solutions. The equations of motion for entrance flow and unsteady flow of generalized Bingham fluids in a concentric annulus have been derived with a group of dimensionless variables. A control volume based finite difference technique was used to solve the governing equations. The effects of generalized Bingham number Pl, flow index n and radius ratio s on velocity profiles and pressure drop in the annulus are presented. Velocity profiles of start-up flow of generalized Bingham fluids in an eccentric annulus were obtained from finite difference solutions of the equation of motion after transformation into bipolar coordinates. The effects of eccentricity were also considered.

abstract: Doctor of Philosophy (PhD)


title: Study of III-V Semiconductors by Spatially-resolved and Polarization-resolved Photoluminescence

contributor:
Cassidy, D.T.
Engineering Physics

subject:
Engineering Physics
Engineering Physics

abstract: Spatially-resolved and polarization resolved photoluminescence has been used to study the photoelastic effect and the correlation between strain fields on the facet and along the active region in semiconductor diode lasers. The spectral mapping ability of this technique has been developed and has been demonstrated to be a useful tool for the study of quantum well intermixing processes in InGaAsP systems.

abstract: Doctor of Philosophy (PhD)


title: Novel Water Soluble Polymers as Flocculants

contributor:
Pelton, Robert H.
Hamielec, Archie E.
Chemical Engineering

abstract:
High molecular weight poly(ethylene oxide) (PEO) is used in conjunction with a cofactor such as phenol formaldehyde resin (PFR) as flocculants for newsprint manufacture. The objectives of the work described in this thesis were to prepare flocculants superior to PEO and to determine the flocculation mechanism. A series of novel comb copolymers consisting of a polyacrylamide backbone with short pendant poly(ethylene glycol) (PEG) chains was prepared and characterized. Additionally, polymerization conversion curves and reactivity ratios were measured. An interesting finding was that the reactivity of the macromonomer in free radical copolymerization decreased with PEG chain length.

Flocculation results with both model latex dispersions and commercial wood pulp suspensions showed that copolymer chain length was the most important variable; molecular weights greater than 3 million were required for good flocculation. On the other hand, the PEG pendant chains could be as short as 9 ether repeat units. Also, only 1 to 2 PEG chains for every 100 acrylamide backbone moieties were required.

No published flocculation mechanisms could predict all the behaviors of the PEO or copolymer system. A new mechanism called complex bridging was proposed. According to this mechanism PEO or copolymer chains aggregate in the presence of cofactor to form colloidally dispersed polymer complex which heteroflocculates with the colloidal particles.

Given in this work is the first explanation of the requirement for extremely high PEO or copolymer molecular weights for flocculation. It is proposed that polymer chains with molecular weights less than 10⁶ collapse in the presence of PFR to an inactive precipitate before flocculation can occur whereas complexes based on very high molecular weight PEO collapse slowly enough to permit flocculation.

Published mechanistic studies are hindered by the fact that PFR has poorly defined structures. It is shown for the first time in this work that well-defined, linear, poly(p-vinyl phenol) (PVPh) is an effective cofactor.

abstract: Doctor of Philosophy (PhD)


title: A Comparative Investigation of Regulatory Reform in the Ontario For-hire Trucking Industry

contributor:
Kanaroglou, P.S.
Geography

subject: Geography Geography

abstract:
This thesis examines the reform of economic regulation as it applies to the for-hire trucking industry in Ontario through a comparative analysis of industry structure and performance before and after the introduction of the Truck Transportation Act (Dec. 15, 1988). The analysis employs intra-provincial shipment level data obtained from Statistics Canada as well as aggregate indicators of industry structure (firm size and numbers) and finances (costs).

With respect to industry structure, the findings suggest that the Ontario for-hire industry may have become more concentrated following reform. However, it is difficult to identify specific industry segments with the data employed. Financial data suggests that while Ontario firms spent more on brokers and rental equipment following reform, their expenditure on taxes and licenses did not change.

With respect to industry performance, there is no apparent widespread decline in average rate levels although certain industry segments do exhibit significant rate declines in the years following reform. This is particularly evident in the truckload segment. The rates for service involving small, less accessible communities do not appear to be affected by regulatory reform. Introducing more sensitive measures into the revenue model to capture the: influence of community size (market conditions) has not provided further insight into this question. Price-discrimination based on commodity type is similarly not affected by reform.

In general, the findings in this thesis suggest that in the case of Ontario, the reform of trucking regulation has not had a substantial impact on the for-hire trucking industry as a whole. This result contradicts the predictions of both the proponents and opponents of regulatory reform.

abstract: Doctor of Philosophy (PhD)


title: High-Strength, High-Conductivity, Two-Phase Materials

contributor:
Embury, J.D.
Materials Science

abstract:
Heavily deformed, two-phase materials have been shown to exhibit strengths well in excess of the rule-of-mixtures prediction using the bulk properties of the constituents. The work described in this thesis investigates a number of aspects regarding high-strength, high-conductivity, two-phase materials. Microstructural observations and mechanical testing were used to examine the process of co-deformation, the evolution of mechanical properties, and the thermal stability of these heavily deformed structures. Materials selection procedures for the design of high-field magnet coils were developed.

The sustained co-deformation of the two-phases leads to the conclusion that the second phase behaves as a shearable obstacle to dislocation motion. The increase in strength displayed by the two-phase material over the bulk constituent strengths may be explained by existing models of particle shearing if increased interfacial energy due to residual stress is accounted for. The increased work hardening displayed by copper-silver alloys subjected to intermediate annealing treatments is explained by a continuum description of the evolution of slip line length.

The combination of materials selection procedures and investigations into the strengthening and resistive mechanisms have led to a new approach to the design of non-uniform composite materials to optimize strength and resistivity in two-phase materials.

abstract: Doctor of Philosophy (PhD)


title: Synthesis, Characterization and Properties of Some Xenonium(II) Salts Containing Xe-O and Xe-N Bonds

contributor:
Schrobilgen, G.J.
Chemistry

subject: Chemistry Chemistry

abstract:
This Thesis describes the syntheses and spectroscopic characterization of noble-gas compounds containing xenon(II)-nitrogen and xenon(II)-oxygen bonds in solution by multinuclear magnetic resonance (multi-NMR) and in the solid state by low-temperature Raman spectroscopy.

The key synthetic approach for the preparation of novel xenon(II) compounds containing xenon-nitrogen and xenon-oxygen bonds involved the HF elimination reactions of XeF₂ with the AsF₆ˉ salts of several protonated oxygen and nitrogen bases in HF and BrF₅ solvents at low temperatures. In particular, CF₃C(OH)NH₂+AsF₆ˉ,F₅TeNH₃⁺AsF₆ˉ, and FO₂SNH₃⁺AsF₆ˉ reacted with XeF₂ by HF elimination to give CF₃C(OXeF)NH₂⁺AsF₆ˉ, F₅TeN(H)-Xe⁺AsF₆ˉ and FO₂SN(H)-Xe⁺AsF₆ˉ. The latter two salts are examples of a rare class of compounds in which xenon(II) is directly bonded to formally sp³-hybridized nitrogen atoms. Their characterization in solution by multi-NMR was facilitated by preparing the xenon compounds with ¹⁵N-enriched(99.5 atom %) starting materials, i.e., F₅TeNH₃⁺AsF₆ˉ and FO₂SNH₃⁺AsF₆ˉ. This allowed for the observation of the one-bond ¹²⁹Xe-¹⁵N scalar couplings in the ¹²⁹Xe and ¹⁵N NMR spectra.

The salts, CF₃C(OH)NH₂⁺AsF₆ˉ, F₅TeNH₃⁺AsF₆ˉ, and FO₂SNH₃⁺AsF₆ˉ, were prepared for the first time, and were characterized in the solid state by Raman spectroscopy, and in solution by ¹³C, ¹⁹F, ¹H and ¹²⁵Te NMR spectroscopy. The assignments of the Raman spectra of F₅TeNH₃⁺AsF₆ˉ and FO₂SNH₃⁺AsF₆ˉ were facilitated by recording the spectra of the natural abundance and 99.5 atom % ¹⁵N-enriched salts, resulting in ¹⁴/¹⁵N isotopic shifts for bands that involved vibrational motions of the nitrogen centers.

The compounds, F₅TeN(H)-Xe⁺AsF₆ˉ and CF₃C(OXeF)NH₂⁺AsF₆ˉ, were isolated in the solid state and characterized by low-temperature Raman spectroscopy. Assignment of the Raman bands associated with the vibrational motions of the nitrogen atom in F₅TeN(H)-Xe⁺AsF₆ˉ were facilitated by recording the Raman spectrum of the ¹⁵N-enriched compound and observing the ¹⁴/¹⁵N isotopic shifts. The compound, FO₂SN(H)-Xe⁺AsF₆ˉ, was too unstable to be isolated from solution and therefore was not characterized by Raman spectroscopy.

The compounds, CF₃C(OXeF)NH₂⁺AsF₆ˉ, F₅TeN(H)-Xe⁺AsF₆ˉ and FO₂SN(H)-Xe⁺AsF₆ˉ, were characterized in solution by use of ¹²⁹Xe, ¹²⁵Te, ¹⁵N, ¹⁹F, ¹H and ¹³C NMR spectroscopy. The assignment of the ¹H NMR resonances for CF₃C(OH)NH₂⁺ and CF₃C(OXeF)NH₂⁺ were facilitated by performing two dimensional heteronuclear (¹H-¹⁹F) NOESY experiments, providing the first use of this technique in noble-gas chemistry.

The decomposition of F₅TeN(H)-Xe⁺AsF₆ˉ in HF and BrF₅ solvents has been studied in detail, primarily by ¹⁹F NMR spectroscopy. The primary decomposition product, F₅TeNF₂, results from nucleophilic fluorination of F₅TeN(H)-Xe⁺, and has been characterized for the first time by use of ¹⁵N and ¹⁹F NMR spectroscopy. The compound, F₅TeNF₂, was shown to react with F₅TeNH₃⁺AsF₆ˉ in AsF₅-acidified HF to give FN≡N⁺ AsF₆ˉ and TeF₆ by ¹⁹F NMR spectroscopy.

abstract: Doctor of Philosophy (PhD)


title: Synthetic, Structural and Spatial Studies of Rhenium Compounds

contributor:
Lock, C.J.L.
Chemistry

subject: Chemistry Chemistry

abstract:
A new concept, Virtual Radii, is introduced to define the non-bonding interactions of ligating atoms in the coordination sphere of six coordinated transition metal compounds. The interactions of structural parameters in the coordination sphere and their chemical consequences are discussed within the bounds of a systematic study of Vinual Radii and Solid Angle Factors were extracted for six coordinated rhenium compounds with the use of the Cambridge Structural Database, recent publications, and structures determined in this study.

Thirteen structures were determined to answer chemical questions as well as to provide additional data for the spatial studies. The questions were: i. What was the real structure of the compound formulated as K[Re₂O₂H(CO)₈] by Hieber and Schuster? ii. Is the cyanide ion bonded to the rhenium atom through the nitrogen atom in the compound "K₂[ReN(NC)₄]∙H₂O" as proposed in the literature? iii. Is it possible to synthesize some new neutral or monocationic rhenium or technetium species with ligands that contain pyrazole?

Reactions of Re(CO)₅CI and KOH under various conditions produced several products. The structures of five of them, KRe₃(CO)₉(OMe)₄ (3A), Re₄(CO)₁₂(OH)₂(OEt)₂∙2EtOH (3B), Re₄(CO)₁₂(OH)₄∙8H₂O (3C), KRe₂(CO)₆(OH)₃∙2H₂O(3D), KRe₃(CO)₉(OH)₄ (3E), were determined by single-crystal X-ray diffraction methods. The structure of 3D clarified question (i).

X-ray crystal structure determination of (AsPh₄)₂[ReN(CN)₄(H₂O)]∙5H₂O (4B) indirectly answered question (ii) and showed that the literature was wrong.

As part of the basic research on the development of new radiopharmaceuticals, new compounds with pyrazole-containing ligands, ReO(HBPz₃)(NCS)₂ (5A), ReO(HBPz₃)(PzOCMe₂)∙ReO₄ (5B), ReOCl₂(PPh₃)(PzOCMe₂) (5C), ReOCl₂(PPh3)(PzOCHMe)∙0.5CHOCHO (5D), Re₂O₃Cl₂(PPh₃)₂(Pz)₂∙CHCl₃ (5E), Re₂O₃Cl₂(3,5-Me₂-Pz)₂(3,5-Me₂-HPz)₂ (5F) were prepared and characterized. The investigations were extended to new compounds [ReOCl₂(PPh₃)L]∙2H₂O (5G) and [TcOL₂(HL)]TcO₄ (5H), where HL was 4-hydroxymethyl-1,5-dimethyl-imidazole. The X-ray crystal structures of all compounds, except 5A, were determined.

abstract: Doctor of Philosophy (PhD)


title: Investigation of Regulation of Transfer RNA Gene Expression in Mammalian Cells: Utilization of a Human Nonsense Suppressor Transfer RNA

contributor:
Capone, John P.
Biochemistry

subject: Biochemistry Biochemistry

abstract:
The regulation of eukaryotic transfer RNA gene expression serves largely to adapt the abundance of each isoacceptor tRNA species to the codon frequencies and amino acid usages particular to different cell types. tRNA genes are independently transcribed and, even within an isoacceptor family, can display considerable differences in transcriptional activity in vitro which cannot be ascribed to the highly conserved nature of their intragenic promoter elements. In this regard, it is well documented that expression of transfer RNA genes can be dramatically influenced in a wide variety of species by 5' flanking sequences. Unfortunately, it remains uncertain what role the majority of these modulatory elements play in their normal cellular context since most of these studies have utilized in vitro transcription systems whose ability to faithfully reproduce cellular conditions is questionable. Unfortunately, it is difficult to monitor the expression of an individual tRNA gene in vivo since the gene for any particular isoacceptor is reiteratedin the eulcaryotic genome. To overcome this, a nonsense suppressor transfer RNA gene has been utilized to study the regulation of tRNA gene expression in mammalian cells. Specifically, the functional expression of a human serine amber suppressor tRNA gene has been quantified in vivo by assaying its ability to suppress an amber nonsense mutation in the Escherichia coli chloramphenicol acetyltransferase gene following cotransfection in mammalian cells.

Through utilization of the aforementioned in vivo assay the suppression activity of a series of upstream deletion and substitution mutants of the human serine tRNA gene was determined. Mutant genes in which the 18 nucleotides 5' proximal to the coding region were deleted and replaced with heterologous sequences, were 2 to 5 fold more active in vivo in comparison to the wild type gene. The serine tRNA gene constructs were also transcribed in vitro using HeLa cell nuclear extracts. The strong correlation between the transcriptional activity in vitro and functional expression in vivo of the various mutants indicates that this negative element acts by modulating the transcriptional activity of the serine tRNA gene and suggests that this element plays a physiologically relevant role within the mammalian cell. Second template competition experiments demonstrate that the element reduces the ability of the serine tRNA gene to stably sequester limiting transcription components. The results from several insertion mutants, which effectively alter the orientation and upstream position of this negative element, suggest that it acts in a dominant negative manner in vivo and in vitro.

The precise mechanism by which extragenic flanking sequences modulate tRNA gene transcription is unknown and a direct comparison of identified modulatory regions has failed to reveal conserved sequence elements that could be ascribed to being positive or negative transcriptional modulators. One possibility is that specific regulatory factors bind these upstream sequences and attenuate tRNA gene transcription, but the isolation of any such activity has been difficult to demonstrate since the composition of higher eukaryotic tRNA gene transcription complexes is unknown. As an alternative approach to examining this possibility, an oligonucleotide containing the recognition site for the Escherichia coli lac repressor was inserted at various positions in the 5' flanking region of the human serine tRNA gene and the consequences of binding lac repressor on in vitro transcription by RNA polymerase III was investigated. lac repressor prebound to operator sites centered at positions -9, -15, -35, and -37 upstream of the mature tRNA coding region completely inhibited transcription by interfering with the formation or stability of transcription complexes. lac repressor also inhibited transcription of serine tRNA gene derivates containing operator sites at -9 and -15 when added following transcription complex assembly or during ongoing synthesis, but had no effects on the other tRNA gene derivatives if added subsequent to complex assembly. lac repressor prebound at position -43 and -46 partially inhibited transcription and redirected initiation to sites farther downstream. These results show that the functional human RNA polymerase III transcription complex extends at least 35 nucleotides upstream of the tRNA gene coding region and that the sequences surrounding the transcription start site remain accessible to DNA-binding proteins throughout multiple rounds of transcription. Normal transcription was restored with the addition of the allosteric inducer IPTG demonstrating that these effects require the continued presence of bound repressor protein. In addition, lac repressor inhibited the functional expression of the human serine tRNA gene in vivo since inclusion of a plasmid expressing the lac repressor in the above cotransfection assay resulted in inhibition of suppression activity of lac operator-linked genes. This effect was also alleviated with IPTG. These results demonstrate that a heterologous DNA binding protein bound to 5' flanking sequences can be used to regulate the expression of a mammalain tRNA gene in vivo and in vitro. Although artificial in its approach, this study shows that this is a potential mechanism by which naturally occcuring regulatory proteins may modulate the expression of cellular tRNA genes. In addition, these experiments revealed information regarding the upstream spatial arrangement and topological boundaries of functional mammalian tRNA gene transcription complexes.

abstract: Doctor of Philosophy (PhD)


title: Nonsense Suppressor tRNAs in the Study of Class II and Class III Gene Expression and Regulation

subject: Biochemistry Biochemistry

abstract: The ability of suppressor (su⁺) tRNAs to abrogate the effects of otherwise-lethal nonsense mutations forms the basis of a genetic screen for the identification of essential genes. The availability of numerous nonsense su⁺ tRNA strains of E. coli and yeast led to the rapid development of prokaryotic and yeast genetics. The recent availability of mammalian nonsense su⁺ tRNA genes has afforded not only the opportunity of applying similar strategies towards the advancement of mammalian viral and cellular genetics, but also the opportunity to examine the regulation of transcription by RNA polymerase III (polIII) in vivo. This thesis comprises two parts. The initial aim of this work involved the development and use of mammalian systems of nonsense mutation suppression to examine the mechanisms of eukaryotic class II gene expression and regulation. Herpes simplex virus type-1 (HSV-1) was chosen as a model system since HSV-1 genes are expressed in a regulated cascade. A natural progression of this work involved the study of the molecular mechanisms of mammalian polIII transcription in vivo and in vitro. Initial work involved the identification and propagation of conditional-lethal nonsense mutants of HSV-1 using a mammalian cell line which can be induced to express high levels of a human amber su⁺ tRNA^(Ser) gene as the permissive host in a simple host-range screening system. Several HSV-1 mutants have been isolated from virus stocks mutagenized with nitrous acid and have been partially characterized. Such mutants exhibit a number of interesting temperature- and/or host-range-dependent phenotypes including variations in growth, cell-to-ceil spread, and plaque morphology. Mutant A7'(A9-2) is particularly interesting since this isolate is defective in an essential function required for HSV-1 late gene expression. Isolate A7'(A9-2) is a potential nonsense mutant since a growth enhancement of 100 fold is exhibited under conditions of suppression. To enhance the utility of mammalian systems of nonsense mutation suppression, a novel and more generally applicable means of efficiently regulating the expression of a su⁺ tRNA gene was developed. Stringent control of su⁺ tRNA gene expression is required since constitutive high levels of nonsense suppression activity is deleterious to mammalian cells. The Escherichia coli (E. coli) lac operator/repressor system has been adapted to confer inducibility upon the human su⁺ tRNA^(Ser) gene both in vivo and in vitro. Lac repressor protein, bound to its cognate lac operator site appropriately positioned upstream of the su⁺ tRNA gene, stringently inhibited tRNA gene expression in vivo, as determined by quantitating suppression of an indicator gene nonsense mutation following transfection of mammalian cells. However, su⁺ tRNA gene expression was quantitatively restored with the allosteric inducer isopropylthio-β-D-galactoside (lPTG). Similarly, lac repressor effected the complete inhibition of lac operator-linked tRNA gene transcription in vitro in HeLa cell nuclear extracts by precluding the assembly of an active polIII transcription complex, and this inhibition was reversible with IPTG. The results demonstrate that a DNA binding protein positioned upstream of a eukaryotic tRNA gene may impart transcriptional regulation upon tRNA gene expression, a novel and particularly intriguing finding in view of the intragenic nature of tRNA gene promoters. The ability to conveniently and reversibly manipulate su⁺ tRNA gene expression may foster rapid progress in the development of mammalian nonsense su⁺ tRNA genetics, perhaps through the establishment of additional mammalian cell lines which conditionally express a variety of nonsense su⁺ tRNA genes. The second aspect of this thesis involved an examination of the molecular mechanisms that govern transcription by polIII which, in mammalian systems, has remained largely refractory to study through conventional approaches. A novel approach was adopted and involved use of the lac repressor protein as a reagent to probe various stages of polIII transcription to define the promoter disposition and functional properties of mammalian polIII transcription complexes. The effect on tRNA gene transcription, of varying the position of lac repressor protein upstream and downstream of the tRNA gene, was examined in vitro in HeLa cell nuclear extracts. Lac repressor differentially and reversibly interfered with different stages of transcription complex assembly and productive initiation. Such analyses have identified distinct functional and structural properties of mammalian polIII transcription complexes, and have provided a view of the spatial arrangement of mammalian polIII preinitiation complexes. The mammalian polIII transcription complex extends at least 35 nucleotides (nts) upstream, and to within 10 nts downstream of the tRNA gene. Moreover, sequences directly upstream of the coding region remain accessible to DNA binding proteins throughout multiple rounds of transcription. The results illustrate a number of potential mechanisms whereby DNA binding factors may modulate transcription initiation by polIII. The lac operator/repressor system has also afforded a novel means of examining transcription elongation and termination by mammalian polIII. Lac repressor protein, appropriately positioned downstream of the tRNA gene coding region, reversibly blocked elongation by polIII in vitro in HeLa cell nuclear extracts, thereby resulting in either the formation of paused polIII ternary transcription complexes, a subset of which maintained the ability to undergo direct transcriptional readthrough of the lac repressor obstacle, or in premature transcription termination. The formation of paused polIII ternary complexes effectively mediated the inhibition of tRNA gene transcriptional activity, which was restored upon removal of the repressor-mediated block with IPTG. The results demonstrate that DNA binding proteins can modulate elongation and termination by polIII in vitro, and suggest that conditional factor-mediated blocks to elongation by polIII may function in vivo to attenuate transcription of class III genes. The ability to selectively arrest elongation by polIII at defined positions within the tRNA gene transcription unit has permitted the identification of discrete functional properties of paused mammalian polIII ternary complexes and may afford a novel strategy for the generation of homogeneous populations of stalled polIII ternary complexes, in which to study their biochemical properties.

abstract: Doctor of Philosophy (PhD)


title: Inhibition of Bacterial Sporulation by Various Agents: An Ultrastructural Analysis

contributor:
Takahashi, I.
Biology

subject: Biology Biology

abstract: An electron microscopic analysis of Bacillus subtilis cells revealed that relatively that relatively high concentrations of rapidly metabolizable carbon sources blocked sporulation at stage O. Acridine orange blocked sporulation only after stage IV whereas nalidixic acid and novobiocin blocked sporulation at stage O. Mutants that are able to sporulate in the presence of these agents showed the characteristic morphological changes observed in uninhibited cultures. These results are discussed in terms of the different modes of action exerted by these agents in repressing sporulation.

abstract: Master of Science (MS)


title: Dynamic Mathematical Modelling of Polymerization of Olefins Using Heterogeneous and Homogeneous Ziegler-Natta Catalysts

contributor:
Hamielec, Archie E.
Chemical Engineering

abstract:
An integrated methodology based on Stockmayer's bivariate distribution for the dynamic mathematical modelling of the kinetics of olefin polymerization using heterogeneous and homogeneous Ziegler-Natta catalysts has been developed. This methodology uses polymer characterization via size exclusion chromatography (SEC), temperature rising elution fractionation (TREF), and carbon-13 nuclear magnetic resonance (¹³C NMR) to estimate polymerization kinetics parameters and provide information about the types of active sites of the catalyst.

A novel and versatile mathematical model for the dynamic simulation of binary copolymerization of olefins using Ziegler-Natta catalysts has been proposed. This model calculates the complete distributions of chemical composition and molecular weight of polyolefins made with catalysts containing multiple active site types and subject to intraparticle mass and heat transfer resistances. This model has a very attractive mathematical formulation that permits easy adaptation to situations in which intraparticle mass and heat transfer resistances are negligible and can also be conveniently combined with mathematical models for the dynamic macroscopic simulation of polymerization reactors for process simulation, optimization and control studies.

The homopolymerization of propylene and ethylene using a titanium-based heterogeneous catalyst was investigated. The presence of hydrogen during the polymerization of propylene was found to increase the rate of propylene polymerization by creating new active site types. This was clearly shown using SEC and TREF analyses of the polypropylenes.

A systematic methodology for the deconvolution of the molecular weight distribution (MWD) of linear polyolefins made with multiple site type catalysts has been developed. The MWD of polyolefins measured by SEC is deconvoluted into individual most probable chain length distributions using a mathematical method that takes advantage of the conditional linearity of the optimization problem.

A mathematical model for simulation of TREF fractionation of binary copolymers made with multiple site type catalysts using Stoclanayer's bivariate distribution has been developed. This is the first time a mathematical model is proposed to describe the MWD of TREF fractions using a phenomenological approach considering the influence of the bivariate distribution of molecular weights and copolymer composition in the fractionation. The modelling of TREF with this model provides an ideal limiting case for the fractionation of binary linear copolymers with broad molecular weight and composition distributions and is useful in interpreting TREF fractionation results.

abstract: Doctor of Philosophy (PhD)


title: Studies of Genetic Variation in Murine Intestinal Disaccharidases

contributor:
Underdown, Brian J.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract:
Intestinal disaccharidases are enzymes located in the apical membrane of enterocytes of the small intestine. These proteins are responsible for the breakdown of dietary carbohydrates. Despite the central importance of mouse genetics to modern biomedical research, little is known concerning the structure and regulation of the expression of murine intestinal disaccharidases. Moreover, limited information exists on the variations in molecular and genetic characteristics that the murine enzymes display between mouse strains.

In this thesis a partial characterization of murine intestinal disaccharidases expressed by seven different mouse strains was performed. Data obtained in these studies indicated the existence of two independent congenital deficiencies of murine intestinal disaccharidases. The two described murine deficiencies constitute the only cases in which normal and altered phenotypes are available in genetically related strains of animals. Therefore, these two deficiencies may serve as excellent models for the study of disaccharidase deficiencies.

One of the deficiencies consisting of relative low levels of sucrase activity, was found to be present in CBA/Ca mice and other two CBA/Ca-derived strains. These CBA/Ca mouse strains displayed aproximatedly 50% of intestinal sucrase activity compared to the other four mouse strains analysed. Experiments using papain-solubilized intestinal disaccharidases, molecular sieving HPLC, heat-inactivation and kinetic analysis of the sucrase activity, demonstrated that the deficiency was most likely caused by a structural alteration of the SucraseIsomaltase complex expressed by the CBA/Ca and derived mouse strains.

The second observed deficiency consisted in a virtual absence of y-Glucoamylase maltase activity exclusively in CBA/Ca mice. When analysed by heat-inactivation, molecular sieving HPLC and 2D-electrophoresis, the absence of y-Glucoamylase maltase activity was demonstrated to be caused by a lack of synthesis of y-Glucoamylase molecules in CBA/Ca mice.

The genetic background of the two disaccharidase deficiencies was analysed by cross-breeding CBA/Ca mice with CBA/J mice; the first strain displaying low sucrase and lack of y-GA expression and the second displaying normal phenotypes. The levels of activity of intestinal sucrase, maltase and palatinase expressed in the resulting F1 mice indicated that each of these deficiencies is most probably caused by a single defective gene, respectively. In addition, the defects were of a somatic nature and codominantly expressed with the respective normal phenotype.

Finally, data obtained from a partial molecular characterization of murine intestinal y-Gluccamylase indicated that the enzyme may be originally synthezised as a single polypeptide with approximated M.W. of 410 kDa. This polypeptide constitutes a precursor of four additional polypeptides with M.W. of 275, 260, 140 and 130 kDa, respectively, generated by proteolytic cleavage at two alternative points along the precursor molecule. The enzyme contains one single type of active site and variable proportion of N-linked carbohydrates. These data provide additional information on the inter-species structural variation of this enzyme and probable posttranslational processing experienced by y-Glucoamylase.

abstract: Doctor of Philosophy (PhD)


title: Non-normal analysis of variance and regression procedures based on modified maximum likelihood estimators

contributor:
Tiku, M.L.
Mathematics

subject: Mathematics Mathematics

abstract:
The assumption of normality appears prevalently in well-known statistical procedures. This may be a drawback, since it is very often the case that the data under study is not normally distributed. It is of interest to relax this normality assumption, and extend many commonly used statistical procedures to include non-normal situations.

With this in mind, we have proposed non-normal Regression and Analysis of Variance schemes based on Tiku and Suresh's (1992) Modified Maximum Likelihood procedure, for a symmetric non-normal family of distributions. The results have been derived both for complete and censored samples. The resulting non-normal procedures are exactly similar in form to the classical results, and are no more difficult to implement. They are also asymptotically fully efficient. Simulation studies have shown that the new methods are extremely efficient, even for distributions far from normal, and for small samples.

It is hoped that these new techniques present viable alternatives for data analysis when the normality assumption may not be justified.

abstract: Doctor of Philosophy (PhD)


title: The Effects of Membrane Physical Properties on Insulin Receptor Autophosphorylation and Signalling

contributor:
Epand, Richard
Biochemistry

subject: Biochemistry Biochemistry

abstract:
Many membrane functions are modulated by the bulk biophysical properties of the membrane. Various compounds which alter membrane physical properties were investigated for their ability to modulate insulin receptor autophosphorylation and signaling. Compounds of diverse structure, which raise the lamellar to inverted hexagonal phase transition temperature (Tʜ) in model membranes, including carbobenzoxy-dipeptides, apolipoprotein A-I, acyl carnitines, and lysophosphatidylcholine, inhibited insulin-stimulated tyrosine phosphorylation of isolated receptors, as well as of receptors in cells over-expressing human insulin receptor. For compounds of similar structure, the inhibition of insulin receptor tyrosine phosphorylation correlates well with their bilayer stabilizing potency. All of the compounds tested exert their effects independently of changes in insulin binding to the receptor or changes in the basal tyrosine kinase activity of the receptor. We suggest that the membrane additives tested affect insulin receptor activity through alterations of the bulk physical properties of the membrane. This is further supported by the inability of these compounds to influence the soluble insulin receptor kinase domain activity, measured in the absence of phospholipids. In addition, stereoisomers of dipeptide analogues had identical effects on insulin receptor phosphorylation, suggesting that their mode of action did not involve specific interactions with the receptor.

Most of the compounds which inhibit tyrosine phosphorylation of the insulin receptor also inhibited glucose uptake in the same cells. Insulin-stimulated fluid phase pinocytosis was also inhibited by peptides which raise Tʜ. This suggests that alteration of membrane physical properties affects the divergent pathways involved in insulin receptor signal transduction.

Compounds which lower the bilayer to hexagonal phase transition temperature in model membranes enhanced insulin stimulation of autophosphorylation in isolated receptors, with no effect on insulin receptor phosphorylation or signalling to glucose uptake in intact cells. The effects of cationic amphiphiles were not readily predictable from their membrane modulating activity.

This thesis provides evidence that the mechanism of modulation of insulin signalling by these additives lies in the ability of such compounds to alter the bulk physical properties of the membrane. The results suggest that membrane monolayer curvature strain is a factor contributing to the efficiency of insulin signal transduction.

abstract: Doctor of Philosophy (PhD)


title: Some Properties of S and D--Wave 2 Dimensional Superconductors

contributor:
Carbotte, J.P.
Physics

subject: Physics Physics

abstract:
We utilize Eliashberg theory, up to the Migdal approximation, to study some properties of two dimensional superconductors. The mechanism of superconductiviiy in this thesis is bosonic, either caused by phonons or by spin fluctuations. The order parameter is an s-wave for the phonon mechanism or a d-wave when considering spin fluctuations.

The two dimensional (2D) superconductor is modeled by a stack of conducting sheets and coupling between the sheets is neglected for simplicity. The electronic density of states (EDOS) of a 2D electron gas on a lattice possesses a singular peak usually called a van Hove singularity (vHs). The presence of a vHs near the Fermi level is shown to enhance the superconducting transition temperature, Tc, for both mechanisms as well as reduce the isotope effect, β, from its standard value of 0.5 (predicted by BCS theory).

The Eliashberg equations (EE) on the imaginary axis are handled in two ways i) the EDOS is used directly when integrating out the energy dependence of the EE to get analytical expressions that can be solved numerically ii) the k-sum is handled numerically from the start and the whole 2D Brillouin zone is used. In the first approach, infinite band models of EDOS are used, in the second only the dispersion of the electron gas has to be specified.

Some of the properties calculated in this thesis are the critical temperature, the isotope effect (for phonons only), the specific heat difference and its jump at Tc, the thermodynamic critical field, the upper critical field and the London penetration depth. Impurity scattering is also considered, in Born approximation and in resonance scattering (for d-wave only). Experimental comparison with our results show that the isotope effect and the specific heat jump at Tc correlate very well with an s-wave order parameter, while the low temperature dependence of the London penetration depth and some superconducting specific heat results are best described by a d-wave order parameter.

abstract: Doctor of Philosophy (PhD)


title: Augmented levels of tolerance and physical dependence in rats self-administering morphine compared to those passively receiving the drug

contributor:
Siegel, S.
Psychology

subject: Psychology Psychology

abstract: Two physiological changes (namely tolerance and physical dependence) reliably emerge following repeated exposure to the opiate drugs and are considered to be important contributors to the behavioural state of addiction. As such, they are often induced in experimental subjects prior to examining addictive behaviour. An assumption implicit in such work is that the physiological effects of passively-administered drugs are equivalent to those of actively self-administered drugs. Two experiments are presented which demonstrate that the development of both tolerance and physical dependence is attenuated in rats passively receiving morphine compared to those self-administering identical doses of the drug. An additional experiment found evidence for the ability of a schedule of passive drug delivery to attenuate physical dependence and tolerance established through drug self-administration. Furthermore, in all three experiments, tolerance and physical dependence were found to develop rapidly and reliably following the self-administration of surprisingly small doses of morphine. One means by which self-administration might facilitate the acquisition of tolerance and physical dependence is through the inherently greater predictability of self-administered drug doses. An experiment designed to assess whether increased signalling of impending drug doses would likewise facilitate the acquisition of tolerance and physical dependence failed to demonstrate any such effect.

abstract: Doctor of Philosophy (PhD)


title: The Genetic Basis Of Variation in a Polygenic Character: Bristle Number in Drosophila melanogaster

contributor:
Singh, R.S.
Biology

subject: Biology Biology

abstract: Quantitative traits are important in medicine, evolution, and plant and animal breeding, yet very little is known about the nature of standing variation at the loci that affect quantitative traits. This thesis describes experiments designed to determine the nature of standing genetic variation for a model train; bristle number in Drosophila melanogaster. The first experiment mapped factors responsible for response to short term selection on abdominal bristle number. Eight factors of large effect which accounted for much of the difference between the parental lines were mapped to the X and third chromosomes. Sex specific and epistatic effects of the same order of magnitude as the allelic effects were associated with the mapped factors. In addition, factors mapped to the approximate positions of likely candidate loci (ASC, bb, emc, h, mab, Dl, and E(spl)), previously characterized by mutations with large effect on bristle number. In a second experiment restriction variation among 47 naturally occurring second chromosomes was associated with variation in abdominal and sternopleural bristle number. Unlike previous studies, the molecular variants associated with phenotypic variation were not large insertion and deletions, but intermediate frequency restriction site variants. A new permutation test based statistical method was developed in this work in order to assess the significance of the observed associations between molecular and phenotypic variation. The experiments described in this thesis do not support the infinitesimal model of quantitative variation, and instead suggest that a great deal of quantitative genetic variation in nature may be due to alleles of large effect at candidate loci that are at intermediate frequency.

abstract: Doctor of Philosophy (PhD)


title: Adaptive Neurocontrol and Its Application to Robots

contributor:
ElMaraghy, Hoda A.
Mechanical Engineering

abstract:
This thesis is devoted to investigating adaptive neurocontrol of nonlinear systems with uncertain or unknown dynamic models. Novel theoretical synthesis and analysis of neurocontrol systems have been conducted, and applied to the control of flexible joint robots with experimental tests. The contributions of this thesis fall into the following three areas: (1) neural networks, (2) adaptive neurocontrol and (3) control of flexible joint robots.

The aim of my research in the neural network area is to search for fast and global convergent learning algorithms with reduced computation burden. The localized neural networks with competitive lateral inhibitory cells were introduced. The developed extended Kalman filtering algorithm with UD factorization can make the localized polynomial networks and localized pi-sigma networks possess fast learning convergence and less computation. The multi-step localized adaptive learning algorithm was derived for RBF networks which leads to about 10 fold improvement in the speed of learning convergence. New neural network models of nonlinear systems were introduced to facilitate neurocontroller design.

In the adaptive neurocontrol area, theoretical issues of the existing backprop-based adaptive neurocontrol schemes were first clarified. Then new direct and indirect adaptive neurocontrol schemes, with better performance, were proposed. It is noticed that the system stability of many existing neurocontrol schemes cannot be proved. In addition, few stability-based adaptive neurocontrol schemes are available and can only be applied to feedback linearizable nonlinear systems. The thesis provides two major contributions to the stability-based adaptive neurocontrol approach. The first contribution is extending the classical self-tuning control methodologies for linear systems to the self-tuning neurocontrol of nonlinear systems by using localized neural networks. This extension greatly enriches the neurocontrol algorithms with guaranteed system stability. The second contribution is proposing the variable index control approach, which is of great significance in the control field, and applying it to derive new stable robust adaptive neurocontrol schemes. Those new schemes possess inherent robustness to system model uncertainty, which is not required to satisfy any matching condition. They do not impose any growth condition and infinite differentiability assumption on the system nonlinearity. They can also be applied to nonlinear systems which are not feedback-linearizable.

As applications and extensions of the above theory, three different robust adaptive neurocontrol schemes for general flexible joint robots were derived with proven system stability. All three schemes are able to incorporate a priori information about the robot dynamics into the neurocontroller design to simplify the neural network design. No acceleration and jerk signals are required in these control laws. Moreover, arbitrary joint stiffness is allowed in the control algorithms.

To demonstrate the feasibility of the proposed learning algorithms and adaptive neurocontrol schemes, intensive computer simulations were conducted based on different nonlinear systems and functions. Different types of adaptive tracking problems and regulation problems were considered. Furthermore, the proposed adaptive neurocontrol schemes were experimentally tested using an existing experimental flexible joint robot. Both the simulation and experimental results confirm the practicability of the proposed schemes.

The thesis concludes that the neurocontrol approach, along with the development of neural computers and large scale parallel distributed processors, is capable of solving the complex control problem of nonlinear systems with uncertain or unknown dynamic models.

abstract: Doctor of Philosophy (PhD)


title: Dynamic Simulation and Computer Control of a Pilot Scale Fluidized Bed Reactor

contributor:
MacGregor, J.F.
Hoffman, T.W.
Chemical Engineering

abstract:
A dynamic simulation of the pilot scale fluidized bed reactor in the Department of Chemical Engineering is developed based on mass/energy balance equations of the process. The unknown parameters in the model equations are estimated using dynamic data from the reactor. A preliminary control strategy for the reactor system is tested by simulation, and the results are used to aid in the implementation of the control system to the reactor. The control strategy is a cascade control system in which the inner loop regulates reaction temperature by proportional-integral control, using the ratio of hydrogen to n-butane feedrates as manipulated variable. The outer loop is a Dahlin's algorithm controller. which maintains the selectivity of propane at a specified setpoint by manipulating the reaction temperature setpoint to the inner loop.

The control system performed less favourably on the real system than it did on the simulation model. This result is attributed primarily to the inability of fixed-parameter controllers to deal with highly non-linear and time varying processes. Alternate control methods are suggested which are designed to deal with these problems.

abstract: Master of Engineering (ME)


title: Nonlinear Adaptive Prediction of Nonstationary Signals and its Application to Speech Communications

contributor:
Haykin, Simon
Electrical and Computer Engineering

abstract:
Prediction of a signal is synonymous with modeling of the underlying physical mechanism responsible for its generation. Many of the physical signals encountered in practice exhibit two distinct characteristics: nonlinearity and nonstationary. Consider, for example, the important case of speech signals. The production of a speech signal is known to be the result of a dynamic process that is both nonlinear and nonstationary. To deal with the nonstationary nature of signals, the customary practice is to invoke the use of adaptive filtering. Unfortunately, the nonlinear nature of the signal generation process has not received the attention which it deserves in that much of the literature on the prediction of speech signals has focused almost exclusively on the use of linear adaptive filtering schemes.

This thesis is aimed at the study of nonlinear adaptive prediction of nonstationary signals using neural networks and its application to real-time speech communication. In this thesis, three basic questions are answered: 1) What kind of neutral networks are suited for real-time adaptive signal processing? 2) How can an adaptive neural network predictor be designed? 3) Can a neural network predictor be used for the application of real-time communication?

In this thesis, a new Pipelined Recurrent Neural Network (PRNN) is designed. The PRNN is composed of M separate modules. The modules are identical, each designed as a recurrent neural network with a single output neuron. Information flow into and out of the modules proceeds in a synchronized fashion.

A new scheme for the nonlinear adaptive prediction of nonstationary signals is proposed. The nonlinear neural network-based filter, which consists of a PRNN and a linear filter, learns to adapt to statistical variations of the incoming time series while, at the same time, the prediction is going on. The dynamic behavior of the pipelined recurrent neural network-based predictor is demonstrated in the case of several speech signals; for these applications it is shown that the nonlinear adaptive predictor outperforms the traditional linear adaptive scheme in a significant way. It should however, be emphasized that the nonlinear adaptive predictor has a much wider range of applications such as the adaptive prediction of sea clutter.

The PRNN-based adaptive predictor is applied to the adaptive differential pulse code modulation. In the encoder and decoder parts of an ADPCM system, the predictor is successfully incorporated with an adaptive quantizer for low bit-rate speech communication. The research work involves a novel combination of pipelined recurrent neural network and a robust linear adaptive filter, and the design of a new 4-, 8- or 16-level adaptive quantizer. The nonlinear adaptive differential pulse code modulation algorithm is tested with different speech signals. The new algorithm is compared with a linear ADPCM algorithm, recommended by CCITT, from several aspects such as time domain, frequency domain, and listening tests. Speech experiments show that nonlinear adaptive differential pulse code modulation provides a promising new approach for high-quality communication at low bits rates.

abstract: Doctor of Philosophy (PhD)


title: ESR Plateau dating of fault rocks

contributor:
Schwarcz, Henry P.
Geology

subject: Geology Geology

abstract:
Past movement on faults can be dated by measurement of the intensity of ESR signals in quartz. These signals are reset by lattice deformation and heating on grain contacts during faulting. The ESR signals then grow back as a result of bombardment by ionizing radiation from surrounding rock. The age is obtained from the ratio of the equivalent dose, Dᴇ, needed to produce the observed signal, to the dose rate. Fine grains are more completely reset during faulting, and a plot of age vs. grain size shows a plateau for grains with radius r < 75 μm; these grains are presumed to have been completely zeroed by the last strain event, the age of which they record with a precision of 5-15 %.

Two major fault zones (San Gabriel and Santa Susana-Sierra Madre) and folds are developed in the Little Tujunga region, in southern California. The trace of thrust faults and folds of the Santa Susana-Sierra Madre fault zone are roughly parallel to the San Gabriel fault zone, indicating that the maximum horizontal stress was nearly perpendicular to the San Gabriel fault zone. Bends in the main strands of the San Gabriel fault zone yielded local transpressive regimes and changed the direction of maximum horizontal stress to a lower angle to the main strands, resulting in the development of subsidiary faults and folds oblique to the main trend of the fault. These structural features can be explained by the process of low drag-decoupled shear combined with transpression.

Type I and II fault zones in a single outcrop can give us the age of each stage of the evolution of fault rock zones. For Type III fault zone, we can determine only the age of last movement. The sequence of ESR plateau ages is consistent with the sequence of fault movement recognized by geological intersection relationship.

ESR ages from both the main strands and subsidiary faults range from 1170 to 40 ka. The ages show temporal clustering into active and inactive periods, analogous to that seen in historic and Holocene earthquake fault activity. Within a given active period, activity is spread out at a restraining bend in the San Gabriel fault zone. Historic earthquake faults similarly show that fault strain was prohibited in restraining bends and that fault activities spread out up to several km away from the main strand.

The San Gabriel fault zone was formerly considered to be an exhumed ancient fault of the San Andreas fault system. The results suggest that although much less active than the San Andreas fault zone (average recurrence interval in Pallett Creek: 132 a; Sieh et aI., 1989), the long term (80-120 ka) cyclic fault activity of the San Gabriel fault zone continued during the Pleistocene.

I have studied the temporal distribution of paleoseismic records of earthquakes in several regions of California over time scales ranging from decades to several hundreds of thousands years, using dates obtained by ESR plateau dating of fault gouge, ¹⁴C dated sediments from fault zones and records of historic earthquakes. The historical record in the San Andreas fault zone of central California, and the paleoseismic record of the San Gabriel fault zone both exhibit self similarity with a fractal dimension of 0.43-0.46. The fractal dimension of the San Andreas fault zone in Southern California both in historic and paleoseismic time scales is 0.67 indicating more evenly distributed fault movements than that of the central California. On time scales < 1 y, the distribution is largely random.

Seven out of ten samples collected at the URL site of AECL, Pinawa, Manitoba were saturated. The three ESR plateau ages appear to lie in interglacials, which is consistent with a model in which movement on the thrust fault is triggered by melting of an ice sheet at the end of a glacial stage.

abstract: Doctor of Philosophy (PhD)


title: Hunter, Adult Adolescent, and Wounded Warlock: Images of Men in English-Canadian Women's Fiction (1960-93)

contributor:
Coldwell, Joan
English

subject:
English Language and Literature
English Language and Literature

abstract:
Although the fiction written by women in English-Canada since the 1960's has experimented widely with literary form, a remarkably consistent set of literary archetypes of masculinity emerges from their work. I have named the three particularly vivid and pervasive images of men en which I focus, the Hunter, the Adult Adolescent, and the Wounded Warlock. My project is essentially a sketching out of these beings, a contouring of their recurring literary reality.

Toril Moi rightly criticizes the project of evaluating literary images of women in terms of their true or false relation to 'real life' as one that "resolutely refuses to consider textual production as a highly complex, 'overdetermined' process with many different and conflicting literary and nonliterary determinants" (Moi 45). In looking at the images of men that dominate Canadian women's writing, I do not wish to claim that these images are 'true' or 'false', but simply that they exist in the literature.

My critical approach here is essentially one of description. My descriptions are original in that they are not applications of previously-defined archetypes of personality as in, for example, the work of Carl Jung. No description is, however, free of context, and in describing the images of men that emerge from this fiction, I draw repeatedly upon several feminist and philosophical texts for inspiration and clarification. Susan Griffin's exploration of the 'pornographic mind', Martin Buber's religious ontology of the "I-Thou", Jean-Paul Sartre's articulation of the meaning of the Look, and Christopher Lasch's discussion of narcissism, have been particularly useful.

Although my dissertation does not attempt to engage directly the large question of the relation of the artistic image to life, I do suggest indirectly, by drawing upon thinkers whose subject is not primarily literature, but indeed 'the real world', that the images of men I define have some connection with that real world. My conclusion briefly raises, therefore, some ethical as well as aesthetic questions about the implications of their existence.

abstract: Doctor of Philosophy (PhD)


title: Exploring the synthetic utility of vinyldichlorosilanes and vinylarylsilanes

contributor:
Brook, Michael A.
Chemistry

subject: Chemistry Chemistry

abstract:
The addition of electrophiles to styrylsilanes when electronegative chloride ligands replaced electron-donating ligands on silicon has been investigated. These addition reactions were shown to be advantageous over the normal electrophilic substitution reactions found in the literature, in that the retained silicon may subsequently direct the regiocbemistry and stereochemistry of further synthetic reactions. In addition, the retained silicon offers the advantage of being replaced by other useful functional groups, in a controllable manner, as we have demonstrated by an oxidative cleavage reaction. Our results showed that allylsilanes, unlike vinyl silanes, perhaps due to their inherently higher reactivity (relative to vinylsilanes), are not prone to electrophilic addition when electron-withdrawing ligands are placed on silicon. Our experimental results also suggest that the success of these addition reactions depends on the stability of the intermediate adduct cations formed; addition products are typically obtained for the more stable cations.

Carbocationic organosilicon chemistry has been dominated by the ability of silicon to electronically stabilize positive charges in the β-position, thereby influencing the reactivity of species that pass through such stabilized intermediates. However, steric influences on reactivity are not so well documented. Therefore, the reactivity of arylsilylstyrenes when the silylaryl group is sterically crowded with methyl substituents was investigated. The ability of silicon to effect electrophiIic substitution on the silylaryl substituent of (E)-β-dimethylmesitylsilyl)styrene rather than on the silylstyryl substituent, even though substitution on the arene required destroying aromaticity, is reported. This anomaly has been rationalized as being primarily due to steric factors.

abstract: Doctor of Philosophy (PhD)


title: Picosecond Photoresponse of High-Tc Superconductor Thin Films

contributor:
Preston, John S.
Physics

subject: Physics Physics

abstract:
The origin of the fast photoresponse observed below Tc from current-biased, epitaxial YBa₂CU₃O₇_₈ (YBCO) thin films has been a source of controversy for several years now. The photoresponse signals have been attributed to either bolometric (thermal or equilibrium) or nonbolometric (nonthermal or nonequilibrium) mechanisms. A variety of nonbolometric mechanisms have been proposed to explain the fast photoresponse transients, such as nonequilibrium electron heating and transient flux dynamics.

We have studied the fast photoresponse of epitaxial YBCO thin film bridge structures using 100 ps and 5 ps laser pulses. Both fast and slow voltage transients were observed. In the resistive transition region, a slow component was seen in the photoresponse wave form with a decay time of several nanoseconds which could be attributed to a resistive bolometric response. However, below the resistive transition region and well into the superconducting state, we have observed for the first time fast voltage transients with subnanosecond widths that were not followed by a slow resistive component. The fast transients cannot be explained by a simple resistive bolometric response.

We have developed what is called the kinetic inductive bolometric (KIB) model to explain the origin of the fast photoresponse signals. The KIB model assumes equilibrium heating of the film by the laser pulse, contrary to some of the nonbolometric mechanisms that have been proposed. We show that the KIB model provides excellent qualitative and reasonable quantitative agreement with the observed photoresponse using 100 ps and 5 ps laser pulses. With 5 ps laser pulses, we have observed voltage transients as fast as 16 ps wide from a 200 nm YBCO film. To our knowledge, this is the fastest photoresponse signal reported to date (September, 1994) from epitaxial YBCO thin films. The implications that the success of the KIB model has on the nature of superconductivity in the high-Tc materials is also discussed.

abstract: Doctor of Philosophy (PhD)