title: Restrained Rocking Response of Equipment on Rigid Floors

subject:
Civil Engineering
Civil Engineering

abstract:
Equipment can be mounted on rigid floors by placing the equipment freely on the floor without fastening, fixing it tightly to the floor. This study investigates the rocking response of equipment resting freely on rigid floors and also the effect of restrained rocking on the response of partially fixed equipment under seismic excitations.

Equipment which rests freely on rigid floors is simulated as a rigid rectangular block. The overturning of rigid blocks is studied under the effects of three types of base motion, namely, pulsive, critical, and harmonic excitations.

When the effect of pulse shapes on the overturning potential of rigid blocks under pulsive excitations is examined. It is found that the rectangular pulse will require the least peak acceleration for a specified duration. Under critical excitations, it is found that the extent of response amplification depends on the coefficient of restitution and the initial angle of rotation in addition to the peak acceleration of the pulses. TO amplify the motion by a specified ratio, pulses with lower peak acceleration are required for cases of large initial angles and for cases with large values of the coefficient of restitution. Under harmonic excitation, the conditions for steady-state periodic motion is derived. It is also found that as the coefficient of restitution decreases, the system becomes more stable against overturning and can withstand higher accelerations.

Also in this research, the response of partially fixed equipment resting on rigid floors under the effect of harmonic and earthquake excitations is investigated. For systems restrained by non-yielding bolts, it is found that the existence of gaps has the effect of decreasing the deformation of the mounted equipment relative to the base compares to the case of complete fixation. The existence of gaps also decreases the natural frequency of the system. In systems with yielding bolts, the presence of the gaps affects the deformation of the equipment more than is systems with non-yielding bolts. In the latter, the total rocking angle after all stretching takes place is not sensitive to the initial gap size and depends only on the level of excitation.

Based on this study, it is recommended hat equipment systems be allowed to rock on their bases by providing gaps in their anchorage systems. This kind of mounting has the advantage of allowing the equipment to rock with out the rock without the risk of overturning. Also, larger gaps are recommended for higher floor acceleration levels.

abstract: Doctor of Philosophy (PhD)


title: Seismic Response of Inelastic Structures Subjected to Bidirectional Excitations

contributor: Civil Engineering and Engineering Mechanics

subject:
Civil Engineering
Other Engineering
Civil Engineering

abstract:
A study has been made of the inelastic seismic response of single story structures having symmetrical as well as symmetrical configurations and subjected to bidirectional excitations. The intent of this investigation was (i) to assess the significance of force interaction in yielding of columns in the analysis of inelastic structures, (ii) to privude guidelines as how to account for the bidirectionality of the ground motion, and (iii) to clarify the role of "eccentricity" in the lateral-torsional response of inelastic asymmetrical systems.

The elasto-plastic responses of symmetrical systems, with interactions effects included or ignored are presented for sinusoidal base motions as well as earthquake ground motions. The latter excitation consisted of five pairs of recorded earthquake ground motions. It is found that the interaction effect is significant for stiff structures with low yield strength and it increases the response. The increase becomes substantial for very stiff structures. For this type of structure, an elasto-plastic analysis using uniaxial excitation could seriously underestimate the displacement ductility demand. It is recommended herein that such structures to be designed remain elastic or almost elastic under expected earthquake disturbances. Taking the interaction effect and the critical orientation of ground motion components into account, the ductility demand can be up to 40% larger than the estimates calculated otherwise.

An inelastic analysis of single mass monosymmetrical structural models subjected to the two horizontal components of ground motion is performed. A new concept of eccentricity based on the yield properties of the resisting elements is proposed as a better index to denote the severity of torsion on the inelastic response of asymmetric systems. The ductility demand of asymmetric structures with uniform strength distribution, i.e. with zero plastic eccentricity, are found to be not much different from those of symmetric structures.

abstract: Doctor of Philosophy (PhD)


title: Methionine Transfer RNA from an extremely halophilic bacterium

contributor:
Bayley, S.T.
Biology

subject: Biology Biology

abstract: This thesis proposed to investigate the role played by Methionine transfer RNA in the initiation of protein synthesis in the extreme halophile Halobacterium cutirubrum. Techniques were demonstrated for the isolation of two isoaccepting tRNA^not on BD-cellulose and RPC-5, was tentatively identified as a non-formylated initiator.

abstract: Master of Science (MS)


title: Locus of the Stimulus Probability Effect in Item Recognition

contributor: Medical Sciences (Growth and Development)

subject:
Medical Sciences
Medical Sciences

abstract:
Part 1 of the present investigation was designed to examine Sternberg's model of information retrieval. In particular, Experiments 1 through 3 focused on the confounding between frequency of occurrences, P, and positive set size, s. These experiments were designed to examine the possibility that the increase in RT with increases in s is, in whole or in part, an effect of variations in the frequency of occurrences of individual positive items. In shot, each experiment examined the memory scanning stage of the linear additive model.

In Experiment 1, the two variables, s and P, were unconfounded for some trials by holding constant the frequency of occurrences for one item in each set size. Here, it was found that when P was unconfounded by s, there remained a small but significant effect of s, supporting the conclusion that increases in mean RTs are largely accounted for by the associated decreases in P.

To determine whether or not the variable P has additive or interacting effects in the scanning stage, the additive-factors method was employed in the subsequent experiments. Mean RTs were obtained where at least two positive items within each memory set were assigned different P values and these particular values of P were found in all set sizes. In Experiment 2, it was found that P had additive effects when values of P were held constant across s at .25 and . 15. In contrast, in Experiment 3 when P was held constant across s at .25 and .05, it was found that P had interacting effects on the scanning stage, strongly suggesting that the serial and exhaustive scanning model, as proposed by Sternberg, is unable to handle the effects of P.

In an attempt to explain some of the features of the data, Stanovich and Pachella's temporal overlap model, Theios et al. 's self-terminating model, and Atkinson and Juola's familiarity model were examined separately. The general features of the data reconciled best with the familiarity model where it is hypothesized that subjects do not always serially and exhaustively scan the memorized list on every trial. The supposition is that repetitions of an item as a probe will result in an increase in its familiarity value, and thereby increase the likelihood of a fast positive response.

Working within the basic concepts underlying the familiarity model, Part 2 of this Thesis describes an experiment which examined aspects of repetition that affect the memory scanning stage of the item recognition process. In general, the data revealed that repetition is an important variable since scanning of the memory list seems to be influenced by how often a positive item is probed and by the number of intervening items occurring between consecutive tests of positive item (lag length).

abstract: Doctor of Philosophy (PhD)


title: MULTIVARIATE STATISTICAL ANALYSIS OF DATA FROM AN INDUSTRIAL FLUIDIZED CATALYTIC CRACKING PROCESS USING PCA AND PLS

contributor:
MacGregor, J.F.
Chemical Engineering

subject:
Chemical Engineering
Engineering
Chemical Engineering

abstract:
Principal Components Analysis (PCA) and Partial Least Squares (PLS, or Projection to Latent Structures) were used to evaluate the process history of a fluidized catalytic cracking unit (FCCU). Specifically, the goals of the work were to identify interesting periods in the process history, identify relationships amongst process variables, develop a predictive model of the product yields and selectivities, and to create a monitoring space to detect process changes and disturbances.

Major process changes of feed rate, feed quality and production modes were easily modelled by the first few latent variables (LVs) in both the PCA and PLS analyses. Later LVs highlighted transients obvious to operations. Plots of the process behaviour in the space of these latent variables were able to clearly reveal where major changes occurred in the process, implying that this approach is useful for the post analysis of historicaldata bases. Diagnosing the reasons for changes, however, was much more difficult.

PLS was quite successful in obtaining predictive models for the product yields and selectivities. A linear model of eleven dimensions was able to predict 81.3% of the cross-validated sum of squares in the Y space and 78.3% of the sum of squares in the X space. The hierarchical PLS approach of Wold et al. (1987) was also applied to the data set and generated results of similar predictive ability and interpretation.

abstract: Master of Engineering (ME)


title: Analyses and applications of generalized transformed domain least-mean square (LMS) adaptive filters

contributor:
Wong, K.M.
Engineering

subject: Engineering Engineering

abstract: In this thesis, a comprehensive analysis of the transformed domain adaptive filtering algorithms is presented. The idea behind this study is to expand the time domain filter impulse response as a set of weighted orthogonal functions. The least-mean square (LMS) adaptation algorithm is applied to the weights. In brief, we systematize and generalize the existing transformed domain algorithms and study their convergence properties. Based on the concept described above, we develop two types of transformed domain LMS (TDLMS) adaptive algorithm and the block transformed domain LMS (BTDLMS) adaptive algorithm. For the purpose of comparison, time domain expressions of various transformed domain adaptive algorithms are also obtained. We show that the TDLMS algorithm with the Karhunen-Loève (K-L) transform is equivalent to the time domain LMS adaptive algorithm. Whereas, the time domain expression of the TDLMS algorithm with the normalized K-L transform is equivalent to the generalized Newton-Raphson method. To study the effect of the normalized K-L TD:MS adaptive algorithm, we have derived an analytic expression of mean-square error (MSE) in terms of weight vector, weight covarience matrix, input autocorrelation matrix and the minimum MSE in the application of adaptive line-enhancer (ALE). An analytic expression of MSE using the time domain LMS algorithm in the ALE will also be obtained for comparison. It will be proved that the convergence rate, in terms of MSE, of the time domain LMS algorithm not only depends on the eigenvalue spread of the input autocorrelation matrix, but also depends highly on the power ratio between the sinusoidal signals in the ALE. However, the convergence rate of the normalized K-L TDLMS algorithm is independent of the eigenvalue spread and power ratio but depends only on the stepsize. The problem of employing different orthogonal transforms is also studied. The discrete cosine transform (DCT) is used to investigate the effect on convergence rate due to incomplete diagonalization of the autocorrelation matrix. To reduce the computational-effort, a recursive equation for evaluating the DCT output is obtained. Furthermore, in order to apply the transmultiplexer transform (TMT) to the transformed domain adaptive algorithms, the simplified form of TMT is also obtained. Finally, for limited supply of input data, an algorithm of re-circulating the input data in the BTDLMS adaptive algorithm with the discrete Fourier transform (DFT) is proposed. An analysis of the performance, in terms of MSE, of such an algorithm indicates that superior performance can be achieved compared to the algorithm without re-circulation.

abstract: Doctor of Philosophy (PhD)


title: The effects of microstructural inhomogeneity on damage accumulation and fracture

contributor:
Embury, J.D.
Wilkinson, D.S.
Metallurgy and Materials Science

subject:
Materials Science and Engineering
Metallurgy
Materials Science and Engineering

abstract: A theoretical and experimental study has been made which indicates the importance of the spatial distribution of damage and a complete physical description of the operative damage processes in providing a fracture condition. A continuum damage model is presented which investigates the influence of void coalescence in accelerating damage levels, for a random array of voids growing via a ductile hole growth mechanism. A simple geometric coalescence condition was assumed. The dependence of fracture strain upon initial void volume fraction and stress state history is predicted. This approach is extended in a simulation to predict the void size distribution which develops. The Dirichlet tessellation was evaluated as a method for characterizing dispersions of points or particles. Point dispersions were generated, ranging from strongly periodic to strongly clustered, and properties of their associated tessellations were evaluated. This suggested parameters which were sensitive indicators of periodicity or clustering in a dispersion. this approach was extended to the characterization of inclusion and particle distributions in steels and several other alloys. The influence of temperature and stress on damage and fracture was studied in several continuously-cast HSLA steels. Fracture was controlled by the inclusions, the centre-line transformation products, or the interaction between these two sources of damage. Observations also suggested that the distribution of the banded transformation products could influence damage levels in the ferritic regions. This study concludes with an investigation of the creep fracture in a Ni-Sn alloy, which contained an inhomogeneous tin distribution. The regions with high tin content accumulated damage rapidly, however, ductility was promoted by the material low in tin which did not cavitate as readily. The influence of stress level on the strain dependence of damage accumulation rate, and the shift to surface crack-controlled fracture was interpreted as an effect of the enhanced relative contribution of grain boundary sliding to total strain at lower stresses.

abstract: Doctor of Philosophy (PhD)


title: Liquid-liquid extraction of chromium by diphenyl-2-pyridylmethane

contributor:
Tomlinson, R.H.
Biology

subject: Biology Biology

abstract: The liquid-liquid extraction of chromium from aqueous solutions of hydrochloric acid by diphenyl-2-pyridylmethane (DPPM) dissolved in hydrogen-bonding organic diluents has made possible the separation, concentration and speciation of chromium at trace concentrations. In the extraction of Cr(VI) the most effective diluents employed were, in order: CH₂ClCH₂Cl, CH₂Cl₂ and CHCl₃. While Cr(VI) was extracted best from HCl solutions the actual order of extraction of the inorganic acids themselves, used in the protonation of the DPPM, was found to be: HClO₄ > HNO₃ > HBr > HCl > H₂SO₄, H₃PO₄. The extraction of Cr(VI) was followed by using commercial high specific activity ⁵¹Cr or enriched material prepared by a Szilard-Chalmers reaction. The distribution ratio (D) in all 0.10M DPPM/diluent extractions increased with an increase in the acid concentration up to about IM in HCl but decreased thereafter. To account for the extraction a model is proposed which suggests that the distribution of Cr(VI) depends mainly upon the availability of DPPMH⁺ in the aqueous phase and the form of the Cr(VI). Both the model and spectral evidence support the extraction of the CrO₃Cl⁻ species. With the large separation factors available, Cr(VI) may be separated from inorganic Cr(III), organic Cr(III) complexes, such as Cr(C₂O₄)₃³⁻, and many other metallic species. Total chromium in the aqueous sample may be determined by an analysis of the extract after a Ce(IV) oxidation. Further, with a distribution ratio as high as D≃700, it is possible to concentrate the chromium from an aqueous sample to facilitate the analysis in the simplified matrix of the organic phase. This extraction may overcome the problems associated with chromium analysis at trace concentrations, where samples are so subject to loss by adsorption or changes in oxidation state upon storage. While back extractions have been examined, the direct analysis of the chromium in the extract by atomic absorption (ng/mK concentrations) or spectrophotometric (μg/mL concentrations) methods is advocated.

abstract: Doctor of Philosophy (PhD)


title: Development of an epithermal/fast neutron scattering technique for void fraction measurement in two-phase systems with portable neutron sources

contributor: Engineering Physics and Nuclear Engineering

subject:
Engineering Physics
Nuclear Engineering
Engineering Physics

abstract: A technique to measure void fraction in a two-phase flow system using the multiple scattering of neutrons from portable neutron sources was investigated. There exists evidence from a previous investigation with a neutron beam extracted from a nuclear research reactor, that the basic technique is attractive. The counting rate of multiply-scattered, thermalized neutrons was found to be nearly linear with void fraction and independent of flow regime. However, early investigation with a portable neutron source revealed that these advantages were not realized in all situations. In the present work, the objective, then was to determine the conditions under which the advantages of linearity and flow pattern independence could be achieved with portable neutron sources. Experiments were carried out to study the effect of various parameters like symmetry of neutron sources, test-section to detector distances, and detection energy bn did not affect the technique significantly. More significant parameters were flow patterns, test-section inside diameter, test-section wall thickness, presence of neutron reflector material around the test section, and incident neutron spectrum. From the trends observed in the parametric study, it was found that near linearity with void fraction and flow pattern independence could be achieved by tailoring the energy spectrum of the incident neutron beam, e.g. by moderating neutrons emitted by a given source. The amount of moderation required decreased with test-section inside diameter, test section wall thickness, and he addition of neutron reflector material surrounding the test-section. This finding was verified with experiments conducted for four different test sections. The reasons for these experimental observations were clarified by studying the effect of monoenergetic incident neutron groups with Monte Carlo simulation, the result of which was further interpreted with thermalization probability considerations. The Monte Carlo study revealed that each monoenergetic neutron group results in a different response in terms of thermalized neutron counting rate, which, in general, is neither linear with void fraction nor flow regime independent. However, linearity and flow regime independence could be achieved by superimposing the effect of different energy groups, i.e. by tailoring the neutron spectrum. In practice, this is achieved by appropriately moderating the neutron beam from a given source. Based on the understanding achieved, a conceptual design of a portable void fraction meter, and a design procedure are suggested.

abstract: Doctor of Philosophy (PhD)


title: A HIGH-CAPACITY TERRESTRIAL DIGITAL MICROWAVE RADIO EMPLOYING ADAPTIVE TECHNIQUES

contributor:
Taylor, D.P.
Engineering

subject: Engineering Engineering

abstract: A prototype 90 Mbit/s, 4.5 bits/cycle digital microwave radio is constructed which uses 49QPRS modulation. Feedback is used to linearize the transmitter power amplifier and in the receiver an adaptive decision feedback equalizer (DFE) is used to counter the effects of multipath distortion. The modulation envelope at the output of the cascade of a quadrature amplitude modulator and a microwave GaAsFET power amplifier is linearized with respect to the baseband signal, by feedback of the coherently demodulated microwave output. The power amplifier was operated at the 0.5dB compression point with only a very small increase in the receiver bit error rate (BER). To be practical, the feedback loop must have small physical size so that the loop transit time is small relative to the modulation symbol period. The receiver sampling phase and DFE tap-weights are jointly adapted to minimize the mean squared error and peak error respectively, of the DFE output. A one bit quantized estimated gradient algorithm is used to digitally adjust the adapted parameters. In the presence of a two-ray multipath, causing a transmission zero at the mid-band frequency of the receiver, the adaptive receiver can operate with only a small increase in the BER. In addition, the adaptive receiver can track easily between the minimum phase and non-minimum phase regions which are separated by the transmission zero. A recursive matrix equation is derived to describe the joint steepest descent adjustment of the equalizer tap-weights and sampling phase. The eigenvalues of the adjustment matrix of that equation are used to explain the observed behaviour of the constructed system.

abstract: Doctor of Philosophy (PhD)


title: SYNTHETIC AND FLUXIONALITY STUDIES OF SMALL ORGANOTRANSITION METAL CLUSTERS

contributor:
McGlinchey, M. J.
Chemistry

subject: Chemistry Chemistry

abstract:
A series of chiral organotransition metal clusters of the type (PhC≡CCO₂CHMe₂)MM' where M = CpNi and M' = CpMo(CO)₂, Co(CO)₃ or CpNi have been treated with Fe₂(CO)₉ to give clusters of the general formula (RC≡CR')MM'Fe(CO)₃. These clusters are predicted to adopt a square pyramidal geometry and this has been confirmed by X-ray crystallographic studies. In the case of M' = CpNi or Co(CO)₃ the Fe(CO)₃ moiety caps the basal plane whereas when M' = CpMo(CO)₂, it is this moiety which serves as the capping vertex. The former arrangement leads to all the metals pbeying the eighteen electron rule while in the latter the Fe and Mo atoms possess electron counts of 17 and 19 respectively.

These trimetallic-alkyne clusters have been shown to exhibit fluxional behaviour. This behaviour has been explained in terms of an alkyne rotation relative to the triangle of metals. When M' = CpNi, the cluster has been shown to undergo racemisation while when M' = CpMo(CO)₂ or Co(CO)₃, the clusters exhibit interconversion of diastereomers thus demonstrating the fluxional process to be intramolecular. The mechanism of isomerisation of these M₃C₂ clusters is compared to those predicted by theoretical calculations and is shown to be related to that of the analogous C₅H₅⁺ cation.

A series of synthetic manipulations carried out on the cluster system Co₃(CO)₉CR where R = CO₂CHMe₂, led to a variety of mixed metal clusters being obtained. Treatment with Cp₂Ni, [CpNi(CO)₂] or [CpMo(CO)₃]₂ resulted in replacement or modification of one, two or all three of the original Co(CO)₃ vertices. The problems of employing Cp₂Ni as a reagent in cluster synthesis are demonstrated. Reaction of these tetrahedral M₃CR clusters with Fe₂(CO)₉ yielded not only the expected square pyramidal systems but in one case a molecule adopting a closo trigonal bipyramidal structure. This latter geometry has been confirmed by X-ray crystallography. The concept of isolability has been used to compare the structure of this molecule with the previously known Fe₄CR clusters of similar geometry. Qualitative molecular orbital arguments are presented to rationalise the substitution and addition of metal vertices to the tetrahedral clusters.

The geometry of the acylium cation Co₃(CO)₉CCO⁺ has been examined by ¹³C NMR and evidence is outlined for a tilted configuration of the CCO ligand. A stable hexafluorophosphate salt of CpMoCo₂(CO)₈CCO⁺ has been obtained by addition of HPF₆ to a solution of CpMoCO₂(CO)₈COO₂CHMe₂in propionic anhydride. The presence of the acylium cation has been confirmed by its treatment with various nucleophiles resulting in formation of the appropriate derivatives.

abstract: Doctor of Philosophy (PhD)


title: Structures of Some Mercury Compounds in Low Oxidation States

contributor:
Brown, I.D.
Chemistry

subject: Chemistry Chemistry

abstract:
Structures of Hg compounds in fractional oxidation states lower than +1, Hg₃-δMF₆ (M = Sb, Nb, Ta), Hg₃MF₆ (M = Nb, Ta), Hg₄(Ta₂F₁₁)₂ and Hg₃(NbF₅)₂SO₄, were determined at room temperature and at lower temperatures using X ray and neutron diffraction. The Hg₃-δMF₆ compounds, isostructural with Hg₃-δAsF₆, contain infinite chains of Hg which are incommensurate and thus disorder with the MF₆ host lattice. A comparison between the structures showed that the differences observed in the parameters of the chain compounds are completely accounted for by the difference in anion size. The chain-host lattice incommensurability also results in disorder among the chains at room temperature but an ordering develops at lower temperatures. As in Hg₃-δAsF₆, short and long range order phases were observed in experiments with Hg₃-δSbF₆ and Hg₃-δTaF₆. The characteristics of the short range order phase are different in each compound indicating that the details of chain-chain interactions are not the same. Emery-Axe order parameter theory which predicts the development of long range order phase was tested for M = As, Sb, Ta but agreement was obtained only for Hg₃-δSbF₆.

A structure consisting of hexagonal closed-packed layers of Hg atoms was proposed for the Hg₃MF₆ compounds. The unusual 2-dimensional Hg-Hg bonding of these compounds represents an intermediate stage between the elemental solid Hg and the Hg₃-δMF₆ compounds which form 3- and 1-dimensional Hg-Hg bonds respectively.

The Hg₄(Ta₂F₁₁)₂ and Hg₃(NbF₅)₂SO₄ consists of finite polyatomic Hg ions. The former shows a tendency of cations to link into infinite zigzag chains, a feature also seen in Hg₄(AsF₆)₂, while the latter does not show such a tendency.

abstract: Doctor of Philosophy (PhD)


title: Ion Implantation Damage In Cds Using Tem and RBS/Channeling

contributor:
Thompson, D.A.
Metallurgy and Materials Science

subject:
Metallurgy
Other Materials Science and Engineering
Metallurgy

abstract:
Lattice disorder produced by heavy ion implantation of cadmium sulphide crystals at 50 K and 300 K has been investigated using Transmission Electron Microscopy (TEM) and Rutherford Backscattering (RBS)/- Channeling techniques.

TEM observations of Bi⁺, Ar⁺ and Ne⁺ implanted samples showed that two types of dislocation loops were produced, type I with a Burgers vector b= 1/2 <0001> and type II with a Burgers vector b = 1/3' <1120>. Type II loops were nearly twice as large in size and two to three times greater in number density then type I loops. The large loops of type II were predominantly vacancy loops. Both types of loops lie predominantly in the {1100} and {1120} prism planes. The loop size and number density increased with increasing energy deposited into elastic collisions. For increasing ion dose the loop size increased while the number density decreased.

In-situ measurements of the lattice disorder have been made using the RBS/ channeling technique with 0.6 MeV to 2.8 MeV He⁺ channeled along the a- and c-axes of the CdS crystals. The amount of disorder was measured in terms of the areal density of cadmium scattering centers (ND), and the minimum dechanneling yield (xmin) . Measured Nd values were found to be two orders of magnitude lower than theoretical prediction and the Xmin values were about an order of magnitude higher than those calculated assuming randomly displaced scattering centers. The disorder was greater measured along the c-axis than along the a-axis. It was also greater at 300 K than at 50 K. These observations suggest that the lattice distortion is greater in the direction perpendicular to the c-axis. It was also found that Nd increased with increasing E₀, while Xmin values were energy independent over the energy range investigated. These results and the rapid increase in Nd values observed when the crystal is tilted slightly away from the channeling direction ('Off-Axis' measurements) are consistent with the presence of dislocation loops as observed by the TEM.

abstract: Doctor of Philosophy (PhD)


title: Physiology ecology and stress responses in the genus Peltigera

contributor:
Kershaw, K.A.
Biology

subject: Biology Biology

abstract: The multivariate examination of nitrogenase activity in two populations of the lichen Peltigera canina is described. Only a small increase in activity was observed with increasing radiant flux density and a marked but relatively constant temperature optimum was noted for both varieties that was independent of all other variables. However, very large rate changes were observed for all light levels and temperatures throughout the year. The influence of snowmelt on subsequent rates of nitrogenase activity is also described. While temperature was intimately involved in the velocity of the recovvery of nitrogenase activity after snowmelt, the prime requirement appeared to be one of light. Lichens are believed to be extremely resistant to high temperature stress when dessicated. A reexamination of this concept for several temperature and northern populations of lichens in the genera Peltigera and Stereocaulon indicated that some air-dry lichen thalli can be extremely sensitive to even moderate levels of heat stress whereas others exhibited a considerable degree of heat resistance. These differential levels of thermal resistance correlated exactly with the ecology of these populations. Thermal sensitvity was identified as an important influence in the succession of plant species following forest fire and it is suggested that thermal stress may be one of the dominant parameters in the ecology of lichens. Lichens are also believed to be extremely resistant to high light levels when in the air-dry state. A reexamination of this concept identified light stress as another ecological factor of considerable importance to some lichens. A seasonal adjustment of net photosynthetic capacity is described for the woodland population of Peltigera canina. Changes in the maximal rates of net photosynthesis and respiration correlated strongly with concurrent changes in the leaf canopy. The seasonal adjustment of net photosynthetic rates is considered to be essential to the success of the organism which must adapt to a continually changing light environment.

abstract: Doctor of Philosophy (PhD)


title: Nichiren's Doctrine of the Age of the Last Law According to the Senji Shō

contributor:
Shinohara, K.
Religious Studies

subject: Religion Religion

abstract:
In this thesis, the bulk of which is the translation of a heretofore untranslated apocalyptic text of Nichiren (1222-1281), I have sought primarily to make available a translation of the Senji shō, produced in 1274. The fourth of Nichirent's major essays, the Senji shō, or Essay on the Selection of the Proper Time, represented the culmination of his thinking in regard to the Age of the Last Law. In this essay, Nichiren reviewed the history of the Age of the Last Law in Japan, specified the errors to which he believed the Pure Land and Shingon schools had succumbed, and set forth in vivid relief his own understanding of salvation in the Age of the Last Law.

Chapter One offers a brief history of Buddhism up to the time of Nichiren, a biography of Nichiren, establishing his place in the cultural milieu of Kamakura Japan, and a discussion of his interpretation of and teaching on the Age of the Last Law. Developed by Nichiren prior to the writing of the Senji shō, primarily in the Rissho Ankoku Ron (1260) and the Kaimoku shō (1273), the unique understanding of the meaning of historical events in Japan and the rationale he offered for the destruction of Pure Land teachings are expounded in sufficient detail to make his elaboration of the significant themes in the Senji shō more accessible to the reader.

Chapter One, then, helps to develop a contaxt in which the Senji shō may be read. The reader is introduced to the stormy Kamakura period in Japan, given some notion of the complexity of Nichiren himself, and

given insight into the tension at the centre of his teachings concerning the Age of the Last Law.

A proper understanding of the text, however, demands more than a close reading. Nichiren's doctrine evolved from earlier understandings of the Age of the Last Law within Indian and Chinese Buddhism and in sharp contradistinction to the schools which flourished in Kamakura Japan. In Chapter Two, therefore, Nichiren's doctrine of the Age of the Last Law is placed in historical perspective: the Age of the Last Law is

traced through its development in India, its significance in China, and its interpretation in Japan prior to Nichiren. In this chapter, also, special doctrinal differences among the schools of Buddhism in Japan

during Nichiren's own lifetime are elaborated.

Significant for an interpretation of the translation of the

Senji shō is Nichiren's own interpretation of Buddhist history and of the uniqueness of his place in the history of the religion. Thus, Chapter Three contrasts the Nichiren of the Senji shō with the Nichiren of popular knowledge. In particular, this chapter clarifies the way in which the Senji sho adds to the understanding of Nichiren himself, of his school

of Buddhism, and of the history of Japanese Buddhism.

Chapter Four consists of a foreword to the Senji shō and the translation itself. It is the translation and notes which I believe to be the major contribution of the thesis, for within this essay Nichiren can be seen to have brought to final formulation his long struggle to convince the rulers, the intellectuals, and the common people of Japan of the possibility of seeing religious significance in particular periods of historical

transition.

Nichiren so enraged the powerful people of his day that they reviled, tortured and banished him. Nevertheless, it can be seen in the full translation of the text of the Senji shō that he communicated his radical understanding with such vigour that he became a powerful new force in Japanese Buddhism. He is here revealed as a forceful opponent and a skilled teacher, gifted with humour and a unique personal vision.

abstract: Doctor of Philosophy (PhD)


title: The Preparation and Characterization of a Photoreactive Glucagon Analogue and its Interaction with Rat Liver Plasma Membranes

contributor:
Epand, R. M.
Biochemistry

subject: Biochemistry Biochemistry

abstract:
A heterobifunctional crosslinking reagent 2-nitro-4-azido-phenylsulfenyl chloride (NASPCl) was synthesized and characterized. This reagent can be used to specifically attach a photoactivatable nitrophenyl azide to tryptophan containing polypeptides and proteins lacking sulfhydryl groups. The reaction of NAPSCI with glucagon, a peptide hormone containing a single tryptophan residue at position 25 and no cysteine gave one major product which could be effectively photolysed at wavelengths above 300 nm. Glucagon-NAPS could be radiolabeled by the lactoperoxidase catalyzed iodination of the peptide. The covalent labeling of protein molecules with radiolabeled glucagon-NAPS upon photolysis was demonstrated. The photosensitive glucagon was shown to activate the adenylate cyclase of hepatocyte plasma membranes with a slightly higher potency than the native hormone at equimolar concentrations. Glucagon-NAPS was, therefore, considered as an effective photoaffinity probe for labeling the glucagon receptor sites in plasma membranes with a target cells.

Irradiation of hepatocyte plasma membranes in the presence of glucagon-NAPS resulted in an activated state of adenylate cyclase. The enzyme displayed a lower response to further stimulation by native glucagon, glucagon-NAPS or NaF than the response displayed by similarly treated membranes in the dark, suggestive of covalent labeling of the derivative to glucagon functional sites on the membrane.

Competitive binding studies at steady state using radio-labeled ¹²⁵I-glucagon and ¹²⁵I-glucagon-NAPS demonstrated binding of glucagon-NAPS to the same receptor sites on hepatocyte plasma membranes as native glucagon. Scatchard plot analysis of the binding isotherm curves indicated two orders of specific receptor sites: a) a high affinity-low capacity site, (glucagon, Kd = 3.52 (± 0.72) x 10ˉ¹⁰M, Bmax = 0.34 ± 0.15 pmole/mg membrane protein; glucagon-NAPS, Kd = 1.31 (± 0.10) x 10ˉ¹⁰M, Bmax = 0.67 ± 0.10 pmole/mg membrane protein) and b) a low affinity-high capacity site, (glucagon, Kd = 4.17(± 1.05) x 10ˉ⁹ M, Bmax = 3.08 ± 0.63 pmole/mg membrane protein; glucagon-NAPS, Kd = 7.28(± 1.11) x 10ˉ¹⁰M, Bmax = 2.19 (± 0.95) pmole/mg membrane protein). The binding characteristics of glucagon and glucagon-NAPS were similarly affected by guanosine 5'-triphosphate (GTP). Saturation of the binding sites at concentrations of glucagon and glucagon-NAPS producing maximal stimulation of adenylate cyclase suggested the requirement of interactions with both sites for a functional adenylate cyclase system. Hill plot analysis indicated noncooperative interactions of the peptides with the high affinity-low capacity sites and cooperative interactions with the low affinity-high capacity sites.

Covalent crosslinking of bound ¹²⁵I-glucagon-NAPS to hepatocyte plasma membranes upon irradiation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis identified a number of radiolabeled membrane components of which a 67,000-70,000 daltons component was significantly labeled above background and was displaced by more than 90% in the presence of excess unlabeled glucagon or glucagon-NAPS. This membrane component was identified as the glucagon specific binding site. The apparent molecular weight of detergent solubilized glucagonreceptor complex in a GTP sensitive state was estimated by gel fractionation as 200,000-250,000. SDS-gel electrophoresis of detergent solubilized, ¹²⁵I-glucagon-NAPS-receptor complex, covalently crosslinked by irradiation, identified the 67,000-70,000 as well as a 50,000 and 27,500 daltons components, also observed in unsolubilized membranes. Since the latter components were not significantly labeled above background or displaced in membrane samples irradiated in the presence of unlabeled peptide, they may not be called specific receptor sites. The inhibition of covalent crosslinking of all three components in trypsinized membranes demonstrated their protein nature. Anomalous electrophoretic mobilities with different acrylamide concentrations were suggestive of the receptor peptide being a glycoprotein. Similar behaviour under reducing and nonreducing conditions was suggestive of the presence of intramolecular disulfide bonds.

In these studies we have demonstrated that the glucagon-NAPS derivative has the advantage for labeling the glucagon receptor in hepatocyte plasma membranes because it is biologically active and the binding sites for the derivative can be linked to a physiological response. The receptor site identified should represent the true glucagon receptor or a receptor subunit since upon irradiation it was covalently crosslinked by the ligand, with the receptor still being in a biologically active state.

abstract: Doctor of Philosophy (PhD)


title: Studies on various aspects of the vanadium chemistry of the Stretford process

contributor:
Hileman, O.E.
Biology

subject: Biology Biology

abstract: This work touches on a wide variety of subjects with the vanadium process chemistry in the Stretford Process. A comprehensive literature survey of desulfurization systems is presented in chapter 1 and appendix II. Experimental work is focused on vanadium oxidation, reduction, and precipitation in Stretford-like solutions.

abstract: Master of Science (MS)


title: Doctrines and methods used by Sankara and Ramanuja to elucidate the relation between self-knowledge and Dharma in their commentaries on Bhagavad-Gita

contributor:
Sivaraman, K.
Whiller, W.
Religion (Indian Philosophy)

subject: Religious Thought, Theology and Philosophy of Religion

abstract:
Careful study of the commentaries of both Sankara and Rāmānuja concerning the relationship between Self-knowledge and dharma confirmed the usual doctrinal differences between them which have been the focal point of scholarship on Vedānta but as well it also uncovered areas of structural convergence co-existing with the former. Accordingly this investigation proceeded on two levels: the first level was concerned with those difference in their ontologies; the second level was concerned with the "meaning-structures" common to both. Previous scholarship on Vedānta has not made reference to these areas of structural convergence. The objective of this work has been to verify how these areas of structural convergence throw light on their respective explicit positions.

The following are the major findings of this work: Whereas generally Sankara and Rāmānuja have been understood in terms of their doctrinal differences, with special attention to Rāmānuja's explicit refutation both of Sankara's māyā-vāda and his doctrine of Brahman as Nirguna, I have sought out and argued for a common ground between them. Sankara is usually understood as arguing for a radical discontinuity between Self-knowledge and dharma. I have demonstrated his implicit concession to their community is sāndhana and his use of two key categories to explain this apparent continuity: (i) Self-knowledge in its "secondary sense" as vrtti-jnana and (ii) dharma in its "primary sense" and jnana-yoga. Rāmānuja is usually understood as arguing for a continuity between Self-knowledge and dharma. I have shown his implicit emphasis on their discontinuity which is especially evident when dealing with the question of prapatti where a discontinuity is set up between dharma, understood as man's own isolated efforts and Self-knowledge, understood as Self-surrender, which is surrender to the Lord as the "eternally established means".

Two distinct but inseparable strands were discovered in both Sankara and Rāmānuja. They were respectively designated as the "explicit Sankara", the "implicit Sankara" , and the "explicit Rāmānuja" and "implicit Rāmānuja". Two major areas of structural convergence were discovered between these strands: between the "implicit Rāmānuja" and the "explicit Sankara"; and between the "explicit Rāmānuja" and the "implicit Sankara", The structural convergence between the "implicit Rāmānuja" and the "explicit Sankara" threw light on their explicit areas of agreement on the nature of dharma which they share as Vedānta. The structural convergence between the "explicit Rāmānuja" and the "implicit Sankara" threw light on their explicit areas of agreement, which they share as Vedānta, on the nature of Self-knowledge.

Areas of tension between their doctrines and methods were uncovered. The most striking example of such a tension is illustrated by Rāmānuja's explicit rejection both of Sankara's two levels of truth and of his māyā-vāda, in the context of Rāmānuja's use of methodological equivalents.

abstract: Doctor of Philosophy (PhD)


title: A THEORY OF OPTIMAL WORST-CASE DESIGN EMBODYING CENTERING, TOLERANCING AND TUNING, WITH CIRCUIT APPLICATIONS

contributor:
Bandler, John W.
Electrical Engineering

subject:
Electrical and Computer Engineering
Electrical and Computer Engineering

abstract: This thesis presents a unified treatment of circuit and system design methods embodying centering, tolerancing and tuning. The approach incorporates the nominal parameter values, the corresponding tolerances and tuning variables simultaneously into an optimization procedure designed to obtain the best values for all of them in an effort to reduce cost, or make an otherwise impractically toleranced design more attractive. Intuitively, the aim is to produce the best nominal point to permit the largest tolerances and the smallest tuning ranges (preferably zero) such that one can guarantee, in advance, that in the worst case, the design will meet all the constraints and specifications. Reduced problems are formulated for digital computer implementation. Interpretations are given. Implications of biquadratic functions in the circuit tolerance problems are investigated. Practical implementation in circuit design problems in the frequency domain is treated. The thesis also includes illustrative examples and two realistic problems.

abstract: Doctor of Philosophy (PhD)


title: THE GENETICS OF AUTISM/PDD: AN INVESTIGATION OF SEROTONIN, NOREPINEPHRINE AND DOPAMINE TRANSPORTER GENES IN THE ETIOLOGY OF AUTISM AND THE RELATED PERVASIVE DISORDERS

contributor:
White, Bradley N.
Biology

subject:
Biology
Life Sciences
Biology

abstract:
Autism is a pervasive developmental disorder (PDD) characterized by behavioral abnormalities which include: lack of social relationships, delayed or deviant language development, motor stereotypes and preoccupation with repetitive movements or activities. Twin and family studies have suggested that a strong genetic component exists for this condition, however, attempts to identify the genes involved have failed. Current investigations into the etiology and pathophysiology of many neuropsychiatric disorders implicate the involvement of neurotransmitter systems. Previous studies from this laboratory have identified possible maternal effect loci that in conjunction with alleles of fetal susceptibility genes could explain many of the complex features of the etiology and genetics of autism/PDD.

This study involves the analysis of monoamine (biogenic amine) transport systems in relation to autism. Markers linked to and with in the serotonin, norepinephrine and dopamine transporter genes were used for assessing concordance or allele sharing among affected sib pairs and allele and genotype distributions among first-degree relatives and affected children. The presence of linkage with autism was observed for all three candidate genes. Significant levels of identity by descent (IBD) allele sharing were observed among affected sibling pairs for the serotonin transporter (Mean statistic; t2=2.27, p<0.05), dopamine transporter (t2=1.20, p<0.05) and norepinephrine transporter (t2=164, p<0.05). A separate analysis of each microsatellite locus revealed a trend towards increased maternal concordance. Symmetry between transmitted and non-transmitted alleles was noted at microsatellite and VNTR loci when transmission disequilibrium of alleles was analyzed. Application of the transmission disequilibrium test (TDT) to STin2/5HTTLPR haplotypes demonstrated association to the 12 copy (304 bp) allele of STin2 and the long variant of the functional polymorphism, 5HTTLPR. Mothers of two affected children showed STin2 (SERT intronic VNTR) genotype frequency differences when compared to female controls (%2= 20.97, d.f.=l 1, p=0.0099). Significant differences between parental allele frequencies and population-based control frequencies tested for all microsatellite loci were observed. Correlation between those sib pairs sharing two alleles IBD for SERT loci and mothers with a del/del genotype at the DβH locus (associated with low serum DβH) supports the interaction between this locus and the maternal effect genes. Susceptibility, conferred by biogenic amine transporters, SERT, NET and DAT1, is supported by linkage and allelic association observed for all three genes. Correlation between concordance for SERT markers and maternal genotype at the DPH locus lends support to a maternal effect / fetal susceptibility model of autism. The presence of a possible parent-of-origin effect is also indicated by the presence of increased maternal concordance at microsatellite loci linked to SERT, NET and DAT1.

abstract: Master of Science (MS)


title: Environmental Signals in Coral Tissue and Skeleton: Examples from the Caribbean and Indo-Pacific

contributor:
Risk, M.J.
Geology

subject: Geology Geology

abstract:
Coral tissue and skeleton contain physical and chemical proxy signatures of the surrounding environment. The purpose of this thesis is to broaden or refine the use of corals as environmental recorders/tracers by examining the fidelity of both new and existing techniques. Corals from the Caribbean and Indo-Pacific are utilised, with primary reference to samples from Jamaica and Indonesia.

Coral skeletons from Banda Api, Indonesia, contain evidence of a short term pulse of volcanic ash and hydrothermal fluids which affected the surrounding reef during a May, 1988 eruption. Partial burial of corals by volcanic ash led to the formation of highly bioeroded death surfaces and the incorporation of ash into underlying skeletal pores. Subsequent recovery of the coral resulted in preservation of these features as death/regrowth surfaces. Hydrothermal activity is preserved in the skeleton as a distinct orange layer of iron hydroxide which has been termed the "Banda Band". X-radiography confirms that the location of these features within the coral skeletons coincides with the timing of the eruption. Preservation of an environmental pulse lasting only a few days demonstrates the fine scale resolution that can be obtained from coral skeletal records.

Coral tissues from Jamaica and Zanzibar, collected along depth/light gradients, were analysed for δ¹⁵N. Coral tissue δ¹⁵N was found to decrease with decreasing light availability. A conceptual steady state model has been developed to explain this relationship. In higher light conditions, corals and/or their symbiotic algae significantly deplete the internal pool of dissolved inorganic nitrogen, resulting in minimal fractionation during uptake. Under lower light conditions, however, less dissolved nitrogen is assimilated and fractionation is more fully expressed, with the light isotope of nitrogen being taken up preferentially. These results suggest corals are not conservative tracers of nitrogen. It is proposed, however, that shallow water (<5 m), autotrophic species of corals may exhibit minimal fractionation and prove to be excellent tracers of dissolved inorganic nitrogen on reefs.

δ¹⁵N and δ¹³C signals of shallow water corals collected from seven different reefs were compiled. Significant inter-reef variability in δ¹⁵N was found. Both light availability and the isotopic composition of source nitrogen are thought to contribute to the variation between reefs. Other factors such as nutrient concentration may also be important. δ¹³C variability was much less significant in the data set, with most reefs having enriched coral tissue signals, consistent with a primarily autotrophic diet.

The tissue and underlying skeleton of Jamaica and Zanzibar corals were also analysed for δ¹³C. Tissue δ¹³C was found to decrease with decreasing light availability. Skeletal δ¹³C, however, shows no relationship with depth/light availability. It is proposed that strong kinetic isotope effects associated with the rate of calcification mask any such relationship. A simple data transformation is applied to account for the presence of kinetic isotope effects, the result of which is a much clearer relationship between skeletal δ¹³C and light availability. These results suggest that it is possible to correct for the presence of kinetic isotope effects associated with the rate of skeletogenesis and to resolve meaningful environmental/metabolic information from skeletal carbon isotopic records.

abstract: Doctor of Philosophy (PhD)


title: Study of Temperature Characteristics of 1.3μm Strain-Layer Multiple Quantum Well Lasers

contributor:
Simmons, J.G.
Jessop, P.E.
Engineering Physics

subject:
Engineering Physics
Engineering Physics

abstract:
This thesis presents a theoretical and experimental study of the temperature characteristics of 1.3μm strained layer multiple quantum well (MQW) lasers over a wide temperature range. A number of achievements have been made toward understanding the temperature sensitivity of the performance of the lasers.

Under assumptions that the deterioration of optical gain with temperature dominates the temperature sensitivity of the laser performance and that the differential gain coefficient decreases linearly with temperature, two formulae, which include a maximum operating temperature, were derived to describe the threshold current, Ith, and the external quantum efficiency, ηd, as functions of temperature. The formulae produce a very good fit to the experimental data that were extracted from the shortpulse L-I characteristics of 1.3μm 0.7% compressive strained layer MQW lasers containing varying number of wells. The maximum operating temperatures obtained from fitting the formulae to Ith vs. T and ηd vs. T data are consistent with each other, which experimentally supports the theory and the underlying assumptions. Based on the same assumptions, the conventional method of determining the internal quantum efficiency and internal loss from a set of lasers with different length was scrutinized. It was concluded that the internal quantum efficiency is a function of temperature, even if the true internal quantum efficiency is independent of temperature, and that the internal loss is a sublinear function of temperature around room temperature, as available experimental results show. The experimental results from 1.3μm ten 0.7% compressively strained wells lasers with varying cavity length support the theoretical conclusions.

The experimental observation of the far-field patterns for 1.3μm 1.2% tensile strained layer MQW lasers containing 3 wells with varying ridge width over a wide temperature range indicated that the injected carriers exert little effect on the refractive index, and that the change in the far field distribution with temperature is the result of spatial hole-burning.

The final part of this thesis presents a technique to determine the temperature rise of the lasers during CW operation, which was then used to calculate the thermal impedances of different ridge width lasers. It was concluded that a wider ridge laser has a smaller thermal impedance and a lower available CW maximum operating temperature.

abstract: Doctor of Philosophy (PhD)


title: Changing Rural Land Uses in the Toronto Centred Region Commutershed 1955 - 1977

contributor:
Reeds, L.G.
Geography

subject: Geography Geography

abstract: Rural land uses in the western Toronto Centred Region were studied in order to determine whether trends were in accordance with the stated public policy for the area. Three types of land use were studied, agricultural, recreational and non-farm rural residential. Within the study period, agriculture in the commutershed townships experienced changes in structure as well as decreases in scale. Many acres of the western Toronto Centred Region were under recreational uses, but a large number had access restriction or financial deterrents to use by the general public. Lot fragmentation and rural residence construction trends indicated a significant increase in the number of land owners and residences, especially in those areas adjacent to metropolitan Toronto. Past land uses were found not to be in accordance with desired land-use patterns and a re-evaluation of policy or a greater intervention in land-use controls is urged.

abstract: Master of Arts (MA)


title: Fabrication and Photochemical Surface Modification of Photoreactive Thin-Film Composite Membranes and Model Development for Thin Film Formation by Interfacial Polymerization

contributor:
Childs, R. F.
Dickson, J. M.
Chemistry

subject: Chemistry Chemistry

abstract:
A simple route for the synthesis of a monomer containing a diazoketone functionality and two disulfonyl chloride groups has been developed. Polymerization of this monomer by reaction with a diamine leads to the formation of a polymer in which the photoreactive group is incorporated as a side chain. The polymer can be formed as a thin film in a thin-film composite membrane.

The factors that affect the interfacial polymerization, membrane morphology and performance have been systematically investigated. It was found that monomer concentration, the presence or absence of a surfactant, solvent and polymerization time are important factors in determining membrane morphology and separation/flux performance.

Small molecule model reactions have been studied in order to establish the chemistry of the photochemical surface modification of diazoketones. The range of photochemical transformations of diazoketones has been broadened, potentially leading to the photochemical conversion of the surface barrier layer of the diazoketone containing thin-film composite membranes to carboxylic acid, hydroxyl, ethyl ester and suIfur-containing crown ether.

A method for the preparation of specimens for surface characterization of the thin-film composite membranes by infrared spectroscopy has been developed. Surface analysis techniques, such as Attenuated Total Reflectance Fourier Transform Infrared (ATR-FT-IR) Spectroscopy and Scanning Electron Microscopy (SEM), proved to be useful in monitoring the photochemical surface modifications of the photolabile thin-film composite membranes.

The performance of the initial diazoketone precursor membrane and photochemically modified membranes has been examined with a series of aqueous solutions of inorganic salts. It was found that photochemical surface modification can significantly alter the separation/flux performance of the membranes.

A theoretical model that considers both diffusion- and reaction-controlled interfacial polymerization, under nonsteady-state conditions, has been developed. The model can describe the formation of both dense and porous thin films. The results predicted by the model are consistent with experimental results. The general model developed in this thesis for thin film formation by interfacial polymerization can include the special model already reported in the literature. The work conducted in this thesis significantly extends existing theories for the formation of thin films by interfacial polymerization and provides an important guide for effective control of the thickness of the surface barrier layer of thin-film composite membranes prepared by interfacial polymerization.

abstract: Doctor of Philosophy (PhD)


title: A Study of the Magnetic and Structural Properties of Ultrathin Fe/Ni(111)/W(110) Films

contributor:
Venus, David
Physics

subject: Physics Physics

abstract:
The structural and magnetic properties of ultrathin Fe/Ni(111)/W(110) films are investigated using LEED, two Auger electron spectroscopy techniques and magneto-optic Kerr magnetometry. A 2 ML Ni(111) buffer layer is used to grow fcc Fe(111) films to a thickness of 3 monolayers. The Ni substrate aIIows good wetting and lattice matching of the Fe without significant interfacial diffusion. Above 3ML a continuous structural transition from fcc to bcc is observed.

An electron energy analyser for use with a spin polarised low energy electron diffraction (SPLEED) electron spin analyser was designed and built. The energy analyser is used to study the growth mode and structure of ultrathin Fe/Ni(111)/W(110) films using angle resolved auger emission spectroscopy (ARAES). A method is developed to fit computer simulations to the ARAES data to determine the growth mode of ultrathin films.

Preliminary magnetic measurements of the fcc phase below 4 ML indicate that the Fe films are ferromagnetic with a magnetic moment perpendicular to the surface at coverages of 0.25 to 2.0 ML. At 2.5 ML a spin reorientation transition appears to occur and both perpendicular and in plane magnetic moments are observed. At 3.0 ML the magnetic moment is in the plane of the film.

abstract: Doctor of Philosophy (PhD)


title: Business location and consumer behaviour 1882-1910, Eastern Grey County, Ontario

contributor:
Gentilcore, R.L.
Engineering

subject: Engineering Engineering

abstract: The major objective of this thesis is to comprehend a changing pattern of nineteenth century places and markets in terms of the business location decision and consumer behaviour. A deterministic model of consumer behaviour is developed, which assumes partial multipurpose tripping, a spatially uniform consumption mix, and a distance decay effect on purchase frequency. This model provides a measure of the attraction and accessibility of places. The business location decision is inferred; it is shown that perfect order of entry of businesses in places and non-uniform spacing of places are corollaries of the assumed nature of consumer behaviour. Businessmen in fifty post office settlements serving four Ontario townships between 1882 and 1910 are identified using directory sources. Consumers' location and choice of post office, is reconstructed for 1882 and 1898. Applied to real world conditions, results obtained from the consumer choice model suggest that choice inertia and restricted opportunities for multi-purpose tripping modify market division. Conditions approach the theoretical norm between 1887 and 1898. Consumer choice and business location are associated with population turnover. Choice inertia is positively associated with population persistence. Imitative choice behaviour at the farm level is detected, and consumer choice of post office reflects rural community as well as market structure. Business duration is brief; business relocation within the study area is, however, rare. The quality of business location choice is shown to be related to the changing vacancy rate in the business patter. Business duration varies with the suitability of locations and the size of available markets. It is concluded that the static and dynamic interdependence of market division and business locations accords with expected conditions; change is effected and modified by endemic populations transience. The decline of small places between 1895 and 1910 is implemented through market contraction and business avoidance in a retail environment of continuous change.

abstract: Doctor of Philosophy (PhD)


title: Phosphate uptake in Rhizobium meliloti

contributor:
Finan, T.M.
Biology

subject: Biology Biology

abstract:
The soil bacterium Rhizobium meliloti fixes dinitrogen when associated with root nodules formed on its plant host Medicago sativa (alfalfa). A previously identified locus in R. meliloti 1021, ndvF, is required for nodule invasion and N₂-fixation. Genetic analysis of the locus revealed the presence of four genes, phoCDET which encode an ABC-type phosphate transport system. The transporter had a high affinity for phosphate (Km: 0.2μM) and took up phosphate with low velocity (Vmax: 6.7nmol/min/mg protein). It also showed a low specificity for phosphate as it likely transports phosphonate compounds as well. Expression of transcriptional lacZ fusions to phoD and phoE revealed that these genes were induced upon phosphate limitation and required a functional PhoB protein for their expression. phoCDET mutants grew poorly in MOPS-buffered minimal media containing 2mM Pi as sole phosphorus source, and failed to transport phosphate at concentrations usually found in the soil (1-10μM). This suggested that the symbiotic phenotype associated with mutation in this locus was the result of poor growth in this environment.

Analysis of two classes of mutation that suppressed the Fix⁻ phenotype of phoCDET mutants confirmed the function of this Pi transporter and provided insides into its regulation. Sequence analysis of the ClassI (sfx1) suppressor locus revealed the presence of two genes orfA and pit which likely form an operon. While orfA did not share any significant homology with proteins found in the Data Bank, pit showed homology to phosphate transport systems of various organisms, including the pit gene of Escherichia coli. The sfx1 mutation appeared to be a thymidine deletion in a hepta-thymidine sequence located 80 nucleotides upstream of orfA. orfA pit expression increased in a sfx1 background (compared to the wild type) leading us to hypothesize that suppression by sfx1 occurred by increasing Pi uptake by the Pit (OrfA) phosphate transport system.

The class II suppression mutations (sfx2 and sfx3 alleles) were unable to express the alkaline phosphatase enzyme (AP) suggesting that the mutations probably affect the Pho regulatory genes of R. meliloti. Three AP⁻ Tn5-132 mutants linked in transduction to sfx2 were isolated. Sequence analysis of the DNA flanking these insertions revealed that they were located within the phoU and phoB genes of R. meliloti. These phoU and phoB mutations were able to suppress all the phenotypes associated with phoCDET mutations in a manner similar to sfx2. PhoB was also shown to be required for the uptake and/or metabolism of phosphonate compounds and activation of phoCDET expression. On the other hand, the product of the phoB gene, either directly or indirectly, negatively regulated pit expression in a phosphate dependent manner (i.e. repression under low phosphate conditions and in the phosphate starved environment of phoCDET mutant strains). Suppression of the symbiotic defect of phoCDET mutants by phoUB (sfx2) mutations appeared then to occur by derepressing the pit system of R. meliloti, allowing increased phosphate uptake via this transporter.

abstract: Doctor of Philosophy (PhD)


title: PYRIMIDINE METABOLISM IN PBS 1-INFECTED BACILLUS SUBTILIS

contributor:
Takahash, I.
Biology

subject: microbiology Microbiology Microbiology

abstract: The pathways in the motobolism of pyrimidine bases, nucleosides and nucleotides in Bacillue and subtilia were determined and the relative importance of the pathways in the synthesis of dTTP was evaluated. Pathways involved in the metabolism of pyrimidine compounds in PBS 1-infected cells of B,subtilia were proposed on the basis of the present results and those of earlier studies. The contribution of the various pathways to the biosynthesis of dUTP in PBS 1-infected cells was investigated by labelling the phase DNA with radioactive bases and nucleosides in mutant strains blocked at various stops of the metabolism.

abstract: Doctor of Philosophy (PhD)


title: Characterization of quantum wells using degree of polarization of photoluminescence

contributor:
Cassidy, D.T.
Engineering Physics

subject:
Engineering Physics
Other Engineering
Other Engineering

abstract: The state of polarization of photoluminescence that is emitted along (001) and (110) crystallographic orientations has been studied to obtain quantitative information on the interfacial strain, thickness and biaxial strain in InP/InGaAs(P)/InP quantum wells. It is demonstrated that the edge emission from quantum wells is a sensitive function of the strain and thickness of the quantum well. The anisotropic polarization of photoluminescence that is emitted normal to the plane of the quantum well provides information regarding the interfacial features. This anisotropy has been correlated to the anisotropic strain field that is associated with the strained bonds at the interfaces of the quantum wells.

abstract: Doctor of Philosophy (PhD)


title: MEASUREMENT OF DYNAMIC CUTTING FORCE COEFFICIENTS

contributor:
Tlusty, J.
Mechanical Engineering

subject:
Mechanical Engineering
Mechanical Engineering

abstract: The dynamic behaviour of metal cutting process is investigated by measuring the various components of dynamic cutting force. For the complete description of dynamics of metal cutting it is necessary to give eight components belonging to the resultant dynamic cutting force in an orthogonal cutting process. These components originate from the two sides of chip, which under vibratory cutting conditions have undulations and are termed as inner and outer modulations respectively. The dynamic cutting forces are phase shifted with respect to their own modulations and are given respectively by real part and imaginary part of inner modulation, real part and imaginary part of outer modulation. Each of these four components are determined separately for main cutting force and thrust force and are specified as cutting force per unit amplitude of modulation per unit chip width, termed as dynamic cutting force coefficients. An experimental technique termed as the Double Modulation Method has been developed to measure the above eight coefficients for various cutting conditions of speed, feed, frequency, tool wear and work piece materials. The method is based on the Fast Fourier Transform of the measured signals of dynamic cutting forces and tool work piece relative displacement. The accuracy and reliability of the technique is established by comparing some of the results obtained from this method with those obtained from other two methods which are far simpler and conceptually more direct. These methods are termed as Kal's Method and Inner Modulation Method. The effects of various cutting conditions stipulated above on the individual coefficients have been investigated and the results are shown to be in agreement with the general practical observations. The result of stability analysis as performed by Moriwaki (21) using the coefficients measured in this work is included, to highlight the practical significance of the dynamic cutting force coefficients, for predicting the limit of stability.

abstract: Doctor of Philosophy (PhD)


title: Moral Education

contributor:
Najm, S.M.
Philosophy

subject: Philosophy Philosophy

abstract:
This thesis initially sets forth a program of moral education which teaches moral reasoning is the only program that could be adopted within the educational aim to "educate" and not to "indoctrinate" the child. This is the case because one does not want to implement a program of moral education that adopts a normative system of predetermined judgements because; 1) there is no agreement as to which normative judgements one would adopt as the correct ones, and, 2) by teaching normative judgements one is limiting the cognitive perspective of the child which means he does not have the knowledge or understanding that enables him to be on the "inside" of his "moral knowledge". The child who is taught normative judgements is not educated.

However, even though moral reasoning appears to be a plausible educational option it is not as neutral as one is led to believe. The teaching of a method whereby one can make moral judgments involves second order beliefs about first order moral discourse that may in some instances determine one's moral judgements. One cannot claim that teaching moral reasoning does not indirectly indoctrinate the child. Second, it is not clear that teaching moral knowledge will result in a morally educated child. Morality, as Aristotle points out, not only involves knowledge but also a disposition to habitually perform right acts. A child cannot be morally educated if he only has moral knowledge. He must also be taught how to act. It is only after he habitually performs right acts that moral knowledge is relevant.

The aim of education must then be changed so that one can inculcate in the child a disposition to perform right acts. The thesis concludes then, that a program of education for attitudes and emotions may in the end be a more comprehensive method whereby we can morally educate children.

abstract: Master of Arts (MA)


title: Generic solid modelling based machining process simulation

contributor:
Elbestawi, M.A
Spence, A.D.
Mechanical Engineering

abstract: In machining, the ability to automatically generate an optimum process plan is an essential step toward achieving automation, higher productivity, and better accuracy. These requirements are particularly emphasized in die and mold manufacturing, where complex tool and workpiece geometries involved make generation of the process plan a difficult task. High die production costs, narrow tolerance requirements, and the continuous demand for new components make process planning and NC code generation very complex and error-prone tasks. The current research need is to develop a system that is based on a simulation of the actual machining process, rather than simple geometric verification. Such a machining process simulator is needed to respond to the current need to enhance CAD/CAM technology with a machining process simulation that accounts for process mechanics and dynamics. A major impediment to implementing these systems is the lack of a general and accurate method for extracting the required geometric information. In this thesis, a novel approach to perform this task is presented. It uses general and accurate representations of the part shape, removed material, cutting edge and rake face. Solid models are used to represent the part and removed volume, B-spline curves are used for the cutting edge representation and B-spline surfaces for the rake face. Next, a generic solid modeler based milling process simulation system for 3-axis machining of complex parts using flat and ball end mills is implemented. It consists of geometric and physical simulators. In the geometric simulation, the tool swept volume is generated for every completed tool path (one NC block) and intersected with the part, yielding the corresponding removed material volume. The tool cutting edges are then intersected with that volume to produce the tool-part immersion geometry in the form of in-cut segments. These and an expression for the chip thickness are used to determine the chip load distribution along the cutting edge. The updated part can be used instead of the removed volume in the intersection step to generate the in-cut segments. The physical simulator models the mechanics and dynamics of the cutting process and uses the chip load to compute instantaneous cutting forces and predict other process parameters. The milling process simulation is demonstrated and verified experimentally for 2 1/2- and 3-axis ball end milling. In addition, it is shown that geometric modelling of 4- and 5-axis milling using different tool shapes as well as other machining processes such as turning and drilling can be performed using the same approach.

abstract: Doctor of Philosophy (PhD)


title: Nonlinear dynamics and seismic response of power transmission lines

contributor:
Aziz, T.S.
Ghobarah, A.
Civil Engineering

subject:
Civil Engineering
Civil Engineering

abstract: Electric power transmission lines have been traditionally designed for wind and ice loads. The earthquake load has not been considered in the analysis of transmission lines. During recent earthquakes, there have been indications of damage to transmission lines. Due to the complex nature of the problem, there is a lack of research work in the area of seismic analysis of transmission lines. The objective of this study is to evaluate the response of transmission lines to earthquake ground motion in order to evaluate the current design code methodology. The scope of this research program includes: (1) Modelling of different parts of the transmission line to analyze its seismic response, (2) comparison between the forces generated in the transmission tower members by wind, ice and earthquake loads, and (3) analyzing the probabilistic characteristics of the cable response to earthquake ground motion in order to establish a seismic design procedure for transmission lines. An intermediate span of a typical transmission line is chosen for the analysis. The tower members are modelled as truss elements. The cables are modelled by two node elements that retain their geometric nonlinearity. The dynamic characteristics of different components of the line (towers and cables) are determined in order to obtain a better understanding of the line behaviour. The in-plane and out-of-plane vibrations of the line are analyzed. The transmission line response to multiple support as well as uniform support excitations is evaluated. A closed form analytical solution for the cable vibration is carried out for a more detailed study of the cable nonlinear behaviour. It is concluded from the analysis that earthquake ground motion may cause substantial displacements and internal forces in the transmission line elements. The forces in transmission tower members due to the earthquake load may exceed those caused by the wind loads specified by the National Electrical Safety Code (NESC, 1993). Seismic ground motion may cause large displacement in the transmission line cables. This suggests that the cable motion during earthquakes should be included in the design of the line clearances to avoid having cables touch each other, which may cause power failure.

abstract: Doctor of Philosophy (PhD)


title: Complicated dynamics of a three species chemostat food chain

contributor:
Wolkowicz, G.S.K.
Mathematics

subject: Mathematics Mathematics

abstract: We consider a model of the chemostat that involves a three species food chain with no imposed periodicities. The bottom trophic level species depends on a single, essential, growth-limiting nutrient. For a particular choice of prototype response functions, numerical simulations exhibit complicated dynamical behavior for reasonable parameter values. Using bifurcation theory methods we show the possibility of chaotic dynamics in a neighborhood of a particular equilibrium point. Moreover, we examine the role of each of the response functions with respect to the dynamics (i.e. chaos) of the model by systematically changing one response function at a time from linear to a more biologically reasonable Michaelis-Menten response function.

abstract: Doctor of Philosophy (PhD)


title: Somatic growth, body composition and energy expenditure in infants with bronchopulmonary dysplasia

contributor:
Atkinson, S.A.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract: Extremely low birth weight infants who develop severe chronic lung disease, known as bronchopulmonary dysplasia (BPD), commonly experience long term growth failure. A randomized, blinded study was designed with the objective to enhance growth in this population using aggressive nutritional intervention. Growth and body composition were assessed during four months of formula feeding that was either: (1) enriched in energy, protein and minerals (EF) or (2) enriched in energy (isoenergetic to EF) but with standard concentrations of protein and minerals (SF). We hypothesized that between randomization (37 weeks post-menstrual age) and 3 months corrected age (CA) the EF group would demonstrate a faster rate of growth with greater lean (versus fat) mass deposition, and greater bone mineral accretion. In addition, higher energy expenditure (EE) as determined by the doubly labelled water method (DLW) would accompany the enhanced rate of growth. The measurements continued after the intervention ended to determine if any growth benefits derived from the enhanced nutrition up to 3 mo CA would be sustained to 12 mo CA. Body composition of the infants was measured with dual energy x-ray absorptiometry (DXA), which was validated against the reference method of chemical analysis. Repeated measures and carcass analysis of infant pigs identified that DXA was accurate and precise in determining bone and lean masses of piglets weighing 6 kg; thus, validating the methodology for use in infants of post-term age. At the end of the nutrition intervention (3 mo CA) infants in the EF group were longer, with greater absolute amounts of lean and bone mass compared to the SF group. The highest velocity of growth occurred between 37 wk PMA and 1 mo CA. No differences in EE were detected, but the high variability within treatment groups (for undetermined reasons) likely precluded our ability to detect significant results. Thus, the DLW method requires further validation for use in BPD infants. Nine months after the intervention ended (12 mo CA), EF and SF groups were similar in weight, length and body composition. When plotted on standard reference growth curves, both groups became significantly more negative in weight-for-length between 3 and 12 mo CA, despite energy and protein intakes deemed adequate by current recommendations for term infants. A longer nutritional intervention study would determine whether growth benefits provided by EF are sustainable, such that catch-up is inducible. Alternatively, catch-up growth may not be possible in infants of such extremely low birth weights under the influence of nutrition alone, and investigations of other factors such as the disease process may be warranted.

abstract: Doctor of Philosophy (PhD)


title: The role of mannose 6-phosphate receptors during herpes simplex virus replication and glycoprotein D binding

contributor:
Johnson, David C.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract: The focus of my research has been to identify cellular proteins which facilitate herpes simplex virus (HSV) entry and cell-to-cell spread. Previous research had demonstrated that HSV glycoprotein gD bound to a cell surface protein which was required by the virus for entry into cells. I began efforts to identify and characterize cellular proteins which bound to a soluble form of gD which lacked the transmembrane domain and cytoplasmic tail. I demonstrated that both the 275 kDa and 46 kDa mannose 6-phosphate receptors (MPRs) bound to soluble and full-length gD. The interaction between gD and the 275 kDa MPR was mediated primarily through mannose 6-phosphate (M6P) residues present on N-linked oligosaccharides. There was evidence that interactions between HSV and MPRs were important for virus entry. When the interaction between HSV and MPRs was blocked, HSV entry into cells was inhibited by 60% to 80%. However, HSV was able to enter into a mouse cell line that did not express MPRs. In addition to functioning during entry, there was evidence that MPRs also played a role in HSV egress or cell-to-cell spread. Blocking MPRs or preventing the addition of M6P residues to HSV glycoproteins resulted in inefficient viral egress and cell-to-cell spread. Therefore blocking the ability of HSV to interact with MPRs renders the virus less efficient at entry, cell-to-cell spread, and egress. To determine whether MPRs functioned during HSV egress from cells, I examined the intracellular localization of HSV gD by indirect immunofluorescence. I demonstrated that the HSV proteins gD, gI, and HSV capsids localized to the same compartment as the 275 kDa MPR. However, the intracellular retention of gD was not dependent on M6P residues. These data provide evidence that HSV proteins accumulate in intracellular compartments. These intracellular compartments represent a site involved in HSV exit from cells.

abstract: Doctor of Philosophy (PhD)


title: Optical coatings for improved semiconductor diode laser performance

contributor:
Mascher, P.
Engineering Physics

subject:
Engineering Physics
Nuclear Engineering
Other Engineering
Nuclear Engineering

abstract: Optical coatings have been applied to the facets of semiconductor diode lasers using the electron cyclotron resonance plasma enhanced chemical vapour deposition technique. Processes have been developed for the fabrication of optical interference filters from silicon oxynitride thin films using both tris dimethylaminosilane and silane as the silicon precursor. An important component for the fabrication of filters with a controlled reflectance index by ellipsometry. Using the ellipsometer, it is shown that, after correcting for systematic errors, an accurate measurement of the film index of refraction can be made during a deposition. Three separate applications of these optical coatings are discussed. The fabrication of anti-reflection coatings, the fabrication of narrow band reflectance coatings which could potentially have beneficial effects on the spectral properties of the laser and the use of silicon nitride layers, in conjunction with a sulphur based passivation, to improve the reliability of high power AlGaAs based lasers. Single and double layer anti-reflection coatings have been designed for specific laser waveguide structures. An existing theoretical model of the spectral output of a semiconductor laser has been modified to include the effect of an optical filter with a highly wavelength dependent reflectance, in order to understand the limitations of this technique. Finally, improvements in the surface properties of passivated and encapsulated AlGaAs material have been observed through an increase in the yield of photoluminescence after the passivation process was applied.

abstract: Doctor of Philosophy (PhD)


title: Seismic behaviour of existing and rehabilitated reinforced concrete frame connectionsment resisting frame building structures

contributor:
Ghobarah, A.
Aziz, T.S.
Civil Engineering

subject:
Civil Engineering
Civil Engineering

abstract: Many multi-story reinforced concrete frame structures were designed before the availability of current seismic design codes. The lateral load resistance of these structures may not be adequate even for a moderate earthquake due to the non-ductile reinforcement details of this type of structures. Recent post-earthquake investigations indicated that extensive damage occurs as a result of excessive shear deformation of the beam-column joints in the non-ductile frames, thus leading to full collapse of structures. The objectives of this study are to investigate the seismic behaviour of existing reinforced concrete frames under simulated seismic loading; as well as develop a rehabilitation technique for strengthening non-ductile frames. The first major part of the study is an experimental program conducted to: (i) investigate the inelastic behaviour of the non-ductile beam-column connections under cyclic loading; (ii) compare the response of the non-ductile beam-column connections with the response of beam-column connections designed according to the current concrete design code; and (iii) propose a practical method of rehabilitating existing connections and investigate their cyclic behaviour. The tested connections represent one-third scale model of existing connections. Six beam-column connections were tested under cyclic loading. The variables in the test specimens included the amount of joint and column transverse reinforcement and jacketing of the column only or both the column and the beam. Based on the test results, a design procedure is proposed for the rehabilitation of beam-column connections using corrugated steel jackets. The second major part of the study is to develop a suitable analytical procedure to simulate the behaviour of existing reinforced concrete joints so as to predict the proper behaviour of the non-ductile frames and develop a strategy for rehabilitation of such frames. Two joint elements are developed to represent the joint shear deformation and the beam reinforcing bar bond slip. The two elements are introduced into a non-linear dynamic analysis program which is used to simulate existing and rehabilitated frames. From the experimental and analytical research findings, recommendations for the design and detailing of the corrugated steel jacketing system for existing reinforced concrete frames are developed. In addition, a rehabilitation strategy is proposed to improve the performance of existing structures. The effects of the rehabilitation system on the confinement of beam-column connections, the provision of adequate development length for the positive bottom beam bars and the provision of full joint shear capacity are assessed and quantified. Test results indicated that corrugated steel jacketing system was found to be efficient in the rehabilitation of existing structures which do not meet the current seismic code requirements. A method is proposed for the design of the corrugated steel jacket to enhance the shear strength and ductility of the beam-column joint.

abstract: Doctor of Philosophy (PhD)


title: Chemistry of compounds containing sulphur-nitrogen bonds

contributor:
Eaton, D.R.
Biology

subject: Biology Biology

abstract:
The sulfur-nitrogen bonds in N,N'-monothiobisdialkylamines (N,N,N',N'-tetraalkylsulfoxylic diamides) and N,N'-dithiobisdialkyl-amines have been shown to undergo new reactions. The reaction of the former compounds with heptasulfurmide, (S₇NH), has led to the formation of the new compounds N,N-dialkyl-N,N'-cycloheptathiosul-foxylic diamides (S₇NSNR₂, R=CH₃, C₂H₅, CH(CH₃)₂, C₆H₁₁) in good yields. These compounds have been shown by NMR spectroscopy to have slow N-S bond rotation at room temperature. Structural studies suggested that the slow bond rotation is caused by strong pπ-dπ bonding in the single N-S bonds. The strengths of the π-interaction appears to be a function of the substituents of the and sulfur atoms. A synergic type of bonding is used to describe these saturated sulfur-nitrogen systems.

The S-N bonds in the N,N'-thiobisdialkylamines have also been found to be very reactive towards chlorine substituted phosphorus compounds. The reaction proceeds via an electrophilic attack of phosphorus on sulfur with subsequent loss of chloride ion from the intermediate. This species then rapidly rearranges to give a product in which the phosphorus atom has inserted into the sulfur-nitrogen bond. The stability of this species has been found to be dependent on the number of phenyl group the insertion product loses N,N- dialkyl-N-sulfenyl chloride. Further reactions of these species are discussed. With two phenyl groups, the insertion product is quite stable. It, however, has been found to be susceptible to attack by another mole of (C₆H₅)₂PCl to give further products. A discussion of the mechanisms of reactions in this system is given.

The sulfur-nitrogen bonds in the N,N'-dithiobisdialkylamines are considerably more stable towards these phosphorus compounds. The reactions that these compounds undergo suggest that the initial reaction involves fission of the sulfur-sulfur bond rather than N-S bond insertion. The reaction of (C₆H₅)₃P with these compounds to produce (C₆H₅)₃PS and the N,N'-thiobisamine offers a convenient method of purifying this latter compound from its major contaminant, the former compound. The reactions with (C₆H₅)PCl₂ and PCl₃ offer convenient methods of preparation of the compounds (C₆H₅)P(S)(Cl)(N(CH₃)₂) and ((CH₃)N₂)P(S)Cl₂ which have applications as insecticides. (C₆H₅)₂PCl and ((CH₃)₂N)₂S₂ have been shown to form a more complicated system in which reactions analogous to the two systems just discussed, occur. A discussion of the mechanisms of these reactions is presented. The chemical behaviour of these compounds suggests that the N-S bonds is the N,N'-dithiobisdialkylamines are considerably less reactive towards chlorine substituted phosphorus compounds than those in the monothio analogues.

abstract: Doctor of Philosophy (PhD)


title: A Hydrodynamic Study of Stellar Collapse

contributor:
Sutherland, P.G.
Physics

subject: Physics Physics

abstract: The purely hydrodynamical behaviour of collapsing stellar core is investigated. Adiabaticity and spherical symmetry are assumed. The equation of state consists of a high and low density branch. Both branches are parametrized by constant adiabatic indices. The evolution of the collapsing core is examined for various parametrizations of the equation of state. Emphasis is placed upon seeking parametrizations favouring mass ejection. No mass ejection occurred for any parametrization considered. However, behaviour most suggestive of mass ejection was observed in those models where the adiabatic index rapidly changed from slightly below 4/3 to slightly above.

abstract: Master of Science (MS)


title: Inhomogeneous d-wave Supercondutors

contributor:
Kallin, Catherine
Physics

subject: Physics Physics

abstract: Inhomogeneous superconductors with an order parameter of dx²-y² (d-wave) symmetry are investigated within the Ginzburg-Landau (GL) and Bogoliubov-de Gennes (BdG) formalisms. The inhomogeneities considered in detail are external magnetic fields, twin boundaries, and external currents. The Ginzburg-Landau equations are derived within the context of two microscopic lattice models used to describe the high-temperature superconductors: an extended Hubbard model and the Antiferromagnetic-van Hove model. Analytical results are obtained for the extended Hubbard model at low electron densities and weak to intermediate coupling. The variation of the coefficients in the GL equations with carrier density, temperature, and coupling constants are calculated numerically for both models. The anisotropic higher-order terms in the GL free energy are considered, with emphasis on the consequences for the structures of isolated vortices and the vortex lattice in the mixed-state. Twin boundaries are investigated numerically using the BdG formalism within the context of the extended Hubbard model. The twin boundaries are represented by tetragonal regions of variable width, with a reduced chemical potential. For sufficiently large twin boundary width and change in chemical potential, an induced s-wave component may break time-reversal symmetry at a low temperature T*.$ The temperature T*, and the magnitude of the imaginary component, are found to depend strongly on electron density. The results are compared with recent tunneling and transport measurements. The behaviour of d-wave superconductors in the presence of external currents is investigated numerically for both clean systems and those containing twin boundaries. The current response is studied with emphasis on critical currents and the superfluid density. The effect of the external currents on the subdominant s-wave components is characterized. Comparison is made with recent transport and tunneling measurements.

abstract: Doctor of Philosophy (PhD)


title: Toward a Comprehensive Understanding of Rta in the Rg Veda

contributor:
Whillier, W.
Arapura, J. G.
Weeks, I.
Religious Studies

subject: Religion Religion

abstract: In this thesis, it is my contention that the attempts by modern scholars to provide a precise definition of essence for rta, through an analysis of this term's etymological roots and by the application of modern English and European terms as possible cognates for rta, have failed to account for the rich significance of this complicated term. I suggest that such a precise definition cannot, and need not, be found for rta, and that the rich significance of this term can be grasped only in terms of the interrelated network of images, associations and specific applications which encompass it in the Rg Veda. To this end, I lay the groundwork for a more comprehensive study of rta by demonstrating that this term is associated with images of wide/safe/ree space, pathways upon which entities may travel free from harm, light, and the sound which destroys evil and dispels ignorance. Furthermore, I indicate that in its specific applications--as the mode of being of the sat, as that which regulates and stabilized all phenomena in space and time, as the sacrifice and the effective force of the sacrifice, and as "truth" in speech--rta works to provide the cosmos with the benefits inherent in the images and associations which encompass it. The conclusion of the thesis is that although no single image, association or specific application can adequately define rta, these, when melted together into a unified bond, provide the rationale for viewing this complicated term as a kind of "force" or "power" which is the necessary precondition for the freedom, safety, security, stability, truth, order, law, etc. of the cosmos.

abstract: Master of Arts (MA)