title: Domestic water demand in rural semi-arid Nigeria

contributor:
Kanaroglou, P.S.
Geography

subject: Geography Geography

abstract: Many rural water projects fail because planners do not understand how local populations relate to, and use domestic water. Although domestic use accounts for about 9% of the consumptive use of water in sub-Saharan Africa, the benefits associated with improved access to it are immense. The study investigated domestic water use in the water-deficient semi-arid Nigeria, using a case study of Katarko. Detailed socio-demographic data known to affect water demand, were compared with aggregate data at the national and regional levels. The high population growth rate, low economic status of the women and the declining water availability present a good recipe for unsustainable water resource development and use in Katarko. Katarko relies on stream flow, rainfall, ground water and ponds for its domestic needs, with ground water being the only source that can supply perennial water. Distance was identified as the most important factor in the choice of a water source. A tradeoff exists between using good quality water and the effort it takes to obtain it. Using culturally-constructed measures of water quality, the study found that the locals perceive the quality of water they use as higher in the rainy, than in the dry season. Cloth filtration is the preferred method of water purification, followed by the addition of anthill soil, while boiling ranks third. Multiple regression models were used to study demand in the dry and rainy seasons, when water is scarce and abundant respectively. The levels of explanation provided by the rainy season and dry season models are 51.2% and 91.1%, respectively. The lower explanatory power of the rainy season model may be an indication of wasteful use when water is abundant. Overall, the results show that although most of the determinants of water demand in both seasons are subject to socio-cultural interpretations, one can approach the management of it with economic principles. Incorporating the socio-demographic variables that affect domestic water demand into projections further reveals how changes in the variables affect future demand. Modeling seasonal variations in demand provides a glimpse of how consumers will adapt their demands to increased water supply. Geographical accessibility is a major factor in the underutilization of rural water facilities in Nigeria, because facilities are often not optimally sited. This research demonstrates the utility of location-allocation modeling as a decision support tool in siting rural water facilities, where they are accessible to users and yield the highest social welfare returns. The option of either providing new wells that are optimally distributed, or rehabilitating existing wells as requested by the community was examined. The research recommended the provision of a new set of optimal wells, in view of the offsetting benefits associated with them. The results of the study contribute conceptually and factually to the understanding of domestic water demand in rural areas of developing countries.

abstract: Doctor of Philosophy (PhD)


title: A Study of the Mechanism and Kinetics of the Synthesis of Methanol and Higher Alcohols Over Alkali Promoted Copper/Zinc-Oxide/Chromia Catalysts

contributor:
Anderson, R.B.
Smith, Dr. K.J.
Chemical Engineering

subject:
Chemical Engineering
Chemical Engineering

abstract:
Methanol and higher alcohols are produced when mixtures of CO, CO₂ and H₂ are reacted over Cu/ZnO catalysts at temperatures above about 250°C and pressures of 5 to 10 MPa. Relatively little is known about the synthesis of this mixed alcohol product, which has potential usefulness as a liquid fuel, or as a non-lead octane improver for gasoline. In the present work, various aspects of the synthesis of methanol and higher alcohols over Cu/ZnO/Cr₂O₃ catalysts have been investigated.

Addition of ¹³C labelled methanol to the reactor feed gas showed that methanol is incorporated directly into the higher alcohol product. Enrichment patterns of ¹³C in the higher alcohols suggested that CO is also a direct precursor of C₁ intermediates which produce higher alcohols.

A kinetic model of the higher alcohol synthesis (HAS), derived on the basis of direct mechanistic information, has not been reported. In the present work, the kinetics of the HAS have been successfully modelled by a scheme in which CH₃OH, CO, and CO₂ are converted directly into higher alcohols. The model was found to be consistent with the kinetic observations made for a wide range of reactor operating conditions including: H₂/(CO+CO₂) ratios of 0.36 to 1.8, CO₂/CO ratios of 0 to 1.35, CH₃OH feed concentrations of 0 to 5.3 percent, for (CO+H₂) conversions of 3.5 to 18 percent and at total pressures ranging from 5 to 10 MPa.

The kinetic observations of the methanol synthesis, made under the same operating conditions, were well described by a model based on the assumption that methanol is formed from both CO and CO₂ in parallel reactions, on different catalytic sites. This model is unique in that it is consistent with the most recent mechanistic and kinetic observations of other workers, and in that it describes the methanol synthesis behaviour at conditions suitable for the HAS.

Similarities between the methanol and higher alcohol synthesis models suggest that sites which convert CO to methanol also convert CO to higher alcohols, while sites that convert CO₂ to methanol also convert CO₂ to higher alcohols. Experiments with catalysts promoted with various amounts of K₂CO₃ promoter suggest that CO conversion is associated with alkali sites or alkali/copper interfaces, while CO₂ conversion is associated with unpromoted copper sites. This view reconciles many apparently contradictory results which have been reported in the literature.

abstract: Doctor of Philosophy (PhD)


title: Rare Earth and Other Geochemical Studies of Archean Banded Iron Formation: Sherman and Adams Mines, Ontario

contributor:
Crocket, James H.
Geology

subject: Geology Geology

abstract:
Banded iron-formation (BIF), an iron-rich chemical sediment of Precambrian age, from the Sherman Mine at Temagami and the Adams Mine at Kirkland Lake, Ontario, were the subject of a detailed geochemical study. The rare earth elements were extensively studied with lesser emphasis on sulphur isotope, trace element and major element compositions. Procedures were developed to quantitatively estimate the relative chemical and clastic components of mixed sediment lithologies and to correct both volcanic and volcaniclastic major element analyses for alteration resulting from weathering or metamorphism.

Analyses of the rare earth patterns suggest inputs from diverse sources; from clays resulting from submarine weathering, from direct addition of fine grained volcaniclastic detritus, from ambient seawater and from submarine hydrothermal vents. In addition, the concave-down curvature of the light rare earths of some samples suggests a mineral control such as marine apatite. Also, the positively anomalous values of La suggest a component whose REE contents were controlled by the solubility product of sparingly soluble solids as opposed to the ion speciation and exchange equilibria which control the rare earth contents of normal marine waters. Combinations of rare earths from these sources allowed synthesis of all patterns measured, frequently to a precision of 5% or better.

Analyses of sulphur isotopes of pyrite found in the iron formation showed greater variability in volcanic as opposed to clastic sediment host lithologies. Sulphide-facies iron formation had an isotopic signature indistinguishable from volcanic sulphides and it was not possible to unambiguously infer the presence of biological activity.

Anomalies in the distribution of tungsten in BIF were interpreted to be the result of either syngenetic or epigenetic processes. BIF may become enriched in tungsten as a result of either its tendency to deform by brittle fracture or because of primary volcanic exhalative addition.

The data suggest that Archean basinal water were enriched in Fe, Si, Eu, Mn and P compared to modern counterparts. The absolute abundances of the REE and trace elements in the iron-formations studied were low compared to previously published values.

Higher statistical variability in both the sulphur isotope data and REE from BIF hosted in volcanic as compared with detrital rocks, and a persistent large positive Eu anomaly, all suggest inputs of hydrothermal fluids to the depositional basin. However, the lack of internal correlation of the volcanogenic elements suggests depositional sites were not necessarily proximal to source vents. This results in a decoupling of source from sink in the case of iron formation deposition in Archean marine basins having very low oxygen content. Any correlation of BIF with massive sulphide or other exhalitive type mineralization would be on a basinal rather than a deposit scale.

abstract: Doctor of Philosophy (PhD)


title: Water use in the rural economy of a semi-arid environment: A northern Nigeria case study

contributor:
Anderson, William P.
Geography

subject: Geography Geography

abstract: Environmental (climatic) and economic (human) influences have contributed to the problem of water scarcity in arid and semi-arid areas of the world, particularly in the less developed countries. This has impeded economic development in these regions. Thus, the call for better methodological approaches for investigating the problem from an interdisciplinary perspective and at a local scale--the "bottom-up" approach. This study investigates the nature of water use in a selected drought-inflicted village and develops an analytical framework for assessing the water demands of alternative economic development scenarios in the village. A review of hydro-climatological characteristics, land use practices, and technological development provides information on water resources availability and human activities in the region. Surveys of human activities and water use in the study village, Katarko indicate the following conditions: water scarcity, unsustainable agricultural development, and subsequent food and economic insecurity. Further investigations indicate that groundwater is the most dependable source of water. Its use is dominated by agricultural activities especially irrigation and animal rearing. These are also the most water intensive activities based on the ratio of water use to income generation. Results of the initial survey provide useful background information for the development of predictive models and water conservation strategies. A commodity-by-industry economic-ecological model (CIEEM) is developed for this purpose. Estimates of direct and total requirements of both economic and ecological commodities showed sparse sectoral interdependence within the economic system but a heavy dependence of the economy on the environment. Such dependence is more on water, a scarce commodity in this semi-arid environment. The most intensive users of water based on the direct effects include animal husbandry, building and irrigated agriculture; based on total effects are catering, building and animal husbandry, in descending order. A number of policy scenarios for local economic development and water conservation are formulated. They are derived based on our own observations in Katarko village and relevant literature for the semi-arid zone, and incorporate elements of indigenous knowledge systems and technologies (local initiatives) regarding water scarcity and drought mitigating strategies in terms of water procurement, delivery and processing, as well as national development strategies. These scenarios are simulated using the model to determine economic and environmental impacts in terms of changes in water use. An increase in production will require an increase in groundwater input while changes in the production process and water application efficiency will ensure a reduction in groundwater input and other environmental commodities. Results show that some of the production scenarios are more water intensive than others. The water conservation strategies discussed here will serve as policy options for sustainable development in this water-scarce village as well as other areas with similar economic and environmental conditions.

abstract: Doctor of Philosophy (PhD)


title: Rehabilitation of nonductile reinforced concrete buildings using steel systems

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

subject:
Civil Engineering
Civil Engineering

abstract: Many of the existing reinforced concrete (RC) structures performed poorly during recent earthquakes. Most of these structures were designed for gravity loads only with inadequate lateral load resistance. Several of the construction details in existing gravity load designed buildings do not conform to current code requirements for seismic design and may lead to nonductile inelastic behaviour. The objective of this research program is to investigate the use of steel systems for the rehabilitation of existing nonductile RC buildings. The study is limited to low-and mediumrise frame buildings. A beam-column element capable of representing the behaviour of nonductile RC frame members is developed. The model is capable of representing the strength decay of nonductile RC members and the effects of the axial force on the yield moment and the deformation capacities of the member at peak strength. A procedure for evaluating the damage to nonductile RC structures following an earthquake is developed. The damage procedure depends on calculating the deterioration of the building stiffness and lateral load carrying capacity due to the application of the earthquake loading. The building stiffness and lateral load carrying capacity before and after the application of the earthquake loading were determined by conducting a pushover analysis. Two nonductile RC buildings, three- and nine-stories, representing low-and mediumrise existing nonductile structures, were analyzed using various ground motion records. The seismic behaviour of the nonductile buildings when rehabilitated using various structural steel systems was determined. The investigated steel systems include the addition of concentric X-bracing, eccentric bracing and attached steel frames. The effectiveness of the various steel systems in rehabilitating the three- and nine-story buildings were examined. The effect of the distribution of the steel bracing along the height and along the bays of the RC frames on the seismic performance of the rehabilitated building was studied. A simplified approach was proposed for selecting the proper brace distribution. The seismic performance of the nonductile three-story budding when using well designed eccentric bracing rehabilitation was compared with the performance of the building when using concentric bracing. The relationship between the deformation capacity of the rehabilitated building and the link deformation angle was evaluated. The distribution of the link strength along the building height was investigated. The seismic performance of the rehabilitated nine-story building was evaluated when using both flexible and stiff steel frames.

abstract: Doctor of Philosophy (PhD)


title: A Network Model of Small Intestinal Electrical Activities

contributor:
Sarna, S. K.
Electrical Engineering

subject:
Electrical and Electronics
Electrical and Electronics

abstract:
An electronic circuit based on a modified version of the four branch Hodgkin-Huxley electrical equivalent circuit (Roy, 1972) has been proposed and implemented to simulate the pattern of the electrical activities present in the muscle cells of the mammalian small intestine.

The analog's implementation comprises two main circuits to simulate these activities. One of them is concerned with generating subthreshold oscillations, while the other is basically a spike-generator circuit. Additional circuitry is included to interface them. Furthermore, the analog provides a parameter set by means of which its performance may be varied. Such settings may alter the intrinsic frequency, the magnitude of the depolarizing phase of the control potential for the response activity to occur, and also the frequency of the electrical response activity.

Four such electronic oscillators, having different intrinsic frequencies, were coupled together in a chain structure with passive elements to simulate "frequency pulling" and "entrainment". The model qualitatively reproduced the observed pattern of electrical activities in the small intestine.

abstract: Master of Engineering (ME)


title: Poly(N-isopropylacrylamide) at the air/water interface

contributor:
Pelton, Robert
Chemical Engineering

abstract: Linear polymers, copolymers, microgels and macrogels based on N -isopropylacrylamide were prepared and the properties of these materials at the air/water interface were investigated. Dynamic surface tensions were measured by pendent drop experiments in which either the drop volumes were constant or were oscillated. The ability of colloidal microgels to lower surface tension is unusual and, for the first time, Environmental Scanning Electron Microscopy provided images showing an ordered array of 500 nm diameter microgels adsorbed at the air/water interface. The surface tension of poly(N -isopropylacrylamide) homopolymers and microgels was about 43 mJ/m2 at 25°C, and surface tension decreased slightly with increasing temperature between 25∼40°C. The temperature insensitivity of surface tension is remarkable because in solution the linear polymer phase separated and the microgel were dehydrated when the temperature was raised from 25 to near 40°C. The introduction of hydrophilic acrylamide moieties increased surface tension and the results were fit to a one-parameter model analogous to the Margules model for the fire energy of mixing of solutions. Kinetic models were developed and fitted to the dynamic surface tension data. A key challenge was relating surface tension to the amount of adsorbed material at the interface. Results are shown for calculations based on both published data and statistical mechanical models of adsorbed polymer. The inability of mass transport models to predict the kinetics suggested that rearrangement of gels or linear polymer at the interface contributed to the kinetics. Macroscopic water swollen gels like the linear polymers and the microgels displayed a low surface energy due to the accumulation of isopropyl groups at the interface. However, unlike the microgels and linear polymers, the surface characteristics reflected in contact angle measurements was sensitive to temperature in the critical range 35 to 40°C.

abstract: Doctor of Philosophy (PhD)


title: Germline minisatellite mutations in herring gulls: Induced mutations at colonies situated near steel mills

contributor:
Quinn, James S.
Biology

subject: Biology Biology

abstract: The study of induced heritable mutations occurring in nature is difficult as mutations are extremely rare and large sample sizes are needed to measure statistical differences between populations. Minisatellites are tandemly repeated units of DNA, 10 to 100 bp in length, predominantly found in non-coding regions of the genome. With multi-locus DNA fingerprinting, several loci are examined simultaneously increasing the sampling efficiency. Minisatellites have the highest mutation rate detected in the genome to date, making them ideal targets for mutational screening. I examined minisatellite mutation rates in herring gulls (Larus argentalus ) colonizing areas near steel mills, urban centers, and rural areas of the Great Lakes, to assess the application of minisatellite DNA mutation rates as biomarkers for induced germline mutations. I showed that gulls inhabiting contaminated environments near steel mills inherit significantly more mutations than gulls from rural locations. I found a negative correlation between proximity to industrial coking ovens and minisatellite mutations; the mutation rate increased almost 3 fold from rural to the most heavily impacted site. My data were not consistent with either of the alternative hypotheses put forth to explain differences in minisatellite mutation rates: (1) genetic differences in the populations and (2) differences in the age of parents sampled (i.e., older parents may be more susceptible to mutations). I suggest that minisatellite mutations are induced by chemical contaminants in the industrial environment, and that minisatellite DNA provides a sensitive biomarker for induced germline mutations in urban industrial environments. I investigated the levels of DNA adducts in herring gulls from our primary steel industry site, Hamilton, Ontario, and from one rural location, in order to clarify exposure. The levels and patterns of DNA adducts in erythrocytes of gulls from these two locations were identical, suggesting that DNA adducts in gull erythrocytes are not appropriate biomarkers of exposure.

abstract: Doctor of Philosophy (PhD)


title: The classification of sympatric forms of bottlenose dolphins (genus Tursiops) in Chinese waters

contributor:
White, B.N.
Biology

subject: Biology Biology

abstract: The classification within bottlenose dolphins (genus: Tursiops ) is controversial. The prevalent view is that of a single species. To test this hypothesis, osteological, molecular and external morphological data from two sympatric forms of bottlenose dolphins in Chinese waters were examined. Multivariate cluster analysis of meristic osteological characters identified two distinct groups that were consistent with the field classifications of the specimens into two forms. The main contributor to the separation of the two groups was total number of vertebrae. Cluster analyses of principal components scores for cranial morphometric data resulted in two distinct groups that agreed completely with the meristic analysis and field classifications. A series of discriminant analyses revealed highly significant differences in cranial characters between the two forms, helped to identify important characters for an identification key and generated classification functions for separating the two forms. A portion of the mitochondrial DNA control region (386 base pairs) from 47 specimens was analysed. Separation of the haplotypes of the two forms was revealed independently by maximum likelihood, neighbor-joining and maximum parsimony analyses. Separation of the two forms in Chinese waters was also supported by bootstrap and consensus values, a large divergence of ∼4.4%, and seven fixed site differences. Congruence between the osteological and molecular data provided strong evidence that reproductive isolation between the two sympatric forms exists. According to the Biological Species Concept, the two forms in Chinese waters represent separate species. Furthermore, the results also satisfied the criteria of other species concepts. To determine if these species can be differentiated externally, several morphological characters were subjected to a discriminant analysis. The results were highly significant. Examining individual characters revealed non-overlapping distributions in rostrum length and rostrum length as a proportion of total body length or snout-to-eye length. These characters are potentially useful for identifying free-ranging dolphins.

abstract: Doctor of Philosophy (PhD)


title: "An Unpredicted Terrain": The Poetry of Charles Tomlinson

contributor:
John, Brian
English

subject:
English Language and Literature
English Language and Literature

abstract:
To some extent, Charles Tomlinson has been the victim--and continues to be--of two general trends in criticism. On the one hand, in America, as a post-war British poet, he suffers from the scant attention accorded to this group by American critics. On the other hand, in Britain, as a postwar British poet with strong American influences, he suffers a similar neglect at the hands of British critics. Tomlinson himself, both as a poet and as a critic, has sought to break down the British barriers to outside cultural influence. More than many poets, he has developed a poetic which is bound up with the idea of influence. The idea of influence is related to a number of important issues both in Tomlinson's poetry and poetic and to modern poetry generally: to the idea of modernist internationalism, to the strained relations between modern British and American poets, to translation, and, perhaps most importantly for his work, to the idea of chance and the poetic self.

This thesis examines the problem of the self in the poetry of Charles Tomlinson by reading it within the dialectic of possessiveness and possibility which he describes in the Preface to his Collected Poems (1985). My first chapter considers Tomlinson's approach to these issues in relation to Harold Bloom's theory of influence and to recent theories of literary entitling and metaphor. After examining a number of ways by which Tomlinson endeavours to defend his poetic space of possibility, the chapter concludes by showing how p pervasive and important is his poetic of misperception or chance.

My second chapter considers the influence of Wallace Stevens's poetry and poetics on Tomlinson and tries to set that relationship in the more general context of the British reception of--more often, resistance to--Stevens's writing. Tomlinson was most indebted to Stevens in his early volume, The Necklace. Since that time, he has sought to distance himself from his American mentor's rhetoric and theory. However, Tomlinson maintains a strong interest in his poetry and, to some extent, Tomlinson may derive a poetic of misperception from his work.

Each of the subsequent chapters discusses a different aspect of possessiveness and possiblity. Chapters three and four look at both the ideal, Edenic facet of locality, and at the most significant features, for Tomlinson's poetry, of actual places. His attack on cultural insularity is bound up with his aesthetic of giving the thing its due: to go outward to things is akin to going out to other cultures. My final chapter examines the broadest implications of Tomlinson's dialectic, in his travel and political poems: the centre of his poetic concerns.

abstract: Doctor of Philosophy (PhD)


title: Techniques for the Recognition of Silhouettes

contributor:
Kitai, R.
Tlusty, J.
Electrical Engineering

abstract:
A representative set of binary image processing techniques selected from the literature is described. The measurement of shape as the fundamental information contained in silhouettes is examined. Operations on digital binary images are demonstrated including smoothing, connectivity analysis and determination of position and orientation. The effects of digitizing errors at the boundary of a silhouette are discussed and examples of industrial vision systems which use binary images are presented.

A binary image processing system has been designed and implemented. The apparatus is based on a General Electric TN2500 digital television camera and an Intel iSBC 86/12A microcomputer. Hardware for the acquisition of binary images from the camera is described followed by the software for calculating areas and centroids. The system is capable of "learning" a set of objects in a "Teach" mode and then making an identification based on their area in the "Run" mode.

abstract: Master of Engineering (ME)


title: Hydrodynamic Characteristics of a Horizontal Pulsed Solvent Extraction Column

contributor:
Vijayan, S.
Woods, D.R.
Chemical Engineering

abstract:
A horizontal configuration for a pulsed solvent extraction contactor has been recognized as having a great potential in replacing standard vertical pulsed columns (VPC) in the separation of heavy elements in the reprocessing of spent nuclear fuel. Published work examining the performance of the horizontal pulsed column (HPC) has been sparse to date, thus preventing the design of large-scale units.

The hydrodynamic studies were conducted in a 0.072-m by 1-m long column with a perforated-plate cartridge arrangement using a 30% tributyl phosphate +70% Isopar M -2.0 mol/L nitric acid system. The hydrodynamic behaviour was characterized in terms of throughput capacity, dispersed phase holdup, axial mixing of both phases and power dissipation. Emphasis in this study was given to the effects of the major operating variables that include: aqueous and organic flowrates, and pulse amplitude and frequency, on the key hydrodynamic factors. The effects of physical properties for liquid-liquid systems and plate geometry were also examined for selected hydrodynamic factors.

The variation of throughput capacity with the operating variables was found to be similar to that reported for the VPC when presented on standard flooding diagrams. The flooding behaviour of the HPC was strongly dependent on both pulse amplitude and frequency, as well as on the coupled pulse effect represented by pulse velocity. A procedure for constructing flooding diagrams from correlations derived from experimental results was demonstrated. Mechanisms to determine the onset of flooding and flooding anomalies were investigated and the results compared with experimental data.

A detailed analysis of the dispersed (aqueous) phase holdup was made. The aqueous holdup did not vary significantly along the column, however, local radial variations are reported. Correlations based on experimental data for the average holdup for the HPC indicated the effect of the major operating variables is similar to that reported for the VPC in the mixer-settler region of operation. However, the range of the aqueous holdup observed for the HPC (0.15 - 0.50) is several times larger than that typically reported for the VPC.

Axial mixing, as determined by a two-point tracer method of measurement, was well represented by a backflow model. Axial mixing of the dispersed (aqueous) phase was found to be insignificant. The organic phase axial mixing was significant with backflow coefficients as large as 25.4 (dispersion coefficient of 18.2 cm²/s) were observed. The effects of the major operating variables on the organic phase axial mixing in the HPC were consistent with similar data reported for the VPC.

Power dissipation studies, by the force-displacement method, revealed a pronounced dependency on the pulse amplitude-frequency product. Individual phase flowrates were found to have a minimal effect on the time-averaged power dissipation. Experimental results were in good agreement with a quasi-steady state model commonly used for the VPC.

A comparison of the major hydrodynamic factors for the HPC with the VPC suggested that the HPC can be a viable alternative where space and portability factors are critical.

abstract: Doctor of Philosophy (PhD)


title: Feasibility of a Bone Mineral Measurement Technique Based on Coherent Scattering of Gamma Rays

contributor:
Webber, C.E.
Physics

subject:
Biological and Chemical Physics
Biological and Chemical Physics

abstract:
The investigation of the feasibility of a bone mineral measurement technique based on coherent scattering of gamma rays was performed using a HPGe detector.

Considerations of detector efficiency and resolution, absorbed dose to bone, spectral separation between coherent and Compton peaks, variation of differential coherent cross section and scattering volume with scattering angle led to the selection of a photon soruce energy of 103.2 keV (Sm153) and a scattering angle of 40 degree.

Bone phantoms (aqueous solutions of K2HPO4) were used to examine how the coherent intensity emanating from a scattering volume at the centre of an object varied with object dimensions and solution effective atomic number. Simulation and experimental measurements with solutions in cylindrical polyethylene containers of varying sizes indicated that the ratio of the coherent count rate to the transmission count rate was independent of container dimensions (at least up to 7 cm diameter). For ease of comparison, all the ratios at different concentrations were normalised to that of water obtained in an identical measurement geometry. The normalised coherent-to-transmission ratios were related to solution effective atomic number by a power function with a exponent of 3.30 plus minus 0.15.

When the rate of change of the normalised ratio with effective atomic number is used as an indicator of the sensitivity of the technique, the coherent-to-transmission method is almost twice as sensitive as a coherent-to-Compton technique.

In-citro bone mineral measurements were made in the calcaneus (heel bone), an easily accessible site in which 90% of bone mineral is trabecular. Prior to the measurements the spatial distribution of mineral was investigated with a Norland 278-A single photon absorptiometry (SPA) machine in slices of several calcanei. Cortical bone was restricted to a thin peripheral region of the calcaneus.

Three whole calcanei, one of which had its calcium content deliberately reduced by soaking overnight in hydrochloric acid, were selected for measurement using the coherent-to-transmission technique. For the first measurement each bone was submerged in water only. For the second measurement the trabeculae were filled with corn oil, to simulate marrow fate, and again each bone were submerged in water. The latter measurements were about 50% lower than the first, indicating a large "marrow fat" effect. However, both sets of results can by explained by assuming a power relationship between the normalised coherent-to-transmission ratio and the effective atomic number of the scattering volume contents.

Cuboid samples of side approximately 16 mm were cut out of the posterior region of each calcaneus and ashed. A plot of the normalised coherent-to-transmission ratio versus the ashed weight per unit volume (bone mineral density) of the three calcanei yielded a straight line. While this indicates that the normalised coherent-to-transmission ratio is an indicator of bone mineral, a larger number of samples will be required to establish a robust calibration curve.

abstract: Doctor of Philosophy (PhD)


title: Enemies at Home: Upper Canada and the War of 1812

contributor:
Weaver, John
History

subject: History History

abstract: This study challenges several common assumptions about the War of 1812. Most writers have stressed that the inhabitants of Upper Canada played a large role in the defence of the colony and that the conflict created a greater sense of unity among an already cohesive population. Some authors have even suggested that the war was responsible for Confederation since it produced a wave of anti-Americanism that "knit together" British North Americans. In economic terms, it is usually claimed that the colonists benefited from military spending and that the war set the province on a course for future prosperity. Before the war, however, Upper Canada was a fragmented and pluralistic community. Colonists were divided by racial, religious, linguistic, and class differences. Most settlers had no strong ties to either the United States or Britain and few appeared eager to fight for either government. The atomistic nature of Upper Canadian society made concerted action against an invader an impossiblity and a majority of Upper Canadian males avoided service altogether during the conflict. A computer-assisted study of 2,055 claims submitted by inhabitants for war damages reveals that British soldiers and their Indian allies were responsible for much of the damage done to private property. That information explains why there was little increase in anti-Americanism after the conflict. Most wartime destruction was restricted to the Niagara region and areas to the west and residents in eastern Upper Canada lost little by the fighting. Some merchants in that area made small fortunes by breaking laws relating to currency or by taking advantage of civilian and military customers but many other inhabitants saw little benefit from increased spending by the British army. While a handful of shopkeepers gouged the public, other Upper Canadians who stole or traded with Americans were branded as rebels and eight "traitors" were hanged for such activities. Upper Canada was ill-prepared to deal with the legacy of the fighting. The economic depression which gripped the colony for almost a decade was, in part, a result of the damages and dislocation caused by the war. The creation of a reform group in the Assembly can also be linked to issues that arose out of the conflict. Disputes over compensation, militia pay, land grants, pensions, and medals for heroism enlivened post-war politics for many years. War damage claims, for example, were not liquidated until 1837. The assumption of that debt helped drive the colony into bankruptcy and it was this fiscal embarassment, not unity arising from the war, which 100 to the union of Upper and Lower Canada.

abstract: Doctor of Philosophy (PhD)


title: Modelling and compensation of errors in five-axis machining

contributor:
Elbestawi, M.A.
Mechanical Engineering

subject:
Mechanical Engineering
Mechanical Engineering

abstract: This thesis outlines a modelling approach and compensation strategy for understanding and improving the accuracy of five-axis machining. The kinematic model of the machine was based on Homogeneous Transformation Matrices (HTM), which used small angle approximations to form shape and joint transformations. HTMs were chosen in this form because they allowed the kinematic model to include the geometric, kinematic, and thermal errors of the machine. These sources of error result in a significant loss of accuracy in the production of dies, molds, aircraft parts, and many other critical industrial components. The individual error terms in the HTM's formulation are difficult to measure on an assembled machine. Therefore, a test procedure was designed to isolate the error terms and an allocation strategy, using the kinematic model, was developed to associate the error measured in the work space to the error in each of the main components of the machine. The kinematic model of the machine was also used in calculating the compensation values to capture the interaction of the error components and all of the axis motions. The compensation strategy was implemented by adjusting each axis in the motion code with offset values based on the expected error. The motion code was modified just before being sent to the machine tool for processing. Due to the difficulties in measuring the error continuously on-line, empirical models were used to estimate the errors. The empirical models related temperature distribution and various machine conditions to the error in the machine tool's components. The empirical models took advantage of a priori information in the form of known physical relationships which described the deformation of the structures under thermal loading. A multiple linear regression model was chosen as the empirical model for implementation in the compensation strategy. It was chosen because of its simplicity, robustness, and ease of implementation. Through the recasting of the linear model's parameters, nonlinearities could also be included in the model. The regression model was found to be able to interpolate within the experimental data set. Through the inclusion of physical relationships in the development of the model, it was found to provide reasonable estimates when extrapolating. A neural network model was also considered, but was not implemented in the final compensation strategy because of the model's limitations when extrapolating beyond the training set conditions. A means of updating the error model on-line was included in the compensation strategy using measurements made from reference surfaces in the work space. This was done to account for any unmodelled variation not captured during off-line testing. Also, this includes any slowly varying changes which can occur to the machine over time due to wear and structural material instability. Realistic cutting tests using light finishing cuts, high spindle speed and axis feed were conducted. These machining conditions are typical of the mold and die industry. The cutting tests showed that a reduction of dimensional error from 0.082 mm to 0.012 mm was possible using the proposed compensation strategy.

abstract: Doctor of Philosophy (PhD)


title: Chronic Giardiasis in CBA/N Mice: Use of Genetically Immunodeficient Mice to Study Mechanisms of Immunity to an Intestinal Parasite

contributor:
Underdown, Brian J.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract:
Giardia muris is an intestinal parasite of mice. It has a simple life cycle and is non-invasive. Therefore, G. muris infection provides a model to study immune mechanisms that operate at mucosal surfaces. Immunocompetent mice eliminate primary G. muris infections. T cell-dependent humoral immune mechanisms are involved in this process.

The CBA/N mouse bears an X-linked immunodeficiency gene (Xid), the expression of which results in defective B cell maturation and consequent impairment of certain humoral immune responses. The antibody responses of CBA/N mice are particularly defective in certain isotypes and specificities.

CBA/N mice fail to eliminate G. muris. The major focus of this dissertation was an attempt to elucidate the basis for chronic giardiasis in this strain.

Cellular reconstitution experiments showed that the ability to eliminate G. muris was transferred to CBA/N mice with lymphoid cells from immunocompetent, CBA/Ca mice. Reconstitution required prior irradiation of recipient mice, and was not effective with semi-purified B cells and T cells. These results indicate that conventional B cells and T cells are insufficient, and that another cell type is also required. This cell may be the Lyl+ B cell.

CBA/N mice make quantitatively deficient serum IgG antibody responses to G. muds infection. Providing CBA/N mice with this antibody failed to induce elimination of the parasite, thus this isotype defect was ruled out as the cause of their susceptibility to chronic giardiasis.

Analysis of G. muris antigen recognition failed to reveal a specificity defect in the antibody response of CBA/N mice. However, a glycolipid component of G. muris bound serum IgM from CBA/J and BALB/c mice, but not serum IgM from CBA/N mice. These results indicate a possible structural defect in IgM from CBA/N mice.

Although unable to eliminate primary G. muris infection, drug-cured CBA/N mice are resistant to reinfection. These results indicate that the immune mechanisms that mediate elimination of G. muris are different from those that mediate resistance to reinfection.

abstract: Doctor of Philosophy (PhD)


title: Social capital and regional health governance in Saskatchewan, Canada

contributor:
Matthews, Ralph D.
Sociology

subject: Sociology Sociology

abstract: The relationship between social capital in a community and effective political governance by regional health boards in Canada was explored. A model was proposed that identified components of social capital such as trust, commitment and identity, associational and civic participation and collaborative problem-solving. These concepts were theoretically linked to effective governance--in particular to reflection of health needs, policy making and implementation, fiscal responsibility and the integration and coordination of services. The theoretical model was then tested empirically in Saskatchewan, Canada, where district health boards (DHBs) have been in operation since 1993. We found little evidence of a relationship between social capital in health districts and the performance of corresponding DHBs. Using a survey of randomly selected citizens from eight districts (n = 534) we explored relationships among the individual-level components of social capital delineated in the model. The behavioural components of the model--associational and civic participation and past experience collaborating to solve community problems--were significantly and positively related to one another. After controlling for socio-demographic characteristics we found that certain forms of trust, identity and commitment were positively and significantly related to these social capital behaviours.

abstract: Doctor of Philosophy (PhD)


title: The Imunomodulation of Intestinal Smooth Muscle Function

contributor:
Collins, Stephen M.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract: In response to an enteric infection, the host mobilizes inflammatory and immune cells to combat the invading pathogen. Studies suggest that physiologic tissues such as smooth muscle are also recruited to aid in host defense, and that this recruitment depends on the hosts immune response. The purpose of this thesis was to use the intestinal phase of a primary Trichinella spiralis infection in mice to study the accompanying changes in smooth muscle contraction, including their role in host defense and their immunological basis. Naive mice were infected with the nematode parasite T. spiralis . Infection caused a significant increase in intestinal longitudinal muscle contraction in response to carbachol in vitro . Testing several mouse strains, we found that the strains that developed the greatest increases in muscle contraction also expelled the infection the most rapidly. Two phases of increased contraction were identified, the early phase when muscle contraction first increases, and the persistent phase, when the increased muscle tension was sustained until at least day 21 post-infection. We also found that infected mice lacking T cells, and specifically CD4 +ve T cells, exhibited an attenuated increase in both phases of muscle contraction. We also tested the role of the Th2 cytokines, interleukins 4 and 5, which are produced by CD4 +ve T cells during a nematode infection. We found that during infection, IL-5 deficient mice developed a normal early phase of increased muscle contraction, but were significantly impaired in the persistent muscle response. We also examined the role of IL-4, through gene transfer. Following surgery, we infected the intestinal surface with either control adenoviral vectors, or a virus encoding the cytokine IL-4. IL-4 overexpression significantly increased intestinal muscle contraction, while the control virus had no effect. In summary, my studies show that intestinal longitudinal muscle function is subject to immunomodulation, specifically by the actions of CD4 +ve T cells, and through the cytokine mediators IL-4 and 5.

abstract: Doctor of Philosophy (PhD)


title: Effects of Operating Variables of Red Mud Deep Thickening

contributor:
Woods, D. R.
Noteboom, Mr. D.
Chemical Engineering

abstract:
The effects of operating variables of red mud deep thickening have been examined. The independent (operating) variables studied were 1) The dosage of an anionic polymeric flocculant and 2) the solids throughput. The dependent variables were the concentration of underflow solids, underflow withdrawal rate, overflow rate, overflow quality and steady state solids concentration profile.

The major effect of the flocculant dose was an increase in the separation efficiency (a measure of the degree of thickening) for an increase of flocculant dose.

The solids concentration profiles obtained showed that the majority of the thickening of the mud occurred in the bottom fifth of the column. Therefore, for a given thickener and mud type, there exists a certain bed depth above which no substantial gain in separation efficiency is achieved.

When all other variables are the same, the column diameter-to-length ratio and operational temperature had the most significant effect on the separation efficiency.

abstract: Master of Engineering (ME)


title: Studies on the Preconcentration of Mercury in Natural Waters: Electrothermal Atomization of Mercury from a Gold Surface for Measurement by Atomic Absorption Spectroscopy

contributor:
Corsini, A.
Chemistry

subject: Chemistry Chemistry

abstract:
A method has been developed for the direct determination of mercury in aqueous samples using electrothermal atomic absorption spectroscopy (AAS). This method is based on the thermal stabilization of mercury on the surface of a gold-plated graphite tube during the heating cycles of the furnace. The effect of various parameters such as charring and atomization temperatures, acid strength, presence of other metal ions and complexing agents was examined. Based on these investigations, optimal conditions for the determination of mercury at trace levels were established.

The method provided a detection limit of 0.07 ng of Hg and was found to be faster and simpler than other available techniques. In addition, the method is well suited to the determination of mercury in samples that have been preconcentrated for multielement determination.

The mechanism of thermal stabilization on the surface of gold-plated tubes and platforms was studied. Likely reactions are the reduction of mercury(II) from solution and the formation of a mercury-gold amalgam on the surface of the gold layer. Two forms of stabilized mercury were observed; one form at the surface which began to atomize above 300°C and another form dissolved in the gold which began to atomize above 1400°C.

The gold-plated tube AAS technique was used to study the retention and elution behaviour of mercury on a column of the macroporous resin, XAD-7, for the purpose of enrichment (i.e., preconcentration) of mercury from natural waters. The effect on retention of parameters such as pH and the nature of the mercury species was investigated. For the elution of mercury from the column, several parameters were examined, the most important being solvent strength, which governs the magnitude of the preconcentration factor. The system was then applied to the preconcentration, speciation and measurement of mercury in synthetic water samples.

abstract: Doctor of Philosophy (PhD)


title: Collectivity in A approximately equal to 60 nuclei: Superdeformed and smoothly terminating rotational bands

contributor:
Waddington, J.C.
Physics

subject: Physics Physics

abstract: The proton-rich nuclei in the A ? 60 mass region provide an excellent laboratory for studying the interplay between single-particle and collective nuclear excitations. In order to increase the sensitivity of spectroscopic studies of these nuclei, a new method of channel selection based on the measurement of the total energy of all ? rays and charged particles emitted in fusion-evaporation reactions has been developed. This method has been used to identify and study deformed and superdeformed (SD) rotational bands in 62 Zn and the N = Z nucleus 60 Zn. Two sets of strongly coupled rotational bands have been identified in 62 Zn and have been observed up to the terminating states of their respective configurations. Lifetime measurements indicate that the transition quadrupole moments in these bands decrease as termination is approached. These results represent the first observation of the terminating states of rotational bands in the A ? 60 mass region and confirm the predicted loss of collectivity associated with the phenomenon of smooth band termination. The first superdeformed rotational band in the A ? 60 mass region has also been identified in 62 Zn, establishing a new region of superdeformation for nuclei with neutron and proton numbers N , Z [approximate] 30. The doubly-magic superdeformed band in the N = Z nucleus 60 Zn has been identified. This band corresponds to filling the single-particle orbitals up to the large SD shell gaps at N , Z = 30 and is the natural reference core for the study of A ? 60 superdeformation. In addition, the observation of linking transitions connecting this band to normal deformed (ND) states provides the first spin, parity, and excitation energy measurements for A ? 60 SD states. The stretched- E 2 character and relatively large B (E 2) values of these linking transitions indicate that the decay-out mechanism in 60 Zn differs significantly from that observed in heavier nuclei.

abstract: Doctor of Philosophy (PhD)


title: Modelling of Single Component and Bicomponent Extrusion Flows

contributor:
Hrymak, A.N.
Vlachopoulos, J.
Chemical Engineering

abstract:
Flow phenomena associated with die extrusion and coextrusion have a significant impact on the final product shape and layer uniformity. The present work is concerned with the mathematical modelling and numerical simulation of three dimensional single-component and stratified multi-component extrusion. The objective is to provide an understanding of the flow phenomena involved and investigate their impact on the shape and interface configuration of the extruded article.

A three dimensional non-isothermal study of viscous free-surface flows with exponential dependence of viscosity on temperature is presented. The effects of non-isothermal conditions and/or geometry on the extrudate shape are investigated with a fully three dimensional finite element/Galerkin formulation. Special free surface update schemes (pathline, spine and hybrid spine/pathline methods) are presented and enable the study of the extrudate swelling out of very complicated 3-D geometric shapes. Apart from the well known thermally induced extrudate swelling phenomenon, bending and distortion of the extrudate may occur because of temperature differences and/or geometric asymmetries. A temperature difference across the die can be imposed by heating or cooling the die walls, but can also arise because of asymmetric viscous heat generation due to the die geometry. Temperature differences affect velocity profiles because of the temperature dependence of viscosity and lead to extrudate bending and distortion. It is also shown numerically and confirmed experimentally that the die geometry can induce extrudate bending even in the case of isothermal Newtonian flows.

A powerful finite element algorithm for the 3-D numerical simulation of bicomponent stratified free surface flows is described. The presence of multiple free surfaces (interface, external free surfaces) is tackled with advanced free surface update schemes. The pressure and viscous stress discontinuity at the interface occurring because of the viscosity mismatch is handled with both a double node (u-v-w-P₁-P₂-h₁-h₂) formulation and a penalty function (u-v-w-P-h₁-h₂) formulation.

The interface shape development and extrudate swelling behaviour of stratified flows in a sheath- core configuration is examined. The viscosity mismatch has an effect on both the interface and the external free surface shapes. The flowrate ratio, die geometry and layer configuration are also shown to affect the areas of flow of the individual layers and the extrudate swelling behaviour of the bicomponent system.

The experimentally observed tendency of the less viscous layer to encapsulate the more viscous layer in stratified bicomponent flows of a side-by-side configuration is established with the aid of both a fully 3-D analysis and a 1-D optimization analysis, in agreement with experimental evidence. It is shown that the direction and degree of encapsulation depend directly on the viscosity ratio. For shear thinning fluids exhibiting a viscosity crossover point, interface curvature reversal may occur if the shearing level is such that the crossover point is exceeded. The effects of the length of flow and slip at the wall on the degree of encapsulation are investigated. The effect of initial conditions and design of the layer merging part on the interface shape development downstream is also examined and potential sources of instabilities are identified. The extrudate bending and distortion of the bicomponent system because of the viscosity mismatch is also shown.

abstract: Doctor of Philosophy (PhD)


title: Three essays on unemployment and social assistance

contributor:
Dooley, Martin
Jones, Stephen
Magee, Lonnie
Economics / Economic Policy

subject: Economics Economics

abstract: This thesis is comprised of three essays concerning unemployment and social assistance. The first essay examines the impact of health status on the duration of unemployment spells and finds that individuals with impaired health will have significantly longer unemployment spells. These longer unemployment spells will result in the stock of the unemployed being composed of a larger proportion of individuals with impaired health than the stock of the employed. Hence, it may not be appropriate to interpret the difference between the mortality rates of the unemployed and employed as a health consequence of unemployment as some studies have done. The second essay examines the duration of welfare and off-welfare spells for lone mothers in Ontario from 1990 to 1994. We find that there is significant variation in the distribution of the spell lengths. Personal characteristics, such as the number and age of children, and policy parameters, such as welfare benefit levels, have significant impacts on the duration of spells. We also find evidence of negative duration dependence, that is, the probability of leaving the state decreases as the spell lengthens. However, for welfare spells, the evidence for negative duration dependence is weakest in our most preferred specification. The third essay examines the dramatic increase in the welfare participation rate in Ontario from 1983 to 1994. We are interested in what role benefit levels, minimum wage levels, the labour market conditions, and the UI system played in the rise. We focus on four family types; lone mothers, single males, single females, and couples with children. Our results indicate that there is significant difference in how the welfare participation rate of each family type changes in response to the four factors we are interested in exploring. Also, we are unable to explain the dramatic increase using these four factors which indicates that other factors were contributed to the increase.

abstract: Doctor of Philosophy (PhD)


title: An Integrated Macroeconometric and Input-Output Model of Nigeria

contributor:
Spencer, B. G.
Denton, F. T.
Mestelman, S.
Economics / Economic Policy

subject: Economics Economics

abstract: An integrated macroeconometric and input-output model of Nigeria is formulated and tested in this thesis. The linkage between final demand and value added by sector is achieved through a 1973 input-output table of Nigeria. The input-output table is combined with national accounts, budgeting, monetary and balance of payments accounts using annual observations over the period 1960-1983. The residuals in value added equations based on fixed input-output coefficients are modeled with the explicit inclusion of capital stock to capture supply constraints in a developing economy. The complete model is made up of 5 input-output equations, 29 stochastic equations and 38 identities and definitions. The predictive ability of the model is evaluated based on dynamic historical simulation results. According to the tests the model performs reasonably well for most variables. It is intended that the integrated model should help us to understand the structure and important features of the Nigerian economy and be of assistance in the analysis of macroeconomic and sectoral policy initiatives, forecasting and development planning. The integration also facilitates a number of analytical possibilities since the macro-model of final demand is complemented by the inter-sector supply flows and the input-output model by the stochastic macroeconometric relationships. The model is used to evaluate growth prospects for the Nigerian economy up to 2000 and the sensitivity of the growth paths to changes in the world price of oil. These simulation experiments have policy implications for the government. Oil price may increase in the future but such increase will be temporary. In the medium-term it will be prudent for the federal government to establish a stabilization fund that would reduce the impact of the cyclical patterns of foreign exchange earnings from oil exports. Given the uncertainties in the world oil market and Nigeria's vulnerability to what happens, it is essential to promote the non-oil sectors of the economy in the long-term. Questions concerning the ways in which the structure of the economy could be altered, or which sectors of the economy should be emphasised in order to facilitate sustained economic growth could be analysed with the model. Simulation results from the model suggest that agricultural sector promotion strategy would reduce dependence on oil and would constitute a source of long-term economic development. This involves a shift in production and consumption activities toward agriculture. The inter-sectoral allocation of investments is also essential for the growth strategy for Nigeria. A higher priority for investments in agriculture stimulates long-term increases in sectoral output and overall economic growth.

abstract: Doctor of Philosophy (PhD)


title: New dominance orders for scheduling problems

contributor:
Steiner, George
Business Administration

subject: Business Administration, Management, and Operations

abstract: A sequencing problem involves finding a sequence in which to process a set of jobs that minimizes a given cost function. The primary difficulty with such problems is that as the number of jobs increases the number of sequences grows astronomically large, and the problems become intractable. Pairwise job interchange is one of the most commonly used solution techniques for sequencing problems. It compares the cost of sequences that differ only in the interchange of two jobs. In this way the cost function indicates a preference for the ordering of certain pairs of jobs such that if a pair of jobs is not in preference order, then the jobs can be interchanged with no increase in cost. The traditional method of pairwise job interchange assumes that either there are no intermediate jobs (adjacent pairwise interchange ) or that an interchange can be performed no matter what the intermediate jobs are (nonadjacent pairwise interchange ). In this thesis we introduce a generalization that permits the pairwise interchange of a pair of jobs provided that the intermediate jobs belong to a restricted subset of jobs (subset -restricted pairwise interchange ). We use subset-restricted pairwise interchange to derive a dominance order on the jobs. This is a partial ordering of the jobs that consists of pairs whose relative order can be fixed in an optimal sequence. The search space can then be reduced to consist of only those sequences that satisfy the relative job orderings in the dominance order. We apply this technique to certain one- and two-machine sequencing problems, and show that the use of our dominance orders significantly reduces the computation time necessary to solve these problems.

abstract: Doctor of Philosophy (PhD)


title: Infrared properties of high-temperature superconductors with single and triple copper oxygen planes

contributor:
Timusk, T.
Physics

subject: Physics Physics

abstract: This thesis includes work on two high temperature superconducting systems (HTSC), namely, La2-x Sr x CuO4 and HgBa2 Ca2 Cu 3 O8+δ . The CuO2 planes contained within the crystal structure of these materials, as well as in all the other HTSC, hold the key to superconductivity. From one point of view the two systems described in this thesis represent two extremes within a wide variety of HTSC. La2-x Srx CuO 4 is the classic representative of a material with a single CuO 2 plane per unit cell and has one of the lowest critical temperatures. On the other hand, the crystallographic structure of HgBa2 Ca 2 Cu3 O8+δ is based on three CuO2 planes. Despite the fact that both of these systems were discovered quite some time ago relatively little work has been done on them. Infrared spectroscopy has established itself as a very powerful technique for studying the properties of superconductors. One out of the vast majority of excitations that infrared spectroscopy can probe is the excitation responsible for the pairing mechanism in superconductivity. Furthermore, the energy range covered is compatible with the predicted value of the superconducting energy gap. This work is focused on, but not confined to, the infrared study of the normal properties of both La2-x Sr x CuO4 and HgBa2 Ca2 Cu 3 O8+δ . The reflectivity of La2- x Srx CuO4 single crystals has been measured in the frequency range 30-9,000 cm-1 (0.004-1 eV) in directions parallel and perpendicular to the CuO2 planes (ab -plane), whereas HgBa2 Ca 2 Cu3 O8+δ single crystals were studied only in the direction of the ab -plane. Both the doping and the temperature dependence were studied. For the first time, the high-temperature optical spectra were obtained. This allowed us to investigate the charge dynamics of the anomalous normal state up to 400 K. We observe a gap-like depression in the effective scattering rate 1/τ(ω, T ) below a temperature T* in both systems. This characteristic behavior of the frequency and temperature dependent scattering rates suggests the existence of a pseudogap state in both the under- and overdoped regimes of the single-layer HTSC system La2-x Sr x CuO4 for temperatures exceeding 300 K as well as in the underdoped regime of HgBa2 Ca2 Cu3 O 8+δ . The signature of the pseudogap state in the direction perpendicular to the CuO2 planes is also discussed.

abstract: Doctor of Philosophy (PhD)


title: Feasibility of a Cascade Type Hydroelectric Generator System

contributor:
Siddall, J.N.
Latto, B.
Mechanical Engineering

abstract: The feasibility of an alternative concept of a small scale hydroelectricity generation system which is suited to high volume, low head flows was investigated. The device consists of a cascade of hydrofoils which are mounted in an arrangement which resembles a conveyor belt. The investigation included the use of a computer model which simulated the water flow through the cascade. A sensitivity analysis was done using the model to establish the effects of varying the design variables which defined the system. On the basis of the analysis, a prototype was designed with the consideration of the material, configuration, safety and environmental requirements. A cost estimate and economic analysis were made of the prototype and subsequently the concept was evaluated.

abstract: Master of Engineering (ME)


title: Mutational activation of the Neu receptor tyrosine kinase during mammary tumorigenesis in the transgenic mice

contributor:
Muller, W.J.
Biology

subject: Biology Biology

abstract: Overexpression of the Neu/ErbB-2 receptor has been implicated in the genesis of human breast cancer. Indeed, transgenic mice expressing the neu proto-oncogene develop focal tumors arising next to hyperplastic mammary epithelium after a long latency period. Induction of mammary tumors in these mice was associated with activation of the receptor's tyrosine kinase activity. In this thesis, I demonstrate that oncogenic activation of the Neu tyrosine kinase occurs through somatic mutation in a large proportion of MMTV/wild-type neu mammary tumors. These alterations occur within the neu transgene itself and comprise both in-frame deletions and insertions within the receptor's extracellular domain. These mutations promote constitutive dimerization of Neu through the formation of intermolecular disulfide bonds. To directly assess the importance of Neu activation during mammary tumorigenesis, I have expressed two such altered receptors in the mammary epithelium of transgenic mice. Females from several independent lines develop multiple mammary tumors that frequently metastasize to the lung. Interestingly, an alternatively spliced form of erbB - 2 , closely resembling spontaneously activated forms of neu , was detected in human breast cancers. The ErbB-2 receptor encoded by this novel transcript lacks 16 amino acids of the extracellular domain and transforms Rat-1 fibroblasts. These observations raise the possibility that activating mutations in the ErbB-2 receptor may also contribute to human breast cancer progression.

abstract: Doctor of Philosophy (PhD)


title: Modifications to the simple method for buoyancy-driven flows

contributor:
Sheng, G.
Shoukri, M.
Wood, P.
Mechanical Engineering

abstract: Numerical analysis for turbulent buoyancy-driven flows shares many common topics with other computational fluid dynamics (CFD) fields. However, it has several special problems that must be dealt with. The major contribution of this thesis is the development of a new algorithm, SIMPLET, for buoyancy-driven flows. The essence of the SIMPLE method lies in its coupling between the momentum and continuity equations. Almost all the algorithms of the SIMPLE family are based on one precondition, that is, the corrected velocity is obtained from the corrected pressure only. However, in buoyancy-driven flows, there are two major forces driving the fluid movement: the force caused by the temperature gradients and the force caused by the pressure (including kinetic pressure) gradients. In this thesis, the effect of the temperature correction on the velocity correction is considered during the derivation of the pressure linked equation. A modification to the SIMPLE algorithm--SIMPLET--was proposed. The development of the SIMPLET is divided into two stages. The first version of SIMPLET was developed on the basis of the Boussinesq assumption. Since the temperature variation in the flow fields encountered in modern electronic equipment and other industrial facilities is large enough that the Boussinesq assumption is not acceptable, the second version of SIMPLET was developed to remove this restriction so that it can be used for general cases. Because large temperature variations invariably cause turbulence, the flows with appreciable length scales are nearly always turbulent. As a preview of the application of the SIMPLET algorithm to real industrial problems, this thesis investigates several cases of turbulent mixed convection flows in a cavity problem using the RNG turbulence model. The test cases show that the SIMPLET method can speed up the energy equation convergence rate because of its linkage between temperature and velocity. When the convergence rate of the energy equation becomes the determinant in reaching a solution, the advantage of the SIMPLET method will be prominent.

abstract: Doctor of Philosophy (PhD)


title: Transient simulation of non-Newtonian coextrusion flows in complex geometrics

contributor:
Dr, A.N. Hrymak
Vlachopoulos, J.
Chemical Engineering

abstract: Coextrusion is the simultaneous extrusion from a single die of two or more homogeneous melts which form a lamellar structure. Each resin needs its own extruder and a single extruder can supply more than one layer of the same resin. In recent years, coextrusion has gained importance because it is an economical and effective method to obtain plastic products that meet specific market requirements. From the fluid mechanics point of view, one of the main features of the coextrusion process is the presence of internal interfaces (that separate the fluid phases) and contact lines (which are formed when an interface intersects the die wall). Two types of problems exist in the coextrusion process; interfacial flow instability and non-uniform layer thickness distribution. Non-uniform layer distribution refers to the change in thickness of the distribution of the layers across the width of the sheet. Interfacial flow instability appears as an unsteady waviness of the interface between the two polymers. Materials with different theological properties such as apparent viscosity, elasticity and shear stress effects, give rise to irregular interfaces, which lead to high scrap rates and undesired mechanical and optical properties. This work focuses on the problem of interfacial instability. The study examines the main parameters involved in coextrusion operations, i.e., die design, processing conditions and rheological properties of polymer systems, in order to understand both their influence on the interfacial instability and suggest ways to control the instability. By means of a transient solution, the interfacial stability of a given coextrusion flow system can be analyzed in terms of the evolution of the interface in time in response to a external perturbation. Two-dimensional time-dependent finite element solutions of the bi-component flow of Newtonian, generalized Newtonian (Carreau model) and viscoelastic (Criminale-Ericksen-Filbey or CEF) fluids in complex geometries (parallel plates, abrupt and tapered expansions and contractions, and a coat-hanger die geometry), are presented. For the case of Newtonian and generalized Newtonian fluid systems through parallel plates, solutions have been successfully compared against experimental data from the literature and previous results provided by linear stability analysis (LSA). An industrial problem has been studied and the numerical simulation of a two layer homopolymer LDPE 1321(TM) (Dow Chemical Co.) through a tear drop coat-hanger die has been carried out. Finally, CEF flow solutions show that for given elasticity, viscosity and flowrate ratios, the interface between the two fluids has an irregular shape even in the steady state. This anomaly at the interface is qualitatively similar to that observed in experimental results from unstable coextrusion samples.

abstract: Doctor of Philosophy (PhD)


title: Allostratigraphy and River- and Wave-dominated Depositional Systems of the Upper Cretaceous (Cenomanian) Dunvegan Formation, Alberta

contributor:
Walker, R.G.
Geology

subject: Geology Geology

abstract:
This study, of 130 cores and about 500 well logs, shows that the Dunvegan Formation (Cenomanian, Cretaceous Western Interior Seaway, Alberta) can be subdivided into seven allomembers, A through G. Each member represents a regression and contains several offlapping shingled sandstones and associated mudstones deposited in about 150,000 to 300,000 years. Members are separated from each other by bounding discontinuities produced by rapid transgressive flooding events.

Isolith maps of sand body geometries, along with facies associations seen in core, show that individual shingles represent various types of prograding shallow marine to non-marine environments ranging from highly river-dominated deltas in the lower members (G, F, and E) to storm- and wave-dominated prograding deltas, barriers, and transgressive sheet sands in the upper members (D, C, B, and A). Shingles are autocyclic in nature and are related to river avulsion and delta switching while members are allocyclic in nature and are probably related to episodic thrusting events in the rising Cordillera to the northwest.

The Dunvegan Formation was deposited during a time of active tectonism (Columbian Orogen), which caused rapid foreland- type subsidence but which did not allow conglomerate phases to be deposited on the shelf. A global third-order eustatic lowstand of sea-level is also associated with deposition of the Dunvegan.

abstract: Doctor of Philosophy (PhD)


title: Rate constants and mechanisms for reactions of carbenes and cations from oxadiazolines and other precursors

contributor:
Warkentin, John
Chemistry

subject: Chemistry Chemistry

abstract: The doctorate work presented is in the area of physical organic chemistry and has involved the study of reactive intermediates. Various oxadiazolines (A ) have been prepared as photochemical and thermal precursors for the study of dialkoxycarbenes (C ), dialkylcarbenes ( D ), as well as alkanediazonium ions (E ), and carbocations (F ) derived from them.* Intramolecular rearrangement reactions were studied in several dialkylcarbenes, and in the excited states of their precursors using both steady-state and laser flash photolytic techniques. Rate constants for both intra- and intermolecular reactions of dialkylcarbenes were determined. Alkanediazonium ions (E ), the conjugate acids of diazoalkanes (B ), have been implicated in the carcinogenicity and mutagenicity of N-alkyl-N-nitroso compounds. Work described within has involved exploratory photochemistry of oxadiazoline precursors in acidic media. Rate constants of proton transfer reactions to diazoalkanes, generated from oxadiazoline precursors, were determined and the sensitivity of these reactions towards acid strength have been evaluated. Methodology for estimating lifetimes and determining the reactivity of alkanediazonium ions and dialkylcarbenium ions using laser flash photolytic techniques has been developed using novel probe reactions. Conclusions about how these reactive intermediates alkylate DNA (which leads to the development of cancer) have been drawn. Preparation of the oxadiazoline precursor to methoxytriphenylsiloxycarbene (C , R1 = CH3 , R2 = SiPh 3 ) was accomplished. The 1,2-silicon migration from oxygen to carbon as well as the competitive extrusion of CO in methoxytriphenylsiloxycarbene were studied. The reactivity of dimethoxycarbene (C , R1 , R2 = CH3 ) toward polychlorinated olefins was also studied. Products of SN 2 displacement of chlorine as well as additions to carbonyl moieties were discovered, the structures of these products were elucidated using a variety of spectroscopic techniques as well as x-ray crystallography in some cases, and mechanisms for their formation proposed. *Please refer to dissertation for diagram.

abstract: Doctor of Philosophy (PhD)


title: Einstein Metrics on Bundles

contributor:
Wang, McKenzie Y.
Mathematics

subject: Mathematics Mathematics

abstract: Given a principal circle bundle with a nontrivial connection over a compact Kähler manifold, there is a Riemannian metric on the bundle by horizontal lift of the metric from the base. It is shown that, if the curvature form of the connection is of type (1,1) and the bundle is Einstein, then the base is a finite product of Kähler-Einstein manifolds with positive first Chern classes and the Euler class of the bundle must be a linear combination of the first Chern classes of the manifolds in the base. This is the uniqueness of a construction of Einstein metrics given by M.Y. Wang and W. Ziller. It is pointed out that the uniqueness theorem also holds for a class of principal torus bundles and some uniqueness for principal bundles with non-abelian structure groups are given as well. The existence of Einstein metrics is given on some S²-bundles. Given finitely many Kähler-Einstein manifolds with positive first Chern classes, we have principal circle bundles over their product whose Euler classes are linear combinations of their first Chern classes. To every such circle bundle an S²-bundle can be associated. I show that there are at least two families of Einstein metrics on these S²-bundles. For those with positive first Chern classes with respect to a natural complex structure on the total space, I present non-Kählerian Einstein metrics when the Futaki obstruction to the existence of Kähler-Einstein metrics does not vanish. An antipodal identification of every fibre of an S²-bundle will yield an RP² bundle and the other family of Einstein metrics are lifts of those constructed on the associated RP² bundles. Finally, the author suggests new constructions of Einstein metrics on certain principal S¹-bundles which allow the total spaces to be even dimensional.

abstract: Doctor of Philosophy (PhD)


title: Neuronal connectivity in the larval visual system of Drosophila melanogaster: Cellular and molecular analyses

contributor:
Campos, Ana R.
Biology

subject: Biology Biology

abstract: In this study the Drosophila melanogaster larval visual system development was used as a model to identify cellular interactions and uncover molecular mechanisms that govern the formation of precise neuronal pathways during nervous system development. The first part of this study demonstrates that the outgrowth of two serotonergic processes and their contact with the larval optic nerve at the larval visual center are dependent on the proper development of larval optic nerve (LON). The second part of this study reports identification of molecular interactions that may be important for larval visual system development. A tissue-specific autoregulatory activity of a putative transcription factor DISCONNECTED (DISCO) has been shown to be important for proper larval visual system connectivity formation. To understand the molecular mechanisms that govern disco function in the visual system, two new proteins (DIP1 and DIP2; DISCO-interacting proteins 1 and 2) and a previously known protein that interact with DISCO in yeast and in vitro were identified. These proteins also show overlapping mRNA expression patterns with DISCO during embryogenesis. This study has also led to the identification of a putative activation domain in the DISCO protein. Furthermore, the results of this study suggest a possible protein-binding function of the second zinc-finger domain of DISCO. The dip1 gene encodes a protein with two putative dsRNA-binding motifs. An unusual repeated element is present in the 3' untranslated region of dip1 cDNAs. Northern analysis revealed expression of three different size transcripts of the gene during embryogenesis. The genetic location of the dip1 gene is similar to that of a gene called flamenco . The dip2 gene located at the polytene chromosome band 61B, codes for a highly conserved protein with presently unknown function. The amino acid sequence and mRNA expression pattern of the Drosophila DIP2 protein are very similar to its mouse homolog. This study contributes towards understanding the cellular and molecular mechanisms of neuronal connectivity formation.

abstract: Doctor of Philosophy (PhD)


title: Small angle scattering studies of phospholipids in excess water

contributor:
Gaulin, B. D.
Physics

subject: Physics Physics

abstract: Model membrane systems composed of homogeneous suspensions of phospholipids in an aqueous environment have been of great interest for their biological relevance and for their intriguing physical properties. When placed in excess water, phospholipids will spontaneously self-assembly into multilamellar vesicles consisting of repeating bilayer-water layer units which are ideally suited for examination via scattering techniques. Small angle scattering techniques have played an integral role in the study of the morphology and phase behaviour of model membrane systems. This thesis focuses on small angle neutron scattering (SANS) work on two different model membrane systems, dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoylphosphatidylethanolomine (POPE). Three main results, which contribute new information or ideas, are presented. SANS and X-ray diffraction studies of DPPC and DPPC in which the quaternary ammonium hydrogens have been replaced with deuterium (DPPC-d 9 ) have been performed as a function of temperature in a range from 20°C to 50°C. DPPC will display three distinct phases in this range: a low temperature gel (Lβ' ) phase, an intermediate ripple (Pβ' ) phase, and a high temperature liquid crystalline (Lα ) phase. The Pβ' phase, which spans an eight degree range from 35°C to 42°C, is known to exhibit non-equilibrium behaviour. On cooling from the Lα phase, the Pβ' phase formed is metastable but long lived. We present complementary SANS and X-ray diffraction work which shows a complex multipeak pattern for the metastable Pβ' phase. A simple, single wavelength model is proposed that explains our data and also previously published synchrotron X-ray data which was interpreted in terms of a more complex model of competing rippled domains. We also show that the metastability persists into the Lβ' phase. High resolution SANS work on large unilamellar vesicles (LUVs) of DPPC shows that we are able to extract such parameters as vesicle radius and bilayer thickness from the small angle scattering profile. We present, for the first time, diffraction evidence for the development of a ripple modulation of the bilayer surface in LUVs. Calorimetric work done in conjunction with the SANS offers supporting evidence for this claim. An examination of the high resolution SANS profiles of multilamellar samples of POPE, DPPC, and DPPC-d9 is presented which shows that the interfacial properties of model membrane systems can be inferred from scattering techniques. Results show that POPE, which has a relatively small headgroup, displays a smooth water-lipid interface, which can be described using Porod's law of surface scattering, in both its gel and liquid crystalline phases. DPPC and DPPC-d9 , on the other hand, are consistent in showing that the interface between the phosphatidylcholine (PC) headgroups and the water in the Lβ ' and Pβ' phases is rough and disordered. On raising the temperature into the Lα phase of DPPC, this interface becomes smooth.

abstract: Doctor of Philosophy (PhD)


title: Assessment of hybridization between Typha spp. in North America

contributor:
White, Bradley N.
Biology

subject: Biology Biology

abstract: Typha species form a large portion of the biomass in North American marshes. Hybridization between the introduced species T. angustifolia and the native species T. latifolia has resulted in the formation of T. glauca . Studies examining the hybrid nature of T. glauca have reached different conclusions: T. glauca has been described as a separate hybrid species, a hybrid swarm, and an F1 hybrid. To discern between these hypotheses, 17 T. angustifolia -specific and 13 T. latifolia -specific markers were identified using Random Amplified Polymorphic DNA (RAPD). Specimens collected from Manitoba, Ontario, New York, Quebec and Massachusetts were examined. Each of the specimens identified as a hybrid contained all of the species-specific markers indicating an F1 hybrid status. T. angustifolia 's role as the maternal parent was supported with a species-specific chloroplast marker. Reports in the literature suggest that T. glauca may be more prevalent than the parental species at disturbed sites. To verify these reports, the species composition of a highly degraded Great Lakes marsh was examined. Since morphological variation limits accurate identification, specimens were identified using RAPD markers. Approximately 63% of the specimens were identified as T. glauca ; the hybrid dominated 4 of the 7 sites examined. Thus, changes in species composition need to be considered prior to forming revegetation plans. Since molecular analysis may not always be feasible, morphological characters were examined for genetically-identified specimens. Discriminant analysis of leaf width, spike length, spike interval and stigma width provided quantitative identification of the three taxa, although identification was more accurate for T. latifolia (95%) and T. angustifolia (93%) than for T. glauca (83%). These characters can be used to examine the ecological role of T. glauca ; however, molecular markers are still necessary for the identification of seedlings, rootstocks, and plants without flowering spikes, as well as for the classification of hybrids.

abstract: Doctor of Philosophy (PhD)


title: Cellular origin and regulation of the electrical slow wave in the murine small intestinal musculature

contributor:
Huizinga, Jan D.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract: The electrical pacemaker slow wave is responsible for the generation of anally propagating phasic contractions underlying the peristaltic motor activity of the gastrointestinal musculature. Yet, the cellular origins of the slow wave and mechanisms of the slow wave regulation or generation still remain unresolved and constituted primary goals of the current thesis. As described in detail in Chapters Three-Six, spontaneously genetic knock out mice with genetic mutations affecting the structure (W / Wν mice), expression (Wbd / Wbd mice), or the ligand (Sl / Sld mice) of the kit tyrosine kinase receptor were shown to lack both the network of interstitial cells of Cajal associated with the myenteric plexus and the slow wave activity in the small intestine, hence, supporting the proposed role of the interstitial cells of Cajal as pacemaker cells responsible for the slow wave generation. In the absence of the slow wave, the mutant musculature was either electrically quiescent or showed action potentials in regular or irregular patterns as recorded with a standard microelectode technique. The observed action potentials were also clearly distinguished from the slow waves by their shape and pharmacological sensitivities to L-type Ca2+ channel and K+ channel blockade. The mechanisms of the slow wave generation and regulation are addressed in Chapters Seven-Nine. The data indicate that the slow wave generation involves primarily Na+ and Ca2+ conductances not mediated by TTX- or mexiletine-sensitive Na+ channels, gadolinium sensitive nonselective cation channels, or L-type Ca2+ channels. Cl- channels may be also involved in the regulation but not in the slow wave initiation. Pharmacological agents acting on cytosolic Ca2+ , SR Ca2+ ATPase, and intracellular Ca 2+ release mechanisms support the role of intracellular Ca 2+ release mechanisms, sensitive to IP3 , in the regulation of the slow wave frequency and amplitude. Furthermore, activation of the Ca 2+ induced Ca2+ release (CICR) mechanism leads to depolarization not mediated predominantly by chloride channels nor likely by KCa channels. The CICR may be also involved in the regulation of the slow wave. These experiments importantly identify intracellular metabolic pathways that may potentially lead to the development of therapeutic approaches aimed at treating certain gastrointestinal motor disorders by modifying the slow wave frequency or amplitude.

abstract: Doctor of Philosophy (PhD)


title: Bayesian and empirical Bayesian analysis for the truncation parameter distribution families

contributor:
Balakrishnan, Narayanaswamy
Mathematics

subject: Mathematics Mathematics

abstract: Modern Bayesian analysis and empirical Bayesian analysis are dominated by the exponential distribution family; lots of research works have been done in the literature. However, for nonexponential distribution families, there are still no systematic results from Bayesian and empirical Bayesian analysis. In this Ph.D. thesis, some systematic Bayesian and empirical Bayesian analysis results are obtained for the one-parameter truncation distribution families which are nonexponential distribution families. It consists of six main chapters. In Chapter 2, the general forms of conjugate prior distributions are obtained for the two different types of truncation parameter distributions and the particular conjugate priors for the truncated exponential, Pareto and power function distributions are presented. In Chapter 3, the explicit relations between the mixing distributions and the mixture distributions are obtained and the identifiability for the mixture of these trunction parameter distributions is established. Based on these obtained relations, some procedures for estimating the mixing distributions are proposed and studied. In Chapter 4, the explicit analytical expressions of posterior moments for the two general truncation parameter likelihood functions with arbitrary priors are given by using the sufficient statistics for these truncation parameters. In particular, the explicit forms for the posterior mean and variance are presented. In Chapter 5, based on the relations between the Bayes estimators under squared error loss and the marginal distributions, the empirical Bayes estimators are proposed and the asymptotic optimalities of the proposed empirical Bayes estimators are investigated. Finally, in Chapter 6, the problems of empirical Bayes estimation for the truncated exponential distributions and the empirical Bayes rule for selecting the best of exponential populations are discussed and the convergence rates of the proposed empirical Bayes estimators and the empirical Bayes selection rule are established. And in Chapter 7, a location parameter family of gamma distribution, which is not a typical truncation parameter distribution, is considered. The empirical Bayes estimator and the empirical Bayes testing rule for the two-action problem are studied and the convergence rates for the proposed empirical Bayes estimator and the empirical Bayes testing rule are established.

abstract: Doctor of Philosophy (PhD)


title: Application of Dual Cycloconverters to a Double Fed Motor for Traction Drives

contributor:
Szabados, Barna
Electrical Engineering

abstract:
Variable speed AC drives have become the new standard for high performance drive systems. Very high power traction drives present a particular challenge for AC drive technology because of the simultaneous need for high-torque vibration-free operation at standstill, traction-limited dynamic braking, and high speed operation.

In this work, two independently controlled cycloconverters are used with a wound rotor machine to provide a double fed drive system that overcomes the frequency limitations of the cycloconverters and provides a stable high power drive, with potential for rapid torque response and power factor control.

A new 'Jitter' control method is derived for the firing angle control of the cycloconverter. This method effectively spreads the cycloconverter output harmonics over a broader spectrum and thus minimizes the filtering requirements.

The double fed motor (DFM) equations are applied to the DFM circle diagram and a simulation program has been written to plot the circle diagram and give a geometric interpretation of the developed torque. A new algorithm is proposed using δν, the pseudo torque angle, to give direct control of the torque using only position feed-back. A novel frequency hopping algorithm is also derived that allows the cycloconverters to be operated at high frequencies without generating harmonic torques.

A dual cycloconverter drive was built to verify the stability and torque-speed performance of such a system. Reliable operation was achieved by using bank switching sensors based on detecting the reverse bias across a series connected diode, and by short circuit detection circuits with automatic reset facilities. The control software displays system status information on the screen, with on-line parameter modification, and provides a complete range of manual and automatic modes of operation to facilitate system development and testing.

abstract: Doctor of Philosophy (PhD)


title: External and Internal Oxidation Properties of Ternary Fe-Si-Al, Ni-Cr-Al and Ni-Si-Al Alloys

contributor:
Smeltzer, W.W.
Materials Science

subject:
Engineering
Materials Science and Engineering
Engineering

abstract:
The oxidation properties of binary and ternary Fe-Si-Al alloys containing 0-6 at% Si and 0-6 at% Al were investigated at 1073 K in 0.04-0.07 torr and 760 torr of oxygen. In combination with Si, the Al concentration required to form a protective Al₂O₃ scale on the ternary alloys is significantly lower than that for binary Fe-Al alloys. Theoretical and experimental results are consistent with the hypothesis that there is a synergistic effect due to the combined presence of Si and Al, resulting in improved oxidation resistance of the ternary Fe-Si-Al alloys. Si appears to limit the oxidation of Fe during the transient stage of oxidation and increase the activity and outward diffusion flux of Al to re oxide/alloy interface through ternary interactions during the subsequent stage of parabolic oxidation kinetics.

A criterion has been established for the onset of internal oxidation beneath the external scale when oxidizing conditions favor formation of the oxide of the least noble metal in a dilute ternary alloy. This criterion was applied to the oxidation of ternary Fe-Si-Al and Ni-Cr-Al alloys. Theoretical predictions of minimum Al concentrations required to form a protective Al₂O₃ scale on these two alloys are consistent with the experimental observations.

Attempts were made to give expressions describing the kinetics of internal oxidation of dilute ternary alloys during simultaneous internal oxidation of the two solutes. Good agreement was obtained between theoretically predicted and experimentally observed values of the depths of internal oxidation zones in Ni-1at%Si-4at%Al alloys at 1073 K in Ni/NiO packs or in 760 torr of oxygen.

abstract: Doctor of Philosophy (PhD)