title: Electric Quadrupole Radiation Strength in Neutron Capture

contributor:
Prestwich, W.V.
Physics

subject: Physics Physics

abstract:
A high resolution NaI(Tl) -Ge pair spectrometer has been used to detect the primary E2 transitions following thermal neutron capture in ¹⁴³Nd, ¹⁶²Dy, ¹⁶⁴Dy, ¹⁶⁵Ho, ¹⁶⁷Er, ¹⁷³Yb and ¹⁷⁹Hf. These data, as well as other thermal, resonance and average-resonance data have been analyzed to study the radiative quadrupole strength. Some calculations have been done to retrieve the E2 intensities from the average-resonance work. A quantitative theoretical expression for the quadrupole strength function on the basis of the giant quadrupole resonance model is deduced. A comparison between the experimental and theoretical values for nuclei spanning the mass region between A=12 to A=239 shows the presence of the influence of the GQR on the radiation strength. A depression in the quadrupole strength has been observed in the mass range 144

The energy and intensity of all the observed high energy transitions in most of the nuclei under study are presented. A set of neutron separation energies of 15 isotopes of Nd, Gd, Dy, Ho, Er, Yb and Hf has been estimated. The thermal radiative capture cross section of ¹⁴N, a standard used in this work, is determined with improved precision.

abstract: Doctor of Philosophy (PhD)


title: A Task Analysis of Lexical Decisions

contributor:
Jacoby, L.L.
Psychology

subject: Psychology Psychology

abstract:
A task analysis of the Lexical Decision Task (LDT) was performed. Several alternative explanations are explored, and experiments designed to investigate these models are reported. These experiments provide strong evidence for the use of multiple decision strategies in the LDT. Subjects responded to both visual and semantic attributes of targets.

Lexical decisions to repeated nonwords resulted in both increased errors and decision latencies. Apparently, the familiarity of specific visual graphemes serves as one basis for performance in the LDT. A basis that is independent of an item's true lexical status. Also, lexical decisions were biased by typography. This was interpreted as confirming the visual basis of information in the LDT.

Meaning in lexical decisions was studied by varying both the type of word referent (concrete or abstract), and the availability of meaning from a prior presentation. While meaning contributed to lexical decisions, its use depended upon both a stimuli's visual familarity and the nature of the task demands.

It was concluded that the LDT does not measure a single process or memory structure (i.e., Lexical Memory), rather it reflects knowledge about the visual familiarity and the semantic uses of graphemes.

An additional topic was the nature of the psychological mechanisms supporting recognition. Several general models of retrieval are contrasted. It is found that criterion bias models describe both the accuracy and latency of lexical decisions better than models which assume an ordered search of memory.

An extension of the Random Walk decision process is presented. Within this model biases in decision often reflect differences in what is actually known about stimuli relative to a single criterion, rather than multiple and separate decision biases located at separate decision loci. The benefits of this analysis in explaining the effects of word frequency, stimulus repetition and typographic information in lexical decisions are discussed.

abstract: Doctor of Philosophy (PhD)


title: Spallation-Fission Symbiosis

contributor:
Harms, A. A.
Nuclear Engineering

subject:
Nuclear Engineering
Nuclear Engineering

abstract:
The search for an enhancement of nuclear energy suggests that breeding of fissile fuel from fertile materials as well as the rejuvenation of spent nuclear fuel is of major importance. With the development of linear accelerator breeders it is possible, in principle, to enrich depleted nuclear fuel and to reenrich spent thermal reactor fuel for continued burnup without reprocessing. The management of separated fissile isotope is thus largely avoided.

The symbiotic nuclear reactor system analyzed here consists of a linear accelerator breeder and a conventional nuclear converter reactor capable of burning natural uranium fuel. With repeated breed-burn cycles the system nuclear fuel can be brought to fuel burnups of up to and exceeding 27 times the conventional system once-through fuel burnup.

The analysis undertaken here shows considerable potential for uranium based fuel cycles relative to that for thorium fuel cycles for the case of low fuel burnup rejuvenation without reprocessing. Consequently uranium-plutonium fuel cycles are analyzed for schemes with periodic chemical fuel reprocessing as well as without reprocessing.

This analysis involves the development of a detailed symbiotic system dynamic mass-energy conservation formulation, yielding results ranging from detailed system isotopic concentration histories to general system fuel mass flow and energy flow. A comparison is made between the major parameters of the symbiotic reactor system and its equivalent conventional system.

Optimum symbiotic system characteristics are generally obtained for net accumulated fuel burnups below 9 times the conventional once-through fuel burnup. For the presently estimated fuel to capital-operational cost fraction a marginally favorable symbiotic system is only obtained with an energy self-sufficient breeder subsystem. For increased fuel cost fractions, however, the symbiotic system shows, highly improved system characteristics even for net power consuming breeder subsystems.

abstract: Doctor of Philosophy (PhD)


title: Chemical and Physiological Investigations on Heavy Metal - Phytoplankton Interactions

contributor:
Harris, G. P.
Biology

subject: Biology Biology

abstract:
Binding of zinc-65 to the surface of Chlamydomonas was reduced by 60-80% under suboptimal physiological conditions of light, temperature, and pH. Zinc bound to the surface was composed of a labile fraction and a non-exchangeable fraction. The non-exchangeable fraction corresponded to the quantity bound under suboptimal conditions. Maximum surface binding capacities for zinc in 7 species of phytoplankton were compared and support metal ion exclusion as a potential tolerance mechanism. Factorial experiments were conducted to assess the effects of Cu, Sr, Ni, Cd, Mn, Ca, Mg, and Co (singly and in all combinations) on zinc uptake, fluorescence, and photosynthesis in 5 species of phytoplankton. The results provide valuable insights into the nature of interaction between metals and the observed response (antagonistic, synergistic, or independent).

The effects of metals on the growth of Chlamydomonas were as follows; Hg>Cu>Cd>Ni=Zn>Co>Cr>Fe=Be=Sr. Growth of laboratory strains and field isolates exposed to metals could be classified either by an extended lag phase or a gradual reduction in cell numbers over time. The nature of the response was related to changes in the available metal concentration over time, kinetics of binding and uptake, and the mode of toxic action (surface or internal sites).

Field studies were conducted on the fates of Ni, Cd, Cu, Pb, Zn, Co, and Sr added to closed, 8000 L limnocorals located in Hamilton Harbour, Hamilton, Ontario. Sedimentation was the principal mechanism regulating the availability of heavy metals in situ with rates dependent upon; 1. the reactivity of individual metals (affinity for particulates), 2. biological factors (contributions to particulate phase) and 3. physical stability and chemical composition of the water column.

Important kinetic interactions between variables and processes regulating the binding of metal to the cell surface, uptake, and the observed toxic response were incorporated into a dynamic model to simulate the effects of metal stress on phytoplankton growth and metal uptake.

abstract: Doctor of Philosophy (PhD)


title: The Magnetic Properties of the Systems La͓Y₁₋͓TiO₃, La͓Gd₁₋͓TiO₃, LaTiO₃ and CeTiO₃

contributor:
Greedan, J.E.
Chemistry

subject: Chemistry Chemistry

abstract:
The magnetic structures of LaTiO₃ and CeTiO₃ were determined by neutron diffraction. LaTiO₃ is a G-type antiferromagnet. The Ti³⁺ sublattice in CeTiO₃ displays G-type and possibly F-type ordering. The Ce³⁺ sublattice exhibits F-type and C-type components.

Solid solutions of the form La͓Y₁₋͓TiO₃ and La͓Gd₁₋͓TiO₃ were prepared. Magnetic measurements suggest a weakening of the antiferromagnetic Ti-O-Ti exchange as the Ti-O-Ti bond angle decreases from 157°(LaTiO₃). For sufficiently small bond angle, the Ti-Ti exchange becomes ferromagnetic. Crystal field calculations based on a localized Ti³⁺ 3d¹ electron have reproduced the general features of susceptibility data reported for La͓Y₁₋͓TiO₃ (x=0,.1,.2,.4,.7). This is in agreement with resistivity measurements undertaken on La.₁.₉TiO₃ and La.₂Y.₈TiO₃ which are characteristic of an activated transport mechanism.

abstract: Doctor of Philosophy (PhD)


title: Diode Laser Dynamics

contributor:
Garside, B.K.
Electrical Engineering

subject:
Electrical and Electronics
Electrical and Electronics

abstract:
The work described in this thesis concerns the investigation of diode laser dynamics on the time scale of 100 picoseconds or less. Predictive models based upon the diode laser rate equations are developed. A requirement of such predictive models is that the necessary parameter values be determined by methods independent of the comparison between model predictions and experimental verification. For this reason, a great deal of effort has been directed towards the careful utilization of existing techniques for parameter determination and the development of new techniques where existing techniques were lacking or inadequate.

Two dynamical operating regimes are investigated. The first deals with single current pulse pumping of the laser. A time domain model (JLASER), allowing explicitly for wavelength dependence of system parameters and dynamics, was developed and is shown to generate good agreement with experimental measurements of the relaxation oscillation response to the current pulse excitation. The spontaneous emission and the multi-mode nature of the laser are shown to be of particular importance in determining the diode laser pulsed response.

The other operating regime investigated is active modelocking of the diode laser in an external cavity. This mode of operation allows extremely short pulses to be obtained, with a much milder current modulation requirement and therefore better spectral control, than in the case of single current pulse pumping. A frequency domain model, incorporating the effects of chip facet reflectivity and gain saturation, is developed. Good agreement is found between this model and experimental measurements of the modelocked pulse characteristics. The detailed characterization carried out on the external cavity coupling efficiency is shown to be critical for accurate model predictions.

abstract: Doctor of Philosophy (PhD)


title: The Mechanisms of Cellular Sensitivity to Photofrin-mediatd photodynamic therapy.

contributor:
Rainbow, A. J.
Singh, G.
Biology

subject: Biology Biology

abstract: Photodynamic therapy (PDT) is a cancer treatment in which a photosensitizing drug is retained by tumor cells and activated by visible light to create toxic photoproducts including singlet oxygen and other free radicals. Photofrinmediated PDT is being applied in many clinics throughout the world. Although PDT is a promising treatment for many types of tumors, the response of cells to PDT varies between different cell types. The mechanisms of cell response to PDT are not fully understood. Therefore, an improved understanding of mechanisms of cell response to PDT may lead to novel strategies for increasing the cellular response to PDT, which has the potential to improve significantly the cure rate of cancers. Although there is evidence that the p53 tumor suppressor plays a role in tumor response to the chemotherapy and radiation therapy, its role in the response of human cells to PDT is less clear. In the present study, Li-Fraumeni syndrome (LFS) skin fibroblast cells that express only mutant p53 and normal human skin fibroblasts (NHF) strains expressing wild-type p53 were used to elucidate the role of p53 in the cell response to Photofrin-mediated PDT. NHF cells were found to have a higher sensitivity to Photofrin-mediated PDT compared to LFS cells. Reintroduction of wild-type p53 reduced the viability of LFS cells following PDT. These data suggest a role for p53 in the response of human cells to PDT. Although the treatment of PDT resulted in an increased level of p53 proteins in NHF cells, no apoptosis or any alteration in the cell cycle was found. Whereas LFS cells displayed a prolonged accumulation of cells in G2/M phase and the cells underwent apoptosis. Thus, the loss of p53 may result in a prolonged G2/M arrest that contributes to the photoresistance of LFS cells. In order to see the possible role of p53 in the cellular response to Nile Blue A (NBA), a secondary photosensitizer-mediated PDT, the clonogenic survival assay was used to compare the viability of LFS cells to NHF cells following NBA-mediated PDT. We found an extreme sensitivity of NHF cells compared to LFS and several tumour cells for treatment with NBA alone. In addition, Nile Blue A was found to be unable to produce a significant photo-cytotoxic effect on human cells using NBA concentrations which have relatively low toxicity for normal human fibroblasts. Since the LFS cells and the human tumour cells examined have some alteration in the expression of p53, these data suggest that p53 contributes to the high sensitivity of NHF cells to Nile Blue A. PDT eradicates tumor cells through the intracellular generation of reactive oxygen species (ROS). ROS is able to trigger several cellular events including cell apoptosis and several signaling pathways. It has been suggested that mitogen-activated protein kinases (MAPKs) playa crucial role in controlling cell proliferation, differentiation and cell survival. However, the activation of MAPKs by Photofrinmediated PDT and its role in the cell response to PDT are lacking. We report here that Photofrin-mediated PDT rapidly activated MAPKs including extracellular signal-regulated kinase 1 and 2(ERK1/2), c-jun NH2-terminal kinase 1(JNK1) and p38 MAPK in both LFS and NHF cells. The more PDT resistant LFS cells exhibited a sustained activation of MAPKs while the activation of MAPKS in the PDT sensitive NHF cells was transient. Blocking of the sustained activation of ERK1/2 pathway in LFS cells led to a reduction in cell viability following PDT. In contrast, blocking of prolonged p38 activation in LFS cells has no effect on the cell sensitivity to PDT. These data suggest that sustained ERK1/2 activation protects cells from cell killing by Photofrin-mediated PDT. However, the p38 pathway alone does not playa major role in the sensitivity of LFS cells to Photofrin-mediated PDT. The role of JNK1 activation remains to be clarified. Several studies have suggested the importance of raf-1 in the regulation of ERK1/2 activity, as well as the importance of MAPK phosphatase 1 (MKP-1) in the negative regulation of ERK1/2 activity. In the present study, it was found that Photofrin-mediated PDT increased expression of MKP-1 at both mRNA and protein levels. The levels of MKP-1 were inversely correlated with the kinetics of ERK1/2 activity following PDT. In addition, PDT resulted in a rapid reduction of the raf-1 expression. These data demonstrated a role of MKP-1 in the regulation of PDT-induced ERK1/2 activation, and suggested that PDT-induced ERK1/2 activity was raf-1 independent.

abstract: Doctor of Philosophy (PhD)


title: Cellular Responses to the Anti-Cancer Drug, Cisplatin.

contributor:
Rainbow, A. J.
Biology

subject: Biology Biology

abstract: cis-Diamminedichloroplatinum (cisplatin) and other platinum-based drugs, represent the best hope for cancer patients with ovarian tumours and many other types of solid tumours. Sadly, the clinical efficacy of cisplatin is often limited by the emergence of drug-resistant tumours. The research presented here is intended to expand understanding of the molecular characteristics that make cells resistant to cisplatin. Cisplatin kills cells by damaging the genome and inducing cell suicide (apoptosis). Despite having been used for more than twenty years, the cellular responses responsible for this drug's cytotoxic effect remain fundamentally unknown. When cisplatin reacts with DNA, a spectrum of addition products (adducts) are formed. Most of these adducts can be repaired by nucleotide excision repair (NER) and cells with defects in NER are extremely sensitive to the drug. In this thesis, we show that human and Chinese hamster ovary (CRO) cells with defects in NER are reduced in their capacity to repair cisplatin-damaged adenovirus (Ad) DNA. Excision repair cross complementing gene-1 (ERCC 1) is required for NER and many researchers have proposed that clinical cisplatin-resistance results from enhanced ERCC1 expression. To study the role of this gene in cisplatin resistance and DNA repair, we have constructed Ad viruses that express ERCC 1. Cells infected with these viruses express very high levels of the protein. We report here that these very high expression levels actually impede DNA repair and make some human tumour cells cisplatin-sensitive. The response to DNA damaging agents like cisplatin is dynamic. Upon exposure to cisplatin, many mechanisms that affect cell survival are induced. We show here that some human tumour cells are much more sensitive to low doses of cisplatin (per unit of dose) than they are to higher doses. This hypersensitivity suggests that, at some critical dose of the drug, a mechanism that protects cells from death is triggered. Treating cells with other DNA damaging agents (including ultraviolet light (UV) and ionising radiation) before cisplatin exposure can induce this resistance. We have also induced resistance to low doses of cisplatin by infecting cells with UV -irradiated Ad suggesting that it is the DNA damage per se that triggers the mechanism of cisplatin resistance. The Jun N-terminal kinase (JNK) is a family of mitogen-activated protein kinases (MAPKs) that responds to a broad range of cellular stresses. While the contribution of JNK activity to determining cell fate is complex, it is generally considered a proapoptotic factor. Several research groups have proposed that JNK activity is important in cisplatin-induced cell death. By studying cisplatin-induced JNK activity in human xeroderma pigmentosum (XP) and Cockayne syndrome (CS) cells with well known DNA repair defects, we have shown that it is the persistence of cisplatin-DNA lesions that is associated with prolonged JNK activation. This is the first direct evidence that it is DNA lesions that promote JNK activity in cisplatin- reated cells. Further, we have used human cells with defective transcription-coupled repair (TCR) to show that damage in actively transcribing genes causes persistent JNK activity while persistent DNA damage in untranscribed regions does not. Our results support a role of JNK activation in cisplatin-induced cell death by showing that cells with defects in TCR are extremely sensitive to cisplatin while cells with defects in global genome repair are not.

abstract: Doctor of Philosophy (PhD)


title: Creep and Fracture Simulation of Ice using the Finite Element Method

contributor:
Mirza, Farooque A.
Civil Engineering

subject:
Civil Engineering
Civil Engineering

abstract:
A review of fracture mechanics, fracture toughness and creep behavior of ice is presented. An expression for evaluating the energy releases rate (J-integral) for fracture of ice under creep is developed and incorporated in the finite element program for implicit, incremental, non-linear creep analysis.

It is assumed that the energy release rate due to fracture of ice at any creep stage is dependent on the recoverable strain energy and not affected by the non-recoverable work done during creep. A zone classification of the finite element mesh around the crack tip and the equivalent elastic displacements for the stress state at a given creep stage are used to compute the fracture toughness of ice. This is then compared with the prescibeed values of K(ic) (the crack initiation fracture toughness) or K(ia) (the crack arrest fracture toughness) for either the crack initiation or crack propogation, respectively.

Two examples are analyzed using the method mentioned above.

(i) A rectangular plate with symmetric edge cracks, under plane strain and subjected to uniform tension.

(ii) A double slope ice mass with uniform thickness, and an initial crack at the knee, subjected to gravity load.

It is assumed that the crack path is predetermined and the crack opening is of mode type I. In both examples the displacements, redistribution of stress around the crack tip and the stress intensity factors are computed at various creep stages. For the double slope example, K(i) is compared with K(ic) or K(ia) and the knee crack is propagated through a finite extension accordingly. Finally, the effect of varying the two slope angles on the stress intensity factor and crack propagation for the double slope example is investigated and was found to be sensitive to the difference between the two slope angles.

abstract: Master of Engineering (ME)


title: Cytology, Taxonomy and Ecology of Species in the Genus Hellichiella (Diptera: Simuliidae)

contributor:
Davies, D.M.
Biology

subject: Biology Biology

abstract:
The relationship among simuliid species in the genus Hellichiella from Europe and North America was studied on the basis of their salivary gland chromosomes, morphology and ecology. The banding pattern of polytene chromosomes of eight species was examined and compared with that of H. congareenarum defined by Dunbar (1967) as the standard. Species studied for the first time are H. rendalense (from Norway), H. latipes (subexcisum syn. from Britain) and H. saccai (from Italy) and the undescribed "Opinaga" (from Quebec) and "near dogieli" (from Norway). H. congareenarum, H. anatinum and H. innocens were restudied. These species were found to differ from the standard by a minimum of one and maximum of three fixed inversions. It is concluded that the sibling distinction between congareenarum and congareenarum 'b' proposed by Dunbar (1967) is not valid and that H. anatinum differs from standard by only one inversion.

The genus Hellichiella Riv.&Card. is redefined and distinguished from Eusimulium annulum group sensu stricto. Described for the first time are the larva, pupa and male of both H. rendalense and H. near dogieli and the pupa of H. fallisi. The close relationship of these species is confirmed both chromosomally and morphologically.

The immature stages of H. rendalense s.l. were discovered in shallow seepages with water current 1-30 cm/sec and temperature 10°-16°C in sloping sedge-Sphagnum bogs. This habitat is the source of larvae of these simuliids and the origin of first order streams which are secondarily colonized by these and other bog species. The occurrence of related species in similar habitats in the Nearctic and Palaearctic regions establishes that sloping Sphagnum bogs, primarily in the Boreal region, are the main source of Hellichiella species. Thus species of this taxon, some of which are known vectors of Leucocytozoon, are linked ecologically with Anopheline mosquitoes and Ceratopogonid flies. The theory is proposed that the breeding habitat of these vectors of haematozoa is the unifying factor in the epizootiology of Haemosporidia.

abstract: Doctor of Philosophy (PhD)


title: Vestibulo-ocular interactions with body tilt: Gender differences and afferent-efferent interplay.

contributor:
Elliott, Digby
Kinesiology

subject: Kinesiology Kinesiology

abstract: This dissertation investigated the importance of information from various sensory receptors on the perception of self-orientation. In five experiments, we systematically manipulated the relative orientation between the gravitational inertial forces and the body. The first experiment was originally designed to evaluate the effect of body inversion on the perception of straight-ahead. Interestingly, when participants were inverted, females presented a greater footward bias in the perception of straight-ahead than males. Two follow-up experiments revealed that whole-body rotation and altered blood-distribution could not explain the gender differences in the perception of straightahead. As a result, we attributed the gender differences in the perception of self-orientation to differences in the use of afferent information from stable gravireceptors (i.e., otoliths). A fourth experiment examined the contribution of perceptual strategy to the perception of self-orientation. Once again, females exhibited a greater footward bias than males in the perception of straight-ahead. However, this bias was reduced slightly when female participants were instructed to focus on cues arising from inside the body. This finding indicates that, at least to some extent, strategy mediates gender differences in perceptual decision- making. The final experiment was designed to examine the importance of limb movement on the perception of spatial orientation. Five response modes were used to gradually increase the motor demands associated with perceptual judgments about self-orientation. This study was designed to test a theory of visual information processirig (i.e., Milner & Goodale, 1995), which claims that the use of distinct visual processing modules depend on the motor demands of a visual perception task. Interestingly, we found that whole limb movements affect the perception of an egocentric illusion (Le., oculogravic illusion; see Graybiel, 1952).

abstract: Doctor of Philosophy (PhD)


title: Two Struggles Into One? Labour and Environmental Movement Relations and the Challenge to Capitalist Forestry in British Columbia, 1900-2000

contributor:
Storey, Robert
Sociology

subject: Sociology Sociology

abstract: This dissertation places contemporary struggles over logging in old-growth coastal forests within a historical analysis of the development of capitalist forestry in British Columbia. In part A we argue that the history of capitalist forestry has been profoundly marked by labour and environmental movements. It is argued that these movements have resisted the exploitation of capital, engendered both political and economic crisis, and (generally) pushed capital and the state into more social forms of production. Speaking to silences in academic and popular accounts, the work of these social movements is centred and it is argued that their relation offers a key to understanding the remaking of capitalist forestry. Particular attention is given to moments of inter-movement cooperation, the environmental politics of forestry unions and the ideological projects of capital and the state. Part B is a case study of capitalist forestry and forest worker/environmental movement relations in Squamish, British Columbia. Drawing from historical records and interviews with forestry workers and environmental group members, struggles over loggingin the nearby Upper Elaho Valley are grounded in a historical political ecology of the area Special attention is directed at the job-environment tradeoffs of capitalist forestry and to the potential of forestry unions to resist this job blackmail. Throughout this work we draw from, and seek to elaborate, radical political ecology as the nexus of class theory and environmental sociology. We contend that this theoretical lens offers the greatest hope for understanding the relation of natural environment, capitalist production and class and environmental politics.

abstract: Doctor of Philosophy (PhD)


title: Free Radical Polymerization of N-Vinylformamide and Novel Comb-structure Polyelectrolytes

contributor:
Zhu, Shiping
Hrymak, Andrew N.
Chemical Engineering

subject:
Chemical Engineering
Chemical Engineering

abstract: This thesis summarizes experimental and theoretical studies on N-vinylformamide (NVF) free radical polymerization and the synthesis and evaluation of cationic grafted copolymers for flocculation purpose. The free radical polymerization of N-vinylformamide was studied in bulk and aqueous solution processes. The molar heat of reaction for NVF polymerization was measured to be 79.4 kJ/mo!. The polymerization kinetics, including the conversion versus time, molecular weight and molecular weight distribution, was examined systematically. Significant "gel effect" was observed in bulk and solution polymerization when the monomer concentration was over 40wt% (5.63 moI/L). A semi-empirical model based on the free volume theory was proposed to describe both the bulk and solution polymerizations. It was also confirmed that amide group provided crosslinking points that formed PNVF gel during NVF free radical polymerization. The subsequent acidic and basic hydrolysis to convert PNVF to PV Am was also studied systematically. The effect of temperature, polymer/acid (or base) ratios and polymer concentrations were examined. Two methods were used to synthesize cationic grafted copolymers for flocculation purposes. In the first method, NVF monomer was copolymerized with two cationic poly dimethylaminoethyl methacrylate (polyDMAEMA) methyl chloride macromonomers to produce a series of comb-grafted copolymers with different cationic contents. One cationic macro monomer had a molecular weight of 14,100 (50 repeating units) and the other had a molecular weight of 28,200 (100 repeating units). The copolymerization reactivity ratio (r₁) of the comonomer pair (NVF(M₁)-macromonomer(M₂)) was determined to be 3.82 and 6.39 for the two macromonomers with 50 and 100 repeating units. The flocculation performance of the graft copolymers was tested on a TiO₂ aqueous dispersion model system. The graft copolymers were found to be more effective in flocculation than their random linear counterparts. In the second method, poly diallydimethyl ammonium chloride (polyDADMAC) was grafted onto polyacrylamide (PAM) using a mini-mixer in melts with an organic peroxide, Lupersol 130. This process resembled reactive processing usually carried out at a larger scale in extruders to handle highly viscous polymer reactions. The grafting was confirmed and successful. However, severe gelation problem with PAM that occurred during the process hampered the grafting efforts. Parallel to these studies based on experimental data, a theoretical model was derived to describe the bivariate distribution of molecular weight and branching density for comb-grafted copolymers. This model was based on the random grafting of pre-formed side chains onto backbones (grafting-onto) mechanism. However, it is also applicable to the comb polymers synthesized by grafting-from and grafting-through mechanisms as long as the inclusion of the branching point is a random process.

abstract: Doctor of Philosophy (PhD)


title: Modelling the Spectra of Distributed Feedback Lasers

contributor:
Cassidy, D.T.
Engineering Physics

subject:
Engineering Physics
Engineering Physics

abstract: Distributed feedback (DFB) semiconductor lasers have a periodic modulation of refractive index, or Bragg grating, in the active region of the device. The Bragg grating causes a wavelength dependent distributed feedback of light. This thesis develops a below-threshold model for the spectra of DFB lasers. The model is shown to treat spontaneous emission in a manner that is quantum mechanically correct. Most other models in the literature do not treat spontaneous emission correctly, and are shown to yield spurious spectral predictions for truncated quantum-well DFB lasers. Techniques for fitting the model to spectral data are explained, and the model is demonstrated to be a useful diagnostic tool for understanding the performance and behaviour of DFB lasers. The effects of facet phase on DFB laser spectra are documented and explained. The model is then expanded to the above threshold regime, and is used to predict correctly spatial hole burning phenomena in DFB laser spectra.

abstract: Doctor of Philosophy (PhD)


title: Impulsive Differential Equations with Applications to Self-Cycling Fermentation

contributor:
Wolkowicz, G.S.K.
Mathematics

subject: Mathematics Mathematics

abstract: Self-cycling fermentation is a computer-aided process used for culturing microorganisms. Cells feeding off a growth-limiting nutrient in a tank grow and reproduce until a computer determines the time to end the cycle. At this point, a fraction of the volume of the tank is removed and replaced with an equal volume of fresh nutrient. The remaining cells then consume the fresh medium, grow, and reproduce. The process continues, releasing a fraction of the tank containing only a small amount of nutrient at the end of each cycle. Applications include sewage treatment, toxic waste cleanup, the production of antibiotics, and the examination of cell evolution. A basic model of growth will be formulated in terms of a system of impulsive differential equations. The predictions of the dynamics of the model will be discussed. The model will be refined to better describe the process for nutrient-minimizing applications such as sewage treatment. Criteria to ensure a positive, orbitally attractive periodic orbit with one impulse per period will be given. The predictions of the analysis will be supported by numerical simulations. The model will also be refined to include size-structured populations and a more accurate description of cell reproduction. The predictions of these refined models will be described. Competition of populations will also be considered and criteria for coexistence of more than one population on a single nonreproducing growth limiting nutrient will be given, and supported by numerical simulations.

abstract: Doctor of Philosophy (PhD)


title: Multi-Segment Waveguide Photodetectors For High Resolution Wavelength Monitoring Near 1.55 μm

contributor:
Jessop, P.E.
Engineering Physics

subject:
Engineering Physics
Engineering Physics

abstract: This thesis documents the development of a new optoelectronic device capable of functioning as a high resolution wavelength monitor near 1.55 μm. The primary objective of this work was to devise a simple and potentially low cost approach to monitor wavelength shifts in wavelength division multiplexing (WDM) networks and fiber Bragg grating optical strain sensors. The presented technique utilizes in-line pairs of quantum well waveguide photodiodes fabricated in an InGaAsP /InP material system. The ratio of photocurrents produced between two consecutive waveguide detectors is taken as a sensitive measure of wavelength near the absorption band edge of the quantum wells. The device is shown to function over the conventional wavelength band with near pm wavelength sensitivity, while performing independently of the optical input power and signal polarization. The simultaneous monitoring of several incoming wavelengths is also demonstrated, where arrays of in-line detectors are utilized with a wavelength demultiplexer. In this thesis, several unique methods are presented to improve the performance of the devices, including the use of the quantum confined Stark effect to expand the wavelength operating range and to reduce the thermal sensitivity. Finally, as a practical demonstration, the in-line detectors are used to track the small wavelength shifts induced in various types of fiber Bragg grating optical strain sensors.

abstract: Doctor of Philosophy (PhD)


title: Geological, Geochemical and Rb-Sr and U-Pb Zircon Geochronological Investigations of Granitoid Rocks from the Winnipeg River Belt, Northwestern Ontario and Southeastern Manitoba

contributor:
McNutt, Robert H.
Geology

subject: Geology Geology

abstract:
An integrated geological, geochemical and geochronological study of granitoid rocks from the Winnipeg River belt has revealed a complex geologic history spanning at least 500 Ma. Detailed Rb-Sr and U-Pb zircon isotopic investigations have revealed complexities that caution against simplistic application of these geochronological techniques in similar terrains.

Rb-Sr whole rock isochron ages are sufficiently imprecise and/or inaccurate that they can not be used to establish relative and absolute-time scales. Late to post-tectonic plutons, classically considered perfect candidates for Rb-Sr geochronology commonly have non-ideal Rb-Sr isotope systematics and suggested ages are slightly to significantly younger than U-Pb zircon ages for the same units. There is no independent evidence for a geologic event that could reset the Rb-Sr system and these younger ages should not be interpreted as representing discrete geologic events. The U-Pb zircon system is inherently a more precise geochronometer and these ages are interpreted to represent the age of crystalization.

Detailed studies of a biotite tonalite gneiss layer from the Kenora area reveals a complex redistribution of mineralogical, chemical and isotopic species during metamorphism. For certain elements, including Rb and Sr, parts of the layer have acted as an open system suggesting that whole rock Rb-Sr isochron ages for such rocks may not be reliable. Model initial ratios offer a more reliable, though more qualitative, approach to the problem of identifying ancient crust. Several different ages of zircon growth occurred in this tonalite but it is feasible to select specific morphological types of zircon and to determine more than one age from the same rock.

The earliest rocks in the Winnipeg River belt were a "greenstone-type" supracrustal sequence that are now preserved as highly metamorphosed and deformed inclusions in younger plutonic rocks. These supracrustal rocks are not abundant, but are widespread, and their occurrence as inclusions in tonalite gneiss interpreted to be as old as 3.0 Ga, indicates that a greenstone belt significantly older than those in the Wabigoon subprovince was once approximately coextensive with the Winnipeg River belt.

Massive sedic plutons and complex, banded, predominantly tonalitic gneisses are slightly to considerably older (2.76 to >3.0 Ga) than volcanism in the Wabigoon subprovince (2.70-2.75 Ga). The tonalite gneiss and sodic plutons are geochemically similar to other early Precambrian tonalites and are interpreted to be a product of the partial melting of metamorphosed tholeiitic basalt.

During the interval 2.7-2.75 Ga, most terrains in the western Superior province received voluminous juvenile additions from the mantle, either directly (basalt) or indirectly (felsic plutonic and felsic volcanic and volcaniclastic rocks derived from the melting of the basalts). The consequences of this thermotectonic event (the Kenoran orogeny) in the Winnipeg River belt was to partially melt and upwardly mobilize the earlier basalt-tonalite association with little addition of new material from the mantle.

Late to post-tectonic mafic plutons and voluminous potassic plutons were emplaced between 2.65 and 2.7 Ga. The potassic plutons have geochemical signatures and elevated Sr isotope initial ratios that indicate they originated from the partial melting of the early tonalites. The volume of these plutons requires that the early tonalites were extensive and it is probable that much of the present volume of the Winnipeg River belt represents relatively old (3.0 Ga) crust reworked during the Kenoran orogeny. This implies that the Winnipeg River belt could have acted as a sialic microcontinent during the deposition of younger (2.7-2.75 Ga) supracrustal sequences.

The pattern of pre-existing sialic nuclei and younger, coeval, interdigitating volcanic arcs and sedimentary basins is geometrically, though not necessarily genetically, analogous to modern plate tectonic regimes.

abstract: Doctor of Philosophy (PhD)


title: Atom Transfer Radical Polymerization and Its Continuous Processes

contributor:
Zhu, Shiping
Pelton, Robert H.
Chemical Engineering

abstract: Atom transfer radical polymerization (ATRP), a transition metal-mediated living radical polymerization, has been developed as a powerful tool for synthesizing polymers of controlled structure, but its catalyst residue remains challenging. Described in this thesis is a comprehensive study on the ATRP applications in macromonomer preparation and the solutions to its catalyst residue problem by catalyst supporting. A novel continuous process for the production of polymers and block copolymers with controlled molecular weights has also been developed using packed column reactor technologies. New versatile vinyl-containing initiators, 2'-vinyloxyethyl 2-bromoisobutyrate (VBIB) and 3'-vinyloxylpropyl trichloroacetamide (VTCA), were screened for the macromonomer synthesis of different vinyl monomer types by ATRP. Polymethacrylate and polystyrene macromonomers of well-controlled molecular weights were obtained without consumption of the initiators' vinyl moieties at monomer conversions lower than 80%. However, the ATRP of acrylates started to consume the vinyl moieties at medium conversions. Therefore, the polymerization of acrylates must be terminated at an early stage in order to obtain their macromonomers. Three catalyst supporting systems have been developed to solve the catalyst contamination problem for batch ATRP. Firstly, the CuBr/HMTETA complex was supported onto silica gel by physical adsorption for ATRP of MMA in toluene. The supported complex mediated a living polymerization of MMA. The recycled catalysts had a high retention of catalyst activity and improved control over the polymer molecular weights. Secondly the catalyst was immobilized on silica gel by covalent bonding for polar solvent/monomer systems. In this supporting method, the supporting spacer length was found to strongly affect the catalyst activity and control of the polymerization. The catalyst supported via three-unit PEG had highest activity and regulated the polymerization best. Longer or shorter spacer deteriorated catalyst activity and control of polymerization. Thirdly, the catalyst was grafted onto soluble and recoverable PE and PE-b-PEG supports to overcome the adverse effects of insoluble support. Catalyst directly grafted on the long PE chains had low activities, poor control over polymerization and low retention of the catalyst activity upon recycling. Using PEG as spacer to graft the catalyst onto the PE support minimized these adverse effects of the PE support. PE₂₅-PEG₄-TEDETA-CuBr effectively mediated the ATRP of MMA, and retained 90% activity of the fresh catalyst upon recycling with good polymer molecular weight control. Catalyst recycling for batch ATRP was found laborious and time-demanding. A continuous ATRP using column reactors packed with silica gel supported CuBr/HMTET A was developed for homo- and block-copolymerization of MMA. The reactor showed good stability in both catalyst activity and molecular weight control of resulting PMMA. The polymerization in the reactor was still a living process. Thus, adjusting the MMA flow rate, which determined the monomer conversion, readily changed the molecular weight of PMMA. The block copolymerization of MMA with nbutyl methacrylate (nBMA) was carried out using two reactors in series. The produced block copolymers had little contamination of PMMA prepolymer. The chain length of nBMA block could be adjusted by the flow rate of nBMA in the second reactor.

abstract: Doctor of Philosophy (PhD)


title: SYNTHESIS OF CATIONIC MACROMONOMERS BY LIAVING POLYMERIZATIONS FOR COMB-BRANCHED POLYELECTROLYTES

contributor:
Zhu, Shiping
Pelton, Robert
Chemical Engineering

abstract: Cationic macromonomers of poly [2-(dimethylamino) ethyl methacrylate dimethyl sulfate] polyDMAEMA-DMS) were synthesized by both living nitro-anionic polymerization with a novel capping technique and atom-transfer radical polymerization (ATRP). The macromonomers were copolymerized with acrylamide to give well-defined comb-branched polyelectrolytes having polyacrylamide (PAM) backbone and polyDMAEMA-DMS side chains by free radical processes. First, the radical mechanism involved in ATRP was investigated using an electron spin resonance (ESR) spectrometer and a differential scanning calorimeter (DSC). Poly (ethylene glycol) dimethacrylate (PEGDMA) was used as a model system for this purpose of mechanism elucidation. The network-forming feature of the system imposed diffusion limitations to radical deactivation reactions and thus allowed us to directly observe the radical intermediates during the polymerization by the first time. The polyDMAEMA macromonomers bearing terminal allyl moieties were synthesized by the A TRP method using allyl-containing organic halide as initiator. The polyDMAEMA macromonomers with styrenic end groups were prepared by the living nitro-anionic polymerization. A novel capping technique was developed to improve the initiator efficiency in the anionic polymerization. The polyDMAEMA macromonomers were quatemized with dimethyl sulfate yielding cationic polyDMAEMA-DMS macromonomers. The copolymerization of acrylamide with polyDMAEMA-DMS macromonomers was conducted using 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AlBA) as free radical initiator in aqueous solution. The reactivity ratios in copolymerization were measured for the two series of cationic macromonomers with terminal styrenic or allyl groups. PolyDMAEMA-DMS macromonomer with styrenic end group was found to have a much higher reactivity than acrylamide. It was attributed to the hydrophobic characteristic of styrenic group and the micelle formation of the macromonomer in aqueous media. In contrast, the PolyDMAEMA-DMS macromonomer with terminal allyl group had lower reactivity than acrylamide. This difference in reactivities caused a chemical composition drifting during the copolymerization. A semi-batch method was used to control the copolymer composition for synthesizing comb-branched cationic polyelectrolytes.

abstract: Doctor of Philosophy (PhD)


title: Abelian Groups in a Topos of Sheaves on a Locale

contributor:
Banaschewski, Bernhard
Mathematics

subject: Mathematics Mathematics

abstract:
This thesis is devoted to the study of Abelian Groups in the topos Shℒ of sheaves on a locale ℒ. The main topics considered are: injectivity, essential extensions of torsion groups, divisibility, purity, internal hom-functor, tensor product and flatness.

We derive some general results about these notions. Also, we prove the Baer Criterion for injectivity in AbShℒ. For a well-ordered locale ℒ, we describe the injective hulls in AbShℒ and for some special locales we characterize the injectives in AbShℒ.

We further discuss essential extensions of torsion groups and show amongst other things, that a first countable Hausdorff space X is discrete iff essential extensions in AbShX preserve torsion.

Divisible groups are characterized here as absolutely pure groups. We discuss the internal adjointness between the tensor product and the internal hom-functor.

Finally, we consider the notion of flatness, and show that the flat groups in AbShℒ are characterized the same way as in Ab, that is, flat = torsion free, and that A is flat in AbShℒ iff A* = [A,P] is an injective group, where P is an injective cogenerator.

abstract: Doctor of Philosophy (PhD)


title: High-Sensitivity Detection with Tunable Diode Lasers

contributor:
Reid, J.
Physics

subject: Physics Physics

abstract:
This thesis describes methods for high-sensitivity detection of trace gases using tunable diode lasers (TDL). TDL absorption spectrometers have been widely used to acquire infrared spectra since 1970. However, high-sensitivity measurements have been limited mainly to the detection of low-pressure gases by harmonic techniques. The detection of atmospheric-pressure gases and the development of a rapid sweep technique for the accumulation of weak-absorption data over ~0.4 cmˉ¹ spectral regions are emphasized in this thesis. The results of this work may be divided into four areas where major accomplishments have been realized.

Optical interference fringes generated by scattered light often limit the sensitivity of measurements performed with TDL spectrometers. The effect of fringes can be minimized by applying a jitter modulation. An investigation was undertaken to understand and quantify the effects of the jitter on the fringe and absorption signals. Simple analytical expressions describing the effects of the jitter modulation are derived and compared to experiment. Good agreement between theory and experiment is found.

The limiting noise sources of a TDL spectrometer were carefully investigated and identified. Detection methods insensitive to the noise were developed. Application of these methods leads to sensitivity limits equivalent to detecting an absorption of ~10ˉ²% for atmospheric-pressure gases and ~10ˉ³% for low-pressure gases over path lengths ≤ 200 m. This represents a substantial improvement over previous work.

A rapid-sweep technique capable of detecting absorptions due to low-pressure gases of ~10ˉ³% over path lengths ≤ 200 m is described. Data accumulation by the rapid-sweep technique allows direct determination of line shapes and linewidths from the measurements.

An investigation of the TDL output power and frequency stabilitiy was performed as these laser characteristics directly affect the achievable sensitivity. The development of a new method to determine the TDL linewidth is reported. This technique permits the linewidth of any tunable laser to be quickly and easily measured.

Throughout this thesis, the sensitivity of the various detection techniques is demonstrated by the detection of pollutants and trace gases. Whenever applicable, techniques for further increasing the sensitivity are discussed.

abstract: Doctor of Philosophy (PhD)


title: The Conflict for the Earthly Rome: an Aspect of the Early Christian-pagan Struggle

contributor:
Wightman, E.M.
History

subject: History History

abstract:
The mutual hatred and prejudice of Christians and pagans in the pre-Decian era (before A.D. 250) is analysed in this study in the context of the function of prejudice in ancient society as a whole. The symbolic expressions, the uses, and the meaning of prejudice in the early pagan-Christian conflict are elucidated from both the social and the historical perspective. Use is made of psycho-logical theories of prejudice, to help define the significance of prejudice in the pre-Decian period.

Once analysed in context, the expression of the Christian prejudice against the pagans suggest that for many of the early Christians the struggle was seen as a battle for possession of this earth, and not solely as a necessary toil in preparation for posthumous celestial felicity. This conclusion is contrary to the generally accepted view, and arguably broadens our insight into the unconscious and conscious motives of early Christians, and their pagan antagonists.

abstract: Doctor of Philosophy (PhD)


title: Dynamics of a Discharge-Excited CO₂ Lasers

contributor:
Garside, B.K.
Reid, J.
Physics

subject: Physics Physics

abstract:
A tunable diode laser (TDL) operating in the region of 2150 to 2350 cm⁻¹ wavenumber is used in this work to investigate the dynamics of level populations in CO₂ lasers. The wide tunability of the TDL is exploited in determining the populations in any level of the CO₂ molecule. Thus, the vibrational population distributions in a CW CO₂ laser discharge under both lasing and non-lasing conditions are measured and are compared with the mode temperature model.

The relaxation processes associated with the upper and lower levels of CO₂ lasers are also investigated. In particular, the electron excitation and de-excitation rates of the upper laser level in typical CO₂ discharges are determined directly from the experiment, and it is shown that electron de-excitation is responsible for the saturation of v₃ mode temperature in electrically excited CO₂ lasers at high discharge currents, and imposes a fundamental limitation on the gain attainable in CO₂ lasers.

The relaxation of the lower laser level is complicated by the occurrence of several competitive vibration-vibration (V-V) processes. The TDL measurements enable us, for the first time, to monitor separately the population in all levels of concern to the relaxation of the lower laser level and to determine the rate constant of each of the available decay channels. It is shown that the O2²O level plays an important role in the relaxation of the lower laser level.

abstract: Doctor of Philosophy (PhD)


title: The Application of Monochromatic Photoneutron Spectroscopy In An Examination of Nuclear Energy Levels of ¹⁸⁰Ta, ²⁰²Tl And ²⁰⁴Tl

contributor:
Kennett, T.J.
Physics

subject: Physics Physics

abstract:
Monochromatic photons from in-core neutron capture sources of aluminum, copper, iron, nickel and chromium were used to initiate the (Υ,n) reaction on the ¹⁸¹Ta, ²⁰⁵Tl and ²⁰³Tl nuclei. The use of this method allows precise measurement of the Q values for the ¹⁸¹Ta(Υ,n) ¹⁸⁰Ta (7579 ± 2 Kev) and the ²⁰⁵Tl(Υ,n)²⁰⁴Tl (7549 ± 1 Kev) reactions. Comparison of the ¹⁸¹Ta(Υ,n) data with the ¹⁸⁰Ta(n,Υ) data confirms the existence of an isomeric state in ¹⁸⁰Ta at 73 ± 2 Kev. Over twenty previously unobserved levels in ¹⁸⁰Ta were populated with typically ²Kev precision in energy determination. Well-documented levels ²⁰⁴Tl were observed to also be populated.

The total (Υ, cross sections were measured and the gamma ray strength functions were deduced for the stronger (Υ,n) channels. The small incident gamma ray energy spread of a few ev allows excitation of individual excited state resonances in ²⁰⁵Tl, while averaging over many compound resonances in ¹⁸¹Ta is observed. The number of degrees of freedom for a Porter-Thomas distribution of reduced widths was also estimated and gave some credence to the deduced Υ-ray strength functions. Attempts to assign spin and parity in the residual ¹⁸⁰Ta and ²⁰⁴Tl nuclei were thwarted by the assumption of a dominant electric-dipole absorption cross section, and by the half-integer ground state spins of the ²⁰⁵Tl and ¹⁸¹Ta targets.

abstract: Doctor of Philosophy (PhD)


title: Aspects of Technetium Chemistry

contributor:
Lock, L. C. J.
Chemistry

subject: Chemistry Chemistry

abstract:
Interest in technetium chemistry is derived from the fact that it is a recently-discovered element and from the use of technetium-99m as a radioactive label in diagnostic medicine. Compounds related to both sources of interest have been characterized by X-ray crystallography, vibrational spectroscopy and multinuclear nuclear magnet resonance spectroscopy.

The crystal structure of a penicillamine complex of technetium consists of an oxotechnetium(V) core bonded to the S, N, and O atoms of one penicillamine moiety and the S and N atoms of a second. Further characterization, including tracer studies with ⁹⁹ᵐTc, indicate that this complex is identical to an hepatobiliary agent erroneously formulated as a technetium(IV) species. The crystal structure of an anionic catechol complex of technetium also contains the oxotechnetium(V) core and suggests that the technetium(IV) formulation for a number of other radio-pharmaceuticals is incorrect. The crystal structure determination of a complex containing the ethylenebis(2-mercaptoacetamide) ligand forms part of a larger program to design, systematically, new scanning agents.

Technetium complexes involving cyanide ligands are shown to be similar to their rhenium analogs.

Several new technetium(VII) species were synthesized and used to establish ranges for parameters in the nuclear magnetic resonance spectroscopy of ⁹⁹Tc.

abstract: Doctor of Philosophy (PhD)


title: Neutron Radiographic Unsharpness and Dimensional Analysis

contributor:
Harms, A. A.
Nuclear Engineering

subject:
Nuclear Engineering
Nuclear Engineering

abstract:
The neutron image unsharpness which generally limits radiographic resolution to a qualitative assessement has been studied in detail and found to exhibit unique features at object boundaries and material discontinuities. These radiographic features provide intrinsic criteria for accurate dimensional measurements and the determination of material boundaries.

As a basis for our investigation, the analysis of the underlying radiation-conversion and transport phenomena of the neutron imaging process was undertaken. The resultant functional image characterizations were found to be dependent on the radiographed object geometry, object dimensions, and material composition. Two avenues for extracting quantitative details from radiographs have thereupon been identified. Firstly, the coordinates bounding an object or regions of material discontinuities were found to be obtainable by an adaptation of the experimental optical density data to the functional representation. Secondly, the optical density variations due to image unsharpness was found to possess functional inflections at object boundaries and material discontinuities.

The applications of both methods to the determination of limits of internal material discontinuities and dimensions of objects have been investigated in some detail. Experimental tests of the inflection approach show excellent agreement with theory. A mathematical-theoretical characterization of the neutron imaging phenomenon has thus been established and developed into a practical tool for extracting dimensional information from a neutron radiographic image.

abstract: Doctor of Philosophy (PhD)


title: LANDSAT and Airborne Radar for Land Cover/Use Mapping and Change Detection in Southern Ontario

contributor:
Howarth, P.J.
Geography

subject: Geography Geography

abstract:
Several remote sensing systems have been evaluated to determine their capabilities for providing land cover/use information. The systems studied were LANDSAT Multispectral Scanner (MSS) visual and digital data, LANDSAT Return Beam Vidicon (RBV) imagery and Synthetic Aperture Radar (SAR) imagery, Standard panchromatic aerial photography provided the ground information against which the imagery was evaluates. The study was carried out in the Hamilton-Wentworth Region of southern Ontario.

The visual data were analyzed using transparencies in a Zoom Transfer Scope to produce a land cover/use map at a scale of 1:50,000. The digital data were preprocessed using the Digital Image Correction System (DICS) at the Canada Centre for Remote Sensing. Land cover/use maps were produced from the data using both a maximum likelihood classifier and a parallelepiped classifier.

It was found that the visual data gave a higher classification accuracy than the digital data. With an increasing number of classes, the accuracy of classification decreases.

Using LANDSAT data from two dates, several digital enhacements were tested for their change detection capability. The overlay of Band 5 data from both dates, combined to give a colour image, was the most effective way to identify areas of change.

abstract: Master of Science (MS)


title: Macro-Economic Influences on the Distribution of Income: A Case Study of Canada

contributor:
Denton, Frank T.
Johnson, James A.
Robb, Leslie A.
Economics / Economic Policy

subject: Economics Economics

abstract: The purpose of this thesis is to estimate the effects of macro-economic variables, such as unemployment, inflation and labor force participation rates, on the size distribution of income in Canada. Most previous studies of this kind have been based on U.S. data. These include studies by T. Paul Schultz Lester Thurow, Charles Metcalf, Charles Beach, Alan Blinder and Howard Esaki, and others. Recently, however, a study in the Canadian context has been published by Adolf Buse, in which he analyzes the distribution of incomes of individuals, based on income tax returns. In our study, in addition to the income distribution for all individuals, we analyze a number of other distributions. These includes ones for all male individuals combined, particular age groups of male individuals, all families and unattached individuals combined, all families only, and families with age of head in a particular age group. There are two sources of distribution data: Taxation Statistics of Revenue Canada and the Survey of Consumer Finances of Statistics Canada. Data for family distributions are available only from the latter source. Our framework of analysis is highly disaggregative. Changes in income inequality are characterized by fluctuations in decile income levels relative to the mean of the distribution. The effects of macro-economic variables on these relative decile levels are estimated by econometric methods. The problem of multicollinearity is handled by using approaches based on principal components, including an approach suggested recently by Yair Mundlak. The responses of various points on the distribution to changes in the macro-economic variables are examined first. The decile model results are then analyzed in terms of single-valued measures of inequality such as the coefficient of variation, the Gini coefficient and the Atkinson index. The results indicate that the effects of unemployment are disequalizing, but this is not true for all the distributions. The effects of inflation on inequality are not very clear in most cases. On the other hand, the effects of the unanticipated component of inflation, as approximated by changes in the inflation rate appear to be disequalizing. There are some interesting results relating to the effects of labor force participation rates. Unemployment insurance benefits appear to improve the relative position of lower income groups. Evidence seems to suggest that lower income groups in the age range 65 and over gain more from retirement and old age benefits than do other groups in that age range.

abstract: Doctor of Philosophy (PhD)


title: Dynamics of a Discharge-Excited XeCl Laser

contributor:
Ballik, E.A.
Physics

subject: Physics Physics

abstract:
The optical output characteristics of a photo-preionized avalanche discharge XeCl exciplex laser are studied experimentally and analytically. Experimental results are presented for the employing a range of He/Xe/HCl mixtures and discharge conditions. An output energy of ~200 mJ, in an almost flat-topped 60-ns duration (FWHM) optical pulse, has been attained. A viable kinetic scheme has been developed for modelling the laser output pulses, and for investigating the dynamical processes in a pulsed discharge.

The B ²∑⁺₁₂→X ²∑⁺₁₂ emission is characterized by means of Franck-Condon calculations using wavefunctions derived from a Rittner-type potential for the excimer B-state, and a new potential-energy function for the ground X-state. This new function reproduces accurately (~±1%) published experimentally-derived data, and demonstrates the "super-harmonicity" of the ground state molecule. The primary exciplex formation channels, deduced from the electronic structure, are the recombination of Xe⁺ and Cl⁻ ions and the "harpooning" processes via the Rydberg molecules Xe(³P₂) Cl(²P₃/₂) and Xe(³P₁) Cl(²P₃/₂). The latter two processes contribute to high optical gain when ion densities are low.

A comprehensive kinetic model is developed on the basis of achieving good agreement between computed and observed optical pulse-shapes, in terms of total energy, peak power, pulse duration, delay time for onset of emission, and rise- and fall-times. The rate coefficients for electron collision processes are calculated using electron-energy distribution functions derived from Monte-Carlo electron transport simulations (electron-electron scattering is included). Calculated intrinsic laser parameters (unsaturated gain, absorption coefficient and saturation irradiance) are in good agreement with values determined from output-power measurements (employing different output couplers and in-cavity attenuators) used together with gain-saturation theory.

abstract: Doctor of Philosophy (PhD)


title: Designing Hydrogel Microspheres from Liquid-Liquid Phase Transitions of Aqueous Polymer Solutions

contributor:
Stover, Harald D.
Chemistry

subject: Chemistry Chemistry

abstract: This thesis focuses on reactive water-soluble polymers suitable for forming liquid-liquid phase transitions from both polyelectrolyte complexation and thermal induction. Novel hydrogel microspheres are formed by liquid-liquid phase transition followed by crosslinking reactions. Besides studying the properties of polymers and hydrogel microspheres formed, the mechanism of liquid-liquid phase transitions as well as potential applications of these systems in protein separation and encapsulation are discussed. Chapter 1 describes the background of liquid-liquid phase transitions of aqueous polymer solutions, including polyelectrolyte complexation, thermally nduced phase transition and their application in designing hydrogel microspheres. Chapter 2 describes the thermo-responsive properties of fully MPEG-grafted maleic anhydride copolymers in aqueous solutions. The phase transitions are ascribed to the cooperative effects of intra/intermolecular hydrogen bonding and hydrophobic interactions. Chapter 3 describes the use of analogous partially MPEG-grafted maleic anhydride copolymers as reactive polyanions to form phase-separated liquid polyelectrolyte complexes with polycations, and to prepare hydrogel micro spheres by crosslinking the polyelectrolyte complexes with polyamines. Chapter 4 and Chapter 5 extend this two-stage approach of liquid-liquid phase transition followed by crosslinking reaction to thermally induced phase transitions. Thermally induced liquid-liquid phase transitions of poly(N,N-dimethacrylamide-coglycidyl methacrylate) and poly(N,N-dimethylacrylamide-co-allyl methacrylate) aqueous solutions are thus used to prepare hydrogel microspheres. The morphology of the resulting micro spheres is studied by electron microscopy. The mechanism of thermally induced liquid-liquid phase transitions ofpoly(N,Ndimethacrylamide) copolymer solutions is discussed in Chapter 6, together with the preparation of well-defined model copolymers using atom transfer radical polymerization.

abstract: Doctor of Philosophy (PhD)


title: Indicator Polynomial Functions and Their Applications in Two-Level Factorial Designs

contributor:
Balakrishnan, Narayanaswamy
Mathematics

subject: Mathematics Mathematics

abstract: In this thesis, we discuss some properties of indicator polynomial functions. We extend some existing results from regular designs to non-regular designs. More general results which were not obtained even for regular designs are also provided. First, we study indicator polynomial functions with one, two, or three words. Classification of indicator polynomial functions with three words are provided. Second, we consider the connections between resolutions of general two level factorial designs. As special cases of our results, we generalize the results of Draper and Lin [14]. Next, we discuss the indicator polynomial functions of partial fold over design, especially, semifoldover designs. Using the indicator polynomial functions, we examine various possible semifoldover designs. We show that the semifoldover resolution II I.x design obtained by reversing the signs of all the factors can de-alias at least the same number of the main factors as the semifoldover design obtained by reversing the signs of one or more, but not all, the main factors. We also prove that the semifoldover resolution III.x designs can de-alias the same number of two-factor interactions as the corresponding full foldover designs. More general results are also provided. Finally, we present our conclusions and outline possible future work.

abstract: Doctor of Philosophy (PhD)


title: Investigation of Immunomodulatory Concepts in a Murine Model of Airway Mucosal Sensitization to Innocuous Antigen

contributor:
Jordana, Manel
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract: The epidemic rise in the prevalence of allergy and asthma, primarily in the "developed" world, has impelled prolific nodes of inquiry into the epidemiology, aetiology, immunology and management of these syndromes. While studies in human patients have revolutionized pharmacological treatment of asthma and allergy, and have also intimated some of the environmental agents and conditions conducive to disease expression in susceptible populations, only animal models of asthma afford the experimental flexibility upon which detailed in vivo analysis of immunology and pathogenesis depends. Because asthma arises through airway mucosal contact with allergens, chemical pollutants and/ or infectious agents, an authentic animal model of asthma should preserve the airway as the interface of incipient contact with antigen and, by extension, as the immune microenvironment that conditions allergic sensitization. This heuristic is particularly relevant when considering questions about the immunomodulatory effects of local, anti-inflammatory intervention. The research documented in this thesis investigates several immunomodulatory concepts- including pharmacological intervention (Chapter 2), costimulatory molecule blockade (Chapter 3) and chemokinetic manipulation of cell trafficking (Chapters 4 and 5)-in a murine model of airway mucosal sensitization to an innocuous antigen. The salient message informed by these studies is that the outcome of an immune-inflammatory response is very much a reflection of the airway microenvironment in which the immune system initially processes antigen. Of substantive clinical interest, these data indicate that the efficacy of acute, therapeutic intervention must be reconciled with the status of the antigen-specific response once treatment has ceased.

abstract: Doctor of Philosophy (PhD)


title: The role of β-integrin signaling in mammary gland tumourigenesis

contributor:
Muller, William J.
Medical Sciences

subject:
Medical Sciences
Medical Sciences

abstract: Experimental and clinical evidence implicate the β-integrin subunit and its associated intracellular effector ILK in the initiation and progression of human breast cancer. Roles for these proteins in promoting the oncogenic process, however, have not been demonstrated in vivo. As a result, experiments were designed to test the tumour-promoting properties of β-integrin and ILK in the mammary glands of transgenic mice. The first of these experiments involved the targeted ablation of a conditional allele of β-integrin in a transgenic mouse model of human breast cancer. Using this approach, it was found that the expression of β-integrin is required for oncogeneinduced transformation of the mammary gland epithelium in vivo. This requirement for β1-integrin expression was observed during both the initiation of tumourigenesis, as well as for maintaining the growth of established tumours. In addition, a block in tumour cell proliferation following ablation of β1-integrin expression was found to be associated with the suppression of F AK autophosphorylation, providing a molecular mechanism underlying the requirement for β1-integrin expression during tumourigenesis. The second experiment was designed to test the oncogenic properties of ILK, through the establishment of transgenic mice overexpressing ILK in the mammary gland epithelium. Following the induction of a hyperplastic mammary gland phenotype, these mice developed solid mammary tumours showing evidence of epithelial-to-mesenchymal transition, confirming that ILK overexpression can contribute to mammary tumourigenesis in vivo. Since expression of both β-integrin and ILK have been reported in samples of aggressive human tumours, these results may have clinical significance to the treatment of human breast malignancies.

abstract: Doctor of Philosophy (PhD)


title: Methanation of Carbon Monoxide and Carbon Dioxide on Raney Nickel, and Computer Simulation of Chain Growth in the Fischer-Tropsch Synthesis

contributor:
Anderson, R.B.
Chemical Engineering

abstract:
The methanation of carbon monoxide and carbon dioxide was studied over Raney nickel. The catalyst was characterized by chemisorption techniques. A differential plug-fIow reactor was used to obtain kinetic data. The reaction rates were investigated as a function of temperature, reactants and products concentrations. The power rate law was found inadequate in representing the kinetic data of carbon dioxide methanation. The orders of reaction for hydrogen and carbon monoxide were obtained. Carbonaceous species were found on the catalyst surface after methanation reaction, which could react with hydrogen give methane. Multilayers of carbon species were deposited on the catalyst surface during CO methanation; less than a monolayer was found when carbon dioxide was used as feed. The effects of reaction conditions on the amount of residual carbon was also investigated.

The data in general agrees with a mechanism involving the hydrogenation of carbonaceous species as the rate determining step. The differences between CO and CO₂ methanations were also discussed.

The carbon chain growth process in the Fischer-Tropsch synthesis was simulated using available data in the literature. The simulation was done by representing the hydrocarbon chains by numbers stored in vectors. Various chain growth schemes were tested. The results suggested that the carbon chain growth process could involve the stepwise additions of both one-carbon and two-carbon units.

abstract: Doctor of Philosophy (PhD)


title: Classification, Zoogeography, and Phylogeny of the Genus Sinophorus Foerster (Hymenoptera: ichneumonidae)

contributor:
Davies, D.M.
Biology

subject: Biology Biology

abstract: The world species of the genus Sinophorus Foerster (Porizontinae=Campopleginae) are revised. One hundred and three species and 5 subspecies are recognized. Eighty species and 5 subspecies are described as new: albipalpus, alpinus, androsae, anisodontis, apiculus, armillatus, betulellae, bilimbus, boreus, brevistyIus, brochus (b. brochus, b. brevipilus), brunnefemur, columbiensis, constrictus, cotidianus, curvatus, dilatus, erectus, falcatus, graeciensis, halli, heliothae, hydriae, idahoensis, inclivous, indistinctus, infimus, inflatus, japonicus, kasparyani, lanceolatus, latifossus, leptofemur, longifacies, masoni, megadontis, minutus, moroccoensis, neofurus, neoprocerus, nigricoxa, nigridontis, obtusus, orientis (o. euronotis, o. occidentalis, o. orientis), pallidus, pectinatus, peteri, petiolus, planus, platyfacies, poropleuron, porosus, prismatis, procerus, punctatus, punctifrons, rhyacioniae, robustus, rotundus, ruficoxa, rufitergum, rugosus, sabulum, sapporoensis, sarissophorus, splendidus, sticticalae, striatus, tahoensis, tibialis, townesorum, triangularis, tumidus, variabilis, varianae, ventosus, vericulus, villosus, woodorum, xanthocoxa. Twenty-three species are re-described: albidus (Gmelin), canadensis (Viereck), caradrinae (Viereck), costalis (Thomson), desertus Kasparyan, eruficinctus (Walkley), exartemae (Uchida), furus (Cresson), fuscicarpus (Thomson), geniculatus (Gravenhorst), juniperinus (Holmgren), montanus (Cresson), nigritellus (Thomson), nitidus (Brischke), pleuralis (Thomson), popofensis (Ashmead), relativus (Viereck), renominatus (Morley), sulcatellus (Viereck), turionus (Ratzeburg), validus (Cresson), xanthostomus (Gravenhorst). Two lectotype designations were made: pleuralis (Thomson), quettaensis (Cameron) (=nitidus (Brischke)). Three species were removed from synonymy and recognized as valid species: canadensis (Viereck) and montanus (Cresson) from validus (Cresson); renominatus (Morley) from turionus (Ratzeburg). One new combination was created: relativus (Viereck) from Campoplex. Seven names were pIaced in synonymy: albicinctus (Viereck), quettaensis (Cameron) and tegularis (Thomson) = nitidus (Brischke); alkae (Ellinger and Sachtleben) and rufifemur (Thomson) = turionus (Ratzeburg); juniperinus alpinator Aubert = juniperinus (Holmgren); pineticola (Thomson) = xanthostomus (Gravenhorst). The limits of the genus Sinophorus are defined. Keys to the world species, females and males, of Sinophorus are presented. Zoogeography, phylogeny and biology of Sinophorus are discussed. Taxonomic characters used to separate spp. of Sinophorus are illustrated by means of line drawings and scanning electron micrography and distribution maps are provided for each species.

abstract: Doctor of Philosophy (PhD)


title: The Sprouting of High-Threshold Cutaneous Nerves and its Acceleration by Neural Activity

contributor:
Diamond, Jack
Neuroscience

subject:
Neuroscience and Neurobiology
Neuroscience and Neurobiology

abstract:
Previous studies have shown that in the rat the sprouting of low-threshold ("touch''-sensitive) nerves into adjacent denervated skin can occur only during a brief "critical period" of post-natal life that ends at about 20 d of age. Additionally, for any segmental nerve this sprouting occurred only in the region of that nerve's sensory dermatome. One objective of my thesis was to examine whether the sprouting of high-threshold ("pain"-sensitive) cutaneous nerves is also temporally and spatially constrained.

The presence of high-threshold nerve endings in skin was detected behaviourally by pinching with toothed forceps; normally this elicits a reflex contraction of an underlying skeletal muscle, causing visible skin puckering. Denervated skin failed to respond in this way for the first 2-3 weeks after nerve section, but then a gradual recovery of the response occurred spreading from the adjacent innervated region of skin progressively further into the deprived area. That this recovery was due to sprouting was shown by histological examination of skin, and the findings of nerve fibres within the dermis in sensitive but not insensitive skin. The sprouting occurred in the adult animal, and proceeded beyond the dermatome border of a nerve, showing that intact high-threshold nerves are not under any obvious spatial and temporal constraints.

During the examination for the presence of high-threshold nerve sprouting I noted that repeated skin pinching apparently accelerated the return of high-threshold sensitivity. The second main objective of the thesis was to examine what this phenomenon depended upon. In animals that were repeatedly stimulated physiologically every 4 d, all of the denervated skin became reinnervated by 20 d, compared to the 40 d or more needed for unstimulated animals. The accelerating affect was mimicked by direct electrical excitation of the remaining nerve. The results revealed that it was the latency for sprouting that was affected; once begun, the rate of sprouting was normal. The effects of electrical stimulation of the intact nerve were prevented if TTX was applied so as to block impulses proceeding centrally from the site of electrical stimulation, but not if they were only prevented from proceeding peripherally. A hypothetical mechanism to explain the effects of impulse activity in causing acceleration of sprouting is provided.

abstract: Doctor of Philosophy (PhD)


title: Stable Isotope Studies of Water Extracted from Speleothems

contributor:
Schwarcz, Henry P.
Ford, Derek C.
Geology

subject: Geology Geology

abstract:
Calcite speleothems, if shown to be formed under conditions of isotopic equilibrium with their parent seepage waters, can be used to determine relative changes in the past climates from measurement of δ¹ ⁸O of the calcite. Furthermore, if δ¹ ⁸O of the parent seepage water can be estimated and shown to be equivalent to meteoric precipitation falling at the cave site, then depositional temperatures can be recovered from the temperature dependent oxygen isotope fractionation of the calcite-water pairs. Cave temperatures generally reflect mean annual surface temperatures above the cave. Thus, should the depositional temperature accurately record the cave temperature, then analysis of successive growth layers in speleothems should provide a direct measure of past temperature change at a given site. Estimates of δ¹ ⁸O of past seepage water can be made, in principle, because speleothems incorporate seepage water within inclusions as they grow. However, since oxygen in the fluid inclusion water may exchange with that in the carbonate phase, hydrogen isotopes, which cannot exchange, are measured instead. δ¹ ⁸O of the original seepage water can then be inferred from δD, if seepage water can be shown to be equivalent to included water, because meteoric relationships exist which link them. Work prior to this study suggested that following the method outlined above, isotopic temperatures could be recovered from speleothems.

The early part of this study involved the construction and operation of a mass spectrometer and associated extraction line for δD analyses and some, modification to existing apparatus for δ¹ ⁸O analysis.

Water samples were then analysed from a number of cave sites, mainly in the Eastern U.S., to check the isotopic equivalence of seepage water to meteoric precipitation and observe seasonal isotopic variations in seepage and soil water with respect to meteoric precipitation. The general conclusion reached was that seepage water was equivalent to meteoric precipitation and that no seasonal variation occurred in those caves studied in detail. Study of an Antarctic Ice Core showed that the δ¹ ⁸O-δD relation of meteoric precipitation during the Wisconsin Glacial Maximum was different from that at present.

The latter part of this study was concerned with the systematics of water extraction and the isotopic measurement of water-calcite pairs from speleothems. A previously developed technique, involving crushing of the sample in vacuum prior to freezing over the liberated water, was found not to be as reproducible as had been stated in the literature, and, as a result, an extraction method by heating was developed to replace it. Although great difficulty was encountered in getting this technique to function, it was found, eventually, to save time in operation, to liberate up to 2.4 times more water and give greater reproducibility than the crushing method. Attempts to demonstrate the isotopic equality of the two methods was only partially successful however, but both methods seemed to yield water from speleothems that was isotopically depleted with respect to their parent seepage waters.

For the latter reason, experiments were undertaken to characterize the water within the calcite because of the possible presence of structural, isotopically modified water. Petrographic observations left no doubt as to the presence of fluid inclusions from 50μm down to unresolvable dimensions but it was questionable as to whether or not all the water lay in these sites. IR, polarized IP and neutron diffraction spectroscopy of powders in the 100μm range failed to reveal the presence of oriented water in the calcite lattice although 'liquid' water was still observed.

The isotopic depletion of calcite-bound water with respect to parent seepage water in modern samples was found to be 22.1 ± 3.9% in δD. This value, when applied to δD profiles of six fossil speleothems to retrieve original seepage water δD gives rise to calculated calcite-water paleotemperatures that are above zero. Comparison of these modified δD and temperature profiles with other records, such as deep sea and ice cores suggested that paleoclimatic information can be obtained from isotopic studies of speleothems. The mechanism(s) responsible for the isotopic fractionation of calcite-bound water as it is incorporated into the speleothems during growth is speculated upon as an absorption-like phenomenon but no firm conclusions are reached.

abstract: Doctor of Philosophy (PhD)


title: The Effects of Kindling on GABA-mediated Inhibition in the Dentate Gyrus of the Rat

contributor:
Racine, R.J.
Psychology

subject: Psychology Psychology

abstract:
Brief, localized electrical stimulation of the brain can elicit a short electrographic afterdischarge (AD). In the rat, repeated stimulation permanently increases the duration of the AD and can lead to the development of a generalized motor seizure. This process has been labelled "kindling" and has been utilized as a model of epilepsy and neural plasticity.

Hypotheses concerning the mechanism of the neural change produced by kindling typically specify either an excitatory enhancement or an inhibitory decrement. Of the inhibitory neurotransmitters that are likely to be involved, Υ-aminobutyric acid (GABA) is probably the least studied. The hypothesis that GABA hypofunction contributes to the establishment of the kindled response was tested by the experiments in this thesis. GABA is known to mediate recurrent inhibition in the dentate gyrus of the hippocampus, a structure ideally suited for electrophysiological investigation.

Double pulse stimulation of the perforant path input to the dentate gyrus was used in the following experiments to produce paired pulse depression in that site. This depression effect provided an estimate of GABA-mediated recurrent inhibition. The depression was, for example, enhanced by GABA agonist drugs and attenuated by drugs which block GABA transmission. Paired pulse depression was significantly increased following amygdala kindling and was further enhance to near maximal levels by subsequent kindling in the dentate. These results indicated that kindling increased, rather than reduced, inhibition in the dentate gyrus.

In addition, kindling did not increase the rate at which inhibition fails under conditions of excessive activation. Trains of 5 Hz stimulation, applied to the perforant path, caused paired pulse depression to disappear and elicited a brief AD. Following kindling, the latency to AD onset tended to be increased rather than shortened, suggesting an enhanced resistance to inhibitory failure.

Finally, receptor binding estimates of the number of GABA and associated benzodiazepine (Bz) receptors were made in several brain regions following kindling. While the number of GABA receptors, as measured by both ³H-GABA and ³H-Muscimol binding, was unaltered by kindling, Bz receptors were significantly increased in kindled amygdala and hippocampus. As the Bz receptor apparently functions to enhance GABA transmission, this finding suggests a possible mechanism for the enhanced inhibition observed in the evoked potential experiments.

Taken together, the results indicate that kindling does not produce a decrement in GABA-mediated inhibition in the hippocampus and, in fact, enhances it in an apparently compensatory manner. A possible mechanism for this long-term inhibitory potentiation is suggested to be the up-regulation of the Bz receptor.

abstract: Doctor of Philosophy (PhD)


title: Finite Element Modelling of Creep and Instability of Large Ice Masses

contributor:
Mirza, F. A.
Civil Engineering

subject:
Civil Engineering
Civil Engineering

abstract:
Detailed descriptions of finite element models for deformation, temperature and instability analyses of large ice masses are presented. Two non-Newtonian, creeping flow models are developed for steady-state creep situations; one enforces incompressibility, the other near incompressibility. The third creep model incorporates a large displacement formulation and an implicit time-marching scheme for transient creep analysis. To allow for basal sliding, a time-dependent sliding element is also developed. In addition to the creep models above, a transient heat transfer model is presented. By stepwise uncoupling of the stress and temperature dependent creep, it is possible to carry out transient thermal creep analysis for surging of the Barnes Ice Cap. An upwind scheme for triangular elements is given for thermal analysis where the influence of thermal advection is required.

It is demonstrated that the three finite element creep models predict similar steady-state creep behaviour for simple ice masses with simple boundary conditions. For more complex problems, agreement of the computed velocities by the models is found to be very sensitive to the boundary conditions at the ice-bedrock interface. Results from the finite element simulations suggest that it may be premature to assume that the influence of elastic strains is negligible.

The thermal regime of the Erebus Glacier Tongue is studied assuming steady-state conditions. It is shown that the temperature field is mainly influenced by the near horizontal thermal advection. Reasonable velocity fields for the thermal analysis could only be attained by assuming that the ice is not frozen to bedrock at the transition from a land-based glacier to a floating glacier.

Finally, a basal instability model is presented. In this model, the basal shear resistance is reduced according to the excess sliding energy dissipated above some threshold value. The time for a surge to propagate is characterized by a lubrication factor incorporated in the basal instability model. It is confirmed that a geothermal flux approaching 1.9 HFU is required to bring most of the south-west ice-bed interface of the Barnes Ice Cap to pressure melting which would allow for basal sliding and instability. Furthermore, it is shown that the temperature changes during a surge are negligible. The numerical examples analyzed and presented indicate the appropriateness of the analytical modelling and versatility of the finite element method for incorporating complex material properties and boundary conditions.

abstract: Doctor of Philosophy (PhD)


title: The Magnetic Properties of the Series R₂V₂O₇ ; R= Lu, Yb, Tm

contributor:
Greedan, J.E.
Chemistry

subject: Chemistry Chemistry

abstract: The magnetic behaviour of a series of pyrochlores R₂V₂O₇ (R= Lu, Yb, Tm) has been studied. They are all ferromagnetic below 70K, with the exchange interactions between vanadium atoms providing the driving force for the ordering. While the rare-earths, Yb(+3) and Tm(+3), remain paramagnetic down to 4K, an exchange field created by vanadium atoms causes the rare-earth and vanadium moments to align parallel. This positive exchange coupling is unusual. The low saturation magnetizations of Yb₂V₂O₇ and Tm₂V₂O₇ have been attributed to the effects, on the rare-earth ions, of the crystalline electric field.

abstract: Doctor of Philosophy (PhD)


title: Jacques Maritain's Social Critique and His Personalism

contributor:
Vallée, Gérard
Religious Studies

subject: Religion Religion

abstract: The purpose of this study is to show the attunement of Jacques Maritain's social thought to the concrete circumstances of the twentieth century, by explaining how the influence of his critical analysis of modern theory and praxis helped determine the development of his personalism as personalist democracy, i.e. as a prescription for action in the world of today. Previous interpretations of Maritain's social thought have failed to delineate the intention of his project and the questions with which he himself was concerned. Often these interpretations either tend to discuss Maritain exclusively in terms of his allegiance to the Thomist tradition, thereby inviting the accusation that his social thought is exclusivist and anachronistic, or they tend to acknowledge the contemporaneity of his social thought without a proper understanding of his commitment to the past, thereby prompting the criticism that Maritain's social thought is the unrealistic contrivance of a duplicitous mind. The purpose of this study is to point to Maritain's relevance as a contemporary thinker, by directing attention to the questions behind his social thought and to the fundamental purpose of that thought. The influence of Maritain's social critique on the development of his personalism enables us to see both the intention of his social thought and the questions which engendered it. Maritain's social critique emerged from his encounter with the exigencies of the current historical situation. Having experienced modern man's egocentrism, evident in the bourgeois world of the Third Republic in France and later in the aspirations of the totalitarian regimes which brought about the Second World War, end having studied the philosophical basis of ego-centrism in contemporary thought, Maritain was concerned with the question of how to overcome modern man's preoccupation with the self. In addition to this negative appraisal of modernity, he came to appreciate the constructive influence of modern man's acknowledgment of human rights and the attempt to establish democratic forms of polity. Having experienced the intellectual stability and social cohesion evident in Thomism and the Church, and having discovered the basis for this unity in the transcendent orientation of the past; he asked how modern man's quest for autonomy and self fulfillment can be brought into harmony with man's earlier transcendent orientation. The intention of Maritain's social thought was to bring about this harmony through personalist democracy. Maritain's personalism is therefore co-determined by his experience in the world of today and by his intellectual heritage. Personalist democracy is thus a relevant or historically responsible position. The proper understanding of Maritain's intention to bring about harmony between traditional modes of transcendence and the current search for autonomy dispels much of the criticism directed against him. However, there still remains a pronounced generality and abstraction in his social project, indicating the necessity for the further theoretical and practical adjustment of his fundamental purpose. For this reason, both the strength and the weakness of Maritain's position are said to reside in his professed intention to harmonize transcendence and autonomy, for he thereby exhibits his attunement to the exigencies of the present situation while failing, through the immensity of his project, to attend to fine details as demanded by cautious scholarship.

abstract: Doctor of Philosophy (PhD)


title: A Field Study of the Acoustical Insulation of Residential Construction

contributor:
Hall, F.L.
Civil Engineering

subject:
Civil Engineering
Civil Engineering

abstract:
The angle of incidence is a major variable for calculating transmission loss from field data [A.S.T.M 336-77]. This suggests that the acoustical insulation of residential construction may vary with the relative location of the flight paths and the housing. Alternatively, the Central Mortgage and Housing Corporation assumes in its guideline that the number of reflected paths in normal residential areas is so great as to override any such effect.

The first objective of this study is to investigate the effect of the angle of incidence on the acoustical insulation in residential construction. The second objective is to compare the acoustical insulation as calculated from field transmission loss data with the one estimated in the C.M.H.C. guideline.

Field transmission loss data were collected for each one-third octave band for 30 rooms in the Toronto airport area. The first objective is studied using data from rooms affected by aircraft noise, where the flight path is perpendicular to the place defined by the element of interest, as well as from rooms affected by road traffic noise. The variation of the acoustical insulation over time is studied. The results suggest that there is a noticeable effect of the angle of incidence for the houses exposed to aircraft noise. The second objective is studied using data from rooms affected by aircraft noise. The acoustical insulation estimated by C.M.H.C. is found to be lower than the one calculated from field transmission loss data.

abstract: Master of Engineering (ME)