Molecular dynamics and Monte Carlo simulations are used to study ferroelectric liquid crystals. The effect of molecular shape on the stability and nature of ferroelectric phases is examined. The effect of molecular flatness on the stability of uniaxial nematic liquid crystal phases is studied. Most liquid crystal molecules are elongated and have a degree of flatness. However, most models used in computer simulation of liquid crystals are axially symmetric. A series of molecular dynamics simulations, specially designed to isolate the effects of molecular flatness on liquid crystal phases, are performed. Molecular shape is approximated with a generalization of the Gaussian overlap model [ B. J. Berne and P. Pechukas, J. Chem. Phys. 56, 4213 (1972)]. The form presented here has been extended to include ellipsoidal particles with non-degenerate semi-axes. It is found that small amounts of molecular biaxiality can drive an isotropic to nematic phase transition. Simulations of randomly frozen and dynamically disordered dipolar soft spheres are used to study ferroelectric ordering in spatially amorphous materials. Systems where the dipole moment has 1, 2, and 3 components are considered. It is found that the 1 component (Ising) model has ferroelectric phases. The systems with 2 and 3 dipolar components form disordered phases at low temperatures. A ferroelectric phase diagram is constructed for oblate molecules with point dipoles embedded along the particle symmetry axes. The role of particle shape on the stability of ferroelectric liquid crystals is examined with molecular dynamics simulation. Molecular shape is modeled with the generalized Gaussian overlap. Ferroelectric phases are found in systems with weak (short-ranged) columnar correlations. Systems with long-ranged columnar order are found to be antiferroelectric. It is found that the stability of ferroelectric phase is very sensitive to details of molecular shape, and exists only in small regions of the phase diagram. A more robust model for a ferroelectric liquid crystal is developed. Monte Carlo calculations are used to examine ferroelectric order in fluids of disc-shape particles with embedded dipoles. The dipoles are uniformly distributed over a circular "patch" of finite size, placed in the central plane of the particle. It is shown that such systems may undergo spontaneous polarization to form a stable ferroelectric discotic nematic phase. / Science, Faculty of / Chemistry, Department of / Graduate

Paradoxical results on object-recognition delayed nonmatching-to-sample (DNMS) tasks have been found in monkeys and rats that receive either partial, ischemia-induced hippocampal lesions or complete hippocampal ablation. Ischemia results in severe DNMS impairments, which have been attributed to circumscribed CA1 cell loss. However, ablation studies indicate that the hippocampus plays only a minimal role in the performance of the DNMS task. Two hypotheses have been proposed to account for these discrepant findings (Bachevalier & Mishkin, 1989). First, the "hippocampal interference" hypothesis posits that following ischemia, the partially damaged hippocampus may disrupt activity in extrahippocampal structures that are important for object-recognition memory. Second, previously undetected ischemia-induced extrahippocampal damage may be responsible for the DNMS impairments attributed to CA1 cell loss. To test the "hippocampal interference" hypothesis, the effect of partial NMDAinduced lesions of the dorsal hippocampus were investigated on DNMS performance in rats. These lesions damaged much of the same area, the CA1, as did ischemia; but did so without depriving the entire forebrain of oxygen, thereby reducing the possibility of extrahippocampal damage. In Experiment 1, rats were trained on the DNMS task prior to receiving an NMDA-lesion. Postoperatively, these rats reacquired the nonmatching rule at a rate equivalent to controls and were unimpaired in performance at delays up to 300 s. In Experiment 2, naive rats were given NMDA-lesions and then trained on DNMS. These rats acquired the DNMS rule at a rate equivalent to controls and performed normally at delays up to 300 s. These findings suggest that interference from a partially damaged hippocampus cannot account for the ischemia-induced DNMS impairments and that they are more likely produced by extrahippocampal neuropathology. In Experiment 3, rats from the previous study were tested on the Morris water-maze. Compared to sham-lesioned animals, rats with partial lesions of the dorsal hippocampus were impaired in the acquisition of the water-maze task. Thus, subtotal NMDA-lesions of the hippocampus impaired spatial memory while leaving nonspatial memory intact. Mumby et al. (1992b) suggested that the ischemia-induced extrahippocampal damage underlying the DNMS deficits is mediated or produced by the postischemic hippocampus. To test this idea, preoperatively trained rats in Experiment 4 were subject to cerebral ischemia followed within 1hr by hippocampal aspiration lesions. It was hypothesized that ablation soon after ischemia would block the damage putatively produced by the postischemic hippocampus and thereby prevent the development of postoperative DNMS deficits. Unlike "ischemia-only" rats, the rats with the combined lesion were able to reacquire the nonmatching rule at a normal rate and performed normally at delays up to 300 s. Thus, hippocampectomy soon after ischemia eliminated the pathogenic process that lead to ischemia-induced DNMS deficits. Experiment 5 investigated the role of ischemiainduced CA1 cell death as a factor in the production of extrahippocampal neuropathology. Naive rats were given NMDA-lesions of the dorsal hippocampus followed 3 weeks later by cerebral ischemia. If the ischemia-induced CA1 neurotoxicity is responsible for producing extrahippocampal damage then preischemic ablation should attenuate this process and prevent the development of DNMS impairments. This did not occur: Rats with the combined lesion were as impaired as the "ischemia-only" rats in the acquisition of the DNMS task. This suggests that the ischemia-induced pathogenic processes that result in extrahippocampal neuropathology comprise more than CA1 neurotoxicity. The findings presented in this thesis are consistent with the idea that ischemiainduced DNMS deficits in rats are the result of extrahippocampal damage mediated or produced by the postischemic hippocampus. The discussion focuses on three main points: 1) How might the post-ischemic hippocampus be involved in the production of extrahippocampal neuropathology? 2) In what brain region(s) might this damage be occurring? 3) What anatomical, molecular, or functional neuropathology might ischemia produce in extrahippocampal brain regions? The results are also discussed in terms of a specialized role for the hippocampus in mnemonic functions and the recently emphasized importance of the rhinal cortex in object-recognition memory. / Arts, Faculty of / Psychology, Department of / Graduate

In this paper we consider three topics in reliability and maintenance. Their common feature is the explicit consideration of interdependence, either amongst components within a machine, amongst stages in a logistics chain, or amongst machines sharing maintenance facilities. Chapter 1 examines measures of the contribution of a component towards a system's reliability; these measures include structural importance, marginal reliability importance, joint reliability importance, and link importance. We review these different measures and examine how they relate to each other. We show that some structural results previously derived for independent components continue to hold for associated components. We then propose extensions to each importance measure to cover components which have two failure modes rather than the conventional one, and show that these extensions largely retain the properties of the original definitions. Chapter 2 examines a system containing one machine subject to random failure, for which we wish to determine a maintenance policy and a spare ordering policy. We consider the solvability and desirability of jointly optimizing these two traditionally separate policies. We discuss why the general form of the problem is intractable and show how it might be approached using bounds and heuristic policies; more importantly, we examine several special cases which are more tractable. Particular attention is paid to systems which contain only one spare at a time; we show that these systems have some convexity properties which facilitate cost minimization. We subsequently consider systems which allow more than one spare, but make use of other restrictions or assumptions to simplify analysis. Chapter 3 examines how to coordinate maintenance for machines sharing repair facilities, a task which is commonly called the machine repairman problem. Existing studies of this problem make the restrictive assumption that repairs are performed only after machine failure; our work extends the machine repairman model by allowing preventive repair. We derive analytical results for a single critical age repair policy, and then use numerical studies to investigate other heuristic policies which can improve the system's cost effectiveness. / Business, Sauder School of / Graduate

A mathematical model to predict the through-thickness microstructure and texture changes during hot tandem rolling has been developed for two commercially significant aluminum alloys - AA5182 and AA5052. The model includes a plasticity component to model the temperature and deformation during rolling as well as an interpass component to model the microstructure, texture and temperature changes which occur in the strip between the rolling passes. The plasticity model was developed using a commercial finite element package DEFORM - a 2-D transient Lagrangian model which couples the thermal and deformation phenomena which occur during strip rolling and is able to predict the temperature, strain rate and strain distribution in the strip at any position in the roll bite. The interstand model includes semi-empirical equations describing the microstructure (percent recrystallization and recrystallized grain size) and texture changes occurring in the strip between the rolling passes. The interstand model also includes a temperature module to predict the through-thickness temperature distribution in the strip based on the one-dimensional heat conduction equation which is solved by a finite difference method. The semi-empirical equations used in the interstand model were developed using experimental data for the two alloys. The experimental programme was carried out at Alcan International's Banbury and Kingston Laboratories, as well as at the Atomic Energy of Canada Limited Chalk River Laboratories. The experimental programme involved plane strain compression testing industrial rolled samples of AA5182 and AA5052 aluminum alloys based on a test matrix which covered similar temperature, strain and strain rate conditions as those seen in industrial hot tandem rolling. The samples were given a single deformation and then quenched immediately to preserve the as-deformed structure. The samples were then heat-treated in a salt bath for various lengths of time and the percent recrystallization, recrystallized grain size and texture changes during recrystallization were measured. A temperature compensated time parameter was used to convert the isothermal recrystallization and texture kinetics to non-isothermal applications. Validation of the model using industrial data and samples indicated that it gave reasonable predictions for the temperature, grain size and volume fraction of some of the deformation texture components after recrystallization was completed. However, the model tended to over-estimate the mill loads in the last stands for both the AA5182 and AA5052 alloys and tended to underestimate the amount of cube and S texture in the recrystallized strip. A sensitivity analysis of the process parameters indicated that both the microstructure and texture were most sensitive to the rolling temperature. Indicating the need for good control of temperature during rolling operations as well as accurate temperature predictions for process modelling activities. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A major problem currently facing astrophysics and cosmology is the question of dark matter. Although there is little doubt about the existence of dark matter, there is considerable uncertainty about the abundance and nature of this matter. One possibility is that dark matter consists of weakly interacting massive particles (WIMPs), such as the lightest stable particle in supersymmetry models. Direct detection experiments look for nuclear recoils from WIMPs scattering in a detector. The first generation of direct detection experiments were ultimately limited by radioactive backgrounds. The Cryogenic Dark Matter Search (CDMS) is a direct detection experiment based on novel particle detectors operated at millikelvin temperatures that provide intrinsic background rejection. This capability, however, is not 100% effective. Therefore a low background environment is essential to the experiment. To create such an environment, all possible background sources have been extensively studied both by measuring the background contribution from muons, photons and neutrons and by performing detailed Monte Carlo simulations of the photon and neutron backgrounds. The results of this investigation, as discussed in this thesis, have influenced all aspects of the CDMS experiment. The initial site for the CDMS experiment is the Stanford Underground Facility. The relatively high muon flux at this site due to its shallow depth was balanced against the convenience of a local site with the unlimited access necessary for operating a complicated cryogenic system and developing new detector technology. The cryostat used to house the detectors was designed to accommodate the extensive shielding necessary to reduce the ambient backgrounds to acceptable levels and to minimize the amount of radioactive contamination near the detectors. Simulations and measurements of the local backgrounds led to a layered shield design that consists primarily of plastic scintillators to veto muons, lead and copper to attenuate photons and polyethylene to moderate neutrons. With the background rejection capabilities of the cryogenic detectors and the low background environment created in the Stanford Underground Facility, we expect to extend the current limit on WIMP dark matter by more than an order of magnitude and begin testing models for the lightest supersymmetric particle. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Hematopoiesis is controlled by a dynamic equilibrium between positive and negative growth regulatory signals. Initially, much investigation focused on the positive regulatory signals. The importance of the negative regulators in maintaining the tightly controlled limits on cell numbers seen in vivo is now being appreciated. This thesis describes research into the role of negative regulation in normal and leukemic hematopoiesis. The proteins believed to be responsible for the inhibitory activity of two crude neutrophil preparations, one from patients suffering from chronic myeloid leukemia (CML) and one from normal donors, have been identified. Limited characterization of these activities on normal and leukemic hematopoiesis has also been performed. Previous work in our laboratory described an activity derived from immunoaffinity enriched cell lysates of patients with chronic or acute myeloid leukemia (CML or AML). This material demonstrated significant inhibition of growth of committed progenitor cells (especially CFU-GM) from normal individuals (both human and murine) but did not inhibit equivalent colonies from samples taken from patients with CML. Preliminary attempts to characterize this material (referred to previously as CAMAL) isolated the active constituent to within a 30 to 35 kDa molecular size fraction. Further purification of this activity was undertaken. Using reverse phase high pressure liquid chromatography (rpHPLC) to fractionate the immunoaffinity enriched material, the inhibitory activity was found to elute exclusively in a single rpHPLC fraction corresponding to the leading portion of the peak corresponding to the 29 to 37 kDa serine protease homologue azurocidin/CAP37. The main portion of the azurocidin peak was found to have no inhibitory activity. Two-dimensional gel analysis of the active part of the peak and a reference of azurocidin (isolated from normal azurophilic granules) showed no entity distinct from the higher molecular weight glycoforms of azurocidin. As azurocidin is found within normal neutrophils, we purified this molecule from this source. Only one of six azurocidin preparations from normal donors was found to contain inhibitory activity on normal CFU-GM. Recently, we have devoted our efforts to extend the identification and characterization of a myelopoietic inhibitory activity originally described by Boyum and colleagues from normal neutrophils (147). Using density gradient fractionation of neutrophil lysates, we localized the activity to the cytosol and the specific granules fraction. Using sub-fractionation of granulocytes, ammonium sulfate and heat precipitation coupled with size exclusion and anion exchange chromatography, we have purified the molecule responsible for the inhibitory activity on myeloid progenitors to a single, silver stained band of approximately 15 kDa. Identification of this material as cytidine deaminase (CD) was established by Western blot analysis, the use of recombinant cytidine deaminase and blockage of the inhibitory activity by the known inhibitor of CD activity tetrahydrouridine (THU). Normal human, murine and CML progenitors were equally susceptible to the inhibitory activity of this molecule. In addition the proliferation and clonogenicity of various leukemic cell lines was also inhibited. Interestingly, even at high concentrations (> 60 ng/ml) of pure recombinant CD, no more than a 70% inhibition of myeloid colony formation was seen. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

Anti-sperm monoclonal antibodies (mAbs) were evaluated as biomarkers to assess capacitation, acrosome reaction, cryodamage and fertility of bull spermatozoa in vitro. Three anti-human sperm mAbs crossreacting with bull sperm antigens were identified. They showed time-dependent changes in binding to bull spermatozoa incubated under capacitation conditions when assessed by indirect immunofluorescence, with maximum binding at 4 h. Bull and human sperm antigens recognized by one mAb (HS-11) were isolated and their immunological relatedness shown by ELISA. The possible relationship between fertility and the binding of HS- 11 to bull (n=8) spermatozoa was tested in a bovine in vitro fertilization system. In vitro fertility based on cleavage of oocytes and mAb-binding to spermatozoa at 4 h incubation under capacitation conditions were correlated (r=0.43; n=32; P<0.05), but in vivo fertility and sperm-HS-11 binding were not correlated. In the next set of experiments, 15 mAbs specific to bull sperm antigens were generated. The mAbs were sperm-specific, but not species-specific. The mAbs identified five distinct antigenic domains of bull spermatozoa. Seven of the 13 mAbs tested, recognized bull sperm proteins of >200 kDa in western blots. Three detected more than one protein band (40-200 kDa), while three recognized none. Thirteen of the 15 mAbs were tested for their influence on bovine sperm-zona interactions in vitro. Sperm-zona binding was not affected by 12 mAbs. However, sperm-zona binding in the presence of one surface-reacting mAb was higher than the control (23.6+5.6 vs 10.0+2.4 sperm/zona, mean+SE; P<0.001). Four mAbs specific to intra-acrosomal antigens exhibited a time dependent increase (P<0.05) in binding to bull spermatozoa incubated under capacitation conditions. In contrast, the binding of mAbs specific to surface antigens decreased (P < 0.05) after 4 h incubation in the presence of heparin. Following induced acrosome reaction, a significant decrease (P<0.01) in the binding of acrosome-specific mAbs was observed. Four selected mAbs were then evaluated as possible indicators of cryodamage in frozen-thawed bull spermatozoa. Even though the mAbs showed higher binding to frozen-thawed spermatozoa, there was no conclusive evidence to support the hypothesis that the mAbs will be useful to detect live membrane-damaged spermatozoa. / Land and Food Systems, Faculty of / Graduate

Raman spectroscopy was used to study the protein structure in raw and salted surimi from Pacific whiting, and in gels formed by setting (32°C), cooking (86°C) or setting followed by cooking. The intensity of the peaks assigned to disulfide bond stretching vibrations increased considerably in the cooked and set-cooked gels. A smaller increase was found in the gels that were subject to setting alone. Secondary structure estimation based on the amide I band indicated a change from predominantly a-helical structure in raw surimi to similar proportions of a-helical and anti-parallel p-sheet after setting. A further increase in anti-parallel p-sheet and decrease in a-helix content occurred during the kamaboko stage. The intensity of C-H stretching vibrations of the aliphatic residues decreased after salting, setting and cooking. The set and cooked gel had a better gel strength and fold score than the cooked gel which, in turn, had better properties than the set gel. Response surface methodology was used to determine the optimal setting and cooking time and temperature conditions resulting in a maximized gel strength, fold score and color, (whiteness index), and a minimized gel expressible liquid. Cooking temperature was the variable that had the strongest influence on the gel quality characteristics. Level set programming, a global optimization method, gave essentially the same results as a gradient based optimization method. The results obtained by these two methods were better than those generated by the Simplex technique. Using a formulation composed of pink salmon surimi, salt, whey protein concentrate and wheat starch, an optimal final product, kamaboko sausage, was developed. In addition, when this formulation was applied to herring surimi, the kamaboko obtained had similar gel strength and elasticity as a commercial surimi-based product. The effects of frozen storage conditions of roe herring on its gel making ability (GMA) were investigated. Frozen storage at around -45°C maintained the GMA for seventy days while storage at -83°C further increased the GMA period. The viscous properties of a salmon surimi paste were studied using a rotational viscometer. The paste behaved as a shear thinning fluid with a yield stress that increased with temperature up to 21 °C. Viscosity also increased with temperature up to 21 °C, possibly because of protein-protein interactions. The Theological data were reasonably well represented by a simple model which takes into consideration the effects of both shear rate and temperature. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Some researchers believe that all French immersion students speak the same way and that they make many transfer errors (borrowing English structures). Although these beliefs are not founded on rigorous observations, current teaching strategies emphasize repeating correct patterns rather than teaching according to student's individual differences. My study posed two main questions. First, are there individual differences in the quality of French spoken by French immersion students? Second, do individual differences in cognitive and linguistic processes influence the type and frequency of errors observed in French immersion students' language production? To analyse individual differences in linguistic processes, I used variables from verbal learning theory that measure Paradigmatic and Syntagmatic processes. I analysed differences in cognitive processes with the PASS (Planning, Arousal/Attention, Simultaneous and Successive processes) cognitive theory. PASS is operationalized in the Cognitive Assessment System test (CAS). These theories generated a secondary purpose for the study: to verify and explain the findings of Jarman's (1980) study concerning the parallelism between Paradigmatic and Simultaneous processes, and between Syntagmatic and Successive processes. Data came from 89 girls and 63 boys from anglophone families in grade three French immersion schools in British Columbia. I analysed four areas of individual differences (Paradigmatic and Syntagmatic processes; Simultaneous and Successive processes; Planning; and Attention), and the relationship between these processes with Vocabulary, Grammar, and Transfer Errors in oral and written French language production. LISREL measurement models did not converge due to variables' low correlation. Relationships between the variables were not found probably because of low reliabilities of the CAS measures. A subsequent analysis used observed variables' models (multiple regressions), rather than latent variables' models. The strongest relation was between Planning and Attention, and Transfer Errors. Grammar Errors, rather than Transfer Errors prevailed. Consequently, I suggested teaching methods reinforcing communicative sentence structures. As in Jarman (1980), cognitive and linguistic processes were not demonstrably parallel. Contrary to what verbal learning researchers thought, various linguistic processes' measures are not equivalent. Linguistic measures' constraint level as well as Planning level affected my results. For further research, I proposed a model of linguistic tasks of various constraint levels. / Education, Faculty of / Graduate

The primary purpose of the present study was to investigate the joint effects of culture and attribution of outcome feedback on reasoning performance. This study attempted to address four major research questions: (a) Do Canadian and Chinese students have different cultural values and causal attribution patterns? (b) Do pre-experimental individual differences in causal attribution patterns lead to differences in Canadian and Chinese students' inductive reasoning performance? (c) Does attribution of outcome feedback affect Canadian and Chinese students' inductive reasoning performance? (d) Do Canadian and Chinese students conduct deductive reasoning differently as a function of outcome feedback and reasoning task contents? A total of 120 college students (60 Canadian and 60 Chinese) performed three phases of computerized experimental tasks. The research design involved 2 types of culture groups (Canadian and Chinese) under 3 conditions of outcome feedback (success, failure, and control) as two independent variables. The dependent variables observed were the number of instances used or correct responses made and response time, when possible. In terms of culture differences, Canadian students appear to be distinct and articulate about the matters of socio-cultural values, while Chinese students are relatively less distinct and articulate. When making attribution for other people's success, both Canadian and Chinese students held internal factors (i. e., good effort and high ability) as responsible. When accounting for other people's failure, Canadian students picked controllable factors (i.e., lack of effort), while Chinese students picked both controllable and uncontrollable factors (i.e., largely lack of effort and occasionally difficult task) as the reasons. However, following the success outcome feedback about their own reasoning performance, Canadian students emphasized mostly high ability and, occasionally, effort as the reasons, while Chinese students picked mostly good luck and, occasionally, high ability. Given the failure outcome feedback about their own task performance, Canadian students attributed to lack of effort and bad luck as causes, while Chinese students exclusively picked lack of effort as the explanation. Chinese subjects' inductive and deductive reasoning performances remained relatively unswayed by success or failure outcome feedback, whereas Canadian subjects' reasoning performance remained good only when success feedback was received. When failure feedback was provided, Canadian subjects' reasoning performances deteriorated and remained poor throughout the experiment. While Chinese students' reasoning performance is not predictable from their low-ability attribution of other people's failure outcome, Canadian students' reasoning performance is highly predictable; that is, the more they attributed others' failure to low ability, the faster they completed the culture-fair inductive reasoning task. On the other hand, when making attribution based on their own experience, given success feedback, Canadian students attributed their performance to their high ability. Given failure feedback, Canadian students attributed their performance to their lack of effort, with improved performance commensurable to their verbal causal attribution. The present findings indicate that Canadian and Chinese college students showed differences in causal attribution patterns, depending on when they explain others' success/failure experiences or their own, and further that upon receipt of failure outcome feedback, Canadian students' reasoning performance deteriorated, while Chinese students' performance remained insensitive to success or failure outcome feedback. Further fine-grained analyses of such causal attribution patterns interacting with outcome feedbacks and cognitive performance needs some more careful studies. / Education, Faculty of / Educational and Counselling Psychology, and Special Education (ECPS), Department of / Graduate