VictorJuiz/thesis huggingface dataset:
Misclassification of exposure, coffee as a surrogate for caffeine and methylxanthine intake

This cross-sectional study obtained, by mail, 481 self-administered questionnaires from a sample of men and women aged 30-75 years from Southern Ontario. Questions were designed to assess daily and lifetime intake of coffee, caffeine and methylxanthine (MTX) in foods, beverages and medications. Exposure estimates were used to determine misclassification which occurs when coffee is used as a surrogate measure for caffeine and MTX consumption. The effect of misclassification was studied in two ways: preselecting odds ratios (ORs) by constructing a hypothetical case-control distribution, and "correcting" OR estimates reported in the literature. The kappa statistic revealed coffee as a poor measure of caffeine and MTX intake for daily and lifetime intake. OR corrections for multiple levels of exposure showed that using coffee as a surrogate measure for caffeine would mask any true association regardless of age, sex, and dose-response for daily and lifetime exposures.
Enhancement of the interfacial transfer of iodine by chemical reaction

Enhancement of the interfacial transfer of iodine by chemical reaction was studied by developing a mechanistic model to simulate the interfacial transfer of iodine, and then testing the model experimentally. The reactions considered were those of iodine with thiosulphate, iodide, and hydroxide ions and radiolytic reactions. Two separate systems were studied; one for evaporation and one for absorption of iodine. It was found that impingement had a significant effect on interfacial transfer, promoting absorption into solution and impeding evaporation from solution. Also, the overall mass transfer coefficient of iodine was dependent upon the concentration of I$\sb2$(g) in the system and/or the equilibrium constant of the reaction, depending on the reaction involved. As well, radiolytic reactions enhanced the interfacial transfer of iodine, and the degree of enhancement was dependent upon the dose rate of the radiation field present and the pH of the solution.
The population dynamics and reproductive tactics of yellow perch (Perca flavescens) and white perch (Morone americana) in western Lake Erie

Commercial catch per unit effort statistics in the west and west central basins of Lake Erie indicate that yellow perch (Perca flavescens) populations have been declining from the 1970s to present, and particularly since 1988, as a result of poor recruitment. The first chapter of this thesis tested the hypothesis that white perch (Morone americana) may limit the success of yellow perch through competition. Variations in the abundance of adult and young-of-the-year white perch did not relate to changes in recruitment or growth of yellow perch. The hypothesis considered in the second chapter was that yellow perch are spawn intermittently whereas white perch are obligate annual spawners. Female yellow perch may skip spawning events when energy is limiting, while white perch females adjust their reproductive effort to their energetic condition. The growth dynamics of mature female yellow perch suggest that intermittent reproduction occurs in Lake Erie.
Evaluating the Surgical Scientist Program, an examination of the satisfaction and careers of research trainees

Programs have been implemented to provide clinicians with research training. This study sought (1) to describe a research training experience from the trainees' perspective and to assess their satisfaction with it; and, (2) to compare the careers of the graduates (SSPPs) of one program with those of research trainees (SSPNPs) who did not participate in it. Two questionnaires were developed using focused interviews. These questionnaires were mailed to 269 clinicians and the results for the SSPPs and SSPNPs compared. Overall response rates of 61.7% (N = 166) for the questionnaire addressing satisfaction and 55.8% (N = 110) for the questionnaire examining graduates' careers were achieved. Trainees reported being satisfied with their research training experience. Suggestions are provided for improvements in the delivery of the program. SSPPs did not differ significantly from SSPNPs on three career indicators (publications, presentations, funding). SSPNPs moved more quickly through academics ranks than did SSPPs in their current institution.
Role of glutathione S-transferases in the resistance of human colon cancer cell lines to doxorubicin

Doxorubicin (Dox) is effective in many types of cancer but has little activity against colorectal cancers. It is hypothesized that this is due to a multifactorial resistance mechanism in which the glutathione S-transferases (GST) may play a role. We have studied the relationship between GST isozyme expression, catalytic activity and Dox resistance in four human colon adenocarcinoma cell lines (HT-29, LoVo, SW620 & Caco-2) with the goal of modulating GST activity to overcome drug resistance. Levels of multidrug resistance associated protein (MRP) and P-glycoprotein (Pgp) were also determined. No relationship was observed between GST Pi expression and Dox resistance. A highly Dox-resistant cell line (Caco-2) showed a unique GST Alpha immunoreactivity not detectable in the other cell lines. GST class-selective inhibitors were not able to potentiate the cytotoxic effects of Dox in these colon carcinoma cell lines. The limited or absent expression of Pgp and MRP could not account for the 1,000-fold range of Dox sensitivities across the four cell lines.
Transient evoked otoacoustic emissions elicited by bone-conducted ultrasonic stimuli

The ear's ability to generate sounds was first postulated 50 years ago. Twenty years ago Otoacoustic Emissions (OAEs), as these signals are now being called, were recorded using a sensitive microphone inserted in the ear canal. Due to their clinical investigation potential, growing attention has been given to Otoacoustic Emissions elicited by tones or clicks (TEOAEs). The phenomenon of ultrasonic hearing is even more intriguing. When signals are presented via bone conduction, normal hearing subjects can detect tones as high in frequency as 100 kHz. Significant evidence indicate that the cochlea is the most probable candidate as an ultrasonic receiver. We postulated that it was possible to elicit TEOAEs with ultrasonic stimulation. To study this, we developed new equipment and a modified investigation technique. We elicited and recorded TEOAEs using 40 kHz, 1 ms long stimuli and studied their main features and the method's potential as a hearing investigation tool.
A simulator for small positron emission tomography cameras

Previous research indicates a need for a dedicated small positron emission tomography (PET) camera for use in animal experiments in radiopharamaceutical developments. This thesis is the creation of a Monte Carlo simulator to be used as a tool in the design of such a camera. The simulator models the physics of PET, such that a variety of source distributions and camera configurations can be simulated and compared. This simulator provides a fast, first-order camera performance comparison, to identify weaknesses and strengths in a camera configuration. The performance of the simulator was validated by comparing it with the actual PET camera at the Clarke Institute. The simulator successfully passed the resolution, scatter, and count rate tests. Future work includes upgrading the simulator to provide in-depth second-order camera performance comparisons.
The strength of angle-ply laminates and composites with misaligned fibres

In the first part of this work, single fibre of E-glass, carbon AS4, Kevlar 49 were embedded normally in epoxy resin and cured at room temperature. The oblique tensile strength of these fibres was measured. A 50% angle, $\phi\sb{\rm h}$, was described. This was the angle of pull at which the fibre breaks at half its normal strength. These 50% angles were $20\sp\circ,\ 30\sp\circ$-40$\sp\circ$, and 45$\sp\circ$ for glass, carbon and Kevlar respectively. Also it was found that Kevlar fibres contributed more strength than carbon and carbon more than glass, if they were used to make random fibre composites. In the second part, the strength of relatively wide angle-ply laminates, ($\pm\phi\rbrack\sb{\rm s},\ \phi = 0\sp\circ$-60$\sp\circ$, with very short gauge-lengths for glass and carbon was studied. These specimens proved to be very much stronger than the results expected based on the Tsai-Hill work. It indicated that the previous theory for tensile strength involved excessive edge effects. This was confirmed by reviewing the results from tests on pressurized tubes. These tubes strength results were an order of magnitude higher than the early laminate test results. So, it can be concluded that design with angle-ply laminates, based on the earlier theory, may be unduly conservative. This work was extended to investigate the effect of test specimen width, 3-100 mm, on the tensile strength of (${\pm}45\sp\circ\rbrack\sb{\rm S}$ laminates. The strength increased monotonically by increasing the width. It again indicated that the previous theories were relevant to edge effects. Also, the relative stiffness has been estimated from the cross head movement. The widest specimen gave the highest stiffness values. The stiffness results suggest that laminate theory for elastic constants may also be influenced by edge effects. So these results indicate that the way is open for much greater use of angle-ply laminates in real structures.
The role and cellular mechanism of protein kinase C in ischemic preconditioning of porcine skeletal muscle against infarction

The objective of this thesis was to investigate the role and cellular mechanism of protein kinase C (PKC) in ischemic preconditioning (IPC) of skeletal muscle against infarction, using the pig latissimus dorsi (LD) muscle flap model. It was observed that the muscle sustained 43 $\pm$ 5% infarction when subjected to 4 h of global ischemia and 24 h of reperfusion. IPC with three cycles of 10 min ischemia/reperfusion reduced the infarction to 25 $\pm$ 3% (p $<$ 0.05). This anti-infarction effect of IPC was mimicked by PKC activators and blocked by PKC inhibitors (p $<$ 0.05) administered prior to the sustained ischemia. In addition, the anti-infarction effect of PKC activators was blocked by an ATP-sensitive K$\sp+$ (K$\rm\sb{ATP})$ channel antagonist (p $<$ 0.05). Immunoblot analysis of muscle biopsies demonstrated presence of nine PKC isoforms, with nPKC$\epsilon$ alone undergoing cytosol to membrane translocation during ischemia following IPC. Furthermore, IPC and preischemic, but not postischemic, PKC activation reduced (p $<$ 0.05) muscle myeloperoxidase activity during reperfusion compared to ischemic controls. Taken together, these observations indicate that PKC plays a central role in the anti-infarction effect of IPC, likely through a PKC-K$\rm\sb{ATP}$ channel-linked signal tranduction pathway.
Biology of the recently introduced pine shoot beetle Tomicus piniperda (L.) (Coleoptera, scolytidae) in Southern Ontario

This study examined the biology of an introduced species, the pine shoot beetle, Tomicus piniperda, in southern Ontario. Timing of spring emergence and colonization occurred in mid- to late-April or early-May, following a similar pattern as found previously in Europe. Emergence of the new generation occurred in late-July (heat sum of 1249.8 degree-days $>$ 0$\sp\circ$C) and the adults fed in the shoots until mid-October. Production per gallery was negatively influenced only at high gallery densities (1996). Brood production was approximately 900-1000 beetles per m$\sp2$. Mortality of the juvenile stages was high (79% in 1996). Gallery density declined with increasing height on a given tree and with increasing tree diameter. Shoots with longer needles and larger diameters were preferred by adult beetles for feeding. The majority of the shoot-feeding by the new generation of beetles occurred in current-year shoots. Results indicate that European information may be used with confidence when creating management protocols.
A randomized, double-blind, placebo-controlled crossover trial of nimodipine for geriatric urge incontinence

This randomized controlled crossover trial evaluated the efficacy of nimodipine for geriatric urge incontinence. Eighty-six participants with irreversible geriatric urge incontinence, who met inclusion criteria were randomized to receive nimodipine, or placebo during the first treatment period. Participants received 30 milligrams of nimodipine twice daily for three weeks, and matched placebo twice daily for three weeks, separated by a two week washout period. The primary outcome was number of incontinent episodes, as measured by self completion of a five day voiding record. Secondary outcomes included questionnaires assessing other urinary symptoms, and the psychosocial impact of urinary incontinence. Seventy-six participants completed the study. There was no significant difference in number of incontinent episodes with nimodipine versus placebo (.03 fewer incontinent episodes with placebo, p =.965, 95% confidence intervals $-$2.7 to 2.7 incontinent episodes over the five day voiding record). Scores on the Incontinence Impact Questionnaire and the American Urologic Association Benign Prostatic Hypertrophy Symptom Score were not significantly different with nimodipine versus placebo (P =.068, and.215, respectively). Based upon the lack of a significant improvement in voiding records, urinary symptom scores, or psychosocial impact of urinary incontinence, nimodipine is ineffective for the treatment of geriatric urge incontinence.
Vascular endothelial and smooth muscle cell apoptosis in vivo and in vitro

Blood flow in the left common carotid arteries of rabbits was reduced following ligation above the thyroid ostium. After 48 hours, the number of non-viable cells detected by in vivo labeling with propidium iodide was above that seen in control vessels. Labeling rates for endothelial (0.16%) and for smooth muscle (0.084%) cells were used to estimate a cell death rate per day of 3% and 1.5% respectively. A role for apoptosis in flow-induced vascular remodeling was suggested since low detection of apoptotic cells was indicative of many cell deaths per day. Labeled nuclei were ovoid or displayed chromatin condensation and clumping, a hallmark of apoptosis. These nuclei were also observed in cultured endothelial cells induced to undergo apoptosis by sphingomyelinase treatment. Therefore, cells may display two distinct nuclear morphologies during apoptosis. Also, the in vitro model of apoptosis was used to demonstrate decreased expression of connexin-43 in apoptotic cells.
Condom use among First Nations people living on-reserve in Ontario

Objective. To describe patterns of condom use among First Nations people living on-reserve in Ontario. Methods. Analysis of secondary data from the Ontario First Nations AIDS and Healthy Lifestyle Survey, a cross-sectional survey of 658 men and women living in eleven reserve communities. Individuals who had sexual intercourse in the last twelve months were included (n = 400). Descriptive statistics and multiple logistic regression were used to analyze condom use in the last twelve months. Results. Eight percent always, 31% sometimes, and 61% never used condoms. Of those who used condoms, 8% used them for sexually transmitted disease (STD) prevention only, 10% used them for birth control only, and 82% used them for both purposes. Multiple logistic regression revealed that age, gender, familiarity with the traditional way of life, having a steady sex partner, number of sex partners, worry about pregnancy, knowledge about HIV, knowing someone with AIDS, and embarrassment obtaining condoms had significant effects on condom use. Conclusions. The results have implications for the promotion of condoms for HIV/STD prevention among First Nations people living on-reserve in Ontario.
Extrapolation of wideband speech from the telephone band

Telephone speech is bandlimited to the frequency range between 300 and 3300 Hz, which compromises its quality. Wideband speech, accommodating frequencies up to 7000 Hz, provides higher quality but at a cost of increased transmission bandwidth. The proposed pseudo-wideband (PWB) speech algorithm regenerates approximations of the bands missing from telephone speech. This is possible because of the strong inter-band correlations which stem from the acoustics of the production apparatus. For this receiver-based algorithm, the improvement in effective bandwidth requires no extra transmission bandwidth, and involves no codec standardization issues. The spectral envelope and spectral detail are deconvolved via linear predictive analysis, and each is mapped independently to its PWB counterpart. The algorithm is based on parametric analysis using a uniform tube tract model, and has good potential for speaker independence. Performance was encouraging for a preliminary investigation, but a more sophisticated acoustic model is desirable for additional quality improvement.
Perceived control and parent-child coercive exchanges, a dynamic systems analysis

To expand on past inquires regarding parent-child coercive exchanges this study adopted a dynamic systems approach. Parent and child were regarded as a self-organizing system, and the emergence of communicative patterns in real time interaction was highlighted. Specifically, this study was designed to explore differences in communicative patterns among parent-child dyads during a stressful situation, and to explore the relation of these differences to both parental and child perceptions of control. Eight parent-preadolescent dyads were videotaped while discussing three topics: (1) a pleasant topic, (2) an unpleasant topic (i.e., stressful situation), (3) a pleasant topic. All verbal utterances were coded for affect and content. Results are consistent with the expectation that the onset of a stressful situation reveals systematic differences in the intensity, timing, and stability of negative parent-child communication patterns, as a function of perceptions of control. The theoretical and clinical implications of these findings are discussed.
Attentional control in children and adolescents after a unilateral temporal-lobe excision for intractable seizures

Attentional control in children and adolescents with unilateral temporal-lobe excisions was examined using two experimental tasks, a lexical-decision and a spatial-cue task, and a standardized vigilance task. Experiment 1 tested healthy adults on the experimental tasks to confirm that the tasks elicited expected response-time differences in valid, neutral, and invalid conditions. Experiment 2 compared the performance of children and adolescents with temporal lesions and controls. Participants with left temporal excisions took longer than controls to reorient their attention after invalid cues compared to neutral or valid cues in the lexical task and they made more errors on each task. Few significant differences were found between either lesion group and controls on reaction-time measures of the spatial or vigilance tasks. The results suggest that a material-specific impairment, as well as a sustained-attention deficit, may result from a left temporal excision in childhood or adolescence.
ELSA, an Internet agent that adapts world wide web pages to users' learning styles

The Experimental Learning Styles Agent (ELSA) dynamically parses specially tagged HTML-like documents and renders them differently based on individual users' learning styles. Normally, these documents are parts of a self-contained learning module. The agent is programmed using the perl programming language and employs an SQL-based back-end for access to user profiles. Appropriately tagged pages (i.e. those with $\langle$ELSA$\rangle$ tags) are dynamically parsed so the resulting page is customized for a particular user's learning style as stored in the database. As the user moves through a learning module on the World Wide Web (WWW), her user profile is updated based on her choices and subsequently requested pages ate parsed according to the updated information. The initial profile of a user is created using a WWW-based form that presents the Inventory of Learning Processes. Each user's profile comprises scores on four scales. The form uses JavaScript to check for valid data.
Subcloning, purification and characterization of the GLY1 gene product of Saccharomyces cerevisiae

In Saccharomyces cerevisiae the inactivation of both the cytosolic and mitochondrial isozymes of serine hydroxymethyltransferase, as well as a third gene, designated GLY1, are necessary to yield glycine auxotrophs. The functional characterization of the GLY1 gene was approached by assaying for threonine aldolase activity catalyzing the conversion of threonine to glycine and acetaldehyde using the GLY1 enzyme purified on a nickel column. In the pursuit of showing that the expression of the GLY1 gene might be up-regulated by threonine and down-regulated by glycine, a yeast shuttle vector in which the promoter and the 5$\sp\prime$ coding region of the GLY1 gene were fused to a reporter gene (Lac Z) was used to transform the yeast strain YM 22 to leucine prototrophy. The transformed yeast cells were grown in the presence and absence of L-threonine in minimal medium. A $\beta$-galactosidase assay was done on the crude extracts. We next examined the hypothesis that GLY1 may be part of the "glyoxylate anaplerotic pathway" coding for an enzyme with a glyoxylate aminotransferase activity. To characterize the possible aminotransferase activity of the GLY1 protein, a yeast shuttle vector containing the entire GLY1 gene sequence was used to transform the ser1 yeast strain to uracil prototrophy. (Abstract shortened by UMI.)
Judging differences between visually textured materials

Observers were asked to compare pairs of natural materials in two ways: ratings of innate overall dissimilarity $(\Delta)$ and ratings of specific dissimilarity according to each of six candidate attributes $(\Delta\sp{A})$ (Lightness, Contrast, Edginess, Coarseness, Directionality and Regularity). Unlike some previous studies, we present the overall dissimilarity task first to avoid possible bias from knowledge of attributes. Multidimensional scalings of $\Delta$ ratings suggest a dimensionality of around four. Dimensionality is also low when the task is identifying materials. It is particularly interesting that cross-validation and redundancy analyses show good agreement for $\Delta$ ratings across observers and texture sets. All six $\Delta\sp{A}$ attributes were significant in accounting for the $\Delta$ ratings, including texture Lightness, a factor not previously examined in the literature. The consistently best predictors were Coarseness and Regularity. Although there was a range where judgements were fairly constant, sufficiently distant viewing or dim lighting reduced dimensionality and Lightness became the important attribute.
A flow cell to study formation potential of pulps

The objectives of this study were to design a flow cell for the study of flowing fibre suspensions and to commission it by comparing the propensity of fibres to flocculate under different conditions for some typical pulps. The flow cell was developed to a design that allowed the capture of optical transmission images of suspensions. These images were analyzed using similar statistical geometric procedures to those applied to radiographs of paper. As expected, measurements revealed the much greater propensity of softwood kraft pulp to flocculate under all conditions, compared with hardwood kraft and TMP furnishes. There appeared to be a tendency for hardwood kraft flocs to be larger and denser than those from TMP. Canadian TMP, alone and in mixtures, tends to be more tolerant of adverse forming conditions than United States TMP.