McGill University Thèses et mémoires par auteur commençant par T

Mayo, Nancy (Supervisor2)  Read more

La croissance et la plasticité synaptiques sont des éléments critiques pour le bon fonctionnement du cerveau, et participent aux processus de la mémoire et l'apprentissage. Le but de nos recherches est d'identifier et de caractériser les mécanismes moléculaires qui sous-tendent le règlement de la plasticité synaptique morphologique ainsi que fonctionnelle. À cette fin, nous avons élaboré un crible d'augmentation-de-fonction génétique dont le but était d'identifier de nouveaux régulateurs de croissance synaptique, en utilisant la jonction neuromusculaire (JNM) larvaire de la mouche drosophile (Drosophila melanogaster) comme synapse modèle. Grâce à ce crible, nous avons identifié un groupe de microARN (miARN) bien …  Read more

"Group home atmosphere was heitherto remained a clinical concept of the changeable social phenomenon ob­served in various types of group homes. In terms of an initial conceptualization, it was a qualitative amalgram of physical, personal and affective influences of place and people in the home. An attempt was made to opera­tionalize this concept using research procedures based upon the assumption that the more cohesive the group home, the more constructive the atmosphere. The focus of this study was a comparison between four Summerhill Homes of Montreal, two for boys and two for girls, which were categorized either as more or …  Read more

RFIC's are traditionally implemented in III--V compounded semiconductors or in bipolar technologies, due to their superior RF performances (e.g. low noise) when compared to CMOS technologies. The challenges are not only to design RF transceivers in standard CMOS processes, but also to establish design methodologies and optimization techniques for their building blocks. This thesis is concerned with one of the key building blocks, namely the Low Noise Amplifier (LNA). Several low-voltage LNA's were successfully implemented in a standard 0.18 mum CMOS technology, operating in the 5--9 GHz frequency band, targeted for future wireless applications. A new and very simple gain …  Read more

That some kind of network plays a central role in the rheology of high molecular weight, amorphous polymers is inferred from such phenomena as a change in the slope of the curve of viscosity versus molecular weight and the plateau in the stress relaxation curve. However, these data give no explicit information about the rates of network destruction and reformation. A new method which involves the reduction in shear rate in transient shearing flow was used to obtain such network kinetics information for three polyethylene melts at 170(DEGREES)C. Other methods of characterization have also been used. These include steady simple …  Read more

Les récepteurs nucléaires sont des facteurs de transcription qui, suite à différents stimuli physiologiques, contrôlent des processus moléculaires variés en modulant l'expression de leurs gènes cibles. Le récepteur ERRα (Estrogen-related receptor) est considéré comme un récepteur orphelin, car jusqu'à présent aucun ligand pour ce récepteur n'a été identifié. Par conséquent, les différents stress affectant la voie d'ERRα modifie son activité via des modifications post-traductionnelles ou en changeant l'activité de ses corégulateurs. La modification O-GlcNac est unique à la voie biosynthétique hexosamines glucose-dépendante et plusieurs auteurs suggèrent qu'elle sert de « senseur nutritionnel » de la cellule. Dans le présent mémoire, …  Read more

The existing literature on adaptation to childhood cancer is integrated within the stress and coping paradigm (Lazarus & Folkman, 1984) to demonstrate its functional utility. The coping resources (i.e. psychological and social resources) and coping efforts of 21 children (9 male, 12 female) diagnosed with cancer were assessed and compared with standardized norms. Within-group differences were explored as the cancer sample was subdivided by stage of therapy (i) newly diagnosed, (ii) currently in treatment, and (iii) off treatment. Results suggest that children with cancer differed significantly from typical children on measures of coping effort (Coping Inventory) in that they demonstrated …  Read more

Morphological and clinical signs of lumbar intervertebral disc disruption are pronounced in the posterior and postero-lateral inner annulus fibrosus. The regional intervertebral disc predisposition to disruption suggests that intradiscal stresses and strains may also be region specific and possibly initiate the disruption. Quantitative data describing intradiscal deformations have been limited to the mid-sagittal plane using techniques that compromise the intervertebral disc integrity. No experimental study has quantified intradiscal strain patterns. The initial objectives of the present work were to use experimental cadaveric methods and finite element techniques to develop and validate methods of measuring intradiscal deformations and strains along the …  Read more

The author quantified the initial stability provided by five different anterior interbody fusion implants. Multi-segmental cadaveric specimens were tested intact in axial rotation, flexion/extension and lateral bending. Tests were repeated for an L3/4 instrumented intervertebral disc space using one of five different implants. Mechanical testing was concluded with an anterior implant pull-out. Changes in neutral zone, range of motion and stiffness were analyzed. None of the tested implants managed to achieve a neutral zone decrease compared to intact, suggesting that interbody implants fail to eliminate micromotion at the bone-implant interface. However, implants were effective in reducing range of motion and …  Read more

A stable transferred arc was produced with plasmagas containing up to 20 percent molar TiCl$ sb4$ in argon, helium and argon/hydrogen mixtures. This was achieved by replacing the commonly-used thoriated tungsten cathode tip with a tantalum carbide tip. Thus, corrosive reactions at the cathode surface, which were shown to be the cause of the observed instability, were prevented. This allowed the characteristics of stable titanium tetrachloride plasmas in a transferred arc reactor to be investigated. Furthermore, an investigation was conducted into the feasibility of collecting titanium metal from the dissociated TiCl$ sb4$ molecule in the plasmagas. The titanium metal was …  Read more

Ogilvie, Kelvin (Supervisor)  Read more

The performance of a device, for certain design parameters, can be modeled using finite element analysis (FEA); however, this can be computationally complex and time consuming. But because this performance can be modeled as a continuous function over the parameter ranges, it is efficient to combine FEA with interpolation to rapidly estimate the performance for any variables. While there exists many interpolation techniques, FEA can provide sensitivities at little extra cost, so these methods should take advantage of this information. In this thesis, a new adaptive interpolation scheme is proposed which uses radial basis functions (multiquadrics) while making use of …  Read more

Chronic pain, defined as pain persisting for three or more months, is a multifactorial problem with a heterogeneous genetic architecture and diverse phenotypic expressions, including chronic musculoskeletal pain (CMSKP). Individuals with chronic pain often present with comorbidities, most commonly psychiatric disorders, cardiovascular conditions, and autoimmune diseases. Standard genome-wide association (GWA) studies typically focus on single phenotypes, potentially overlooking shared genetic and comorbidity patterns. To address this limitation, we explored the application of Graph-Embedded Topic Modeling (GETM) (Wang et al., iScience 2022) to UK Biobank self-reported non-cancer conditions, medications, and hospital-derived ICD-10 codes to identify latent comorbidity patterns. Using data from …  Read more

Raymond, Martine (Internal/Supervisor)  Read more

Aujourd'hui le problème du changement climatique lié à l'utilisation de combustibles fossiles est complexe et décisif pour tout le genre humain. En 1997, trois mécanismes de flexibilité ont été introduits par le Protocol de Kyoto. Parmis eux, le commerce des émissions a effet de serre est le plus proche des lois du marché, c'est pourquoi la tendance dominante est de supporter ce mécanisme pour résoudre les problèmes environementaux liés au changement climatique. Cependant de nombreux pays se questionnent sur les risques que pourraient provoquer ces transactions financières. Ils n'ont donc toujours pas inclus ce mecanisme dans leurs politiques environementales.En 2008, …  Read more

Les protéines ont des fonctions différentes dans une cellule comme un soutien structurel, une activité enzymatique, une voie de signalisation et un transport de fret. L'interaction binaire de protéines signale souvent des fonctions biologiques qui sont communes entre les deux partenaires. Toutefois, les interactions entre deux protéines dans le contexte de complexes multi-protéiques présentent une gamme plus complète de fonctionnalités dans le temps et l'espace. Notre objectif est de comprendre comment les complexes protéiques se manifestent dans différentes conditions spatiales et temporelles, comment ils réagissent aux entrées de signalisation, et quelles protéines agissent comme des échafaudages.Le développement et le raffinement …  Read more

Hasegawa, Robert (Supervisor1)  Read more

This thesis explores the topic of solidarity as understood in political theory and Hegelian thought, building on Rahel Jaeggi’s work on solidarity as cooperation. Across various works, analyses of solidarity frequently situate it as a matter of abstract moral obligation or universal human rights. Focusing on the question of why solidarity matters at all, I suggest that there exist possibilities in the Hegelian tradition of modern political philosophy that merits careful attention. Drawing on this tradition, I argue that support for liberatory struggles is intrinsically valuable in ways that abstract claims for universal human rights do not capture. I further …  Read more

Previous studies have shown the presence of L-idopyranosyluronic acid in heparin. This thesis describes the syntheses and properties of some uronic acid derivatives as model substances for studies of the proton magnetic resonance spectra, molecular rotation and colour reactions of heparin.  Read more

The Internet is becoming a widely used medium for communications and electronic commerce. However, in the current state of the Internet, user applications need to be installed to ensure that these kinds of communications are kept confidential and private. The long term solution is to use IPv6, the new Internet Protocol, which incorporates authentication and encryption in the lower part of the network layers, but until then there are higher level protocol such as SSL and SSH, to name a few. In this thesis, a general problem that can be used to "hack" into computer systems is outlined. This is …  Read more

The separation bubble at the leading edge of a thin sharp-edged aerofoil in steady, incompressible and two-dimensional flow was studied. A simple method, using irrotational flow and source singularities, has been developed for predicting bubble reattachment length, drag and lift. For a flat-plate aerofoil predictions compare favourably with new experiments. The non-dimensional reattachment length $x sb R over rm c$ is proportional to the square of the incidence $( alpha)$ and the slope $x sb R over rm c alpha sp2$ depends on the growth of the outer part of the separated shear layer. The value of the term $x …  Read more

The biocatalytic activity of mushroom tyrosinase was optimized in chloroform medium, using five selected phenolic substrates, including catechin (CT), vanillin (VA), chlorogenic acid (CA), p-aminophenol (pAP) and hydroquinone (HQ). The specific activity (SA) of tyrosinase determined as the change in absorbance at the selected wavelength per $ mu$g protein per sec ($ delta$A/$ mu$g protein/sec) in chloroform was much higher than that obtained in aqueous media. The optimal amount of enzymatic protein for tyrosinase biocatalysis in chloroform was found to be 44.0 mg protein/L for CT and VA, 31.6, 180.5 and 90.3 mg protein/L, respectively, for CA, pAP and HQ. …  Read more

Colonic mucins bind to the E. histolytica Gal/GalNAc adherence lectin and inhibit amoebic adherence to and lysis of epithelial cells. High $M sb{ rm r}$ rat colonic mucins isolated from Sepharose 4B and subfractionated by Cellex-E (ECTEOLA) ion-exchange chromatography demonstrated a minor neutral and a major acidic species with distinct amino acid composition and immunogenicity. Virulent E. histolytica trophozoites elicited a generalized secretory response of both neutral and acidic mucin species which was confirmed by thin-section histochemistry. Such activity may function to deplete the host's protective layer to facilitate invasion. In rats immunized against E. histolytica, enhanced mucin secretion was …  Read more

Rosenzweig, Derek (Supervisor1)  Read more

Little is known about the pathway leading from a stressful stimulus such as hyperthermia or cadmium to a malformation, and the possibility of the heat shock response being linked to this phenomenon prompted the studies in this thesis. In order to determine the relationship between the ability of heat or cadmium to induce a heat shock response and the ability of these stressors to induce abnormal embryogenesis, rat embryos were cultured during organogenesis and the steady-state mRNAs of two heat shock proteins were used as indicators of the stress response in these embryos. The extent of mRNA accumulation for each …  Read more

More than half of mammalian genes express alternative polyadenylation (APA) transcript isoforms that differ solely in the 3’ untranslated regions (3’UTRs) by utilizing alternative poly(A) signals (PASs). This thesis investigates the regulation of APA, as well as its impact on transcript stability and expression across mammalian cell lines and mouse cancer model systems. The functions of 3’UTRs arise from the dynamic interplay between their encoded cis-regulatory elements and a diverse network of RNA-binding proteins, microRNAs, and their effectors. Inclusion and exclusion of cis-regulatory elements through APA can thus have a broad impact on post-transcriptional regulation of mRNA stability, translatability, and …  Read more

We study machine learning for remote sensing when few labels are available. Low-label regimes are common in remote sensing, where maps encompass large spatial areas but many domains require in-situ labels which can be difficult or impossible to access. A common approach to developing algorithms which perform well even with few labels consists of starting from methods developed for computer vision, and applying them to remote sensing; as a consequence, it is typical to treat remote sensing data like natural imagery (i.e. single timestep RGB imagery). This approach fails to capture some of the rich attributes of remote sensing data, …  Read more

A novel S1 nuclease mapping method was devised to measure the efficiency and sites of transcription termination in vivo by RNA polymerase II on polyomavirus DNA. To determine termination efficiency, pulse-labeled nuclear RNA was hybridized with a DNA fragment which spans the transcription initiation region. Since polyomavirus DNA is circular, any RNA polymerases which do not terminate transcription will traverse the entire genome and pass through the initiation region again. Hybrids were treated with ribonuclease, bound to nitrocellullose filters, eluted from the filters by degrading single-stranded DNA with S1 nuclease, and analyzed by gel electrophoresis. The results show that about …  Read more

Background: Accumulating evidence indicates that exposure to urban air pollution can reduce cognitive abilities in children and adults, and increase risk of dementia. Less understood is whether exposure to household air pollution emitted from solid fuel (i.e., coal and biomass) burning is also associated with reduced cognitive function. Almost half (49%) of the world’s population, including over 450 million Chinese, live in homes that cook and space heat with highly-polluting solid fuel stoves. Methods: Among 401 peri-urban adults in northern China (mean age=62.5 y, 58% women) enrolled in the INTERMAP China Prospective (ICP) study, exposure to household air pollution was …  Read more

Extracellular vesicles (EVs) are oval membrane-bound structures that play important roles in intercellular communication by transporting their contents between cells over short and long distances. EVs have been shown to carry highly diverse molecular cargo including oncoproteins, transcripts and non-coding RNAs, as well as oncogenic genomic sequences with mutated DNA (gDNA). Indeed, the genesis and roles of EV-associated gDNA in cellular communication and liquid biopsy remain presently unexplained. This thesis characterizes various factors that influence the release of gDNA from cancer cells bearing specific oncogenic mutations. Our results show that H-RAS-dependent oncogenic insult results in spontaneous formation of micronuclei enriched …  Read more

The phenomenon of selective retention of cations from aqueous solutions by microbial biomass has been termed biosorption. Samples of waste microbial biomass, originating from industrial fermentations and biological waste water treatment plants, have been tested for their uranium and thorium biosorption potential. Optimum biosorption conditions have been identified. Rhizopus arrhizus was identified as the biomass presenting the highest U or Th uptake capacity, in excess of 170 mg/g. The effect of solution co-ions (namely Fe('+2), Zn('+2)) on the equilibrium biosorptive uptake capacity of Rhizopus arrhizus has been examined. The study of the rapid kinetics of U and Th biosorption has …  Read more

The relationships between parasitic infections, environmental and living conditions, and health outcomes were studied in subdivisions of lower (LSES) and higher (HSES) socio-economic status Lubumbashi, Zaire. The two LSES subdivisions had higher prevalences of Plasmodium infection and higher rates of stunting, abdominal pain and low packed cell volume (PCV) than the HSES subdivision. The prevalence and intensity of Ascaris lumbricoides and Trichuris trichiura was not associated with socio-economic status. Maternal education was a significant predictor of A. lumbricoides intensity in both LSES and HSES subdivisions. Factors related to poor sanitation were risk factors for A. lumbricoides in LSES subdivisions, whereas …  Read more

Many questions of interest in various fields ranging from machine learning to computational biology and finance require the solution of an optimization problem. Frequently such problems are classified as large scale in the sense that they involve complex computations over very large datasets. The increasing interest in distributed optimization algorithms is motivated by two main reasons. First, the problem complexity pushes today's processors to their limits and the need for distributed algorithms arises quite naturally. A second and more practical reason is that sometimes the data is collected in a distributed manner and transmitting it to a single location is …  Read more

Dans cette thèse, nous explorons certains aspects universels des Théories Conformes des Champs (TCCs) compactes et unitaires avec une charge centrale c. Nous commençons avec l'observation que les TCCs en deux dimensions possèdent une infinité de charges centrales commutantes, nommées charges quantiques de KdV, qui sont construites à partir du tenseur de stress-énergie. Nous étudions la fonction de partition de l’Ensemble de Gibbs Généralisé (EGG) dans différentes limites. À charge centrale et température finies, nous trouvons de manière perturbative dans le potentiel chimique que la fonction de partition de l’EGG devient une somme d’opérateurs différentiels quasi-modulaires d’ordres appropriés agissant sur …  Read more

Dans cette thèse, nous étudions les conséquences de définir des Théories Conformes des Champs (CFTs) en deux dimensions sur une surface non-orientable ainsi que leurs duals gravitationnels en trois dimensions décrits par la correspondance AdS/CFT. Nous nous concentrons en particulier sur les Modèles Minimaux, des théories conformes qui décrivent de manière conjecturale des théories gravitationnelles dans un régime hautement quantique. La partie la plus importante de ce travail est les résultats non-triviaux que nous fournissons par rapport aux constantes de normalisation des fonctions de corrélation à un point pour les modèles de Ising et Tricritique de Ising sur plan projectif …  Read more

La stéatose hépatique associée à un dysfonctionnement métabolique (MASLD) est devenue un problème de santé de plus en plus préoccupant au cours des dernières décennies. Sa principale caractéristique est l'accumulation excessive de graisse dans le foie, qui peut ne provoquer aucun symptôme. Elle était autrefois appelée stéatose hépatique non alcoolique (NAFLD). Elle commence par une stéatose hépatique silencieuse et sans danger, puis évolue vers une stéatohépatite associée à un dysfonctionnement métabolique (MASH), qui s'accompagne généralement d'une fibrose et de lésions des cellules hépatiques pouvant entraîner des affections graves et irréversibles, telles que la cirrhose et le carcinome hépatocellulaire (CHC). Il …  Read more

The author proved independently, every 2-tough graph is hamiltonian (3), that if G is a K-tough graph with n vertices and if kn is even then G has a k-factor (4) is best possible by showing that for every positive integer k and for every positive $ varepsilon$ there is a (k-$ varepsilon$)-tough graph G with no k-factor; furthermore, if k is odd then G can be made to have an even number of vertices; this result makes chapter 1 of the present thesis. Enomoto elaborated further on the subject and gave two results, in (4) and (5) respectively, which …  Read more

Maloney, Alexander (Internal/Cosupervisor2)  Read more

In standard supervised machine learning, it is necessary to provide a label for every input in the data. While raw data in many application domains is easily obtainable on the Internet, manual labelling of this data is prohibitively expensive. To circumvent this issue, contrastive learning methods produce low-dimensional vector representations (also called features) of high-dimensional inputs on large unlabelled datasets. This is done by training with a contrastive loss function, which enforces that similar inputs have high inner product and dissimilar inputs have low inner product in the feature space. Rather than annotating each input individually, it suffices to define …  Read more

The reactions $ gamma gamma$ $ to$ 2$ pi sp+2 pi sp-2 pi sp0$ and $ gamma gamma to pi sp+ pi sp- pi sp0 pi sp0$ have been studied by using the ARGUS detector at the $e sp+e sp-$ storage ring DORIS II at DESY. In the $2 pi sp+2 pi sp-2 pi sp0$ final state the production of $ omega$-mesons is observed and in particular the reaction $ gamma gamma$ $ to$ $ omega omega$ is seen for the first time. The cross section for $ gamma gamma to omega omega$ is found to have an enhancement at …  Read more

Microbiome research has expanded rapidly over the last 15 years, revealing links between microbial communities and human health. Most studies, however, still rely on association-based analyses of observational data, limiting the ability to draw robust etiological conclusions. Integrating modern causal inference paradigms provides a structured approach to move beyond description, quantify intervention-relevant effects, and address challenges posed by high-dimensional, interdependent microbiome data. This doctoral work aimed to adapt established causal inference frameworks to strengthen causal interpretation in microbiome research.The thesis comprises four projects evaluating current methodological practices and establishing a framework for systematic application of causal inference. First, a systematic …  Read more