McGill University Thèses et mémoires par auteur commençant par N

We propose an approach for representing an object by its constituent parts and their spatial connections. The approach is based on a set of primitive volumes called geons. We utilize the edge-junction graph of an object range image as input. This is a graph whose nodes are the junctions and whose arcs are the edges detected from the range image. The three-dimensional geometrical information at T junctions allows us to group pairs of corresponding T junctions. By following occluding, limb, concave edges and linking pairs of corresponding T junctions, we decompose the edge-junction graph into different subgraphs. Each of these …  Read more

Moodie, Erica (Supervisor2)  Read more

BACKGROUND: Personal health records (PHRs) are tools that allow individuals to access, share and manage their health information online. PHRs have received considerable interest and investment in recent years, because they are thought to have the potential to promote patient self-management and greater involvement in their own care. Despite apparent public interest and a proliferation of available options, adoption rates remain low. There is a gap in our understanding as to why people are choosing to use or not use PHRs, and what different populations of users might want from such a tool. In particular, young adults could be a …  Read more

Arsenault, D. (Supervisor)  Read more

Classical methodologies for carbon-carbon bond formation often require stoichiometric amount of reagent to prefunctionalize a C-H bond. Such methods generate a lot of waste and are therefore not atom-efficient. On the other hand, the use of catalysts for the direct use of C-H bond without prior functionalization is a more desirable approach for carbon-carbon formation. For example, an overall addition reaction is 100% atom economical. This thesis focuses on the catalytic addition of the three types of C-H bonds (Csp-H, Csp2-H and Csp3-H) to unsaturated molecules such as conjugated dienes, imines and carbon dioxide to form heterocycles. The first chapter …  Read more

The field of restorative dentistry and the problem of ultrasonic airframe corrosion in aerospace are introduced as motivation for the construction of a miniature ultrasonic pulser/receiver. A broadly applicable ultrasonic pulser and receiver system is developed. Two pulsers, a 5V square and a 100V spike, and a 52dB amplifier with a 57MHz 6dB bandwidth were constructed as a result. These battery powered devices are tailored for compatibility with a custom built wireless data transmission system, also driven by the same voltage. It is demonstrated that the new pulser/receiver is comparable to the commercial system in performance in certain areas. The …  Read more

Graft copolymers using biodegradable and biocompatible bacterial poly([ R]-3-hydroxybutyrate) blocks were synthesized and tested as biomaterial candidates for orthopaedic surgery applications. Low molecular weight poly([ R]-3-hydroxyalkanoates), namely poly([R]-3-hydroxybutyrate), poly([R]-3-hydroxyvalerate), and their copolymers poly([ R]-3-hydroxybutyrate-co-[R]-3-hydroxyvalerate), were prepared by thermal degradation in the melt at 190°C. The chemical composition of the oligomers was well-defined, featuring the same repeat unit as their high molecular weight analogues, a carboxylic acid end, and an alkenyl end mostly in the trans configuration (crotonate-type). Increase in the reaction temperature, time, or [R]-3-hydroxyvalerate content decreased the molecular weight of the products. Methacrylic macromonomers of PHB were obtained by …  Read more

Immune checkpoint inhibitors (ICIs) have produced significant clinical responses in metastatic melanoma patients, quickly becoming the standard-of-care treatment for this disease. Nevertheless, despite these unprecedented results, a large fraction of melanoma patients still do not benefit from this therapy. Recent whole exome sequencing studies of ICI non-responders have identified mutations in interferon (IFN)γ signaling pathway genes as possible mechanisms of resistance. In support, a number of functional CRISPR screens have identified key regulators of the IFN signaling pathway as ICI resistance genes. IFNs signal through the IFN receptors-JAK-STAT axis to upregulate interferon-stimulated genes (ISGs) that have anti-proliferative, adaptive immune, as …  Read more

Le « Sarrasin » est un personnage archétypal récurrent dans le roman médiéval qui sert souvent de véhicule pour des buts politiques. Les auteurs chrétiens représentaient généralement les Sarrasins comme des convertis volontaires au christianisme, des doubles imitatifs ou des monstres moralement dégénérés. Les romans médiévaux Bevis of Hampton et Emaré (tous deux écrits de manière anonyme), ainsi que Man of Law’s Tale de Chaucer utilisent tous des stratégies rhétoriques similaires dans leurs représentations de la figure sarrasine. Alors que plusieurs de ces tentatives cherchaient à circonscrire les Sarrasins dans un cosmos chrétien, ceux-ci s’échappent de ce confinement et deviennent …  Read more

There are a number of engineering situations where fluid-saturated geological media can be subjected to thermal effects. These include the disposal of heat-emitting nuclear fuel wastes in saturated geological formations, extraction of energy resources such as oil and natural gas by steam injection and the recovery of geothermal energy by ground source heat exchangers. The objective of this thesis is to study the coupled thermal-hydrological-mechanical (T-H-M) response of fractured geological media by the computational implementation of mathematical models. From the generalization of Biot's classical theory of consolidation of a saturated porous elastic medium to include thermal effects, we first derived …  Read more

The morphology of diblock ionomers consisting of non ionic polystyrene blocks and ionic poly(cesium methacrylate), or poly(cesium acrylate), or poly(4-vinylpyridinium methyl iodides) blocks in solution and in the solid state is investigated by small angle x-ray scattering (SAXS). When the polystyrene blocks are kept short, they self-assemble in bulk to form spherical microdomains. Furthermore, the polystyrene segments are highly stretched in the non ionic microdomains, as was also observed previously for the ionic segments of comparable lengths in the ionic microdomains. These findings support the hypothesis that chain extension in microdomains of diblock ionomers in bulk is the result of …  Read more

Meiotic recombination initiates with the introduction of programmed double-stranded breaks (DSBs) in most species. Only a limited number of DSBs are processed into crossovers (COs). In Caenorhabditis elegans (C. elegans), each pair of homologous chromosomes receives only one CO due to CO interference. These obligate COs then manifest as cytologically visible physical attachments called chiasmata, which ensure proper homolog segregation during meiosis I. Previous analyses have revealed that C. elegans ZHP-3 is an ortholog of S. cerevisiae Zip3p and is required for crossover formation (Jantsch et al. 2004). We have identified three additional ZHP-3 (three) paralogs: ZTP-1, ZTP-2 and ZTP-3, …  Read more

Ubiquinone (UQ) is a lipid found in all cellular membranes. It is involved in multiple cellular processes, either directly or through its effect on the redox status of the cell. clk-1 encodes a highly conserved hydroxylase required for UQ biosynthesis. In C. elegans, mutations in clk-1 result in the accumulation of an UQ precursor, DMQ, and a pleiotropic phenotype in the mutants characterized by the slowing down of development, behaviors and aging. Additionally, in the absence of dietary UQ, clk-1 mutants also show a transient growth arrest and are sterile. Mutants that can suppress both sets of phenotypes in the …  Read more

La γ-tubuline est un composant du centre d'organisation des microtubules (COMT) et intervient dans la nucléation des microtubules in vivo. Des études récentes suggèrent que le rôle de la γ-tubuline pourrait s'étendre au-delà de cette fonction. Ainsi, la délétion du domaine DSYL à l'extrémité C-terminale acide et non structurée de Tub4 abolit la voie de positionnement du fuseau mitotique dépendant de Kar9. In vivo, la γ-tubuline est modulée par phosphorylation et le résidu tyrosine 445 est un site de phosphorylation de Tub4. De plus, une mutation phospho-mimétique (tub4-Y445D) provoque des défauts de ségrégation des chromosomes. Nous posons l'hypothèse que le …  Read more

Pare, Anthony W. (Supervisor2)  Read more

The chelating effect on regio- and stereochemical control of the homoallyl alcohol synthesis and electrophilic substitution of allylsilane was studied, using 2,2-dimethyl-1-$ {$1- ((S)-2-(2-methoxyethoxy)methyl) pyrrolidinyl$ }$-2-sila-4-pentene (S1) and 2,2-Dimethyl-1-$ {$1- ((S)-2-hydroxymethyl) pyrrolidinyl$ !$-2-sila-4-pentene (S2), with S1 synthesized from L-Prolinol. The synthesis of homoallyl alcohol was carried out by allyl transformation from S1 and S2 to a Lewis acid activated aldehyde. Chelation between the allylsilyl ligand and the Lewis acid:aldehyde complex was found to favor the cyclic syn-clinal over the acyclic anti-periplanar transition state, in the asymmetric synthesis of the alcohol 1-dodecen-4-ol (P1). The bulky, remote and weak chelating ligand resulted …  Read more

Research has shown that approaching intimate relationships with feelings of insecurity can constrain the perception and memory of interpersonal experiences (Dykas & Cassidy, 2011). Attachment theory (Bowlby, 1969/1982, 1980) put forth that this happens because insecure individuals navigate their relationships guided by memories of previous relational difficulties, which can lead to more defensive and limiting thinking processes. This thesis examined this proposition more closely, and argued that interpersonal memory processing will be limited especially if insecure people tacitly presume that their relational history mirror what they can therefore expect in relationships. Specifically, the present research examined the general hypothesis that …  Read more

Sjogren’s syndrome and radiotherapy for head and neck cancer result in irreversible loss of functional salivary acini; known as xerostomia, for which no adequate treatment is available. Our group has been testing different biomaterials, extracellular matrix proteins, and graft cells for the development of an orally implantable tissue-engineered artificial salivary gland device. However, to be able to achieve this future therapeutic option for xerostomia, we need to be able to provide an available pool of acinar cells for transplantation or engineering of an artificial gland. Therefore, the aim of this thesis was to develop a reproducible protocol to isolate, cultivate …  Read more

Traditional screens for female sterile mutants have revealed only two genes which when mutant, give a fully penetrant 16 nurse cell phenotype. One way to gain a better understanding of the function of these genes in oocyte determination, is to identify genes which interact with them. Using P-element mutagenesis, I have isolated one dominant suppressor and five dominant enhancers of Bicaudal-D, and begun the phenotypic and molecular characterization of three of these genes. By deficiency screening, I have identified two different loci which act as dominant enhancers of Bic-D, and eight different loci which act as dominant suppressors of Bic-D. …  Read more

The experimental investigation of blood flow using in vitro models is very important to derive relevant and quantitative information in order to understand the biomechanical conditions resulting from blood flow dynamics. Furthermore, such studies can help us analyze and evaluate flow disturbances caused by pathologies and by cardiovascular prostheses such as aortic valves and left ventricular assist devices (LVAD). For example, these disturbances can range from high shear flow regions causing blood hemolysis to low shear regions resulting in plaque deposition. Flow visualization studies represent a family of methods to study fluid flow through cardiovascular hydraulic models using blood analogs. …  Read more

Information on the variability of extreme rainfalls in time and in space is of critical importance for many types of hydrologic studies. In addition, in recent years, climate change has been recognized as having a profound impact on the hydrologic cycle at different temporal and spatial scales. The present study is therefore was carried out to develop appropriate methods for improving the accuracy of design rainfall estimation at gauged and ungauged locations in the current climate as well as in the context of climate change. This study can be divided into five primary parts.The first part presents a general procedure …  Read more

Contexte: La tête et le cou sont constitués d'un agencement complexe d'os, de muscles et de voies respiratoires jouant un rôle central dans l'esthétique du visage, la communication, la mastication, la déglutition et la respiration. Comprendre les caractéristiques craniofaciales ainsi que leurs modèles de croissance chez les enfants est essentiel dans le diagnostic orthodontique et la planification du traitement. Rationale: De nombreuses études distinctes rapportent des données normatives sur les structures craniofaciales dans des études transversales ou longitudinales. Cependant, il n'existe actuellement aucune revue systématique compilant ces informations pour évaluer la cohérence et la nécessité de poursuivre la collecte de …  Read more

Evans, Alan C. (Internal/Cosupervisor2)  Read more

Récemment, l'apprentissage par renforcement (RL) est devenu le cadre de choix pour l'apprentissage par essais et erreurs dans des environnements dynamiques très complexes tels que le jeu, la conduite autonome et la biologie moléculaire \cite{surveyapplied}. L'apprentissage par renforcement hiérarchique (HRL) décompose un problème d'apprentissage par renforcement en sous-tâches en utilisant des abstractions temporelles ou d'état, dans lequel le contrôle de niveau supérieur appelle des sous-tâches de niveau inférieur comme s'il s'agissait d'actions primitives \cite{sammut2011encyclopedia}. La HRL bénéficie en particulier dans les situations où les sous-problèmes sont petits et très répétitifs, car une solution à un sous-problème peut être recyclée à …  Read more

Dufour, Jean-Marie (Supervisor1)  Read more

Despite impressive advances in biomedical science, the resurgence of infectious diseases poses an emerging threat to global public health. These developments underscore the importance of considering the relationship between biological and social change. This dissertation uses the epicentre of the HIV epidemic in West Africa---Abidjan, Cote-d'Ivoire---as a case study to show how epidemics are "crystallizations" of local biological and social factors. The Abidjan epidemic is accounted for in terms of the city's sexual modernity, rather than the common view that migration and prostitution explain the proportions the epidemic took there early on. This view supports recent epidemiological work demonstrating the …  Read more

This thesis presents a theoretical and experimental study of the stability of cantilevered coaxial cylindrical shells conveying incompressible, viscous fluid inside the inner shell and/or in the annulus between the two shells. Two analytical models are developed with experimental verification. In the first model, fluid viscous effects are partially taken into consideration. Both shells are generally considered flexible. Shell motions are described by Flugge's shell equations, modified to take into account the steady viscous loads--flow pressurization and skin friction--acting on the shells. These equations are solved by means of the extended Galerkin method, in which the shell equations and the …  Read more

Dasgupta, Kaberi (Internal/Supervisor)  Read more

Since type B adverse drug reactions tend to be rare and serious, they tend to be treated by tertiary-care specialists; and since they are commonly iatrogenic, the specialists should be concerned to document carefully not only the case per se but also the drug use history, leading to practice data of good research quality. The specialist should also be concerned to submit the data record to a central facility that would supply the probabilities, evidence-based, that a recent drug use by a patient caused the adverse event. Continual and systematic accumulation of these data records at the central facility--using the …  Read more

RAC1 is a member of the Rho family of small GTPases. Next-generation sequencing studies discovered that 5-10% of cutaneous melanoma possess an activating hotspot p.P29S mutation. Previous studies have shown that RAC1-P29S promotes proliferation of melanocytes and modulates response to mitogen-activated protein kinase (MAPK)-targeted therapy. However, the mechanism of action of RAC1-P29S remains unknown. To gain a better understanding of the role of RAC1-P29S in melanoma, we performed unbiased transcriptomic and proteomic analyses to elucidate signaling pathways affected by the p.P29S mutation. We performed RNA-sequencing (RNA-seq) on melanocytes engineered to overexpress RAC1-P29S. We integrated our analysis with human melanoma data …  Read more

The first part of the research deals with the estimation of extreme rainfalls for locations where rainfall records are sufficiently available (gaged sites); the second part is concerned with cases where rainfall data are limited (partially-gaged sites); and finally the third part involves the most complex situation where rainfall data are unavailable (ungaged sites). For gaged sites, two methods were developed for estimating the annual extreme (AE) rainfalls based on the simple scaling behaviour of the first three non-central moments (NCMs) of the AE rainfall processes and using the Generalized Extreme Value (GEV) distribution as the parent distribution. The first …  Read more

The impact of paternal age on the health of the gamete and the offspring has not been as widely studied compared to maternal age. However, studies have shown that advanced paternal age is correlated with infertility and genetic disorders in the offspring. As the paternal age is gradually increasing in the population, it is important to study the molecular changes that may occur. The antioxidant defense system responsible for scavenging reactive oxygen species (ROS) is less efficient in aging males than in younger males; this leads to redox dysfunction and damage to cellular components. Previous studies have demonstrated that aged …  Read more

The origin of the gel formation in dilute solutions of ultra high molecular weight polyethylene (UHMWPE) is the subject of this thesis. At low heating rates v, 0.5 12 K/h, it cannot be detected in the usual DSC runs made at v = 600 K/h or higher. The crystallinity found including fraction (III) (0.84-0.94) upgrades the calorimetric crystallinity to the values found by techniques not involving melting. Arrested melting which occurs between fractions (II) and (III) reveals the existence of a network whose cohesive junctions are unmelted and stabilized by strain. The amount of fraction (III) which is about 20% …  Read more

Westley, Frances (Supervisor)  Read more

This thesis examines hidden Markov filter models and their applications in speech segmentation. A method of segmenting the speech waveform is proposed. This method uses the Baum-Welch reestimation algorithm applied to the hidden filter models. Since speech signals are handled at the sample level, the amount of computations needed is very large. We will show how this issue can be dealt with effectively by using a staircase approach in the trellis calculations. The hidden Markov filters are used to segment speech signals. Test results show very consistent locations of phone boundaries. The hidden filter model fits vocalic segments very well …  Read more

Some of the age-related changes in the structure of human proteoglycan aggregate, and the depletion of proteoglycan in arthritic cartilage have been attributed to the action of proteolytic agents. However, the identity of these agents is still uncertain. In this study, the cartilage matrix protein, link protein, has been used as an in situ probe of endogenous proteolysis, due to its relative resistance to proteolysis and the accumulation of its proteolytically-modified form with age in the matrix. Stromelysin, a metalloproteinase secreted in a latent form by human articular cartilage in organ culture, was shown to play a major role in …  Read more

"Background: Systematic mixed studies reviews (SMSRs), i.e., systematic reviews combining qualitative, quantitative and mixed methods studies, are growing in popularity owing to their potential to provide a rich and practical understanding of complex health interventions and problems. Due to the heterogeneity of the included studies, one challenging issue concerns the critical appraisal of studies. A critical appraisal tool was developed to address this challenge: the Mixed Methods Appraisal Tool (MMAT). The MMAT includes criteria for appraising the methodological quality of five categories of studies: (a) qualitative studies, (b) randomized controlled trials, (c) non-randomized studies, (d) quantitative descriptive studies, and (e) …  Read more

Daniel, Sam Joseph (Supervisor1)  Read more

Douglas, Peter (Supervisor1)  Read more

Nandini, Dendukuri, (Internal/Cosupervisor2)  Read more

La stabilisation d'un double pendule spatiale inversé actionné à la hanche peut-être considérée comme un problème de contrôle de la posture d'un robot humanoïde. Basé sur un modèle existant de ce système mécanique sous-actionné avec quatre degrés de liberté, l'ultime objectif est de concevoir un régulateur approprié pour obtenir une stabilisation globale autour de l'instable position d'équilibre debout. Cette thèse présente un certain nombre d'algorithmes de contrôle et les résultats de simulation qui permettent une stabilisation locale ou semi-globale pivoter-vers-le-haut. Pour l'effort de stabilisation locale dans le voisinage de la position d'équilibre en position verticale, à la fois un contrôleur …  Read more