Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Polyketides are a class of natural products that exhibit remarkable structural and functionally diversity and are highly sought after due to their medicinally important activities. For many decades now, polyketide synthases (PKSs), the mega-enzymes responsible for biosynthesis of polyketides have been the focus of extensive investigation to make new polyketides by polyketide engineering strategies. While there are many established methods to investigate polyketide enzymes and biosynthesis mechanisms, they have substantial shortcomings that have limited the extent of success with polyketide engineering efforts. This thesis focuses on developing simple, flexible yet powerful tools for examining polyketide biosynthesis by overcoming some deficiencies in currently used techniques. Reactive heterocylces have been designed for direct labeling of key polyketide synthase enzymes to provide a direct insight into its functions and mechanisms. First β-lactones and then β-lactams have been used as small molecule probes to perform site-specific labeling of acyl carrier proteins and further used for mechanistic interrogation of key steps in polyketide biosynthesis. The utility of these probes has been demonstrated by comparison to traditional probes and has been successfully applied to examine substrate selectivity of keto synthases, key enzymes in polyketide biosynthesis. The applications of the tools described in this manuscript only scratch the surface of their capabilities and are expected to significantly aid in the study of new and existing PKS systems leading to improved understanding of how these extraordinary biosynthetic machines function.

<p> This work was the first study at the beam port # 4 at the McMaster Nuclear Reactor, involving prompt gamma in vivo neutron activation analysis. The project consisted of experimental and computational parts. The computational part was done using MCNP program, which simulates the neutron and photon transport in the medium. The first thing assessed was the energy dependent neutron fluence rate in the collimated neutron beam, at the site. This was done in order to figure out the complete source (sdef) card for further MCNP calculations. This was combined experimental and computational work. For the experimental part, various activation foils were used and computational part was done by using MCNP programming.</p> <p> The second part of the project involved experimental prompt gamma in vivo activation analysis using 7 different phantoms, ranging from 30 mL to 2 L. Three different elements were observed. The prompt gamma in vivo detection of cadmium was the preliminary calibration study and the experiments were done with all seven phantoms. The calibration lines and MDL were assessed for all phantoms, with concentration ranging from 0 to 50 ppm. The prompt gamma in vivo detection of boron and mercury was done using 30 mL phantoms. Calibration lines and MDL for both elements were assessed as well.</p> <p> MCNP experimental simulations for 30 mL water phantoms were done and they were in close agreement with the experimental results. Furthermore, the MCNP gamma and neutron dose survey in the cave was done.</p> <p> The results obtained showed that there are numerous open possibilities for improvement in terms of in vivo prompt gamma analysis at the site. It predominantly includes the improvements in prompt gamma detection techniques and MCNP source definition. Furthermore, it was found that MCNP programming is the ideal tool for assessment and control of the experimental results in this case. It means that in the future research, the MCNP modeling will be the essential part of the in vivo prompt gamma activation analysis at this beam port.</p> / Thesis / Master of Science (MSc)

<p> As older adults increasingly make use of the Internet to enhance their personal and professional lives, the study of web site usability for older adults is becoming increasingly relevant. Web site usability is concerned with both utilitarian (i.e. functional) and hedonic (i.e. pleasure-related) aspects. This study explores the impact of age on select utilitarian (mental model accuracy and performance) and hedonic (disorientation and engagement) measures of web site usability, and the subsequent impact of these utilitarian and hedonic measures on user satisfaction. A laboratory experiment was conducted where 50 younger and 51 older participants interacted with an experimental web site. The results of the PLS analysis suggest that age has a more pronounced impact on utilitarian constructs than hedonic ones. Specifically, older adults were less able to create an accurate mental model of the web site and in turn had poorer performance with the web site. In terms of impact on user satisfaction, the contribution of hedonic constructs was significant while the impact of utilitarian constructs was not. </p> / Thesis / Doctor of Philosophy (PhD)

<p> Factors affecting cottage site desirability are investigated two ways. A step-wise compilation of the regression model is used to rank the cottage site desirability variables, and determine the proportion of variation that the variables contribute in explaining cottage land values. The simple regression and correlation technique is used to determine the existence of possible relationships. between distance measures, and measures of both cottage land values and cottage road values. </p> / Thesis / Master of Arts (MA)

La création de Facebook en 2004, l’augmentation grandissante du nombre d’abonnés dans le monde depuis, et la place que prend ce réseau social peuvent être perçu pour certains positivement, alors que pour d’autres, c’est plutôt négativement. Facebook fait partie du quotidien de plusieurs personnes. La présente recherche consiste à élaborer un questionnaire portant sur l’usage problématique de Facebook (UPF) à partir des étapes proposées par Dussault, Valois et Frenette (2007). La théorie développée par Davis (2001) et adaptée par Caplan (2002) sur l’usage problématique d’Internet a servi de point de départ pour l’UPF. Les dimensions retenues pour la création du questionnaire sont : Perte de contrôle, Négligence et Distraction. Suite à un prétest, le questionnaire a été envoyé à deux listes de courriel d’une université québécoise (étudiants et travailleurs), puis il a été mis sur le groupe Facebook de cette dernière. Un total de 925 étudiants et travailleurs, dont 692 femmes, 204 hommes, a répondu à la version finale du questionnaire. Les résultats obtenus démontrent que le modèle qui représente le mieux les données, parmi les quatre modèles testés, est un modèle avec trois facteurs corrélés (Perte de contrôle, Négligence et Distraction). Ce questionnaire pourrait servir de point de départ pour définir ce concept. Des recherches futures visant à définir les antécédents menant à l’UPF sont nécessaires.

Three cholesterol interventions were evaluated in a work-site setting to determine which was most effective in modifying physiological, behavioral, and knowledge measures related to total serum cholesterol. Of the 246 employees initially screened, 135 (55%) were identified as having elevated total serum cholesterol levels (>200 mg/dl) and were eligible for the study. Treatment consisted of either a six-session cholesterol reduction course requiring 30 days dietary monitoring, a six-session course without dietary monitoring, or an incentive only approach. Significant increases in cholesterol knowledge and dietary fiber consumption was found in both the education intervention with logging and intervention without logging groups. The results indicate that positive learning effects can take place in work-site settings and that such learning can lead to dietary changes that reduce the effects of high serum cholesterol.

Yes