Published online: 26 April 2013

Smoking rates among senior students have been related to smoking initiation in younger students. Opportunities to select smoking friends may be one explanation, however our understanding of this process has been limited by cross-sectional designs. <br ><br /> The purpose of this longitudinal study was to determine whether senior student smoking rates a) predict smoking initiation in younger elementary school students, controlling for individual exposure to family and friends who smoke and b) are related to the selection of smoking friends, increasing risk of smoking initiation as a result. <br ><br /> This study involved secondary data analysis of 2798 students from 84 Ontario elementary schools involved with the Third Waterloo Smoking Prevention Project (WSPP3). Grade 8 students completed a questionnaire at baseline to obtain the percentage of senior students who smoke in each school. Students in grade 6 completed a similar questionnaire at baseline, and were surveyed again in grades 7 and 8. Multilevel regression analyses were used to examine school and individual characteristics simultaneously. <br ><br /> Each 5% increase in the senior student smoking rate at a school increased the risk that a non-smoking grade 6 student would try smoking more than once by grade 8 (OR 1. 05) and that a non-smoking grade 6 student with no smoking friends would gain a smoking friend by grade 7 (OR 1. 10). Students who remained non-smokers in grade 7 but gained a smoking friend were more likely to try smoking more than once by grade 8 (OR 4. 31). <br ><br /> In schools where a high proportion of senior students smoked, younger students were more likely to initiate smoking, and gain a smoking friend. Anti-smoking policies and interventions may be more urgently required in these schools to lower senior student smoking rates and reduce initiation among younger students. Tailoring the intensity and content of programs to match the needs of schools is one way to potentially maximize effectiveness.

Both physiological and emotional arousal can increase romantic attraction towards a desirable potential partner. Such attraction reflects relationship-initiation motivation, a connection motivation directed at a new partner, because attraction increases the drive to pursue a social interaction or relationship with another person. Therefore, arousal appears to influence the need to belong, the inherent motivation for positive social interactions. A large body of research also reveals that self-esteem influences people’s pursuit of belongingness, especially during relationship initiation. Yet the literature linking arousal and attraction and the research linking self-esteem and attraction have never been connected. The present research shows that self-esteem moderates how arousal influences relationship-initiation motivation. To examine the moderating effect of self-esteem on the relation between arousal and relationship-initiation motivation, I conducted three studies. Study 1 involved manipulating women’s physiological arousal in an anticipated social interaction. Results showed that arousal directly increased relationship-initiation motivation for higher self-esteem individuals (HSEs) but not lower self-esteem individuals (LSEs). Study 2 replicated Study 1 with men, showing that arousal increased relationship-initiation motivation for HSEs but not LSEs, but in this case, the effect wholly depended on men applying a positive emotional label to their arousal. Study 3 involved manipulating both men’s and women’s arousal in an imagined social interaction. For women, arousal directly decreased HSEs’ but increased LSEs’ relationship-initiation motivation, the opposite result to Study 1. For men, arousal directly increased HSEs’ but decreased LSEs’ relationship-initiation motivation, replicating the results of Study 2. My package of studies connects self-esteem and arousal research, unifying two formerly separate subject areas. These findings provide an underlying mechanism (i.e., arousal) that explains how social risk interacts with self-esteem to influence relationship-initiation motivation. Consequently, my research increases the breadth and depth of current self-esteem theories. / Graduate

The DEAD-Box RNA helicase family is a conserved group of enzymes that function in gene expression through ATP-dependent RNA unwinding and ribonucleoprotein (RNP) remodeling. DEAD-Box helicases function in multiple cellular processes, including pre-mRNA processing, translation, mRNA export, and mRNA decay. Although DEAD-Box proteins are critical for gene expression, much of their mechanistic activities are poorly understood. DEAD-Box proteins have increasingly been linked to tumorigenesis in humans, and better defining their activity at the mechanistic level will aid in understanding the underlying disease pathology. In this study, we used the model organism Saccharomyces cerevisiae to study the human DEAD-Box protein DDX3 orthologue, Ded1, and its role in translation initiation during cellular stress. Recently, we have found that Ded1 is an important mediator of the cellular stress response in a TOR-dependent manner. TOR regulates protein synthesis dependent on energy availability in the cell by regulating the assembly of the eukaryotic translation initiation complex. Human DDX3 has been found to interact with translation initiation complex subunit eIF4E and Ded1 has been found to interact with the translation initiation complex subunit eIF4G. In this study, we examined the purported interaction region between Ded1 and eIF4G on the C-terminus of Ded1 and found that ded1 Δ591-604 prevents eIF4G degradation under rapamycin treatment and confers resistance to rapamycin-induced growth inhibition. We also examined putative regulatory phosphorylation sites in the purported Ded1 eIF4G binding region. We propose that the Ded1/eIF4G interaction is critical for the repression of translation by Ded1 and that eIF4G degradation may be regulated by Ded1 under stress conditions.

In packaging industries, the demand for usage of Low Density Poly Ethylene foil is of profound interest. In the past, research was carried out on finite and infinite plates with varying crack lengths but having constant crack width. In this thesis, a detailed analysis on crack initiation is carried out on finite plates by varying width of the hole. The hole shapes for stress analysis include circle, ellipse and rectangular notch. Initially, maximum stress is found out using Linear Elastic Fracture Mechanics (LEFM) theory and compared with Finite element method (FEM) results. Secondly using Elastic Plastic Fracture Mechanics theory (EPFM), critical stress and geometric function are evaluated theoretically by Modified Strip Yield Model (MSYM) and numerically by ABAQUS. Finally, a tensile test is conducted to validate the theoretical and numerical results.  By varying the width of the hole, a study on the parameters like critical stress, geometric function is presented. A conclusion is drawn that the effect of hole width should be considered when calculating fracture parameters.

Single-molecule Förster resonance energy transfer (smFRET) has emerged as an important tool for studying biological reactions. This thesis describes smFRET investigations into the mechanism of bacterial transcription initiation. We developed protocols to immobilize RNAP-DNA initiation complexes using vesicles and antibodies. We used these techniques to show that the transcription bubble conformation in immobilized complexes exhibits inter-molecular heterogeneity. We observed large FRET changes that we attribute to transcription bubble opening and closing dynamics. We found that σ⁷⁰ region 3.2 (σR3.2) influences the kinetics of the bubble dynamics, which supports proposals that σR3.2 interacts with the transcription bubble template strand. We extended our investigations to RNA synthesis and were able to observe abortive initiation cycles directly. We observed RNAP pausing and backtracking for the first time in transcription initiation. We obtained data suggesting that σR3.2 stabilises short RNAs at the active centre and forms a barrier to the extension of RNAs longer than 5-nt in length. We extended our abortive initiation assay to observe signal changes that we attribute to promoter escape. Our data revealed the number of abortive cycles that occur prior to escape, the kinetics of promoter escape, and pausing events that may have some regulatory function. We investigated the conformational dynamics of the RNAP β clamp and observed dynamic conformational changes between clamp-open and clamp-closed states. Our work confirms proposals that the clamp remains stably closed once the open complex (RPO) is formed. We investigated what affect the antibiotics Myxopyronin and Lipiarmycin have on the clamp conformation. Our results revealed that Myxopyronin traps the clamp in a closed conformation, while Lipiarmycin traps it in an open conformation. Overall, we made a number of novel observations that we believe advance our understanding of the mechanism of transcription. We hope that the discoveries reported here will direct future research efforts into RNAP function.

The effect of family structure on youth adjustment has received increasing attention as historical trends in single parenting, divorce, remarriage, and cohabitation with partners and extended family members have produced a diverse constellation of structures. African American youth are less likely than Caucasian youth to live in an “intact” family. Links between family structure and a variety of indices of youth adjustment have been established, although a relatively understudied outcome is that of substance initiation, despite its association with dependence and other negative sequelae. The dynamic effect of transitions has additionally been less studied than the static effect of structure. Differences in family structure and transitions may influence outcomes via parental socialization (monitoring and attachment) as well as strain (residential mobility and changes in income). These mechanisms may operate differently for Caucasian and African American youth, and may partially explain differences in adjustment. Relations between youth adjustment and transitions may be reciprocal in nature, a less often studied premise. This project made use of a nationally representative sample of more than 2,000 adolescents aged 12 to 13 in 1997 assessed across 3 waves. Regression analyses were employed to examine the associations among family structure and transitions, parenting, income, residential mobility, and substance initiation over time. This study found that living in non- two-parent family structures was consistently associated with higher concurrent levels of substance initiation, lower parental monitoring and relationship quality, lower income, and higher residential mobility. The effects of transitions on substance initiation and parenting were less robust than hypothesized, but reinforced the notion that consistently living outside a two-parent family, or consistently living in a single-parent family, is negatively associated with parenting, income, and residential stability over time. Evidence for mediated effects via changes in parenting, residential mobility, and income were significant but small in magnitude, and varied by race, such that they were significant for Caucasian but not African American youth . Partial evidence for reciprocal causality was found. Alcohol initiation at the first wave predicted separations, but marijuana initiation did not. These findings have important implications for parents, clinicians, and policy makers.

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

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

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