Preterm birth is the leading cause of neonatal mortality and long-term morbidity. Neonatologists can adjust nutrition to preterm neonates to control their weight gain so that the possibility of long-term morbidity can be minimized. This optimization of growth trajectories of preterm infants can be achieved by studying a cohort of selected healthy preterm infants with weights observed during day 1 to day 21. However, missing values in such a data poses a big challenge in this case. In fact, missing data is a common problem faced by most applied researchers. Most statistical softwares deal with missing data by simply deleting subjects with missing items. Analyses carried out on such incomplete data result in biased estimates of the parameters of interest and consequently lead to misleading or invalid inference. Even though many statistical methods may provide robust analysis, it will be better to handle missing data by imputing them with plausible values and then carry out a suitable analysis on the full data. In this thesis, several imputation methods are first introduced and discussed. Once the data get completed by the use of any of these methods, the growth trajectories for this cohort of preterm infants can be presented in the form of percentile growth curves. These growth trajectories can now serve as references for the population of preterm babies. To find out the explicit growth rate, we are interested in establishing predictive models for weights at days 7, 14 and 21. I have used both univariate and multivariate linear models on the completed data. The resulting predictive models can then be used to calculate the target weight at days 7, 14 and 21 for any other infant given the information at birth. Then, neonatologists can adjust the amount of nutrition given in order to preterm infants to control their growth so that they will not grow too fast or too slow, thus avoiding later-life complications. / Thesis / Master of Science (MSc)

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Homelessness is an important social problem in Canada, and the needs and experiences of women may differ from those of other homeless people. Little research has looked beyond rehousing to examine community integration following homelessness. Predictive models of three distinct facets of community integration for women who have experienced homelessness are presented and tested in this thesis. The first model examines physical integration, which is defined in terms of attaining and retaining stable housing. The second model predicts economic integration, defined in terms of participation in work or education. The third model predicts psychological integration, defined as psychological sense of community in one’s neighbourhood. Data for this research comes from a two-year longitudinal study conducted in Ottawa. Participants were women aged 20 and over (N =101) who were homeless at the study’s outset. Family status was an important predictor of community integration. Women who were accompanied by dependent children were more likely than those unaccompanied by children to be physically, economically and psychologically integrated in their communities. Having access to subsidized housing predicted becoming rehoused and living in one’s current housing for longer. Greater perceived social support predicted living in one’s current housing for longer. Past work history and mental health functioning predicted economic integration. Lower levels of education predicted returns to full-time studies. Living in higher quality housing and having more positive contact with neighbours predicted psychological integration, while living in one’s current housing for longer predicted lower levels of psychological integration. Overall, participants achieved a moderate level of community integration. The majority had been housed for at least 90 days at follow-up. However, only a minority were participating in the workforce or education at follow-up. Participants achieved only a moderate level of psychological integration. Results are discussed in terms of implications for policy and service provision. Improvements in the availability and quality of affordable housing, as well as employment support are recommended. Special attention needs to be paid to providing adequate and effective services for women who are unaccompanied by dependent children. / Fonds québécois de la recherche sur la societé et la culture

The term dementia refers to a progressive decline in cognitive functioning resulting in a significant impairment in daily living. Given the devastating impacts of the disease and lack of a cure, it is reasonable to expect people fear developing a dementia. Alzheimer's disease ranks high among the most feared diseases in national samples of the American population. As a topic of study, little is known about the determinants of fear of Alzheimer's disease and how this fear may change as a function of aging, time, or experience. The current study sought to fill this gap by investigating the nature of changes in fear of Alzheimer's disease by following participants (N = 227) over the course of two years. Volunteers completed measures on fear of dementia, knowledge about Alzheimer's disease, knowledge about the aging process, personality traits, memory self-efficacy, anxiety about aging, and Alzheimer's-related experiences (i.e., family history, caregiving experience, number of people known with the disease, personal diagnosis, etc.). Results supported the notion that fear for becoming a burden to others, a component of fear of dementia, decreased over the two years. In addition, personality traits and memory self-efficacy mediated the two-year change in concerns about perceived symptoms of cognitive decline. In predicting fear for various aspects of Alzheimer's disease, anxiety about aging and experience/exposure to the disease emerged as prominent predictors. These results highlight dementia concerns and offer guidance for early interventions, such as an open communication with family and health care providers about fear of dementia.

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<p> In this report we explore how the effect of meteorological factors, allergens, and air pollution on respiratory conditions in children using longitudinal data. Our analysis makes use of a dataset from the DAVIS study in southern Ontario. The response variables are children's lower respiratory tract (URT) and upper respiratory tract (URT) scores. The explanatory variables are readings of various meteorological, allergen, and air pollution factors. First we make use of generalized estimating equations to find the main factors that are associated with certain respiratory conditions in children as measured by LRT and URT scores. Then we determine whether there are any interactions between the significant factors associated with LRT /URT scores. Comparisons between case and control groups are made to determine whether children with asthma are more sensitive to any of the changes in meteorological, allergen, and air pollution factors. The analysis results show that the significant factor that is associated with LRT scores for children with asthma is the two-day lag daily average changes in air pressure. On average an increase in air pressure will result in an increase in children's LRT scores. The interaction terms that remained in the final model show some degree of significance but without strong evidence to support it. Children in the case groups are more sensitive to meteorological factors, allergens, and air pollution than the children in control groups. </p> / Thesis / Master of Science (MSc)

The overall objective of this thesis is to develop, validate and assess a probabilistic collision damage model to support ongoing work by the Society of Naval Architecture and Marine Engineering (SNAME) Ad Hoc Panel #6 and IMO working groups. It is generally agreed that structural design has a major influence on tanker oil outflow and damaged stability in grounding and collision, but crashworthiness is not considered in present regulations. The proposed methodology provides a practical means of considering structural design in a regulatory framework, and when implemented would improve the safety and environmental performance of ships. This thesis continues the development and applies a Simplified Collision Model (SIMCOL) to calculate damage extent (transverse, vertical and longitudinal) and oil outflow in ship collisions. The primary contribution of this thesis is the development and validation of a theory for the determination of energy absorbed in longitudinal extent of damage, and the implementation of the theory within SIMCOL. SIMCOL is sufficiently fast to be applied to thousands of collision cases as is required for a probabilistic analysis. The following specific tasks were completed using SIMCOL in support of this project: Completed the development of SIMCOL Version 3.0 including: 1) Deformable Bow sub model 2) Implementation and validation of theory for the determination of energy absorbed in longitudinal extent of damage. • Developed the capability to model collision events using LSDYNA. • Validated Virginia Tech LSDYNA ship collision modeling procedure. • Validated SIMCOL using real collision data, and probabilistic collision data for penetrating collisions. / Ph. D.

Adolescence is a transition period during which individuals have increasing autonomy in decision-making for themselves (Casey, Jones, and Hare, 2008), often choosing among options about which they have little knowledge and experience. This process of individuation and independence is reflected as real-world risk taking behaviors (Silveri et al., 2004), including higher motor accidents, unwanted pregnancies, sexually transmitted diseases, drug addictions, and death (Casey et al., 2008). The extent to which adolescents continue to display increased behaviors with negative consequences during this period of life depends critically on their ability to explore and learn potential consequences of actions within novel environments. This learning is not limited to the value of the outcome associated with making choices, but extends to the levels of risk taken in making those choices. While the existing adolescence literature has focused on neural substrates of risk preferences, how adolescents behaviorally and neurally learn about risks remain unknown. Success or failure to learn the potential variability of these consequences, or the risks involved, in ambiguous decisions is hypothesized to be a crucial process to allow the individuals to make decisions based on their risk preferences. The alternative in which adolescents fail to learn about the risks involved in their decisions leaves the adolescent in a state of continued exploration of the ambiguity, reflected as continued risk-taking behavior. This dissertation comprises 2 papers. The first paper is a perspective paper outlining a paradigm that risk taking behavior observed during adolescents may be a product of each adolescent's abilities to learn about risk. The second paper builds on the hypothesis of the perspective paper by first examining neural correlates of risk learning and quantifying individual risk learning abilities and then examining longitudinal risk learning developmental trajectories in relation to real-world risk-trajectories in adolescent individuals. / Doctor of Philosophy / Adolescence is a transition period during which individuals have increasing autonomy in decision-making for themselves, often choosing among options about which they have little knowledge and experience. This process of individuation and independence begins with the adolescent exploring their world and those options they are ignorant of. This is reflected as real-world risk-taking behaviors, including higher motor accidents, unwanted pregnancies, sexually transmitted diseases, drug addictions, and death. We hypothesized and tested the premise that whether adolescents who succeeded or fail to learn about the negative consequences of their actions while exploring will continue to partake in behaviors with negative consequences. This learning is not limited to the value of the outcome associated with making choices, but extends to the range of possible outcomes of the choices or the risks involved. Indeed, the failure to learn the risks involved in decisions with no known information show continued and greater risk-taking behavior, perhaps remaining in a state of continued exploration of the unknown.

Persistently high attrition rates from STEM majors present a stubborn challenge for researchers, administrators, and faculty alike. To approach this problem, my dissertation examined the socialization processes by which students develop a sense of belonging to both their institution and their discipline. Previously identified as an important factor in students' persistence and overall satisfaction with their undergraduate experience, belonging is a critical piece of the retention puzzle. However, not every student experiences or develops belonging in the same way. This dissertation applied the theoretical lens of socialization to deepen the understanding of how social interactions help or hinder students' belonging to their university and chosen major alike. My dissertation work was grounded in the synthesis of two theoretical frameworks: Conrad et al.'s (2006) model of socialization and Strayhorn's (2018e) conceptualization of sense of belonging. The study took the form of an embedded case study of two similar disciplinary contexts within a large public land-grant Research 1 institution, with four students from each context for a total of eight participants. By leveraging four years of interview data from each participant, supported by institutional documentation, I addressed the question: In what ways does a student's socialization experience influence, if at all, their sense of belonging to both their chosen discipline and their university? Data analysis included qualitative coding, trajectory mapping, and thematic analysis. Trajectories were produced for each participant before expanding the analysis to examine patterns across and between the contexts. My findings addressed the mechanisms of socialization at the undergraduate level and how they evolved over time. The primary outcome of my work was a set of three distinct socialization trajectories, named the Anchored, who built strong socializing relationships early and maintained them throughout their undergraduate years; Independents, who neither sought nor wanted such relationships; and Wanderers, whose socializing relationships tended to be short-lived and inconsistent, although desired. Fourteen unique groups of socializing agents were identified, along with five common drivers for intentionally engaging with specific agents: personal and academic support, research and industry aspirations, and finding a path. Pre-college socialization experiences were salient for developing anticipatory belonging, as students who were exposed to their discipline or institution prior to arriving as students had an easier time becoming integrated to their communities. Once students arrived, their socialization trajectories tended to shape their feelings of belonging to the institution, with close ties forming for the Anchored, appreciation for general support among the Independents, and a mix of happiness and frustration for the Wanderers. By contrast, disciplinary belonging was more reliant on the individual participant's goals and interests. Disciplinary differences between the two contexts were identified but were limited in scope and generally linked to the career outcomes students associated with their chosen major rather than their experiences in the major. Finally, my research revealed that a strong sense of belonging in one domain of undergraduate life could be sufficient for a student to persist to degree completion despite weak or absent feelings of belonging in other areas. / Doctor of Philosophy / For decades, students have been leaving STEM majors at alarmingly high rates despite the efforts of researchers, administrators, and faculty. To approach this problem, my dissertation examined how social interactions and relationships can help students feel like they belong in their chosen major and university. Previous research identified such feelings of belonging as an important factor in helping students persist to the completion of their degrees, and my work added onto this body of work by specifically examining the role of students' social connections. My dissertation utilized data from eight total students. Four of the students were chemical engineering students, with the remaining four from chemistry and biochemistry, together called the "chemical sciences." The data for this work included four years of interview data supported by institutional documents. Such documents provided information like curricular requirements, demographic and population information, and course information, which helped provide background for the students' interviews. Leveraging these data, I addressed the aforementioned interaction of students' social interactions and their feelings of belonging on campus and in their major. My data analysis was based around the creation of trajectories that would capture the evolution of a student's experiences over the course of their undergraduate career. Once trajectories were generated for each student, I was then able to look across the trajectories and identify patterns between and within them. The primary finding of my dissertation work was the emergence of three distinct patterns of how students' social interactions evolved over time, labeled the Anchored, who built strong and consistent networks that they maintained over two or more years; the Independents, who neither sought nor wanted such relationships; and the Wanderers, who had relationships and interactions that were often short-lived or inconsistent, but wanted more. Fourteen unique groups with whom students interacted were identified, along with the respective impacts said groups could have on students' feelings of belonging. Additionally, five drivers for seeking out interaction with these groups were identified: personal and academic support, research and industry aspirations, and finding a path. The experiences students had with their university or major prior to enrolling were found to be important for shaping the way students perceived their future, and those with greater exposure to their institution or discipline had an easier time seeing themselves fitting in and finding a place for themselves on campus once they enrolled. Once students arrived, their trajectory of interaction tended to shape how they felt about their institution, with close ties forming for the Anchored, appreciation for general support among the Independents, and a mix of satisfaction and frustration for the Wanderers. By contrast, belonging within the discipline was more reliant on the individual participant's goals and interests. Disciplinary differences between the two contexts were identified but were limited generally linked to the career outcomes students associated with their chosen major rather than their experiences in the major. Finally, my work revealed that when students felt like they belonged in one area of their undergraduate life, those feelings could support lacking feelings in other areas, helping them to persist to graduation.