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Physical activity is a powerful modifiable lifestyle factor that reduces the risk of cardiovascular disease (CVD) in adults through favorable changes in conventional risk factors including serum lipids, blood pressure and glycemia. Recent evidence suggests that the cardioprotective effects of physical activity may also be mediated through beneficial effects on vascular function, in particular arterial stiffness. While the beneficial effects of physical activity in CVD risk in adults are irrefutable, data in youth are limited, especially for arterial stiffness. Purpose: The purpose of this project is to explore the continuous association between physical activity and arterial stiffness in youth. Hypothesis: We hypothesized that physical activity is negatively associated with arterial stiffness, whereby highly active youth would display lesser degrees of arterial stiffness than their less active (sedentary) peers. Methods: 485 youth (12-13 yrs) were recruited from the 1995 Manitoba birth cohort involved in the GreatICE asthma and allergy study. Youth were stratified into tertiles (high, medium, low) of self-reported physical activity. Global cardiometabolic risk was determined from a composite score of conventional risk factors including, LDL, SBP, Insulin, Glucose and Triglycerides. Arterial stiffness was assessed non-invasively using conventional pulse wave analysis and velocity. Results: Of the 485 youth who participated in this wave of the study, measures of PWV and PWA were available on 357 and 335 youth respectively. Cardiometabolic risk decreased with increasing levels of vigorous physical activity. Neither measure of arterial stiffness was associated with physical activity. Conclusion: Increased vigorous physical activity is associated with reduced cardiometabolic risk in youth independent of arterial stiffness.

Observations of the Crab nebula region and of the unusual active galaxy NGC1275 made during a balloon flight of the Durham high spectral resolution gamma ray telescope are described. From the Crab, spectral line fluxes were detected at 79 keV (transient), 405 keV, and at 1050 keV. The first two are possible confirmation of previous results. From NGC1275, evidence of two-photon electron-positron annihilation radiation with the expected redshifted energy of 502 keV was observed. Possible interpretations are suggested.

Studies examining descriptive norms in the activity area have demonstrated that an individual’s perceptions of others’ behaviour were related to (Priebe & Spink, 2011; Spink, Crozier, & Robinson, 2013), and influenced (Priebe & Spink, 2012, 2014) individual behaviour. Guided by focus theory of normative conduct (Cialdini, Reno, & Kallgren, 1990), the purposes of the studies examined in this thesis were three-fold: (1) to assess whether norms are related to an intention that is not a direct reflection of the norm, (2) to add to the examination of the relationship between norms and self-reported activity to include both descriptive (i.e., perceptions about others’ behaviour) and injunctive (i.e., perceptions about others’ approval) norms, and (3) to use a construct from another theory (i.e., positive outcome expectations from social cognitive theory, Bandura, 1986) to strengthen the predictions from focus theory of normative conduct to individual’s physical activity. In Study 1, which was concurrent in design, the relationship between descriptive norms reflecting prosocial behaviour and an individual’s intention to return to the group in youth sport camp participants was examined. A positive relationship emerged wherein individuals were more likely to intend to return to their group in the future when they also perceived that more group members provided encouragement, congratulations, positive and constructive feedback (i.e., prosocial) to other group members. Study 2 was an experimental field study, where the influence of normative (descriptive, injunctive) and non-normative (personal, team) motivational messages on self-reported frequency of maximal effort in adult volleyball athletes was examined. Individuals exposed to the normative messages about others exerting effort reported significantly higher frequencies of maximal effort compared to those exposed to messages highlighting personal reasons for exerting effort (i.e., to improve athletic ability). However, no differences emerged between normative messages about the effort levels of others and those who received messages about working hard for the team. In Study 3, an online experimental study, exposure to messages differing in levels of descriptive norms and positive outcome expectations was examined in relation to the exercise patterns of university students during a final exam period. All students reported decreases in their activity from their typical levels during the exam period. However, between-group differences emerged between the two groups exposed to the message that many others were active during exams (high descriptive norm). When that message was coupled with a high positive outcome expectation, individuals reported significantly greater levels of moderate and vigorous physical activity than when the normative message was accompanied with a low positive outcome expectation. Results from these three studies suggested the following: (1) a descriptive norm surrounding one class of behaviours related to an individual’s perceptions regarding an intention to return in the future to that setting, (2) normative messages influenced an individual’s perceptions of how often he/she exerted maximum effort more than non-normative personal messages in sport, and (3) a message highlighting that many others were active during an exam period (high descriptive norm) influenced self-reported individual physical activity differently depending on the level (high, low) of positive outcome expectation provided.

Factor VIII is a complex of two proteins, the von Willebrand factor (or factor VIII related antigen) and the procoagulant protein. Both are essential for normal haemostasis. Problems exist in the purification of factor VIII as it is present in only low concentrations in plasma, and its procoagulant activity is unstable. As a result, therapeutic factor VIII concentrates prepared by the Blood Transfusion Service (for the treatment of heamophilia and von Willebrand's disease) are relatively impure, and the yield from existing purification processes is low. The studies presented in this thesis are aimed towards increasing the quality and yield of therapeutic concentrates. Attention has been focussed on improving methods for the purification and assay of factor VIII. Novel affinity purifications reagents for factor VIII have been studied, and methods for removing the major impurity (fibrinogen) from conventional factor VIII concentrates have been investigated. The factor VIII related antigen (FVIIIR:Ag) and the procoagulant antigen (FVIII:CAg) have been purified, and used as immunogens for the production of specific antibodies. A large volume of polyclonal antibody to FVIIIR:Ag has been produced in sheep. This was subsequently used to develop an immunopurification method for FVIII:CAg. Immunisation of mice with purified FVIII:CAg gave a valuable panel of ten monoclonal antibodies to procoagulant factor VIII. These have important applications in the assay, purification and biochemical study of this protein. Sensitive radiometric assays for FVIIIR:Ag and FVIII:CAg have been established. This work involved the development of methods for the preparation of ¹²⁵I-FVIIIR:Ag, and for the purification and labelling of human anti-FVIII:CAg Fab' fragments from inhibitor plasma. An artificial factor VIII-deficient substrate has been prepared on a large scale for the one-stage bioassay of procoagulant activity (FVIII:C).

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