The identification and characterization of molecular biomarkers using mass spectrometry on an orbiting or fly-by spacecraft is one of the preferred analytical techniques in the search for life beyond the Earth. However, analysis is complicated by unwanted molecular dissociation occurring when sampled native molecules impact the instrument at high velocity. The mechanisms of chemical changes produced in high velocity impacts have been studied experimentally in some cases; however, there are significant experimental limitations to these techniques. Here I present the design, construction, and testing of a new experimental technique to produce high velocity molecular and microparticle collisions under a controlled lab setting using a high-speed spinning rotor. Chapter 1 of this manuscript gives a scientific review of the astrobiological importance of this project for future and current space missions as well as describing previous techniques used to produced hypervelocity impacts and their limitations. Chapter 2 presents the design, construction, calibration, and preliminary experiments of the new technique involving the high-speed rotor. Chapter 3 describes the fabrication of a molecular beam system from the ground up to be coupled with the high-speed rotor. Chapter 4, describes future project directions and presents future experiments using the rotor as a stand-alone instrument. Lastly, the appendix contains the standard operation procedures and design notes regarding the operation of these two instruments.

One way of reducing the examination time in magnetic resonance imaging (MRI) is to reduce the amount of raw data acquired, by performing so-called undersampling. Conventionally, MRI data is acquired line-by-line on a Cartesian grid. In the field of Cardiovascular Magnetic Resonance (CMR), however, radial k-space sampling is seen as a promising emerging technique for rapid image acquisitions, mainly due to its robustness against motion disturbances occurring from the beating heart. Whereas Cartesian undersampling will result in image aliasing, radial undersampling will introduce streak artifacts. The objective of this work was to train the deep learning architecture, CycleGAN, to reduce streak artifacts in radially undersampled CMR images, and to evaluate the model performance. A benefit of using CycleGAN over other deep learning techniques for this application is that it can be trained on unpaired data. In this work, CycleGAN network was trained on 3060 radial and 2775 Cartesian unpaired CMR images acquired in human subjects to learn a mapping between the two image domains. The model was evaluated in comparison to images reconstructed using another emerging technique called GRASP. Whereas more investigation is warranted, the results are promising, suggesting that CycleGAN could be a viable method for effective streak-reduction in clinical applications.

Cette thèse est consacrée à l'élaboration de nouvelles méthodes d'acquisition et de traitement de données en IRM de diffusion (IRMd) afin de caractériser la diffusion des molécules d'eau dans les fibres de matière blanche à l'échelle d'un voxel. Plus particulièrement, nous travaillons sur un moyen de reconstruction précis de l'Ensemble Average Propagator (EAP), qui représente la fonction de probabilité de diffusion des molécules d'eau. Plusieurs modèles de diffusion tels que le tenseur de diffusion ou la fonction de distribution d'orientation sont très utilisés dans la communauté de l'IRMd afin de quantifier la diffusion des molécules d'eau dans le cerveau. Ces modèles sont des représentations partielles de l'EAP et ont été développés en raison du petit nombre de mesures nécessaires à leurs estimations. Cependant, il est important de pouvoir reconstruire précisément l'EAP afin d'acquérir une meilleure compréhension des mécanismes du cerveau et d'améliorer le diagnostique des troubles neurologiques. Une estimation correcte de l'EAP nécessite l'acquisition de nombreuses images de diffusion sensibilisées à des orientations différentes dans le q-space. Ceci rend son estimation trop longue pour être utilisée dans la plupart des scanners cliniques. Dans cette thèse, nous utilisons des techniques de reconstruction parcimonieuses et en particulier la technique connue sous le nom de Compressive Sensing (CS) afin d’accélérer le calcul de l'EAP. Les multiples aspects de la théorie du CS et de son application à l'IRMd sont présentés dans cette thèse. / This thesis is dedicated to the development of new acquisition and processing methods in diffusion MRI (dMRI) to characterize the diffusion of water molecules in white matter fiber bundles at the scale of a voxel. In particular, we focus our attention on the accurate recovery of the Ensemble Average Propagator (EAP), which represents the full 3D displacement of water molecule diffusion. Diffusion models such that the Diffusion Tensor or the Orientation Distribution Function (ODF) are largely used in the dMRI community in order to quantify water molecule diffusion. These models are partial EAP representations and have been developed due to the small number of measurement required for their estimations. It is thus of utmost importance to be able to accurately compute the EAP and order to acquire a better understanding of the brain mechanisms and to improve the diagnosis of neurological disorders. Estimating the full 3D EAP requires the acquisition of many diffusion images sensitized todifferent orientations in the q-space, which render the estimation of the EAP impossible in most of the clinical dMRI scanner. A surge of interest has been seen in order to decrease this time for acquisition. Some works focus on the development of new and efficient acquisition sequences. In this thesis, we use sparse coding techniques, and in particular Compressive Sensing (CS) to accelerate the computation of the EAP. Multiple aspects of the CS theory and its application to dMRI are presented in this thesis.

With the quality of our South African public education system internationally in question we need to look into supplemental ways to improve the education of our country’s children. Numerous studies have shown that parental involvement has a positive effect on student academic achievement. This study aimed to quantitatively determine the current extent and types of parental involvement in the education of their school-going children, in single-parent/guardian and two-parent/guardian households in Durban, KwaZulu-Natal. This included General Education and Training (GET) and Further Education and Training (FET) levels. The method of time-space sampling was used to administer a researcher-created questionnaire ‒ based on Epstein’s (2009) framework of six types of involvement ‒ pertaining to parents/guardians in the Durban CBD. The findings of the study resulted in recommendations pertaining to: the aspects of parental involvement that elicited low levels of involvement such as significant numbers of parents from single-parent households indicating that they would attend parent days at school if they were given a choice of possible attendance days; the need to identify and support parents that are unable to participate as much as they would like to by offering transportation for school meetings or activities, including school governing body and budget meetings; and the requests from parents/guardians regarding the use of technology in the form of sms communication in helping them to stay more informed regarding the progress etc. of their child at school. / ABET and Youth Development / M. Ed. (Adult Education)