[Truncated abstract] This thesis describes the development, clinical validation and initial application of a technique for taking measurements of the shape and dimensions of the human upper airway, called anatomical optical coherence tomography (aOCT). The technique uses a transparent catheter containing a rotating optical probe which is introduced transnasally and positioned in the airway and oesophagus. Optical coherence tomography is used to take calibrated cross-sectional images of the airway lumen as the probe rotates. The probe can also be advanced or withdrawn within the catheter during scanning to build up three-dimensional information. The catheter remains stationary so that the subject is not aware of the probe motion. The initial application of the system is research into obstructive sleep apnoea (OSA), a serious condition characterized by repetitive collapse of the upper airway during sleep and an independent risk factor for deaths by heart disease, strokes or car accidents. Measurement of upper airway size and shape is important for the investigation of the pathophysiology of OSA, and for the development and assesment of new treatments. . . We have used aOCT to capture three-dimensional data sets of the airway shape from upper oesophagus to the nasal cavity, undertaken measurements of compliance and other airway characteristics, and recorded dynamic airway shape during confirmed sleep apnoea events in a hospital sleep laboratory. We have shown that aOCT generates quantitative, real-time measurements of upper airway size and shape, allowing study over lengthy periods during both sleep and wakefulness. These features should make it useful for study of upper airway behavior to investigate OSA pathophysiology, and aid clinical management and treatment development.

The objectives of this study were to: (1) determine the relationship between locus of control (measured by the Locus of Control Inventory), work engagement (measured by the Utrecht Work Engagement Scale) and sense of coherence (measured by the Orientation to Life Questionnaire); (2) determine whether coping and non-coping individuals (measured by a coping scale) differ significantly regarding these variables, and (3) the strategies they employ to deal with change in their lives (determined by means of structured interviews). A survey design, and correlational and inferential statistical procedures were used to achieve the quantitative research objectives. Qualitative content analysis was used to analyse and interpret the research data obtained from the open-ended questions on coping strategies. A convenience sample (n = 69) of individuals employed in the manufacturing sector participated in the study. The quantitative results revealed a significant relationship between the three variables and that copers and non-copers differ significantly regarding their coping. The qualitative data analysis indicated that copers and non-copers differ in terms of the coping strategies they employ to deal with change. The study represents original research which contributes new knowledge and insights for organisational employee wellness practices aimed at helping employees cope more positively with organisational change in the South African organisational context. / Industrial and Organisational Psychology / M.A. (Industrial and Organisational Psychology)

Cache replacement policies can play a pivotal role in the overall performance of a system by preserving data locality and thus limiting the o -chip accesses. In a shared memory system, a cache coherence protocol is necessary to ensure correctness of data computations by maintaining the state of entries in the cache. In this work we attempt to build and investigate the effect of cache replacement policies using the information provided by cache coherence protocol states. The cache coherence protocol states give us an idea about the state of entry with respect to other cores in the system. State based analysis of SPLASH-2 and PARSEC benchmark suites show that this information hints us towards the locality patterns of cache blocks, which can be used to prioritize the order of replacement of a cache states in a replacement policy. We model ten di erent cache state based replacement policies, three having xed priorities and seven whose priorities vary dynamically over the most recently used state. We compare these policies against the standard replacement policies (LRU, FIFO and Random) in terms of system performance and ease of implementation. We develop our simulation framework using the Multi2Sim simulator, where we model cache state based replacement policies. We simulate SPLASH-2 and PARSEC benchmark suites over a variety of con gurations, where we vary the number of cores, associatively for each level of cache, private/shared L2 cache. We characterize the programs to find out critical components for performance. For an 8-core system we observe that the best case among these state based replacement policies shows marginal improvements in IPC over the Random and FIFO policies, falling slightly short of LRU. We design the state based replacement policies using a smaller cache (CSL-cache), which is used to store the state information of the blocks in the main cache. The CSL cache communicates with the controller to provide the replacement entry. The complexity associated with the system is equal to FIFO and is independent of the associatively of the cache.

Indiana University-Purdue University Indianapolis (IUPUI) / An algorithm was developed in to efficiently segment the inner-limiting membrane (ILM) and retinal pigmented epithelium (RPE) from spectral domain-optical coherence tomography image volumes. A deformable model framework is described and implemented in which free-form deformations (FFD) are used to direct two deformable sheets to the two high-contrast layers of interest. Improved accuracy in determining retinal thickness (the distance between the ILM and the RPE) is demonstrated against the commercial state-of-the-art Spectralis OCT native segmentation software. A novel adaptation of the highest confidence first (HCF) algorithm is utilized to improve upon the initial results. The proposed adaptation of HCF provides distance-based clique potentials and an efficient solution to layer-based segmentation, reducing a 3D problem to 2D inference.

Optical coherence imaging, including tomography (OCT) and microscopy (OCM), has been a growing research field in biomedical optical imaging in the last decade. In this imaging modality, a broadband light source, thus of short temporal coherence length, is used to perform imaging via interferometry. A challenge in optical coherence imaging, as in any imaging system towards biomedical diagnosis, is the quantification of image quality and optimization of the system components, both a primary focus of this research. We concentrated our efforts on the optimization of the imaging system from two main standpoints: axial point spread function (PSF) and practical steps towards compact low-cost solutions. Up to recently, the criteria for the quality of a system was based on speed of imaging, sensitivity, and particularly axial resolution estimated solely from the full-width at half-maximum (FWHM) of the axial PSF with the common practice of assuming a Gaussian source power spectrum. As part of our work to quantify axial resolution we first brought forth two more metrics unlike FWHM, which accounted for side lobes in the axial PSF caused by irregularities in the shape of the source power spectrum, such as spectral dips. Subsequently, we presented a method where the axial PSF was significantly optimized by suppressing the side lobes occurring because of the irregular shape of the source power spectrum. The optimization was performed through optically shaping the source power spectrum via a programmable spectral shaper, which consequentially led to suppression of spurious structures in the images of a layered specimen. The superiority of the demonstrated approach was in performing reshaping before imaging, thus eliminating the need for post-data acquisition digital signal processing. Importantly, towards the optimization and objective image quality assessment in optical coherence imaging, the impact of source spectral shaping was further analyzed in a task-based assessment method based on statistical decision theory. Two classification tasks, a signal-detection task and a resolution task, were investigated. Results showed that reshaping the source power spectrum was a benefit essentially to the resolution task, as opposed to both the detection and resolution tasks, and the importance of the specimen local variations in index of refraction on the resolution task was demonstrated. Finally, towards the optimization of OCT and OCM for use in clinical settings, we analyzed the detection electronics stage, which is a crucial component of the system that is designed to capture extremely weak interferometric signals in biomedical and biological imaging applications. We designed and tested detection electronics to achieve a compact and low-cost solution for portable imaging units and demonstrated that the design provided an equivalent performance to the commercial lock-in amplifier considering the system sensitivity obtained with both detection schemes.

Engineers and scientists have to cope with the challenges of a complex work environment. This study investigated the relationship between burnout, coping and sense of coherence amongst engineers and scientists. The Maslach Burnout Inventory, COPE and Sense of Coherence questionnaires were used. The study was conducted with 272 engineers and scientists at a global petro-chemical company with its head office based in South Africa. A theoretical relationship was determined and an empirical investigation provided evidence of such a relationship. The results confirmed a relationship between burnout, coping and sense of coherence amongst engineers and scientists. / Industrial and Organisational Psychology / M. Com. (Industrial and Organisational Psychology)

Engineers and scientists have to cope with the challenges of a complex work environment. This study investigated the relationship between burnout, coping and sense of coherence amongst engineers and scientists. The Maslach Burnout Inventory, COPE and Sense of Coherence questionnaires were used. The study was conducted with 272 engineers and scientists at a global petro-chemical company with its head office based in South Africa. A theoretical relationship was determined and an empirical investigation provided evidence of such a relationship. The results confirmed a relationship between burnout, coping and sense of coherence amongst engineers and scientists. / Industrial and Organisational Psychology / M. Com. (Industrial and Organisational Psychology)

The aim of the dissertation was to investigate the demographical differences on Work-SoC, and the relationship between work-related sense of coherence (Work-SoC) and work engagement in a motor retail organisation in Gauteng. The Work-related sense of coherence (Work-SoC) scale, Utrecht work engagement (UWES-9) scale and a biographical questionnaire were applied in the data collection from 326 employees in a motor retail organisation in Gauteng. The results indicated a strong relationship between Work-SoC and work engagement and that Work-SoC does predict work engagement. Except for tenure and gender, all demographical variables showed statistically significant mean differences on Work-SoC. The study has added valuable knowledge to the existing literature as it was the first to investigate mean differences on Work-SoC for different demographical groups and also investigate the relationship between Work-SoC and work engagement in the South African environment. / Industrial and Organisational Psychology / M. Com. (Industrial and Organisational Psychology)

This thesis deals with imaging through diffuse media in coherence-controlled holographic microscope (CCHM) developed in IPE FME BUT. The mutual coherence function as well as the signal dependence on the lateral mutual shift between both arms of the CCHM are calculated. Both functions are related to each other. The latter dependence is measured experimentally. A principle of imaging with CCHM through diffuse media with both ballistic and diffuse light is explained by a simple geometrical model. This model is then verified experimentally by imaging a sample through diffuse medium. The point spread function (PSF) of CCHM for imaging through diffuse media is then calculated. Results of PSF calculation are proved experimentally.

The present study aimed to investigate the relationships between, personal meaning, sense of coherence, organisational commitment and selected biographical variables, specifically age, tenure and occupational level. It was found that mostly significant positive relationships exist between personal meaning and sense of coherence. Personal meaning and sense of coherence exhibit predictive value for organisational commitment. It was established that self-transcendence plays a significant role in the development of affective and normative organisational commitment. Some significant differences were found between management and non-management employees in the manifestation of personal meaning. Management approximate more personal meaning to achievement, self-acceptance, and fair treatment. On sense of coherence and organisational commitment there were no significant differences between management and non-management employees. It was recommended that the relationship between personal meaning and other positive psychology variables be researched in order to determine the significance of such relationships so as to add to this relatively new body of research. / Industrial and Organisational Psychology / M.Comm.