The purpose of this study was threefold: (1) to determine the degree of pupil failure as it exists in the Senior High School, Stamford, Texas; (2) to consider the extent to which the "basic factors" of failure contribute to pupil failure in this school; and (3) to submit suggestions as to how pupil failure may be reduced to a minimum in the Stamford Senior High School.

The study involved retrospective data analysis using statistical methods to re-analyse data collected during a long-term study in a Human Immunodeficiency Virus infected population of South African National Defence Force employees and their dependents, where different parameters related to treatment and disease status of HIV infected patients were collected. This study attempted to identify possible predictors of both early and late occurrence of first-line antiretroviral therapy virologic failure, potential predictors of first-line antiretroviral virologic failure and for switching to second line therapy were identified. / Dissertation (MSc)--University of Pretoria, 2018. / HJF- Phidisa project / Pharmacology / MSc / Unrestricted

Background: Diastolic function (DF) guidelines have been simplified but lack extensive outcome data. Using a rural university heart failure (HF) database, we assessed whether DF grading could predict HF, HF readmission, and all-cause mortality (ACM). Methods: In this single-center retrospective study that included 613 patients in sinus rhythm hospitalized for HF (HF with preserved—254 patients, with mid-range—216 patients, and reduced ejection fraction—143 patients), we recorded demographics, Doppler-echo, Framingham HF score, laboratories, HF readmission, and ACM with follow-up to 2167 days. Results: Diastolic dysfunction (Ddys) parameters (left atrial volume index [LAVI] > 34 ml/m2, tricuspid regurgitation [TR] velocity > 2.8 m/sec, and E/e’ > 14) had moderate sensitivity (46.2%–65.0%) for predicting HF among all phenotypes combined with DF grading having moderate predictability and additive to a clinical composite for HF prediction (AUC =.677, P < 0.0001; difference =.043, P < 0.001) for combined phenotypes. Ddys parameters and Ddys severity (2016 ASE criteria: grade II and III) were significantly associated with HF readmission for decompensated HF within 60–2167 days of follow-up (LAVI > 34 ml/m2: HR 1.56 [1.26–2.19]; E/e’ > 14: HR 1.44 [1.21–1.99]; TR > 2.8 m/sec: H1.43 [1.19–1.88]; LV Dys grade II: HR 2.12 [1.42–2.96]; LV Ddys grade III: HR 2.39 [1.57–4.82]). Conclusion: The findings of this study highlight the clinical and prognostic relevance of determining the severity of LV Ddys in patients with HF with regard to HF verification and HF readmission.

1. Little work has been done on the response of regular haemodialysis patients to dynamic exercise. A systematic study of exercise capacity and the underlying mechanisms is of particular importance because these patients are encouraged to return to as normal a way of life as possible. Accordingly, a select group of healthy young male patients and a group of older males have been studied during submaximal cycling. The young male patients were compared to a closely matched sedentary control group. The 17 subjects discussed represent the fittest of 40 patients tested. 2. In both groups there was decreased work capacity associated with disproportionate tachycardia, which was not obvious at rest. Blood pressure was measured with a sphygmomanometer. During exercise there was a striking rise in the systolic blood pressure in about half the patients from currently acceptable resting levels. This occurred in the absence of any clinical circulatory overload. Mild hyperventilation and disproportionate lactic acidosis was seen towards peak exercise, probably because, in spite of the decreased work capacity, the patients were much closer to their maximum performance. However, the limiting factors were clearly circulatory and not respiratory. 3. A number of the younger male patients were more intensively studied to determine why some remained relatively 'normotensive' during exercise while others developed systolic hypertension. Total blood volume, total body water and plasma renin activity were measured at rest. It was found that the 'normotensive' patients had normal body volumes and normal to high plasma renin activity, while the hypertensive subgroup had increased volumes and normal to low plasma renin activity. Thus, in these patients the blood pressure responses to exercise were largely volume dependent, albeit at a subclinical level. 4. Cardiac output was measured at rest and during exercise. All patients developed a variable hyperkinetic circulation during exercise which was not apparent at rest. The patients were all anaemic and (xi) their cardiac output response was very like that described in patients with anaemia unassociated with renal disease. However, some patients with striking anaemia developed a less hyperkinetic circulation than others who were not so anaemic. When the body volume and the blood pressure response on exercise were considered, those patients who were normovolaemic and 'normotensive' developed a hyperkinetic circulation on exercise appropriate to their degree of anaemia. Those with subclinical volume overload and a hypertensive response to exercise developed a much less striking hyperkinetic circulation, suggesting that the blood pressure and volume excess was depressing the anticipated cardiac output response to their underlying anaemia. 5. One patient with an arteriovenous shunt was studied twice, initially when hypervolaemic with a haemoglobin of 9,1gm/100 ml and again after ultrafiltration when he was normovolaemic but his haemoglobin had risen to 12,5 gm/100 ml. On the first occasion his cardiac output response was moderately hyperkinetic but he developed increasing hypertension with a high calculated total peripheral resistance. On the second occasion his cardiac output response fell within the normal range, his blood pressure was lower but not normal and his calculated total peripheral resistance was even higher than before. Thus, the blood pressure of these volume dependent patients is due to a high total peripheral resistance, but may not simply be on the basis of 'waterlogging' of the peripheral vasculature. Some other factor, such as structural thickening, must be considered. 6. It is suggested that the combination of tachycardia and hypertension which develop on mild exertion and which may not be obvious at rest, is the most potent cause of the increased cardiovascular mortality seen in dialysis patients. Simple exercise testing will reveal those with subclinical volume overload who are most at risk. It was striking that in the two groups tested those who developed striking hypertension on exercise were usually older, between 35 and 50 years. This accelerated aging of their vascular tree would correspond with recent data showing that dialysis mortality increases with age, and is about a decade earlier than in the general population. It is suggested that a more aggressive policy be adopted towards blood pressure fluctuations and that the resting blood pressure should be kept below 140/90 mm Hg at all times, if necessary by complementing ultrafiltration with drug therapy and/or bilateral nephrectomy at an early stage. 7. Thus simple exercise testing with blood pressure recordings not only serves as a yardstick of physical rehabilitation and long-term follow-up, but may also reveal or magnify abnormalities not obvious at rest.

Research areas within the automotive industry are dedicated to reducing the weight and emissions of vehicles. Through the application of lightweight materials, such as polymers, fuel consumption and production costs can be decreased. Therefore, understanding the mechanical responses and failure mechanisms of these materials is significant to the development and design of vehicular structural components. Experimental tests were performed to capture the time, temperature, and stress state dependence, as well as failure mechanisms and large-strain mechanical responses of polypropylene (PP) and copolymer polypropylene (co-PP). Alongside studying the mechanical responses of PP and co-PP, the deformation mechanisms associated with the ductile and brittle failures were also examined. By applying an Internal State Variable (ISV) model, the mechanical behavior of PP and co-PP under various strain rates and temperatures was predicted. Phenomenological, mechanics based failure criteria were also applied to the model to predict the ductile or brittle failure of the materials.

In order to remain competitive in the global market businesses are under ever increasing pressure to ramp up production rates whilst simultaneously improving cost effectiveness to allow continued profitable growth. This requirement is particularly challenging in high value manufacturing which is characterised by expensive product and manufacturing systems and relatively low production volume. This thesis introduces a method for the design of robust and reliable manufacturing processes through the prevention of identified potential failure modes that is based on the principles of the existing Failure Mode Avoidance framework used for automotive system design. The tools and techniques that exist in the literature are reviewed in order to understand the best practice, and subsequently a Manufacturing Failure Mode Avoidance framework is designed. This framework is demonstrated through two unique case studies conducted in a real life manufacturing environment in order to validate its appropriateness to provide robust countermeasures to failure which will allow right first time manufacture. The outcomes of the implementations are discussed, conclusions drawn and opportunities for further research are provided.

A simulation-based reliability analysis method is presented and evaluated. This method is intended for problems for which most probable point of failure (MPP) search-based methods fail or provide inaccurate results, and for which Monte Carlo simulation and its variants are too costly to apply. This may occur in the evaluation of complex engineering problems of low failure probability. The method used to address this problem is a variant of conditional expectation and works by sampling on the failure boundary without relying on the MPP. The effectiveness of the method is compared to a selection of other commonly available reliability methods considering a variety of analytical as well as more complex engineering problems. The results indicate that the method has the potential to deliver solutions of high efficiency and accuracy for a wide range of difficult reliability problems.

Shutdowns in a chemical processing plant are detrimental both to plant economics and critical product characteristics. These situations can be due to routine maintenance, or due to the more extreme case of equipment failure due to wear. Nevertheless, both are cases of non-normal plant operation, and are often unavoidable. These situations are complicated further when many units are linked, and subjected to a high degree of integration. In this case, the shutdown of any unit within the plant can have immediate and potentially severe impacts on other areas of the operation. Since these events are unavoidable, the challenge is to minimize their economic impact through careful design of operating practices, and potentially plant design retrofits. This thesis focuses on developing generic and systematic methods of determining economically optimal operating policies and plant designs in the face of failures in multi-unit operations. This includes determining the optimal trajectory of critical plant variables (flows through units, flows between units, buffer tank levels, etc.), as well as determining whether plant design changes would improve plant economics during such events. Such ventures lead to mixed-integer dynamic optimization (MIDO) problems. A dynamic model of the process is presented, accounting for the major flows of process materials through units, between units, as well as the accumulation of these in the intermediate buffer capacities. The approach used was to assume that the processing units operated at pseudo-steady-state, with dynamics confined to the intermediate buffer capacities. All models developed were based on a combination of empirical and fundamental elements. For use of the model in an optimization study, a simultaneous approach, in which the differential equations are discretized and included as equality constraints, was employed. This yielded a nonlinear optimization problem involving only algebraic equations. Optimal responses to scenarios involving planned maintenance shutdowns, as well as unplanned shutdowns (unit failures) were computed, with plant economics used as the merit function. Sensitivity to parameters such as preparation time, shutdown length, and restoration time were studied. In all cases, it was desired to maximize plant economics, while maintaining a smooth operation. While several methods are available for use in a multi-criterion optimization problem, a two-tiered approach was developed and applied in which the plant economics were maximized first, and input usage subsequently minimized as a secondary objective. After identifying key failure scenarios through a review of industrial data and downtime reports, a multiple-model formulation was developed involving the probability distribution of failure scenarios. Optimal steady-state operating levels for the buffer capacities were computed. This formulation is then extended to a mixed-integer programming problem in which the addition of extra buffer capacity is included as a decision variable. / Thesis / Master of Applied Science (MASc)

Patients with severe heart failure (HF) are often excluded from exercise training studies due to their potentially unstable nature and severe exercise intolerance. Steady state cycling and walking have been the most common interventions and it is unknown whether these training modalities are appropriate and safe for patients with severe HF as they can produce significant cardiovascular stress. Body-weight supported treadmill (BWST) training may be beneficial in patients with severe HF by improving the periphery while minimizing cardiac loading. The purpose of this study was to: 1) assess the safety and feasibility of BWST training in severe HF patients and 2) to evaluate the effect of BWST training on functional capacity, health-related quality of life (HRQL ), cardiopulmonary function, and blood vessel function. Three male patients with severe HF participated in the study. On study entry and at the end of 24 sessions of physician supervised BWST training, patients completed a cardiopulmonary exercise test, two HRQL questionnaires, a 6-Minute Walk Test (6-MWT), and a Doppler ultrasound study. Although there were no study-related adverse events, only one subject (Patient 1) was able to complete post-testing. However, all three patients seemed to demonstrate a general trend towards increased exercise tolerance. By the seventeenth exercise session, the BWS was reduced to zero for Patient 1. In addition, Patient 1 achieved an average walking speed of2.0 km/hr and was completing 34 minutes ofwalking with minimal rest periods by the end of the training program. Patients 2 and 3 also responded to the training as evidenced by a slight increase in exercise duration. However due to fluctuations in their health status, they did not have any substantial improvement. Patient 1 experienced substantial increases in functional capacity: a 64% increase in V02 peak (7.2 to 11.7 ml/kg/min); a 33% increase in peak power output (300 to 400 kpm/min); a 37% increase in VE peak (28 to 39 L/min); and a 28% increase in 6-MWT distance (223. 5 to 286m). In addition, Patient 1 's NYHA-FC improved after training from class III to II. A significant training effect was also evident by reductions in HR at rest (96 to 79 bpm) and during submaximal exercise (100 kpm/min) (105 to 84 bpm). HRQL also tended to improve for Patient 1. Based on these findings and observations, two conclusions can be made. First, patients with severe HF can safely participate in BWST training and may derive considerable benefits. Second, the feasibility of training patients with severe HF is highly dependent on their cardiac condition and other co-morbidities remaining stable enough to allow consistent training. / Thesis / Master of Science (MS)

Laminated composite structures have started to play a very significant role in today's aircraft industry. The application of composite materials has now gone beyond the borders of aircraft design and has entered into such fields as automotive, athletics and recreational equipment, etc. The light weight and high specific strength of composite material helps design vehicles with higher fuel efficiency and longevity. In order to understand the influence of design parameters related to the use of composite materials in these applications, a proper study of the laminated composite structures requires a complete failure analysis, which includes both initiation and propagation of damage. In this work a progressive failure methodology is developed and implemented in the commercial Finite Element software package, Abaqus. Out of the numerous failure criteria available in the literature to study damage initiation and propagation in unidirectional fiber reinforced composites, Puck and Schurmann's failure criteria have been chosen due to their ability to predict results close to those observed experimentally. Key features of the Puck and Schurmann's failure criteria for three-dimensional deformations of unidirectional fiber reinforced composites have been summarized. Failure modes in the matrix and the fiber are considered separately. The failure criteria are simplified for plane stress deformations. Whereas the failure plane can be analytically identified for plane stress deformations, a numerical search algorithm is needed for three-dimensional problems. Subsequent to the initiation of matrix failure, elastic moduli are degraded and values of these degradation parameters and fracture plane angles are found by using a Continuum Damage Mechanics (CDM) approach. It is found that the assumption that the material response remains transversely isotropic even after the matrix failure has initiated requires the degradation of the transverse Poisson's ratio. The Puck and Schurmann's failure criteria and the material degradation process have been implemented as a User Defined Field (USDFLD) subroutine in Abaqus. The implementation has been verified by analytically computing results for simple loadings and comparing them with predictions from using the USDFLD in Abaqus. Subsequently, both two- and three-dimensional problems of more realistic geometries and loadings have been analyzed and computed results compared with either experimental findings or results available in the literature. Major contributions of the work include identifying the degradation parameter for the transverse Poisson's ratio in terms of the matrix degradation parameter for the matrix failure in compression, development of the USDFLD based on Puck and Schurmann's failure criteria, implementing the USDFLD in the commercial finite element software, Abaqus, and verifying that results computing using the USDFLD for various laminates and loadings agree with those from either the analytical solution of the problem or those available in the literature. / Ph. D.