3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item A life cycle analysis and assessment of chemical emulsions(2011-05-24) Ram Reddi, ManogaranThis study utilises the Life Cycle Environmental Management tool, Life cycle Assessment (LCA) to compare the overall environmental impact of the life cycles of three manufactured emulsions. The emulsions - Aquapel, Hi-phase/composite (liquid/solid rosin) - fulfil a specific function as a sizing agent in the cardboard box industry within the confines of South Africa. As the origins and use of these emulsions are different, the impact assessments of each were evaluated. Using the Simapro Impact 2002+ assessment method, the mid-point impact categories show the most significant impacts in descending order to be Toxicity Impacts on terrestrial ecosystems, Respiratory Inorganics, Climate Change and Non Renewable Energy resources. It would appear that toxicity impacts on terrestrial ecosystems, is the most significant impact. Emission of respiratory inorganics followed by effluent treatment, then electricity used in the emulsion process itself has the next highest contribution in all three processes. The higher contribution to respiratory inorganics by the process using liquid rosin is due to a relatively high contribution from the production of tall oil, a relatively energy intensive process. Climate change is the third most significant contribution. Non renewable energy resources for the Aquapel process shows the highest impact because of its raw material, wax. It is also based on a non-renewable energy resource, crude-oil, whilst the raw material for the Hi-phase/composite process, rosin, is bio-based. When comparing the three emulsion processes according to the Impact 2002+ damage or end point impact categories the relative contributions of the processes shows the relatively close performance of the three processes. The liquid rosin process shows slightly higher potential damages in three out of the four damage categories. The explanation for the differences between the systems follows from the explanations given for the mid-point impact categories. The sensitivity analysis for the Aquapel emulsion process shows negative impacts are produced in descending order for liquid effluent in the ecosystem and human health damage categories. For electricity and paraffin wax negative impacts in the human health and climate change damage categories. The best interventions to reduce life cycle damages is to reduce water and electricity consumption and if possible to find a substitute for paraffin wax. For the Hi-phase/composite liquid / solid rosin emulsion process shows negative impacts are produced in descending order for liquid effluent in the ecosystem and human health / climate change and resources damage categories respectively. The electricity and steam used in both the liquid / solid process produce negative impacts in the human health and climate change damage categories. The best interventions to reduce life cycle damages for the rosin emulsion process are to reduce water, electricity and steam consumption.Item Comparative outcomes between HIV positive and negative endodontic patients(2009-05-05T10:20:06Z) Tootla, SaidahPurpose: To compare the presenting symptoms and the outcomes of root canal therapy between HIV positive and HIV negative endodontic patients over a 6-12 month period. Methods: Fifty-nine HIV negative and 46 HIV positive patients presented for endodontic treatment. Signs and symptoms were noted and compared for both groups of patients, together with demographic data and CD4 counts for the HIV positive patients. Endodontic procedures were evaluated after an 18-month period. Endodontic treatment was assessed using clinical factors (palpation, percussion, sensitivity to hot and cold, swellings, excessive bleeding), and radiographic factors (periapical radiolucency, root resorption, periodontal ligament space). Results: There was no statistically significant difference in the preoperative presenting symptoms of endodontic infections/conditions between HIV positive and HIV negative patients. The prevalence of radiographic caries in the presenting teeth was only 24% in the HIV positive patients compared with 95% in the HIV negative patients. For the HIV positive patients, the treatment time required to resolution of the endodontic infection was nearly twice (113 minutes) that of the HIV negative patients (52 minutes). Amongst the HIV positive patients still experiencing symptoms at 18 months, pain was more severe in those patients with lower CD4 counts (significance at the 90% level of confidence). Conclusion: Within the limitations of this study the following conclusions emerge: 1. Although the success rate was lower over the period of this study in HIV positive patients, the rate is sufficiently high to warrant treatment. 2. Patients who are HIV positive may present with more severe symptoms and during treatment more bleeding may be expected. 3. In keeping with best practice for immuno-compromised patients, it would be advantageous to put HIV positive patients on antibiotic cover during treatment. 4. The process of anachoresis may explain the high incidence of endodontic infections in teeth with no history of trauma or caries in the HIV positive group.