Thesis (Ph. D.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2004. Directed by Ashok Saxena. / Includes bibliographical references (leaves 143-146).

Thesis (Ph. D.)--Lehigh University, 2001. / Includes vita. Includes bibliographical references (leaves 666-672).

Thesis (M. Phil.)--University of Hong Kong, 1974. / Mimeographed.

Thesis (Ph.D.)--University of Central Florida, 2009. / Adviser: Yong-ho Sohn. Includes bibliographical references.

Over the last few years the World Health Organization (WHO) has endorsed several tests for the rapid detection of multidrug-resistant tuberculosis (MDR-TB) in resource-poor settings. The objective of this study was to compare the cost-effectiveness of a line probe assay test (less than one week for results) to conventional (bacterial culture) drug susceptibility testing (one month for results) for the detection of MDR-TB in an HIV-positive South African population by estimating the incremental cost-effectiveness ratio (ICER) per disability-adjusted life-year (DALY) averted. Costs of testing, drug treatment, hospitalization, as well as estimates for mortality, treatment success, and failure rates were obtained from literature sources, the South African Department of Health, the WHO, the Foundation of Innovative Diagnostics (FIND), and expert opinion. The willingness-to-pay threshold for a DALY averted was pre-set at 3 times the 2009 GDP per capita (about $17,400) for South Africa. In the base-case scenario for a prevalence of 30% of MDR-TB among HIV-positive patients, the average cost per person for the line probe assay testing strategy was $3,539/0.458 DALY averted and the conventional testing approach was $3,011/0.430 DALY averted. The base-line ICER was about $18,800 per DALY averted – about $1,400 above the pre-set threshold. In sensitivity analyses, the model was robust to changes in prevalence (+ 50%); costs (+ 10%), and probabilities of death, success and failure (+ 20%). However, when the treatment success rate for the line probe assay test was increased to 60% (one of the targets set by WHO in TB treatment) the ICER was below the willingness-to-pay level (i.e., cost-effective). The probabilistic sensitivity analysis showed there is a 70% chance that the additional cost of the line probe assay, compared with conventional testing, was less than $30,000 per DALY averted. However, the model may have underestimated the benefits of the line probe assay because it did not account for a decrease in the transmission of the disease due to earlier treatment nor did it measure any benefits more than a year after testing. / text

published_or_final_version / Microbiology / Master / Master of Medical Sciences

Tuberculosis (TB) is a highly infectious disease that causes the second highest mortality rate in human worldwide. The emergence of multi-drug resistance tuberculosis (MDR-TB) leads to a major public health problem in controlling TB-caused mortality. Pyrazinamide (PZA) is an important first-line drug in the treatment of MDR-TB. However, since the challenge in performing susceptibility test on PZA, World Health Organization has not published any data on the prevalence of PZA resistance in Mycobacterium tuberculosis (M. tuberculosis). Since the occurrence of PZA resistance makes MDR-TB more difficult to treat with poor prognosis, rapid detection method in PZA resistance is urgently needed. Since pncA mutation is highly associated with up to 98% PZA resistant M. tuberculosis strains, it is worthwhile to develop rapid molecular method for detecting PZA resistance. This study aims to identify the mutations in PZA resistant M. tuberculosis strains. The first part of this study aims to characterize the pattern of pncA mutation among PZA-resistant and PZA-susceptible M. tuberculosis using Sanger sequencing method. Among all clinical isolates, 12 out of 29 cases of M. tuberculosis were resistant to PZA. All PZA-resistant M. tuberculosis strains harbored pncA mutation, whereas no known mutations were found among those PZA-susceptible strains, giving the positive predictive value to be 100%. Eight mutation patterns were found among 12 resistant isolates. Four of these pncA mutations have not been described previously by other studies. Study also characterizes the pattern of pncA mutation in 19 sputum specimens, with 2 mutation patterns found. Overall 10 mutation patterns were found in this study. Results show that the mutation of pncA gene is highly associated with PZA-resistant M. tuberculosis. Results also suggest the scattered and more extensive mutations in pncA gene that confer PZA resistance to M. tuberculosis. The second and the last part of this study aims to evaluate the possibility of using molecular method to detect PZA resistance in routine clinical laboratory. Results show that using molecular sequencing to detect PZA resistance can shorten the turnaround time to about 3-4 working days. Since mutation of pncA was scattered along the entire pncA gene, using DNA sequencing approach may be the best strategy for the rapid detection of PZA resistance in M. tuberculosis. / published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

D. Tech. Chemical, Metallurgical and Materials Engineering / Corrosion is the chemical or electrochemical interaction between a material, especially metals, and their environment resulting in mild to severe deterioration of the material and its properties. The economic impact and problems resulting from corrosion has drawn strong attention from scientists and engineers worldwide. Stainless steel is the most important engineering metal worldwide, and industrially stainless steel is used extensively due to its resistance to corrosion e.g. in acid pickling, industrial acid cleaning, acid descaling, oil well acidizing and the petroleum industry. The corrosion resistance of stainless steels is due to the formation of a protective film which covers the steel surface instantaneously when exposed to mild operational conditions in the presence of oxygen; however, the oxide is most often porous and insufficient to protect the steel from further oxidation and corrosion attack in harsh environments. It is hypothesized that: In-depth understanding of the electrochemical behaviour of ferrous alloys in interaction with selected organic compounds in acidic environments will enhance inhibitor application for corrosion control; Failure and poor performance of most inhibitor admixtures can be eliminated with comprehensive knowledge of electrochemical interaction at the metal-inhibitor interface, passive film formation, duration and breakdown, adsorption characteristics, bond formation and molecular structure effect; Optimization of the current electroanalytical method will enhance effective pitting corrosion detection, analysis and control with the use of organic inhibiting compounds. The primary aim of this research is to develop the science required for the effective assessment, development and confident use of organic compounds (heterocyclic compound, organosulphur compound, simple alcohol, aromatic amine compound, aromatic amine derivative and aminoalcohol) and tested alloys (austenitic stainless steel type 304 and mild steel) for applications in astringent environments through conventional and optimized corrosion monitoring techniques.

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