The effect of nonstirred aqueous Portland cement solution on the corrosion rates of zinc and cadmium metal using Tafel extrapolation and linear polarization measurements has been investigated. Results indicate that for the corrosion systems under investigation, zinc metal has a higher corrosion potential and lower corrosion rate than cadmium metal.

Cohesionless sands are known to be susceptible to failure by liquefaction when they are saturated and subjected to earthquake shaking. Considerable study has been directed towards this subject over the past 20 years in recognition of the possibility of large-scale property damage or loss of life due to this type of failure. Recent evidence has shown that small degrees of cementation in a sand significantly reduce the likelihood of liquefication. However, the work to date has been limited to studies with conventional testing devices and simple loading paths. These devices are suspected of inducing premature failure in cemented soils, and are not capable of modeling the effects of multiaxial loading. In this investigation, there were two major objectives. The first involved the development and fabrication of a new three~dimensional shear device with the capability of applying load to cemented sands with a minimum of stress concentration effects, and of using load paths which are more representative of the true effects of an earthquake than is possible in conventional equipment. The second concerned performance of a series of production tests to investigate the behavior of cemented sands under a range of earthquake loading paths. The production tests were largely performed using the new three—dimensional shear device. The test results showed that cemented soils have more resistance to earthquake loading than previously thought since stress concentration effects in conventional testing do induce premature failure through the effects of stress concentrations. On the other hand, it was found that either cemented or uncemented sands show less resistance to earthquake loadings if multiaxial stress conditions are applied to the sample as opposed to uniaxial loadings. This is important in explaining the fact that sites with seemingly similar conditions often show different behavior, since slightly different earthquake loading pattems can cause different responses. One factor explaining differences in response is found to be the mean normal stress, which is not the same for all loadings, and plays an important role in the pore pressures developed in the soil. / Ph. D. / incomplete_metadata

Carbohydrates and fats are the main fuel sources for energy production during exercise. Consumption of low glycemic index foods slows digestion and absorption in the small intestine. The slow digestibility of resistant starch containing foods contributes to the slow and sustained release of glucose into the bloodstream, minimizing occurrence of hyperinsulinemia-induced suppression of lipolysis. The objectives of this study were to determine the consumption of resistant starch (RS) by regular exercisers (Blacksburg and San Jose (SJ)); and to analyze the eating and exercise habits of the subjects. Subjects were recruited at gyms in SJ (n=27) and Blacksburg (n=26). Participants kept 3-day food records and completed a questionnaire on eating habits and physical activity. Mean body mass index for the subjects was similar (SJ: 23.06 Kg/m² ± 2.55; Blacksburg: 23.53 Kg/m² ± 3.09). Average exercise time was 12 hours/week, and > 50% engaged in weight training in addition to aerobic type exercise. Percentage contribution of carbohydrates to the total energy intake was significantly higher for SJ males (53.53% ± 8.06%) compared to Blacksburg males (48.39% ± 6.33%; alpha=0.10). Prominent RS food sources in both groups were pasta, potatoes, bananas, and corn. Rice and various legumes were more frequent in the SJ group. It appears that consumption of RS is higher among SJ subjects. Consumption of RS prior to prolonged exercise could cause stable glycemic and insulinemic responses that may help delay the onset of fatigue during exercise. / Master of Science

結核病仍是全球疾病和死亡的主要原因。雖然人均新發結核病例自2003年以來一直下降，耐多藥（MDR）和廣泛耐藥（XDR）的結核病例的突然增加為全球疾病控制帶來了新的威脅。結核分枝杆菌（MTB）北京株在過去十年越来越受重視，皆因其席捲亞洲，前蘇聯，和包括美國在內的好幾個地方。北京株在動物實驗中也表現出高毒性和耐多藥的傾向。目前結核菌廣泛耐藥定義為至少對異煙肼和利福平耐藥，再加上任何氟喹諾酮類，和至少一個二線藥物。我們對這種病菌的生物知識仍然有限。在這研究，我們為來自香港和福建五株MTB北京株進行了基因組測序，其中兩株的耐藥性遠超XDR標準 - “全耐藥“（TDR）的表型。五個北京株的比較基因組學為我們提供了在北京株的毒力相關基因的啟示。一個約4 KB大小的片段被找出来了，此片段是所有已知MTB中都没有的。我們討論了此片段對MTB進化的含義。當我們研究在北京耐藥株的獨特基因變化時發現，DNA修復和香葉醇降解有關連。我們還觀察到大的缺失（D）和截斷（T）的事件，顯著高於框移位（F）的突變。此外，在TDR菌株出現的FDT事件更頻繁地涉及到最佳生長和麻風分枝杆菌的基因組中保留的基因。這方面的証據表明，MTB通過缩减進化發展極端耐藥性。適應度的顯著降低也許解釋了TDR菌株的稀缺 。 / Tuberculosis (TB) remains one of the major causes of illness and death globally. Although the number of new TB cases per capita has been falling since 2003, the emergence of multidrug resistant (MDR) and extensively drug resistant (XDR) cases of TB poses new threat to the successful worldwide control of the disease (WHO, 2008; Iseman, 2007). The Beijing lineage of Mycobacterium tuberculosis (MTB) has received much attention over the past decade due to its prevalence throughout Asia, parts of the former Soviet Union, and several other geographical locations including the United States. The strain also demonstrated hypervirulence in animal models and an increased likelihood to develop multidrug resistance. The current definition of XDR in TB is defined as resistance to at least isoniazid and rifampicin, any fluoroquinolone, and with at least one of the three second-line drugs. Here we show that our knowledge of the biology of this pathogen is still limited. We performed genome sequencing and reported the complete genomes of five Beijing isolates from Hong Kong and Fujian, of which two were shown to have drug resistance that is far beyond the current XDR standard - a "Totally Drug Resistance" (TDR) phenotype. Comparative genomics of the five Beijing isolates provided us insights into the virulence-related genes in the Beijing family. A distinct region of about 4 kb in size that are absent in all known complete genomes of MTB was also identified. The evolutionary implications of this region were discussed. When we investigated the unique genetic changes in drug resistant Beijing strains, a correlation to DNA repair and geraniol degradation was implicated. We have also observed that the big deletions (D) and truncations (T) events were significant higher when compare with frameshift (F) mutations. Moreover, the FDT events in TDR strains were more frequently found in genes that are involved in growth attenuation and retained in the genome of the Mycobacterium leprae. This evidence suggests that MTB develops its extreme drug resistance through the reductive evolution. The significant decrease in the fitness may explain the rareness of TDR strains. / Detailed summary in vernacular field only. / Leung, Ka Kit. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 93-108). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Epidemiology - a ubiquitous threat --- p.1 / Chapter 1.2 --- Surviving the Hell --- p.3 / Chapter 1.3 --- Relatives of M. tuberculosis --- p.4 / Chapter 1.4 --- The age of M. tuberculosis --- p.5 / Chapter 1.5 --- Characteristics of Beijing strains --- p.6 / Chapter 1.6 --- Drug resistance --- p.7 / Chapter 1.7 --- Genome sequencing --- p.9 / Chapter 1.7.1 --- Conventional sequencing --- p.9 / Chapter 1.7.2 --- High-throughput sequencing --- p.10 / Chapter 1.8 --- Sequence assembly --- p.11 / Chapter 1.8.1 --- De novo assembly --- p.11 / Chapter 1.8.2 --- Reference mapping --- p.12 / Chapter Chapter 2 --- Materials and Methods --- p.14 / Chapter 2.1 --- Sample preparation --- p.14 / Chapter 2.2 --- DNA extraction and genome sequencing --- p.18 / Chapter 2.3 --- Gap filling and finishing --- p.20 / Chapter 2.3.1 --- In silico gap verification --- p.20 / Chapter 2.3.2 --- Comparison among different reference mapped contigs --- p.24 / Chapter 2.3.3 --- Experimental work --- p.26 / Chapter 2.4 --- Bioinformatics analysis --- p.27 / Chapter 2.4.1 --- Genome annotation --- p.27 / Chapter 2.4.2 --- Phylogeny analysis --- p.27 / Chapter 2.4.3 --- Variation analysis --- p.28 / Chapter 2.4.4 --- In silico functionality analyses --- p.29 / Chapter Chapter 3 --- Results --- p.30 / Chapter 3.1 --- Genome features of M. tuberculosis Beijing genotype strains --- p.30 / Chapter 3.2 --- Phylogeny of M. tuberculosis Beijing genotype strains --- p.36 / Chapter 3.3 --- Evolutionary implications of a 4kb-insertion in Beijing strains --- p.40 / Chapter 3.4 --- Beijing family specific gene variations --- p.48 / Chapter 3.5 --- Drug resistance --- p.52 / Chapter Chapter 4 --- Discussions --- p.75 / Chapter 4.1 --- 4kb insertion, a potential bridge to our knowledge gap --- p.75 / Chapter 4.2 --- Beijing common and Beijing drug resistant specific variations --- p.77 / Chapter 4.3 --- Regions of deletion --- p.79 / Chapter Chapter 5 --- Conclusions --- p.82 / Chapter Chapter 6 --- Future Work --- p.84 / Chapter 6.1 --- Compensatory mutation study --- p.84 / Chapter 6.1.1 --- Database construction for drug resistance compensatory mutations --- p.85 / Chapter 6.2 --- Non-protein coding region study --- p.92

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / Ph.D.

結核病是由結核桿菌感染而引起的慢性傳染病，它是危害人類健康的主要殺手。根據世界衛生組織的報導，目前在全球範圍內有三分之一的人口感染了結核桿菌，每年約有915 萬人口被確診患有結核病。耐藥結核病尤其是對最有效的一線抗結核藥物異煙阱和利福平產生抗藥的耐多藥結核病的出現，令有效的控制結核病更加棘手。 / 在本研究中，我們首先用利福平誘導得到五株伴有明顯生長緩慢的高水平利褔卒耐藥的恥垢分支桿菌。通過比較基因組學研究發現，在編碼區有四個突變，其中兩個位於中rpoB 基因(N484T and 1488F) ，一個位於MSMEG_0436 (V49M) ,一個位於MSMEG_6872 (V181L)。rpoB 基因突變是該恥垢分支桿菌利福平耐藥的主要原因。而生長緩慢主要源於MSMEG_6872基因的影響。更為有趣的是，我們發現一個與MSMEG_6872具有相同的蛋白模序的結核分支桿菌蛋白質Rv1367 在不間的結核分支桿菌菌株之間存在I193V 多態性。193V 主要存在于北京株或者在耐藥的非北京株上。進一步的研究發現，過量表達MSMEG_6872或者Rv1367c 的恥垢分支桿菌形態上呈現為細長棒狀，而他們的親代則為短棒狀。 / 為獲得耐藥性，以及在高濃度的抗生素環境下生存，細菌必須付出一定的生物學代價。本研究中，恥垢分支桿菌以生長缺陷為代價獲得了對利褔平的耐藥，而這個代價可能是由於MSMEG_6872 基因的突變或者過量表達打破了細胞壁延長和分裂的平衡引起。 / Mycobacterium tuberculosis (MTB), which is the pathogen of tuberculosis (TB), remains a major human public health problem throughout the world. According to the report from the World Health Organization, currently about one third of the world's population was infected by MTB and there is globally 9.15 million recorded cases of TB annually. The occurrence of resistance to drugs used to combat TB, particularly multi-drug resistant TB (MDR-TB), defined as resistance to at least isoniazid and rifampin (RIF), has become a significant public health problem in a number of countries and an obstacle to effective global TB control. / In this project, we firstly obtained high level RIF resistant Mycobacterium smegmatis (MSM) strains with obviously growth retardation by repeated drug selection. Comparative analysis of genomic sequences revealed 4 mutations in coding sequences, including two in rpoB (N484T and I488F), one in MSMEG 0436 (y 49M), and one in MSMEG 6872 (y181L). Characterization of these four mutations showed that the two mutations in rpoB were correlated to RIF resistance. The one in MSMEG_6872 can render obviously growth retardation when MSMEG_6872 is over-expressed. Interestingly, we found an MTB protein, Rv1367c, which has the same motif with MSMEG_6872, had an I193V polymorphism in different MTB strains. The 193V variant was mainly found in Beijing/W or drug resistant non-Beijing/W family strains. The transformants, no matter MSMEG_6872 or Rv 1367 c, all exhibited slim and long rod shape compared to stocky and short rod appearance of the parental strain. / Mycobacterial cells must pay biological cost in order to obtain RIF resistance and survive in the high concentration of RIF. In our case, the growth arrest may be due to the mutation of MSMEG_6872 which disrupts the balance of cell wall elongation and cell division. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Guan, Bing. / "November 2011." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 139-143). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Acknowledgements --- p.I / Abstract --- p.II / Abstract in Chinese --- p.IV / List of Abbreviations --- p.V / List of Tables --- p.VI / List of Figures --- p.VII / Contents --- p.IX / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Overview of Tuberculosis --- p.1 / Chapter 1.1.1 --- Pathogens --- p.2 / Chapter 1.1.2 --- Syndromes --- p.2 / Chapter 1.1.3 --- Transmission --- p.3 / Chapter 1.1.4 --- Diagnosis --- p.4 / Chapter 1.1.5 --- Epidemiology --- p.6 / Chapter 1.1.6 --- Mortality --- p.8 / Chapter 1.2 --- The Anti-TB Strategies --- p.8 / Chapter 1.2.1 --- Chemotherapy Treatment for MTB --- p.8 / Chapter 1.2.2 --- Vaccine Development for MTB --- p.9 / Chapter 1.3 --- Genome Sequencing of MTB Isolates --- p.9 / Chapter 1.4 --- Drug Resistance of MTB --- p.13 / Chapter 1.4.1 --- MDR-TB and XDR-TB --- p.15 / Chapter 1.4.2 --- Mechanism of Drug Resistance --- p.18 / Chapter 1.4.2.1 --- Intrinsic Resistance of Mycobacterium Species --- p.20 / Chapter 1.4.2.2 --- Acquired Resistance of Mycobacterium Species --- p.22 / Chapter 1.4.3 --- RIF Resistant MTB --- p.24 / Chapter 1.5 --- Useful tool for MTB Research --- p.26 / Chapter 1.6 --- The Biological Cost of Antibiotic Resistance in MTB --- p.27 / Chapter 1.6.1 --- The meaning of Biological Cost --- p.27 / Chapter 1.6.2 --- Factors Involved in Biological Cost of Mycobacterium Species --- p.29 / Chapter 1.17 --- Objectives of the Project and Experimental Strategies --- p.30 / Chapter CHAPTER 2 --- MATERIALS AND METHODS / Chapter 2.1 --- Selection of RIF Resistant MSM mc²155 Strains --- p.31 / Chapter 2.1.1 --- Bacterial Strains, Media, and Growth Conditions --- p.31 / Chapter 2.1.2 --- Selection of RIF Resistant Strain --- p.31 / Chapter 2.2 --- Minimum-Inhibitory-Concentration (MIC) Assay --- p.34 / Chapter 2.3 --- Detection of Mutations in the rpoB Gene of RIF Resistance Strains --- p.36 / Chapter 2.3.1 --- Primers Design --- p.36 / Chapter 2.3.2 --- PCR and Direct Sequencing --- p.36 / Chapter 2.4 --- Characterization of the RpoB Gene --- p.38 / Chapter 2.4.1 --- Construction of Recombinant Clones --- p.38 / Chapter 2.4.2 --- Preparation of MSM competent cell. --- p.38 / Chapter 2.4.3 --- Electroporation of plasmid into MSM competent cells --- p.39 / Chapter 2.4.4 --- Site-directed Mutagenesis of the RpoB Clone --- p.39 / Chapter 2.5 --- Whole Genome Sequencing of Parental and Drug --- p.43 / Chapter 2.5.1 --- MSM Genomic DNA Extraction --- p.43 / Chapter 2.5.2 --- Genomic Sequencing --- p.44 / Chapter 2.5.3 --- Data Analysis and SNPs Identification --- p.45 / Chapter 2.6 --- Validation of Mutations by PCR and Direct Sequencing --- p.46 / Chapter 2.6.1 --- PCR Primers Design --- p.46 / Chapter 2.6.2 --- PCR and Direct Sequencing --- p.46 / Chapter 2.7 --- Characterization of MSMEG 0436 and MSMEG 6872 --- p.47 / Chapter 2.7.1 --- Construction of the recombinant clones --- p.47 / Chapter 2.8 --- Assay of Ethidium Bromide in Intact Cells --- p.48 / Chapter 2.9 --- Quantitative Real-time PCR to Expression of the Measure the ATP-binding Cassette (ABC) Superfamily Efflux Pumps --- p.49 / Chapter 2.9.1 --- RNA Extraction --- p.49 / Chapter 2.9.2 --- Synthesis of Double-stranded cDNA from Total RNA --- p.49 / Chapter 2.9.3 --- Real-time PCR to Quantify the Efflux Pump Gene Expression Level --- p.49 / Chapter 2.10 --- The construction of the Growth Curve --- p.53 / Chapter 2.11 --- Generation of ΔMSMEG_6872 Mutant Strain --- p.54 / Chapter 2.11.1 --- Preparation of Recombination Strain Stocks --- p.54 / Chapter 2.11.2 --- Preparation of the Electrocompetent Cells of the Recombination Strain --- p.54 / Chapter 2.11.3 --- Preparation of Allelic Exchange Substrate (AES) for Generating Gene Replacement Mutants --- p.55 / Chapter 2.12 --- Validation of Rv1367c (MT1414) in MTB --- p.60 / Chapter 2.12.1 --- Primer Design --- p.60 / Chapter 2.12.2 --- Strain Selection --- p.60 / Chapter 2.12.3 --- PCR and Direct Sequencing --- p.60 / Chapter 2.12.4 --- Alignment the Gene Sequence of Rv1367c of Different MTB Strains --- p.61 / Chapter 2.13 --- Model building of the RpoB protein --- p.62 / Chapter 2.14 --- MSM staining method --- p.63 / Chapter CHAPTER 3 --- RESULTS / Chapter 3.1 --- dentification of RIF Resistant Related-genes Using Induced RIF Resistant MSM Model --- p.64 / Chapter 3.1.1 --- Emergence ofRIF Resistant Strains after the Prolonged Drug Exposure --- p.64 / Chapter 3.1.2 --- Induced RIF Resistance Were Stable In the Absence of Selection --- p.66 / Chapter 3.1.3 --- The Growth State of 5 RIF Resistance MSM mc²155 Strain --- p.68 / Chapter 3.1.4 --- Involvement of RpoB in the Mechanisms of the Emergence of RIF Resistance in MSM --- p.71 / Chapter 3.1.4.1 --- Mutations in the RpoB Gene --- p.71 / Chapter 3.1.4.2 --- Identical Mutations of RpoB Gene in Different RIF Resistance Isolates from Different Generation --- p.74 / Chapter 3.1.4.3 --- Characterization of RpoB in MSM strains --- p.76 / Chapter 3.1.4.4 --- Rifampin-Binding Pockets of RpoB Protein Model --- p.80 / Chapter 3.1.5 --- Other Genetic Alternations possibly Involved in RIF Resistance --- p.83 / Chapter 3.1.5.1 --- Whole Genome Sequencing of the Patental and P5 MSM mc²155 Strains --- p.83 / Chapter 3.1.5.2 --- Validation of the 32 Selected Alterations --- p.88 / Chapter 3.1.5.3 --- Characterization of MSMEG_0436 and MSMEG_6872 in RIF Resistance --- p.91 / Chapter 3.1.5.4 --- Characterization of MSMEG_0436 in the Growth Rate of MSM --- p.93 / Chapter 3.1.5.5 --- Characterization of MSMEG_6872 in the Growth Rate of MSM --- p.95 / Chapter 3.1.5.6 --- MSMEG_6872 Knock-out Strain Exhibited Normal Phenotype as its Parent --- p.98 / Chapter 3.1.5.7 --- Identification of Mutations in the Beta-Iactamase Gene of Mycobacterium Tuberculosis (MTB) --- p.101 / Chapter 3.1.5.8 --- Characterization of Rv 1367 c in Mycobacterium Growth Rate --- p.108 / Chapter 3.1.5.9 --- Morphology Changes of the Rv1367c and MSMEG_6872 Transformants --- p.110 / Chapter 3.2 --- Genetic Alterations in Non-coding Sequence --- p.112 / Chapter 3.2.1 --- ATP-binding Cassette (ABC) Superfamily Efflux Pumps Up-regulated in Drug Resistant M Smegmatis Strain --- p.112 / Chapter 3.2.2 --- RIF Resistant M smegmatis mc²155 Strain exhibited Low Level Cross-drug Resistance to INH --- p.115 / Chapter 3.2.3 --- RIF Resistant M smegmatis mc²155 Strain Showed Low level Accumulation of Ethidium Bromide --- p.117 / Chapter CHAPTER 4 --- DISCUSSION / Chapter 4.1 --- The Protocol for the Preparation RIF Resistant Strains --- p.121 / Chapter 4.2 --- RIF Induced Stable Chromosomal Mutations in RIF Resistant MSM Strains --- p.123 / Chapter 4.3 --- MIC Levels of the RIF Resistant Strains --- p.125 / Chapter 4.4 --- Factors May involved in RIF Resistant MSM Strains --- p.128 / Chapter 4.5 --- Cell Shape and Growth Regulation --- p.129 / Chapter 4.6 --- MSMEG _6872 and Twin-Arginine Translocase (TAT) Secretion System --- p.135 / Chapter 4.7 --- Conclusion --- p.137 / Chapter 4.8 --- Future Perspectives --- p.138 / REFERENCES --- p.139

Thesis (M.Cur) --University of Limpopo, 2011 / The aim of this study was to determine the factors that contribute to the increase in the number of tuberculosis (TB) patients in Mpumalanga Province, and to develop guidelines and recommendations to address the challenges of this health issue. The design of the study was qualitative phenomenological. The population consisted of all TB patients who were receiving treatment either at the intensive or the continuation phase. The sampling method was purposive and the sample size comprised 20 participants, of whom 10 were drawn from Shatale clinic at Bushbuckridge, and 10 from Mashishing clinic at Thabachweu municipalities in the Ehlanzeni district of Mpumalanga Province. The data was gathered by means of semi-structured interviews. Data analysis was performed, from which themes and categories were derived. This study revealed several factors that contributed to the increase in the number of TB patients at the study sites. The factors considered most important in this study were the general lack of knowledge of TB among participants, despite their various levels of education, poverty, overcrowding, poor ventilation in the shacks and Reconstruction and Development Program (RDP) houses, unemployment, lack of support while taking treatment, religious and ritual beliefs, and the influence of traditional healers who dispense herbal medicines with the dictum that participants have been possessed by evil spirits and witches. The majority of patients developed TB as a secondary opportunistic infection because of their HIV-positive status, and lack of capacity to practice personal hygiene and proper infection control. Guidelines, strategies and recommendations were formulated to address these public health challenges in the context nursing education, research, administration and practice

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2009. / Härtill 4 uppsatser.

A systematic study of the effect of sulphidizing atmosphere on the High Temperature Low Cycle Fatigue (HTLCF) properties of coated and uncoated unidirectionally solidified MARM002 nickel base superalloy was performed at 870°C. The coating systems investigated were, aluminide coating, three types of platinum modified aluminide coatings, and platinum coating. The creep-plasticity mode of the strain range partitioning method was used for creep-fatigue loading. A constant loading regime (Strain range 6.6 x 10-3 ) was used to test the samples in argon, air and Ar + 5%S02 and a lower strain range of3.8 x 10-3 was used to investigate the creep-fatigue properties in Ar + 5%S02 only. The results were analysed using scanning electron microscopy including spot analyses (SEM-EDS), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) techniques. The synergistic effect of sulphidizing environment and the creep fatigue loading (Strain range - 0.66%) resulted in accelerated failure in all the materials systems tested, except for the TYPE I platinum aluminide coated sample. This coating displayed a "self-healing" mechanism which enhanced its fatigue life under sulphidizing conditions. In general, the coatings had an adverse effect on the fatigue properties of the material systems. This was due to the poor mechanical properties of the coating. The mechanical properties of the coating was influenced by the coating microstructure and the chemical composition. The modification of the NiAI zone with platinum in the platinum aluminide coatings improved the fatigue properties of the coating by altering the crack propagation mechanism in the NiAl zone. The higher the platinum content in this region the more brittle it became. The platinum modified aluminide coating showed an improvement in the corrosion fatigue properties in the S02 containing environment at the higher strain range when compared with the uncoated, aluminide coated and platinum coated samples. However, at the lower strain range all the coating systems performed worse than the uncoated alloy. This was mainly due to the brittle failure of the coating. The platinum modified aluminides performed the worst due to the presence of brittle platinum aluminide phases. The interdiffusion and interaction of platinum with the substrate alloying elements, resulted in this coating being ineffective for corrosion protection. The resultant coating layer produced poor corrosion-fatigue properties. Although the coating systems did show evidence of resistance to sulphidation and oxidation there were relatively ineffective under the combination of sulphidizing environment and fatigue loading due to their poor mechanical properties. The mechanism of sulphidation was consistent for all the material systems tested with oxidation proceeding first and sulphidation proceeding at the corrosion scale/substrate interface. The crack propagation in the coating and substrate was controlled by the sulphidation attack at the crack tip and failure of the oxide scales formed in the cracks. / Thesis(M.Sc.Eng.)- University of Natal, Durban, 1998.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 6 uppsatser.