Dissertation submitted to the faculty of Engineeung, University if the Witwatersrand, Johannesburg. in fulfilment of the requirements for the degree of Master of Science in Engineering. / This dissertation deals with alloys containing between 0.2 and 9.5wt%, carbon and between 3.2 and 64.3wt% vanadium with the balance iron. Alloys were produced by induction melting and followed by remelting in vacuum tungsten arc furnaces. No heat-treatment was performed, as the aim was to identify useful alloys that may be applied by hardfacing techniques in the field. The requirement of post weld heat-treatment would greatly limi~ the use af hardfacing alloys. TIle experimental techniques aimed at characterising the alloys included X-ray diffraction analyses, Mosshauer Spectroscopy, optical, scanning and transmission electron microscopy and chemical analyses white density measurements, hardness tests and 2 and 3 -body abrasion test gave the material properties. (Abbreviation abstract) / AC 2018

Thesis (M Med (Paediatrics and Child Health)) -- University of Limpopo, 2011. / ABSTRACT BACKGROUND AND OBJECTIVES: Iron deficiency anaemia (IDA) is the most common nutritional disorder in the developing world. A large number of children under the age of 5 years do not reach their developmental potential, IDA and iron deficiency being well documented risk factors. IDA has been shown to be an important cause for decreased attention span, reduced alertness and learning difficulties in both young children and adolescents. South Africa has a growing burden of anaemia and iron deficiency and the most affected areas are the poor communities. There is vast evidence on the negative effects of iron deficiency to a child's developing brain from studies done internationally but limited data on the subject in South Africa, despite the huge burden of iron deficiency. We investigated the association between IDA and school performance and intelligence and also determined the local prevalence of IDA in the Winterveldt region, North of Tshwane, South Africa. METHODS: Three primary schools from Winterveldt were sampled. All subjects with parental consent were screened for anaemia using Hemocue 201+ Hb meter (n=194). Blood for iron studies and CRP was collected on all anaemic pupils (n=75) to define IDA (Hb<I1.5g/dl, ferritin<12ug/L and CRP<10). Cases and controls were recruited after results using matching anthropometry at a 1:2 ratio (one case to two controls). A total of 90 pupils (30 cases & 60 controls) were compared using 2009 school reports. Analysis was done per subject using the national scoring system, where one means incompetent and four means excellent achievement. The Raven's Coloured Progressive Matrices (RCPM) was used as our psychometric test and scores were recorded as percentiles and interpreted by the educational psychologist who conducted the test. RESUL TS: Point prevalence of iron deficiency anaemia for the Winterveldt region was found to be 9.8%. The prevalence of under-weight was 19% and that of stunting 23% with no significant differences between cases and controls (P=0.368 for under-weight and p=0.863 for stunting). There was no statistically significant association between IDA and performance in mathematics (X2=1.34 and p=0.511). However, cases scored poorly in life skills (P=0.00017) and in literacy the test for level of significance approaches significance (P=0.071). There was also no statistically significant association between IDA and low scores on the RCPM test (X2=3.31 and p=0.65). CONCLUSION: The point prevalence was high compared to the national prevalence of IDA which is about 5%. This could be related to a number of factors including the socio-economic background of the pupils. Since dietary history and knowledge of fortified food was not investigated, we cannot draw conclusions on the cause of this high prevalence. The study also found that the general population was under-nourished, which is consistent with the poor socio¬ economic status of the study area. However, our participants were more under-weight and stunted when the data was compared with previous national surveys. The study found a negative correlation between IDA and two areas of academic performance which is consistent with international data. In mathematics however, we believe that the low curriculum standard in all South African schools affected the outcome. The results of the psychometric test were not consistent with international data where most studies showed a negative correlation between IDA and the Ravens Matrices. South African studies have demonstrated poor performance of black students on the Ravens Matrices when compared to other races and our results followed this trend as our scores were similar to most of the studies.

xii, 153 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (M.D.)--University of Adelaide, Dept. of Medicine, 1973

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Thesis--University of Chicago. / "Literature on the limonite ores": p. 25-28. Also available on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 112-115). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis--University of Chicago. / "Literature on the limonite ores": p. 25-28.

Iron is essential in nearly all organisms. It is a cofactor in many proteins and enzymes. This transition metal can also be toxic because it participates in reactions which produce reactive oxygen species. To avoid these toxic effects while still being used for essential processes, the cell must regulate tightly iron import, metabolism, trafficking, and homeostasis. These processes were studied using biophysical methods centered on Mossbauer spectroscopy supplemented by electron paramagnetic resonance, electronic absorption spectroscopy, and inductively coupled plasma mass spectrometry. This integrated biophysical approach was applied to yeast cells, isolated yeast mitochondria, and mouse brains. We determined the concentration of Fe, and the proportion of that Fe present as iron-sulfur clusters, heme centers, mononuclear nonheme centers, and as Fe3+ oxyhydroxide (phosphate) nanoparticles for each system. In yeast, the dependence of metabolic mode of growth and iron in the growth medium on this distribution was studied. Approximately three-quarters of the iron in fermenting cells was located in vacuoles, where it was present as high-spin mononuclear Fe3+ species with rhombic symmetry. The remaining quarter was present in the mitochondria. In fermenting mitochondria 4 distinct species of iron were observed, including [Fe4S4]2+ clusters and low-spin Fe2+ hemes arising from respiratory complexes, non-heme high spin (NHHS) Fe2+ species, high spin nonheme Fe3+ species, and nanoparticles. These distributions (in both the cells and mitochondria) change when the cells are grown on iron deficient medium but remained relatively unaltered as iron in the growth medium was increased. Respiring cells had less Fe associated with vacuoles, and more Fe present as HS Fe2+. Respiring mitochondria contain more [Fe4S4]2+ clusters and low-spin Fe2+ hemes, more S = 1/2 [Fe2S2]1+ clusters, and less NHHS Fe2+, HS Fe3+ species and Fe3+ nanoparticles. These changes were rationalized by assuming that the NHHS Fe2+ and Fe3+ species, and the nanoparticles were in equilibrium within the matrix of the mitochondria, and that the Fe2+ species served as feedstock for the synthesis of iron-sulfur clusters and heme centers. The iron in the mouse brain consisted mostly of [Fe4S4]2+ clusters and Fe2+ hemes from mitochondria respiratory complexes, and of ferritin, an Fe storage protein complex. NHHS Fe2+ and Fe3+ species were also observed. The ratio of stored Fe to mitochondrial Fe was sensitive to age. The brains of prenatal animals were dominated by ferritin. Following birth up to the first 4 weeks of life, there was an increase in mitochondrial Fe and a decline of ferritin Fe. Beyond 4 weeks up to 58 weeks, levels of ferritin increased and mitochondrial Fe remained constant. The brains of mice fed an Fe-deficient diet were also studied; most of the Fe in these brains was present as mitochondrial Fe, with little stored as ferritin. A model was developed to explain these changes.

Metal dusting corrosion has been known for more than a 100 years as an industrial problem. As a result of extensive research over the last five decades several mechanisms have been evolved involving ferritic materials. However, a complete understanding is yet lacking. One of the most referred models, developed by Hochman-Grabke, suggests that formation of metastable cementite and its subsequent decomposition is the central aspect of the process. To verify this hypothesis, an Fe-Si model was designed based on silicon's ability to retard cementite formation. However, this strategy was unsuccessful because silicon oxidized and amount of silicon remaining after silica formation was not sufficient to suppress cementite. On the other hand, germanium does not form a stable oxide in the conditions employed. A alloying with germanium did prevent Fe3C formation, but not dusting, which resulted from an alternative mechanism. Dusted particles were confirmed to be cementite for pure iron specimens (where cementite scale formed) and ferrite for alloys that did not form cementite. These observations are inconsistent with the prior model. In addition, the general features of metal dusting corrosion have been characterized. Kinetics of coking and metal wastage for ferritic materials (Fe, Fe-Si, Fe-Ge and Fe-Ge-Ni) were found to be linear in nature, though respective rates may vary due to the differences in alloy catalytic activity and reaction morphologies. The carbon diffusion coefficient in cementite was evaluated from Fe3C scaling rates. Crystallographic orientations of different forms of cementite were established. Internal cementite precipitates in pure iron accounted for by a very high degree of supersaturation with respect to carbon, indicating a non-equilibrium situation. Coking and dusting rates were found to be strongly correlated and their gas composition dependence indicate the contribution of the Boudouard reaction. Reactions with fixed carbon activity gases demonstrated that kinetics rather than thermodynamics control the reaction rates. However, at a particular temperature, these rates increase with carbon activity. Activation energies for coking and dusting are equal for a given alloy, meaning that the same process controls them. For Fe-lOGe alloy, in the early stages of reaction, grains with near (001) surfaces were more susceptible to graphitization than grains having near (110) surfaces, but the underlying cause has not been revealed.