No description available.

No description available.

No description available.

No description available.

No description available.

A series of experiments was conducted to investigate the potential influence of pre- and post adding of catalysts to a demineralized coal char. The catalysts were chosen according to yield better catalytic activity and be inexpensive. CO2 gasification was conducted on the samples in a temperature range of 500 °C to 900 °C. The coal chosen was a high-inertinite, high-ash, Highveld bituminous coal. The catalysts chosen were sodium carbonate, potassium carbonate, and a mixture of the two catalysts. Different methods were used to investigate the factors influencing the reactivity of the demineralized coal char, and the extent of the influence from the catalysts. Proximate analysis, ultimate analysis and ash yields were conducted on the starting material to determine the change the demineralization had on the coal. Ash fusion temperatures of the samples were also obtained. The results indicated that demineralization lowered the ash content, as well as the ash fusion temperatures, but the ultimate analysis showed consistency in both sets of samples. Mass losses obtained during the thermal treatment experiments under CO2 atmosphere showed an increase in mass loss in the order of samples without addition of catalysts to the smallest amount of addition. Potassium carbonate showed the largest increase in mass loss during CO2 thermal treatment, together with the mixture of the two catalysts. Samples with pre-added catalysts also had a larger mass loss than samples with post-added catalysts. According to the XRD and QEMSCAN results, some potassium species are retained in the ash, which is confirmed by XRF results. The XRF results also showed that the amount of alkali species retained is quite large. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011

No description available.

Mutagenesis studies on the four EF-hands of KChIP2.2 (Potassium channel-interacting protein 2.2) were carried out to explore the conformational transition upon the binding of Ca2+ and Mg2+ and the subsequent effect on the interaction between KChIP2.2 and Kv4.2. CD spectra indicated that Ca2+- and Mg2+-loaded wild-type and mutated KChIP2.2 altered the secondary structure contents. In contrast to other mutants, mutation on EF1 caused a notably change in the secondary structure of KChIP2.2. Fluorescence measurement revealed that EF-hands 3 and 4 were high affinity Ca2+-binding sites within KChIP2.2 molecule, but the binding of Mg2+ with KChIP2.2 was marginally affected by EF-hand mutations. The results of size-exclusion chromatography showed that mutations on EF-1, EF-2 and EF-3 induced the oligomerization of KChIP2.2 and the extent of oligomerization was enhanced by Ca2+ and Mg2+. No significant differences were noted when wild-type and mutated KChIP2.2 bound with porcine brain membrane and liposome either in the absence or presence of Ca2+- and Mg2+. Pull down assay showed that KChIP2.2 and EF-hand mutants could bind with Kv4.2 in the absence of Ca2+ and Mg2+, but the interaction was enhanced by Ca2+ and Mg2+. However, the binding capability of mutants for Kv4.2 was notably lower than that observed for wild-type KChIP2.2. It was found that, in sharp contrast to that EF1 mutant exclusively localized in the nucleus, the other EF-hand mutants and wild-type protein distributed within nucleus as well as cytoplasm. Elevating intracellular Ca2+ concentration caused the translocation of EF1 mutant to cytoplasm but no appreciable effect on other mutants and wild-type KChIP2.2. . Taken together, these results suggest that the integrity of the four EF-hands are involved in function to stabilize conformation for binding with Kv channel, but this conformational transition is not essential for the binding to cell membrane.

Thesis (doctoral)--Helsinki University of Technology, 2000. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Hong Kong, 1970. / Typewritten.