The completion of this research would not have been possible without the generous support of many individuals and institutions. These are specific obligations which I wish to acknowledge here. I would like to express my gratitude to my thesis supervisors. I am highly indebted to Professor Franz Waldenberger for his invaluable help and - couragement from the very beginning of this research project. Not only this research but I personally greatly benefited from his guidance and - pervision over the years. I am also indebted to Professor Ralf Elsas for his support and detailed comments which...