BY

I devote this thesis to my mother Tomi who died on 5 April 2005. ORIGINALITY STATEMENT `I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another per-son, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, ex-cept where due acknowledgment is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explic-itly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.&apos