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AcknowledgementsThanks to my Senior Supervisor, Professor C. Michael Hall, whose perceptive, intelligent and above all, patient questions, and his determination to make sure that I didn't lose track of what was important, made this thesis much better than it otherwise would have been. Thanks also for your good humour and willingness to remain involved through times of slow progress. Your continued commitment is much appreciated. To Dr Lucie Ozanne, thank you for your valuable time and your constructive comments.