Authorís Declaration



This thesis is an account of work carried out between October 1997 and December 2000 at the University of Bristol under the supervision of Dr D. J. Riley.


I declare that the work in this dissertation was carried out in accordance with the Regulations of the University of Bristol. The work is original except where indicated by special reference in the text and no part of the dissertation has been submitted for any other degree.


Any views expressed in the dissertation are those of the author and in no way represent those of the University of Bristol.


The dissertation has not been presented to any other University for examination either in the United Kingdom or overseas.


Date:28th September 2001