it never was a single person's achievement. In the formation of the present work various people contributed, each at a different level.My supervisor, Professor Malcolm Rowland, has been a source of inspiration with his enthousiasm about the work and his insight. Dr. Leon Aarons has patiently clarified obscure aspects of data analysis, put things into prospective and relieved a lot of tension with his stoic sense of humour. Eva Nilsson, apart from assisting in part of the experimental work, has been a valuable companion in the exploration of ideas. Diane Matthew proof read the final text and knew when to provide support and advice. George Fleming put up with panic attacks and made possible the optimal use of instrumentation. The personel in MEDEVAL, especialy Frank Mullins, assisted in various experimental and analytical matters.My brother, Stelios, and my friend, Victoria, stayed with me through long working hours and sustained my morale, with their caring and love.