This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or w p y subrnitted. Ttius, some thesis and dissertation copies are in typewriter face, M i l e others rnay be from any type of cornputer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct pnnf wlored or paor qualÏty illustrations and photographs, print bleedttirough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversi...