License granted by Matthew Zimmerman (matthew.zimmerman@utsouthwestern.edu) on 2010-06-30T22:50:24Z (GMT): This electronic thesis or dissertation (ETD) was submitted by the author in accordance with the rules and regulations of The University of Texas Southwestern Medical Center at Dallas (“the University”). The author has certified that any copyrighted material used in the ETD is included with written permission of the copyright owner. The author also agreed to indemnify and save harmless the University from any and all claims that may be asserted or that may arise from any copyright violation. The University certifies that no alterations have been made to the content of the submitted ETD (or any supporting material) beyond either minor corrections to the title-fly or title pages (to conform to institutional standards) or conversions to alternate file formats (to provide better access or for preservation purposes).