BY

I would never have been able to finish my dissertation without the guidance of my committee members and support from my family. I would like to acknowledge my sincere gratitude to my advisor, Dr. Marilyn DeLong who have generously given her time and expertise to better my work. I thank her for all the advising, mentoring and motivation she provided during my graduate studies at the University of Minnesota, for giving me the opportunity to work on her other research projects and for providing the financial support to publish and present research. I a