Acknowledgments

This dissertation would not be possible without several contributions. First and foremost I want to thank my advisor, Gestur Ólafsson, for his intel-lectual and material support. It is a pleasure to thank Professors Mark Davidson, Ray Fabec, Jimmie Lawson, Richard Litherland, Frank Neubrander, James Oxley, and Robert Perlis, for their valuable instructions, priceless advice, and professional help provided during my graduate studies. I want to thank my family and to all my friends who ever helped me throughout my graduate studies. Last but not least, I thank my husband. Without his endless patience, love, and support of all kind, intellectual, technical and moral, this dissertation would not be what it is now. Thank you, Michael