First and foremost, I would like to express my deepest gratitude to my supervisor Prof. Dr. Hande Seber, who has been a real role-model for me since my first day in the department. I have benefited a lot from her experience and expertise. She has tirelessly read numerous drafts of the dissertation; her feedback and suggestions have brought it to fruition. Therefore, without the constructive feedback, constant support, encouragement, motherly affection and unending energy of my supervisor, I would not have completed this doctoral work.