After an exciting period of working and doing research at ITC Faculty, today is the day: writing this note of appreciation is the finishing touch on my PhD research. It has been a time of profound learning for me, not only in the scientific arena but also on a personal level. Doing this research has had a significant impact on me. I would like to deliberate on the people who have helped and encouraged me so much throughout this period. I would first like to express my special appreciations to my promoter Prof. Alfred Stein for his advice, support and continuous encouragements have contributed significantly to the completion of this research. I would remarkably like to single out my supervisor Dr. Valentyn Tolpekin: I want to thank you for your excellent assistance and for all of the opportunities I was given to conduct my research. I would like to extend my appreciation to Dr. Ali Sharifi for his support, advice and critical comments. I would also like to thank my family for the love of my life my loving mother Fariba, my father Jamshid, my brothers Mohamadamin and Amirali, and my lovely grandma, thank you for giving me a stable mind to think and work for science. I am thankful to you for all what you have done for me. Because of you, I am standing here.