for their generous support and for many wonderful moments away from work. Special thanks to my friends, who always managed to change my outlook and maintain a healthy distance from my dissertation, especially in difficult times. I particularly want to mention the help of my friends Dorothee and Miriam, who gave me very valuable insights into particular research projects. I owe my family, especially my siblings and my mother, but also my parents-in-law and brothers-inlaw, a big thank you for accompanying me on this journey and for always giving me courage and helping me to follow my path over the last years. Finally, my biggest thanks go to my dear wife, Maike, and my son, Jonathan. Maike has always believed in me, supported me in every possible way and bolstered me with her love. Without her, this dissertation would not have been possible. My special thanks also to Jonathan for the creative breaks and the endless joy he brings to my life.