Acknowledgement It is a desire from the bottom of my heart to say thanks at this point. Thanks to my dear Claudia, who, in all the years of activity on this research work, was undaunted by my side. Her advice, comments and considerations have always been a precious and constructive help. Her mental support, if I once wanted to despond, when my strength reached their limits, has always built me up again. She kept my back free, granted me all the required free space and subordinated her own needs. My heartfelt appreciation for this tireless support and help I can not adequately put into words. It was so important to me: her backing, her contribution. Sincerely thank you, Claudia!