Reviewers

To my mother and father Acknowledgments My first special thanks goes to my colleague and friend Pierangelo. The help and advices that he provided during my master thesis were invaluable. Thanks to his effort I started soon my Ph.D.; without his support, I would never have been able to publish my first international scientific article. Without his way of being everyday, these three years together in room B120 would have been so different. There are not appropriate words in any language of the world for express-ing my gratitude for my advisor prof. Francesco Quaglia. Francesco has been able to lead me in these three years, trying to solve together with me all the problems that manifested during my doctorate. He taught me the approach to scientific research. He taught me that the quality of the work is the only target that must be addressed. He is a wonderful person, a confidant, a friend and last but not least, a big AS Roma supporter. I hope, sooner or later, t