Many people contributed to this doctoral thesis and to the student during this process. I'm sure that this section will be too short and my words inadequate to describe the size of my acknowledgements and my sincere gratitude for the pleasure of having all these people in my life. Trully sorry if I have forgotten anyone. Firstly I would like to thank my advisor Eduardo Mario Mendiondo, for accepting to do this straigh PhD and full of 'sandwiches' travels. For giving me so many opportunities for personal and professional growth, and above all, for the trust placed in me which was key during this period of so many doubts. I want to thank my co-supervisor Raghavan Srinivasan, for accepting me at Texas A & M University. For all the teachings and discussions that made this study possible, the willingness to help allways and for the example of dedication, vision and humility.