I would like to express my sincere and deep gratitude to my supervisor Nicola Santoro and my co-supervisor Elio Velazques for their infinite patience, the continuous support, and for all the knowledge they shared with me. Thank you very much. I am very grateful for all the love, patience, and encourage that Glenda gives me every single day. You are the best of my life. Thank for believing in me and for supporting my decisions. Finally, I would like to thank my family and friends for the love, and support they shared with me.