To my parents, Enivaldo and Elcione, and my brother, Hélder, by the love, incentive and unconditional support, because without them, nothing would be possible. To my beautiful lifemate, Sara Fernandes, that always give me strength and support in all my decisions. Her dedication inspires me and it is very important to the conclusion of this thesis. To my friends Jean Ponciano and Everton Lira that were a crucial part of all my academic courses, always being helpful and partners. To the professors Bruno Travençolo, José Gustavo and Luis Rocha, by the guidance, support, and trust. To all that were directly or indirectly a part of my formation, I appreciate it. To the research funding agency CAPES for the scholarship granted to me.