First Author:   Pedro Hemsley UFRJ pedro.hemsley@ie.ufrj.br   Avenida Pasteur, 250, Sala 108 Rio de Janeiro, 22.290-240, Brazil   +5521981198363(Phone) +5521981198363(Fax) Second Author: Marcio Firmo PUC-Rio marciogoldfirmo@gmail.com         Third Author: Vitor Onuki UFRJ vitoronuki@yahoo.com.br