1. Universidade CEUMA, No. 100, 65903-093 Imperatriz, MA, Brazil
2. Laboratory for Biological Information Processing, Universidade Federal do Maranhão, S/N, São Luís, MA, Brazil
3. Graduate School of Information Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi 464-8603, Japan