1. Simulations Plus, Lancaster, CA 93534 USA.
2. Corresponding author. Centro de Bioinformática Médica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
3. Department of Mathematics, The Ohio State University, Columbus, OH 43210 USA.
4. Corresponding author. Department of Mathematics, The Ohio State University, Columbus, OH 43210 USA.
5. Department of Biology, Duke University, Durham, NC 27708 USA.
6. Department of Mathematics, Duke University, Durham, NC 27708 USA.
7. Mathematics Institute, University of Warwick, Coventry, CV4 8GY, UK.