1. Laboratory of Mathematics and Complex Systems (Ministry of Education of China), School of Mathematical Sciences, Beijing Normal University, Beijing 100875 China.
2. Co-corresponding author. Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, OH 44106 USA.
3. Co-corresponding author. Laboratory of Mathematics and Complex Systems Ministry of Education of China, School of Mathematical Sciences, Beijing Normal University, Beijing 100875 China.
4. Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 USA.