1. Department of Mathematics, Michigan State University, East Lansing, MI 48824, USA
2. Department of Mathematics, King Fahd University of Petroleum and Minerals, Dhahran 31261, KSA
3. Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA
4. Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA