1. Department of Mathematical Sciences, Northern Illinois University, DeKalb, Illinois 60115, United States;
2. Department of Geology and Environmental Geosciences, Northern Illinois University, DeKalb, Illinois 60115, United States;
3. Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States;
4. Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois 60115, United States;