1. Botswana International University of Science and Technology, Palapye, Botswana
2. Laboratory of Biophysics, Department of Physics, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon
3. Department of Physics, Faculty of Science, University of Maroua, Maroua, Cameroon
4. Laboratoire de Mécanique, Département de Physique, Faculté des Sciences, Université de Yaoundé I, Yaoundé, Cameroun