1. Department
of Physics, University of Eldoret, P.O Box 1125-30100, Eldoret, Kenya
2. The Abdus Salam
International Centre for Theoretical Physics, Condensed Matter and
Statistical Physics Section, Strada
Costiera 11, 34151 Trieste, Italy
3. Department
of Physics and Space Science, The Technical University of Kenya, P.O Box 52428-00200, Nairobi, Kenya