1. Senior Lecturer, Dept. of Physics, Obafemi Awolowo Univ., 220005 Ile-Ife, Nigeria; presently, Director and Chief Executive, Engineering Materials Development Institute, Km. 4, Ondo Rd., P.M.B. 611, Akure 340001, Nigeria (corresponding author). E-mail: bbabatop@oauife.edu.ng
2. Professor, Centre for Complex Fluids Processing, Dept. of Chemical Engineering, Univ. of Swansea, Singleton Park, Swansea. SA2 8PP, U.K.
3. Professor, Dept. of Chemical Engineering, Univ. of Swansea, Singleton Park, Swansea SA2 8PP, U.K.