1. Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, 70 Prospect Street, Princeton, NJ 08540, USA
2. Department of Physics, University of Nairobi, P.O. Box 30197, Nairobi, Kenya
3. Department of Civil and Environmental Engineering, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA
4. Department of Physics, Kyambogo University, P.O. Box 1 Kyambogo, Kampala, Uganda
5. Mintek, Advanced Materials Division, MINTEK, 200 Hans Strijdom Drive, Private Bag X3015, Randburg 2125, South Africa
6. Department of Mechanical and Aerospace Engineering, Princeton University, Olden Street, Princeton, NJ 08544, USA