1. Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093-0411, U.S.A.
2. Department of Mechanical Engineering, University of Hong Kong, Pokfulam, Hong Kong
3. College of Engineering, King's College, University of Aberdeen, Aberdeen AB24 3UE, Scotland, U.K.
4. Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
5. Department of Physics, National Institute of Technology, Rourkela-769008, Orissa, India