1. Department of Physics and Astronomy University of Tennessee Knoxville TN 37996 USA
2. Min H. Kao Department of Electrical Engineering and Computer Science University of Tennessee Knoxville TN 37996 USA
3. Department of Physics University of Vermont Burlington VT 05405 USA
4. Department of Physics and Astronomy University of Missouri Columbia MO 65211 USA
5. Department of Mathematics & Statistics University of Vermont Burlington VT 05405 USA