1. Department
of Physics and Astronomy, Trinity University, San Antonio, Texas 78212, United
States
2. Department of Physics, Texas Tech University, Lubbock, Texas 79409, United
States
3. Nano Science Center,
Department
of Chemistry, University of Jyväskylä, Jyväskylä, Finland
4. Institute of Biomedicine, Department
of Biochemistry and Developmental Biology, University of Helsinki, Helsinki, Finland