1. Photophysics Group, Department of Physics, University of Strathclyde, Scottish Universities Physics Alliance, Glasgow G4 0NG, U.K.
2. BHF Centre for Cardiovascular Science, The Queen’s Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, U.K.
3. School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QQ, U.K.