1. Conway Institute of Biomolecular and Biomedical Research; University College Dublin; Belfield Dublin 4 Ireland
2. Asylum Research an Oxford Instruments Company; 6310 Hollister Avenue Santa Barbara CA 93117 USA
3. Conway Institute of Biomolecular and Biomedical Research, University College Dublin; Belfield, Dublin 4, Ireland; School of Physics; University College Dublin; Belfield Dublin 4 Ireland