1. Department of Biomedical Engineering Washington University in St. Louis St. Louis MO 63130 USA
2. Department of Electrical and Systems Engineering Washington University in St. Louis St. Louis MO 63130 USA
3. Department of Energy, Environmental, and Chemical Engineering Washington University in St. Louis St. Louis MO 63130 USA
4. MRC Prion Unit UCL Institute of Prion Diseases Gower Street London WC1E 6BT UK