1. School of Physics and Advanced Materials; University of Technology, Sydney; 15 Broadway Ultimo New South Wales 2007 Australia
2. Harvard-Smithsonian Center for Astrophysics; 60 Garden Street Cambridge Massachusetts 02138 USA
3. Space Sciences Laboratory; University of California at Berkeley; Berkeley California 94720 USA
4. Smithsonian Institution; Museum Conservation Institute; 4210 Silver Hill Road Suitland California 20746 USA
5. Materials Sciences Division; Lawrence Berkeley National Laboratory; Berkeley California 94720 USA