There was an error in the Supplementary Material file: table S1 was inadvertently omitted. In addition, the colors were incorrect in Fig. 2 and its caption. The corrected online version of the article and Supplementary Material is at http://stm.sciencemag.org/content/3/96/96ra77.full, and the corrected PDF version of the article is at http://stm.sciencemag.org/content/3/96/96ra77.full.pdf.
- Copyright © 2011, American Association for the Advancement of Science