Reader Comments

Post a new comment on this article

Publisher's Note: Figure Quality in PDF

Posted by PLOS_ONE_Group on 21 Mar 2014 at 21:23 GMT

The journal apologizes for the poor figure image quality in the PDF version of this article. This error was introduced during the typesetting production process. For a better quality version of the figures, please view and download the figures from the XML version of the article.

No competing interests declared.