Nature Communications 6, Article number: 7131 (2015); Published 19 May 2015; Updated: 26 August 2015.

The original version of this Article contained an error in the spelling of circulation in the title of the paper, and in Fig. 1e, a scale bar and arrows were inadvertently omitted. These errors have now been corrected in both the PDF and HTML versions of the article.

Figure 1
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