Scientific Reports 5: Article number: 11380; published online: 16 June 2015; updated: 03 August 2015

The Competing financial interests statement in this Article should read:

“This study was supported by grants from the National Natural Science Foundation of China (No. 81170810 and 81471098) and the Natural Science Foundation of Beijing (No. 7112022). The fund agencies had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.”