Scientific Reports 4, Article number: 4027 (2014); Published: 7 February 2014; Updated: 12 March 2014

Due to a technical error, one corresponding author was incorrectly given as Chungui Tian rather than Guohui Tian in the HTML version of this Article. For correspondence and requests for materials, please contact Honggang Fu (fuhg@vip.sina.com) or Guohui Tian (tiangh@hlju.edu.cn). This error has now been updated in the original Article.