Funding for this research was provided by:
National Research Foundation Singapore (NRF-CRP13-2014-02)
Science and Technology Program of Guangdong Province of China (2016A050502058)
Article History
Received: 13 June 2018
Accepted: 16 August 2018
First Online: 25 September 2018
Competing Interests
: The authors declare that they have no competing interests.
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