Funding for this research was provided by:
KDDI Foundation, Japan
Article History
First Online: 25 November 2017
Compliance with ethical standards
:
: Ryoichi Shinkuma has received research grants from KDDI foundation, Japan. Yuki Sugimoto declares that he has no conflict of interest. Yuichi Inagaki declares that he has no conflict of interest.
: This article does not contain any studies with human participants performed by any of the authors.