Ormö, Jens
Sturkell, Erik
Alwmark, Carl
Melosh, Jay
Article History
Received: 27 June 2014
Accepted: 25 September 2014
First Online: 23 October 2014
Competing interests
: I declare that the authors have no competing interests as defined by Nature Publishing Group, or other interests that might be perceived to influence the results and/or discussion reported in this paper.