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First Online: 18 August 2018

Compliance with Ethical Standards

: All of the authors are employees of the US Government. This work was prepared as part of their official duties. Title 17 U.S.C.§105 provides that “Copyright protection under this title is not available for any work of the United States Government.” Title 17 U.S.C. §101 defined a US Government work as a work prepared by a military service member or employees of the US Government as part of that person’s official duties. The opinions or assertions contained in this paper are the private views of the authors and are not to be construed as reflecting the views, policy or positions of the Department of the Navy, the Department of the Army, Department of Defense nor the US Government. Each author certifies that his or her institution approved the animal protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. All reported studies/experiments with human or animal subjects performed by the authors have been previously published and complied with all applicable ethical standards (including the Helsinki declaration and its amendments, institutional/national research committee standards, and international/national/institutional guidelines).

: The authors declare no conflicts of interest relevant to this manuscript.

: This article does not contain any studies with human or animal subjects performed by any of the authors.