170417-N-UJ980-176 SAN DIEGO (April 17, 2017) Vice Adm. Nora Tyson, left, commander of U.S. 3rd Fleet, listens as Dr. Rachel Markwald provides an overview of a current study to examine different methods of evaluating sleep in operational environments during a visit to the Naval Health Research Center. Scientists at the center conduct ongoing research to improve the operational readiness and health of military service members. Markwald and her team are conducting research to mitigate the effects of sleep loss and fatigue on warfighter performance and health. (U.S. Navy photo by Regena Kowitz/Released)