 Complete the following phrase:  Jackson became a Navy officer in 1995, when he received his M.D. from the University of Texas Medical Branch. He graduated from the Undersea Medical Officer Program in 1996. Jackson had a series of operational postings, as officer-in-charge and diving medical officer at Explosive Ordce Disposal Mobile Unit 8 at the naval base in Sigonella, Sicily and diving safety officer at the Naval Safety Center in Norfolk, Virginia. In 2001, he started a residency in emergency medicine, which he completed in 2004. He was clinical faculty physician in the Emergency Medical Residency Program in Portsmouth, Virginia for an additional year before being 