In 1905, Levene was appointed as head of the biochemical laboratory at the Rockefeller Institute of Medical Research. He spent the rest of his career at this institute, and it was there that he identified the components of DNA.
It also takes anywhere from 18 to 24 months to get promoted to O-2 following entry to the Army, so the effective minimum age to join the Rangers for officers is around 23 to 24 years old. Officers can then continue to apply until they are promoted to O-5.
Army Rangers are light infantrymen that perform many of the same duties as the Green Berets--raids, ambushes, and airfield seizures by land, by sea, or by air.. Any 18-year-old male may apply to the Rangers when enlisting. The specialized training takes one and a half to two years.