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.
RANGERS: A Day in the Life of an Army Ranger. Combat Deployments. The 75th Ranger Regiment deploys more often, but for shorter durations, than conventional military units. The Operations Tempo, or OpTempo, is so high that it is necessary to frequently rotate Rangers in and out of combat theaters to give them time to recuperate.