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.
In the United States Army, Army Reserves, and Army National Guard, the maximum age allowed to enlist and ship to basic training is 35 years old. The Army experimented for quite some time allowing anyone up to the age of 42 years old to enlist and complete basic training. On April 1st, 2011, they reverted this to the lower age limit.