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.
I plan on being in the US Army Special Forces in the future once I start enlisting in the US Army for 5 or 6 years active duty as an Army Ranger(If it's possible for me to become a Ranger and then Green Beret later on during my 5 or 6 years of active duty) after graduating high school.