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.
For the racehorse, see US Army Ranger (horse). The United States Army Rangers are an elite military formation of the United States Army, that serve in designated U.S. Army Ranger units or are graduates from the U.S. Army Ranger School. The term ranger has been in use unofficially in a military context since the early 17th century.