And in sports news, Baltimore Ravens offensive lineman John Urschel said Thursday he will retire from the NFL after a recent study found virtually all pro football players show signs of a degenerative brain disease known as CTE. The 26-year-old player called the decision difficult, but said he would move on to pursue a doctorate in mathematics at MIT. Two years ago, Urschel suffered a concussion in a helmet-to-helmet collision, which he says affected his ability to think well mathematically. A study published this week in The Journal of the American Medical Association found that of 111 NFL players whose brains were studied, 110 of them had signs of CTE, which can lead to memory loss, depression and dementia—often years or even decades after players retire.