Julia Thorne, an author, activist, and former wife of US Senator John F. Kerry, died yesterday in Concord. She was 61. The cause of death was transitional-cell carcinoma, a form of cancer, according to her daughter Vanessa Kerry. In a telephone interview, John Kerry called Ms. Thorne "a great friend to a lot of people" and spoke with emotion of her accomplishments as a parent. "She was the best mom two daughters could want," he said. "She was completely committed to the kids and their future." Her daughter echoed that view. "She was a phenomenal mother," said Vanessa Kerry, of...