Entrepreneur Michael Bloomberg announced a $55-million donation to Johns Hopkins University and Johns Hopkins Hospital and Health System. The gift, believed to be the largest private gift in the area, by the 1964 Johns Hopkins graduate is part of a $900-million capital campaign by the university and the health system. The campaign is headed by Bloomberg, 53, who will become chairman of the university's board of trustees in May. Most of the donation will be divided among the university's eight schools and its library. Some of the gift will be used to build cancer treatment and research facilities.