At 350 pages, the state's new health cost control law contains multitudes. We'll surely be focusing on a wide range of the law's elements, but here's one called to our attention today by the Massachusetts Nurses Association: The bill that Gov. Patrick signed into law today bans mandatory overtime for nurses. In short, mandatory overtime is out as a means of dealing with a nursing crunch. But those crunches are expected to grow. Word also arrived today from the Massachusetts Hospital Association that the nurse vacancy rate has been rising, and in the coming years, a shortage is predicted.