One day, a serious fracture might not take months to heal. Instead, with the injection of a putty made of stem cells, soldiers and athletes might be back on their feet in two weeks’ time. Steven Stice, the director of the University of Georgia’s Regenerative Bioscience Center, told a group of Gainesville Rotarians on Monday that researchers he’s working with are collaborating with the Department of Defense to develop the putty for soldiers in the field.