Dr. Denham Harman, a renowned scientist who developed the most widely accepted theory on aging that’s now used to study cancer, Alzheimer’s disease and other illnesses, has died in Nebraska at age 98. Harman, who worked into his mid-90s at the Univ. of Nebraska Medical Center-arriving each day at 7 a.m.-died after a brief illness at a hospital in Omaha, medical center spokesman Tom O’Connor said.