Stephanie Kwolek is the scientist behind the discovery of the strong, lightweight fiber known as Kevlar. More than 3,000 law enforcement officers have survived potentially fatal or disabling injuries because of the golden-colored fiber that is spun into sheets used in bulletproof vests, helmets and shields . . . Kwolek’s advice for young women interested in a science career is that they get a doctorate and have at least two majors — for example, chemistry and math.