Knotty girls could face a brush with disaster.  Hair maintenance is an all-too-important, albeit tricky form of self-care that, if mishandled, could leave folks with spilt ends, warns a new, hair-raising report.  Rather than traumatizing one’s tresses with excessive heat — which causes hair to become brittle — followed by immediate brushing, researchers from the University of Dublin suggest treating freshly straightened strands to a 30-minute to two-hour recovery phase before styling.  “Application of heat causes a dramatic reduction in performance…which is completely restored by a period of resting” study authors explained. “This well–known effect, presumably due to dehydration and rehydration, is clearly and…