UPDATE 1-Study finds flaws in criticism of St. Jude cyber security

(Adds comment from Muddy Waters) By Ransdell Pierson Aug 30 (Reuters) - University of Michigan researchers on Tuesday said their own experiments undermine recent allegations of security flaws in St. Jude Medical Inc's pacemakers and other implantable medical devices. Shares of St. Jude fell 5 percent on Thursday after short-selling firm Muddy Waters and its business partner, cyber security company MedSec Holdings Inc, alleged finding significant security bugs in the company's Merl