Michio Kaku (lev radin / Shutterstock.com) A string of researchers connected to advanced weapons, space, and nuclear programs have turned up dead or vanished in recent years — and physicist Michio Kaku thinks treating each case in isolation is a mistake the government can't afford to keep making. "If 10 scientists suddenly die or vanish who all have access to sensitive research, this is cause for national concern," Kaku told Fox News Digital, according to Newsweek's Steve Mollman . Kaku called the situation "unheard of" and said nothing like it has crossed his desk in a long career in physics and science policy. Among the higher-profile cases: retired Air Force Major General William Neil McCasland, who commanded the Air Force Research Laboratory and worked with scientists at Los Alamos, walked out of his Albuquerque-area house at some point this year and never came back — his phone and glasses found sitting where he left them.…