Cathie Wood's recent buying activity suggests she sees national security technology as an emerging theme -- one that sits alongside more obvious artificial intelligence (AI) applications.CEO and chief investment officer of Ark Invest Cathie Wood earned a reputation for making high-conviction bets on disruptive, speculative opportunities aimed at toppling legacy incumbents in markets such as financial services, technology, and pharmaceuticals. When it comes to artificial intelligence (AI) stocks, it's no sur ...