It’s no secret that more and more hedge funds are aggressively using exchange traded funds, and not just to hedge. Many of them are using these index-like investments to make single-sector — or single-market — bets. For example, at the end of the first quarter, Traxis Partners, headed up by former Morgan Stanley strategist Barton Biggs, held a dozen ETFs, and six of them were his largest holdings, including funds that specialize in health care and Brazil.