Updated from 4:05 p.m. EDTStocks closed mixed Monday as general cautiousness ahead of Federal Reserve Chairman Alan Greenspan's testimony before Congress couldn't weigh down the Nasdaq, which posted its best single-day gain in two weeks. The Nasdaq ended up 24.67 points, or 1.24%, at 2020.41; the Dow Jones Industrial Average closed down 14.12 points, or 0.14%, to 10,437.85; and the S&P 500 turned positive in the final hour of trading to finish up 1.23 points, or 0.11%, at 1135.84. The 10-year Treasury note was trading down 8/32 in price to boost the yield 4.37%, while the dollar was lower against the euro but stronger against the yen. The Nasdaq was powered by strength in telecommunications and biotechnology stocks. The Amex Biotech Index closed up 2.8% as investors searched for safe havens in the face of interest rate risk. The Philadelphia Semiconductor Index rebounded from last week's selloff to finish up more than 1.4%. With Monday's surge, the Nasdaq finished above its 50-day simple moving average and put itself back in positive territory for the year. Volume on the New York Stock Exchange stayed under 1.2 billion shares, and decliners outnumbered advancers by a tiny margin. On the Nasdaq, almost 1.7 billion shares changed hands, and advancers edged out decliners by about 5 to 4. "We're sort of between a rock and a hard place," said Peter Dunay, chief market strategist at Wall Street Access. "Earnings look good, but we know they're slowing down. The economy is strong, but people know it's going to slow down, so investors just sit on their hands here." Dunay attributed strength in the Nasdaq to the recent dominance in the markets of financial professionals who are buying shorter-term movements. "The Nasdaq got torn up pretty good last week," he said. "So, they see a sector that's down, they hope to buy into it quickly and then start selling, just playing for short-term movement. I think that's a driver here."