If there's one thing that markets don't like, it's uncertainty, and this afternoon's plunge in the Dow Jones Industrials (DJINDICES:^DJI) shows just how uncertain investors feel about the direction of the financial markets. With bond yields once again spiking higher, even the safe-haven status that U.S. stocks have enjoyed lately wasn't enough to avoid a late-day drop that sent the Dow down 209 points on the day. The S&P 500 had similar losses on a percentage basis.

Only two stocks managed to end slightly higher on the day. Intel (NASDAQ:INTC) rose about a quarter percent after finally getting some long-awaited good news on the mobile-chip front. Samsung reportedly chose Intel's Clover Trail+ for its Galaxy Tab 3 tablet, thereby validating the chipmaker's efforts to move past its PC dominance and seek to take advantage of the fast-growing mobile market. If Intel can leverage this victory to win spots in other key mobile devices, then the company just might have turned the corner toward demonstrating its growth potential to a skeptical investor base.

The other gainer in the Dow today was Alcoa (NYSE:AA), which managed to survive a Moody's downgrade of its bond rating from Baa3 to Ba1 yesterday with a share-price gain of $0.01. The downgrade is especially important, because it cuts Alcoa's debt to junk status, with substantial implications for the company's financing costs should Alcoa choose to tap the credit markets for further financing down the road. Until aluminum prices recover, Alcoa will continue to face challenges in producing the financial results that investors would like to see.

Outside the Dow, there were a few winners. Guess? (NYSE:GES) climbed 8% after a better-than-expected earnings performance, despite the fact that profits fell from year-ago levels. The retailer repeated what we've heard from its peers about bad weather conditions having a negative impact on the company, and its European operations also struggled. Meanwhile, biotech IPO Epizyme (NASDAQ:EPZM) soared more than 50% after coming public at $15 this morning. The company has a promising technology in treating cancer caused by carcinogenic genes, and it has collaborations with several major drug companies that should help it push some of its potential treatments through the pipeline.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool recommends Guess? and Intel. The Motley Fool owns shares of Guess? and Intel. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.