BEIJING -- Queen Harrison kept her dream of an Olympic medal alive Sunday.

The 19-year-old from Virginia Tech advanced to the semifinals of the 400-meter hurdles with a time of 55.96 seconds at the Bird's Nest.

Harrison, the first female Tech athlete to ever compete in the Olympics, finished 13th overall out of the 27 competitors.

Harrison, who will soon begin her junior year at Tech, finished fourth in her heat. The top three finishers in each of the four heats advanced, as did the next four fastest hurdlers overall.

"I had to push a little at the end," said Harrison, according to the USA Track and Field Web site. "It was faster than I thought it would be.

"I have a lot left in my tank. I have to get mentally prepared."

Harrison and the 15 other semifinalists will compete again today. The eight-woman final is set for Wednesday.

Harrison earned an Olympic berth with a second-place finish of 54.60 seconds at the U.S. trials in June.

Melanie Walker of Jamaica, the winner of Harrison's heat, had the best time in the entire field Sunday at 54.46 seconds.

All three Americans moved on. Tiffany Ross-Williams won her heat in 55.51 seconds; it was only the eighth-best time overall. Sheena Tosta was only fifth in her heat but still qualified with a time of 56.12.

In other action at the track Sunday night, Jamaica's Shelly-Ann Fraser won the women's 100 meters.

Right fist thrust overhead as she crossed the finish line all alone, silver braces shining as she hopped in celebration like the 21-year-old she is, Fraser finished in 10.78 seconds.

Fraser was followed across the line, steps later, by teammates Sherone Simpson and Kerron Stewart, who both finished in 10.98 and both collected silvers -- giving Jamaica the first sweep of medals in a women's 100 by any nation at any Olympics or world championships.

That impressive display came one day after Usain Bolt's victory in the men's 100 -- giving Jamaica the first sweep of men's and women's 100 golds at any Olympics since 1988.

The single 100 bronze for the United States, earned by Walter Dix, amounts to the country's worst combined showing in the men's and women's dashes at an Olympics since earning zero medals in the 100 at both the 1980 Moscow Games -- where a boycott prevented any Americans from competing -- and the 1976 Montreal Games.

"We've dominated for years, and now it's their time," said Lauryn Williams, one of three U.S. women who never mounted a challenge during Sunday's final. "We're getting a pretty good taste of what it's like to be at the bottom."

The United States protested the results in the women's 100, asking that the race be reviewed because of a possible false start by American Torri Edwards -- who wound up last. The appeal was swiftly rejected.

It was part of a rough night for the Stars and Stripes.

In the men's 1,500 meters, two-time Olympic medalist Bernard Lagat, U.S. team flagbearer Lopez Lomong and NCAA champion Leo Manzano -- all naturalized citizens making their Olympic debuts for their new country -- failed to reach the final.

There was more bad news for the U.S. when Dee Dee Trotter and Mary Wineberg flopped in the women's 400 semifinals, although Sanya Richards did advance.

The American's bad day had begun in the morning when 2004 bronze medalist Deena Kantor had to quit the women's marathon three miles into the race because of a broken foot.