Kendra Harrison's hopes of winning a medal at this week's World Track and Field Championships in Beijing, China, were lost to a disqualification on Friday morning.
Harrison was dismissed from the semifinals of the 100-meter hurdles after a false start, an unforgiving rule that allows for no second chances.
Harrison, who won the same event for the University of Kentucky at the NCAA Championships in May, was competing in her first senior international competition.
Danielle Williams went on to win the 100-meter hurdles gold medal later Friday morning in 12.57 seconds.
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The 22-year-old Jamaican held off Cindy Roleder of Germany, who won silver in 12.59. Alina Talay took bronze in a Belarus record 12.66.
Defending champion Brianna Rollins of the United States was fourth in 12.67, 0.01 ahead of European champion Tiffany Porter of Britain.
Sharika Nelvis, who had the fastest time of the season and was a medal contender for the United States, placed last in the final.
Dawn Harper-Nelson, the 2008 Olympic champion for the U.S., fell in the semifinals.