Linda B. Buck, who shared the 2004 Nobel Prize in Physiology or Medicine for deciphering the workings of the sense of smell, has retracted two scientific papers after she and her colleagues were unable to repeat the findings.

The retractions, which did not concern the work for which Dr. Buck won the Nobel, were published Thursday on the Web sites of the journals where the papers appeared. One had been published in the Proceedings of the National Academy of Sciences in 2005, the other in the journal Science in 2006.

“I sincerely apologize for any confusion that its publication may have caused,” Dr. Buck wrote in the retraction of the Science paper.

The retractions follow a separate one, two years ago, of a paper by Dr. Buck that was published in the journal Nature in 2001.