Only two women in the group have done so, she said, both with negative results.

Conflict in the group need not lead to negative results, however.

But in science a negative result is not at all the same thing as a failure.

In many cases, a roll of 12 has particularly negative results.

"They came back too quickly for a negative result," I said.

In some cases, a negative result might not give any useful information.

But negative results may simply mean that researchers did not look in the right places.

The group continued to search throughout the night with negative results.

They also stress that a negative result is not the end of the process.

"I think this will put all the negative results of Vietnam behind us."