But Joshua Plotnik of the Think Elephant International Foundation modified the test.

WSJ: The Brains of the Animal Kingdom

The researchers trialled the test on genetically modified mice, which are highly susceptible to forming tumours.

BBC: One test may 'find many cancers'

Halliburton then conducted another test using a modified procedure, the letter said, and the result for the first time indicated the slurry design would be stable.

CNN: STORY HIGHLIGHTS

Likewise, BMW withdrew its own test fleet of 100 cars with internal-combustion engines modified to run on hydrogen.

ECONOMIST: Tech.view: Hydrogen tries again | The

If it proves successful, the modified two-challenge rule will also be introduced for Australia's Test tour to South Africa, which is the last tour included in the referral trial.

BBC: Referrals change for England tour

The U.S. Air Force is currently test-flying an optionally piloted supersonic drone over the Gulf of Mexico based on a modified F-16 fighter jet.

FORBES: Pilot-Optional Flight Is Closer Than You Think