The result is that the light field will start modifying the photonic crystal in such a way as to reduce the refractive index contrast.

"There was a concern among Reagan's conservative base that he might start modifying on his principles," said Kenneth L. Khachigian, a Reagan speechwriter.

But when you start modifying it, it's not the same.

The Land Transport Authority started modifying and extending the highway in the late 1990s, in response to the increased amount of traffic using it.

Brothers Herbert and Rolf Hartge started modifying BMW's in small numbers in Merzig, Germany around 1971.

Once the manufacturers started modifying their products, Mr. Sokolof continued to make the point, writing a book, "Add Years to Your Life" (2002).

Maybe the first thing that happens when species diverge is that they start modifying genes - imprinting them - and eventually, as a consequence, they cannot mate.

We started modifying our equipment in preparation for that," Mr. O'Connor said, "and we've spent millions developing this technology.

"I'll go in and sometimes scan a product right into my computer and start modifying it in Photoshop," Mr. Call said.

Robert Kronfeld took over the company and started modifying the surviving Planettes to produce a more practical single-seat light aeroplane known as the B.A.C. Drone.