In response to an action for declaration of noninfringement of a patent, the patentee’s counterclaim of infringement of the patent was compulsory and should not have been dismissed by the district court, the U.S. Court of Appeals for the Federal Circuit held December 29 (.Vivid Technologies Inc. v. American Science & Engineering Inc, Fed. Cir., No. 98-1303, 12/29/99).

X-ray machines, such as those used in airports, commonly use two types of radiation: transmitted radiation and backscattered radiation. Transmitted radiation tends to travel straight through objects. For instance, threat objects with high atomic weights, such as metal weapons, block transmitted radiation. Backscattered radiation, on the other hand, tends to be deflected from objects. For instance, threat materials with low atomic weights, such as plastic explosives, deflect scattered radiation.