21.   Specialists have said in recent days that the signal could be blocked by thick debris.

22.   Somehow that signaling leads to the release of endorphins and monoamines, chemicals that block pain signals in the spinal cord and the brain.

23.   The drug blocks chemical signals sent by an abnormal, cancer-causing protein, the principle known as molecular targeting.

24.   They also had a fairly short range and signals were often blocked by walls or floors.

25.   They will be lower in the sky than the Sirius craft, making it more likely that the signal will be blocked by hills, trees or buildings.

26.   Through the blood circulation, the drug reaches the spinal cord, where it blocks pain signals by binding to opioid receptors.

27.   Gleevec works by blocking chemical signals sent by cancerous cells and researchers hope it will also prove useful in treating stomach tumors and perhaps other cancers.

28.   Gleevec blocks a signal that the abnormal protein sends out, preventing the abnormal growth and production of other cancerous cells.

29.   Gleevec blocks a signal that the abnormal protein sends out, preventing the growth and production of other cancerous cells.

30.   Ham radio operators, who usually keep links with the Sarajevo government in such areas, had signals blocked by the Serbs, Sarajevo officials said.