"We have stepped up the monitoring of the checkpoints," said Elizabeth Isham Cory, a spokeswoman for the agency.
The added monitoring of security checkpoints by F.A.A. agents is on top of the heightened surveillance generally at airports across the country since the terrorist attacks of Sept. 11, officials of the aviation agency said.
Some of it will be visible and intentionally so, such as the teams of heavily armed police officers at sensitive locations including landmarks and financial institutions, and the increased monitoring of truck traffic and checkpoints on our bridges and tunnels.
There are also competitions called alleycats, in which bicyclists pick their own routes between a series of checkpoints where monitors stamp their paper manifests.
Subsequent research showed that cells employ a series of checkpoints that monitor progression through the cell cycle and delay the division process until any faulty DNA is repaired.
Also, these signals are actively monitored and regulated by a number of checkpoints within the system.
Thus, the COC may serve as a model system to study a new class of checkpoints that specialize in monitoring division orientation in multicellular organisms.
