barrier(redirected from blood-brain barrier (BBB))
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(in Russian, zaval), an antitank, antitransport, or anti-infantry obstacle. Barriers are made of lumber, stones, or snow on probable enemy routes of travel in places where it is difficult to bypass them. When setting up a timber barrier, trees of more than 20 cm in diameter are used. They are sawed down at a height of 60–120 cm and piled criss-cross with the crowns facing the enemy. In order to make it difficult to pull the barrier apart, the trees are not completely separated from their stumps; they are secured to them, woven with barbed wire, and also reinforced by the placement of land mines and high-explosive charges. During the Great Patriotic War of 1941–45 timber barriers were used extensively by Soviet troops on the defense in forested regions. Stone barriers are set up in mountains or in populated areas by demolishing cliffs or urban stone structures. Barriers made of snow can be devised in mountain and northern regions. In mining the Russian word zaval signifies the accidental destruction of a large rock mass in a mining excavation that disrupts its normal use.
a lifting or sliding beam, usually installed at a railroad crossing to stop automobile, cart, and pedestrian traffic prior to the passing of a train. Barriers may be operated manually, mechanically, or automatically. Automatic barriers are operated by signals from the railroad’s automation and remote control systems; signal lights and acoustic devices may be used. The normal position for automatic barriers is the open position; for nonauto-matic barriers it is the closed position.
What does it mean when you dream about a barrier?
A barrier may signify that the dreamer is experiencing some obstacle in an arena of his or her life.
ii. A net forming part of an arrester, or crash barrier system meant to arrest forward motion of an aircraft that is likely to overshoot the runway. Normally, the net lies horizontally on the ground and is raised when required. The vertical ropes of the barrier net are made of nylon, which are attached to the steel ropes at the top and the bottom of the barrier net.