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plein-air

(Encyclopedia)plein-air plān-ârˈ, Fr. plĕn-ĕrˈ [key] [Fr.,=open-air], term used for paintings or drawings made directly from nature and infused with a feeling of the open air. Painting outdoors is a relativel...

air embolism

(Encyclopedia)air embolism: see embolus.

air forces

(Encyclopedia)air forces, those portions of a nation's military organization employing heavier-than-air aircraft for reconnaissance, support of ground troops, aerial combat, and bombing of enemy lines of communicat...

air lock

(Encyclopedia)air lock, compartment connecting two different environments, usually at different pressures, that enables personnel to transfer from one environment to the other. Space capsules have air locks to enab...

Aïr Massif

(Encyclopedia)Aïr Massif or Aïr Mountains, Africa: see Sahara. ...

air navigation

(Encyclopedia)air navigation, science and technology of determining the position of an aircraft with respect to the surface of the earth and accurately maintaining a desired course (see navigation). Basic to air ...

air plant

(Encyclopedia)air plant: see epiphyte.

air pollution

(Encyclopedia)air pollution, contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health. The major sources of air pollution are t...