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hydrazine

(Encyclopedia)hydrazine hīˈdrəzēnˌ [key], chemical compound, formula NH2NH2, m.p. 1.4℃, b.p. 113.5℃, specific gravity 1.011 at 15℃. It is very soluble in water and soluble in alcohol. At ordinary tempera...

diffusion

(Encyclopedia)diffusion, in chemistry, the spontaneous migration of substances from regions where their concentration is high to regions where their concentration is low. Diffusion is important in many life process...

Ryan, Kay

(Encyclopedia)Ryan, Kay, 1945–, American poet, b. San Jose, Calif., grad. Univ. of California at Los Angeles (B.A., 1967; M.A., 1968). She taught remedial English in a Marin co. community college for more than 30...

Enceladus

(Encyclopedia)Enceladus ĕnsĕlˈədəs [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn II (or S2), Enceladus is 310 mi (500 km) in diameter, orbits Saturn at a m...

aqueduct

(Encyclopedia)aqueduct ăkˈwədŭkt [key] [Lat.,=conveyor of water], channel or trough built to convey water, chiefly for providing a densely populated region with a supply of freshwater. The flow in aqueducts is ...

ballistics

(Encyclopedia)ballistics bəlĭsˈtĭks [key], science of projectiles. Interior ballistics deals with the propulsion and the motion of a projectile within a gun or firing device. Its problems include the ignition a...

urinalysis

(Encyclopedia)urinalysis yo͝orˌənălˈĭsĭs [key], clinical examination of urine for the purpose of medical diagnosis. Urine is initially examined for such characteristics as color, odor, and specific gravity. ...

dam

(Encyclopedia)dam, barrier, commonly across a watercourse, to hold back water, often forming a reservoir or lake; dams are also sometimes used to control or contain rockslides, mudflows, and the like in regions whe...

centering

(Encyclopedia)centering, the framework of wood or of wood and steel built to support a masonry arch or vault during its construction. The centering itself must be rigidly supported, either by posts from the ground ...

Stefan, Josef

(Encyclopedia)Stefan, Josef yōˈzĕf shtĕfˈän [key], 1835–93, Austrian physicist. At the Univ. of Vienna he became a professor of physics and later director of the Physical Institute. From his observations on...