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thermodynamics

(Encyclopedia)thermodynamics, branch of science concerned with the nature of heat and its conversion to mechanical, electric, and chemical energy. Historically, it grew out of efforts to construct more efficient he...

narwhal

(Encyclopedia)narwhal närˈwəl [key], a small arctic whale, Monodon monoceros. The males of the species, and an occasional female, bear a single, tightly spiraled tusk that measures up to 9 ft (2.7 m) in length. ...

ophthalmology

(Encyclopedia)ophthalmology ŏfˌthălmŏlˈəjē [key], branch of medicine specializing in the anatomy, function and diseases of the eye. Ophthalmologists specialize in the medical and surgical treatment of eye di...

Navalny, Alexei Anatolyevich

(Encyclopedia)Navalny, Alexei Anatolyevich, 1976–, Russian lawyer and political activist. Navalny joined the Russian United Democratic party...

botulism

(Encyclopedia)botulism bŏchˈəlĭzˌəm [key], acute poisoning resulting from ingestion of food containing toxins produced by the bacillus Clostridium botulinum. The bacterium can grow only in an anaerobic atmosp...

brittlestar

(Encyclopedia)brittlestar, common name for echinoderms belonging to the class Ophiuroidea. The name is derived from their habit of breaking off arms as a means of defense. New arms are easily regenerated. They are ...

symmetry, biological

(Encyclopedia)symmetry, biological, similarity or balance between parts of an organism so that when a straight cut is made through a point or along a line, equal, mirror-image halves are formed. Symmetry in body sh...

carbon dioxide

(Encyclopedia)carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. It does not bur...

Allegheny

(Encyclopedia)Allegheny ălˈəgāˌnē, ălˈəgäˌnē [key], river, 325 mi (523 km) long, rising in N central Pa., and flowing NW into N.Y., then SW through Pa. to the Monongahela, with which it forms the Ohio R...

color index

(Encyclopedia)color index, in astronomy, difference in an object's brightness as recorded between any two well-defined bands of the electromagnetic spectrum by using optical filters of different colors. If blue and...