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Olympiad

(Encyclopedia)Olympiad, unit of a chronological era of ancient Greece, a four-year period, each one beginning with the Olympic games. Timaeus (c.356–c.260 b.c.) of Sicily was the first to use, as a check on chron...

Oroville Dam

(Encyclopedia)Oroville Dam, 770 ft (235 m) high and 7,600 ft (2,317 m) long, on the Feather River, N Calif., near the city of Oroville. The highest dam in the United States and the largest unit of the Feather River...

Sporades

(Encyclopedia)Sporades spôrˈədēz, spŏrˈ– [key], islands, E and SE Greece, in the Aegean Sea. They have been grouped variously at different times. The Northern Sporades are generally understood to include Sk...

Yakima, river, United States

(Encyclopedia)Yakima yăkˈəmô, –mə [key], river, 203 mi (327 km) long, rising in the Cascade Range, central Wash., and flowing SE past Yakima to the Columbia River near Kennewick. The U.S. Bureau of Reclamati...

turbine

(Encyclopedia)CE5 Types of turbines turbine, rotary engine that uses a continuous stream of fluid (gas or liquid) to turn a shaft that can drive machinery. A water, or hydraulic, turbine is used to drive electr...

dissociation

(Encyclopedia)dissociation, in chemistry, separation of a substance into atoms or ions. Thermal dissociation occurs at high temperatures. For example, hydrogen molecules (H2) dissociate into atoms (H) at very high ...

light-year

(Encyclopedia)light-year, in astronomy, unit of length equal to the distance light travels in one sidereal year. It is 9.461 × 1012 km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars n...

mole, in chemistry

(Encyclopedia)mole, in chemistry, a quantity of particles of any type equal to Avogadro's number, or 6.02×1023 particles. One gram-molecular weight of any molecular substance contains exactly one mole of molecules...

Maillart, Robert

(Encyclopedia)Maillart, Robert mīyärˈ [key], 1872–1940, Swiss engineer, renowned for his inventive and beautiful reinforced-concrete bridges. Maillart's basic structural principles—integration of the support...

barn

(Encyclopedia)barn, abbr. b, in physics, unit of nuclear cross section, i.e., the effective target presented by a nucleus for collisions leading to nuclear reactions; it is equal to 10−24 square centimeters. The ...