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Balkan Peninsula

(Encyclopedia)Balkan Peninsula, southeasternmost peninsula of Europe, c.200,000 sq mi (518,000 sq km), bounded by the Black Sea, Sea of Marmara, Aegean Sea, Mediterranean Sea, Ionian Sea, and Adriatic Sea. Although...

radioactive isotope

(Encyclopedia)radioactive isotope or radioisotope, natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reache...

Obregón, Álvaro

(Encyclopedia)Obregón, Álvaro älˈvärō ōbrāgōnˈ [key], 1880–1928, Mexican general and president (1920–24). A planter in Sonora, he supported Francisco I. Madero in the revolution against Porfirio Díaz...

octane number

(Encyclopedia)octane number, figure of merit representing the resistance of gasoline to premature detonation when exposed to heat and pressure in the combustion chamber of an internal-combustion engine. Such detona...

Staples, Mavis

(Encyclopedia) Staples, Mavis, 1939- , African American popular singer, b. Chicago, Il. Staples began performing at age 11 with her father, Roebuck “Pops” St...

cerium

(Encyclopedia)cerium sērˈēəm [key] [from the asteroid Ceres], metallic chemical element; symbol Ce; at. no. 58; at. wt. 140.116; m.p. 799℃; b.p. 3,426℃; sp. gr. 6.77 at 25℃; valence +3 or +4. Cerium is a ...

urea

(Encyclopedia)CE5 urea yo͝oēˈə [key], organic compound that is the principal end product of nitrogen metabolism in most mammals. Urea was the first animal metabolite to be isolated in crystalline form; its c...

dating

(Encyclopedia)dating, the determination of the age of an object, of a natural phenomenon, or of a series of events. There are two basic types of dating methods, relative and absolute. In relative dating, the tempor...

livermorium

(Encyclopedia)livermorium, artificially produced radioactive chemical element; symbol Lv; at. no. 116; mass number of most stable isotope 292; m.p., b.p., sp. gr., and valence unknown. Situated in Group 16 of the p...

lemur

(Encyclopedia)lemur lēˈmər [key], name for prosimians, or lower primates, of two related families, found only on Madagascar and adjacent islands. Lemurs have monkeylike bodies and limbs, and most have bushy tail...

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