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immunity

(Encyclopedia)immunity, ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian...

Americas, antiquity and prehistory of the

(Encyclopedia)Americas, antiquity and prehistory of the, study of the origins of the aboriginal peoples of the Americas. Archaeologists believe humans had entered and occupied much of the Americas by the end of the...

ammonium group

(Encyclopedia)ammonium group, in chemistry, a positively charged nitrogen atom joined by single bonds to four other atoms or groups. The simplest ammonium group, NH4+, is formed by protonation of ammonia, NH3, e.g....

hydrogenation

(Encyclopedia)hydrogenation hīdrôjˈənāˌshən, hīˌdrəjənāˈshən [key], chemical reaction of a substance with molecular hydrogen, usually in the presence of a catalyst. A common hydrogenation is the harde...

ibuprofen

(Encyclopedia)ibuprofen īˈbyo͞oprōˌfən [key], nonsteroidal anti-inflammatory drug (NSAID) that reduces pain, fever, and inflammation. Along with naproxen and ketoprofen, ibuprofen belongs to the propionic aci...

drypoint

(Encyclopedia)drypoint, an intaglio printing process in which the lines are scratched directly into a metal plate with a needle; also, the print made from such a plate. Although it is often used in combination with...

Crofton, Sir John Wenman

(Encyclopedia)Crofton, Sir John Wenman, 1912–2009, British physician, b. Dublin. He served in the British medical corps during World War II and during 1946–52 was part of a research team studying the effects of...

cyanide process

(Encyclopedia)cyanide process or cyanidation, method for extracting gold from its ore. The ore is first finely ground and may be concentrated by flotation; if it contains certain impurities, it may be roasted. It i...

alanine

(Encyclopedia)CE5 alanine ălˈənēnˌ [key], organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of proteins (see stereochemi...

Roethke, Theodore

(Encyclopedia)Roethke, Theodore rĕtˈkə [key], 1908–63, American poet, b. Saginaw, Mich., educated at the Univ. of Michigan and Harvard. A poet of the Midwest, Roethke combined a love of the land with his visio...