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osmium

(Encyclopedia)osmium ŏzˈmēəm [key], metallic chemical element; symbol Os; at. no. 76; at. wt. 190.23; m.p. 3,045±30℃; b.p. 5,027±100℃; sp. gr. 22.57 at 20℃; valence usually +0 to +8. Osmium is a very ha...

leucine

(Encyclopedia)CE5 leucine lo͞oˈsēn [key], organic compund, one of the 20 amino acids commonly found in animal proteins. Only the l-stereooisomer appears in mammalian protein. It is one of several essential am...

mass extinction

(Encyclopedia)mass extinction, the extinction of a large percentage of the earth's species, opening ecological niches for other species to fill. There have been at least ten such events. The five greatest were thos...

chromium

(Encyclopedia)chromium krōˈmēəm [key] [Gr.,=color], metallic chemical element; symbol Cr; at. no. 24; at. wt. 51.9961; m.p. about 1,857℃; b.p. 2,672℃; sp. gr. about 7.2 at 20℃; valence +2, +3, +6. Chromiu...

bromine

(Encyclopedia)bromine brōˈmēn, –mĭn [key] [Gr.,=stench], volatile, liquid chemical element; symbol Br; at. no. 35; at. wt. 79.904; m.p. –7.2℃; b.p. 58.78℃; sp. gr. of liquid 3.12 at 20℃; density of va...

flying lemur

(Encyclopedia)flying lemur, gliding mammal native to the tropical lowland forests of S Asia, Malaya, and the Philippines. Also called the colugo, the flying lemur is brownish or grayish above and paler below. It ra...

liana

(Encyclopedia)liana lēänˈ [key], name for any climbing plant that roots in the ground. The term is most often used for the woody vines that form a characteristic part of tropical rain-forest vegetation; they are...

addax

(Encyclopedia)addax ădˈăks [key], large, desert-dwelling antelope. It is a single species, Addax nasomaculatus. The addax is yellowish-white in color, has a brown mane and throat fringe, and may stand as high as...

umbrella

(Encyclopedia)umbrella, a small canopy used as a protection against the sun in China, Egypt, and elsewhere in remote antiquity. It was often an emblem of rank. During the Middle Ages the umbrella became almost exti...

Ypres, battles of

(Encyclopedia)Ypres, battles of, three major engagements of World War I fought in and around the town of Ypres in SW Belgium. The first battle of Ypres (Oct.–Nov., 1914) was the last of the series of engagements ...