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zone

(Encyclopedia)zone [Gr.,=girdle], in geography, area with a certain physical and/or cultural unity that distinguishes it from other areas. The division of the earth into five climatic zones probably originated (5th...

cortisol

(Encyclopedia)cortisol kôrˈtĭsôlˌ [key] or hydrocortisone, steroid hormone that in humans is the major circulating hormone of the cortex, or outer layer, of the adrenal gland. Like cortisone, cortisol is class...

glutamic acid

(Encyclopedia)CE5 glutamic acid glo͞otămˈĭk [key], organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer occurs in mammalian proteins. Like aspartic acid, glu...

alumina

(Encyclopedia)alumina əlo͞oˈmĭnə [key] or aluminum oxide, Al2O3, chemical compound with m.p. about 2,000℃ and sp. gr. about 4.0. It is insoluble in water and organic liquids and very slightly soluble in stro...

niobium

(Encyclopedia)niobium nīōˈbēəm [key], metallic chemical element; symbol Nb; at. no. 41; at. wt. 92.90638; m.p. about 2,468℃; b.p. 4,742℃; sp. gr. 8.57 at 20℃; valence +2, +3, +4, or +5. Niobium is a rare...

acid rain

(Encyclopedia)acid rain or acid deposition, form of precipitation (rain, snow, sleet, or hail) containing high levels of sulfuric or nitric acids (pH below 5.5–5.6). Produced when sulfur dioxide and various nitro...

lipoprotein

(Encyclopedia)lipoprotein lĭpˌəprōˈtēn [key], any organic compound that is composed of both protein and the various fatty substances classed as lipids, including fatty acids and steroids such as cholesterol. ...

virology

(Encyclopedia)virology, study of viruses and their role in disease. Many viruses, such as animal RNA viruses and viruses that infect bacteria, or bacteriophages, have become useful laboratory tools in genetic studi...

tantalum

(Encyclopedia)tantalum tănˈtələm [key] [from Tantalus], metallic chemical element; symbol Ta; at. no. 73; at. wt. 180.94788; m.p. 2,996℃; b.p. 5,400±100℃; sp. gr. 16.65 at 20℃; valence +2, +3, +4, or +5....

biochemistry

(Encyclopedia)biochemistry, science concerned chiefly with the chemistry of biological processes; it attempts to utilize the tools and concepts of chemistry, particularly organic and physical chemistry, for elucida...