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autoimmune disease

(Encyclopedia)autoimmune disease, any of a number of abnormal conditions caused when the body produces antibodies to its own substances. In rheumatoid arthritis, a group of antibody molecules called collectively RF...

nitric acid

(Encyclopedia)nitric acid, chemical compound, HNO3, colorless, highly corrosive, poisonous liquid that gives off choking red or yellow fumes in moist air. It is miscible with water in all proportions. It forms an a...

lipids

(Encyclopedia)lipids, a broad class of organic products found in living systems. Most are insoluble in water but soluble in nonpolar solvents. The definition excludes the mineral oils and other petroleum products o...

ruthenium

(Encyclopedia)ruthenium ro͞othēˈnēəm [key], metallic chemical element; symbol Ru; at. no. 44; at. wt. 101.07; m.p. about 2,310℃; b.p. about 3,900℃; sp. gr. 12.41 at 20℃; valence commonly +2, +3, +4, +6, ...

tracer

(Encyclopedia)tracer, an identifiable substance used to follow the course of a physical, chemical, or biological process. In chemistry the ideal tracer has the same chemical properties as the molecule it replaces a...

selenium

(Encyclopedia)selenium səlēˈnēəm [key], nonmetallic chemical element; symbol Se; at. no. 34; at. wt. 78.96; m.p. 217℃; b.p. about 685℃; sp. gr. 4.81 at 20℃; valence −2, +4, or +6. Selenium is directly ...

aldehyde

(Encyclopedia)CE5 Aldehydes aldehyde ălˈdəhīd [key] [alcohol + New Lat. dehydrogenatus=dehydrogenated], any of a class of organic compounds that contain the carbonyl group, >C=-->O, and in which t...

citrus fruits

(Encyclopedia)citrus fruits, widely used edible fruits of plants belonging to Citrus and related genera of the family Rutaceae (orange family). Included are the tangerine, citrange, tangelo, orange, pomelo, grapefr...

detergent

(Encyclopedia)detergent dētûrˈjənt, dĭ– [key], substance that aids in the removal of dirt. Detergents act mainly on the oily films that trap dirt particles. The detergent molecules have a hydrocarbon portion...

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...