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optical activity
(Encyclopedia)optical activity, the ability of asymmetric compounds to rotate the orientation of planar polarized light. Such compounds and their mirror images are know as enantiomers, or optical isomers. Although ...Moronobu
(Encyclopedia)Moronobu (Hishikawa Moronobu) hēshēkäˈwä mōrōˈnōbo͞o [key], c.1618–c.1694, Japanese painter and color-print designer of the ukiyo-e school. He began his career as an embroiderer. His first...mastic
(Encyclopedia)mastic, resin obtained from the small mastic tree Pistacia lentiscus (of the sumac family), found chiefly in Mediterranean countries. When the bark of the tree is injured, the resin exudes in drops. I...asphalt
(Encyclopedia)asphalt ăsˈfôlt, –fălt [key], brownish-black substance used commonly in road making, roofing, and waterproofing. Chemically, it is a natural mixture of hydrocarbons. It varies in consistency fro...phlogiston theory
(Encyclopedia)phlogiston theory flōjĭsˈtŏn [key], hypothesis regarding combustion. The theory, advanced by J. J. Becher late in the 17th cent. and extended and popularized by G. E. Stahl, postulates that in all...photoengraving
(Encyclopedia)photoengraving, photomechanical process in the graphic arts, used principally for reproducing illustrations. The subject is photographed, and the image is recorded on a sensitized metal plate, which i...Percheron horse
(Encyclopedia)Percheron horse pûrˈchərŏnˌ [key], breed of draft horse developed in NW France, originally of Flemish origin, but also containing some Arabian blood (see Arabian horse). For a heavy horse, it has...chloroplast
(Encyclopedia)chloroplast klōrˈəplăstˌ, klôrˈ– [key], a complex, discrete green structure, or organelle, contained in the cytoplasm of plant cells. Chloroplasts are reponsible for the green color of almost...cherub
(Encyclopedia)cherub chĕrˈəb [key], plural cherubim, kind of angel. Cherubim were probably thought of in the ancient Middle East as composite creatures like the winged creatures of Assyria. In Jewish tradition, ...fuller's earth
(Encyclopedia)fuller's earth, mineral substance characterized by the property of absorbing basic colors and removing them from oils. It is composed mainly of alumina, silica, iron oxides, lime, magnesia, and water,...Browse by Subject
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