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quadratic

(Encyclopedia)quadratic, mathematical expression of the second degree in one or more unknowns (see polynomial). The general quadratic in one unknown has the form ax2+bx+c, where a, b, and c are constants and x is t...

anthracene

(Encyclopedia)CE5 anthracene ănˈthrəsēn [key], C14H10, solid organic compound derived from coal tar. It melts at 218℃ and boils at 354℃. When pure it is colorless and has a violet fluorescence; it darken...

ketone

(Encyclopedia)CE5 Ketones ketone kēˈtōn [key], any of a class of organic compounds that contain the carbonyl group, C=O, and in which the carbonyl group is bonded only to carbon atoms. The general formula fo...

3D printer

(Encyclopedia)3D printer, computerized device that produces a three-dimensional object by creating it as a series of thin layers. The object is created from a model stored in computer-aided design file; the model i...

sundial

(Encyclopedia)sundial, instrument that indicates the time of day by the shadow, cast on a surface marked to show hours or fractions of hours, of an object on which the sun's rays fall. Although any object whose sha...

leaf

(Encyclopedia)CE5 Microscopic cross section of the leaf blade CE5 Types of leaves leaf, chief food-manufacturing organ of a plant, a lateral outgrowth of the growing point of stem. The typical leaf consist...

semiconductor

(Encyclopedia)CE5 N-type and P-type crystals: In a pure silicon crystal each silicon atom (Si) is surrounded by four valence electrons. In the N-doped semiconductor, illustrated in the left-hand figure, some sil...

formula, in chemistry

(Encyclopedia)formula, in chemistry, an expression showing the chemical composition of a compound. Formulas of compounds are used in writing the equations (see chemical equations) that represent chemical reactions....

needlefish

(Encyclopedia)needlefish, common name for members of the family Belonidae, which comprises species of elongated, surface-swimming predaceous fish abundant in warm seas. They have beaklike jaws armed with sharp teet...

Fitzgerald, Ella

(Encyclopedia)Fitzgerald, Ella, 1917–96, American jazz singer, b. Newport News, Va. Probably the most celebrated jazz vocalist of her generation, Fitzgerald was reared in Yonkers, N.Y., moving after her mother's ...