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ratchet and pawl

(Encyclopedia)ratchet and pawl, mechanical device that permits motion in one direction only. The ratchet is usually a wheel with slanting teeth. The pawl is a lever tangential to the wheel with one end resting on t...

motor, electric

(Encyclopedia)CE5 Motor: In the AC motor, current fed to the conducting loop of wire causes it to rotate in the magnetic field, thus turning the shaft on which the loop is mounted. In the DC motor, the direction...

Hockney, David

(Encyclopedia)Hockney, David, 1937–, English painter, studied Royal College of Art. Moving from a distorted, semiexpressionist form of pop art, Hockney developed a highly personal realistic style, producing image...

Van Dyck, Sir Anthony

(Encyclopedia)Van Dyck or Vandyke, Sir Anthony both: văn dīk [key], 1599–1641, Flemish portrait and religious painter and etcher, b. Antwerp. In 1618 he was received as a master in the artists' guild, but even ...

Ceres, in Roman religion and mythology

(Encyclopedia)Ceres sîrˈēz [key], in Roman religion and mythology, goddess of grain; daughter of Saturn and Ops. She was identified by the Romans with the Greek Demeter. Her worship was connected with that of th...

Yom Kippur

(Encyclopedia)Yom Kippur [Heb.,=day of atonement], in Judaism, the most sacred holy day, falling on the 10th day of the Jewish month of Tishri (usually late September or early October). It is a day of fasting and p...

Baladhuri, al-

(Encyclopedia)Baladhuri, al- äl-bäläˈᵺo͝orē [key], d. c.892, Arab historian. One of the most important Arab historians, he spent most of his life in Baghdad and enjoyed great influence at the court of the c...

Democritus

(Encyclopedia)Democritus dĭmŏkˈrĭtəs [key], c.460–c.370 b.c., Greek philosopher of Abdera; pupil of Leucippus. His theory of the nature of the physical world was the most radical and scientific attempted up ...

airfoil

(Encyclopedia)airfoil, surface designed to develop a desired force by reaction with a fluid, especially air, that is flowing across the surface. For example, the fixed wing surfaces of an airplane produce lift, whi...

Cunningham, Imogen

(Encyclopedia)Cunningham, Imogen, 1883–1976, American photographer, b. Portland, Oreg. Cunningham began taking pictures in 1901. After study abroad she opened a studio in Seattle in 1910 and for six decades produ...