cathode ray Stream of electrons leaving the negative electrode, or cathode, in an evacuated or gas-filled discharge tube or emitted by a heated filament in certain electron tubes. Cathode rays cause fluorescent mate¬ rials to luminesce and are utilized in cathode-ray oscilloscopes and tele¬ vision tubes (see cathode-ray tube).
cathode-ray tube (CRT) Vacuum tube that produces images when its phosphorescent surface is struck by electron beams. CRTs can be mono¬ chrome (using one electron gun) or colour (typically using three electron guns to produce red, green, and blue images that, when combined, ren¬ der a multicolour image). They come in a variety of display modes, including CGA (Color Graphics Adapter), VGA (Video Graphics Array), XGA (Extended Graphics Array), and the high-definition SVGA (Super Video Graphics Array). See illustration on opposite page.
Catholic church. Old See Old Catholic church
Catholic Emancipation Freedom from discrimination and civil dis¬ abilities granted to the Roman Catholics of Britain and Ireland in the late 18th and early 19th century. After the Reformation, Roman Catholics in Britain could not purchase land, hold offices or seats in Parliament, inherit property, or practice their religion without incurring civil penalties. Irish Catholics faced similar limitations. By the late 18th century, Catholicism no longer seemed so great a social and political danger, and a series of laws, culminating in the Emancipation Act of 1829, eased the restrictions. A major figure in the struggle for full emancipation was Daniel O'Connell.
Catholic League (1609-35) Military alliance of the Catholic powers of Germany, led by Maximilian I, duke of Bavaria, and designed to stem the growth of Protestantism in Germany. Plans for a league had long been discussed, but the formation of the Protestant Union in 1608 finally caused the Catholics to unite. In alliance with the Habsburg emperors, the League’s forces, led by Graf von Tilly, played a key role in the Thirty Years' War. The league was abolished by the Peace of Prague (1635).
Catholic Reformation See Counter-Reformation
Catiline \ , kat- 3 l-,In\ orig. Lucius Sergius Catilina (b. c. 108—d. 62
bc, Pistoria, Etruria [Italy]) Roman aristocrat turned demagogue who sought to overthrow the republic. He was first suspected of conspiracy in 65, after which he sought to be elected consul. Failing twice, he planned a coup, known as Catiline’s conspiracy (63), assembling an army outside Rome from his supporters among the alienated and discontented elements
Catherine of Aragon.
ANN RONAN PICTURE UBRARY/HERITAGE-IMAGES
© 2006 Encyclopaedia Britannica, Inc.
cation ► Catt i 353
of society. Cicero, then consul, learned of the conspiracy; with Senate approval, he caught and executed a group of the plotters in Rome, and later sent the army to defeat and kill Catiline in northern Italy (62).
cation Vkat-,I-9n\ Atom or group of atoms carrying a positive electric charge, indicated by a superscript plus sign after the chemical symbol. Cations in a liquid subjected to an electric field collect at the negative pole (cathode). Examples include sodium (Na + ), calcium (Ca 2+ ), and ammonium (NH 4 + ; see ammonia). See also ion; compare anion.
catkin Elongated cluster of single-sex flowers bearing scaly bracts and usually lacking petals. Many trees bear catkins, including willows, birches, and oaks. Wind carries pollen from male to female catkins or from male catkins to female flowers that take a different form (e.g., in spikes).
Catlett, Elizabeth (b. April 15, 1919, Washington, D.C., U.S.) Expa¬ triate U.S. sculptor and printmaker. Catlett was born into a middle-class family. After studying sculpture, she went to Mexico City in 1946 to work at the Taller de Grafica Popular, an artists’ collective, where she created prints depicting Mexican life. About 1962 she took Mexican citizenship. In her sculptures and prints, Catlett focused on mother-child pairings, famous subjects such as Harriet Tubman and Malcolm X, and anonymous workers—notably strong, solitary black women.
Catlin, George (b. July 26, 1796, Wilkes-Barre, Pa., U.S.—d. Dec. 23, 1872, Jersey City, N.J.) U.S. painter and author. He practiced law briefly before becoming a self-taught portrait painter in Philadelphia (1823). Long interested in Native American life, in 1830 he began a series of visits to various tribes on the Great Plains. He produced some 500 paintings and sketches based on his travels and exhibited them in the U.S.
heater accelerating anodes
graphite coating
electron beam
| electron-emitting insulator glass neck / i cathode of tube /
red, green, and blue / electron guns
green
beam
blue beam
aperture
grille
"glass tube face ^phosphor coating on back of glass
In a colour-television tube, three electron guns (one each for red, green, and blue) fire electrons toward the phosphor-coated screen. The electrons are directed to a specific spot (pixel) on the screen by magnetic fields, induced by the deflection coils. To prevent "spillage" to adjacent pixels, a grille or shadow mask is used. When the electrons strike the phosphor screen, the pixel glows. Every pixel is scanned about 30 times per second.
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and Europe. In 1854-57 he traveled to Central and South America; in 1858-70 he lived in Europe. He published several illustrated books on Native American life. Most of his collection was acquired by the Smith¬ sonian Institution for its ethnographic and historical interest.
catnip or catmint Aromatic herb {Nepeta cataria ) of the mint family. Catnip has spikes of small, purple- dotted flowers. It has been used as a seasoning and as a medicinal tea for colds and fever. Because its mintlike flavour and aroma are particularly exciting to domestic cats, it is often used as a stuffing for cat toys.
Cato \'ka-to\, Marcus Porcius known as Cato the Censor or Cato the Elder (b. 234, Tusculum,
Latium—d. 149 bc) Roman states¬ man and orator, the first important Latin prose writer. Born of plebeian stock, he fought in the Second Punic War. His oratorical skills paved the way for his political career. He held conservative anti-Hellenic views and opposed the pro-Hellenic Scipio family, whose power he broke. Elected censor (magistrate in charge of censuses, taxes, and the public good) in 184, he tried to restore the mos majorum (“ancestral custom”) and com¬ bat Greek influence, which he believed undermined Roman morality. He crafted laws against luxury and the financial freedom of women and never ceased to demand the destruction of Carthage. His writings include works on history, medicine, law, military science, and agriculture. His great- grandson Cato the Younger (b. 95—d. 46 bc) was a leading Optimate (see Optimates and Populares) who sought to preserve the republic against Julius Caesar.
Catnip (Nepeta cataria).
WALTER CHANDOHA
Cats \'kats\, Jacob(us) known as Father Cats (b. Nov. 10, 1577, Brouwershaven, Zeeland, Spanish Netherlands—d. Sept. 12, 1660, Zorgvliet, near The Hague) Dutch poet. A magistrate and high official, he was enormously popular as a writer of emblem books, consisting of wood- cuts or engravings with verses possessing a moral. His Mirror of Old and New Times (1632) contains many quotations that have become household sayings in the Netherlands, and he used it to express the ethical concerns of Dutch Calvinists, especially about love and marriage.
that display a luminous band remi-
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cat's-eye Any of several gemstones niscent of the eye of a cat. Grayish green or greenish quartz cat’s-eye is the most common type; although it comes from the Orient, it is often called occidental cat’s-eye to differ¬ entiate it from the rarer, and more valuable, precious or oriental cat’s- eye, which is a greenish variety of chrysoberyl. Crocidolite cat’s-eye (African cat’s-eye) is more com¬ monly known as tigereye. Corundum cat’s-eye is an imperfect star sap¬ phire or ruby in which the star is reduced to a luminous zone.