battery: Zinc–manganese dioxide systems: …first patented in 1899, the zinc chloride battery is really a modern adaptation of the zinc-carbon battery. Its commercial success is attributable in part to the development of plastic seals that have made it possible largely to dispense with the use of ammonium chloride. The manganese dioxide of the cathode…

chromium processing: Pigments: Zinc yellow, a basic zinc chromate, is used as a corrosion-inhibiting primer on aircraft parts fabricated from aluminum or magnesium. Molybdate orange is a combination of lead chromate with molybdenum salts. Chrome green is a mixture of lead chromate with iron blue. This pigment has excellent covering and hiding…

nutritional disease: Zinc: Zinc deficiency in humans was first reported in the 1960s in Egypt and Iran, where children and adolescent boys with stunted growth and undeveloped genitalia responded to treatment with zinc. Deficiency of the mineral was attributed to the regional diet, which was low in meat…

zinc group element, any of the four chemical elements that constitute Group 12 (IIb) of the periodic table—namely, zinc (Zn), cadmium (Cd), mercury (Hg), and copernicium (Cn). They have properties in common, but they also differ in significant respects. Zinc, cadmium, and mercury are metals with a

cadmium: Properties, occurrence, and uses: …cadmium in a specimen of zinc oxide. Both zinc compounds were being examined because their purity as pharmaceuticals was suspect.

bioceramics: Dental ceramics: …systems are zinc phosphate and zinc oxide-eugenol (ZOE). Zinc phosphate is typically used for permanent cementation, whereas ZOE is used for temporary cementation. Both can serve as insulating bases to protect tissues from heat or cold passing through highly conductive amalgam restorations. Polycarboxylate cements consist of ceramic powders (zinc oxide…

bioceramics: Dental ceramics: …ceramic dental cement systems are zinc phosphate and zinc oxide-eugenol (ZOE). Zinc phosphate is typically used for permanent cementation, whereas ZOE is used for temporary cementation. Both can serve as insulating bases to protect tissues from heat or cold passing through highly conductive amalgam restorations. Polycarboxylate cements consist of ceramic…

zinc processing, the extraction of zinc from its ores and the preparation of zinc metal or chemical compounds for use in various products. Zinc (Zn) is a metallic element of hexagonal close-packed (hcp) crystal structure and a density of 7.13 grams per cubic centimetre. It has only moderate

spectroscopy: Infrared instrumentation: as calcium fluoride (CaF2), zinc selenide (ZnSe), cesium iodide (CsI), or potassium bromide (KBr), coated with silicon or germanium are employed. Below 200 cm−1 Mylar films of varying thickness are used to cover narrow portions of the region. Thermal detection of infrared radiation is based on the conversion of

lithopone: …solutions of barium sulfide and zinc sulfate. The precipitate is recovered by filtration, then calcined (roasted) at temperatures above 600° C (1,112° F). Although lithopone has been replaced in many applications by titanium dioxide, introduced after World War I, it is still widely used in a number of products, such…

electricity: Electroluminescence: …across a thin layer of zinc sulfide powder causes just such an electroluminescent effect. Electroluminescent panels are of more interest as signal indicators and display devices than as a source of general illumination.

chromium processing: Pigments: Zinc yellow, a basic zinc chromate, is used as a corrosion-inhibiting primer on aircraft parts fabricated from aluminum or magnesium. Molybdate orange is a combination of lead chromate with molybdenum salts. Chrome green is a mixture of lead chromate with iron blue. This pigment has…

battery: Zinc–manganese dioxide systems: There are three variations: the zinc-carbon battery, the zinc chloride battery, and the alkaline battery. All provide an initial voltage of 1.55 to 1.7 volts, which declines with use to an end point of about 0.8 volt.

zinc processing: The zinc-lead blast furnace: Sintered zinc and lead concentrates, mixed with metallurgical coke, are charged into the top of a shaft furnace, into which preheated air is blown through nozzles, or tuyeres, at the base (see figure). This procedure is similar to that followed in an…

battery: Zinc–manganese dioxide systems: These batteries are the most commonly used worldwide in flashlights, toys, radios, compact disc players, and digital cameras. There are three variations: the zinc-carbon battery, the zinc chloride battery, and the alkaline battery. All provide an initial voltage of 1.55 to 1.7…

battery: Zinc–mercuric oxide battery: This is an alkaline-electrolyte battery system. In earlier times it was used in the form of button-sized cells for hearing aids and watches. Its energy density (watt-hours per cubic centimetre) is approximately four times greater than that of the alkaline zinc–manganese dioxide…

battery: Zinc–silver oxide battery: Another alkaline system, this battery features a silver oxide cathode and a powdered zinc anode. Because it will tolerate relatively heavy current load pulses and has a high, nearly constant 1.5-volt operating voltage, the zinc–silver oxide battery is commonly used in the…

pre-Columbian civilizations: Settlement in the Cuzco Valley: …bore him a son named Sinchi Roca (Zinchi Roq’a). Eventually, the Inca arrived at the fertile area around Cuzco, where they attacked the local residents and drove them from the land. They then established themselves in Cuzco and gradually began to meddle in the affairs of their neighbors, forcing them…

Zincirli Höyük, archaeological site in the foothills of the Anti-Taurus Mountains, south-central Turkey. Samal was one of the Late Hittite city-states that perpetuated the more or less Semitized southern Anatolian culture for centuries after the downfall of the Hittite empire (c. 1190 bc). The

Zincirli Höyük, archaeological site in the foothills of the Anti-Taurus Mountains, south-central Turkey. Samal was one of the Late Hittite city-states that perpetuated the more or less Semitized southern Anatolian culture for centuries after the downfall of the Hittite empire (c. 1190 bc). The

zincite, mineral consisting of zinc oxide (ZnO), usually found in platy or granular masses. Its blood-red colour and orange-yellow streak are characteristic, as is also its common association with black franklinite and white calcite. Notable specimens have been found at Franklin and Sterling Hill,

Paul Zindel was an American playwright and novelist whose largely autobiographical work features poignant, alienated characters who deal with life’s difficulties in pragmatic and straightforward ways. Zindel developed an interest in science at a young age, and from his early years he wrote plays

Zinder, city, south-central Niger. The country’s second largest city, it was the capital of a Muslim dynasty established in the 18th century, which freed itself from the sovereignty of Bornu in the mid-19th century. The city was occupied by French troops in 1899, and it served as the capital of the

Norton David Zinder was an American biologist who discovered the occurrence of genetic transduction—the carrying of hereditary material from one strain of microorganisms to another by a filterable agent such as a bacteriophage, or bacterial virus—in species of the Salmonella bacteria. After

zine, a small-circulation print or online publication that is produced through noncommercial means and is meant to appeal to a niche audience. The term zine derives from fanzine, an amalgamation of the words fan and magazine. Zines are typically defined as self-published, free or low-cost, and

Niccolò Antonio Zingarelli was one of the principal Italian composers of operas and religious music of his time. Zingarelli studied at the conservatory at Loreto and earned his living in his youth as a violinist. His first opera, Montezuma, was successfully produced at the San Carlo Theatre in

I.J. Singer was a Polish-born writer of realistic historical novels in Yiddish. Singer’s father was a rabbi who was a fervent Ḥasid, and his mother was from a distinguished Mitnagged family. Singer began writing tales of Ḥasidic life in 1915 and then worked as a newspaper correspondent in Warsaw

I.J. Singer was a Polish-born writer of realistic historical novels in Yiddish. Singer’s father was a rabbi who was a fervent Ḥasid, and his mother was from a distinguished Mitnagged family. Singer began writing tales of Ḥasidic life in 1915 and then worked as a newspaper correspondent in Warsaw

Isaac Bashevis Singer was a Polish-born American writer of novels, short stories, and essays in Yiddish. He was the recipient in 1978 of the Nobel Prize for Literature. His fiction, depicting Jewish life in Poland and the United States, is remarkable for its rich blending of irony, wit, and wisdom,

ginger, (Zingiber officinale), herbaceous perennial plant of the family Zingiberaceae, probably native to southeastern Asia, or its pungent aromatic rhizome (underground stem) used as a spice, flavoring, food, and medicine. Ginger’s generic name, Zingiber, is derived from the Greek zingiberis,

Zingiberaceae, the ginger family of flowering plants, the largest family of the order Zingiberales, containing about 56 genera and about 1,300 species. These aromatic herbs grow in moist areas of the tropics and subtropics, including some regions that are seasonably dry. Members of the family are

Zingiberales, the ginger and banana order of flowering plants, consisting of 8 families, 92 genera, and more than 2,100 species. Members of Zingiberales are widely distributed in the tropics, particularly as shade plants in tropical regions. Several genera of the order are of major economic

Olduvai Gorge: …Zinjanthropus boisei (later reclassified as Paranthropus boisei). Officially labeled OH 5 (Olduvai Hominid 5) but dubbed “Nutcracker Man” because of its huge molars (indicative of a vegetarian diet), the skull was dated to about 1.75 million years ago. The discovery indicated that hominins evolved in Africa. Specimens of Homo habilis,…

jewelry: Islamic: …designs, however, have persisted in Zīnjanāb and among the Kurdish mountaineers of northwest Iran. Silver decorated with twisted wire arranged in scrolls is a feature of the former. The Kurdish goldsmiths also work in silver, which they decorate with chased or repoussé designs, sometimes reminiscent of motifs found on Sāsānian…

Mary Douglas Leakey: …lineage) that her husband named Zinjanthropus, or “eastern man,” though it is now regarded as Paranthropus, a type of australopith, or “southern ape.”

Zincirli Höyük, archaeological site in the foothills of the Anti-Taurus Mountains, south-central Turkey. Samal was one of the Late Hittite city-states that perpetuated the more or less Semitized southern Anatolian culture for centuries after the downfall of the Hittite empire (c. 1190 bc). The

cornett, wind instrument sounded by lip vibration against a cup mouthpiece; it was one of the leading wind instruments of the period 1500–1670. It is a leather-covered conical wooden pipe about 24 inches (60 centimetres) long, octagonal in cross section, with finger holes and a small horn or ivory

Donald Trump: Cabinet appointments: …Secretary Steven Mnuchin, Interior Secretary Ryan Zinke, and Veterans Affairs Secretary David Shulkin were also criticized for inappropriate use of chartered or military aircraft, leading to Shulkin’s firing in March 2018. Zinke, who faced several federal investigations of his conduct as interior secretary, including one that was referred to the…

Rolf M. Zinkernagel is a Swiss immunologist and pathologist who, along with Peter C. Doherty of Australia, received the Nobel Prize for Physiology or Medicine in 1996 for their discovery of how the immune system distinguishes virus-infected cells from normal cells. Zinkernagel received an M.D. from

Svetlana Alexievich: …Forgotten War; also translated as Zinky Boys: Soviet Voices from the Afghanistan War) exposed the hidden, undocumented futility of the Soviet intervention (1979–89) in the Afghan War (1978–92) and served to demystify the role of nationalism and Soviet autonomy. The title referred to the zinc coffins used by the military…

Svetlana Alexievich: …Forgotten War; also translated as Zinky Boys: Soviet Voices from the Afghanistan War) exposed the hidden, undocumented futility of the Soviet intervention (1979–89) in the Afghan War (1978–92) and served to demystify the role of nationalism and Soviet autonomy. The title referred to the zinc coffins used by the military…

human eye: General description: …transparent fibres—the suspensory ligament or zonule of Zinn—from the ciliary body; the aqueous humour, a clear fluid filling the spaces between the cornea and the lens and iris; and the vitreous body, a clear jelly filling the much larger cavity enclosed by the sclera, the ciliary body, and the lens.…

Daniel Berrigan: …1968 he traveled with historian Howard Zinn to North Vietnam to negotiate the release of three captured U.S. pilots. Later that year Daniel, Philip, and seven others broke into the office of the draft board of Catonsville, Maryland, and burned the records. Daniel dramatized the federal trial that resulted from…

Walter Henry Zinn was a Canadian-born nuclear physicist, who contributed to the U.S. atomic bomb project during World War II and to the development of the nuclear reactor. In 1934 Zinn received a Ph.D. from Columbia University in New York. He was recruited by Enrico Fermi for the Manhattan Project,

Fred Zinnemann was an Austrian-born American motion-picture director whose films are distinguished by realism of atmosphere and characterization and often grounded in crises of conscience. He was nominated seven times for Academy Awards as best director, and two of his films were honoured as best

zinnia, (genus Zinnia), any of about 22 species of herbs and shrubs constituting the genus Zinnia of the family Asteraceae (Compositae) and native primarily to North America. They are perennial where they are native—from the southern United States to Chile, being especially abundant in Mexico—but

zinnia, (genus Zinnia), any of about 22 species of herbs and shrubs constituting the genus Zinnia of the family Asteraceae (Compositae) and native primarily to North America. They are perennial where they are native—from the southern United States to Chile, being especially abundant in Mexico—but

zinnia: …well-known species of zinnia is Z. angustifolia, which grows 0.5 metre tall and has small yellow or orange blossoms.

zinnia: …the species Zinnia violacea (Z. elegans). The solitary flower heads are borne at the ends of branches, growing at the junction of a bract (leaflike structure) and the receptacle. The flowers occur in a wide range of colours except blue. Different types of garden zinnias range from dwarf compact…

subatomic particle: Testing supersymmetry: …known as the photino, wino, zino, gluino, and gravitino, respectively. If they indeed exist, all these new supersymmetric particles must be heavy to have escaped detection so far.

Sir Eyre Crowe: …the decision to publish the Zinoviev Letter (addressed to the Communist Party in Britain and advising on revolutionary procedures), which contributed to the defeat of the Labour Party in the parliamentary election shortly thereafter.

Grigory Yevseyevich Zinovyev was a revolutionary who worked closely with Lenin in the Bolshevik Party before the Russian Revolution of 1917 and became a central figure in the Communist Party leadership in the Soviet Union in the 1920s. He later was a victim of Joseph Stalin’s Great Purge. (Read

Sir Eyre Crowe: …the decision to publish the Zinoviev Letter (addressed to the Communist Party in Britain and advising on revolutionary procedures), which contributed to the defeat of the Labour Party in the parliamentary election shortly thereafter.

Russian literature: Thaws and freezes: …the End of the Line), Zinovyev’s Ziyayushchiye vysoty (1976; The Yawning Heights), and Voynovich’s satire Zhizn i neobychaynyye priklyucheniya soldata Ivana Chonkina (1975; The Life and Extraordinary Adventures of Private Ivan Chonkin).

Grigory Yevseyevich Zinovyev was a revolutionary who worked closely with Lenin in the Bolshevik Party before the Russian Revolution of 1917 and became a central figure in the Communist Party leadership in the Soviet Union in the 1920s. He later was a victim of Joseph Stalin’s Great Purge. (Read

Kirovohrad, city, south-central Ukraine. It lies along the upper Inhul River where the latter is crossed by the Kremenchuk-Odesa railway. Founded as a fortress in 1754, it was made a city, Yelysavethrad, in 1765 and developed as the centre of a rich agricultural area. It was renamed Zinovyevsk in

Émile Derlin Zinsou was a nationalist politician and president (1968–69) of Dahomey (now Benin), noted for the success of his attempts to solve his country’s overwhelming economic and financial problems. Zinsou, though trained as a physician, became active in journalism and politics after World War

Hans Zinsser was an American bacteriologist and epidemiologist. He taught principally at the Columbia (1913–23) and Harvard (1923–40) medical schools. He isolated the bacterium that causes the European type of typhus, developed the first anti-typhus vaccine, and, with colleagues, found a way to

Nikolaus Ludwig, count von Zinzendorf was a religious and social reformer of the German Pietist movement who, as leader of the Moravian church (Unitas Fratrum), sought to create an ecumenical Protestant movement. Zinzendorf was the son of a Saxon minister of state of Austrian noble descent. His

Custer: …of a mountain; American sculptor Korczak Ziolkowski (1908–82) began carving the monumental portrait of the Sioux chief Crazy Horse in 1948 (the face was completed in 1998). Other museums display frontier and wood-carving memorabilia; a log cabin built in 1875 is preserved as a pioneer museum. Inc. 1883. Pop. (2010)…

Zion, in the Old Testament, the easternmost of the two hills of ancient Jerusalem. It was the site of the Jebusite city captured by David, king of Israel and Judah, in the 10th century bce (2 Samuel 5:6–9) and established by him as his royal capital. Some scholars believe that the name also

Zion, city, Lake county, northeastern Illinois, U.S. It lies along Lake Michigan, near the Wisconsin border. The area was originally inhabited by the Neshnabe (Potawatomi) people. Zion was founded in 1900 by John Alexander Dowie, an evangelist originally from Scotland, as the headquarters of his

Zion National Park: The park’s principal feature is Zion Canyon, which received its name from the Mormons who discovered it (1858) and settled there in the early 1860s. A portion of the area was first set aside as Mukuntuweap National Monument in 1909. The monument was enlarged and renamed Zion National Monument in…

Jerusalem: Architecture: …the east, the Dung and Zion gates to the south, and the Jaffa Gate to the west. An eighth gate, the Golden Gate, to the east, remains sealed, however, for it is through this portal that Jewish legend states that the messiah will enter the city. The Jaffa and Damascus…

Zion National Park, dramatic landscape of colourful deep canyons, high cliffs, mesas, and forested plateaus in southwestern Utah, U.S. The park lies on the northwestern edge of the Colorado Plateau about 30 miles (50 km) northeast of the city of St. George. Cedar Breaks National Monument is nearby

Hadassah, American religious organization dedicated to preserving and promoting Jewish social and religious values in the United States and to strengthening ties between U.S. and Israeli Jewish communities. The organization is one of the largest volunteer women’s organizations in the United States;

biblical literature: Psalms: …type are the Songs of Zion, which glorify Yahweh’s presence in the city of Jerusalem, and the Enthronement Songs, which—though their number, setting, and interpretation have been the subject of much debate—acclaim Yahweh’s kingship over the whole world.

Judah ha-Levi: Life: …celebrating the Holy Land is “Zionide” (“Ode to Zion”), his most famous work and the most widely translated Hebrew poem of the Middle Ages. He also carried on a heated controversy in verse with the opponents of his Zionist ideas.

Zionism, Jewish nationalist movement with the goal of the creation and support of a Jewish national state in Palestine, the ancient homeland of the Jews (Hebrew: Eretz Yisraʾel, “the Land of Israel”). Though Zionism originated in eastern and central Europe in the latter part of the 19th century, it

Zionist church, any of several prophet-healing groups in southern Africa; they correspond to the independent churches known as Aladura (q.v.) in Nigeria, “spiritual” in Ghana, and “prophet-healing churches” in most other parts of Africa. The use of the term Zion derives from the Christian Catholic

Theodor Herzl: The First Zionist Congress: Herzl went to London in an effort to organize the Jews there in support of his program. Not all the Jewish leaders in England were happy to see him, because his political approach was not in tune with their ideas, but at public…

Stephen Samuel Wise: …year he helped found the Zionist Organization of America (ZOA), of which he served as president in 1936–38. He also helped found and led the permanent American Jewish Congress and the World Jewish Congress (1936). As a prominent member of the Democratic Party and an acquaintance of President Woodrow Wilson,…

Israel Labour Party: Decline in influence: The new alliance, named the Zionist Union, looked poised to perform well in the polls, with analysts predicting an extremely close race between it and the other front-runner, Likud. The results, however, showed that the Zionist Union won only 24 seats, finishing second to Likud, which garnered 30 seats. Still,…

ZIP Code, system of zone coding (postal coding) introduced by the U.S. Post Office Department (now the U.S. Postal Service) in 1963 to facilitate the sorting and delivery of mail. After an extensive publicity campaign, the department finally succeeded in eliciting from the public a widespread

Song of the South: … introduced the famous song “Zip-a-Dee-Doo-Dah,” which won an Academy Award. Baskett was also awarded an honorary Academy Award “for his able and heart-warming characterization of Uncle Remus, friend and story teller to the children of the world, in Walt Disney’s Song of the South.” Although the film was a…

Zip2, former American technology company (1995–99) that was the first enterprise founded by Elon Musk. It provided a searchable business directory that could be described as an Internet version of the yellow pages telephone directory with maps included. Musk conceived the idea of making it possible

Max Apple: In Zip: A Novel of the Left and the Right (1978), a Jewish man from Detroit manages the career of a middleweight Puerto Rican boxer named Jesus Goldstein, and brief appearances are made by J. Edgar Hoover, Fidel Castro, and Jane Fonda.

Diane di Prima: …number of plays (collected in Zipcode [1992]); and several autobiographical works, including Memoirs of a Beatnik (1969) and Recollections of My Life as a Woman: The New York Years (2001), a memoir of her abusive childhood in Brooklyn and her experiences as a woman in the male-dominated Beat movement.

Zipf’s law, in probability, assertion that the frequencies f of certain events are inversely proportional to their rank r. The law was originally proposed by American linguist George Kingsley Zipf (1902–50) for the frequency of usage of different words in the English language; this frequency is

information theory: Linguistics: …proposed by the American linguist George Zipf in Selected Studies of the Principle of Relative Frequency in Language (1932). Zipf’s Law states that the relative frequency of a word is inversely proportional to its rank. That is, the second most frequent word is used only half as often as the…

information theory: Linguistics: …proposed by the American linguist George Zipf in Selected Studies of the Principle of Relative Frequency in Language (1932). Zipf’s Law states that the relative frequency of a word is inversely proportional to its rank. That is, the second most frequent word is used only half as often as the…

beaked whale, (family Ziphiidae), any of more than 20 species of medium-sized toothed whales that have an extended snout, including the bottlenose whales. Little is known about this family of cetaceans; one species was first described in 1995, two others are known only from skeletal remains, and

beaked whale: Paleontology and classification: Genus Ziphius (Cuvier’s beaked, or goose-beaked, whale) 1 species of temperate and tropical waters. Assorted

zipper, device for binding the edges of an opening such as on a garment or a bag. A zipper consists of two strips of material with metal or plastic teeth along the edges and with a sliding piece that draws the teeth into interlocking position when moved in one direction and separates them again

Moses: Moses in Midian: …with Jethro and eventually married Zipporah, one of the daughters. In assuming the responsibility for Jethro’s flocks, Moses roamed the wilderness looking for pasture.

Cipszer: …present-day north-central Slovakia known as Špis (Hungarian: Szepes; German: Zips). The Cipszers originated in the lower Rhine region, Flanders, Saxony, and Silesia. King Géza II (ruled 1141–62) of Hungary moved them to the Szepes area in the middle of the 12th century. Their local self-government was first recognized in writing…

Cipszer, a Germanic people formerly living in a region of present-day north-central Slovakia known as Špis (Hungarian: Szepes; German: Zips). The Cipszers originated in the lower Rhine region, Flanders, Saxony, and Silesia. King Géza II (ruled 1141–62) of Hungary moved them to the Szepes area in

Abbas Kiarostami: …final film in the trilogy, Zīr-e darakhtān-e eyton (1994; Through the Olive Trees), is about an actor’s difficult romantic pursuit of a fellow actress during the filming of And Life Goes On…. During this period Kiarostami also made Namay-e nazdīk (1990; Close-Up), which tells the true story of a film…

ziran, in Chinese philosophy, and particularly among the 4th- and 3rd-century bce philosophers of early Daoism (daojia), the natural state of the constantly unfolding universe and of all things within it when both are allowed to develop in accord with the Cosmic Way (Dao). Chinese cosmologies

Veszprém: At Zirc, high in the Cuha valley, is a 12th-century abbey, and in Nagyvázsony are the ruins of the legendary Kinizsi Castle. Balatonfelvideki National Park is located on the Tihany Peninsula. Area 1,781 square miles (4,613 square km). Pop. (2011) 353,068; (2017 est.) 342,501.

nuclear reactor: Advanced gas-cooled reactor: …AGR, fuel pins clad in Zircaloy (a trademark for alloys of zirconium having low percentages of chromium, nickel, iron, and tin) and loaded with approximately 2 percent enriched uranium dioxide are placed into zirconium-alloy channels that pierce a graphite moderator block. This design utilizes fast neutron energies and is therefore…

nuclear reactor: Advanced gas-cooled reactor: …AGR, fuel pins clad in Zircaloy (a trademark for alloys of zirconium having low percentages of chromium, nickel, iron, and tin) and loaded with approximately 2 percent enriched uranium dioxide are placed into zirconium-alloy channels that pierce a graphite moderator block. This design utilizes fast neutron energies and is therefore…

zircon, silicate mineral, zirconium silicate, ZrSiO4, the principal source of zirconium. Zircon is widespread as an accessory mineral in felsic igneous rocks. It also occurs in metamorphic rocks and, fairly often, in detrital deposits. It occurs in beach sands in many parts of the world,

zirconia, zirconium dioxide, an industrially important compound of zirconium and oxygen usually derived from the mineral zircon (see

zirconium (Zr), chemical element, metal of Group 4 (IVb) of the periodic table, used as a structural material for nuclear reactors. atomic number 40 atomic weight 91.22 melting point 1,852 °C (3,366 °F) boiling point 3,578 °C (6,472 °F) specific gravity 6.49 at 20 °C (68 °F) oxidation state +4

zirconia, zirconium dioxide, an industrially important compound of zirconium and oxygen usually derived from the mineral zircon (see

dating: Uranium–lead method: Today, however, baddeleyite (ZrO2) and zirconolite (CaZrTi2O7) have been found to be widespread in the silica-poor mafic igneous rocks. In addition, perovskite (CaTiO3), a common constituent of some ultramafic igneous rocks, has been shown to be amenable to precise uranium–lead dating. As a result of these developments, virtually all igneous…

piddock: The great piddock (Zirfaea crispata), which attains lengths of up to eight centimetres (about three inches), occurs on both sides of the Atlantic Ocean. Found from the intertidal zone to depths of 75 metres (250 feet), Z. crispata bores into limestone and wood.

North Africa: The Fāṭimids and Zīrids: …Fāṭimids were loyally supported by Zīrī ibn Manād, chief of the Takalata branch of the Ṣanhājah confederation, to which the Kutāma Berbers belonged. The parts of the Maghrib that the Fāṭimids controlled therefore consisted only of the former province of Ifrīqiyyah, ruled before them by the Aghlabids.

Zīrid dynasty, Muslim dynasty of Ṣanhājah Berbers whose various branches ruled in Ifrīqiyyah (Tunisia and eastern Algeria) and Granada (972–1152). Rising to prominence in the mountains of Kabylie, Algeria, where they established their first capital, Ashīr, the Zīrids became allies of the Fāṭimids