galena, a gray lead sulfide (PbS), the chief ore mineral of lead. One of the most widely distributed sulfide minerals, it occurs in many different types of deposits, often in metalliferous veins, as at Broken Hill, Australia; Coeur d’Alene, Idaho, U.S.; Clausthal Zellerfeld, Ger.; and Cornwall,

flint glass, heavy and durable glass characterized by its brilliance, clarity, and highly refractive quality. Developed by George Ravenscroft (q.v.) in 1675, it ushered in a new style in glassmaking and eventually made England the leading glass producer of the world. Ravenscroft’s experimentation

weather modification: General considerations: …example, when silver iodide and lead iodide are burned, they create a smoke of tiny particles. These particles produce ice crystals in supercooled clouds below temperatures of about −5° C as the supercooled cloud droplets evaporate. The water vapour is then free to deposit onto the silver iodide or lead…

surface coating: Catalysts and driers: …determined that the presence of lead oxide pigments such as red lead caused oil-based coatings to cure more rapidly and thoroughly than in their absence. The reactive species that causes this reaction is the Pb2+ ion, which forms organic salts with the fatty acid components of the drying oil. The…

capacitor dielectric and piezoelectric ceramics: Piezoelectric ceramics: …titanate, Pb[Zr,Ti]O2) and PMN (lead magnesium niobate, Pb[Mg13Nb23]O3). These materials are processed in a similar manner to capacitor dielectrics except that they are subjected to poling, a technique of cooling the fired ceramic piece through the Curie point under the influence of an applied electric field in order to…

glass: Optical and high-temperature glass: …of superior tableware; by using lead monoxide (PbO) as a flux, it is possible to obtain a glass with a high refractive index and, consequently, the desired sparkle and brilliance.

pencil, slender rod of a solid marking substance, such as graphite, enclosed in a cylinder of wood, metal, or plastic; used as an implement for writing, drawing, or marking. In 1565 the German-Swiss naturalist Conrad Gesner first described a writing instrument in which graphite, then thought to be

lead poisoning, deleterious effect of a gradual accumulation of lead in body tissues, as a result of repeated exposure to lead-containing substances. In humans the main sources of lead are usually lead-based paint and drinking water carried through lead pipes; lead-based paints are especially

lead processing, preparation of the ore for use in various products. Lead (Pb) is one of the oldest metals known, being one of seven metals used in the ancient world (the others are gold, silver, copper, iron, tin, and mercury). Its low melting point of 327 °C (621 °F), coupled with its easy

human sensory reception: Salt: …some of the salts of lead (especially lead acetate) and beryllium are sweet. Both parts of the molecule (e.g., lead and acetate) contribute to taste quality and to stimulating efficiency. The following is a series for degree of saltiness, in decreasing order: ammonium (most salty), potassium, calcium, sodium,

lead processing: Silicates: Lead silicates are considered to be the most versatile of lead chemical compounds in the ceramics industry. Three types are available commercially: lead monosilicate (PbO·0.67SiO2), lead bisilicate (PbO·0.03Α12O3·1.95SiO2), and tribasic lead silicate (PbO·0.33SiO2). The silicates are used extensively in finely divided form for glazes…

anglesite, naturally occurring lead sulfate (PbSO4). A common secondary mineral that is a minor ore of lead, it is usually formed by the oxidation of galena and often forms a concentrically banded mass surrounding a core of unaltered galena. The formation of cerussite (lead carbonate) often

electricity: Piezoelectricity: …and 3 × 10−10 for lead zirconate titanate.

glass: Optical and high-temperature glass: …of superior tableware; by using lead monoxide (PbO) as a flux, it is possible to obtain a glass with a high refractive index and, consequently, the desired sparkle and brilliance.

lead processing: Oxides: Lead dioxide (PbO2) is an oxidizing agent used in the manufacture of dyes, matches, and rubber substitutes. Orange mineral (Pb3O4), having the same chemical composition as red lead but differing in colour and tone, is exploited in the manufacture of printing inks and pigments. Black…

Jane Leade was an English mystic and proponent of Universalist Christianity. Leade’s religious views were based on the thought of the German philosopher and mystic Jakob Böhme (1575–1624) and on her own visions and dreams, particularly those of the Virgin Sophia, an embodiment of wisdom. In 1681,

dating: Model ages: For example, the ratio of lead of mass 206 relative to that of mass 204 has changed from an initial value of about 10 present when Earth was formed to an average value of about 19 in rocks at the terrestrial surface today. This is true because uranium is continuously…

geologic history of Earth: The pregeologic period: …evolution of the isotopes of lead-207 and lead-206 is studied from several lead deposits of different age on Earth, including oceanic sediments that represent a homogenized sample of Earth’s lead, the growth curve of terrestrial lead can be calculated, and, when this is extrapolated back in time, it is found…

lead-210 dating, method of age determination that makes use of the ratio of the radioactive lead isotope lead-210 to the stable isotope lead-206. The method has been applied to the ores of uranium. In the series of unstable products from the radioactive decay of uranium-238, lead-210 results from

Gaston Planté: …resulted in construction of a battery for the storage of electrical energy; his first model contained two sheets of lead, separated by rubber strips, rolled into a spiral, and immersed in a solution containing about 10 percent sulfuric acid. A year later he presented a battery to the Academy of…

amorphous solid: Properties of oxide glasses: …a partial replacement for soda, lead-alkali-silicate glasses result that have lower softening points than lime glasses. The refractive indices, dispersive powers, and electrical resistance of these glasses are generally much greater than those of soda-lime-silica glasses.

branch and twig borer: The lead-cable borer, or short-circuit beetle (Scobicia declivis), bores into the lead covering of older telephone cables. Moisture entering through the hole can cause short circuits. This beetle lives in oak, maple, or other trees and does not feed on the cable sheathing.

chamber process, method of producing sulfuric acid by oxidizing sulfur dioxide with moist air, using gaseous nitrogen oxides as catalysts, the reaction taking place primarily in a series of large, boxlike chambers of sheet lead. The lead-chamber process has been largely supplanted in modern

breeder reactor: Fast breeder reactors: with helium, and sodium-cooled and lead-cooled fast reactors. Additionally, a supercritical water fast reactor has been proposed that would operate at a supercritical pressure to utilize fluid water that is neither steam nor liquid.

petroleum refining: Octane rating: Since the advent of unleaded fuels in the mid-1970s, however, motor octane measurements have frequently been found to limit actual engine performance. As a result a new measurement, road octane number, which is a simple average of the research and motor values, is most frequently used to define fuel…

pottery: Decorative glazing: …principal kinds of glazes: feldspathic, lead, tin, and salt. (Modern technology has produced new glazes that fall into none of these categories while remaining a type of glass.) Feldspathic, lead, and salt glazes are transparent; tin glaze is an opaque white. Hard porcelain takes a feldspathic glaze, soft porcelain usually…

automation: Robot programming: One method is called lead-through programming. This requires that the manipulator be driven through the various motions needed to perform a given task, recording the motions into the robot’s computer memory. This can be done either by physically moving the manipulator through the motion sequence or by using a…

media convergence: Social media: …online content, while British author Charles Leadbeater discussed the “pro-am revolution” and “mass collaboration,” where the tools of content creation become cheaper and simpler to use, distinctions between amateurs and experts become blurred, and media content production becomes increasingly shared, social, and collaborative in nature. The Organisation for Economic Co-operation…

Gordon Parks: Literature and film: …Cops (1974) and the drama Leadbelly (1976) as well as several television films.

Lead Belly was an American folk-blues singer, songwriter, and guitarist whose ability to perform a vast repertoire of songs in a variety of styles, in conjunction with his notoriously violent life, made him a legend. Born Huddie William Ledbetter in Louisiana, Lead Belly was musical from childhood.

Jane Leade was an English mystic and proponent of Universalist Christianity. Leade’s religious views were based on the thought of the German philosopher and mystic Jakob Böhme (1575–1624) and on her own visions and dreams, particularly those of the Virgin Sophia, an embodiment of wisdom. In 1681,

Jane Leade was an English mystic and proponent of Universalist Christianity. Leade’s religious views were based on the thought of the German philosopher and mystic Jakob Böhme (1575–1624) and on her own visions and dreams, particularly those of the Virgin Sophia, an embodiment of wisdom. In 1681,

petroleum refining: Octane rating: The advent of leaded, or ethyl, gasoline led to the manufacture of high-octane fuels and became universally employed throughout the world after World War II. However, beginning in 1975, environmental legislation began to restrict the use of lead additives in automotive gasoline. It is now banned in the…

Richard Rogers: …Hyde Park (2011), London; the Leadenhall Building (2014; called the “Cheese Grater”), London; International Towers Sydney (2016); and 3 World Trade Center (2018), New York. Rogers retired from his firm in 2020.

supreme leader of Iran, head of state in Iran, overseeing virtually all functions of government either directly or indirectly. The post was instituted as rahbar (“leader”) in 1979 with the creation of Iran’s Islamic Republic, which blends democratic elements with theocratic oversight from Islamic

lightning: Next, a stepped leader (initial lightning stroke) forms and propagates downward, following channels created by the preliminary breakdown process. The leader is highly branched in the direction of its propagation. Most leader channels are negatively charged. When the stepped leader nears the ground, an upward, connecting discharge of…

driving and coaching: …other, and called, respectively, the leaders and the wheelers. Three horses, two wheelers and a single leader, are known as a unicorn team. In Russia and Hungary three horses are driven abreast, the centre horse trotting and the outside horses galloping; such a team is known as a troika.

the Shangri-Las: “Leader of the Pack,” which topped the charts in 1964, is a tale of rebellion punctuated by the crack of a motorcycle engine. About that time, Betty Weiss left the band, but the Shangri-Las continued as a trio, touring throughout 1965–66 and scoring a top…

The Red Pony: …Mountains,” “The Promise,” and “The Leader of the People,” in which Jody develops empathy and also learns from his grandfather about “westering,” the migration of people to new places and the urge for new experiences.

operon: …the mRNA is called the leader sequence; it includes the attenuator region, which can fold back on itself, forming a stem-and-loop structure that blocks the RNA polymerase from advancing along the DNA.

George Henry Lewes: … founded a radical weekly called The Leader, for which he wrote the literary and theatrical features. His Comte’s Philosophy of the Sciences (1853) originally appeared as a series of articles in The Leader.

Germany is a federal multiparty republic with two legislative houses. Its government is headed by the chancellor (prime minister), who is elected by a majority vote of the Bundestag (Federal Assembly) upon nomination by the president (head of state). The table provides a chronological list of the

Until the 17th century, political power in Ireland was shared among small earldoms. Afterward, Ireland effectively became an English colony, and, when the Act of Union came into effect in 1801, Ireland was joined with England and Scotland under the name of the United Kingdom of Great Britain and

Russia is a federal multiparty republic with a bicameral legislative body; its head of state is the president, and the head of government is the prime minister. What is now the territory of Russia has been inhabited from ancient times by various peoples, and as such the country has gone through

collective behavior: Rescue period: …creates an urgent demand for leadership. People turn first to established community leaders, and, when they are equal to the demands, such figures as police and fire officials, school principals, and mass-media personages are quickly accepted as leaders. Frequently these public figures are as bewildered and distracted as everyone else…

Sister Simone Campbell: …though informal role in the Leadership Conference of Women Religious (LCWR), a coalition representing the majority of American sisters. Campbell was also active on international issues and took part in religious delegations to Chiapas, Mexico (1996), Iraq (2002), Syria (2008), and Lebanon (2008).

Leadership Conference on Civil and Human Rights, U.S. nongovernmental organization (NGO) founded in 1950 that promotes civil rights and human rights for a variety of groups facing discrimination. The organization functioned primarily through lobbying for amenable legislation and public policy. The

Leadership Conference on Civil and Human Rights, U.S. nongovernmental organization (NGO) founded in 1950 that promotes civil rights and human rights for a variety of groups facing discrimination. The organization functioned primarily through lobbying for amenable legislation and public policy. The

LEED® standards, a certification program devised in 1994 by the U.S. Green Building Council (USGBC; founded 1993) to encourage sustainable practices design and development by means of tools and criteria for performance measurement. It is “a voluntary, consensus-based, market-driven building rating

political action committee: Among them are Leadership PACs, which are often formed by politicians who might aspire to higher office (particularly the presidency) or more influence within their political party by raising funds and disbursing them to the campaigns of other candidates; Super PACs, which were established in 2010 following the…

political action committee: Among them are Leadership PACs, which are often formed by politicians who might aspire to higher office (particularly the presidency) or more influence within their political party by raising funds and disbursing them to the campaigns of other candidates; Super PACs, which were established in 2010 following the…

stained glass: …assembly with grooved strips of leading is an indispensable feature of the art. Indeed, the leaded window may well have been preceded by windows employing wooden or other forms of assembly such as the cement tracery that has long been traditional in Islamic architecture, and the single most important technical…

economic forecasting: Selection of turning points: …which are known as “leading indicators.” Other statistical series normally move in line with overall activity (“coincident indicators”), and a third group changes direction after the economy does (“lagging indicators”). Although careful study of these groupings of statistics can be helpful, unfortunately there is no fixed relation between the…

leitmotif, a recurring musical theme appearing usually in operas but also in symphonic poems. It is used to reinforce the dramatic action, to provide psychological insight into the characters, and to recall or suggest to the listener extramusical ideas relevant to the dramatic event. In a purely

harmony: The regulation of dissonance: …and is thus called the leading note. Because the leading note is a member of the dominant chord, this chord also has a strong pull toward the tonic chord.

harmony: The regulation of dissonance: …and is thus called the leading note. Because the leading note is a member of the dominant chord, this chord also has a strong pull toward the tonic chord.

baseball: The batting order: …batting order (known as the leadoff man). In succeeding innings, the first batter up is the man in the order who follows the last batter (with a complete at bat) from the previous inning. The leadoff man is typically a player who is fast afoot, makes frequent contact with the…

the Eagles: …2016, New York, New York), Bernie Leadon (b. July 19, 1947, Minneapolis, Minnesota), and Randy Meisner (b. March 8, 1946, Scottsbluff, Nebraska—d. July 26, 2023, Los Angeles, California). Later members included Don Felder (b. September 21, 1947, Topanga, California), Joe Walsh (b. November 20, 1947, Wichita, Kansas), and Timothy B.…

drawing: Metalpoints: …of sketches in London with leadpoint drawings on tinted paper is a particularly valuable example of this technique, even if individual portions and, indeed, entire pages that had become effected were drawn over long ago. One can see little more than the traces left by the pencil because, as in…

Theresa May: Ascent to power: …to emerge with Energy Minister Andrea Leadsom as the final candidates, to be voted upon by general party members by September 9. Almost before that process could begin, Leadsom withdrew her candidacy in response to a controversy surrounding comments she had made about motherhood as a qualification for leadership (May…

Leadville, city, seat (1878) of Lake county, central Colorado, U.S., located 103 miles (166 km) west of Denver and 38 miles (61 km) south of Vail. It is situated in the upper Arkansas River valley in an area of national forests, at an elevation of some 10,200 feet (3,105 metres). It is the centre

leadwork, sculpture, ornamental objects, and architectural coverings and fittings made of lead. Although the ease with which lead is smelted from lead ores ensured its early discovery, the softness of the metal restricted its use until Roman times. The earliest known use of lead dates from about

Caryophyllales: Plumbaginaceae: Economically, Plumbaginaceae, the leadwort family, is important mainly for its many garden ornamentals. Among these are a number of species of Armeria that go by the common name thrift, especially A. maritima, also called sea pink, a plant with small red flowers that is…

Sergei Novikov: …manifolds into smaller ones, called leaves. Leaves can be either open or closed, but at the time Novikov started his work it was not known whether leaves of a closed type existed. Novikov’s demonstration of the existence of closed leaves in the case of a three-sphere led to a good…

leaf, in botany, any usually flattened green outgrowth from the stem of a vascular plant. As the primary sites of photosynthesis, leaves manufacture food for plants, which in turn ultimately nourish and sustain all land animals. Botanically, leaves are an integral part of the stem system. They are

electric car: …vehicles, such as the Nissan LEAF (2010) and the Renault ZOE (2012). Many of the world’s major car companies planned either to make mostly or only electric or hybrid cars or to stop developing new car models with internal-combustion engines by the 2030s.

pottery: Tin-glazed ware: “Leaf and strapwork” (Laub-und-Bandelwerk) was a much used type of motif, and excellent work was done by A.F. von Löwenfinck (who is known particularly for his work on porcelain) and Joseph Philipp Danhofer. Perhaps the finest 18th-century faience was made by the factory at Höchst, near Mainz, which…

angiosperm: Leaves: …leaf is composed of a leaf base, two stipules, a petiole, and a blade (lamina). The leaf base is the slightly expanded area where the leaf attaches to the stem. The paired stipules, when present, are located on each side of the leaf base and may resemble scales, spines, glands,…

chard, (Beta vulgaris), one of the four cultivated forms of the plant Beta vulgaris of the amaranth family (Amaranthaceae), grown for its edible leaves and leafstalks. Fresh chard is highly perishable and difficult to ship to distant markets. The young leaves can be eaten raw in salads, while

leaf beetle, (family Chrysomelidae), any of approximately 35,000 species of beetles that occur throughout the world but are concentrated in the tropics. They are oval-shaped and short-legged, with the antennae about half the body length, and tend to be less than 12 mm (0.5 inch) long. The family

Helminthosporium: …as asexual anamorphs and causes leaf blight, especially of grasses (e.g., bluegrass, corn, oats), in humid areas. Symptoms include grayish green, tan, or brown elliptical spots that appear on lower leaves and spread later to upper leaves. Control is possible through spraying of fungicide and use of resistant plants.

leaf blister, worldwide disease of many woody plants and ferns caused by fungi of the genus Taphrina. Peach leaf curl, caused by T. deformans, affects peaches, nectarines, and almonds and can cause agricultural losses. Red oaks are commonly afflicted with oak leaf blister, caused by T.

plant bug: The members of the family Miridae, which is one of the largest heteropteran families (about 10,000 species), are also known as leaf bugs. They are brightly coloured and feed primarily on plant sap, causing serious crop damage. Plant bugs occur throughout the world and have been found north of the…

angiosperm: Leaves: A slight bulge (a leaf buttress) is produced, which in eudicots continues to grow and elongate to form a leaf primordium. (Stipules, if present, appear as two small protuberances.) Marginal and submarginal meristems on opposite flanks of the primordium initiate leaf-blade formation. Differences in the local activity of marginal…

leaf cactus, (genus Epiphyllum), genus of about 15 species of cacti (family Cactaceae), native to tropical and subtropical America, including the West Indies. The plants are mostly epiphytic (grow on other plants) but sometimes grow from the ground. A number of species and hybrids are often grown

leaf blister, worldwide disease of many woody plants and ferns caused by fungi of the genus Taphrina. Peach leaf curl, caused by T. deformans, affects peaches, nectarines, and almonds and can cause agricultural losses. Red oaks are commonly afflicted with oak leaf blister, caused by T.

muntjac: Named the miniature muntjac (M. putaoensis), or leaf deer, it weighs only 11 kg (about 24 pounds). Although M. putaoensis was catalogued on the basis of one specimen, others have been found in the rainforests of Arunachal Pradesh in far northeastern India.

leaf fibre, hard, coarse fibre obtained from leaves of monocotyledonous plants (flowering plants that usually have parallel-veined leaves, such as grasses, lilies, orchids, and palms), used mainly for cordage. Such fibres, usually long and stiff, are also called “hard” fibres, distinguishing them

filtration: Filter types: Leaf filters are also used for pressure filtration on a batch basis. The leaves consist of a centre section of coarse metal mesh that supports the filter medium and permits the filtrate to escape. This centre section is covered on either side with the filter…

leaf fish, any of about 10 species of fishes in the family Nandidae (order Perciformes). All live in fresh water, although some species may enter brackish water. Their geographic distribution is circumtropical, including the Amazon River basin, western Africa, India, southeastern Asia, and the

angiosperm: Stems: …toward the leaf is a leaf gap, called a lacuna. The number of lacunae varies among angiosperm groups and remains a characteristic for classifying the various species.

gate: Leaf gates, planes perpendicular to the direction of fluid flow, open either by swinging about one hinged side or by sliding upward. Radial gates are segments of cylinders that lift entirely clear of the water. The rolling gate, often used on the crest of a…

leaf insect, (family Phylliidae), any of more than 50 species of flat, usually green insects that are known for their striking leaflike appearance. Leaf insects feed on plants and typically inhabit densely vegetated areas. Their natural range extends from islands in the Indian Ocean, across parts

lettuce: …into a compact head; (3) leaf, or curled, lettuce (variety crispa), with a rosette of leaves that are curled, finely cut, smooth-edged, or oak-leaved in shape; and (4) cos, or romaine, lettuce (variety longifolia), with smooth leaves that form a tall, oblong, loose head. There are two classes of head…

leaf miner, any of a number of insect larvae that live and feed within a leaf. Leaf miners include caterpillars (order Lepidoptera), sawfly larvae (order Hymenoptera), beetle and weevil grubs or larvae (order Coleoptera), and maggots (larvae) of true flies (order Diptera). Most leaf-miner burrows

langur: Leaf monkeys and other langurs are gregarious, diurnal, and basically arboreal monkeys with long tails and slender bodies. The limbs, hands, and feet are also long and slender. Depending on species, the head and body are about 40 to 80 cm (16 to 31 inches)…

protein concentrate: …common of such substances are leaf protein concentrate (LPC) and fish protein concentrate (FPC). Whey protein concentrate is also common.

leaf roller moth, any member of the worldwide insect family Tortricidae (order Lepidoptera), named for the characteristic leaf rolling habit of the larvae. The name bell moth arises from the shape of the adult’s folded, squarish forewings. These moths are characterized by their stout bodies, small

sugarcane: Diseases: Leaf scald is a vascular disease caused by the bacterium Xanthomonas albilineans, characterized by creamy or grayish streaking and later withering of the leaves. Eyespot, characterized by yellowish oval lesions on leaves and stems, is a disease caused by the fungus Helminthosporium sacchari. Epidemics of…

leaf: Senescence: …closes the wound, leaving the leaf scar, a prominent feature in many winter twigs and an aid in identification.

shutter: The leaf shutter, positioned between or just behind the lens components, consists of a number of overlapping metal blades opened and closed either by spring action or electronically. The focal-plane shutter, located directly in front of the image plane, consists of a pair of overlapping blinds…

spring: The leaf spring is used mainly for vehicle suspension and in one form consists of a stack of slightly curved narrow plates of equal width and varying length clamped together, with the shorter plates in the centre to form a semielliptical shape. The ends of the…

Gabriel García Márquez: Works: …two novels, La hojarasca (1955; The Leaf Storm) and La mala hora (1962; In Evil Hour); a novella, El coronel no tiene quien le escriba (1961; No One Writes to the Colonel); and a few short stories. Then came One Hundred Years of Solitude, in which García Márquez tells the…

angiosperm: Stems: …base of the leaf as leaf traces, connecting the vascular system of the stem with that of the leaf. The point at which the stem bundle diverges from the vascular cylinder toward the leaf is a leaf gap, called a lacuna. The number of lacunae varies among angiosperm groups and…

bat: Annotated classification: Family Mormoopidae (leaf-chinned bats) 10 small species in 2 genera of tropical Central and South America. Some walk. All lack nose leaf but have elaborate lip leaves. Tail and interfemoral membrane well developed. Colour ranges from brown through orange, red, and yellow. Feed on flying insects. Densely…

leafcutter ant, any of nearly 50 species of ants abundant in the American tropics, easily recognized by their foraging columns composed of hundreds or thousands of ants carrying small pieces of leaves. These moving trails of cut foliage often stretch over 30 meters (100 feet) across the forest

leaf-cutter bee, (family Megachilidae), any of a group of bees (order Hymenoptera), particularly genus Megachile, that differ from most other bees in that they collect pollen on their abdomens rather than on their hind legs. The solitary female, after mating, makes a nest in soil, a hollow plant

leaf-cutter bee, (family Megachilidae), any of a group of bees (order Hymenoptera), particularly genus Megachile, that differ from most other bees in that they collect pollen on their abdomens rather than on their hind legs. The solitary female, after mating, makes a nest in soil, a hollow plant

coreid bug, (family Coreidae), any of 2,000 widely distributed species of bugs (order Heteroptera), many of which are important plant pests. Coreid bugs are large, usually more than 10 mm (0.4 inch) in length. They occur in a wide range of environments and vary in size, shape, and colour. Their

leaf-nosed bat, any of almost 250 species of New World and Old World bats belonging to the families Phyllostomidae and Hipposideridae that have a flat projection on the muzzle that often resembles a leaf. The purpose of the leaf structure is not known for certain, but it may aid in echolocation.