1212 résultats pour "such"

• Geology.

  terminology. Today the geologic time scale is generally agreed upon and used by scientists around the world, dividing time into eons, eras, periods, and epochs. Everyfew years, the numerical time scale is refined based on new evidence, and geologists publish an update. Geologists use several methods to determine geologic time. These methods include physical stratigraphy, or the placement of events in the order of their occurrence,and biostratigraphy, which uses fossils to determine geologic time...

• Business.

  The most common form of ownership is a sole proprietorship —that is, a business owned by one individual. At the beginning of the 21st century, there were more than 17 million sole proprietorships in the United States. These businesses have the advantage of being easy to set up and to dissolve because few laws exist to regulatethem. Proprietors, as owners, also maintain direct control of their businesses and own all their profits. On the other hand, owners of proprietorships are personallyrespon...

• Forensic Science.

  barbiturates, cocaine, amphetamines, and heroin. When a body is discovered in a lake, stream, river, or ocean and the lungs are found to be filled with water, the medical examiner must determine if the drowningoccurred where the body was found or elsewhere. A standard microscope that can magnify objects to 1500 times their actual size is used to look for the presence orabsence of diatoms, single-celled algae that are found in all natural bodies of water. The absence of diatoms raises the possi...

• Musical I INTRODUCTION George Gershwin American pianist, songwriter, and composer George Gershwin was one of the most important figures in popular song in the 1920s and 1930s.

  C Extravaganzas Another predecessor of musical comedy, the extravaganza, evolved soon after the American Civil War (1861-1865) from traditional English pantomime. Extravaganzaswere typically based on fairy tales and Mother Goose. They introduced some of the elements—songs, dances, and comedy combined with spectacular stage sets andeffects—that American musical comedy later became known for. The first and most famous extravaganza show was The Black Crook (1866), often described as America’s fi...

• Gambling.

  C Lotteries Lotteries are another form of gambling. In a lottery, tickets are sold for a set amount and a share of the proceeds is returned to the winners, usually through a randomdraw. Most games allow players to pick their own numbers or let a computer randomly pick for them. Lotteries offer a wide variety of games, including weekly drawings,instant “scratch” tickets, daily games, and superlottos with prizes increasing until there is a winner. Large lottery prizes sometimes exceed $100 millio...

• Toys. I INTRODUCTION Toys, objects that serve as playthings for children. Although the

  clay. These readily available elements were also used to make more elaborate toys as human society advanced. Archaeologists have found primitive, handmade toys such as wooden or cloth dolls, clay marbles, and terracotta figures that date back thousands of years. In ancientEgypt, Greece, and Rome, people placed dolls or clay figures in the graves or tombs of children for them to play with in the afterlife. The yo-yo may seem like a 20th-century fad, but it actually dates back at least 2,500 years...

• Comics I INTRODUCTION Comics, series of drawings arranged to tell a story.

  is still used to refer to sensationalistic techniques that publishers use to draw more readers to their newspapers. Outcault finally won the right to continue his strip andgradually adopted the panel style and balloon narration that mark “The Yellow Kid” as the first true comic strip. Other early comics included “Little Bears” by JamesSwinnerton, which first appeared in the San Francisco Examiner in 1892, and “The Katzenjammer Kids” by Rudolph Dirks, which first appeared in The American Humo...

• Flower - biology.

  insects. The sepals unfurl as the flower opens and often resemble small green leaves at the flower’s base. In some flowers, the sepals are colorful and work with thepetals to attract pollinators. E Variations in Structure Like virtually all forms in nature, flowers display many variations in their structure. Most flowers have all four whorls—pistil, stamens, petals, and sepals. Botanists callthese complete flowers. But some flowers are incomplete, meaning they lack one or more whorls. Incomplet...

• Water Pollution.

  Cryptosporidium in the water supply of Milwaukee, Wisconsin, sickened more than 400,000 people and killed more than 100. H Thermal Pollution Water is often drawn from rivers, lakes, or the ocean for use as a coolant in factories and power plants. The water is usually returned to the source warmer than when itwas taken. Even small temperature changes in a body of water can drive away the fish and other species that were originally present, and attract other species in placeof them. Thermal pol...

• Magnetism I INTRODUCTION Magnetism, an aspect of electromagnetism, one of the fundamental forces of nature.

  the French physicist Paul Langevin produced a theory regarding the temperature dependence of the magnetic properties of paramagnets (discussed below), which wasbased on the atomic structure of matter. This theory is an early example of the description of large-scale properties in terms of the properties of electrons and atoms.Langevin's theory was subsequently expanded by the French physicist Pierre Ernst Weiss, who postulated the existence of an internal, “molecular” magnetic field inmaterials...

• Globalization.

  higher living standard for their people. The World Bank made loans to developing countries for dams and other electrical-generating plants, harbor facilities, and otherlarge projects. These projects were intended to lower costs for private businesses and to attract investors. Beginning in 1968 the World Bank focused on low-cost loansfor health, education, and other basic needs of the world’s poor. B International Monetary Fund The IMF makes loans so that countries can maintain the value of thei...

• Mental Illness.

  note that under this definition, political dissidents could be considered mentally ill for refusing to accept the dictates of their government. VI PREVALENCE Mental illness affects people of all ages, races, cultures, and socioeconomic classes. The prevalence of mental illness refers to how many people experience a mentalillness during a specified time period. A United States and Worldwide In the United States, researchers estimate that about 24 percent of people 18 or older, or about 44 mill...

• Bacteria - biology.

  A2 b Bacterial Killers Some dramatic infectious diseases result from exposure to bacteria that are not part of our normal bacterial community. Cholera, one of the world’s deadliest diseasestoday, is caused by the bacterium Vibrio cholerae . Cholera is spread in water and food contaminated with the bacteria, and by people who have the disease. After entering the body, the cholera bacteria grow in the intestines, often along the surface of the intestinal wall, where they secrete a toxin (poiso...

• Cloning - biology.

  found that such embryo cells are totipotent (able to give rise to all the different cell types in the body). Exploiting this characteristic, scientists developed three techniques to clone embryo cells: blastomere separation, blastocyst division, and somatic cell nuclear transfer. A Blastomere Separation In blastomere separation, scientists fertilize an egg cell with a sperm cell in a laboratory dish. The resulting embryo is allowed to divide until it forms a mass of aboutfour cells. Scientist...

• Bat - biology.

  tomb bat has rather small ears. The shapes of bat ears are extremely varied. The wide ears of the Australian false vampire bat meet above the head and are fused.Many bats are able to turn their ears in the direction of faint noises. Bat hearing and its use in echolocation are highly developed. Some bats have large, conspicuous eyes, while others may have small beady eyes. This variation suggests that vision plays different roles in the lives of various species.Despite the familiar expression, 'b...

• Genetic Engineering.

  Pseudomonas fluorescens bacterium. The genetically altered Pseudomonas fluorescens bacterium produces light in proportion to the amount of its activity in breaking down the naphthalene, thus providing a way to monitor the efficiency of the process ( see Bioremediation). A3 Medicine In 1982 the United States Food and Drug Administration (FDA) approved for the first time the medical use of a recombinant DNA protein, the hormone insulin, whichhad been cloned in large quantities by inserting th...

• Suicide.

  C Sociological Theories Most social scientists believe that a society’s structure and values can influence suicide rates. French sociologist Émile Durkheim argued that suicide rates are related tosocial integration —that is, the degree to which an individual feels part of a larger group. Durkheim found suicide was more likely when a person lacked social bonds or had relationships disrupted through a sudden change in status, such as unemployment. As one example of the significance of social bond...

• Ear. I INTRODUCTION Ear, organ of hearing and balance. Only vertebrates, or animals

  line or rotates in any direction. Each canal also contains sensory areas with sensory hair cells that project into a cone-shaped cap of gelatin. Two of the semicircularcanals are in a vertical position and are used to detect vertical movement, such as jumping or falling. The third canal is horizontal and detects horizontal movement,such as turning or spinning. The action of the canals depends on the inertia of the fluid inside. When the motion of the body changes, the fluid lags behind, causing...

• Fire - chemistry.

  were usually natural caves. Eventually people learned to dip branches in pitch to form torches. They created crude lamps by filling a hollowed out piece of stone withmoss soaked in oil or tallow (a substance derived from animal fat). By cooking with fire, prehistoric people made the meat of the animals they killed more palatable and digestible. They learned to preserve meat by smoking it over a fire,vastly decreasing the danger of periodic starvation. Cooking also enabled them to add some for...

• Airplane.

  For example, the Anglo-French Concorde, a commercial supersonic aircraft, was generally limited to over-water routes, or to those over sparsely populated regions ofthe world. This limitation impacted the commercial viability of the Concorde, which ended its regular passenger service in October 2003. Designers today believe theycan help lessen the impact of sonic booms created by supersonic airliners but probably cannot eliminate them. One of the most difficult practical barriers to supersonic fl...

• Antelope - biology.

  antelopes still display complex patterns of behavior, although much of it is instinctive rather than learned. In open habitats, antelopes run a high risk of predation (being preyed upon). To survive they use several kinds of defensive strategy, including living in herds. Herd living ensures that many pairs of eyes and ears are on the alert for danger. Herd living also gives individuals a better chance of avoiding attack, because predators canchoose from many potential targets. When danger thre...

• Insect - biology.

  they almost always have six legs. In some insects, such as beetles, the legs are practically identical, but in other insects each pair is a slightly different shape. Still otherinsects have specialized leg structures. Examples are praying mantises, which have grasping and stabbing forelegs armed with lethal spines, and grasshoppers andfleas, which have large, muscular hind legs that catapult them into the air. Mole crickets’ front legs are modified for digging, and backswimmers have hind legs de...

• Supernova - astronomy.

  The term hypernova has been proposed for an extremely massive core-collapse supernova—possibly more than 100 times the mass of the Sun. A hypernova is thought to form a black hole. Just before it explodes, a hypernova may release a huge burst of gamma rays in a jet from the rotating black hole at its center. These jets mayexplain the so-called long gamma-ray bursts detected by astronomers. According to some researchers, massive stars with over 40 solar masses may sometimescollapse directly int...

• Pablo Picasso.

  Color juxtapositions—between blue and orange, for instance—are intentionally strident and unharmonious. The representation of space is fragmented and discontinuous. While the left side of the canvas is largely Iberian-influenced, the right side is inspired by African masks, especially in its striped patterns and oval forms. Suchborrowings, which led to great simplification, distortion, and visual incongruities, were considered extremely daring in 1907. The head of the figure at the bottom right,...

• Taxation.

  Thus, corporate income faces a higher tax burden than income earned by individuals or by other types of businesses. Tax legislation passed in 2003 in the United Statesattempted to address this issue by lowering the tax rate on dividends. Some economists have proposed abolishing the corporate income tax and instead taxing the owners of corporations (shareholders) through the personal income tax.Other students of the tax system see the corporate income tax as the price corporations pay in return f...

• Nunavut - Canadian History.

  The Arctic Lands is a complex geological area that is centered on the Arctic Ocean. It includes coastal plains, plateaus, and mountains. Coastal plains and plateaus arefound in the western Northwest Territories section of the Arctic Lands, such as on Victoria Island, which is mostly a large, flat plateau. In striking contrast to theserelatively gentle landscapes, the eastern Nunavut section of the Arctic Lands is dominated by a jagged chain of ice-covered mountains. The mountains on EllesmereIsl...

• Gravitation I INTRODUCTION Gravitation, the force of attraction between all objects that tends to pull them toward one another.

  precise observations possible, and Galileo was one of the first to use a telescope to study astronomy. In 1609 Galileo observed that moons orbited the planet Jupiter, afact that could not reasonably fit into an earth-centered model of the heavens. The new heliocentric theory changed scientists' views about the earth's place in the universe and opened the way for new ideas about the forces behind planetarymotion. However, it was not until the late 17th century that Isaac Newton developed a theory...

• Gravitation - astronomy.

  precise observations possible, and Galileo was one of the first to use a telescope to study astronomy. In 1609 Galileo observed that moons orbited the planet Jupiter, afact that could not reasonably fit into an earth-centered model of the heavens. The new heliocentric theory changed scientists' views about the earth's place in the universe and opened the way for new ideas about the forces behind planetarymotion. However, it was not until the late 17th century that Isaac Newton developed a theory...

• Christianity.

  history of architecture. See Basilica; Church; Early Christian Art and Architecture;Prayer. C Christian Life The instruction and exhortation of Christian preaching and teaching concern all the themes of doctrine and morals: the love of God and the love of neighbor, the twochief commandments in the ethical message of Jesus (see Matthew 22: 34-40). Application of these commandments to the concrete situations of human life, bothpersonal and social, does not produce a uniformity of moral or polit...

• Camping.

  Commercial campgrounds serve as campsites for RV and car campers on the outskirts of national and state parks and along highways throughout North America.Owners of commercial campgrounds charge campers on a daily or weekly basis, and provide campsites equipped with hookups for electricity and water. They may alsoprovide such amenities as showers, laundry facilities, or a swimming pool. Many commercial campgrounds belong to a club or network that allows its members toreserve campsites in advance....

• Human Sexuality.

  About six weeks after conception, if a Y chromosome is present in the embryo's cells (as it is in normal males), a gene on the chromosome directs the undifferentiatedgonads to become testes. If the Y chromosome is not present (as in normal females), the undifferentiated gonads will become ovaries. If the gonads become testes, they begin to produce androgens (male hormones, primarily testosterone) by about eight weeks after conception. These androgens stimulate development of the one set of the...

• Maya Civilization.

  destruction was directed mostly at temples in the ceremonial precincts; it had little or no impact on the economy or population of a city as a whole. Some city-states didoccasionally conquer others, but this was not a common occurrence until very late in the Classic period when lowland civilization had begun to disintegrate. Until thattime, the most common pattern of Maya warfare seems to have consisted of raids employing rapid attacks and retreats by relatively small numbers of warriors, most o...

• Maya Civilization - History.

  destruction was directed mostly at temples in the ceremonial precincts; it had little or no impact on the economy or population of a city as a whole. Some city-states didoccasionally conquer others, but this was not a common occurrence until very late in the Classic period when lowland civilization had begun to disintegrate. Until thattime, the most common pattern of Maya warfare seems to have consisted of raids employing rapid attacks and retreats by relatively small numbers of warriors, most o...

• Radar.

  gathers the weak returning radar signals and converts them into an electric current. Because a radar antenna may both transmit and receive signals, the duplexerdetermines whether the antenna is connected to the receiver or the transmitter. The receiver determines whether the signal should be reported and often does furtheranalysis before sending the results to the display. The display conveys the results to the human operator through a visual display or an audible signal. B1 The Antenna The rec...

• Canadian Parliament.

  government’s legislative program. Members of Commons can also present a motion in response to the Budget Speech, which reviews the government’s economicrecord, taxation, and expenditure plans, and to Supply Motions, which concern budgets for individual departments. If a majority of MPs support a no-confidence motion,the government must resign. Also, if Parliament rejects a significant government proposal, the government is expected to resign and request the governor-general to call an election....

• United States House of Representatives.

  Because of the high cost of elections and the short two-year term of office, members of the House campaign almost constantly. They spend much of their time raisingcampaign funds, and they frequently return to their districts to keep in touch with voters. Because the elections are so frequent, House members tend to pay closeattention to how their votes in Congress will be seen in the short term. House members tend to come from wealthier family backgrounds than average Americans. Few working class...

• Civil Rights and Civil Liberties.

  A Religious Freedom Although religious freedom has not generally been curtailed in the United States, Roman Catholics, Jews, and members of such unconventional Protestant groups as theOneida Community and the Church of Jesus Christ of Latter-day Saints have historically been discriminated against and sometimes have even been persecuted,although today overt discrimination has almost vanished. The federal Civil Rights Act of 1964, as well as many state and local laws, prohibits religious discrimi...

• Acquired Immunodeficiency Syndrome.

  child transmission is particularly prevalent in Africa. D Misperceptions About HIV Transmission The routes of HIV transmission are well documented by scientists, but health officials continually grapple with people’s unfounded fears concerning the potential for HIVtransmission by other means. HIV differs from other infectious viruses in that it dies quickly if exposed to the environment. No evidence has linked HIV transmission tocasual contact with an infected person, such as a handshake, huggi...

• Criminal Punishment.

  In the United States and Canada, younger offenders may be sentenced to highly regimented, military-style correctional programs known as boot camps. Generally,offenders volunteer to participate in boot camp programs to avoid other types of incarceration. At boot camps, officials subject offenders to strict discipline and physicaltraining. They also provide educational or vocational programs. Boot camps serve as an alternative to traditional, long-term incarceration and attempt to train offenderst...

• Ant - biology.

  The workers of many ant species carry a stinger within the hind end of the gaster. These ants use the stinger to defend against their enemies. In some species, workerants lack a stinger but use the tip of their gaster to squirt or dab poison at other small animals and when fighting battles with other ants, fending off predators, or killinginsects or other animals that they use as food. III PHYSIOLOGY Ants have a rigid, external skeleton called an exoskeleton that gives the soft, inner body its...

• Europe .

  D Vegetation Although much of Europe, particularly the west, was originally covered by forest, the vegetation has been transformed by human habitation and the clearing of land.Only in the most northerly mountains and in parts of north central European Russia has the forest cover been relatively unaffected by human activity. On the otherhand, a considerable amount of Europe is covered by woodland that has been planted or has reoccupied cleared lands. The largest vegetation zone in Europe, cuttin...

• Europe - Geography.

  D Vegetation Although much of Europe, particularly the west, was originally covered by forest, the vegetation has been transformed by human habitation and the clearing of land.Only in the most northerly mountains and in parts of north central European Russia has the forest cover been relatively unaffected by human activity. On the otherhand, a considerable amount of Europe is covered by woodland that has been planted or has reoccupied cleared lands. The largest vegetation zone in Europe, cuttin...

• Light - astronomy.

  Each different frequency or wavelength of visible light causes our eye to see a slightly different color. The longest wavelength we can see is deep red at about 700 nm.The shortest wavelength humans can detect is deep blue or violet at about 400 nm. Most light sources do not radiate monochromatic light. What we call white light,such as light from the Sun, is a mixture of all the colors in the visible spectrum, with some represented more strongly than others. Human eyes respond best to greenlight...

• Colonialism and Colonies.

  by plundering the riches of existing civilizations in the Americas and by seizing the area’s mineral wealth through mining. These practices were promoted by the policy of mercantilism that many European colonial powers adopted. Those who advocated mercantilism believed that exports toforeign countries were preferable both to trade within a country and to imports because exports brought more money into the country. They also believed that thewealth of a nation depended primarily on the possession...

• Colonialism and Colonies .

  by plundering the riches of existing civilizations in the Americas and by seizing the area’s mineral wealth through mining. These practices were promoted by the policy of mercantilism that many European colonial powers adopted. Those who advocated mercantilism believed that exports toforeign countries were preferable both to trade within a country and to imports because exports brought more money into the country. They also believed that thewealth of a nation depended primarily on the possession...

• Tiger - biology.

  have a simple digestive system designed to process meat so that the nutrients can be readily absorbed into the bloodstream. With the exception of white tigers, which have blue eyes, all tigers have yellow eyes. Tigers mainly use vision to find prey. Although tigers see about as well as humansduring the day, their large eye openings gather more light than do human eyes, making tiger night vision far superior to that of humans. In addition, a special structurein the tiger’s eye, called the tapetu...

• Hormone.

  women is called a follicle-stimulating hormone. When a follicle-stimulating hormone binds to an ovary cell, it stimulates the enzymes needed for the synthesis ofestradiol, a female sex hormone. Another gonadotropin called luteinizing hormone regulates the production of eggs in women and the production of the male sexhormone testosterone. Produced in the male gonads, or testes, testosterone regulates changes to the male body during puberty, influences sexual behavior, and playsa role in growth. T...

• Hinduism.

  they do not share any basic terms. B Sanātana Dharma Evidence from inscriptions indicates that Hindus had begun to use the word dharma for their religion by the 7th century. After other religions of Indian origin also began to use this term, Hindus then adopted the expression san ātana dharma to distinguish their dharma from others. The word san ātana, meaning immemorial as well as eternal, emphasized the unbroken continuity of the Hindu tradition in contrast to the other dharmas . The Bu...

• Ontario - Geography.

  governed Ontario’s initial settlement and development. The province’s most important river is the St. Lawrence. Its route was much improved and enlarged by dredgingand canal building in the mid-20th century. This enabled large ocean-going vessels to reach Great Lake ports ( see St. Lawrence Seaway). The Ottawa River was an important early route to the interior for fur traders and timber merchants. The Niagara River, because of its falls, is a great center of hydroelectric power as well as aninte...

• Ontario - Canadian History.

  governed Ontario’s initial settlement and development. The province’s most important river is the St. Lawrence. Its route was much improved and enlarged by dredgingand canal building in the mid-20th century. This enabled large ocean-going vessels to reach Great Lake ports ( see St. Lawrence Seaway). The Ottawa River was an important early route to the interior for fur traders and timber merchants. The Niagara River, because of its falls, is a great center of hydroelectric power as well as aninte...