466 résultats pour "become"
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Calculus (mathematics)
I
INTRODUCTION
Limits
This graph, which charts the function f(x)=1x, shows that the value of the function approaches zero as x becomes larger
and larger.
DerivativesThe derivative of a function at a given point is equal to the slope of the line that is tangent to the function at that givenpoint. In this example, the derivative of f(x) at x0 is defined as the slope of AB in the limit of h going to zero. As hbecomes increasingly smaller, B moves along the curve towards A, and AB increasingly approximates T, the tangent to thecurve at x0.© Microsoft Corporation. All Rights Reserved. Let the dependent variable y be a function of the independent vari...
- 'One is not born a hero, one becomes a hero'
- Would you be ready to become an activist for affirmative action ? state your reasons
- Sidney Poitier Sidney Poitier, born in 1927, American motion-picture actor, the first black to become a major Hollywood star.
- Magic Johnson Magic Johnson, born in 1959, American professional basketball player, who helped the Los Angeles Lakers become one of the dominating professional basketball teams of the 1980s.
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Quantum Theory
I
INTRODUCTION
Quantum Theory, in physics, description of the particles that make up matter and how they interact with each other and with energy.
electron in the same way a particle with momentum would: It bumps the electron and changes the electron’s path. The light is also affected by the collision as though itwere a particle, in that its energy and momentum changes. Momentum is a quantity that can be defined for all particles. For light particles, or photons, momentum depends on the frequency, or color, of the photon, which in turndepends on the photon’s energy. The energy of a photon is equal to a constant number, called Planck’s cons...
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Alcoholism.
Although a consensus is growing among health professionals that alcohol dependence is a disease, society’s attitudes toward individuals with drinking problems remainambivalent and confused. Until the mid-20th century, the typical picture of the alcoholic was of someone without steady employment, unable to sustain familyrelationships and most likely in desperate financial straits. But this stereotype was largely dispelled when highly respected people publicly admitted their alcoholdependence and...
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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...
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Marketing.
Where advertising reaches a mass audience, personal or direct selling focuses on one customer at a time. That kind of individual attention makes direct sellingexpensive, but it also makes it effective. As the costs of personal selling have risen, the utilization of salespeople has changed. Simple transactions are completed byclerks. Salespeople are now used primarily where the products are complex and require detailed explanation, customized application, or careful negotiation over priceand paym...
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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...
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Collectibles and Collecting.
common blond and thus commands a higher price. If there are different variations to a collectible, the least common one is usually worth more. Often there areinteresting stories behind rarities, such as the highly sought-after 1909 Honus Wagner baseball card. At that time tobacco companies manufactured and distributedbaseball cards, and when the antitobacco Wagner complained, his card was pulled from production. Very few copies in good condition have ever been found. C Age Age is often an indic...
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Sun - astronomy.
A The Sun’s Place in the Milky Way The Milky Way Galaxy contains about 400 billion stars. All of these stars, and the gas and dust between them, are rotating about a galactic center. Stars that arefarther away from the center move at slower speeds and take longer to go around it. The Sun is located in the outer part of the galaxy, at a distance of 2.6 × 10 17 km (1.6 × 10 17 mi) from the center. The Sun, which is moving around the center at a velocity of 220 km/s (140 mi/s), takes 250 million y...
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Sigmund Freud.
reminiscences from the past and about her daydreams. Remarkably, as her narrative revisited memories from the past, which were associated with the onset of aparticular symptom, each symptom disappeared when accompanied by an emotional outburst. Breuer made use of this discovery to eliminate her symptoms one at atime. He called the treatment the cathartic technique (from the Greek katharsis meaning “purgation”). The treatment was time consuming and required considerable effort to reach dimly re...
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Texas - geography.
D Climate Eastern Texas has a humid subtropical climate, while a semiarid low latitude climate prevails in central areas, and an arid low latitude climate in the extreme west. Alongthe coast the climate is much milder, with fewer extremes in temperatures. Hurricanes sometimes hit the coastal areas of Texas from late July through September, andtornadoes are common in north-central Texas in April and May. D1 Temperature Summers are hot throughout the state, and temperatures exceeding 35°C (95°F)...
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Texas - USA History.
D Climate Eastern Texas has a humid subtropical climate, while a semiarid low latitude climate prevails in central areas, and an arid low latitude climate in the extreme west. Alongthe coast the climate is much milder, with fewer extremes in temperatures. Hurricanes sometimes hit the coastal areas of Texas from late July through September, andtornadoes are common in north-central Texas in April and May. D1 Temperature Summers are hot throughout the state, and temperatures exceeding 35°C (95°F)...
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Diving (underwater).
compensator (or control) device (BCD or BC), which the diver wears as a vest. By adding air to the BCD, the diver becomes more buoyant and rises. By releasing air,the diver becomes less buoyant and sinks. With minor adjustments of air, the diver can achieve neutral buoyancy. A third hose attaches to pressure gauges that diversuse to monitor how much air remains in the tank. A fourth hose attaches to a backup breathing device called an alternate air source, or octopus. Divers also wear a belt w...
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Rock (mineral).
pressure mineral assemblage. In a sense, the rock is stuck in a state that is characteristic of its earlier high-temperature and high-pressure environment. Thus,metamorphic rocks carry with them information about the history of temperatures and pressures to which they were subjected. The size, shape, and distribution of mineral grains in a rock are called the texture of the rock. Many metamorphic rocks are named for their main texture. Textures giveimportant clues as to how the rock formed. As t...
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Igneous Rock.
As a magma cools, the first crystals to form will be of minerals that become solid at relatively high temperatures (usually olivine and a type of feldspar known asanorthite). The composition of these early-formed mineral crystals will be different from the initial composition of the magma. Consequently, as these growing crystalstake certain elements out of the magma in certain proportions, the composition of the remaining liquid changes. This process is known as magmatic differentiation.Sometime...
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Astronaut - astronomy.
Every operation during a flight is important and interesting, but many might be boring to an observer. Much of an astronaut’s job is entering computer instructions,preparing samples, making measurements, recording data, fixing what breaks, and adjusting the checklist when something unexpected happens. Sometimes astronautsretrieve or repair satellites, rendezvous or dock with other spacecraft, and do important emergency repairs. The adaptability of the human crew is crucial to the successof missi...
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Circulatory System.
C Additional Functions In addition to oxygen, the circulatory system also transports nutrients derived from digested food to the body. These nutrients enter the bloodstream by passingthrough the walls of the intestine. The nutrients are absorbed through a network of capillaries and veins that drain the intestines, called the hepatic portal circulation.The hepatic portal circulation carries the nutrients to the liver for further metabolic processing. The liver stores a variety of substances, suc...
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William Henry Harrison.
in September 1813, Harrison recaptured the city of Detroit, which the British had taken in 1812. The following month he overtook the British and Tecumseh's forces onthe Thames River in Canada. He captured the entire British force. Tecumseh was killed, and his forces were routed. Harrison's triumph on the Thames, although won over inferior forces badly placed, was vitally important because the victory secured the Northwest from the threat of aBritish invasion from Canada. It also added considerab...
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William Henry Harrison
in September 1813, Harrison recaptured the city of Detroit, which the British had taken in 1812. The following month he overtook the British and Tecumseh's forces onthe Thames River in Canada. He captured the entire British force. Tecumseh was killed, and his forces were routed. Harrison's triumph on the Thames, although won over inferior forces badly placed, was vitally important because the victory secured the Northwest from the threat of aBritish invasion from Canada. It also added considerab...
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Electricity
I
INTRODUCTION
Electricity, one of the basic forms of energy.
electrons in the neutral object are attracted to the positive object. Some of these electrons flow to the side of the neutral object that is nearest to the positive object.This side of the neutral object accumulates electrons and becomes negatively charged. Because electrons leave the far side of the neutral object while its protonsremain stationary, that side becomes positively charged. Since the negatively charged side of the neutral object is closest to the positive object, the attraction bet...
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United States (Overview) - country.
parts. IV UNITED STATES PEOPLE When Europeans first reached North America in the 1520s, they encountered other people—Native Americans—and they also encountered a new geography. Someimagined they were entering “a howling wilderness”—an environment filled with exotic flora and fauna but sparsely populated. In reality, they found their way to alandmass that was widely settled. But soon after the Europeans’ arrival, the population of the Americas plummeted, largely because Native Americans lacked...
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United States Government.
Article II establishes an executive department headed by a president and vice president. The article further describes the powers of the offices, the manner of election,and the qualifications for office. Of special significance is the president’s constitutional role as commander of the nation’s armed forces, which assures civilian controlover the military. Because the president is the head of the armed forces and only Congress can declare war, the authority of the military is diffused and its po...
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Molecule - chemistry.
attracted to the negatively charged electrons between them. The electrons belong to the molecule as a whole. However, each hydrogen atom now has a complete outershell of two electrons. The formula H 2 describes a hydrogen molecule, a discrete unit. When a molecule contains just two atoms, such as the hydrogen molecule does, it is called a diatomic molecule. Some atoms can form covalent bonds with more than one other atom and thus create a larger molecule. Atoms form molecules with covalent bo...
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Australia - country.
itself forms most of the border between New South Wales and Victoria. Considerable lengths of the Murray, Darling, and Murrumbidgee rivers are navigable during thewet seasons. The central plains region, also known as the Channel Country, is interlaced by a network of rivers. During the rainy season these rivers flood the low-lying countryside,but in dry months they become merely a series of water holes. The Victoria, Daly, and Roper rivers drain a section of the Northern Territory. In Queensland...
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Australia - Geography.
itself forms most of the border between New South Wales and Victoria. Considerable lengths of the Murray, Darling, and Murrumbidgee rivers are navigable during thewet seasons. The central plains region, also known as the Channel Country, is interlaced by a network of rivers. During the rainy season these rivers flood the low-lying countryside,but in dry months they become merely a series of water holes. The Victoria, Daly, and Roper rivers drain a section of the Northern Territory. In Queensland...
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Christmas.
The new custom of Christmas gift giving allowed the marketplace to exert an unprecedented influence on holiday celebrations. Commercial innovations such asdepartment stores and mass advertising further expanded the custom of exchanging Christmas gifts. Seasonal retail sales helped fuel the economy, causing merchantsand advertisers to become some of the season’s most ardent promoters. Many holiday celebrants regretted these changes, however, and began voicing the nowcommon lament that Christmas h...
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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...
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Perception (psychology).
A4 Closure According to the law of closure, we prefer complete forms to incomplete forms. Thus, in the drawing below, we mentally close the gaps and perceive a picture of a duck. This tendency allows us to perceive whole objects from incomplete and imperfect forms. A5 Common Fate The law of common fate leads us to group together objects that move in the same direction. In the following illustration, imagine that three of the balls are moving in one direction, and two of the balls are mo...
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Tree - biology.
The major parts of a tree are its roots, trunk, leaves, flowers, and seeds. These components play vital roles in a tree’s growth, development, and reproduction. A Roots Trees are held in place by anchoring organs called roots. In addition to anchoring the tree, roots also absorb water and minerals through tiny structures called roothairs. From the roots the water and mineral nutrients are carried upward through the wood cells to the leaves. Although the internal structure of most kinds of roots...
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Chemical Reaction - chemistry.
Many groups of elements occur so often as ions that they are given names: nitrate, NO 3-; sulfate, SO 42-; and phosphate, PO 43-. The suffix -ate usually indicates the presence of oxygen. The positive ion, NH 4+, is called ammonium, as in NH 4Cl, ammonium chloride, or (NH 4)3PO4, ammonium phosphate. Rules for naming more complicated compounds exist, but many compounds have been given trivial names—for example, Na 2B4O7·10 H 2O, borax—or proprietary names—F(CF 2)nF, Teflon. These nonsystemat...
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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...
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Giraffe - biology.
One of the most striking elements of giraffe behavior is the duel between males fighting for mating privileges. Giraffe duels are among the most extraordinary in theanimal kingdom. They start when two males approach each other and begin to rub and intertwine their necks. This behavior—known as necking—allows the opponentsto assess each other’s size and strength. Often, necking alone is enough to establish seniority. If not, the rivals begin to exchange blows with their heads. Each giraffebraces...
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true love
or to play games. At the time the first computers were built the people maybe thought they were dangerous and could get out of control. Even before Asimov, some people wrote about machines that could become mightier than humans. But those presentations said that a machine, for example a computer, was like a wild beast that could kill you if you did not pay enough attention. I think Asimov's thoughts about computers and their future were not wrong. It is true that we try to improve the ...
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Cat.
I
INTRODUCTION
Cat, small, mainly carnivorous animal, Felis silvestris catus, member of
D Coat Colors The domestic cat's original coat color was probably grayish-brown with darker tabby stripes, a color that provides excellent camouflage in a variety of environments. Allother coat colors and patterns are the result of genetic mutations; for example, solid coat colors such as black and blue are the result of a gene that suppresses tabbystripes; an orange coat is the result of a gene that transforms black pigment to orange; and a solid white coat is the result of a gene that complet...
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Cat - biology.
D Coat Colors The domestic cat's original coat color was probably grayish-brown with darker tabby stripes, a color that provides excellent camouflage in a variety of environments. Allother coat colors and patterns are the result of genetic mutations; for example, solid coat colors such as black and blue are the result of a gene that suppresses tabbystripes; an orange coat is the result of a gene that transforms black pigment to orange; and a solid white coat is the result of a gene that complet...
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Air Pollution.
Several pollutants attack the ozone layer. Chief among them is the class of chemicals known as chlorofluorocarbons (CFCs), formerly used as refrigerants (notably in airconditioners), as agents in several manufacturing processes, and as propellants in spray cans. CFC molecules are virtually indestructible until they reach thestratosphere. Here, intense ultraviolet radiation breaks the CFC molecules apart, releasing the chlorine atoms they contain. These chlorine atoms begin reacting withozone, br...
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Hydrogen - chemistry.
Hydrogen gas does not usually react with other chemicals at room temperature. That is, it does not split into two hydrogen atoms to combine with other chemicals. Thebond between the hydrogen atoms is very strong and can only be broken with a large amount of energy. However, when heated with a flame or a spark, hydrogen gaswill react violently with oxygen in the air to produce water in the following reaction: 2H2 + O 2 → 2H 2O This chemical equation shows that two hydrogen molecules (H 2) and o...
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Abortion.
Intact dilation and extraction, also referred to as a partial birth abortion, consists of partially removing the fetus from the uterus through the vaginal canal, feet first,and using suction to remove the brain and spinal fluid from the skull. The skull is then collapsed to allow complete removal of the fetus from the uterus. III SOCIAL AND ETHICAL ISSUES Abortion has become one of the most widely debated ethical issues of our time. On one side are pro-choice supporters—individuals who favor a...
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Laser.
their atoms into laser light. Consequently, they are the most powerful continuous wave (CW) lasers—that is, lasers that emit light continuously rather than in pulses. C Liquid Lasers The most common liquid laser media are inorganic dyes contained in glass vessels. They are pumped by intense flash lamps in a pulse mode or by a separate gas laserin the continuous wave mode. Some dye lasers are tunable, meaning that the color of the laser light they emit can be adjusted with the help of a prism lo...
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God.
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INTRODUCTION
God, the center and focus of religious faith, a holy
C Islam Islam arose as a powerful reaction against the ancient pagan cults of Arabia, and as a consequence it is the most starkly monotheistic of the three biblically rootedreligions. The name Allah means simply “the God.” He is personal, transcendent, and unique, and Muslims are forbidden to depict him in any creaturely form. The primary creed is that “There is no god but Allah, and Muhammad is the apostle of Allah.” Allah has seven basic attributes: life, knowledge, power, will, hearing, se...
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Ballet
I
INTRODUCTION
Tchaikovsky's The Nutcracker
The Nutcracker is a classic ballet with music by Peter Ilyich Tchaikovsky.
Joffrey Ballet SchoolTraining for classical ballet dancers must begin when the students are very young. Here, teacher Dorothy Lister workswith her pre-ballet class of six-year-olds at the Joffrey Ballet School. These students are learning the five basic positions ofclassical ballet.Susan Kunklin/Photo Researchers, Inc. Different systems of ballet training have evolved, named after countries (Russia, France) or teachers (Italian dancer Enrico Cecchetti, Danish choreographer AugustBournonville). T...
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River.
IV RIVER PATTERNS River patterns, or general shapes, depend on the geologic zone and the climate of the location. There are four river patterns: meandering, braided, anastomosing, andstraight. A meandering pattern follows a winding, turning course. A braided pattern has connected channels that resemble a hair braid. An anastomosing river patterncombines features of the meandering and braided patterns. Some river patterns are simply straight channels. Meandering and braided are the most common...
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River - Geography.
IV RIVER PATTERNS River patterns, or general shapes, depend on the geologic zone and the climate of the location. There are four river patterns: meandering, braided, anastomosing, andstraight. A meandering pattern follows a winding, turning course. A braided pattern has connected channels that resemble a hair braid. An anastomosing river patterncombines features of the meandering and braided patterns. Some river patterns are simply straight channels. Meandering and braided are the most common...
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Human Disease.
disease can be transmitted through food infected with mutated proteins. B Spread of Infectious Disease Some pathogens are spread from one person to another by direct contact. They leave the first person through body openings, mucous membranes, and skin wounds,and they enter the second person through similar channels. For example, the viruses that cause respiratory diseases such as influenza and the common cold are spreadin moisture droplets when an infected person coughs or sneezes. A hand that...
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Atlantic Slave Trade.
members of the planters’ society. Through most of the years of the Atlantic trade, prices for Africans remained favorable in relation to the price of the crops theyproduced. They were, thus, the best economic solution for plantation owners seeking inexpensive labor. The Atlantic slave trade began as a trickle in the 1440s and grew slowly through the 17th century. By 1700, 25,000 slaves, on average, were crossing the Atlantic everyyear. After 1700 the trade grew much more rapidly to a peak in the...
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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...
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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...