583 résultats pour "often"
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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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Yemen - country.
port. Al Ḩudaydah (155,110), in the Tih āmah, is the second largest port. Ta‘izz, (178,043), in the highlands above Aden, is an important commercial and light industrialcenter. Among Yemen’s larger towns are Şa‘dah, far to the north; Dham ār, Yarim, and Ibb, in the middle region; Al Mukall ā, on the southern coast; and in Hadhramaut,the towns of Shib ām, Say‘ ūn, and Tar īm. C Language Nearly all Yemenis speak Arabic. However, the country’s extremely rugged terrain, widely separated population...
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Attention-Deficit Hyperactivity Disorder.
Although the drugs are prescribed most often to treat ADHD among children, increasingly adults are taking the drugs for ADHD. From 2002 to 2005 the number ofprescriptions written for adults reportedly increased by 90 percent. In the United States about 2.5 million children and about 1.5 million adults take ADHD drugs. Amember of the FDA advisory panel noted that adults are more likely to have a higher risk of heart problems. Most of the 25 sudden deaths, however, were amongchildren. The prelimin...
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Anxiety.
A Genetics and Neurobiology Studies suggest that anxiety disorders run in families. That is, children and close relatives of people with disorders are more likely than most to develop anxietydisorders. Some people may inherit genes that make them particularly vulnerable to anxiety. These genes do not necessarily cause people to be anxious, but the genesmay increase the risk of anxiety disorders when certain psychological and social factors are also present. Anxiety also appears to be related to...
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Social Psychology.
During the 1960s, American psychologist Stanley Milgram studied a form of social influence stronger than conformity: obedience to authority. In a famous series ofexperiments that attracted controversy about human research ethics, Milgram put each of 1,000 subjects into a situation in which they were ordered by anexperimenter to administer painful electric shocks to a confederate (who did not actually receive any shocks). The subjects in these studies were led to believe that theywere acting as '...
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Psychology.
Clinical psychology is dedicated to the study, diagnosis, and treatment of mental illnesses and other emotional or behavioral disorders. More psychologists work in this field than in any other branch of psychology. In hospitals, community clinics, schools, and in private practice, they use interviews and tests to diagnose depression,anxiety disorders, schizophrenia, and other mental illnesses. People with these psychological disorders often suffer terribly. They experience disturbing symptoms t...
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Dolphin (aquatic mammal) - biology.
Scientists have observed dolphins displaying three types of caregiving behaviors: standing by, excitement, and supporting. In standing-by behavior, dolphins remain inthe vicinity of an injured or ill companion without offering aid. In excitement behavior, dolphins swim swiftly in circles around an injured dolphin, responding aggressivelytoward threats to the injured animal. For instance, they may bite harpoon lines or charge boats that come too close to the animal. In supporting behavior, one or...
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Gemstones.
In the late 1960s a method was developed for “growing” diamonds by heating a diamond particle to a high temperature and subjecting it to methane gas. The gasdecomposes into carbon atoms, which adhere to the diamond crystal. The crystal structure of the enlarged diamond is identical to that of a natural diamond. Diamondsof about 1 carat (200 mg or 0.007 oz) have been produced by this method, but their cost is still considerably higher than that of naturally occurring diamonds. Sapphires are made...
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Rain Forest.
dropped into the heart of the forest by helicopters. Suspended from the crane’s long, movable arm is a large gondola that functions as a mobile treetop laboratory.Moving from tree to tree, forest researchers collect specimens, conduct experiments, and observe life in the canopy frontier. The highest stratum of the rain forest is made up of the emergent trees, those individuals that stick up above the forest canopy. Emergents, which do not form acontinuous layer, are usually the giants of the for...
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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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Child Abuse.
C Social Isolation and Low Community Involvement Parents and caretakers who abuse children tend to be socially isolated. Few violent parents belong to any community organizations, and most have little contact withfriends or relatives. This lack of social involvement deprives abusive parents of support systems that would help them deal better with social or family stress. Moreover,the lack of community contacts makes these parents less likely to change their behavior to conform with community va...
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Baroque Art and Architecture
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INTRODUCTION
German Baroque Architecture
The baroque style of architecture flourished in Germany in the 18th century.
C Early baroque styles Conversion of Saint PaulItalian baroque painter Caravaggio painted scenes of realism and drama, often selecting lofty, religious themes anddepicting them with lower-class characters and settings with dramatic spotlighting. With its unidealized characters andfocus on the horse’s body, his Conversion of Saint Paul seems to record a stable accident, not a miraculous conversion byGod. This work was painted in 1601 and is in the Cerasi Chapel, Santa Maria del Popolo, Rome, Ita...
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Advertising.
Advertising agencies make money in a variety of ways. When the agency uses the client’s advertising budget to buy time for an ad on the radio or on television or whenit buys space for an ad in a newspaper or magazine, the media outlet allows the agency to keep 15 percent of the cost of the space or the time as a commission. The15 percent commission has become an advertising industry standard and usually accounts for the largest portion of the agency’s income. Agencies also charge clientsfor the...
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Surgery.
III SURGICAL PROCEDURES Surgical procedures are classified as optional, required, elective, urgent, and emergent based on the patient’s medical condition. Optional surgery consists of operationsthat are not required but which the patient chooses to undergo as with some types of cosmetic surgery. Required surgery is performed when only surgery will correct aproblem—such as cataracts—but the surgery can be delayed for a period of weeks or months. Elective surgical procedures usually involve cond...
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Portraiture
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INTRODUCTION
Portraiture, visual representation of individual people, distinguished by references to the subject's character, social position, wealth, or profession.
CaracallaCaracalla is a Roman portrait bust in marble of the emperor Marcus Aurelius Antoninus, probably done circa ad 215. Theson of Septimius Severus, Caracalla (as he was known) was a brutal man whose qualities come through in this piece withits dramatic realism. The bust, which is now in the Louvre, Paris, evidently served as the inspiration for Michelangelo’sbust of Brutus more than one thousand years later.Bridgeman Art Library, London/New York The first representations of identifiable ind...
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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...
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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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Health Insurance.
needs services. Essentially, individuals make regular payments to the plan rather than having to pay especially large sums at any one time in the event of sudden illnessor injury. In this way, the group as a whole funds expensive treatments for those few who need them. Many people believe that in addition to providing financial stability, health insurance can promote good health. Supporters of this idea claim that by lowering thepersonal cost of services, insurance induces individuals to seek he...
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Modern Art
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INTRODUCTION
American Gothic
American Gothic was painted by the 20th-century American artist Grant Wood in 1930.
while at the other side a woman in black appears to mourn the end of her participation in the dance. Click on the buttonsto learn more.© Microsoft Corporation. All Rights Reserved. In view of this diversity, it is difficult to define modern art in a way that includes all of 20th-century Western art. For some critics, the most important characteristic ofmodern art is its attempt to make painting and sculpture ends in themselves, thus distinguishing modernism from earlier forms of art that had con...
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Coronary Heart Disease.
when a patient is at rest may indicate that the blood supply of the heart is not normal, and the ECG can often detect damage from a previous heart attack. In anexercise stress test, an ECG is recorded while a patient is performing physical activity such as walking on a treadmill or riding a stationary bicycle. As the intensity ofexercise increases, the doctor looks for specific changes in the ECG that indicate the heart is not getting enough oxygen. In cardiac catheterization, a long, thin, flex...
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Latin American Music
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INTRODUCTION
Tito Puente Playing the Drums
Since the 1950s American drummer Tito Puente has popularized Latin American music, especially the mambo, in the
United States.
Panpipe Music of BoliviaWell before the Spanish conquest, native peoples such as the Quechua and Aymara living in the Andes Mountains inBolivia, Peru, and Ecuador, developed a rich musical tradition. Panpipes (set of tuned pipes), made of ceramic, sugarcane,or bone were paired with shell trumpets, cane flutes, and drums, which accompanied dancers during religious and secularceremonies. Large ensembles of 4 to 20 panpipe players are still the norm, and Spanish influences have since beenintegrated...
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Tennessee (state) - geography.
The climate of Tennessee is characterized by hot summers, mild winters, and abundant rainfall. C1 Temperature Average July temperatures range from less than 21° C (70° F) in the Blue Ridge region to 27° C (80° F) at Nashville and Memphis. Maximum daytime temperatures insummer often rise above 35° C (95° F) in central and western Tennessee. Daytime temperatures in the mountains rarely rise above 32° C (90° F). Summer nights tendto be warm and muggy in central and western Tennessee, but temperatu...
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Tennessee (state) - USA History.
The climate of Tennessee is characterized by hot summers, mild winters, and abundant rainfall. C1 Temperature Average July temperatures range from less than 21° C (70° F) in the Blue Ridge region to 27° C (80° F) at Nashville and Memphis. Maximum daytime temperatures insummer often rise above 35° C (95° F) in central and western Tennessee. Daytime temperatures in the mountains rarely rise above 32° C (90° F). Summer nights tendto be warm and muggy in central and western Tennessee, but temperatu...
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Aboriginal Australians - History.
Until Europeans began to settle in Australia in 1788, the Aboriginal way of life was supported by hunting, gathering, and fishing. Like other hunting and gatheringpeoples, Aboriginal people had an extremely detailed knowledge of their environment, especially plant ecology and animal behavior. The deep connection betweenAboriginal people and the natural world influenced every part of their culture, including their food gathering, tools, trade, religion, art, music, language, and socialorganizatio...
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Child Development.
developmental scientists have studied how cultural values guide the skills and attitudes that children acquire as they mature, and how brain maturation influences thedevelopment of thinking and feeling. For a more detailed discussion of child development theories, see the Theories of Child Development section of this article. III BASIC QUESTIONS A Nature and Nurture Scholars have long debated the relative importance of nature (hereditary influences) and nurture (environmental influences) i...
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Immigration.
1655, only to lose all of their North American colonies to the British in 1664. These early colonies were often quite cosmopolitan, drawing settlers from many nations.When the English seized New Amsterdam, the city was home to perhaps 1500 residents, including Walloons, Huguenots, Swedes, Dutchmen, and African Americans. C The French and Spanish The French and Spanish also established colonies in North America. The Spanish established the oldest permanent European settlement in Saint Augustine,...
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Immigration - U.
1655, only to lose all of their North American colonies to the British in 1664. These early colonies were often quite cosmopolitan, drawing settlers from many nations.When the English seized New Amsterdam, the city was home to perhaps 1500 residents, including Walloons, Huguenots, Swedes, Dutchmen, and African Americans. C The French and Spanish The French and Spanish also established colonies in North America. The Spanish established the oldest permanent European settlement in Saint Augustine,...
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William Shakespeare
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INTRODUCTION
William Shakespeare (1564-1616), English playwright and poet, recognized in much of the world as the greatest of all dramatists.
Shakespeare’s reputation today is, however, based primarily on the 38 plays that he wrote, modified, or collaborated on. Records of Shakespeare’s plays begin toappear in 1594, when the theaters reopened with the passing of the plague that had closed them for 21 months. In December of 1594 his play The Comedy of Errors was performed in London during the Christmas revels at Gray’s Inn, one of the London law schools. In March of the following year he received payment for two playsthat had been per...
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William Shakespeare.
Shakespeare’s reputation today is, however, based primarily on the 38 plays that he wrote, modified, or collaborated on. Records of Shakespeare’s plays begin toappear in 1594, when the theaters reopened with the passing of the plague that had closed them for 21 months. In December of 1594 his play The Comedy of Errors was performed in London during the Christmas revels at Gray’s Inn, one of the London law schools. In March of the following year he received payment for two playsthat had been per...
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United States Senate.
providing for military forces, and declaring war. Article I, Section 8, also gives Congress implied powers—to “make all laws which shall be necessary and proper” forcarrying out the enumerated powers, and to investigate and oversee the executive branch. The Senate also has the power to conduct impeachment trials against thepresident, federal judges, and other officials. The Senate can only impeach someone after the House brings charges, however. A two-thirds majority vote of thesenators in the c...
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Birding - biology.
swallows, and rock doves nest on buildings in cities, towns, and farms. The chimney swift has abandoned hollow trees for chimneys as a nest site in urban areas.Mallards and Canada geese—once exclusively wild, migratory species—now live year-round in the open spaces found in city parks and golf courses. Nearly all purplemartins, a songbird species that once used the abandoned nests of woodpeckers or the natural cavities of cliffs or dead trees, now live primarily in structures specificallyconstru...
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Astronomy - astronomy.
Telescopes may use either lenses or mirrors to gather visible light, permitting direct observation or photographic recording of distant objects. Those that use lenses arecalled refracting telescopes, since they use the property of refraction, or bending, of light ( see Optics: Reflection and Refraction ). The largest refracting telescope is the 40-in (1-m) telescope at the Yerkes Observatory in Williams Bay, Wisconsin, founded in the late 19th century. Lenses bend different colors of light by d...
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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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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...
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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...
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Washington (state) - geography.
The crest of the Cascade Range divides Washington into two distinct climatic regions. The area west of the Cascades, which is exposed throughout the year to rain-bearing winds from the Pacific Ocean, has a temperate marine type of climate that is characterized by mild wet winters and cool summers. The Cascades prevent themoist air blowing in from the Pacific from reaching eastern Washington. The Rocky Mountains on the eastern border also represent a climatic barrier. As a result, thesevere winte...
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Washington (state) - USA History.
The crest of the Cascade Range divides Washington into two distinct climatic regions. The area west of the Cascades, which is exposed throughout the year to rain-bearing winds from the Pacific Ocean, has a temperate marine type of climate that is characterized by mild wet winters and cool summers. The Cascades prevent themoist air blowing in from the Pacific from reaching eastern Washington. The Rocky Mountains on the eastern border also represent a climatic barrier. As a result, thesevere winte...
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United Nations.
and programs to carry out its recommendations. It elects members to serve on certain agencies and programs, and it coordinates those programs through variouscommittees. B Security Council The Security Council is the most powerful body in the UN. It is responsible for maintaining international peace, and for restoring peace when conflicts arise. Its decisionsare binding on all UN members and have the force of international law. The Security Council has the power to define what is a threat to sec...
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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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Domestic Violence.
socialization teaches boys and girls a belief system that devalues women—especially unmarried women—and creates a sense of female responsibility for themaintenance of the family. Women who believe that the end of a relationship or of a marriage represents a personal failure are less likely to leave abusive relationships. V TREATMENT AND PREVENTION A variety of programs and services, both for victims and offenders, exist to treat and prevent domestic violence. Since 1964, more than 1800 shelters...
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Courts in the United States.
The term circuit derives from the original structure of these courts. Under the Judiciary Act of 1789, trials of certain cases were required to be held before three-judge circuit courts consisting of two Supreme Court justices and the federal trial judge in the district court. In addition to their regular duties, Supreme Court justices were required to ride circuit, traveling from district to district within their assigned circuit, often covering great distances. In 1891 Congress establishe...
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Shark - biology.
Sharks have two-chambered hearts that are relatively small compared to the rest of their bodies. Blood flows from the heart to the gills, where it collects oxygen fromwater and then distributes it to the other organs and tissues. The small heart produces weak blood pressure, and many sharks must swim continuously to create themuscular contractions needed to circulate blood throughout their bodies. Most sharks are cold-blooded—that is, they do not generate heat by digesting food. Instead, the bod...
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Kansas - geography.
at the adjoining cities of Kansas City, Kansas, and Kansas City, Missouri. Its chief headstreams are the Republican and Smoky Hill rivers, which join to form the KansasRiver at Junction City. Each of the headstreams has numerous tributaries. The Kansas River proper is only 270 km (170 mi) long, but the Smoky Hill River has a lengthof 870 km (540 mi), and the Republican River has a length of 720 km (450 mi). The main tributary flowing into the Kansas River is the Big Blue River. The Arkansas Rive...
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Kansas - USA History.
at the adjoining cities of Kansas City, Kansas, and Kansas City, Missouri. Its chief headstreams are the Republican and Smoky Hill rivers, which join to form the KansasRiver at Junction City. Each of the headstreams has numerous tributaries. The Kansas River proper is only 270 km (170 mi) long, but the Smoky Hill River has a lengthof 870 km (540 mi), and the Republican River has a length of 720 km (450 mi). The main tributary flowing into the Kansas River is the Big Blue River. The Arkansas Rive...
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Agatha Christie
b. Miss Jane Marple : Miss Jane Marple, another famous character of the work of Agatha Christie appeared in 1930 in the novel The Murder at the Vicarage "and continue his career until 1979, having starred in a dozen novels inwhich it solves the murders of the most interesting as those "train from 16h50" or "At Bertram's Hotel". It is already old when it was discovered in the first book but that did not stop carrying out its various investigations. She leads a quiet life of single hardened in...
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Comedy
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INTRODUCTION
Laurel and Hardy
Stan Laurel, in overalls, and Oliver Hardy, left, formed one of the most popular comedy teams in motion-picture history.
The elements and techniques of comedy are diverse and differ from culture to culture. More than tragedy or serious drama, comic entertainment is controlled by socialconventions that define the boundaries of acceptable humor and topics that are taboo or off-limits for humor. What is considered funny in one place and time may beforbidden culturally or viewed as infantile or in poor taste in another. Virtually every component of human behavior is subject to comic treatment. This includes bodilyfunc...
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Radio Astronomy - astronomy.
equivalent to the apparent angular dimensions of a basketball at the distance of the moon. In 1984, the U.S. government appropriated funds for the construction of aninstallation called the very long baseline array (VLBA), a network of 10 radio antennas spread from the U.S.-Canadian border to Puerto Rico and from Hawaii to the U.S.Atlantic coast. The VLBA is expected to provide angular resolutions in the range of 200-millionths of an arc second. Canada and Australia are both planning similarprogr...
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Cheetah - biology.
animals such as zebras. Unlike most cats, cheetahs hunt during the day, when lions and hyenas that compete with them for prey are less likely to be active. Still,scientists in Tanzania have observed that cheetahs lose 10 to 13 percent of their kills to lions and hyenas. Alerted by the panic of a gazelle herd or by the circling ofvultures, lions and hyenas close in and easily drive the more timid cheetah away from a fresh kill. A cheetah usually stalks prey to within about 10 m (about 33 ft) and...
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Animation
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INTRODUCTION
Finding Nemo
A clown fish named Marlin, left, and his friend Dory search for Marlin's son in the computer-animated feature film Finding
Nemo (2003).
Animator at WorkAnimators use computers for every part of the animation process, from creating a storyboard (a scene-by-sceneillustration of the plot) to imitating camera movement. This animator is creating a scene for the motion picture Antz(1998).C. Lepetit/Liaison Agency If an animator is basing the animation project on drawings, one of the most common animation techniques, he or she will first create a series of rough sketches thatoften will be filmed in a pencil test (simple line drawings...
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Madrid - geography.
stores and offices on the first one or two levels. While many people rent their apartments, most own them and participate in cooperatives that maintain the building.Because living spaces are small by American standards, madrileños do most of their socializing in the streets, bars, restaurants, and parks of their neighborhoods. Onlya few very wealthy areas north of the city have single family houses with gardens and yards similar to those in American suburbs. Many of the newest neighborhoodsare c...