583 résultats pour "often"

• Paleolithic Art I INTRODUCTION Cave Painting, Lascaux This portion of a cave painting in what is now Lascaux, France, was done by Paleolithic artists about 13,000 bc.

  Venus of WillendorfThis so-called Venus figurine from the area of Willendorf, Austria, is one of the earliest known examples of sculpture,dating from about 23,000 bc. The figure, which is carved out of limestone, is only 11.25 cm (4.5 in) high, and wasprobably designed to be held in the hand. It is believed the Venus may be a fertility symbol, which would explain theexaggerated female anatomy.Ali Meyer/Bridgeman Art Library, London/New York Paleolithic art usually is classified as either figura...

• Poetry I INTRODUCTION Phyllis McGinley American poet and author Phyllis McGinley composed light, witty verse, much of which deals with family life.

  repetition of certain lines and the rhyming of certain lines. The Provençal sestina features a set of six words that end lines (end-words), repeated in a dizzyingly complexpattern. The range of effects created by the poetic line varies tremendously depending on its length, its patterns of repetition, and whether the sentence stops at the end of theline (end-stopped) or carries over the end of the line (enjambed). Many of the earliest examples of Old English poetry feature an accentual line with...

• Heart.

  situation. A Cardiac Cycle Although the right and left halves of the heart are separate, they both contract in unison, producing a single heartbeat. The sequence of events from the beginning ofone heartbeat to the beginning of the next is called the cardiac cycle. The cardiac cycle has two phases: diastole, when the heart’s chambers are relaxed, and systole,when the chambers contract to move blood. During the systolic phase, the atria contract first, followed by contraction of the ventricles. T...

• Stone Age.

  limestone, quartzite, and indurated shale. Ground stone tools could be made on a wider range of raw material types, including coarser grained rock such as granite. Flaking produces several different types of stone artifacts, which archaeologists look for at prehistoric sites. The parent pieces of rock from which chips have beendetached are called cores, and the chips that have been removed from cores are called flakes. A flake that has had yet smaller flakes removed from one or more edgesin orde...

• Alzheimer's Disease.

  compared residents of Ibadan, Nigeria, who eat a mostly low-fat vegetarian diet, with African Americans living in Indianapolis, Indiana, whose diet included a variety ofhigh-fat foods. The Nigerians were less likely to develop Alzheimer’s disease compared to their U.S. counterparts. Some researchers suspect that health problems suchas high blood pressure, atherosclerosis (arteries clogged by fatty deposits), high cholesterol levels, or other cardiovascular problems may play a role in the devel...

• 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...

• Exercise.

  broad, and most studies suggest a positive relationship between physical fitness and mental achievement. The relationship between regular aerobic exercise and cardiovascular health and longevity is well established. Regular exercise leads to a reduction in the risk ofcoronary heart disease, in which fatty deposits (plaque) form in blood vessels supplying the muscular wall of the heart, compromising oxygen delivery to the heartmuscle. In addition, with regular exercise the efficiency of the heart...

• Asian Theater I INTRODUCTION Asian Theater, live performance, featuring actors or puppets, native to Asia, a continent with more than 2 billion people of many nations and cultures.

  III THEATER IN EAST ASIA Theater in East Asia includes the traditions of China, Japan, and Korea. Most Chinese theater is urban, secular (nonreligious) entertainment, influenced by the ethics of Confucianism. However, a belief in spirits influences rituals performed by ethnic minorities in China, and Buddhism dominates traditional Tibetan performance. Japanesedramatic forms combine native shamanistic performance, secular entertainment, and cultural or religious influences from China and Kore...

• Church of Jesus Christ of Latter-day Saints.

  yearly visited a book written in a hieroglyphic script on golden plates buried in a nearby hill; the book’s location, he said, had been disclosed to him by an angel. In 1830he completed the translation of these plates, “by the gift and power of God,” and published the Book of Mormon, which he believed to be a religious record of theancient inhabitants of North America. On April 6, 1830, he organized the Church of Christ, soon known by its present title, the Church of Jesus Christ of Latter-daySa...

• Artificial Intelligence.

  Work in AI has primarily focused on two broad areas: developing logic-based systems that perform common-sense and expert reasoning, and using cognitive andbiological models to simulate and explain the information-processing capabilities of the human brain. In general, work in AI can be categorized within three research anddevelopment types: symbolic, connectionist, and evolutionary. Each has characteristic strengths and weaknesses. A Symbolic AI Symbolic AI is based in logic. It uses sequences...

• Native Americans of North America.

  addition to smallpox and measles, explorers and colonists brought a host of other diseases: bubonic plague, cholera, typhoid fever, scarlet fever, pleurisy, mumps,diphtheria, pneumonia, whooping cough, malaria, yellow fever, and various sexually transmitted infections. Despite the undisputed devastation wreaked on Indian populations after European contact, native populations showed enormous regional variability in their response todisease exposure. Some peoples survived and, in some cases, even...

• Native Americans of North America - Canadian History.

  addition to smallpox and measles, explorers and colonists brought a host of other diseases: bubonic plague, cholera, typhoid fever, scarlet fever, pleurisy, mumps,diphtheria, pneumonia, whooping cough, malaria, yellow fever, and various sexually transmitted infections. Despite the undisputed devastation wreaked on Indian populations after European contact, native populations showed enormous regional variability in their response todisease exposure. Some peoples survived and, in some cases, even...

• 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...

• Race - biology.

  distributed as a cline, generally varying along a north-south line. Skin color is lightest in northern Europeans, especially in those who live around the Baltic Sea, andbecomes gradually darker as one moves toward southern Europe, the Mediterranean, the Middle East, and into northern Africa and northern subtropical Africa. Skin isdarkest in people who live in the tropical regions of Africa. The lack of clear-cut discontinuities makes any racial boundary based on skin color totally arbitrary. Sim...

• Middle Ages .

  Saints were very important in Late Antiquity. They were considered both models of virtue and powerful miracle workers. One of the most well-known saints of the periodwas Saint Anthony. Anthony gave away all his possessions and left his hometown in Egypt to live alone in the desert and pray. Anthony was one of the first Christianmonks. The word monk comes from a term meaning 'alone.' Gradually Anthony attracted followers, and he eventually became the center of a whole community of monks who wis...

• Roman Empire .

  A Government Augustus did not derive his power from any single office, but from the authority of his name and his victory. In fact, he carefully pieced together a patchwork of powersthat allowed him to be an absolute ruler and yet avoid the hatred Caesar aroused as dictator. In Latin, the name Augustus implies both political authority and religiousrespect. The Romans had for some time called Octavian imperator , a title once awarded to victorious generals that soon became associated with the r...

• Roman Empire - History.

  A Government Augustus did not derive his power from any single office, but from the authority of his name and his victory. In fact, he carefully pieced together a patchwork of powersthat allowed him to be an absolute ruler and yet avoid the hatred Caesar aroused as dictator. In Latin, the name Augustus implies both political authority and religiousrespect. The Romans had for some time called Octavian imperator , a title once awarded to victorious generals that soon became associated with the r...

• Charles Dickens.

  The Old Curiosity Shop broke hearts across Britain and North America when it first appeared. Later readers, however, have found it excessively sentimental, especially the pathos surrounding the death of its child-heroine Little Nell. Dickens’s next two works proved less popular with the public. Barnaby Rudge, Dickens’s first historical novel, revolves around anti-Catholic riots that broke out in London in 1780. The events in Martin Chuzzlewit become a vehicle for the novel’s theme: selfishne...

• Wolfgang Amadeus Mozart.

  including the sacred style of church music and the so-called galant (courtly) idiom. The elegant though often superficial galant style dominated much instrumental music of the 1760s and 1770s. Mozart’s mastery often demonstrates itself in an ability to expand and deepen the stylistic possibilities of the time. The manner in which heextended the character and form of the concerto, for instance, owes much to his experience in writing operatic arias. A Musical Expressiveness In the masterful Je...

• Blood.

  substances. For example, a person who is blood type A positive will not make antibodies against the A or Rh markers, but will make antibodies against the B marker,which is not on that person’s own red blood cells. If blood containing the B marker (from types B positive, B negative, AB positive, or AB negative) is transfused into thisperson, then the transfused red blood cells will be rapidly destroyed by the patient’s anti-B antibodies. In this case, the transfusion will do the patient no good a...

• Native Americans of Middle and South America.

  A line that snakes across central Mexico near the Tropic of Cancer forms the northern boundary of Mesoamerica; north of this line rainfall sharply declines and theclimate is much drier. The ancient civilizations of Mesoamerica all arose and developed in the area between this line and the Guatemalan highlands far to the south. Richvolcanic soils are found throughout much of the region. A2 People and Languages Mesoamerica was a great melting pot, home to many peoples and interrelated cultures. In...

• Roman Art and Architecture - History.

  Racecourses or circuses were also built in many cities for holding chariot races and horse races. Rome’s circus-shaped Piazza Navona occupies the site of one that wasbuilt during the reign ( AD 81-96) of the emperor Domitian. The largest circus in Rome, the Circus Maximus, held about 200,000 spectators. E Public Baths Large cities and small towns alike also had public baths ( thermae ); under the Republic they were generally made up of a suite of dressing rooms and bathing chambers with hot- ,...

• African American History - U.

  In their day-to-day lives, slaves and servants shared similar grievances and frequently formed alliances. Advertisements seeking the return of slaves and servants whohad run away together filled colonial newspapers. When a slave named Charles escaped in 1740, the Pennsylvania Gazette reported that two white servants, a 'Scotch man' and an Englishman, escaped with him. Sometimes interracial alliances involved violence. During Bacon's Rebellion in 1676, slaves and servants took up armsagainst Na...

• Segregation in the United States - U.

  acts of discrimination. Writing for the court, Justice Joseph Bradley declared: “When a man has emerged from slavery, and by the aid of beneficent legislation ... theremust be some stage in the progress of his elevation when he takes the rank of a mere citizen, and ceases to be the special favorite of the laws, and when his rights as acitizen, or a man, are to be protected in the ordinary modes by which other men’s rights are protected.” Rather than being the “special favorites” of the law, blac...

• 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...

• Asia - Geography.

  Borneo, the world’s third largest island after Greenland and New Guinea. To the southeast is the Timor Sea separating the Asian island of Timor from the Australiancontinent. The Indian subcontinent is flanked by the Bay of Bengal on the east and the Arabian Sea on the west. The island of Sri Lanka and the much smaller Maldives andNicobar Islands trail away to the south. The Arabian Sea’s Gulf of Aden, the Red Sea, the Mediterranean Sea, and the Black Sea form an arc along the western rim of Asia...

• Asia - History.

  Borneo, the world’s third largest island after Greenland and New Guinea. To the southeast is the Timor Sea separating the Asian island of Timor from the Australiancontinent. The Indian subcontinent is flanked by the Bay of Bengal on the east and the Arabian Sea on the west. The island of Sri Lanka and the much smaller Maldives andNicobar Islands trail away to the south. The Arabian Sea’s Gulf of Aden, the Red Sea, the Mediterranean Sea, and the Black Sea form an arc along the western rim of Asia...

• Asteroid - astronomy.

  Asteroids of the S type, related to the stony iron meteorites, make up about 15 percent of the total population of asteroids that can be seen from Earth. Much rarer arethe M-type objects, corresponding in composition to the meteorites known as “irons.” These objects are made up of an iron-nickel alloy and may represent the cores ofbodies that were large enough to differentiate into layers and to melt deep inside. Their rocky outer layers may have been removed by impacts with other asteroids . A...

• Mountain Climbing.

  teeth on one side, and a straight, flat, metal blade called an adze on the other. Ice axes have many uses. One of the most common is to help the climber stay balanced on steep slopes. The climber swings the axe with a short, quick movement to lodge the pick in snow or ice, creating a secure anchor. If a climber should slip and beginsliding down a snowfield, a self-arrest can be performed by turning face down on the snow and burying the pick in the snow surface. The climber’s weight over the...

• Czech Republic - country.

  enforcement of environmental regulations. Environmental considerations have also led some government officials to promote nuclear energy as a key source of powerfor the country’s future. The Czech Republic produces most of its energy by burning domestic coal. Much of the coal burned is low quality with a high ash and sulfur content—a key componentof acid rain—producing high levels of air pollution. Forests in the Czech Republic are among the most seriously affected by acid rain in all of Europe....

• 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...

• Spanish Empire.

  Spain’s royal government quickly imposed its own officials, first to collect taxes and then to administer the colony. Its goal was to assert royal control over both settlersand indigenous peoples. In Spain the government established a House of Trade to supervise colonial affairs and to oversee, license, and tax all trade and commerce. Asthe royal government asserted more authority over colonial activities, Columbus lost effective power, and was eventually replaced by other colonial governors. Wi...

• Spanish Empire .

  Spain’s royal government quickly imposed its own officials, first to collect taxes and then to administer the colony. Its goal was to assert royal control over both settlersand indigenous peoples. In Spain the government established a House of Trade to supervise colonial affairs and to oversee, license, and tax all trade and commerce. Asthe royal government asserted more authority over colonial activities, Columbus lost effective power, and was eventually replaced by other colonial governors. Wi...

• United States History - U.

  and improved upon the designs of Arab sailing ships and learned to mount cannons on those ships. In the 15th century they began exploring the west coast ofAfrica—bypassing Arab merchants to trade directly for African gold and slaves. They also colonized the Madeira Islands, the Azores, and the Cape Verde Islands andturned them into the first European slave plantations. The European explorers were all looking for an ocean route to Asia. Christopher Columbus sailed for the monarchs of Spain in 149...

• United States History - U.

  and improved upon the designs of Arab sailing ships and learned to mount cannons on those ships. In the 15th century they began exploring the west coast ofAfrica—bypassing Arab merchants to trade directly for African gold and slaves. They also colonized the Madeira Islands, the Azores, and the Cape Verde Islands andturned them into the first European slave plantations. The European explorers were all looking for an ocean route to Asia. Christopher Columbus sailed for the monarchs of Spain in 149...

• Michigan - geography.

  The interior location of Michigan in the northern part of North America results in a continental climate, characterized by four definite seasons with moist, mild to hotsummers and snowy, cold winters. Winds off of Lakes Michigan and Superior in winter create heavy snow accumulations in nearby areas. The tempering effects of LakeMichigan account for the presence of the state’s famous fruit-growing belt along the lake’s shore. Since the water is colder than the land in spring, the westerly windspa...

• Michigan - USA History.

  The interior location of Michigan in the northern part of North America results in a continental climate, characterized by four definite seasons with moist, mild to hotsummers and snowy, cold winters. Winds off of Lakes Michigan and Superior in winter create heavy snow accumulations in nearby areas. The tempering effects of LakeMichigan account for the presence of the state’s famous fruit-growing belt along the lake’s shore. Since the water is colder than the land in spring, the westerly windspa...

• American Westward Movement - U.

  British expansion. However, Native Americans of the Great Lakes and Ohio Valley lashed out against the English in an attempt to preserve their independence, theirland, and their way of life. With the Ottawa chief Pontiac as their most visible leader, the tribes waged a bloody and costly war. As a result, the British governmentdecided to keep the white settlers apart from the Native Americans. It issued the Royal Proclamation of 1763, banning all white settlement beyond the Appalachians andstatin...

• Rhythm-and-Blues Music I INTRODUCTION Tina Turner American singer Tina Turner began performing rhythm-and-blues music in a band led by her former husband, Ike Turner, in the 1960s.

  thousands of black Americans migrated from the rural South to Midwest, Northeast, and West Coast cities. In popular music, new styles were created to meet thechanging tastes of this demographic group, leading to the development of the urbane sounds of R&B. The profound sociological changes of the World War II period were accompanied by two significant technological developments: the invention of the electric guitar in thelate 1930s and the discovery of the German-invented tape recorder by the mu...

• Ancient Rome .

  attributed to Numa, including the selection of virgins to be priestesses of the goddess Vesta. He also established a calendar to differentiate between normal workingdays and those festival days sacred to the gods on which no state business was allowed. His peaceful reign lasted from 715 to 673 BC. Under Tullus Hostilius (672–641 BC) the Romans waged an aggressive foreign policy and began to expand their lands by the conquest of nearby cities like Alba Longa. When the warlike King Hostilius co...

• Ancient Rome - USA History.

  attributed to Numa, including the selection of virgins to be priestesses of the goddess Vesta. He also established a calendar to differentiate between normal workingdays and those festival days sacred to the gods on which no state business was allowed. His peaceful reign lasted from 715 to 673 BC. Under Tullus Hostilius (672–641 BC) the Romans waged an aggressive foreign policy and began to expand their lands by the conquest of nearby cities like Alba Longa. When the warlike King Hostilius co...

• Prints and Printmaking I INTRODUCTION Prints and Printmaking, pictorial images that can be inked onto paper, and the art of creating and reproducing them.

  Bewick’s The SkylarkBritish engraver Thomas Bewick’s The Skylark is part of his History of British Birds (2 vols., 1797 and 1804). Bewick wasthe first artist to demonstrate the full potential of wood engraving and is renowned for his fine natural history illustrations.Each illustration shows some of the bird’s natural habitat.Folio Society, London/Bridgeman Art Library, London/New York Historically, the wood engraving was chiefly used for illustrations in magazines and books. It is similar to th...

• Spain - country.

  B Natural Resources Spain has a number of mineral resources. The largest known deposits are of iron ore, zinc, and lead. Spain also produces significant quantities of copper and mercury.These deposits are mined mainly in Huelva province in southwestern Spain, around Cartagena on the Mediterranean, and at various points along the Bay of Biscay inthe north. Additionally, uranium is mined in the region of Extremadura, near the Portuguese frontier, where pyrites, fluorspar, gypsum, tungsten, and po...

• Guatemala - country.

  C Climate The climate of Guatemala varies according to elevation, from hot coastal plains to cold mountain heights. Most of the population lives between 900 and 2,400 m (3,000and 8,000 ft) above sea level, where there are warm days and cool nights with average annual temperatures of 20°C (68°F). The coastal regions are hot and humid,with average annual temperatures of 28°C (83°F). A rainy season, from May through October, is sometimes called “winter” because it brings cloudy afternoons andlower...

• Wetland.

  Other plants and animals have special adaptations suited for living in a wet environment. Most emergent plants have air spaces in their stems that enable oxygen to betransported to roots that grow in sediments with no oxygen. Some of the trees that grow in swamps form a set of roots above the soil surface or above the water thatallows them to get oxygen to the lower roots. In saltwater wetlands, specialized cells can limit the amount of salt that enters a plant, or specialized organs can excrete...

• Archaeology.

  Prehistoric archaeology is practiced by archaeologists known as prehistorians and deals with ancient cultures that did not have writing of any kind. Prehistory, a term coined by 19th-century French scholars, covers past human life from its origins up to the advent of written records. History—that is, the human past documented insome form of writing—began 5000 years ago in parts of southwestern Asia and as recently as the late 19th century AD in central Africa and parts of the Americas. Becaus...

• Bible.

  collection of many different books. The Old Testament is by no means a unified book in terms of authorship, date of composition, or literary type; it is instead a veritablelibrary. Generally speaking, the books of the Old Testament and their component parts may be identified as narratives, poetic works, prophetic works, law, or apocalypses.Most of these are broad categories that include various distinct types or genres of literature and oral tradition. None of these categories is limited to the...

• Pennsylvania - geography.

  B Rivers and Lakes There are three major river basins in Pennsylvania: the Susquehanna, the Ohio, and the Delaware. Together they drain more than 90 percent of Pennsylvania’s landarea. Most of eastern and central Pennsylvania is drained by the Susquehanna and Delaware systems. The western part of the state is drained by the Allegheny andMonongahela rivers, which join at Pittsburgh to form the Ohio. In addition to the three major river basins, short streams flowing into Lake Erie drain the north...

• Pennsylvania - USA History.

  B Rivers and Lakes There are three major river basins in Pennsylvania: the Susquehanna, the Ohio, and the Delaware. Together they drain more than 90 percent of Pennsylvania’s landarea. Most of eastern and central Pennsylvania is drained by the Susquehanna and Delaware systems. The western part of the state is drained by the Allegheny andMonongahela rivers, which join at Pittsburgh to form the Ohio. In addition to the three major river basins, short streams flowing into Lake Erie drain the north...