327 résultats pour "once"

• London (England) - geography.

  In the northern part of the West End is Bloomsbury, the city’s traditional intellectual center, with its concentration of bookshops and homes of writers and academics. Inthe early 20th century a number of famous writers, critics, and artists who lived here became known as the Bloomsbury Group. Here, too, is the British Museum, one ofLondon’s chief tourist attractions. Nearby is the giant complex of the University of London, whose various colleges and departments have taken over much ofBloomsbury...

• 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...

• Orthodox Church.

  formally defined by an ecumenical council, as it was in Catholicism, some Orthodox theologians have taught that the act of becoming a monk or the service of burial canalso be sacraments. The sacramental practice of the Orthodox differs in many details from Western customs. Baptism is administered by immersing the child or adult three times under thewater, each time in the name of one of the persons of the Trinity. It is followed immediately by anointment with chrism, a sacred perfumed oil that r...

• Electron I INTRODUCTION Models of the Atom Once scientists discovered the electron, they set out to explain how electrons behave in atoms.

  Electron Density and Orbital ShapesAtomic orbitals are mathematical descriptions of where the electrons in an atom (or molecule) are most likely to be found.These descriptions are obtained by solving an equation known as the Schrödinger equation, which expresses ourknowledge of the atomic world. As the angular momentum and energy of an electron increases, it tends to reside indifferently shaped orbitals. The orbitals corresponding to the three lowest energy states are s, p, and d, respectively....

• Tecumseh: "Once a Happy Race" Early in the 19th century, Governor William Henry Harrison of the Indiana Territory made a number of treaties with Native Americans that involved the ceding of land to the United States government.

• Nicolaus Copernicus I INTRODUCTION Nicolaus Copernicus (1473-1543), Polish astronomer, best known for his astronomical theory that the sun is at rest near the center of the universe, and that the earth, spinning on its axis once daily, revolves annually around the sun.

• Excerpt from Antony and Cleopatra - anthology.

  They seize Cleopatra Guard her till Caesar comes. Exit Gallus IRAS. Royal queen! CHARMIAN. O Cleopatra! Thou art taken, queen. CLEOPATRA. Quick, quick, good hands! She draws a dagger PROCULEIUS. Hold, worthy lady, hold! He disarms her Do not yourself such wrong, who are in thisRelieved, but not betrayed. CLEOPATRA. What, of death too,That rids our dogs of languish? PROCULEIUS. Cleopatra,Do not abuse my master's bounty byTh'undoing of yourself. Let the world seeHis nobleness well acted, which you...

• D-Day Invasion.

  The Allied planners focused on the beaches around Caen and the Cotentin Peninsula in northern France rather than those of Calais, even though it meant the forcewould be crossing at a wider part of the English Channel. That disadvantage was far outweighed by what the site offered: comparatively scanty defensive fortificationsand beachhead ideally suited for successful exits. The clincher was an isolated battlefield that the Germans would have difficulty reinforcing. The date was set for May 1, 19...

• Computer Memory.

  been created, information can be retrieved but not changed. Newer technologies allow ROMs to be semi-permanent—that is, the information can be changed, but ittakes several seconds to make the change. For example, a FLASH memory acts like a ROM because values remain stored in memory, but the values can be changed. C External Memory External memory can generally be classified as either magnetic or optical, or a combination called magneto-optical. A magnetic storage device, such as a computer'shar...

• Scramble for Africa.

  additional territorial grabs. The most significant of these rules stated that colonial powers were obligated to notify each other when they claimed African territory.Further, subsequent “effective occupation” of the claimed area was necessary for the claim to remain valid. Through it all, as Europeans negotiated their rights toAfrican territory, not a single African was present. Once the conference was over, it was clear that a European Scramble for African territories was underway. Southern Afr...

• Glacier.

  covered. In spring the snow cover begins to melt in the lower reaches, exposing the ice surface. As temperatures increase, the melting moves up the glacier. Thesnowline is the highest position the melting reaches during the year. Firn is old granular snow. The firn limit may not exactly coincide with the annual snowline since insome years rapid melting leaves behind firn patches below the snowline. Some glaciers exhibit features called ice streams and icefalls. Ice streams are valley glaciers th...

• 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...

• Human Nutrition.

  is one of the most preventable types of cancer. Nutritionists caution that most Americans need to eat more complex carbohydrates. In the typical American diet, only 40 to 50 percent of total calories come fromcarbohydrates—a lower percentage than found in most of the world. To make matters worse, half of the carbohydrate calories consumed by the typical American comefrom processed foods filled with simple sugars. Experts recommend that these foods make up no more that 10 percent of our diet, bec...

• Learning.

  B1 Acquisition The acquisition phase is the initial learning of the conditioned response—for example, the dog learning to salivate at the sound of the bell. Several factors can affect the speed of conditioning during the acquisition phase. The most important factors are the order and timing of the stimuli. Conditioning occurs most quickly when theconditioned stimulus (the bell) precedes the unconditioned stimulus (the food) by about half a second. Conditioning takes longer and the response is...

• 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....

• Planetary Science - astronomy.

  III ORIGINS AND COMPOSITIONS OF PLANETS Astronomers believe that planetary systems are formed of elemental materials that were created in the interiors of giant stars. Some of this material comes from giantstars that shed material into space as they age. Most of the matter to form planets, however, comes from stars that explode as supernovas and spread debris enrichedwith the heavier chemical elements into space. According to the currently accepted views, the most likely first stage in the evo...

• New Jersey - geography.

  C Soils Broadly defined, all of New Jersey’s soils are podzolic soils; that is, they are acidic and contain fairly high amounts of iron oxides. The soils in northern New Jersey areirregular in quality and contain rock fragments and small stones deposited by the continental glaciers of the last Ice Age. The soils of the inner coastal plain, unaffectedby glaciation, are the richest in the state, while those of the outer coastal plain are generally infertile. The newer soil classification system d...

• New Jersey - USA History.

  C Soils Broadly defined, all of New Jersey’s soils are podzolic soils; that is, they are acidic and contain fairly high amounts of iron oxides. The soils in northern New Jersey areirregular in quality and contain rock fragments and small stones deposited by the continental glaciers of the last Ice Age. The soils of the inner coastal plain, unaffectedby glaciation, are the richest in the state, while those of the outer coastal plain are generally infertile. The newer soil classification system d...

• France - country.

  In both the Paris and Aquitaine basins, fertile soils derived from limestone and wind-deposited dust, called loess, have supported prosperous agriculture since ancienttimes. Other lowlands in France are scattered and relatively small. They include the Alsace Plain in the east, bordering Germany, the valley of the Rhône River in thesoutheast, and the Languedoc Plain along the Mediterranean coast. A2 Uplands France contains several regions of uplands, the worn down remains of ancient mountain sys...

• 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...

• United Kingdom - country.

  B Natural Regions and Topography The island of Great Britain can be divided into two major natural regions—the highland zone and the lowland zone. The highland zone is an area of high hills andmountains in the north and west. The lowland zone in the south and east consists mostly of rolling plains. The zones are divided by an imaginary line running throughEngland from the River Exe on the southwest coast to the mouth of the River Tees on the northeast coast. The lowland zone has a milder climat...

• Abraham Lincoln I INTRODUCTION Abraham Lincoln (1809-1865), 16th president of the United States (1861-1865) and one of the great leaders in American history.

  fence in 4 hectares (10 acres) to grow corn. Then he hired out to neighbors, helping them to split rails. That year, Lincoln attended a political rally and was persuaded tospeak on behalf of a local candidate. It was his first political speech. A witness recalled that Lincoln “was frightened but got warmed up and made the best speech of theday.” In 1831 Lincoln made a second trip to New Orleans. He was hired, along with his stepbrother and a cousin, by Denton Offutt, a Kentucky trader and specul...

• Abraham Lincoln.

  fence in 4 hectares (10 acres) to grow corn. Then he hired out to neighbors, helping them to split rails. That year, Lincoln attended a political rally and was persuaded tospeak on behalf of a local candidate. It was his first political speech. A witness recalled that Lincoln “was frightened but got warmed up and made the best speech of theday.” In 1831 Lincoln made a second trip to New Orleans. He was hired, along with his stepbrother and a cousin, by Denton Offutt, a Kentucky trader and specul...

• Abraham Lincoln

  fence in 4 hectares (10 acres) to grow corn. Then he hired out to neighbors, helping them to split rails. That year, Lincoln attended a political rally and was persuaded tospeak on behalf of a local candidate. It was his first political speech. A witness recalled that Lincoln “was frightened but got warmed up and made the best speech of theday.” In 1831 Lincoln made a second trip to New Orleans. He was hired, along with his stepbrother and a cousin, by Denton Offutt, a Kentucky trader and specul...

• Abraham Lincoln - USA History.

  fence in 4 hectares (10 acres) to grow corn. Then he hired out to neighbors, helping them to split rails. That year, Lincoln attended a political rally and was persuaded tospeak on behalf of a local candidate. It was his first political speech. A witness recalled that Lincoln “was frightened but got warmed up and made the best speech of theday.” In 1831 Lincoln made a second trip to New Orleans. He was hired, along with his stepbrother and a cousin, by Denton Offutt, a Kentucky trader and specul...

• Japan - country.

  island’s fertile soils support agriculture and provide the vast majority of Japan’s pasturelands. In addition, Hokkaidō contains coal deposits, and the cold currents off itsshores supply cold-water fish. Winters are long and harsh, so most of Hokkaid ō is lightly settled, housing about 5 percent of Japan’s population on approximately 20 percent of its land area. However,its snowy winters and unspoiled natural beauty attract many skiers and tourists. Hokkaid ō is thought of as Japan’s northern fr...

• China - country.

  North China lies between the Mongolian Steppe on the north and the Yangtze River Basin on the south. It stretches west from the Bo Hai gulf and the Yellow Sea to theeastern edge of the Tibetan Plateau. Administratively, North China includes Beijing and Tianjin municipalities; Shandong and Shanxi provinces; most of Hebei, Henan,and Shaanxi provinces; and portions of Ningxia Hui Autonomous Region and of Jiangsu, Anhui, and Gansu provinces. Humans have lived in the agriculturally rich region of Nor...

• Genetics - biology.

  construct identical buildings. Just as each contractor would require a full copy of the blueprint to construct a complete building, each new cell needs a complete copy ofan organism’s genetic information to function properly. Organisms use two types of cell division to ensure that DNA is passed down from cell to cell during reproduction. Simple one-celled organisms and other organisms thatreproduce asexually—that is, without the joining of cells from two different organisms—reproduce by a proces...

• Comparative Anatomy.

  In comparing two species, anatomists have to be careful to differentiate between homologous structures, which are ones that have evolved from a shared ancestor, andanalogous structures, which have developed from different origins. Homologous structures are built on the same underlying plan. A human arm, a bat’s wing, and awhale’s flipper look quite different from the outside, but the bones inside reveal that these limbs all have the same basic structure. Analogous structures, by contrast,often l...

• Paris (city, France) - geography.

  Théâtre Musical de Paris and the Théâtre de la Ville. Just north of the Hôtel de Ville is the Pompidou Center, also known as Beaubourg, an arts complex devoted to modern and contemporary art and design. The structure,in steel and glass and featuring brightly colored, exposed pipes and ducts, is the work of Italian architect Renzo Piano and British architect Richard Rogers. Itscontroversial pop-art design contrasts sharply with the overall gray hue of the city, and was criticized by many followin...

• Massachusetts - geography.

  mi). Other large artificial lakes include Wachusett Reservoir, East Brimfield Reservoir, and Cobble Mountain Reservoir. Assawompsett Pond, covering about 10 sq km(about 4 sq mi), is the largest natural lake. North Watuppa Pond and Long Pond are other large natural lakes. Lake Chaubunagungamaug, near Webster, is usuallycalled Webster Lake, because the Algonquian name is difficult to pronounce and spell. The full version of the Native American name is said to be the longest place-namein North Amer...

• Arthurian Legend I INTRODUCTION King Arthur Legend and lore surround the life of Arthur, a medieval king of the Britons.

  Merlin and ArthurIn the tales of Arthurian legend, Merlin is an aged magician who helps bring King Arthur to power. Some authors alsodescribe Merlin as the young king’s tutor.Corbis Arthur is conceived when King Uther Pendragon falls in love with a married woman, Ygraine, and arranges for the magician Merlin to transform him into the likeness ofYgraine's husband. The husband, Gorlois, dies in battle, and Arthur's parents marry soon thereafter. Arthur Receiving ExcaliburAccording to legend, soon...

• 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...

• 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...

• Alaska - geography.

  depression surrounded by highlands and have the coldest winter and hottest summer temperatures in Alaska. Once the Kuskokwim River passes through theKuskokwim Mountains, it forms the southern edge of a vast lake-studded alluvial plain bounded on the north by the Yukon River. This water-logged lowland is a majorsummer nesting area for birds. Fairbanks is the major city in this region, while Fort Yukon is the major community in the Yukon Flats and Bethel the largest settlementon the Lower Kuskokwi...

• Alaska - USA History.

  depression surrounded by highlands and have the coldest winter and hottest summer temperatures in Alaska. Once the Kuskokwim River passes through theKuskokwim Mountains, it forms the southern edge of a vast lake-studded alluvial plain bounded on the north by the Yukon River. This water-logged lowland is a majorsummer nesting area for birds. Fairbanks is the major city in this region, while Fort Yukon is the major community in the Yukon Flats and Bethel the largest settlementon the Lower Kuskokwi...

• Plate Tectonics.

  ridges. The Mid-Atlantic Ridge is an underwater mountain range created at a divergent plate boundary in the middle of the Atlantic Ocean. It is part of a worldwidesystem of ridges made by seafloor spreading. The Mid-Atlantic Ridge is currently spreading at a rate of 2.5 cm per year (1 in per year). The mid-ocean ridges today are60,000 km (about 40,000 mi) long, forming the largest continuous mountain chain on earth. Earthquakes, faults, underwater volcanic eruptions, and vents, oropenings, along...

• Ship. I INTRODUCTION Ship, vessel that is buoyant in the water and used

  B1 Biremes Experience soon proved that longer ships posed a new set of problems: They were weaker structurally, more difficult to maneuver, and presented a larger target to anyenemy ship with a ram. In the 8th century BC Mediterranean shipbuilders eliminated these problems with the bireme , a war galley built to accommodate two levels, or banks , of oarsmen. Oarsmen on the lower level rowed oars from ports cut into the side of the vessel, while those above rowed from the deck. This arrangemen...

• Memory (psychology).

  memory span —how many items people can correctly recall in order. Researchers would show people increasingly long sequences of digits or letters and then ask them to recall as many of the items as they could. In 1956 American psychologist George Miller reviewed many experiments on memory span and concluded that peoplecould hold an average of seven items in short-term memory. He referred to this limit as “the magical number seven, plus or minus two” because the results of thestudies were so consi...

• 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...

• American Revolution.

  C1 The South Southern agriculture was founded on the cultivation of tobacco, wheat, and corn in Virginia, Maryland, and North Carolina, and of rice and indigo (a blue dye) in SouthCarolina and Georgia. There was a large demand for these crops in Europe. These crops were cultivated with the help of black slaves imported from Africa. The whiteplanter class in the South was the most powerful, both politically and economically. C2 The North Wheat was the main cash crop of the mid-Atlantic colonies...

• American Revolution - U.

  C1 The South Southern agriculture was founded on the cultivation of tobacco, wheat, and corn in Virginia, Maryland, and North Carolina, and of rice and indigo (a blue dye) in SouthCarolina and Georgia. There was a large demand for these crops in Europe. These crops were cultivated with the help of black slaves imported from Africa. The whiteplanter class in the South was the most powerful, both politically and economically. C2 The North Wheat was the main cash crop of the mid-Atlantic colonies...

• Mumbai - geography.

  number of people employed by them increased from 7,000 in the 1860s to 73,000 in 1900. Mumbai also prospered as an international port with the 1869 opening ofthe Suez Canal, which shortened the shipping route to Europe. Today most of India’s cotton continues to be grown in the Mumbai hinterland on a fertile, lava-based soilknown as black cotton soil. Textiles remain the dominant industry, employing more than half the workforce. Other important products of Mumbai include refined oil,petrochemical...

• Dog Family - biology.

  muzzles, long and bushy tails, and large ears. Many foxes hunt by stalking prey and then leaping on it with a distinctive, stiff-legged pounce. Once thought to besolitary animals, foxes are now known to live in groups of up to six individuals. The remaining canids are each highly distinctive. Raccoon dogs and bush dogs are the least doglike canids in appearance. Raccoon dogs, found in eastern Asia, havestubby legs, a stout body, short ears, shaggy fur, and a black face mask that resembles a racc...

• Poliomyelitis.

  Physical therapy helps patients with paralytic polio stretch and move affected muscles. This movement minimizes the atrophy, or shrinkage, of affected muscles andlimbs and builds strength. Exercises can also retrain working muscles to compensate for other muscles that have permanently lost the ability to move. Rehabilitativetherapy trains patients to use braces, crutches, and other devices that provide support and aid mobility. V PREVENTION OF POLIO Immunization with polio vaccine is the best w...

• Excerpt from The Old Curiosity Shop - anthology.

  'Well!' muttered Quilp, as he marked her earnest look. 'I believe you. Humph! Gone already? Gone in four-and-twenty hours I What the devil has he done with it,that's the mystery!' This reflection set him scratching his head and biting his nails once more. While he was thus employed his features gradually relaxed into what was with him acheerful smile, but which in any other man would have been a ghastly grin of pain, and when the child looked up again she found that he was regarding her with...

• Boxing.

  C Offensive Techniques To be effective, boxers must have an assortment of punches that are coordinated with their footwork. Less powerful punches often serve the important role of settingup the fighter’s chief “weapons,” as boxing analysts sometimes call a boxer’s main offensive skills. C1 Feinting Moving the hands or head to confuse an opponent is called feinting. A smart boxer will first test the opponent by trying different feints, noting the reaction to each onebefore deciding which will b...