583 résultats pour "often"

• Plant - biology.

  B1 Vacuoles Vacuoles are membrane-bound cavities filled with cell sap, which is made up mostly of water containing various dissolved sugars, salts, and other chemicals. B2 Plastids Plastids are types of organelles, structures that carry out specialized functions in the cell. Three kinds of plastids are important here. Chloroplasts contain chlorophyllsand carotenoid pigments; they are the site of photosynthesis, the process in which light energy from the sun is fixed as chemical energy in the b...

• Money.

  A Early Monetary Regulations In the American colonies, coins of almost every European country circulated, with the Spanish dollar predominating. Because of the scarcity of coins, the colonists alsoused various primitive mediums of exchange, such as bullets, tobacco, and animal skins. Many of the colonies issued paper money that circulated at varying rates ofdiscount. The first unified currency consisted of the notes issued by the Continental Congress to finance the American Revolution. These no...

• Elephant - biology.

  B Trunk An elephant's nose and upper lip are combined in a long, limber trunk, an exceptionally supple appendage with an estimated 150,000 muscles. The versatile trunk actslike a hand for grasping low-growing shrubs and other food and placing it into the mouth; an arm for breaking off tree branches; or a snorkel for breathing when theelephant's body is submerged. Elephants also use their trunks to suck up water and squirt it into their mouths for drinking or over their bodies for bathing. Nostr...

• Pollution.

  One of the greatest challenges caused by air pollution is global warming, an increase in Earth’s temperature due to the buildup of certain atmospheric gases such ascarbon dioxide. With the heavy use of fossil fuels in the 20th century, atmospheric concentrations of carbon dioxide have risen dramatically. Carbon dioxide and othergases, known as greenhouse gases, reduce the escape of heat from the planet without blocking radiation coming from the Sun. Because of this greenhouse effect,average glob...

• 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...

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

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

• Religion.

  By the end of the 19th century, scholars were making religion an object of systematic inquiry. Müller’s comparative approach was adopted in many European andJapanese universities, and as a result the common features of world religions (such as gods, prayer, priesthood, and creation myths) were the subjects of sustainedscholarly investigation. In addition, field anthropologists had begun to compile firsthand accounts of the religions of peoples who previously had been dismissed assavages. The stu...

• Marriage.

  In many traditional societies, marriage typically involved transfers of property from the parents to their marrying children or from one set of parents to the other. Thesecustoms persist in some places today and are part of the tradition of arranged marriages. For example, in some cultures the bride’s parents may give property (knownas a dowry) to the new couple. The practice of giving dowries has been common in countries such as Greece, Egypt, India, and China from ancient times until thepresen...

• Ghana - country.

  times of depressed cacao prices, Ghana has significantly increased exports of timber to generate needed revenue. In 1988 Ghana initiated a conservation plan called the Forest Resource Management Project. In 1989 Ghana restricted the export of 18 tree species, and in 1994 thecountry banned the export of raw logs. About 4.8 percent (1997) of the country’s land is officially protected, but illegal logging threatens Ghana’s remaining forests. Deforestation, overgrazing, and periodic drought have led...

• Kenya - country.

  threatens fish and other water life in the lake by depriving them of oxygen. Kenya is well known for its game parks—including Masai Mara Game Park and Tsavo National Park in the south, and Marsabit National Reserve in the north—whichattract large numbers of tourists and much revenue. Conservation of wildlife within reserves has thus received high priority. About 13 percent (2007) of Kenya’s totalland is protected. There are 229 (2004) threatened species in Kenya. Threatened habitats include the...

• 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...

• Mississippi - geography.

  The climate of Mississippi is characterized by long, hot, and humid summers and generally mild winters. The higher lands in the northeast are usually cooler than otherareas of the state. D1 Temperature Average January temperatures range from about 6° C (about 42° F) in northeastern Mississippi to about 12° C (about 54° F) along the Gulf Coast. No part of the stateis entirely free from freezing temperatures, but prolonged periods of extreme cold rarely occur. Temperatures more than 15° C (30° F)...

• Mississippi - USA History.

  The climate of Mississippi is characterized by long, hot, and humid summers and generally mild winters. The higher lands in the northeast are usually cooler than otherareas of the state. D1 Temperature Average January temperatures range from about 6° C (about 42° F) in northeastern Mississippi to about 12° C (about 54° F) along the Gulf Coast. No part of the stateis entirely free from freezing temperatures, but prolonged periods of extreme cold rarely occur. Temperatures more than 15° C (30° F)...

• New Mexico - geography.

  New Mexico’s major river is the Río Grande, originating in southern Colorado, and flowing southward for 760 km (470 mi) through the state. Between the San LuisValley and Española Valley the river flows in a deep canyon known as the Río Grande Gorge; then, below White Rock Canyon, it flows through several valleys containingagricultural land. Most of the water of the Río Grande is used to irrigate these valleys. The Río Grande’s waterflow in New Mexico is extremely low. One of the major tributarie...

• New Mexico - USA History.

  New Mexico’s major river is the Río Grande, originating in southern Colorado, and flowing southward for 760 km (470 mi) through the state. Between the San LuisValley and Española Valley the river flows in a deep canyon known as the Río Grande Gorge; then, below White Rock Canyon, it flows through several valleys containingagricultural land. Most of the water of the Río Grande is used to irrigate these valleys. The Río Grande’s waterflow in New Mexico is extremely low. One of the major tributarie...

• World War II .

  the Nazi-Soviet Pact was signed. In the part published the next day, Germany and the Soviet Union agreed not to go to war against each other. A secret protocol gaveStalin a free hand in Finland, Estonia, Latvia, eastern Poland, and eastern Romania. See also German-Soviet Nonaggression Pact. III MILITARY OPERATIONS In the early morning hours of September 1, 1939, the German armies marched into Poland. On September 3 the British and French surprised Hitler by declaring war onGermany, but they...

• Turkey - country.

  has a general elevation of 900 to 1,500 m (3,000 to 5,000 ft) above sea level. The eastern highlands region is the most mountainous and rugged portion of Turkey; Mount Ararat (Ağrı Da ğı) is the highest peak in the country at 5,165 m (16,945ft). Many Christians and Jews believe it to be the same Mount Ararat mentioned in the Bible as the place where Noah’s ark came to rest. The eastern highlands are thesource for both the Tigris (Dicle) and Euphrates (Fir āt)—two of southwestern Asia’s principal...

• South Africa - country.

  The major soil zones are conditioned largely by climatic factors. In the semiarid north and west, soils are alkaline and poorly developed. In the southern part of WesternCape Province, rain falls mostly in the winter months, and soils there form slowly and are generally thin and immature. The moderate temperatures and summer rainfallof the High Veld and eastern coastal areas create conditions for more productive organic decomposition, leading to dark, fertile soils, or chernozems, similar to tho...

• Iraq - country.

  The Euphrates begins in Turkey, crosses Syria, and enters Iraq at Abū Kam āl. The flow of the Euphrates into Iraq has been greatly reduced by dams built by Turkeyand Syria. The gradient of the Euphrates above the town of H īt, in west central Iraq, is steep. In the 2,640 km (1,640 mi) from its source in Turkey to H īt, the river fallsfrom 3,000 m (10,000 ft) to a low water elevation of 50 m (170 ft) above sea level, an average drop of 1 m per km (6 ft per mi). In Iraq below H īt the fall is very...

• Slavery in Africa.

  The spread of Islam from Arabia into Africa after the religion’s founding in the 7th century AD affected the practice of slavery and slave trading in West, Central, and East Africa. Arabs had practiced slave raiding and trading in Arabia for centuries prior to the founding of Islam, and slavery became a component of Islamic traditions.Both the Qur'an (Koran) (the sacred scripture of Islam) and Islamic religious law served to codify and justify the existence of slavery. As Muslim Arabs conquered...

• Slavery in Africa - history.

  Arab Slave TradersThis 19th-century engraving depicts an Arab slave trading caravan transporting black African slaves across the Sahara. The trans-Saharan slave trade developed in the 7th and 8th centuries, as Muslim Arabs conquered most of North Africa. The trade grewsignificantly from the 10th to the 15th century and peaked in the mid-19th century.Archive Photos The spread of Islam from Arabia into Africa after the religion’s founding in the 7th century AD affected the practice of slavery and...

• Lamia

  reason would tell him that it is not safe enough to depend only on a career as a poet. He saw in himself the ability and didn't let count anything else what could speak against the life of poet. This alike attitude is seen in Lycius when he listens to Lamia not to invite Appolonius to the marriage, even though he had learned everything by Appolonius, had always listen to his advices and obeyed his words. It is as if Keats saw himself turning away from his reason, shutting it out from his dream-l...

• Map - geography.

  Relief MapRelief maps are three-dimensional models of the terrain in an area; on them, color and scale are used to indicate geographicalfeatures rather than simply to delineate political boundaries. Because of this feature, relief maps are extensively used in engineeringand the military. This map shows portions of Alaska and northwestern Canada.United States Geological Survey Among the most important of the special-purpose maps are hydrographic and aviation charts. Hydrographic charts are used f...

• Compositionality

  sentence construction, an operation on meanings, such that the meaning of any sentence is mechanically determined by applying the operations on meanings (given by the rules used in constructing the sentence) to the meanings of the simple parts. (Often a host of extra restrictions are incorporated. For example: the operations may be limited to applying function to argument; the order in which operations are applied may be settled by the structure of the sentence.) Some see such principles as prov...

• Poker.

  After the ante and the initial deal, the first round of betting starts with the player to the left of the dealer. This bettor can check (make no bet), make a bet, or fold. To stay in the game, subsequent bettors must call (match the current bet) or raise (increase the total bet). A round of betting ends when no player makes a further bet or a set limit of turns around the table has been reached. In the next round of betting, the player to the left of the bettor that started the last round o...

• Network (computer science).

  computer. Since there is only one token in the network, only one computer can transmit information at a time. Token Ring networks are now quite rare. Most LANs nowuse Ethernet technology. International Business Machines Corporation (IBM), the company that invented Token Ring in the early 1980s, no longer promotes thetechnology. In the mid-1990s a new protocol called Asynchronous Transfer Mode (ATM) was introduced. This protocol encodes data in fixed-sized packets called cells rather thanvariable...

• William Faulkner I INTRODUCTION William Faulkner Twentieth-century American novelist William Faulkner wrote novels that explored the tensions between the old and the new in the American South.

  Faulkner’s “powerful and artistically unique contribution to the modern American novel.” He also wrote numerous short stories, many of the best of which werepublished in book form in Go Down, Moses (1942) and The Collected Stories (1950; Pulitzer Prize, 1951). In-between his fiction works, which until late in his career did not always pay well, Faulkner wrote screenplays for Hollywood; two of his more prominent scripts were for the motion pictures To Have and Have Not (1944) and The Big S...

• Fur Trade in North America - Canadian History.

  Injured by the competition from the North West Company, the Hudson’s Bay Company changed its methods in the late 18th century and began extending its operationsinland. After a period of intense and often violent conflict, the two companies merged in 1821 under the charter of the Hudson’s Bay Company. The trade monopoly andpower to govern that had been originally given to Hudson’s Bay in 1670 were extended to all British-held territory west of Rupert’s Land. The company dominated mostof present-d...

• Crafts.

  VI POTTERY Ceramic objects can be molded completely by hand or thrown (shaped) on a potter's wheel, a device with a rotating horizontal disk. When the clay hardens, it is fired ina high-temperature oven, or kiln, to strengthen it. To make the object waterproof, glazes may then be applied and the piece fired again. Although hand construction iseasy to master, throwing on the potter's wheel requires practice. Several simple tools are used by potters, including sponges, trimming tools, wooden sha...

• Mercury (planet) - astronomy.

  In 1991 powerful radio telescopes on Earth revealed signs of possible deposits of ice in the polar regions of Mercury. These ice deposits occur in areas where sunlightnever falls, such as crater bottoms near both of the planet’s poles. Similar ice deposits may have been found during the 1990s near the poles of the Moon by theClementine and Lunar Prospector spacecrafts. The ice on Mercury likely comes from comets or water-bearing meteorites that have hit Mercury over the planet’s historyup throug...

• Homosexuality.

  that “the history of our nation has demonstrated that separate is seldom, if ever, equal,” in affirming that homosexuals are entitled to the same rights of marriage asheterosexuals. On May 17, 2004, same-sex marriages became legal in Massachusetts, and authorities there began to marry gay couples. State legislators pledged toamend the state constitution to ban gay marriage but allow civil unions. Such an amendment would require voter approval. A growing number of local governments and private co...

• Chester Arthur.

  confidence by reappointing them to the Senate. Despite Arthur's help, the legislature did not reappoint the two men. Conkling and Platt never again held public office. In the middle of the political conflict, on July 2, 1881, Garfield was shot by Charles J. Guiteau, a disappointed office-seeker. Garfield died 11 weeks later, on September19, 1881. The following morning, Arthur took the oath of office at his home in New York City. IV PRESIDENT OF THE UNITED STATES Arthur's record of party loyalt...

• Chester Arthur I INTRODUCTION Chester Arthur (1829-1886), 21st president of the United States (1881-1885), who gained the presidency when President James A.

  confidence by reappointing them to the Senate. Despite Arthur's help, the legislature did not reappoint the two men. Conkling and Platt never again held public office. In the middle of the political conflict, on July 2, 1881, Garfield was shot by Charles J. Guiteau, a disappointed office-seeker. Garfield died 11 weeks later, on September19, 1881. The following morning, Arthur took the oath of office at his home in New York City. IV PRESIDENT OF THE UNITED STATES Arthur's record of party loyalt...

• Forensic Science.

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

• Interstellar Matter - astronomy.

  silhouette of a cloud of dust. At other times, it blocks only a percentage of the light from behind it, a process known by astronomers as extinction . The long, narrow dark lanes in the Milky Way as seen from Earth are examples of extinction. The amount of extinction is different for different wavelengths of light. A2 Reddening Starlight that does not get completely absorbed by interstellar dust can still be changed by the dust’s effects. As light passes through less dense patches of interstel...

• Teeth.

  treatments to reduce the risk of tooth decay; clear plastic coatings painted on the teeth, called dental sealants, and applications of the mineral fluoride, which fortifiestooth enamel, are two such treatments. Fluoride is also added to public water supplies in a process called fluoridation, which benefits more than 150 million Americans. Gum disease, or periodontal disease, is a progressive condition that worsens with age. Gum disease occurs when bacteria eat away at gum tissue, causing it to p...

• Woman Suffrage - U.

  form the National American Woman Suffrage Association. For many years thereafter the association worked to advance women’s rights on both the state and federallevels. Besides Stone, Anthony, and Stanton, leaders and supporters of the association included the noted American feminists Harriet Beecher Stowe, Julia Ward Howe,Clara Barton, Jane Addams, and Carrie Chapman Catt. Largely as a result of agitation by the association, suffrage was granted in the states of Colorado (1893), Utahand Idaho (18...

• Ludwig van Beethoven I INTRODUCTION Ludwig van Beethoven Ludwig van Beethoven is considered possibly the greatest Western composer of all time.

  the other hand, breaks up the opening theme into contrasting segments in different tempi, whereas customary practice called for stating the theme in its entirety at thebeginning of a movement. In the first movement of the Eroica Symphony, one of the major works from Beethoven’s middle period, he again sought ways to expand upon the prevailing musical forms. At that time, composers usually organized movements in three major parts. First, the exposition introduces the musical themes of the pie...

• Mesopotamian Art and Architecture I INTRODUCTION Mesopotamian Art and Architecture, the arts and buildings of the ancient Middle Eastern civilizations that developed in the area (now Iraq) between the Tigris and Euphrates rivers from prehistory to the 6th century BC.

  arts. III EARLY DYNASTIC PERIOD Figures from Tell AsmarCreated around 2700 bc, these stone figures are from the city of Tell Asmar in what today is Iraq. From the Temple ofAbu, the statuettes stood in watchful prayer with the wide, staring eyes often found in Sumerian sculpture. The figuresare in the Iraq Museum, Baghdād, Iraq.Art Resource, NY The first historical epoch of Sumerian dominance lasted from about 3000 BC until about 2340 BC. While earlier architectural traditions continued, a ne...

• Book I INTRODUCTION Kelmscott Chaucer The Kelmscott Chaucer was published in 1896 by William Morris' company, the Kelmscott Press.

  B Medieval European Books Illustration of Saint Mark in the Ebbo GospelsThis is a page from the illuminated manuscript known as the Ebbo Gospels (about 816-835). It depicts Saint Mark lookingheavenward for inspiration as he writes his gospel account, and is drawn in an expressive, energetic style typical ofmedieval art of that period. The full name of the Ebbo Gospels is the Gospel Book of Archbishop Ebbo of Reims. This pagemeasures about 25 by 20 cm (about 10 by 8 in).Bridgeman Art Library, Lo...

• Virus (computer).

  how closely it resembles a virus. It relies on experience with previous viruses to predict the likelihood that a suspicious file is an as-yet unidentified or unclassified newvirus. Other types of antiviral software include monitoring software and integrity-shell software. Monitoring software is different from scanning software. It detects illegal orpotentially damaging viral activities such as overwriting computer files or reformatting the computer's hard drive. Integrity-shell software establis...

• Puzzle.

  Visual puzzles involve searching a picture to find hidden or disguised figures or answering a question about some part of a visual illusion. For instance, the popular 19th- century prints of American lithographic company Currier & Ives featured hidden people, animals, and other objects. A 16th-century painting from Bukhara, Uzbekistan,of a camel includes hidden figures of 17 people, 10 rabbits, a monkey, and a dragon (Metropolitan Museum of Art, New York City). B Mathematical Puzzles and Logic...

• Digestive System.

  The stomach, located in the upper abdomen just below the diaphragm, is a saclike structure with strong, muscular walls. The stomach can expand significantly to storeall the food from a meal for both mechanical and chemical processing. The stomach contracts about three times per minute, churning the food and mixing it with gastricjuice. This fluid, secreted by thousands of gastric glands in the lining of the stomach, consists of water, hydrochloric acid, an enzyme called pepsin, and mucin (the...

• Natural Satellite - astronomy.

  Titan, Saturn’s largest moon, also has few impact craters. Although icy volcanism from water and ammonia may occur along with some tectonic activity, Titan’s youngsurface is most likely the result of weather processes. Titan’s dense, cold atmosphere precipitates particles of complex organic molecules that accumulate as dunes andmountains. Methane rain erodes the surface and creates lakes at the moon’s poles. Triton’s young surface also may result from processes in its atmosphere, as well aserupt...

• Psychoanalysis.

  A cornerstone of modern psychoanalytic theory and practice is the concept of anxiety, which institutes appropriate mechanisms of defense against certain dangersituations. These danger situations, as described by Freud, are the fear of abandonment by or the loss of the loved one (the object), the risk of losing the object's love,the danger of retaliation and punishment, and, finally, the hazard of reproach by the superego. Thus, symptom formation, character and impulse disorders, andperversions,...

• Discrimination.

  Throughout United States history many other groups have suffered racial or religious discrimination. Since Europeans first came to America, Native Americans havebeen forcibly deprived of their lands and denied civil rights. Congress enacted the Indian Civil Rights Act in 1968, and the federal courts have entertained a number ofsuits designed to restore to Native American tribes ancestral lands and hunting and fishing rights. Many religious groups, including Roman Catholics, Jews, and others,have...

• Electronics.

  electronic circuits. The resistors are made from carbon mixtures, metal films, or resistance wire and have two connecting wires attached. Variable resistors, with anadjustable sliding contact arm, are often used to control volume on radios and television sets. E Capacitors Capacitors consist of two metal plates that are separated by an insulating material ( see Capacitor). If a battery is connected to both plates, an electric charge will flow for a short time and accumulate on each plate. If th...

• Assyria - USA History.

  villages and cities were ransacked and razed, but no attempt was made to annex their territories. In the course of time this pattern of conquest changed, and the Assyrian rulers began to make Assyria the center of a new empire by incorporating the conquered landsinto their domain, although probably not according to a conscious plan. Toward the end of the 10th century BC, for example, Adad-nirari II annexed the Aramaean state centering on Nisibis, east of the Habur River. His son, Tukulti-Ninurt...

• Excerpt from Martin Chuzzlewit - anthology.

  But there is one other piece of evidence, bearing immediate reference to their close connextion with this memorable event in English History, which must carryconviction, even to a mind (if such a mind there be) remaining unconvinced by these presumptive proofs. There was, within a few years, in the possession of a highly respectable and in every way credible and unimpeachable member of the Chuzzlewit Family (for hisbitterest enemy never dared to hint at his being otherwise than a wealthy man...

• Neandertals.

  Neandertals made stone tools by striking flakes from rock “cores.” The cores were carefully selected and prepared so that only a single blow was normally required todetach a flake. A number of relatively standardized flakes were sometimes produced from a single core. These sharp flakes served as “blanks” that were further workedand shaped into the desired tools. Suitable stone was sometimes rare, and often tools were sharpened and resharpened to make new tools, yielding a whole variety ofshapes...