359 résultats pour "usually"

• North Dakota - geography.

  Bismarck, the growing season averages 134 days, as the average date of the last killing frost is May 11 and that of the first killing frost is September 22. The length ofthe growing season drops to about 110 days in the northerly reaches of the state. The long periods of summer sunshine at this latitude, providing as much as 16 hoursof daylight in summer, help crops to mature quickly, thus compensating somewhat for the relatively short growing season. Temperatures in the north are, on the averag...

• North Dakota - USA History.

  Bismarck, the growing season averages 134 days, as the average date of the last killing frost is May 11 and that of the first killing frost is September 22. The length ofthe growing season drops to about 110 days in the northerly reaches of the state. The long periods of summer sunshine at this latitude, providing as much as 16 hoursof daylight in summer, help crops to mature quickly, thus compensating somewhat for the relatively short growing season. Temperatures in the north are, on the averag...

• Native American Architecture I INTRODUCTION Native American Architecture, traditional architecture of the peoples of who lived in North America before Europeans arrived.

  Mound Builders who resided in the area.John Elk III/Bruce Coleman, Inc. Another mound building culture, named Hopewell, also appears to have originated in Ohio but expanded west to Iowa, Kansas, and Oklahoma, south to Louisiana,Mississippi, and Alabama, east to Georgia and the Appalachian Mountains, and north to Wisconsin, Michigan, and lower Ontario in Canada. The Hopewell culture lastedfrom about 200 BC to 400 AD. Hopewell people built large, linear mounds to create enclosures in geometrical...

• Mars (planet) - astronomy.

  The Martian core is probably much like Earth’s, consisting mostly of iron, with a small amount of nickel. If other light elements, particularly sulfur, exist there as well, thecore may be larger than presently thought. From studying Earth’s magnetic field and core, scientists theorize that the motions of the liquid rock in Earth’s core generateits magnetic field. Mars does not have a significant magnetic field, so scientists believe that Mars’s core is probably solid. However, spacecraft data in...

• Vietnam - country.

  E Natural Resources Vietnam’s most valuable natural resource is its land, particularly the fertile, alluvial soils in the Red and Mekong deltas. Some 29 percent of the land is currently beingcultivated. Vietnam has some valuable mineral resources, including gold, iron, tin, zinc, phosphate, chromite, apatite, and anthracite coal. Most deposits are located in the northernpart of the country. Few attempts were made to extract these minerals until the French takeover of Vietnam at the end of the 1...

• Blue Whale - biology.

  Mature females may give birth once every two or three years. The gestation period lasts about 11 months. A single young is usually born the following spring; twins arerare. The females migrate to warm regions to give birth. The young nurse for seven or eight months, gaining as much as 90 kg (200 lb) per day. VII CONSERVATION STATUS Blue whales were not targeted by the whaling industry until the late 1800s after faster steam-powered ships were developed. The peak slaughter of blue whalesoccurre...

• Bullfighting.

  V THE GREAT MATADORS Ranking the great matadors is highly subjective. Most aficionados would agree, however, that the following names must be included in any list of the modern greats:Rodolfo Gaona, Armillita (Fermín Espinosa), and Arruza, of Mexico; and Belmonte, Manolete, and Antonio Ordoñez, of Spain. Few South Americans have made an impacton the international bullfighting world. Although several North Americans have attempted careers as matadors, only Sidney Franklin and John Fulton Short m...

• Game Theory I INTRODUCTION Game Theory, mathematical analysis of any situation involving a conflict of interest, with the intent of indicating the optimal choices that, under given conditions, will lead to a desired outcome.

  C Zero-Sum Games A game is said to be a zero-sum game if the total amount of payoffs at the end of the game is zero. Thus, in a zero-sum game the total amount won is exactly equal tothe amount lost. In economic contexts, zero-sum games are equivalent to saying that no production or destruction of goods takes place within the “game economy” inquestion. Von Neumann and Oskar Morgenstern showed in 1944 that any n-person non-zero-sum game can be reduced to an n + 1 zero-sum game, and that such n...

• 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...

• Genghis Khan I INTRODUCTION Genghis Khan (1167?

  died in August 1227, in his summer quarters in the district of Qingshui south of the Liupan Shan (Liupan Mountains) in Gansu, China. IV THE MONGOL FORCES Genghis Khan unleashed a seemingly invincible military force. Although usually outnumbered, his forces prevailed on the battlefield through absolute discipline, a well-understood chain of command, superior mobility, and innovative military tactics. The Mongol forces were organized into several formations of 10,000 horse-mounted soldiers, the...

• Genghis Khan.

  died in August 1227, in his summer quarters in the district of Qingshui south of the Liupan Shan (Liupan Mountains) in Gansu, China. IV THE MONGOL FORCES Genghis Khan unleashed a seemingly invincible military force. Although usually outnumbered, his forces prevailed on the battlefield through absolute discipline, a well-understood chain of command, superior mobility, and innovative military tactics. The Mongol forces were organized into several formations of 10,000 horse-mounted soldiers, the...

• Genghis Khan - History.

  died in August 1227, in his summer quarters in the district of Qingshui south of the Liupan Shan (Liupan Mountains) in Gansu, China. IV THE MONGOL FORCES Genghis Khan unleashed a seemingly invincible military force. Although usually outnumbered, his forces prevailed on the battlefield through absolute discipline, a well-understood chain of command, superior mobility, and innovative military tactics. The Mongol forces were organized into several formations of 10,000 horse-mounted soldiers, the...

• Jakarta - geography.

  voluntary movement of families to Indonesia's less populated islands). Jakarta is a magnet for migrants from other areas of Indonesia; during the late 1980s an estimated 250 migrants arrived daily. Most were between the ages of 15 and39 years, many with six years of education or less. There is also a significant number of commuters and seasonal migrants who work in government, manufacturing,and services. In addition, many of these temporary residents are engaged in informal employment as drivers...

• Mental Retardation.

  For example, measles, chicken pox, and whooping cough may lead to encephalitis and meningitis, which can damage the brain. Physical trauma to the brain can also cause mental retardation. Brain damage may result from accidental blows to the head, near drowning, severe child abuse, andchildhood exposure to such toxins as lead and mercury. Experts believe that poverty and a lack of stimulation during infancy and early childhood can be factors inmental retardation. Children raised in poor environmen...

• Inuit.

  VII HOUSING, TRANSPORTATION, AND CLOTHING Inuit homes are of two kinds: walrus or sealskin tents for summer and huts or houses for winter. Winter houses are usually made of stone, with a driftwood orwhalebone frame, chinked and covered with moss or sod. The entrance is a long, narrow passage just high enough to admit a person crawling on hands and knees.During long journeys some Canadian Inuit build igloos, winter houses of snow blocks piled in a dome shape (the term igloo comes from the I...

• Indian Music I INTRODUCTION Classical Dance of South India The southern Indian kathakali is a dance drama that dates from the 17th century.

  Sangita Ratnakara, was written in the 13th century. However, subsequent writers tended to focus on the emotional connotations of individual ragas, associating them with moods, performance times, colors, and deities, and grouping them in terms of families. The modern theoretical system began in the 16th century, when ragasbegan to be classified according to scale—72 in the Karnāṭak system and 10 principal ones in the Hindustani. The 72 mela, as the Karn āṭak scales are called, are derived thro...

• Water - chemistry.

  flourides in drinking water has been found to reduce tooth decay. See Fluorine. Seawater contains, in addition to concentrated amounts of sodium chloride, or salt, many other soluble compounds, as the impure waters of rivers and streams areconstantly feeding the oceans. At the same time, pure water is continually lost by the process of evaporation, and as a result the proportion of the impurities that givethe oceans their saline character is increased. See Ocean and Oceanography. VII WATER...

• Statistics I INTRODUCTION Statistics, branch of mathematics that deals with the collection, organization, and analysis of numerical data and with such problems as experiment design and decision making.

  frequency, column (d), is the ratio of the frequency of an interval to the total count; the relative frequency is multiplied by 100 to obtain the percent relative frequency.The cumulative frequency, column (e), represents the number of students receiving grades equal to or less than the range in each succeeding interval; thus, thenumber of students with grades of 30 or less is obtained by adding the frequencies in column (c) for the first three intervals, which total 53. The cumulative relativef...

• Mount Everest - geography.

  endangered or killed when their tents collapsed or were ripped to shreds by the gales. Hypothermia, the dramatic loss of body heat, is also a major and debilitatingproblem in this region of high winds and low temperatures. Another hazard facing Everest climbers is the famous Khumbu icefall, which is located not far above Base Camp and is caused by the rapid movement of the Khumbuglacier over the steep rock underneath. The movement breaks the ice into sérac (large, pointed masses of ice) cliffs...

• Magnetism I INTRODUCTION Magnetism, an aspect of electromagnetism, one of the fundamental forces of nature.

  the French physicist Paul Langevin produced a theory regarding the temperature dependence of the magnetic properties of paramagnets (discussed below), which wasbased on the atomic structure of matter. This theory is an early example of the description of large-scale properties in terms of the properties of electrons and atoms.Langevin's theory was subsequently expanded by the French physicist Pierre Ernst Weiss, who postulated the existence of an internal, “molecular” magnetic field inmaterials...

• 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...

• Law. I INTRODUCTION Law, body of official rules and regulations, generally found in

  their rules are reviewable by the courts. U.S. constitutional law is the most extensive and pervasive of any country in the world. It is embodied in the Constitution and in the opinions of the U.S. Supreme Courtrendered over time. Through its power of judicial review, the Supreme Court may invalidate any legislation or other governmental actions that it finds to be in violationof the Constitution. Constitutional courts in some civil-law countries have similar powers. In the United Kingdom no equ...

• Leukemia.

  leukemia, and normal or mildly decreased in chronic lymphocytic leukemia. Nearly all chronic leukemia patients have increased white cell counts. In chronic myelocyticleukemia, some of these leukemic white cells are capable of functioning as normal cells do by fighting infectious microbes. Hence, infection is no more common than in ahealthy individual. In chronic lymphocytic leukemia the blood contains large numbers of malignant lymphocytes that do not function normally. Normal lymphocytescoexist...

• Zebra - biology.

  C Life Span Captive zebras have lived into their late 30s. Life expectancy in the wild, where predators abound, is probably not much more than 12 years. IV SOCIAL BEHAVIOR Like horses, zebras have large brains and a wide variety of social behaviors. Although they cannot match the overall intelligence of mammals that hunt, zebras interactwith each other in complex ways. Zebras usually live in groups known as herds, but the social structure of these groups depends on the species. The plains zeb...

• Shang Dynasty - History.

  The dynastic ancestors belonged to an elaborate religious pantheon that also included various nature powers and the Shang high god, Di. The higher powers were lessconcerned with the well-being of Shang society than the ancestors were. Di, whose wishes were often hard to determine, could even cause the Shang harm. The naturepowers could occasionally influence the wind, rain, and harvests, but only Di could actually order the weather. For an agricultural society such as the Shang, this wasperhaps...

• Immune System.

  The humoral immune response involves a complex series of events after antigens enter the body. First, macrophages take up some of the antigen and attach it to classII MHC molecules, which then present the antigen to T helper cells. The T helper cells bind the presented antigen, which stimulates the T helper cells to divide andsecrete stimulatory molecules called interleukins. The interleukins in turn activate any B lymphocytes that have also bound the antigen. The activated B cells then divide...

• Sailing.

  the sails sweep across the decks of the vessel from one side to the other, and also because of the danger of breaking spars. In wild jibing, control can be lostmomentarily and, if the seas are high, a small boat can broach —that is, veer on its side with danger of swamping or capsizing. An unintentional jibe in a heavy wind frequently has enough force to break the masts of a vessel. When jibing intentionally, careful sailors always haul in on the boom while turning, so that the boom willtravel...

• Gambling.

  C Lotteries Lotteries are another form of gambling. In a lottery, tickets are sold for a set amount and a share of the proceeds is returned to the winners, usually through a randomdraw. Most games allow players to pick their own numbers or let a computer randomly pick for them. Lotteries offer a wide variety of games, including weekly drawings,instant “scratch” tickets, daily games, and superlottos with prizes increasing until there is a winner. Large lottery prizes sometimes exceed $100 millio...

• Feudalism I INTRODUCTION Feudalism, contractual system of political and military relationships existing among members of the nobility in Western Europe during the High Middle Ages.

  lord”; thus, it was not rebellion for a subvassal to fight against his lord’s lord. In England, however, William the Conqueror and his successors required their vassals’vassals to take oaths of fealty to them. B Duties of a Vassal Military service in the field was basic to feudalism, but it was far from all that the vassal owed to his lord. When the lord had a castle, he might require his vassals togarrison it, a service called castle-guard. The lord also expected his vassals to attend his cour...

• Diabetes Mellitus.

  Once diabetes is diagnosed, treatment consists of controlling the amount of glucose in the blood and preventing complications. Depending on the type of diabetes, thiscan be accomplished through regular physical exercise, a carefully controlled diet, and medication. Individuals with Type 1 diabetes must receive insulin, often two to four times a day, to provide the body with the hormone it does not produce. Insulin cannot be takenorally, because it is destroyed in the digestive system. Consequent...

• Babylonia - USA History.

  Pharmacology, too, doubtless had made considerable progress, although the only major direct evidence of this comes from a Sumerian tablet written several centuriesbefore Hammurabi. C Legal System and Writing Law and justice were key concepts in the Babylonian way of life. Justice was administered by the courts, each of which consisted of from one to four judges. Often theelders of a town constituted a tribunal. The judges could not reverse their decisions for any reason, but appeals from their...

• Collectibles and Collecting.

  common blond and thus commands a higher price. If there are different variations to a collectible, the least common one is usually worth more. Often there areinteresting stories behind rarities, such as the highly sought-after 1909 Honus Wagner baseball card. At that time tobacco companies manufactured and distributedbaseball cards, and when the antitobacco Wagner complained, his card was pulled from production. Very few copies in good condition have ever been found. C Age Age is often an indic...

• Ice Skating.

  cold climate. Competitors for these events are chosen from the best skaters in each participating country, usually through preliminary national competitions. Speedskaters also compete on a World Cup circuit, which pits the world’s best skaters against one another during the year. A Figure Skating The major types of competitive figure skating are individual men’s and women’s competitions, pairs skating, ice dancing, and precision skating. In individualcompetitions a single skater performs requir...

• 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...

• Virus (life science) - biology.

  RNA into DNA earned them their name because this process is the reverse of the usual transfer of genetic information, from DNA to RNA.) The DNA form of theretrovirus genome is then integrated into the cellular DNA and is referred to as the provirus. The viral genome is replicated every time the host cell replicates its DNA and is thus passed on to daughter cells. Hepatitis B virus can also transcribe RNA to DNA, but this virus packages the DNA version of its genome into virus particles. Unlike...

• Han Dynasty - History.

  However, these reforms faced serious opposition. The feudal barons formed an alliance and rebelled against Wang Mang. They were joined by members of the Liufamily, who were descended from Jingdi (Ching-ti), a former Han emperor, and a civil war followed. As the empire fell into disorder, militant secret societies formedarmed bands and attacked villages and towns. Wang Mang had believed that proper institutions would eventually bring peace to China, but in AD 23, an army led by the Liu clan brea...

• Tiger - biology.

  have a simple digestive system designed to process meat so that the nutrients can be readily absorbed into the bloodstream. With the exception of white tigers, which have blue eyes, all tigers have yellow eyes. Tigers mainly use vision to find prey. Although tigers see about as well as humansduring the day, their large eye openings gather more light than do human eyes, making tiger night vision far superior to that of humans. In addition, a special structurein the tiger’s eye, called the tapetu...

• Electricity I INTRODUCTION Electricity, one of the basic forms of energy.

  electrons in the neutral object are attracted to the positive object. Some of these electrons flow to the side of the neutral object that is nearest to the positive object.This side of the neutral object accumulates electrons and becomes negatively charged. Because electrons leave the far side of the neutral object while its protonsremain stationary, that side becomes positively charged. Since the negatively charged side of the neutral object is closest to the positive object, the attraction bet...

• Maryland - geography.

  Maryland has no large natural lakes. The largest body of water is a reservoir, Deep Creek Lake, which has a surface area of only 18 sq km (7 sq mi). It lies on theAllegheny Plateau, behind a dam on a tributary of the Youghiogheny River. C Coastline The deeply indented shoreline has a length of 5,134 km (3,190 mi), of which only 50 km (31 miles) fronts on the Atlantic Ocean. The most significant coastal feature isChesapeake Bay. In the bay are many islands and Kent Island is the largest. The sta...

• Maryland - USA History.

  Maryland has no large natural lakes. The largest body of water is a reservoir, Deep Creek Lake, which has a surface area of only 18 sq km (7 sq mi). It lies on theAllegheny Plateau, behind a dam on a tributary of the Youghiogheny River. C Coastline The deeply indented shoreline has a length of 5,134 km (3,190 mi), of which only 50 km (31 miles) fronts on the Atlantic Ocean. The most significant coastal feature isChesapeake Bay. In the bay are many islands and Kent Island is the largest. The sta...

• First Aid.

  IV SEVERE BLEEDING The presence of blood over a considerable area of a person’s body does not always indicate severe bleeding. The blood may ooze from multiple small wounds or besmeared, giving the appearance of more blood than is actually present. The rate at which blood is lost from a wound depends on the size and kind of blood vesselruptured. Bright red, spurting blood indicates injury to an artery while welling or steadily flowing, dark red blood indicates injury to a vein. Welling or spur...

• Ear. I INTRODUCTION Ear, organ of hearing and balance. Only vertebrates, or animals

  line or rotates in any direction. Each canal also contains sensory areas with sensory hair cells that project into a cone-shaped cap of gelatin. Two of the semicircularcanals are in a vertical position and are used to detect vertical movement, such as jumping or falling. The third canal is horizontal and detects horizontal movement,such as turning or spinning. The action of the canals depends on the inertia of the fluid inside. When the motion of the body changes, the fluid lags behind, causing...

• 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...

• 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)...

• Saskatchewan (province) - Geography.

  The length of the frost-free season varies within the province. In the southwest, particularly in the valley lands along the South Saskatchewan River, the frost-freeperiod ranges from 150 to 160 days. Regina enjoys about 123 frost-free days, and Saskatoon has about 111. The far north has only from 85 to 95 frost-free days. One important characteristic of Saskatchewan’s climate is the great variability in temperature and precipitation from year to year, which is often critical for agriculture.The...

• Saskatchewan (province) - Canadian History.

  The length of the frost-free season varies within the province. In the southwest, particularly in the valley lands along the South Saskatchewan River, the frost-freeperiod ranges from 150 to 160 days. Regina enjoys about 123 frost-free days, and Saskatoon has about 111. The far north has only from 85 to 95 frost-free days. One important characteristic of Saskatchewan’s climate is the great variability in temperature and precipitation from year to year, which is often critical for agriculture.The...

• 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...

• 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...

• World Energy Supply.

  In the 1990s, oil production by non-OPEC countries remained strong and production by OPEC countries rebounded. The result at the end of the 20th century was aworld oil surplus and prices (when adjusted for inflation) that were lower than in 1972. Experts are uncertain about future oil supplies and prices. Low prices have spurred greater oil consumption, and experts question how long world petroleum reservescan keep pace with increased demand. Many of the world’s leading petroleum geologists beli...