132 résultats pour "factor"
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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...
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Síndrome de inmunodeficiencia adquirida (SIDA) - ciencias de la
naturaleza.
se multiplica a una gran velocidad, sufriendo diversas mutaciones genéticas. Al principio, se produce un descenso de la cifra de linfocitos T CD4 pero, al poco tiempo, lascifras normales se recuperan en respuesta a una activación del sistema inmunológico. Durante esta etapa los individuos son altamente contagiosos. El paciente entra entonces en un periodo libre de síntomas (fase asintomática) cuya duración puede ser superior a diez años. Durante ésta, el virus continúa replicándosecausando una d...
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Sound
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INTRODUCTION
Sound, physical phenomenon that stimulates the sense of hearing.
A fundamental law of harmony states that two notes an octave apart, when sounded together, produce a pleasant-sounding combination. Other combinations of notescan also be pleasing. Physically, an interval of a fifth consists of two notes, the frequencies of which bear the arithmetical ratio 3 to 2, and a major third, the ratio 5 to4. Fundamentally, the law of harmony states that two or more notes sound pleasant when played together if their frequencies bear small, whole number ratios; if thefreq...
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Diseases of Animals.
infected animal. It may also spread in milk or in garbage that contains contaminated meat. Typical symptoms include blisters that appear on the mouth and feet;animals may become lame when their hooves degenerate. Canine distemper is a highly contagious disease caused by the paramyxovirus, which is transmitted in discharges from the nose and eyes. Symptoms begin with fever,malaise, and nasal and ocular discharges and may progress to convulsions and other nervous system disorders. Parvoviruses aff...
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Greenhouse Effect.
addition, humans cut down huge tracts of trees for lumber or to clear land for farming or building. This process, known as deforestation, can both release the carbonstored in trees and significantly reduce the number of trees available to absorb carbon dioxide. As a result of these human activities, carbon dioxide in the atmosphere is accumulating faster than Earth’s natural processes can absorb the gas. By analyzing airbubbles trapped in glacier ice that is many centuries old, scientists have d...
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Acid Rain.
the Adirondack Mountains of New York State, a quarter of the lakes and ponds are acidic, and many have lost their brook trout and other fish. In the middleAppalachian Mountains, over 1,300 streams are afflicted. All of Norway’s major rivers have been damaged by acid rain, severely reducing salmon and trout populations. E Plants and Animals The effects of acid rain on wildlife can be far-reaching. If a population of one plant or animal is adversely affected by acid rain, animals that feed on tha...
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Evolución humana - ciencias de la naturaleza.
Los cambios genéticos pueden mejorar la capacidad de los organismos para sobrevivir, reproducirse y, en animales, criar a su descendencia. Este proceso se denominaadaptación. Los progenitores transmiten mutaciones genéticas adaptativas a su descendencia y finalmente estos cambios se generalizan en una población —un grupo de organismos de la misma especie que comparten un hábitat local particular. Existen numerosos factores que pueden favorecer nuevas adaptaciones, pero los cambios delentorno d...
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United States (Overview) - country.
parts. IV UNITED STATES PEOPLE When Europeans first reached North America in the 1520s, they encountered other people—Native Americans—and they also encountered a new geography. Someimagined they were entering “a howling wilderness”—an environment filled with exotic flora and fauna but sparsely populated. In reality, they found their way to alandmass that was widely settled. But soon after the Europeans’ arrival, the population of the Americas plummeted, largely because Native Americans lacked...
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Toys.
I
INTRODUCTION
Toys, objects that serve as playthings for children. Although the
clay. These readily available elements were also used to make more elaborate toys as human society advanced. Archaeologists have found primitive, handmade toys such as wooden or cloth dolls, clay marbles, and terracotta figures that date back thousands of years. In ancientEgypt, Greece, and Rome, people placed dolls or clay figures in the graves or tombs of children for them to play with in the afterlife. The yo-yo may seem like a 20th-century fad, but it actually dates back at least 2,500 years...
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British Empire .
B1 The Seven Years’ War During the Seven Years’ War in Europe (1756-1763), Britain made large imperial gains at the expense of France. The North American segment of the Seven Years’ Warwas known as the French and Indian War. It was launched by the British against French possessions in North America in 1754, and in 1758 the British captured theFrench fortress of Louisbourg, which gave them access to French territory in the St. Lawrence Valley. In the following year Québec was captured, marking t...
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Submarine.
B Propulsion Modern submarines use either diesel-electric or nuclear power to drive the sub's propeller and to provide internal electric power. Diesel-electric power emerged as themost efficient propulsion system for submarines in the early 20th century, following unsuccessful attempts to use steam or gasoline power. While on the surface, thesubmarine uses a diesel engine to drive the propeller and generate electricity. When submerged, a battery-driven electrical motor takes over for propulsion...
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Kansas City (Missouri) - geography.
Major institutions of higher education in Kansas City are a branch (established in 1929) of the University of Missouri, Avila College (1916), Rockhurst College (1910),DeVry Institute of Technology (Missouri) (1931), and the Kansas City Art Institute (1885). Schools in neighboring suburbs include Park University (1875), in Parkville,and William Jewell College (1849), in Liberty. Baptist, Nazarene, and Methodist theological schools are also located in the area. Midwest Research Institute, one of t...
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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...
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Mesoamerica.
for cooking. In other regions, the earliest ceramics are more sophisticated technically and aesthetically. At around 1800 BC in the Pacific coastal region of Soconusco (in what is now southeastern Chiapas State, Mexico), the earliest pottery was very complex both in forms and decoration. It seems to have had a social function and beenused primarily for ritual feasting. III MAJOR CIVILIZATIONS Over a period of 3000 years, beginning in about 1500 BC, a number of important cultures emerged in M...
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Great Depression in the United States - U.
prices would continue to rise and they could soon sell their stocks at a profit. The widespread belief that anyone could get rich led many less affluent Americans into the market as well. Investors bought millions of shares of stock “on margin,” arisky practice similar to buying products on credit. They paid only a small part of the price and borrowed the rest, gambling that they could sell the stock at a highenough price to repay the loan and make a profit. For a time this was true: In 1928 the...
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Fire - chemistry.
were usually natural caves. Eventually people learned to dip branches in pitch to form torches. They created crude lamps by filling a hollowed out piece of stone withmoss soaked in oil or tallow (a substance derived from animal fat). By cooking with fire, prehistoric people made the meat of the animals they killed more palatable and digestible. They learned to preserve meat by smoking it over a fire,vastly decreasing the danger of periodic starvation. Cooking also enabled them to add some for...
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Automobile Racing.
beginning in 1906 at Le Mans it came to refer to the principal F1 auto race in a given nation, except in the United States, where the term continues to be used lessdiscriminately. After the end of World War I in 1918, when automobile racing blossomed internationally, a series of GP races in several nations became reserved for F1competition, and an annual GP calendar was developed consisting of national races, such as the French Grand Prix and the British Grand Prix. An annual award calledthe Wor...
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Latvia - country.
The population of Latvia is about 2,245,423 (2008 estimate), yielding an average population density of 35 persons per sq km (91 per sq mi). Latvia is highly urbanized.Some 66 percent of the population lives in urban areas, with nearly one-third of the total population residing in the capital, Rīga. Other important cities includeDaugavpils, an industrial center in the southeast, on the Daugava River; Liep āja, an important port on the Baltic Sea; Jelgava, an industrial center near Rîga; J ūrmala,...
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Track and Field.
VI RUNNING EVENTS Running events are competitions that test athletes’ quickness, speed, and endurance. Athletes win running races by completing the distance or course in the leastamount of time. A Sprints The shortest running events, called sprints or dashes, are the premier events at a track-and-field meet. The outdoor sprints consist of the 100-meter, 200-meter, and400-meter events. Sprints contested at indoor meets include the 50-meter, 60-meter, 200-meter, and 400-meter events. Past champ...
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Holocaust
I
INTRODUCTION
Holocaust, the almost complete destruction of Jews in Europe by Nazi Germany and its collaborators during World War II (1939-1945).
relation to the Jews. He claimed that the Jews had achieved economic dominance and the ability to control and manipulate the mass media to their own advantage. Hewrote of the need to eradicate their powerful economic position, if necessary by means of their physical removal. IV UNIQUENESS OF NAZI ANTI-SEMITISM The linking of anti-Semitic accusations to race struggle is what made Nazism so genocidal. The Nazis believed the Jews were responsible for what they regarded as thedegeneracy of modern...
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Holocaust .
relation to the Jews. He claimed that the Jews had achieved economic dominance and the ability to control and manipulate the mass media to their own advantage. Hewrote of the need to eradicate their powerful economic position, if necessary by means of their physical removal. IV UNIQUENESS OF NAZI ANTI-SEMITISM The linking of anti-Semitic accusations to race struggle is what made Nazism so genocidal. The Nazis believed the Jews were responsible for what they regarded as thedegeneracy of modern...
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Belgium - country.
European Union (EU) directives aimed at improving Belgium’s environmental conditions concern water treatment and water quality, both significant issues in such anindustrial center. Before these directives were issued, the Meuse River, a major source of drinking water, had become polluted from steel production wastes. Otherrivers were polluted with animal wastes and fertilizers. However, Belgium failed to meet EU targets set for the early 2000s for protecting its rivers from farm pollutionand for...
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Manhattan Project - U.
other possible uses of nuclear energy, such as using uranium to operate large power plants or, perhaps, as power sources for ships or submarines. Then Nazi Germanyinvaded Poland on September 1, 1939, and Europe plunged into war. The scientists realized that any plans to build large-scale nuclear power plants would have to waituntil the war was over. Two weeks after the invasion of Poland, Hitler made a radio speech in which he threatened Britain with “a weapon against which there is no defense.”...
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Boston - geography.
The neighborhoods of Allston and Brighton occupy the northwest corner of the city to the west of Fenway. The Allston-Brighton area is bordered to the east, north, andwest by the Charles River and to the south by the Massachusetts Turnpike and the town of Brookline. It is an industrial and residential neighborhood that is also thelocation of Boston College and Harvard University Business School. Boston has been unsuccessful in annexing Brookline, the birthplace of U.S. president John F.Kennedy an...
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Bill Clinton.
When Arkansas governor David Pryor ran for the U.S. Senate in 1978, Clinton ran for governor. He promised to improve the state’s schools and highways and toimprove economic conditions so that more jobs would be created. At that time, the average income of people in Arkansas ranked 49th among the 50 states. Clinton woneasily, receiving 60 percent of the vote against four opponents in the Democratic primary election and 63 percent against the Republican candidate, Lynn Lowe, in thegeneral election...
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Bill Clinton - USA History.
When Arkansas governor David Pryor ran for the U.S. Senate in 1978, Clinton ran for governor. He promised to improve the state’s schools and highways and toimprove economic conditions so that more jobs would be created. At that time, the average income of people in Arkansas ranked 49th among the 50 states. Clinton woneasily, receiving 60 percent of the vote against four opponents in the Democratic primary election and 63 percent against the Republican candidate, Lynn Lowe, in thegeneral election...
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Supreme Court of the United States.
The Constitution does not specify formal qualifications for membership on the Supreme Court. From the beginning, though, justices have all been lawyers, and mostpursued legal and political careers before serving on the Court. Many justices served as members of Congress, governors, or members of the Cabinet. One president,William Howard Taft, was later appointed chief justice. Some justices came to the Court from private law practice, and others were appointed from positions as lawprofessors. Man...
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Africa.
The highest elevations in Africa are found in the various ranges of East Africa. After Kilimanjaro, the next highest peaks are Mount Kenya (5,199 m/17,057 ft), north ofKilimanjaro in central Kenya; Margherita Peak (5,109 m/ 16,762 ft) in the Ruwenzori Range on the border between Uganda and the Democratic Republic of the Congo(DRC); Ras Dashen (4,620 m/ 15,157 ft) in the Ethiopian Highlands of northern Ethiopia; Mount Meru (4,565 m/ 14,977 ft), close to Kilimanjaro in Tanzania; and MountElgon (4,...
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Africa - Geography.
The highest elevations in Africa are found in the various ranges of East Africa. After Kilimanjaro, the next highest peaks are Mount Kenya (5,199 m/17,057 ft), north ofKilimanjaro in central Kenya; Margherita Peak (5,109 m/ 16,762 ft) in the Ruwenzori Range on the border between Uganda and the Democratic Republic of the Congo(DRC); Ras Dashen (4,620 m/ 15,157 ft) in the Ethiopian Highlands of northern Ethiopia; Mount Meru (4,565 m/ 14,977 ft), close to Kilimanjaro in Tanzania; and MountElgon (4,...
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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...
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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...
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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...