93 résultats pour "needed"
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Machine
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INTRODUCTION
Machine, simple device that affects the force, or effort, needed to do a certain amount of work.
to decrease the amount of force needed to do work or to change the direction of the force. The wheel and axle and some levers can also be used to increase the speedof performance of a task, but doing so always increases the amount of force needed. A Inclined Plane NutsNuts are pieces of metal with a hole in the middle. They are screwed on the end of a bolt as a fastening. Nuts come invarying shapes, depending on their intended use.© Microsoft Corporation. All Rights Reserved. Ramps and staircas...
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Adolf Hitler
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INTRODUCTION
Adolf Hitler (1889-1945), German political and military leader and one of the 20th century's most powerful dictators.
A Economic Collapse At the end of World War I, the Allies (those countries who had fought against Germany) had demanded that Germany pay reparations—that is, payments for wardamages. The government refused to pay all that was demanded by the Allies. When Germany failed to pay enough, France and Belgium occupied the coal mines in theRuhr industrial area in west central Germany in January 1923. In protest, the German government halted all reparation payments and called for passive resistance by a...
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Adolf Hitler.
A Economic Collapse At the end of World War I, the Allies (those countries who had fought against Germany) had demanded that Germany pay reparations—that is, payments for wardamages. The government refused to pay all that was demanded by the Allies. When Germany failed to pay enough, France and Belgium occupied the coal mines in theRuhr industrial area in west central Germany in January 1923. In protest, the German government halted all reparation payments and called for passive resistance by a...
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Adolf Hitler .
A Economic Collapse At the end of World War I, the Allies (those countries who had fought against Germany) had demanded that Germany pay reparations—that is, payments for wardamages. The government refused to pay all that was demanded by the Allies. When Germany failed to pay enough, France and Belgium occupied the coal mines in theRuhr industrial area in west central Germany in January 1923. In protest, the German government halted all reparation payments and called for passive resistance by a...
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Cell (biology) - biology.
proteins, or other proteins required by the cell. While relatively simple in construction, prokaryotic cells display extremely complex activity. They have a greater range of biochemical reactions than those found in theirlarger relatives, the eukaryotic cells. The extraordinary biochemical diversity of prokaryotic cells is manifested in the wide-ranging lifestyles of the archaebacteria andthe bacteria, whose habitats include polar ice, deserts, and hydrothermal vents—deep regions of the ocean un...
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THAT
LONE.
MY FEELINGS They areannouncing flightsoverthespeakers. Wearenot listening. Theydonot matter tous, because weare not going anywhere. I miss youalready, Oskar.Imissed youeven when Iwas with you.That's beenmyproblem. Imiss what Ialready have, and Isurround myselfwiththings thataremissing. Every timeIput inanew page, Ilook atyour grandfather. Iam sorelieved tosee hisface. Itmakes mefeel safe. His shoulders arepinched. Hisspine iscurved. InDresden hewas agiant. I'mglad thathishands arestill rough....
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Helicopter.
naturally flaps down so as to increase lift. Flapping allows the differences in lift caused by uneven rotor tip speed to cancel out, producing a stable ride. Many helicoptersuse mechanical hinges with lubricated bearings, but some use flexible straps made of a composite material in order to reduce the required maintenance. Helicopters require different amounts of lift and thrust at different times during flight, because the aerodynamic forces acting on them change during hovering andacceleration...
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Vitamin.
Vitamin B 1, or thiamine, promotes the metabolism of carbohydrates, enabling these nutrients to release their energy. Thiamine also plays a role in the functioning of the nervous system, muscles, and heart. The body does not store thiamine and people who are malnourished may develop thiamine deficiency. Mild thiamine deficiency cancause fatigue, muscle weakness, and loss of appetite. Severe thiamine deficiency causes beriberi, a disease characterized by muscle weakness, swelling of the heart,and...
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White House - geography.
Each Thanksgiving, the pardoning of the turkey takes place in the Rose Garden. This ceremony of rescuing a turkey and sending it to a petting zoo began during HarryTruman’s term, although Abraham Lincoln is said to have set a precedent by sparing his son’s pet turkey from the oven. III INSIDE THE WHITE HOUSE A large complex is needed for the many activities that take place at the White House. The White House has 132 rooms, 4 dining rooms, 35 bathrooms, 8 staircases, 3elevators, a clinic, a den...
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Roman Empire - history.
the master of Rome. Three years later the Senate proclaimed him Augustus, the supreme ruler. III THE EMPIRE UNDER AUGUSTUS Roman Emperor AugustusAugustus, the first Roman emperor, brought peace, order, and prosperity to Rome after the civil wars that followed the assassinationof Roman leader Julius Caesar. Caesar had adopted the young Octavian, later known as Augustus, as his heir. After a victory overMark Antony and Cleopatra at Actium, Augustus had absolute power over the entire Roman Empire....
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Telephone.
digits is dialed. The development of inexpensive and reliable amplification provided by the introduction of the transistor in the 1960s made practical the design of adialing system based on the transmission of relatively low power tones instead of the higher-power dial pulses. Today most telephones have push buttons instead of a rotary dial. Touch-Tone is an optional service, and telephone companies still maintain the ability to receive pulsedialing. Push-button telephones usually have a switch...
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Native American Architecture.
B Relationship to the Universe and Nature A more profound difference between European American and Native American perceptions lay in how human beings saw themselves in relationship to the universe andin what they believed their responsibilities were to the natural world and to each other. Most European Americans saw themselves as separate from creation andadversaries of nature, ever struggling to conquer and subdue nature and force it to yield to their will. Native Americans saw themselves as...
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Native American Architecture
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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...
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Economics.
Malthus, nature's check was “positive”: “The power of population is so superior to the power of the earth to produce subsistence for man, that premature death must insome shape or other visit the human race.” The shapes it took included war, epidemics, pestilence and plague, human vices, and famine, all combining to level theworld's population with the world's food supply. The only escape from population pressure and the horrors of the positive check was in voluntary limitation of population, no...
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Automobile.
Electric motors have been used to power automobiles since the late 1800s. Electric power supplied by batteries runs the motor, which rotates a driveshaft, the shaftthat transmits engine power to the axles. Commercial electric car models for specialized purposes were available in the 1980s. General Motors Corporation introduced amass-production all-electric car in the mid-1990s. Automobiles that combine two or more types of engines are called hybrids. A typical hybrid is an electric motor with ba...
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Metabolism (chemistry) - biology.
nearly perfect balance. Although much remains to be revealed about metabolic processes, biochemists now agree that regulatory, or rate-limiting, enzymes figure largely in the reactionsinvolved ( see Enzyme). Affecting metabolic pathways at the earliest steps, each enzyme molecule has a specific, or active, site that matches, or “fits,” its particular substrate—the compound with which the enzyme forms a product. The precision with which rate-limiting enzymes and substrates join to set off a parti...
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Rutherford B.
Governor Hayes gave Ohio an honest administration. During his two separate terms (from 1868 to 1872 and then from 1876 to 1877) were conspicuous, in that age ofpolitical corruption, for freedom from scandal and irregularities. Even newspapers that supported the opposition Democratic Party praised his administration. Although a Democratic legislature in Hayes's first term obstructed many of his liberal measures, he was able to reform the prison system. During his second term aRepublican majority...
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Artificial Satellite - astronomy.
The first stage of a multistage rocket consists of rocket engines that provide a huge amount of force, or thrust. The first stage lifts the entire launch vehicle—with itsload of fuel, the rocket body, and the satellite—off the launch pad and into the first part of the flight. After its engines use all their fuel, the first stage portion of therocket separates from the rest of the launch vehicle and falls to Earth. The second stage then ignites, providing the energy necessary to lift the satellit...
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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...
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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...
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Rocket.
the vacuum of space, however, demonstrated that this belief was not true. In fact, rockets produce more thrust in the vacuum of space than on Earth. Air pressure andfriction with the air reduce a rocket’s thrust by about 10 percent on Earth as compared to the rocket’s performance in space. B Thrust and Efficiency Thrust is a measurement of the force of a rocket, or the amount of “push” exerted backward to move a rocket forward. Thrusts vary greatly from rocket to rocket.Engineers measure thrust...
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Rocket - astronomy.
the vacuum of space, however, demonstrated that this belief was not true. In fact, rockets produce more thrust in the vacuum of space than on Earth. Air pressure andfriction with the air reduce a rocket’s thrust by about 10 percent on Earth as compared to the rocket’s performance in space. B Thrust and Efficiency Thrust is a measurement of the force of a rocket, or the amount of “push” exerted backward to move a rocket forward. Thrusts vary greatly from rocket to rocket.Engineers measure thrust...
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Ancient Greece.
The first culture of Aegean civilization on the Greek mainland is named Mycenaean for the palace at Mycenae on the Pelopónnisos. Scholars call the Mycenaeans the“earliest Greeks” because they are the first people known to have spoken Greek. Mycenaean culture developed later than Minoan. The ancestors of the Mycenaean people wandered onto the mainland from the north and the east from about 4000 to2000 BC, mixing with the people already there, and by about 1400 BC the Mycenaeans had become very...
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Ancient Greece .
The first culture of Aegean civilization on the Greek mainland is named Mycenaean for the palace at Mycenae on the Pelopónnisos. Scholars call the Mycenaeans the“earliest Greeks” because they are the first people known to have spoken Greek. Mycenaean culture developed later than Minoan. The ancestors of the Mycenaean people wandered onto the mainland from the north and the east from about 4000 to2000 BC, mixing with the people already there, and by about 1400 BC the Mycenaeans had become very...
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Ancient Greece - USA History.
The first culture of Aegean civilization on the Greek mainland is named Mycenaean for the palace at Mycenae on the Pelopónnisos. Scholars call the Mycenaeans the“earliest Greeks” because they are the first people known to have spoken Greek. Mycenaean culture developed later than Minoan. The ancestors of the Mycenaean people wandered onto the mainland from the north and the east from about 4000 to2000 BC, mixing with the people already there, and by about 1400 BC the Mycenaeans had become very...
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George Bush.
1986 it was folded into Harken Energy Corporation, another Texas petroleum company. Bush served as a consultant and a member of Harken’s board of directors. In 1987 Bush relocated his family to Washington, D.C., to assist his father in his bid to become president. He worked as a campaign adviser at his father’s nationalcampaign headquarters, serving as a liaison to the media and to conservative and Christian leaders. He was a trusted confidant of his father and mother, whosometimes dispatched Bu...
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George Bush - USA History.
1986 it was folded into Harken Energy Corporation, another Texas petroleum company. Bush served as a consultant and a member of Harken’s board of directors. In 1987 Bush relocated his family to Washington, D.C., to assist his father in his bid to become president. He worked as a campaign adviser at his father’s nationalcampaign headquarters, serving as a liaison to the media and to conservative and Christian leaders. He was a trusted confidant of his father and mother, whosometimes dispatched Bu...
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Middle Ages .
Saints were very important in Late Antiquity. They were considered both models of virtue and powerful miracle workers. One of the most well-known saints of the periodwas Saint Anthony. Anthony gave away all his possessions and left his hometown in Egypt to live alone in the desert and pray. Anthony was one of the first Christianmonks. The word monk comes from a term meaning 'alone.' Gradually Anthony attracted followers, and he eventually became the center of a whole community of monks who wis...
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Argentina Wins World Cup.
Dutch team responded with two unanswered goals to earn the victory. In the consolation match Brazil squeaked past Italy, 2-1, in what was the final high-profileappearance of Brazilian star Roberto Rivelino, a three-time World Cup participant. The championship match was held at Río de la Plata stadium in Buenos Aires on Sunday, June 25. In a classic match-up, a methodical, disciplined European teamplayed against a spontaneous, mercurial South American squad. According to Argentina's coach, Ce...
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Television.
A charge-coupled device (CCD) can be much smaller than a camera tube and is much more durable. As a result, cameras with CCDs are more compact and portablethan those using a camera tube. The image they create is less vulnerable to distortion and is therefore clearer. In a CCD, the light from a scene strikes an array ofphotodiodes arranged on a silicon chip. Photodiodes are devices that conduct electricity when they are struck by light; they send this electricity to tiny capacitors. Thecapacitors...
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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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Chicago Black Sox Scandal.
With the series back in Cincinnati and the Reds leading the series, 4-1, the White Sox took game six, 5-4. Gandil knocked in the winning run in the 10th inning.Cicotte won game seven, 4-1, with Jackson supplying a two-run double. The Reds led the series by only a 4-3 count. Rothstein told Sullivan that the series needed toend early in game eight. Sullivan hired a strongman, who the night before the game threatened harm to Williams and his wife if Williams lasted more than an inningon the mound....
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Heat (physics)
I
INTRODUCTION
Heat Loss from a House
A thermograph shows the large amount of heat lost through a house's windows during winter.
Theoretically, the molecules of a substance would exhibit no activity at the temperature termed absolute zero. See Molecule. III TEMPERATURE SCALES Five different temperature scales are in use today: the Celsius scale, known also as the Centigrade scale, the Fahrenheit scale, the Kelvin scale, the Rankine scale, andthe international thermodynamic temperature scale ( see Thermometer). The Celsius scale, with a freezing point of 0° C and a boiling point of 100° C, is widely used throughout the...
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Endocrine System.
thermostat. When the heat in a house falls, the thermostat responds by switching the furnace on, and when the temperature is too warm, the thermostat switches thefurnace off. Usually, the change that a hormone produces also serves to regulate that hormone's secretion. For example, parathyroid hormone causes the body toincrease the level of calcium in the blood. As calcium levels rise, the secretion of parathyroid hormone then decreases. This feedback mechanism allows for tight controlover hormon...
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Ancient Greece - history.
Palace of KnossosThe ancient city of Knossos was a center of the Minoan civilization, an advanced society on Crete named after Minos, a legendaryCretan king. Skilled in such fields as engineering and architecture, the Minoans constructed the palace at Knossos in 1700 bc. Aserious fire at least three centuries later caused the collapse of the palace and foreshadowed the subsequent decline of the city.Wolfgang Kaehler Settlers had begun sailing from Asia Minor to Crete about 6000 BC because the i...
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Louis Stephen St.
St. Laurent brought to office a new concept of government. His broad, all-national view firmly rejected Québec's traditional isolationism. He made his decisions with coolimpartiality, giving first consideration to the welfare of Canada as a whole. St. Laurent's foreign policy involved Canada in world politics. He supported the UN, fully endorsing the initiatives proposed by Pearson, his representative there. St.Laurent actively sponsored and subsequently cooperated with the North Atlantic Treaty...
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Louis Stephen St.
St. Laurent brought to office a new concept of government. His broad, all-national view firmly rejected Québec's traditional isolationism. He made his decisions with coolimpartiality, giving first consideration to the welfare of Canada as a whole. St. Laurent's foreign policy involved Canada in world politics. He supported the UN, fully endorsing the initiatives proposed by Pearson, his representative there. St.Laurent actively sponsored and subsequently cooperated with the North Atlantic Treaty...
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Circulatory System.
C Additional Functions In addition to oxygen, the circulatory system also transports nutrients derived from digested food to the body. These nutrients enter the bloodstream by passingthrough the walls of the intestine. The nutrients are absorbed through a network of capillaries and veins that drain the intestines, called the hepatic portal circulation.The hepatic portal circulation carries the nutrients to the liver for further metabolic processing. The liver stores a variety of substances, suc...
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Blood.
substances. For example, a person who is blood type A positive will not make antibodies against the A or Rh markers, but will make antibodies against the B marker,which is not on that person’s own red blood cells. If blood containing the B marker (from types B positive, B negative, AB positive, or AB negative) is transfused into thisperson, then the transfused red blood cells will be rapidly destroyed by the patient’s anti-B antibodies. In this case, the transfusion will do the patient no good a...
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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...
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Fruit - biology.
from a flower with several pistils. The ovary may have a single compartment, or carpel, which houses the ovule or ovules. Or the ovary may consist of two or morecarpels, each of which may contain one or more ovules. A drupe develops from an ovary with a single carpel and is characterized by an edible exocarp and mesocarp and an inedible, hard endocarp, or pit that encloses asingle seed. Cherries, peaches, apricots, and plums are examples of drupes. Almonds also are classified as drupes, but in a...
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French and Indian War.
Virginia as well as the French governor-general of Canada had attempted to seize their lands. After receiving large presents of supplies and arms, the Iroquoisgrudgingly renewed their alliances with the British colonies. Delegates then moved on to plan other defensive measures. An important topic was a plan of union developed by Benjamin Franklin. The Albany Plan, as it became known, proposed a single institution to govern all of the Britishcolonies in America. Under the plan, each colony would...
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French and Indian War - Canadian History.
Virginia as well as the French governor-general of Canada had attempted to seize their lands. After receiving large presents of supplies and arms, the Iroquoisgrudgingly renewed their alliances with the British colonies. Delegates then moved on to plan other defensive measures. An important topic was a plan of union developed by Benjamin Franklin. The Albany Plan, as it became known, proposed a single institution to govern all of the Britishcolonies in America. Under the plan, each colony would...
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Gardening - biology.
of synthetic and organic fertilizers, see Organic Farming.) Fertilizers usually are sold in packages, on which the percentage by weight of the macronutrients nitrogen (N), phosphorus (P), and potassium (K) are listed on thelabel—always in the order N-P-K. For example, a fertilizer that is labeled 10-5-3 is 10 percent nitrogen, 5 percent phosphorus, and 3 percent potassium. V PLANTING AND TRANSPLANTING Before planting seeds, gardeners prepare, or till, the soil using a variety of methods. Some...
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Winston Churchill
I
INTRODUCTION
Winston Churchill (1874-1965), British politician and prime minister of the United Kingdom (1940-1945, 1951-1955), widely regarded as the greatest British leader of
the 20th century.
sufficient tools to break the stalemate on the western front and he worked on developing armored fighting vehicles (tanks) to break the deadlock and end theslaughter. As the lines hardened on the western front, Churchill focused on a campaign to force open the Dardanelles Strait, controlled by the Ottoman Empire, to give the Allies adirect route to Russia through the Black Sea. Such a move would bring much-needed supplies to the Russian armies and eliminate the Ottomans from the war. Whenthe nav...
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Winston Churchill.
sufficient tools to break the stalemate on the western front and he worked on developing armored fighting vehicles (tanks) to break the deadlock and end theslaughter. As the lines hardened on the western front, Churchill focused on a campaign to force open the Dardanelles Strait, controlled by the Ottoman Empire, to give the Allies adirect route to Russia through the Black Sea. Such a move would bring much-needed supplies to the Russian armies and eliminate the Ottomans from the war. Whenthe nav...
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Winston Churchill .
sufficient tools to break the stalemate on the western front and he worked on developing armored fighting vehicles (tanks) to break the deadlock and end theslaughter. As the lines hardened on the western front, Churchill focused on a campaign to force open the Dardanelles Strait, controlled by the Ottoman Empire, to give the Allies adirect route to Russia through the Black Sea. Such a move would bring much-needed supplies to the Russian armies and eliminate the Ottomans from the war. Whenthe nav...
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Rain Forest.
dropped into the heart of the forest by helicopters. Suspended from the crane’s long, movable arm is a large gondola that functions as a mobile treetop laboratory.Moving from tree to tree, forest researchers collect specimens, conduct experiments, and observe life in the canopy frontier. The highest stratum of the rain forest is made up of the emergent trees, those individuals that stick up above the forest canopy. Emergents, which do not form acontinuous layer, are usually the giants of the for...
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Dwight D.
maneuvers in Louisiana in 1941, he played a leading role as a staff officer, adding to his reputation and securing him a promotion to brigadier general. On December 7,1941, Japan attacked Pearl Harbor, Hawaii, and the next day the United States entered World War II against the Axis Powers (Japan, Germany, and Italy). A weeklater, the army’s new chief of staff, General George C. Marshall, called Eisenhower to Washington, D.C., and put him in charge of the War Plans Division. Opinions differed on...
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Health Insurance.
needs services. Essentially, individuals make regular payments to the plan rather than having to pay especially large sums at any one time in the event of sudden illnessor injury. In this way, the group as a whole funds expensive treatments for those few who need them. Many people believe that in addition to providing financial stability, health insurance can promote good health. Supporters of this idea claim that by lowering thepersonal cost of services, insurance induces individuals to seek he...