494 résultats pour "low"

• Massachusetts - geography.

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

• 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...

• South Dakota - geography.

  C1 Temperatures Average January temperatures are everywhere less than -4° C (24° F) and decrease to less than -12° C (10° F) in some northern sections. The January temperaturesin Sioux Falls range from -16° to -4° C (3° to 24° F). Nightime lows of -29° C (-20° F) occur during most winters. July averages are in the low and middle 20°s C (lowand middle 70°s F) throughout most of the state, and are somewhat lower in the Black Hills. The average temperature range in Sioux Falls in July is 17° to 30...

• South Dakota - USA History.

  C1 Temperatures Average January temperatures are everywhere less than -4° C (24° F) and decrease to less than -12° C (10° F) in some northern sections. The January temperaturesin Sioux Falls range from -16° to -4° C (3° to 24° F). Nightime lows of -29° C (-20° F) occur during most winters. July averages are in the low and middle 20°s C (lowand middle 70°s F) throughout most of the state, and are somewhat lower in the Black Hills. The average temperature range in Sioux Falls in July is 17° to 30...

• Pennsylvania - geography.

  B Rivers and Lakes There are three major river basins in Pennsylvania: the Susquehanna, the Ohio, and the Delaware. Together they drain more than 90 percent of Pennsylvania’s landarea. Most of eastern and central Pennsylvania is drained by the Susquehanna and Delaware systems. The western part of the state is drained by the Allegheny andMonongahela rivers, which join at Pittsburgh to form the Ohio. In addition to the three major river basins, short streams flowing into Lake Erie drain the north...

• Pennsylvania - USA History.

  B Rivers and Lakes There are three major river basins in Pennsylvania: the Susquehanna, the Ohio, and the Delaware. Together they drain more than 90 percent of Pennsylvania’s landarea. Most of eastern and central Pennsylvania is drained by the Susquehanna and Delaware systems. The western part of the state is drained by the Allegheny andMonongahela rivers, which join at Pittsburgh to form the Ohio. In addition to the three major river basins, short streams flowing into Lake Erie drain the north...

• Wetland.

  Other plants and animals have special adaptations suited for living in a wet environment. Most emergent plants have air spaces in their stems that enable oxygen to betransported to roots that grow in sediments with no oxygen. Some of the trees that grow in swamps form a set of roots above the soil surface or above the water thatallows them to get oxygen to the lower roots. In saltwater wetlands, specialized cells can limit the amount of salt that enters a plant, or specialized organs can excrete...

• Maine - geography.

  temperatures range from 17° to 21°C (62° to 70°F) with the southern interior being the warmest and the east coast and north the coolest. However, daytime summertemperatures may reach the lower 30°s C (lower 90°s F), and temperatures in winter have fallen as low as -44°C (-48°F) in the interior. D2 Precipitation Precipitation (rainfall and snowfall) in Maine is evenly distributed throughout the year. Most areas receive from 860 to 1,020 mm (34 to 40 in) yearly, although parts ofthe coast are som...

• Maine - USA History.

  temperatures range from 17° to 21°C (62° to 70°F) with the southern interior being the warmest and the east coast and north the coolest. However, daytime summertemperatures may reach the lower 30°s C (lower 90°s F), and temperatures in winter have fallen as low as -44°C (-48°F) in the interior. D2 Precipitation Precipitation (rainfall and snowfall) in Maine is evenly distributed throughout the year. Most areas receive from 860 to 1,020 mm (34 to 40 in) yearly, although parts ofthe coast are som...

• Heart.

  situation. A Cardiac Cycle Although the right and left halves of the heart are separate, they both contract in unison, producing a single heartbeat. The sequence of events from the beginning ofone heartbeat to the beginning of the next is called the cardiac cycle. The cardiac cycle has two phases: diastole, when the heart’s chambers are relaxed, and systole,when the chambers contract to move blood. During the systolic phase, the atria contract first, followed by contraction of the ventricles. T...

• Virginia (state) - geography.

  C Coastline Virginia’s coastline, for both the mainland and the Eastern Shore counties, is 180 km (112 mi) long. The state’s tidal shoreline measures 5,335 km (3,315 mi), includingall bays, inlets, tidal estuaries, and other indentations. Major indentations include Chesapeake Bay; Hampton Roads, the excellent natural harbor on which are locatedNewport News, Norfolk, and Portsmouth; and the wide tidal estuaries of the lower Potomac, James, Rappahannock, and York rivers. Cape Henry, in the southe...

• Virginia (state) - USA History.

  C Coastline Virginia’s coastline, for both the mainland and the Eastern Shore counties, is 180 km (112 mi) long. The state’s tidal shoreline measures 5,335 km (3,315 mi), includingall bays, inlets, tidal estuaries, and other indentations. Major indentations include Chesapeake Bay; Hampton Roads, the excellent natural harbor on which are locatedNewport News, Norfolk, and Portsmouth; and the wide tidal estuaries of the lower Potomac, James, Rappahannock, and York rivers. Cape Henry, in the southe...

• Leaf - biology.

  The mesophyll, sandwiched between the upper and lower epidermis, consists of many thin-walled cells that are usually arranged in two layers. The palisade layer is next to the upper epidermis. It consists of cylindrical cells that are packed closely together. Next to the palisade layer and making up most of the thickness of the leaf bladeis the spongy layer. The spongy layer consists of roundish cells that are packed loosely together and have numerous air spaces between them. In most plants t...

• 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...

• 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...

• Star (astronomy) - astronomy.

  absorbing the missing colors of light. For example, the set of dark lines made by hydrogen includes a dark red line, the set of dark lines made by sodium includes a pairof dark yellow lines, and the set of dark lines made by iron includes lines of nearly every color. Each element in the gaseous outer layer of a star produces its ownparticular pattern of dark spectrum lines, depending on the temperature and pressure of the gas. Astronomers have observed spectrum lines, or spectra, for hundredsof...

• South America - Geography.

  South America is dominated by relatively warm climatic regimes. Spanning nearly the entire continent along the equator is a belt of humid tropical climate that grades tothe north and south into broad zones where the length of the rainy season and the amount of rainfall diminish. These zones have wet summers and dry winters and aresubject to prolonged droughts. Droughts are a particularly serious problem in northeastern Brazil and along the northern coast of Venezuela and Colombia. The areas ofra...

• Panama Canal - geography.

  LockA lock is a section of a waterway enclosed by gates at either end to allow ships to be raised or lowered to a different water level. Inthis example, a ship enters the upper level and the gates close behind it. The water is then allowed to drain into the lower level,lowering the water level of the lock and the ship. When the water level of the lock equals the level of the lower canal, the lower gateswill open and the ship can proceed.© Microsoft Corporation. All Rights Reserved. The canal’s 1...

• Internal-Combustion Engine.

  any Otto-cycle engine and in actual engines today is slightly more than 40 percent. Diesels are, in general, slow-speed engines with crankshaft speeds of 100 to 750revolutions per minute (rpm) as compared to 2500 to 5000 rpm for typical Otto-cycle engines. Some types of diesel, however, have speeds up to 2000 rpm. Becausediesels use compression ratios of 14 or more to 1, they are generally more heavily built than Otto-cycle engines, but this disadvantage is counterbalanced by theirgreater effici...

• Himalayas - geography.

  result of deforestation the habitat of most of the wildlife has been destroyed. They are now restricted to special protected areas such as the Jaldapara and Kazirangasanctuaries in India ( see Kaziranga National Park) and the Chitawan preserve in Nepal. There are few animals in the Middle Himalayas because of extensive deforestation. In the Great Himalayas musk deer, wild goats, sheep, wolves, and snow leopards are found. The existence of the Abominable Snowman or Yeti has beenreported by highla...

• Child Abuse.

  C Social Isolation and Low Community Involvement Parents and caretakers who abuse children tend to be socially isolated. Few violent parents belong to any community organizations, and most have little contact withfriends or relatives. This lack of social involvement deprives abusive parents of support systems that would help them deal better with social or family stress. Moreover,the lack of community contacts makes these parents less likely to change their behavior to conform with community va...

• Soil. I INTRODUCTION Soil, the loose material that covers the land surfaces of

  an exchange between plants and the atmosphere, as oxygen diffuses into the soil and is used by roots for respiration. In turn, the resulting carbon dioxide diffusesthrough pore spaces and returns to the atmosphere. This exchange is most efficient in soils with a high degree of porosity. For farmers, gardeners, landscapers, andothers with a professional interest in soil health, the process of aeration—making holes in the soil surface to permit the exchange of air—is a crucial activity. Theburrowi...

• Turtle.

  Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtlescommonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants.Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food. C Limb Structu...

• Turtle - biology.

  Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtlescommonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants.Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food. C Limb Structu...

• Optics I INTRODUCTION Mirage Mirages appear because differences in air temperature cause light rays from an object to take different paths to a viewer's eye.

  Refraction of Light by DiamondsThe brilliance of diamonds is due to their high refractive index, a measure of how strongly a transparent material bendslight rays. The skill of the gem-cutter lies in angling the facets of the stone so that each light ray entering it is reflectedmany times before it emerges again.Spencer Grant/Photo Researchers, Inc. The amount of light reflected depends on the ratio of the refractive indexes for the two media. The plane of incidence contains the incident ray and...

• Shark - biology.

  Sharks have two-chambered hearts that are relatively small compared to the rest of their bodies. Blood flows from the heart to the gills, where it collects oxygen fromwater and then distributes it to the other organs and tissues. The small heart produces weak blood pressure, and many sharks must swim continuously to create themuscular contractions needed to circulate blood throughout their bodies. Most sharks are cold-blooded—that is, they do not generate heat by digesting food. Instead, the bod...

• Welfare.

  industrializing societies. Governments typically financed social insurance programs with tax funds and direct levies on the wages of potential recipients. Social insurancereplaced part of incomes lost when workers became disabled, were laid off, or had reached an age that forced them out of the labor market. Later, governments of Germany, France, Belgium, Sweden, and other countries developed forms of social insurance that provided population-wide, or universal,coverage. Such forms included chil...

• 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...

• 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...

• 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...

• 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...

• Coronary Heart Disease.

  when a patient is at rest may indicate that the blood supply of the heart is not normal, and the ECG can often detect damage from a previous heart attack. In anexercise stress test, an ECG is recorded while a patient is performing physical activity such as walking on a treadmill or riding a stationary bicycle. As the intensity ofexercise increases, the doctor looks for specific changes in the ECG that indicate the heart is not getting enough oxygen. In cardiac catheterization, a long, thin, flex...

• 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...

• Herbert Hoover.

  E Postwar Work Even after the armistice, the Allies continued their blockade around Germany. Hoover, in Europe again, worked to have it relaxed. He was appointed chairman of theAmerican Relief Administration to assist in the economic restoration of Europe, receiving from the U.S. Congress $100 million to fight famine and plague. In this officialrole, and afterward as a private citizen, Hoover oversaw the distribution of 46 million tons of food to people in 30 countries. He controlled shipping,...

• Herbert Hoover

  E Postwar Work Even after the armistice, the Allies continued their blockade around Germany. Hoover, in Europe again, worked to have it relaxed. He was appointed chairman of theAmerican Relief Administration to assist in the economic restoration of Europe, receiving from the U.S. Congress $100 million to fight famine and plague. In this officialrole, and afterward as a private citizen, Hoover oversaw the distribution of 46 million tons of food to people in 30 countries. He controlled shipping,...

• William Howard Taft.

  considered him an ideal successor. Because Roosevelt himself was satisfied that Taft's election would ensure that his reform programs were continued, he used hisinfluence with each state's Republican Party to get Taft the nomination. As a result, Taft became the Republican candidate on the first ballot. He was elected president in1908 with a popular vote of 7,675,320 to 6,412,294 for Nebraska editor and Democratic candidate William Jennings Bryan, and an electoral vote of 321 to Bryan's 162.Alth...

• William Howard Taft

  considered him an ideal successor. Because Roosevelt himself was satisfied that Taft's election would ensure that his reform programs were continued, he used hisinfluence with each state's Republican Party to get Taft the nomination. As a result, Taft became the Republican candidate on the first ballot. He was elected president in1908 with a popular vote of 7,675,320 to 6,412,294 for Nebraska editor and Democratic candidate William Jennings Bryan, and an electoral vote of 321 to Bryan's 162.Alth...

• Taxation.

  Thus, corporate income faces a higher tax burden than income earned by individuals or by other types of businesses. Tax legislation passed in 2003 in the United Statesattempted to address this issue by lowering the tax rate on dividends. Some economists have proposed abolishing the corporate income tax and instead taxing the owners of corporations (shareholders) through the personal income tax.Other students of the tax system see the corporate income tax as the price corporations pay in return f...

• 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...

• 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...

• 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...

• Whale - biology.

  III BEHAVIOR OF WHALES Studies of whales in captivity have taught scientists much about the complex social behavior of whales. Since the late 1980s, advances in the use of satellite trackingsystems have also broadened opportunities for scientists to observe how whales behave in the wild. A Swimming and Diving Whales swim by making powerful up-and-down movements of the tail flukes, which provide thrust. The power comes from body muscles that flex the lower spine upand down in a wavelike motion...

• Kentucky - geography.

  The climate of Kentucky is characterized by warm or hot summers and cool winters. Throughout the year, temperatures do not vary greatly from place to place,although they are generally slightly lower in the Appalachian Plateaus region than elsewhere in the state. Average July temperatures are usually from 24° to 27°C (76°to 80°F) in the central and western areas and from 23° to 24°C (74° to 76°F) in the east. January averages range from below 1°C (34°F) in the northern Bluegrassregion to more tha...

• Kentucky - USA History.

  The climate of Kentucky is characterized by warm or hot summers and cool winters. Throughout the year, temperatures do not vary greatly from place to place,although they are generally slightly lower in the Appalachian Plateaus region than elsewhere in the state. Average July temperatures are usually from 24° to 27°C (76°to 80°F) in the central and western areas and from 23° to 24°C (74° to 76°F) in the east. January averages range from below 1°C (34°F) in the northern Bluegrassregion to more tha...

• Spain - country.

  B Natural Resources Spain has a number of mineral resources. The largest known deposits are of iron ore, zinc, and lead. Spain also produces significant quantities of copper and mercury.These deposits are mined mainly in Huelva province in southwestern Spain, around Cartagena on the Mediterranean, and at various points along the Bay of Biscay inthe north. Additionally, uranium is mined in the region of Extremadura, near the Portuguese frontier, where pyrites, fluorspar, gypsum, tungsten, and po...

• Alabama (state) - geography.

  indentations along the coast are measured, the state’s shoreline is 977 km (607 mi) long. It includes the shores of Mobile Bay, an inlet 56 km (35 mi) long at the mouthof the Mobile River. Barrier beaches partly block the entrance to the bay, leaving narrow openings on either side of Dauphin Island. Dauphin and other islands alongAlabama’s coast west of Mobile Bay are separated from the mainland by Mississippi Sound. D Climate Alabama has a humid subtropical climate, with short, relatively mild...

• Alabama (state) - USA History.

  indentations along the coast are measured, the state’s shoreline is 977 km (607 mi) long. It includes the shores of Mobile Bay, an inlet 56 km (35 mi) long at the mouthof the Mobile River. Barrier beaches partly block the entrance to the bay, leaving narrow openings on either side of Dauphin Island. Dauphin and other islands alongAlabama’s coast west of Mobile Bay are separated from the mainland by Mississippi Sound. D Climate Alabama has a humid subtropical climate, with short, relatively mild...

• Native Americans of North America.

  addition to smallpox and measles, explorers and colonists brought a host of other diseases: bubonic plague, cholera, typhoid fever, scarlet fever, pleurisy, mumps,diphtheria, pneumonia, whooping cough, malaria, yellow fever, and various sexually transmitted infections. Despite the undisputed devastation wreaked on Indian populations after European contact, native populations showed enormous regional variability in their response todisease exposure. Some peoples survived and, in some cases, even...

• Native Americans of North America - Canadian History.

  addition to smallpox and measles, explorers and colonists brought a host of other diseases: bubonic plague, cholera, typhoid fever, scarlet fever, pleurisy, mumps,diphtheria, pneumonia, whooping cough, malaria, yellow fever, and various sexually transmitted infections. Despite the undisputed devastation wreaked on Indian populations after European contact, native populations showed enormous regional variability in their response todisease exposure. Some peoples survived and, in some cases, even...

• Asia - Geography.

  Borneo, the world’s third largest island after Greenland and New Guinea. To the southeast is the Timor Sea separating the Asian island of Timor from the Australiancontinent. The Indian subcontinent is flanked by the Bay of Bengal on the east and the Arabian Sea on the west. The island of Sri Lanka and the much smaller Maldives andNicobar Islands trail away to the south. The Arabian Sea’s Gulf of Aden, the Red Sea, the Mediterranean Sea, and the Black Sea form an arc along the western rim of Asia...