1113 résultats pour "only"
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Human Evolution.
Strepsirhines are the most primitive types of living primates. The last common ancestors of strepsirhines and other mammals—creatures similar to tree shrews andclassified as Plesiadapiformes—evolved at least 65 million years ago. The earliest primates evolved by about 55 million years ago, and fossil species similar to lemursevolved during the Eocene Epoch (about 55 million to 38 million years ago). Strepsirhines share all of the basic characteristics of primates, although their brains are notpa...
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Uganda - country.
Uganda’s population is predominantly rural and is concentrated in the south, particularly in the crescent at the edge of Lake Victoria and in the southwest. Almost allUgandans are black Africans. Foreign residents make up less than 4 percent of the population and come mostly from neighboring states. In 2008 Uganda’s population was estimated at 31,367,972. The estimated growth rate of the population in 2008 was 3.6 percent. The birth rate was 48 per 1,000people and the death rate 12 per 1,000. Th...
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John Quincy Adams.
man of my whole country.” When President Thomas Jefferson requested Senate approval of his treaty for the purchase of the French colony of Louisiana, Adams was the only New EnglandFederalist to vote in favor of it. He realized that the power and influence of his own New England would be reduced if the vast territory were added to the nation, but hewas convinced that the national interest would best be served by the purchase of Louisiana ( see Louisiana Purchase). Adams again broke with his New...
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John Quincy Adams
man of my whole country.” When President Thomas Jefferson requested Senate approval of his treaty for the purchase of the French colony of Louisiana, Adams was the only New EnglandFederalist to vote in favor of it. He realized that the power and influence of his own New England would be reduced if the vast territory were added to the nation, but hewas convinced that the national interest would best be served by the purchase of Louisiana ( see Louisiana Purchase). Adams again broke with his New...
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Human Evolution - biology.
classified as Plesiadapiformes—evolved at least 65 million years ago. The earliest primates evolved by about 55 million years ago, and fossil species similar to lemursevolved during the Eocene Epoch (about 55 million to 38 million years ago). Strepsirhines share all of the basic characteristics of primates, although their brains are notparticularly large or complex and they have a more elaborate and sensitive olfactory system (sense of smell) than do other primates. B Haplorhines B1 Tarsiers T...
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Cloning - biology.
found that such embryo cells are totipotent (able to give rise to all the different cell types in the body). Exploiting this characteristic, scientists developed three techniques to clone embryo cells: blastomere separation, blastocyst division, and somatic cell nuclear transfer. A Blastomere Separation In blastomere separation, scientists fertilize an egg cell with a sperm cell in a laboratory dish. The resulting embryo is allowed to divide until it forms a mass of aboutfour cells. Scientist...
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Crusades.
modern Lebanon; the Principality of Antioch, in modern Syria; and the County of Edessa, in modern northern Syria and southern Turkey. IV CRUSADES OF THE 12TH CENTURY The Crusades of the 12th century, through the end of the Third Crusade in 1192, illustrate the tensions and problems that plagued the enterprise as a whole. For thelords of Outremer a compromise with the residents and Muslim powers made sense; they could not live in constant warfare. And yet as European transplants theydepended on...
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Crusades .
modern Lebanon; the Principality of Antioch, in modern Syria; and the County of Edessa, in modern northern Syria and southern Turkey. IV CRUSADES OF THE 12TH CENTURY The Crusades of the 12th century, through the end of the Third Crusade in 1192, illustrate the tensions and problems that plagued the enterprise as a whole. For thelords of Outremer a compromise with the residents and Muslim powers made sense; they could not live in constant warfare. And yet as European transplants theydepended on...
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Western Philosophy.
the popular belief in personal deities, but he failed to explain the way in which the familiar objects of experience could develop out of elements that are totally differentfrom them. Anaxagoras therefore suggested that all things are composed of very small particles, or “seeds,” which exist in infinite variety. To explain the way in whichthese particles combine to form the objects that constitute the familiar world, Anaxagoras developed a theory of cosmic evolution. He maintained that the activ...
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Democratic Republic of the Congo - country.
Except in the high elevations, the country’s climate is very hot and humid. The average annual temperature in the low central area is about 27°C (about 80°F).Temperatures are considerably higher in February, the hottest month. At altitudes above about 1,500 m (about 5,000 ft) the average annual temperature is about 19°C(about 66°F). Average annual rainfall is about 1,500 mm (about 60 in) in the north and about 1,300 mm (about 50 in) in the south. Frequent heavy rains occur fromApril to November...
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Algebra
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INTRODUCTION
Algebra, branch of mathematics in which symbols (usually letters) represent unknown numbers in mathematical equations.
B Order of Operations and Grouping Algebra relies on an established sequence for performing arithmetic operations. This ensures that everyone who executes a string of operations arrives at the sameanswer. Multiplication is performed first, then division, followed by addition, then subtraction. For example: 1 + 2 · 3 equals 7 because 2 and 3 are multiplied first and then added to 1. Exponents and roots have even higher priority than multiplication: 3 · 2 2 = 3 · 4 = 12 Grouping symbols override...
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Paleolithic Art
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INTRODUCTION
Cave Painting, Lascaux
This portion of a cave painting in what is now Lascaux, France, was done by Paleolithic artists about 13,000 bc.
Venus of WillendorfThis so-called Venus figurine from the area of Willendorf, Austria, is one of the earliest known examples of sculpture,dating from about 23,000 bc. The figure, which is carved out of limestone, is only 11.25 cm (4.5 in) high, and wasprobably designed to be held in the hand. It is believed the Venus may be a fertility symbol, which would explain theexaggerated female anatomy.Ali Meyer/Bridgeman Art Library, London/New York Paleolithic art usually is classified as either figura...
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Slavery in the United States - U.
tripled, from about 1.2 million to almost 4 million in 1860. The natural growth of the slave population meant that slavery could survive without new slave imports. Natural population growth also hastened the transition from an African to an African American slave population. By the 1770s, only about 20 percent of slaves in thecolonies were African-born, although the concentration of Africans remained higher in South Carolina and Georgia. After 1808 the proportion of African-born slavesbecame tin...
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Christopher Columbus
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INTRODUCTION
Christopher Columbus (1451-1506), Italian-born Spanish navigator who sailed west across the Atlantic Ocean in search of a route to Asia but achieved fame by making
landfall in the Americas instead.
explorers, adventurers, entrepreneurs, merchants, and any others who saw their fortunes tied to the trade winds and ocean currents. Columbus’s brother Bartholomewworked in Lisbon as a mapmaker, and for a time the brothers worked together as draftsmen and book collectors. Later that year, Columbus set sail on a convoy loadedwith goods to be sold in northern Atlantic ports. In 1478 or 1479 Columbus met and married Felipa Perestrello e Moniz, the daughter of a respected, though relatively poor, nob...
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Christopher Columbus.
explorers, adventurers, entrepreneurs, merchants, and any others who saw their fortunes tied to the trade winds and ocean currents. Columbus’s brother Bartholomewworked in Lisbon as a mapmaker, and for a time the brothers worked together as draftsmen and book collectors. Later that year, Columbus set sail on a convoy loadedwith goods to be sold in northern Atlantic ports. In 1478 or 1479 Columbus met and married Felipa Perestrello e Moniz, the daughter of a respected, though relatively poor, nob...
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Christopher Columbus.
explorers, adventurers, entrepreneurs, merchants, and any others who saw their fortunes tied to the trade winds and ocean currents. Columbus’s brother Bartholomewworked in Lisbon as a mapmaker, and for a time the brothers worked together as draftsmen and book collectors. Later that year, Columbus set sail on a convoy loadedwith goods to be sold in northern Atlantic ports. In 1478 or 1479 Columbus met and married Felipa Perestrello e Moniz, the daughter of a respected, though relatively poor, nob...
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Christopher Columbus - explorer.
explorers, adventurers, entrepreneurs, merchants, and any others who saw their fortunes tied to the trade winds and ocean currents. Columbus’s brother Bartholomewworked in Lisbon as a mapmaker, and for a time the brothers worked together as draftsmen and book collectors. Later that year, Columbus set sail on a convoy loadedwith goods to be sold in northern Atlantic ports. In 1478 or 1479 Columbus met and married Felipa Perestrello e Moniz, the daughter of a respected, though relatively poor, nob...
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Brazil - country.
occasional droughts. Brazil contains a wealth of mineral and plant resources that have not yet been fully explored. It possesses some of the world’s largest deposits of iron ore and containsrich deposits of many other minerals, including gold and copper. Brazil’s fossil fuel resources are modest, but this limitation is offset by the considerable hydroelectricpotential of the nation’s many rivers. Although Brazil is an important producer of tropical crops, areas of highly fertile land are limited...
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Northwest Territories - Geography.
million years ago by the severe bending (folding) and faulting (breaking) of sedimentary rock that was once part of the Interior Plains. During the Wisconsin Ice Age,alpine glaciers covered the Cordillera, and the movement of the glaciers created razor-sharp peaks and ridges in these mountains. The moving glaciers also createdbroad U-shaped valleys. To the east of the Interior Plains, the ancient rocks of the Canadian Shield are exposed at the Earth’s surface, resulting in a rough, rolling terra...
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Northwest Territories - Canadian History.
million years ago by the severe bending (folding) and faulting (breaking) of sedimentary rock that was once part of the Interior Plains. During the Wisconsin Ice Age,alpine glaciers covered the Cordillera, and the movement of the glaciers created razor-sharp peaks and ridges in these mountains. The moving glaciers also createdbroad U-shaped valleys. To the east of the Interior Plains, the ancient rocks of the Canadian Shield are exposed at the Earth’s surface, resulting in a rough, rolling terra...
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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...
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Bangladesh - country.
F Environmental Issues Waterborne diseases such as cholera are a serious threat to public health in Bangladesh. Until the 1970s, many of Bangladesh’s people became sick from drinkingpolluted water drawn from surface rivers. Aid agencies such as the United Nations Children’s Fund (UNICEF) built shallow wells throughout the country to help provide asafe source of drinking water to Bangladesh’s poor. In the 1990s, however, it was discovered that many of these wells were contaminated by arsenic, a...
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New York - geography.
The Adirondack province consists of a large highland area occupying 26,000 sq km (10,000 sq mi) in the northeastern quarter of the state. The region is domelike inshape, with the higher elevations toward the east. The western Adirondack province is more a rugged hill region and not truly mountainous. Geologically, this area isrelated to the Laurentian Upland, or Canadian Shield, which lies north of the St. Lawrence River, for it is composed of the same very old igneous rocks, principallygranite...
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New York - USA History.
The Adirondack province consists of a large highland area occupying 26,000 sq km (10,000 sq mi) in the northeastern quarter of the state. The region is domelike inshape, with the higher elevations toward the east. The western Adirondack province is more a rugged hill region and not truly mountainous. Geologically, this area isrelated to the Laurentian Upland, or Canadian Shield, which lies north of the St. Lawrence River, for it is composed of the same very old igneous rocks, principallygranite...
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Atlantic Slave Trade.
members of the planters’ society. Through most of the years of the Atlantic trade, prices for Africans remained favorable in relation to the price of the crops theyproduced. They were, thus, the best economic solution for plantation owners seeking inexpensive labor. The Atlantic slave trade began as a trickle in the 1440s and grew slowly through the 17th century. By 1700, 25,000 slaves, on average, were crossing the Atlantic everyyear. After 1700 the trade grew much more rapidly to a peak in the...
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Ice Hockey.
Each period begins with a face-off at the blue dot at center ice. During the face-off one player from each team lines up at the dot with the stick blade on the ice. After the referee drops the puck, the two players attempt to gain possession of it. Quick hands and strength are essential qualities for players participating in the face-off. Once the puck is dropped, it is in play until an official’s whistle stops it, a goal is scored, or time expires. The team on offense tries to move the puck f...
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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...
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Virus (computer).
how closely it resembles a virus. It relies on experience with previous viruses to predict the likelihood that a suspicious file is an as-yet unidentified or unclassified newvirus. Other types of antiviral software include monitoring software and integrity-shell software. Monitoring software is different from scanning software. It detects illegal orpotentially damaging viral activities such as overwriting computer files or reformatting the computer's hard drive. Integrity-shell software establis...
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Human Nutrition.
is one of the most preventable types of cancer. Nutritionists caution that most Americans need to eat more complex carbohydrates. In the typical American diet, only 40 to 50 percent of total calories come fromcarbohydrates—a lower percentage than found in most of the world. To make matters worse, half of the carbohydrate calories consumed by the typical American comefrom processed foods filled with simple sugars. Experts recommend that these foods make up no more that 10 percent of our diet, bec...
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Soccer.
Two assistants, known as linesmen or referees’ assistants, aid the referee. Their primary job is to alert the referee when balls go out of the playing area and to assist inmaking offsides calls (see Rules section below). The assistants carry flags, which they wave when the ball leaves the playing area or use to point to the spot where a foul was committed. V EQUIPMENT Soccer is played with a round leather ball. It is between 68 and 71 cm (27 and 28 in) in circumference and weighs between 396...
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Nunavut - Canadian History.
The Arctic Lands is a complex geological area that is centered on the Arctic Ocean. It includes coastal plains, plateaus, and mountains. Coastal plains and plateaus arefound in the western Northwest Territories section of the Arctic Lands, such as on Victoria Island, which is mostly a large, flat plateau. In striking contrast to theserelatively gentle landscapes, the eastern Nunavut section of the Arctic Lands is dominated by a jagged chain of ice-covered mountains. The mountains on EllesmereIsl...
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US Beats USSR in Hockey.
The two sides once again exchanged goals during the first period. Sergei Makarov briefly gave the Soviets a lead when he beat Craig. The goal outraged many in thecrowd who felt that referee Karl Kaisla of Finland missed a holding violation by a USSR player in front of the net. Controversy also played a role in the Americans'game-tying goal at the end of the period. With a few seconds left on the clock, Ken Morrow unleashed an 80-foot slap shot that ricocheted to center Mark Johnson,who deposited...
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Angola (country) - country.
Portugal in 1975, it had approximately 400,000 Portuguese settlers. The vast majority of the Portuguese community has since departed for Portugal. A Population Characteristics The 2008 estimated population of Angola, including Cabinda, was 12,531,357. The population distribution, however, was uneven, with about 70 percent of thepopulation concentrated in the north and along the coast. The rate of population increase was 2.1 percent annually in 2008. The population is overwhelmingly rural; only3...
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From "The Metamorphosis" - anthology.
As all this was running through his mind at top speed without his being able to decide to leave his bed—the alarm clock had just struck a quarter to seven—therecame a cautious tap at the door behind the head of his bed. 'Gregor,' said a voice—it was his mother's—'it's a quarter to seven. Hadn't you a train to catch?' Thatgentle voice! Gregor had a shock as he heard his own voice answering hers, unmistakably his own voice, it was true, but with a persistent horrible twittering squeakbehind it lik...
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Big Bang Theory - astronomy.
hydrogen atoms. Hydrogen atoms can only absorb and emit specific colors, or wavelengths, of light. The formation of atoms allowed many other wavelengths of light,wavelengths that had been interfering with the free electrons prior to the cooling of the universe, to travel much farther than before. This change set free radiation thatwe can detect today. After billions of years of cooling, this cosmic background radiation is at about 3 K (-270°C/-454°F).The cosmic background radiation was first d...
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Calvin Coolidge.
By 1923 President Harding was faced with a number of difficulties. A business depression, which had begun in 1922, continued. In addition, the Republican majorities inboth houses of Congress were reduced in the election of 1922, and a discontented farm bloc of Western Republican senators threatened to destroy the Senate majorityby allying with the Democrats. Finally, it was rumored that major scandals involving Harding's friends were about to break. The rumors were soon proved accurate. The dire...
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Calvin Coolidge
By 1923 President Harding was faced with a number of difficulties. A business depression, which had begun in 1922, continued. In addition, the Republican majorities inboth houses of Congress were reduced in the election of 1922, and a discontented farm bloc of Western Republican senators threatened to destroy the Senate majorityby allying with the Democrats. Finally, it was rumored that major scandals involving Harding's friends were about to break. The rumors were soon proved accurate. The dire...
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John Macdonald.
dissolution of the existing Union. The Atlantic colonies, which consisted of Nova Scotia, Prince Edward Island, New Brunswick, and Newfoundland, were considering the question of their own union andplanned to meet at Charlottetown, Prince Edward Island, on September 1, 1864. Macdonald saw his opportunity and secured an invitation for the Canadians to attend.The delegates of the Atlantic colonies put off their own discussion until they had heard the Canadians. Macdonald spoke of the advantages in...
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John Macdonald - Canadian History.
dissolution of the existing Union. The Atlantic colonies, which consisted of Nova Scotia, Prince Edward Island, New Brunswick, and Newfoundland, were considering the question of their own union andplanned to meet at Charlottetown, Prince Edward Island, on September 1, 1864. Macdonald saw his opportunity and secured an invitation for the Canadians to attend.The delegates of the Atlantic colonies put off their own discussion until they had heard the Canadians. Macdonald spoke of the advantages in...
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John Macdonald - Canadian History.
dissolution of the existing Union. The Atlantic colonies, which consisted of Nova Scotia, Prince Edward Island, New Brunswick, and Newfoundland, were considering the question of their own union andplanned to meet at Charlottetown, Prince Edward Island, on September 1, 1864. Macdonald saw his opportunity and secured an invitation for the Canadians to attend.The delegates of the Atlantic colonies put off their own discussion until they had heard the Canadians. Macdonald spoke of the advantages in...
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Nuclear Weapons.
Regardless of the method used to attain a supercritical assembly, the chain reaction proceeds for about a millionth of a second, liberating vast amounts of heat energy.The extremely fast release of a very large amount of energy in a relatively small volume causes the temperature to rise to tens of millions of degrees. The resultingrapid expansion and vaporization of the bomb material causes a powerful explosion. VI PRODUCTION OF FISSILE MATERIAL Much experimentation was necessary to make the p...
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Disputed Presidential Election of 2000 - U.
counts. At oral arguments on November 20, the justices seemed to be most interested in one issue: At what point did allowing re-counts risk making Florida too late toparticipate in the electoral college vote? Gore’s lawyers, led by David Boies, argued that the state had until December 12 to pick its electors, which allowed plenty oftime for the re-counts. Electors from each state would meet on December 18 to cast their votes. The next day the court ruled unanimously for Gore and granted a five-d...
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From Bush v.
legal requirements. This case has shown that punch card balloting machines can produce an unfortunate number of ballots which are not punched in a clean, complete way by the voter.After the current counting, it is likely legislative bodies nationwide will examine ways to improve the mechanisms and machinery for voting. B The individual citizen has no federal constitutional right to vote for electors for the President of the United States unless and until the state legislature chooses astatewide...
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Inorganic Chemistry - chemistry.
two electrically charged plates (positively charged top plate and negatively charged bottom plate). By measuring the difference in how fast these electron-laden oildrops fell when the metal plates were charged and uncharged, Millikan was able to calculate the total charge on each oil drop. Because each measurement was a wholenumber multiple of -1.60 × 10 -19 coulombs, Millikan concluded this was the charge carried by a single electron. Using Thomson’s electron charge-to-mass ratio, Millikan then...
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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...
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Criminal Procedure.
B State Criminal Procedure A person prosecuted in the courts of a particular state on a charge of violating the criminal laws of that state is subject to state criminal procedure. State criminalprocedure is found in the constitution, statutes, rules, and judicial decisions of that state. Furthermore, portions of the U.S. Constitution are applicable to state criminaldefendants. State constitutions generally guarantee a state criminal defendant most of the same rights that a federal defendant is...
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Quark
I
INTRODUCTION
Quark, smallest known building block of matter.
Constituents of MatterMatter is composed of tiny particles called quarks. Quarks come in six varieties: up (u), down (d), charm (c), strange (s),top (t), and bottom (b). Quarks also have antimatter counterparts called antiquarks (designated by a line over the lettersymbol). Quarks combine to form larger particles called baryons, and quarks and antiquarks combine to form mesons.Protons and neutrons, particles that form the nuclei of atoms, are examples of baryons. Positive and negative kaons aree...
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Teeth.
treatments to reduce the risk of tooth decay; clear plastic coatings painted on the teeth, called dental sealants, and applications of the mineral fluoride, which fortifiestooth enamel, are two such treatments. Fluoride is also added to public water supplies in a process called fluoridation, which benefits more than 150 million Americans. Gum disease, or periodontal disease, is a progressive condition that worsens with age. Gum disease occurs when bacteria eat away at gum tissue, causing it to p...
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Eagle - biology.
States, is a member of this group found only in North America. It is named for its snow-white head. However, the name bald does not refer to a lack of feathers but comes instead from an outdated word meaning marked with white, as in piebald. The adult bald eagle is blackish brown, with a white head and tail. Its bill, legs, and feet are bright yellow. The bill, which is longer and heavier than the gray bill of golden eagles, is useful for piercing the skin of fish. Bald eagles vary in size....
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Wireless Communications.
were large, heavy units. After the invention of the transistor in 1948, radios shrank in size to small handheld radio transceivers. Public two-way radios with severalfrequency options are widely available as well. Usually limited in range to a few miles, these units are great aids for such mobile professionals as construction workers,film crews, event planners, and security personnel. Simpler two-way radios, called walkie-talkies, have been popular children’s toys for years. Most walkie-talkiesb...