1365 résultats pour "time"

• 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...

• Ancient Egypt.

  around 4500 BC. The style and decoration of the pottery found at these sites differ from those of pottery found in Upper Egypt. The northern type eventually fell out of use. Other differences between the peoples in Upper Egypt and Lower Egypt include the nature of their architecture and the arrangements for burial of the dead, thelatter perhaps signifying differing religious beliefs. B Unification and Early Dynastic Period By 3500 BC, the settlement of Hierakonpolis, located on the west bank...

• Ancient Egypt - USA History.

  around 4500 BC. The style and decoration of the pottery found at these sites differ from those of pottery found in Upper Egypt. The northern type eventually fell out of use. Other differences between the peoples in Upper Egypt and Lower Egypt include the nature of their architecture and the arrangements for burial of the dead, thelatter perhaps signifying differing religious beliefs. B Unification and Early Dynastic Period By 3500 BC, the settlement of Hierakonpolis, located on the west bank...

• Animal Courtship and Mating - biology.

  activity. These animals frequently copulate in water, and the penis helps transfer sperm before it is carried away by the currents Ostriches and rheas also contain apenis within the cloaca. Virtually all snakes and lizards display yet another variation of internal fertilization. Located in the tail are two penises, called hemepenes, which are covered by spinesand knobs that help lock it into place during mating. The male uses one hemepene at a time for copulation. Male salamanders secrete large...

• 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...

• Global Warming.

  some of the warming influence of increasing greenhouse gases. A1 Carbon Dioxide Carbon dioxide is the second most abundant greenhouse gas, after water vapor. Carbon dioxide constantly circulates in the environment through a variety of naturalprocesses known as the carbon cycle. It is released into the atmosphere from natural processes such as eruptions of volcanoes; the respiration of animals, whichbreathe in oxygen and exhale carbon dioxide; and the burning or decay of plants and other organic...

• Mars (planet) - astronomy.

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

• Internet.

  usually pays a fixed monthly fee for a dedicated connection. In exchange, the company providing the connection agrees to relay data between the user’s computer andthe Internet. Dial-up is the least expensive access technology, but it is also the least convenient. To use dial-up access, a subscriber must have a telephone modem, a device thatconnects a computer to the telephone system and is capable of converting data into sounds and sounds back into data. The user’s ISP provides software that con...

• Ice Skating.

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

• Washington, D.

  structures built according to L’Enfant’s plan. During the War of 1812, British troops set fire to the White House, destroying its interior. President James Madison and hisfamily lived in the Octagon while the White House was being rebuilt. South of the Federal Triangle is the Mall, a narrow park stretching roughly 1.6 km (1 mi) from the Capitol to the Washington Monument. Although the Mall officially endsat 14th Street, landscaped greenery extends to the Potomac. The Washington Monument, whose m...

• Space Exploration - astronomy.

  to produce 250,000 newtons (56,000 lb) of thrust. The Germans launched thousands of V-2s carrying explosives against targets in Britain and The Netherlands. Whilethey did not prove to be an effective weapon, V-2s did become the first human-made objects to reach altitudes above 80 km (50 mi)—the height at which outer spaceis considered to begin—before falling back to Earth. The V-2 inaugurated the era of modern rocketry. A2 Early Artificial Satellites During the years following World War II, the...

• Apollo Program - astronomy.

  Moon’s orbit; rendezvousing and docking with the CSM; and finally, setting a course home to Earth. On return to Earth, the spacecraft was slowed by drag from Earth’satmosphere and by parachutes (just before splashdown), before landing in the ocean. The transit time to and from the Moon was approximately three days each way.Depending on the specific mission, the time in lunar orbit ranged from less than one day for Apollo 8 to over six days for the final three missions, and the time on thelunar s...

• Apollo Program - U.

  Moon’s orbit; rendezvousing and docking with the CSM; and finally, setting a course home to Earth. On return to Earth, the spacecraft was slowed by drag from Earth’satmosphere and by parachutes (just before splashdown), before landing in the ocean. The transit time to and from the Moon was approximately three days each way.Depending on the specific mission, the time in lunar orbit ranged from less than one day for Apollo 8 to over six days for the final three missions, and the time on thelunar s...

• James Monroe.

  In October 1786, Monroe resigned from Congress and settled with his bride in Fredericksburg, Virginia, where he began a law practice. His retirement from politics wasbrief. He was soon elected to the town council, and then once again to the Virginia legislature. However, Monroe never lost touch with national politics. He corresponded regularly with both Jefferson and Madison. In 1786 Monroe attended the AnnapolisConvention, which had been called to consider interstate commerce and other matters...

• James Monroe - USA History.

  In October 1786, Monroe resigned from Congress and settled with his bride in Fredericksburg, Virginia, where he began a law practice. His retirement from politics wasbrief. He was soon elected to the town council, and then once again to the Virginia legislature. However, Monroe never lost touch with national politics. He corresponded regularly with both Jefferson and Madison. In 1786 Monroe attended the AnnapolisConvention, which had been called to consider interstate commerce and other matters...

• Ireland - country.

  F Plants and Animals Ireland’s animal life does not differ markedly from that of England or France. Over many centuries of human settlement almost all of Ireland’s natural woodlands werecleared, and indigenous animals such as bear, wolf, wildcat, beaver, wild cattle, and the giant Irish deer (a type of fallow deer) gradually disappeared. However, thehardy and versatile Connemara pony, Ireland’s only native pony breed, has been used by Irish farmers since prehistoric times. The great auk, or gar...

• Bird. I INTRODUCTION Bird, animal with feathers and wings. Birds are the only

  B Physical Adaptations for Flight The internal body parts of all birds, including flightless ones, reflect the evolution of birds as flying creatures. Birds have lightweight skeletons in which many of themajor bones are hollow. A unique feature of birds is the furculum, or wishbone, which is comparable to the collarbones of humans, although in birds the left and rightportions are fused together. The furculum absorbs the shock of wing motion and acts as a spring to help birds breathe while they...

• Bird - biology.

  B Physical Adaptations for Flight The internal body parts of all birds, including flightless ones, reflect the evolution of birds as flying creatures. Birds have lightweight skeletons in which many of themajor bones are hollow. A unique feature of birds is the furculum, or wishbone, which is comparable to the collarbones of humans, although in birds the left and rightportions are fused together. The furculum absorbs the shock of wing motion and acts as a spring to help birds breathe while they...

• House (architecture) I INTRODUCTION Trulli in Alberobello, Italy Alberobello, in the Apulia region of southeastern Italy, is noted for its unusual limestone houses known as trulli (from Greek trullos, dome).

  Fresco in the Villa of the Mysteries, PompeiiThe Villa of the Mysteries, Pompeii, Italy (built about 50 bc), featured a large hall with this mural encircling it. The mural ispainted in the Second Style of Roman painting. (Historians of art recognize four periods or styles in Roman wall painting.)The mural in the Villa of the Mysteries is thought to depict the initiation rituals of a mystery religion. For this reason, it hasbeen conjectured that the hall was used for cult rituals.Bridgeman Art Li...

• 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...

• 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...

• Wolfgang Amadeus Mozart.

  including the sacred style of church music and the so-called galant (courtly) idiom. The elegant though often superficial galant style dominated much instrumental music of the 1760s and 1770s. Mozart’s mastery often demonstrates itself in an ability to expand and deepen the stylistic possibilities of the time. The manner in which heextended the character and form of the concerto, for instance, owes much to his experience in writing operatic arias. A Musical Expressiveness In the masterful Je...

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

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

• Orthodox Church.

  formally defined by an ecumenical council, as it was in Catholicism, some Orthodox theologians have taught that the act of becoming a monk or the service of burial canalso be sacraments. The sacramental practice of the Orthodox differs in many details from Western customs. Baptism is administered by immersing the child or adult three times under thewater, each time in the name of one of the persons of the Trinity. It is followed immediately by anointment with chrism, a sacred perfumed oil that r...

• Environment.

  escape into space of the infrared energy radiated back out by Earth. This process is referred to as the greenhouse effect. These gases, primarily carbon dioxide,methane, nitrous oxide, and water vapor, insulate Earth’s surface, helping to maintain warm temperatures. Without these gases, Earth would be a frozen planet with anaverage temperature of about -18°C (about 0°F) instead of a comfortable 15°C (59°F). If the concentration of these gases rises, they trap more heat within theatmosphere, caus...

• 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...

• 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...

• 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...

• George Herbert Walker Bush.

  Lebanon. More troubling was the disclosure that agents operating under direct White House supervision used profits from the arms sales to buy weapons for thecontras, a group of anti-government Nicaraguan rebels, despite an explicit congressional ban on such aid. Bush later claimed that he opposed the arms-for-hostagesdeal, but offered little evidence to back his claims ( see Iran-Contra Affair). C 1988 Presidential Election While the Reagan-Bush program helped produce prosperity for the wealth...

• George Herbert Walker Bush - USA History.

  Lebanon. More troubling was the disclosure that agents operating under direct White House supervision used profits from the arms sales to buy weapons for thecontras, a group of anti-government Nicaraguan rebels, despite an explicit congressional ban on such aid. Bush later claimed that he opposed the arms-for-hostagesdeal, but offered little evidence to back his claims ( see Iran-Contra Affair). C 1988 Presidential Election While the Reagan-Bush program helped produce prosperity for the wealth...

• Greek Art and Architecture - history.

  powerful independent city-states. From 334 to 323 BC, Alexander the Great extended his father's empire into Asia Minor (now Turkey), Syria, Egypt, Persia, Afghanistan, and as far as India. D The Hellenistic Period (323-31 BC) Although Alexander the Great extended Greek civilization far beyond the Greek mainland and the boundaries of the Aegean Sea, his empire did not survive his death in 323.After Alexander died, his generals and successors divided the empire into a number of kingdoms: Ptolem...

• Ecology.

  an input of nutrients exceeding the capability of the ecosystem to process them. Nutrients eroded and leached from agricultural lands, along with sewage and industrialwastes accumulated from urban areas, all drain into streams, rivers, lakes, and estuaries. These pollutants destroy plants and animals that cannot tolerate theirpresence or the changed environmental conditions caused by them; at the same time they favor a few organisms more tolerant to changed conditions. Thus,precipitation filled...

• Ecology - biology.

  an input of nutrients exceeding the capability of the ecosystem to process them. Nutrients eroded and leached from agricultural lands, along with sewage and industrialwastes accumulated from urban areas, all drain into streams, rivers, lakes, and estuaries. These pollutants destroy plants and animals that cannot tolerate theirpresence or the changed environmental conditions caused by them; at the same time they favor a few organisms more tolerant to changed conditions. Thus,precipitation filled...

• Saturn - astronomy.

  measurements of the magnetic field made by the Voyager space probes in the 1980s. Additional Cassini findings reported in March 2007 suggested that particles originating from geysers on the moon Enceladus may provide a partial explanation for thechange. The neutral gas particles become electrically charged and are captured by Saturn’s magnetic field, forming a disk of hot, ionized gas around the planet’sequator. The charged particles interact with the magnetic field and slow down the rotation of...

• Alcoholism.

  Although a consensus is growing among health professionals that alcohol dependence is a disease, society’s attitudes toward individuals with drinking problems remainambivalent and confused. Until the mid-20th century, the typical picture of the alcoholic was of someone without steady employment, unable to sustain familyrelationships and most likely in desperate financial straits. But this stereotype was largely dispelled when highly respected people publicly admitted their alcoholdependence and...

• Charles Dickens I INTRODUCTION Charles Dickens English author Charles Dickens ranks as one of the most popular writers in the history of world literature.

  Papers of the Pickwick Club (1836-1837; 1837); The Adventures of Oliver Twist (1837-1839; 1838); The Life and Adventures of Nicholas Nickleby (1838-1839; 1839); The Old Curiosity Shop (1840-1841; 1841); Barnaby Rudge (1841); The Life and Adventures of Martin Chuzzlewit (1843-1844; 1844); Dombey and Son (1846-1848; 1848); The Personal History of David Copperfield (1849-1850; 1850); Bleak House (1852-1853; 1853); Hard Times (1854); Little Dorrit (1855-1857; 1857); A Tale of Tw...

• Dwight Clark's Catch.

  On third down and three, with 51 seconds left, and in need of a touchdown, San Francisco called time-out. Montana and Walsh discussed the play, which wasdesigned to go to Solomon. But as Montana rolled to his right, he spotted Clark behind the defense. With Cowboys defensive linemen D. D. Lewis, Larry Bethea, andJones closing, Montana threw a hurried jump pass that Clark reached up and gathered in. A final point by Ray Wersching gave the 49ers the victory, 28-27. “I hear all the time, especi...

• Joyner Breaks World Records.

  track. In the 200 meters Griffith Joyner set an Olympic record with a time of 21.76 seconds in the quarterfinals; broke the world record in the semifinals with a time of21.56 seconds; and then, 100 minutes later, again broke the record with a time of 21.34 seconds in the finals. She added another gold medal as a member of the U.S.4 x 100 relay team and a silver medal as part of the 4 x 400 relay team. Her three gold medals and one silver made her one of the stars of the U.S. team. Microso...

• Charles Dickens.

  The Old Curiosity Shop broke hearts across Britain and North America when it first appeared. Later readers, however, have found it excessively sentimental, especially the pathos surrounding the death of its child-heroine Little Nell. Dickens’s next two works proved less popular with the public. Barnaby Rudge, Dickens’s first historical novel, revolves around anti-Catholic riots that broke out in London in 1780. The events in Martin Chuzzlewit become a vehicle for the novel’s theme: selfishne...

• Glacier.

  covered. In spring the snow cover begins to melt in the lower reaches, exposing the ice surface. As temperatures increase, the melting moves up the glacier. Thesnowline is the highest position the melting reaches during the year. Firn is old granular snow. The firn limit may not exactly coincide with the annual snowline since insome years rapid melting leaves behind firn patches below the snowline. Some glaciers exhibit features called ice streams and icefalls. Ice streams are valley glaciers th...

• Amphibian (animal) - biology.

  strong enough to kill potential predators. C Hearing, Vision, and Vocalizations Amphibians rely on their senses to find food and evade predators. Amphibians lack external ears but have well-developed internal ears. Hearing is most acute in frogs,which typically have a middle ear cavity for transferring sound vibrations from the eardrum, or tympanum, to the inner ear. Frogs and toads also use their keen hearingin communicating with one another. Using a true voice box, or larynx, and a large, exp...

• Animal Behavior - biology.

  The first motor program analyzed in much detail was the egg-rolling response of geese. When a goose sees an egg outside its nest, it stares at the egg, stretches itsneck until its bill is just on the other side of the egg, and then gently rolls the egg back into the nest. At first glance this seems a thoughtful and intelligent piece ofbehavior, but it is a mechanical motor program; almost any smooth, rounded object (the sign stimulus) will release the response. Furthermore, removal of the egg on...

• Radar.

  gathers the weak returning radar signals and converts them into an electric current. Because a radar antenna may both transmit and receive signals, the duplexerdetermines whether the antenna is connected to the receiver or the transmitter. The receiver determines whether the signal should be reported and often does furtheranalysis before sending the results to the display. The display conveys the results to the human operator through a visual display or an audible signal. B1 The Antenna The rec...

• Commentary The adeventures of Huck Finn

  same hundrun is emphasized by the use of the modals « would », « could » and the verbal form « used to ». So, this everyday life is depicted by the narrator as « lovely ». The child describes his habits as sacred ones. The way it is depicted seems mechanical : everything has a time to be done and is done by the time the children are allowing it. For instance, they are eating first, then having a nap, then shaving « soon as it was night ». The actions are ennumerated, which emphasize the idea o...

• X-Ray Astronomy - astronomy.

  Some neutron stars have weaker magnetic fields that allow incoming material to settle onto the entire surface of the neutron star. Eventually, so much material buildsup that the surface layer becomes dense enough to set off a vast thermonuclear explosion, called an outburst. The explosion heats gas to produce X rays. Such aneutron star—called an X-ray burster—can increase its X-ray production by a million times during an outburst. The X-ray glow fades over time, and the binary systementers a lon...

• Accounting and Bookkeeping.

  The proliferation of mandated notes that accompany financial statements is a particularly visible example. Such notes disclose information that is not already included inthe body of the financial statement. One of the very first notes identifies the accounting methods adopted when acceptable alternative methods also exist, or when theunique nature of the company's business justifies an otherwise unconventional approach. The notes also disclose information about lease commitments, contingent liab...

• 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...

• Men's Swimming: Olympic Gold Medalists.

  1896 Alfréd Hajós Hungary 1:22.20 1904 1 Zoltán Halmay Hungary 1:02.80 1906 Charles Daniels United States 1:13.40 1908 Charles Daniels United States 1:05.60 1912 Duke Kahanamoku United States 1:03.40 1920 Duke Kahanamoku United States 1:00.40 1924 Johnny Weissmuller United States 59.00 1928 Johnny Weissmuller United States 58.60 1932 Yasuji Miyazaki Japan 58.20 1936 Ferenc Csík Hungary 57.60 1948 Walter Ris United States 57.30 1952 Clarke Scholes United States 57.40 1956 Jon Henricks Austria 55...

• Men's Swimming: Olympic Gold Medalists.

  1896 Alfréd Hajós Hungary 1:22.20 1904 1 Zoltán Halmay Hungary 1:02.80 1906 Charles Daniels United States 1:13.40 1908 Charles Daniels United States 1:05.60 1912 Duke Kahanamoku United States 1:03.40 1920 Duke Kahanamoku United States 1:00.40 1924 Johnny Weissmuller United States 59.00 1928 Johnny Weissmuller United States 58.60 1932 Yasuji Miyazaki Japan 58.20 1936 Ferenc Csík Hungary 57.60 1948 Walter Ris United States 57.30 1952 Clarke Scholes United States 57.40 1956 Jon Henricks Austria 55...

• The New York Times