29 résultats pour "attached"
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Atom
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INTRODUCTION
Water Molecule
A water molecule consists of an oxygen atom and two hydrogen atoms, which are attached at an angle of 105°.
spontaneously break apart and change, or decay, into other atoms. Unlike electrons, which are fundamental particles, protons and neutrons are made up of other, smaller particles called quarks. Physicists know of six different quarks.Neutrons and protons are made up of up quarks and down quarks —two of the six different kinds of quarks. The fanciful names of quarks have nothing to do with their properties; the names are simply labels to distinguish one quark from another. Quarks are unique amo...
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Flower - biology.
insects. The sepals unfurl as the flower opens and often resemble small green leaves at the flower’s base. In some flowers, the sepals are colorful and work with thepetals to attract pollinators. E Variations in Structure Like virtually all forms in nature, flowers display many variations in their structure. Most flowers have all four whorls—pistil, stamens, petals, and sepals. Botanists callthese complete flowers. But some flowers are incomplete, meaning they lack one or more whorls. Incomplet...
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In-Line Skating.
the foot using a combination of laces and buckles. Many skaters prefer a simple closure system that has laces on the lower portion of the skate and a buckle at the top.The boot liner is made of a soft, padded, cloth portion that fits inside the outer shell. Boot liners should be vented, which keeps the feet cool by allowing perspiration toescape during strenuous workouts or long trips. Attached to the bottom of each skate is the wheel frame. The frame houses from three to five wheels. The wheels...
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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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Mountain Climbing.
teeth on one side, and a straight, flat, metal blade called an adze on the other. Ice axes have many uses. One of the most common is to help the climber stay balanced on steep slopes. The climber swings the axe with a short, quick movement to lodge the pick in snow or ice, creating a secure anchor. If a climber should slip and beginsliding down a snowfield, a self-arrest can be performed by turning face down on the snow and burying the pick in the snow surface. The climber’s weight over the...
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Fishing.
directly to the spool and turns the spool one rotation at a time. C Fishing Lines Fishing lines serve as the link between the angler’s reel and the lure or bait. The most popular line used for sportfishing is monofilament nylon line, which is strong anddurable and has a certain amount of stretch, which helps when an angler sets the hook. The line comes in a variety of strengths, from 2-pound test to more than 100-pound test. (Pound test is the amount of pressure that can be put on a line before...
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Immune System.
The humoral immune response involves a complex series of events after antigens enter the body. First, macrophages take up some of the antigen and attach it to classII MHC molecules, which then present the antigen to T helper cells. The T helper cells bind the presented antigen, which stimulates the T helper cells to divide andsecrete stimulatory molecules called interleukins. The interleukins in turn activate any B lymphocytes that have also bound the antigen. The activated B cells then divide...
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Bicycle.
narrow as possible to minimize weight and interference with pedaling. F Specialty Bicycles Many other types of bicycles are designed for special purposes. Although not as common as standard single-rider racing, touring, mountain, or recreational bicycles,they nonetheless have significant niches. Recumbent bicycles are bicycles on which the rider sits upright as if in a chair, with legs and feet stretched out in front. Because they support the rider’s lower back,recumbents allow the rider far mo...
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Airplane.
For example, the Anglo-French Concorde, a commercial supersonic aircraft, was generally limited to over-water routes, or to those over sparsely populated regions ofthe world. This limitation impacted the commercial viability of the Concorde, which ended its regular passenger service in October 2003. Designers today believe theycan help lessen the impact of sonic booms created by supersonic airliners but probably cannot eliminate them. One of the most difficult practical barriers to supersonic fl...
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Puppets
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INTRODUCTION
Punch and Judy
Punch and Judy are characters in an English hand puppet show that first appeared in 1662.
Rod puppets are controlled by rods attached to their limbs, heads, and bodies. Although the traditional rod puppets of Belgium and Sicily are worked from above, likemarionettes, most contemporary rod figures are operated from below. In theaters, rod puppeteers are frequently concealed from view by drapery or stage flats (fabric stretched across frames). On television and in films, rod and hand puppeteers usually hold their figures either above their heads or in front of their faces. In the lat...
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Stone Age.
limestone, quartzite, and indurated shale. Ground stone tools could be made on a wider range of raw material types, including coarser grained rock such as granite. Flaking produces several different types of stone artifacts, which archaeologists look for at prehistoric sites. The parent pieces of rock from which chips have beendetached are called cores, and the chips that have been removed from cores are called flakes. A flake that has had yet smaller flakes removed from one or more edgesin orde...
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Organic Chemistry - chemistry.
B Alkenes and Alkynes Isomeric with the cyclanes, or cycloalkanes as they are sometimes called, is the family of alkenes, also represented by the general formula C nH2n. This family of hydrocarbons is characterized by one or more double bonds between carbon atoms. Propene and cyclopropane, for example, are isomers, as are 1,3-dimethylcyclohexane and 3,4-dimethyl-2-hexene. (The location of the double bond is indicated by the 2-hexene part of the name.) Double bonds may also occur incyclic compou...
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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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Shang Dynasty - History.
The dynastic ancestors belonged to an elaborate religious pantheon that also included various nature powers and the Shang high god, Di. The higher powers were lessconcerned with the well-being of Shang society than the ancestors were. Di, whose wishes were often hard to determine, could even cause the Shang harm. The naturepowers could occasionally influence the wind, rain, and harvests, but only Di could actually order the weather. For an agricultural society such as the Shang, this wasperhaps...
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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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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...
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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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Meteorology.
to find the corresponding relative humidity and dew-point temperature. III SPECIAL METEOROLOGICAL INSTRUMENTS Meteorologists have developed several sophisticated instruments that measure multiple physical characteristics of the air simultaneously and at more than one location.The most important of these special instruments are radiosondes, Doppler radar, and weather satellites. A Radiosonde A radiosonde measures air temperature, air pressure, and humidity from the earth’s surface up to an alt...
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Army.
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INTRODUCTION
Army, military land forces of a nation, assembled, drilled, disciplined,
disappearance for several centuries of large standing armies in Europe. A Middle Ages Feudalism was based on a concept of local defense, each baron or landowner governing land that had been given him by the king, and each lord having his ownpersonal protective forces recruited from among men who worked for him. In return, each lord and his men were pledged to annual service to the monarch and couldbe called on in special instances, as in the defense of Christendom during the Crusades. National...
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Frog (animal).
which means that their body temperature depends on the temperature of the surrounding environment. Few species can tolerate temperatures below 4°C (40°F) orabove 40°C (104°F), and many species can survive only within a narrower range of temperatures. In addition, frogs’ thin, moist skin offers little protection againstwater loss, and when on land the animals must guard against drying out. Many frogs are active at night because temperatures are cooler and humidity is higher thanduring the day. In...
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Frog (animal) - biology.
which means that their body temperature depends on the temperature of the surrounding environment. Few species can tolerate temperatures below 4°C (40°F) orabove 40°C (104°F), and many species can survive only within a narrower range of temperatures. In addition, frogs’ thin, moist skin offers little protection againstwater loss, and when on land the animals must guard against drying out. Many frogs are active at night because temperatures are cooler and humidity is higher thanduring the day. In...
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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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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...
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Renaissance
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INTRODUCTION
Renaissance, series of literary and cultural movements in the 14th, 15th, and 16th centuries.
the great writings of ancient Greece and Rome. Intellectuals continued to build on the ideas of the Renaissance during the 18th century Age of Enlightenment, a time when scientific advancements led to a newemphasis on the power of human reason. One of the early Enlightenment thinkers was French philosopher and writer Voltaire. He claimed that the Renaissance was acrucial stage in liberating the mind from the superstition and error that he believed characterized Christian society during the Middl...
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Renaissance .
the great writings of ancient Greece and Rome. Intellectuals continued to build on the ideas of the Renaissance during the 18th century Age of Enlightenment, a time when scientific advancements led to a newemphasis on the power of human reason. One of the early Enlightenment thinkers was French philosopher and writer Voltaire. He claimed that the Renaissance was acrucial stage in liberating the mind from the superstition and error that he believed characterized Christian society during the Middl...
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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...
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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...
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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...