24 résultats pour "crystal"
- Crystal Palace - architecture.
- Crystal Palace - architecture.
- DARK CRYSTAL
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Le crystal Palace
consacrer une large étude à la ventilation du bâtiment.,Il décida alors de créer un grand nombre d'aérations afin de permettre la circulation de l'air. Paxton n'était pas un architecte mais chef jardinier à Chatsworth au service du Duc du Devonshire.Il avait conçu précédemment de grandes serres constituées d'une ossature métallique et d'un remplissage de verre combiné au bois.Il appliqua cette technique lors de la conception des plans du bâtiment de l'exposition de Londres, dans la mesure où el...
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Igneous Rock.
As a magma cools, the first crystals to form will be of minerals that become solid at relatively high temperatures (usually olivine and a type of feldspar known asanorthite). The composition of these early-formed mineral crystals will be different from the initial composition of the magma. Consequently, as these growing crystalstake certain elements out of the magma in certain proportions, the composition of the remaining liquid changes. This process is known as magmatic differentiation.Sometime...
- Camille PISSARRO LE CRYSTAL PALACE
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Gemstones.
In the late 1960s a method was developed for “growing” diamonds by heating a diamond particle to a high temperature and subjecting it to methane gas. The gasdecomposes into carbon atoms, which adhere to the diamond crystal. The crystal structure of the enlarged diamond is identical to that of a natural diamond. Diamondsof about 1 carat (200 mg or 0.007 oz) have been produced by this method, but their cost is still considerably higher than that of naturally occurring diamonds. Sapphires are made...
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Molecule - chemistry.
attracted to the negatively charged electrons between them. The electrons belong to the molecule as a whole. However, each hydrogen atom now has a complete outershell of two electrons. The formula H 2 describes a hydrogen molecule, a discrete unit. When a molecule contains just two atoms, such as the hydrogen molecule does, it is called a diatomic molecule. Some atoms can form covalent bonds with more than one other atom and thus create a larger molecule. Atoms form molecules with covalent bo...
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Physical Chemistry - chemistry.
by the system in the form of the flow of electrical currents, formation of surfaces and changes in surface tension, changes in volume or pressure, and formation ordisappearance of chemical species. B Chemical Kinetics This field studies the rates of chemical processes as a function of the concentration of the reacting species, of the products of the reaction, of catalysts and inhibitors, ofvarious solvent media, of temperature, and of all other variables that can affect the reaction rate. It is...
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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...
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Computer Memory.
been created, information can be retrieved but not changed. Newer technologies allow ROMs to be semi-permanent—that is, the information can be changed, but ittakes several seconds to make the change. For example, a FLASH memory acts like a ROM because values remain stored in memory, but the values can be changed. C External Memory External memory can generally be classified as either magnetic or optical, or a combination called magneto-optical. A magnetic storage device, such as a computer'shar...
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Carbon - chemistry.
Graphite is black and slippery and conducts electricity. In graphite, the atoms form planar, or flat, layers. Each layer is made up of rings containing six carbon atoms.The rings are linked to each other in a structure that resembles the hexagonal mesh of chicken wire. Each atom has three sigma bonds (with 120° between any two ofthe bonds) and belongs to three neighboring rings. The fourth electron of each atom becomes part of an extensive pi bond system. Graphite conducts electricity,because th...
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Moon - astronomy.
B Volcanic Features Maria, domes, rilles, and a few craters display indisputable characteristics of volcanic origin. Maria are plains of dark-colored rock that cover approximately 40 percent ofthe Moon's visible hemisphere. The maria formed when molten rock erupted onto the surface and solidified between 3.16 billion and 3.96 billion years ago. This rockresembles terrestrial basalt, a volcanic rock type widely distributed on Earth, but the rock that formed the maria has a higher iron content an...
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Jupiter (planet) - astronomy.
Beneath the supercritical fluid zone, the pressure reaches 3 million Earth atmospheres. At this depth, the atoms collide so frequently and violently that the hydrogenatoms are ionized—that is, the negatively charged electrons are stripped away from the positively charged protons of the hydrogen nuclei. This ionization results in asea of electrically charged particles that resembles a liquid metal and gives rise to Jupiter’s magnetic field. This liquid metallic hydrogen zone is 30,000 to 40,000 k...
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Planetary Science - astronomy.
III ORIGINS AND COMPOSITIONS OF PLANETS Astronomers believe that planetary systems are formed of elemental materials that were created in the interiors of giant stars. Some of this material comes from giantstars that shed material into space as they age. Most of the matter to form planets, however, comes from stars that explode as supernovas and spread debris enrichedwith the heavier chemical elements into space. According to the currently accepted views, the most likely first stage in the evo...
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Paxton, sir Joseph - biographie du peintre.
Paxton, Intérieur du Crystal Palace (Londres) Le Crystal Palace, œuvre de Joseph Paxton, a été construit à l'occasion de l'Exposition universelle de 1851 à Londres. Entièrement fabriqué en fer et en verre, il marque une étape charnière dansl'histoire de l'architecture moderne. Il a été détruit par un incendie en 1936.Bridgeman Art Library, London/New York Élu à la Chambre des communes en 1854, Paxton ne se consacre plus alors qu’à l’architecture et à l’urbanisme. Il imagine ainsi en 1855 la Vic...
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Antarctica - geography.
The geographic South Pole lies near the center of the continent in East Antarctica. This point is where all map lines of longitude converge at the southern end ofEarth’s axis of rotation. Distinct from the geographic south pole is the south magnetic pole, where the lines of force of Earth’s magnetic field emerge vertically,arching upward over the planet to enter Earth again at the north magnetic pole. The south-seeking end of a compass needle points to the south magnetic pole. Thesouth magnetic...
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Water - chemistry.
flourides in drinking water has been found to reduce tooth decay. See Fluorine. Seawater contains, in addition to concentrated amounts of sodium chloride, or salt, many other soluble compounds, as the impure waters of rivers and streams areconstantly feeding the oceans. At the same time, pure water is continually lost by the process of evaporation, and as a result the proportion of the impurities that givethe oceans their saline character is increased. See Ocean and Oceanography. VII WATER...
- the great exhibition
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Transistor.
During the late 1960s a new electronic technique, the integrated circuit, began to replace the transistor in complex electronic equipment. Although roughly the samesize as a transistor, an integrated circuit performs the function of 15 to 20 transistors. A natural development from the integrated circuit in the 1970s has been theproduction of medium-, large-, and very large-scale integrated circuits (MSI, LSI, and VLSI), which have permitted the building of a compact computer, orminicomputer, con...
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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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Chemistry - chemistry.
parts of oxygen by weight, which is a ratio of about 1 to 8, regardless of whether the water came from the Mississippi River or the ice of Antarctica. In other words, acompound has a definite, invariable composition, always containing the same elements in the same proportions by weight; this is the law of definite proportions. Many elements combine in more than one ratio, giving different compounds. In addition to forming water, hydrogen and oxygen also form hydrogen peroxide.Hydrogen peroxide h...
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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...
- The Alchimist