212 résultats pour "gas"

• Dientes - ciencias de la naturaleza.

  © Microsoft Corporation. Reservados todos los derechos. El ser humano tiene 20 dientes que utiliza durante la fase inicial del desarrollo de los maxilares y que reciben el nombre de dientes de leche o de la infancia. A medida quelos maxilares crecen, estos dientes son reemplazados por otros 32 dientes permanentes de mayor tamaño. Como resultado del crecimiento y ampliación de los maxilares,las raíces de los dientes de leche se separan y dejan espacio para que los dientes permanentes, más grandes...

• Dark Matter - astronomy.

  observed, and the measured frequency of such events has placed limits on how much dark matter can take the form of MACHOs. From the observations that have beenmade by astronomers, it is now known that MACHOs cannot be the dominant constituent of dark matter. There are simply not enough such gravitational lenses. Physicists suspect that a more exotic form of cold dark matter must exist. This form is not baryonic. Like neutrinos, this form barely interacts with ordinary matter, butis some type of...

• Thermodynamics I INTRODUCTION Thermodynamics, field of physics that describes and correlates the physical properties of macroscopic systems of matter and energy.

  Carnot EngineThe idealized Carnot engine was envisioned by the French physicist Nicolas Léonard Sadi Carnot, who lived during theearly 19th century. The Carnot engine is theoretically perfect, that is, it converts the maximum amount of energy intomechanical work. Carnot showed that the efficiency of any engine depends on the difference between the highest andlowest temperatures reached during one cycle. The greater the difference, the greater the efficiency. An automobileengine, for example, wou...

• Turbine.

  steam turbine has supplanted the reciprocating engine as a prime mover in large electricity-generating plants and is also used as a means of jet propulsion. Steam turbines are used in the generation of nuclear power and in nuclear ship propulsion. They operate with fuel-fired boilers for power generation. In cogenerationapplications requiring both process heat (heat used in an industrial process) and electricity, steam is raised at high pressure in the boiler and extracted from the turbineat th...

• Evolución - ciencias de la naturaleza.

  Los pulmones de los organismos que respiran aire y la vejiga natatoria de casi todos los peces actuales han evolucionado a partir delos sacos aéreos dobles de los primitivos peces óseos. En éstos, igual que la vejiga natatoria en los actuales, los sacos aéreos seinflaban y desinflaban para determinar la profundidad a la que nadaba el pez. En otros grupos de peces se transformaron enpulmones primitivos, provistos de abundantes repliegues para maximizar la absorción de oxígeno en un medio pobre en...

• Millennium.

  Postmillennialism, also referred to as progressive millennialism, interprets the Bible less literally than premillennialism does. Postmillennialists regard the millennium as a1,000-year reign of Christian ideals that will end with the return of Christ. In this view, the millennium will not start suddenly through an apocalypse, but graduallythrough the efforts of human beings. Postmillennialists believe that through social reform and by upholding Christian ideals, the kingdom of God will be built...

• Neptune (planet) - astronomy.

  The gaseous atmosphere of Neptune contains hydrogen, helium, and about 3 percent methane. It extends about 5,000 km (about 3,000 mi) above the planet’s ocean.Light reflected from Neptune’s deep atmosphere is blue, because the atmospheric methane absorbs red and orange light but scatters blue light. In 1998 astronomersalso identified molecules of methyl in Neptune’s atmosphere. Methyl molecules each contain one carbon atom and three hydrogen atoms. Methyl molecules are knownas hydrocarbon radical...

• Iran-Iraq War - History.

  The Iranian offensives of 1982 set a pattern that continued for the rest of the war. Exploiting their superiority in numbers, Iran sent its Revolutionary Guard on theattack, supported by regular military forces. Outnumbered Iraqi forces inflicted heavy losses on the Iranians but ultimately fell back. As soon as the initial Iranian thrusthad exhausted itself, however, the Iraqi army exploited Iranian disorganization and lack of equipment to retake much of the lost territory. As the war continued,...

• Fish - biology.

  pectoral fins provide fine movements, add forward thrust, or, together with the pelvic fins, serve as brakes. Typically, fins consist of a thin membrane stretched over afanlike series of thin rods called spines or rays. Most fish breathe underwater with the help of special respiratory organs called gills. Gills are made of a series of thin sheets or filaments through which blood circulates.As water moves into a fish’s mouth and passes over the gills, dissolved oxygen passes across the thin gill...

• Ear. I INTRODUCTION Ear, organ of hearing and balance. Only vertebrates, or animals

  line or rotates in any direction. Each canal also contains sensory areas with sensory hair cells that project into a cone-shaped cap of gelatin. Two of the semicircularcanals are in a vertical position and are used to detect vertical movement, such as jumping or falling. The third canal is horizontal and detects horizontal movement,such as turning or spinning. The action of the canals depends on the inertia of the fluid inside. When the motion of the body changes, the fluid lags behind, causing...

• Hawaii (state) - geography.

  limestone along the coast. The volcanoes of the Hawaiian Islands are all so-called shield volcanoes, or lava domes. Unlike the volcanoes of Alaska and South America, those of Hawaii were notcreated by very explosive eruptions. Formed mostly by lava flows, they are great rounded mountain masses, rather than steep-sided cones. Mauna Kea, dormant forcenturies, is the highest mountain in the state. It rises to 4,205 m (13,796 ft) above sea level, and its summit is dotted with cinder cones formed by...

• Hawaii (state) - USA History.

  limestone along the coast. The volcanoes of the Hawaiian Islands are all so-called shield volcanoes, or lava domes. Unlike the volcanoes of Alaska and South America, those of Hawaii were notcreated by very explosive eruptions. Formed mostly by lava flows, they are great rounded mountain masses, rather than steep-sided cones. Mauna Kea, dormant forcenturies, is the highest mountain in the state. It rises to 4,205 m (13,796 ft) above sea level, and its summit is dotted with cinder cones formed by...

• Chile - country.

  D Plant and Animal Life The indigenous plant life of Chile varies according to climatic zone. Plant life in the northern region includes brambles and cactus and has little variety. Here, theAtacama provides one of the best examples on Earth of an absolute desert. The more humid Central Valley supports several species of cacti, espino (a thorny shrub),grasses, and the Chilean pine, which bears edible nuts. Dense rain forests are located south of Valdivia with laurel, magnolia, false beech, and v...

• DEGAS Hilaire Germain Edgar de Gas : Course de gentlemen Avant le départ

  DEGAS Hilaire Germain Edgar de Gas Course de gentlemen Avant le départ Né à Paris. 1834 Mort à Paris . 1917 La date de 1862 paraît surprenante si ron se réfère aux tableaux d'histoire de la même épo­ que : Petites filles Spartiates prol'oquant les gar­ çons . Sémiramis ... Mais ses carnets révèlent son intérêt pour les mœurs contemporaines . dont les courses de chevaux qui deviendront un de ses thèmes favoris. Degas s'intéresse...

• TP chimie de gaz et de pétrole: Détermination du point éclair et la température d’inflammabilité du gas-oil.

  2022/2023 Introduction : Le point d'inflammabilité, autre nom du point éclair, est un concept pétrolier et les premiers appareils qui permettent de définir un point d'éclair ont été décrits dans des normes pétrolières. Il faut par conséquent toujours préciser l'appareil qui a été utilisé lorsque on donne une valeur de point d'éclair. But De TP : Détermination du point éclair et la température d’inflammabilité du gas-oil. Les points d'éclair et de feu : donnent une indication de la...

• Neon - chemistry.

• La respiración de los animales - (exposé gratuit en espagnol).

• La atmósfera - (exposé gratuit en espagnol).

• Las energías no renovables - (exposé gratuit en espagnol).

• Radon - chemistry.

• 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...

• Resumen protocolo de Kyoto

• Io (astronomy) - astronomy.

• 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...

• 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...

• Volcano.

  before eruption. Very violent explosive eruptions are called Plinian eruptions, after Roman naturalist Pliny the Elder. These eruptions can last for several hours to daysand eject a large amount of pyroclastic material. Some volcanoes can produce much more energetic eruptions that eject materials farther from the vents because oftheir andesitic and dacitic composition. Andesitic and dacitic lava is generally thicker than basaltic lava. Stiff lava generally produces more-explosive eruptions. B No...

• Automóvil - ciencia y tecnologia.

  Sección transversal de un carburadorSección simplificada de un carburador de flujo descendente, uno de los tipos de carburador más habituales.© Microsoft Corporation. Reservados todos los derechos. En el carburador se mezcla aire con gasolina pulverizada. La bomba de gasolina impulsa el combustible desde el depósito hasta el carburador, donde se pulveriza medianteun difusor. El pedal del acelerador controla la cantidad de mezcla que pasa a los cilindros, mientras que los diversos dispositivos de...

• Camerún (república) - geografía.

  La densa selva de CamerúnLa valiosa región de selva ecuatorial de la llanura costera camerunense, al sur del país, contiene un gran número de especiesarbóreas.Guenay Ulutuncok/laif/Aurora Photos Las valiosas selvas de Camerún contienen un gran número de especies arbóreas, en especial palmera de aceite, bambú, caoba, teca, ébano y caucho. La fauna es variada yabundante e incluye monos, chimpancés, gorilas, antílopes, leones y elefantes, así como numerosas especies de pájaros y serpientes. 2.3 Rec...

• Ulysses (spacecraft) - astronomy.

  Ulysses was also used to study comet Hale-Bopp, which was first seen in 1995. Hale-Bopp travels an unusual path at a large angle to the ecliptic, and the trajectory ofUlysses was well suited to capture images of Hale-Bopp as it made its way around the Sun. Astronomers paid particular attention to Hale-Bopp’s plasma tail—a plume ofionized, or electrically charged, gas within the main tail that streams away from the comet when it approaches within about 1.5 AU from the Sun. They found that theplas...

• Nuclear Energy I INTRODUCTION Gundremmingen Nuclear Power Plant, Germany The first of three boiling-water nuclear reactors at Germany's Gundremmingen plant began operating in 1966 but was permanently shut down after being decommissioned in 1983.

  such as ¯U is induced by the absorption of a neutron as in producing cesium-140, rubidium-93, three neutrons, and 200 MeV, or 3.2 × 10 -11 J (7.7 × 10 -12 cal). A nuclear fission reaction releases 10 million times as much energy as is released in a typical chemical reaction. See Nuclear Chemistry. III NUCLEAR ENERGY FROM FISSION The two key characteristics of nuclear fission important for the practical release of nuclear energy are both evident in equation (2). First, the energy per fiss...

• Atom - chemistry.

  Atoms have several properties that help distinguish one type of atom from another and determine how atoms change under certain conditions. A Atomic Number Each element has a unique number of protons in its atoms. This number is called the atomic number (abbreviated Z). Because atoms are normally electrically neutral,the atomic number also specifies how many electrons an atom will have. The number of electrons, in turn, determines many of the chemical and physical properties ofthe atom. The ligh...

• Bolivia - country.

  E Plants and Animals Because of the wide variations in elevation, plant and animal species of nearly every climatic zone are found in Bolivia. A coarse grass, called ichu, grows on the largelybarren high plateau in the west. Para rubber trees, more than 2,000 species of hardwood trees, and vanilla, sarsaparilla, and saffron plants are common in the tropicalforests of the east. The llama, found chiefly on the Altiplano, is an efficient beast of burden. Alpacas and vicuñas also inhabit the platea...

• Atom I 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...

• Physics I INTRODUCTION Physics, major science, dealing with the fundamental constituents of the universe, the forces they exert on one another, and the results produced by these forces.

  Starting about 1665, at the age of 23, Newton enunciated the principles of mechanics, formulated the law of universal gravitation, separated white light into colors,proposed a theory for the propagation of light, and invented differential and integral calculus. Newton's contributions covered an enormous range of naturalphenomena: He was thus able to show that not only Kepler's laws of planetary motion but also Galileo's discoveries of falling bodies follow a combination of his ownsecond law of m...

• Pulmones - ciencias de la naturaleza.

  Respiración en seres humanosCuando el diafragma se contrae y se mueve hacia abajo, los músculos pectorales menores y los intercostales presionan las costillashacia fuera. La cavidad torácica se expande y el aire entra con rapidez en los pulmones a través de la tráquea para llenar el vacíoresultante. Cuando el diafragma se relaja, adopta su posición normal, curvado hacia arriba; entonces los pulmones se contraen y elaire se expele.© Microsoft Corporation. Reservados todos los derechos. Durante la...

• Atmosphere.

• Kuiper Belt - astronomy.

  III RESEARCH The Kuiper Belt is an exciting area of research in astronomy. The discovery and astronomical exploration of the Kuiper Belt over the past decade have fueled arevolution in scientists’ views of the solar system. Today astronomers recognize the Kuiper Belt as the third major region of the solar system (the other two regions arethe inner solar system, with its small rocky planets, and the outer solar system, with its gas-giant planets). They believe that the belt helps explain Pluto’...

• Oxygen - chemistry.

• 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...

• 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...

• Ecosistema - ciencias de la naturaleza.

  Todos los medios y ecosistemas naturales se enfrentan ahora a una dificultad sin precedentes: la humanidad. El ser humano ha comprimido en unos pocos siglos cambiosque en su ausencia hubiesen exigido miles o millones de años. Las consecuencias de estos cambios están todavía por ver. A continuación se describen los impactos másimportantes de la actividad de los seres humanos sobre los ecosistemas ( véase Impacto ambiental). 4.1 Destrucción y fragmentación de hábitats La influencia más directa...

• Neutron I INTRODUCTION Neutron, electrically neutral elementary particle that is part of the nucleus of the atom.

  Beta DecayBeta decay can occur in two ways. As shown on the left, a neutron turns into a proton by emitting an antineutrino and anegatively charged beta particle. As shown on the right, a proton turns into a neutron by emitting a neutrino and apositively charged beta particle. Positive beta particles are called positrons and negative beta particles are called electrons.After the decay, the nucleus of the atom contains either one less or one more proton. Beta decay changes an atom of oneelement i...

• Texas - geography.

  D Climate Eastern Texas has a humid subtropical climate, while a semiarid low latitude climate prevails in central areas, and an arid low latitude climate in the extreme west. Alongthe coast the climate is much milder, with fewer extremes in temperatures. Hurricanes sometimes hit the coastal areas of Texas from late July through September, andtornadoes are common in north-central Texas in April and May. D1 Temperature Summers are hot throughout the state, and temperatures exceeding 35°C (95°F)...

• Texas - USA History.

  D Climate Eastern Texas has a humid subtropical climate, while a semiarid low latitude climate prevails in central areas, and an arid low latitude climate in the extreme west. Alongthe coast the climate is much milder, with fewer extremes in temperatures. Hurricanes sometimes hit the coastal areas of Texas from late July through September, andtornadoes are common in north-central Texas in April and May. D1 Temperature Summers are hot throughout the state, and temperatures exceeding 35°C (95°F)...

• Algeria - country.

  areas to fishing. National parks, including the giant Tassili N’Ajjer National Park in the eastern corner of the country, comprise a large proportion of the protected area. The effects of Algeria’s human population on the fragile landscape have been severe. The greatest ecological threats are deforestation and burning of scrub vegetation,conversion of steppe habitat to arable land, and soil erosion due to overgrazing and poor farming practices. Pollution of Mediterranean coastal waters is pervas...

• Uranus (planet) - astronomy.

  V COMPOSITION AND STRUCTURE A Interior of Uranus Uranus contains mostly rock and water, with hydrogen and helium (and trace amounts of methane) in its dense atmosphere. Astronomers believe that Uranus, likeNeptune, formed from the same material—principally frozen water and rock—that composes most of the planet’s moons. As the planet grew, pressures andtemperatures in the planet’s interior increased, heating the planet’s frozen water into a hot liquid. Uranus probably has a relatively small roc...

• Japón - geografía.

  parte a los vientos noroccidentales procedentes de Siberia y la corriente fría de Ojotsk (u Oya Shivo), que fluye hacia el sur en el mar del Japón (mar Oriental). Hacia el sury el este de esta región la influencia de la corriente cálida de Kuro-Shivo modera los inviernos. En Shikoku, Kyūsh ū y en el sur de Honsh ū los veranos son cálidos yhúmedos, casi subtropicales, y los inviernos son templados con pocas nevadas. Japón se encuentra en el camino de los monzones surorientales, que aportan bastan...

• Toronto - geography.

  now a museum. In the far northeast side of the City is the Toronto Zoo, a modern zoo covering many acres and with well-designed animal displays. Originally known as the SkyDome, the Rogers Centre is a state-of-the-art stadium complex that opened in 1989. The stadium features a retractable roof that can openin 20 minutes to expose the playing field and most of the 50,000 seats to the open air. It is the home of the Toronto Argonauts of the Canadian Football League and theToronto Blue Jays of Majo...

• Toronto - Geography.

  now a museum. In the far northeast side of the City is the Toronto Zoo, a modern zoo covering many acres and with well-designed animal displays. Originally known as the SkyDome, the Rogers Centre is a state-of-the-art stadium complex that opened in 1989. The stadium features a retractable roof that can openin 20 minutes to expose the playing field and most of the 50,000 seats to the open air. It is the home of the Toronto Argonauts of the Canadian Football League and theToronto Blue Jays of Majo...

• Alemania - geografía.

  vecinos. Un acuerdo internacional ejemplar obliga a Alemania a ayudar en la protección medioambiental del Waddenzee o mar de Wadden, el brazo oriental del mar delNorte que comparte con Países Bajos y Dinamarca. Alemania firmó el Convenio sobre el Patrimonio de la Humanidad en 1976 y cuenta con nueve reservas de la biosferareconocidas por el programa El Hombre y la Biosfera de la Organización de las Naciones Unidas para la Educación, la Ciencia y la Cultura (UNESCO). Además, existen unaserie de l...