409 résultats pour "liquider"

• La Table périodique des éléments

  139 La Table périodique des éléments I réaliser que les changements d'état de certains corps, lorsqu'ils étaient chauffés dans de l'air, étaient en fait dus à des recombinaisons avec de l'oxygène. On connait désormais ce phénomène sous le nom d'oxydation. Entre-temps, les travaux sur la nature de la matière se précisaient. En 1811, le chimiste anglais John Dalton publiait sa théorie sur la nature atomique de la matière, postulant que les éléments différaient par leur masse...

• 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...

• oiseaux.

  Les oiseaux ont une ouïe très développée, malgré l’absence d’oreille externe (pavillon). La structure de l’oreille interne est également différente de celle des mammifères.Elle leur permet de percevoir deux sons séparés par un intervalle de deux millièmes de seconde, ce qui est dix fois mieux que la performance humaine. La gamme des sonsaudibles par les oiseaux est la même que celle de l’homme : les oiseaux ne perçoivent ni les infrasons, ni les ultrasons. 2.6. 3 Odorat et goût L’odorat des ois...

• Cours droit bancaire

• 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...

• Extrasolar Planets - astronomy.

  When a planet passes in a front of the star it orbits—an event called a transit—it causes a small dip in the brightness of the star. Measuring the slight change in thebrightness can be used not only to directly detect a planet, but to determine its size and orbit. However, the planet needs to orbit in a plane that lies in a telescope’sline of sight on the star. Despite long odds, Earth-based telescopes have detected and studied a few exoplanets using this method. The first space telescope design...

• Saturn (rocket) - astronomy.

• Drug. I INTRODUCTION Drug, substance that affects the function of living cells, used

  normalizing chemical activity in the emotional centers of the brain. Antianxiety drugs, also referred to as tranquilizers, treat anxiety by decreasing the activity in theanxiety centers of the brain. Sedative-hypnotic drugs are used both as sedatives to reduce anxiety and as hypnotics to induce sleep. Sedative-hypnotic drugs act by reducing brain-cell activity.Stimulant drugs, on the other hand, increase neuronal (nerve cell) activity and reduce fatigue and appetite. Analgesic drugs reduce pain...

• Comet - astronomy.

  may exceed the planet Jupiter in size, however. Observations from telescopes on Earth and in space indicate that most of the gases in the coma and tail of a comet are fragmentary molecules, or radicals, of the mostcommon elements in space: hydrogen, carbon, nitrogen, and oxygen. The radicals, for example, of CH, NH, and OH may be broken away from the stable molecules CH 4 (methane), NH 3 (ammonia), and H 2O (water), which may exist as ices or more complex, very cold compounds in the nucleus. Al...