[英语学习]IBT listening keyworld background I.doc

black smokers海底黑烟囱Black smokers are a type of hydrothermal vent found on the ocean floor. The vents are formed in fields hundreds of meters wide when superheated water from below the Earth's crust comes through the ocean floor. It can also be known as a Sea Vent. The superheated water is rich in dissolved minerals from the crust, most notably sulfides, which crystallize to create a chimney-like structure around each vent. When the superheated water in the vent comes in contact with the cold ocean water, many minerals are precipitated, creating the distinctive black color. The metal sulfides that are deposited can become massive sulfide ore deposits in time.Although life is very sparse at these depths, black smokers are the center of entire ecosystems. Sunlight is nonexistent, so many organisms such as archaea and extremophiles must convert the heat, methane, and sulfur compounds provided by black smokers into energy through a process called chemosynthesis. In turn, more complex life forms like clams and tubeworms feed on these organisms. The organisms at the base of the food chain also deposit minerals into the base of the black smoker, thus completing the life cycle.A species of phototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of 2500 m. No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis. This is the first organism discovered in nature to use a light other than sunlight for the photosynthetic process.Polar Bear北极熊The polar bear (Ursus maritimus), also known as the white bear, northern bear, sea bear, ice bear or nanuq in some Inuit languages, is a species of bear that is native to the Arctic and the apex predator within its range. Its thick blubber and fur insulate it against the cold. Its fur, commonly mistaken as white or cream-colored due to the way light refracts within each hair, is translucent, providing camouflage from its prey. The bear has a short tail and small ears that help reduce heat loss, as well as a relatively small head and long, tapered body to streamline it for swimming. The polar bear is a semi-aquatic marine mammal that depends mainly upon the pack ice and the marine food web for survival. It has uniquely adapted for life on a combination of land, sea, and ice and is now dependent on this combination.2Scientists and climatologists believe that the projected decreases in the polar sea ice due to global warming will have a significant negative impact or even lead to extinction of this species within this century.13An alternative theory downplays the effect climate change is having on the polar bear and hypothesizes that the species may survive through adaptation. 4The polar bear is the most carnivorous member of the bear family, and the one that is most likely to prey on humans as food. It feeds mainly on seals, especially ringed seals(环斑海豹) that poke holes in the ice to breathe, but will eat anything it can kill: birds, rodents, shellfish, crabs, beluga whales(白鲸), young walruses, occasionally musk oxen or reindeer, and very occasionally other polar bears.The polygamous（一夫多妻） polar bears mate in the spring (March to May); pairing only lasts for the actual mating with few permanent bonds observed. Testosterone levels increase in the spring for the males and the testicles increase in size. Once fertilized the females ova undergoes a delayed implantation, which takes hold in September or October. The gestation period is between 195 and 265 days (about 8 months) with the cubs born soon after the ova implant in early winter (November to December). The mother digs a two-chambered cave in deep snow for the birth in October after a period of heavily feeding. Usually, two cubs are born, less often one or three; litters of four cubs have been recorded.The most immediate and topically recognized threat to the polar bear is the drastic changes taking place in their natural habitat, which is literally melting away due to global warming.3738The United States Geological Survey, for example, in November 2006, stated that the loss of sea ice in the Alaskan portion of the Beaufort Sea has lead to a higher death rate for polar bear cubs.39Ragtime 拉格泰姆音乐(1890-1915期间在美国流行的一种音乐)Ragtime is an American musical genre which enjoyed its peak popularity between 1899 and 1918. It has had several periods of revival since then and is still being composed today. Ragtime was the first truly American musical genre, predating jazz. It began as dance music in popular music settings years before being published as popular sheet music for piano. Being a modification of the then popular march, it was usually written in 2/4 or 4/4 time (meter) with a predominant left hand pattern of bass notes on odd-numbered beats and chords on even-numbered beats accompanying a syncopated melody in the right hand. A composition in this style is called a "rag". A rag written in 3/4 time is a "ragtime waltz".Ragtime is not a "time" (meter) in the same sense that march time is 2/4 meter and waltz time is 3/4 meter; it is rather a musical genre that uses an effect that can be applied to any meter. The defining characteristic of ragtime music is a specific type of syncopation in which melodic accents fall between metrical beats. This results in a melody that seems to be avoiding some metrical beats of the accompaniment by emphasizing notes that either anticipate or follow the beat. The ultimate (and intended) effect on the listener is actually to accentuate the beat, thereby inducing the listener to move to the music. Scott Joplin, the composer/pianist known as the "King of Ragtime", called the effect "weird and intoxicating". He also used the term "swing" in describing how to play ragtime music: "Play slowly until you catch the swing.".1 The name swing later came to be applied to an early genre of jazz that developed from ragtime. Converting a non-ragtime piece of music into ragtime by changing the time values of melody notes is known as "ragging" the piece. Original ragtime pieces usually contain several distinct themes, four being the most common number.Ash Tree （白蜡树/灰树）Etching (蚀刻版画, 蚀刻术, 铜版画)Etching is the process of using strong acid to cut into the unprotected parts of a metal surface to create a design in intaglio (凹雕, 阴雕) in the metal (the original process - in modern manufacturing other chemicals may be used on other types of material). As an intaglio method of printmaking, it is, along with engraving, the most important technique for old master prints, and remains widely used today.In pure etching, a metal (usually copper, zinc or steel) plate is covered with a waxy ground which is resistant to acid. The artist then scratches off the ground with a pointed etching needle1 where he wants a line to appear in the finished piece, so exposing the bare metal. The échoppe, a tool with a slanted oval section is also used for "swelling" lines.2 The plate is then dipped in a bath of acid, technically called the mordant (from the French for "bite"), or has acid washed over it.3 The acid "bites" into the metal, where it is exposed, leaving behind lines sunk into the plate. The remaining ground is then cleaned off the plate. The plate is inked all over, and then the ink wiped off the surface, leaving only the ink in the etched lines.The plate is then put through a high-pressure printing-press together with a sheet of paper (often moistened to soften it).4 The paper picks up the ink from the etched lines, making a print. The process can be repeated many times; typically several hundred impressions (copies) could be printed before the plate shows much sign of wear. The work on the plate can also be added to by repeating the whole process; this creates an etching which exists in more than one state.Etching can be, and very often has been, combined with other intaglio techniques like engraving (eg Rembrandt) or aquatint (eg Goya).Sea salt (海盐)Sea salt, obtained by evaporating seawater, is used in cooking and cosmetics. Its mineral content gives it a different taste from table salt, which is pure sodium chloride, usually refined from mined rock salt (halite) or from sea salt. Areas that produce specialized sea salt include the Cayman Islands, France, Ireland, Colombia, Sicily, Apulia in Italy, Maine and Cape Cod in the United States. Generally more expensive than table salt, it is commonly used in gourmet cooking and premium potato chips.Where mineral salt has been readily obtainable it has long been mined. The salt mines of Hallstatt go back at least to the Iron Age. However, it has not been readily obtainable everywhere and the alternative coastal source has also been exploited for thousands of years. The principle of the production is the evaporation of the water from the brine of the sea. In warm and dry climates this may be done entirely by solar energy, but in other climates, fuel must be used. For this reason, sea salt production is now almost entirely an industry of Mediterranean and other warm, dry climates.Gourmands often believe sea salt to be superior to ordinary table salt in taste and texture, though one cannot always taste the difference when dissolved. In applications where sea salt's coarser texture is retained, it can provide different mouthfeel and changes in flavor due to its different rate of dissolution. The mineral content also affects the taste. It may be difficult to distinguish sea salt from other salts with a high mineral content, such as pink Himalayan salt, or grey colored rock salt. Because sea salt is not high in iodine, an ion essential for human health, it is not necessarily a healthy substitute for iodized table salt, which is supplemented with the element, unless another source of dietary iodine is available. Iodized forms of sea salt are now marketed to address this concern.Sea salt can also be used (in solution) as a hair product. It is sprayed lightly into the hair creating a tousled, messy texture and is often used in creating larger, more adventurous styles. Just add water, and scrunch.SONAR（声波定位仪）SONAR (Sound Navigation And Ranging)  or sonar  is a technique that uses sound propagation under water (primarily) to navigate, communicate or to detect other vessels. There are two kinds of sonar  active and passive. Sonar may be used as a means of acoustic location.Acoustic location in air was used before radar. Sonar may also be used in air for robot navigation while SODAR (an upward looking in-air sonar) is used for atmospheric investigations. Acoustic emission measurements can also be made for crack detection.The term sonar is also used for the equipment used to generate and receive the sound. The frequencies used in sonar systems vary from infrasonic to ultrasonic.The study of underwater sound is sometimes known as hydroacoustics.Protostar (原恒星)A Protostar is an object that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. The protostellar phase is an early stage in the process of star formation. For a solar-mass star it lasts about 100,000 years. It starts with a core of increased density in a molecular cloud and ends with the formation of a T Tauri star, which then develops into a main-sequence star.Stars are often found in groups known as clusters which appear to have formed at around the same time. This can be explained if it is assumed that as a cloud contracts it does not do so uniformly. In fact, as first pointed out by Richard Larson, the giant molecular clouds in which stars are formed are universally observed to have turbulent velocities imposed on all scales within the cloud. These turbulent velocities compress the gas in shocks, which generate filaments and clumpy structures within the giant molecular cloud over a wide range of sizes and densities. This process is referred to as turbulent fragmentation. Some clumpy structures will exceed their Jeans mass and become gravitationally unstable, and may again fragment to form a single or multiple star system.Whatever the reason, the cloud breaks up into smaller, denser areas which may again break into still smaller areas - the outcome being a cluster of protostars. This certainly agrees with the observation that star clusters are common.As the cloud continues to contract it begins to increase in temperature. This is not caused by nuclear reactions but by the conversion of gravitational energy to thermal kinetic energy. As a particle (atom or molecule) decreases its distance from the centre of the contracting fragment this will result in a decrease in its gravitational energy. The total energy of the particle must remain constant so the reduction in gravitational energy must be accompanied by an increase in the particle's kinetic energy. This can be expressed as an increase in the thermal kinetic energy, or temperature, of the cloud. The more the cloud contracts the more the temperature increases.Collisions between molecules often leave them in excited states which can emit radiation as those states decay. The radiation is often of a characteristic frequency. At these temperatures (10 to 20 kelvins) the radiation is in the microwave or infrared range of the spectrum. Most of this radiation will escape hence preventing the rapid rise in temperature of the cloud.As the cloud contracts the number density of the molecules increases. This will eventually make it more difficult for the emitted radiation to escape. In effect, the gas becomes opaque to the radiation and the temperature within the cloud will begin to rise more rapidly.The fact that the cloud becomes opaque to radiation in the infrared makes it difficult for us to observe directly what is happening. We must look to longer wavelength radio radiation which does escape even the densest clouds. In addition, theory and computer modelling are necessary to understand this phase.Until the surrounding matter is falling onto the central condensation, it is considered to be in protostar stage. When the surrounding gas/dust envelope disperses and accretion process stops, the star is considered as pre-main sequence star.Warm-bloodedWarm-blooded animals maintain thermal homeostasis; which is keeping your body temperature at a constant level. This involves the ability to cool down or produce more body heat. Warm-blooded animals mainly control their body temperature by regulating their metabolic rates (e.g. increasing their metabolic rate as the surrounding temperature begins to decrease).A large proportion of the creatures traditionally called "warm-blooded" (mammals and birds) fit all three of these categories. However, over the past 30 years, studies in the field of animal thermophysiology have revealed many species belonging to these two groups that don't fit all these criteria. For example, m