【正文】 s exciting to us is the application of this highpressure chemistry to understanding the outer plas, Jeanloz said. As more plas are found in unexpected orbits around other stars, the effects of internal chemical processes will need to be further clarified in order to obtain a general understanding of pla formation and evolution, the authors concluded in the Science paper. Our solar system39。70s were responsible for recurrences of dust storms in the region. 補(bǔ)充：由于 dust bowl 導(dǎo)致的洛杉磯地區(qū)的移民增加 In the 1930s and 1940s, the region also received two waves of major migrations: that of farm families from the southern Great Plains migrating west to escape the Dust Bowl, and that of African Americans moving out of the American South. During World War II (19391945) the need for labor, especially in ship and aircraft production, boosted the population even more. The population of Los Angeles County jumped from 3 million to million between 1940 and 1950. 托福聽力背景知識(shí) (十 ) 天上掉鉆石 Is It Raining Diamonds On Uranus？ Berkeley October 1, 1999 If experiments at the University of California, Berkeley, are any indication, future explorers of our solar system may well find diamonds hailing down through the atmospheres of Neptune and Uranus. These plas contain a high proportion of methane, which UC Berkeley researchers have now shown can turn into diamond at the high temperatures and pressures found inside these plas. Once these diamonds form, they fall like raindrops or hailstones toward the center of the pla, said Laura Robin Benedetti, a graduate student in physics at UC Berkeley. The team, led by Benedetti and Raymond Jeanloz, professor of geology and geophysics, produced these conditions inside a diamond anvil cell, squeezing liquid methane to several hundred thousand times atmospheric pressure. When they focused a laser beam on the pressurized liquid, heating it to some 5,000 degrees Fahrenheit, diamond dust appeared. They report their experimental findings in a paper in the Oct. 1 issue of Science. The demonstration that methane can convert to diamond as well as other plex hydrocarbons in the interiors of giant plas like Neptune hint at a plex chemistry inside gaseous plas and even brown dwarf stars. Brown dwarfs are small, dim stars barely larger than the largest gas giant plas. This is opening the door to study of the interesting types of chemical reactions taking place inside plas and brown dwarfs, Jeanloz said. Now that technology is able to reproduce the high pressures and temperatures found there, we are getting much better quality information on the chemical reactions taking place under these conditions. It is not amazing that chemistry like this happens inside plas, it39。 3year rotation of wheat and shum and of lying fallow。當(dāng)?shù)竭_(dá)一定的數(shù)量以后，會(huì)組成新的病毒粒子。 侵入和脫殼：病毒粒子被宿主細(xì)胞通過吞噬作用給“吞進(jìn)”了細(xì)胞。它不能單獨(dú)進(jìn)行繁殖，必須在活細(xì)胞內(nèi)才能繁殖。大多數(shù)病毒是由核酸和蛋白質(zhì)組成的。由此可見病毒是多么微小。它的大小用納米（ nm )表示。但總的來說 ,真菌對 人類還是大有益處的。真菌與植物的主要區(qū)別在 于 :真菌貯藏的養(yǎng)料是肝糖 ,而綠色植物主要是淀粉。 真菌與細(xì)菌的主要區(qū)別在于 :真菌是真核生物 ,而細(xì)菌是原核生物。細(xì)菌將永遠(yuǎn)生活在我們身邊。還有厭氧細(xì)菌；好氧細(xì)菌和兼性細(xì)菌。細(xì)菌的細(xì)胞壁由肽聚糖組成，十分堅(jiān)固。細(xì)菌微小，大多數(shù)只有 微米，但少數(shù)卻有 毫米，如納米比亞硫磺珍珠細(xì)菌。支原體沒有細(xì)胞壁，故細(xì)胞柔軟，形成分枝狀的細(xì)胞，故稱支原體。分布廣泛，繁殖快且類型多樣。s mass balance. To find mass balance, scientists measure the area of each region and observe amounts of accumulation and ablation relative to preset stakes. After density measurements are made they may calculate how much water has been added or lost to the glacier. After a series of positive mass balance years, the glacier may respond to the increased thickness by making a glacial advance downvalley. A series of negative years may cause a glacial retreat, meaning that the terminus is melting faster than the ice is moving downvalley. Glaciers have been likened to mighty rivers of ice. Although they move many times more slowly, glaciers have equivalent changes in flow rate and often form falls of fastmoving ice above slowmoving ice pools. Glaciers flow faster down their centers than at ice margins, and more quickly at the surface than at the bed. ... How fast a glacier moves is mostly dependent on the thickness of the ice, and on the angle of its surface slope. Glacier speeds vary when changes are made in this geometry. They respond to excessively high seasonal snow accumulations by generating bulges of thicker ice that may move downvalley many times faster than the glacier39。 they are found on all the continents except Australia and they span the globe from high altitudes in equatorial regions to the polar ice caps. There is a delicate balance between climatic factors that allows snow to remain beyond its season. Scientists and skiers alike can note that within a few days of falling, snowflakes have noticeably begun to change. ... The snowflakes are pressed under the weight of the overlying snowpack. Individual crystal near the melting point have slick liquid edges allowing them to glide along other crystal planes and to readjust the space between them. Where the crystals touch they bond together, squeezing the air between them to the surface or into bubbles. During summer we might see the crystal metamorphosis occur more rapidly because of water percolation between the crystals. By summer39。 行星系統(tǒng)如何與其它星系共處？已有了木星般大小的在附近軌道運(yùn)動(dòng) 的對象的恒星的極好的證據(jù)。 地外行星看起來通常是完整的，或近乎完整的。 地內(nèi)行 星看起來的如同地球上看有時(shí)不完整的月亮。 外層行星：木星，土星，天王星，海王星和冥王星。 巨行星的直徑大于 48000 公里。 冥王星。不過，這些當(dāng)代天體物理學(xué)的最新成果不是在這里三言兩語能說清楚的。所以，我們可以毫不費(fèi)力地觀察到黑洞背面的星空，就像黑洞不存在一樣，這就是黑洞的隱身術(shù)。形象地講，好象光本來是要走直線的，只不過強(qiáng)大的引力把它拉得偏離了原來的方向。我們都知道，光是沿直線傳播 的。而當(dāng)它的半徑一旦收縮到一定程度 (史瓦西半徑 )，正象我們上面介紹的那樣，巨大的引力就使得即使光也無法向外射出，從而切斷了恒星與外界的一切聯(lián)系 —— “黑洞”誕生了。 質(zhì)量小一些的恒星主要演化成白矮星，質(zhì)量比較大的恒星則有可能形成中子星。 我們曾經(jīng)比較詳細(xì)地介紹了白矮星和中子星形成的過程。到這時(shí)，恒星就變成了黑洞。 根據(jù)廣義相對論，引力場將使時(shí)空彎曲。七十年代中國精神病發(fā)病率是 ?，現(xiàn)在上升到 ?，大約一千五百萬人。經(jīng)過化驗(yàn)，發(fā)現(xiàn)這些人體內(nèi)的汞比一般人都高，病因就是 這些人愛吃海魚。