2014考研大作文美文范例：顯微技術_跨考網(wǎng)

　　2014考研大作文美文范例：顯微技術

　　The Microscopic Technique

　　Each advance in microscopic technique has provided scientists with new perspectives on the function of living organisms and the nature of matter itself. The invention of the visible light microscope late in the sixteenth century introduced a previously unknown realm of single celled plants and animals. In the twentieth century, electron microscopes have provided direct views of viruses and minuscule surface structures. Now another type of microscope, one that utilizes x rays rather than light or electrons, offers a different way of examining tiny details; it should extend human perception still farther into the natural world. The dream of building an x ray microscope dates to back 1895; its development, however was virtually halted in the 1940's because the development of the electron microscope was progressing rapidly. During the 1940's, electron microscopes routinely achieved resolution better than that poss ible with a visible light microscope, while the performance of x ray microscopes resisted improvement. In recent years, however, interest in x ray microscopes has revived, largely because of advances such as the developmen t of new sources of x ray illumination. As a result, the brightness available today is millions of times tha t of x ray tubes, which, for most of the century, were the only available sources of soft x rays.The new x ray microscopes considerably improve on the resolution provided by optical microscopes. They can also be used to map the distribution of certain chemical elements. Some can form pictures in extremely short times; others hold the promise of special capabilities such as three dimensional imaging. Unlike conventional electron microscope, x ray microscope enables specimens to be kept in air and in water, which means that biological samples can be studied under conditions similar to their natural state. The illumination used, so called soft x rays in the wavelength range of twenty to forty angstroms (an angstrom is one ten billionth of a meter), is also sufficiently penetrating to image intact biological cells in ma ny cases. Because of the wavelength of the x rays used, soft x ray microscopes will never match the highest resolution possible with electron microscopes. Rather, their special properties will make possible investigations that will complement those performed with light and electron based instruments.

　　全文翻譯：顯微技術

　　顯微鏡技術的每一個進步都給科學家提供了看待生物體的功能和其性質(zhì)的新觀察方式。16世紀晚期可視光顯微鏡的發(fā)明引入了一個以前一無所知的單細胞植物和動物的領域。20世紀電子顯微鏡提供了對病毒和極微物體的表面結構的直接觀察?，F(xiàn)在一種新的顯微鏡，利用X光而不是自然可見光或電子，為觀察微小細節(jié)提供了不同的觀察方式，它將擴展人類對自然世界進行的更深入的認識。研制X光顯微鏡的夢想可追溯到1875年;但它的發(fā)展卻在20世紀40年代實際上停止了，因為電子顯微鏡的發(fā)展進行很快。在40年代，電子顯微鏡毫無例外地比可見光顯微鏡獲得了更好的分辨能力。然而X光顯微鏡的表現(xiàn)卻沒有改進。但近年來，對它的興趣又復活了，這很大程度是因為例如X射線在新光源上的發(fā)展的結果。結果，今天可得到的亮度是大半個世紀以來唯一可得到的X光源-X光管的幾百萬倍。新的X光顯微鏡相當大地提高了電子學顯微鏡提供的分辨能力。它們也可用來給某些化學元素繪制分布圖。某些X光顯微鏡可以在極短的時間里成像。另一些可望具備三維成像的特殊功能。與傳統(tǒng)的電子顯微鏡成像術不同，X光顯微鏡成像術可使分析樣本保留在空氣或水中。這就意味著生物樣品可以在與它們自然環(huán)境相近的條件下被觀察研究。其使用的照明度，即所謂的軟性X射線，其波長在20到40埃之間(1米的100億分之一為1埃)。在許多情況下也能夠穿透完整無缺的生物細胞并成像。由于使用的X射線的波長使軟性X射線顯微鏡永遠比不上電子顯微鏡可能具有的最高分辨力。不過他們特殊的功能將可能補充那些用自然光和電子儀器所進行的觀察。