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.

顯微技術(shù)

顯微鏡技術(shù)的每一個進(jìn)步都給科學(xué)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(jì)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(xì)胞植物和動物 的領(lǐng)域。  20  世紀(jì)電子顯微鏡提供了對病毒和極微物體的表面結(jié)構(gòu)的直接觀察。

現(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(xì)節(jié)提供了不同的觀察方式， 它將擴(kuò)展人類對自然世界進(jìn)行的更深入的認(rèn)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(jì)  40  年代實(shí)際上停止了，因?yàn)殡娮语@微鏡的發(fā)展進(jìn)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(jìn)。

但近年來，對它的興趣又復(fù)活了，這很大程度是因?yàn)槔��?X 射線在新光 源上的發(fā)展的結(jié)果。 結(jié)果，今天可得到的亮度是大半個世紀(jì)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(dāng)大地提高了電子學(xué)顯微鏡提供的分辨能力。  它們也 可用來給某些化學(xué)元素繪制分布圖。  某些

X  光顯微鏡可以在極短的時(shí)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(shù)不同，X 光顯微鏡成像術(shù)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(xì)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(yuǎn)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(bǔ)充那些用自然光和電子儀器所進(jìn)行的觀察。

譯路通武漢漢口翻譯公司整理

2012.7.1