解放军文职招聘考试The Microscopic Technique

 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.

显微技术显微镜技术的每一个进步都给科学家提供了看待生物体的功能和其性质的新 观察方式。  16

世纪晚期可视光显微镜的发明引入了一个以前一无所知的单细胞植物和动物 的领域。  20  世纪电子显微镜提供了对病毒和极微物体的表面结构的直接观察。 

现在一种 新的显微镜，利用 X 光而不是自然可见光或电子，为观察微小细节提供了不同的观察方式， 它将扩展人类对自然世界进行的更深入的认识。 研制 X

光显微镜的梦想可追溯到 1875 年； 但它的发展却在  20  世纪  40  年代实际上停止了，因为电子显微镜的发展进行很快。  在  40

年代，电子显微镜毫无例外地比可见光显微镜获得了更好的分辨能力。  然而 X 光显微镜的 表现却没有改进。 

但近年来，对它的兴趣又复活了，这很大程度是因为例如 X 射线在新光 源上的发展的结果。 结果，今天可得到的亮度是大半个世纪以来唯一可得到的 X

光源-X 光 管的几百万倍。  新的  X  光显微镜相当大地提高了电子学显微镜提供的分辨能力。  它们也 可用来给某些化学元素绘制分布图。  某些 

X  光显微镜可以在极短的时间里成像。  另一些

可望具备三维成像的特殊功能。  与传统的电子显微镜成像术不同，X 光显微镜成像术可使 分析样本保留在空气或水中。 

这就意味着生物样品可以在与它们自然环境相近的条件下被 观察研究。  其使用的照明度，即所谓的软性 X 射线，其波长在 20 到 40 埃之间(1 米的

100 亿分之一为 1 埃)。  在许多情况下也能够穿透完整无缺的生物细胞并成像。  由于使用的 X 射线的波长使软性 X

射线显微镜永远比不上电子显微镜可能具有的最高分辨力。 不过他们 特殊的功能将可能补充那些用自然光和电子仪器所进行的观察。