经济学人231:清洁水源 Clean water

 　　Clean water

　　清洁水源

　　Silver threads of life

　　生命的银丝带

　　A water filter that kills bacteria, rather than just removing them

　　新滤水器能够消灭细菌，而不单单是排除细菌

　　MORE than a billion people lack clean water—and in most cases the lack is just of cleanliness, rather than of the water itself. The result is disease, particularly diarrhoea. This kills millions of children a year and stunts¹ the growth of millions more. Better water filters, then, could save many lives and improve many others, and Yi Cui of Stanford University thinks he has come up with one.

　　超过十亿人口缺少饮用水，并且在绝大多数情况下缺少的只是纯净的水，而不是水本身。其结果是给人们带来了疾病，特别是每年夺取数百万儿童性命并使更多的儿童生长发育受阻的腹泻。所以更好的滤水器就能挽救许多生命，提高人们的健康水平。而来自斯坦福大学的崔毅教授认为他已经研制出了这样的滤水器。

　　Traditional filters work by forcing water through pores to weed out bacteria. That needs power, as well as frequent changes of the filter element as the pores fill up with bugs². Dr Cui’s filter, though, does not screen the bacteria out. It kills them.

　　传统的滤水器使水流流过微孔从而排除细菌。这需要消耗电力，而且由于微孔上积满了细菌，滤水器元件也需经常更换。但是崔教授研制的滤水器并不是将细菌排除出去，而是将其消灭。

　　The filter element he and his team have designed is a mesh³ of tiny carbon cylinders⁴, known as nanotubes, and silver wires laid on top of a thin strip of cotton cloth. Silver is well known to kill bacteria, so Dr Cui conjectured⁵ that forcing bugs to pass close to the metal without actually trapping them might lead to their destruction. He also suspected that running an electric current through the silver might help the process, because electrical fields have the ability to break down the membranes⁶ that surround bacterial⁷ cells. Though silver is a good conductor, carbon is cheaper, and the nanotubes provide the extra electrical conductivity needed.

　　崔教授及其团队所设计的滤水器元件采用微小的碳圆柱形网状物，也就是碳纳米管。薄薄的棉布覆盖着碳纳米管一端，并用银丝固定。金属银因能够杀死细菌而为人所知。崔教授据此推测将细菌引至银丝附近而不是使其进入微孔，即可消灭细菌。他同时猜测，使银丝接通电流，将有助于整个过滤工序，因为电场具有穿透细菌细胞膜的特性。因此虽然银是良好导体，碳也很便宜，但是纳米管却可以额外提供必需的导电性。

　　To make their new filter, the team first dipped strips of woven cotton into “ink” containing nanotubes. They then used pipettes to drop the silver wires, which were suspended in methanol, on to the surface of the strips.

　　制作新型滤水器，首先把棉布条浸入含有碳纳米管的“墨水“中，然后用吸管将浸泡在甲醇中的银丝滴在棉布条的表面。

　　Once dried, the new filters were ready to try. To do that Dr Cui connected them to a battery and ran water containing E. coli, a common bacterial contaminant of water, through them. A few drops of the filtered water from each experimental run were then scattered⁸ on an incubation plate to see what was left to grow.

　　置干后，新的滤水器就可以工作了。崔教授将这些碳纳米管与电池相连接，并使含有导致水污染的一种常见细菌——大肠杆菌的水流经其中。随后每次过滤实验得到的几滴水被放在孵化盘中用以观察水中剩余物质的状况。

　　As they report in the latest edition of Nano Letters, Dr Cui and his team found that when the filter was operated at -20 volts⁹ it killed 89% of the bacteria and that at +20 volts it killed 77%. At zero volts, most of the bacteria survived. In a follow-up experiment, in which contaminated water was run through three of the new filters in sequence, 98% of the bacteria were killed.

　　正如在最新一期《纳米快报》中报道的一样，崔教授与其团队发现滤水器在-20伏的电压下工作时，可消灭89%的细菌，在+20伏的电压下工作时，可消灭77%的细菌。而在不通电的情况下，大部分细菌都得以存活。在进一步的实验中，受污染的水依次流经三个新型滤水器，结果98%的细菌被消灭了。

　　Using silver this way might sound expensive, but it is not. The amount involved is minuscule¹⁰, as is the quantity of electricity needed to keep the filter charged (a small solar panel would be sufficient to supply it). And the filter itself would be expected to last indefinitely.

　　如此使用银乍听起来十分昂贵，实则不然。银的使用量非常小，与维持滤水器运转所需电量（一小块太阳能电池板就足够了）一般。此外，滤水器本身还可望永久使用。

　　The next test, then, is to see if the new device kills the full range of dangerous bacteria found in polluted water. If it does then potable water, one of the necessities of life, may become easier for many people to obtain.

　　随后的测试将证明这种新型滤水器是否能消灭在受污染的水中所发现的各种有害细菌。如果确实如此，那么许多人就可以更容易获得生活的必需品——纯净的饮用水了。

1 stunts   

n.惊人的表演( stunt的名词复数 )；（广告中）引人注目的花招；愚蠢行为；危险举动v.阻碍…发育[生长]，抑制，妨碍( stunt的第三人称单数 )

参考例句：

• He did all his own stunts. 所有特技都是他自己演的。
• The plane did a few stunts before landing. 飞机着陆前做了一些特技。 来自《简明英汉词典》

2 bugs   

adj.疯狂的，发疯的n.窃听器( bug的名词复数 )；病菌；虫子；[计算机]（制作软件程序所产生的意料不到的）错误

参考例句：

• All programs have bugs and need endless refinement. 所有的程序都有漏洞，都需要不断改进。 来自《简明英汉词典》
• The sacks of rice were swarming with bugs. 一袋袋的米里长满了虫子。 来自《简明英汉词典》

3 mesh   

n.网孔，网丝，陷阱；vt.以网捕捉，啮合，匹配；vi.适合； [计算机]网络

参考例句：

• Their characters just don't mesh.他们的性格就是合不来。
• This is the net having half inch mesh.这是有半英寸网眼的网。

4 cylinders   

n.圆筒( cylinder的名词复数 )；圆柱；汽缸；（尤指用作容器的）圆筒状物

参考例句：

• They are working on all cylinders to get the job finished. 他们正在竭尽全力争取把这工作干完。 来自《简明英汉词典》
• That jeep has four cylinders. 那辆吉普车有4个汽缸。 来自《简明英汉词典》

5 conjectured   

推测，猜测，猜想( conjecture的过去式和过去分词 )

参考例句：

• The old peasant conjectured that it would be an unusually cold winter. 那老汉推测冬天将会异常地寒冷。
• The general conjectured that the enemy only had about five days' supply of food left. 将军推测敌人只剩下五天的粮食给养。

6 membranes   

n.（动物或植物体内的）薄膜( membrane的名词复数 )；隔膜；（可起防水、防风等作用的）膜状物

参考例句：

• The waste material is placed in cells with permeable membranes. 废液置于有渗透膜的槽中。 来自辞典例句
• The sarcoplasmic reticulum is a system of intracellular membranes. 肌浆网属于细胞内膜系统。 来自辞典例句

7 bacterial   

a.细菌的

参考例句：

• Bacterial reproduction is accelerated in weightless space. 在失重的空间，细菌繁殖加快了。
• Brain lesions can be caused by bacterial infections. 大脑损伤可能由细菌感染引起。

8 scattered   

adj.分散的，稀疏的；散步的；疏疏落落的

参考例句：

• Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来，塞进文件夹里。

9 volts   

n.（电压单位）伏特( volt的名词复数 )

参考例句：

• The floating potential, Vf is usually only a few volts below ground. 浮置电势Vf通常只低于接地电位几伏。 来自辞典例句
• If gamma particles are present, potential differences of several thousand volts can be generated. 如果存在γ粒子，可能产生几千伏的电位差。 来自辞典例句

10 minuscule   

adj.非常小的；极不重要的

参考例句：

• The human race only a minuscule portion of the earth's history.人类只有占有极小部分地球历史。
• As things stand,Hong Kong's renminbi banking system is minuscule.就目前的情况而言，香港的人民币银行体系可谓微不足道。