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Science and Technology
科技
Clean water
清潔水源
Silver threads of life
生命的銀絲帶
A water filter that kills bacteria, rather than just removing them
新濾水器能夠消滅細菌，而不單單是排除細菌
MORE than a billion people lack clean water-and in most cases the lack is just of cleanliness, rather than of the water itself.
超過十億人口缺少飲用水，并且在絕大多數情況下缺少的只是純凈的水，而不是水本身。
The result is disease, particularly diarrhoea. This kills millions of children a year and stunts the growth of millions more.
其結果是給人們帶來了疾病，特別是每年奪取數百萬兒童性命并使更多的兒童生長發育受阻的腹瀉。
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.
所以更好的濾水器就能挽救許多生命，提高人們的健康水平。而來自斯坦福大學的崔毅教授認為他已經研制出了這樣的濾水器。
Traditional filters work by forcing water through pores to weed out bacteria.
傳統的濾水器使水流流過微孔從而排除細菌。
That needs power, as well as frequent changes of the filter element as the pores fill up with bugs.
這需要消耗電力，而且由于微孔上積滿了細菌，濾水器元件也需經常更換。
Dr Cui's filter, though, does not screen the bacteria out. It kills them.
但是崔教授研制的濾水器并不是將細菌排除出去，而是將其消滅。
The filter element he and his team have designed is a mesh of tiny carbon cylinders, known as nanotubes, and silver wires laid on top of a thin strip of cotton cloth.
崔教授及其團隊所設計的濾水器元件采用微小的碳圓柱形網狀物，也就是碳納米管。
Silver is well known to kill bacteria, so Dr Cui conjectured that forcing bugs to pass close to the metal without actually trapping them might lead to their destruction.
薄薄的棉布覆蓋著碳納米管一端，并用銀絲固定。金屬銀因能夠殺死細菌而為人所知。崔教授據此推測將細菌引至銀絲附近而不是使其進入微孔，即可消滅細菌。
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 membranes that surround bacterial cells.
他同時猜測，使銀絲接通電流，將有助于整個過濾工序，因為電場具有穿透細菌細胞膜的特性。
Though silver is a good conductor, carbon is cheaper, and the nanotubes provide the extra electrical conductivity needed.
因此雖然銀是良好導體，碳也很便宜，但是納米管卻可以額外提供必需的導電性。
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.
制作新型濾水器，首先把棉布條浸入含有碳納米管的"墨水"中，然后用吸管將浸泡在甲醇中的銀絲滴在棉布條的表面。
Once dried, the new filters were ready to try.
置干后，新的濾水器就可以工作了。
To do that Dr Cui connected them to a battery and ran water containing E. coli, a common bacterial contaminant of water, through them.
崔教授將這些碳納米管與電池相連接，并使含有導致水污染的一種常見細菌——大腸桿菌的水流經其中。
A few drops of the filtered water from each experimental run were then scattered on an incubation plate to see what was left to grow.
隨后每次過濾實驗得到的幾滴水被放在孵化盤中用以觀察水中剩余物質的狀況。
As they report in the latest edition of Nano Letters, Dr Cui and his team found that when the filter was operated at -20 volts it killed 89% of the bacteria and that at +20 volts it killed 77%.
正如在最新一期《納米快報》中報道的一樣，崔教授與其團隊發現濾水器在-20伏的電壓下工作時，可消滅89%的細菌，在+20伏的電壓下工作時，可消滅77%的細菌。
At zero volts, most of the bacteria survived.
而在不通電的情況下，大部分細菌都得以存活。
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.
在進一步的實驗中，受污染的水依次流經三個新型濾水器，結果98%的細菌被消滅了。
Using silver this way might sound expensive, but it is not.
如此使用銀乍聽起來十分昂貴，實則不然。
The amount involved is minuscule, as is the quantity of electricity needed to keep the filter charged (a small solar panel would be sufficient to supply it).
銀的使用量非常小，與維持濾水器運轉所需電量（一小塊太陽能電池板就足夠了）一般。
And the filter itself would be expected to last indefinitely.
此外，濾水器本身還可望永久使用。
The next test, then, is to see if the new device kills the full range of dangerous bacteria found in polluted water.
隨后的測試將證明這種新型濾水器是否能消滅在受污染的水中所發現的各種有害細菌。
If it does then potable water, one of the necessities of life, may become easier for many people to obtain.
如果確實如此，那么許多人就可以更容易獲得生活的必需品——純凈的飲用水了。
