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https://www.economist.com/babbage/2011/07/04/reducing-the-barnacle-bill
Technology monitor
Reducing the barnacle bill
At the moment, ships’ hulls are kept clean using poisonous chemicals. Alternatives would be welcome
Jul 4th 2011
by J.E. | NEW YORK
IN THE decades-long duel for naval supremacy that was fought out between Britain and France at the end of the 18th century, the British fleet had a secret weapon. It was, as secret weapons often are, hugely expensive. But it paid off, giving British ships more speed, manoeuvrability and staying power than their French rivals. It was copper.
By covering the underwater parts of their ships' hulls with copper plates, which slowly dissolved, releasing toxic copper ions as they did so, the British admirals stopped barnacles, mussels and burrowing clams from taking up residence. In fleets that were otherwise well-matched the result was decisive. France lost. The British Empire became the global superpower of the 19th century. And the world speaks English, not French.
Ship-fouling, then, can have serious consequences. Even now, when naval supremacy is less of an issue, the problem is rife. The drag imposed by a heavy infestation of barnacles may push a ship's fuel consumption up by as much as 40%. The solution usually adopted is similar to the Royal Navy's: poison. Copper is still used, though in the form of copper-containing paint. Another popular chemical is tri-butyl tin. But releasing toxic heavy metals into the sea is frowned on these days—indeed, tri-butyl tin is now illegal in many places—so the search is on for alternatives.
One possibility is to use one of a group of chemicals called avermectins. These are antiparasite agents (the most familiar is called, confusingly, ivermectin) that are used against fleas and gut worms. They also, according to Hans Elwing of the University of Gothenburg, in Sweden, prevent barnacle colonies from taking hold by stunting their growth. A barnacle that runs into the chemical finds it cannot bind as strongly to the surface. Only a tiny amount, about one part in a thousand of the paint by weight, is needed, and other marine species are not, as far as can be ascertained, affected.
Another way of discouraging barnacles is to confuse them. A formula developed by Giancarlo Galli of the University of Pisa uses polymer molecules that are water-attracting on one side and water-repellent on the other. When they are painted onto a surface this arrangement forces them into a kind of chequerboard pattern which makes it much harder for barnacles and mussels to stick, according to David Williams, who is in charge of commercialising the idea at AkzoNobel, a multinational chemical company.
P4：另一种方法：在船上刷上一种无毒无害的物质，它不能杀死这个海洋生物，但是当船速加快时，这种生物就不能继续附着在船体上了（被甩掉），现在海洋上行驶的大型船只都能够达到这一速度，但是科学界还在探索其他的方法以使小的船只可以不用行驶得那么快。
If chequerboarding does not work out, AkzoNobel has an alternative: create a surface so smooth that barnacles cannot hold onto it. This is done using a fluoropolymer—a chemical similar in structure to Teflon. The paint does not stop the animals attaching themselves to a hull in the first place, but once the vessel is moving faster than ten knots, the water sweeps them away. That is no problem for commercial vessels, which are always on the go. But for pleasure boats, which may spend a lot of time idle, Dr Williams's team is trying to improve the formula so that a boat need not be moving so fast before the paint does its job.
Small boats, particularly on inland waterways, are also the target of work by John Schetz of the University of North Texas and Robert McMahon, of the University of Texas. They have been experimenting with a mixture containing a molecule similar to capsaicin (the active ingredient of hot peppers) and another that is similar to THC (the active ingredient of cannabis).
P5:和这种情况类似的是另外一种在freshwater里生长的生物，也会附着在在freshwater里行驶的船上面，传统的方法是船在两段河道之间采取陆路运输的方式（总之就是不让船接触水，让生物干死），但是这种方法在这个生物身上不可行，因为这个生物是两栖的，不会干死。
Fouling is less of a problem for boats in fresh water, as barnacles are purely marine. But, recently, the inland waterways, docks and freshwater-intakes of North America have been overrun by zebra and quagga mussels—species that originate from the area around the Black Sea. The mixture Dr Schetz and Dr McMahon have come up with seems particularly effective against these animals, though they have yet to commercialise it.
Their aim is not just to help boat owners, but also to stop them unwittingly spreading the mussels still further. According to Dr McMahon, a big part of the problem is that both species can survive out of the water for several days, so transporting a boat overland from one river basin to another, as is common practice in North America, will not necessarly kill them. Also, boat owners are not always as diligent as they might be about inspecting their vessels for signs of infestation—and even if they do look, the mussels can be hard to see, especially when they are young, and therefore small.
There is thus a lot to play for. Saving fuel will save money, as well as cutting shipping's contribution to greenhouse-gas emissions. And stopping the spread of invasive mussels will make life easier for those who run the waterways of America and Canada. The prize may not, this time round, be world domination. But whoever comes up with the winning formula is at least likely to become rich.
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发表于 2018-8-19 11:56:22
一看时间，心态崩了，这篇阅读5、6道题，做得恍恍惚惚，后面回过神来已经掉进了低分库里，后面几道题目都比较简单。但是心态崩掉救不回来了，做数学的时候一看到长题目就烦躁，最后数学只有49分。构筑昨天反思了一天，今天早上来放狗。
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