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来源:豆瓣大全    发布时间:2019年06月26日 02:32:12    编辑:admin         

Science and Technology Pesticides Smoking them out科技 农药 把它们熏死Tobacco extracts protect plants from pests and pathogens烟草提取物可用于植物病虫害THERE are, as Paracelsus put it, no poisons—only poisonous doses. That is certainly true of nicotine. The amount in a puff from a cigarette acts as a pleasant stimulus. The amount in a packet of 20, injected in one go, would kill you.巴拉赛尔士曾说:世上其实没有毒药,所谓的毒药只是有毒性罢了(更正:所谓的毒性只是剂量变化引起的而已)。对于尼古丁,这当然是确切无疑的。吸一口烟你可能会觉得神清气爽,但如果一次性把一包20的烟全下去(更正:但是如果一次性注射一包20烟的尼古丁剂量),可是会要了你的命的。The Victorians understood this and regularly used nicotine as a lethal poison—not for people (except in the minds of a few crime novelists) but for insects. The invention of modern, synthetic insecticides has more or less killed that practice off. But Cedric Briens of the University of Western Ontario is thinking of reviving it, and is also asking whether tobacco has any other pesticidal properties that might be exploited by the hard-pressed horticulturalist.维多利亚时代的人明白这一点,并且逐渐把尼古丁当做一种致命毒药来使用(更正:并且已经把尼古丁作为一种常见的致命毒药来使用)——不是用来杀人(除了在一些犯罪小说家的构思中),而是用来杀虫。而现代合成杀虫剂的发明在一定程度上结束了尼古丁的使命。现在,西安大略大学的塞德里克?布里安则又在考虑重新启用尼古丁,同时在设法验烟草是否具有一些穷困潦倒的园艺家曾苦苦追寻的杀虫效果(更正:同时在设法验烟草是否还有其他杀虫功能,期望可为饱受病虫害之苦的园艺家所利用)。To find out, Dr Briens and his colleagues at Canadas agriculture ministry ground up dried tobacco leaves using a blender and a sieve. They then heated the result in a pressurised, oxygen-free environment to distil out what they could in the form of a treacly oil. They tested this oil on 11 species of fungus and four types of bacterium that are common agricultural problems. They also tried it on the larvae of Colorado beetles, a notorious pest of potatoes.为此,布里安士和他在加拿大农业部的同事们用搅拌机和筛子将烟叶碾碎,然后将碾碎后的烟叶在高压、无氧环境下加热,提取出一种以粘稠油状存在的物质。他们用这种油对农业中常见的11种真菌和4种杆菌,以及一种常见的令人闻之生厌的马铃薯害虫——科罗拉多甲虫进行了试验。As they report in Industrial and Engineering Chemistry Research, the researchers found that several pestilential organisms were affected by the oil. Specifically they discovered that Pythium ultimum, a fungus that attacks aubergines, peppers, lettuces, tomatoes and cucumbers as seedlings, Clavibacter michiganensis, a bacterium that kills young plants and deforms fruits, and Streptomyces scabies, a second bacterium, which causes potatoes to develop revolting scabs and for which no treatment currently exists, all stopped growing in the presence of the oil. The beetle larvae, too, were killed—though that was no surprise, since the oil contained a lot of nicotine.他们的研究结果发表在《工业化学与工程化学研究》上。研究报告显示这种油对好几种有害的有机生物有作用。研究明确地发现,在这种油的作用下,危害幼苗期茄子、青椒、莴苣、番茄、黄瓜的真菌——腐霉病菌,可使幼苗致死、果实畸形的杆菌——马铃薯环腐病菌,以及另一种导致马铃薯烂痂病,且目前没有有效防治方法的杆菌——疥链霉菌,均被抑制生长。此外,甲虫幼虫也可被杀死——这其实是意料之中的,因为这种油里含有大量的尼古丁。What was a surprise was that removing this nicotine did not diminish the oils effectiveness against bacteria and fungi, and made it only marginally less effective against beetle larvae. The crude oil killed all of the larvae whereas the nicotine-free stuff left a fifth of them alive after two days. Clearly, there are other pesticides at work, and finding what they are is the next task. Meanwhile tobacco has proved itself a more useful substance than even the Victorians realised. Can its rehabilitation be far off?但意料之外的是,将这种油去除后,对细菌和真菌的影响作用却并没有降低,只是对甲虫幼虫的作用在一定程度上减轻了。布满这种油的环境中,所有的甲虫幼虫都被杀死,散乱分布的情况下,两天后也只有五分之一存活。显然,其它具有杀虫作用的物质在起作用,下一步任务就是找出这些物质。这些发现明了烟草不止可以用来做香烟,它甚至具有比维多利亚时代的发现更大的作用。如此,烟草的这种;复兴;还会远吗? /201301/222706。

Sometimes its easy to understand how an evolutionary change took place, but its more difficult to understand why.有时候去理解生物进化演变的过程很容易,想知道原因却很难。For example, consider the beautiful birds of paradise which live in the forests of New Guinea. The males of many bird-of-paradise species have evolved colorful plumage, used for dramatic courtship displays. How this plumage evolved is no mystery: The healthiest males usually have the most spectacular plumage, so females choose whichever male has the gaudiest feathers. With this criterion, its not surprising that male plumage would grow more and more elaborate over the generations.就拿居住在新几内亚森林中的极乐鸟作例子吧。极乐鸟种群中的雄性常常会利用它们绚丽多的羽毛上演一幕又一幕的求爱话剧。这羽毛是怎样进化来的并不神秘:最健壮的雄性往往拥有最绚丽的羽毛,所以雌性往往会选择有艳丽羽毛的雄性。在这种标准的要求下,雄性鸟儿拼命想长出比同类更抢眼,更精致的羽毛,这一点不足为奇。Understanding why the plumage evolved is a little trickier. After all, there are some bird-of-paradise species that are really quite drab. These birds devote most of their energy to finding food and raising their young, instead of wasting it on courtship. What makes these near neighbors so different?了解羽毛色泽为什么会进化就有点棘手了。毕竟,有几种极乐鸟的颜色十分单调。这些鸟把它们主要的精力都放在寻找食物和抚养后代上了,而不是用于求爱。是什么导致这些近邻如此不同?The answer is diet. Those species with the most elaborate plumage also have the most diverse and reliable diet: a variety of insects, and fruits rich in complex nutrients. With this healthy, reliable food supply, females can raise the hatchlings without help from the males. This frees the males for their extravagant courtship behavior, and the complex diet provides them with chemicals to make their brightly colored feathers.就是日常饮食。那些有着最美丽羽毛的鸟儿有各式各样并且稳定的食物:各种昆虫和富含多种营养的水果。有了这种健康的、可靠的食物供应,雌性极乐鸟可以完全不依靠雄性而独立抚养后代。这样就使得雄性有闲暇时间去发展求爱行为,而且多样饮食中的化学物质能让他们的羽毛更鲜亮。In contrast, the drabber birds have a limited diet of simple figs, which are available more sporadically. Theyre monogamous, and both parents need to spend most of their time foraging. This means less time for elaborate courtship behavior.与此相反,拥有单调毛色的鸟儿的食谱就相对简单,仅限于零星分布的无花果。同时它们实行一夫一妻制,父母双方都需要花费大量的时间寻找食物,这就大大缩短了用于考虑花哨的求爱方式的时间。So different diets lead to different behaviors, which results in the evolution of different plumage. These exotic birds show just how complex evolution can be! 所以,不同的食物产生不一样的生活方式,也是进化出不同毛色的原因。这些奇异的鸟儿向我们解释了进化有多么复杂!201206/185346。

Castles are usually enormous structures requiring strong foundations and the use of heavy construction materials such as stone. If the foundations are not strong enough, the castle could collapse. The idea of building a castle in the air-with no foundation at all-is, of course, ridiculous. That is why this idiom is used to describe ideas that are not realistic, as if they are dreams or fantasies. So when someone describes a plan or course of action that we believe may be impossible to achieve, we tell him, ;Youre building castles in the air.;城堡通常是一个很大的建筑,需要有坚实的基础,还要用到大量石头之类的建筑材料。如果城堡的基础不够牢固,很可能会坍塌。建立在空中的城堡是没有基础的。因此,“在空中建城堡”当然是一个很荒谬的想法。因此,我们可以使用这个成语形容那些不太现实的想法——因为这种想法往往是梦想或幻想罢了。所以,当有人描述一个计划或行动时,我们觉得那是不可能实现的,就可以告诉他:“你的想法就如空中楼阁一样。”A similar idiom is ;building castles in the sand.; We know that, on a beach, sand castles are inevitably and easily destroyed by the tide. They are not built to last a long time. So when we say someone is ;building castles in the sand,; we mean they are creating something that wont endure very long.类似的一个成语是“在沙滩上建城堡。”我们知道,沙滩上的城堡不可避免地而且很容易被海浪摧毁,不可能持久。所以,我们说有人是“在沙滩上建城堡”,意思就是他们正在创造的东西持续不了多长时间。注:本文译文属原创,,。201204/178335。

For many scientists, a species’ success is measured by sheer numbers. In that case, the most successful species known to man is a type of bacterium known as S-A-R-11, or SAR-11 for short. Scientists estimate that there are two-hundred and forty times a billion billion billion SAR11 cells floating around in the oceans. Now that makes six-billion humans sound like a mere handful.对很多科学家来说,一个物种的成功完全取决于数量。如果是那样是话,为人类所知的最成功的物种就是一种简称“SAR-11”的细菌。科学家们估计海洋中的SAR11细胞的数量超过2 x 10的28次方个。那让60亿人类听起来屈指可数。SAR11 bacteria are known for their ability to transform one substance into another, which is why they are such an important part of the Earth’s chemical cycles. Although scientists are still uncertain about SAR11′s specific role, it appears to produce carbon dioxide using the oxygen and carbon from organic matter that’s derived from photosynthesis. Scientists speculate that SAR11 plays a major role in the way the ocean’s surface acts as a giant carbon pump that removes carbon dioxide from the atmosphere.SAR11细菌以其转换物质的能力为人所知。而这也使得它们成为地球化学循环中重要的部分。尽管科学家不能确定SAR11的具体作用。但它似乎可以使来自于光合作用的氧气和有机物种的碳发生作用,产生二氧化碳。科学家推测SAR11在海洋表面扮演着重要的作用,作为一个巨大的碳泵移除空气中的二氧化碳。The catch is that SAR11 is what is known as an uncultured organism, which means that scientists haven’t been able to cultivate it under laboratory conditions. This requires scientists to develop pretty indirect genetic methods just to be able to study SAR11 cultures. Now that this technology is available, scientists are sequencing the SAR11 genome in order to figure out exactly what kinds of carbon it uses, and why it’s so successful at ocean living.但目前SAR11是为培养生物,也就是说科学家不能在实验室里培养出这种细菌。因此需要科学家们研制出间接遗传方法,来研究SAR11。既然这项技术可用,科学家为了弄清楚究竟SAR11用的是哪种碳以及为什么它会如此的成功在海洋中生活,正在排序它的基因组。 /201304/233496。