什么叫扩散通风？-查字典考试网

什么叫扩散通风？

查看答案

正确答案：

扩散通风――就是利用矿井中空气自然扩散运动或利用主风流紊流脉动作用使与周围空气中发出渗混和交换而排除掘进工作面、盲巷或硐室内的有害气体和粉尘，供给一定新鲜空气的通风方式。

答案解析：

暂无解析

上一题下一题

你可能感兴趣的试题

队员a5掷界外球时，球触及篮圈后弹回，被站在场内的a6接住并投中篮，裁判员判2分或3分有效

查看答案

弹簧托架是油箱与车架之间的中间装置。

查看答案

除用于移动式和手持式电气设备外，其他电气设备作保护接地用的电缆芯线电阻值不得超过2Ω。

查看答案

橡套电缆的接地芯线，除用做监测接地回路外，还可以兼作他用。

查看答案

井下机车司机离开座位时，切断电源，扳紧车闸，方可以离开。

查看答案

热门试题更多>

According to UK official statistics, every year about 2000 lives are lost through occupational disease or injury, about 20,000 major industrial injuries occur (e.g. skull fracture, loss of sight) and there are about 200,000 injuries resulting in a work disability of 3 days or more.
兼职要求学生遵守纪律并相应地分配时间。
News media are important in modern society.Why are they so important? Are their influences generally positive or negative?
Childcare vouchers
An increasing number of museums tend to charge admission fees from tourists rather than providing service free of charge. Do you think the advantages outweigh the disadvantages?
Don't wash those fossils! Standard museum practice can wash away DNA. 1.Washing, brushing and varnishing fossils — all standard conservation treatments used by many fossil hunters and museum curators alike — vastly reduces the chances of recovering ancient DNA. 2.Instead, excavators should be handling at least some of their bounty with gloves, and freezing samples as they are found, dirt and all, concludes a paper in the Proceedings of the National Academy of Sciences today. 3.Although many palaeontologists know anecdotally that this is the best way to up the odds of extracting good DNA, Eva-Maria Geigl of the Jacques Monod Institute in Paris, France, and her colleagues have now shown just how important conservation practices can be.This information, they say, needs to be hammered home among the people who are actually out in the field digging up bones. 4.Geigl and her colleagues looked at 3,200-year-old fossil bones belonging to a single individual of an extinct cattle species, called an aurochs.The fossils were dug up at a site in France at two different times — either in 1947, and stored in a museum collection, or in 2004, and conserved in sterile conditions at -20 oC. 5.The team's attempts to extract DNA from the 1947 bones all failed.The newly excavated fossils, however, all yielded DNA. 6.Because the bones had been buried for the same amount of time, and in the same conditions, the conservation method had to be to blame says Geigl."As much DNA was degraded in these 57 years as in the 3,200 years before," she says. Wash in, wash out 7.Because many palaeontologists base their work on the shape of fossils alone, their methods of conservation are not designed to preserve DNA, Geigl explains. 8.The biggest problem is how they are cleaned.Fossils are often washed together on-site in a large bath, which can allow water — and contaminants in the form of contemporary DNA — to permeate into the porous bones."Not only is the authentic DNA getting washed out, but contamination is getting washed in," says Geigl. 9.Most ancient DNA specialists know this already, says Hendrik Poinar, an evolutionary geneticist at McMaster University in Ontario, Canada.But that doesn't mean that best practice has become widespread among those who actually find the fossils. 10.Getting hold of fossils that have been preserved with their DNA in mind relies on close relationships between lab-based geneticists and the excavators, says palaeogeneticist Svante P bo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.And that only occurs in exceptional cases, he says. 11.P bo's team, which has been sequencing Neanderthal DNA, continually faces these problems."When you want to study ancient human and Neanderthal remains, there's a big issue of contamination with contemporary human DNA," he says. 12.This doesn't mean that all museum specimens are fatally flawed, notes P bo.The Neanderthal fossils that were recently sequenced in his own lab, for example, had been part of a museum collection treated in the traditional way.But P bo is keen to see samples of fossils from every major find preserved in line with Geigl's recommendations — just in case. Warm and wet 13.Geigl herself believes that, with cooperation between bench and field researchers, preserving fossils properly could open up avenues of discovery that have long been assumed closed. 14.Much human cultural development took place in temperate regions.DNA does not survive well in warm environments in the first place, and can vanish when fossils are washed and treated.For this reason, Geigl says, most ancient DNA studies have been done on permafrost samples, such as the woolly mammoth, or on remains sheltered from the elements in cold caves — including cave bear and Neanderthal fossils. 15.Better conservation methods, and a focus on fresh fossils, could boost DNA extraction from more delicate specimens, says Geigl.And that could shed more light on the story of human evolution. (640 words nature ) Glossary Palaeontologists 古生物学家 Aurochs 欧洲野牛 Neanderthal (人类学)尼安德特人，旧石器时代的古人类。 Permafrost (地理)永冻层 Questions 1-6 Answer the following questions by using NO MORE THAN THREE WORDS for each answer. 1.How did people traditionally treat fossils? 2.What suggestions do Geigl and her colleagues give on what should be done when fossils are found? 3.What problems may be posed if fossil bones are washed on-site? Name ONE. 4.What characteristic do fossil bones have to make them susceptible to be contaminated with contemporary DNA when they are washed? 5.What could be better understood when conservation treatments are improved? 6.The passage mentioned several animal species studied by researchers.How many of them are mentioned? Questions 7-11 Do the following statements agree with the information given in the passage? Please write TRUE if the statement agrees with the writer FALSE if the statement does not agree with the writer NOT GIVEN if there is no information about this in the passage. 7.In their paper published in the Proceedings of the National Academy of Sciences，Geigl and her colleagues have shown what conservation practices should be followed to preserve ancient DNA. 8.The fossil bones that Geigl and her colleagues studied are all from the same aurochs. 9.Geneticists don't have to work on site. 10.Only newly excavated fossil bones using new conservation methods suggested by Geigl and her colleagues contain ancient DNA. 11.Paabo is still worried about the potential problems caused by treatments of fossils in traditional way. Questions 12-13 Complete the following the statements by choosing letter A-D for each answer. 12.“This information” in paragraph 3 indicates: [A] It is critical to follow proper practices in preserving ancient DNA. [B] The best way of getting good DNA is to handle fossils with gloves. [C] Fossil hunters should wear home-made hammers while digging up bones. [D] Many palaeontologists know how one should do in treating fossils. 13.The study conducted by Geigl and her colleagues suggests: [A] the fact that ancient DNA can not be recovered from fossil bones excavated in the past. [B] the correlation between the amount of burying time and that of the recovered DNA. [C] the pace at which DNA degrades. [D] the correlation between conservation practices and degradation of DNA.
Reading Comprehension Section A Directions: There are ten incomplete sentences in this section. For each sentence there are four choices marked A, B, C and D. Choose the ONE that best completes the sentence. Then write down the right answer in the brackets for each sentence. This section totals 10 points, one point for each sentence. ( )1.We can supply all the bicycles you required ____________ stock and are arranging shipment by M.V. Mermaid. A. for B. from 　C. to 　D. against ( )2.We would like to remind you that the __________ L/C must reach us before March 10 so that we can make shipment in good time. A. covering B. cover 　C. covered 　　D. being covered ( )3.We have received your letter of 28 March, ___________ us to modify the previous arrangements for the shipment of the captioned order. A. asked B. to ask 　C. being asked 　　D. asking ( )4.In our letter of May 5, we made __________ clear that shipment is to be effected in June. A. you B. them 　C. that 　　D. it ( )5.We always deal _______________ payment by sight L/C. A. with　　　　　B. in 　　　C. at 　D. on ( )6.This offer is _____________ to your reply reaching us before the 20th of February. A. subjecting B. subject 　C. subjected D to subject ( )7.____________ we are appreciating the good quality of your black tea, we regret that your price appears to be on the high side. A. While　　　　B. When　　　　　C. However　　　　D. Therefore ( )8.We hereby authorize you to ___________ on us at 60 days after sight to the extent of USD20,000.00. A. open　　　　　B. establish　　　　　C. draw 　 D. build ( )9.If parties to a contract desire to settle disputes, an arbitration clause is usually made in the contract well before a dispute _____________ . A. rises B. arises C. look 　　D. appear ( )10.Some customers requested us to _____________ our price because they considered it too high. A. put down B. get down C. take down 　D. bring down
The order is so urgently required that we must ask you to make the earliest possible shipment.
I hoped we can cooperate happily.
Benefits system