导线的布设形式有哪些?其外业工作主要包括哪些?-查字典考试网

导线的布设形式有哪些?其外业工作主要包括哪些?

查看答案

正确答案：

导线的布设形式主要有闭合导线、附合导线和支导线。导线测量的外业工作主要包括：(1)踏勘选点;(2)测角;(3)量边;(4)起始边方位角确定;(5)记录与外业成果整理

答案解析：

暂无解析

上一题下一题

你可能感兴趣的试题

垂直角是指什么？

查看答案

水准测量时对前后视距的要求是______。

查看答案

为了满足矿井建设和生产的需要，在矿井工业广场附近布设的高程控制点叫（）

A、近井点
B、井口水准基点
C、导线点
D、贯通点

查看答案

地形图的比例尺用分子为1的分数形式表示时（）

A、分母大，比例尺大，表示地形详细
B、分母小，比例尺小，表示地形概略
C、分母大，比例尺小，表示地形详细
D、分母小，比例尺大，表示地形详细

查看答案

等高距是指什么？

查看答案

热门试题更多>

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.
We feel great regret that we can no longer supply the goods you order as the production has been discontinued since last August.
There is so many rich people in your area ,to them a high price means a good quality product.
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?
请简述索赔的一般程序及所涉及的主要单证。
什么是“十字”作业法？
In order to extend our export business to your country we wish to enter into direct business relations with you.
从概念、编制方法和应用的角度，对居民消费价格指数(CPI)和购买力平价(PPP)进行比较。
These figures are gross underestimates of the true incidence of occupational ill-health.
We are too heavily committed to be able to entertain fresh orders.