雅思阅读题.docx

1、雅思阅读题雅思阅读题Dont 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

2、 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 DN

3、A, 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 colleagu

4、es 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 C. 5

5、. The teams 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

6、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 wa

7、shed 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, sa

8、ys Hendrik Poinar, an evolutionary geneticist at McMaster University in Ontario, Canada. But that doesnt 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

9、between lab-based geneticists and the excavators, says palaeogeneticist Svante Pbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. And that only occurs in exceptional cases, he says. 11. Pbos team, which has been sequencing Neanderthal DNA, continually faces these prob

10、lems. When you want to study ancient human and Neanderthal remains, theres a big issue of contamination with contemporary human DNA, he says. 12. This doesnt mean that all museum specimens are fatally flawed, notes Pbo. The Neanderthal fossils that were recently sequenced in his own lab, for example

11、, had been part of a museum collection treated in the traditional way. But Pbo is keen to see samples of fossils from every major find preserved in line with Geigls recommendations just in case. Warm and wet 13. Geigl herself believes that, with cooperation between bench and field researchers, prese

12、rving 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, G

13、eigl 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 mo

14、re delicate specimens, says Geigl. And that could shed more light on the story of human evolution.(640 words nature )Why did a promising heart drug fail?Doomed drug highlights complications of meddling with cholesterol. 1. The failure of a high-profile cholesterol drug has thrown a spotlight on the

15、complicated machinery that regulates cholesterol levels. But many researchers remain confident that drugs to boost levels of good cholesterol are still one of the most promising means to combat spiralling heart disease.2. Drug company Pfizer announced on 2 December that it was cancelling all clinica

16、l trials of torcetrapib, a drug designed to raise heart-protective high-density lipoproteins (HDLs). In a trial of 15000 patients, a safety board found that more people died or suffered cardiovascular problems after taking the drug plus a cholesterol-lowering statin than those in a control group who

17、 took the statin alone.3. The news came as a kick in the teeth to many cardiologists because earlier tests in animals and people suggested it would lower rates of cardiovascular disease. There have been no red flags to my knowledge, says John Chapman, a specialist in lipoproteins and atherosclerosis

18、 at the National Institute for Health and Medical Research (INSERM) in Paris who has also studied torcetrapib. This cancellation came as a complete shock.4. Torcetrapib is one of the most advanced of a new breed of drugs designed to raise levels of HDLs, which ferry cholesterol out of artery-cloggin

19、g plaques to the liver for removal from the body. Specifically, torcetrapib blocks a protein called cholesterol ester transfer protein (CETP), which normally transfers the cholesterol from high-density lipoproteins to low density, plaque-promoting ones. Statins, in contrast, mainly work by lowering

20、the bad low-density lipoproteins.Under pressure5. Researchers are now trying to work out why and how the drug backfired, something that will not become clear until the clinical details are released by Pfizer. One hint lies in evidence from earlier trials that it slightly raises blood pressure in som

21、e patients. It was thought that this mild problem would be offset by the heart benefits of the drug. But it is possible that it actually proved fatal in some patients who already suffered high blood pressure. If blood pressure is the explanation, it would actually be good news for drug developers be

22、cause it suggests that the problems are specific to this compound. Other prototype drugs that are being developed to block CETP work in a slightly different way and might not suffer the same downfall.6. But it is also possible that the whole idea of blocking CETP is flawed, says Moti Kashyap, who di

23、rects atherosclerosis research at the VA Medical Center in Long Beach, California. When HDLs excrete cholesterol in the liver, they actually rely on LDLs for part of this process. So inhibiting CETP, which prevents the transfer of cholesterol from HDL to LDL, might actually cause an abnormal and irr

24、eversible accumulation of cholesterol in the body. Youre blocking a physiologic mechanism to eliminate cholesterol and effectively constipating the pathway, says Kashyap.Going up7. Most researchers remain confident that elevating high density lipoproteins levels by one means or another is one of the

25、 best routes for helping heart disease patients. But HDLs are complex and not entirely understood. One approved drug, called niacin, is known to both raise HDL and reduce cardiovascular risk but also causes an unpleasant sensation of heat and tingling. Researchers are exploring whether they can bypa

26、ss this side effect and whether niacin can lower disease risk more than statins alone. Scientists are also working on several other means to bump up high-density lipoproteins by, for example, introducing synthetic HDLs. The only thing we know is dead in the water is torcetrapib, not the whole idea o

27、f raising HDL, says Michael Miller, director of preventive cardiology at the University of Maryland Medical Center, Baltimore.(613 words nature)Questions 1-7This passage has 7 paragraphs 1-7.Choose the correct heading for each paragraph from the list of headings below.Write the correct number i-ix i

28、n boxes 1-7 on your answer sheet.List of Headingsi. How does torcetrapib work?ii. Contradictory result prior to the current trialiii. One failure may possibly bring about future successiv. The failure doesnt lead to total loss of confidencev. It is the right route to followvi. Why its stoppedvii. Th

29、ey may combine and theoretically produce ideal resultviii. Whats wrong with the drugix. It might be wrong at the first placeExample answerParagraph 1 iv1 Paragraph 22 Paragraph 33 Paragraph 44 Paragraph 55 Paragraph 66 Paragraph 7Questions 7-13Match torcetrapib，HDLs，statin and CETP with their functi

30、ons （Questions 8-13）.Write the correct letter A, B, C or D in boxes 8-13 on your answer sheet.NB You may use any letter more than once.7It has been administered to over 10,000 subjects in a clinical trial.8It could help rid human body of cholesterol.9Researchers are yet to find more about it. 10. It

31、 was used to reduce the level of cholesterol.11. According to Kashyap, it might lead to unwanted result if its blocked.12. It produced contradictory results in different trials.13. It could inhibit LDLs.List of choicesA. TorcetrapicB. HDLSC. StatinD. CETPThe Triumph of UnreasonA. Neoclassical econom

32、ics is built on the assumption that humans are rational beings who have a clear idea of their best interests and strive to extract maximum benefit (or “utility”, in economist-speak) from any situation. Neoclassical economics assumes that the process of decision-making is rational. But that contradicts growing evidence that decision-making draws on the emotionseven when reason is clearly involved. B.The role of emotions in decisions makes perfect sense. For situ