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隧道洞口原則，確定洞口的因素

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正確答案：

原則：

1. 洞口不宜設置在隘口、溝谷的中心或溝底低洼處；

2. 洞口應避開不良地質地段；

3. 當隧道線路通過巖壁陡立基巖裸露處時，最好不刷動或少刷動原聲地表，以保持山體的天然平衡；

4. 減少洞口路塹段長度，延長隧道提前進洞；

5. 洞口線路宜與等高線正交；

6. 線路位于有可能被水淹沒的河灘或水庫回水影響范圍內時， 隧道洞口標高應高出洪水位加波浪高度，以防洪水灌入隧道；

7. 為了確保洞口的穩定安全，邊坡及仰坡均不宜開挖過高； . 隧道洞口原則，確定洞口的因素。

8. 當洞口附近遇有水溝或水渠橫跨線路時，可設置拉槽開溝的橋梁或涵洞，以排泄水流；

9. 當洞口地勢開闊，有利于施工場地布置時，可利用棄渣有計劃有目的地改造洞口場地，以便布置運輸便道、材料堆放場、生產設施用地及生產生活用房等。因素：工程地質、水文地質、人文景觀等綜合因素。

答案解析：

暫無解析

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1.The failure of a high-profile cholesterol drug has thrown a spotlight on the 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 clinical 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 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 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-clogging 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 the 'bad' low-density lipoproteins. Under pressure 5.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 some 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 because 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 directs 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 irreversible accumulation of cholesterol in the body."You're blocking a physiologic mechanism to eliminate cholesterol and effectively constipating the pathway," says Kashyap.Going up 7.Most researchers remain confident that elevating high density lipoproteins levels by one means or another is one of the 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 bypass 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 of raising HDL," says Michael Miller，director of preventive cardiology at the University of Maryland Medical Center，Baltimore. Questions 7-13 Match torcetrapib，HDLs，statin and CETP with their functions (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. 7.It has been administered to over 10,000 subjects in a clinical trial. 8.It could help rid human body of cholesterol. 9.Researchers are yet to find more about it. 10.It was used to reduce the level of cholesterol. 11.According to Kashyap，it might lead to unwanted result if it's blocked. 12.It produced contradictory results in different trials. 13.It could inhibit LDLs.List of choices A.TorcetrapicB.HDLSC.StatinD.CETP
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