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當(dāng)前位置:考試網(wǎng)  > 試卷庫(kù)  > 外語(yǔ)類  > 雅思  > 閱讀  >  1 There's a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years - exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star's core. 2 Robert Ehrlich of George Mason University in Fairfax, Virginia, modelled the effect of temperature fluctuations in the sun's interior. According to the standard view, the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion. However, Ehrlich believed that slight variations should be possible. 3 He took as his starting point the work of Attila Grandpierre of the Konkoly Observatory of the Hungarian Academy of Sciences. In 2005, Grandpierre and a collaborator, Gábor ágoston, calculated that magnetic fields in the sun's core could produce small instabilities in the solar plasma. These instabilities would induce localised oscillations in temperature. 4 Ehrlich's model shows that whilst most of these oscillations cancel each other out, some reinforce one another and become long-lived temperature variations. The favoured frequencies allow the sun's core temperature to oscillate around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years. Ehrlich says that random interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other. 5 These two timescales are instantly recognisable to anyone familiar with Earth's ice ages: for the past million years, ice ages have occurred roughly every 100,000 years. Before that, they occurred roughly every 41,000 years. 6 Most scientists believe that the ice ages are the result of subtle changes in Earth's orbit, known as the Milankovitch cycles. One such cycle describes the way Earth's orbit gradually changes shape from a circle to a slight ellipse and back again roughly every 100,000 years. The theory says this alters the amount of solar radiation that Earth receives, triggering the ice ages. However, a persistent problem with this theory has been its inability to explain why the ice ages changed frequency a million years ago. 7 "In Milankovitch, there is certainly no good idea why the frequency should change from one to another," says Neil Edwards, a climatologist at the Open University in Milton Keynes, UK. Nor is the transition problem the only one the Milankovitch theory faces. Ehrlich and other critics claim that the temperature variations caused by Milankovitch cycles are simply not big enough to drive ice ages. 8 However, Edwards believes the small changes in solar heating produced by Milankovitch cycles are then amplified by feedback mechanisms on Earth. For example, if sea ice begins to form because of a slight cooling, carbon dioxide that would otherwise have found its way into the atmosphere as part of the carbon cycle is locked into the ice. That weakens the greenhouse effect and Earth grows even colder. 9 According to Edwards, there is no lack of such mechanisms. "If you add their effects together, there is more than enough feedback to make Milankovitch work," he says. "The problem now is identifying which mechanisms are at work." This is why scientists like Edwards are not yet ready to give up on the current theory. "Milankovitch cycles give us ice ages roughly when we observe them to happen. We can calculate where we are in the cycle and compare it with observation," he says. "I can't see any way of testing [Ehrlich's] idea to see where we are in the temperature oscillation." 10 Ehrlich concedes this. "If there is a way to test this theory on the sun, I can't think of one that is practical," he says. That's because variation over 41,000 to 100,000 years is too gradual to be observed. However, there may be a way to test it in other stars: red dwarfs. Their cores are much smaller than that of the sun, and so Ehrlich believes that the oscillation periods could be short enough to be observed. He has yet to calculate the precise period or the extent of variation in brightness to be expected. 11 Nigel Weiss, a solar physicist at the University of Cambridge, is far from convinced. He describes Ehrlich's claims as "utterly implausible". Ehrlich counters that Weiss's opinion is based on the standard solar model, which fails to take into account the magnetic instabilities that cause the temperature fluctuations. Questions 1-4 Complete each of the following statements with One or Two names of the scientists from the box below. Write the appropriate letters A-E in boxes 1-4 on your answer sheet. A. Attila Grandpierre B. Gábor ágoston C. Neil Edwards D. Nigel Weiss E. Robert Ehrlich 1. ...claims there a dimmer switch inside the sun that causes its brightness to rise and fall in periods as long as those between ice ages on Earth. 2. ...calculated that the internal solar magnetic fields could produce instabilities in the solar plasma. 3. ...holds that Milankovitch cycles can induce changes in solar heating on Earth and the changes are amplified on Earth. 4. ...doesn't believe in Ehrlich's viewpoints at all. Questions 5-9 Do the following statements agree with the information given in the reading passage? In boxes 5-9 on your answer sheet write TRUE if the statement is true according to the passage FALSE if the statement is false according to the passage NOT GIVEN if the information is not given in the passage 5. The ice ages changed frequency from 100,000 to 41,000 years a million years ago. 6. The sole problem that the Milankovitch theory can not solve is to explain why the ice age frequency should shift from one to another. 7. Carbon dioxide can be locked artificially into sea ice to eliminate the greenhouse effect. 8. Some scientists are not ready to give up the Milankovitch theory though they haven't figured out which mechanisms amplify the changes in solar heating. 9. Both Edwards and Ehrlich believe that there is no practical way to test when the solar temperature oscillation begins and when ends. Questions 10-14 Complete the notes below. Choose one suitable word from the Reading Passage above for each answer. Write your answers in boxes 10-14 on your answer sheet. The standard view assumes that the opposing pressures of gravity and nuclear fusions hold the temperature ...10...in the sun's interior, but the slight changes in the earth's ...11... alter the temperature on the earth and cause ice ages every 100,000 years. A British scientist, however, challenges this view by claiming that the internal solar magnetic ...12... can induce the temperature oscillations in the sun's interior. The sun's core temperature oscillates around its average temperature in ...13... lasting either 100,000 or 41,000 years. And the ...14... interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other, which explains why the ice ages changed frequency a million years ago.
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1 There's a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years - exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star's core.

2 Robert Ehrlich of George Mason University in Fairfax, Virginia, modelled the effect of temperature fluctuations in the sun's interior. According to the standard view, the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion. However, Ehrlich believed that slight variations should be possible.

3 He took as his starting point the work of Attila Grandpierre of the Konkoly Observatory of the Hungarian Academy of Sciences. In 2005, Grandpierre and a collaborator, Gábor ágoston, calculated that magnetic fields in the sun's core could produce small instabilities in the solar plasma. These instabilities would induce localised oscillations in temperature.

4 Ehrlich's model shows that whilst most of these oscillations cancel each other out, some reinforce one another and become long-lived temperature variations. The favoured frequencies allow the sun's core temperature to oscillate around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years. Ehrlich says that random interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other.

5 These two timescales are instantly recognisable to anyone familiar with Earth's ice ages: for the past million years, ice ages have occurred roughly every 100,000 years. Before that, they occurred roughly every 41,000 years.

6 Most scientists believe that the ice ages are the result of subtle changes in Earth's orbit, known as the Milankovitch cycles. One such cycle describes the way Earth's orbit gradually changes shape from a circle to a slight ellipse and back again roughly every 100,000 years. The theory says this alters the amount of solar radiation that Earth receives, triggering the ice ages. However, a persistent problem with this theory has been its inability to explain why the ice ages changed frequency a million years ago.

7 "In Milankovitch, there is certainly no good idea why the frequency should change from one to another," says Neil Edwards, a climatologist at the Open University in Milton Keynes, UK. Nor is the transition problem the only one the Milankovitch theory faces. Ehrlich and other critics claim that the temperature variations caused by Milankovitch cycles are simply not big enough to drive ice ages.

8 However, Edwards believes the small changes in solar heating produced by Milankovitch cycles are then amplified by feedback mechanisms on Earth. For example, if sea ice begins to form because of a slight cooling, carbon dioxide that would otherwise have found its way into the atmosphere as part of the carbon cycle is locked into the ice. That weakens the greenhouse effect and Earth grows even colder.

9 According to Edwards, there is no lack of such mechanisms. "If you add their effects together, there is more than enough feedback to make Milankovitch work," he says. "The problem now is identifying which mechanisms are at work." This is why scientists like Edwards are not yet ready to give up on the current theory. "Milankovitch cycles give us ice ages roughly when we observe them to happen. We can calculate where we are in the cycle and compare it with observation," he says. "I can't see any way of testing [Ehrlich's] idea to see where we are in the temperature oscillation."

10 Ehrlich concedes this. "If there is a way to test this theory on the sun, I can't think of one that is practical," he says. That's because variation over 41,000 to 100,000 years is too gradual to be observed. However, there may be a way to test it in other stars: red dwarfs. Their cores are much smaller than that of the sun, and so Ehrlich believes that the oscillation periods could be short enough to be observed. He has yet to calculate the precise period or the extent of variation in brightness to be expected.

11 Nigel Weiss, a solar physicist at the University of Cambridge, is far from convinced. He describes Ehrlich's claims as "utterly implausible". Ehrlich counters that Weiss's opinion is based on the standard solar model, which fails to take into account the magnetic instabilities that cause the temperature fluctuations.

Questions 1-4

Complete each of the following statements with One or Two names of the scientists from the box below.

Write the appropriate letters A-E in boxes 1-4 on your answer sheet.

A. Attila Grandpierre

B. Gábor ágoston

C. Neil Edwards

D. Nigel Weiss

E. Robert Ehrlich

1. ...claims there a dimmer switch inside the sun that causes its brightness to rise and fall in periods as long as those between ice ages on Earth.

2. ...calculated that the internal solar magnetic fields could produce instabilities in the solar plasma.

3. ...holds that Milankovitch cycles can induce changes in solar heating on Earth and the changes are amplified on Earth.

4. ...doesn't believe in Ehrlich's viewpoints at all.

Questions 5-9

Do the following statements agree with the information given in the reading passage?

In boxes 5-9 on your answer sheet write

TRUE if the statement is true according to the passage

FALSE if the statement is false according to the passage

NOT GIVEN if the information is not given in the passage

5. The ice ages changed frequency from 100,000 to 41,000 years a million years ago.

6. The sole problem that the Milankovitch theory can not solve is to explain why the ice age frequency should shift from one to another.

7. Carbon dioxide can be locked artificially into sea ice to eliminate the greenhouse effect.

8. Some scientists are not ready to give up the Milankovitch theory though they haven't figured out which mechanisms amplify the changes in solar heating.

9. Both Edwards and Ehrlich believe that there is no practical way to test when the solar temperature oscillation begins and when ends.

Questions 10-14

Complete the notes below.

Choose one suitable word from the Reading Passage above for each answer.

Write your answers in boxes 10-14 on your answer sheet.

The standard view assumes that the opposing pressures of gravity and nuclear fusions hold the temperature ...10...in the sun's interior, but the slight changes in the earth's ...11... alter the temperature on the earth and cause ice ages every 100,000 years. A British scientist, however, challenges this view by claiming that the internal solar magnetic ...12... can induce the temperature oscillations in the sun's interior. The sun's core temperature oscillates around its average temperature in ...13... lasting either 100,000 or 41,000 years. And the ...14... interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other, which explains why the ice ages changed frequency a million years ago.

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1. E

See the sentences in paragraph 1(There's a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years - exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star's core.) and para.2 (Robert Ehrlich of George Mason University in Fairfax, Virginia, modelled the effect of temperature fluctuations in the sun's interior.)

2. A B

See para.3: Grandpierre and a collaborator, Gábor ágoston, calculated that magnetic fields in the sun's core could produce small instabilities in the solar plasma.

3. C

See para.8: Edwards believes the small changes in solar heating produced by Milankovitch cycles are then amplified by feedback mechanisms on Earth.

4. D

See para.11: Nigel Weiss, a solar physicist at the University of Cambridge, is far from convinced. He describes Ehrlich's claims as "utterly implausible".

5. False

See para.5: for the past million years, ice ages have occurred roughly every 100,000 years. Before that, they occurred roughly every 41,000 years.

6. False

See para.7: "In Milankovitch, there is certainly no good idea why the frequency should change from one to another," ... Nor is the transition problem the only one the Milankovitch theory faces.

7. Not Given

See para.8: if sea ice begins to form because of a slight cooling, carbon dioxide?is locked into the ice. That weakens the greenhouse effect. (The passage doesn抰 mention anything about locking Co2 into ice artificially.)

8. True

See para.9: there is no lack of such mechanisms. "If you add their effects together, there is more than enough feedback to make Milankovitch work,"?"The problem now is identifying which mechanisms are at work." This is why scientists like Edwards are not yet ready to give up on the current theory.

9. True

See the sentences in para.9 (According to Edwards, he says. "I can't see any way of testing [Ehrlich's] idea to see where we are in the temperature oscillation.") and para.10 (Ehrlich concedes this. "If there is a way to test this theory on the sun, I can't think of one that is practical).

10. constant

See para.2: According to the standard view, the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion.

11. orbit

See para.6: Most scientists believe that the ice ages are the result of subtle changes in Earth's orbit, Earth's orbit gradually changes shape from a circle to a slight ellipse and back again roughly every 100,000 years.

12. instabilities

See para.3: magnetic fields in the sun's core could produce small instabilities in the solar plasma. These instabilities would induce localised oscillations in temperature.

13. cycles

See para.4: …allow the sun's core temperature to oscillate around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years.

14. random

See para.4: Ehrlich says that random interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other.

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(640wordsnature)

Glossary

Palaeontologists古生物學(xué)家

Aurochs歐洲野牛

Neanderthal(人類學(xué))尼安德特人,舊石器時(shí)代的古人類。

Permafrost(地理)永凍層

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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

Thelocalgovernmentwill_____morecollegesformorestudentstoreceivehighereducation.

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