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Passage One For more than thirty years after astronauts first set foot on the Moon, scientists have been unable to unravel the mystery of where the Earth’s only satellite came from. But now there is direct evidence that the Moon was born after a giant collision between the young Earth and another planet. Previous studies of rocks from the Earth and the Moon have been unable to distinguish between the two, suggesting that they formed from the same material. But this still left room for a number of theories explaining how—for example, that the Moon and Earth formed from the same material at the same time. It was even suggested that the early Earth spun so fast it formed a bulge that eventually broke off to form the Moon. Franck Poitrasson, and his colleagues at the Swiss Federal Institute of Technology have compared Moon rocks with rocks from Earth and discovered a surprising difference. They analysed the weight of the elements present in the rock using a highly accurate form of mass spectroscopy(光谱研究) that involves vaporising a sample by passing it through an argon (氩) flame. Although they appeared very similar in most respects, the Moon rocks had a higher ratio of iron-57 to iron-54 isotopes(同位素)than the Earth rocks. "The only way we could explain this difference is that the Moon and the Earth were partly vaporised during their formation," says Poitrasson. Only the popular "giant planetary impact" theory could generate the temperatures of more than 1700℃ needed to vaporise iron. In this scenario, a Mars-sized planet known as Theia crashed into Earth 50 million years after the birth of the Solar System. This catastrophic collision would have released 100 million times more energy than the impact believed to have wiped out the dinosaurs—enough to melt and vaporise a large portion of the Earth and completely destroy Theia. The debris from the collision would have been thrown into orbit around the Earth and eventually coalesced to form the Moon. When iron is vaporised, the lighter isotopes burn off first. And since the ejected debris that became the Moon would have been more thoroughly vaporised, it would have lost a greater proportion of its lighter iron isotopes than Earth did. This would explain the different ratios that Poitrasson has found. Which of the following statement is NOT TRUE according to the passage
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Passage Three Scraps of food could soon be helping power your home, thanks to an ultra-cheap bacteria-driven battery. Its developers hope that instead of feeding the dog or making garden compost(混合肥料) ,organic household waste could top up your home’s electricity. Although such "microbial fuel cells" (MFCs)have been developed in the past, they have always proved extremely inefficient and expensive. Now Chris Melhuish and technologists at the University of the West of England(UWE)in Bristol have come up with a simplified MFC that costs as little as ￡10 to make. Right now, their fuel cell runs only on sugar cubes, since these produce almost no waste when broken down, but they aim to move on to carrot power. "It has to be able to use raw materials, rather than giving it a refined fuel," says Melhuish. Inside the Walkman-sized battery, a colony of E. coil bacteria produce enzymes that break down carbohydrates, releasing hydrogen atoms. The cell also contains chemicals that drive a series of redox, or reduction and oxidation reactions, stripping electrons from the hydrogen atoms and delivering them steadily to the fuel cell’s anode(正极). This creates a voltage that can be used to power a circuit. To prove the MFC works, the researchers are using it to power a small light-sensitive robot. And when a number of the cells are connected in series, they could power domestic appliances, running a 40-watt bulb for eight hours on about 50 grams of sugar. Earlier MFCs were inefficient because they relied on energy-hungry filters and pumps. By experimenting with different anode materials, the UWE team have figured out how to make their system work: they dump the bacteria and redox chemicals directly into the cell. In its current form, the UWE team says its organic battery can produce eight times as much power as any previous MFC. But Melhuish wants to improve this, both by scaling it up and finding a better mix of redox chemicals. Earlier MFCs were inefficient because they ______.
Why did man have to track his target at a close range when using a short bow
Directions: This section is designed to test your ability to understand spoken English. You will hear a selection of recorded materials and you must answer the questions that accompany them. There are two parts in this section, Part A and Part B. Remember, while you are doing the test, you should first put down your answers in your test booklet. At the end of the listening comprehension section, you will have 3 minutes to transfer your answers from your test booklet onto your ANSWER SHEET 1. If you have any questions, you may raise your hand. Now as you will not be allowed to speak once the test is started. Now look at Part A in your test booklet.Part A You will hear 10 short dialogues. For each dialogue, there is one question and four possible answers. Choose the correct answer--A, B, C or D, and mark it in your test booklet. You will have 15 seconds to answer the question and you will hear each dialogue ONLY ONCE. Now look at question 1 What does the woman imply
What do we know about modern bows
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