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China's Five-hundred-meter Aperture Spherical Radio Telescope(FAST)has detected a repeating fast radio burst(FRB)-mysterious radio signals from outer space-for the first time, Science and Technology Daily reported.
Scientists on the FAST project with the National Astronomical Observatories of China(NAOC)revealed the news last Wednesday. The FRB originated some three billion lightyears away from Earth. Other factors including aircraft and satellites have been dismissed and cross examination is being carried out, the scientists said.
FRB has since become one of the hottest topics in astronomy. It was not until 2007 when the first FRB was discovered by humans. Fewer than 100 FRBs have been detected internationally. There is still no reasonable explanation for the origin of FRB in the international scientific community at present. FRBs mostly only appear once, which makes them very hard to track.
The FRB detected by FAST's real-time detection terminal(终端), however, is one that has been observed before, said Zhang Xinxin, an assistant engineer with the NAOC. Known as FRB121102,it was first discovered in 2012 and found to repeat in 2015.Analysis of data later located the source of the signal coming from a dwarf galaxy(矮星系) three billion light years away. The first pulse from FRB121102 was spotted by FAST on Aug 30 2019.After this, the telescope recorded dozens of pulses from the FRB over the course of days. On Sept 3 2019 alone, more than 20 pulses were detected.
The number of mysterious bursts detected so far is too small to draw any conclusions, Zhang said. FAST, the world's largest single-dish radio telescope, has a certain edge in detecting repeated FRBs. This is because the 19-beam receiver installed on FAST, covering frequency ranges of 1.05-1.45 GHz, is very sensitive to radio signals, Zhang said.
1.The whole text mainly gives us an introduction to________.
A.a brief introduction of FAST. B.a discovery of FAST
C.the validation of FAST D.the usage of FAST
2.Which of the following statements is TRUE?
A.FRB121102 is the first fast radio burst that was discovered by humans.
B.The FRB detected by China's FAST this time has not been observed before.
C.FRBs mostly only appear once, which makes them very hard to track.
D.We can infer that billion-light year is a term of time in astronomy.
3.Aperture Spherical Radio Telescope(FAST)/_______
A.is the world's largest radio telescope
B.has detected more than 100 FRBs
C.found reasonable explanation for the origin of FRB
D.has been installed with the 19-beam receiver
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A Lighter Touch
In recent years, superheroes such as Superman, Thor, Iron Man, and Black Panther have starred in film series with complex, serious storylines about the end of the universe. However, the makers of Shazam! which came out in China on April 5,have a different opinion on the superhero movie.
It’s “just a light, funny...action comedy about a boy in a superman's body”, wrote Owen Gleiberman in his review for Variety magazine.
Billy Batson, the film's main character, is a 14-year-old who's been in and out of foster homes(寄养家庭). One day, on the way to another home, Batson escapes to the subway and meets a wizard(巫师), who gives him magical powers. Whenever Batson says "Shazam", he changes into an adult-sized man with superhuman strength.
But how does he use his new superpowers? With the help of his new foster brother Freddie Freeman, Batson tests his strength like any teenager would do-by breaking the rules. He breaks a soda machine to get a drink, tricks his teachers, and even buys beer.
While the film is fun and joyous, it also has emotional weight. A major part of the story is Batson searching for his real mother. And later when Batson faces the evil Dr. Thaddeus Sivana, a former misfit kid himself, he realizes that his new found superpowers can't solve all the problems, and that he has something valuable to protect-his new family.
“With strong messages about families of all shapes and sizes and the importance of supporting and educating young people, Shazam! really feels like the movie we need right now,” Den of Geek website noted.
1.How is Shazam different from other superhero movies?
A.It has a complex, serious storyline. B.It is about the end of the universe.
C.It has several important characters. D.It has a light and funny atmosphere.
2.What do we know about Billy Batson in Shazam!?
A.He was born with magical powers.
B.He lives with a wizard near the subway.
C.He enjoys his time with his foster family.
D.He has no idea who his real mother is.
3.What can we learn about Batson from the second to last paragraph?
A.He fails to find his real mother in the end.
B.He loves playing tricks with his magic powers.
C.He realizes what his new family means to him.
D.He teaches Dr. Thaddeus Sivana to be a good person.
4.What's the main purpose of the article?
A.To share the author's view about families.
B.To introduce the movie, Shazam!.
C.To persuade readers to watch Shazam!.
D.To teach readers how to write a movie review.
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The fact that your hair turns grey because of stress is nothing more than an old wives' tale. It's true that stress isn't good for you, but it's not going to turn you into a silver fox just yet. In fact, the answer comes from the cells in your hair. These are what decide the color and, eventually, the fade to grey.
Most of us start to notice our first grey hairs by the time we hit our thirties. A general rule to go by is that by the age of 50,half of the population will have lost the color in 50 percent of their hair.
But why does it happen? Firstly, we need to understand how hair gets its color.
Your hair is made up of cells called melanocytes(黑色素细胞) which produce pigments(色素) as they grow into the hair fiber. There are two different types of melanins: eumelanins and pheomelanins. The former produces black and brown pigments, while the latter produces red and yellow pigments. The exact amount of these pigments decides whether a person has black, brown, blonde or red hair.
As we age, the ability of the melanocytes to produce more pigments weakens. That's because our hair grows in different periods.
The growing period lasts between three and five years, after which our follicles(毛囊) turn off for about three months to rest and get ready to grow more hairs. This goes round and round and, after a time, our bodies aren't as good at producing new hairs.
Scientists are continuing to try and find ways to prevent greying hair. A team of scientists in France is working to try and stop the melanocytes from being damaged at the end of each hair cycle. They are trying to use a special enzyme(酶) to protect the cells from damage. If successful, it could lead the way for new products that keep our hair full of color for years to come.
1.The phrase “an old wives' tale” in Paragraph 1 probably mean________？
A.a wrong belief B.useful talk
C.a scientific rule D.helpful experience
2.What do we know about red hair?
A.It doesn't turn grey as people get older.
B.It contains more pheomelanin’s than eumelanin’s.
C.The amount of pigments in it doesn't change over time.
D.People with red hair have weaker ability to produce pigments.
3.What do the French scientists aim to do?
A.To repair damaged hair follicles.
B.To protect hair cells against damage.
C.To shorten the hair cycle to protect the hair.
D.To study the relationship between health and hair color.
4.What can we infer from the article?
A.Grey hair has nothing to do with stress.
B.Grey hair is a symbol of declining health.
C.It takes three months for new hair to grow.
D.The growth and color change of hair depend on cells.
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The great recession may be over,but this era of high joblessness is probably beginning.Before it ends,it will likely change the life course and character of a generation of young adults.And eventually,it is likely to reshape our politics,our culture,and the character of our society for years.
No one tries harder than the jobless to find silver linings in this national economic disaster. Many said that unemployment, while extremely painful, had improved them in some ways: they had become less materialistic and more financially prudent(节俭的); they were more aware of the struggles of others. In limited respects, perhaps the recession will leave society better off. At the very least, it has awoken us from our national fever dream of easy riches and bigger houses, and put a necessary end to an era of reckless(鲁莽的) personal spending.
But for the most part,these benefits seem thin,uncertain,and far off.In The Moral Consequences of Economic Growth,the economic historian Benjamin Friedman argues that both inside and outside the U.S.,lengthy periods of economic stagnation or decline have almost always left society more mean-spirited and less inclusive,and have usually stopped or reversed the advance of rights and freedoms.Anti-immigrant sentiment typically increases,as does conflict between races and classes.
Income inequality usually falls during a recession, but it has not shrunk in this one. Indeed,this period of economic weakness may reinforce class divides, and decrease opportunities to cross them-especially for young people. The research of Till Von Wachter, the economic at Columbia University, suggests that not all people graduating into a recession see their life chances dimmed: those with degrees from elite(精英) universities catch up fairly quickly to where they otherwise would have been if they had graduated in better times;it is the masses beneath them that are left behind.
In the Internet age, it is particularly easy to see the resentment that has always been hidden within American society. More difficult, in the moment, is discerning precisely how these lean times are affecting society's character. In many respects, the U.S. was more socially tolerant entering this recession than at any time in its history, and a variety of national polls on social conflict since then have shown mixed results. We will have to wait and see exactly how these hard times will reshape our social fabric(组织). But they certainly will reshape it,and all the more so the longer they extend.
1.By saying "to find silver linings" (Para.2) the author suggests that the jobless try to_____.
A.seek help from the government
B.explore reasons for the unemployment
C.make profits from the troubled economy
D.look on the bright side of the recession
2.Benjamin Friedman believes that economic recessions may_
A.impose a heavy burden on immigrants
B.bring out more evils of human nature
C.promote the advance of rights and freedoms
D.ease conflicts between races and classes
3.The research of Till Von Wachter suggests that in the recession graduates from elite universities tend to ____
A.lag behind the others due to decreased opportunities
B.catch up quickly with experienced employees
C.see their life chances as dimmed as the others
D.recover more quickly than the others
4.The author thinks that the influence of hard times on society is____
A.certain B.positive
C.unimportant D.destructive
)，并在其下面写出该加的词。
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