Where are the young pulsars
重庆市新高考2022-2023学年高二下学期期末英语试卷(含答案)
重庆市新高考2022-2023学年高二下学期期末英语试卷学校：___________姓名：___________班级：___________考号：___________一、阅读理解Donna Strickland was awarded the 2018 Nobel Prize for physics jointly with Arthur Ashkin and Gérard Mourou. It’s the first time in 55 years that a woman has won this famous prize, but why has it taken so long? We look at five other pioneering female physicists—past and present—who actually deserve the prize.Jocelyn Bell BurnellPerhaps the most famous snub (冷落):then-student Bell discovered the first radio pulsars in 1967, when she was a PhD student at Cambridge. The Nobel Prize that recognised this landmark discovery in 1974, however, went to her male supervisor, Antony Hewish. Recently awarded a ￡2.3 million Breakthrough Prize, which she gave away to help under-represented students, she joked to the Guardian, “I feel I’ve done very well out of not getting a Nobel Prize.”Lene HauHau is best known for leading the research team at Harvard University in 1999 that managed to slow a beam of light, before managing to stop it completely in 2001. Often topping Nobel Prize prediction lists, could 2022 be Hau’s year?Vera RubinRubin discovered dark matter in the 1980s, opening up a new field of astronomy. She died in 2016, without recognition from the committee.Chien-Shiung WuWu’s “Wu experiment” helped disprove the “law of conservation of parity”. Her experimental work was helpful but never honoured,and instead, her male colleagues won the 1957 Nobel Prize for their theoretical work behind the study.Lise MeitnerMeitner led groundbreaking (开创性的) work on the discovery of nuclear fission. However, the discovery was acknowledged by the 1944 Nobel Prize for chemistry, which was won by her male co-lead, Otto Hahn.1、When was the discovery of radio pulsars recognised by the Nobel?A. In 1944.B. In 1967.C. In 1974.D. In 1980.2、Which woman is most likely to win a Nobel Prize later according to the text?A. Lene Hau.B. Vera Rubin.C. Donna Strickland.D. Jocelyn Bell Burnell.3、What do we know about the five females?A. The five female scientists did greatly in chemistry.B. Vera Rubin had opened up a new field in geometry.C. Lise Meitner’s teacher won a Noble Prize for her work.D. All their findings haven’t been recognised by the Nobel.If humans were truly at home under the light of the moon and stars, we would go in darkness happily, the midnight world as visible to us as it is to the vast number of nocturnal (夜间活动的) species on this planet. Instead, we are diurnal creatures, with eyes adapted to living in the sun’s light. This is a basic evolutionary fact, even though most of us don’t think of ourselves as diurnal beings. Yet it’s the only way to explain what we’ve done to the night:The benefits of this kind of engineering come with consequences — called light pollution — whose effects scientists are only now beginning to study. Light pollution is largely the result of bad lighting design, which allows artificial light to shine outward and upward into the sky. Ill-designed lighting washes out the darkness of night and completely changes the light levels — and light rhythms — to which many forms of life, including, ourselves, have adapted. Wherever human light spills into the natural world, some aspect or life is affected.In most cities the sky looks as though it has been emptied of stars, leaving behind a vacant haze (霾) that mirrors our fear of the dark. We’ve grown so used to this orange haze that the original glory of an unlit night — dark enough for the planet Venus to throw shadow on Earth — is wholly beyond our experience, beyond memory almost.We’ve lit up the night as if it were an unoccupied country, when nothing could be further from the truth. Among mammals alone, the number of nocturnal species is astonishing. Light is a powerful biological force, and on many species it acts as a magnet (磁铁). The effect is so powerful that scientists speak of songbirds and seabirds being “captured” by searchlights on land or by the light from gas flares on marine oil platforms. Migrating at night, birds tend to collide with brightly lit tall buildings.Frogs living near brightly lit highways suffer nocturnal light levels that are as much as a million times brighter than normal, throwing nearly every aspect of their behavior out of joint, including their nighttime breeding choruses. Humans are less trapped by light pollution than the frogs. Like most other creatures, we do need darkness. Darkness is as essential to our biological welfare, to our internal clockwork, as light itself.Living in a glare of our own making, we have cut ourselves off from our evolutionary and cultural heritage — the light of the stars and the rhythms of day and night. In a very real sense light pollution causes us to lose sight of our true place in the universe, to forget the scale of our being, which is best measured against the dimensions of a deep night with the Milky Way — the edge of our galaxy — arching overhead.4、According to the passage, human beings__________.A. prefer to live in the darknessB. are used to living in the day lightC. were curious about the midnight worldD. had to stay at home with the light of the moon5、The writer mentions birds and frogs to __________.A. provide examples of animal protectionB. show how light pollution affects animalsC. compare the living habits of both speciesD. explain why the number of certain species has declined6、It is implied in the last paragraph that _________.A. light pollution dose harm to the eyesight of animalsB. light pollution has destroyed some of the world heritagesC. human beings cannot go to the outer spaceD. human beings should reflect on their position in the universe7、What might be the best title for the passage?A. The Magic LightB. The Orange HazeC. The Disappearing NightD. The Rhythms of NatureIn this digital age, people measure their popularity by the number of “likes” and followers they get on social media. But as it turns out, people are happier when their friends are of high quality rather than huge quantity.Scientists from the University of Leeds in the UK studied data from two online surveys of nearly 1,500 people. Those who took the survey gave details about their age, social interactions, and how satisfied they were with their social lives. The researchers found that those who had a small number of close friends generally tended to be happier than those who had a large number of superficial (关系浅表的) friends.“Loneliness has less to do with the number of friends you have, and more to do with how you feel about your friends,” said Bruine de Bruin, one of the researchers.He found that older people tended to have smaller social circles than young people, but the people in these circles tended to be closer to them. He also found that younger people tended to have larger social circles that were made up of “peripheral(次要的) others”—people who are not their true friends, but just the ones they know. These people had no influence on their happiness.The results of the study show that the opinion society has about old people being sad and lonely might not be accurate.“The research shows that older adults’ smaller networks don’t decrease their social satisfaction and happiness. In fact, older adults tend to report a better sense of well-being than younger adults,” said Bruine de Bruin.8、According to the study, people tend to be happier when they ______.A. have friends of huge quantityB. have a small circle of close friendsC. have a lot of followers on social mediaD. make friends with older people9、What do we know from paragraph 4?A. Older people’s friends seem to be of higher quality.B. Younger people don’t need to make peripheral friends.C. Older people’s happiness has nothing to do with their friends.D. Both older and younger people find it hard to make close friends.10、Which word might Bruine de Bruin use to describe older adults?A. Sad.B. Happy.C. Lonely.D. Concerned11、What is the focus of this article?A. Different types of friends in one’s life.B. Changes in people’s happiness levels.C. Interactions between older and younger people.D. The relationship between happiness and the quality and quantity of friends.From composer, musician, and philanthropist(慈善家)Peter Buffett comes, a warm, wise, and inspirational, book that asks, “Which win you choose: the path of least resistance or the path of potentially greatest sailsfaction?”You may think that with a last name like his, Buffett has enjoyed a life of endless privilege. But the son of billionaire investor Warren Buffett says that the only real inheritance handed down from his parents is a philosophy: Build your own path in life.It is a principle that has allowed him to follow his own passions, establish his own identity, and reap his own successes.In Life Is What You Make It.Buffett expounds on(阐释)the strong set of values given to him by his trusting and broadminded mother, his hardworking and talented father, and the many life teachers he has met along the way.Today’s society, Buffett assumes, has begun to replace a work ethic, enjoying what y ou do, with a wealth ethic, honoring the payoff instead of the process.We confuse privilege with material wealth, character with external validation(认可). Yet, by focusing more on substance and less on reward, we can open doors of opportunity and strive toward a greater sense of fulfillment.In clear and brief terms, Buffett reveals a great truth: Life is random, neither fair nor unfair.From there it becomes easy to recognize the equal dignity and value of every human life our circumstances may vary but our essence does not. We see that our journey in life rarely follows a straight line but is often met with false starts, crises, and mistakes.How we push through and persevere in these challenging moments is where we begin to create the life Of our dreams—from discovering our vocations to giving back to others.Personal and instructive, Life Is What You Make It is about challenging your circumstances, taking control of your destiny, and living your life to the fullest.12、What is the purpose of the passage?A. To describe a famous person.B. To introduce a book.C. To talk about what life is about.D. To discuss how to live a meaningful life.13、What can we infer about Peter Buffett?A. His father is very rich.B. One of his hobbies is music.C. He achieved success by himself.D. He wrote the book Life Is What You Make It.14、What is today’s society like according to Peter Buffett?A. People are following their interests.B. People are seeking spiritual enjoyment.C. People pay more attention to the process.D. People focus more on the results.15、Which proverb can best express the main idea of the fifth paragraph?A. Living without an, aim is like sailing without a compass.B. Life is full of ups and downs.C. Where there is a will, there is away.D. Life isn’t about getting and having, it’s about giving and being.二、七选五16、The Upside to Being OutsideResearch shows that being in nature makes people feel good, whether they’re roughing it in the wilderness for days or just hanging out at a local park for a while. One study was conducted in the city of Birmingham, Alabama. Researchers found that most participants’ mood and well-being improved significantly when they spent time in urban parks, even though the average visit was only around half an hour.①________ F or example, scientists in the United Kingdom studied the impact of the “30 Days Wild” campaign. It challenged people to interact with nature for 30 days by enjoying earthy activities like feeding birds and planting flowers. Participants were measurably happier and healthier throughout the challenge…and for months afterwards, too. ②________ How does nature boost people’s happiness? Scientists say that spending time in natural settings reduces stress and anxiety, which benefits mental and physical health. Research shows our brains are more relaxed in natural settings.To most people, it’s not news that nature can be calming. But multiple studies have found that spending time in nature also has some more surprising benefits, like improving creativity and problem-solving. ③________ Another found that exposure to nature helped people score better on tests. That’s more proof that going outside is a smart move!What accounts for the connection with cognition and creativity? It could be that a good dose of nature acts as a cure to information overload. Everyday life involves a lot of multitasking. Some scientists theorize that spending time in nature enables our brains to rest and recover from mental tiredness. ④________Naturally, scientific studies don’t cover everything that’s great about the great outdoors.⑤________ From recreation and exercise to happiness and creativity, there are lots of upsides to getting outside.A. One study revealed that people were better at figuring out puzzles after a four-day camping trip.B. According to many scientific studies, there’s a good chance it’ll make you happier, healthier, and more creative.C. What’s more, the lift people get from nature is long lasting.D. Lots of people enjoy fun activities outside, like swimming, riding bikes, or climbing trees.E. When the only light you’ve seen all day is the glow of a screen, it might be a good idea to switch it off.F. This means that whether you’re studying or playing video games, heading outside to giveyour brain a break might help you get to the next level.G. So, kicking back in a park is a bit like treating your mind to a restful mini vacation.三、完形填空（15空）I’m a college professor teaching people how to think more creatively. Interestingly, thisAt a family picnic for employees of the company where my father worked, they held athe little ones, took mighty wind-ups(挥臂动作), but when the cloth left their hands, itand being 13, I didn’t like adults laughing at us.inside the handkerchief? No, it was “throw a handkerchief”, not “a rock and a handkerchief”.逃脱).tying knot after knot until it was the size of a large rock. I took a long wind-up and threw theand I felt proud.creative thinking.17、A. awaken B. created C. enhanced D. spread18、A. students B. throwers C. runners D. tutors19、A. kilometers B. meters C. inches D. miles20、A. impossible B. essential C. unclear D. obvious21、A. tied B. cast C. hid D. drew22、A. included B. unemployed C. disqualified D. involved23、A. separated B. disappeared C. combined D. sank24、A. time B. reason C. chance D. excuse25、A. baby B. kid C. genius D. adult26、A. casually B. immediately C. secretly D. eventually27、A. arrowed B. balled C. light D. soft28、A. died B. rose C. declined D. doubled29、A. loser B. judge C. winner D. audience30、A. responded B. protested C. admitted D. announced31、A. criticalB. modern C. innovative D. conventional四、短文填空32、Archaeological (考古的) ①________(discover) of Changsha wares (陶器) have occurred randomly over the decades, and key findings of kiln (窑) ruins ②________ (make) particularly since 2010. There were not only Tang Dynasty Changsha wares ③________ (unearth), but also some celadons (青瓷) from an even ④________ (early) period.They’re key witnesses ⑤________ the Silk Road on the sea and Sino-foreign exchanges of material culture. Archaeological findings show that Changsha wares were exported to about 30 countries, ⑥________ (range) from East and Southeast Asian neighbors to North Africa. Craftsmen and workshop owners in Changsha participated in a wave of globalization⑦________ actively explored overseas markets.⑧________ (consequent), shapes of Changsha wares were also influenced by foreign elements. Seeing the antiques, we can also understand ⑨________ public aesthetics (审美) of their time. They tell ⑩________ was viewed as traditional Chinese beauty.五、书面表达33、为增强学生体质，你校将在下周举办一次“Love Sports, Love Life ”的体育活动。
Life Cycles of Stars
Beyond Helium
• • • • • He + particle = mass 5: not stable He + He = Mass 8: Not Stable The Mass 5-8 Bottleneck Sometimes three He collide to make C Li, Be, B rare in Universe
Early Stars and Planets
• • • • (Class 0) Early main accretion phase (Class I) Late accretion phase (Class II) PMS stars with protoplanetary disks (Class III) PMS stars with debris disks
• Type I Supernova
– White dwarf attracts matter from neighboring star – White dwarf core resumes fusion
• Type II Supernova
– Collapse of massive single star
All Objects Exist Because of a Balance Between Gravity and Some Other Force
• • • • • • People, Planets-Interatomic Forces Normal Stars-Radiation White Dwarfs-Electron Repulsion Neutron Stars-Nuclear Forces Quark Stars? Black Holes-No Known Force
写南仁东与中国天眼作文600
写南仁东与中国天眼作文600 示例回答如下1:Title: Nan Rendong and China's Tianyan TelescopeIntroduction:In recent years, one of the most significant achievements in China's scientific community has been the construction and operation of the world's largest single-dish radio telescope, known as the Tianyan (Heavenly Eye) or FAST (Five-hundred-meter Aperture Spherical Telescope). Nan Rendong, a prominent Chinese astronomer, played a crucial role in the development of this groundbreaking project. This essay aims to explore the contributions of Nan Rendong and the significance of the Tianyan telescope for China and the global scientific community.Body:1. Background on Nan Rendong:Nan Rendong, born in 1964, was a Chinese radio astronomer and chief scientist of the Tianyan telescope project. He dedicated his career to the study of pulsars and was recognizedinternationally for his contributions in this field. Nan Rendong's passion for astronomy and his expertise in radio astronomy made him the perfect candidate to lead the Tianyan telescope project.1.1 南仁东的背景：南仁东，1964年生，是中国的一位射电天文学家，也是天眼望远镜项目的首席科学家。
19-20版：（步步高）Listening and Talking，Reading for Writ
Listening and Talking，Reading for Writing，Assessing YourProgress & Video Time基础巩固Ⅰ.单词拼写1．To avoid knee pain，you can run on soft surfaces，do exercises to strengthen your leg muscles(肌肉)．2．Rather than getting up to check on whether the laundry is done，users will instead monitor(监控) it on their phones while watching TV.3．The shortage of water has become a global(全球的) problem that needs to be solved urgently. 4．Though lacking(缺乏) money，his family lived an enjoyable life.5．The smell of new bread floated(飘动) up from the kitchen.6．You need to sit down and analys(z)e(分析) why you feel so upset.7．I don’t want to argue with you.Just do what you like since you never listen to me. 8．Thanks for your directions to the house；we wouldn’t have found it otherwise.9．The river is very shallow，so you can swim in it.10．Many lifestyle patterns do such great harm to health that they actually speed up the weakening of the human body.Ⅱ.选词填空run out of，as a result，figure out，result in，attach to，for lack of11．It is difficult to figure out a global population of polar bears as much of the range has been poorly studied.12．His carelessness resulted in the terrible accident that happened last night.13．They failed to pass the exam for lack of experience.14．Most parents attach great importance to their children’s education.15．I am running out of money.I have to go home and ask my father for some.16．He made a big mistake，and，as a result，he lost his job.Ⅲ.单句语法填空17．It was raining so hard that we couldn’t help wondering how long it would take to get there. 18．The envelop is made from recycled(recycle) paper.19．Stress and tiredness often result in a lack of concentration.20．He stood by the window，looking at the floating(float) islands.21．Currently(current)，a great many people buy something on the Internet.22．Learning(learn) to think critically is an important skill today’s children will need for thefuture.(2019·天津)23．I don’t know why the young couple are getting into an argument(argue)．24．Mr Brown is a regular(regularly) customer in my shop and he comes here once a week. 25．This middle school is attached(attach) to a teachers’ college.26．Provided(provide) you didn’t try to make sense of it，it sounded beautiful.Ⅳ.单句写作27．真遗憾，星期六晚上我不能和你一起去看电影了。
Unit,24年小学4年级下册第二次英语基本全练全测(含答案)
Unit,24年小学4年级下册英语基本全练全测(含答案)考试时间：80分钟（总分:140）B卷考试人：_________题号一二三四五总分得分一、综合题(共计100题)1、填空题：My ___ (小猫) chases after its tail.2、填空题：The __________ (历史的价值观念) evolve with society.3、What do you call a person who studies animals?A. BiologistB. ZoologistC. BotanistD. Ecologist4、填空题：I want to learn about different _______ (文化). It broadens my _______ (视野).5、填空题：The _____ (蜗牛) curls up when it feels threatened.6、听力题：A _______ is formed when two or more elements combine chemically.7、听力题：Pulsars are rotating neutron _______ that emit beams of radiation.8、填空题：The __________ (历史的复兴) fosters renewal.9、Which animal is known as "the king of the jungle"?a. Lionb. Tigerc. Beard. Elephant答案:a10、What do you call a person who studies the weather?A. AstronomerB. MeteorologistC. GeologistD. Biologist答案:B11、听力题：The ____ has bright feathers and often sings sweetly.12、听力题：The cake is ______ (frosted) with chocolate icing.13、填空题：The country known for kangaroos is ________ (澳大利亚).14、填空题：He can ________ (跑) fast.15、Which fruit is red and often mistaken for a vegetable?A. TomatoB. PotatoC. CarrotD. Onion答案:A16、填空题：I can ______ (帮助) my parents with chores.17、填空题：My mom is a __________ (心理治疗师).18、Where do penguins live?A. DesertB. ForestC. AntarcticaD. Jungle答案:C19、What do you call the process of making cheese?A. CurdlingB. FermentingC. PasteurizingD. Aging20、What is the coldest season of the year?A. SpringB. SummerC. FallD. Winter答案:D21、填空题：My ________ (玩具名称) is a great companion.22、填空题：For Christmas, I asked for a ________ (电子游戏机). I want to play ________ (足球比赛) games.23、What is the capital of Ghana?A. AccraB. KumasiC. TamaleD. Takoradi24、填空题：The __________ (文化表达) reflects identity.25、听力题：The chemical formula for gallium nitride is _____.26、听力题：A mixture of gases is called an ______.27、What is the name of the animal known for its ability to change colors?A. ChameleonB. GeckoC. IguanaD. Lizard28、听力题：I see a __ in the park. (cat)29、What is the largest planet in our Solar System?A. SaturnB. JupiterC. EarthD. MarsWhat do we call the color of the grass?A. GreenB. YellowC. BrownD. Blue31、What do we call the part of the plant that provides support?A. RootB. StemC. LeafD. Flower答案:B32、What do we call the tool we use to write on paper?A. BrushB. PenC. RulerD. Scissors答案:B33、听力题：The flowers smell ________.34、听力题：A ________ is a large, naturally occurring community of flora and fauna.35、听力题：The ______ is a predator of many small animals.36、填空题：My _____ (爷爷) loves to play chess.37、听力题：I have _____ (one/two) pet cats.38、听力题：The chemical formula for glucose is ______.39、What is the name of the sweet substance produced by bees?A. Maple SyrupB. HoneyC. JamD. Molasses答案:BMy grandma is a fantastic ____.41、填空题：在历史上，________ (discoveries) 为社会的进步奠定了基础。
关于外太空的神话故事英语
关于外太空的神话故事英语Once upon a time, in a galaxy far, far away, there existed a mythical planet called Zephyrion. Zephyrion was a world shrouded in mystery and wonder. Its inhabitants, known as Zephyrians, were said to possess extraordinary powers and a deep connection with the cosmos. Legends spoke of their ability to manipulate time and space, harnessing the energies of the stars to create awe-inspiring works of art and engineering.The Zephyrians believed that their planet was the center of the universe, a belief reinforced by the spectacular celestial events that occurred there. Every few years, Zephyrion's twin suns would align, causing the skies to burst into a mesmerizing display of vibrant colors and pulsating lights. The Zephyrians regarded this phenomenon as a gift from the gods, a sign of their cosmic significance.It was said that the Zephyrians were born from stardust, the remnants of a long-dead star that had exploded eons ago. As infants, their eyes shimmered with the brilliance of distant galaxies, and their touch emitted a soothing warmth. They were a peaceful species, cherishing harmony and balance in all aspects of life.The Zephyrians also possessed a deep knowledge of the cosmos. They believed that the universe was teeming with sentient beings, each residing on their own little celestial oasis. They dreamt of a day when they could make contact with these distant neighbors, exchanging knowledge and forging alliances. To prepare for this momentous event, the Zephyrians built an immense observatory on the highest peak of their planet. From there, they would tirelessly scan the stars, hoping to catch a glimpse of another civilization.One Zephyrian, named Solara, possessed an insatiable curiosity about the universe. From a young age, she would spend hours gazing at the heavens, pondering the secrets they held. Solara had a special affinity for auroras, the mesmerizing lights that danced across the night sky. She believed that these lights were a form of communication, a language spoken by the universe itself.Driven by her passion, Solara dedicated herself to deciphering the language of auroras. She spent years studying ancient texts and consulting with the wise elders of her people. As she delved deeper into her research, Solara began to notice patterns and symbols hidden within the vibrant hues of the auroras. She realized that they formed a complex code, a message waiting to be decrypted.Eager to share her discovery, Solara approached the Zephyrian council, hoping they would lend their support and resources to her cause. However, the council dismissed her findings as mere fantasies and insisted that the Zephyrians were the sole beings in the universe. Undeterred, Solara decided to embark on her own journey into space, determined to prove them wrong.Using her innate abilities, Solara constructed a small spaceship, equipped with state-of-the-art technology capable of navigating through the vastness of space. She bid farewell to her fellow Zephyrians and embarked on a solitary mission to make contact with extraterrestrial beings.As her spacecraft soared through the stars, Solara marveled at the beauty and complexity of the universe. She encountered distant planets and encountered breathtaking phenomena such as nebulae and pulsars. The more she explored, the more convinced she became that they were not alone.After months of searching, Solara finally detected a faint signal coming from a nearby star system. With bated breath, she followed the source of the transmission, leading her to a hidden planet known as Celestia. Celestia was home to a highly advanced civilization, known for their mastery of intergalactic travel.Solara was warmly welcomed by the Celestians, who shared her desire for interstellar communication and collaboration. Together, they embarked on a new era of exploration, exchanging knowledge and expanding the boundaries of their understanding.In the years that followed, the Zephyrians and Celestians forged a strong alliance, extending their reach beyond their respective planets. Their combined efforts led togroundbreaking discoveries in science, art, and technology, forever altering the course of their civilizations.Solara's journey not only shattered the myth of Zephyrion's cosmic solitude but also sparked a new era of intergalactic unity. The universe was no longer a vast, silent void but a tapestry of interconnected worlds, brimming with endless possibilities.And so, the story of Solara and her quest for extraterrestrial communication became a legend, inspiring generations of explorers and dreamers to seek their own adventures beyond the confines of Earth. And who knows, perhaps one day, we too will discover our own mythical planet and unravel the interstellar mysteries that lie before us.。
2021-2022学年江苏省苏州市振华中学九年级(上)期中英语试卷(附答案详解)
2021-2022学年江苏省苏州市振华中学九年级（上）期中英语试卷一、单选题（本大题共10小题，共10.0分）1.Tom is a true friend.He be punished tell the truth.（）A. prefer；toB. prefer to；rather thanC. prefers；thanD. would rather；than2.The student works so hard that you praise him too much.（）A. mustB. mustn'tC. canD. can't3.She couldn't take too much work because she was ill in bed.（）A. offB. upC. onD. down4.My grandpa is 92 years old but he exercises every day and looks .（）A. organizedB. creativeC. energeticD. practical5.Mum was angry when she found that my brother I was willing to do the dishes.（）A. either；orB. neither；norC. not only；but alsoD. both；and6.As soon as the war out,he joined the army to protect his country.（）A. was brokenB. brokeC. have been brokenD. have broken7.Dr.Ma's speech is worth .We can learn a lot from it.（）A. very；to listen toB. very；listening toC. well；being listened toD. well；listening to8.The new government's first challenge is what to the problem of pollution.（）A. do withB. deal withC. solveD. work out9.- Why do you look so sad？- Because I am worrying about .（）A. if Mum will punish me for failing the examB. whether or not I have hurt Mum's heartC. that I got low marksD. when can we know the result of the exam10.--It is said that boys do better than girls in science and math.-- There are many great female scientists in the world.（）A. That's not the case.B. I think so.C. You'd better not.D. I can't agree more.二、完形填空（本大题共15小题，共15.0分）请认真阅读下面短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑.Something that I learnt from both my parents was the importance of having respect for other people.I remember one day when we were travelling on a bus and(11)sat down while other people were standing.My mother shouted at me"(12)immediately!You have young legs and you don't need to sit down." At the time I felt embarrassed about being told of(13)，but now I understand.I think children nowadays have(14)that respect and it really makes me angry if I see children siting down while (15)people are standing.One area in which we had a lot of rules was table (16).For example,we weren't allowed to start our meal(17)the oldest person had started.We had to say ""thank you" when our food was(18)，and eat everything on our plates before we could(19)the table.We couldn't make any noise when eating.Worse than that,we were only(20)to have sweets at the weekend,as a special(21)if we had been good.Although my upbringing （养育）was perhaps a bit(22)compared with modern children,I'm very thankful to my parents for giving me a clear (23)in life.Even though I was sometimes (24)，I think it has made me a better person.In my view,children need clear rules,but more than that they need to learn how to get on with (25)people and realize they are not the center of the world.11. A. they B. you C. I D. she12. A. Get up B. Sit up C. Give up D. Look up13. A. in order B. in public C. in surprise D. in person14. A. won B. shown C. wasted D. lost15. A. older B. richer C. taller D. heavier16. A. designs B. manners C. materials D. sizes17. A. if B. because C. until D. though18. A. cooked B. eaten C. prepared D. served19. A. move B. book C. leave D. lay20. A. allowed B. forced C. warned D. advised21. A. lesson B. treat C. choice D. need22. A. simple B. interesting C. normal D. strict23. A. direction B. answer C. introduction D. plan24. A. protected B. encouraged C. fooled D. punished25. A. some B. other C. few D. several三、阅读理解（本大题共12小题，共24.0分）AYou must have many hobbies,reading,painting and so on.One day,you happen to see a poster；"World Book Day." Interested,you stop and read the poster：Hello and welcome to World Book DayWorld Book Day is here to change livesthrough a love of books and sharedreading,and bring books to the childrenwho need them most.World Book Day isan excellent chance for everyone tocelebrate the joy of reading.●Share A Story Live-our exciting digitalevents programme beaming authors （作家）straight into your school.●Raising money,raising readers-our fundraising ideas to help us change lives through reading.●World Book Day Book Club-a new online reading community.●Share A Story Corner-stories to encourage families to read together.Happy World Book Day!For up-to-date information,visit our website !26.World Book Day is a special day for people to ______ .A. celebrate the joy of readingB. change lives by raising moneyC. meet famous authors at homeD. enjoy writing in local communities27.According to the poster,if you want to read stories with your parents,you can join ______ .A. Share A Story LiveB. Share A Story CornerC. World Book Day Book ClubD. Raising money,raising readers28.The designer uses words and pictures in the poster to ______ .A. catch readers' attentionB. encourage families to write booksC. help readers form reading habitsD. recommend different types of booksBAccording to a research,more than 130 billion pounds of uneaten food go to waste in Laura's country each year.That is about 30% of the yearly food supply（供应）.It is a sad fact,especially when you consider how many families and homeless people are in hunger.When Laura saw her school dining hall throw away food that was not eaten at all every day,she came up with an idea.She started a project to help her school dining hall to give away uneaten food to homeless shelters （庇护所）in her community.In the past three years,the same project has spread to other schools and some fast food restaurants throughout the city.The project is called Feed & Find,and has already fed thousands of people in her city.How does it work？Through an app,Feed & Find matches local homeless shelters with school dining halls and restaurants that have uneaten food to provide.When dining halls or restaurants have uneaten food left,they can use the app to share the information about the food.A truck driver working for the project is then sent to pick it up and take it to a shelter.Pretty cool,right？It's not surprising that people in other cities have got in touch with Laura,hoping that she could help develop similar projects for their communities.Some people,however,have concerns about the safety of the uneaten food.They think such food may not be clean enough.Still,this project is a clever way to help solve the problem,of food waste and it helps those in need.29.The numbers in Paragraph One tell us ______ .A. some people are poorB. food waste is seriousC. the population is largeD. the research is interesting30.People in other cities would like Laura to ______ .A. find a truck driverB. visit their communitiesC. give away food to themD. help develop projects like hers31.The underlined word " concerns" in this passage means ______ .A. waysB. secretsC. worriesD. decisionsCShashiyu was once a poor village in Hebei Province,but now it has changed into a rich and livable place.In the 1940s,villagers in Shashiyu had little food and few clothes,but they had a strong wish for a better life.Zhang Guishun,the Party secretary of Shashiyu,encouraged his villagers to do their best to pull themselves out of poverty, "In the ancient Chinese story,Yu Gong could move mountains with his strong will and hard work,why can't we？Nobody was born to be poor？" Hearing his words,the villagers decided to make a difference.Led by the Communist Party of China （中国共产党），the villagers carried water and soil to their village from faraway places to improve their land.From 1966 to 1971，they reclaimed （开垦）lots of land and greatly improved their life.However,the village encountered a new problem two decades later as the environment became heavily polluted by chemical plants （化工厂）and mine refineries （冶炼厂）built in 1990s.The polluting factories were shut down in 2004，and villagers started grape cultivation,which soon became a main industry in Shashiyu.In 2009，the city-level government invested over 1 million yuan （＄152.723）to change the village's exhibition hall into a museum in memory of development efforts made by earlier generations.After 10 years,the village was called "National Forest Village".Zhang said that the village started a yearly tourism festival in 2015 to attract travelers to pick grapes. "The grapes could be sold at a better price once Shashiyu becomes famous through this festival.Our villagers can then live even better lives," he said.32.From 1966 to 1971，what did the villagers do to improve their living situation？______A. They planted grapes to earn money.B. They carried water and soil to their village to improve their lands.C. They moved to another place to live a better life.D. They built a lot of factories.33.When was Shashiyu called "National Forest Village"？______A. In 2009.B. In 2004.C. In 2015.D. In 2019.34.Where can you probably read the passage？______A. In a storybook.B. In a newspaper.C. In a sports magazine.D. In a science book.DHave you ever heard voices from the universe？What secrets lurk （潜藏）in the signals of pulsars （脉冲星Y 16，000 light-years from Earth？Our eyes may not be able to explore these distant mysteries,but "Sky Eye" allows us to "see" farther.China's Five-hundred-meter Aperture Spherical Radio Telescope （望远镜）（FAST），commonly known as"Sky Eye"，the world's largest single-aperture （单口径）radio telescope,officially opened to the world on March 31.The giant telescope is the size of 30 soccer fields. "Before FAST was put into use,China's radio telescopes usually had a diameter of fewer than 50 meters," said Wang Qiming,FAST's chief technologist."FAST marks a huge leap （飞跃）forward"Not only is the telescope leading in size,but it's also leading in terms of sensitivity （敏感度）.FAST is about 2.5 times as sensitive as the second-largest telescope in the world,the Arecibo,Observatory in Puerto Rico,and can "see" objects some 13.7 billion light-years away,reported Shine,a Shanghai-based media platform.That is to say,if you make a phone call from the moon,it can detect the signal,according to CNR News.Since its completion in September 2016，it has found more than 300 pulsars （脉冲星）-objects thought to be rapidly rotating neutron （中子）stars that emit （发射）regular pulses （脉冲）of radio waves.To date,FAST has expanded（扩大）four times the volume of the space range that radio telescopes can effectively explore,which means that scientists can discover more unknown cosmic （宇宙的）phenomena （现象），according to Shine.Experts believe"Sky Eye" will surprise us in the future."FAST has the potential （潜力）to detect signals from thousands of superior planets.Maybe aliens with much more advanced technologies live there," Li Di,chief scientist of FAST，told China Daily."TAST may well be the instrument （仪器）enabling great discoveries,perhaps even discoveries that will earn Nobel or other,significant prizes," Sheldon Glashow,winner of the 1979 Nobel Prize in Physics,told China Daily.He also has high expectations （期望）for FAST. Now "Sky Eye" has changed from "China's eye" to" the world's eye".About 10 percent of FAST's observation （观测）time in the first year,roughly 450 hours,is expected to be allocated （分配）to foreign scientists,said Li Di."FAST provides astronomical （天文的）capabilities not available anywhere else in the world.Astronomers and physicists who need those capabilities will surely take advantage of China's generosity in making the tools widely available,Joseph Taylor Jr.，recipient of Nobel Prize in Physics in 1993，told China Daily.35.What does the article tell us about FAST？______A. It is about 2.5 times as large as Arecibo.B. It can "see" objects 30 million light- years away.C. It helped Chinese physicists win a Nobel Prize.D. It has been available to foreign scientists since March 31.36.What has FAST allowed scientists to do？______A. Send pulses of radio waves into the universe.B. Know more about pulsars in the universe.C. Answer phone calls from the moon. .D. Change the way neutron stars emit pulses.37.What is the main purpose of the article？______A. To compare FAST and Arecibo.B. To describe how FAST works.C. To introduce a new way to observe neutron stars.D. To inform readers of advantages and potential use of FAST.四、任务型阅读-简答（本大题共1小题，共6.0分）38.请认真阅读下面短文，用英语回答短文后的问题。
小学上册第十二次英语第一单元测验试卷
小学上册英语第一单元测验试卷英语试题一、综合题(本题有50小题，每小题1分，共100分.每小题不选、错误，均不给分)1 What do you call a person who studies plants and animals?A. ScientistB. DoctorC. ArtistD. Teacher答案: A. Scientist2 The mountains are ________ (高).3 Which is a mode of transportation?A. BicycleB. TableC. ChairD. Lamp答案: A4 My mom makes the best ________ (汤).5 Many galaxies are moving away from us, suggesting the universe is ______.6 ts can grow in ______ (贫瘠) soil. Some pla7 What is the tallest animal in the world?A. ElephantB. GiraffeC. HorseD. Camel答案:B8 What do we call the natural satellite that orbits Earth?A. MoonB. StarC. PlanetD. Comet答案：A9 What is the capital city of France?A. LondonB. BerlinC. ParisD. Madrid答案: C10 The chemical symbol for carbon is ______.11 The cupcakes are _______ (frosted) with icing.12 The Earth is divided into ______ hemispheres.13 What is the name of the famous ship that sank in 1912?A. Queen MaryB. TitanicC. LusitaniaD. Britannic14 The ancient Greeks contributed greatly to ________ and literature.15 I like ________ (solving) puzzles.16 A saturated solution cannot dissolve any more ______.17 The element with atomic number is __________.18 What type of tree produces pine cones?A. DeciduousB. EvergreenC. Fruit TreeD. Flowering答案：B19 A __________ is an area of land that is very wet.20 The basic unit of matter is the _____.21 What is the name of the famous dog in the movie "The Wizard of Oz"?A. TotoB. SpikeC. RexD. Max答案: A22 She is my _____ (好朋友) from school.23 The goldfish has a round ______ (身体).24 My friend is very __________ (调皮的) sometimes.25 A __________ is an area of land that is very mountainous.26 The ______ is the path of the Earth around the sun.27 The _____ (forest) is home to many plants and animals.28 What is the capital of Bhutan?A. ThimphuB. ParoC. PunakhaD. Phuentsholing答案:A. Thimphu29 _____ (deciduous) trees lose their leaves in winter.30 What is the capital of Italy?A. FlorenceB. RomeC. VeniceD. Milan31 My teacher teaches us __________. (英语)32 The flowers in the garden are ______ (colorful).33 What is the capital of Serbia?A. BelgradeB. Novi SadC. NišD. Kragujevac答案: A34 In a chemical reaction, the enthalpy change can indicate whether heat is absorbed or_____ released.35 The __________ (历史的启示) guides our future.36 The ancient Greeks were known for their ________ philosophy.37 A _______ is a reaction that produces a pungent aroma.38 What is the name of the famous scientist known for his work on the structure of DNA?A. James WatsonB. Francis CrickC. Rosalind FranklinD. Gregor Mendel答案: A39 The blanket is very ___ (soft/hard).40 What is 8 ÷ 2?A. 4B. 5C. 6D. 7答案:A41 The stars are ___. (bright)42 A __________ is a large body of saltwater.43 What is the name of the famous dinosaur known for its long neck?A. T-RexB. StegosaurusC. BrachiosaurusD. Triceratops44 The ______ (小鸟) sings sweet songs in the morning.45 What is the capital city of Thailand?A. BangkokB. PhuketC. Chiang MaiD. Pattaya答案: A46 What is the term for stars that explode at the end of their life cycles?A. NovaeB. SupernovaeC. PulsarsD. Black Holes47 A _______ can demonstrate how sound travels through different materials.48 I enjoy planting ________ in my backyard.49 I enjoy making ________ (手工艺) for holidays.50 The process of making ice cream involves ______.51 She can _______ (speak) three languages.52 A ______ (青蛙) has long legs for jumping.53 The atomic number of an element tells you the number of _____ (protons) it has.54 In a combustion reaction, the products are typically _____ and water.55 A base can neutralize an ______.56 The chemical formula for sulfuric acid is ________.57 The _______ can provide beauty to any landscape.58 What is the term for the natural home of an animal?A. HabitatB. EnvironmentC. EcosystemD. Territory答案: A59 The __________ is the energy needed to start a chemical reaction.60 What is the name of the famous artist known for his abstract works?A. Pablo PicassoB. Claude MonetC. Vincent van GoghD. Leonardo da Vinci61 How many continents are there?A. FiveB. SixC. SevenD. Eight62 The ______ (草坪) needs mowing.63 She is _____ (playing) the violin.64 My ________ (玩具名称) helps me learn math.65 What is the opposite of ‘dry’?A. WetB. MoistC. HumidD. Damp66 The _______ (狐狸) is cunning.67 We will have a ________ (家庭聚会) soon.68 The ____ is a small animal that enjoys exploring its surroundings.69 The rabbit has soft ______ (毛).70 I enjoy listening to ________ (音乐) while working.71 What do you call a tool used for cutting wood?A. HammerB. ScrewdriverC. Saw答案:C72 I look up to my ____.73 A __________ is an area that is permanently frozen.74 I have a _______ (hat) on my head.75 Honey is made by ______.76 What is the term for a young dolphin?a. Calfb. Pupc. Kitd. Chick答案:a77 I have a _______ (计划) for the weekend.78 n Tea Party was a protest against the ________ (茶税). The Brit79 Which gas do we breathe out?A. OxygenB. Carbon dioxideC. NitrogenD. Hydrogen答案:B80 I like to play ______ (basketball) with my friends.81 Some stars are part of a _____ system, orbiting each other.82 A telescope helps us to observe ______.83 A barracuda is a fast and fierce ______ (鱼).84 Which instrument has strings and is played with a bow?B. ViolinC. PianoD. Drum答案: B85 The __________ can affect the growth of plants and animals.86 What do we call the small, round fruit that is typically blue or purple?A. BlackberryB. BlueberryC. RaspberryD. Cranberry答案:B87 The ________ is a gentle giant in the jungle.88 The ______ (小鸟) finds a cozy spot to rest in the tree.89 The ________ (goal) is achievable.90 What is the capital of Indonesia?A. JakartaB. BaliC. SurabayaD. Bandung答案:A91 I have a toy _______ that makes music.92 I can create a dance party with my toy ________ (玩具名称).93 My dad likes to go ____ (camping) in the mountains.94 The __________ (历史的回顾) informs our present.95 The __________ can provide insights into the health of an ecosystem.96 The ancient Egyptians created elaborate _____ for their elite.97 The chemical formula for lithium bromide is _______.98 The teacher is _____ the students to listen. (asking)99 The __________ was a major event in the history of civil rights. (马丁·路德·金的演讲)100 The __________ (历史的探索者) uncover stories long forgotten.。
无锡“PEP”2024年小学四年级上册第七次英语第六单元期末试卷
无锡“PEP”2024年小学四年级上册英语第六单元期末试卷考试时间：100分钟（总分:140）A卷考试人：_________题号一二三总分得分一、选择题(共计20题，共40分)1、Which animal is known for its stripes?A. LionB. ElephantC. ZebraD. Giraffe2、选择题：What is the capital of Argentina?A. SantiagoB. Buenos AiresC. LimaD. Bogotá3、What do you call a person who studies rocks?A. BiologistB. GeologistC. AstronomerD. Chemist4、选择题：How many months are there in a year?A. TenB. ElevenC. TwelveD. Thirteen5、What is the first month of the year?A. DecemberB. JanuaryC. FebruaryD. March6、How many players are on a volleyball team?A. FiveB. SixC. SevenD. Eight7、What is the term for a baby goat?A. KidB. CalfC. LambD. Foal8、选择题：What do you call the part of the plant that absorbs sunlight?A. RootB. LeafC. StemD. Flower9、Which object helps us tell time?A. CompassB. ClockC. MapD. Book10、What do we call a young deer?A. FawnB. CalfC. KidD. Pup11、What color is the sky on a clear day?A. GreenB. BlueC. YellowD. Red12、How many seconds are in a minute?A. 30B. 60C. 90D. 12013、What is the capital of France?A. BerlinB. MadridC. ParisD. Rome14、选择题：What do we call the seasonal change from winter to spring?A. TransformationB. ChangeoverC. TransitionD. Thaw15、What is the capital of Thailand?A. BangkokB. PhuketC. Chiang MaiD. Pattaya16、Which season comes after summer?A. FallB. WinterC. SpringD. Autumn17、What do we call a story that teaches a lesson?A. FableB. MythC. LegendD. Tale18、What is the term for stars that explode at the end of their life cycles?A. NovaeB. SupernovaeC. PulsarsD. Black Holes19、Which animal is known for its ability to swim?A. OstrichB. LionC. FishD. Elephant20、选择题：Which day comes before Monday?A. SaturdayB. SundayC. FridayD. Thursday二、听力题(共计20题，共40分)1、听力题：The process of combustion produces ______ and heat.2、听力题：Nonmetals are usually poor _____ of heat and electricity.3、听力题：The boiling point of water is _____ degrees Celsius.4、听力题：A reaction that produces a gas and heat is called a ______ reaction.5、听力题：The _______ can provide beauty to your garden.6、听力题：The ______ helps flowers to grow.7、听力题：The children are _____ around the tree. (running)8、听力题：The process of filtration is used to separate __________ from liquids.9、听力题：A __________ is a place where people fish.10、听力题：The chemical symbol for cerium is _______.11、听力题：The bird is singing a ______ (song).12、听力题：The atomic mass of an element is approximately equal to the number of _____ and neutrons.13、听力题：A __________ is a chemical change that can be reversed.14、听力题：The Earth's surface is subject to a variety of natural ______.She enjoys ________ (facilitating) workshops.16、听力题：The __________ plays a critical role in protecting biodiversity.17、听力题：Evaporation is a type of ______ change.18、听力题：The baby is ______ her bottle. (drinking)19、听力题：We are going to ___ a trip. (take)20、听力题：The sandwiches are ___ (fresh/old).三、填空题(共计20题，共10分)1、填空题：It’s fun to jump in __________ after a rain. (水坑)2、填空题：Herbs can be dried for ______ (储存).3、填空题：A rabbit's nose twitches when it is ________________ (警觉).4、填空题：The ______ (鸟) sings sweetly in the morning.5、填空题：My favorite stuffed ________ is a bear.6、填空题：I want to _______ (学习) how to cook.7、填空题：A _____ (plumeria) tree smells lovely.8、填空题：The __________ (历史的启迪) inspires us to act.The _____ (狮子) is a social animal that lives in groups.10、填空题：My dad teaches me how to ______ (骑自行车). I am learning to balance and pedal.11、填空题：I like to dress up my dolls in different ________ (服装). It’s like a fashion ________ (秀).12、填空题：My favorite _____ is a stuffed elephant.13、填空题：A ____(collaborative project team) works towards a common goal.14、填空题：Whenever we face challenges, we support each other. If I have a problem, I know I can always talk to ______. They give the best advice and always cheer me up.15、填空题：I can ______ (保持) a positive mindset.16、填空题：A parrot can mimic human ______ (语言).17、填空题：I saw a ________ in the shade of the tree.18、 (Civilizations) of Mesopotamia are known as the cradle of civilization.填空题：The ____19、填空题：My rabbit loves to chew on ______ (蔬菜).20、填空题：The ancient Greeks are known for their contributions to _____.。
广州2024年10版小学四年级上册第二次英语第二单元真题试卷(含答案)
广州2024年10版小学四年级上册英语第二单元真题试卷(含答案)考试时间：80分钟（总分:140）A卷考试人：_________题号一二三四五总分得分一、综合题(共计100题)1、What do you call a place where animals are kept for public display?A. ParkB. ZooC. FarmD. Aquarium答案: B2、听力题：A ______ helps to spread seeds.3、填空题：The falcon is known for its _________ (速度).4、填空题：My sister is my best _______ who loves to share laughter and secrets.5、填空题：I have a _____ (跳绳) that I use to exercise. 我有一根用来锻炼的跳绳。
6、What do you call a vehicle that travels on water?A. PlaneB. CarC. BoatD. Train答案:C7、听力题：My favorite book is ________.8、听力题：Pulsars are rotating neutron _______ that emit beams of radiation.The __________ is a famous natural landmark in Canada. (尼亚加拉瀑布)10、How many states are in the USA?A. 48B. 50C. 52D. 54答案:B11、听力题：A dolphin is a friendly ______.12、What is 12 divided by 4?A. 2B. 3C. 4D. 5答案:B13、选择题：What do we call the natural disaster caused by the movement of tectonic plates?A. TornadoB. EarthquakeC. FloodD. Hurricane14、填空题：My favorite toy is a ________ (拼图). I enjoy putting the pieces ________ (在一起).15、填空题：My sister loves to write ____.16、What do you call a group of fish?a. Schoolb. Packc. Flockd. Herd答案:A17、填空题：My favorite type of food is ______.18、填空题：I like _______ (画画) pictures of nature.I enjoy _____ (painting/drawing).20、What do we call a place where animals are kept for public display?A. AquariumB. ZooC. FarmD. Wilderness答案:B21、What do you call a young starfish?A. LarvaB. PupaC. JuvenileD. Kit22、听力题：My dad works in an ________.23、填空题：I have a ________ that twirls.24、What do you call a young female horse?A. ColtB. FillyC. FoalD. Mare答案: B25、填空题：The ancient Egyptians used hieroglyphics for ______ (书写).26、填空题：Gardeners often use ______ to help their plants grow strong.(园艺师常常使用肥料来帮助植物健康成长。
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arXiv:astro-ph/9911473v2 28 Nov 1999WhereAreTheYoungPulsars?ArnonDarDepartmentofPhysicsandSpaceResearchInstituteTechnion,Haifa32000,Israel
ABSTRACTWeshowthatyoungpulsarswithnormalmagneticfields,whicharebornasfastrotatingneutronstars(NSs)inTypeII/Ibsupernovaexplosions,canslowdownquicklybyrelativisticparticlesemissionalongtheirmagneticaxis.Whentheyslowdownsufficiently,theycanundergophasetransitionsandcollapsetostrangestars,quarkstarsorblackholesinexplosionsthatremoveasubstantialfractionoftheirinitialangularmomentum.Thenewlybornstrangeorquarkstarscontinuetocoolandspindownveryquicklyassoftgammarayrepeaters(SGRs)andanomalousX-raypulsars(AXPs)tobecomeslowlyrotating,radio-quiet,dimX-raypulsarsorstellarblackholes,dependingontheirinitialmass.ItcanexplaintheapparentdearthofyoungradiopulsarsinSNRsandintheGalaxy.
Subjectheadings:pulsars,softgammarayrepeaters,anomalousX-raypulsars,strangestars,quarkstars,blackholes
1.IntroductionItiswidelybelievedthatneutronstars(NSs)whichareborninTypeII/Ibsupernovaexplosions(SNeII)ofmassivestarsarerapidlyrotatingneutronstars(NSs)withlargemagneticfields,thatarespinningdownbymagneticdipoleradiationoftheirrotationalenergy(e.g.ShapiroandTeukolsky1983).SuchCrab-likepulsarsandtheiraccompanyingsupernovaremnants(SNRs)areexpectedtobehighlyvisiblefortensofthousandsofyears.ThemeanrateofSNeIIinourgalaxyhasbeenestimatedtobeR≈1/50y(TammanandVandenBergh1991).Itisconsistentwiththe220knownyoungGalacticSNRs(Green1998)if,ontheaverage,theyareobservablefor∼104y.Lessthan30%oftheSNRsareTypeISNeremnants(TammanandVandenBergh1991)whichdonotproduceNSs.But,despitedetailedradiosearches,only<20radiopulsarsoutofover1100detectedradiopulsars(Camiloetal.1999)werefoundwithin/nearyoungSNRsandsomeofthemcanbe–2–duetochanceoverlap(GaenslerandJohnston1995).SowherearealltheyoungpulsarsborninGalacticSNRs?
Traditionalargumentsinvokingbeaming,largenatalkickvelocitiesanddirectcollapsetoblackholeshavebecomelesscompellingwiththeaccumulatingresultsfromnewsurveys.Thus,analternativeexplanationfortheapparentdearthofradiopulsarsseemstobeneeded.GotthelfandVasisht(1999)havesuggestedthatnewlybornCrab-likeNSswithatypicalsurfacemagneticfield,B∼1013Gauss,arerare,whilethemajorityarebornasmagnetars-neutronstarswithhugesurfacemagneticfields,B∼1015Gauss(DuncanandThompson1992;ThompsonandDuncan1993,1995,1996).Theirenormousmagneticfieldprovidesanaturalmechanismforbrakingthesepulsarsandspinningthemdownveryquickly.Suchpulsarsbecomeunobservableintheradioinaveryshorttimeduetotheirslowrotationand/orthefastdecayoftheirmagneticfield.Theirsuggestionwasmotivatedbytheclaimedsuccessofthemagnetarmodelforsoftgammarayrepeaters(SGRs)(e.g.,Kouveliotouetal.1998;Kouveliotouetal.1999)andanomalousX-raypulsars(e.g.,Gotthelfetal.1999):The4knownSGRsandthe6knownAXPsareallslowlyrotating(P=5-12s)pulsars,surprisinglyyoung,asevidentfromthefactthatallthe4knownSGRsand3outofthe6knownAXPsarefoundin/nearyoungSNRs(Clineetal.1982;KulkarniandFrail1993;Vasishtetal.1994;Gotthelf&Vasisht1997:Hurleyetal.1999b,c;Parmaretal.1998;Gaensleretal.1999).TheirrotationalenergyistoosmalltopowereithertheirpersistentX-rayemissionortherepeatedgammarayburstsfromSGRs.Theyspindownveryquicklyatarate˙P∼10−10−10−12,toolargetobeexplainedbymagneticbrakingduetoB≤1013Gausssurfacemagneticfieldsofordinaryradiopulsars.Thehugemagneticfieldsofmagnetarscanexplainboththefastspin-downrateandthepowersourceofSGRsandAXPs.
However,themagnetarmodelforSGRsfacessevereproblems(Dar1999;DarandDeR´ujula1999a).Itfacesan‘ageproblem’-themagneticspin-downagesofSGRs,τs≤P/2˙P,aremuchshorterthantheagesoftheexpandingSNRsfromtheirbirth.Italsofacesa‘separationproblem’-theSGRsarefoundatdistancestoofarfromthecentersoftheSNRswheretheywereborn,iftheirmagneticspindownageistheirtrueageandtheirnatalkickvelocityislikethatofordinarypulsars,v⊥∼350±70kms−1(e.g.,LyneandLorimer1994;Toscanoetal1999).Moreover,themagnetarmodelofSGRsandAXPsalsofacesan‘energycrisis’:Magneticbrakingimpliesthattheirspin-downrateisproportionaltothesquareoftheirsurfacemagneticfield.IftheenergysourceofSGRsistheirmagneticfieldenergy,Em≈B2R3/12,thenincreaseintheirspin-downrateimpliessimilarincreaseintheirmagneticfieldenergy.Consequently,thelargeincrease(morethandoubling)inthespin-downrateofSGR1900+14duringitsintensiveburstactivityaroundAugust27,1998(e.g.,Marsdenetal.1999;Woodsetal.1999)impliesasimilarincreaseinitshugemagnetic