On the Cluster Sunyaev-Zel'dovich Effect and Hubble Constant

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2019年12月英语六级试卷及解答第一套

2019年12月英语六级试卷及解答（第一套）Part Ⅰ Writing (30 minutes) Directions: For this part, you are allowed 30 minutes to write an essay on the importance of having a sense of community responsibility. You should write at least 150 words but no more than 200 words.【参照范文】There is no doubt that community responsibility plays an indispensable role in personal development, for instance, in the workplace.There are several factors accounting for this perspective and the following are the most typical ones. First and foremost, a strong sense of community responsibility is helpful to develop harmonious interpersonal relationships. As we all know, we are very likely to spend more time with our colleagues than our families after entering the workplace. Therefore, the sound wor atmosphere and interpersonal relationships among employees are crucial to both physical and mental pleasure. In addition, community responsibility can improve efficiency. In the fast-paced modern society, time is money and efficiency holds the key to saving time. As the saying goes, two heads are better than one. So great importance should be attached to the cultivation of the sense of community responsibility and we will eventually benefit from it.From what has been mentioned above, we can come to the conclusion that the sense of community responsibility is a kind of good personal quality, which deserves our attention.【参照译文】毫无疑问，集体责任在个人发展中起着不可或缺的作用，例如在工作场所。

tpo32三篇托福阅读TOEFL原文译文题目答案译文背景知识

tpo32三篇托福阅读TOEFL原文译文题目答案译文背景知识阅读-1 (2)原文 (2)译文 (5)题目 (7)答案 (16)背景知识 (16)阅读-2 (25)原文 (25)译文 (28)题目 (31)答案 (40)背景知识 (41)阅读-3 (49)原文 (49)译文 (53)题目 (55)答案 (63)背景知识 (64)阅读-1原文Plant Colonization①Colonization is one way in which plants can change the ecology of a site.Colonization is a process with two components:invasion and survival.The rate at which a site is colonized by plants depends on both the rate at which individual organisms(seeds,spores,immature or mature individuals)arrive at the site and their success at becoming established and surviving.Success in colonization depends to a great extent on there being a site available for colonization–a safe site where disturbance by fire or by cutting down of trees has either removed competing species or reduced levels of competition and other negative interactions to a level at which the invading species can become established.For a given rate of invasion,colonization of a moist,fertile site is likely to be much more rapid than that of a dry, infertile site because of poor survival on the latter.A fertile,plowed field is rapidly invaded by a large variety of weeds,whereas a neighboring construction site from which the soil has been compacted or removed to expose a coarse,infertile parent material may remain virtually free of vegetation for many months or even years despite receiving the same input of seeds as the plowed field.②Both the rate of invasion and the rate of extinction vary greatly among different plant species.Pioneer species-those that occur only in the earliest stages of colonization-tend to have high rates of invasion because they produce very large numbers of reproductive propagules(seeds,spores,and so on)and because they have an efficient means of dispersal(normally,wind).③If colonizers produce short-lived reproductive propagules,they must produce very large numbers unless they have an efficient means of dispersal to suitable new habitats.Many plants depend on wind for dispersal and produce abundant quantities of small,relatively short-lived seeds to compensate for the fact that wind is not always a reliable means If reaching the appropriate type of habitat.Alternative strategies have evolved in some plants,such as those that produce fewer but larger seeds that are dispersed to suitable sites by birds or small mammals or those that produce long-lived seeds.Many forest plants seem to exhibit the latter adaptation,and viable seeds of pioneer species can be found in large numbers on some forest floors. For example,as many as1,125viable seeds per square meter were found in a100-year-old Douglas fir/western hemlock forest in coastal British Columbia.Nearly all the seeds that had germinated from this seed bank were from pioneer species.The rapid colonization of such sites after disturbance is undoubtedly in part a reflection of the largeseed band on the forest floor.④An adaptation that is well developed in colonizing species is a high degree of variation in germination(the beginning of a seed’s growth). Seeds of a given species exhibit a wide range of germination dates, increasing the probability that at least some of the seeds will germinate during a period of favorable environmental conditions.This is particularly important for species that colonize an environment where there is no existing vegetation to ameliorate climatic extremes and in which there may be great climatic diversity.⑤Species succession in plant communities,i.e.,the temporal sequence of appearance and disappearance of species is dependent on events occurring at different stages in the life history of a species. Variation in rates of invasion and growth plays an important role in determining patterns of succession,especially secondary succession. The species that are first to colonize a site are those that produce abundant seed that is distributed successfully to new sites.Such species generally grow rapidly and quickly dominate new sites, excluding other species with lower invasion and growth rates.The first community that occupies a disturbed area therefore may be composed of specie with the highest rate of invasion,whereas the community of the subsequent stage may consist of plants with similar survival ratesbut lower invasion rates.译文植物定居①定居是植物改变一个地点生态环境的一种方式。

虚拟天文台

• Virtual
• not tied to a single “brick-and-mortar” location • supports astronomical “observations” and discoveries
via remote access to digital representations of the sky
Infrared
Optical
National Virtual Observatory
用户需要做的事情:
1. 提出科学思想, 及对数据库的需要 2. 检索数据库 (用户到不同站点寻找) 3. 下载所需的数据 (x TB ? 包括各种元数据, 定标数据……) 4. 对数据进行标准化处理 (需要软件平台) 5. 数据的匹配 (如果使用二个以上数据库的资料 ) 6. 发展各种软件工具 (可视化, 统计工具… … )
National Virtual Observatory
时代
National Virtual Observatory
两百多年来，天文研究通常都是单个天文学家或者天文学家小组进行为数有限的天体的观测。
National Virtual Observatory
过去天文学家常常花整个一生所获得的资料, 仅仅够得出有统计意义的结论。加上威力大的设备的观测时间是非常有限，那些需要大量数据来解决的天体物理问题就不能进行研究
• Observatory
• general purpose • access to large areas of the sky at multiple wavelengths • supports a wide range of astronomical explorations • enables discovery via new computational tools

2021年12月大学英语四级阅读200篇第104篇：冰岛之珠—雷克雅

2021年12月大学英语四级阅读200篇汇总Reykjavik1: The Pear l On The IcelandVisit Iceland and you'll enter a whole new realm of experience . You'll discover original nature as you've never seen it before, and the equally original people. Timeless nature, ancient heritage and modern lifestyle coexist in harmony here .Reykjavik, the capital of Iceland, is just a part of the Icelandic experience with its midnight sun or the magical landscapes forged by ice and fire. Reykjavik has a population of around 110 000 and offers an interesting mix of cosmopolitan culture and local village roots.Old accounts say the ancient gods themselves guided Iceland's first settler to make his home in Reykjavik. He named the place Reykjavik ( steamy Bay) after the geothermal steam he saw, which today heats homes and outdoor swimming pools throughout the city, a pollution-free energy source that leaves the air outstanding fresh and clean.A beautiful river runs through the city limits, and so do fine parks. In the outskirts are places for horse trekking and golf. But against this backdrop2 of nature, Reykjavik has a packed program of city joys too: art museums, several theaters, an opera house and symphony orchestra spanning the whole spectrum of age and taste.One must for all visitors is dinning out on Icelandic specialties, including delicious seafood, ocean-fresh from the morning's catch, highland lamb and varieties of game. Its purely natural food imaginatively served to delight the most discerning3 of diners. Reykjavik is also renowned as one of Europe 's hottest nightspots, where the action on the friendly pub and nightlife scene lasts right through the night. In the evening, the downtown area teems with activity, reaching its peak on Friday or Saturday. The number of pubs, café, discos, and other night-sports in the downtown area is astonishing. There is a rich variety of places to go : European-style coffee shop, nightclubs with live entertainment, dance halls for seniors, sports-theme pubs with big TV screens, coffee shop that offer over 100 types of beer, an Irish pub, a Spanish café, a French wine bar . . .Walking distances are short downtown, and everything worth seeing outside the city center can be quickly and conveniently reached by bus. With its long easy-going4 main street and large shop too —with a bonus of tax-free shopping for visitors! Be on the lookout just for souvenirs (especially woolens and handicrafts) but also for stylish consumer goods and designer labels at competitive prices.A full range of accommodations is available in Reykjavik, from international-standard hotels with good conference facilities,through smaller hotels and cozy guesthouses, to a campsite in the city's biggest park.练习题：Ⅰ. Complete the sentences with words from the passage:1. Visit Iceland and you'll enter a whole new of experience.2. Reykjavik offers an interesting of cosmopolitan culture and local village roots.3. A full rang of accommodation is in Reykjavik.Ⅱ. True or False:1. In Reykjavik, the air is fresh and clean, because people use geothermal energy.2. Reykjavik is famous for its nightlife .3. There are many places outside city worth seeing, but traffic is not convenient.答案：Ⅰ. 1. realm 2. mix 3. availableⅡ. 1. T 2. T 3. F参考译文：冰岛之珠——雷克雅未克到冰岛旅游你会有一种全新的体验。

英语四级阅读理解科学家集资

英语四级阅读理解科学家集资Scientists say they have discovered hints of alienlife on th e Saturn’s moon. The discovery of a sort oflife was announc ed after researchers at the USspace agency,NASA,analyzed da ta from spacecraftCassini,which pointed to,the existence of m ethane-based form of life on Saturn’s biggest moon. Scientists have reportedly discovered cluesshowing primitive alien bein gs are"breathing" inTitan’s dense atmosphere filled with hy drogen.They argue that hydrogen gets absorbedbefore hittin g Titan’s planet-like surface coveredwith methane lakes and rivers. This,they s ay,points to the existence of some"bugs" consumingthe hydr ogen at the surface of the moon less than half the size of the Earth."We suggested hydrogen consumption because it’s the obvious gas for life to consumeon Titan,similar to the way we consume oxygen on Earth,"says NASA scientist Chris McKay."Ifthese signs do turn out to be a sign of life,it would be doubly exciting because it wouldrepresent a second form of life inde pendent from water-based life on Earth." To date,scientists have not yet detec ted this form of life anywhere,though there are liquid- water-based microorganisms on Earth that grow well on methane o r produce it as a wasteproduct. On Titan, where temperatures are around 90 Kelvin(minus 290 degrees Farenheit),amethan ebased organism would have to use a substance that is liquid as its medium forliving processes, but not water itself. Water is frozen solid on Titan’s surface and much too coldto supp ort life as we know it. Scientists had expected the Sun’s i nteractions with chemicals in the atmosphere toproduce a co ating of acetylene on Titan’s surface. But Cassini detected n o acetylene on thesurface. The absence of detectable ace tylene on the Titan’s surface can very well have a non-biological explanation,said Mark Allen,a principal investigator of the NASA Titan team."Scientific conservatism suggests that a biological explanation should be the last choiceafter all non-biological explanations are addressed,"Allen said."We have a lot of work to do torule out possible non-biological explanations. It is more likely that a chemical proce ss,withoutbiology,can explain these results."1、What have scientists found about Saturn?A.They have found a new moon orbiting Saturn.B.They have found methane-based life on Saturn.C.They have found methane-based life on Titan.D.They have found earthlike life on a Saturn’s moon.2、What do scientists say about Titan?A.There are life clues there.B.There is acetylene there.C.Water on Titan exists in the form of ice.D.Rivers and lakes there contain life formls.3、To date,scientists have not yet detected this form of life.(para graph 5)What does"thisform of life" refer to?A.Water-based life.B.Methane-based life.C.Liquid-water-based microorganisms.D.Gas-based life.4、What can be inferred from what Allen said?A.Scientists have different arguments over whether there is lif e on Titan.B.Scientists all agree that there is life on Titan.C.Scientists all suggest that a biological explanation is reason able.D.Scientists all agree that a non-biological chemical reaction is a possible explanation.5、Which of the following can replace the title of this passage?A.Earthlike Living Beings Found on Titan.B.Finding of One More Moon of Saturn.C.Titan,a New Satellite Found.D.A different Life Form, a Possibility.。

tpo35三篇阅读原文译文题目答案译文背景知识

tpo35三篇阅读原文译文题目答案译文背景知识阅读-1 (1)原文 (2)译文 (5)题目 (8)答案 (17)背景知识 (18)阅读-2 (21)原文 (21)译文 (24)题目 (27)答案 (36)背景知识 (36)阅读-3 (39)原文 (39)译文 (43)题目 (46)答案 (54)背景知识 (55)阅读-1原文Earth’ s Age①One of the first recorded observers to surmise a long age for Earth was the Greek historian Herodotus, who lived from approximately 480 B.C. to 425 B.C. He observed that the Nile River Delta was in fact a series of sediment deposits built up in successive floods. By noting that individual floods deposit only thin layers of sediment, he was able to conclude that the Nile Delta had taken many thousands of years to build up. More important than the amount of time Herodotus computed, which turns out to be trivial compared with the age of Earth, was the notion that one could estimate ages of geologic features by determining rates of the processes responsible for such features, and then assuming the rates to be roughly constant over time. Similar applications of this concept were to be used again and again in later centuries to estimate the ages of rock formations and, in particular, of layers of sediment that had compacted and cemented to form sedimentary rocks.②It was not until the seventeenth century that attempts were madeagain to understand clues to Earth's history through the rock record. Nicolaus Steno (1638-1686) was the first to work out principles of the progressive depositing of sediment in Tuscany. However, James Hutton (1726-1797), known as the founder of modern geology, was the first to have the important insight that geologic processes are cyclic in nature. Forces associated with subterranean heat cause land to be uplifted into plateaus and mountain ranges. The effects of wind and water then break down the masses of uplifted rock, producing sediment that is transported by water downward to ultimately form layers in lakes, seashores, or even oceans. Over time, the layers become sedimentary rock. These rocks are then uplifted sometime in the future to form new mountain ranges, which exhibit the sedimentary layers (and the remains of life within those layers) of the earlier episodes of erosion and deposition.③Hutton's concept represented a remarkable insight because it unified many individual phenomena and observations into a conceptual picture of Earth’s history. With the further assumption that these geologic processes were generally no more or less vigorous than they are today, Hutton's examination of sedimentary layers led him to realize that Earth's history must be enormous, that geologic time is anabyss and human history a speck by comparison.④After Hutton, geologists tried to determine rates of sedimentation so as to estimate the age of Earth from the total length of the sedimentary or stratigraphic record. Typical numbers produced at the turn of the twentieth century were 100 million to 400 million years. These underestimated the actual age by factors of 10 to 50 because much of the sedimentary record is missing in various locations and because there is a long rock sequence that is older than half a billion years that is far less well defined in terms of fossils and less well preserved.⑤Various other techniques to estimate Earth's age fell short, and particularly noteworthy in this regard were flawed determinations of the Sun's age. It had been recognized by the German philosopher Immanuel Kant (1724-1804) that chemical reactions could not supply the tremendous amount of energy flowing from the Sun for more than about a millennium. Two physicists during the nineteenth century both came up with ages for the Sun based on the Sun's energy coming from gravitational contraction. Under the force of gravity, the compressionresulting from a collapse of the object must release energy. Ages for Earth were derived that were in the tens of millions of years, much less than the geologic estimates of the lime.⑥It was the discovery of radioactivity at the end of the nineteenth century that opened the door to determining both the Sun’s energy source and the age of Earth. From the initial work came a suite of discoveries leading to radio isotopic dating, which quickly led to the realization that Earth must be billions of years old, and to the discovery of nuclear fusion as an energy source capable of sustaining the Sun's luminosity for that amount of time. By the 1960s, both analysis of meteorites and refinements of solar evolution models converged on an age for the solar system, and hence for Earth, of 4.5 billion years.译文地球的年龄①希腊历史学家希罗多德是最早有记录的推测地球年龄的观察家之一，他生活在大约公元前480年到公元前425年。

RevModPhys.82.331

CONTENTS
I. The Cosmological Standard Model A. Historical outline B. Friedmann models 1. The metric 2. Redshift and expansion 3. The radiation-dominated phase 4. Age, distances, and horizons C. Structures 1. Structure growth 2. The power spectrum 3. Nonlinear evolution II. The Age of the Universe A. Nuclear cosmochronology 1. The age of the Earth 2. The age of the Galaxy B. Stellar ages C. Cooling of white dwarfs D. Summary III. The Hubble Constant A. Hubble constant from Hubble’s law 1. Hubble’s law 2. The distance ladder 3. The HST key project B. Gravitational lensing C. Summary IV. Big-Bang Nucleosynthesis A. The origin and abundance of 4He 1. Elementary considerations 2. The Gamow criterion 3. Elements produced 4. Helium abundance 5. Expected abundances and abundance trends B. Observed element abundances 1. Principles 2. Evolutionary corrections 3. Speciﬁc results 332 332 333 333 333 334 335 335 335 336 337 337 337 337 338 339 340 340 340 340 340 341 342 342 343 343 343 343 344 344 345 345 346 346 346 346

练案[34] 选择性必修第四册 UNIT 3 SEA EXPLORATION

练案[34]　选择性必修第四册　UNIT 3　SEA EXPLORATIONⅠ.阅读理解A(2022·江苏省七校调测) High-pitched (高音的) and yet distinct, the sound of a voice calling the name “Amy” is unmistakable. But this isn’t a human cry—it’s the voice of a killer whale called Wikie.New research reveals that orcas (虎鲸) are able to imitate human speech, saying words such as “hello”，“one, two” and “bye bye”. The study also shows that the creatures are able to copy unfamiliar sounds produced by other orcas.Writing in the journal Biological Sciences, researchers from institutions in Germany, U. K．，Spain and Chile, describe how they carried out the latest research with Wikie, a 14-year-old female orca living in an aquarium(水族馆) in France.After first brushing up Wikie’s grasp of the“copy” command, she was trained to imitate three familiar orca sounds made by her 3-year-old Moana. Wikie was then additionally exposed to five orca sounds she had never heard before, including noises sounding like a creaking (嘎吱响) door. Finally, Wikie was exposed to a human making three of the orca sounds, as well as six human sounds，including “hello”，“Amy”，“ah ha”，“one, two”and“bye bye”．The team found that Wikie was often quickly able to copy the sounds, whether from an orca or a human, with all of the novel noises copied within 17 trials. What’s more, two human sounds and all of the human-produced orca sounds were managed on the first attempt—although only one human sound “hello” was correctly produced more than 50% of the time on subsequent trials.The creatures are already known for their ability to copy the movements of other orcas, with some reports suggesting they can also copy the sounds of bottlenose dolphins and sea lions after several trials.Scientists say the discovery helps to cast light on how different groups of wild killer whales have ended up with distinct accents, adding weight to the idea that they are the result of imitation between orcas.语篇解读：本文是一篇说明文。

2014高考英语二轮阅读理解限时训练精品题(17)

2014高考英语二轮阅读理解限时训练精品题〔17〕与答案[科普知识型阅读理解(二)]------BStudying volcanoes is a demanding profession. Hazel Rymer frequently has to struggle through rainforests, climb to the top of mountains, then climb 200 metres into the crater of active volcanoes. But the 38yearold volcanologist does her best to make it sound less alarming than it is. “Driving to work is more risky，〞 she insists. “And the deepest I go into the crater of a volcano is about 300 metres，〞she adds, trying to make it all sound as ordinary as taking the dog for a walk.Hazel has been studying volcanoes for a long time, so it's not surprising she is used to the danger. Her interest in volcanoes began at school. A teacher gave her a book about Pompeii. “I remember reading about the eruption of Ve suvius and the destruction of the city，〞she explains. “The thought of all those people just frozen in time had quite an effect on me and I am still excited by their dangerous beauty today.〞Nowadays, volcanoes are getting more and more unpredictable. There have been many changes in sea level caused by global warming and melting ice caps. These have resulted in some dormant volcanoes erupting, so studying them is more dangerous than ever before. Hazel says that although she doesn't take any unnecessary risk, she has had some frightening moments. Her worst experience was on the slopes of Mount Etna in Sicily, when she was slowly surrounded by lava. “I had a choice of walking ten hours to get around the lava flow or just walking across it，〞 she explains. She chose to pick a path across the cooler rocks in the lava stream. “I guess it was five metres. The flow was 1，000°C, so if you hesitated, your boots would begin to melt. It was scary, but it really was a practical decision—there wasn't time to do anything else.〞And what about the future? “I haven't been to the volcanoes in Indonesia yet. And I would love to spend some time working in the Antarctic，〞she says. “I wouldalso like to know why quiet lava flows erupt from some volcanoes and why other volcanoes go bang.〞 In other words, Hazel Rymer won't be exchanging her volcanoes for the relative safety of driving to work just yet.1. Hazel's claim that “driving to work is more risky〞 than exploring volcanoes shows that ________．A．people have exaggerated the dangers of volcanoes in the pastB．Hazel does not really understand the dangerous situations she puts herself inC．there are many bad drivers in the place where Hazel livesD．Hazel is being modest and understating the dangers she faces2. When did Hazel first become interested in volcanoes?A．When she was visiting Italy.B．When she was at school.C．When she was twenty.D．When she saw Vesuvius.3. The underlined word “These〞(in Paragraph 3) refers to “________〞．A．melting ice capsB．volcanic eruptionsC．changes in sea levelD．higher temperatures4. When Hazel was on Mount Etna, she had to ________．A．take a dangerous routeB．take an unnecessary riskC．leave her boots behindD．walk for ten hours around the mountain5. In the future, Hazel wants to ________．A．revisit volcanoes she knowsB．go on holiday to the AntarcticC．find a less dangerous jobD．discover new things about volcanoes【参考答案解析】B【要点综述】本文主要介绍了火山学家Hazel Rymer的一些关于火山的研究活动。

重大版高中英语必修第1册第5单元阅读材料 How Whales, Fish Might Adapt To Warming Ocean

Studies: How Whales, Fish Might Adapt To Warming OceanTwo new science studies provide a glimpse of how some important Pacific Ocean sea creatures could adapt to a changing climate.One study describes how gray whales successfully adapted to previous cycles of global warming and cooling. The second predicts a fish shift on the west coast of North America. The study suggests that some West Coast fishermen will need to pursue different prey if the Pacific Ocean warms as projected over the next 50 years.Nick Pyenson is a paleobiologist who curates the marine fossil collection at the Smithsonian's Natural History Museum in Washington, D.C. The famous collection includes lots of creatures driven to extinction by environmental changes. It also includes some of the long fossil record for gray whales, a species that still lives in the Pacific Ocean today."Grey whales fit into this question about ongoing climate change," says Pyenson. He and his former doctoral advisor from UC Berkeley wondered how gray whales survived through previous cycles of global warming and cooling."In the past two million years, the Northern Hemisphere has undergone dramatic changes with ice sheets going all the way down to Chicago and Seattle," says Pyenson. "In doing so, that sucks up a lot of the water that would be otherwise be put in the ocean and drops sea level dramatically."According to Pyenson, historic sea level changes periodically expanded and closed off vast feeding grounds. He theorizes gray whales hung on through bad times by either migrating less, switching food sources or both. Even today, there are small numbers of gray whales that stay in one place and eat fish and krill, while most of their species migrate long distances and bottom feed."What we think is telling is that those who don't migrate are telling us about the range in behavior and what these animals can do ecologically."Pyenson says that adaptability bodes well for how the whales may respond to future climate changes. He adds one caveat though, saying the current cycle of human-induced global warming is developing faster and more powerfully than the historic episodes he examined.Fish shiftIn a separate study, a group of Canadian and American researchers examined how a warming ocean could affect fish common along the West Coast of North America.The science team studied 28 fish species whose biology and distribution is well understood. Oceanographer Ric Brodeur of the NOAA Northwest Fisheries Science Center in Newport, Oregon, says the list includes salmon, smelt, sharks, pollock and sardines. Brodeur says the researchers simulated what could happen if the North Pacific heats up due to global warming."Because these fish are so mobile, they can move up and down the coast or inshore or offshore to find the preferred temperature that they want."The federal science agency, NOAA, predicts the ocean's surface waters off Oregon and Washington will warm about two degrees Celsius over the next 50 years. Brodeur says that's enough to cause significant moves. A forthcoming research paper models how much. If you combine the home ranges of all the fish that the team studied, there's an average shift northward of roughly 40 kilometers per decade. Over time, Brodeur predicts fishermen and seafood consumers will notice."A lot of the species that we consider very important - like hake - things that are commercially fished here might be gone and replaced by other species that may or may not be commercially important."Across Yaquina Bay from Brodeur's office, charter fishing boats unload sun-burned anglers. Veteran captain Robert Waddell says he's already seen some evidence of warm water species shifting northward."I've noticed in the last 12-13 years, we've been starting to see some marlin off and on out there and we've hooked them a few times," says Waddell.Blue fin tuna is another possible newcomer that could fill the vacancy if, say, salmon left for cooler waters off Canada. Waddell is optimistic the local fishing fleet can adapt."People will make adjustments," he says. "Fifty years from now, we might be the marlin capital of the world. You never know."。

黑龙江省龙东十校2024-2025学年高二上学期开学考试英语试题

黑龙江省龙东十校2024-2025学年高二上学期开学考试英语试题一、阅读理解We are currently seeking a qualified and experienced individual to join our team as a marketing manager. As a key leadership position within our organization, the marketing manager will play a crucial role in driving the department’s success and contributing to our overall business objectives.Qualifications:*Bachelor’s degree in business administration, management or related fields.*Proven experience in a marketing role, with a track record of successfully leading teams and achieving results.*Strong communication, interpersonal and problem-solving skills.*Proficiency in relevant software apps.Responsibilities:*Overseeing daily operations of the department, including staff management, budgeting and goal setting.*Developing and implementing strategies to meet departmental targets and enhance efficiency.*Cooperating with cross-functional teams to ensure seamless coordination and communication.*Providing leadership and guidance to team members to develop a positive work culture and professional growth.If you are a motivated and enthusiastic leader with a passion for driving organizational success, we invite you to apply for the position. Join us in shaping the future of our department and making a lasting impact on our company.To apply, please submit your resume and a cover letter detailing your relevant experience and why you are the ideal candidate for this role. We look forward to welcoming a dedicated and ************************************************************.1．What is a must to apply for the position?A．A master’s degree.B．A strong body.C．The related work experience.D．The ability to develop software.2．What does the marketing manager have to do?A．Communicate with consumers regularly.B．Assist the leaders to develop annual plans.C．Achieve the overall goal of the industry.D．Help co-workers develop their business. 3．How can you get in touch with the interviewer?A．By filling out a form.B．By sending an email.C．By writing a letter.D．By making a phone call.Over the weekend, a Pennsylvania man risked his life to save his neighbors from a burning home, as captured in dramatic video footage.Oscar Rivera was playing with his children in his backyard on April 14 when he heard a loud boom (响声). Rushing to the front yard, he saw that the house across the street was engulfed in flames, with his neighbors trapped inside.According to WFMZ-TV, Rivera didn’t hesitate. He climbed up the three-story building, which was already covered in flames. On a narrow ledge (窗台) at the burning home, a woman was trying to pull a man out of an attic window as smoke poured out. The man was calling for help.Rivera and a neighbor quickly grabbed a ladder and rushed to assist. “I just started jumping, jumping and jumping,” Rivera told WFMZ-TV. He managed to reach the top floor and pulled the man from the window, who had yelled, “Help me. I can’t walk.”Eyewitness Janeen Huth, who recorded the rescue, praised Rivera for risking his life while his young children watched from the door. “Come on! Come on!” Huth can be heard shouting in the video, as other onlookers and firefighters worked to assist. “Rivera is a true hero,” she told The Morning Call. Rivera managed to get the victim onto the ledge, and firefighters then took over, bringing the man to safety.The rescued man sustained critical burns and was taken to the hospital, according to WFMZ-TV. The fire damaged six homes and led to the evacuation (疏散) of 20 people. The cause of the fire is currently under investigation. “I hope he’s okay,” Rivera said about the man he saved.4．What does the text describe?A．An investigation into a fire.B．A man’s heroic rescue.C．A fire department’s response.D．A fire that destroyed several homes. 5．What made Rivera rush to the front yard?A．Hearing a loud boom.B．Seeing the flame.C．Hearing a call for help.D．Being informed about the fire.6．What did Rivera do in the rescue?A．He provided first aid.B．He helped guide firefighters.C．He called emergency services.D．He pulled the man out.7．How did Janeen Huth react to Rivera’s action?A．She was indifferent.B．She admired his bravery.C．She criticized him for risking his life.D．She thought he should wait for firefighters.The immune (免疫的) system has special defense and attack strategies reserved for viruses (病毒). These involve tagging the viruses with antibodies and killing cells infected (使感染) by the virus. A global health crisis can bring the world to its knees, highlighting the huge impact a virus can have. This tiny organism, invisible under a normal microscope, can wreak havoc on worldwide.There are more viruses on Earth than stars in the universe, so why haven’t we always been maintaining social distance? Primarily because not all viruses can infect us, and for those that do, the body handles them quite well. To put it simply, viruses are extremely small parasites that infect all sorts of life, from the smallest bacteria to the largest mammals; they are considered parasites because they can’t survive by themselves. Viruses infect health y host cells and use their cellular “tools” to make more copies of themselves.Viruses are everywhere—in the air we breathe, the water we drink, and the land on which we walk. Yet, even after being bombarded with viruses, our body still manages to stay strong. This is because of our immune system and its clever strategies to fight back against viral attacks! Fortunately, with our modern healthcare advancements, we have extra help to fight viruses. These include vaccines, antiviral drugs, and other health technologies to keep us going in this never-ending war.As time goes by and our bodies encounter more viruses, we develop better immunological memory. This is the body’s way of remembering past infections, making it better prepared for future ones.8．Which can replace the underlined phrase “wreak havoc on” in paragraph 1?A．Depend heavily on.B．Have a bad effect on.C．Take the side effect off.D．Cut the whole power off.9．Why do we always fail to maintain social distance despite lots of viruses?A．Not all viruses infect humans.B．Not all viruses are small.C．Viruses need host cells.D．Viruses infect all life forms.10．What is one of the strategies our body uses to fight viral attacks?A．Reducing the number of viruses in the environment.B．Avoiding contacting with infected individuals.C．Taking advantage of the immune system.D．Increasing exposure to viruses.11．What can be the best title for the text?A．What is the definition of unusual viruses?B．How to know well the immune system?C．How does our body fight viruses?D．How to break down the viruses?A major tech company has expanded options for keeping personal information from online searches. The company stated earlier this week that it would allow people to request the removal of more types of content, such as personal contact information like phone numbers, email addresses, and physical addresses, from search results. The new policy also permits the removal of other information that may pose a risk for identity theft, such as confidential (机密的) login accounts.In a statement, the company said that open access to information is vital. “But so is empowering (授权) people with the tools they need to protect themselves and keep their sensitive, personally identifiable information private,” the statement continued. “Privacy and online safety go hand in hand. And when you’re using the Internet, it’s important to have control over how your sensitive, personally identifiable information can be found.”Previously, the company had allowed people to request the removal of highly personalcontent that could cause direct harm. This included information such as bank account or credit card numbers that could be used for fraud (欺诈).“However, as information increasingly appears in unexpected places and is used in new ways, policies need to evolve,” the company said. Having personal contact information openly available online can also pose a threat, and the company reported receiving requests to remove such content as well. It states that when it receives such requests, it will review all the content on the web page to avoid limiting the availability of useful information or content on public record on government or other official websites. “It’s important to remember that removing content from our search results won’t remove it from the Internet, which is why you may wish to contact the hosting site directly, if you’re comfortable doing so,” the company advised.12．What can we learn from the company’s statement?A．Keeping online private information safe is a must.B．Improving the net environment for citizens is a dream.C．The exposure of public information causes a discussion.D．Making a balanced approach to online safety is a fashion.13．Why does the company review web page content before removing personal information?A．To obey data privacy laws.B．To take down the entire website.C．To increase online personal information.D．To avoid removing useful or publicinformation.14．What is the main idea of the text?A．Personal information can be removed from online searches.B．Tech companies can find more images and information.C．Privacy risks arise from publishing private information.D．Tech companies know what you’ve done over the years.15．What is the text likely to be?A．A research paper on online privacy.B．A new approach to using a search engine.C．An advertisement for a data privacy service.D．A news report about privacy protection.Do you know what carpet cleaning is and how it works? This article will discuss it with you.Carpet cleaning is a service to remove the dirt, stains and other things from carpets and make them clean. People hire different carpet cleaning services to make their carpets look cleaner, more appealing and away from harmful infections. According to experts, people must clean their carpets once or twice a year. 16 .According to carpet manufacturers, hot water extraction is one of the most professional and recommended ways of cleaning carpets. 17Dry cleaning is also used for cleaning the carpets but this is far easier than wet cleaning.18 However, it is still used for cleaning the carpets which are not that dirty.Vacuum (真空) cleaning is mostly used in offices and houses by people themselves. People use a vacuum cleaner to clean the carpets and it is an effective method.19 Therefore, carpet cleaning must be done minimum 1-2 times a year to prevent yourself from infections, allergies, and so on. Another benefit is that it saves you a lot of money. If you don’t clean them on a regular basis, you have to purchase them.You have understood a lot about carpet cleaning. 20 Do not regard this as a trivial (琐碎的) matter. It concerns the health of you and your family.A．It is time for you to take action.B．Prepare yourself before you begin.C．It is not that better than wet cleaning.D．Dirty carpets damage your health a lot.E．Dry cleaning is more effective than wet cleaning.F．Now, the question is what methods are used to clean them.G．It can remove the dirt and other things deep from the carpets.二、完形填空My husband and I had been married for ten years when I got Stevens-Johnson syndrome (综合征). With painful blisters (水疱) all over my body, I, who had been independent, rapidly became 21 .My husband, Scott, was occupied taking care of kids and cooking dinners. He also became my personal caretaker, applying the 22 to all of my blisters because my hands couldn’t dothe job. I was 23 at total reliance on someone other than myself. At one point, I mentally and physically hit 24 , thinking I was a weak person. And that 25 me.I recovered from my illness, but I couldn’t recover from the negative 26 . This loss of27 affected the rest of my recovery. Fortunately, things 28 . Recently Scott and I went ona long bike ride. At one point with sharp pain 29 in my tired legs, I couldn’t go any further. Seeing me 30 , Scott stopped in front of me, saying, “Stay close behind me.” Scott was 31 me along. My legs quit burning 32 as my cycling became easier, and I was able to catch my breath.I now 33 that love between us is powerful. True love is forged (锻造) by the fire of late nights with sick family and days of 34 to make ends meet. I also believe that during these 35 times, love has the power to make us become stronger. 21．A．worthless B．helpless C．fearless D．homeless 22．A．medicine B．disease C．mission D．strategy 23．A．shocked B．amused C．embarrassed D．puzzled 24．A．goal B．bottom C．future D．desire 25．A．taught B．forgave C．inspired D．troubled 26．A．thought B．plan C．comment D．aspect 27．A．direction B．confidence C．dream D．success 28．A．took over B．showed off C．turned around D．stood out 29．A．extending B．reducing C．escaping D．disappearing 30．A．relieve B．complain C．leave D．struggle 31．A．walking B．sending C．pulling D．bringing 32．A．frequently B．initially C．strangely D．quickly 33．A．hope B．argue C．permit D．believe 34．A．trying B．daring C．choosing D．promising 35．A．common B．difficult C．pleasant D．primary三、语法填空阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。

kSZ效应的组分分析

kSZ效应的组分分析苗寒【摘要】The kinetic Sunyaev-Zel'dovich (kSZ) effect is becoming a possible probe of the missing baryons, owing to the recent advance in CMB experiments and galaxy surveys. The kSZ power spectrum has been detected by various existing experiments, however significant improvement of accuracy is still required. Through a set of hydrodynamic simulations, we quantify the relative contribution of various gas components to the kSZ signals. We find that the warm-hot intergalactic medium (WHIM) contributes significantly to the kSZ power spectrum. This makes the kSZ power spectrum a promising probe of missing baryons. However, we find that contribution from the intracluster medium (ICM) is also significant. Therefore, apart from the diffculties in observational measurements, the interpretation of kSZ power spectrum requires careful investigation in order to reliably constrain the WHIM fraction.%运动学Sunyaev Zel'dovich效应(kSZ效应)是探索失踪重子这一天体物理学核心问题的新兴手段.近期的一系列CMB实验正逐步实现对kSZ效应功率谱的测量,并将在可预见的未来实现精确测量.但是,kSZ功率谱中各气体组分的贡献还缺乏细致的研究,导致其探索失踪重子的能力缺乏量化.通过一组初始条件相同,气体物理不同的流体力学数值模拟,定量地分析了不同的气体组分对kSZ效应的贡献.其中,作为研究失踪重子的热门候选,温热星系际介质对于kSZ功率谱的贡献很大,因此kSZ功率谱是用于寻找宇宙中失踪重子很有效的方法之一.但由于星系团内热气体也贡献相当程度的kSZ功率谱,因此,用kSZ功率谱的观测作为探测和定量分析失踪重子方法,还需要更仔细的分析.【期刊名称】《天文学进展》【年(卷),期】2016(034)001【总页数】9页(P111-119)【关键词】宇宙学;CMB;大尺度结构;SZ效应【作者】苗寒【作者单位】中国科学院上海天文台星系与宇宙学重点实验室,上海 200030;中国科学院大学,北京 100049【正文语种】中文【中图分类】P159根据大爆炸核合成理论(Big-bang Nucleosynthesis,BBN)，宇宙中重子物质的密度此预言也得到QSO吸收线的氘丰度观测[?]，以及自WMAP首次观测[?]起至最新的Planck 2015[?]等众多的CMB观测的支持。

高考英语阅读理解(4月)训练(4)

落堕市安心阳光实验学校2013高考英语阅读理解（4月）训练（04）及答案ATonight’s TV Hot List: Sunday January 31, 2010Grammy Awards 8/7c CBSBeyoncé and Taylor Swift are ready to take home a lot of hardware tonight as they lead all artists with 10 and eight nominations. The ladies also perform, along with fellow Album of the Year nominees the Black Eyed Peas, Lady Gaga and the Dave Matthews Band. In addition, Bon Jovi, Green Day, Lady Antebellum, Maxwell, Pink and Zac Brown Band will also take the stage. But perhaps the most expected moment is the Michael Jackson tribute（吊唁礼物）, which features the 3-D mini-movie "Earth Song" and will be highlighted by performers Celine Dion, Jennifer Hudson, Smokey Robinson, Carrie Underwood and Usher.Maurer 9/8c NBCA mysterious company named Sabre, headed by an attractive, stubborn CEO （Kathy Bates）, appears out of nowhere and buys out Dunder Mifflin. As Michael is unwilling to follow Sabre's new policies, Andy and Erin write a welcome song to greet the company. Meanwhile, Pam and Jim hope to get accepted into a desired local day-care center.Surviving Survivor 8/7c CBSIt's hard to believe it's been 10 years since the first season of Survivor. But tonight ten of the game's most iconic players, including previous winners Richard Hatch, Parvati Shallow and Tom Westman, discuss the series in detail and provide insights into how the game is actually played and the impact it's had on their lives. In addition, updates on beloved former castaways, like Ethan Zohn, Rupert Boneham and Elisabeth Hasselbeck, are given.Private Practice 10:01/9:01c ABCSo Maya's pregnant and wants to have the baby. What to do now? Dink （Stephen Lunsford）, the boy who did his part to get her into this mess, has a solution: He wants to marry her. You can imagine how Sam and Naomi will feel about that. And if that won't raise the histrionic level enough for you, how about this: A couple has two dying daughters, and only one can be saved. Their choice. And Brian Benben is back, so expect more Pete-Violet- Sheldon angst.11. Edna is crazy about pop stars, so she will most likely choose ________to enjoy.A. Grammy AwardsB. MaurerC. Surviving SurvivorD. Private Practice12. From the passage, we can learn that Dunder Mifflin is ________.A. a CEOB. a companyC. an employee in the companyD. a piece of officeequipment13. According to the passage, Surviving Survivor is most probably________.A. a musical playB. a game showC. a love storyD. a culturaldocumentary14.The above programs ________]A. are loved by all viewersB. are on the top list for the weekC. are broadcast on the same channelD. are accessible onthe same night参考答案11-14 ABBD*****************************************************结束DMost of us spend our lives seeking the natural world. To this end, we walk the dog, play golf, go fishing, sit in the garden, drink outside rather than inside the pub, have a picnic, live in the suburbs, go to the seaside, buy a weekend place in the country. The most popular free time activity in Britain is going for a walk. And when joggers (慢跑者) jog, they don’t run the streets. Every one of them automatically heads to the park or the river. It is my firm belief that not only do we all need nature, but we all seek nature, whether we know we are doing so or not.But despite this, our children are growing up nature-deprived (丧失). I spent my boyhood climbing trees. These days, children are robbed of these ancient freedoms, due to problems like crime, traffic, the loss of the open spaces and strange new ideas about what is best for children, that is to say, things that can be bought, rather than things that can be found.The truth is to be found elsewhere. A study in the US: families had moved to better housing and the children were assessed for ADHD (多动症). Those whose housing had more natural views showed an improvement of 19%; those who had the same improvement in material surroundings but no nice view improved just 4%.A study in Sweden indicated that kindergarten children who could play in a natural environment had less illness and greater physical ability than children used only to a normal playground. A US study suggested that when a school gave children access to a natural environment, the entire school would do better in studies.Another study found that children play differently in a natural environment. In playgrounds, children create a hierarchy (等级) based on physical abilities, with the tough ones taking the lead. But when a grassy area was planted with bushes, the children got much more into fantasy play, and the social hierarchy was now based on imagination and creativity.Most bullying (恃强凌弱) is found in schools where there is a tarmac (柏油碎石) playground; the least bullying is in a natural area that the children are encouraged to explore. This reminds me unpleasantly of Sunnyhill School, with its hard tarmac, where I used to hang about in corners dreaming about wildlife.But children are frequently discouraged from involvement with natural spaces, for health and safety reasons, for fear that they might get dirty or that they might cause damage. So, instead, the damage is done to the children themselves: not to their bodies but to their souls.One of the great problems of modern childhood is ADHD, now increasingly and expensively treated with drugs. Yet one study after another indicates that contact with nature gives huge benefits to ADHD children. However, we spend money on drugs rather than on green places.The life of old people is much better when they have access to nature. The most important for the growing population of old people is in quality rather than quantity of years. And study after study finds that a garden is the single most important thing in finding that quality.In wider and more difficult areas of life, there is evidence to indicate that natural surroundings improve all kinds of things. Even problems with crime and aggressive behaviour are reduced when there is contact with the natural world.Dr William Bird, researcher from the Royal Society for the Protection of Birds, states in his study, “A natural environment can reduce violent behaviour because its process helps reduce anger and behavior that people might regret later.” Wild places need encouraging for this reason, no matter how small their contribution.We tend to think human beings are doing nature some kind of favour when we are protecting nature. The error here is far too deep: not only do humans need nature for themselves, but the very idea that humanity and the natural world are separable things is damaging.Human beings are a species of animals. For seven million years we lived on the planet as part of nature. So we miss the natural world and long for contact with non-human life. Anyone who has patted a dog, stroked a cat, sat under a tree with a glass of beer, given or received a bunch of flowers or chosen to walk through the park on a nice day, understands that.We need the wild world. It is necessary to our well-being, our health, our happiness. Without other living things around us we are less than human.15. What is the author’s firm belief?A. People seek nature in different ways.]B. People should spend most of their lives in the wild.C. People have quite different ideas of nature.D. People must make more efforts to study nature.16. What does the author say people prefer for their children nowadays?A. Personal freedom.B. Things that are natural.C. Urban surroundings.D. Things that are purchased17. What does a study in Sweden show?A. The natural environment can help children learn better.B. More access to nature makes children less likely to fall ill.C. A good playground helps kids develop their physical abilities.D. Natural views can prevent children from developing ADHD.18. Children who have chances to explore natural areas ________.A. tend to develop a strong love for scienceB. are more likely to dream about wildlifeC. tend to be physically tougher in adulthoodD. are less likely to be involved in bullying19. What does the author suggest we do to help children with ADHD?A. Find more effective drugs for them.B. Provide more green spaces for them.C. Place them under more personal care.D. Engage them in more meaningful activities.20. In what way do elderly people benefit from their contact with nature?A. They look on life optimistically.B. They enjoy a life of better quality.C. They are able to live longer.D. They become good-humoured.参考答案15-20 ADBDBB**********************************************************结束2.（2011·陕西卷）BMost people know that Marie Curie was the first woman to win the Nobel Prize, and the first person to win it twice. However, few people know that she was also the mother of a Nobel Prize winner.Born in September, 1987, Irene Curie was the first of the Curies’ two daughters. Along with nine other children whose parents were also famous scholars, Irene studied in their own school, and her mother was one of the teachers. She finished her high school education at the College of Sévigné in Paris.Irene entered the University of Paris in 1914 to prepare for a degree in mathematics and physics. When World War I began, Irene went to help her mother, who was using X-ray facilities（设备） to help save the lives of wounded soldiers.Irene continued the work by developing X-ray facilities in military hospitals in France and Belgrum. Her services were recognised in the form of a Military’s Medal by the French government.In 1918, Irene became her mother’s assistant at the Curie Institute. In December 1924, Frederic Joliot joined the Institute, and Irene taugh him the techniques required for his work. They soon fell in love and were married in 1926. Their daughter Helene was born in 1927 and their son********************************************************结束Pierre five years later.Like her mother, Irene combined family and career. Like her mother,Irene was awarded a Nobel Prize, along with her husband, in 1935.Unfortunately, also like her mother, she developed leukemia because ofher work with radioactivity（辐射能）. Irene Joliot-Curie died fromleukemia on March 17, 1956.49．Why was Irene Curie awarded a Military Medal?【B】A.Because she received a degree in mathematics.B.Because she contributed to saving the wounded.C.Because she won the Nobel Prize with Frederic.D. Because she worked as a helper to her mother.50．Where did Irene Curie meet her husband Frederio joliot?【A】A.At the Curie Institute.B.At the Cniversity of Paris.C.At a military hospital.D.At the College of Sevigne.51．When was the second child of Irene Curie and Frederic Joliot born?【A】A. In 1932.B. In 1927.C. In 1897.D. In 1926.52． In which of the following aspects was Irene Cuire different fromher mother?【C】A.Irene worked with radioactivity.B.Irene combined family andcareer.C.Irene won the Nobel Prize onceD.Irene died from leukemia.。

Entropy changes in the clustering of galaxies in a

Vol.3, No.1, 65-68 (2011)doi:10.4236/ns.2011.31009Natural ScienceEntropy changes in the clustering of galaxies in an expanding universeNaseer Iqbal1,2*, Mohammad Shafi Khan1, Tabasum Masood11Department of Physics, University of Kashmir, Srinagar, India; *Corresponding Author:2Interuniversity Centre for Astronomy and Astrophysics, Pune, India.Received 19 October 2010; revised 23 November 2010; accepted 26 November 2010.ABSTRACTIn the present work the approach-thermody- namics and statistical mechanics of gravitating systems is applied to study the entropy change in gravitational clustering of galaxies in an ex-panding universe. We derive analytically the expressions for gravitational entropy in terms of temperature T and average density n of the par-ticles (galaxies) in the given phase space cell. It is found that during the initial stage of cluster-ing of galaxies, the entropy decreases and fi-nally seems to be increasing when the system attains virial equilibrium. The entropy changes are studied for different range of measuring correlation parameter b. We attempt to provide a clearer account of this phenomena. The entropy results for a system consisting of extended mass (non-point mass) particles show a similar behaviour with that of point mass particles clustering gravitationally in an expanding uni-verse.Keywords:Gravitational Clustering; Thermodynamics; Entropy; Cosmology1. INTRODUCTIONGalaxy groups and clusters are the largest known gravitationally bound objects to have arisen thus far in the process of cosmic structure formation [1]. They form the densest part of the large scale structure of the uni-verse. In models for the gravitational formation of struc-ture with cold dark matter, the smallest structures col-lapse first and eventually build the largest structures; clusters of galaxies are then formed relatively. The clus-ters themselves are often associated with larger groups called super-clusters. Clusters of galaxies are the most recent and most massive objects to have arisen in the hiearchical structure formation of the universe and the study of clusters tells one about the way galaxies form and evolve. The average density n and the temperature T of a gravitating system discuss some thermal history of cluster formation. For a better larger understanding of this thermal history it is important to study the entropy change resulting during the clustering phenomena be-cause the entropy is the quantity most directly changed by increasing or decreasing thermal energy of intraclus-ter gas. The purpose of the present paper is to show how entropy of the universe changes with time in a system of galaxies clustering under the influence of gravitational interaction.Entropy is a measure of how disorganised a system is. It forms an important part of second law of thermody-namics [2,3]. The concept of entropy is generally not well understood. For erupting stars, colloiding galaxies, collapsing black holes - the cosmos is a surprisingly or-derly place. Supermassive black holes, dark matter and stars are some of the contributors to the overall entropy of the universe. The microscopic explanation of entropy has been challenged both from the experimental and theoretical point of view [11,12]. Entropy is a mathe-matical formula. Standard calculations have shown that the entropy of our universe is dominated by black holes, whose entropy is of the order of their area in planck units [13]. An analysis by Chas Egan of the Australian National University in Canberra indicates that the col-lective entropy of all the supermassive black holes at the centers of galaxies is about 100 times higher than previ-ously calculated. Statistical entropy is logrithmic of the number of microstates consistent with the observed macroscopic properties of a system hence a measure of uncertainty about its precise state. Statistical mechanics explains entropy as the amount of uncertainty which remains about a system after its observable macroscopic properties have been taken into account. For a given set of macroscopic quantities like temperature and volume, the entropy is a function of the probability that the sys-tem is in various quantumn states. The more states avail-able to the system with higher probability, the greater theAll Rights Reserved.N. Iqbal et al. / Natural Science 3 (2011) 65-6866 disorder and thus greater the entropy [2]. In real experi-ments, it is quite difficult to measure the entropy of a system. The technique for doing so is based on the thermodynamic definition of entropy. We discuss the applicability of statistical mechanics and thermodynam-ics for gravitating systems and explain in what sense the entropy change S – S 0 shows a changing behaviour with respect to the measuring correlation parameter b = 0 – 1.2. THERMODYNAMIC DESCRIPTION OF GALAXY CLUSTERSA system of many point particles which interacts by Newtonian gravity is always unstable. The basic insta-bilities which may occur involve the overall contraction (or expansion) of the system, and the formation of clus-ters within the system. The rates and forms of these in-stabilities are governed by the distribution of kinetic and potential energy and the momentum among the particles. For example, a finite spherical system which approxi-mately satisfies the viral theorem, contracts slowlycompared to the crossing time ~ ()12G ρ- due to the evaporation of high energy particles [3] and the lack of equipartition among particles of different masses [4]. We consider here a thermodynamic description for the sys-tem (universe). The universe is considered to be an infi-nite gas in which each gas molecule is treated to be agalaxy. The gravitational force is a binary interaction and as a result a number of particles cluster together. We use the same approximation of binary interaction for our universe (system) consisting of large number of galaxies clustering together under the influence of gravitational force. It is important to mention here that the characteri-zation of this clustering is a problem of current interest. The physical validity of the application of thermody-namics in the clustering of galaxies and galaxy clusters has been discussed on the basis of N-body computer simulation results [5]. Equations of state for internal energy U and pressure P are of the form [6]:(3122NTU =-)b (1) (1NTP V=-)b (2) b defines the measuring correlation parameter and is dimensionless, given by [8]()202,23W nb Gm n T r K Tτξ∞=-=⎰,rdr (3)W is the potential energy and K the kinetic energy ofthe particles in a system. n N V = is the average num-ber density of the system of particles each of mass m, T is the temperature, V the volume, G is the universalgravitational constant. (),,n T r ξ is the two particle correlation function and r is the inter-particle distance. An overall study of (),n T r ξ has already been dis-cussed by [7]. For an ideal gas behaviour b = 0 and for non-ideal gas system b varies between 0 and 1. Previ-ously some workers [7,8] have derived b in the form of:331nT b nT ββ--=+ (4) Eq.4 indicates that b has a specific dependence on the combination 3nT -.3. ENTROPY CALCULATIONSThermodynamics and statistical mechanics have been found to be equal tools in describing entropy of a system. Thermodynamic entropy is a non-conserved state func-tion that is of great importance in science. Historically the concept of entropy evolved in order to explain why some processes are spontaneous and others are not; sys-tems tend to progress in the direction of increasing en-tropy [9]. Following statistical mechanics and the work carried out by [10], the grand canonical partition func-tion is given by()3213212,1!N N N N mkT Z T V V nT N πβ--⎛⎫⎡=+ ⎪⎣Λ⎝⎭⎤⎦(5)where N! is due to the distinguishability of particles. Λrepresents the volume of a phase space cell. N is the number of paricles (galaxies) with point mass approxi-mation. The Helmholtz free energy is given by:ln N A T Z =- (6)Thermodynamic description of entropy can be calcu-lated as:,N VA S T ∂⎛⎫=- ⎪∂⎝⎭ (7)The use of Eq.5 and Eq.6 in Eq.7 gives()3120ln ln 13S S n T b b -⎛⎫-=-- ⎪ ⎪⎝⎭- (8) where S 0 is an arbitary constant. From Eq.4 we write()31bn b T β-=- (9)Using Eq.9, Eq.8 becomes as3203ln S S b bT ⎡⎤-=-+⎢⎣⎦⎥ (10)Again from Eq.4All Rights Reserved.N. Iqbal et al. / Natural Science 3 (2011) 65-68 6767()13221n b T b β-⎡⎤=⎢⎣⎦⎥ (11)with the help of Eq.11, Eq.10 becomes as()011ln ln 1322S S n b b b ⎡-=-+-+⎡⎤⎣⎦⎢⎥⎣⎦⎤ (12) This is the expression for entropy of a system consist-ing of point mass particles, but actually galaxies have extended structures, therefore the point mass concept is only an approximation. For extended mass structures we make use of softening parameter ε whose value is taken between 0.01 and 0.05 (in the units of total radius). Following the same procedure, Eq.8 becomes as()320ln ln 13N S S N T N b Nb V εε⎡⎤-=---⎢⎥⎣⎦(13)For extended structures of galaxies, Eq.4 gets modi-fied to()()331nT R b nT R εβαεβαε--=+ (14)where α is a constant, R is the radius of a cell in a phase space in which number of particles (galaxies) is N and volume is V . The relation between b and b ε is given by: ()11b b b εαα=+- (15) b ε represents the correlation energy for extended mass particles clustering gravitationally in an expanding uni-verse. The above Eq.10 and Eq.12 take the form respec-tively as;()()3203ln 111bT b S S b b ααα⎡⎤⎢⎥-=-+⎢⎥+-+-⎢⎥⎣⎦1 (16) ()()()120113ln ln 2111b b b S S n b b ααα⎡⎤-⎡⎤⎢⎥⎣⎦-=-++⎢⎥+-+-⎢⎥⎣⎦1 (17)where2R R εεεα⎛⎫⎛⎫=⎪ ⎪⎝⎭⎝⎭(18)If ε = 0, α = 1 the entropy equations for extended mass galaxies are exactly same with that of a system of point mass galaxies approximation. Eq.10, Eq.12, Eq.16and Eq.17 are used here to study the entropy changes inthe cosmological many body problem. Various entropy change results S – S 0 for both the point mass approxima-tion and of extended mass approximation of particles (galaxies) are shown in (Figures 1and2). The resultshave been calculated analytically for different values ofFigure 1. (Color online) Comparison of isothermal entropy changes for non-point and point mass particles (galaxies) for an infinite gravitating system as a function of average relative temperature T and the parameter b . For non-point mass ε = 0.03 and R = 0.06 (left panel), ε = 0.04 and R = 0.04 (right panel).All Rights Reserved.N. Iqbal et al. / Natural Science 3 (2011) 65-68 68Figure 2. (Color online) Comparison of equi-density entropy changes for non-point and point mass particles (galaxies) for an infinite gravitating system as a function of average relative density n and the parameter b. For non-point mass ε= 0.03 and R = 0.04.R (cell size) corresponding to different values of soften-ing parameter ε. We study the variations of entropy changes S – S0with the changing parameter b for differ-ent values of n and T. Some graphical variations for S – S0with b for different values of n = 0, 1, 100 and aver-age temperature T = 1, 10 and 100 and by fixing value of cell size R = 0.04 and 0.06 are shown. The graphical analysis can be repeated for different values of R and by fixing values of εfor different sets like 0.04 and 0.05. From both the figures shown in 1 and 2, the dashed line represents variation for point mass particles and the solid line represents variation for extended (non-point mass) particles (galaxies) clustering together. It has been ob-served that the nature of the variation remains more or less same except with some minor difference.4. RESULTSThe formula for entropy calculated in this paper has provided a convenient way to study the entropy changes in gravitational galaxy clusters in an expanding universe. Gravity changes things that we have witnessed in this research. Clustering of galaxies in an expanding universe, which is like that of a self gravitating gas increases the gases volume which increases the entropy, but it also increases the potential energy and thus decreases the kinetic energy as particles must work against the attrac-tive gravitational field. So we expect expanding gases to cool down, and therefore there is a probability that the entropy has to decrease which gets confirmed from our theoretical calculations as shown in Figures 1 and 2. Entropy has remained an important contributor to our understanding in cosmology. Everything from gravita-tional clustering to supernova are contributors to entropy budget of the universe. A new calculation and study of entropy results given by Eqs.10, 12, 16 and 17 shows that the entropy of the universe decreases first with the clustering rate of the particles and then gradually in-creases as the system attains viral equilibrium. The gravitational entropy in this paper furthermore suggests that the universe is different than scientists had thought.5. ACKNOWLEDGEMENTSWe are thankful to Interuniversity centre for Astronomy and Astro-physics Pune India for providing a warm hospitality and facilities during the course of this work.REFERENCES[1]Voit, G.M. (2005) Tracing cosmic evolution with clus-ters of galaxies. Reviews of Modern Physics, 77, 207- 248.[2]Rief, F. (1965)Fundamentals of statistical and thermalphysics. McGraw-Hill, Tokyo.[3]Spitzer, L. and Saslaw, W.C. (1966) On the evolution ofgalactic nuclei. Astrophysical Journal, 143, 400-420.doi:10.1086/148523[4]Saslaw, W.C. and De Youngs, D.S. (1971) On the equi-partition in galactic nuclei and gravitating systems. As-trophysical Journal, 170, 423-429.doi:10.1086/151229[5]Itoh, M., Inagaki, S. and Saslaw, W.C. (1993) Gravita-tional clustering of galaxies. Astrophysical Journal, 403,476-496.doi:10.1086/172219[6]Hill, T.L. (1956) Statistical mechanics: Principles andstatistical applications. McGraw-Hill, New York.[7]Iqbal, N., Ahmad, F. and Khan, M.S. (2006) Gravita-tional clustering of galaxies in an expanding universe.Journal of Astronomy and Astrophysics, 27, 373-379.doi:10.1007/BF02709363[8]Saslaw, W.C. and Hamilton, A.J.S. (1984) Thermody-namics and galaxy clustering. Astrophysical Journal, 276, 13-25.doi:10.1086/161589[9]Mcquarrie, D.A. and Simon, J.D. (1997) Physical chem-istry: A molecular approach. University Science Books,Sausalito.[10]Ahmad, F, Saslaw, W.C. and Bhat, N.I. (2002) Statisticalmechanics of cosmological many body problem. Astro-physical Journal, 571, 576-584.doi:10.1086/340095[11]Freud, P.G. (1970) Physics: A Contemporary Perspective.Taylor and Francis Group.[12]Khinchin, A.I. (1949) Mathamatical Foundation of statis-tical mechanics. Dover Publications, New York.[13]Frampton, P., Stephen, D.H., Kephar, T.W. and Reeb, D.(2009) Classical Quantum Gravity. 26, 145005.doi:10.1088/0264-9381/26/14/145005All Rights Reserved.。

Effect of Gravitational Lensing on Measurements of the Sunyaev-Zel'dovich Effect

a rXiv:as tr o-ph/96148v18Oct1996Submitted to ApJ Letters ,October 1996Eﬀect of Gravitational Lensing on Measurements of the Sunyaev-Zel’dovich Eﬀect Abraham Loeb 1,3and Alexandre Refregier 2,41.Astronomy Department,Harvard University,60Garden St.,Cambridge,MA 021382.Columbia Astrophysics Laboratory,538W.120th Street,New York,NY 10027ABSTRACT The Sunyaev–Zel’dovich (SZ)eﬀect of a cluster of galaxies is usually measured after background radio sources are removed from the cluster ﬁeld.Gravitational lensing by the cluster potential leads to a systematic deﬁcit in the residual intensity of unresolved sources behind the cluster core relative to a control ﬁeld far from the cluster center.As a result,the measured decrement in the Rayleigh–Jeans temperature of the cosmic microwave background is overestimated.We calculate the associated systematic bias which is inevitably introduced into measurements of the Hubble constant using the SZ eﬀect.For the cluster A2218,we ﬁnd that observations at 15GHz with a beam radius of 0′.4and a source removal threshold of 100µJy underestimate the Hubble constant by 6–10%.If the proﬁle of the gas pressure declines more steeply with radius than that of the dark matter density,then the ratio of lensing to SZ decrements increases towards the outer part of the cluster.Subject headings:cosmic microwave background –diﬀuse radiation –galaxies:clusters:general,individual (A2218)–gravitational lensing1.IntroductionThe Sunyaev–Zel’dovich (SZ)eﬀect describes the distortion introduced to the Cosmic Microwave Background (CMB)spectrum due to its Compton scattering oﬀfree electrons,which are either hot (the thermal eﬀect)or possess a bulk peculiar velocity (the kinematic eﬀect;see reviews of both eﬀects in Sunyaev &Zel’dovich 1980and Rephaeli 1995).The thermal SZ eﬀect provides an important diagnostic of the hot gas in clusters of galaxies,and by now has beenmeasured in a number of systems(see Table1in Rephaeli1995).The kinematic eﬀect has an amplitude which is typically an order-of magnitude smaller and has not yet been deﬁnitively detected(see Rephaeli&Lahav1991and Haehnelt&Tegmark1995,regarding prospects for a future detection).It has long been realized that a measurement of the thermal SZ eﬀect,combined with X–ray observations,can be used to estimate the distance to the cluster and hence the Hubble constant, H0,under the assumption that the cluster is spherical(Cavaliere,Danese,&De Zotti1977,Gunn 1978,Silk&White1978,Birkinshaw1979).The inferred value of the Hubble constant is inversely proportional to the square of the SZ temperature decrement.This approach had led to values of the Hubble constant which are typically on the low side of the range inferred from other methods (see,e.g.,Table2in Rephaeli1995).An often cited systematic eﬀect that could account for this bias is elongation of the selected clusters along the line-of-sight.In this Letter,we explore a diﬀerent eﬀect which leads to a systematic bias towards low–H0values even if these clusters are perfectly spherical.The eﬀect results from gravitational lensing by the cluster potentials.Measurements of the decrement in the Rayleigh–Jeans(RJ)temperature of the microwave background due to the thermal SZ eﬀect are routinely accompanied by the removal of background radio sources down to someﬂux threshold(see,e.g.,Birkinshaw,Hughes,&Arnaud1991).In this process,it is implicitly assumed that theﬂux threshold for the removal of sources behind the cluster core is the same as in a controlﬁeld far from the cluster center.However,this assumption is not strictly true due to the inevitable magniﬁcation bias which is introduced by the gravitational lensing eﬀect of the cluster potential.In reality,the cluster acts as a lens which magniﬁes and thus resolves sources that are otherwise below the detection threshold.The residual intensity of unresolved sources is therefore systematically lower behind the cluster core,as compared to that in the controlﬁeld.Lensing artiﬁcially increases theﬂux deﬁcit behind the cluster core and thus leads to a systematic underestimate of the Hubble constant.In this Letter we calculate the eﬀect of lensing on SZ measurements of the Hubble constant. Our discussion on lensing follows closely the approach developed in an earlier paper(Refregier& Loeb1996,hereafter RL)which focused on lensing of the X–ray background by galaxy clusters; the interested reader should consult this earlier paper for more details.Here,we describe our models for the background population of radio sources and for the cluster potential in§2.We then show in§3how the lensing eﬀect leads to a systematic decrement in the intensity of unresolved sources.In§4,we present numerical results for diﬀerent values of our model parameters and for the speciﬁc example of A2218.Finally,§5summarizes the main conclusions of this work.2.ModelWe model the gravitational potential of the cluster as a Singular Isothermal Sphere(SIS)(e.g. Schneider et al.1992).This model provides a goodﬁrst–order approximation to the projectedmass distribution of known cluster lenses(Tyson&Fischer1995,Narayan&Bartelmann1996, Squires et al.1996a,b).The SIS potential causes background sources to appear brighter but diluted on the sky by the magniﬁcation factorµ(θ)= 1−α3.The Lensing EﬀectIn a region of the sky where the magniﬁcation factor isµ,the apparent diﬀerential count of sources obtains the value(dn/dS)|S=µ−2(dˆn/dˆS) S/µ,where hat denotes unlensed quantities.In particular,for a power law diﬀerential count relation,(dˆn/dˆS) ˆS∝ˆS−λ,the observed diﬀerential count is,(dn/dS)|S∝µλ−2S−λ.The diﬀerential count therefore increases(decreases)asµincreases ifλis above(below)the critical slopeλcrit≡2.Whenλ=λcrit,lensing has no eﬀect on the apparent diﬀerential count.Interestingly,ﬁgure1shows that the actual radio count slope oscillates aroundλcrit forﬂuxes S4.86∼<1Jy.In measurements of the SZ eﬀect,discrete sources are typically removed down to a given detectionﬂux threshold,S d.The mean residual intensity i(<S d)due to the superposition of all undetected discrete sources withﬂuxes below S d is then assumed to be equal to its sky–averaged valueˆi(<Sd)= S d0dˆSˆS dˆndˆS S/µ=ˆi(<S d/µ),(3) whereµ=µ(θ)is given by equation(1).Lensing conserves the total intensity of the radio source background and merely reduces the eﬀectiveﬂux threshold for resolving sources by a factorµ.The intensity oﬀset due to lensing is then,∆i lens≡i(<S d)−ˆi(<S d).In the RJ regime,this can be expressed more conveniently in terms of the brightness temperature diﬀerence,∆T lens=(c2/2ν2k B)∆i lens,where k B is Boltzmann’s constant.Forµ>1(i.e.,θ>α/2),the unresolved intensity is decreased,implying a negative∆T lens,and so the SZ decrement in the RJ regime,∆T SZ,is overestimated due to lensing.Note that forθ≫α,equation(1)yieldsµ≈1+α/θand∆T lens∝θ−1.The eﬀect of lensing on estimates of H0can be easily found from the scaling,H0∝(∆T SZ)−2, where∆T SZ is the temperature oﬀset produced by the SZ eﬀect.The small systematic correction (∆H0)lens=H0(true)−H0(observed),which must be incorporated in order to compensate for the lensing eﬀect is,to leading order,(∆H0)lens.(4)∆T SZForθ∼>α/2and the RJ spectral regime,both∆T lens and∆T SZ are negative and so(∆H0)lens is positive.The lensing correction will then tend to increase the estimated value of the Hubble constant.4.ResultsFigure2shows∆T lens as a function of angular separation from the cluster center,θ,for several values of the detection threshold S d.The values for∆T lens and S d correspond to a frequency of 4.86GHz.The dependence of∆T lens on the Einstein angleαand on frequencyνwere conveniently factored out.The Einstein angles for clusters with observed optical arcs are in the range of10–50′′(Le F`e vre et al.1994).The lensing decrement,∆T lens,shows a sharp peak near the Einstein angle.Forθ≫α,∆T lens isﬁrst weakened and then enhanced as S d varies from10−2to10−5Jy.This is due to the fact that the count slopeλcrosses the critical valueλcrit=2around S d∼10−3Jy(see Fig.1). The enhancement in∆T lens as S d decreases below10−3Jy occurs in spite of the decrease in the unlensed intensityˆi(<S d)there.At theseﬂuxes,the removal of fainter radio sources paradoxically makes the lensing decrement more pronounced.Note that because of the large shot noise in the source counts(with an rms ofσi/i≈0.5in a1arcmin2cell for S d(4.86GHz)=10−3Jy),∆T lens will not necessarily be realized in each individual cluster.The lensing induced decrement should be regarded as a systematic eﬀect that must be corrected for statistically,when a large sample of clusters is considered.For observations with a largeﬁeld of view,the lensing signature might appear in the outer part of each individual cluster.As a speciﬁc example we consider A2218,an Abell richness class4cluster at a redshiftz l=0.175,which shows several optical arcs(Pell´o et al.1992,Le Borgne et al.1992).Arc no.359 in Pell´o et al.(1992)is separated by20′′.8from the central cD galaxy and has a measured redshift of0.702,close to the probable median redshift of sub-mJy sources(z s∼0.5–0.75;cf.Windhorst et al.1993).We therefore model the cluster potential as a SIS with an Einstein angle ofα=20′′.8 for our radio sources(see also Miralda-Escud´e&Babul1995).Interferometric imaging of the SZ eﬀect in this cluster was performed by Jones et al.(1993)at15GHz,after the removal of point sources withﬂuxes above S d(15GHz)≈1mJy.The restoring beam for their short baseline image had a FWHM of129′′×120′′.The observed angular dependence of∆T SZ wasﬁtted by aβ–model,∆T SZ(θ)=∆T0 1+θ2of∼0.65(Sarazin1988,Jones&Forman1984,Bahcall&Lubin1994).Weak lensing studies in the optical band could be used in conjunction with X–ray observations to predict the relative radial behavior of the lensing and SZ decrements in each individual cluster.It is convenient to average the temperature oﬀset over a circular“top hat”beam of radius θb centered on the cluster center, ∆T(θb) ≡2θ−2b θb0θ∆T(θ)dθ.For the above model of A2218with S d(4.86GHz)=10−4Jy,the15GHz mean temperature oﬀsets due to lensingare ∆T lens ≈−28,−14,and−1.6µK,forθb=0.4,1,and60arcmin,respectively.The corresponding decrement ratios are ∆T lens / ∆T SZ ≈0.05,0.03,0.18,for theβ=1.5ﬁt,and 0.03,0.02,0.002for theβ=0.6ﬁt.The fractional correction to the Hubble constant(Eq.[4])is then∆H0/H0≈6–10%,4–6%,and0.4–40%forθb=0.4,1,and60arcmin,respectively,where the ranges reﬂect the ambiguity in theﬁt parameters of∆T SZ(θ).5.ConclusionsWe have shown that gravitational lensing of unresolved radio sources leads to a systematic overestimate of the SZ temperature decrement at anglesθ>α/2.The amplitude of the lensing eﬀect peaks close to the Einstein angle of the cluster,α∼30′′(cf.Fig.2).While∆T SZ is independent of frequency in the RJ regime,the lensing decrement∆T lens∝ν−2−γ(withγ≈0.35) is signiﬁcant only at frequenciesν∼<30GHz.In clusters where the radial proﬁle of the gas pressure is steeper than that of the dark matter density(e.g.,due to a gradient in the gas temperature), the ratio of the lensing to the SZ decrement increases at large projected radii.For observations of A2218at15GHz with a source removal threshold of S d(4.86GHz)=10−4Jy,H0could be overestimated by∼0.4–40%,for a beam radius in the range of0.4–60arcminutes(cf.Fig.3). The importance of the lensing eﬀect will be enhanced in future observations(including attempts to detect the kinematic SZ eﬀect)with greater sensitivity,higher angular resolution,and fainter source removal threshold.Lensing should also aﬀect the power spectrum of microwave background anisotropies on∼1′scales behind the cluster.These anisotropies are expected to originate primarily from the Ostriker–Vishniac eﬀect(Hu&White1996)and the cumulative SZ eﬀect of other background clusters(Colafrancesco et al.1994,Rephaeli1995).Future SZ experiments might be contaminated by noise from theseﬂuctuations(∆T/T∼<10−6),especially in the outer parts of clusters.However, since these diﬀuseﬂuctuations will not be removed,lensing will conserve their net intensity and will not systematically oﬀset the SZ decrement as it does in the case of discrete sources.We thank D.Helfand for useful comments on the manuscript.This work was supported in part by the NASA grants NAG5-3085(for AL)and NAGW2507(for AR).REFERENCESBahcall,N.A.,&Lubin,L.M.1994,ApJ,426,513Birkinshaw,M.1979,MNRAS,187,847Birkinshaw,M.,Hughes,J.P.,&Arnaud,K.A.1991,ApJ,379,466Cavaliere,A.,Danese,L.,&De Zotti,G.1977,ApJ,217,6Colafrancesco,S.,Mazzotta,P.Rephaeli,Y.,&Vittorio,N.1994,ApJ,433,454Fomalont,E.B.,Windhorst,R.A.,Kristian,J.A.,&Kellermann,K.I.1991,AJ,102,1258 Grainge,K.,et al.1996,MNRAS,278,L17Gunn,J.1978,in Observational Cosmology,ed. A.Maeder,L.Martinet,&G.Tammann (Sauverny:Geneva Observatory),1Haehnelt,M.G.,&Tegmark,M.1995,MNRAS,submitted,preprint astro-ph/9507077Hu,W.,&White,M.1996,A&A,in press,preprint astro-ph/9507060Jones,C.,&Forman,W.1984,ApJ,276,38Jones et al.1993,Nature,365,320Le Borgne,J.F.,Pell´o,R.,&Sanahuja,B.1992,A&AS,95,87Le F`e vre,O.,Hammer,F.,Angonin,M.C.,Gioia,I.,M.,&Luppino,G.A.1994,ApJ,422,L5 Miralda-Escud´e,J.,&Babul,A.1995,ApJ,449,18Narayan,R.,&Bartelmann,M.1996,Lectures held at the1995Jerusalem Winter School,preprint astro-ph/9606001Pell´o,R.,Le Borgne,J.F.,Sanahuja,B.,Mathez,G.,&Fort,B.1992,A&A,266,6 Refregier, A.,&Loeb, A.1996,ApJ,submitted,(RL),preprint available at ∼refreg/publications.htmlRephaeli,Y.1995,ARA&A,33,541Rephaeli,Y.,&Lahav,O.1991,ApJ,372,21Schneider,P.,Ehlers,J.,&Falco,E.E.1992,Gravitational Lenses,(New York:Springer-Verlag) Sarazin,C.L.,1988,X–ray Emissions from Clusters of Galaxies,(Cambridge:Cambridge Univ.Press)Silk,J.,&White,S.D.M.1978,ApJ,226,L103Squires,G.,Kaiser,N.,Babul,A.,Fahlman,G.,Woods,D.,Neumann,D.,&B¨o hringer,H.1996a, ApJ,461,572Squires,G.,Kaiser,N.,Fahlman,G.,Babul,A.,&Woods,D.1996b,ApJ,submitted,preprint astro-ph/9602105Sunyaev,R.A.,&Zel’dovich.Ya.,B.1980,ARA&A,18,537Tyson,J.A.,&Fischer,P.1995,ApJ,446,L55Wall,J.V.1994,Austr.J.Phys.,47,625White,R.L.,Becker,R.H.,Helfand,D.J.,&Gregg,M.D.1997,ApJ,Feb.1issue,preprint available at /ﬁrst/publications.htmlWindhorst,R.A.,Fomalont,E.B.,Partridge,R.B.,&Lowenthal,J.D.1993,ApJ,405,498Fig.1.—Number–ﬂux relation for radio sources at4.86GHz.The counts were normalized to S−2, the relation which remains invariant under lensing.The approximate mean counts summarized by Windhorst et al.(1993)are shown as squares.The dotted line corresponds to the limits inferred from aﬂuctuation analysis of the unresolved background(Fomalont et al.1991).The solid lineshows our model with its six power–law components.Fig. 2.—Temperature oﬀset∆T lens induced by gravitational lensing as a function of angular separation from the cluster center.The oﬀset is shown for several values of the source detection threshold S d.Values for∆T lens and S d correspond to a frequencyν=4.86GHz.The dependence of∆T lens on the Einstein angle of the cluster,α,and on frequency,ν,were factored out.The parameterγis the mean spectral index of the radio sources,andν4.86≡ν/(4.86GHz).–11–Fig.3.—Lensing eﬀect in A2218.The ratio of the temperature decrement induced by lensing at15 GHz,∆T lens,to that induced by the SZ eﬀect,∆T SZ,is shown for two values of theﬂux detection threshold S d(4.86GHz).The decrement ratio is evaluated for the two extremeﬁts obtained by Jones et al.(1993)to the observed radial dependence of∆T SZ.The curves which converge(diverge)at large radii correspond to theβ=0.6(β=1.5)ﬁt.。

轻暗物质SZ效应-课件

第十届全国粒子物理学术会议
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三类SZ效应：
热电子的随机运动——热SZ效应电子集体(星系团)的整体运动——运动学SZ效应其它非热电子集体——非热SZ效应
SZ效应
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暗物质简述 Sunyaev-Zel’dovich (SZ)效应 ~MeV暗物质所致SZ效应总结和讨论
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MeV暗物质，被引入解释银心511keV发射 MeV暗物质SZ效应
→e+e- , dN/dE=(E-m) 传播过程：扩散，能量损失

<v>(1MeV/m)2~10-30cm3/s PRL, 2004, 92, 101301
A&A, 2006, 455, 21
湮灭电子密度平方依赖于暗物质数密度分布：低质量暗物质粒子能产生更多正负电子
在频率217GHz处，热SZ效应为零 M=10MeV，T~3K M=100MeV，T~30K
第十届全国粒子物理学术会议
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暗物质简述 Sunyaev-Zel’dovich (SZ)效应 ~MeV暗物质所致SZ效应总结和讨论
第十届全国粒子物理学术会议
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总结
暗物质自湮灭产生正负电子对，正负电子和CMB光子相互作用导致SZ效应
第十届全国粒子物理学术会议
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暗物质简述 Sunyaev-Zel’dovich (SZ)效应 ~MeV暗物质所致SZ效应总结和讨论
第十届全国粒子物理学术会议
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Sunyaev & Zel’dovich
SZ效应
CMB光子与宇宙中高能电子逆康普顿散射，低能光子变少，高能光子增多，导致CMB黑体谱的畸变。

2021年5月高考英语考前冲破阅读明白得能力国际时事要闻美国众议院通过决议对委内瑞拉进行制裁

美国众议院通过决议对委内瑞拉进行制裁The US House of Representatives has ap proved a bill to introduce sanctions against Venezuelan offici als involved in human rights abuses.美国众议院通过一项法案，决定对委内瑞拉涉及踩踏人权的官员进行制裁。

The legislation calls for a travel ban on some members of the Venezuelan government and for their assets in US banks to be frozen.The US Foreign Relations Committee advanced a similar bill l ast we ek.At least 42 people have been killed since protests against President Nicolas Maduro beg an in February.Th e victims are from both sides of the political divide in the South American nation."The United States Congress must stand ready to act on the cause of freedom and democracy around the globe," Republican Representative Ileana Ros-Lehtinen said during the debate in the House.The White House opposes sanctions against Mr Maduro's government.It says such measures could undermine（破坏）efforts to find a political solution to the crisis. Democratic Representative Gregory Meeks says the bil l will undermine efforts by regional leaders to encourage dialogue between the government and the opposition."This bi ll does not advance US interests. It sends a message to our regional allies that we do not care about what they think," Mr Meeks told Reuters.Foreign ministers from the Unasur regional group left Caracas last week after the oppositi on pulled out of talks.。

sz效应宇宙学

SZ效应，全称为Sunyaev-Zel'dovich effect（汉语音译为“孙-泽效应”），是指宇宙微波背景辐射的光子在和宇宙中的高能电子碰撞时，获得了能量，从而改变了光子能量分布。

这种效应在宇宙学中非常重要，因为它可以帮助我们间接观测到星系际温热介质，进而研究宇宙纤维结构。

在具体的研究过程中，科学家们通过观察SZ效应对宇宙微波背景辐射信号的影响，发现这些区域的物质密度比其他地方高，其质量足以形成纤维结构。

这些纤维结构可能由星系际温热介质构成，从而间接证明了星系际温热介质的存在。

专业英语四级(阅读)模拟试卷146(题后含答案及解析)

专业英语四级（阅读）模拟试卷146(题后含答案及解析)题型有：1. 2.SECTION AIn this section there are several passages followed by ten multiple-choice questions. For each question, there are four suggested answers marked [A], [B], [C] and [D]. Choose the one that you think is the best answer.(1)Glass making in Eastern Europe and Romania comes from the Murano style in Italy as most of the artisans studied glassmaking there. Up to the 13th century, European glassmaking was exclusive to Venice. But frequent fires prompted Venetian authorities to shift the furnaces to the island of Murano. (2)There has been a long history of making glass in Romania. Romanian glassmakers have successfully passed on this art for several generations and the craft continues to thrive in this part of Eastern Europe. In Romania, it is said that artisans only pass on the secrets of glass making to members of their family. More importantly, there is a rigid hierarchy in obtaining the coveted position as a glass blower. For example, a young man may take years before he can get to that stage within this strict hierarchy. (3)Romanian glass is comparable to any great piece of Eastern European mouth blown glass. And they are nothing like the ones that are made by machinery or inexpensive duplicates. Traditionally Romanian factories and glass studios manufacture clear glass utilizing pellets that are distinct and commonly found in Western Europe. And depending on the artisan, German pigments are popularly used for coloring or painting glass. The combination of this blend makes Romanian crafted glass truly a superior product anywhere in Europe. Though Romanian glasswork is normally not made from crystal, nonetheless, it carries a similar purity and shine. Glass products in Romania are not just great looking, they are also being produced to suit a host of lifestyles, from the traditional to modern and the line of products are guaranteed quality glassware that is both functional and decorative. (4)Romanian mouth-blown glassware is made by highly skilled artisans. They are very creative pieces with exceptional quality. They are also a prized collector’s item. Some of the work includes vases and bowls that are made as centerpieces as well as plates—the artisans who create these masterpieces learned their skills in Murano itself. (5)The contemporary glassware is not just placed in galleries to be on display, they also make great gifts, particularly wedding gifts, and decorations especially in restaurants, businesses and hotels. They can also be used as decorations while designing your home.1．What is NOT true about the glass making in Murano?A．It was originated from the glass making in Venice.B．It spread to Eastern Europe through Venice.C．The Romanian glass making comes from Murano.D．Glass making didn’t begin in Murano until after the 13th century.正确答案：B解析：根据题干中的Murano定位到第1段。

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1. Introduction
The Sunyaev-Zel’dovich (SZ) eﬀect of a cluster of galaxies on the cosmic microwave background (CMB) photons can be used to determine the distance to the cluster hence the Hubble constant (H0), when analysed in conjunction with X-ray observations of the cluster (Cavaliere, Danese, & De Zotti 1977; Gunn 1978; Silk & White 1978; Birkinshaw 1979). For an excellent recent review on this subject and other SZ related topics, see Rephaeli (1995 and references therein). The accuracy of the Hubble constant determination depends upon the accuracy of several assumptions involving both sets of observations (radio and X-ray). Perhaps among the most important are the assumptions of sphericity, isothermality of clusters of galaxies (e.g., Inagaki et al. 1995). In this Letter we point out a completely separate eﬀect on the determination of the Hubble constant due to preexistent, small-amplitude CMB temperature ﬂuctuations before the photons undergo the SZ eﬀect through a cluster. The eﬀect is signiﬁcantly ampliﬁed by the gravitational lensing of the CMB photons by the cluster, because the SZ observational beam size is typically comparable to Einstein radius of the source-lens system. This eﬀect, when coupled with some systematic eﬀects such as the one proposed by Loeb & Refregier (1997) due to the systematic over-removal of background point radio sources in the beam, may provide an explanation for the observed distribution of H0 determined by SZ eﬀect.
On the Cluster Sunyaev-Zel’dovich Eﬀect and Hubble Constant
Renyue Cen Princeton University Observatory, Princeton, NJ 08544
cen@
arXiv:astro-ph/9803250v1 20 Mar 1998
2. CMB Fluctuations and H0 Determination Using SZ Eﬀect
The detections of CMB temperature ﬂuctuations on arcminute scales are mostly upper limits or marginal (e.g., Partridge et al. 1997), primarily because of limited sky coverages and instrumental sensitivities. However, there are a number of physical mechanisms suggested, which should generate appreciable ﬂuctuations on the relevant scales. For example, Persi et al. (1995) (see also Scaramella, Cen, & Ostriker 1993) show that SZ
Subject headings: Cosmology: large-scale structure of Universe – cosmology: cosmic microwave background – cosmology: distance scale – cosmology: gravitational lensing – galaxies: clusters
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eﬀect due to non-cluster gas can generate ∆T /T ∼ 10−6 − 10−5 on the arcminute scale, produced naturally by shock heated gas in a network of ﬁlaments and sheets during the phase of gravitational collapse of large-scale structure. Loeb (1996) shows that one would expect ∆T /T ∼ 10−6 − 10−5 due to bremsstrahlung emission from Lyα clouds, given the observed/required meta-galactic ultraviolet radiation ﬁeld. Depending on the universal ionization history, the Ostriker-Vishniac Eﬀect (Ostriker & Vishniac 1986; Vishniac 1987) could also make appreciable contributions to the CMB ﬂuctuations on the relevant scales (e.g., Persi et al. 1995). To be quantitatively deﬁnitive, we will adopt CMB temperature ﬂuctuations observed by Partridge et al. (1997) and assume that they are background CMB temperature ﬂuctuations, meaning that they exist before CMB ﬂuctuations are further induced by hot gas in clusters of galaxies. This is not to say that these ﬂuctuations are primordial; all that we need to assume is that there exists appreciable CMB ﬂuctuations at redshift higher than that of the clusters for which we study their individual SZ eﬀect and then determine the Hubble constant (when coupled with X-ray observations of the clusters).
To clearly illustrate the point, we will ﬁrst adopt a set of numbers and make a few simplifying assumptions:
1) the true Hubble constant is H0,true = 65km/s/Mpc;
Received
; accepted
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ABSTRACT
This study shows one important eﬀect of preexistent cosmic microwave background temperature ﬂuctuations on the determination of the Hubble constant through Sunyaev-Zel’dovich eﬀect of clusters of galaxies, especially when coupled with the gravitational lensing eﬀect by the same clusters. The eﬀect results in a broad distribution of the apparent Hubble constant. The combination of this eﬀect with other systematic eﬀects such as the Loeb-Refregier Eﬀect seems to provide an explanation for the observationally derived values of the Hubble constant currently available based on the Sunyaev-Zel’dovich eﬀect, if the true value of the Hubble constant is 60 − 80 km/s/Mpc. It thus becomes possible that the values of the Hubble constant measured by other techniques which generally give a value around 60 − 80 km/s/Mpc be reconciled with the SZ eﬀect determined values of the Hubble constant, where are systematically lower than others and have a broad distribution.