Stellar populations in the nuclear regions of nearby radiogalaxies

高三英语培优外刊阅读班级：____________学号：____________姓名：____________外刊精选｜《时代》2023年度人物：泰勒·斯威夫特近日，美国流行音乐歌手泰勒·斯威夫特当选为《时代》杂志2023年度人物，成为近百年以来第一位单独拥有这一称号的艺人，也是该杂志第一位两次获评年度人物的女性。

2023年，泰勒·斯威夫特的时代（Eras）巡回演唱会在全球掀起追捧热潮，其个人净资产也高达11亿美元。

这位歌手到底有着怎样的魅力？她曾经历过怎样的人生低谷，又如何脱胎换骨，成为更强大的自己？Taylor Swift named Time Magazine's person of the yearBy Mark SavageTaylor Swift has capped off a stellar 2023 by being named Time Magazine's person of the year. The award goes to an event or person deemed to have had the most influence on global events over the past year.Already a superstar before 2023, her career has reached new heights thanks to the Eras tour -which sees the singer perform a career-spanning 45-song set every night. In Seattle, her concerts generated seismic activity equivalent to a 2.3 magnitude earthquake."It feels like the breakthrough moment of my career, happening at 33," she told Time. "And for the first time in my life, I was mentally tough enough to take what comes with that."Swift's imperial phase comes after a period where she was vilified for her positions on feminism - although her silence stemmed from nothing more sinister than a lack of confidence. After speaking out against Donald Trump and in favour of abortion rights, she hit a creative purple patch with the pandemic-era albums Folklore and Evermore.Time editor-in-chief Sam Jacobs said the US pop icon was "the rare person who is both the writer and hero of her own story", adding that Swift had "found a way to transcend borders and be a source of light".【词汇过关】请写出下面文单词在文章中的中文意思。

The Mass Assembly History for Galaxies with MaNGA Xue Ge;Hong-Tao Wang;Cheng-Long Lei;Yun-Jun Guo;Yi-Long Jiang;Xiao-Xiao Cao【期刊名称】《Research in Astronomy and Astrophysics》【年(卷),期】2024(24)3【摘要】How galaxies assemble masses through their own star formation or interaction with the external environment is still an important topic in the field of galaxy formation and evolution.We use Value Added Catalogs with galaxy features that are spatially and temporally resolved from Sloan Digital Sky Survey Data Release 17 to investigate the mass growth histories of early-type galaxies(ETGs)and late-type galaxies(LTGs).We find that the mass growth of ETGs is earlier than that of LTGs for massivegalaxies(M_(*)>10^(10)M_⊙),while low-mass(M_(*)≤10^(10)M_⊙)ETGs have statistically similar mass assembly histories as low-mass LTGs.The stellar metallicity of all massive galaxies shows a negative gradient and basically does not change with time.However,in low-mass galaxies,the stellar metallicity gradient of elliptical galaxies is negative,and the stellar metallicity gradient of lenticular and spiral galaxies evolves from positive to negative.ETGs are not all in a high-density environment,but exhibit mass dependence.As the tidal strength increases,the star formation rate of low-mass ETGs rapidly decreases.These results support a picture where massive galaxies exhibit inside-out quenching mode,while low-mass galaxies showoutside-in quenching mode.Environmental effects play an important role in regulating the mass assembly histories of low-mass ETGs.【总页数】12页(P58-69)【作者】Xue Ge;Hong-Tao Wang;Cheng-Long Lei;Yun-Jun Guo;Yi-Long Jiang;Xiao-Xiao Cao【作者单位】School of Physics and Information Engineering Second Normal University;Jiangsu Province Engineering Research Center of Basic Education Big Data Application Second Normal University;Key Laboratory of Modern Astronomy and Astrophysics University of Education;School of Science Normal University【正文语种】中文【中图分类】P15【相关文献】1.A thick-disk galaxy model and simulations of equal-mass galaxy pair collisions2.Radial stellar populations of AGN-host dwarf galaxies in SDSS-Ⅳ MaNGA survey3.Spatially resolved properties of supernova host galaxies in SDSS-IV MaNGA4.Velocity Dispersionσ_(aper)Aperture Corrections as a Function of Galaxy Properties from Integral-field Stellar Kinematics of 10,000 MaNGA Galaxies5.Measuring stellar populations,dust attenuation and ionized gas at kpc scales in 10010 nearby galaxies using the integral field spectroscopy from MaNGA因版权原因，仅展示原文概要，查看原文内容请购买。

The Milky WayMilky Way probably looks likeAndromeda.The band of light we see is really 100 billion starsMilky WayBefore the 1920’s, astronomers used a “__________model” for the galaxyTried to estimate our location in the galaxy by counting stars in different __________Because some stars are _______ by dust, the true shape of this group of stars was unclear.A Globular ClusterFinding the Centerthe Solar System.The Milky WayParts of OurGalaxyDisk: The ____ Resides in theNuclear Bulge: The dense_______ regionHalo: Spherical regionsurrounding the disk where the_______ ________ live.Questions:How big is the Milky Way?Where are stars forming (or not forming)?How much mass is in the Milky Way?What’s going on at the center?so stars are still forming Car Headlights are standard candles:We use them to determine the car’s distanceHenrietta Leavitt Cepheid stars change in brightness. They pulsate in a very regular way. Large, bright Cepheids pulsate_____, while small, dim Cepheids pulsate _______.Milky Way Galaxy, we map out its structureA modern map of the Milky WayMeasuring the Mass of the Milky WayWe use the Sun’s ______around the center of the MilkyWayThe greater the mass insidethe orbit, the ______ the Sunhas move around the center.This way we can measure themass of the Milky Way.Total mass: about ___ _______ MThe Center of the Milky Wayat the center of the galaxy!Chapter 13Galaxies____)M 100NGC 300Less gas and dustAre generally ______ than spirals and ellipticals_______ Galaxies (E): Classified according to shape (E0-E9)_______ GalaxiesA Barred Spiral Galaxy with only 2 arms.Candles••Supernova in galaxy NGC4526 (HST Image)Hubble’s Original DataHubble Law/ Hd = vrClassifying Galaxies Lecture Tutorial: Page 127•Work with a partner or two•Read directions and answer all questions carefully. Take time to understand it now!•Discuss each question and come to a consensus answer you all agree on before moving on to the next question.•If you get stuck, ask another group for help.•If you get really stuck, raise your hand and I will come around.。

福岛核电站地下水受到放射污染High levels of a toxic radioactive isotope have been found in groundwater at Japan's Fukushima nu clear plant, its operator says.福岛核电站附近的地下水中发现高剂量有毒的放射性同位素。

Tokyo Electric Power Company (Tepco) said tests showed strontium-90 was present at 30 times the legal rate.The radioactive isotope tritium has also been detected at elevated levels.The plant, crippled by the 2011 earthquake and tsunami, has recent ly see n a series of water leaks and power failures.The tsunami knocked out cooling systems to the reactors, which melted down.Water is now being pumped in to the re actors to cool them but this has left Tepco with the problem of how to safely store the cont aminated water.There have been several reports of leaks from storage tanks or pipes.Sea samplesStrontium-90 is for med as a by-product of nuclear fission. Tests showed that levels of stront ium in grou ndwater at the Fukushima plant had increased 100-fold since the end of last year, Toshihiko Fukuda, a Tepco official, told media.Mr Fukuda said Tepco believed the elevated levels originated from a lea k of contaminated water in April 2011 from one of the reactors."As it's near where the leak from reactor number two happened and taking into account the situation at the time, we believe that water left over from that time is the highest possibility," he said.Tritium, used in glow-in-the-dark watc hes, was found at eight times the allowable level.Mr Fukuda said that samples from the sea showed no rise in either substance and the company believed the groundwater was being contained by concrete foun dations."When we look at the impact that is having on the ocean, the levels seem to be within past trends and so we don't believe it's having an effect."But the discovery is another set-back for Tepco's plan to pump groundwater from the plant into the sea, correspondents say.Nuclear chemist M ichiaki Furukawa told Reuters news agency that Tepco should not release contaminated water into the ocean."They have to keep it somewhere so that it can't escape outside the plant," he said. "Tepco needs to carry out more regular testing in specific areas and disclose everything they find."The Fukushima power plant has faced a series of problems this ye ar. Early this month, radioactive water was found leaking from a storage tank.The plant also suffered three power failures in five weeks earlier this year. A leak of radioactive water from one of the plant's underground storage pools was also detected in April.。

中考有关核污染的英语作文题目全文共3篇示例，供读者参考篇1Nuclear Pollution - A Looming Threat to Our PlanetAs a high school student, the issue of nuclear pollution is one that deeply concerns me and my generation. We are the inheritors of this planet, and the actions we take today will shape the world we live in tomorrow. Nuclear pollution, a silent and insidious threat, has the potential to cause catastrophic damage to our environment, our health, and our very existence.At the core of this issue lies the nuclear power industry and the management of radioactive waste. While nuclear power has been touted as a clean and efficient source of energy, the reality is far more complex and fraught with risks. The process of generating nuclear power produces a vast amount of highly radioactive waste, which must be stored and managed with the utmost care and precision.One of the most significant challenges we face is thelong-term storage of this radioactive waste. Many countries around the world have opted for temporary storage solutions,such as above-ground facilities or deep geological repositories. However, these solutions are far from perfect. Leaks, accidents, and natural disasters can all lead to the release of radioactive materials into the environment, with devastating consequences.The effects of nuclear pollution on human health arewell-documented and deeply troubling. Exposure to ionizing radiation can cause a wide range of health issues, including cancer, genetic mutations, and birth defects. Even low-level exposure over an extended period can increase the risk of developing these conditions. This is a particular concern for communities living near nuclear facilities or in areas affected by nuclear accidents, such as the infamous disasters at Chernobyl and Fukushima.But the impact of nuclear pollution extends far beyond human health. The release of radioactive materials into the environment can have far-reaching and long-lasting effects on entire ecosystems. Radioactive contamination can accumulate in the soil, water, and air, affecting plant and animal life in ways that we are still trying to fully understand. The consequences of this contamination can ripple through food chains, disrupting the delicate balance of nature and threatening entire species with extinction.As a student, I am deeply troubled by the prospect of inheriting a world marred by the scars of nuclear pollution. It is a burden that my generation did not create, but one that we may be forced to bear. We must ask ourselves difficult questions about the true costs of nuclear power and whether the risks outweigh the benefits.Equally concerning is the potential for nuclear materials to fall into the wrong hands. The specter of nuclear terrorism looms large, and the consequences of such an attack are almost too horrific to contemplate. We must remain vigilant and take every possible measure to secure nuclear facilities and prevent the proliferation of these deadly materials.However, it would be remiss of me not to acknowledge the complexities of this issue. Nuclear power, for all its risks, has played a role in meeting our ever-increasing energy demands and reducing our reliance on fossil fuels. The challenge lies in striking a balance between meeting our energy needs and ensuring the safety and well-being of our planet and its inhabitants.As we grapple with these challenges, it is clear that a multifaceted approach is required. We must invest in research and development of safer and more sustainable energy sources,such as renewable energy technologies. At the same time, we must work tirelessly to improve the management and storage of existing nuclear waste, employing the best available science and technology to minimize the risks of contamination.Education and public awareness are also crucial components of this effort. It is essential that we, as students and as members of society, understand the risks and implications of nuclear pollution. We must engage in open and honest dialogue, free from political or corporate influence, to make informed decisions about the role of nuclear power in our future.Ultimately, the issue of nuclear pollution is one that transcends borders and generations. It is a global challenge that demands a global response. We must work together, as nations and as individuals, to find solutions that protect our planet and safeguard the future for generations to come.As a student, I am filled with a sense of urgency and a determination to be part of the solution. We cannot afford to be complacent or to ignore the warning signs. The time to act is now, before the consequences of nuclear pollution become irreversible.I implore my fellow students, educators, policymakers, and leaders to join me in this fight. Let us be the generation thattakes a stand against nuclear pollution, that works tirelessly to protect our planet and our future. Together, we can create a world where the promise of a clean and sustainable future is not just a dream, but a reality.篇2Nuclear Pollution: A Threat to Our PlanetAs a student deeply concerned about the welfare of our planet, I can't help but feel a sense of urgency when it comes to the issue of nuclear pollution. The effects of radioactive contamination pose a grave threat not only to the environment but also to the health and well-being of all living beings, including humans. It's a complex and multifaceted problem that demands our immediate attention and action.To begin with, it's crucial to understand the sources of nuclear pollution. One of the primary culprits is the nuclear power industry. While nuclear energy has been touted as a clean alternative to fossil fuels, the process of generating it carries significant risks. Nuclear power plants, despite stringent safety measures, can experience accidents or malfunctions that lead to the release of radioactive materials into the environment. Thecatastrophic events at Chernobyl in 1986 and Fukushima in 2011 serve as grim reminders of the devastation that can ensue.Another major contributor to nuclear pollution is the production and testing of nuclear weapons. The detonation of these weapons, even for experimental purposes, releases vast amounts of radioactive particles into the atmosphere, soil, and water sources. The long-lasting effects of radiation can persist for decades, posing a continuous threat to the surrounding ecosystems and human populations.The consequences of nuclear pollution are far-reaching and alarming. Radioactive contamination can wreak havoc on the delicate balance of ecosystems, causing genetic mutations, birth defects, and even the extinction of certain species. Plants and animals exposed to high levels of radiation can suffer from various health issues, including cancer, immunodeficiency, and reproductive problems.s are not immune to the dangers of nuclear pollution either. Exposure to radioactive materials can lead to a host of severe health implications, such as an increased risk of cancer, genetic abnormalities, and organ damage. Children and fetuses are particularly vulnerable, as radiation can interfere with their developmental processes and potentially cause long-term health problems.Furthermore, nuclear pollution has a lasting impact on the environment itself. Radioactive particles can contaminate soil, water sources, and air, making entire regions uninhabitable for extended periods. The cleanup and decontamination efforts required in the aftermath of a nuclear accident are often lengthy, costly, and pose additional risks to the workers involved.As global citizens, it is our collective responsibility to address this critical issue head-on. We must demand stricter regulations and oversight for the nuclear industry, ensuring that safety protocols are rigorously enforced and constantly updated. Additionally, we should advocate for increased investment in alternative energy sources, such as solar, wind, and hydroelectric power, which offer cleaner and more sustainable solutions.On a personal level, we can also contribute to mitigating the effects of nuclear pollution. Educating ourselves and others about the risks and consequences is crucial. By raising awareness and encouraging open dialogue, we can foster a deeper understanding of the issue and inspire collective action.Moreover, supporting organizations and initiatives dedicated to environmental protection, nuclear disarmament, and the development of safer nuclear technologies can make a significant difference. Our voices, combined with those ofmillions of others, can influence policymakers and drive positive change.In conclusion, nuclear pollution is a grave threat that cannot be ignored. Its consequences extend far beyond our current generation, affecting the very future of our planet. As students, we have a responsibility to educate ourselves, raise awareness, and demand action from those in positions of power. By working together and embracing sustainable solutions, we can mitigate the risks of nuclear pollution and create a safer, cleaner world for ourselves and future generations.篇3Nuclear Pollution: A Looming Threat to Our PlanetAs a student deeply concerned about the well-being of our planet, I can't help but feel a sense of unease when I think about the issue of nuclear pollution. It's a topic that has been weighing heavily on my mind, and one that I believe deserves our utmost attention and action.Nuclear pollution is a silent, invisible threat that has the potential to wreak havoc on our environment and the health of all living beings. It's a byproduct of the nuclear industry, a consequence of our reliance on nuclear power and thedevelopment of nuclear weapons. And while the benefits of nuclear energy are undeniable, the risks associated with it are simply too great to ignore.What exactly is nuclear pollution, you might ask? It's the release of radioactive materials into the environment, either through accidents, leaks, or the improper disposal of nuclear waste. These radioactive materials can contaminate the air we breathe, the water we drink, and the soil that sustains our crops. And the effects of this contamination can be devastating.One of the most alarming aspects of nuclear pollution is its ability to cause genetic mutations and cancer in living organisms. Exposure to high levels of radiation can damage cells and DNA, leading to the development of various types of cancers, including leukemia, thyroid cancer, and lung cancer. Children and fetuses are particularly vulnerable, as their cells are rapidly dividing and growing.But the effects of nuclear pollution don't stop there. It can also have a profound impact on entire ecosystems, disrupting the delicate balance of nature and endangering countless species. Radioactive materials can accumulate in the food chain, causing birth defects, stunted growth, and even sterility inanimals. Entire populations of wildlife can be decimated, and once-thriving habitats can become barren wastelands.Perhaps one of the most haunting examples of the devastating consequences of nuclear pollution is the Chernobyl disaster of 1986. On April 26th of that year, a catastrophic explosion occurred at the Chernobyl Nuclear Power Plant in Ukraine, then part of the Soviet Union. The accident released massive amounts of radioactive materials into the environment, contaminating vast areas of Ukraine, Belarus, and even parts of Western Europe.The aftermath of the Chernobyl disaster was nothing short of horrific. Thousands of people were evacuated from the surrounding areas, and the long-term effects on human health and the environment were staggering. Cancer rates skyrocketed, and entire towns and villages were abandoned, left as ghostly reminders of the price we pay for our reliance on nuclear power.But Chernobyl is not an isolated incident. Nuclear accidents have occurred in various parts of the world, from Three Mile Island in the United States to Fukushima in Japan. Each time, the consequences have been severe, with radioactive contamination spreading across vast areas and affecting countless lives.It's important to note that nuclear pollution isn't just a threat during accidents or disasters. Even the routine operation of nuclear power plants can release small amounts of radioactive materials into the environment, and the storage and disposal of nuclear waste pose significant challenges. Improper handling of these materials can lead to leaks and contamination, putting entire communities at risk.So, what can we do to combat this looming threat? First and foremost, we need to acknowledge the severity of the issue and take proactive measures to reduce our reliance on nuclear power. While nuclear energy may seem like a clean and efficient alternative to fossil fuels, the risks associated with it are simply too great to ignore.Instead, we should focus our efforts on developing and investing in truly renewable and sustainable energy sources, such as solar, wind, and hydroelectric power. These technologies have the potential to meet our energy needs without the risk of nuclear pollution or the emission of greenhouse gases.Additionally, we need to prioritize the safe and responsible handling of existing nuclear waste. This means investing in advanced storage solutions and exploring innovative methodsfor decontaminating and disposing of radioactive materials in a way that minimizes their impact on the environment.But perhaps most importantly, we need to raise awareness about the dangers of nuclear pollution and educate ourselves and future generations about the importance of environmental stewardship. Only by understanding the gravity of this issue can we truly appreciate the urgency of taking action.As students, we have a unique opportunity to be agents of change. We can use our voices to advocate for policies that prioritize environmental protection and the development of sustainable energy sources. We can participate in community initiatives that promote awareness and education about the risks of nuclear pollution. And we can make conscious choices in our daily lives to reduce our environmental footprint and support companies and organizations that share our values.The path ahead may be challenging, but it is one that we must embrace with determination and resolve. Nuclear pollution is a global issue that transcends borders and affects us all. It's a threat that looms over our planet, casting a shadow on the future we hope to build for ourselves and generations to come.But if we act now, if we unite our efforts and channel our collective will, we can overcome this challenge. We can create aworld where nuclear pollution is a thing of the past, where our reliance on harmful and dangerous energy sources is replaced by clean, sustainable alternatives that respect and nurture the delicate balance of our planet.It won't be easy, but it's a fight worth fighting. For the sake of our health, our ecosystems, and the very future of our planet, we must confront the issue of nuclear pollution head-on. We must be the generation that says "enough is enough" and takes decisive action to protect the world we call home.So let us embrace this challenge with courage and conviction. Let us be the voices that echo through the halls of power, demanding change and accountability. And let us never forget that the future of our planet lies in our hands, and it is our responsibility to ensure that it remains a place where life can thrive for generations to come.。

银河系漫游指南英文版pdfHere is the English essay with a word count of over 1000 words, as requested:The Milky Way Galactic OdysseyEmbark on a captivating journey through the vast expanse of the Milky Way Galaxy, a celestial wonder that has captivated the human imagination for millennia. As we delve into the mysteries and marvels of this galactic realm, prepare to be awestruck by the sheer scale and beauty of the cosmos that lies beyond our earthly confines.Let us begin our odyssey by venturing to the heart of the Milky Way, where the supermassive black hole known as Sagittarius A* resides. This gravitational behemoth, nearly 4 million times the mass of our Sun, anchors the center of our galaxy and exerts a powerful influence on the surrounding stars and stellar matter. As we approach this enigmatic cosmic phenomenon, we will witness the intricate dance of stars and gas clouds as they are drawn inexorably towards the event horizon, their fate forever sealed within the crushing grip of the black hole.Venturing outwards from the galactic center, we will encounter the diverse and vibrant neighborhoods that make up the Milky Way. Spiral arms, such as the Orion Arm in which our Solar System resides, are vast regions of star formation, with newborn stars and stellar nurseries dotting the landscape. We will marvel at the brilliant nebulae, glowing clouds of gas and dust that serve as the birthplaces of these young celestial bodies, their ethereal hues and intricate structures a testament to the dynamic processes that shape the galaxy.As we traverse the spiraling arms, we will come across the globular clusters – ancient, densely packed collections of stars that orbit the galactic center. These spherical assemblages, some of the oldest objects in the Milky Way, harbor valuable insights into the early history and evolution of our galaxy, their stars dating back to a time when the universe was a mere fraction of its current age.Amidst the stellar tapestry, we will discover the diverse array of stellar populations that call the Milky Way home. From the towering red giants, their brilliant crimson hues a testament to their advanced age and increased size, to the compact and enigmatic neutron stars, the collapsed remnants of once-mighty suns. Each type of star, with its unique properties and life cycle, contributes to the rich tapestry of the galactic landscape.But the Milky Way is not merely a collection of stars – it is a dynamic and ever-changing system, influenced by the complex interplay of gravity, stellar evolution, and the ever-present threat of cosmic catastrophes. We will explore the regions where massive stars meet their explosive demise, supernovae that briefly outshine entire galaxies and leave behind the dense, spinning neutron stars known as pulsars. These cataclysmic events not only shape the galactic environment but also provide the building blocks for new generations of stars and planets.As we venture deeper into the Milky Way, we will encounter the harrowing regions where the fabric of space-time is stretched and distorted by the intense gravitational fields of neutron stars and black holes. Here, we will witness the bizarre and mind-bending phenomena predicted by Einstein's theory of general relativity, from the warping of spacetime to the accretion disks that feed these cosmic monsters.Throughout our journey, we will be in awe of the sheer scale and majesty of the Milky Way. The galaxy, spanning nearly 100,000 light-years in diameter, is home to an estimated 200 to 400 billion stars, each one a unique and fascinating world unto itself. We will ponder the possibility of life elsewhere in this vast cosmic tapestry, wondering if intelligent civilizations have arisen on distant worlds and if they, too, gaze up at the night sky, marveling at the splendorof our shared galactic home.As our odyssey draws to a close, we will reflect on the profound impact that the study of the Milky Way has had on our understanding of the universe. From the groundbreaking work of pioneering astronomers to the cutting-edge research conducted with the most advanced observational tools, the Milky Way has been a constant source of fascination and discovery. And as we look to the future, we know that there are countless more secrets and mysteries waiting to be unveiled, beckoning us to continue our exploration of this awe-inspiring celestial realm.So let us embark on this Milky Way galactic odyssey, armed with a sense of wonder and a thirst for knowledge. For in unraveling the mysteries of our galactic home, we may just find the answers to some of the most profound questions that have puzzled humanity since the dawn of time.。

我心目中的英雄医生英语范文英文回答：The Physician Who Inspires Me.In the realm of healthcare, there are countless individuals who dedicate their lives to alleviating suffering and promoting well-being. Among them, one physician stands out as a beacon of hope and inspiration in my eyes. Her unwavering compassion, exceptional medical expertise, and unwavering dedication to serving the underserved have left an enduring mark on my life and the lives of countless others.Dr. Emily Carter, a renowned cardiologist, has spent her career tirelessly advocating for equitable access to healthcare for all. Raised in a working-class family, she witnessed firsthand the disparities in medical care faced by marginalized communities. This experience ignited within her a deep-seated determination to break down thesebarriers and ensure that everyone has the opportunity to live a healthy life.Dr. Carter's medical journey began with a stellar academic career. She graduated magna cum laude from Harvard Medical School and went on to complete her residency in cardiology at Johns Hopkins Hospital. Throughout her training, she immersed herself in research, publishing groundbreaking papers on the diagnosis and treatment of cardiovascular disease. Her passion for scientific inquiry has led to advancements in the field that have improved the outcomes of countless patients.Beyond her clinical practice, Dr. Carter is an ardent advocate for healthcare reform. She has testified before Congress, written op-eds in major publications, and worked tirelessly to raise awareness about the importance of universal healthcare. She firmly believes that healthcareis a fundamental human right and that no one should be denied access to quality medical care due to financial or social circumstances.As an educator, Dr. Carter is equally passionate about nurturing the next generation of physicians. She holds a professorship at the University of California, San Francisco, where she mentors medical students and residents, instilling in them the values of empathy, inclusivity, anda commitment to social justice. Her dedication to teaching extends beyond the classroom, as she frequently volunteers her time to provide medical care to underserved populations in both domestic and international settings.What truly sets Dr. Carter apart is her unwavering empathy for her patients. She treats each individual with dignity and respect, regardless of their background orability to pay. Her compassionate bedside manner andability to connect with patients on a personal level create a healing environment that fosters trust and understanding.The impact of Dr. Carter's work has been profound. She has not only saved countless lives but has also transformed the healthcare landscape for the better. Her advocacy for equitable access to healthcare has inspired others to join the fight for social justice, and her mentorship has shapedthe careers of countless future physicians.Dr. Emily Carter is a true hero in my eyes. Her unwavering compassion, exceptional medical expertise, and unwavering dedication to serving the underserved are an inspiration to me and to countless others. Her work has made a tangible difference in the lives of her patients,and her legacy will continue to inspire generations to come.中文回答：我心目中的英雄医生。

中国应进一步发展核能，因为核电目前只占其总发电量的2%，该比例在所有核国家中居第30位，几乎是最低的。

2011年3月日本核电站事故后，中国的核能开发停了下来，中止审批新的核电站，并开展全国性的核安全检查。

到2012年10月，审批才能又谨慎的恢复。

随着技术和安全措施的改进，发生核事故的可能性完全可以降低到最低限度。

换句话说核能是可以安全开发和利用的。

China should further develop nuclear energy because nuclear power accounts for only 2% of its total generating capacity currently. Such proportion ranks the thirtieth in all the countries possessing nuclear power, which is almost the last.After Japan’s nuclear power accident in March 2011, nuclear power development in China was suspended, so was the approval of new nuclear power plants. Also, the national safety check for the nuclear power was carried out. IT was not until October 2012 that the approval was prudently resumed.With the improvement of technology and safety measures, there is little possibility for nuclear accidents to happen. In other words, there won’t be any trouble to develop and exploit the nuclear power.以上就是2014.6四级翻译答案：发展核能的全部内容，希望对大家有所帮助。

散发光成为光英语作文Radiating Light: The Luminary of the Universe.In the vast expanse of the cosmos, countless celestial bodies emit radiant energy, illuminating the darkness and illuminating our understanding of the universe. Among these luminous celestial objects, stars reign supreme as the primary source of light, energy, and awe for observers both on Earth and beyond.Stars, the building blocks of galaxies, are incandescent beacons of plasma held together by their own gravitational forces. Within their nuclear furnaces, the fusion of hydrogen atoms into helium releases prodigious amounts of energy, a process that sustains their brilliance for billions of years. This energy manifests as electromagnetic radiation, which travels through space as a spectrum of light waves.The light emitted by stars encompasses a vast range ofwavelengths, from short-wavelength gamma rays to long-wavelength radio waves. However, the human eye is only capable of perceiving a narrow band within this spectrum, known as visible light. Visible light ranges from violet to red, with each wavelength corresponding to a different color.Stars exhibit a remarkable diversity in their light output, ranging from faint and barely visible to dazzling and brilliant. The brightness of a star, as perceived by an observer on Earth, depends on several factors, includingits size, temperature, and distance from Earth.Large stars, with greater masses and hence more fuel to burn, typically emit more light than smaller stars. Temperature also plays a crucial role in determining astar's luminosity. Hotter stars emit blue and white light, while cooler stars radiate yellow or red light.The distance between a star and Earth also influences its apparent brightness. Stars that are closer to Earth appear brighter than those that are farther away. This isbecause the inverse square law of light dictates that the intensity of light decreases with the square of the distance from the source.The light of stars serves as a valuable tool for astronomers and astrophysicists. By analyzing the spectrum of light emitted by stars, scientists can determine their temperature, chemical composition, and other physical characteristics. This information helps us understand the evolution of stars, the nature of stellar populationswithin galaxies, and the history of the universe itself.Moreover, the light of stars provides a celestial beacon for navigators and explorers. For centuries, seafarers relied on the positions of stars to guide their ships across vast oceans. Even today, spacecraft venturing into the depths of space utilize star charts and celestial navigation to determine their location and trajectory.Beyond its practical applications, the light of stars also holds profound aesthetic and philosophical significance. Throughout human history, stars have capturedthe imagination of poets, artists, and philosophers. Their twinkling radiance has inspired countless works of art, literature, and music. Stars have also been associated with spirituality, divinity, and the pursuit of knowledge and enlightenment.In conclusion, the light of stars permeates our existence, providing both practical and profound benefits. It illuminates the darkness, guides our paths, and fuels our understanding of the universe. As we continue to explore the cosmos and unravel its mysteries, the light of stars will forever remain a constant and awe-inspiring source of wonder and inspiration.。

核能源英语作文Title: The Pros and Cons of Nuclear Energy。

Nuclear energy has been a topic of significant debate and discussion for many years. It offers both advantages and disadvantages, and understanding these can help in making informed decisions about its use as a source of power.Firstly, let's delve into the advantages of nuclear energy. One of its primary benefits is its low greenhouse gas emissions. Unlike fossil fuels, which release large amounts of carbon dioxide and other pollutants into the atmosphere when burned, nuclear power plants produce minimal greenhouse gases during operation. This makes nuclear energy an attractive option for combating climate change and reducing air pollution.Secondly, nuclear energy is highly efficient. A small amount of nuclear fuel can generate a large amount ofelectricity, making it a reliable and cost-effective source of power. Additionally, nuclear power plants can operate continuously for long periods without the need for frequent refueling, ensuring a steady supply of electricity to meet demand.Moreover, nuclear energy is relatively reliable and less susceptible to fluctuations in fuel prices compared to fossil fuels. Uranium, the primary fuel used in nuclear reactors, is abundant and widely available in many parts of the world. This reduces dependence on foreign energy sources and helps stabilize energy prices in the long term.Furthermore, nuclear power plants have a small land footprint compared to renewable energy sources like wind and solar. They require less space to generate the same amount of electricity, making them suitable for areas with limited land availability.Despite these advantages, nuclear energy also poses several challenges and risks that cannot be ignored. One of the most significant concerns is the issue of nuclear wastedisposal. Radioactive waste generated by nuclear power plants remains hazardous for thousands of years and requires secure storage facilities to prevent environmental contamination and public health risks.Another major drawback of nuclear energy is the potential for accidents and meltdowns, as demonstrated by disasters such as Chernobyl and Fukushima. These incidents not only result in immediate human and environmental impacts but also undermine public confidence in the safety of nuclear power.Furthermore, the proliferation of nuclear technology raises security concerns, as it can potentially be exploited for the development of nuclear weapons by rogue states or terrorist organizations. Safeguarding nuclear materials and preventing their misuse requires stringent regulations and international cooperation.Additionally, the high initial costs and long construction times associated with building nuclear power plants make them less attractive investment optionscompared to renewable energy alternatives. The complexity of nuclear technology also presents challenges in terms of regulatory compliance and operational safety.In conclusion, nuclear energy offers both advantages and disadvantages as a source of power. While it provides low-carbon electricity and is highly efficient, it also poses significant risks in terms of waste disposal, safety, and security. Ultimately, the decision to embrace nuclear energy should be based on a careful consideration of its benefits and drawbacks, weighing its potential contribution to energy security and sustainability against the need to address its associated challenges.。

a rXiv:083.1619v2[astro-ph]12Mar28Massive Star Formation in the Galactic Center By D o n F.F i g e r Rochester Institute of Technology,Rochester,NY,USA The Galactic center is a hotbed of star formation activity,containing the most massive star formation site and three of the most massive young star clusters in the Galaxy.Given such a rich environment,it contains more stars with initial masses above 100M ⊙than anywhere else in the Galaxy.This review concerns the young stellar population in the Galactic center,as it relates to massive star formation in the region.The sample includes stars in the three massive stellar clusters,the population of younger stars in the present sites of star formation,the stars surrounding the central black hole,and the bulk of the stars in the field population.The fossil record in the Galactic center suggests that the recently formed massive stars there are present-day examples of similar populations that must have been formed through star formation episodes stretching back to the time period when the Galaxy was forming.2 D.F.Figer et al.:Massive Star Formation in the Galactic CenterMorris&Serabyn(1996)review the content and conditions of the interstellar mediumin the“Central Molecular Zone”(CMZ),noting that the molecular clouds in the regionare extraordinarily dense(n>104cm−3)and warm(T∼70K)with respect to those found in the disk of the Galaxy.Stark et al.(1989)argue that the density and internal velocities of clouds in the GC are a direct result of the strong tidalfields in the region,i.e.only the dense survive.Serabyn&Morris(1996)argue that the inexorable inflow of molecular material from further out in the Galaxy powers continuous and robust star formation activity in the region.It is still unclear how magneticfield strength affects star formation.If it does matter,then the GC might be expected to reveal such effects.The strength of the magneticfield inthe GC has been estimated through far infrared polarized light from aligned dust grains (Hildebrand et al.1993;Chuss et al.2003)and Zeeman splitting of the OH molecule (Plante,Lo,&Crutcher1995).In both cases,thefield is inferred to be of milliGuass strength.However,Uchida&Guesten(1995)argue strongly that these strengths are localized to bundles that delineate the extraordinary non-thermalfilaments in the region (Yusef-Zadeh&Morris1987),and are not representative of thefield strength that is pervasive in the region.If this is correct,then thefields inside GC molecular clouds maynot be so strong versus those inside disk clouds(B∼3µG).Metals in molecular clouds can provide cooling that aids protostellar collapse,butthey also create opacity to the UVflux,winds,and bipolar outflows that emanate from newly formed stars.Measurements of metallicty in the Galactic center span a rangeof solar,observed in stars(Ram´ırez et al.2000;Carr,Sellgren,&Balachandran2000; Najarro et al.2004),to twice solar,observed in the gas phase(Shields&Ferland1994),to four times solar,observed through x-ray emission near the very center(Maeda et al. 2002).The errors from the stellar measurements are the smallest and suggest that starsin the GC are formed from material with roughly solar abundances.3.Present-day star formation in the GCPresent-day star formation in the GC is somewhat subdued compared to the episodesthat produced the massive clusters we now see.A dozen or so ultra-compact HII regionsare distributed throughout the central50pc,each containing one or a few O-stars still embedded in their natal environs.Yusef-Zadeh&Morris(1987)identify most of these sources in radio continuum observations(see Figure1).Zhao et al.(1993)and Goss et al. (1985)infer lyman-continuumfluxes that are comparable to that expected from a singleO7V star in each of the H1-H5and A-D UCHII regions.Cotera et al.(1999)find that several of the recently formed stars in these regions have broken out of their dust shroud, revealing spectra of young massive stars;see also Figer et al.(1994)and Muno et al. (2006)for additional examples.A bit further from the GC,the Sgr B2molecular cloud harbors a massive star clus-ter in the making and is home to the most intense present-day star formation site inthe Galaxy(Gaume et al.1995;de Pree et al.1995;McGrath,Goss,&De Pree2004; Takagi,Murakami,&Koyama2002;de Vicente et al.2000;Liu&Snyder1999;Garay&Lizano 1999;de Pree et al.1996).Within the next few Myr,this activity should produce a star cluster that is comparable in mass to the Arches cluster(see Figure2).Sato et al.(2000)note evidence in support of a cloud-cloud collision as the origin for the intense star formation in Sgr B2;these include velocity gradients,magneticfield morphology,shock-enhanced molecular emission,shock-induced molecular evaporation from dust grains,and distinctly different densities of certain molecular species throughout the cloud.D.F.Figer et al.:Massive Star Formation in the Galactic Center3Figure1.Radio emission from the GC region at6cm,adapted in Figure1by Cotera et al. (1999)from Yusef-Zadeh&Morris(1987).The star symbols represent the three massive clusters. Hot stars in the Quintuplet and Arches clusters ionize gas on the surfaces of nearby molecular clouds to produce the radio emission in the“Sickle”and“G0.10+0.02/E1/E2Filaments,”re-spectively.The radio emission near the Galactic center is due to a combination of thermal and non-thermal emission.The“H1-8”and“A-D”regions are ultra-compact HII regions surrounding recently formed stars.4.Continuous star formation in the GCThere is ample evidence for persistent star formation in the GC in the form of upper-tip asymptotic giant branch stars distributed throughout the region(Lebofsky&Rieke1987; Narayanan,Gould,&Depoy1996;Frogel,Tiede,&Kuchinski1999;Sjouwerman et al. 1999).Figure3shows a plot for some of these stars,based on spectroscopic data,overlaid with intermediate age model isochrones(Blum et al.2003).Note that the giants and supergiants in this plot require ages that span a few Myr to a few Gyr.One comes to similar conclusions by analyzing photometry of thefield population in the GC.Figer et al.(2004)use observed luminosity functions to determine that the star formation rate has been roughly constant for the lifetime of the Galaxy in the GC,similar to the suggestion in Serabyn&Morris(1996)based on the sharp increase in unresolved infrared light towards the center and a mass-budget argument.Figure4shows model and observed luminosity functions(right)for various star formation scenarios(left)over the lifetime of the Galaxy,assuming a Salpeter IMF(Salpeter1955)for masses above10M⊙,4 D.F.Figer et al.:Massive Star Formation in the Galactic CenterFigure2.Figure3from McGrath,Goss,&De Pree(2004)showing H2O and OH masers over-plotted on7mm contours for a small portion of the Sgr B2cloud.The activity in this region is typical of that found near thefifty or so ultra-compact HII regions in Sgr B2.and aflat slope below this mass.The observations were obtained with HST/NICMOS and have been corrected for incompleteness.The“burst”models(panels1,2,4,and5) produce unrealistic ratios of bright to faint stars in the luminosity functions,especially for the red clump near a dereddened K-band magnitude of12.The continuous star formation model(panel3)bestfits the data.5.Properties of the Three Massive ClustersThe majority of recent star formation activity in the GC over the past10Myr pro-duced three massive clusters:the Central cluster,the Arches cluster,and the Quintuplet cluster.The following sections describe the stellar content in the clusters and the re-sultant implications for star formation in the region.They closely follow recent reviews (Figer et al.1999a;Figer2003,2004),with updates,as summarized in Table1.The three clusters are similar in many respects,as they are all young and contain 104M⊙in stars.They have very high central stellar mass densities,up to nearly 106M⊙pc−3,exceeding central densities in most globular clusters.They have luminosi-ties of107−8L⊙,and are responsible for heating nearby molecular clouds.They also generate1050−51ionizing photons per second,enough to account for nearby giant HII regions.The primary difference between the clusters is likely to be age,where the Quin-tuplet and Central clusters are about twice the age of the Arches cluster.In addition,the Central cluster is unique for its population of evolved massive stars that have broad and strong helium emission lines(Krabbe et al.1991,and referenes therein).While the Quin-tuplet cluster has a few similar stars(Geballe et al.1994;Figer et al.1999a),the Central cluster has far more as a fraction of its total young stellar population(Paumard et al. 2006).Table2summarizes the massive stellar content of the clusters.D.F.Figer et al.:Massive Star Formation in the Galactic Center5Figure 3.Estimates of absolute magnitude versus temperature for stars in the GC from Blum et al.(2003).The lines correspond to model isochrones having ages of10Myr,100Myr, 1Gyr,5Gyr,and12Gyr.The supergiants(above the horizontal line)are descendant from stars having M≈15-25M⊙,whereas fainter stars are descendant from lower mass main sequence stars having a few to15M⊙.The presence of these stars in the GC demonstrates intermediate age star formation of massive stars.5.1.Central clusterThe Central cluster contains many massive stars that have recently formed in the past 10Myr(Becklin et al.1978;Rieke,Telesco,&Harper1978;Lebofsky,Rieke,&Tokunaga 1982;Forrest et al.1987;Allen,Hyland,&Hillier1990;Krabbe et al.1991;Najarro et al. 1994;Krabbe et al.1995;Najarro1995;Libonate et al.1995;Blum,Depoy,&Sellgren6 D.F.Figer et al.:Massive Star Formation in the Galactic CenterFigure4.Afigure adapted from Figer et al.(2004)showing various star formation scenarios (left),and resultant model luminosity functions(right,thick)compared to observed luminosity functions(right,thin)in the GC.The models assume a Salpeter IMF slope,an elevated lower–mass turnover of10M⊙,and are additionally constrained to produce2(108)M⊙in stars withinthe region.The observations have been corrected for incompleteness.The third panels from the top,i.e.continuous star formation,bestfit the data.The observed turn-down at the faint end appears to be real and is only wellfit only by assuming a very high lower mass turnover.1995a;Blum,Sellgren,&Depoy1995b;Genzel et al.1996;Tamblyn et al.1996;Najarro et al. 1997).In all,there are now known to be at least80massive stars in the Central cluster (Eisenhauer et al.2005;Paumard et al.2006),including≈50OB stars on the main se-quence and30more evolved massive stars(see Figure5).These young stars appear tobe confined to two disks(Genzel et al.2003;Levin&Beloborodov2003;Paumard et al. 2006;Tanner et al.2006;Beloborodov et al.2006).There is also a tight collection of a dozen or so B stars(the“s”stars)in the central arcsecond,highlighted in the small boxin thefigure.The formation of so many massive stars in the central parsec remains as much a mystery now as it was at the time of thefirst infrared observations of the region. Most recently,this topic has largely been supplanted by the even more improbable notion that star formation can occur within a few thousand AU of the supermassive black hole,D.F.Figer et al.:Massive Star Formation in the Galactic Center7Figure 5.K-band image of the Central cluster obtained with NAOS/CONICA fromSch¨o del et al.(2006).The100or so brightest stars in the image are evolved descendants frommain sequence O-stars.The central box highlights the“s”stars that are presumably young andmassive(M initial≈20M⊙).an idea that will be addressed in Section7.See Alexander(2005)for a thorough reviewof the“s”stars and Paumard et al.(2006)for a review of the young population in theCentral cluster.5.2.Arches clusterThe Arches cluster is unique in the Galaxy for its combination of extraordinarily highmass,M≈104M⊙,and relatively young age,τ=2Myr(Figer et al.2002).Being soyoung and massive,it contains the richest collection of O-stars and WNL stars in any clus-ter in the Galaxy(Cotera et al.1996;Serabyn,Shupe,&Figer1998;Figer et al.1999b;Blum et al.2001;Figer et al.2002).It is ideally suited for testing theories that predictthe shape of the IMF up to the highest stellar masses formed(see Section6).The cluster is prominent in a broad range of observations.Figure6shows an HST/NICMOS image of the cluster–the majority of the bright stars in the image have masses greaterthan20M⊙.The most massive dozen or so members of the cluster have strong emissionlines at infrared wavelengths(Harris et al.1994;Nagata et al.1995;Cotera1995;Figer1995;Cotera et al.1996;Figer et al.1999b;Blum et al.2001;Figer et al.2002).Theselines are produced in strong stellar winds that are also detected at radio wavelengths (Lang,Goss,&Rodr´ıguez2001;Yusef-Zadeh et al.2003;Lang et al.2005;Figer et al. 2002),and x-ray wavelengths(Yusef-Zadeh et al.2002;Rockefeller et al.2005;Wang,Dong,&Lang 2006).5.3.Quintuplet clusterThe Quintuplet cluster was originally noted for itsfive very bright stars,the Quintu-plet Proper Members(QPMs)(Glass,Moneti,&Moorwood1990;Okuda et al.1990;8 D.F.Figer et al.:Massive Star Formation in the Galactic CenterFigure 6.F205W image of the Arches cluster obtained by Figer et al.(2002)using HST/NICMOS.The brightest dozen or so stars in the cluster have M initial 100M⊙,and there are≈160O-stars in the cluster.The diameter is≈1lyr,making the cluster the densest in the Galaxy withρ>105M⊙pc−3.Nagata et al.1990).Subsequently,a number of groups identified over30stars evolved from massive main sequence stars(Geballe et al.1994;Figer,McLean,&Morris1995; Timmermann et al.1996;Figer et al.1999a).Given the spectral types of the massive stars identified in the cluster,it appears that the Quintuplet cluster is≈4Myr old and had an initial mass of>104M⊙(Figer et al.1999a).An accounting of the ionizingflux produced by the massive stars in the cluster conclusively demonstrates that the clus-ter heats and ionizes the nearby“Sickle”HII region(see Figure1).The Quintuplet is most similar to Westerlund1in mass,age,and spectral content(Clark et al.2005; Negueruela&Clark2005;Skinner et al.2006;Groh et al.2006;Crowther et al.2006). Of particular interest in the cluster,the QPMs are very bright at infrared wavelengths, m K≈6to9,and have color temperatures between≈600to1,000K.They are lu-minous,L≈105L⊙,yet spectroscopically featureless,making their spectral classifica-tion ambiguous.Figer,Morris,&McLean(1996),Figer et al.(1999a),and Moneti et al. (2001)argue that these objects are not protostars,OH/IR stars,or protostellar OB stars.Instead,they claim that these stars are dust-enshrouded WCL stars(DWCLs), similar to other dusty Galactic WC stars(Williams,van der Hucht,&The1987),i.e. WR104(Tuthill,Monnier,&Danchi1999)and WR98A(Monnier,Tuthill,&Danchi 1999).Chiar et al.(2003)tentatively identify a weak spectroscopic feature at6.2µm that they attribute to carbon,further supporting the hypothesis that these stars are indeed DWCLs.The stars have also been detected at x-ray wavelengths(Law&Yusef-Zadeh 2004),and at radio wavelengths(Lang et al.1999,2005).Recently,Tuthill et al.(2006)convincingly show that the QPMs are indeed dusty WC stars.Figure8shows data that reveal the pinwheel nature of their infrared emission,char-D.F.Figer et al.:Massive Star Formation in the Galactic Center9Figure7.Paschen-αimage of the region surrounding the Pistol star from Figer et al.(1999c).North is to the upper right,and east is to the upper left.The Pistol star ejected≈10M⊙ofmaterial approximately6,000yr ago to form what now appears to be a circumstellar nebulathat is ionized by two WC stars to the north of the nebula.Moneti et al.(2001)use ISO datato show that the nebula isfilled with dust that is heated by the Pistol star.acteristic of binary systems containing WCL plus an OB star(Tuthill,Monnier,&Danchi1999;Monnier,Tuthill,&Danchi1999).This identification raises intruiging questionsconcerning massive star formation and evolution.With their identifications,it becomesclear that every WC star in the Quintuplet is dusty,and presumably binary.There aretwo possible explanations for this result.Either the binary fraction for massive stars isextremely high(Mason et al.1998;Nelan et al.2004),or only binary massive stars evolvethrough the WCL phase(van der Hucht2001).The Quintuplet cluster also contains two Luminous Blue Variables,the Pistol star(Harris et al.1994;Figer et al.1998,1999c),and FMM362(Figer et al.1999a;Geballe,Najarro,&Figer 2000).Both stars are extraordinarily luminous(L>106L⊙),yet relatively cool(T≈104K),placing them in the“forbidden zone”of the Hertzsprung-Russell Diagram,above theHumphreys-Davidson limit(Humphreys&Davidson1994).The Pistol star is particu-larly intriguing,in that it is surrounded by one of the most massive(10M⊙)circumstel-lar ejecta in the Galaxy(see Figure7;Figer et al.1999c;Smith2006).Both stars are spectroscopically(Figer et al.1999a)and photometrically variable(Glass et al.2001).They present difficulties for stellar evolution and formation models.Their inferred initialmasses are>100M⊙,yet such stars should have already gone supernova in a clusterthat is so old,as evidenced by the existence of WC stars(Figer et al.1999a)and thered supergiant,q7(Moneti,Glass,&Moorwood1994;Ram´ırez et al.2000).Figer&Kim(2002)and Freitag,Rasio,&Baumgardt(2006)argue that stellar mergers might explainthe youthful appearance of these stars.Alternatively,these stars might be binary,al-though no evidence has been found to support this assertion.Note that in a similar case,LBV1806−20is also surrounded by a relatively evolved cluster(Eikenberry et al.2004;Figer et al.2005),yet it does appear to be binary(Figer,Najarro,&Kudritzki2004).10 D.F.Figer et al.:Massive Star Formation in the Galactic CenterFigure8.Tuthill et al.(2006)find that the Quintuplet Proper Members are dusty Wolf-Rayet stars in binary systems with OB companions.The insets in this illustration show high-resolution infrared imaging data for two Quintuplet stars,overlaid on the HST/NICMOS image from Figer et al.(1999b).All of the Quintuplet WC stars are dusty,suggesting that they are binary.6.The initial mass function in the Galactic centerThe IMF in the Galactic center has primarily been estimated through observations of the Arches cluster(Figer et al.1999b;Stolte et al.2003),although there have been several attempts to extract such information through observations of the Central clus-ter(Genzel et al.2003;Nayakshin&Sunyaev2005;Paumard et al.2006)and the back-ground population in the region(Figer et al.2004).These studies suggest an IMF slope that isflatter than the Salpeter value.6.1.The slopeFiger et al.(1999b)and Stolte et al.(2003)estimate a relativelyflat IMF slope in the Arches cluster(see Figure9).Portegies Zwart et al.(2002)interpret the data to indicate an initial slope that is consistent with the Salpeter value,and a present-day slope that has beenflattened due to dynamical evolution.Performing a similar analysis,Kim et al. (2000)arrive at the opposite conclusion–that the IMF truly was relativelyflat.The primary difficulty in relating the present-day mass function to the initial mass function is the fact that n-body interactions operate on relatively short timescales to segregate the highest stellar masses toward the center of the cluster and to eject the lowest stellar masses out of the cluster.Most analysis is needed to resolve this issue.6.2.Upper mass cutoffThe Arches cluster is the only cluster in the Galaxy that can be used to directly probe an upper mass cutoff.It is massive enough to expect stars at least as massive as400M⊙, young enough for its most massive members to still be visible,old enough to have broken out of its natal molecular cloud,close enough,and at a well-established distance,for us to discern its individual stars(Figer2005).There appears to be an absence of stars with initial masses greater than130M⊙in the cluster,where the typical mass functionD.F.Figer et al.:Massive Star Formation in the Galactic Center11Figure9.Figer(2005)find an apparent upper-mass cutoffto the IMF in the Arches cluster. Magnitudes are transformed into initial mass by assuming the Geneva models forτage=2Myr, solar metallicity,and the canonical mass-loss rates.Error bars indicate uncertainty from Poisson statistics.Two power-law mass functions are drawn through the average of the upper four mass bins,one having a slope of−0.90,as measured from the data,and another having the Salpeter slope of−1.35.Both suggest a dramatic deficit of stars with M initial>130M⊙,i.e.33or18are missing,respectively.These slopes would further suggest a single star with very large initial mass (M MAX).The analysis suggests that the probability of there not being an upper-mass cutoffis ≈10−8.predicts18(see Figure9).Figer(2005)therefore claim afirm upper mass limit of150M⊙. There is additional support for such a cutoffin other environments(Weidner&Kroupa 2004;Oey&Clarke2005;Koen2006;Weidner&Kroupa2006).6.3.Lower mass rolloverMorris(1993)argue for an elevated lower mass rollover in the GC based on the envi-ronmental conditions therein,and only recently have observations been deep enough to address this claim.Stolte et al.(2005)claim observational evidence for an elevated cutoffaround6M⊙in the Arches cluster;however,in that case,confusion and incompleteness are serious problems.In addition,even if the apparent turn-down is a real indication of the initial cluster population,the lack of low mass stars might result from their ejection through n-body interactions(Kim et al.2000;Portegies Zwart et al.2002).Field obser-vations should not suffer from such an effect,as thefield should be the repository for low mass stars ejected from massive clusters in the GC.Figure4reveals a turn-down in the observed luminosity function of thefield in the GC at a dereddened K-band magnitude greater than16.This appears to not be a feature of incompleteness,as the data are greater than50%complete at these magnitudes(Figer et al.1999b).A more convincing argument,based on this type of data,will await even deeper observations(Kim et al. 2006).7.The“s”starsFigure5shows a dense collection of about a dozen stars within1arcsecond(0.04pc) of Sgr A*(Genzel et al.1997;Ghez et al.1998,2000;Eckart et al.2002;Sch¨o del et al.12 D.F.Figer et al.:Massive Star Formation in the Galactic Center2002;Ghez et al.2003;Sch¨o del et al.2003;Ghez et al.2005).This cluster stands out for its high stellar density,even compared to the already densefield population in the GC.Sch¨o del et al.(2003)and Ghez et al.(2005)(and refereces therein)have tracked the proper motions of the“s”stars,finding that they are consistent with closed orbits surrounding a massive,and dark,object having M≈2−4(106)M⊙,consistent with previous claims based on other methods(Lynden-Bell&Rees1971;Lacy et al.1980; Serabyn&Lacy1985;Genzel&Townes1987;Sellgren et al.1987;Rieke&Rieke1988; McGinn et al.1989;Lacy,Achtermann,&Serabyn1991;Lindqvist,Habing,&Winnberg 1992;Haller et al.1996).The orbital parameters for these stars are well determined,as seen in Figure10(left),and they require the existence of a supermassive black hole in the Galactic center.While these stars are useful as gravitational test particles,they are also interesting in their own right,as they have inferred luminosities and temperatures that are similar to those of young and massive stars(Genzel et al.1997;Eckart et al.1999; Figer et al.2000;Ghez et al.2003;Eisenhauer et al.2003,2005;Paumard et al.2006). Figure10(right)shows the absorption lines that suggest relatively high temperatures. Oddly,the increased density of the young stars in the central arcsecond is not matched by the density distribution of old stars.Indeed,there is a curious absence of late-type stars in the central few arcseconds,as evidenced by a lack of stars with strong CO absorption in their K-band spectra(Lacy,Townes,&Hollenbach1982;Phinney1989; Sellgren et al.1990;Haller et al.1996;Genzel et al.1996,2003).This dearth of old stars represents a true“hole”in three dimensional space,and not just a projection effect.Even the late-type stars that are projected on to the central parsec generally have relatively low velocities,suggesting dynamical evidence that the region nearest to the black hole lacks old stars(Figer et al.2003).The existence of such massive and young stars in the central arcseconds is puzzling, although it is perhaps only an extension of the original problem in understanding the origins of the young stars identified in the central parsec over20years ago.Table3gives a list of recent papers regarding the origin of the“s”stars.While there are over30papers listed in this table,they can be reduced to a few basic ideas.One class of ideas considers the“s”stars as truly young.In this case,the“origin”of the“s”stars is often reduced to the case of massive star formation in the Galactic center region and transportation of the products to the central arcsecond.The other class regards the“s”stars as old stars that only appear to be young,i.e.via atmospheric stripping,merging,or heating. Both classes require new mechanisms that would be unique to the GC,and they both have considerable weaknesses.For example,Figer et al.(2000)argue that stripped red giants would not be as bright as the“s”stars(see Dray,King,&Davies2006,for detailed confirmation).See Alexander(2005)for a more thorough discussion of the strengths and weaknesses of these ideas.If the“s”stars are truly young,then that would require massive clumps to form OB stars(M initial 20M⊙).In addition,the clumps would have to form from very high density material in order for them to be stable against tidal disruption.Assuming that the stars formed as far away from the supermassive black hole as possible,while still permitting dynamical friction to transport them into the central arcsecond during their lifetimes, then the required densities must be>1011cm−3(Figer et al.2000).The average molecular cloud density in the GC is aboutfive orders of magnitude less,so highly compressive events might be required to achieve the necessary densi-ties.Alternatively,the required densities can be reduced if the stars are gravitationally bound to significant mass,i.e.a surrounding stellar cluster.Indeed,Gerhard(2001), Portegies Zwart,McMillan,&Gerhard(2003),and Kim&Morris(2003)showed that particularly massive clusters could form tens of parsecs outside of the center and be deliv-D.F.Figer et al.:Massive Star Formation in the Galactic Center13ered into the central parsec in just a few million years.The efficiency of this method is im-proved with the presence of an intermediate black hole in the cluster(McMillan&Portegies Zwart 2003;Kim,Figer,&Morris2004).It is key in any of these cluster transport models thatthe host system have extremely high densities of>106M⊙pc−3,comparable to the14 D.F.Figer et al.:Massive Star Formation in the Galactic CenterFigure10.(left)Figure2in Ghez et al.(2005)and(middle)Figure6in Sch¨o del et al.(2003), stretched to the same scale.Bothfiguresfit similar model orbits through separate proper motion data sets for the“s”stars.(right)Paumard et al.(2006)find that one of the“s”stars,S2,has a K-band spectrum that is similar to those of OB stars in the central parsec(see also Ghez et al. 2003).highest estimated central density of the Arches cluster after core collapse(Kim&Morris 2003).Detailed n-body simulations suggest that while these ideas may be relevant for the origins of the young stars in the central parsec,it is unlikely that they could explain the existence of the“s”stars in the central arcsecond.parisons to other massive star populations in GalaxyThere are relatively few clusters in the Galaxy with as many massive stars as in the GC clusters.NGC3603has about a factor of two less mass than each of the GC clusters (Moffat et al.2002);whereas,W1has at least a factor of two greater mass(Clark et al. 2005;Negueruela&Clark2005;Skinner et al.2006;Groh et al.2006).The next nearest similarly massive cluster is R136in the LMC(Massey&Hunter1998).All of these clusters,and the GC clusters,appear to have IMF slopes that are consistent with the Salpter value(or slightlyflatter)and are young enough to still possess a significant massive star population.It is remarkable to note that these massive clusters appear quite similar in stellar content,whether in the Galactic disk,the GC,or even the lower metallicity environment of the LMC.Evidently,the star formation processes,and natal environments,that gave birth to these clusters must be similar enough to produce clusters that are virtually indistinguishable.There are probably more massive clusters yet to be found in the Galaxy.The limited sample of known massive clusters is a direct result of extinction,as most star formation sites in the Galaxy are obscurred by dust at optical wavelengths.While infrared observa-tions have been available for over30years,they have not provided the necessary spatial resolution,nor survey coverage,needed to probe the Galactic disk for massive clusters. Recently,a number of groups have begun identifying candidate massive star clusters us-ing near-infrared surveys with arcsecond resolution(Bica et al.2003;Dutra et al.2003; Mercer et al.2005).Indeed,these surveys have already yielded a cluster with approxi-mate initial mass of20,000to40,000M⊙(Figer et al.2006),and one would expect more to be discovered from them.The present-day sites of massive star formation in the Galaxy have been known for some time through radio and far-infrared observations,as their hottest members ion-ize and heat nearby gas in molecular clouds.As one of many examples,consider W49。

如何写好狮子英语作文To craft a stellar essay on lions in English, you'll need to delve into their characteristics, habitat, behavior, and significance. Here's a structured approach to ensure your essay shines:Introduction:Begin with an attention-grabbing statement or anecdote about lions to pique the reader's interest. Provide a brief overview of what your essay will cover.Example:Lions, often referred to as the kings of the jungle, command awe and respect with their majestic presence and ferocious roar. In this essay, we will explore the fascinating world of lions, from their physical attributesto their social structure and conservation status.Body Paragraphs:1. Physical Characteristics:Describe the physical features of lions, such as their golden fur, muscular build, and distinctive mane in males. Explain how these features contribute to their survival in the wild, including camouflage and intimidation of rivals.2. Habitat and Distribution:Discuss the natural habitat of lions, primarily the grasslands and savannas of Africa, as well as the dwindling populations in Asia. Explain the importance of these habitats for their survival and the challenges they face due to habitat loss and human encroachment.3. Behavior and Social Structure:Explore the social structure of lion prides, highlighting the roles of males, females, and cubs. Discusstheir hunting techniques, reliance on teamwork, and communication through vocalizations. Touch upon the hierarchical nature of prides and the dynamics of dominance within them.4. Role in the Ecosystem:Examine the ecological significance of lions as apex predators. Describe how they help maintain the balance of their ecosystems by regulating prey populations and preventing overgrazing. Discuss the ripple effects of their presence or absence on the entire ecosystem.5. Conservation Status and Threats:Address the conservation challenges facing lions, including habitat loss, poaching, and human-wildlife conflict. Highlight the efforts of conservation organizations and governments to protect lion populations through measures such as habitat preservation and anti-poaching initiatives.Conclusion:Summarize the key points discussed in the essay and reiterate the importance of lions in the natural world. Encourage readers to appreciate and support conservation efforts to ensure the survival of these magnificent creatures for future generations.Example:In conclusion, lions are not merely symbols of strength and majesty but crucial components of their ecosystems. As human activities continue to encroach upon their habitats, it is imperative that we take proactive measures to conserve these iconic species. By raising awareness, supporting conservation initiatives, and promoting coexistence between humans and lions, we can ensure that the king of the jungle continues to reign supreme for years to come.By following this structure and delving deep into each aspect of lion biology and ecology, you can create acompelling and informative essay that captivates your audience.。

Unit 1Helium---------------------氦uranium------------铀Gaseous state-----------气态的artificially------------人工的The perfect gas law------理想气体定律Boltzmann constant--- 玻尔兹曼常数neutrons --------------中子electrostatic -------静电的，静电学的Specific heat capacity--- 比热容Plank constant---------普朗克常量Fission----------------裂变fusion-----------------聚变Maxwellian distribution--麦克斯韦分布microscopic------------微观的Macroscopic-----------宏观的quantum number-------量子数Laser-----------------激光deuterium--------------氘Tritium----------------氚deuteron---------------氘核Trition----------------氚核atomic mass unit------原子质量单位Avogadro’s number----阿伏伽德罗常数binding energy----------结合能Substance-------------物质internal-----------------内部的Spontaneously --------自发地circular-----------------循环的Electronic ------------电子的neutral-----------------中性的Qualitative -----------定性的dissociation-------------分解分离Disrupt--------------使分裂A complete understanding of the microscopic structure of matter and the exact nature of the forces acting (作用力的准确性质) is yet to be realized. However, excellent models have been developed to predict behavior to an adequate degree of accuracy for most practical purposes. These models are descriptive or mathematical often based on analogy with large-scale process, on experimental data, or on advanced theory.一个完整的理解物质的微观结构和力的确切性质(作用力的准确性质)尚未实现。