Disappearance of Hard X-ray Emission in the Last BeppoSAX Observation of the Z Source GX 34
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UNIT 3ENVIRONMENTAL PROTECTIONTest1Ⅰ.重点词汇1.melt vi.& vt. (使)融化;熔化;软化→melting adj. 融化的;熔化的melt down 将……熔化melt into sth 消失;逐渐融入;渐渐与某物成为一体melt away 慢慢消失,消散;逐渐散去2.starve vi.& vt. (使)挨饿;饿死→starvation n. 饥饿;饿死starve to death 饿死starve sb out 用饥饿迫使某人屈服starve for sth 渴望得到某物3.release vt.& n. 排放;释放;发布release from 从(某物)中释放release of 解除,使放出4.trend n. 趋势;趋向;动向→trendy adj. 时髦的;赶时髦的trend of ……的形势trend in ……的趋势set a/the trend 开风气之先,带领新潮流5.broadcast vt.& vi. 播送;广播;传播n. 广播节目;电视节目broadcast sth to sb/sth (向……)传播,乱传broadcast on/upon 用……广播;播放……的新闻live broadcast 现场直播worldwide broadcast 向世界广播6.restrict vt. 限制;限定;束缚→restriction n. 限制规定;限制法规;约束→restrictive adj. 受限制的restrict oneself sb to (doing) 限制自己/某人(做)7.seize vt. 抓住;夺取;控制seize sth from sb 从……夺走seize sb by sth 抓住某人某部位seize up (身体某部分因紧张或上了年纪而)发僵,无法动弹8.reform vi.& vt. 改革;(使)改正;改造n. 改革;变革;改良→reformer n. 改革者;改良者reform ... into ... 把……改造成……reform (sb) through ... 通过……改造(某人)reform of ……的改革9.moderate adj. 适度的;中等的;温和的vi.& vt. 缓和;使适中→moderately adv. 适度;适量;适中moderate in 在……方面稳健的/有节制的10.submit vt.& vi. 提交;呈递;屈服→submission n. 投降;提交(或呈递)的文件;服从submit sth to sb 向某人呈交某物submit (oneself) to sb/sth/doing 服从于某人/某事/做某事11.sensitive adj. 敏感的;善解人意的;灵敏的→sensitively adv. 敏感地;易受伤害地be sensitive to 对……敏感be sensitive about 在乎,在意……12.originate vi.& vt. 起源;发源;创立→originator n. 创始人;首次提出者originate from 发源于;起源于13.restore vt. 恢复;使复原;修复→restoration n. 整修;修复;(规章制度等的)恢复restore to 恢复到……restore sb/sth to sth 使某人/某物恢复原状14.dozen n. (一)打;十二个dozens of 许多;很多by the dozen成打地15.disposal n. 去掉;清除;处理→dispose v. 去掉;清除;处理at sb's disposal 任某人处理;供某人任意使用;由某人自行支配disposal of ……的处理;……的处置权dispose of sb/sth 去掉;清除;处理16.fine vt. 对……处以罚款fine sb for sth/doing 因……而罚(款)fine sb/sth for sth/doing 因……而罚某人……pay a fine 交罚款17.carbon dioxide 二氧化碳18.fossil fuel 化石燃料(如煤或石油)19.on behalf of 代表(代替)某人Test21.global climate change/warming 全球气候变化/变暖2.air/water pollution 空气/水污染3.emphasize environmental protection 强调环境保护4.air quality 空气质量5.red alert 红色预警6.be full of traffic 交通拥挤7.a vast area of forest 莽莽苍苍的森林8.public transportation 公共交通9.reduce our carbon footprint 减少我们的碳足迹10.Earth's atmosphere 地球大气11.fresh air 新鲜空气12.greenhouse gases 温室气体13.forest fires 森林火灾14.prevent the deserts from spreading 阻止沙漠扩大15.environment-friendly agriculture 生态农业16.water/limited resources 水/有限的资源17.the disappearance of rare animals 珍稀动物的消失18.the number of wild animals 野生动物的数量19.forest coverage rate 森林覆盖率20.without mercy 毫不留情地21.take measures to do sth 采取措施做某事22.soil and water conservation 水土保持23.at all costs 不惜任何代价24.damage to the environment 对环境的破坏25.recycled materials 可回收的材料26.green policies 环保政策27.cherish the source of nature 珍惜自然之源28.a carpet of green grass 绿草如茵29.a tourist attraction 旅游胜地30.the beauty of nature 大自然的美31.water shortage 水资源短缺32.improve the present situation 改善现状33.get/become worse and worse 变得越来越糟34.a rubbish dump/heap/tip 垃圾场/堆/倾倒处35.take the responsibility 承担责任36.waste time/food/energy 浪费时间/食物/能源37.develop renewable energy 开发可再生能源38.garbage collection 垃圾收集39.the destruction of wildlife habitat 野生动植物栖息地的破坏40.emission controls 排放控制41.industrial chemicals 工业化学品42.an enormous challenge 巨大的挑战43.nuclear fuels 核燃料44.garbage sorting/classification 垃圾分类45.on-the-spot fine 当场处罚46.make joint efforts 共同努力47.throw away 丢弃48.in the long run 从长远看49.save water/energy 节约水/能源50.carbon emission 碳排放51.on a large scale 大规模地52.keep the balance of ecosystem 保持生态平衡53.reduce the use of single served chopsticks 减少使用一次性筷子54.radiation sickness 放射病55.preserve endangered species 保护濒危物种。
人教版高中英语选修六阅读训练:global__warming阅读训练: Global WarmingSection A本文词数:302 参考时间:2'40''Rising temperatures in coming years would lead to less sea ice in the Southern Ocean that surrounds Antarctica and fewer habitats and feeding grounds for penguins, says the World Wildlife Fund (世界自然基金会) in its report 2 Degrees is T oo Much.Antarctica and the Arctic are the most threatened regions from climate change. In the Antarctica, the temperature has risen 2.5 degrees in the past 50 years. This speed is nearly five times faster than that before the Industrial Revolution. It is mainly caused by burning fossil fuels. Unless nations reduce carbon dioxide emission1, the world will warm by an average of 2 degrees in less than 40 years. Rich nations should agree to reduce greenhouse gas emission. Temperatures near the Poles have risen much faster, which has led glaciers2 on the Antarctic Peninsula to melt3 quickly.The situation is quite critical, because in the past 50 years the number of emperor penguins (帝企鹅) has decreased by 50 percent across the whole Antarctica. On the Antarctic Peninsula’s northwest coast, the number of Adelie penguins (阿德里企鹅) has dropped surprisingly over the past 25 years.Fifty percent of the habitats of the emperor penguin and 75 percent of the habitats of the Adelie penguin face a rapid reduction, or even disappearance, if the global temperature rises 2 degrees above pre-industrial levels.With a 2-degree increase in global temperature and the decrease in sea ice thickness, emperor penguins will find itdifficult to find new areas to live. With less sea ice, penguins could be pushed further south, but this could prevent them from hunting for food during the dark winters, because they need at least a few hours of daylight to find their food.Notes:1. emission n. 排放2. glacier n. 冰川3. melt v. 融化词数:150处理时间:2′45″Read the passage and then choose the best answer for each question.1. The purpose of the passage is to _____.A. introduce readers to the Adelie penguins and emperor penguinsB. tell readers about the rising temperatures in the AntarcticaC. tell readers about the effect of global warmingD. warn people that Antarctica is becoming smaller and smaller2. In the writer’s opinion, what has caused global warming?A. That the earth is getting hotter and hotter.B. That the atmosphere of the earth is becoming thinner.C. That carbon dioxide emission is too high.D. That the use of oxygen in the air is out of control.3. From the first paragraph, what do you think the author wants to tell us?A. Temperatures will rise in the coming years.B. Sea ice will disappear in the coming years.C. Penguins will suffer a lot in the future.D. 2 degrees will have a great effect on the WWF.Section B本文词数:293 参考时间:2'42''In the movie, The Day After Tomorrow, many climate changes including an ice age are caused by global warming. Much of the science in the movie has been questioned by people. However, there may be some truth to the idea in the movie that global warming could cause an ice age.The theory starts with an understanding of why Europe and Scandinavia are not colder already. After all, other places at the same latitude1 are covered with ice. The ocean current2called the Gulf Stream (墨西哥湾流) brings warm waters from the Caribbean to the UK and Europe. These waters warm the countries around their path. This is why the UK, Europe and Scandinavia have a warmer climate than Alaska. Global warming has nothing to do with this. Global warming is significant3. It could slow the Gulf Stream, or even stop it. If this were to happen, the cold waters wouldstay in the area of Europe, the UK, Scandinavia and the North-eastern US. It could mean an ice age for those regions.Some weakness in the Gulf Stream could happen for different reasons. These days, it could happen due to global warming, caused by human activities, such as the burning of fossil fuels.If a new ice age happens, it will probably be caused by the melting of the polar ice. This will lead large quantities of cold and fresh water to come into the ocean. This would disrupt the Gulf Stream and cause the cooling of many areas that now have a mild climate.Scientists have gathered a lot of data from the oceans and the land to try to determine whether an ice age could be caused by global warming. With all this information at hand, it appearsthat it is indeed possible that global warming could lead to an ice age.Notes:1. latitude n. 纬度2. current n. 水流3. significant adj. 有重大意义的;显著的词数:171 处理时间:2'00''Read the passage and then choose the best answer for each question.1. What does the author tell us in the second paragraph?A. Global warming has created a warmer climate in the UK, Europe and Scandinavia.B. The Gulf Stream plays an important role in the warm climate of the UK, Europe and Scandinavia.C. Only the burning of fossil fuels can cause global warming.D. The climate of Alaska is also affected by the Gulf Stream.2. By saying "Global warming is significant.", the author means the following except ______.A. the Gulf Stream will be slowed down or stoppedB. the cold water will stay in the ocean of these areasC. people don’t have to suffer from coldD. an ice age is just waiting to happen in some areas3. Why does the author write this passage?A. To warn people of the dangerous effects of global warming.B. To prove that the polar ice will disappear.C. To prove that a new ice age is no way to come.D. To introduce the causes and effects of Gulf Stream.阅读新题型本文词数:279 参考时间:2'45''阅读短文,根据要求完成文后题目。
提高人们的环保意识英语作文六级全文共3篇示例,供读者参考篇1Raising Environmental AwarenessWe are currently facing an unprecedented environmental crisis that demands our immediate attention and action. The Earth, our home, is suffering from the detrimental effects of human activities, threatening the very foundation of life as we know it. As students and future leaders, it is our responsibility to raise environmental awareness and promote sustainable practices to safeguard our planet for generations to come.The environmental challenges we face today are multifaceted and deeply rooted in our way of life. Climate change, driven by the excessive emission of greenhouse gases, is causing rising temperatures, sea-level rise, and extreme weather events. Deforestation, driven by the insatiable demand for land and resources, is destroying irreplaceable habitats and biodiversity. Pollution, in the form of plastic waste, toxic chemicals, and air contaminants, is poisoning our air, water, andsoil, putting both human health and the health of ecosystems at risk.Addressing these issues requires a fundamental shift in our mindset and behavior. We must move away from the prevailing mindset of overconsumption and exploitation of natural resources towards a more sustainable and eco-friendly approach. This transformation begins with raising environmental awareness among individuals, communities, and societies.Education is the cornerstone of environmental awareness. From an early age, children should be taught about the intricate workings of our planet, the importance of preserving its natural resources, and the consequences of our actions on the environment. Schools and universities must integrate environmental studies into their curricula, fostering an understanding of ecological principles and sustainable practices. By equipping students with knowledge and critical thinking skills, we can empower them to make informed decisions and take responsible actions towards environmental protection.Furthermore, public awareness campaigns play a crucial role in disseminating information and inspiring behavioral change. Through various media channels, such as social media, television, and public events, we can raise awareness about pressingenvironmental issues and encourage individuals to adopteco-friendly habits. Simple actions like reducing plastic waste, conserving energy, and supporting sustainable businesses can have a profound impact when collectively embraced by society.Governments and policymakers also have a vital role to play in promoting environmental awareness. By implementing comprehensive environmental education programs, incentivizing sustainable practices, and enacting stricter regulations on polluters, governments can create an enabling environment that encourages individuals and businesses to prioritize environmental protection.Moreover, environmental awareness should extend beyond individual actions and encompass a broader understanding of the interconnectedness of socio-economic and environmental factors. We must recognize that environmental degradation often disproportionately affects marginalized communities and exacerbates social inequalities. By fostering environmental awareness, we can promote social justice and address the root causes of environmental injustice.As students, we have a unique opportunity to be agents of change and shape the future of our planet. We can participate in environmental clubs, organize awareness campaigns, andintegrate sustainable practices into our daily lives. By setting an example and inspiring others around us, we can create a ripple effect that encourages more individuals to embrace environmental responsibility.Furthermore, we can leverage our academic pursuits to contribute to environmental solutions. Through research and innovation, we can develop new technologies, sustainable materials, and eco-friendly practices that can mitigate the impact of human activities on the environment. Interdisciplinary collaboration among students from various fields, such as engineering, biology, and economics, can yield innovative solutions that address environmental challenges from multiple perspectives.Environmental awareness is not merely a passing trend; it is a fundamental necessity for the survival of our planet and the well-being of future generations. By raising awareness and promoting sustainable practices, we can collectively work towards a greener, cleaner, and more sustainable future.In conclusion, the environmental challenges we face are daunting, but they are not insurmountable. By embracing environmental awareness and taking collective action, we can inspire positive change and pave the way for a more sustainableworld. As students, we have the power to shape the future and leave a lasting legacy of environmental stewardship. Let us rise to the challenge and become the catalysts for a greener, healthier, and more harmonious coexistence with our planet.篇2Raising Environmental AwarenessAs a student, I am increasingly concerned about the state of our environment and the need to raise awareness about the critical issues we are facing. Environmental degradation poses a severe threat to our planet and its inhabitants, and it is our collective responsibility to take action and address this pressing challenge. In this essay, I will explore the importance of raising environmental awareness, discuss the key environmental problems we face, and propose strategies to promote greater understanding and encourage positive change.The impact of human activities on the environment has been profound and far-reaching. Climate change, driven by the emission of greenhouse gases, is causing rising temperatures, sea level rise, and extreme weather events. Deforestation, pollution, and the overexploitation of natural resources are also contributing to the deterioration of our planet's ecosystems.These issues not only endanger wildlife and biodiversity but also threaten human health, food security, and economic stability.One of the most pressing environmental concerns is climate change. The burning of fossil fuels for energy production and transportation has released vast quantities of carbon dioxide and other greenhouse gases into the atmosphere, trapping heat and causing global temperatures to rise. The consequences of this phenomenon are already being felt around the world, including more frequent and intense heatwaves, droughts, wildfires, and storms. Rising sea levels threaten coastal communities, and the melting of glaciers and polar ice caps could disrupt global weather patterns and water cycles.Another significant environmental issue is the loss of biodiversity. Human activities, such as deforestation, habitat destruction, and pollution, have driven countless species to the brink of extinction. The disappearance of these species can have cascading effects on entire ecosystems, disrupting food chains and diminishing the planet's ability to sustain life. Preserving biodiversity is not only important for maintaining a healthy and balanced environment but also for safeguarding potential sources of food, medicine, and other valuable resources.Pollution, in its various forms, also poses a severe threat to the environment and human health. Air pollution, caused by the burning of fossil fuels and industrial emissions, can lead to respiratory diseases and contribute to climate change. Water pollution, from industrial effluents, agricultural runoff, and improper waste disposal, contaminates our rivers, lakes, and oceans, endangering aquatic life and making water unsafe for human consumption. Plastic pollution, in particular, has become a global crisis, with vast amounts of plastic waste polluting our oceans and harming marine life.To address these environmental challenges, it is crucial to raise awareness and promote sustainable practices among individuals, communities, and governments. Education plays a vital role in this effort, as it empowers people with the knowledge and understanding necessary to make informed decisions and adopt environmentally responsible behaviors.Schools and universities should incorporate environmental education into their curricula, teaching students about the impacts of human activities on the environment and the importance of conservation and sustainability. Hands-on activities, such as school gardens, recycling programs, and field trips to natural areas, can help students develop a deeperconnection with the natural world and cultivate a sense of environmental stewardship.Beyond篇3Raising Environmental AwarenessWe live on a planet that's becoming sicker by the day. Human activities like pollution, deforestation, and overconsumption of natural resources are taking a massive toll on the environment. If we don't act now, future generations will inherit an uninhabitable world plagued by climate change, lack of clean air and water, and depleted natural resources. That's a future no one wants, which is why raising environmental awareness is so crucial.The impacts of environmental degradation are already evident all around us. Just look at the smog blanketing major cities, the shocking amounts of plastic polluting our oceans, or the rising global temperatures causing more frequent and intense natural disasters. These aren't just temporary issues - they're symptoms of humanity's careless treatment of our planet over decades. We simply cannot continue down this destructive path.Protecting the environment seems like an overwhelming challenge, but it becomes more manageable when every citizen does their part. After all, we all share the responsibility of being custodians of the Earth. Individuals can start by educating themselves on eco-friendly practices and being more conscious consumers. Simple things like reducing energy usage at home, minimizing plastic waste, and eating less meat can collectively make a big difference.Schools also play a pivotal role in nurturing environmental stewardship from a young age. More educational institutions should incorporate sustainability into their curriculums, teaching the next generation about conservation, renewable energy sources, and living in harmony with nature. Hands-on learning through school gardens, recycling initiatives, and field trips can go a long way in shaping eco-conscious mindsets early on.However, individual action alone isn't enough - governments and corporations must also prioritize environmental protection through stronger policies and regulations. Oil and gas companies need to transition towards renewable energy sources. Manufacturers should explore greener production methods and sustainable product designs. Agricultural practices have to shift from industrial farming thatrelies heavily on pesticides towards more eco-friendly techniques.Protecting forests, a critical carbon sink that slows climate change, should be another top priority. Deforestation, mainly caused by illegal logging and clearing land for agriculture, has had devastating consequences on biodiversity and indigenous communities who rely on forest resources for survival. Developed nations should provide more funding and resources towards conservation and reforestation efforts globally.In our consumer-driven society, the private sector's involvement is essential for raising environmental awareness as well. Brands have immense power to influence consumer behavior through their messaging and products. Companies should opt for eco-friendly packaging, sustainable sourcing of materials, and marketing that encourages shoppers to adopt greener lifestyles. Corporate social responsibility initiatives can fund environmental education programs and restoration projects.The media also needs to give more prominence to environmental reporting. Instead of burying climate news or giving undue airtime to skeptics, they should make this an urgent, front-page issue. Using their platforms to amplify thevoices of environmental activists, indigenous communities affected by eco-degradation, and scientific experts would go a long way in galvanizing public support for conservation efforts.On an individual level, each of us can be powerful agents of change through voting and activism. We should elect leaders who have robust, science-backed policies for environmental protection rather than those backed by corporate fossil fuel interests. Actively participating in protests, petitions, community clean-ups and other grassroots initiatives raises awareness and shows there is strong public demand for immediate climate action.Raising environmental awareness is the first step, but awareness without action is meaningless. As temporary inhabitants of this planet, it's our moral obligation to be responsible stewards and pass on a healthy, thriving Earth to future generations. We cannot afford inertia or complacency any longer. The time to protect our planet is now, before it's too late. Through collective action driven by a conscious society, we can absolutely build a more sustainable future for all.。
1. Elemental Analysis 元素分析Atomic absorption spectroscopy 原子吸收光谱Auger electron spectroscopy (AES) 俄歇电子能谱Electron probe microanalysis (EPMA) 电子探针微分析Electron spectroscopy for chemical analysis (ESCA) 化学分析电子能谱Energy dispersive spectroscopy (EDS) 能量色散谱Flame photometry 火焰光度法Wavelength dispersive spectroscopy (WDS)X-ray fluorescence X射线荧光2. Molecular and Solid State Analysis 分子与固态分析Chromatography [gas chromatography (GC), size exclusion chromatography (SEC)]色谱[气相色谱,体积排除色谱]Electron diffraction 电子衍射Electron microscopy [scanning electron microscopy (SEM),transmission electron microscopy (TEM),scanning TEM (STEM)] 电子显微镜Electron spin resonance (ESR) 电子自旋共振Infrared spectroscopy (IR) 红外光谱Mass spectrometry 质谱Mercury porosimetry 压汞法Mossbauer spectroscopy 穆斯堡尔谱Nuclear magnetic resonance (NMR) 核磁共振Neutron diffraction 中子衍射Optical microscopy 光学显微镜Optical rotatory dispersion (ORD) 旋光色散Raman spectroscopy 拉曼光谱Rutherford back scattering (RBS) 卢瑟福背散射Small angle x-ray scattering (SAXS) 小角X射线散射Thermal analysis [differential scanning calorimetry (DSC),thermal gravimetric analysis (TGA),differential thermal analysis (DTA) temperature desorption spectroscopy (TDS),thermomechanical analysis (TMA)]热分析[差示扫描量热计法,热-重分析,微分热分析,升温脱附,热机械分析]UV spectroscopy 紫外光谱X-ray techniques [x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), x-ray emission,x-ray absorption] X射线技术[x射线光电子能谱,x射线衍射,x射线发射,x射线吸收]3. Surface Characterization Techniques 表面表征技术Electron energy loss spectroscopy (EELS) 电子能量损失谱Ellipsometry 椭圆偏振术Extended x-ray absorption fine structure (EXAFS) 扩展X射线吸收精细结构Helium (or atom) diffractionLateral (or frictional) force microscopy (LFM) 横向(摩擦)力显微镜Low-energy electron diffraction (LEED) 低能电子衍射Magnetic force microscopy (MFM) 磁力显微镜Near-edge x-ray adsorption fine structure (NEXAFS) 近边X射线吸收精细结构Near field scanning 近场扫描Reflection high-energy electron diffraction (RHEED) 反射高能电子衍射Scanning tunneling microscopy (STM) 扫描隧道显微镜Scanning force microscopy (SFM) 扫描力显微镜Secondary ion mass spectroscopy (SIMS) 二次离子质谱Surface enhanced raman spectroscopy (SERS) 表面增强拉曼光谱Surface extended x-ray adsorption fine structure (SEXAFS) 表面扩展X射线吸收精细结构Surface force apparatus 表面力仪器。
环保英文比赛演讲稿(五篇)篇一:环保英文比赛演讲稿There are still many problems of environmental protection in recent years。
One of the most serious problems is the serious pollution of air,water and soil。
the polluted air does great harm to people’s health。
The polluted water causes diseases and death。
What is more,vegetation had been greatly reduced with the rapid growth of modern cities。
To protect the environment,governments of many countries have done a lot。
Legislative steps have been introduced to control air pollution,to protect the forest and sea resources and to stop any environmental pollution。
Therefore,governments are playing the most important role in the environmental protection today。
In my opinion,to protect environment,the government must take even more concrete measures。
First,it should let people fully realize the importance of environmental protection through education。
关于人类不当行为伤害地球的英语作文全文共3篇示例,供读者参考篇1Our Planet is Suffering Because of Humanity's ActionsAs students, we are often reminded by our teachers and parents about the importance of taking care of our planet. They tell us that the Earth is our home and that we need to protect it for future generations. However, despite all the warnings and pleas, human activities continue to inflict immense damage upon the environment, pushing our planet to the brink of crisis. It is time for us to wake up and acknowledge the grave consequences of our actions before it's too late.One of the most significant threats to our planet is the issue of climate change, primarily driven by the excessive emission of greenhouse gases. The burning of fossil fuels for energy production, transportation, and industrial activities has led to a steady increase in atmospheric carbon dioxide levels. This, in turn, has caused a rise in global temperatures, resulting in melting glaciers, rising sea levels, and more frequent and intense weather events such as hurricanes, droughts, and heatwaves.The effects of climate change are already being felt across the globe. Many regions are experiencing prolonged droughts, leading to water scarcity and crop failures, which could potentially trigger food shortages and famine. Rising sea levels are also threatening coastal communities, with some low-lying islands at risk of being submerged entirely. Furthermore, the loss of biodiversity due to habitat destruction and changing environmental conditions is a grave concern, as countless plant and animal species face the risk of extinction.Another pressing issue is the rampant deforestation occurring in many parts of the world. Forests are crucial for maintaining the Earth's delicate ecological balance, as they act as carbon sinks, absorbing and storing vast amounts of carbon dioxide from the atmosphere. However, the insatiable demand for agricultural land, timber, and urbanization has led to the widespread clearing of forests, releasing stored carbon back into the atmosphere and further exacerbating climate change.The consequences of deforestation extend beyond just its impact on climate. It also contributes to soil erosion, loss of biodiversity, and disruption of the water cycle, potentially leading to droughts and floods. Indigenous communities thatrely on forests for their livelihoods and cultural practices are also adversely affected, as their ancestral lands are stripped away.Pollution is another significant threat to our planet'swell-being. The reckless disposal of waste, the release of industrial effluents into waterways, and the burning of fossil fuels have all contributed to the contamination of our air, water, and soil. This pollution not only harms the environment but also poses serious health risks to humans and other living beings.Plastic pollution, in particular, has become a global crisis. Millions of tons of plastic waste end up in our oceans each year, forming massive garbage patches that endanger marine life. Microplastics, the tiny fragments resulting from the breakdown of larger plastic pieces, have even made their way into the food chain, potentially causing long-term health implications for both humans and animals.Overconsumption and unsustainable resource exploitation are also taking a toll on our planet. The relentless pursuit of economic growth and material wealth has led to theover-exploitation of natural resources, such as forests, minerals, and fossil fuels. This unsustainable rate of consumption not only depletes these finite resources but also generates vast amounts of waste and pollution.Furthermore, our current linear economic model, based on the principles of "take, make, and dispose," is fundamentally flawed. We extract resources from the Earth, transform them into products, and discard them after use, without considering the environmental impact of this process. This approach is simply not sustainable in the long run, as it fails to account for the limited carrying capacity of our planet.As students, we have a crucial role to play in addressing these pressing environmental issues. We must educate ourselves and others about the severity of the situation and the urgency for action. It is our responsibility to make informed choices and adopt sustainable lifestyles, such as reducing our carbon footprint, minimizing waste, and supporting eco-friendly initiatives.We can start by making simple changes in our daily lives, such as conserving energy, reducing our plastic consumption, and adopting a plant-based diet. These small steps may seem insignificant individually, but when multiplied by millions of people, they can have a profound impact on the environment.Additionally, we should actively participate in environmental campaigns, protests, and initiatives that raise awareness and advocate for policy changes. By raising our voices anddemanding action from governments and corporations, we can drive the necessary systemic changes required to protect our planet.Education is also a powerful tool in our fight against environmental degradation. As students, we have the opportunity to learn about sustainable practices, ecological principles, and the interconnectedness of all living beings. By incorporating environmental education into our curricula, we can foster a generation of informed and responsible citizens who are equipped to tackle these challenges head-on.Ultimately, the fate of our planet lies in our hands. We cannot afford to remain passive observers as the Earth's resources are depleted and its ecosystems are pushed to the brink of collapse. It is our moral imperative to take decisive action and course-correct before it's too late.We must remember that we are not separate from nature; we are intrinsically connected to it. The well-being of our planet is inextricably linked to our own survival and prosperity. By preserving and protecting the Earth, we are ensuring a habitable and sustainable future for ourselves and generations to come.Let us not be remembered as the generation that stood idly by as our planet suffered. Instead, let us be the generation thattook bold and courageous steps to safeguard our home, our Earth. The time to act is now, and the responsibility falls upon each and every one of us.篇2Our Planet in Peril: A Plea to Protect Mother EarthAs a young person growing up in today's world, I can't help but feel a deep sense of concern and even fear for the future of our planet. Everywhere I look, I see evidence of human actions causing immense harm to the delicate balance of nature that sustains all life on Earth. It's a harsh reality that we can no longer ignore.One of the most pressing issues facing our generation is climate change, a phenomenon largely driven by human activities that release greenhouse gases into the atmosphere. The burning of fossil fuels for energy, transportation, and industrial processes has led to a significant increase in carbon dioxide levels, trapping more heat within our atmosphere and causing global temperatures to rise at an alarming rate.The consequences of this warming trend are far-reaching and already manifesting in devastating ways. We are witnessing more frequent and intense natural disasters, such as hurricanes,wildfires, and droughts, which not only endanger human lives but also disrupt entire ecosystems and threaten the survival of countless species. Rising sea levels due to melting glaciers and ice caps are putting coastal communities at risk of flooding and displacement.But climate change is just one facet of the environmental crisis we face. Deforestation, another major issue exacerbated by human activity, is robbing our planet of its vital green lungs. Vast swaths of forests are being cleared, often illegally, to make way for agricultural expansion, urbanization, and resource extraction. Not only does this destroy the habitats of countless species, but it also diminishes the Earth's ability to absorb carbon dioxide and produce oxygen, further compounding the effects of climate change.The loss of biodiversity is another alarming consequence of our unsustainable practices. Species are going extinct at an unprecedented rate, primarily due to habitat loss, pollution, and overexploitation. Each species plays a crucial role in the intricate web of life, and their disappearance can have cascading effects on entire ecosystems, disrupting the delicate balance that has taken millions of years to evolve.Our oceans, which cover over 70% of the planet's surface, are also under severe stress due to human activities. Overfishing has depleted many marine populations to critical levels, while plastic pollution and chemical runoff are choking the very life out of these vast waters. Coral reefs, often referred to as the rainforests of the ocean, are dying at an alarming rate due to rising ocean temperatures and acidification caused by increased carbon dioxide absorption.It's easy to feel overwhelmed and powerless in the face of such daunting challenges, but we mustn't succumb to despair or inaction. As the inheritors of this planet, it is our collective responsibility to take immediate and decisive steps to protect and preserve the natural world for future generations.One of the most important things we can do is to educate ourselves and others about the urgency of the environmental crisis. Knowledge is power, and by spreading awareness and understanding, we can inspire more people to make sustainable choices and demand action from our leaders and policymakers.We must also make concerted efforts to reduce our individual carbon footprints by adopting eco-friendly practices in our daily lives. This can include simple actions such as conserving energy, reducing waste, recycling, and choosingmore sustainable transportation options. Every small step counts, and when multiplied by millions of people, these actions can have a profound impact.Furthermore, we should support and encourage the development of renewable energy sources, such as solar, wind, and hydroelectric power, as alternatives to fossil fuels. Investing in clean technologies and promoting their widespread adoption is crucial for mitigating the effects of climate change and reducing our reliance on finite, polluting resources.Protecting and restoring natural habitats is another critical aspect of safeguarding our planet's biodiversity. We must advocate for the preservation of remaining wilderness areas and support conservation efforts aimed at protecting endangered species and their habitats. Additionally, we should promote sustainable agriculture and forestry practices that work in harmony with nature rather than against it.Ultimately, addressing the environmental crisis requires a collective effort from individuals, communities, governments, and international organizations. We must demand stronger environmental regulations and policies that prioritize the health of our planet over short-term economic gains. Governmentsmust take bold and decisive action to transition towards a more sustainable and eco-friendly future.As a student, I recognize that my generation has a unique opportunity and responsibility to shape the future of our planet. We are the ones who will inherit the consequences of today's actions, and we must use our voices, our knowledge, and our passion to drive positive change.I implore you, my fellow students, to join me in this fight to protect our planet. Let us be the generation that turns the tide against environmental destruction and ushers in a new era of sustainability and harmony with nature. Our actions today will determine the fate of countless species, including our own, and the health of the planet we call home.The time for complacency and inaction has passed. We must rise to the challenge and become champions of the Earth, fighting tirelessly to preserve its beauty, its diversity, and its ability to sustain life for generations to come. Our planet is in peril, but it is not too late to reverse the damage if we act now with unwavering determination and a shared commitment to protect our precious Mother Earth.篇3The Devastating Impact of Human Activities on Our PlanetAs a student, it pains me to see the destruction we are causing to the Earth through our reckless and unsustainable actions. Every day, we witness the alarming consequences of our behavior, from melting glaciers and rising sea levels to deforestation, pollution, and the rapid extinction of countless plant and animal species. It's a sobering reality that demands our immediate attention and collective action.One of the most pressing issues is the ongoing climate crisis, fueled primarily by our reliance on fossil fuels and the resulting greenhouse gas emissions. The burning of coal, oil, and natural gas for energy, transportation, and industrial processes has led to a significant increase in atmospheric carbon dioxide levels, trapping heat and disrupting the planet's delicate climate systems. The effects of this are already evident in the form of extreme weather events, such as hurricanes, wildfires, droughts, and heatwaves, which have become more frequent and intense in recent years.Moreover, the melting of polar ice caps and glaciers due to rising temperatures is a grave concern. These vast reservoirs of freshwater are vital for regulating global weather patterns and sustaining countless ecosystems. Their rapid disappearance notonly contributes to rising sea levels, which threaten coastal communities and entire nations, but also disrupts the intricate balance of our planet's water cycle, with far-reaching consequences for agriculture, biodiversity, and human survival.Deforestation, another devastating human activity, has had a catastrophic impact on our planet's ecosystems. Forests, often referred to as the "lungs of the Earth," play a crucial role in absorbing carbon dioxide and producing oxygen, regulating temperatures, and providing habitats for countless species. However, due to human activities such as logging, agriculture, and urbanization, we are destroying these invaluable resources at an alarming rate. The loss of forests not only exacerbates climate change but also contributes to soil erosion, water scarcity, and the extinction of countless plant and animal species, many of which have yet to be discovered or understood.Pollution, another byproduct of human activities, is a silent killer that threatens the very fabric of life on our planet. From plastic waste choking our oceans and poisoning marine life to toxic emissions from factories and vehicles contaminating the air we breathe, the impact of pollution is far-reaching and devastating. It not only harms ecosystems and biodiversity but also poses grave risks to human health, contributing torespiratory illnesses, cancer, and other life-threatening conditions.As if these challenges weren't daunting enough, the rapid extinction of species due to human activities is a tragic reality that must be addressed. Every day, countless plant and animal species are pushed to the brink of extinction due to habitat loss, poaching, climate change, and other human-induced pressures. This loss of biodiversity not only robs our planet of its rich tapestry of life but also disrupts the delicate balance of ecosystems, which we rely upon for our own survival.It's easy to feel overwhelmed and powerless in the face of such monumental challenges, but we must not lose hope. As students, we have the opportunity to be agents of change, armed with knowledge, passion, and a deep understanding of the urgency of this crisis. We must embrace sustainability as a way of life, making conscious choices in our daily lives to reduce our carbon footprint, conserve resources, and protect the environment.This starts with simple actions, such as reducing energy consumption, recycling, and minimizing waste. It means advocating for renewable energy sources and supporting policies that promote environmental protection. It involveseducating ourselves and others about the impact of our actions and the importance of preserving our planet's precious resources.Furthermore, we must demand accountability from governments, corporations, and institutions that contribute to environmental degradation. We must use our voices to call for stricter regulations, sustainable practices, and a shift towards a more eco-friendly and circular economy that prioritizes the well-being of our planet over short-term profits.Ultimately, the fate of our planet lies in our hands. We can no longer afford to be complacent or indifferent to the consequences of our actions. As the future stewards of this Earth, we must embrace a mindset of responsibility, empathy, and foresight, recognizing that our choices today will shape the world we leave for future generations.The path ahead is undoubtedly challenging, but it is a journey we must undertake with unwavering determination and collective effort. By embracing sustainability, promoting environmental awareness, and demanding action from those in positions of power, we can slowly but surely heal the wounds we have inflicted upon our planet and pave the way for a brighter, more sustainable future.Let us not be remembered as the generation that stood idly by as our planet suffered. Instead, let us be the generation that took a stand, made sacrifices, and fought tirelessly to protect the Earth, our one and only home. The time for action is now, and the future of our planet depends on the choices we make today.。
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a rXiv:as tr o-ph/37385v122J ul23Disappearance of Hard X-ray Emission in the Last BeppoSAX Observation of the Z Source GX 349+2R.Iaria 1,T.Di Salvo 1,2,N.R.Robba 1,L.Burderi 3,L.Stella 3,F.Frontera 4,5,M.van der Klis 2ABSTRACT We report on the results from two BeppoSAX observations of the Z source GX 349+2performed in February 2001and covering the broad energy range 0.12–200keV.The light curve obtained from these observations shows a large flaring activity,the count rate varying from ∼130to ∼260counts s −1,indi-cating that the source was in the flaring branch during these observations.The average spectrum is well described by a soft blackbody (kT BB ∼0.5keV)and a Comptonized component having a seed-photon temperature of kT 0∼1keV,an electron temperature of kT e ∼2.7keV,and optical depth τ∼11.To well fit the energy spectrum three gaussian lines are needed at 1.2keV,2.6keV,and 6.7keV with corresponding equivalent widths of 13eV,10eV,and 39eV,probably associated to L-shell emission of Fe XXIV,Ly αS XVI,and Fe XXV,respectively.These lines may be produced at different distances from the neutron star,which increase when the count rate of the source increases.An absorption edge is also needed at 9keV with an optical depth of ∼3×10−2.From the Color-Color Diagram (CD)we selected five zones from which we extracted the correspond-ing energy spectra.The temperatures of the blackbody and of the Comptonized component tend to increase when the intensity of the source increases.We dis-cuss our results comparing them to those obtained from a previous BeppoSAX observation,performed in March 2000,during which the source was a similarposition of its Z-track.In particular we find that,although the source showed similar spectral states in the 2000and the 2001observations,a hard tail,that was significantly detected in March 2000,is not observed in these recent observations.Subject headings:accretion discs–stars:individual:GX349+2—stars:neutronstars—X-ray:stars—X-ray:spectrum—X-ray:general1.IntroductionLow Mass X-ray Binaries(LMXB)containing old and low magnetic-field neutron stars (NS)are usually divided into Z and Atoll sources,according to the path they describe in an X-ray Color-Color Diagram(CD)or hardness-intensity diagram(Hasinger&van der Klis1989)assembled by using the source count rate over a typical(usually2–20keV)X-ray energy range.Atoll sources are usually characterized by relatively low luminosities (∼0.01−0.2L Edd)and some show transient behavior,while the six known Z sources in the Galaxy are among the most luminous LMXBs,accreting persistently close to the Eddington limit(L Edd)for a1.4M⊙NS.The instantaneous position of an individual source in the CD, which determines most of the observed spectral and temporal properties of the source,is thought to be an indicator of the mass accretion rate(e.g.Hasinger et al.1990;see van der Klis1995for a review).It has been suggested that the mass accretion rate(but not necessarily the X-ray luminosity)of individual sources increases along the track from the top left to the bottom right,i.e.from the islands to the banana branch in atoll sources and from the horizontal branch(hereafter HB)to the normal branch(NB)and to theflaring branch (FB)in Z sources.However,while there is a general correlation between temporal variability properties (in particular frequencies of the observed quasi periodic oscillations,QPOs,see van der Klis 2000for a review)and position in the CD,the correlation with the source X-ray count rate or X-rayflux in the2–50keV energy range is complex;a correlation is observed on short time scales(hours to days),but not on longer time scales.A possible explanation of this behavior is that most timing and spectral parameters are determined by the dynamical properties of the accretion disk,while the X-rayflux is determined by the total accretion rate,which may be different from the instantaneous accretion rate through the disk if,for instance,matter canflow radially close to the NS(see e.g.van der Klis2001).Hard X-ray spectra extending up to energies of several tens to hundred keV have been revealed in about20“faint”NS LMXBs(some of them are confirmed Atoll sources,see Di Salvo&Stella2002for a review).In these systems a power law-like component is observed, with typical photon indices of∼1.5−2.5,and a high energy exponential cutoffbetween ∼20and many tens of keV.This component is interpreted in terms of unsaturated thermal Comptonization.Sometimes,in the so called”hard state”of atoll sources,there is no evidence for a cutoffup to∼100−200keV.Some sources appear to spend most of thetime in this state(e.g.4U0614+091,Ford et al.1996;Piraino et al.1999,and references therein).In others a gradual transition from the soft to the hard state has been observed in response to a decrease of the source X-ray luminosity and/or the source drifting from the banana branch to the island state.This transition is often modelled in terms of a gradual decrease of the electron temperature(and increase of the optical depth)of the Comptonizing region.On the other hand,the spectrum of the Z sources is much softer,with cutoffenergies usually well below10keV.However,hard tails were occasionally detected in their spectra.A variable hard component dominating the spectrum of Sco X–1above∼40keV was detected as early as1966(Peterson&Jacobsen1966;see also Riegler et al.1970;Agrawal et al. 1971;Haymes et al.1972).In other occasions the hard tail in Sco X–1was not found(e.g., Miyamoto&Matsuoka1977,and references therein;Soong&Rothschild1983;Jain et al. 1984;Ubertini et al.1992),perhaps owing to pronounced variations.Evidence for a hard component was also found in Cyg X–2(Peterson1973),GX349+2(Greenhill et al.1979), and in Ginga data of GX5–1(although in this case a contribution from a contaminating source could not be excluded,Asai et al.1994).Renewed interest in the hard X-ray emission properties of luminous LMXBs was moti-vated by some recent observations,mostly using the broad band capabilities of BeppoSAX (0.1–200keV)and RXTE(2–220keV).Recently a hard tail was detected in GX17+2, observed by BeppoSAX.In this case the intensity variations of the hard tail were clearly correlated with the source spectral state:a factor of20decrease was observed moving from the HB to the NB(Di Salvo et al.2000).The presence of a variable hard tail in Sco X–1was recently confirmed by OSSE and RXTE observations(Strickman&Barret2000;D’Amico et al.2001).A hard tail was also detected in GX349+2(Di Salvo et al.2001,hereafter Paper I)and Cyg X–2(Frontera et al.1998;Di Salvo et al.2002),as well as in the peculiar bright LMXB Cir X–1(Iaria et al.2001).These hard components can befitted by a power law,with photon index in the range1.9–3.3,contributing up to10%of the total source luminosity.GX349+2,also known as Sco X–2,was called an odd-ball among the Z sources(Ku-ulkers&van der Klis1998).Similar to the case of Sco X–1,GX349+2shows a short and underdeveloped HB(if at all).The source variability in the frequency range below100Hz is closely correlated with the source position on the X-ray CD,as in other Z sources.Quasi periodic oscillations at kHz frequencies(kHz QPO)were detected in the NB of its Z-track (Zhang,Strohmayer,&Swank1998).However,GX349+2,which sometimes shows broad noise components changing not only with the position in the Z,but also as a function of the position in the hardness-intensity diagram,differs somewhat from the other Z sources andshows similarities to the behavior seen in bright atoll sources,such as GX13+1and GX 3+1(Kuulkers&van der Klis1998;see also O’Neill et al.2001,2002).Using a BeppoSAX observation performed in March2000,Di Salvo et al.(2001)showed that the source energy spectrum below30keV could be wellfit by a blackbody(with a temperature of0.5–0.6keV) and a Comptonized component(with seed-photon temperature of∼1keV and electron tem-perature of∼2.7keV).Three discrete features were observed in the spectrum:an emission line at1.2keV,probably associated to Ne X or a complex L-shell of Fe XXIV,an emission line at6.7keV and an absorption edge at8.5keV,both corresponding to emission from the K-shell of highly-ionized iron(Fe XXV).Above30keV,during the non-flaring state,a power-law component was significantly detected having a photon index of∼1.9and aflux of∼1.2×10−10erg cm−2s−1in the energy band10–60keV.Because there was no evidence of contaminating sources,the authors concluded that the most probable candidate for the hard emission was GX349+2itself.The hard component detected in GX349+2is one of the hardest among the high energy components detected so far in bright LMXBs,with no evidence for a high energy cutoffin the BeppoSAX range(up to∼100keV).In this paper we report the results of a spectral study of a long(∼200ks)BeppoSAX observation of GX349+2in the energy range0.1–200keV.Wefind that,although the spec-trum below30keV is similar to that observed during the observation reported on Paper I, the hard component is not present(or significantly weaker)during our observation,demon-strating that these hard tails can be highly variable and are probably not univocally related to the position in the CD.2.ObservationsThe Narrow Field Instruments(NFI)on board the BeppoSAX satellite are four co-aligned instruments which cover more than three decades in energy,from0.1keV up to 200keV,with good spectral resolution over the whole range(see Boella et al.1997a for de-tailed description of BeppoSAX instruments).These are two Medium Energy Concentrator Spectrometers,MECS(position sensitive proportional counters operating in the1.3–10keV band,Boella et al.1997b),a Low Energy Concentrator Spectrometer,LECS(a thin window position sensitive proportional counter with extended low energy response,0.1–10keV;Par-mar et al.1997),a High Pressure Gas Scintillation Proportional Counter(HPGSPC;energy range of7–60keV;Manzo et al.1997)and a Phoswich Detection System(PDS;energy range of13–200keV;Frontera et al.1997).In this paper we report on two BeppoSAX observations of GX349+2.The source was observed from2001February1211:23UT to2001February1317:43UT and from2001February1716:15UT to2001February1920:42UT.The total effective exposure times are ∼30ks for the LECS,∼138ks for the MECS,∼130ks for the HPGSPC,and∼66ks for the PDS.We selected the data for the spectral analysis in circular regions centered on the source with8′and4′radius for LECS and MECS,respectively.The background subtraction was obtained with standard methods by using blank sky observations.The background subtraction for the high-energy(non-imaging)instruments was obtained by using off-source data for the PDS and Earth occultation data for the HPGSPC.In Figures1and2(lower panels)we show the200s binned MECS light curve of GX349+2in the1.8–10.5keV range for thefirst and the second observation,respectively; the light curve presents a large variability and the count rate varies from130c/s up to260 c/s.In the upper and middle panels we plot the Soft Color(SC),i.e.the ratio of the counts in the4.5–7keV to the1.8–4.5keV band,and the Hard Color(HC),i.e.the ratio of the counts in the7–10.5keV to the4.5–7keV energy band,as functions of time.In Figure3we show the CD of GX349+2,where the HC and the SC are as defined above.The red triangles and the black stars indicate the positions of the source in the CD during a previous BeppoSAX observation taken in March2000(see Paper I)and during our observations,respectively.From thisfigure it is clear that the position in the Z-track was approximately the same during all the observations.To study the spectral variability along the CD we selectedfive regions in the CD:SC<0.47(interval1),0.47<SC<0.50(interval 2),0.50<SC<0.55(interval3),0.55<SC<0.60(interval4),SC>0.64(interval5),from which we extracted the corresponding count spectra.In Figure4we show the Hardness-Intensity Diagram(HID)where the Color on the y-axis is the SC and the Intensity is the count rate of the source in the energy band1.8–10.5 keV.The SC is a linear function of the Intensity.Wefitted the points using a linear relation y=mx+q obtaining as bestfit m=(1.65±0.02)×10−3and q=0.235±0.004.This allows us to associate to the regions selected in the CD the corresponding count rate.In Table1we report the exposure times of the four instruments for each selected region and the corresponding count rate.3.Spectral AnalysisWe extracted an averaged spectrum from the whole observation which is discussed in §3.1.In section§3.2we present the results obtained from the spectra selected in different regions of the CD.Relative normalizations of the four NFIs were treated as free parameters in modelfitting,except for the MECS normalization which wasfixed to a reference value of1.We checked after thefitting procedure that these normalizations were in the standard range for each instrument6.The energy ranges used in the spectral analysis were:0.12–3.5keV for the LECS,1.8–10keV for the MECS,7–30keV for the HPGSPC,and15–200keV for the PDS.We rebinned the energy spectra in order to have approximately the same number of bins per instrument resolution element across the entire energy range.A1%systematic error was applied to the spectra selected in different regions of the CD,and a2%systematic error was applied to the averaged spectrum to take into account possible variability of the spectrum during the observation.3.1.The Averaged SpectrumWe extracted an averaged spectrum from the two BeppoSAX observations.Following the results of Paper I,we startedfitting the continuum with a blackbody plus a Comptonized component(Comptt,Titarchuk1994)obtaining aχ2(d.o.f.)of309(197).In the residuals with respect to this model(see Fig.5,middle panel)wefind the presence of a weak hard excess at energies higher than35keV.Evident localized excesses are also present around1.2 keV,2.6keV and6.7keV and an absorption feature is present between9and10keV.Thefit can be significantly improved by the addition of the components described below. We added a power-law component with photon index of1.52tofit the hard excess;an F-test gives a probability of chance improvement of thefit for the addition of this component of 1.9×10−7.We added an absorption edge tofit the feature between9and10keV;the energy of the absorption edge is∼9keV and its optical depth isτ∼3×10−2.Tofit the localized excesses we used three narrow gaussian emission lines.Initially we added a gaussian line having its centroid at1.18keV and equivalent width∼13eV,its addition gave a probability of chance improvement of1.1×10−8;then we added a gaussian line having its centroid at2.6keV and equivalent width∼10eV,its addition gave a probability of chance improvement of∼2.1×10−5;andfinally we added a gaussian line having its centroid at6.75 keV and equivalent width∼39eV,its addition gave a probability of chance improvement of∼1.6×10−9.Theχ2(d.o.f.)of the bestfit model is149(184).In Figure5(upper and lower panels)we plot the data and the residuals corresponding to the bestfit model described above and in Figure6we plot the corresponding unfolded spectrum.In Tables2and3we report the parameters of the continuum and of the narrow features,respectively.Theflux of the blackbody and of the Comptonized component in the energy band0.1-200keV are0.45×10−8erg cm−2s−1and∼2×10−8erg cm−2s−1,respectively.Theflux of the power-law component in the energy band10-60keV is∼2.2×10−11erg cm−2s−1,approximately one order of magnitude lower than the hard power-lawflux during the observation reported on Paper I.3.2.Spectral analysis as a function of the source position in the CDWefitted thefive spectra extracted from different positions in the source CD(see Fig.3) using the model adopted for the averaged spectrum,keeping the photon index of the power-law componentfixed at1.52,the value obtained from thefit of the averaged spectrum.This model gives an acceptablefit for all the spectra.In Tables4and5we report the parameters of the continuum and of the narrow features for each spectrum.Going from interval1 to interval5,that is going to higher intensity of the source,theflux of the blackbody component increases from0.39×10−8erg cm−2s−1to0.50×10−8erg cm−2s−1,theflux of the Comptonized component increases from∼1.45×10−8erg cm−2s−1to∼3.0×10−8erg cm−2 s−1;the temperatures of the blackbody and of the Comptonized components also increase. In Figure7we show thefluxes and the temperatures of the blackbody and Comptonized components as function of the count rate.The addition of the gaussian line at1.18keV is statistically significant in intervals1,2 and3,and its equivalent width varies between12and20eV.The addition of the gaussian line at2.6keV is significant in intervals1,2,3and4and its equivalent width is8eV. The addition of the the gaussian line at6.7keV is statistically significant in each interval and its equivalent width decreases from80eV to18eV going from interval1to interval5. The decrease of the equivalent width is due to both an increase of the continuumflux and a decrease of the line intensity.The addition of an absorption edge at∼9keV,with an optical depth of∼0.03,is always statistically significant.The addition of the power-law component is significant in interval1and interval3and theflux,in the energy band10–60 keV is between1.4×10−11erg cm−2s−1and2.8×10−11erg cm−2s−1,as reported in Table 4,similar to the value found for the averaged spectrum.4.DiscussionWe studied the BeppoSAX energy spectra of GX349+2,extracted at different positions of the source in the CD.The bestfit model up to energies of∼30keV consists of a blackbody and a Comptonization spectrum(described by the Comptt model),three emission lines and an absorption edge.The equivalent hydrogen column,N H,derived from the best-fit model is∼0.67×1022 cm−2,in agreement with the results of Paper I.Cooke&Ponman(1991),using data from the medium and low energy X-ray detectors on EXOSAT,obtained a value of(0.86±0.01)×1022 cm−2,and evaluated the visual extinction in the direction of the source to be A V=3.9±0.5 mag;a similar value of∼0.8×1022cm−2,which implies a distance to GX349+2of5 kpc,was reported by Christian&Swank(1997)using the Einstein solid-state spectrometer (SSS;0.5–4.5keV).Using the value of the equivalent hydrogen column to the source that we obtain from the BeppoSAX observations,we can recalculate the visual extinction from the observed correlation between visual extinction and absorption column(Predehl&Schmitt, 1995);this gives A V≃3.6−4.1mag,still compatible with the values previously reported (Cooke&Ponman1991;Penninx&Augusteijn1991).In the direction of GX349+2,this would correspond to a distance between3.6and4.4kpc(Hakkila et al.1997).These values are not very different from5kpc.Therefore we will continue to adopt5kpc for the distance to GX349+2to facilitate the comparison with previous results.Note,however,that all the luminosities quoted here can be lower by a factor of∼1.3−1.9.The blackbody temperature is kT BB∼0.5−0.6keV,its luminosity,in the energy range 0.1–200keV,is∼1.34×1037erg s−1and the radius of the blackbody emitting region is R BB∼36km.The blackbody temperature andflux both increase with increasing the source luminosity(see Fig.7),while the blackbody radius does not significantly change.The lumi-nosity of the Comptonized component,in the0.1-200keV band,is∼3.4×1037erg s−1,80%of the total luminosity,and is∼20%of the Eddington luminosity for a1.4M⊙NS.The temper-ature of the soft seed photons for the Comptonization is kT0∼1keV.These are Comptonized in a hotter(kT e∼3keV)region of moderate optical depth(τ=10−12for a spherical geometry).The radius of the region emitting the seed-photon Wien spectrum,calculated as in In’t Zand et al.(1999),is R W=3×104Dincreasing the source luminosity,which can be associated with emission from the L-shell of Fe XXIV(see e.g.Kallman et al.1996),and an emission line at2.6keV,with equivalent width of10eV,which can be associated with Lyαemission from S XVI.The ionization parameters,Log10ξ,corresponding to S XVI,Fe XXIV and Fe XXV are 3.1,3.04and3.67,respectively.Fromξ=L x/n e r2(see Krolik,McKee&Tarter1981)and L line=4πD2I line=n2e VαAf we can obtain the distance,r,from the central source,and the corresponding densities,of the region where the lines are produced.In these formulas L x is the total unabsorbed luminosity of the source,n e the electron density,L line the luminosity of the line,D the distance to the source,I line the intensity of the line,V the emitting volume,αthe recombination parameter,A the cosmic abundance of the element and f the fractional number of ions in the given ionization state of the considered element.We assumed a spherical volume of radius r andfixed f=1.The recombination parameterαwas obtained using the relation and the bestfit parameters for S XVI,Fe XXIV and Fe XXV reported by Verner&Ferland(1996),where wefixed the plasma temperature at the electron temperature of the Comptonizing cloud.For the averaged spectrum wefind that the Fe XXV line is produced at r=5.1×109cm with a corresponding electron density of n e=5.9×1014cm−3,the S XVI line at r=1.0×1010cm with n e=5.7×1014cm−3 and,finally,the Fe XXIV line at r=2.6×1010cm with n e=9.2×1013cm−3.On the other hand if we assume that the Comptonizing cloud is indeed an Accretion Disc Corona (ADC),where the coronal temperature is the electron temperature of the cloud,then the coronal radius is R c∼M NS/M⊙T−17R⊙(White&Holt1982),where M NS is the NS mass and T7the coronal temperature in units of107K.Assuming a NS mass of1.4M⊙and the electron temperature obtained from thefit wefind R c∼3×1010cm.This implies that the Fe XXV line is produced at r∼0.17R c,the S XVI line at r∼0.34R c and the Fe XXIV line at r∼0.87R c.The Fe XXV line is broader than the S XVI and Fe XXIV lines probably because it is produced in the inner region of the corona and the the escaping photons are more affected by Compton scattering.A weak narrow absorption feature is present at∼4.2keV.Wefitted this component using an absorption edge and found an upper limit of the optical depth ofτ∼3.82×10−2. This absorption edge could correspond to K-edge of Ar XVII,dominating at a ionization parameter of Log10ξ∼3.The corresponding Ar XVII emission line should be found at∼3.14 keV.Supposing that it is produced in the same region of Fe XXIV,that is the external region of the corona,and using the parameters of density and radius obtained for Fe XXIV,the cosmic abundance of Ar and the corresponding recombination parameter(Verner&Ferland 1996)we obtain an intensity of the Ar XVII line of∼1.1×10−3photons cm−2s−1;from thefit wefind a compatible upper limit of the intensity of∼2×10−3photons cm−2s−1 implying that the Ar XVII line may be overwhelmed by the continuum emission.We repeated the same procedure for the spectra extracted in the different region of the CD in order to study the emission region of the lines at different source luminosities;the results,for the statistically significant lines,are reported in Table6.It is evident that when the count rate increases the formation region of the lines moves at larger radii where the density is lower.One of the main results of this paper regards the hard component.At energies higher30 keV a hard excess is indeed present in our observations.However,the10–60keVflux of the power-law component that we used tofit this hard excess is one order of magnitude lower than that measured during the BeppoSAX observation of March2000(Paper I),although the source was in a similar position of the Z track.In Paper I a hard component was required to match the spectrum above30keV during the non-flaring emission.This component could befit by a power-law with photon index∼2and with aflux of1.2×10−10ergs cm−2s−1 in the energy range10–60keV.In our observations the photon index of the power law is 1.5(still compatible with the previous value),while theflux in the same energy band is ∼2×10−11ergs cm−2s−1.Indeed we cannot exclude that the power law wefit during our observations is due to the hard diffuse emission of the Galactic ing data from Valinia&Marshall(1998),for latitudes1.5◦<|b|<4◦and longitudes|l|<15◦(the region of GX349+2)theflux of the diffuse Galactic emission is∼3.2×10−11ergs cm−2s−1in the10–60keV energy range for the effective solid angle of the PDS FOV and the photon index of the power-law is1.7±0.2.These values are compatible to those we found in our analysis of GX349+2.We conclude that the hard power-law component during these new BeppoSAX observations is much weaker or even absent.A hard power-law component was observed in several Z sources,indicating that this is probably a common feature of these sources.The presence(or strength)of these components appears sometimes to be related to the source state or its position in the CD.The only clear example of this behavior was given by a BeppoSAX observation of GX17+2.In this source the intensity of the hard component(a power-law with photon index of∼2.7)showed the strongest intensity in the HB of its CD;a factor of∼20decrease was observed when the source moved from the HB to the NB,i.e.from low to high inferred mass accretion rate.For other sources some evidence was found that the hard component becomes weaker for higher accretion rates(GX5–1,Asai et al.1994;GX349+2,Paper I;Cyg X–2,Di Salvo et al.2002; Cir X–1,Iaria et al.2001).However,in recent RXTE/HEXTE observations of Sco X–1,a hard power-law tail was detected in5out of16observations,without any clear correlation with the position in the CD(D’Amico et al.2001).GX349+2may show a behavior that is similar to the one observed in Sco X–1.Indeed GX349+2,as well as GX17+2,is classified as a Sco-like source,which are thought to have a lower inclination than the other Z sources (referred to as Cyg-like sources;Kuulkers et al.1994;Kuulkers&van der Klis1995),andsimilarly to Sco X–1(but not to GX17+2),does spend a relatively short time in the HB (i.e.at the lowest inferred mass accretion rates).The behavior of Sco X–1and GX349+2suggests that there might be a second pa-rameter,besides mass accretion rate or position of the source in the Z-track,regulating the presence of hard emission in these systems.As already mentioned,the second parameter regulating the spectral state transitions might be the truncation radius of the optically thick disc.However,what determines the radius at which the disc is truncated is not clear yet: this could be the mass accretion rate through the disk normalized by its own long-term average(as proposed by van der Klis2001),but also magneticfields,the fraction of power dissipated in a hot,optically thin,corona(see e.g.Chen1995),or the formation/quenching of a jet could play a role.Interestingly,Strickman&Barret(2000)suggest that the hard X-ray emission present in Sco X–1data from OSSE may be correlated with periods of radio flaring.This might be generally true for this kind of systems.Although the mass accretion rate appears to be the main parameter driving the spectral hardness of atoll sources,there is evidence that at least on occasions an additional parameter controls the soft/hard spectral transitions.A clear example is given by a recent observation of4U1705–44,in which the source underwent a soft to hard state transition while the0.1–200keV bolometric luminosity of the source decreased by a factor of∼3from the soft to the hard state and increased by only a factor of∼1.2in the opposite transition from the hard to the soft state(Barret& Olive2002).On another occasion the same source displayed hard and soft states in which the source luminosity was different by a much larger factor,up to one order of magnitude.Again, the second parameter regulating the spectral state transitions might be the truncation radius of the optically thick disc.Note also that even though variations of the mass accretion rate appear to be the main cause of the spectral transitions of accreting black hole candidates (BHCs),there is some evidence that a second,yet unknown,parameter can give rise to these transitions.The existence of a second parameter was indeed proposed to explain the soft/hard spectral transitions observed in the BHCs XTE J1550–564(Homan et al.2001) and GS2000+25(Tanaka1989).There might be,however,another explanation for the difference in the hard X-ray component between the March2000and the February2001BeppoSAX observations.From the light curves shown in Figures1and2it can be seen that the source was continuously flaring diring the last BeppoSAX observation.The longest continuous time interval that the source spent in a persistentflux level(below∼200counts/s)is∼25ks.On the other hand,the source spent a longer continuous time in a persistentflux level during the previous observation,showing only one big(i.e.with a count rate higher than200counts/s)flare。