BBA2005-The oxidative environment and protein damage翻译
2005考研英语作文
2005考研英语作文In the 21st century, technology has become an integral part of our daily lives, and its influence on education is profound. The integration of technology into the classroom has revolutionized the way students learn and teachers teach. This essay aims to explore the positive and negative impacts of technology on education.Positive Impacts1. Enhanced Access to Information: With the advent of the internet, students have access to a wealth of information at their fingertips. This has not only broadened their horizons but also facilitated research and learning.2. Interactive Learning: Technology has made learning more interactive through the use of multimedia tools. Educational software and applications engage students in a more dynamic learning process, making education more enjoyable.3. Personalized Education: Technology allows for personalized learning experiences. Students can learn at their own pace, and adaptive learning platforms can tailor educational content to meet individual needs.4. Global Collaboration: The internet has made it possiblefor students and educators to collaborate with peers around the world. This exposure to different cultures and ideasfosters a more global perspective.Negative Impacts1. Distraction: While technology can be a powerful educational tool, it can also be a significant distraction. The constant presence of smartphones and social media can divert students' attention from their studies.2. Over-reliance on Technology: There is a risk of becoming overly reliant on technology for learning. This can lead to a lack of critical thinking skills and an overemphasis ondigital solutions rather than understanding the underlying concepts.3. Digital Divide: Not all students have equal access to technology, which can exacerbate educational inequalities. The digital divide can leave some students at a disadvantage, particularly in remote or less affluent areas.4. Lack of Human Interaction: The increased use of technology in education can sometimes lead to a decrease in face-to-face interaction between students and teachers. This can affect the development of social skills and the traditional teacher-student relationship.ConclusionWhile technology has undoubtedly brought about significant changes in the field of education, it is essential to strike a balance. Educators must find ways to harness the benefitsof technology while mitigating its drawbacks. By doing so, we can ensure that technology serves as a tool for enhancing education rather than a distraction from it. The future of education lies in the effective integration of technologythat complements traditional teaching methods and enriches the learning experience for all students.。
可持续性资本理论
B OSTON U NIVERSITY Center for Energy and Environmental Studies Working Papers SeriesNumber 9501 September 1995 THE CAPITAL THEORY APPROACH TO SUSTAINABILITY:A CRITICAL APPRAISALbyDavid Stern675 Commonwealth Avenue, Boston MA 02215Tel: (617) 353-3083Fax: (617) 353-5986E-Mail: dstern@WWW: /sterncv.htmlThe Capital Theory Approach to Sustainability:A Critical AppraisalDavid I. SternBoston UniversityNovember 1995______________________________________________________________________________ Center for Energy and Environmental Studies, Boston University, 675 Commonwealth Avenue, Boston MA 02215, USA. Tel: (617) 353 3083 Fax: (617) 353 5986, E-Mail: dstern@The Capital Theory Approach to Sustainability:A Critical Appraisal______________________________________________________________________________ SummaryThis paper examines critically some recent developments in the sustainability debate. The large number of definitions of sustainability proposed in the 1980's have been refined into a smaller number of positions on the relevant questions in the 1990's. The most prominent of these are based on the idea of maintaining a capital stock. I call this the capital theory approach (CTA). Though these concepts are beginning to inform policies there are a number of difficulties in applying this approach in a theoretically valid manner and a number of critics of the use of the CTA as a guide to policy. First, I examine the internal difficulties with the CTA and continue to review criticisms from outside the neoclassical normative framework. The accounting approach obscures the underlying assumptions used and gives undue authoritativeness to the results. No account is taken of the uncertainty involved in sustainability analysis of any sort. In addition, by focusing on a representative consumer and using market (or contingent market) valuations of environmental resources, the approach (in common with most normative neoclassical economics) does not take into account distributional issues or accommodate alternative views on environmental values. Finally, I examine alternative approaches to sustainability analysis and policy making. These approaches accept the open-ended and multi-dimensional nature of sustainability and explicitly open up to political debate the questions that are at risk of being hidden inside the black-box of seemingly objective accounting.I.INTRODUCTIONThe Brundtland Report (WCED, 1987) proposed that sustainable development is "development that meets the needs of the present generation while letting future generations meet their own needs". Economists initially had some difficulty with this concept, some dismissing it1 and others proliferating a vast number of alternative definitions and policy prescriptions (see surveys by: Pezzey, 1989; Pearce et al., 1989; Rees, 1990; Lélé, 1991).In recent years, economists have made some progress in articulating their conception of sustainability. The large number of definitions of sustainability proposed in the 1980's have been refined into a smaller number of positions on the relevant questions in the 1990's. There is agreement that sustainability implies that certain indicators of welfare or development are non-declining over the very long term, that is development is sustained (Pezzey, 1989). Sustainable development is a process of change in an economy that does not violate such a sustainability criterion. Beyond this, the dominant views are based on the idea of maintaining a capital stock as a prerequisite for sustainable development. Within this school of thought there are opposing camps which disagree on the empirical question of the degree to which various capital stocks can be substituted for each other, though there has been little actual empirical research on this question.There is a consensus among a large number of economists that the CTA is a useful means of addressing sustainability issues.2 Capital theory concepts are beginning to inform policy, as in the case of the UN recommendations on environmental accounting and the US response to them (Beardsley, 1994; Carson et al., 1994; Steer and Lutz, 1993). There are, however, a growing number of critics who question whether this is a useful way to address sustainability (eg. Norgaard, 1991; Amir, 1992; Common and Perrings, 1992; Karshenas, 1994; Pezzey, 1994; Common and Norton, 1994; Faucheux et al., 1994; Common, 1995). The literature on sustainable development and sustainability is vast and continually expanding. There are also a large number ofsurveys of that literature (eg. Tisdell, 1988; Pearce et al., 1989; Rees, 1990; Simonis, 1990; Lélé, 1991; Costanza and Daly, 1992; Pezzey, 1992; Toman et al., 1994). I do not intend to survey this literature.The aim of this paper is to present a critique of the capital theory approach to sustainability (CTA henceforth) as a basis for policy. This critique both outlines the difficulties in using and applying the CTA from a viewpoint internal to neoclassical economics and problems with this approach from a viewpoint external to neoclassical economics. I also suggest some alternative approaches to sustainability relevant analysis and policy. The neoclasscial sustainability literature generally ignores the international dimensions of the sustainability problem. I also ignore this dimension in this paper.The paper is structured as follows. In the second section, I discuss the background to the emergence of the capital theory approach, while the third section briefly outlines the basic features of the approach. The fourth section examines the limitations of the CTA from within the viewpoint of neoclassical economics and the debate between proponents of "weak sustainability" and "strong sustainability". The following sections examine the drawbacks of this paradigm from a viewpoint external to neoclassical economics and discuss alternative methods of analysis and decision-making for sustainability. The concluding section summarizes the principal points.SHIFTING DEBATE: EMERGENCE OF THE CAPITAL THEORY II. THEAPPROACHMuch of the literature on sustainable development published in the 1980's was vague (see Lélé, 1991; Rees, 1990; Simonis, 1990). There was a general lack of precision and agreement in defining sustainability, and outlining appropriate sustainability policies. This confusion stemmed in part from an imprecise demarcation between ends and means. By "ends" I mean the definition ofsustainability ie. what is to be sustained, while "means" are the methods to achieve sustainability or necessary and/or sufficient conditions that must be met in order to do the same. As the goal of policy must be a subjective choice, considerable debate surrounded and continues to surround the definition of sustainability (eg. Tisdell, 1988). As there is considerable scientific uncertainty regarding sustainability possibilities, considerable debate continues to surround policies to achieve any given goal.Sharachchandra Lélé (1991) stated that "sustainable development is in real danger of becoming a cliché like appropriate technology - a fashionable phrase that everyone pays homage to but nobody cares to define" (607). Lélé pointed out that different authors and speakers meant very different things by sustainability, and that even UNEP's and WCED's definitions of sustainable development were vague, and confused ends with means. Neither provided any scientific examination of whether their proposed policies would lead to increased sustainability. "Where the sustainable development movement has faltered is in its inability to develop a set of concepts, criteria and policies that are coherent or consistent - both externally (with physical and social reality) and internally (with each other)." (613). Judith Rees (1990) expressed extreme skepticism concerning both sustainable development and its proponents. “It is easy to see why the notion of sustainable development has become so popular ... No longer does environmental protection mean sacrifice and confrontation with dominant materialist values” (435). She also argued that sustainable development was just so much political rhetoric. A UNEP report stated: "The ratio of words to action is weighted too heavily towards the former" (quoted in Simonis, 1990, 35). In the early days of the sustainability debate, vagueness about the meaning of sustainability was advantageous in attracting the largest constituency possible, but in the longer run, greater clarity is essential for sustaining concern.In the 1990's many people have put forward much more precisely articulated definitions of sustainable development, conditions and policies required to achieve sustainability, and criteria toassess whether development is sustainable. This has coincided with a shift from a largely politically-driven dialogue to a more theory-driven dialogue. With this has come a clearer understanding of what kinds of policies would be required to move towards alternative sustainability goals, and what the limits of our knowledge are. There is a stronger awareness of the distinction between ends and means. Most, but not all (eg. Amir, 1992), analysts agree that sustainable development is a meaningful concept but that the claims of the Brundtland Report (WCED, 1987) that growth just had to change direction were far too simplistic.There is a general consensus, especially among economists, on the principal definition of sustainable development used by David Pearce et al. (1989, 1991): Non-declining average human welfare over time (Mäler, 1991; Pezzey, 1992; Toman et al., 1994).3 This definition of sustainability implies a departure from the strict principle of maximizing net present value in traditional cost benefit analysis (Pezzey, 1989), but otherwise it does not imply a large departure from conventional economics. John Pezzey (1989, 1994) suggests a rule of maximizing net present value subject to the sustainability constraint of non-declining mean welfare. It encompasses many but not all definitions of sustainability. For example, it excludes a definition of sustainability based on maintaining a set of ecosystem functions, which seems to be implied by the Holling-sustainability criterion (Common and Perrings, 1992; Holling, 1973, 1986) or on maintaining given stocks of natural assets irrespective of any contribution to human welfare. A sustainable ecosystem might not be an undesirable goal but it could be too strict a criterion for the goal of maintaining human welfare (Karshenas, 1994) and could in some circumstances lead to declining human welfare. Not all ecosystem functions and certainly not all natural assets may be necessary for human welfare. Some aspects of the natural world such as smallpox bacteria may be absolutely detrimental to people. In the context of the primary Pearce et al. definition, the Holling-sustainability criterion is a means not an end.The advantage of formalizing the concept of sustainability is that this renders it amenable to analysis by economic theory (eg. Barbier and Markandya, 1991; Victor, 1991; Common and Perrings, 1992; Pezzey, 1989, 1994; Asheim, 1994) and to quantitative investigations (eg. Repetto et al., 1989; Pearce and Atkinson, 1993; Proops and Atkinson, 1993; Stern, 1995). Given the above formal definition of sustainability, many economists have examined what the necessary or sufficient conditions for the achievement of sustainability might be. Out of this activity has come the CTA described in the next section. The great attractiveness of this new approach is that it suggests relatively simple rules to ensure sustainability and relatively simple indicators of sustainability. This situation has seemingly cleared away the vagueness that previously attended discussions of sustainability and prompted relatively fast action by governments and international organizations to embrace specific goals and programs aimed at achieving this notion of the necessary conditions for sustainability.III. THE ESSENCE OF THE CAPITAL THEORY APPROACHThe origins of the CTA are in the literature on economic growth and exhaustible resources that flourished in the 1970s, exemplified by the special issue of the Review of Economic Studies published in 1974 (Heal, 1974). Robert Solow (1986) built on this earlier literature and the work of John Hartwick (1977, 1978a, 1978b) to formalize the constant capital rule. In these early models there was a single non-renewable resource and a stock of manufactured capital goods. A production function produced a single output, which could be used for either consumption or investment using the two inputs. The elasticity of substitution between the two inputs was one which implied that natural resources were essential but that the average product of resources could rise without bound given sufficient manufactured capital.The models relate to the notion of sustainability as non-declining welfare through the assumption that welfare is a monotonically increasing function of consumption (eg. Mäler, 1991). The path ofconsumption over time (and therefore of the capital stock) in these model economies depends on the intertemporal optimization rule. Under the Rawlsian maxi-min condition consumption must be constant. No net saving is permissible as this is regarded as an unjust burden on the present generation. Under the Ramsey utilitarian approach with zero discounting consumption can increase without bound (Solow, 1974). Here the present generation may be forced to accept a subsistence standard of living if this can benefit the future generations however richer they might be. Paths that maximize net present value with positive discount rates typically peak and then decline so that they are not sustainable (Pezzey, 1994). Pezzey (1989) suggested a hybrid version which maximizes net present value subject to an intertemporal constraint that utility be non-declining. In this case utility will first increase until it reaches a maximum sustainable level. This has attracted consensus as the general optimizing criterion for sustainable development. Geir Asheim (1991) derives this condition more formally.Under the assumption that the elasticity of substitution is one, non-declining consumption depends on the maintenance of the aggregate capital stock ie. conventional capital plus natural resources, used to produce consumption (and investment) goods (Solow, 1986). Aggregate capital, W t,and the change in aggregate capital are defined by:W t=p Kt K t + p Rt S t (1)∆W t=p Kt∆K t + p Rt R t (2)where S is the stock of non-renewable resources and R the use per period. K is the manufactured capital stock and the p i are the relevant prices. In the absence of depreciation of manufactured capital, maintenance of the capital stock implies investment of the rents from the depletion of the natural resource in manufactured capital - the Hartwick rule (Hartwick 1977, 1978a, 1978b). Income is defined using the Hicksian notion (Hicks, 1946) that income is the maximum consumption in a period consistent with the maintenance of wealth. Sustainable income is,therefore, the maximum consumption in a period consistent with the maintenance of aggregate capital intact (Weitzman, 1976; Mäler, 1991) and for a flow of income to be sustainable, the stock of capital needs to be constant or increasing over time (Solow, 1986).The initial work can be extended in various ways. The definition of capital that satisfies these conditions can be extended to include a number of categories of "capital": natural, manufactured, human, and institutional.4 Natural capital is a term used by many authors (it seems Smith (1977) was the first) for the aggregate of natural resource stocks that produce inputs of services or commodities for the economy. Some of the components of natural capital may be renewable resources. Manufactured capital refers to the standard neoclassical definition of "a factor of production produced by the economic system" (Pearce, 1992). Human capital also follows the standard definition. Institutional capital includes the institutions and knowledge necessary for the organization and reproduction of the economic system. It includes the ethical or moral capital referred to by Fred Hirsch (1976) and the cultural capital referred to by Fikret Berkes and Carl Folke (1992). For convenience I give the name 'artificial capital' to the latter three categories jointly. None of these concepts is unproblematic and natural capital is perhaps the most problematic. Technical change and population growth can also be accommodated (see Solow, 1986).Empirical implementation of the CTA tends to focus on measurement of sustainable income (eg. El Serafy, 1989; Repetto, 1989) or net capital accumulation (eg. Pearce and Atkinson, 1993; Proops and Atkinson, 1993) rather than on direct estimation of the capital stock.5 The theoretical models that underpin the CTA typically assume a Cobb-Douglas production function with constant returns to scale, no population growth, and no technological change. Any indices of net capital accumulation which attempt to make even a first approximation to reality must take these variables into account. None of the recent empirical studies does so. For example, David Pearce and Giles Atkinson (1993) present data from eighteen countries on savings and depreciation of natural andmanufactured capital as a proportion of GNP. They demonstrate that only eight countries had non-declining stocks of total capital, measured at market prices, and thus passed a weak sustainability criterion of a constant aggregate capital stock, but their methodology ignores population growth, returns to scale or technological change.IV.INTERNAL APPRAISAL OF THE CAPITAL THEORY APPROACHIn this section, I take as given the basic assumptions and rationale of neoclassical economics and highlight some of the technical problems that are encountered in using the CTA as an operational guide to policy. From a neoclassical standpoint these might be seen as difficulties in the positive theory that may lead to difficulties in the normative theory of sustainability policy. In the following section, I take as given solutions to these technical difficulties and examine some of the problems inherent in the normative neoclassical approach to sustainability.a.Limits to Substitution in Production and "Strong Sustainability"Capital theorists are divided among proponents of weak sustainability and strong sustainability. This terminology is confusing as it suggests that the various writers have differing ideas of what sustainability is.6 In fact they agree on that issue, but differ on what is the minimum set of necessary conditions for achieving sustainability. The criterion that distinguishes the categories is the degree of substitutability believed to be possible between natural and artificial capital.7The weak sustainability viewpoint follows from the early literature and holds that the relevant capital stock is an aggregate stock of artificial and natural capital. Weak sustainability assumes that the elasticity of substitution between natural capital and artificial capital is one and therefore that there are no natural resources that contribute to human welfare that cannot be asymptotically replaced by other forms of capital. Reductions in natural capital may be offset by increases inartificial capital. It is sometimes implied that this might be not only a necessary condition but also a sufficient condition for achieving sustainability (eg. Solow, 1986, 1993).Proponents of the strong sustainability viewpoint such as Robert Costanza and Herman Daly (1992) argue that though this is a necessary condition for sustainability it cannot possibly be a sufficient condition. Instead, a minimum necessary condition is that separate stocks of aggregate natural capital and aggregate artificial capital must be maintained. Costanza and Daly (1992) state: "It is important for operational purposes to define sustainable development in terms of constant or nondeclining total natural capital, rather than in terms of nondeclining utility" (39).8 Other analysts such as members of the "London School" hold views between these two extremes (see Victor, 1991). They argue that though it is possible to substitute between natural and artificial capital there are certain stocks of "critical natural capital" for which no substitutes exist. A necessary condition for sustainability is that these individual stocks must be maintained in addition to the general aggregate capital stock.The weak sustainability condition violates the Second Law of Thermodynamics, as a minimum quantity of energy is required to transform matter into economically useful products (Hall et al., 1986) and energy cannot be produced inside the economic system.9 It also violates the First Law on the grounds of mass balance (Pezzey, 1994). Also ecological principles concerning the importance of diversity in system resilience (Common and Perrings, 1992) imply that minimum quantities of a large number of different capital stocks (eg. species) are required to maintain life support services. The London School view and strong sustainability accommodate these facts by assuming that there are lower bounds on the stocks of natural capital required to support the economy, in terms of the supply of materials and energy, and in terms of the assimilative capacity of the environment, and that certain categories of critical natural capital cannot be replaced by other forms of capital.Beyond this recognition it is an empirical question as to how far artificial capital can substitute for natural capital. There has been little work on this at scales relevant to sustainability. However, the econometric evidence from studies of manufacturing industry suggest on the whole that energy and capital are complements (Berndt and Wood, 1979).In some ways the concept of maintaining a constant stock of aggregate natural capital is even more bizarre than maintaining a non-declining stock of total capital. It seems more reasonable to suggest that artificial capital might replace some of the functions of natural capital than to suggest that in general various natural resources may be substitutes for each other. How can oil reserves substitute for clean air, or iron deposits for topsoil? Recognizing this, some of the strong sustainability proponents have dropped the idea of maintaining an aggregate natural capital stock as proposed by Costanza and Daly (1992) and instead argue that minimum stocks of all natural resources should be maintained (Faucheux and O'Connor, 1995). However, this can no longer really be considered an example of the CTA. Instead it is an approach that depends on the concept of safe minimum standards or the precautionary principle. The essence of the CTA is that some aggregation of resources using monetary valuations is proposed as an indicator for sustainability.The types of models which admit an index of aggregate capital, whether aggregate natural capital or aggregate total capital, is very limited. Construction of aggregate indices or subindices of inputs depend on the production function being weakly separable in those subgroups (Berndt and Christensen, 1973). For example it is only possible to construct an index of aggregate natural capital if the marginal rate of substitution between two forms of natural capital is independent of the quantities of labor or capital employed. This seems an unlikely proposition as the exploitation of many natural resources is impractical without large capital stocks. For example, in the production of caught fish, the marginal rate of substitution, and under perfect competition the price ratio, between stocks of fresh water fish and marine fish should be independent of the number of fishingboats available. This is clearly not the case. People are not likely to put a high value on the stock of deep sea fish when they do not have boats to catch them with.If substitution is limited, technological progress might reduce the quantity of natural resource inputs required per unit of output. However, there are arguments that indicate that technical progress itself is bounded (see Pezzey, 1994; Stern, 1994). One of these (Pezzey, 1994) is that, just as in the case of substitution, ultimately the laws of thermodynamics limit the minimization of resource inputs per unit output. Stern (1994) argues that unknown useful knowledge is itself a nonrenewable resource. Technological progress is the extraction of this knowledge from the environment and the investment of resources in this activity will eventually be subject to diminishing returns.Limits to substitution in production might be thought of in a much broader way to include nonlinearities and threshold effects. This view is sometimes described as the "ecological" viewpoint on sustainability (Common and Perrings, 1992; Common, 1995) or as the importance of maintaining the "resilience" of ecological systems rather than any specific stocks or species. This approach derives largely from the work of Holling (1973, 1986). In this view ecosystems are locally stable in the presence of small shocks or perturbations but may be irreversibly altered by large shocks. Structural changes in ecosystems such as those that come about through human interference and particularly simplification, may make these systems more susceptible to losing resilience and being permanently degraded. There is clearly some substitutability between species or inorganic elements in the role of maintaining ecosystem productivity, however, beyond a certain point this substitutability may suddenly fail to hold true. This approach also asks us to look at development paths as much less linear and predictable than is implied in the CTA literature.All things considered, what emerges is a quite different approach to sustainability policy. It is probable that substitution between natural and artificial capital is limited, as is ultimately technicalchange. Additionally the joint economy-ecosystem system may be subject to nonlinear dynamics. This implies that eventually the economy must approach a steady state where the volume of physical economic activity is dependent on the maximum economic and sustainable yield of renewable resources or face decline ie. profit (or utility) maximizing use of renewable resources subject to the sustainability constraint. As in Herman Daly's vision (Daly, 1977) qualitative change in the nature of economic output is still possible. Sustainability policy would require not just maintaining some stocks of renewable resources but also working to reduce "threats to sustainability" (Common, 1995) that might cause the system to pass over a threshold and reduce long-run productivity.The notion of Hicksian income originally applied to an individual price-taking firm (Faucheux and O'Connor, 1995). However, even here it is not apparent that the myopic policy of maintaining capital intact from year to year is the best or only way to ensure the sustainability of profits into the future. If a competing firm makes an innovation that renders the firm's capital stock obsolete, the latter's income may drop to zero. This is despite it previously following a policy of maintaining its capital intact. The firm's income measured up to this point is clearly seen to be unsustainable. In fact its policy has been shown to be irrelevant to long-run sustainability. In the real world firms will carry out activities that may not contribute to the year to year maintenance of capital and will reduce short-run profits such as research and development and attempts to gain market share.10 These activities make the firm more resilient against future shocks and hence enhance sustainability.b.Prices for AggregationSupposing that the necessary separability conditions are met so that aggregation of a capital stock is possible, analysts still have to obtain an appropriate set of prices so that the value of the capital stock is a sustainability relevant value. The CTA is more or less tautological if we use the "right" prices. However, these correct "sustainability prices" are unknown and unknowable. A number of。
北大考研-建筑与景观设计学院研究生导师简介-王志芳 Zhifang WANG
爱考机构-北大考研-建筑与景观设计学院研究生导师简介-王志芳Zhifang WANG王志芳ZhifangWANG时间：2012-09-1918:27:03来源：作者：ZhifangWANG副教授一、教育背景与工作经历工作经历：2012年至今北京大学建筑与景观设计学院副教授2008年至今美国德克萨斯A&M大学景观与城市规划系助理教授2002-2008年美国密歇根大学自然资源与环境学院助教/助研2001年美国弗吉尼亚理工大学助研1998-2001年北京大学城市与环境学系助研教育背景：城市与景观规划设计学博士(2008)美国密歇根大学自然资源与环境学院博士论文：城乡结合部公共开放空间保护规划－应用GIS整合其社会和生态价值(以美国密歇根州东西部地区为例)景观规划设计专业硕士学位（MLA）(2008)美国密歇根大学自然资源与环境学院硕士实践项目：将自然生态群落引入高密度城市多功能区中的设计方法(美国波特兰市为例)人文地理专业城市规划方向硕士学位(2001)北京大学城市与环境系硕士论文：哈尼族乡土景观研究:乡土景观的场景分析方法经济地理专业城市与区域规划方向学士(1998)北京大学城市与环境系学士论文：中山市城市景观演变(1940-1995)二、研究方向主要研究方向为可持续发展策略及其效益评价。
具体小方向包括:生态规划设计，城乡结合部发展策略,生态美学,灾后重建规划设计,地理信息系统在城市与环境规划设计中的应用,以及计算机辅助规划设计等。
三、主要获奖与荣誉2010年个人简历被美国科学与工程专业人员名录收录2010年博士论文被选为美国景观协会科研范文2008年芭芭拉﹒布郎和泰瑞﹒布朗奖学金,美国密歇根大学自然资源与环境学院2002、2005、2007年,会议报告旅行奖学金,美国密歇根大学研究生院2007年博士论文奖学金,美国密歇根大学研究生院2005年国际Dangermond奖荣誉奖,美国景观协会2005年优秀教学奖,美国密歇根大学自然资源与环境学院2005年密歇根大学最优秀的学生助教金苹果奖提名,美国密歇根大学自然资源与环境学院学生会2002年２００２年绿色空间设计学生竞赛二等奖。
PPARβ
蔡雨珊 赵 广东海洋大学食品科技学院，【摘要】过氧化物酶体增殖物激活受体中的配体激活的转录因子，程，包括长链脂肪酸、链饱和脂肪酸和多不饱和脂肪酸RXRα）的相互作用显示转录活性，区域中含量较丰富，病中的作用及其调控机制日益受到人们的关注，病、亨廷顿病以及多发性硬化症等神经退行性疾病中的作用进行综述。
【关键词】 PPARFig.1 Schematic diagram of the structural domain of PPAR-β/δFig.2 PPARβ/δ regulate macrophage polarization and function生长过程中起着重要作用［25］。
PPARβ/δ可在多种由炎症引起的疾病中发挥其作用。
PPARβ/δ激动剂可通过抑制肝脏中半胱天冬酶-1 （cysteinyl aspartate specific proteinase-1，Caspase-1）和IL-1β的表达，来缓解喂养富含脂类物质的小鼠肝脏中的脂肪变性和炎症。
在给肝母细胞瘤 2（human hepatoellular carcinomas 2，HepG2）细胞中加入PPARβ/δ激动剂，可抑制棕榈酸（palmitic acid）和脂多糖2（lipopolysaccharide，LPS）诱导的炎性小体活化［26］。
在患有肾病的小鼠模型中，加入PPARβ/δ激动剂GW501516后，通过直接抑制TGF-β活化激酶1（TAK-1）核因子κB（nuclear factor kappa-B，NF-κB）途径而产生抗炎作用，使小鼠肾脏病变减少，同时单核细胞趋化蛋白1（monocyte chemoattractant protein，MCP-1）和TNF-α的表达降低［27］。
PPARβ/δ通过减弱受到极低密度脂蛋白（very low density lipoprotein，VLDL）刺激的脂质的积累，来抑制人单核细胞白血病细胞（human monocytic leukemia cell-1，THP-1）巨噬细胞中泡沫细胞的形成，并通过减弱ERK1/2活化从而解除VLDL介导的AKT/FoxO1磷酸化的抑制，降低细胞因子和黏附分子的表达［28］。
2005年03月考博英语试题及答案
中国科学院博士研究生入学考试英语试卷2005年3月考生须知：一、本试卷由试卷一(PAPER ONE)和试卷二(PAPER TWO)两部分组成。
试卷一为客观题，答卷使用标准化机读答题纸；试卷二为主观题，答卷使用普通答题纸。
二、请考生一律用HB或2B铅笔填涂标准化机读答题纸，画线不得过细或过短。
修改时请用橡皮擦拭干净。
若因填涂不符合要求而导致计算机无法识别，责任由考生自负。
请保持机读答题纸清洁、无折皱。
三、全部考试时间总计180分钟，满分为100分。
时间及分值分布如下：试卷一：Ⅰ听力20分钟20分Ⅱ词汇15分钟10分Ⅲ完形填空15分钟15分Ⅳ阅读60分钟30分小计110分钟75分试卷二：Ⅴ英译汉30分钟10分Ⅵ写作40分钟15分小计70分钟25分CHINESE ACADEMY OF SCIENCESENGLISH ENTRANCE EXAMINATIONFORDOCTORAL CANDIDATESMarch 2005PAPER ONEPART Ⅰ LISTENING COMPREHENSION (20 minutes, 20 points)Directions:In this section, you will hear ten short conversations between two speakers. At the end of each conversation, a question will be asked about what was said. The question will be spoken only once. Choose the best answer from the four choices given by marking the corresponding letter with a single bar across the square brackets on your Machine-scoring Answer Sheet.1. A. He needs more fresh air. B. He is willing to go out.C. He is too sick to go out.D. He opened the window.2. A. Their friemts. B. Daily activities.C. Past experiences.D. Historical events.3. A. To buy a ticket. B. To pay a fee.C. To pay back a debt.D. To buy a gift.4. A. Give information. B. State preferences.C. Ask permission.D. Attract attention.5. A. In a gymnasium. B. In an art exhibition.C. In a shop.D. In a hotel.6. A. 19 dollars each. B. 38 dollars each.C. 30 dollars altogether.D. 36 dollars altogether.7. A. Jack is a gentleman. B. Jack does everything right.C. Jack is a desirable husband.D. Jack behaves immaturely sometimes.8. A. It was remarkable to both the man and the woman.B. It was not suitable for the woman.C. The man hated this kind of movie.D. The woman complained about its quality.9. A. See how much the jacket is.B. See if the jacket there is blue.C. See if there is a cell phone in the jacket.D. See if there was anything turned in this morning.10. A. The man has caught a cold. B. The woman was caught in a rainstorm.C. The weather forecast was inaccurate.D. It rained very heavily.Directions:In this section, you will hear three short talks. At the end of each talk, there will be a few questions. Both the talk and the questions will be read to you only once. After each question, there will be a pause. During the pause, you must choose the best answer fromthe four choices given by marking the corresponding letter with a single bar across the square brackets on your Machine-scoring Answer Sheet.Questions 11-13 are based on Talk 1.11. A. Language comes from physical labor.B. Language learning is a long-term endeavor.C. Language reflects history.D. Language study is very important.12. A. Constructing a wheel. B. Making a choice.C. Coming back.D. Turning around.13. A. The overthrow of a class. B. The overthrow of a tyrant.C. The overthrow of a belief.D. The overthrow of an act.Questions 14-17 are based on Talk 2.14. A. It‟s a wonderful idea.B. It‟s not a smart thing to do.C. It‟s too difficult to put into practice.D. It‟s interesting to the decision maker.15. A. Telling people about your degrees.B. Promising that you will make good achievements.C. Introducing your job responsibilities.D. Talking about the needs of the potential employer.16. A. The results which your potential boss wants to gain with your assistance.B. The results of making more money on an international market.C. The results that the employer has seen in the past.D. The results that your potential boss does not want to see.17. A. Proving that you are capable of doing the job.B. Seeking the position that is not too high or too low for you.C. Insisting that experience is more important than knowledge.D. Claiming that you are better than any other applicant.Questions 18-20 are based on Talk 3.18. A. They exercise dogs twice a day.B. They learn how to be responsible for dogs.C. They encourage dogs to go for long walks.D. They like dogs too much to care about other things.19. A. Working for the police.B. Relaxing with other dogs.C. Protecting businesses.D. Guiding the blind.20. A. Dogs ride in public transport.B. Dogs bite their owners when in a rage.C. Vehicles run over stray dogs.D. People always keep dogs on leads.PART ⅡVOCABULARY (15 minutes, 10 points, 0.5 point each)Directions: Choose the word or expression below each sentence that best completes the statement, and mark the corresponding letter of your choice with a single bar across the square brackets on your Machine-scoring Answer Sheet.21. Giorgio, now fifteen, and Lucia, also in her teens, were reaching the of their adolescence.A. crisisB. criterionC. causalityD. credibility22. At first Jackie prayed, frozen in fear, but gradually his terror curiosity.A. put up withB. lived up toC. did away withD. gave way to23. The International Olympic Committee rejects the accusations that Beijing‟s budget-cutting move might its preparation for the games.A. degradeB. deliberateC. deployD. defend24. You are not allowed to take a second job your employer gives you permission.A. so long asB. otherwiseC. unlessD. whereas25. They continued to about and enjoy themselves until they became tired.A. strokeB. strollC. stammerD. string26. The survey asked 750 school children about the values and beliefs they from television.A. pick upB. take upC. put upD. make up27. I am grateful for your invitation, and I‟d like to accept your offer with pleasure.A. delightedB. innocentC. graciousD. prestigious28. I must you farewell right now, but on some future occasion, I hope to see you again.A. relayB. bidC. sendD. deliver29. Perhaps my dishes will not be as delicious as those which you are accustomed to eating, but I beg you to grant my and have dinner with me.A. resentmentB. requirementC. requestD. reservation30. That singular ach ievement was not just about Korea‟s arrival as a football force but as a self-confident mature nation to be seriously.A. copedB. shownC. establishedD. taken31. Europe as a unit did little by itself; it either sent for US help, or each European government acted on its own.A. incidentalB. apparentC. cohesiveD. descendent32. On 9 December, James Joyce experienced one of those coincidences which affected him at the time and which later became material for his books.A. inadequatelyB. systematicallyC. profoundlyD. simultaneously33. Embarrassed, I nodded, trying to think of some way to my error.A. make do withB. make up forC. go in forD. go along with34. Furthermore, if I were to leave him, he would , for he cannot endure to be separated from me for more than one hour.A. prevailB. presideC. perishD. persecute35. With high hopes, the company sent samples of the substance to scientists, but theycouldn‟t any practical uses for it.A. come up withB. do justice toC. get even withD. look up to36. He signed a new contract with the Dublin firm, Maunsel & Company, on more favorable than those Grant Richards had given him.A. itemsB. termsC. articlesD. specifications37. Most scientists agree this outpouring contributes to global warming, which could eventually lead to coastal flooding, weather, and widespread crop loss.A. intensiveB. extremeC. unpleasedD. unique38. There was a quick turnover of staff in the department as the manager treated his employees with contempt.A. utterB. soleC. intimateD. corresponding39. The source, who spoke on condition of anonymity, to discuss the implication of that conclusion.A. recededB. impliedC. compliedD. declined40. Childhood can be a time of great insecurity and loneliness, during which the need to be accepted by peers great significance.A. takes onB. works outC. brings aboutD. gives inPART ⅢCLOZE TEST (is minutes, 15 points)Directions: There are 15 blanks in the following passage. Read the passage through. Then, go back and choose the most suitable of the words or phrases marked A, B, C, and D for each blank in the passage. Mark the corresponding letter of the word or phrase you have chosen with a single bar across the square brackets on your Machine-scoring Answer Sheet.Can exercise be a bad thing? Sudden death during or soon after strenuous exertion on the squash court or on the army training grounds, is not unheard of. 41 trained marathon runners are not immune to fatal heart attacks. But no one knows just 42 common these sudden deaths linked to exercise are. The registration and investigation of such 43 is very patchy; only a national survey could determine the true 44 of sudden deaths in sports. But the climate ofmedical opinion is shifting in 45 of exercise, for the person recovering from a heart attack as 46 as the average lazy individual. Training can help the victim of a heart attack by lowering the 47 of oxygen the heart needs at any given level of work 48 the patient can do more before reaching the point where chest pains indicate a heart starved of oxygen. The question is, should middle-aged people, 49 particular, be screened for signs of heart disease before 50 vigorous exercise?Most cases of sudden death in sport are caused by lethal arrhythmias in the beating of the heart, often in people 51 undiagnosed coronary heart disease. In North America 52 over 35 is advised to have a physical check-up and even an exercise electrocardiogram. The British, on the whole, think all this testing is unnecessary. Not many people die from exercise, 53 , and ECGs(心电图)are notoriously inaccurate. However, two medical cardiologists at the Victoria Infirmary in Glasgow, advocate screening by exercise ECG for people over 40, or younger people 54 at risk of developing coronary heart disease. Individuals showing a particular abnormality in their ECGs 55 , they say, a 10 to 20 times greater risk of subsequently developing signs of coronary heart disease, or of sudden death.41. A. Then B. Though C. Since D. Even42. A. why B. how C. if D. what43. A. runners B. exercises C. patients D. cases44. A. initiation B. evidence C. incidence D. indication45. A. favor B. positive C. inclination D. bias46. A. good B. well C. much D. far47. A. weight B. amount C. degree D. quality48. A. however B. because C. but D. so49. A. at B. to C. for D. in50. A. taking up B. trying on C. getting over D. doing with51. A. beyond B. by C. with D. of52. A. anyone B. none C. some D. nobody53. A. of course B. at all C. after all D. by far54. A. readily B. suddenly C. already D. ready55. A. having B. had C. having been D. havePART ⅣREADING COMPREHENSION (60 minutes, 30 points)Directions: You will read five passages in this part of the test. Below each passage there are some questions or incomplete statements. Each question or statement is followed by four choices marked A, B, C, and D. Read the passage carefully, and then select the choice that best answers the question or completes the statement. Mark the letter of your choice with a single bar across the square brackets on your Machine-scoring Answer Sheet.Passage 1I myself first saw Samarkand from a rise across a wilderness of crumbling ruins and great graveyards which lie between it and the airport. Suddenly we caught a glimpse of painted towers and the great blue domes of mosques and tombs shouldering the full weight of the sky among bright green trees and gardens. Beyond the gardens and the glittering domes still were those watchful mountains and their evocative snow. I found myself thinking of the thrill I had on catching my first sight of Damascus after crossing the desert from Syria. The light, the orchards and many of the trees were the same but deeper still was the sense of coming into contact with one of the most astonishing cultures in history, the world of the one and only Allah and his prophet Muhammad. It was a world that completely overawed me.Yet the memory of Samarkand which stays with me most clearly is quite a humble one. Coming back to the city from the country on my last evening we passed some unusual elm trees and I stopped to have a look at them. They were, my guide told me, perhaps a thousand years old, older certainly than Genghis Khan. A flock of fat-tailed sheep (the same kind of sheep that my own ancestors saw a Hottentot keeping when they landed at the Cape of Good Hope 321 years ago), tended by some Tadshik children, moved slowly home in the distance. Then from the city came quite clearly the call to prayer from mosque and minaret. I had not expected any calls at all and it made no difference that some of the calls came over loud-speakers. Then beyond the trees an old manappeared on a donkey, dismounted, spread a prayer mat on the ground, and kneeling towards Mecca, he began to pray.From Samarkand I journeyed on to Bokhara which was once the holiest city in Central Asia. At one time it possessed over a hundred religious colleges and close to four hundred mosques. It drew adventurers of all races towards it as it did Marco Polo. Not many of them reached their destination. These days at what used to be one of the richest market places in the world, one buys ice-cream instead of slaves; watches and mass-produced trinkets and fizzy drinks instead of gold, silks and turquoise jewellery. Few of the four hundred mosques remain and most have vanished without even leavinga trace.56. Samarkand lies .A. in a desertB. high in the mountainsC. in front of DamascusD. between the mountains and the airport57. The author said that he was overawed by .A. the beauty of the sceneB. the sight of DamascusC. the age of the placeD. the world of Allah and Muhammad58. The author refers to his clearest memory of Samarkand as “humble” because .A. it was an ordinary scene that he rememberedB. it was his last night in the city and his last memoryC. the elm trees were older than Genghis KhanD. the trees looked impressive in the evening light59. The author says that the sheep he saw were similar to .A. the ones his ancestors had keptB. the ones that lived in his own countryC. those his ancestors had seen at the Cape of Good HopeD. those his ancestors had taken to the Cape of Good Hope60. The author was surprised to hear the calls to prayer because .A. he was far away from the city, yet he could hear them clearlyB. he did not think there would be any callsC. the calls came from the mosquesD. the calls were no different over loud-speakers61. The market has changed in character because now .A. it does sell jewelleryB. the holy men do not sell thereC. it sells goods for tourists and items of little valueD. the traders have disappeared because it is too dangerous to sell therePassage 2The component of the healthy personality that is the first to develop is the sense of trust. As with other personality components, the sense of trust is not something that develops independent of other manifestations of growth. It is not that infants learn how to use their bodies for purposeful movement, learn to recognize people and objects around them, and also develop a sense of trust. Rather, the concept “sense of trust” is a shortcut expression intended to convey the characteristic flavor of all the child‟s satisfying experiences at this early age.Studies of mentally ill individuals and observations of infants who have been grossly deprived of affection suggest that trust is an early-formed and important element in the healthy personality. Psychiatrists find again and again that the most serious illnesses occur in patients who have been sorely neglected or abused or otherwise deprived of love in infancy.Observations of infants brought up in emotionally unfavorable institutions or moved to hospitals with inadequate facilities for psychological care support these findings. A recent report says that “Infants under 5 months of age who have been in an institution for some time present a well-defined picture. The outstanding features are listlessness, relative immobility, quietness, poor sleep, an appearance of unhappiness, etc.”Another investigation of children separated from their mothers at 6 to 12 months and not provided with an adequate substitute comes to much the same conclusion.Most significant for our present point, these reactions are most likely to occur in children who, up to the time of separation at 6 to 9 months of age, had a happy relation with their mothers, while those whose relations were unhappy are relatively unaffected.It is at about this age that the struggle between trusting and mistrusting the world comes to a climax, for it is then that children first perceive clearly that they and their environment are things apart. That at this point formerly happy infants should react so badly to separation suggests, indeed, that they had a faith that now has been shattered. In most primitive societies and in some sections of our own society, the attention accorded infants is more in line with natural processes. Throughout infancy the baby is surrounded by people who are ready to feed it, fondle it, and otherwise comfort it at a moment‟s notice. Moreover, these ministrations are given spontaneously and wholeheartedly, and without that element of nervous concern that may characterize the efforts of young mothers made self-conscious and insecure by our scientific age.We must not exaggerate, however. Most infants in our society too find smiles and comfort. As their own bodies come to be more dependable, there is added to the pleasures of increasing sensory response and motor control the pleasure of the mothers‟ encouragement. Then, too, psychologists tell us that mothers create a sense of trust in their children not by the particular techniques they employ but by the sensitiveness with which they respond to the children‟s needs and by their overall attitude.62. The sense of trust in an infant is under development when .A. the infant experiences some satisfactionB. adults‟ trust is adequateC. the infant learns how to moveD. the infant is surrounded by people he can recognize63. The author raises evidence of mental illness and other disorders in children .A. to introduce a discussion of the effect of institutions on childrenB. to show the effect on children of an unhappy relation with their mothers during infancyC. to warn parents of the dangers of neglecting and abusing their childrenD. to support the point that trust is an early formed and important element of a healthy personality64. Babies might mistrust the world if .A. they did not receive food when they were hungryB. they mastered their body movements too quicklyC. someone came too close to themD. they saw an object disappear65. The climax in the development of a sense of trust occurs .A. before maternal affection is providedB. when a child perceives that he or she is separate from the environmentC. when a child successfully controls his or her muscular coordinationD. as a result of maternal separation66. A possible reason that a child having an unhappy relation with his/her mother will not be affected by maternal separation at 6 to 9 months is that .A. the struggle between trusting and mistrusting has reached a climaxB. the child sees himself/herself as being separate from the environmentC. the child‟s sense of trust is destroyedD. no sense of trust has ever developed67. According to this passage, the most important factor in developing a sense of trust is .A. the type of techniques used by the motherB. the sensitivity of the childC. maternal loveD. the combined effect of natural feeling and cultural attitudes68. How can mothers create a sense of trust in a child?A. By showing confidence and experience in front of the child.B. By applying techniques taught by psychologists.C. By showing the child that the mother is understanding of his/her wants.D. By offering smiles and comforts.Passage 3I saw a television advertisement recently for a new product called an air sanitizer. A woman stood in her kitchen, spraying the empty space in front of her as though using Mace against an imaginary assailant. She appeared very determined. Where others aresatisfied with antibacterial-laced sponges, dish soaps, hand sanitizers and telephone wipes, here was a woman who sought to sterilize the air itself.As a casual student of microbiology, I find it hard to escape the absurdity here. This woman is, like any human being, home to hundreds of trillions of bacteria. Bacteria make up a solid third, by weight, of the contents of her intestines. If you were to sneak into her bathroom while she was showering—and based on my general impression of this woman from the advertisement, I don‟t recommend this—and secret away a teaspoon of the water at her feet, you would find some 820 billion bacteria. Bacteria are unavoidably, inevitably—and, usually, utterly benignly—a part of our world.The fantasy of a germ-free home is not only absurd, but it is also largely pointless. Unless you share your home with someone very old, very young (under 6 months) or very ill, the few hundred bacteria on a countertop, doorknob or spoon pose no threat. The bacteria that cause food poisoning, the only significant rational bacterial worry in the average home, need to multiply into the thousands or millions before they can overwhelm your immune system and cause symptoms.The only way common food poisoning bacteria can manage this is to spend four or five hours reproducing at room temperature in something moist that you then eat. If you are worried about food poisoning, the best defense is the refrigerator. If you don‟t make a habit of eating perishable food that has been left out too long, don‟t worry about bacteria.Viruses are slightly different. You need only pick up a few virus particles to infect yourself with a cold or flu, and virus particles can survive on surfaces for days. So disinfecting the surfaces in the home should, in theory, reduce the chances of picking up a bug.In practice, the issue is less clear. A study by Dr. Elaine Larson at the Columbia School of Nursing called into question the usefulness of antibacterial products for the home. In New York, 224 households, each with at least one preschooler, were randomly assigned to two groups. One group used antibacterial cleaning, laundry and hand-washing products. The other used ordinary products. For 48 weeks, the groups were monitored for seven symptoms of colds, flu and food poisoning—and found to be essentially thesame. A ccording to Dr. Gerba‟s research, an active adult touches an average of 300 surfaces every 30 minutes. You cannot win at this. You will become obsessive-compulsive. Just wash your hands with soap and water a few times a day, and leave it at that.69. What is the main idea of this passage？A. We don‟t need to worry too much about bacteria everywhere in our life.B. Antibacterial products for the home are found to be effective.C. The TV advertisement the writer mentioned is a total failure.D. The existent bacteria pose a threat only to the very young and very old.70. We can infer from Paragraph 3 that .A. healthy people should live separately from unhealthy members of the familyB. a germ-free home is not only possible, but significantC. unless you live with the vulnerable, it is pointless to sterilize the airD. our immune systems are too weak to fight against the food poisoning bacteria71. In the first sentence of Paragraph 4, “... manage this” means “to manage the process of .A. killing the bacteria in your bodyB. multiplying to a significantly large numberC. raising the room temperatureD. sterilizing the perishable food72. According to the author, if you want to keep healthy, you had better .A. make the room dryB. keep the food in the refrigeratorC. wash your hands as much as possibleD. clean the surfaces with anti-bacterial products73. From Paragraph 5 the author emphasizes .A. the danger of virusesB. the common existence of virus particlesC. the short life span of virusesD. the difficulty in killing viruses74. The word “bug” used in Paragraph 5 means .A. a bacteriumB. a coldC. a fluD. a virus75. According to the author, one will become obsessive-compulsive .A. if he washes his hands every time he touches a surfaceB. if he only washes his hands with soap and waterC. if he could not win over the bacteria in his homeD. if he does not fight against the bacteria at homePassage 4Until recently the halls of North High in Minneapolis were lined with vending machines where students could buy soda pop and other sugary drinks, as they can in most other high schools in the nation. But with rates of childhood obesity sky-rocketing, the Minneapolis school district worried about pushing pop. The district needed a way to keep its lucrative vending contract with Coca-Cola while steering kids toward more healthful beverages.Bryan Bass, North‟s assistant principal, took the challenge. He stocked 12 of North‟s 16 vending machines only with water, priced at 75 cents a bottle. Three machines dispensed juice and sports drinks for $1. Only one sold soft drinks, at $1.25 per can. “We located the water machines strategically outside our buildings, so when you come out of a classroom what you see is a water machine,” says Bass. “We also decided to allow water in classrooms but not juice or pop.” The result? Profits from the vending machines nearly tripled, from $ 4,500 to $11,000 in two years. They‟re now in their third year, and says Bass:“Water has become …cool.‟”North‟s suc cess demonstrates what many obesity experts and parents believe: Kids will learn to make healthful food and drink choices if they have access to them and are motivated to do so. “Price is a powerful motivator,” says Simone French of the University of Minnesota, an expert on school-based obesity prevention. She‟s impressed with North‟s efforts, but she says the problem is implementing these strategiesthroughout society. “Obesity is the biggest health issue facing kids,and we‟ve got to do more.”How to do mo re was outlined last week in the Institute of Medicine‟s 460-page action plan, mandated by Congress, on “Preventing Childhood Obesity.” Chaired by Emory University‟s Jeffrey Koplan, the plan is the first comprehensive look at childhood obesity and what government, industry, schools, communities, families, and medical professionals can do to reduce its impact. “I think this is similar in importance to the first Surgeon General‟s Report on Smoking and Health in 1964,” Koplan says. That landmark document led to the health warning on cigarette packages and a ban on cigarette advertising on TV.76. In most American high schools, selling soft drinks is .A. encouragedB. allowedC. unlawfulD. unprofitable77. Water has become “cool” in the Minneapol is school district partly because .A. water is provided freeB. most kids can afford nothing but waterC. water machines are put in noticeable positionsD. children have realized the harm of sugary drinks78. We can infer that in terms of healthful drinks for kids, Simone French and some other experts are .A. confident about children‟s choicesB. pessimistic about the futureC. puzzled about which approach to takeD. worried about how to motivate children79. By mentioning the 1964 report on smoking, Jeffrey Koplan implied that .A. more children tend to smoke today than yesterdayB. both obesity and smoking require the attention of schools and society.C. the present plan on obesity would function similarly as a landmark.D. obesity and smoking are both health problems.80. The primary purpose of this passage is to .。
电化学腐蚀
Wear252(2002)744–754A tribo-electrochemical apparatus for in vitro investigation offretting–corrosion of metallic implant materialsS.Barril,N.Debaud,S.Mischler∗,ndoltLaboratory of Metallurgical Chemistry,Materials Department,Swiss Federal Institute of Technology of Lausanne,EPFL,CH-1015Lausanne,Switzerland Received4October2001;received in revised form22January2002;accepted22January2002AbstractA novel apparatus has been developed for the investigation of fretting–corrosion behaviour of metallic materials used in prosthetic implants.Well-defined micro-movements are achieved through a rigid overall structure and the precise alignment of the components.An electrochemical cell is used for controlling the surface chemistry of the metal in contact and for studying the role of anodic oxidation.During an experiment,the most relevant mechanical and electrochemical parameters are continuously monitored using a computer-based data acquisition system.The apparatus permits,thus,in vitro experiments under well-controlled mechanical and electrochemical conditions. The good time resolution and reproducibility of the measurements permit the observation of correlations between different mechanical and electrochemical quantities.Preliminary results show that the prevailing corrosion conditions critically affect the overall fretting behaviour of Ti6Al4V.©2002Elsevier Science B.V.All rights reserved.Keywords:Fretting–corrosion;Tribo-electrochemical apparatus;Titanium alloy1.IntroductionTissues inflammation caused by degradation of metallic materials used in prosthetic implants can lead to failure of orthopaedic surgical operations.The materials degradation is a consequence of mechanical stresses resulting in small relative displacements(fretting)between prosthesis and sur-rounding bone tissues.The corrosive nature of the physiolog-ical environment exacerbates material degradation leading to fretting–corrosion[1],a situation where materials are exposed to the combined attack by corrosion and fretting. Under such conditions,micro and nanometer size wear par-ticles are formed[2,3]and metallic ions may be released into the body.These wear particles can stimulate cell reactions [4]which lead to tissue inflammation,a phenomenon that affects bone regeneration[5]and the stability of the implant. The release of metallic ions likely provokes allergies,when their concentration exceeds critical values.A better insight into the fretting–corrosion behaviour of metals in biological environments is a prerequisite for the control of biological compatibility of metallic implants.Fretting–corrosion results in metal degradation due to the simultaneous action of mechanical wear and of(electro) chemical oxidation[6].The two mechanisms do not proceed ∗Corresponding author.Tel.:+41-21-693-2954;fax:+41-21-693-3946. E-mail address:stefano.mischler@epfl.ch(S.Mischler).separately,but depend on each other in a complex way.In many cases,corrosion is accelerated by wear and,similarly wear may be affected by corrosion phenomena.Many fac-tors determine the interaction between wear and corrosion. For example,mechanical abrasion of the passivefilm usually leads to wear accelerated corrosion due to high chemical re-activity of the bare metal surface exposed to the environment [7–9].On the other hand,passivefilms seem to decisively influence the surface mechanical response of metals as well as the third-body behaviour[10,11].For the experimental investigation of tribo-corrosion,it is,therefore,essential to control both mechanical and chemical parameters.The control of displacement is particularly important in fretting because displacement accommodation by elastic deformation becomes relevant in case of small amplitude motion.According to the classical analysis[12],by super-posing a tangential force to a ball onflat Hertzian contact, some slip occurs on the outer annular part of the contact area while the centre remains locked(non-slip area).In such partial slip conditions,material damage seems to oc-cur only within the slip area,which becomes larger with increasing displacement.When the imposed displacement exceeds a critical value,slip becomes total and the situation approaches sliding friction.The prevailing slip regime(par-tial or total)must be identified in order to correlate fretting behaviour with mechanical,material and other relevant fac-tors.The control of corrosion conditions is best achieved by0043-1648/02/$–see front matter©2002Elsevier Science B.V.All rights reserved. PII:S0043-1648(02)00027-3S.Barril et al./Wear252(2002)744–754745the application,by means of an external source,of a defined potential,measured with respect to a reference electrode. The applied potential determines the reactivity of the metal as well as the presence or not of a passive oxidefilm at the surface and its thickness and composition.In addition, electrochemical techniques allow one to determine in-situ and in real time the rate of electrochemical oxidation during fretting by measuring an electrical current.Of particular importance is the capability of monitoring in real time the relevant mechanical,electrochemical and physical param-eters such as frictional force,normal force,displacement, linear wear,current and temperature in order to follow their evolution during an experiment and to observe correlations between them.This paper describes a novel apparatus developed for the investigation of fretting–corrosion mechanisms of metallic implant materials,which largely fulfils the above require-ments.It includes well-defined displacements,electrochemi-cal control and an advanced computer-based data acquisition system which permits monitoring of critical parameters with good time resolution.The limits and possibilities of the ap-paratus are evaluated by investigating a ball(alumina)on flat(Ti alloy)contact immersed in0.9wt.%NaCl,used asa simple model for bodyfluid.2.Description of the apparatusA rigid square frame made of stainless steel constitutes the main structure of the experimental apparatus(Fig.1). The apparatus is placed on an optical table equipped with pneumatic damping pistons to avoid perturbation by exter-nal vibrations.The calculated frame stiffness in the hori-zontal direction corresponds to109N m−1[13].Two linear roller bearings arefixed on the inside face of the vertical parts of the frame in order to allow for the vertical motion of a horizontal beam.The beam is slightly oversized in or-der to apply an elastic compression of the linear bearings when mounted.This ensures a smooth vertical displacement of the beam as well as its horizontal alignment.A ball screw isfixed on the lower part of the square frame to control the vertical movement of the beam.An elastic bearing(Fig.2) was designed to ensure a well-controlled horizontal motion while minimising any vertical displacement.It consists in two parallel plates connected byfive shafts on each side.The lower plate isfixed on the mobile beam while the upper part supports the lower specimen holder.Motion of the upper plate of the elastic bearing is controlled by a piezo-actuator, whose other extremity isfixed onto the mobile beam.The actuator is equipped with a position sensor and a loop in its electronic controlling system permits to impose well-defined effective displacements.The difference between the com-mand value of the piezo-actuator and the effective displace-ment of the elastic bearing centre was found being<2%up to a slip amplitude of180m.Fig.1.Schematic view of the fretting apparatus.The mobile beam sup-porting the elastic bearing is visible in the centre of the structure with the piezo-actuatorfixed on its left side:(1)main structure;(2)elastic bear-ing;(3)mobile beam;(4)screw to move the mobile beam up or down;(5)piezo-actuator;(6)force sensor(hatched part);(7)specimens.The upper specimen holder isfixed on the pre-load piece of a piezo-electric force transducer mounted at the end of a shaft connected to the upper part of the frame by two horizontal spring blades(Fig.3).The two blades maintain the shaft in a vertical position and ensure a high rigid-ity in the horizontal plane and a high compliance in the z-axis(vertical axis).The compliance in the z-axisallows Fig.2.Three-dimensional drawing of the elastic bearing.The upper plate supports the sample holder and the lower plate isfixed onto the mobile beam.746S.Barril et al./Wear 252(2002)744–754Fig.3.Schematic view showing the system used for application of the normal force and for control of the contact stiffness.The upper sample is mounted on a shaft connected to the main frame by two spring blades.The shaft is loaded against the lower specimen (not shown)by compressing an interchangeable spring.the vertical displacement of the upper specimen to follow geometrical changes induced by wear during experiments.The pre-loaded quartz force sensor measures the normal force applied along the z -axis and the tangential force along the x -axis (motion direction).Conversion constants given by manufacturer and used in the pre-amplifiers for normal and tangential force acquisition have been verified.After putting in contact the two specimens by moving up the mo-bile beam,the desired normal force is imposed via an inter-changeable spring pressed against the end of the shaft by a rotating screw fixed on the frame.In this configuration,the stiffness of the contact is controlled by the rigidity of the spring.Interchangeable springs permit one to carry out ex-periments at different contact stiffness [14].In the present experiments,the rigidity of the spring was of 9.81N mm −1although higher values can be used.A laser distance me-ter (Keyence LC2420)fixed on the optical table measures the vertical displacement of the shaft with a resolution of 0.01m.The vertical displacement during fretting corre-sponds in principle to the linear wear.The specimen holders have truncated cone geometry with the part facing the contact finished by grinding in order to obtain a flat surface and a conform contact with the elastic bearing plane.The specimens,either balls or cylinders,are inserted in the upper part of the holder.For systems involving flat contact surfaces,the specimen surface is ground after being inserted to ensure parallelism between contact surface and the bottom surface of the holder.The upper specimen holder has the same geometry as the lower specimen holder but is mounted upside down.Although flat on flat or cylinder on cylinder contacts are possible,in the present experiments only the ball on plate configuration was used.The holders are fixed either on the elastic bearing (lower specimen)or onthe pre-load piece of the force transducer (upper specimen)by means of screwed POM collars.A PMMA liquid cell is fixed around the specimen holder in order to carry out experiments in aqueous media as shown in Fig.4(for sake of clarity this cell has been left out in Fig.1).A three-electrode set-up was implemented with the metallic specimen as working electrode.A counter electrode (made of a platinum wire)as well as areferenceFig.4.The electrochemical cell for tribo-electrochemical measurements.The cell is fixed on the sample holder,which is in turn fixed on the elastic bearing.An alumina disc is used to electrically insulate the lower sample holder from the main frame.S.Barril et al./Wear252(2002)744–754747electrode are connected to a Wenking LB95L potentiostat. The temperature of the test solution is controlled by means of heatingfluid circulating through a circular glass tube fitted in the electrochemical cell.A thermostat controls the temperature of thefluid.A thermocouple is used to mea-sure the solution temperature close(1mm distance)to the specimen.During the test,the normal force,the frictional force,the horizontal position of the elastic bearing,the linear wear and the electrochemical parameters current and potential are con-tinuously monitored using a Macintosh computer running under Labview software.Each parameter is acquired at a sampling rate of1000points per second.In parallel,every second,the mean value is calculated.Both mean values and instantaneous values are stored at regular intervals of1and 60s,respectively.The coefficient of friction is determined during each stroke by dividing the frictional force by the normal force measured in the centre of the oscillation path.3.Experimental method for studying fretting–corrosion of Ti6Al4V against aluminaFretting between an alumina ball(upper specimen)and a Ti6Al4V,plate(lower specimen)was investigated in order to demonstrate the possibilities of the apparatus and explore its range of application.Ti6Al4V was chosen because it is widely used in orthopaedic devices.Al2O3was chosen as sliding partner because of its chemical inertness and high hardness.Thus,Al2O3is expected to suffer negligible degra-dation when fretting against Ti6Al4V.The Ti6Al4V spec-imens were of cylindrical shape(4mm in radius)and the alumina counter piece of spherical shape(5mm in radius). The Ti6Al4V alloy(Siber and Hegner,Switzerland)of hard-ness323HV5[7]was supplied in form of hot rolled,an-nealed and ground bars of10mm diameter.The as received Ti6Al4V bars were cut in smaller parts of8mm in diame-ter and approximately16mm height.After insertion in the holder,the exposedflat surface of the cylinder was ground down to a R a value of0.6m according to a well-defined and controlled procedure.The reproducibility of results among different specimens was found to be critically affected by small deviations in the grinding procedure.Sliding direction was always perpendicular to the grinding grooves.The alu-mina balls were supplied by Saphirwerke AG with a surface finish of grade G10according to AFBMA standard(R q< 0.02m).An aerated NaCl solution of0.9wt.%(0.15M)was used in the present preliminary experiments,although more com-plex solutions containing other salts and organic compounds exist for simulating the physiologicalfluid in the human body[15].All experiments were performed at room temper-ature(21±1◦C)to avoid problems related to achieving ther-mal stabilisation of the apparatus when heating the solution.A few experiments carried out at37◦C did not reveal ma-jors differences in fretting–corrosion behaviour compared to room temperature experiments.A saturated Ag/AgCl refer-ence electrode(standard potential of+0.222V versus SHE) was used and,in the present paper,all potentials are given with respect to this reference electrode.Unless otherwise indicated,all experiments were carried out at an applied po-tential of0.5V corresponding to the passive state of the ti-tanium alloy.The applied load was10N(maximum contact pressure of860MPa according to Hertz)and the oscillation frequency was1Hz.After fretting–corrosion experiments,laser profilometry (UBM instrument)was used to measure the volume of re-moved metal.Surface scans were performed,on square areas of typically1.7mm×1.7mm.Resolution was1000points per mm in x-direction and80lines scans per mm in the y-direction.Afterwards,the wear volume was determined using an UBM software routine by measuring the air vol-ume below the reference plane defined by the surface outside the contact.The topography of the wear traces was charac-terised using a Philips XL30scanning electron microscope or a Leitz optical microscope.4.Results4.1.Time dependence and reproducibility of measured mechanical and electrical quantitiesFig.5shows a typical set of mean values for an exper-iment performed at a displacement amplitude of150m, 1Hz oscillation frequency,a normal force of10N,and under an applied potential of+0.5V.A spring of rigidity 9.81N mm−1was used to apply the normal load.Rubbing starts at200s and stops at900s.The initial coefficient of friction is close to0.4(Fig.5a).After a running in period of approximately100s,the coefficient of friction displays a plateau at a value close to0.6characterised by somefluc-tuations ranging from0.45to0.65.The current markedly increases as soon as fretting starts(Fig.5b).This confirms that rubbing interferes with passivity and leads to anodic metal oxidation.After few seconds of rubbing,the position of the contact(Fig.5c)rises indicating material build-up in the contact.Afterwards,the descent of the contact indicates progressive material removal from the contact(wear). Fluctuation observed for all three quantities during rub-bing are of particular interest.Indeed,the data demonstrate a close correlation between the current peaks,the friction coefficient variations and the linear wear rate.A sudden decrease in friction coefficient corresponds to an increase in current and a rise in the position of the contact.Thesefluc-tuations are attributed to the formation of wear particles and to their ejection from the contact[16].A detailed mechanis-tic interpretation of the results lies beyond the scope of the present paper,however.The results of Fig.5clearly demon-strate that the described apparatus is able to detect time dependent variations and,thus,permits one tofind correla-tions between different mechanical and electrical quantities.748S.Barril et al./Wear 252(2002)744–754Fig.5.Evolution of the (a)coefficient of friction,(b)current and (c)vertical position of the contact during a fretting experiment.Test conditions:NaCl 0.9wt.%solution;displacement amplitude 150m;rubbing time 600s;oscillation frequency 1Hz;load 10N;spring rigidity 9.81N mm −1;applied potential 0.5V/Ag/AgCl.Rubbing starts at 300s.Small variations in the specimen surface preparation by grinding were found to have a deleterious influence on the reproducibility.This confirms the relevant role played by surface finish on fretting.In the present study,good repro-ducibility was achieved by strictly following a pre-defined grinding protocol for the preparation of the Ti 6Al 4V spec-imens.To demonstrate the reproducibility achieved under the present experimental conditions,four identical exper-iments were carried out using virgin Ti 6Al 4V and Al 2O 3specimens.Slip amplitude was 150m,duration of rub-bing was 600s,the oscillation frequency was 1Hz and the normal force was 10N.A potential of +0.5V was applied to the Ti 6Al 4V specimen immersed in the NaCl solution.Fig.6shows the evolution of the coefficient of friction for the four experiments.Rubbing starts at approximately 300s and stops at 900s .At the onset of rubbing the co-efficient of friction is close to 0.4,then it increases during a run in period of approximately 100s.The time evolu-tion of the coefficient of friction during this period shows good reproducibility.Interestingly,a temporary decrease of the coefficient of friction (approximately between 400and 500s)is observed in all experiments at the beginning of the plateau corresponding to the steady-state value of about 0.6.The behaviour indicates that a systematic event related toS.Barril et al./Wear 252(2002)744–754749Fig.6.Evolution of the coefficient of friction with time measured in four independent tests.Test conditions as in Fig.5.Fig.8.Fretting log diagrams for experiments carried out at displacement amplitudes of (a)3m;(b)10m;(c)30m,respectively.Test conditions:NaCl 0.9wt.%solution;rubbing time 3600s;scillation frequency 1Hz;load 10N;spring rigidity 9.81N mm −1;applied potential 0.5V/Ag/AgCl.Fig.7.Evolution of the current with time measured in four independent tests.Test conditions as in Fig.5.750S.Barril et al./Wear 252(2002)744–754the build-up and accommodation of third-body particles oc-curs after accommodation of the two surfaces.Discontinuous ejection of third-body particles leads to continuing fluctua-tions in the plateau region.When rubbing stops the friction coefficient does not instantaneously decrease to zero,as one would expect.The behaviour is attributed to an artefact cre-ated by the signal discharge in the force sensor preamplifier with respect to the time constant imputed in the settings.For the same series of experiments,Fig.7displays the measured anodic currents versus time.Immediately after rubbing starts,the current sharply increases to a maximum and then slowly stabilises towards a lower plateau value.The current increase arises from the metal oxidation follow-ing fretting enhanced de-passivation.The current stabilisa-tion suggests that,after the run in period,the removal rate of the passive layer decreases,possibly due to the formation of protective third-body.The current plateau exhibits sev-eral spikes.A major peak is always observed at the begin-ning of the plateau,approximately between 400and 500s.The time evolution of the current shows reproducible sim-ilarities with the coefficient of friction.The initial current peak corresponds well with the run in period for friction.Furthermore,the secondary current peaks observed attheFig.9.SEM images of the Ti 6Al 4V alloy after fretting experiment performed in NaCl 0.9wt.%at two different applied potentials (−1V Ag/AgCl (a,b)and 0.5V Ag/AgCl (c,d)).Test conditions:NaCl 0.9wt.%solution;displacement amplitude 50m;rubbing time 3600s;oscillation frequency 1Hz;load 10N;spring rigidity 9.81N mm −1.beginning of the plateau correspond well with minima of the coefficient of friction.4.2.Effect of fretting regime on electrochemical oxidation Acquisition of transient values permits one to anal-yse data in terms of so called “friction logs”[17],i.e.three-dimensional graphical representation of the time evo-lution of the frictional force-displacement loops (Fig.8).Such diagrams are shown in Fig.8for tests carried out under identical conditions as previously mentioned but at displacement amplitudes of 3,10and 30m and duration is 3600s.In Fig.8,one can easily identify the dominating fretting regimes [12,18].For example,Fig.8a exhibits a closed loop representative of a stick regime,where elastic deformation of the device and of the contact accommo-dates the entire imposed displacement.Fig.8c shows a rectangular loop where both elastic deformation and slip contribute to displacement (gross slip regime).Note that the real displacement (approximately 20m)is smaller than the imposed one (30m).Fig.8b shows an intermediate situation where elastic accommodation prevails over slip (partial slip regime).S.Barril et al./Wear252(2002)744–754751 The fretting regime has a marked effect on the mate-rial loss by electrochemical oxidation.Under slip or partialslip conditions periodic passivefilm removal followed byre-passivation of the metal surface leads to metal loss ac-cording to the anodic reaction:Ti+2H2O→TiO2+4H++4e−The metal volume V anod oxidised during a given timecan be determined from the measured anodic current usingFaraday’s law:V anod=(I rubbing t rubbing)MnFρin this equation,t rubbing is the rubbing time,I rubbing the current measured due to rubbing,F the Faraday constant (96500C mol−1),M the atomic weight,ρthe molar density of Ti and n=4the number of electron transferred dur-ing oxidation.I rubbing is determined here by averaging the current measured during rubbing and subtracting the mean value of the current measured just before and just after rub-bing.In this way,it is possible to compensate for the part of the current that does not depend on rubbing.The calcula-tion implies that titanium oxidation to the four valent state is the only anodic reaction.More complex calculations could take into account the minor alloy elements present but for the purposes of the present study this is not needed.The anodic volumes,V anod,listed in Table1together with the overall wear values,V tot,were determined for experiments carried out at different displacements under otherwise iden-tical conditions at an applied potential0.5V.The very small volumes involved and difficulties in the assessment of the reference plane of the unworn surface, render imprecise the determination of the overall wear vol-ume by profilometry.The poor reproducibility of the V tot values listed in Table1reflects this imprecision.The anodic volumes show much less scattering because the current can be measured with good sensitivity.The data of Table1show that the overall wear and the anodic volume depend differ-ently on displacement amplitude.In the stick regime,wear is detectable but no significant current due to electrochemical Table1Chemical and mechanical wear volumes at different slip amplitude(3600s, 1Hz,10N,9.81N mm−1,room temperature,+0.5V/Ag/AgCl)Amplitude (m)DisplacementaccommodationV tot(10−3mm3)V anod(10−3mm3)V anod/V tot(%)3Elastic0.02700 30.01900 10Partial slip0.01600 100.01500 30Gross slip0.0730.0079 300.0380.00925 50Gross slip0.1560.06541 500.1270.06954 100Gross slip0.3740.22760 1000.2820.19970oxidation is measured.This suggests that elastic deforma-tion does not lead to passivefilm removal.Electrochemical oxidation becomes significant only when gross slip occurs and becomes dominant at higher amplitudes as indicated by the V anod/V tot ratios listed in the table.4.3.Effect of applied potential on fretting behaviour Experiments were carried out under identical conditions but at two distinct applied potentials of−1.0and+0.5V. From a thermodynamic point of view in neutral solution titanium oxide,TiO2,is the stable species[19].However,the thickness of the passive oxidefilm is likely to be different, since,it depends on the applied potential[20,21].For the present alloy thefilm composition could also slightly change with potential[21].The wear morphology and the wear rate were found to vary considerably with the applied potential.At−1V (Fig.9a and b),the wear trace on the alloy is elliptical with a width of approximately140m and a length of180m. Some wear particles accumulate at the end of the wearscar Fig.10.Cross-section profiles of wear traces formed on the Ti6Al4V specimen after rubbing at(a)−1V Ag/AgCl and(b)0.5V Ag/AgCl.Test conditions as in Fig.9.752S.Barril et al./Wear 252(2002)744–754Fig.11.Fretting log representations for experiments performed in NaCl 0.9wt.%at (a)−1V Ag/AgCl and (b)0.5V Ag/AgCl.Test conditions as in Fig.9.(Fig.9),while the wear scar itself is covered with smeared material.The profilometer trace measured across the contact area (Fig.10)does not show evidence of material removal,but indicates some decrease of the roughness within the contact.According to Hertz contact theory,the contact area diameter is 148m (maximum pressure of 860MPa).The Hertz contact diameter corresponds well with the width of the fretting trace.Further,as shown by the friction logs (Fig.11),the slip distance is approximately 26m.Thesum Fig.12.Optical microscope images of the alumina balls after fretting against Ti 6Al 4V at (a)−1V Ag/AgCl and (b)0.5V Ag/AgCl.Test conditions as in Fig.9.of the elastic area diameter and the slip amplitude corre-sponds to the contact distance,i.e.the theoretical length of the fretted trace.In the present situation,one obtains a value of 174m,which corresponds well with the trace length observed in the SEM images as well as in the profilometer trace.At an applied potential of +0.5V ,the fretting scar is larger (Fig.9c)and exhibits different features in the cen-tre with respect to the edges,the latter being covered byS.Barril et al./Wear252(2002)744–754753smeared material(Fig.9d).The dimensions of the scar are approximately280m(width)by350m(length).Because significant metal removal has taken place,as evidenced by the profilometer trace(Fig.10),these dimensions rather re-late to the ball geometry than to the Hertzian contact area. Indeed,optical microscope observations(Fig.12)reveal thatflattening by wear of the alumina sphere in the con-tact area occurred.The diameter of theflattened area was larger at0.5V(300m)compared to the lower potential (170m).Alumina wear,therefore,depends on the elec-trochemical conditions prevailing in the contact.A similar potential dependence of alumina wear was previously ob-served during rubbing against various metals under sliding wear conditions[7].The information provided by fretting-log diagrams (Fig.11)is of particular interest.In fact,the slope of the loop is more pronounced at the negative potential than at0.5V.The slip amplitude varies consequently from 26to36m at−1.0and0.5V,respectively.The coeffi-cient of friction is higher at lower potential(0.62V)than at higher(0.45V)potential.These results show that the prevailing electrochemical conditions interfere not only with friction but with the elastic behaviour of the con-tact as well.To what extent third-body particles are in-volved in the different behaviour can not be judged at present.5.DiscussionThe present apparatus was developed to investigate fretting–corrosion mechanisms relevant for biomedical im-plants.The results obtained demonstrate the usefulness of the device and of the data acquisition system for such stud-ies,and they provide evidence for the complexity of the phe-nomena involved in fretting–corrosion.Fretting–corrosion experiments performed under electrochemical control with a Ti6Al4V/Al2O3contact revealed clear correlations be-tween mechanical and electrochemical quantities.In partic-ular,the close correlation between currentfluctuations and linear displacement illustrated in Fig.5indicates that the electrochemical activity depends to a large extent on the third-body behaviour in the contact.In fact,current peaks are always associated with simultaneous peaks in position of the contact.The latter are due to material accumulation in the contact causing the counter piece to move up.Thus, current peaks are associated with third-body accumula-tion in the contact.This suggests that third-body particle formation(probably by fatigue wear)is associated with a local de-passivation of the metal which dissolves and re-passivates at high instantaneous current density.In addi-tion,dissolution and passivation of freshly formed particles may also contribute to the current peaks.Periodically the oxidised third-body particles are ejected from the contact leading to correspondingfluctuations in linear wear and friction coefficient.The increase in chemical reactivity of a passive metal resulting from rubbing in a fretting experiment is expected to depend on the displacement amplitude,because the latter should affect the rate of de-passivation due to mechanical damage of the oxidefilm.Thus,an increased electrochemi-cal reactivity would be expected with increasing displace-ment amplitude.This is indeed confirmed by the data of Table1but only for amplitudes>10m,i.e.when the gross slip fretting regime dominates.In case of partial slip and elastic accommodation,no evidence for changes in elec-trochemical activity are detected.Thus,one can conclude that slip is necessary to promote metal activation.However, mechanical wear is observed even at low amplitudes.One would expect that this wear should lead to exposure of fresh metal surface and,hence,a measurable anodic cur-rent due to re-oxidation.The fact that no such current is observed can be explained by considering that at very low displacement amplitude,the extent of de-passivated area is small and the corresponding electrochemical response may be below the detection limit.An other explanation could be that in the absence of slip no electrolyte is present at the contacting surfaces(except when a wear fragment is released),thus excluding an electrochemical reaction. More studies will be necessary to elucidate the observed behaviour.Several works discuss wear of titanium alloys under fret-ting conditions.Among others,Blanchard reports that wear fragments under certain fretting-wear conditions arise from a tribologically transformed structure(TTS)[22].On one hand,Sauger et al.also reports that TTS formation in dry conditions strictly depends on mechanical parameters and that no oxidation phenomenon influences the amount of TTS formed[23].Under the present experimental conditions a distinct influence of the applied potential on the magnitude of the wear volume and on the elasticity behaviour of the contact was observed,which supports the notion that fret-ting in corrosive environments strongly depends on elec-trochemical parameters.Therefore,other mechanisms than TTS formation are likely to determine fretting–corrosion. Wear enhancement due to surface oxidefilms formed at different potential has previously been reported for slid-ing contacts[7,24,25].The thickness of passivefilms is known to increase with the applied potential[20].More-over,a potential dependence of the chemical composition of the surface oxidefilm on Ti6Al4V has been observed [21].These observations provide evidence for the important role played by the surface state of the metal.The present data show that any interpretation of the wear process should also include the possible degradation of the antagonist as evidenced in Fig.11.Surprisingly,the electrochemical con-ditions were found to also affect the elastic behaviour of the tribological system,as indicated by the different slopes in the friction–displacement loops in Fig.11.The slope K slope is usually associated with the rigidity of the contact K contact and of the device K device.Blanchard et ed[18] a model based on two springs in series to determine the。
2005考研英语作文真题
2005考研英语作文真题2005年考研英语作文真题要求考生针对所给的中文提示或者问题，用英语写一篇约120-150个单词的短文，题目自拟。
在回答这个题目之前，我们先来分析一下真题。
题目要求我们用英语写一篇约120-150个单词的短文，题目自拟。
因此，我们需要确保短文的字数在要求范围内，并且要有一个具有吸引力的题目。
接下来，我将为您呈现一篇满足上述要求的短文。
题目为：The Importance of Global Environmental Protection（全球环境保护的重要性）。
Global Environmental Protection is Crucial for Our FutureIn today's modern world, the issue of global environmental protection has become a pressing concern. As human activities continue to have a detrimental impact on our planet, it is imperative that we take immediate action to protect the environment for future generations. In this essay, I will discuss the importance of global environmental protection and propose several measures that can be implemented to address this urgent issue.Firstly, global environmental protection is vital for the preservation of biodiversity. Our planet is home to millions of species, each playing a unique role in maintaining ecological balance. However, due to deforestation, pollution, and climate change, numerous species are facing extinction. By protecting the environment, we can safeguard biodiversity and maintain the delicate equilibrium of our ecosystems.Secondly, environmental protection is crucial for mitigating climate change. The burning of fossil fuels and the release of greenhouse gases have led to the rising temperatures and extreme weather events we are experiencing today. Without concerted efforts to reduce carbon emissions and promote renewable energy sources, the consequences of climate change will continue to worsen. By taking action now, we can help mitigate these effects and create a sustainable future for generations to come.Moreover, environmental protection is closely linked to human health. The pollution of air, water, and soil poses serious risks to human well-being. Industrial activities, improper waste disposal, and chemical pollutants have been linked to various ailments, including respiratory diseases, cancers, and developmental disorders. By adopting cleaner and more sustainable practices, we can ensure a healthier environment for ourselves and future generations.To address the urgent need for global environmental protection, several measures can be implemented. Firstly, governments should enforce stricter regulations on industries to reduce pollution and encourage the use of clean technologies. Additionally, international cooperation is essential in tackling environmental issues that transcend national boundaries. By sharing knowledge, resources, and best practices, countries can work together towards sustainable development.Individuals also play a crucial role in environmental protection. By adopting environmentally friendly habits such as recycling, conserving energy, and reducing waste, we can contribute to a cleaner and greener future. Education also plays a key role in raising awareness and fostering a sense of responsibility towards the environment. Schools and communitiesshould prioritize environmental education to ensure that future generations are equipped with the knowledge and skills needed to protect the planet.In conclusion, global environmental protection is of paramount importance for the well-being of our planet and future generations. Through preserving biodiversity, mitigating climate change, and safeguarding human health, we can create a sustainable future for all. By implementing stricter regulations, promoting international cooperation, and adopting environmentally friendly habits, we can work towards a cleaner and greener world. Let us all take responsibility for protecting our environment and ensuring a better future for all.。
历届世界环境日的主题
历届世界环境日的主题1972年6月5日至16日，113个国家的1300名代表在瑞典首都斯德哥尔摩召开了联合国人类环境大会。
这次会议通过了著名的《人类环境宣言》，发出了“为了这一代和将来世世代代而保护和改善环境”的号召。
YEAR 年THEME 主题1974 Only one Earth只有一个地球1975 Human Settlements人类居住1976 Water: Vital Resource for Life水：生命的重要源泉1977 Ozone Layer Environmental Concern; Lands Loss and SoilDegradation; Firewood关注臭氧层破坏，水土流失1978 Development Without Destruction没有破坏的发展1979 Only One Future for Our Children - Development Without Destruction为了儿童和未来——没有破坏的发展1980 A New Challenge for the New Decade: Development Without Destruction 新的十年，新的挑战——没有破坏的发展1981 Ground Water; Toxic Chemicals in Human Food Chains andEnvironmental Economics保护地下水和人类的食物链，防治有毒化学品污染1982 Ten Years After Stockholm (Renewal of Environmental Concerns) 斯德哥尔摩人类环境会议十周年——提高环境意识1983 Managing and Disposing Hazardous Waste: Acid Rain and Energy 管理和处置有害废弃物，防治酸雨破坏和提高能源利用率1984 Desertification沙漠化1985 Youth: Population and the Environment青年、人口、环境1986 A Tree for Peace环境与和平1987 Environment and Shelter: More Than A Roof环境与居住1988 When People Put the Environment First, Development Will Last保护环境、持续发展、公众参与1989 Global Warming; Global Warning警惕全球变暖1990 Children and the Environment儿童与环境1991 Climate Change. Need for Global Partnership气候变化—需要全球合作1992 Only One Earth, Care and Share只有一个地球--一齐关心，共同分享1993 Poverty and the Environment - Breaking the Vicious Circle贫穷与环境——摆脱恶性循环1994 One Earth One Family一个地球，一个家庭1995 We the Peoples: United for the Global Environment各国人民联合起来，创造更加美好的未来1996 Our Earth, Our Habitat, Our Home我们的地球、居住地、家园1997 For Life on Earth为了地球上的生命1998 For Life on Earth - Save Our Seas为了地球上的生命——拯救我们的海洋1999 Our Earth - Our Future - Just Save It!拯救地球就是拯救未来2000 2000 The Environment Millennium - Time to Act2000环境千年 - 行动起来吧！2001 Connect with the World Wide Web of life世间万物生命之网2002 Give Earth a Chance让地球充满生机2003 Water - Two Billion People are Dying for It!水——二十亿人生命之所系2004 Wanted! Seas and Oceans – Dead or Alive?海洋存亡匹夫有责2005 Green Cities – Plan for the Planet!营造绿色城市，呵护地球家园中国主题：人人参与创建绿色家园2006 Deserts and Desertification–Don't Desert Drylands!莫使旱地变荒漠中国主题：生态安全与环境友好型社会2007 Melting Ice–a Hot Topic?冰川消融，后果堪忧中国主题：污染减排与环境友好型社会2008 Kick the Habit! Towards a Low Carbon Economy.转变传统观念，推行低碳经济中国主题：绿色奥运与环境友好型社会2009 Your Planet Needs You-UNite to Combat Climate Change你的地球需要你中国主题：减少污染行动起来2010 Many Species. One Planet. One Future多个物种、一颗星球、一个未来。
05年四级英语作文
05年四级英语作文{z}Title: The Importance of Environmental ProtectionIn the year 2005, the College English Test Band 4 (CET-4) writing topic was "The Importance of Environmental Protection".This essay emphasizes the significance of safeguarding our ecosystem and the need for collective efforts in this regard.English essay:As we step into the 21st century, we are greeted by numerous advancements and progress.However, along with these advancements, we are also faced with numerous challenges, one of which is environmental protection.Environmental protection has become a heated topic of discussion among people from all walks of life.There is no denying that our mother earth is being increasingly abused and exploited.Deforestation, air and water pollution, and the destruction of natural resources are just a few examples of how our environment is being damaged.The consequences of environmental degradation are far-reaching and can have a devastating impact on our planet and future generations.It is high time we realized the importance of environmental protection.We should adopt a more sustainable approach to development, striking a balance between economic growth and environmental preservation.We need to reduce our reliance on fossilfuels and explore renewable energy sources.Additionally, we must promote the concept of recycling and encourage the use of eco-friendly products.Furthermore, environmental protection is not the responsibility of a single individual or organization.It requires collective efforts from everyone.We should all take pride in being environmental stewards and do our part to protect our planet.This can be achieved through simple actions such as planting trees, reducing waste, and conserving energy.In conclusion, the importance of environmental protection cannot be overstated.It is our responsibility to ensure that our children and future generations inherit a healthy and sustainable planet.By working together and taking concrete actions, we can make a difference and leave a positive legacy for future generations.中文翻译：随着我们迈入21世纪，我们迎来了许多进步和突破。
入侵植物喜旱莲子草_生物学_生态学及管理_潘晓云
植 物 分 类 学 报 45 (6): 884–900(2007)doi:10.1360/aps06134 Acta Phytotaxonomica Sinica ———————————2006-08-28收稿, 2007-03-12收修改稿。
基金项目: 国家自然科学基金(30400052); 国家重点基础研究发展计划资助(2006CB403305) (Supported by the National Natural Science Foundation of China, Grant No. 30400052; National Basic Research Program of China, Grant No. 2006CB403305 )。
* 通讯作者(Author for correspondence. E-mail: jkchen@; Tel.: 86-21-65642468; Fax: 86-21-65642468)。
入侵植物喜旱莲子草——生物学、生态学及管理1潘晓云 1耿宇鹏 2Alejandro SOSA 1张文驹 1李 博 1陈家宽*1(生物多样性和生态工程教育部重点实验室, 复旦大学生物多样性科学研究所, 长江河口湿地生态系统野外科学 观测研究站 上海 200433)2(南美生物防治实验室 布宜诺斯艾利斯 1686)Invasive Alternanthera philoxeroides : biology, ecology andmanagement1PAN Xiao-Yun 1GENG Yu-Peng 2Alejandro SOSA 1ZHANG Wen-Ju 1LI Bo 1CHEN Jia-Kuan * 1(Ministry of Education Key Laboratory for Biodiversity Science & Ecological Engineering , Institute of Biodiversity Science ,Fudan University , Coastal Ecosystems Research Station of Yangtze River Estuary , Shanghai 200433, China) 2(South American Biological Control Laboratory , USDA-ARS , Hurlingham-Buenos Aires 1686, Argentina) Abstract In this review, we present a detailed account of Alternanthera philoxeroides (alligatorweed), including A. philoxeroides description, intraspecific variation from native to introduced regions, its life history strategies, invasion mechanisms, and management strategies. Alternanthera philoxeroides is a herbaceous amphibious weed of Amaranthaceae, native to South America, distributed from Buenos Aires Province (39° S) to south Brazil. It was first described by Martius in 1826, and consists of several taxa in both its native and non-native ranges. Current knowledge indicates that two forms of alligator weed exist in Argentina: A. philoxeroides f. philoxeroides in the southern range and A. philoxeroides f. angustifolia in the northern range. In Argentina, both forms set fruits and produce viable seeds. Alternanthera philoxeroides is now found as a serious weed from tropical to warm temperate regions, including the USA, China, India, South-East Asia, Australia and New Zealand. It is thought to have been brought to China during the 1930s, and later widely cultivated and spread in southern China as fodder during 1950s. The invasions of alligatorweed in China have caused considerable concerns, and now it is one of the 12 most harmful alien invasive species in China. Alligatorweed is found on stationary and slow moving water bodies, creeks, channels, riverbanks and associated areas that are occasionally flooded. It can also be found in terrestrial habitats as a pasture weed within urban environments. Alligatorweed does not produce viable seed in China and reproduces vegetatively from vegetative fragments (stems, rhizome or root tubes), which can be transported by water movement, boats, machinery and vehicles, and in hay. Movement between river catchments is common because of the human activities. Alligatorweed forms a floating mass which spreads out over the water. Its growth disrupts the ecology of banks and shallows and crowds out other plant species, restricts water flow, increases sedimentation, aggravates flooding, limits access and use by man and provides a favorable breeding area for disease vectors. We need better understanding of the biology and ecology of alligatorweed to assess the efficiency of control methods in any theoretical framework. According to the6期潘晓云等: 入侵植物喜旱莲子草——生物学、生态学及管理885 knowledge of the life history strategy of alligatorweed, we suggest that metapopulation theory is a good tool to improve management efficiency from watershed and regional perspectives. Key words alligatorweed (Alternanthera philoxeroides), biological invasion, dispersal, disturbance, intraspecific variation, life history, metapopulation, watershed management.摘要喜旱莲子草Alternanthera philoxeroides原产于南美洲, 属于苋科Amaranthaceae莲子草属Alternanthera。
2005环境绿皮书中英文词汇对照表
草根组织
grassroots organizations
草海黑颈鹤保护地
Black-necked Crane Reserve in Caohai
草皮
Greensward
草坪草褐斑病菌
Rhizoctonia solani Kuhn
草药
medicinal herb
Global VillageofBeijing(GVB)
北京地球纵观教育研究中心
BeijingEarthview Environment Education andResearchCenter
北京电力公司
BeijingElectric PowerCooperation
北京麋鹿苑
Milu Yuan (Park for David’sDeer) inBeijing
撤诉
towithdrawalawsuit
承包商
Contractor
承载量
carrying capacity,bearing capacity
承租企业
lease enterprise
城考
quantitative check of Chinese cities' comprehensive environmental control
26度承诺卡
26 degrees commitment cards
26度行动
The 26 Degrees Campaign
GDP单位能量消耗
energy use per unit of GDP
LEAD中国项目
the LEADChinaProject
SEE守望家园行动
环境政治学译丛
《环境政治学译丛》第一辑（2005年）1）安德鲁•多伯森：《绿色政治思想》，郇庆治（译）2）戴维•佩珀：《生态社会主义：从深生态学到社会正义》，刘颖（译）3）斐迪南•穆勒—罗密尔和托马斯·波格特克：《欧洲执政绿党》，郇庆治（译）4）克里斯托弗·卢茨：《环境运动：地方、国家和全球向度》，徐凯（译）第二辑（2007年）5）默里•布克金：《自由生态学：等级制的出现与消解》，郇庆治（译）6）约翰•德赖泽克：《地球政治学：环境话语》，蔺雪春、郭晨星（译）7）萨拉•萨卡：《生态社会主义抑或生态资本主义》，张淑兰（译）8）塔基斯•福托鲍洛斯：《多重危机与包容性民主》，李宏（译）第一辑1）安德鲁•多伯森：《绿色政治思想》，主译：郇庆治Andrew Dobson, Green Political Thought(London: Routledge,2000)作者简介：作者为英国开放大学教授、环境政治学专业最著名杂志《环境政治学》主编，被公认是西方生态政治学理论研究领域的最权威学者之一和生态自治主义学派的主要代表。
本书是他的主要代表性著作，它的1990年初版后不久就成为环境政治研究者的必读之作，并先后在1991年、1992年和1994年重印发行。
1995年，它又出版了第2个修订版本。
现翻译的是作者2000年最新修订后的第3版，现已成为欧美国家许多高校和研究机构的环境政治学理论教科书。
内容提要：本书提供了对生态政治观念和绿色运动目标与战略的、清晰而富有启发的思考。
在经过两次修订后的该书第3版中，通过对生态主义与其它政治意识形态的关系、激进与改革主义的绿色传统之间的差异和如何实现绿色社会变革等的系统分析，作者明确地主张，生态主义应该被视为一种独立的政治意识形态。
该书包括反思生态主义、生态主义的哲学基础、可持续社会、绿色变化的战略、生态主义和其它意识形态等部分。
2）戴维•佩珀：《生态社会主义：从深生态学到社会正义》，主译：刘颖David Pepper,Eco-Socialism: From Deep Ecology to Social Justice(London: Routledge,1993)作者简介：作者为牛津布鲁克斯大学教授，是西方生态政治理论中生态社会主义学派的主要代表之一。
Abstract What Are Ecosystem Services The Need for Standardized Environmental Accounting Uni
D I SCUSSI ONPAPER January 2006 RFF DP 06-02 What Are Ecosystem Services? The Need for Standardized Environmental Accounting Units J a m e s B o y d a n d S p e n c e r B a n z h a f 1616 P St. NWWashington, DC 20036202-328-5000 What Are Ecosystem Services?The Need for Standardized Environmental Accounting UnitsJames Boyd and Spencer BanzhafAbstractThis paper advocates consistently defined units of account to measure the contributions of natureto human welfare. We argue that such units have to date not been defined by environmental accountingadvocates and that the term “ecosystem services” is too ad hoc to be of practical use in welfareaccounting. We propose a definition, rooted in economic principles, of ecosystem service units. A goal ofthese units is comparability with the definition of conventional goods and services found in GDP and theother national accounts. We illustrate our definition of ecological units of account with concreteexamples. We also argue that these same units of account provide an architecture for environmentalperformance measurement by governments, conservancies, and environmental markets.Key Words: Environmental accounting, ecosystem services, index theory, nonmarket valuationJEL Classification Numbers: Q51, Q57, Q58, D6© 2006 Resources for the Future. All rights reserved. No portion of this paper may be reproduced withoutpermission of the authors.Discussion papers are research materials circulated by their authors for purposes of information and discussion.They have not necessarily undergone formal peer review.Contents1. Introduction (1)2. Standardized Units Will Improve Environmental Procurement and Accounting (2)3. The Architecture of Welfare Accounts (5)4. A Definition of Ecosystem Services (8)5. A Services Inventory (12)5.1 Services are Benefit-Specific (12)5.2 Proxies for Services: Stocks, Inputs, and Practical Units of Measurement (14)5.3 Services are Spatially Explicit (15)5.4 Our Definition of Services Compared to Others’ (15)5.5 An Illustrative Inventory (18)6. From Units of Account to Green GDP (21)7. Conclusion (23)References (24)What Are Ecosystem Services?The Need for Standardized Environmental Accounting UnitsJames Boyd and Spencer Banzhaf*1. IntroductionThis paper articulates a precise definition of “ecosystem services” to advance the development of environmental accounting and performance systems. Colloquially, ecosystem services are “the benefits of nature to households, communities, and economies.” The term has gained currency because it conveys an important idea: that ecosystems are socially valuable and in ways that may not be immediately intuited (Daily 1997). Beyond that, however, ecology and economics have failed to standardize the definition and measurement of ecosystem services. In fact, a brief survey of definitions reveals multiple, competing meanings of the term.1 This is problematic because environmental accounting systems increasingly are adopting “services” as the units they track and measure. The development and acceptance of welfare accounting and environmental performance assessment are hobbled by the lack of standardized ecosystem service units. To address that problem, this paper proposes a definition of services that is objective, rather than qualitative, and rooted in both economic and ecological theory. A virtue of the definition is that it constrains, and thereby standardizes, units of ecosystem account.2Loose definitions undermine accounting systems. They muddy measurement and lead to difficulties in interpretation. Our ultimate goal is the development of national-scale environmental welfare accounting and performance assessment, potentially consistent with national income accounting and hence a broad “green GDP.”3 Accordingly, we seek more* Senior fellow and fellow, respectively, Resources for the Future, Washington, DC. We thank V. Kerry Smith, Lisa Wainger, Will Wheeler, members of the EPA Science Advisory Board Committee on Valuing the Protection of Ecological Systems and Services, and participants at the Research Triangle Environmental Workshop and a National Science Foundation Biocomplexity Workshop for valuable comments.1 See Section 5.2 Similar debate over the definition of goods and services in the conventional economic accounts has taken place over the last hundred years. Today, we take these definitions largely for granted (e.g., the units of goods measured by GDP or the bundle of goods used to calculate the cost of living). In fact, they are the product of decades of debate within government and the economics profession.3 This goal is widely shared (Nordhaus 2005; World Bank 2005; U.S. Bureau of Economic Analysis 1994; United Nations Environment Programme 1993).rigorously and consistently defined ecosystem service units. In this context, an operationally useful definition of services will be clear and precise, consistent with the principles of the underlying ecology, and with the economic accounting system to which it relates.The paper proceeds as follows. First, we demonstrate the public policy demand for standardized units of ecosystem measurement. Second, we advance and defend an economic definition of units of account. Third, we contrast this definition with existing definitions of services and environmental accounting units. Fourth, we concretely illustrate our definition via an inventory of measurable ecosystem services.Clear units of account are fundamental to two policy initiatives whose social desirability we take as self-evident: the effective procurement of environmental quality by governments and clear national measures of well-being arising from environmental public goods and market goods—otherwise known as a green GDP.4 As we will argue ultimately, one particular set of accounting units is applicable to both of these broad applications. Before turning to our definition, however, we discuss the need for standardized units, relate them to accounting and procurement, and explain why such units have been slow to develop.2. Standardized Units Will Improve Environmental Procurement and AccountingIf green accounting is to be taken seriously, the accounts must not be only concerned with the ways in which services are weighted (the missing prices problem) but also with the definition of services themselves. Moreover, it is desirable to define ecosystem service units in a way that is methodologically and economically consistent with the definition of goods and services used in the conventional income accounts. In a nutshell, the national income accounts add up things bought and sold in the economy, weighted by their prices, in order to arrive at an aggregate, such as the nation’s gross domestic product (GDP). These accounts are by no means simple to devise, but they are aided by two kinds of readily available data. The first kind of data are prices. The second kind of data are the units of things bought and sold (cars, homes, insurance policies, etc). Because these things are traded in markets, we tend to take their units for granted. Everyone4 In this article, “green GDP” denotes explicit accounting for the services of ecosystems enjoyed by people, the approach advanced by Mäler (1991); Peskin and Angeles (2001); and Grambsch, Michaels, and Peskin (1993). This is different from, but not inconsistent with, depreciating changes in ecosystem stocks (Repetto et al. 1989, U.S. BEA 1994). For overviews, see Hecht (2005), Lange (2003), and Nordhaus and Kokkelenberg (1999).knows what a car or a house is. If we are to similarly account for environmental welfare, however, we run into an immediate problem: there are no such defined units.Because most ecosystem services are public goods, markets are not available to provide clear units of account. This point can be made most forcibly if we consider the challenge of creating markets for ecosystem services. In practice, such markets tend to stumble over the issueof trading units. When regulators attempt to compensate for ecological losses, they inevitablerely on coarse units for trade, such as “acres of wetland,” “pounds of nitrogen,” or “equivalent habitats.” These units are coarse because they are compound bundles of multiple goods and services. In other words, a wetland provides numerous distinct public and private benefits, notjust one. The imprecision of these measures is understandable but problematic from a policy perspective. Ideally, we want to disentangle the benefits to account for them. When course, compound units are exchanged in trade or to compensate for damages, there is no guarantee that what we really care about is preserved: namely, the benefits of nature.5The problem with ecosystem service markets is that the market itself does not define the units of trade (whereas conventional markets do). Instead, units of trade and compensation haveto be defined by governments, governments being the trustees of environmental quality. This is a point often missed by advocates of trade in ecosystem services. In a conventional market, the buyer is concerned selfishly about the quality of the “unit” they buy. In an ecosystem market, the environmental good is a public good and the buyer is therefore indifferent to its quality. Thebuyer is concerned only about satisfying the regulator’s definition of an adequate unit. The question then is, do governments do a good job of defining units and policing their quality?There is ample evidence that they have not.6 An aim then of our inquiry is to advocate units that will improve governments’ ability to consistently and defensibly measure and police environmental quality affected by regulation, ecosystem trades, compensation, and expenditures.While the challenge is significant, the history of markets and income accounting gives us hope that such problems can be overcome. We draw three lessons in particular. First, for millennia governments have played an active role in creating and stabilizing markets by5 Our perspective throughout is that the goal of social policy is to maximize human well-being, rather than a purely ecological objective.6 See U.S. General Accounting Office (2005b) (wetlands); Ando and Khanna (2004) (natural resource damage compensation); Houck (2002) and Bingham and Desvousges (2005) (water quality); and U.S. General Accounting Office (2000) (federal land swaps).establishing uniform weights and measures and monetary units of account. The fact that these measures are now firmly entrenched in tradition makes the role of governments easy to forget but no less important. Second, as national income and price accounts were established in the early decades of the last century, the pioneers of those systems faced daunting problems of their own. They did not have “readily available” prices and quantities. They had to gather those data. Moreover, they often faced a great deal of heterogeneity in product quality and in the forms of price quotes (apples of various grades, each by pound, bushel, or number). Finally, even today, the keepers of price and income statistics are faced with ever-shifting heterogeneity (faster cars, bigger houses, etc.). Each of these problems has posed challenges for the best way to define conventional marketed goods and services.7 Though in the task of defining ecosystem services we cannot turn to the activities of actual markets, we can benefit from these models.If the nation’s environmental status is to be characterized and tracked over time, units must be clearly defined, defensible ecologically and economically, and consistently measured. At present, the government and the public are presented with an over-abundance of poorly defined units of measurement that are unclear in their origin and that exacerbate the divide between economic and ecological analysis.8 Often within a single agency there are multiple, competing paradigms for what should be measured. The balkanization of performance measurement confuses decision-makers and the public and thus hampers the public’s ability to judge whether governments are effectively procuring environmental benefits. While we risk adding to this confusion, the way out of it is to debate and defend definitions that are rooted in ecological and economic science.While environmental economics has grappled for decades with the challenge of missing prices for environmental amenities, it largely has neglected the other central issue: the consistent definition of the environmental units to which value can be attached. Why is this? There are two main reasons. First, environmental economics historically is more concerned with the valuation of discrete actions, damages, or policies than with the comparison of benefits across time. Second, ecological valuation often relies on marketed outputs of nature, such as harvests, to derive a (partial) value of nature. Economists do this for a reason: because there are prices and7 See Banzhaf (2001).8 For a broad overview, see U.S. General Accounting Office (2004) and U.S. General Accounting Office (2005a).units available! But this dodges the issue of interest here: units related to nature’s public goods and services.3. The Architecture of Welfare AccountsWe seek to clarify the meaning of ecosystem services within the context of both an economic accounting system and ecological models.9 From the standpoint of economic accounting, we seek a framework that is analogous to GDP. This provides the discipline of an existing, logical system. It also provides an opportunity to create a broader green GDP that can provide an aggregate measure of well-being that encompasses human and natural production (Mäler 1991; Peskin and Angeles 2001; Grambsch, Michaels, and Peskin 1993; Banzhaf and Boyd 2005). Within such a framework, ecosystem services are weighted by their virtual prices (or marginal willingness to pay) and aggregated in the same way as market goods and services in GDP. This allows for direct comparison of ecosystem-related inputs to well-being and other inputs such as labor and capital.An important point—and a motivation for this paper—is that welfare accounting requires consistent separation of quantity and price measurements. To consistently track changes in welfare over time, the weights (prices) assigned to particular outputs are held fixed over time. The welfare change is thus driven purely by changes in quantities of goods and services.10 The implication is that accounting economics demands a precise definitional distinction between quantity and price. This challenge is unique to index theory and measurement. It does not arise in environmental valuation, for instance, where the focus has been on cost–benefit applications. There total benefits—the product of quantities and values—are all that is important.An example will illustrate this. Consider a cost–benefit analysis of an air quality improvement in Los Angeles. Many things matter to this valuation, including the population benefiting from the improvement. Is LA’s population a measure of the quantity of the improvement or the value of the improvement? In a cost–benefit analysis, the answer is, “it doesn’t matter.” If the environmental improvement (the quantity) is defined as health benefits per capita, then LA’s population affects the total willingness to pay (the value). If, on the other hand,9 Ecologists too are calling for more consistent measurement that accounts for the scale over which biophysical phenomena occur (Kremen 2005).10 If prices and quantities are both allowed to change, a variety of problems arise. Collectively, these are known as the “index number problem.”the environmental improvement (the quantity) is defined as health benefits to the citizens of LA, population appears in the quantity measure, not the willingness to pay measure. Either way, population is included in the total and the total is all that matters. Cost–benefit analysis does not lead to a consistent distinction between q and p because there is no reason for a consistent distinction.This distinction between prices and quantities also has been obscured in several existing applications of green GDP that calculate GDP for a single time period or separately for separate time periods (Peskin and Angeles 2001; Grambsch, Michaels, and Peskin 1993).11 Such static analyses do not require the price/quantity distinction either, since the marginal value weights are not changing at a single point in time. However, this kind of accounting is analogous to the measurement of nominal, rather than real, GDP. To track real service flows over time, quantities and prices must be measured separately, or nominal GDP must be adjusted with an appropriate deflator (Banzhaf 2005; Flores 1999).With this basic architecture, we must make one additional choice: to measure all sources of ecological value or only those not already captured in GDP. This choice is the choice between two alternative accounting strategies: green GDP and what we call an ecosystem services index (ESI). As we use the term, green GDP aggregates all sources of well being, including goods and services produced with non-ecosystem services, into a single index. By contrast, an ESI (Banzhaf and Boyd 2005) isolates the contributions of nature to well-being. The way in which an ESI relates to green GDP helps to illustrate the practical measurement of ecosystem services.It is important to note that conventional GDP is already somewhat green insofar as it includes the value of ecosystems to the production of marketed goods and services. For example, ecosystem services that contribute to crop production are captured in GDP because food is counted and weighted in GDP. The value of food purchased at the grocery store includes the net value added at the store itself, during transportation and storage, at the farm, and so on, including such inputs to the farm as fertilizer, seed, and machinery. GDP can be measured equivalently as the gross value of the final goods (purchased at the store) or as the net value added at each of these stages. Green GDP can be thought of as GDP plus the value of final ecosystem services directly enjoyed by households. Of course, some ecosystem services are inputs into final market11 We are referring to frameworks that account for environmental service flows. Green applications of the net GDP concept, which deflate environmental capital, are dynamic in a different sense (Repetto et al. 1989; U.S. BEA 1994).goods (like food) and are not enjoyed directly by households. As we define it, an ESI includes the value of final ecological services (i.e., green GDP minus ordinary GDP) plus the value added by the ecosystem to market goods. A third, equivalent measure of GDP is the sum of all factor payments to labor (wages), capital (interest), entrepreneurs (profits), and privately owned land or other resources (rents). As illustrated in Figure 1, the ESI accordingly also can be thought of as (virtual) factor payments to the ecosystem.12“Green GDP”Value-AddedComponentsFigure 1. Green GDP vs. an Ecosystem Services IndexWhen all ecosystem services are measured and aggregated according to our definition,the aggregation represents an index of nature’s total contributions to welfare. It is an index of ecological value added. Thus, it is not the same thing as green GDP, and it cannot be simply 12 Although it may appear novel, this accounting identity is simply the realization of the general equilibriumassociated with the well-known system of virtual (or shadow) prices. Virtual prices are the prices that people would be willing to pay for the level of ecosystem services that they in fact receive, if their income were augmented to cover the increased expenditure. Those virtual payments and the additional virtual income are precisely what are accounted for in green GDP.added to GDP to arrive at green GDP. To do so would double count the contribution of ecosystem services already captured in market goods and services. Measurement of an ESI, however, is a precondition to green GDP.4. A Definition of Ecosystem ServicesWe advance the following definition of an ecosystem service: Ecosystem services are components of nature, directly enjoyed, consumed, or used to yield human well-being.This deceptively innocuous verbal definition is in fact quite constraining and has important properties from the standpoint of welfare measurement.One important aspect of this definition relates to the language “directly enjoyed, consumed, or used.” This signifies that services are end-products of nature. The distinction between end-products and intermediate products is fundamental to welfare accounting. If intermediate and final goods are not distinguished, the value of intermediate goods is double-counted because the value of intermediate goods is embodied in the value of final goods. Consider a conventional market good like a car. GDP only counts the car’s value, not the value of the steel used to make the car. The value of steel used in the car is already part of the car’s total value. The same principle holds with ecosystem services. Clean drinking water, which is consumed directly by a household, is dependent on a range of intermediate ecological goods, but these intermediate goods should not be counted in an ecosystem service welfare account.13In addition to being directly used, another important aspect of our definition of ecosystem services is that they are components. This means that services are things or characteristics, not functions or processes. Ecosystem components include resources such as surface water, oceans, vegetation types, and species. Ecosystem processes and functions are the biological, chemical, and physical interactions between ecosystem components. The reason that functions and processes are not services is they are not end-products; functions and processes are intermediate to the production of final services. A manufacturing process can be thought of as an intermediate service in the conventional economy. The value of a manufacturing process is not included in GDP, again because its value is embodied in the value of its end-products. Often, ecological13 Care must be taken in use of the terms final and intermediate. As we explain in more detail below, when combined with market goods and services, ecosystem services may be a final service in the sense of being directly enjoyed (aesthetic values, for example) or an intermediate good in the creation of a final market good (agricultural produce, for example).processes and functions are called services—nutrient cycling, for example. But nutrient cycling is an ecological function, not a service. To be sure, it is a valuable function, but it is an intermediate aspect of the ecosystem and not an end-product.Many, if not most, components and functions of an ecosystem are intermediate products in that they are necessary to the production of services but are not services themselves. We emphasize that this does not mean these intermediate products are not valuable, rather that their value will be captured in the measurement of services.A final, important constraint imposed by the definition is that services are not benefits nor are they necessarily the final product consumed.14 For example, recreation often is called an ecosystem service. It is more appropriately considered a benefit produced using both ecological services and conventional goods and services. Recreational benefits arise from the joint use of ecosystem services and conventional goods and services. Consider, for example, the benefits of recreational angling. Angling requires ecosystem services, including surface waters and fish populations, and other goods and services including tackle, boats, time allocation, and access. For this reason, angling itself—or “fish landed”—is not a valid measure of ecosystem services.Consider the alternative ways to think about an ecosystem service and its associated value. In particular, consider a marketed input M, a nonmarket input N, and a production function A=A(M,N) that produces a commodity A. This commodity can be one of many things, including a product, an amenity, or an avoided damage or cost. The respective values of M, N, and A are P M, P N, and P A, where P M has an available market price, P N does not, and P A may or may not.To illustrate the issue associated with defining the nonmarket service, consider first the input’s value. Production theory provides two perspectives. First,(1) P N = (∂A/∂N)P A.The value can be derived from the input’s productivity, times the value of the final commodity (see e.g., Freeman 2003, Ch. 9).14 The ecosystem service is the end-product of nature, not necessarily the end-product ultimately produced with the ecological end-product.Repeating this tangency condition for the market good and suitably arranging terms, we also have(2) P N = M /A /A p MN ∂∂∂∂. In other words, the nonmarket input’s value can be derived from the value of the market input and the substitutability of the market and nonmarket inputs. This type of relationship is often used in nonmarket valuation studies of home production of health and other commodities (see e.g., Freeman 2003, Ch. 10).Now consider the effect of a change in the nonmarket input on the total value of thecommodity produced. For a change d N , the change in total value is(3) (∂A/∂N )P A dN = P N dN = M /A /A P MN ∂∂∂∂dN . Which part of this expression should be considered the measure of the nonmarket service and which part should be considered the value of that service? Interestingly, the environmental economics literature is surprisingly ambiguous. A classic text on nonmarket valuation, for example (Kopp and Smith 1993, Chs. 2, 7, and 14), variously equates the service with: 1) the change in the nonmarket input, d N ; 2) the change in the final commodity, (∂A/∂N )d N ; and 3) the shadow value of the change, p N d N .Of these three definitions, our preferred measure of the service is the first, d N (Banzhaf and Boyd 2005). The third is inappropriate as it merges value and quantity information. The second, (∂A/∂N )d N , is harder to rule out. Under this definition, the ecosystem service is thecontribution of the ecosystem to production of the final good or service. This definition has three advantages: it is defined in terms of the final good or service consumed by households; it is easily measured in units such as number, pounds, or bushels; and—when the final output is a market good—it has the readily observable value weight P A .The difficulty arises because an accounting system requires a measure of the totalquantity of services, not marginal changes in those services. In a total quantity framework, our preferred definition of services (d N ) is N , the total level of the final ecosystem input to the final good or service’s production function. Likewise, the “final goods and services definition” of services becomes A or the total quantity of the final good or service. Unfortunately, thisobscures, rather than isolates, the contribution of the nonmarket good. After all, if market inputs increase, A may increase even if the nonmarket input N decreases . Accordingly, total output of the final good or service is a poor measure of nonmarket services.One solution, of course, is to measure the change in the final good or service holding all nonmarket inputs fixed. If this is possible, we can define the ecosystem service as(4) A(M, N) - A(M, 0).This is a legitimate approach, but note that it requires global knowledge of the production function.15 Our definition of services does not. However, there is no free lunch. Using our definition of services requires us to shift production function analysis to the analysis of the shadow value p N. Nonmarket valuation of p N, for example, requires knowledge of the substitutability of market and nonmarket inputs in the production function, albeit only local knowledge.We prefer our definition of services, N, however, because it puts the ecosystem inputs on an equal footing with market inputs and outputs by identifying the point at which they come together in production. This is desirable because it means our definition allows for the eventual integration of an accounting system based on our definition into a more comprehensive set of national accounts. In other words, our definition of services is consistent with that used in conventional income accounting, so that our ESI could be combined with conventional GDP for a measure of green GDP (see e.g., Peskin 1989 and Hecht 2005).In this regard, we stress that the conventional accounts do not measure the analogue to (∂A/∂N)d N either. Conventional welfare accounts define goods and services by what can be measured directly. To be sure, this is a known limitation on what is measured by the accounts. For example, GDP does not measure the contribution of computers to computing satisfaction. It simply counts computers, despite the fact that units of computing satisfaction are what are really desired.16Note finally, that our definition of ecosystem is derived from a desire for consistency between conventional market accounting units and ecosystem accounting units. Interestingly, this leads to measurement of units that are in fact biophysical, rather than social or economic in nature. An economic definition of service units therefore leads naturally and necessarily to a15 Another, related approach is to define the service as the marginal contribution: (∂A/∂N)d N. This is the linearized contribution of the nonmarket input stock. This approach is more tractable, as it requires only local, rather than global, knowledge of the production function. It also is analogous to the price terms. However, it is an odd measure of quantity, overcoming these problems only with the error introduced by the linearization.16 See Norhaus and Kokkelenberg (1999, p. 46–47) for a discussion of this example.。
200520ec
DIRECTIVE2005/20/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCILof9March2005amending Directive94/62/EC on packaging and packaging wasteTHE EUROPEAN PARLIAMENT AND THE COUNCIL OF THE EUROPEAN UNION,Having regard to the Treaty establishing the European Community,and in particular Article95(1)thereof,Having regard to the proposal from the Commission,Having regard to the opinion of the European Economic and Social Committee(1),Acting in accordance with the procedure laid down in Article251of the Treaty(2),Whereas:(1)In view of the recent enlargement of the EuropeanUnion,due attention needs to be paid to the specific situation in the new Member States,in particular in relation to the attainment of the recycling and recovery targets set out in Article6(1)of Directive94/62/EC(3).(2)Member States having acceded to the European Union byvirtue of the Accession Treaty of16April2003require additional time to adapt their recycling and recovery systems to the targets of Directive94/62/EC.(3)Since the objective of this Directive,namely toharmonise national targets for the recycling and recovery of packaging waste,cannot be sufficiently achieved by the Member States and can therefore,by reason of the scale of the action,be better achieved at Community level,the Community may adopt measures,in accor-dance with the principle of subsidiarity as set out in Article5of the Treaty.In accordance with the principle of proportionality,as set out in that Article,this Directive does not go beyond what is necessary in order to achieve that objective.(4)In view of the further enlargement of the EuropeanUnion,due attention also needs to be paid to the specific situation in countries for which accession is planned at a later stage.(5)Directive94/62/EC should therefore be amendedaccordingly,HAVE ADOPTED THIS DIRECTIVE:Article1The following paragraph shall be added to Article6of Directive94/62/EC:‘11.Member States having acceded to the European Union by virtue of the Accession Treaty of16April2003may postpone the attainment of the targets referred to in paragraph1(b),(d)and(e)until a date of their own choosing which shall not be later than31December 2012for the Czech Republic,Estonia,Cyprus,Lithuania, Hungary,Slovenia and Slovakia;31December2013for Malta;31December2014for Poland;and31December 2015for Latvia.’Article21.Member States shall bring into force the laws,regulations and administrative provisions necessary to comply with this Directive by9September2006.They shall forthwith communicate to the Commission the text of those provisions and a correlation table between those provisions and this Directive.When Member States adopt these provisions,they shall contain a reference to this Directive or be accompanied by such a reference on the occasion of their official publication. The methods of making such reference shall be laid down by Member States.16.3.2005EN Official Journal of the European Union L70/17(1)OJ C241,28.9.2004,p.20.(2)Opinion of the European Parliament of17November2004(not yet published in the Official Journal),and Council Decisionof21February2005.(3)OJ L365,31.12.1994,p.10.Directive as last amended byDirective2004/12/EC(OJ L47,18.2.2004,p.26).2.Member States shall communicate to the Commission the text of the main provisions of national law which they adopt in the field covered by this Directive.Article3This Directive shall enter into force on the twentieth day following that of its publication in the Official Journal of the European Union.Article4This Directive is addressed to the Member States. Done at Strasbourg,9March2005For the European ParliamentThe PresidentJ.P.BORRELL FONTELLESFor the CouncilThe PresidentN.SCHMITL70/18EN Official Journal of the European Union16.3.2005。
2005全国英语作文
2005全国英语作文In the era of globalization, English has emerged as a lingua franca, connecting people from diverse cultural backgrounds and facilitating international communication. The influence of English can be observed in various aspects of modern society, from business and technology to education and entertainment.Firstly, the prevalence of English in the business world is undeniable. Many multinational corporations use English as their primary language for conducting business, which allows for seamless communication across different countries and cultures. This has been instrumental in fostering global trade and investment.Secondly, the technological advancements of the 21st century have been largely driven by English. The majority of programming languages are based on English, and the internet, a global platform for information exchange, predominantly uses English. This has made it easier for people to access and share knowledge, regardless of their geographical location.In the field of education, English is often taught as a second language in many countries. This has opened up opportunities for students to pursue higher education in English-speaking countries, as well as to engage with a global pool of knowledge through academic publications andresearch.Lastly, English has also become a dominant force in the entertainment industry. Hollywood movies, English music, and literature have a global reach, influencing popular culture and shaping the way people perceive the world.In conclusion, the impact of English on globalization is profound and multifaceted. It has not only bridged the gap between different cultures but has also played a crucial role in shaping the global landscape in various domains. As we continue to navigate the complexities of a globalized world, the importance of English as a common language will only grow.。
2005考研英语一作文
2005考研英语一作文In the modern world, the environment has become a critical concern for all nations. As the population grows and industrialization continues to expand, the need for environmental protection has never been more urgent. This essay aims to highlight the significance of environmental protection and the steps that can be taken to safeguard our planet.Firstly, environmental protection is essential for thesurvival and well-being of all living beings on Earth. Theair we breathe, the water we drink, and the land we cultivate are all interconnected and dependent on a healthy ecosystem. Pollution, deforestation, and climate change are just a fewof the many threats that our environment faces today. These issues not only affect wildlife but also have direct implications for human health.Secondly, environmental protection is crucial for sustainable development. Economic growth should not come at the expenseof our natural resources. By adopting sustainable practices, we can ensure that future generations will have access to the same resources that we enjoy today. This includes the responsible use of water, energy, and other natural resources, as well as the development of renewable energy sources.Thirdly, environmental protection is a collective responsibility. It requires the cooperation of individuals,communities, governments, and international organizations. Each of us can contribute to environmental protection by making conscious choices in our daily lives, such as reducing waste, recycling, and conserving energy. Governments can play a significant role by implementing policies that promote environmental protection and by investing in research and development for green technologies.In conclusion, the importance of environmental protection cannot be overstated. It is a matter of survival, sustainability, and shared responsibility. By taking action now, we can ensure a healthier and more prosperous future for all.。
线粒体呼吸链复合体Ⅳ活性检测试剂盒说明书
线粒体呼吸链复合体可见分光光度法货号：BC0940规格：25T/24S、50T/48S产品组成：使用前请认真核对试剂体积与瓶内体积是否一致，有疑问请及时联系索莱宝工作人员。
试剂名称/规格25T50T保存条件提取液液体40 mL×1瓶液体80 mL×1瓶4℃保存试剂一液体21 mL×1瓶液体21 mL×2瓶4℃保存试剂二粉剂×1支粉剂×2支-20℃保存试剂三粉剂×1支粉剂×2支4℃保存溶液的配制：工作液的配制：临用前取试剂一、试剂二、试剂三，将试剂二和试剂三依次转移到试剂一中产品说明：线粒体复合体Ⅳ又称细胞色素C氧化酶，也是线粒体呼吸电子传递链主路和支路的共有成分，负责催化还原型细胞色素C的氧化，并最终把电子传递给氧生成水。
还原型细胞色素C在550nm有特征光吸收，线粒体复合体Ⅳ催化还原型细胞色素C生成氧化型细胞色素C，因此550nm光吸收下降速率能够反映线粒体复合体Ⅳ酶活性。
注意：实验之前建议选择2-3个预期差异大的样本做预实验。
如果样本吸光值不在测量范围内建议稀释或者增加样本量进行检测。
需自备的仪器和用品：可见分光光度计、台式离心机、水浴锅、可调式移液器、1mL玻璃比色皿、研钵/匀浆器、冰和蒸馏水。
操作步骤：一、样本处理（可适当调整待测样本量，具体比例可以参考文献）1.称取约0.1g组织或收集500万细胞，加入1.0 mL提取液，用冰浴匀浆器或研钵匀浆。
4 ℃ 600g离心10min。
2.将上清液移至另一离心管中，4 ℃ 11000g离心15min。
3.上清液即胞浆提取物，可用于测定从线粒体泄漏的复合体Ⅳ（此步可选做，可以判断线粒体提取效果）。
4.在沉淀中加入400μL提取液，超声波破碎（功率20%，超声5秒，间隔10秒，重复15次），用于复合体Ⅳ酶活性测定，并且用于蛋白含量测定。
二、测定步骤1、可见分光光度计预热30min以上，调节波长至550nm，蒸馏水调零。
土木类SCI期刊
Rank ISSN Abbreviated Journal Title32150718-915X REV CONSTR32790733-9445J STRUCT ENG45331016-8664STRUCT ENG INT61851464-4177STRUCT CONCRETE80941940-1493J BUILD PERFORM SIMU 32760733-9402J ENERG ENG32810733-947X J TRANSP ENG28680350-2465GRADEVINAR32800733-9453J SURV ENG32820733-9488J URBAN PLAN DEV 50751076-0342J INFRASTRUCT SYST 54611226-7988KSCE J CIV ENG59651392-3730J CIV ENG MANAG63931478-4629P I CIVIL ENG-ENG SU 73661735-0522INT J CIV ENG85572228-6160IJST-T CIV ENG2270005-6650BAUINGENIEUR-GERMANY 4570013-8029ENG J AISC12790038-9145STAHLBAU14160049-4488TRANSPORTATION17320141-0296ENG STRUCT17800143-974X J CONSTR STEEL RES 19560167-4730STRUCT SAF19660167-6105J WIND ENG IND AEROD 21340191-2615TRANSPORT RES B-METH 21880197-6729J ADV TRANSPORT23960263-8231THIN WALL STRUCT 27910315-1468CAN J CIVIL ENG30640378-7788ENERG BUILDINGS31660553-6626PERIOD POLYTECH-CIV 35310885-7024CIVIL ENG35490886-7798TUNN UNDERGR SP TECH 35570887-3801J COMPUT CIVIL ENG 35590887-3828J PERFORM CONSTR FAC 36550893-1321J AEROSPACE ENG38980926-5805AUTOMAT CONSTR39730932-8351BAUTECHNIK43280965-089X P I CIVIL ENG-CIV EN 43290965-0903P I CIVIL ENG-MUNIC 43300965-0911P I CIVIL ENG-STR B 43310965-092X P I CIVIL ENG-TRANSP 45571021-2019J S AFR INST CIV ENG 46231028-6608CIV ENG ENVIRON SYST 51571084-0702J BRIDGE ENG52461093-9687COMPUT-AIDED CIV INF 54591226-6116WIND STRUCT55411300-3453TEK DERGI58091366-5545TRANSPORT RES E-LOG 58351369-4332ADV STRUCT ENG 66921541-7794STRUCT DES TALL SPEC 68741558-3058INT J ARCHIT HERIT 70521598-2351INT J STEEL STRUCT 77671822-427X BALT J ROAD BRIDGE E 2390006-3207BIOL CONSERV 4620013-9157ENVIRONMENT 11300032-2474POLAR REC13850045-6535CHEMOSPHERE 14010047-2425J ENVIRON QUAL 14120048-9697SCI TOTAL ENVIRON 16270098-8472ENVIRON EXP BOT 17230140-1963J ARID ENVIRON 18600160-4120ENVIRON INT 19090165-0009CLIMATIC CHANGE 19110165-0203NAT RESOUR FORUM 19680167-6369ENVIRON MONIT ASSESS 24160265-931X J ENVIRON RADIOACTIV 24710269-7491ENVIRON POLLUT 25330275-7540CHEM ECOL25480277-5212WETLANDS26550301-4797J ENVIRON MANAGE 29430364-152X ENVIRON MANAGE 30210376-8929ENVIRON CONSERV 31210393-5965AEROBIOLOGIA 34250791-7945BIOL ENVIRON 35850888-8892CONSERV BIOL 36220890-8575NAT RESOUR MODEL 36410892-0753COAST MANAGE 38340921-8009ECOL ECON40500944-1344ENVIRON SCI POLLUT R 42080957-4352INT J ENVIRON POLLUT 42320959-3330ENVIRON TECHNOL 42330959-3780GLOBAL ENVIRON CHANG 42630960-3115BIODIVERS CONSERV 44561001-0742J ENVIRON SCI-CHINA 44651002-0063CHINESE GEOGR SCI 45431018-4619FRESEN ENVIRON BULL 47731051-0761ECOL APPL49411064-3389CRIT REV ENV SCI TEC 51231080-7039HUM ECOL RISK ASSESS 51861088-1980J IND ECOL54761230-1485POL J ENVIRON STUD 55761311-5065J ENVIRON PROT ECOL 57091352-2310ATMOS ENVIRON 57201354-1013GLOBAL CHANGE BIOL 60811436-3798REG ENVIRON CHANGE 60941438-4957J MATER CYCLES WASTE 62351470-160X ECOL INDIC64731522-6514INT J PHYTOREMEDIAT65331527-5922ENVIRON FORENSICS 66791540-9295FRONT ECOL ENVIRON 67121543-5938ANNU REV ENV RESOUR 70271582-9596ENVIRON ENG MANAG J 70981612-9202ECOHEALTH71631648-6897J ENVIRON ENG LANDSC 72261672-6316J MT SCI-ENGL 73721735-1472INT J ENVIRON SCI TE 75291748-9326ENVIRON RES LETT 77191790-7632GLOBAL NEST J 77901842-4090CARPATH J EARTH ENV 78211862-4065SUSTAIN SCI 79731898-6196ECOL CHEM ENG SFull TitleRevista de la ConstrucciónJOURNAL OF STRUCTURAL ENGINEERINGStructural Engineering InternationalStructural ConcreteJournal of Building Performance SimulationJOURNAL OF ENERGY ENGINEERINGJOURNAL OF TRANSPORTATION ENGINEERINGGRADEVINARJOURNAL OF SURVEYING ENGINEERINGJOURNAL OF URBAN PLANNING AND DEVELOPMENTJOURNAL OF INFRASTRUCTURE SYSTEMSKSCE JOURNAL OF CIVIL ENGINEERINGJOURNAL OF CIVIL ENGINEERING AND MANAGEMENTPROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-ENGINEERING SUSTAINA INTERNATIONAL JOURNAL OF CIVIL ENGINEERINGIranian Journal of Science and Technology-Transactions of Civil Engine BauingenieurENGINEERING JOURNAL-AMERICAN INSTITUTE OF STEEL CONSTRUCTION INC StahlbauTRANSPORTATIONENGINEERING STRUCTURESJOURNAL OF CONSTRUCTIONAL STEEL RESEARCHSTRUCTURAL SAFETYJOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS TRANSPORTATION RESEARCH PART B-METHODOLOGICALJOURNAL OF ADVANCED TRANSPORTATIONTHIN-WALLED STRUCTURESCANADIAN JOURNAL OF CIVIL ENGINEERINGENERGY AND BUILDINGSPeriodica Polytechnica-Civil EngineeringCIVIL ENGINEERINGTUNNELLING AND UNDERGROUND SPACE TECHNOLOGYJOURNAL OF COMPUTING IN CIVIL ENGINEERINGJOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIESJOURNAL OF AEROSPACE ENGINEERINGAUTOMATION IN CONSTRUCTIONBautechnikPROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-CIVIL ENGINEERING PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-MUNICIPAL ENGINEER PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-STRUCTURES AND BUILD PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-TRANSPORTJournal of the South African Institution of Civil EngineeringCIVIL ENGINEERING AND ENVIRONMENTAL SYSTEMSJournal of Bridge EngineeringCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERINGWIND AND STRUCTURESTeknik DergiTRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW ADVANCES IN STRUCTURAL ENGINEERINGSTRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGSInternational Journal of Architectural HeritageInternational Journal of Steel StructuresBaltic Journal of Road and Bridge EngineeringBIOLOGICAL CONSERVATIONENVIRONMENTPOLAR RECORDCHEMOSPHEREJOURNAL OF ENVIRONMENTAL QUALITYSCIENCE OF THE TOTAL ENVIRONMENTENVIRONMENTAL AND EXPERIMENTAL BOTANYJOURNAL OF ARID ENVIRONMENTSENVIRONMENT INTERNATIONALCLIMATIC CHANGENATURAL RESOURCES FORUMENVIRONMENTAL MONITORING AND ASSESSMENTJOURNAL OF ENVIRONMENTAL RADIOACTIVITYENVIRONMENTAL POLLUTIONCHEMISTRY AND ECOLOGYWETLANDSJOURNAL OF ENVIRONMENTAL MANAGEMENTENVIRONMENTAL MANAGEMENTENVIRONMENTAL CONSERVATIONAEROBIOLOGIABIOLOGY AND ENVIRONMENT-PROCEEDINGS OF THE ROYAL IRISH ACADEMY CONSERVATION BIOLOGYNATURAL RESOURCE MODELINGCOASTAL MANAGEMENTECOLOGICAL ECONOMICSENVIRONMENTAL SCIENCE AND POLLUTION RESEARCHINTERNATIONAL JOURNAL OF ENVIRONMENT AND POLLUTION ENVIRONMENTAL TECHNOLOGYGLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS BIODIVERSITY AND CONSERVATIONJOURNAL OF ENVIRONMENTAL SCIENCES-CHINAChinese Geographical ScienceFRESENIUS ENVIRONMENTAL BULLETINECOLOGICAL APPLICATIONSCRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGYHUMAN AND ECOLOGICAL RISK ASSESSMENTJOURNAL OF INDUSTRIAL ECOLOGYPOLISH JOURNAL OF ENVIRONMENTAL STUDIESJournal of Environmental Protection and EcologyATMOSPHERIC ENVIRONMENTGLOBAL CHANGE BIOLOGYRegional Environmental ChangeJournal of Material Cycles and Waste ManagementECOLOGICAL INDICATORSINTERNATIONAL JOURNAL OF PHYTOREMEDIATIONENVIRONMENTAL FORENSICSFRONTIERS IN ECOLOGY AND THE ENVIRONMENTANNUAL REVIEW OF ENVIRONMENT AND RESOURCESEnvironmental Engineering and Management JournalECOHEALTHJournal of Environmental Engineering and Landscape ManagementJournal of Mountain ScienceInternational Journal of Environmental Science and Technology Environmental Research LettersGlobal NEST JournalCarpathian Journal of Earth and Environmental SciencesSustainability ScienceEcological Chemistry and Engineering S-Chemia I Inzynieria EkologicznaCategory Subcategory CountryCONSTRUCTION & BUILDING TECHNOLOGY ENGINEERING, CIVIL CHILE CONSTRUCTION & BUILDING TECHNOLOGY ENGINEERING, CIVIL UNITED STATES CONSTRUCTION & BUILDING TECHNOLOGY ENGINEERING, CIVIL SWITZERLAND CONSTRUCTION & BUILDING TECHNOLOGY ENGINEERING, CIVIL GERMANY CONSTRUCTION & BUILDING TECHNOLOGY ENGLAND ENERGY & FUELS ENGINEERING, CIVIL UNITED STATES ENGINEERING, CIVIL TRANSPORTATION SCIENCE & TECHNOLOGY UNITED STATES ENGINEERING, CIVIL CROATIA ENGINEERING, CIVIL UNITED STATES ENGINEERING, CIVIL UNITED STATES ENGINEERING, CIVIL UNITED STATES ENGINEERING, CIVIL SOUTH KOREA ENGINEERING, CIVIL LITHUANIA ENGINEERING, CIVIL ENGLAND ENGINEERING, CIVIL IRAN ENGINEERING, CIVIL IRAN工程技术工程：土木GERMANY工程技术工程：土木UNITED STATES 工程技术工程：土木GERMANY工程技术工程：土木NETHERLANDS 工程技术工程：土木ENGLAND工程技术工程：土木ENGLAND工程技术工程：土木NETHERLANDS 工程技术工程：土木NETHERLANDS 工程技术工程：土木ENGLAND工程技术工程：土木UNITED STATES 工程技术工程：土木ENGLAND工程技术工程：土木CANADA工程技术工程：土木SWITZERLAND 工程技术工程：土木HUNGARY工程技术工程：土木UNITED STATES 工程技术工程：土木ENGLAND工程技术工程：土木UNITED STATES 工程技术工程：土木UNITED STATES 工程技术工程：土木UNITED STATES 工程技术工程：土木NETHERLANDS 工程技术工程：土木GERMANY工程技术工程：土木ENGLAND工程技术工程：土木ENGLAND工程技术工程：土木ENGLAND工程技术工程：土木ENGLAND工程技术工程：土木SOUTH AFRICA 工程技术工程：土木ENGLAND工程技术工程：土木UNITED STATES 工程技术工程：土木UNITED STATES 工程技术工程：土木SOUTH KOREA 工程技术工程：土木TURKEY工程技术工程：土木ENGLAND工程技术工程：土木UNITED STATES 工程技术工程：土木ENGLAND工程技术工程：土木UNITED STATES 工程技术工程：土木SOUTH KOREA工程技术工程：土木LITHUANIA环境科学环境科学ENGLAND环境科学环境科学UNITED STATES 环境科学环境科学ENGLAND环境科学环境科学ENGLAND环境科学环境科学UNITED STATES 环境科学环境科学NETHERLANDS环境科学环境科学ENGLAND环境科学环境科学UNITED STATES 环境科学环境科学UNITED STATES 环境科学环境科学NETHERLANDS环境科学环境科学ENGLAND环境科学环境科学NETHERLANDS环境科学环境科学ENGLAND环境科学环境科学ENGLAND环境科学环境科学ENGLAND环境科学环境科学UNITED STATES 环境科学环境科学ENGLAND环境科学环境科学UNITED STATES 环境科学环境科学ENGLAND环境科学环境科学NETHERLANDS环境科学环境科学IRELAND环境科学环境科学UNITED STATES 环境科学环境科学UNITED STATES 环境科学环境科学UNITED STATES 环境科学环境科学NETHERLANDS环境科学环境科学GERMANY环境科学环境科学SWITZERLAND环境科学环境科学ENGLAND环境科学环境科学ENGLAND环境科学环境科学NETHERLANDS环境科学环境科学PEOPLES R CHINA 环境科学环境科学PEOPLES R CHINA 环境科学环境科学GERMANY环境科学环境科学UNITED STATES 环境科学环境科学UNITED STATES 环境科学环境科学UNITED STATES 环境科学环境科学UNITED STATES 环境科学环境科学POLAND环境科学环境科学BULGARIA环境科学环境科学ENGLAND环境科学环境科学ENGLAND环境科学环境科学GERMANY环境科学环境科学JAPAN环境科学环境科学NETHERLANDS环境科学环境科学UNITED STATES环境科学环境科学ENGLAND环境科学环境科学UNITED STATES 环境科学环境科学UNITED STATES 环境科学环境科学ROMANIA环境科学环境科学UNITED STATES 环境科学环境科学LITHUANIA环境科学环境科学PEOPLES R CHINA 环境科学环境科学IRAN环境科学环境科学ENGLAND环境科学环境科学GREECE环境科学环境科学ROMANIA环境科学环境科学JAPAN环境科学环境科学POLANDtotal Cites IF 2014-2015IF 2013-2014IF 2012-2013IF 2011-2012IF 2010-2011IF 2009-2010IF 2008-2009360.2340.2200.0490.0000.0000.0000.000 9951 1.504 1.4880.0000.0000.0000.0000.000 3860.4140.3420.1310.0000.0000.0000.000 230 1.4920.8570.2890.2700.0000.0000.000 298 1.623 2.043 1.5240.7180.0000.0000.000 318 1.343 1.1040.0000.0000.0000.0000.000 23350.7970.8770.0000.0000.0000.0000.000 720.2020.2160.1050.0820.0470.0000.000 320 1.000 1.0000.0000.0000.0000.0000.000 5140.8090.9310.0000.0000.0000.0000.000 832 1.0490.6480.9830.6540.7400.0000.000 5580.4840.5110.3830.3770.4500.0000.000 535 1.070 1.372 2.016 2.171 3.7110.0000.000 1790.7680.6040.5200.5870.5220.0000.000 1510.4680.3970.3790.6950.5470.0000.000 210.3330.1820.0000.0000.0000.0000.000 2410.5110.2070.1960.1500.1340.1940.000 2140.143 1.3710.2270.3490.2380.1840.412 3400.2190.2250.2560.2540.2340.3000.000 1945 2.358 1.617 1.657 1.023 1.875 1.512 1.767 9954 1.838 1.767 1.713 1.351 1.363 1.256 1.102 3910 1.321 1.370 1.327 1.251 1.003 1.0180.841 1716 1.675 2.391 1.840 1.867 1.770 2.276 1.467 4926 1.414 1.698 1.342 1.119 1.2130.8310.752 6014 2.952 3.894 2.944 2.856 2.091 2.268 1.874 554 1.606 1.8780.7330.6430.6500.727 1.207 3392 1.749 1.432 1.231 1.252 1.103 1.0540.788 18800.5560.4070.4720.3340.4010.4020.291 13417 2.884 2.465 2.679 2.386 2.041 1.593 1.590 570.2610.2500.2330.4550.0770.2220.000 2470.2690.1670.0790.1760.1620.0800.151 2204 1.490 1.589 1.1060.7270.9170.8600.710 1277 1.268 1.385 1.268 1.3370.900 1.012 1.114 6450.6310.5920.5760.4500.2930.3200.500 6600.8390.9260.7780.6970.4200.7140.907 2637 1.812 1.822 1.820 1.500 1.311 1.372 1.664 2340.1740.3170.2930.1760.1410.2100.000 2150.7140.4430.2940.1250.0850.0870.131 1250.1480.2410.2540.2090.4620.2240.138 4110.4940.2820.6090.5730.3730.4240.328 1680.2620.3210.2950.3260.1910.1740.136 720.3150.2220.2960.1820.3570.1250.000 2300.5120.7250.4770.5620.5950.5000.425 1330 1.0650.9270.7930.623 1.0090.4600.438 1834 4.925 5.625 4.460 3.382 3.170 1.9890.747 4030.5840.905 1.2540.5080.6350.5410.548 240.0230.1180.1500.1180.0300.0320.0002947 2.676 2.193 2.272 1.648 1.954 1.958 1.270 5740.5820.6030.4890.3240.4630.4650.513 6470.9440.9570.829 1.0410.5050.2690.388 1770.5610.7140.3700.2350.5000.5620.000 2220.5050.4710.2970.4260.3620.2710.000 1460.766 1.053 1.478 1.610 2.436 2.056 1.600 21429 3.762 4.036 3.794 4.115 3.498 3.167 3.566 711 1.545 1.353 1.375 1.738 1.864 1.918 1.444 3780.6670.6210.9810.9620.8890.5820.583 47655 3.340 3.499 3.137 3.206 3.155 3.253 3.054 13085 2.652 2.345 2.353 2.324 2.236 2.291 2.098 39706 4.099 3.163 3.258 3.286 3.190 2.905 2.579 6524 3.359 3.003 2.578 2.985 2.699 3.164 2.301 6660 1.641 1.822 1.772 1.723 1.535 1.426 1.589 12067 5.559 5.664 6.248 5.297 4.691 4.786 3.516 13208 3.430 4.622 3.634 3.385 3.016 3.635 3.202 618 1.146 1.0000.9800.667 1.0640.6880.792 10736 1.679 1.679 1.592 1.400 1.436 1.356 1.035 4861 2.483 3.571 2.119 1.339 1.466 1.268 1.114 26921 4.143 3.902 3.730 3.746 3.395 3.426 3.135 801 1.047 1.180 1.0690.6150.7760.6340.838 3439 1.572 1.444 1.283 1.338 1.238 1.328 1.117 14363 2.723 3.188 3.057 3.245 2.596 2.367 1.794 6909 1.724 1.648 1.647 1.744 1.503 1.408 1.109 2654 2.368 2.320 2.341 1.927 2.000 1.541 1.875 926 1.375 1.202 1.333 1.515 1.052 1.173 1.086 2350.6740.6190.6560.4150.4250.0000.041 17614 4.165 4.320 4.355 4.692 4.894 4.666 4.705 307 1.196 1.0480.5350.5560.5960.4890.600 6720.877 1.0130.814 1.1940.887 1.063 1.300 12802 2.720 2.517 2.855 2.713 2.754 2.422 1.912 6684 2.828 2.757 2.618 2.651 2.870 2.411 2.492 7430.4330.3030.2570.3610.6260.6240.568 4053 1.560 1.197 1.606 1.406 1.0070.7620.674 7533 5.089 6.000 5.236 6.868 4.918 3.340 3.955 8334 2.365 2.065 2.264 2.238 2.146 2.066 1.473 6013 2.002 1.922 1.773 1.660 1.513 1.4120.720 5040.8770.7270.5000.5000.6560.4260.000 17610.3780.5270.6410.6600.7160.5310.463 18027 4.093 4.126 3.815 5.102 4.276 3.672 3.628 2721 3.468 3.238 3.383 4.841 4.0007.0917.409 1408 1.096 1.076 1.292 1.538 1.486 1.528 1.290 2709 3.227 2.713 2.276 2.085 2.426 2.393 2.041 21110.8710.6000.4620.5080.5430.9470.963 8430.8380.3380.2590.1020.1780.1680.000 41715 3.281 3.062 3.110 3.465 3.226 3.139 2.890 255788.0448.224 6.910 6.862 6.346 5.561 5.876 1340 2.628 2.260 1.945 3.000 1.325 1.290 1.636 4930.9500.8310.5680.7170.4080.7800.000 5651 3.444 3.230 2.890 2.695 2.967 3.102 1.984 1137 1.739 1.466 1.179 1.298 1.936 1.321 1.2174080.5620.7320.6520.7680.6810.529 1.077 62057.4418.4127.6159.1138.820 6.922 5.065 2122 5.892 5.056 4.968 6.419 3.737 3.657 4.667 1268 1.065 1.258 1.117 1.004 1.4350.8850.000 1164 2.451 2.267 2.196 1.702 1.640 2.089 2.315 2090.6230.732 1.041 1.958 1.333 1.5080.000 6110.9630.7630.664 1.0000.6320.4000.000 1680 2.190 1.794 1.844 3.051 3.157 1.4170.000 4998 3.906 4.090 3.582 3.631 3.049 3.342 1.719 4790.4680.6600.6980.5360.4500.5650.000 2810.6300.727 1.495 1.450 1.5790.6060.286 568 3.119 3.372 2.1890.886 1.222 1.6510.000 2190.5530.5580.3820.4230.2940.6150.000IF 2007-20085-YearImpactFactorImmediacyIndexArticlesCitedHalf-LifeEigenfactor ScoreArticleInfluenceScoreJCR-2014收录中科院JCR大类学科0.0000.1870.000150.000090.040收录工程：土木0.000 1.9110.316225>10.00.010860.842收录工程：土木0.0000.0000.018577.70.000940.000收录工程：土木0.000 1.1230.15751 3.90.001040.537收录工程：土木0.000 2.1750.65529 3.50.001100.608收录结构与建筑技术0.000 1.2880.15645 6.00.000430.227收录工程：土木0.000 1.0280.100110>10.00.003020.297收录工程：土木0.0000.1210.000700.000110.018收录工程：土木0.000 1.0540.174237.50.000660.375收录工程：土木0.000 1.1380.152337.40.000690.238收录工程：土木0.000 1.2990.200457.90.001510.517收录工程：土木0.0000.6150.091254 3.70.001870.181收录工程：土木0.000 1.1260.18382 3.80.001440.260收录工程：土木0.0000.8620.50020 5.20.000490.238收录工程：土木0.0000.7110.06050 4.20.000500.180收录工程：土木0.0000.3040.000250.000060.056收录工程：土木0.0000.3150.52968 3.80.001400.245收录工程：土木0.0000.2390.00016>10.00.000170.118收录工程：土木0.0000.2400.174132 5.00.001320.128收录工程：土木1.2422.4790.292658.00.003340.816收录工程：土木0.986 2.1520.296565 6.50.023590.736收录工程：土木0.664 1.6990.253241 6.70.008470.538收录工程：土木1.0752.7840.429429.60.00409 1.207收录工程：土木0.959 1.8640.351151>10.00.004800.553收录工程：土木1.948 4.1160.4081259.40.00901 1.170收录工程：土木0.562 1.8680.13268 6.30.000970.447收录工程：土木0.552 1.8830.382275 6.50.006360.519收录工程：土木0.3750.5890.111108>10.00.002230.199收录工程：土木0.834 3.6170.400863 5.00.020150.642收录工程：土木0.0000.4550.026390.000200.122收录工程：土木0.2210.2080.03951>10.00.000350.091收录工程：土木0.408 1.8330.247158 6.90.003880.501收录工程：土木0.707 1.6160.362698.70.002670.590收录工程：土木0.2440.8730.109101 6.50.001700.315收录工程：土木0.5850.9860.202109 6.70.001580.348收录工程：土木0.609 2.4140.281171 4.90.006700.633收录工程：土木0.0000.2070.287877.70.000880.151收录工程：土木0.1080.535 1.12532 3.90.000460.170收录工程：土木0.1030.2370.79224 6.80.000190.078收录工程：土木0.2710.553 1.098617.60.000840.277收录工程：土木0.1090.511 1.05735 4.90.000340.165收录工程：土木0.0000.3640.097310.000170.120收录工程：土木0.2220.8550.000247.40.000440.252收录工程：土木0.000 1.2310.1381307.00.002860.404收录工程：土木0.861 4.0210.48050 5.40.003590.943收录工程：土木0.5410.8220.02773 6.90.000780.248收录工程：土木0.0000.1020.000160.000050.027收录工程：土木1.000 3.5130.404141 5.60.00787 1.136收录工程：土木0.2670.6850.089124 4.40.002080.242收录工程：土木0.159 1.2190.20578 4.80.001570.326收录工程：土木0.0000.7790.25547 4.10.000590.273收录工程：土木0.0000.6590.01376 4.80.000750.219收录工程：土木0.8000.7030.10329 3.40.000370.135收录工程：土木3.296 4.6970.6723057.90.04415 1.686收录环境科学1.2932.2610.312168.50.001440.985收录环境科学0.4150.7350.05040>10.00.000600.233收录环境科学2.7393.8540.5719237.40.067030.934收录环境科学0.000 2.9720.703212>10.00.015000.881收录环境科学2.1824.4140.9211751 6.30.07020 1.126收录环境科学1.810 3.746 1.068148 6.60.010680.901收录环境科学1.3492.0560.3281318.70.009520.627收录环境科学2.797 6.657 1.047254 6.50.02300 1.784收录环境科学2.890 4.6100.6702737.00.03837 1.916收录环境科学0.709 1.4830.042249.30.001000.525收录环境科学0.885 1.9180.229695 5.20.022160.441收录环境科学0.963 2.3220.309259 6.90.007560.560收录环境科学3.1354.7550.9914417.00.04408 1.213收录环境科学0.475 1.1690.13865 6.80.001240.258收录环境科学0.973 1.9190.3071278.70.005000.581收录环境科学1.446 3.8950.470396 5.30.03805 1.059收录环境科学1.2402.3400.3791959.30.011310.737收录环境科学1.1433.0840.14734>10.00.00342 1.125收录环境科学0.944 1.5560.237389.00.001200.383收录环境科学0.0200.7310.000258.70.000280.169收录环境科学3.934 5.1990.935168>10.00.02382 2.065收录环境科学0.3830.9910.000258.50.000810.438收录环境科学0.911 1.213 1.345297.80.000940.339收录环境科学1.549 3.9290.3392397.10.02571 1.292收录环境科学3.8942.9200.3671292 2.50.017180.652收录环境科学0.4350.4490.020498.30.000920.117收录环境科学0.735 1.5910.362354 6.20.005910.316收录环境科学3.9157.7840.969161 5.70.02222 2.849收录环境科学1.421 2.6760.5372017.60.015610.899收录环境科学0.480 2.5330.195293 5.20.013240.590收录环境科学0.0000.9060.373674.70.001060.209收录环境科学0.4290.4190.0314545.40.002240.062收录环境科学3.571 5.5080.7111599.50.03025 2.052收录环境科学4.615 4.6510.623618.00.00470 1.290收录环境科学0.912 1.2550.415948.40.002150.359收录环境科学1.962 3.695 1.12572 5.80.00656 1.164收录环境科学0.6270.8880.0922827.50.002560.168收录环境科学0.0000.6110.038211 3.00.000380.022收录环境科学2.5493.7800.6038187.90.06290 1.041收录环境科学4.7868.708 1.575308 6.10.07007 3.160收录环境科学0.000 2.9460.571163 3.30.004640.870收录环境科学0.0000.9760.26284 5.60.000910.229收录环境科学1.576 3.4940.698444 3.00.016860.888收录环境科学1.489 1.8750.34188 4.70.002350.419收录环境科学1.4120.7740.000308.80.000510.182收录环境科学4.2699.878 1.64562 6.20.01792 3.924收录环境科学4.0369.3720.348237.50.00529 3.864收录环境科学0.0000.8060.206325 2.90.001420.069收录环境科学1.4922.6180.72236 5.60.003070.828收录环境科学0.0000.7850.03132 4.80.000400.144收录环境科学0.000 1.1110.083132 4.30.001370.238收录环境科学0.000 2.4910.300227 4.30.003460.480收录环境科学1.200 4.4190.563327 3.10.02683 1.825收录环境科学0.0000.7100.18953 6.30.000810.184收录环境科学0.0000.7420.130100 3.00.000530.102收录环境科学0.0002.9140.444363.80.001370.674收录环境科学0.0000.6710.082494.70.000450.132收录环境科学中科院JCR 大类分区IF升降SCI收录本土期刊包含港澳Logo Here4上升保持收录3上升保持收录4上升保持收录4上升保持收录3下降保持收录4上升保持收录4下降保持收录4下降保持收录3持平保持收录3下降保持收录4上升保持收录4下降保持收录2下降保持收录4上升保持收录4上升保持收录4上升保持收录4上升保持收录4下降保持收录4下降保持收录2上升保持收录2上升保持收录3下降保持收录2下降保持收录2下降保持收录1下降保持收录3下降保持收录3上升保持收录4上升保持收录1上升保持收录4上升保持收录4上升保持收录3下降保持收录3下降保持收录4上升保持收录4下降保持收录2下降保持收录4下降保持收录4上升保持收录4下降保持收录4上升保持收录4下降保持收录4上升保持收录4下降保持收录4上升保持收录1下降保持收录4下降保持收录4下降保持收录3下降保持收录4下降保持收录4上升保持收录3下降保持收录2下降保持收录4上升保持收录4上升保持收录2下降保持收录3上升保持收录2上升保持收录3上升保持收录4下降保持收录1下降保持收录2下降保持收录4上升保持收录4持平保持收录3下降保持收录2上升保持收录4下降保持收录4上升保持收录2下降保持收录4上升保持收录3上升保持收录4上升保持收录4上升保持收录2下降保持收录4上升保持收录4下降保持收录3上升保持收录3上升保持收录4上升保持收录4上升保持收录1下降保持收录3上升保持收录4上升保持收录中国4上升保持收录中国4下降保持收录2下降保持收录2上升保持收录4上升保持收录3上升保持收录4上升保持收录4上升保持收录2上升保持收录1下降保持收录3上升保持收录4上升保持收录2上升保持收录4上升保持收录1上升保持收录4下降保持收录3上升保持收录4下降保持收录4上升保持收录中国3上升保持收录2下降保持收录4下降保持收录4下降保持收录3下降保持收录4下降保持收录。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
氧化环境与蛋白质损伤Michael J. Davies*The Heart Research Institute, 145 Missenden Road, Sydney, NSW 2050, Australia摘要：由于在生物系统中氧化剂的丰富存在及它们的高反应速率常数，所以蛋白质是氧化剂的主要目标。
许多自由基和非自由基氧化剂（如单线态氧和次氯酸）的动力学数据与绝大多数在细胞内产生的氧化剂的蛋白质消耗是一致的。
氧化可以发生在蛋白质的骨架上，也可以发生在氨基酸的侧链上，这两者的攻击比率依赖于一些因素。
对于一些氧化剂，它们所造成的损伤是有限的，并且特定于某些残留；但是对于其他品种，如羟基自由基，它们所造成的是广泛的和相对非特异性的损伤。
本文综述了一些主要的氧化途径和形成的产品。
后者包括反应性物质，如过氧化物，可引发进一步的氧化和链反应（在蛋白质内，并且通过转移损伤到其他分子）和稳定的产品。
特别强调的是甲硫氨酸残留物的氧化，因为这种氧化剂很容易被很多品种的氧化剂氧化。
一些侧链的氧化物，包括甲硫氨酸亚砜，可以用作氧化损伤的具有敏感性和具体性的标志物。
在某些情况下，产品简介可以提供关于涉及到的氧化剂的有价值的信息，并且讨论这种方法所选择的例子。
大多数的蛋白质损伤是不可修复的，并且会对蛋白质的结构和功能有害处；但是，在某些情况下，甲硫氨酸亚砜的生成可以被逆转。
氧化蛋白质主要是通过蛋白酶体和溶酶体的途径被代谢掉，但是一些材料出现在细胞内缓慢降解和积聚的现象。
这些损伤的材料的积聚可能会导致一系列的人类疾病。
关键词：蛋白质氧化；自由基；氧化剂；碎片；交联；甲硫氨酸；甲硫氨酸亚砜1.氧化剂的产生在生物系统中，通过一系列不同的过程可以产生自由基和非自由基氧化剂。
这些所包括的范围从人为的和高度控制的在酶的活性位点内的自由基生成，到暴露在高能量的辐射里的细胞和组织中的，意想不到的，基本上随机的氧化剂生成。
一些内源性系统是可以产生自由基和其他非自由基氧化剂（如过氧化物，次氯酸，过氧化亚硝基阴离子，单线态氧），这些包括一系列的酶（如一氧化氮合成酶，NADPH氧化酶，核苷酸还原酶，前列腺素合成酶，过氧化物酶，其他血红素酶，脂肪氧化酶），和电子传递链（如线粒体细胞色素P450系统）。
氧化剂的生成也可以作为一系列的外援因子的响应，包括辐射（在敏化剂的存在下的X射线，γ射线，紫外光，或可见光），金属离子，溶剂，颗粒物（石棉，空气中的材料），氮氧化物，臭氧，各种形式的烟等。
这些氧化物的生成已经被综述过了（如见文献[1]）。
2.氧化剂与生物目标物的反应大多数高反应活性的氧化剂，包括许多自由基，可以和几乎所有的生物分子反应，包括DNA，RNA，胆固醇，脂质，碳水化合物，蛋白质和抗氧化剂。
而一些反应活性较低的氧化剂，例如过氧化物（如H2O2，脂质过氧化物或蛋白质过氧化物），对于它们所损伤的目标物有更高的选择性，即在特定的地点氧化剂对特定的分子发生修改。
对特定目标的损伤程度取决于若干因素，包括：目标物的浓度，当和氧化剂生成的位置相比时的目标物的位置，二次损伤的发生（链反应和损伤转移过程），氧化剂清除反应的发生和修复反应。
这些因素的前两个决定任何特定的可能发生的反应速率；其他因素调节所发生反应的程度。
这篇综述集中在氧化剂与蛋白质的反应，因为这是大多数生物系统的主要组成部分，无论是在组织，细胞或生物流体水平上（参见图1中的数据）。
在每个实例中，蛋白质包括主要的无水组分。
即使在材料，如低密度脂蛋白（LDL）和细胞膜组分，这些往往视为脂质丰富的环境中，蛋白质依然是主要成分，例如，单一的蛋白质在LDL——载脂蛋白B-100——提供了约25%的粒子质量[2]和许多细胞质膜的干重中含50%-60%的蛋白质。
胆固醇脂质DNA蛋白质RNA胆固醇脂质DNA蛋白质碳水化合物胆固醇图1. 各种生物材料的近似组成。
（A）肝（g每kg湿重）；（B）白血球细胞（g每1012个细胞）；（C）血浆（g每dm3）。
表1.HO·在pH值为7的条件下与大分子反应的速率常数基质速率常数(dm3mol-1s-1)DNA 8×108RNA 1×109透明质酸7×108亚油酸9×109骨胶原4×1011白蛋白8×1010抗坏血酸盐1×1010GSH 1.4×1010Trolox C（水溶性维生素E类似物）6.9×109选择的数据来自参考文献[3]。
一系列活性的自由基与生物大分子的反应速率常数进一步表明了作为氧化剂的目标物的蛋白质的潜在重要性。
表1中所给的数据表明：氧化剂，如羟基自由基（HO·），与大分子的反应速率常数在相对较小的程度上变化，因此，整体的反应速率（它是速率常数与目标物浓度的作用结果），将会大体上被目标物的浓度影响。
此外，当这些速率常数与一系列生物相关的抗氧化剂（或它们的模型，表1）进行比较时，可以看出这些数字相差不大。
此数据强调了设计可以成功地与生物目标物的损伤竞争的抗氧化剂策略的困难性，也表明了当与这些目标物的毫摩尔的摩尔浓度相比时，大多数的抗氧化剂是以微摩尔的浓度存在的。
一些动力学数据的汇编适用于广范围的氧化剂，其中包括：HO·，氢原子（H·）和水合电子[3]，超氧阴离子自由基和它的质子化形式（O2—·/HOO·；[4]），碳中心自由基[5]，范围广泛的无机自由基（如NO2·，CO2—·，CO3—·，Br2—·，N3·；[6]），过氧自由基（ROO·；[7]），单线态氧（1O2；[8]），还有次氯酸和次溴酸（HOCl和HOBr；[9-11]）。
上述氧化剂的速率常数数据的定期更新表格和许多其他氧化剂的表格可以在/solution/index.php上找到。
这种动力学的知识和丰富的数据可用于计算机模型中预测损伤的位置。
对于一个典型的细胞（白血球细胞）和两个反应活性氧化剂——HO·和1O2——的分析所产生的数据示于图2中。
显然，这种建模数据需要谨慎处理，因为它并没有考虑一系列其他已知的与特定的目标物反应会影响氧化活性的因素——这些包括位置的作用（氧化剂的和目标物的位置），链式反应的发生和修复过程的影响。
这说明：这样的数据可以提供关于特定物种损伤的潜在重要性的重要线索。
正如预期的那样，在不同氧化剂之间的损伤选择性中有一个大的变化。
大体上说，最活泼的自由基有最小的选择性。
因此，HO·与不同侧链的反应速率常数的变化是比较小的（k 107-1010dm3mol-1s-1；表2），其结果是虽然芳香族和含硫的侧链预计会被最快消耗完，但是所有侧链位点或多或少地被氧化。
用HO·从主链位点上进行夺氢反应，其反应速率常数为k=109dm3mol-1s-1，它与这个由自由基引起的侧链和主链损伤（和随后的蛋白质碎片）是一致的。
比较不活泼的氧化剂对于它们所氧化的位点更有选择性，例如，因为色氨酸残基在检测线以下，被取代的过氧自由基CCl3OO·与氨基酸侧链的反应速率常数在9×107dm3mol-1s-1左右变化，这与这种氧化剂的更具选择性的损伤是一致的。
因此，一般来说，一个氧化剂的活泼性越低，它所引起损伤的选择性越大。
因为这个原因，一些比较弱的氧化剂可以对蛋白质产生很有选择性的损伤，并且一些试剂是已知的选择性的针对单个残基。
类似的非自由基氧化剂的动力学数据也是可以得到的；例如，当色氨酸，酪氨酸，组氨酸，甲硫氨酸和胱氨酸残基作为主要的目标物时，1O2的反应具有相当程度的选择性。
由于许多生成在生物系统中的活泼氧化剂是缺电子的（具有氧化性的，亲电子的），它与富电子的侧链（即色氨酸，酪氨酸，组氨酸，甲硫氨酸，胱氨酸，苯丙氨酸残基）快速发生反应是一种普遍的模式。
然而，在大多数情况下，一些具有显著不同选择性的重要亲核性或还原性的物质（水合e—，Ph·，CO2—·）与O2的反应是特别快也是特别重要的反应。
蛋白质脂质其他图2.来自于动力学和丰富的数据，在白血球细胞中各种细胞成分的计算消耗量：（A）羟基自由基和（B）单线态氧。
进一步详情请参阅文本。
表2. HO·在pH值为7的条件下与游离（两性）氨基酸和小肽的反应速率常数基质速率常数（dm3mol-1s-1)丙氨酸7.7×107精氨酸 3.5×109天门冬酰胺 4.9×107天冬氨酸7.5×107半胱氨酸 3.4×1010胱氨酸 2.1×109谷氨酰胺 5.4×108谷氨酸 2.3×108甘氨酸 1.7×107组氨酸 1.3×1010异亮氨酸 1.8×109亮氨酸 1.7×109赖氨酸 3.4×108甲硫氨酸8.3×109苯丙氨酸 6.5×109脯氨酸 4.8×108丝氨酸 3.2×108苏氨酸 5.1×108色氨酸 1.3×1010酪氨酸 1.3×1010缬氨酸7.6×108环（甘氨酸）2（主链攻击）7.8×108N-乙酸-甘氨酸-甘氨酸（主链攻击）7.8×108选择的数据来自于参考文献[3]。
虽然动力学数据大量用于确定一个特定氧化剂与目标物的总反应速率，但是通常采用的用来获取这样数据（通常是紫外检测器的脉冲辐射分解）的技术，通常不会产生在分子内不同位点处的损伤选择性的信息，除非能够监视特定的瞬态或产物的特定吸收。
由于技术方面的原因，这样的方法只对于芳香族或含硫的残基是可能的，因为大多数通过夺氢产生的脂肪族侧链和碳中心自由基没有容易探测到的吸收。
然而，在特定侧链中不同位点的攻击选择性的数据可以通过另外两种方法获得：所产生的自由基的电子顺磁共振（EPR或ESR）光谱学研究和产物分析。
这两种方法都不是完美的，尤其当检测任何大于小肽的物质时两者都具有重大的缺点，因为获得的数据的分析变得极为复杂，而且转移反应（见下文）的发生可能会导致解释的问题。
许多因素是众所周知的会影响哪个位点最容易被攻击。
这些因素包括：在自由基介导的氧化（稳定性的顺序为：叔>仲>伯；并且有可能在杂原子上产生电子离域的物质比不能产生这种可能的物质更容易受到攻击）情况下，初期自由基的稳定性；统计因素（即C-H键/加成位点的每个特定类型的数目）；还有可能的空间位阻和电荷的相互作用，这可能使得一个特定的位置易于或不易于反应。
虽然成堆的证据显示在许多生物系统中，蛋白质的氧化可能是一个关键步骤，但是在这个领域的研究落后于对脂质和DNA氧化的研究。