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  • 中文名称: 性质
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  • ISSN: 0028-0836
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  • 机译 日本预算增加了科学经费
    摘要:Japan's largest ever budget, aimed at reviving the nation's ailing economy through increased public spending, includes a generous 8.1 per cent boost in expenditure on science, with a strong emphasis on basic research. The budget for the 1999 fiscal year, which begins on 1 April, takes overall science spending across all ministries and agencies to ¥963 billion (US$8.5 billion), with large increases for life sciences in particular. Also featured are support for creating new businesses through 'commercially applicable research', and the promotion of collaborative research between universities and industry.
  • 机译 互联网可能有助于弥合差距
    摘要:Until recently, many feared that increasing use of the Internet would widen yet further the knowledge gap between industrialized and developing countries. But such pessimism is giving way to optimism that the new technology may instead help spur a renaissance of science and technology in poorer countries. Indeed, the prospect that Internet access will eventually become widely available seems to be shifting the focus of the debate onto issues related to access to and the production of the content of websites.
  • 机译 东欧仍然束手无策...
    摘要:None of the central-east European countries that are candidates for membership of the European Union (EU) plans to significantly increase its research spending next year, despite announcements that they would do so in anticipation of joining the EU. The European Commission is concerned that, unless the governments of Poland, Hungary, the Czech Republic and Slovenia increase their spending soon, they will be badly placed to exploit their new status as full associates of the commission's fifth Framework programme of research (FP5), which will be launched this year.
  • 机译 知识经济的前景和威胁
    • 作者:;
    • 刊名:Nature
    • 1999年第6714期
    摘要:The need to place scientific knowledge at the heart of economic and social policy has underlined some of the limitations of focusing on trade liberalization. Developing countries should be a prime beneficiary. Suddenly everyone is talking about it. For years, the idea that knowledge in general—and scientific knowledge in particular — plays a role in the global economy comparable to more tangible forms of resources and capital has been confined largely to the writing of left-leaning sociologists and policy analysts. As such, it has often been dismissed in political circles as little more than a woolly minded bid for extra funding from the scientific community and tax breaks on R&D spending from industry. Over the past year, however, the concept that we live in an age when both the social and economic health of any society depends critically on its ability to harness scientific (and other) knowledge has gained wide political currency.
  • 机译 空中交通可能会增加卷云混浊
    摘要:High-level cirrus clouds can evolve from the condensation trails of aircraft, which form as the mixture of warm, humid exhaust gases and colder, drier air exceeds water saturation. In addition, the particles in exhaust plumes from aircraft may allow ice nude-ation at lower supersaturations than those required under natural conditions. This mechanism is sensitive to environmental conditions, but may occur downstream of the exhaust aerosol source regions. Here I show that cirrus clouds increased in occurrence and coverage in the main air-traffic flight corridors between 1982 and 1991.
  • 机译 世界银行投资全球科学基地
    摘要:After 50 years of paying for roads, power and schools, and helping poor countries to liberalize their economies, the World Bank — the financial arm of the United Nations system — has started shifting some of the focus of its activities to supporting 'knowledge development', including science. Two separate internal World Bank task groups are investigating a potential role for the bank in supporting science in developing countries. Each group will report back this year with proposals on how the bank can best support basic research, something it has never before considered, how to make its expertise more available to developing countries, and whether it needs a science department to oversee its new initiatives.
  • 机译 招聘时空
    摘要:Six years ago, in an address to the Ecological Society of America, Simon Levin wrote that "the problem of pattern and scale is the central problem in ecology, unifying population biology and ecosystem science, and marrying basic and applied ecology". Interest in scale effects has since grown, and patterns or processes have been examined contemporaneously over several scales of space and time. On page 59 of this issue, Terry Hughes and colleagues2 report an important field study on patterns of recruitment and adult abundance of corals on the Great Barrier Reef.
  • 机译 大堡礁沿岸珊瑚的吸收和丰富模式
    摘要:Different physical and biological processes prevail at different scales. As a consequence, small-scale experiments or local observations provide limited insights into regional or global phenomena. One solution is to incorporate spatial scale explicitly into the experimental and sampling design of field studies, to provide a broader, landscape view of ecology. Here we examine spatial patterns in corals on the Great Barrier Reef, across a spectrum of scales ranging from metres to more than 1,700 km. Our study is unusual because we explore large-scale patterns of a process (recruitment by juveniles) as well as patterns of adult abundance, revealing the relationship between the two. We show that coral-reef assemblages that are similar in terms of abundance may nonetheless show profound differences in dynamics and turnover, with major implications for their ecology, evolution and management.
  • 机译 从Mo_(176)到Mo_(248)簇的分子生长
    摘要:In polyoxometalate chemistry a large variety of compounds, clusters and solid-state structures can be formed by the linking together of well-defined metal-oxygen building blocks. These species exhibit unusual topological and electronic properties, and find applications ranging from medicine to industrial processes. The recently reported ring-shaped mixed-valence polyoxomolybdates of the type {Mo_(154)} (refs 5, 6) and {Mo_(176)} (refs 7, 8) represent a new class of giant clusters with nanometre-sized cavities and interesting properties for host-guest chemistry. Here we describe the formation of related clusters of the type {Mo_(248)} formed by addition of further units to the inner surface of the {Mo_(176)} 'wheel'. The additional units arrange themselves into two {Mo_(36)} 'hub-caps' on the initial wheel—clusters that are not stable in isolation. These findings reveal a new pathway to the development of complex coordination clusters.
  • 机译 使黑暗的状况变得光明
    摘要:When the seedlings of flowering plants are grown in the dark (etiolated seedlings), they cannot make chlorophyll because the enzyme that reduces protochlorophyllide to chlorophyllide — protochlorophyllide oxidoreductase (POR) — requires light. As well as collecting light for photosynthesis, chlorophylls protect the plant by dissipating excess light energy. So, when etiolated seedlings emerge from the soil into the sunlight they lack these photo-protective mechanisms. Moreover, if a seedling emerges into low light it may not be able to synthesize chlorophyll rapidly enough to take full advantage of this photo-synthetic opportunity. On page 80 of this issue, Reinbothe et al. show that POR, which presents the plant with these dilemmas, also provides it with the solution.
  • 机译 污染中的胶体元凶
    摘要:Perhaps nowhere have the details of contaminant transport in ground-water systems been more contentious than in the area of nuclear waste disposal. Over the past decade, the discovery of colloidal forms of actinides, such as plutonium (Pu), has often been at the centre of concern over underground storage of radionuclides. On page 56 of this issue Kersting et al. provide an illustration of the striking influence colloids may have on contaminant transport. The authors have studied groundwater migration of Pu from a nuclear detonation site in Nevada. However, the particular significance of their report lies in reinforcing a general awareness of colloid-facilitated contaminant transport.
  • 机译 褐矮星:失败的星星
    摘要:In recent years, new astronomical instruments have reversed three decades of fruitless searching for brown dwarfs, the failed stars that are too small to burn nuclear fuel. These discoveries have confirmed predictions about the Importance of methane and dust In the atmospheres of brown dwarfs. But they also demonstrate that, contrary to expectation, brown dwarfs do not contribute significantly to our Galaxy's dark matter.
  • 机译 高温超导体中转变温度的定标和CuO_2平面屈曲
    摘要:A characteristic feature of the high-temperature superconductors is the existence of a chemical composition that gives a maximum transition temperature, T_c, separating the so-called under-doped and over-doped regimes. This behaviour is thought to be universal for high-temperature superconductors. In practice, there are only a few high-T_c compounds for which the composition can be varied continuously throughout the entire doping range. Here we report a study of correlations between structure and T_c in a compound with the '123' structure in which both the under-doped and over-doped regimes can be accessed. We observe a clear scaling between T_c and the buckling of the copper oxide planes; both go through a maximum at the same oxygen composition (and hence doping level), so implying a common origin. Previous work has shown that, for a fixed chemical composition, increased CuO_2 plane buckling lowers the transition temperature. Thus the observation of a maximum in the budding at the maximum T_c indicates that, as the composition is changed to increase T_c, there is a structural response that competes with superconductivity.
  • 机译 科学推动了欧洲的援助议程
    摘要:"Five years ago, research was almost a dirty word in development aid circles," says Barend Mons, a senior adviser to the Dutch research organization NWO. Today, however, research is no longer considered "a luxury toy for rich countries", but a fundamental component of economic success in all countries. The change represents a major shift in European attitudes towards Third World aid in the past few years. Research has been a significant beneficiary.
  • 机译 地球下地幔俯冲的玄武岩壳的命运
    摘要:The subduction of oceanic lithosphere into the Earth's deep interior is thought to drive convection and create chemical heterogeneity in the mantle. The oceanic lithosphere as a whole, however, might not subduct uniformly: the fate of basaltic crust may differ from that of the underlying peridotite layer because of differences in chemistry, density and melting temperature. It has been suggested that subducted basaltic crust may in fact become buoyant at the mantle's 660-km discontinuity, remaining buoyant to depths of at least 800 km, and therefore might be gravitation-ally trapped at this boundary to form a garnetite layer. Here we report the phase relations and melting temperatures of natural mid-ocean ridge basalt at pressures up to 64 GPa (corresponding to ~ 1,500 km depth). We find that the former basaltic crust is no longer buoyant when it transforms to a perovskitite lithology at about 720 km depth, and that this transition boundary has a positive pressure-temperature slope, in contrast to the negative slope of the transition boundary in peridotite. We therefore predict that basaltic crust with perovskitite lithology would gravitationally sink into the deep mantle. Our melting data suggest that, at the base of the lower mantle, the former basaltic crust would be partially molten if temperatures there were to exceed 4,000 K.
  • 机译 瑞士军刀的新工具
    摘要:Life as a virus is demanding. Tiny in size, and with limited genetic material, a virus must successfully take over comparatively gigantic cells or multicellular organisms. Unlike symbiotic invaders it will face a hostile reception, and it is no surprise that viruses have evolved to carry simplified, multifunctional conquest weapons, resembling the sophisticated equipment in the pocket of 007's dinner suit. A good example of such a weapon is the 'helper component protease' (HC-Pro), which is found in the group of potyviruses that infect, and cause severe disease in, a spectrum of plant species. Three papers published in Proceedings of the National Academy of Sciences, EMBO Journal and Cell now tell us something about why HC-Pro makes these viruses so successful.
  • 机译 内华达州试验场中地下水中of的迁移
    摘要:Mobile colloids—suspended particles in the submicrometre size range—are known to occur naturally in ground water and have the potential to enhance transport of non-soluble contaminants through sorption. The possible implications of this transport mechanism are of particular concern in the context of radio-nuclide transport. Significant quantities of the element plutonium have been introduced into the environment as a result of nuclear weapons testing and production, and nuclear power-plant accidents. Moreover, many countries anticipate storing nuclear waste underground. It has been argued that plutonium introduced into the subsurface environment is relatively immobile owing to its low solubility in ground water and strong sorption onto rocks. Nonetheless, colloid-facilitated transport of radio-nuclides has been implicated in field observations, but unequivocal evidence of subsurface transport is lacking. Moreover, colloid filtration models predict transport over a limited distance resulting in a discrepancy between observed and modelled behaviour. Here we report that the radionuclides observed in groundwater samples from aquifers at the Nevada Test Site, where hundreds of underground nuclear tests were conducted, are associated with the colloidal fraction of the ground water. The ~(240)Pu/~(239)Pu isotope ratio of the samples establishes that an underground nuclear test 1.3 km north of the sample site is the origin of the plutonium. We argue that colloidal groundwater migration must have played an important role in transporting the plutonium. Models that either predict limited transport or do not allow for colloid-facilitated transport may thus significantly underestimate the extent of radionuclide migration.
  • 机译 愿原力与你同在
    摘要:Many of us grew up with the simplifying assumptions of biology in a test tube — dilute solutions, purified biomolecules and the like. But the biomolec-ular machinery evolved in a much more complex environment than this. I can remember, several years ago, seeing a cartoon that depicted the remarkably crowded and organized environment of the cytoplasm. I was struck for the first time by the implications of chaperonins for the protein-folding field. It isn't that the biophysics we learned in the test tube is wrong, or cannot be extrapolated to the living cell, but we must acknowledge that questions of relevance and adequacy sometimes arise.
  • 机译 候鸟的新陈代谢率高
    摘要:The ability to increase metabolic rate during locomotion has been important in the structural evolution and evolutionary success of both birds and mammals. Greater endurance capabilities are conferred directly by greater maximal metabolic rates, which vary between species. These maximal rates are known for many mammals but have not been determined for birds. We have measured oxygen consumption in a large flightless bird, the rhea, Shea americana, while it was running on an inclined treadmill, and find an upper limit to aerobic metabolism that is 36 times greater than the minimum resting rate, a factorial increase exceeding that reported for nearly all mammals.
  • 机译 出行的伯劳
    摘要:Getting from one place to another is a problem for a plant. One of the most efficient solutions is to wrap seeds in an attractive, preferably tasty, envelope and so encourage gluttonous animals to transport them. Wandering frugivores may thus become inadvertent vehicles of plant migration, but they could also find themselves the target of higher predators — so what then is the fate of the fruits? Is this where the story ends for the passively mobile plant? Apparently not. Work on fruit-eating lizards from the Canary Islands by Nogales, Delgado and Medina, reported in the Journal of Ecology, shows that viable seeds can be ingested by the predator with its prey and taken to further destinations, thus adding a new dimension to dispersal.
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