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1.
Observations of Io in eclipse demonstrate conclusively that Io emits substantial amounts of radiation at 4.8 and 3.8 micrometers and a measurable amount at 2.2 micrometers. Color temperatures derived from the observations fit blackbody emission at 560 K. The required source area to yield the observed 4.8-micrometer flux is approximately 5 x 10(-5) of the disk of Io and is most likely comprised of small hot spots in the vicinity of the volcanoes.  相似文献   

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Excess volcanism and crustal swelling associated with hot spots are generally attributed to thermal plumes upwelling from the mantle. This concept has been tested in the portion of the Mid-Atlantic Ridge between 34 degrees and 45 degrees (Azores hot spot). Peridotite and basalt data indicate that the upper mantle in the hot spot has undergone a high degree of melting relative to the mantle elsewhere in the North Atlantic. However, application of various geothermometers suggests that the temperature of equilibration of peridotites in the mantle was lower, or at least not higher, in the hot spot than elsewhere. The presence of H(2)O-rich metasomatized mantle domains, inferred from peridotite and basalt data, would lower the melting temperature of the hot spot mantle and thereby reconcile its high degree ofmelting with the lack of a mantle temperature anomaly. Thus, some so-called hot spots might be melting anomalies unrelated to abnormally high mantle temperature or thermal plumes.  相似文献   

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正The 2017 International Bovine Mastitis ConferenceThe National Mastitis Council Regional in China was successfully held in Beijing on August 25–27,2017.Nearly 650participants from more than eight countries(regions)and international organizations attended this conference.The conference provided an communication platform for international counterparts,and the content was closely related  相似文献   

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The statistical correlation between the locations of hot spots at the surface of Earth and the distribution of ultra-low-velocity zones at the base of the mantle has about a 1 percent chance of arising randomly. This correlation is more significant than that between hot spots and negative velocity anomalies in tomographic models of deep mantle compressional and shear velocity. This correlation is consistent with the notion that many hot spots originate in a low-velocity, probably partially molten layer at the core-mantle boundary and undergo little lateral deflection on ascent.  相似文献   

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Saturn's poles exhibit an unexpected symmetry in hot, cyclonic polar vortices, despite huge seasonal differences in solar flux. The cores of both vortices are depleted in phosphine gas, probably resulting from subsidence of air into the troposphere. The warm cores are present throughout the upper troposphere and stratosphere at both poles. The thermal structure associated with the marked hexagonal polar jet at 77 degrees N has been observed for the first time. Both the warm cyclonic belt at 79 degrees N and the cold anticyclonic zone at 75 degrees N exhibit the hexagonal structure.  相似文献   

7.
自然保护区学当前应该解决的几个科学问题   总被引:33,自引:2,他引:33  
自然保护区已成为一类特殊的土地利用类型,总面积约占国土面积的14%以上;其不仅具有保护野生动植物资源的功能,而且在维护国土生态安全中发挥着关键作用.我国自然保护区建设工程实施过程中,迫切需要解决的主要科学技术问题包括自然保护区体系规划和合理布局方案研究制定、分类经营管理系统建立、野生动植物资源本底调查和动态监测等.自然保护区学是新建立的二级学科.该文定义了自然保护区学的内涵,提出了主要研究领域和方向.指出了当前研究热点问题,如“生态岛屿”状态的自然保护区内野生动植物小种群恢复与调控、自然保护区最小面积确定、生物廊道的设计、规划设计中的功能区划、自然资本评估与经济管理等.  相似文献   

8.
Large-scale nonlinear simulations of Jupiter's 5-micron hot spots produce long-lived coherent structures that cause subsidence in local regions, explaining the low cloudiness and the dryness measured by the Galileo probe inside a hot spot. Like observed hot spots, the simulated coherent structures are equatorially confined, have periodic spacing, propagate west relative to the flow, are generally confined to one hemisphere, and have an anticyclonic gyre on their equatorward side. The southern edge of the simulated hot spots develops vertical shear of up to 70 meters per second in the eastward wind, which can explain the results of the Galileo probe Doppler wind experiment.  相似文献   

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VOSriewer1992-2011年国内外数字图书馆研究的进展和热点进行了对比分析。  相似文献   

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The recent discovery of a hyper-metal-poor (HMP) star, with a metallicity Fe/H smaller than 1/100,000 of the solar ratio, together with one earlier HMP star, has raised a challenging question whether these HMP stars are the actual first-generation, low-mass stars of the universe. We argue that these HMP stars are second-generation stars formed from gases that were chemically enriched by the first-generation supernovae. The key to this solution is the very unusual abundance patterns of these HMP stars and the similarities and differences between them. We can reproduce these abundance features with core-collapse "faint" supernova models that include extensive matter mixing and fallback during explosions.  相似文献   

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Hot spots (HSs) are regions of enhanced radio emission produced by supersonic jets at the tip of the radio lobes of powerful radio sources. Obtained with the Very Large Telescope (VLT), images of the HSs in the radio galaxy 3C 445 show bright knots embedded in diffuse optical emission distributed along the post-shock region created by the impact of the jet into the intergalactic medium. The observations reported here confirm that relativistic electrons are accelerated by Fermi-I acceleration processes in HSs. Furthermore, both the diffuse emission tracing the rims of the front shock and the multiple knots demonstrate the presence of additional continuous re-acceleration processes of electrons (Fermi-II).  相似文献   

14.
A study was made of the anti-inflammatory activity of the fractionated components of a citrus flavonoid complex. Several highly active components, distinct from hesperidin and naringin, were isolated and tested for anti-inflammatory activity. A method for evaluation of this biological activity is recommended.  相似文献   

15.
Transforming growth factor-beta: biological function and chemical structure   总被引:104,自引:0,他引:104  
Transforming growth factor-beta (TGF-beta) is a multifunctional peptide that controls proliferation, differentiation, and other functions in many cell types. Many cells synthesize TGF-beta and essentially all of them have specific receptors for this peptide. TGF-beta regulates the actions of many other peptide growth factors and determines a positive or negative direction of their effects. Its marked ability to enhance formation of connective tissue in vivo suggests several therapeutic applications.  相似文献   

16.
Biotite alteration under acid conditions proceeds differently from the generally accepted pathway of transformation to vermiculite in which hydrated cations cause interlayer expansion, resulting in a dark-colored peripheral band on mica particles. Acid solutions of synthetic or biologic origin remove octahedral ions, leaving a fragile matrix of amorphous material.  相似文献   

17.
本文汇集了1982年4月至1983年4月,1985年4月,1986年10月,1987年5月和1988年5至6月,以及1992年8月至6月各时段的渤海和黄海多种基础调查的鱼卵、仔稚鱼表层水平拖网资料。调查期间共采集了98种硬骨鱼类的于卵、仔稚鱼。详细阐述了其产卵期、卵径和油球径的大小、卵膜和卵黄构造、孵化时间和初孵仔鱼大小等生物学特征。  相似文献   

18.
渤、黄海硬骨鱼类鱼卵与仔稚鱼种类组成及其生物学特征   总被引:29,自引:2,他引:29  
本文汇集了1982年4月至1983年4月,1985年4月,1986年10月,1987年5月和1988年5至6月,以及1992年8月至6月各时段的渤海和黄海多种基础调查的鱼卵、仔稚鱼表层水平拖网资料。调查期间共采集了98种硬骨鱼类的于卵、仔稚鱼。详细阐述了其产卵期、卵径和油球径的大小、卵膜和卵黄构造、孵化时间和初孵仔鱼大小等生物学特征。  相似文献   

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为明确国内外昆虫性别决定基因研究的发展历程、研究热点及趋势,为未来研究方向提供参考与建议,本研究整理并筛选了1933—2022年中国知网(CNKI)和Web of Science(WOS)数据库收录的昆虫性别决定基因的论文,运用文献计量学分析软件CiteSpace对发文年代、关键词、作者和机构等进行可视化分析。结果表明:2001—2005年昆虫性别决定基因研究的发文量呈现上升趋势,发文量最多的国家是美国(446篇),其次是中国(111篇)和日本(88篇);国内外载文量最多的期刊分别是《昆虫学报》(9篇)和Genetics(94篇);通过关键词共现和聚类分析表明昆虫性别决定在国内外都是广泛关注的热点问题,且国内外研究方向大体一致,研究热点均集中在模式生物上;通过关键词共现和突现词分析发现利用昆虫性别决定基因进行害虫防治是未来研究的新趋势。  相似文献   

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