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Our perception of the universe has been altered by recent discoveries in astronomy, discoveries of new objects and of new phenomena, coming from a wide range of observing techniques. By 1990 astronomers expect to know more about the distribution of mass in the universe, the physics of energetic sources, and the intricate interconnections of astrophysical processes on a variety of spatial and temporal scales.  相似文献   

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For most of history, few things have mattered more to human communities than their relations with soil, because soil provided most of their food and nutrients. Accordingly, some of the earliest written documents were agricultural manuals intended to organize, preserve, and impart soil knowledge. Indeed, ancient civilizations often worshipped the soil as the foundry of life itself. For the past century or two, nothing has mattered more for soils than their relations with human communities, because human action inadvertently ratcheted up rates of soil erosion and, both intentionally and unintentionally, rerouted nutrient flows.  相似文献   

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Whereas hundreds of social movements and NGOs all over the world have embraced the concept of food sovereignty, not many public authorities at the national and international level have adopted the food sovereignty paradigm as a normative basis for alternative agriculture and food policy. A common explanation of the limited role of food sovereignty in food and agriculture policy is that existing power structures are biased towards maintaining the corporatist food regime and neo-liberal thinking about food security. This article sets out to provide an alternative explanation for this limited role by critically reflecting on the debate about food sovereignty itself. The main argument is that this debate is characterized by deadlock. Two mechanisms underlying the deadlock are analyzed: confusion about the concept of sovereignty and the failure of the epistemic community to debate how to reconcile conflicting values, discourses, and institutions regarding food. To overcome this deadlock and organize meaningful debate with public authorities, it is proposed that the food sovereignty movement uses insights from legal pluralism and debates on governance and adopts the ending of “food violence” as a new objective and common frame.  相似文献   

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"Natural measures of quantity, such as fathoms, cubits, inches, taken from the proportion of the human body, were once in use with every nation," taught Adam Smith in his lecture "Money as the measure of value and medium of exchange," delivered in 1763. "But by a little observation," he continued, "they found that one man's arm was longer or shorter than another's, and that one was not to be compared with the other; and therefore wise men who attended to these things would endeavour to fix upon some more accurate measure, that equal quantities might be of equal values. Their method became absolutely necessary when people came to deal in many commodities, and in great quantities of them." Smith's comments and the rationale underpinning them became increasingly urgent toward the end of the eighteenth century.  相似文献   

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为系统了解湖南省虾类的生物多样性,从1987年起,采集了湖南省各类水域题指虾类标本近10000号,并对其进行了系统研究。研究发现,湖南省共有匙指虾科虾类31种(亚种),隶属于米虾属、新米虾属、拟米虾属和缺鞭米虾属,其中有20种为湖南特有种,缺鞭米虾属为湖南特有属,报道了新米虾属、拟米虾属和缺鞭米虾属三属共10种的主要鉴别特征,地理分布与生活习性,并提供了种的检索表。  相似文献   

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阐述了阿拉斯加管道腐蚀产生的原因,提出了为避免管道因腐蚀而穿孔,应加强管道内检测的措施;对阿拉斯加管道的通信设备及SCADA系统进行了介绍,并结合我国西部管道的具体情况,提出了管道通讯今后的发展趋势;由于阿拉斯加管道是在严寒地区施工,故碰到一系列难题,如管道的轴向压力问题及水压试验问题,对此进行了详细的分析论证;论述了Valdez末站油库的油罐为锥顶的优点,同时对油库的消防设施做了说明。  相似文献   

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cis,trans-Nepetalactone, the biologically active component of catnip, was force-fed to the domestic cat. When the (14)C-labeled compound was fed, 86 to 94 percent of the radioactivity was recovered in the urine, 1 to 2 percent was found in the feces, and 1 to 12 percent was collected as carbon dioxide. The major (50 to 75 percent) metabolite was alpha-nepetalinic acid, which was excreted in the urine together with small amounts of dihydronepetalactone, unchanged cis,-trans-nepetalactone, and several unidentified compounds. No marked physiological or histological eflects were observed when 20 to 80 milligrams of cis, trans-nepetalactone was administered orally. This is the first report on the metabolism of a mammalian attractant.  相似文献   

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The identification of human artifacts at the early archaeological site of Monte Verde in southern Chile has raised questions of when and how people reached the tip of South America without leaving much other evidence in the New World. Remains of nine species of marine algae were recovered from hearths and other features at Monte Verde II, an upper occupational layer, and were directly dated between 14,220 and 13,980 calendar years before the present ( approximately 12,310 and 12,290 carbon-14 years ago). These findings support the archaeological interpretation of the site and indicate that the site's inhabitants used seaweed from distant beaches and estuarine environments for food and medicine. These data are consistent with the ideas that an early settlement of South America was along the Pacific coast and that seaweeds were important to the diet and health of early humans in the Americas.  相似文献   

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