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Deforestation trends in tropical Africa 总被引:1,自引:0,他引:1
R. F. W. BARNES 《African Journal of Ecology》1990,28(3):161-173
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Ted C. Lewellen 《American anthropologist》1997,99(3):643-643
Tropical Deforestation: The Human Dimension. Leslie E. Sponsel. Thomas N. Headland, and Robert C. Bailey, eds. New York: Columbia University Press,1996. 365 pp. 相似文献
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M. K. Mani 《BMJ (Clinical research ed.)》1971,3(5771):407-408
Sodium nitroprusside is a readily available, powerful hypotensive agent. It was administered intravenously in four cases when all other available hypotensive agents had failed, and blood pressure was controlled promptly and with no side effects. This is a valuable drug and deserves wider use. 相似文献
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Interest in the developmental basis of symmetry and asymmetry,as old as experimental embryology itself, has recently becomereactivated. A brief survey is made of recent or current activitiesin the following areas: (i) development of asymmetry in thechick limb bud, as related to the so-called zone of polarizingactivity (Saunders et al.); (ii) situs inversus viscerum inamphibians, as induced by transplantation and defect experiments,radiation, and chemical treatment (von Woellwarth, von Kraft,Wehrmaker); (iii) situs inversus viscerum in mammals as relatedto (a) twinning (Cockayne, Torgerson, Baker-Cohen); (b) genetics(Feldman, Cockayne, Torgerson for man, Tihen et al., Hummeland Chapman for mouse); and (c) teratogens (Layton and associates);(iv) ultrastructure in snails (Morrill and Perkins); (v) asymmetrydeveloping as a result of changes in chemical instability inhomogeneous systems (Ortoleva and Ross); (vi) asymmetrical mentality(Sperry and associates). No general conclusions are attempted. 相似文献
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Androgenesis Revisited 总被引:1,自引:0,他引:1
José M. Seguí-Simarro 《The Botanical review》2010,76(3):377-404
Androgenesis can be defined as the set of biological processes leading to an individual genetically coming exclusively from a male nucleus. Androgenesis was traditionally considered as the spontaneous, in vivo development of a male-derived haploid embryo from a fertilized egg where the female nucleus is eliminated. However, at present it is also possible to generate androgenic haploids/doubled haploids through in vitro microspore embryogenesis and by in vitro meiocyte-derived callogenesis. These three androgenic alternatives clearly differ in the inducible stage, but lead to the same final haploid or doubled haploid product. Whereas microspore embryogenesis is widely studied and applied, the other two routes are much less known. In this paper, the evidence accounting for the existence of these three alternative pathways is revised, as well as the mechanisms potentially involved in their induction. Their differences and similarities are discussed from a biological perspective, leading to the notion that they might represent an ancient survival mechanism triggered by similar factors. 相似文献
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Many of the world’s forests are being destroyed at a rapid rate. This article analyzes the decisions of landowners in Maine, where forests have been heavily harvested and much land has been converted to non-forest use. Data on these landowners and their land were obtained from primary and secondary sources, satellite change detection analysis, and structured interviews. We found that there are several different landowner groups making different harvesting decisions in response to different incentives. In northern Maine, deforestation occurred at a rapid rate in the 1970s–1990s due to the activities of paper companies, which were harvesting heavily in the aftermath of a spruce budworm epidemic and which were doing liquidation harvesting preparatory to leaving Maine. In the southern area of the state, deforestation is due primarily to small landowners converting land for development and contractors doing “cut and run” forestry. The Maine case shows that even in a small area, there can be multiple causes for deforestation. 相似文献
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In Disney/Pixar's phenomenally popular animated film Finding Nemo (Stanton, 2003), one of the central themes of fish welfare was highlighted when the moorish idol, Gill, commented, “Fish aren't meant to be kept in a box, kid. It does things to you.” The notion that fish might have the capacity to suffer in captivity (Chandroo, Duncan, & Moccia, 2004a, 2004b) links to the larger question of sentiency, which remains a fundamental tenet when justifying concerns for nonhuman animal welfare (Dawkins, 2006; Huntingford et al., 2006). Although terrestrial nonhuman-animal welfare has been discussed and explored for many years, the development of aquatic animal welfare concepts and approaches remains relatively new and beyond public awareness (Braastad, Damsgård, & Juell, 2006; Broom, 2007; Farmed Animal Welfare Council, 1996; Fisheries Society of the British Isles, 2002; Håstein, Scarfe, & Lund, 2005; Iwama, 2007; Schreck, 1981). 相似文献
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Deforestation and land use in the Brazilian Amazon 总被引:4,自引:0,他引:4
Emilio F. Moran 《Human ecology: an interdisciplinary journal》1993,21(1):1-21
Deforestation in the Brazilian Amazon was less than 1% before 1975. Between 1975 and 1987 the rate increased exponentially. By 1985, world opinion and attention to the destruction of the richest biome on earth led to elimination of some of the major incentives that had fueled deforestation. Favorable credit policies for cattle ranchers, rather than population growth, explains the process of deforestation in the Brazilian Amazon. The paper suggests other actions that may be taken to reduce deforestation, and examines the rapid growth rates of secondary successional species in a colonization area. 相似文献