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991.
This paper reviews current trends in the development of agricultural biotechnology, including (1) the recent and potential biotechnology products and processes in the plant, animal and food sciences, and (2) the enormous increase in Federal and State government and industrial investments in biotechnology research. Next we analyze the impacts and possible consequences of agricultural biotechnology for public and private agricultural research and for the structure and nature of the food system in this country and around the world. We conclude with a range of proposals for agricultural research policies. Among the possible consequences we discuss are: (1) a shift in disciplinary emphasis in the research community to molecular biology, (2) reduction of research on systems, ecology, and the social sciences, (3) increased concentration of research funds at a small number of institutions, (4) reduction of long-term research in the public sector, (5) increased collaboration between industry, government and universities with a restriction of scientific communication, and a potential for conflict of interest, favoritism and increased scientific misconduct, (6) a change of the primary goals and agenda of the public sector research community, and (7) increased concentration in the agribusiness sector and the industrialization of the food system. Our policy suggestions include: (1) maintaining and strengthening an independent public research and teaching system, (2) striking a balance between short-term proprietary biotechnology and long-term nonproprietary research, (3) maintaining an extension system that delivers biotechnology information and products to all potential users, (4) developing a regulatory system that adequately protects the public and provides clear guidelines to industry. (5) assisting developing nations to reap the benefits of the biotechnology revolution, and (6) establishing mechanisms to foster broad-based understanding of the social and ethical issues relating to agricultural biotechnology and to promote research on the social and ethical impacts. 相似文献
992.
In order to investigate the behavior of single molecules under conditions far from equilibrium, we have coupled a microfabricated laminar-flow mixer to a confocal optical system. This combination enables time-resolved measurement of F?rster resonance energy transfer after an abrupt change in solution conditions. Observations of a small protein show the evolution of the intramolecular distance distribution as folding progresses. This technique can expose subpopulations, such as unfolded protein under conditions favoring the native structure, that would be obscured in equilibrium experiments. 相似文献
993.
Hydrotalcites are used in technology as catalysts and anion exchangers and are important sinks for environmental contaminants. Their compositional variability makes it important, but difficult, to estimate their aqueous solubility. We report calorimetric measurements of the heats of formation of cobalt-aluminum hydrotalcite phases. The heat and free energy of formation from the elements are equal to those of mechanical mixtures of binary compounds, namely hydroxides and carbonates. The interlayer anion is much more important than the cation in determining the solubility of the hydrotalcite phase and its ability to contain or release heavy metals to the environment. Because hydrotalcites do not have an unreactive polymer as a structural core, their aqueous stability will change dramatically with composition, particularly with anion content. This simple mechanical mixture model allows prediction of aqueous solubilities and trace metal retention in a variety of geochemical settings. 相似文献
994.
Head JW Chapman CR Strom RG Fassett CI Denevi BW Blewett DT Ernst CM Watters TR Solomon SC Murchie SL Prockter LM Chabot NL Gillis-Davis JJ Whitten JL Goudge TA Baker DM Hurwitz DM Ostrach LR Xiao Z Merline WJ Kerber L Dickson JL Oberst J Byrne PK Klimczak C Nittler LR 《Science (New York, N.Y.)》2011,333(6051):1853-1856
MESSENGER observations from Mercury orbit reveal that a large contiguous expanse of smooth plains covers much of Mercury's high northern latitudes and occupies more than 6% of the planet's surface area. These plains are smooth, embay other landforms, are distinct in color, show several flow features, and partially or completely bury impact craters, the sizes of which indicate plains thicknesses of more than 1 kilometer and multiple phases of emplacement. These characteristics, as well as associated features, interpreted to have formed by thermal erosion, indicate emplacement in a flood-basalt style, consistent with x-ray spectrometric data indicating surface compositions intermediate between those of basalts and komatiites. The plains formed after the Caloris impact basin, confirming that volcanism was a globally extensive process in Mercury's post-heavy bombardment era. 相似文献
995.
Transmission of equine influenza virus to dogs 总被引:1,自引:0,他引:1
Crawford PC Dubovi EJ Castleman WL Stephenson I Gibbs EP Chen L Smith C Hill RC Ferro P Pompey J Bright RA Medina MJ Johnson CM Olsen CW Cox NJ Klimov AI Katz JM Donis RO 《Science (New York, N.Y.)》2005,310(5747):482-485
Molecular and antigenic analyses of three influenza viruses isolated from outbreaks of severe respiratory disease in racing greyhounds revealed that they are closely related to H3N8 equine influenza virus. Phylogenetic analysis indicated that the canine influenza virus genomes form a monophyletic group, consistent with a single interspecies virus transfer. Molecular changes in the hemagglutinin suggested adaptive evolution in the new host. The etiologic role of this virus in respiratory disease was supported by the temporal association of rising antibody titers with disease and by experimental inoculation studies. The geographic expansion of the infection and its persistence for several years indicate efficient transmission of canine influenza virus among greyhounds. Evidence of infection in pet dogs suggests that this infection may also become enzootic in this population. 相似文献
996.
Defining the epithelial stem cell niche in skin 总被引:4,自引:0,他引:4
Tumbar T Guasch G Greco V Blanpain C Lowry WE Rendl M Fuchs E 《Science (New York, N.Y.)》2004,303(5656):359-363
997.
McClintock WE Bradley ET Vervack RJ Killen RM Sprague AL Izenberg NR Solomon SC 《Science (New York, N.Y.)》2008,321(5885):92-94
During MESSENGER's first Mercury flyby, the Mercury Atmospheric and Surface Composition Spectrometer measured Mercury's exospheric emissions, including those from the antisunward sodium tail, calcium and sodium close to the planet, and hydrogen at high altitudes on the dayside. Spatial variations indicate that multiple source and loss processes generate and maintain the exosphere. Energetic processes connected to the solar wind and magnetospheric interaction with the planet likely played an important role in determining the distributions of exospheric species during the flyby. 相似文献
998.
Murchie SL Watters TR Robinson MS Head JW Strom RG Chapman CR Solomon SC McClintock WE Prockter LM Domingue DL Blewett DT 《Science (New York, N.Y.)》2008,321(5885):73-76
The Caloris basin, the youngest known large impact basin on Mercury, is revealed in MESSENGER images to be modified by volcanism and deformation in a manner distinct from that of lunar impact basins. The morphology and spatial distribution of basin materials themselves closely match lunar counterparts. Evidence for a volcanic origin of the basin's interior plains includes embayed craters on the basin floor and diffuse deposits surrounding rimless depressions interpreted to be of pyroclastic origin. Unlike lunar maria, the volcanic plains in Caloris are higher in albedo than surrounding basin materials and lack spectral evidence for ferrous iron-bearing silicates. Tectonic landforms, contractional wrinkle ridges and extensional troughs, have distributions and age relations different from their counterparts in and around lunar basins, indicating a different stress history. 相似文献
999.
1000.