Public health and biosecurity. Adaptations of avian flu virus are a cause for concern     

Berns KI  Casadevall A  Cohen ML  Ehrlich SA  Enquist LW  Fitch JP  Franz DR  Fraser-Liggett CM  Grant CM  Imperiale MJ  Kanabrocki J  Keim PS  Lemon SM  Levy SB  Lumpkin JR  Miller JF  Murch R  Nance ME  Osterholm MT  Relman DA  Roth JA  Vidaver AK 《Science (New York, N.Y.)》2012,335(6069):660-661

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Comment on "Nonreciprocal light propagation in a silicon photonic circuit"     

Fan S  Baets R  Petrov A  Yu Z  Joannopoulos JD  Freude W  Melloni A  Popović M  Vanwolleghem M  Jalas D  Eich M  Krause M  Renner H  Brinkmeyer E  Doerr CR 《Science (New York, N.Y.)》2012,335(6064):38; author reply 38

We show that the structure demonstrated by Feng et al. (Reports, 5 August 2011, p. 729) cannot enable optical isolation because it possesses a symmetric scattering matrix. Moreover, one cannot construct an optical isolator by incorporating this structure into any system as long as the system is linear and time-independent and is described by materials with a scalar dielectric function.  相似文献   

PrP antibodies do not trigger mouse hippocampal neuron apoptosis     

Klöhn PC  Farmer M  Linehan JM  O'Malley C  Fernandez de Marco M  Taylor W  Farrow M  Khalili-Shirazi A  Brandner S  Collinge J 《Science (New York, N.Y.)》2012,335(6064):52

Intraperitoneal administration of ICSM18 and 35, monoclonal antibodies against prion protein (PrP), has been shown to significantly delay the onset of prion disease in mice, and humanized versions are candidate therapeutics for prion and Alzheimer's diseases. However, a previous report of severe and widespread apoptosis after intracerebral injection of anti-PrP monoclonal antibodies raised concerns about such therapy and led to an influential model of prion neurotoxicity via cross-linking of cell surface PrP by disease-related PrP aggregates. In extensive studies including ICSM18 and 35, fully humanized ICSM18, and the previously reported proapoptotic antibodies, we found no evidence of apoptosis, thereby questioning this model of prion neurotoxicity.  相似文献   

Climate change. Regional sea-level projection     

Willis JK  Church JA 《Science (New York, N.Y.)》2012,336(6081):550-551

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The structures of COPI-coated vesicles reveal alternate coatomer conformations and interactions     

Faini M  Prinz S  Beck R  Schorb M  Riches JD  Bacia K  Brügger B  Wieland FT  Briggs JA 《Science (New York, N.Y.)》2012,336(6087):1451-1454

Transport between compartments of eukaryotic cells is mediated by coated vesicles. The archetypal protein coats COPI, COPII, and clathrin are conserved from yeast to human. Structural studies of COPII and clathrin coats assembled in vitro without membranes suggest that coat components assemble regular cages with the same set of interactions between components. Detailed three-dimensional structures of coated membrane vesicles have not been obtained. Here, we solved the structures of individual COPI-coated membrane vesicles by cryoelectron tomography and subtomogram averaging of in vitro reconstituted budding reactions. The coat protein complex, coatomer, was observed to adopt alternative conformations to change the number of other coatomers with which it interacts and to form vesicles with variable sizes and shapes. This represents a fundamentally different basis for vesicle coat assembly.  相似文献   

Dislocation damping and anisotropic seismic wave attenuation in Earth's upper mantle     

Farla RJ  Jackson I  Fitz Gerald JD  Faul UH  Zimmerman ME 《Science (New York, N.Y.)》2012,336(6079):332-335

Crystal defects form during tectonic deformation and are reactivated by the shear stress associated with passing seismic waves. Although these defects, known as dislocations, potentially contribute to the attenuation of seismic waves in Earth's upper mantle, evidence for dislocation damping from laboratory studies has been circumstantial. We experimentally determined the shear modulus and associated strain-energy dissipation in pre-deformed synthetic olivine aggregates under high pressures and temperatures. Enhanced high-temperature background dissipation occurred in specimens pre-deformed by dislocation creep in either compression or torsion, the enhancement being greater for prior deformation in torsion. These observations suggest the possibility of anisotropic attenuation in relatively coarse-grained rocks where olivine is or was deformed at relatively high stress by dislocation creep in Earth's upper mantle.  相似文献   

Market Information on Sourcing Cellulosic Feedstock for Biofuel Production in Northern Plains Region of the United States     

Thein A. Maung  Cole R. Gustafson  David M. Saxowsky  Tatjana Miljkovic  John F. Nowatzki 《农业科学与技术》2012,(1):10-23

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The Ability of Phosphate Solubilizing Bacteria Isolated from Coffee Plant Rhizosphere and Their Effects on Robusta Coffee Seedlings     

John Bako Baon  Sri Wedhastri  Andi Kumiawan 《农业科学与技术》2012,(9):1064-1070

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中国化肥需求弹性计算     

黄文芳  John K.Dagsvik 《上海农业学报》2012,28(1):86-90

为了分析国家政策对化肥消费的影响,选取1998-2007年不同省份单位面积化肥消费量、化肥价格指数以及农民纯收入为变量,对化肥支出函数进行了回归分析,计算出10年间不同省份化肥需求的价格弹性和收入弹性。结果表明:目前我国农业发展的化肥基本消费量为0.35 t/hm~2,部分省份化肥消费过度;化肥市场还没有真正建立,价格对需求的影响较小。这表明化肥是农业经济发展的必需品,化肥施用量随农民收入的增加而增加,国家政策对化肥价格的干预是其需求不断上升的根本原因之一。这也在一定程度上说明仅通过环境税方式来改变农民化肥消费的政策效果有限,还需要转变现有的单纯促进农业经济发展的政策,朝着依据农民施肥方式是否有利于环境给予差异性补贴转变。  相似文献   

Evaluation of the biliary and brain distribution of technetium Tc 99m sestamibi in healthy dogs with the ABCB1 wildtype genotype before and after treatment with spinosad     

MacKay CS  Mattoon JS  Roberts GD  Tucker RL  Morimoto TR  Mealey KL 《American journal of veterinary research》2012,73(6):814-820

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