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排序方式: 共有180条查询结果,搜索用时 15 毫秒
71.
Principles for Sustainable Governance of the Oceans 总被引:1,自引:0,他引:1
R Costanza F Andrade P Antunes den Belt M D Boersma DF Boesch F Catarino S Hanna K Limburg B Low M Molitor JG Pereira S Rayner R Santos J Wilson M Young 《Science (New York, N.Y.)》1998,281(5374):198-199
Pressures being exerted on the ocean ecosystems through overfishing, pollution, and environmental and climate change are increasing. Six core principles are proposed to guide governance and use of ocean resources and to promote sustainability. Examples of governance structures that embody these principles are given. 相似文献
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Lupinosis was produced in sheep in four experiments by administering a toxic extract of Phomopsis leptostromiformis by various routes and at various dose rates. The course of the intoxication was followed by plasma biochemical analyses for a number of electrolytes, metabolites and enzymes. Results from these analyses suggested that in addition to being an hepatotoxicity, lupinosis also resulted in injury to muscle, kidney and adrenal cortex. This was confirmed by microscopic examination of these tissues. 相似文献
75.
Powdery mildew and leaf rust resistance genes on the 1RS arm of the T1BL·1RS translocated chromosome were mapped in relation to the Sec‐1 locus and AFLP and restriction fragment length polymorphism markers, respectively, employing segregating F3 populations. Integration of molecular markers indicated that Pm17 lies between the Lr26 and Sec‐1 loci, with both resistance genes allocated distally to the Sec‐1 locus in the satellite of the 1RS arm. 相似文献
76.
Five soils from Austria that have high contents of arsenic (As)due to anthropogenic and/or geogenic sources were separated intosand, silt, and clay fractions. The distribution of As among theparticle-size fractions was clay >> silt > sand. Theparticle-size fractions were analysed according to an 8-stepsequential extraction procedure (SEP) designed to assess theprimary reservoirs and extractability of As. Steps 1 and 2,(i.e. NH4NO3 and (NH4)2SO4) extractedthe least As, while considerably greater amounts were extractedin steps 3, 4 and 5 (i.e. NH4H2PO4,NH2OH-HCl, and NH4F). The greatest amounts of As wereextracted in steps 6 and 7, both NH4-oxalate extractantstargeting the amorphous and crystalline oxide fractions. Theresidual fraction (step 8) was typically low. The extraction ofthe clays contained generally more As in steps 3 to 8, while Asrelease in the first two steps was typically highest in the sandand silt fractions. These findings are in accord with factoranalysis indicating that the extractants of the SEP areseparated into weak (steps 1 and 2) and strong (steps 3 to 8)extractants. SEP data along with microprobe analyses (X-raymicroanalyses) indicate that most As is associated with Fe andis therefore not readily mobile. Anyhow, As could be releasedupon changes in redox potential or pH. The greaterextractability of As from sand fractions using weak extractantsmay explain the higher toxicity of As in coarse-textured soils,as found in previous studies. 相似文献
77.
Arriola DJ Carnahan EM Hustad PD Kuhlman RL Wenzel TT 《Science (New York, N.Y.)》2006,312(5774):714-719
We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of alpha-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes. 相似文献
78.
Givens MD Riddell KP Zhang Y Galik PK Stringfellow DA Brodersen BW Jackson JA Ellsworth MA Ficken MD Carson RL Wenzel JG Marley MS 《Veterinary therapeutics : research in applied veterinary medicine》2006,7(3):305-318
A commercial vaccine containing modified-live bovine viral diarrhea virus (BVDV; types 1 and 2) was administered to one group of 22 peripubertal bulls 28 days before intranasal inoculation with a type 1 strain of BVDV. A second group of 23 peripubertal bulls did not receive the modified-live BVDV vaccine before intranasal inoculation. Ten of 23 unvaccinated bulls--but none of the vaccinated bulls--developed a persistent testicular infection as determined by immunohistochemistry and polymerase chain reaction. Results of this study indicate that administration of a modified-live vaccine containing BVDV can prevent persistent testicular infection if peripubertal bulls are vaccinated before viral exposure. 相似文献
79.
Volker Mohler Rudy Lukman Sophia Ortiz-Islas Manilal William Anthony John Worland Janny van Beem Gerhard Wenzel 《Euphytica》2004,138(1):33-40
Photoperiod response is a major determinant of duration of growing stages in wheat. Conscious selection for these photoperiod
response genes in plant breeding programs will yield genotypes with better adaptation to diverse environments. To provide
a starting point for the development of molecular markers useful for the selection process, genetic maps around the photoperiod
insensitive gene Ppd-B1 were built employing three segregating populations. Of 25 markers that were selected for the Ppd-B1 region, only two could be mapped across all three populations. In pairwise comparisons, the extent of transferable markers
ranged from three to eight. Recombination frequencies of markers distal to Ppd-B1 were more homogeneous than those of proximal markers. This finding suggested a closer proximity of Ppd-B1 to the markers that were mapped distal to breakpoint 0.83 in the physical map of chromosome 2BS.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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