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排序方式: 共有912条查询结果,搜索用时 15 毫秒
61.
Stuart J. SmythMichael Gusta Kenneth BelcherPeter W.B. Phillips David Castle 《Agricultural Systems》2011,104(5):403-410
The commercial production of herbicide tolerant (HT) canola began in Western Canada in 1997. With more than a decade of use, the actual farm-level environmental impact of HT canola can be evaluated. This article reports on a spring 2007 survey of nearly 600 canola farmers in the three prairie provinces of Western Canada. Producers were asked about their crop production experiences for 2005 and 2006 and expected crop planting for 2007. A reduction in the total number of chemical applications over the 3-year period was reported, resulting in a decrease of herbicide active ingredient being applied to farmland in Western Canada of nearly 1.3 million kg annually. Fewer tillage passes over the survey period were reported, improving moisture conservation, decreasing soil erosion and contributing to carbon sequestration in annual cropland. An estimated 1 million tonnes of carbon is either sequestered or no longer released under land management facilitated by HT canola production, as compared to 1995. The value of this carbon off-set is estimated to be C$5 million. Comparisons with similar studies and against non-adoption of HT canola can guide future decisions about HT canola adoption. 相似文献
62.
Delayed leaf senescence has been found in a soybean population which maintains its chlorophyll and ribulosebisphosphate carboxylase activity in leaves and nitrogen fixation (acetylene reduction) activity in root nodules throughout seed maturation. Incorporation of delayed leaf senescence into an agronomically desirable genetic background may help to increase seed yield and symbiotic nitrogen fixation during seed development. 相似文献
63.
64.
Phillips RE Thomas GW Blevins RL Frye WW Phillips SH 《Science (New York, N.Y.)》1980,208(4448):1108-1113
The no-tillage cropping system, a combination of ancient and modern agricultural practices, has been rapidly increasing in use. By the year 2000, as much as 65 percent of the acreage of crops grown in the United States may be grown by the no-tillage practice. Soil erosion, the major source of pollutants in rural streams, is virtually eliminated when no-tillage agriculture is practiced. The no-tillage system reduces the energy input into corn and soybean production by 7 and 18 percent, respectively, when compared to the conventional tillage system of moldboard plowing followed by disking. In addition, crop yields are as high as or higher than those obtained with traditional tillage practices on large areas of agricultural land. 相似文献
65.
66.
Denschlag J Simsarian JE Feder DL Clark CW Collins LA Cubizolles J Deng L Hagley EW Helmerson K Reinhardt WP Rolston SL Schneider BI Phillips WD 《Science (New York, N.Y.)》2000,287(5450):97-101
Quantum phase engineering is demonstrated with two techniques that allow the spatial phase distribution of a Bose-Einstein condensate (BEC) to be written and read out. A quantum state was designed and produced by optically imprinting a phase pattern onto a BEC of sodium atoms, and matter-wave interferometry with spatially resolved imaging was used to analyze the resultant phase distribution. An appropriate phase imprint created solitons, the first experimental realization of this nonlinear phenomenon in a BEC. The subsequent evolution of these excitations was investigated both experimentally and theoretically. 相似文献
67.
The structure of ferrihydrite, a nanocrystalline material 总被引:2,自引:0,他引:2
Michel FM Ehm L Antao SM Lee PL Chupas PJ Liu G Strongin DR Schoonen MA Phillips BL Parise JB 《Science (New York, N.Y.)》2007,316(5832):1726-1729
Despite the ubiquity of ferrihydrite in natural sediments and its importance as an industrial sorbent, the nanocrystallinity of this iron oxyhydroxide has hampered accurate structure determination by traditional methods that rely on long-range order. We uncovered the atomic arrangement by real-space modeling of the pair distribution function (PDF) derived from direct Fourier transformation of the total x-ray scattering. The PDF for ferrihydrite synthesized with the use of different routes is consistent with a single phase (hexagonal space group P6(3)mc; a = approximately 5.95 angstroms, c = approximately 9.06 angstroms). In its ideal form, this structure contains 20% tetrahedrally and 80% octahedrally coordinated iron and has a basic structural motif closely related to the Baker-Figgis delta-Keggin cluster. Real-space fitting indicates structural relaxation with decreasing particle size and also suggests that second-order effects such as internal strain, stacking faults, and particle shape contribute to the PDFs. 相似文献
68.
Myxovirus antibody increases in human connective tissue disease 总被引:12,自引:0,他引:12
Antibodies to measles and parainfluenza type 1 viruses were significantly increased in systemic lupus erythematosus and Reiter's syndrome. Of the individuals with highest titers of measles antibody, 75 percent had neurologic illness. Persistent virus infection may be a factor in the pathogenesis of these diseases. 相似文献
69.
Phillips JC 《Science (New York, N.Y.)》1913,37(958):717-718
70.
Huntington's disease: two families with differing clinical features show linkage to the G8 probe 总被引:8,自引:0,他引:8
S E Folstein J A Phillips D A Meyers G A Chase M H Abbott M L Franz P G Waber H H Kazazian P M Conneally W Hobbs 《Science (New York, N.Y.)》1985,229(4715):776-779
To test the hypothesis that interfamily variability in Huntington's Disease (HD) is due to mutation at different loci, linkage analysis was undertaken in two large HD kindreds that differed in ethnicity, age-at-onset, and neurologic and psychiatric features. Both families showed linkage of the HD locus to the G8 probe. Several recombinants were documented in each family, and the best estimate of the recombination fraction for the two families was 6 percent with a 95 percent confidence interval of 0 to 12 percent. Although the data support the existence of a single HD locus, use of the G8 probe for presymptomatic testing in these kindreds would have resulted in a 12 percent error rate in genotype assignment at the HD locus. 相似文献