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71.
Experimentally damaged leaves of Cucurbita moschata mobilize substances to the damaged region within 40 minutes. These substances stimulate feeding by Acalymma vittata (Coleoptera: Chrysomelidae) and inhibit feeding by Epilacha tredecimnotata (Coleoptera: Coccinelidae). Under natural conditions, Epilachna cuts a circular trench in the leaf before feeding on the encircled leaf material, thus preventing mobilization of the deterrent substances to the feeding area. 相似文献
72.
Timely and accurate information on crop conditions obtained during the growing season is of vital importance for crop management.
High spatial resolution satellite imagery has the potential for mapping crop growth variability and identifying problem areas
within fields. The objectives of this study were to use QuickBird satellite imagery for mapping plant growth and yield patterns
within grain sorghum fields as compared with airborne multispectral image data. A QuickBird 2.8-m four-band image covering
a cropping area in south Texas, USA was acquired in the 2003 growing season. Airborne three-band imagery with submeter resolution
was also collected from two grain sorghum fields within the satellite scene. Yield monitor data collected from the two fields
were resampled to match the resolutions of the airborne imagery and the satellite imagery. The airborne imagery was related
to yield at original submeter, 2.8 and 8.4 m resolutions and the QuickBird imagery was related to yield at 2.8 and 8.4 m resolutions.
The extracted QuickBird images for the two fields were then classified into multiple zones using unsupervised classification
and mean yields among the zones were compared. Results showed that grain yield was significantly related to both types of
image data and that the QuickBird imagery had similar correlations with grain yield as compared with the airborne imagery
at the 2.8 and 8.4 m resolutions. Moreover, the unsupervised classification maps effectively differentiated grain production
levels among the zones. These results indicate that high spatial resolution satellite imagery can be a useful data source
for determining plant growth and yield patterns for within-field crop management. 相似文献
73.
74.
Naturally acquired antibodies to sporozoites do not prevent malaria: vaccine development implications 总被引:12,自引:0,他引:12
S L Hoffman C N Oster C V Plowe G R Woollett J C Beier J D Chulay R A Wirtz M R Hollingdale M Mugambi 《Science (New York, N.Y.)》1987,237(4815):639-642
The first human vaccines against the malaria parasite have been designed to elicit antibodies to the circumsporozoite protein of Plasmodium falciparum. However, it is not known whether any level of naturally acquired antibodies to the circumsporozoite protein can predict resistance to Plasmodium falciparum malaria. In this study, 83 adults in a malaria-endemic region of Kenya were tested for circumsporozoite antibodies and then treated for malaria. They were monitored for the development of new malaria infections for 98 days. Antibody levels, as determined by four assays in vitro, were indistinguishable between the 60 individuals who did and the 23 who did not develop parasitemia during follow-up, and there was no apparent relation between day of onset of parasitemia and level of antibodies to circumsporozoite protein. Unless immunization with sporozoite vaccines induces antibodies that are quantitatively or qualitatively superior to the circumsporozoite antibodies in these adults, it is unlikely that such antibodies will prevent infection in areas with as intense malaria transmission as western Kenya. 相似文献
75.
76.
Genetic restriction of energy conservation in Schizophyllum 总被引:2,自引:0,他引:2
A genetically determined malfunction of energy conservation reduces assimilation of substrate to half or less its normal level while leaving oxidative processes apparently unchanged. This metabolic defect, which differs in many ways from any previously described, is related to the function of the B incompatibility factor and occurs both in the common A heterokaryon (A = B not equal)-in which two compatible, wild B factors interact-and in mutant-B homokaryons. 相似文献
77.
78.
79.
Hoffman SL 《Science (New York, N.Y.)》2000,290(5496):1509
Solving the enormous problem of malaria worldwide will require a balance between investments in research and control. In this point-counterpoint, two scientists describe the rationales for these very different strategies. Steve Hoffman believes that genomics research is the best investment in the future if we have the vision of malaria eradication. Chris Curtis presents an opposing viewpoint, that low-tech control approaches are the practical ones under current conditions. 相似文献
80.
Alper J 《Science (New York, N.Y.)》2003,300(5620):729-730