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51.
Daniel S. Levine 《Bulletin of mathematical biology》1983,45(6):901-915
A system of mixed integrodifferential and partial differential equations for an agestructured predator-prey system is studied here. The predator eats all ages of prey, but more of the very young and very old than of the intermediate ages. The existence of periodic solutions corresponding to stable coexistence is proved for a suitable range of parameters by bifurcation theory. 相似文献
52.
Regulation of Newly Evolved Enzymes. I. Selection of a Novel Lactase Regulated by Lactose in ESCHERICHIA COLI 总被引:17,自引:2,他引:15 下载免费PDF全文
Thirty-four lactose-utilizing strains of E. coli were selected from a lac Z deletion strain. In 31 of these, the synthesis of the newly evolved lactase is regulated by lactose. The lactase activity in all the strains is indistinguishable from the ebg(+) activity identified by Campbell, Lengyel and Langridge (1973). 相似文献
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The influence of gibberellic acid over a wide range of concentrations on the rate of elongation of root hairs of redtop grass was investigated. The rate of root hair elongation was increased by GA over the concentration range of 10?7 to 10?12 M inclusive, with peak stimulation occurring at 10?6 M. Although root hair growth was slightly accelerated by 10?6 M GA, this concentration damaged many root hairs and caused some to stop growing altogether. Rate of root hair elongation was reduced to less than 84% of the control by 10?5 M GA. 相似文献
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New Diagnostic System for the Identification of Lactose-fermenting Gram-negative Rods 总被引:7,自引:6,他引:1 下载免费PDF全文
The identification of prompt lactose-fermenting gram-negative rods has generally relied heavily upon colonial morphology coupled with one or more indole, methyl red, Voges-Proskauer, citrate (IMViC) parameters, hydrogen sulfide, and motility. Studies were undertaken to compare diagnoses dependent solely upon the more orthodox criteria to a system for identification based upon hydrogen sulfide, ornithine decarboxylase, and citrate utilization (HOC). The results suggest that the IMViC scheme of identification is neither consistent nor applicable when applied to the current nomenclature of the above group of organisms and should be discarded, whereas the HOC system may prove to be of significant value to clinical microbiologists. 相似文献
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