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1.
对于二维非自治捕食-被捕食系统,本文讨论了它的解的有界性,进而得到周期解和正周期解的存在性。  相似文献   

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本文讨论一个多食性天敌与害虫系统的有界性和稳定性,给出了该系统有界性和稳定性的充分条件,与之同时还阐述了它们的生态意义.  相似文献   

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本文根据单种群动态ALLEE效应的特点,引入一个适当的数学模型,并对其解的振动性、有界性和渐近稳定性进行了研究。  相似文献   

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本文研究了具有Gompertz增长率的两种群随机捕食-食饵模型,证明了模型具有全局正解,并对模型的正解进行了有界性估计.  相似文献   

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本文利用图论和Liapunov方法研究了非自治LOTKA-VOLTERRA生态系统的有界性和周期解的存在性,得到了一些新的结果.  相似文献   

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本文引入部分变元持久性的定义,借鉴稳定性理论的基本思想方法,讨论了Kolmogrov模型关于部分变元强持久的充要条件及永久共存的充分条件;并以此为工具,讨论了有界性与持久性的关系,得到了有界性的新判据.  相似文献   

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在对运用超声技术诊断子宫内膜癌进行研究的过程中,我们可通过"二维"与"四维"超声的对比来形成分析,进而探索四维超声在对于诊断子宫内膜癌的应用价值。在本文研究的过程中,对多例患者进行二维四维多普勒超声检查,对两种方法的检出率和术前分析准确率与术中情况进行比较,四维超生比二维超声病理诊断符合率高。据此分析,四维超生能多方位的去观察病变,与彩色多普勒搭配应用,更能做出精确的诊断,并能更好的进行术前临床分析,是医学发展的又一个里程碑。  相似文献   

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本文研究了一类具有时滞的随机捕食-食饵系统,证明了系统全局正解的存在性和系统的解的随机最终有界性,确定了系统灭绝和平均持续生存的充分条件.最后,用数值模拟验证理论结果的正确性.  相似文献   

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非自治阶段结构合作系统的持久性与周期解   总被引:11,自引:2,他引:9  
本文研究一类非自治阶段结构的合作系统,得到系统的最终有界性,对应周期系统正周期解的存在性,唯一性以及全局渐近稳定性的充分条件。  相似文献   

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研究了一类具有脉冲收获和放养的食物链模型,该模型具有有界性,并通过脉冲微分方程的比较原则和Floquet乘子理论给出食饵,顶级捕食者灭绝的周期解的全局渐近稳定性以及持续生存的充分条件.此外,通过数值模拟验证主要结论.  相似文献   

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Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.  相似文献   

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Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.  相似文献   

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Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.  相似文献   

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正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases  相似文献   

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