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本文研究了一类具有不同生存能力竞争效应的差分方程生态模型中的同步二点周期环现象.结果表明,当存活率为密度制约时,除始终存在唯一的一个正奇点外,还同时存在唯一的一个同步二点周期环,其稳定性正好与这一正奇点的性态相反. 相似文献
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用定性分析的方法对一类Kolmogorov's系统进行了研究,讨论了系统平衡点的性态,给出了系统无闭轨的充分条件以及存在唯一稳定极限环的条件.改进了李万同(1992)和颜向平(2004)等人的工作.获得了一些新结果. 相似文献
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一类食饵种群具有常数存放率的Kolmogorov系统的定性分析 总被引:2,自引:0,他引:2
本文对一类食饵种群具有常数存放率的Kolmogorov系统进行了定性分析,研究了系统平衡点的性态,证明了极限环的存在和唯一性. 相似文献
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应用上、下解方法和抛物型方程的极值原理,研究了带存放率的竞争扩散系统ut-D1△u=u(a-bu-cv) h1vt-D2△v=v(d-eu-fv) k在齐次Neumann边界条件下解的渐近性态。 相似文献
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一类食饵种群具有常数收获率的Kolmogolov系统的非线性分析 总被引:6,自引:0,他引:6
本文对一类食饵种群具有常数收获率的Kolmogolov系统进行了非线性分析,研究了 系统平衡点的性态,在较宽的条件下证明了系统不存在闭轨线;并获得了系统存在两个极限环的条件。 相似文献
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一个竞争模型的一致持续生存 总被引:1,自引:0,他引:1
本文研究一个带有时滞的竞争模型的一致持续生存。首先证明了离散时滞不影响种群的一致持续生存,接着在种群增长率是周期的假设下讨论了正周期解的存在性,最后给出了连续时滞模型一致持续生存的充分条件。 相似文献
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本文讨论了一类主要由昆虫自食引起的非线性种群动态模型的稳定性.首先给出确定性模型,并着重讨论其一个特殊情形.通过在参数空间中辨识稳定域的边界,可以相对直观地分析种群动态.对于随机模型,是利用在确定性模型中加入对数尺度下的正态随机项形成的,该模型具有较好的统计性质,便于将现实的非线性时间序列数据引进系统中来. 相似文献
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Lightner DV Riggs A Corbin JS Ostrowski AC 《Diseases of aquatic organisms》2007,74(1):77-9; discussion 81-3
It is the opinion of the authors of the Comment on Do et al. (2006), that those authors incorrectly interpreted their test results, which are more likely the result of mislabeling of samples or within-laboratory contamination, and that the TSV isolates found in Penaeus vannamei in Korea in 2004 and 2005 did not originate from Hawaii as claimed by the authors, but from a country (or countries) in southeast Asia. Finally, we believe that the authors did not follow proper international guidelines, extend a professional courtesy to the supplier of the disputed shrimp sample, nor take a critical approach in interpreting their own data. It is unfortunate that the authors did not follow through with additional testing, or seek a second opinion from an independent laboratory, before implicating shrimp imported from Hawaii as the source of TSV in Korea. 相似文献
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Background
Many journals now require authors share their data with other investigators, either by depositing the data in a public repository or making it freely available upon request. These policies are explicit, but remain largely untested. We sought to determine how well authors comply with such policies by requesting data from authors who had published in one of two journals with clear data sharing policies.Methods and Findings
We requested data from ten investigators who had published in either PLoS Medicine or PLoS Clinical Trials. All responses were carefully documented. In the event that we were refused data, we reminded authors of the journal''s data sharing guidelines. If we did not receive a response to our initial request, a second request was made. Following the ten requests for raw data, three investigators did not respond, four authors responded and refused to share their data, two email addresses were no longer valid, and one author requested further details. A reminder of PLoS''s explicit requirement that authors share data did not change the reply from the four authors who initially refused. Only one author sent an original data set.Conclusions
We received only one of ten raw data sets requested. This suggests that journal policies requiring data sharing do not lead to authors making their data sets available to independent investigators. 相似文献17.
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Xin Li was inadvertently dropped from the list of authors for this article. The authors regret this error. 相似文献
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The authors report three cases of a new syndrome which characteristic anomalies are facial dysmorphism with anteverted nose, down slanting palpebral fissures, ptosis, severe microretrognatia, polydactyly. The authors insist on the particular severe genital anomalies, the failure to thrive and the constant lethal issue. The authors discuss the diagnosis of Smith-Lemli-Opitz syndrome and suggest the possibility of a new entity always confounded with others associations characterized by a polydactyly and a sexual reversion in male. 相似文献
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In June of 2000, the U.K. Medical Device Agency recommended the removal of Trilucent implants as a precautionary maneuver in response to reports of local inflammatory reactions. This decision allowed the authors to operate on 115 consecutive patients between June of 2000 and January of 2001. On the preoperative examination, the authors found a very high incidence of rippling (66 percent), whereas capsular contracture was seen in only three patients (2.6 percent). Rippling was significantly more common in patients with subglandular implants. Five implants were found ruptured during the operation. This figure, together with the relative ease of implant breakage at removal, shows a premature deterioration of the implant shell. The authors also comment on implant bleeding, which seems common in this type of breast implant. The authors think that this is a possible cause for the rippling phenomenon, resulting from a reduction of the implant content. On the basis of these findings, the authors conclude that Trilucent implants are associated with a poor cosmetic outcome and a high rate of complications. 相似文献