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Global stability results for models of commensalism

International Journal of Biomathematics 2017年第3期10卷 125-149页

作者： paul georgescu Daniel Maxin Hong Zhang Department of Mathematics Technical University of Iasi Bld. Copou 11A 700506 Iasi Romania Department of Mathematics and Computer Science Valparaiso University 1900 Chapel Drive Valparaiso IN 56383 USA Department of Financial Mathematics Jiangsu University Zhenjiang Jiangsu 212013 P. R. China

We analyze the global stability of the coexisting equilibria for several models of commensalism, first by devising a procedure to modify several Lyapunov functionals which were introduced earlier for corresponding models of mutualism, further confirming their usefulness. It is seen that commensalism promotes global stability, in connection with higher-order self-limiting terms which prevent unboundedness. We then use the theory of asymptotically autonomous systems to prove global stability results for models of commensalism which are subject to Allee effects, finding that commensalisms of appropriate strength can overcome the influence of strong Allee effects.

关键词： Commensalism global stability Lyapunov functional Allee effects asymptotically autonomous systems.

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Impulsive perturbation and bifurcation of solutions for a model of chemostat with variable yield

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Applied Mathematics and Mechanics(English Edition) 2009年第7期30卷 933-944页

作者：张弘 paul georgescu Juan J.Nieto 陈兰荪 Department of Mathematics Jiangsu University Department of Mathematics and Mathematical Statistics Ume University Department of Mathematics "Gh.Asachi" Technical University of Iasi Departamento de Análisis Matemático Facultad de Matemáticas Universidadde Santiago de Compostela Institute of Mathematics Chinese Academy of Sciences

In this paper, we consider a variable yield model of a single-species growth in a well-stirred tank containing fresh medium, assuming the instances of time as triggering factors in which the nutrient refilling process and the removal of microorganisms by the uptake of lethal external antibiotic are initiated. It is also assumed that the periodic nutrient refilling and the periodic antibiotic injection occur with the same periodicity, but not simultaneously. The model is then formulated in terms of autonomous differential equations subject to impulsive perturbations. It is observed that either the population of microorganisms essentially washes out, or more favorably, the system is permanent. To describe this dichotomy, some biologically significant integral conditions are introduced. Further, it is shown that in a certain critical situation, a nontriviai periodic solution emerges via a bifurcation phenomenon. Finally, the dynamics of the model is illustrated with numerical experiments and computer simulations.

关键词： chemostat impulsive differential equation permanence extinction fixedpoint approach bifurcation

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一类具有变消耗率的恒化器模型的脉冲扰动与分支

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应用数学和力学 2009年第7期30卷 873-882页

作者：张弘 P.齐奥塞斯库 J.J.涅托陈兰荪江苏大学数学系江苏镇江212013 于默奥大学数学与数学统计系雅西"戈奥尔基-阿萨季"技术学院数学系圣地亚哥德孔波斯特拉大学数学分析系中国科学院数学研究所北京100080

提出和研究了一个具有变消耗率和非同步脉冲的恒化器模型,并且得到了一组像阈值一样的条件来确保系统半平凡周期解的全局渐稳性,系统的持久性以及出现非平凡分支周期解.最后,一些数值模拟体现了该模型的动力学性态.

关键词：恒化器脉冲微分方程持久性灭绝不动点方法分支

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Evaluation of Doppler-ultrasonography in the diagnosis of transjugular intrahepatic portosystemic shunt dysfunction: A prospective study

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World Journal of Hepatology 2017年第27期9卷 1125-1132页

作者： Charlotte Nicolas Amelie Le Gouge Louis d’Alteroche Jean Ayoub Monica georgescu Vincent Vidal Denis Castaing Jean-Pierre Cercueil Patrick Chevallier Jerome Roumy Herve Trillaud Louis Boyer Vincent Le Pennec Christophe Perret Bruno Giraudeau Jean-Marc Perarnau STIC-TIPS group Service d’Hepato-Gastroenterologie Hopital TrousseauCHRU Tours CIC CHRU de Tours INSERM United’echographie-doppler Hopital TrousseauCHRU Tours Service de Radiologie Hopital de la Timone Centre Hepato-Biliaire Hopital Paul Brousse Service de Radiologie CHRU Dijon Service d’Imagerie Medicale Diagnostique et interventionnelle Hopital de l’ArchetⅡNice Service de Radiologie et Echographie CHRU Poitiers Service d’Imagerie Medicale Hopital Saint Andre CHRU Bordeaux Service d’Imagerie viscerale et vasculaire CHRU Clermont Ferrand Service de Radiologie CHRU Caen Service de Radiologie CHRU Nantes 不详

AIM To prospectively evaluate the performance of Dopplerultrasonography(US) for the detection of transjugular intrahepatic portosystemic shunt(TIPS) dysfunction within a multicenter cohort of cirrhotic *** This study was conducted in 10 french teaching hospitals. After TIPS insertion, angiography and liver Doppler-US were carried out every six months to detect dysfunction(defined by a portosystemic gradient ≥ 12 mm Hg and/or a stent stenosis ≥ 50%). The association between ultrasonographic signs and dysfunction was studied by logistic random-effects models, and the diagnostic performance of each Doppler criterion was estimated by the bootstrap method. This study was approved by the ethics committee of *** Two hundred and eighteen pairs of examinations performed on 87 cirrhotic patients were analyzed. Variables significantly associated with dysfunction were: The speed of flow in the portal vein(P = 0.008), the reversal of flow in the right(P = 0.038) and left(P = 0.049) portal branch, the loss of modulation of portal flow by the right atrium(P = 0.0005), ascites(P = 0.001) and the overall impression of the operator(P = 0.0001). The diagnostic performances of these variables were low; sensitivity was < 58% and negative predictive value was < 73%. Therefore, dysfunction cannot be ruled out from Doppler-US. CONCLUSION The performance of Doppler-US for the detection of TIPS dysfunction is poor compared to angiography. New tools are needed to improve diagnosis of TIPS dysfunction.

关键词： Transjugular intrahepatic portosystemic shunt Dysfunction Doppler-ultrasonography

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