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A new hypothesis to explain the coexistence of n species in the presence of a single resource Inra
Lobry, C.; Harmand, J..
Cet article présente une hypothèse permettant d’expliquer la coexistence de plusieurs espèces (ici des micro-organismes) en compétition sur une seule ressource (substrat) dans un chémostat. Nous introduisons une nouvelle classe de cinétiques qui ne dependent pas seulement de la concentration en substrat du milieu, mais également des concentrations en microorganismes. À partir de considérations relatives aux interactions élémentaires (i) entre microorganismes, (ii) entre microorganismes et le milieu dans lequel ils croissent, et en utilisant des simulations, nous montrons que cette modélisation peut être interprétée comme une limitation diffusionnelle. L’étude rigoureuse de cette nouvelle classe de modèles nous permet d’avancer l’hypothèse selon laquelle...
Tipo: Journal Article Palavras-chave: COEXISTENCE D’ESPÈCES; RATIO-DÉPENDANCE; DENSITÉ-DÉPENDANCE; LIMITATION DIFFUSIONNELLE COMPETITION; BIOLOGY; MICROBIAL ECOLOGY; SPECIES COEXISTENCE; RATIO-DEPENDENCE; DENSITY-DEPENDENCE; LIMITATION BY DIFFUSION.
Ano: 2006 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD201049ac0e09&uri=/notices/prodinra1/2011/01/
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Association between competition and obligate mutualism in a chemostat Inra
El Hajji, M.; Harmand, J.; Chaker, H.; Lobry, C..
In this paper, we consider a simple chemostat model involving two obligate mutualistic species feeding on a limiting substrate. Systems of differential equations are proposed as models of this association. A detailed qualitative analysis is carried out. We show the existence of a domain of coexistence, which is a set of initial conditions in which both species survive. We demonstrate, under certain supplementary assumptions, the uniqueness of the stable equilibrium point which corresponds to the coexistence of the two species.
Tipo: Journal Article Palavras-chave: SURVIE DES ESPECES; COMPORTEMENT ASYMPTOTIQUE; EQUATION DIFFERENTIELLE; INTERACTION MICROBIOLOGIQUE MICROBIAL INTERACTIONS; MICROBIAL ECOLOGY; YEAST; SACCHAROMYCES CEREVISIAE; CHEMOSTAT; COMPETITION; MUTUALISM; ASYMPTOTIC BEHAVIOUR; COEXISTENCE; DULAC CRITERION; THIEME’S RESULT; ;  .
Ano: 2009 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD201035ecf34a&uri=/notices/prodinra1/2010/12/
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Denaturing gradient electrophoresis (DGE) and single-strand conformation polymorphism (SSCP) molecular fingerprintings revisited by simulation and used as a tool to measure microbial diversity Inra
Loisel, P.; Harmand, J.; Zemb, O.; Latrille, E.; Lobry, C.; Delgenes, J.P.; Godon, J.J..
The exact extent of microbial diversity remains unknowable. Nevertheless, fingerprinting patterns [denaturing gradient electrophoresis (DGE), single-strand conformation polymorphism (SSCP)] provide an image of a microbial ecosystem and contain diversity data. We generated numerical simulation fingerprinting patterns based on three types of distribution (uniform, geometric and lognormal) with a range of units from 10 to 500 000. First, simulated patterns containing a diversity of around 1000 units or more gave patterns similar to those obtained in experiments. Second, the number of bands or peaks saturated quickly to about 35 and were unrelated to the degree of diversity. Finally, assuming lognormal distribution, we used an estimator of diversity on in...
Tipo: Journal Article Palavras-chave: DENATURING GRADIENT ELECTROPHORESIS; SINGLE STRAND CONFORMATION POLYMORPHISM.
Ano: 2006 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD2007ca36bcb3&uri=/notices/prodinra1/2008/02/
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Effect on persistence of intra-specific competition in competition models Inra
Lobry, C.; Mazenc, F..
An ecological model describing the competition for a single sub-strate of an arbitrary number of species is considered. The mortality rates of the species are not supposed to have all the same value and the growth function of the substrate is not supposed to be linear or decreasing. Intra-specific competion is taken into account. Under additional technical assumptions, we establish that the model admits a globally asymptotically stable positive equilibrium point. This ensures persistence of the species. Our proof relies on a Lyapunov function.
Tipo: Journal Article Palavras-chave: COEXITENCE DES ESPECES; COMPETITION; FONCTION LYAPUNOV; SURVIE DES ESPECES SPECIES COEXISTENCE; ECOLOGY; POPULATION DYNAMICS;  .
Ano: 2007 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD20107fe8a70e&uri=/notices/prodinra1/2011/01/
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Modèle mathématique de croissance d'une espèce structurée en deux stades dans l'environnement variable IRD
Durand, J.L.; Lobry, C..
Les auteurs décrivent les conditions de croissance d'une population structurée en 2 classes d'âge et soumise à des conditions environnementales variables. La dynamique d'une population structurée en 2 stades est représentée par un système de 2 équations différentielles dépendant explicitement du temps et les variations environnementales sont simulées par 2 jeux de paramètres de ce système. On montre que pour des conditions environnementales défavorables à la croissance de la population décrite (i.e. qui sont susceptibles de provoquer son extinction), des oscillations suffisamment rapides entre ces deux conditions permettent à la population de croître. La réciproque est également vraie. (Résumé d'auteur)
Tipo: Text Palavras-chave: DYNAMIQUE DE POPULATION; POPULATION ANIMALE; CROISSANCE; GROUPE D'AGE; ENVIRONNEMENT; VARIABILITE; MODELE MATHEMATIQUE.
Ano: 1995 URL: http://www.documentation.ird.fr/hor/fdi:42113
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Modèles de croissance d'une population de filtreurs IRD
Sciandra, A.; Lobry, C..
Tipo: Text Palavras-chave: OSTREICULTURE; AZOTE; BILAN MINERAL; BIOMASSE; MODELE MATHEMATIQUE.
Ano: 1996 URL: http://www.documentation.ird.fr/hor/fdi:010009653
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Multiple stable equilibrium profiles in tubular bioreactors Inra
Dramé, A.K.; Lobry, C.; Harmand, J.; Rapaport, A.; Mazenc, F..
This paper deals with the existence and stability of multiple equilibrium profiles in tubular bioreactors. We prove here that a tubular biological reactor can posses one or several equilibrium profiles according to the dispersion and convection terms as long as the kinetic function belongs to a general class of non-monotonic functions. Such systems allow the characterization of the hydrodynamic behavior of most real systems in classifying them between completely mixed systems and perfect Plug Flow systems. The stability analysis of equilibrium profiles is also carried out and it is shown that they are alternatively stable, unstable, stable, etc.
Tipo: Journal Article Palavras-chave: BIOREACTEUR TUBULAIRE; STABILITE; PROFIL D’EQUILIBRE MULTIPLE; HYDRODYNAMIQUE; CALCUL DES VARIATIONS HYDRODYNAMIC; CALCULUS OF VARIATION; TUBULAR BIOREACTOR; CONVECTION-DISPERSION; MULTIPLE EQUILIBRIUM PROFILES; STABILITY.
Ano: 2008 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD2008ca7db242&uri=/notices/prodinra1/2010/12/
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Nonstandard analysis and representation of reality Inra
Lobry, C.; Sari, T..
The aim of this paper is to show that the representation with the help of Nonstandard Analysis of a real phenomenon, presenting different observation scales, allows an important simplification of language. Indeed, it is convenient to have available the concept of infinitely small and infinitely large quantities in dealing with the macroscopic effects of microscopic phenomena. This is illustrated on two examples : the representation of two time scales systems and the representation of noise.
Tipo: Journal Article Palavras-chave: BRUIT; ENSEMBLE FINI; ANALYSE NON STANDARD CONTROL ENGINEERING; DYNAMICAL SYSTEM; NON STANDARD ANALYSIS; STABILIZATION; PEAKING; MOIRE; AVERAGING; INTEGRATION ON FINITE SETS; NOISE.
Ano: 2008 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD201065b9dfa4&uri=/notices/prodinra1/2010/12/
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Persistence in ratio-dependent models of consumer-resource dynamics Inra
Lobry, C.; Mazenc, F.; Rapaport, A..
In a recent work Cantrell, Cosner and Ruan show that intraspecific interference is responsible for coexistence of many consumers for one resource with a logistic like growth rate. Recently, we have established a similar result for the case of a chemostat using a rather different technique. In the present note, we complement these two works to the case of an unknown nonlinear growth rate for the resource satisfying mild assumptions.
Tipo: Journal Article Palavras-chave: COEXISTENCE DES ESPECES; ECOLOGIE SPECIES COEXISTENCE; ECOLOGY; POPULATION DYNAMICS..
Ano: 2007 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD2008aec41396&uri=/notices/prodinra1/2008/08/
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Stability analysis of an ecological model Inra
Mazenc, F.; Lobry, C.; Rapaport, A..
For a new family of ecological systems, we prove the global asymptotic stability of a positive equilibrium point. That way, we show how the consideration of an intra-specific dependency in the population growth functions can explain not only the persistence of several species in. competition for a single resource but, also attractivity of a positive equilibrium point.
Tipo: Conference Paper Palavras-chave: MODELE ECOLOGIQUE STABILITY ANALYSIS; ECOLOGICAL MODEL.
Ano: 2006 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD20077bbca22&uri=/notices/prodinra1/2008/02/
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Stability loss delay in the chemostat with a slowly varying washout rate Inra
Lobry, C.; Rapaport, A.; Sari, T..
In this paper, we propose to study a model with two competitors competing for a single nutrient in a chemostat with a slowly varying washout rate. We show that the model exhibits the delayed loss of stability phenomenon when the washout rate crosses the bifurcation value at which the growth curves of the two competitors intersect.
Tipo: Conference Paper Palavras-chave: CHEMOSTAT; TRAITEMENT DES EAUX USES; STABILITE WASHOUT RATE.
Ano: 2009 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD2009d9c56dad&uri=/notices/prodinra1/2010/12/
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Sur un modèle densité-dépendant de compétition pour une resource Inra
Lobry, C.; Rapaport, A.; Mazenc, F..
Nous utilisons le concept de caractéristique à l’équilibre d’une population, consommant une unique ressource limitante, pour discuter de façon simple de l’issue de la compétition de plusieurs espèces pour cette seule ressource. La caractéristique à l’équilibre est une courbe qui est associée à chaque espèce et qui est susceptible d’être déterminée empiriquement. Les données de la caractéristique à l’équilibre et de la dynamique de renouvellement de la ressource permettent, sous certaines hypothèses, de donner des conditions de coexistence ou d’exclusion des espèces
Tipo: Journal Article Palavras-chave: RESSOURCE; COMPETITION; DENSITE-DEPENDANCE; RATIO-DEPENDANCE RESOURCE; DENSITY-DEPENDENCE; RATIO-DEPENDENCE.
Ano: 2006 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD200785d6681&uri=/notices/prodinra1/2008/02/
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The peaking phenomenon and singular perturbations Inra
Lobry, C.; Sari, T..
On étudie le comportement asymptotique, lorsque le paramètre ε tend vers 0, de systèmes triangulaires singulièrement perturbés de la forme x˙ = f(x, y), y˙ = G(y, ε). On suppose que toutes les solutions de la deuxième équation tendent vers zéro arbitrairement rapidement quand ε tend vers 0. On suppose que le système x˙ = f(x, 0) admet l’origine comme équilibre globalement asymptotiquement stable. Certaines solutions de la deuxième équation peuvent présenter un transitoire avec un pic très grand avant de décroître rapidement vers zéro. C’est ce phénomène de peaking qui peut destabiliser la première équation. On introduit le concept de stabilité instantanée, pour mesurer la décroissance rapide vers zéro des solutions de la deuxième équation, et le concept de...
Tipo: Journal Article Palavras-chave: PHENOMENE DU PEAKING; STABILITE ASYMPTOTIQUE; PERTURBATIONS SINGULIERES; ANALYSE NON STANDARD PEAKING PHENOMENON; ASYMPTOTIC STABILITY; SINGULAR PERTURBATIONS; NONSTANDARD ANALYSIS.
Ano: 2008 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD201046cece6c&uri=/notices/prodinra1/2010/12/
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Variations sur le thème de la modélisation de la "tragédie" du libre accès aux ressources renouvelables IRD
Romagny, B.; Lobry, C..
Tipo: Text Palavras-chave: EXPLOITATION DES RESSOURCES NATURELLES; MODELISATION; METHODOLOGIE; THEORIE.
Ano: 1996 URL: http://www.documentation.ird.fr/hor/fdi:010009655
Registros recuperados: 14
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