La maîtrise des invasions biologiques : un modèle bio-économigue appliqué à la jussie

Diffusion du document : INRA Station d'Economie et Sociologie rurales 65 rue de Saint-Brieuc 35042 Rennes Cedex (FRA)La prolifération d'espèces invasives non indigènes soulève des problèmes écologiques et économiques très importants, dans la plupart des continents et pays du monde. Il peut s'agir d'espèces animales ou végétales,terrestres ou aquatiques. Les invasions biologiques sont à l'origine de la dégradation des écosystèmes et des fluxde services écologiques : modification de la biodiversité et des habitats en liaison avec la compétition entreespèces, altération de la qualité de l'eau et modification du régime des eaux, dans le cas d'espèces aquatiques,etc.. A ces altérations des écosystèmes correspondent des dommages économiques imposés aux activitéshumaines ayant pour support les actifs naturels subissant ces perturbations

The mutable nature of particle-core excitations with spin in the one-valence-proton nucleus ¹³³Sb

The γ-ray decay of excited states of the one-valence-proton nucleus ¹³³Sb has been studied using cold-neutron induced fission of ²³⁵U and ²⁴¹Pu targets, during the EXILL campaign at the ILL reactor in Grenoble. By using a highly efficient HPGe array, coincidences between γ-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 μs isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr₃(Ce) scintillators, revealed a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus ¹³²Sn and the valence proton, using the Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin

La maîtrise des invasions biologiques : un modèle bio-économigue appliqué à la jussie

Diffusion du document : INRA Station d'Economie et Sociologie rurales 65 rue de Saint-Brieuc 35042 Rennes Cedex (FRA)La prolifération d'espèces invasives non indigènes soulève des problèmes écologiques et économiques très importants, dans la plupart des continents et pays du monde. Il peut s'agir d'espèces animales ou végétales,terrestres ou aquatiques. Les invasions biologiques sont à l'origine de la dégradation des écosystèmes et des fluxde services écologiques : modification de la biodiversité et des habitats en liaison avec la compétition entreespèces, altération de la qualité de l'eau et modification du régime des eaux, dans le cas d'espèces aquatiques,etc.. A ces altérations des écosystèmes correspondent des dommages économiques imposés aux activitéshumaines ayant pour support les actifs naturels subissant ces perturbations

La maîtrise des invasions biologiques : un modèle bio-économigue appliqué à la jussie

La prolifération d'espèces invasives non indigènes soulève des problèmes écologiques et économiques très importants, dans la plupart des continents et pays du monde. Il peut s'agir d'espèces animales ou végétales, terrestres ou aquatiques. Les invasions biologiques sont à l'origine de la dégradation des écosystèmes et des flux de services écologiques : modification de la biodiversité et des habitats en liaison avec la compétition entre espèces, altération de la qualité de l'eau et modification du régime des eaux, dans le cas d'espèces aquatiques, etc.. A ces altérations des écosystèmes correspondent des dommages économiques imposés aux activités humaines ayant pour support les actifs naturels subissant ces perturbations

Management strategies for invasive species : the importance of stock externalities

Diffusion du document : INRA Station d'Economie et Sociologie rurales 65 rue de Saint-Brieuc 35042 Rennes Cedex (FRA)The management of an invasive species presents some similarities with rerlewable resources. However, the objective function is the sum of two positive and often increasing components : environmental damages and management costs. The paper stresses the importance of stock externalities to ensure that a non zero stock is optimal. In a static approach, the paper shows that when the damage function is always increasing, the absence ofstock externalities leads to a solution of eradication (zero stock) under usual assumptions. If the damage is decreasing (and negative as sometimes assumed) it is still possible that a non zero stock to be optimal. In the presence of externalities it is more likely that an interior solution be optimal, although it needs not to be the case. If the cost externalities tend to be infinitely large for low stock levels, then an eradication is ruled out. In the dynamic approach, conditions are given for an interior solution to exist. Again it is shown that the existence of externalities helps satisfy both first and second order (convexity) conditions for a solution stopping short from full eradication. An empirical illustration for Lud,wi,gi,a spp. will be given at the conference

Management strategies for invasive species : the importance of stock externalities

Diffusion du document : INRA Station d'Economie et Sociologie rurales 65 rue de Saint-Brieuc 35042 Rennes Cedex (FRA)The management of an invasive species presents some similarities with rerlewable resources. However, the objective function is the sum of two positive and often increasing components : environmental damages and management costs. The paper stresses the importance of stock externalities to ensure that a non zero stock is optimal. In a static approach, the paper shows that when the damage function is always increasing, the absence ofstock externalities leads to a solution of eradication (zero stock) under usual assumptions. If the damage is decreasing (and negative as sometimes assumed) it is still possible that a non zero stock to be optimal. In the presence of externalities it is more likely that an interior solution be optimal, although it needs not to be the case. If the cost externalities tend to be infinitely large for low stock levels, then an eradication is ruled out. In the dynamic approach, conditions are given for an interior solution to exist. Again it is shown that the existence of externalities helps satisfy both first and second order (convexity) conditions for a solution stopping short from full eradication. An empirical illustration for Lud,wi,gi,a spp. will be given at the conference

Management strategies for invasive species : the importance of stock externalities

The management of an invasive species presents some similarities with rerlewable resources. However, the objective function is the sum of two positive and often increasing components : environmental damages and management costs. The paper stresses the importance of stock externalities to ensure that a non zero stock is optimal. In a static approach, the paper shows that when the damage function is always increasing, the absence ofstock externalities leads to a solution of eradication (zero stock) under usual assumptions. If the damage is decreasing (and negative as sometimes assumed) it is still possible that a non zero stock to be optimal. In the presence of externalities it is more likely that an interior solution be optimal, although it needs not to be the case. If the cost externalities tend to be infinitely large for low stock levels, then an eradication is ruled out. In the dynamic approach, conditions are given for an interior solution to exist. Again it is shown that the existence of externalities helps satisfy both first and second order (convexity) conditions for a solution stopping short from full eradication. An empirical illustration for Lud,wi,gi,a spp. will be given at the conference

Clostridium butyricum Strains and Dysbiosis Linked to Necrotizing Enterocolitis in Preterm Neonates

International audienceBackground. Necrotizing enterocolitis (NEC) is the most common and serious gastrointestinal disorder among preterm neonates.We aimed to assess a specific gut microbiota profile associated with NEC. Methods. Stool samples and clinical data were collected from 4 geographically independent neonatal intensive care units, over a 48-month period. Thirty stool samples from preterm neonates with NEC (n = 15) and controls (n = 15) were analyzed by 16S ribosomal RNA pyrosequencing and culture-based methods. The results led us to develop a specific quantitative polymerase chain reaction (qPCR) assay for Clostridium butyricum, and we tested stool samples from preterm neonates with NEC (n = 93) and controls (n = 270). We sequenced the whole genome of 16 C. butyricum strains,analyzed their phylogenetic relatedness, tested their culture supernatants for cytotoxic activity, and searched for secreted toxins. Results. Clostridium butyricum was specifically associated with NEC using molecular and culture-based methods (15/15 vs 2/15; P < .0001 1) or qPCR (odds ratio, 45.4 [95% confidence interval, 26.2-78.6]; P < .0001 1). Culture supernatants of C. butyricum strains from preterm neonates with NEC (n = 14) exhibited significant cytotoxic activity (P = .008), and we identified in all a homologue of the β-hemolysin toxin gene shared by Brachyspira hyo-dysenteriae,the etiologic agent of swine dysentery.The corresponding protein was secreted by a NEC-associated C. butyricum strain. Conclusions. NEC was associated with C. butyricum strains and dysbiosis with an oxidized,acid, and poorly diversified gut microbiota.Our findings highlight the plausible toxigenic mechanism involved in the pathogenesis of NEC