Reinterpreting the relationship between number of species and number of links connects community structure and stability

This is the first release of the code accompanying the paper: Carpentier et al. (2021). Reinterpreting the relationship between number of species and number of links connects community structure and stability. In Nature Ecology and Evolution. Read online or View at Publisher The code allows to (1) carry out in-silico extinction experiments, (2) estimate the shape of the link-species relationship for a given network and (3) compute the network's robustness and local stability. More information is available in the readme file (or on the Github repository)

Horizontal and vertical diversity jointly shape food web stability against small and large perturbations

The biodiversity of food webs is composed of horizontal (i.e. within trophic levels) and vertical diversity (i.e. the number of trophic levels). Understanding their joint effect on stability is a key challenge. Theory mostly considers their individual effects and focuses on small perturbations near equilibrium in hypothetical food webs. Here, we study the joint effects of horizontal and vertical diversity on the stability of hypothetical (modelled) and empirical food webs. In modelled food webs, horizontal and vertical diversity increased and decreased stability, respectively, with a stronger positive effect of producer diversity on stability at higher consumer diversity. Experiments with an empirical plankton food-web, where we manipulated horizontal and vertical diversity and measured stability from species interactions and from resilience against large perturbations, confirmed these predictions. Taken together, our findings highlight the need to conserve horizontal biodiversity at different trophic levels to ensure stability

Cardiorenal ketone metabolism: a positron emission tomography study in healthy humans

Ketones are alternative energy substrates for the heart and kidney but no studies have investigated their metabolism simultaneously in both organs in humans. The present double tracer positron emission tomography (PET) study evaluated the organ distribution and basal kinetic rates of the radiolabeled ketone, 11C-acetoacetate (11C-AcAc), in the heart and kidney compared to 11C-acetate (11C-Ac), which is a well-validated metabolic radiotracer. Both tracers were highly metabolized by the left ventricle and the renal cortex. In the heart, kinetic rates were similar for both tracers. But in the renal cortex, uptake of 11C-Ac was higher compared to 11C-AcAc, while the reverse was observed for the clearance. Interestingly, infusion of 11C-AcAc led to a significantly delayed release of radioactivity in the renal medulla and pelvis, a phenomenon not observed with 11C-Ac. This suggests an equilibrium of 11C-AcAc with the other ketone, 11C-D-beta-hydroxybutyrate, and a different clearance profile. Overall, this suggests that in the kidney, the absorption and metabolism of 11C-AcAc is different compared to 11C-Ac. This dual tracer PET protocol provides the opportunity to explore the relative importance of ketone metabolism in cardiac and renal diseases, and to improve our mechanistic understanding of new metabolic interventions targeting these two organs

Proceedings of the Second International Workshop on Striga

More than 1800 phanerogamic parasites have been recorded throughout the world. Among the most important are the parasitic figworts or Scrophulariaceae, which are economically damaging root parasites. The genus Striga, with more than 50 species, belongs to this family; however, only a few are completely parasitic and damaging to their hosts. Undoubtedly, the major species are S. hermonthica-a widespread and important pest of cereals in Af r ica-and S, asiatica, an important pest both in Asia and in eastern and southern Africa. Although precise estimates of crop loss are difficult to make and data are incomplete, it is well known that severe losses, amounting in many seasons to total crop failure, are caused by these parasitic weeds. However, there is still a general lack of awareness of the magnitude and importance of the problem. These Proceedings bring together the results of discussions held at Ouagadougou, Upper Volta, in October 1981, where the latest research findings and proposals for further research were presented. They highlight the important advances made in knowledge of the pest species, methods of control, and techniques for breeding for resistance to these noxious weeds. It is hoped that this publication will prompt increased effort to be focused on methods of combat ing Striga and reducing the serious losses it causes to cereal production, and on strengthening links between scientists working in numerous programs to produce solutions to outstanding research roblems

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Explorer le vécu des personnes aphasiques à la suite d’un AVC et de leurs aidant.e.s : une approche psychosociale des situations de handicap et de participation sociale

Aphasia is a language disorder and results in 70% of cases from a stroke. This thesis focuses on the social construction of disability or social participation situations of people with aphasia following a stroke, using the Modèle de Développement Humain – Processus de Production du Handicap (MDH-PPH) model. First, the aim is to propose a methodology adapted to aphasic disorders. Secondly, the aim is to identify the psychosocial determinants of disability and social participation, with a particular focus on the social sharing of emotions and social representations of disability. The first part consists of an exploratory study in a hospital setting based on observations of the relationships between nurses/nursing assistant (CNA) and aphasic patients. The participative analysis (grounded theory) highlighted the major role of communication in establishing a care relationship and in achieving patient-centered care. The second part is composed of two studies. The first is based on life stories (n=13) and aims to retrace the trajectories of aphasic patients leading them to an association. The data were subjected to a thematic analysis of the trajectories. This analysis highlighted identity processes that could facilitate or hinder recourse. The association proves to be a place conducive to sharing emotions. The second study is composed of semi-directed dyadic interviews (n=6). A phenomenological interpretative analysis (IPA) revealed an isolation felt by the dyad due to a difficulty for their entourage to understand and adjust to the aphasia: the latter being an invisible disorder.L’aphasie est un trouble du langage qui résulte dans 70% des cas d’un Accident Vasculaire Cérébral (AVC). Cette thèse porte sur la construction sociale des situations de handicap ou de participation sociale des personnes aphasiques à la suite d’un AVC, en mobilisant le Modèle du Développement Humain – Processus de Production du Handicap (MDH-PPH). L’objectif est tout d’abord de proposer une méthodologie adaptée aux troubles aphasiques puis d’identifier les déterminants psychosociaux des situations de handicap et de participation sociale, en s’intéressant particulièrement au partage social des émotions et aux représentations sociales du handicap. Le 1er volet de recherche est composé d’une étude exploratoire en milieu hospitalier fondée sur des observations des relations infirmiersères/aides-soignantes et patientes aphasiques. L’analyse participative (grounded theory) a mis en évidence le rôle majeur de la communication pour fonder une relation de care et réaliser des soins centrés sur lela patiente. Le 2nd volet est composé de deux études. La première fondée sur des récits de vie (n=13) visant à retracer les trajectoires des personnes aphasiques les menant au recours à une association. L’analyse thématique réflexive des trajectoires a mis en évidence des processus identitaires pouvant faciliter ou freiner le recours. L’association s’avère être un lieu propice au partage social des émotions. La deuxième étude est composée d’entretiens semi-dirigés dyadiques (n=6) et vise à explorer le vécu des situations de handicap de la dyade. Une analyse interprétative phénoménologique (IPA) a mis en évidence un isolement ressenti par la dyade en raison d’une difficulté pour leur entourage de comprendre et de s’ajuster à l’aphasie : celle-ci étant un trouble invisible

La maladie thrombo-embolique du voyageur aérien

Les données des études sont insuffisantes pour affirmer une relation de cause à effet entre le vol aérien et la thrombose veineuse profonde du voyageur. Certains auteurs d'études récentes concluent même à l'absence de lien entre maladie thromboembolique et avion. Cependant, il apparaît qu'il existe une relation entre les voyages aériens et la thrombose veineuse, mais l'incidence est vraisemblablement faible et concerne surtout les passagers qui présentent des FDR habituels de MTE (antécédents de MTE, obésité, varices, trouble de la coagulation). Récemment, des études ont permis de calculer l'incidence de survenue de la MTE en fonction de la durée du vol. Un voyage aérien de plus de 5000 KM multiplie le risque par 150.Nous avons conduit une étude prospective cas-contrôle sur l'année 1997 afin de déterminer la fréquence de la MTE après les vols Paris/Réunion et définir les facteurs influençant l'apparition d'une EP ou d'une TVP. Nous avons cherché à différencier les patients qui ont présenté une EP et ceux qui ont présenté une TVP. Quarante-six patients ont présenté une MTE suite à un voyage entre Paris et St Denis de la Réunion. Trente-trois avaient une TVP et 13 une EP. Trente-huit patients (82%) avaient un FDR. Si on compare les FDR entre le groupe MTE et le groupe contrôle nous n'avons pas observé de différence reliée à l'âge, au sexe, à la consommation d'alcool ou de somnifère ou à la prise d'un traitement oestroprogestatif. Nous n'avons pas mis en évidence de différence reliée à la classe ce qui tendrait à infirmer la notion de " Syndrome de la classe économique ". Certains facteurs sont significativement plus élevés dans le groupe MTE : obésité (p<0.001), antécédent de TVP (p<0.005), présence de varices (p<0.0001), insuffisance cardiaque (p<0.001), traumatisme récent (p<0.005) et immobilité (p<0.0002). Si on compare les FDR entre le groupe TVP et le groupe EP, nous retrouvons l'immobilité complète pendant le vol comme un facteur favorisant la survenue d'une EP. L'âge des patients et la mortalité est significativement plus importante dans le groupe des EP. Le délai d'apparition des symptômes est inférieur à 24 heures pour 69 % des cas d'EP et 21 % des cas de TVP. L'analyse critique de la littérature nous permet d'affirmer avec une quasi certitude que le voyage aérien doit être considéré comme un facteur de risque de MTE chez des personnes prédisposées. De nombreux auteurs et l'OMS s'accordent pour recommander des mesures simples de prévention contre l'immobilité et la déshydratation afin de limiter les MTE liés au transport aérien. Pour les personnes à risques, les bas de contention sont préconisés et les HBPM ont montré leur efficacité chez les sujets à moyen et haut risque. En revanche l'intérêt de l'aspirine est contesté, son efficacité n'a pas été démontrée et elle serait plutôt utile dans la prise en charge des maladies artérielles. Ces notions de populations à risque sont méconnues des médecins généralistes et spécialistes ce qui est paradoxal si on considère l'augmentation croissante du transport aérien. Ce manque d'informations limite les mesures de prophylaxie pour les voyageurs. Il est donc nécessaire de réaliser des études prospectives à grande échelle impliquant la participation des compagnies sur le risque de TVP en avion afin de déterminer l'incidence exacte de la thrombose du voyageur, de quantifier le risque et proposer une prévention efficace systématique aux sujets à risque.GRENOBLE1-BU Médecine pharm. (385162101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Discrete-event models for conservation assessment of integrated ecosystems

International audienceEcosystems are complex and data-intensive systems, and the ecologists still struggle to understand them in an integrated manner. Models that miss key dynamics can possibly lead to fallacious conclusions about the ecosystem fate. To address these limits and encompass whole and realistic ecosystems, we develop here a qualitative model with the help of discrete-event models. This model, based on formal Petri nets, was able to integrate biotic, abiotic and human-related components (e.g. grazing) along with their processes into the same interaction network. The model was also able to grasp ecosystem development, as defined by sharp changes of the interaction network structure itself. Furthermore, the model was possibilistic and thus rigorously computed all possible ecosystem states reached after a specific (present-day) initial state. This innovative approach in ecology then allows to rigorously and exhaustively identifying all possible ecosystem trajectories and to study their impacts and outcomes. For the first time in a realistic ecosystem, we illustrated such discrete and qualitative models in the case study of temporary marshes in the Mediterranean part of France, the Camargue delta. The model demonstrated that when marshes are exposed to extensive grazing the presence of marsh heritage species (i.e. with a conservation value) is facilitated by opening up the vegetation through various trajectories. This supports the commonly used management practices of extensive grazing to conserve certain protected habitats. The detailed analysis of the computed ecosystem trajectories allows exploring a range of recommendations for management strategies

Discrete-event models for conservation assessment of integrated ecosystems

International audienceEcosystems are complex and data-intensive systems, and the ecologists still struggle to understand them in an integrated manner. Models that miss key dynamics can possibly lead to fallacious conclusions about the ecosystem fate. To address these limits and encompass whole and realistic ecosystems, we develop here a qualitative model with the help of discrete-event models. This model, based on formal Petri nets, was able to integrate biotic, abiotic and human-related components (e.g. grazing) along with their processes into the same interaction network. The model was also able to grasp ecosystem development, as defined by sharp changes of the interaction network structure itself. Furthermore, the model was possibilistic and thus rigorously computed all possible ecosystem states reached after a specific (present-day) initial state. This innovative approach in ecology then allows to rigorously and exhaustively identifying all possible ecosystem trajectories and to study their impacts and outcomes. For the first time in a realistic ecosystem, we illustrated such discrete and qualitative models in the case study of temporary marshes in the Mediterranean part of France, the Camargue delta. The model demonstrated that when marshes are exposed to extensive grazing the presence of marsh heritage species (i.e. with a conservation value) is facilitated by opening up the vegetation through various trajectories. This supports the commonly used management practices of extensive grazing to conserve certain protected habitats. The detailed analysis of the computed ecosystem trajectories allows exploring a range of recommendations for management strategies