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Bottleneck size manipulation through the introduction of large-radius alkali ions in Na sites of a NaSICON solid electrolyte: A computational proof of concept
No full textInternational audienceNaSICON electrolytes, such as Na1+xZr2(SiO4)x(PO4)3–x (NZSP), constitute promising candidates for solid-state battery (SSB) development. Research on such fast superionic conductors has primarily focused on two key phenomena acting specifically on Na+ ion migration: (i) the Na-concentration-driven modulation effect and (ii) the incidence of substitution. While numerous experimental and computational studies have established the fundamental role of concerted migration in ionic conduction, the precise influence of bottleneck size along with its dependence on NaSICON composition remains elusive. In view of participating in this research field and following an experimentally tested strategy, suggesting that the migration bottleneck can be expanded by partially substituting diffusing Na+ ions with larger-radius alkali elements, we investigated the impact of the introduction of such point defects (i.e. K+ or Cs+ replacing Na+) on structural and Na+ diffusion aspects in the NZSP crystal structure. A proof of concept of the interest linked to this unconventional doping approach has been searched for. Theoretical investigations relying on density functional theory (DFT) and subsequent kinetic Monte Carlo simulations were involved to unravel interrelations between the ionic radius of the substituting ion and bottleneck sizes, structural changes, diffusion pathways, and ionic conductivity features. Apart from an opening of the bottleneck along the migration path as a common feature, a clear differentiation between both kinds of substituents was evidenced on various aspects, K-NZSP outperforming the undoped counterpart and effectively enabling the maximization of ionic conductivity in these envisaged NaSICON-type matrices. Furthermore, the identification─emerging from this study─of a critical bottleneck size in such systems may contribute to provide a further key clue and lead to well thought-out crystal chemical engineering of improved materials for this research area
L-Type Cav1.3 and HCN Channels Mediate Heart Rate Acceleration by Catecholamines
No full textInternational audienceBackground: The ionic mechanism by which catecholamines increase the heart rate is incompletely understood. In this study, we have assessed the roles of sinoatrial node L-type Cav1.3 (α1D) Ca2+ channels, phosphorylation of L-type channel regulatory partner protein Rad (Ras-related RGK GTP-binding protein), and cAMP-dependent regulation of hyperpolarization-activated HCN (hyperpolarization-activated cyclic nucleotide-gated) channels.Methods: We studied β-adrenergic regulation of heart rate and sinoatrial pacemaker activity in mice lacking Cav1.3 channels and in mice expressing dihydropyridine-insensitive L-type Cav1.2 channels alone or concomitantly expressing cAMP-insensitive HCN4 subunits in a heart-specific and time-controlled manner. We also studied the chronotropic response to sympathomimetics of sinoatrial pacemaker myocytes under conditions of specific inhibition of cAMP-dependent regulation of HCN4 by the cyclic dinucleotide cyclic di-(3',5')-GMP and ablation of PKA (protein kinase A)-dependent phosphorylation of Rad.Results: Mutant mice with knockout of Cav1.3 and cAMP-insensitive HCN4 subunits in the heart lacked diurnal variation in heart rate and failed to increase their heart rate after administration of catecholamines or during physical activity. Selective pharmacological inhibition of Cav1.3 prevented the enhancement of pacemaker activity by sympathomimetics or by direct activation of adenylate cyclase, as well as by phosphodiesterase inhibitors, when cAMP-dependent regulation of HCN was simultaneously silenced. Upregulation of Cav1.3 and HCN-mediated funny current (If) accounted for the total change in diastolic current on activation of β-adrenoceptors, explaining the loss of chronotropic effect of catecholamines. Preventing PKA phosphorylation of Rad abrogated the chronotropic response to sympathomimetics of intact hearts under HCN blockade, or in pacemaker myocytes on preventing cAMP-dependent regulation of HCN4, respectively.Conclusions: PKA phosphorylation of Rad, which disinhibits Cav1.3 channels and cAMP-dependent activation of HCN channels, are key effectors in β-adrenergic regulation of cardiac pacemaker activity and can sustain positive chronotropic effects independently. These findings on Rad-mediated regulation of Cav1.3 and HCN channels unravel the ionic mechanisms underlying the catecholaminergic acceleration of the heart rate
Climatic and nutrient drivers affect long-term phytoplankton temporal trends in coastal lagoons
No full textInternational audienceUnderstanding how climate influences phytoplankton dynamics is crucial for anticipating temporal trends and cascading consequences on ecosystem functioning under climate change. This study explores long-term dynamics in contrasted Mediterranean lagoons and investigates the effects of climatic (air temperature, rainfall, wind speed) and nutrient (inorganic nutrient concentrations) drivers on phytoplankton chlorophyll a, abundances, and pigment composition. 17 years of summer monitoring were analyzed using univariate trend tests and multivariate approaches to highlight changes and to disentangle the contributions of abiotic factors to phytoplankton variability. Our results revealed contrasts among lagoons in physicochemical conditions and phytoplankton community, which strongly structured their temporal trends. Climatic drivers significantly influenced phytoplankton, but their importance was context-dependent. In nutrient-enriched systems, phytoplankton dynamics were primarily controlled by inorganic nutrient concentrations, while climatic effects were weak by comparison. Conversely, in nutrient-poor systems, climatic signals became more visible and influential: wind events were associated with higher chlorophyll a, warmer conditions with increases in phycoerythrin-rich picocyanobacteria, and rainfall with higher picoeukaryote abundances, potentially through indirect effects on water column stability and nutrient and light availability. However, under nutrient limitation, abundances remained low and dominated by small cells, suggesting that nutrient control exerts the strongest influence on phytoplankton, which may explain why nutrient control tends to mask diffuse climatic signals. Yet, climate change modulates physicochemical patterns and may progressively shape lagoon functioning. This study emphasizes the need to account for lagoon features and vulnerabilities, and supports adaptive and site-specific management strategies to safeguard coastal lagoons under future changes
Combinatorial and algorithmic analysis of oriented hierarchies in statistical implicative analysis
No full textInternational audienceThis paper introduces a novel and more efficient method for constructing oriented hierarchies within the framework of Statistical Implicative Analysis. The primary focus of this study is the computational complexity of the original algorithm proposed by Gras, whose cubic time complexity is established in this work. To address this limitation, a detailed combinatorial analysis of hierarchical structures is performed, leveraging tools from analytic combinatorics. This methodology facilitates the enumeration of the number of possible configurations as a function of input size and enables the investigation of both the depth and width characteristics of the hierarchy’s block structure. This study then proposes a reconstruction algorithm based on a formal correspondence between the statistical implication graph and the oriented hierarchy. The proposed method achieves quadratic worst-case complexity, thereby resulting in a substantial improvement in computational performance. Moreover, the analytic framework also makes it possible to characterise the average-case behaviour of the algorithm. The findings of the comparative computational experiments demonstrate the clear advantage of the proposed method over Gras’s algorithm, both in terms of execution time and overall algorithmic efficiency
Evaluation of a combined symptom-based questionnaire and capillary natriuretic peptides testing for early detection of heart failure: a heart failure awareness days nationwide screening study (DEPIC FR)
No full textInternational audienceAbstract Aims Early diagnosis of heart failure (HF) remains challenging, as symptoms are often nonspecific or absent. We aimed to evaluate the performance of a two-step screening strategy combining a symptom-based questionnaire—based on the acronym EPOF (dyspnoea, weight gain, oedema, fatigue in french)—and capillary NT-proBNP fingerstick testing to identify individuals with elevated cardiovascular risk or preclinical HF. Methods and results We screened 2,481 adults without known HF during a nationwide, community-based campaign held in 21 hospital cardiology centres across France. All participants underwent capillary NT-proBNP testing using a point-of-care assay. A threshold of >125 pg/mL, per ESC guidelines for ruling out HF in ambulatory settings, was exceeded in 419 individuals (16.9%), of whom 36.5% were asymptomatic. Conversely, 30.5% of those with NT-proBNP ≤125 pg/mL reported at least one symptom. Symptom-based screening alone had limited diagnostic accuracy for detecting NT-proBNP >125 pg/mL. The presence of ≥1 symptom yielded a sensitivity of 63.2% and a specificity of 42.4%. Dyspnoea was the most sensitive symptom (47.7%), while weight gain had the highest specificity (84.7%). In contrast, the absence of both symptoms and NT-proBNP elevation was associated with a high negative predictive value (85.4%). Among the 198 participants with NT-proBNP >125 pg/mL who underwent cardiologist-led evaluation, 40.9% were classified as symptomatic HF (Stage C), and 24.2% as preclinical HF (Stage B). Conclusion Combining symptom assessment with NT-proBNP testing improves early identification of at-risk individuals and may help uncover a significant proportion of undiagnosed or early-stage HF
Assessing the non-target effects of herbicides on field margin plant communities after controlling for soil, climate, local context and landscape metrics
No full textInternational audiencePesticides are often identified as one of the major causes of biodiversity decline in farmlands. However, our knowledge about this relationship has mostly being inferred from small to landscape-scale studies, or from indirect indicators of agricultural practices at large scales. Here, we used a national network of more than 500 sites monitored yearly from 2013 to 2018 in France to assess the non-target effects of herbicides on field margin plant communities. We used hierarchical generalized linear models to investigate the effects of practices on plant species richness, plant species evenness, proportion of nature-value plants, and proportion of grasses in field margins, while controlling for a large number of possible confounding effects. The intensity of herbicide use had a negative effect on plant species richness, and on the proportion of nature-value plants. In the margin of cereal fields, there was a negative effect of dicotyledon herbicides on richness and a negative effect of grass herbicides on species evenness. We also identified, in some specific crops, a negative effect of non-herbicide treatments on margin flora richness and on the proportion of nature-value plants. The presence of surrounding grasslands had a consistent favourable effect on richness and on the proportion of nature-value plants in field margins. Finally, situations of risk for pesticides drift had a negative effect on margin flora. This study confirms that reducing herbicide use represents a robust lever to maintain the floristic diversity of field margins, which could be combined with strategies reducing the risk of pesticide drift
Early hominins from Morocco basal to the Homo sapiens lineage
No full textInternational audiencePalaeogenetic evidence suggests that the last common ancestor of present-day humans, Neanderthals and Denisovans lived around 765–550 thousand years ago (ka)1. However, both the geographical distribution and the morphology of these ancestral humans remain uncertain. The Homo antecessor fossils from the TD6 layer of Gran Dolina at Atapuerca, Spain, dated between 950 ka and 770 ka (ref. 2), have been proposed as potential candidates for this ancestral population3. However, all securely dated Homo sapiens fossils before 90 ka were found either in Africa or at the gateway to Asia, strongly suggesting an African rather than a Eurasian origin of our species. Here we describe new hominin fossils from the Grotte à Hominidés at Thomas Quarry I (ThI-GH) in Casablanca, Morocco, dated to around 773 ka. These fossils are similar in age to H. antecessor, yet are morphologically distinct, displaying a combination of primitive traits and of derived features reminiscent of later H. sapiens and Eurasian archaic hominins. The ThI-GH hominins provide insights into African populations predating the earliest H. sapiens individuals discovered at Jebel Irhoud in Morocco4 and provide strong evidence for an African lineage ancestral to our species. These fossils offer clues about the last common ancestor shared with Neanderthals and Denisovans
Rapport sur les services climatiques réussis dans le monde et leurs critères de succès: Livrable commun au Projet ciblé TRACCS-PC1-DIALOG (D5.3) et au Projet Ciblé TRACCS-PC3-DEMOCLIMA (D1)
No full textLes enjeux socio-économiques liés aux effets du réchauffement climatique sont tels qu’une demande croissante d’informations climatiques adaptées pour la mise en place de stratégies d’atténuation et/ou d’adaptation est clairement exprimée par les secteurs économiques (e.g. agriculture, énergie, tourisme, infrastructures terrestres ou maritimes, etc…) et par les territoires/régions qui mesurent pleinement leursvulnérabilités. En réponse à ces demandes, de nombreux projets de recherche nationaux (e.g., la "Convention relative à l’attribution d’un appui financier au bénéfice des services climatiques", signée entre le Ministère de la Transition Écologique et Solidaire (MTES) et le CNRS en mars 2017, ou le développement du portail DRIAS), européens (e.g., le programme ERA4CS « European Research Area for Climate Services » du JPI Climate, ou encore Copernicus) ou internationaux (e.g., les outils développés par la NASA, le GIEC…) ont permis le financement de « services climatiques ». Plusieurs acteurs opérationnels nationaux et européens développent et mettent à disposition des « services climatiques » via des plateformes souvent libres d’accès et enfin, apparaissent sur le marché des bureaux d’études dont l’activité commerciale vise le développement de « services climatiques » à la carte et adaptés aux demandes des clients.L’offre pour les « services climatiques » est donc aujourd’hui multiforme par l’information fournie (données climatiques « simples », indicateurs, outils d’aide à la décision) et par son mode de développement. Face à cette diversité, les enjeux sont de documenter et comprendre le paysage des services climatiques actuels, de faire ressortir les besoins, et de se munir de moyens pour caractériser la réussite des services climatiques, pour évaluer l'existant et guider le développement de nouveaux projets. Menée conjointement par les projets ciblés DIALOG (PC1) et DEMOCLIMA (PC3) du PEPR TRACCS, cette étude vise quatre objectifs :i) Documenter le paysage actuel des services climatiques (section 2) en France et dans le monde (identifiés par la communauté TRACCS) en les présentant par usages et cibles ;ii) Identifier des besoins non satisfaits vis-à-vis des services climatiques (section 4) ;iii) Identifier un ensemble de critères de réussite d'un service climatique pour les évaluer (section 5) ;iv) Proposer des bonnes pratiques pour atteindre ces critères de réussite (section 6); ces éléments guideront les choix des futurs démonstrateurs qui seront conçus et développés au sein de DEMOCLIMA.Notre travail repose en grande partie sur le recueil de dires d'acteurs des "services climatiques", dans une approche "bottom-up"
How contrasted environments in the Humboldt Current System, Pacific Warm Pool and South Pacific Gyre, shape contrasted ecosystems. A modelling approach using APECOSM
No full textInternational audiencePelagic ecosystems exhibit a strong regional heterogeneity, driven by physical and biogeochemical characteristics. Using the global 3D marine ecosystem model APECOSM, we simulate six high-trophic-level communities, capturing their size structure, spatial distribution, and trophic interactions up to 1,000 metres depth. We examine how different environments shape their contrasting organisation and interactions in three Pacific Ocean regions: the productive Humboldt Current System, the oligotrophic South Pacific Gyre, and the thermally stratified Pacific Warm Pool. Simulations reveal strong regional contrasts in ecosystem responses. In the Humboldt, high primary production supports important biomass of small coastal pelagic fish. Seasonal warming enables tuna to forage in these productive waters, while low-oxygen conditions restrict the vertical range and abundance of mesopelagic organisms and concentrate epipelagic organisms close to the surface. In the Warm Pool, apex predators remain abundant despite low primary production, thanks to efficient trophic transfer and biomass import from neighbouring regions. Seamounts concentrate mesopelagic organisms into shallow layers, making them accessible to epipelagic predators. In contrast, the South Pacific Gyre supports sparse, imported high-trophic-levels with limited trophic coupling and strong intra-community predation. We quantify regional differences in trophic transfer efficiency and network complexity, identifying thresholds below which high-trophic-levels collapse. These findings illustrate the emergent plasticity of pelagic ecosystems and the importance of bottom-up control of high-trophic-level biomass. They emphasise the importance of temperature, transport, light and oxygen in modulating horizontal and vertical distributions, controlling the co-occurrence of predators and prey, and influencing the formation of schools, ultimately impacting trophic interactions and community assemblages
Block-Additive Gaussian Processes under Monotonicity Constraints
No full textInternational audienceWe generalize the additive constrained Gaussian process framework to handle interactions between input variables while enforcing monotonicity constraints everywhere on the input space. The block-additive structure of the model is particularly suitable in the presence of interactions, while maintaining tractable computations. In addition, we develop a sequential algorithm, MaxMod, for model selection (i.e., the choice of the active input variables and of the blocks). We speed up our implementations through efficient matrix computations and thanks to explicit expressions of criteria involved in MaxMod. The performance and scalability of our methodology are showcased with several numerical examples in dimensions up to 120, as well as in a 5D real-world coastal flooding application, where interpretability is enhanced by the selection of the blocks