HAL-Université de Bretagne Occidentale
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Agriculture, aquaculture et pêche : impacts des modes de production labellisés sur la biodiversité. Synthèse du rapport scientifique de l'étude
No full textLa loi Climat et résilience de 2021 a instauré la mise en place d’un affichage environnemental sur les produits alimentaires afin d’informer les consommateurs du coût environnemental de leurs achats. La construction de cet affichage a suscité un important travail méthodologique ouvert aux acteurs. Un bilan intermédiaire a souligné la difficulté à appréhender toutes les dimensions de la biodiversité. C’est dans ce cadre que les ministères en charge de la transition écologique, et de l’agriculture et de l’alimentation, ainsi que l’ADEME, ont sollicité INRAE et l’Ifremer courant 2022 pour mieux documenter ce volet biodiversité, en se focalisant sur les pratiques de production. Afin d’éclairer plus largement les politiques publiques, les pouvoirs publics ont choisi de s’appuyer sur les labels dont les cahiers des charges certifient des pratiques et parce que leur développement les place au cœur de nombreux débats sur les relations entre production et consommation durables. L’étude, intitulée « BiodivLabel », a été menée par un comité pluridisciplinaire d’experts scientifiques issus d’organismes publics de recherche et d’enseignement supérieur
Cooperative Spin-Crossover in a Neutral Dinuclear Complex Based on a Functionalized Triazole Ligand
No full textInternational audienceA novel spin-crossover (SCO) dinuclear complex, [Fe2(μ2-cp-trz)3(cp-trz)2(tcm)4] (cp-trz = 4-cyclo-pentyl-1,2,4-triazole, tcm- = tricyanomethanide anion), was synthesized and thoroughly characterized. Crystallographic analyses at 250 and 180 K revealed a centrosymmetric dinuclear structure with Fe(II) centers bridged by triazole ligands. The complex exhibits a cooperative hysteretic thermally induced abrupt one-step spin transition between high-spin (HS) and low-spin (LS) states. Magnetic measurements (Magn), X-rays diffraction (XRD), and optical microscopy (OM) show the following switching temperatures: T1/2↓Magn = 202 K and T1/2↑Magn = 212 K, and T1/2↓OM ≃ T1/2↓XRD = 203 K and T1/2↑OM ≃ T1/2↑XRD = 207 K. Moreover, structural and OM studies reveal significant anisotropic lattice changes, driven by strong hydrogen bonding along the c axis, which underpins the cooperative behavior of the SCO transition, and propagation of the HS/LS interface along the spin transitio
Catalytic and stoichiometric stepwise conversion of side-on bound dinitrogen to ammonia mediated by a uranium complex
No full textInternational audienceThe well-defined catalytic conversion of dinitrogen (N 2 ) to ammonia (NH 3 ) by molecular complexes is of fundamental interest and important for providing an atomic-level understanding of reactivity that can be related to industrial and biological nitrogen-fixation processes. Molecular catalytic N 2 to NH 3 conversion currently involves the reduction and protonation of terminal or bridging end-on bound metal-N 2 complexes. However, catalytic N 2 to NH 3 conversion by side-on bound metal-N 2 molecular complexes is relevant to both the industrial and biological nitrogen-fixation processes.Here, using a uranium triamidoamine complex, we report catalytic N 2 to NH 3 conversion involving side-on bound N 2 binding. Stoichiometric reactions reveal stepwise reduction of N 2 from free N 2 to bridging side-on bound forms and subsequently to bridging nitrides, uniquely accessing four different states of side-on bound N 2 for the same molecular system. This reveals the roles of N 2 , N 2 2-, N 2 3-, N 2 4-and N 3-in the catalytic conversion of N 2 to NH 3 when involving side-on bridging N 2 .</div
Heteropolynuclear Lanthanide(III) Complexes for Cooperative Sensitization Upconversion in Water
No full textInternational audienceWe report the synthesis of a tritopic ligand, L2, composed of two strongly binding lanthanide (Ln) sites using tris-functionalized triazacyclononane (tacn) scaffolds bridged by a weaker Ln binding triethylene glycol chain. Coordination chemistry of Ln3+ (Ln = Eu, Tb, Yb, Lu) was investigated by using NMR and photoluminescent spectroscopies. The first two Ln3+ ions are coordinated by the tacn scaffolds to form [LnL2] and [Ln2L2] species, followed by tri- and tetranuclear complexes, [Ln(Ln2L2)] and [Ln2(Ln2L2)]. The third and fourth exomacrocyclic binding events occur at the polyethylene glycol binding site, buttressed by a synergistic interaction of the phosphonate arms, confirmed by DFT modeling. [Ln2L2] (Ln = Tb, Eu, Yb, and Lu) homobimetallic complexes were prepared, and characterized and their spectroscopic properties determined in H2O and D2O. Titration of the [Yb2L2] dinuclear complex by Tb salts in D2O confirmed the formation of the tri- and tetranuclear species. Upon excitation into the 2F5/2 ← 2F7/2 absorption band of Yb at 980 nm, a cooperative sensitization upconversion process is evidenced, displaying visible Tb emission bands. Heating resulted in Ln scrambling in the tacn coordination sites, increasing the UC efficiency by ca. 103. The most efficient emitter for UC is the tetranuclear [TbYb(TbYbL2)], with one of each Ln3+ species in the tacn scaffolds and one of each Ln3+ species coordinated by the polyethylene glycol chain. Optimization on the pD led to an overall 9.0 × 10–7 UC quantum yield (λexc = 980 nm, P = 10.8 W·cm–2). The same experiment was repeated in water, affording UC at the molecular level
Un Nouveau Critère d'arrêt adaptatif pour l'estimation du canal parcimonieux en communications acoustiques sous-marines MIMO-OFDM
No full textInternational audienceMultiple inputs, multiple outputs (MIMO) systems are an attracting method for establishing high data rate underwater acoustic (UWA) communications. While the estimation of MIMO channels is challenging, sparse decomposition algorithms may enable efficient estimation methods. In this paper, a new stopping criterion for the compressed sampling matching pursuit channel estimation algorithm is proposed. Based on the residual statistics, it enables accurate channel estimation without prior knowledge of the channel sparsity level and signal-to-noise ratio (SNR).L'utilisation de systèmes à entrées et sorties multiples (MIMO, multiple inputs, multiple outputs) est une solution prometteuse pour réaliser des communications acoustiques sous-marines à haut débit. Si l'estimation de canaux MIMO peut être difficile, l'utilisation d'algorithmes de décomposition parcimonieuse peut conduire à des méthodes d'estimation efficiente. Dans cet article, un nouveau critère d'arrêt pour l'estimation de canal par la méthode de matching pursuit en acquisition compressée est proposé. En s'appuyant sur les statistiques du résidu, ce critère permet une estimation de canal précise sans connaissance a priori du degré de parcimonie du canal ni du rapport signal-à-bruit
Estimation aveugle des paramètres d'une forme d'onde OTFS pour le renseignement satellitaire
No full textInternational audienceDans le cadre du renseignement basé sur l'interception de télécommunications, cet article propose une méthode d'analyse aveugle pour l'estimation des paramètres d'une forme d'onde Orthogonal Time Frequency Space (OTFS). Les paramètres de cette forme d'onde sont estimés à partir d'un critère mesurant la gaussianité des échantillons obtenus dans le plan délai-Doppler. Les performances de cet estimateur sont évaluées selon différents cas d'interception
Design and Analysis of Thermistors in Low Temperature Cofired Ceramics
No full textInternational audienceIn this work we investigate the integration possibility of a thermistor paste from ESL (ElectroScience Laboratory, now Vibrantz) to see if it is adapted for Vibrantz Low Temperature Cofired Ceramics (LTCC) L8 and A6M-E materials. An alumina-based sample is used as a reference circuit throughout this study. Square, two-squares-in-parallel and two-squares-in-series thermistors are tested, placed internally and externally. Resistive values are measured in a range from 25 °C to 300 °C. The variation in the resistive values among similar thermistors is significant, with a maximum standard deviation of 67%. However, in all cases, there is a positive linear relationship between resistance and temperature. The Temperature Coefficient of Resistance (TCR) value is calculated before and after annealing. In general, the L8 and Al2O3 samples exhibit higher TCR values than the A6M-E sample. Additionally, when placed internally, the TCR value decreases approximately 30% for both tested LTCC materials. An Energy-Dispersive X-ray Spectroscopy (EDX) material analysis has also been conducted on the samples, revealing that the main chemical components are oxide, silicon, calcium, and ruthenium but also some barium and titanium, which indicates SiO2, TiO2, BaTiO3 and RuO2 oxides in the thermistor paste. The possibility to implement thermistors internally and externally on Vibrantz LTCC without delamination problems is endorsed by this study
Petrogenetic processes in alkaline magmatism in the southern Mozambique Channel
No full textInternational audienceWhereas the northern part of the Mozambique Channel, between the eastern coast of Africa and Madagascar, is intensively studied, the southern part remains poorly investigated. The 2014 PAMELA-MOZ01 and 2015 PAMELA-MOZ04 cruises enabled us to collect volcanic rocks from the submarine flanks of the Bassas da India-Europa complex, including Bassas da India atoll, Europa Island, and Jaguar and Hall Banks. Despite significant alteration, probably due to their prolonged stay in seawater and the hydrothermal circulation they underwent, we are able to describe the main petrological and geochemical aspects of these largely unknown lavas. To achieve this, we integrated petrographic and mineralogical observations with geochemical analyses of the dredged rocks, aiming to identify the key aspects of the alteration and to characterize their petrological and geochemical properties.The volcanism of this region is characterized by strongly silica-undersaturated alkaline magmas. Here, we demonstrate that this volcanism is marked by a bimodal magmatic activity with ultrabasic and basic compositions, and more silica-rich compositions. Using isotopic signatures and trace elements, we suggest that magmas are produced by a low degree of partial melting (1 to 5 %) of a metasomatized mantle at about 80 km depth. These mafic magmas then rise from the source to the surface via several magma storage levels, located at about 25–30 km and 15 km depth, the latter corresponding to the mantle-crust boundary as identified by geophysical methods. Fragments of zoned sanidine phenocrysts within intermediate lavas (olivine-free nephelinite or tephri-phonolite) also suggest the presence of differentiated magma reservoirs. Our observations strongly support frequent magmatic recharges, coupled with magma differentiation through olivine + clinopyroxene crystallization/assimilation, in long-lived magma reservoirs. In many respects, this volcanism has similar characteristics (nature of the source, degree of partial melting, composition of the lavas, age, and spatial distribution) to those of the Miocene to Quaternary volcanic provinces of Madagascar, the northern Mozambique Channel or the East African Rift. We propose that this volcanism might result from regional extension through the Mozambique Channel and the southern part of the East African Rift System, coupled with a thermal erosion of a mantle plume
The impact of isolated inspiratory muscle training on exercise capacity, dyspnea, and quality of life in heart failure patients: a systematic review and meta-analysis
No full textInternational audienceIntroductionRecently, inspiratory muscle training (IMT) has emerged as an alternative therapeutic approach for patients with heart failure (HF), characterized by ventilation inefficiency and reduced functional capacity. However, the evidence regarding the effects of IMT on patients with HF remains ambiguous. This meta-analysis aims to ascertain the impact of isolated IMT on the 6-minute walk test (6MWT), VO2peak, dyspnea, resting heart rate (RHR), and Quality of Life (QoL) in patients with HF.MethodsA systematic literature search was conducted across four databases: Science Direct, PubMed, Cochrane, and EBSCO. Two reviewers independently performed literature searches and screenings. The quality and risk of bias were assessed using the Physiotherapy Evidence Database (PEDro) scale and the Cochrane Risk-of-Bias tool for randomized trials (RoB2). Meta-analysis was conducted using Revman 5.4.1 and Open Meta-analyst.ResultsSeven clinical trials involving 211 patients with HF were included. Meta-analysis revealed that IMT with intensity above 25% Maximum Inspiratory Pressure (MIP) significantly improved the 6MWT (61.81 m; 95% CI: 10.99 − 112.63 m), VO2peak (3.82 ml/kg/min; 95% CI: 3.25 − 4.39 ml/kg/min), dyspnea (−0.44; 95% CI: −0.76 to −0.12), and QoL (−12.23; 95% CI: −21.28 to −3.19), but not in RHR (−4.59; 95% CI: −10.91 to 1.72).ConclusionIMT with intensity above 25% MIP demonstrated improvements in the 6MWT, VO2peak, dyspnea, and QoL in patients with HF
