HAL Université de Toulouse, et Toulouse INP
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KuQuinone-sensitized cobalt oxide nanoparticles for photoelectrocatalytic oxygen evolution with visible light
No full textInternational audiencePhotocatalytic nanomaterials offer promising solutions for conducting chemical transformations under safe, green and sustainable conditions. In particular, the storage of solar energy into chemical bonds is an appealing but challenging goal in the field of artificial photosynthesis. Using water as the source of electrons and protons through the photodriven water oxidation (WO) reaction is at the core of this endeavour. In this work, we disclose photoactive hybrid nanomaterials designed through a dyadic approach. We exploit Co3O4 nanoparticles (NPs) covalently functionalized with a fully organic pentacyclic polyquinoid KuQuinone (KuQ) dye, providing a rare example of a noble metal-free photocatalytic dyadic nanomaterial (hereafter denoted as KuQ3Pn@Co3O4). KuQ3Pn@Co3O4 NPs have been characterized by electron microscopy and optical and core-level spectroscopy studies. When cast onto a SnO2 photoanode, they are active towards WO upon visible light irradiation (400–580 nm) with a faradaic efficiency for O2 evolution of ca. 90%. This work provides a novel contribution to the rational design and mechanistic understanding of hybrid photocatalytic nanomaterials relevant for energy and sustainable synthesis applications
Source, fate, and effects of plastic litters in the European land-sea continuum
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Large Eddy Simulations of multi-component swirling-spray flames' dynamics under acoustic oscillations
No full textInternational audienceWell-understanding and mastering Sustainable Aviation Fuels (SAF) composition, as well as the impact of their initial component concentrations on flame dynamics, is of critical importance in today’s energy transition and safe operability context. In this study, the focus lies on conducting Large Eddy Simulations (LES) to understand the impact of species concentration changes in well-controlled multi-component fuel blends on flame dynamics under forced acoustic oscillations. To do so, the SICCA-spray rig from the EM2C laboratory, operated with two blends of n-dodecane and n-heptane in varying proportions, is specifically addressed in light of available data. While LES successfully capture key trends, phase lag predictions and absolute time delays are found to deviate from experimental flame transfer function measurements but remain within the correct order of magnitude. Across the two investigated blends, results suggest that increasing the proportion of n-heptane enhances flame dynamics, particularly in terms of heat release rate fluctuations and spray penetration length oscillations. Higher proportions of n-heptane promote faster evaporation, increasing the local equivalence ratio and, consequently, the flame response to acoustic perturbations. In contrast, blends with more n-dodecane lead to longer characteristic times with extended evaporation and combustion delays, reducing the amplitude of the flame dynamics. Close to the injector exit, n-heptane exhibits greater spatial fluctuations modulated via variations in the inner recirculation zone size. During an oscillation, the latter is observed to deflect the flame/flow opening angle by up to 50% relative to values obtained under steady-state conditions. Ultimately, these effects are closely tied to the evaporation properties of each fuel and their concentration proportions within the blend. This insight highlights the intricate relationship between fuel properties, their ratios within blends, and the resulting flame dynamics, shedding light on the complexities of multi-component fuel combustion and thermo-acoustic instabilities
Thiophosphate-Based Covalent Organic Framework (COF) or Porous Organic Polymer (POP)?
No full textInternational audienceThere are few examples of covalent organic frameworks (COFs) based on phosphorus as the building element, probably because the structure of most phosphorus derivatives is pyramidal, which may prevent the stacking expected for classical 2-dimensional COFs. In addition, they are generally associated with linear difunctional derivatives. In this paper is reported the original association of a trifunctional 3-D compound with a trifunctional 2-D compound in an attempt to get a new COF. The condensation reaction between a thiophosphate derivative bearing three aldehydes and the trihydrazinotriazine has been carried out with the aim of obtaining either a COF or simply a porous organic polymer (POP), consisting in both cases of associated macrocycles, affording a new covalent triazine framework (CTF). The material resulting from this condensation has been characterized by multinuclear MAS NMR (31P, 1H, and 13C), IR, and thermogravimetric analysis (TGA). All these data confirmed the condensation reactions. However, BET (Brunauer–Emmett–Teller) measurements indicated that the porosity of this material is low. Trapping dyes in solution, as a model of pollutants, by the insoluble porous material 3 has been attempted
Rôles et gestions des lisières dans les paysages ruraux
No full textNational audienceLes espaces arborés dans les paysages ruraux constituent des infrastructures écologiques importantes, notamment par leurs liens avec différents aspects des activités agricoles et d’élevage. Les haies sont plus particulièrement reconnues en tant que composantes agroforestières pouvant jouer des rôles déterminants dans les transitions agroécologiques. D’autres formations arborées linéaires, et notamment les lisières entre les bois et les zones agricoles, ont été bien moins considérées alors qu’elles présentent des similarités avec les haies. A partir d’une analyse systémique et d’enquêtes de terrain, la présentation mettra en évidence les points communs et les différences entre les haies et les lisières en tant qu’infrastructures écologiques arborées linéaires des paysages ruraux, ainsi que la diversité des pratiques de gestion qui les façonnent et déterminent leurs dynamiques respectives. Les résultats montrent que les origines et structures végétales des haies et des lisières sont différentes et résultent de processus qui n’ont pas les mêmes déterminants dans le cas général. Cependant, dans les zones de déprise agricole, d’anciennes haies peuvent devenir des lisières de boisements spontanés sur d’anciennes parcelles agricoles. Par contre, les pratiques de gestion des haies et des lisières par les agriculteurs semblent peu différentes, mobilisant les mêmes techniques et imposant les mêmes contraintes. Cependant, les statuts fonciers des haies et des lisières sont souvent différents et peuvent de ce fait induire des pratiques particulières selon les modalités d’interactions entre les acteurs concernés de part et d’autre. La compréhension de ces différences est nécessaire pour élaborer des projets de développement et d’entretien de ces infrastructures écologiques dans les paysages ruraux, dans la perspective de transitions agroécologiques, en tenant compte concrètement et précisément des besoins, mais aussi des contraintes, des gestionnaires et bénéficiaires de ces espaces. Du fait de leurs rôles écologiques similaires, les haies et les lisières forestières devraient être plus souvent envisagées de façon complémentaires. Elles sont de fait gérées conjointement par les agriculteurs qui appréhendent globalement l’ensemble des interfaces entre leurs parcelles de culture et d’élevage, et les espaces arborés, de haie ou de lisière. Deux recommandations sont proposées en conclusion : 1) mieux comprendre quelles sont les pratiques effectives de gestion des haies et lisières mise en œuvre par les agriculteurs ; 2) mieux cartographier conjointement les haies et les lisières dans les outils de planification écologique territorialisée
Nucleation in Confinement: A Pathway to Size-Controlled Ultra-Small Icosahedral Silver Nanoparticles
No full textInternational audienceThe size and structural control of ultra-small metal nanoparticles (NPs) remains a key area of research, as their unique nanoscale properties can significantly impact their utility and applications in industry. Among the different synthesis strategies, the formation of large clusters of metal precursors in solution, which favours a confined nucleation, has been less explored. Here, we report a simple synthesis protocol of ultra-small silver nanoparticles with an icosahedral structure, a mean diameter of 3 nm and low polydispersity (down to 6%), through the reduction of AgNO3 by trialkylsilanes in a solution of oleylamine (OY) and hexane. Smalland wide-angle X-ray scattering (SAXS, WAXS) and pair distribution function (PDF) analysis reveal that the Ag NP size and structure remain constant regardless of Ag and reducing agent concentrations, or temperatures up to 120°C. The lack of correlation between the final NP size and the initial Ag concentration, temperature, and reaction rate -despite variations spanning two orders of magnitude -does not align with a classical nucleation/growth mechanism of isolated monomers in solution. SAXS analysis of the precursor solutions revealed the presence of {OY-Ag (I) -NO3}n clusters, which interact repulsively in solution. The final Ag particle size is closely tied to the size of the Ag(I) clusters. This suggests that size control is governed by a nucleation process involving Ag atoms within the clusters. The separation of nucleation and growth appears to be achievable through nucleation confined within the repulsively interacting {OY-Ag (I) -NO3}n clusters. Only two factors have been found to decrease the mean NP size: increasing the OY concentration, or substituting AgNO3 with silver trifluoro-sulfonate or trifluoro-acetate, which reduces the mean size, in agreement with smaller initial Ag (I) clusters. The advantage of this synthesis route is the very high concentration of metals that can be achieved without degrading the morphological and structural quality of the final particles
Solute transport due to periodic loading in a soft porous material
No full textInternational audienceIn soft porous media, deformation drives solute transport via the intrinsic coupling between flow of the fluid and rearrangement of the pore structure. Solute transport driven by periodic loading, in particular, can be of great relevance in applications including the geomechanics of contaminants in the subsurface and the biomechanics of nutrient transport in living tissues and scaffolds for tissue engineering. However, the basic features of this process have not previously been systematically investigated. Here, we fill this hole in the context of a one-dimensional model problem. We do so by expanding the results from a companion study, in which we explored the poromechanics of periodic deformations, by introducing and analysing the impact of the resulting fluid and solid motion on solute transport. We first characterise the independent roles of the three main mechanisms of solute transport in porous media -advection, molecular diffusion and hydrodynamic dispersion -by examining their impacts on the solute concentration profile during one loading cycle. We next explore the impact of the transport parameters, showing how these alter the relative importance of diffusion and dispersion. We then explore the loading parameters by considering a range of loading periods -from slow to fast, relative to the poroelastic time scale -and amplitudes -from infinitesimal to large. We show that solute spreading over several loading cycles increases monotonically with amplitude, but is maximised for intermediate periods because of the increasing poromechanical localisation of the flow and deformation near the permeable boundary as the period decreases
Vision is not olfaction: impact on the insect Mushroom Bodies connectivity
No full textThe Mushroom Bodies, a prominent and evolutionary conserved structure of the insect brain, are known to be the support of olfactory memory. There is now evidence that this structure is also required for visual learning, but the hypotheses about how the view memories are encoded are still largely based on what is known of the encoding of olfactory information. The different processing steps happening along the several relays before the Mushroom Bodies is still unclear, and how the visual memories actually may allow navigation is entirely unknown. Existing models of visual learning in the Mushroom Bodies quickly fall short when used in a navigational context. We discuss how the visual world differs from the olfactory world and what processing steps are likely needed in order to form memories useful for navigation, and demonstrate it using a computational model of the Mushroom Bodies embedded in an agent moving in through a virtual 3D world
Lipschitz Pruning: Hierarchical Simplification of Primitive‐Based SDFs
No full textEurographics 2025 Best Paper Honorable MentionInternational audienceRendering tree‐based analytical Signed Distance Fields (SDFs) through sphere tracing often requires to evaluate many primitives per tracing step, for many steps per pixel of the end image. This cost quickly becomes prohibitive as the number of primitives that constitute the SDF grows. In this paper, we alleviate this cost by computing local pruned trees that are equivalent to the full tree within their region of space while being much faster to evaluate. We introduce an efficient hierarchical tree pruning method based on the Lipschitz property of SDFs, which is compatible with hard and smooth CSG operators. We propose a GPU implementation that enables real‐time sphere tracing of complex SDFs composed of thousands of primitives with dynamic animation. Our pruning technique provides significant speedups for SDF evaluation in general, which we demonstrate on sphere tracing tasks but could also lead to significant improvement for SDF discretization or polygonization
Robust inference with incompleteness for logistic regression model
No full textInternational audienceLogistic regression models traditionally assume observed covariates. However, practical scenarios often involve missing data and outliers, which pose significant challenges. This short communication presents a new approach to solve these issues by integrating random covariates following a Student t-distribution within the framework of logistic regression. We propose a Robust Stochastic Approximation Expectation-Maximization algorithm suitable for Logistic Regression (REM-LR) that, in addition, is able to improve the resilience of the model against both missing values and outliers.</div