HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
Not a member yet
13939 research outputs found
Sort by
Failed, Aborted Replication of “Carbon-Dot-Based Dual-Emission Nanohybrid Produces a Ratiometric Fluorescent Sensor for In Vivo Imaging of Cellular Copper Ions”
No full textInternational audienceThis study presents the results of a replication effort aimed at reproducing key findings fromthe 2012 article "Carbon-Dot-Based Dual-Emission Nanohybrid Produces a Ratiometric Flu-orescent Sensor for In Vivo Imaging of Cellular Copper Ions" by Zhu et al. The original studyclaimed that CQDs functionalized with AE-TPEA (CQDs-TPEA) and their hybrid withCdSe/ZnS quantum dots (CdSe@C-TPEA) exhibited ratiometric fluorescence quenching uponexposure to Cu2+ ions, enabling their application as a dual-emission sensor for intracellular Cu2+imaging. Despite closely following the described synthesis and characterization protocols, wewere unable to reproduce the Cu2+-induced fluorescence quenching, undermining the primaryclaim of the original study and making it impossible to pursue the investigation in live cells.Furthermore, upon close examination of the original data, concerns regarding spectral anoma-lies and potential inconsistencies were raised, prompting us to abort the replication study
Protective TiO x N y -based multilayer coatings for 316L stainless steel bipolar plates in a PEM water electrolyzer
No full textInternational audienceThe present work reports the optimization of magnetron-sputtered titanium/titanium oxynitride thin-film coatings for application on 316L stainless steel bipolar plates (BPP) in proton exchange membrane water electrolyzers (PEMWE). As it will be shown, these coatings display tunable electrical conductivity and mechanical hardness to optimize the interfacial contact resistance (ICR). By controlling the elemental composition and thickness of the coating, and by using multilayers instead of single TiON layers, the ICR can be reduced to 1.5 mΩ cm 2 , a value lower than the targeted ICR (10 mΩ cm 2 ) for BPP in PEMWE. Moreover, due to its stable oxide nature, in contrast to uncoated steel, the coated steel was undamaged after 168 h at 60 • C under the experimental conditions found in PEMWE, in which the BPP surface potential is decoupled from the cell voltage. This proposed low-cost coating should therefore be considered as a promising material to enhance the competitiveness of the PEMWE technology.</div
BPS2025 - The glycoprotein-rich cell wall architecture of Chlamydomonas reinhardtii
No full textInternational audienceCellulose is the most abundant biopolymer on earth as it represents the major component of the cell wall of vascular plants. As a polymer of glucose molecules, its biosynthesis by photosynthetic organisms accounts for a significant annual reduction in atmospheric carbon dioxide. In addition to plant and fungal cell walls, cellulose also serves as a bacterial biofilm component and as a tissue scaffold in some tunicates. Cellulose is synthesized and secreted across the plasma membrane by cellulose synthase, a membrane-embedded, processive glycosyltransferase. While the core biosynthetic machinery is evolutionarily conserved, cellulose biosynthesis shows species-specific variations for the production of tailored cellulosic biomaterials. These include the alignment of cellulose chains into cablelike fibers as the load-bearing components of plant cell walls and the chemical modification of cellulose with small molecules in certain biofilms. We present detailed mechanistic insights into cellulose biosynthesis in plants and bacteria. Combining structural and functional analyses, we explain how cellulose synthase elongates a nascent cellulose polymer, how the elongated chain is translocated across the plasma membrane, and how plant cellulose synthase promotes the alignment of cellulose polymers into fibrillar structures. We also provide insights into the chemical modification of cellulose with lipid-derived phosphoethanolamine by Enterobacteriaceae. Here, cellulose synthase is part of a macromolecular complex that catalyzes the synthesis, chemical modification, and secretion of cellulose across the gram-negative cell envelope. Together, our work provides insights into the molecular and mechanistic principles necessary to design novel cellulosic biomaterials.95-Symp BPS2025 -The glycoprotein-rich cell wall architecture of Chlamydomonas reinhardtii</p
On the MIA Vulnerability Gap Between Private GANs and Diffusion Models
No full textGenerative Adversarial Networks (GANs) and diffusion models have emerged as leading approaches for high-quality image synthesis. While both can be trained under differential privacy (DP) to protect sensitive data, their sensitivity to membership inference attacks (MIAs), a key threat to data confidentiality, remains poorly understood. In this work, we present the first unified theoretical and empirical analysis of the privacy risks faced by differentially private generative models. We begin by showing, through a stability-based analysis, that GANs exhibit fundamentally lower sensitivity to data perturbations than diffusion models, suggesting a structural advantage in resisting MIAs. We then validate this insight with a comprehensive empirical study using a standardized MIA pipeline to evaluate privacy leakage across datasets and privacy budgets. Our results consistently reveal a marked privacy robustness gap in favor of GANs, even in strong DP regimes, highlighting that model type alone can critically shape privacy leakage
Mid-infrared optical valve based on VO2
No full textInternational audienceWe demonstrate an efficient optical binary-switch effect in nanoslit arrays achieved via the temperature-induced phase transition of VO 2 . Experimental measurements reveal a polarization-dependent 60% reduction in reflectivity during the insulator-to-metal transition. Tuning a single parameter of the slit enables control over the "optical-valve" effect. Full numerical simulations support these findings, predicting a reflectivity reduction up to 90%. The nearly one-to-null transition in reflectivity mimics the operation of a digital switch, with the high-reflectivity and the lowreflectivity states providing a binary response much like digital electronics
Waviness and self-sustained turbulence in plane Couette-Poiseuille flow
No full textDirect numerical simulations of a Couette-Poiseuille flow were performed near the transition to turbulence to investigate the nonlinear relationship between streak waviness and rolls. This relationship is a key step in Waleffe's model for a self-sustaining process (SSP). Simulations were conducted for Reynolds numbers ranging from 500 to 940, and a range of initial perturbation amplitudes were used. In these simulations, the streaks, rolls, and streak waviness initially increase. The optimal time for this growth is close to the linear transient growth period for small perturbations, but much shorter for large, highly nonlinear perturbations. For higher Reynolds numbers and large initial perturbations, the velocity field reaches a turbulent steady state, whereas it relaxes to a laminar state in other cases. The main result is that the waviness of the streaks is a quadratic function of the rolls, provided that its value is sufficiently large.Direct numerical simulations of a Couette-Poiseuille flow were performed near the transition to turbulence to investigate the nonlinear relationship between streak waviness and rolls. This relationship is a key step in Waleffe's model for a self-sustaining process (SSP). Simulations were conducted for Reynolds numbers ranging from 500 to 940, and a range of initial perturbation amplitudes were used. In these simulations, the streaks, rolls, and streak waviness initially increase. The optimal time for this growth is close to the linear transient growth period for small perturbations, but much shorter for large, highly nonlinear perturbations. For higher Reynolds numbers and large initial perturbations, the velocity field reaches a turbulent steady state, whereas it relaxes to a laminar state in other cases. The main result is that the waviness of the streaks is a quadratic function of the rolls, provided that its value is sufficiently large
Stereoselective Redox Switching between Möbius and Hückel Aromatic π Systems in a Three-Type Chirality Totem
No full textInternational audienc
Supramolecular “sergeants”: in situ and multi-level induction of chirality in helical assemblies of triarylamine trisamide monomers
No full textInternational audienceThe induction and transmission of chirality across multiple length scales is fundamental to many (bio) chemical processes. For the majority of macromolecular and supramolecular structures adopting a helical configuration, this is harnessed by means of a monomer embedding a stereogenic element, also called a “sergeant” because of its ability to transfer its chirality preference to achiral monomers. Herein, we devise a triarylamine trisamide (TATA) monomer embedding a (thio)urea unit able to interactwith a chiral phosphate anion through hydrogen bonding. Thanks to the orthogonal nature of the amide and (thio)urea functions, the anion specifically binds to the (thio)urea unit, thus yielding a supramolecular monomer acting as a “sergeant” i.e. allowing efficient chirality induction in amide-bonded TATA helical copolymers composed of various types of achiral TATA monomers. Unlike covalent “sergeants”, chirality can be induced in situ by binding of the chiral anion to pre-formed coassemblies. In addition, the catalytic performance of TATA coassemblies embedding intrinsically achiral phosphine-functionalized TATA monomers has been evaluated: higher enantioselectivities are reached with the supramolecular versus covalent “sergeant”. Our work may facilitate the design and development of supramolecular“sergeants” as a modular approach to induce chirality in supramolecular helical copolymers and catalysts
Auto-Emulsification of Water at the Crude Oil/Water Interface: Role of the Solid Walls and Wettability Alteration
No full textInternational audienceUsing confocal fluorescence microscopy in both hydrophilic and hydrophobic glass capillaries, this study explores (i) the influence of wall wettability on spontaneous emulsification at the oil/water interface and (ii) the mechanisms governing the interaction of water/oil microdroplets with solid surfaces, ultimately enhancing oil recovery during low-salinity water injection. Our findings reveal that microdroplet formation predominantly occurs on solid surfaces when they are hydrophilic, whereas in hydrophobic environments, droplets emerge at the water/oil interface, specifically within the thin film between the meniscus and the solid wall. The growth dynamics of these droplets follows distinct scaling laws depending on the wettability of the surface. Upon injection of low-salinity water, the apparent contact angle increases on hydrophilic walls but remains unchanged on hydrophobic walls. In both cases, however, the advancing meniscus leaves behind a residual oil film containing trapped water microdroplets. The mobility of these droplets whether sessile or not, depends on surface properties. Over time, they merge with the surrounding water, forming water patches within the residual oil film. As these patches expand and coalesce, they create a structure reminiscent of a two-dimensional foam. Ultimately, these patches continue to grow until the solid wall is fully exposed to the free water phase
Site-specific D-H exchange of amino acids under asteroidal hydrothermal conditions
No full textInternational audienceAmino acids detected in carbonaceous chondrites are commonly enriched in heavy isotopes of hydrogen compared to terrestrial counterparts. This is interpreted as the consequence of synthesis processes happening in cold extraterrestrial environments. However, the magnitude of this enrichment is variable among classes of chondrites and among individual amino acid in a given chondrite. In this study, we investigated the evolution of the D/H isotope ratio of amino acids experimentally exposed to pure D2O at 150 ◦C. We observed that not all the hydrogen-specific sites are prone to deuterium-hydrogen exchange under hydrothermal conditions. Ab-initio modeling pinpoints the higher acidity of the carbon in α position (Cα) leading to a site-specific preferential D- H exchange, affecting the hydrogen atoms bonded to Cα (α-H). This explains the low exchange rate of 2-amino- isobutyric acid and isovaline, these branched amino acids lacking α-H, and the rather high exchange rate of glycine, α-alanine and β-alanine, their α-H exchanging faster. By extrapolating these results, it can be assumed that chondritic amino acids lacking α-H and containing only primary hydrogen (i.e., –CH3 group) have better retained their pre-accretional D/H values despite hydrothermal alteration on the parent body