HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Impact of Chelation on Reactivity and Cytotoxicity of Hemilabile Biphenyl Gold(III) N‐Heterocyclic Carbene Complexes
No full textInternational audienceAlthough great progresses have been accomplished in the field of antineoplastic treatments, the need for chemotherapy agents with new mechanisms of action remains essential. Metal complexes presenting hemilabile ligands could combine structural toxicity upon full coordination of the ligand and reactive toxicity upon ligand partial decoordination and direct coordination of the metal center to biological targets. To investigate the relevance of hemilability in the case of Au(III) complexes, we synthesized eight open biphenyl gold(III) N‐heterocyclic carbene complexes coined BGC of general formula [(C^C)Au(NHC^het)Cl] where het is a pyridine‐type entity and C^C is 4,4′‐diterbutylbiphenyl. Chloride abstraction afforded the chelated cationic complexes [(C^C)Au(NHC^N)]PF 6 in which the pyridine arm coordinates the gold ion. Quantitative irreversible conversion of the cationic forms to the neutral ones in the presence of chloride ions was demonstrated through extensive speciation studies by 1 H NMR spectroscopy on both forms in different media including DMSO/cell culture medium mixture. The BGC complexes exhibited antiproliferative activity in the low micromolar range with equivalent activities for each open neutral/chelated cationic pair. Time lapse fluorescence videomicroscopy studies demonstrated the activation of effector caspases 3/7, suggesting the induction of apoptosis. Preliminary mechanistic studies suggest that apoptotic cell death may arise partially from mitochondrial membrane depolarization
AML patient blasts exhibit polarization defects upon interaction with bone marrow stromal cells
No full textInternational audienceHematopoietic stem and progenitor cells (HSPCs) polarize in contact with the bone marrow stromal cells constituting their niche. Given the role of cell polarity in protection against tumorigenesis and the importance of the niche in the progression of acute myeloid leukemias (AMLs), we investigated the polarization capacities of leukemic blasts. Using engineered micro-niches and centrosome position with respect to the contact site with stromal cells as a proxy for cell polarization, we show that AML cell lines and primary cells from AML patient blasts are unable to polarize in contact with healthy stromal cells. Exposure to AML patient-derived stromal cells compromises the polarization of healthy adult HSPCs and AML blasts from patients. When cultured in “bone-marrow-on-a-chip”, stromal cells from a leukemic niche stimulate the migration of healthy HSPCs and AML blast. These results reveal the detrimental influences of both intrinsic transformation and extrinsic contact with transformed stromal cells on the polarization of AML blasts
First Row Transition Metals in Olefin Metathesis: The Role of Iron and Manganese
No full textInternational audienceOlefin metathesis has traditionally been dominated by molybdenum and ruthenium-based catalysts, but the pursuit of sustainable and earth-abundant alternatives has driven interest in first-row transition metals particularly iron. While iron is an attractive candidate due to its abundance, low toxicity, and cost-effectiveness, significant challenges hinder its successful implementation in metathesis reactions. This review examines the electronic and structural properties of iron that contribute to its catalytic limitations, including high-spin configurations, weak metal-alkylidene interactions, and a pronounced tendency toward cyclopropanation. Computational and experimental efforts to overcome these obstacles are discussed, focusing on ligand design strategies and mechanistic insights. Additionally, the potential of manganese as an alternative to iron is explored. This work underscores the complexities of first-row transition metal catalysts in olefin metathesis and highlights future directions for achieving practical, efficient iron-based systems. Future research should focus on refining ligand architectures to stabilize key intermediates, leveraging computational insights to predict reactivity trends, and further investigating the role of metal oxidation states in metathesis activity. While the transition to first-row transition metals remains a challenge, ongoing advancements continue to push the boundaries of sustainable catalysis, bringing the dream of practical iron- or manganese-based olefin metathesis closer to reality
Recueil de communications école d'hiver 2025 GDR ARCHI-META - DN METACMED
No full textNational audienceThe last 20 years have seen a remarkable growth in scientific interest in(elastic and mechanical) metamaterials. One of the reasons for this is thegreat potential that this subject area has in itself as a “link between differentdisciplines”, particularly acoustics and solid mechanics. In addition, through abetter mastery of architecture, it makes it possible to create complex enginee-ring systems with unconventional dynamic and quasi-static behavior.However, the literature seems to show that since its introduction in the early2000s, two almost independent macro-communities have formed around thissubject: that of acousticians, more focused on phenomenology, and that ofmechanics, more focused on methodology.However, it is clear that 1) these two communities are dealing with thesame scientific problem, and that 2) certain differences in purpose and lan-guage have given, and still give, the impression that these are two looselycoupled fields of research. This has made intercommunity dialogue insufficientuntil now. However, it is easy to see that the subjects investigated and the me-thodologies used are generally complementary. The time has come for a newcommunity to emerge, particularly at the international level.In this context, the ARCHI-META GdR proposes to seize this spontaneousconvergence and act as a catalyst to go beyond the specificities related toacoustics and mechanics, and thus to bring together a new community aroundarchitectured metamaterials. The overall objective is to get the communities(mechanics and acousticians) to work together to identify and resolve thecommon scientific issues that have come to light in recent years and to sharethe theoretical tools specific to the two communities in order to establish acommon language. This synergy will make it possible to address more effec-tively the scientific issues limiting the development of these promising techno-logies
Indentation stress fields in brittle materials: A micro-photoelastic investigation in silicate glasses
No full textInternational audienceIndentation experiments have helped understand non linear mechanical properties of brittle materials such as plasticity, damage and fracture. However, our understanding of stress fields under indentation remains limited due to the general lack of direct measurements. This study introduces a novel approach to characterizing indentation stress fields in silicate glasses by combining high sensitivity birefringence measurements, photoelastic calculations and finite element analysis (FEA). We extensively investigated the elastoplastic response of soda-lime-silicate (SLS) and silica glasses under different indentation conditions, highlighting the effects of composition and indenter geometry on the photoelastic distributions. To predict the photoelastic response under indentation, we carefully calibrated an elastoplastic constitutive relation for silicate glasses using a combination of high-pressure (up to 25 GPa) and nanoindentation experiments. Computed indentation stress fields can then be validated through the comparison of full 3D photoelastic calculations and measured birefringence patterns. One key finding is that the residual stresses arising from the calibrated constitutive relations offered a far more realistic representation of the indentation stress fields than a commonly used approximate analytical elastoplastic model. With this method, stress fields can be investigated not only in oxide glasses but also in any other transparent isotropic material. While the calculated stress fields were generally satisfactory for both glass compositions, they also evidenced that improvements in the constitutive relation are needed for amorphous silica, which is known to undergo significant densification
In Situ Synthesis of Iron Oxide-Polyisobutylene Multifunctional Nanocomposites: Size Control, Magnetic and Mechanical Properties Enhancement
No full textInternational audiencePolymer nanocomposites with precisely controlled nanoparticle size and narrow polydispersity offer substantialpotential for multifunctional applications, particularly in energy and healthcare. In this study, we introduce an in situ synthesis approach for creating iron oxide nanoparticle-polyisobutylene nanocomposites, where the nanoparticle size distribution and spatial dispersion are finely tuned by adjusting the polymer concentration and molecular weight. This method allows us to investigate and control the growth dynamics of nanoparticleswithin the polymer solution, providing insights into how the polymer molecular weight and concentration influence nucleation, growth, and assembly. Beyond achieving precise size control, our approach enables the rational design of nanocomposites with significantly enhanced mechanical strength, evidenced by an increased storage modulus, while preserving their superparamagnetic behavior. This strategy advances the development of high-performance magnetic polymer nanocomposites and opens up possibilities for applications that require both robust mechanical properties and responsive magnetic features, marking a significant step forward in nanocomposite design and functionality
RecurGreen - Recursive Green method to solve the wave equation in a disordered waveguide
No full textRecurGreen is a Fortran 2008 program to compute the Green function corresponding to the propagation of a scalar wave in a 2D disordered waveguide. The algorithm used is a variant of the recursive Green method in the basis of the transverse eigenmodes of the waveguide. The focus of this program is the computation of the transmission matrix and the distribution of transmission eigenvalues when averaging over the realizations of the disorder
Structure, function and formation of the amniote skin pattern
No full textInternational audienceFrom feather and hair dotted arrays to pigmented stripes and spots, the spatial distribution of skin appendages and colouration often forms visible ornaments crucial for fitness in the coat of birds and mammals. These geometrical motifs are extremely diverse in nature. Yet, phenotypic surveys evidenced common themes in variation: the orientation, appendage-specificity or pigmentation of a given region may be conserved across groups or species. Here, we review naturalist observations of natural variation in the anatomy and ecological function of the skin pattern in amniotes. We then describe several decades of genetics, mathematical modelling and experimental embryology work aiming at understanding the molecular and morphogenetic mechanisms responsible for pattern formation. We discuss how these studies provided evidence that the morphological trends and differences representative of the phenotypic landscape of skin patterns in wild amniote species is rooted in the mechanisms controlling the production of distinct compartments in the embryonic skin
Mechanical Tuning of Residual Stress, Memory, and Aging in Soft Glassy Materials
No full textInternational audienceGlassy materials rapidly quenched from a liquid to a solid state upon flow cessation or cooling solidify in an out-of-equilibrium configuration, trapping residual stresses and retaining the memory of the processing conditions for very long times, which compromises their physical characterization and can adversely affect processing operations. Erasing the mechanical history encoded in disordered materials constitutes a great challenge. Here, we address this problem using experiments and particle dynamic simulations for the case of colloidal glasses made of soft particles densely packed at high volume fractions. We propose a conceptual framework that connects residual stresses, directional memory, and aging of colloidal glasses to the distribution of local shear stresses in the shearing plane. The mean value of the distribution corresponds to the macroscopic stress, the skewness carries information about directional memory, and the standard deviation is related to mechanical aging. Periodically training soft particle glasses near the yield point with a sequence of stress-controlled oscillations provides a fine-tuning of the particle stress distribution. Asymmetric shear stress distributions resulting from previous flow are transformed into symmetric distributions, thereby successfully erasing residual stresses and directional memory. The same methodology is successfully applied to colloidal and polymer gels with thixotropic properties, suggesting that it is general and may be extended to other classes of disordered materials.</div
Retinal axial motion analysis and implications for real-time correction in human retinal imaging
No full textHigh-resolution ophthalmic imaging devices including spectral-domain and full-field optical coherence tomography (SDOCT and FFOCT) are adversely affected by the presence of continuous involuntary retinal axial motion. Here, we thoroughly quantify and characterize retinal axial motion with both high temporal resolution (200,000 A-scans/s) and high axial resolution (4.5 µm), recorded over a typical data acquisition duration of 3 s with an SDOCT device over 14 subjects. We demonstrate that although breath-holding can help decrease large-and-slow drifts, it increases small-and-fast fluctuations, which is not ideal when motion compensation is desired. Finally, by simulating the action of an axial motion stabilization control loop, we show that a loop rate of 1.2 kHz is ideal to achieve 100% robust clinical in-vivo retinal imaging