HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Theory of charge-to-spin conversion under quantum confinement
No full textInternational audienceThe interplay between spin and charge degrees of freedom in low-dimensional systems is a cornerstone of modern spintronics, where achieving all-electrical control of spin currents is a major goal. Spin-orbit interactions provide a promising mechanism for such control, yet understanding how spin and charge transport emerge from microscopic principles remains a fundamental challenge. Here, we develop a spin-dependent scattering matrix approach to describe spin and charge transport in a multiterminal system in the presence of Rashba spin-orbit interaction. Our framework generalizes the Büttiker formalism by offering expressions for spin and charge current densities as a function of the lead position, along with the corresponding linear response function. It simultaneously captures the effects of quantum confinement, the response to external magnetic fields, and the intrinsic properties of the electronic bands, offering a comprehensive description of the spin-charge interconversion mechanisms at play in a Hall bar, in agreement with experiments
A continuous damage accumulation scenario for elastomeric frictional wear
No full textUnderstanding how materials wear off following frictional sliding is a long-standing question in tribology. In this respect, the particular case of the wear of soft rubbery elastomeric materials stands apart: tire wear produces several million tonnes of abraded materials per year, bearing immense industrial and environmental impact, while the soft nature of elastomers and their inability to accommodate plastic deformation before failure renders their wear mechanisms almost intractable. Here, we harness mechanochemical approaches on model elastomeric materials, to reveal that mild elastomeric wear does not proceed from crack propagation processes, but rather from the continuous accumulation of diffuse damage by chain scission, extending well below the surface of the material. Damage accumulates in a discontinuous manner through micro-slippage events at the rough contacting asperities, with in-depth damage extension set by the characteristic asperity size. Surprisingly, damage grows through a slow logarithmic-like process over successive cycles, which we interpret as the occurrence of stress-activated scission events in a broad strand elastic energy landscape. These observations point to the probabilistic nature of this fatigue-like damage accumulation mechanism and allow us to formulate the wear rate as an integral of the damage cumulated over successive asperity sliding. Finally, by tuning the molecular architecture of our materials, we evidence an antagonistic relation between fracture resistance and wear resilience, set by the sensitivity of the material to stress fluctuations. Revealing the role of previously invisible subsurface damage in elastomeric wear, our approach should stimulate further physical-based approaches allowing for the development of sustainable and wear-resilient materials
Micro-displacement tensor
No full textWe propose an extended kinematics of nominally elastic continuum solids allowing one to describe their mechanical interaction with micro-scale loading devices. The main new ingredient is the concept of a micro-displacement tensor which extends the conventional description of the deforming elastic solids in terms of macroscopic displacement vectors. We show that micro-displacement tensors are particularly useful in dealing with active incompatibility acquisition and its subsequent passive relaxation. We use the proposed approach to describe the energetics of surface deposition while accounting for the presence of micro-mechanical controls.To illustrate the effectiveness of the new conceptual scheme we present two case studies: crystallization from a melt resulting in pre-stress, and winding of a coil with controlled pre-stretch.</div
A novel RNP compartment boosts translation in growing mouse oocytes to avoid cytoplasm dilution
No full textPosted March 04, 2025 on bioRxiv.International audienceMammalian oocytes undergo a long growth phase in the ovary, during which transcriptional levels gradually decrease. Growing oocytes must therefore accumulate maternal stores and regulate their translation to achieve successful divisions and early embryo development. Using immunofluorescence, mass spectrometry and electron microscopy, we identified a novel and transient compartment, the Zollo Body, in late growing mouse oocytes, constituted of RNPs and organelles. Morphologically, this structure resembles the Balbiani body found in most vertebrate species but it stains positively for nascent translation and active phospho-mTOR. RNAseq analysis and dry mass measurements of growing oocytes with or without this compartment further support its key role in boosting translation, allowing growing oocytes to avoid cytoplasmic dilution despite their rapid size increase, ultimately ensuring their developmental potential
Extreme wave skewing and dispersion spectra of anisotropic elastic plates
No full textInternational audienceGuided wave dispersion is commonly assessed by Fourier analysis of the field along a line, resulting in frequency-wave-number dispersion curves. In anisotropic plates, a point source can generate multiple dispersion branches pertaining to the same modal surface, which arise due to the angle between the power flux and the wave vector. We show that this phenomenon is very particular near zero-group-velocity points and occurs in all directions independent of the degree of anisotropy. Stationary phase points accurately describe measurements on a monocrystalline silicon plate
Floquet scattering of shallow water waves by a vertically oscillating plate
No full textInternational audienceWe report on the scattering of a plane wave from a vertically oscillating plate in the low frequency approximation by means of Floquet theory. In the case of a static plate, the scattering coefficients are evaluated via mode matching method for the full two-dimensional linearized water wave problem and are compared with the coefficients obtained from a reduced onedimensional model in the shallow water approximation. The main part of the analysis is the extension of this 1D shallow water approximation to the case of a vertically oscillating plate, where time modulation is only encapsulated in the blockage coefficient. We show that the incident wave is scattered into Floquet sidebands and extract the scattering coefficients for each harmonic using a Floquet scattering formalism. Finally, considering a slowly oscillating plate, we propose a quasistatic approximation which appears to be particularly accurate.</div
Mesoscopic light transport in nonlinear disordered media
No full textInternational audienceNonlinear disordered media uniquely combine multiple scattering and second-harmonic generation. Here, we investigate the statistical properties of the nonlinear light generated within such media. We report super-Rayleigh statistics of the second-harmonic speckle intensity, and demonstrate that it is caused by the mesoscopic correlations arising in extreme scattering conditions. The conductance measured is exceptionally low for an isotropically scattering three-dimensional medium, enabling applications in broadband second-harmonic generation, wavefront shaping in nonlinear disordered media, and photonic computing
Targeted fluorescent lipid microparticles for quantitative measurement of phagosomal pH
No full textInternational audienceABSTRACT Phagosomal acidification plays a pivotal role in pathogen destruction and immune signaling, yet tools capable of reporting these biochemical changes with spatial and mechanistic precision remain scarce. A modular biosensing strategy is presented in which BODIPY-derived hydrophilic fluorophores are conjugated to phospholipids and incorporated at the surface of targeted lipid microparticles. These soft and biomimetic particles combine receptor-specific uptake with ratiometric fluorescence readouts, enabled by pairing pH-responsive dyes at the interface with a pH-invariant reference probe in the core. Following Fcγ receptor-mediated internalization by macrophages, the particles deliver real-time insight into the onset and progression of phagosomal acidification. This versatile platform provides a direct means to couple defined surface recognition events to intracellular pH measurements, offering new opportunities to unravel how particle identity and ligand presentation modulate phagosomal physiology
Phase Separation in Lead-Saponified Drying Oils: Implications for Historical Painting Techniques and Paint Stability
No full textInternational audienceRenaissance Masters often prepared siccative oils by heating linseed oil with siccatives, particularly lead oxide, inducing partial saponification and altering its properties. Our reconstructions show that lead-saponified oils naturally separate into two phases. In this study, we investigate the differences between these two phases through a comprehensive set of analytical methods, from macro-level assessments (rheology) to micro-level characterizations (SAXS, WAXS, optical microscopy, SEM), and chemical analyses (FTIR, GC-MS and SFC-HRMS, TGA and DSC).The lower phase is enriched in free fatty acids and lead carboxylates, especially saturated species-both as free acids and metal soaps-prone to self-organization. As a result, the lower phase displays a pronounced lamellar organization with partial crystallization, and exhibits viscoelastic and shear-thinning properties. In contrast, the unstructured upper phase behaves as a Newtonian fluid. The observed phenomena share similarities with the formation of soap-related defects such as protrusions, linked to saturated lead soaps. Teaser Spontaneous phenomenon of phase separation in saponified oils influences the structure and behavior of historical paint systems
SPARC is a new driver of early breast tumor progression via TGF-β -dependent mechanism
No full textAbstract Ductal carcinoma in situ (DCIS) is a pre-invasive lesion that is thought to be a precursor of invasive ductal carcinoma (IDC). The challenge lies in discriminating between DCIS progressors and DCIS non-progressors, often resulting in over- or under-treatment in many cases. Membrane type 1 (MT1)-matrix metalloproteinase (MMP) has been previously identified as an essential gene involved in DCIS progression. Here, RNA-sequencing analysis of MT1-MMP high subpopulation derived from invasive breast tumors in the intraductal xenograft model was compared against a dataset of human high-grade DCIS, and Secreted Protein Acidic and Cysteine Rich (SPARC) has emerged as a master candidate involved in early breast tumor progression. We report that SPARC is up-regulated in DCIS as compared to normal breast epithelial tissues, and further increased in IDC relative to synchronous DCIS foci. We found a positive correlation between SPARC and MT1-MMP expression in DCIS lesions. At the mechanistic level, depletion of SPARC reduced MT1-MMP expression, the degradative capacity of the cells and the activation of the TGF-β signalling canonical pathway. Pharmacological inhibition of the TGF-β signalling pathway decreased SPARC and MT1-MMP at the mRNA and protein level, and concomitantly the cell degradative capacity and 3D cell migration. Strikingly, inhibition of the TGF-β signalling pathway limits the invasive transition of breast tumors in a new triple-negative mouse intraductal syngeneic xenograft model. Moreover, high SPARC expression was positively correlated with both, TGF-β and its receptor, TGFBRI, in a basal type of breast cancer collection supporting our findings. This study identifies SPARC as a new driver of early breast tumor progression via a TGF-β-dependent mechanism, suggesting TGF-β signaling pathway as a potential target for patients with high SPARC expression