HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Rapid spectral shaping for time domain and swept source full field OCT
No full textInternational audienceFull-field optical coherence tomography (FFOCT) has recently regained attention thanks to the development of high-resolution dynamic OCT and cross-talk-free swept source FFOCT. However, the choice of wavelength and axial resolution is often a limiting factor with few existing commercial solutions. Here, we developed a novel method to provide rapid spectral shaping for FFOCT imaging. Combining a supercontinuum laser, a fast controllable acousto-optic tunable filter (AOTF), and a multimode fiber with passive and active mode mixing, we obtained an extremely flexible light source compatible with FFOCT. By tuning the AOTF frequency and integrating the resulting wavelength over one camera exposure time, it becomes possible to build any spectrum of interest in the 575-1000 nm range in time domain FFOCT. Alternatively, the designed source module enables achieving swept source FFOCT at up to 100 kfps at an unprecedented axial resolution of 1.1 μm
Towards non-invasive assessment of myocardial work using myocardial stiffness and strain: a human pilot study
No full textInternational audienceAbstract Aims Myocardial work assessment has emerged as a promising tool for left ventricular (LV) performance evaluation. Existing non-invasive methods for assessing it rely on assumptions on LV pressure and geometry. Recently, shear wave elastography allowed to quantify changes in myocardial stiffness throughout the cardiac cycle. Based on Hooke’s law, it becomes theoretically possible to calculate myocardial stress and work from myocardial stiffness and strain measurements. The main objective of this study is to demonstrate the feasibility of this comprehensive ultrasound approach and to compare myocardial work values between populations where variations are anticipated. Methods and results Children with hypertrophic cardiomyopathy (HCM), aortic stenosis (AS) and healthy volunteers (HV) were included in this study. Segment dimensions, strain, thickness, and segmental myocardial stiffness were assessed in the basal antero-septal segment throughout the cardiac cycle. One-beat segmental work, the stress–strain loop area, and contributive and dissipative work were compared between groups. Twenty HV (9.8 ± 5.3 years of age), 20 HCM (10.0 ± 6.1 years of age), and 5 AS (5.3 ± 4.3 years of age) subjects were included. One-beat segmental work was significantly higher in AS (272.0 ± 102.9 µJ/mm) and lower in HCM (38.2 ± 106.9 µJ/mm) compared with HV (131.1 ± 83.3 µJ/mm), P = 0.02 and P = 0.01, respectively. Desynchronized work was prevailing in HCM with dissipative work during systole measured at 17.3 ± 28.9 µJ/mm and contributive work during diastole measured at 15.3 ± 18.0 µJ/mm. The stress–strain loop area was higher in AS (95.2 ± 31.1 kPa%) and HV (66.2 ± 35.9 kPa%) than in HCM (5.8 ± 13.0 kPa%), P < 0.01. Conclusion Calculating segmental myocardial work based on myocardial stiffness and strain measurements is technically feasible. This approach overcomes the inherent limitations of current methods by introducing a direct quantitative measure of myocardial stress
Homogenization and dispersion in granular flows
No full textInternational audienceGranular mixing in continuous flow conditions remains poorly understood. We investigate mixing in a 2D bidisperse granular system stirred by a rod in a chaotic flow; by tracking individual particles, we characterize exponential stretching, a hallmark of chaotic advection. Dispersion analysis reveals that the concentration field variance follows an exponential decay, confirming efficient mixing. Our results establish a link between granular mixing and fluid chaotic advection, suggesting that multidirectional shear enhances dispersion
Calcium Alginate Aerogel-MIL160 Nanocomposites for CO2 Removal
No full textInternational audienceHigh-emission industries like cement and steel are major contributors to increasing CO2 concentration in the atmosphere. Traditional CO2 capture methods face issues with degradation, while adsorption offers a promising alternative. Metal-organic frameworks (MOFs) have been recognized as ideal nanomaterials for CO2 capture thanks to their crystalline and tunable structures with high porosity, and stability. However, using adsorbents in powder form brings mass transfer limitations and large pressure drops through the adsorption column. Preparation and use of MOF/aerogel composites (called MOFACs) in bead form could overcome these challenges without compromising the MOF’s adsorption performance, as observed with other shaping methods, such as the use of polymeric binders. In this study, Ca-alginate-MIL160(Al) MOFACs (AlgMIL160) were prepared via sol/gel and direct mixing methods followed by supercritical drying. The gas sorption, PXRD, FTIR, and SEM characterization analysis results showed that the MOF was successfully incorporated into the aerogel while the structure was preserved. Adsorption measurements were carried out at both static single-component and dynamic binary gas mixture modes. Obtained isotherms were successfully fitted to Langmuir model followed by Ideal Adsorbed Solution Theory (IAST). The single-component gas adsorption isotherms showed that CO2 capture per unit weight of MOFACs was higher than that of pure MOF (3.97 mmol/g) considering the MOF loading in the composites, showing the synergistic effect of aerogel and MOF composites. Incorporation of MIL-160(Al) into an aerogel network which is comprised of 75% MIL-160(Al) and 25% Ca-alginate enhanced MIL-160(Al)’s CO2/N2 IAST selectivity from 53 to 70 at 25 °C and 1000 mbar. Both experimental and simulated CO₂ adsorption isotherms showed good agreement. The dynamic adsorption performance of the MOFACs studied by using binary mixture of 15%CO2/85%N2 was close to the single-component CO2 adsorption with slightly decreased uptake showing the competitive adsorptions between CO2 and N2 molecules. This study showed that the MIL-160(Al) was successfully incorporated into the aerogel structure without causing any structural degradation, and its adsorption performance remained unaffected. This novel nanocomposite with remarkable CO2 capture performance can be used in gas adsorption columns without facing large pressure drops
Inhibition of bacterial growth by antibiotics: a minimal model
No full textInternational audienceAbstract Growth in bacterial populations generally depends on the environment (availability and quality of nutrients, presence of a toxic inhibitor, product inhibition..). Here, we build a minimal model to describe the action of a bacteriostatic antibiotic, assuming that this drug inhibits an essential autocatalytic cycle of the cell metabolism. The model recovers known growth laws, can describe various types of antibiotics and confirms the existence of two distinct regimes of growth-dependent susceptibility, previously identified only for ribosome targeting antibiotics. We introduce a proxy for cell risk, which proves useful to compare the effects of various types of antibiotics. We also develop extensions of our model to describe the effect of combining two antibiotics targeting two different autocatalytic cycles or a regime where cell growth is inhibited by a waste product
Torque-based immune cell chemotaxis in complex environments
No full textDirected migration in chemical gradients is crucial to the immune response, yet how immune cells navigate complex tissues remains incompletely understood. Using in vitro migration assays and theoretical modeling, we uncover distinct chemotactic strategies in two key immune cell types: neutrophils and dendritic cells (DCs). DCs actively steer toward chemokine gradients via a deterministic torque-like reorientation, while neutrophils bias movement by modulating angular noise and speed. A quantitative Fokker-Planck framework decomposes these behaviors into deterministic and stochastic components. Cytoskeletal perturbations show that microtubules enable torque-based navigation in DCs in collagen gels, whereas actomyosin contractility is required for noise modulation employed by neutrophils and DCs in 2D confined migration assays. Despite both achieving directed migration, the two strategies result in opposing macroscopic outcomes: torque-driven cells minimize dispersion, while noise-biased migration enhances population spread. These results reveal distinct navigation aligned with immune function and demonstrate that immune cell chemotaxis is tuned by cytoskeletal architecture and environmental context
Generalized Clapeyron's theorem
No full textClapeyron's Theorem in classical linear elasticity provides a way to explicitly express the energy stored in an equilibrium configuration in terms of the work of the forces applied on the boundary. We derive several new integral relations which can be viewed as nonlinear analogs of this classical result, reinterpreting them as rather general statements within Calculus of Variations. In the framework of nonlinear elasticity these relations reflect various partial symmetries of the material response, for instance, scale-invariance or scaling homogeneity. In particular, when the energy functional is scale-free, the obtained result can be interpreted as the Generalized Clapeyron's Theorem (GCT). Remarkably, it combines rather naturally the work of physical and configurational forces. We present a series of illuminating case studies showing the variety of applications of various obtained relations in different seemingly unrelated problems of mechanics.</div
Reactive mixing enables enzymatic depolymerization of recalcitrant or unsortable polyester wastes
No full textInternational audienceEnzyme-catalyzed depolymerization allows efficient recycling of poly(ethylene terephthalate) (PET) bottles, which are easy to sort and made of slowly crystallizing PET. However, because crystalline phases are recalcitrant to enzymatic hydrolysis, this technology fails for rapidly crystallizing polyester wastes such as poly(butylene terephthalate) (PBT), unsortable mixed polyesters, or heterogeneous formulated PET waste streams. We show that melt transesterification and vitrimerization of mixtures of rapidly crystallizing polyester wastes, leveraging catalysts already present, produce copolyesters that crystallize slowly and are readily depolymerized. For example, reactive blending of a rapidly crystallizing postindustrial PET nonwoven waste with PBT improves depolymerization yields from 20% (PET nonwoven) and 1% (PBT) to 90%. Synergistic mixing can replace sorting, extending the scope of enzymatic recycling to recalcitrant, heterogeneous, and unsortable wastes
Nano-resolved sensing of 3D electromagnetic fields via single emitters' extreme variation of enhanced spontaneous emission
No full textControlling quantum light-matter interactions at scales smaller than the diffraction limit at the single quantum emitter level is a critical challenge to the goal of advancing quantum technologies. We introduce a novel material platform that enables precise engineering of spontaneous emission changes in molecular single emitters through 3D nanofields. This platform is based on a 3D hollow plasmonic nanomaterial arranged in a square lattice, uniformly scalable to the centimeter scale while maintaining unit cell geometry. This coupled system leads to billions of Purcell-enhanced single emitters integrated into a nanodevice. Using far-field single-molecule super-resolution microscopy, we investigate emission modifications at the single-emitter level, enabling molecular position sensing with resolution surpassing the diffraction limit. By combining the nanolocalization with time correlation single photon counting, we probe molecule per molecule enhanced quantum light-matter interactions. This 3D plasmonic geometry significantly enhances light-matter interactions, revealing a broad range of lifetimes -- from nanoseconds to picoseconds -- significantly increasing the local density of states in a manner that depends on both molecular position and dipole orientation, offering extreme position sensitivity within the 3D electromagnetic landscape. By leveraging these plasmonic nanostructures and our method for measuring single-molecule Purcell-enhanced nano-resolved maps, we enable fine-tuned control of light-matter interactions. This approach enables the on-demand control of fast single-photon sources at room temperature, providing a powerful tool for molecular sensing and quantum applications at the single-emitter level
Stepwise molecular specification of excitatory synapse diversity onto cerebellar Purkinje cells
No full textInternational audienceBrain function relies on the generation of a large variety of morphologically and functionally diverse, but specific, neuronal synapses. Here we show that, in mice, the initial formation of synapses on cerebellar Purkinje cells involves a presynaptic protein-CBLN1, a member of the C1q protein family-that is secreted by all types of excitatory inputs. The molecular program then evolves only in one of the Purkinje cell inputs, the inferior olivary neurons, with the additional expression of the presynaptic secreted proteins C1QL1, CRTAC1 and LGI2. These molecules work in concert to specify the mature connectivity pattern on the Purkinje cell target. These results show that some inputs actively and gradually specify their synaptic molecular identity, while others rely on the 'original molecular code'. Thus, the molecular specification of excitatory synapses, crucial for proper circuit function, is acquired in a stepwise manner during mouse postnatal development and obeys input-specific rules