HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Mesure des courbes de dispersion des modes de bord d’ordre supérieur par ultrasons laser
No full textUltrasons laser, interaction son-lumière; GAPSUS - Acoustique Physique, Sous-Marine et Ultra-SonoreNational audienceLes ultrasons laser permettent la génération et la détection sans contact des ondes élastiques dans les matériaux avec une bonne résolution spatiale. Parmi les ondes utiles au contrôle non destructif (CND), les ondes guidées par les bords présentent des caractéristiques intéressantes. À l’instar des ondes de Rayleigh, elles sont fortement localisées et se propagent le long des frontières. Théoriquement décrites comme une superposition de modes de Lamb propagatifs et évanescents (1), elles restent peu étudiées expérimentalement, en particulier les modes d’ordre supérieur. La mesure de la dispersion du premier mode de bord symétrique a pu être obtenue dans une plaque isotrope, avec un transducteur fixé au bord de la plaque (2). En CND, la détection d’une réflexion de ce mode a permis de détecter une fissure sur le bord d’une poutre en H (3). Dans ce travail, nous nous intéressons aux modes de bords d’ordre supérieurs avec une génération et une détection par laser. Une impulsion laser est utilisée pour générer les ondes élastiques et ce laser est balayé le long du bord. Un laser continu, à une position fixe, est employé pour la détection interférométrique du champ de déplacement normal pour chaque position de la génération. Les données ainsi recueillies sont analysées par transformée de Fourier spatio-temporelle, révélant les courbes de dispersion expérimentales. Celles-ci sont comparées avec succès aux courbes théoriques pour des échantillons isotropes (verre teinté) et anisotropes (silicium). À l’aide de cette approche, nous visons désormais à analyser les ondes élastiques guidées le long de fissures afin de les caractériser. Références (1) A. Galinde et al., Adv. Acoust. Vib. 2012,685326 (2012). (2) M. V. Wilde et al, J. Sound Vib. 441, 26-49 (2019). (3) J. M. Hughes et al., Struct. Health Monit. 20(I), 74-83 (2020)
Self-Healing and Creep-Resistant Injectable Hydrogel from Aminoborinate Chemistry and Phase Separation
No full textInternational audienceBoronate-based hydrogels are of particular interest for diagnostics, drug-delivery, cell culture or 3D fabrication. The short lifetime of the reversible boronate cross-links makes them self-repairing and injectable. However, the high dynamics and low hydrolytic stability of boronates make it very difficult to produce hydrogels that behave like viscoelastic solids and exhibit stable properties. Here, we address these limitations by designing structured hydrogels incorporating aminoborinate cross-links. Using model studies, we demonstrate that aminoborinates undergo fast exchange reactions at room temperature and use this finding to prepare hydrogels by reacting a polyacrylamide bearing 1,2-amino alcohol side groups with an aryl-rich bis-borinic cross-linker. The resulting cross-links aggregate into large hydrophobic domains, leading to structured hydrogels with a unique combination of solid-like behavior, injectability, autonomous self-healing ability, and long-term stability. Confining dynamic covalent cross-links within long-lived hydrophobic domains opens new avenues for designing injectable hydrogels with excellent chemical stability, tunable mechanical properties, and selfhealing ability.</div
Mechanochemical and Piezo‐Accelerated Stereoselective Synthesis of Isoindolinones
No full textInternational audienceIn this study, we report on the use of mechanochemistry for the synthesis of trifluoromethylated isoindolinones via a cascade radical sequence involving intermolecular addition/cyclization reactions of ynamides. This minimum solvent approach, involving liquid‐assisted grinding, provides the products in good yields with complete E stereoselectivity, contrasting with the E/Z mixtures obtained under previously reported photoredox conditions. Mechanistic investigations revealed two complementary activation pathways: mechanical activation alone can trigger the radical cascade, while the presence of piezoelectric materials (BaTiO 3 ) significantly accelerates product formation. Furthermore, we identified an unexpected role of Celite® as an abrasive agent that promotes metal leaching and enables alternative activation pathways. This methodology showcases mechanochemistry as a valuable alternative to photoredox catalysis for stereoselective radical transformations, with distinct mechanistic advantages that can be strategically exploited
Plasmonic multipod clusters as emitters of magnetic light
No full textInternational audienceThe Purcell effect can be used in plasmonic multipod structures to enhance the spontaneous emission of magnetic dipole transitions, which are notoriously weak in nature, while inhibiting the emission of the electric dipole transition. Here, the optical emission from a magnetic dipole transition in a dielectric particle surrounded by metallic satellites, positioned so as to be formal solutions to the Thomson problem, are optimized. Quasi-normal modes (QNMs) are employed for the analysis, offering a significant advantage over traditional real-frequency approaches in reducing a vast parameter space and providing more physical insight. We demonstrate that highly symmetrical N-pods, which can currently be fabricated, are excellent candidates for achieving a large, orientation- and volume-independent magnetic Purcell factor with minimal Ohmic losses. Additionally, we successfully suppress the electric dipole transition, obtaining a magnetic branching ratio exceeding 95% for nearly all N-pod particles. For particles exhibiting a high degree of symmetry, radiated magnetic Purcell factors in excess of 180 are predicted after optimization of the core and satellite radii
SPARC is a new driver of early breast tumor progression via TGF-β -dependent mechanism
No full textInternational audienceAbstract 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
Nernst effect and its thickness dependence in superconducting NbN films
No full textInternational audienceSuperconducting thin films and layered crystals display a Nernst signal generated by short-lived Cooper pairs above their critical temperature. Several experimental studies have broadly verified the standard theory invoking Gaussian fluctuations of a two-dimensional (2D) superconducting order parameter. Here, we present a study of the Nernst effect in granular NbN thin films with a thickness varying from 4 to 30 nm, exceeding the short superconducting coherence length and putting the system in the three-dimensional (3D) limit. We find that the nernst conductivity decreases linearly with reduced temperature (αxy ∝ T −Tc Tc ), but the amplitude of αxy scales with thickness. While the temperature dependence corresponds to what is expected in a 2D picture, scaling with thickness corresponds to a 3D picture. We argue that this behavior indicates a 2 + 1D situation, in which the relevant coherence length along the thickness of the film has no temperature dependence. We find no visible discontinuity in the temperature dependence of the Nernst conductivity across Tc. Explaining how the response of the superconducting vortices evolves to the one above the critical temperature of short-lived Cooper pairs emerges as a challenge to the theory
Microwave sink using plasma-based localized surface plasmons
No full textInternational audienceOvercoming the diffraction limit, meaning focusing waves on a sub-wavelength scale, has received considerable attention for applications involving light and acoustics. Indeed, the intense focusing achieved enhances the interactions between waves and matter, and the improved spatial resolution opens up possibilities in fields such as imaging, detection and communication. In optics, a passive sink may be obtained if the incident light couples to localized surface plasmon (LSP) resonances, resulting in Coherent Perfect Absorption condition. The presence of optical surface plasmons at metal interfaces is due to the angular frequency of metals, which lies in the optical regime due to their high density of free electrons. Plasmas, which consists of ionized gazes with a lower electron density, can support surface plasmons in the microwave regime. Hence, we demonstrate in this paper that sub-wavelength plasmas behave as a passive microwave sink by exciting LSP resonance inside the plasma
Immune Cells Infiltration of Patient Derived Glioblastoma Cells spheroids in Acoustic Levitation in Bulk Acoustic Wave devices
No full textWe describe an acoustofluidic device that allows scaffold-free structuration and culture of multi-cellular tumoroids composed of patient-derived glioblastoma cells only or in combination with non-cancerous cell. A PDMS chip of controlled height was created to allow acoustic levitation of cells using a 2 MHz transducer held on top of the chip. Cells are introduced into the chip through a dedicated inlet upstream of the resonant cavity. The specific design of the cavity together with the acoustic field allow the formation of tumoroids of cells in a precise and controlled manner within the levitation chamber. The acoustic and fluidic environment of the device was determined through experiments confronted with numerical simulations. The control of the flow within the chip was optimized to allow long-term culture of tumoroids and injection of cell culture media without disturbing the tumoroids in levitation. The tumoroids can be also structured, with sequential injections of the different cell types. Using microglia, we show that the acoustofluidic device allows the formation and culture in acoustic levitation of tumoroids mixing cancer cells with other cells populating the tumor as well as immune cell infiltration within the tumoroids. These results demonstrate the suitability of acoustofluidic levitation as an original 3D culture method adapted to the exploration of cancer growth at multiple levels
EEG and Computational Aspects of How Ageing Affects Sleep Slow Waves
No full textInternational audienceABSTRACT Ageing is known to affect sleep slow waves, but the underlying mechanisms are unknown. Here we aim to precisely quantify the effect of aeging on the shape and dynamics of sleep slow waves in a large cohort of human subjects, and to explore possible underlying mechanisms using a computational model. We analyzed EEG sleep recordings from 2377 healthy individuals aged 19 to 85, collected over multiple nights in their natural environments using the DREEM headband. The fine‐structure analysis of slow waves was conducted to assess changes in frequency, amplitude, and variability with age. Additionally, we developed a computational model to investigate possible underlying mechanisms. The study reveals that with aeging, sleep slow waves show a significant reduction in frequency, increase in variability, and decrease in amplitude. Older individuals also experience more sleep fragmentation. REM sleep changes are less consistent, with some findings of minor decreases and others showing no significant changes. The computational model supports these observations by replicating the age‐related changes in slow waves from a decrease in excitatory drive, suggesting that ageing affects excitatory interactions at large scales. In conclusion, by examining individuals free from sleep disorders and controlled lab environments, this study provides a detailed characterisation of age‐related changes in sleep slow waves and proposes a potential mechanism involving alterations in cortical network connectivity