HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Full Disappearance of PC3‐Luc Prostate Tumors Mediated by Hyperthermia Under Low Intensity Ultrasound Application in the Presence of Magnetosomes
No full textInternational audienceIron oxide nanoparticles have been proposed for magnetic hyperthermia treatment of tumors. However, efficacy depends on the injection of large amounts of such nanoparticles and the equipment is costly. Here, a new thermal cancer treatment is described, in which a tumor containing a low concentration of nonpyrogenic pure iron oxide nanominerals coated with carboxy‐methyl‐dextran (M‐CMD), corresponding to modified magnetosomes, are exposed to ultrasound. Heating PC3 prostate carcinoma cells between 43 and 46°C using ultrasound in the presence of M‐CMD resulted in significant necrotic cell death. Furthermore, deposition of M‐CMD containing 3 µg of iron per mm3 of tumor in subcutaneous xenografts of PC3‐Luc tumors of 150 mm3 followed by 6 to 10 sessions of ultrasound application (1 W cm−2, 1 MHz) of 10 min each led to a tumor temperature of 43–46°C per session and to total tumor disappearance without regrowth over 6 months following treatment start. Sequential histological analyses of the tumor tissues revealed partial tumor occupation by M‐CMD and an increase in cell death over time. Neither lesions, nor magnetosome accumulation were found in microscopic sections of various internal organs collected from treated mice euthanized 6 months after the beginning of the treatment, indicating that M‐CMD may not lead to long‐term side effects
Angle-dependent spin crossover properties in polymorphic iron(ii) complexes based on pyridine-triazole derivatives
No full textInternational audienceTwo new Fe(ii) compounds based on a pyridine-triazole ligand with an NCS− co-ligand were synthesized as thermodynamic (1) and kinetic (2) products. Single crystal X-ray diffraction evidenced that these compounds are polymorphs. The magnetic susceptibility of each compound was recorded, which showed that 1 undergoes a sharp spin crossover, while 2 remains in the high spin state across the temperature range. We discussed here the importance and impact of crystalline packing on the switching properties of these compounds
Ondes élastiques guidées dans un tube gaine en alliage de zirconium chromé
No full textUltrasons laser, interaction son-lumière; GAPSUS - Acoustique Physique, Sous-Marine et Ultra-SonoreNational audienceLes ondes élastiques guidées sont utilisées pour le contrôle des tubes, notamment pour la détection de fissures ou la mesure d'épaisseur. Ces ondes sont engendrées efficacement par impact laser et peuvent être détectées par interférométrie laser, offrant des mesures à large bande et sans contact. Cette étude exploite les ondes guidées, engendrées et détectées par ultrasons laser, pour évaluer les propriétés mécaniques d’un revêtement de chrome déposé sur un tube en alliage de zirconium (M5). La dispersion ainsi que l’observabilité des modes par notre dispositf ultrasons-laser, sont calculées pour différentes épaisseurs de revêtements à l’aide du code GEWtool (1). Dans un tube non-revêtu, les premier et second modes longitudinaux L(0,1) et L(0,2), respectivement analogues aux modes A0 et S0 dans une plaque, convergent vers le mode Rayleigh. Un dépôt de chrome modifie la dispersion et l’observabilité des modes, notamment celles du mode L(0,2). Ce mode est bien observé et particulièrement sensible à l’épaisseur du revêtement dans une gamme de fréquences bornée par la fréquence de coupure du mode de surface existant pour une même épaisseur de chrome déposée sur un substrat semi-infini en M5 (2). En revanche, en haute fréquence, la vitesse de phase de ce mode converge vers la vitesse de cisaillement du M5 et il n’est plus observable. Nous concluons que l'utilisation du mode L(0,2) est limitée aux couches très fines. Ces prédictions théoriques sont comparées à des mesures réalisées par ultrasons laser sur différents tubes. (1) D. A. Kiefer (2023). GEWtool. https://doi.org/10.5281/zenodo.10114243 (https://github.com/dakiefer/GEWtool) (2) G.W. Farnell and E.L. Adler. “Elastic Wave Propagation in Thin Layers”. 9 (1972). Physical Acoustics Elsevier, pp. 35–127
Inverse identification method for the mechanical characterization of nanoporous silicon membranes using elastic guided waves and GEWTool
No full textMatériaux poreux et métamatériaux acoustiques; GAPSUS - Acoustique Physique, Sous-Marine et Ultra-Sonore: GVB - Vibro acoustique et Contrôle du Bruit: GABE - Acoustique du Bâtiment et de l'EnvironnementNational audienceNanoporous silicon can be obtained through electrochemical etching of monocrystalline silicon. The resulting structure enables the development of hybrid materials with tunable mechanical properties, owing to its self-organized tubular pore architecture, which is oriented perpendicular to the membrane surface. Although monocrystalline silicon naturally exhibits cubic anisotropy, the creation of a network of nanopores perpendicular to the surface modifies this initial anisotropy by inducing tetragonal symmetry that predominates over the original crystalline structure. The incorporation of liquid into these pores further modifies the effective anisotropy of the hybrid material (1). To characterize the mechanical properties of empty and liquid-loaded membranes, we employed laser-generated guided elastic waves (GEW) detected contactless. The dispersive and multimodal nature of GEW enables access to different components of the anisotropic elastic tensor, while their non-contact excitation prevents perturbation of these materials' properties. We measured spatio-temporal displacements from which dispersion curves were obtained through two-dimensional Fourier transform for frequencies up to 40 MHz. Using GEWtool (2), a numerical tool based on the spectral element method allowing precise modeling of guided wave propagation in complex multilayer structures (3), we implemented a genetic optimization algorithm to compare experimental and numerically predicted data to quantitatively identify the mechanical properties (thickness, elastic constants, density, and orientation) of these hybrids. (1) M. Thelen, N., Bochud, N., M. Brinker et al. Laser-excited elastic guided waves reveal the complex mechanics of nanoporous silicon. Nat Commun 12, 3597 (2021). https://doi.org/10.1038/s41467-021-23398-0 (2) D. A. Kiefer (2023). GEWtool. https://doi.org/10.5281/zenodo.10114243 (https://github.com/dakiefer/GEWtool) (3) H. Gravenkamp, B. Plestenjak, D. A. Kiefer, and E. Jarlebring, « Computation of leaky waves in layered structures coupled to unbounded media by exploiting multiparameter eigenvalue problems », J Sound Vib, 596:118716 (2025), doi: 10.1016/j.jsv.2024.118716
Mesure en Réflexion du Libre Parcours Moyen de Diffusion dans les Milieux Hétérogènes
No full textOndes en milieu hétérogène; GAPSUS - Acoustique Physique, Sous-Marine et Ultra-SonoreNational audienceLa diffusion multiple des ondes constitue un défi pour l'imagerie des milieux complexes, mais offre un potentiel pour leur caractérisation. Son apparition est en fait régie par le libre parcours moyen de diffusion qui fournit des informations cruciales sur la micro-architecture du milieu. Nous présentons ici une méthode basée sur le concept de matrice de réflexion et conçue pour estimer ce paramètre à partir de la décroissance temporelle du taux de diffusion simple (1). Notre méthode est d'abord validée par une expérience ultrasonore sur un fantôme reproduisant les propriétés acoustique des tissus biologiques avant d'être appliquée in vivo à un foie humain (2). Ce travail ouvre des perspectives importantes pour l'imagerie quantitative des milieux hétérogènes par les ondes acoustiques ou élastiques, que ce soit pour le contrôle non destructif, les applications bio-médicales ou géophysiques. (1) C. Brütt et al., On the weight of single and recurrent scattering in the reflection matrix of complex media, Phys. Rev. E 106, 025001, 2022 (2) A. Goïcoechea et al., Reflection Measurement of the Scattering Mean Free Path at the Onset of Multiple Scattering, Phys. Rev. Lett. 133, 176301, 202
Vers le développement de la viscoélastographie passive : comment estimer la vitesse et l’atténuation des ondes de cisaillement par corrélation ?
No full textUltrasons biomédicaux - Élasticité et visco-élasticité; GAPSUS - Acoustique Physique, Sous-Marine et Ultra-SonoreNational audienceL'estimation de l'élasticité et de la viscosité est une préoccupation majeure pour le diagnostic. Ces paramètres représentent des biomarqueurs importants pour la détection des tumeurs. Les approches standards sont basées sur des sources actives d'ondes de cisaillement qui sont, soit externes, soit internes par pression de radiation acoustique. Cependant, le corps humain est rempli d'ondes naturelles. Ces ondes se propagent dans toutes les directions sous forme de champs d'ondes diffus, utilisable pour l'estimation de l'élasticité à l'aide d'algorithmes de corrélation au cœur de l'élastographie passive. Ces techniques reposent sur l'hypothèse de sources de champ lointain pour un milieu purement élastique, négligeant l'effet et donc la possibilité d'estimer directement l'atténuation. Cependant, la faisabilité de l’estimation de l'atténuation a été démontrée en sismologie avec des techniques de corrélation de bruit sur le champ d'ondes diffus généré par des distributions volumiques de sources, distribution de sources directement présentes dans le milieu à caractériser. Notre objectif est donc d'adapter les méthodes d’élastographie passive à partir des connaissances en sismologie pour mesurer l’atténuation des tissus. L’étude proposée se base sur une première évaluation de la faisabilité à partir de modèles semi-analytiques. Des champs diffus à deux dimensions sont générés à partir de distributions surfaciques aléatoires de sources, avec des phases aléatoires. La propagation est modélisée à partir des fonctions de Green pour les milieux acoustiques puis viscoélastiques
Embracing the Modern Biochemistry of Brain Metabolism
No full textInternational audienceABSTRACT This editorial challenges the long‐held neuron‐centered view of brain metabolism, relying on ample evidence that it is a cooperative, multicellular process. Astrocytes, oligodendrocytes, and other glia play active roles providing lactate, antioxidant support, and substrate shuttles that fuel neuronal function and memory. Despite mounting data, some critics persist in refuting intercellular metabolic exchange, often guided more by entrenched creeds than concrete evidence, slowing constructive, hypothesis‐driven discourse and delaying clinical and neuroprotective advances. The authors call for a rigorous research agenda: cell‐type‐specific manipulations, advanced biosensors, imaging and biomarkers, and integration with behavior and electrophysiology. They urge redirecting focus from outdated dogma to physiology‐driven exploration of glia–neuron metabolic partnerships. imag
Perceptual maps reveal rampant convergence in butterfly wing patterns across the Neotropics
No full textIn 1879, Fritz Müller formulated the first mathematical evolutionary model to explain mutualistic mimicry between coexisting defended prey. Yet, whether local mimicry drives the structure of aposematic prey signals across their entire geographic distribution remains untested because the perception of pattern similarity has never been assessed at large spatial scale. Here, we implement a citizen science survey to map, throughout the Neotropics, variation in the wing patterns of heliconiine butterflies (Nymphalidae) as perceived by vertebrate cognitive systems. We show that despite a continuum of perceived similarity in wing patterns at the continental scale, the convergence of sympatric species into discrete mimicry rings is ubiquitous among local communities. These results expand Müller’s historical predictions by quantifying the rampant convergence of prey signals across an entire continent
Acoustic Positioning for Deep Sea Neutrino Telescopes with a System of Piezo Sensors Integrated into Glass Spheres
No full textInternational audiencePosition calibration in the deep sea is typically done by means of acoustic multilateration using three or more acoustic emitters installed at known positions. Rather than using hydrophones as receivers that are exposed to the ambient pressure, the sound signals can be coupled to piezo ceramics glued to the inside of existing containers for electronics or measuring instruments of a deep sea infrastructure. The ANTARES neutrino telescope operated from 2006 until 2022 in the Mediterranean Sea at a depth exceeding 2000m. It comprised nearly 900 glass spheres with 432mm diameter and 15mm thickness, equipped with photomultiplier tubes to detect Cherenkov light from tracks of charged elementary particles. In an experimental setup within ANTARES, piezo sensors have been glued to the inside of such - otherwise empty - glass spheres. These sensors recorded signals from acoustic emitters with frequencies from 46545 to 60235Hz. Two waves propagating through the glass sphere are found as a result of the excitation by the waves in the water. These can be qualitatively associated with symmetric and asymmetric Lamb-like waves of zeroth order: a fast (early) one with mm/s and a slow (late) one with mm/s. Taking these findings into account improves the accuracy of the position calibration. The results can be transferred to the KM3NeT neutrino telescope, currently under construction at multiple sites in the Mediterranean Sea, for which the concept of piezo sensors glued to the inside of glass spheres has been adapted for monitoring the positions of the photomultiplier tubes
Toward Complete CO2 Electroconversion: Status, Challenges, and Perspectives
No full textInternational audienceElectrocatalytic conversion of carbon dioxide (CO2) into valuable carbon-based fuels and chemicals represents a promising approach to closing the carbon cycle and setting a circular economy. Nevertheless, for current electrocatalytic CO2 reduction reaction (ECO2 RR) systems, realizing 100% CO2 conversion with simultaneously high overall CO2 conversion rate (i.e., single-pass conversion) and high Faradaic efficiency (FE) remains a significant challenge. Enhancing CO2 conversion rate often results in a decrease in FE, conversely, improving FE may limit the CO2 conversion rate. Metal-CO2 (M-CO 2 ) batteries with CO2 conversion functions face similar challenges, particularly for reversible M-CO2 batteries, which do not accomplish net CO2 reduction because nearly all of CO2 RR products are reoxidized to CO2 during subsequent charging process. Such electrocatalytic CO2 conversion system for carbon neutrality poses substantial challenges. This perspective provides an in-depth analysis of state-of-the-art ECO2 RR systems and M-CO2 batteries, alongside the main strategies employed to address their respective challenges. The critical importance of achieving both a high CO2conversion rate and high Faradaic efficiency is underscored for practical applications and to effectively close the carbon cycle. Furthermore, a strategic roadmap that outlines future research directions is presented, thereby facilitating the advancement of comprehensive CO2 electroconversion technologies