Topology optimization for microwave control with reconfigurable intelligent metasurfaces in complex media Karamanos, T. D., M. Fink, and F. Lemoult Physical Review Applied 21, no. 4 (2024)
Résumé: Reconfigurable intelligent metasurfaces have been proposed as an efficient solution for improving wireless telecommunication systems in multiple-scattering or reverberating media. Concurrently, topology optimization has been successfully used as an inverse-design technique in many fields, and particularly in electromagnetics. In this work, we apply a gradient-based topology optimization for tuning the binary elements of a metasurface for a focusing goal in a complex environment. First, the metasurface unit cells are approximated as point sources and, then, the optimization problem is formulated. Afterwards, the proposed method is applied to find the optimal parameter sets for three distinct environments of increasing complexity, and the resulting focus for each case is demonstrated via numerical simulations. The combination of a reverberating cavity and a metasurface inside the latter is very powerful since everything can be solved analytically for focusing outside the cavity.
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Asymmetrical wakes over anisotropic bathymetries Euvé, L.-P., A. Maurel, P. Petitjeans, and V. Pagneux Journal of Fluid Mechanics 984 (2024)
Résumé: The study investigates the impact of a vertically layered bathymetry, consisting of submerged vertical plates, on a ship wake through theoretical analysis and experimental realization. For subwavelength distances between the plates, the analysis relies on a homogenized model that provides an effective, anisotropic, dispersion relation for the propagation of water waves. Our findings reveal that a highly asymmetric wake can be achieved, with the degree of asymmetry contingent upon the ship propagation direction in relation to the plate orientation. This anisotropy is characterized with respect to water depth and to ship length using the dimensionless depth and hull Froude numbers. Laboratory experiments align closely with theoretical predictions, confirming that the asymmetry of the wake can indeed be managed through manipulation of bathymetric conditions.
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Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study Wintzenrieth, F., M. Couade, F. Lehanneur, P. Laveneziana, M. C. Niérat, N. Verger, M. Fink, T. Similowski, and R. K. Ing AIP Advances 14, no. 3 (2024)
Résumé: Physical examination of the thorax is key to the clinical diagnosis of respiratory diseases. Among other examination techniques, palpation evaluates the transmission of high-frequency vibrations produced by vocalizations (tactile fremitus), which helps the physicians to identify abnormalities within the respiratory system. We propose the use of an airborne ultrasound surface motion camera (AUSMC) to quantitatively map the vibrations induced by subject vocalization. This approach could make the examination of vocal fremitus quantifiable, reproducible, and archivable. Massive data collection of vocal fremitus could allow using artificial intelligence algorithms to isolate vibration patterns that could help disease identification. Until now, in contrast, the interpretation of vocal fremitus has been subject to the physician’s experience and remains subjective. In the present work, we demonstrate the capabilities of the AUSMC to measure vocal fremitus thoracic vibration maps on 77 healthy volunteers. We have observed a spatial dependence of vibration maps on vocalization frequency. We observed that the left lung generates fewer surface vibrations than the right one, which was expected according to their respective dimensions. We also discuss the implications of our findings.
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Multiple scattering theory in one dimensional space and time dependent disorder: average field [Invited] Selvestrel, A., J. Rocha, R. Carminati, and R. Pierrat Optical Materials Express 14, no. 3, 801-815 (2024)
Résumé: We theoretically study the propagation of light in one-dimensional space- and time-dependent disorder. The disorder is described by a fluctuating permittivity ε(x, t) exhibiting short-range correlations in space and time, without cross correlation between them. Depending on the illumination conditions, we show that the intensity of the average field decays exponentially in space or in time, with characteristic length or time defining the scattering mean-free path ℓs and the scattering mean-free time τs. In the weak scattering regime, we provide explicit expressions for ℓs and τs, that are checked against rigorous numerical simulations.
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A simplified PPG based approach for automated recognition of five distinct emotional states Paul, A., A. Chakraborty, D. Sadhukhan, S. Pal, and M. Mitra Multimedia Tools and Applications 83, no. 10, 30697-30718 (2024)
Résumé: Emotion is a complicated state of mind, which normally reflects human perceptions and attitudes. Proper recognition of emotional states and its quality plays crucial role for the detection of critical diseases and subsequent treatment procedures. Generally, multi-lead, complicated Electroencephalogram (EEG) based analysis predominate the characterization of emotion detection. Nowadays, user-friendly, rich-cardiac-information and wearable characteristics of the photoplethysmogram (PPG) signal are also being used to identify the emotional states. However, a majority of the reported emotion detection techniques mostly uses PPG signal in multimodality approach. In this paper, a simple methodology is proposed to identify multiple emotional states via the analysis of the PPG signal alone. Normally, emotion induced alteration in the heart rate causes variation in the blood ejection rate and a subsequent deviation in the balance of the systolic and the diastolic phases. Consequently, a specific time-domain characteristic is identified to quantify such imbalance and its variability is then used as a feature to discriminate between the five most prominent emotional states via a threshold-based classification technique. The algorithm presents superior performance while evaluated on the PPG data collected from the standard DEAP dataset with an average detection accuracy of 97.78%. Compared to existing literatures, the superior results establish the effectiveness of the proposed algorithm for the detection of multiple emotional states using PPG signal only. Moreover, the use of a single PPG feature and the application of a simple threshold-based classification technique also justify its promises for implementation in real-life, healthcare applications.
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Vectorial phase retrieval in super-resolution polarization microscopy Gutiérrez-Cuevas, R., L. A. Alemán-Castañeda, I. Herrera, S. Brasselet, and M. A. Alonso APL Photonics 9, no. 2 (2024)
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Dynamic structured illumination for confocal microscopy Nœtinger, G., F. Lemoult, and S. M. Popoff Optics Letters 49, no. 5, 1177-1180 (2024)
Résumé: Structured illumination enables the tailoring of an imaging device’s optical transfer function to enhance resolution. We propose the incorporation of a temporal periodic modulation, specifically a rotating mask, to encode multiple transfer functions in the temporal domain. This approach is demonstrated using a confocal microscope configuration. At each scanning position, a temporal periodic signal is recorded. By filtering around each harmonic of the rotation frequency, multiple images of the same object can be constructed. The image carried by the nth harmonic is a convolution of the object with a phase vortex of topological charge n, similar to the outcome when using a vortex phase plate as an illumination. This enables the collection of chosen high spatial frequencies from the sample, thereby enhancing the spatial resolution of the confocal microscope.
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Flexible implementation of modulated localisation microscopy based on DMD Illand, A., P. Jouchet, E. Fort, and S. Lévêque-Fort Journal of Microscopy (2024)
Résumé: Localisation microscopy of individual molecules allows one to bypass the diffraction limit, revealing cellular organisation on a nanometric scale. This method, which relies on spatial analysis of the signal emitted by molecules, is often limited to the observation of biological objects at shallow depths, or with very few aberrations. The introduction of a temporal parameter into the localisation process through a time-modulated excitation was recently proposed to address these limitations. This method, called ModLoc, is demonstrated here with an alternative flexible strategy. In this implementation, to encode the time-modulated excitation a digital micromirror device (DMD) is used in combination with a fast demodulation approach, and provides a twofold enhancement in localisation precision. Layout: Nowadays, we can use an optical microscope to observe how proteins are organised in 3D within a cell at the nanoscale. By carefully controlling the emission of molecules in both space and time, we can overcome the limitations set by the diffraction limit. This allows us to pinpoint the exact location of molecules more precisely. However, the usual spatial analysis method limits observations to shallow depths or causing low distortion of optical waves. To overcome these restrictions, a recent approach introduces a temporal element to the localisation process. This involves changing the illumination over time to enhance the precision of localisation. This method, known as ModLoc, is showcased here using a flexible and alternative strategy. In this setup, a matrix of micrometric mirrors, working together with a fast demodulation optical module, is used to encode and decode the time-modulated information. This combination results in a twofold improvement in localisation precision.
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Optimizing multi-user indoor sound communications with acoustic reconfigurable metasurfaces Zhang, H., Q. Wang, M. Fink, and G. Ma Nature Communications 15, no. 1, 1270 (2024)
Résumé: Sound in indoor spaces forms a complex wavefield due to multiple scattering encountered by the sound. Indoor acoustic communication involving multiple sources and receivers thus inevitably suffers from cross-talks. Here, we demonstrate the isolation of acoustic communication channels in a room by wavefield shaping using acoustic reconfigurable metasurfaces (ARMs) controlled by optimization protocols based on communication theories. The ARMs have 200 electrically switchable units, each selectively offering 0 or π phase shifts in the reflected waves. The sound field is reshaped for maximal Shannon capacity and minimal cross-talk simultaneously. We demonstrate diverse acoustic functionalities over a spectrum much larger than the coherence bandwidth of the room, including multi-channel, multi-spectral channel isolations, and frequency-multiplexed acoustic communication. Our work shows that wavefield shaping in complex media can offer new strategies for future acoustic engineering.
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Characterization of ejecta in shock experiments with multiple light scattering Don Jayamanne, J. A., J. R. Burie, O. Durand, R. Pierrat, and R. Carminati Journal of Applied Physics 135, no. 7 (2024)
Résumé: Upon impact, the free surface of a solid metal may eject a cloud of fast and fine particles. Photon Doppler Velocimetry (PDV) is one of the optical diagnostics used to characterize these ejecta. Although the technique provides a direct way to estimate the particle velocities in the single scattering regime, it has been shown that multiple scattering cannot be neglected in real ejecta. Here, we derive a model for PDV measurements starting from the first principles of wave scattering. We establish rigorously the relationship between the specific intensity and the measured signal, as well as the Radiative Transport Equation (RTE) that describes the evolution of the specific intensity upon scattering and absorption in dynamic ejecta, including the effects of inelastic scattering and inhomogeneities in the optical properties. We also establish rigorously the connection between the Monte Carlo scheme used for numerical simulations and the solution to the RTE. Using numerical simulations, we demonstrate the crucial contribution of multiple scattering to PDV spectrograms as well as the effect of statistical inhomogeneities in particle size distribution. These results could substantially impact the analysis of ejecta by PDV.
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Acoustic monitoring of compaction in cohesive granular materials Canel, V., X. Jia, M. Campillo, and I. Ionescu Physical Review E 109, no. 2 (2024)
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Viscoelastic dynamics of a soft strip subject to a large deformation Delory, A., D. A. Kiefer, M. Lanoy, A. Eddi, Prada C., and F. Lemoult Soft Matter (2024)
Résumé: To produce sounds, we adjust the tension of our vocal folds to shape their properties and control the pitch. This efficient mechanism offers inspiration for designing reconfigurable materials and adaptable soft robots. However, understanding how flexible structures respond to a significant static strain is not straightforward. This complexity also limits the precision of medical imaging when applied to tensioned organs like muscles, tendons, ligaments and blood vessels among others. In this article, we experimentally and theoretically explore the dynamics of a soft strip subject to a substantial static
extension, up to 180%. Our observations reveal a few intriguing effects, such as the resilience of certain vibrational modes to a static deformation. These observations are supported by a model based on the incremental displacement theory. This has promising practical implications for characterizing soft materials but also for scenarios where external actions can be used to tune properties.
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Experimental Investigation of the Thermal Emission Cross Section of Nanoresonators Using Hierarchical Poisson-Disk Distributions Langevin, D., C. Verlhac, J. Jaeck, L. Abou-Hamdan, E. Taupeau, B. Fix, N. Bardou, C. Dupuis, Y. De Wilde, R. Haïdar, and P. Bouchon Physical Review Letters 132, no. 4 (2024)
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Efficient detection of cardiac abnormalities via a simplified score-based analysis of the ECG signal Dhar, S., A. Chakraborty, D. Sadhukhan, S. Pal, and M. Mitra Journal of Ambient Intelligence and Humanized Computing (2024)
Résumé: Nowadays, automated analysis of the electrocardiogram (ECG) signal is a popular choice to facilitates easy and expert-independent detection of lethal cardiovascular diseases (CVDs). Although, a majority of the state-of-the-art algorithms are found to be lagging due to the use of complicated methodologies, limited dataset, high feature dimension, feature selection or intense classification techniques. In this research an original, easy-to-use ECG based methodology is proposed for completely automated identification of multiple types of critical CVDs. Primarily, after preprocessing the algorithm uses a simplified technique for exact detection of ECG fiducial points. Then, based on detected fiducial points, some well interpretable and prominent ECG time domain features are efficiently extracted and a binary feature matrix has been derived using those features from different leads. Finally, a distinctive score is evaluated from the binary feature matrix calculating the sum of weighted feature value and only by utilizing the score,discrimination between the various types of CVDs is highly detectable. Proficiency of the algorithm is widely evaluated on the 12-lead ECG signal data collected from Physikalisch-Technische-Bundesanstalt (PTB) and PTB-XL database. The algorithm presents promising outcome with average accuracy, sensitivity and specificity of 99.43%, 98.27% and 99.59%, respectively. Evidently, the algorithm is capable enough and efficient as well in comparison with other reported techniques till date. Moreover, the use of a unique score derived from the binary matrix ascertains the exact detection of multiple cardiac abnormalities and the superior classification accuracy makes the algorithm promising for personal computerized health monitoring applications.
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Ray and caustic structure of Ince-Gauss beams Gutiérrez-Cuevas, R., M. R. Dennis, and M. A. Alonso New Journal of Physics 26, no. 1 (2024)
Résumé: The Ince-Gauss beams, separable in elliptic coordinates, are studied through a ray-optical approach. Their ray structure can be represented over a Poincaré sphere by generalized Viviani curves (intersections of a cylinder and a sphere). This representation shows two topologically different regimes, in which the curve is composed of one or two loops. The overall beam shape is described by the ray caustics that delimit the beams’ bright regions. These caustics are inferred from the generalized Viviani curve through a geometric procedure that reveals connections with other physical systems and geometrical constructions. Depending on the regime, the caustics are composed either of two confocal ellipses or of segments of an ellipse and a hyperbola that are confocal. The weighting of the rays is shown to follow the two-mode meanfield Gross-Pitaevskii equations, which can be mapped to the equation of a simple pendulum. Finally, it is shown that the wave field can be accurately estimated from the ray description.
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3D-Architected Alkaline-Earth Perovskites Winczewski, J. P., J. Arriaga Dávila, M. Herrera-Zaldívar, F. Ruiz-Zepeda, R. M. Córdova-Castr, C. R. Pérez De La Vega, C. Cabriel, I. Izeddin, H. Gardeniers, and A. Susarrey-Arce Advanced Materials (2024)
Résumé: 3D ceramic architectures are captivating geometrical features with an immense demand in optics. In this work, an additive manufacturing (AM) approach for printing alkaline-earth perovskite 3D microarchitectures is developed. The approach enables custom-made photoresists suited for two-photon lithography, permitting the production of alkaline-earth perovskite (BaZrO3, CaZrO3, and SrZrO3) 3D structures shaped in the form of octet-truss lattices, gyroids, or inspired architectures like sodalite zeolite, and C60 buckyballs with micrometric and nanometric feature sizes. Alkaline-earth perovskite morphological, structural, and chemical characteristics are studied. The optical properties of such perovskite architectures are investigated using cathodoluminescence and wide-field photoluminescence emission to estimate the lifetime rate and defects in BaZrO3, CaZrO3, and SrZrO3. From a broad perspective, this AM methodology facilitates the production of 3D-structured mixed oxides. These findings are the first steps toward dimensionally refined high-refractive-index ceramics for micro-optics and other terrains like (photo/electro)catalysis.
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Single-emitter super-resolved imaging of radiative decay rate enhancement in dielectric gap nanoantennas Córdova-Castro, R. M., B. Van Dam, A. Lauri, S. A. Maier, R. Sapienza, Y. De Wilde, I. Izeddin, and V. Krachmalnicoff Light: Science and Applications 13, no. 1 (2024)
Résumé: High refractive index dielectric nanoantennas strongly modify the decay rate via the Purcell effect through the design of radiative channels. Due to their dielectric nature, the field is mainly confined inside the nanostructure and in the gap, which is hard to probe with scanning probe techniques. Here we use single-molecule fluorescence lifetime imaging microscopy (smFLIM) to map the decay rate enhancement in dielectric GaP nanoantenna dimers with a median localization precision of 14 nm. We measure, in the gap of the nanoantenna, decay rates that are almost 30 times larger than on a glass substrate. By comparing experimental results with numerical simulations we show that this large enhancement is essentially radiative, contrary to the case of plasmonic nanoantennas, and therefore has great potential for applications such as quantum optics and biosensing.
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3D topographies promote macrophage M2d-Subset differentiation Carrara, S. C., A. Davila-Lezama, C. Cabriel, E. J. W. Berenschot, S. Krol, J. G. E. Gardeniers, I. Izeddin, H. Kolmar, and A. Susarrey-Arce Materials Today Bio 24 (2024)
Résumé: In vitro cellular models denote a crucial part of drug discovery programs as they aid in identifying successful drug candidates based on their initial efficacy and potency. While tremendous headway has been achieved in improving 2D and 3D culture techniques, there is still a need for physiologically relevant systems that can mimic or alter cellular responses without the addition of external biochemical stimuli. A way forward to alter cellular responses is using physical cues, like 3D topographical inorganic substrates, to differentiate macrophage-like cells. Herein, protein secretion and gene expression markers for various macrophage subsets cultivated on a 3D topographical substrate are investigated. The results show that macrophages differentiate into anti-inflammatory M2-type macrophages, secreting increased IL-10 levels compared to the controls. Remarkably, these macrophage cells are differentiated into the M2d subset, making up the main component of tumour-associated macrophages (TAMs), as measured by upregulated Il-10 and Vegf mRNA. M2d subset differentiation is attributed to the topographical substrates with 3D fractal-like geometries arrayed over the surface, else primarily achieved by tumour-associated factors in vivo. From a broad perspective, this work paves the way for implementing 3D topographical inorganic surfaces for drug discovery programs, harnessing the advantages of in vitro assays without external stimulation and allowing the rapid characterisation of therapeutic modalities in physiologically relevant environments.
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Optical tomography in a single camera frame using fringe-encoded deep-learning full-field OCT Mazlin, V. Biomedical Optics Express 15, no. 1, 222-236 (2024)
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Decomposition of acousto-elastic matrices for contactless modal analysis and vibration shaping Palerm, C., C. Prada, B. Gerardin, A. Talon, and J. De Rosny Journal of Sound and Vibration 571 (2024)
Résumé: A contactless method based on acousto-elastic transmission matrix analysis is proposed to recover the modal properties of weakly damped mechanical structures. The matrix is acquired using eight loudspeakers and a laser vibrometer probing hundreds of points. The matrix analysis is particularly interesting in case of overlapping modes. The proposed measurement set-up and associated data processing using the Singular Value Decomposition are applied to two symmetric samples, a gear and two monobloc impellers. Further analysis are performed taking advantage of their particular modal behavior, common to many rotationally symmetric structures. The method also enables to clearly identify the effect of damages on the modal organization. Additionally, the setup can also be used to excite specific patterns on the elastic structures. Finally, the acousto-elastic results are compared to the ones obtained with a classical impact hammer and high resolution algorithms.
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