Waves in bubbly liquids with phase change

International audienceIn a previous paper (C. Boutin, J.-L. Auriault, Acoustics of a bubbly fluid at large bubble concentration, Eur. J. Mech. B/Fluids, 12(3) (1993) 367-399), the homogenization technique was used to investigate how acoustic waves propagate in a bubbly fluid at finite concentration. Three different equivalent macroscopic behaviours were shown to exist, for "large"-, "medium"- and "small"-size bubble systems, respectively. In the present paper, we extend the analysis by taking into consideration possible phase change effects. We show that phase change effects are negligible in the case of large-size bubbles, whereas they strongly modify the medium-size bubble system behaviour. For small-size bubbles capillarity dominates the process

Acoustique d'un fluide au voisinage du point d'ébullition

International audienceDans une étude précédente (Boutin et Auriault 1993), la propagation d'ondes acoustiques dans un fluide à bulles en concentration finie était analysée au moyen de la méthode des échelles multiples. Trois comportements différents étaient mis en évidence suivant la taille des bulles, grande, moyenne ou petite. Dans la présente note, nous étendons cette étude par la prise en compte d'un possible changement de phase. Nous montrons que les effets de celui-ci sont négligeables dans le cas de grandes bulles, et modifient fortement le comportement des bulles moyennes en diminuant de plusieurs orders de grandeur la rigidité effective. Pour les petites bulles la capillarité devient le phénomène prépondérent

Long wavelenght inner-resonance cut-off frequencies in elastic composite materials

International audienceWe revisit an ancient paper (Auriault and Bonnet, 1985) which points out the existence of cut-off frequencies for long acoustic wavelength in high-contrast elastic composite materials, i.e. when the wavelength is large with respect to the characteristic heterogeneity length. The separation of scales enables the use of the method of multiple scale expansions for periodic structures, a powerful upscaling technique from the heterogeneity scale to the wavelength scale. However, the results remain valid for non-periodic composite materials which show a Representative Elementary Volume (REV). The paper extends the previous investigations to three-component composite materials made of hard inclusions, coated with a soft material, both of arbitrary geometry, and embedded in a connected stiff material. The equivalent macroscopic models are rigorously established as well as their domains of validity. Provided that the stiffness contrast within the soft and the connected stiff materials is of the order of the squared separation of scales parameter, it is demonstrated (i) that the propagation of long wave may coincide with the resonance frequencies of the hard inclusions/soft material system and (ii) that the macroscopic model presents a series of cut-off frequencies given by an eigenvalue problem for the resonating domain in the cell. These results are illustrated in the case of stratified composites and the possible microstructures of heterogeneous media in which the inner dynamics phenomena may occur are discussed

Acoustics of a bubbly fluid at large bubble concentration

International audienceThe homogenization process is used to investigate how acoustic waves propagate in a bubbly fluid at finite concentration. This method involves the consideration of waves whose lengths are large compared with the bubble size. We focus on the linear domain, with viscous, thermal and capillary effects. It is shown that this medium displays three different macroscopic descriptions according to bubble diameter and wave frequency. For bubbles of small size, the capillary effect leads to a model where in acoustic waves are either propagative with low celerity or diffusive. On increasing the bubble diameter we obtain waves which are damped and dispersed by both viscous and thermal effects. Finally for large bubbles, we get biphasic undamped and dispersed waves. Moreover, the homogenization method allows us to predict the kind of behaviour and the accuracy of the model from a knowledge of the physical characteristics of the mixture. Applications of these results are presented in the case of water containing air bubbles in equal proportion

Melanin-concentrating hormone receptors in GtoPdb v.2023.1

Melanin-concentrating hormone (MCH) receptors (provisional nomenclature as recommended by NC-IUPHAR [32]) are activated by an endogenous nonadecameric cyclic peptide identical in humans and rats (DFDMLRCMLGRVYRPCWQV; mammalian MCH) generated from a precursor (PMCH, P20382), which also produces neuropeptide EI and neuropeptide GE

Melanin-concentrating hormone receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Melanin-concentrating hormone (MCH) receptors (provisional nomenclature as recommended by NC-IUPHAR [31]) are activated by an endogenous nonadecameric cyclic peptide identical in humans and rats (DFDMLRCMLGRVYRPCWQV; mammalian MCH) generated from a precursor (PMCH, P20382), which also produces neuropeptide EI and neuropeptide GE

Spin-Exchange optical pumping in a van

International audienceThe advent of spin-hyperpolarization techniques designed to overcome the sensitivity issue of nuclear magnetic resonance owing to polarization transfer from more ordered systems has recently raised great enthusiasm. However, the out-of-equilibrium character of the polarization requires a close proximity between the area of production and the site of use. We present here a mobile spin-exchange optical pumping setup that enables production of laser-polarized noble gases in a standalone mode, in close proximity to hospitals or research laboratories. Only compressed air and mains power need to be supplied by the host laborator

A Holistic Approach to Unifying Automatic Concept Extraction and Concept Importance Estimation

In recent years, concept-based approaches have emerged as some of the most promising explainability methods to help us interpret the decisions of Artificial Neural Networks (ANNs). These methods seek to discover intelligible visual 'concepts' buried within the complex patterns of ANN activations in two key steps: (1) concept extraction followed by (2) importance estimation. While these two steps are shared across methods, they all differ in their specific implementations. Here, we introduce a unifying theoretical framework that comprehensively defines and clarifies these two steps. This framework offers several advantages as it allows us: (i) to propose new evaluation metrics for comparing different concept extraction approaches; (ii) to leverage modern attribution methods and evaluation metrics to extend and systematically evaluate state-of-the-art concept-based approaches and importance estimation techniques; (iii) to derive theoretical guarantees regarding the optimality of such methods. We further leverage our framework to try to tackle a crucial question in explainability: how to efficiently identify clusters of data points that are classified based on a similar shared strategy. To illustrate these findings and to highlight the main strategies of a model, we introduce a visual representation called the strategic cluster graph. Finally, we present https://serre-lab.github.io/Lens, a dedicated website that offers a complete compilation of these visualizations for all classes of the ImageNet dataset

Radiomic analysis of abdominal organs during sepsis of digestive origin in a French intensive care unit

Background Sepsis is a severe and common cause of admission to the intensive care unit (ICU). Radiomic analysis (RA) may predict organ failure and patient outcomes. The objective of this study was to assess a model of RA and to evaluate its performance in predicting in-ICU mortality and acute kidney injury (AKI) during abdominal sepsis. Methods This single-center, retrospective study included patients admitted to the ICU for abdominal sepsis. To predict in-ICU mortality or AKI, elastic net regularized logistic regression and the random forest algorithm were used in a five-fold cross-validation set repeated 10 times. Results Fifty-five patients were included. In-ICU mortality was 25.5%, and 76.4% of patients developed AKI. To predict in-ICU mortality, elastic net and random forest models, respectively, achieved areas under the curve (AUCs) of 0.48 (95% confidence interval [CI], 0.43–0.54) and 0.51 (95% CI, 0.46–0.57) and were not improved combined with Simplified Acute Physiology Score (SAPS) II. To predict AKI with RA, the AUC was 0.71 (95% CI, 0.66–0.77) for elastic net and 0.69 (95% CI, 0.64–0.74) for random forest, and these were improved combined with SAPS II, respectively; AUC of 0.94 (95% CI, 0.91–0.96) and 0.75 (95% CI, 0.70–0.80) for elastic net and random forest, respectively. Conclusions This study suggests that RA has poor predictive performance for in-ICU mortality but good predictive performance for AKI in patients with abdominal sepsis. A secondary validation cohort is needed to confirm these results and the assessed model