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#### Upcoming Seminars 16 Octobre : Benjamin Apffel (ENS de Lyon) 23 Octobre : Vacances de la Toussaint 30 Octobre : Vacances de la Toussaint 6 Novembre : Constantino Tsallis (Brésil) 13 Novembre : Nicolas Bain (ILM, Lyon) Full list at www.pmmh.espci.fr/Seminaires

Séminaires PMMH

Together with a model of the unsteady flow in the anisotropic, porous tip of the brush, these experiments allow us to identify different splatting regimes and to understand how splatter painting artists adjust their working conditions.

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I present our efforts to unravel physical phenomena in splatter painting. We perform experiments on real and simplified brushes, subjected to a controlled impact on their handle. We study the dependence of the expelled liquid and the resulting patterns on the liquid viscosity and brush acceleration.

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In this technique, perhaps most emblematically used by American painters Jackson Pollock (1912-1956) and Sam Francis (1923-1994), the brush never touches the canvas, and tuning the final pattern becomes a challenge for the artist.

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In art, splatter painting consists in subjecting a paint-loaded brush to an acceleration (for example by “flicking” the brush or tapping its handle) to detach paint droplets or filaments. Those are projected onto the substrate to be painted, leaving filamentary or spotty patterns.

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Dear colleagues, The PMMH seminar on 9 Oct at 11am will host Lorène Champougny (LGC, Toulouse) The Fluid Mechanics of Splatter Painting Abstract below. Zoom link upon request. Directions to PMMH laboratory: www.pmmh.espci.fr/Contact-357

Physique et Mécanique des Milieux Hétérogènes UMR 7636 : Come to PMMH

#### Upcoming Seminars 2 Octobre : Mathis Guéneau (MPI, Dresde) 9 Octobre : Lorène Champougny (LGC, Toulouse) 16 Octobre : Benjamin Apffel (ENS de Lyon) 23 Octobre : Vacances de la Toussaint 30 Octobre : Vacances de la Toussaint Full list at www.pmmh.espci.fr/Seminaires

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We discuss how interactions between active filaments lead to swarm formation and collective force generation. [1] M. R. Rashid, M. Akter, A. M. R. Kabir, K. Sada, T. Hiraiwa, A. Kuzuya, I. Kawamata, M. Tani*, and A. Kakugo*, ACS Nano 20, 18, 13586–13597 (2026).

The collective force increases linearly with the inferred number of kinesin motors over a wide range of swarm sizes, although the measured force is smaller than expected from a purely additive contribution of individual motors [1].

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Here, we generate swarms of kinesin-driven microtubules (MTs), filamentous biopolymers driven by molecular motors, by introducing attractive DNA interactions between MTs. We quantify the collective force generated by the MT swarms using a custom-built electromagnetic tweezer setup.

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Collective motion is widely observed in nature, from schools of fish to bird flocks and insect colonies, where groups can accomplish tasks beyond the capability of individuals. Such collective behavior raises an interesting question: can a group of active agents also generate force collectively?

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On Friday 25 September at 11am, the PMMH seminar will host Marie Tani (Kyoto University). Title: Swarming of Active Filaments and Collective Force Generation Abstract follows. Zoom link upon request. Directions to PMMH laboratory: www.pmmh.espci.fr/Contact-357

Physique et Mécanique des Milieux Hétérogènes UMR 7636 : Come to PMMH

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#### Next Seminars 25 Sept: Broadcasting of Assises and discussions (to be confirmed) 2 Oct: Mathis Guéneau (MPI, Dresde) 9 Oct: Lorène Champougny (LGC, Toulouse) 16 Oct: Benjamin Apffel (ENS de Lyon) 23 Oct: Holiday Toussaint 30 Oct: Holiday Toussaint Full list at www.pmmh.espci.fr/Seminaires

References [1] A. Altieri, F. Roy, C. Cammarota, G. Biroli, Phys. Rev. Lett. 126, 258301 (2021) [2] J. Pasqualini, A. Maritan, A. Rinaldo, S. Facchin, E. V. Savarino, A. Altieri & S. Suweis, eLife 14, RP105948 (2026) [3] N. Patil, A. Altieri, arXiv:2607.24328 (2026)

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Finally, I will discuss extensions beyond the standard logistic-growth and purely competitive frameworks that can promote coexistence, thereby offering a new perspective on the long-standing diversity–stability debate.

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Through dataset analysis from both healthy individuals and patients with inflammatory bowel disease, I will show that distinct physiological states of the gut microbiome map onto different noise-driven and disorder-driven regimes of the Generalized Lotka-Volterra model.

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I present a high-dimensional version of the Lotka–Volterra model incorporating demographic fluctuations and heterogeneous interactions among species. I will then explore its relevance to the human gut microbiome.

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Inferring species interactions in highly heterogeneous ecological communities and developing a robust, predictive theory of ecological stability remain major challenges, due both to the amount of data required and the complexity of the underlying interaction network.

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The PMMH seminar on Friday 18 Sept at 11:00 will be given by Ada Altieri of the MSC laboratory in Paris. Title: From disordered Generalized Lotka-Volterra models to gut microbiome complexity Abstract follows. Zoom link upon request. #### Come to PMMH laboratory: www.pmmh.espci.fr/Contact-357

Physique et Mécanique des Milieux Hétérogènes UMR 7636 : Come to PMMH

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Next Seminars 18 September: Ada Altieri (MSC, Paris) 2 October: Mathis Guéneau (MPI, Dresde) 9 October: Lorène Champougny (LGC, Toulouse) 16 October: Benjamin Apffel (ENS de Lyon) 23 October: Vacances de la Toussaint 30 October: Vacances de la Toussaint Full list at www.pmmh.espci.fr/Seminaires.

Then, I will use DNS to discuss how the inhomogeneous tidal heating of this ocean might alter its large-scale circulation through a competition between zonal flows and global overturning.

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I will discuss the interaction between this turbulent flow and topography using laboratory experiments of centrifugal convection that reproduce a beta-effect using a rapidly rotating water tank with a free surface.

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In icy moon oceans (and indeed any spherical shell), turbulent convection is influenced by the beta-effect arising from the variation of the Coriolis force with latitude. This leads to the propagation of Rossby waves and the emergence of strong self-organized zonal (east–west) flows.

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In this talk, I will provide an overview of the key mechanisms driving flows in icy moon oceans, and how buoyancy-driven flows (thermal convection) can be modelled using rotating laboratory experiments and direct numerical simulations.

Séminaires PMMH

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The dynamics of subsurface oceans control heat and mass exchange between the rocky interior and the ice shell and might influence observable features, yet they remain poorly constrained due to limited observations, complex physical processes acting in concert, and extreme dynamical regimes.

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Several icy moons of Jupiter and Saturn host liquid oceans beneath their icy crusts. They have become primary targets in planetary science and astrobiology, with two missions currently en route to the Jovian system to explore Europa and Ganymede.

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CNRS Ingénierie @cnrsingenierie.bsky.social · 02/09/2026

The PMMH seminar on Friday 11 Sept at 11am will be given by Daphné Lemasquerier of the University of St Andrews, UK. Abstract below, Zoom link upon request. Fluid Dynamics of Icy Moon Oceans: turbulent zonal flows, topography, and tidal heating Directions to PMMH: www.pmmh.espci.fr/Contact-357

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Reposted by PMMH Laboratory

#RésultatScientifique 🔎 | Des motifs répétitifs pour former des structures gonflables complexes 🔬 #Navier 🤝 @cnrs.fr @ecoledesponts.bsky.social #UnivGustaveEiffel 📍 @cnrs-idf-villejuif.bsky.social ➡️ insis.cnrs.fr/fr/cnrsinfo/des-motifs-repetitifs-pour-former-des-structures-gonflables-complexes

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Reposted by PMMH Laboratory

ISYEB @isyeb.mnhn.fr · 02/09/2026

Comment la science puise dans les formes et les stratégies du vivant pour répondre aux grands défis de notre époque Camille Aracheloff @cnrs.fr @ucauvergne.bsky.social parlera de son parcours de thèse à l'@isyeb.mnhn.fr & au @pmmh-lab.bsky.social En savoir+ www.paris-centre.cnrs.fr/fr/evenement...

paris-centre.cnrs.fr

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#### Come to PMMH laboratory: www.pmmh.espci.fr/Contact-357 #### Next seminars September 11th: Daphné Lemasquerier (U. Saint-Andrews, Scotland) September 18th: Ada Altieri (MSC, U. Paris Cité) September 25th: to be announced October 2nd: Mathis Guéneau (MPI Dresden, Germany)

Physique et Mécanique des Milieux Hétérogènes UMR 7636 : Come to PMMH

this approach demonstrates the ability of Brillouin spectroscopy to resolve mechanical properties at the single-microparticle level and provides a methodology to investigate how local changes in structure, charge, and environment affect elasticity at the microscale.

Finally, I will show how Brillouin microscopy can probe changes in the elastic properties of individual Stöber silica microparticles whose mechanics are finely tuned by electron-beam irradiation. Beyond potential technological applications,

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As a benchmark example, I will present our recent work combining Brillouin-Raman microscopy and microfluidics to probe the mechano-adaptation of breast tumor spheroids subjected to controlled cyclic compression, mimicking mechanical stresses encountered in vivo.

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Then I will present my main research activities at the Dept. of Physics, Univ. of Perugia. I will briefly introduce correlative Brillouin and Raman spectroscopy as a contactless, high-spatial-resolution approach to investigate the viscoelastic properties of biological and soft-matter systems.

between which stochastic fluctuations and flow-induced buckling induce switching. This establishes periodically driven Brownian flexible filaments as an experimentally accessible realization of stochastic symmetry breaking, attractor hopping, and intermittency in a minimal nonequilibrium system.

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from the suppression of buckling during part of the oscillation cycle, even under strong compressional flows, to alternating regimes of quasi-reversibility and chaotic dynamics over longer timescales. This intermittent behavior originates from two coexisting symmetry-related dynamical attractors,

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I will first present recent experimental and numerical work on the conformational dynamics of an elastic Brownian filament subjected to time-dependent viscous forces in a periodic flow. Unlike in steady shear flows, an independent timescale gives rise to a variety of unexplored phenomena,

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The PMMH seminar resumes this week with Francesco Bonacci of the University of Perugia, Italy. Title: Recent Works on Flexible Filaments and Brillouin Microscopy As usual, the seminar will take place on Friday at 11am in the PMMH meeting room. Abstract below. Zoom link upon request.

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📣 Il y aura des mousses et des libellules signées PMMH !

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Moreover, often melting ice appears next to other pieces of ice such that collective effects can also become important, we will show idealized simulations investigating the presence of nearby ice. Lastly, we will look into the melting of ice in oscillatory flow in order to investigate tidal flows.

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For example, we will discuss the dynamics of melting with prescribed morphology and how this morphology evolves. We will look into the case where the ice contains particulate contaminants to mimic the sand and debris inside glacial ice. We investigate how this further modifies the melting process.

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In this talk we will focus on the melting dynamics of controlled experiments and simulations in canonical geometries to further our understanding of melting processes. In particular, we will showcase a variety of configurations with different complications.

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We hope to see you for our last seminar before the summer break given by Sander Huisman (U. Twente, the Netherlands) at 11am on Friday 10 July. Please find the abstract below. Zoom link upon request. Title: Melting with complications

even though no reason for this particular value is known. We show that about this percentage of inhibitory synapses is able to provide the best performance of the network in multi-task learning, since it is able to organize the most efficient synaptic paths for information transmission.

The learning dynamics exhibits universal scaling and indicates that systems with slower synaptic adaptations give better performances, as observed in fMRI measurements on human brains. Finally, neurobiological measurements indicate that about 30% of synapses in mammalian brains are inhibitory,

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We show that this economy of scale is a universal outcome of avalanche dynamics. Finally, this model not only reproduces spontaneous activity but also “evoked behavior”, i.e., the network is able to learn very complex rules, which usually require special adaptations in traditional models.

Another common property of living systems is allometric scaling with size, such as Kleiber’s law for metabolic rate, highlighting efficiency. The brain's characteristic sublinear scaling of activity, has long posed a puzzle: why do larger brains operate with disproportionately lower firing rates?

Recently attention has also focused on the profile of neuronal avalanches in vitro and in vivo, exhibiting a tendency to leftward asymmetry. Following the scaling theory proposed for critical avalanches in crackling noise, the model suggests that inhibitory neurons are the cause of the asymmetry.