HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Exploring Quantum Analogies: Superradiance, Bipartite Correlations, and static Bell Tests in Pilot-Wave Hydrodynamics
No full textInternational audienceSince its discovery in 2005, the hydrodynamic pilot-wave system has provided a macroscopic realization of wave-particle duality, reproducing an increasing number of quantum-like effects. A key question is how closely particle-particle correlations in this classical system can mimic those at the quantum scale. Here, we introduce a numerical model of cooperative tunneling in a bipartite pilot-wave system as a new platform for exploring this question.We first establish bipartite hydrodynamic analogs of superradiance, both numerically and experimentally, demonstrating a sinusoidal modulation of the excited-to-ground state transition rate as a function of the separation between the two subsystems. Additionally, we conduct a static Bell test, where the system’s geometry remains fixed while the two subsystems are coupled through the intervening wave field. This wave-mediated coupling does not conform to the assumptions underlying Bell’s theorem, providing a rationale for the observed violations. However, these violations are elusive, emerging only within a narrow region of parameter space
Interfacial fracture in soft solids -how geometry and viscoplasticity make crack fronts unstable
No full textInternational audiencePolyvinylbutyral (PVB) is a polymer with sizeable viscoelastic dissipation at room temperature. It is often used in laminated glass to impart shock resistance to glazings. We have investigated adhesion rupture in glass/PVB interfaces in the through crack tensile test (TCT) geometry, representative of laminated glass rupture. We find that even though, in the high velocity range, interfacial rupture apparently follows the linear viscoelastic predictions, at low velocity a much richer behaviour appears: the system bifurcates, the front undulates, and at still lower velocities, it stops. Such instabilities cannot be explained by linear viscoelastic fracture. Prompted by the measured tensile response of PVB at high strain rates/low temperatures, we have explored steady state viscoplastic fracture, using a generic numerical model. The results show that the TCT geometry enhances the viscoplastic response in the rupture process. They also demonstrate that with viscoplasticity, the rupture energy decreases with velocity, a characteristic which indeed accounts for the observed crack front instabilities. We further discuss the implications of these findings for a better understanding of adhesion and rupture in soft matter and their connection to viscoplasticity
The nuclear lamin network passively responds to both active or passive cell movement through confinements
No full textInternational audiencePhysical models of cell motility rely mostly on cytoskeletal dynamical assembly. However, when cells move through the complex 3D environment of living tissues, they have to squeeze their nucleus that is stiffer than the rest of the cell. The lamin network, organised as a shell right underneath the nuclear membrane, contributes to the nuclear integrity and stiffness. Yet, its response during squeezed cell motility has never been fully characterised. As a result, up to now, the interpretations on the lamin response mechanism are mainly speculative. Here, we quantitatively map the lamin A/C distribution in both a microfluidic migration device and a microfluidic aspiration device. In the first case, the cell is actively involved in translocating the nucleus through the constriction, while in the second case, the cell behaves as a passive object that is pushed through the constriction by an external pressure. Using a quantitative description of the lamin shell response based on mass conservation arguments applied on the fluorescence signal of lamin, we show that in both cases of migration and aspiration, the response of the lamin network is passive. In this way, our results not only further elucidate the lamin response mechanism, but also allow to characterise that this deformation is passive even when the cell is actively migrating, thus paving the way to further investigate which active nuclear responses may occur whencells migrate in confinement
High-resolution Molecular Dynamics Simulations of the Pyruvate Kinase Muscle Isoform 1 and 2 (PKM1/2)
No full textInternational audienceGlucose metabolism plays a pivotal role in both normal physiological processes and cancer cell growth. The final stage of glycolysis, converting phosphoenolpyruvate (PEP) into pyruvate, is catalyzed by the pyruvate kinase (PK) enzyme. Whereas PKM1 (isoform 1) is mainly expressed in cells with high energy requirements, PKM2 (isoform 2) is preferentially expressed in proliferating cells, including many tumor cells. Structural analysis of both PKM1 and PKM2 is essential to the design of new molecules with anti-tumor activity. To understand the structural dynamics of PKM1 and PKM2, we performed extensive high-resolution molecular dynamics (MD) simulations using adaptive sampling techniques coupled to the polarizable AMOEBA force field. Performing more than 6 s of simulation, we consider PKM2 in its various oligomerization states and propose structural insights for PKM1. We particularly focus on the structuring of key sites including the active site and the natural substrate Fructose Bi-Phosphate (FBP) fixation pocket. Additionally, we propose the first high-resolution MD simulation of the biologically active PKM1 and uncover important similarities between the constitutive, tetrameric form of PKM1 and its PKM2 counterpart bound to FBP. Finally, we analyze the impact of the fixation of TEPP-46, a pharmacological activator, on PKM2 structuring and highlight the structural differences with PKM2 bound to FBP
Tubulin glutamylation regulates axon guidance via the selective tuning of microtubule-severing enzymes
No full textInternational audienceThe microtubule cytoskeleton is a major driving force of neuronal circuit development. Fine-tuned remodelling of this network by selective activation of microtubule-regulating proteins, including microtubule-severing enzymes, has emerged as a central process in neuronal wiring. Tubulin posttranslational modifications control both microtubule properties and the activities of their interacting proteins. However, whether and how tubulin posttranslational modifications may contribute to neuronal connectivity has not yet been addressed. Here we show that the microtubule-severing proteins p60-katanin and spastin play specific roles in axon guidance during zebrafish embryogenesis and identify a key role for tubulin polyglutamylation in their functional specificity. Furthermore, our work reveals that polyglutamylases with undistinguishable activities in vitro, TTLL6 and TTLL11, play exclusive roles in motor circuit wiring by selectively tuning p60-katanin- and spastin-driven motor axon guidance. We confirm the selectivity of TTLL11 towards spastin regulation in mouse cortical neurons and establish its relevance in preventing axonal degeneration triggered by spastin haploinsufficiency. Our work thus provides mechanistic insight into the control of microtubule-driven neuronal development and homeostasis and opens new avenues for developing therapeutic strategies in spastin-associated hereditary spastic paraplegia
Unlocking New Frontiers: Photo‐Isomerism and Magnetic Properties in Multifunctional Hetero‐Tetra‐Metallic Complexes
No full textInternational audienceHetero‐tetra‐metallic complexes, FeNOCuLnCo (Ln = Gd, Tb, Dy), combining magnetic properties and photo‐isomerism, were obtained through the rational assembly of the photo‐switching nitroprusside anion FeNO with new magnetic Schiff base CuLnCo precursors. Herein, we describe the synthesis and characterisation of these compounds followed by a demonstration of their multifunctional character. Particularly noteworthy is the FeNOCuTbCo complex, one of the few examples of a photo‐isomerizable single‐molecule magnet (SMM) and a significant first step toward achieving synergistic properties
Lifetime and fluctuations of specific bonds between anisotropic colloids mediated through depletion interactions
No full textInternational audienceSelf-assembly of colloidal particles is a promising avenue to control the shape and dynamics of larger aggregates. However, achieving the necessary fine control over the dynamics and specificity of the bonds between such particles remains a challenge. Here we demonstrate such control in bonds mediated by depletion interactions between anisotropic colloids that we 3D-print in the shape of half disks with sub-micron resolution. When brought together by diffusion, the particles interact in different configurations but the interaction through the flat faces is by far the longest-lasting. All bonds are flexible and transient, and we demonstrate control over their life time through the depletant concentration in quantitative agreement with a simple physical model. This basic design could be extended to manufacture particles with multiple binding sites to engineer directional assembly with multiple particles
DeepCristae, a CNN for the restoration of mitochondria cristae in live microscopy images
No full textInternational audienceMitochondria play an essential role in the life cycle of eukaryotic cells. However, we still don't know how their ultrastructure, like the cristae of the inner membrane, dynamically evolves to regulate these fundamental functions, in response to external conditions or during interaction with other cell components. Although high-resolution fluorescent microscopy coupled with recently developed innovative probes can reveal this structural organization, their long-term, fast and live 3D imaging remains challenging. To address this problem, we have developed a convolutional neural network, called DeepCristae, to restore mitochondria cristae in low spatial resolution microscopy images. Our network is trained from 2D STED images using a novel loss specifically designed for cristae restoration. To efficiently increase the size of the training set, we also developed a random image patch sampling centered on mitochondrial areas. To evaluate DeepCristae, quantitative assessments were carried out using metrics we derived by focusing on the mitochondria and cristae pixels rather than on the whole image as usual. Depending on the conditions of use indicated, DeepCristae works well on broad microscopy modalities (Stimulated Emission Depletion (STED), Live-SR, AiryScan and Lattice Light Sheet Microscopy). It is ultimately applied in the context of mitochondrial network dynamics during interaction with endo/lysosome membranes
From dark modes to topology: light-induced skyrmion generation in a plasmonic nanostructure through the inverse faraday effect
No full textInternational audienceSkyrmions are topological structures characterized by a winding vectorial configuration that provides a quantized topological charge. In magnetic materials, skyrmions are localized spin textures that exhibit unique stability and mobility properties, making them highly relevant to the burgeoning field of spintronics. In optics, these structures open new frontiers in manipulating and controlling light at the nanoscale. The convergence of optics and magnetics holds therefore immense potential for manipulating magnetic processes at ultrafast timescales. Here, we explore the possibility of generating skyrmionic topological structures within the magnetic field induced by the inverse Faraday effect in a plasmonic nanostructure. Our investigation reveals that a gold nanoring, featuring a dark mode, can generate counter-propagating photocurrents between its inner and outer segments, thereby enabling the magnetization of gold and supporting a skyrmionic vectorial distribution. We elucidate that these photocurrents arise from the localized control of light polarization, facilitating their counter-propagative motion. The generation of skyrmions through the inverse Faraday effect at the nanoscale presents a pathway towards directly integrating this topology into magnetic layers. This advancement holds promise for ultrafast timescales, offering direct applications in ultrafast data writing and processing
Indanone Building Blocks from Lignin Related C-9 Plaform Molecules
No full textLignin-based aryl 3-hydroxypropanones were converted into indanones via domino dehydration/Nazarov cyclization in the presence of a superacid. The cyclization was studied in detail, and the resulting indanones were engaged in two postfunctionalizations: a reduction/elimination domino sequence and a ring expansion. Lastly, the method has been successfully applied to the synthesis of the anti-Alzheimer drug donepezil.</div