HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Dehydrogenative Coupling Reaction for the Synthesis of 5‐ and 6‐Heterocyclic Derivatives including Arylquinolin‐2(1H)‐ones
No full textInternational audienceHeterocycle synthesis is an intense research area due to their significant importance in pharmaceutical, material chemistry and fine synthesis. Key innovations include transition metal‐based‐catalyzed heterocyclic derivatives synthesis, which facilitates diverse structural modifications, enhances selectivities and efficiency. The necessity to develop more greener technologies for the construction of new C‐C and C‐N bonds has strived chemists to re‐design their synthetic strategy plan and to introduce abundant starting materials. Among these new transformations, acceptorless dehydrogenative coupling (ADC) reactions have received increased attention thanks to their atom‐economy, the use of alcohols as pro‐electrophiles and the formation of water and hydrogen gas as only by‐products. These methods exemplify the interplay between traditional and cutting‐edge techniques, providing a robust synthetic toolkit to address the growing demand for biologically relevant compounds with tailored functionalities. This review will focus on the acceptorless dehydrogenative coupling methodologies for the synthesis of nitrogen‐containing 5‐ and 6‐membered heterocyclic derivatives (such as pyrroles, pyrimidines, quinazolines, and quinoxalines) in the presence of 3d‐metal complexes. The state of the art of the ADC process underscores the continuous evolution of synthetic strategies and emphases its importance in creating valuable and structurally diverse compounds, ensuring their centrality in both academic and pharmaceutical research
Stability of an elongated thickness fluctuation in a horizontal soap film
No full textInternational audienceEven though liquid foams are ubiquitous in everyday life and industrial processes, their ageing and eventual destruction remain a puzzling problem. Soap films are known to drain through marginal regeneration, which depends upon periodic patterns of film thickness along the rim of the film. The origin of these patterns in horizontal films (i.e. neglecting gravity) still resists theoretical modelling. In this work, we theoretically address the case of a flat horizontal film with a thickness perturbation, either positive (a bump) or negative (a groove), which is initially invariant under translation along one direction. This pattern relaxes towards a flat film by capillarity. By performing a linear stability analysis on this evolving pattern, we demonstrate that the invariance is spontaneously broken, causing the elongated thickness perturbation pattern to destabilise into a necklace of circular spots. The unstable and stable modes are derived analytically in well-defined limits, and the full evolution of the thickness profile is characterised. The original destabilisation process we identify may be relevant to explain the appearance of the marginal regeneration patterns near a meniscus and thus shed new light on soap-film drainage
Differentially Private Gradient Flow based on the Sliced Wasserstein Distance
No full textInternational audienceSafeguarding privacy in sensitive training data is paramount, particularly in the context of generative modeling. This can be achieved through either differentially private stochastic gradient descent or a differentially private metric for training models or generators. In this paper, we introduce a novel differentially private generative modeling approach based on a gradient flow in the space of probability measures. To this end, we define the gradient flow of the Gaussian-smoothed Sliced Wasserstein Distance, including the associated stochastic differential equation (SDE). By discretizing and defining a numerical scheme for solving this SDE, we demonstrate the link between smoothing and differential privacy based on a Gaussian mechanism, due to a specific form of the SDE's drift term. We then analyze the differential privacy guarantee of our gradient flow, which accounts for both the smoothing and the Wiener process introduced by the SDE itself. Experiments show that our proposed model can generate higher-fidelity data at a low privacy budget compared to a generator-based model, offering a promising alternative
Unveiling the Reactivity of Li1+xAlxTi2–x(PO4)3 with Lithium Salts to Reduce Its Sintering Temperature
No full textInternational audienceNaSICON-type materials, such as Li1.3Al0.3Ti1.7(PO4)3 (LATP), are considered promising solid electrolytes due to their good total ionic conductivity of 10-4 S.cm-1 at room temperature and their stability at high potentials (4.1 V vs Li/Li+). However, decreasing their densification temperature is crucial for their integration into all-solid-state batteries (ASSBs). The minimum required heat treatment temperature for densification of LATP is 900 °C, which is incompatible with its integration in composite electrode of ASSBs due to reactivity with the positive electrode material (cathode). To lower this temperature, lithium salts are often proposed as sintering aids to promote liquid-phase sintering. However, the systematic formation of impurities, such as LiTiOPO4 and Li4P2O7, suggests that chemical reactivity plays a significant role in LATP densification. In this work, the chemical reactivity mechanism of lithium salts with LATP during densification and sintering was investigated. Various characterization techniques, including in situ and ex situ X-ray diffraction, TGA-DTA-MS, DSC, ex situ Raman and solid-state NMR spectroscopy (7Li, 27Al, 31P), were employed to elucidate the mechanism. The formation of intermediate decomposition products Li3PO4 and TiO2 is identified for the first time via the reactivity of the lithium salt with LATP prior to the melting temperature of the salt. These intermediates subsequently react with LATP at higher temperature, resulting in the formation of final impurities LiTiOPO4 and Li4P2O7. This unified mechanism provides important insights on the enhanced densification of LATP at lower temperatures with the use of Li salt sintering aids
Translocation of cell-penetrating peptides involving calcium-dependent interactions between anionic glycosaminoglycans and phosphocholine bilayer
No full textInternational audienceCell-penetrating peptides can internalize ubiquitously in many, if not all, cell types. To explore the specific targeting issue of cell-penetrating peptides (CPPs), we studied glycosaminoglycan (GAG)-binding peptides previously identified in Otx2 and En2 homeoproteins (HPs), alone or extended with the penetratin-like third helix (H3) of En2. HPs are indeed known to internalize in specific cells, thanks to their GAG-targeting sequence (Joliot et al. 2022; Cardon et al. 2023). We quantified the capacity of these peptides to enter into various cell lines known to express different levels and types of heparan sulfates (HS) and chondroitin sulfates (CS) GAGs. We also analyzed by calorimetry (DSC, ITC) and fluorescence spectroscopy, the binary and ternary interactions between heparin (HI), (4S, 6S)CS (CS-E), zwitterionic phosphocholine (PC) model membranes and those peptides. Altogether, our results demonstrate the existence of Ca2+-dependent interactions between CS-E or HI and PC lipid bilayers, the major phospholipid found in animal cell plasma membrane. Importantly, we show that CS-E can act as a Ca2+-dependent bridge with PC membranes that can be exploited by a chimeric CS-E-recognition motif-H3 peptide to bind and cross the membrane lipid bilayer and get access directly to the cytosol of cells. Altogether, this study brings further information uncovering the molecular mechanism of the translocation process of CPPs that implies specific GAGs at the cell-surface. It also shed light on the role of GAGs in the paracrine activity and cell specificity of HPs
Ultrasound-induced dense granular flows: a two-time scale modeling
No full textInternational audienceUnderstanding the mechanisms behind the remote triggering of landslides by seismic waves at micro-strain amplitude is essential for quantifying seismic hazards. Granular materials provide a relevant model system to investigate landslides within the unjamming transition framework, from solid to liquid states. Furthermore, recent laboratory experiments have revealed that ultrasound-induced granular avalanches can be related to a reduction in theinterparticle friction through shear acoustic lubrication of contacts. However, investigating slip at the scale of grain contacts within an optically opaque granular medium remains a challenging issue. Here, we propose an original coupling model and numerically investigate 2D dense granular flows triggered by basal acoustic waves. We model the triggering dynamics at two separated time-scales—one for grain motion (milliseconds) and the other for ultrasound (10 microseconds)—relying the computation of vibrational modes with a discrete element method through the reduction of the local friction. We show that ultrasound predominantly propagates through the strong-force chains, while the ultrasound-induced decrease of interparticle friction occurs in the weak contact forces perpendicular to the strong-force chains. This interparticle-friction reduction initiates local rearrangements at the grain scale that eventually lead to a continuous flow through a percolation process at the macroscopic scale—with a delay depending the proximity to the failure. Consitent with theexperiment, we show that ultrasound-induced flow appears more uniform in space than pure gravity-driven flow, indicating the role of an effective temperature by ultrasonic vibration
Hippocampal reactivation of aversive experience enables safety learning and slow-breathing state for recovery from stress
No full textAbstract Adaptive threat responses require both defensive behaviours to minimize danger and recovering from the induced physiological stress. However, the behavioural and neural basis of these recuperative strategies are still elusive. Using a novel two-location fear conditioning paradigm in mice, we have identified a slow-breathing immobility state of recovery that emerges when animals identify safe environments after threat avoidance. This immobile state was characterized by a 2-4 Hz breathing profile and replay of the aversive experience in the hippocampus. Suppressing hippocampal sharp-wave ripples (SWRs) inhibited the emergence of this recovery state, suggesting their role in learning safe locations. Anxiolysis with diazepam directly promoted the recovery state while suppressing SWRs, showing this treatment to be a double-edged sword that facilitates immediate relief but impairs long-term safety learning. These results demonstrate the importance of hippocampal replay for emotional resilience through its role in recovery
Comparative analysis of dynamic balance descriptors in humanoids and humans during perturbed bipedal locomotion and fall
No full textInternational audienceThis study identifies a robust parameter for quantifying instability in general biped systems by comparing three mechanical stability descriptors: the distance between the center of mass to the minimal moment axis (d CoM-MMA ), the margin of stability (MoS), and whole-body angular momentum (WBAM) in both humans and humanoid biped robots. We analyzed these metrics during normal and perturbed walking, including robot falls, a dynamic whose observation is limited in human trials due to safety concerns. Our comparative analyses demonstrate that d CoM-MMA is more predictive of different levels of instability and shows a clearer distinction between fall and non-fall states, compared to MoS and WBAM. These findings were consistent for both humans and biped robots, regardless of gait variability or the type and intensity of the perturbation methods. These qualities highlight its potential use in unified stability analysis in both fields, offering insights that can inform the design of exoskeletons, fall monitoring systems, and other gait-assistive devices for aging populations
Brightness demixing for simultaneous multi-target imaging in 3D single-molecule localization microscopy
No full textAbstract Single-Molecule Localization Microscopy (SMLM) has revolutionized high-resolution imaging, but the simultaneous detection of multiple fluorophores traditionally relies on spectral-based separation, which is inherently constrained by spectral overlap. Here, we introduce Brightness Demixing, a novel method for fluorophore discrimination that exploits brightness, which directly depends on the fluorophores extinction coefficient and quantum yield. By oversampling blinking events, we precisely quantify photon flux as a proxy for brightness, enabling robust differentiation of fluorophores independent of their spectral properties, without requiring additional spectral separation. Brightness Demixing operates within a single detection channel, eliminating the need for additional spectral filters or cameras. We demonstrate this approach with simultaneous two- and three-target imaging in both 2D and 3D configurations. By maintaining single-wavelength excitation and minimizing chromatic aberrations, this method significantly enhances multiplexing in SMLM while remaining fully compatible with existing setups. Brightness Demixing thus offers a simple yet powerful approach for expanding multi-target imaging capabilities in super-resolution microscopy
Digital PCR: from early developments to its future application in clinics
No full textInternational audienceThis review explores the evolution of digital PCR (dPCR), highlighting early advancements, key technological innovations, and its promising future applications in clinical diagnostics, particularly in oncology and infectious diseases