HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Argonaute 2 targets viral transcripts but not genomes of RNA viruses during antiviral RNA interference in Drosophila
No full textInternational audienceRNA interference (RNAi) mediated by the small interfering RNA (siRNA) pathway is a major antiviral mechanism in insects. This pathway is triggered when double-stranded RNA (dsRNA) produced during virus replication is recognized by Dicer-2, leading to the formation of virus-derived siRNA duplexes. These siRNAs are loaded onto the programmable nuclease Argonaute-2 (AGO2), with one strand serving as a guide to target and cleave fully complementary sequences of viral RNAs. While siRNAs are generated from viral dsRNA, the specific viral RNA species targeted for silencing during RNA virus replication remains unclear. In this study, we characterized the primary viral RNA targets of the Drosophila siRNA pathway during infections caused by negative and positive RNA viruses, namely Vesicular stomatitis virus (VSV) and Sindbis virus (SINV). Our findings reveal that polyadenylated transcripts of VSV and SINV are the major targets of silencing by the siRNA pathway during infection, likely when they are poised for translation. Consistent with earlier findings, we show that AGO2 is associated with ribosomes in control and virus infected cells. Therefore, we propose that the inhibition of the replication of RNA viruses in Drosophila results from the silencing of incoming viral transcripts, facilitated by the association of AGO2 with ribosomes
Sulfur isotopes evidence spatial ecology of Late Pleistocene ungulates in southwestern France
No full textInternational audienceUnderstanding prey species spatial behaviour is key to unravelling contemporary hunter-gatherer subsistence and movement patterns. Here, we use sulfur (δ 34 S), carbon (δ 13 C) and nitrogen (δ 15 N) isotope compositions of bone collagen extracted from Rangifer, Equus, Bovinae, Capreolus, and Cervus (n = 244) to explore isotope spatial and dietary niches of several key hunter-gatherer prey species from three Late Pleistocene sites in southwestern France between MIS 5 and MIS 3. Alongside morphological identification, Zooarchaeology by Mass Spectrometry (ZooMS) was used to confirm deer taxa (n = 125) allowing for a better interpretation of the isotopic data. δ 34 S analysis identifies differences in ranging sizes between ungulates with known large ranging sizes from those with small to medium size ranges. Rangifer, who, today, have large home ranges, have the largest range of δ 34 S values and lowest δ 34 S values with low to no overlap with other ungulate species through time. This indicates that Rangifer had a larger range size with a distinct isotopic area that is different to other ungulates, potentially farther inland and farther north. Bovines and Equus have largely overlapping δ 34 S values that are similar to the modern local δ 34 S value of the sites, and Cervus and Capreolus have δ 34 S values that overlap but are slightly higher than the modern δ 34 S values, potentially indicating a ranging area to the west of the sites. These results reveal that Neanderthals hunted three different groups of game who occupied different areas of the landscape
Influence of gravity variations on the activity of neuronal spheroids in an acoustic trap
No full textInternational audienceAmong biological models, cell culture constitutes an important paradigm that allows rapid examination of cell phenotype and behavior. While cell cultures are classically grown on a 2D substrate, the recent development of organoid technologies represents a paradigmatic shift in biological experimentation as they pave the way for the reconstruction of minimalist organs in 3D. Manipulating these 3D cell assemblies represents a considerable challenge. While there is growing interest in studying the behavior of cells and organs in the space environment, manipulating 3D cultures in microgravity remains a challenge. But with cellular research underway aboard the International Space Station (ISS), optimizing techniques for handling 3D cellular assemblies is essential. Here, in order to cultivate 3D models of spheroids in microgravity, we developed and used an acoustic bioreactor to trap levitating cellular organoids in a liquid cell culture medium. Indeed, in a Bulk Acoustic Wave (BAW) resonator, spherical objects, such as cells, can be maintained in an equilibrium position, inside a resonant cavity, away from the walls. In the acoustic levitation plane, gravity is counterbalanced by the acoustic radiation force (ARF) making it possible to maintain an object even in weightlessness. A dedicated setup was designed and built to perform live calcium imaging during parabolic flights. During a parabolic flight campaign, we were able to monitor the calcium activity of 3D neural networks trapped in an acoustic field during changes in gravity during different parabolas. Our results clearly indicate a change in calcium activity associated with variations in gravity
Localization structure of electronic states in the quantum Hall effect
No full textInternational audienceWe investigate the localization of electronic states in the integer quantum Hall effect using a magnetic localization landscape (MLL) approach. By studying a continuum Schrödinger model with disordered electrostatic potential, we demonstrate that the MLL, defined via a modified landscape function incorporating magnetic effects, captures key features of quantum state localization. The MLL effective potential reveals the spatial confinement regions and provides predictions of eigenstate energies, particularly in regimes where traditional semiclassical approximations break down. Numerical simulations show that below a critical energy, states localize around minima of the effective potential, while above it they cluster around maxima—with edge effects becoming significant near boundaries. Bridging the gap between semiclassical intuition and full quantum models, the MLL offers a robust framework to understand transport and localization in disordered quantum Hall systems and extends the applicability of landscape theory to magnetic systems
Measuring the local mechanical properties of a floating elastic sheet
No full textInternational audiencePolar regions are covered by sea ice, which can be seen as a thin solid elastic sheet with heterogeneous mechanical properties. The dynamics of deformation of a floating solid sheet are primarly governed by gravity, water density, and the flexural modulus, which depends on its mechanical properties, namely the thickness, the Young's Modulus and the Poisson ratio. Non-invasive methods from seismology can retrieve these three parameters from sheet deformation dynamics. In this article, we developed another method to extract locally the flexural modulus of a floating thin elastic sheet from the spatio-temporal deformations of the sheet. We perform laboratory experiment to test the accuracy and the robustness of this method on silicon membranes of controlled mechanical properties. Using patches of different thicknesses and shapes, we eventually draw maps of sheet thickness, with a sub-wavelength spatial resolution
Distributed network of smartphone sensors: a new tool for scientific field measurements
No full textSmartphones sensors are now commonly used by a worldwide audience thanks to their availability, high connectivity, and versatility. Here, we present a methodology to use a collection of smartphones, namely a fleet, as a distributed network of time-synchronized mechanical sensors. We first present the mechanical tests we develop to evaluate the smartphone sensor accuracy. We then describe how to use efficiently a distributed network of smartphones as autonomous sensors. We use a combination of an Android application hosted on each phone (Gobannos), and a server application (Phonefleet) on a controlling host to perform the tasks in parallel remotely. We detail the time synchronisation protocol we implemented, based on UDP communication. We achieved an accuracy of the time synchronisation of 60 microseconds, more than enough for all mechanical applications. Eventually, we present two test cases in which we use a smartphone fleet for mechanical wave measurements in field conditions
Steady-state neuron-predominant LINE-1 encoded ORF1p protein and LINE-1 RNA increase with aging in the mouse and human brain
No full textRecent studies have established a reciprocal causal link between aging and the activation of transposable elements, characterized in particular by a de-repression of LINE-1 retrotransposons. These LINE-1 elements represent 21% of the human genome, but only a minority of these sequences retain the coding potential essential for their mobility. LINE-1 encoded proteins can induce cell toxicity implicated in aging and neurodegenerative diseases. However, our knowledge of the expression and localization of LINE-1-encoded proteins in the central nervous system is limited. Using a novel approach combining atlas-based brain mapping with deep-learning algorithms on large-scale pyramidal brain images, we unveil a heterogeneous, neuron-predominant and widespread ORF1p expression throughout the murine brain at steady-state. In aged mice, ORF1p expression increases significantly which is corroborated in human post-mortem dopaminergic neurons by an increase in young LINE-1 elements including those with open reading frames. Mass spectrometry analysis of endogenous mouse ORF1p revealed novel, neuron-specific protein interactors. These findings contribute to a comprehensive description of the dynamics of LINE-1 and ORF1p expression in the brain at steady-state and in aging and provide insights on ORF1p protein interactions in the brain
Multi-lens ultrasound arrays enable large scale three-dimensional micro-vascularization characterization over whole organs
No full textInternational audienceMapping microcirculation at the whole-organ scale in 3D is crucial for understanding vascular pathologies and improving diagnostics. Although 3D ultrasound localization microscopy (ULM) enables microscopic resolution by localizing intravenously injected microbubbles in small animal models, visualizing entire organs in large animals or humans remains challenging due to limited field of view, low sensitivity, and probe technological complexity. Here, we demonstrate how a multi-lens array method overcomes these limitations. Combined with 3D ULM, it maps and quantifies large vascular volumes (up to 120 × 100 × 82 mm³) at high spatial resolution (125–200 µm) with a volumetric acquisition rate of 312 Hz, using low-cost technology. This approach enables deeper insights into hemodynamics from large vessels to pre-capillary arterioles, by providing vast and rich datasets of whole-organ vascularization. It could also facilitate diagnosis of microcirculation disorders and monitoring of small-vessel disease treatments by addressing key limitations of current imaging modalities
In situ Investigation of 1T′/1H Phase Transition in Colloidal WS₂ Monolayers
No full textInternational audienceControlling the crystal phase of two-dimensional transition metal dichalcogenides (TMDs) is essential for tailoring their electronic and optical properties. Among the polymorphs of WS₂, the metastable 1T′ phase exhibits semimetallic or narrow-bandgap character and hosts quantum functionalities distinct from the semiconducting 1H phase. Here, we investigate the temperatureinduced 1T′/1H phase transition in colloidally synthesized monolayer WS₂ nanosheets functionalized with organic ligands. The reducing conditions of the synthesis stabilize the 1T′ phase via electron doping. Through in situ analyses of both the structural and electronic properties, we monitor the phase evolution during annealing and find that the 1T′ phase remains stable up to 300 °C, accompanied by a relative lattice contraction. Between 300 and 350 °C, a mixed 1T′/1H regime appears, where the 1H content can be finely tuned by controlling the annealing time. Above 350 °C, a rapid and complete transformation to the 1H phase occurs. We demonstrate that the decomposition of the reducing ligand serves as the primary trigger of the structural transition, revealing a strong interplay among doping, surface chemistry, and lattice structure. Notably, nanosheets with smaller lateral dimensions exhibit slower phase transition kinetics, suggesting that finite size could influence the structural rearrangement underlying the phase transformation
Characterization of Pyrolysis Oils Using a Combination of GC×GC/TOFMS and GC/HRMS Analysis: The Impact of Data Processing Parameters
No full textInternational audienceHuman population growth and increasing transportation demands have led to rising global tire consumption and associated waste. In response, various material and energy recovery strategies, such as pyrolysis, have been developed to produce high-value-added products such as pyrolysis oils, which can be reused as materials or fuels. However, these oils often contain heteroatom-containing compounds (e.g., nitrogen, oxygen, sulfur) that can hinder their valorization and must therefore be identified and removed. To characterize heteroatomic compounds present in distillation fractions of pyrolysis oils, GC×GC/TOFMS and GC/HRMS were employed. For non-target analysis, data processing parameters were optimized using a Central Composite Design (CCD). The most influential parameters for GC×GC/TOFMS were the minimum number of mass-to-charge ratio (m/z) signals kept in the deconvoluted spectra (minimum stick count) and peak signal-to-noise ratio (S/N), while for GC/HRMS, optimization focused on the m/z S/N threshold, peak S/N, and total ion current (TIC). Under optimal conditions, 129 and 92 heteroatomic compounds were identified via GC×GC/TOFMS and GC/HRMS, respectively, within a single distillation fraction, with 57 compounds identified using both techniques. Notably, GC×GC/TOFMS exclusively identified 72 compounds, while there were only 5 unique to GC/HRMS. These results highlight the effectiveness of GC×GC/TOFMS in characterizing heteroatomic compounds in complex mixtures, while also underlining the complementary value of GC/HRMS