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Différentes stratégies spatio-temporelles pour contrôler un geste de frappe afin de faire glisser un objet vers une distance cible
No full textHumans never perform the same movement twice, and there is interindividual variability in the spatio-temporal regulation of movements. The literature on striking gestures suggests that three types of spatio-temporal control can be observed when coping with task difficulty: increasing the amplitude of the movement while keeping its duration constant; keeping the amplitude of the movement constant and reducing the duration of the movement; or increasing both amplitude and duration of the movement by varying on the acceleration at impact. In this study, participants (n = 33) striked a cube which slides inside a gutter toward a target distance. Task difficulty varied as a result of the combination of three factors: surface material at the base of the gutter (aluminum and balsa), target distance (25 cm and 50 cm) and surface slope (-10°, 0°, + 10°). Clustering (K-Means) and correlational analyses on the hand movement data as a function of task difficulty confirmed that participants used the above-mentioned three strategies for the spatio-temporal control of the ballistic strike gesture. Although each cluster differed in how they exploited strike amplitude and duration to control movement, impact speed functioned as an invariant control variable across clusters, which did not differ in mean performance (spatial error).Les êtres humains n'effectuent jamais deux fois le même mouvement, et il existe une variabilité interindividuelle dans la régulation spatio-temporelle des mouvements. La littérature sur les gestes de frappe suggère que trois types de contrôle spatio-temporel peuvent être observés lorsqu'il s'agit de faire face à la difficulté d'une tâche : augmenter l'amplitude du mouvement tout en conservant sa durée constante ; maintenir l'amplitude du mouvement constante et réduire sa durée ; ou augmenter à la fois l'amplitude et la durée du mouvement en variant l'accélération à l'impact. Dans cette étude, les participants (n = 33) ont frappé un cube qui glissait à l'intérieur d'une gouttière vers une distance cible. La difficulté de la tâche variait en fonction de la combinaison de trois facteurs : le matériau de la surface à la base de la gouttière (aluminium et balsa), la distance cible (25 cm et 50 cm) et la pente de la surface (-10°, 0°, +10°). Le clustering (K-Means) et les analyses corrélationnelles des données relatives aux mouvements de la main en fonction de la difficulté de la tâche ont confirmé que les participants utilisaient les trois stratégies susmentionnées pour le contrôle spatio-temporel du geste de frappe balistique. Bien que chaque groupe différait dans la manière dont il exploitait l'amplitude et la durée de la frappe pour contrôler le mouvement, la vitesse d'impact fonctionnait comme une variable de contrôle invariante entre les groupes, qui ne différaient pas en termes de performance moyenne (erreur spatiale)
New oxy- and fluoro-hydrides compounds by topochemical intercalation of anions in electride intermetallics RScSi (R= rare earth)
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Comprehensive mapping of transcription terminator Rho utilization (Rut) sites across the Bacillus subtilis genome
No full textInternational audienceAbstract Recent evidence indicates that the bacterial Rho helicase regulates Bacillus subtilis gene expression in a growth-dependent manner. This regulation, along with extensive in vivo trimming of Rho-dependent transcript 3′-ends, complicates the identification of Rho-dependent transcription terminators using standard transcriptomic approaches. To overcome this challenge, we applied Helicase-SELEX to precisely map Rho utilization (Rut) sites genome-wide. Using B. subtilis Rho (BsRho), we identified 600 putative Rut sites, while the more permissive Escherichia coli Rho (EcRho) revealed 4189 sites, including specimens known to regulate B. subtilis genes. Comparative analysis showed that both enzymes recognize similar pyrimidine-rich sequences, though BsRho favors short unstructured Rut motifs whereas EcRho can act on presumably more structured RNAs without requiring accessory factors. In vivo validation of selected Rut sites confirmed Rho-dependent regulation and extensive PNPase-mediated processing of Rho-terminated transcripts. Collectively, our results reveal a rich and complex Rho-dependent regulatory network in B. subtilis, encompassing the widespread control of antisense transcription and genes/operons of both primary and secondary metabolism. Although nonessential under standard laboratory conditions, Rho thus likely contributes to B. subtilis fitness and survival in more demanding environments. Our comprehensive compendium of Rut sites offers a valuable resource for exploring this adaptive regulatory landscape
Microbial Sulfate Reduction Fed with Phytostabilization Biomass Compost: An Integrated Bioremediation Strategy for Mine Tailings and Drainage
No full textInternational audienceThis study aimed to acquire proof of concept validity, at the laboratory and theoretical levels, of an integrated remediation strategy involving sulfate-reducing bacteria (SRB) and composted phytostabilization plant biomass. A model mine site presenting both historic mine waste dumps and acid mine drainage (AMD) was chosen to test the integrated bioremediation scheme. A microbial consortium from a SRB bioreactor treating AMD was adapted to grass compost as the sole carbon and energy source. It was then used to assess the feasibility of feeding SRB with the AMD of a former tin mine and compost prepared with phytostabilization plant biomass from the site, inducing SO4 reduction and the precipitation of metals (Fe, Co, Ni). A 7-week-old grass compost used at 1–5% (wet weight) efficiently supported SBR activity. Results showed a decrease of sulfate concentration whose maximum amplitude was reached (from 1500 to less than 100 mg/L SO4) with 10% compost (wt% in liquid medium). Sulfate reduction rate increased with compost concentration from 1 to 5%, and the highest efficiency, in terms of mg reduced SO4 by mg of provided compost was obtained with 1% compost. All inoculated cultures induced precipitation of Fe, Co, and Ni. The proportion of SRB genera in the final bacterial communities ranged from 13 to 20%. The proportion of Desulfoscipio and Desulfallas in the SRB community increased with increasing compost concentration. The results suggest that compost from phytostabilization plant biomass is suitable to feed SRB bioreactors for AMD treatment on-sit
Enhanced Electromagnetic Wave Absorption in Mapbi<sub>3</sub> Hybrid Perovskite Through a Defect‐Tunable Green Synthesis
No full textInternational audienceDefect engineering and structure‐property relationship understanding in methylammonium lead iodide (MAPI) hybrid perovskites (HPs) attract significant scientific interest, as synthesis‐related defects may strongly influence intrinsic properties. We have explored a green solvent‐free synthesis—mechanosynthesis—leading to large quantities of MAPI powder with tuneable defect density suitable to study MAPI as an electromagnetic wave absorbing (EMWA) material. A dielectric loss enhancement was revealed at 11.4 GHz (X‐band) for 4 h‐ground MAPI powders (MAPI4h), compared to 30 min‐ground powders (MAPI30) when the particle size was <20 μm. MAPI powders display a fractal microstructure with agglomerates of clusters of (nano)grains (≈80 nm for MAPI4h), consisting further of oriented smaller nanograin (5–10 nm) clusters. A strong reabsorption in smaller particles was evidenced due to a surface‐defective layer. MAPI4h was shown to display a more surface‐defective layer with a higher defect density gradient from surface to (nano)grains core and unique open defects different from those in solution‐processed MAPI. These vacancy‐type surface defects would enhance dipole polarization by stabilizing methylammonium dipoles, thereby increasing permittivity. The improved dispersion of MAPI particles (<20 μm) in polymeric matrixes enhanced the surface effects and effective interactions with electromagnetic waves. This study demonstrated the potential of this green synthesis for producing large amount of HPs and tuning defects, opening new avenues for HPs EMWA application
Conformal anomaly and gravitational pair production
No full text14 pagesInternational audienceWe conjecture that the time-reversal-even component of the pair production rate Γ of particles in background fields in conformal 3+1 dimensional field theories is given by the anomalous trace ⟨Tμ μ⟩ of the energy-momentum tensor: Γ=(π/2)⟨Tμ μ⟩Θ(⟨Tμ μ⟩), where Θ(x) is the Heaviside step function. We show that this relation, written in mostly-plus metric, correctly describes the one-loop Schwinger pair creation of massless particles both in scalar and spinor versions of quantum electrodynamics. It also accurately points to the Savvidi instability of the gluonic vacuum towards the formation of the chromomagnetic condensate. The conjectured formula also reproduces (presumably, non-Hawking) radiation generated by static gravitational fields in the absence of an event horizon via a new evaporation mechanism suggested in [Phys. Rev. Lett. 130, 221502 (2023)]. A concurrent mechanism of the particle production due to the axial anomaly is briefly discussed and critical remarks on the state-dependence are also given
Avis sur le rapport d’opération 2024 du PCR ‘La sidérurgie en Bourgogne-Franche-Comté avant le haut fourneau’ et demande de renouvellement pour 2025-2027
No full textImpact of rotation on synthetic mass–radius relationships of two-layer rocky planets and water worlds
No full textInternational audienceWe analyze the effects of rotation on mass–radius relationships for single-layer and two-layer planets with a core and an envelope made of pure materials that includes iron, perovskite, and water in solid phase. The numerical surveys we adopted employ the DROP code updated with a modified polytropic equation of state (EoS). We investigated the flattening parameters, f, up to 0.2. In the mass range of 0.1 M⊕ ≲ M ≲ 10 M⊕, we find that the rotation systematically shifts the curves of composition towards larger radii and/or smaller masses. Relative to the spherical case, the equatorial radius, Req, is increased by about 0.36f for single-layer planets and by 0.30f to 0.55 f for two-layer planets (depending on the core size fraction, q, and the planet mass, M). Rotation is an additional source of confusion in deriving planetary structures, as the radius alterations are of the same order as i) current observational uncertainties for super-Earths and ii) EoS variations. We established a multivariate fit of the form Req(M, f, q), which enables a fast characterisation of the core size and rotational state of rocky planets and ocean worlds. We discuss how the observational data must be shifted in the diagrams to self-consistently account for an eventual planet spin, depending on the geometry of the transit (i.e. circular or oblate). A simple application to the recently characterised super-Earth candidate LHS 1140 b is discussed in this work
Los feluses en el noreste de al-Andalus: Numismática de la conquista de la Tarraconense oriental y de la Narbonense
No full textInternational audienceLos feluses se encuentran de manera desigual en al-Andalus. En el noreste del antiguo reino visigodo, en la Tarraconense oriental y la Narbonense, los hallazgos revelan diferencias sugiriendo distintas fases de la conquista. En efecto, considerando estas monedas de cobre como huellas arqueológicas de la conquista, los feluses son una fuente primordial para el estudio de este periodo. Se puede presentar su acuñación en relación con las necesidades del ejército, con apoyo al estudio numismático y arqueométrico
Photoelectric Effect in Air Explains Lightning Initiation and Terrestrial Gamma Ray Flashes
No full textInternational audienceTerrestrial gamma ray flashes (TGFs) are high‐energy photon bursts that have been linked to short bursts of electromagnetic radiation associated with lightning activity. The most puzzling unexplained aspect of these events is that gamma rays originate from very compact regions of space while the source regions often seem to be optically dim and radio silent when compared to processes in ordinary lightning discharges. In this work, we report a mechanism that allows precise quantitative explanation of these peculiar features of TGFs and their relationships to the observed waveform characteristics of associated radio emissions. The mechanism represents an extension of earlier ideas on feedback processes in growth of relativistic runaway electron avalanches (Dwyer, 2003, https://doi.org/10.1029/2003GL017781 ), and is based on a recent demonstration of the dominant role of the photoelectric feedback on compact spatial scales (Pasko, Celestin, et al., 2023, https://doi.org/10.1029/2022GL102710 ). Since discussed events often occur in isolation or precede formation of lightning discharges, the reported findings propose a straightforward solution for the long‐standing problem of lightning initiation