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The near-infrared silhouette of the Flying Saucer edge-on disc revealed by the JWST JEDIce program
No full textAims. Edge-on discs offer a unique opportunity to probe radial and vertical dust and gas distributions in the protoplanetary phase. This study aims to investigate the distribution of micron-sized dust particles in the Flying Saucer in Rho Ophiuchi by leveraging the unique observational conditions of a bright infrared background that enables the edge-on disc to be seen in both silhouette and scattered light at specific wavelengths.
Methods. We used NIRSpec IFU observations from the JWST Edge-on Disc Ice program (JEDIce) of the Flying Saucer serendipitously observed against a Polycyclic Aromatic Hydrocarbons-emitting background to constrain the dust distribution and grain sizes via radiative transfer modelling.
Results. The observation of the Flying Saucer in silhouette at 3.29 μm reveals that the midplane radial extent of small dust grains is ∼235 au, i.e. larger than the large-grain disc extent previously determined to be 190 au from millimetre data. The scattered light observed in emission probes micron-sized icy grains at large vertical distances above the midplane. The vertical extent of the disc silhouette is similar at visible, near-IR, and mid-IR wavelengths, corroborating the conclusion that dust settling is inefficient for grains as large as tens of microns, both vertically and radially
High-resolution mapping of molecular tori with ALMA
No full textRecent high-resolution mapping of the circumnuclear regions of active galactic nuclei (AGNs) has revealed the existence of geometrically thin nuclear disks, in general randomly oriented with respect to their galaxy hosts. These molecular tori have typical radii of 10 pc, and contain a few 107 M⊙ of H2, with H2 column densities between 1023 and 1025 cm−2. We mapped two of the most massive of these molecular tori with a higher resolution, in order to unveil their morphology and kinematics, their possible warp and clumpiness, and derive their stability and lifetime. We used the highest resolution possible with ALMA (16 km baseline) in Band 7, taking into account for mapping CO(3–2) and HCO+(4–3) the compromise between sensitivity and resolution. New features are discovered at the high resolution, obtained with a beam of 0.015″, equivalent to ∼1 pc scale, at their ∼15 Mpc distance. The molecular torus in NGC 613 appears similarly to a ring, depleted in molecular gas near the center. The depletion region is displaced by 3 pc toward the NW from the AGN position, meaning some m = 1 asymmetry in the torus. The molecular torus in NGC 1672 has a different position angle from previous lower-resolution observations, and is edge-on, revealing a geometrically very thin torus (axis ratio 6.5–10), with a clear warp. This confirms that the classical model of a simple geometrically thick dusty torus is challenged by high-resolution observations. The nuclear disks appear to be clumpy, and slightly lopsided. The molecular outflow in NGC 613 is now resolved out. Well inside the sphere of influence of the black holes (BH), we are now able to determine more accurately their mass, for those Seyfert spiral galaxies, in a region of the M-sigma relation where the scatter is maximum
Revisiting the unification of tidal disruption events with polarimetry
No full textAims. Tidal disruptions of stars by supermassive black holes produce emission at different wavelengths, but the optical emission is of ambiguous origin. A unification scenario of tidal disruption events (TDEs) has been proposed to explain the different classes of X-ray and optically selected events by introducing a dependence on the viewing angle and geometry. This work aims to test the unification scenario among optically bright TDEs using polarimetry.
Methods. By studying the optical linear polarisation of nineteen TDEs (nine of which are newly analysed in this work), we placed constraints on their photosphere geometry, inclination, and the emission process responsible for the optical radiation. We also investigated how these properties correlate with the relative X-ray brightness of the events, quantified by the LX/Lg ratio.
Results. We find that 14 of the 16 non-relativistic events can be accommodated by the unification model. The continuum polarisation levels of the non-relativistic TDEs most often lie in the range P ∼ 1 − 2% (13 events), and for all except one event, they remain below 6%. For those optical TDEs that have multiple epochs of polarimetry, the continuum polarisation levels decrease with time after peak light for five of the ten events, increase for three events, and stay approximately constant for two events. When observed after +70 days (7/16 events), they become consistent with zero polarisation within uncertainties (5/7 events). This implies that the photosphere geometries of TDEs are at least initially asymmetric and evolve rapidly, which if tracing the formation of the accretion disc, suggests efficient circularisation. The polarisation signatures of emission lines of seven TDEs directly support a scenario in which optical light is reprocessed in an electron-scattering photosphere. TDEs are most often weak in X-rays when significantly polarised. However, a subset of events deviates from the unification model to some extent, suggesting this model may not fully capture the diverse behaviour of TDEs. Multi-epoch polarimetry plays a key role in understanding the evolution and emission mechanisms of TDEs
Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at
No full textWe aim to characterise the mass-metallicity relation (MZR) and the 3D correlation between the stellar mass, metallicity, and star formation rate (SFR) known as the fundamental metallicity relation (FMR) for galaxies at 5 < z < 7. Using ∼800 [O II
IA et organisations à haute fiabilité : garder le contrôle pour préserver la sûreté
No full textLe déploiement continu de l’IA transforme profondément les entreprises, bien au-delà des secteurs historiquement concernés par l’automatisation. Les domaines intellectuels – conseil, recherche, ingénierie – voient à leur tour leurs pratiques et leurs équilibres internes (dynamiques collectives, répartition du travail cognitif, place du jugement humain) potentiellement modifiés. Le rôle de l’IA et la confiance qui lui est faite dans le secteur nucléaire doivent être précisément examinés
Rehabilitation robot trajectory planning method for upper limb based on healthy limb motion using multi-objective constrained reinforcement learning
No full textStroke patients with hemiplegia require personalized upper-limb rehabilitation, yet designing safe and effective robot-assisted trajectories that mimic natural human movement remains a significant challenge. This paper proposes a trajectory planning and optimization method to address this need by leveraging multi-objective constrained reinforcement learning. The method involves dynamically capturing motion data from the patient's healthy limb to define personalized Activities of Daily Living (ADL). A reinforcement learning algorithm, guided by a specially designed reward-punishment function, then optimizes the trajectory with objectives for smoothness, jerk minimization, and accurate tracking of key points. The approach was validated on a 4-degree-of-freedom (4-DOF) upper limb rehabilitation robot, which successfully achieved multi-joint coordinated trajectory tracking based on the learned ADL movements. The experiments confirm the method's effectiveness in designing personalized rehabilitation trajectories that improve the continuity and smoothness of robot-assisted movements, offering a promising solution for patient-specific therapy
Climate risk assessment in urban environments
No full textThe majority of climate change vulnerability and health concerns are concentrated in informal settlements. Hazardous locations can be found in many communities, including low-lying ground along exposed riverbanks and ocean coasts, degraded slopes, and buildings that don't adhere to building rules. A complex network of interrelated social, ecological, and technical processes makes up the urban environment. Global warming is expected to have a wide range of repercussions on ecosystems and society, which naturally increases complexity, in addition to other environmental, economic, and political concerns.By integrating satellite, environmental, and socioeconomic data using an integrated method that included remote sensing, statistical modeling (PCA), and geographical analysis, this work created a spatially explicit diagnosis of urban climate risks in Rabat. Three primary risk factors were investigated: air pollution (PM2.5 and NO2), urban heat (heat island), and related socioeconomic vulnerability
Alternative methods for wastewater treatment. Case study: Phytopurification
No full textWastewater management is a major environmental and sanitary preoccupation for people around the world. impacted by urbanization and population growth, water management is becoming more complex than ever. Conventional treatment systems, such as wastewater treatment plants, are often expensive to build and to maintain, and can have negative impacts on the environment. given these challenges, it is essential to explore alternative wastewater treatment methods that are efficient, economical and ecologically sustainable. These new systems include phyto-purification, a method based on the treatment of wastewater by plants. The aim of our work is to describe the fundamental principles of phyto-purification, its advantages and disadvantages, its economic and environmental impact, and to project a case study on the implementation of this treatment method
Theoretical confirmation of benzothiazole derivatives as corrosion inhibitors for carbon steel in hydrochloric acid
No full textThis study presents an in-depth theoretical approach based on density functional theory (DFT) to elucidate the mechanisms of corrosion inhibition of benzothiazole derivatives 2-mercaptobenzothiazole (MBT) and 2-aminobenzothiazole (ABT) on carbon steel in a 1 M HCl solution. Quantum chemistry parameters, including Frontier molecular orbitals energies, electrostatic potential maps (MEP), and Fukui indices were calculated in order to evaluate the inhibition mechanisms of these two drifts.
The results indicate that MBT has a higher HOMO energy and greater electron donor capacity than ABT, thus promoting stronger chemisorption on the steel surface. In addition, MBT's tendency to protonate enhances its physisorption due to electrostatic forces acting on the metal surface in an acidic environment. These theoretical results are consistent with experimental observations from electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM), confirming the superior inhibitory performance of MBT compared to ABT, especially after prolonged immersion time. This study highlights the essential role of molecular electronic properties in determining inhibitor efficacy and supports the rational design of high-performance benzothiazole-based corrosion inhibitors
Seasonal Variation in Nutritional Composition and Antioxidant Potential of
No full textThe coastal areas of Doukkala, Morocco, are recognized for its abundant populations of Gelidium corneum, an acknowledged red alga used for agar production. This study focused the valorization of G. corneum beyond agar extraction, focusing on its nutritional composition, antioxidant properties, and socio-economic significance. Seasonal changes in biochemical composition were analyzed by measuring ash, crude protein, total lipid, and carbohydrate contents throughout the year.The antioxidant capacity of aqueous algal extracts was evaluated seasonally using DPPH, ABTS, and FRAP assays, along with total phenolic content (TPC). Results indicated that the biomass contained substantial amounts of protein (up to 19.22 ± 0.13%) and carbohydrates (up to 43.9 ± 0.07%), while lipid content remained relatively low (up to 2.37 ± 0.7%), particularly in autumn. Moderate antioxidant activity was observed, with DPPH inhibition reaching 14.44 ± 0.12%, ABTS inhibition 20.55 ± 0.18%, FRAP 1.66 ± 0.35 mg AAE g-1, and TPC 12.34 ± 0.28 mg GAE g-1. These findings underscore the value of G. corneum as a natural resource with both nutritional and functional potential, supporting its prospective use in food applications while contributing to the socio-economic development of the Doukkala region