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Merging cyclopentadienone tuning and CO to isonitrile substitution to develop photo-activated iron cyclopentadienone catalysts
No full textInternational audienceThis study explores the development and reactivity of novel iron cyclopentadienone complexes incorporating isonitrile ligands for photo-activated borrowing hydrogen (BH) catalysis. By merging strategies of cyclopentadienone tuning with isonitrile functionalization, this work aims to enhance the efficiency of photoactivation processes. New complexes featuring 4-nitrophenyl isonitrile ligands combined with electron-rich cyclopentadienones (L2 and L3) were synthesized and characterized through X-ray crystallography, IR, and M & ouml;ssbauer spectroscopy. Despite promising structural and electronic properties, these complexes showed reduced catalytic activity compared to classical Kn & ouml;lker-type analogues under photoactivation, particularly in allylic alcohol functionalization and BH amine alkylation. Mechanistic studies revealed that the diminished reactivity stemmed from light-induced demetallation of the L2 and L3-based complexes, contrasting with the stability of their L1-based counterparts. Adding exogenous ligands like PPh3 mitigated this demetallation, explaining the catalytic activity of L2 and L3 based complexes. The findings highlight the interplay of ligand design, light activation, and catalytic performance, providing a basis for advancing sustainable photocatalysis
The late rise of sky-island vegetation in the European Alps
No full textInternational audienceOur understanding of the emergence of mountain floras rests on our ability to infer how orogeny, landscape dynamics and climate change altered their evolutionary trajectories. Here, we reconstruct the assembly of the diverse sky-island flora of the European Alps and test the impact of key geo-climatic events. We use a dated 5,231-species phylogeny, including 96% of the sky-island flora. The assembly of this flora occurred through the colonisation of over a thousand distinct lineages, of which 46% speciated from their lowland ancestor and 6% underwent in situ cladogenesis. The young ages of extant sky-islands lineages show that their accumulation was decoupled from ancient geo-climatic events, but accelerated throughout the Plio-Pleistocene. The sky-island vegetation therefore assembled through recent lineage turnover, which was triggered, rather than impeded, by Pleistocene glacial intensification. This perspective challenges previous assumptions and highlights the complex interplay of geo-climatic factors in shaping the intricate tapestry of alpine floras
Nuclear Astrophysics in the Storage Ring: Background Suppressed Simultaneous Measurement of <math display="inline"><mrow><mo stretchy="false">(</mo><mi>p</mi><mo>,</mo><mi>γ</mi><mo stretchy="false">)</mo></mrow></math> and <math display="inline"><mrow><mo stretchy="false">(</mo><mi>p</mi><mo>,</mo><mi>n</mi><mo stretchy="false">)</mo></mrow></math> Reactions
No full textInternational audienceWe report the application of the new elimination of Rutherford elastic scattering technique for the measurement of proton-induced reaction cross sections utilizing stored ions decelerated to astrophysical energies. This approach results in a background reduction factor of about 1 order of magnitude, enabling the first measurement of a (p, n) cross section in a storage ring. Here, the reaction channels Xe124(p,n) and Xe124(p,γ) have been studied just above the neutron threshold energy. The new data provide valuable constraints for Hauser-Feshbach theory and extrapolation of the (p,γ) cross section to lower energies. Most importantly, for nuclei of limited availability, the method represents a powerful improvement to efficiently study proton-induced reactions at energies within or close to the astrophysical Gamow window, bringing many reaction measurements within reach that were previously inaccessible in the laboratory
Superconducting multipole triplets magnets commissioning for the S3 spectrometer at GANIL
No full textInternational audienceThe “Super Separator Spectrometer” project S3 is under technical commissioning at the GANIL facility (Caen-France). It is a new research installation designed for fundamental physics experiments with high intensity radioactive heavy ions beams produced by the SPIRAL2 linear accelerator. This spectrometer will open new horizons for nuclear physics. The S3 spectrometer is made of seven Superconducting Multipole Triplets (SMT) to guide and focalize the beam and select the particles of interest.This paper presents SMTs technology and their magnetic, electrical and cryogenic operating characteristics as well as their technical commissioning for the S3 project
Single-Ion Conducting Polymer Electrolyte with Excellent Interfacial Stability toward the Lithium Metal
No full textInternational audienceTo improve the safety and energy density of lithium metal batteries, polymer electrolytes address the challenge by replacing flammable liquid electrolytes. We herein design an amorphous solid-state single-ion conducting polymer electrolyte (SIPE) with a strict alternating sequence of perfluorosulfonate lithium salt and polyethylene glycol (PEG) with a very homogeneous dispersion of lithium salt in the electrolyte. Amorphous SIPE tailored with a moderate crosslink degree and reinforced with nanocrystals cellulose (NCC) exhibits a high Li+ conductivity exceeding 10-5 S cm 1 at 60 °C with a lithium transference number close to unity and excellent stability with Li metal. A long-term lithium stripping/plating was achieved in symmetric Li|SIPE|Li cells for over 80 days without dendrite growth. The Li|SIPE|LiFePO4 cells provide an excellent rate capability performance with a high specific capacity of 163 and 132 mAh g 1 at C/20 and C respectively. The long-term cycling tests exhibited good performance and an average coulombic efficiency of 99.9% for over 160 cycles. These excellent results confirmed the potential of the rational-designed single-ion conducting polymers as a safe and efficient solid-state electrolyte for next-generation high-performance energy storage
Gapped commensurate antiferromagnetic response in a strongly underdoped model cuprate superconductor
No full textInternational audienceIt is a distinct possibility that spin fluctuations are the pairing interactions in numerous unconventional superconductors. In the high-transition-temperature (high-T c ) cuprates, superconductivity emerges upon doping antiferromagnetic Mott insulators, and spin fluctuations might furthermore drive unusual pseudogap phenomena. Here we use magnetic neutron scattering to study the highly underdoped cuprate HgBa 2 CuO 4+δ (hole concentration p ≈ 0.064). In contrast to prior results for other underdoped cuprates, we find no evidence of incommensurate magnetic order associated with spin-density-wave or stripe correlations. Instead, the antiferromagnetic response in both the superconducting and pseudogap states is gapped below Δ AF ≈ 6 meV, commensurate over a wide energy range, and disperses above about 55 meV. Given the pristine nature of HgBa 2 CuO 4+δ , which exhibits high structural symmetry and minimal point disorder effects, this behavior likely signifies the unmasked response of the underlying CuO 2 planes near the Mott-insulating state. These results serve as a benchmark for a refined theoretical understanding of the cuprates
SO 2 , silicate clouds, but no CH 4 detected in a warm Neptune
No full textInternational audienceWASP-107b is a warm (∼740 K) transiting planet with a Neptune-like mass of ∼30.5 M ⊕ and Jupiter-like radius of ∼0.94 R J 1, 2 whose extended atmosphere is eroding 3 . Previous observations showed evidence for water vapour and a thick high-altitude condensate layer in WASP-107b's atmosphere 4, 5 . Recently, photochemically produced sulphur dioxide (SO 2 ) was detected in the atmosphere of a hot (∼1,200 K) Saturn-mass planet from transmission spectroscopy near 4.05 µm 6, 7 , but for temperatures below ∼1,000 K sulphur is predicted to preferably form sulphur allotropes instead of SO 2 8-10 . Here we report the 9σ-detection of two fundamental vibration bands of SO 2 , at 7.35 µm and 8.69 µm, in the transmission spectrum of WASP-107b using the Mid-Infrared Instrument (MIRI) of the JWST. This discovery establishes WASP-107b as the second irradiated exoplanet with confirmed photochemistry, extending the temperature range of exoplanets exhibiting detected photochemistry from ∼1,200 K down to ∼740 K. Additionally, our spectral analysis reveals the presence of silicate clouds, which are strongly favoured (∼7σ) over simpler cloud setups. Furthermore, water is detected (∼12σ), but methane is not. These findings provide evidence of disequilibrium chemistry and indicate a dynamically active atmosphere with a super-solar metallicity. WASP-107b was observed with JWST MIRI on 19 -20 January 2023. The SLITLESS-PRISM subarray of the low-resolution spectrometer was used, offering a spectral resolution rang-(Program identifier (PID) 1280; P.I. P.O. Lagage).</div
Steps toward the 5FGL Fermi-LAT source catalog
No full textInternational audienceThe current Fermi-LAT source catalog (4FGL-DR4: 7194 sources over 14 years) was built incrementally from the 8-year catalog. In a survey mission like Fermi, data accumulate on each source over time, so after 16 years (reached in August 2024) and twice the data for the original 4FGL sources we have much more precise localization. It is then time to generate a new original catalog (5FGL), which implies, beyond adding the sources newly detectable after twomore years, changing the existing source names (derived from their coordinates) and reviewing the associations.The systematic errors due to our imperfect knowledge of the Galactic diffuse emission, which dominates the gamma-ray sky, are the major limiting factor of the sensitivity and quality of the point source catalog at low energies (a few 100 MeV over the extragalactic sky, up to a few GeV in the Galactic ridge). Two parallel efforts are ongoing to improve on this situation, using more advanced methods to modulate the interstellar gas templates with the LAT data themselves. In parallel an early 16-year list (FL16Y) of 7217 sources is presented, which relocalizes all sourcesand improves a few aspects of the catalog analysis, but still uses the same diffuse model as 4FGL-DR4
Reducing glioblastoma cell aggressiveness via static and dynamic magneto-mechanical stimulation with vortex microdiscs on substrates of physiological stiffness
No full textExternal mechanical stresses acting on cellular compartments critically regulate cell behaviour and can induce cell death. Magnetically actuated particles present a promising strategy to apply such forces in a controlled manner, with potential applications in cancer therapy. In this study, we investigate the effects of actuating vortex magnetic microdiscs on a glioblastoma cell line cultured on soft, biomimetic substrates that mimic in vivo stiffness. Using a Halbach array, we applied either static mechanical compression or a combination of compressive and low-frequency vibrational stresses (2–20 Hz). Our results demonstrate that both compressive and vibrational stresses impair important cellular functions associated with glioblastoma persistence in a dose-dependent and stiffness-dependent manner. In particular on soft 2D substrates, sufficiently strong compressive loads limit proliferation, while the addition of vibrations alter cell motility, cell morphology and the acto-myosin machinery. Our findings demonstrate that magnetic particles-mediated mechanical stimulation can disrupt glioblastoma cell aggressiveness in physiologically relevant 2D substrates, supporting its potential as an adjunct to conventional chemo-and radiotherapies by both inducing cell death and limiting resistant populations
In-situ open-hole tensile testing and modeling of hybrid PEEK thermoplastic laminates under burn-through kerosene flame exposure
No full textInternational audienceThe objective of the present work is to investigate the thermo-mechanical behavior of open-hole hybrid carbon/ glass fiber reinforced PolyEther Ether Ketone (CG/PEEK) thermoplastic laminate subjected to the kerosene flame exposure (1100 • C and 116 kW/m 2 heat flux) in combination with tensile loading. A specialized flame testing bench has been developed, integrating a tensile mechanical loading and a kerosene burner, to induce in-situ firemechanical test conditions. The novel prototype has been employed to monitor the temporal evolution of several physical quantities in the range of fire exposure times up to 900 s, including back surface and through thickness temperature, open-hole deformation and swelling ratio of thickness. The mechanisms of fire-and mechanicallyinduced damage are examined through the fractographic analysis using tomography and microscopy. One-sided burn-through flame exposure causes the in-plane (4.0 K/mm) and through-thickness (40.1 K/mm) temperature gradients after 300 s. Compared to the virgin state, there is a considerable reduction in the equivalent stiffness (-67%) and axial strength (-55%) following a 900 s of flame exposure, indicating the severely damaged structural integrity. The modeling of the in-situ mechanical properties over multiple phase transition temperatures of the PEEK matrix is applied to characterize and ultimately predict the thermo-mechanical response of laminate under tensile loading in fire. The approach is based on the experimental measurement of mechanical properties over a wide temperature range (isothermal heating from the glass transition temperature to the PEEK matrix pyrolysis). The model shows a high degree of effectiveness in representing the in-situ open-hole tensile behavior of TP-based laminates under fire conditions as a function of flame exposure time.</div