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Measurements of the Thermal Sunyaev-Zel'dovich Effect with ACT and DESI Luminous Red Galaxies
No full textInternational audienceCosmic Microwave Background (CMB) photons scatter off the free-electron gas in galaxies and clusters, allowing us to use the CMB as a backlight to probe the gas in and around low-redshift galaxies. The thermal Sunyaev-Zel'dovich effect, sourced by hot electrons in high-density environments, measures the thermal pressure of the target objects, shedding light on halo thermodynamics and galaxy formation and providing a path toward understanding the baryon distribution around cosmic structures. We use a combination of high-resolution CMB maps from the Atacama Cosmology Telescope (ACT) and photometric luminous red galaxy (LRG) catalogues from the Dark Energy Spectroscopic Instrument (DESI) to measure the thermal Sunyaev-Zel'dovich signal in four redshift bins from to , with a combined detection significance of 19 when stacking on the fiducial CMB Compton- map. We discuss possible sources of contamination, finding that residual dust emission associated with the target galaxies is important and limits current analyses. We discuss several mitigation strategies and quantify the residual modelling uncertainty. This work complements closely-related measurements of the kinematic Sunyaev-Zel'dovich and weak lensing of the same galaxies
Paramagnetic fluctuations of the magnetocaloric compound MnFe 4 Si 3
No full textInternational audienceAn inelastic neutron scattering technique is employed to investigate the paramagnetic spin dynamics in a single-crystalline sample of the magnetocaloric compound MnFe 4 Si 3 . In the investigated temperature range, 1.033 × T C to 1.5 × T C , where T C is the Curie temperature, the spin fluctuations are well described by the ferromagnetic Heisenberg model predictions. Apart from the Heisenberg exchange, additional pseudodipolar interactions manifest through a finite long-wavelength relaxation rate that vanishes at the transition temperature ( T C = 305 K). Based on the characteristic extent of spin fluctuations in wave-vector and energy space, we determine that the nature of magnetism in MnFe 4 Si 3 is localized above room temperature. This contrasts with the most celebrated Mn- and Fe-based magnetocaloric materials that are considered as itinerant magnets. The field dependence of the paramagnetic spectra shows a strong suppression of the quasielastic excitations, while a field-induced spin-wave mode appears at finite-energy transfers for a magnetic field of 2 T. This modification of the spectra suggests a decrease of magnetic entropy with applied magnetic field that finds echo in the magnetocaloric properties of the system. Published by the American Physical Society 202
Enhanced CH4 emissions from global wildfires likely due to undetected small fires
No full textInternational audienceMonitoring methane (CH4) emissions from terrestrial ecosystems is essential for assessing the relative contributions of natural and anthropogenic factors leading to climate change and shaping global climate goals. Fires are a significant source of atmospheric CH4, with the increasing frequency of megafires amplifying their impact. Global fire emissions exhibit large spatiotemporal variations, making the magnitude and dynamics difficult to characterize accurately. In this study, we reconstruct global fire CH4 emissions by integrating satellite carbon monoxide (CO)-based atmospheric inversion with well-constrained fire CH4 to CO emission ratio maps. Here we show that global fire CH4 emissions averaged 24.0 (17.7-30.4) Tg yr-1 from 2003 to 2020, approximately 27% higher (equivalent to 5.1 Tg yr-1) than average estimates from four widely used fire emission models. This discrepancy likely stems from undetected small fires and underrepresented emission intensities in coarse-resolution data. Our study highlights the value of atmospheric inversion based on fire tracers like CO to track fire-carbon-climate feedback
Cryogenics of a superconducting LINAC : SPIRAL2 from commissioning to operation
No full textInternational audienceThe SPIRAL2 superconducting linear accelerator (LINAC), which has been operational since 2019, employs superconducting, independently phased RF resonators to deliver a wide range of particle beams. Designed for flexibility in particle types, intensities, and energies, it utilizes superconducting quarter-wave resonators (QWRs), whose performances are critically dependent on the reliability of the cryogenic operation. This paper reviews the evolution from commissioning to the routine operation of the SPIRAL2 cryogenic system, initially commissioned in 2017. It highlights the key challenges encountered, including thermo-acoustic oscillations, thermal management, and abnormal behavior of cavities. Furthermore, it explores the integration of thermodynamic modeling and machine learning techniques to enhance system control and diagnose issues. This work serves as a comprehensive resource for advancing the cryogenic operation and performance of superconducting LINACs
Real-time SER measurements of CMOS bulk 40 nm and 65 nm SRAMS combined with neutron spectrometry at the JET Tokamak during its final D-T plasma operation
No full textInternational audienceWe performed soft error rate (SER) characterization of 40 nm and 65 nm bulk CMOS SRAMs combined with neutron spectrometry in the deuterium-tritium fueled JET tokamak during its final D-T plasma operation (Sept-Oct 2023) producing a series of several dozens of power pulses. Our experimental results demonstrate the impact of machine operation on the electronics reliability, emulating realistic conditions for circuits exposed to the partially radiation-shielded environment of future fusion reactors. Typical bit flip rates of 493 h -1 Gbit -1 for 65 nm SRAMs and of 2342 h -1 Gbit -1 for 40 nm SRAMs were measured for a residual machine induced neutron flux of ~3.15 x 10 5 cm -2 s -1 below the reinforced concrete slab (thickness of 1,045 mm) supporting the tokamak chamber. To complete this characterization work, a general methodology for the SER prediction in such a mixed-field D-T neutron radiation environment composed of both thermal and fast neutrons (up to 14 MeV) is presented and validated from this ensemble of experimental data for the two SRAM technologies. Finally, the interest of this approach for future tokamaks and high energy physics accelerators is discussed
Brittle fracture mechanisms and toughness of model low alloy steels chemically representative of macrosegregated forgings
No full textInternational audienceThe influence of the chemical composition on the brittle fracture behaviour of quenched and tempered low alloy bainitic steels was investigated thanks to the laboratory elaboration of three model alloys which have underwent a heat treatment to improve their chemical homogeneity. Two model materials with chemical compositions simulating zones of large (0.29%C) and intense (0.38%C) positive macrosegregation were characterized and compared with the nominal composition material (0.18%C). The ductile to brittle transition temperatures T56J and T0 of the materials with nominal and large carbon content are similar, whilst those of the material with the highest carbon content are unexpectedly significantly lower. Fractographic analyses indicate that the brittle fracture mechanisms depend also on the chemical composition. For 0.18 and 0.29%C, cleavage is the dominant brittle fracture mechanism, whilst a mix of cleavage and intergranular failure is observed for 0.38%C at the same levels of fracture energy or toughness. When cleavage failure is the dominant mechanism, it often originates at large molybdenum and manganese-enriched carbides located at grain boundaries likely identified as former austenitic grain ones. Microstructural analyses show variations of the large carbide population and ferritic grain size between the three alloys. Also, as carbon content increases, an evolution towards a lower bainite/martensite crystallographic microstructure is observed. The effects of these microstructural differences on the brittle fracture behavior is discussed
Early stages impact of volcanism on sedimentary diagenesis: The case of the newly born volcano, Fani Maoré
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La perte de la kinase neuronale DCLK3 conduit à un comportement de type anxieux et des déficits mnésiques
No full textInternational audienceDCLK3 (Doublecortin-like kinase 3) is a kinase preferentially expressed in neurons. Dclk3 variants are risk factors for psychiatric disorders and brain alterations linked to age-related mild cognitive impairment, suggesting this kinase could be important to cognition. However, the physiological role of DCLK3 remains unknown. Here, we generated and characterized mice with constitutive or brain-region specific Dclk3 knockout. We found that constitutive pan-deletion of Dclk3 is associated with an anxiety phenotype in male, associated with changes in brain metabolites in absence of major neuroanatomical alterations, motor or memory deficits. Moreover, virally mediated loco-regional conditional Dclk3 knockout in the dorsal hippocampus of adult mice led to spatial memory deficits and transcriptomic changes, characterized by increased expression of α2, β1, and β2 subunits of the GABAA receptor, down-regulation of neuronal activity-regulated genes such as the immediate early genes (e.g. Egr1, Fos, Per1 and Nr4r1), and transcriptional regulator-activity enriched in polycomb-repressive complexes (PRC). These new data reveal that Dclk3 modulates behavior and cognition in association with transcriptomic changes in the hippocampus, providing direct physiological evidence that this kinase is involved in synaptic plasticity, consistent with its crucial role in neurodegenerative and psychiatric diseases.DCLK3 (Doublecortin-like kinase 3) est une kinase préférentiellement exprimée dans les neurones. Les variants de DCLK3 sont des facteurs de risque de troubles psychiatriques et d'altérations cérébrales liés à une déficience cognitive légère liée à l'âge, suggérant que cette kinase pourrait être importante pour la cognition. Cependant, le rôle physiologique de DCLK3 reste inconnu. Ici, nous avons généré et caractérisé des souris avec un "knockout" constitutif ou spécifique à une région cérébrale du gène Dclk3. Nous avons constaté que la pan-délétion constitutive de Dclk3 est associée à un phénotype d'anxiété chez les mâles, associé à des changements dans les métabolites cérébraux en l'absence d'altérations neuroanatomiques majeures, de déficits moteurs ou de mémoire. De plus, l'inactivation virale de Dclk3 dans l'hippocampe dorsal de souris adultes a entraîné des déficits de la mémoire spatiale et des modifications transcriptomiques, caractérisées par une expression accrue des sous-unités α2, β1 et β2 du récepteur GABAA, une régulation négative des gènes régulés par l'activité neuronale tels que les gènes précoces immédiats (par exemple Egr1, Fos, Per1 et Nr4r1) et une activité régulatrice transcriptionnelle enrichie dans les complexes polycomb-répressifs (PRC). Ces nouvelles données révèlent que Dclk3 module le comportement et la cognition en association avec des modifications transcriptomiques dans l'hippocampe, fournissant une preuve physiologique directe que cette kinase est impliquée dans la plasticité synaptique, ce qui est cohérent avec son rôle crucial dans les maladies neurodégénératives et psychiatriques
Selective area molecular beam epitaxy of InSb on InP(111) : from thin films to quantum nanostructures
No full textInternational audienceInSb is a material of choice for infrared as well as spintronic devices but its integration on large lattice mismatched semi-insulating III–V substrates has so far altered its exceptional properties. Here, we investigate the direct growth of InSb on InP(111) B substrates with molecular beam epitaxy. Despite the lack of a thick metamorphic buffer layer for accommodation, we show that quasi-continuous thin films can be grown using a very high Sb/In flux ratio. The quality of the films is further studied with Hall measurements on large-scale devices to assess the impact of the InSb surface and InSb/InP interface on the electronic properties. Taking advantage of the optimized growth conditions for the formation of thin films, the selective area molecular beam epitaxial growth of nanostructures is subsequently investigated. Based on cross-sectional transmission electron microscopy and scanning near-field optical microscopy in the middle-wave infrared, ultra-thin and very long in-plane InSb nanowires as well as more complex nanostructures such as nano-rings and crosses are achieved with a good structural quality
Phytophthora alni Infection Reinforces the Defense Reactions in Alnus glutinosa - Frankia Roots to the Detriment of Nodules
No full textInternational audienceAlnus glutinosa, able to establish symbiosis with mutualistic bacteria of the genus Frankia, is one of the main species in European riparian environments, where it performs numerous biological and socio-economic functions. However, riparian ecosystems face a growing threat from Phytophthora alni, a highly aggressive waterborne pathogen causing severe dieback in A. glutinosa. To date, the tripartite interaction between the host plant, the symbiont Frankia and the pathogen remains unexplored but is critical for understanding how pathogen-induced stress influences the nodule molecular machinery and so on the host-symbiont metabolism. In the present study, we aimed to explore for the first time how P. alni affects the overall molecular processes of Alnus glutinosa – Frankia nodules, with a special focus on unraveling the spatial expression of defense mechanisms within these tissues. We conducted a laboratory experiment based on P. alni infection of young A. glutinosa seedlings nodulated with Frankia alni ACN14a, non-infected or infected with the pathogen P. alni. Multi-omics analyses were carried out on nodules (N) and associated roots (AR) of the same plant in order to underline the impact on the nodule molecular processes (i.e. N/AR markers) when the host plant is infected compared to non-infected plants. Our results revealed that P. alni infection modified the molecular nodule processes and induced reprograming of defense-related markers by a shift in associated roots to the detriment of nodules. These findings suggest that A. glutinosa reinforces locally its immune responses in roots but moderates this activation in nodule to preserve its Frankia symbiont