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Yield of the Four-Carbon Stabilized Criegee Intermediates from Isoprene Ozonolysis
No full textInternational audienceIsoprene is the single most abundant nonmethane hydrocarbon emitted into the atmosphere. Despite this, uncertainties in the oxidation chemistry remain. Here, we investigate the yields of Criegee intermediates that are produced from the ozonolysis reaction, where we conduct a series of atmospheric simulation chamber experiments in which the transient stabilized Criegee intermediates (sCIs) are titrated in the gas phase using either biacetyl or acetylpropionyl. This reaction yields a stable ketone-substituted secondary ozonide (SOZ), which was observed directly in the gas phase using a proton-transfer-reaction time-of-flight mass spectrometer operated in NH4+ mode. Both C1 and C4 sCIs were observed in this way, with the mass of the NH4+ adduct shifting according to the mass of the sCI and its diketone titrant. The relative abundance of the C4 sCI was constrained against C1 assuming a similar sensitivity for the two SOZ derivatives. This was supported by quantum chemical calculations that demonstrated very similar binding energies between NH4+ and the C1 and C4 SOZ adducts. Our results demonstrate an overall yield of ∼11% for the long-lived C4 sCIs, which may survive long enough to participate in various bimolecular reactions in the atmosphere
Adaptive local maxima windows for tree detection: A point process perspective
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Archétypes et avatars de la figure du Grand Méchant Loup dans la littérature jeunesse (et quelques à-côtés)
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Probing hard carbon fiber fabric synthesized by CO2 laser for Na-ion battery anodes
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Rapid cell turnover to model adipocyte size distribution
No full textInternational audienceWhite adipose tissue, composed of adipocyte cells, primarily stores energy as lipid droplets. The size of adipocytes varies significantly within the tissue according to the amount of stored lipids. A striking observation is that the adipocyte size distribution is bimodal, and thus, this tissue is lacking a characteristic size. We propose a novel dynamical model, based on a partial differential equation, to represent the adipocyte size distribution. The model assumes continuous adipocyte growth, with a velocity dependent on cell radius and extracellular lipid availability, together with constant rates of cell recruitment and death. We prove the existence and local stability of a unique stationary solution for a broad range of growth velocity functions. Choosing a parcimonious formulation, we show that only three parameters are enough to describe adipocyte size distributions measurements in rats. These parameters are robustly estimated through approximate Bayesian computation, and the model demonstrates excellent agreement with experimental data. This mechanistic, three-parameter framework offers a new and interpretable approach to characterizing adipocyte size distributions
Impact of Strain on Carbonaceous Matter Crystallinity: Insights from Raman Spectroscopy and microstructural analysis of strain gradients from exhumed accretionary complexes
No full textInternational audienceHighlights (to remove in a single file after correction)• RSCM parameter R1 reflects CM maturity evolution • CM maturity is increased in ductile and brittle high-strain zones• In shear zones, strain is the main cause of increased CM maturity• In breccia zone frictional heating cannot be ruled out.• RSCM signal stems from ~50-100nm particles distributed throughout the rock 0.</div
Neon Isotopes in Individual Vesicles of Icelandic Basaltic Glasses: Insights into the Origin of Light Volatile Elements on Earth
No full textInternational audienceThe origin of Earth's volatile elements remains a topic of debate due to the diverse sources within the solar system. Noble gases, owing to their chemical inertness, serve as powerful tracers for investigating planetary formation and mantle evolution. Noble gas isotopic studies suggest the existence of a preserved, relatively undegassed mantle reservoir, which is tapped by deep-rooted mantle plumes, such as those beneath the Galápagos, Hawaii, and Iceland. We present the first measurements of neon isotopic ratios in individual vesicles from a subglacially erupted basalt from Iceland. This method allows for the measurement of noble gas isotopes free from atmospheric contamination. Through statistical analyses of neon isotopic ratios in individual vesicles, we derive the isotopic composition for Ne of the Iceland mantle to be 12.63 ± 0.14 for the 20Ne/22Ne ratio. This value is in excellent agreement with the Galápagos mantle source and the signature expected for implanted solar wind, and lower than that of the value expected for the dissolution of a primordial atmosphere in the magma ocean. These results suggest a dominant role for solar wind implantation in accounting for Earth's mantle neon isotopic signature, and therefore as the source of light volatile elements. However, neither the implantation nor the nebular dissolution model is entirely satisfactory to explain all observations. Both models are not necessarily mutually exclusive, and more work should be conducted to tackle this long-standing issue
Immersive Environments
No full textInternational audienceImmersive environments present significant management opportunities for businesses, enabling innovative approaches toemployee engagement, customer interactions, and operational efficiency. Through the integration of virtual and augmented realitytechnologies, organizations can enhance training programs, improve workplace safety, and optimize operational support in sectorssuch as manufacturing and engineering. Additionally, immersive environments facilitate remote collaboration, talent acquisition,and the creation of engaging work environments, addressing the challenges of a competitive job market. Looking forward,advancements in technology and user experience will drive the widespread adoption of immersive environments, fosteringinterdisciplinary collaboration to create personalized and interactive experiences. As immersive technologies become moreaccessible and widespread, accompanied by supplementary tools and techniques, they hold immense potential to revolutionizeindustries beyond entertainment, including healthcare and education. The trajectory of immersive environments points towardscontinued growth, innovation, and enhanced human engagement across various sectors, signaling a transformative shift in howbusinesses operate and interact with their stakeholders. Also, we propose the holistic framework for immersive environments,comprising three interconnected elements: immersive technology, environment, and experiences. These elements collectively shapeand define the nature of immersive environments, influencing their creation, deployment, and impac
Supramolecular rotaxanes and polyrotaxanes as potential MRI contrast agents: a comprehensive 17O NMR and relaxometric study
No full textInternational audienceRotaxanes and polyrotaxanes made of substituted cyclodextrins (CDs) were designed as potential MRI contrast agents or bimodal optical and MRI probes. After characterization of the threading kinetics and the exact composition of the polyrotaxanes, their MRI properties have been investigated by 1 H relaxometry and 17 O NMR. We demonstrated that the relaxivity of these systems is increasing with increasing size (modified CDs, rotaxanes, and polyrotaxanes). 17 O NMR studies show that the various systems have similar water exchange rates, in the same range as that of Gd-DOTA-monoamide complexes. Interestingly, NMRD data of the smaller systems can be only analyzed by considering both local and global motions via Lipari-Szabo approach, underlining the importance of internal flexibility. On the other hand, the disubsituted rotaxane and the polyrotaxanes are highly rigid and can be characterized with a single rotational correlation time. Their relaxivity is considerably enhanced by a second sphere contribution which is strongly dependent on the structure. It increases from the rotaxane to the mono-and the disubstituted polyrotaxanes, and as expected, it diminishes with decreasing coverage of the axle. The fundamental understanding provided by this comprehensive study will help the design of versatile and more efficient supramolecular interlocked systems such as rotaxanes and polyrotaxanes for MRI applications.</div
