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Di‐tert‐Butyl‐Peroxide–CuI Promoted Radical Hydrogermylation of Alkenes
No full textInternational audienceA new protocol for alkene hydrogermylation with hydrogermanes involving a radical chain‐transfer mechanism initiated by di‐ tert ‐butyl peroxide (DTBP) and CuI in methyl tert ‐butyl ether (MTBE) is disclosed. The method has good generality regarding both appropriate alkene substrate‐types and hydrogermanes, and compares well to other existing protocols, sometimes improving them, while being easy‐to‐implement. The developed system is particularly well‐suited for indenes and allows for the preparation of original 2‐germylated indanes through a previously unexplored approach
Playing with quantum-ness: exploring rare-earth ion spectroscopy for optical frequency metrology (invited)
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L’os et la carapace : instruments de communication avec les dieux et avec les hommes dans la Chine archaïque
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Du “montage intellectuel” au “cinéma de la chaine de montage” : penser l’image générative à partir d’Eisenstein
No full textInternational audienceCet article propose de comparer la théorie du « montage intellectuel » née sous la plume du cinéaste et théoricien soviétique S.M. Eisenstein à la fin des années 1920 et la place dévolue au montage dans les films réalisés par ce qu’on appelle aujourd’hui l’ « intelligence artificielle ». Sans entrer ici dans une étude du sens que la notion d’intelligence recouvrait pour Eisenstein, ni comparer celle-ci à l’épistémologie héritée de la cybernétique sur laquelle l’IA contemporaine se fonde, j’interrogerai le montage intellectuel à partir des écrits d’Eisenstein selon deux directions principales.J’appellerai problème sémiotique le questionnement relatif aux processus de signification qui émergent d’une conception « générative » de l’image et du montage. Dans cette optique, je m’attacherai d’abord à comparer l’opération de généralisation proposée par Eisenstein avec les formes de générativité employées par les IA génératives, notamment celles produisant des séquences d’images en mouvement. D’autre part, en revenant à l’objet spécifique sur lequel travaillait Eisenstein pendant sa théorisation du montage intellectuel (l’adaptation du Capital de Marx), je mettrai en évidence le rôle structurant joué par la mise au jour de la chaîne d’approvisionnement globalisée indispensable au développement du mode de production capitaliste. Pour le dire autrement, je voudrais examiner les liens qui existent entre les formes esthétiques du montage et ce qu’on pourrait appeler la « chaîne de montage » du capitalisme mondialisé. J’appellerai ce second versant problème matérialiste – qui concerne surtout l’usage intentionnel que l’on peut faire des images générées, dans un but discursif et critique – que je discuterai, pour finir, en relation avec une œuvre filmique utilisant l’IA, en suggérant que le montage qu’elle met en œuvre gagnerait à être considéré en réunissant ces deux aspects du montage intellectuel esquissé par Eisenstein
Reversal of Cushing syndrome by antibody-mediated neutralization of ACBP/DBI
No full textInternational audienceCushing syndrome (CS) is caused by an increase in endogenous or exogenous glucocorticoids, leading to major alterations in body composition, including visceral obesity, sarcopenia, osteoporosis, type 2 diabetes, and dyslipidemia. Cardiovascular complications resulting from CS are often lethal. We previously demonstrated that CS induced by oral corticosterone (CORT) supplementation in mice can be prevented by inhibition of the peptide hormone acyl-CoA binding protein (ACBP), encoded by the gene diazepam binding inhibitor (DBI). Here, we investigated whether ACBP/DBI inhibition could be used to treat, rather than prevent, CS. To this end, we initiated treatment with anti-ACBP/DBI monoclonal antibodies (mAbs) in mice three weeks after the start of CORT supplementation, when hyperphagia and body weight gain were already established. Two anti-ACBP/DBI mAbs, 7G4a (specific for mouse ACBP/DBI only) and 82 (which recognizes both mouse and human ACBP/DBI), were able to normalize food intake and halt weight gain in mice under continuous CORT treatment. In addition, both mAbs attenuated CORT-induced sarcopenia, adiposity in inguinal, perigonadal, and visceral fat depots, and fully restored metabolic parameters, including type-2 diabetes, insulinemia, free fatty acids, triglycerides, and liver transaminases. In conclusion, neutralization of ACBP/DBI may serve as an effective therapeutic strategy for the treatment of established CS
Low temperature brine formation by serpentinization on asteroid (162173) Ryugu
No full textInternational audienceSecondary mineral prevalence in Ryugu samples, similar to primitive carbonaceous-Ivuna type (CI) chondrites, suggests that aqueous alteration was a key factor in its formation. However, this general consensus masks our limited understanding of the specific mechanisms and environmental conditions involved in water-rock interactions on primitive asteroids. Highresolution cathodoluminescence (CL) analysis of the ubiquitous dolomite crystals in Ryugu samples reveals concentric epitaxial overgrowths with varying levels of Mn 2+ -activated luminescence. CL panchromatic images and spectral deconvolution provide compelling evidence for the evolution of aqueous fluids toward highly saturated brines. Given the close association of dolomite with widespread intergrowths of serpentine and saponite in the matrix, we propose that brine formation occurs as a byproduct of serpentinization. Unlike large-scale evaporation or freezing, this process can locally cause the hydrothermal fluid to dry out, significantly increasing its salinity over time. This leads to the sporadic precipitation of an evaporite mineral sequence, with dolomite forming at an early stage. This serpentinizationdriven brine formation model offers a convincing alternative to a purely prograde alteration history for Ryugu. It may also provide a better explanation for the alteration processes of Bennu and other CI chondrite parent bodies
Weak trophic position–body mass relationships undermine simple size-spectrum models for coral reefs
No full textInternational audienceAbstract Unravelling food web dynamics across biological communities is a central goal of ecology. In size-structured ecosystems, the shape of trophic pyramids is often inferred from their size spectra—the distribution of biomass across body-mass classes. Size-spectrum analysis has become a popular tool to study ecosystem functioning in aquatic ecosystems, including coral reefs. However, the key assumption behind size spectra, that body size directly and positively correlates with trophic position, has rarely been evaluated in these systems. Here, we test this assumption by quantifying body mass, population densities and estimating trophic position from stable isotopes for 325 fish species across four Indo-Pacific locations. Consistent with prior studies, we found a positive relationship between biomass and body mass. However, weak and variable relationships between body mass and trophic position led to higher biomass in primary consumers than in predators, as expected in traditional bottom-heavy or diamond-shaped trophic structures. Our findings thus challenge previous reports of coral reef fish biomass prevalence in higher trophic levels (e.g. inverted biomass pyramids), supporting earlier suggestions that simple size-spectrum models do not adequately represent the trophic structure of reef fish communities
On A Class Of Dynamical Poisson-Voronoi Tessellations
No full textConsider a dynamical network model featuring mobile stations on the Euclidean plane. The initial locations of the stations are given by a homogeneous Poisson point process. The stations are all moving at a constant speed and in a random direction. Consider fixed users located in the Euclidean plane, which are served by the mobile stations. Each user stays connected to the nearest station at any given point of time. Since the stations are moving, an user disconnects and connects with different stations over time, by always selecting which ever station is the closest. This gives rise to a dynamical version of the Poisson-Voronoi tessellation. The focus of this paper is on the sequence of "handover" events of a typical user, which are the epochs when its association changes. This defines a point process on the time-axis, the "handover point process". We show that this point process is stationary and we determine its main properties, in particular its intensity and the joint distribution of its inter-event times. We also analyze the handover Palm distributions of several variables of practical interest. This includes the distance to the closest mobile stations and the point process of all other mobile stations at handover epochs. The analysis is conducted both in the single-speed and in the multi-speed scenarios. It leads to the identification of the three dimensional state variables that "Markovize" the association dynamics. The analysis is based on a specific system of non-compact particles. The motivations are in the modeling of low or medium orbit satellite wireless communication networks. The model studied here is a planar "caricature" of this problem, which is initially defined on the sphere
