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Late gas released in the young Kuiper belt could have significantly contributed to the carbon enrichment of the atmospheres of Neptune and Uranus
No full textInternational audienceContext. Exo-Kuiper belts have been observed for decades, but the recent detection of gas in some of them may change our view of the Solar System’s youth. Late gas produced by the sublimation of CO (or CO2) ices after the dissipation of the primordial gas could be the norm in young planetesimal belts. Hence, a gas-rich Kuiper belt could have been present in the Solar System. The high C/H ratios observed on Uranus and Neptune could be a clue to the existence of such late gas that could have been accreted onto young icy giants.Aims. The aim of this paper is to estimate the carbon enrichment of the atmospheres of Uranus and Neptune caused by the accretion of the gas released from a putative gas-rich Kuiper belt. We want to test whether a young, massive Kuiper belt such as that usually assumed by state-of-the-art models can explain the current C/H values of ~50–80 times the protosolar abundance for Uranus and Neptune.Methods. We developed a model that can follow the gas released in the Kuiper belt, as well as its viscous evolution and its capture onto planets. We calculated the final C/H ratio and compared it to observations. We studied the influence of several important parameters such as the initial mass of the belt, the viscosity of the disc, and the accretion efficiency.Results. We find that the assumption of a primordial Kuiper belt with a mass of tens of Earth masses leads to significant CO gas accretion onto the giants, which can lead to high C/H ratios, especially for Uranus and Neptune. We find that an initial Kuiper belt of ~50 M⊕ could entirely account for the present-day C/H enrichment in the atmospheres of Uranus and Neptune. However, given the fact that S/H is also significantly enriched in the deep atmospheres of these planets, but still less enriched than C/H, a more likely scenario is that these planets first accreted an envelope enriched in C/H and S/H in similar amounts, and that the sublimation of CO from the Kuiper belt led to an additional enrichment in C/H of perhaps 30 times the protosolar value in Neptune, and 20 times in Uranus. For the same model, the additional enrichments in C/H are 2 and 0.2 in Saturn and Jupiter, respectively.Conclusions. Our model shows that a relatively massive gas-rich Kuiper belt could have existed in the Solar System’s youth, which significantly enriched the atmospheres of Uranus and Neptune with carbon. Late gas accretion and its effect on the metallicities of the outer giant planets could be a universal scenario that also occurs in extrasolar systems. Observations of sub-Jupiter exoplanets could provide very useful information to better constrain this scenario, with an enrichment in carbon and oxygen (for sufficiently war planets) compared to other elements that should be inversely proportional to their envelope mass
Comment susciter le plaisir d'écrire quand la norme prime ?
No full textInternational audienceThe aim of this study is to identify the relationship to writing of future teachers in training, who wrote a story about a school memory of writing. Analysis of 140 writings shows that compliance with the school norm is a source of anxiety for writers, and damages the pleasure of writing, which lies not in the act of writing itself, but in the school or social judgment passed on the writings. Our analyses confirm that the relationship with writing is not constructed in an isolated or abstract way: it is profoundly shaped by learning and teaching experiences.Cette étude vise à cerner le rapport à l’écriture de futurs enseignants en formation qui ont rédigé un récit sur un souvenir scolaire de rédaction. L’analyse de 140 écrits montrent que le respect de la norme scolaire est une source d’angoisse pour les scripteurs et endommage le plaisir d’écrire lequel ne réside pas dans l’acte d’écrire lui-même, mais dans le jugement scolaire ou social porté sur les écrits. Nos analyses confirment que le rapport à l’écriture ne se construit pas de manière isolée ou abstraite : il est profondément façonné par les expériences d'apprentissage et d'enseignement vécues
Products of Sublimated Ammonium Salts
No full textInternational audienceAmmonium salts are increasingly suspected to play an important role in astrochemistry, both as a reservoir, particularly of sulfur and nitrogen, and as a potential source of complex molecules, in spite of the lack of knowledge on their sublimation process and products. We have studied the sublimation of four ammonium salts using mass-selected photoelectron spectroscopy coupled to VUV synchrotron radiation to identify most of the sublimation products. We show that if proton transfer yields stable products without rearrangement, leading to NH3 or CH3NH2, this route will be favored. Furthermore, we suggest that the sublimation of salts could lead to the formation of complex molecules such as formamide and also constitute a possible route for the formation of isonitriles.</div
Diversité des mémoires : éclairage des sciences sociales. Intervention de Anne Hertzog
No full textInternational audienceL'intervention porte sur la réappropriation contemporaine des mémoires de la Grande Guerre, et les processus de patrimonialisation portés par les communautés des diasporas chinoises et indiennes en France
Towards CMC measurement using an inductive RF technique for non-ionic surfactants in complex media
No full textInternational audienceDue to their unique chemical feature – associating hydrophilic and lipophilic parts in thesame molecule, surfactants are strongly used in cosmetics applications. In particular, the stability of emulsions is due to their ability to reduce surface tension. When the concentration of surfactants is enough, the barrier that they form at interfaces being saturated, they begin to aggregate in spherical micelles which are also amphiphilic structures. The associated concentration is known as Critical Micellar Concentration (CMC). On their own, i.e. with surfactants in solution, the formation of micelles can help with active product delivery control or optimization of detergency properties.In order to measure the CMC value, most methods resort to surface tension, conductivity, or fluorescence measurements. However, those techniques can lead to inaccurate evaluations due to impurities, additional compounds necessary for the stability of the product, and even surfactant nature. The CMC is particularly difficult to obtain for a complex fluid containing multiple surfactants.This work proposes an alternative technique based on inductive measurement of the complexpermittivity at RF frequencies. This quantity is directly linked to the polarizability of the electriccharges dispersed around the micelles, as explained by Gouy-Chapman’s and Stern’s models.This inductive RF technique is tested with surfactants dispersed in water, thickened water,and oil. The results are compared with ones obtained from classic methodology using tensiometer.Furthermore, the assessment of CMC value of mixture is discussed. Results demonstrate that thetechnique is sensitive enough to measure the CMC of one or multiple surfactants in various media, anticipating the interest of the technique for complex fluids usually used in cosmetic field
Rule-based Approaches to the Automatic Generation of Puns Based on Given Names in French
No full textInternational audienceHumor is a cornerstone of human interactions. Because puns and word plays lie in the margins of phonology, syntax and semantics, large language models struggle with their generation. In this paper, we present two versions of a tool designed to create a typical kind of French joke known as "Monsieur et Madame" jokes. We then discuss the main challenges and limitations rule-based systems face when creating this kind of puns
Le livre blanc de l’AFLA
No full textInternational audienceCe livre blanc couvre les projets financés et en collaboration avec des partenaires extérieurs (y compris les thèses), les revues en linguistique appliquée et les cursus existants
Les lieux de l'ENA, un état des lieux
No full textThis text provides a brief overview of the history of the successive or concurrent locations of the Ecole nationale d'administration (France) in Paris and Strasbourg between 1945 and 2025.Ce texte propose une rapide survol de l'histoire des localisations successives ou concomitantes de l’École nationale d’administration (France)à Paris et à Strasbourg, entre 1945 et 2025