Diversity of eruptive styles inferred from the microlites of Mt Pelée andesite (Martinique, Lesser Antilles).

International audienceWe have studied the compositional and textural characteristics of plagioclase microlites from several dome-forming eruptions (dome, block-and-ash flows, and surges) and plinian fallouts of the recent period of activity of Mt Pelée in order to infer magma ascent dynamics. Dome-forming and plinian samples display a wide range of plagioclase microlite compositions, from An35 to An90 and An55 to An90, respectively. Microlites with compositions > An50-60 crystallized from a mafic melt that intruded the andesitic reservoir in proportion of ~10 vol %. During magma ascent in the conduit, the fraction, number density, and morphology of the decompression-induced microlites (compositions < An50-60) suggest that the plinian magmas experienced a nucleation-dominated crystallization regime with high undercooling. In contrast magmas from domes and block-and-ash flows were dominated by a growth regime with low undercooling, and the surges were influenced by both regimes. According to these crystallization regimes and new experimental data on H2O content of the matrix glasses, we propose magma relative ascent rates and fragmentation pressures for the different eruptive styles observed at Mt Pelée that may explain why surges are explosive events and why they may or may not be followed by a plinian event

Expérimentation d'une nouvelle méthode culturale sur billons (BED) pour produire des pommes de terres de semences destinées à l'exportation

Affiche présentée dans le cadre du Colloque de l'ARC, «Des racines et des ailes pour la recherche collégiale», dans le cadre du 85e Congrès de l’Acfas, Université McGill, Montréal, les 8 et 9 mai 2017.Pour le marché de l’exportation, la taille de la semence de pomme de terre est un important critère de qualité : un tubercule entier mesurant entre 38 et 55 mm est recherché. L’objectif du projet était d’évaluer l’impact de la taille et de la densité de plantation sur la taille des tubercules produits. Deux variétés, Chieftain et Harmony, ont été expérimentées avec deux distances entre les rangs, trois distances sur le rang et deux grosseurs de plantons. La production en plateforme a été comparée à la production traditionnelle en rang unique. Pour la variété Harmony, la production de tubercules de 38 à 55 mm a été significativement supérieure avec une distance entre les rangs de 40 cm, une distance sur le rang de 20 cm et un planton de 100 g. Le système en plateforme a généré un rendement total supérieur et a produit davantage de tubercules de la taille recherchée. Pour la variété Chieftain, la production de tubercules de 38 à 55 mm a été considérablement plus élevée avec une distance entre les rangs de 40 cm, des distances sur le rang de 20 et 25 cm et un planton de 100 g. Le projet a démontré que le système en plateforme est plus performant pour la production de semences de la taille recherchée pour l’exportation, que la densité de plantation, tant entre les rangs que sur le rang, a un impact sur la taille des tubercules produits, et enfin, que les variétés répondent différemment aux traitements de densité de plantation

Pouvons-nous réduire la dose d’azote après un retour de prairie?

Affiche présentée dans le cadre du Colloque de l'ARC, «Des racines et des ailes pour la recherche collégiale», dans le cadre du 85e Congrès de l’Acfas, Université McGill, Montréal, les 8 et 9 mai 2017.Au Québec, les émissions de gaz à effet de serre (GES) d’origine agricole représentent près de 8 % des émissions totales. Environ 40 % des émissions agricoles découle de l’usage des engrais minéraux et des engrais de ferme. Tout apport excédentaire d’engrais azoté dans les cultures se traduit par des émissions supplémentaires d’oxyde nitreux (N2O), un puissant gaz à effet de serre qui contribue aux émissions de GES. Plusieurs études ont démontré que la culture de maïs n’avait pas besoin d’apports importants d’azote en postlevée, après des retours de prairie. En collaboration avec des producteurs agricoles, 16 sites d’essais de fertilisation azotée ont été implantés sur des retours de prairie ayant reçu des engrais de ferme. Les traitements consistaient à apporter 4 doses d’azote minéral (0, 40, 80 et 120 kg N/ha). La teneur en nitrates du sol ainsi que les rendements à la récolte ont été évalués. La teneur en nitrates a confirmé l’effet significatif de la prairie et des engrais de ferme sur la teneur en azote disponible pour le maïs. L’apport d’azote minéral n’a pas eu d’effet significatif sur les rendements en azote, à l’exception d’un site. Le maïs cultivé sur un retour de prairie ne nécessite pas un ajout d’engrais minéral. Éliminer l’apport d’azote réduit tant les émissions de GES que les dépenses en engrais pour les producteurs

Equilibration Scales in Silicic to Intermediate Magmas - Implications for Experimental Studies

International audienceExperimental phase equilibrium studies are increasingly being used for the determination of intensive variables (P, T, fH2O, fO2 ) in silicic to intermediate magmas. In contrast, silicic igneous bodies are now perceived as open, periodically recharged, systems involving only limited chemical equilibration. Thus, the use of laboratory-determined crystal–liquid equilibrium data needs clarification. Here we review the field, petrological and geochemical evidence concerning states and scales of chemical equilibrium in silicic magma bodies. It is concluded that total chemical equilibrium is generally not the rule. However, a subsystem in local equilibrium (the reactive magma) can be identified. Equilibration scales in silicic magmas are rate-limited either by diffusive flux in crystals (DICL regime) or by diffusive flux in the melt (MD regime). The recognition that equilibrium in magmas is limited to a reactive subsystem requires phase equilibrium studies to be chemically scaled. Experiments, either of total or partial equilibrium type, should aim at a close reproduction of equilibrium states specific to natural systems. The laboratory reconstruction of the natural equilibrium states guarantees a precise determination of the pre-eruptive parameters and a reliable application of the experimental data to active volcanic systems

Routing Heterogeneous Traffic in Delay-Tolerant Satellite Networks

Delay-tolerant networking (DTN) offers a novel architecture that can be used to enhance store-carry-forward routing in satellite networks. Since these networks can take advantage of scheduled contact plans, distributed algorithms like the Contact Graph Routing (CGR) can be utilized to optimize data delivery performance. However, despite the numerous improvements made to CGR, there is a lack of proposals to prioritize traffic with distinct quality of service (QoS) requirements. This study presents adaptations to CGR to improve QoS-compliant delivery ratio when transmitting traffic with different latency constraints, along with an integer linear programming optimization model that serves as a performance upper bound. The extensive results obtained by simulating different scenarios show that the proposed algorithms can effectively improve the delivery ratio and energy efficiency while meeting latency constraints

(Eta6-arene) ruthenium(II) complexes and metallo-papain hybrid as Lewis acid catalysts of Diels-Alder reaction in water.

International audienceCovalent embedding of a (eta(6)-arene) ruthenium(II) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels-Alder reaction enhanced by two orders of magnitude in water

Evolution of High Throughput Satellite Systems: Vision, Requirements, and Key Technologies

High throughput satellites (HTS), with their digital payload technology, are expected to play a key role as enablers of the upcoming 6G networks. HTS are mainly designed to provide higher data rates and capacities. Fueled by technological advancements including beamforming, advanced modulation techniques, reconfigurable phased array technologies, and electronically steerable antennas, HTS have emerged as a fundamental component for future network generation. This paper offers a comprehensive state-of-the-art of HTS systems, with a focus on standardization, patents, channel multiple access techniques, routing, load balancing, and the role of software-defined networking (SDN). In addition, we provide a vision for next-satellite systems that we named as extremely-HTS (EHTS) toward autonomous satellites supported by the main requirements and key technologies expected for these systems. The EHTS system will be designed such that it maximizes spectrum reuse and data rates, and flexibly steers the capacity to satisfy user demand. We introduce a novel architecture for future regenerative payloads while summarizing the challenges imposed by this architecture

Inactivation of TIF1γ Cooperates with KrasG12D to Induce Cystic Tumors of the Pancreas

Inactivation of the Transforming Growth Factor Beta (TGFβ) tumor suppressor pathway contributes to the progression of Pancreatic Ductal AdenoCarcinoma (PDAC) since it is inactivated in virtually all cases of this malignancy. Genetic lesions inactivating this pathway contribute to pancreatic tumor progression in mouse models. Transcriptional Intermediary Factor 1 gamma (TIF1γ) has recently been proposed to be involved in TGFβ signaling, functioning as either a positive or negative regulator of the pathway. Here, we addressed the role of TIF1γ in pancreatic carcinogenesis. Using conditional Tif1γ knockout mice (Tif1γlox/lox), we selectively abrogated Tif1γ expression in the pancreas of Pdx1-Cre;Tif1γlox/lox mice. We also generated Pdx1-Cre;LSL-KrasG12D;Tif1γlox/lox mice to address the effect of Tif1γ loss-of-function in precancerous lesions induced by oncogenic KrasG12D. Finally, we analyzed TIF1γ expression in human pancreatic tumors. In our mouse model, we showed that Tif1γ was dispensable for normal pancreatic development but cooperated with Kras activation to induce pancreatic tumors reminiscent of human Intraductal Papillary Mucinous Neoplasms (IPMNs). Interestingly, these cystic lesions resemble those observed in Pdx1-Cre;LSL-KrasG12D;Smad4lox/lox mice described by others. However, distinctive characteristics, such as the systematic presence of endocrine pseudo-islets within the papillary projections, suggest that SMAD4 and TIF1γ don't have strictly redundant functions. Finally, we report that TIF1γ expression is markedly down-regulated in human pancreatic tumors by quantitative RT–PCR and immunohistochemistry supporting the relevance of these findings to human malignancy. This study suggests that TIF1γ is critical for tumor suppression in the pancreas, brings new insight into the genetics of pancreatic cancer, and constitutes a promising model to decipher the respective roles of SMAD4 and TIF1γ in the multifaceted functions of TGFβ in carcinogenesis and development

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29