Publications scientifiques de l'Université de Reims Champagne-Ardenne
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Multi-step biocatalytic strategy to produce a library of original xylosides with various ester functions for cosmetic applications
No full textInternational audienceA biocatalytic strategy was developed to prepare a series of b-xylopyranosides with one or two ester functions using a multistep enzymatic transformation from biobased xylans. Transglycosylation reactions with a,u-diols were first performed using a commercially available xylanase to produce b-xylosides in good yields. In a second step, a selective esterification of the primary hydroxyl group of the aglycone moiety was carried out by reaction with carboxylic acids of cosmetic interest catalyzed by an immobilized commercial lipase. Finally a transesterification step led to the formation of xylosides esterified with two different acyl chains
3T MRI 4D flow sequence acquisition time reduction on a vascular phantom
No full textInternational audienceThis study aims to optimize 4D flow MRI of cerebral vessels by reducing scan time while preserving quantitative accuracy. A rigid internal carotid artery phantom with three aneurysms (Elastrat, Switzerland) was scanned on a 3T system using the Siemens BEAT FQ 4D flow sequence. Flow was generated by an MCP-Z pump under steady conditions. Sequences with various acceleration factors, such as reduced spatial resolution, GRAPPA, and partial Fourier, were compared to a fully sampled reference using pointwise velocity correlations (R²), with accuracy defined as at least 90% of the velocity variance explained. Acquisition time was reduced to 21s (20.6-fold). With R2 values between 0.91 and 0.97, the optimized parameter set preserved velocity information with only 23% of the variance remaining unexplained. With simulated cardiac gating (75 bpm), scan time was 4min 27s (24.6-fold reduction). The proposed acceleration framework enables rapid, accurate 4D flow MRI of cerebral vessels for potential neurovascular applications
Between Autonomy and Determinism: The Meso-Régulation Approach Applied to Digital Platforms
No full textInternational audienceThis article shows that the French régulation approach, although never explicitly framed as such, relies on methods rooted in meso-level analysis, situated between micro and macro perspectives. This paves the way for a research agenda that explores how the socioeconomic arenas under study are differentiated and how their actors develop diverse institutional arrangements across groups of interest. Building on multiple case studies, we propose a conceptual framework to examine meso-régulation dynamics. These cases highlight sectoral, territorial, or professional forms of régulation that do not, however, amount to an “accumulation regime” in the classical sense. Digital platforms serve as an empirical example to test the heuristic potential of the meso-régulation perspective
4D (space + time) datasets of spruce wood enzymatic hydrolysis
No full textInternational audienceThe conversion of lignocellulosic biomass from plant cell walls into bioproducts can contribute to reducing dependence on fossil sources and achieving sustainable development. Biotechnological conversion of lignocellulosic biomass has several advantages over other conversion approaches such as thermochemical and chemical conversions. These advantages include improved efficiency and specificity for desired products, ecological compatibility and reduced toxicity. Enzymatic transformation is a key step in biotechnological conversion. To achieve a cost-effective conversion, a comprehensive understanding of cell wall enzymatic hydrolysis is required. Despite progress, the enzymatic hydrolysis at microscale is comparatively understudied and lacks comprehensive investigation. Addressing this gap requires collection of time-lapse image datasets of cell wall enzymatic hydrolysis which is a technically demanding task. Furthermore, accurate processing of the time-lapse images to identify and track individual cell walls is particularly challenging, notably because of the sample drift present in the images. Recently, an efficient image processing pipeline, called AIMTrack, has been developed which uses an enhanced divide-and-conquer strategy to divide time-lapse images into clusters whose sizes are dynamically adjusted to the deconstruction extent. The image registrations are then limited to clusters and the resulting transformations are combined to correct sample drift across time-lapse images. Subsequently AIMTrack provides segmentation of time-lapse images where voxels belonging to the same cell walls are labelled with a unique identifier. The time-lapse image datasets presented here consist of time-lapse images of spruce wood cell walls acquired during enzymatic hydrolysis using a cellulolytic enzyme cocktail at two enzyme loadings of 15 and 30 FPU/g biomass. Control time-lapse datasets which are acquired under the identical conditions, but without addition of enzymes, are also included. Both control and hydrolysis datasets are processed using AIMTrack to track the cell walls from time-lapse images. The generated segmentations are also provided
Adaptation de domaine pour la segmentation biomédicale à l’ère des modèles de fondation
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La gestion des connaissances à l’ère de l’IAG
No full textInternational audienceCe séminaire propose une réflexion exploratoire sur la gestion des connaissances à l’ère de l’intelligence artificielle générative, en mettant en évidence les principaux enjeux et perspectives de recherche. Il s’appuie à la fois sur des travaux empiriques antérieurs et sur une revue de la littérature, dans une démarche exploratoire privilégiant l’identification de questionnements ouverts plutôt que la production de résultats stabilisés.Après un retour sur les fondements de la gestion des connaissances et ses manifestations organisationnelles, l’analyse examine les transformations induites par l’IA générative dans les processus de création, de partage et d’utilisation des connaissances. Elle souligne en particulier que la valeur du knowledge management ne réside pas dans l’automatisation de l’accès ou de l’application des connaissances, mais dans la capacité des acteurs à les interpréter, les contextualiser et les mobiliser de manière réflexive.Dans cette perspective, la gestion des connaissances à l’ère de l’IA générative apparaît moins comme un enjeu technique que comme une problématique organisationnelle, humaine et éthique
Cumulative lung dose–volume predictors of radiation pneumonitis in thoracic reirradiation: A systematic scoping review
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Influence of salinity on the larval development and juvenile fitness of the estuarine shrimp Palaemon longirostris
No full textInternational audienceSalinity fronts structure the nursery habitat of the estuarine shrimp Palaemon longirostris. This species inhabits estuaries in Western Europe and North Africa. Using a salinity gradient representative of estuarine conditions (10, 15, 20, 25, and 30 PSU), we evaluated the effects of salinity on larval history traits (including larval survival, developmental pathways, duration of larval development, metamorphosis success, larval weight gain and juvenile weight). Our results demonstrate that increasing salinity towards marine levels shortened larval development time and improved metamorphosis success, with the best results observed at 25 PSU. Juvenile weight and weight gain were significantly higher at elevated salinities, indicating a positive relationship between salinity and larval fitness. Conversely, low salinities were associated with reduced survival and performance, indicating limited osmoregulatory capacity in response to osmotic stress. These findings emphasize the important role of salinity in determining the phenotypic plasticity and survival of P. longirostris larvae. Together, these results highlight an operational optimum of around 25 PSU in the laboratory and sharp declines in performance at the extremes of the estuarine gradient. By clearly demonstrating for the first time an optimum high salinity level for the larval development of P. longirostris, this study provides original insights into the life cycle and population dynamics of this species
