BRIEFS Sulfonated mesoposous carbons efficiently catalyze the glycosylation of various monosaccharides with alkyl alcohols.
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•Sulfonated mesoporous carbons exhibit high catalytic ...performances in the glycosylation of glucose with fatty alcohols.•Mesoporous channel improved the glycosylation rate of carbohydrates, thus limiting the side formation of humins.•Limiting the formation of humins concomitantly limit the deactivation rate of the catalyst which was successfully recycled.•Sulfonated mesoporous carbons was found applicable from different carbohydrates and different alkyl alcohols.•Space time yields of the Fischer glycosylation reactions are in line with the industrial requirements of the field.
Herein we investigated the catalytic performances of sulfonated mesoporous carbons in the glycosylation of carbohydrates with alkyl alcohols. Catalytic performances were compared to common solid acid catalysts previously reported for this reaction. Under optimized conditions, the targeted alkyl glycosides were obtained in 85% yield, together with a turn over frequency and a space time yield higher than those of the best heterogeneous catalysts reported so far in such reaction. Furthermore, the presence of mesoporous channels significantly lowered the deactivation rate of the catalyst in comparison to a non-porous sulfonated carbon.
This paper presents a reasoned synthetic overview of the major works on the preposition en. Taking a fundamentally cumulative approach, it aims at showing that each of the linguistic currents which ...dominated 20th-century research has contributed in its own way to a significant increase in our knowledge on en. Adapted from the source document
This paper presents a reasoned synthetic overview of the major works on the preposition en. Taking a fundamentally cumulative approach, it aims at showing that each of the linguistic currents which ...dominated 20th-century research has contributed in its own way to a significant increase in our knowledge on en. Cet article dresse un tableau synthétique et raisonné des travaux qui ont marqué I'étude de la préposition en. L'objectif consiste à montrer, dans une perspective fondamentalement cumulative, que les courants linguistiques qui ont dominé les recherches au XXe siècle ont chacun à leur manière contribué à accroître significativement nos connaissances sur en.
Magic angle spinning dynamic nuclear polarization (MAS-DNP) has become a key approach to boost the intrinsic low sensitivity of NMR in solids. This method relies on the use of both stable radicals as ...polarizing agents (PAs) and suitable high frequency microwave irradiation to hyperpolarize nuclei of interest. Relating PA chemical structure to DNP efficiency has been, and is still, a long-standing problem. The complexity of the polarization transfer mechanism has so far limited the impact of analytical derivation. However, recent numerical approaches have profoundly improved the basic understanding of the phenomenon and have now evolved to a point where they can be used to help design new PAs. In this work, the potential of advanced MAS-DNP simulations combined with DFT calculations and high-field EPR to qualitatively and quantitatively predict hyperpolarization efficiency of particular PAs is analyzed. This approach is demonstrated on AMUPol and TEKPol, two widely-used bis-nitroxide PAs. The results notably highlight how the PA structure and EPR characteristics affect the detailed shape of the DNP field profile. We also show that refined simulations of this profile using the orientation dependency of the electron spin-lattice relaxation times can be used to estimate the microwave
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field experienced by the sample. Finally, we show how modelling the nuclear spin-lattice relaxation times of close and bulk nuclei while accounting for PA concentration allows for a prediction of DNP enhancement factors and hyperpolarization build-up times.
From the polarizing agent geometry and EPR properties to the prediction of magic angle spinning dynamic nuclear polarization efficiency.
In the face of political and environmental uncertainty, adaptive management methods are needed to respond to variable natural resources and changing management frameworks. Based on close to real-time ...information updates, and harnessing modern technology, Real-Time Incentive (RTI) fisheries management is designed to co-evolve with the resource, enabling efficient responses to management issues as they arise, without the need for major structural changes. Through spatio-temporal management, and the use of a credit system, incentives can be incorporated as rewards for desirable actions. In order for such a new system to be useful and accepted, stakeholders must be involved in the development and design process. This paper details the consultative process carried out with Irish demersal fishery stakeholders in an effort to identify their likes and dislikes of the system, and work towards tailoring the RTI system into a practical solution that works for them. In this process, we achieved a detailed understanding of the fishery, the complexity of the system, and the challenges faced by the stakeholders, all of which must be considered when attempting to implement a new system such as RTI. A range of solutions were proposed, including new ideas for the future development of the RTI system. Most striking were the numerous ideas and approaches to tackling key issues currently facing the industry, many of which have relevance to existing fisheries management. Given the freedom and support to do so, fishing industry stakeholders appear eager to contribute to solving many of their own problems.
•Real-time Incentives (RTI) is an innovative spatio-temporal fisheries management proposal.•Irish demersal fishery stakeholders were consulted for their views.•Stakeholders advised how to adapt the system to real-world practicalities.•Stakeholders proposed new ideas for future development of the RTI system.•Stakeholders provided invaluable suggestions to improve current fisheries management.
This paper focuses on a set of utterances that all contain a prepositional phrase (PP) in intrapredicative position, in the form en + NP,
and mainly denoting a behaviour, a disguise or a fictitious ...role. The study first proposes a brief overview of previous studies of these
uses of en since G. Guillaume (1919), before going on to examine the PPs from a syntactic and semantic point of view. Lastly, it is argued
that in all the utterances examined, the PPs denote the result of a more or less abstract transformation process.
Non-thermal atmospheric plasma (NTAP) is a physical technology that has been previously employed for surface treatment (cleaning, coating, erosion, etc.) and water or air depollution. We show here ...that, beyond surface effects, NTAP is capable of enabling the complete and fast polymerization of various mono- and disaccharides in the solid state within only a few minutes and at low temperature (40-80 degree C). NTAP-induced polymerization involves a radical mechanism and yields water soluble polysaccharides with a mean molar mass of up to 100 000 g mol super(-1) and a mean hydrodynamic radius of 3 nm. Although polymerization reactions promoted by NTAP occurs in a random manner, the alpha -1,6 and beta -1,6 linkages are however dominant. Furthermore, we discovered that NTAP is highly selective, strongly favoring glycosylation over other chemical transformations in the bulk. Under our working conditions, glycosyl units are preserved that constitute the repeating units of the polysaccharide product. No chemical degradation (e.g. intramolecular dehydration reactions) was observed, allowing a white powder to be recovered with a yield higher than 93 wt%. From a practical point of view, NTAP has great potential for breakthrough in the production of polysaccharides, notably because it does not require the use of a solvent or catalyst, thus by-passing the traditional post-treatment of aqueous effluents and catalyst recycling characteristic of biotechnological polysaccharide production. Its efficiency at low temperature also prevents carbohydrates from degradation. Finally, NTAP proceeds on an on/off switch basis, allowing the polymerization reaction to be started and stopped quasi instantaneously.
The possibility of enriching in 17O the water molecules within hydrated biominerals belonging to the Ca-pyrophosphate family was investigated, using liquid assisted grinding (LAG) in the presence of ...17O-labelled water. Two phases with different hydration levels, namely triclinic calcium pyrophosphate dihydrate (Ca2P2O7·2H2O, denoted t-CPPD) and monoclinic calcium pyrophosphate tetrahydrate (Ca2P2O7·4H2O, denoted m-CPPT β) were enriched in 17O using a “post-enrichment” strategy, in which the non-labelled precursors were ground under gentle milling conditions in the presence of stoichiometric quantities of 17O-enriched water (introduced here in very small volumes ∼10 μL). Using high-resolution 17O solid-state NMR (ssNMR) analyses at multiple magnetic fields, and dynamic nuclear polarisation (DNP)-enhanced 17O NMR, it was possible to show that the labelled water molecules are mainly located at the core of the crystal structures, but that they can enter the lattice in different ways, namely by dissolution/recrystallisation or by diffusion. Overall, this work sheds light on the importance of high-resolution 17O NMR to help decipher the different roles that water can play as a liquid-assisted grinding agent and as a reagent for 17O-isotopic enrichment.
Chemical composition of river sediments and dissolved load is classically used to infer controls on continental weathering and, therefore, exert an important role on the understanding of the global ...carbon and biogeochemical cycles. To date, most studied river basins are strongly impacted by dam constructions; however, the effects of dams on sediment chemical compositions are little known. The Three Gorges Dam is one of the largest dams in the world and began impounding water in 2003 in the Changjiang basin. In order to investigate the impact of this dam on downstream sediment chemistry, temporal variation of sediment weathering intensity is reported here based on analyzed and compiled data between 1997 and 2018. Downstream sediments collected before 2003 are characterized by weak weathering intensity, in agreement with the overwhelming flux and fast transfer of sediments derived from the mountainous upper watershed. After the Three Gorges Dam operation, strong midlower riverbed erosion changed the roles of the midlower reaches from important sinks to major sources of sediments delivered to the East China Sea. This resulted in a progressive change of the sediment chemistry because the eroded midlower riverbed sediments were more deeply weathered, as confirmed by 150‐year‐old sediment cored in the lower mainstream and by mass‐balance calculations. This more intensive weathering may be explained by warmer climate and longer water‐rock interaction time in the midlower basin. Thus, this study suggests the need to quantify potential bias in weathering intensity and controls caused by damming activity in large river systems.
Key Points
Sediments collected downstream of the Three Gorges Dam displayed progressive but significant increase in weathering intensity since 2003
Simple mass balance calculation indicates progressive addition of strongly weathered sediments since the Three Gorges Dam operation
A core collected in the lower mainstream demonstrates that in situ weathered midlower riverbed sediments correspond to the missing source
La présente contribution propose de nouvelles avancées dans le but de relever l’un des défis majeurs posé par la classe des prépositions complexes à la communauté des chercheurs en linguistique : la ...possibilité d’en dresser une liste. En vue du développement d’une méthode entièrement automatisée pour extraire des candidats appartenant à cette classe, nous proposons une étude expérimentale où sont croisées deux approches pour caractériser les prépositions complexes : d’une part, l’application d’une grille multicritère proposée par Vigier & Kahng (2022) (suite à Stosic & Fagard (2019)) qui nécessite de combiner des tests manuels avec des mesures statistiques extraites de corpus ; d’autre part l’extraction automatisée d’une série d’indices textométriques, dont certains sont originaux, comme le taux d’insertion ou une mesure de dispersion composite. Nos observations montrent que sur une liste de candidats comportant de nombreux intrus, quelques indices peuvent se révéler discriminants, tels que le taux d’insertion, la dispersion par année ou par fichier, ainsi que, dans une moindre mesure, des mesures d’association statistique comme le t-score et log rapport de vraisemblance. Mais nous montrons également, en étudiant une liste de candidats construits avec la préposition « en », que ces observations sont à nuancer et dépendent notamment du comportement syntaxique des prépositions mises en jeu.
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