Characterization Study of CO2, CH4, and CO2/CH4 Hydroquinone Clathrates Formed by Gas–Solid Reaction

Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO2 and CH4. This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO2, pure CH4, and an equimolar CO2/CH4 mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and 13C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications

Actes de la 9ème conférence des Technologies de l’Information et de la Communication pour l’Enseignement (TICE 2014)

National audienceLe cycle de conférence TICE a pour objectif de faire tous les deux ans le point sur les résultats de recherches, les nouvelles applications, les derniers usages, et les retours d’expériences dans le domaine de l’éducation supérieure numérique. Le colloque TICE 2014 est organisé par l’IUT de Beziers, une composante de l’Université Montpellier 2. Cette neuvième édition du colloque TICE sera l’occasion de rassembler à Béziers, du 18 au 20 Novembre 2014, la communauté scientifique et industrielle des TICE autour du thème « Nouvelles pédagogies et sciences et technologies du numérique »

CO2–Hydroquinone Clathrate: Synthesis, Purification, Characterization and Crystal Structure

Organic clathrate compounds, particularly those formed between hydroquinone (HQ) and gases, are supramolecular entities recently highlighted as promising alternatives for applications such as gas storage and separation processes. This study provides new insights into CO2–HQ clathrate, which is a key structure in some of the proposed future applications of these compounds. We present a novel synthesis and purification of CO2–HQ clathrate monocrystals. Clathrate crystals obtained from a single synthesis and native HQ are characterized and compared using Raman/Fourier transform infrared/NMR spectroscopies, optical microscopy, and thermogravimetric analysis coupled to mass spectrometry. The molecular structure of the clathrate has been resolved by X-ray diffraction analysis, and detailed crystallographic information is presented for the first time

alpha-Tocopherol Acetate Attenuates Mitochondrial Oxygen Consumption and Maintains Primitive Cells within Mesenchymal Stromal Cell Population

We present here the data showing, in standard cultures exposed to atmospheric O-2 concentration, that alpha-tocopherol acetate (alpha-TOA) has a positive impact on primitive cells inside mesenchymal stromal cell (MstroC) population, by maintaining their proliferative capacity. alpha-TOA decreases the O-2 consumption rate of MStroC probably by impacting respiratory chain complex II activity. This action, however, is not associated with a compensatory increase in glycolysis activity, in spite of the fact that the degradation of HIF-1 alpha was decreased in presence of alpha-TOA. This is in line with a moderate enhancement of mtROS upon alpha-TOA treatment. However, the absence of glycolysis stimulation implies the inactivity of HIF-1 alpha which might - if it were active - be related to the maintenance of stemness. It should be stressed that alpha-TOA might act directly on the gene expression as well as the mtROS themselves, which remains to be elucidated.This is the peer reviewed version of the paper: Loncarić, D., Rodriguez, L., Debeissat, C., Touya, N., Labat, V., Villacreces, A., Bouzier-Sore, A.-K., Pasquet, J.-M., de la Grange, P. B., Vlaski-Lafarge, M., Pavlović, S., & Ivanović, Z. (2021). Alpha-Tocopherol Acetate Attenuates Mitochondrial Oxygen Consumption and Maintains Primitive Cells within Mesenchymal Stromal Cell Population. Stem Cell Reviews and Reports, 17(4), 1390–1405.[ https://doi.org/10.1007/s12015-020-10111-9]Related to published version: [https://imagine.imgge.bg.ac.rs/handle/123456789/1491

Contrôle de l'activité de l'apprenant : suivi, guidage pédagogique et scénarios d'apprentissage

International audienceL'objet de ce chapitre est de faire le point sur les principaux modèles traitant du contrôle de l'activité de l'apprenant ou de groupes d'apprenants au sein de dispositifs de formation reposant sur l'utilisation d'environnements informatiques

Interannual variations in euphausiid life stage distribution in the Dumont d'Urville Sea from 2004 to 2008

Euphausiid larvae were caught by oblique tows of a double-framed bongo net at 118 stations along the coast of Terre Adelie during every summer from 2004-2008. Larvae of Euphausia crystallorophias Holt and Tattersall and Thysanoessa macrura G.O. Sars were observed in the study area every year in contrast to larvae of Euphausia superba which were absent during the entire period of sampling. Highest abundances of both species were observed during the summer of 2005 and the lowest in the summer of 2004. Larvae of E. crystallorophias dominated every year and comprised more than 80% of the total abundance of euphausiid larvae. Within species, the calyptopis stages especially calyptopis 1 of E. crystallorophias dominated compared to furcilia stages of T. macrura which were less abundant. For both species, spatio-temporal variations in abundances of developmental stages were significantly correlated to density and salinity of the deep water layer. In the case of calyptopis 3 of E. crystallorophias, spatio-temporal variations were correlated with the number of days between the end of the sea ice retreat and the sampling day and for T. macrura inversely correlated to temperature of surface water layer. These variations are discussed and related to the timing of sea ice retreat, the sea ice concentration as well as metabolic conditions of adults of both species during their spawning period

Étude du comportement analytique de la mirtazapine en chromatographie liquide haute performance et électrophorèse capillaire de zone

La mirtazapine est un antidépresseur de nouvelle génération, antagoniste des récepteurs α2 présynaptiques d'action centrale, permettant l'augmentation de la neurotransmission noradrénergique et sérotoninergique. L'identification et le dosage dans les milieux biologiques de cette molécule et de son metabolite actif, la déméthylmirtazapine, peuvent être réalisés par chromatographie liquide haute performance (CLHP) et par électrophorèse capillaire de zone (ECZ). La mirtazapine possède deux fonctions amine de propriétés acido-basiques très différentes. Le pKa du groupement amino-2-pyridine est de 3,60 ± 0,05, et celui de la fonction amine tertiaire, de 7,50 ± 0,05. Nous avons étudié l'incidence de ces constantes d'ionisation sur le comportement analytique de la mirtazapine parmi les antidépresseurs de nouvelle génération, dans le cadre du développement de méthodes de séparation en CLHP et en ECZ. Nous présentons la séparation d'un mélange de 12 antidépresseurs, dont la mirtazapine et la déméthylmirtazapine, en CLHP sur une colonne Satisfaction® RP 18 AB maintenue à 45° C avec une phase mobile acétonitrile/tampon pH 4,8 (35 : 65, v/v). En ECZ, la séparation a été optimisée à 15° C sur un capillaire en silice fondue conditionné par un tampon borate 42 mM (pH 9,5) et méthanol (80 : 20, v/v) et une tension appliquée de 15 kV. En CLHP, nous avons mis en évidence l'influence particulièrement importante du pH de la phase mobile (pH 3 à pH 4,95) et de la température (25° C à 50° C) sur les temps de rétention de la mirtazapine et de son metabolite. En ECZ, le pH du tampon de migration (entre pH 9,2 et pH 9,9) a une influence homogène sur la migration de l'ensemble des antidépresseurs, tous faiblement ionisés dans ces conditions. Les comportements analytiques de la mirtazapine et de la déméthylmirtazapine sont donc très dépendants des variations de pH dans des zones proches des deux pKa

Isotopic niches and trophic levels of myctophid fishes and their predators in the Southern Ocean

International audienceWe report the trophic structure of a myctophid assemblage by measuring the isotopic niches of 14 species living in Kerguelen waters, southern Indian Ocean. Most of the species show distinct isotopic niches that differ by at least one of the two niche axes (d13C habitat and d15N trophic position), indicating trophic partitioning within the assemblage. Strong niche segregation occurs within each of the three most common genera of myctophids (Electrona, Gymnoscopelus, and Protomyctophum), illustrating the different mechanisms (habitat and dietary segregation) that allow coexistence of closely related species. Calculated trophic levels (TLs) of myctophids ranged from 3.3 to 4.2, showing that they are secondary and tertiary consumers in the pelagic ecosystem. The positive relationship between TL and standard length of fish points out a structuring effect of size, with larger species (Gymnoscopelus spp.) occupying a higher trophic position than smaller species (Krefftichthys anderssoni and Protomyctophum spp.). Myctophids occupy an intermediate trophic position between macrozooplanktonic crustaceans and seabirds and marine mammals within the pelagic ecosystem. However, the TLs of large myctophids overlap those of crustacean-eating seabirds [e.g., Eudyptes spp. (crested penguins) and Pachyptila belcheri]. The isotopic niche of myctophids indicates that Aptenodytes patagonicus (king penguin) adults prey upon K. anderssoni when they feed for themselves, thus exemplifying the usefulness of isotopic datasets on potential prey of predators to depict trophic relationships

A GIS approach to estimating interannual variability of sea ice concentration in the Dumont d'Urville Sea near Terre Adelie from 2003 to 2009

A Geographic Information System (GIS)-based investigation into the interannual variability of sea ice concentration was conducted in the Dumont d'Urville Sea off the Terre Adelie coastline, south of 65 degrees S and between 139 and 146 degrees E. Sea ice concentration data derived from Advanced Microwave Scanning Radiometer-EOS (AMSR-E) data were analysed for the period 2003 to 2009. Sea ice concentration was found to be least variable in three regions, namely the Buchanan Bay/Watt Bay region (143-145 degrees E), along similar to 65.5 degrees S (west of 144.5 degrees E), and the Adelie Bank northeast of Dumont d'Urville near 66 degrees S, 140.5 degrees E. The remaining areas had relatively high interannual variability, in particular the Adelie Basin (similar to 66 degrees S, similar to 140 degrees E) and the outer fringe of the Mertz Glacier Polynya (MGP). In general, higher sea ice concentration conditions were experienced in the west of the study area (i.e., where annual fast ice recurs), and open water dominated in the MGP and in the northeast. The years 2007-2009 experienced greater persistence of higher sea ice concentration than earlier years. This study provides a baseline for assessing changes in the regional sea ice regime that may occur since the calving of the Mertz Glacier in February 2010. (C) 2011 Elsevier B.V. and NIPR. All rights reserved

Phytoplankton biodiversity and NW Mediterranean Sea warming: changes in the dinoflagellate genus Ceratium in the 20th century

International audienceOur knowledge of the response of phytoplankton to climate change is restricted by the lack of phytoplankton long-term studies, especially those reporting species data. To circumvent this problem, we combined recent data from sampling at monitoring sites with old bibliographic data. The study was conducted on the genus Ceratium (planktonic dinoflagellates) in the NW Mediterranean, as numerous studies have been conducted in the area since the beginning of the 20th century. In addition, species of this highly diverse genus are known to be particularly sensitive to water temperature, and should thus be responsive to global warming. The temporal distribution of Ceratium species over the last century showed a progressive disappearance from the surface layer of likely stenothermic species, which may have moved to deeper layers in response to water warming, along with a decrease of species richness during the annual cycle. Seasonal and phenological aspects of Ceratium assemblages were also affected, as illustrated by the earlier timing in the minimum of richness. A change in the overall species assemblage also occurred from past to present in the Ligurian Sea, suggesting a warming in this area consistent with the development in surface water temperatures. Our results suggest that Ceratium species may constitute good biological indicators of warming in the NW Mediterranean Sea. In addition, the present study showed the importance of time-series data and the value of historical literature as the basis for ecological studies of long-term trends needed to substantiate our current understanding of the impact of global change on marine biodiversity