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Study of essential oil extraction from Moroccan Rosmarinus officinalis L. by distillation based on quantum chemical calculation and molecular dynamics simulation
No full textInternational audienceIn this work, essential oils were extracted from rosemary leaves (Rosmarinus officinalis L.) from the eastern region of Morocco using hydrodistillation (Hd) and steam distillation (Sd). The yield, chemical composition, thermal stability, and antioxidant activity of the essential oils obtained by the two methods were compared. Determining the chemical composition of rosemary essential oil, with GC-MS, showed a significant qualitative and quantitative difference in certain components. The Sd method improved the extraction of sesquiterpene compounds with high molecular weight and low vapour pressure. The findings reveal that sesquiterpene and oxygenated monoterpenes in essential oils improved the antioxidant activity and thermal stability. Determining antioxidant activity using DPPH and the β-carotene bleaching assay showed that the Sd and Hd oils presented good radical scavenging activity (IC50 = 4960 μg/mL for Hd oil and 4570 μg/mL for Sd oil), capable of delaying β-carotene discolouration with 16.3 and 9.71% inhibition for Sd and Hd respectively. Thermal stability analysis of the oil products was performed using TGA/DTG analysis, and the results showed that the decomposition points of Hd oil and Sd oil were 362 and 368 K respectively. Furthermore, to identify intermolecular interactions and develop better knowledge of phenomena occurring during the extraction of the family of sesquiterpene compounds by water, quantum chemical calculation and molecular simulation by molecular dynamics (MD) were performed. The results suggested the relative stability of caryophyllene-water and the development of intermolecular bonding interactions of van der Walls and steric effect, improving extraction of the substance studied under steam distillation conditions
Selective extraction of carnosic acid, carnosol, and rosmarinic acid from Rosmarinus officinalis L. using supercritical fluid and their antioxidant activity
No full textInternational audienceRosmarinus officinalis L. is one of the most widely exploited medicinal plants for its bioactive compounds, including rosmarinic acid (RA), carnosic acid (CA) and carnosol (CAR). This study aims to selectively extract these compounds, using supercritical fluids extraction with carbon dioxide and ethanol as co-solvents, based on the Hansen solubility parameters approach. This approach predicted that CA and CAR are highly soluble in the supercritical fluid. However, a weak interaction was predicted between RA and this fluid. The experimental findings indicated the highest amounts of RA and CA were observed at 150 bar and 80°C, resulting in yields of 3.43 mg/g dry weight (DW), and 18.9 mg/g DW, respectively. Favourable extraction conditions for CAR were recorded at 250 bar and 40°C, with a content of 19.1 mg/g DW. Evaluation of antioxidant activity using DPPH tests revealed that extracts obtained at 250 bar at 40 and 80°C rich in CAR have a stronger antioxidant power
Sugar-Based Surfactants: Effects of Structural Features on the Physicochemical Properties of Sugar Esters and Their Comparison to Commercial Octyl Glycosides
No full textInternational audienceTwo series of sugar esters with alkyl chain lengths varying from 5 to 12 carbon atoms, and with a head group consisting of glucose or galactose moieties, were synthesized. Equilibrium surface tension isotherms were measured, yielding critical micellar concentration (CMC) surface tensions at CMC (γcmc) and minimum areas at the air–water interface (Amin). In addition, Krafft temperatures (Tks) were measured to characterize the ability of molecules to dissolve in water, which is essential in numerous applications. As a comparison to widely used commercial sugar-based surfactants, those measurements were also carried out for four octyl d-glycosides. Impacts of the linkages between polar and lipophilic moieties, alkyl chain lengths, and the nature of the sugar head group on the measured properties were highlighted. Higher Tk and, thus, lower dissolution ability, were found for methyl 6-O-acyl-d-glucopyranosides. CMC and γcmc decreased with the alkyl chain lengths in both cases, but Amin did not appear to be influenced. Both γcmc and Amin appeared independent of the ester group orientation. Notably, alkyl (methyl α-d-glucopyranosid)uronates were found to result in noticeably lower CMC, possibly due to a closer distance between the carbonyl function and the head group
Numerical study of the spark ignition of hydrogen-air mixtures at ambient and cryogenic temperature
No full textInternational audienceAn accurate determination of minimum ignition energy (MIE) is essential for assessing electrostatic hazards and characterising potential for occurrence of combustion in flammable mixtures. This is of utmost importance for hydrogen-air mixtures characterised by a MIE equal to 0.017 mJ, whereas conventional flammable gases are characterised by MIE typically higher than 0.1 mJ. The study aims at developing and validating a CFD three-dimensional model capable to simulate complex unsteady physical and chemical phenomena underlying capacitive discharge spark. The model accounts for the experimental apparatus details, including the effect of electrodes' gap and associated heat losses. The numerical approach accurately reproduced the experimental measurements of MIE for mixtures of hydrogen with air at initial temperature ranging from ambient (T = 288 K) to cryogenic (T = 123 K). Hydrogen concentration in air was included in the range 10–55% for tests at T = 288 K, and 20–60% for tests at T = 173 K and 123 K respectively. Simulations assess the impact of experimental characteristics and design, such as the electrodes’ dimension, and numerical features on process dynamics, growth of the flame kernel and MIE predictions
Electrical capacitance and mechanical performances of embedded piezo-polymer transducers in polymer-matrix composites under monotonic tensile tests
No full textInternational audienceIn this study, the capacitance variation of piezoelectric polymeric transducers embedded in Polymer Matrix Composites (PMC) under monotonic tensile testing was studied. The aim was to draw out a comparison between the experimental and numerical results obtained via a high-order kinematics 2D model. In parallel, Non-Destructive Testing (NDT) including specimen temperature and Acoustic Emission (AE) signatures were obtained, and a Micro-tensile test was performed directly on the sensor material to further investigate the behaviour of capacitance of P(VDF-TRFE) films directly under tensile tests. The tensile tests were numerical modelled under static electro-mechanically coupled layer-wise 2D models. A sensitivity analysis was performed to determine the effects of the different parameters of the transducer. Under all the presented results, it was found that further investigation regarding the quantitative capacitance variation modelling needs to be carried out, as the presented modelling approach neglects capacitance non-linear behaviour, piezoelectric material discharge and the effects of capacitance measurement
Two convergent NPA-like hierarchies for the quantum bilocal scenario
No full textCharacterising the correlations that arise from locally measuring a single part of a joint quantum system is one of the main problems of quantum information theory. The seminal work [M. Navascués et al, NJP 10,7,073013 (2008)], known as the NPA hierarchy, reformulated this question as a polynomial optimisation problem over noncommutative variables and proposed a convergent hierarchy of necessary conditions, each testable using semidefinite programming. More recently, the problem of characterising the quantum network correlations, which arise when locally measuring several independent quantum systems distributed in a network, has received considerable interest. Several generalisations of the NPA hierarchy, such as the Scalar Extension [Pozas-Kerstjens et al, Phys. Rev. Lett. 123, 140503 (2019)], were introduced while their converging sets remain unknown. In this work, we introduce a new hierarchy, prove its equivalence to the Scalar Extension, and characterise its convergence in the case of the simplest network, the bilocal scenario, and explore its relations with the known generalisations
De l’ordolibéralisme à l’ordo-communalisme
No full texthttps://aoc.media/opinion/2024/04/11/de-lordoliberalisme-a-lordo-communalisme/Peut-on tirer les leçons de l’ordolibéralisme pour transformer en profondeur nos institutions et promouvoir un nouveau modèle de société ? Face aux limites de l’économie de marché, notamment son incapacité à répondre aux défis écologiques et sociaux, l’idée d’un ordo-communalisme émerge
Carotenoids bioproduction by two psychrophilic microalgae Sphaerocystis sp. and Pleurastrum sp.
No full textInternational audienceMicroalgae-derived carotenoids have found a wide range ofapplications across various industries including food, feed,cosmetics, and pharmaceuticals. Researchers have been seekingmicroalgae strains that can withstand or adapt to diverseconditions. Among these, microalgae that have adapted to coldclimates, known as ‘psychrophilic microalgae’, hold particularpromise. They are potential sources of valuable carotenoids,such as astaxanthin and canthaxanthin. Despite the potentialthey hold, there is a noticeable scarcity of data on these specificmicroalgae. This gap in knowledge underscores the need forfurther research and exploration. As such, the objective of thisthesis project was to enhance the accumulation of carotenoids intwo specifically selected psychrophilic strains, Sphaerocystissp., and Pleurastrum sp. These strains have been effectivelyadapted to our laboratory settings, which promoted cell growthand carotenoid accumulation and extraction
Caractérisation d’incertitude pour la stéréophotogrammétrie à partir d’images satellites
No full textCurrently, Digital Surface Models (DSMs) are required in many applications, such as for managing water resources, monitoring biomass, evaluating damages caused by natural catastrophes, or for urban planning. DSMs can mainly be produced by Radar interferometry, photogrammetry or LiDAR scanning. In this context, CNES and Airbus are planning the launch of the CO3D constellation of satellites to massively provide highly accurate DSMs using photogrammetry. A performance map will also be provided alongside the DSM to characterize potential errors resulting from the uncertainty on input data or on its processing. The objective of this thesis is to characterize the uncertainty associated with the production of DSMs using photogrammetry. To do so, special uncertainty models, namelyimprecise probabilities, and more specifically possibility distributions, are employed to characterize the uncertainty arising from stereo images processing. Those models define credal sets, which are convex sets of probability distributions. Credal sets are well-suited to represent uncertainty resulting from incomplete or imperfect knowledge, which can be a limitation for a single probability distribution. In the presence of multiple sources of uncertainty, their dependency must also be considered. For this purpose, it is possible to consider copulas, which are models used to represent the dependency between multiple random variables. In this thesis, three different methods are introduced to join marginal credal sets into multivariate credal sets using copulas. The relationships between those methods are then investigated, for specific copulas and different models of imprecise probabilities. An application of those multivariate credal sets is then proposed, for propagating the uncertainty of stereo images in a dense stereo-matching problem. Different optimizations and ways to facilitate the uncertainty propagation are presented. The correct uncertainty propagation is validated using Monte Carlo sampling. A second contribution of this thesis concerns the uncertainty modeling of the dense matching algorithm itself using possibility distributions. A method is presented for generating confidence intervals associated with the results of the dense-matching step. Those intervals are then propagated to the end of the stereo pipeline, therefore producing elevation confidence intervals for the DSMs. The size and accuracy of intervals are then evaluated, using real satellites images and DSMs for which a ground truth is available. Elevation intervals correctly contain the ground truth at least 90% of the time.Actuellement, les Modèles Numériques de Surface (MNS) sont nécessaires pour de nombreuses applications, telles que la gestion des ressources en eau, le suivi de la biomasse, l’évaluation des dommages causés par les catastrophes naturelles ou la planification urbaine. Les MNS peuvent principalement être produits par interférométrie Radar, photogrammétrie ou en utilisant des instruments LiDAR. Dans ce contexte, le CNES et Airbus préparent le lancement de la constellation de satellites CO3D afin d’assurer la production massive de MNS à haute résolution par photogrammétrie. Fournie avec le MNS, une carte de performance permettra de caractériser les erreurs liées aux incertitudes dans les données d’entrée ainsi qu’aux incertitudes des méthodes utilisées. L’objectif de cette thèse et de caractériser l’incertitude associée à la production de MNS par photogrammétrie. Nous utilisons des modèles d’incertitude spécifiques, à savoir des probabilités imprécises, et plus particulièrement des distributions de possibilité, afin de caractériser l’incertitude résultant du traitement des images stéréo. Ces modèles définissent des “ensembles crédaux”, qui sont des ensembles convexes de distributions de probabilité. L’intérêt de ces ensembles crédaux est d’être mieux adaptés pour représenter l’incertitude résultant de connaissances incomplètes ou imparfaites, par rapport aux simples distributions de probabilité. En présence de plusieurs sources d’incertitudes, il est également nécessaire de considérer leurs relations de dépendance. Pour cela, il est courant d’utiliser des copules, qui sont des modèles représentant la dépendance entre plusieurs variables aléatoires. Dans cette thèse, trois méthodes distinctes sont introduites afin de joindre des ensembles crédaux marginaux en des ensembles crédaux multivariés à l’aide de copules. Les relations entre ces méthodes sont ensuite étudiées pour des copules spécifiques ainsi que pour différents modèles de probabilités imprécises. Une application de ces ensembles crédaux multivariés est ensuite proposée, afin de propager l’incertitude d’images stéréo dans un problème d’appariement. Différentes optimisations et façons de faciliter la propagation de l’incertitude sont présentées. La propagation correcte de l’incertitude est enfin validée à l’aide de méthodes de Monte-Carlo. Une seconde contribution de cette thèse concerne la modélisation de l’incertitude intrinsèque de l’algorithme d’appariement en utilisant des distributions de possibilité. Une méthode est proposée pour générer des intervalles de confiance associés aux résultats de l’étape d’appariement, et ces intervalles sont propagés jusqu’à la fin du pipeline stéréo, produisant ainsi des intervalles de confiance d’élévation pour les MNS. La taille et la précision de ces intervalles est évaluée en utilisant des images satellites réelles et des MNS pour lesquels une vérité terrain est disponible. Les intervalles ainsi créés contiennent correctement la vérité terrain au moins 90 % du temps