XMOISE: A Logical Spreadsheet to Elicit Didactic Knowledge

International audienceKnowledge elicitation is a critical problem in computerized learning environments that make use of a knowledge base. Fortunately, contrary to usual expertise elicitation situations, didactic scientific knowledge is quite often well formalized, and authors are used to deal with the logical organization of the domain they teach. We want to propose here an original tool, a logical spreadsheet which, if included in an authoring package, will help authors organize concepts and at the same time make both conception and maintenance of didactic knowledge bases much easier

Encapsulation of betalain into w​/o​/w double emulsion and release during in vitro intestinal lipid digestion

A water-in-oil-in-water (w/o/w) double emulsion was prepared with water extract of red beet as the inner water phase, rapeseed oil as the oil phase and polysaccharides solution as the outer water phase. Polyglycerol polyricinoleate and polar lipid fraction from oat were used as emulsifiers for primary water-in-oil (w/o) emulsion and secondary w/o/w emulsion, respectively. Their mean droplet sizes were approximately 0.34 μm and 5.5 μm, respectively. The double emulsion showed a high encapsulation efficiency of 89.1% and had a pink coloration due to encapsulated betalain. The double emulsion was subjected to in vitro intestinal lipid digestion and the evolution of structures and release of betalain were monitored. During the first 2 h of digestion, coalescence of the inner water phase droplets was observed, and the sizes of the double emulsion droplets increased quickly because of aggregation. This period also corresponded to release of betalain, reaching about 35%. After 3 h of digestion, no more release was measured, corresponding to no further increase in droplet sizes. In contrast, the encapsulation efficiency and droplet sizes were not affected after 3 h in the same digestion conditions but without the bile salts and lipase, showing they were responsible for the release.</p

Couplages expérimentaux des propriétés interfaciales et volumiques des mousses aqueuses (les cas de l'imbibition en micropesanteur et de la rhéologie)

Ce mémoire de thèse rapporte des résultats sur deux problèmes de la physique des mousses aqueuses 3D : le transport de fluide par imbibition capillaire et la rhéologie. Ils sont tous deux traités par une approche physico-chimique et multi-échelles, les mesures en volume étant reliées à des mesures aux interfaces gaz / liquide. Lors de ce travail, les types de tensioactif et de gaz ont été variés pour contrôler les propriétés interfaciales. De plus, l effet de la fraction volumique de liquide a été étudié.Les caractéristiques de l imbibition capillaire ont été mesurées par des techniques optiques et électriques au cours de vols paraboliques, permettant de supprimer la composante gravitationnelle du drainage. Les équations théoriques décrivent correctement les résultats expérimentaux en dessous d une fraction volumique de liquide de 0,12. Au-delà, j ai calculé une nouvelle équation pour tenir compte d une autre répartition du liquide dans la mousse.La rhéologie a été mesurée en modes oscillatoire et continu. Le premier mode permet d attribuer l origine de la viscoélasticité des mousses aqueuses à la pression de Laplace, avec une possible correction par l épaisseur des films. En outre, j ai développé un modèle basé sur l analogie de la fraction volumique de liquide à une température. Le second mode, assisté par DWS, permet de relier l écoulement macroscopique à des réarrangements microscopiques, tout en tenant compte du glissement en paroi. Une dilatance a été mise en évidence pour la première fois dans les mousses. Elle conduit à des écoulements de la phase liquide, semblant être contrôlés, à première vue, par les mêmes paramètres que les écoulements de drainage.This thesis sheds light on two problems in 3D aqueous foams physics : fluid transport by capillary imbibition and rheology. A multiscale physicochemical approach is chosen, bulk measurements being linked to measurements at the gas / liquids interfaces. To do so, different surfactants and gas have been used, in order to control interfacial properties. On top of these parameters, the effect of the liquid volume fraction has been studied.Some capillary imbibition characteristics have been measured by optical and electrical techniques during parabolic flights, allowing the suppression of gravitational drainage. Theoretical equations correctly describe the experimental results below a liquid volume fraction of 0,12. Above this limit, I have derived a new equation taking into account another distribution of liquid within the foam. Technical results from ESA / CNES programmes phases are also reported.Rheology has been measured in both oscillatory and continuous modes. The first mode allows to originate the aqueous foams viscoelasticity from the Laplace pressure, with a possible correction by the film thickness. Moreover, I have developed a model based on the analogy between the liquid volume fraction and a temperature. The second mode, together with DWS (Diffusing-Wave Spectroscopy), allows to link macroscopic flow to microscopic rearrangements, while taking wall slip into account. Dilatancy phenomena have been evidenced for the first time in foams. Those lead to liquid phase flows which seem to be controlled, at first glance, by the same parameters than drainage flows.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Aqueous foam slip and shear regimes determined by rheometry and multiple light scattering

International audienceBy using simultaneously rheometry and a multiple light scattering technique, diffusing wave spectroscopy (DWS), we have studied the steady flows of three-dimensional aqueous foams. A number of parameters--the surfactants, the liquid volume fraction, and the roughness of the rheometer surfaces--are widely varied in order to determine which quantities have an impact on the macroscopic flow behaviors. By comparing to previous theoretical and experimental results, we show that flow regimes can either be slip or shear dominated. Two opposite slip regimes are identified; the transition from one to the other is obtained either by changing the surfactant or the liquid fraction, and we quantitately discuss which regime is selected for any given foam properties. Similarly, different shear regimes are also found, and we discuss the link between the macroscopic rheometry measurements, the nature of the flow, and the interfacial microscopic properties. Despite the occurrence of slip, we show how we can recover the actual shear rate by DWS, and how we can quantitatively explain the measured slip velocities

Oscillatory rheometry of aqueous foams : surfactant, liquid fraction, aging and protocol effects

International audienceWe report a new set of rheological data on well controlled aqueous foams. We investigate and analyze how the linear viscoelastic regime, the foam yielding and the non-linear regimes above yielding actually depends on the interfacial properties, bubble size, liquid fraction and foam age. Results are compared to previous works on foams and emulsions, and to models. The viscoelastic linear properties and yield stress are strongly dependent on the liquid fraction, and for a low molecular weight surfactant, providing "fluid-like" interfaces, a universal behavior is recovered. However, discrepancies are observed for protein foams, and are discussed in relation to the interface and thin film properties. We also discuss the features of the non linear regimes above the yield stress, which cannot be fully explained by recent models. As the foam ages, the evolution of the viscoelastic properties can be interpreted in terms of foam drainage and coarsening; nevertheless, some of the aging effects remain unexplained. We also present the results of a new mode of oscillatory experiments, at constant shear rate the macroscopic results obtained with this new protocol turn out to be strikingly well correlated to microscopic measurements at the bubble scale. We then show that a same solid-liquid transition is obtained either by applying a deformation, or by the foam coarsening; we propose that the transition is controlled by a Deborah number De, which can be seen either as a frequency ratio or a deformation ratio. For De 1)

Studying the real-time interplay between triglyceride digestion and lipophilic micronutrient bioaccessibility using droplet microfluidics. 2 application to various oils and (pro)vitamins

International audienceThe kinetics of micellar solubilization of lipophilic micronutrients (bioaccessibility) in relation with triglyceride digestion remains poorly known. To study this interplay in real-time, a droplet microfluidic method was designed and used as reported in the first part of this article series. In this second part, the interplay between the micellar solubilization of (pro)vitamins (beta-carotene or retinyl palmitate) and the digestion of triglyceride oils (tricaprylin TC, or high-oleic sunflower seed oil HOSO, or fish oil FO) during simulated gastrointestinal digestion was investigated. The relation between the release of both micronutrients and of triglyceride lipolytic products was found to be non-linear. The kinetics of beta-carotene was found to follow the kinetics of lipolytic products, depending on the oil type (TC > HOSO > FO). The effect of the gastric phase on the intestinal phase was also found to follow this order, mostly due to partial lipolysis during the gastric phase

Encapsulation of betalain into w/o/w double emulsion and release during in vitro intestinal lipid digestion

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XMOISE: A Logical Spreadsheet to Elicit Didactic Knowledge

International audienceKnowledge elicitation is a critical problem in computerized learning environments that make use of a knowledge base. Fortunately, contrary to usual expertise elicitation situations, didactic scientific knowledge is quite often well formalized, and authors are used to deal with the logical organization of the domain they teach. We want to propose here an original tool, a logical spreadsheet which, if included in an authoring package, will help authors organize concepts and at the same time make both conception and maintenance of didactic knowledge bases much easier

Microfluidics-based observations to monitor dynamic processes occurring in food emulsions and foams (online)

Food design is often done based on a trial-and-error basis,using structure properties as an indicator of product quality.Although this has led to many good p roducts in the market, this‘cook and look’ approach could benefit from insights into dynamic processes as they occur during food formation, storage, and digestion. Currently microfluidic devices are being developed to allow these types of observations, and here we show the latest examples in the field of emulsions and foams, including effects that occur during digestion. We expect that these techniques will supply a stepping stone to thorough understanding at various length and timescales that are all instrumental in designing high-quality food products, and ultimately creating foods with health benefits

In vitro solubilization of fat-soluble vitamins in structurally defined mixed intestinal assemblies

International audienceThe structures of fed state intestinal assemblies containing bile components, dietary fat, and fat-solublevitamins are not well known, although they are involved in lipid transport. In this study, several methodswere used to investigate structural transitions upon various dietary lipids or various fat-soluble vitaminsincorporation in bile intestinal assemblies. In particular, DLS and turbidimetry were used to study tran-sition points as a function of component concentration, and cryo-TEM and SAXS were used to resolveassembly structures at microscopic and supramolecular scales, respectively. Results showed that increas-ing the concentration of dietary lipids in bile assembly induced a transition from core-shell micelles tounilamellar vesicles (except with caprylate lipids, always yielding micelles). In these specific assemblies,increasing the concentration of a fat-soluble vitamin either induced a systematic structural transition,defining a solubilization capacity (a-tocopherol or phylloquinone), or induced a structural transition onlyin micelles (retinol), or did not induce any structural transition up to very high concentrations (cholecal-ciferol). Using SAXS data, ideal molecular organizations are proposed for assemblies in the absence orpresence ofa-tocopherol