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Production scientifique
Matière molle pour l’agronomie et l’environnement
(13) Production(s) de l'année 2021
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Floating plastics in oceans: A matter of size
Auteur(s): George M., Fabre P.
(Article) Publié:
Green Chemistry, vol. 32 p.100543 (2021)
Ref HAL: hal-04186920_v1
DOI: 10.1016/j.cogsc.2021.100543
Exporter : BibTex | endNote
Résumé: The amount and characteristics of plastic waste in the environment are closely monitored with the regular expansion of their collection to smaller debris sizes and new compartments, such as atmosphere, soil and even food. These data, subject to constant re-evaluation, are necessary to assess the threat that plastic particles pose. In this article, we take stock of the most recent measurements of their size distribution on the ocean surface. We confront the observed size distribution to the commonly invoked degradation modes of plastics and propose a scenario that accounts for the quite unusual features of the size distribution of floating debris. We conclude that delamination alone could be a major mechanism explaining the large number of small microplastics (<150 μm) in the ocean.
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Les dangers de l'invasion plastique
Auteur(s): Fabre P., Lagarde Fabienne, Bruzaud Stephane, Duflos Guillaume, Galgani François, Gastaldi Emmanuelle, George M., Ghiglione Jean-François, Huvet Arnaud, Paul-Pont Ika, Halle Alexandra Ter
Chapître d'ouvrage: Livre Vert 2021, vol. p. (2021)
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Instabilities in freely expanding sheets of associating viscoelastic fluids
Auteur(s): Arora S., Louhichi A., Vlassopoulos D., Ligoure C., Ramos L.
(Article) Publié:
Soft Matter, vol. 2021 p.10935 (2021)
Texte intégral en Openaccess :
Ref HAL: hal-03672529_v1
Ref Arxiv: 2111.06144
DOI: 10.1039/d1sm01075a
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We use the impact of drops on a small solid target as a tool to investigate the behavior of viscoelastic fluids under extreme deformation rates. We study two classes of transient networks: semidilute solutions of supramolecular polymers and suspensions of spherical oil droplets reversibly linked by polymers. The two types of samples display very similar linear viscoelastic properties, which can be described with a Maxwell fluid model, but contrasting nonlinear properties due to different network structure. Upon impact, weakly viscoelastic samples exhibit a behavior qualitatively similar to that of Newtonian fluids: A smooth and regular sheet forms, expands, and then retracts. By contrast, for highly viscoelastic fluids, the thickness of the sheet is found to be very irregular, leading to instabilities and eventually formation of holes. We find that material rheological properties rule the onset of instabilities. We first provide a simple image analysis of the expanding sheets to determine the onset of instabilities. We then demonstrate that a Deborah number related to the shortest relaxation time associated to the sample structure following a high shear is the relevant parameter that controls the heterogeneities in the thickness of the sheet, eventually leading to the formation of holes. When the sheet tears-up, data suggest by contrast that the opening dynamics depends also on the expansion rate of the sheet.
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Dense Phases of γ-Gliadins in Confined Geometries
Auteur(s): Banc A., Navailles Laurence, Leng Jacques, Renard Denis
(Article) Publié:
Colloids And Interfaces, vol. 5 p.51 (2021)
Texte intégral en Openaccess :
Ref HAL: hal-03443023_v1
DOI: 10.3390/colloids5040051
Exporter : BibTex | endNote
Résumé: The binary phase diagram of γ-gliadin, a wheat storage protein, in water was explored thanks to the microevaporator, an original PDMS microfluidic device. This protein, usually qualified as insoluble in aqueous environments, displayed a partial solubility in water. Two liquid phases, a very dilute and a dense phase, were identified after a few hours of accumulation time in the microevaporator. This liquid–liquid phase separation (LLPS) was further characterized through in situ micro-Raman spectroscopy of the dilute and dense protein phases. Micro-Raman spectroscopy showed a specific orientation of phenylalanine residues perpendicular to the PDMS surfaces only for the diluted phase. This orientation was ascribed to the protein adsorption at interfaces, which would act as nuclei for the growth of dense phase in bulk. This study, thanks to the use of both aqueous solvent and a microevaporator, would provide some evidence for a possible physicochemical origin of the gliadin assembly in the endoplasmic reticulum of albumen cells, leading to the formation of dense phases called protein bodies. The microfluidic tool could be used also in food science to probe protein–protein interactions in order to build up phase diagrams
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Food as complex soft matter physics systems - Is gluten a polymer gel like any others? A journey into the complexity of wheat proteins?
Auteur(s): Ramos L.
Conférence invité: 1st International Seminar on Soft Matter & Food: 1st Polish-Slovenian Edition. Physico-Chemical mode (hybride (Lasek and on-line), PL, 2021-11-22)
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Rheology of model gluten gels
Auteur(s): Ramos L.
Conférence invité: Probing out-of-equilibrium soft matter (Fribourg, CH, 2021-10-22)
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Sunflower Proteins at Air–Water and Oil–Water Interfaces
Auteur(s): Poirier A., Stocco A., Kapel Romain, In M., Ramos L., Banc A.
(Article) Publié:
Langmuir, vol. 37 p.2714 - 2727 (2021)
Texte intégral en Openaccess :
Ref HAL: hal-03189744_v1
DOI: 10.1021/acs.langmuir.0c03441
Exporter : BibTex | endNote
Résumé: The adsorption of a sunflower protein extract at two air− water and oil−water interfaces is investigated using tensiometry, dilational viscoelasticity, and ellipsometry. For both interfaces, a three step mechanism was evidenced thanks to master curve representations of the data taken at different aging times and protein concentrations. At short times, a diffusion limited adsorption of proteins at interfaces is demonstrated. First, a two-dimensional protein film is formed with a partition of the polypeptide chains in the two phases that depends strongly on the nature of the hydrophobic phase: most of the film is in the aqueous phase at the air−water interface, while it is mostly in the organic phase at the oil−water interface. Then a three-dimensional saturated monolayer of proteins is formed. At short times, adsorption mechanisms are analogous to those found with typical globular proteins, while strong divergences are observed at longer adsorption times. Following the saturation step, a thick layer expands in the aqueous phase and appears associated with the release of large objects in the bulk. The kinetic evolution of this second layer is compatible with a diffusion limited adsorption of the minor population of polymeric complexes with hydrodynamic radius R H ∼ 80 nm, evidenced in equilibrium with hexameric globulins (R H ∼ 6 nm) in solution. These complexes could result from the presence of residual polyphenols in the extract and raise the question of the role of these compounds in the interfacial properties of plant protein extracts.
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