Ref HAL: hal-02274942_v1
DOI: 10.1016/j.jcis.2019.07.083
WoS: 000488652300058
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3 Citations
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Microgels specific structural and functional features are attracting high research interest in several appli- cations such as bioactives and drug delivery or functional food ingredients. Whey protein microgels (WPM) are obtained by heat treatment of whey protein isolate (WPI) in order to promote intramolecular cross-linking. In the present work, atomic force microscopy (AFM) was used in contact mode and in liquid to investigate WPM particles topography and mechanical properties at the nanoscale at native pH (6.5) and acid pH (5.5 and 3.0). Prior to AFM, WPM particles were captured on a gold substrate via low energy interactions by means of specific monoclonal antibodies. AFM images clearly showed an increase in the size of WPM particles induced by pH decrease. AFM in force spectroscopy mode was employed to monitor the elasticity of WPMs. The obtained effective Young’s modulus data showed a significant increase in stiffness at pH 5.5 and pH 3.0, over 15-fold compared to native pH. These findings indicate that the mechanical profile of the WPM network varied with the pH decrease. The WPM topographic and nanome- chanical changes induced by acidification were most likely due to substantial changes in the shape and inner structure of WPM particles. Our results suggest that internally cross-linked structures, modified by acidification could display interesting functional properties when used as a food ingredient.

Ref HAL: hal-02274931_v1
DOI: 10.1021/acsami.9b09337
WoS: 000486360500005
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Chronic kidney disease is characterized by a gradual decline in renal function that progresses toward end-stage renal disease.Podocytes are highly specialized glomerular epithelial cells which form with the glomerular basement membrane (GBM) and capillaryendothelium the glomerular filtration barrier. GBM is an extracellular matrix (ECM) that acts as a mechanical support and providesbiophysical signals that control normal podocytes behavior in the process of glomerular filtration. Thus, the ECM stiffness represents anessential characteristic that controls podocyte function. Hydrolyzed Polyacrylamide (PAAm) hydrogels are smart polyelectrolytes materials.Their biophysical properties can be tuned as desired to mimic the in natural ECM. Therefore, these hydrogels are investigated as new ECM-like constructs to engineer a podocyte-like basement membrane that forms with cultured human podocytes a functional glomerular-like filtration barrier. Such ECM-like PAAm hydrogel construct will provide unique opportunity to reveal podocyte cell biological responses in an in vivo-like setting by controlling the physical properties of the PAAm membranes. In this work, Hydrolyzed PAAm scaffolds having different stiffness ranging between 0.6− 44 kPa are prepared. The correlation between the hydrogel structural and mechanical properties and Podocytes morphology, elasticity, cytoskeleton reorganization, and podocin expression is evaluated. Results show that hydrolyzed PAAm hydrogels promote good cell adhesion and growth and are suitable materials for the development of future 3D smart scaffolds. In addition, the hydrogel properties can be easily modulated over a wide physiological range by controlling the cross-linker concentration. Finally, tuning the hydrogel properties is an effective strategy to control the cells function. This work addressed the complexity of podocytes behavior which will further enhance our knowledge to develop a kidney-on-chip model much needed in kidney function studies on both healthy and diseased states.

Ref HAL: hal-02272702_v1
Ref Arxiv: 1902.02974
DOI: 10.1021/acs.nanolett.9b00914
WoS: 000481563800013
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Dipolar excitons offer a rich playground for both design of novel optoelectronic devices and fundamental many-body physics. Wide GaN/(AlGa)N quantum wells host a new and promising realization of dipolar excitons. We demonstrate the in-plane confinement and cooling of these excitons, when trapped in the electrostatic potential created by semitransparent electrodes of various shapes deposited on the sample surface. This result is a prerequisite for the electrical control of the exciton densities and fluxes, as well for studies of the complex phase diagram of these dipolar bosons at low temperature.

Ref HAL: hal-02267857_v1
DOI: 10.1039/C9SM00966C
WoS: 000477986500011
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We investigate by time-resolved synchrotron ultra-small X-ray scattering the dynamics of liquid–liquid phase-separation (LLPS) of gluten protein suspensions following a temperature quench. Samples at a fixed concentration (237 mg ml−1) but with different protein compositions are investigated. In our experimental conditions, we show that fluid viscoelastic samples depleted in polymeric glutenin phase-separate following a spinodal decomposition process. We quantitatively probe the late stage coarsening that results from a competition between thermodynamics that speeds up the coarsening rate as the quench depth increases and transport that slows down the rate. For even deeper quenches, the even higher viscoelasticity of the continuous phase leads to a “quasi” arrested phase separation. Anomalous phase-separation dynamics is by contrast measured for a gel sample rich in glutenin, due to elastic constraints. This work illustrates the role of viscoelasticity in the dynamics of LLPS in protein dispersions.

Ref HAL: hal-02267129_v1
DOI: 10.1103/PhysRevB.100.085426
WoS: 000481468900005
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Metasurfaces, the two-dimensional (2D) counterpart of metamaterials, have recently attracted a great deal ofattention due to their amazing properties, including negative refraction, hyperbolic dispersion, and manipulationof the evanescent spectrum. In this work, a theory model is proposed for the near field radiative heat transfer(NFRHT) between two nanoparticles in the presence of an anisotropic metasurface. Specifically, the metasurfaceis modeled as an array of graphene strips (GS), which is an ideal platform to implement any metasurfacetopology, ranging from isotropic to hyperbolic propagation. The NFRHT between two nanoparticles aresignificantly amplified when they are placed in the proximity of the GS, and regulated over several ordersof magnitude. In this configuration, the anisotropic surface plasmon polaritons (SPPs) supported by the GSare excited and provide a new channel for the near-field energy transport. The dependence of conductancebetween two nanoparticles on the orientation, the structure parameters, the chemical potential of the GS, andthe interparticle or the particle-surface distances are analyzed by clearly identifying the characteristics of theanisotropic SPPs such as dispersion relations, propagation length, and decay length. These results demonstrate apowerful method to regulate the energy transport in particle systems, and create a way to explore the anisotropicoptical properties of the metasurface based on the measured heat transfer properties.

Ref HAL: hal-02266321_v1
Ref Arxiv: 1908.00117
Ref INSPIRE: 1747566
DOI: 10.1103/PhysRevD.100.083503
WoS: 000488510300002
Ref. & Cit.: NASA ADS
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We perform here a global analysis of the growth index γ behavior from deep in the matter era till the far future. For a given cosmological model in general relativity (GR) or in modified gravity, the value of γ(Ωm) is unique when the decaying mode of scalar perturbations is negligible. However, γ∞, the value of γ in the asymptotic future, is unique even in the presence of a non-negligible decaying mode today. Moreover, γ becomes arbitrarily large deep in the matter era. Only in the limit of a vanishing decaying mode do we get a finite γ, from the past to the future in this case. We find further a condition for γ(Ωm) to be monotonically decreasing (or increasing). This condition can be violated inside GR for varying wDE though generically γ(Ωm) will be monotonically decreasing (like ΛCDM), except in the far future and past. A bump or a dip in Geff can also lead to a significant and rapid change in the slope dγdΩm. On a ΛCDM background, a γ substantially lower (higher) than 0.55 with a negative (positive) slope reflects the opposite evolution of Geff. In Dvali-Gabadadze-Porrati (DGP) models, γ(Ωm) is monotonically increasing except in the far future. While DGP gravity becomes weaker than GR in the future and wDGP→-1, we still get γ∞DGP=γ∞ΛCDM=23. In contrast, despite GeffDGP→G in the past, γ does not tend to its value in GR because dGeffDGPdΩm|-∞≠0.

Ref HAL: hal-02200519_v1
Ref Arxiv: 1903.02778
DOI: 10.1103/PhysRevB.99.224425
WoS: 000473011200002
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We present the full phase diagram of the dumbbell model of spin ice as a function of temperature, chemical potential and staggered chemical potential which breaks the translational lattice symmetry in favour of charge crystal ordering. We observe a double winged structure with five possible phases, monopole fluid (spin ice), fragmented single monopole crystal phases and double monopole crystal, the zinc blend structure. Our model provides a skeleton for liquid-liquid phase transitions and for the winged structures observed for itinerant magnets under pressure and external field. We relate our results to recent experiments on Ho$_2$Ir$_2$O$_7$ and propose a wide ranging set of new experiments that exploit the phase diagram, including high pressure protocols, dynamical scaling of Kibble-Zurek form and universal violations of the fluctuation-dissipation theorem.

Commentaires: 14 pages, 14 figures. Réf Journal: Phys. Rev. B 99, 224425 (2019)