Ref HAL: hal-03147027_v1
DOI: 10.1016/j.neuint.2021.104961
Exporter : BibTex | endNote
Résumé:

With their potent regenerative and protective capacities, stem cell-derived conditioned media emerged as an effective alternative to cell therapy, and have a prospect to be manufactured as pharmaceutical products for tissue regeneration applications. Our study investigates the neuroregenerative potential of human dental pulp cells (DPCs) conditioned medium (CM) and defines an optimization strategy of DPC-CM for enhanced neuronal outgrowth. Primary sensory neurons from mouse dorsal root ganglia were cultured with or without DPC-CM, and the lengths of βIII-tubulin positive neurites were measured. The impacts of several manufacturing features as the duration of cell conditioning, CM storage, and preconditioning of DPCs with some factors on CM functional activity were assessed on neurite length. We observed that DPC-CM significantly enhanced neurites outgrowth of sensory neurons in a concentration-dependent manner. The frozen storage of DPC-CM had no impact on experimental outcomes and 48 h of DPC conditioning is optimal for an effective activity of CM. To further understand the regenerative feature of DPC-CM, we studied DPC secretome by human growth factor antibody array analysis and revealed the presence of several factors involved in either neurogenesis, neuroprotection, angiogenesis, and osteogenesis. The conditioning of DPCs with the B-27 supplement enhanced significantly the neuroregenerative effect of their secretome by changing its composition in growth factors. Here, we show that DPC-CM significantly stimulate neurite outgrowth in primary sensory neurons. Moreover, we identified secreted protein candidates that can potentially promote this promising regenerative feature of DPC-CM.

Ref HAL: hal-03197323_v1
Ref Arxiv: 2104.03753
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

Minimal varying $\Lambda$ theories are defined by an action built from the Einstein-Cartan-Holst first order action for gravity with the cosmological constant $\Lambda$ as an independent scalar field, and supplemented by the Euler and Pontryagin densities multiplied by $1/\Lambda$. We identify the canonical structure of these theories which turn out to represent an example of irregular systems. We find five degrees of freedom on generic backgrounds and for generic values of parameters, whereas if the parameters satisfy a certain condition (which includes the most commonly considered Euler case) only three degrees of freedom remain. On de Sitter-like backgrounds the canonical structure changes, and due to an emergent conformal symmetry one degree of freedom drops from the spectrum. We also analyze the self-dual case with an holomorphic action depending only on the self-dual part of the connection. In this case we find two (complex) degrees of freedom, and further discuss the Kodama state, the restriction to de Sitter background and the effect of reality conditions.

Ref HAL: hal-03194024_v1
DOI: 10.1039/d0nj05933a
WoS: WOS:000623596600015
Exporter : BibTex | endNote
Résumé:

Pesticide sensing is an important object of study due to its increasing use worldwide. Herein, we report a SERS study of 4-nitrophenol (PNP), which is product of neutralization processes of various pesticides such as Paraoxon, and can be used as a target molecule for monitoring. PNP is also widely used in the chemical industry and due to its high toxicity is considered a concerning pollutant. The sensing was carried out with a reduced graphene oxide nanocomposite functionalized with cysteamine and Ag nanoparticles (rGOSHAg), and compared with raw reduced graphene oxide and a commercial SERS substrates (SERStrate (TM)). A mechanistic evaluation was also carried out, focused in the degradation of PNP caused by the different exciting laser lines, evidencing the PNP dimerization in substrates containing Ag NPs (under 532 nm laser), which has important outcomes for sensing purposes. The nanocomposite rGOSHAg presented the highest sensitivity towards PNP, detecting concentrations as low as 10(-6) mol L-1 and with a high potential for field applications and real-time measurements of molecules commonly present in pesticides and industrial contaminants.

Ref HAL: hal-03189697_v1
DOI: 10.3390/polym13071153
Exporter : BibTex | endNote
Résumé:

PNIPAm microgels synthesized via free radical polymerization (FRP) are often considered as neutral colloids in aqueous media, although it is well known, since the pioneering works of Pelton and coworkers, that the vanishing electrophoretic mobility characterizing swollen microgels largely increases above the lower critical solution temperature (LCST) of PNIPAm, at which microgels partially collapse. The presence of an electric charge has been attributed to the ionic initiators that are employed when FRP is performed in water and that stay anchored to microgel particles. Combining dynamic light scattering (DLS), electrophoresis, transmission electron microscopy (TEM) and atomic force microscopy (AFM) experiments, we show that collapsed ionic PNIPAm microgels undergo large mobility reversal and reentrant condensation when they are co-suspended with oppositely charged polyelectrolytes (PE) or nanoparticles (NP), while their stability remains unaffected by PE or NP addition at lower temperatures, where microgels are swollen and their charge density is low. Our results highlight a somehow double-faced electrostatic behavior of PNIPAm microgels due to their tunable charge density: they behave as quasi-neutral colloids at temperature below LCST, while they strongly interact with oppositely charged species when they are in their collapsed state. The very similar phenomenology encountered when microgels are surrounded by polylysine chains and silica nanoparticles points to the general character of this twofold behavior of PNIPAm-based colloids in water.

Ref HAL: hal-03191119_v1
DOI: 10.1103/PhysRevB.103.155404
Exporter : BibTex | endNote
Résumé:

Twisted two-dimensional bilayer anisotropy materials exhibit many exotic physical phenomena. Manipulating the “twist angle” between the two layers enables the hybridization phenomenon of polaritons, resulting in fine control of the dispersion engineering of the polaritons in these structures. Here, combined with the hybridization phenomenon of anisotropy polaritons, we study theoretically the near-field radiative heat transfer (NFRHT) between two twisted hyperbolic systems. These two twisted hyperbolic systems are mirror images of each other. Each twisted hyperbolic system is composed of two graphene gratings, where there is an angle φ between these two graphene gratings. By analyzing the photonic transmission coefficient as well as the plasmon dispersion relation of the twisted hyperbolic system, we prove the enhancement effect of the topological transitions of the surface state at a special angle [from open (hyperbolic) to closed (elliptical) contours] on radiative heat transfer. Meanwhile the role of the thickness of dielectric spacer and vacuum gap on the manipulating the topological transitions of the surface state and the NFRHT are also discussed. We predict the hysteresis effect of topological transitions at a larger vacuum gap, and demonstrate that as the thickness of the dielectric spacer increases, the transition from the enhancement effect of heat transfer caused by the twisted hyperbolic system to a suppression.

Ref HAL: hal-03186214_v1
Ref Arxiv: 2103.06721
Ref INSPIRE: 1851112
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

We find a parametrically light dilaton in special confining theories in three dimensions. Their duals form what we call a scion of solutions to the supergravity associated with the large-N limit of the Coulomb branch of the N=4 Super-Yang-Mills (SYM) theory. The supergravity description contains one scalar with bulk mass that saturates the Breitenlohner-Freedman unitarity bound. The new solutions are defined within supergravity, they break supersymmetry and scale invariance, and one dimension is compactified on a shrinking circle, yet they are completely regular. An approximate dilaton appears in the spectrum of background fluctuations (or composite states in the confining theory), and becomes parametrically light along a metastable portion of the scion of new supergravity solutions, in close proximity of a tachyonic instability. A first-order phase transition separates stable backgrounds, for which the approximate dilaton is not parametrically light, from metastable and unstable backgrounds, for which the dilaton becomes parametrically light, and eventually tachyonic.

Ref HAL: hal-03184640_v1
Ref Arxiv: 2102.13214
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

The Miles theory of wave amplification by wind is extended to the case of finite depth h and a shear flow with (constant) vorticity {\Omega}. Vorticity is characterised through the non-dimensional parameter {\nu} = {\Omega} U_1 /g, where g the gravitational acceleration, U_1 a characteristic wind velocity and k the wavenumber. The notion of 'wave age' is generalised to account for the effect of vorticity. Several widely used growth rates are derived analytically from the dispersion relation of the wind/water interface, and their dependence on both water depth and vorticity is derived and discussed. Vorticity is seen to shift the maximum wave age, similar to what was previously known to be the effect of water depth. At the same time, a novel effect arises and the growth coefficients, at identical wave age and depth, are shown to experience a net increase or decrease according to the shear gradient in the water flow.