We investigate the quantum optical torque on an atom interacting with an inhomogeneous electromagneticenvironment described by the most general linear constitutive relations. The atom is modeled as a two-levelsystem prepared in an arbitrary initial energy state. Using the Heisenberg equation of motion (HEM) and underthe Markov approximation, we show that the optical torque has a resonant and nonresonant part, associated,respectively, with a spontaneous-emission process and Casimir-type interactions with the quantum vacuum,which can both be written explicitly in terms of the system Green function. Our formulation is valid forany three-dimensional inhomogeneous, dissipative, dispersive, nonreciprocal, and bianisotropic structure. Weapply this general theory to a scenario in which the atom interacts with a material characterized by strongnonreciprocity and modal unidirectionality. In this case, the main decay channel of the atom energy is representedby the unidirectional surface waves launched at the nonreciprocal material-vacuum interface. To provide relevantphysical insight into the role of these unidirectional surface waves in the emergence of nontrivial optical torque,we derive closed-form expressions for the induced torque under the quasistatic approximation. Finally, weinvestigate the equilibrium states of the atom polarization, along which the atom spontaneously tends to aligndue to the action of the torque. Our theoretical predictions may be experimentally tested with cold Rydbergatoms and superconducting qubits near a nonreciprocal material. We believe that our general theory may findbroad application in the context of nanomechanical and biomechanical systems.

Based on the theory of macroscopic quantum electrodynamics, we generalize the expression of theCasimir force for nonreciprocal media. The essential ingredient of this result is the Green’s tensor betweentwo nonreciprocal semi-infinite slabs, including a reflexion matrix with four coefficients that mixes opticalpolarizations. This Green’s tensor does not obey Lorentz’s reciprocity and thus violates time-reversal symmetry.The general result for the Casimir force is analyzed in the retarded and nonretarded limits, concentrating on theinfluences arising from reflections with or without change of polarization. In a second step, we apply our generalresult to a photonic topological insulator whose nonreciprocity stems from an anisotropic permittivity tensor,namely InSb. We show that there is a regime for the distance between the slabs where the magnitude of theCasimir force is tunable by an external magnetic field. Furthermore, the strength of this tuning depends on theorientation of the magnetic field with respect to the slab surfaces.

Extensive use of porous silicon (PSi) for tissue engineering is due to its convenient properties as it is both non-toxic and bioresorbable. Moreover, PSi surface modification is an important step to enhance cell adhesion and proliferation. In this work, a combination of optical and electrochemical studies is performed to elaborate a suitable PSi multilayer substrate for cell culture. For this study, we modified PSi surface by silanization and antibody grafting (APTES-anti STRO1), the 12-mer specific peptide to silicon p+type coating and the peptide modified with the antibody recognition sequence. Electrochemical characterization of PSi multilayers is performed to investigate its electrical behavior, determine the optimal measuring conditions and reveal the most stable PSi surfaces. Then, the behavior of dental pulp stem cells (DPSC) was investigated on various modified PSi surfaces. An electrochemical method was applied for the first time monitoring the electrical behavior of stem cell adhesion. The cells electrochemical behavior depends on the nature of the surface coating and the peptide-anti STRO1 improved adhesion and cell spreading onto the PSi surface compared to bare surface and the one coated with the peptide. Fluorescent microscopy revealed that all surface modi cation methods enhance cell adhesion compared to the bare PSi surface. An increased cell number is observed on APTES-anti STRO1, peptide and peptide-anti STRO1 coated PSi. The peptide-anti STRO1 provided the best cell proliferation results suggesting the improved accessibility of the recognition fragment of the antibody anti-STRO1.

We present a semi-analytical model of the resonance phenomena occurring in a hybrid system made of a 1D array of periodic subwavelength slits deposited on an insulator/graphene layer. We show that the spectral response of this hybrid system can be fully explained by a simple semi-analytical model based on weak and strong couplings between two elementary sub-systems.

Natural protein sources often display a huge complexity, being composed of a blend of polypeptides of various molecular weight, pHi and charge density. Gluten, the proteins extracted from wheat flour is one of such. Gluten is widely used for its viscoelastic properties as an improver of cereal products (bread, pastry, etc.). It is composed of two classes of proteins, named gliadin and glutenin, similar in their amounts in glutamine (30%) and proline (10%). The more than 25 different polypeptides belonging to the gliadin class are hard to fractionate into individual components because of high redundancy in the primary sequences. Glutenin are in the form of polymers made from several distinct polypeptides concatenated through inter-chain disulfide bonds. Their molecular weights are evenly distributed from 100 kg/mol to 7,000 kg/mol.While it is well established that gliadin confers viscosity to gluten whereas glutenin polymers are at the origin of its elastic resistance, the interactions existing between both classes of gluten protein remain unknown. We previously showed by SLS and multi-angle DLS that gluten proteins suspended in ethanol/water (50/50, v/v), a theta solvent, includes large proteins assemblies (26,000 kg/mol, Rh 100nm) displaying an internal dynamic1. To get a better insight of the composition of those assemblies, we combined biochemical and physicochemical approaches. On the one hand, gluten proteins suspended in ethanol/water were fractionated by Asymmetrical- Flow-Field-Flow Fractionation (A4F) coupled to UV, SLS and QELS detectors. On the other hand, gluten proteins were partitioned by liquid-phase decomposition in respect with temperature. Protein composition of partitioned phases and eluting fractions recovered from A4F were characterized by size-exclusion chromatography. A specific interaction between omega-gliadin and glutenin polymers was evidenced.This result strengthens a very recent study that demonstrates a significant positive correlation between glutenin polymeric proteins, the ω‐gliadin fraction, and dough properties.

A combined small-angle scattering of neutrons (SANS) and X-rays (SAXS) study of thestructure of polymer layers pre-adsorbed on silica nanoparticles (NP) which are subsequentlyincorporated into polymer nanocomposites (PNCs) is presented. Pre-adsorbed chains are foundto promote ideal dispersion, before desorption in the late stages of nanocomposite formation.The microstructure of the interfacial polymer layer is characterized by detailed modeling of X-rayand neutron scattering. Only in ideally well-dispersed systems a static interfacial layer ofreduced polymer density over a thickness of ca. 2 nm is evidenced based on the analysis with aform-free density profile optimized using reverse Monte Carlo simulations. This interfacialgradient layer is found to be independent of the thickness and mass of the initially adsorbedpolymer, but appears to be generated by out-of-equilibrium packing and folding of the preadsorbedlayer. The impact of annealing is investigated to study the approach of equilibrium,showing that initially ideally well-dispersed systems adopt a repulsive hard-sphere structure,while the static interfacial layer disappears.In parallel, SANS and the use of zero average contrast conditions allow the measurement ofchain conformation in the PNCs with and without pre-adsorption. Surprisingly, we evidenced thespontaneous formation of thermally-stable adsorbed layers in PNCs containing matrix chains ofdifferent mass, whereas a symmetric matrix of identical chain masses does not show this effect.This study contributes thus to the fundamental understanding of the interplay betweeneffects which are decisive for macroscopic material properties: polymer-mediated interparticleinteractions, and particle interfacial effects on surrounding polymer.