The paper focuses mainly on the experimental study of two charateristic times: the retardation time of the elastic response and the relaxation time of a commercial magnetorheological suspension as functions of the applied magnetic field and temperature. For practical applications these characteristic times are as important as the response time to the application of a magnetic field. However, to our best knowledge, the two characteristic times were not investigated in detail before. Also, the thixotropy and reversibility of the magnetoviscous effect, which are also important for practical applications, are evaluated in the paper.
This paper considers the problem of surface TE wave propagation along the interface between a nonlinear medium with an electro-optical Pockels response and a medium with an exponential refractive index profile. The mathematical formulation is reduced to a boundary value problem for a second-order ordinary differential equation with a piecewise given permittivity dependent on the field in the nonlinear region. The conjugation conditions on the flat boundary and the field decay conditions at infinity are supplemented by the requirement to fix the total power, which transforms the original problem with a continuous spectrum into a normalized problem with a discrete set of eigenvalues. Analytical expressions are obtained for the transverse field profile, total power, and partial energy flows in terms of Bessel functions. The uniqueness of the solution to the normalized problem for each admissible value of the propagation constant is proven. An analysis is performed of the dependence of the total power flow and energy concentration on the spectral parameter, exponential profile parameters, background dielectric constant, and nonlinearity coefficient. The existence of a bifurcation value of the spectral parameter corresponding to the minimum total power and the maximum difference in partial fluxes is demonstrated. The behavior of the confinement factors (relative energy fractions concentrated in each medium) is studied as the physical parameters of the system vary.
This paper demonstrates that certain p-adic and adelic constraints on the description of the dynamics of the flat Friedmann model over a non-Archimedean space naturally lead to a discrete spectrum of admissible values of the cosmological constant Λ. Such a discretisation follows from the requirement for the existence of padic vacuum states and from adelisation, which in turn implies discrete values of the model’s evolution parameter. An analysis of the resulting expression for Λ shows that the discrete quantum indices of the model satisfy a specific relation that, for values of the cosmological constant characteristic of the present epoch, favours a late-time adelic phase corresponding to small-integer values of one of these indices. This mechanism is identified as a late-time selection rule.
The photoluminescence properties of Pr3+ -doped Ca6Ba(PO4)4O are reported and analyzed for the first time. The phosphors were synthesized via a conventional solid-state method with Pr3+ concentrations ranging from 0.5 to 2.0 mol% and Li+ co-doping for charge compensation. X-ray diffraction confirmed the formation of a single-phase monoclinic structure (C2/m) for all compositions. Photoluminescence studies showed both interconfigurational 4f5d → 4f 2 and intraconfigurational 4f 2 → 4f 2 transitions of Pr3+, producing UV and visible emissions. The dominant red emission originates from the 1D2 → 3H4 transition, indicating efficient nonradiative relaxation from the 4f 5d states in the phosphate host. Maximum emission intensity was achieved at 0.5 mol% Pr3+, with concentration quenching observed at higher dopant levels. Timeresolved measurements revealed nanosecond 4f5d lifetimes and microsecond 1D2 lifetimes. These findings enhance the understanding of luminescence mechanisms in phosphatebased materials and confirm Ca6Ba(PO4)4O as a stable and efficient host for Pr3+ -activated phosphors.
The main objectives of this research work were: i) the valorization of Citrus clementina waste by “green” synthesis of silver nanoparticles (AgNPs), and ii) the evaluation of their impact on metabolic activity of brewing yeast (Saccharomyces cerevisiae). The developed bio-based entities were characterized by UV-Vis absorption spectroscopy, and their morphology was analyzed by optical microscopy. The antioxidant properties were estimated by DPPH assay. The bio-impact of phyto-developed AgNPs was firstly evaluated in vitro, on artificial cells mimicking yeasts (by fluorescence emission spectroscopy), then in vivo on Saccharomyces cerevisiae (by investigating the yeast metabolic activity). The yeast cells treated with Citrus-derived AgNPs demonstrated antioxidant properties which can be exploited in biomedical applications.
