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Anomalous guided waves appearing at a non-semisimple degeneracy of the fundamental matrix are observed and analyzed in the framework of the Cauchy sextic formalism. The non-semisimple degeneracy condition is explicitly constructed for the most general case of Lamb waves propagating in a traction-free layer with arbitrary elastic anisotropy. A new type of dispersion equation and the corresponding dispersion solution are obtained. The connection with surface waves of the non-Rayleigh type is discussed. [ABSTRACT FROM AUTHOR]

Down‐conversion (DC) is a phenomenon that can enable the observation of photoluminescent quantum yield (PLQY) values exceeding 100%. A comprehensive study of the DC properties of BaF2–based single crystals with different Er3+ doping levels (1–25 mol.%) is presented. The samples exhibit a PLQY of 110% in the 1550–1650 nm under 405 nm excitation. This remarkable PLQY is attributed to a cross‐relaxation process within the energy levels of Er3+. Furthermore, when considering all emitted photons in the 1000–1650 nm range, the PLQY reaches 153% for a sample doped with 5 mol.% of Er3+. By integrating the emission of this single crystal with a Ge diode, serving as an example of a photovoltaic device sensitive to short‐wave infrared light, a significant enhancement in short‐circuit current is demonstrated. In a broader context, the presented material holds promise for improving the spectral response of low‐bandgap photovoltaic devices. [ABSTRACT FROM AUTHOR]

Dispersion analysis of acoustic guided waves, propagating in a stratified medium, containing an internal sandy layer in contact with the isotropic elastic substrate and the upper elastic isotropic layer, is developed by applying the modified Cauchy formalism coupled with the exponential fundamental matrices and the Thomson–Haskell transfer matrix method. The developed approach is suitable for analyzing dispersion properties of guided waves at the broad variation of the sandy parameter. Several phenomena, concerning anomalous dispersion of guided waves at varying sandy parameter, are observed, revealing the possibility of nondestructive evaluation of sandy layers within the upper crust. [ABSTRACT FROM AUTHOR]

The current research concerns with the analysis of Stoneley waves propagation along an interface between two dissimilar homogeneous and isotropic halfspace having negative Poisson's ratios (auxetics). The main attention is paid to the case when both contacting media satisfy the Wiechert condition ensuring the existence of Stoneley wave. Closed form expressions are derived for derivatives of the Stoneley secular equation. The velocity of Stoneley waves is analyzed both theoretically and numerically in a broad range of the Wiechert parameter variation. [ABSTRACT FROM AUTHOR]

The analytical and geometrical conditions for the possible appearance of the infinite group velocity (IGV) points belonging to the dispersion curves of Lamb waves propagating in traction-free plates are studied by a combined method comprising Cauchy sextic formalism and the exponential fundamental matrix method. According to the obtained geometrical condition, the IGV corresponds to the coincidence of a tangent line to any of the dispersion curves with a straight line passing through the origin. The developed technique is demonstrated by applying to the analysis of Lamb wave dispersion in three-layered plates with a soft inner core. [ABSTRACT FROM AUTHOR]

The Ce0.5Y0.35Tb0.15F3 nanoparticles with a CeF3 hexagonal structure were synthesized using the co-precipitation technique. The average nanoparticle diameter was 14 ± 1 nm. The luminescence decay curves of the Ce0.5Y0.35Tb0.15F3 nanoparticles (λem = 541 nm, 5D4–7F5 transition of Tb3+) conjugated with Radachlorin using polyvinylpyrrolidone coating as well as without Radachlorin were detected. Efficient nonradiative energy transfer from Tb3+ to the Radachlorin was demonstrated. The maximum energy transfer coefficients for the nanoparticles conjugated with Radachlorin via polyvinylpyrrolidone and without the coating were 82% and 55%, respectively. The average distance between the nanoparticle surface and Radachlorin was R0 = 4.5 nm. The best results for X-ray-induced cytotoxicity were observed for the NP-PVP-Rch sample at the lowest Rch concentration. In particular, after X-ray irradiation, the survival of A549 human lung carcinoma cells decreased by ~12%. [ABSTRACT FROM AUTHOR]

Using the method of non‐reactive sintering of nanocrystalline powders, highly transparent samples of optical ceramics based on solid solutions of yttrium‐scandium aluminum garnets containing 50 at.% scandium in the dodecahedral position and doped with erbium (1 at.%) and ytterbium (0–49 at.%) cations (YSAG:Yb:Er) were produced. The influence of Yb3+ concentration on the crystal lattice parameter, density, refractive index, stability of YSAG:Yb:Er solid solutions during high‐temperature sintering, thermal conductivity, optical transmittance and absorption coefficients in the wavelength range from 200 to 1100 nm, as well as Stokes and anti‐Stokes luminescence, was determined. The revealed patterns make it possible to fine‐tune the physical and chemical characteristics of ceramics for the design of composite laser materials. [ABSTRACT FROM AUTHOR]