Determination of optical characteristics of biological tissues by temporal distribution of an ultrashort laser pulse passed through homogeneous scattering layer

The determination of optical characteristics of biological tissues by the temporal distribution of an ultrashort laser pulse passed through a homogeneous scattering layer is considered. Four nonstationary models used to describe passing of laser pulses through a highly scattering medium are compared for the first time. The domains of applicability for the diffusion models are determined. It has been shown that the determination of optical characteristics of highly scattering media by experimental temporal distributions leads to different numerical values depending on the used model. Nevertheless, any of these models can be used because the performed study does not permit one to give preference to any of them. However, in determining optical characteristics of the scattering samples, it is necessary to specify the used model, as well as the conditions under which the initial experimental data (in particular, the thickness of the layer of a studied sample) are obtained.     

Optical properties of BiTeI semiconductor with a strong Rashba spin-orbit interaction

We have modeled the 4f ¹-5d ¹ absorption spectrum of a LiYF₄:Ce³⁺ crystal at zero temperature using a microscopic model of the electron-phonon interaction and the real spectrum of LiYF₄ lattice vibrations. Effects caused by mixing of the wave functions of different states of the 5d ¹ excited configuration of the Ce³⁺ ion, which is induced by the electron-phonon interaction, are considered based on the calculations of the second-, third-, and fourth-order exact moments of curvature of the spectrum envelope. We have shown that the large value of the splitting between the maxima of the bands in the absorption spectrum that correspond to transitions to the third and fourth 5d ¹ levels is a result of the nonadiabatic interaction of 5d electrons with lattice vibrations.     

Investigation of the thermal diffusion during the formation of a quasicrystalline phase in thin Al-Pd-Re films

The layer mixing during the formation of the Al₇₀Pd₂₀Re₁₀ icosahedral quasicrystalline phase in thin (55 nm) Al-Pd-Re layered film systems subjected to vacuum annealing has been studied. It is shown that a combined layer of Pd and Al atoms (with the Al₃Pd₂ phase dominating) is formed in the first stage (at 350°C), while the rhenium layer remains invariable. In the second annealing stage (at 450°C), the β′-AlPd phase is formed and the Re layer is diffused. In the third stage (700°C), Pd and Re atoms are uniformly distributed throughout the film with the formation of a quasicrystalline phase.     

Acid Co(II) and Ni(II) trifluoroacetate complexes: Synthesis and crystal structure

Anhydrous and partially hydrated acid trinuclear trifluoroacetates of divalent transition metals of the composition [M₃(CF₃COO)₆(CF₃COOH)₆)](CF₃COOH) and [M₃(CF₃COO)₆(CF₃COOH)₂(H₂O)₄)](CF₃COOH)₂, respectively, where M = Co (I, III) Ni (II, IV), were synthesized and studied by X-ray diffraction. Complexes I and II were obtained by crystallization from solutions of M(CF₃COO)₂ · 4H₂O in trifluoroacetic anhydride; complexes III and IV were synthesized under the same conditions with the use of 99% trifluoroacetic acid as a solvent. Crystals I are triclinic: space group $P\bar 1$ , a = 13.199(6) Å, b = 14.649(6) Å, c = 15.818(6) Å, α = 90.04(4)°, β = 114.32(4)°, γ = 108.55(4)°, V = 2611.3(19) ų, Z = 2, R = 0.0480. Crystals II are trigonal: space group $R\bar 3$ , a = 13.307(2) Å, c = 53.13(1) Å, V = 8148(2) ų, Z = 6, R = 0.1112. Crystals III are triclinic: space group $P\bar 1$ , a = 9.001(8) Å, b = 10.379(9) Å, c = 12.119(9) Å, α = 83.67(5)°, β = 72.33(5)°, γ = 83.44(5)°, V = 1068.3(15) ų, Z = 1 Å, R = 0.1031. Crystals IV are triclinic: space group $P\bar 1$ , a = 9.121(18) Å, b = 10.379(2) Å, c = 12.109(2) Å, α = 84.59(3)°, β = 72.20(3)°, γ = 82.80(3)°, V = 1080.94(40) ų, Z = 1, R = 0.0334.     

Wind-Power Transforming Systems

In this article, we give a brief account of theoretical and experimental investigations, as well as engineering designs, of different types of rotors (propeller-type rotors and Darrieus-type rotors). In numerical studies, we used the vortex lattice method. We obtained instant and averaged-in-time values of the coefficients of the centrifugal, drag, side, and head forces, as well as the value of the relative torque, the wind-power use coefficient, the configuration of the vortex trace, and the velocity field and contour lines. The results of numerical studies agree well with experimental data.