Structural Transitions in Elemental Tin at Ultra High Pressures up to 230 GPa

The quantum heat generation, interaction force, and friction torque for two rotating spherical nanoparticles with the radius R are calculated. In contrast to a static case where an upper bound in the radiative heat transfer between two particles exists, the quantum heat generation for two rotating particles diverges at distances between particles d < d ₀ = R(3/ε″(ω₀))^1/3 (where ε″(ω₀) is the imaginary part of the dielectric function for the material of a particle at the resonance frequency ω₀), when the rotation frequency coincides with poles in the excitation generation rate at Ω = 2ω₀. These poles are due to the anomalous Doppler effect and the mutual polarization of particles and exist even in the presence of dissipation in particles. The anomalous heat generation is associated with the conversion of mechanical rotation energy into heat mediated by quantum friction. Similar singularities also exist for the interaction force and friction torque. The results can be of significant importance for biomedical applications.     

Structural phase transitions and the equation of state of SnTe at high pressures up to 2 mbar

Synchrotron X-ray diffraction studies of the structure of SnTe have been performed at room temperature and high pressures under the conditions of quasihydrostatic compression up to 193.5 GPa created in diamond anvil cells. Two structural phase transitions have been detected at P ≈ 3 and 23 GPa. The first phase transition is accompanied by a stepwise decrease in the volume of the unit cell by 4% because of the orthorhombic distortion of the initial SnTe-B1 cubic structure of the NaCl type. It has been found that two intermediate rhombic phases of SnTe with the space groups Cmcm and Pnma coexist in the pressure range of 3–23 GPa. The second phase transition at 23 GPa occurs from the intermediate rhombic modification to the SnTe-B2 cubic phase with the CsCl structure type. This phase transition is accompanied by an abrupt decrease in the volume of the unit cell by 8%. The pressure dependence of the volumes per formula unit at room temperature has been determined.     

QCD factorization for forward hadron scattering at high energies

We calculate the branching ratios and CP asymmetries of the B???Ц?, ?Ц? decays in the perturbative QCD factorization approach up to the next-to-leading-order contributions. We find that the next-to-leading-order contributions can interfere with the leading-order part constructively or destructively for different decay modes. Our numerical results have a much better agreement with current available data than previous leading-order calculations, e.g., the next-to-leading-order corrections enhance the B ⁰???? ⁰ ?? ⁰ branching ratios by a factor 2.5, which is helpful to narrow the gaps between theoretic predictions and experimental data. We also update the direct CP-violation parameters, the mixing-induced CP-violation parameters of these modes, which show a better agreement with experimental data than many of the other approaches.     

Estimate of the precision of determination of elastic parameters by the diffraction tomography method with the use of the finite-difference method (the SV-problem)

In the present paper, the finite-difference method is used for the solution of the direct problem, which enables us to take into account the diffraction phenomenon on local inhomogeneities of not weak contrast. Examples that allow us to estimate the precision of restoration of the parameters of such inhomogeneities, depending on the degree of their contrast, are given. The possibility of restoring the parameters of a local inhomogeneity in a medium containing interfaces with stepwise change of elastic properties for the case where source and receiver points are located on the free surface is demonstrated. An example of the numerical estimation of the precision of calculation of a scattered field in the Born approximation, approximating the wave field by the zero term of the ray method, is offered. Bibliography: 11 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 250, 1998, pp. 136–152. Translated by Yu. V. Kiselev     

Mikrochemie

Ohne Zusammenfassung     

Anreicherung von Spuren Seltener Erden aus Mineralwässern durch Ionenaustausch

In the described analysis of mineral waters, after the throughflow of the sample through a column with Dowex 50 WX 12 in H⁺ form, the main cations are first eluted by 1.6 N HCl and then the rare earths by 6 N HCl. The latter are separated by ion-exchange chromatography on Dowex 50WX8 in NH₄ ⁺ form, the elution being performed with ammonium citrate pH 4.19. The presence of rare earths in the eluate was ascertained spectrophotometrically by means of their reaction with xylenol orange in the presence of cetylpyridinium bromide. In mineral waters from the West-Bohemian spa region it was possible to find traces of trivalent La, Ce, Pr, Nd, Sm + Gd, Y, Dy, Ho, Er, Tm, Yb and Lu.     

Investigation of Electrophysical Properties of ITO Films

Russian Physics Journal - The results of a study of the electrophysical characteristics of ITO films obtained by magnetron sputtering are presented. It is shown that a significant increase in the...     

Synthesis and Magnetic Properties of Iron Polyhydrides at Megabar Pressures

JETP Letters - Iron polyhydrides have been synthesized at pressures of 77–157 GPa and temperatures up to 2000 K by the laser heating of an iron–borazane (ammonia borane NH3BH3) sample...     

High-spin-low-spin transition in magnesiowüstite (Mg<Subscript>0.75</Subscript>,Fe<Subscript>0.25</Subscript>)O at high pressures under hydrostatic conditions

The spin states of Fe²⁺ ions in (Mg_0.75,Fe_0.25)O magnesiowüstite crystals at hydrostatic pressures up to 90 GPa created in a diamond-anvil cell with helium as a pressure-transmitting medium have been investi-gated by transmission and synchrotron Mössbauer spectroscopy at room temperature. An electron transition from the high-spin (HS) state to the low-spin (LS) state (HS-LS crossover) has been observed in the pressure range of 55–70 GPa. The true HS-LS transition occurs in a narrow pressure range and the extension of the electron transition to ～15 GPa is attributed to the effect of the nearest environment and to thermal fluctuations between the high-spin and low-spin states at finite temperatures. It has been found that the lowest pressure at which the electron HS-LS transition can occur in the Mg_{1 ? x} Fe _x system is 50–55 GPa.     

Time and temperature dependent breakdown characteristics of ZnS:Mn films obtained by rf-magnetron sputtering

Breakdown delay times (t_del) for films of managanese-doped zinc sulfide (ZnS:Mn) were measured in the range 10^–6–10^–1 s. The maximum value was t_del=10^–3–10^–2 s. The electrical strength (E_br) was found to increase as the voltage pulse duration was reduced, the more so the thinner the ZnS:Mn film. The temperature dependence of E_br exhibited a weak reduction in E_br as the temperature was raised to roughly 80°C and a sharp reduction in E_br for T>130°C. A maximum in E_br was observed at T130°C which is presumably explained by a structural modification of the ZnS:Mn film. The experimental results obtained are explained in terms of a combined electronic and thermal breakdown mechanism.State Academy of Control Systems and Radioelectronics, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 3–6, April, 1994.