Physics of Wave Phenomena最新文献

The concentration of hydrogen peroxide and hydroxyl radicals in dependence of the intensity (strength) of water drop impact on a solid surface has been measured. The intensity was varied by changing the fall height from 1 to 4 m and the tilt angle of the surface onto which drops fell. It is shown that the content of hydrogen peroxide and hydroxyl radicals in solution increases after the drop impact on the solid surface. Apparently, the main mechanism of the observed effects is the generation of singlet oxygen and its further reduction.

Two solvent models, COSMO (old parametrization) and COSMO2 (new parametrization) are compared for a set of protein–ligand complexes in quantum quasi-docking, which is two-stage docking: positioning of a ligand in a target protein and calculation of binding enthalpy of the protein–ligand system using the PM7 quantum-chemical semiempirical method. In quantum quasi-docking, a wide spectrum of unique low-energy minima of the protein–ligand system is first found while employing the classical force field. Then energies of all these minima are recalculated within one of the continual models using the modern PM7 method with allowance for the solvent, and the global energy minimum is determined among the recalculated energies. The solution of the quantum quasi-docking problem is the position of the ligand in the protein corresponding to the global minimum of the protein–ligand system energy calculated by the quantum-chemical method with allowance for the solvent. Effectiveness of quantum quasi-docking is defined by the value (below 2 Å) of the root-mean-square deviation of ligand atoms from one another in two positions, namely, the position of the ligand in the protein corresponding to the calculated global energy minimum and the experimentally found crystallized position of the ligand with the protein. Comparison is performed for ten protein–ligand test complexes with well-defined structures taken from the Protein Data Bank, for which the ligand–protein binding enthalpy is measured and the positioning of the ligand in the protein is successful in quasi-docking within both solvent models used. In both methods, PM7 + COSMO and PM7 + COSMO2, a high correlation coefficient of the experimental and calculated ligand–protein binding enthalpy is obtained for both calculation techniques. Allowance for moveability of protein atoms in calculations of binding enthalpy leads to an increase in its negative values and to a slight decrease in the correlation coefficient of the experimental and calculated values. The role of hydrogen bonds between protein and ligand atoms is revealed: their contribution to binding enthalpy ranges from 14 to 24% for different complexes. The results indicate the way of implementing quantum docking so that the global minimum of the protein–ligand system energy calculated by the quantum-chemical technique is immediately obtained using the global optimization procedure.

The possibility is considered of using asymmetric distributions to analyze emission/absorption spectra, which enables revealing the structure of polymodal spectra. A necessary condition for existence of the spectrum is a nonnegative relative increment of tis amplitude (emission/absorption intensity). The use of asymmetric distributions in spectrum shape simulation involves a certain type of differential equation, where the left-hand side is a relative amplitude increment and the right-hand side is the decreasing nonlinear function. As a result, a model is obtained, in which the signal amplitude increment is defined by classical results of statistical physics (L. Boltzmann, M Planck) and information theory (C. Shannon) that correspond to the limited growth model (Gompertz model). On the basis of the anamorphism of this model, relaxation parameters of the spectrum are determined, which are treated as objective characteristics of emission/absorption spectra. The result is illustrated by the analysis of the luminescence spectrum of deionized water.

A new type of diode laser with a scalable (fundamentally unlimited) aperture for the output optical beam has been proposed and calculated. Such an aperture can be implemented due to the use of a vertical cavity with one of the mirrors in the form of a surface diffraction grating. The threshold current density and differential efficiency of the proposed laser are calculated for the material parameters characteristic of the InGaAs/AlGaAs heterostructure and the spectral range at 0.98 µm.

Computer simulation of two-dimensional colloidal systems, in which interactions between particles are induced and controlled by an external rotating magnetic field, has been performed. The effective interaction potential of particles, along with the conventional pair potential, includes also three-particle interaction. It is shown that one of the parameters of the potential—field precession angle—radically changes the character of particle interaction and the phase diagram. In particular, at small angles the system behaves like a two-dimensional system with a purely repulsive soft-disk potential, whereas at large angles it behaves like a generalized Lennard-Jones system with the (nm)-potential; the presence of the three-particle part of potential reduces the temperature of the gas–liquid critical point. At intermediate field precession angles the phase diagram contains melting lines of triangular crystals of high and low density, between which a phase with a Kagome lattice was found. Our results serve an important guide for future experiments and simulation of colloidal systems, as well as for solving many problems in the fields of “soft” matter, physical chemistry, chemical physics, photonics, and materials science

We suggest and describe the protocol of measurements providing completely probabilistic representation of all parameters of polarization biphoton qutrits, i.e. providing explicit expressions for all parameters of qutrits via the probabilities of getting those or other results in measurements.

The content of H₂O spin isomers in saturated vapor during its fast evaporation from the surface of water in a cell at room temperature has been analyzed. The experiment was performed using the two-compartment scheme of simultaneous fast laser analysis of the concentration ratio of H₂O ortho- and para-isomers in saturated vapor in two analytical cells. One of these cells cointained water and its saturated vapor. The other was previously evacuated, and saturated vapor from the first cell was fed to it. Simultaneous analysis of the relative content of ortho- and para-water molecules during gas probe sampling, which lasted about 0.8 s, was performed with a rate of 10 measurements per second using a two-channel spectrophotometer based on tunable diode lasers (TDLs). The spectral range near 7355 cm^–1, where the ortho- and para-Н₂О absorption lines are closely located, was chosen for analysis. During the fast evaporation, which accompanied saturated vapor sampling, the evaporating vapor was found to be enriched with ortho-H₂O isomer, whose content amounted to ~20% of the equilibrium value 3 : 1. An important fact is that this result is indicative of possible enhanced mobility and the absence of hydrogen bonds for some of ortho-Н₂О molecules in the surface water layer, which is consistent with the known fact that water vapor transmitted through porous materials becomes enriched with ortho-H₂O isomers.

To reduce the ohmic loss of the encoding metasurface and achieve continuous control of the scattering angle larger than 70°, we numerically study all dielectric reflective metasurface in the mid-infrared waveband. Free control of the deflection angle of the far-field scattered beam is achieved. The unit structure designed consists of the Ge₂Sb₂Te₅ phase change material and the substrate. The phase difference between each two-unit structures is 90° and has high reflectivity in the working band. We can arrange the four units to construct metasurfaces with different coding sequences and perform Fourier convolution operations on the metasurfaces with different coding sequences to obtain flexible control of the reflected beam. The reflection characteristics of the coding sequence in the crystalline and amorphous states of the Ge₂Sb₂Te₅ phase change material are demonstrated. The abnormal reflection angle phenomenon of the simulated structure was theoretically analyzed.

We carried out a Raman study of a series of poly(L-lactide) (PLLA) samples annealed for different periods of time and therefore having different crystallinity degree. We compared the results with our recent study of the series of poly(L-lactide-co-ε-caprolactone) (PLCL) copolymers with the ε-caprolactone (CL) content ranging from 5 to 30 mol %. X-ray diffraction (XRD) analysis showed that the crystallinity degree of the analyzed PLLA-based materials is in the range of 0–86%. We suggest using the ratio of the peak intensities of the PLLA Raman bands at 411 and 874 cm^–1 to evaluate the crystallinity degree of PLLA homopolymers as well as PLLA blocks in the PLCL copolymers. This ratio does not depend on the CL content in the copolymers, it strongly depends on the crystallinity degree of PLLA (PLLA blocks in the PLCL copolymers) and it is a linear function of the crystallinity degree, measured by XRD analysis. We carried out quantum chemical calculations of the optimized geometries and Raman spectra of PLLA oligomers in the conformation of helix 10₃ with the number of monomeric units from 5 to 12. The results of the calculations revealed that the ratio of the intensities of the bands at 411 and 874 cm^–1 weakly depends on the oligomer length for the number of the PLLA monomeric units more than 7.

The results of theoretical investigation of magnetooptical properties of CoPt-based nanostructures are presented. Within the effective medium method, namely, the symmetrized Maxwell Garnett approximation, spectral dependences of the transverse effect are calculated for ferromagnetic granules with allowance for the size effect. The simulation showed good agreement of the experimental and theoretical data in the visible region of the spectrum.