Physics of Wave Phenomena最新文献

In the present article, we analyzed the effects of Tsallis (or nonextensive) polarization force on nonlinear dust acoustic waves (DAWs). The polarization force acting on dust particles in a nonuniform dusty plasma is then revisited within the theoretical framework of the nonextensive statistical mechanics. The behavior of the polarization force is considerably changed due to the presence of nonextensive ions. Specifically, we showed that, for both experimental and space dusty plasmas, the magnitude of the polarization force (in the case where q > 1) increases as the ion nonextensivity becomes significant. As an application, we studied the changes caused by the nonextensive polarization force on the intrinsic properties of the DAW, namely, the wave profile, the transported energy, and the electric field. In particular, we have shown that due to the presence of nonextensive polarization force, the DA wave profile becomes deeper and the transported energy undergoes depletion. For a good understanding, we have also carried out a comparative study on the effects of the nonextensive polarization force on the DAW and its energy associated with both space and experimental dusty plasmas. We have found that, for a given value of the nonextensive parameter q, the DAW profile of the experimental dusty plasma seems more affected by the presence of the Tsallis polarization force.

A two-dimensional system characterized by the Hertz potential with the parameter α = 7/2 in the region of crystal-phase stability has been studied by the molecular dynamics method. It is shown that the anomaly of the density and thermal expansion, found previously for this system in the equation of state along isochores, also manifests itself on isotherms. A study of the translational and orientational order parameters revealed their drop in the density anomaly region, which is most pronounced for the translational order parameter. The obtained results are also in good agreement with the previous data on the attenuation of the transverse phonon mode in this region. This correlation indicates the presence of a strongly diffuse isostructural transformation in the anomalous region of the phase diagram.

The results are reported of processing luminescence spectra from samples obtained by successive dilution of the aqueous solution of antibodies to S100 protein with the initial concentration C = 1 µM. It is found that the intensity of the light scattering background increases as compared to the control water, which indicates relaxation of optical properties of the solution, probably due to modification of its structure at successive dilution.

The structure of aqueous solutions has been studied for a long time; however, many things still remain unclear. One of the ways to describe the water structure is the statistical approach, within which the distribution of water molecules over mobility, connectivity, number of hydrogen bonds, etc. is analyzed. An important parameter in this consideration is the equilibrium number of free water molecules, which are not bound by hydrogen bonds and do not enter the composition of hydrate shells. There are not any completely justified approaches for calculating the fraction of free water molecules in solutions. Aqueous solutions are known to have a weak band of the relaxation type (differing from the classical Debye relaxation band) in the THz frequency range. This band is assigned to the orientational relaxation of free water molecules. In this paper we theoretically consider the process of orientational relaxation of free water molecules in an aqueous solution in the THz range. The theory is based on the Onsager polarization model, modified for application in the THz range. The field screening due to the higher frequency polarization processes is taken into account. Particular attention is paid to the field screening due to the orientational polarization of bound water molecules. Based on this consideration the ratio between the fractions of free water molecules in solution and the parameters of spectral bands of water molecular dynamics is obtained. The calculated numbers of free water molecules, obtained within the proposed theory and other known (simpler) approaches, are compared for some solutions. It is shown that, if the field screening is taken into account when considering the orientational polarization of free water molecules, their number increases. For example, the number of free molecules for liquid water at 25°С, with complete consideration of screening, is about 9%.

A comparative study of the sizes and spatial structure of single dielectric colloidal nanoparticles of lanthanum fluoride, doped with rare-earth neodymium ions (Nd³⁺:LaF₃), and their conglomerates in an aqueous solution has been performed. Nanoparticles were synthesized by aqueous co-precipitation method with subsequent hydrothermal microwave (HTMW) treatment. Experiments were performed using three methods: transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and dynamic light scattering (DLS). An analysis of the results has shown that a stable colloidal solution of nanoparticles is formed during synthesis. The solution consists of single lanthanum fluoride nanoparticles, having a narrow (10–30 nm) size distribution, and nanoclusters formed on their basis. It is also shown that the spatial structure of nanoclusters cannot be described in terms of the fractal model, which is widely used to describe clusters formed in colloidal solutions of nanoparticles of various nature.

A procedure is discussed for obtaining various solutions to the Schrödinger equation by the Monte Carlo method. Water clusters, namely, the hexamer 6(H₂O), dodecamer 12(H₂O), and tetradecamer 14(H₂O) are used as quantum systems to illustrate the procedure. Various solutions to the Schrödinger equation are derived from the algorithm earlier proposed by the author, which is based on the intersection of the finite-difference and Monte Carlo approaches and on the water-cluster-tested methods for spatially reducing scattering centers of particle nuclei and scattering centers of electrons of an arbitrary quantum system. Ultimately, it has become possible to construct an algorithm for generating an unlimited number of various spatial structures of scattering clouds of particle nuclei and electrons at a given dissociation energy of a quantum system.

Analysis of the results of nonempirical simulations of Met⁺(H₂O)_n clusters with Met = Li, Na, and K, and n = 20–55 carried out at the density functional level with B3LYP exchange-correlation functional and extended double-zeta basis sets revealed the prevailing structure motifs of the aqua complexes of alkali metal ions and their fingerprints in the infrared absorption spectra in the range of 2000–4000 cm^–1. The hydration structures of the ions are found to be predetermined by the balance between the conjugated H-bonded rings and extended ordered H-bonded sequences. The extension of the latter is shown to decrease with an increase in the effective radius of the ion, which is reflected in the stronger localization of the coupling of OH oscillators within the homodromic structural rings and the respective shift in the characteristic frequencies within the OH stretching domain.

A characteristic feature of water and aqueous solutions is spontaneous chemiluminescence. Previously we have discovered the phenomenon of activation of the spontaneous chemiluminescence of water during shaking, with subsequent decreasing chemiluminescence intensity and reaching a stationary level. It is unclear how spontaneous chemiluminescence of water depends on the shaking conditions. It is also of interest how such physical factors as mechanical shaking or alternating magnetic field may affect the chemiluminescence in solutions with biological objects, for example, in aqueous protein solutions. In this study we investigated the dependence of the spontaneous chemiluminescence of bovine serum albumin solution on the mechanical impact conditions (frequency, amplitude, and duration), as well as the influence of ac magnetic field on the spontaneous chemiluminescence of immunoglobulin G solution. In the case of albumin solution a vibration impact with an amplitude of 12 mm caused a decrease in the chemiluminescence intensity in comparison with a control albumin sample, which was not exposed to vibrations. The severity of the effect was independent of the time and frequency of the vibration impact. Shaking with a frequency of 30 Hz and an amplitude of 2.3 mm increased the average chemiluminescence intensity. Spontaneous chemiluminescence of water depends to a greater extent on the amplitude and duration of the mechanical impact rather than on its frequency. The chemiluminescence intensity of a bovine serum albumin solution with a concentration of 1 mg/mL decreased in comparison with the check sample in all shaking modes. The most pronounced effects were observed for an amplitude of 12 mm and/or a frequency of 30 Hz. Time dependence was observed for the mode with an amplitude of 12 mm and a frequency of 30 Hz. Therefore, the spontaneous chemiluminescence of aqueous protein solutions depends to a greater extent on the amplitude and vibration frequency and to a lesser extent on the impact duration. The influence of ac magnetic field on the physical characteristics of water is described. We found that the magnetic field did not affect the water chemiluminescence parameters but changed the intensity and RMS deviation of the chemiluminescence intensity of IgG aqueous solutions. The effect severity depended on both the frequency of applied ac magnetic field and on the protein concentration.

The study of the induction periods of hydration and structure formation of cement stone is one of the most urgent problems of modern building materials science. Water and aqueous solutions of inorganic salts are the most widespread forms of mixing liquids for cement systems. The properties of distilled water and aqueous solutions of sodium chloride with different concentrations have been investigated by dielectrometry. It is proposed to consider the structural organization of water and aqueous solutions as a combination of strongly and weakly bound water. The strongly bound water is the result of manifestation of hydrogen bond forces; this type of water specifies the ordered state of the system. Weakly bound water causes fragmentation of the initial water continuum into smaller structural units. The change in the impedance and admittance spectra of cement paste during hardening has been analyzed. Spectra were measured in the frequency range from 20 Hz to 2 MHz using a capacitor measurement cell. Investigations have been performed to find the optimal equivalent electric circuits describing the transformation of the electrical properties of cement paste and the interface phenomena occurring in the near-electrode layer of the measurement cell in dependence of the hardening time. It is found that the equivalent circuit parameters are sensitive to different stages of cement paste hardening. A relationship between the spectra of electrical parameters and the processes of cement stone hardening is demonstrated.