Physics of Wave Phenomena最新文献

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.

Probable structural mechanisms with structural invariants based on a chain of six-membered cycles linked through a common atom are proposed for some transitions between crystal water phases. It is shown that in the II → Ic transition with the structural invariant under consideration, 5/6 of the hydrogen bonds of the initial structure are retained, while in the same transition considered previously with the structural invariant in the form of a band of six-membered cycles linked through a shared bond, only 3/4 of the bonds of the initial structure are retained. In the V → Ic transition, both structural invariants (chains of six-membered cycles linked through a common atom and bands of six-membered cycles linked through a shared bond) are shown to be retained simultaneously. For the structural mechanism of the V → Ic transition with these structural invariants, 11/14 of hydrogen bonds of the initial structure are retained. It is shown that structural invariants of the mechanisms for the IX → Ic, VI → Ic, IX → II, and II → III transitions may also be based on a chain of six-membered cycles linked through a common atom.

The thermodynamic properties of hafnium under the high pressures obtained behind the shock wave front are described. A simple model in the form of a dependence of pressure on the specific volume and specific internal energy is proposed. The thermodynamic characteristics of the body-centered cubic (bcc) solid phase and melt of hafnium under high shock-compression pressures are calculated. The calculation results are compared with the available data of shock-wave experiments. The resulting equation of state of hafnium can be used in numerical simulation of the processes occurring at high pressures in shock waves.

The role of hydrogen peroxide molecule (Н₂О₂) in the vital functions of biological objects has been considered. The mechanisms of Н₂О₂ formation and its relationship with redox reactions, as well as some possible methods of analyzing the Н₂О₂ content in liquid and gaseous media, are discussed. In particular, the possibility of using highly sensitive methods of laser spectral analysis for detecting Н₂О₂ traces in exhaled air, which are promising for diagnostics of various pathologies, is considered. The absorption spectra of exhaled air are analyzed, and the strongest H₂O₂ spectral lines (isolated from the influence of other gaseous metabolites), applicable for detecting Н₂О₂ by diode laser spectroscopy, are chosen.

The application of wide-gap semiconductor nanoparticles for improving optical characteristics of dye-sensitized solar cells (DSSCs) is considered. Here, silicon carbide nanoparticles (nSiC) are used as wide-gap quantum dots, and chromophores (lutetium diphthalocyanine and delphinidin) play the role of sensitizers. The influence of SiC nanoparticles on the absorption spectra of chromophores in tetrahydrofuran solutions, as well as their direct influence on substrates with titanium dioxide after introduction of sensitizers, is investigated. The characteristics of designed DSSCs are measured, and the DSSC performance is estimated based on the measurement data. The DSSC power and efficiency are calculated. It is found that addition of wide-gap semiconductor nanoparticles to a sensitizer improves significantly the characteristics of solar cells and increases essentially their stability. This improvement can be explained by the exciton decay, at which an electron passes initially to a nanoparticle of wide-gap SiC and then to a titanium dioxide (TiO₂) nanoparticle. The best characteristics of the solar cell versions under consideration correspond to those obtained for delphinidin with SiC nanoparticles.

Adiabatic compressibility β_S of the 4-methylpyridine + water solution is investigated in a wide concentration and temperature variation interval using Mandelstam–Brillouin scattering spectroscopy. The adiabatic compressibility minimum caused by the microinhomogeneous structure of the solution is experimentally established at the concentration of 0.06 M. The results of the investigations allow constructing a diagram of possible states caused by a continuous three-dimensional hydrogen bond network of water.

A technique of two-stage three-dimensional mapping of the optical breakdown threshold in diamond crystals is proposed. In the first stage diamond is irradiated by high-energy ultrashort laser pulses, which initiate multiple microbreakdowns in the probed volume of material; these breakdowns cause formation of graphite microinclusions. A sharp decrease in the spatial density of microinclusions in some crystal zone indicates a significant increase in the average value of breakdown threshold in this zone as compared with the neighborhood. The second stage of mapping implies measurement of the absolute values of breakdown threshold by choosing the minimum laser pulse energy necessary for the formation of a graphite microinclusion at a point studied. The “abnormal” crystal zones revealed in the first stage are investigated especially thoroughly, with optimal spatial resolution. Application of this technique to synthetic diamond single crystals from different manufacturers, grown by chemical vapor deposition (CVD), revealed zones in these crystals where the breakdown threshold changes by a factor of more than 10. The boundaries of these zones are located parallel to the (100) growth face; the layer thickness and position vary unpredictably.

Investigation is carried out to experimentally study concentration of microwave radiation with a wavelength ranging from 2.46 to 3.55 cm in a compact subwavelength region by a spherical resonator consisting of a dielectric sphere with a waveguide branch 1.15, 2, or 2.26 mm in diameter connected to the sphere tangentially to its surface or normally along its radius. The microwave radiation with a frequency ranging from 8.45 to 12.2 GHz excites Mie resonance oscillations in the spherical resonator with the attached waveguide branch. Frequency dependences of radiation from the waveguide branches show that the radiation intensity at the Mie resonance is almost two orders of magnitude higher than the intensity of the radiation exciting the resonant sphere.

Structural transformations under chlorine adsorption on the Ag(100) surface have been studied with scanning tunneling microscopy (STM) and within the density functional theory (DFT) calculations. The DFT method reveals that the preferable adsorption site of chlorine atoms is the fourfold hollow position. The STM technique is used to study the disorder–order structural phase transition occurring at a gradual increase in the chlorine coverage, which results in formation of the с(2 × 2) structure on the Ag(100) surface. It is found that the critical coverage of the ordering corresponds to ≈0.34–0.35 monolayer (ML). The chemisorbed chlorine monolayer is saturated at the coverage of 0.5 ML corresponding to the formation of the c(2 × 2) structure. Further chlorine absorption leads to nucleation and growth of AgCl islands near the edges of atomic steps.