The influence of low-intensity non-thermal electromagnetic waves of the millimeter range on the surface and volume properties of water, saline, and DNA solutions was studied. It is demonstrated that non-thermal millimeter electromagnetic waves (MMEMW), which coincide in frequency with the resonant frequencies of water structures’ oscillations, produce a specific effect in vivo and in vitro [1–3], affecting living organisms through the aqueous component of their environment. The non-thermal EW is not absorbed by the surface layer of aqueous solutions and penetrates the deeper layers of liquid, leading to the dehydration of salt ions and DNA, and an increase in the density of the aqueous solutions. Irradiation of DNA solutions with low-intensity resonance frequencies for aqueous molecular structures for 90 minutes leads to an increase in the thermal stability of DNA by approximately 1°C. As the temperature increases, the density of non-irradiated and irradiated solutions decreases. However, there is a significant difference between the behavior of density dependence on temperature for non-irradiated and irradiated saline and DNA solutions. Calculations show that for studied solutions, the coefficient of thermal expansion (α) increases with increasing temperature, and the growth of α occurs differently for water structures irradiated and not irradiated with resonant oscillation frequencies.
We present the results of the analysis of the possibility of detecting single photons of the extreme ultraviolet range using a multilayer thermoelectric sensor with an operating temperature of 4.2 K. The sensor with a surface area of 1 or 100 μm2 consists of an absorber (W), a heat sink (Mo) and a dielectric substrate (Al2O3) with thicknesses of 40, 10 and 100 nm, respectively. The thickness of the thermoelectric layer (CeB6) was 5 and 10 nm. The equivalent noise power of the sensor is determined. To calculate the efficiency of detecting photons with energies of 22.5, 38, 39 and 44.7 eV, the processes of heat propagation in the considered sensor after absorption of photons in the center of the absorber surface are studied by computer simulation and the signal power is determined. Using the obtained results, the efficiency of the thermoelectric sensor of the proposed designs at an operating temperature of 4.2 K is assessed.
The effect of an electric field on a graphite coating deposited on an aluminum plate was studied experimentally. The experiments were made under electrolysis conditions, and ordinary water was used as the electrolyte. Samples of aluminum plates with graphite coatings served as the cathode and anode. The electrodes were tested under the influence of electric pulses with a sharp front. After exposure to the electric field for 72 hours, changes in the integrity of the cathode coating were observed. No changes were detected on the surface coating of the anode. Using a scanning electron microscope equipped with an energy-dispersive X-ray microanalysis system, the chemical composition of the cathode surface coating was analyzed before and after the electric pulses’ influence on the electrolyzer. A significant degradation of the graphite coating structure on the aluminum plate was recorded as a result of the electric field exposure. A possible physical mechanism of carbon transformation on the graphite coating of the aluminum plate under the application of a negative electric field is presented.
The article presents a device for detecting and localizing humans over long distances in the thermal infrared region, featuring an ultra-large coverage area. The device consists of eight conical horn elements and corresponding thermal sensors. The horns are positioned in such a way that the angle of view of adjacent elements partially overlaps. Theoretical considerations enabled the identification of a suitable solution for the angles between adjacent horns, resulting in an almost uniformly distributed angular detection profile with a total angle of view of 110°. This enabled the optimal design of the horn element arrangement in the device to effectively detect and localize humans, with a detection range of 30 m and a horizontal coverage area of 863.9 m2. The summed level of thermal signals from two adjacent sensors allows estimation of the distance to a human, and their ratio determines the observation angle.
We present simulation and analysis of the magnetic field evolution generated by human-sized copper coils when extrinsic metallic objects are introduced in their proximity. The magnetic field variation can be effectively detected by leveraging the Zeeman effect, when light interacts resonantly with alkali atoms confined in nanometric or micrometric thin cells. To precisely quantify these changes, we analyse spectra of light-atom interaction in the presence of a magnetic field and introduce an algorithm capable of measuring magnetic field variations induced by a relatively small iron sphere. The key strength of our approach lies in its robustness, as it can extract meaningful information from experimental spectra without requiring a direct reference spectrum.
The optical properties of a cholesteric structure with homotropoic boundary conditions were investigated using computer modeling methods of the wave equation in the quasi-isotropic approximation of geometric optics. A translation-invariant configuration was obtained for thicknesses greater than the critical thickness, as well as for thicknesses less than the critical thickness, by applying a destabilizing electric field. At large spiral pitch values, the dependence of the ellipticity of the outgoing radiation on the spiral pitch is not monotonic, and one reaches its maximum in the region of a spiral pitch of 40 μm. It is shown that for some discrete values of the maximum angle of exit of molecules from the plane of the cell walls, the rotation of the polarization plane of incident linearly polarized light does not depend on either the polarization angle of the incident light or the wavelength of the light, at least in the visible range.
The incorporation of Li+ ions into crystalline materials enables the controlled modification of their physical properties; however, the efficiency of this process is determined by the mechanism of incorporation and charge compensation, which depend on many factors and are not always straightforward. In the present study, thulium aluminum garnet (Tm3Al5O12), also known as TmAG, was chosen as a model system. Single crystals of TmAG, TmAG:Li, and TmAG:Ce, Li with Li concentrations of 50 and 150 ppm were grown by the Bridgman method, and polycrystalline samples of TmAG and TmAG:Li with Li concentrations up to 600 ppm were synthesized using solid-state reaction and melt-quenching techniques. The unit cell parameters of the samples were measured and compared with calculated values obtained from theoretical models. Absorption spectra of TmAG:Li and TmAG:Ce, Li single crystals were recorded before and after γ-irradiation. Experimental results have shown that at least a portion of the Li+ ions in TmAG occupy crystallographic lattice sites, like the behavior of Li+ ions in lutetium alumina garnet. It is suggested that Li+ ions are most likely to replace Al3+ ions.
This paper presents a pioneering first-principles investigation into the structural, elastic, electronic, and optical properties of novel ternary alloys YNxBi1 – x and YAsxBi1 – x which are considered promising candidates for advanced photonic and electronic applications. We employed the full-potential linearized augmented plane wave (FP-LAPW) method, based on density functional theory (DFT), as implemented in the WIEN2K simulation code, for compounds crystallizing in the NaCl-type structure. Structural properties, including lattice constants, bulk modulus and elastic properties, such as elastic constants, shear modulus, anisotropy factor, Poisson’s ratio, Young’s modulus, and the Kleinman parameter were calculated using the generalized gradient approximation (GGA) for the exchange-correlation (XC) potential. Furthermore, the Wu-Cohen generalized gradient approximation (WC-GGA) and the modified Becke and Johnson (mBJ) approaches were applied to examine electronic (band structure) and optical (real and imaginary parts of the dielectric function, refractive index) properties, respectively. These findings highlight the significant potential of these materials for use in advanced optoelectronic technologies, opening new avenues for future innovation.
The influence of ultrasonic exposure on the processes of nucleation and growth of synthetic diamond under high-pressure, high-temperature (HPHT) conditions was investigated. It was shown that an acoustic field with frequencies around 100 kHz and amplitudes of about 1.5–2.5 μm leads to a significant reduction in the energy barrier of the graphite–diamond phase transition, acceleration of stable nucleus formation, and improvement in growth kinetics. Experimental data demonstrate an increase in diamond yield, enhanced monocrystallinity, and reduced structural defectiveness under ultrasonic action. Based on the analysis of processes in the solid phase and at the interfacial region, a physico-mathematical model of the acoustically stimulated phase transition was proposed, taking into account the dynamic change of the critical nucleus radius, reduction of the barrier ΔG*, enhanced diffusion, and increased efficiency of crystal doping with impurities. The results confirm the promise of ultrasonic stimulation as a tool for controlled intensification of HPHT diamond synthesis and optimization of the structure of growing crystals.
By doping zinc with transition metals (Ag + Fe + Cu), the following targets were formed: Zn/Ag/Fe/Cu (Zn95, Ag2, Fe2, Cu 1
The interaction of serotonin with DNA has been studied by methods of fluorescence and absorption spectroscopies. Serotonin fluorescence intensity was shown to decrease (quench) with increasing concentrations of DNA in the solution. Based on the intensity measurements, the values of the quenching constants (Stern–Volmer constant)—KSV were determined in the temperature interval 298–311 K. It was also shown that the absorption spectra at increasing concentrations of serotonin showed a higher degree in the absence of DNA, as compared to the presence of DNA. Based on the fluorescence and absorption spectra of the serotonin complexes with DNA, the adsorption isotherms were obtained, and the values of the binding constant K and the number of base pairs per binding site n were determined.
A hydrothermal-microwave method for the synthesis of cadmium metasilicate was developed using water-soluble cadmium compounds and sodium silicate, demonstrating enhanced efficiency compared to conventional thermal techniques. The synthesized product, cadmium metasilicate, is a nanodispersed powder with high photocatalytic activity and radiation resistance. The physicochemical properties of the synthesized cadmium metasilicate were investigated using differential thermal analysis, X-ray diffraction, UV–VIS and IR spectroscopy, as well as electron microscopy. The results showed that the band gap (Eg) of the synthesized powder, depending on the heat-treatment temperature and proton irradiation, varies in the range of 5.06–5.46 eV. The material obtained by the proposed method can be used as a dielectric, a photocatalyst, and for protection against ionizing radiation.
The electron mobility due to scattering by acoustic phonons has been studied in a cylindrical GaN semiconductor nanowire embedded in a nonpolar medium. Taking into account the spin–orbit interaction, the dependences of electron mobility on the nanowire radius, the linear electron concentration, the Rashba spin–orbit coupling parameter, and the temperature have been obtained. It is demonstrated that the inclusion of spin–orbit interaction leads to an increase in electron mobility, with the rate of growth being particularly pronounced at low temperatures. A significant technological issue is examined: the impact of spin-orbit interaction on electron mobility in quasi-one-dimensional transport devices based on GaN nanowires at low temperatures, where scattering by acoustic phonons prevails.
A theoretical evaluation of the activity of the medical radioisotope 68Ga produced by cyclotron irradiation of zinc targets via the 68Zn(p, n)68Ga reaction has been performed. Using SRIM/TRIM, proton energy losses in the target material and the dependence of proton energy on target depth (thickness) were determined. Effective cross–sections σ(E) for the 68Zn(p, n)68Ga reaction were obtained using the TALYS 1.9 code. It was established that the optimal proton energy range (12.5–4.6 MeV) provides a high theoretical product yield while minimizing side reactions. For irradiation of natural and enriched zinc targets, the calculated theoretical yields were 0.82 and 4.36 GBq/(μA h), respectively, which agree with literature data. The results obtained can be used to optimize the technical parameters for the production of 68Ga for medical applications.
The energy pathways of possible reactions of the ethoxyl radical and its conformers were investigated by quantum chemical computational methods. It was shown that isomers of the radical with the general formula C2H5O can exist. In this case, the global energy minimum of the system corresponds to the total energy of the anti-CH3CHOH radical. Transition states for the reactions leading to the formation of vinyl alcohol, ethylene oxide, and acetaldehyde were identified computationally, and their thermochemical parameters were determined.
The present problem investigates nonlinear interaction of Hermite–Cosh Gaussian (HChG) beam in cold collisionless plasma. The ponderomotive force results in carriers redistribution away from beam’s axis thereby leading to generation of gradients of intensity inside plasma. These gradients of intensity cause self-focusing of beam. The beam’s field vector wave equation in cold collisionless plasma is solved with established paraxial theory to obtain 2nd order ODE for beam waist of beam. Since, analytical solution of this equation is not possible. So, this is numerically solved using Runge–Kutta 4th order method for examining response of beam waist against dimensionless distance. We have also examined effect of notable parameters of laser and plasma including plasma density, plasma temperature, beam intensity, decentered parameter and beam radius on response of beam waist of beam.
In the present work, an attempt is made to carry out a comprehensive theoretical analysis and interpretation of a large body of industrial and laboratory experimental data accumulated in the field of the synthesis of polycrystalline diamond of the carbonado type. The study covers the physicochemical mechanisms of phase transitions in carbon systems, barodiffusion processes, and the role of catalytic components, as well as the kinetic aspects of crystal structure growth. The analysis is based both on experimental data obtained from industrial high-pressure high-temperature (HPHT) installations and on results of targeted laboratory series in which key parameters—pressure, temperature, composition, and dwell time—were varied. Particular attention is paid to correlating industrial and laboratory results with theoretical models of phase equilibrium and growth dynamics, which not only makes it possible to explain the observed phenomena but also to propose approaches for the targeted optimization of the process.
This paper investigates the nonrelativistic approximation in the first-order 39-component theory for a spin-3/2 particle in curved spacetime under external electromagnetic fields. Starting from the generally covariant matrix equations, generalized via the Weyl-Fock-Ivanenko tetrad method, we employ explicit forms of the four main Γ^a matrices of dimension 16 × 16 within the corresponding first-order system. The analysis is carried out for spacetime metrics that permit the existence of nonrelativistic equations. To separate the large and small components of the complete wave function, three projective operators are constructed from the fourth-order minimal polynomial of the Γ _16 × 16^0 matrix. The explicit forms of these components are obtained, and the set of independent variables is identified; in particular, only four large components are independent. Following the standard procedure, we derive the nonrelativistic system of equations for a 4-component wave function. The resulting Hamiltonian includes contributions from the electromagnetic field and additional geometric terms expressed through the Ricci rotation coefficients, Ricci scalar R and Ricci tensor R_ab . We also isolate the term describing the interaction between the magnetic moment of the spin-3/2 particle and the external magnetic field. This interaction term is expressed via the spin matrices S_i and the components of the magnetic field vector B.
A method of optical transmission imaging of strongly scattering objects is proposed, based on point-by-point spatial scanning of a beam of pulsed-periodic laser radiation over the surface of the object under study and recording the number of transmitted light pulses at each scanning point using a patented photoreceiver that selectively registers short light pulses regardless of the level of background illumination. The conditions for obtaining “proportional” and “contour” images of model and biological objects are determined. The features of the method are a low level of required average radiation power, high image recording speed, and a wide operational spectral range, which makes it promising for use in biomedical diagnostics, materials quality control, security, and other areas.
The dielectric properties of nanocrystalline glass-ceramics based on perlite were investigated in the frequency range of 100 – 1 × 106 Hz and the temperature range of 25–350°C. Relaxation peaks were observed in the temperature dependences of the dielectric permittivity and dielectric losses, shifting toward higher temperatures with increasing frequency, which made it possible to determine the activation energy of the relaxation process. The frequency dependence of the temperature coefficient of dielectric permittivity additionally confirms the relaxation nature of the observed phenomenon. The obtained results are consistent with the Maxwell–Wagner interfacial polarization model, indicating a heterogeneous structure of the material.
