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This study analyzes the amplitude-frequency characteristics (AFC) of deep GPR data gathered using variable offsets within the permafrost of the Nadym District, Yamalo-Nenets Autonomous Okrug. The initial frequency response of the raw data, which underwent only basic pre-processing, is presented, evaluating the effects of transmitter-receiver separation (100–750 m) as well as the spatial and depth-based placement of the analysis zone. This approach reveals the spectral evolution of electromagnetic signals within the geological environment during the late stages of the process. Results indicate that as the distance from the source increases, the signal undergoes standard attenuation, alongside three primary spectral effects: a downward frequency shift of the peak amplitude, a narrowing of the spectral bandwidth, and a significant rise in low-frequency components—the latter being primarily attributed to zero-line drift. Adopting spectral analysis techniques from seismic exploration for deep GPR data is a promising way to refine data processing and improve subsurface interpretation.

Sobolevite with low Mn content from the Karnasurt deposit (Lovozero, Kola peninsula) has been characterized by electron microprobe analysis, single-crystal structure refinement, high-temperature X-ray diffraction and density functional theory (DFT) calculations. The chemical formula can be written as Na_7.04(Ca_0.87Mg_0.16)_S=1.03(Ti_1.48Zr_0.20Mn²⁺_0.18 Nb_0.10Fe²⁺_0.06)_S=2.02Si_2.05P_2.02O_17.12F_0.88. The crystal structure refined to R₁ = 0.037 (P2₁/c, a = 7.0908(3), b = 5.4108(2), c = 40.6179(19) Å, b = 93.095(4)^o, V = 1556.11(11) ų) is based upon the [Ti₂O₂[Si₂O₇](PO₄)]^5- titanosilicate-phosphate HOH layers (TS blocks). The interlayer space is occupied by the AC complex formed by Na⁺, Ca²⁺ and Mg²⁺ cations along with (P1O₄)^3- groups and F^- anions. The F- anions are coordinated octahedrally by Na and Ca to form antiperovskite [FA₃] chains (A = Ca, Na) running parallel to the b axis. The crystal chemical formula of sobolevite is (Na_6.92Ca_0.92Mg_0.16)_S=2.00(Ti_1.46Zr_0.18Mn²⁺_0.15Nb_0.15Fe²⁺_0.06)_S=2.00(Si₂O₇)(PO₄)(F_0.81O_0.19)_S=1.00, which corresponds to the idealized formula Na₇CaTi₂O₂[Si₂O₇](PO₄)₂F and allows to consider it as a polymorph of quadruphite. The relations between sobolevite and quadruphite are pseudo-polytypic. The thermal behavior of sobolevite is typical for layered structures corrected by shear deformations. According to DFT calculations, sobolevite exhibits p-type semiconductor behavior with a band gap of approximately 2.75 eV. Altering the Ti/Nb ratio influences the band structure, inducing magnetism in the crystal and transforming it from a semiconductor to a semimetal or even a metal. The material exhibits strong absorption in the ultraviolet region, with an absorption coefficient reaching up to 2×10⁵ cm^-1. The overall structural architecture of sobolevite combines features of both titanosilicates and antiperovskite-type structures, which makes it an interesting example of hybrid structures with potentially interesting functional properties.

The article presents a methodology for quantitative verification of three-dimensional geoelectric models constructed from electrical tomography (ET) data in complex geological conditions. As an example of real data, a set of measurements is considered in the fault zone of the southeastern boundary of the Gorlovka depression (Novosibirsk region), where an increase in seismic activity has been observed in recent years. It is probably caused by the development of large coal mines. The relevance of the work is due to the interpretative ambiguity of ET data in heterogeneous geological environments and the appearance of artifacts in inversion models, which can subsequently lead to false interpretation of the results. It is proposed to move from the traditional visual comparison of the results of inversion of field and synthetic data to quantitative analysis. For this purpose, the ERT_Comp software tool has been developed, which calculates the relative difference between the model and field values ​​of apparent resistivity at specific spacings. The use of the technique for field data from three parallel profiles made it possible to quantitatively substantiate the choice of the optimal 3D geoelectric model reflecting the presence of a subvertical fault zone. The proposed approach does not completely remove ambiguity, but significantly increases the reliability of interpretation. Prospects for the work involve the use of gradient models and the establishment of standardized threshold values ​​of relative deviations to select the best interpretive model.

In natural and artificial water bodies, photolysis is the primary process that determines the transformation and fate of many pharmaceuticals. However, there is a lack of information on the degradation products of sulfonamide antibiotics and their toxicity. Phenols are potential transformation products of pharmaceutical contaminants and pose a threat to human health. This paper presents the results of an experimental study of the phototransformation of sulfamethoxazole in water. The irradiation experiments were carried out in a stationary photoreactor using KrCl (222 nm), XeBr (282 nm), and XeCl (308 nm) lamps and a bactericidal irradiator UVb-04 (180-275 nm) as sources of UV radiation. To determine the total phenol content in the photoproducts of sulfamethoxazole, a colorimetric method with Folin-Ciocalteu reagent was used. The changes observed in the absorption and fluorescence spectra after irradiation of aqueous sulfanilamide solutions are described in detail. The formation of three fluorescent photoproducts is shown, one of which is stable and accumulates in the solution regardless of the selected UV radiation source. The total phenol content increased after UV irradiation. It has been established that after 128 min of exposure to a KrCl excimer lamp, the total phenol content is 4 times higher than the initial value and amounts to 331.89 mg GAE/g. The results can be of interest for studying the degradation mechanism of sulfonamides, identifying toxic degradation products, and evaluating their antioxidant activity.

Phenol enters the environment during the combustion of plants and biomass, as well as through anthropogenic emissions. Phenolic compounds can act as precursors to organic aerosols, adversely affects human health, and reduces atmospheric visibility. The static absorption spectra of phenol and its volatile substituted compounds ( p-cresol and vanillin) presented in this work were obtained and analyzed using computer simulations based on quantum-mechanical molecular dynamics. The optical spectra were averaged over excited instantaneous molecular conformers fluctuating along system's evolution trajectories. The photodynamic dissipation of electronically excited states of the molecules was studied by generating trajectories in nonadiabatic molecular dynamics. Changes in the electronic structure of phenol, p-cresol, and vanillin, along with the crossing points and dissociation of potential energy surfaces, were obtained using the mixed-reference spin-flip approach within the time-dependent density functional theory. The O-H bond breaking in the hydroxyl group followed by deprotonation causes minor structural deformations for the molecules under study. It is shown that, upon excitation, the dissociation of the hydroxyl group occurs via an electronic transition to the σ-MO localized on the elongated O-H bond.

Properties of high-altitude discharges in the atmosphere of the Earth and other planets and their satellites are actively studied in past three decades due to the acquisition of new data, primarily because of improvement of optical observation methods. This work experimentally and theoretically studies the ratios W₁₊/W₂₊ of radiation energy spectral density of four bands of the 1st positive nitrogen system (1+) to a band of the 2nd positive nitrogen system (2+) with a wavelength of 337 nm. The ratios are compared for atmospheric air and nitrogen with low impurity content at pressures of 0.04-0.4 torr. It is shown that the quenching rate of C³Π_u triplet states of molecular nitrogen increases in a nitrogen-oxygen mixture, which decreases the ratios W₁₊/W₂₊. It is confirmed that quenching of B³Π_g state by nitrogen and oxygen molecules increases with the air density in the Earth's atmosphere. The results can be useful for studying physical processes occurring against the background of the interaction of high-energy electrons with gases in the atmospheres of a number of planets and their satellites, which predominantly contain nitrogen.

The development of laser radiation sources in the yellow-red spectral region with an extended range of adjustable generation parameters is a relevant and sought-after task in biomedical applications. This work experimentally studies spectral, temporal, spatial, and energy characteristics of neon atom radiation excited by a pulsed inductive cylindrical discharge. Lasing was obtained at 3 p → 3 s transitions of neutral neon atoms with wavelengths of 594.4 nm and 614.3 nm. The intensity ratio of these spectral components I ₅₉₄ : I ₆₁₄ depended on the pumping conditions and varied from 1 : 1 at pressures of 0.2-0.3 torr to 1 : (2...4) at an optimal pressure of about 0.13 torr. A maximal lasing energy of 17 μJ was achieved at a charging voltage of 29 kV (limited by the excitation system characteristics). A decrease in charging voltage below 20 kV resulted in the breakdown of lasing. The study of the temporal lasing characteristics revealed that lasing at the both wavelengths began simultaneously. The pulse duration was identical and attained an average of 12.5 ± 0.5 ns (FWHM), which corresponded to a pulse power of over 1.4 kW. These results can be used to develop gas-discharge lasers with tunable radiation parameters for ophthalmic applications.

A gas discharge is an effective converter of electrical energy into optical radiation. The mechanisms of current development and the quantitative contribution of electron multiplication and emission processes remain undetermined, even in the simplest discharge types, such as the abnormal glow discharge. In this work, the current-voltage characteristics and the voltage distribution in the cathode sheath region of a DC discharge in helium were investigated in the pressure range 3.5-9 torr and the voltage range 200-1700 V. The non-monotonic behavior of the current-voltage characteristics was demonstrated under conditions minimizing controlled and uncontrolled impurities. It was shown that at powers deposited into the discharge exceeding 3.5 W, a deviation from the asymptotic approximation of the cathode fall length to a value of 0.37 of the normal length is observed, which is associated with a change in particle concentration in the near-cathode region. The derived empirical law made it possible to refine known approximations for the dependence of temperature and particle concentration on the power deposited into the discharge, which is relevant for description of the kinetics of processes in high-voltage gas discharges used as sources of optical radiation.

One of the fundamental directions in the development of lasers based on self-terminating transitions (RM transitions) in metal atoms and ions is their application in brightness amplification systems. Improving such systems requires expanding the operational spectral range and increasing the pulse repetition frequency. A promising approach to addressing these challenges is the use of a new class of high-speed high-frequency switches based on a slit discharge (eptrons) for pumping RM lasers, particularly those operating in the UV range. Within the framework of this approach, this paper studies the frequency-energy characteristics of a mercury ion RM laser (λ = 398.4 nm). The use of a high-speed slit-discharge switch made it possible to generate voltage pulses with a rise time of 2-3 ns across the electrodes of a gas-discharge tube and achieve lasing in a double-pulse mode at repetition frequencies up to 300 kHz.It was determined that the laser pulse energy strongly depends on temperature and repetition frequency, with the optimal frequency decreasing as the temperature increases. Lasing in the form of bursts consisting of four pulses has been demonstrated. The achieved high pulse repetition frequencies of the laser radiation along with its short wavelength can contribute to the creation of unique brightness amplification systems based on the Hg⁺ RM laser.

The dynamics and spatial distribution of atmospheric pressure glow discharge plasma radiation in an argon flow in the plasma generation mode with metal particles is studied. The discharge system consisted of two symmetrical tantalum crucible-electrodes with inserts of a low-melting metal (magnesium) and operated at a current of 100-600 mA, a relatively high discharge voltage of 150 to 200 V, and an argon flow rate of 1-3 L/min, without changing to spark or arc discharge modes. Such parameters ensured the stable generation of magnesium atom fluxes in the discharge plasma, resulting from discharge initiation in the presence of afterglow from the decaying plasma in the interelectrode gap. It is shown that the most intense emission from metal atoms is observed near the electrode which acts as a cathode of the glow discharge during a given pulse half-period. The results of this work are of interest to researchers engaged in aerosol flux generation, synthesis of nanostructured materials, and the application of gas discharge for optical emission generation.