Dichroism and birefringence in X-ray spectra of forbidden reflections
Dichroism and birefringence in X-ray spectra of forbidden reflections
M. V. Gorbunova$^1$, E. N. Ovchinnikova$^1$, A. P. Oreshko$^1$
The paper implements an approach using a propagation matrix to calculate the intensity of Bragg reflections in resonant X-ray diffraction. This allows one to take into account anisotropic effects that lead to a change in the polarization of radiation during propagation. Using the example of processing the spectra of forbidden reflections in an iron orthoborate crystal, performed using a program based on this approach, an improvement in the results of calculations with experimental data is demonstrated in comparison with standard methods.
Show AbstractAlgebraic resonance perturbation theory in problems of nonlinear and quantum optics
Algebraic resonance perturbation theory in problems of nonlinear and quantum optics
A. M. Basharov
The algebraic resonance perturbation theory (ARPT) is formulated, general formulas of the theory are written out, with the help of which effective Hamiltonians are concisely derived, interference interactions are described, kinetic equations for various cases of interaction of electromagnetic radiation with quantum systems are obtained. It is pointed out that the method of stochastic differential equations is naturally integrated into ARPT and that the principles of selecting ARPT terms are physically justified in the case of an approximation of the environment of an open system by delta-correlated noise. The inevitability of the appearance of interference interactions is emphasized due to the formulated ARPT requirements regarding the selection of only slowly time-varying terms in the Dirac picture into an effective Hamiltonian.
Show AbstractRegistration of pulsed terahertz radiation by a superconducting bolometer in the process of parametric dowm-conversion
Registration of pulsed terahertz radiation by a superconducting bolometer in the process of parametric dowm-conversion
K. A. Kuznetsov$^2$, N. I. Tatyana$^2$, I. V. Pentin$^3$, G. K. Kitaeva$^{1,2,4}$
The statistical distributions of the output signals of a superconducting bolometer exposed to weak photon pulses with a frequency of 1 THz from a pump with a pulse duration of 30 ps are investigated. Terahertz pulses are obtained by the method of strongly nondegenerate parametric scattering in a LiNbO3 crystal cooled to 4.8 K. Various scenarios of the response of superconducting bolometer to excitation by a small number of terahertz photons are discussed.
Show AbstractOn modeling acoustic fields in a marine waveguide with refined boundary conditions on the surface and bottom
On modeling acoustic fields in a marine waveguide with refined boundary conditions on the surface and bottom
Yu. I. Papkova$^1$, S. O. Papkov$^2$
The problem of the sound field of a point sound source situated in a non-ideal marine waveguide is considered. The boundaries of the waveguide are assumed to be plane-parallel, there are three layers: a water layer with a non-uniform refractive component of the speed of sound, a layer of liquid sediments, and a bottom elastic layer on a rigid base. The water layer is limited by a homogeneous air half-space. Analytical expressions for impedance functions at the boundaries of the water layer were obtained for the first time for this waveguide model, which makes it possible to construct the Green's function of the vertical boundary value problem. Moreover, exact values for the residues of the Green's function are found, which allow one to write an exact analytical representation for the sound pressure potential as a sum of normal modes. It is shown that the influence of the continuous spectrum (integrals along the branch cuts) is small even at small distances from the source. As the thickness of the elastic layer decreases, the discrete spectrum of the problem tends to the values for a classical waveguide, and at a sufficiently large thickness and attenuation it is similar to the discrete spectrum of the Pekeris elastic waveguide. Examples of numerical implementation for waveguide parameters typical for the Black Sea waters are given.
Show AbstractSPRING ATMOSPHERIC BLOCKINGS IN THE NORTHERN HEMISPHERE: CHANGES IN RECENT DECADES (1993-2023)
SPRING ATMOSPHERIC BLOCKINGS IN THE NORTHERN HEMISPHERE: CHANGES IN RECENT DECADES (1993-2023)
I. I. Mokhov$^{1,2}$, J. R. Eremin$^1$
This paper presents an analysis of the spring atmospheric blockages (SAB) in the Northern Hemisphere (NH) in 1992-2023. The results of the analysis indicate a significant increase in blocking activity in the atmosphere of the joint venture in recent decades. The noted trend is manifested against the background of a general increase in the near-surface temperature of the NH in the spring seasons. The following SAB parameters were used in the study: quantity, average duration, total duration, intensity, and size. There were obtained estimates of the statistically significant increase in the total duration of the SAB, their number and size with an increase in the average spring near-surface temperature in the NH.
Show AbstractSome physical factors in the development of secondary cancers in patients who have undergone radiation therapy.
Some physical factors in the development of secondary cancers in patients who have undergone radiation therapy.
A. A. Shcherbakov$^{1,2}$, I. V. Khramov$^1$, E. N. Lykova$^{1,2}$, S. A. Gavrilova$^3$, F. R. Studenikin$^{1,2}$, A. P. Chernyaev$^{1,2}$
The review presents methods of assessment and statistical data on the occurrence of secondary malignant neoplasms in patients who have undergone radiation therapy. The influence of factors such as the age and sex of the patient, the location of the primary tumor, and the method of radiation treatment is examined. It has been established that the highest risks of developing secondary cancer are observed in children, women, and with the use of photon radiation therapy. A comparison with experimental data obtained from animals, which revealed similar patterns, is provided. Special attention is given to risk assessment models depending on the radiation dose. The main models used for risk assessment are highlighted. Certain factors that may influence the development of secondary cancer during radiation therapy are identified, including the impact of secondary particles and the use of medical imaging.
Show AbstractFluorescence of various antropogenic pollutants of hydrosphere when probing of water column by pulsed ultraviolet lidar
Fluorescence of various antropogenic pollutants of hydrosphere when probing of water column by pulsed ultraviolet lidar
L. E. Yakushkin
A criterion has been developed for detecting anthropogenic debris floating on the water surface when probing the water column with a pulsed ultraviolet laser with a wavelength of 355 nm probing radiation. The criterion was applied to lidar sounding data of the near-surface layer of the sea in several expeditions to the Black Sea. The conditions of applicability of the proposed criterion for the detection of marine debris are formulated. The results obtained using this criterion are compared with visual observation data. The possibility of using the criterion to assess the extent of pollution of the World Ocean is shown.
Show AbstractNeural networks assisted reconstruction wavefront of laser radiation based on intensity profile near focus of converging lens
Neural networks assisted reconstruction wavefront of laser radiation based on intensity profile near focus of converging lens
N. V. Iakushkin$^{1,2}$, A. V. Mitrofanov$^{1,2,3}$, A. V. Vasil'ev$^1$, A. V. Larichev$^{1,3}$, N. G. Iroshnikov$^1$, D. A. Sidorov-Biryukov$^{1,2,3}$
The architecture ConvFormer S18 network allows reconstruct the shape of the laser radiation wavefront from the intensity distribution near the lens focus. The use of normilizing method for sparse data can reduce RMS error of wavefront reconstruction by the factor of 2. Ability of neural network to reconstruct laser radiation wavefront based on its intensity profile near focus of converging lens is experimentally demonstrated for set of abberations applied simultaneosly. RMS-error of wavefront reconstruction in the experiment from the intensity distribution taken behind the focus, in front of the focus, and from the data from both positions were estimated as 𝜆/18 , 𝜆/13 and 𝜆/31. The correctness of the technique is proven by the coincidence of the calculated intensity distribution based on data obtained by the neural network with the measured experimental values.
Show AbstractNarrow-linewidth IR laser modulation by quantum cascade laser structure
Narrow-linewidth IR laser modulation by quantum cascade laser structure
S. A. Chakhlov$^{1,2}$, L. A. Miklashevich$^1$, A. A. Lastovkin$^1$, N. G. Zakharov$^1$
The effect of modulation of narrow-linewidth laser radiation in the 1590 nm range, passed through the waveguide structure of a quantum cascade laser, is obtained, observed when applying an electric voltage to the structure. This effect reveals the thermodynamics of the active region of a quantum cascade laser operating in a pulsed mode, which is relevant in the problem of optical communication implemented on the principle of high-frequency amplitude signal modulation.
Show AbstractWater Formation in Asteroids
Water Formation in Asteroids
A. Yu. Dubinsky$^1$, S. I. Popel$^1$, J. S. Reznichenko$^{1,2}$
The issue of the formation of water molecules in asteroid regolith is considered. The possibility of oxygen atoms release as parts of silver hydroxide molecules from the crystal lattice of silicon dioxide in regolith has been demonstrated. Silver hydroxide, in turn, can react with hydrogen relatively easily, resulting in the formation of water and silver. This demonstrates the possibility of the formation of water molecules included in the near-surface soil of an asteroid. The proposed mechanism for the formation of water molecules does not require such an unlikely event as two solar wind protons hitting the same point. In the situation under consideration, it is only required that the end of the proton track fall in the region where the elements of the quartz lattice, for example, metal sulfide, are in contact with each other. The presence of water molecules in the soil of an asteroid can affect the photoelectric properties of its regolith and the parameters of the plasma-dust system above the asteroid. A way to identify the nature of the formation of water on an asteroid can be a combination of the method of finding water on asteroids, based on the detection of dust near the surfaces of these space objects, as well as a method using the detection of neutron fluxes passing through areas of the surface of the space body.
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