Moscow University Physics Bulletin最新文献

The characteristics of the Zeeman ring laser (ZRL) have been investigated theoretically and experimentally under conditions of two- and three-frequency generation. The influence of the running wave, excited at the third frequency, on the frequency bias and the intensities of counterpropagating waves is examined. A comparison of experimentally measured characteristics with calculations based on vector theory has been conducted. It has been found that when a running wave is excited in a neighbouring longitudinal mode, kinks appear in the dependence of counterpropagating wave intensities on the detuning of the generation frequency from the gain-line center. It is shown that excitation at the third frequency results in a stronger dependence of the frequency bias on the detuning from the gain-line center compared to the two-frequency generation regime. Based on the comparison of theory with experiment, it is demonstrated that among the known values of the isotopic shift between Ne({}^{20}) and Ne({}^{22}) at a wavelength of 0.63 (mu)m reported in the literature, the value (sigma=1050) MHz leads to results that do not agree with the experiment, allowing for a refinement of the parameter (sigma).

We present a method for designing one-dimensional photonic structures whose phase response has a predefined shape and characteristics. An algorithm for constructing such photonic crystal structures has been developed, and numerical modeling of their phase and spectral responses have been performed.

The problem of diffusive propagation of cosmic rays (CRs) with a general tensor in a model homogeneous magnetic field of the Galaxy has been solved, and its stability has been investigated. An algorithm for generating stencils of second-order accuracy finite-difference schemes for a three-dimensional differential equation with tensor components is implemented. The components of the diffusion tensor are calculated with a specified spatial step and are determined based on the magnitudes of the large-scale magnetic field vector and the magnitude of the random field component, which is assumed to be 6 (mu)G. The study demonstrates the fundamental possibility of determining the energy spectra of CRs in various regions of the Galaxy, where the free parameters are the distribution of CR sources and the structure of the magnetic field.

The ({}_{1}textrm{S}_{1}) mode of the Earth’s free oscillations (Slichter mode) arises from the oscillations of the Earth’s inner solid core relative to the outer liquid core. This study conducts the search for and estimation of the Slichter mode following the 2011 Tohoku earthquake based on data from the Baksan laser interferometer–strainmeter. An algorithm based on the maximum likelihood method (MLM) was used to detect and estimate the mode parameters. The most probable estimates of the degenerate mode frequency and its splitting parameters have been obtained, which may be associated with the excitation of the Slichter mode in the analyzed data. An estimate of the density jump between the Earth’s inner and outer core has been derived for the found mode period. For the first time, a comparison has been made between the potential capabilities of the Baksan strainmeter and the superconducting gravimeters of the IGETS network for the task of observing the Slichter mode after the same earthquake. The similarity of the obtained mode estimate from strain observations with the previously obtained estimate from gravimetric observations, as well as with the theoretical value from the PREM model, is noted.

The study of the biological effects of accelerated protons with ultrahigh dose rates in and outside the Bragg peak on tumour and normal cell lines is essential for understanding the consequences of such exposure and for selecting optimal doses and modes for further application in tumour radiotherapy. In this study, human colorectal adenocarcinoma cells (HT-29) and normal human adipose-derived mesenchymal stem cells (ADSC)—fibroblasts—were irradiated. The irradiation was performed using the high-current linear proton accelerator at the Institute for Nuclear Research of the Russian Academy of Sciences, which allows for energy variation in the range of 70–230 MeV. The dose was delivered in three modes: conventional mode (dose rate (dot{D}<1) Gy/s), Splash mode ((dot{D}sim 100) Gy/s), and single-pulse Flash mode ((dot{D}>10^{4}) Gy/s, denoted as Splash from single-pulse Flash) in the region of the spread out Bragg peak. To analyze cell death, staining with propidium iodide and annexin was performed. The proliferative potential was assessed using the EdU assay. After 24 h, an increase in the number of apoptotic HT-29 cells was observed in all irradiation modes, while for fibroblasts, a relative increase in the number of necrotic cells was noted under conventional irradiation with a higher dose compared to other modes. After 48 h, a tendency toward a dose-dependent decrease in the number of necrotic HT-29 cells was observed in Flash/Splash modes, with consistently low levels of necrotic fibroblasts. The number of DNA-synthesizing cells decreased significantly by 120 h across all doses and irradiation modes. The curves for Flash and Splash irradiation modes were nearly parallel. Further studies involving a broader range of cell lines and doses are required.

Assessment of platelet function is of key importance for the diagnosis of bleeding disorders and monitoring the effectiveness of antiplatelet drugs. Relatively recently, a method for assessing platelet aggregation based on the phenomenon of low angle light scattering was developed. Measurements are carried out in a medium with a known pH value and calcium concentration. The aim of this work was to investigate the influence of preanalytical and analytical variables, as well as to compare the results with the light transmission aggregometry method already widely used in clinical practice. It was found that transporting the sample by car for two hours does not affect the parameters of collagen-induced aggregation. It was discovered that the low angle light scattering method for measuring collagen-induced platelet aggregation exhibits good precision under repeatable conditions and is short-term reproducible. The aggregation parameters obtained by the low angle light scattering method directly correlate with the aggregation parameters measured by the transmission aggregometry method. The accelerating role of adenosine diphosphate secreted from dense granules in collagen-induced platelet aggregation was demonstrated.

A new formulation of the two-planet problem is proposed and investigated, where orbits with small eccentricities and mutual inclinations can have an arbitrary orientation relative to the main (picture) plane. The model enables the study of a broad class of exoplanetary systems with orbital inclination angles different from ({pimathord{left/{vphantom{pi 2}}right.kern-1.2pt}2}). To derive the equations for the secular evolution of the orbits, the mutual gravitational energy of Gaussian rings, expressed as a series up to second-order small terms, is used instead of the classical perturbation function. A theoretical method has been developed in which, for each orbit, a vector perpendicular to the orbital plane and two Poincaré variables are introduced instead of the osculating Lagrange elements, without loss of information. A closed system of 10 differential equations is obtained and solved analytically. The method is applied to investigate the secular evolution of the TOI-1130 exoplanetary system.

In order to achieve a high-quality transfer of the mask pattern onto the substrate in plasma etching, it is important to minimize charging effects. This study investigates the potential use of a specialized design for rectangular mask holes to counteract charging effects. The research examines the behavior of a single and deformed rectangular mask hole with varying length-to-width ratios and two types of mask arrays. A particle simulation program was utilized to analyze the changes in electric field distribution and simulated opening during etching time. The findings indicate that ions tend to bombard the long side rather than the short side or vertexes, leading to flattening of deformed sides and resulting in an approximately rectangular etched opening. Specialized designs based on specific arrays can aid in achieving nearly perfect rectangular etched openings, with potential underlying mechanisms extensively discussed in this study. These results offer valuable insights into specialized design strategies for plasma etching processes.

In this study, copper cobalt ferrite nanoparticles were synthesized by chemical formula Co({}_{1-x})Cu({}_{x})Fe({}_{2})O({}_{4}) and ((x=0), (0.2), (0.4), (0.6), (0.8), (1)) by coprecipitation method. The X-ray diffraction pattern of the samples confirmed the single-phase spinel structure of the fabricated nanoparticles and the average size of the crystals was calculated from the entire width of the diffraction peak with the highest intensity and Scherrer’sequation. Using transmission electron microscope images, the nanoparticle size was about 10 nm. The magnetic properties of copper cobalt ferrite nanoparticles were measured by Alternative Gradient Force Magnetometer (AGFM) and it was seen that with increasing substitution of copper cations instead of cobalt cations in the samples, the amount of induction decreased and the saturation magnetization first increased and then decreased. In order to investigate the Faraday’s effect on copper cobalt ferrite nanoparticles, the transmittance values were measured using a laboratory experiment and their graphs were plotted in terms of the applied magnetic field, all of which were in agreement with the theory. In addition, transmittance was investigated for two angular positions of the analyzer at (-45^{circ}) and (+45^{circ}) in different fields.

The contributions of geostrophic and wind-driven factors to the formation of the mean Antarctic circumpolar current (ACC) climatic structure were studied using the general ocean circulation model INMOM (Institute of Numerical Mathematics Ocean Model). The aim of the study was to separate the geostrophic and wind-driven components of the ACC. The simulation was carried out for summer (February) and winter (August) conditions in the Southern Hemisphere during the climatic period from 1993 to 2012. It is shown that, despite strong winds over the Southern Ocean, the geostrophic circulation factor is usually much stronger than the wind-driven factor. Nevertheless, the contribution of the wind-driven component to the increase in the near-surface zonal velocity can reach 15–20(%) of the geostrophic velocity. Winds contribute to a decrease in the mean dynamic topography (MDT) from the open ocean to the coast of Antarctica. The influence of wind on the formation of the barotropic stream function of the current is more pronounced than on the MDT. Geostrophic transport of the ACC remains nearly the same in winter and summer. Due to wind effects, the total transport of ACC around Antarctica increases on average by 10–15 Sv in summer and 15–20 Sv in winter. The three-jet structure of the ACC was confirmed using numerical modelling and the ‘‘diagnosis–adaptation’’ method according to EN4 data. It is demonstrated that the three-jet structure of the ACC has a geostrophic nature.