Izvestiya of Saratov University. Physics

Background and Objectives: The development of magnonics, focusing on the transfer of magnetic moment or electron spin instead of charge, has opened new opportunities for the application of spin waves (SW) in the design of devices for data processing, transmission, and storage in the microwave and terahertz ranges. Yttrium iron garnet (YIG) films are used as the magnetic material for forming spin-waveguiding structures due to their exceptionally low SW damping, even at nanometer thicknesses. One promising approach to controlling SW is the use of two-dimensional arrays of magnetic nanostructures, such as cylinders and half-cylinders made of magnetite. Materials and Methods: This study involves numerical micromagnetic modeling of a microwave waveguide with an array of magnetite cylinders and half-cylinders on its surface. The modeling focuses on varying the geometric parameters of the nanostructures and the direction of the external magnetic field to investigate their influence on SW propagation characteristics. Magnetite was chosen due to its unique magnetic properties and compatibility with modern micro- and nanofabrication technologies. The micromagnetic modeling was based on the numerical solution of the Landau–Lifshitz–Gilbert equation. Results: The results of the modeling provide insights into the ability to predict and control SW behavior depending on the geometry of the magnetic elements and the orientation of the external magnetic field. This opens new perspectives for the development of highly efficient magnonic devices. Identifying optimal configurations for the cylinders and half-cylinders could lead to the creation of more compact and energy-efficient components for magnonic logic circuits and other applications in the field of magnonics. Conclusion: The study has presented a significant step towards the development of new magnonic devices operating on the principles of spin electronics. The findings offer potential for further exploration and optimization of spin wave dynamics in nanostructured waveguides, contributing to the advancement of magnonic technology.

Background and Objectives: The construction of quantum mechanical structural-dynamic models of molecular systems has become a necessary part of studies of the structure, optical spectra and properties of matter. The results obtained in the harmonic approximation followed by a scaling procedure guarantee a reliable interpretation of the fundamental vibration bands of the measured vibrational spectra. However, if the spectrum has a complex structure determined by fundamental vibrations, overtones, composite frequencies, resonances, the interpretation is not complete. An approach based on taking into account mechanical anharmonicity makes it possible to significantly minimize the discrepancy between calculated and measured frequencies of fundamental vibrations, identify overtones and composite frequencies in the measured spectra, and establish the presence of resonant interactions. The advantage of this approach manifests itself to varying degrees in specific cases. In this article, using the density functional theory method, taking into account mechanical anharmonicity, structural-dynamic models of two conformers of the cyclohexanol molecule are constructed. The goal is to identify in this particular case the advantages of taking anharmonicity into account, which consists in minimizing the discrepancies between calculated and measured frequencies, identifying overtones, composite frequencies and resonances, refining and replenishing the interpretation of the measured spectra. Materials and Methods: Cyclohexanol (C6H11OH), used in many industries, has been the subject of extensive scientific research. The IR spectra of samples of crystalline phases II and III of cyclohexanol were used, measured on a Bruker IFS-88 Fourier spectrometer at a temperature of 12 K. Using the B3LYP/6-31G(d) method using the GAUSSIAN’03 software package, structural-dynamic models of conformers 1 and 2 isolated cyclohexanol molecules with an equatorial orientation of the hydroxyl group relative to the carbon backbone of the molecule. Results: The main parameters of adiabatic potentials have been calculated: minimum energies, optimal geometries, dipole moments of conformers 1 and 2 of an isolated cyclohexanol molecule. The frequencies of normal vibrations in the anharmonic approximation and the intensities of fundamental bands in the IR spectra have been calculated. A vibrational analysis of the IR spectra of cyclohexanol samples in crystalline phases II and III, measured in the range 400–3800 cm–1, has been carried out in order to identify overtones, vibrations of compounds and resonances. An assessment of the results obtained in comparison with those obtained in the harmonic approximation has been given. Their interpretation of the measured IR spectra has been refined. Conclusions: Based on the results of taking into account mechanical anharmonicity when constructing structural-dynamic models of isolated conformers 1 and 2 of cyclohexanol, it has been established that the agreement between the measured and calculated frequencies in the regions of 1080–1550 cm–1 and 2800–2940 cm–1 of the IR spectrum has significantly improved compared to harmonic scaled frequencies. The consequence of this improvement is a refinement of the interpretation of the frequencies ν₄₀ and ν₄₁ of the stretching vibrations of the C–H bonds closest to the core of the H-complex, and the band with a maximum at a frequency of 1517 cm–1 in the spectrum of crystalline phase II, which is a superposition of the composite vibrations ν₈ + ν₁₈, ν₅ + ν₂₃, ν₉ + ν₁₆. It has been established that resonance interactions in cyclohexanol conformers are small and resonances are unlikely. This conclusion is consistent with experimental data on the IR spectra of cyclohexanol.

Background and Objectives: Doped manganites of La-Sr system exhibiting effects of colossal magnetoresistance, giant magnetostriction, and electrical switching are promising functional materials for various technical applications, in particular for sensor and information devices. However, the influence of characteristics of doping ions, especially those introduced into various sublattices, on the properties of manganites and their frequency dependences has not been sufficiently studied. The aim of this work is to establish the influence of Ce4+(5p6) and Zn2+(3d10) ions, which are donors and acceptors, on crystal lattice parameters of manganites, their magnetization, Curie point, magnetoresistance, and dependences of the resistance on the frequency and amplitude of electric field. Materials and Methods: For the first time, single-phase ceramic La0.625Sr0.35Ce0.025Mn0.975Zn0.025O3 manganite was synthesized. Parameters of crystal structure were determined from powder X-ray diffractograms. Specific magnetization measurements were performed in magnetic field with an induction of 0.56 T. Curie point was determined by the maximum modulus of the derivative of magnetic permeability with respect to temperature. Measurements of the resistance were performed in the frequency range from 100 kHz to 4 MHz at two values of measuring voltage. Dependences of magnetoresistance on the temperature were measured in transverse field with an induction of 0.92 T. Results: The synthesized manganite has a rhombohedral crystal structure. Specific magnetization (91.2 A · m2/kg at 80 K) is higher, and Curie temperature (222 K) is lower than that of the manganite of basic composition La0.65Sr0.35MnO3. A significant width of the temperature range of ferromagnetic–paramagnetic transition (about 45 K) indicates a high inhomogeneity of obtained manganite. At the temperatures exceeding 285 K, manganite exhibits semiconductor properties. The modulus of negative magnetoresistance varies with temperature nonmonotonically and reaches a maximum (18%) at the temperature of 231 K. With an increase in frequency in the range from 100 kHz to 4 MHz, the resistance of manganite decreases with a slowdown of the fall process in the region of 1.5–2 MHz. Conclusion: The results obtained are explained by diamagnetic dilution of octahedral sublattice with zinc ions, formation of Mn2+ ions, increase in spin fluctuations near Curie point, relationship of electronic band structure with magnetic subsystem of manganite, phase stratification and formation of the clusters of different-valence ions, competition and change of charge transfer mechanisms (hopping, tunneling, percolation) depending on temperature and frequency. Established dependencies are important for understanding the mechanisms of the effect of simultaneous introduction of quadrivalent and divalent ions into various sublattices of manganites on their properties, and are also of interest for obtaining manganites with required parameters.

Background and Objectives: The venuloarteriolar reflex is a crucial part of the circulation regulation system, and it’s particularly evident in the lower limbs compared to the upper limbs due to the higher transmural pressure in the arteries and veins of the legs. When testing with changes in arm position, vascular responses to increased blood pressure are usually checked by lowering the arm below heart level. The proposed sample examines the vascular response to both a decrease in blood pressure and an increase to its initial level. Materials and Methods: The study was conducted on two groups of volunteers, one of which included 7 healthy young people aged 21–28 years, who did not have a pronounced venuloarteriolar reflex during the exercise test, and the second 7 people aged 45–65 years, in whom the venuloarteriolar reflex was well expressed. Using the method of laser Doppler flowmetry we measured the microcirculation index during the sequence of tests with the change of the hand position according to the set of parameters characterising the dynamics of blood circulation in the microvessels of the finger. Results: When raising the arm, the microcirculation index in the “up” arm position in young volunteers has decreased significantly, while in the age group, the microcirculation index in the “up” arm position has tended to increase after a sharp decrease. We have defined such a significant discrepancy in the blood flow response of young and aged volunteers as an appearance of the venulo-arteriolar reflex. The amplitudes of neurogenic and myogenic fluctuations of microvascular blood flow were mainly multidirectional in different age groups. The experimentally measured increase in blood filling of the arm vessels in age-related volunteers, caused by the appearance of fluctuations in blood flow in the neurogenic range, is explained by the reaction of the sympathetic nervous system, leading to the appearance of the venuloarteriolar reflex, which helps to restore the volume of blood filling. At a young age, the venulo-arteriolar reflex caused by a change in the position of the arm may not appear. Conclusion: The test with the change of limb position can provide valuable information on the preservation of peripheral innervation of microvessels, which justifies the prospect of using this test in the detection of various forms of neuropathies and age-related peculiarities of blood flow regulation.

Background and Objectives: This study covers the biophysical aspects of the use of emulsion microgels stabilized with whey protein isolate (WPI) for targeted drug delivery to the urinary system. Emulsion microgels were prepared by the ultrasonic homogenization method which leads to denaturation of the WPI adsorbed on the water-oil interface and formation of WPI microgel layer at the oil droplet. Materials and Methods: The study of the release profile of the model substance Cyanine 7 immobilized in emulsion microgels has demonstrated a prolonged pattern over 72 hours. The effect of emulsion microgels on the viability of various cell cultures (normal fibroblasts (L929), kidney cells (Hek239), renal carcinoma (Renca) and bladder carcinoma (T24)) has been studied, which has shown a dependence of the cytotoxicity level on the cell type. The Hek239 cells have demonstrated particularly increased sensitivity to emulsion microgels. Results: The accumulation and distribution behaviour of emulsion microgels in laboratory mice have also been studied depending on the route of their administration: intravesical or intravenous. The efficiency of targeting the microgels for urinary system components of the urinary system (kidney or bladder) has been assessed by biodistribution using in vivo fluorescence imaging. Systemic administration has demonstrated selective accumulation not only in the liver but also in the kidneys. Intravesical administration has made it possible to maintain a high local concentration of Cyanine 7 in the bladder at least during 2 h. Histological analysis has validated the safety of WPI-based microgels for delivery into the bladder and kidney. Conclusions: The presented delivery system based on the developed emulsion microgels opens up new prospects for the treatment of diseases of the urinary system using both systemic administration and minimally invasive intravesical instillations.

Background and Objectives: Cadmium sulfide (CdS) is one of the most promising materials for photovoltaic devices, but it is increasingly used as part of complex heterostructures and heterophase materials that provide expanded functionality and perspective for use. This article presents the results of studies on the production of semi-magnetic semiconductor material CdS-FeS, conventionally designated CdS:Fe, using the Langmuir–Blodgett technology. The morphology of the surface layers and the photoelectric characteristics of the obtained material are considered in detail in comparison with the original sample. Methods: A nanosized coating of iron arachinate (ArchFe) was prepared on the surface of CdS using the Langmuir–Blodgett method. The parameters of ArchFe monolayers were controlled using compression isotherms. The CdS/ArchFe structure was annealed in air. Energy-dispersive analysis and mass spectrometric studies were carried out to control the current processes before and after annealing. The main methods for studying hybrid structures of CdS/ArchFe and heterophase material CdS:Fe were atomic force microscopy and analysis of photoelectric characteristics using steady-state and kinetic approaches. Results: The resulting material is a matrix of CdxFe1–xS solid solution with nanoinclusions of the FeS phase. Analysis of atomic force microscopy images has confirmed the high reproducibility of the proposed method. We have shown the occurrence of the effect of “negative photofatigue” and an increase in integral photosensitivity by 70 times for a heterophase sample compared to “pure” CdS. Conclusion: It has been shown that the resulting material has unique properties, such as increased photosensitivity and negative photofatigue, which is very perspective for creating devices that can operate in conditions high illumination and whose characteristics can be controlled by illumination.

Background and Objectives: In the article, we highlight episodes from the biography of the outstanding Soviet designer of unique multipurpose and cargo aircraft Oleg K. Antonov (1906–1984), related to the almost 15-year period of his life in Saratov. Having arrived in Saratov with his parents in 1911–1912, he received his secondary education here, studying at the Alexander-Mariinsky Real School (in pre-revolutionary times) and the Unified Labor School. Even in his childhood, he was distinguished by a serious attitude to the history of aviation (he compiled his own chronicle of its development), aspiration to create perfect aircraft and a dream of becoming a pilot. The first stage of his path to the sky in the 1920s was the design of gliders in Saratov, in which he achieved professional mastery, publishing, in particular, brochures on the modeling and design of gliders. In 1922–1923, Oleg Antonov was a first-year student at the Faculty of Railway Engineering at Saratov University (until its closure). At the same time, in Saratov, he was engaged in organizing gliding, being the executive secretary of the sports section and gliding of the Society of Friends of the Air Fleet since 1923. Materials and Methods: By writing the article, we used the materials of the State Archives of the Saratov Region, the Saratov Regional Museum of Local History, the archives of the Saratov University, and the memoirs by O. K. Antonov. Conclusion: It has been noted that the Saratov period of Oleg K. Anton’s life became decisive in his choice of further study at the Leningrad Polytechnic Institute and many years of professional activity. On the house where he lived in Saratov and on the building of the former real school where he studied, memorial plaques were installed in his honor.

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