Moscow University Physics Bulletin最新文献

Additive manufacturing (AM) is a modern developing group of technologies based not on material removal, but on the layer-by-layer growth and synthesis of an object according to a CAD (computer-aided design) model. The main disadvantages of objects manufactured by AM technologies are a high degree of porosity and surface roughness. This study examines the possibility of modifying the surface of additive materials Ti({}^{6})Al({}^{4})V and AlSi({}^{10})Mg by irradiation with Ar({}^{+}) ions with energies ranging from 2 to 9 keV. Using SEM, the surface topography was obtained before and after irradiation and mechanical polishing. A reduction in surface porosity and roughness was demonstrated, as well as the influence of beam energy on the final surface topography.

By numerically solving the self-consistent system of the Schrödinger equations and Poisson electroneutrality, zone diagrams of LED heterostructures with In({}_{x})Ga({}_{1-x})N/GaN multiple quantum wells have been calculated. The effect of electron–phonon interaction, nonparabolicity of the dispersion relation, and hybridization of the wave function on the values of the effective mass of major charge carriers in the In({}_{x})Ga({}_{1-x})N/GaN quantum wells has been studied. The long-wave shift of 2D-plasmon resonances is associated with the temperature renormalization of the effective mass of two-dimensional carriers. To describe the temperature dependence of the effective mass, the function for the displacement of the 2D-plasmon resonance frequency is introduced.

First-principles calculations using the plane-wave ultrasoft pseudopotential technique have been performed to investigate structural parameters, mechanical, electronic, chemical bonding, and optical properties of cubic Cu({}_{2})O. The optimized structure of cubic Cu({}_{2})O is in good agreement with previous theoretical and experimental work. The calculated independent elastic constants of cubic Cu({}_{2})O are consistent with previous results. The bulk, shear, and Young’s modulus, Poisson coefficient, compressibility, Lamé constants, shear, longitudinal and average sound velocity, Debye temperature of cubic Cu({}_{2})O are obtained using Voigt–Reuss–Hill method and Debye–Grüneisen model, which are consistent with previous results. Electronic structure and chemical bonding have been calculated and analyzed to describe the electronic properties of cubic Cu({}_{2})O. Moreover, the complex dielectric function, refractive index, and extinction coefficient of cubic Cu({}_{2})O are gained, which are consistent with previous results.

A new model of Dark Energy is proposed within the flat FLRW model in RTG (Relativistic Theory of Gravitation). It is a global scalar field (Phi) with a quadratic potential, which ensures cosmological acceleration at present times and a bounce at late times. During the contraction stage, the growing Kasner-type anisotropy of Riemannian metrics will break a graviton-mass bounce mechanism near the Big Bang in the FLRW case. There is also a noncyclic scenario, with sufficiently small graviton-mass terms significant only at the final stage of expansion. After bounce, during the next compression epoch, anisotropy will increase, and the matter density will finally reach the Planck value.

In the study, surface binding energies for pure Ni and Pd metals were calculated using density functional theory. The values obtained were 5.32 and 4.65 eV, respectively, which represents good accuracy for ab initio calculations. The work also included calculations of surface binding energy for different configurations of NiPd alloys with nickel and palladium concentrations of 66, 50, and 33(%). Calculations were performed for each type of lattice for both Ni and Pd surface binding energies. Several types of lattices were simulated, and it was found that the average surface binding energies for Ni and Pd are: 5.02 and 4.36 eV, respectively in the alloy with a Ni concentration of 50(%); 4.89 and 4.22 eV, respectively in the alloy with a Ni concentration of 66(%); 5.12 and 4.40 eV, respectively in the alloy with a Ni concentration of 33(%).

A universal technique is developed for the detection of high harmonics generated by relativistic and subrelativistic laser pulses irradiating a solid target. Features in the spectra of harmonics generated by a parametric mid-IR laser system and near-IR laser system based on chirped pulse amplification were analyzed. Experimental spectra of harmonics in the range up to 35 nm were recorded. They can be used as a source of coherent radiation in the extreme UV region.

The work is dedicated to the study of the magnetic response of a metasurface made of split ring resonators (meta-atoms) in the MHz and GHz ranges. A new method for calculating the local permeability of a metasurface in the MHz frequency range is proposed, taking into account the finite sizes of the elements, and for the first time, a result of high degree of accuracy matching with experimental values has been obtained. In the GHz range, additional factors such as the retardation effect, nonuniform current distribution in the meta-atom, and the complexity of the nature of meta-atoms’ interaction compared to the MHz range are also considered, in particular, the emergence of electrical interaction between them.

A lot of literature sources discuss diseases associated with the hemoglobin protein [1, 2]. In the modern world, more than 800 million people suffer from anemia [3]. Assessing the level of hemoglobin in the circulatory system is one of the ways to diagnose anemia. Hemoglobin protein is also a promising source of bioactive peptides [4]. The aim of the work was to identify the reasons leading to conformation changes of this protein. It still remains unclear what exactly causes disruption of its functionality. Human hemoglobin from Sigma H7379 was studied in the work; all experiments were conducted on a dynamic light scattering spectrometer—Photocor Complex. Experimental data were obtained using optical methods of static and dynamic light scattering. The work included an analysis of the behaviour of hemoglobin protein molecules in aqueous and aqueous-saline solutions with changes in solution parameters (pH, addition of iron chloride III). At values of pH (<(3.56pm 0.15)) and pH (>(10.4pm 0.2)), the hemoglobin molecule underwent conformational changes, resulting in the disintegration of the quaternary structure into (alphabeta)-dimers and individual (alpha)- and (beta)-globules. As a result of the study, it was found that the addition of FeCl({}_{3}) to aqueous solutions of hemoglobin increases the size and mass of scattering particles, which can be explained by the adsorption of Fe({}^{3+}) ions on the protein surface. However, upon reaching a certain concentration of FeCl({}_{3}), the pH of the solution was lowered to such an extent that it caused conformational changes in hemoglobin, leading to the disintegration of its quaternary structure. These results can be taken into account when creating medicinal drugs for the treatment of anemia and other diseases associated with the hemoglobin protein.

Phenomenological models of phase transitions for two interacting order parameters, one-component and two-component, are constructed. The construction was carried out based on the number of control parameters depending on external thermodynamic conditions by methods of the equivariant catastrophe theory (singularity theory), taking into account the symmetry of the order parameters. The classification of phenomenological models according to the number of control parameters is carried out. Phase diagrams of the models are constructed and the theoretical temperature dependence of the heat capacity is calculated, which shows a satisfactory qualitative correspondence with the experimental dependence in the (textrm{Rb}_{2}textrm{KInF}_{6}) elpasolite crystal.

In the paper, the existence of a stable stationary solution in a reaction-diffusion system with slow and fast components in a two-dimensional spatial variable case is investigated. The theorem of the existence of a stationary solution with boundary layers in the case of Dirichlet boundary conditions is proven, its asymptotic approximation is constructed, and conditions for Lyapunov asymptotic stability of this solution are obtained. The research is based on the asymptotic method of differential inequalities, applied to a new class of problems. This result is practically important both for various applications described by similar systems and for the application of numerical stationing methods when solving elliptical boundary value problems.