Journal of Contemporary Physics (Armenian Academy of Sciences)

The influence of a reaction channel on the isomeric cross-section ratio (ICR) of the production of ^184m,gRe was investigated. The excitation functions for the ^184m,gRe isomeric pair produced through the ¹⁸⁴W(p,n), ¹⁸⁶W(p,3n), ¹⁸⁴W(d,2n), ¹⁸⁶W(d,4n), ¹⁸¹Ta(α,n) and ¹⁸⁵Re(γ,n) reactions were calculated by different models of the TALYS 1.9 and EMPIRE 3.2 codes. The ICR calculations for the above-mentioned isomeric pair through the various reaction channels (proton, deuteron, alpha and gamma induced reactions) was determined for incident energy ranges from the threshold up to 50 MeV. The comparison of theoretical calculations and available experimental data was done.

The continuum elasticity model is applied to investigate quantitatively the growth features and nucleation mechanism of quantum dots, nanopits, and joint QD-nanopits structures in CdZnHgTe quasyternary material system. We have shown that for the CdZnHgTe solid solution deposited on the CdTe substrate, the sign of the critical energy and volume of island is changed at the critical strain of ɛ^* = 0.006 and ɛ^* = 0.009 (ɛ = Δa/a), It is assumed that the mechanism of the nucleation is changed from the growth of quantum dots to the nucleation of nanopits at ɛ = ɛ^*. Obviously, at the small mismatch (ɛ < ɛ^*) the bulk nucleation mechanism dominates. However, at ɛ > ɛ^*, when the energy barrier becomes negative and a large mismatch provides a low-barrier path for the formation of dislocations, the nucleation of pits becomes preferable energetically.

Armenia has significant reserves of obsidian, the volcanic glass, produced when the volcanic lava rapidly cools through to the glass transition temperature and does not give enough sufficient time for crystallization. Translucent obsidian samples from the Arteni deposit were investigated. The analysis of obsidian samples were carried out by different methods (scanning electron microscopy–energy dispersive spectroscopy SEM–EDS, the X-ray diffraction analysis, the absorption, reflection and Raman spectroscopy, as well as differential thermal and thermogravimetric analysis) for characterization of translucent obsidian from Arteni.

The influence of an aluminum compensation filter of complicated form on the signal-tonoise ratio in microtomography of geological cores was investigated. When scanning the core, a compensation filter in the form of an aluminum parallelepiped with a hole approximately equal to the diameter of the core was used. The filter is fixed rigid over the object table, the core is placed in the hole and rotates inside the filter. It is shown that the filter provides the maximal contrast of the useful signal over the entire dynamic range of the scintillation panel detector. After normalizing the projection of the core onto the filter projection without the core, the obtained projections were used in the standard reconstruction algorithm for cone beam tomography. The use of a compensation filter made it possible to increase the signal-to-noise ratio of the resulting tomograms by more than two times, as compared with the case of a conventional flat filter made of aluminum.

The adsorption of ligands to macromolecules is theoretically investigated in this work in the case when the structure of the adsorption center changes when a ligand is bound to the macromolecule. In this case, the adsorption kinetics is described by a set of two nonlinear differential equations. This consideration results in such properties that the adsorption center acquires the multiplicity of stationary states (including the bistable states), trigger and hysteresis behavior. It is shown that taking into account the deformation of the adsorption center results in an S-shaped adsorption isotherm.