Vol 61, No 6 (2016)

The history of the development and application of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray microanalysis (EDXMA) in studies of cultural heritage sites is considered. In fact, investigations based on these methods began when electron microscopes became a commercial product. Currently, these methods, being developed and improved, help solve many historical enigmas. To date, electron microscopy combined with microanalysis makes it possible to investigate any object, from parchment and wooden articles to pigments, tools, and objects of art. Studies by these methods have revealed that some articles were made by ancient masters using ancient “nanotechnologies”; hence, their comprehensive analysis calls for the latest achievements in the corresponding instrumental methods and sample preparation techniques.

The design and production of innovative materials based on nanocrystalline sp²- and sp³-coordinated carbons is presently a focus of the scientific community. We present a review of the nanostructures obtained in our labs using a series of synthetic routes, which make use of chemical vapor deposition (CVD) techniques for the selective production of non-planar graphitic nanostructures, nanocrystalline diamonds, and hybrid two-phase nanostructures.

It is known that a set of additional reflections (satellites) may arise on rocking curves in the case of X-ray diffraction in the Bragg geometry from crystals where high-frequency ultrasonic vibrations are excited. It is shown that, under certain conditions, the pulse wave fields of the satellites and main reflection may be intersected in space (playing the role of pump and probe beams) and in time (forming interference superlattices).

Cs₆H(HSO₄)₃(H₂PO₄)₄ crystals, grown for the first time based on an analysis of the phase diagram of the CsHSO₄–CsH₂PO₄–H₂O ternary system, have been investigated by structural analysis using synchrotron radiation. The atomic structure of the crystals is determined and its specific features are analyzed.

The pyroxferroite and pyroxmangite from xenoliths of aluminous gneisses in the alkaline basalts of Bellerberg paleovulcano (Eifel, Germany) have been studied by electron-probe and X-ray diffraction methods and IR spectroscopy. The parameters of the triclinic unit cells are found to be a = 6.662(1) Å, b = 7.525(1) Å, c = 15.895(2) Å, α = 91.548(3)°, β = 96.258(3)°, and γ = 94.498(3)° for pyroxferroite and a = 6.661(3) Å, b = 7.513(3) Å, c = 15.877(7) Å, α = 91.870(7)°, β = 96.369(7)°, and γ = 94.724(7)° for pyroxmangite; sp. gr. \(P\overline 1 \). The crystallochemical formulas (Z = 2) are, respectively, ^M(1–2)(Mn_0.5Ca_0.4Na_0.1)₂^M(3–6)(Fe, Mn)₄^M7[Mg_0.6(Fe, Mn)_0.4][Si₇O₂₁] and ^M(1–3)(Mn, Fe)₃^M(4–6)[(Fe, Mn)_0.7Mg_0.3]₃^M7[Mg_0.5(Fe, Mn)_0.5][Si₇O₂₁]. For these and previously studied representatives of the pyroxmangite structural type, an analysis of the cation distribution over sites indicates wide isomorphism of Mn²⁺, Fe²⁺, and Mg in all cation M(1–7) sites and the preferred incorporation of Сa and Na into large seven-vertex M1O₇ and M2O₇ polyhedra and Mg into the smallest five-vertex M7O₅ polyhedron.

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan–hyaluronic acid, chitosan–alginic acid, and chitosan–carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

In many types of human tumor cells and infectious agents, the demand for pyrimidine nitrogen bases increases during the development of the disease, thus increasing the role of the enzyme uridine phosphorylase in metabolic processes. The rational use of uridine phosphorylase and its ligands in pharmaceutical and biotechnology industries requires knowledge of the structural basis for the substrate specificity of the target enzyme. This paper summarizes the results of the systematic study of the three-dimensional structure of uridine phosphorylase from the pathogenic bacterium Vibrio cholerae in complexes with substrates of enzymatic reactions—uridine, phosphate anion, thymidine, uracil, and thymine. These data, supplemented with the results of molecular modeling, were used to consider in detail the structural basis for the substrate specificity of uridine phosphorylases. It was shown for the first time that the formation of a hydrogen-bond network between the 2′-hydroxy group of uridine and atoms of the active-site residues of uridine phosphorylase leads to conformational changes of the ribose moiety of uridine, resulting in an increase in the reactivity of uridine compared to thymidine. Since the binding of thymidine to residues of uridine phosphorylase causes a smaller local strain of the β-N1-glycosidic bond in this the substrate compared to the uridine molecule, the β-N1-glycosidic bond in thymidine is more stable and less reactive than that in uridine. It was shown for the first time that the phosphate anion, which is the second substrate bound at the active site, interacts simultaneously with the residues of the β5-strand and the β1-strand through hydrogen bonding, thus securing the gate loop in a conformation

Comparative investigations of homoepitaxial diamond films with natural and modified isotopic compositions, grown by chemical vapor deposition (CVD) on type-Ib diamond substrates, are carried out using double-crystal X-ray diffractometry and topography. The lattice mismatch between the substrate and film is precisely measured. A decrease in the lattice constant on the order of (Δa/a)_relax ∼ (1.1–1.2) × 10^–4 is recorded in isotopically modified ¹³С (99.96%) films. The critical thicknesses of pseudomorphic diamond films is calculated. A significant increase in the dislocation density due to the elastic stress relaxation is revealed by X-ray topography.

The instrumental realization of neuromorphic systems may form the basis of a radically new social and economic setup, redistributing roles between humans and complex technical aggregates. The basic elements of any neuromorphic system are neurons and synapses. New memristive elements based on both organic (polymer) and inorganic materials have been formed, and the possibilities of instrumental implementation of very simple neuromorphic systems with different architectures on the basis of these elements have been demonstrated.

A complex investigation of the domain structure and dielectric properties of triglycine sulfate (TGS) crystals containing profile layers doped with D,L-α-alanine (DLATGS) and L-α-alanine (LATGS) impurities is carried out. The images of the DLATGS and LATGS layers and ferroelectric domains are obtained by piezoelectric force microscopy; the parameters of the domain structure and the degree of unipolarity are determined. It is established that DLATGS layers are multidomain and LATGS stripes are mainly single-domain. The experimental data on the macroscopic dielectric properties of the crystals are compared with the results of a microscopic analysis of the domain structure.

The transport of silver nanoparticles in the organism of laboratory animals has been investigated. A mathematical model of the biokinetics of prolonged administration of nonmetabolizable and nonaglomerating pharmaceutical preparations is proposed, and its analytical solution is found. Based on the experimental data on the prolonged introduction and excretion of colloidal silver nanoparticles and the numerical approximation of the solutions to the equations for the proposed model, time dependences of the silver mass content in brain and blood are obtained and some other important biokinetic parameters are determined. It is concluded that both chronic¹ and subchronic² peroral application of these nanoparticles as an biologically active additive or antiseptic is potentially dangerous.

The phase diagram of the K₂Ni(SO₄)₂ · 6H₂O–K₂Co(SO₄)₂ · 6H₂O–H₂O ternary system is investigated in the temperature range of 30–70°С, and a relationship between the compositions of the equilibrium phases of the K₂Co_xNi_(1–x)(SO₄)₂ · 6H₂O (KCNSH) solid solution and the growth solution is established. It is shown how the salt compositions of the liquid and solid phases change during crystal growth upon slow cooling of solution. A dependence of the lattice parameters of the KCNSH solid solution on the concentration of isomorphic components is experimentally found.