Kristallografiâ

The results of an experimental study at the KISI-Kurchatov synchrotron source of a new phase-contrast imaging scheme for micro-objects using a nanofocusing compound refractive lens are presented. Visualization with submicron spatial resolution of a Fresnel zone plate, with the width of outer zones less than 0.5 µm, has been demonstrated. It was found that in the conducted experiments the main contribution to the instrumental function, which limits spatial resolution, is due to the vibrations of the optical scheme elements. The possibility of using the proposed scheme to determine the beam transverse size at the focus of the compound refractive lens, considering the instrumental function, is shown.

The samples of EP741NP alloy destroyed during fatigue testing were investigated by means of transmission electron microscopy, energy-dispersive X-ray microanalysis and electron diffraction. The composition and crystal structure of defects detected at the boundaries of fatigue cracks were studied in details. It was shown that such defects mainly have the morphology of elongated flat "carpets" containing NiO, CTi_xNb_1–x, amorphous AlO_x, HfO₂, Al₂O₃, β-Al₂O₃, Al₂MgO₄, Co₇Mo₆, Co₃O₄, S₄Ti₃, NbO₂, TiO₂, as well as amorphous regions containing C, O, Ca, S, Na and Cl. Assumptions were made about the source and of time formation of the studied defects.

The α-Na_0.4R_0.6F_2.2 crystals (R = Ho–Lu, Y) were studied by X-ray diffraction analysis at 293 and 85 K. A unified cluster model of nanostructured crystals with a fluorite-type structure based on the polymorphism of KR₃F₁₀ (R = Er, Yb) was used to model their defect structure. The α-Na_0.4R_0.6F_2.2 matrix component contained Na⁺ and R³⁺ in a ratio of 1 : 1. Part of the matrix anions was shifted from 8c to 32f position (sp. gr. Fm3m). Excess R³⁺ cations formed with Na⁺ octa-cubic clusters with nuclei in the form of cuboctahedra {F₁₂} formed by interstitial anions at the 48i position. The α-Na_0.4R_0.6F_2.2 cluster component was formed by octa-cubic clusters of type i. The electron diffraction method showed that the clusters had the shape of plates about 5 nm thick with superstructural ordering. Their structural model based on the K_0.265Gd_0.735F_2.47 structure was proposed. For the first time, experimental confirmation of the affiliation of α-Na_0.5–xR_0.5+xF_2+2x to nanostructured crystals was obtained by electron diffraction. When the temperature decreases from 293 to 85 K, the type of cluster component of the defect α-Na_0.4R_0.6F_2.2 structure with R = Ho–Lu, and Y was not change. At 293 K, the boundary of the type change of the defect structure in the α-Na_0.5–xR_0.5+xF_2+2x series was located between R = Dy (with the Z = 66 atomic number) and Ho (with Z = 67). When the temperature drops from 293 to 85 K, the position of the boundary was not change.

A comparative study of the characteristics of high-molecular organic matter (cotton lint) subjected to pyrolytic carbonisation under conditions of high-intensity microwave radiation in various gaseous media (N₂, CO₂, Ar) has been conducted. The methods employed included the determination of adsorption activity through the use of a methylene blue indicator, X-ray fluorescence analysis, transmission electron microscopy with microanalysis, and X-ray phase analysis. Electrodes derived from carbon materials produced through microwave carbonisation with varying gases were constructed, and symmetric cells were assembled in accordance with the two-electrode configuration. The electrochemical properties were investigated using cyclic voltammetry and galvanostatic charge-discharge methods. The results demonstrated that the materials obtained using a CO₂ gaseous medium exhibited the most optimal characteristics.

The interest in spiral particles lies in their resemblance to authentic nanostructures that emerge through the self-organisation of biopolymers (such as carrageenans, DNA, and so forth). Conversely, the determination of the structural parameters of such particles based on small-angle scattering data is challenging due to the lack of conditioning in the inverse problem. This is demonstrated by the utilisation of established bead structure modelling software. This paper considers a modification of the search algorithm in a limited area of space and the behaviour of solutions depending on the values of the parameters of the objective function responsible for the connectivity and looseness of the structure, the type of weighing of the scattering intensity curve, and the width of the angular range of data. In order to statistically assess the stability of the solutions, a sequential model search mode was applied, with varying amounts of contributions of penalty terms. The empirical dependences of the optimal values of the search parameters with respect to the parameters of the distribution curve of paired distances were determined.

A subunit vaccine against the African swine fever virus (ASF) has been designed using immunoinformatics and molecular dynamics methods. The three-dimensional structure of the selected immunogenic protein of the ASF-CD2v virus was modelled, and its topology relative to the membrane was predicted. B- and T-cell epitopes for the supramembrane part of CD2v were predicted, and their immunogenicity, allergenicity, and toxicity were evaluated. In order to facilitate the development of a subunit vaccine, the least variable site was identified on the basis of an analysis of the conservatism of the predicted epitopes. The stability of the selected supramembrane site in an aqueous salt solution was evaluated using molecular dynamics methods, and it was demonstrated that the site is structurally stable. The immunomodulation method has demonstrated that the developed candidate vaccine is capable of eliciting a sustained immune response and does not result in the development of a cytokine storm.

The effect of the bias electric field E₌ (0–10 kV/cm) on the dielectric properties of the VDF₆₀/Tr₄₀ copolymer was studied within the temperature range of 20–110°C. It was found that the dielectric nonlinearity De, is negative in the polar phase and becomes positive above the Curie temperature (T_C). The increase in T_C under the field E₌ is not uniform. At E₌ < E_c (E_c is the threshold field), the Curie temperature is practically independent of E₌. At E₌ > E_c, the increase of T_C is observed. The presence of the threshold field indicates the presence of sources of random electric fields in the material under study. It is assumed that they are responsible for the smearing of the ferroelectric phase transition.

The results of the study of the photoluminescent and X-ray luminescent properties of the p-terphenyl crystalline element made from a single crystal grown from a melt using the Bridgman method are presented. The transmission, photoluminescence and X-ray luminescence spectra of the crystals were obtained and analyzed. The kinetics of photoluminescence and X-ray luminescence decay have been studied for p-terphenyl single crystal and the absolute light yield of X-ray luminescence has been determined.

A theoretical investigation is conducted into the behaviour of TE and TM-polarised surface plasmon polaritons in a metal film situated between a periodic superlattice and a homogeneous dielectric, or alternatively, between two periodic superlattices. The dispersion equations are derived in the form of the determinant of a real symmetric matrix equalling zero. The matrix is constituted by the surface impedances of the media and the film. A number of general properties of the impedances and eigenvalues of the matrices entering the dispersion equations are established.

Bi low dimensional structures were obtained on the Si(100) substrates by thermal evaporation method in Ar. Bi nanocrystals and nanowires were condensed on the Si substrates at 10–20 s deposition time. Computer processing of SEM-images was used to determine the sizes of Bi nanocrystals and microcrystals and their distribution densities. The distribution density of nanocrystals was larger than its the microcrystals by a factor of 85–260. The increase of deposition time up to 20 s reduced the nanocrystal density by a factor of 2 with the increase of their sizes. X-ray diffraction analysis revealed oxide layers on the Bi nanocrystals and the Si substrates. The decrease in the sizes of the Bi nanocrystals and the increase in their density on the Si substrates in comparison with those on glassy carbon substrates were observed.

This study presents an investigation into the crystallization and absorptive-fluorescent properties of linear conjugated molecules derived from 2,1,3-benzothiadiazole, specifically 4,7-bis(2,5-dimethyl-[1,1'-biphenyl]-4-yl)benzothiadiazole (Ph-Xy-BTD) and 4,7-bis(4'-hexyl-2,5-dimethyl-[1,1'-biphenyl]-4-yl)benzothiadiazole (Hex-Ph-Xy-BTD). The synthesis of a new derivative of Hex-Ph-Xy-BTD is described. It was found that the presence of terminal n-hexyl substituents in Hex-Ph-Xy-BTD leads to a lower melting point, increased solubility and has a positive effect on crystallization compared to Ph-Xy-BTD. Single crystals of Hex-Ph-Xy-BTD were grown from hexane solution, and their structure was elucidated using single-crystal X-ray diffraction, confirming a monoclinic system (space group P2₁/c, Z = 4). Absorption and fluorescence spectra were obtained and analyzed for solutions in tetrahydrofuran as well as for the crystals of Ph-Xy-BTD and Hex-Ph-Xy-BTD, alongside investigations of quantum yield and fluorescence lifetime.

This study considers the elemental composition and manufacturing technology of mirrors of the so-called Sarmatian type. The examined mirrors are fortuitous discoveries originating from the territory of the Kerch Peninsula. All three objects are pendant mirrors with radial-beam ornamentation, which appeared at the turn of the 1st and 2nd centuries AD and existed until the beginning of the 3rd century AD. The results of X-ray fluorescence analysis of the alloy composition indicate that the mirrors are made of an alloy of copper, tin and lead with similar qualitative characteristics. The method of X-ray tomography clarified the details of the relief ornamentation, which was poorly expressed on the items due to corrosion.

A comprehensive study of antique red-glazed pottery fragments (terra sigillata) belonging to the Pontic, Bosporan and Eastern groups has enabled the identification of distinctive technological characteristics of the slip layer and ceramic mass. The Eastern sigillata samples exhibited superior technological characteristics. The small size of the pores and inclusions is indicative of the utilisation of finely dispersed clay. Furthermore, the presence of a mixture comprising two distinct clay types was identified: a ferrous clay and a more refractory calcareous clay. The particular and likely meticulous preparation of the clay suspension for the slip layer production was indicated by the addition of a potassium-containing preparation, presumably potassium potash, to enhance the glazing of the layer, as well as an iron-containing pigment, probably ocher. The samples were fired at a temperature of approximately 1000°C. Pontic sigillata products were distinguished by the addition of potassium potash in accordance with Eastern techniques and the absence of a specially added pigment in the varnish mixture. The firing temperature was lower, falling within the range of 850–900°C.