Objectives. The increased use of unmanned aerial vehicles necessitates the search for jet fuels based on hydrocarbon materials with high energy intensity and physical density. The purpose of the work was to analyze the influence of various factors on the mass energy intensity of hydrocarbons. This analysis is required to substantiate the algorithm for locating energy-intensive CnHm structures.
Methods. Combustion energy was calculated using additive procedures. The calculations were performed using Microsoft Excel.
Results. During the analysis of the mass energy intensity of CnHm hydrocarbons, the m/n ratio was discovered to be the decisive factor for achieving high values of the mass energy intensity of hydrocarbons. The energy intensity decreases when moving from alicyclic to cyclic hydrocarbons, and this decrease is not compensated by the production of strain energy. An additive scheme that allows the molar volume of hydrocarbons to be predicted with sufficient accuracy is proposed for calculating the volumetric enthalpies of combustion.
Conclusions. According to the thermodynamic analysis, n-alkanes have the highest mass energy intensities. The technology for extracting n-alkanes from oil fractions is well developed, and a decrease in the hydrogen content in the fuel results in a decrease in the mass energy intensity. It appears improbable that the mass and volumetric energy intensities of hydrocarbons seem will reach their maximum values simultaneously. Hydrocarbons that have a high m/n value, 2, 3, 4, 5, 6-membered rings, and phenyl fragments may have relatively high mass and volumetric energy intensities at the same time.

Objectives. Biogenic polyamines are widely present in nature. They are characteristic of both protozoan cells and multicellular organisms. These compounds have a wide range of biological functions and are necessary for normal growth and development of cells. Violation of polyamine homeostasis can cause significant abnormalities in cell functioning, provoking various pathological processes, including oncological and neuropsychiatric diseases. The impact on the “polyamine pathway” is an attractive basis for the creation of many pharmacological agents with a diverse spectrum of action. The purpose of this review is to summarize the results of the studies devoted to understanding the biological activity of compounds of the polyamine series, comparing their biological action with action on certain molecular targets. Due to the structural diversity of this group of substances, it is impossible to fully reflect the currently available data in one review. Therefore, in this work, the main attention is paid to the derivatives, acyclic saturated polyamines.
Results. The following aspects are considered: biological functionality, biosynthesis and catabolism, cell transport, and localization of biogenic polyamines in the living systems. Structural analogs and derivatives of biogenic polyamines with antitumor, neuroprotective, antiarrhythmic, antiparasitic, antibacterial, and other biological activities are represented; the relationship between biological activity and the target of exposure is reflected. It was found that the nature of the substituent, the number of cationic centers, and the length of the polyamine chain have a great influence on the nature of the effect.
Conclusions. At present, the use of polyamine structures is restrained by cytotoxicity and nonspecific toxic effects on the central nervous system. Further research in the field of biochemistry, cell transport, and a deeper understanding of receptor interaction mechanisms will help making polyamines as the basis for potential drug formulation.

Objectives. To develop a method for the microfluidic synthesis of oligohexamethylene guanidine salts in a flow-type reactor and to evaluate its effectiveness in relation to the synthesis in a traditional capacitive reactor and compare the purities of products obtained by these methods.
Methods. The synthesis of oligohexamethylene guanidine bihydrocarbonate (OHMG-BHC) was done using microfluidic hardware and the classical approach in volume. The purity and structure of the resulting product were confirmed by 13C NMR spectroscopy and high-performance liquid chromatography (HPLC).
Results. The 13C NMR spectrum of OHMG-BHC in classical bulk synthesis demonstrates that the product is unbranched and contains additionally unidentifiable impurities, in contrast to the sample obtained by the microfluidic method. Furthermore, the HPLC analysis showed that the OHMG-BHC sample synthesized using microfluidic technology has a 1.5-fold lower content than the initial monomers.
Conclusions. The advantage of synthesizing OHMG-BHC in a flow-type reactor compared to the traditional method of synthesis in volume is demonstrated since a product with a higher degree of purity is obtained.

Objectives. Over the last decade, hematopoietic stimulants have grown increasingly popular in elite sports. This is supported by the growing number of high-profile doping scandals linked to their use. A group of these stimulants includes cobalt salts, which cause an increase in the oxygen capacity of the blood as well as a powerful stimulation of metabolic processes, resulting innoticeable competitive advantages. The use of cobalt salts is regulated according to the Prohibited List of the World Anti-Doping Agency (WADA). Currently, only a few works have been dedicated to solving the problem of detecting the abuse of cobalt salts in anti-doping control. Only a few laboratories have included cobalt salt determination in their methodological bases. The purpose of this review is to attract the attention of the scientific community to the toxicity of cobalt compounds, consequences of their intake, and pharmacokinetics, as well as the problems in their detection methods due to their widespread availability in the modern market and the growing number of abuse cases.
Results. The main biological functions of cobalt, cellular levels of exposure, toxicity, and symptoms of cobalt salt poisoning are presented in detail in this review article. The data from the literature on the main methods for detecting cobalt as a doping agent have been generalized and systematized. There is a major focus on the amount of cobalt in dietary supplements that could cause an athlete to test positive for cobalt when they are consumed.
Conclusions. After analyzing promising cobalt detection approaches and methods, it was determined that high-performance liquid chromatography in combination with inductively coupled plasma mass spectrometry has an undeniable advantage for detecting cobalt as a doping agent. The lack of explicit WADA requirements for detection methods and the lack of its obligation to determine cobalt make it tempting for unscrupulous athletes to use its salts. Therefore, antidoping laboratories must implement the abovementioned method as soon as possible.

Objectives. Investigation of aqueous polyvinyl alcohol (PVA) foaming process and the influence of its water solution structure, when possessed of different molecular weights and concentrations, on foaming multiplicity.
Methods. Solution foaming analysis was performed on the data of dynamic light scattering obtained on the Zetasizer Nano particle analyzer.
Results. In this work, the foaming ability and foaming multiplicity of aqueous PVA solutions (as a main component for obtaining special-purpose foams) have been studied. It is shown that PVA solutions in water are colloidal dispersed systems consisting of different-sized associates (from 4.8 to 68.1 nm), depending on the molecular weight of PVA. Dependencies of aqueous PVA solution foaming multiplicities on the concentration, molecular weight, and solution temperature were given. Optimal values of concentration and molecular PVA weight, as well as optimal foaming process conditions from aqueous PVA solutions, were established.
Conclusions. Increasing PVA concentrations in aqueous solutions cause foaming multiplicity to decrease for all molecular weights by 1.5 times, and increasing molecular weight increases foaming multiplicity by 2 times. The foaming ratio of aqueous PVA solutions with different concentrations and molecular weights (depending on a solution temperature characterized by a maximum of 30 °C) is associated with decreased viscosity and surface tension.

Objectives. To study the relationship between bending deformation and the change in the electrical resistance of carbon black polypropylene composites.
Methods. Conductive polypropylene composites filled with carbon black UM-76 were investigated. The samples were deformed and kept under constant bending at temperatures of 20–155 °C.
Results. The deformation of the samples led to a reversible increase in their electrical resistance, while subsequent holding of the samples in the deformed state was accompanied by an exponential drop in their electrical resistance. The average times and activation energies of the electrical relaxation of the deformed polypropylene composites were calculated (30–32 kJ/mol) and compared with similar characteristics of polyethylene composites (15–16 kJ/mol).
Conclusions. The electrical resistance relaxation of deformed carbon black polypropylene composites at elevated temperatures is similar to their stress relaxation. The average times and activation energies of the electrical relaxation of deformed polypropylene composites are comparable with similar data on their mechanical relaxation. It was found that these electrical and mechanical phenomena are based on the same underlying physical processes.

Objectives. The study was devoted to considering the features of the synthesis and crystal structure of calcium trifluoroacetate Ca₂(CF₃COO)₄·8CF₃COOH and investigating the products of its thermal behavior.
Methods. The compositions of the proposed structural form were characterized by various physicochemical methods (X-ray diffraction, IR spectroscopy), and the products of thermal decomposition were determined under dynamic vacuum conditions.
Results. The reaction between calcium carbonate and 99% trifluoroacetic acid yielded a new structural type of calcium trifluoroacetate Ca₂(CF₃COO)₄·8CF₃COOH (I) in the form of colorless prismatic crystals unstable air. X-ray diffraction results confirmed the composition I: space group P2₁, with unit cell parameters: a = 10.0193(5) Å, b = 15.2612(7) Å, c = 16.3342(8) Å, β = 106.106(2)°, V = 2399.6(2) ų, Z = 2. The structure is molecular, constructed from Ca₂(CF₃COO)4·8CF₃COOH dimers. The end molecules of the trifluoroacetic acid were involved in the formation of intramolecular hydrogen bonds with oxygen atoms of the bidentate bridging anions CF₃COO⁻. There were strongly pronouncedsymmetric and asymmetric absorption bands of COO and CF₃-groups in the IR spectrum of the resulting compound in the range of 1200–1800 cm⁻¹. The definite peak of the oscillation of the OH-group at 3683 cm⁻¹ corresponds to the trifluoroacetic acid molecules present in the structure. The broadpeak of the valence oscillations in the range of 3300–3500 cm⁻¹ is caused by the presence of intramolecular hydrogen bonds. Decomposition began at 250°C and 10⁻² mm Hg with calcium fluoride CaF₂ as the final decomposition product.
Conclusions. We obtained a previously undescribed calcium–trifluoroacetic acid complex whose composition can be represented by Ca₂(CF₃COO)₄·8CF₃COOH. The crystal island structure is a dimeric molecule where the calcium atoms are bound into dimers by four trifluoroacetate groups. The complex was deposited in the Cambridge Structural Data Bank with a deposit number CCDC 2081186. Although the compound has a molecular structure, thermal decomposition leads to the formation of calcium fluoride characterized by a small particle size, which may further determine its applications.

Objectives. This study described the 4-circle goniometer Syntex P1N and its possible applications in X-ray and neutron structure analysis of single crystals.
Methods. The 4-circle goniometer Syntex P1N, due to its high-precision mechanical characteristics and individual components from domestic equipment (sets of DRON type X-ray diffractometers), formed the basis for developing an instrument complex for X-ray and neutron-structure studies.
Results. The neutron diffractometer was upgraded based on the Syntex P1N goniometer. Therefore, the ¹⁰BF₃-based end neutron counter, included in the diffractometer kit, was replaced by the ³He-based domestic side counter, SNM-16. Such a significant reduction in the linear dimensions of the detector allowed us to expand the range of measured angles of 2θ from 90° to 140° and increase the accuracy of the measured interplanar distances accordingly. The goniometer was adjusted relative to the primary neutron beam by placing it on a specially designed plate. Highly accurate measured parameters of the unit cell and the intensity of the reflexes were achieved by optimizing the installation geometry and the protection of the goniometer and detector. Based on the Syntex P1N goniometer, an instrument complex for X-ray diffraction studies has also been developed. Both the developed X-ray and the upgraded neutronography facilities were used to perform experiments to measure the unit cell parameters, the coordinates of atoms, and the parameters of their thermal vibrations on several crystals of domestic synthetic samples: diamond C, silicon Si, halite, or rock salt NaCl, and corundum α-Al₂O₃. An excellent correlation was achieved by comparing the data obtained with the corresponding chemical crystals’ parameters and reference samples recommended by the International Union of Crystallographers.
Conclusions. This paper described a neutron installation and a Syntex P1N neutron diffractometer for the study of single crystals. Based on the latter, an instrument complex for X-ray diffraction studies has also been developed. Experiments on standard samples have shown a high level of accuracy in measuring the lattice parameters, the coordinates of atoms, and the parameters of their thermal vibrations on both the X-ray and neutron diffractometers.