Synthesis and properties of vinyl benzyl alcohol copolymers with styrene

Objectives. Synthesis and study of the properties of copolymers of vinyl benzyl alcohol (VBA) with styrene with antimicrobial properties.Methods. The study employed infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy, thin-layer chromatography, viscometry, and elemental analysis. The sessile drop method and the pencil method were respectively utilized to determine the contact angles and hardness of the films. The process of testing the film coatings’ resistance to the effects of molds consisted of contaminating the film coatings applied to the glass with mold spores of the All-Russian Collection of Microorganisms in a solution of mineral salts without sugar (Czapek–Dox medium).Results. Homopolymers of vinyl benzyl acetate and its copolymers with styrene were synthesized in this study. Homo- and copolymers of VBA were obtained by saponification. IR and proton NMR (1H NMR) spectroscopy determined the composition of the copolymers. Employing IR spectroscopy, the degree of saponification was monitored by the appearance of the hydroxyl group absorption band and the disappearance of the ester group absorption band. According to the IR spectroscopy data, only an insignificant (~3%) amount of ester groups remains in the saponified copolymers. The influence of the copolymers’ composition on their solubility in various solvents is demonstrated. IR spectroscopy of the copolymers revealed hydrogen-bond formation between the unreacted ester groups and hydroxyl groups formed due to the saponification. The viscometry of the solutions of mixtures of saponified and unsaponified copolymers, solutions of mixtures of saponified copolymer with polyvinyl acetate, and viscometry of saponified copolymers in various solvents all support this conclusion. These bonds’ concentration depends on the copolymer’s composition and can be controlled by the nature of the solvent from which these copolymers’ films are formed. Saponified copolymer solutions form smooth, transparent film coatings with excellent adhesion to metals and silicate glass surfaces. The contact angle of these films, like the hardness, decreases as the VBA units’ concentration in the copolymers increases and depends on the solvent polarity used to form the films. It has been demonstrated that increasing the VBA units concentration suppresses the microorganisms’ growth.Conclusions. Film coatings made of copolymers of styrene with VBA have been shown to have high biocidal activity against molds; can be used to protect structural materials and products from the effects of microorganisms.

Characterization of iron-doped crystalline silicon nanoparticles and their modification with citrate anions for in vivo applications

Objectives. This paper presents data on the development and study of the structural properties of iron-doped crystalline silicon (nc-Si/SiOx/Fe) nanoparticles obtained using the plasma-chemical method for application in magnetic resonance imaging diagnostics and treatment of oncological diseases. This work aimed to use a variety of analytical methods to study the structural properties of nc-Si/SiOx/Fe and their colloidal stabilization with citrate anions for in vivo applications.Methods. Silicon nanoparticles obtained via the plasma-chemical synthesis method were characterized by laser spark emission spectroscopy, atomic emission spectroscopy, Fouriertransform infrared spectroscopy, and X-ray photoelectron spectroscopy. The hydrodynamic diameter of the nanoparticles was estimated using dynamic light scattering. The toxicity of the nanoparticles was investigated using a colorimetric MTT test for the cell metabolic activity. Elemental iron with different Fe/Si atomic ratios was added to the feedstock during loading.Results. The particles were shown to have a large silicon core covered by a relatively thin layer of intermediate oxides (interface) and an amorphous oxide shell, which is silicon oxide with different oxidation states SiOx (0 ≤ x ≤ 2). The samples had an iron content of 0.8–1.8 at %. Colloidal solutions of the nanoparticles stabilized by citrate anions were obtained and characterized. According to the analysis of the cytotoxicity of the modified nanosilicon particles using monoclonal K562 human erythroleukemia cells, no toxicity was found for cells in culture at particle concentrations of up to 5 µg/mL.Conclusions. Since the obtained modified particles are nontoxic, they can be used in in vivo theranostic applications.

Synthesis and X-ray-graphical characteristics of the MеSn2F5 (Mе = Na, K, Rb, Cs) fluoride-ion conductors

Objectives. Pentafluorodistannates of alkali metals are promising materials for use as electrolytes in fluoride-ion batteries due to their electrophysical properties, such as high fluoride-ion conductivity. This work aims to synthesize crystals of alkali metals MeSn2F5 (Me = Na, K, Rb, Cs), carry out X-ray diffraction studies on them, and investigate the possibility of obtaining lithium fluorostannates.Methods. Supersaturated aqueous solutions were employed to synthesize the crystals. The X-ray diffraction (XRD) analysis was carried out.Results. Oversaturated solutions yield microcrystalline powders of sodium, potassium, rubidium, and cesium pentafluorodistannates. The presence of a single-phase was confirmed by XRD analysis of the powders corresponding to the MеSn2F5 (Mе = Na, K, Rb, Cs) composition. XRD data analysis and literature indicated that MеSn2F5 (Mе = K, Rb, Cs) have a fluorite-like structure, with the cations forming three-layer closest packing. The RbSn2F5 compound was discovered to be isostructural to KSn2F5. Based on this discovery, RbSn2F5 was reindexed to a hexagonal unit cell with parameters a = 7.40(3) Å, с = 10.12(6) Å (KSn2F5 P3, a = 7.29(3) Å, с = 9.86(2) Å). The CsSn2F5 compound was reindexed to a monoclinic unit cell (a = 10.03(4) Å, b = 5.92(7) Å, c = 11.96(9) Å, β = 107.4(5)°). A crystallochemical analysis of the pentafluorodistannates was carried out, and common structural motifs were discovered. The motifs are similar to lead tetrafluorostannate PbSnF4, the best fluoride-ion conductor. The effect of the pentafluorodistannates structures on the ionic conductivity is considered. The LiF–SnF2 system contains no compounds; the compositions were obtained by melting the original fluorides. Conclusions. MеSn2F5 (Mе = Na, K, Rb, Cs) were synthesized and investigated by XRD analysis. The structural characteristics of the RbSn2F5 and CsSn2F5 compounds have been redefined. The crystallochemical structure is analyzed in relation to the electrophysical properties of the alkali metal pentafluorodistannates. Pentafluorodistannates MеSn2F5 (Mе = K, Rb, Cs) have a fluorite-like structural motif with cubic parameters а = 5.694 Å (KSn2F5), а = 5.846 Å (RbSn2F5), а = 6.100 Å (CsSn2F5), with the cations forming three-layer closest packing. The cationic layers alternate like Me–Sn–Sn–Me (Mе = K, Rb, Cs). For KSn2F5 and RbSn2F5, they are normal to the three-fold axis and normal to the four-fold axis in the case of CsSn2F5.

Algorithm and software for the optimal technological design of a system of simple distillation columns

Objectives. The formalized problem of the optimal design of distillation column systems belongs to the class of mixed integer nonlinear program problems. Discrete search variables are the number of trays in the rectifying and stripping sections of columns, whereas the continuous ones are the operating modes of columns. This study aimed to develop an algorithm and a software package for the optimal technological design of a system of simple distillation columns based on the criterion of total reduced capital and energy costs using rigorous mathematical distillation models.Methods. The solution to this problem is based on the branch and bound method. A computer model of the distillation column system was developed in the environment of the Aspen Hysys software package. The Inside–Out module was used as the distillation model. The developed algorithm is implemented in the software environment of the Matlab mathematical package. To solve the conditional optimization problem, a sequential quadratic programming method-based model was used. The interaction between software add-ins in Matlab and Aspen Hysys is implemented using a Component Object Model interface.Results. Approaches to obtain the lower and upper bounds of the optimality criterion and the branching method for the implementation of the branch and bound method have been developed. In addition, an algorithm for the optimal design of a distillation column of a given topology based on the branch and bound method has been developed. Furthermore, using Matlab, a software package that implements the developed algorithm and is integrated with the universal modeling software AspenHysys has been created.Conclusions. An algorithm and a software package have been developed and implemented that allows automating the design process of distillation column systems and integration with advanced mathematical programming packages, respectively. The performance of the algorithm and software package has been evaluated using the optimal design of the debutanization column as an example.

Hydrodynamic activation of heavy oil residues

Objectives. Recently, there has been a tendency to increase the volume of high-viscosity heavy oils in the total volume of oil produced. The processing of these oils requires new technological approaches. This task is closely related to the need to increase the depth of oil refining. Among the approaches proposed to solve these problems, mechanochemical activation, which is based on the cavitation effect produced by ultrasonic or hydrodynamic methods, has been suggested. This study evaluated the effects of cavitation in increasing the depth of oil refining.Methods. Straight-run and “secondary” oil products were used as raw materials: vacuum gas oil, catalytic cracking gas oil, and fuel oil. Activation was carried out in a high-pressure disintegrator. The principle of operation was to compress the oil product and then pass it through a diffuser. When the oil was passed through the diffuser, there was a sharp pressure release to atmospheric pressure, which caused cavitation in the hydrodynamic flow. The pressure gradient on the diffuser and the number of processing cycles ranged from 20 to 50 MPa and 1 to 10, respectively. The density, refractive index, and the fractional composition of petroleum products were determined using standard and generally accepted methods.Results. This paper reports the influence of mechanochemical activation of petroleum products on their physical and chemical characteristics. An increase in the pressure gradient and the number of processing cycles leads to a decrease in the boiling point of the petroleum products and their density and an increase in the yield of fractions that boil off below 400 °C. The yield of the fractions with boiling points of 400–480 °C and the remainder were reduced. The density and refractive index of fractions with boiling points up to 480 °C decreased, and the density of the residue increased. The effects of cavitation (an increase in the yield of fractions with boiling points up to 400 °C and a decrease in the density of the petroleum products) increased with increasing pressure gradient and the number of processing cycles.Conclusions. The changes in the density, boiling point, and the yield of fractions increased with increasing the pressure from 20 to 50 MPa and the number of hydrodynamic cavitation cycles from 1 to 5. Increasing the number of processing cycles to more than five had little additional effect. The effects of cavitation increased with increasing initial density of the oil product. The average molecular weight of these fractions was estimated from the densities and boiling points of individual fractions of the petroleum products. The calculation confirmed the assumption regarding the course of cracking reactions of petroleum products under the influence of cavitation and indicates the course of the compaction processes.

Application of pulse current for dissolution of heat-resistant GS32-VI alloy

Objectives. To identify the regularities of electrochemical processing of the heat-resistant GS32-VI alloy in a sulfuric acid electrolyte with a concentration of 100 g/dm3 under the action of a pulsed current in a pulsed mode.Methods. Using the electrochemical technological complex EHK-1012 (developed by IP Tetran) and a non-compensatory method of measuring potential, polarization and depolarization curves with a change in pulse duration and a pause between them were recorded. The current pulses had an amplitude ranging from 0 to 3.5 A (when recording the polarization and depolarization curves), pulse durations ranging from 200 to 1200 ms, and a pause (delay) between pulses ranging from 50 to 500 ms. There were no reverse current pulses.Results. The parameters of the current program that provide the maximum values of the alloy dissolution rate and current output were determined: with a current pulse amplitude of 2 A, a current pulse duration of 500 ms, and a pause duration between pulses of 250 ms, the maximum dissolution rate of the alloy is 0.048 g/h·cm2, while the current output for nickel is 61.6% with an anode area of 10 cm2. The basic technological scheme for processing the heat-resistant GS32-VI alloy, which includes anodic alloy dissolution in a pulsed mode, is proposed.Conclusions. Electrochemical dissolution of GS32-VI alloy under pulsed current action results in an optimal dissolution rate ratio of the alloy components, ensuring the production of a cathode precipitate with a total nickel and cobalt content of 97.5%.

Structure and biological action of analogs and derivatives of biogenic polyamines

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.

Energy intensity of hydrocarbons in liquid and solid states

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.

A novel сalcium trifluoroacetate structure

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) Å3, 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.