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Objective: Cholesterol is an important structural component of the plasma membrane of mammalian cells. Cholesterol, among other important roles, plays a special role in sperm membranes. Change in the lipid composition of the sperm membrane, particularly the outflow of cholesterol, is an integral part of the process of capacitation and subsequent acrosomal reaction necessary for the sperm to fertilize an egg. Deviations in cholesterol concentration in sperm membrane may indicate a decrease in the fertilizing potential of sperm. To determine the optimal method for rapid analysis of the cholesterol content in human sperm membranes in the IVF laboratory, four methods of quantitative determination of cholesterol were compared in terms of practicality and effectiveness of their use to assess the concentration of cholesterol in human sperm membranes: the method of enzymatic colorimetric detection, the Lieberman–Burchard method, infrared spectroscopy and high-performance liquid chromatography. Methods: 101 ejaculates of patients with established normozoospermia (according to WHO criteria) were used in the work. Spermatozoa were separated from the semen by double centrifugation with the addition of DPBS medium. The resulting cellular pellet was used to determine the concentration of cholesterol in a sample by one of four methods: enzymatic colorimetric detection (FCD), HPLC, Lieberman-Burchard method, infrared spectroscopy. Results and Discussion: The following cholesterol concentrations were obtained by enzymatic colorimetric detection, Lieberman–Burchard, infrared spectroscopy and high-performance liquid chromatography: 1.0 ± 0.3, 1.32 ± 0.15, 5.1 ± 1.8 and 1.53 ± 0.18 nmol/106 cells, respectively. The Lieberman–Burchard method, enzymatic colorimetric detection and HPLC showed similar results, the obtained average cholesterol concentrations coincide within the error. The mean cholesterol concentration in sperm membranes obtained using infrared spectroscopy method significantly exceeds the values presented in the literature and the values obtained using other methods. In addition, this method requires an amount of analyzed material that significantly exceeds the volume of one ejaculate. Conclusions: As a result of comparing four methods of quantitative cholesterol analysis, the method of enzymatic colorimetric detection is proposed as a method of rapid analysis of cholesterol in human sperm membranes suitable for routine use in a clinical laboratory. The advantages of this method include the low toxicity of the method, it's cost-effectiveness and a significant reduction in the time of complete analysis: from sample preparation to obtaining the result. [ABSTRACT FROM AUTHOR]

In this study, the interaction of -carboxymethyl cyclodextrins (CMCD) with monomolecular layers composed of a mixture of electroneutral and cationic lipids on the surface of an aqueous subphase was investigated. The monolayers were transferred onto mica substrates using the Langmuir–Blodgett method and examined by atomic force microscopy. Analysis of the monolayer compression isotherms and AFM images showed that the adsorption of CMCD on the cationic Langmuir lipid monolayer is accompanied by the formation of supramolecular ensembles of similar morphology regardless of the concentration of the added oligosaccharides. [ABSTRACT FROM AUTHOR]

The effect of a high-velocity flow of dissociated nitrogen on a sample of HfB2–30 vol % SiC ultrahigh-temperature ceramic materials modified with low amounts of reduced graphene oxide was studied to evaluate the potential of these materials in creating aerospace equipment intended for use in N2-based atmospheres. It was determined that, under the selected treatment conditions during a stepwise increase in the anode supply power of the plasma torch and, accordingly, in the acting heat flux at certain process parameters, the surface temperature of the sample sharply increases from ~1750 to 2000–2100°C. A further increase in the heat flux does not have an obvious and proportional effect on the surface temperature of the sample, which may indicate its high catalyticity with respect to surface recombination reactions of atomic nitrogen. It was shown that the surface layers of the material undergo a chemical transformation (removal of silicon-containing substances and formation of a new phase based on HfN), which is accompanied by a significant change in the microstructure (formation of dendrite-like structures), affecting the optical and catalytic characteristics of the surface. [ABSTRACT FROM AUTHOR]

Crystal structure, morphology, and electrochromic properties of V2O5 film prepared using vanadyl alkoxoacetylacetonate as precursor have been studied. We have shown that the obtained vanadium pentoxide contains significant amount of V4+ cations, which is indicated by low electron work function. This results in material possessing anodic electrochromism (coloring upon oxidation) with rapid bleaching process (1 s upon the corresponding potential application). Anodic coloration is observed in the whole visible light spectrum, as well as in near IR region up to 1100 nm. The obtained data show high prospects for approach to formation of V2O5-based films using vanadyl acetylacetonate as precursor and application of these films as components of smart windows and displays, optical properties of which could be controlled by electrical current application. [ABSTRACT FROM AUTHOR]

A study was made of the effect of the nature of the MF–HCl (M = Li+, Na+, ) etching systems on the synthesis of Ti3C2Tx MXenes based on the Ti3AlC2 MAX phase, microstructure, phase purity, interlayer distance, composition of functional surface groups, thermal behavior, and work function of the resulting products. The gas-sensing properties of Ti3C2Tx receptor layers deposited by microplotter printing were tested to a wide range of gaseous analytes (H2, CO, NH3, NO2, O2, benzene, acetone, methane, and ethanol) at room temperature. An increased sensitivity to ammonia was detected for MXenes produced by exposure to hydrochloric acid solutions of sodium and ammonium fluorides, and an elevated sensitivity to carbon monoxide was determined for a sample synthesized using the LiF–HCl system. High responses (~20–30% per 100 ppm NO2) were measured for all three receptor materials; however, sensor recovery processes were much more difficult. To improve the sensory characteristics, the sensitive Ti3C2Tx layers were subjected to relatively low temperature heat-treatment in an air atmosphere to form Ti3C2Tx/TiOx nanocomposites. It was detected that partially oxidized MXenes exhibit a high selective response to oxygen at very low operating temperatures (125–175°C), which is especially typical of the material produced using the HCl–NaF system. [ABSTRACT FROM AUTHOR]

The formation of hierarchically organized MoS2 films on various substrates by a hydrothermal method was studied. The influence of synthesis conditions and the substrate (a glass or a flexible carbon paper substrate) on the crystal structure of sulfide films was determined using X-ray powder diffraction (XRD). Scanning electron microscopy (SEM) showed that the films on glass substrates comprised structurally different elements, namely a continuous dense layer of spherical nanoparticles on the surface of which hierarchically organized globular agglomerates of two types are arranged. A molybdenum disulfide shell about 1.5 μm thick, consisting of hierarchically organized nanosheets less than 10 nm thick, was formed on the surface of carbon fibers that make up the carbon paper. Elemental mapping was used to evaluate the homogeneity of the MoS2 film formed on the carbon paper. Atomic force microscopy (AFM) showed that an individual carbon fiber modified with a sulfide film had a mean square roughness of about 13 nm (over an area of about 100 μm2). According to Kelvin-probe force microscopy (KPFM) data, the electron work function of the material was 4.53 eV. The electrochemical characteristics of the manufactured flexible electrode based on a hierarchically organized molybdenum disulfide film were investigated. The specific capacitance and the stability of functional and microstructural properties of the manufactured supercapacitor electrode in 2000 charge–discharge cycles were evaluated. Thus, the proposed strategy is promising for the fabrication of efficient hierarchically organized MoS2 electrodes for flexible supercapacitors. [ABSTRACT FROM AUTHOR]

The behavior of the ceramic material Ta4HfC5-30 vol % SiC has been studied under the effect of supersonic flow of dissociated nitrogen, which is necessary to assess the potential application of these materials in oxygen-free gas environments at temperatures >1800°C. It has been found that as a result of heating the surface to ~2020°C in a few minutes there is a decrease to ~1915°C followed by a slow decrease to 188°C. This is probably due to the chemical processes occurring on the surface and the formation of an extremely rough microstructure. The ablation rate has been determined; it has been shown that neither at introduction of the sample into a high enthalpy nitrogen flow nor at sharp cooling (temperature drop to ~880°C in 9–10 s) cracking of the sample or detachment of the near-surface region has been observed. X-ray powder diffraction and Raman spectroscopy data allow us to conclude the complete removal of silicon carbide from the surface layer and the transformation of complex tantalum-hafnium carbide into the nitride. [ABSTRACT FROM AUTHOR]

The formation of nanocrystalline Co3O4 by chemical precipitation has been studied. The validation of the obtained semiproduct has been carried out using simultaneous thermal analysis, infrared spectroscopy, and X-ray powder diffraction analysis. The process of thermal decomposition of the semiproduct with the formation of the target oxide, which is a highly dispersed powder (the average CSR size was about 17 ± 2 nm), free of impurities has been investigated. An approach to microplotter printing of miniature planar Co3O4 nanostructures of different geometries on the surface of silicon substrates with the use of functional inks made on the basis of the obtained nanopowder has been proposed. The features of the morphology of the formed thin-film structures have been investigated. It is shown that there is practically no "coffee ring" effect. As part of the local electrophysical characteristics study of the obtained samples, the distribution maps of surface potential and capacitance contrast have been built, and the value of the electronic work function has been calculated. As a result of the study, the possibility of using the developed technology for the manufacturing of electrode structures Co3O4 for supercapacitors of planar type has been shown. [ABSTRACT FROM AUTHOR]

As part of the study, we have developed a method for obtaining a single-layer Ti2CTx MXene by the interaction of Ti2AlC with a mixture of hydrochloric acid and sodium fluoride followed by delamination using a tetramethylammonium hydroxide solution and ultrasonic exposure. The obtained stable aqueous dispersion of Ti2CTx has been applied by microplotter printing onto a specialized sensor chip, which has been dried at a temperature of 150°C under reduced pressure. The coating has been studied using modern physicochemical methods of analysis. According to the data of X-ray spectral elemental microanalysis, the ratio n(Ti) : n(F + Cl) = 2 : (0.82–0.85), n(F) : n(Cl) ≈ 6 : 4; aluminum impurity does not exceed 1.5–2.0%. Data have been obtained on the local electrophysical properties of the Ti2CTx coating: on the value of the electron work function from the surface of the material, the distribution of charge carriers, and the capacitance gradient of the "probe tip–sample microregion" capacitor. For the first time, at an operating temperature of 30°C, extremely high chemoresistive responses of the Ti2CTx receptor layer to the content of 1 and 5% oxygen in nitrogen have been determined, which amounted to 8.6 and >276, respectively. [ABSTRACT FROM AUTHOR]