This article examined the mechanisms and results of applying various cold sintering methods, including specialized heating conditions and other innovative approaches. Particular attention was given to emerging promising technologies, such as cold sintering process (CSP), FLASH sintering, and spark plasma sintering (SPS). These methods enabled a significant reduction in the energy required for ceramic synthesis and ensured the preservation of the unique properties of the initial materials, including nanostructure and performance characteristics. The discussed approaches demonstrated substantial advantages, such as a drastic reduction in sintering temperature to as low as 300°C and the achievement of high-density products.
Silver nanoparticles (AgNPs) stabilised with quercetin (Que) were obtained by chemical polyol reduction. The optimization of the hybrid system synthesis was based on varying the heating time, the molar ratio of AgNO3-Que, and the pH. The formation of AgNPs was monitored using UV-visible spectroscopy. The structures of small silver clusters (Ag, Ag2, Ag3) and their interaction with the quercetin were calculated using density functional theory (DFT) with B3LYP5 parameterisation. Trends in the geometric structure and interaction energy of Agn—quercetin were evaluated depending on the cluster size and coordination site. It was shown that the dissociation energy increases with the growth of the metal cluster size. The preferred coordination of Ag atoms is via the carbonyl oxygen conjugated with the benzoic fragment of quercetin in ring A. The highest binding energy was obtained for the Ag3-Que system (10.3 kcal/mol).
A digital colorimetry method using a consumer device (smartphone camera) was applied for the first time to measure the characteristics of photonic crystal sensor arrays. Sensor arrays consist of an array of polystyrene spheres (average diameters of 190, 250, and 280 nm) coated with a layer of polydimethylsiloxane on polycarbonate and polyethylene terephthalate substrates. Photography conditions and parameters were identified that yield the most stable and intense analytical signal in RGB coordinates for photonic crystal arrays with violet, green, and red source colors. The feasibility of measuring the chromaticity coordinates and the Ar vector integral length of a sensor array, which change when exposed to volatile organic compounds (using hexane vapor as an example), was demonstrated.
A structural rheological model is used to explain the dynamic measurement results obtained for polyacrylamide and xanthan polymer solutions. The model describes a dependence of dynamic viscosity and dynamic elasticity on deformation amplitude at a fixed shear oscillation frequency. The structural rheological model allows the interpretation of experimental curves caused by the changes in structure of a polymer solution sample under the action of oscillation shear flow. The number of macromolecules bound by contacts to form certain macromolecular associates is an integral characteristic of the structure. No concept of a continuous or discrete relaxation spectrum is used to analyze rheological curves. Experimental data are approximated by the equations of the structural model for individual sections of the deformation amplitude, which correspond to different states of the polymer solution structure.
Cryochemical technologies enable targeted modification of the morphology and structure of drug powders, which in turn affects their dissolution rate, specific surface area, equilibrium solubility, and pharmacological activity. This paper demonstrates how cryomodification using cryogenic spray drying allows for modification of the structure and morphology of antibacterial drug dioxidine, directly affecting its physicochemical properties (dissolution rate, specific surface area, particle size distribution, and antibacterial activity). Influence of key cryogenic drying parameters (concentration and temperature of sprayed precursor solution) on the structural and morphological properties of the resulting drug powder was determined. The original pharmacopoeial and cryomodified drug’s phase composition and structure were determined using X-ray phase analysis, UV, and IR spectroscopy. Morphology and specific surface area of samples were characterized using scanning electron microscopy and low-temperature argon adsorption.
The complexation of copper(II) with ligands (L)—2-methoxy-N-(1S)-1-phenyl-2-[(prop-2-en-1-yl)oxy]ethylaniline (L1) and 2-methoxy-N-(1S)-1-phenyl-2-[(prop-2-yn-1-yl)oxy]ethylaniline (L2)— was studied. The optimal acidity range for the Cu(II)–L1 (1) and Cu(II)–L2 (2) complexes is at pHopt 3.1–6.2 (pHform 1.2–8.7) and pHopt 3.3–7.4 (pHform 1.3–8.9), respectively. The molar absorption coefficients are ε445 = 4.21 × 104 (for complex 1) and ε450 = 4.37 × 104 (for complex 2). The composition of the complexes per 1 mole of metal accounts for 2 moles of L1,2. On the basis of the results, a photometric method for determination of copper in steel for use in different trade-marks and in food preparation has been proposed.
Comprehensive immunophenotyping of sarcoma cell cultures was performed for expression of tumor markers associated with key biological characteristics of malignant neoplasms: TUBB3, EMT/MET, PD-L1, ERα, and ERβ. Two pairs of cell cultures with differences in molecular phenotype were formed: metastatic Mg-63 vs. primary MNNG-Hos osteosarcoma and Mg-63 osteosarcoma vs. HT-1080 fibrosarcoma. These pairs may be useful for assessing the contribution of the studied markers to various biological characteristics of tumor cells and studying the interactions between their regulatory mechanisms in mesenchymal tumors.
Since its discovery in 1946, nuclear magnetic resonance spectroscopy become as a method to solve structural and dynamic problems in modern chemistry. Currently, it is hard to find a university in the world without various NMR spectrometers in its laboratories. Achievements in this field, over the course of almost 80 years of its development, were recognized with four Nobel Prizes in Physics and Chemistry. Fifth-generation high-resolution NMR spectrometers were developed during this period. They are as complex measurement and computing systems, in which the latest advances in electronics, cryogenics, and computing technology are utilized. Scientists from the USSR and Russia made the significant contributions to this remarkably rapid progress. This year marks the 60th anniversary of the establishment of the first NMR laboratory at the Faculty of Chemistry of Moscow State University that focused to solve complex chemical problems. The history of its creation and several scientific projects to solve not only specific chemical problems but to develop an NMR methodological arsenal are described in this work.
Based on the adhesion tension isotherms γLVcosθ = f(γLV), the relationship between the adsorption values of surfactants at the solution/solid surface (ГSL) and solution/air (ГLV) interfaces was examined by wetting Teflon and polystyrene with aqueous solutions of the nonionic surfactant Triton X-100 (TX-100). The approach presented in this paper demonstrates the feasibility of predicting the wettability of hydrophobic surfaces for practical applications, using an existing database on the surface tension of aqueous surfactant solutions and their adsorption on the surface of solid adsorbents.
The phenomenon of metal concentration by plants is discussed. The metal content in plants can be tens or hundreds of times higher than the metal content in the soil. A kinetic model of phytomining is developed. The model is verified based on experimental data, the two-chamber nature of the process is demonstrated, a parametric analysis of the model is performed elucidating the role of the metal transfer rate from the geological substrate and metal translocation in the plant, and the dynamics of metal bioaccumulation is described. Natural coals are characterized by exceptionally high ash content (metal content up to 50
For elemental analysis of candidate reference materials for the composition of black shales (SLg-1A and SChS-1A), we used inductively coupled plasma mass spectrometry (ICP-MS) after fusion of samples with lithium metaborate and microwave acid digestion without prefiring. The use of the proposed sample preparation techniques, which offer high speed and ease of implementation, enabled ICP-MS determination of a wide range of elements in each material, including Cd, Mo, Sb, Sn, Te, W, Tl, and Bi, for which data were missing or whose concentrations were evaluated only approximately in SLg-1 and SChS-1 certification. The percentages of analytes were determined in a single measurement cycle on an Element magnetic sector mass spectrometer with low, medium, and high resolution, using external calibration against solutions having a similar matrix composition, in combination with an internal standard in order to reduce the matrix effect and monitor the signal drift. For most elements, the relative standard deviation in ICP-MS analysis is under 10
The complex formation in a Fe(II)–Fe(III)–Gly–Na(H)ClO4–H2O system is studied by the method of Clark–Nikolsky oxidation potential at 308.15 K, I = 0.50, CFe(II) = CFe(III) = 1 × 10–3, and CGly = 2 × 10–3 mol/L in a range of pH of 0.5–8.5. The experimental curves of the dependence of the EMF of the system on the concentration parameters such as pH, pCFe(III), pCFe(II), and pCL are obtained. A method of successive approximations of theoretical and experimental oxidative functions is used for the calculation of the formation constants of the complexes with the use of the Excel program.
This paper examines the equilibrium state of an electrolyte solution containing an acid and a base in arbitrary ratios. An equation relating the concentrations of the solution components (connection equation) is derived. A method for solving this equation with respect to the hydrogen ion concentration is proposed. The theoretical predictions are compared with experimental titration curves.
The key requirements are outlined for an effective pre-column derivatization reagent used in the HPLC determination of chromophore-free organic compounds. Nitrofluorostyrenes, dichlorostyrenes, and diethyl 2-(4-nitrobenzylidene) malonate were studied as new reagents. Diethyl 2-(4-nitrobenzylidene) malonate was selected as the optimal reagent. 2-Methylmercaptoacetate was derivatized as a test analyte under mild conditions for 20 min at room temperature. The reaction proceeded to completion, forming a single product. The detection limit of 2-methylmercaptoacetate decreased by a factor of 67 (to 15 ng mL–1) compared to the initial value.
An azido derivative of the mitochondrial uncoupler carbonyl cyanide-m-chlorophenylhydrazone (CCCP), namely carbonyl cyanide-2-nitro-4-azidophenyl hydrazone (N3 CCP), has previously been used to study the binding sites of uncouplers on mitochondrial proteins. In this study, we compared the protonophoric activity of N3 CCP and CCCP on an artificial bilayer lipid membrane (BLM) and the uncoupling activity of these compounds in isolated rat liver mitochondria. Both compounds induced electrical current through the BLM at micromolar concentrations and uncoupled mitochondria at submicromolar concentrations. Both protonophoric and uncoupling activities of N3 CCP were effectively inhibited by UV light, whereas CCCP was light-insensitive. These results indicate that N3 CCP is modified by UV light to form products incapable of hydrogen ion transport across artificial or natural membranes.
A comparative analysis of the structure and sorption properties of nano- and microporous materials based on large-capacity industrial polymers in the form of films, fibers, nonwoven and foam materials, including those manufactured as packaging materials, geotextiles, and medical devices, was carried out. It has been shown that the sorption capacity, sorption kinetics and buoyancy of the studied materials are determined by the geometric size and shape of the sorbent, the size and volume of the pores. The most effective were foam materials (polyurethane foam, polyethylene foam), which retain buoyancy at high sorption capacity (17-39 g/g). The possibility of using porous polymer materials as carriers of bacteria-biodegraders of oil and oil products has been demonstrated.
A structural rheological model is used to interpret the viscosity curves and flow curves of concentrated emulsions consisting of water droplets in oil. It is shown that the rheological curves can be divided into separate intervals of shear rates, within which the experimental data are approximated by the rheological equations of the structural model. The generalized flow equation describes the breakdown of the emulsion structure under the action of tensile hydrodynamic forces. The second rheological equation additionally includes a rate constant related to the process of droplet aggregate formation under the action of compressive hydrodynamic forces. The dependence of the generalized flow equation coefficients η _c^1/2 and τ _c^1/2 on the volume fraction Φ is described by separate equations which utilize hydrodynamic parameters. The compactness coefficient χ, associated with the spontaneous rupture of droplets, changes in a complex manner with increasing concentration, which may be related to the formation of aggregates and the change in droplet shape due to deformation upon droplet contact.
CexZr1–xO2 hydrosols with different particle compositions (x = 0.8, 0.5, 0.2) were synthesized, and flow curves were measured over a wide range of dispersed‑phase concentrations and dispersion‑medium pH values. It was found that, under the conditions studied, the CexZr1–xO2 hydrosols behave as Newtonian fluids. At the same time, the Einstein equation is obeyed only within a rather narrow range of dispersed‑phase concentrations. Based on the particle density data and their effective volume fraction, the influence of surface layers on the viscosity increase of the hydrosols was evaluated. The effects of both primary and secondary electroviscosity were identified, and their contributions to the measured viscosity of the hydrosols were shown to depend on the dispersed‑phase concentration, the pH of the dispersion medium, and the particle composition.
De novo expression of the mesenchymal protein vimentin in the cells expressing epithelial cytokeratins was quantified by double immunofluorescence staining of serous ovarian cancer samples (n = 56). The median value was shown to be 1.6 times higher (p = 0.006) in the group of resistant tumors compared with that of sensitive tumors (disease relapse after chemotherapy with platinum drugs and taxanes for ≤6 months and ≥12 months). Conclusions. The level of de novo vimentin expression is a predictor of the efficacy of platinum drugs and taxanes with the calculated specificity and sensitivity of the assay of more than 80
Based on non-empirical data obtained using a high-level multi-configurational quantum chemistry method, neural networks with the architectures of a multilayer perceptron and an E(3)-equivariant graph network were constructed and trained to predict the energies of the ground and the first two electronically excited states of the methaniminium cation, CH_2NH_2^ + . It is shown that the E(3)-equivariant graph neural network architecture demonstrates higher accuracy. Using the trained network, a segment of the cation’s potential energy surfaces near the region of the conical intersection between the first excited and the ground states was investigated; this region plays an important role in the mechanism of internal conversion and photoisomerization reactions. It is demonstrated that the neural network accurately reproduces the topography of the potential energy surfaces of the two electronic states in the region of their conical intersection.
