Vol 74, No 3 (2019)

It is shown that, from the viewpoint of the theory of fuzzy sets, a set of generating (key) contacts in any molecular agglomerate can be considered as a fuzzy set. Sets of generating contacts are investigated and systematized for monosystemic chain molecular agglomerates. The degrees of fuzziness of fuzzy sets of generating contacts are compared.

The atomic absorption analysis of trace elements in natural solid samples with the use of an improved crucible atomizer with several condensation/evaporation zones is shown to be advantageous. A new approach to fractional preconcentration is proposed, including two stages of thermal decomposition (high-temperature and low-temperature) of solid sample components when elements are evaporated and their vapors are condensed in heated and unheated zones. This approach facilitates the efficient suppression of non-selective interferences and matrix effects. It also improves the metrological characteristics of the element analysis of samples of complex composition.

The possibility of synthesizing aromatic polyamine hardeners for epoxy resins based on the adducts of the interaction of 4,4'-dihydroxy-2,2-diphenylpropane (Bisphenol A), formaldehyde, and N,N '-bis(2-aminoethyl)-1,2-ethanediamine in several solvents under various conditions is studied. The examination and comparison of the physical characteristics of the obtained hardeners and a comparative analysis of the test results on the coatings hardened by the obtained compound with the characteristics of the coatings obtained using a commercial hardener is performed.

A quaternary compound GeSnSb₄Te₈ formed in the GeSnSb₂Te₄–SnSb₂Te₄ system in a ratio of GeSnSb₂Te₄ : SnSb₂Te₄ = 1 : 1 is studied for the first time with various physicochemical methods and thermodynamic calculations in a wide temperature range. The compound GeSnSb₄Te₈ melts congruently at 950 K. The enthalpy of the formation Δ$H_{298}^0,$ standard entropy $S_{298}^0,$ and isobaric heat capacity $c_{p,298}^0$ of this compound are –254.3 kJ mol^–1, 787.2 J mol^–1 K^–1, and 342.6 J mol^–1 K^–1, respectively. Single crystals of GeSnSb₄Te₈ are obtained via chemical transport reactions. The unit cell parameters of the GeSnSb₄Te₈ compound crystallized in a rhombic syngony are as follows: a = 4.92 Å, b = 9.70 Å, c = 11.28 Å, space group is P_nnm, V = 837.44 ų, and Z = 2.

The technique of the quantitative determination of GSB-106 in the blood plasma of rats is developed and validated. The analysis is performed by HPLC–MS. The method is linear in the range of 50 to 1000 ng/mL. The GSB-106 recovery from blood plasma was 82.15%. The lower limit of quantification was 50 ng/mL.

In this research, we present an overview of the biometals content in serum and hair samples taken from children with autism spectrum disorder (ASD). Under the observation were 38 children with ASD (age 7.9 ± 2 years). The comparison group included 20 children without ASD symptoms (age 7.7 ± 2 years). We found elevated levels of magnesium and phosphorus (4.3 and 2.8 times), as well as iron and selenium deficiencies in hair samples collected from children with ASD. Children with ASD had a statistically significant excess cadmium content in the hair compared with the control group (U = 91, p = 0.038); an excess of toxic elements (aluminum, mercury, cadmium) was detected in the blood serum of children with ASD. It was found that the level of elements essential for the functioning of the nervous and immune systems was lower, and the amount of toxic trace elements was significantly higher in children with ASD.