The antioxidant properties of ethyl acetate extracts from 13 plant species of the Asteraceae family growing in the Goris region of Armenia were studied using the inhibited cumene oxidation method. The total antioxidant content (f·[InH]) and antioxidant activity (rate constant k?) of the extracts were determined. It was established that the highest antioxidant content was found in extracts of meadow cornflower flowers (Centaurea jacea, f·[InH]·10? = 1.30 mol/L) and annual sunflower leaves (Helianthus annuus, 1.10 mol/L). The highest antioxidant activity was detected in cutleaf coneflower (Rudbeckia laciniata, k?·10–4 = 31.30 L/mol·s) and alpine aster (Aster alpinus, 19.51 L/mol·s). It was shown that high antioxidant activity does not always correlate with high total antioxidant content, indicating significant differences in the qualitative composition of inhibitors among different species.
In the framework of this study, the behavior of stochastic dynamics in the hydroquinone system – oxygenated mixed ligand complexes of iron (II) was analyzed by flicker-noise spectroscopy. There are stable correlations between successive events, indicating the presence of memory in the system. The revealed dependence allows us to conclude that the resulting oscillatory modes are not random, but deterministic in nature, due to the internal nonlinear organization of the process.
Background. Time-to-hire (TTH), defined as the number of calendar days from a recruiter’s first contact with a candidate to the candidate’s hiring, is a key efficiency metric in high-volume recruitment. In Russian retail, the factors affecting TTH have not previously been examined systematically using quantitative methods. Objective. To determine which recruitment-process factors affect TTH for sales assistants/cashiers and to what extent, and to quantify the observed nonlinear effect of the number of recruiter contacts with a candidate. Materials and methods. We used anonymized event logs from the corporate Applicant Tracking System (ATS) of a large retail chain for 2018–2020 (861,762 event records). The analysis included statistical hypothesis testing (chi-square tests, rank-based tests, analysis of variance, and logistic regression) and ordinary least squares regression modeling of log-transformed TTH with heteroskedasticity-robust standard errors. Results. Median TTH was 7 days. The regression model explained 45 % of the variance in log-transformed TTH. The duration of the paperwork stage was the strongest contributor to longer hiring times. A nonlinear relationship was identified and quantified: beyond 5–7 recruiter contacts, each additional contact was statistically associated with longer TTH. This association is likely due to reverse causality, as more challenging candidates require more contacts. Conclusion. Based on the estimated model coefficients, practical rules for reducing hiring time were formulated. An illustrative calculation of the potential economic effect of their implementation is provided.
This work presents a study of methane adsorption energetics on pristine and B-, N-, and O-monodoped graphene quantum dots. Circumcoronene was selected as a model system for the graphene quantum dots. Quantum chemical calculations were performed using the r2SCAN-3c composite method, ensuring accurate treatment of dispersion effects at a moderate computational cost. The nature of the intermolecular interaction was analyzed in detail using Energy Decomposition Analysis (EDA) within the ORCA package. It was found that in all systems studied, dispersion interaction is the dominant stabilizing factor, accounting for the bulk of the binding energy and confirming the physisorption nature of the nonpolar methane molecule. Heteroatom doping, particularly with nitrogen and oxygen atoms, moderately enhances the interaction due to an increase in electrostatic and dispersion contributions. However, a compensating increase in Pauli exchange repulsion, caused by a decrease in the equilibrium distance, significantly limits the overall gain in binding energy.
A technology for obtaining CuInSe2 films via multi-stage selenizationhas has been developed during the research. The surface morphology of thin CuInSe2 films was obtained and studied in the temperature range of Tsel = 200÷550 °C. It was shown that as the selenization temperature increases, the film surface undergoes transformation. At Tsel = 350÷400 °C, the film surface smooths out to a nearly homogeneous state. A mathematical calculation of the size distribution of surface micro-inclusions was performed. The minimum selenization temperature Tsel. min ≈ 180 °C, at which the formation of micro-inclusions is observed was determined, which is close to the formation temperature of the Cu2Se compound.
