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The present work addresses the quantitative structure–antioxidant activity relationship in a series of 148 sulfur-containing alkylphenols, natural phenols, chromane, betulonic and betulinic acids, and 20-hydroxyecdysone using GUSAR2019 software. Statistically significant valid models were constructed to predict the parameter logk7, where k7 is the rate constant for the oxidation chain termination by the antioxidant molecule. These results can be used to search for new potentially effective antioxidants in virtual libraries and databases and adequately predict logk7 for test samples. A combination of MNA- and QNA-descriptors with three whole molecule descriptors (topological length, topological volume, and lipophilicity) was used to develop six statistically significant valid consensus QSPR models, which have a satisfactory accuracy in predicting logk7 for training and test set structures: R2TR > 0.6; Q2TR > 0.5; R2TS > 0.5. Our theoretical prediction of logk7 for antioxidants AO1 and AO2, based on consensus models agrees well with the experimental value of the measure in this paper. Thus, the descriptor calculation algorithms implemented in the GUSAR2019 software allowed us to model the kinetic parameters of the reactions underlying the liquid-phase oxidation of organic hydrocarbons.

A design of terahertz (THz) radiation source has been developed based on an AlGaAs/GaAs superlattice grown by molecular-beam epitaxy. The gain and optical loss level are calculated, and the source parameters at which THz generation can be implemented are determined. The resonance behavior of gain, caused by strong mixing of tunnel-coupled electronic states, is investigated.

We analyze a new type of the plasmon mode in nanosize semiconductor crystals. Rotational dipole plasmon resonance, in which only angular degrees of freedom are excited, prevails in the optical spectra of photodoped nanocrystals. Such a collective mode differs basically from surface plasmon resonances in typical photoabsorption spectra of metallic nanoclusters and can be described as an excited state in a finite Fermi system as well as a rotational motion of a quantum liquid. We demonstrate that such dipole oscillations are harmonic, which makes it possible to identify them as a plasmon resonant excitation.

Organometallic compounds based on selenochromene are known as potential drugs. Currently in the creation of new drugs in pharmacology their role as antioxidants is given great importance, since this characteristic is important for inhibiting the possible radical chain oxidation processes of cell membrane lipids, which is the cause of much pathology. In this regard an important task of researchers is to study the mechanism and quantitative characteristics of the effectiveness of their antioxidative action. In this work, based on the previously studied kinetics of the antioxidant action of the additives 2-(4-biphenyl)-5,6-dihydro-4H-benzo-[h]-selenochromene (S1) and 2-(4-chlorophenyl)-4-phenyl-5,6-dihydro-4H-benzo-[h]-selenochromene (S2) in a model reaction of radical-chain oxidation of 1,4-dioxane (Khairullina et al. in Kinet Catal 54:14–17, 2013), by means of mathematical modeling a kinetic model of the process was constructed, with the help of which the analysis of the reaction mechanism was carried out, a complete kinetic picture of the process was obtained and stage rate constants.

A quantitative analysis of the structure-antioxidant activity relationship was performed for 128 derivatives of phenols, amines, uracil, benzopyrane, and benzofuran using the GUSAR 2013 program. Nine statistically significant QSAR consensus models characterized by a high accuracy of prediction of the chain termination rate constant of oxidation on the antioxidant molecules were constructed. The results of the structural analysis performed in the GUSAR 2013 program are in good agreement with the literature data.

We report on an experimental and theoretical study of postcollision interaction (PCI) effects on L2−M4,5N2,3 Auger electrons measured above the Kr K-edge in which L2 vacancies are primarily generated by KL2 x-ray emission. Such cascade processes, in which a deep inner-shell vacancy decays first by x-ray emission followed by Auger electron emission, is a strong decay mode in heavy atoms. The L2−M4,5N2,3 Auger electron peak is observed to become increasingly asymmetric with a shifting peak maximum as the absorbed x-ray energy approaches the K-shell ionization threshold. This is attributed to PCI energy exchanges of the Auger electron with the 1s photoelectron. To model the PCI effects, we have applied a semiclassical approach modified to account for the combined lifetimes of the K and L2 hole states. In addition, our analysis treats several closely spaced Auger transitions with final ionic states having different terms and angular momenta.

Postcollision-interaction (PCI) effects involving multistep decay processes following Ar 1s photoionization has been studied by Auger electron spectroscopy. The experiment focused on LMM Auger electrons measured in small photon energy steps across the Ar 1s photoionization threshold. Decay pathways that we studied include (1) the Ar+*2p–1→Ar2+3p–2 LMMα Auger process due to a single L hole created by KL fluorescence, (2) the Ar2+*2p–2→Ar3+*2p–13p–2 LMM1 Auger process following double L shell hole states produced by a KLL Auger processes, and (3) the subsequent Ar3+*2p–13p–2→Ar4+3p–4 LMM2 Auger transitions. Particularly pronounced PCI shifts and unusual line shapes compared to the ordinary one-step PCI process were found in the spectra of Auger processes following a KLL Auger first step. The experimental results were compared with calculations based on the semiclassical approach to PCI. Good agreement was found between the calculated and experimental PCI shifts. The result opens possibilities for further studies of the multielectron dynamics between Auger electrons mediated through the photoelectron in these and similar systems.

Promising semiconductor devices, such as quantum-cascade lasers and similar to them heterostructures with multiple strongly-coupled quantum wells, may contain hundreds and even thousands of layers. Independent methods of photoluminescence (PL) and transmission electron microscopy (TEM), along with X-ray diffractometry and reflectometry, make it possible to characterize super-multiperiod (SMP—superlattices with 100 and more periods) structures and to determine, with high accuracy, the thicknesses of layers, the roughness/diffusion of interfaces and the composition of solid solutions. The difference between the expected and measured using PL and TEM thicknesses of the layers of GaAs/AlGaAs samples synthesized by molecular beam epitaxy was 5–10%. The SMP structures are characterized by stable thicknesses of the layers in depth and sharp boundaries with a width of transition interfaces of the order of several A that is consistent with the X-ray analysis. Based on the data obtained on thicknesses of layers, by comparing the theoretical and experimental values of photoluminescence intensities it is possible to accurately determine the composition of Al0.3Ga0.7As which corresponds to the X-ray diffraction data.

A mechanism of angular-momentum transfer between photoelectrons and Auger electrons is applied to Auger electron emission in process of photoionization of deep inner atomic shells followed by Auger decay. This mechanism proofs to be the leading contribution to distortion of angular distribution of the Auger electrons and highlights important features of postcollision interaction effect in the inner shells photoionization. The theory developed is applied to the photoionization of $n{s}^{2}$ shells of noble gases. Calculations show the noticeable influence of angular-momentum transfer on the Auger-electron angular distribution in a number of cases. Photoionization processes suitable for experimental observation of the proposed effect are discussed.

A quantitative structure–activity relationship analysis of the 2-methylquinazolin-4-one and quinazolin-4-imine derivatives, well-known antifolate thymidylate synthase (TYMS) inhibitors, has been performed in the range IC50 = 0.4÷380000.0 nmoL/L using the GUSAR 2013 program. Based on the MNA and QNA descriptors using the self-consistent regression, 6 statistically significant consensus models for predicting the IC50 numerical values have been constructed. These models demonstrate high and moderate prognostic accuracies for the training and external validation test sets, respectively. The molecular fragments of TYMS inhibitors regulating their antitumor activity are identified. The obtained data open opportunities for developing novel promising inhibitors of TYMS.

A new type of dipole plasmon excitations in colloidal highly doped ZnO nanocrystals has been studied by means of many-body quantum mechanical approach. We demonstrate that in photodoped ZnO nanocrystals, the conduction band electrons are localized close to the surface and the plasmon oscillations are induced by their angular motion. The transition of this plasmon mode from classical to quantum regime is defined by the nanocrystal size. The size dependence of the resonance frequency which results from quantum effects is in remarkable agreement with experimental observations. Published version

Thymidylate synthase (ThS) is a target for antimetabolite antitumor drugs. Such drugs have been used in the clinic although they cause several severe side effects and accumulate in tissues. Therefore, new less toxic ThS inhibitors must be sought and created. The GUSAR 2013 program was used to study the quantitative structure – activity relationship (QSAR) of a series of antifolate ThS inhibitors in the IC50 range 0.52 – 24,800.00 nM. Statistically significant QSAR models were constructed using MNA- and QNA-descriptors and self-consistent regression. They typically predicted highly accurately the structures of the training and test sets ( $$ {\mathrm{R}}_{\mathrm{train}}^2 $$ : 0.855 – 0.922; $$ {\mathrm{R}}_{\mathrm{train}}^3 $$ : 0.810 – 0.895; $$ {\mathrm{R}}_{\mathrm{test}1}^2 $$ : 0.734 – 0.790; $$ {\mathrm{R}}_{\mathrm{test}2}^2 $$ : 0.800 – 0.835).

The ground state properties of an multi-exciton (ME) complex localized in a nanoscale semiconductor quantum dot (QD) have been studied. The calculations have been performed using the envelope function approximation for electron and hole motion in the QD. The many-body quantum mechanical treatment of the electron-hole dynamics was done within the Density Functional Theory approach. The ground state energy dependencies upon QD radius, number of electron-hole pairs, QD dielectric function and effective masses of electron and holes have been analyzed. It is demonstrated that when multi-exciton complex is strongly localized within the QD, the physical properties of the system are determined by a single parameter, the ratio of QD and free exciton radii, and its binding energy is given by the function of this parameter multiplied by the binding energy of an isolated exciton in bulk semiconductor.

The kinetics and mechanism of the antioxidative action of С60 fullerene are studied via highly sensitive manometry and kinetic spectrophotometry, based on the example of a model reaction of the initiated oxidation of 1,4-dioxane. The adequacy of the proposed mechanism according to the experimental data is analyzed by means of mathematical modeling. The mechanism behind the inhibiting process is found to be a multi-center radical reaction. The rate constants of the elementary stages are determined.

Electron-ion coincidence experimental data obtained following argon 1s photoionization are reported. Slow photoelectrons were measured in coincidence with Ar+ and Ar2+ ions, and the beta angular di ...

Using the GUSAR 2013 program, the quantitative structure–antioxidant activity relationship has been studied for 74 phenols, aminophenols, aromatic amines and uracils having lgk7 = 0.01–6.65 (where k7 is the rate constant for the reaction of antioxidants with peroxyl radicals generated upon oxidation). Based on the atomic descriptors (Quantitative Neighborhood of Atoms (QNA) and Multilevel Neighborhoods of Atoms (MNA)) and molecular (topological length, topological volume and lipophilicity) descriptors, we have developed 9 statistically significant QSAR consensus models that demonstrate high accuracy in predicting the lgk7 values for the compounds of training sets and appropriately predict lgk7 for the test samples. Moderate predictive power of these models is demonstrated using metrics of two categories: (1) based on the determination coefficients R2 (R2TSi, R20, Q2(F1), Q2(F2), ) and based on the concordance correlation coefficient (CCC)); or (2) based on the prediction lgk7 errors (root mean square error (RMSEP), mean absolute error (MAE) and standard deviation (S.D.)) The RBF-SCR method has been used for selecting the descriptors. Our theoretical prognosis of the lgk7 for 8-PPDA, a known antioxidant, based on the consensus models well agrees with the experimental value measure in the present work. Thus, the algorithms for calculating the descriptors implemented in the GUSAR 2013 program allow simulating kinetic parameters of the reactions underling the liquid-phase oxidation of hydrocarbons.

Solution processable p- and n-type organic semiconductors are candidates for low-cost, large-area, and roll-to-roll printing of inexpensive mass-production electronics. In these organic semiconductors, it is the π-conjugated backbone that plays the major role in charge-carrier transport across the channel. In order to achieve better device performance, it is required to have better packing/crystallinity to minimize defects and avoid deep traps, so that effective transfer of charge carriers can take place in the solid state. Excellent results have been reported by blending crystal-forming organic semiconductors with amorphous polymers that serve as binders or passivating agents. We show that, for some molecular structures and processing conditions, mixtures of stereoisomers can separate and self-arrange into a thin amorphous layer covered by a polycrystalline layer. In this work, we focus on two families of constitutional isomers that differ only in the position of the pyridine groups on the π-skeleton and...

Dipole plasmon resonances are ubiquitous in nano-particles with delocalized charge carriers. Doped semi-conductor colloidal nano-crystals constitute a novel paradigm for plasmon excitations in a finite electron system and offer the possibility to tune the carrier density and thus the dipole resonance from visible to infra-red, which cannot be achieved with metallic clusters. Restricting ourselves to highly n-doped ZnO nano-crystals, we explain the observed smooth transition from small sizes dominated by quantum effects to large sizes where the resonance reaches its classical value. A schematic two interacting highly degenerate level quantum model, validated by a full Random Phase Approximation calculation, yields nicely the experimentally observed trends.

Docking of a series of methanepyrido[1,2-a][1,5]diazocin[(-)-cytisine derivatives to the active center of the nicotinic acetylcholine receptor was used to generate a set of potential substances for the treatment of cognitive dysfunction. The results from these studies led to the conclusion that six of the 21 structures were potential inhibitors of the nicotinic acetylcholine receptor. Experimental testing confirmed that the study compounds had nootropic actions and allowed the most active of these to be selected for further investigation.

The kinetics and mechanism of the reaction between uracil and hydrogen peroxide in aqueous solution have been investigated. Iron ion admixtures in the solution have been demonstrated to bring about two reaction pathways, one free-radical and the other molecular. The mechanism of the reaction has been analyzed by mathematical modeling methods, kinetic curves illustrating the variation of intermediate product concentrations have been obtained, and the rate constants of elementary reactions have been calculated.

The kinetics of vertical electron transport in a semiconductor superlattice is considered taking into account partial localization of electrons. The time dependences of photoemission currents from samples based on a strained semiconductor superlattice calculated by numerically solving the kinetic equation are in good agreement with experimental data. Comparison of the theory with experiment makes it possible to determine the characteristic electron localization and thermoactivation times, the diffusion length, and losses of photoelectrons in the superlattice.

The aim is to analyze transients in inter-aircraft navigation system with hierarchical timing that com.prises the sequential rank override that determines access sequence to a single com.munication channel. On the analysis of specific cases of changing the stru.cture of user connections (reconfigurations) refined rank calculation function and local synchronizing user select function at each step of work. As result the transients gain finiteness that provides the mobile units collaboration stability under the reconfiguration.

The free-radical chain oxidation of 1,4-dioxane in the presence of an inhibitor has been investigated by mathematical modeling. The forward kinetic problem has been solved, and complete kinetic information about the reaction has been gained, including the variation of the concentrations of all reaction participants. The inverse kinetic problem has also been solved to determine the rate constants of all elementary steps.

A concrete mechanism of angular-momentum transfer in photoionization process is proposed for electron photoemission from deep inner atomic shells. It is demonstrated that the leading contribution to angular-momentum transfer is provided by postcollision interaction of the photoelectrons and Auger electrons. The standard theoretical approach to postcollision interaction has been considerably improved by taking into account angular-momentum transfer. The theory developed is applied to the photoionization of $1{s}^{2}$ shell in Ar. Calculations show the noticeable influence of angular-momentum transfer on the photoelectron angular distribution.

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We study the optical properties of nanosize two-component Fermi systems. The photoabsorption spectra in Fermi systems containing not more than 102 pairs of oppositely charged particles are calculated. The main focus is on the role of collective plasmon excitations. The dependences of the position of the plasmon resonance on the number of particles and the ratio of their masses in the system are investigated.

The structural characteristics typical of highly and moderately effective antagonists of BLT1 and BLT2 receptors were identified and the extents of their influences on the target property were evaluated. Two models for predicting inhibitory activity were constructed for series of sulfur-, nitrogen- and oxygen-containing heterocyclic compounds with significant prognostic levels of greater than 80% using two methods based on sample recognition theory. These structural patterns can be used for virtual screening of potential drugs for antiallergic activity associated with blockade of leukotriene LTB4-sensitive BLT1 and BLT2 receptors.

This article addresses mathematical modeling of the reaction of inhibited organic compounds oxidation. It was proposed to solve the inverse problems of chemical kinetics by using the index method of constrained global minimization of the deviation between the calculated and experimental data. This approach allows us to use more complete information about the chemical process which, in its turn, reduces the range of possible solutions, narrows down the domain of uncertainty, and improves the quality of mathematical model of chemical reactions. The index method was applied to solving inverse kinetic problem for the reaction of n-decane oxidation in the presence of a p-oxydiphenylamine/n-decyl alcohol inhibitory composition.

We designed an algorithm and software for inverse kinetic problem solving by conditional global minimization of the deviation of calculated data from experimental data. This approach allows use of more complete information on the process, which narrows the region of feasibility and increases the quality of mathematical simulation of chemical reactions. The algorithms designed were tested in the kinetic description of a complex liquid-phase chain reaction, specifically, the oxidation of n-decane in the presence of an inhibiting composition, viz., para-oxydiphenylamine + n-decanol.

The dependence of the properties of finite two-component Fermi systems containing two types of oppositely charged particles on the ratio of their masses has been studied. A theoretical model for the quantum-mechanical description of a system containing a finite number of pairs of particles has been proposed on the basis of the Hartree-Fock approximation and the random-phase approximation with exchange. A method that makes it possible to exclude the motion of the center of mass of the system from the spectrum of excited states has been developed in the random-phase approximation with exchange. This method has been used to calculate the binding energies and static dipole polarizabilities of systems containing 8, 20, and 40 pairs of oppositely charged particles at various ratios of their masses.

A new software package is suggested for solving the inverse kinetic problem for inhibited oxidation reactions of organic compounds. The software has been developed using inhibited n-decane oxidation as the model reaction.

A new method for the detection and identification of nucleophiles based on a luminescence turn-on mechanism is presented. Electrophilic luminophores bearing a heavy atom as a leaving group are applied to the detection and identification of nucleophiles using a PET-like method. The presence of the heavy atom on the electrophilic luminophore induces heavy atom luminescence quenching through spin–orbit coupling and increased S1 → T1 intersystem crossing efficiency. Upon reaction with a nucleophile the heavy atom is replaced by the nucleophile and the luminescence of the luminophore is regained. The potential of this approach is demonstrated by detecting and identifying various nucleophiles using 9-anthrylmethyl 2-iodoacetate and N-(9-anthrylmethyl)-2-iodo-acetamide. The two poorly luminescent systems turn-on upon reacting with nucleophiles both in solutions and in the solid-state (films).

The antioxidant properties of 2,4-diphenyl-7,8-benzo-5,6-dihydro(4H)selenochromene, some of its chlorine-containing derivatives, and selected chromilium salts based on these derivatives have been investigated using the initiated oxidation of 1,4-dioxane as a model reaction. The antioxidant activity of these compounds is quantitatively characterized by the apparent inhibition rate constant fk7.

Structural features characteristic of high-, medium-, and low-efficiency inhibitors of 5-lipoxygenase (5-LOG) catalytic activity were established. The degree of their influence on the inhibition efficiency was assessed. Two models (M1 and M2) were constructed for the prediction and recognition of the efficiency intervals of 5-LOG inhibitors. The confidence level of activity prediction for M1 and M2 reached 90 and 70%, respectively. The revealed structural features could be used for constructing highly selective inhibitors of 5-LOG catalytic activity.

The kinetics of the reactions of 5-hydroxy-6-methyluracil and 6-methyluracil with hydrogen peroxide in aqueous solutions has been investigated. The reactions proceed via two competitive mechanisms, namely, free-radical and nonradical ones. The iron ions present in water as impurities make possible the free-radical mechanism.

Antioxidant properties of technical-grade mixtures containing 4, 6-methyl-substituted derivatives of isobornylphenol were studied. The antioxidant activity of samples was characterized by the inhibition rate constant kIn. The effect of isobornylphenol on the kinetics of inhibition of the thermooxidative dehydrochlorination of poly(vinyl chloride) plasticized with dioctyl phthalate was examined.

Sequence-independent or “click” chemistry is applied for the preparation of a series of novel and structurally similar π-conjugated oligomers. The new oligomers are prepared using Wittig–Horner chemistry from bifunctional building blocks that can be interconnected to one another at any desired sequence. The bifunctional building blocks consist of aromatic skeletons with acetal protected aldehyde groups on one side and a phosphonic acid diethyl ester group para to the aldehyde functionality. The first step in the arylenevinylene formation is a Wittig–Horner coupling of a functionalized aldehyde with the methyl phosphonate ester ylide of a bifunctional monomer. A stepwise protection–deprotection process is applied for the preparation of structurally similar π-conjugated oligo-phenylene vinylenes. New di-, tri-, penta-, and hepta-phenylenevinylenes are prepared and characterized. Selected penta-arylenevinylenes are incorporated as the semiconductor channel in organic field-effect transistors.

A structure–antiarrhythmic activity relationship has been investigated using a chloroform model of arrhythmia in rats. A mathematical model capable of predicting and recognizing antiarrhythmic activity with 84% reliability is formulated. Optimization of the molecular design of lidocaine and procainamide, which have weak antiarrhythmic activity, has resulted in modeling and predicting 51 much more effective antiarrhythmic compounds that can be synthesized for further testing.