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A three-level model of symmetry-breaking charge transfer (SBCT) in excited octupolar molecules is developed. The model describes the joint dynamics of the solvent and the dye in the excited state. For this, a distribution function in the space of two reaction coordinates is introduced. An evolution equation of this function is derived. A strict definition of the reaction coordinates is given, and its dynamic characteristics are determined. The free energy surface in the space of these coordinates is calculated. To quantify the symmetry-breaking degree, a two-dimensional dissymmetry vector is introduced. The model predicts the absence of SBCT in apolar solvents and an abrupt increase in its degree to half the maximum value in weakly polar solvents. The dye dipole moment is revealed to be directed along a molecular arm independently of the direction and the strength of the electric field of the solvent created by its orientational polarization. The conditions for the occurrence and nature of this effect are discussed. The effect of the degeneracy of excited states, which is inherent in octupolar dyes in the excited state, on SBCT is revealed. Degeneracy of energy levels is shown to lead to a significant increase in the symmetry-breaking degree. The effect of SBCT on the dependence of the Stokes on the solvent polarity is calculated and compared with the available experimental data.

SUMMARYWe have demonstrated 30-Hz three-photon imaging using a single 24-MHz mode-locked Cr:forsterite oscillator with a center wavelength at 1260 nm. By managing the dispersion distribution in the resonator using double-chirped mirrors, we have produced 32-fs pulses with 22-nJ pulse energy. Using the oscillator as a driving source, we have realized multi-color three-photon images using a GFP-labeledDrosophilabrain and an AF647-labeled mouse brain. To demonstrate the capability of deep-tissue imaging, we have obtained a 10-times higher SBR from the three-photon images than the two-photon results at different depths in a GFP-labeledDrosophilabrain dissection. Furthermore, we have shown the impact of excitation pulse width on three-photon deep-tissue imaging. Our results indicate the superiority of using shorter pulses for deeper-tissue imaging, especially in theDrosophilabrain. In addition, we have recorded the three-photon calcium imagingin vivofrom theDrosophilamushroom body in response to external electric shocks. We believe our demonstration provides a robust approach for high-speed three-photon microscopy applications, especially for intravital investigations in theDrosophilabrain.

Esophageal anastomoses leakage is a serious and urgent problem of surgical complications with high mortality rates. With the development of endoscopic technologies, minimally invasive methods of treatment are widely introduced into clinical practice with the development of endoscopic technologies in various non-standard situations, including esophageal anastomoses leakage. Stenting is one of the methods of choice in this case. However, the indicators of their effectiveness differ significantly across studies. A retrospective analysis of the stenting results in this severe complication demonstrates many factors influencing the success of esophageal stent implantation. Stents are often selected without due regard to their characteristics, which may affect the results of implantation. One of the most frequent and unfavorable outcomes of stenting is stent migration, which significantly affects the prognosis of the treatment. In this regard, in Russian practice, stenting, as a method of treating for esophageal anastomoses leakage, is introduced only in some institutions. However, many complications can be avoided at present due to the development in endoscopy and the constant improvement of stent designs. The objective of this review was to highlight the main advantages and problemsof stenting in esophageal anastomoses leakage today.

By precisely managing fiber-optic nonlinearity with anomalous dispersion, we have demonstrated the control of generating plural few-optical-cycle pulses based on a 24-MHz Chromium:forsterite laser, allowing multicolor two-photon tissue imaging by wavelength mixing. The formation of high-order soliton and its efficient coupling to dispersive wave generation leads to phase-matched spectral broadening, and we have obtained a broadband continuum ranging from 830 nm to 1200 nm, delivering 5-nJ pulses with a pulse width of 10.5 fs using a piece of large-mode-area fiber. We locate the spectral enhancement at around 920 nm for the two-photon excitation of green fluorophores, and we can easily compress the resulting pulse close to its limited duration without the need for active pulse shaping. To optimize the wavelength mixing for sum-frequency excitation, we have realized the management of the power ratio and group delay between the soliton and dispersive wave by varying the initial pulse energy without additional delay control. We have thus demonstrated simultaneous three-color two-photon tissue imaging with contrast management between different signals. Our source optimization leads to efficient two-photon excitation reaching a 500-µm imaging depth under a low 14-mW illumination power. We believe our source development leads to an efficient and compact approach for driving multicolor two-photon fluorescence microscopy and other ultrafast investigations, such as strong-field-driven applications.

Kinetics of radical-ion pairs (RIPs) formed by photoinduced electron transfer in solution, as well as triplet and singlet products of their recombination, are studied within a general theory of spin-selective charge transfer assisted by diffusion of reactants in solution. The RIPs are assumed to be created in the singlet state, and their coherent singlet–triplet evolution is described in terms of isotropic hyperfine interaction (HFI) and $$\Delta g$$ mechanisms. A set of quantum-classical model equations is solved numerically using the time propagator splitting technique. Numerical simulations are carried out on a prototype photochemical reaction involving bimolecular electron transfer between 9,10-dimethylanthracene (DMeA) and phthalonitrile (PN) in acetonitrile (ACN) solution. Time-dependent populations of all electronic and spin states, as well as spatial distributions of reactants in the course of forward and backward charge transfer are calculated and analysed. Particularly, spatial profiles of charge recombination (CR) in singlet and triplet RIPs are shown to differ significantly, with a significant part of the singlet RIPs undergoing distant (non-contact) recombination. The effect of a strong (saturating) magnetic field on the triplet CR product yield in these reactions is studied. For the HFI-induced coherent spin transitions, the time-dependent magnetic field effect is shown to decrease with time. A phenomenon of suppressing the triplet CR product yield in RIPs with the HFI- and $$\Delta g$$ -induced coherent spin transitions in moderate magnetic fields is investigated and its physical origins are discussed.

Interactions of the electronic subsystem of the quadrupolar fluorophore with intramolecular highfrequency antisymmetric vibrations and solvent polarization are responsible for charge transfer symmetry breaking (SB), which is observed after optical excitation of such molecules in polar solvents. It is known that although these two interactions are mathematically described in similar ways, only the interaction of the fluorophore with solvent orientational polarization can create a state with broken symmetry if this interaction is strong enough. Nevertheless, the interaction of a quadrupolar fluorophore with intramolecular highfrequency antisymmetric vibrations in nonpolar solvents leads to a considerable reconstruction of the electronic subsystem. The analysis of the excited state of quadrupolar molecules in nonpolar solvents performed in this study reveals that such molecules can behave like quantum twostate systems, that is, as a quasispin s = 1/2, having an electric dipole moment instead of a magnetic one. This feature of excited quadrupolar molecules may be of interest to emerging technologies of molecular electronics.

The article considers the problem related to the correlation and regression analysis. The use of correlation and regression analysis methods is shown in the specific example illustrating the study of a particular economic situation. Special attention is paid to the use of the Excel Analysis Package, which significantly simplifies the solution of the problem from a computational standpoint.

В работе представлены полиорганосилоксановые адсорбенты, имеющие в своем составе один из органических радикалов с функциональными группами или без них, а также изучение их адсорбционных свойств по макрокомпонентам воздуха. В качестве базовой методики была выбрана схема «золь-гель» процесса, направленной сополиконденсации смеси реагентов. На основе отработанной методики синтеза были получены образцы полиорганосилоксанов с различными функциональными группами, имеющих в своем составе как четырехфункциональные фрагменты (Q-звенья), так и трехфункциональные (T-звенья). В свою очередь T-звенья имели один из органических радикалов с функциональными группами или без них. Равновесные емкости по азоту, кислороду и аргону были определены по кинетическим кривым адсорбции этих газов при 25оС и атмосферном давлении. В качестве меры адсорбционной селективности образцов по отношению к аргону использовали коэффициент разделения смеси аргон-кислород, который рассчитывали, как соотношение коэффициентов Генри. Для описания кинетики сорбции азота, кислорода и аргона были применены модель внутридиффузионной кинетики физической адсорбции, модели псевдопервого и псевдовторого порядка. В результате обработки кинетических данных показано, что механизм адсорбции макрокомпонентов воздуха на синтезированных полиорганосилоксанах имеет сложный характер, при этом влияние оказывают как свойства исследуемых газов, так и тип функциональной группы. Адсорбция аргона на полученных образцах лимитируется внутренней диффузией и с высоким уровнем достоверности описывается моделью квазигомогенного пористого тела. Адсорбция азота на полиорганосиланах определяется взаимодействием с локальными активными центрами поверхности, которыми являются силанольные группы кремнезема. Механизм адсорбции с высокой степенью достоверности описывается моделью химической кинетики псевдо-второго порядка. В скорость сорбции кислорода вносят вклад как внутридиффузионное лимитирование, так и скорость локализованной физической адсорбции, при этом влияние оказывает тип функциональной группы. Из представленных данных видно, что введением функциональных групп в полиорганосилоксаны можно влиять на адсорбционные свойства полученных материалов по макрокомпонентам воздуха. Наибольшую селективность к аргону проявил образец, содержащий диэтиламинометильную функциональную группу; значение коэффициента разделения составило 2.4.

Endoscopic esophageal stent implantation is an effective method for dysphagia management in malignant esophageal stricture. However, this technology is associated with the risk of many complications, including those fatal to life. These include bleeding, restenosis, stent fragmentation and destruction, stent migration, pneumomediastinum, the formation of esophageal fistulas, perforations, clogging of the stent with food, retrosternal pain, gastroesophageal reflux changes, airway compression, aspiration pneumonia, and fever. The overall complication rate is 3640%. Mortality rates associated with stenting is between 3.9 and 27.2%. Nevertheless, today there are ways to minimize the incidence of complications due to the constant progress of endoscopic technologies and improvements in the design of modern stents. In addition, most endoscopic interventions can manage the vast majority of complications effectively after stent implantation subject to their early detection. Optimal selection of an esophageal stent and careful selection of patients with a low risk of complications associated with stent implantation are important problems in the prevention of complications to achieve high efficiency of stenting. Evaluation of risk factors for possible complications, the design of stents and their characteristics, as well as using modern methods of effective management of possible complications improves the quality and duration of life in incurable patients with esophageal cancer. The review reflects all possible complications of stenting in esophageal and gastroesophageal junction, factors affecting the occurrence of complications, as well as modern and effective methods of their correction and prevention.

The porous silicon film surface region containing silver particles is studied by scanning electron microscopy and Raman spectroscopy. The porous silicon film is formed by metal-assisted etching of a single-crystal silicon substrate. It is found that the distribution of silver particles is controlled by the porous layer morphology. The formation of silver particles by chemical deposition results in certain smoothing of the por-Si film surface relief. In this case, the silicon crystallite structure does not change significantly.

The influence of symmetry breaking caused by charge transfer in excited quadrupole molecules of the D-π-A-π-D or A-π-D-π-A type, where A and D are the electron-acceptor and electron-donor groups, respectively, on spectra of characteristic vibrations is investigated. Types of possible changes in IR spectra with increase in molecule’s asymmetry are classified within the earlier developed theory of symmetry breaking and its manifestation in nonstationary IR spectra. Physical interpretation of the revealed trends is presented, and the latter are compared with currently available experimental data.

An approach is developed that allows estimation of excited quadrupole molecule parameters responsible for changes in vibration frequencies in states with symmetry breaking by charge transfer from time-resolved IR spectra. The approach is tested on a molecule like A-π-D-π-A composed of an electron-accepting group A coupled with electron-donating group D by means of π-conjugated bonds, a D pyrrolopyrrole core, and two cyanophenyl acceptors. The expression derived for the IR spectrum of a molecule with symmetry breaking is shown to perfectly describe experimental data. The numerical values of the parameters of asymmetry in a series of solvents with different polarities and the solvent-independent parameters of the molecule itself are determined.

Aim. To analyze the results of one and two-step endoscopic submucosal dissection in the treatment of colorectal neoplasms. Methods. Between 2018 and 2019, 17 patients (6 men and 11 women) aged 33 to 79 years underwent 21 endoscopic submucosal dissections of colorectal neoplasms ranging in size from 1.0 to 6.0 cm. Submucosal fibrosis was identified in 2 (11.8%) patients, epithelial neoplasms in 15 (88.2%) patients including laterally spreading tumors in 9 (60%), and large sessile colorectal polyps in 6 (40%) patients. Histological examination revealed a carcinoid tumor (11.8%), adenoma with low-grade (64.7%) and high-grade (23.5%) intraepithelial neoplasia. 13 patients were subjected to the one-step operation, and 4 patients required the two-step operation with a 1-day interval. Follow-up examinations after the operation were performed, on average, between 2 and 6 months. Results. En bloc endoscopic submucosal dissection was performed in 11 (64.7%) patients, 4 of them in combination with mucosal resection. Endoscopic piecemeal resection of the neoplasia was performed in 6 (35.3%) patients. The average operative time was 15573 minutes (range 40320 min). Intraoperative complications, which were eliminated endoscopically, occurred during 8 (38.1%) of 21 operations: intensive bleeding in 6 (75%) patients, diastasis of muscle fibers in 1 (12.5%) patient, perforation of the intestinal wall in 1 (12.5%) patient. At the follow-up at 6 months, all patients formed the scar at the surgical area, while 3 patients required endoscopic removal of residual adenoma 2 months after the operation. Conclusion. Endoscopic submucosal dissection is an effective method for removing colorectal neoplasms, while two-step dissection is a promising approach to the development of the technique.Keywords: one and two-step dissection, endoscopic submucosal dissection (ESD), colorectal neoplasms.

Nonequilibrium states of excited quadrupole molecules in polar solvents are described. The energy profile of a molecule and the polar medium interacting with it is determined along the collective coordinate characterizing the degree of medium polarization. It is shown that the transition from the initial state of a molecule with a symmetric charge distribution generated by a pulse of optical excitation to an asymmetric state does not require activation, so it must occur during solvent relaxation timescale.

A significant number of quadrupolar dyes with a D-$pi$-A-$pi$-D or A-$pi$-D-$pi$-A structure, where D and A are electron donor and acceptor groups, were shown to undergo symmetry breaking (SB) upon optical excitation. During this process, the electronic excitation, originally distributed evenly over the molecule, concentrates on one D-$pi$-A branch, and the molecule becomes dipolar. This process can be monitored by time resolved infra-red (TRIR) spectroscopy and causes significant spectral dynamics. A theoretical model of excited-state SB developed earlier ( extit{J. Phys. Chem. C}, extbf{2018}, extit{132}, 29165) is extended to account for the temporal changes taking place in the IR spectrum upon SB. This model can reproduce the IR spectral dynamics observed in the $-mathrm{C}equiv mathrm{C}-$ stretching region with a D-$pi$-A-$pi$-D dye in two polar solvents using a single set of molecular parameters. This approach allows estimating the degree of asymmetry of the excited state in different solvents as well as its change during SB. Additionally, the relative contribution of the different mechanisms responsible for the splitting of the symmetric and antisymmetric $-mathrm{C}equiv mathrm{C}-$ stretching bands, which are both IR active upon SB, can be determined.

The dynamic solvent effect (DSE) in reactions of ultrafast proton-coupled electron transfer (PCET) under nonequilibrium conditions is studied. It is found in particular that the effect depends on angle φ between the directions of the reaction coordinates that correspond to the step of photoexcitation of the system, and to the step of product formation. Several trends characteristic of such reactions are established: (i) the highest DSE value should be observed in the region of the increased exergonicity of the reaction, and the effect is weak in the region of low exergonicity; (ii) upon an increase in the transition matrix element, the maximum in the curve of the dependence of the PCET rate constant on the reaction’s exergonicity shifts toward the region of lower values; (iii) the dependence of the effective reaction time on angle φ has a pronounced minimum, the position of which depends on the energy parameters of the reactants.

An acridine-dione derivative (3,3,11,11-tetramethyl-8,16-diphenyl-3,4,8,10,11,12,13,16-octahydroacridino[4,3-c]acridine-1.9(2H,5H)dion) with quadrupolar motif has been synthesized and its stationary and transient spectra have been measured. Stationary absorption and fluorescence spectra as well as nonstationary spectra show no signs of symmetry breaking (SB) in aprotic solvents, even of high polarity. The specific features of SB are revealed in alcohol solvents through a considerable red shift of stationary fluorescence spectra and the appearance of a new excited state absorption band in transient absorption spectra. SB is due to the formation of asymmetric strong hydrogen bonds, mainly on one side of the molecule. An unexpected regularity of symmetry breaking is found in mixtures of aprotic dimethylformamide and protic methanol, where methanol acts as a fluorescence quencher. It is revealed that there is no quenching as long as the methanol concentration is less than the critical value of 9 M. This leads to the conclusion that SB in such mixtures is possible only if the concentration of the protic solvent exceeds a certain threshold value.

The paper analyses the parameters of deep oxidation of zinc and tin by copper (II) compounds and molecular iodine in the presence of molecular oxygen and hydrogen peroxide, as second oxidizers working synchronously with them in various media (aqueous, aqueous-organic and organic) with the participation of mineral and carboxylic acids close to room temperature. The contribution of the reactivity of the metal to its rate of consumption, especially the average, is often much less than the contribution associated with the release characteristics of the working surface, determined by the rates of accumulation of surface deposits of metal oxidation products, their strength and adhesion characteristics their destruction and shifting into the bulk phase.

Referring to the past era often intends to show the social and political system and, accordingly, focus is on the opinion of philosophers, sociologists, political scientists, etc. In this case, often on the sidelines is a person, his feelings, and attitude. This is evident in the attitude to the recent Soviet past of our country. In this regard, along with the coverage of the problem of time fixation in the artistic consciousness, we analyze the spiritual life of the transitional period, the main feature of which is the contradictory assessment of the 70-year history of the USSR. And it is not only about the nihilistic attitude, in the simplified denial of the Soviet experience, but also on ignoring the spiritual quest, the history of the formation of images and meanings inherent in our nation. The past time is not only economics and ideology, it is also artistic culture. Nihilistic atti-tude to the Soviet era is the way to oblivion of a huge cultural layer. It is an axiom which for some reason needs to be proved again and again. The social and cultural approach to the understanding of the past and present time has a greater tolerance in judgments and allows to fill the gaps in the public consciousness, to present spiritual life in diversity and uniqueness. The works of words, screen masters, sociologists conclusions contribute to the understanding of the recent past and the rapidly changing reality of the transition time.

Quadrupolar molecules of the structure AL–D–AR, where D is an electron donor and AL and AR are identical acceptors, are investigated. A general theory of vibrational spectra of such molecules undergoing symmetry breaking after photoexcitation is developed. The approach is based on the expansion of the electron–vibrational interaction in a series in powers of the displacements of the vibrational modes and the dissymmetry parameter. The theory provides a possibility to calculate the intensities of the IR bands and the splitting of the frequencies of local vibrations associated with vibrations of small groups of atoms symmetrically located in the left and right arms of the molecule. The theory explains the regularities of influence of symmetry breaking on the IR band intensities and the splitting of the frequencies observed recently using time-resolved infrared spectroscopy.

A model of photoinduced intramolecular proton-coupled electron transfer is derived. The model includes three states as follows: the ground, excited, and product states. The charge transfer is associated with both stages, photoexcitation and product formation. A larger part of the model parameters can be extracted from the stationary absorption and fluorescence spectra of a particular fluorophore. Two different reaction coordinates are associated with the two stages, which are not independent. The angle between the reaction coordinates strongly influences on the kinetics of ultrafast product formation. The stochastic multichannel approach is exploited for simulations of the kinetics. The simulations well reproduce the kinetics of ultrafast intramolecular proton-coupled electron transfer in 2-((2-(2-hydroxyphenyl)benzo[d]oxazol-6-yl)methylene)malononitrile in a few solvents. The transfer is shown to occur totally or partly, depending on the solvent, in the nonequilibrium regime. Analysis of the kinetics of ...

A consistent theory of electron transfer symmetry breaking (SB) dynamics in excited quadrupolar molecules in polar solvents is developed. The interaction of the electronic subsystem of the molecule with intramolecular degrees of freedom and solvent polarization is taken into account and is divided into interaction with inertial and inertialess degrees of freedom. A strong influence of the inertialess polarization of the solvent on the extent of symmetry breaking is revealed. The theory is nonlinear due to the equilibration of inertialess degrees of freedom to the solute electronic state. The interaction of a molecule with the inertial solvent polarization is described in terms of a single variable-the reaction coordinate, for which a rigorous definition is given. The free energy of the system is derived, and the motion of the system along the reaction coordinate is modeled by the Smoluchowski equation. The theory is adapted to describe the dynamics of SB in real solvents characterized by several relaxation time scales. Conditions for the applicability of a much simpler stationary SB model are formulated. The role of thermal fluctuations in the solvent polarization is clarified. Instead of the magnitude of the dissymmetry parameter, a distribution function of molecules over this parameter is introduced. An analysis of the Franck-Condon state created by a short pump pulse shows that it has distinct features of a state with broken symmetry for a wide range of parameters. Thermal fluctuations of the solvent polarization are shown to crucially affect SB.

The efficiency of photoinduced charge separation (CS) in electron donor-acceptor compounds is commonly limited due to fast deactivation processes, such as the excited-state internal conversion and ultrafast hot reverse electron transfer to the acceptor, charge recombination (CR). A traditional way to avoid undesired energy losses due to CR is to put the reverse electron transfer into the Marcus inverted region, thus effectively suppressing it. This method, however, is not generally applicable when considering CS from the second locally excited state because the driving force of CR to the first excited state is small, and thus charge recombination is ultrafast and efficient. In this paper, we study the kinetic features of CS/CR from the second locally excited state of the donor using a semiclassical stochastic model of electron transfer. Particular attention is paid to the CS efficiency as well as the influence of the polar environment and intramolecular high-frequency vibrational modes on the kinetics of the charge-separated state. The influence of a number of model parameters on the CS yield and the energy efficiency has been analyzed using the results of numerical simulations. Several simple practical recipes for creating molecular compounds with high CS yields have been suggested. Simulations have also revealed a strong and non-monotonous (double-humped) dependence of both the yield and energy efficiency of CS on the driving force.

FSDS is Fluorescence Spectral Dynamics Simulator, designed to investigate photoinduced charge transfer and its manifestations in time-resolved fluorescence spectra of a dye in a solvent. The project is implemented in C, using the MPI library. The computer model simulates stationary absorption and fluorescence spectra, as well as the time evolution of population distributions along the solvent reaction coordinate, to calculate spectral dynamics. Excitation and relaxation of intramolecular high-frequency vibrations are described at the quantum level. FSDS can fit the physical parameters of the dyes to experimental data. The dye excitation is consistently described accounting for the finite duration of the pump pulse. The program code implements two evolutionary models: a spin-boson model within the harmonic potential and a stochastic model based on the Smoluchowski diffusion operator for an arbitrary free energy surface. Computer simulation shows the numerical coincidence of the calculations performed in the framework of these models for the harmonic free energy surface. The detail description of the code and numerical schemes are presented. Program summary Program Title: Fluorescence Spectral Dynamics Simulator (FSDS) CPC Library link to program files: https://doi.org/10.17632/d39rrrkvhr.1 Code Ocean capsule: https://codeocean.com/capsule/6544976 Licensing provisions: GPLv3 Programming language: C Supplementary material: Sample configuration files, User Manual Nature of problem: The time-resolved spectra contain reach information about photochemical processes. However, the chemically important information about separate elementary processes is entangled due to they proceed in parallel. Time-resolved spectra modeling allows extracting information about these processes. The presented program code makes it possible to determine the relaxation characteristics of the solvent and the times of intramolecular relaxation. Solution method: Finite-difference time-domain and Brownian dynamics simulation methods.

A general analytical expression for the transient fluorescence spectrum is derived. The formation of a wave packet in the excited state of a fluorophore is described, assuming that the pump pulse has a Gaussian time-profile. The expression explicitly connects the relaxation characteristics of the medium with the spectral dynamics of a fluorophore. Fitting the expression to experimental spectral dynamics allows obtaining the solvent relaxation function. So far this approach was applicable for the analysis of experimental data when the pump pulse does not populate excited sublevels of intramolecular high-frequency vibrational modes. Here, the approach is generalized to include vibrational relaxation in the excited electronic state. In this case, fitting to the experimental spectral dynamics provides reliable information not only on the solvent relaxation, but also on the relaxation time constants of intramolecular high-frequency vibrational modes. This approach is applied to the excited state dynamics of coumarin 153 in multiple solvents, obtained from broadband fluorescence upconversion spectroscopy.

An analytical solution of a three-level model of symmetry breaking in excited AL-D-AR quadrupolar triads with an electron donor D and identical electron acceptors AL and AR is derived, in particular, an analytical expression for the dissymmetry parameter (difference in charges, in electron charge units, on the left and right arms of the molecule) is obtained. The model predicts the threshold dependence of the symmetry breaking degree on the parameters of the molecule and its interaction with the solvent. It is shown that for typical molecular parameters, symmetry breaking occurs as a charge transfer from one arm of the molecule to the other with nearly invariable donor charge. A considerable variation of the donor charge in the course of symmetry breaking is predicted for triads with small energy gap between the ground and first excited states. Analysis of the results shows that for a large parameter area, they are very similar to those obtained in a much simpler two-level model, which suggests that instead of a more realistic three-level model, we can use a two-level model to describe symmetry breaking in excited quadrupole molecules. The theory of symmetry breaking effect on the intramolecular vibrational spectra is developed. A comparison of the effect of solvent polarity on IR spectra changes due to an increase in the degree of symmetry breaking with the available experimental data shows that the model adequately describes this phenomenon.

Using methods of stationary and time-resolved femtosecond laser spectroscopy, as well as time-dependent density functional theory, the spectral-kinetic properties of excited electronic states of synthesized 2,7-diaminoxanthone (DAX) have been studied in polar protic and aprotic solvents. The intramolecular charge transfer from amino-groups to the central oxygen-containing moiety manifests itself in appearance of a new intensive long-wavelength absorption band in DAX. Considerable bathochromic Stokes shift observed in DAX fluorescence spectra with increasing aprotic solvents polarity indicates growth of charge transfer degree and, respectively, of transition dipole moment between the ground to the first singlet-excited states. In alcohols, hydrogen bond formation between DAX and solvent results in an increase of Stokes shift and fluorescence quenching. The observed spectral dynamics reflects the solvent relaxations and is well reproduced with the dynamic parameters of the solvents measured and reported elsewhere.

To elucidate the regularities inherent in the kinetics of ultrafast charge recombination following photoinduced charge separation in donor-acceptor dyads in solutions, the simulations of the kinetics have been performed within the stochastic multichannel point-transition model. Increasing the solvent relaxation time scales has been shown to strongly vary the dependence of the charge recombination rate constant on the free energy gap. In slow relaxing solvents the non-equilibrium charge recombination occurring in parallel with solvent relaxation is very effective so that the charge recombination terminates at the non-equilibrium stage. This results in a crucial difference between the free energy gap laws for the ultrafast charge recombination and the thermal charge transfer. For the thermal reactions the well-known Marcus bell-shaped dependence of the rate constant on the free energy gap is realized while for the ultrafast charge recombination only a descending branch is predicted in the whole area of the free energy gap exceeding 0.2 eV. From the available experimental data on the population kinetics of the second and first excited states for a series of Zn-porphyrin-imide dyads in toluene and tetrahydrofuran solutions, an effective rate constant of the charge recombination into the first excited state has been calculated. The obtained rate constant being very high is nearly invariable in the area of the charge recombination free energy gap from 0.2 to 0.6 eV that supports the theoretical prediction.

Regularities of ultrafast charge recombination kinetics in photoinduced intramolecular electron transfer in polar solvent are investigated. The multichannel stochastic model is used to simulate kinetics of charge separation and ensuing ultrafast charge recombination. The rate constant of ultrafast charge recombination occurring in non-equilibrium mode is shown to depend on the free energy gap of the preceding charge separation stage. This is a clear demonstration of violation of one of the fundamental principles of formal chemical kinetics, namely, the postulate of independence of elementary chemical reactions. The simulations revealed two main trends: (i) the charge recombination rate constant typically increases with decreasing the charge separation free energy gap, (ii) the maximum of the charge recombination rate constant, as a function of the charge recombination free energy gap, |ΔGCR|, shifts toward smaller values of |ΔGCR| with decreasing the free energy gap at the previous, charge separation, stage of the reaction. The prediction of ultrafast charge recombination in donor–acceptor dyads with small charge recombination free energy gap is shown to be supported by the experimental data on the kinetics of charge recombination into the first excited state followed the charge separation from the second excited state.

The dependence of the photoinduced charge transfer rate constant on the pump pulse carrier frequency is shown to be strong, and it is considerably affected by the value of the reorganization energy of low-frequency modes at the stage of excitation. In the area of small values of the reorganization energy, the dependence of the charge transfer rate constant on the pump pulse carrier frequency is strongly nonmonotonic that is caused by vibrational resonances and variation of the initial position of the wave packet on the term of the locally excited state. Increasing the reorganization energy smoothes the dependence. The smoothing is caused by the broadening of the vibrational resonances and their overlapping. The high-frequency vibrational mode excitation typically accelerates the charge transfer in both areas of high and low exergonicity and decelerates it in the vicinity of the Marcus barrierless region.

Fast decay of both the reactant and product states is shown to strongly increase the intrinsic electron transfer rate in donor–acceptor dyads. The decay is associated with redistribution/relaxation of excited vibrational states that typically participate in the reaction. Although the role of the reorganization of high-frequency vibrational modes in electron-transfer dynamics is well understood and it is commonly accepted to strongly affect the ultrafast electron transfer dynamics, the influence of the relaxation of excited vibrational states on electron transfer is not accounted for in experimental data analysis. In photoinduced electron transfer, excited states of high-frequency vibrational modes are often produced by laser pump pulse so that the ultrafast charge separation, at least partly, occurs from excited vibrational states. The charge recombination accompanying the charge separation also essentially occurs from excited vibrational states of intermediates to form a final excited vibrational state. ...

A new compound, 1,3-dimethoxy xanthione (DXT), has been synthesized and its absorption (stationary and transient) and luminescence spectra have been measured in n-hexane and compared with xanthione (XT) spectra. The pronounced broadening of xanthione vibronic absorption band related to the electronic transition to the second singlet excited state has been observed. Distinctions between the spectra of xanthione and its methoxy derivatives are discussed. Quantum chemical calculations of these compounds in the ground and excited electronic states have been accomplished to clarify the nature of electronic spectra changes due to modification of xanthione by methoxy groups. Appearance of a new absorption band of DXT caused by symmetry changes has been discussed. Calculations of the second excited state structure of xanthione and its methoxy derivatives confirm noticeable charge transfer (about 0.1 of the charge of an electron) from the methoxy group to thiocarbonyl group. Fitting of the transient spectra of XT and DXT has been fulfilled and the time constants of internal conversion S 2 → S 1 and intersystem crossing S 1 → T 1 have been determined. A considerable difference between the time constants of internal conversion S 2 → S 1 in XT and DXT is uncovered.

The aim of our research was to determine the possibilities to stratify patients with papillary thyroid cancer (PTC) on the group’s forecast, depending on the status of the mutation BRAF v600e and Ki-67 expression. The study included 89 PTC patients with the known prognosis for the period of 2005-2015. They were treated in the Altai regional oncology center and underwent surgery for PTC over the period of 2005-2013. Mutation p. Val600Glu (V600E) BRAF gene was determined with the use of allele-specific real-time PCR kit «Real-time-PCR-BRAF-V600E («BioLink»)». Immunohistochemical examination was performed with antibodies Ki-67 (clone MIB1, «DAKO») on stainer «Ventana XT» according to standard protocols. We revealed BRAF V600E not to be an independent predictor. Different variants of PTC, depending on the level of expression of Ki-67 in combination with a mutation of BRAF V600E was allowed to identify 3 groups of molecular types of PTC: a lack of mutation and a low Ki-67 (type I), with mutation and a low Ki-67 (type II) and with the presence and/or absence of a mutation and high level Ki-67 (type III). I molecular type PTC is the most favorable from the point of view of survival: 100% of patients live 10 years. Molecular type II is characterized by an intermediate prognosis: 76% of patients lived out up to 10 years. Molecular type III is characterized by the poor prognosis: only 36.8 percent of cases lived up to 10 years. In multivariate analysis of survival in PTC patients the independent prognostic factor happened to be the molecular type of tumor. In this case χ2 = 35 at p ≤ 0.000005.

Control of charge transfer requires knowledge of its detailed mechanism. Due to the large number of known mechanisms, the identification of the mechanism in specific systems is a challenge so far. In this article we propose the idea of how to distinguish between thermal and nonequilibrium modes of charge recombination in excited donor-acceptor complexes. Simulations of the effect of solvent relaxation time scale on ultrafast charge recombination kinetics in photoexcited donor-acceptor complexes within the framework of the multichannel stochastic model have shown that a series of regularities inherent to the thermal and nonequilibrium charge transfer can strongly differ. Among them there are opposite regularities, for example, the dependence of the dynamic solvent effect on the free energy gap. In particular, theory predicts that in ultrafast charge recombination of excited donor-acceptor complexes the dynamic solvent effect is weak in the area of weak exergonicity and becomes stronger in the area of stronger exergonicity whereas for the thermal reactions an opposite trend is expected. Comparison of such trends with experimental data implemented in this article allowed establishing the regime in which the reaction proceeds. It is shown that observation of dynamic solvent effect in the region of strong exergonicity for ultrafast charge recombination is decisive evidence in favor of nonequilibrium mechanism.

In molecular zinc-porphyrin-based donor–acceptor systems, the electron transfer from the second singlet excited state S2 is accompanied by ultrafast recombination into the first excited state, resulting in a low quantum yield of the thermalized charge-separated state (20%). It is demonstrated that the quantum yield of ultrafast charge separation in donor–acceptor triads D–A1–A2 can be close to 100% in molecular systems with lifetimes of the S2 state longer than 150 ps. As prototypes of such systems, donor–acceptor diads D–A1 and triads D–A1–A2 are considered, wherein the xanthione molecule plays the role of a donor. The ranges of the model parameters are determined in which the efficiency of charge separation is high. The twostage photoinduced charge transfer is studied within the framework of a multichannel stochastic model that takes into account the reorganization of a polar solvent and a high-frequency intramolecular vibrational mode.

In this article, regularities of ultrafast charge recombination (CR) kinetics in photoinduced intramolecular electron transfer in polar solvents are studied. The kinetics of charge separation and ensuing ultrafast CR are simulated within the framework of the multichannel stochastic model. This model accounts for the reorganization of both the solvent and a number of intramolecular high-frequency vibrational modes. The solvent relaxation is described in terms of two relaxation modes. For ultrafast CR, the free-energy-gap law strongly depends on the parameters: the electronic coupling, reorganization energy of intramolecular high-frequency vibrational modes, and the vibrational and solvent relaxation times. The semilog dependence of the CR rate constant on the free-energy gap varies from a parabolic shape to a nearly linear one with increasing the electronic coupling and decreasing the vibrational relaxation time. The dynamic solvent effect in CR is predicted to be large in the area of strong exergonicity and small in the area of weak exergonicity. This regularity is opposite to that observed for the thermal reactions.