THE MACROKINETICS PARAMETERS OF THE HYDROCARBONS COMBUSTION IN THE NUMERICAL CALCULATION OF ACCIDENTAL EXPLOSIONS IN MINES

Purpose. Obtaining effective parameters of the macrokinetics of combustion of hydrocarbons in the deflagration and detonation regime for the numerical calculation of emergency explosions in mine workings. Methodology. Mathematical modeling, numerical experiment, kinetics analysis of explosive combustion reaction, analysis and synthesis. Findings. The paper analyzes the parameters of the kinetic equation against experimental data. Obtaining such data in a physical experiment for explosive chemical reactions meets serious difficulties. This is due to the size of the reaction zone not exceeding fractions of a millimeter, the lack of time resolution of experimental techniques and other factors leading to errors in direct measurements and the emergence of multiple solutions. This possibility contributes to obtaining a simultaneous numerical solution of the equations of gas dynamics and chemical kinetics. In the numerical experiment, a direct relationship between the macrokinetic characteristics of the chemical reaction and the parameters of the discontinuous flow of the reacting gas stream is established: velocity, pressure in the front and behind the front of the detonation and deflagration wave. Based on this, Arrhenius characteristics of the reaction – preexponential and effective activation energy for the hydrocarbons under consideration are obtained. Originality. Macrokinetic parameters are established for simulating one-stage ignition and burning of the most probable hydrocarbons of the mine atmosphere in the deflagration and detonation regime. Modeling of explosive combustion of premixed hydrocarbons in stoichiometric concentrations is performed. It is shown that the values of the effective activation energy in explosive combustion reactions are of less importance in contrast to steady-state combustion reactions because of the effect of the gas-dynamical effects of the shock wave on the reaction rate. The Arrhenius characteristics of the reaction – the pre-exponential and the effective activation energy – have been agreed upon, according to the gas dynamic and kinetic parameters of the course of the explosive combustion reaction. Practical value. The obtained parameters of the macrokinetics of the explosive combustion reaction make it possible to apply simple kinetic mechanisms in practical calculations of the processes of deflagration and detonation combustion, and to predict the parameters of emergency explosions in conditions of mine workings with sufficient accuracy. This also makes it possible to solve the problem of accounting for the presence of heavy hydrocarbons in themine atmosphere as products of coal pyrolysis in underground fires as factors of increasing the risk of emergency explosions

Profiled detonation waves in the technologies of explosion treatment of metals

A short review is represented concerning physicotechnical features of current technologies, plane-wave, converging cylindrical and spherical detonation waves used in physics and chemistry of high energy densities, physics of metals, materials science, machine building, and mining and metallurgical industry. The main drawbacks of existing technologies are shown, and attention is focused on the technical nature of the reasons limiting their application. Attention is paid to solving the problem of simultaneous initiation of detonation of the entire surface layer of a light-sensitive explosive, regardless of the shape of the surface. A physical and mathematical methodology for estimating shock-wave parameters of an explosive during initiation of detonation in it by explosion of the initiation layer of the charge of a lightsensitive explosive composite is proposed. Prospects of practical application of detonation (shock) waves of the specified profile formed by laser ignition of the surface of a light-sensitive explosive composite are discussed. Physicochemical potential of the system of laser initiation of detonation makes it possible to form any wave profiles and get pulses of the intensity from 0.1 to 1.0 kPa⋅s on the surfaces being more than 1 m2. Precision and safe system of laser initiation can be used during any types of blasting operations including the ones that cannot be implemented principally, while applying standard systems for initiating explosives and means of explosion

НОВЫЕ ПОДХОДЫ В РЕГУЛЯЦИИ АКТИВНОСТИ ФАГОЦИТОВ КРОВИ И СНИЖЕНИЕ ОБРАЗОВАНИЯ РАДИКАЛОВ КИСЛОРОДА У ПАЦИЕНТОВ С СЕРДЕЧНОЙ НЕДОСТАТОЧНОСТЬЮ

Aim: The purpose was to study the effect of actovegin on the formation of reactive oxygen species by blood phagocytes of patients with heart failureand on SK-N-SH neuron necrosis. Materials and methods: The generation of superoxide anion (O2-•) were recorded on whole blood samples (50–100 μl). Change lucigenin-dependent hemiluminescence determined on a hemi-luminometer «Biotoks-7». As a stimulator of the phagocyte phorbol ester (PMA, 1 μm) was used. Necrosis of neurons induced by hydrogen peroxide was determined by fluorescence of propidium iodit. Results: Blood phagocytes of heart failure patients are initially pre-activated (primed). These cells spontaneous generated oxygen radicals. Actovegin dosadependent decreased radicals level and radical induced by PMA (1 μm). After PMA maximal inhibitory effect of actovegin observed in doses higher than 2–3 mg/ml. The impact of actovegin on the viability of human SK-N-SH neurons in the presence hydrogen peroxide (100 μm) was studied invitro. Under these conditions hydrogen peroxide triggered radical-dependent neurons necrosis Actovegin dosa-dependent decreased of neuron death.Conclusion: Actovegin inhibits spontaneous and induced formation of reactive oxygen species generated by blood phagocytes of patients with heart failure. Actovegin suppressed necrosis of human SK-N-SH neuroblastoma cells caused by hydrogen peroxide. It is assumed that actovegin protects cells of various organs and tissues, including blood cells and neurons that die as a result of ischemia and inflammation by reducing levels of reactive oxygen species.Цель исследования: изучить влияние актовегина (гемодиализат крови телят) на образование радикалов кислорода фагоцитами крови у пациентов с сердечной недостаточностью (СН) II–III функционального класса по NYHA. Материалы и методы. Секрецию супероксиданионов (О2-•) регистрировали на образцах цельной крови (50–100 мкл) по изменению люцигенинзависимой хемилюминесценции на люминометре «Биотокс-7». В качестве стимулятора фагоцитов использовали форболовый эфир (РМА, 1 мкМ). Некроз нейронов, индуцированный пероксидом водорода, определяли по флуоресценции пропидия йодида. Результаты. Фагоциты крови пациентов с СН были исходно предактивированы (праймированы), о чем свидетельствует спонтанное образование радикалов кислорода в результате их взаимодействия с кюветой, а также выраженный последующий ответ на РМА. Впервые на образцах крови пациентов с СН установлено, что актовегин дозозависимым образом снижал спонтанную и РМА-индуцированную генерацию О2-•. Достоверный ингибиторный эффект наблюдали в дозе 2 мг/мл и выше. Актовегин тормозил, но не подавлял полностью ответ фагоцитов на РМА. Ишемия вызывала гибель нейронов в центральной нервной системе, в т.ч. в результате оксидативного стресса. На перевиваемых нейробластомных клетках человека линии SK-N-SH актовегин снижал гибель нейронов в результате некроза, индуцированного Н2О2 (100 мкМ). Выводы. Актовегин ингибирует спонтанное и индуцированное образование радикалов кислорода, генерируемых фагоцитами крови пациентов с сердечной недостаточностью. Препарат подавляет некроз нейробластомных клеток SK-N-SH человека, вызываемый пероксидом водорода. Высказано предположение, что актовегин защищает клетки различных органов и тканей человека, включая клетки крови и нейроны, погибающие в результате ишемии и воспаления, благодаря снижению уровня радикалов кислорода.

Cantor and band spectra for periodic quantum graphs with magnetic fields

We provide an exhaustive spectral analysis of the two-dimensional periodic square graph lattice with a magnetic field. We show that the spectrum consists of the Dirichlet eigenvalues of the edges and of the preimage of the spectrum of a certain discrete operator under the discriminant (Lyapunov function) of a suitable Kronig-Penney Hamiltonian. In particular, between any two Dirichlet eigenvalues the spectrum is a Cantor set for an irrational flux, and is absolutely continuous and has a band structure for a rational flux. The Dirichlet eigenvalues can be isolated or embedded, subject to the choice of parameters. Conditions for both possibilities are given. We show that generically there are infinitely many gaps in the spectrum, and the Bethe-Sommerfeld conjecture fails in this case.Comment: Misprints correcte

Models for Type Ia supernovae and related astrophysical transients

We give an overview of recent efforts to model Type Ia supernovae and related astrophysical transients resulting from thermonuclear explosions in white dwarfs. In particular we point out the challenges resulting from the multi-physics multi-scale nature of the problem and discuss possible numerical approaches to meet them in hydrodynamical explosion simulations and radiative transfer modeling. We give examples of how these methods are applied to several explosion scenarios that have been proposed to explain distinct subsets or, in some cases, the majority of the observed events. In case we comment on some of the successes and shortcoming of these scenarios and highlight important outstanding issues.Comment: 20 pages, 2 figures, review published in Space Science Reviews as part of the topical collection on supernovae, replacement corrects typos in the conclusions sectio

Hole and electron traps in the InGaAs/GaAs heterostructures with quantum dots

International audienceHole and electron traps at a p–n heterostructure with InGaAs/GaAs quantum dots (QD) grown by metal organic chemical vapor deposition (MOCVD) are investigated by capacitance–voltage (C–V) and deep level transient spectroscopy (DLTS). The C–V and DLTS measurements allowed to detect that the region of the accumulation of the electron concentration is characterized by the presence of hole and electron traps. We have observed by means of deep level defects, the population of the energy states of InGaAs quantum dots as a function of temperature of isochronous annealing as well as under bias-on–bias-off cooling conditions and white light illumination

Thermal annealing of defects in InGaAs/GaAs heterostructures with three-dimensional islands

International audienceA report is presented on the investigation of the influence of in situ annealing of the InGaAs layer in p-n InGaAs/GaAs structures grown by the metalloorganic chemical vapor deposition upon the formation of coherently strained three-dimensional islands. The structures were studied by the methods of capacitance-voltage measurements, deep-level transient spectroscopy, transmission electron microscopy, and photoluminescence. It is established that three-dimensional islands with misfit dislocations are formed in the unannealed structure A, while quantum dots are formed in the annealed structure B. The deep-level defects were investigated. In structure A, defects of various types (EL2, EL3 (I3), I2, HL3, HS2, and H5) are present in the electron-accumulation layer. Concentrations of these traps are comparable to the shallow donor concentration, and the number of hole traps is higher than that of the electron traps. On the in situ annealing, the EL2 and EL3 defects, which are related to the formation of dislocations, disappear, and concentrations of the other defects decrease by an order of magnitude or more. For structure A, it is established that the population of the quantum states in the islands is controlled by the deep-level defects. In structure B, the effect of the Coulomb interaction of the charge carriers localized in the quantum dot with the ionized defects is observed