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The initiation of combustion of a large mass of condensed mixture being in local contact with the end of the burning layer was mathematically modelled and experimentally studied. The influence of the instability of stationary combustion front in the igniting layer on the penetration of gasless combustion into large volume was showed. It was revealed that the critical conditions for initiating combustion of large volume are determined by front curvature. [ABSTRACT FROM AUTHOR]

The isogeny graphs of supersingular curves are one of the promising mathematical structures in postquantum cryptography algorithms. However, the recently reported attack on the SIDH protocol [1] demonstrates that the isogeny graphs require a more detailed investigation when applied to real protocols. In this study, we analyze the structure of the graphs of isogenies of degree and consider the set of vertices of a special type to which an attack on reconstruction of the path in the graph is applicable [7]. [ABSTRACT FROM AUTHOR]

The stability of combustion of titanium + carbon black powder mixture to a local excess of the component was experimentally studied. The influence of the spreading of titanium melt or liquid reaction product on the stability of the combustion transition through transverse carbon powder barrier was considered. The direction of melt movement with respect to the front propagation direction was determined. It was shown that the stability of the combustion transition through the barrier is determined by thermal interaction between the combustion wave and the barrier and is not directly related to the convective heat transfer by the melt. [ABSTRACT FROM AUTHOR]

Experimental studies of combustion stability to the local excess of the component in a dispersed mixture of titanium and carbon powder are presented. It is shown how the spreading of a melt of a low-melting or liquid reaction product affects the stability of combustion transition through a solid and perforated carbon powder target. The melt motion direction with respect to the front propagation direction is revealed. It is indicated that the stability of the combustion transition through the target is determined by thermal interaction between the combustion wave and the target and is not directly related to the convective heat transfer by the melt. [ABSTRACT FROM AUTHOR]

A mathematical model is proposed to analyze the effect of compression and stretching of the filtration combustion front highly of porous metal samples. The processes of structuring of a quasi-isobaric wave of combustion of a titanium powder layer with a change in the transverse size of the layer in the direction of the movement of the front are experimentally studied. [ABSTRACT FROM AUTHOR]

The influence of geometric factors on the filtration combustion of metal powder layer was mathematically modelled and experimentally studied. The structure and stability of combustion front of porous sample were studied in conditions of compression and stretching of the reaction zone. Experimental methods were used to study the change in the structure of a cellular front during the combustion of variable cross-section titanium powder layer. [ABSTRACT FROM AUTHOR]

A list of the Crimean bird fauna is presented to reflect the current state of knowledge and to characterize the status and environmental specificity of the species involved. For the first time, an analysis of the phenological and ecological structure of the Crimean avifauna as a whole is carried out, separately for the mountain and plain parts which support various zoochorological subunits. The special position of foothills as an area transitional between the coastal zone and the forested steppe belt is shown. Based on the literature record and collections available for the territory of the peninsula during the entire period of research (1795–2019), 385 species of birds are listed, including nine found only as fossils. The present avifauna encompasses 320 species belonging to 53 families and 19 orders. Four orders (Passeriformes, Charadriiformes, Anseriformes, Falconiformes) comprise 254 species, or 78.6% of the Crimean avifauna, while the remaining orders contain from one to 13 species each. As regards the ecological structure, limnophiles (42.3%) and dendrophiles (34.5%) dominate, while campophiles account for 11.3%. In distribution, the largest number belong to the group of migrants (252 species, or 79% of the Crimean avifauna), including species the local populations of which are settled (20), nesting-migratory (82), and those arriving for wintering (69). For 197 species (61.8%), nesting has been reliably documented, and a further eight species can be classified as most probably nesting. There are 99 migrant species, of which 17 overwinter and five more do this sporadically. As many as 167 species (52.4%) have been recorded during the winter season, 58 of them being sedentary, 63 species regularly passing the winter, 42 rarely or sporadically doing so, and 31 species occurring only in winter. The summering group includes 45 species, most of which are northern migrants (Charadriiformes, 21, and Anseriformes, five), as well as western Palaearctic ones (four). At least 26 species, as well as probably a further 17, can be assigned to the group of "vagrant birds," while six species are classified as "nomadic birds." Features of the distribution of birds over the territory are revealed when comparing the avifauna of various zoochorological subunits. The bird species diversity is decreased both from the plain (97.5% of all fauna) to the mountainous (90.3%) areas of Crimea and from the foothills (89.9%) to the mountain forest belt (53.6%). Within the steppe zone, there are more migrants (242 vs. 218), nesting (159 vs. 128) and nesting-migratory (83 vs. 62) species than in the mountains. At the same time, most of the sedentary species have been recorded in the mountainous area: 31 vs. 18 on the plain. Migrations of birds due to diurnal and seasonal rhythms are known for at least 54 species, but only 23 of them roam the steppe, and 21 species are nomadic in the mountains. [ABSTRACT FROM AUTHOR]

The Co–28Cr–6Mo medical alloy after homogenization is tested in uniaxial compression at temperatures of 1000, 1100, and 1200°C and strain rates of 1, 10, and 50 s–1 using the Gleeble System 3800. The stress-strain curves describing the deformation behavior of the alloy are obtained. Using three models (power-law, exponential, and hyperbolic sine function) describing the flow stress, hot deformation parameters are calculated (activation energy and Zener–Hollomon parameter). The results of calculations based on the power-law and hyperbolic sine functions show the highest degree of convergence. These models can be used to accurately calculate the flow stress for given parameters of temperature and strain rate or to simulate the deformation process. Also, based on processing maps, the strain-rate modes of hot deformation of the Co–28Cr–6Mo alloy are developed, which will make it possible to select the optimal rolling modes in the future. According to the data obtained, as strain accumulates, the favorable temperature-rate conditions for hot deformation shift to the region of high temperatures and low strain rates. In this case, the extremely unfavorable zone with negative values of the plastic flow stability criterion ξ, which appears at values of the deformation parameter e = 0.3–0.4, continues to grow quite significantly with increasing strain. Hot deformation of the Co–28Cr–6Mo alloy at low compression ratios (e < 0.2) is more appropriate at temperatures above 1150°C and strain rates of at least 20 s–1. As the degree of deformation increases, lower strain rates (1–5 s–1) and higher deformation temperature should be used. [ABSTRACT FROM AUTHOR]

The unstable propagation of combustion of a layer of titanium powder in horizontal and inclined channels under conditions of natural gas filtration is experimentally studied. The critical conditions for the disruption and restructuring of the combustion modes with an abrupt change in heat loss during the combustion of a layer on an inert substrate of variable composition is analyzed. The influence of the convective removal of impurity and inert gases on the processes of the passage of the combustion front over the boundary of dissimilar substrates is studied. The results are interpreted in the model of the heat-filtration stability of combustion in porous media. [ABSTRACT FROM AUTHOR]

A computational and experimental study of the passage of a gasless combustion wave through a wedge-shaped inert obstacle was performed. The stability of the transient combustion process to a change in the thermophysical and geometric parameters of the obstacle and the energy-kinetic parameters of chemically active layers was studied. By the region of stable transient combustion process is meant the range of parameters in which the passage of the combustion wave through the contact boundary ends with the establishment of its steady-state propagation regime in the ignited composition. The dynamics of transient combustion under near-critical conditions of its existence was investigated. [ABSTRACT FROM AUTHOR]

Using a two-dimensional mathematical model, the dynamics of the transition of a combustion wave between layers of a multilayer system through an inert barrier, taking into account the influence of the geometric characteristics of the barrier's elements and heat loss, are analyzed. The characteristic parameters of the process, which determine the transition and establishment of a stationary wave mode of combustion behind the obstacle, are revealed. The optimal geometric characteristics of the wedge-shaped obstacle, which ensure the stability of the transition of the combustion wave under nonadiabatic conditions, are found. [ABSTRACT FROM AUTHOR]

The relay of combustion wave through a thin wedge-shaped obstacle was explored by 2D mathematical modeling and experimentally, with special emphasis on the role of wedge parameters. Predictions of theory well agreed with experiment. Steady passage of combustion wave through the obstacle was found to occur at some optimal wedge configurations, which should be kept in mind in some special applications. [ABSTRACT FROM AUTHOR]

The transition of the combustion wave of a titanium powder layer in air through an inert shaped obstacle has been experimentally studied. It has been shown that an inhomogeneous wave-like structure of the combustion front can form due to the limited supply of gaseous reagents and the thermal instability of combustion of the titanium powder layer. Conditions of the optimal transient combustion mode in the presence of gaseous impurities affecting gas exchange in the reaction zone and the stability of the front in the layered system are obtained. It is shown that there exists a phenomenological criterion for assessing the nature of the transient combustion mode of titanium powder depending on the shape of the inert obstacle and the combustion front. [ABSTRACT FROM AUTHOR]

Experimentally and theoretically (using mathematical modeling) the combustion of the undeformed porous matrix of cylindrically symmetric forms, in which the active gas reagent is fed from outside through the permeable surface part owing to difference between outside and inside pore pressure in the reaction zone, has been studied. It has been shown that under conditions of the instability of many-dimensional filtration combustion separate cells of exothermic chemical combustion form, which propagated in self-sustained mode. Structure of cellular waves, distribution dynamics and moving direction are determined by totality of factors: temperature field, gas pressure gradients, intensity of exothermic heat release, geometric parameters of porous layer, and heat loss value. The cellular combustion modes of the titanium powder layer were experimentally studied in the circular bath as the flat dish. The comparative analysis of theoretic and experimental results of combustion dynamics of cylindrical sample under cellular mode is given. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the effect of impurity and inert gases on the formation and propagation of cellular-combustion regimes for their inhomogeneous distribution above the surface of the reacting metal layer. The gas-dynamic aspects of the formation and steady propagation of inhomogeneous wave structures in the combustion of a titanium powder layer in through and semi-closed inclined air canals and in channels with uneven loading are considered. The gas composition heterogeneity over the reaction zone and the gas stratification, i.e., the stratification of a gas mixture of different densiies above the reacting layer, are shown to lead to the formation of inclined non-uniform and cellular fronts under conditions of a lack of active gas in the reaction zone and the loss of stability of the planar front. [ABSTRACT FROM AUTHOR]

In this paper, using mathematical modeling, we study combustion wave stability in transition through the interface of gasless systems. The effect of a gas layer separating two chemically active gasless layers on the combustion wave stability was studied at all stages of the transition. Using the criteria obtained, we estimate the stability conditions of the transition combustion wave. The nonstationary dynamics of the combustion wave transition through the gas gap is studied with allowance for competing mechanisms of heat transfer, such as conductive and radiant transfer. We analyze the effect of radiation heat transfer in the gas gap on the characteristics and stability of the transient combustion process. The failure region of the igniter combustion wave is determined through the approach to the ignition system, while estimates of temperature and heat flux at the interface of the systems are given with respect to the time of the igniter combustion completion under conditions of dominant conductive and radiant heat transfer. [ABSTRACT FROM AUTHOR]

The formation and propagation of cellular combustion of porous media under near-critical combustion existence conditions were investigated. The sizes and structure of cells in which the condensed component reacted with the gas depended nonlinearly on the heat loss to the environment. With increasing heat loss, the oscillation frequency of the cellular front, its average propagation velocity, and the intensity of the exothermic transformation of the condensed phase increased, and the cell sizes decreased. Cellular combustion was extinguished only when the transformation of the condensed component within a cell was completed. [ABSTRACT FROM AUTHOR]

The results of comparative studies of the structure, mechanical properties, and resistance to stresscorrosion cracking (SCC) in the chloride solutions of a Cr-Mn-Ni austenitic nitrogen-containing steel (20Cr-6Ni-11Mn-1.5Mo-N-V-Nb) produced with the use of different regimes of the high-temperature thermomechanical treatment (HTTMT) have been presented. An unfavorable effect of the grain-boundary precipitates of the nitride phase on the impact toughness and resistance to SCC has been found. It has been shown that the strengthening of nitrogen-containing steel upon HTTMT, which ensures an increase in the yield stress by 1.8 times compared to the austenitized state, does not decrease the resistance to SCC. [ABSTRACT FROM AUTHOR]

Influence of gas convection on cellular combustion of Ti powder in slit-like reactors was studied experimentally. Heterogeneous combustion in inclined and dead-ended reactors was accompanied by diffusional and convective mass exchange between gaseous reactant and metal powder. Free convection of the gases evolved during combustion was found to favor the formation of inclined and cellular combustion fronts. [ABSTRACT FROM AUTHOR]

Stability of combustion wave during its passage through a gaseous gap between two reactive layers was studied by mathematical modeling. The character of transient processes in the gap was explored as a function of thermophysical parameters of the layers, kinetic parameters, and gap width at a predominant role of radiative heat transfer. The passage of combustion wave through the gap was found to be accompanied by the attainment of superadiabatic temperatures within the transition zone. A critical temperature for burning failure at the interface was determined. [ABSTRACT FROM AUTHOR]

Investigated was nonadiabatic propagation of cellular structures in conditions of unsteady infiltration-mediated combustion in porous media. The size and structure of cellular hot spots was found to be a non-linear function of governing parameters, including heat sink into environment. Quasi-stationary dynamics of cell propagation in near-critical conditions was simulated in terms of a quasi-3D mathematical model. The evolution of cellular combustion was investigated as a function of heat losses. Experimental data for cellular combustion of Ti powders in a slit-like reactor were found to agree with predictions of the model. [ABSTRACT FROM AUTHOR]

Austenitic steel Kh20N6G11AM2BF with a nitrogen content of 0.4 wt % exhibits enhanced mechanical properties, high wear, and high resistance to stress-corrosion cracking (SCC) after quenching from rolling heating and after quenching from 1150°C and 15% cold deformation. This shows that it can be used in arctic shipbuilding as a cladding material for hull plates. Strong bonding of Kh20N6G11M2AFB austenitic steel cladding with a nitrogen content of 0.4 wt % with 10N3KhDMBF hull steel is obtained. The shear resistance is registered to be 437-520 MPa. Redistribution of the alloying elements with the formation of a martensitic layer, which is observed at the interface between the cladding layer and the base material, must be taken into account in the final heat treatment considering different processing conditions. [ABSTRACT FROM AUTHOR]

The paper summarizes the results of experimental studies of the structuring of the infiltration combustion front in a burning titanium powder layer. The unsteady processes of formation and propagation of cellular and nonuniform combustion waves in heterogeneous media in straight-through and semi-closed channels in conditions of restricted gas exchange and presence of inert gaseous impurities are analyzed. The structural characteristics of cellular combustion waves in a metal powder layer under conditions of natural gas infiltration are reported. [ABSTRACT FROM AUTHOR]

The paper describes the formation of the combustion zone structure of a titanium powder layer in inclined rectangular air channels with natural gas filtration. It is shown that heterogeneous combustion near the critical conditions of its existence with limited supply of gaseous reagent in the reaction zone and under the effect of gravitational forces is accompanied by rearrangement of the plane homogeneous front into more complex wave structures: cellular, cross-cellular, and heterogeneous. The features of the process under study is the presence of gaseous impurities affecting the gas exchange in the reaction zone, the destabilization of the plane front, and the formation and propagation of heterogeneous and cellular wave structures. [ABSTRACT FROM AUTHOR]

Combustion of two-layer SHS systems was numerically modeled in order to shed new light on the stability of a combustion wave passing through the interface between two reactive heterogeneous systems. Thermal conditions at the interface have been numerically calculated for all stages of a transient process taking place at the interface, with special emphasis on the influence of a gaseous gap between the constituent green pellets. [ABSTRACT FROM AUTHOR]

The structural state and the resistance to stress-corrosion cracking (SCC) at constant loads have been studied using samples with a grown crack by the method of the cantilever bending on quenched austenitic stainless steels of the 20Cr-6Ni-11Mn-2Mo-N-V-Nb (Kh20N6G11M2AFB) type, with different contents of nitrogen (0.17, 0.34, 0.43, and 0.50 wt % N). The tests were conducted in a 3.5% aqueous solution of NaCl (without providing polarization) and in a similar solution under cathodic polarization, which causes the formation of hydrogen. It has been shown that, in a chloride solution without polarization, the steels do not undergo SCC for 2000 h. In the case of significant cathodic polarization via employment of a magnesium protector, there was revealed a brittle character of fracture upon SCC in all steels. It has been shown that steel with a nitrogen content of 0.43 wt % possesses the maximum absolute values of rupture stresses under the conditions of cathodic polarization. [ABSTRACT FROM AUTHOR]

The study examines the modes of propagation of cellular infiltration combustion waves through a high-porosity layer of an energetic composition yielding condensed reaction products. Under conditions of instability, a planar infiltration combustion front breaks into individual exothermic reaction cells, which propagate through the heterogeneous mixture in the pulsation mode. Based on video records and theoretical analysis of the process, the dynamics of propagation of a pulsating cellular front is investigated. The dependences and mechanisms of transformation of cellular combustion modes are established. The evolution of a cellular frontal structure within a separate pulsation period is investigated. [ABSTRACT FROM AUTHOR]

The experimental results on the unsteady propagation of cellular waves during the infiltration-controlled combustion of a titanium powder layer are presented. The modes of frontal combustion of a porous medium with a nonuniform thermal structure that arise because of the loss of stability of the front under conditions of controlled gas transport into the exothermic reaction zone are examined. The conditions of transformation of an irregular combustion front into a cellular combustion wave are determined. The effects of the key thermal parameters of the heterogeneous system on the structure of the irregular and cellular fronts and on the characteristics of the oscillatory dynamics of their propagation are examined. [ABSTRACT FROM AUTHOR]

Explored was infiltration-mediated combustion of Ti powder in an inclined rectangular straight-through air flow reactor in conditions of natural coflow and counter flow convection in the field of gravity forces. In conditions of limited supply of gaseous reagent, a continuous combustion front was found to rearrange into more complicate modes. A distinctive feature of the process under study was the presence of inert gaseous impurities that markedly affected the process of gas exchange within the reaction zone. The results may turn useful in designing reactors and in predicting fire hazards in difficult-to-access sites. [ABSTRACT FROM AUTHOR]

Structural changes and resistance to the stress-corrosion cracking of the nitrogen-bearing austenitic steels 04Kh20N6G11M2AFB and 09Kh20N6G11M2AFB (with 0.04 and 0.09 wt % C, respectively) after different treatments, including thermomechanical action, quenching from 1200°C, and aging at 700°C for 2 and 10 h, have been studied. It has been shown that aging at 700°C of the air-melted austenitic steel 09Kh20N6G11M2AFB leads to a decrease in the strength of samples with an induced crack upon the cantilever bending in air and in a 3.5% aqueous solution of NaCl as compared to the strength of the steel 04Kh20N6G11M2AFB-EShP with a smaller carbon content after high-temperature mechanical treatment or quenching from 1200°C. The smallest resistance to stress-corrosion cracking is observed in the samples of 09Kh20N6G11M2AFB steel after 10 h of aging, which is accompanied by the most intense acoustic emission and by brittle intergranular fracture. This is explained by the high rate of the anodic dissolution of the metal near chromium-depleted grain boundaries due to the formation of continuous chains of grain-boundary chromium-containing precipitates of carbides and nitrides. [ABSTRACT FROM AUTHOR]

External manifestations of the heterogeneous combustion front are characterized. Gasdynamic aspects of the phenomenon are considered, and experimental data on the change of combustion modes during natural filtering of an air mixture are analyzed. Results of an investigation of the bifrontal structure of the combustion zone in a horizontal plane layer during convective gas transfer are presented. [ABSTRACT FROM AUTHOR]

A mathematical model of two-zone infiltration-mediated combustion of a porous solid reagent (Ti) in an isobaric counterflow of three-component gaseous reagent (air) was constructed and numerically analyzed. We explored structural features, stability issues, and also the influence of inert impurity gas on the initiation and structure/stability of two-zone combustion waves. The relevant experimental results are also presented. [ABSTRACT FROM AUTHOR]

Unsteady infiltration-mediated combustion of Ti powder in air was explored in conditions of regulated quasi-isobaric flow of gaseous reagent. Variation in the parameters/geometry of air flow was found to affect the structure of reaction zone, burning velocity, composition of combustion products, and extent of conversion. [ABSTRACT FROM AUTHOR]

The cellular filtration combustion of porous energetic compositions that interact with an active gas reagent and form condensed reaction products is studied for titanium powder combustion as an example. A simple and visually accessible quasi-experimental analysis of the nonlinear propagation of the combustion front with adjustable filtration transport of gas is proposed. Under conditions of a deficiency of the gas reagent and instability, the flat front of filtration combustion is divided into isolated cells of exothermic chemical reaction propagating in a pulsating mode. The results obtained are interpreted within a model of thermal filtration stability of the filtration combustion front. [ABSTRACT FROM AUTHOR]

In conditions of instability, a planar front of infiltration-assisted combustion was found to split into individual hot spots (cells) propagating in an oscillation mode and leaving behind combustion products with the imprints of their periodic motion. Discussed are some subtle details of the phenomenon. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the cellular modes of filtration combustion. It says that high-temperature synthesis of construction materials is conducted through filtration combustion of porous high energy compositions that interacts with an active gas reagent and forms condensed reaction products. The results show that the pulsing mode of cells motion of the exothermic chemical transformation was discovered for the first time.

The combustion of Ti-C mixtures of bulk density under inert gas blowing conditions produced by evacuation of one end of the reaction cell was studied for the first time. The experiments showed that the tested mixtures in quartz cups were not ignited and did not burn without the inert gas (argon) flow. Increasing the rate of gas evacuation from the sample increased the rate of steady-state combustion of the mixture of titanium with carbon black, and for the mixture of titanium with graphite, stabilization of the flat combustion front was observed. It is shown that the presence of small pressure difference (up to 105 Pa) allows control of the combustion process and confirms the basic postulates of the convective-conductive theory of combustion for heterogeneous condensed systems. [ABSTRACT FROM AUTHOR]

The filtration combustion of a layered porous fill consisting of alternating layers of a mixture of Ti + 0.5C a titanium powder with forced concurrent filtration of nitrogen was studied for the first time. The gas flow through the sample was provided by a vacuum pump attached to the lower end of the fill. The presence of the concurrent gas flow radically changes the character of propagation of the combustion front and the structure and composition of the products obtained. The layers consisting of carbonitride and titanium nitride make a single unit. The experiments provided scientific bases for the production of new laminated and composite ceramic materials by dynamic filtration combustion. [ABSTRACT FROM AUTHOR]

Combustion of bulk density Ti-Si and Zi-Al mixtures an a coflow of argon was studied in the presence/absence of (1) applied pressure difference δ P along the direction of wave propagation, (2) thermal treatment of green samples in vacuum, and (3) blowing agent (borax). The data on variation of the burning velocity U c were rationalized in terms of the convection-conduction combustion theory for heterogeneous condensed systems. [ABSTRACT FROM AUTHOR]

Explored is the filtration combustion in Ti-(Ti + 0.5C) layered powder systems in a coflow of nitrogen gas. The presence/absence of nitrogen coflow through the layered system was found to drastically affect the character of wave propagation and structure/properties of product. The obtained data can be regarded as a basis for fabrication of new layered and composite materials in the mode of dynamic filtration combustion. [ABSTRACT FROM AUTHOR]

The burning velocity of bulk density Ti-C powder mixtures was found to increase with increasing flow rate of inert gas. In some cases, it was also accompanied by stabilization of planar combustion front. The obtained data were rationalized in terms of convention-conduction theory (CCT). The effect can be used as a simple and effective mean for controlling the combustion process and purification of products from impurity gases. [ABSTRACT FROM AUTHOR]

For combustion of bulk density N + Al mixtures an a coflow of argon, the burning velocity U c was found to markedly depend on the flow rate. The effect (unexplainable in terms of classical combustion theory) has been rationalized in terms of the convective-conductive theory. Preliminary thermal treatment of green mixtures in vacuum was found to increase the initial value of U c and to decrease the effect of pressure difference Δ P on the extent of flow-induced increase in the burning velocity. [ABSTRACT FROM AUTHOR]

This article surveys and analyzes the literature data on nanotechnologies for copper and copper alloys. It describes the main methods used to obtain nanomaterials, including powder metallurgy, crystallization from the liquid state with a controlled rate of cooling, intensive plastic deformation, dispersion hardening, and dispersion strengthening with internal oxidation. Preference is given to nanophase materials in the discussion. [ABSTRACT FROM AUTHOR]

The specific features of dynamics of the thermal explosion in systems porous reagent- active gas-solid product under conditions where the heat-transfer and mass-transfer regions are separated from the ambient medium are considered. In addition to the competition of heat release and heat removal, the process of initiation of exothermal chemical interaction in these systems under normal pressures depends significantly on conditions of filtration transport of the gaseous reagent. The induction and post- induction periods of the thermal explosion are studied. The theoretical analysis of thermal-explosion issues is supplemented by an experimental study of the process for the porous titanium-nitrogen-titanium nitride system. [ABSTRACT FROM AUTHOR]

Discusses an analytical method of calculation of the temporal characteristics of ignition of hybrid gas-solid suspensions by a heated body. Parameter ranges of the kinetically controlled and diffusion-controlled ignition modes; Effect of the heat release in gas-phase reactions on the temporal characteristics of ignition; Model of the process.

We solve the problem of identifying the structure of a stochastic process during nonlinear measurements of its state vector in the given finite time interval. The possible variants of practical implementation of the proposed method are analyzed and a numerical example demonstrating its efficiency is considered. [ABSTRACT FROM AUTHOR]

The propagation of the filtration—diffusion combustion front deep in a bulk of titanium powder in a nitrogen medium is studied experimentally. The dependence of the combustion–propagation depth on the height of a fill of titanium powder and the pressure of gaseous nitrogen, the effect of degassing impurities on the limit, and some specific features of combustion are revealed. A model of the process by means of which a formula for estimation of the burning–out depth of the fill is derived is proposed. [ABSTRACT FROM AUTHOR]

Numerical results of an experimental study of burning through steel tubes in a water medium by thermite-combustion products are presented. Based on the analysis of experimental data, recommendations on the optimal organization of the process are given, and an empirical formula for calculating the thermite mass necessary for burning through a steel wall is derived. [ABSTRACT FROM AUTHOR]

Myocytes can die by necrosis or by apoptosis and the characteristics of both kinds of cell death are so typical that a differentiation can be made by histological and molecular-biological methods using electron microscopy, dUTP labeling with fluorescence or peroxidase stainig (TUNEL) and the DNA laddering method. However, the problem of quantification of apoptotic cells has not been completely solved because of lack of standardization as well as uncritical use and interpretation of the TUNEL method. Equally, quantification of apoptotic cells is not optimal until now because of three reasons: methodological (overinterpretation of results, no differentiation between myocytes and non-myocytes), experimental (global or regional acute ischemia, chronic conditions such as heart failure or hibernating myocardium), and interpretation (unknown time period for the completion of apoptosis). This problem is reflected in the large differences in incidence of apoptosis reported. Our own data show that in dog myocardium made globally ischemic for 90 min, 8% of the myocytes showed a positive staining for apoptosis (TUNEL method) after 6 h of reperfusion. Despite these results the question of reperfusion injury and the influence of apoptosis still remains open, because it can not be excluded until now that the apoptotic process is initiated during the ischemic period. Studies in hibernating myocardium and chronic heart failure show a similar situation, because of a wide variation of numbers of apoptotic cells and the limited possibility to investigate human tissue. There is no doubt that apoptosis plays an important role in chronic pathophysiological situations such as heart failure and hibernating myocardium but the importance of apoptosis in the acute situation of ischemia/reperfusion still has to be clarified. [ABSTRACT FROM AUTHOR]