A Self-Similar Solution to the Problem of Lava Dome Growth on an Arbitrary Conical Surface

Within the framework of the asymptotic thin-film equations for a highly viscous heavy Newtonian fluid, a hydrodynamic model of non-axisymmetric lava dome growth on a conical surface is constructed. A new class of self-similar solutions describing the flow on a conical surface with finite inclination to the horizontal and a point mass supply at the apex is found analytically for power-law or exponential growth of the liquid volume with time. For a conical surface with a small inclination to the horizontal, the free-surface shape is found numerically. The asymptotics of this solution are compared with the solutions describing the flow on a horizontal plane and a conical surface with finite inclination to the horizontal.     

Generation and evolution of cavitation in magma under dynamic unloading

The full system of equations for the problem of rarefaction-wave passage over the magma-melt column in the gravity field is derived with the use of the kinetic theory of phase transformations, and the problem is numerically solved. With allowance for diffusion zones and nucleation frequency as a function of supersaturation, the dependence of the number of cavitation nuclei formed in the course of phase transformations behind the rarefaction-wave front is found. The dynamics of the size distribution of cavitation bubbles along the magma-melt column (1 km) whose viscosity varies dynamically as a function of the concentration of dissolved water is studied.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 2, pp. 71–80, March–April, 2005.     

The influence of magnetic field on the physical explosion of a heavy gas cloud

Richtmyer–Meshkov (RM) instability arises during the eruption of heavy gas cloud. In this study, we numerically study the effects of magnetic fields on the RM instability induced by the ionised cylindrical and spherical heavy gas cloud eruption using corner transport upwind + constrained transport algorithm. Our numerical results show that magnetic fields can suppress the formation of spike and bubble structures induced by the eruption in both cylindrical and spherical cases. The magnetic pressure of the interface along the perpendicular direction of magnetic field is the main factor to control the distortion of the interface. Even weak magnetic fields can drastically alter the evolution of the cloud and result in different distributions and amplifications of the magnetic pressure, which will affect further transformation of RM instability during the ionised gas eruption. Meanwhile, the magnetic pressure on the interface decreases gradually when the initial magnetic field is relatively large; when the initial magnetic field is small enough, the opposite results will occur.     

硝酸镧引起Escherichia coli B代谢过程热爆发及其机理研究

采用微量热法研究了硝酸镧对Escherichia coli B生长代谢过程的影响, 发现高浓度硝酸镧引起E. coli B热谱图出现异常变化: 生长速率常数k值增大、产热峰显著升高和总发热量异常增加. 当硝酸镧浓度为300和500 mg/L时, 培养物在培养过程的总发热量分别是正常条件下的3.89和2.54倍. 用生物学方法对细胞存活率和生物量进行测定结果表明, 细胞在高浓度硝酸镧条件下增殖受到抑制、细胞生物量减少. 表明高浓度的硝酸镧存在时, E. coli B细胞生长受到抑制反而释放出比正常生长细胞多得多的热量, 将抑制状态细胞释放大量热量的现象称为热爆发. 分析热爆发的原因, 认为是La^3＋离子破坏细胞壁外膜而增加其透性, 导致细胞膜与外膜间的质子电化学势因质子外泄而降低或者不能形成, 氧化磷酸化过程中的能量不能有效地转化为ATP, 而以热能的方式释放出来. 细胞由于缺乏生物通用能量ATP, 因而其生长受到抑制.     

Spontaneous Nucleation of Bubbles in a Gas‐Saturated Melt under Instantaneous Decompression

Based on the kinetic theory of phase transitions, the problem of spontaneous nucleation of gas bubbles in a gassaturated melt under instantaneous decompression is considered. The total number of nucleation centers formed in the process and their size distribution function are found.     

Gas-dynamic signs of explosive eruptions of volcanoes. 1. Hydrodynamic analogs of the pre-explosion state of volcanoes, dynamics of the three-phase magma state in decompression waves

Experimental data and results of numerical simulations of the magma state dynamics in explosive eruptions of volcanoes are presented. The pre-explosion state of volcanoes and the cavitation processes developed in the magma under explosive decompression are studied under the assumption that the intensity of explosive volcanoes does not exert any significant effect on the eruption mechanisms. In terms of the structural features of the pre-explosion state, a number of explosive volcanic systems are close to hydrodynamic shock-tube schemes proposed by Glass and Heuckroth. High-velocity processes initiated by shock-wave loading of the liquid may be considered as analogs of natural volcanic processes, which have common gas-dynamic features and common kinetics responsible for their mechanisms, regardless of the eruption intensity. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 3–12, November–December, 2008.     

Asymptotic models of solidification in cooling thin-layer flows of a highly viscous fluid

Asymptotic models are constructed for the solidification process in a highly viscous film flow on the surface of a cone with a given mass supply at the cone apex. In the thin-layer approximation, the problem is reduced to two parabolic equations for the temperatures of the liquid and the solid coupled with an ordinary differential equation for the solidification front. For large Péclet numbers, an analytical steady-state solution for the solidification front is found. A nondimensional parameter which makes it possible to distinguish flows (i) without a solid crust, (ii) with a steady-state solid crust, and (iii) with complete solidification is determined. For finite Péclet numbers and large Stefan numbers, an analytical transient solution is found and the time of complete flow solidification is determined. In the general case, when all the governing parameters are of the order of unity, the original system of equations is studied numerically. The solutions obtained are qualitatively compared with the data of field observations for lava flows produced by extrusive volcanic eruptions.     

Non-Isothermal Lava Flows over a Conical Surface

Using the equations of a non-isothermal thin layer of viscous fluid with an exponential dependence of the viscosity on temperature, a family of hydrodynamic models of a cooling lava flow over a conical surface in the presence of mass supply is constructed. These models correspond to asymptotically different rates of heat exchange with the ambient medium. The evolution of the free-surface shape and the temperature fields is investigated numerically for a stationary mass supply. Using the matched asymptotic expansions method, solutions valid both near and very far from the mass supply region are constructed. The solutions obtained are compared with known analytical solutions for isothermal flow.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, 2005, pp. 62–75.Original Russian Text Copyright © 2005 by Osiptsov.     

Impact of gamma radiation on the eruption rate of rat incisors

The present work aims to test the effect of gamma radiation on the rate of eruption of rat incisors. One hundred and five adult male albino rats were used and irradiated at different gamma doses. The effects of irradiation were investigated by numerical measurements of eruption rate, histological investigation using light microscope and spectral analysis using Fourier Transform Infra-Red (FTIR). No detectable changes were observed in the groups with smaller radiation doses. There was a significant decrease in the eruption rate starting from the 4?Gy radiation dose. The observation of histological sections revealed disturbance in cellular elements responsible for eruption as well as periodontal disturbance in the samples irradiated with 4 and 6?Gy. FTIR Spectroscopy of control group and the group irradiated by 0.5?Gy showed similar absorption bands with minor differences. However, samples irradiated by 1?Gy showed significant changes in both molecular structure and conformation related to carbonates and hydroxyl groups. From the previous results, it could be concluded that gamma irradiation negatively affects the eruption rate of the rat incisors especially with higher doses.     

Study on eruption of heat for Escherichia coli B aroused by lanthanum nitrate and its mechanism

Biological effect of rare-earth lanthanum nitrate on the growth of Escherichia coli B was studied using the calorimetric method. There were exceptional changes on the growth thermogenic curves for high concentrations of lanthanum nitrate. For example, the peak high, the total quantity of heat (Q) of cultures and the growth rate constants (k) are evidently increased when compared with normal E. coli B cultures. When the concentration of lanthanum nitrate was at 300 mg/L and 500 mg/L, and Q of the cultures reached 3.89 and 2.54 times of normal cultures, respectively. The survivability of cells and the biomass of the cultures were measured using biological methods and the results show that the growth and multiplication of cells were inhibited and that the biomass decreased at high concentration of lanthanum nitrate. These revealed that the inhibiting cells discharged more quantity of heat than the normal growing cells. We named this phenomenon as “eruption of heat”. It was suggested that the mechanism for the eruption of heat was that La³⁺ ion damages the outer cell membrane and increases its permeability and the proton-electron potential energy across the cell membrane was reduced or couldn’t even be initiated. Energy could not be translated into ATP effectively in the course of oxidative phosphorylation resulting in heat release. So, the growth of the cells was inhibited due to scarceness of energy ATP. __________ Translated from Acta Chimica Sinica, 2007, 65(10): 917–922 [译自: 化学学报]