Search

AbstractThe formation of the spectrum of ions leaving the Z-pinch constriction during its compression is considered in the framework of the thermal mechanism corresponding to collisional regimes at high density. This mechanism refers to the heating of all ions due to compression without consideration of the electromagnetic acceleration of any selected group of ions. It is shown that such conditions can be implemented in relatively high-density regimes in which the product of precompression density and radius is n0a0 ≫ 1024 m–3. Neutron yield is analyzed. Possible parameters of a fusion reactor based on a high-density Z-pinch are estimated and found to be extremely high in terms of today’s technology.

Phase stability of a mixture at given conditions is studied. The modelling of equilibrium phase compositions is considered when the original phase of the mixture is unstable. The tangent plane distance criterion is used for stability analysis and the Gibbs energy minimisation is employed for phase equilibrium calculation when the successive substitution does not work well. With the Helmholtz free energy equation of state, thermodynamic properties in single phase and two-phase equilibrium were calculated for methane-ethane mixtures. Phase envelopes were also calculated.

A recently developed approximate approach for modeling of carbon nanotubes and for evaluation of the effective properties of carbon nanotubes reinforced materials is applied to analysis of square plate with hole under uniaxial tension. It is assumed, that the plate is made of polymer with randomly distributed and randomly oriented carbon nanotubes. Distributions of carbon nanotubes volume fraction is varied over the surface of the plate, with the constraint that the total volume of nanotubes in the structure is the same, and the effects of that on stress concentration is evaluated. Such special variation volume fraction makes the carbon nanotubes reinforced polymer a functionally graded material. In evaluation of the local effective properties the Gutrin–Murdoch material surface model is applied to a hollow cylinder of finite thickness and combined with the notion of energy equivalence to replace carbon nanotube with an equivalent solid cylinder. The interphase, if any, can be modeled as a spring layer and subsequently added to obtain another equivalent solid cylinder. The material reinforced with such solid cylinders is then evaluated using the method of conditional moments, a stochastic homogenization approach proposed earlier for determination of the effective properties of random materials. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of the possible use of magneto-inertial fusion (MIF) to create a neutron source. We consider the configuration of the target in the form of an axially symmetric magnetic trap with magnetic “plugs” or so-called “probkotron”. Heating and compression of a plasma target in the magnetic field is studied numerically. Parameters of the neutron source based on plasma-jet driven magneto-inertial fusion with a cylindrical target are given.

AbstractA numerical model of ion kinetics is considered for the axially symmetrical magnetic trap. The trap contains warm Maxwellian plasma and strongly non-Maxwellian high-energy (fast) ions. The steady-state fast ion population is supported by the ionization of high-energy neutral atoms injected into the plasma. The physical model is based on the kinetic equation with the two-dimensional Fokker–Planck collision operator in the velocity phase space. Regimes of plasma exhaust through the mirrors are considered taking into account the possibility of electrostatic barrier formation. Parameters of power balance are discussed for the system under consideration.

AbstractElectromagnetic drift instabilities are considered for tandem mirror and field reversed plasma configurations taking into account effects of magnetic drift and finite β (β = plasma pressure / magnetic pressure). Stabilization of drift modes due to finite plasma length along magnetic field lines is studied. Dispersion equation includes effects of the common actions of gradients of plasma density, ion temperature and electron temperature with no assumption of adiabatic response of ions or electrons for the ranges of perpendicular wave number values from k⊥< 1/ρTiup to k⊥~ 1/ρTe(ρTiand ρTeare ion and electron thermal gyroradiuses). Instability induced turbulent transport is considered for mirror and field reversed magnetic configurations. Effect of sheared E × B flow on fluctuation level and transport is discussed.

In the early periods after irradiation of muscles in a dose of 800 rad changes in the activity of the enzymes of cyclic AMP metabolism are found in the lymphocytes of the spleen and thymus. The postradiation disturbance of the relative activities of these enzymes leads to changes in the steady-state intracellular cyclic AMP concentration. It is also shown that irradiation reduces the ability of lymphocytes to respond to isoproterenol by accumulating cyclic AMP.

Conclusions 1.Conditions have been established providing existence and uniqueness for solutions to general boundary-value problems in strain plasticity theory, which incorporates the stress deviator form. An iterative process has been proposed for solving nonlinear boundary-value problems, and optimal convergence-rate bounds have been defined. Conditions have been formulated under which simple loading occurs.2.The results are applicable to formally similar problems in creep involving ageing theory with the incorporation of the stress deviator form.

The conditions ensuring the single-value solution of elastoplastic edge problems that take into account hydrostatic stress under proportional loading are established.

Conclusions 1.The stresses exceed the permissible levels in the region of the concentrators (the joint between the bottom edge of the radial ribs and the shell and between the radial ribs and the annular ribs); obviously, design modifications will be necessary to reduce these stresses.2.The stresses in the remaining regions of the structure are at permissible levels.3.It is not possible to reduce the weight of the cover with the present design. New designs will have to be found to solve this problem.

Summary The sulphur-containing radioprotectors mercaptoethylamine (MEA), aminoethylisothiourea (AET), 2-aminothiazoline, 4-oxo-2-aminothiazoline, and S-S-3-oxapentane-1,5-diisothiourea, and the radioprotective biogenic amines serotonin, histamine, and dopamine, caused the elevation of cAMP content and intensified the rate of cAMP-dependent protein phosphorylation in tissues of animals following intraperitoneal injection at radioprotective doses. Biogenic amines stimulated the adenylate cyclase activity in membrane preparations from liver, spleen, and small-intestine mucosa; sulphur-containing radioprotectors caused no such effects. None of the radioprotectors affected cAMP and cGMP phosphodiesterases in vitro. AET and MEA inhibited guanylate cyclase in vitro, whereas serotonin and dopamine stimulated the enzyme. A biphasic change in the level of cGMP was observed in tissues after the administration of MEA and AET (more than 2-fold fall by 1–3 min after the administration of drug and 1.4-fold rise after 15–20 min); serotonin and dopamine caused a slow rise in the cGMP level; the cAMP/cGMP ratio in liver showed biphasic changes in level during the 20 min following injection of serotonin.

The emergence of critical conditions in a meta-stable melt is considered under the influence of two main factors: pre-crystallization super-cooling and overcooling rate. The average density of free energy in such conditions is highly inhomogeneous. External impacts are considered as factors controlling the properties of materials. The solidification of the overcooled meta-stable melt is considered in a quasi-chemical approximation, assuming a transition state corresponding to an ideal solution type system. The finite time of existence of the meta-stable state is taken into account. The dimensions of the structural cell are determined by the ratio between the rate of diffusion and heat removal. The obtained estimate of the structure parameter is in qualitative agreement with the experimental dependence.

The ability of radioprotectors (serotonin, aminoethylisothiouronium) in radioprotective doses to stimulate cyclic AMP-dependent phosphorylation of mouse liver cytosol and nuclear and spleen cytosol proteins in vivo was demonstrated. In experiments in vitro, the radioprotectors had no direct action on protein kinase activity or its stimulation by cyclic AMP. It is postulated on the basis of these results and those of previous investigations that activation of cyclic AMP-dependent phosphorylation is due to an increase in the intracellular cyclic AMP concentration under the influence of the radioprotectors.

The activity of human platelet guanylate cyclase, and the activation of the enzyme by sodium nitroprusside were decreased in platelets with increased aggregability; these platelets were obtained from diabetes mellitus patients. Anomalies in guanylate cyclase activity and ADP-induced aggregation were more pronounced in platelets from subjects with type II than those with type I diabetes.

In mixed culture of Chinese hamster fibroblatst, clone 431, and transformed murine L fibroblasts, clone B-82, isoproterenol was found to protect only 431 cells against ionizing radiation. It was shown that 431 cells, in contrast to B-82 cells, possessβ-adrenoreceptors, and the radioprotective effect of isoproterenol can be realized only if this agent interacts withβ-adrenoreceptors coupled with the cAMP system. Since malignization often causes the disappearance ofβ-adrenergic and other hormone receptors, the combined culturing and irradiation of the cells studied can be regarded as a model of the growth of malignant cells (B-82) among normal tissue cells (431 cells) under conditions of radiation therapy. A possibility of selective protection against radiation damage of normal tissue cells, with retention of the former radiosensitivity of tumor cells, is discussed.

The effect of a stimulating dose of 0.15 Gy on the cyclic adenosine 3′,5′ monophosphate system has been studied. A rapid change is shown in intracellular level of cAMP and in the response of the system to a β-adrenoagonist.