Intermediate structure in the cross section for the subbarrier fission of 241Am

The cross section for the neutron-induced fission of ²⁴¹Am at neutron energies between 0.2 eV and 10 keV was measured by means of a lead slowing-down spectrometer (LSDS-100). The parameters of the intermediate structure in the behavior of the fission strength function were estimated.     

Numerical construction of the continuous spectrum Eigenfunctions of the three body Schrödinger operator: Three particles on the axis with short-range pair potentials

Based on a new method of the numerical construction of the three-body Schrödinger operator continuous spectrum eigenfunctions an analysis of the solutions of the problem of three identical particles on the axis with quickly decreasing repulsive pair potentials is offered. The initial problem is reduced to solving an inhomogeneous boundary problem for an elliptical partial differential equation in a twodimensional domain as a circle with radiation boundary conditions, with a ray approximation of the solution with diffraction corrections, contributing to a smoothness of a solution sought, being used. The approach offered allows a natural generalization for a case of slowly decreasing potentials of the Coulomb type and higher configuration space dimensions.     

Effect of collision cascade induced fluctuations in point defect concentrations on the void growth kinetics

Abstract

The point defect production in collision cascades causes fluctuations of vacancy and interstitial concentrations. These fluctuations are shown to affect the void growth kinetics in irradiated metals. In the present paper the analysis of the void distribution behaviour as a function of void sizes is considered. Remarkable changes in void kinetics can exist when the dislocation density is comparatively small. Under conditions determined in the present paper, the cascade induced fluctuations of the void growth rate lead to some decrease in the void density in irradiated metals. Moreover, the spatially inhomogeneous void shrinkage prevails over the homogeneous one.     

Stable azomethine imines derived from pyrazolidin-3-one and their cycloaddition to <Emphasis Type="Italic">N</Emphasis>-arylmaleimides

Reactions of (Z)-1-arylmethylidene-3-oxopyrazolidin-1-ium-2-ides (stable analogs of azomethine imines generated by thermal opening of the diaziridine fragment in 6-aryl-1,5-diazabicyclo[3.1.0]hexanes) with N-arylmaleimides having no ortho substituents in the aryl group are stereoselective: the products are mixtures of the corresponding cis and trans adducts, the latter prevailing (∼1.4–2.6: 1). trans Adducts are formed as the only products in the reactions with di-ortho-substituted N-arylmaleimides. (Z)-1-[(2,6-Dichlorophenyl) methylidene]-3-oxopyrazolidin-1-ium-2-ide reacts with both para- and ortho-substituted N-arylmaleimides to give exclusively trans adducts. Labile azomethine imines generated by thermolysis of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes are likely to have Z configuration as well.     

Simulation of thermal decomposition of a polymer at random scissions of C-C bonds

A mathematical formulation of the polymer thermal decomposition model at random scissions of C-C bonds in the backbone is presented. The model is based on ideas about a macrokinetic character of the observed process Polymer ?? Gaseous products, and the thermofluctuation nature of the bond scission. The suggested approach makes it possible to calculate the decomposition rate in a wide pressure range at any initial molecular weight distribution of the polymer. As an example, a comparison of the calculation results for temperature-time dependences of the conversion degree and decomposition rate with experimental data obtained in isothermal and non-isothermal regimes is performed for linear polyethylene.     

Statistical model of thermal degradation of linear polymers

Thermal degradation of a high-molecular-mass linear polymer is revisited for PE in terms of the theory of random ruptures. The polymer → gaseous products process is shown to proceed as a continuous sequence of chemical reactions accompanied by the occurrence of such physical phenomenon as evaporation of the formed fragments of macromolecules. Quantitative estimates suggest that the experimental conditions for vapor formation (pressure, heating rate, geometric dimensions, shape of the test sample, etc.) exert a marked effect on the overall rate of conversion and on the resultant brutto effect of thermal degradation. Hence, comparison of empirical “kinetic constants” of thermal degradation for polymers prepared by different methods and under different temperature-time regimes seems to be incorrect.