Stability of difference schemes in terms of Riemann invariants for a polytropic gas

The monotonicity and stability of a finite difference scheme with respect to initial data in the supremum norm are analyzed as applied to the polytropic gas equations written in terms of Rie-mann invariants for subsonic flows with 1 < γ < 3. Conditions on the initial and boundary data are obtained under which subsonic flows with no shock waves develop in the medium. The theoretical conclusions are supported by numerical results.     

Low temperature survival of slender naiad (Najas flexilis) seeds

The response to drying and storage at -20 degrees C or in liquid nitrogen was studied in seeds of the freshwater aquatic plant Najas flexilis. The seeds of this species show some desiccation sensitivity, although post-harvest storage in water at 16 degrees C resulted in improvements in desiccation tolerance. There was 63% germination of seeds dried to 9.5% moisture content (30% RH) following this maturation period. Optimum moisture contents for seeds stored at -20 degrees C for 3 months and in liquid nitrogen for 1 week were ~11% and ~15%, respectively.     

Investigation into the rotational bands of ~(185)Pt with the particle-rotor model

Theoretical calculations have been performed for the ν9/2+[624](i13/2) and ν7/2-[503](f7/2) bands of 185Pt in the framework of particle-rotor model. The band properties of signature splitting and configuration mixing have been analyzed. The level energy and signature splitting before the band crossing can be well interpreted by introducing triaxiality. The positive-parity yrast band is pro posed to be dominated by the ν9/2+[624](i13/2) component, while the negative-parity band shows strong mixing of ν7/2-[5...     

Distributions of the implanted impurity and energy release in high-energy ion implantation

A new model for high-energy ion implantation is proposed, based on the use of the Fokker-Planck equation. An efficient algorithm of the adaptive type is devised for the numerical solution of the problem. A simulation of the implantation of boron in silicon is carried out for energies ranging from 10 to 100 MeV. Good agreement is obtained with the experimental data and the results of Monte Carlo simulations. Zh. Tekh. Fiz. 67, 61–67 (January 1997)     

Difference Schemes on Nonuniform Grids for the Two-Dimensional Convection–Diffusion Equation

New second-order accurate monotone difference schemes on nonuniform spatial grids for two-dimensional stationary and nonstationary convection–diffusion equations are proposed. The monotonicity and stability of the solutions of the computational methods with respect to the boundary conditions, the initial condition, and the right-hand side are proved. Two-sided and corresponding a priori estimates are obtained in the grid norm of C. The convergence of the proposed algorithms to the solution of the original differential problem with the second order is proved.     

Scattering of an acoustic pulse by a rigid sphere on a sedimentary (fluid) bottom

We study the problem of scattering of acoustic pulses on a rigid sphere located near the interface of two media in one of which (the bottom) sound absorption is taken into account. To find the amplitudes of the echo-signal in the distal field we apply the Fourier transform with respect to time and the method of T-matrices. Translated fromMatematichni Metodi ta Fiziko-Mekhanichni Polya, Vol. 40, No. 2, 1997, pp. 137–141.     

Fullerene local order in Na2CsC60 by23Na NMR

We have investigated the alkali metal fulleride Na₂CsC₆₀ by²³Na nuclear magnetic resonance (NMR), The NMR line of the tetrahedral site is split below 170 K (T and T′ lines) similarly to the A₃C₆₀ compounds with A=Rb or K. The intensity fraction of the T′ line follows the same temperature dependence as the¹³C NMR line width. We have also found that the spectrum is independent of the cooling rate. Spin-echo double resonance measurements show that T and T′ sites are mingled on a microscopic scale. We propose that the different²³Na NMR lines correspond to different fullerene orientational environments of the tetrahedral alkaline site.     

Identification of oxo,epoxy and somecis-carotenoids in high-performance liquid chromatography

Summary Methods of identification of aldehyde, ketonic, 5,6-epoxy, 5,8-epoxy groups andcis double bonds with highcis-peaks in carotenoids in HPLC have been investigated with selected models and a plant extract.