Determination of chromium in biological reference materials by instrumental NAA using Compton suppression

Instrumental neutron activation analysis in conjunction with Compton suppression methods has been used to determine chromium concentrations in 13 biological reference materials. Special attention was focussed on the interferences and the ways of lowering their contribution. Separate data was obtained for normal and Compton suppressed modes of counting so that a comparison could be performed. The results for chromium as compared to the certified or compilation values were in excellent agreement.     

Classification of all Poisson-Lie structures on an infinite-dimensional jet group

A local classification of all Poisson-Lie structures on an infinite-dimensional group G of formal power series is given. All Lie bialgebra structures on the Lie algebra G of G are also classified.     

The approximation order of polysplines

We show that the scaling spaces defined by the polysplines of order provide approximation order For that purpose we refine the results on one-dimensional approximation order by -splines obtained by de Boor, DeVore, and Ron (1994).

     

Dielectric Properties of Lithium–Titanium Ferrite Ceramics

The temperature dependences of the real and imaginary parts of the complex dielectric permittivities of ceramic Li–Ti ferrospinel are measured within the frequency range 10²–10⁶ Hz. The empirical expressions describing these dependences are derived and the frequency-independent electrophysical parameters of the material under study are obtained. The best agreement between the experimental and calculation data is achieved when the time constant and the static dielectric permittivity are decreasing functions of frequency. A model of relaxational processes accounting for this result is proposed. A certain role in polarization of the relaxation agents, whose reorientation is controlled by tunneling electron transitions inside the two-valence iron ion – three-valence metal ion, is assumed. It is stated that under certain conditions, the relaxation agent reorientation is likely to possess a collective character. The temperature dependences and are derived for a number of dc currents at different electric field strengths. Sharp variations in the dielectric characteristics of the ceramics are found.     

Two-wavelength self-seeded pulsed tunable laser

A compact self-seeded pulsed tunable laser is described. Its optical cavity comprises a diffraction grating, operating at a grazing angle of incidence as a spectral selector and narrow-band spectral gate. The grating couples two partially overlapping laser channels: a highly selective master laser and a nonselective slave laser. Due to the implemented efficient intracavity self-seeding the laser emits spectrally pure single-longitudinal-mode radiation at two independently tunable wavelengths, with an efficiency and output energy that are typical for nonselective lasers. Results of the experimental investigation of the laser’s output characteristics are presented. Received: 12 March 2001 / Revised version: 10 December 2001 / Published online: 7 February 2002     

Definiteness of the Peano Kernel Associated with the Polyharmonic Mean Value Property

The definiteness of the Peano kernel is proved for a functionalassociated with the mean-value property of Picone and Brambleand Payne for polyharmonic functions in the ball. An importantcorollary of this is that if a function f satisfying (–1)^ppf>0vanishes on p concentric spheres centered at 0, then f(0)>0.This generalizes a well-known property of subharmonic functions(which arise in the special case p = 1).