Eine Bemerkung zur Regularität stationärer Punkte von konform invarianten Variationsintegralen

Ohne Zusammenfassung     

Amorphous and crystalline IrSi Schottky barriers on silicon

The electro-optical properties of the films are studied by measuring the infrared optical absorption and the yield of hole photoemission across the Schottky barrier to the p-Si substrate. The Schottky barrier height of the amorphous a-IrSi to the valence band of Si is 0.17–0.18 eV. The barrier height of the polycrystalline c-IrSi depends on the degree of texturing of the silicide; the Schottky barrier height increases from 0.14 eV to 0.18 eV when the substrate temperature is increased from room temperature to 400 °C during the Ir metal deposition prior to the 500 °C silicidation. The non-linearity of the photoemission yield observed for the amorphous a-IrSi in the Fowler plot is due to an energy-dependent photon absorption of these amorphous films. An evaluation of the scattering events in the metal films shows that the mean free path for inelastic scattering is λ_in=500 nm in the amorphous a-IrSi which is one order of magnitude larger than that in the crystalline c-IrSi. The mean free path for quasi-elastic scattering λ_qe=0.3 nm, of the amorphous a-IrSi is in the order of the interatomic distance, indicating a localization of the electronic states. Received: 14 November 1997/Accepted: 12 January 1998     

Possibility of ESR-dating without determination of the annual dose

It should, in principle, be possible to date a sample without determination of annual dose rate, when two ESR centers of different stability are present. The method assumes that the centers are independent and decay according to a first order process and that their concentration is far from saturation. The model is presented with emphasis on its inherent difficulties.     

A brief survey of the state of mathematical modeling aroung the world

We briefly survey and discuss the issues and perspectives presented in the two special issues of the Zentralblatt für Didaktik der Mathematik on mathematical modeling and pose open questions to the community of researchers interested in this domain of inquiry.     

Eine Bemerkung zur Anordnungsfähigkeit von Fastkörpern

On the basis of the Artin-Schreier-characterization for fully orderable nearfields due to F. Kalhoff, we constract an example of an ordered nearfield which is not fully orderable.

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Helmut Karzel zum 70. Geburtstag gewidmet     

Irregular sampling of wavelet and short-time Fourier transforms

We obtain irregular sampling theorems for the wavelet transform and the short-time Fourier transform. These sampling theorems yield irregular weighted frames for wavelets and Gabor functions with explicit estimates for the frame bounds.     

A Riesz basis for Bargmann-Fock space related to sampling and interpolation

It is shown that the Bargmann-Fock spaces of entire functions, A^p (C),p≧1 have a bounded unconditional basis of Wilson type [DJJ] which is closely related to the reproducing kernel. From this is derived a new sampling and interpolation result for these spaces.     

Study of the first-excited K π=0+ and 2+ bands in 228Th in the 226Ra(α,2n) reaction

Excited bands of ²²⁸Th were studied in the ²²⁶Ra(α,2n) reaction by gamma-ray and conversion-electron spectroscopy. The first-excited K ^π=0⁺ and 2⁺ bands were identified up to I ^π= 12⁺ and 10⁺, respectively. The spin dependence of the moments of inertia is discussed. The experimental data indicate a structural change of these bands from ²²⁸Th to ²³⁰Th and ²³²Th. Received: 11 August 1997 / Revised version: 19 September 1997