Rainer Radtke

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The nest of the stingless bee,Trigona (Tetragonisca) angustula, is guarded by bees positioned in the nest entrance and others hovering in front of it. Hovering guard bees track returning foragers sideways along the last 10 cm in front of the nest, but intercept and incapacitate nest intruders by clinging with mandibles to wings and legs. When attacked by(More)
The radiation emitted from highly charged tungsten ions has been measured at the Berlin Electron Beam Ion trap using high-resolution x-ray and EUV spectrometers. Highly charged tungsten ions ranging from Pm-like W to N-like W have been produced and excited in EBIT. The line emission originating from electric and magnetic dipole transitions is studied in a(More)
We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm(3)) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10° and 20° divergent) and 5 mm self-tapping locking screws underwent(More)
Recent angle-resolved photoemission (ARPES) experiments have indicated that the electronic dispersion in some of the cuprates possesses an extended saddle point near the Fermi level which gives rise to a density of states that diverges like a power law instead of the weaker logarithmic divergence usually considered. We investigate whether this strong(More)
Extreme ultraviolet radiation from highly charged argon was investigated at the Berlin Electron Beam Ion Trap with a 2 m grazing incidence spectrometer. Lines in the wavelength range 150 to 660 Å originating from C-like Ar to Li-like Ar ions have been identified and are compared with database information from solar line lists and predictions. Line ratios(More)
The n=2-1 spectral emission pattern of heliumlike argon, together with the associated satellite emission originating from lithiumlike argon have been measured with high-resolution x-ray spectroscopy at the Berlin electron-beam ion trap. The observed line intensity across a wide range of excitation energies was weighted by an electron-energy distribution to(More)
We address the question of whether anisotropic superconductivity is compatible with the evidently weak sensitivity of the critical temperature Tc to sample quality in the high-Tc copper oxides. We examine this issue quantitatively by solving the strongcoupling Eliashberg equations numerically as well as analytically for s-wave impurity scattering within the(More)
There is a great deal of interest in attributing the high critical temperatures of the cuprates to either the proximity of the Fermi level to a van Hove singularity or to structure of the superconducting pairing potential in momentum space far from the Fermi surface, the latter being particularly important for spin-fluctuation-mediated pairing mechansims.(More)
In a recent article, Kim and Overhauser have found fault with the theory of impure superconductors by Abrikosov and Gor’kov and have proposed an alternative formalism based on Green’s functions which are not derivable from a Dyson equation. Although the corrections to the Abrikosov-Gor’kov theory found by Kim and Overhauser are correct for non-retarded(More)
Experiments on the cuprate superconductors demonstrate that these materials may be viewed as a stack of Josephson junctions along the direction normal to the CuO2 planes (the c-axis). In this paper, we present a model which describes this intrinsic Josephson coupling in terms of incoherent quasiparticle hopping along the c-axis arising from wave-function(More)