Frobenius-perron resonances for maps with a mixed phase space

Resonances of the time evolution (Frobenius-Perron) operator P for phase space densities have recently been shown to play a key role for the interrelations of classical, semiclassical, and quantum dynamics. Efficient methods to determine resonances are thus in demand, in particular, for Hamiltonian systems displaying a mix of chaotic and regular behavior. We present a powerful method based on truncating P to a finite matrix which not only allows us to identify resonances but also the associated phase space structures. It is demonstrated to work well for a prototypical dynamical system.     

Out-diffusion and precipitation of copper in silicon: An electrostatic model

Concentrations of mobile interstitial copper and precipitated copper in silicon were studied after a high temperature intentional contamination and quench to room temperature. It was found that below a critical contamination the copper predominantly diffuses out to the surface, while for higher initial copper concentrations it mainly precipitates in the bulk. The critical copper contamination equals the acceptor concentration plus 10(16) cm (-3). This behavior can be explained by the electrostatic interaction between the positively charged interstitial copper and the forming copper precipitates.     

Lifetime of electrons on the liquid surface of superfluid 4He

The lifetime of electrons deposited on the liquid surface of ⁴He was measured. It is smaller than 8 μs at 0.5 K and, as is concluded from its temperature dependence, governed by the electronic mobility parallel to the superfluid surface.     

Search for narrow resonances in e+e− annihilation at c.m. energies between 29.90 and 31.46 GeV

A search for narrow resonances in e⁺e^? annihilation at c.m. energies between 29.90 and 31.46 GeV provides no evidence for the existence of such states. The 90% confidence upper limit on the integrated resonance cross section is 38 nb MeV, significantly below the value expected for the lowest (t,t?) bound state.     

Magnetic phase transitions in the 1D ising antiferromagnet CsCoCl3

We report on Raman scattering from the magnons in CsCoCl₃ with particular emphasis on two magnetic phase transitions occurring at T_N = 20.82 K and at 8 K. The T → 0 magnon spectrum is fitted by a $\text{S =}\text{1}\text{2}$ anisotropic Heisenberg model. With a simple cluster model we can explain the temperature behaviour of the magnon frequencies and intensities. The physics of the 8 K phase transition is also discussed.     

Trace analysis of chloramphenicol residues in egg powders by capillary gas chromatography-electron capture detection

Chloramphenicol (CAP) in egg powder samples was extracted with acetonitrile by sonication. After centrifugation, the supernatant was diluted with water and defatted with n-hexane, and cleanup was performed on a microcolumn of graphitized carbon black (GCB). Different silylation methods were compared for the derivatization of the analytes. Trimethylsilyl N,N-dimethylcarbamate produced stable di-TMS derivatives which were analyzed by capillary gas chromatography-electron capture detection (CGC-ECD) after splitless injection. The meta isomer of the chloramphenicol served as the internal standard for quantitation, and 80% + mean recovery was obtained in the 0.1-10 micrograms/kg (ppb) concentration range.     

Polarization conversion of light in thin-film waveguides

Polarization conversion in optical waveguides on birefringent substrates is discussed with the aid of a coupled wave model. Structures are described which tolerate large thickness variations (up to 45%) while achieving the phase matching necessary for high conversion efficiency. Polarization conversion is experimentally demonstrated in two such arrangements using ADP substrates and organic polymer films. Conversion efficiencies in excess of 98% have been obtained.     

Plastische Wellen in Stabwerken

Übersicht Die Ausbreitung plastischer Wellen in einem Stabwerk wird mit Hilfe eines einfachen bilinearen Werkstoffmodells theoretisch untersucht und mit experimentellen Werten verglichen. Es zeigt sich, daß bis zum ersten vollen Durchlauf der plastischen Schockfronten die dynamische Beanspruchung sehr gut beschrieben wird. Die danach reflektierten plastischen Wellen lassen sich zwar nicht mehr im Detail erfassen, da ihr Schockcharakter verloren geht. Doch erhält man auch dann noch eine recht gute Näherung für die bleibenden Formänderungen. Ferner wird die für praktische Anwendungen erhebliche Vereinfachung gerechtfertigt, daß die Stabmassen in den Knoten zusammengefaßt werden dürfen.

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Summary The propagation of plastic waves in pin-jointed trusses is investigated theoretically with the aid of a simple bilinear constitutive law. The results of the analysis are compared with experimental results and good agreement is found. In addition, it is shown that the masses of the bars can be considered to be concentrated in the joints which leads to a considerable simplification of the analysis.

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Herrn Prof. Dr.-Ing. Dr. rer. nat. h. c. H. Neuber zum 70. Geburtstag gewidmet.