Paramagnetic defects in BaTiO3 and their role in light-induced charge transport — Optical studies

On the basis of a previous identification of paramagnetic defects in nominally undoped as grown BaTiO₃ single crystals, we have investigated the changes of the concentrations of these centers and their optical absorptions under illumination with light of varying wavelengths. The most pronounced charge transfers occur by hole ionization of Fe⁴⁺ and — to a lesser extent — of Cr⁵⁺ and Cr⁴⁺. At low temperatures the created holes are trapped in the form of O^–-ions next to Al³⁺ or unknown acceptor defects. Corresponding Fe⁴⁺ and O^– absorptions have been identified.     

The experimental structure of199Au and the interacting boson-fermion model

Gamma rays of¹⁹⁹Au obtained after double neutron capture in¹⁹⁷Au were measured at the ILL high flux reactor. A level scheme up to 1770 keV excitation energy is established. The result is compared with IBFM and Boson-Fermion-Symmetry calculations.     

Die Lasker-Bedingung für Nicht Endlich Erzeugte Moduln

Ohne Zusammenfassung

---

     

Aerodynamics of ski jumping: experiments and CFD simulations

The aerodynamic behaviour of a model ski jumper is investigated experimentally at full-scale Reynolds numbers and computationally applying a standard RANS code. In particular we focus on the influence of different postures on aerodynamic forces in a wide range of angles of attack. The experimental results proved to be in good agreement with full-scale measurements with athletes in much larger wind tunnels, and form a reliable basis for further predictions of the effects of position changes on the performance. The comparison of CFD results with the experiments shows poor agreement, but enables a clear outline of simulation potentials and limits when accurate predictions of effects from small variations are required.     

Synthesis and characterization of poly(vinyl alcohol)‐graft‐[poly(D,L‐lactide)/poly(D,L‐lactide‐co‐glycolide)] hydrogels

Poly(D ,L ‐lactide) and poly(D ,L ‐lactide‐co‐glycolide) with various composition and with one methacrylate and one carboxylate end group were synthesized and grafted onto poly(vinyl alcohol) (PVA) via the carboxylate group. The graft copolymers were crosslinked via the methacrylate groups using a free radical initiator. The polymer networks were characterized by means of NMR and studied qualitatively by means of IR spectroscopy. The influence of the glycolide content in the polyester grafts and of the number of ester units in the grafts on thermal properties and swellability were studied as well. The high swellability in water is characteristic of all hydrogels. Differential scanning calorimetry (DSC) showed a single glass transition temperature that occurs in the range between 51 and 69 °C. Thermogravimetric analysis (TGA) of the networks showed the main loss in weight in the temperature range between 290 and 370 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4536–4544, 2007     

L-shell X-ray production cross section measured by heavy ion impact on selected rare earth elements

The production cross sections of L-shell X-ray of some rare earth elements have been measured by collision of ¹²C⁴⁺ and ¹⁶O⁴⁺ ions of 0.5 to 0.75 MeV/amu. The results were compared with experimental data of other authors and with theoretical predictions gained by the ECPSSR and ECPSSR plus multiple ionization (ECPSSR+MI) models. For atomic parameters (fluorescence yields and probabilities for Coster-Kronig transitions) the role of several databases were studied. The ECPSSR theory underestimates cross sections when compared with experimental results obtained in the present work, but ECPSSR+MI has a better agreement with the experimental data. This revised version was published online in July 2006 with corrections to the Cover Date.     

The reconstructed final state of Au+AU collisions from PHENIX and STAR data at √s=130 AgeV— Indication for quark deconfinement at RHIC

The final state of Au+Au collisions at √s=130 AGeV at RHIC has been reconstructed within the framework of the Buda-Lund hydrodynamical model, by performing a simultaneous fit to final data on twoparticle Bose-Einstein correlations of the STAR and PHENIX Collaboration, and final identified single-particle spectra as measured by the PHENIX Collaboration. The results indicate a strongly three dimensional expansion, with a four-velocity field that is almost a spherically symmetric Hubble flow. We find large transverse geometrical source sizes, R _G=9.8±1.2 fm, relatively short mean freeze-out time, τ₀=6.1±0.3 fm/c and a short duration of particle emission, Δτ=0.02±1.5 fm/c. Most strikingsly, we find an indication for a hot central part of the hydrodynamically evolving core, characterized by a central temperature T ₀=202±13 MeV that is close to (or even above) the deconfinement temperature of the quark-hadron phase transition. The best fit indicates a cold surface temperature T _s=110±16 MeV. When the possibility of the hot center is excluded, the confidence level of the fit decreases from 28.9% to 1.0%. Predictions are made for the rapidity dependence of the slope parameters and for the transverse mass depedence of the rapidity width of the single-particle spectra, and the transverse mass dependence of the non-identical particle correlations.