On the luminescent properties of ZnS phosphors prepared at room temperature

We prepared ZnS phosphors and crystals without any firing at room temperature and atmospheric pressure directly from solutions of Zn-salts.The luminescent properties of the ZnS powders prepared by us are quite different from those previously described in the literature. Similarly, we also obtained from solutions ZnS crystals 100–200 in size.The authors wish to express their thanks to Dr. P. Gado for the X-ray measurements and helpful discussions.     

Aussagen der Theorie von Kraichnan für die isotrope hydromagnetische Turbulenz

The theory ofKraichnan is applied to quasi-stationary isotropic hydromagnetic turbulence. The average infinitesimal-impulse-response functionsg(k, τ), g _m (k, τ) and the time-correlationsr(k, τ), r _m (k, τ) are evaluated by the non-local direct-interaction approximation within the inertial range. For the range of ohmic but no viscous dissipation it is found that the magnetic energy spectrumE _m (k) obeys aE(k)k ^?2-law in accordance with results ofGolitsyn andMoffatt.     

Hydrogen motions and the α-relaxation in glass-forming polymers: Molecular dynamics simulation and quasi-elastic neutron scattering results

The combination of molecular dynamics simulations and neutron scattering measurements on three different glass-forming polymers (polyisoprene, poly(vinyl ethylene) and polybutadiene) has allowed to establish the existence of a crossover from Gaussian to non-Gaussian behavior for the incoherent scattering function in the α-relaxation regime. The deviation from Gaussian behavior observed can be reproduced assuming the existence of a distribution of discrete jump lengths underlying the sublinear diffusion of the atomic motions during the structural relaxation.     

Diode pumping of a continuous-wave Pr3+-doped LiYF4 laser

We report, for the first time to our knowledge, diode-pumped cw laser oscillation of Pr3+:LiYF4 in the red spectral range. The pump power is provided by a GaN laser diode emitting a maximum output power of 25 mW at a wavelength of approximately 442 nm. The Pr3+ laser emits 1.8 mW of output power at a 639.7-nm wavelength. Threshold pump power and slope efficiency in a nonoptimized setup are determined to be 5.5 mW and 24%, respectively.     

Protection of Erythrocytes Against Organometals-Induced Hemolysis

The hemolytic toxicity of tributyllead (TBL) and triphenyllead (TPhL) chlorides and its prevention by dithiotreitol (DTT), diethylenetriaminepentamethylenephosphonic acid pentasodium (PMP) and sodium disulfide (Na2S) was studied. It was found that both TBL and TPhL efficiently hemolyzed pig erythrocytes when used in micromolar concentrations; tributyllead chloride being about twice more efficient than triphenyllead chloride. The hemolytic efficiency of these compounds was blocked by PMP, DTT and Na2S in a concentration-dependent manner. However, significant differences in anti-hemolytic efficiency of these compounds were found. Namely, DTT and Na2S were very efficiently protecting erythrocytes against the action of organoleads, while the PMP protection was weak. Also, differences between DTT and Na2S protective efficiency were found. They more efficiently prevented erythrocyte hemolysis by TPhL than by TBL. Moreover, erythrocytes were better protected against the action of TBL by Na2S than by DTT. Such differentiation may be connected with possible differences in localization of the organolead compounds and protective agents in the erythrocyte membrane. To check these possibilities a series of experiments was performed using the fluorescence technique and various fluorimetric probes. These measurements enabled to determine fluidity changes induced in erythrocyte membranes by the organoleads and the protective compounds and to formulate some remarks concerning the differences in the mechanism of interaction of the organoleads with these membranes.     

Phase shift experiments identifying Kramers doublets in a chaotic superconducting microwave billiard of threefold symmetry

The spectral properties of a two-dimensional microwave billiard showing threefold symmetry have been studied with a new experimental technique. This method is based on the behavior of the eigenmodes under variation of a phase shift between two input channels, which strongly depends on the symmetries of the eigenfunctions. Thereby a complete set of 108 Kramers doublets has been identified by a simple and purely experimental method. This set clearly shows Gaussian unitary ensemble statistics, although the system is time-reversal invariant.     

Measurement of the η production in proton-proton collisions with the COSY time-of-flight spectrometer

The reaction pp → ppη was measured at excess energies of 15 and 41 MeV at an external target of the Jülich Cooler Synchrotron COSY with the time-of-flight spectrometer. About 25000 events were measured for the excess energy of 15 MeV and about 8000 for 41 MeV. Both protons of the process ppη were detected with an acceptance of nearly 100% and the η was reconstructed by the missing-mass technique. For both excess energies the angular distributions are found to be nearly isotropic. In the invariant-mass distributions strong deviations from the pure phase space distributions are seen. Received: 24 May 2002 / Accepted: 20 September 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: e.roderburg@fz-juelich.de Communicated by M. Gar?on     

Pentacene disproportionation during sublimation for field-effect transistors

At moderate temperatures in flowing gas, pentacene undergoes a disproportionation reaction to produce 6,13-dihydropentacene (DHP) and a series of polycondensed aromatic hydrocarbons, including the previously unknown peripentacene (PP). The process requires activation by heating to 320 degrees C and is possibly catalyzed by impurities such as DHP, 6,13-pentacenequinone (PQ), Al, or Fe found in the starting materials. These impurities also result in a decrease in the intrinsic field-effect mobility (FEM) of pentacene crystals. Subsequent purifications remove such impurities, thus inhibiting the formation of the disproportionation products and increasing the FEM of pentacene (2.2 cm(2)/Vs). These results clarify the importance of purification of semiconductive materials for measurements of intrinsic mobility and optimal device performance.     

Index abstracts

Abstract

Index abstracts     

Invertible modules for commutative -algebras with residue fields

The aim of this note is to understand under which conditions invertible modules over a commutative -algebra in the sense of Elmendorf, Kriz, Mandell & May give rise to elements in the algebraic Picard group of invertible graded modules over the coefficient ring by taking homotopy groups. If a connective commutative -algebra R has coherent localizations for every maximal ideal , then for every invertible R-module U, U_*=π_*U is an invertible graded R_*-module. In some non-connective cases we can carry the result over under the additional assumption that the commutative -algebra has ‘residue fields’ for all maximal ideals if the global dimension of R_* is small or if R is 2-periodic with underlying Noetherian complete local regular ring R₀. We apply these results to finite abelian Galois extensions of Lubin-Tate spectra.