Zum 70. Geburtstag von Josef Reitstötter

Ohne Zusammenfassung     

Hydromechanische Grundlagen für die Behandlung von stationären und instationären Grundwasserströmungen

Ohne Zusammenfassung     

Über den Begriff der uniformen Struktur und die Konvergenz in Booleschen Algebren

Ohne Zusammenfassung     

Zur Nullpunktabhängigkeit der Nevanlinnaschen Defekte

Ohne ZusammenfassungHerrn Professor A. Dinghas zum 60. Geburtstag gewidmet     

Charge-density waves in self-assembled halogen-bridged metal chains

Self-assembled growth of an ordered layer of Pt-Br-Pt chains on a Pt(110) surface is demonstrated. Upon slight doping with excess bromine, charge-density wave (CDW) domains separated by well-localized solutions are observed in the Br/Pt layer by scanning tunneling microscopy. Depending on annealing and adatom concentration, a global, long-range-ordered CDW ground state can be established. Angle-resolved UV photoemission data reveal the corresponding Fermi surface and its removal upon the Peierls transition. The CDW phase is stable to well above room temperature.     

Pyrazolylborate-zinc alkoxide complexes. 1. Basic properties, methylations, and heterocumulene insertions

While a solution of TpPh,MeZn-OH in methanol contains only traces of TpPh,MeZn-OMe, according to the equilibrium constant K = 5.8 x 10(-4), the reactions of TpPh,MeZn-OH with the electronegative alcohols trifluoroethanol and hexafluoro-2-propanol easily yield TpPh,MeZn-OCH2CF3 and TpPh,MeZn-OCH(CF3)2. The extremely hydrolytically sensitive TpPh,MeZn-OR complexes, with R = Me, Et, i-Pr, and CH2CH2F, as well as TpCum,MeZn-OR, with R = Me and i-Pr, are accessible from the Tp*Zn-hydride complexes and the corresponding alcohol. Alkylations with methyl iodide have revealed the high nucleophilicity of TpPh,MeZn-OMe by conversion to dimethyl ether and TpPh,MeZn-I. This conversion occurs rapidly not only with pure TpPh,MeZn-OMe but also with TpPh,MeZn-OH (as such or in the presence of methanol) and with TpPh,MeZn-OCOOMe. A relation of the Tp*Zn-alkoxides to the function of the zinc enzyme alcoholdehydrogenase exists in the reaction of TpPh,MeZn-OCH(CH3)2 with aromatic aldehydes, which yields acetone and the corresponding benzyl oxides TpPh,MeZn-OH2Ar. The heterocumulenes carbon dioxide, carbon disulfide, isothiocyanates, and one isocyanate are inserted into the Zn-OR bonds, yielding one alkyl carbonate complex (TpPh,MeZn-OC(O)OMe), two xanthogenate complexes (TpPh,MeZn-SC(S)OR), three iminothiocarbonate complexes (TpPh,MeZn-SC(NR')OR), and one alkyl carbamate complex (TpPh,MeZn-NR-COOMe). All insertion reactions can be described by a common mechanism involving a four-center intermediate in which the most basic heteroatom of the heterocumulene is attached to zinc.     

Engineering of layer-by-layer coated capsules with the prospect of materials for efficient and directed electron transfer

Intermolecular electron transfer is investigated in a dye-doped polyelectrolyte (PE) multilayer film. Hollow PE capsules, with a mean diameter of 2 microm, were prepared by stepwise adsorption of a pyrene (PY)-labeled polyanion and various polycations onto charged colloids and subsequent dissolution of the colloidal core. The high concentration of dye molecules within the capsule wall and the control of the medium polarity on a nanometer length scale are proposed to facilitate light-induced charge separation over distances of a few nanometers. In particular, a PY-labeled poly(styrene sulfonate) (PSS-PY) has been synthesized and used as polyanion for the polyelectrolyte capsule preparation. A polarity gradient across the wall of the PE shells is assumed to be achieved by adsorbing diverse polycations at different film positions. The high effective film area followed by high optical density of the PE capsule solution enables time-resolved optical spectroscopy. Using pulsed excited state absorption (ESA) the transient absorption peaks of the radical anion and cation state of pyrene were measured, respectively. In the presence of additional electron donor (or acceptor) molecules in the capsule solution the pyrene anion (cation) is observed in the ESA spectra, while both transient states are seen if no additional molecules are present. These results are interpreted as an electron transfer from pyrene to the donor (acceptor) molecule or between two pyrene molecules. An asymmetry of the electron donor and electron acceptor efficiency was observed when multilayer shells were used that are supposed to carry an internal polarity gradient.     

Optimal quadrature for Haar wavelet spaces

This article considers the error of the scrambled equidistribution quadrature rules in the worst-case, random-case, and average-case settings. The underlying space of integrands is a Hilbert space of multidimensional Haar wavelet series, . The asymptotic orders of the errors are derived for the case of the scrambled -nets and -sequences. These rules are shown to have the best asymptotic convergence rates for any random quadrature rule for the space of integrands .

     

A small step towards the hydrodynamic limit of a colored disordered lattice gas

We consider a system of colored particles in ${\mathbb{Z}}^d$ driven by a disordered Markov generator similar to that of Faggionato and Martinelli (Probab. Theory Related Fields 127 (2003) 535–608) and submitted to two external chemical potentials. We construct Gibbs measures such that the dynamics is time reversible. To cite this article: A. Dermoune, P. Heinrich, C. R. Acad. Sci. Paris, Ser. I 339 (2004).