Photoreactive Langmuir–Blodgett–Kuhn multilayer assemblies from functionalized liquid-crystalline side chain polymers,I. Homopolymers containing azobenzene chromophores

Stable monomolecular layers of a liquid-crystalline homopolymer bearing azobenzene chromophores in the mesogenic side groups could be prepared at the water–air interface by slow compression at room temperature. From the area per monomer unit of A₀≈0.25 nm² a structural model with tightly packed azobenzene groups oriented nearly parallel to the surface normal was deduced. After transfer to a solid support in a Y-type mode the obtained Langmuir–Blodgett–Kuhn (LBK) multilayer assemblies of varying thicknesses (from a double layer to a thick film of d = 238 nm, capable of guiding optical modes) were prepared and analyzed by X-ray reflection and optical evanescent wave techniques. A monolayer thickness of d₀ = 2.52 nm, as well as the anisotropic index of refraction of these layers, could thus be evaluated. Photo-isomerization by UV-irradiation (at λ = (360±30)nm) was examined by UV-VIS absorption spectroscopy. X-ray reflectivity data of samples illuminated for 30 min showed a complete loss of the layered structure of the LBK samples. As a result strongly light-scattering films were obtained. Surface plasmon microscopy was used to demonstrate the usefulness of this photo-induced order–disorder transition for optical information storage.     

Perturbative contributions to the electroweak interface tension

The main perturbative contribution to the free energy of an electroweak interface is due to the effective potential and the tree level kinetic term. The derivative corrections are investigated with one-loop perturbation theory. The action is treated in derivative, in heat kernel, and in a multi local expansion. The massive contributions turn out to be well described by the Z-factor. The massless mode, plagued by infrared problems, is numerically less important. Its perturbatively reliable part can by calculated in derivative expansion as well. A self consistent way to include the Z-factor in the formula for the interface tension is presented.     

Accessible Fixed Points on the Boundary of Stable Domains

Let U be an invariant stable domain of a rational function R and z ₀ ∈ ? U a weakly repelling fixed point of R. Assuming a “local surjective condition”, which is obviously satisfied in the case of a completely invariant domain U, we show that zq is an accessible boundary point of U. This generalizes theorems of several authors.     

ROMPgel-supported tris(triphenylphosphine)rhodium(I) chloride: a selective hydrogenation catalyst for parallel synthesis

ROMPgel-supported tris(triphenylphosphine)rhodium(I) chloride has been prepared and the immobilised catalyst has been effectively employed in selective hydrogenations of a variety of alkenes and terminal alkynes.     

Convex interval interpolation with cubic splines,II

The problem of convex interval interpolation with cubicC ¹-splines has an infinite number of solutions, if it is solvable at all. For selecting one of the solutions a regularized mean curvature is minimized. The arising finite dimensional constrained program is solved numerically by means of a dualization approach.Dedicated to Professor Julius Albrecht on the occasion of his 65th birthday.     

Lidar calibration experiments

A series of atmospheric aerosol diffusion experiments combined with lidar detection was conducted to evaluate and calibrate an existing retrieval algorithm for aerosol backscatter lidar systems. The calibration experiments made use of two (almost) identical mini-lidar systems for aerosol cloud detection to test the reproducibility and uncertainty of lidars. Lidar data were obtained from both single-ended and double-ended lidar configurations. A backstop was introduced in one of the experiments and a new method was developed where information obtained from the backstop can be used in the inversion algorithm. Independent in-situ aerosol plume concentrations were obtained from a simultaneous tracer gas experiment with SF, and comparisons with the two lidars were made. The study shows that the reproducibility of the lidars is within 15%, including measurements from both sides of a plume. The correspondence with in-situ measurements is excellent. Finally, the new backstop method is able to reveal information which can close the lidar equation by obtaining the relation between backscatter and extinction in an aerosol cloud. Received: 21 December 1995 / Revised version: 25 July 1996     

Luminescence Properties of Eu3+ Complexes of Tripode and Tetrapode Ligands Containing 2,2′-Bipyridine Units

The Eu³⁺ complexes of the tripode and tetrapode ligands 1 and 2 , respectively, containing 2,2′-bipyridine coordinating units have been prepared. The UV absorption and luminescence spectra, lifetimes, and quantum yields have been measured under a variety of experimental conditions. The contributions of different paths to the decay of the luminescent excited state are evaluated, and the structures of the complexes are discussed on the basis of spectroscopic and photophysical data.     

Transverse momentum distributions of neutral pions from central and peripheral16O+Au collisions at 200A·GeV

The production of neutral pions by the interaction of 200A·GeV p and¹⁶O projectiles with a Au target has been studied in the pseudorapidity range 1.5≦η≦2.1. Transverse momentum spectra have been measured between 0.4 GeV/c and 3.6 GeV/c and their dependence on the centrality of the collision has been investigated. The peripheral-collision spectra display a marked change of slope with a hard component starting at about 1.8 GeV/c, in contrast to central-collision data. The data are discussed in comparison to p+p and α+α data from the ISR.     

Existence of solutions to an anisotropic phase‐field model

We consider an anisotropic phase‐field model for the isothermal solidification of a binary alloy due to Warren–Boettinger ( Acta. Metall. Mater. 1995; 43 (2):689). Existence of weak solutions is established under a certain convexity condition on the strongly non‐linear second‐order anisotropic operator and Lipschitz and boundedness assumptions for the non‐linearities. A maximum principle holds that guarantees the existence of a solution under physical assumptions on the non‐linearities. The qualitative properties of the solutions are illustrated by a numerical example. Copyright © 2003 John Wiley & Sons, Ltd.