Asymptotic behavior of positive solution branches of elliptic problems with linear part at resonance

We consider Dirichlet problems for semilinear elliptic equations whose linear part is at resonance. For various types of nonlinearities we provide sufficient conditions for the solvability of these problems for certain types of forcing terms. Depending upon the dimension of the independent variable and the shape of the domain, we obtain multiple existence results and show that in some cases infinitely many solutions may exist.Dedicated to Klaus Kirchgässner on the occasion of his 60th birthdayThe authors' work on this project has been supported by several institutions and thanks are due to the University of Utah for granting Schaaf a one year's visiting professorship during 1989–1990, to the DFG and the University of Stuttgart for providing Schmitt with the opportunity to visit that institution during the summer semester 1989. Final preparation was supported by a grant from NSF.     

Nonlinear optical ferroelectric liquid crystals and device configurations

Ferroelectric Liquid Crystals (FLCs) are presented which comprise charge-transfer functional groups, such that highly efficient NonLinear Optical (NLO) properties and pronounced ferroelectricity result. By operating the NLO-FLCs in one of the two Bistable states of the Short-pitch Ferroelectric (SPF) conformation, stable, planar waveguides result. The NLO-FLCs exhibit exceptionally large second-order NLO-coefficientsd ₂₂ = 5 pm/V. Moreover, their linear electrooptical effect is shown to be essentially electronic in nature. This renders ultrafast electrooptical modulators with NLO-FLCs feasible.     

A comprehensive picture of magnetic recording: theory and experiment part I: fundamentals and digital recording

The present paper summarizes and extends previous publications on magnetic recording which described a recording model, that offers the possibility of quantifying the importance of various parameters of the medium and the hardware. Within this model computer simulations of the read/write process elucidate the broad scope of magnetic recording to an extent, nonexistent so far. All computations follow or adapt common measuring procedures which facilitate the verification of our theoretical findings by comparison with experimental data. In this first of two papers the theoretical analysis applies to digital recording, only. The presented results permit objective comparisons between different techniques and media. Moreover, they yield clear statements about the feasibility for improvements of magnetic recording.     

Simulation von Einspiel- und Rißbildungsvorgängen in Faserverbundwerkstoffen mit metallischer Matrix

Übersicht Faserverbundstrukturen mit metallischer Matrix sind oft Belastungen ausgesetzt, die zu einer Plastifizierung der Matrix führen. Wird die Struktur zudem zyklisch belastet, so kann sie als Folge fortschreitender Plastifizierung versagen. Vor diesem Hintergrund ist besonders die Einspielneigung und die Rißbildung der Struktur von großem Interesse. In der vorliegenden Arbeit werden daher verschiedene Faser/Matrix-Kombinationen in einer numerischen Simulation untersucht. Der Zugang erfolgt dabei über die Finite-Element-Methode.

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Study of shakedown and crack initiation in fibre composites with metallic matrices

Summary Composite materials with a metal matrix are often subjected to loads which lead to plastification of the matrix. If, in addition, the structure undergoes cyclical loading, it may fail as a result of the continuing plastification. Under these circumstances, the shakedown and the crack growth of the structure are of special interest. Hence, in the present work various fibre/matrix combinations have been investigated by numerical simulation using the finite element method.

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Herrn Prof. Dr.-Ing. E. h. Th. Lehmann zum 70. Geburtstag am 10. August 1990 gewidmet.     

Nannocystin A: an Elongation Factor 1 Inhibitor from Myxobacteria with Differential Anti‐Cancer Properties

Cultivation of myxobacteria of the Nannocystis genus led to the isolation and structure elucidation of a class of novel cyclic lactone inhibitors of elongation factor 1. Whole genome sequence analysis and annotation enabled identification of the putative biosynthetic cluster and synthesis process. In biological assays the compounds displayed anti‐fungal and cytotoxic activity. Combined genetic and proteomic approaches identified the eukaryotic translation elongation factor 1α (EF‐1α) as the primary target for this compound class. Nannocystin A ( 1 ) displayed differential activity across various cancer cell lines and EEF1A1 expression levels appear to be the main differentiating factor. Biochemical and genetic evidence support an overlapping binding site of 1 with the anti‐cancer compound didemnin B on EF‐1α. This myxobacterial chemotype thus offers an interesting starting point for further investigations of the potential of therapeutics targeting elongation factor 1.     

Diketopyrrolopyrrole‐Porphyrin Conjugates with High Two‐Photon Absorption and Singlet Oxygen Generation for Two‐Photon Photodynamic Therapy

Two‐photon photodynamic therapy is a promising therapeutic method which requires the development of sensitizers with efficient two‐photon absorption and singlet‐oxygen generation. Reported here are two new diketopyrrolopyrrole‐porphyrin conjugates as robust two‐photon absorbing dyes with high two‐photon absorption cross‐sections within the therapeutic window. Furthermore, for the first time the singlet‐oxygen generation efficiency of diketopyrrolopyrrole‐containing systems is investigated. A preliminary study on cell culture showed efficient two‐photon induced phototoxicity.