Analysis of the Dynamics of Slender Continua Using Karhunen-Loève-Transformation

The dynamics of continua with very small diameter–to–length ratio, like bridges or drill–strings, has been object of mechanical analysis for a long time. While it is often possible to create a well–suited mechanical model, it is difficult to determine the exact current loads and the exact operational state. For drill–strings, the load of the drill–bit depends on the material of the rock, but also on other unknown disturbances like differential sticking which can occur along the drill–string without being noticed directly. Karhunen–Loève–Transformation (KLT) provides a possibility to describe the dynamics of a continuous system with few Characteristic Functions (CF), as long as the motion of the system is stationary. On the other hand, the resulting CFs of the KLT are sensitive to changes in the dynamic system behavior. These changes can result e. g. from the occurrence of stick–slip of the bit or differential sticking of the string. On the basis of a simple model, we show that this sensitivity can be used to detect and characterize such changes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical Approximation of Uncertain Nonlinear Systems

We address qualitative characteristics of dynamical systems and their approximation using set–valued numerical methods, where we aim at robust results. In this spirit, model uncertainties are incorporated into the problem formulation as outcomes of an external stochastic process. The systems under consideration are described in terms of finite state Markov chains. An example serves to illustrate the procedure. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Activity-based probes for studying the activity of flavin-dependent oxidases and for the protein target profiling of monoamine oxidase inhibitors

High profile: new activity-based protein profiling (ABPP) probes have been designed that target exclusively monoamine oxidases A and B within living cells (see picture; FAD=flavin adenine dinucleotide, FMN=flavin monodinucleotide). With these probes it could be shown that the MAO inhibitor deprenyl, which is in clinical use against Parkinson's disease, shows unique protein specificity despite its covalent mechanism of action.     

Electrophilic natural products and their biological targets

The study of biologically active natural products has resulted in seminal contributions to our understanding of living systems. In the case of electrophilic natural products, the covalent nature of their interaction has largely facilitated the identification of their biological binding partners. In this review, we provide a comprehensive compilation of electrophilic natural products from all major chemical classes together with their biological targets. Covering Michael acceptor systems, ring-strained compounds and other electrophiles, such as esters or carbamates, we highlight representative and instructive examples for over 20 electrophilic moieties. The fruitful cooperation of natural product chemistry, medicinal chemistry and chemical biology has produced a collection of well-studied examples for how electrophilic natural products exert their biological functions that range from antibiotic to antitumor effects. Special emphasis is put on the elucidation of their respective biological targets via activity-based protein profiling, which together with the recent advancements in mass spectrometry has been crucial to the success of the field. The wealth of naturally occurring electrophilic moieties and their chemical complexity enables binding of a large variety of biological targets, such as enzymes of all classes, nonenzymatic proteins, DNA and other cellular compounds. With approximately 30,000 genes in the human genome but only 266 confirmed protein drug targets, the study of biologically active, electrophilic natural products has the potential to provide insights into fundamental biological processes and to greatly aid the discovery of new drug targets.     

Monitoring of the Nonlinear Dynamics of Railway Wheelsets

This paper focuses on the identification of dominant coherent structures in the nonlinear dynamic behavior of railway wheelsets by Karhunen-Loève-Transform (KLT). The ultimate goal is the characterization of the rolling quality of railway wheelsets. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Prediction of Extreme Ship Motions in Irregular Waves

The occurrence of indirectly excited large amplitude roll motions of ships is investigated under the influence of a time-varying righting lever curve in waves. In order to account for the irregular character of ocean waves appropriately, the ship motions are described within the framework of nonlinear dynamics and stochastic process theory. The analysis of roll motions in regular waves provides a qualitative understanding of the occurrence of unpredictable large amplitude roll motions as observed in ocean waves. However, quantitative information on the rolling behavior in irregular waves may be retrieved only from a probabilistic analysis. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multibody Dynamics of Cargo Airships During the Load Exchange Process

Projected cargo airships for the flexible transport of large loads exceed the dimensions of existing aircrafts and gave rise to various technical problems. In order to study the dynamics of the load exchange process mathematical models of the airship including the oscillating load frame are developed. The hull and the load frame are represented by a multibody system. Crucial aspects contributing to the system's dynamics are the floatation of the flying crane and nonlinear couplings between hull and load frame. Furthermore, added masses of the surrounding air are considered. Oscillations of the load frame are excited by wind loads, airship maneuvers, and winding up the cables. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dynamik von verankerten meerestechnischen Konstruktionen

The dynamical behaviour of moored structures in ocean engineering in an irregular sea is usually investigated by means of simplified mathematical models. Nonlinear phenomena like the influence of the motion on the mooring geometry or the fluid‐structure interaction are not considered. In this paper a method is described for analyzing the dynamical behaviour of mooring systems including the hydrodynamic forces due to the fluid surrounding the structure. The model for the dynamic analysis is generated using the multibody system method.