Bøger udgivet af Sudwestdeutscher Verlag Fur Hochschulschriften AG

Creep deformation influences the serviceability limit state as well as the ultimate limit state of timber structures. In order to consider this time-dependent behavior, creep coefficients and rheological models have been developed by various researchers. Comparing the rheological models, quite different temporal deformations are evaluated for a duration of load of 50 years. In order to find the model, which is most suitable to the situation in the region of Tübingen, South-West Germany, the existing deformations of several beams in roof structures in opened, protected but not heated buildings are measured. By loading the structure the elastic global stiffness of the particular element is determined. So creep coefficients can be evaluated, which should have been used by the engineer in order to get the existing deflection after 50 years. Within the region of Tübingen, on average a creep coefficient of 2.23 was found based on these measurements. However, the standard deviation of 0.97 is quite large. For the numerical evaluation of the time-dependent behavior Toratti's model is modified, so that it matches the measured deformations.

This thesis describes the design of a full-¿edged XML storage and query architecture, which represents the core of the Open Source database system BaseX. In contrast to numerous other works on XML processing, which either focus on theoretical aspects or practical implementation details, we have tried to bring the two worlds together: well-established and novel concepts from database technology and compiler construction are consolidated to a powerful and extensible software architecture that is supposed to both withstand the demands of complex real-life applications and comply with all the intricacies of the W3C Recommendations.

In many technical and engineering applications, numerical simulation is becoming more and more important for the design of products or the optimization of industrial production lines. However, the simulation of complex processes like the forming of sheet metal or the rolling of a car tire is a very challenging task, as nonlinear elastic or elastoplastic material behaviour needs to be combined with frictional contact and dynamic effects. In addition, these processes often feature a small mobile contact zone which needs to be resolved very accurately to get a good picture of the evolution of the contact stress. In order to be able to perform an accurate simulation of such intricate systems, there is a huge demand for a robust numerical scheme that combines a suitable multiscale discretization of the geometry with an efficient solution algorithm capable of dealing with the material and contact nonlinearities. The aim of this work is to design such an algorithm by combining domain decomposition methods with a suitable space discretization and efficient solvers for the resulting nonlinear systems.

This thesis focuses on functional traits of salt marsh plants. Plant traits most responsive to environmental constraints were identified and tested for their applicability to trait-environmental concepts. Trait-trait relationships were investigated and ultimately, the effects of plant traits on ecosystem properties were assessed and the role of biodiversity in the maintenance of those ecosystem properties was highlighted. The study was conducted in salt marshes along the mainland coast of Northwest Germany and on the island of Mellum. The most important findings of this study were that nutrient availability and water-related environmental conditions most strongly influence trait expressions of salt marsh plants. Morphology-based traits were partly different from those of other terrestrial plants and trait-trait relationships of element-based traits were consistent to the findings of other studies. Different plant traits were found to affect different ecosystem properties. Multifunctionality of salt marshes can be ensured by conserving functional diversity via species diversity, and its loss might adversely affect adjacent ecosystems, like the Wadden Sea system.

Integrin-mediated adhesive interactions of cells with the extracellular matrix (ECM) regulate important cellular functions and play a critical role in disease. Therefore, studying the mechanisms underlying integrin-binding and regulation is of great interest. In the presented work three respective biological questions have been addressed using Atomic Force Microscopy based Single Cell Force Spectroscopy (AFM-SCFS). The work is split into six chapters. The first chapter provides an introduction into cell-ECM interactions. Thereafter different adhesion assays are compared and contrasted, and the theoretical Bell-Evans model is discussed. In chapter four, alpha2beta1-integrin mediated cell adhesion to collagen I is quantified. Thereafter the effects of the exposure of cryptic integrin binding sites within collagen I on pre-osteoblasts are analysed. At last, the role of BCR/ABL in modulating myeloid progenitor cell adhesion to stromal cells and ECM-coated substrates is studied. Taken together, the work demonstrates that AFM-SCFS is a versatile tool that permits monitoring of cell adhesion from single-molecule recognition events to the formation of more complex adhesion sites.

It was shown that c-Myc is required for adequate vasculogenesis and angiogenesis. To investigate the contribution of Myc to these processes, we conditionally expressed c-Myc in adult and embryonic endothelial cells. C-Myc expression in adult endothelial cells induced the development of angiosarcomas and/or adenomas. Double transgenic mice died in average with 36 weeks. Inactivation of the transgene system in vivo results in partial tumor regression. C-Myc expressing embryos suffer from widespread edema formation and hemorrhagic lesions. They die between embryonic day (E) E14.5 and E17.5. The changes in vascular permeability are not caused by defects in vascular basement membrane composition or pericyte coverage. Alterations in the architecture of capillary networks were found. Endothelial cells show increased levels of both proliferation and apoptosis. The dermal vasculature of C-Myc expressing embryos show a reduction in vessel branching, which occurs despite up-regulation of the pro-angiogenic factors VEGF-A and angiopoietin-2 (Ang-2). Thus, the net outcome of an excess of VEGF-A and Ang-2 in the face of an elevated cellular turnover appears to be a defect in vascular integrity.