Die Schleiereule: flexibel durch das Leben : Gedanken über einen Kulturfolger

Schleiereulen leben in Deutschland als Gebäudebrüter eng angeschlossen an den Menschen. Der Beitrag spiegelt Gedanken wider, ob und wie Schleiereulen in Mitteleuropa bereits vor der Besiedlung durch den Menschen geeignete Lebensräume vorfanden und eine Population etablieren konnten. Das flexible Verhalten der Schleiereule, insbesondere das variable Paarungssystem, wird auf der Basis verhaltensökologischer Überlegungen vorgestellt und erläutert.Due to their dependence on breeding places in buildings Barn owl Tyto alba occurrence in Germany is closely connected to human settlements. The present contribution approaches the question if Tyto alba was able to spread over Central Europe already before colonization by humans. Further its flexibility in behaviour is described and discussed, especially concerning the reproduction strategy

A generalized marching cubes algorithm based on non-binary classifications

We present a new technique for generating surface meshes from a uniform set of discrete samples. Our method extends the well-known marching cubes algorithm used for computing polygonal isosurfaces. While in marching cubes each vertex of a cubic grid cell is binary classified as lying above or below an isosurface, in our approach an arbitrary number of vertex classes can be specified. Consequently the resulting surfaces consist of patches separating volumes of two different classes each. Similar to the marching cubes algorithm all grid cells are traversed and classified according to the number of different vertex classes involved and their arrangement. The solution for each configuration is computed on base of a model that assigns probabilities to the vertices and interpolates them. We introduce an automatic method to find a triangulation which approximates the boundary surfaces- implicitly given by our model- in a topological correct way. Look-up tables guarantee a high performance of the algorithm. In medical applications our method can be used to extract surfaces from a 3D segmentation of tomographic images into multiple tissue types. The resulting surfaces are well suited for subsequent volumetric mesh generation, which is needed for simulation as well as visualization tasks. The proposed algorithm provides a robust and unique solution, avoiding ambiguities occuring in other methods. The method is of great significance in modeling and animation too, where it can be used for polygonalization of non-manifold implicit surfaces.

A 3D Statistical Shape Model Of The Pelvic Bone For Segmentation

Statistical models of shape are a promising approach for robust and automatic segmentation of medical image data. This work describes the construction of a statistical shape model of the pelvic bone. An interactive approach is proposed for solving the correspondence problem which is able to handle shapes of arbitrary topology, suitable for the genus 3 surface of the pelvic bone. Moreover it allows to specify corresponding anatomical features as boundary constraints to the matching process. The model’s capability for segmentation was tested on a set of 23 CT data sets. Quantitative results will be presented, showing that the model is well suited for segmentation purposes