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A polygon with two distinguished vertices, s and g, is called a street iff the two boundary chains from s t o g are mutually weakly visible. For a mobile robot with on-board vision system we describe a strategy for finding a short path from s t o g in a street not known in advance, and prove that the length of the path created does not exceed 1 + 2. times(More)
Given a simple polygon in the plane with two distinguished vertices, s and g, is it possible for two guards to simultaneously walk along the two boundary chains from s to g in such a way that they are always mutually visible? We decide this question in time O(n logn) and in linear space, where n is the number of edges of the polygon. Moreover, we compute a(More)
Abstract Voronoi diagrams were introduced by R . Klein [Kle89b, Kle88a, Kle88b] as an axiomatic basis ofVoronoi diagrams. We show how to construct abstract Voronoi diagrams in time O(nlogn) by a randomized algorithm, which is based on Clarkson and Shor's randomized incremental construction technique [CS89]. The new algorithm has the following advantages(More)
BACKGROUND A new instrument to assess stress scoliosis patients have whilst wearing their brace has been developed. Aim of this study was to test the reliability of this new instrument. METHODS Eight questions are provided focussing on this topic only, including two questions to test the credibility. A max. score of 24 can be achieved (from 0 for most(More)
BACKGROUND In recent years, the relevance of vitamin D receptor (VDR) gene restriction fragment length polymorphisms for various types of cancer has been investigated by a great number of studies. It has been hypothesized that VDR polymorphisms may influence both the risk of cancer occurrence and prognosis. However, studies investigating the associations(More)
Next-generation sequencing technologies can be used to analyse genetically heterogeneous samples at unprecedented detail. The high coverage achievable with these methods enables the detection of many low-frequency variants. However, sequencing errors complicate the analysis of mixed populations and result in inflated estimates of genetic diversity. We(More)
Initial environmental pyrosequencing studies suggested highly complex protistan communities with phylotype richness decisively higher than previously estimated. However, recent studies on individual bacteria or artificial bacterial communities evidenced that pyrosequencing errors may skew our view of the true complexity of microbial communities. We(More)