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| 2. |
- Eberhardt, F., et al.
(author)
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A Uniform and Isotropic Cytoskeletal Tiling Fills Dendritic Spines
- 2022
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In: eNeuro. - : Society for Neuroscience. - 2373-2822. ; 9:5
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Journal article (peer-reviewed)abstract
- Dendritic spines are submicron, subcellular compartments whose shape is defined by actin filaments and associated proteins. Accurately mapping the cytoskeleton is a challenge, given the small size of its components. It remains unclear whether the actin-associated structures analyzed in dendritic spines of neurons in vitro apply to dendritic spines of intact, mature neurons in situ. Here, we combined advanced preparative methods with multitilt serial section electron microscopy (EM) tomography and computational analysis to reveal the full three-dimensional (3D) internal architecture of spines in the intact brains of male mice at nanometer resolution. We compared hippocampal (CA1) pyramidal cells and cerebellar Purkinje cells in terms of the length distribution and connectivity of filaments, their branching-angles and absolute orientations, and the elementary loops formed by the network. Despite differences in shape and size across spines and between spine heads and necks, the internal organization was remarkably similar in both neuron types and largely homogeneous throughout the spine volume. In the tortuous mesh of highly branched and interconnected filaments, branches exhibited no preferred orientation except in the immediate vicinity of the cell membrane. We found that new filaments preferentially split off from the convex side of a bending filament, consistent with the behavior of Arp2/3-mediated branching of actin under mechanical deformation. Based on the quantitative analysis, the spine cytoskeleton is likely subject to considerable mechanical force in situ.
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| 4. |
- Brunton, A., et al.
(author)
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A Low-Dimensional Representation for Robust Partial Isometric Correspondences Computation
- 2014
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In: Graphical Models. - : Elsevier. - 1524-0703 .- 1524-0711. ; 76:2, s. 70-85
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Journal article (peer-reviewed)abstract
- Intrinsic shape matching has become the standard approach for pose invariant correspondence estimation among deformable shapes. Most existing approaches assume global consistency. While global isometric matching is well understood, only a few heuristic solutions are known for partial matching. Partial matching is particularly important for robustness to topological noise, which is a common problem in real-world scanner data. We introduce a new approach to partial isometric matching based on the observation that isometries are fully determined by local information: a map of a single point and its tangent space fixes an isometry. We develop a new representation for partial isometric maps based on equivalence classes of correspondences between pairs of points and their tangent-spaces. We apply our approach to register partial point clouds and compare it to the state-of-the-art methods, where we obtain significant improvements over global methods for real-world data and stronger guarantees than previous partial matching algorithms.
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| 5. |
- Günther, D., et al.
(author)
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Efficient Computation of a Hierarchy of Discrete 3D Gradient Vector Fields
- 2012
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In: Topological Methods in Data Analysis and Visualization II. - : Springer. ; , s. 15-30
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Book chapter (other academic/artistic)abstract
- This paper introduces a novel combinatorial algorithm to compute a hierarchy of discrete gradient vector fields for three-dimensional scalar fields. The hierarchy is defined by an importance measure and represents the combinatorial gradient flow for different levels of detail. The presented algorithm is based on Forman’s discrete Morse theory, which guarantees topological consistency and algorithmic robustness. In contrast to previous work, our algorithm combines memory and runtime efficiency. It thereby lends itself to the analysis of large data sets. A discrete gradient vector field is also a compact representation of the underlying extremal structures - the critical points, separation lines and surfaces. Given a certain level of detail, an explicit geometric representation of these structures can be extracted using simple and fast graph algorithms.
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| 6. |
- Günther, D., et al.
(author)
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Extraction of Valley Networks in Mars Elevation Maps
- 2010
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In: European Planetary Science Congress (Poster). - : Europea Planetary Science Congress.
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Conference paper (peer-reviewed)abstract
- The identification of valley networks and channels is an essential tool for geomorphological interpretations of the fluvial, glacial and volcanic history of Mars. While the creation of valley networks by erosion is an accepted hypothesis, the flow of water as the sole cause has recently been put into question. To investigate the origin of the networks, their detailed properties have to be mapped at a global scale. In previous attempts of computer-generated global mapping, manual verification of the results was necessary. Herein, we present a novel algorithm to automatically extract valley networks in terms of extremal lines and compare the extraction results with an area that has already been manually mapped in the literature. Extremal lines are a subset of the topological skeleton from an elevation map. The skeleton encodes the essential information and can be iteratively simplified to obtain different levels of detail in the elevation map. The hierarchization process is thereby fully automatic and does not involve any algorithmic parameters. Using the measure separatrix persistence, we are able to assess the topological importance of each element of the skeleton. This enables a reduction to the most dominant extremal lines. This topological analysis allows for an unbiased extraction of all extremal lines in an elevation map. The data analyst is provided with a slider to choose an appropriate level of detail for further analysis.
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| 7. |
- Hege, H. -C, et al.
(author)
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Distributed Visualization and Analysis of Fluid Dynamics Data
- 2004
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In: Proc. Fourth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration.
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Conference paper (peer-reviewed)abstract
- Fluid dynamics applications require a good understanding of the underlying physical phenomena. Therefore, effective procedures are necessary for analyzing and visualizing the various physical fields. Beside interactive and perceptually efficient techniques for visualizing flow fields directly, there is strong demand for methods that uncover hidden flow structures. %as well as the structural changes due to parameter variations. Some recently developed feature based visual analysis methods are exemplarily presented. Fluid flow data typically are large and often are stored remotely or distributedly. The interactive visual analysis of such large data sets requires new software architectures – ideally utilizing emerging Grid standards. We discuss such architectures and report on specific realizations in the framework of the visualization system Amira.
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| 8. |
- Hege, H. -C, et al.
(author)
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Towards Distributed Visualization and Analysis of Large Flow Data
- 2005
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In: JSME international journal. Series B, Fluids and thermal engineering. - : JAPAN SOC MECHANICAL ENGINEERS. - 1340-8054 .- 1347-5371. ; 48:2, s. 241-246
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Journal article (peer-reviewed)abstract
- Fluid dynamics applications require a good understanding of the underlying physical phenomena. Therefore, effective procedures are necessary for analyzing and visualizing the various physical fields. Beside interactive and perceptually efficient techniques for visualizing flow fields directly, there is strong demand for methods that uncover hidden flow structures. Some recently developed feature based visual analysis methods are exemplarily presented. Fluid flow data typically are large and often are stored remotely or distributedly. The interactive visual analysis of such large data sets requires new software architectures – ideally utilizing emerging Grid standards. We discuss such architectures and report on specific software realizations.
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| 9. |
- Laramee, R. S., et al.
(author)
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Applications of Texture-Based Flow Visualization
- 2008
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In: Engineering Applications of Computational Fluid Mechanics. - : HONG KONG POLYTECHNIC UNIV. - 1994-2060 .- 1997-003X. ; 2:3, s. 264-274
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Journal article (peer-reviewed)abstract
- Flow visualization is a classic sub-field of scientific visualization. The task of flow visualization algorithms is to depict vector data, i.e., data with magnitude and direction. An important category of flow visualization techniques makes use primarily of textures in order to convey the properties of a vector field. Recently, several research advances have been made in this special category, of dense, texture-based techniques. We present the application of the most recent texture-based techniques to real world data from (1) oceanography and meteorology, (2) computational fluid dynamics (CFD) in the automotive industry, and (3) medicine. We describe the motivations for using texture-based algorithms as well as the important recent advancements required for their successful incorporation into industry grade software. Our goal is to appeal to practitioners in the field interested in learning how these recent techniques can help them gain insight into problems that engineers and other professionals may be faced with on a daily basis. Many of these applications have only recently become possible.
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