493 research outputs found

    Vesicle computers: Approximating Voronoi diagram on Voronoi automata

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    Irregular arrangements of vesicles filled with excitable and precipitating chemical systems are imitated by Voronoi automata --- finite-state machines defined on a planar Voronoi diagram. Every Voronoi cell takes four states: resting, excited, refractory and precipitate. A resting cell excites if it has at least one excited neighbour; the cell precipitates if a ratio of excited cells in its neighbourhood to its number of neighbours exceed certain threshold. To approximate a Voronoi diagram on Voronoi automata we project a planar set onto automaton lattice, thus cells corresponding to data-points are excited. Excitation waves propagate across the Voronoi automaton, interact with each other and form precipitate in result of the interaction. Configuration of precipitate represents edges of approximated Voronoi diagram. We discover relation between quality of Voronoi diagram approximation and precipitation threshold, and demonstrate feasibility of our model in approximation Voronoi diagram of arbitrary-shaped objects and a skeleton of a planar shape.Comment: Chaos, Solitons & Fractals (2011), in pres

    Vinculin binding angle in podosomes revealed by high resolution microscopy

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    Podosomes are highly dynamic actin-rich adhesive structures formed predominantly by cells of the monocytic lineage, which degrade the extracellular matrix. They consist of a core of F-actin and actin-regulating proteins, surrounded by a ring of adhesion-associated proteins such as vinculin. We have characterised the structure of podosomes in macrophages, particularly the structure of the ring, using three super-resolution fluorescence microscopy techniques: stimulated emission depletion microscopy, structured illumination microscopy and localisation microscopy. Rather than being round, as previously assumed, we found the vinculin ring to be created from relatively straight strands of vinculin, resulting in a distinctly polygonal shape. The strands bind preferentially at angles between 116° and 135°. Furthermore, adjacent vinculin strands are observed nucleating at the corners of the podosomes, suggesting a mechanism for podosome growth

    Latest developments in 3D analysis of geomaterials by Morpho+

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    At the Centre for X-ray Tomography of the Ghent University (Belgium) (www.ugct.ugent.be) besides hardware development for high-resolution X-ray CT scanners, a lot of progress is being made in the field of 3D analysis of the scanned samples. Morpho+ is a flexible 3D analysis software which provides the necessary petrophysical parameters of the scanned samples in 3D. Although Morpho+ was originally designed to provide any kind of 3D parameter, it contains some specific features especially designed for the analysis of geomaterial properties like porosity, partial porosity, pore-size distribution, grain size, grain orientation and surface determination. Additionally, the results of the 3D analysis can be visualized which enables to understand and interpret the analysis results in a straightforward way. The complementarities between high-quality X-ray CT images and flexible 3D software are opening up new gateways in the study of geomaterials

    MORPHOLOGICAL SPATIAL PATTERN ANALYSIS: OPEN SOURCE RELEASE

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    Abstract. The morphological segmentation of binary patterns provides an effective method for characterising spatial patterns with emphasis on connections between their parts as measured at varying analysis scales. The method is widely used for the analysis of landscape patterns such as those related to the fragmentation of forests or other natural land cover classes. This can be explained by its effectiveness at capturing the complexity of binary patterns and their connections by partitioning the foreground pixels of the corresponding binary images into mutually exclusive classes. While the principles of the method are conceptually simple, the definition of the classes relies on a series of advanced mathematical morphology operations whose actual implementation is not straightforward. In this paper, we propose an open source code for MSPA and detail its main components in the form of pseudo-code. We demonstrate its effectiveness for asynchronous processing of tera-pixel images and the synchronous exploratory analysis and rendering with Jupyter notebooks

    Preprocessing Techniques in Character Recognition

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    Extraction of tidal channel networks from airborne scanning laser altimetry and aerial photography

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    The study of the morphodynamics of tidal channel networks is important because of their role in tidal propagation and the evolution of salt-marshes and tidal flats. Channel dimensions range from tens of metres wide and metres deep near the low water mark to only 20-30cm wide and 20cm deep for the smallest channels on the marshes. The conventional method of measuring the networks is cumbersome, involving manual digitising of aerial photographs. This paper describes a semi-automatic knowledge-based network extraction method that is being implemented to work using airborne scanning laser altimetry (and later aerial photography). The channels exhibit a width variation of several orders of magnitude, making an approach based on multi-scale line detection difficult. The processing therefore uses multi-scale edge detection to detect channel edges, then associates adjacent anti-parallel edges together to form channels using a distance-with-destination transform. Breaks in the networks are repaired by extending channel ends in the direction of their ends to join with nearby channels, using domain knowledge that flow paths should proceed downhill and that any network fragment should be joined to a nearby fragment so as to connect eventually to the open sea

    Determining an accurate method for estimating the post-mortem interval of decomposed remains found in a temperate Australian environment

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    Estimating the post-mortem interval (PMI) is one of the most important determinations to make in a forensic investigation. However, at present, an accurate and reliable forensic anthropological method for estimating the PMI, based on the gross morphological changes occurring during decomposition, is currently unavailable. This is due to a multitude of variables influencing the rate and processes of decomposition in any given environment. Forensic anthropologists have traditionally relied on their knowledge and experience of the decomposition stages to make an assessment of the time since death. However, recently new, quantitative methods that are not solely based on the anthropologists observations, have been developed in a number of regions that have been proposed to accurately determine the PMI based on the observed decomposition changes alongside important taphonomic variables. The aim of the current study was to examine and document the decomposition process of pig carcasses, as an analogue for human remains, in the summer and winter climate of the Greater Western Sydney region. Secondly, the study aimed to evaluate the accuracy and replicability of the Megyesi et al. [1] ADD method, the Marhoff et al. [2] formula and the Vass [3] universal PMI formula, for their applicability as PMI methods in this region. Thirdly, should the methods mentioned above fail to accurately determine the PMI of remains within this region, a new method for PMI determinations will be created based on the observed decomposition changes and the most influential taphonomic variables affecting decay rates within the Greater Western Sydney region. Over an 18 month period, from June 2014 to March 2016, four experimental trials were undertaken: two summer trials and two winter trials. Eight adult pig carcasses per trial were left to decompose naturally on a soil surface at Western Sydney University’s Hawkesbury campus. During each trial, four carcasses were left to decompose in the shade under the canopy of trees and the other four carcasses were deposited in the open, with direct exposure to the sun. This was to examine the differences in decay rates between a sun and shaded microclimate. The published methods [1-3] and their associated scoring protocols were applied to determine the PMI of the remains. Through linear mixed modelling, the variation between the true PMI and the estimated PMI. The results showed that of the three methods validated in the present study, none could accurately determine the PMI in the Greater Western Sydney region. The Vass [3] formula overestimated the PMI during the winter trials but underestimated the PMI of the summer remains. The Megyesi et al. [1] and Marhoff et al. [2] methods were both found to underestimate the PMI when they were applied during the winter but overestimated the PMI when they were applied during the summer. As it was found that the currently published protocols for PMI estimates could not accurately determine the PMI of remains found within this region, a new method (the Marhoff-Beard method) for PMI determinations specific to the Western Sydney region was created. Using the degree of soft tissue decomposition observed at the time of discovery alongside the climatic variables humidity, wind speed, and rainfall, new regression equations were created. To determine if the new Marhoff-Beard formulae were accurately estimating the PMI for the Western Sydney region, the method was validated retrospectively from photographs of pig and human remains, and was applied longitudinally from the start to the end of the decomposition process on a donated human body. The validation showed this new method can accurately determine the PMI in a Western Sydney winter and summer climate and results were comparable when it was applied to both human remains and pig carcasses. The method performed consistently well during the fresh and early decomposition stages with a maximum error of eight days. As the remains dried and progressed through the advanced and skeletonisation stages, the accuracy of the method became compromised. It is likely the Marhoff-Beard method failed after this time point, as the decomposition process during the later stages is affected by further variables which were not accounted for by this method. Continued testing of the Marhoff-Beard method for PMI determinations should be undertaken both within this region and other temperate Australian locations. It should also be determined what variables are affecting decay rates during the more advanced stages of decomposition as this will help refine the PMI formula for its use during these stages
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