Image processing techniques for the characterization of explosively driven dispersions

PresentationDispersions driven by explosions are challenging to characterize mainly due to the extreme test conditions, the different time and spatial scales of the flow, and the variation of intensity due to the combustion. An intensity based optical method to characterize the dispersion driven by an explosion is proposed. The velocity and intensity maps of the dispersion are accessed through the post- processing of the images of the dispersion. These images can be obtained either from a global visualization (using a light source, such as in the image given in Figure 1, or the combustion light itself) or from a transversal visualization (using a laser sheet illuminating inside the cloud, such as in the image given in Figure 2). The developed method is organized into three steps. First, the contour of the cloud is detected via a dynamic grey-scale threshold criterion. The dispersion contours allow the computation of the velocity of the expansion as long as the plume presents a regular edge. Then, Large-Scale Particle Image Velocimetry technique is applied to obtain the velocity map of the dispersion. Additionally, information about the combustion phenomenon can also be accessed via an intensity-based analysis. The method has been initially verified using a numerical test case. It has been thereafter applied on different experimental measurements presenting challenging features such as variations of light intensity, time scales, and spatial scales

Molecular Phylogeny Restores the Supra-Generic Subdivision of Homoscleromorph Sponges (Porifera, Homoscleromorpha)

Homoscleromorpha is the fourth major sponge lineage, recently recognized to be distinct from the Demospongiae. It contains <100 described species of exclusively marine sponges that have been traditionally subdivided into 7 genera based on morphological characters. Because some of the morphological features of the homoscleromorphs are shared with eumetazoans and are absent in other sponges, the phylogenetic position of the group has been investigated in several recent studies. However, the phylogenetic relationships within the group remain unexplored by modern methods.Here we describe the first molecular phylogeny of Homoscleromorpha based on nuclear (18S and 28S rDNA) and complete mitochondrial DNA sequence data that focuses on inter-generic relationships. Our results revealed two robust clades within this group, one containing the spiculate species (genera Plakina, Plakortis, Plakinastrella and Corticium) and the other containing aspiculate species (genera Oscarella and Pseudocorticium), thus rejecting a close relationship between Pseudocorticium and Corticium. Among the spiculate species, we found affinities between the Plakortis and Plakinastrella genera, and between the Plakina and Corticium. The validity of these clades is furthermore supported by specific morphological characters, notably the type of spicules. Furthermore, the monophyly of the Corticium genus is supported while the monophyly of Plakina is not.As the result of our study we propose to restore the pre-1995 subdivision of Homoscleromorpha into two families: Plakinidae Schulze, 1880 for spiculate species and Oscarellidae Lendenfeld, 1887 for aspiculate species that had been rejected after the description of the genus Pseudocorticium. We also note that the two families of homoscleromorphs exhibit evolutionary stable, but have drastically distinct mitochondrial genome organizations that differ in gene content and gene order

Experimental and modelling study of dynamic powder compaction in the scope of DDT

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Oscarella lobularis (Homoscleromorpha, Porifera) Regeneration: Epithelial Morphogenesis and Metaplasia.

Sponges are known to possess remarkable reconstitutive and regenerative abilities ranging from common wounding or body part regeneration to more impressive re-building of a functional body from dissociated cells. Among the four sponge classes, Homoscleromorpha is notably the only sponge group to possess morphologically distinct basement membrane and specialized cell-junctions, and is therefore considered to possess true epithelia. The consequence of this peculiar organization is the predominance of epithelial morphogenesis during ontogenesis of these sponges. In this work we reveal the underlying cellular mechanisms used during morphogenesis accompanying ectosome regeneration in the homoscleromorph sponge model: Oscarella lobularis. We identified three main sources of novel exopinacoderm during the processes of its regeneration and the restoration of functional peripheral parts of the aquiferous system in O. lobularis: (1) intact exopinacoderm surrounding the wound surface, (2) the endopinacoderm from peripheral exhalant and inhalant canals, and (3) the intact choanoderm found on the wound surface. The basic morphogenetic processes during regeneration are the spreading and fusion of epithelial sheets that merge into one continuous epithelium. Transdifferentiation of choanocytes into exopinacocytes is also present. Epithelial-mesenchymal transition is absent during regeneration. Moreover, we cannot reveal any other morphologically distinct pluripotent cells. In Oscarella, neither blastema formation nor local dedifferentiation and proliferation have been detected, which is probably due to the high morphogenetic plasticity of the tissue. Regeneration in O. lobularis goes through cell transdifferentiation and through the processes, when lost body parts are replaced by the remodeling of the remaining tissue. Morphogenesis during ectosome regeneration in O. lobularis is correlated with its true epithelial organization. Knowledge of the morphological basis of morphogenesis during Oscarella regeneration could have important implications for our understanding of the diversity and evolution of regeneration mechanisms in metazoans, and is a strong basis for future investigations with molecular-biological approaches

NK homeobox genes with choanocyte-specific expression in homoscleromorph sponges.

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Diagram of transdifferentiation of the choanocytes (A) and successive steps of choanocyte layer transdifferentiation into a new exopinacoderm (B-D).

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134566#pone.0134566.g001" target="_blank">Fig 1</a> inset for the legends of (<b>B</b>). bm—basal membrane, f—flagellum, mv—microvilli, n—nucleus.</p

DNA synthesis in unwounded <i>Oscarella lobularis</i> (6 hours incubation with EdU); Z-stacks of confocal sections.

<p><b>A</b>. DNA synthesis in choanocytes. <b>B</b>. DNA synthesis in exopinacocytes. Insert: part of the exopinacoderm—labeled nucleus marked with arrowheads. EdU is red, DNA is green, tubulin is blue. cc—choanocyte chamber. Scale bar—15 μm.</p