Article
Snakes With an EllipseReproducing Property
Biomed. Imaging Group, Ecole Polytech. federate de Lausanne, Lausanne, Switzerland
IEEE Transactions on Image Processing (Impact Factor: 3.2). 04/2012; DOI: 10.1109/TIP.2011.2169975 Source: DBLP

Conference Paper: Bilateral smoothing of gradient vector field and application to image segmentation
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ABSTRACT: Medical image segmentation finds application in computeraided diagnosis, computerguided surgery, measuring tissue volumes, locating tumors, and pathologies. One approach to segmentation is to use active contours or snakes. Active contours start from an initialization (often manually specified) and are guided by imagedependent forces to the object boundary. Snakes may also be guided by gradient vector fields associated with an image. The first main result in this direction is that of Xu and Prince, who proposed the notion of gradient vector flow (GVF), which is computed iteratively. We propose a new formalism to compute the vector flow based on the notion of bilateral filtering of the gradient field associated with the edge map  we refer to it as the bilateral vector flow (BVF). The range kernel definition that we employ is different from the one employed in the standard Gaussian bilateral filter. The advantage of the BVF formalism is that smooth gradient vector flow fields with enhanced edge information can be computed noniteratively. The quality of image segmentation turned out to be on par with that obtained using the GVF and in some cases better than the GVF.Image Processing (ICIP), 2012 19th IEEE International Conference on; 01/2012  [Show abstract] [Hide abstract]
ABSTRACT: Our interest is to characterize the splinelike integershiftinvariant bases capable of reproducing exponential polynomial curves. We prove that any compactsupport function that reproduces a subspace of the exponential polynomials can be expressed as the convolution of an exponential Bspline with a compactsupport distribution. As a direct consequence of this factorization theorem, we show that the minimalsupport basis functions of that subspace are linear combinations of derivatives of exponential Bsplines. These minimalsupport basis functions form a natural multiscale hierarchy, which we utilize to design fast multiresolution algorithms and subdivision schemes for the representation of closed geometric curves. This makes them attractive from a computational point of view. Finally, we illustrate our scheme by constructing minimalsupport bases that reproduce ellipses and higherorder harmonic curves.Computer Aided Geometric Design. 01/2012; 29:109128. 
Article: Divergent ChemosymbiosisRelated Characters in Thyasira cf. gouldi (Bivalvia: Thyasiridae).
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ABSTRACT: Within the marine bivalve family Thyasiridae, some species have bacterial chemosymbionts associated with gill epithelial cells while other species are asymbiotic. Although the abundance of symbionts in a particular thyasirid species may vary, the structure of their gills (i.e., their frontalabfrontal thickening) does not. We examined gill structure in a species tentatively identified as Thyasira gouldi from a Northwest Atlantic fjord (Bonne Bay, Newfoundland) and found remarkable differences among specimens. Some individuals had thickened gill filaments with abundant symbionts, while others had thin filaments and lacked symbionts. We could differentiate symbiotic and asymbiotic specimens based on the size and outline of their shell as well as 18S rRNA, 28S rRNA and CO1 sequences. The wide morphological, genetic and symbiosisrelated disparity described herein suggests that chemosymbiosis may influence host divergence, and that Thyasira gouldi forms a cryptic species complex.PLoS ONE 01/2014; 9(3):e92856. · 3.53 Impact Factor
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