The whole mesh Deformation Model for 2D and 3D image segmentation

In this paper we present a novel approach for image segmentation using Active Nets and Active Volumes. Those solutions are based on the Deformable Models, with slight difference in the method for describing the shapes of interests - instead of using a contour or a surface they represented the segmented objects with a mesh structure, which allows to describe not only the surface of the objects but also to model their interiors. This is obtained by dividing the nodes of the mesh in two categories, namely internal and external ones, which will be responsible for two different tasks. In our new approach we propose to negate this separation and use only one type of nodes. Using that assumption we manage to significantly shorten the time of segmentation while maintaining its quality

Active contour segmentation with a parametric shape prior: Link with the shape gradient

International audienceActive contours are adapted to image segmentation by energy minimization. The energies often exhibit local minima, requiring regularization. Such an a priori can be expressed as a shape prior and used in two main ways: (1) a shape prior energy is combined with the segmentation energy into a trade-off between prior compliance and accuracy or (2) the segmentation energy is minimized in the space defined by a parametric shape prior. Methods (1) require the tuning of a data-dependent balance parameter and methods (1) and (2) are often dedicated to a specific prior or contour representation, with the prior and segmentation aspects often meshed together, increasing complexity. A general framework for category (2) is proposed: it is independent of the prior and contour representations and it separates the prior and segmentation aspects. It relies on the relationship shown here between the shape gradient, the prior-induced admissible contour transformations, and the segmentation energy minimization

Mechanistic and pathological study of the genesis, growth, and rupture of abdominal aortic aneurysms

Postprint (published version

An adaptive preconditioner for steady incompressible flows

This paper describes an adaptive preconditioner for numerical continuation of incompressible Navier--Stokes flows. The preconditioner maps the identity (no preconditioner) to the Stokes preconditioner (preconditioning by Laplacian) through a continuous parameter and is built on a first order Euler time-discretization scheme. The preconditioner is tested onto two fluid configurations: three-dimensional doubly diffusive convection and a reduced model of shear flows. In the former case, Stokes preconditioning works but a mixed preconditioner is preferred. In the latter case, the system of equation is split and solved simultaneously using two different preconditioners, one of which is parameter dependent. Due to the nature of these applications, this preconditioner is expected to help a wide range of studies

Surface Reconstruction from Noisy and Sparse Data

We introduce a set of algorithms for registering, filtering and measuring the similarity of unorganized 3d point clouds, usually obtained from multiple views. We contribute a method for computing the similarity between point clouds that represent closed surfaces, specifically segmented tumors from CT scans. We obtain watertight surfaces and utilize volumetric overlap to determine similarity in a volumetric way. This similarity measure is used to quantify treatment variability based on target volume segmentation both prior to and following radiotherapy planning stages. We also contribute an algorithm for the drift-free registration of thin, non- rigid scans, where drift is the build-up of error caused by sequential pairwise registration, which is the alignment of each scan to its neighbor. We construct an average scan using mutual nearest neighbors, each scan is registered to this average scan, after which we update the average scan and continue this process until convergence. The use case herein is for merging scans of plants from multiple views and registering vascular scans together. Our final contribution is a method for filtering noisy point clouds, specif- ically those constructed from merged depth maps as obtained from a range scanner or multiple view stereo (MVS), applying techniques that have been utilized in finding outliers in clustered data, but not in MVS. We utilize ker- nel density estimation to obtain a probability density function over the space of observed points, utilizing variable bandwidths based on the nature of the neighboring points, Mahalanobis and reachability distances that is more dis- criminative than a classical Mahalanobis distance-based metric

Mud bank biology

Mud banks are unique, clearly demarked naturally occurring calm areas which occur mainly in the inshore waters along the Kerala coast during the southwest monsoon period. Formation of mud banks can be either just before the onset of SW monsoon or during the monsoon. Mud banks are popularly known as “Chakara” or “Shanthakara “ (meaning calm area) and fishermen consider mud banks as ‘gift of God’ since these are safe fishing areas for launching and berthing the fishing crafts when the rest of coastal belt is surf ridden, with high swells and unsuitable for small scale fishing operations

Afghanistan

Since 1905 Britain had paid the Afghan ruler, Amir Habibullah, a subsidy and had controlled Afghanistan's foreign relations, and he maintained Afghanistan's neutrality throughout WWI in spite of strong pressure to induce him to join the Central Powers. The war did not have much of an impact on most Afghans (although there were shortages of some commodities), but many died in the global influenza outbreak which began in 1918. When the war ended Britain failed to reward the Amir for his refusal to take advantage of British weakness during it, and he was assassinated early in 1919. His successor, Amir Amanullah, launched the third Anglo-Afghan War, following which the country became fully independent, but Amanullah's hasty modernization was to lead to his overthrow in 1929

Finite-element modelling of mechanobiological factors influencing sesamoid tissue morphology in the patellar tendon of an ostrich

The appearance and shape of sesamoid bones within a tendon or ligament wrapping around a joint are understood to be influenced by both genetic and epigenetic factors. Ostriches (Struthio camelus) possess two sesamoid patellae (kneecaps), one of which (the distal patella) is unique to their lineage, making them a good model for investigating sesamoid tissue development and evolution. Here we used finite-element modelling to test the hypothesis that specific mechanical cues in the ostrich patellar tendon favour the formation of multiple patellae. Using three-dimensional models that allow application of loading conditions in which all muscles, or only distal or only proximal muscles to be activated, we found that there were multiple regions within the tendon where transformation from soft tissue to fibrocartilage was favourable and therefore a potential for multiple patellae based solely upon mechanical stimuli. While more studies are needed to better understand universal mechanobiological principles as well as full developmental processes, our findings suggest that a tissue differentiation algorithm using shear strain and compressive strain as inputs may be a roughly effective predictor of the tissue differentiation required for sesamoid development

River Otter in Arkansas. IV. Winter Food Habits in Eastern Arkansas

Stomachs and intestines of 89 river otters (Lutra canadensis) collected in eastern Arkansas during the trapping seasons (December- January) of 1978-1983 were examined for food remains. Fish (primarily centrarchids, catostomids, and clupeids) dominated the diet (71.2%). The next most abundant prey was crayfish (18.3% of the diet). Other foods included gray squirrel (Sciurus carolinensis), wood duck (Aixsponsa), snakes (Thamnophis proximus), frogs (Ranidae and Hylidae), and beetles (Coleoptera)