Stina Svensson

The Human Skin Barrier Is Organized as Stacked Bilayers of Fully Extended Ceramides with Cholesterol Molecules Associated with the Ceramide Sphingoid Moiety

The skin barrier is fundamental to terrestrial life and its evolution; it upholds homeostasis and protects against the environment. Skin barrier capacity is controlled by lipids that fill the extracellular space of the skins surface layer--the stratum corneum. Here we report on the determination of the molecular organization of the skins lipid matrix in situ, in its near-native state, using a methodological approach combining very high magnification cryo-electron microscopy (EM) of vitreous skin section defocus series, molecular modeling, and EM simulation. The lipids are organized in an arrangement not previously described in a biological system-stacked bilayers of fully extended ceramides (CERs) with cholesterol molecules associated with the CER sphingoid moiety. This arrangement rationalizes the skins low permeability toward water and toward hydrophilic and lipophilic substances, as well as the skin barriers robustness toward hydration and dehydration, environmental temperature and pressure changes, stretching, compression, bending, and shearing.

Curve skeletonization of surface-like objects in 3D images guided by voxel classification

Skeletonization is a way to reduce dimensionality of digital objects. Here, we present an algorithm that computes the curve skeleton of a surface-like object in a 3D image, i.e., an object that in ...

Using distance transforms to decompose 3D discrete objects

Object decomposition into simpler parts greatly diminishes the complexity of a recognition task. In this paper, we present a method to decompose a 3D discrete object into nearly convex or elongated ...

On Reversible Skeletonization Using Anchor-Points from Distance Transforms

In many applications thinning of objects is of great interest. We here present a skeletonization algorithm that is based on the idea of iteratively thinning the distance transform of an object layer by layer until either an anchor-point is reached or the connectivity breaks. Our algorithm is general in the sense that any metric and any connectivity can be used. Also, it is based on ideas that are not specific for 2D. The properties of the resulting skeletons are evaluated according to the “Lee?Lam?Suen properties.”

The CEACAM1 N-terminal Ig domain mediates cis- and trans-binding and is essential for allosteric rearrangements of CEACAM1 microclusters

Structural analyses reveal that oligomerization between cell adhesion molecules in the same membrane is influenced by their interactions across opposing membranes (see also in this issue the accompanying paper by Müller et al.).

Digital distance transforms in 3D images using information from neighbourhoods up to 5 × 5 × 5

A 3D distance image, or a distance transform, is an image where each feature voxel is labeled with the distance to its closest nonfeature voxel. Distance transforms are useful for many binary (shape) image analysis tasks. The distance transform can be computed by propagating local distance information between neighboring voxels. In a weighted distance transform, the local distances are optimized to make the distance transform more stable under rotation: We present results from optimization for 3D images when using from one to six local distances, all in the 5 × 5 × 5 neighborhood of a voxel.

Simplifying curve skeletons in volume images

The curve skeleton of a 3D solid object provides a useful tool for shape analysis tasks. In this paper, we use a recent skeletonization algorithm based on voxel classification that originates a nearly thin, i.e., at most two-voxel thick, curve skeleton. We introduce a novel way to compress the nearly thin curve skeleton to one-voxel thickness, as well as an efficient pruning algorithm able to remove unnecessary skeleton branches without causing excessive loss of information. To this purpose, the pruning condition is based on the distribution of significant elements along skeleton branches. The definition of significance depends on the adopted skeletonization algorithm. In our case, it is derived from the voxel classification used during skeletonization.

Estimation of curvature along curves with application to fibres in 3D images of paper

Space curves can be used to represent elongated objects in 3D images and furthermore to facilitate the computation of shape measures for the represented objects. In our specific application (fibres in 3D images of paper), we want to analyze the fibre network on a voxel level with respect to elongation and bending. For this purpose, it is of interest to estimate the curvature in each voxel along a curve. We present a new discrete curvature estimator fulfilling the multigrid convergence property. Moreover, we present results from a study where curvature together with other shape measures are used to analyze the fibre network.

Surface Skeletons Detected on the D6 Distance Transform

We present an algorithm for extracting the surface skeleton of a 3D object from its D6 distance transform. The skeletal voxels are directly detected and marked on the distance transform within a small number of inspections, independent of object thickness. This makes the algorithm preferable with respect to algorithms based on iterative application of topology preserving removal operations, when working with thick objects. The set of skeletal voxels is centred within the object, symmetric, and topologically correct. It is at most 2-voxel wide (except for some cases of surface intersections) and includes all centres of maximal D6 balls, which makes skeletonization reversible. Reduction to a unit wide surface skeleton can be obtained by suitable post-processing.

Note on the multiscale representation of 2D and 3D shapes

Abstract Binary pyramids in two and three dimensions can be used for multiresolution representation. The “standard” OR and AND pyramids have serious drawbacks, as they distort the shape significantly; therefore they can seldom be used effectively. Here we present alternative approaches to build binary pyramids, aimed at improving shape preservation (and, as far as possible, topology preservation) in lower resolutions. The algorithms are easy to implement and produce good results.