Search

In this chapter we describe computer-based tomographic methods using magnetic resonance imaging (MRI) and X-ray absorption as well as Xray phase-contrast imaging techniques. The latter are based on refraction and near-field diffraction of X-rays and are gaining increased attention due to the increase in sensitivity they offer over conventional, attenuationbased X-ray techniques. The increased sensitivity is of particular interest in marine biology imaging, especially for soft tissue visualization and analysis. The basic principles of the imaging techniques are described, starting with an analysis of the image formation process, followed by a review of several tomography methods, such as MRI or X-ray imaging, and practical guidelines for parameter selection. Finally, two relevant examples of imaging are presented: imaging in marine biology (segmentation and visualization) and small animal (sea horse) imaging. These examples illustrate imaging under different conditions and using different reconstruction options.

Seahorses are intriguing fishes for several reasons, one being their prehensile tail. Syngnathid fishes, to which seahorses, pipefish, seadragons and pipehorses belong, are characterised by a body armour of bony plates. They form a serially articulated system that encloses the vertebral column and its musculature. In the ancestral condition, as in pipefish, the tail is straight with limited flexibility, and mainly used for steering (pectorals and dorsal used for swimming). During evolution, the tail became modified into a grasping apparatus multiple times independently within the syngnathid family. Less known than the seahorse prehensile capabilities, pipehorses also show different morphologies related to grasping performance. To better understand the structural basis of tail grasping mechanics, a parameterized model of the seahorse tail was developed. By combining multibody dynamics analysis with finite element analysis, we analysed the implication of partial contribution of epaxial and hypaxial muscles, versus ventral median muscle, as well as that of the bony plate geometry. Natural bending postures, as observed in living seahorses, can be obtained up to some degree. The analyses showed particular relations between morphology and bending kinematics. Using this seahorse model, functional implications of evolutionary changes in in syngnathid tails can be further analysed, as well as to develop biomimetic designs of serially articulated systems that meet particular application demands.

The current paper emphasizes on the effect of internal yarn nesting (shifting) on the local structural response, such as, local stress - strain and the local damage of a satin weave composite. Detailed study of the variation of the local stress – strain behavior in the plies of a satin weave composite leads to the following conclusions: 1) local longitudinal strain in the plies of a satin weave composite is not influenced by the internal yarn nesting of the adjacent plies (position of the ply in the laminate); 2) local transverse stress as well as the weft yarn transverse damage is sensitive to the position of the ply in the laminate.