Phenomenological analysis of constrained in-plane compression of paperboard using micro-computed tomography Imaging

Large deformations under in-plane compression of paperboard appear in forming processes like hydroforming, pressforming and deep drawing, but the mechanisms of deformation have not been studied on a micromechanical level. A constrained in-plane compression test is presented. This test allows for in-plane compression, buckling, wrinkling and compaction. The constrained compression test is realized using a DEBEN CT-500 in-situ tester for laboratory microtomography and synchrotron microtomography. Experiments with five different materials spanning from laboratory handsheets to commercially available multi-layered paperboards are performed. Image processing is used to observe the local out-of-plane fiber orientation and compaction. A phenomenological investigation of the deformation behavior of these materials is presented. Delamination is found to be the primary mechanisms of failure in the multi-layered boards. Furthermore, a porous network structure, created by using long and minimally refined softwood fibers, is found to facilitate the formation of uniform wrinkles and compaction.

A myriad of melt inclusions: a synchrotron microtomography study of melt inclusions and vapour bubbles from Colli Albani (Italy)

<p>Melt inclusions provide a window into the inner workings of magmatic systems. Both mineral chemistry and volatile distributions within melt inclusions can provide valuable information about the processes modulating magma ascent and preceding volcanic eruptions. Many melt inclusions host vapour bubbles which can be rich in CO<sub>2</sub> and H<sub>2</sub>O and must be taken into consideration when assessing the volatile budget of magmatic reservoirs. These vapour bubbles can be the product of differential volumetric contraction between the melt inclusion and host phase during an eruption or indicate an excess fluid phase in the magma reservoir. Thus, determining the distribution of volatiles between melt and vapour bubbles is integral to our fundamental understanding of melt inclusions, and by extension the evolution of volatiles within magmatic systems.</p><p>A large dataset of 79 high-resolution tomographic scans of clinopyroxene and leucite phenocrysts from the Colli Albani Caldera Complex (Italy) was recently acquired at the German Electron Synchrotron (DESY). These tomograms allow us to quantify the volume of melt inclusions and associated vapour bubble both glassy and microcrystalline melt inclusions. Notably, in the glassy melt inclusions the vapour bubbles exist either as a single large vapour bubble in the middle of the melt inclusion or as several smaller vapour bubbles distributed around the edge of the melt inclusion. These two types of melt inclusions can coexist within a single crystal. We suggest that the occurrence of these rim- bubbles is caused by one of two exsolution pathways, either pre-entrapment and bubble migration or post entrapment with preferential exsolution at the rims. By combining the analysis of hundreds of melt inclusions with the chemistry of the host phase we aim to unveil magma ascent rates and distribution of excess fluids within the magmatic system of Colli Albani, which produced several mafic-alkaline large volume ignimbrites.</p>

The developmental relationship between teeth and dermal odontodes in the most primitive bony fish Lophosteus

The ontogenetic trajectory of a marginal jawbone of Lophosteus superbus (Late Silurian, 422 Million years old), the phylogenetically most basal stem osteichthyan, visualized by synchrotron microtomography, reveals a developmental relationship between teeth and dermal odontodes that is not evident from the adult morphology. The earliest odontodes are two longitudinal founder ridges formed at the ossification center. Subsequent odontodes that are added lingually to the ridges turn into conical teeth and undergo cyclic replacement, while those added labially achieve a stellate appearance. Stellate odontodes deposited directly on the bony plate are aligned with the alternate files of teeth, whereas new tooth positions are inserted into the files of sequential addition when a gap appears. Successive teeth and overgrowing odontodes show hybrid morphologies around the oral-dermal boundary, suggesting signal cross-communication. We propose that teeth and dermal odontodes are modifications of a single system, regulated and differentiated by the oral and dermal epithelia.