Post-processing technique for improved assessment of hard tissues in the submicrometer domain using local synchrotron radiation-based computed tomography

During the last two decades micro-computed tomography has become the method of choice for the non-destructive assessment and quantitative morphometry of hard tissues in three dimensions. With the advent of third-generation synchrotron radiation sources, micro-computed tomography in the micrometer range has become feasible and has been employed to analyze local bone tissue properties. However, owing to limitations regarding the tradeoff between object size and spatial resolution, non-destructive conventional global computed tomography of hard tissues, such as bone, remains unachievable in the submicrometer domain so far. Here, we report on a post-processing technique for the assessment of hard tissues using local synchrotron radiation-based computed tomography, which overcomes this experimental limitatio

A Charcoalified Ovule Adapted for Wind Dispersal and Deterring Herbivory from the Late Viséan (Carboniferous) of Scotland

International audiencePremise of research : Mississippian (Lower Carboniferous) anatomically preserved ovules are pivotal to our present understanding of the Paleozoic primary seed plant radiation, but few are known from the late Viséan stratigraphic interval approximately 330 million years ago. Here, we document an exceptionally well-preserved mesoscopic charcoalified ovule from late Viséan limestones that is adapted for wind dispersal and for deterring herbivory.Methodology : We use synchrotron radiation X-ray tomographic microscopy (SRXTM) and low-vacuum scanning electron microscopy (LVSEM) to analyze histological features not identifiable through traditional methods.Pivotal results:The ovule is small, 2 mm long and 1.25 mm in maximum diameter, and has a dense covering of spirally arranged, long, slender, hollow hairs with glandular apexes and a distal papilla. The nucellus is fused to the integument up to the nucellar apex, and above this, the integument comprises eight apical lobes, each with a single vascular bundle. The nucellar apex has a domed pollen chamber and large central column characteristic of hydrasperman-type (lagenostomalean) pteridosperms, but it lacks the distal salpinx seen in most hydrasperman ovules, leaving an exposed distal opening to the pollen chamber for pollination. Differences with existing taxa lead to the erection of Hirsutisperma rothwellii gen. et sp. nov.Conclusions : The apical glands presumably functioned as granivory deterrents; coprolites (fossilized feces) from herbivorous arthropods are abundant in the fossiliferous horizon and at this stratigraphic interval. The small ovule size and its dense covering of hairs indicate Hirsutisperma was adapted for wind dispersal and was an r-selected species, producing large numbers of small offspring in unstable or changing environments. Taphonomic implications are discussed, including preservational biases for charcoalification. Hirsutisperma provides the first clear evidence for ecological niche partitioning in Mississippian hydrasperman-type ovules

Application areas of synchrotron radiation tomographic microscopy for wood research

Possible applications for synchrotron radiation tomographic microscopy in the field of wood research were tested and evaluated at the TOMCAT beamline (TOmographic Microscopy and Coherent rAdiology experimenTs) at the Swiss Light Source (SLS) at the Paul Scherrer Institute (Villigen, Switzerland). For this study, small cylindrical samples (∅ 1 and 3mm) were examined with different experimental setups resulting in a nominal voxel size of approximately 1.48×1.48×1.48 and 3.7×3.7×3.7μm3, respectively. Suitability of the TOMCAT microscope for 3D investigations of wood anatomy was tested on several softwood and hardwood species revealing microscopic features (e.g. tyloses, wall thickenings or pits) down to the nominal pixel size. The results suggest that even features in the sub-voxel range can be made visible. Tomographic microscopy was also tested for wood technological applications, i.e. penetration behaviour of a wood preservative and also of three wood adhesives (poly-urethane resins) with different viscosities. Although the experiments with the preservative yielded no clear results, the method seems suitable for examining the penetration of the different adhesives. The adhesive penetrates the wood mainly by the vessels where it can be easily discerned from the wood structur

Synchrotron-based tomographic microscopy (SbTM) of wood: development of a testing device and observation of plastic deformation of uniaxially compressed Norway spruce samples

To understand better the structure-property relationships of wood in situ, nondestructive synchrotron-based tomographic microscopy (SbTM) with subcellular resolution is useful. In this context, an in situ testing device was developed to determine the cellular response of wood to mechanical loading. Different rotationally symmetric specimens were tested to synchronize the failure areas to the given scanning areas. Norway spruce samples were uniaxially compressed in the longitudinal direction and scanned in situ at several increasing relative forces ending up in the plastic deformation regime. A sufficiently high quality in situ tomography was demonstrated. The reconstructed data allowed the observation of the load-dependent development of failure regions: cracks and buckling on the microstructure were clearly visible. Future investigations with SbTM on different wood species, loading directions, and different moisture contents are promising in terms of the micromechanical behavior of woo

A comparative study of X-ray tomographic microscopy on shales at different synchrotron facilities: ALS, APS and SLS.

Synchrotron radiation X-ray tomographic microscopy (SRXTM) was used to characterize the three-dimensional microstructure, geometry and distribution of different phases in two shale samples obtained from the North Sea (sample N1) and the Upper Barnett Formation in Texas (sample B1). Shale is a challenging material because of its multiphase composition, small grain size, low but significant amount of porosity, as well as strong shape- and lattice-preferred orientation. The goals of this round-robin project were to (i) characterize microstructures and porosity on the micrometer scale, (ii) compare results measured at three synchrotron facilities, and (iii) identify optimal experimental conditions of high-resolution SRXTM for fine-grained materials. SRXTM data of these shales were acquired under similar conditions at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory, USA, the Advanced Photon Source (APS) of Argonne National Laboratory, USA, and the Swiss Light Source (SLS) of the Paul Scherrer Institut, Switzerland. The data reconstruction of all datasets was handled under the same procedures in order to compare the data quality and determine phase proportions and microstructures. With a 10× objective lens the spatial resolution is approximately 2 µm. The sharpness of phase boundaries in the reconstructed data collected from the APS and SLS was comparable and slightly more refined than in the data obtained from the ALS. Important internal features, such as pyrite (high-absorbing), and low-density features, including pores, fractures and organic matter or kerogen (low-absorbing), were adequately segmented on the same basis. The average volume fractions of low-density features for sample N1 and B1 were estimated at 6.3 (6)% and 4.5 (4)%, while those of pyrite were calculated to be 5.6 (6)% and 2.0 (3)%, respectively. The discrepancy of data quality and volume fractions were mainly due to different types of optical instruments and varying technical set-ups at the ALS, APS and SLS

Propagation-based phase-contrast synchrotron imaging of aortic dissection in mice : from individual elastic lamella to 3D analysis

In order to show the advantage and potential of propagation-based phase-contrast synchrotron imaging in vascular pathology research, we analyzed aortic medial ruptures in BAPN/AngII-infused mice, a mouse model for aortic dissection. Ascending and thoraco-abdominal samples from n = 3 control animals and n = 10 BAPN/AngII-infused mice (after 3, 7 and 14 days of infusion, total of 24 samples) were scanned. A steep increase in the number of ruptures was already noted after 3 days of BAPN/AngII-infusion. The largest ruptures were found at the latest time points. 133 ruptures affected only the first lamella while 135 ruptures affected multiple layers. Medial ruptures through all lamellar layers, leading to false channel formation and intramural hematoma, occurred only in the thoraco-abdominal aorta and interlamellar hematoma formation in the ascending aorta could be directly related to ruptures of the innermost lamellae. The advantages of this technique are (i) ultra-high resolution that allows to visualize the individual elastic lamellae in the aorta; (ii) quantitative and qualitative analysis of medial ruptures; (iii) 3D analysis of the complete aorta; (iv) high contrast for qualitative information extraction, reducing the need for histology coupes; (v) earlier detection of (micro-) ruptures

Failure and failure mechanisms of wood during longitudinal compression monitored by synchrotron micro-computed tomography

The lasting plastic deformation of the cellular elements of beech, fir, and spruce wood under uniaxial compression has been investigated by the combination of in situ loading and synchrotron micro-computed tomography. The deformation of singular elements embedded in the tissue and their influence on the deformation lines and surrounding tissue was examined by tomographic reconstructions. An automatic observation of the failure area was applied in the case of the softwoods, which permitted the determination of the densification degree. The development of failure lines differed from the expected pattern by often showing branching. However, the 3D observations confirmed the effects known from 2D examinations in many cases