Search

Premise of the study: Fossilized seeds similar to Cissus (Vitaceae) have been recognized from the Miocene of Kenya, though some were previously assigned to the Menispermaceae. We undertook a comparative survey of extant African Cissus seeds to identify the fossils and consider their implications for the evolution and biogeography of Cissus and for African early Miocene paleoenvironments. Methods: Micro-computed tomography (µCT) and synchrotron-based X-ray tomographic microscopy (SRXTM) were used to study seed morphology and anatomy. Virtual taphonomy, using SRXTM data sets, produced digital fossils to elucidate seed taphonomy. Phylogenetic relationships within Cissus were reconstructed using existing and newly produced DNA sequences for African species. Paleobiology and paleoecology were inferred from African nearest living relatives. Key results: The fossils were assigned to four new Cissus species, related to four modern clades. The fossil plants were interpreted as climbers inhabiting a mosaic of riverine woodland and forest to more open habitats. Virtual taphonomy explained how complex mineral infill processes concealed key seed features, causing the previous taxonomic misidentification. Newly sampled African species, with seeds most similar to the fossils, belong to four clades within core Cissus, two of which are early diverging. Conclusions: Virtual taphonomy, combined with X-ray imaging, has enabled recognition of the first fossil Cissus and Vitaceae from Africa. Early-divergent members of the core Cissus clade were present in Africa by at least the early Miocene, with an African origin suggested for the Cissus sciaphila clade. The fossils provide supporting evidence for mosaic paleoenvironments inhabited by early Miocene hominoids.

Premise of research. Reproductive structures of modern genera of heterosporous water ferns (Marsileaceae and Salviniaceae) are widespread and abundant in plant mesofossil assemblages from the Paleogene. For Salviniaceae, whole fertile fossil plants give a good understanding of morphology. These fossils can be applied in paleoenvironmental analysis and to study water fern origin, evolution, and diversification. Methodology. New specimens were examined by SEM and TEM. Synchrotron x-ray tomographic microscopy (SRXTM) is evaluated as a nondestructive tool for investigating Azolla Lam. morphology. Pivotal results. Azolla anglica Martin and Salvinia cobhamii Martin (earliest Eocene, United Kingdom) are fully characterized using SEM and TEM. SRXTM enables digital rendering of the float system in Azolla, but individual floats are difficult to distinguish. Modern water fern genera characterize the Paleogene, but extinct sister taxa characterize the Cretaceous. Literature review documents that water ferns are intolerant of salinity over 5 psu. Conclusions. The oldest fully documented Salvinia Séguier sori and spores occur in earliest Eocene deposits at Cobham, United Kingdom, probably linked to warm climates. An unusual co-occurrence of Salvinia with Azolla is preserved at this site. The Azolla species differs from those present in the same region during other Eocene warm-climate intervals. SRXTM offers potential to retrieve taxonomically useful information on internal structures of Azolla. There is a major turnover in water ferns (dominantly extinct to almost entirely modern genera) across the Cretaceous-Paleogene transition. The utility of water ferns as indicator taxa is exemplified by recognition of freshwater ocean surfaces and widespread continental wetlands during the latest Early to earliest Middle Eocene in and around the Arctic and Nordic Seas.

Full-field X-ray microscopy is a valuable tool for 3D observation of biological systems. In the soft X-ray domain organelles can be visualized in individual cells while hard X-ray microscopes excel in imaging of larger complex biological tissue. The field of view of these instruments is typically 10(3) times the spatial resolution. We exploit the assets of the hard X-ray sub-micrometer imaging and extend the standard approach by widening the effective field of view to match the size of the sample. We show that global tomography of biological systems exceeding several times the field of view is feasible also at the nanoscale with moderate radiation dose. We address the performance issues and limitations of the TOMCAT full-field microscope and more generally for Zernike phase contrast imaging. Two biologically relevant systems were investigated. The first being the largest known bacteria (Thiomargarita namibiensis), the second is a small myriapod species (Pauropoda sp.). Both examples illustrate the capacity of the unique, structured condenser based broad-band full-field microscope to access the 3D structural details of biological systems at the nanoscale while avoiding complicated sample preparation, or even keeping the sample environment close to the natural state.

Understanding the transport properties of porous materials plays an important role in the development and optimization of polymer electrolyte fuel cells (PEFCs). in this study numerical simulations of different transport properties are compared and validated with data obtained using recently developed experimental techniques. The study is based oil a Toray TGP-H-060 carbon paper, a common gas diffusion layer (GDL) material in PEFC. Diffusivity, permeability, and electric conductivity of the anisotropic, porous material are measured experimentally under various levels of compression. A sample of the GDL is imaged with synchrotron-based X-ray tomography under three different compression levels. Based oil these three-dimensional images, diffusivity, permeability, and conductivity are calculated numerically. Experimental and numerical results agree in general. Deviations are observed for the through-plane conductivity. An explanation for the discrepancy is presented and affirmed by numerical simulations on a virtually created structure model. This proves that numerical simulation based oil tomography data is a versatile tool for the investigation and development of porous structures used in PEFCs.

Wood Science and Technology, 44 (1), ISSN:0043-7719, ISSN:1432-5225

Phase-sensitive X-ray imaging methods can provide substantially increased contrast over conventional absorption-based imaging, and therefore new and otherwise inaccessible information. Differential phase-contrast (DPC) imaging, which uses a grating interferometer and a phase-stepping technique, has been integrated into TOMCAT, a beamline dedicated to tomographic microscopy and coherent radiology experiments at the Swiss Light Source. Developments have been made focusing on the fast acquisition and post-processing of data to enable a high-throughput of samples, with obvious advantages, also through increasing the efficiency of the detecting system, of helping to reduce radiation dose imparted to the sample. A novel aquarium design allows a vertical rotation axis below the sample with measurements performed in aqueous environment. Optimization of the data acquisition procedure enables a full phase volume (1024 X 1024 pixels X 1000 projections X 9 phase steps, i.e. 9000 projections in total) to be acquired in 20 min (with a pixel size of 7.4 mm), and the subsequent post-processing has been integrated into the beamline pipeline for sinogram generation. Local DPC tomography allows one to focus with higher magnification on a particular region of interest of a sample without the presence of local tomography reconstruction artifacts. Furthermore, 'widefield' imaging is shown for DPC scans for the first time, enabling the field of view of the imaging system to be doubled for samples that are larger than the magnification allows. A case study is illustrated focusing on the visualization of soft tissue features, and particularly the substantia nigra of a rat brain. Darkfield images, based on local X-ray scattering, can also be extracted from a grating-based DPC scan: an example of the advantages of darkfield contrast is shown and the potential of darkfield X-ray tomography is discussed. (C) 2009 International Union of Crystallography Printed in Singapore - all rights reserved

The potential of X-rays for the non-invasive investigation of the interior of bulky samples has long been recognized and their penetration depth is presently widely exploited [1]. Although initially third generation synchrotron sources were almost exclusively the realm of academic scientific experiments, the use of synchrotron light for industrial research is becoming increasingly important and relevant for both technology development and non-destructive testing, in particular when the requirements in terms of spatial, temporal, and density resolution are exceptional.