Abstract Localized tephra deposition in marine sequences is the product of many complex primary and secondary depositional processes. These can significantly influence the potential applicability of tephra deposits as isochronous marker horizons and current techniques, used in isolation, may be insufficient to fully unravel these processes. Here we demonstrate the innovative application of X‐ray microtomography (µCT) to successfully identify tephra deposits preserved within marine sediments and use these parameters to reconstruct their internal three‐dimensional structure. Three‐dimensional visualizations and animations of tephra dispersal in the sediment permit a more thorough assessment of postdepositional processes revealing a number of complex microsedimentological features that are not revealed by conventional methods. These features include bioturbation burrows and horizontally discontinuous tephra packages, which have important ramifications for the stratigraphic placement of the isochron in a sedimentary sequence. Our results demonstrate the potential for utilizing rigorous two and three‐dimensional microsedimentological analysis of the ichnofabric to enhance and support the use of tephra deposits as isochronous marker horizons and to identify the stratigraphic position that best reflects the primary fallout of ash. The application also provides an exceptional insight into the style and rate of sedimentation processes and permits an assessment of the stratigraphic integrity of a tephra deposit. We discuss the possibility of applying these µCT methods to the identification of cryptotephras within various paleoclimatic sequences and to enhance our understanding of marine sedimentation processes.
Bite forces play a key role in animal ecology: they affect mating behaviour, fighting success, and the ability to feed. Although feeding habits of arthropods have a significant ecological and economical impact, we lack fundamental knowledge on how the morphology and physiology of their bite apparatus controls bite performance, and its variation with mandible gape. To address this gap, we derived a biomechanical model that characterizes the relationship between bite force and mandibular opening angle from first principles. We validate this model by comparing its geometric predictions with morphological measurements on the muscoloskeletal bite apparatus of Atta cephalotes leaf-cutter ants, using computed tomography (CT) scans obtained at different mandible opening angles. We then demonstrate its deductive and inductive utility with three examplary use cases: Firstly, we extract the physiological properties of the leaf-cutter ant mandible closer muscle from in vivo bite force measurements. Secondly, we show that leaf-cutter ants are specialized to generate extraordinarily large bite forces, equivalent to about 2600 times their body weight. Thirdly, we discuss the relative importance of morphology and physiology in determining the magnitude and variation of bite force. We hope that a more detailed quantitative understanding of the link between morphology, physiology, and bite performance will facilitate future comparative studies on the insect bite apparatus, and help to advance our knowledge of the behaviour, ecology and evolution of arthropods.
Journal Article Great White Pelican Mandible as Bioinspiration for Vehicle Design - Structural Bioprospecting Via X-Ray Micro-CT and Finite Element Analysis Get access Nicola C Thomas, Nicola C Thomas Faculty of Science and Engineering, Swansea University, Swansea, UK Search for other works by this author on: Oxford Academic Google Scholar William Harrison, William Harrison Faculty of Science and Engineering, Swansea University, Swansea, UK Search for other works by this author on: Oxford Academic Google Scholar Caroline Buttler, Caroline Buttler Natural Sciences, Amgueddfa Cymru – National Museum Wales, Cardiff, UK Search for other works by this author on: Oxford Academic Google Scholar Richard E Johnston Richard E Johnston Faculty of Science and Engineering, Swansea University, Swansea, UK Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 212–214, https://doi.org/10.1017/S1431927622001702 Published: 01 August 2022
Abstract Timber is the only widely used construction material we can grow. The wood from which it comes has evolved to provide structural support for the tree and to act as a conduit for fluid flow. These flow paths are crucial for engineers to exploit the full potential of timber, by allowing impregnation with liquids that modify the properties or resilience of this natural material. Accurately predicting the transport of these liquids enables more efficient industrial timber treatment processes to be developed, thereby extending the scope to use this sustainable construction material; moreover, it is of fundamental scientific value — as a fluid flow within a natural porous medium. Both structural and transport properties of wood depend on its micro-structure but, while a substantial body of research relates the structural performance of wood to its detailed architecture, no such knowledge exists for the transport properties. We present a model, based on increasingly refined geometric parameters, that accurately predicts the time-dependent ingress of liquids within softwood timber, thereby addressing this long-standing scientific challenge. Moreover, we show that for the minimalistic parameterisation the model predicts ingress with a square-root-of-time behaviour. However, experimental data show a potentially significant departure from this $$\sqrt{{\boldsymbol{t}}}$$ t behaviour — a departure which is successfully predicted by our more advanced parametrisation. Our parameterisation of the timber microstructure was informed by computed tomographic measurements; model predictions were validated by comparison with experimental data. We show that accurate predictions require statistical representation of the variability in the timber pore space. The collapse of our dimensionless experimental data demonstrates clear potential for our results to be up-scaled to industrial treatment processes.
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Poster presented at ToScA 2015 (Tomography for Scientific Advancement conference) held at Manchester University.
The poster outlines preliminary studies applying x-ray microtomography to the analysis of volcanic ash horizons preserved in lake sediments. This work has application to the field of tephrochronology, the study of volcanic ash (tephra) to determine the age, either relative or absolute, of sedimentary deposits.
This work relates to a larger project investigating the effect of sedimentary reworking on the position of the tephra isochrons.
This is a Swansea University funded project using equipment at Swansea's AIM facility.
This poster has a lightening talk associated with it found in the links below.
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