Anton du Plessis

Functional trade-off between strength and thermal capacity of dermal armor: Insights from girdled lizards

The presence of dermal armor is often unambiguously considered the result of an evolutionary predator-prey arms-race. Recent studies focusing predominantly on osteoderms - mineralized elements embedded in the dermis layer of various extant and extinct vertebrates - have instead proposed that dermal armor might exhibit additional functionalities besides protection. Multiple divergent functionalities could impose conflicting demands on a phenotype, yet, functional trade-offs in dermal armor have rarely been investigated. Here, we use high-resolution micro-computed tomography and voxel-based simulations to test for a trade-off between the strength and thermal capacity of osteoderms using two armored cordylid lizards as model organisms. We demonstrate that high vascularization, associated with improved thermal capacity might limit the strength of osteoderms. These results call for a holistic, cautionary future approach to studies investigating dermal armor, especially those aiming to inspire artificial protective materials.

Laboratory X-ray micro-computed tomography : a user guideline for biological samples

Abstract Laboratory x-ray micro–computed tomography (micro-CT) is a fast-growing method in scientific research applications that allows for non-destructive imaging of morphological structures. This paper provides an easily operated “how to” guide for new potential users and describes the various steps required for successful planning of research projects that involve micro-CT. Background information on micro-CT is provided, followed by relevant setup, scanning, reconstructing, and visualization methods and considerations. Throughout the guide, a Jacksons chameleon specimen, which was scanned at different settings, is used as an interactive example. The ultimate aim of this paper is make new users familiar with the concepts and applications of micro-CT in an attempt to promote its use in future scientific studies.

Three-dimensional model of an ancient Egyptian falcon mummy skeleton

– The purpose of this paper is to present the first detailed three-dimensional (3D) print from micro-computed tomography data of the skeleton of an ancient Egyptian falcon mummy. , – Radiographic analysis of an ancient Egyptian falcon mummy housed at Iziko Museums of South Africa was performed using non-destructive x-ray micro-computed tomography. A 1:1 physical replica of its skeleton was printed in a polymer material (polyamide) using 3D printing technology. , – The combination of high-resolution computed tomography scanning and rapid prototyping allowed us to create an accurate 1:1 model of a biological object hidden by wrappings. This model can be used to study skeletal features and morphology and also enhance exhibitions hosted within the museum. , – This is the first replica of its kind made of an ancient Egyptian falcon mummy skeleton. The combination of computed tomography scanning and 3D printing has the potential to facilitate scientific research and stimulate public interest in Egyptology.

The quantitative analysis of tungsten ore using X-ray microCT

Volumetric quantification of ore minerals is of interest using non-destructive laboratory X-ray tomography, as it allows high throughput, fast analysis, without any/limited sample preparation. This means traditional chemical analysis can still be performed on the same samples, but good information can be provided in a very short time assisting in exploration, mining and beneficiation decision making as well as sample selection for further chemical analysis. This paper describes a case study in which tungsten WO3/scheelite is quantified in 35mm diameter drill core samples and compared to subsequent traditional chemical analysis for the same samples. The results show a good correlation and indicates that laboratory X-ray CT scanning could replace the more time consuming traditional analytical methods for ore grading purposes in some types of deposits. Different image processing methods are compared for these samples, including an advanced thresholding operation which reduces operator input error. The method should work equally well for other types of ore minerals in which the mineral of interest is the most dense particle in the scan volume, and for which the bulk of the particle sizes are at least 3 times larger than the scan resolution. Performing X-ray microCT scans on drill core samples containing tungsten.Using the microCT data to quantify the grade of tungsten ore non-destructively.Illustrating the advantage of local threshold segmentation over global threshold.Correlating the microCT ore grade results to the industry standard results.

Beauty is more than skin deep: a non‐invasive protocol for in vivo anatomical study using micro‐CT

Micro Computed Tomography (μCT) is a widely used tool in biomedical research, employed to investigate tissues and bone structures of small mammals in vivo. The application of in vivo μCT scanning in non-medical studies greatly lags behind the rapid advancements made in the biomedical field wherein the methodology has evolved to allow for longitudinal studies and eliminate the need to sacrifice the animal. Ecological and evolutionary studies often involve morphological measurements of a large sample of live animals, however, the potential of in vivo μCT imaging as a method for data acquisition has yet to be delineated. Here we describe a protocol for in vivo μCT imaging of the internal anatomy of reptiles and amphibians, commonly used study organisms in ecological and evolutionary research. We consider the skeletal and extra-skeletal (i.e. osteoderms) bones of a lizard as a case study to elucidate the potential of in vivo μCT imaging. Firstly, we explore the effects of various parameter settings on radiation dose, scan time and image quality. Secondly, we develop a protocol to immobilise and restrain study organisms during scanning without need for the administration of anaesthetics and compare the results of the in vivo protocol to images obtained post mortem. To immobilise animals, we replace the use of anaesthetics by cooling, thereby allowing the use of previously unsuitable rotating gantry μCT scanners that are readily available in scientific institutions. The resultant image quality of in vivo μCT scans is similar to that of post-mortem μCT scans, especially in the abdominal region. We discuss the effect of tube voltage, distance to x-ray source and metal filtration on radiation dose, and how these parameters could be altered to reduce the cumulative radiation dose while maintaining optimal image quality. The proposed in vivo μCT protocol offers a new approach to acquire anatomical information for non-biomedical studies. We offer specific suggestions as to how the protocol can be employed to suit a variety of model organisms. This article is protected by copyright. All rights reserved.

Laser induced and controlled chemical reaction of carbon monoxide and hydrogen

Bimolecular chemical reaction control of gaseous CO and H(2) at room temperature and atmospheric pressure, without any catalyst, using shaped femtosecond laser pulses is presented. High intensity laser radiation applied to a reaction cell facilitates non-resonant bond breakage and the formation of a range of ions, which can then react to form new products. Stable reaction products are measured after irradiation of a reaction cell, using time of flight mass spectroscopy. Bond formation of C-O, C-C, and C-H bonds is demonstrated as CO(2)(+), C(2)H(2)(+), CH(+), and CH(3)(+) were observed in the time of flight mass spectrum of the product gas, analyzed after irradiation. The formation of CO(2) is shown to be dependent on laser intensity, irradiation time, and on the presence of H(2) in the reaction cell. Using negatively chirped laser pulses more C-O bond formation takes place as compared to more C-C bond formation for unchirped pulses.

Has snake fang evolution lost its bite? New insights from a structural mechanics viewpoint

Venomous snakes—the pinnacle of snake evolution—are characterized by their possession of venom-conducting fangs ranging from grooved phenotypes characterizing multiple lineages of rear-fanged taxa to tubular phenotypes present in elapids, viperids and atractaspidines. Despite extensive research, controversy still exists on the selective pressures involved in fang phenotype diversification. Here, we test the hypothesis that larger fangs and consequently a shift to an anterior position in the maxilla evolved to compensate for the costs of structural changes, i.e. higher stress upon impact in tubular fangs compared to grooved fangs. Direct voxel-based stress simulations conducted on high-resolution µCT scans, analysed within a phylogenetic framework, showed no differences in stress distribution between the three fang phenotypes, despite differences in (relative) fang length. These findings suggest that additional compensatory mechanisms are responsible for the biomechanical optimization and that fang length might instead be related to differential striking behaviour strategies.

Using X-ray computed tomography analysis tools to compare the skeletal element morphology of fossil and modern frog (Anura) species

Computed tomography (CT) analysis software has predominantly been developed for medical and industrial use. Thus far there have not been detailed reports in the palaeontological literature of CT analysis tools utilizing automatic analysis functions for visual 3D comparisons between different taxa/species in order to assess and quantify differences. This paper presents the methodology for the general morphological comparison and analysis of fossil and modern bones–in this case frog femora are showcased. Industrial X-ray computed tomography analysis functions are applied to the analysis, and specifically, the comparison, of bone morphologies and micro-anatomical differences (e.g., cortical wall thickness) of differentially sized frog taxa. In contrast to traditional landmark analysis, this method makes use of the higher detail of the full surface data in the form of a CAD (Computer-aided drafting) data set output from the microCT scan. The application of these industrial analysis functions is shown to be useful for viewing of qualitative, as well as quantitative, differences. Differences are highlighted using 3D nominal/actual comparisons, and wall thickness is compared using the wall thickness analysis function applied to both samples side by side. Single bones as well as complete frog specimens were scanned and, in the case of the latter, femora were virtually extracted (segmented) for the purposes of comparison with other specimens. These techniques may be used for the effective identification and quantification of morphological differences between fossil and extant taxa. Thalassa Matthews. Iziko South African Museum, 25 Queen Victoria Street, Cape Town 8000, South Africa and DST-NRF Centre of Excellence in Palaeosciences, Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits, 2050, South Africa. tmatthews.matthews@gmail.com Anton du Plessis. CT Scanner Facility, Central Analytical Facilities, Paul Sauer Building, Bosman Street, University of Stellenbosch, Stellenbosch, 7602, South Africa/Physics Department, University of Stellenbosch, Stellenbosch, 7602, South Africa. anton2@sun.ac.za

Standard method for microCT-based additive manufacturing quality control 1: Porosity analysis

Graphical abstract

Snake fangs: 3D morphological and mechanical analysis by microCT, simulation, and physical compression testing

Abstract This Data Note provides data from an experimental campaign to analyse the detailed internal and external morphology and mechanical properties of venomous snake fangs. The aim of the experimental campaign was to investigate the evolutionary development of 3 fang phenotypes and investigate their mechanical behaviour. The study involved the use of load simulations to compare maximum Von Mises stress values when a load is applied to the tip of the fang. The conclusions of this study have been published elsewhere, but in this data note we extend the analysis, providing morphological comparisons including details such as curvature comparisons, thickness, etc. Physical compression results of individual fangs, though reported in the original paper, were also extended here by calculating the effective elastic modulus of the entire snake fang structure including internal cavities for the first time. This elastic modulus of the entire fang is significantly lower than the locally measured values previously reported from indentation experiments, highlighting the possibility that the elastic modulus is higher on the surface than in the rest of the material. The micro–computed tomography (microCT) data are presented both in image stacks and in the form of STL files, which simplifies the handling of the data and allows its re-use for future morphological studies. These fangs might also serve as bio-inspiration for future hypodermic needles.