Use Of X-ray Micro-computed Tomography Research Articles

On new genera and species of crack-leg spiders (Araneae, Udubidae) from Madagascar

Two new genera, Tabiboka gen. nov. and Zorascar gen. nov., are described to accommodate five new Udubidae species from Madagascar: Tabiboka milleri gen. et sp. nov. (type species; ♂♀), T. milloti gen. et sp. nov. (♂♀), T. polotowae gen. et sp. nov. (♂♀), Zorascar pasunepipe gen. et sp. nov. (type species; ♂♀) and Z. pasunepomme gen. et sp. nov. (♀). In addition, two new species of Zorodictyna Strand, 1907 are described: Zorodictyna almae sp. nov. (♂♀) and Z. silvadavilae sp. nov. (♂♀). Uduba inhonesta Simon, 1906 is declared to be a junior synonym of Zorodictyna oswaldi (Lenz, 1891). The descriptions of the new species are complemented with a phylogenetic analysis to tentatively place them into an existing phylogenetic framework. Phylogenetic analyses based on COI and 16S rRNA genes and morphological data show that they are separate species and confirm their familial and supraspecific placement within the Udubidae. The new species are further described using high quality colored photographs, drawings, SEM and (for Zorascar gen. nov. ssp.) by the use of X-Ray micro-computed tomography to recreate virtual 3D models without destroying the original specimens. A dichotomous key to identify Malagasy Ububidae is provided. Whereas many undescribed Udubidae remain in Madagascar, the phylogenetic and generic arrangement that we present here succinctly summarizes the higher classification of Madagascar Udubidae.

Volume X-Ray Micro-Computed Tomography Analysis of the Early Cephalized Central Nervous System in a Marine Flatworm, Stylochoplana pusilla.

Platyhelminthes are a phylum of simple bilaterian invertebrates with prototypic body systems. Compared with non-bilaterians such as cnidarians, the bilaterians are likely to exhibit integrated free-moving behaviors, which require a concentrated nervous system "brain" rather than the distributed nervous system of radiatans. Marine flatworms have an early cephalized 'central' nervous system compared not only with non-bilaterians but also with parasitic flatworms or freshwater planarians. In this study, we used the marine flatworm Stylochoplana pusilla as an excellent model organism in Platyhelminthes because of the early cephalized central nervous system. Here, we investigated the three-dimensional structures of the flatworm central nervous system by the use of X-ray micro-computed tomography (micro-CT) in a synchrotron radiation facility. We found that the obtained tomographic images were sufficient to discriminate some characteristic structures of the nervous system, including nerve cords around the cephalic ganglion, mushroom body-like structures, and putative optic nerves forming an optic commissure-like structure. Through the micro-CT imaging, we could obtain undistorted serial section images, permitting us to visualize precise spatial relationships of neuronal subpopulations and nerve tracts. 3-D micro-CT is very effective in the volume analysis of the nervous system at the cellular level; the methodology is straightforward and could be applied to many other non-model organisms.

Phenotyping xylem connections in grafted plants using X-ray micro-computed tomography.

Plants are able to naturally graft or inosculate their trunks, branches and roots together, this mechanism is used by humans to graft together different genotypes for a range of purposes. Grafts are considered successful if functional vascular connections between the two genotypes occur. Various techniques can evaluate xylem connections across the graft interface. However, these methods are generally unable to assess the heterogeneity and three-dimensional (3D) structure of xylem vessel connections. Here we present the use of X-ray micro-computed tomography to characterize the 3D morphology of grafts of grapevine. We show that xylem vessels form between the two plants of natural root and human-made stem grafts. The main novelty of this methodology is that we were able to visualize the 3D network of functional xylem vessels connecting the scion and rootstock in human-made stem grafts thanks to the addition of a contrast agent to the roots and improved image analysis pipelines. In addition, we reveal the presence of extensive diagonal xylem connections between the main axial xylem vessels in 2-year old grapevine stems. In conclusion, we present a method that has the potential to provide new insights into the structure and function of xylem vessels in largetissue samples.

A microscopic interpretation of hysteresis in the water retention curve of sand

The hysteresis observed in a water retention curve was experimentally studied through the use of X-ray micro-computed tomography (μCT). The CT images were acquired during the main drying and wetting processes of a water retention test for uniform sand. The porosity and degree of saturation (Sr) of pore-scale local subsets were calculated using images segmented into soil, water and air phases. The simultaneous distribution of the local porosity and Sr was also analysed to investigate the relationship between the pore size and retained water volume. At similar suction levels, only small pore spaces retained water during wetting, while relatively large pore spaces retained water during drying, demonstrating the ink-bottle effect. At similar saturation levels, the simultaneous distribution was independent of the wetting and drying processes, indicating no significant difference in the water retention state between the two processes. Another image analysis was performed to calculate the principal curvatures of the air–water interface. At similar saturation levels, the calculated curvature of the drying process was greater than that of the wetting process, indicating contact angle hysteresis. The contact angle between the soil particles and water is different at the microscopic level, whereas the water retention states of the two processes are similar.

X-ray micro-computed tomography of Xenopus tadpole reveals changes in brain ventricular morphology during telencephalon regeneration.

Xenopus tadpoles serve as an exceptional model organism for studying post-embryonic development in vertebrates. During post-embryonic development, large-scale changes in tissue morphology, including organ regeneration and metamorphosis, occur at the organ level. However, understanding these processes in a three-dimensional manner remains challenging. In this study, the use of X-ray micro-computed tomography (microCT) for the three-dimensional observation of the soft tissues of Xenopus tadpoles was explored. The findings revealed that major organs, such as the brain, heart, and kidneys, could be visualized with high contrast by phosphotungstic acid staining following fixation with Bouin's solution. Then, the changes in brain shape during telencephalon regeneration were analyzed as the first example of utilizing microCT to study organ regeneration in Xenopus tadpoles, and it was found that the size of the amputated telencephalon recovered to >80% of its original length within approximately 1 week. It was also observed that the ventricles tended to shrink after amputation and maintained this state for at least 3 days. This shrinkage was transient, as the ventricles expanded to exceed their original size within the following week. Temporary shrinkage and expansion of the ventricles, which were also observed in transgenic or fluorescent dye-injected tadpoles with telencephalon amputation, may be significant in tissue homeostasis in response to massive brain injury and subsequent repair and regeneration. This established method will improve experimental analyses in developmental biology and medical science using Xenopus tadpoles.

Larval anatomy of the digestive and excretory systems of the pharyngeal bot fly, Pharyngomyia picta (Diptera: Oestridae).

Oestrid flies (Diptera: Oestridae) are obligate parasites of mammals during their larval stage and show anatomical adaptations for the infestation of host tissues. Unlike the species that parasitize domestic mammals, those oestrid species that infest wild mammal hosts remain poorly known. With the use of x-ray micro-computed tomography, we describe for the first time the anatomy of the digestive and excretory systems of the second and third larval instars of Pharyngomyia picta (Meigen), a parasite of cervids that, like other species within the subfamily Oestrinae, causes nasopharyngeal myiasis. Both larval instars of P. picta show a pair of remarkably large salivary glands arranged in a characteristic 'glandular band', a convoluted and thickly uniform midgut and a greatly enlarged distal region of the anterior pair of Malpighian tubules. These anatomical features also have been described in other species within the subfamily Oestrinae, whereas they differ from the observations in other oestrid subfamilies. We discuss the potential functional significance of the anatomy of the digestive and excretory systems of Oestrinae larvae as specific adaptations to parasitize the nasopharyngeal cavities of mammal hosts.

Use of X-ray micro-computed tomography for the investigation of drying processes in porous media: A review

Drying processes in porous materials and their optimization are of interest in research and in many industrial applications. X-ray micro-computed tomography presents a versatile instrument for the experimental investigation of those processes in three-dimensional on a microscopic level. In this review article, the basic principles of the technique shall be elucidated and an overview of the existing literature shall be given. Published studies performed with laboratory-based tomography setups and at synchrotrons are included alike. Different experimental workflows and their limitations with focus on the investigation of drying processes are considered, as well as the further usability of the obtained data and insights for the validation of analytical models and numerical simulations. The number of publications on this topic has greatly increased in the early 2000s and there is still research demand.

Use of X-ray micro-computed tomography to study the moult cycle of the freshwater amphipod Gammarus pulex

Stages of the moult cycle of the amphipod Gammarus pulex have been previously characterised based on the examination of either apolysis of the 3rd dactyl, or the whole body and eye appearance. In the current study the aim was to compare these two established moult staging techniques with a novel X-ray micro-computed tomography (micro-CT) scan method. The micro-CT provides information on the degree of calcification of the external integument and of the internal structures, such as the gastric mill. The degree of calcification is predicted to change during the moult cycle. Successful micro-CT scans were obtained from 80 G. pulex specimens and the radiological appearance of the 28 specimens immediately immersed in 4 % PFA were not different to the 52 specimens stored in 4 % PFA for at least 28 days prior to scanning. These specimens could be classified into moult stages A, B, C, early D or late D based on the degree of calcification. Good agreement was obtained between all three methods of moult stage classification if fresh specimens were used, but if specimens had been preserved in 4% Paraformaldehyde (PFA) for more than 24 hours the loss of colour from the whole body and eye meant these methods were not suitable. This is the first time that a micro-CT method has been used to study G. pulex and shows that this method of moult staging is accurate and reliable.

Study of the evolution of transport properties induced by additive processing sand mold using X-ray computed tomography

Abstract Accurate characterization of the mass transport properties of additively processed sand molds is essential in order to achieve reproducibility of the produced castings and control of gas defects in foundry industries. The present work highlights the potential use of X-ray micro-computed tomography (μ-CT) to characterize the evolution of permeability and some major microstructural features of such additively processed sand molds. The evolution of mass transport properties of sand mold samples under specific processing conditions met in additive manufacturing and its influence on the porosity, the permeability, the tortuosity, and the pore and throat size distributions were characterized from 3D images provided by X-Ray μ-CT. The obtained results showed that the mass transport properties of additively processed sand molds can be closely predicted by using non-destructive in situ methods, such that improvements to the casting can be made to create more optimized 3D printed structures for foundry applications.

Effects of internal porosity and crystallographic texture on Charpy absorbed energy of electron beam melting titanium alloy (Ti-6Al-4V)

The effects of internal porosity and crystallographic texture on miniaturized Charpy absorbed energy behavior of electron beam melting (EBM) titanium alloy (Ti-6Al-4V) are shown through investigation of material in two heat treatment conditions (As-Built and Hot Isostatically Pressed (HIPed)) and two specimen orientations (Vertical and Horizontal). Internal porosity was assessed by use of x-ray micro-computed tomography (CT) and fractography. Electron backscatter diffraction (EBSD) was used to characterize crystallographic texture. Charpy absorbed energy was measured over a range of temperatures (−196 to 600 °C). Results suggested internal porosity has a deleterious effect on Charpy absorbed energy. Internal porosity was observed in the As-Built condition (99.8% dense) but not in the HIPed condition, and the HIPed material had a higher Charpy absorbed energy. An observed increase in α lath thickness due to HIPing also contributed to this trend in Charpy absorbed energy. Crystallographic texture and anisotropic grain morphology (i.e., prior-β grains elongated in the build direction) influenced the measured Charpy absorbed energy. It was observed that for similar texture, crack pathways that crossed more prior-β grain boundaries resulted in higher Charpy absorbed energy. However, differing textures were found to negate the prior-β grain boundary strengthening effect, emphasizing the influence of texture and variations in texture on Charpy absorbed energy. Mixed textures were measured for all heat treatment conditions and specimen orientations, ranging from predominantly ⟨001⟩β to predominantly ⟨110⟩β (both in the build direction), but none matched the most commonly reported texture for this material (i.e., exclusive ⟨001⟩β-fiber in the build direction). Hypothesized processing parameters leading to these textures are discussed.

The use of x-ray micro-computed tomography for evaluation of bone growth in 3D printed metal implants - Correlation with histology

The use of x-ray micro-computed tomography for evaluation of bone growth in 3D printed metal implants - Correlation with histology

Hair imprints in Pleistocene cave sediments and the use of X-ray micro-computed tomography for their reconstruction

Detailed studies of cave sediments in the Divje babe I cave, in western Slovenia, have revealed both fossil hairs and the imprints of such hairs present within phosphate aggregates in the clastic sediments. These aggregates consist of fine rock and bone fragments, as well as hairs cemented by phosphate precipitated from pore water. The hairs and their imprints were discovered by means of scanning electron microscopy and are likely to have belonged to cave bears, which were the most frequent inhabitants of this cave. From X-ray micro-computed tomography showing the spatial distribution of the hair imprints, and their number, it appears that the hairs did not belong to one particular animal which died at the location where the samples were collected, rather the hairs probably accumulated on the floor of the cave not only from cadavers, but also because hairs were shed during the hibernation of bears and their visits to the cave.

Microtomographic Characterization of Dissolution-Induced Local Porosity Changes Including Fines Migration in Carbonate Rock

Summary The microstructure of carbonate rocks experiences substantial changes under reactive processes, in particular chemical dissolution and deposition, including dissolution-released-fines migration occurring during acidizing. A better understanding of such changes at the pore scale and their influences on rock properties is of great value for the effective design and implementation of reactive processes in carbonate reservoirs. In this work, we demonstrate the use of X-ray micro-computed tomography (micro-CT) to quantitatively investigate the local porosity changes in a meso-/microporous carbonate core sample during chemical dissolution. A reactive flooding experiment in a core sample by a nonacidic solution is designed such that changes in pore space from before to after the reactant injection could be imaged in exactly the same locations with micro-CT at a resolution of less than 5 μm. A methodology with three-phase segmentation and 2D histograms of image intensity is used to quantify distributions of the evolution of each image voxel. This technique allows the incorporation of microporosity into the calculation of the evolution regions, including the migration of fines, to accurately quantify the evolution scenarios. The micro-CT images reveal a quasiuniform dissolution pattern and allow characterizing the accompanying migration of fines within the core sample. The 3D pore networks are derived from the image data, which quantify changes in network structure and the pore geometry. The 2D histograms of image intensity derived from the pre- and post-dissolution images show quantitatively how macro- and micropores are enlarged by dissolution close to the inlet, whereas the deposition of fines mainly occurs in pores far from the inlet boundary. These results can explain why permeability of the sample initially decreases and then increases when injection time increases. Pore-surface area between each region is computed on the basis of the spatially resolved voxel evolution scenarios. This allows calculation of local distribution of reactive surface area, which, in turn, will assist in the prediction of local reaction rates in reactive flow simulators.