μCT Scans Research Articles

Identification of inflammatory regulation roles of thalidomide/ruxolitinib in nucleus pulposus and construction of polyelectrolyte nanocomplexes-impregnated injectable hydrogels for synergistic intervertebral disk degeneration treatment

Degeneration of the intervertebral discs (IVD) is an important underlying etiology of degenerative diseases contributor to lower back and neck pain. Alleviation of inflammation is recognized as the most direct way for the treatment of IVD. Repurposing of approved drugs is a viable alternative strategy to de novo drug discovery and development. The aim of this study is to identify the inflammatory regulation roles of the small molecule thalidomide (an immunomodulatory and TNF-α inhibitor) and ruxolitinib (a selective JAK1/2 inhibitor) in nucleus pulposus (NP) cells and investigate the combinational therapeutic potentials of thalidomide and ruxolitinib for ameliorating IVD degeneration. RNA-sequencing (RNA-seq) was used to detect differentially expressed genes (DEGs) after treatment of human NP cells with individual thalidomide and ruxolitinib, and relevant signaling pathways and functions of DEGs were detected by enrichment analysis. Western blot and immunofluorescence were applied to explore the mechanisms by which thalidomide and ruxolitinib regulated inflammatory factors in human NP cells. Moreover, we developed ruxolitinib and thalidomide co-delivered polyelectrolyte nanocomplexes (RTNPs) by the assembly of chitosan derivatives of positively charged chitosan hydrochloride (CS) and negatively charged carboxymethyl chitosan (CMCS). In vitro studies revealed that RTNPs could efficiently deliver drugs into NP cells and corresponding extracellular matrix (ECM)-related genes and proteins were adjusted. Furthermore, The RTNPs were assembled with Pluronic F127 to form a RTNPs/F127 injectable thermoresponsive hydrogels to maintain resident time within the nucleus pulposus, achieve sustained drugs release and achieve long-term therapy effects. The caudal disc degeneration model of SD rats was established by acupuncture, and X-ray, magnetic resonance scanning, μCT scanning, and histological methods were performed to detect the therapeutic effects of RTNPs/F127 hydrogel on IVD in vivo. As was demonstrated in the in vivo studies, in situ intradiscal injection of RTNPs/F127 composite displayed a relatively slower disc degenerating progression in a puncture-induced IVD rat model compared with the monotherapy pattern.

Early incisor lesions and Equine Odontoclastic Tooth Resorption and Hypercementosis: Reliability of radiographic findings.

In clinical practice, early diagnosis of Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) and other resorptive incisor diseases is difficult to achieve. The radiographic appearance of subtle pathological changes has not been described in detail and might be confused with age-related changes. The study was performed to define typical radiographic signs of early incisor lesions and to evaluate the reliability of the radiographic findings. Descriptive and comparative study using post mortem clinical, radiographic, macroscopic and µCT examination. The incisor region of 20 cadaveric horse heads, divided into three different age groups, was examined visually and by palpation. Intraoral radiographs were taken. After extraction, each incisor was macroscopically evaluated. Micro-computed tomography (µCT) scans were obtained. These scans were processed with Scry (v6.0, Kuchel & Sautter GbR) to obtain surface meshes which then were transferred to Meshlab (ISTI-CNR, version 2016.12). Attached tissues were virtually removed and surface curvature was computed to visualise and evaluate the quantity of unevenness (roughness) of the teeth's surface. Scoring systems for each diagnostic modality were developed. Scores were compared to describe and evaluate the radiographic appearance of early incisor lesions. The prevalence and severity of incisor lesions increased with age. Early, subtle lesions develop on the palatal/lingual side of incisors. While radiographically detected lesions were confirmed macroscopically and on the µCT scans, numerous teeth which were radiographically classified as healthy displayed lesions by macroscopic inspection (13.7%) and µCT analysis (58.1%). Cadavers were studied and dental history was unknown. The detection of early and subtle incisor lesions indicating first signs of EOTRH on dorsoventral intraoral radiographs is limited due to the typical localisation of the lesions on the palatal/lingual side of the incisors.

Systematics of Neotropical electric knifefish Tembeassu (Gymnotiformes, Apteronotidae)

A new species of the poorly known and critically endangered ghost knifefish Tembeassu is described from the upper Paraná and Araguari rivers, Brazil, using external anatomy and X-ray microcomputed tomography (µCT scan). Tembeassu titanicus sp. nov. is distinguished from its sole congener, T. marauna, by a unique set of morphometric and meristic characters, in addition to the absence of a tooth patch at the anterior portion of the roof of the oral cavity and the external corner of the mouth slightly passing the vertical through the posterior margin of the posterior nare. To test the monophyly of Tembeassu and reassess its phylogenetic position, a total-evidence approach was performed through a Bayesian inference (BI) and maximum-parsimony analysis (MP). Our results indicate that Tembeassu is monophyletic and the sister taxon of a clade formed by Apteronotus s.s., Megadontognathus, and Parapteronotus (BI); or as part of a large polytomy at the base of Apteronotidae (MP). Species of Tembeassu co-occur in the Paraná River basin, and the absence of the patch of accessory teeth in T. titanicus sp. nov. may indicate that this species accesses a different food resource, and also putatively occupies a different habitat than T. marauna. Comments on the evolution of the mandibular lobe in Gymnotiformes, dentition pattern in Tembeassu, and apteronotid diversity in the Paraná River are provided. http://zoobank.org/urn:lsid:zoobank.org:act:691CB9A5-5CDB-4BF9-8A6FEAE877563C12

They like to move it (move it): walking kinematics of balitorid loaches of Thailand.

Balitorid loaches are a family of fishes that exhibit morphological adaptations to living in fast flowing water, including an enlarged sacral rib that creates a 'hip'-like skeletal connection between the pelvis and the axial skeleton. The presence of this sacral rib, the robustness of which varies across the family, is hypothesized to facilitate terrestrial locomotion seen in the family. Terrestrial locomotion in balitorids is unlike that of any known fish: the locomotion resembles that of terrestrial tetrapods. Emergence and convergence of terrestrial locomotion from water to land has been studied in fossils; however, studying balitorid walking provides a present-day natural laboratory to examine the convergent evolution of walking movements. We tested the hypothesis that balitorid species with more robust connections between the pelvic and axial skeleton (M3 morphotype) are more effective at walking than species with reduced connectivity (M1 morphotype). We predicted that robust connections would facilitate travel per step and increase mass support during movement. We collected high-speed video of walking in seven balitorid species to analyze kinematic variables. The connection between internal anatomy and locomotion on land are revealed herein with digitized video analysis, μCT scans, and in the context of the phylogenetic history of this family of fishes. Our species sampling covered the extremes of previously identified sacral rib morphotypes, M1 and M3. Although we hypothesized the robustness of the sacral rib to have a strong influence on walking performance, there was not a large reduction in walking ability in the species with the least modified rib (M1). Instead, walking kinematics varied between the two balitorid subfamilies with a generally more 'walk-like' behavior in the Balitorinae and more 'swim-like' behavior in the Homalopteroidinae. The type of terrestrial locomotion displayed in balitorids is unique among living fishes and aids in our understanding of the extent to which a sacral connection facilitates terrestrial walking.

Impact of sedimentary fabrics on small-scale permeability variations within fine-grained sediments: Early Silurian Qusaiba Member, Northern Saudi Arabia

The main aim of this study is to constrain the range of reservoir properties observed in various depositional environments of the fine-grained sandstones of the early Silurian middle Qusaiba Member, Qalibah Formation, northwestern Saudi Arabia. Facies analysis, micro-X-ray fluorescence (μXRF), lamina-scale permeability measurements, automated helium porosity-permeability measurement, and pore system visualization were integrated to observe variations in these various environments. Seven main facies were recognized and interpreted to be deposited in an offshore “turbiditic-influenced” to lower shoreface paleoenvironments. These facies include current rippled siltstone (F1); Contorted silty sandstone (F2); current rippled fine-grained sandstone (F3); planar-laminated fine-grained sandstone (F4); Bioturbated to current-rippled argillaceous siltstone to silty sandstone (F5); Current rippled silty sandstone (F6); bioturbated sandstone (F7) facies. These facies were clustered into several fabric classes; 1) contorted fabrics associated with load casts flame structure that is characteristic of F2: These typically revealed slightly higher porosity and permeability values than the surrounding media with a spherical and relatively low anisotropy. 2) Planar-laminated fabrics in F4 that overlain by cryptic bioturbation: It comprises of clay mineral-rich laminae with higher porosity and permeability and the quartz-rich laminae with lower porosity and permeability probably due to abundant calcite cement associated with detrital quartz. Higher anisotropy, associated with this fabric, was observed. Cryptic bitourbated interval showed relatively low permeability. 3) In F7, three types of rock fabrics were observed, (1) Vertical sand-filled Piscichnus trace fossil: The burrow fill shows significantly higher porosity and permeability values than the laminated matrix; this fabric reveals an elliptical and highly anisotropic variance map. (2) Horizontal sand-filled Thalassinoides burrow (with iron oxide cement).: The internal core of this fabric was highly porous and permeable compared to the laminated fabric. Thalassinoides fabric had the most elliptical and highest anisotropic variance map in F7. (3) Entirely laminated fabric with bed-parallel gypsum veins: The permeability of the veins was slightly higher than that of the matrix, this resulted in a less anisotropic variance map. μCT scanning was used for F5 and F6; In the F5 facies, more significant porosity associated with quartz-rich lamina than iron oxide (e.g., siderite) and gypsum-rich lamina were observed probably due to higher chlorite alignment in the iron oxide-rich lamina. We found lower porosity and permeability within the vertical mud-filled burrows (Piscichnus) than the laminated fabric; this was also observed in the 3D pore system imaged by μCT scanning. These findings could have significant implications for different fabric types in fluid flow conduits in argillaceous sandstone and siltstone systems.

High-resolution imaging sheds new light on a multi-tier symbiotic partnership between a "walking" solitary coral, a sipunculan, and a bivalve from East Africa.

Marine symbioses are integral to the persistence of ecosystem functioning in coral reefs. Solitary corals of the species Heteropsammia cochlea and Heterocyathus aequicostatus have been observed to live in symbiosis with the sipunculan worm Aspidosiphon muelleri muelleri, which inhabits a cavity within the coral, in Zanzibar (Tanzania). The symbiosis of these photosymbiotic corals enables the coral holobiont to move, in fine to coarse unconsolidated substrata, a process termed as “walking.” This allows the coral to escape sediment cover in turbid conditions which is crucial for these light‐dependent species. An additional commensalistic symbiosis of this coral‐worm holobiont is found between the Aspidosiphon worm and the cryptoendolithic bivalve Jousseaumiella sp., which resides within the cavity of the coral skeleton. To understand the morphological alterations caused by these symbioses, interspecific relationships, with respect to the carbonate structures between these three organisms, are documented using high‐resolution imaging techniques (scanning electron microscopy and µCT scanning). Documenting multi‐layered symbioses can shed light on how morphological plasticity interacts with environmental conditions to contribute to species persistence.

Treatment of Infection-Related Non-Unions with Bioactive Glass-A Promising Approach or Just Another Method of Dead Space Management?

The treatment of infected and non-infected non-unions remains a major challenge in trauma surgery. Due to the limited availability of autologous bone grafts and the need for local anti-infective treatment, bone substitutes have been the focus of tissue engineering for years. In this context, bioactive glasses are promising, especially regarding their anti-infective potential, which could reduce the need for local and systemic treatment with conventional antibiotics. The aim of this study was to investigate the osteoinductive and osteoconductive effects, as well as the anti-infectious potential, of S53P4 using a standardized non-union model, which had not been investigated previously. Using an already established sequential animal model in infected and non-infected rat femora, we were able to investigate bioactive glass S53P4 under realistic non-union conditions regarding its osteoinductive, osteoconductive and anti-infective potential with the use of µCT scans, biomechanical testing and histological, as well as microbiological, analysis. Although S53P4 did not lead to a stable union in the non-infected or the infected setting, µCT analysis revealed an osteoinductive effect of S53P4 under non-infected conditions, which was diminished under infected conditions. The osteoconductive effect of S53P4 remained almost negligible in histological analysis, even 8 weeks after treatment. Additionally, the expected anti-infective effect could not be demonstrated. Our data suggested that S53P4 should not be used in infected non-unions, especially in those with large bone defects.

Development of radiopaque FFF filaments for bone and teeth representation in 3D printed radiological objects

The use of 3D printing technologies is growing widely, including the possibility of design phantoms for imaging and dosimetry. For that, high attenuation tissues such as cortical bone, dentin and enamel need to be mimicked to accurately produce 3D printed phantoms, especially for Fused Filament Fabrication (FFF) printing technology. A Radiopaque FFF filament commercially available had been hard to be found; and this study aims to report, step-by-step, the development of a radiopaque FFF filament. A combination of radiopaque substances (Barium Sulfate - BaSO4 and Calcium Carbonate - CaCO3) was selected using the National Institute of Standards and Technology (NIST) XCOM tool theoretical data and added as filler in an Acrylonitrile Butadiene Styrene (ABS) matrix. The filament was homogenized and gone under first characterizations by analyzing its density, Scanning Electron Microscopy (SEM), Computed Tomography (CT) and micro-CT (µCT) scans. Three filaments were produced with different Hounsfield Units (HU) equivalences: XCT-A (1607HU), XCT-B (1965HU) and XCT-C (2624HU) with respective densities of 1.166(6) g/cm³, 1.211(2) g/cm³ and 1.271(3) g/cm³. With these values, high attenuation tissues, such as bones, dentine and enamel, can now be mimicked with FFF 3D printing technology, at a low cost of production.

X-ray μCt extracted pore attributes to predict and understand Sor using ensemble learning techniques in the Barra Velha Pre-salt carbonates, Santos Basin, Offshore Brazil

The residual oil saturation (Sor) evaluation is relevant for developing oil fields, standing out as an input to flow simulation models for production forecasting. Also, Sor understanding is crucial to guide enhanced oil recovery techniques. Moreover, Sor laboratory measurement tends to be time-consuming and expensive. This work aims to understand and predict Sor from X-ray μCt and RCAL data employing Ensemble Learning techniques (AdaBoost, Gradient Boost, and XGBoost) in Pre-salt carbonates of the Barra Velha Formation, Santos Basin. Morphological attributes related to pore size, shape, and orientation were extracted from X-ray μCt scans. Hence, these attributes, together with routine core analysis (RCAL) data, were used to build machine learning (ML) models for the prediction of Sor. The results indicated strong faciological control in Sor, where the genesis of the rock implies different characteristics of the porous framework, impacting Sor and other petrophysical features. Rocks with larger pores usually lead to larger heterogeneity, which tends to trap more oil. Furthermore, the shape and orientation of the pores have substantial faciological control, given the textural organization of the different rock facies. These attributes showed weak control over Sor, impacting each type of facies differently, depending on the rock fabric. Even though the ML algorithms have similar results, the Gradient Boosting showed the best results. Furthermore, the inclusion of RCAL data does not increase the accuracy of the models. So, it is possible to predict the Sor only with morphological pore attributes reasonably. The most important features are mainly related to pore size and subordinately to orientation, confirming their impact on Sor. Finally, this methodology, in addition to predicting and bringing understanding to Sor in Pre-Salt rocks, can be adapted for use in other reservoirs.

Development of a manufacturing process for Binder Jet 3D printed porous Al2O3 supports used in heterogeneous catalysis

A complete preparation route for the direct 3D printing of Al2O3 supports made from boehmite and bayerite was established using the Binder Jetting technology. The application of the ceramic supports as reactor packing material employed in heterogeneous catalysis requires high porosity but simultaneously a certain robustness which has not been thoroughly investigated for powder-based 3D printing technologies before. With a calcination temperature of only 600 °C, sufficient consolidation by sintering does not occur as it would be the case for conventional Binder Jetting procedures so that the post-processing step of ambient slurry infiltration after debinding binds the particles after calcination at relatively low temperatures and significantly stabilizes the alumina framework while keeping the surface area and open porosity at catalytically relevant values of up to 223 m2/g and 80%, respectively. Uniaxial compression tests, density measurements and N2 physisorption elucidated the chemical composition, size accuracy, shrinkage behavior, side crushing strength, density, porosity and specific surface area of the green body as well as post-processed parts. Additionally, μCT scans offered a method to analyze the 3D printed character of the alumina carrier structure, effect of post-processing and an alternative way to assess part shrinkage next to size measurement.

On the feeding biomechanics of nectarivorous birds.

Nectar-feeding birds employ unique mechanisms to collect minute liquid rewards hidden within floral structures. In recent years, techniques developed to study drinking mechanisms in hummingbirds have prepared the groundwork for investigating nectar feeding across birds. In most avian nectarivores, fluid intake mechanisms are understudied or simply unknown beyond hypotheses based on their morphological traits, such as their tongues, which are semi-tubular in sunbirds, frayed-tipped in honeyeaters and brush-tipped in lorikeets. Here, we use hummingbirds as a case study to identify and describe the proposed drinking mechanisms to examine the role of those peculiar traits, which will help to disentangle nectar-drinking hypotheses for other groups. We divide nectar drinking into three stages: (1) liquid collection, (2) offloading of aliquots into the mouth and (3) intraoral transport to where the fluid can be swallowed. Investigating the entire drinking process is crucial to fully understand how avian nectarivores feed; nectar-feeding not only involves the collection of nectar with the tongue, but also includes the mechanisms necessary to transfer and move the liquid through the bill and into the throat. We highlight the potential for modern technologies in comparative anatomy [such as microcomputed tomography (μCT) scanning] and biomechanics (such as tracking BaSO4-stained nectar via high-speed fluoroscopy) to elucidate how disparate clades have solved this biophysical puzzle through parallel, convergent or alternative solutions.

Finite element analysis of crenulated and non‐crenulated hominid molars: A functional hypothesis explaining the adaptive significance of molar crenulation

AbstractObjectivesThe occlusal surface of many mammalian teeth has grooves that have been collectively called crenulations. The evolutionary significance of this trait is unknown, but it has been associated with a hard diet. It has not been explained, however, why crenulated molars may present an increased mechanical resistance. The objective of this study was to determine whether a crenulated surface dissipate mechanical stress more efficiently than a smooth one.Materials and methodsUsing μCT scans we built 3D models of lower second molars from Homo, Pan, Gorilla, and Pongo. The crenulated models from Homo and Pongo were modified to remove crenulations. Finite element analysis was used to determine the distribution of mechanical stress in all the models when a vertical force was applied.ResultsThe results show that crenulated molars have a distinctive pattern of mechanical stress, namely the stress is higher in the valleys than in the crests of the crenulations. In non‐crenulated molars, mechanical stress is more homogeneously distributed. Highly crenulated molars of orangutans show the smallest values of mean stress among the compared species. Artificially removing crenulations results in more homogeneous distribution of stresses and increased mean stress values.ConclusionsMolar crenulations may increase molar resistance by canalizing mechanical stress from the tip to the base of the cusps. The overall cusp shape also influences the distribution of stress. This mechanism may be a functional hypothesis to explain the association between crenulated molars and mechanically demanding diets.

Further analyses of the structural organization of Homo luzonensis teeth: Evolutionary implications

The species Homo luzonensis has recently been described based on a set of dental and postcranial elements found at Callao Cave (Northern Luzon, Philippines) and dated to at least 50–67 ka. Seven postcanine maxillary teeth are attributed to this taxon, five of them belonging to the same individual (CCH6) and representing the holotype of H. luzonensis, whereas the isolated upper premolar CCH8 and the upper third molar CCH9 are paratypes of the species. The teeth are characterized by their small dimensions associated with primitive features, as also found in Homo floresiensis, another hominin having evolved in an insular environment of Southeast Asia. Postcranial bones of the hands and feet of H. luzonensis and H. floresiensis show Homo habilis–like or australopith-like features, whereas cranial and dental morphology are more consistent with the Asian Homo erectus morphology. Due to this mosaic morphology, the origin and phylogenetic relationships of both H. luzonensis and H. floresiensis are still debated. To test the hypotheses that H. luzonensis derives from H. erectus or from an earlier small-brained hominin, we analyzed the µCT scans of the teeth. We investigated both external and internal tooth structure using morphometric methods including: crown outline shape, tooth crown tissue proportions, enamel-dentine junction shape, and pulp morphology. Homo luzonensis external crown morphology aligns more with H. erectus than with H. habilis/H. rudolfensis. The internal structural organization of H. luzonensis teeth exhibits more affinities with that of H. erectus and H. floresiensis than with Neanderthals and modern humans. Our results suggest that both H. floresiensis and H. luzonensis likely evolved from some H. erectus groups that dispersed in the various islands of this region and became isolated until endemic speciation events occurred at least twice during the Pleistocene in insular environments.

Effect of pore size on tissue ingrowth and osteoconductivity in biodegradable Mg alloy scaffolds.

Magnesium has mechanical properties similar to those of bone and is being considered as a potential bone substitute. In the present study, two different pore sized scaffolds of the Mg alloy LAE442, coated with magnesium fluoride, were compared. The scaffolds had interconnecting pores of either 400 (p400) or 500 µm (p500). ß-TCP served as control. Ten scaffolds per time group (6, 12, 24, 36 weeks) were implanted in the trochanter major of rabbits. Histological analyses, µCT scans, and SEM/EDX were performed. The scaffolds showed slow volume decreases (week 36 p400: 9.9%; p500: 7.5%), which were accompanied by uncritical gas releases. In contrast, ß-TCP showed accelerated resorption (78.5%) and significantly more new bone inside (18.19 ± 1.47 mm3). Bone fragments grew into p400 (0.17 ± 0.19 mm3) and p500 (0.36 ± 0.26 mm3), reaching the centrally located pores within p500 more frequently. In particular, p400 displayed a more uneven and progressively larger surface area (week 36 p400: 253.22 ± 19.44; p500: 219.19 ± 4.76 mm2). A better osseointegration of p500 was indicated by significantly more trabecular contacts and a 200 µm wide bone matrix being in the process of mineralization and in permanent contact with the scaffold. The number of macrophages and foreign body giant cells were at an acceptable level concerning resorbable biomaterials. In terms of ingrown bone and integrative properties, LAE442 scaffolds could not achieve the results of ß-TCP. In this long-term study, p500 appears to be a biocompatible and more osteoconductive pore size for the Mg alloy LAE442.

Purse of Medieval Silver Coins from Royal Shipwreck Revealed by X-Ray Microscale Computed Tomography (Μct) Scanning

Purse of Medieval Silver Coins from Royal Shipwreck Revealed by X-Ray Microscale Computed Tomography (Μct) Scanning

Effect of different preparation finishing procedures on the marginal and internal fit of CAD-CAM-produced restorations: A microcomputed tomography evaluation

Statement of problemAccurate fit is an important factor for the longevity of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic restorations. Few studies have compared how restoration finishing procedures affect the marginal and internal fit of these restorations by using microcomputed tomography (μCT). PurposeThe purpose of this in vitro study was to evaluate the preparations with different surface finishing procedures for the fit of CAD-CAM restorations by using μCT. Material and methodsA total of 28 anatomic contour monolithic feldspathic ceramic crowns were produced for 4 typodont teeth prepared according to the different surface finishing procedures (n=7). The generated experimental groups were finishing with extra-coarse (181 μm) diamond rotary instruments (EC), finishing with fine (40 μm) diamond rotary instruments after extra-coarse diamond rotary instruments (F), finishing with very fine (20 μm) diamond rotary instruments after extra-coarse and fine diamond rotary instruments (VF), and finishing with extra-coarse, fine, and very fine diamond rotary instruments followed by polishing rubber points (P). μCT scans were obtained to measure the gaps between the typodont teeth and the crowns. Reference points such as the margin, chamfer (the deepest point), cusp tips, and central fossa were determined, and 196 measurements were made. Data were analyzed by using 2-way analyses of variance and the Tukey HSD test (α=.05). ResultsThe highest gap values in all sections were observed in the finishing with extra-coarse (181 μm) diamond rotary instruments group. The lowest gap value in the marginal point was observed in the P group (P<.05). In total, the gap values of the reference points were in the order of margin, chamfer, cusp, and central fossa. ConclusionsμCT evaluation showed that tooth preparation finishing procedure with finer grit rotary instruments yielded better marginal fit for monolithic feldspathic CAD-CAM restorations. The internal gap values of all groups were also in the range of clinically acceptable values, important for mechanical properties.

Inputs of root-derived carbon into soil and its losses are associated with pore-size distributions

Placement and fate of photo-assimilated carbon (C) newly added to the soil are important contributors of soil health. Soil pores control the movement of gasses, water, and microorganisms, thus potentially influencing new photo-assimilated C gains and losses. The objective of this study was to explore the associations between soil pores and additions and losses of root-derived C. Young cereal rye (Secale cereale L.) plants were grown in soil with inherent pore architecture destroyed by sieving and in soil with intact pore architecture, with each rye planted container having a section inaccessible to plant roots. Plants were pulse labeled with 13CO2, followed by sampling of intact soil cores and subjecting them to X-ray computed micro-tomography (µCT) scanning, some immediately after collection and some after a 21-day incubation. From the scanned cores we obtained soil micro-samples in specific locations corresponding to µCT images. The µCT images were used to quantify pore size distributions of the micro-sample soils, while soil δ13C signatures provided a quantitative measure of the presence of root-derived C before and after the incubation. In the intact soils, δ13C was positively associated with > 90 µm Ø pores, likely reflecting preferential rye root growth into legacy root channels. In soils where existing pore architecture was destroyed, 13C was preferentially added to 15–90 μm Ø pores when the soil was accessible to roots and to 7–40 μm Ø pores when the soil was accessible only to fungi, yet after the incubation the associations between 13C and pores were lost. The results identified the pore sizes associated with root-derived C additions to the soil via root and fungal routes and highlighted the importance of inherent pore architecture on the placement and persistence of such additions.

Quantifying Crack Self-Healing in Concrete with Superabsorbent Polymers under Varying Temperature and Relative Humidity

During their service life, concrete structures are subjected to combined fluctuations of temperature and relative humidity, which can influence their durability and service life performance. Self-healing has in recent years attracted great interest to mitigate the effects of such environmental exposure on concrete structures. Several studies have explored the autogenous crack self-healing in concrete incorporating superabsorbent polymers (SAPs) and exposed to different environments. However, none of the published studies to date has investigated the self-healing in concrete incorporating SAPs under a combined change in temperature and relative humidity. In the present study, the crack width changes due to self-healing of cement mortars incorporating SAPs under a combined change of temperature and relative humidity were investigated and quantified using micro-computed tomography and three-dimensional image analysis. A varying dosage of SAPs expressed as a percentage (0.5%, 1% and 2%) of the cement mass was incorporated in the mortar mixtures. In addition, the influence of other environments such as continuous water submersion and cyclic wetting and drying was studied and quantified. The results of segmentation and quantification analysis of X-ray µCT scans showed that mortar specimens incorporating 1% SAPs and exposed to environments with a combined change in temperature and relative humidity exhibited less self-healing (around 6.58% of healing efficiency). Conversely, when specimens were subjected to cyclic wetting and drying or water submersion, the healing efficiency increased to 19.11% and 26.32%, respectively. It appears that to achieve sustained self-healing of cracks, novel engineered systems that can assure an internal supply of moisture are needed.

Feeding behaviour and functional morphology of the neck in the long-snouted aquatic fossil reptile Champsosaurus (Reptilia: Diapsida) in comparison with the modern crocodilian Gavialis gangeticus.

The extinct freshwater choristoderan reptiles Champsosaurus and Simoedosaurus are characterised by large body size and an elongated snout. They have often been considered as eco-analogues of crocodilians based on superficial similarities. The slender-snouted Champsosaurus has been described as a 'gavial-like reptile', which implies it feeds underwater with a lateral swipe of the head and neck, as in the living slender-snouted crocodilians such as Gavialis gangeticus. In contrast, the short-snouted Simoedosaurus is often compared with short-snouted living crocodilians and is considered to take single prey items. However, the neck mobility and flexibility needed for feeding movements are poorly understood even in extant crocodilians. This study explores the relationship between cervical morphology and neck flexion, focusing particularly on lateral and dorsal movements in G. gangeticus by comparison with shorter-snouted crocodilians. The paper also describes a method to estimate the maximum angle of neck dorsiflexion in choristoderes based on the cervical morphology of extant crocodilian species. Three indices were used in this study, of which Index 3 is newly proposed, to compare cervical morphology and intervertebral joint flexibility: (1) Enclosed zygapophyseal angles (EZA) as an index of dorsoventral/ bilateral flexibility, (2) moment arm (M) of dorsiflexor muscles as an Index of resistance against ventroflexion and (3) the orientations of zygapophysial facets for a maximum angle of dorsiflexion. These Indices were validated using µCT scanning of fresh specimens of G. gangeticus and Caiman latirostris in lateral and dorsal flexion. A unique mechanism of lateral flexion was identified in G. gangeticus that uses a combination of the following features: (1) lateral flexion mainly restricted to the anterior cervical vertebrae (v2/v3: high EZA, with more horizontal zygapophyses) and (2) high degree of dorsiflexion at the v3/v4 and v4/v5 joints with potential for dorsal flexibility through the middle-posterior neck, which is used in inertial feeding. In contrast, Champsosaurus and Simoedosaurus possess relatively short cervical vertebrae, as in short-snouted crocodilians. The middle-posterior cervical vertebrae of Champsosaurus are specialised for lateral flexion (high EZA), and there is only limited capacity for dorsiflexion throughout the neck. Like G. gangeticus, therefore, Champsosaurus may have used its slender snout to grab fish from shoals using lateral sweeping motions of the head and neck, but the movement is through the neck, not the craniocervical joint. However, inertial feeding is less likely to have occurred in this genus, and the aligned palatal dentition may have aided the lingual transport of prey into the mouth. Simoedosaurus, on the other hand, appears to have been less specialised, with a neck that combined lateral and dorsolateral flexion, a move that could have been effective in catching both terrestrial and aquatic prey. Where these two choristoderan genera occurred in the same place, they may have divided their niche by prey types.

Influence of internal volumetric imperfections on the tearing resistance curve of welded Single Edge notched Tension (SENT) specimens

The acceptance of volumetric weld imperfections is subjected to workmanship guidelines, which are subjective quality criteria loosely related to fitness for purpose assessments. However, the relative impact of such imperfections may be accentuated in fracture toughness tests, given the relatively small dimensions of the test specimens. This study analyses the impact of weld volumetric imperfections on the outcome of fracture toughness tests. Single Edge Notched Tensile (SENT) specimens were machined from steel plates joined by robotic Metal Inert Gas (MIG) welding. The specimens contained different levels of volumetric imperfections which were characterized by high-resolution X-ray Computed Tomography (µCT) scans. Single specimen fracture toughness tests were conducted and crack growth was monitored by applying both the Unloading Compliance (UC) technique and the Direct Current Potential Drop (DCPD) technique. Tearing resistance curves (R-curves) were constructed based on UC and DCPD data. Results showed that specimens containing volumetric imperfections acceptable by workmanship guidelines may yield significantly inferior fracture initiation toughness values compared to imperfection-free specimens.