Search

Biodegradable magnesium (Mg) implants are emerging as a potential game changer in implant technology in situations where the implant temporarily supports the bone thereby avoiding secondary surgery for implant removal. However, the consequences of the alteration in the degradation rate to bone healing and the localization of degradation and alloying products in the long term remain unknown. In this study, we present the long-term osseointegration of three different biodegradable Mg alloys, Mg-10Gd, Mg-4Y-3RE and Mg-2Ag, which were implanted into rabbit femur for 6 and 9 months. In addition, we have investigated the effect of blood pre-incubation on the in vivo performance of the aforementioned alloys. Using high-resolution synchrotron radiation based micro computed tomography, the bone implant contact (BIC), bone volume fraction (BV/TV) and implant morphology were studied. The elemental traces have been characterized using micro X-ray fluorescence. Qualitative histological evaluation of the surrounding bone was also performed. Matured bone formed around all three implant types and Ca as well as P which represent parts of the degradation layer were in intimate contact with the bone. Blood pre-incubation prior to implantation significantly improved BIC in Mg-2Ag screws at 9 months. Despite different implant degradation morphologies pointing toward different degradation dynamics, Mg-10Gd, Mg-4Y-3RE and Mg-2Ag induced a similar long-term bone response based on our quantified parameters. Importantly, RE elements Gd and Y used in the alloys remained at the implantation site implying that they might be released later on or might persist in the implantation site forever. As the bone formation was not disturbed by their presence, it might be concluded that Gd and Y are non-deleterious. Consequently, we have shown that short and mid-term in vivo evaluations do not fully represent indicators for long-term osseointegration of Mg-based implants. [ABSTRACT FROM AUTHOR]

Copyright of Methods in Ecology & Evolution is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Burmese amber preserves a diverse assemblage of Cretaceous arachnids, and among pseudoscorpions (Arachnida: Pseudoscorpiones), ten species in five families have already been named. Here, we describe a new fossil species from Burmese amber in the pseudoscorpion family Hyidae, providing detailed measurements, photographs and 3D-models from synchrotron scanning. Based on morphology, the new fossil, Hya fynni sp. nov. is placed in the genus Hya, and is nearly identical to extant species in the genus, except for the position of trichobothrium est on the pedipalpal chela, thereby indicating extreme morphological stasis in this invertebrate lineage over the last 99 million years. Hya fynni represents the first described fossil species in Hyidae, and the third described Burmese fossil in the superfamily Neobisioidea. It also joins the garypinid, Amblyolpium burmiticum, in representing the oldest fossil records for extant pseudoscorpion genera. Considering proposed divergence dates, the newly described fossil species bolsters a Gondwanan origin for Hyidae, and provides evidence for the "Late Jurassic Rifting" hypothesis for the Burma Terrane, in which this landmass rifted from Gondwana in the Late Jurassic and collided with Eurasia by the Cretaceous/Eocene. Like Hya species today, H. fynni likely inhabited humicolous microhabitats in tropical forests on the Burma Terrane, supporting ecological niche stasis for this family since the Mesozoic. [ABSTRACT FROM AUTHOR]

Solute diffusion in partially saturated porous media is an important fundamental process in many natural and environmental systems. At low water saturation, the solute transport is governed by the diffusion in thin water films on the surfaces of solids. In this study, we established an improved pore‐scale simulation framework successfully describing the solute diffusion in variably saturated porous media (e.g., soils), which considers the contribution of the diffusion within the thin water film on the surface of the solid matrix. The model takes into account the liquid–gas distribution in the underlying porous media by the Shan‐Chen lattice Boltzmann Method (LBM) and simulates the solute diffusion in the bulk liquid phase and the water film. Based on the numerical results, an easy‐to‐use theoretical formula was also developed to predict the effective diffusivity in microporous materials at low saturation levels. The average relative error of its prediction with respect to the experimental data from the literature is about 30%, while that of the classical power law exceeds 70%. A simple phase diagram was defined, which allows us to identify the situations under which it is necessary to take the influence of surface water films on the effective diffusivity in unsaturated microporous media into account. The present study improves the pore‐scale model to address solute diffusion in the water films at low water saturation and elucidates the contribution of thin water films on solute transport. Core Ideas: Solute transport in porous media at low water saturation is governed by the diffusion in thin water films.This study presents a modified pore‐scale model involving the transport pathway in thin water films.A physically based formula is given to better predict the unsaturated effective diffusivity.A phase diagram is defined to identify the influence of surface water films on the effective diffusivity. [ABSTRACT FROM AUTHOR]

Simple Summary: The majority of dipterans (flies, mosquitoes, and their allies) spend most of their lifetimes as immatures (larvae and pupae). Yet, immature dipterans are seldom reported in the fossil record. Studying this life stage can provide crucial insights into the evolution of these insects, how distinct evolutionary lineages relate to each other, and their ecological interactions during the significant changes of the Mesozoic Era (about 252–66 Ma). In this work, based on a range of imaging techniques, we describe and discuss several fossil dipteran larvae from amber and compression fossils, exhibiting forms not known in the modern fauna. These specimens possess structures similar to those found in present day larvae of awl-flies and water snipe-flies. Additionally, we report new specimens of stratiomyomorphan larvae, which appear to have dominated over other terrestrial dipteran immatures, suggesting a potentially larger ecological role in the past than in present times. Finally, we describe two additional specimens of a highly distinctive dipteran, known only as a larva, Qiyia jurassica Chen et al., 2014. Our findings suggest differences in the ecology of some fly groups compared to their modern relatives. They also challenge some postulated evolutionary relationships within these lineages. Diptera are one of the four megadiverse groups of holometabolan insects. Flies perform numerous ecological functions, especially in their larval stages. We can assume that this was already the case in the past; however, fly larvae remain rare in most deposits. Here we report new dipteran larvae preserved in Cretaceous (about 99 Ma) Kachin amber from Myanmar and, even older, Jurassic (about 165 Ma) compression fossils from China. Through light microscopy and micro-CT scanning we explore their peculiar morphology and discuss their possible phylogenetic affinities. Several larvae seem to represent the lineage of Stratiomyomorpha. A few others present characters unique to Xylophagidae (awl-flies), as well as to Athericidae (water sniper-flies), resulting in a chimeric morphology. Understanding the exact relationships of most of these specimens with a particular lineage remains challenging, since they differ considerably from any other known dipteran larvae and present some unique traits. Additionally, we report new specimens of Qiyia jurassica Chen et al., 2014, supposedly parasitic larvae, most likely representatives of Athericidae. These new findings offer valuable insights into the evolution of the early diversification of the brachyceran flies and underscore the importance of immature stages in understanding the evolutionary history and ecology of flies. [ABSTRACT FROM AUTHOR]

Direct information about the soil structure can be obtained with X‐ray computed microtomography, and the imaged macropore networks can be used as geometries in the lattice Boltzmann flow simulations. This method has not been widely applied for near‐saturated flows due to methodological issues related to diffuse‐interface two‐phase flow simulations in samples with limited resolution. Here, a simple pore‐scale lattice Boltzmann approach to simulate steady‐state water flow in partially saturated soil macropore networks that circumvents these problems is presented. The actual simulation is preceded by the determination of water–air distribution, for example, by using morphological operations. Flow through the water‐filled part of the pore space is done by using no‐slip conditions at water–solid boundaries and slip conditions at water–air interfaces. The method was tested by simulating film flow over a solid surface, and the numerical results are shown to agree with the analytical expression available for this flow geometry. The method is further tested, and its use is demonstrated with real tomographic reconstructions of clay soil samples. Core Ideas: Lattice Boltzmann method was used to simulate near‐saturated flow in the imaged soil macropore system.The approach uses static water–air distribution in soil macropores that were determined by a morphological model.Slip boundary condition at water–air interfaces was realized with a bounce‐back rule from a moving boundary.The approach reduces the computational costs for simulating water flow in pore networks at near‐saturated condition. [ABSTRACT FROM AUTHOR]

Introduction: Synchrotron radiation micro-computed tomography (SRμCT) has been used as a non-invasive technique to examine the microstructure and tissue integration of biodegradable bone implants. To be able to characterize parameters regarding the disintegration and osseointegration of such materials quantitatively, the three-dimensional (3D) image data provided by SRμCT needs to be processed by means of semantic segmentation. However, accurate image segmentation is challenging using traditional automated techniques. This study investigates the effectiveness of deep learning approaches for semantic segmentation of SRμCT volumes of Mg-based implants in sheep bone ex vivo. Methodology: For this purpose different convolutional neural networks (CNNs), including U-Net, HR-Net, U[sup 2]-Net, from the TomoSeg framework, the Scaled U-Net framework, and 2D/3D U-Net from the nnU-Net framework were trained and validated. The image data used in this work was part of a previous study where biodegradable screws were surgically implanted in sheep tibiae and imaged using SRμCT after different healing periods. The comparative analysis of CNN models considers their performance in semantic segmentation and subsequent calculation of degradation and osseointegration parameters. The models' performance is evaluated using the intersection over union (loU) metric, and their generalization ability is tested on unseen datasets. Results and discussion: This work shows that the 2D nnU-Net achieves better generalization performance, with the degradation layer being the most challenging label to segment for all models. [ABSTRACT FROM AUTHOR]

The functions of soils are intimately linked to their three‐dimensional pore space and the associated biogeochemical interfaces, mirrored in the complex structure that developed during pedogenesis. Under stress overload, soil disintegrates into smaller compound structures, conventionally named aggregates. Microaggregates (<250 µm) are recognized as the most stable soil structural units. They are built of mineral, organic, and biotic materials, provide habitats for a vast diversity of microorganisms, and are closely involved in the cycling of matter and energy. However, exploring the architecture of soil microaggregates and their linkage to soil functions remains a challenging but demanding scientific endeavor. With the advent of complementary spectromicroscopic and tomographic techniques, we can now assess and visualize the size, composition, and porosity of microaggregates and the spatial arrangement of their interior building units. Their combinations with advanced experimental pedology, multi‐isotope labeling experiments, and computational approaches pave the way to investigate microaggregate turnover and stability, explore their role in element cycling, and unravel the intricate linkage between structure and function. However, spectromicroscopic techniques operate at different scales and resolutions, and have specific requirements for sample preparation and microaggregate isolation; hence, special attention must be paid to both the separation of microaggregates in a reproducible manner and the synopsis of the geography of information that originates from the diverse complementary instrumental techniques. The latter calls for further development of strategies for synlocation and synscaling beyond the present state of correlative analysis. Here, we present examples of recent scientific progress and review both options and challenges of the joint application of cutting‐edge techniques to achieve a sophisticated picture of the properties and functions of soil microaggregates. [ABSTRACT FROM AUTHOR]

As a well-known natural protein biomaterial, silk fibroin (SF) has shown broad application prospects in typical biomedical fields. However, the mostly used SF from Bombyx mori silkworm lacks specific cell adhesion sites and other bioactive peptide sequences, and there is still significant room for further improvement of their biological functions. Therefore, it is crucial to develop a facile and effective modification strategy for this widely researched biomaterial. In this study, the SF electrospun scaffold has been chosen as a typical SF biomaterial, and air plasma etching has been adopted as a facile nanopattern modification strategy to promote its biological functions. Results demonstrated that the plasma etching could feasibly and effectively create nano-island-like patterns on the complex surface of SF scaffolds, and the detailed nanopattern features could be easily regulated by adjusting the etching time. In addition, the mesenchymal stem cell responses have illustrated that the nanopattern modification could significantly regulate corresponding cell behaviors. Compared with the non-etched scaffold, the 10 min-etched scaffolds (10E scaffold) significantly promoted stem cell proliferation and osteogenic differentiation. Moreover, 10E scaffold has also been confirmed to effectively accelerate vascularization and ectopic osteogenesis in vivo using a rat subcutaneous implantation model. However, the mentioned promoting effects would be weakened or even counteracted with the increase of etching time. In conclusion, this facile modification strategy demonstrated great application potential for promoting cell proliferation and differentiation. Thus, it provided useful guidance to develop excellent SF-based scaffolds suitable for bone and other tissue engineering. [ABSTRACT FROM AUTHOR]

A focused ion beam scanning electron microscope (FIB-SEM) is a powerful tool that is routinely used for scale imaging from the micro- to nanometer scales, micromachining, prototyping, and metrology. In spite of the significant capabilities of a FIB-SEM, there are inherent artefacts (e.g., structural defects, chemical interactions and phase changes, ion implantation, and material redeposition) that are produced due to the interaction of Ga+ or other types of ions (e.g., Xe+, Ar+, O+, etc.) with the sample. In this study, we analyzed lattice distortion and ion implantation and subsequent material redeposition in metallic micropillars which were prepared using plasma focus ion beam (PFIB) milling. We utilized non-destructive synchrotron techniques such as X-ray fluorescence (XRF) and X-ray nanodiffraction to examine the micropillars prepared using Xe+ ion energies of 10 keV and 30 keV. Our results demonstrate that higher Xe ion energy leads to higher density of implanted ions within the redeposited and milled material. The mixing of ions in the redeposited material significantly influences the lattice structure, causing deformation in regions with higher ion concentrations. Through an X-ray nanodiffraction analysis, we obtained numerical measurements of the strain fields induced in the regions, which revealed up to 0.2% lattice distortion in the ion bombardment direction. [ABSTRACT FROM AUTHOR]

During the Paleogene, the Holarctic experienced drastic climatic oscillations, including periods of extensive glaciation. These changes had a severe impact on both the flora and fauna causing widespread extinction and range shifts with some taxa retreating to refugia in the Mediterranean Basin. Here we provide evidence for this hypothesis using fossils from the pseudoscorpion family Garypinidae Daday, 1889 (Arachnida: Pseudoscorpiones). This family comprises 21 extant genera from all continents except Antarctica but is restricted to low mid-latitudes (<44°N) in the Northern Hemisphere. We provide the second record of garypinids from the European succinite ambers of the Eocene by describing the first extinct genus in Garypinidae, Baltamblyolpium gen. nov., which includes two species: Baltamblyolpium gizmotum sp. nov. from Baltic amber and Baltamblyolpium grabenhorsti sp. nov. from Bitterfeld amber. The new genus exhibits a morphology that closely resembles Neoamblyolpium Hoff, 1956 from western North America and the genus Amblyolpium Simon, 1898, which is widespread but includes taxa restricted to Mediterranean refugia in Europe. The discovery of a new fossil genus of Garypinidae from Europe confirms that the family was found at more northerly latitudes during the Eocene, however, extinction and range contraction resulted in their present-day relictual distribution in southern Europe like many other lineages that once thrived in the European "Baltic amber forest" of the Eocene. [ABSTRACT FROM AUTHOR]

Filamentous fungi produce a wide range of relevant biotechnological compounds. The close relationship between fungal morphology and productivity has led to a variety of analytical methods to quantify their macromorphology. Nevertheless, only a µ‐computed tomography (µ‐CT) based method allows a detailed analysis of the 3D micromorphology of fungal pellets. However, the low sample throughput of a laboratory µ‐CT limits the tracking of the micromorphological evolution of a statistically representative number of submerged cultivated fungal pellets over time. To meet this challenge, we applied synchrotron radiation‐based X‐ray microtomography at the Deutsches Elektronen‐Synchrotron [German Electron Synchrotron Research Center], resulting in 19,940 3D analyzed individual fungal pellets that were obtained from 26 sampling points during a 48 h Aspergillus niger submerged batch cultivation. For each of the pellets, we were able to determine micromorphological properties such as number and density of spores, tips, branching points, and hyphae. The computed data allowed us to monitor the growth of submerged cultivated fungal pellets in highly resolved 3D for the first time. The generated morphological database from synchrotron measurements can be used to understand, describe, and model the growth of filamentous fungal cultivations. [ABSTRACT FROM AUTHOR]

Simple Summary: Various physiological activities of organisms, including movement, feeding, reproduction, breathing, excretion, etc., all require the participation of their neuromuscular systems. Echinoderms, a phylum closely related to chordates, possess a well-differentiated but simpler muscular system, which provides a great opportunity to trace the evolutionary origins of the vertebrate muscular system. Here, we review the morphology of different musculatures and the effects of different neurotransmitters and neuropeptides involved in muscle regulation in echinoderms. In addition, we highlight the potential molecular mechanisms underpinning the action of these chemical messengers on echinoderm muscles. The muscular systems of echinoderms play important roles in various physiological and behavioral processes, including feeding, reproduction, movement, respiration, and excretion. Like vertebrates, echinoderm muscle systems can be subdivided into two major divisions, somatic and visceral musculature. The former usually has a myoepithelial organization, while the latter contains muscle bundles formed by the aggregation of myocytes. Neurons and their processes are also detected between these myoepithelial cells and myocytes, which are capable of releasing a variety of neurotransmitters and neuropeptides to regulate muscle activity. Although many studies have reported the pharmacological effects of these chemical messengers on various muscles of echinoderms, there has been limited research on their receptors and their signaling pathways. The muscle physiology of echinoderms is similar to that of chordates, both of which have the deuterostome mode of development. Studies of muscle regulation in echinoderms can provide new insights into the evolution of myoregulatory systems in deuterostomes. [ABSTRACT FROM AUTHOR]

Choroid plexus, pineal gland, and habenula tend to accumulate physiologic calcifications (concrements) over a lifetime. However, until now the composition and causes of the intracranial calcifications remain unclear. The detailed analysis of concrements has been done by us using X-ray diffraction analysis (XRD), X-ray diffraction topography (XRDT), micro-CT, X-ray phase-contrast tomography (XPCT), as well as histology and immunohistochemistry (IHC). By combining physical (XRD) and biochemical (IHC) methods, we identified inorganic (hydroxyapatite) and organic (vimentin) components of the concrements. Via XPCT, XRDT, histological, and IHC methods, we assessed the structure of concrements within their appropriate tissue environment in both two and three dimensions. The study found that hydroxyapatite was a major component of all calcified depositions. It should be noted, however, that the concrements displayed distinctive characteristics corresponding to each specific structure of the brain. As a result, our study provides a basis for assessing the pathological and physiological changes that occur in brain structure containing calcifications. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings are essential materials systems for insulating and protecting substrates exposed to high temperatures. In such systems, the heat transfer has three possible paths: conduction, convection and irradiation. The higher the operating temperature, the more important it is to control or protect against the radiative component, since the radiative heat flux becomes non-negligible. The radiation can be controlled by the use of ceramic-based photonic nanostructures, namely photonic crystals and photonic glasses, creating so-called reflective thermal barrier coatings. In this work, mullite inverse photonic glasses (PhG) have been produced by thermally induced reaction on sol–gel-based silica structures coated with nanometric films of Al2O3 by atomic layer deposition. The conversion to mullite was carried out following a two-stage heat-treatment. The pre-annealing associated with the further mullite formation results in an excellent structural stability of these PhGs up to 1500 °C, being able to retain their high reflectivity in the near infrared range. Therefore, this structure can be considered for next-generation reflective thermal barrier coatings. [ABSTRACT FROM AUTHOR]

The charosphere is a thin soil one surrounding the biochar with highly active biochemical functions. Yet, little is known about the spatial and temporal distribution of charosphere hotspots. In this study, repacked soil cores were incubated with a central layer of biochar (pristine or acid-modified) with or without nitrogen (N) additions for 30 days and sliced at the millimeter scale for analyzing soil pH, mineral N, bacterial and fungal communities as well as the putative functions. We aimed to determine gradient distributions (in millimeter scale) of charosphere affected by biochar under different N additions. Our results showed narrower gradient changes (3 mm) of microbial community composition and wider shifts (6 mm) in pH and inorganic N contents in charosphere. The pristine biochar increased the soil pH up to 1.5 units in the charosphere, and subsequently boosted the relative abundance of Proteobacteria, Acidobacteria, and Zygomycota. With N addition, both the biochar site and charosphere were observed with decreased complexity of microbial networks, which might imply the limited microbial functionality of charosphere. These results will advance the understanding and prediction of biochar's environmental impacts in soil. Highlights: The charosphere hotspots of soil pH and mineral N content reached 6 mm. Soil microbial compositions fluctuated within 3 mm of charosphere. Pristine biochar site fostered higher fungal diversity than that in bulk soils. Lower bacterial diversity in pristine biochar site was found. The microbial network complexity declined with N addition in charosphere. [ABSTRACT FROM AUTHOR]

Combining spatially localized X-ray diffraction (XRD) with X-ray microtomography (XMT) enables the mapping of the micro- and nanoscale structures simultaneously. The combination of these methods results in a powerful tool when considering the structural studies of hierarchical materials, allowing one to couple the relationships and connections of the structures at various scales. In this study, XMT was used to map the anatomy and cellular structures in 3D in tension and opposite wood with 1.5 µm resolution, while XRD was used to determine the cellulose crystallite widths and microfibril orientations with 100 µm spatial resolution within the same tissues. Tension wood (TW) has an important biological function with clearly distinct properties to opposite (OW) and normal wood, e.g. differing cellular structures with a higher cellulose content. This is the first study of very young hybrid aspen saplings (1-month-old) using the combined diffraction tomography method. The TW tissues could be identified from the OW tissues based on both the XMT and XRD results: TW had a higher average size of the cellulose crystallites and smaller mean microfibril angles (mMFA) than those in OW. With the XRD data, we were able to reconstruct the images of the cross sections of the saplings using the structural parameters (cellulose crystallite width and mMFA) as contrast mechanisms. As far as the authors know, there are no previous studies with images on any TW samples using the XRD-based contrast. Home laboratory bench-top set-up offers its advantages for these studies, considering the number of samples characterized, time-dependent studies and larger field of views. [ABSTRACT FROM AUTHOR]

Background: To gain a better understanding of bark layer structure and function, especially of the phloem fibres and their contribution to the posture control of trees, it is important to map the structural properties of these cells. The role of bark can also be linked to the reaction wood formation and properties which are essential when it comes to studying the questions related to tree growth. To offer new insights into the role of bark in the postural control of trees, we studied the micro- and nanoscale structures of the phloem and its nearest layers. This study is the first time, in which phloem fibres in trees have been extensively examined using X-ray diffraction (XRD). We determined the orientation of cellulose microfibrils in phloem fibres of Silver birch saplings by using scanning synchrotron nanodiffraction. The samples consisted of phloem fibres extracted from tension, opposite and normal wood (TW, OW, NW). Results: Using scanning XRD, we were able to obtain new information about the mean microfibril angle (MFA) in cellulose microfibrils in phloem fibres connected to reaction wood. A slight but consistent difference was detected in the average MFA values of phloem fibres between the TW and OW sides of the stem. Using scanning XRD, different contrast agents (intensity of the main cellulose reflection or calcium oxalate reflection, mean MFA value) were used to produce 2D images with 200 nm spatial resolution. Conclusions: Based on our results, the tension wood formation in the stem might be related to the structure and properties of phloem fibres. Thus, our results suggest that the nanostructure of phloem fibres is involved in the postural control of trees containing tension and opposite wood. [ABSTRACT FROM AUTHOR]

Increasing evidence indicates that microscale heterogeneity is critical to interpret and predict macroscopic soil processes and functions. However, the difficulty of measuring soil characteristics, such as soil organic carbon (SOC) and microbial biomass, at the micron level greatly hinders our understanding of how microscale soil heterogeneity quantitatively regulates macroscopic soil behaviors. Here, we investigated the effect of microscale distributions of soil water saturation (S), SOC content (CSOC), and microbial biomass (CMB) on soil heterotrophic respiration (SHR) using a microscale process-based model. The microscale distributions of S, CSOC, and CMB were mathematically determined by assuming they varied linearly with local soil porosity, which was derived from X-ray computed tomography, and the effect of microscale heterogeneity on SHR rates was examined under different water saturations and carbon availabilities. The results show that microscale soil heterogeneity stimulated macroscopic SHR only when it alleviated resource limits or environmental stress. For instance, the heterogeneous S improved the SHR rate by reducing microbial water stress or enhancing dissolved organic carbon (DOC) diffusion, whereas the heterogeneous CSOC enhanced CO2 flux by increasing DOC availability. In addition, the heterogeneous CMB promoted CO2 flux by increasing microbial accessibility of substrates. The interactions among water, SOC, and microbes at the micron scale may stimulate or restrict CO2 emission, depending on soil water saturation and DOC availability. Given the nature of soil heterogeneity at the micron scale and the challenge of measuring microscale soil characteristics, this study provided invaluable insights into how microscale heterogeneity regulates macroscale soil behaviors. [ABSTRACT FROM AUTHOR]

High activity of a catalyst and its thermal stability over a lifetime are essential for catalytic applications, including catalytic gas sensors. Highly porous materials are attractive to support metal catalysts because they can carry a large quantity of well-dispersed metal nanoparticles, which are well-accessible for reactants. The present work investigates the long-term stability of mesoporous Co3O4-supported Au–Pd catalyst (Au–Pd@meso-Co3O4), with a metal loading of 7.5 wt% and catalytically active mesoporous Co3O4 (meso-Co3O4) for use in catalytic gas sensors. Both catalysts were characterized concerning their sensor response towards different concentrations of methane and propane (0.05–1%) at operating temperatures ranging from 200 °C to 400 °C for a duration of 400 h. The initially high sensor response of Au–Pd@meso-Co3O4 to methane and propane decreased significantly after a long-term operation, while the sensor response of meso-Co3O4 without metallic catalyst was less affected. Electron microscopy studies revealed that the hollow mesoporous structure of the Co3O4 support is lost in the presence of Au–Pd particles. Additionally, Ostwald ripening of Au–Pd nanoparticles was observed. The morphology of pure meso-Co3O4 was less altered. The low thermodynamical stability of mesoporous structure and low phase transformation temperature of Co3O4, as well as high metal loading, are parameters influencing the accelerated sintering and deactivation of Au–Pd@meso-Co3O4 catalyst. Despite its high catalytic activity, Au–Pd@meso-Co3O4 is not long-term stable at increased operating temperatures and is thus not well-suited for gas sensors. [ABSTRACT FROM AUTHOR]

To describe various important soil processes like the release of greenhouse gases or the proliferation of microorganisms, it is necessary to assess quantitatively how the geometry and in particular the connectivity of the air‐filled pore space of a soil evolves as it is progressively dried. The availability of X‐ray computed microtomography (μCT) images of soil samples now allows this information to be obtained directly, without having to rely on the interpretation of macroscopic measurements using capillary theory, as used to be the case. In this general context, we present different methods to describe quantitatively the configuration of the air‐filled pore space in 3D μCT images of 20 separate samples of a loamy soil equilibrated at different matric potentials. Even though measures using μCT on such multi‐scale materials strongly depend on image resolution, our results show that in general, soil samples most often behave as expected, for example, connectivity increases with higher negative matric potential, while tortuosity decreases. However, simple correlations could not be found between the evolution of quantitative descriptors of the pore space at the different matric potentials and routinely measured macroscopic soil parameters. A statistical analysis of all soil samples concurrently confirmed this lack of correspondence. [ABSTRACT FROM AUTHOR]

Solid dosage forms such as tablets are extensively used in drug administration for their simplicity and large-scale manufacturing capabilities. High-resolution X-ray tomography is one of the most valuable non-destructive techniques to investigate the internal structure of the tablets for drug product development as well as for a cost effective production process. In this work, we review the recent developments in high-resolution X-ray microtomography and its application towards different tablet characterizations. The increased availability of powerful laboratory instrumentation, as well as the advent of high brilliance and coherent 3rd generation synchrotron light sources, combined with advanced data processing techniques, are driving the application of X-ray microtomography forward as an indispensable tool in the pharmaceutical industry. [ABSTRACT FROM AUTHOR]

Two new species of the genus Plecia (Diptera: Bibionidae) are described. The only occurrence of the genus Plecia in the Miocene amber of Dominican Republic was formerly identified as P. pristina, a species having previously been described in the Mexican Miocene fauna. The Dominican specimen is hereby studied again and attributed to a new species, Plecia jorgecaridadi n. sp., alongside another new species, Plecia surieli n. sp. [ABSTRACT FROM AUTHOR]

Knowing the molecular makeup of an organ system is required for its in-depth understanding. We analyzed the molecular repertoire of the adult tracheal system of the fruit fly Drosophila melanogaster using transcriptome studies to advance our knowledge of the adult insect tracheal system. Comparing this to the larval tracheal system revealed several major differences that likely influence organ function. During the transition from larval to adult tracheal system, a shift in the expression of genes responsible for the formation of cuticular structure occurs. This change in transcript composition manifests in the physical properties of cuticular structures of the adult trachea. Enhanced tonic activation of the immune system is observed in the adult trachea, which encompasses the increased expression of antimicrobial peptides. In addition, modulatory processes are conspicuous, in this case mainly by the increased expression of G protein-coupled receptors in the adult trachea. Finally, all components of a peripheral circadian clock are present in the adult tracheal system, which is not the case in the larval tracheal system. Comparative analysis of driver lines targeting the adult tracheal system revealed that even the canonical tracheal driver line breathless (btl)-Gal4 is not able to target all parts of the adult tracheal system. Here, we have uncovered a specific transcriptome pattern of the adult tracheal system and provide this dataset as a basis for further analyses of the adult insect tracheal system. [ABSTRACT FROM AUTHOR]

Background: The formation of concrements in human pineal gland (PG) is a physiological process and, according to many researchers, is associated with the involution of PG structures. The majority of scientific publications concern progressive calcification of PG, leaving out studies on the destruction of already formed calcified concrements. Our study fills the gap in knowledge about calcified zones destruction in PG in normal aging and neuropathological conditions, which has not been addressed until now. Purpose: Our objective is to gain insight into human PG tissue impairment in both normal aging and neurodegenerative conditions. X-ray phase-contrast tomography (XPCT) allowed us to study PG tissue degeneration at high spatial resolution and, for the first time, to examine the damaged PG concrements in detail. Our research finding could potentially enhance the understanding of the PG involvement in the process of aging as well as in Alzheimer’s disease (AD) and vascular dementia (VD). Methods: The research was carried out on human PG autopsy material in normal aging, VD, and AD conditions. Laboratory-based micro-computed tomography (micro-CT) was used to collect and evaluate samples of native, uncut, and unstained PG with different degrees of pineal calcification. The detailed high-resolution 3D images of the selected PGs were produced using synchrotron-based XPCT. Histology and immunohistochemistry of soft PG tissue confirmed XPCT results. Results: We performed via micro-CT the evaluation of the morphometric parameters of PG such as total sample volume, calcified concrements volume, and percentage of concrements in the total volume of the sample.XPCT imaging revealed high-resolution details of age-related PGalteration.In particular,we noted signs of moderate degradation of concrements in some PGs from elderly donors. In addition, our analysis revealed noticeable degenerative change in both concrements and soft tissue of PGs with neuropathology. In particular, we observed a hollow core and separated layers as well as deep ragged cracks in PG concrements of AD and VD samples. In parenchyma of some samples,we detected wide pinealocyte-free fluid-filled areas adjacent to the calcified zones. Conclusion: The present work provides the basis for future scientific research focused on the dynamic nature of PG calcium deposits and PG soft tissue in normal aging and neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Full-field X-ray nanoimaging is a widely used tool in a broad range of scientific areas. In particular, for low-absorbing biological or medical samples, phase contrast methods have to be considered. Three well established phase contrast methods at the nanoscale are transmission X-ray microscopy with Zernike phase contrast, near-field holography and near-field ptychography. The high spatial resolution, however, often comes with the drawback of a lower signal-to-noise ratio and significantly longer scan times, compared with microimaging. In order to tackle these challenges a single-photon-counting detector has been implemented at the nanoimaging endstation of the beamline P05 at PETRA III (DESY, Hamburg) operated by Helmholtz-Zentrum Hereon. Thanks to the long sample-to-detector distance available, spatial resolutions of below 100 nm were reached in all three presented nanoimaging techniques. This work shows that a single-photon-counting detector in combination with a long sample-todetector distance allows one to increase the time resolution for in situ nanoimaging, while keeping a high signal-to-noise level. [ABSTRACT FROM AUTHOR]

Background: High-dose-rate radiotherapy has shown promising results with respect to normal tissue preservation. We developed an ex vivo model to study the physiological effects of experimental radiotherapy in the rodent esophageal smooth muscle. Methods: We assessed the physiological parameters of the esophageal function in ex vivo preparations of the proximal, middle, and distal segments in the organ bath. High-dose-rate synchrotron irradiation was conducted using both the microbeam irradiation (MBI) technique with peak doses greater than 200 Gy and broadbeam irradiation (BBI) with doses ranging between 3.5–4 Gy. Results: Neither MBI nor BBI affected the function of the contractile apparatus. While peak latency and maximal force change were not affected in the BBI group, and no changes were seen in the proximal esophagus segments after MBI, a significant increase in peak latency and a decrease in maximal force change was observed in the middle and distal esophageal segments. Conclusion: No severe changes in physiological parameters of esophageal contraction were determined after high-dose-rate radiotherapy in our model, but our results indicate a delayed esophageal function. From the clinical perspective, the observed increase in peak latency and decreased maximal force change may indicate delayed esophageal transit. [ABSTRACT FROM AUTHOR]

Spatiotemporal characterisation of the soil redox status within the capillary fringe (CF) is a challenging task. Air‐filled porosities (ε), oxygen concentration (O2) and soil redox potential (EH) are interrelated soil variables within active biogeochemical domains such as the CF. We investigated the impact of water table (WT) rise and drainage in an undisturbed topsoil and subsoil sample taken from a Calcaric Gleysol for a period of 46 days. We merged 1D (EH and matric potential) and 2D (O2) systems to monitor at high spatiotemporal resolution redox dynamics within self‐constructed redoxtron housings and complemented the data set by a 3D pore network characterization using X‐ray microtomography (X‐ray μCT). Depletion of O2 was faster in the organic matter‐ and clay‐rich aggregated topsoil and the CF extended >10 cm above the artificial WT. The homogeneous and less‐aggregated subsoil extended only 4 cm above the WT as indicated by ε–O2–EH data during saturation. After drainage, 2D O2 imaging revealed a fast aeration towards the lower depths of the topsoil, which agrees with the connected ε derived by X‐ray μCT (εCT_conn) of 14.9% of the total porosity. However, small‐scaled anoxic domains with O2 saturation <5% were apparent even after lowering the WT (down to 0.25 cm2 in size) for 23 days. These domains remained a nucleus for reducing soil conditions (EH < −100 mV), which made it challenging to characterise the soil redox status in the CF. In contrast, the subsoil aeration reached O2 saturation after 8 days for the complete soil volume. Values of εCT_conn around zero in the subsoil highlighted that soil aeration was independent of this parameter suggesting that other variables such as microbial activity must be considered when predicting the soil redox status from ε alone. The use of redoxtrons in combination with localised redox‐measurements and image based pore space analysis resulted in a better 2D/3D characterisation of the pore system and related O2 transport properties. This allowed us to analyse the distribution and activity of microbiological niches highly associated with the spatiotemporal variable redox dynamics in soil environments. Highlights: The time needed to turn from reducing to oxidising (period where all platinum electrodes feature EH > 300 mV) condition differ for two samples with contrasting soil structure.The subsoil with presumably low O2 consumption rates aerated considerably faster than the topsoil and exclusively by O2 diffusion through medium‐ and fine‐sized pores.To derive the soil redox status based upon the triplet ε–O2–EH is challenging at present in heterogeneous soil domains and larger soil volumes than 250 cm3.Undisturbed soil sampling along with 2D/3D redox measurement systems (e.g., redoxtrons) improve our understanding of redox dynamics within the capillary fringe. [ABSTRACT FROM AUTHOR]

Moth lacewings (Ithonidae) are a rare group of Neuroptera with an unusual subterranean larval life‐style. We examined external and internal head structures of an older‐instar larva of Ithone Newman with a broad spectrum of techniques. Larval autapomorphies, likely correlated with the subterranean habits, are the compact and shovel‐shaped head, unusually massive mandibular‐maxillary stylets, and a C‐shaped postcephalic body. Other cephalic autapomorphies are the massive X‐shaped tentorium, incurved antennae, and a strongly developed M. verticopharyngalis. The visual organs are distinctly simplified but a single functional stemma on each side of head is retained despite of the subterranean habits. In contrast to previous studies, a well‐developed gular sclerite is present in Ithonidae, possibly a secondary acquisition. A cephalic gland complex and poison channel are present, with an unexpected additional lateral accessory gland and an additional lateral channel. The poison glands and dual channels very clearly indicate that the larvae are predators, contradicting the phytophagous habits formerly postulated. Compared with soil‐inhabiting scarabaeoid beetle larvae, striking differences of head structures are due to different feeding habits and phylogenetic constraints. Morphological similarities like a C‐shaped postcephalic body and strongly developed legs suitable for burrowing in soil are evolutionary parallels associated with the subterranean life‐style in the two non‐related groups. Bayesian phylogenetic analysis was carried out with an updated morphological matrix. The results were compared with a phylogeny based on anchored hybrid enrichment data. The evolutionary transformations of selected characters were evaluated using phylogenies estimated from both datasets. [ABSTRACT FROM AUTHOR]

Cover crops (CC) could improve soil physical, chemical, and biological properties; however, the micrometer scale quantification of geometric pore characteristics in CC soil is limited in the literature. The objective of this study was to differentiate geometrical pore characteristics between CC and no CC (NCC) by computed tomography (CT). The study design consisted of winter CC and summer corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation with no‐till management. The sample cores were collected after 7 yr of mixed species CC establishment. Six 0‐to‐65‐mm‐long soil cores (28‐mm diam.) were imaged at 29‐μm resolution, and three‐dimensional volumes were analyzed using Fiji‐ImageJ2 software. Slice thickness was 29 μm, and the minimum achievable voxel size was 90 nm. Images within the top and bottom 7.25 mm were removed, and two depths within a core were analyzed for soil pore parameters. The total pore volume was significantly greater (P <.05) in CC compared with NCC, with 8.4 and 2.5 times greater values in CC at 7.25–27.25 and 37.25–57.25 mm, respectively. The total (individual + branched) and the individual pore count were significantly greater (P <.05) in CC compared with NCC for both depths. The porosity of CC soil at 7.25‐to‐27.25‐mm depth was 10 times greater than that of NCC. The branched pore count was not significantly different between two treatments. Overall, the micrometer scale determination of geometrical pore network characteristics showed added benefits of CC use compared with NCC; thus, the use of CC can be beneficial in improving soil pore networks. Core Ideas: Cover crops improve soil pore volume measured by micro‐computed tomography (μCT).Cover crops improve soil physical characteristics.μCT‐measured imageJ analysis is a good method for soil geometrical pore characteristic identification. [ABSTRACT FROM AUTHOR]

Purpose: Simultaneously interacting rhizosphere processes determine emergent plant behaviour, including growth, transpiration, nutrient uptake, soil carbon storage and transformation by microorganisms. However, these processes occur on multiple scales, challenging modelling of rhizosphere and plant behaviour. Current advances in modelling and experimental methods open the path to unravel the importance and interconnectedness of those processes across scales. Methods: We present a series of case studies of state-of-the art simulations addressing this multi-scale, multi-process problem from a modelling point of view, as well as from the point of view of integrating newly available rhizosphere data and images. Results: Each case study includes a model that links scales and experimental data to explain and predict spatial and temporal distribution of rhizosphere components. We exemplify the state-of-the-art modelling tools in this field: image-based modelling, pore-scale modelling, continuum scale modelling, and functional-structural plant modelling. We show how to link the pore scale to the continuum scale by homogenisation or by deriving effective physical parameters like viscosity from nano-scale chemical properties. Furthermore, we demonstrate ways of modelling the links between rhizodeposition and plant nutrient uptake or soil microbial activity. Conclusion: Modelling allows to integrate new experimental data across different rhizosphere processes and scales and to explore more variables than is possible with experiments. Described models are tools to test hypotheses and consequently improve our mechanistic understanding of how rhizosphere processes impact plant-scale behaviour. Linking multiple scales and processes including the dynamics of root growth is the logical next step for future research. [ABSTRACT FROM AUTHOR]

In this study, double-multilayer monochromators that generate intense, high-energy, pink X-ray beams are designed, installed and evaluated at the SPring-8 medium-length (215 m) bending-magnet beamline BL20B2 for imaging applications. Two pairs of W/B4C multilayer mirrors are designed to utilize photon energies of 110 keV and 40 keV with bandwidths of 0.8% and 4.8%, respectively, which are more than 100 times larger when compared with the Si double-crystal monochromator (DCM) with a bandwidth of less than 0.01%. At an experimental hutch located 210 m away from the source, a large and uniform beam of size 14 mm (V) × 300 mm (H) [21 mm (V) × 300 mm (H)] was generated with a high flux density of 1.6 × 109 photons s-1 mm-2 (6.9 × 1010 photons s-1 mm-2) at 110 keV (40 keV), which marked a 300 (190) times increase in the photon flux when compared with a DCM with Si 511 (111) diffraction. The intense pink beams facilitate advanced X-ray imaging for large-sized objects such as fossils, rocks, organs and electronic devices with high speed and high spatial resolution. [ABSTRACT FROM AUTHOR]

Recent advances in non-invasive imaging methods have revitalized the field of comparative anatomy, and reproductive anatomy has been no exception. The reproductive systems of female amniotes present specific challenges, namely their often internal "hidden" anatomy. Quantifying female reproductive systems is crucial to recognizing reproductive pathologies, monitoring menstrual cycles, and understanding copulatory mechanics. Here, we conduct a review of the application of non-invasive imaging techniques to female amniote reproductive anatomy. We introduce the commonly used imaging modalities of computed tomography (CT) and magnetic resonance imaging (MRI), highlighting their advantages and limitations when applied to female reproductive tissues, and make suggestions for future advances. We also include a case study of micro CT and MRI, along with their associated staining protocols, applied to cadavers of female adult stoats (Mustela erminea). In doing so, we will progress the discussion surrounding the imaging of female reproductive anatomy, whilst also impacting the fields of sexual selection research and comparative anatomy more broadly. [ABSTRACT FROM AUTHOR]

Based on these results, we test the hypothesis that the fossils belong to Aneuretinae, revise the key to global ant subfamilies and certain higher taxa of the Formicidae, and we discuss the definition of Aneuretinae and the evolution of ant mandibles. In the light of recent phenomic [[26], [41]] and phylogenomic [[16]] studies, a systematic comparison of male mandibles across all ant subfamilies, including stem lineages (unpubl. data), indicates new hypotheses for the evolution of the ants and diagnoses of the family-group classification. Hist. 2011; 355: 1-90. 10.1206/355.1 47 Yoshimura M., Fisher B.L. A revision of male ants of the Malagasy region (Hymenoptera: Formicidae): Key to subfamilies and treatment of the genera of Ponerinae. In this context, the foundational work for contemporary ant classification is the informally Hennigian I Synopsis and Classification i of Bolton [[11]], which built on Bolton's I Identification Guide to the Ant Genera of the World i [[12]], several cladistic and comparative anatomical results of the prior decade, and the Mayr-Emery-Forel-Wheeler-Brown system that came before. [Extracted from the article]

The structure of soil aggregates plays an important role for the turnover of particulate organic matter (POM) and vice versa. Analytical approaches usually do not disentangle the continuous re‐organization of soil aggregates, caught between disintegration and assemblage. This led to a lack of understanding of the mechanistic relationship between aggregation and organic matter dynamics in soils. In this study, we took advantage of a process‐based mechanistic model that describes the interaction between the dynamic (re‐)arrangement of soil aggregates, based on dynamic image analysis data of wet‐sieved aggregates, to analyze the turnover of POM, and simultaneous soil surface interactions in a spatially and temporally explicit way. Our novel modeling approach enabled us to unravel the temporal development of aggregate sizes, organic carbon (OC) turnover of POM, and surface coverage as affected by soil texture, POM input, and POM decomposition rate comparing a low and high clay soil (18% and 33% clay content). Our results reveal the importance of the dynamic re‐arrangement of soil structure on POM‐related turnover of OC in soils. Firstly, aggregation was largely determined by the POM input fostering aggregates through additional gluing joints outweighing soil texture at lower decomposition rate, whereas at higher decomposition rate, soil texture had a higher influence leading to larger aggregates in the high clay soil. Secondly, the POM storage increased with clay content, showing that surface interactions may delay the turnover of OC into CO2. Thirdly, we observed a structural priming effect in which the increased input of POM induced increased structural re‐arrangement stimulating the mineralization of old POM. This work highlights that the dynamic re‐arrangement of soil aggregates has important implications for OC turnover and is driven by underlying surface interactions where temporary gluing spots stabilize larger aggregates. [ABSTRACT FROM AUTHOR]

The human olfactory bulb (OB) has a laminar structure. The segregation of cell populations in the OB image poses a significant challenge because of indistinct boundaries of the layers. Standard 3D visualization tools usually have a low resolution and cannot provide the high accuracy required for morphometric analysis. X-ray phase contrast tomography (XPCT) offers sufficient resolution and contrast to identify single cells in large volumes of the brain. The numerous microanatomical structures detectable in XPCT image of the OB, however, greatly complicate the manual delineation of OB neuronal cell layers. To address the challenging problem of fully automated segmentation of XPCT images of human OB morphological layers, we propose a new pipeline for tomographic data processing. Convolutional neural networks (CNN) were used to segment XPCT image of native unstained human OB. Virtual segmentation of the whole OB and an accurate delineation of each layer in a healthy non-demented OB is mandatory as the first step for assessing OB morphological changes in smell impairment research. In this framework, we proposed an effective tool that could help to shed light on OB layer-specific degeneration in patients with olfactory disorder. [ABSTRACT FROM AUTHOR]

Background: The evolution of the brain and its major neuropils in Panarthropoda (comprising Arthropoda, Tardigrada and Onychophora) remains enigmatic. As one of the closest relatives of arthropods, onychophorans are regarded as indispensable for a broad understanding of the evolution of panarthropod organ systems, including the brain, whose anatomical and functional organisation is often used to gain insights into evolutionary relations. However, while numerous recent studies have clarified the organisation of many arthropod nervous systems, a detailed investigation of the onychophoran brain with current state-of-the-art approaches is lacking, and further inconsistencies in nomenclature and interpretation hamper its understanding. To clarify the origins and homology of cerebral structures across panarthropods, we analysed the brain architecture in the onychophoran Euperipatoides rowelli by combining X-ray micro-computed tomography, histology, immunohistochemistry, confocal microscopy, and three-dimensional reconstruction. Results: Here, we use this detailed information to generate a consistent glossary for neuroanatomical studies of Onychophora. In addition, we report novel cerebral structures, provide novel details on previously known brain areas, and characterise further structures and neuropils in order to improve the reproducibility of neuroanatomical observations. Our findings support homology of mushroom bodies and central bodies in onychophorans and arthropods. Their antennal nerve cords and olfactory lobes most likely evolved independently. In contrast to previous reports, we found no evidence for second-order visual neuropils, or a frontal ganglion in the velvet worm brain. Conclusion: We imaged the velvet worm nervous system at an unprecedented level of detail and compiled a comprehensive glossary of known and previously uncharacterised neuroanatomical structures to provide an in-depth characterisation of the onychophoran brain architecture. We expect that our data will improve the reproducibility and comparability of future neuroanatomical studies. [ABSTRACT FROM AUTHOR]

In order to gain further insights into early solar system aggregation processes, we carried out an experiment on board the International Space Station, which allowed us to study the behavior of dust particles exposed to electric arc discharges under long‐term microgravity. The experiment led to the formation of robust, elongated, fluffy aggregates, which were studied by scanning electron microscopy, electron backscatter diffraction, and synchrotron micro‐computed tomography. The morphologies of these aggregates strongly resemble the typical shapes of fractal fluffy‐type calcium‐aluminum‐rich inclusions (CAIs). We conclude that a small amount of melting could have supplied the required stability for such fractal structures to have survived transportation and aggregation to and compaction within planetesimals. Other aggregates produced in our experiment have a massy morphology and contain relict grains, likely resulting from the collision of grains with different degrees of melting, also observed in some natural CAIs. Some particles are surrounded by igneous rims, which remind in thickness and crystal orientation of Wark–Lovering rims; another aggregate shows similarities to disk‐shaped CAIs. These results imply that a (flash‐)heating event with subsequent aggregation could have been involved in the formation of different morphological CAI characteristics. [ABSTRACT FROM AUTHOR]

We performed an experiment under long-term microgravity conditions aboard the International Space Station (ISS) to obtain information on the energetics and experimental constraints required for the formation of chondrules in the solar nebula by 'nebular lightning'. As a simplified model system, we exposed porous forsterite (Mg 2 SiO 4 ) dust particles to high-energetic arc discharges. The characterization of the samples after their return by synchrotron microtomography and scanning electron microscopy revealed that aggregates had formed, consisting of several fused Mg 2 SiO 4 particles. The partial melting and fusing of Mg 2 SiO 4 dust particles under microgravity conditions leads to a strong reduction of their porosity. The experimental outcomes vary strongly in their appearance from small spherical melt-droplets ( ∅ ≈ 90 µm) to bigger and irregularly shaped aggregates ( ∅ ≈ 350 µm). Our results provided new constraints with respect to energetic aspects of chondrule formation and a roadmap for future and more complex experiments on Earth and in microgravity conditions. [ABSTRACT FROM AUTHOR]

X-ray computed tomography (XCT) is a well-established technique to characterize the 3D spatial arrangement of soil structure. However, 4D XCT (3D + time) has been demonstrated to be an essential step into new insights on dynamic processes occurring in the soil (e.g., fluid flow, plant root development, hydro-mechanical behavior). With the recent advances in X-ray sources such as fourth-generation synchrotron light sources, the temporal resolution of 4D XCT experiments has increased to the order of seconds. Therefore, this paper seeks to describe the current state of the art regarding 4D XCT applied in two hot topics in soil science: (i) fluid flow and water distribution and (ii) soil-root interactions. In addition, future perspectives involving the XCT beamline (Mogno) at the new Brazilian synchrotron facility (Sirius) are presented aiming to enlighten possibilities of innovative 4D XCT investigations in soil science. The main capabilities of this beamline that will be linked with currently identified soil-related research limitations and gaps are increased spatial and temporal resolutions, multiscale analysis, high energy, and phase contrast imaging. [ABSTRACT FROM AUTHOR]

Bio‐tillage has recently been proposed as a measure to alleviate soil compaction through biopores created by cover crop roots. The objective of this study was to determine the effect of different cover crops on soil physical properties and the succeeding maize (Zea mays L.) growth in compacted soil. Four treatments, including no cover crop as a control (Con), alfalfa (Medicago sativa L.), oilseed rape (Brassica napus L.), and radish and hairy vetch mixture (Raphanus sativus L. and Vicia villosa Roth), were carried out under both compacted and noncompacted soil conditions. Soil physical properties, such as the volumetric soil water content (SWC), bulk density, saturated hydraulic conductivity (Ks) and air permeability at water potential of −60 hPa (Ka60), and maize root characteristics and yield were measured. The cover crops did not affect the soil bulk density but significantly decreased the SWC in both the compacted and noncompacted soils relative to the Con treatment. The alfalfa treatment presented significantly higher Ks in the noncompacted soil and Ka60 in both the compacted and noncompacted soils than the Con treatment in the soil layer depth of 20–50 cm. The three cover crop treatments improved the maize root biomass density (173.2% for 2018 and 35.6% for 2019) and root length density (50.9% for 2018 and 51.8% for 2019) relative to the Con treatment in the soil layer depth of 10–70 cm in 2018 and soil layer depth of 10–50 cm in 2019 in the compacted soil rather than in the noncompacted soil. Compared with the Con treatment, the radish mixed with hairy vetch treatment in 2018 and the oilseed rape treatment in 2019 significantly enhanced the maize yield in the compacted soil. Our results suggest that alfalfa is the best crop for improving air permeability; however, the oilseed rape and mixture of radish and hairy vetch lead to better maize growth in the compacted soil. Bio‐tillage using cover crops is effective in alleviating soil compaction. Core Ideas: Cover crops significantly reduced soil water content but did not alter bulk density.Alfalfa was the best crop for improving air permeability in compacted soil.Cover crops improved the maize root characteristics and yield in compacted soil.Oilseed rape and a mixture of radish and hairy vetch had better effects on maize growth. [ABSTRACT FROM AUTHOR]

In this study, we investigated the potential and limitations of using joint X‐ray and time‐of‐flight (TOF) neutron imaging for mapping the 3‐dimensional organic carbon distribution in soil. This approach is viable because neutron and X‐ray beams have complementary attenuation properties. Soil minerals consist to a large part of silicon and aluminium, and elements that are relatively translucent to neutrons but attenuate X‐rays. In contrast, attenuation of neutrons is strong for hydrogen, which is abundant in soil organic matter (SOM), while hydrogen barely attenuates X‐rays. In theory, TOF neutron imaging does further more allow the imaging of Bragg edges, which correspond to d‐spacings in minerals. This could help to distinguish between SOM and clay minerals, the mineral group in soil that is most strongly associated with hydrogen atoms. We collected TOF neutron image data at the IMAT beamline at the ISIS facility and synchrotron X‐ray image data at the I12 beamline at the Diamond Light source, both located within the Rutherford Appleton Laboratory, Harwell, UK. The white beam (the full energy spectrum) neutron image clearly showed variations in neutron attenuation within soil aggregates at approximately constant X‐ray attenuations. This indicates a constant bulk density with varying organic matter and/or clay content. Unfortunately, the combination of TOF neutron and X‐ray imaging was not suited to allow for a distinction between SOM and clay minerals at the voxel scale. While such a distinction is possible in theory, it is prevented by technical limitations. One of the main reasons is that the neutron frequencies available at modern neutron sources are too large to capture the main d‐spacings of clay minerals. As a result, inference to voxel scale SOM concentrations is presently not feasible. Future improved neutron sources and advanced detector designs will eventually overcome the technical problems encountered here. On the positive side, combined X‐ray and TOF neutron imaging demonstrated abilities to identify quartz grains and to distinguish between plastics and plant seeds. Highlights: Full understanding of biogeochemical processes requires three‐dimensional (3‐D) maps of organic matter in soil (SOM).This study investigates a novel method to map voxel‐scale SOM contents with 3‐D resolution.The method is based a combination of X‐ray and time‐of‐flight neutron tomography.At present, technical limitations prevent distinguishing between SOM and clay mineral contents.More advanced neutron sources are required to overcome the encountered technical obstacles. [ABSTRACT FROM AUTHOR]

Platinum (Pt)‐tipped electrodes are frequently employed to measure the soil redox potential (EH). Thereby, the timely transition from reducing towards oxidising soil conditions is one of the most important biogeochemical changes that can occur in soil. This condition is mainly linked to the air‐filled pore volume (ε) and pore geometries. However, even when the Pt electrodes are located in close vicinity to each other, EH readings behave non‐uniformly, presumably due to the millimetre scaled heterogeneity of pore spaces controlling oxygen (O2) availability and transport. In this study, we examined the ε distribution and pore connectivity in the close vicinity of a Pt electrode during an artificial evaporation experiment using an undisturbed soil sample (Ah‐horizon, Calcaric Gleysol). We combined physio‐chemical methods with non‐destructive X‐ray computed microtomography (μCT) and 3D‐image analysis. μCT scans were conducted at three‐time points, that is, reducing conditions with EH < −100 mV (CT‐1), the transition from reducing towards oxidising conditions with an EH increase > 5 mV h−1 (CT‐2), and oxidising conditions with EH > 300 mV (CT‐3). We observed that the shift from reducing towards oxidising conditions took place at an air‐filled porosity (εCT) of ~0.03 cm3 cm−3, which matches very with gravimetrically calculated data obtained by tensiometry of ε ~0.05 cm3 cm−3. Besides the relation of EH and ε, image analysis revealed that a connected εCT (εCT_conn) of ~0.02 cm3 cm−3 is needed to enable enhanced O2 diffusion from the soil surface towards the Pt surface and facilitate a straightforward EH response. We conclude that εCT_conn is a critical parameter to assess aeration processes in temporarily water‐saturated soils to characterise a switch in redox conditions. Highlights: Usually, soil redox dynamics are related to the air‐filled porosity (εCT) but here its connected portion (εCT_conn) was found more relevant.3D X‐ray computed microtomography imaging close to a redox electrode enabled us to understand the soil aeration process.Connected εCT (εCT_conn) of ~0.02 cm3 cm−3 facilitated oxidising soil conditions.εCT_conn is a critical parameter to assess the aeration process in temporarily water‐saturated soils. [ABSTRACT FROM AUTHOR]