Description Of Microstructure Research Articles

Graph-enhanced deep material network: multiscale materials modeling with microstructural informatics

AbstractThis study addresses the fundamental challenge of extending the deep material network (DMN) to accommodate multiple microstructures. DMN has gained significant attention due to its ability to be used for fast and accurate nonlinear multiscale modeling while being only trained on linear elastic data. Due to its limitation to a single microstructure, various works sought to generalize it based on the macroscopic description of microstructures. In this work, we utilize a mechanistic machine learning approach grounded instead in microstructural informatics, which can potentially be used for any family of microstructures. This is achieved by learning from the graph representation of microstructures through graph neural networks. Such an approach is a first in works related to DMN. We propose a mixed graph neural network (GNN)-DMN model that can single-handedly treat multiple microstructures and derive their DMN representations. Two examples are designed to demonstrate the validity and reliability of the approach, even when it comes to the prediction of nonlinear responses for microstructures unseen during training. Furthermore, the model trained on microstructures with complex topology accurately makes inferences on microstructures created under different and simpler assumptions. Our work opens the door for the possibility of unifying the multiscale modeling of many families of microstructures under a single model, as well as new possibilities in material design.

Effects of Size Polydispersity and Dense Media on Quantitative Ultrasound Estimates.

Quantitative ultrasound (QUS) techniques based on the backscatter coefficient (BSC) aim to characterize the scattering properties of biological tissues. A scattering model is fit to the measured BSC, and the fitted QUS parameters can provide local tissue microstructure, namely, scatterer size and acoustic concentration. However, these techniques may fail to provide a correct description of tissue microstructure when the medium is polydisperse and/or dense. The objective of this study is to investigate the effects of scatterer size polydispersity in sparse or dense media on the QUS estimates. Four scattering models (i.e., the monodisperse and polydisperse sparse models, and the monodisperse and polydisperse concentrated models based on the structure factor) are compared to assess their accuracy and reliability in quantifying the QUS estimates. Simulations are conducted with different scatterer size distributions for sparse, moderately dense, and dense media (volume fractions of 1%, 20%, and 73%, respectively). The QUS parameters are estimated by using model-based inverse methods at different center frequencies between 8 and 50 MHz. Experimental data are also analyzed using colon adenocarcinoma HT29 cell pellet biophantoms to further validate the results obtained from simulations at the volume fraction of 73%. Our findings reveal that the choice of scattering model has a significant impact on the accuracy of QUS estimates. For sufficiently high frequencies and dense media, the polydisperse concentrated model outperforms the other models and enables more accurate quantification. Furthermore, our results contribute to advancing our understanding of the complexities associated with scatterer size polydispersity and dense media in spectral-based QUS techniques.

3D Imaging of PEMFC Electrode Microstructure by Electron Tomography and 3D FIB/SEM

Scanning and transmission electron microscopies (SEM and TEM) are two imaging techniques widely used in the study of PEMFC electrode microstructure. They have played a significant role in the improvement of electrode components and the understanding of their main degradation mechanisms. However, the currently available description of the electrode microstructure does not allow yet to unambiguously identify the key microstructural factors that limit gas and proton transport within the electrode. These factors are crucial as they control the performance of the PEMFC, especially at high current density, and are therefore the subject of numerous studies, using either fine electrochemical measurements or modeling approaches.The objective of our work is to provide an improved description of the electrode microstructure by giving quantitative information on its porosity at different scales as well as on the ionomer distribution. For this purpose, we develop 3D characterization techniques applied to the PEMFC electrodes such as electron tomography and 3D FIB/SEM.The studied cathode electrode was prepared using TEC10E50E catalyst from Tanaka that is 50 wt % loading of Pt deposited on high-specific area carbon (HSAC), and Nafion D2020. The Pt loading of the electrode is 0.2 mgPtcm-2 and the ionomer/carbon ratio is 0.8.As a first step, electron tomography analyses were performed on the Pt/HSAC powder to determine the distribution of Pt nanoparticles (NPs) which can be located either on the carbon surface (outer NPs) or inside the carbon porosity (inner NPs)[1-3]. Our strategy is to record tilt image series by using two annular detectors: i) a high angle annular detector avoiding Pt NP diffraction contrast for the 3D image reconstruction of Pt NPs (without diffraction artifact) and ii) a lower angle annular detector that enhances carbon contrast for the 3D image reconstruction of the carbon phase. These two segmented images were then combined (Figure 1), allowing the calculation of the NP size histogram but also of the volume and the surface area of the two NP populations (inner and outer NPs).On the second step, the porosity of the electrode was analyzed by 3D FIB/SEM. A volume of around 10 X 10 x 5 μm3 was imaged with a cubic voxel size of 5 × 5 × 5 nm3. The solid phase (carbon, Pt NPs and ionomer) segmentation was based on a composite image created from two electron detectors (secondary and backscattered electrons) and using a machine learning software. Quantitative data such as the total porosity, the pore size distribution or the agglomerate size distribution of the solid phase were extracted from this volume. Figure 2a shows a 2D slice of this segmented volume where the solid phase is in black and the porosity in white.In order to analyze the electrode porosity with a higher spatial resolution, electron tomography experiment was also performed on a 150 nm thick slice of the electrode cut by ultramicrotomy after being embedded in an epoxy resin. The tilt image series were recorded with a pixel size of 0.5 nm and a field of view of 2 x 2 µm2. The 2D slice of the reconstructed volume (Figure 2b) shows that the largest solid agglomerates detected on the 3D FIB/SEM image can be identified as an agglomeration of numerous carbon particles. The challenge now is to quantify the porosity created between these carbon particles and to determine how many Pt NPs are located in these large agglomerates.Finally, the distribution of the ionomer was analyzed within the electrode similarly to [4]. For this analysis, a 150 nm slice of the electrode was cut by cryo-ultramicrotomy without embedding in epoxy resin as described in [5]. TEM images show that the ionomer is not homogeneously distributed on the surface of the entire carbon particles but is often observed in the concave surface created between the carbon particles (Figure 3). These observations suggest a ionomer distribution in agreement with the heterogeneous ionomer coating model proposed by Inoue et al. [6]. We also suggest that a part of the ionomer could be localized in the small pores located inside the large carbon agglomerates described in the previous paragraph. This could explain why the ionomer is so difficult to detect on TEM images. This work has been done in the frame of the FURTHER-FC project. This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under Grant Agreement No 875025. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research. Figure 1

The importance of the microstructure on hydro-mechanical behaviour of compacted granular bentonite

Granular bentonite (GB) with extended grain size distribution, a candidate material to construct engineered barriers, has low water permeability, high swelling potential and self-sealing capacity and is desirable in portability and workability. However, few systematic data combining microstructural descriptions and hydro-mechanical (HM) behavioural features are available. The present work investigates the HM performance of Wyoming (MX80)-type GB samples compacted at different initial water contents and at a fixed dry density of 1550 kg/m3. The samples' microstructure and its evolution along stress paths were studied using X-ray micro-computed tomography and mercury intrusion porosimetry. The results highlighted that the compacted GB presented local density heterogeneity and a multi-porosity network. Compaction at low initial water content increased the proportion of macropores and contributed to the enhancement of the compressibility and collapse on wetting under high stresses. During isochoric saturation, two stages of swelling development were identified. First, the flooding of macropores and matric suction reduction was related to the initial increase in swelling pressure. The secondary swelling was due to the water absorption of clay sheets in micropores and the expansion of micropores within granules and aggregates, during which the density of pore water increased. A decrease in the compaction water content can result in a higher pore water density after isochoric saturation and a lower water permeability. Finally, the water retention behaviour of the compacted sample within drying/wetting cycles was less sensitive to the initial pore size distribution. The current outcomes underline the critical role of the microstructure on the HM behaviour of compacted GB.

Multi-scale model to study gas transport processes in clay materials

In the field of radioactive waste confinement, the question of gas transfers in clay formations is a crucial issue [1]. A certain amount of gas, such as Hydrogen may be generated during the exploitation phase in the nearfield by the deterioration of the metal components of the system. Since the host medium is characterised by a very low permeability, the mechanisms of gas transport by advection and diffusion within the groundwater remain insufficient to evacuate the gas generated and a free gas phase is formed. If the gas pressure keeps increasing and reaches the minimum principal stress acting on the rock, micro-fractures, known as preferential gas pathways could develop through the rock mass [2], and affect the clay barrier integrity.
 There is a growing body of experimental evidences [3, 4] that separation planes such as bedding planes or pre-existing fractures and heterogeneities in clay-rich materials represent preferred weaknesses for the process of opening discrete gas-filled pathways. Capturing the related transport mechanisms therefore requires to go from macroscopic to microscopic scale. In this context, the adopted numerical approach would ideally take into account the effect of each constituent of the material microstructure on the macroscopic gas flow. Yet, direct modelling of the entire microstructure using small-scale models is usually not possible due to the huge computational costs it would require at the scale of a repository. Conversely, indirect modelling of the behaviour of all the micro-constituents by collective closed-form macroscopic constitutive equations using large-scale models [5] has also limits in terms of assumptions formulation and parameters identification. Hence, the use of a multi-scale approach that models the micro-scale effects explicitely on their specific length scale and couples their homogenized effects to the macro-scale is proposed in the present work. Based on a periodicity assumption of the microstructure, the physical and geometrical properties of the microstructure are embedded on a Representative Element Volume (REV) which contains a detailed model of the microstructure constituents, i.e. the pore network, the bedding planes and the bridging planes, while eluding a complex description of the whole microstructure over the domain. From this local description of the material, the macroscopic response to loading can be derived using numerical homogenisation techniques [6].
 The multi-scale model proposed here has been implemented in the finite element code Lagamine, and validated against a well established and documented macro-scale THM coupled model [7]. The size and structure of the REV comes from experimental data acquired from scanning images in clay material, like for instance the Boom Clay formation which is envisaged as a potential host rock for a deep geological disposal in Belgium. Such scans reveal the opening of large aperture with a repeated distance in-between, which make it possible to extrapolate a physical idealisation of the microstructure (Figure 1a), built with one of these fractures corresponding to the bedding planes (red) and the pore network substituted by an assembly of tubes (green). Narrow-aperture fissures, known as the bridging planes (blue) were also identified to contribute to the flow normal to the predominant direction of fissure [4], by connecting the natural discontinuities which were initially closed. These micro-scale constituents are defined in such a way as to satisfy the conditions of pore size distribution, macroporosity and intrinsic permeability. For the mechanical behaviour, a simple linear elastic constitutive law was introduced for the tube network while a non-linear stress-strain relationship was used for the interfaces defining the bedding and bridging planes. Concerning the hydraulic behaviour, gas diffusive fluxes were considered and modelled by a Fick’s law while a channel flow based on the Navier-Stokes equations was used for the multiphase flow in the different constituents.
 The model has been subsequently applied to simulate a gas injection test parallel and perpendicular to the bedding of initially saturated samples of Boom Clay [4]. This analysis provides a rather good agreement with the experimental results in terms of injection and outflow pressure response, outflow volume and average axial strain along the sample height. In addition, it allows to simulated the creation of a preferential flow pathway along the sample axis (Figure 1b, top), which serves as basis to numerically reproduce the development of random pathway through the sample in plane strain state (Figure 1b, bottom), and aims to improve the mechanistic understanding of the gas transport processes at play in clayey barriers [8].

Development of an Image-based Method for Tablet Microstructure Description and Its Correlation with API Release Rate

The performance of a pharmaceutical formulation, such as the drug (API) release rate, is significantly influenced by the properties of the materials used, the composition of the final product and the tablet compression process parameters. However, in some cases, the knowledge of these input parameters does not necessarily provide a reliable description or prediction of tablet performance. Therefore, the knowledge of tablet microstructure is desirable to understand such formulations. Commonly used analytical techniques, such as X-ray tomography and intrusion mercury porosimetry, are not widely used in pharmaceutical companies due to their price and/or toxicity, and therefore, efforts are made to develop a tool for fast and easy microstructure description. In this work, we have developed an image-based method for microstructure description and applied it to a model system consisting of ibuprofen and CaHPO4∙2H2O (API and excipient with different deformability). The obtained parameter, the quadratic mean of the equivalent diameter of the non-deformable, brittle excipient CaHPO4∙2H2O, was correlated with tablet composition, compression pressure and API release rate. The obtained results demonstrate the possibility of describing the tablet dissolution performance in the presented model system based on the microstructural parameter, providing a possible model system for compressed solid dosage forms in which a plastic component is present and specific API release is required.Graphical

A study on the vertebral column of the dice snake Natrix tessellata (Serpentes, Natricidae) from Denizli (western Anatolia, Turkey).

The vertebral anatomy of snakes has attracted the attention of researchers for decades and numerous studies have been made for extinct and extant species. The present study investigated the morphological variations in vertebral structure among different vertebral regions in the dice snake Natrix tessellata, and provides a detailed anatomical and microstructural description of the vertebral column. Vertebrae were analyzed and compared using x-ray imaging, scanning electron microscopy, micro-computed tomography, and histological techniques. The vertebral column of N. tessellata is divided into three regions: precloacal, cloacal, and caudal. Unlike in many other tetrapods and snakes, the atlas of N. tessellata does not form a complete ring. It has a flat and roughly trilobate shape with a prominent middle lobe. The axis has two hypapophyses. The anterior precloacal region of the vertebral column has longer and more paddle-shaped hypapophyses, distinguishing it from the posterior and mid-trunk vertebrae. The anterior cloacal vertebrae have a short hypapophysis rather than a hemal keel, and the lymphapophysis extends outward, curving slightly. The cotyle and condyle of the caudal vertebrae exhibited a closer resemblance to a rounded shape, while the pleurapophysis extended ventrolaterally and curved ventrally near its distal end. Paired hemapophyses were present at the posterior-most point of the centrum instead of a hypapophysis. In light of previous fossil findings, our anatomical comparison of the vertebral and transverse processes indicates that the extant Natrix has a more flexible and less rigid spine than its ancestors. Overall, the vertebral differences among snake anatomical regions or taxa are a testament to the remarkable diversity and adaptability of these fascinating reptiles.

Performance analysis and optimisation of spatially-varying infill microstructure within CAD geometries

The article is aimed to provide an effective digital solution in support of the infill microstructural design within objectives generated from normal computer aided design (CAD) systems. The key here is to deploy the microstructure and to analyse the performance of the resulting multiscale objective in the parameter domain, from which a CAD objective is mapped, usually by means of Non-Uniform Rational B-Splines (NURBS) functions. In the regularly shaped domain defined in the parameter space, another set of mapping functions are defined for the description of spatially-varying microstructure (in the parameter space), and the actual multiscale CAD objective gets represented through composition of these mapping functions with the NURBS-based functions for CAD geometry generation. When the introduced mapping functions are also NURBS-based, the proposed representation strategy becomes more favoured by CAD systems, in the sense that the CAD geometry and its infill can be tuned simultaneously but independently with a same set of NURBS basis. Moreover, our computer-aided engineering (CAE) module is also installed over the parameter domain, based on a machine-learning-based homogenisation formulation for compliance and strength analysis. Thus the finite element meshes stay unchanged although the accommodating CAD geometry keeps varying. With the aforementioned treatments, a consecutive CAD-consistent scheme is proposed. Our numerical results show that each time as the control points are moved (by a CAD designer), one may choose to wait several seconds for two-dimensional cases and/or a few minutes for three-dimensional cases, to get a CAD geometry filled with microstructure bearing optimised compliance.

Concurrent Measurement of Local and Global in-Plane Permeability of Reinforcement Fabrics through Real-Time Image Processing.

Properties of reinforcement fabrics, such as permeability, are typically characterized in a volume-averaging sense, whereas the fabric microstructure may vary spatially. This makes designing an effective resin infusion strategy for defect-free composite fabrication challenging. Our work presents a concurrent method for simultaneously measuring the local and global in-plane permeability and offers a handy technique for evaluating spatial variability. This experimental setup was similar to that of unidirectional in-plane permeability tests. The fabric, however, should be cut and tested along the angle bisector of warp and weft directions. The evolution of resin flow fronts was analyzed in real-time using in-house code through live video monitoring. The local and global in-plane permeability components were then obtained by applying Darcy's law regionally and globally. The results are in good agreement with those obtained by radial permeability experiments. Statistical analysis of local permeability reveals that the microstructure variability follows a normal distribution. A complete description of fabric microstructure provided by X-ray microcomputed tomography suggests that local permeability and microstructure variation are closely related, confirming the efficacy of the newly proposed method. This work enables the estimation of fabric structure variability and local and global in-plane permeability in a single test without resorting to expensive volume imaging techniques.

Comprehensive leaf and pistil micromorphology and its taxonomic value in the Korean Luzula species

Micromorphological characteristics provide important diagnostic criteria for differentiating plant groups and have thus been widely used to better understand the taxonomic significance of morphologically complex species. A comprehensive leaf and pistil micromorphological study of the Korean woodrush was performed using light and scanning electron microscopy to determine whether comparisons of these provide systematically informative traits. All six examined Korean Luzula species belonged to two subgenera, Luzula (L. capitata, L. multiflora and L. pallescens) and Pterodes (L. odaesanensis, L. rufescens and L. plumosa), and had hypostomatic leaves, with paracytic stomatal complexes found only on the abaxial surface. The epidermal surface could be divided into two types: verrcuate or scabrate on both abaxial and adaxial leaves. Guard cell length was an important trait for subgeneric identification in Korean Luzula, but highly variable among species, ranging from 23.02 μm in L. capitata to 63.75 μm in L. odaesanensis, in which the size variations might be influenced by different environmental conditions. The occurrence of abnormal stomatal complexes in the Korean Luzula species was reported here for the first time, which could be an adaptation to various environmental factors. We also report a detailed description of the pistil microstructure of Korean woodrush. Despite similar pistil surface ornamentation, the micromorphological features described in this study provide valuable information for developing further systematic context in the Korean Luzula species.

Prediction of radiative properties of spherical microalgae considering internal heterogeneity and optical constants of various components.

Most of the current predictions of the radiative properties of microalgae use the homogeneous sphere approximation based on the Mie scattering theory, and the refractive indices of the model were regarded as fixed values. Using the recently measured optical constants of various microalgae components, we propose a spherical heterogeneous model for spherical microalgae. The optical constants of the heterogeneous model were characterized by the measured optical constants of microalgae components for the first time. The radiative properties of the heterogeneous sphere were calculated using the T-matrix method and were well verified by measurements. It shows that the internal microstructure has a more significant effect on scattering cross-section and scattering phase function than absorption cross-section. Compared with the traditional homogeneous models selected with fixed values as refractive index, the calculation accuracy of scattering cross-section of the heterogeneous model improved by 15%-150%. The scattering phase function of the heterogeneous sphere approximation agreed better with measurements than the homogeneous models due to the more detailed description of the internal microstructure. It can be concluded that considering the internal microstructure of microalgae and characterizing the microstructure of the model by the optical constants of the microalgae components helps to reduce the error caused by the simplification of the actual cell.

Local Maxima in Martensite Start Temperatures in the Transition Region between Lath and Plate Martensite in Fe-Ni Alloys

In the binary Fe-rich Fe-Ni system, martensite start temperatures MS decrease from 500 to 200 K when Ni concentrations increase from 20 to 30 at.%. It is well known that alloys with Ni concentrations below 28.5 at.% exhibit lath martensite (LM) microstructures (athermal transformation, small crystals, accommodation by dislocations). Above this concentration, plate martensite (PM) forms (burst-like transformation, large crystals, accommodation by twins). The present work is based on a combination of (i) ingot metallurgy for the manufacturing of Fe-Ni alloys with varying Ni-concentrations, (ii) thermal analysis to measure phase transformation temperatures with a special focus on MS, and (iii) analytical orientation imaging scanning electron microscopy for a quantitative description of microstructures and crystallographic features. For Ni-concentrations close to 28.5 at.%, the descending MS-curve shows a local maximum, which has been overlooked in prior works. Beyond the local maximum, MS temperatures decrease again and follow the overall trend. The local maximum is associated with the formation of transition martensite (TM) microstructure, which exhibits LM and PM features. TM forms at higher MS temperatures, as it is accommodated by simultaneous twinning and dislocation slip. An adopted version of the Clausius-Clapeyron equation explains the correlation between simultaneous accommodation and increased transformation temperatures.

Macroanatomical, Histological and Microtomographic Study of the Teeth of the Komodo Dragon (Varanus komodoensis)—Adaptation to Hunting

The present study aimed to characterize the macrostructure and microstructure of the mandibular teeth of the Komodo dragon (Varanus komodoensis) and the methods it uses to obtain food. Examinations were performed using a stereoscopic microscope, autofluorescence method, histological method and computed microtomography. A detailed macro- and micro-structural description of V. komodoensis mandibular teeth were made. The mandibular teeth are laterally flattened along their entire length and the dental crown is hooked caudally. The part of the nasal margin of the tooth crown is irregular, while the caudal margin of the tooth is characteristically serrated, except for the tooth base area. There are longitudinal grooves on the lingual and vestibular surfaces up to the lower third of the tooth height. The mandibular tooth is surrounded by a cuff made of the oral mucosa, containing the opening of the venom gland. In the histological structure of the tooth, the enamel covering the tooth crown and the dentin under the enamel are distinguished. The inside of the tooth, except its basal part, is filled with the tooth chamber, while the inside of the lower part of the tooth is filled with plicidentine, which corresponds to external furrows on the enamel. The plicidentine arrangement resembles a honeycomb. A small amount of dentine folds reach up to the tooth apex. Characteristic features of the structure of the mandibular teeth in V. komodoensis may indicate their significant role, in addition to the venom glands, in obtaining food in the natural environment of this species.

Effects of microstructure on THM behaviour of geomaterials

In this paper, we discuss the thermo-hydro-mechanical behaviour of geomaterials at the light of their microstructure and its changes induced by multiphysics loading. After recalling the strong links between the microstructure and the water retention properties of unsaturated soils, the relation between themicrostructure and the physical properties ruling heat and mass transfers are discussed. The mechanical behaviour of unsaturated soils is then discussed focussing on the definition of an effective stress based on a microstructure description. The experimental determination of this microstructurally-based effective stressis presented, including recent advances to identify the stress coefficient from Mercury Intrusion Porosimetry data. Opening remarks towards macroscopic modelling of unsaturated geomaterials accounting for their microstructure and its changes is finally discussed.

The effect of risk volume on the fatigue life of stainless steels subjected to high-frequency loading

In this study, fatigue lifetime of two types of specimens with different volumes (given by the gauge length and the diameter of the central part of the specimen) subjected to high-frequency loading is investigated. Studied materials are austenitic stainless steels 1.4306 and 1.407, both commonly known as AISI 304L. An ultrasonic testing machine working at frequency of 20 kHz was used to reach very high cycle fatigue region. Fatigue tests were carried out under uniaxial symmetric tension/compression loading (R = - 1) at room temperature. The study includes a microstructural description of investigated materials, fracture surface analysis, and conclusions.

Application of Microstructural Studies in the Development of Complicated Fault-block

The geological conditions of the Liaohe oilfield are complex and the fracture system is developed. It is particularly important to study the tectonic characteristics of development blocks in the process of oil and gas resources and geothermal resources development. How to effectively identify microstructures becomes the key to capacity building and rolling stock increase during the development of old areas. By carrying out microstructural research, the research idea of microstructural description for complex fault blocks is proposed, and the fracture system is finely carved through different fault distance faults with hierarchical and methodological interpretation, and the velocity field establishment method is preferably selected, combined with the inclination guide body to finely carve the micro-amplitude tectonic morphology, which can effectively carve microstructures and provide reliable geological foundation support for the development of oil and gas resources and geothermal resources in complicated fault-blocks.

Hip osteoarthritis: A novel network analysis of subchondral trabecular bone structures.

Hip osteoarthritis (HOA) is a degenerative joint disease that leads to the progressive destruction of subchondral bone and cartilage at the hip joint. Development of effective treatments for HOA remains an open problem, primarily due to the lack of knowledge of its pathogenesis and a typically late-stage diagnosis. We describe a novel network analysis methodology for microcomputed tomography (micro-CT) images of human trabecular bone. We explored differences between the trabecular bone microstructure of femoral heads with and without HOA. Large-scale automated extraction of the network formed by trabecular bone revealed significant network properties not previously reported for bone. Profound differences were discovered, particularly in the proximal third of the femoral head, where HOA networks demonstrated elevated numbers of edges, vertices, and graph components. When further differentiating healthy joint and HOA networks, the latter showed fewer small-world network properties, due to decreased clustering coefficient and increased characteristic path length. Furthermore, we found that HOA networks had reduced length of edges, indicating the formation of compressed trabecular structures. In order to assess our network approach, we developed a deep learning model for classifying HOA and control cases, and we fed it with two separate inputs: (i) micro-CT images of the trabecular bone, and (ii) the network extracted from them. The model with plain micro-CT images achieves 74.6% overall accuracy while the trained model with extracted networks attains 96.5% accuracy. We anticipate our findings to be a starting point for a novel description of bone microstructure in HOA, by considering the phenomenon from a graph theory viewpoint.

Automated Methodology for Volume Fraction Measurement of Three Phase Steel Micrograph Using Image Processing Techniques

A quantitative description of microstructure governs the characteristics of the material. Various heat and excellent treatments reveal micro-structures when the material is prepared. Depending on the microstructure, mechanical properties like hardness, ductility, strength, toughness, corrosion resistance, etc., also vary. Microstructures are characterized by morphological features like volume fraction of different phases, particle size, etc. Relative volume fractions of the phases must be known to correlate with the mechanical properties. In this work, using image processing techniques, an automated scheme was presented to calculate relative volume fractions of the phases, namely Ferrite, Martensite, and Bainite, present in the microscopic image of high strength low alloy steel. First, the microscopic image was segmented into Ferrite, Martensite, and Bainite regions. The phase structure's geometric property was used to identify different phases present inside the micrograph. After phase detection, the volume fraction of each region is calculated.

ANN-aided evaluation of dual-phase microstructural fabric tensors for continuum plasticity representation

The evolution and orientation-dependent behavior of microstructures in dual-phase materials significantly affect the mechanical properties. How to quantify the microstructural effect in a continuum constitutive model, especially considering anisotropic elastic–plastic properties, is still a tough research topic for multiscale mechanics. In the present paper, the fabric tensors are successfully correlated with elastic–plastic mechanical properties of dual-phase materials with the help of the artificial neural network (ANN). The fabric tensors can be decomposed into isotropic and deviatoric components, which describe voluminal changes and orientation-dependent properties of the microstructural material through data-driven analysis. A correlation analysis combined with gradient-based attributions revealed, furthermore, that a lower-order fabric tensor with fewer components was sufficient for the complex morphology of microstructures. For crystal symmetric materials, the second-order fabric tensors are sufficient to generate an adequate description of anisotropic dual-phase microstructures. The fabric tensors provide a bridge to connect the microstructural characteristics with phenomenological continuum plasticity for complex materials. • Verified the correlation between fabric tensors and elastic–plastic mechanical properties. • Achieved an adequate description of dual-phase microstructures by second-order fabric tensors. • Identified the key fabric tensor components through data-driven analysis. • Provided a microstructural material’s state variable for continuum plasticity.

Proteomic and Transcriptomic Analyses in the Slipper Snail Crepidula fornicata Uncover Shell Matrix Genes Expressed During Adult and Larval Biomineralization.

SynopsisThe gastropod shell is a composite composed of minerals and shell matrix proteins (SMPs). SMPs have been identified by proteomics in many molluscs, but few have been studied in detail. Open questions include (1) what gene regulatory networks regulate SMP expression, (2) what roles individual SMPs play in biomineralization, and (3) how the complement of SMPs changes over development. These questions are best addressed in a species in which gene perturbation studies are available; one such species is the slipper snail, Crepidula fornicata. Here, SEM and pXRD analysis demonstrated that the adult shell of C. fornicata exhibits crossed lamellar microstructure and is composed of aragonite. Using high-throughput proteomics we identified 185 SMPs occluded within the adult shell. Over half of the proteins in the shell proteome have known biomineralization domains, while at least 10% have no homologs in public databases. Differential gene expression analysis identified 20 SMP genes that are up-regulated in the shell-producing mantle tissue. Over half of these 20 SMPs are expressed during development with two, CfSMP1 and CfSMP2, expressed exclusively in the shell gland. Together, the description of the shell microstructure and a list of SMPs now sets the stage for studying the consequences of SMP gene knockdowns in molluscs.