Focused Ion Beam-scanning Electron Research Articles

Characterization of 3D pore nanostructure and stress-dependent permeability of organic-rich shales in northern Guizhou Depression, China

The three-dimensional (3D) pore structures and permeability of shale are critical for forecasting gas production capacity and guiding pressure differential control in practical reservoir extraction. However, few investigations have analyzed the effects of microscopic organic matter (OM) morphology and 3D pore nanostructures on the stress sensitivity, which are precisely the most unique and controlling factors of reservoir quality in shales. In this study, ultra-high nanoscale-resolution imaging experiments, i.e. focused ion beam-scanning electron microscopy (FIB-SEMs), were conducted on two organic-rich shale samples from Longmaxi and Wufeng Formations in northern Guizhou Depression, China. Pore morphology, porosity of 3D pore nanostructures, pore size distribution, and connectivity of the six selected regions of interest (including clump-shaped OMs, interstitial OMs, framboidal pyrite, and microfractures) were qualitatively and quantitatively characterized. Pulse decay permeability (PDP) measurement was used to investigate the variation patterns of stress-dependent permeability and stress sensitivity of shales under different confining pressures and pore pressures, and the results were then used to calculate the Biot coefficients for the two shale formations. The results showed that the samples have high OM porosity and 85% of the OM pores have the radius of less than 40 nm. The OM morphology and pore structure characteristics of the Longmaxi and Wufeng Formations were distinctly different. In particular, the OM in the Wufeng Formation samples developed some OM pores with radius larger than 500 nm, which significantly improved the connectivity. The macroscopic permeability strongly depends on the permeability of OM pores. The stress sensitivity of permeability of Wufeng Formation was significantly lower than that of Longmaxi Formation, due to the differences in OM morphology and pore structures. The Biot coefficients of 0.729 and 0.697 were obtained for the Longmaxi and Wufeng Formations, respectively.

Influence of Porosity of Sulfide-Based Artificial Solid Electrolyte Interphases on Their Performance with Liquid and Solid Electrolytes in Li and Na Metal Batteries

Realization of all-solid-state batteries combined with metallic Li/Na is still hindered due to the unstable interface between the alkali metal and solid electrolytes, especially for highly promising thiophosphate materials. Artificial and uniform solid-electrolyte interphases (SEIs), serving as thin ion-conducting films, have been considered as a strategy to overcome the issues of such reactive interfaces. Here, we synthesized sulfide-based artificial SEIs (LixSy and NaxSy) on Li and Na by solid/gas reaction between the alkali metal and S vapor. The synthesized films are carefully characterized with various chemical/electrochemical techniques. We show that these artificial SEIs are not beneficial from an application point of view since they either contribute to additional resistances (Li) or do not prevent reactions at the alkali metal/electrolyte interface (Na). We show that NaxSy is more porous than LixSy, supported by (i) its rough morphology observed by focused ion beam-scanning electron microscopy, (ii) the rapid decrease of Rinterface (interfacial resistance) in NaxSy-covered-Na symmetric cells with liquid electrolyte upon aging under open-circuit potential, and (iii) the increase of Rinterface in NaxSy-covered-Na solid-state symmetric cells with Na3PS4 electrolyte. The porous SEI allows the penetration of liquid electrolyte or alkali metal creep through its pores, resulting in a continuous chemical reaction. Hence, porosity of SEIs in general should be carefully taken into account in the application of batteries containing both liquid electrolyte and solid electrolyte.

Transverse endoplasmic reticulum expansion in hereditary spastic paraplegia corticospinal axons.

Hereditary spastic paraplegias (HSPs) comprise a large group of inherited neurologic disorders affecting the longest corticospinal axons (SPG1-86 plus others), with shared manifestations of lower extremity spasticity and gait impairment. Common autosomal dominant HSPs are caused by mutations in genes encoding the microtubule-severing ATPase spastin (SPAST; SPG4), the membrane-bound GTPase atlastin-1 (ATL1; SPG3A) and the reticulon-like, microtubule-binding protein REEP1 (REEP1; SPG31). These proteins bind one another and function in shaping the tubular endoplasmic reticulum (ER) network. Typically, mouse models of HSPs have mild, later onset phenotypes, possibly reflecting far shorter lengths of their corticospinal axons relative to humans. Here, we have generated a robust, double mutant mouse model of HSP in which atlastin-1 is genetically modified with a K80A knock-in (KI) missense change that abolishes its GTPase activity, whereas its binding partner Reep1 is knocked out. Atl1KI/KI/Reep1-/- mice exhibit early onset and rapidly progressive declines in several motor function tests. Also, ER in mutant corticospinal axons dramatically expands transversely and periodically in a mutation dosage-dependent manner to create a ladder-like appearance, on the basis of reconstructions of focused ion beam-scanning electron microscopy datasets using machine learning-based auto-segmentation. In lockstep with changes in ER morphology, axonal mitochondria are fragmented and proportions of hypophosphorylated neurofilament H and M subunits are dramatically increased in Atl1KI/KI/Reep1-/- spinal cord. Co-occurrence of these findings links ER morphology changes to alterations in mitochondrial morphology and cytoskeletal organization. Atl1KI/KI/Reep1-/- mice represent an early onset rodent HSP model with robust behavioral and cellular readouts for testing novel therapies.

A morphometric analysis of the osteocyte canaliculus using applied automatic semantic segmentation by machine learning.

Osteocytes play a role as mechanosensory cells by sensing flow-induced mechanical stimuli applied on their cell processes. High-resolution imaging of osteocyte processes and the canalicular wall are necessary for the analysis of this mechanosensing mechanism. Focused ion beam-scanning electron microscopy (FIB-SEM) enabled the visualization of the structure at the nanometer scale with thousands of serial-section SEM images. We applied machine learning for the automatic semantic segmentation of osteocyte processes and canalicular wall and performed a morphometric analysis using three-dimensionally reconstructed images. Six-week-old-mice femur were used. Osteocyte processes and canaliculi were observed at a resolution of 2nm/voxel in a 4 × 4μm region with 2000 serial-section SEM images. Machine learning was used for automatic semantic segmentation of the osteocyte processes and canaliculi from serial-section SEM images. The results of semantic segmentation were evaluated using the dice similarity coefficient (DSC). The segmented data were reconstructed to create three-dimensional images and a morphological analysis was performed. The DSC was > 83%. Using the segmented data, a three-dimensional image of approximately 3.5μm in length was reconstructed. The morphometric analysis revealed that the median osteocyte process diameter was 73.8 ± 18.0nm, and the median pericellular fluid space around the osteocyte process was 40.0 ± 17.5nm. We used machine learning for the semantic segmentation of osteocyte processes and canalicular wall for the first time, and performed a morphological analysis using three-dimensionally reconstructed images.

Influence of boron addition on the phase transformation, microstructure, mechanical and in-vitro cellular properties of bredigite-type coatings deposited by a spin coating technique

Doped calcium silicates, e.g. bredigite (Ca7MgSi4O16) have recently become a growing interest in biomedicine thanks to outstanding biocompatibility, bioactivity, and improved mechanical properties when compared to calcium phosphate counterparts. Here, we have produced thin bredigite-type coatings on Ti6Al4V substrate by the polyvinyl alcohol (PVA) assisted sol-gel spin-coating technique and studied the influence of boron incorporation (0.5 and 1.0 mol) on the microstructural, phase, nanomechanical, and in-vitro cellular properties of deposited coatings. Chemical and structural analysis of the coatings was thoroughly performed by Focussed Ion Beam Scanning Electron Microscope (SEM/FIB), Atomic Force Microscopy (AFM), differential thermal analysis (DTA-TG), X-ray diffraction (XRD), and Fourier-Transform Infrared spectroscopy (FTIR), while the nanomechanical properties were evaluated by nanoindentation and nanoscratch tests. Overall, all deposited films were smooth and porous composed of ∼25–50 nm nanoparticles. The boron incorporation increased the coating thickness as a result of PVA interaction with borate ions. The nanomechanical properties (Young's modulus, nanohardness, critical load for cracking) decreased by the boron addition as a result of decreasing the strength of grain boundaries between the nanoparticles. The in-vitro contact cytotoxicity testing revealed high proliferation of the osteoblast cells in all coatings giving the potential of application in orthopedics.

Changes in Envelope Structure and Cell-Cell Communication during Akinete Differentiation and Germination in Filamentous Cyanobacterium Trichormus variabilis ATCC 29413.

Planktonic freshwater filamentous cyanobacterium Trichormus variabilis ATCC 29413 (previously known as Anabaena variabilis) can differentiate heterocysts and akinetes to survive under different stress conditions. Whilst heterocysts enable diazotrophic growth, akinetes are spore-like resting cells that make the survival of the species possible under adverse growth conditions. Under suitable environmental conditions, they germinate to produce new vegetative filaments. Several morphological and physiological changes occur during akinete formation and germination. Here, using scanning electron microscopy (SEM), we found that the mature akinetes had a wrinkled envelope, and the surface of the envelope smoothened as the cell size increased during germination. Thereupon, the akinete envelope ruptured to release the short emerging filament. Focused ion beam–scanning electron microscopy (FIB/SEM) tomography of immature akinetes revealed the presence of cytoplasmic granules, presumably consisting of cyanophycin or glycogen. In addition, the akinete envelope architecture of different layers, the exopolysaccharide and glycolipid layers, could be visualized. We found that this multilayered envelope helped to withstand osmotic stress and to maintain the structural integrity. Furthermore, by fluorescence recovery after photobleaching (FRAP) measurements, using the fluorescent tracer calcein, we found that intercellular communication decreased during akinete formation as compared with the vegetative cells. In contrast, freshly germinating filaments restored cell communication.

Multiscale investigation of pore network heterogeneity and permeability of fluid catalytic cracking (FCC) particles

Pore network is regarded as one of the most important aspects of FCC (Fluid Catalytic Cracking) catalysts for delivering reactants to active sites and transporting out products, and the structure of which can significantly influence the process efficiency. In this work, six characterization methods complementing each other were employed to study the full-scale pore structure (0.4 nm − 20 µm) of fresh FCC particles, especially the X-ray computed tomography (CT) and focused ion beam-scanning electron microscope (FIB-SEM). To focus on nano-scale pores, 3D reconstruction of a whole FCC particle was achieved based on nano-CT, from which the pore network model (PNM) was successfully extracted. Then, permeability simulations along different directions and through various sub-volumes were carried out to demonstrate the anisotropy and heterogeneity of pore structure, respectively. It was also found that the tortuosity of the pores distributed in the outer layer of the FCC particle was more significant than that in the central part of the particle, which could be the mass transfer limiting region during catalysis. Comprehensive acknowledgment of pore structure provides guidance for the optimization of the design of FCC particles, and the multi-scale characterization strategy is a generic strategy for in-depth investigation of structured porous materials.

In Situ Fabrication, Manipulation, and Mechanical Characterization of Free‐Standing Silica Thin Films Using Focused Ion Beam Scanning Electron Microscopy

AbstractDetermination of mechanical properties of (silica) thin films is important for the development of new applications. However, a versatile approach for small‐scale sample fabrication and in situ mechanical testing of these materials is currently lacking which can overcome the existing difficulties in conventional testing approaches. Here, it is shown that by combining focused ion beam scanning electron microscopy (FIB‐SEM) with micromanipulators free‐standing silica beams of the desired dimensions can be fabricated. Using in situ bending tests on such beams inside the SEM and finite element method simulations, the Young's modulus of thin‐film silica and the effects of gallium ion beam radiation on Young's modulus are determined. Furthermore, the effects of controlled relative humidity on the mechanical behavior of silica beams are investigated. The demonstrated FIB‐SEM approach can be extended to other materials and preparation conditions to measure, model, and optimize mechanical properties of thin films for a wide range of (coating) applications.

High-Resolution Numerical Simulation of Microfiltration of Oil-in-Water Emulsion Permeating through a Realistic Membrane Microporous Structure Generated by Focused Ion Beam Scanning Electron Microscopy Images.

Owing to the limitations of visualization techniques in experimental studies and low-resolution numerical models based on computational fluid dynamics (CFD), the detailed behavior of oil droplets during microfiltration is not well understood. Hence, a high-resolution CFD model based on an in-house direct numerical simulation (DNS) code was constructed in this study to analyze the detailed dynamics of an oil-in-water (O/W) emulsion using a microfiltration membrane. The realistic microporous structure of commercial ceramic microfiltration membranes (mullite and α-alumina membranes) was obtained using an image processing technique based on focused ion beam scanning electron microscopy (FIB-SEM). Numerical simulations of microfiltration of O/W emulsions on the membrane microstructure obtained by FIB-SEM were performed, and the effects of different parameters, including contact angle, transmembrane pressure, and membrane microporous structure, on filtration performance were studied. Droplet deformation had a strong impact on filtration behavior because coalesced droplets with diameters larger than the pore diameter permeated the membrane pores. The permeability, oil hold-up fraction inside the pores, and rejection were considerably influenced by the contact angle, while the transmembrane pressure had a little impact on the permeability and oil hold-up fraction. The membrane structure, especially the pore size distribution, also had a significant effect on the microfiltration behavior and performance.

A Probabilistic Formulation of the Diffusion Coefficient in Porous Media as Function of Porosity

We investigate the upscaling of diffusive transport parameters using a stochastic framework. At sub-REV (representative elementary volume) scale, the complexity of the pore space geometry leads to a significant scatter of the observed diffusive transport. We study a large set of volumes reconstructed from focused ion beam-scanning electron microscopy data. Each individual volume provides us sub-REV measurements on porosity and the so-called transport-ability, being a dimensionless parameter representing the ratio of diffusive flux through the porous volume to that through an empty volume. The detected scatter of the transport-ability is mathematically characterized through a probability distribution function (PDF) with a mean and variance as function of porosity, which includes implicitly the effect of pore structure differences among sub-REV volumes. We then investigate domain size effects and predict when REV scale is reached. While the scatter in porosity observations decreases linearly with increasing sample size as expected, the observed scatter in transport-ability does not converge to zero. Our results confirm that differences in pore structure impact transport parameters at all scales. Consequently, the use of PDFs to describe the relationship of effective transport coefficients to porosity is advantageous to deterministic semiempirical functions. We discuss the consequences and advocate the use of PDFs for effective parameters in both continuum equations and data interpretation of experimental or computational work. The presented statistics-based upscaling technique of sub-REV microscopy data provides a new tool in understanding, describing and predicting macroscopic transport behavior of microporous media.

Technology Focus: Digital Data Acquisition (January 2022)

This third installment of the Digital Data Acquisition Technology Focus will focus on computer vision (CV) for improved data acquisition. CV is defined as a field of study that seeks to develop techniques to help computers “see” and understand the content of digital images such as photographs and videos. The field of computer vision has seen significant growth in recent years because of the convergence of multiple events, such as advancements in machine-learning technology (e.g., deep learning), an exponential increase in availability of visual data from mobile phones and platforms such as YouTube, and the growth of new use cases such as autonomous driving. As such, it is no wonder that CV is also having a major effect on the oil and gas industry, reflected in the number of papers this year on this subject alone. The oil and gas industry is awash with image and video data such as core images, seismic profiles, maps, video feeds for monitoring remote operations, and, these days, even drone images. The traditional approach to interpreting and acting on this data has been highly manual, which can be extremely time-consuming and prone to bias and error. CV technology intends to automate these processes and significantly improve the turnaround time from data to decisions. The papers chosen this year include application of CV for reservoir characterization, such as source-rock reconstruction, facies identification, and seismic data enhancement; and safety applications such as rig-state identification and automated corrosion mapping. Given the versatility of CV technology, its application across the oil and gas industry clearly will continue to grow. Recommended additional reading at OnePetro: www.onepetro.org. SPE 204216 - Deep-Learning-Based Vuggy Facies Identification From Borehole Images by Jiajun Jiang, Baylor University, et al. SPE 202710 - Machine-Learning-Based Seismic Data Enhancement Toward Overcoming Geophysical Limitations by Shotaro Nakayama, INPEX, et al. SPE 205347 - Machine-Learning-Assisted Segmentation of Focused Ion Beam Scanning Electron Microscopy Images With Artifacts for Improved Void-Space Characterization of Tight Reservoir Rocks by Andrey Kazak, Skolkovo Institute of Science and Technology, et al.

Does dentine mineral change with anatomical location, microscopic site and patient age?

ObjectiveTo determine the effect of patient age (young or mature), anatomical location (shallow/deep and central/peripheral) and microscopic site (intertubular/peritubular) on dentine mineral density, distribution and composition. MethodsExtracted posterior teeth from young (aged 19–20 years, N = 4) and mature (aged 54–77 years, N = 4) subjects were prepared to shallow and deep slices. The dentine surface elemental composition was investigated in a SEM using Backscattered Electron (BSE) micrographs, Energy Dispersive X-ray Spectroscopy, and Integrated Mineral Analysis. Qualitative comparisons and quantitative measures using machine learning were used to analyse the BSE images. Quantitative outcomes were compared using quantile or linear regression models with bootstrapping to account for the multiple measures per sample. Subsequently, a Xenon Plasma Focussed Ion Beam Scanning Electron Microscopy (Xe PFIB-SEM) was used to mill large area (100 µm) cross-sections to investigate morphology through the dentine tubules using high resolution secondary electron micrographs. ResultsWith age, dentine mineral composition remains stable, but density changes with anatomical location and microscopic site. Microscopically, accessory tubules spread into intertubular dentine (ITD) from the main tubule lumens. Within the lumens, mineral deposits form calcospherites in the young that eventually coalesce in mature tubules and branches. The mineral occlusion in mature dentine increases overall ITD density to reflect peritubular dentine (PTD) infiltrate. The ITD observed in micrographs remained consistent for age and observation plane to suggest tubule deposition affects overall dentine density. Mineral density depends on the relative distribution of PTD to ITD that varies with anatomical location. SignificanceAdhesive materials may interact differently within a tooth as well as in different age groups.

Influence of external stack pressure on the performance of Li-S pouch cell

The lithium-sulfur (Li-S) cell system is promising to satisfy the increasing need for cost-efficient energy storage with high theoretical energies due to the enormous theoretical gravimetrical capacity and the abundance of sulfur. Furthermore, the technology readiness level of Li-S batteries increased steadily in recent years due to extensive research, as well as the number of reported prototype cells. However, an often ignored test parameter is the application of external pressure to the cell stack. In this study, the influence of external pressure on the performance of Li-S cells is investigated. Therefore, five-layered pouch cells with solvent-free processed cathodes are assembled. These cells are tested under lean electrolyte conditions (electrolyte to sulfur ratio of 4.5 µl mg(S)−1). To evaluate the influence of the used electrolyte system either the state-of-the-art 1,2-dimethoxyethane/1,3-dioxolane electrolyte or the sparing polysulfide solvating hexyl methyl ether/1,3-dioxolane electrolyte is deployed. The impact of pressure application is evaluated electrochemically as well as by post-mortem focused ion beam-scanning electron microscopy of the cycled electrodes. Moreover, a technique for infiltration of sulfur into the carbon host matrix is presented, discussed, and successfully implemented.

Focused Ion Beam-Scanning Electron Microscopy for Investigating Plasmodesmal Densities.

Plasmodesmata (PD) facilitate the exchange of nutrients and signaling molecules between neighboring plant cells, and they are therefore essential for proper growth and development. PD have been studied extensively in efforts to elucidate the ultrastructure of individual PD nanopores and the distribution of PD in a variety of cell walls. These studies often involved the use of serial ultrathin sections and manual quantification of PD by transmission electron microscopy (TEM). In recent years, a variety of techniques that offer more amenable approaches for quantifying PD distribution have been reported. Here, we describe the quantification of PD densities using the serial scanning electron microscopy technique called focused ion beam-scanning electron microscopy (FIB-SEM). For this, resin-embedded samples prepared by standard TEM methods undergo successive rounds of imaging by SEM interspersed with milling of the sample surface by a focused beam of gallium ions to reveal a new surface. In this way, the details of the sample are sequentially revealed and imaged. Over the course of a few hours, repetitive milling and imaging facilitates the automated collection of nanometer-resolution data of several μm of sample depth. FIB-SEM can be targeted to interrogate specific cell walls and cell wall junctions, and the subsequent three-dimensional renderings of the data can be used to visualize the ultrastructural details of the sample. PD densities can then be rapidly quantified by calculating the number of PD per μm2 of cell wall observed in the renderings.

Three-dimensional ultrastructure and histomorphology of mouse circumvallate papillary taste buds before and after birth using focused ion beam-scanning electron microscope tomography

Early taste buds are formed from placode cells. Placode cells differentiate into Type I–Ⅲ cells at birth; however, the ultrastructure of these first taste cells remain elusive. Here, we used focused ion beam-scanning electron microscopy (FIB-SEM) to analyze taste buds on the dorsal surface of the circumvallate papilla on embryonic day (E) 18.5 and postnatal day (P) 1.5. The taste buds on E18.5 existed as a mass of immature cells. One of the immature cells extended the cell process to the surface of the epithelium from the taste bud mass. Cytoplasm of this cell contained many mitochondria and vesicles in the apical region. The taste buds at P1.5 had small taste pores and had an onion-shaped structure. Most of the cells in the taste buds extended toward the taste pores. Some of the cells in the taste buds were Type II-like cells with glycogen in their cytoplasm. In this study, it was shown in three dimensions that immature cells extend to the surface of epithelium before the formation of the taste pore. Subsequently, the formation of taste pores and maturation of taste buds progress simultaneously.

Dynamic changes in the association between maternal mRNAs and endoplasmic reticulum during ascidian early embryogenesis

Axis formation is one of the most important events occurring at the beginning of animal development. In the ascidian egg, the antero-posterior axis is established at this time owing to a dynamic cytoplasmic movement called cytoplasmic and cortical reorganisation. During this movement, mitochondria, endoplasmic reticulum (ER), and maternal mRNAs (postplasmic/PEM RNAs) are translocated to the future posterior side. Although accumulating evidence indicates the crucial roles played by the asymmetrical localisation of these organelles and the translational regulation of postplasmic/PEM RNAs, the organisation of ER has not been described in sufficient detail to date owing to technical difficulties. In this study, we developed three different multiple staining protocols for visualising the ER in combination with mitochondria, microtubules, or mRNAs in whole-mount specimens. We defined the internally expanded “dense ER” using these protocols and described cisterna-like structures of the dense ER using focused ion beam-scanning electron microscopy. Most importantly, we described the dynamic changes in the colocalisation of postplasmic/PEM mRNAs and dense ER; for example, macho-1 mRNA was detached and excluded from the dense ER during the second phase of ooplasmic movements. These detailed descriptions of the association between maternal mRNA and ER can provide clues for understanding the translational regulation mechanisms underlying axis determination during ascidian early embryogenesis.

Release Mechanisms and Practical Percolation Threshold for Long-acting Biodegradable Implants: An Image to Simulation Study

The development of long-acting drug formulations requires efficient characterization technique as the designed 6–12 months release duration renders real-time in vitro and in vivo experiments cost and time prohibitive. Using a novel image-based release modeling method, release profiles were predicted from X-Ray Microscopy (XRM) of T0 samples. A validation study with the in vitro release test shows good prediction accuracy of the initial burst release. Through fast T0 image-based release prediction, the impact of formulation and process parameters on burst release rate was investigated. Recognizing the limitations of XRM, correlative imaging with Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) was introduced. A water stress test was designed to directly elucidate the formation of pores through polymer-drug-water interplay. Through an iterative correction method that considers poly(lactic-co-glycolic acid) (PLGA) polymer degradation, good agreement was achieved between release predictions using FIB-SEM images acquired from T0 samples and in vitro testing data. Furthermore, using image-based release simulations, a practical percolation threshold was identified that has profound influence on the implant performance. It is proposed as an important critical quality attribute for biodegradable long-acting delivery system, that needs to be investigated and quantified.

Numerical Investigations on the Damage Behaviour of a Reconstructed Anode for Solid Oxide Fuel Cell Application

This paper addresses the damage behaviour of a nickel/yttria-stabilised zirconia (Ni-YSZ) anode, in order to understand microstructural degradation processes of Solid Oxide Fuel Cells (SOFCs) during long-term operation. Numerical investigations are carried out to analyse the failure mechanisms in detail. For this purpose, finite element (FE) models are generated from focused ion beam-scanning electron microscopy 3D image data, representing the anode microstructure with varying phase compositions. A brittle model and a ductile material model were assigned to the YSZ phase and the nickel phase, respectively. The porosity is found to affect the strength of the microstructure significantly, leading to low compressive strength results. A high Ni content generally increases the toughness of the overall structure. However, the orientation and the geometry of the nickel phase is essential. When the Ni phase is aligned parallel to the loading direction, a supporting effect on the microstructure is observed, resulting in a significant high toughness. On the contrary, a rapid failure of the sample occurs when the Ni phase is oriented perpendicular to the loading direction. Two main failure mechanisms are identified: (i) cracking at the Ni/YSZ interface and (ii) cracking of struts at the location of the smallest diameter.

Structural Analysis of the Caenorhabditis elegans Dauer Larval Anterior Sensilla by Focused Ion Beam-Scanning Electron Microscopy.

At the end of the first larval stage, the nematode Caenorhabditis elegans developing in harsh environmental conditions is able to choose an alternative developmental path called the dauer diapause. Dauer larvae exhibit different physiology and behaviors from non-dauer larvae. Using focused ion beam-scanning electron microscopy (FIB-SEM), we volumetrically reconstructed the anterior sensory apparatus of C. elegans dauer larvae with unprecedented precision. We provide a detailed description of some neurons, focusing on structural details that were unknown or unresolved by previously published studies. They include the following: (1) dauer-specific branches of the IL2 sensory neurons project into the periphery of anterior sensilla and motor or putative sensory neurons at the sub-lateral cords; (2) ciliated endings of URX sensory neurons are supported by both ILso and AMso socket cells near the amphid openings; (3) variability in amphid sensory dendrites among dauers; and (4) somatic RIP interneurons maintain their projection into the pharyngeal nervous system. Our results support the notion that dauer larvae structurally expand their sensory system to facilitate searching for more favorable environments.

High-Resolution 3D Reconstruction of Human Oocytes Using Focused Ion Beam Scanning Electron Microscopy

The egg plays a pivotal role in the reproduction of our species. Nevertheless, its fundamental biology remains elusive. Transmission electron microscopy is traditionally used to inspect the ultrastructure of female gametes. However, two-dimensional micrographs contain only fragmentary information about the spatial organization of the complex oocyte cytoplasm. Here, we employed the Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) to explore human oocyte intracellular morphology in three dimensions (3D). Volume reconstruction of generated image stacks provided an unprecedented view of ooplasmic architecture. Organelle distribution patterns observed in nine donor oocytes, representing three maturational stages, documented structural changes underlying the process by which the egg acquires developmental competence. 3D image segmentation was performed to extract information about distinct organelle populations, and the following quantitative analysis revealed that the mitochondrion occupies ∼ 4.26% of the maturing oocyte cytoplasm. In summary, this proof-of-concept study demonstrates the potential of large volume electron microscopy to study rare samples of delicate female gametes and paves the way for applying the FIB-SEM technique in human oocyte research.