Focused Ion Beam Scanning Electron Microscopy Research Articles

Characterizing PEM fuel cell catalyst layer properties from high resolution three-dimensional digital images, part I: A numerical procedure for the ionomer distribution reconstruction

In this work, a numerical approach is presented to reconstruct the ionomer three-dimensional distribution in the microstructure of the cathode catalyst layer (CCL) of a polymer electrolyte membrane fuel cell (PEMFC) from a 3D segmented image of the CCL obtained by focused ion beam-scanning electron microscopy (FIB-SEM). Three forms of ionomer are distinguished: the ionomer filaments, the coating ionomer and the inter-carbon grains ionomer. The ionomer filaments are identified by applying a filtering procedure to the size distribution in the segmented solid phase obtained via a maximum sphere inscription algorithm. The coating ionomer is reconstructed via a filtering procedure of the curvature distribution computed over the interface between the two segmented phases from the consideration that concave regions are preferential ionomer accumulation zones during the drying step of the CCL fabrication procedure. This procedure of coating controlled by the local curvature is applied until a desired value of coverage is reached. In a last step, catalyst nanoparticles, also not visible in the FIB-SEM image, are reconstructed in the image.

Characterizing PEM fuel cell catalyst layer properties from high resolution three-dimensional digital images, Part II: Oxygen effective diffusion and proton effective conductivity tensors

The oxygen effective diffusion and proton effective conductivity tensors of a cathode catalyst layer (CCL) are computed using a two-scale approach on CCL microstructure three-dimensional images obtained by focused ion beam-scanning electron microscopy (FIB-SEM) after reconstruction of the ionomer distribution. The results show that the obtained tensors are not isotropic. It is also found that some off-diagonal components are not negligible in the case of the proton effective conductivity tensor. The simulations confirm that Knudsen diffusion has a significant impact on oxygen diffusion. The results are comparable to those obtained in previous works on synthetic images as regards the oxygen effective diffusion through-plane component but differ as regards the proton conductivity through-plane component. Contrary to previous works using synthetic images which tend to underestimate the proton conductivity, they are globally in better agreement with experimental data. The results also show that the effective proton conductivity is heterogeneous at the scale of the computational domains typically considered in several previous works due to the variability in the ionomer distribution at this scale. The impact of liquid water in the primary pores on the proton transport is explored and found to have a significant impact.

Lipid droplet dynamics are essential for the development of the malaria parasite Plasmodium falciparum.

Lipid droplets (LDs) are organelles central to lipid and energy homeostasis across all eukaryotes. In the malaria-causing parasite Plasmodium falciparum the roles of LDs in lipid acquisition from its host cells and their metabolism are poorly understood, despite the high demand for lipids in parasite membrane synthesis. We systematically characterised LD size, composition and dynamics across the disease-causing blood infection. Applying split fluorescence emission analysis and 3D Focused Ion Beam-Scanning Electron Microscopy, we observed a decrease in LD size in late schizont stages. LD contraction likely signifies a switch from lipid accumulation to lipid utilisation in preparation for parasite egress from host red blood cells. We demonstrate connections between LDs and several parasite organelles, pointing to potential functional interactions. Chemical inhibition of triacylglyerol (TAG) synthesis or break-down revealed essential LD functions for schizogony and in counteracting lipid toxicity. The dynamics of lipid synthesis, storage and utilisation in P. falciparum LDs might provide a target for new anti-malarial intervention strategies.

Mesoscale characterization of osseointegration around an additively manufactured genistein-coated implant

Given the hierarchical nature of bone and bone interfaces, osseointegration, namely the formation of a direct bone-implant contact, is best evaluated using a multiscale approach. However, a trade-off exists between field of view and spatial resolution, making it challenging to image large volumes with high resolution. In this study, we combine established electron microscopy techniques to probe bone-implant interfaces at the microscale and nanoscale with plasma focused ion beam-scanning electron microscopy (PFIB-SEM) tomography to evaluate osseointegration at the mesoscale. This characterization workflow is demonstrated for bone response to an additively manufactured Ti-6Al-4V implant which combines engineered porosity to facilitate bone ingrowth and surface functionalization via genistein, a phytoestrogen, to counteract bone loss in osteoporosis. SEM demonstrated new bone formation at the implant site, including in the internal implant pores. At the nanoscale, scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the gradual nature of the bone-implant interface. By leveraging mesoscale analysis with PFIB-SEM tomography that captures large volumes of bone-implant interface with nearly nanoscale resolution, the presence of mineral ellipsoids varying in size and orientation was revealed. In addition, a well-developed lacuno-canalicular network and mineralization fronts directed both towards the implant and away from it were highlighted.

Quantitative atlas of collagen hydrogels reveals mesenchymal cancer cell traction adaptation to the matrix nanoarchitecture

Collagen-based hydrogels are commonly used in mechanobiology to mimic the extracellular matrix. A quantitative analysis of the influence of collagen concentration and properties on the structure and mechanics of the hydrogels is essential for tailored design adjustments for specific in vitro conditions. We combined focused ion beam scanning electron microscopy and rheology to provide a detailed quantitative atlas of the mechanical and nanoscale three-dimensional structural alterations that occur when manipulating different hydrogel's physicochemistry. Moreover, we study the effects of such alterations on the phenotype of breast cancer cells and their mechanical interactions with the extracellular matrix. Regardless of the microenvironment's pore size, porosity or mechanical properties, cancer cells are able to reach a stable mesenchymal-like morphology. Additionally, employing 3D traction force microscopy, a positive correlation between cellular tractions and ECM mechanics is observed up to a critical threshold, beyond which tractions plateau. This suggests that cancer cells in a stable mesenchymal state calibrate their mechanical interactions with the ECM to keep their migration and invasiveness capacities unaltered. STATEMENT OF SIGNIFICANCE: The paper presents a thorough study on the mechanical microenvironment in breast cancer cells during their interaction with collagen based hydrogels of different compositions. The hydrogels' microstructure were obtained using state-of-the-art 3D microscopy, namely focused ion beam-scanning electron microscope (FIB-SEM). FIB-SEM was originally applied in this work to reconstruct complex fibered collagen microstructures within the nanometer range, to obtain key microarchitectural parameters. The mechanical microenvironment of cells was recovered using Traction Force Microscopy (TFM). The obtained results suggest that cells calibrate tractions such that they depend on mechanical, microstructural and physicochemical characteristics of the hydrogels, hence revealing a steric hindrance. We hypothesize that cancer cells studied in this paper tune their mechanical state to keep their migration and invasiveness capacities unaltered.

Quantitative 3D electron microscopy characterization of mitochondrial structure, mitophagy, and organelle interactions in murine atrial fibrillation

Atrial fibrillation (AF) is the most common clinical arrhythmia, however there is limited understanding of its pathophysiology including the cellular and ultrastructural changes rendered by the irregular rhythm, which limits pharmacological therapy development. Prior work has demonstrated the importance of reactive oxygen species (ROS) and mitochondrial dysfunction in the development of AF. Mitochondrial structure, interactions with other organelles such as sarcoplasmic reticulum (SR) and T-tubules (TT), and degradation of dysfunctional mitochondria via mitophagy are important processes to understand ultrastructural changes due to AF. However, most analysis of mitochondrial structure and interactome in AF has been limited to two-dimensional (2D) modalities such as transmission electron microscopy (EM), which does not fully visualize the morphological evolution of the mitochondria during mitophagy. Herein, we utilize focused ion beam-scanning electron microscopy (FIB-SEM) and perform reconstruction of three-dimensional (3D) EM from murine left atrial samples and measure the interactions of mitochondria with SR and TT. We developed a novel 3D quantitative analysis of FIB-SEM in a murine model of AF to quantify mitophagy stage, mitophagosome size in cardiomyocytes, and mitochondrial structural remodeling when compared with control mice. We show that in our murine model of spontaneous and continuous AF due to persistent late sodium current, left atrial cardiomyocytes have heterogenous mitochondria, with a significant number which are enlarged with increased elongation and structural complexity. Mitophagosomes in AF cardiomyocytes are located at Z-lines where they neighbor large, elongated mitochondria. Mitochondria in AF cardiomyocytes show increased organelle interaction, with 5X greater contact area with SR and are 4X as likely to interact with TT when compared to control. We show that mitophagy in AF cardiomyocytes involves 2.5X larger mitophagosomes that carry increased organelle contents. In conclusion, when oxidative stress overcomes compensatory mechanisms, mitophagy in AF faces a challenge of degrading bulky complex mitochondria, which may result in increased SR and TT contacts, perhaps allowing for mitochondrial Ca2+ maintenance and antioxidant production.

Physicochemical investigation on the hard carbon interface in ionic liquid electrolyte

An investigation of the solid electrolyte interphase (SEI) on hard carbon (HC) anodes in aprotic sodium batteries was carried out by post-mortem analyses. Electrodes cycled in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIFSI), and N-trimethyl-N-butylammonium bis(fluorosulfonyl)imide (N1114FSI) ionic liquid electrolytes have been collected and studied: benchmark electrodes cycled in commercial organic solutions were examined for comparison purpose. The SEI composition and morphology of post-mortem HC electrodes were analyzed by X-ray Photoelectron Spectroscopy (XPS) and focused ion beam scanning electron microscopy (FIB-SEM) analysis. Overall, the HC electrodes cycled in carbonate-based electrolyte have shown thicker SEI mainly composed of organic compounds, whereas in ILs electrolytes they have shown thinner layer richer in inorganic species, such as NaF, Na2CO3, N-containing species, and “small” sulfide-based compounds, these improving the SEI interfacial properties towards the Na+ migration kinetics. Focusing on ILs based cell formulations, anodes cycled in the EMIFSI-based electrolyte shows several cracks on its surface.

Editors’ Choice—Visualizing the Impact of the Composite Cathode Microstructure and Porosity on Solid-State Battery Performance

The kinetics of composite cathodes for solid-state batteries (SSBs) relies heavily on their microstructure. Spatial distribution of the different phases, porosity, interface areas, and tortuosity factors are important descriptors that need accurate quantification for models to predict the electrochemistry and mechanics of SSBs. In this study, high-resolution focused ion beam-scanning electron microscopy tomography was used to investigate the microstructure of cathodes composed of a nickel-rich cathode active material (NCM) and a thiophosphate-based inorganic solid electrolyte (ISE). The influence of the ISE particle size on the microstructure of the cathode was visualized by 3D reconstruction and charge transport simulation. By comparison of experimentally determined and simulated conductivities of composite cathodes with different ISE particle sizes, the electrode charge transport kinetics is evaluated. Porosity is shown to have a major influence on the cell kinetics and the evaluation of the active mass of electrochemically active particles reveals a higher fraction of connected NCM particles in electrode composites utilizing smaller ISE particles. The results highlight the importance of homogeneous and optimized microstructures for high performance SSBs, securing fast ion and electron transport.

Quantifying Microstructure Features for High-Performance Solid Oxide Cells.

The drive for sustainable energy solutions has spurred interest in solid oxide fuel cells (SOFCs). This study investigates the impact of sintering temperature on SOFC anode microstructures using advanced 3D focused ion beam-scanning electron microscopy (FIB-SEM). The anode's ceramic-metal composition significantly influences electrochemical performance, making optimization crucial. Comparing cells sintered at different temperatures reveals that a lower sintering temperature enhances yttria-stabilized zirconia (YSZ) and nickel distribution, volume, and particle size, along with the triple-phase boundary (TPB) interface. Three-dimensional reconstructions illustrate that the cell sintered at a lower temperature exhibits a well-defined pore network, leading to increased TPB density. Hydrogen flow simulations demonstrate comparable permeability for both cells. Electrochemical characterization confirms the superior performance of the cell sintered at the lower temperature, displaying higher power density and lower total cell resistance. This FIB-SEM methodology provides precise insights into the microstructure-performance relationship, eliminating the need for hypothetical structures and enhancing our understanding of SOFC behavior under different fabrication conditions.

The physical and cellular mechanism of structural color change in zebrafish

Many animals exhibit remarkable colors that are produced by the constructive interference of light reflected from arrays of intracellular guanine crystals. These animals can fine-tune their crystal-based structural colors to communicate with each other, regulate body temperature, and create camouflage. While it is known that these changes in color are caused by changes in the angle of the crystal arrays relative to incident light, the cellular machinery that drives color change is not understood. Here, using a combination of 3D focused ion beam scanning electron microscopy (FIB-SEM), micro-focused X-ray diffraction, superresolution fluorescence light microscopy, and pharmacological perturbations, we characterized the dynamics and 3D cellular reorganization of crystal arrays within zebrafish iridophores during norepinephrine (NE)-induced color change. We found that color change results from a coordinated 20° tilting of the intracellular crystals, which alters both crystal packing and the angle at which impinging light hits the crystals. Importantly, addition of the dynein inhibitor dynapyrazole-a completely blocked this NE-induced red shift by hindering crystal dynamics upon NE addition. FIB-SEM and microtubule organizing center (MTOC) mapping showed that microtubules arise from two MTOCs located near the poles of the iridophore and run parallel to, and in between, individual crystals. This suggests that dynein drives crystal angle change in response to NE by binding to the limiting membrane surrounding individual crystals and walking toward microtubule minus ends. Finally, we found that intracellular cAMP regulates the color change process. Together, our results provide mechanistic insight into the cellular machinery that drives structural color change.

Ultrastructural 3D Microscopy for Biomedicine: Principles, Applications, and Perspectives.

Modern biomedical research often requires a three-dimensional microscopic analysis of the ultrastructure of biological objects and materials. Conceptual technical and methodological solutions for three-dimensional structure reconstruction are needed to improve the conventional optical, electron, and probe microscopy methods, which to begin with allow one to obtain two-dimensional images and data. This review discusses the principles and potential applications of such techniques as serial section transmission electron microscopy; techniques based on scanning electron microscopy (SEM) (array tomography, focused ion beam SEM, and serial block-face SEM). 3D analysis techniques based on modern super-resolution optical microscopy methods are described (stochastic optical reconstruction microscopy and stimulated emission depletion microscopy), as well as ultrastructural 3D microscopy methods based on scanning probe microscopy and the feasibility of combining them with optical techniques. A comparative analysis of the advantages and shortcomings of the discussed approaches is performed.

Volume microscopic analysis of membrane contact sites in mouse kidney renal proximal tubule epithelial cells

Subcellular organelles communicate with one another and with the plasma membrane (PM). A wide variety of membrane contact sites (MCS) tether subcellular structures to one another and mediate inter-organelle communication and exchange. The nature, distribution and function of membrane contact sites within the segment-specific architecture of renal epithelial cells has only just begun to be elucidated. We have used advanced imaging techniques, including Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) and machine learning-based segmentation, to create a comprehensive, high resolution, 3D and quantifiable volume microscopic atlas of the ultrastructure of proximal tubule epithelial cells of the mouse kidney. We applied this data set to identify and quantify MCS between the endoplasmic reticulum and mitochondria and the PM in these cells. FIB-SEM was performed on a 50 μm by 50 μm by 44 μm block of tissue prepared from the renal cortex of a perfusion fixed 12-week-old male mouse. OsO4-stained tissue was embedded in Durcupan and a 3D X-ray tomogram of the block was used to select a volume of interest that included extended lengths of multiple proximal tubule (PT). The volume was imaged by a customized enhanced FIB-SEM system. The X-Y scanning resolution was set to 4-nm, and 4-nm FIB milling was used to expose surfaces for successive imaging. Generation of the complete image stack required ~11,000 cycles of scanning/FIB ablation over ~4 weeks of uninterrupted imaging. Segmentation of the resultant image set was performed with Zeiss Arivis Pro technology. The boundary box for reconstruction had the dimensions of 29.2 μm x 24.8 μm x 8 μm with a volume of 5793.280 μm3 comprising of 2000 consecutive images at an isotropic voxel size of 4 nm. Deep learning segmentation teased apart 10 cells with distinct boundaries in the PT structure. The volume of the cells in our clipped volume ranged from 8.79 μm3 to 1438.53 μm3 with a median of 45.20 μm3. In one representative proximal tubule cell the volume of mitochondria makes up 84.91 μm3 (31.62%) of the cell volume and the volume of Endoplasmic Reticulum (ER) makes up 23.92 μm3 (8.91%) of the cell volume. The 3D reconstruction and quantitative analysis revealed that there is one dominant ER object accounting for most of the ER volume in the whole cell: i.e., the largest ER object takes up 22.37 μm3 or 93.5% of the ER volume in the cell. A post deep-learning processing algorithm used 3D object modifications to identify 11,109 3D MCS between mitochondria and ER in the 10 cells. The Mito-ER MCS ranged from 512 nm3 to 354,304 nm3 with a median volume of 1792 nm3. Visually we can see Mito-ER and Mito-PM MCS extending across a region of up to ~45 nm between the two organelles. Taken together, these data show that the basal lateral surfaces of PT cell PMs are generously invested with fenestrated smooth ER, as are mitochondria and peroxisomes. Extensive regions of direct contact between mitochondria and PM are also observed. The biochemical identities of these contacts and their physiological functions are being actively pursued. NIDDK DK072612 NIDDK DK120534. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

High Resolution Reconstruction of the Proximal Tubule Apical Endocytic Pathway

Kidney proximal tubule (PT) cells are specialized for effcient apical uptake of albumin and other proteins that escape the glomerular filtration barrier. The apical endocytic pathway is uniquely organized to maintain highly dynamic retrieval of these proteins via binding to the multiligand receptors megalin and cubilin. Ultrastructural studies following the fate of internalized markers have provided a temporal model for the delivery of receptor-bound ligands and fluid phase markers to lysosomes. In this model, internalization from the apical membrane occurs via budding of irregular clathrin-coated invaginations that form at the base of microvilli. After uncoating, budded vesicles fuse with apical early endosomes (AEEs) where acidification triggers dissociation of ligands from their receptors. AEEs further mature and expand into apical vacuoles (AVs) that ultimately deliver ligands and fluid to lysosomes. Receptor recycling to the apical membrane is thought to occur via dense apical tubules (DATs) that have a uniform diameter and membrane thickness and which appear to bud from both AEEs and AVs. We used Zeiss Arivis Pro technology to annotate and reconstruct apical membrane invaginations and endocytic compartments in a 3D volume of mouse kidney with isotropic voxels of 4 nm, acquired using focused ion-beam scanning electron microscopy (FIB-SEM). Strikingly, 3D reconstruction of DATs revealed a large and highly interconnected network of tubules in the subapical region of PT cells. Connections were observed between the DAT network and endosomal compartments, as well as between DATs and apical membrane invaginations. Our data suggest the possibility that DATs exist as a stable compartment that interacts transiently with the apical membrane to enable receptor recycling. Current studies are underway to better understand how PT cells modulate endocytic entry and recycling via the same portals. National Institute of Health: 5T32GM133353-03, R01 DK118726, R01 DK125049, U54 DK137329. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Synchrotron micro-computed tomography analysis of neutron-irradiated U-Mo fuel

The three-dimensional (3D) microstructure of neutron-irradiated uranium-10 wt.% molybdenum (U-10Mo) fuel with a burn-up of 9.8 × 1021 fissions/cm3 was characterized using a novel, multi-modal synchrotron micro-computed tomography approach combining propagation-based phase-contrast enhanced and absorption contrast techniques. The porosity development, porosity interconnectedness, swelling, composition, local thickness of the zirconium (Zr) diffusion barrier, and the influence of the fuel–cladding interaction on the local composition and pore morphology, were uniquely determined in 3D. Two cuboids were produced using a focused ion beam-scanning electron microscope at the Zr diffusion barrier–fuel interface and in the bulk fuel. The bulk fuel sample swelled by 53.3 [+9.7/−3.1]%, while the fuel near the Zr–fuel interface swelled by 63.3 [+14.7/−7.2]%. The average local thickness of the Zr diffusion barrier decreased by 53 %, compared to the expected pre-irradiated thickness. Four pore morphology regions were identified initiating parallel to the fuel–Zr interaction region: (1) an interaction layer of suppressed porosity, (2) a layer of elongated and interconnected porosity, (3) a transition zone of low porosity, and (4) a layer of unoriented porosity representative of the bulk fuel behavior. The increase in porosity near the diffusion barrier corresponded to a higher U concentration compared to that in the bulk fuel. The interconnected porosity in the fuel near the diffusion barrier was extensive and oriented parallel to the diffusion barrier, while the bulk fuel had more compact and isolated pore networks. The interaction layer, despite having suppressed porosity, was nearly 100 wt.% U. Porosity suppression at the diffusion barrier corresponds to the expected reduction in radiation-driven diffusion of Xe at the interface despite the anticipated increase in fission product nucleation originating from a higher U concentration. The novel 3D insights of the porosity, swelling, and compositional variations characterized herein can improve the fidelity of fuel performance codes for proliferation-resistant fuels for research and test reactors.

Approaching Technological Limit for Wet‐Pulling Technique

Carbon nanotube fibers (CNTFs) are a promising economical replacement material for contemporary metallic wired conductors due to their lightweight and advanced electromechanical properties. The wet‐pulling technique for CNTF manufacturing is highly versatile, adaptable for both laboratory as well as industrial‐scale production, and can be optimized for the maximum enhancement of electrophysical properties. Herein, a mechanosolvent‐based postfabrication approach for maximizing densification and improving electrical properties of wet‐pulled CNTFs is examined. The experimental process results in fibers achieving 60% of the theoretically maximum density and conductivity of maximally densified metallic single‐walled carbon nanotube bundles. The technique allows a corresponding increase of ≈700% in fiber density (from 100 to 704 kg m−3), a simultaneous ≈530% increase in electrical conductivity (from 748 to 3990 S cm−1), and reduced volume defects from 18% to 2%. The approach was combined with a step‐wise microstructure monitoring using focused ion beam–scanning electron microscopy to determine the mechanisms behind the optimized structures. This work is the first to provide an experimental and theoretical base for the postfabrication optimization of wet‐pulled CNTFs and lays the foundation for further enhancement with techniques such as chemical doping, fiber compounding, and combined infiltration/densification mechanisms.

High-Precision 3D reconstruction and quantitative structure description: Linking microstructure to macroscopic heat transfer of aerogels

The intricate interplay between microstructure and macroscopic transfer processes in porous materials has long been recognized, yet achieving a definitive link between them remains a formidable challenge. Herein, we propose an effective approach to address this challenge by introducing a high-precision 3D reconstruction and structure descriptor database analysis method of nanoporous aerogels, which enables deeper understanding and accurate predictions of structure-directed properties. By employing focused ion beam-scanning electron microscope (FIB-SEM) technique supplemented with image preprocessing and image segmentation, we successfully built a 3D reconstruction model that exhibits high consistency with experimental results. Then, a structure descriptor database from the view of original porous structure, structure connectivity, and topological information is established, and 10 descriptors are preliminarily filtered relevance with thermal conductivity. Consequently, the quantitative relationship between descriptor and thermal conductivity is evaluated via a back propagation (BP) neural network, and three categories structure descriptors which have the most significant impact are determined as (i) the description of gaseous heat transfer pathways, (ii) the description of three-dimensional connectivity, and (iii) the description of interface complexity. With the profound understanding of structure descriptor, the present work offers a novel, structure-focused strategy that closely link the microstructure to macroscopic properties of porous materials.

Experimental determination of Fe–Mg interdiffusion in orthopyroxene as a function of Fe content

We have measured the dependence of the Fe–Mg interdiffusion coefficient, DFe-Mg, on the ferrosilite component in orthopyroxene, which so far has not been experimentally calibrated. Diffusion couples, consisting of approximately 1 µm thin-films were deposited by pulsed laser ablation on orthopyroxene crystals of En91Fs9 composition. Diffusion experiments were carried out at atmospheric pressure in vertical gas mixing furnaces (CO-CO2) at temperatures between 950 and 1100 °C at constant fO2 = 10–7 Pa. Using a focused ion beam-scanning electron microscope (FIB-SEM), FIB-foils were cut from diffusion couples before and after annealing. Diffusion profiles were extracted by using combined backscattered electron (BSE) imaging and energy dispersive X-ray (EDXS) mapping on FIB-foils which allowed to resolve concentration gradients within 20 nm. The microstructure of the diffusion experiments was investigated using transmission electron microscopy (TEM). Using this method, we obtained the first experimentally determined data on the dependence of DFe-Mg on the ferrosilite content in orthopyroxene at different temperatures, appearing to increase with increasing a temperature. For the temperature range (950 – 1100 °C), log fO2 = -7 Pa, along [001] in the composition Fs9, the log DFe-Mg yields the following Arrhenius equation:DFe-Mg[m2/s]=3.8·10-9exp[-261.07±24[kJ/mol]/(R/T[K])]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{Fe - Mg} [m^2 /s] = 3.8 \\cdot 10^{ - 9} \\exp [ - 261.07 \\pm 24[kJ/mol]/(R/T[K])]$$\\end{document}The effect of XFe on DFe-Mg, given by D(XFe)=D(XFe=0.09)·10m(XFe-0.09),\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D(X_{Fe} ) = D(X_{Fe} = 0.09) \\cdot {10}^{m (X_{Fe} - 0.09)},$$\\end{document} can be calculated by the following parameterization where m follows a linear regression of m on temperature: m=-2.711·104/T(K)+23.5408\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m = - 2.711 \\cdot 10^4 /T(K) + 23.5408$$\\end{document}By considering the DFe-Mg dependence on XFe, the timescales of natural processes obtained from modelling the compositional zoning of natural crystal may considerably differ from previously estimated timescales.

Integrated Physical and Digital Chalk Relative Permeability Evaluation: A Case Study

The Valhall chalk field has produced more than 1 billion barrels of oil equivalents over the last 40 years, primarily from the homogeneous Tor Formation. The underlying Hod Formation is more heterogeneous and is less maturely developed. The extent of heterogeneity poses a challenge in the evaluation of multiphase fluid flow properties. The objective of the work was to use digital core analysis to generate early relative permeability data to leverage and compare with conventional physical steady-state relative permeability data. Accurate digital and physical description of capillary pressure and relative permeability in the high-porosity chalk is complicated by both low permeabilities and heterogeneity. The main challenge with chalk is that flow occurs in a nano-environment. Physically, the nano-environment translates to low permeability, difficult rock preparation, and extensive experimental time, especiallyfor steady-state flow experiments. Representative three-dimensional (3D) digital rocks were generated using a combination of X-ray computed tomography (CT) and focused ion beam-scanning electron microscopy (FIB-SEM) methods. The digital rocks were used to simulate two-phase flow and generate relative permeabilities and sensitivity to wettability. Physical steady-state and digital relative permeabilities on several core plugs and subsets are compared in this study, which discusses the advantages of performing both as part of the formation evaluation process. The physical and digital results compare reasonably well. The physical results provide a relative permeability anchor, and the digital results provide the leverage of early results, parametric sensitivities, and quality assurance. Hence, integration between digital and physical core analysis yields a robust understanding and input for uncertainty modeling.

Indirect Correlative Light and Electron Microscopy (iCLEM): A Novel Pipeline for Multiscale Quantification of Structure From Molecules to Organs.

Correlative light and electron microscopy (CLEM) methods are powerful methods that combine molecular organization (from light microscopy) with ultrastructure (from electron microscopy). However, CLEM methods pose high cost/difficulty barriers to entry and have very low experimental throughput. Therefore, we have developed an indirect correlative light and electron microscopy (iCLEM) pipeline to sidestep the rate-limiting steps of CLEM (i.e., preparing and imaging the same samples on multiple microscopes) and correlate multiscale structural data gleaned from separate samples imaged using different modalities by exploiting biological structures identifiable by both light and electron microscopy as intrinsic fiducials. We demonstrate here an application of iCLEM, where we utilized gap junctions and mechanical junctions between muscle cells in the heart as intrinsic fiducials to correlate ultrastructural measurements from transmission electron microscopy (TEM), and focused ion beam scanning electron microscopy (FIB-SEM) with molecular organization from confocal microscopy and single molecule localization microscopy (SMLM). We further demonstrate how iCLEM can be integrated with computational modeling to discover structure-function relationships. Thus, we present iCLEM as a novel approach that complements existing CLEM methods and provides a generalizable framework that can be applied to any set of imaging modalities, provided suitable intrinsic fiducials can be identified.

Melanin granules morphology and distribution in human black hair investigated by focused ion beam scanning electron microscopy: Differences between Asian and Caucasian hair

Melanin granules (melanosomes) in Asian and Caucasian black hairs were investigated by focused ion beam scanning electron microscopy (FIB-SEM). This technique facilitates a direct evaluation of the three-dimensional distribution and morphology of melanin granules without requiring their isolation from hair. Three-dimensional reconstructed images of melanin granule distribution in hair samples were obtained using serial SEM images observed by FIB-SEM. Melanin granules in black hair tended to be three-dimensionally dense in the outer periphery of the cortex. The morphometric parameters of melanin granules were calculated using the reconstructed three-dimensional images. The results confirmed that melanin granules in Caucasian black hair were much smaller those in Asian black hair. Moreover, it was indicated that the relative frequency distribution of the volume of melanin granules was significantly different between Asians and Caucasians.