Microscopy (Oxford, England)最新文献

The distribution of dopants in host crystals significantly influences the chemical and electronic properties of materials. Therefore, determining this distribution is crucial for optimizing material performance. The previously developed statistical ALCHEMI (St-ALCHEMI), an extension of the atom-location by channeling-enhanced microanalysis (ALCHEMI) technique, utilizes variations in electron channeling based on the beam direction relative to the crystal orientation. It statistically analyzes spectra collected across multiple beam directions. However, the total experimental time can be extensive, particularly for low dopant concentrations, where typical experiments can span several hours. In this study, we propose a scheme based on efficient sampling point selection that reduces the experimental time required while maintaining accuracy. Guidelines for selecting beam directions were derived from theoretical and experimental analyses of data redundancy. The strategies include choosing directions that exhibit greater variances in the host ionization channeling patterns and lower correlation coefficients between them. Additionally, an edge detection scheme using the dual tree complex wavelet transform, applied to electron channeling patterns, is proposed to significantly reduce measurement time. Our findings suggest that effective sampling can reduce experimental duration by at least two orders of magnitude without compromising accuracy. Implementing the proposed guidelines shortens total measurement times, minimizes electron irradiation damage and improves S/N ratio through extended data acquisition per tilt.

High-quality thin lamellae are essential for state-of-the-art scanning transmission electron microscopy (S/TEM) analyses. While the preparation of S/TEM lamellae using focused ion beam (FIB) scanning electron microscopy has been established since the early twenty-first century, two critical factors have only recently been addressed: precise control over lamella thickness and a systematic understanding of FIB-induced damage. This study conducts an experimental investigation and simulation to explore how the intensities of backscattered and secondary electrons (BSEs and SEs, respectively) depend on lamella thickness for semiconductor (Si), insulator (Al2O3), and metallic (stainless-steel) materials. The BSE intensity shows a simple linear relationship with the lamella thickness for all materials below a certain thickness, whereas the relationship between the SE intensity and thickness is more complex. In conclusion, the BSE intensity is a reliable indicator for accurately determining lamella thickness across various materials during FIB thinning processing, while the SE intensity lacks consistency due to material and detector variability. This insight enables the integration of real-time thickness control into S/TEM lamella preparation, significantly enhancing lamella quality and reproducibility. These findings pave the way for more efficient, automated processes in high-quality S/TEM analysis, making the preparation method more reliable for a range of applications.

Characterizing molten corium-concrete interaction (MCCI) fuel debris in Fukushima reactors is essential to develop efficient methods for its removal. To enhance the accuracy of microscopic observation and focused ion beam microsampling of MCCI fuel debris, we developed a 3D focused ion beam scanning electron microscopy technique with a multiphase positional misalignment correction method. This system automatically aligns voxel positions, corrects contrast and removes artifacts from a series of over 500 scanning electron microscopy images. The multiphase positional misalignment correction method, which focuses on time-modulated contrast, considerably reduces charge-up artifacts in glass phases, enabling 3D morphological observation and analytical transmission electron microscopy of crack tips in two types of MCCI debris at the 3D/nanoscale for the first time. In the Fe-ZrSiO4-based debris, metallic balls composed of Fe, Cr2O3 and ZrO2 with dimples on the surface of about 2-58 µm in diameter were observed at the crack tips. In the (Zr, U)SiO4-based debris, a core-shell structure composed of a (U, Zr)O2 core with a diameter of about 1-5 μm and a (Zr, U)SiO4 shell with a diameter of about 2-9 μm in complex MCCI fuel debris at the crack tips.

This paper describes the positioning of the ultra-low accelerating voltage scanning electron microscope (ULV-SEM) equipped with multiple imaging detectors in the history of SEM development. ULV-SEM provides rich information once the user finds the 'sweet spot' for both secondary electron and backscattered electron images based on an understanding of the signal acceptance of the instrument. Use of multiple imaging detectors allows acquisition of various images with a single scan. X-ray microanalysis under the same experimental conditions as the observation 'sweet spot' has become possible with a windowless X-ray spectrometer optimized for use at a short working distance.

Volume electron microscopy (vEM) has become a widely adopted technique for acquiring three-dimensional structural information of biological specimens. In addition to the traditional use of transmission electron microscopy, recent advances in the resolution of scanning electron microscopy (SEM) made it suitable for vEM application. Currently, various types of SEM with different advantages have been utilized. For selecting the appropriate type of SEM to obtain optimal vEM images for the purpose of individual research, it is important to understand the physics underlying each SEM technology. This article aims to explain the physics for signal electron generation, various objective lens configurations and detection systems, employed in SEM to enhance high-resolution imaging and improve signal detection conditions.

Genome-wide profiling of gene expression levels in cells, such as transcriptomics and proteomics, is a powerful experimental approach in modern biology, allowing not only efficient exploration of the genetic elements responsible for biological phenomena of interest, but also characterization of the global constraints behind plastic phenotypic changes of cells that accompany large-scale remodeling of omics profiles. To understand how individual cells change their molecular profiles to achieve specific phenotypic changes in phenomena such as differentiation, cancer metastasis and adaptation, it is crucial to characterize the dynamics of cellular phenotypes and omics profiles simultaneously at the single-cell level. Especially in the last decade, significant technical progress has been made in the in situ identification of omics profiles of cells on the microscope. However, most approaches still remain destructive and cannot unravel the post-measurement dynamics. In recent years, Raman spectroscopy-based methods for omics inference have emerged, allowing the characterization of genome-wide molecular profile dynamics in living cells. In this review, we give a brief overview of the recent development of imaging-based omics profiling methods. We then present the approach to infer omics profiles from single-cell Raman spectra. Since Raman spectra can be obtained from living cells in a non-destructive and non-staining manner, this method may open the door to live-cell omics.

Electron microscopy (EM) is known to be the only research equipment able to resolve the ultrastructure of cells, including intracellular organelles and synapses. Researchers studying the brain connectome have re-evaluated the value of EM. The development of new EM techniques and tools has been active in these two decades. In this review, based on these trends, currently available EM tools and recently developing new techniques are introduced.

Structural observations are essential for the advancement of life science. Volume electron microscopy has recently realized remarkable progress in the three-dimensional analyses of biological specimens for elucidating complex ultrastructures in several fields of life science. The advancements in volume electron microscopy technologies have led to improvements, including higher resolution, more stability and the ability to handle larger volumes. Although human applications of volume electron microscopy remain limited, the reported applications in various organs have already provided previously unrecognized features of human tissues and also novel insights of human diseases. Simultaneously, the application of volume electron microscopy to human studies faces challenges, including ethical and clinical hurdles, costs of data storage and analysis, and efficient and automated imaging methods for larger volume. Solutions including the use of residual clinical specimens and data analysis based on artificial intelligence would address those issues and establish the role of volume electron microscopy in human structural research. Future advancements in volume electron microscopy are anticipated to lead to transformative discoveries in basic research and clinical practice, deepening our understanding of human health and diseases for better diagnostic and therapeutic strategies.

The three-dimensional (3D) anatomical structure of living organisms is intrinsically linked to their functions, yet modern life sciences have not fully explored this aspect. Recently, the combination of efficient tissue clearing techniques and light-sheet fluorescence microscopy for rapid 3D imaging has improved access to 3D spatial information in biological systems. This technology has found applications in various fields, including neuroscience, cancer research and clinical histopathology, leading to significant insights. It allows imaging of entire organs or even whole bodies of animals and humans at multiple scales. Moreover, it enables a form of spatial omics by capturing and analyzing cellome information, which represents the complete spatial organization of cells. While current 3D imaging of cleared tissues has limitations in obtaining sufficient molecular information, emerging technologies such as multi-round tissue staining and super-multicolor imaging are expected to address these constraints. 3D imaging using tissue clearing and light-sheet microscopy thus offers a valuable research tool in the current and future life sciences for acquiring and analyzing large-scale biological spatial information.