Microscopy (Oxford, England)最新文献

The cellular characteristics of the opportunistic fungal pathogen Cryptococcus species were investigated in the infected liver of an immunocompetent host using transmission electron microscopy (TEM). With no records of immunodeficiency, the 3-year-old female patient displayed a high-grade fever, lethargy and increasing jaundice. TEM analysis revealed the presence of round yeast cells in the patient's liver. These fungal yeast cells exhibited an array of cellular events in the host's liver: (i) the formation of polysaccharide capsules outside the cell wall, (ii) vacuolation in the cytoplasm and (iii) phagocytosis by Kupffer cells. The yeast cells were surrounded by electron-transparent polysaccharide capsules (approximately 5 μm thick). A series of yeast vacuolations were observed at different stages of cell development. As vacuoles occupied the cytoplasm of yeast cells, the polysaccharide capsules were thinner and more electron-dense than those of intact yeast cells. Certain yeast cells were phagocytosed by Kupffer cells through the budding scars or discontinued regions in the cell walls. These observations suggested that the patient was suffering from liver cryptococcosis. This study provides insights into the behavior of opportunistic fungal pathogens in the livers of immunocompetent patients.

The self-absorption effects observed in the background intensity just above the Si L-emission spectra of Si and β-Si3N4, and the C K-emission spectra of diamond and graphite were examined. Based on comparisons with reported results, the energy positions of absorption edges - representing the bottom of conduction bands (CBs) - were assigned. The self-absorption profiles in the background intensities were consistent with previously reported data. The simultaneous observation of valence band and CB edges allowed the determination of a bandgap energy of 1.1 eV for Si, which agrees with the indirect bandgap energy of Si. For β-Si3N4, the bandgap energy was evaluated as 5.1 eV. For diamond, the edge positions were matched with reported values, and the bandgap energy was calculated to be 5.0 eV, slightly smaller than the optical gap of 5.5 eV. These observations suggest that both edges can be expected for semiconductors in principle. On the other hand, C K-emission spectrum of graphite, a semimetal also showed an edge structure, which was assigned to the self-absorption edge due to the transitions from 1s to σ* antibonding state of sp2 bonding.

Immunoelectron microscopy is a technique for analyzing molecular localization at the ultrastructural level. In the pre-embedding immunoelectron microscopy, samples are immunolabeled with extremely small gold particles. Gold enhancement then enlarges the gold particles to an easily visible size. During the examination of the optimal conditions, we found that phosphate buffer accelerates the enhancement reaction. Furthermore, disodium hydrogen phosphate was identified as responsible for this effect. Disodium hydrogen phosphate enabled the gold labeling of deep regions within thick tissue samples. In conclusion, our method is useful for increasing the sensitivity, especially in the deeper region of the sample.

Mechanical properties of nanomaterials (∼10 nm or less in size) have attracted much attention for their application in nanoelectromechanical and advanced sensors. Recently, an in situ transmission electron microscope holder with a length extension resonator (LER) of quartz crystal as a force sensor, called the microscopic nanomechanical measurement (MNM) method, has been developed. It enables us to estimate not only Young's modulus but also critical shear stress for nanomaterials precisely. In this review, the principle of this novel method is introduced, and the mechanical characterization of nanomaterials revealed by this method is presented. (i) The size dependence of Young's modulus of gold nanocontacts when stretched in the [111] direction was measured, which could be explained by summing the bulk and surface Young's moduli weighted according to the ratio of internal to surface atoms. Bulk and surface Young's moduli were estimated to be 119 and 22 GPa, respectively. (ii) Young's modulus of MoS2 nanoribbons with armchair edge increased with decreasing the width, which indicated that the armchair edge bonds were stiffer than those inside the nanoribbon. (iii) By measuring the stiffness of Pt atomic chains consisting of two to five atoms, bond stiffnesses at the middle of the chain and at the connection to the base were estimated to be 25 and 23 N/m, respectively, which were higher than the bulk bond stiffness. (iv) Critical shear stress of Au nanocontacts was estimated to be 0.94 GPa by measuring the LER amplitude dependence of dissipative energy.

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.