Microscopy (Oxford, England)最新文献

Collagen fibrils in the dermis are bundled by glycosaminoglycan (GAG) chains of decorin, which contribute to its strength. The three-dimensional structure of collagen fibrils and GAG chains has been discussed on the basis of observations and experiments. This study uses scanning transmission electron microscope (STEM) tomography with high Z-axis resolution to analyze the three-dimensional structure of GAG chains in the dermis from a healthy individual and a patient with musculocontractural Ehlers-Danlos syndrome caused by pathogenic variants in CHST14 (mcEDS-CHST14). This observation revealed that the dermis from a healthy individual featured multiple GAG chains that wrapped around collagen fibrils and formed incomplete ring structures. However, in the dermis from a patient with mcEDS-CHST14, GAG chains were linear and did not form rings. Based on the relationship between collagen fibrils and GAG chains, we suggest the three-dimensional structure of normal GAG chains in a new model named the 'segmented ring-mesh model'. The interactions between collagen fibrils and GAG chains in this model also apply to the dermis of mcEDS-CHST14 patients, in which the GAG chain composition changes to become CS-rich and more linear. This change leads to an increased inter-fibrillar space, which inhibits the dense packing of collagen fibrils. These findings suggest that this phenomenon contributes to the skin fragility observed in mcEDS-CHST14 patients. Our study suggests the 'segmented ring-mesh model' of GAG chains is essential for the dense packing of collagen fibrils in normal dermis. STEM tomography is highly effective in analyzing the three-dimensional structure of collagen fibrils and GAG chains.

Atomic force microscopy (AFM) allows direct imaging of atomic- or molecular-scale surface structures in liquid. However, such subnanoscale measurements are often sensitive to the AFM tip properties. To overcome this problem, 30 nm Si-sputter coating was proposed, and its effectiveness in improving stability and reproducibility has been demonstrated in atomic-scale imaging of various materials. However, this method involves tip blunting, enhancing the tip-induced dilation effect. As an alternative method, here we investigate atomic layer deposition (ALD) Al2O3-coating, where the film thickness is atomically well-controlled. Our transmission electron microscopy, contact angle and force curve measurements consistently suggest that as-purchased tips are covered with organic contaminants, and the initial 20 cycles gradually remove them, reducing the tip radius (Rt) and hydrophobicity. Further deposition increases Rt and hydrophilicity and forms an intact Al2O3 film over 50 cycles. We compared 50-cycle ALD-coated tips with 30 nm Si-sputter-coated tips in imaging mica and chitin nanocrystals (NCs). On mica, ALD coating gives slightly less stability and reproducibility in hydration force measurements than the Si sputter coating, yet they are sufficient in atomic-scale imaging. In imaging chitin NCs, ALD-coated tips give a less tip-induced dilation effect while maintaining molecular-scale imaging capability. We also found that 10-cycle-ALD coated tips covered with carbon give a better resolution and reproducibility in observing subnanoscale features at chitin NC surfaces. This result and our experience empirically suggest carbon-coated tips' effectiveness in observing carbon-based materials.

We have studied the effects of electron irradiation on Pt/a-SiOx thin films by transmission electron microscopy and electron diffraction. Pt2Si was formed by 75 keV electron irradiation at 298 K and 90 K. Such a low-temperature synthesis of Pt2Si can be attributed to the dissociation of a-SiOx induced by electronic excitation; Si-O bonds dissociate through Auger decay of core-holes generated by electronic excitation, and then, dissociated Si atoms form Pt-Si bonds. The morphology of Pt islands extensively changed during Pt2Si formation, even at 90 K. Coalescence and growth of metallic particles are not due to thermal effects during electron irradiation but to athermal processes accompanied by silicide formation. To maintain the reaction interface between metallic particles and the dissociated Si atoms by electronic excitation, a considerable concomitant morphology change occurs. Similarly, Fe2Si was synthesized by using the same technique. In this way, we have demonstrated a versatile method for selectively forming nanoscale metal silicides in electron-irradiated areas at room temperature. We also propose a new mechanism for the crystallization of amorphous alloys, which is mediated by additional solute atoms produced by electronic excitation. Crystallization of amorphous Pd-Si alloy thin films can be realized by 75 keV electron irradiation at 90 K via the electronic excitation, where both knock-on damage and possible thermal crystallization can be excluded. Supply of dissociated Si to the Pd-Si layer may cause instability of the amorphous phase, which serves as the trigger for the remarkable structural change, i.e. additional solute atom-mediated crystallization.

The precision in electron holography studies on electrostatic and magnetic fields depends on the image quality of an electron hologram. Enhancing the image quality of electron holograms is essential for the comprehensive analysis of weak electromagnetic fields; however, extended electron beam irradiation can lead to undesirable radiation damage and contamination. Recent studies have demonstrated that noise reduction using the wavelet hidden Markov model (WHMM) can improve the precision of phase analysis for limited thin-foiled crystals. In this study, we examine the effects of WHMM-based denoising on the electron holography data of weakly charged nanoparticles collected under low-electron-dose conditions. The results indicate that effective noise reduction with the WHMM allows for a reduction in the magnitude of the electron dose by approximately half relative to data collection without WHMM denoising, while maintaining the same level of charge determination precision: less than one elementary charge. Notably, at a low electron dose of 0.40 e-/pixel, WHMM denoising enables the clear visualization of a weak stray electric field outside a charged latex sphere. This method offers significant advantages for electron holography studies of electron-beam-sensitive materials requiring minimal time for electron exposure.

Accurate quantification of the individual layers of the intestinal wall is essential for biomechanical modeling and the development of gastrointestinal medical devices. Traditional microscopy techniques, though widely used, are limited by their two-dimensional nature and potential for tissue distortion due to complex sample preparation. This study evaluates X-ray microscopy (XRM) as a non-destructive, three-dimensional alternative for measuring the thicknesses of the four major layers of porcine large intestinal tissue: serosa, muscularis externa, submucosa, and mucosa. Using the ZEISS Xradia 620 Versa, XRM scans were compared to standard light microscopy. XRM successfully visualized all four layers and yielded thickness measurements that were consistent with those obtained via standard microscopy, despite natural biological variability. Notably, XRM scans allowed for 3D reconstructions of tissue vasculature and did not need extensive preparation or staining. These findings establish XRM as a powerful and practical method for morphological analysis of soft tissues and offer the first reported absolute layer thicknesses for each layer of porcine large intestinal tissue which can be used in layer-specific constitutive biomechanical models. This study compares measurements of intestinal tissue layers obtained using X-ray microscopy to those from traditional light microscopy. The results show that X-ray microscopy provides comparable data while offering the advantages of 3D imaging and minimal tissue preparation. (Figure 2).

Core-loss spectroscopies using electrons and X-rays, such as electron energy loss near-edge structures (ELNES) and X-ray absorption near-edge structures (XANES), are indispensable tools for materials characterization and development. These techniques provide detailed insights into atomic environments, chemical bonding, and vibrational properties that underpin material functionality. Traditionally, ELNES/XANES analyses have relied on qualitative interpretation or comparisons with reference spectra obtained from experiments and/or simulations. Recent advances in data-driven approaches, however, have enabled more quantitative and predictive use of these spectra. This review highlights newly developed data-driven methodologies that extend far beyond conventional ELNES/XANES analysis. These approaches accelerate ELNES/XANES simulations, enable the extraction of radial distribution functions, and quantify multiple material properties directly from spectral data. To enhance the interpretability of machine learning (ML) predictions, sensitivity analysis is employed to elucidate the relationships between specific spectral features and target properties. The rapid growth of open materials databases, coupled with increasingly powerful ML models, has further fueled these developments. Together, these advances would point to a future in which automated, interpretable and scalable spectroscopy serves as a central driver for deeper understandings and accelerated materials discovery.

Scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) has emerged as a state-of-the-art characterization modality in materials science, undergoing transformative advancements over the past decade. Revolutionary developments in monochromator technology have pushed EELS energy resolution into the sub-10 meV regime, enabling investigations of low-energy excitations such as phonons, excitons, plasmons, and polaritons at nanometer and sub-nanometer scales, in addition to traditional core-loss spectroscopy. Besides to the high spatial resolution and high energy resolution, the coherent nature of STEM electron probes now allows momentum-resolved spectral information to be acquired, providing an ideal platform for correlating nanoscale structural features with functional properties at the nanometer and atomic level. This review surveys recent breakthroughs in STEM-EELS methodology, with particular emphasis on the four-dimensional electron energy loss spectroscopy (4D-EELS) technique, which simultaneously captures spectral information across spatial, momentum, and energy dimensions with unprecedented efficiency. We highlight landmark scientific discoveries enabled by this spontaneous spatial-momentum resolving capability, including phonon dispersion mapping, plasmon dispersion mapping, and magnon mapping. The review concludes with perspectives on future technical refinements, such as resolution enhancements, machine learning-driven data analytics, and in-situ characterization capabilities, and the potential of this technology to revolutionize interdisciplinary research in quantum materials and nanophotonics. This review methodically investigates recent breakthroughs in low-loss excitation studies using STEM-EELS with a primary focus on phonon dynamics. Furthermore, we introduce the recently developed 4D-EELS Technique adopting parallel acquisition of spectral information across spatial, momentum, and energy dimensions.

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.