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The three-dimensional spin structure of the magnetic vortex of FeSiB, an amorphous soft magnetic material, was investigated by holography observation and computer simulation. Magnetization distribution in the neighborhood of the vortex center was estimated from the phase distribution obtained by holography observation. To confirm this magnetization distribution, sample-tilting experiments were performed: when the sample was tilted with respect to the electron beam direction, the phase-image center was found to shift along the tilting axis. Finite-element computer simulation was carried out to estimate the amount of shifts of the phase-image center in the sample tilting from the experimental magnetization distributions in the no sample-tilting conditions. We found that the simulated shifts of the phase-image center were in good agreement with those in the sample-tilting experiment, thus confirming the magnetization distribution near the vortex center obtained by holography observation.

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Three-dimensional (3D) reconstruction experiments were carried out by observing high-resolution 3D electrostatic potential distributions of Pt nanoparticles using off-axis electron holographic tomography. These Pt nanoparticles were mounted on the surfaces of amorphous silicon pillars. In order to realize high-resolution observation, we developed a mechanically stable 3D specimen holder with small specimen drifts and vibrations. From the 3D electrostatic potential distribution data of Pt nanoparticles (2.0 nm in diameter), we obtained the resolution of 1.5 nm.

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We study in situ behavior of platinum single atoms on amorphous carbon (a-carbon) using a spherical aberration-corrected transmission electron microscope (AC-TEM). Diffusion of single atoms, bi-atoms, clusters (<1 nm) and nanoparticles (<3 nm) was recorded in the same image with a time resolution of 1 s, and such diffusion matches the expected mechanism of Ostwald ripening, which was seen on these samples. In situ AC-TEM shows promise for dynamical observation of single atom diffusion, which is important for understanding nanosized catalysts and ceramic sintering processes. We apply in situ AC-TEM to image platinum (Pt) nanoparticles on a-carbon, which is a model catalyst system for the real Pt electrode catalysts using alloys and core–shell structures supported on carbon/oxide composite materials in the proton exchange membrane fuel cell.

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In this study, based on a comprehensive numerical simulation of self-consistent charging, we investigate the formation, evolution and influencing factors of space charge distributions for a grounded insulating thin film of SiO₂ negatively charged by a keV non-penetrating focused electron beam. The simulated space charge presents first positive distributions and then negative ones along both the radial and depth directions because of the difference between electron and hole transports. The variations in distribution occur within a range of the minimum potential acting as a potential barrier for carrier transport. The negative space charge is distributed more widely and deeply, though its peak value in density is usually lower than that of the positive one. Electrons trapped outside the minimum potential range dominate the strength of negative charging. With the increase in potential barrier and the occurrence of leakage current, the space charge eventually reaches equilibrium and exhibits an approximately one-dimensional axial distribution outside the minimum potential range. Distribution features of the space charge density in the equilibrium state correlate with the film and beam parameters via transients of the leakage current. These results and analyses provide new insights into the negative charging effects involved in various electron-beam-based surface microscopic methods, analyses and fabrication techniques.

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Scanning electron microscopy (SEM) using osmium-maceration methods has been used for analyzing the three-dimensional structure of cell organelles in tissue samples, but it has been quite difficult to observe free and cultured cells with this technique. The present study was performed to develop a method that can be applied to free and cultured cells for SEM studies of intracellular structures after osmium maceration. The method was also applied to light microscopy (LM) and to transmission electron microscopy (TEM). HeLa cells and human leukocytes were fixed with a mixture of 0.5% paraformaldehyde and 0.5% glutaraldehyde followed by an additional fixation with 1% osmium tetroxide. These cells were embedded in low-melting-point agarose. A temperature-responsive dish was also used for collection of cultured cells before embedding. For LM and TEM, the cell-embedded agarose was further embedded in epoxy resin, and semi- and ultrathin sections were examined conventionally. For SEM, the agarose was freeze-fractured in 50% dimethyl sulfoxide, processed for osmium maceration and observed in a high-resolution SEM. Low-melting-point agarose was useful as an embedding medium for SEM, because it was well preserved during prolonged osmication for SEM. Thus, the fine structure of cell organelles was clearly analyzed by SEM after osmium-maceration treatment. These SEM images could also be compared with those of LM and TEM of the agarose-embedded tissues.

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This study was designed to elucidate details of the structure and formation process of the alternate lamellar pattern known to exist in lamellar bone. For this purpose, we examined basic internal lamellae in femurs of young rats by transmission and scanning electron microscopy, the latter employing two different macerations with NaOH at concentrations of 10 and 24%. Observations after the maceration with 10% NaOH showed that the regular and periodic rotation of collagen fibrils caused an alternation between two types of lamellae: one consisting of transversely and nearly transversely cut fibrils, and the other consisting of longitudinally and nearly longitudinally cut fibrils. This finding confirms the consistency of the twisted plywood model. The maceration method with 24% NaOH removed bone components other than cells, thus allowing for three-dimensional observations of osteoblast morphology. Osteoblasts extended finger-like processes paralleling the inner bone surface, and grouped in such a way that, within a group, the processes arranged in a similar direction. Transmission electron microscopy showed that newly deposited fibrils were arranged alongside these processes. For the formation of the alternating pattern, our findings suggest that: (1) osteoblasts control the collagen fibril arrangement through their finger-like process position; (2) osteoblasts behave similarly within a group; (3) osteoblasts move their processes synchronously and periodically to promote alternating different fibril orientation; and (4) this dynamic sequential deposition of fibrils results in the alternate lamellar (or twisted plywood) pattern.

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The oviduct is an important organ for successful mammalian reproduction. In this work, human oviducts were inseminated and their explants analyzed using scanning electron microscopy in order to study, at a finer ultrastructual level, the interaction between spermatozoon and oviduct in vitro. Results show unequivocally a spermatozoon tightly attached through the acrosomal region of its head to several cilia of the human tubal epithelial cells. This finding proves that spermatozoa do indeed adhere to the endosalpinx, a fact of utmost relevance for the physiology of the reproductive process, since it supports the idea of a spermatozoa reservoir being formed in the oviduct, which is also briefly discussed.

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Mitochondria in all eukaryotes are essential organelles responsible for adenosine triphosphate synthesis, calcium homeostasis and steroidogenesis. Because the structure and distribution of mitochondria are highly diverse depending on their function and cellular conditions, it is important to develop a rapid and accurate method to assess their morphology. In this study, we visualize whole mitochondria in cultured cells using high-voltage electron microscopy (HVEM). Compared with conventional transmission electron microscopic approaches, the present method does not require thin sectioning and thus requires less time for image acquisition and processing. Furthermore, compared with fluorescence-based light microscopic approaches, our method provides more accurate size information. Thus, we propose that HVEM is a useful tool for rapid and accurate analysis of mitochondrial morphology and distribution in a cell.

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The Food and Drug Administration is considering approval of the first over-the-counter HIV test that would allow consumers to quickly test themselves for the virus at home, without medical supervision.FDA reviewers said Friday the OraQuick In-Home HIV test could play a significant role in...

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A spokesman for the family of an 18-month-old girl who was pulled off a flight because airline employees thought her name was on the U.S. no-fly list says the girl's parents do not plan to take any legal action.Rick Abbott told The Associated Press Friday that the family is looking for an...

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W.W. Grainger Inc., a supplier of power tools and other industrial equipment, said Friday that its daily sales in April rose 12 percent from a year earlier.The company said that about 5 percent of the sales growth came from acquisitions. Excluding acquisitions, sales rose 7 percent during the...

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