ALBERT

Description: The electron irradiation damage of MFI-type zeolite was estimated under various accelerating voltages of 100, 200 and 300 kV from successively captured high-resolution transmission electron microscopy (HRTEM) images. To determine the optimal accelerating voltage for HRTEM imaging of electron-sensitive MFI zeolite, the critical dose was estimated from the disappearance of a specific fast Fourier transform spot calculated from experimental images. Based only on the electron dose, a higher voltage was more advantageous. However, taking into account the minimum dose for imaging with a CCD camera, the optimal accelerating voltage for imaging MFI zeolite was 200 kV. The minimum dose for image detection with a CCD camera was surmised from the output/input signal ratio dependence on the accelerating voltage and the contrast range in simulated HRTEM images.

Description: Efficient pre-replication complex (pre-RC) formation on chromatin templates is crucial for the maintenance of genome integrity. However, the regulation of chromatin dynamics during this process has remained elusive. We found that a conserved protein, GRWD1 (glutamate-rich WD40 repeat containing 1), binds to two representative replication origins specifically during G1 phase in a CDC6- and Cdt1-dependent manner, and that depletion of GRWD1 reduces loading of MCM but not CDC6 and Cdt1. Furthermore, chromatin immunoprecipitation coupled with high-throughput sequencing (Seq) revealed significant genome-wide co-localization of GRWD1 with CDC6. We found that GRWD1 has histone-binding activity. To investigate the effect of GRWD1 on chromatin architecture, we used formaldehyde-assisted isolation of regulatory elements (FAIRE)-seq or FAIRE-quantitative PCR analyses, and the results suggest that GRWD1 regulates chromatin openness at specific chromatin locations. Taken together, these findings suggest that GRWD1 may be a novel histone-binding protein that regulates chromatin dynamics and MCM loading at replication origins.

Description: 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.

Description: We quantitatively analyzed the contrast degradation and blur of 20-nm gold nanoparticles adsorbed on the top of amorphous silicon films of thicknesses of 0.54, 1.09, 1.63 and 2.2 μm in bright-field transmission electron microscope (TEM) images taken at accelerating voltages of 0.5, 1, 2 and 3 MeV. The thickness dependence of the transmission was well explained and consistent with our calculations. The blur function, derived by assuming that the TEM image of a thick specimen can be reproduced by convolving the TEM image of a very thin specimen with it, was found to be expressed by a two-dimensional Lorentzian function. Considering the two characteristics of the Lorentzian function, a sharp peak around the center and a long tail, we concluded that, for TEM observations of thick specimens, the image contrast is degraded predominantly by inelastic scattering and the image is blurred predominantly by multiple elastic scattering.

Description: An accurate method using image sharpness to determine the best focusing is proposed for ultra-high-voltage electron microscopy. This method maximizes image sharpness for adjusting the focus. Five images with different defocus values are used to calculate the image sharpness. To obtain the best focus value that produces greatest image sharpness, fitting the quasi-Gaussian function to five image sharpness is a suitable alternative. This method, which maximizes image sharpness, gives better accuracy than the wobbler method for the ultra-high-voltage electron microscope. The focusing area can be selected without moving the field of view, because the focusing area can be selected at almost any area in the image.

Description: In order to know whether principal stress orientations in the source area rotated after the 2011 April 11 M w 6.6 Fukushima-Hamadori earthquake in NE Japan, we investigated detailed spatial distributions of stress orientations for both the pre- and post-main shock periods using a large amount of focal mechanism data. We applied stress tensor inversions to focal mechanism data from Japan's National Research Institute for Earth Science and Disaster Prevention's F-net broadband seismic network and the Japan Meteorological Agency (JMA). The 3 -axes estimated for the pre-main shock period are predominantly oriented WSW–ENE, and are relatively homogeneously in space. In contrast, the orientations of the 3 -axes show a significantly heterogeneous distribution in space for the post-main shock period. In the northern subarea of the focal region, the 3 -axes are oriented NW–SE. In the east and west portions of the central subarea, they are oriented NNW–SSE and WNW–ESE, respectively, almost perpendicular to each other. In the southern subarea, the 3 -axes are oriented WSW–ENE. On the whole, the 3 -axis orientations show concentric circle-like distribution surrounding the large slip area of the M w M w 6.6 main shock rupture. The change of principal stress axis orientations after the earthquake is not significant because of the sparse data set for the pre-main shock period. We calculated static stress changes from the M w 6.6 main shock and three M w 〉 5.5 earthquakes to compare with the observed stress axis orientations in the post-main shock period. The 3 -axis orientations of the calculated total static stress change show a concentric circle-like distribution surrounding the large slip area of the main shock, similar to that noted above. This observation strongly suggests that the spatially heterogeneous stress orientations in the post-main shock period were caused by the static stress change from the M w 6.6 main shock and other large earthquakes. In order to estimate the differential stress magnitude in the focal area, we calculated deviatoric stress tensors in the post-main shock period by assuming that they are the sum of the deviatoric stress tensors in the pre-main shock period and the static stress changes. Comparison of the calculated and observed stress tensors revealed differential stress magnitudes of 2–30 MPa that explain the observed stress orientations, considering the probable range of estimated stress ratios in the pre-main shock period.

Description: In order to know whether principal stress orientations in the source area rotated after the 2011 April 11 M w 6.6 Fukushima-Hamadori earthquake in NE Japan, we investigated detailed spatial distributions of stress orientations for both the pre- and post-main shock periods using a large amount of focal mechanism data. We applied stress tensor inversions to focal mechanism data from Japan's National Research Institute for Earth Science and Disaster Prevention's F-net broadband seismic network and the Japan Meteorological Agency (JMA). The 3 -axes estimated for the pre-main shock period are predominantly oriented WSW–ENE, and are relatively homogeneously in space. In contrast, the orientations of the 3 -axes show a significantly heterogeneous distribution in space for the post-main shock period. In the northern subarea of the focal region, the 3 -axes are oriented NW–SE. In the east and west portions of the central subarea, they are oriented NNW–SSE and WNW–ESE, respectively, almost perpendicular to each other. In the southern subarea, the 3 -axes are oriented WSW–ENE. On the whole, the 3 -axis orientations show concentric circle-like distribution surrounding the large slip area of the M w M w 6.6 main shock rupture. The change of principal stress axis orientations after the earthquake is not significant because of the sparse data set for the pre-main shock period. We calculated static stress changes from the M w 6.6 main shock and three M w 〉 5.5 earthquakes to compare with the observed stress axis orientations in the post-main shock period. The 3 -axis orientations of the calculated total static stress change show a concentric circle-like distribution surrounding the large slip area of the main shock, similar to that noted above. This observation strongly suggests that the spatially heterogeneous stress orientations in the post-main shock period were caused by the static stress change from the M w 6.6 main shock and other large earthquakes. In order to estimate the differential stress magnitude in the focal area, we calculated deviatoric stress tensors in the post-main shock period by assuming that they are the sum of the deviatoric stress tensors in the pre-main shock period and the static stress changes. Comparison of the calculated and observed stress tensors revealed differential stress magnitudes of 2–30 MPa that explain the observed stress orientations, considering the probable range of estimated stress ratios in the pre-main shock period.

Description: We investigated a detailed spatial distribution of principal stress axis orientations in the source area of the 2003 M6.4 Northern Miyagi Prefecture earthquake that occurred in the forearc of northeastern Japan. Aftershock hypocentres were precisely relocated by applying the double difference method to arrival time data obtained at temporary stations as well as at surrounding routine stations. We picked many P -wave polarity data from seismograms at these stations, which enabled us to obtain 312 well-determined focal mechanism solutions. Stress tensor inversions were performed by using these focal mechanism data. The results show that quite a lot of focal mechanisms are difficult to explain by the uniform stress field, especially near the large slip area of the main-shock rupture. Stress tensor inversions at the location of individual earthquakes show that 1 axes are orientated mainly to WSW–ENE in the northern part of the source area, while they are oriented to NW–SE in the southern part. This spatial pattern is roughly similar to those of the static stress change by the main shock, which suggests that the observed spatially heterogeneous stress field was formed by the static stress change. If this is the case, the deviatoric stress magnitude before the main shock was very small. Another possibility is the heterogeneous stress field observed after the main shock had existed even before the main shock, although we do not know why it was formed. Unfavourable orientation of the main shock fault with respect to this stress field suggests that the fault is not strong in this case too.

Description: The catalytic behavior of various noble metal nanoparticles (NPs) supported directly on multiwalled carbon nanotubes (MWCNTs) was observed using environmental transmission electron microscopy (E-TEM). Gasification of the MWCNTs via catalytic hydrogenation or oxidation progressed at ~450°C in conjunction with certain noble metal NP catalysts at the interface between MWCNTs and the NPs. During such catalytic reactions, the NPs were observed to move rapidly over the MWCNT surfaces. The mobility and wettability of the NPs varied depending on the particular metal NPs employed and the ambient atmosphere. While rhodium NPs exhibited high wettability under both hydrogen and oxygen atmospheres, the wettability of platinum, palladium and iridium NPs on MWCNTs varied with the atmosphere. The metal NPs seemed to have high degrees of crystallinity while their morphologies fluctuated throughout the catalytic reactions.