Estimation of wave fields of incident beams in a transmission electron microscope by using a small selected-area aperture

The direction of an electron beam in a nanometer-sized area is measured directly by utilizing a selected-area aperture. By the measurements at several areas in a beam, the wavefront curvature and thus the defocus value of the beam are detected. From the defocus value, the wave field at the specimen plane is also reproduced in consideration of the influences of the condenser aperture and spherical aberration of the illumination lens. The result shows that phase deviation of 2π is caused only at about 10?nm apart from the beam center in a beam with a typical diameter for high-resolution transmission electron microscopy. Based on the defocus value, the convergence angle of the beam is also estimated to be about 6?mrad without being influenced by the partial coherence, that is, independently of the type of the electron gun. Measuring the defocus values for only two beam diameters enables us to determine geometrical parameters peculiar to the illumination system, based on which wave fields of any beam diameters by any condenser aperture sizes can be estimated. The technique proposed in this paper is effective in evaluating the influence of wavefront curvature of incident beams on various kinds of precise measurements conducted in transmission electron microscopes.     

Japanese contribution to the DEMO-R&D program under the Broader Approach activities

Several technical R&D activities mainly related to the blanket materials are newly launched as a part of the Broader Approach (BA) activities, which was initiated by the EU and Japan. According to the common interests for these parties in DEMO, R&Ds on reduced activation ferritic/martensitic (RAFM) steels as structural material, SiC_f/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology are carried out through the BA DEMO R&D program, in order to establish the technical bases on the blanket materials and the tritium technology required for DEMO design. This paper describes overall schedule of those R&D activities and recent progress in Japan carried out by JAEA as the domestic implementing agency on BA, collaborating with Japanese universities and other research institutes.     

Effects of heparin and its 6-O-and 2-O-desulfated derivatives with low anticoagulant activity on proliferation of human neural stem/progenitor cells

Heparin binds various growth factors and activates them to interact with high-affinity cell surface receptors; a specific array of sulfate groups in the heparin backbone structure is very important for this interaction. In the present study, we evaluated the effects of two novel heparin derivatives, 6-O-desulfated heparin (6-DSH) and 2-O-desulfated heparin (2-DSH), on blood coagulation and the proliferation of human neural stem/progenitor cells (NSPCs). 6-DSH showed lower anticoagulant activity than intact heparin or 2-DSH, as measured by the activated partial thromboplastin time and thrombin time. In the presence of FGF-2, 6-DSH and 2-DSH promoted approximately the same rate of proliferation of human NSPCs, without noticeably changing the expression of nestin. The mitotic effects of 6-DSH and 2-DSH on human NSPCs were different from their effects on mouse hematopoietic stem cells and fibroblasts. These findings indicate that 6-DSH and 2-DSH have the same ability to promote the growth of human NSPCs as intact heparin. Our results suggest that these two novel heparin derivates, especially 6-DSH, could be used in clinical applications for ex vivo human NSPC culture, as a lower-risk growth co-adjuvant than intact heparin.     

Vacuolar H(+)-ATPase and plasma membrane H(+)-ATPase contribute to the tolerance against high-pressure carbon dioxide treatment in Saccharomyces cerevisiae

As a non-thermal sterilization process, high-pressure carbon dioxide treatment (HPCT) is considered to be promising. The main sterilizing effect of HPCT is thought to be acidification in cytoplasm of microorganisms. We investigated the tolerance mechanism of Saccharomyces cerevisiae to HPCT with special reference to vacuolar and plasma membrane H(+)-ATPases. HPCT was imposed at 35 degrees C, 4 to 10 MPa, for 10 min. slp1 mutant defective in vacuole morphogenesis was more sensitive to HPCT than its isogenic parent. Concanamycin A, a specific inhibitor of vacuolar H(+)-ATPase (V-ATPase), at 10 microM rendered the parent more HPCT-sensitive to the level of slp1. To confirm further the contribution of V-ATPase to the tolerance against HPCT in S. cerevisiae, we compared vma1 mutant of V-ATPase with its isogenic parent for their HPCT sensitivity. vma1 mutant was more sensitive to HPCT than its parent. Addition of 10 microM vanadate, an inhibitor of plasma membrane H(+)-ATPase (P-ATPase), to the wild type strains also increased the inactivation ratio. These results clearly show that V- and P-ATPases contribute to the tolerance against HPCT in S. cerevisiae by accumulating excess H(+) from cytoplasm to vacuole and excluding H(+) outside of the cell, respectively.     

Internal stress behavior of the short ceramic fiber reinforced aluminum alloy under tensile deformation

The in situ measurement of phase stress under tensile deformation on an A6061 alloy reinforced with SiC whiskers (Al/SiCw MMC: Metal Matrix Composite) was performed using the X-ray diffraction technique. In order to raise a preciseness of measurements, we applied a profile fitting technique to separate the nearby located diffraction peak. Tensile deformation on elastic to plastic range was applied by four points bending device and discussed internal stress behavior in the short ceramic fiber reinforced MMC. Phase stress in Al matrix was increased linearly up to 2800×10⁻⁶ in strain and then saturated immediately. On the other hand phase stress in SiC whiskers shows an unstable stress behavior. It was decreased at first because of the Poisson's effect from Al matrix but reversed over 500×10⁻⁶ applied strain. The measured phase stress behavior in elastic region agreed with the calculations using micromechanics based on Eshelby/Mori–Tanaka model except for this unstable internal stress region. The macro stress behavior in plastic region was extremely small than that of the tensile test results. It supposed that the mechanism of strength is not so much the fiber reinforcing as the dispersion strengthening like the Orowan mechanism. Regarding the fatigue property, ΔK_th of the Al/SiC MMC, this was lower than that of the A6061 alloy. On the Al/SiCw MMC specimen, many micro void formations were observed around the fatigue crack tip even under the ΔK_th of A6061. It was considered that these were caused by the high gradient of residual stress on composite process and the unstable stress behavior in low ΔK region.     

Mechanical Properties of Borosilicate Glass Coated with Two-layered Ceramics by Sputtering

The durability of coated glass materials should be improved in their applications, and the possibility of a two-layer coating was examined as a processing for the improvement. In the present work, the borosilicate glass was coated with two-layered ceramics by the radio-frequency (RF) magnetron sputtering method, and mechanical properties of coated glass materials were investigated. The measured surface roughness and porosity of coating film suggested that relatively smooth and dense coating films were formed under the sputtering condition adopted in this work. Thicker film was found to be harder because of the avoidance of effect due to softer glass substrate. Higher RF output power resulted in harder film. The bending strength was reduced by longer time of sputtering as well as porosity of coating film. By comparison with glass materials coated with single ceramics and the glass substrate, it was clarified that the strength and hardness of coated glass materials were improved by two-layer coating.     

YBa2Cu3O7 − δ thin films with enhanced film properties grown on sapphire using Y2O3/CeO2 bi-layer buffer

Highly epitaxial, microcrack-free thin films of YBa₂Cu₃O_7 − δ (YBCO) have been grown by pulsed laser deposition on sapphire substrates with a double buffer of Y₂O₃/CeO₂. The Y₂O₃ layer, which has excellent compatibility with CeO₂ and YBCO, has been found to be beneficial in reducing the surface porosity of YBCO films as well as inhibiting a-axis-oriented epitaxial growth. The reduction in porosity is attributed to the presence of the Y₂O₃ layer which acts as a suitable barrier for the chemical reaction occurring at high deposition temperatures between YBCO and CeO₂. Due to the improvement in film quality and surface morphology, enhancement of the self-field critical current density (J_c, 77.3 K) by as high as 30% was obtained for a 650-nm thick YBCO film deposited on Y₂O₃/CeO₂ bi-layer buffer compared to simultaneously-deposited YBCO film on CeO₂ single-layer buffer only.     

A Technique to Eliminate Redundant Inter-Processor Communication on Parallelizing Compiler TINPAR

Optimizing inter-processor (PE) communication is crucial for parallelizing compilers for message-passing parallel machines to achieve high performance. In this paper, we propose a technique to eliminate redundant inter-PE messages. This technique utilizes data-flow analysis to find a definition point that corresponds to a use point where the definition and the use occur in different PEs. If several read accesses occurred in the same PE use the data defined at the same definition point in another PE, redundant inter-PE messages are eliminated as follows: only one inter-PE communication is performed for the earliest read access and the previously received data are used for the following read. In order to guarantee the consistency of the data, a valid flag and a sent flag are provided for each chunk of received data. The control of these flags is equivalent to the coherence control by the self invalidation on a compiler aided cache coherence scheme.