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Articles by H Sawada
Total Records ( 5 ) for H Sawada
  H Sawada , T Sasaki , F Hosokawa , S Yuasa , M Terao , M Kawazoe , T Nakamichi , T Kaneyama , Y Kondo , K Kimoto and K. Suenaga

A new concept of a spherical aberration correction system using three dodecapoles is proposed. The system compensates for higher order aberration of 6-fold astigmatism, which generally limits a uniform phase area for image forming and probe forming in an electron microscope with a conventional two-hexapole corrector. Triple 3-fold astigmatism field is used to correct the spherical aberration of the objective lens, and the total 3-fold astigmatism is eliminated by their combination. The optimum azimuth relationship among three dodecapoles is calculated to eliminate the 6-fold astigmatism. The principle of the method was verified using a mathematically complex representation. This new concept was experimentally tested with a scanning transmission electron microscope at 60 kV acceleration. The 6-fold astigmatism was certainly compensated and the coherent convergent angle became almost twice compared to a conventional double hexapole system.

  H Sawada , Y Tanishiro , N Ohashi , T Tomita , F Hosokawa , T Kaneyama , Y Kondo and K. Takayanagi

A spherical aberration-corrected electron microscope has been developed recently, which is equipped with a 300-kV cold field emission gun and an objective lens of a small chromatic aberration coefficient. A dumbbell image of 47 pm spacing, corresponding to a pair of atomic columns of germanium aligned along the [114] direction, is resolved in high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) with a 0.4-eV energy spread of the electron beam. The observed image was compared with a simulated image obtained by dynamical calculation.

  Y Oshima , H Sawada , F Hosokawa , E Okunishi , T Kaneyama , Y Kondo , S Niitaka , H Takagi , Y Tanishiro and K. Takayanagi

We visualized lithium atom columns in LiV2O4 crystals by combining scanning transmission electron microscopy with annular bright field (ABF) imaging using a spherical aberration-corrected electron microscope (R005) viewed from the [110] direction. The incident electron beam was coherent with a convergent angle of 30 mrad (semi-angle), and the detector collected scattered electrons over 20–30 mrad (semi-angle). The ABF image showed dark dots corresponding to lithium, vanadium and oxygen columns.

  N Shibata , Y Kohno , S. D Findlay , H Sawada , Y Kondo and Y. Ikuhara

A new area detector for atomic-resolution scanning transmission electron microscopy (STEM) is developed and tested. The circular detector is divided into 16 segments which are individually optically coupled with photomultiplier tubes. Thus, 16 atomic-resolution STEM images which are sensitive to the spatial distribution of scattered electrons on the detector plane can be simultaneously obtained. This new detector can be potentially used not only for the simultaneous formation of common bright-field, low-angle annular dark-field and high-angle annular dark-field images, but also for the quantification of images by detecting the full range of scattered electrons and even for exploring novel atomic-resolution imaging modes by post-processing combination of the individual images.

  H Hirakawa , H Sawada , Y Yamahama , S. I Takikawa , H Shintaku , A Hara , K Mase , T Kondo and T. Iino

Tetrahydrobiopterin (BH4) acts as a cofactor of the aromatic amino-acid hydroxylases, and its deficiency may result in hyperphenylalaninemia (HPA) and decreased production of the neurotransmitters. BH4 is synthesized by sepiapterin reductase (SPR) from 6-pyruvoyl-tetrahydropterin (PPH4). A patient with SPR deficiency shows no HPA; however, an SPR knockout mouse exhibits HPA. We have reported on the SPR-unrelated novel biosynthetic pathway from PPH4 to BH4 (salvage pathway II) in which 3-hydroxysteroid dehydrogenase type 2 and aldose reductase work in concert. In this study, we performed the expression analysis of both proteins in humans and wild-type mice. The results of expression analysis indicated that salvage pathway II worked in human liver; however, it did not act in human brain or in mouse liver and brain. For this reason, a patient with SPR deficiency may show progressive neurological deterioration without HPA, and SPR knockout mice may exhibit HPA and abnormal locomotion activity.

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