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Now showing items 17 - 32 of 68

  • Effect of metal electrodes on rubrene single-crystal transistors RID G-9009-2011

    Takenobu, Taishi   Takahashi, Tetsuo   Takeya, Jun   Iwasa, Yoshihiro  

    The authors herein have investigated the effect of the metal work function on the performance of rubrene single-crystal transistors using gold and calcium metal electrodes. The current-voltage characteristic is controlled by the metal work function, which offers the possibility of controlling the Schottky barrier height by the choice of the metal. In the process of the study of metal-rubrene contacts, the authors have realized an ambipolar transistor and a Schottky diode in an identical single-crystal device with asymmetric electrodes. These data provide direct evidence of the weak Fermi level pinning and formation of depletion layer on metal-rubrene contacts.
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  • Blocking Effect of NIP-142 on the KCNQ1/KCNE1 Channel Current Expressed in HEK293 Cells

    Namekata, Iyuki   Tsuruoka, Noriko   Tshneoka, Yayoi   Matsuda, Tomoyuki   Takahara, Akira   Tanaka, Yoshio   Suzuki, Takeshi   Takahashi, Tetsuo   Iida-Tanaka, Naoko  

    We examined the effect of NIP-142, a benzopyran compound with terminating effect on experimental atrial arrhythmia, on the KCNQ1/KCNE1 channel, which underlies the slow component of the cardiac delayed rectifier potassium channel (I-Ks) NIP-142, as well as chromanol 293B, showed concentration-dependent blockade of the current expressed in HEK293 cells; the EC50 value of NIP-142 and chromanol 293B for the inhibition of tail current was 13.2 mu M and 4.9 mu M, respectively. These results indicate that NIP-142 has blocking effect on the KCNQ1/KCNE1 channel current.
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  • Effect of reduced pressure on 3C-SiC heteroepitaxial growth on Si by CVD

    Ishida, Yuuki   Takahashi, Tetsuo   Okumura, Hajime   Arai, Kazuo   Yoshida, Sadafumi  

    The difference between atmospheric pressure (AP)CVD and low pressure (LP)CVD in 3C-SiC heteroepitaxial growth on Si(001) surfaces has been investigated. It is found that the difference in the growth mode results in a difference in the secondary nucleation rate. It is suggested that the increase of the secondary nucleation rate causes 2D island growth on {111} faces, and that these 2D islands play an important role in the process of elimination of planar defects. A simulation of the homogeneous chemical reaction in the gas phase suggests that the origin of the difference in the secondary nucleation rate can be attributed to the difference in the mole fraction of atomic hydrogen.
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    An organic photoelectric conversion element includes an anode, a cathode, and a photoelectric conversion portion between the anode and the cathode. The photoelectric conversion portion includes a first organic compound layer containing an organic compound. Also, a second organic compound layer is disposed between the cathode and the photoelectric conversion portion. The second organic compound layer contains an organic compound having an ionization potential of 5.1 eV or less and a band gap of 2.5 eV or more.
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  • Structural insight into photoactivation of an adenylate cyclase from a photosynthetic cyanobacterium

    Ohki, Mio   Sugiyama, Kanako   Kawai, Fumihiro   Tanaka, Hitomi   Nihei, Yuuki   Unzai, Satoru   Takebe, Masumi   Matsunaga, Shigeru   Adachi, Shin-ichi   Shibayama, Naoya   Zhou, Zhiwen   Koyama, Ryuta   Ikegaya, Yuji   Takahashi, Tetsuo   Tame, Jeremy R. H.  

    Cyclic-AMP is one of the most important second messengers, regulating many crucial cellular events in both prokaryotes and eukaryotes, and precise spatial and temporal control of cAMP levels by light shows great promise as a simple means of manipulating and studying numerous cell pathways and processes. The photoactivated adenylate cyclase (PAC) from the photosynthetic cyanobacterium Oscillatoria acuminata (OaPAC) is a small homodimer eminently suitable for this task, requiring only a simple flavin chromophore within a blue light using flavin (BLUF) domain. These domains, one of the most studied types of biological photoreceptor, respond to blue light and either regulate the activity of an attached enzyme domain or change its affinity for a repressor protein. BLUF domains were discovered through studies of photo-induced movements of Euglena gracilis, a unicellular flagellate, and gene expression in the purple bacterium Rhodobacter sphaeroides, but the precise details of light activation remain unknown. Here, we describe crystal structures and the light regulation mechanism of the previously undescribed OaPAC, showing a central coiled coil transmits changes from the light-sensing domains to the active sites with minimal structural rearrangement. Site-directed mutants show residues essential for signal transduction over 45 angstrom across the protein. The use of the protein in living human cells is demonstrated with cAMP-dependent luciferase, showing a rapid and stable response to light over many hours and activation cycles. The structures determined in this study will assist future efforts to create artificial light-regulated control modules as part of a general optogenetic toolkit.
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  • Comparative Study of Heteroepitaxially and Homoepitaxially Grown 3C-SiC Films

    Takahashi, Tetsuo   Ishida, Yuuki   Tsuchida, Hidekazu   Kamata, Isaho   Okumura, Hajime   Yoshida, Sadafumi   Arai, Kazuo  

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    The relative position between a mask and a wafer is adjusted any time even during an exposure process depending on a displacement of a pattern image due to a change in position of reflectors. Dectectors (13, 14) detect the displacements of reflectors (M1, M2) from their respective reference positions. Based on the dectected displacements, an arithmetic system (15) determines a corrective quantity for at least either a photosensitive substrate (4) or a mask for effectively positioning the photosensitive substrate relative to the pattern image formed out of place. At least either the mask or the photosensitive substrate is moved according to the determined corrective quantity.
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  • Improved Image Resolution for Wafer Inspection Tool Using Sub-200-nm Wavelength Light Optical System

    Takahashi, Tetsuo   Miyazaki, Yoko   Takeuchi, Naoya   Tanaka, Toshihiko   Terasawa, Tsuneo  

    In order to extend bright field imaging systems to the 65 nm design rule and beyond, we evaluated inspection imaging characteristics with deep UV (DUV) light with a sub-200 nm wavelength, which is the shortest wavelength in practical use, by reflectivity simulations and with experiments using a pilot proof of concept (POC) tool. The results have confirmed that DUV light has enough reflectivity to enable the inspection of defects in principal semiconductor materials. Furthermore, DUV light shows up to 7 times greater image contrast than UV light (365 nm) for test pattern whose spatial frequency is near the resolution limit of UV optics. When pixel size is reduced, light contrast produced by DUV light is further enhanced to such an extent that it is up to 12 times greater than that produced by V light. Our evaluation has also confirmed that contrast depends not only on resolving power, but also on coat thickness and reflectivity. Based on optical considerations and current UV inspection technology, it can be concluded that our DUV optical inspection system has the possibility of being used in the design rule of half-pitch, 65 nm (hp65 nm) and beyond.
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  • Effect of aluminum addition on the surface step morphology of 4H-SiC grown from Si-Cr-C solution

    Mitani, Takeshi   Komatsu, Naoyoshi   Takahashi, Tetsuo   Kato, Tomohisa   Harada, Shunta   Ujihara, Toru   Matsumoto, Yuji   Kurashige, Kazuhisa   Okumura, Hajime  

    For the solution growth of 4H-SiC with Si1-xCrx solvents, the change in surface step structure by 4 at% Al addition to the solvent was investigated. Without Al addition, step bunching resulted in the formation of giant macrosteps with height greater than several micrometers, and trench-like surface defects formed with solvent inclusion. The edge of the giant macrosteps composing trench-like defects was faceted into low-index facet planes, (1 (1) over bar 0m) (m=3D1-4). The formation of the trench-like surface defects is considered to originate from the self-pinning of macrosteps owing to the step-faceting phenomenon, which facilitates further development of macrosteps. On the other hand, the addition of Al to the solvents significantly improved the surface roughening, and suppressed the formation of the trench-like surface defects. In this case, smaller bunched steps with heights from several nanometers to about 10 nm formed on the terraces of the macrosteps, while regularly arranged trains of unit-cell-size steps formed on the terrace of macrosteps in growth without Al addition. The decrease in step stiffness might be a possible cause for the formation of the smaller bunched steps on the terrace in growth with Al addition. (C) 2015 Elsevier B.V. All rights reserved.
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  • Chlamydomonas reinhardtii Dangeard (Chlamydomonadales, Chlorophyceae) mutant with multiple eyespots

    Nakamura, Shogo   Ogihara, Haruo   Jinbo, Kinue   Tateishi, Midori   Takahashi, Tetsuo   Yoshimura, Kenjiro   Kubota, Mamoru   Watanabe, Masakatsu   Nakamura, Soichi  

    We have isolated a new Chlamydomonas reinhardtii Dangeard (Chlamydomonadales, Chlorophyceae) mutant with from one up to more than four eyespots cell-1. It was designated mes (multiple eyespots)-10. A wild-type cell has a single eyespot, located under the chloroplast envelope, at a certain position near the cell's equator where the chloroplast envelope is in contact with the cell membrane. The eyespot(s) in mes-10, however, are located at various positions on its chloroplast. The mes-10 cells displayed negative phototaxis to 480-500 nm light. This behavior differed from that of a similar mutant, ptx4, which has been shown to have multiple eyespots and display no phototaxis (Pazour et al., J. Cell Biol. 1995; 131: 427-40). Mes-10 may retain a functional photoreceptor and a photosignal transduction system independently of its multiple eyespots. This mutant should be useful for studying how C. reinhardtii responds to light signals, as well as how eyespots are formed in the cell.
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  • Identification and characterization of transcriptional control region of the human beta 1,4-mannosyltransferase gene

    Takahashi, Tetsuo   Nedachi, Takashi   Etoh, Takuya   Tachikawa, Hiroyuki   Gao, Xiao-Dong  

    All asparagine-linked glycans (N-glycans) on the eukaryotic glycoproteins are primarily derived from dolichol-linked oligosaccharides (DLO), synthesized on the rough endoplasmic reticulum membrane. We have previously reported cloning and identification of the human gene, HMT-1, which encodes chitobiosyldiphosphodolichol beta-mannosyltransferase (beta 1,4-MT) involved in the early assembly of DLO. Considering that N-glycosylation is one of the most ubiquitous post-translational modifications for many eukaryotic proteins, the HMT-1 could be postulated as one of the housekeeping genes, but its transcriptional regulation remains to be investigated. Here we screened a 1 kb region upstream from HMT-1 open reading frame (ORF) for transcriptionally regulatory sequences by using chloramphenicol acetyl transferase (CAT) assay, and found that the region from -33 to -1 positions might act in HMT-1 transcription at basal level and that the region from -200 to -42 should regulate its transcription either positively or negatively. In addition, results with CAT assays suggested the possibility that two GATA-1 motifs and an Sp1 motif within a 200 bp region upstream from HMT-1 ORF might significantly upregulate HMT-1 transcription. On the contrary, the observations obtained from site-directed mutational analyses revealed that an NF-1/AP-2 overlapping motif located at -148 to -134 positions should serve as a strong silencer. The control of the HMT-1 transcription by these motifs resided within the 200 bp region could partially explain the variation of expression level among various human tissues, suggesting availability and importance of this region for regulatory role in HMT-1 expression.
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  • Identification and characterization of transcriptional control region of the human beta 1,4-mannosyltransferase gene

    Takahashi, Tetsuo   Nedachi, Takashi   Etoh, Takuya   Tachikawa, Hiroyuki   Gao, Xiao-Dong  

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  • Biochemical Study of Cells Cultured from a Patient with Tuberous Sclerosis

    Takahashi, Tetsuo   Monica-Masuda, Lilia   Ito, Shinichi   Katsumoto, Tetsuo   Ishibashi, Yasumasa   Onodera, Kazukiyo  

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  • Ion etching of 3C-SiC heteroepilayer substrates reduction of defects propagating into 3C-SiC homoepilayers by reactive

    Yun, Jungheum   Takahashi, Tetsuo   Kuroda, Satoshi   Ishida, Yuuki   Okumura, Hajime  

    The crystallinity and morphology of single-crystal 3C-SiC homoepilayers grown on heteroepilayer (0 0 1) substrates by low-pressure chemical vapor deposition were investigated. The crystalline qualities of homoepilayers were critically dependent upon the defects of heteroepilayer substrates because planar defects, predominantly stacking faults and twins, and protrusions existing on the heteroepilayer surface propagated into the homoepilayers. A surface etching process using reactive ion etching (RIE) of the backside of free-standing heteroepilayers, the interface with Si substrates, was proposed to minimize the defect densities on the heteroepilayer surface. Analyses of high resolution X-ray diffraction (HRXRD) and atomic force microscope (AFM) reveal that simultaneous reductions of both surface roughness and defect densities on the heteroepilayer surface are achieved by an etching depth of 4 pm. Cross-sectional scanning electron microscopy (SEM) observation clearly shows that protrusions on the RIE-treated heteroepilayer surface are readily buried by growing homoepilayers. Furthermore, the results of cross-sectional transmission electron microscopy (XTEM) indicate that (i) significant amounts of planar defects are removed by the RIE process of the backside of heteroepilayers and (ii) most of planar defects propagating into the homoepilayers are terminated by coalescences between one another during early homoepitaxial growth stages. (C) 2007 Elsevier B.V. All rights reserved.
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    A photomask which exhibits sufficient durability even against an exposing beam of short wavelength and preventing adhesion of particles to a pattern to be transferred. The photomask is provided with a pattern to be transferred to a substrate (19) to be exposed and directs a specific exposing beam for irradiating the pattern surface (1P) where the transfer pattern is formed to a projection optical system (PL) for forming the image of the pattern. A transmitting substrate (3) having a specified thickness (h) and transmitting the exposing beam is disposed at a specified interval (d0) from the pattern surface. The transmitting substrate is generally square and satisfies specified conditions.
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  • Verification of the system of defect inspection on patterned wafers using sub-200 nm wavelength light - art. no. 615226

    Takahashi, Tetsuo   Miyazakia, Yoko   Tanaka, Toshihiko   Terasawa, Tsuneo   Takeuchi, Naoya  

    Bright-field inspection is still strongly required for 45 rim semiconductor device processes to detect several kinds of defects on patterned wafers. We have been carrying out verification of our defect inspection system using sub-200nm wavelength light. As part of the verification work, we evaluated the system's inspection imaging characteristics by using a pilot POC tool and by simulations. The image evaluation system used has a sub-200 nm wavelength light source. Two kinds of magnifications, 100x or 250x, can be selected. Test wafers with the same patterns and programmed defects were used. Simultaneously, UV (365 nm) images were taken by an inspection tool. The results of the reflectivity simulations suggest that the average reflectance at 198 nm is basically the same as that for present inspection wavelengths. A three dimensional electromagnetic simulator was used to evaluate the images of patterns and programmed defects described above. Image contrasts for Line & Spaces were also calculated. It is confirmed from both the experimental and simulation results that (1) sub-200 nm images are superior to UV images in contrast, and that (2) the image contrast improves with increasing magnification because of a reduction in pixel size. Further, a quantitative defect detection procedure was taken to identify programmed defects. Several sizes of extrusion defects were evaluated. Examination of the differential images under the three optical conditions showed that sub-200 nm light and 250x were most desirable, followed by sub-200 nm light and 100x. Sub-200 nm provided an enough pixel grey level difference value to detect extrusion defects down to 50 nm.
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