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Molecular catalysts for water oxidation toward artificial photosynthesis
Yagi, Masayuki,Syouji, Akinori,Yamada, Satoshi,Komi, Manabu,Yamazaki, Hirosato,Tajima, Syouhei Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.2
Artificial photosynthesis is anticipated as one of the promising clean energy-providing systems for the future. The development of an efficient catalyst for water oxidation to evolve $O_2$ is a key task to yield a breakthrough for construction of artificial photosynthetic devices. Recently, significant progress has been reported in the development of the molecular catalysts for water oxidation based on manganese, ruthenium and iridium. The molecular aspects of the catalysts reported in the last decade were reviewed to provide hints to design an efficient catalyst, as well as to gain clues to reveal the mechanism of $O_2$ evolution at photosynthetic oxygen evolving complex in nature.
Enhancing effect of Panax ginseng on Zip4-mediated zinc influx into the cytosol
Yoshito Ikeda,Masayuki Munekane,Yasuyuki Yamada,Mizuki Kawakami,Ikuko Amano,Kohei Sano,Takahiro Mukai,Taiho Kambe,Nobukazu Shitan 고려인삼학회 2022 Journal of Ginseng Research Vol.46 No.2
Background: Zinc homeostasis is essential for human health and is regulated by several zinc transporters including ZIP and ZnT. ZIP4 is expressed in the small intestine and is important for zinc absorption from the diet. We investigated in the present study the effects of Panax ginseng (P. ginseng) extract on modulating Zip4 expression and cellular zinc levels in mouse Hepa cells. Methods: Hepa cells were transfected with a luciferase reporter plasmid that contains metal-responsive elements, incubated with P. ginseng extract, and luciferase activity was measured. Using <SUP>65</SUP>ZnCl₂, zinc uptake in P. ginseng-treated cells was measured. The expression of Zip4 mRNA and protein in Hepa cells was also investigated. Finally, using a luciferase reporter assay system, the effects of several ginsenosides were monitored. Results: The luciferase activity in cells incubated with P. ginseng extract was significantly higher than that of control cells cultured in normal medium. Hepa cells treated with P. ginseng extract exhibited higher zinc uptake. P. ginseng extract induced Zip4 mRNA expression, which resulted in an enhancement of Zip4 protein expression. Furthermore, some ginsenosides, such as ginsenoside Rc and Re, enhanced luciferase activity driven by intracellular zinc levels. Conclusion: P. ginseng extract induced Zip4 expression at the mRNA and protein level and resulted in higher zinc uptake in Hepa cells. Some ginsenosides facilitated zinc influx. On the basis of these results, we suggest a novel effect of P. ginseng on Zip4-mediated zinc influx, which may provide a new strategy for preventing zinc deficiency.
Tin Doping Mechanism in Indium Oxide by MD Simulation
Utsuno, Futoshi,Yamada, Naoomi,Kamei, Masayuki,Yasui, Itaru The Korean Ceramic Society 1999 The Korean journal of ceramics Vol.5 No.1
In order to investigate Sn substitution sites and interstitial O atoms in tin-doped indium oxide, molecular dynamics (MD) simulations were carried out. There are two kinds of cation sites in $In_2O_3$, namely b-site and d-site. NTP-MD simulations under the condition of 300 K and 0 GPa were performed with two kinds of cells substituted by Sn atoms at each site. The excess oxygen atom accompanied with Sn doping was also taken into consideration. According to the calculations of Sn potential energies in each site, it was revealed that Sn atoms were substituted for b-sites rather than for d-sites. It was also revealed that the interstitial excess oxygen atoms tend to be connected with the Sn atoms substituted for the d-sites Sn rather than for the b-site. There MD simulation results well agreed with the experimental results.
Sakuma, Katsuya,Ogawa, Masayuki,Sugibayashi, Kenji,Yamada, Koh-ichi,Yamamoto, Katsumi The Pharmaceutical Society of Korea 1999 Archives of Pharmacal Research Vol.22 No.4
The oxidation-reduction potentials of cosmetic raw materials, showing tyrosinase inhibitory action, and phenolic compounds structurally similar to L-tyrosine were determined by cylcic voltammetry. The voltammograms obtained could be classified ito 4 patterns (patterns 1-4). Patterns 1, characterized by oxidation and reduction peaks as a pair, was observed with catechol, hydroquinone or phenol, and pattern 2 exhibiting another oxidation peak in addition to oxidation and reduction peaks as a pair was found with arbutin, kojic acid, resorcinol, methyl p-hydroxybenzoate and L-tyrosine as the substrate of tyrosinase. Pattern 3 with an independent oxidation peak only was expressed by L-ascorbic acid, and pattern 4 with a reduction peak only at high potentials, by hinokitiol. The tyrosinase inhibitory activity of these compounds was also evaluated using the 50% inhibitory concentration ($IC_{50}$) and the inhibition constant (Ki) as parameters. Hinokitiol, classified as patterns 4, showed the highest inhibitory activity (lowest $IC_{50}$ and Ki). Hydroquinone showing the second highest activity belonged to pattern 1, which also included compounds exhibiting pattern 2 was relatively low with Ki values being in the order of 10-4 M. Although there was no consistent relationship between oxidation-reduction potentials and tyrosinase inhibitory action, the voltammetry data can be used as an additional index to establish the relationship between the structure and the tyrosine inhibitory activity.
Kim, Seon-Hee,Yang, JiYoung,Park, Jongsun,Yamada, Takayuki,Maki, Masayuki,Kim, Seung-Chul MDPI AG 2019 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.20 No.19
<P>Symplocarpus, a skunk cabbage genus, includes two sister groups, which are drastically different in life history traits and thermogenesis, as follows: The nonthermogenic summer flowering S. nipponicus and thermogenic early spring flowering S. renifolius. Although the molecular basis of thermogenesis and complete chloroplast genome (plastome) of thermogenic S. renifolius have been well characterized, very little is known for that of S. nipponicus. We sequenced the complete plastomes of S. nipponicus sampled from Japan and Korea and compared them with that of S. renifolius sampled from Korea. The nonthermogenic S. nipponicus plastomes from Japan and Korea had 158,322 and 158,508 base pairs, respectively, which were slightly shorter than the thermogenic plastome of S. renifolius. No structural or content rearrangements between the species pairs were found. Six highly variable noncoding regions (psbC/trnS, petA/psbJ, trnS/trnG, trnC/petN, ycf4/cemA, and rpl3/rpl22) were identified between S. nipponicus and S. renifolius and 14 hot-spot regions were also identified at the subfamily level. We found a similar total number of SSR (simple sequence repeat) motifs in two accessions of S. nipponicus sampled from Japan and Korea. Phylogenetic analysis supported the basal position of subfamily Orontioideae and the monophyly of genus Symplocarpus, and also revealed an unexpected evolutionary relationship between S. nipponicus and S. renifolius.</P>
Fuka Ikeda,Yuki Okamoto,Kei Nishikawa,Hiroaki Yamada,Masayuki Okamoto,Toshihiko Tanaka 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a sinusoidal chargingdischarging method of the lithium-ion batteries (LiBs) to reduce the capacitances of the dc-capacitors in the previously proposed smart charger (SC) for electric vehicles (EVs) in single-phase three-wire distribution feeders with power quality compensator. The dc-capacitor current in the three-leg pulse-width-modulated (PWM) rectifier is detected, and then added to the reference value for the output current of the bidirectional dc-dc converter that is used to charge or discharge the LiBs. The addition of the detected dc-capacitor current to the reference value of the bidirectional dc-dc converter achieves the sinusoidal chargingand discharging-operations of the LiBs in EVs. The sinusoidal charging- and discharging-operations sink the voltage ripples in the dc-capacitors of both the PWM rectifier and bidirectional dc-dc converter in the SC. This achieves the substantial reduced dc-capacitors in the SC. The simulation results demonstrate that balanced and sinusoidal source currents with a unity power factor can be achieved reducing the capacitances of dc-capacitors in the SC.
Suzuki Koichi,Nakata Eiji,Minami Masayuki,Hibino Etsuhisa,Tani Tomonori,Sakakibara Jyunichi,Yamada Naouki Korean Society of Earth and Exploration Geophysici 2004 지구물리와 물리탐사 Vol.7 No.1
The objective of this study is to estimate the distribution of a zone disturbed by excavation (EDZ) around tunnels that have been excavated at about 500 m depth in pre-Tertiary hard sedimentary rock. One of the most important tasks is to evaluate changes in the dynamic stability and permeability of the rock around the tunnels, by investigating the properties of the rock after the excavation. We performed resistivity and acoustic tomography using two boreholes, 5 m in length, drilled horizontally from the wall of a tunnel in pre-Tertiary hard conglomerate. By these methods, we detected a low-resistivity and low-velocity zone 1 m in thickness around the wall of the tunnel. The resulting profiles were verified by permeability and evaporation tests performed at the same boreholes. This anomalous zone matched a high-permeability zone caused by open fractures. Next, we performed resistivity monitoring along annular survey lines in a tunnel excavated in pre-Tertiary hard shale by a tunnel-boring machine (TBM). We detected anomalous zones in 2D resistivity profiles surrounding the tunnel. A low-resistivity zone 1 m in thickness was detected around the tunnel when one year had passed after the excavation. However, two years later, the resistivity around the tunnel had increased in a portion, about 30 cm in thickness, of this zone. To investigate this change, we studied the relationship between groundwater flow from the surroundings and evaporation from the wall around the tunnel. These features were verified by the relationship between the resistivity and porosity of rocks obtained by laboratory tests on core samples. Furthermore, the profiles matched well with highly permeable zones detected by permeability and evaporation tests at a horizontal borehole drilled near the survey line. We conclude that the anomalous zones in these profiles indicate the EDZ around the tunnel.