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81.
Xie Y Morikawa T Ninomiya K Imura K Muraoka O Yuan D Yoshikawa M 《Chemical & pharmaceutical bulletin》2008,56(11):1628-1631
The methanolic extract from the flowers of Punica granatum L. (Punicaceae) was found to show inhibitory effect on tumor necrosis factor-alpha (TNF-alpha, 1 ng/ml)-induced cytotoxicity in L929 cells. By bioassay-guided separation, a new taraxastane-type triterpene, punicanolic acid (1), was isolated from the active fraction (ethyl acetate-soluble fraction) together with four triterpenes (2--5), two galloyl glucoses (6, 7), two flavones (8, 9), and beta-sitosterol. Among the constituents, 1, oleanolic acid (2), maslinic acid (4), 1,2,6-tri-O-galloyl beta-D-glucopyranoside (6), 1,2-di-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl beta-D-glucopyranoside (7), and luteolin (8) significantly inhibited TNF-alpha-induced cytotoxicity in L929 cells at 30 microM. 相似文献
82.
We investigated the two-photon-induced photoluminescence properties of single gold nanorods by scanning near-field spectroscopy. The process was found to be initiated by a sequential one-photon absorption for creating a pair of an electron and a hole in the sp and d bands. Photoluminescence is then radiated when the electron near the Fermi surface recombines with the hole near the X and L symmetry points. The polarization characteristics of emitted photons from the X and L regions were found to be different. These characteristics can be understood by the crystalline structure and the band structure of the gold nanorod. We found characteristic spatial oscillatory features along the long axis of the nanorods in photoluminescence excitation images. The images were well reproduced by density-of-states maps of the nanorods calculated with Green's dyadic method and were attributed to the spatial characteristics of the wave functions of the plasmon modes inside the nanorods. 相似文献
83.
Amorphous As2Se1Te2 (a-As2Se1Te2) films, into which Cu or Cd ions were doped by thermal diffusion below the glass transition temperature exhibited the increase of conductivity by several orders of magnitude. In addition, these samples exhibited enhanced photoconductivity and the activation type conduction. From the measurements of the thermoelectric power, it was found that Cu doped samples were p-type and Cd doped samples were n-type. The impurities was also studied by SIMS. 相似文献
84.
85.
Yumi Imura 《Tetrahedron》2010,66(19):3421-3426
Novel ion-supported Ph3P compounds, 4-(diphenylphosphino)- benzyltrimethylammonium bromide (A) and N-methyl-N-[4-(diphenylphosphino) -benzyl]pyrrolidinium bromide (B), were prepared. Because of their stability in air, ion-supported Ph3P A and B could be used for the halogenation of alcohols, the esterification of carboxylic acid with the Mitsunobu reaction, the Mizoroki-Heck reaction, and the Sonogashira reaction. The advantages of using these ion-supported Ph3P A and B are the simple isolation of the products by ether extraction due to their poor solubility in ether, and the easy recovery of the co-product, ion-supported Ph3PO, by filtration in high yields (>90%), which could be regenerated and reused for the same reactions, in the halogenation of alcohols and the esterification of carboxylic acid with the Mitsunobu reaction. On the other hand, ionic liquid reaction media containing Pd(OAc)2 or PdCl2 and ion-supported Ph3P A or B as catalysts could be reused for the same Mizoroki-Heck reaction and the Sonogashira reaction maintaining high yields, using iodotoluene with methyl acrylate and phenylacetylene, respectively. 相似文献
86.
Imura Y Morita C Endo H Kondo T Kawai T 《Chemical communications (Cambridge, England)》2010,46(48):9206-9208
The reversible transfer of Au nanoparticles between water and chloroform phases by pH change was achieved by using a long-chain amine derivative. Further, we demonstrated that the phase transfer method was very effective for the fractionation of Au nanoparticles according to their crystal facet distinction. 相似文献
87.
Odo J Kimura A Matsu-Ura A Ohnishi Y Saeki Y Yoshida A Hayashi K Inoguchi M Ueki T 《Chemical & pharmaceutical bulletin》2010,58(12):1576-1581
The scavenging effects of metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4], Me=H?, Fe3(+), Mn3(+), Mn2(+), Cu2(+), and Zn2(+)) on superoxide anion radicals (O??) generated from the xanthine-xanthine oxidase system were investigated by the nitroblue tetrazolium (NBT) method and electron spin resonance (ESR) spin-trapping method using 5,5-dimethyl-1-pyrroline-N-oxide as a trapping reagent. As a reference, calix[4]arenetetrasulfonate (H?)-CAS[4]), calix[6]arenehexasulfonate (H?-CAS[6]) and calix[8]areneoctasulfonate (H?-CAS[8]) were also examined. The results by the NBT method indicated that Fe3(+)- and Mn3(+)-TCAS[4] exhibited the highest O?? scavenging activity among Me-TCAS[4] and H?-CAS[n] (n = 4, 6, 8) in this study. The IC?? values of Fe3(+)- and Mn3(+)-TCAS[4] for O?? scavenging activity were estimated to be 5.3 and 7.8 μM, respectively, and were almost the same as those of tannin acid, catechin and their derivatives, which are known as very effective scavengers of O??. Scavenging activities were in the order of Fe3(+)- and Mn3(+)-TCAS[4]>Mn2(+)-, Cu2(+)-, and Zn(2+)-TCAS[4]>H(2)-TCAS[4] and H?-CAS[n] (n=4, 6, 8). Each activity of Me-TCAS[4] (Me=Fe3(+), Mn3(+), Mn2(+), Cu2(+), and Zn2(+)) was higher than that of the corresponding metal ion, indicating that H?-TCAS[4] has the ability to raise the activity of the metal ion itself by forming a complex. Also, the ESR spin-trapping method revealed that Fe3(+)- and Mn3(+)-TCAS[4] showed high O?? scavenging activities, similarly to the results by the NBT method. 相似文献
88.
Mohamed Boutchich José Alvarez Djicknoum Diouf Pere Roca i Cabarrocas Meiyong Liao Imura Masataka Yasuo Koide Jean-Paul Kleider 《Journal of Non》2012,358(17):2110-2113
We have fabricated and characterized diamond based heterojunctions composed of homoepitaxial diamond (B-doped film: p type) and hydrogenated amorphous silicon (a-Si:H film: n-type). All devices include an intrinsic amorphous silicon interface (i-a-Si:H). (J–V) characteristics of a-Si:H heterojunctions measured from 300 K to 460 K present a very high rectification ratio (in the range 108–109) and a current density of 10 mA/cm² under 2 V of forward bias. The reverse current up to ? 4 V is below the detection limit in the whole temperature range. The devices present two regimes of operation indicating that more than one mechanism governs the carrier transport. These characteristics are compared with a Schottky barrier diode (SBD) using a tungsten carbide metal on top of the p-type diamond as a Schottky contact. The SBD device exhibits J–V characteristic with an ideality factor n close to one and the heterojunction follows this trend for low bias voltages whereas for bias voltage above 1 V a second regime with larger ideality factors n ~ 3.6 is observed. These results point out the prominent role of transport mechanisms at heterointerface between the a-Si:H layers and the p-type doped diamond which degrades the current injection. The breakdown voltage reached ? 160 V indicating the good quality of the deposited layers. 相似文献
89.
Displacement Plating of a Mesoporous Pt Skin onto Co Nanochains in a Low‐Concentration Surfactant Solution
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Dr. Cuiling Li Dr. Masataka Imura Prof. Yusuke Yamauchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3277-3282
Mesoporous Pt skins on Co nanochains are successfully synthesized by a displacement reaction between Pt species and a Co support with the assistance of surfactant micelles. The assembly of surfactant micelles on Co nanochains plays a key role in the formation of mesoporous Pt layers. The evolution of the mesoporous Pt layers is carefully studied at different time intervals. As the reaction time increases, the mesoporous Pt layers become thicker, and well‐defined mesoporous structures gradually develop. The obtained mesoporous Pt skin exhibits high activity and superior CO tolerance in the electro‐oxidation reaction of methanol. The mesoporous Pt skin also shows very high durability, and only a 20.2 % loss of the Pt electrochemical surface area is found even after a harsh durability test. 相似文献
90.
Electric Double‐Layer Capacitors Based on Highly Graphitized Nanoporous Carbons Derived from ZIF‐67
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Nagy L. Torad Rahul R. Salunkhe Yunqi Li Hicham Hamoudi Masataka Imura Prof. Dr. Yoshio Sakka Prof. Dr. Chi‐Chang Hu Prof. Dr. Yusuke Yamauchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):7895-7900
Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one‐step direct carbonization of cobalt‐containing zeolitic imidazolate framework‐67 (ZIF‐67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp2‐bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge–discharge measurements. Our NPC is very promising for efficient electrodes for high‐performance supercapacitor applications. A maximum specific capacitance of 238 F g?1 is observed at a scan rate of 20 mV s?1. This value is very high compared to previous works on carbon‐based electric double layer capacitors. 相似文献