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81.
The electrical properties of polymer nanocomposites containing a small amount of carbon nanotube (CNT) are remarkably superior to those of conventional electronic composites. Based on three-dimensional (3D) statistical percolation and 3D resistor network modeling, the electrical properties of CNT nanocomposites, at and after percolation, were successfully predicted in this work. The numerical analysis was also extended to investigate the effects of the aspect ratio, the electrical conductivity, the aggregation and the shape of CNTs on the electrical properties of the nanocomposites. A simple empirical model was also established based on present numerical simulations to predict the electrical conductivity in several electronic composites with various fillers. This investigation further highlighted the importance of theoretical and numerical analyses in the exploration of basic physical phenomena, such as percolation and conductivity in novel nanocomposites. 相似文献
82.
Long-chain polyamines (LCPAs) from marine sponge: possible implication in spicule formation 总被引:1,自引:0,他引:1
Matsunaga S Sakai R Jimbo M Kamiya H 《Chembiochem : a European journal of chemical biology》2007,8(14):1729-1735
Two distinct marine organisms, diatoms and sponges, deposit dissolved silicates to construct highly architectural and species-specific body supports. Several factors such as proteins, long-chain polyamines (LCPAs), or polypeptides modified with LCPAs are known to be involved in this process. The LCPAs contained in the silica walls of diatoms are thought to play pivotal roles in the silica deposition. In sponges, however, a protein called silicatein and several other proteins have been reported to be the factors involved in the silica deposition. However, no other factors involved in this process have been reported. We have identified the LCPAs from the marine sponge Axinyssa aculeata and present here some evidence that sponge-derived LCPAs can deposit silica and that the LCPA derivatives are associated with spicules. The results indicate a common chemistry between sponges and diatoms, the two major players in the biological circulation of silicon in the marine environment. A wide variety of organisms are known to utilize silica in their biological processes. Polyamines or other functional molecules might be involved, in combination with proteins, in their biosilicification process. 相似文献
83.
Yoshiteru Yazawa Hisao Yoshida Nobuyuki Takagi Shin-ichi Komai Atsushi Satsuma Tadashi Hattori 《Applied catalysis. B, Environmental》1998,19(3-4):261-266
The oxidation state of palladium on SiO2–Al2O3 used for propane combustion was examined by XPS and XRD, and the correlation of the catalytic activity with the oxidation state of palladium was systematically studied. The propane conversion over 5 wt% Pd/SiO2–Al2O3 was measured in the range 1.0≤S≤7.2 (S is defined as [O2]/5[C3H8] based on stoichiometric ratio). The propane conversion strongly depended on the S value and reached the maximum at S=5.5. The oxidation state of palladium also changed with the S value; palladium particles were more oxidized under the reaction mixture of higher S value. On the sample used for the reaction at S=5.5, both of metallic palladium and palladium oxide were found. It is concluded that partially oxidized palladium which has optimum ratio of metallic palladium to palladium oxide shows the highest catalytic activity in propane combustion. 相似文献
84.
Kazuhiro Nomura Kiyoshi Noro Yasuhisa Nakamura Yoshiteru Yazawa Hisao Yoshida Atsushi Satsuma Tadashi Hattori 《Catalysis Letters》1998,53(3-4):167-169
The examination of the combustion of a trace amount of methane over Pd‐ion‐exchanged silicoaluminophosphate‐5 (Pd‐SAPO‐5)
at low temperature in the presence of water vapor reveals that water vapor strongly depresses methane combustion and causes
a significant decrease in catalytic activity with time. The newly prepared bimetallic catalyst Pd–Pt‐SAPO‐5, on the other
hand, shows higher performance for methane combustion under similar conditions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
85.
Kazuhiro Nomura Kiyoshi Noro Yasuhisa Nakamura Hisao Yoshida Atsushi Satsuma Tadashi Hattori 《Catalysis Letters》1999,58(2-3):127-130
Combustion of a trace amount of CH4 over Pd catalysts supported on calcined ZrO2 was examined under nearly exhaust gas conditions where the temperature is not so high and water vapor coexists. High catalytic
activity was obtained with ZrO2 support calcined at 1073 and 1273 K. The durability test at 673 K for 100 h revealed that the activity of these catalysts
hardly decreased, while that of the Pd catalysts supported on calcined Al2O3 were much decreased in the course of time. These results demonstrated the advantages of ZrO2 as a support for Pd catalysts in the present reaction.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
86.
Keiko Azuma Katsunari Ippoushi Hidekazu Ito Hisao Higashio Junji Terao 《Journal of the science of food and agriculture》1999,79(14):2010-2016
The antioxidative effects of vegetable extracts were evaluated using linoleic acid emulsion and liposomal phospholipid suspension systems. First, the antioxidative activities of water, ethanol and 2% metaphosphoric acid extracts of the vegetables were investigated by measuring the rate of oxygen consumption in the peroxidation of linoleic acid initiated by a radical generator, 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), with a Clark electrode in the absence of metal chelators. Ethanol extracts of moroheiya and perilla exhibited the highest antioxidative activities. Without metal chelators, 12 ethanol extracts and one water extract acted as prooxidants, and this phenomenon could be attributed to the prooxidant action of ascorbic acid in the presence of free transition metal ions. Next, peroxyl radical-scavenging activities of vegetable extracts were examined by adding a metal chelator, diethylenetriaminepentaacetic acid (DTPA), to the linoleic acid emulsion system. The results were compared with their antioxidative activities in phospholipid bilayers by measuring the inhibition of lipid peroxidation in large unilamellar vesicles composed of egg yolk phosphatidylcholine (PC). A good correlation was observed between the antioxidative activities obtained from these two systems. The antioxidative activities in the liposomal phospholipid suspension system correlated with total contents of ascorbic acid and polyphenols in vegetable extracts. © 1999 Society of Chemical Industry 相似文献
87.
A multidirectional interferometer system has been proposed and developed to measure the position and orientation of a positioning stage. In this method the system parameters, such as positions of the corner-cube reflectors and directions of the rays in the interferometers, must be determined beforehand. However, it is difficult to find ways to determine the system parameters for each different system with necessary accuracy. This paper proposes a systematic method for calibrating the system parameters when the number of the interferometers is larger than the degrees of freedom of the stage. The method is verified for a two-dimensional stage by both simulation and experiment. 相似文献
88.
Koyama S Haniu H Osaka K Koyama H Kuroiwa N Endo M Kim YA Hayashi T 《Small (Weinheim an der Bergstrasse, Germany)》2006,2(12):1406-1411
Carbon nanotubes hold great promise for use in biomedical fields. Among numerous potential applications, including DNA and protein sensors, bioseparators, biocatalysts, and tissue scaffolds, this article emphasizes the use of carbon-nanotube-filled polymer composites as medical devices, namely, microcatheters. The currently hot topic of the biocompatibility (e.g., toxic properties) of carbon nanotubes is discussed. In addition, critical issues that must be clarified for the full utilization of current carbon-nanotube science and technology in biomedical fields are discussed. 相似文献
89.
Tabata S Takemura Y Kobayashi M Ikeda M Nishimura S Sato Y Tatsumi R Ikeuchi Y Iwamoto H 《Journal of electron microscopy》2006,55(5):265-271
The mechanism of intracellular calcium ions (Ca(2+)) increase in chicken myoblasts was studied using histological, immunohistochemical, immunoblotting and Ca(2+) imaging techniques. Mononuclear myoblasts at embryonic day 12 (E12) contained myofibrils in the peripheral cytoplasm, and the sarcoplasmic reticulum was observed in the cytoplasm. Several Ca(2+)-related receptors, namely acetylcholine (ACh) receptors, dihydropyridine receptors (DHPRs) and ryanodine receptors (RyRs), were detected in the tissue as early as E12. Western blotting analyses detected one band corresponding to RyR subtype 3 (RyR3) at E12 and two bands corresponding to RyR1 and RyR3 after E13. Ca(2+) imaging of mononuclear myoblasts in vitro revealed an intense Ca(2+)-increase response to ACh stimulation, and this effect was abolished after EGTA addition to the culture medium. Nifedipine treatment also led to a lack of Ca(2+) increase in response to ACh stimulation, while ryanodine treatment led to a weak Ca(2+)-increase response. On the other hand, multinuclear myoblasts showed a Ca(2+)-increase response to ACh stimulation in the presence of not only EGTA but also nifedipine, although ryanodine treatment led to a lack of Ca(2+) increase. These results suggest that the mechanism of Ca(2+) increase in mononuclear myoblasts involves extracellular Ca(2+) entry through DHPRs, which is amplified by Ca(2+) release from the cytoplasmic Ca(2+) store, while multinuclear myoblasts mainly depend on Ca(2+) release from the cytoplasmic Ca(2+) store. 相似文献
90.
Translucent CaGa2S4:Ce thin films were prepared by pulsed laser deposition. Optical absorption associated with the 4f1 (2F5/2) to 5d2 second-highest excited state transition of the Ce3+ ion was clearly observed at 3.60 eV as well as the 4f1 (2F5/2) to 5d1 lowest excited state transition at 2.93 eV. Energy splitting of the 5d state by the crystal field is discussed in terms of a model of a square antiprism structure with D4d symmetry. 相似文献