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排序方式: 共有392条查询结果,搜索用时 20 毫秒
121.
122.
Kato S Kinemuchi T Tatewaki Y Okada S Masuhara A Kasai H Oikawa H 《Journal of nanoscience and nanotechnology》2011,11(4):3340-3344
Butadiyne nanocrystals in water are usually polymerized by UV or gamma-ray irradiation to give polydiacetylene (PDA) nanocrystals. In this study, we confirmed that solid-state polymerization of 1,6-di(N-carbazolyl)-2,4-hexadiyne (DCHD) and 5,7-dodecadiyn-1,12-diyl bis[N-(butoxycarbonyl-methyl)carbamate] (4BCMU) could be stimulated by water-soluble radical initiators. The radical initiators used were potassium peroxodisulfate, three kinds of azo-type compounds and a redox initiator. In all cases, the solid-state polymerization was confirmed by color change into blue indicating that PDA modified by the radical residues at the end was formed. However, nanocrystal cohesion occurred especially when the concentration of the initiators was high or the dispersion was kept for a long time. In order to improve the dispersion stability, two kinds of surfactants, i.e., sodium dodecyl sulfate (SDS) or dodecyltrimethylammonium chloride (DTMAC), were added to the DCHD nanocrystal aqueous dispersion. As a result, when anionic SDS was added, the solid-state polymerization of nanocrystals proceeded without coagulation and quantitative conversion was confirmed for all initiators. Cationic DTMAC has no effect on dispersion stabilization. PDA nanocrystal surfaces in water are negatively charged in nature and electric interaction of nanocrystals with the cations results in decrease of surface charge and aggregation of nanocrystals. 相似文献
123.
Shinya Aikawa Rong Xiang Erik Einarsson Shohei Chiashi Junichiro Shiomi Eiichi Nishikawa Shigeo Maruyama 《Nano Research》2011,4(6):580-588
Field-effect transistors (FETs) have been fabricated using as-grown single-walled carbon nanotubes (SWNTs) for the channel
as well as both source and drain electrodes. The underlying Si substrate was employed as the back-gate electrode. Fabrication
consisted of patterned catalyst deposition by surface modification followed by dip-coating and synthesis of SWNTs by alcohol
chemical vapor deposition (CVD). The electrodes and channel were grown simultaneously in one CVD process. The resulting FETs
exhibited excellent performance, with an I
ON/I
OFF ratio of 106 and a maximum ON-state current (I
ON) exceeding 13 μA. The large I
ON is attributed to SWNT bundles connecting the SWNT channel with the SWNT electrodes. Bundling creates a large contact area,
which results in a small contact resistance despite the presence of Schottky barriers at metallic-semiconducting interfaces.
The approach described here demonstrates a significant step toward the realization of metal-free electronics.
相似文献
124.
Ryutaro Yoshida Yoshihiko Yano Namiko Hoshi Norihiro Okamoto Yunlong Sui Atsushi Yamamoto Naoki Asaji Yuuki Shiomi Eiichiro Yasutomi Yuri Hatazawa Hiroki Hayashi Yoshihide Ueda Yuzo Kodama 《Journal of food science》2022,87(5):2173-2184
Resistant starch (RS) has been reported to improve steatosis as well as obesity. Type 4 resistant starch (RS4), a chemically modified starch, is particularly hard to digest and suggesting higher efficacy. However, because the effects of RS4 on steatosis are not yet fully understood, the effects of RS4 on steatosis were examined using a murine high-fat diet model. Seven-week-old male mice were divided into three groups and fed a normal diet, a high-fat diet (HFD), or a high-fat diet with added RS (HFD + RS). Amylofiber SH® produced from acid-treated corn starch was used as the dietary RS. At 22 weeks old, hepatic steatosis and short chain fatty acid (SCFA) content and gut microbiota in cecum stool samples were analyzed. The ratio of body weight to 7 weeks was significantly suppressed in the HFD + RS group compared to the HFD group (132.2 ± 1.4% vs. 167.2 ± 3.9%, p = 0.0076). Macroscopic and microscopic steatosis was also suppressed in the HFD + RS group. Analysis of cecum stool samples revealed elevated SCFA levels in the HFD + RS group compared with the HFD group. Metagenome analysis revealed that Bifidobacterium (17.9 ± 1.9% vs. 3.6 ± 0.7%, p = 0.0019) and Lactobacillus (14.8 ± 3.4% vs. 0.72 ± 0.23%, p = 0.0045), which degrade RS to SCFA, were more prevalent in the HFD + RS group than the HFD group. In conclusion, RS4 suppressed steatosis, and increased Bifidobacterium and Lactobacillus, and SCFAs. RS4 may prevent steatosis by modulating the intestinal environment. 相似文献
125.
126.
Tesshin Uegaki Taisei Takei Shuhei Yamaguchi Keisuke Fujiyama Yusuke Sato Tomoya Hino Shingo Nagano 《International journal of molecular sciences》2023,24(1)
Ladderane lipids (found in the membranes of anaerobic ammonium-oxidizing [anammox] bacteria) have unique ladder-like hydrophobic groups, and their highly strained exotic structure has attracted the attention of scientists. Although enzymes encoded in type II fatty acid biosynthesis (FASII) gene clusters in anammox bacteria, such as S-adenosyl-l-methionine (SAM)-dependent enzymes, have been proposed to construct a ladder-like structure using a substrate connected to acyl carrier protein from anammox bacteria (AmxACP), no experimental evidence to support this hypothesis was reported to date. Here, we report the crystal structure of a SAM-dependent methyltransferase from anammox bacteria (AmxMT1) that has a substrate and active site pocket between a class I SAM methyltransferase-like core domain and an additional α-helix inserted into the core domain. Structural comparisons with homologous SAM-dependent C-methyltransferases in polyketide synthase, AmxACP pull-down assays, AmxACP/AmxMT1 complex structure predictions by AlphaFold, and a substrate docking simulation suggested that a small compound connected to AmxACP could be inserted into the pocket of AmxMT1, and then the enzyme transfers a methyl group from SAM to the substrate to produce branched lipids. Although the enzymes responsible for constructing the ladder-like structure remain unknown, our study, for the first time, supports the hypothesis that biosynthetic intermediates connected to AmxACP are processed by SAM-dependent enzymes, which are not typically involved in the FASII system, to produce the ladder-like structure of ladderane lipids in anammox bacteria. 相似文献
127.
The laser evaporation method is an attractive technology to synthesize composite materials. We tried to apply the laser evaporation method on fabrication of CdTe-doped glasses for the first time. CdTe microcrystallites embedded in SiO2 films were confirmed by transmission electron microscope images. The third-order nonlinear susceptibility χ(3) and the decay time τ of CdTe-doped glasses were measured by three-beam forward type degenerate four-wave mixing. The maximum value of χ(3) was estimated 4.2 x 10-7 esu when the absorption coefficient was 6000 cm-1. From the limitation of pulse duration of 5 ps, τ was not exactly measured but imagined to be shorter than 10 ps, which was much faster than the other semiconductor-doped glasses ever reported. The figure of merit defined as χ(3)/τ is probably larger than 7. 相似文献
128.
We report magnetic properties of novel nitronyl nitroxide triradicals, ptriNN (1) and m-triNN (2), in which a π-conjugated biradical with a singlet ground state and a doublet monoradical are united byσ-bonds of an ether
bridge. Two kinds of intramolecular exchange interactions, one between the biradical and monoradical entities J(σ) through
theσ-bonds and the other within the biradical moiety J(π) through the π-conjugation, were examined by paramagnetic susceptibility
χm for the sample dispersed in an organic polymer film. The magnitude of J(σ) was found to be much weaker than that of J(π).
This result indicates that the triradicals 1 and 2 can be used as a building block for generalized ferrimagnets, which from
our theoretical calculations have been predicted to exhibit an exotic spin alignment. 相似文献
129.
Kiyoshi Okada Shuhei Uchiyama Toshihiro Isobe Yoshikazu Kameshima Akira Nakajima Taisuke Kurata 《Journal of the European Ceramic Society》2009,29(12):2491-2497
Porous mullite ceramics with unidirectionally oriented pores were prepared by an extrusion method to investigate their capillary rise properties. Rayon fibers 16.5 μm in diameter and 800 μm long were used as the pore formers by kneading with alumina powder, kaolin clay, China earthen clay and binder with varying Fe2O3 contents of 0, 5 and 7 mass%. The resulting pastes were extruded into cylindrical tubes (outer diameter (OD) 30–50 mm and inner diameter (ID) 20–30 mm), dried at room temperature and fired at 1500 °C for 4 h. The bulk densities of the resulting porous ceramics ranged from 1.31 to 1.67 g/cm3, with apparent porosities of 43.2–59.3%. The pore size distributions measured by Hg porosimetry showed a sharp peak at 10.0 μm in the sample without Fe2O3 and at 15.6 μm in the samples containing Fe2O3; these pores, which arose from the burnt-out rayon fibers, corresponded to total pore volumes ranging from 0.24 to 0.34 ml/g. SEM showed a microstructure consisting of unidirectionally oriented pores in a porous mullite matrix. Prismatic mullite crystals were well developed on the surfaces of the pore walls owing to the liquid phase formed by the Fe2O3 component added to color the samples. The bending strengths of the tubular samples ranged from 15.6 to 26.3 MPa. The height of capillary rise, measured under controlled relative humidities (RH) of 50, 65 and 85%, was greater in the ceramics containing Fe2O3 than in those without Fe2O3, especially in the thinner samples. The maximum capillary rise reached about 1300 mm, much higher than previously reported. This excellent capillary rise ability is thought to be due to the controlled pore size, pore distribution and pore orientation in these porous mullite ceramics. 相似文献
130.
Sixty‐seven strains of seven species of Azolla were screened for tolerance to ammonium ion on the basis of their growth on the medium with or without 20 mmol/L ammonium. Azolla nilotica was the most sensitive species followed by Azolla rubra. Azolla pinnata var. pinnata was the most tolerant species. Twelve tolerant strains in Azolla mexicana, Azolla caroliniana, Azolla microphylla and A. pinnata var. pinnata were selected. No tolerant strain was found in Azolla filiculoides containing native strains in Japan. 相似文献