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排序方式: 共有1235条查询结果,搜索用时 15 毫秒
71.
72.
Thermodynamically stable vesicle formation from glycolipid biosurfactant sponge phase 总被引:3,自引:0,他引:3
Imura T Yanagishita H Ohira J Sakai H Abe M Kitamoto D 《Colloids and surfaces. B, Biointerfaces》2005,43(2):115-121
Thermodynamically stable vesicle (L(alpha1)) formation from glycolipid biosurfactant sponge phase (L(3)) and its mechanism were investigated using a "natural" biocompatible mannosyl-erythritol lipid-A (MEL-A)/L-alpha-dilauroylphosphatidylcholine (DLPC) mixture by varying the composition. The trapping efficiency for calcein and turbidity measurements clearly indicated the existence of three regions: while the trapping efficiencies of the mixed MEL-A/DLPC assemblies at the compositions with X(DLPC)< or =0.1 or X(DLPC)> or =0.8 were almost zero, the mixed assemblies at the compositions with 0.1 or =0.8 were multilamellar vesicles (L(alpha)) with diameter from 2 to 10 microm. Meanwhile, dynamic light scattering (DLS) measurement revealed that the average size of the vesicles at the composition of X(DLPC)=0.3 was 633.2 nm, which is remarkably small compared to other compositions. Moreover, the mixed vesicle solution at the composition of X(DLPC)=0.3 was slightly bluish and turbid and kept its dispersion stability at 25 degrees C for more than 3 months, indicating the formation of a thermodynamically stable vesicle (L(alpha1)). These results exhibited the formation of a thermodynamically stable vesicle (L(alpha1)) with a high dispersibility from the MEL-A/DLPC mixture. The asymmetric distribution of MEL-A and DLPC in the two vesicle monolayers caused by the difference in geometrical structures is very likely to have changed their self-assembled structure from a sponge phase (L(3)) to a thermodynamically stable vesicle (L(alpha1)). 相似文献
73.
Koichiro Koyama Yusuke Hirasawa Tomohiro Hoshino Norimichi Nakahata 《Tetrahedron》2005,61(15):3681-3690
Seven new Lycopodium alkaloids, lannotinidines A-G (1-7), have been isolated from the club moss Lycopodium annotinum and L. annotinum var. acrifolium. Stereochemistry of 1-7 was elucidated by combination of NOESY correlations and chemical transformation. Lannotinidines B-E (2-5) elevated NGF mRNA expression. 相似文献
74.
Miyasaka H Nezu T Sugimoto K Sugiura K Yamashita M Clérac R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(5):1592-1602
Mn(III)-Ni(II)-Mn(III) linear-type trinuclear complexes bridged by oximate groups were selectively synthesized by the assembly reaction of [Mn2(5-Rsaltmen)2(H2O)2](ClO4)2 (5-Rsaltmen2-=N,N'-(1,1,2,2-tetramethylethylene) bis(5-R-salicylideneiminate); R=Cl, Br) with [Ni(pao)2(phen)] (pao-=pyridine-2-aldoximate; phen=1,10-phenanthroline) in methanol/water: [Mn2(5-Rsaltmen)2Ni(pao)2(phen)](ClO4)2 (R=Cl, 1; R=Br, 2). Structural analysis revealed that the [Mn(III)-ON-Ni(II)-NO-Mn(III)] skeleton of these trimers is in every respect similar to the repeating unit found in the previously reported series of 1D materials [Mn2(saltmen)2Ni(pao)2(L1)2](A)(2) (L(1)=pyridine, 4-picoline, 4-tert-butylpyridine, N-methylimidazole; A=ClO4-, BF4-, PF6-, ReO4-). Recently, these 1D compounds have attracted a great deal of attention for their magnetic properties, since they exhibit slow relaxation of the magnetization (also called single-chain magnet (SCM) behavior). This unique magnetic behavior was explained in the framework of Glauber's theory, generalized for chains of ferromagnetically coupled anisotropic spins. Thus, in these 1D compounds, the [Mn(III)-ON-Ni(II)-NO-Mn(III)] unit was considered as an S(T)=3 anisotropic spin. Direct-current magnetic measurements on 1 and 2 confirm their S(T)=3 ground state and strong uniaxial anisotropy (D/k(B) approximately -2.4 K), in excellent agreement with the magnetic characteristic deduced in the study on the SCM series. The ac magnetic susceptibility of these trimers is strongly frequency-dependent and characteristic of single-molecule magnet (SMM) behavior. The relaxation time tau shows a thermally activated (Arrhenius) behavior with tau0 approximately 1x10(-7) s and Delta(eff)/k(B) approximately 18 K. The effective energy barrier for reversal of the magnetization Delta(eff) is consistent with the theoretical value (21 K) estimated from |D| S2T. The present results reinforce consistently the interpretation of the SCM behavior observed in the [Mn2(saltmen)2Ni(pao)2(L1)2](A)2 series and opens new perspectives to design single-chain magnets. 相似文献
75.
This paper describes characterization of molecular orientation for azobenzene moieties in a polymer nanosheet. Copolymers of N-[4-(phenylazo)phenyl] acrylamide (PAZoA) with tert-pentyl acrylamide (tPA) were synthesized and the monolayers deposited on tapered quartz waveguides by Langmuir–Blodgett (LB) technique. Spectroscopic properties of the copolymer (p(tPA/PAZoA)) monolayers were monitored by integrated optical waveguide technique on the molecular level. Molecular orientation of the azobenzene was precisely determined by polarized absorption spectra. It was found that the azobenzene groups took a horizontal orientation and distributed uniformly in the p(tPA/PAZoA) monolayer without significant PAZoA aggregation. Photoisomerization process from trans to cis form was also investigated. More than half of the trans form (60–70%) was photoisomerized under unpolarized light irradiation, and the photoisomerization rate was independent on the PAZoA contents. This implies that the microenvironment of PAZoA moieties was almost the same in three different p(tPA/PAZoA) monolayers. 相似文献
76.
Tomohiro Sakata Shingo Ogawa Keiko Inoue Yumiko Shimizu Yusaku Tanahashi 《Surface and interface analysis : SIA》2022,54(6):661-666
To systematically evaluate the quality of SiNx films in multi-stacked structures, we investigated the effects of post-deposition annealing (PDA) on the film properties of SiNx within the SiO2/SiNx/SiO2/Si stacked structure by performing X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), Fourier transform infrared (FT-IR) spectroscopy, and scanning transmission electron microscope–electron energy loss spectroscopy (STEM-EELS) analyses. The XPS results showed that PDA induces the oxidation of the SiNx layer. In particular, new finding is that Si-rich SiNx in the SiNx layer is preferentially oxidized by PDA even in multi-stacked structure. The XRR results showed that the SiNx layer becomes thinner, whereas the interface layer between the SiNx layer and Si becomes thicker. It is concluded by STEM-EELS and XPS that this interface layer is SiON layer. The density of N–H and Si–H bonding within the stacked structure strongly depends on the PDA temperature. Our study helps elucidate the properties of SiNx films in stacked structures from various perspectives. 相似文献
77.
78.
79.
Tomohiro Nuida Toshiya Hozumi Hiroko Tokoro Kazuhito Hashimoto Shin-ichi Ohkoshi 《Journal of Solid State Electrochemistry》2007,11(6):763-772
This article describes novel optical functionalities such as photomagnetic effects and magnetization-induced second harmonic
generation (MSHG) in several cyano-bridged metal assemblies. Single crystal- and film-types of a cyano-bridged Cu–Mo bimetallic
assembly, , were electrochemically prepared. When this compound was irradiated with light, spontaneous magnetization with a Curie temperature
(T
C) of 23 K was observed. Electrochemically prepared FeII[CrIII(CN)6]2/3·5H2O thin film, which was a ferromagnet with T
C=21 K, showed photoreduced magnetization. This photomagnetism is due to the change of ferromagnetic coupling between FeII and CrIII. MSHG was observed in CsICoII[CrIII(CN)6]·0.5H2O. This -type Prussian blue analog-based magnet is proven to be a piezoelectric ferromagnet, i.e., condensed matter with both piezoelectric
and ferromagnetism. This MSHG is due to the coupling between a piezoelectric structure of and ferromagnetism with a T
C of 46 K.
相似文献
Shin-ichi OhkoshiEmail: |