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排序方式: 共有337条查询结果,搜索用时 15 毫秒
61.
F. Kokai K. Takahashi D. Kasuya M. Yudasaka S. Iijima 《Applied Physics A: Materials Science & Processing》2001,73(4):401-407
Single-wall carbon nanotubes (SWNTs) were synthesized by the irradiation of 20-ms CO2 laser pulses onto a graphite–Co/Ni target at room temperature. We investigated the effect of laser power density (10–150 kW/cm2) and ambient Ar gas pressure (150–760 Torr) on the abundance of SWNTs with lengths of up to about 200 nm in soot-like carbonaceous
deposits. For a constant power density (30 kW/cm2), depending on the Ar gas pressure, SWNTs with diameters of 1.2–1.4 nm were synthesized. Expansion behavior and temperature-fall
rates of clusters and/or particles in laser plumes were also analyzed by high-speed video imaging and temporally and spatially
resolved emission spectroscopy. The temperature-fall rates were estimated to be 171–427 K/ms. The SWNT growth on the time
scale of a few milliseconds appeared to be related to some features of condensing clusters and/or particles, including resident
densities, collision frequencies and temperatures.
Received: 16 July 2001 / Accepted: 23 July 2001 / Published online: 30 August 2001 相似文献
62.
Tomoki Nishimura Yusuke Hatatani Mitsuru Ando Yoshihiro Sasaki Kazunari Akiyoshi 《Chemical science》2022,13(18):5243
Nanodiscs have attracted considerable attention as structural scaffolds for membrane-protein research and as biomaterials in e.g. drug-delivery systems. However, conventional disc-fabrication methods are usually laborious, and disc fabrication via the self-assembly of amphiphiles is difficult. Herein, we report the formation of polymer nanodiscs based on the self-assembly of amphiphilic graft copolymers by adjusting the persistence length of the main chain. Amphiphilic graft copolymers with a series of different main-chain persistence lengths were prepared and these formed, depending on the persistence length, either rods, discs, or vesicles. Notably, polymer nanodiscs were formed upon heating a chilled polymer solution without the need for any additives, and the thus obtained nanodiscs were used to solubilize a membrane protein during cell-free protein synthesis. Given the simplicity of this disc-fabrication method and the ability of these discs to solubilize membrane proteins, this study considerably expands the fundamental and practical scope of graft-copolymer nanodiscs and demonstrates their utility as tools for studying the structure and function of membrane proteins.A strategy for the fabrication of nanodiscs via the self-assembly of thermoresponsive amphiphilic graft copolymers is demonstrated. 相似文献
63.
Seijiro Shioi Akiyoshi Shimamoto Yuki Nakagami Lexin Qin Mototsugu Shimokawa Shinya Oda 《Electrophoresis》2021,42(12-13):1323-1332
Despite being commonplace, polymerase chain reactions (PCRs) still contain many unknown aspects. One example is microsatellite PCR, which is now widely used for various purposes from ecology to cancer medicine. Since this category of repetitive DNA sequences induces polymerase slippage not only in vivo but also in vitro, microsatellite PCR products comprise a complex combination of DNA fragments with various lengths and have, therefore, been empirically interpreted. The primary obstacle for understanding microsatellite PCR was the intrinsic inaccuracy in sizing of DNA fragments in capillary electrophoresis (CE), which, however, has been overcome by elucidating intrinsic sizing errors in each fragment length range. Secondly, the slippage properties of the thermostable polymerases were first clarified in detail using primer extension assays. Furthermore, using the obtained slippage parameters and our original program, we have first reconstructed microsatellite PCR in silico. The entire processes of complex microsatellite PCR have, thus, been more clearly understood. 相似文献
64.
H.G. Smith G. Dolling S. Kunii M. Kasaya B. Liu K. Takegahara T. Kasuya T. Goto 《Solid State Communications》1985,53(1):15-19
Lattice dynamics of La11B6 was studied on the neutron triple axis spectrometers at HFIR. The acoustic and optical modes were measured in the high symmetry directions. The rotary motion of the B6 molecule was measured only near the zone boundaries but shows no softening. Instead, very flat low frequency La modes were observed. The agreement with the elastic constants and the temperature dependence of specific heat is satisfactory.In YbB6, the elastic constants and specific heat were measured. Both results give the quite different feature from those of LaB6, no softening of C12 and more softened flat low frequency Yb modes, due to the lack of the metallic bonds. 相似文献
65.
Takeshi Matsumoto Akitami Ichihara Mitsutoshi Yanagiya Tamio Yuzawa Akiyoshi Sannai Hideaki Oikawa Sadao Sakamura Conrad Hans Eugster 《Helvetica chimica acta》1985,68(8):2324-2331
By a simple process, 3-methoxyjuglone (= 8-hydroxy-2-methoxy-1,4-naphthoquinone; 9 ) has been synthesized from 1,2,4-trimethoxybenzene ( 5 ) and converted, after prenylation, to α-caryopterone ( 1 ; Scheme 1), a pyranojuglone pigment from Caryopteris clandonensis. On the other hand, juglone (= 5-hydroxy-1,4-naphthoquinone; 12 ) was regioselectively prenylated at C(2) via its 1-methoxy-cyclohexa-1,3-diene adduct 15 (Scheme 2). The 2-prenyljuglone ( 4 ) thus formed led to 1 after oxidation and other reactions. 相似文献
66.
Laser sputtering process from surfaces of Si and other Group IV elements are analyzed by space/time resolved spectroscopy. Our measurements demonstrate the capability of analyzing dynamical characteristics of cluster formation/fragmentation processes inμm and nanosecond resolution. 相似文献
67.
A new type of biosensor is described. It is based on the use of a Clark-type oxygen electrode placed in an electromagnetic field. The biomolecules used in this sensor are immobilized on small magnetic beads which are added to the system when needed and removed as required. By varying the strength of the magnetic field, a homogeneous distribution of particles at the electrode tip is achieved. The electrode is used for the determination of glucose with immobilized glucose oxidase as well as cells of Saccharomyces cerevisiae. 相似文献
68.
Orito K Horibata A Nakamura T Ushito H Nagasaki H Yuguchi M Yamashita S Tokuda M 《Journal of the American Chemical Society》2004,126(44):14342-14343
We developed a new method for Pd(II)-catalyzed direct aromatic carbonylation in a phosphine-free catalytic system using Pd(OAc)2 and Cu(OAc)2 in an atmosphere of CO gas containing air. The carbonylation proceeded with ortho-palladation, inducing a remarkable site selectivity to afford a variety of five- or six-membered benzolactams from secondary omega-arylalkylamines, such as N-alkylbenzylamines or N-alkylphenethylamines. 相似文献
69.
A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of stable isotopically labelled L-histidine (L-[3,3-2H2,1',3'-15N2]histidine, L-His-[M + 4]) and urocanic acid ([3-2H,1',3'-15N2]urocanic acid, UA-[M + 3]) in human plasma was developed using DL-[2,3,3,5'-2H4,2'-13C,1',3'-15N2]histidine (DL-His-[M + 7]) and [2,3,5'-2H3,2'-13C,1',3'-15N2]urocanic acid (UA-[M + 6]) as internal standards. L-Histidine and urocanic acid were derivatized to alpha N-(trifluoroacetyl)-imN-(ethoxycarbonyl)-L-histidine n-butyl ester and imN-(ethoxycarbonyl)urocanic acid n-butyl ester. Quantification was carried out by selected ion monitoring of the molecular ions of the respective derivatives of L-His-[M + 4], DL-His-[M + 7], UA-[M + 3] and UA-[M + 6]. The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for measuring plasma concentrations of L-His-[M + 4] and UA-[M + 3] following administration of trace amounts of L-His-[M + 4] to humans. 相似文献
70.
A method is described for the rapid, direct emission spectrometric determination of iron in airborne particulate matter collected on polystyrene fiber filters using a conventional high-volume sampler and a Japanese low-volume sampler. The suspension prepared by dissolving the filter material in xylene was directly nebulized into the inductivelycoupled plasma excitation source. An ultrasonic immersion device was used for stirring purposes. Particles within the size range 0.1–100 μm in diameter are collected on the high-volume filters, while the largest particles on low-volume filters do not exceed 10 μm in diameter. The difference in the particle size composition entailed the use of a separate set of standard suspensions for each sample type. Standard suspensions for calibration were prepared from NBS SRM-1648 (urban particulates) as originally received and from its ground powder for high-volume and low-volume samples, respectively. The relative standard deviation was usually below 5%, which is acceptable for large-scale air pollution survey work. The possibility of determining other major and minor elements in airborne particulate matter was also examined. 相似文献