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81.
Two new Phlegmarine-type alkaloids, lycoposerramines-V and -W, were isolated from Lycopodium serratum, and their structures including the absolute configuration were established by asymmetric total synthesis involving such key steps as Johnson-Claisen rearrangement, asymmetric allylation, and ring-closing metathesis (RCM)- or SmI(2)-mediated stereoselective piperidine ring construction. 相似文献
82.
83.
Toshihiko Myojo Takako Oyabu Kenichiro Nishi Chikara Kadoya Isamu Tanaka Mariko Ono-Ogasawara Hirokazu Sakae Tadashi Shirai 《Journal of nanoparticle research》2009,11(1):91-99
Mass production of some kinds of carbon nanotubes (CNT) is now imminent, but little is known about the risk associated with
their exposure. It is important to assess the propensity of the CNT to release particles into air for its risk assessment.
In this study, we conducted aerosolization of a multi-walled CNT (MWCNT) to assess several aerosol measuring instruments.
A Palas RBG-1000 aerosol generator applied mechanical stress to the MWCNT by a rotating brush at feed rates ranging from 2
to 20 mm/h, which the MWCNT was fed to a two-component fluidized bed. The fluidized bed aerosol generator was used to disperse
the MWCNT aerosol once more. We monitored the generated MWCNT aerosol concentrations based on number, area, and mass using
a condensation particle counter and nanoparticle surface area monitor. Also we quantified carbon mass in MWCNT aerosol samples
by a carbon monitor. The shape of aerosolized MWCNT fibers was observed by a scanning electron microscope (SEM). The MWCNT
was well dispersed by our system. We found isolated MWCNT fibers in the aerosols by SEM and the count median lengths of MWCNT
fibers were 4–6 μm. The MWCNT was quantified by the carbon monitor with a modified condition based on the NIOSH analytical
manual. The MWCNT aerosol concentration (EC mass base) was 4 mg/m3 at 2 mm/h in this study. 相似文献
84.
H. Kudo S. Sudo T. Oka Y. Hama A. Oshima M. Washio T. Murakami 《Radiation Physics and Chemistry》2009,78(12):1067-1070
Ion-beam irradiation effects on polyimide, Kapton™, were studied with respect to optical and electronic properties. Stack films of Kapton™ (12.5 μm thick) were irradiated to various ion beams in air or vacuo at room temperature and subjected to ultraviolet–visible (UV–vis) spectroscopy, and change in absorbance and energy gap is discussed. The UV–vis absorption spectrum, which is assigned to the transition of electrons in benzene rings from π to π* orbital, upon He2+ (6 MeV/u) irradiation in air, shifted towards longer wavelength direction for all cases, and the shift was more obvious for higher linear energy transfer (LET) ion beams. The energy gap of the transition was estimated, and the H+ and He2+ ion beams caused little change in the transition energy gap Eg, while the heavier ions such as C6+ and Si14+ caused more significant decrease. This decrease is assumed to the structural changes around benzene rings, and the infrared spectroscopy revealed breakage in imide groups next to benzene ring in the repeating unit of polyimide. 相似文献
85.
Compared with a nano-sized particle, dynamics of a micron-sized particle in a liquid is often associated with sedimentation (or floating) due to its relatively large mass. The motion of more than two particles is dominated by the hydrodynamic interactions, which are known to persist over a fairly long range, e.g., several millimeters, in suspensions. The particle size may be obtained from the dynamic ultrasound scattering (DSS) technique by the analysis of velocity fluctuations, whose origin is believed to take root in the particle-number fluctuations among temporally formed domains involving collective motion of particles with a certain cut-off length. In this study, such collective particle motion in highly turbid solutions was visualized by means of the phase-mode DSS technique with a single element transducer. Quantitative agreement between the velocity fluctuations obtained by the phase- and conventional amplitude-mode analyses was confirmed, followed by examination of the concentration and the particle size dependences on the dynamic structures induced by the long-ranged interactions. It was found that the phase mode-DSS was a promising method to evaluate the time-dependent structures of the micro-particles in highly turbid suspensions. 相似文献
86.
Electronic structures in coupled two quantum dots by 3D-mesh Hartree-Fock-Kohn-Sham calculation 总被引:2,自引:0,他引:2
T. Matsuse T. Hama H. Kaihatsu N. Toyoda T. Takizawa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):391-394
To study the electronic structures of quantum dots in the framework of self-interaction-free including three dimensional effects,
we adopt the theory of nonlocal effective potential introduced by Kohn and Sham [#!ks65!#]. For utilizing the advantageous
point of the real space (3D) mesh method to solve the original nonlinear and nonlocal Hartree-Fock-Kohn-Sham (HFKS)-equation,
we introduce a linearization of the equation in the local form by introducing the local Coulomb potentials which depend on
explicitly the two single particle states. In practice, for solving the local form HFKS-equation, we use the Car-Parrinello-like
relaxation method and the Coulomb potentials are obtained by solving the Poisson equation under proper boundary conditions.
Firstly the observed energy gap between triplet- and singlet-states of N = 4 in DBS [#!tarucha96!#] is discussed to reproduce the addition energies and chemical potentials depending the magnetic
field. Next the coupling between two-quantum dots in TBS [#!aht97!#] is studied by adding the square barrier between two dots.
The spin-degeneracy [#!aht97!#] measured in gate-voltage depending on magnetic field is well reproduced in the limit of small
mismatch. Finally, the electronic states in the ring structure are calculated and discussed how the ring size and magnetic
field affect to the structures.
Received 30 November 2000 相似文献
87.
Mariko Kitajima Mio Nakamura Hiromitsu Takayama Kazuki Saito Joachim Stöckigt Norio Aimi 《Tetrahedron letters》1997,38(52):1017-9000
The regeneration of plantlets was successful from Ophiorrhiza pumila callus cultures, from which a new glucosyloxy camptothecin, 9-β-glucosyloxycamptothecin, together with 15 metabolites including six camptothecin-related alkaloids was isolated. (3S)-Deoxypumiloside, one of the plausible biogenetic precursors of camptothecin, could not be found, whereas the (3R) epimer was isolated from the regenerated plants. 相似文献
88.
Elliptic flow is easy to compute in hydrodynamics. However experimentally it is obtained in an indirect way. The question we address in this paper is how comparable are these two approaches. For both cases, our study is done using the hydrodynamical code
NeXSPheRIO and simulating nuclear collisions at RHIC. 相似文献
89.
Yuma Wakamiya Dr. Makoto Ebine Mariko Murayama Hiroyuki Omizu Prof. Dr. Nobuaki Matsumori Prof. Dr. Michio Murata Prof. Dr. Tohru Oishi 《Angewandte Chemie (International ed. in English)》2018,57(21):6060-6064
Amphidinol 3 (AM3) is a marine natural product produced by the dinoflagellate Amphidinium klebsii. Although the absolute configuration of AM3 was determined in 1999 by extensive NMR analysis and degradation of the natural product, it was a daunting task because of the presence of numerous stereogenic centers on the acyclic carbon chain and the limited availability from natural sources. Thereafter, revisions of the absolute configurations at C2 and C51 were reported in 2008 and 2013, respectively. Reported herein is the revised absolute configuration of AM3: 32S, 33R, 34S, 35S, 36S, and 38S based on the chemical synthesis of partial structures corresponding to the C31–C67 fragment of AM3 in combination with degradation of the natural product. The revised structure is unique in that both antipodal tetrahydropyran counterparts exist on a single carbon chain. The structural revision of AM3 may affect proposed structures of congeners related to the amphidinols. 相似文献
90.
Time-resolved infrared emission spectra in the wavelength region of 2–5 μm were measured for the CO2-laser-induced photolysis of trifluoromethane-d (CDF3) and its mixtures with trifluoromethane-h (CHF3). The reactant pressures were 0.1–20 Torr at room temperature; some collisions were expected to occur within the laser-pulse duration. The emissions due to vibrationally excited CDF 3 * (C-D stretching mode and probably combination mode) and DF* were observed at the same time for the irradiation of pure CDF3. DF* should be produced in the unimolecular decomposition of CDF 3 * . The dependences of the DF* emission on the experimental condition are explicable on the assumption that the collisional energy transfer followed by the decomposition of CDF3 plays an important role in the present IRMPD, besides its direct multiple-photon decomposition. The mixture of CDF3 and CHF3 showed the emissions due to HF* and CHF 3 * in addition to DF* and CDF 3 * . The ratio between the DF* and HF* emission intensities,I DF/I HF, was examined as a function of pressure. The pressure dependences were similar to those of the selectivity determined previously from the concentration changes of CDF3 and CHF3. The irradiation of mixtures with a long furation pulse (80 ns fwhm with a 2μs) resulted in a marked decrease inI DF/I HF. 相似文献