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201.
Using Rh(I) complexes of chiral phosphine–phosphites, hydroformylation of such a variety of olefins as aryl–substituted, alkyl–substituted,
and heteroatom–substituted ones proceeded in high enantioselectivity. A trigonal bipyramidal RhH(CO)2(phosphine–phosphite) complex is suggested as the active species, in which the hydride and the phosphite moiety are located
at the apical positions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
202.
A flow-type, microscale, non-equilibrium plasma reactor was developed for partial oxidation of methane without a catalyst. A wide range of oxygen and methane mixtures was directly processed without dilution or explosion at ambient temperature because the microscale plasma reactor removes excess heat generated by partial oxidation, thereby maintaining a reaction field at temperatures near room temperature. Consequently, the least reactive methane was excited by high-energy electrons, whereas successive destruction of reactive oxygenates was minimized simultaneously within the extremely confined environment. A highly reactive and quenching environment is thereby obtained within a single reactor: these are paradoxical conditions in conventional thermochemical processes. A major product among liquid oxygenates was methanol, whose selectivity reached 34% at 30% of methane conversion. Selectivity of oxygenates such as methanol and formaldehyde depends strongly on the fragmentation pattern of methane dissociation by electron impact. Maximum selectivity of oxygenates, which is estimated from numerical simulation of a filamentary microdischarge, reaches 60% when the applied electric field corresponds to the breakdown field of methane (80 Td, 1 Td = 10−17 V cm2). The discharge current increases markedly with an applied electric field, but the selectivity of oxygenates decreases as the field strength increases. 相似文献
203.
Changyong Chen Kimura S. Nozaki S. Ono H. Uchida K. 《Nanotechnology, IEEE Transactions on》2006,5(6):671-676
The SiOx thin film with a thickness of about 1 mum was formed on a GaAs substrate by bar-coating with the organic solution of the SiOx nanoparticles (~40 nm). The as-formed SiOx thin film consists of the SiOx nanoparticles; thus the thin film is macroscopically discontinuous and is referred to as a nanoparticle thin film. Although there were no silicon (Si) nanocrystals in the as-formed SiOx nanoparticle thin film, Si nanocrystals were observed by Raman scattering measurement after the thin film was exposed to the laser beam. The growth of Si nanocrystals by laser irradiation is referred to as photosynthesis. The photosynthesis of Si nanocrystals is found to be a self-limiting process. After the average size reaches a certain value, further increase of irradiation time or laser power does not increase the average size. The photosynthesis is similar to the thermal synthesis of Si nanocrystals from SiOx but much faster and low-temperature growth of Si nanocrystals from SiO x. Furthermore, the laser irradiation makes nanoparticles larger by merging. This suggests a possibility of low-temperature formation of a Si-nanocrystal array embedded in a SiO2 thin film. Such a structure has many potential device applications 相似文献
204.
A direct and early-stage nondestructive quality inspection method for concrete in structures is proposed. The advantage of
the proposed method is that it can apply ultrasonic pulse velocity and rebound hardness measurements at ages of their highest
sensitivities, 24 hours and 3 days after mixing, and can predict the 28-day compressive strength in a satisfactory accuracy.
The proposed method involves the combined method of pulse velocity and rebound hardness that can provide versatile information
other than strength and possibly predict durability related properties such as tensile strength, dynamic modulus of elasticity,
density and water absorption. 相似文献
205.
Jun Sugiyama Yutaka Ikedo Peter L. Russo Kazuhiko Mukai Hiroshi Nozaki Jess H. Brewer Eduardo J. Ansaldo Kim H. Chow Daniel Andreica Alex Amato Takenori Fujii Atsushi Asamitsu Kingo Ariyoshi Tsutomu Ohzuku 《Journal of Materials Science: Materials in Electronics》2008,19(8-9):883-893
In order to elucidate the nature of layered cobalt dioxides A x CoO2, we have investigated their microscopic magnetism by means of positive muon-spin rotation and relaxation (μ+SR) spectroscopy, in particular for A = Li, Na, and K and x = 0.5. It was found that the temperature dependence of the internal antiferromagnetic field of Na0.5CoO2 (NCO) is very similar to that of K0.5CoO2 (KCO), although the former is more magnetically-anisotropic than the latter. On the other hand, Li0.5CoO2 (LCO) lacked magnetic order down to 1.7 K. The clear difference between LCO and NCO (and KCO) is likely to be caused by movement of Li+ ions in LCO, based on the zero-field μ+SR experiment. 相似文献
206.
The germanium (Ge) nanocrystals were deposited on substrates whose temperature was kept at room or liquid nitrogen (LN2) temperature by the cluster-beam evaporation technique. The deposited films are found to consist of the tetragonal crystalline
structure rather than the diamond structure of bulk Ge. Such a phase-transition has been theoretically predicted for sizes
smaller than 4 nm, which agrees with the size measured by the transmission electron microscopy (TEM). The tetragonal Ge is
expected to have a direct band gap of 1·47 eV. Furthermore, the Ge film deposited at LN2 temperature exhibits unique properties, such as photo-oxidation and blue-light emission. The Ge-nanocrystal films deposited
by the cluster-beam evaporation technique are attractive materials for application to light emitting devices in future. 相似文献
207.
We have developed a solid oxide fuel cell (SOFC) stack with an internal manifold structure. The stack, which is composed of 25 anode-supported 100-mm-diameter SOFCs, provided an electrical conversion efficiency of 56% (based on the lower heating value of methane, which was used as a fuel) and an output of 350 W when the fuel utilization, current density, and operating temperature were 75%, 0.3 A cm−2, and 1073 K, respectively. The electrical efficiency and the output were maintained for 1100 h. The cell voltage fluctuation was ±2% for 25 cells. The relationship between average cell voltage and current density in the 25-cell stack was as almost the same as that in the 1- and 10-cell stacks, which suggests that our stack provides almost the same cell performance regardless the number of the cells. 相似文献
208.
In contrast to the static operations of conventional semiconductor devices, the dynamic conformational freedom in molecular
devices opens up the possibility of using individual molecules as new types of devices such as a molecular conformational
switch or for molecular data storage. Bistable molecules—such as those having two stable cis and trans isomeric configurations—could provide, once clamped between two electrodes, a switching phenomenon in the non-equilibrium
current response. Here, we model molecular switch junctions formed at silicon contacts and demonstrate the potential of such
tunable molecular switches in electrode/molecule/electrode configurations. Using the non-equilibrium Green function (NEGF)
approach implemented with the density-functional-based tight-binding (DFTB) theory, a series of properties such as electron
transmissions, current-voltage characteristics in the different isomer conformations, and potential energy surfaces (PESs)
as a function of the reaction coordinates along the trans to cis transition were calculated for two azobenzene-based model compounds. Furthermore, in order to investigate the stability of
molecular switches under ambient conditions, molecular dynamics (MD) simulations at room temperature were performed and time-dependent
fluctuations of the conductance along the MD pathways were calculated. Our numerical results show that the transmission spectra
of the cis isomers are more conductive than trans counterparts inside the bias window for both model compounds. The current voltage characteristics consequently show the same
trends. Additionally, calculations of the time-dependent transmission fluctuations along the MD pathways have shown that the
transmission in the cis isomers is always significantly larger than that in their trans counterparts, showing that molecular switches can be expected to work as robust molecular switching components.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
209.
210.
M Roederer S De Rosa R Gerstein M Anderson M Bigos R Stovel T Nozaki D Parks L Herzenberg L Herzenberg 《Canadian Metallurgical Quarterly》1997,29(4):328-339
We developed the chemistry, instrumentation, and software technologies needed to measure, simultaneously and independently, eight different fluorescent molecules on individual cells. Conjugation of these fluorochromes to monoclonal antibodies is straightforward; all immunofluorescence staining is accomplished with direct stains only. We built a hybrid flow cytometer with eight fluorescence detectors and two light scatter channels, with excitation provided by three spatially separated laser beams emitting at 407 nm, 488 nm, and 595 nm. The fluorescence compensation required to make the data orthogonal is of sufficient complexity that it cannot be performed manually; thus, we use software to compensate the data post hoc, based on data collected from singly stained compensation control samples. In this report, we evaluate the 8 color staining technology. Of the seven fluorochromes other than fluorescein, six have a useful brightness at least as great as fluorescein. Three of the fluorochromes (phycoerythrin, allophycocyanin, and the Cy5 resonance energy tandem of phycoerythrin) are considerably brighter than fluorescein and are useful for detecting antigens expressed at low levels. Finally, we show the power and utility of the 8 color, 10-parameter technology using staining experiments on both human and murine immune systems. 相似文献