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171.
Atsuya Towata Judy LeeKyuichi Yasui Toru TuziutiTeruyuki Kozuka Yasuo Iida 《Applied Surface Science》2011,257(14):6010-6015
The composite consisting of silver nanoparticles deposited on boehmite hybrid was synthesized by NaBH4 reduction technique. The morphology of the composite was studied by TEM, UV/Vis spectrophotometer and particle sizer. The size of the silver nanoparticles deposited on the surface of the boehmite ranged from 10 nm to 100 nm. The contact of silver nanoparticles increased by means of deposition of silver nanoparticles on the boehmite sol and the aggregation of the composites. This leads to the appearance of a shoulder at 450 nm in the UV-Vis absorption spectra with the addition of 0.15 mg and 1.5 mg boehmite. It was found that the intensity of the SERS in the case of the composite was higher than for silver colloids consisting of a concentration of silver greater than 3.2 mM. 相似文献
172.
Katsuaki Shirai Yusuke Yaguchi Lars Büttner Jürgen Czarske Shinnosuke Obi 《Experiments in fluids》2011,50(3):573-586
The flow in the tip clearance of a hard disk drive model has been investigated with laser Doppler techniques. The flow was
driven by co-rotating disks inside a cylindrical enclosure in order to simulate a hard disk drive used for data storage devices.
The main focus of the investigation was on the understanding of complex flow behavior in the narrow gap region between the
disk tip and the outer shroud wall, which is supposed to be one of the causes of flow induced vibration of the disks. Experiments
in the past have never been able to examine this region because of the lack of the spatial resolution of sensors in the highly
three-dimensional flow in the region. In the present investigation, the flow velocity in the tip clearance region was measured
with optical measurement techniques for the first time. The flow behaviors are investigated for four different conditions
with two different gap widths and two different shapes of the shroud walls with and without ribs. The velocity measurements
were taken both with conventional laser Doppler velocimetry and using a laser Doppler velocity profile sensor with a spatial
resolution in the micrometer range. The circumferential velocity component was measured along the axial and radial directions.
The steep gradients of the circumferential mean velocity in both directions were successfully captured with a high spatial
resolution, which was achieved by the velocity profile sensor. From the supplementary investigations, the existence of vortex
structures in the tip clearance region was confirmed with a dependence on the shroud gap width and the shroud shape. The interactions
of the two boundary layers seem to be the source of the complex three-dimensional behaviors of the flow in this region. 相似文献
173.
Mio Matsumura Aya Tanatani Tomoyo Kaneko Isao Azumaya Hyuma Masu Daisuke Hashizume Hiroyuki Kagechika Atsuya Muranaka Masanobu Uchiyama 《Tetrahedron》2013
We synthesized porphyrinylamide 4b and its N-methylated derivative 5b. Direct N-methylation of porphyrinylamides 4 proved unsuccessful, so 5b was obtained via N-methylation of 5-aminoporphyrin 10 with potassium hexamethyldisilazide. The secondary amide 4b exists in trans-amide form, while N-methylated amide 5b exists in the cis-amide form, both in solution and in the crystal. Thus, N-methylation of the amide bond of 4b resulted in trans to cis conformational alteration. 相似文献
174.
175.
The absolute configuration of a binaphthyl-azobenzene dyad 2b, which has a chiral axis and a chiral plane, was determined by comparing the experimental circular dichroism (CD) spectra with the theoretical CD spectra calculated by the time-dependent (TD)-DFT method. The CD signals of the trans-azobenzene moiety indicated that the two benzene rings of this moiety are twisted unidirectionally. It is suggested that these dyads with shorter linkers may be suitable for use as chiroptical switches. 相似文献
176.
The release rate of intercellular protein from yeast cells by the ultrasonic action is proposed as a method for evaluating the physical (mechanical) effects of the ultrasonic field. The protein concentration was quantitatively determined using UV absorbance of proteins by spectrophotometry. The detail of the procedures, such as the effects of the origin of yeast cells, pretreatment of the cells, and the wavelengths for spectrophotometric determination of protein content, are examined. The effectiveness of the proposed evaluation method was experimentally demonstrated by changing the irradiation conditions of ultrasound, such as the concentration of yeast cells, temperature, ultrasound power, types of sonicator, and the superposition with the mechanical mixing. The results validate the usefulness of the proposed evaluation method for the quantification of the physical effects of ultrasound fields. Also, the range of cavitational effects of ultrasound sensed by the evaluation procedures were discussed. 相似文献
177.
Kyuichi Yasui Toru Tuziuti Judy Lee Teruyuki Kozuka Atsuya Towata Yasuo Iida 《Ultrasonics sonochemistry》2010,17(2):460-472
Numerical simulations of cavitation noise have been performed under the experimental conditions reported by Ashokkumar et al. (2007) [26]. The results of numerical simulations have indicated that the temporal fluctuation in the number of bubbles results in the broad-band noise. “Transient” cavitation bubbles, which disintegrate into daughter bubbles mostly in a few acoustic cycles, generate the broad-band noise as their short lifetimes cause the temporal fluctuation in the number of bubbles. Not only active bubbles in light emission (sonoluminescence) and chemical reactions but also inactive bubbles generate the broad-band noise. On the other hand, “stable” cavitation bubbles do not generate the broad-band noise. The weaker broad-band noise from a low-concentration surfactant solution compared to that from pure water observed experimentally by Ashokkumar et al. is caused by the fact that most bubbles are shape stable in a low-concentration surfactant solution due to the smaller ambient radii than those in pure water. For a relatively high number density of bubbles, the bubble–bubble interaction intensifies the broad-band noise. Harmonics in cavitation noise are generated by both “stable” and “transient” cavitation bubbles which pulsate nonlinearly with the period of ultrasound. 相似文献
178.
Manickam Sivakumar Atsuya Towata Kyuichi Yasui Toru Tuziuti Teruyuki Kozuka Yasuo Iida 《Ultrasonics sonochemistry》2010,17(3):621-627
Using a standing wave sonochemical reactor (SWSR), the influences of parameters of ultrasonic power input, sonication time, sonication temperature and the amount of propanol (which generates the reducing radicals) were systemically investigated to ascertain and optimize the best conditions for the sonochemical reduction of Pt from its precursor hexachloroplatinic acid and then its deposition on rutile TiO2 (platinization of rutile titania) catalysts. Catalytic activity of the prepared platinized catalysts was tested in the reaction of methyl orange degradation. The results of photocatalytic activity study in the degradation of methyl orange further demonstrate that sonochemically as-prepared Pt/TiO2 catalysts show a pronounced increase (~2 times) in photodegradation, even with a deposition of small amounts of platinum (1.4 wt.%), as compared to the unsupported or naked rutile titania. Although there are various parameters that influence the sonochemical platinization of rutile titania, the present optimization results clearly indicate that the best photocatalytic degradation of methyl orange can be obtained when the experimental conditions of the preparation were with an input power of 50 W, an initial hexachloroplatinic acid volume of 70 ml (which results into 1.4 wt.% Pt on TiO2), sonication time of 90 min, 0.18 g of propanol and a temperature of 10 °C were adopted. The method of ultrasound application to prepare metal supported semiconductors has many advantages such as convenience, safety and high efficiency. Furthermore, it is hopeful that this optimization study can also be extended to the generation of similar metal supported semiconductors. 相似文献